Anatomical study of sciatic nerve and common peroneal nerve compression

BACKGROUND： Many diseases of the common peroneal nerve are a result of sciatic nerve injury. The present study addresses whether anatomical positioning of the sciatic nerve is responsible for these injuries. OBJECTIVE： To analyze anatomical causes of sciatic nerve and common peroneal nerve injury by studying the relationship between the sciatic nerve and piriformis. DESIGN, TIME AND SETTING： Observe and measure repeatedly. The experiment was conducted in the Department of Anatomy, Tianjin Medical College between January and June 2005. MATERIALS： Fifty-two adult cadavers 33 males and 19 females, with a total of 104 hemispheres, and fixed with formaldehyde, were provided by Tianjin Medical College and Tianjin Medical University. METHODS： A posterior cut was made from the lumbosacral region to the upper leg, fully exposing the piriformis and path of the sciatic nerve. MAIN OUTCOME MEASURES： （1） Anatomical characteristics of the tibial nerve and common peroneal nerve. （2） According to different areas where the sciatic nerve crosses the piriformis, the study was divided into two types-normal and abnormal. Normal is considered to be when the sciatic nerve passes through the infrapiriform foramen. Remaining pathways are considered to be abnormal. （3） Observe the relationship between the suprapiriform foramen, infrapiriform foramen, as well as the superior and inferior space of piriformis. RESULTS： （1） The nerve tract inside the common peroneal nerve is smaller and thinner, with less connective tissue than the tibial nerve. When pathological changes or variations of the piriformis, or over-abduction of the hip joint, occur, injury to the common peroneal nerve often arises due to blockage and compression. （2） A total of 76 hemispheres （73.08%） were normal, 28 were abnormal （26.92%）. The piriformis can be injured, and the sciatic nerve can become compressed, when the hip joint undergoes intorsion, extorsion, or abduction. （3） The structures between the infrapiriform and suprapiriform foramen are where ＂the first threshold＂ sciatic nerve projects. The structures between the infrapiriform and suprapiriform gap were ＂the second threshold＂. This became the concept of ＂double threshold＂. The reduced area caused by pathological changes of ＂double threshold＂ may block and compress the sciatic nerve. Because the common peroneal nerve lies on the anterolateral side of the sciatic nerve, injury to the common peroneal nerve is more serious. CONCLUSION： Anatomical characteristics of the common peroneal nerve, as well as variation of the sciatic nerve, piriformis, and the reduced ＂double threshold＂, are the main causes of sciatic nerve injury, and are especially common in peroneal nerve injury.

Predictive Reliability of the Phoenix Sign for the Outcome of Common Fibular (Peroneal) Nerve Decompression Surgery

A positive Phoenix sign occurs when a patient, with a suspected focal nerve entrapment of the Common Fibular (Peroneal) Nerve (CFN) at the level of the fibular neck, demonstrates an improvement in dorsifexion after an ultrasound guided infiltration of a sub-anesthetic dose of lidocaine. Less than 5 cc’s of 1% or 2% lidocaine is utilized and the effect is seen within minutes after the infiltration, but usually lasts only 10 minutes. This effect may be due to the vasodilatory action of lidocaine on the microcirculation in the area of infiltration. This nerve block has significant diagnostic utility as it is highly specific in the confirmation of true focal entrapment of the CFN, has high predictive value for a patient who may undergo surgical nerve decompression if they have demonstrated a positive Phoenix Sign, and may help in the surgical decision-making process in patients who have had a drop foot for many years but still may regain some motor function after decompression. In this retrospective review, 26 patients were tested, and 25 of this cohort demonstrated a Positive Phoenix Sign (an increase in dorsiflexion strength of the Extensor Hallucis Longus muscle (EHL)). One patient had no response to the peripheral nerve block. Of the 25 patients who demonstrated a positive “Phoenix Sign” and underwent nerve decompression of the CFN, and 25 (100%) showed an increase in dorsiflexion strength of the EHL after nerve decompression surgery of the CFN. The one patient in this cohort who did not demonstrate any improvement in dorsiflexion of the EHL after the nerve block did not have any improvement after surgery.

Presentation and management outcome of foot drop with tibialis posterior tendon transfer

BACKGROUND Foot drop causes considerable disability.The ankle-dorsiflexion is either weak or lost completely.Additionally,the ankle eversion and toe extensions are also impaired.This results in a high steppage gait while walking.Overall,the gait is awkward;there is greater energy consumption;increased proneness to sustain injury of the forefoot;and more frequent falling during walking.AIM To document the clinical and epidemiological profile of foot drop patients in our population and evaluate the outcome of tibialis posterior(TP)tendon transfer for restoring the lost dorsiflexion in foot drop.METHODS The study was carried out at the National Institute of Rehabilitation Medicine in Islamabad over a period of 7 years.It included patients of all sexes and ages who presented with foot drop and had no contraindications for the procedure of TP tendon transfer.Exclusion criteria were patients who had contraindications for the operation.For instance,paralyzed posterior leg compartment muscles,Achilles tendon contracture,stiff ankle or toes,unstable ankle joint,weak gastrocnemius and scarred skin spanning over the route of planned tendon transfer.Also,patients who had the foot drop as a result of disc prolapses or brain diseases were excluded.Convenience sampling technique was used.The circum-tibial route of TP tendon transfer was employed.RESULTS Out of 37 patients,26(70.27%)were males whereas 11(29.72%)were females.The mean age was 22.59±8.19 years.Among the underlying causes of foot drop,road traffic accidents constituted the most common cause,found among 20(54.05%)patients.The share of complications included wound infections in 3(8.10%)patients and hypertrophic scars in 2(5.40%)patients.At 1-year postoperative follow-up visits,the outcome was excellent in 8(21.62%),good in 20(54.05%)and moderate in 9(24.31%).CONCLUSION The majority of cases of foot drop resulted from road traffic accidents that directly involved the common peroneal nerve.TP tendon transfer through the circumtibial route was found to be an easily executed effective operation which restored good dorsiflexion of the ankle among the majority of patients.

Autologous transplantation with fewer fibers repairs large peripheral nerve defects

Peripheral nerve injury is a serious disease and its repair is challenging. A cable-style autologous graft is the gold standard for repairing long peripheral nerve defects; however, ensuring that the minimum number of transplanted nerve attains maximum therapeutic effect remains poorly understood. In this study, a rat model of common peroneal nerve defect was established by resecting a 10-mm long right common peroneal nerve. Rats receiving transplantation of the common peroneal nerve in situ were designated as the in situ graft group. Ipsilateral sural nerves（10–30 mm long） were resected to establish the one sural nerve graft group, two sural nerves cable-style nerve graft group and three sural nerves cable-style nerve graft group. Each bundle of the peroneal nerve was 10 mm long. To reduce the barrier effect due to invasion by surrounding tissue and connective-tissue overgrowth between neural stumps, small gap sleeve suture was used in both proximal and distal terminals to allow repair of the injured common peroneal nerve. At three months postoperatively, recovery of nerve function and morphology was observed using osmium tetroxide staining and functional detection. The results showed that the number of regenerated nerve fibers, common peroneal nerve function index, motor nerve conduction velocity, recovery of myodynamia, and wet weight ratios of tibialis anterior muscle were not significantly different among the one sural nerve graft group, two sural nerves cable-style nerve graft group, and three sural nerves cable-style nerve graft group. These data suggest that the repair effect achieved using one sural nerve graft with a lower number of nerve fibers is the same as that achieved using the two sural nerves cable-style nerve graft and three sural nerves cable-style nerve graft. This indicates that according to the ‘multiple amplification＇ phenomenon, one small nerve graft can provide a good therapeutic effect for a large peripheral nerve defect.