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.

Functional outcomes following surgery for spastic hip adductor muscles in ambulatory and non-ambulatory adults

OBJECTIVE

To evaluate functional outcomes of surgery of spastic hip adductor muscles (obturator neurotomy with or without adductor longus tenotomy) in ambulatory and non-ambulatory patients, using preoperatively defined personalized goals.

DESIGN

Retrospective observational descriptive study.

PATIENTS

Twenty-three patients with adductor spasticity who underwent obturator neurotomy between May 2016 and May 2021 at the Clinique des Cèdres, Cornebarrieu, France, were included.

METHODS

Postoperative functional results were evaluated in accordance with the Goal Attainment Scaling method. Patients were considered "responders" if their score was ≥ 0. Secondary outcomes included spasticity, strength, hip range of motion and change in ambulatory capacity. When data were available, a comparison of pre- and postoperative 3-dimensional instrumented gait analysis was also performed.

RESULTS

Among the 23 patients only 3 were non-walkers. Seventeen/22 patients achieved their main goal and 14/23 patients achieved all their goals. Results were broadly similar for both walking goals (inter-knee contact, inter-feet contact, fluidity, walking perimeter, toe drag) and non-walking goals (intimacy, transfer, pain, posture, dressing).

CONCLUSION

Surgery of spastic hip adductor muscles results in functional improvement in ambulation, hygiene, dressing and posture and can be offered to patients with troublesome adductor overactivity. The use of a motor nerve block is recommended to define relevant goals before the surgery.

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.

Terminal nerve entry points' locations to muscles of the thigh for selective peripheral neurectomy in the adult population: a cadaveric study

PURPOSE

Spasticity is the result of a variety of lesions to the central nervous system and one of the most common causes of disability worldwide. Selective peripheral neurectomy (SPN) is a surgical procedure that permanently decreases focal spasticity. The authors' objective is to provide recommendations, in terms of probabilities, for locating terminal motor entry points to muscles of the thigh, as alternatives for proximal incision sites to SPN.

METHODS

The femoral, obturator, and sciatic nerves, and its corresponding motor rami, were systematically dissected on cadaveric specimens, and terminal motor entry points to each muscle of the thigh were located and carefully measured, relative to the length of the thigh. Measurement distributions were obtained and normal transformations were used when necessary.

RESULTS

In 23 adult cadaveric specimens, 779 motor rami were dissected. Entry points' locations are presented as a percentage of the length of the thigh in means and standard deviations, which roughly corresponds to 64 and 95% probability of finding a motor entry point.

CONCLUSION

Alternative incisions directly over the motor entry points, for the muscles of the thigh, may be helpful when considering SPN as treatment for focal spasticity. A prior degree of certainty of the location of the nerve to be severed may simplify surgical approach.

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

BACKGROUND

Hamstring spasticity can bring about a flexion deformity of the knee, liable to cause disability. Surgical treatment by selective neurotomies of the sciatic nerve branches leading to the hamstring muscles may then be indicated. Few studies have investigated the precise origin of these branches on the sciatic nerve, describing the innervation pattern of the hamstring muscles. Further anatomical data are needed to enhance surgical techniques in neurotomies of the sciatic nerve branches, to define the best incision and surgical approach and what section and length of the SN need to be exposed. Therefore, we performed an anatomical study to: (1) define a surgical approach to perform selective neurotomies of the sciatic nerve branches for hamstring spasticity?(2) whether the anatomical variants of the hamstring innervation have been identified?

HYPOTHESIS

Our anatomical data could lead to the definition of an approach to the sciatic nerve for the purpose of selective neurotomy.

MATERIAL AND METHODS

Twenty posterior compartments of the thigh were dissected. We counted each branch of the sciatic nerve leading to the hamstring and described their arising point using the centre of the lateral surface of the great trochanter and the lower edge of the gluteus maximus muscle as main anatomical landmarks. We also described the presence of branch divisions and their muscular penetrating points.

RESULTS

The mean distances between the center of the lateral surface of the great trochanter and the emergence of branches from the SN were: 2.2±3.6cm (-5 to 9cm) for the long head of the biceps femoris muscle, 2.3±3cm (-4 to 10cm) for the semitendinosus muscle, and 2.2±3cm (-5 to 8cm) for the semimembranosus muscle. No branches originated from the sciatic nerve below the lower edge of the gluteus maximus muscle. In summary the branches innervating the hamstrings originated from the SN within an interval of 15cm (5cm above and 10cm below the centre of the lateral surface of great trochanter). The average number of sciatic nerve branches for the hamstring muscles was 4.7 (minimum: 3; maximum: 6) with 1.8 branches for the long head of the biceps [1 in 7/20 (35%), 2 in 10/20 (50%), and 3 in 3/20 (15%)], 1.5 branches for the semitendinosus [1 in 11/20 (55%) and 2 in 9/20 (45%)], 1.4 branches for the semimembranosus [1 in 12/20 (60%) and 2 in 8/20 (40%)]. No branches had a common origin with cutaneous nerves.

DISCUSSION

This anatomical study enabled us to propose an approach to exposing the sciatic nerve in order to perform a selective neurotomy: horizontal cutaneous incision on the gluteal fold, incision of the lower edge of the gluteus maximus, exposure of the sciatic nerve to a distance of 10cm below the great trochanter, and visualization of the nerve branches to the hamstring muscles. Exposure of the nerve above the great trochanter is not necessary because the branches which emerge from the SN above the great trochanter are still contiguous with the SN.

LEVEL OF EVIDENCE

IV: prospective study without control.

Dorsal Longitudinal T-Myelotomy (Bischof II Technique): A Useful, Antiquated Procedure for the Treatment of Intractable Spastic Paraplegia

OBJECTIVE

Dorsal longitudinal T-myelotomy is a long-established operation to treat severe spastic paraplegia. The present study aimed to report this surgical technique and investigate the efficacy of T-myelotomy for spasticity relief.

METHODS

All cases undergoing T-myelotomy for treatment of intractable spastic paraplegia during 2009-2017 were included. The severity of spasticity was evaluated with the Modified Ashworth Scale, Penn Spasm Frequency Scale, Adductor Tone Rating Scale, degree of passive range of motion, and occurrence of abdominal muscle spasms. Other clinical assessments included deep tendon reflex assessed by the National Institute of Neurological Disorders and Stroke scale, Babinski sign, healing of decubitus ulcers, and ambulatory status.

RESULTS

Fourteen patients with a mean age of 39.3 ± 13.4 years were included. The 7 patients with abdominal muscle spasms before surgery had no spasms after surgery. The Babinski sign was absent in all cases after surgery. Unhealed pressure ulcers in all 9 cases were healed after surgery. All 4 patients with a preoperative bed-bound condition were able to ambulate with a wheelchair. A statistically significant improvement in mean Modified Ashworth Scale score, degree of passive range of motion, and National Institute of Neurological Disorders and Stroke scale score was found in the subgroup and overall analyses. There was also a statistically significant improvement in the Penn Spasm Frequency Scale and Adductor Tone Rating Scale scores.

CONCLUSIONS

Dorsal longitudinal T-myelotomy remains an effective option for the treatment of intractable spastic paraplegia. It is suitable for, and may be an alternative to, intrathecal baclofen therapy for patients with complete spinal cord lesion or patients without hope of regaining motor function.

Comparison of efficacy between dorsal root entry zone lesioning and selective dorsal rhizotomy for spasticity of cerebral origin

BACKGROUND

Severe spasticity adversely affects patient functional status and caregiving. No previous study has compared efficacy between dorsal root entry zone lesioning (DREZL) and selective dorsal rhizotomy (SDR) for reduction of spasticity. This study aimed to investigate the efficacy of DREZL and SDR for attenuating spasticity, and to compare efficacy between these two methods.

METHODS

All patients who underwent DREZL, SDR, or both for treatment of intractable spasticity caused by cerebral pathology at Siriraj Hospital during 2009 to 2016 were recruited. Severity of spasticity was assessed using Modified Ashworth Scale (MAS) and Adductor Tone Rating Scale (ATRS). Ambulatory status was also evaluated.

RESULTS

Fifteen patients (13 males) with a mean age of 30.3 ± 17.5 years were included. Eight, six, and one patient underwent DREZL, SDR, and combined cervical DREZL and lumbosacral SDR, respectively. Eight of ten patients with preoperative bed-bound status had postoperative improvement in ambulatory status. Spasticity was significantly reduced in the DREZL group (p < 0.001), the SDR group (p < 0.001), and in overall analysis (p < 0.001). SDR was effective in both pediatric and adult spasticity patients. A significantly greater reduction in spasticity as assessed by MAS score (p < 0.001) and ATRS score (p = 0.015) was found in the DREZL group. Transient lower limb weakness was found in a patient who underwent SDR.

CONCLUSIONS

DREZL is more effective for reducing spasticity, but is more destructive than SDR. DREZL should be preferred for bed-ridden patients, and SDR for ambulatory patients. Both operations are helpful for improving ambulatory status. Gait improvement was observed only in patients who underwent SDR. Adult patients with spasticity of cerebral origin benefit from SDR.

Utilization of intraoperative electromyography for selecting targeted fascicles and determining the degree of fascicular resection in selective tibial neurotomy for ankle spasticity

BACKGROUND

Selective tibial neurotomy (STN) is an effective neurosurgical intervention for treating ankle spasticity. The authors use intraoperative electromyography (EMG) for selecting targeted fascicles and determining the degree of fascicular resection in STN. This study reports surgical techniques and outcomes of the operation.

METHODS

Participants who underwent STN with utilization of intraoperative EMG were recruited. Modified Ashworth Scale (MAS), passive range of motion (PROM) of the ankle in plantar flexion and dorsiflexion, Massachusetts General Hospital Functional Ambulatory Classification (MGHFAC) and ability to attain full plantigrade stance were assessed pre- and postoperatively.

RESULTS

Twenty-one STNs were performed in 15 patients. The mean pre- and postoperative MAS and PROM were 2.8 and 0.4 (p < 0.001), 39.5(o) and 66.0(o) (p < 0.001), respectively. The mean level of MGHFAC was improved from 3.3 preoperatively to 4.9 postoperatively (p < 0.01). Six non-ambulators had significant amelioration in MGHFAC level. Postoperatively, 19 of 21 lower limbs achieved full plantigrade, and 6 patients could perform selective voluntary motor control of the ankle.

CONCLUSION

STN is an effective procedure for spastic ankle in well-selected cases. Intraoperative EMG helps in selection of targeted fascicles, increases objectivity in neurotomy and prevents excessive denervation.