An assessment of fatigability following nerve transfer to reinnervate elbow flexor muscles

Reconstructing Pinch Strength after Ulnar Nerve Injury by Transferring the Opponens Pollicis Motor Branch

BACKGROUND

With ulnar nerve injuries, paralysis of the first dorsal interosseous and adductor pollicis muscle weakens the patient's pinch. In the palm, we transferred the opponens pollicis motor branch to the deep terminal division of the ulnar nerve for pinch reconstruction.

METHODS

Sixteen patients with ulnar nerve injuries around the elbow underwent reconstruction and were followed up postoperatively for a minimum of 14 months. Their mean age was 41 ± 16 years, and the mean interval between injury and surgery was 134 ± 126 days (range, 2 to 390 days). Preoperatively and postoperatively, grasp, key, and subterminal key pinch strength were measured using dynamometers.

RESULTS

Reinnervation of the first dorsal interosseous muscle was observed in 15 of the 16 patients. Mean grasp strength improved from 15.5 ± 8.5 kg preoperatively to 24 ± 10 kg postoperatively, achieving 57% ± 16% of contralateral hand strength. Preoperatively, terminal key pinch averaged 3 ± 1 kg, which improved postoperatively to 5.5 ± 2 kg, achieving 71 ± 24% of the strength measured contralaterally. Preoperatively to postoperatively, subterminal key pinch force increased from 0 to 2.4 ± 1.3 kg, achieving 61% ± 27% that of the unaffected side. Patients who underwent surgery within 6 months of their injury showed a mean subterminal key pinch strength recovery of 63% ± 27% of the normal side, whereas those who underwent surgery between 7 and 13 months after injury showed a mean subterminal key pinch strength recovery of 51% ± 29%.

CONCLUSION

Transferring the opponens pollicis motor branch to the deep terminal division of the ulnar nerve improved pinch and grasp strength without jeopardizing thumb function.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Self-assessed outcomes following double fascicular nerve transfer for elbow flexion

Background

Double fascicular nerve transfer (DFT) is often performed to re-animate the elbow flexors. Studies of motor recovery following this surgery have exclusively reported on the objective outcome of muscle power. Questionnaire studies allow researchers and clinicians to learn from patients and better direct care towards their needs. To date, no research has focused on self-assessed recovery following DFT for elbow flexion.

Methods

This observational cross-sectional study aimed to give an account of patient-assessed outcomes following DFT. The bespoke questionnaire included: (a) self-reported strength and (b) the Stanmore percentage of normal elbow assessment.

Results

Sixty-two patients participated in the study. Participants were grouped according to time post-surgery. Statistical analysis confirmed that data were comparable between groups (p=0.10).

Self-assessed strength

Median scores were 0.5 kg <2 years post-surgery, 3 kg at 2 to 5 years, 2 kg at 5 to 8 years and 1.3 kg in the >8 years group.

Stanmore Percentage of Normal Elbow Assessment

Mean scores (%) were 35 (SD ± 25) <2 years, 56 (SD ± 31) at 2 to 5 years, 44 (SD ± 25) at 5 to 8 years and 46 (SD ± 29) >8 years groups.

Conclusions

This is the first study of self-assessed recovery following DFT. Scores peaked around 4 years post-operation. Future research should focus on the long-term self-reported outcome of nerve transfer surgery.

Adult traumatic brachial plexus injuries: advances and current updates

Nerve grafting, tendon transfer and joint fusion are routinely used to improve the upper limb function in patients with brachial plexus palsies. Newer techniques have been developed that provide additional options for reconstruction. Nerve transfer is a tool for restoring upper limb function in total root avulsions where nerve grafting is not possible. In partial brachial plexus injuries, nerve transfers can greatly improve shoulder, elbow, wrist and hand function. Intraoperative electrical stimulation can be used to diagnose precisely which nerve is injured and to choose which nerve fascicles should be transferred. Finally, measuring the postoperative outcome can improve the evaluation of our techniques. The aim of this article was to present the current techniques used to treat patients with brachial plexus injury.

An assessment of co-contraction in reinnervated muscle

Aim: To investigate co-contraction in reinnervated elbow flexor muscles following a nerve transfer. Materials & methods: 12 brachial plexus injury patients who received a nerve transfer to reanimate elbow flexion were included in this study. Surface electromyography (EMG) recordings were used to quantify co-contraction during sustained and repeated isometric contractions of reinnervated and contralateral uninjured elbow flexor muscles. Reuslts: For the first time, this study reveals reinnervated muscles demonstrated a trend toward higher co-contraction ratios when compared with uninjured muscle and this is correlated with an earlier onset of muscle fatigability. Conclusion: Measurements of co-contraction should be considered within muscular function assessments to help drive improvements in motor recovery therapies.

Traumatic peripheral nerve injuries: diagnosis and management

PURPOSE OF REVIEW

To review advances in the diagnostic evaluation and management of traumatic peripheral nerve injuries.

RECENT FINDINGS

Serial multimodal assessment of peripheral nerve injuries facilitates assessment of spontaneous axonal regeneration and selection of appropriate patients for early surgical intervention. Novel surgical and rehabilitative approaches have been developed to complement established strategies, particularly in the area of nerve grafting, targeted rehabilitation strategies and interventions to promote nerve regeneration. However, several management challenges remain, including incomplete reinnervation, traumatic neuroma development, maladaptive central remodeling and management of fatigue, which compromise functional recovery.

SUMMARY

Innovative approaches to the assessment and treatment of peripheral nerve injuries hold promise in improving the degree of functional recovery; however, this remains a complex and evolving area.

Neurotization of musculocutaneous nerve with intercostal nerve versus phrenic nerve – A retrospective comparative study

Background:

Brachial plexus injuries are common after both blunt and penetrating traumas resulting in upper limb weakness. The nerve transfer to the affected nerve distal to the injury site is a good option where proximal stump of the nerve is unhealthy or absent which has shown early recovery and better results. Commonly used procedures to restore elbow flexion are ipsilateral phrenic or ipsilateral intercostal nerves (ICNs) in global plexus injuries. The use of both intercostal and phrenic nerves for elbow flexion is well described and there is no definite consensus on the superiority of one on another.

Methods:

All patients presented in the outpatient department of LNH and MC from January 2014 to December 2017 with pan plexus or upper plexus injury with no signs of improvement for at least 3 months were included in the study. After 3 months of conservative trial; surgery offered to patients.

Results:

A total of 25 patients (n = 25) were operated from January 2015 to December 2017. Patients were followed to record Medical Research Council (MRC) grades at 3, 6, 9, 12, and 18 months. The patients achieved at least MRC Grade 3; 70% at 12 months follow-up to 80% at 18 months in the phrenic nerve transfer group. While in the ICN transfer group, it is 86% and 100% at 12 and 18 months postoperative, respectively.

Conclusion:

Our study has shown better results with ICN transfers to musculocutaneous nerve, recorded on MRC grading system.

Volumetric MRI is a promising outcome measure of muscle reinnervation

The development of outcome measures that can track the recovery of reinnervated muscle would benefit the clinical investigation of new therapies which hope to enhance peripheral nerve repair. The primary objective of this study was to assess the validity of volumetric Magnetic Resonance Imaging (MRI) as an outcome measure of muscle reinnervation by testing its reproducibility, responsiveness and relationship with clinical indices of muscular function. Over a 3-year period 25 patients who underwent nerve transfer to reinnervate elbow flexor muscles were assessed using intramuscular electromyography (EMG) and MRI (median post-operative assessment time of 258 days, ranging from 86 days pre-operatively to 1698 days post- operatively). Muscle power (Medical Research Council (MRC) grade) and Stanmore Percentage of Normal Elbow Assessment (SPONEA) assessment was also recorded for all patients. Sub-analysis of peak volitional force (PVF), muscular fatigue and co-contraction was performed in those patients with MRC > 3. The responsiveness of each parameter was compared using Pearson or Spearman correlation. A Hierarchical Gaussian Process (HGP) was implemented to determine the ability of volumetric MRI measurements to predict the recovery of muscular function. Reinnervated muscle volume per unit Body Mass Index (BMI) demonstrated good responsiveness (R² = 0.73, p < 0.001). Using the temporal and muscle volume per unit BMI data, a HGP model was able to predict MRC grade and SPONEA with a mean absolute error (MAE) of 0.73 and 1.7 respectively. Muscle volume per unit BMI demonstrated moderate to good positive correlations with patient reported impairments of reinnervated muscle; co- contraction (R² = 0.63, p = 0.02) and muscle fatigue (R² = 0.64, p = 0.04). In summary, volumetric MRI analysis of reinnervated muscle is highly reproducible, responsive to post-operative time and demonstrates correlation with clinical indices of muscle function. This encourages the view that volumetric MRI is a promising outcome measure for muscle reinnervation which will drive advancements in motor recovery therapy.

Optimizing nerve transfer surgery in tetraplegia: clinical decision making based on innervation patterns in spinal cord injury

OBJECTIVE

Nerve transfers are increasingly being utilized in the treatment of chronic tetraplegia, with increasing literature describing significant improvements in sensorimotor function up to years after injury. However, despite technical advances, clinical outcomes remain heterogenous. Preoperative electrodiagnostic testing is the most direct measure of nerve health and may provide prognostic information that can optimize preoperative patient selection. The objective of this study in patients with spinal cord injury (SCI) was to determine various zones of injury (ZOIs) via electrodiagnostic assessment (EDX) to predict motor outcomes after nerve transfers in tetraplegia.

METHODS

This retrospective review of prospectively collected data included all patients with tetraplegia from cervical SCI who underwent nerve transfer at the authors' institution between 2013 and 2020. Preoperative demographic data, results of EDX, operative details, and postoperative motor outcomes were extracted. EDX was standardized into grades that describe donor and recipient nerves. Five zones of SCI were defined. Motor outcomes were then compared based on various zones of innervation.

RESULTS

Nineteen tetraplegic patients were identified who underwent 52 nerve transfers targeting hand function, and 75% of these nerve transfers were performed more than 1 year postinjury, with a median interval to surgery following SCI of 24 (range 8-142) months. Normal recipient compound muscle action potential and isolated upper motor neuron injury on electromyography (EMG) were associated with greater motor recovery. When nerve transfers were stratified based on donor EMG, greater motor gains were associated with normal than with abnormal donor EMG motor unit recruitment patterns. When nerve transfers were separated based on donor and recipient nerves, normal flexor donors were more crucial than normal extensor donors in powering their respective flexor recipients.

CONCLUSIONS

This study elucidates the relationship of the preoperative innervation zones in SCI patients to final motor outcomes. EDX studies can be used to tailor surgical therapies for nerve transfers in patients with tetraplegia. The authors propose an algorithm for optimizing nerve transfer strategies in tetraplegia, whereby understanding the ZOI and grade of the donor/recipient nerve is critical to predicting motor outcomes.

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.

How to assess the recovery of muscular function following nerve injury: A view from surgeons and patients

Patient experience of motor recovery from denervation paralysis is complex and textured. The Medical Research Council (MRC) system of grading muscle peak volitional force is widely used as a single measure of assessment. However, it is becoming clear that current motor function assessments are not reflecting the patient lived experience of muscle reinnervation. Therefore, this study aimed to engage international expert nerve surgeons in a classical Delphi process to achieve a consensus of opinion on the ideal clinical assessment of motor function. This was compared with patient-reported impairments of reinnervated muscle. Invitations to engage in the Delphi process were extended to expert peripheral nerve surgeons across two international specialist meetings. For comparison, patients who attended a "Nerve Injury Community Day" were invited to complete a questionnaire on patient-reported impairments of reinnervated muscle. Questions were designed on the basis of a literature review and the clinical experiences of a specialist nerve injury unit. A combination of direct yes/no, multiple choice, open-ended and Likert questions were employed throughout the questionnaires. Eighteen surgeons engaged with the Delphi process; 18 and 11 responded to the first and second rounds respectively. Thirty-one patients responded to the questionnaire. It was found that clinicians were strongly biased towards efferent assessments of muscular function, while patients strongly favoured muscular fatigue, co-contraction and pain when monitoring their own recovery. The findings suggest that current clinical assessments of muscular function are inadequate and should embody measurements of afferent muscular function to better reflect the lived experience of muscle reinnervation.

Intercostal to musculocutaneous nerve transfer in patients with complete traumatic brachial plexus injuries: case series

BACKGROUND

To recover biceps strength in patients with complete brachial plexus injuries, the intercostal nerve can be transferred to the musculocutaneous nerve. The surgical results are very controversial, and most of the studies with good outcomes and large samples were carried out in Asiatic countries. The objective of the study was to evaluate biceps strength after intercostal nerve transfer in patients undergoing this procedure in a Western country hospital.

METHODS

We retrospectively analyzed 39 patients from 2011 to 2016 with traumatic brachial plexus injuries receiving intercostal to musculocutaneous nerve transfer in a rehabilitation hospital. The biceps strength was graded using the British Medical Research Council (BMRC) scale. The variables reported and analyzed were age, the time between trauma and surgery, surgeon experience, body mass index, nerve receptor (biceps motor branch or musculocutaneous nerve), and the number of intercostal nerves transferred. Statistical tests, with a significance level of 5%, were used.

RESULTS

Biceps strength recovery was graded ≥M3 in 19 patients (48.8%) and M4 in 15 patients (38.5%). There was no statistical association between biceps strength and the variables. The most frequent complication was a pleural rupture.

CONCLUSIONS

Intercostal to musculocutaneous nerve transfer is a safe procedure. Still, biceps strength after surgery was ≥M3 in only 48.8% of the patients. Other donor nerve options should be considered, e.g., the phrenic or spinal accessory nerves.

Strategies for Peripheral Nerve Repair

PURPOSE OF REVIEW

This review focuses on biomechanical and cellular considerations required for development of biomaterials and engineered tissues suitable for implantation following PNI, as well as translational requirements relating to outcome measurements for testing success in patients.

RECENT FINDINGS

Therapies that incorporate multiple aspects of the regenerative environment are likely to be key to improving therapies for nerve regeneration. This represents a complex challenge when considering the diversity of biological, chemical and mechanical factors involved. In addition, clinical outcome measures following peripheral nerve repair which are sensitive and responsive to changes in the tissue microenvironment following neural injury and regeneration are required.

SUMMARY

Effective new therapies for the treatment of PNI are likely to include engineered tissues and biomaterials able to evoke a tissue microenvironment that incorporates both biochemical and mechanical features supportive to regeneration. Translational development of these technologies towards clinical use in humans drives a concomitant need for improved clinical measures to quantify nerve regeneration.

Evaluation of functional outcomes after brachial plexus injury

Major nerve injuries such as those of the brachial plexus present a significant challenge for both rehabilitation and evaluation of outcome. With these often complex and multi-faceted injuries, correct selection of outcome measures is important. Healthy nerve function in humans heightens our interactions with the world, creating quality and enjoyment through our experiences of movement and touch. Therefore, assessments should be holistic and representative of all of these features. This article considers the assessment and evaluation of all of the features of nerve injury: sensorimotor, sensation (including that of pain), function and the psychosocial aspects. Current practice is described and combined with clinical experience and research findings to provide suggestions and recommendations for the selection of the most appropriate tools for use with this patient group.