[Applied anatomy study and preliminary clinical application of hyper selective neurectomy of triceps branches combined with partial neurotomy of S 2 nerve root to relieve spastic equinus foot].

Objective: To observe the possibility of hyper selective neurectomy (HSN) of triceps branches combined with partial neurotomy of S ₂ nerve root for relieving spastic equinus foot.

Methods: Anatomical studies were performed on 12 adult cadaveric specimens. The S ₂ nerve root and its branches were exposed through the posterior approach. Located the site where S ₂ joined the sciatic nerve and measured the distance to the median line and the vertical distance to the posterior superior iliac spine plane, and the S ₂ nerve root here was confirmed to have given off branches of the pelvic splanchnic nerve, the pudendal nerve, and the posterior femoral cutaneous nerve. Between February 2023 and November 2023, 4 patients with spastic equinus foot were treated with HSN of muscle branches of soleus, gastrocnemius medial head and lateral head, and cut the branch where S ₂ joined the sciatic nerve. There were 3 males and 1 female, the age ranged from 5 to 46 years, with a median of 26 years. The causes included traumatic brain injury in 2 cases, cerebral hemorrhage in 1 case, and cerebral palsy in 1 case. The disease duration ranged from 15 to 84 months, with a median of 40 months. The triceps muscle tone measured by modified Ashworth scale (MAC) before operation was grade 3 in 2 cases and grade 4 in 2 cases. The muscle strength measured by Daniels-Worthingham manual muscle test (MMT) was grade 2 in 1 case, grade 3 in 1 case, and 2 cases could not be accurately measured due to grade 4 muscle tone. The Holden walking function grading was used to evaluate lower limb function and all 4 patients were grade 2. After operation, triceps muscle tone, muscle strength, and lower limb function were evaluated by the above grading.

Results: The distance between the location where S ₂ joined the sciatic nerve and median line was (5.71±0.53) cm and the vertical distance between the location and posterior superior iliac spine plane was (6.66±0.86) cm. Before joining the sciatic nerve, the S ₂ nerve root had given off branches of the pelvic splanchnic nerve, the pudendal nerve, and the posterior femoral cutaneous nerve. All the 4 patients successfully completed the operation, and the follow-up time was 4-13 months, with a median of 7.5 months. At last follow-up, the muscle tone of the patients decreased by 2-3 grades when compared with that before operation, and the muscle strength did not decrease when compared with that before operation. Holden walking function grading improved by 1-2 grades, and there was no postoperative hypoesthesia in the lower limbs.

Conclusion: HSN of triceps branches combined with partial neurotomy of S ₂ nerve root can relieve spastic equinus foot without damaging other sacral plexus nerves.