Effects of the adducted or abducted position of the arm on the course of the musculocutaneous nerve during anterior approaches to the shoulder

Proportional localisation of the entry point of the coracobrachialis muscle by the musculocutaneous nerve along the humerus

PURPOSE

To project the distance between the tip of the greater tubercle (GT), respectively, the proximal border of the tip of the coracoid process (CP) and the entry point of the coracobrachialis by the musculocutaneous nerve (MCN) proportionally onto the humeral length.

METHODS

Sixty-six upper extremities were included in the study. The distance between the tip of the GT and the distal tip of the lateral humeral epicondyle (LE) was evaluated as the humeral length (HL). The interval between the tip of the GT and the entry point of the coracobrachialis muscle by the MCN was measured. The distance between the proximal border of the tip of the CP and the distal portion of the medial humeral epicondyle (ME) and the entry point of the MCN into the coracobrachialis were evaluated. Proportions were used to project the entry point of the coracobrachialis by the MCN along the HL, respectively, the interval between the proximal border of the tip of the CP and the distal tip of the ME.

RESULTS

The entry point of the MCN into the coracobrachialis muscle can be expected at an interval between 14.9 and 33.9% of the HL (between the tip of the GT and the LE), starting from the tip of the GT. Regarding the reference line between the proximal border of the CP and the ME, the nerve's entry point was located between 14.2 and 34.4%, starting from the CP.

CONCLUSION

Results represent easily applicable intervals for intraoperative localisation of the MCN.

Structures Endangered During Minimally Invasive Plate Osteosynthesis of the Upper Extremity

Minimally invasive plate osteosynthesis is a surgical technique that is becoming increasingly common because radiographic images and implant technologies advance in capabilities. It is imperative for surgeons to enhance their understanding of the surgical anatomy related to new approaches for fracture fixation. While performing minimally invasive plate osteosynthesis, there is a danger of injuring structures in the common percutaneous and submuscular pathways. We describe the critical anatomical structures in these pathways and tips for injury avoidance when operating on the clavicle, scapula, humerus, and wrist.

Anatomic Tunnel Placement Is Not Feasible by Transclavicular-Transcoracoid Drilling Technique for Coracoclavicular Reconstruction: A Cadaveric Study

PURPOSE

To evaluate the feasibility of anatomic tunnel placement by a transclavicular-transcoracoid drilling technique and with reference to the coracoclavicular ligaments' insertional anatomy and their orientations.

METHODS

We used 12 fresh-frozen human cadaveric shoulders (6 matched pairs; mean age, 70 years; age range, 51-82 years) to simulate intraoperative tunnel placement with the transclavicular-transcoracoid drilling technique. After both the conoid and trapezoid ligaments were identified, two 2.5-mm guide pins were inserted from the clavicle to the coracoid, passing the centers of the clavicular and coracoid insertions of the conoid and the trapezoid ligaments, in a collinear fashion to the orientation of both ligaments. The entry point of the drill at the clavicle and the exit point at the coracoid undersurface, as well as the tunnel orientations, were measured. Complications due to the procedure, including a breach of the bone cortex of the clavicle and/or coracoid process, were recorded.

RESULTS

The transclavicular-transcoracoid drilling technique for anatomic conoid ligament tunnel placement resulted in a medial cortical breach at the coracoid process in 6 of 12 shoulders. In the remaining 6 shoulders without a breach, the distance of the exit point from the medial cortex of the inferior coracoid process was only 3.6 ± 4.3 mm. For anatomic trapezoid ligament tunnel placement, no medial cortex breaching at the coracoid process occurred. However, the distance of the exit point was 3.1 ± 4.2 mm, indicating an eccentric location to the medial cortex of the coracoid process, similar to the conoid ligament.

CONCLUSIONS

This cadaveric study showed that anatomic tunnel placement by the transclavicular-transcoracoid drilling technique would not be feasible without breaching or almost breaching the medial cortex of the coracoid process.

CLINICAL RELEVANCE

The transclavicular-transcoracoid drilling technique for CC ligament reconstruction may not reproduce the anatomy of the CC ligaments but may place the coracoid process at high risk of fracture during tunnel placement.

Changes in the Neurovascular Anatomy of the Shoulder After an Open Latarjet Procedure: Defining a Surgical Safe Zone

BACKGROUND

Although previous literature has described the relevant anatomy for an open anterior Bankart approach of the shoulder, there is little known regarding the anatomic relationship changes in the neurovascular structures after an open Latarjet procedure.

PURPOSE

To define the neurovascular anatomy of the native shoulder in relation to the coracoid and to define the anatomy after the Latarjet procedure in relation to the glenoid to determine distances to these neurovascular structures with and without neurolysis of the musculocutaneous nerve (MCN) from the conjoint tendon.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Fourteen fresh-frozen male cadaveric shoulders (7 matched pairs) were utilized. The distances of 7 neurovascular structures (the main trunk of the MCN at its insertion into the conjoint tendon, the MCN at its closest location to the coracoid process, the lateral cord of the plexus, the split of the lateral cord and MCN, the posterior cord of the plexus, the axillary nerve, and the axillary artery) to pertinent landmarks were first measured in the native state in relation to the coracoid. After the Latarjet procedure, these landmarks were measured in relation to the glenoid. In addition, measurements of the MCN distances were performed both with and without neurolysis of the MCN from the conjoint tendon. All measurements were performed using digital calipers and reported as medians with ranges.

RESULTS

The median MCN entry into the conjoint tendon was 56.5 mm (range, 43.0-82.2 mm) and 57.1 mm (range, 23.5-92.9 mm) from the tip of the coracoid in the neurolysis group and nonneurolysis group, respectively ( P = .32). After the Latarjet procedure, the median MCN entry into the conjoint tendon was 43.8 mm (range, 20.2-58.3 mm) and 35.6 mm (range, 27.3-84.5 mm) from the 3-o'clock position of the glenoid in the neurolysis and nonneurolysis groups, respectively ( P = .83). The median MCN entry into the conjoint tendon was 35.6 mm (range, 25.1-58.0 mm) and 36.3 mm (range, 24.4-77.9 mm) from the 6-o'clock position in the neurolysis group and nonneurolysis group, respectively ( P = .99). After the Latarjet procedure, the closest neurovascular structures in relation to both the 3-o'clock and 6-o'clock positions to the coracoid were the axillary nerve at a median 27.4 mm (range, 19.8-40.0 mm) and 27.7 mm (range, 23.2-36.1 mm), respectively.

CONCLUSION

This study identified a minimum distance medial to the glenoid after the Latarjet procedure to be approximately 19.8 mm for the axillary nerve, 23.6 mm for the posterior cord, and 24.4 mm and 20.2 mm for the MCN without and with neurolysis, respectively. Neurolysis of the MCN did not significantly change the distance of the nerve from pertinent landmarks compared with no neurolysis, and routine neurolysis may not be indicated. However, the authors still advise that there may be clinical benefit to performing neurolysis during surgery, especially given that the short length of the MCN puts it at risk for traction injuries during the Latarjet procedure.

CLINICAL RELEVANCE

The findings of this study provide an improved understanding of the position of the neurovascular structures after the Latarjet procedure. Knowledge of these minimum distances will help avoid iatrogenic damage of the neurovascular structures when performing procedures involving transfer of the coracoid process.

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.

Complications associated with open coracoid transfer procedures for shoulder instability

BACKGROUND

Interest has been maintained in the use of coracoid transfer procedures for recurrent shoulder instability despite the significant potential for serious complications. A comprehensive systematic review of the literature was performed to quantify and characterize the complication rate associated with these procedures to better inform practicing surgeons and their patients.

MATERIALS AND METHODS

Medline, Excerpta Medica Database (EMBASE), and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases were searched for therapeutic studies published between 1985 and 2011. Data regarding complications was extracted from selected articles in a standardized manner. Complication rates were determined and expressed as percentages with 95% confidence intervals.

RESULTS

Included were 30 studies describing the results of 1658 coracoid transfer procedures. Repeat surgery was documented in 4.9% ± 1.0% of cases. Recurrent instability occurred in 6.0% ± 1.2%. Hardware complications occurred in 6.5% ± 1.3%. Collectively, the rate of graft nonunion, fibrous union, or postoperative graft migration was 10.1% ± 1.6%; graft osteolysis occurred in 1.6% ± 0.7%. There was a 1.2% ± 0.8% rate of nerve palsy. Surgical site infection occurred in 1.5% ± 0.7%. Intraoperative fractures occurred in 1.1 ± 0.6%.

CONCLUSION

Coracoid transfers for shoulder instability can improve shoulder stability with acceptable recurrence rates. They are challenging procedures associated with a broad range and significant incidence of complications. A detailed appreciation of anatomy and meticulous attention to technical detail, particularly graft placement, is key to reducing complications. These procedures may be best indicated in the setting of glenoid or humeral bony deficiency, although efficacy over open capsular procedures remains equivocal.

Minimally invasive proximal biceps tenodesis: an anatomical study for optimal placement and safe surgical technique

BACKGROUND

An anatomic study specifically investigating the optimal location for proximal biceps tenodesis and detailing the topographic relationship to neurovascular structures has not been conducted.

METHODS

Twelve cadaveric upper extremities were dissected to identify the proximal biceps musculotendinous junction and topographic relationships to neighboring neurovascular structures.

RESULTS

The musculotendinous junction of the long head of the biceps tendon was on average 2.2 cm distal to the superior border and 3.1 cm proximal from the inferior border of the pectoralis major tendon. The musculocutaneous nerve was on average 2.6 cm medial to the long head of the biceps at the musculotendinous junction. The distance from the lesser tuberosity to the musculotendinous junction of the long head of the biceps averaged 5.4 cm. The distance from the anterior humeral circumflex vessels to the musculotendinous junction of the long head of the biceps was 4.6 cm on average. The distance from the musculotendinous junction of the long head of the biceps to the musculocutaneous nerve as it pierces the coracobrachialis was 4.6 cm.

CONCLUSION

In order to restore the appropriate length-tension relationship of the biceps muscle, proximal biceps tenodesis should possibly be placed closer to the superior border of the pectoralis major tendon than previously thought. The lesser tuberosity can be used as a tactile landmark for appropriate intraoperative placement. Although there is a relatively safe "buffer zone" between the location of the tenodesis and adjacent neurovascular structures, extreme caution must be used.

Anatomical considerations of subcoracoid neurovascular structures in anterior shoulder reconstruction

Anterior shoulder surgery, using open or arthroscopic technique, places subcoracoid neurovasculature at risk. This study examines the relationships of the brachial plexus and axillary artery to four bony landmarks and provides clinical correlations for anterior shoulder surgery. The musculocutaneous nerve (MN), posterior cord (PC), lateral cord (LC), and axillary artery (AA) were identified in 27 shoulders. Minimum distances (mm) were measured between neurovasculature and the coracoid tip, anterior midglenoid, inferior surface of the midclavicle, and anteromedial aspect of the acromioclavicular joint. Average distances from the coracoid to the MN, PC, LC, and AA were 69.7 ± 31.6, 50.5 ± 9.2, 41.8 ± 9.4, and 60.0 ± 8.0 mm, respectively; from the glenoid equator to the MN, PC, LC, and AA were 61.5 ± 38.5, 37.0 ± 6.1, 35.2 ± 8.7, and 45.2 ± 7.1 mm, respectively; from the midclavicle to the MN, PC, LC, and AA were 114.1 ± 33.9, 62.0 ± 13.6, 56.0 ± 19.7, and 69.9 ± 7.8 mm, respectively; and from the AC joint to the MN, PC, LC, and AA were 112.7 ± 36.5, 87.9 ± 10.6, 84.0 ± 12.0, and 100.9 ± 1.0 mm, respectively. The lateral cord was the closest structure to each bony landmark. The musculocutaneous nerve was the furthest structure from each bony landmark. Open procedures using a deltopectoral approach with the shoulder in the anatomical position, such as the Neer capsular shift and Warner capsular reconstruction, can use these results to prevent direct or retraction injuries. Results indicate a potential safe zone of 30 mm in diameter around the anteromedial coracoid tip for anteroinferior portal placement.

Review of the surgical anatomy of the axillary nerve and the anatomic basis of its iatrogenic and traumatic injury

The axillary nerve is invariably reported to be one of the most commonly injured nerves during surgical procedures of the shoulder, and the importance of protecting it cannot be overemphasized. Many researchers have tried to identify safe regions, but the results vary among published studies. The axillary nerve may also be injured during acute trauma to the shoulder or by chronic repeated trauma as has been described in the quadrilateral space syndrome. The nerve injury may occur together with shoulder dislocation and rotator cuff tear, thus comprising the so-called "unhappy triad" of the shoulder joint. Simple attention to potential variations in the origin and course of the axillary nerve and its relationship to the shoulder capsule and having a precise knowledge of "safe zones" during operations can enhance clinical outcomes. The objective of this review, therefore, is to discuss the surgical anatomy of the axillary nerve and further emphasize the clinical importance of the its injury following shoulder trauma.

Relationships of the musculocutaneous nerve and the coracobrachialis during coracoid abutment procedure (Latarjet procedure)

PURPOSE

The aim of this study was first to define first the anatomical relationships between the musculocutaneous nerve and the coracobrachialis, and then the induced modifications of these relationships by a preglenoid transposition of the vertical part of the coracoid process.

MATERIALS AND METHODS

Twenty-one embalmed adult trunks and upper limb were dissected. First the coracobrachialis and the musculocutaneous nerve were identified through a deltopectoral approach. We measured the distances between the lateral cord of the brachial plexus and the entry point of the nerve, between the inferior tip of the tip of the coracoid process and the penetration of the nerve or its twigs, and finally the angle between the general axis of the coracobrachialis and the axis of the musculocutaneous nerve. The same measures were performed after the coracoid bone block abutment.

RESULTS

Proximal motor branches destined to the coracobrachialis varied from 0 to 3. Mean distance between the lateral cord of the brachial plexus and entry point of the nerve into the muscle was 47.2 mm before and 48.43 mm after the coracoid transfer. Mean angulations between the nerve and the muscle was 121 degrees before and 136 degrees after the transfer of the coracoid process. Mean distance between the inferior tip of the coracoid process and entry point of the nerve into the muscle was 55.7 mm, reduced to 48.6 mm after the coracoid transposition. Finally, the distance between the tip of the coracoid and the first motor twig entering the coracobrachialis was less than 50 mm in 75% of the cases with a mean value of 40.6 mm.

CONCLUSIONS

Lesion of the musculocutaneous nerve is a known complication of the coracoid bone block abutment procedure (Latarjet-Bristow). From this study we know that they are due to lengthening of the nerve and modification of the penetration angle of the nerve into the coracobrachialis. We also infer that some motor nerve destined to the coracobrachialis might be damaged during the proximal medial release of the muscle after the detachment of the pectoralis minor muscle.