Prophylactic Regenerative Peripheral Nerve Interfaces in Elective Lower Limb Amputations

Managing Major Peripheral Nerves in Forearm-Level Amputations With TMR and RPNI: What's the Best Recipe?

BACKGROUND

Targeted muscle reinnervation (TMR) and regenerative peripheral nerve interface (RPNI) prevent symptomatic neuroma formation in amputees. Forearm-level amputations present multiple muscular targets, making it challenging to determine the ideal treatment. The purpose of this study was to evaluate the best TMR targets, role of RPNI, and appropriate patient-selection criteria in forearm-level amputations. We hypothesized that deep and distal TMR targets would best prevent symptomatic neuromas, RPNI would prove a success adjunct, and patients with poorly controlled diabetes would not develop symptomatic neuromas regardless of nerve management.

METHODS

We retrospectively identified forearm-level amputations performed between 2017 and 2022. Patients with TMR by outside providers, follow-up <6 months, or insufficient documentation were excluded. Demographics, surgical nerve management, and postoperative complications were collected. The primary outcome was development of a painful neuroma determined by the Eberlin criteria. Patients undergoing TMR were divided a priori into two groups, superficial and proximal versus deep and distal TMR targets, and were compared.

RESULTS

Thirty-nine patients met inclusion criteria, and 16 developed a symptomatic neuroma. No patients with a deep or distal TMR target developed a symptomatic neuroma. One nerve out of 12 treated with RPNI developed a symptomatic neuroma. No patient with poorly controlled diabetes developed a symptomatic neuroma, despite no advanced nerve management.

CONCLUSIONS

In a case series of forearm amputations, deep and distal TMR targets prevented symptomatic neuroma formation more than superficial and proximal targets. Regenerative peripheral nerve interface is a useful adjunct for neuroma control, especially for the radial sensory nerve. Patients with poorly controlled diabetes may not require advanced nerve management.

LEVEL OF EVIDENCE

Level IV retrospective case series.

Regenerative peripheral nerve interface reduces the incidence of neuroma in the lower limbs after amputation: a retrospective study based on ultrasound

BACKGROUND

Amputees suffer from symptomatic neuroma and phantom limb pain. Regenerative peripheral nerve interface (RPNI) has recently been regarded as an effective method to prevent neuroma after amputation. However, the verifications of RPNI efficacy are mostly based on subjective evaluation, lacking objective approaches. This study aims to unveil the effect of RPNI on preventing neuroma formation and provide evidence supporting the efficacy of RPNI based on ultrasound.

METHODS

Amputees of lower limb at Peking University People's Hospital from July 2020 to March 2022 were analyzed retrospectively. The clinical data collected consisted of general information, pathology of primary disease, history of limb-salvage treatment, amputation level of nerve, pain scales such as the Numerical Rating Scale (NRS) and the Manchester Foot Pain and Disability Index (MFPDI). Three months after amputation, the transverse diameter, anteroposterior diameter, and cross-sectional area of neuromas in stump nerves at the end of residual limbs were measured using ultrasound and compared to adjacent normal nerves.

RESULTS

Fourteen patients were enrolled in the study, including 7 in the traditional amputation group (TA group) and 7 in the RPNI group. There was no significant difference in basic information and amputation sites between the two groups. The NRS and MFPDI scores of patients in RPNI group were significantly lower than those in TA group, and decreased with the follow-up time increasing, indicating that RPNI could reduce symptomatic neuroma pain. The comparison of preoperative ultrasound and postoperative pathology showed ultrasound could reflect the size of neuroma in vivo. Independent-sample t tests indicated that the ratios of anteroposterior diameter, transverse diameter and area of the cross section of both the neuroma and adjacent normal nerve obtained via ultrasound were significantly reduced in the RPNI group.

CONCLUSION

This study suggested that RPNI can effectively prevent the formation of symptomatic neuroma after amputation using ultrasound.

Regenerative Peripheral Nerve Interfaces Effectively Prevent Neuroma Formation After Sciatic Nerve Transection in Rats

Objective

The disordered growth of nerve stumps after amputation leading to the formation of neuromas is an important cause of postoperative pain in amputees. This severely affects the patients' quality of life. Regenerative peripheral nerve interfaces (RPNIs) are an emerging method for neuroma prevention, but its postoperative nerve growth and pathological changes are yet to be studied.

Methods

The rat sciatic nerve transection model was used to study the effectiveness of RPNI in this experiment. The RPNI (experimental) group (n = 11) underwent RPNI implantation after sciatic nerve transection, while the control group (n = 11) only underwent sciatic nerve transection. Autotomy behavior, ultrasonography, and histopathology were observed for 2 months postoperatively.

Results

Compared to the control group, the incidence and size of the neuromas formed and the incidence and extent of autotomy were significantly reduced in the RPNI group. The axon density in the stump and degree of stump fibrosis were also significantly reduced in the RPNI group.

Conclusion

RPNI effectively prevented the formation of neuromas.