Selective neurotomy of the sciatic nerve branches to the hamstring muscles: An anatomical study

Innervation patterns of hamstring muscles, including morphological descriptions and clinical implication

PURPOSE

The hamstrings muscles are innervated by sciatic nerve branches. However, previous studies assessing which and how many branches innervate each muscle have yielded discrepant results. This study investigated the innervation patterns of hamstrings.

MATERIALS AND METHODS

Thirty-five cadaver limbs were investigated. The average age of subjects was 78.6 ± 17.2 years, with 48.6% male and 51.4% female, while 57.1% were right limbs and 42.9% left. The sciatic nerve, hamstrings and associated structures were dissected. The number of nerve branches for each muscle and the level where they penetrated the muscle were recorded.

RESULTS

The sciatic nerve was connected by a fibrous band to the long head of the biceps femoris. This muscle was innervated by either one or two branches, which penetrated the muscle into its superior or middle third. The short head of the biceps femoris was innervated by a single nerve that usually penetrated its middle third, but sometimes inferiorly or, less commonly, superiorly. The semitendinosus was always innervated by two branches, the superior branch penetrating its upper third, the inferior mostly the middle third. The semimembranosus usually was innervated by a single nerve branch that penetrated the muscle at its middle or lower third. Four specimens revealed common nerves that innervated than one muscle.

CONCLUSIONS

We have characterized hamstring innervation patterns, knowledge that is relevant to neurolysis, surgery of the thigh, and other procedures. Moreover, a mechanical connection between the sciatic nerve and biceps femoris long head was identified that could explain certain neuralgias.

Hyper-selective neurectomy for knee flexion spasticity: anatomic bases and surgical technique

PURPOSE

Spasticity may result from damage to neurons of the corticospinal tracts and loss of inhibitory supraspinal influences following head trauma. Traditionally, peripheral nerve surgeries for spasticity in lower limbs were limited to selective neurectomies. Here we used hyper-selective neurectomy (HSN) to release hamstring spasticity at the muscle spindle level.

METHODS

This study describes anatomic bases and surgical technique of HSN and its results in treating spastic knee flexion in a 23-year-old male who developed severe spasticity following severe brain injury. The spasticity was prominent in the left knee. The surgical technique including resection of over one centimeter of three-quarters of the overstimulated nerve rami at the entry point of the nerve into the muscle is shown in the video 1.

RESULTS

After the surgery Visual Analog Scale and Modified Ashworth Score reduced from 7 to 3 and 4 to 1, respectively. Popliteal angle improved from 118° to 73° at the second months after the surgery.

CONCLUSION

Hyper-selective neurectomy is a safe and reliable therapeutic option for the treatment of permanent trauma induced spasticity in the lower limb.

Hamstring branches of the sciatic nerve as donors for neurotization of the superior gluteal nerve: A cadaveric feasibility study

Although superior gluteal nerve (SGN) injury can have significant morbidity, to date, surgical strategies for its repair are scant in the literature. Specifically, neurotization options have not been explored. To address this deficiency in the literature, the current cadaveric feasibility study was performed. Via a transgluteal approach on 16 cadaveric sides, the proximal sciatic nerve and the entrance of the SGN into the gluteus medius and minimus were identified. Additionally, branches from the sciatic nerve to the hamstring muscles were traced proximally to confirm their position in relation to the sciatic nerve as a whole. These branches were cut at the level of the ischial tuberosity and teased away from the sciatic nerve proximally to the greater sciatic foramen and transferred superolateral to the SGN. The diameter of each nerve branch was measured as well as its available length for reaching the SGN. All branches of the sciatic nerve to the hamstring muscles arose from the anteromedial part of the nerve. The mean diameters of the branches to the semimembranosus, semitendinosus, and biceps femoris muscles were 2.1, 1.9, and 1.5 mm, respectively. The mean diameter of the SGN was 3.1 mm and the mean distance from this entrance point to the ischial spine was 7.2 cm. The mean length of the donor nerve was 8.5 cm. Based on our study, use of a tibial-innervated hamstring branch as a donor for nerve transfer to the SGN is feasible.