Microsurgical anatomy of branches of musculocutaneous nerve: clinical relevance for spastic elbow surgery

The utility of selective partial neurectomy of the musculocutaneous nerve in children with bilateral spastic elbow

PURPOSE

This study aims to determine the utility of selective partial neurectomy of the musculocutaneous nerve (MCN) in pediatric patients with bilateral spastic elbow.

METHODS

A prospective, cross-sectional, case series study was performed in nine pediatric patients (four females and five males) with bilateral spastic elbow, all with a 11.4-year-old average age, where 18 selective partial neurectomies of the MCN were carried out. They were evaluated with goniometry of both spastic elbows at resting position and active amplitude, and staging spasticity employing the Modified Ashworth Scale (MAS) in the preoperative and postoperative period. The results are reported 1 year after surgery.

RESULTS

The etiology of the spasticity was secondary to cerebral palsy in eight patients (88.8%) and in one patient (11.11%) secondary to traumatic brain injury. A clinical improvement was observed in goniometry comparing the preoperative and postoperative resting position, a mean preoperative of 44.38 degrees (SD ± 7.61) versus 98.05 degrees (SD ± 24.44), respectively, and preoperative active amplitude a mean of 86.55 degrees (SD ± 15.97) versus the mean postoperative of 47.33 (SD ± 17.86). A relevant decrease on the MAS after surgical intervention was observed, resulting from an average preoperative state according to MAS of 3.78 (SD ± 0.42) to a postoperative state according to MAS of 1.44 (SD ± 0.51), these changes being statistically significant (p ≤ 0.001). No postoperative complications were observed.

CONCLUSIONS

Selective partial neurectomy of the MCN has shown good results in patients with bilateral spastic elbow in whom antispastic drugs and physical therapy have failed, and has prove permanent effects.

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.

The innervation of the biceps brachii and brachialis muscles in specimens with a high incidence of an accessory biceps head

We describe the patterns of motor branches to the elbow flexors in 106 fresh-frozen cadaveric upper extremities from 53 donors of the Latin American mestizo race. We identified a 20% incidence of an accessory biceps head. The innervation patterns to this accessory head were specifically described and added to the Yang classification as Type IV for the biceps and Type III for the brachialis. The patterns arising from the musculocutaneous nerve to the biceps brachii were of Type I in 69%, Type II in 9%, Type III in 7% and Type IV in 11%, and to the brachialis of Type I in 77%, Type II in 11% and Type III in 9%. In 4%, the branches did not originate from the musculocutaneous nerve. We hypothesize that the branch to the accessory biceps head might be considered as a donor for nerve transfer in selected brachial plexus injuries.