Transfer of the Motor Branch of the Abductor Digiti Quinti for Thenar Muscle Reinnervation in High Median Nerve Injuries

Assessment, management, and rehabilitation of traumatic peripheral nerve injuries for non-surgeons

Electrodiagnostic evaluation is often requested for persons with peripheral nerve injuries and plays an important role in their diagnosis, prognosis, and management. Peripheral nerve injuries are common and can have devastating effects on patients' physical, psychological, and socioeconomic well-being; alongside surgeons, electrodiagnostic medicine specialists serve a central function in ensuring patients receive optimal treatment for these injuries. Surgical intervention-nerve grafting, nerve transfers, and tendon transfers-often plays a critical role in the management of these injuries and the restoration of patients' function. Increasingly, nerve transfers are becoming the standard of care for some types of peripheral nerve injury due to two significant advantages: first, they shorten the time to reinnervation of denervated muscles; and second, they confer greater specificity in directing motor and sensory axons toward their respective targets. As the indications for, and use of, nerve transfers expand, so too does the role of the electrodiagnostic medicine specialist in establishing or confirming the diagnosis, determining the injury's prognosis, recommending treatment, aiding in surgical planning, and supporting rehabilitation. Having a working knowledge of nerve and/or tendon transfer options allows the electrodiagnostic medicine specialist to not only arrive at the diagnosis and prognosticate, but also to clarify which nerves and/or muscles might be suitable donors, such as confirming whether the branch to supinator could be a nerve transfer donor to restore distal posterior interosseous nerve function. Moreover, post-operative testing can determine if nerve transfer reinnervation is occurring and progress patients' rehabilitation and/or direct surgeons to consider tendon transfers.

Distal nerve transfers for peripheral nerve injuries: indications and outcomes

Distal nerve transfer is a refined surgical technique involving the redirection of healthy sacrificable nerves from one part of the body to reinstate function in another area afflicted by paralysis or injury. This approach is particularly valuable when the original nerves are extensively damaged and standard repair methods, such as direct suturing or grafting, may be insufficient. As the nerve coaptation is close to the recipient muscles or skin, distal nerve transfers reduce the time to reinnervation. The harvesting of nerves for transfer should usually result in minimal or no donor morbidity, as any anticipated loss of function is compensated for by adjacent muscles or overlapping cutaneous territory. Recent years have witnessed notable progress in nerve transfer procedures, markedly enhancing the outcomes of upper limb reconstruction for conditions encompassing peripheral nerve, brachial plexus and spinal cord injuries.

Transfer of the palmaris brevis motor branch to the thenar motor branch: A cadaveric preliminary study

OBJECTIVE

High median nerve injuries can lead to poor distal recovery, especially poor functioning of median innervated thenar muscles involved in thumb opposition and palmar abduction. The palmaris brevis (PB) is a small subcutaneous muscle innervated by ulnar nerve. Innervation of the PB is in most of cases provided by the ulnar digital nerve to the little finger. The purpose of this study is to assess the feasibility of transferring the PB motor branch (PBMB) to the median nerve thenar motor branch (TMB), in order to allow for early restoration of thumb palmar abduction and opposition, through a preliminary cadaveric study.

METHODS

Twenty-five cadaver upper limbs were dissected under magnification. The length of the PBMB and TMB, and their origin were recorded. Nerve transfer from PBMB to TMB was conducted, and evaluated on 2 parameters: surgical feasibility, and distance from the coaptation site to the recipient nerve muscle entry point. The PBMB and TMB were harvested, fixated in formalin, then embedded in paraffin. They were sectioned transversely, and stained with a combination of hematoxylin-eosin and Luxol fast blue. Myelinated axons were counted in each specimen and the donor-to-recipient axon ratio was recorded.

RESULTS

The PBMB was constant and originated from the ulnar digital nerve of the little finger in all cases. The transfer from PBMB to TMB was feasible in all cases. Mean myelinated axon counts of PBMB and TMB were 253±142 and 356±198, respectively (p=0.06). The donor-to-recipient axon ratio was 1:1.41. The mean distance from coaptation of the PBMB to the recipient thenar muscles was 23.1±3.0mm.

CONCLUSIONS

Based on our results, PBMB to TMB transfer is feasible. The PBMB has the advantage over other distal nerve transfer donors to be constant and superficial, allowing for an easier harvest. Moreover, this procedure does not sacrifice any intrinsic function of the hand, and the proximity of the PBMB with the carpal tunnel allows for a single incision procedure. Therefore, early restoration of the median innervated thenar muscles may be feasible by the PBMB to TMB transfer in cases of high median nerve lesions.

LEVEL OF EVIDENCE

IV.

Rare Median Nerve and Digital Nerve Tumor Resection and Distal Nerve Transfers: A Report of 2 Cases

CASES

We present 2 cases of median nerve reconstruction using distal nerve transfers after resection of unusual benign median nerve tumors. Critical sensation was restored in case 1 by transferring the fourth common digital nerve to first web digital nerves. Thumb opposition was regained by transferring the abductor digiti minimi ulnar motor nerve branch to the recurrent median motor nerve branch. Critical sensation was restored in case 2 by transferring the long finger ulnar digital nerve to the index finger radial digital nerve.

CONCLUSION

Distal nerve transfers, even with short grafts, are reliable median nerve deficit treatments, sparing the need for larger autologous nerve grafts and late tendon opponensplasties.

Base of the Third Metacarpal as a Palpable and Reliable Landmark for Identifying the Median Nerve's Thenar Branch

PURPOSE

The objective of this study was to investigate whether the base of the third metacarpal can predict the location of the thenar branch (TB) of the median nerve and the accuracy of palpating the base of the third metacarpal.

METHODS

In 15 patients with ulnar nerve lesions around the elbow, we transferred the opponens motor branch to repair the deep terminal division of the ulnar nerve (DTDUN). Before surgery, we located the TB by palpating the base of the third metacarpal volarly. During surgery, we placed three needles at the following places: one at the entrance of the TB into the abductor pollicis brevis, another at the point where the TB contacted the thenar muscles, and third at the DTDUN's trajectory over the third metacarpal. We obtained fluoroscopic images and measured distances between the needles and structures with image software. We also examined the relationship between the TB, DTDUN, and the volar tubercle of the base of the third metacarpal in cadaver hands. Finally, we invited 22 surgeons to palpate the base of the third metacarpal on volunteer hands and verified their accuracy using fluoroscopy.

RESULTS

During surgery, after dissection and palpation of the TB, under fluoroscopy, we confirmed that the palpable bone prominence was the base of the third metacarpal. In cadaver dissections, we observed the TB crossing the volar tubercle of the base of the third metacarpal superficially from proximal to distal and from ulnar to radial. The DTDUN was, on average, 14 mm distal to the base of the third metacarpal distal limit. In total, 19 of the 22 surgeons correctly identified the base of the third metacarpal and consequently the trajectory of the TB.

CONCLUSIONS

The palpable base of the third metacarpal can be used to determine the trajectory of both the TB and DTDUN.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

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.

Interfascicular Anatomy of the Motor Branch of the Ulnar Nerve: A Cadaveric Study

PURPOSE

The motor branch of the ulnar nerve contains fascicles that innervate the intrinsic musculature of the hand. This cadaveric study aimed to describe the organization and consistency of the internal topography of the motor branch of the ulnar nerve.

METHODS

Five fresh-frozen cadaveric specimens with an average age of 74 years (range, 65-88 years) were dissected. The ulnar nerve was exposed and transfixed to the underlying tissues to maintain its orientation throughout the dissection. The dorsal cutaneous branch (DCB) and the volar sensory branch were identified and reflected to expose the motor branch. The fascicles to the first dorsal interosseus (FDI), flexor pollicis brevis, and abductor digiti minimi (ADM) were identified. Internal neurolysis was performed distal to proximal to identify the interfascicular arrangement of these fascicles within the motor branch. The organization of these fascicles was noted, and the branch points of the DCB, FDI, and ADM were measured relative to the pisiform using a handheld electronic caliper.

RESULTS

The internal topography of the motor branch was consistent among all specimens. Proximal to the pisiform, the arrangement from radial to ulnar was as follows: volar sensory branch, flexor pollicis brevis, FDI/intrinsic muscles, ADM, and DCB. The position of these branches remained consistent as the deep motor branch curved radially within the palm and traveled to the terminal musculature. The locations of the average branch points of the FDI, ADM, and DCB with respect to the pisiform were as follows: FDI, 4.6 cm distal (range, 4.1-4.9 cm), 4.5 cm radial (range, 4.1-4.9 cm); ADM, 0.65 cm distal (range, 0.3-1.1 cm), 0.7 cm radial (range, 0.3-1.1 cm), DCB, 7.7 cm proximal (range, 4.2-10.1 cm), and 0.4 cm ulnar (range, 0.3-0.8 cm).

CONCLUSIONS

The internal topography of the ulnar nerve motor branch was consistent among the specimens studied. The topography of the motor branches was maintained as the motor branch turns radially within the palm.

CLINICAL RELEVANCE

This study provides further understanding of the internal topography of the ulnar nerve motor branch at the wrist level.

Adductor Branch of Terminal Divisions of the Ulnar Nerve Transfer to the Thenar Motor Branch in a High Median Nerve Palsy: A Case Report

CASE

The author reports a 4-month-old high median nerve palsy in a 19-year-old man with right forearm fractures, stabilized with dynamic compression plates and screws. Surgical exploration revealed a large median nerve neuroma in the midarm that was excised, and the gap was bridged with sural nerve cable grafts. The extensor carpi radialis nerve was transferred to the anterior interosseous nerve in the forearm. The adductor branch of terminal divisions of the ulnar nerve was transferred to the thenar branch of the median nerve in the hand.

CONCLUSIONS

The adductor branch of ulnar nerve transfer to the thenar motor branch in high median nerve palsy efficiently restored thumb opposition in 10 months of follow-up. In addition, the patient's grasp and pinch improved, preserving thumb adduction.

Innervation of the lumbrical and interosseous muscles in hand: analysis of distribution of nerve fascicles and quantification of their surface projections

We aimed to determine the surface locations of the nerve fascicles that innervate the lumbricals and interossei, re-examine the branching pattern of the deep branch of the ulnar nerve (dUN), and provide a clear description of their course. Eleven fresh-frozen adult cadaver hands were investigated. Nerve fascicles that innervate the lumbricals, interossei, and surface landmarks including the distal wrist crease and 2-5 proximal finger creases were marked by radio opaque fibers and subjected to X-ray. We analyzed the images and set a quadrant-linked hand surface. Subsequently, we measured the lengths of both axes and the coordinates of the branch locations in the quadrant. The surface locations of branches that innervated the lumbricals and interossei were clearly quantified. The branches of dUN exhibited a 4-group distribution pattern. Novel methods for quantitatively locating the surface anatomy of these branches and demonstration of a 4-group branching pattern of the dUN were established.

Functional reconstructions using only ulnar nerve and ulnar nerve-innervated muscles for traumatic musculocutaneous, median and radial nerve palsies

A 20-year-old right-handed fisherman experienced a severe injury in a high-energy traffic accident. These injuries included a shaft fracture of the right humerus, open comminuted fracture of the right forearm and multiple peripheral nerve palsies involving the musculocutaneous, median and radial nerves. Six months after the initial treatment, the patient was referred to our hand surgeons for further treatment. Several operations for functional reconstruction using only the ulnar nerve and ulnar nerve-innervated muscles were performed: the main procedures included a partial ulnar nerve transfer for elbow flexion, flexor carpi ulnaris transfer for reconstruction of wrist and finger extension and opponensplasty using the abductor digiti minimi. Three years after the initial injury, the patient had relatively good function including elbow flexion and stable side pinch and grasp. Functional reconstruction using a combination of the ulnar nerve and ulnar nerve-innervated muscles may be useful in specific cases involving multiple peripheral nerve injuries.

Single incision thenar muscle reconstruction using the free functional pronator quadratus flap

Background

Injuries to the thenar muscle mass or the thenar branch of the median nerve and resulting loss of thumb opposition lead to a massive impairment of hand function. For decades, reconstructive approaches were based on tendon transfers. To broaden the reconstructive repertoire, we present the free functional pronator quadratus flap as a viable alternative for functional reconstruction and provide a specification for its indication. We demonstrate our surgical technique to a single incision reconstruction using the free functional pronator quadratus flap. Based on a series of three patients, which were analyzed for hand function using Kapandji’s score and the angle of Bourrel, grip strength and nerve conduction velocity in a two year follow up, we present an indication algorithm.

Results

After successful reinnervation of all flaps, we found an improvement of Kapandji’s score from 4.3 ± 0.94 preoperatively, to 8.7 ± 0.47 after two years. Accordingly, the angle of Bourrel decreased from 75.75 ± 3.45 degrees to 36.96 ± 3.68 degree. Grip strength also improved from 14 ± 2.2 kg to 26.2 ± 1.2 kg. No impairment of wrist pronation was observed.

Conclusion

We found excellent functional recovery of thumb opposition and strength, showing similar or even superior results compared to results from tendon transfers. With the benefit of a single incision surgery and therefore minimal donor site morbidity, this free functional muscle transfer is a viable alternative to classic tendon transfers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12893-021-01308-x.

Evaluation of muscle strength following peripheral nerve surgery: A scoping review

Peripheral nerve injury (PNI) can result in devastating loss of function, often with poor long-term prognosis. Increased use of peripheral nerve surgical techniques (eg, nerve transfer, nerve grafting, and nerve repair) has resulted in improved muscle strength and other functional outcomes in patients with PNI. Muscle strength has largely been evaluated with the British Medical Research Council (MRC) scale. MRC is convenient to use in clinical settings, but more robust measures of muscle function are necessary to fully elucidate patient recovery. This scoping review aims to examine alternative instruments used to assess muscle function in studies of peripheral nerve surgery for PNI of the upper and lower limbs. A scoping review was conducted using Ovid MEDLINE, CINAHL, EMBASE, and PubMed databases in May and December of 2020, yielding a total of 20 studies pertaining to the review question. Studies pertaining to handheld dynamometry, grip and pinch dynamometry, Rotterdam Intrinsic Hand Myometers, isokinetic dynamometry, ultrasonography, and electromyography were reviewed. We provide a synopsis of each method and current clinical applications and discuss potential benefits, disadvantages, and areas of future research.

[Selective nerve transfers for thenar branch reconstruction]

OPERATIVE

Reconstruction of thump opposition with selective nerve transfer of the motor branch of the abductor digiti minimi muscle (ADM) to the thenar motor branch.

INDICATIONS

Injury of the median nerve or thenar motor branch and resulting loss of thumb opposition.

CONTRAINDICATIONS

Combined median and ulnar nerve injuries or brachial plexus lesions of C8-Th1, or a time interval >12 months since denervation of the thenar branch.

SURGICAL TECHNIQUE

The ADM motor branch is microsurgically dissected and transferred to the thenar branch.

POSTOPERATIVE MANAGEMENT

After successful reinnervation, regular follow-ups and intensive physiotherapy are important for operative outcome.

RESULTS

Reconstruction of the opposition of the thumb results in improved range of motion as well as a gain of grip and pinch force.

A novel nerve transfer: The first palmar interosseous motor branch of the ulnar nerve to the recurrent motor branch of the median nerve

INTRODUCTION

The recovery of recurrent motor branch of the median nerve might be delayed in high level median nerve injuries due to the long reinnervation distance. The aim of this study is to define a novel nerve transfer to restore the opposition and pinch.

METHODS

Two fresh frozen hand cadavers were used for the study. The motor branch of the first palmar interosseous muscle of the ulnar nerve was identified and dissected. Thenar branch of the median nerve was dissected from its insertion site. The motor branch of the first palmar interosseous muscle of the ulnar nerve was transferred to the thenar motor branch of the median nerve. Axon counts were examined histopathologically. Clinically this nerve transfer was performed for two female patients with a high-level median nerve injury. Mehta opposition scores were 21 and 20, respectively and the results were satisfactory six months after the surgery.

DISCUSSION

Although exploration and repair are recommended as the first treatment for median nerve injuries, the waiting time until the motor branch is reinnervated is critical in high level lesions. Nerve transfers become very important for fast recovery.

CONCLUSIONS

This new nerve transfer proposal may be an important step in nerve transfer surgery.

Distal nerve transfer for thenar palsy: A cadaveric study

INTRODUCTION

Severe proximal median nerve palsies often result in irreversible thenar atrophy and thumb abduction function loss. Tendon transfer involves substantial limitations and challenges; but, distal nerve transfer may provide an alternative treatment. Our goal was to validate the anatomical suitability of two distal ulnar nerve branches for thenar muscle reanimation.

MATERIALS AND METHODS

We assessed nerve transfer to the recurrent branch of median nerve (RMN) in 16 embalmed cadaveric hands. The ulnar motor branch to the flexor digiti minimi brevis (FDMBn) and the ulnar motor branch to the third lumbrical (3rdLn) were assessed for transfer. Coaptation success was measured by the overlap of the nerve donor with the RMN and correspondence of nerve diameters.

RESULTS

The mean transferable length and width of the RMN were 20.7 ± 4.5 and 1.0 ± 0.3 mm, respectively. We identified an average of three branches in the branching anatomy from the ulnar nerve to the hypothenar muscles. The maximal transferable lengths and widths of the FDMBn and the 3rdLn were 13.8 ± 4.4 and 0.5 ± 0.1 mm and 24.1 ± 6.4 and 0.4 ± 0.1 mm, respectively. The overlap with the RMN of the FDMBn and 3rdLn was 9.0 ± 3.6 (2.0-15.3) and 17.8 ± 6.0 (4.7-27.5) mm, respectively.

CONCLUSIONS

This anatomical study demonstrates the feasibility of distal nerve transfers between the ulnar and median nerves in the hand for reanimation of thenar muscles. Ulnar motor donors of the BrFDMBn and 3rdLn likely represent the least morbid donors with short distances for regeneration and a single coaptation repair.

Transferring the Motor Branch of the Opponens Pollicis to the Terminal Division of the Deep Branch of the Ulnar Nerve for Pinch Reconstruction

PURPOSE

With ulnar nerve injuries, paralysis of the first dorsal interosseous (FDI) and the adductor pollicis (ADP) muscles weakens pinch. The likelihood that these muscles will be reinnervated following ulnar nerve repair around the elbow is very low. To overcome this obstacle, we propose a more distal repair: transferring the opponens pollicis motor branch (OPB) to the terminal division of the deep branch of the ulnar nerve (TDDBUN).

METHODS

We dissected 10 embalmed hands to study the anatomy of the thenar branches of the median nerve and TDDBUN. We also operated on 3 patients with recent ulnar nerve injuries around the elbow, suturing the ulnar nerve and transferring the OPB to the TDDBUN. Before and after surgery, we measured grasp, key pinch, and pinch-to-zoom strength using dynamometers. Pinch-to-zoom gesture consists of moving the index finger and thumb pulp toward each other for zooming out of an image on screen. Patients were followed for at least 15 months.

RESULTS

The thenar branch of the median nerve innervated the abductor pollicis brevis and opponens pollicis in all specimens, but only half the superficial head of the flexor pollicis brevis. The TDDBUN gave off a single motor branch to the transverse head of the ADP, 1 or 2 branches to the oblique head, and a final branch to the FDI. The ratio of myelinated fibers between the OPB and the TDDBUN was 3:5. Relative to the normal side, pinch-to-zoom strength was mostly affected by the ulnar nerve lesion, with strength decreased by 80% to 90%. After surgery, we observed reinnervation of the FDI and an 80% to 90% improvement in pinch-to-zoom strength.

CONCLUSIONS

Transferring the OPB to the TDDBUN provided reinnervation of the FDI and ADP, thereby contributing to pinch strength improvement.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic V.

A new method of measuring the thumb pronation and palmar abduction angles during opposition movement using a three-axis gyroscope

Background

Thumb opposition is vital for hand function and involves pronation and palmar abduction. The improvement of pronation is often used as one of the evaluation items of the opponensplasty method for severe carpal tunnel syndrome. However, most of the studies used substitution evaluation methods for measurement of the pronation angle. Thus, there is still no appropriate method for measuring thumb pronation angle accurately in carpal tunnel syndrome patients.

In recent reports, a wearable gyroscope was used to evaluate upper extremity motions and it can be possibly used for accurate measurement of the thumb pronation angle along the three-dimensionally moving bone axis.

Thus, we investigated the reliability of measuring thumb pronation using a gyroscope and evaluated whether this method can be used to detect opposition impairment.

Methods

The participants were volunteers with unaffected upper limbs (32 hands) and patients with carpal tunnel syndrome (27 hands). The pronation and palmar abduction angles during opposition movements were measured using a three-axis gyroscope that included a three-axis accelerometer. The gyroscope was fixed onto the first metacarpal bone and the thumb phalanx.

Results

The pronation and palmar abduction angles of the metacarpal bone and the palmar abduction angles of the phalanx significantly decreased in the carpal tunnel syndrome group. The pronation angle of the metacarpal bone during opposition movement peaked later than the palmar abduction angle in all hands.

Conclusions

We were able to measure the thumb pronation and palmar abduction angles using the three-axis gyroscope, and this tool was able to detect impairments of thumb opposition due to carpal tunnel syndrome. This could be a tool for measuring thumb and finger angles and for detecting impairments caused by various diseases.

Transfer of obturator nerve for femoral nerve injury: an experiment study in rats

BACKGROUND

Quadriceps palsy is mainly caused by proximal lesions in the femoral nerve. The obturator nerve has been previously used to repair the femoral nerve, although only a few reports have described the procedure, and the outcomes have varied. In the present study, we aimed to confirm the feasibility and effectiveness of this treatment in a rodent model using the randomized control method.

METHODS

Sixty Sprague-Dawley rats were randomized into two groups: the experimental group, wherein rats underwent femoral neurectomy and obturator nerve transfer to the femoral nerve motor branch; and the control group, wherein rats underwent femoral neurectomy without nerve transfer. Functional outcomes were measured using the BBB score, muscle mass, and histological assessment.

RESULTS

At 12 and 16 weeks postoperatively, the rats in the experimental group exhibited recovery to a stronger stretch force of the knee and higher BBB score, as compared to the control group (p < 0.05). The muscle mass and myofiber cross-sectional area of the quadriceps were heavier and larger than those in the control group (p < 0.05). A regenerated nerve with myelinated and unmyelinated fibers was observed in the experimental group. No significant differences were observed between groups at 8 weeks postoperatively (p > 0.05).

CONCLUSIONS

Obturator nerve transfer for repairing femoral nerve injury was feasible and effective in a rat model, and can hence be considered as an option for the treatment of femoral nerve injury.