The Anatomic Basis for the Arthroscopic Latarjet Procedure: A Cadaveric Study.

BACKGROUND: The Latarjet technique is a reliable treatment option for recurrent anterior shoulder instability. However, the complication rate has been reported to be as high as 30%, with 1.6% of patients suffering a nerve injury. The all-arthroscopic Latarjet procedure has been gaining popularity, even as it has introduced its own challenges. Given that the surgeon is not able to palpate the nerves, their localization and protection can be difficult. Additionally, the use of different instruments can lead to distinct nerve injury mechanisms. PURPOSE: To describe the anatomic trajectory of the musculocutaneous, axillary, and suprascapular nerves in relation to the arthroscopic Latarjet approach. Using this information, guidance is provided for reducing nerve injuries during instrumentation and screw insertion. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 50 cadaveric shoulders from 25 whole-body specimens were examined. The specimens were placed in the beach-chair position, and the deltopectoral and dorsal approaches were used to expose the relevant structures. A subscapularis muscle split was performed between the inferior and middle thirds of the tendon. Digital caliper measurements were taken between various points of the trajectories of the nerves and surrounding anatomic landmarks. The location of the nerves relative to the split was recorded. RESULTS: The musculocutaneous nerve lay within the split in 66% of the shoulders (n = 33); it was medial to the split in 28% (n = 14); it was found lateral to split in 2% (n = 1); and it was not identified in 4% of shoulders (n = 2). The mean length of the axillary nerve was 4.0 cm (95% CI, 3.7-4.2) from the exit of the plexus to the quadrangular space. The axillary nerve was found to be within the split in 50% of the shoulders (n = 25) and medial to the split in the remaining 50% (n = 25). The suprascapular nerve at the level of the supraspinatous fossa passed 3.3 cm (95% CI, 3.1-3.5) medial to the superior rim of the posterior glenoid. The nerve curves around the root of the spine at the spinoglenoid notch level, approximating the glenoid rim to a distance of 2.1 cm (95% CI, 2.0-2.2). Finally, the nerve runs medially again before branching out into smaller fibers to innervate the infraspinatus muscle at a distance of 2.9 cm (95% CI, 2.7-3.1) from the inferior glenoid rim. Based on these findings, there is an approximately 2 cm-wide safe zone from the edge of the glenoid rim for the insertion of graft-fixing screws. CONCLUSION: When performing a subscapularis split in the arthroscopic Latarjet procedure, the risk of injuries to the musculocutaneous and axillary nerves could be reduced by aiming the switching stick inserted through the posterior portal toward the lateral edge of the intended location of the split. Injuries to the suprascapular nerve could be prevented by aiming the graft-fixing screws laterally toward the edge of the glenoid rim. CLINICAL RELEVANCE: This study clarifies the location of the nerves relevant to the arthroscopic Latarjet technique and provides anatomic information that could help the surgeon reduce the risk of injuries to the musculocutaneous, axillary, and suprascapular nerves.

Intraoperative imaging of the shoulder: A comparison of two- and three-dimensional imaging techniques.

BACKGROUND: Isocentric three-dimensional C-arms allow for more effective intraoperative fracture reduction control compared to two-dimensional imaging techniques. However, this design is not appropriate for shoulder scanning. OBJECTIVE: To assess the feasibility of using a newer generation variable isocentric flat detector 3D C-arm for intraoperative glenohumeral and acromioclavicular joint assessment and to compare the accuracy of its intraoperative 3D imaging technology to a standard two-dimensional (2D) flat detector fluoroscope. METHODS: Five whole-body human cadavers were used (ten shoulders). Native shoulder scans were obtained. A glenohumeral arthrotomy was performed and several injuries and procedures were simulated. Five independent orthopaedic surgeons reviewed each scan and filled out a questionnaire assessing the quality of the images using a visual analog scale (VAS) and a points scoring system. RESULTS: The examiners rated the 3D images as very-good-to-excellent according to the established parameters: image quality; visualization of the corticalis and the spongiosa; delineation of the joint surface; presence of artifacts; and clinical assessment capability. This high quality of the images led to a higher interobserver reliability for 3D images compared to 2D images. CONCLUSIONS: Variable isocentric 3D C-arm technology is feasible for intraoperative assessment of shoulder procedures. Assessment of 3D images in shoulder procedures showed better interexaminer reliability in this experiment compared to 2D images. With the aid of intraoperative 3D shoulder imaging, intraoperative 3D C-arm navigation could help improve accuracy in the clinical setting.