Usama Qayyum, MBBS

ABSTRACT

The objective of this study is to determine the reproducibility and feasibility of using 3-dimensional (3-D) computer simulation of proximal humerus fracture computed tomography (CT) scans for fracture reduction. We hypothesized that anatomic reconstruction with 3-D models would be anatomically accurate and reproducible.

Preoperative CT scans of 28 patients with 3- and 4-part (AO classification 11-B1, 11-B2, 11-C1, 11-C2) proximal humerus fractures who were treated by hemiarthroplasty were converted into 3-D computer models. The displaced fractured fragments were anatomically reduced with computer simulation by 2 fellowship-trained shoulder surgeons, and measurements were made of the reconstructed proximal humerus.

The measurements of the reconstructed models had very good to excellent interobserver and intraobserver reliability. The reconstructions of these humerus fractures showed interclass correlation coefficients ranging from 0.71 to 0.93 between 1 observer and from 0.82 to 0.98 between 2 different observers. The fracture reduction was judged against normal proximal humerus geometry to determine reduction accuracy.

The 3-D modeling techniques used to reconstruct 3- and 4-part proximal humerus fractures were reliable and accurate. This technique of modeling and reconstructing proximal humerus fractures could be used to enhance the preoperative planning of open reduction and internal fixation or hemiarthroplasty for 3- and 4-part proximal humerus fractures.

The treatment of proximal humerus fractures is influenced by multiple factors, including patient age, associated injuries, bone quality, and fracture pattern. Three- and 4-part fractures are among the more severe of these fractures, which may result in vascular compromise to the humeral head, leading to avascular necrosis. Surgical goals for the management of these fractures are to optimize functional outcomes by re-creating a stable construct with a functional rotator cuff by open reduction and internal fixation (ORIF), hemiarthroplasty with tuberosity ORIF, or reverse shoulder replacement. Achieving a good outcome following hemiarthroplasty is dependent on many factors, including anatomic tuberosity healing and component positioning.^1,2,3 Repairing the greater tuberosity in a near-anatomic position has been shown to greatly affect the results of hemiarthroplasty for fracture.^3,4

Continue to: Three-dimensional (3-D) modeling...

 

Three-dimensional (3-D) modeling is increasingly being used in preoperative planning of shoulder arthroplasty and determining proper proximal humeral fracture treatment. ⁵ However, no studies have examined the reconstruction of a fractured proximal humerus into native anatomy using computer simulation. The purpose of this study is to determine the accuracy and reliability of anatomically reconstructing the preinjury proximal humerus using 3-D computer models created from postinjury computed tomography (CT) scans. The results of this study could lead to useful techniques employing CT–based models for patient-specific preoperative planning of proximal humeral fracture ORIF and during tuberosity reduction and fixation during hemiarthroplasty for fracture. We hypothesize that it is feasible to reconstruct the original anatomy of the proximal humerus by using 3-D computer modeling of proximal humerus fractures with high reliability based on interobserver and intraobserver review.

METHODS

After Institutional Review Board approval was obtained, we reviewed the medical records of consecutive patients with a diagnosis of proximal humeral fracture and the treatment codes for hemiarthroplasty from 2000 to 2013. Inclusion criteria included 3- and 4-part fractures (AO classifications 11-B1, 11-B2, 11-C1, 11-C2). CT scans with insufficient quality to differentiate bone from soft tissue (inadequate signal-to-noise ratio) were excluded from the study. A total of 28 patients with adequate CT scans met the criteria for inclusion in this study.

The CT scan protocol included 0.5-mm axial cuts with inclusion of the proximal humerus in the Digital Imaging and Communications in Medicine format. These CT scans were converted into patient-specific 3-D computer models of the shoulder using Mimics software (Materialise Inc.). The use of this software to produce anatomically accurate models has previously been verified in a shoulder model.^6,7 The tuberosity fragments were then individually separated from each other using the voxel-selecting capabilities of 3-D software and manipulated with translation and rotation for anatomic reduction (Figures 1A-1D, Figure 2).

 

The de-identified anatomically reconstructed shoulder models were then uploaded into Materialise’s Magics rapid prototyping software, and a user-defined humeral Cartesian coordinate system was defined with anatomic landmarks as reference points to standardize the position of each model (Figure 3).^8,9 

The origin was placed at the center of the best-fit sphere representing the humeral head. The y-axis was defined by the longitudinal axis of the humerus, and the x-axis was defined as the line bisecting the articular surface of the humeral head. This Cartesian coordinate system allowed us to manipulate the models in a standardized fashion, maintaining the exact positions of the humerus while making measurements.

A series of measurements were made on these models to assess the validity and reliability of the reassembly. The bicipital groove at the anatomic neck was used to measure humeral head version as described by Kummer and colleagues.¹⁰ The head-shaft angle, humeral head-greater tuberosity distance, humeral head-bicipital groove angle, and posterior and medial humeral head offset were measured directly on the reconstructed humerus.

Continue to: Two fellowship-trained shoulder...

 

Two fellowship-trained shoulder surgeons independently reassembled these fracture fragments via computer simulation. Interobserver reliability testing was conducted on these reconstructions by measuring the geometry between the 2 different surgeons’ reconstructions. Intraobserver reliability testing was conducted by 1 surgeon repeating the reconstructions with 4-week intervals between trials and measuring the geometry between the 2 different trials. The average dimensions of the reconstructed proximal humerus fractures were compared with the geometry of normal humeri reported in previously conducted anatomic studies.^11,12,13

STATISTICS

The measured dimensions of the 28 reassembled proximal humeri models were averaged across all trials between the 2 fellowship-trained surgeons and compared with the range of normal dimensions of a healthy proximal humerus using the 2 one-sided tests (TOST) method for equivalence between 2 means given a range. The interobserver and intraobserver reliabilities were quantified using the interclass correlation coefficient. An excellent correlation was defined as a correlation coefficient >0.81; very good was defined as 0.61 to 0.80; and good was defined as 0.41 to 0.60.

RESULTS

Of the patients studied, 9 (32.1%) were male, and the average age at the time of CT scanning was 72 years. Of the 28 patients with fracture, 18 (64.2%) had 3-part fractures (AO classifications 11-B1, 11-B2), and 10 (35.8%) had 4-part fractures (AO classifications 11-C1, 11-C2). When examining the location of the intertubercular fracture line, we found that 13 (46.4%) fractures went through the bicipital groove. Of the remaining fracture lines, 9 (32.1%) extended into the greater tuberosity and 6 (21.4%) extended into the lesser tuberosity.

All users were able to reconstruct all 28 fractures using this technique. The average measured dimensions fell within the range of dimensions of a normal healthy proximal humerus specified in the literature to within a 95% confidence interval using the TOST for equivalence, in which we compared measured values with ranges reported in the literature (Table).^11,12,13 

Table. Dimensions of Proximal Humerus Geometry

Normal Parameters	Average Dimensions From Trials	Dimensions From Literature
Head shaft angle	43.5° ± 1°	42.5° ± 12.5°
Head to greater tuberosity distance	4.9 mm ± 0.4 mm	8 mm ± 3.2 mm
Head to bicipital groove angle (anatomic neck)	26.4° ± 2°	27.3° ± 14°
Posterior humeral head offset	1.6 mm ± 0.3 mm	4 mm ± 6 mm
Medial humeral head offset	4.5 mm ± 0.3 mm	9 mm ± 5 mm

The reconstructions of these humerus fractures showed intraclass correlation coefficients ranging from 0.71 to 0.93 in 1 observer and interclass correlation coefficients from 0.82 to 0.98 between 2 different observers (Table).

DISCUSSION

This study demonstrates that it is feasible to reliably and accurately reconstruct the original anatomy of the proximal humerus by using 3-D computer modeling of proximal humerus fractures. Poor outcomes after hemiarthroplasty for proximal humerus fractures are mostly related to tuberosity malpositioning, resorption, or failure of fixation and resultant dysfunction of the rotator cuff.^14,15,16 These studies highlight the importance of accurate tuberosity reduction during surgical care of these fractures.

Continue to: The 3-D computer model...

 

The 3-D computer model reconstruction of 3- and 4-part proximal humerus fractures were reliable and valid. The interclass correlation coefficients showed very good to excellent interobserver and intraobserver reliability for all measurements conducted. The averaged dimensions from all trials fell within the appropriate range of dimensions for a normal healthy humerus reported in the literature, as verified by the TOST method.^11,12,13 The 3-D modeling capabilities demonstrated in this study allowed a greater understanding of the fracture patterns present in 3- and 4-part (AO classifications 11-B1, 11-B2, 11-C1, 11-C2) humerus fractures.

Overreduction of greater tuberosity to create cortical overlap with the lateral shaft may be used to promote bony union. As a result of this distalization, there may be extra strains placed on the rotator cuff, making the patient more prone to rotator cuff tear, as well as improperly balancing the dynamic stabilizers of the shoulder. Poor clinical outcomes in hemiarthroplasty for proximal humerus fractures have been correlated with a greater tuberosity placed distal relative to the humeral head by 1 cm in a study² and by 2 cm in another.³

This study has several limitations. The first is the assumption that our injured patients had preinjury proximal humerus geometry within the range of normal dimensions of a healthy humerus. Unfortunately, because we were unable to obtain CT scans of the contralateral shoulder, we had to use standard proximal humerus geometry as the control. Another limitation, inherent in the technique, is that only cortical and dense trabecular bone was modeled, so that comminuted or osteoporotic bone was not well modeled. This study did not correlate the findings from these models with clinical outcomes. A prospective study is needed to evaluate the impact of this 3-D modeling on fracture reductions and clinical outcomes.

This study demonstrates that patient-specific modeling of proximal humerus fracture 3-D CT scans may help surgeons reliably and accurately reconstruct fractures. This technique may have utility in the preoperative planning of tuberosity fracture reduction and hemiarthroplasty. It gives surgeons the ability to visualize fracture fragments, and the process of reconstructing the fragments may help surgeons understand the required maneuvers for reduction at the time of surgery. This technique also provides dimensions of the patient’s native humerus, thus potentially improving the anatomic accuracy of the reduction or hemiarthroplasty reconstruction. With the new trend toward patient-specific instrumentation, this study also provides a means of planning the size of the humeral prostheses as well as the version relative to the biceps groove and intertubercular fracture line.

CONCLUSION

This study demonstrates the feasibility of using 3-D computer modeling of complex proximal humerus fractures in anatomic reconstruction. These techniques of computer-simulated 3-D models are valid and reliable. We believe that this technique of modeling and reconstructing proximal humerus fractures could be used to enhance the preoperative planning of hemiarthroplasty for 3- and 4-part proximal humerus fractures by providing improved understanding of the patient’s native humeral geometry and tuberosity reduction.

ABSTRACT

The objective of this study is to determine the reproducibility and feasibility of using 3-dimensional (3-D) computer simulation of proximal humerus fracture computed tomography (CT) scans for fracture reduction. We hypothesized that anatomic reconstruction with 3-D models would be anatomically accurate and reproducible.

Preoperative CT scans of 28 patients with 3- and 4-part (AO classification 11-B1, 11-B2, 11-C1, 11-C2) proximal humerus fractures who were treated by hemiarthroplasty were converted into 3-D computer models. The displaced fractured fragments were anatomically reduced with computer simulation by 2 fellowship-trained shoulder surgeons, and measurements were made of the reconstructed proximal humerus.

The measurements of the reconstructed models had very good to excellent interobserver and intraobserver reliability. The reconstructions of these humerus fractures showed interclass correlation coefficients ranging from 0.71 to 0.93 between 1 observer and from 0.82 to 0.98 between 2 different observers. The fracture reduction was judged against normal proximal humerus geometry to determine reduction accuracy.

The 3-D modeling techniques used to reconstruct 3- and 4-part proximal humerus fractures were reliable and accurate. This technique of modeling and reconstructing proximal humerus fractures could be used to enhance the preoperative planning of open reduction and internal fixation or hemiarthroplasty for 3- and 4-part proximal humerus fractures.

The treatment of proximal humerus fractures is influenced by multiple factors, including patient age, associated injuries, bone quality, and fracture pattern. Three- and 4-part fractures are among the more severe of these fractures, which may result in vascular compromise to the humeral head, leading to avascular necrosis. Surgical goals for the management of these fractures are to optimize functional outcomes by re-creating a stable construct with a functional rotator cuff by open reduction and internal fixation (ORIF), hemiarthroplasty with tuberosity ORIF, or reverse shoulder replacement. Achieving a good outcome following hemiarthroplasty is dependent on many factors, including anatomic tuberosity healing and component positioning.^1,2,3 Repairing the greater tuberosity in a near-anatomic position has been shown to greatly affect the results of hemiarthroplasty for fracture.^3,4

Continue to: Three-dimensional (3-D) modeling...

 

Three-dimensional (3-D) modeling is increasingly being used in preoperative planning of shoulder arthroplasty and determining proper proximal humeral fracture treatment. ⁵ However, no studies have examined the reconstruction of a fractured proximal humerus into native anatomy using computer simulation. The purpose of this study is to determine the accuracy and reliability of anatomically reconstructing the preinjury proximal humerus using 3-D computer models created from postinjury computed tomography (CT) scans. The results of this study could lead to useful techniques employing CT–based models for patient-specific preoperative planning of proximal humeral fracture ORIF and during tuberosity reduction and fixation during hemiarthroplasty for fracture. We hypothesize that it is feasible to reconstruct the original anatomy of the proximal humerus by using 3-D computer modeling of proximal humerus fractures with high reliability based on interobserver and intraobserver review.

METHODS

After Institutional Review Board approval was obtained, we reviewed the medical records of consecutive patients with a diagnosis of proximal humeral fracture and the treatment codes for hemiarthroplasty from 2000 to 2013. Inclusion criteria included 3- and 4-part fractures (AO classifications 11-B1, 11-B2, 11-C1, 11-C2). CT scans with insufficient quality to differentiate bone from soft tissue (inadequate signal-to-noise ratio) were excluded from the study. A total of 28 patients with adequate CT scans met the criteria for inclusion in this study.

The CT scan protocol included 0.5-mm axial cuts with inclusion of the proximal humerus in the Digital Imaging and Communications in Medicine format. These CT scans were converted into patient-specific 3-D computer models of the shoulder using Mimics software (Materialise Inc.). The use of this software to produce anatomically accurate models has previously been verified in a shoulder model.^6,7 The tuberosity fragments were then individually separated from each other using the voxel-selecting capabilities of 3-D software and manipulated with translation and rotation for anatomic reduction (Figures 1A-1D, Figure 2).

 

The de-identified anatomically reconstructed shoulder models were then uploaded into Materialise’s Magics rapid prototyping software, and a user-defined humeral Cartesian coordinate system was defined with anatomic landmarks as reference points to standardize the position of each model (Figure 3).^8,9 

The origin was placed at the center of the best-fit sphere representing the humeral head. The y-axis was defined by the longitudinal axis of the humerus, and the x-axis was defined as the line bisecting the articular surface of the humeral head. This Cartesian coordinate system allowed us to manipulate the models in a standardized fashion, maintaining the exact positions of the humerus while making measurements.

A series of measurements were made on these models to assess the validity and reliability of the reassembly. The bicipital groove at the anatomic neck was used to measure humeral head version as described by Kummer and colleagues.¹⁰ The head-shaft angle, humeral head-greater tuberosity distance, humeral head-bicipital groove angle, and posterior and medial humeral head offset were measured directly on the reconstructed humerus.

Continue to: Two fellowship-trained shoulder...

 

Two fellowship-trained shoulder surgeons independently reassembled these fracture fragments via computer simulation. Interobserver reliability testing was conducted on these reconstructions by measuring the geometry between the 2 different surgeons’ reconstructions. Intraobserver reliability testing was conducted by 1 surgeon repeating the reconstructions with 4-week intervals between trials and measuring the geometry between the 2 different trials. The average dimensions of the reconstructed proximal humerus fractures were compared with the geometry of normal humeri reported in previously conducted anatomic studies.^11,12,13

STATISTICS

The measured dimensions of the 28 reassembled proximal humeri models were averaged across all trials between the 2 fellowship-trained surgeons and compared with the range of normal dimensions of a healthy proximal humerus using the 2 one-sided tests (TOST) method for equivalence between 2 means given a range. The interobserver and intraobserver reliabilities were quantified using the interclass correlation coefficient. An excellent correlation was defined as a correlation coefficient >0.81; very good was defined as 0.61 to 0.80; and good was defined as 0.41 to 0.60.

RESULTS

Of the patients studied, 9 (32.1%) were male, and the average age at the time of CT scanning was 72 years. Of the 28 patients with fracture, 18 (64.2%) had 3-part fractures (AO classifications 11-B1, 11-B2), and 10 (35.8%) had 4-part fractures (AO classifications 11-C1, 11-C2). When examining the location of the intertubercular fracture line, we found that 13 (46.4%) fractures went through the bicipital groove. Of the remaining fracture lines, 9 (32.1%) extended into the greater tuberosity and 6 (21.4%) extended into the lesser tuberosity.

All users were able to reconstruct all 28 fractures using this technique. The average measured dimensions fell within the range of dimensions of a normal healthy proximal humerus specified in the literature to within a 95% confidence interval using the TOST for equivalence, in which we compared measured values with ranges reported in the literature (Table).^11,12,13 

Table. Dimensions of Proximal Humerus Geometry

Normal Parameters	Average Dimensions From Trials	Dimensions From Literature
Head shaft angle	43.5° ± 1°	42.5° ± 12.5°
Head to greater tuberosity distance	4.9 mm ± 0.4 mm	8 mm ± 3.2 mm
Head to bicipital groove angle (anatomic neck)	26.4° ± 2°	27.3° ± 14°
Posterior humeral head offset	1.6 mm ± 0.3 mm	4 mm ± 6 mm
Medial humeral head offset	4.5 mm ± 0.3 mm	9 mm ± 5 mm

The reconstructions of these humerus fractures showed intraclass correlation coefficients ranging from 0.71 to 0.93 in 1 observer and interclass correlation coefficients from 0.82 to 0.98 between 2 different observers (Table).

DISCUSSION

This study demonstrates that it is feasible to reliably and accurately reconstruct the original anatomy of the proximal humerus by using 3-D computer modeling of proximal humerus fractures. Poor outcomes after hemiarthroplasty for proximal humerus fractures are mostly related to tuberosity malpositioning, resorption, or failure of fixation and resultant dysfunction of the rotator cuff.^14,15,16 These studies highlight the importance of accurate tuberosity reduction during surgical care of these fractures.

Continue to: The 3-D computer model...

 

The 3-D computer model reconstruction of 3- and 4-part proximal humerus fractures were reliable and valid. The interclass correlation coefficients showed very good to excellent interobserver and intraobserver reliability for all measurements conducted. The averaged dimensions from all trials fell within the appropriate range of dimensions for a normal healthy humerus reported in the literature, as verified by the TOST method.^11,12,13 The 3-D modeling capabilities demonstrated in this study allowed a greater understanding of the fracture patterns present in 3- and 4-part (AO classifications 11-B1, 11-B2, 11-C1, 11-C2) humerus fractures.

Overreduction of greater tuberosity to create cortical overlap with the lateral shaft may be used to promote bony union. As a result of this distalization, there may be extra strains placed on the rotator cuff, making the patient more prone to rotator cuff tear, as well as improperly balancing the dynamic stabilizers of the shoulder. Poor clinical outcomes in hemiarthroplasty for proximal humerus fractures have been correlated with a greater tuberosity placed distal relative to the humeral head by 1 cm in a study² and by 2 cm in another.³

This study has several limitations. The first is the assumption that our injured patients had preinjury proximal humerus geometry within the range of normal dimensions of a healthy humerus. Unfortunately, because we were unable to obtain CT scans of the contralateral shoulder, we had to use standard proximal humerus geometry as the control. Another limitation, inherent in the technique, is that only cortical and dense trabecular bone was modeled, so that comminuted or osteoporotic bone was not well modeled. This study did not correlate the findings from these models with clinical outcomes. A prospective study is needed to evaluate the impact of this 3-D modeling on fracture reductions and clinical outcomes.

This study demonstrates that patient-specific modeling of proximal humerus fracture 3-D CT scans may help surgeons reliably and accurately reconstruct fractures. This technique may have utility in the preoperative planning of tuberosity fracture reduction and hemiarthroplasty. It gives surgeons the ability to visualize fracture fragments, and the process of reconstructing the fragments may help surgeons understand the required maneuvers for reduction at the time of surgery. This technique also provides dimensions of the patient’s native humerus, thus potentially improving the anatomic accuracy of the reduction or hemiarthroplasty reconstruction. With the new trend toward patient-specific instrumentation, this study also provides a means of planning the size of the humeral prostheses as well as the version relative to the biceps groove and intertubercular fracture line.

CONCLUSION

This study demonstrates the feasibility of using 3-D computer modeling of complex proximal humerus fractures in anatomic reconstruction. These techniques of computer-simulated 3-D models are valid and reliable. We believe that this technique of modeling and reconstructing proximal humerus fractures could be used to enhance the preoperative planning of hemiarthroplasty for 3- and 4-part proximal humerus fractures by providing improved understanding of the patient’s native humeral geometry and tuberosity reduction.

ABSTRACT

The objective of this study is to determine the reproducibility and feasibility of using 3-dimensional (3-D) computer simulation of proximal humerus fracture computed tomography (CT) scans for fracture reduction. We hypothesized that anatomic reconstruction with 3-D models would be anatomically accurate and reproducible.

Preoperative CT scans of 28 patients with 3- and 4-part (AO classification 11-B1, 11-B2, 11-C1, 11-C2) proximal humerus fractures who were treated by hemiarthroplasty were converted into 3-D computer models. The displaced fractured fragments were anatomically reduced with computer simulation by 2 fellowship-trained shoulder surgeons, and measurements were made of the reconstructed proximal humerus.

The measurements of the reconstructed models had very good to excellent interobserver and intraobserver reliability. The reconstructions of these humerus fractures showed interclass correlation coefficients ranging from 0.71 to 0.93 between 1 observer and from 0.82 to 0.98 between 2 different observers. The fracture reduction was judged against normal proximal humerus geometry to determine reduction accuracy.

The 3-D modeling techniques used to reconstruct 3- and 4-part proximal humerus fractures were reliable and accurate. This technique of modeling and reconstructing proximal humerus fractures could be used to enhance the preoperative planning of open reduction and internal fixation or hemiarthroplasty for 3- and 4-part proximal humerus fractures.

The treatment of proximal humerus fractures is influenced by multiple factors, including patient age, associated injuries, bone quality, and fracture pattern. Three- and 4-part fractures are among the more severe of these fractures, which may result in vascular compromise to the humeral head, leading to avascular necrosis. Surgical goals for the management of these fractures are to optimize functional outcomes by re-creating a stable construct with a functional rotator cuff by open reduction and internal fixation (ORIF), hemiarthroplasty with tuberosity ORIF, or reverse shoulder replacement. Achieving a good outcome following hemiarthroplasty is dependent on many factors, including anatomic tuberosity healing and component positioning.^1,2,3 Repairing the greater tuberosity in a near-anatomic position has been shown to greatly affect the results of hemiarthroplasty for fracture.^3,4

Continue to: Three-dimensional (3-D) modeling...

 

Three-dimensional (3-D) modeling is increasingly being used in preoperative planning of shoulder arthroplasty and determining proper proximal humeral fracture treatment. ⁵ However, no studies have examined the reconstruction of a fractured proximal humerus into native anatomy using computer simulation. The purpose of this study is to determine the accuracy and reliability of anatomically reconstructing the preinjury proximal humerus using 3-D computer models created from postinjury computed tomography (CT) scans. The results of this study could lead to useful techniques employing CT–based models for patient-specific preoperative planning of proximal humeral fracture ORIF and during tuberosity reduction and fixation during hemiarthroplasty for fracture. We hypothesize that it is feasible to reconstruct the original anatomy of the proximal humerus by using 3-D computer modeling of proximal humerus fractures with high reliability based on interobserver and intraobserver review.

METHODS

After Institutional Review Board approval was obtained, we reviewed the medical records of consecutive patients with a diagnosis of proximal humeral fracture and the treatment codes for hemiarthroplasty from 2000 to 2013. Inclusion criteria included 3- and 4-part fractures (AO classifications 11-B1, 11-B2, 11-C1, 11-C2). CT scans with insufficient quality to differentiate bone from soft tissue (inadequate signal-to-noise ratio) were excluded from the study. A total of 28 patients with adequate CT scans met the criteria for inclusion in this study.

The CT scan protocol included 0.5-mm axial cuts with inclusion of the proximal humerus in the Digital Imaging and Communications in Medicine format. These CT scans were converted into patient-specific 3-D computer models of the shoulder using Mimics software (Materialise Inc.). The use of this software to produce anatomically accurate models has previously been verified in a shoulder model.^6,7 The tuberosity fragments were then individually separated from each other using the voxel-selecting capabilities of 3-D software and manipulated with translation and rotation for anatomic reduction (Figures 1A-1D, Figure 2).

 

The de-identified anatomically reconstructed shoulder models were then uploaded into Materialise’s Magics rapid prototyping software, and a user-defined humeral Cartesian coordinate system was defined with anatomic landmarks as reference points to standardize the position of each model (Figure 3).^8,9 

The origin was placed at the center of the best-fit sphere representing the humeral head. The y-axis was defined by the longitudinal axis of the humerus, and the x-axis was defined as the line bisecting the articular surface of the humeral head. This Cartesian coordinate system allowed us to manipulate the models in a standardized fashion, maintaining the exact positions of the humerus while making measurements.

A series of measurements were made on these models to assess the validity and reliability of the reassembly. The bicipital groove at the anatomic neck was used to measure humeral head version as described by Kummer and colleagues.¹⁰ The head-shaft angle, humeral head-greater tuberosity distance, humeral head-bicipital groove angle, and posterior and medial humeral head offset were measured directly on the reconstructed humerus.

Continue to: Two fellowship-trained shoulder...

 

Two fellowship-trained shoulder surgeons independently reassembled these fracture fragments via computer simulation. Interobserver reliability testing was conducted on these reconstructions by measuring the geometry between the 2 different surgeons’ reconstructions. Intraobserver reliability testing was conducted by 1 surgeon repeating the reconstructions with 4-week intervals between trials and measuring the geometry between the 2 different trials. The average dimensions of the reconstructed proximal humerus fractures were compared with the geometry of normal humeri reported in previously conducted anatomic studies.^11,12,13

STATISTICS

The measured dimensions of the 28 reassembled proximal humeri models were averaged across all trials between the 2 fellowship-trained surgeons and compared with the range of normal dimensions of a healthy proximal humerus using the 2 one-sided tests (TOST) method for equivalence between 2 means given a range. The interobserver and intraobserver reliabilities were quantified using the interclass correlation coefficient. An excellent correlation was defined as a correlation coefficient >0.81; very good was defined as 0.61 to 0.80; and good was defined as 0.41 to 0.60.

RESULTS

Of the patients studied, 9 (32.1%) were male, and the average age at the time of CT scanning was 72 years. Of the 28 patients with fracture, 18 (64.2%) had 3-part fractures (AO classifications 11-B1, 11-B2), and 10 (35.8%) had 4-part fractures (AO classifications 11-C1, 11-C2). When examining the location of the intertubercular fracture line, we found that 13 (46.4%) fractures went through the bicipital groove. Of the remaining fracture lines, 9 (32.1%) extended into the greater tuberosity and 6 (21.4%) extended into the lesser tuberosity.

All users were able to reconstruct all 28 fractures using this technique. The average measured dimensions fell within the range of dimensions of a normal healthy proximal humerus specified in the literature to within a 95% confidence interval using the TOST for equivalence, in which we compared measured values with ranges reported in the literature (Table).^11,12,13 

Table. Dimensions of Proximal Humerus Geometry

Normal Parameters	Average Dimensions From Trials	Dimensions From Literature
Head shaft angle	43.5° ± 1°	42.5° ± 12.5°
Head to greater tuberosity distance	4.9 mm ± 0.4 mm	8 mm ± 3.2 mm
Head to bicipital groove angle (anatomic neck)	26.4° ± 2°	27.3° ± 14°
Posterior humeral head offset	1.6 mm ± 0.3 mm	4 mm ± 6 mm
Medial humeral head offset	4.5 mm ± 0.3 mm	9 mm ± 5 mm

The reconstructions of these humerus fractures showed intraclass correlation coefficients ranging from 0.71 to 0.93 in 1 observer and interclass correlation coefficients from 0.82 to 0.98 between 2 different observers (Table).

DISCUSSION

This study demonstrates that it is feasible to reliably and accurately reconstruct the original anatomy of the proximal humerus by using 3-D computer modeling of proximal humerus fractures. Poor outcomes after hemiarthroplasty for proximal humerus fractures are mostly related to tuberosity malpositioning, resorption, or failure of fixation and resultant dysfunction of the rotator cuff.^14,15,16 These studies highlight the importance of accurate tuberosity reduction during surgical care of these fractures.

Continue to: The 3-D computer model...

 

The 3-D computer model reconstruction of 3- and 4-part proximal humerus fractures were reliable and valid. The interclass correlation coefficients showed very good to excellent interobserver and intraobserver reliability for all measurements conducted. The averaged dimensions from all trials fell within the appropriate range of dimensions for a normal healthy humerus reported in the literature, as verified by the TOST method.^11,12,13 The 3-D modeling capabilities demonstrated in this study allowed a greater understanding of the fracture patterns present in 3- and 4-part (AO classifications 11-B1, 11-B2, 11-C1, 11-C2) humerus fractures.

Overreduction of greater tuberosity to create cortical overlap with the lateral shaft may be used to promote bony union. As a result of this distalization, there may be extra strains placed on the rotator cuff, making the patient more prone to rotator cuff tear, as well as improperly balancing the dynamic stabilizers of the shoulder. Poor clinical outcomes in hemiarthroplasty for proximal humerus fractures have been correlated with a greater tuberosity placed distal relative to the humeral head by 1 cm in a study² and by 2 cm in another.³

This study has several limitations. The first is the assumption that our injured patients had preinjury proximal humerus geometry within the range of normal dimensions of a healthy humerus. Unfortunately, because we were unable to obtain CT scans of the contralateral shoulder, we had to use standard proximal humerus geometry as the control. Another limitation, inherent in the technique, is that only cortical and dense trabecular bone was modeled, so that comminuted or osteoporotic bone was not well modeled. This study did not correlate the findings from these models with clinical outcomes. A prospective study is needed to evaluate the impact of this 3-D modeling on fracture reductions and clinical outcomes.

This study demonstrates that patient-specific modeling of proximal humerus fracture 3-D CT scans may help surgeons reliably and accurately reconstruct fractures. This technique may have utility in the preoperative planning of tuberosity fracture reduction and hemiarthroplasty. It gives surgeons the ability to visualize fracture fragments, and the process of reconstructing the fragments may help surgeons understand the required maneuvers for reduction at the time of surgery. This technique also provides dimensions of the patient’s native humerus, thus potentially improving the anatomic accuracy of the reduction or hemiarthroplasty reconstruction. With the new trend toward patient-specific instrumentation, this study also provides a means of planning the size of the humeral prostheses as well as the version relative to the biceps groove and intertubercular fracture line.

CONCLUSION

This study demonstrates the feasibility of using 3-D computer modeling of complex proximal humerus fractures in anatomic reconstruction. These techniques of computer-simulated 3-D models are valid and reliable. We believe that this technique of modeling and reconstructing proximal humerus fractures could be used to enhance the preoperative planning of hemiarthroplasty for 3- and 4-part proximal humerus fractures by providing improved understanding of the patient’s native humeral geometry and tuberosity reduction.

Take-Home Points

• Pronator teres muscle injuries are rare.
• Injury can be mistaken for MUCL injury in athletes.
• Tenderness and weak/painful forearm pronation are common findings.
• MRI confirms the diagnosis and helps grade the muscle strain injury.
• Conservative treatment is recommended and prognosis is excellent even for high-grade strains.

Pronator teres muscle strain is a rare sporting injury reported only in cricket players, and now in a golfer whose forearm experienced an eccentric force during resisted elbow flexion and pronation.^1,2 The injury occurs when the sporting club or racket strikes the ground during a swing, impeding forward progress and subjecting the pronator teres muscle to eccentric forces in excess of what it can withstand. The pronator teres, one of several muscles that comprise the flexor wad of the forearm, consists of 2 heads, originating proximally from the medical epicondyle and attaching distally to the shaft of the radius on its lateral surface and just distal to the supinator. The oblique orientation of the muscle belly allows it to serve in its primary rotatory role as the main pronator of the forearm. Injuries to the soft tissue of the medial forearm are common in both elite and recreational athletes, especially in racket and club sports.³ Often, these injuries are related to overuse and chronic fatigue of the surrounding soft tissue—caused by repetitive flexing, gripping, or swinging. Even when identified early, these injuries can result in a significant loss of training time.⁴ In this article, we report a case of pronator teres muscle tear at the myotendinous junction. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A right-hand–dominant 36-year-old man presented to the clinic with pain on the medial side of his right elbow after sustaining an injury to the elbow while playing golf several days earlier. The patient, an advertising executive, was playing recreational golf several times a month and had no significant medical history or previous symptoms related to the elbow. Initial pain symptoms began during a second round of play, immediately after the patient miss-hit an iron shot, making contact mostly with the ground and causing the club to forcefully stop. The pain was on the medial side of the elbow and forearm. The patient noted progressive swelling and bruising at the pain site and development of forearm weakness. Physical examination during the clinic presentation revealed ecchymosis on the anterior medial forearm, medial elbow, and medial triceps (Figure 1).

Mild tenderness to palpation was elicited over the medial elbow, specifically over the course of the flexor pronator mass. When the elbow was assessed for tender areas, the medial epicondyle was not tender. Range of motion (ROM) testing revealed 120° of flexion and 10° short of full extension, attributed to swelling from acute injury. The patient had full supination and pronation, but the pain was reproduced with either movement. The pain produced weakness with flexion and pronation. Valgus stress test results were normal; there was no re-creation of symptoms. The median nerve was negative for the Tinel sign, and the rest of the neurovascular examination was unremarkable. The ipsilateral shoulder was normal on examination.

Noncontrast magnetic resonance imaging (MRI) showed a high-grade partial tear of the pronator teres myotendinous junction (Figures 2A-2C).

In the surrounding tissue there was an associated increased signal representing edema. Also found was a small intramuscular hematoma. The median nerve, medial collateral ligament, distal biceps, and triceps were uninjured.

The patient was instructed to rest the elbow from strenuous activity, golf in particular, for 4 weeks. Physical therapy for ROM and forearm strengthening of the surrounding flexor wad was initiated at 2 weeks and continued for 4 weeks. The patient was advised to take over-the-counter nonsteroidal anti-inflammatory drugs as needed for comfort. On repeat examination at 4 weeks, with tenderness or weakness with pronation absent and full ROM regained, the patient was released back to full activity. He was able to return to golf and reported being symptom-free and having no sense of weakness or loss of control.

Discussion

A tear of the pronator teres is an exceedingly rare injury. Our results with conservative treatment and a full return to previous activity level are consistent with the only other case reported in the literature.⁵ In contrast to our patient, the previous patient sustained a tear of the pronator teres after a prolonged period of batting during a recreational cricket match.

 

Our patient’s pronator teres injury occurred at the myotendinous junction, a muscle-tendon transition zone often susceptible to injury. What is unusual for this athletic medial elbow injury is that the patient reported no previous symptoms, and it appears that, though the surrounding muscle may have been fatigued by overuse from the round of golf earlier that day, the pathology was caused by an acute eccentric force. During a golf swing, tremendous forces are put on the entire body, from the lower extremities to the forearm and the fingers. Successful completion of the transfer of energy from the golf club to the ball requires both proper technique and proper functioning of key muscles. Specifically, parameters such as ball positioning, club angle, and wrist control play a major role.⁶ Altered forearm positioning or swing arc can significantly affect club head velocity and energy transfer without putting more stress on the golfer.⁷ Therefore, it is easy to understand how prolonged or extended play may fatigue the surrounding elbow muscles, leading to altered technique and increased susceptibility to acute injury. Biomechanical analysis of shoulder motion can provide a helpful baseline for assessing injury-related changes in golf swing and developing specific exercise and rehabilitation programs.^8,9Although injury to the pronator teres is rare, sport physicians should be aware that, after a valgus stress or force, bruising and swelling along the medial elbow do not always indicate a medial ulnar collateral ligament (MUCL) tear or medial epicondylitis. The key examination findings that differentiate this injury from a MUCL injury are the exact location of pain, the milking maneuver for MUCL incompetence, and the extensive bruising over the muscle course of the pronator teres. MRI plays a pivotal role in proper diagnosis.⁴ In addition, MRI allows for evaluation of any concomitant injuries that may be obscuring the clinical presentation.

Successful treatment of such injuries is important for both elite and recreational athletes. With rest and physical therapy, our patient recovered from this rare isolated injury to the pronator teres with complete resolution of symptoms and full ROM. In the literature, we found no other reports of isolated full-thickness myotendinous rupture of the pronator teres or avulsion from the medial epicondyle. Therefore, it is unclear whether the same outcome can be expected with conservative therapy. However, because of the good outcomes for partial-thickness injuries treated conservatively and the lack of robust tendinous tissue to repair at the myotendinous junction, we recommend an initial course of conservative treatment. Sports physicians should be aware of this exceedingly rare injury to the elbow and understand the large forces experienced by the soft tissues of the forearm during the golf swing.^9,10

Conclusion

Pronator teres muscle strain is a rare sporting injury reported in cricket and golf players. The elbow experiences a large eccentric force during resisted elbow flexion and pronation. The injury appears to occur when the sporting club or racket strikes the ground during a forceful swing impeding forward progress of the arm. The injury can be confused with a MUCL injury, or exacerbation of medial epicondylitis. Physical examination reveals bruising and tenderness over the course of the pronator teres, often distal to the elbow. Advanced imaging confirms the diagnosis and helps grade the severity of muscle strain. Treatment is often conservative, with return to function and sport after 4 to 6 weeks of rest and restricted activities. The patient in this case report had complete return to sporting function, with no residual weakness or pain.

Am J Orthop. 2017;46(2):E105-E107. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.

Take-Home Points

• Pronator teres muscle injuries are rare.
• Injury can be mistaken for MUCL injury in athletes.
• Tenderness and weak/painful forearm pronation are common findings.
• MRI confirms the diagnosis and helps grade the muscle strain injury.
• Conservative treatment is recommended and prognosis is excellent even for high-grade strains.

Pronator teres muscle strain is a rare sporting injury reported only in cricket players, and now in a golfer whose forearm experienced an eccentric force during resisted elbow flexion and pronation.^1,2 The injury occurs when the sporting club or racket strikes the ground during a swing, impeding forward progress and subjecting the pronator teres muscle to eccentric forces in excess of what it can withstand. The pronator teres, one of several muscles that comprise the flexor wad of the forearm, consists of 2 heads, originating proximally from the medical epicondyle and attaching distally to the shaft of the radius on its lateral surface and just distal to the supinator. The oblique orientation of the muscle belly allows it to serve in its primary rotatory role as the main pronator of the forearm. Injuries to the soft tissue of the medial forearm are common in both elite and recreational athletes, especially in racket and club sports.³ Often, these injuries are related to overuse and chronic fatigue of the surrounding soft tissue—caused by repetitive flexing, gripping, or swinging. Even when identified early, these injuries can result in a significant loss of training time.⁴ In this article, we report a case of pronator teres muscle tear at the myotendinous junction. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A right-hand–dominant 36-year-old man presented to the clinic with pain on the medial side of his right elbow after sustaining an injury to the elbow while playing golf several days earlier. The patient, an advertising executive, was playing recreational golf several times a month and had no significant medical history or previous symptoms related to the elbow. Initial pain symptoms began during a second round of play, immediately after the patient miss-hit an iron shot, making contact mostly with the ground and causing the club to forcefully stop. The pain was on the medial side of the elbow and forearm. The patient noted progressive swelling and bruising at the pain site and development of forearm weakness. Physical examination during the clinic presentation revealed ecchymosis on the anterior medial forearm, medial elbow, and medial triceps (Figure 1).

Mild tenderness to palpation was elicited over the medial elbow, specifically over the course of the flexor pronator mass. When the elbow was assessed for tender areas, the medial epicondyle was not tender. Range of motion (ROM) testing revealed 120° of flexion and 10° short of full extension, attributed to swelling from acute injury. The patient had full supination and pronation, but the pain was reproduced with either movement. The pain produced weakness with flexion and pronation. Valgus stress test results were normal; there was no re-creation of symptoms. The median nerve was negative for the Tinel sign, and the rest of the neurovascular examination was unremarkable. The ipsilateral shoulder was normal on examination.

Noncontrast magnetic resonance imaging (MRI) showed a high-grade partial tear of the pronator teres myotendinous junction (Figures 2A-2C).

In the surrounding tissue there was an associated increased signal representing edema. Also found was a small intramuscular hematoma. The median nerve, medial collateral ligament, distal biceps, and triceps were uninjured.

The patient was instructed to rest the elbow from strenuous activity, golf in particular, for 4 weeks. Physical therapy for ROM and forearm strengthening of the surrounding flexor wad was initiated at 2 weeks and continued for 4 weeks. The patient was advised to take over-the-counter nonsteroidal anti-inflammatory drugs as needed for comfort. On repeat examination at 4 weeks, with tenderness or weakness with pronation absent and full ROM regained, the patient was released back to full activity. He was able to return to golf and reported being symptom-free and having no sense of weakness or loss of control.

Discussion

A tear of the pronator teres is an exceedingly rare injury. Our results with conservative treatment and a full return to previous activity level are consistent with the only other case reported in the literature.⁵ In contrast to our patient, the previous patient sustained a tear of the pronator teres after a prolonged period of batting during a recreational cricket match.

 

Our patient’s pronator teres injury occurred at the myotendinous junction, a muscle-tendon transition zone often susceptible to injury. What is unusual for this athletic medial elbow injury is that the patient reported no previous symptoms, and it appears that, though the surrounding muscle may have been fatigued by overuse from the round of golf earlier that day, the pathology was caused by an acute eccentric force. During a golf swing, tremendous forces are put on the entire body, from the lower extremities to the forearm and the fingers. Successful completion of the transfer of energy from the golf club to the ball requires both proper technique and proper functioning of key muscles. Specifically, parameters such as ball positioning, club angle, and wrist control play a major role.⁶ Altered forearm positioning or swing arc can significantly affect club head velocity and energy transfer without putting more stress on the golfer.⁷ Therefore, it is easy to understand how prolonged or extended play may fatigue the surrounding elbow muscles, leading to altered technique and increased susceptibility to acute injury. Biomechanical analysis of shoulder motion can provide a helpful baseline for assessing injury-related changes in golf swing and developing specific exercise and rehabilitation programs.^8,9Although injury to the pronator teres is rare, sport physicians should be aware that, after a valgus stress or force, bruising and swelling along the medial elbow do not always indicate a medial ulnar collateral ligament (MUCL) tear or medial epicondylitis. The key examination findings that differentiate this injury from a MUCL injury are the exact location of pain, the milking maneuver for MUCL incompetence, and the extensive bruising over the muscle course of the pronator teres. MRI plays a pivotal role in proper diagnosis.⁴ In addition, MRI allows for evaluation of any concomitant injuries that may be obscuring the clinical presentation.

Successful treatment of such injuries is important for both elite and recreational athletes. With rest and physical therapy, our patient recovered from this rare isolated injury to the pronator teres with complete resolution of symptoms and full ROM. In the literature, we found no other reports of isolated full-thickness myotendinous rupture of the pronator teres or avulsion from the medial epicondyle. Therefore, it is unclear whether the same outcome can be expected with conservative therapy. However, because of the good outcomes for partial-thickness injuries treated conservatively and the lack of robust tendinous tissue to repair at the myotendinous junction, we recommend an initial course of conservative treatment. Sports physicians should be aware of this exceedingly rare injury to the elbow and understand the large forces experienced by the soft tissues of the forearm during the golf swing.^9,10

Conclusion

Pronator teres muscle strain is a rare sporting injury reported in cricket and golf players. The elbow experiences a large eccentric force during resisted elbow flexion and pronation. The injury appears to occur when the sporting club or racket strikes the ground during a forceful swing impeding forward progress of the arm. The injury can be confused with a MUCL injury, or exacerbation of medial epicondylitis. Physical examination reveals bruising and tenderness over the course of the pronator teres, often distal to the elbow. Advanced imaging confirms the diagnosis and helps grade the severity of muscle strain. Treatment is often conservative, with return to function and sport after 4 to 6 weeks of rest and restricted activities. The patient in this case report had complete return to sporting function, with no residual weakness or pain.

Am J Orthop. 2017;46(2):E105-E107. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.

Take-Home Points

• Pronator teres muscle injuries are rare.
• Injury can be mistaken for MUCL injury in athletes.
• Tenderness and weak/painful forearm pronation are common findings.
• MRI confirms the diagnosis and helps grade the muscle strain injury.
• Conservative treatment is recommended and prognosis is excellent even for high-grade strains.

Pronator teres muscle strain is a rare sporting injury reported only in cricket players, and now in a golfer whose forearm experienced an eccentric force during resisted elbow flexion and pronation.^1,2 The injury occurs when the sporting club or racket strikes the ground during a swing, impeding forward progress and subjecting the pronator teres muscle to eccentric forces in excess of what it can withstand. The pronator teres, one of several muscles that comprise the flexor wad of the forearm, consists of 2 heads, originating proximally from the medical epicondyle and attaching distally to the shaft of the radius on its lateral surface and just distal to the supinator. The oblique orientation of the muscle belly allows it to serve in its primary rotatory role as the main pronator of the forearm. Injuries to the soft tissue of the medial forearm are common in both elite and recreational athletes, especially in racket and club sports.³ Often, these injuries are related to overuse and chronic fatigue of the surrounding soft tissue—caused by repetitive flexing, gripping, or swinging. Even when identified early, these injuries can result in a significant loss of training time.⁴ In this article, we report a case of pronator teres muscle tear at the myotendinous junction. The patient provided written informed consent for print and electronic publication of this case report.

Case Report

A right-hand–dominant 36-year-old man presented to the clinic with pain on the medial side of his right elbow after sustaining an injury to the elbow while playing golf several days earlier. The patient, an advertising executive, was playing recreational golf several times a month and had no significant medical history or previous symptoms related to the elbow. Initial pain symptoms began during a second round of play, immediately after the patient miss-hit an iron shot, making contact mostly with the ground and causing the club to forcefully stop. The pain was on the medial side of the elbow and forearm. The patient noted progressive swelling and bruising at the pain site and development of forearm weakness. Physical examination during the clinic presentation revealed ecchymosis on the anterior medial forearm, medial elbow, and medial triceps (Figure 1).

Mild tenderness to palpation was elicited over the medial elbow, specifically over the course of the flexor pronator mass. When the elbow was assessed for tender areas, the medial epicondyle was not tender. Range of motion (ROM) testing revealed 120° of flexion and 10° short of full extension, attributed to swelling from acute injury. The patient had full supination and pronation, but the pain was reproduced with either movement. The pain produced weakness with flexion and pronation. Valgus stress test results were normal; there was no re-creation of symptoms. The median nerve was negative for the Tinel sign, and the rest of the neurovascular examination was unremarkable. The ipsilateral shoulder was normal on examination.

Noncontrast magnetic resonance imaging (MRI) showed a high-grade partial tear of the pronator teres myotendinous junction (Figures 2A-2C).

In the surrounding tissue there was an associated increased signal representing edema. Also found was a small intramuscular hematoma. The median nerve, medial collateral ligament, distal biceps, and triceps were uninjured.

The patient was instructed to rest the elbow from strenuous activity, golf in particular, for 4 weeks. Physical therapy for ROM and forearm strengthening of the surrounding flexor wad was initiated at 2 weeks and continued for 4 weeks. The patient was advised to take over-the-counter nonsteroidal anti-inflammatory drugs as needed for comfort. On repeat examination at 4 weeks, with tenderness or weakness with pronation absent and full ROM regained, the patient was released back to full activity. He was able to return to golf and reported being symptom-free and having no sense of weakness or loss of control.

Discussion

A tear of the pronator teres is an exceedingly rare injury. Our results with conservative treatment and a full return to previous activity level are consistent with the only other case reported in the literature.⁵ In contrast to our patient, the previous patient sustained a tear of the pronator teres after a prolonged period of batting during a recreational cricket match.

 

Our patient’s pronator teres injury occurred at the myotendinous junction, a muscle-tendon transition zone often susceptible to injury. What is unusual for this athletic medial elbow injury is that the patient reported no previous symptoms, and it appears that, though the surrounding muscle may have been fatigued by overuse from the round of golf earlier that day, the pathology was caused by an acute eccentric force. During a golf swing, tremendous forces are put on the entire body, from the lower extremities to the forearm and the fingers. Successful completion of the transfer of energy from the golf club to the ball requires both proper technique and proper functioning of key muscles. Specifically, parameters such as ball positioning, club angle, and wrist control play a major role.⁶ Altered forearm positioning or swing arc can significantly affect club head velocity and energy transfer without putting more stress on the golfer.⁷ Therefore, it is easy to understand how prolonged or extended play may fatigue the surrounding elbow muscles, leading to altered technique and increased susceptibility to acute injury. Biomechanical analysis of shoulder motion can provide a helpful baseline for assessing injury-related changes in golf swing and developing specific exercise and rehabilitation programs.^8,9Although injury to the pronator teres is rare, sport physicians should be aware that, after a valgus stress or force, bruising and swelling along the medial elbow do not always indicate a medial ulnar collateral ligament (MUCL) tear or medial epicondylitis. The key examination findings that differentiate this injury from a MUCL injury are the exact location of pain, the milking maneuver for MUCL incompetence, and the extensive bruising over the muscle course of the pronator teres. MRI plays a pivotal role in proper diagnosis.⁴ In addition, MRI allows for evaluation of any concomitant injuries that may be obscuring the clinical presentation.

Successful treatment of such injuries is important for both elite and recreational athletes. With rest and physical therapy, our patient recovered from this rare isolated injury to the pronator teres with complete resolution of symptoms and full ROM. In the literature, we found no other reports of isolated full-thickness myotendinous rupture of the pronator teres or avulsion from the medial epicondyle. Therefore, it is unclear whether the same outcome can be expected with conservative therapy. However, because of the good outcomes for partial-thickness injuries treated conservatively and the lack of robust tendinous tissue to repair at the myotendinous junction, we recommend an initial course of conservative treatment. Sports physicians should be aware of this exceedingly rare injury to the elbow and understand the large forces experienced by the soft tissues of the forearm during the golf swing.^9,10

Conclusion

Pronator teres muscle strain is a rare sporting injury reported in cricket and golf players. The elbow experiences a large eccentric force during resisted elbow flexion and pronation. The injury appears to occur when the sporting club or racket strikes the ground during a forceful swing impeding forward progress of the arm. The injury can be confused with a MUCL injury, or exacerbation of medial epicondylitis. Physical examination reveals bruising and tenderness over the course of the pronator teres, often distal to the elbow. Advanced imaging confirms the diagnosis and helps grade the severity of muscle strain. Treatment is often conservative, with return to function and sport after 4 to 6 weeks of rest and restricted activities. The patient in this case report had complete return to sporting function, with no residual weakness or pain.

Am J Orthop. 2017;46(2):E105-E107. Copyright Frontline Medical Communications Inc. 2017. All rights reserved.