Nerve fiber transfer by end-to-side coaptation

Improving outcomes in traumatic peripheral nerve injuries to the upper extremity

Peripheral nerve lesions of the upper extremity are common and are associated with devastating limitations for the patient. Rapid and accurate diagnosis of the lesion by electroneurography, neurosonography, or even MR neurography is important for treatment planning. There are different therapeutic approaches, which may show individual differences depending on the injured nerve. If a primary nerve repair is not possible, several strategies exist to bridge the gap. These may include autologous nerve grafts, bioartificial nerve conduits, or acellular nerve allografts. Tendon and nerve transfers are also of major importance in the treatment of nerve lesions in particular with long regeneration distances. As a secondary reconstruction, in addition to tendon transfers, there is also the option for free functional muscle transfer. In amputations, the prevention of neuroma is of great importance, for which different strategies exist, such as target muscle reinnervation, regenerative peripheral nerve interface, or neurotized flaps. In this article, we give an overview of the latest methods for the therapy of peripheral nerve lesions.

Sensorimotor Outcomes of Upper Extremity End-to-Side Nerve Transfers: A Meta-analysis

BACKGROUND

End-to-side nerve transfer (ETSNT) for treatment of peripheral nerve injuries is controversial given the myriad anatomic locations, injury types, and indications. Efficacy of ETSNT remains debated. We hypothesized differences in age, sex, transfer location, and time to surgery influence outcomes.

METHODS

We performed a search of the PubMed database for ETSNT in the upper extremity from 1988 to 2018. Age, sex, transfer location, time to surgery, donor and recipient axons, and strength and sensation outcomes as measured by Medical Research Council scale were extracted from articles. Meaningful recovery was classified as Medical Research Council Grade 3 or greater. Association between meaningful recovery and younger (<25) and older (≥25) patients, injury mechanism, sex, transfer location, donor axons, and recipient axons were calculated using a χ 2 or Fisher exact test. A logistic mixed effect model was used with time to surgery, age (categorical), transfer location, and injury type as a fixed effect, and a random paper effect was included to account for correlation among patients from the same paper.

RESULTS

One hundred fifteen patients from 11 studies were included. Neither age (continuous variable, P = 0.68) nor time to surgery ( P = 0.28) affected meaningful recovery. Injury mechanism, sex, and younger age (<25 vs ≥25 years) were not associated with meaningful recovery. Within the brachial plexus ETSNT demonstrated median M4 ± 1 postoperative strength, with trunks/cords as the primary axon donor ( P = 0.03). The musculocutaneous nerve demonstrated promising but variable results in 31 patients with median strength M3 ± 4. Digital nerves consistently demonstrated meaningful sensory recovery as both donor and recipient axons (15 of 15, 100%). Logistic regression analysis demonstrated that odds of meaningful recovery after ETSNT are significantly greater for transfers within the brachial plexus compared with the distal arm (odds ratio, 41.9; 95% CI, 1.1-1586.7, P = 0.04), but location does not significantly affect meaningful recovery ( P = 0.22).

CONCLUSIONS

Patients undergoing ETSNT for digital nerve injury demonstrated meaningful recovery. End-to-side nerve transfer seems to be more efficacious when performed within the brachial plexus. This study did not find sex, injury mechanism, or time to surgery to significantly affect meaningful recovery. Additional study is needed to better evaluate the effectiveness of ETSNT in the upper extremity.

Supercharge End-to-Side Nerve Transfer: Systematic Review

Background: To decrease the time to reinnervation of the intrinsic motor end plates after high ulnar nerve injuries, a supercharged end-to-side (SETS) anterior interosseous to ulnar motor nerve transfer has been proposed. The purpose of this study was to compile and review the indications, outcomes, and complications of SETS anterior interosseous to ulnar motor nerve transfer. Methods: A literature search was performed, identifying 73 papers; 4 of which met inclusion and exclusion criteria, including 78 patients. Papers included were those that contained the results of SETS between the years 2000 and 2018. Data were pooled and analyzed focusing on the primary outcomes: intrinsic muscle recovery and complications. Results: Four studies with 78 patients met inclusion and exclusion criteria. Most patients (33.3%) underwent SETS for an ulnar nerve lesion in continuity, the average age was 46.5 years, and the average follow-up was 10 months. The average duration of symptoms before surgery was 99 weeks, all patients had weakness and numbness, nearly all (96%) had atrophy, and half (53%) had pain. Grip and key pinch strength improved 202% and 179%, respectively, from the preoperative assessment. The vast majority (91.9%) recovered intrinsic function at an average of 3.7 months. Other than 8% of patients who did not recover intrinsic strength, no other complications were reported in any of the 78 patients. Conclusions: The SETS is a successful procedure with low morbidity, which may restore intrinsic function in patients with proximal nerve injuries.

Functional Restoration Following Resection of Malignant Peripheral Nerve Sheath Tumour of the Median Nerve: A Case Report

Management of malignant peripheral nerve sheath tumours (MPNSTs) is primarily surgical, involving surgical resection with wide margins, and frequently radiation therapy. When a MPNST involves a major peripheral nerve, wide resection leads to significant distal neurologic deficits. A patient who underwent resection of a MPNST involving the median nerve above the elbow is presented. Staged tendon and nerve transfers were performed to restore sensation to the thumb and index finger, thumb opposition and flexion, finger flexion and forearm pronation. These included: 1. radial sensory nerve branches to digital nerves of thumb and index finger, 2. ulnar nerve branch of flexor carpi ulnaris to pronator teres, 3. brachioradialis to flexor pollicis longus, 4. side-to-side transfer of flexor digitorum profundus tendon of index finger to middle, ring and little fingers, 5. extensor indicis proprius to abductor pollicis brevis. The rationale, approach, and favourable results of functional reconstruction in this patient are detailed.

Comparison Between Supercharged Ulnar Nerve Repair by Anterior Interosseous Nerve Transfer and Isolated Ulnar Nerve Repair in Proximal Ulnar Nerve Injuries

PURPOSE

To compare combined ulnar nerve repair with supercharged end-to-side anterior interosseous nerve to ulnar motor nerve transfer (UR+SETS) with conventional isolated ulnar repair techniques in proximal ulnar nerve transection, with respect to intrinsic muscle power recovery and claw hand deformity correction.

METHODS

We conducted a comparative matched-paired series prospectively on 21 patients with proximal ulnar nerve transection injury. Eleven patients were managed by UR+SETS and 10 by isolated ulnar repair. The outcome was reported at 3, 6, 12, and 18 months using the score of Birch and Raji and Brand's criteria.

RESULTS

A total of 21 patients with acute proximal ulnar nerve transection injury had completed 18 months' follow-up. We observed better results in the UR+SETS group regarding the return of intrinsic function and reduction of deformity with earlier improvement in the score of Birch and Raji and Brand's criteria.

CONCLUSIONS

In the short term, UR+SETS transfer appears to result in better intrinsic muscle reinnervation and clawing deformity correction after proximal ulnar nerve transection injury.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic II.

Incidence, diagnostics and treatment algorithm of nerve lesions after traumatic shoulder dislocations: a retrospective multicenter study

BACKGROUND

The shoulder is the joint most prone to dislocating in the human body and accounts for 45% of all dislocations. In addition to ruptures of the soft tissue and bony injuries, lesions to vascular structures as well as the brachial plexus and its corresponding nerves might occur. With an incidence of up to 65%, nerve lesions are frequently reported after shoulder dislocations. The aim of this study is to obtain information on epidemiology, diagnostics, treatment and duration until remission or late sequelae after shoulder dislocation and concomitant nerve injury in a large patient cohort.

METHODS

The patient cohort consisted of 15,739 patients from three centres who had sustained a shoulder dislocation. All patient files were searched for concomitant injury of the brachial plexus or its corresponding nerves. For epidemiological data analysis, demographic data, clinical follow-ups, electromyography and nerve conduction velocity were evaluated.

RESULTS

In total, 60 patients (32 males, 28 females) with a mean age of 60 years (range 19-88 years) met the inclusion criteria. In the majority of patients (n = 51), the trauma mechanism was a trivial fall on the outstretched arm. The most frequent dislocation direction was anterior-caudal in 61.6%, followed by strictly caudal in 16.6%. The brachial plexus was injured in 46 patients (76.6%) and isolated nerve damage was documented in 14 patients (23.3%). Electroneurographic examinations were performed in less than half of the patients (38.3%).

CONCLUSION

A combination injury of shoulder dislocation and plexus lesion may occur at any age and sometimes has a poor outcome. Electroneurographic examinations should be implemented when managing these patients as a cost-effective and supportive examination.

LEVEL OF EVIDENCE

Level IV, retrospective study.

The role of peripheral nerve surgery in a tissue reinnervation

In modern neuroscience, the most relevant is the study of the problem of reinnervation of tissues after severe injuries. Complete restoration of lost physiological functions is still impossible with lesions of peripheral nerves with the formation of extensive diastasis between their proximal and distal sites. In this case, the standard neurorrhaphy cannot be carried out because of the eruption of the filaments during tension and convergence of the ends. To solve this problem, a technique was developed for autotransplantation of the nerve sections, which is still the gold standard for the reconstruction of extensive nerve defects. However, the presence of significant shortcomings led to the development of the doctrine of the direction of regeneration with the help of conduits. Currently, the use of nerve channels is the most promising technology for peripheral nerve repair after trauma. The most actively developing now is the direction of reinnervation, such as neurotization. Neurotization, in some way, combined all the methods of restoring nerves. The overall goal of all these methods-the restoration of extensive nerve defects-allows them to be combined into a new industry: reinnervating neurosurgery.

Successful recovery of sensation loss in upper brachial plexus injuries

OBJECTIVE

Injuries of the upper trunk of the brachial plexus may trigger motor and sensory deficits. There exists a growing body of literature with respect to the reconstruction of motor deficits in upper trunk brachial plexus injuries by using nerve transfers; albeit to date, very few old reports have focused on the reconstruction of sensory loss resulting from upper trunk injuries. In this case series, we review six cases (five males and one female) with upper trunk brachial plexus injuries undergoing sensory nerve transfers.

METHODS

Sensory reconstruction was carried out by using transfer of the ulnar to the median nerves, innervating adjacent aspects of the little and ring fingers (the fourth web space) and adjacent aspects of the thumb and the index finger (the first web space), respectively.

RESULTS

The mean age of our six patients was 30.5 ± 9 years old (range 20-45). The mean time interval between the injury and subsequent surgery was 6.6 ± 1.8 months (range 5-10). Five patients achieved S3 or S3+ in both the thumb and the index finger while the sixth one regained S2+ in the index finger while also achieving S3 in the thumb according to the Highet-Zachary system scoring scale.

CONCLUSION

These results suggest that nerve transfers can achieve satisfactory outcomes in patients having sensory reconstruction after upper brachial plexus injuries, and thus, we lay emphasis on reviving the use of sensory nerve transfer techniques in such patients.

End-to-side neurotization with the phrenic nerve in restoring the function of toe extension: an experimental study in a rat model

The phrenic nerve being transferred to the posterior division of the lower trunk with end-to-end neurorrhaphy is reported to be effective in restoring the function of digit extension in literature. However, the phrenic nerve is extremely important in respiration. We designed an animal experiment to discover whether the phrenic nerve being transferred to the posterior division of the lower trunk with end-to-side neurotization was feasible and provided the theoretical basis. A sum of 36 Sprague-Dawley rats was randomly assigned to one of two groups. In Group A, the phrenic nerve was transferred to the posterior division of the lower trunk with end-to-side neurotization. In Group B, the posterior division of the lower trunk was directly sutured. The results of behavioral assessment, electrophysiology, histology and nerve fiber count and muscle weight at 12 weeks postoperatively were recorded. In Group A, none of the rats experienced tachypnea. The motion of slight toe extension was observed. The results of electrophysiology, histology and nerve fiber count and muscle weight in Group A were not as well as those of Group B, but gradually improved with time. The phrenic nerve being transferred to the posterior division of lower trunk with end-to-side neurotization can partially restore the function of toe extension in a rat model. Whether the function of digit extension can be restored by the phrenic nerve with end-to-side neurotization in humans still needs more practice in clinic.

The reasons for end-to-side coaptation: how does lateral axon sprouting work?

Nerve fibers are attracted by sutureless end-to-side nerve coaptation into the recipient nerve. Opening a window in the epineurium enhances axon attraction and myelination. The authors analyze the features of nerve repair by end-to-side coaptation. They highlight the known mechanisms of axon sprouting and different hypotheses of start up signals (presence or absence of an epineurial window, role of Schwann cells, signaling from the distal trunk). The clinical literature is also presented and differences between experimental and clinical applications are pointed out. The authors propose their point of view and perspectives deriving from recent experimental and clinical experiences.

Epineurial Window Is More Efficient in Attracting Axons than Simple Coaptation in a Sutureless (Cyanoacrylate-Bound) Model of End-to-Side Nerve Repair in the Rat Upper Limb: Functional and Morphometric Evidences and Review of the Literature

End-to-side nerve coaptation brings regenerating axons from the donor to the recipient nerve. Several techniques have been used to perform coaptation: microsurgical sutures with and without opening a window into the epi(peri)neurial connective tissue; among these, window techniques have been proven more effective in inducing axonal regeneration. The authors developed a sutureless model of end-to-side coaptation in the rat upper limb. In 19 adult Wistar rats, the median and the ulnar nerves of the left arm were approached from the axillary region, the median nerve transected and the proximal stump sutured to the pectoral muscle to prevent regeneration. Animals were then randomly divided in two experimental groups (7 animals each, 5 animals acting as control): Group 1: the distal stump of the transected median nerve was fixed to the ulnar nerve by applying cyanoacrylate solution; Group 2: a small epineurial window was opened into the epineurium of the ulnar nerve, caring to avoid damage to the nerve fibres; the distal stump of the transected median nerve was then fixed to the ulnar nerve by applying cyanoacrylate solution. The grasping test for functional evaluation was repeated every 10-11 weeks starting from week-15, up to the sacrifice (week 36). At week 36, the animals were sacrificed and the regenerated nerves harvested and processed for morphological investigations (high-resolution light microscopy as well as stereological and morphometrical analysis). This study shows that a) cyanoacrylate in end-to-side coaptation produces scarless axon regeneration without toxic effects; b) axonal regeneration and myelination occur even without opening an epineurial window, but c) the window is related to a larger number of regenerating fibres, especially myelinated and mature, and better functional outcomes.

Supercharge nerve transfer to enhance motor recovery: a laboratory study

PURPOSE

To investigate the ability of a supercharge end-to-side (SETS) nerve transfer to augment the effect of regenerating native axons in an incomplete rodent sciatic nerve injury model.

METHODS

Fifty-four Lewis rats were randomized to 3 groups. The first group was an incomplete recovery model (IRM) of the tibial nerve complemented with an SETS transfer from the peroneal nerve (SETS-IRM). The IRM consisted of tibial nerve transection and immediate repair using a 10-mm fresh tibial isograft to provide some, but incomplete, nerve recovery. The 2 control groups were IRM alone and SETS alone. Nerve histomorphometry, electron microscopy, retrograde labeling, and muscle force testing were performed.

RESULTS

Histomorphometry of the distal tibial nerve showed significantly increased myelinated axonal counts in the SETS-IRM group compared with the IRM and SETS groups at 5 and 8 weeks. Retrograde labeling at 8 weeks confirmed increased motoneuron counts in the SETS-IRM group. Functional recovery at 8 weeks showed a significant increase in muscle-specific force in the SETS-IRM group compared with the IRM group.

CONCLUSIONS

An SETS transfer enhanced recovery from an incomplete nerve injury as determined by histomorphometry, motoneuron labeling within the spinal cord, and muscle force measurements.

CLINICAL RELEVANCE

An SETS distal nerve transfer may be useful in nerve injuries with incomplete regeneration such as proximal Sunderland II- or III-degree injuries, in which long regeneration distance yields prolonged time to muscle reinnervation and suboptimal functional recovery.

The embracing end-to-side neurorrhaphy in rats

PURPOSE

Compare two new methods with the traditional end-to-side neurorrhaphy.

METHODS

Rats were divided into four groups. In A-L group the peroneal nerve was sectioned and the distal stump was connected to the lateral of the tibial nerve (donor) with two 10-0 nylon points. In A-R group two perineurium flaps embraced the donor nerve. In the B-R group a suture embraced the donor nerve. Group B-L was the control. After six months tibial cranial muscle mass and morphometry of the distal stump of the peroneal nerve were evaluated.

RESULTS

Muscle mass in groups A-R, A-L and B-R were lower than B-L group (p<0.0001) an equal between themselves (p>0.05). Groups A-R, B-R and A-L had a lower number of nerve fibers when compared with B-L (p=0.0155, p=0.016, p=0.0021).

CONCLUSION

The three types of neurorrhaphy showed no differences related to muscle mass and number of nerve fibers suggesting that the embracing with a single suture has great potential due its simplicity and usefulness in deep areas.

Reverse end-to-side nerve transfer: from animal model to clinical use

PURPOSE

Functional recovery after peripheral nerve injury is predominantly influenced by time to reinnervation and number of regenerated motor axons. For nerve injuries in which incomplete regeneration is anticipated, a reverse end-to-side (RETS) nerve transfer might be useful to augment the regenerating nerve with additional axons and to more quickly reinnervate target muscle. This study evaluates the ability of peripheral nerve axons to regenerate across an RETS nerve transfer. We present a case report demonstrating its potential clinical applicability.

METHODS

Thirty-six Lewis rats were randomized into 3 groups. In group 1 (negative control), the tibial nerve was transected and prevented from regenerating. In group 2 (positive control), the tibial and peroneal nerves were transected, and an end-to-end (ETE) nerve transfer was performed. In group 3 (experimental model), the tibial nerve and peroneal nerves were transected, and an RETS nerve transfer was performed between the proximal end of the peroneal nerve and the side of the denervated distal tibial stump. Nerve histomorphometry and perfused muscle mass were evaluated. Six Thy1-GFP transgenic Sprague Dawley rats, expressing green fluorescent protein in their neural tissues, also had the RETS procedure for evaluation with confocal microscopy.

RESULTS

Nerve histomorphometry showed little to no regeneration in chronic denervation animals but statistically similar regeneration in ETE and RETS animals at 5 and 10 weeks. Muscle mass preservation was similar between ETE and RETS groups by 10 weeks and significantly better than negative controls at both time points. Nerve regeneration was robust across the RETS coaptation of Thy1-GFP rats by 5 weeks.

CONCLUSIONS

Axonal regeneration occurs across an RETS coaptation. An RETS nerve transfer might augment motor recovery when less-than-optimal recovery is otherwise anticipated.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic I.