Relationship of the Musculocutaneous Nerve and Its Twigs to the Coracoid Process: An Operative Exposure

Anatomical Variations of the Musculocutaneous Nerve in the Human Fetus

OBJECTIVES

Knowing the motor branches and variations of the musculocutaneous nerve to the muscles along its course will facilitate the treatment of flexor spasticity and supracondylar fractures of the humerus in order to minimize nerve lesion. In fetal cadavers, the purpose of our study was to determine the number and course of the formation variations and motor branches of the musculocutaneous nerve. The significance of studying fetal nerve variations is due to injury to the brachial plexus roots during birth.

METHODS

Our study was conducted using the anatomical dissection technique on 102 upper limbs from 51 fetuses ages ranged from 17 to 40 weeks. Throughout its course, the variations and motor branches of the musculocutaneous nerve were analyzed.

RESULTS

In 13.7% of cases, the musculocutaneous nerve did not pierce the coracobrachialis. The musculocutaneous nerve gave the muscles 1-3 motor branches. Additionally, motor branches terminated with 1-7 fringes. The biceps brachii motor branches of the musculocutaneous nerve were typed. Accordingly, 15.6% were type 1A, 3.9% were type 1B, 35.4% were type 1C, and 19.6% were type 1D. It was determined that 23.5% of the extremities were type 2 and that 1.9% were type 3. The distance between the musculocutaneous nerve's motor branches and the acromion was proportional to the arm's length. There were no statistically significant differences between the sides and genders for any measurement.

CONCLUSIONS

Our study's findings will aid in the diagnosis and treatment of pediatrics, orthopedics, surgical sciences, and radiology conditions. It reduces the risk of iatrogenic injury and postoperative complications. We also believe that our research will serve as a resource for anatomists and other scientists.

Coracobrachialis muscle morphology and coexisted neural variants: a cadaveric case series

PURPOSE

The current cadaveric case series evaluates the coracobrachialis muscle morphology, the related musculocutaneous nerve origin, course, and branching pattern, as well as associated adjacent neuromuscular variants.

MATERIALS AND METHODS

Twenty-seven (24 paired and 3 unpaired) cadaveric arms were dissected to identify the coracobrachialis possible variants with emphasis on the musculocutaneous nerve course and coexisted neural variants.

RESULTS

Four morphological types of the coracobrachialis were identified: a two-headed muscle in 62.96% (17/27 arms), a three-headed in 22.2% (6/27), a one-headed in 11.1% (3/27), and a four-headed in 3.7% (1 arm). A coracobrachialis variant morphology was identified in 37.04% (10/27). A three-headed biceps brachii muscle coexisted in 23.53% (4/17). Two different courses of the musculocutaneous nerve were recorded: 1. a course between coracobrachialis superficial and deep heads (in cases of two or more heads) (100%, 24/24), and 2. a medial course in case of one-headed coracobrachialis (100%, 3/3). Three neural interconnections were found: 1. the lateral cord of the brachial plexus with the medial root of the median nerve in 18.52%, 2. the musculocutaneous with the median nerve in 7.41% and 3. the radial with the ulnar nerve in 3.71%. Duplication of the lateral root of the median nerve was identified in 11.1%.

CONCLUSIONS

The knowledge of the morphology of the muscles of the anterior arm compartment, especially the coracobrachialis variant morphology and the related musculocutaneous nerve variable course, is of paramount importance for surgeons. Careful dissection and knowledge of relatively common variants play a significant role in reducing iatrogenic injury.

A Review of the Typical Course of the Musculocutaneous Nerve into the Coracobrachialis Muscle: Its Variability and Possible Clinical Implications

OBJECTIVE

This literature review highlights the prevalence of the typical course of the musculocutaneous nerve (MCN) through the coracobrachialis muscle (CB), and evaluates the distance from the entrance point of the MCN to the CB, taking the coracoid process (CP) as a landmark.

METHODS

PubMed (MEDLINE), Scopus, and CINAHL online databases were searched in December 2022 for studies reporting the prevalence of the MCN's typical course and the distance between the CP and the MCN entrance point to the CB.

RESULTS

Twenty-eight studies were included (including 2846 subjects) investigating the MCN's typical course, and eliciting a prevalence of 93.4%. The mean distance of the CP to the entrance point of the MCN's main trunk into the CB was 5.6±2cm (median 6.1cm, in 550 subjects). In 76.12% of cases the MCN's accessory branches entered the CB proximally to the MCN's main trunk. The mean distance from the CP to the entrance point of the MCN's proximal branches to the CB was 3.8±1.2cm (median 3.7cm, in 140 subjects).

CONLCUSION

In the vast majority of cases, the MCN had a typical course through the CB. In cases of altered anatomy, the MCN was either absent or passed medially to the CB (without piercing it). The average entrance point of the MCN into the CB from the CP is 5.6 cm. Proximal motor branches of the MCN to the CB are common and usually arise at a mean distance of 3.8cm from the inferior border of the tip of the CP. Surgeons should be aware of both the MCN's typical and its atypical course and these distances to avoid possible complications when operating in the area.

Safety-driven master's technique of the Latarjet-Walch procedure and its short-term complications: experience in a study of 150 consecutive patients

Background

Although the classic open Latarjet has a low recurrence rate in unstable shoulders, this advantage may be offset by the higher number of complications. We aimed to report the safety-driven nuanced steps and the resulting short-term complications of the Latarjet-Walch technique.

Methods

Between 2016 and 2022, 150 patients who underwent the Latarjet procedure following the key safety-driven technical steps were retrospectively evaluated for intraoperative and short-term (3 months) complications. The complications were divided into 3 types: Any adverse event that did not need a change in the treatment protocol was a type 1 complication. An event that resulted in a prolongation of rehabilitation protocol or an additional medical line of treatment was classified as type 2, and an event that resulted in readmission, a resurgery, or one that affected the outcome was classified as a type 3 complication.

Results

There were 12 (8%) short-term complications in 9 patients. Neurological complications were noted in 3 (2%) patients (1 axillary nerve injury, 1 suprascapular nerve injury, and 1 musculocutaneous nerve injury). Type 1 complications were noted in 2 patients: 2 patients had hematoma that was detected as superficial swelling, but no surgical drainage was needed, and both resolved at their 1-month follow-up. Type 2 complications were noted in 4 patients. One patient had surgical site infection and a second patient had superficial wound dehiscence in the lower part of the wound. The third patient had suprascapular nerve paresis and the fourth had musculocutaneous nerve paresis and shoulder stiffness. Both nerve injuries recovered completely after 6 months of rehabilitation. Type 3 complications were noted in 3 patients. One patient had axillary nerve paresis and shoulder stiffness. The axillary nerve palsy had recovered partially by 8 months. One patient had an intraoperative graft fracture and postoperative shoulder stiffness, and the third patient had shoulder stiffness.

Conclusion

Following the safety-driven nuanced steps in the Latarjet-Walch procedure, the short-term complication rate was 8%, and the neurological complication was 2% (n = 3). The musculocutaneous and suprascapular nerves completely recovered, and the axillary nerve had partially recovered.

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.