Microsurgical Treatment For Large Defects Of The Femoral Nerve

Femoral nerve injury is not uncommon in clinical practice.Beside trauma,a considerable number of femoral nerve injuries are iatrogenic injury.Femoral nerve injury can lead to ipsilateral hip flexion,difficulties in knee extension,and sensory numbness in the inner thigh.When walking,the gait is unstable and falls easily.It is difficult for the patient to stand up from the chair and climb stairs,which brings great inconvenience to the patient’s life.Therefore,prompt repair should be given.Among various types of injuries,long-segment femoral nerve defect is undoubtedly the most difficult to repair.Clinical long-segment defects of the femoral nerve are relatively rare,and the etiology is mostly iatrogenic.For example,femoral nerve is often mistakenly cut in retroperitoneal schwannoma resection.The special causes of injury give the long-segment femoral nervedefect the following characteristics.1.Femoral nerve defects,which are relatively long,are usually IV degree defect;2.Relatively thick femoral nervere quires multi-branch sural nerve grafting,which is difficult to becarried outwith blood vessels;3.Most defects that partly experience trauma or surgeries show severe scar adhesion and poor blood circulation.As a consequence,it is difficult to find the broken ends of the femoral nerve.Also,the tissue bed that can be used for nerve repair is scarred.Therefore,the clinical treatment for long-segment femoral nerve defects is very difficult and is one of the severe challenges faced by trauma surgeons.At present,there are two main treatments for long-segment defects of the femoral nerve.One is a multi-stranded autologous sural nerve cable transplant,and the other is a nerve transfer with a obturator nerve as a donor.With regard to autologous nerve grafting,Gu Yudong believed that the use of free nerves that carry blood vessels should be considered in transplant in those cases where a neural stem defect exists around a long segment larger than 10 cm,the nerve graft bed is scar tissue or non-vascular tissue,or the nerve defect is associated with major vascular injuries in the extremities.Even sural nerve grafts using two arterialized nerves fails to repair femoral nerve with enough power.If a multi-stretch sural nerve is used for transplantation,the transplanted nerves will solely rely on the interstitial fluid to provide nutrition,which takes longer time for their own blood circulation to from.As a result,it will cause necrosis in some transplanted nerve centers and thus affect the treatment effect.Therefore,it is necessary to seek better methods of micro-repair to provide a stable blood supply for the transplanted nerves so that the transplanted nerves can establish their own blood circulation as soon as possible,which,in turn,promotes better regeneration of nerves and treatment effect.In cases where the distance between nerve grafts is too large or the nerve near the end cannot be used,nerve transfer becomes a good choice for repairing defects.However,compared with the surgical methods used for nerve transfer in the upper extremities,there are fewer applications for the lower extremity nerve injuries.Because the obturator nerves have the same advantages as the femoral nerves,they are from the same source,their anatomical locations are similar,and they both contain motor fibers,the study of nerves that can be used to repair femoral nerve focuses mainly on obturator nerves.A number of anatomical studies have also confirmed the feasibility of obturator nerves transfer to repair femoral nerves.Compared with sural nerve transplantation,obturator nerve transfer to repair axon regeneration of femoral nerves only requires the nerve to pass through an anastomosis,and the regeneration distance of axons is shorter,theoretically,better recovery effect can be obtained.However,obturator nerve trunk transfer causes the loss of adduction function,and the anterior branch transfer can not provide enough number of axons.Therefore,it is necessary to go through further research to find the best method of neural transposition,so that the limited number of transferable nerves can be fully utilized to obtain the best repair effect.Part 1 Experimental study on repair of long-segment femoral nerve defect with different nerve graft beds Objective: To observe the blood supply establishment and nerve regeneration of transplanted nerves after autologous nerve grafting on different tissue beds in repairing defects of long-segment femoral nerves in rats.It provides experimental basis for clinical autologous nerve graft in repairing long-segment femoral nerve defect.Methods: An experimental animal model of long-segment femoral nerve defect was established in adult rats.Different tissue beds were selected for autologous nerve graft repair: Group A(muscle tissue bed),artificially constructed blood-rich muscle tissue bed in which the transplanted nerve was embedded.The muscle tissue provides nutrient support for the transplanted nerve;Group B(blank tissue bed)does not artificially construct the tissue bed;the transplanted nerve is placed at the repair site without treatment;and the tissue fluid is used to provide nutrition for the transplanted nerve;Group C(scar tissue bed)The transplanted nerve was placed in a silicone tube to mimic the scar tissue and the tissue fluid provided nutritional support for the transplanted nerve.At different time points(1 week,2 weeks,4 weeks,and 12 weeks)after surgery,samples are collected.The transplanted nerves and quadriceps were subjected to histological examination,neurotic electrophysiological examination,and transmission electron microscopy to observe the establishment of blood supply,nerve regeneration,and muscle function recovery.The results of the 3 groups were analyzed and evaluated.Results: The establishment time of blood circulation in the muscle tissue bed group was significantly shorter than that in the other two groups.The rat BBB motor function score,motor unit potential amplitude,muscle weight recovery rate,muscle cell cross-sectional area recovery rate,and the passing rate of myelinated nerve fibers were all higher than the blank tissue bed group and the scar tissue bed group.Compared with the scar tissue bed group,the indexes of the blank tissue bed group were better than the scar tissue bed group.Conclusions: The muscle tissue bed can provide good blood supply and a stable environment for the transplanted nerve to grow,which greatly shortens the time for the transplanted nerve to establish blood circulation and enters the phase of axon growth and myelination earlier,so that a good nerve regeneration effect can be obtained.Artificially constructing a muscle tissue bed for long-segment nerve grafting is both an innovation in the method of nerve transplantation and a theoretical innovation.This method is not only suitable for the repair of long-segment femoral nerve defects,but also applies to the repair of other peripheral nerve defects.Part 2 Clinical study of microsurgical repair of long-segment femoral nerve defect Objective: To clinically treat two cases of long-segment femoral nerve defect,muscle tissue beds were artificially constructed,and the transplanted nerves were embedded into the muscle.Observation and analysis of the patient were carried out after recovery to provide guidance for clinical autologous nerve transplantation to repair the long segmental femoral nerve defect.Methods: Surgical sural nerve grafting was performed on two patients with long-segment femoral nerve defect.The muscle tissue beds were built during the operation,and the transplanted nerves were embedded into the muscles.The patients’ motor function recovery was observed after operation,and the patients were subjected to electromyography,ultrasound and magnetic resonance imaging,to produce a comprehensive analysis of surgical outcomes.Results: The patient’s quadriceps function recovered satisfactorily.The extensor muscle strength returned to level M4+,and the gait was near normal.Conclusions: In the process of sural nerve grafting to treat long-segment defects of the femoral nerve,artificially constructing the muscle tissue bed and embedding the transplanted nerve into the muscle tissue can promote the regeneration of the transplanted nerve,and can obtain a good clinical curative effect.This method can be popularized and applied in the treatment of long-segment femoral nerve defects and other peripheral nerves.Part III: Study on the repair plan of the muscular branches in femoral nerves.Objective: To evaluate the importance of each muscular branch of the femoral nerve and analyze the outcomes of repairing different combinations of the muscular branches.The study will provide the optimal solution for the clinical treatment of long-segment femoral nerve defects by transferring nerve to the muscular branch.Methods: Animal experiments were divided into two steps.In the first step,20 rats were randomly divided into four groups.For each group,only one particular muscular branch of the femoral nerve was retained.The importance of each muscle branch was analyzed by observing the changes in the knee joint function of the rats.In the second step,20 rats were randomly divided into two groups.One group retained the vastus medialis branch and the rectus femoris branch,and the other group retained the vastus medialis branch and the vastus lateralis branch.The knee joint function was observed in the rats.The the two combinations were evaluated by observing the changes of the knee function of the rats.With the results of the animal experimental studies,the clinical cases and the literature data,different muscular branch combinations to repair the femoral nerve were analyzed and evaluated.Results: According to their importance,the muscular branches of the quadriceps are listed descendingly as follows:the vastus medialis(VM)branch,the vastus lateralis(VL)branch,the rectus femoris(RF)branch,and the vastus internus(VI)branch.The function of the VM and RF branch combination is inferior to that of the VM and VL branch combination.Conclusion: Three muscle branches can be repaired if there are enough number of nerves for transfer,.The best combination is the VL branch + the RF branch + the VM branch.If only two muscular branches can be repaired,the best combination is the VM branch + the VL branch,followed by the VM branch + the RF branch.If only one muscular branch can be repaired,the VM branch should be selected.