John Matthew Felder

Summary: Chronic neuropathic pain following major limb amputation has historically been difficult to treat. In patients undergoing lower extremity amputation, “preemptive” targeted muscle reinnervation (TMR) nerve transfers may be performed concurrently with the amputation to help mitigate the risk of chronic neuropathic postoperative pain. Despite clinical studies demonstrating efficacy of TMR in lower extremity amputations, few procedural descriptions have been written, and none have been written regarding performing TMR at the knee disarticulation (KD) level of amputation. Although uncommonly utilized, the KD amputation has clear functional benefits over other levels of amputation for nonambulatory patients. As nonambulatory patients are also subject to the occurrence of chronic neuropathic postamputation pain, it stands to reason that the addition of TMR to KD surgery could be an improvement to standard techniques. In this report, we provide a technical description for concurrent TMR with KD and describe the rationale for its use.

Summary: Distal lower extremity wounds are a challenging problem for reconstructive surgeons and can lead to major lower extremity amputations in patients with comorbid conditions. The reverse sural artery flap (RSAF) is a local flap supplied by perforators of the peroneal artery that can cover defects of the distal lower extremity, ankle, and foot. There has been concern over performing the RSAF in patients with venous insufficiency, peripheral artery disease, and diabetes, and in older patients due to the increased risk of flap necrosis. In patients who are not microsurgical candidates, the RSAF may be the final option for reconstruction before undergoing major lower extremity amputation. We describe our experience with two patients with significant comorbidities and single vessel runoff from the peroneal artery due to atherosclerotic disease who successfully underwent RSAF reconstruction for distal lower extremity wounds.

Summary: Targeted muscle reinnervation (TMR) has emerged as a useful solution to the problem of painful neuromas and is increasingly being applied in many clinical circumstances. Relatively little has been written about TMR for painful neuromas of the hand, and what has been written describes use of the intrinsic muscles as recipients for the nerve transfer. Except in cases of amputation, intrinsic muscle sacrifice carries morbidity. Furthermore, TMR to intrinsic muscles will place the nerve coaptation in areas subject to pressure with loading of the palm. For these reasons, the pronator quadratus may be a preferable target muscle when performing TMR for painful neuromas of the hand. In this report, we describe the rationale for its use and demonstrate the surgical technique and outcomes with case examples.

Summary: The reconstruction of distal extremity wounds poses a unique surgical challenge. In free tissue transfer, a thin, pliable skin flap is the ideal. Obese patients have a paucity of thin skin donor sites. Herein we report the discovery of a free SHRIMP flap (Superthin Harvest of a Reliable Islanded Medial Pannus flap) based on the SIEA vessels, harvested from a thick abdominal pannus at the time of cosmetic abdominoplasty. A 61-year-old woman with a chronic wound of the right Achilles tendon was evaluated for reconstruction after failing conservative measures. At the time of consultation, the patient expressed interest in abdominoplasty. Therefore, a skin flap from the abdomen or rectus abdominis muscle flap in the context of an abdominoplasty was offered. Despite obesity affecting the pannus, the superficial inferior epigastric vessels were found to course superficially beneath the dermis at time of abdominoplasty. This allowed straightforward harvest of a superthin flap of skin and minimal subcutaneous fat, which contoured to the ankle with an aesthetically pleasing outcome. The patient was satisfied with the results of her abdominoplasty and coverage of her chronic wound. The SHRIMP flap provides a straightforward, axial pattern, superthin free skin flap based on the superficial inferior epigastric vessels, and represents a useful option in obese patients. The flap can be combined with abdominoplasty for an aesthetic donor site.

Background: Although it was initially described for improved myoelectric control, targeted muscle reinnervation (TMR) has quickly gained popularity as a technique for neuroma control. With this rapid increase in utilization has come broadening indications and variability in the described technique. As a result, it becomes difficult to interpret published outcomes. Furthermore, there is no literature discussing the management of failed cases which are undoubtedly occurring. Methods: This is a retrospective case series of two patients who underwent revision surgery for failed TMR. The authors also review the current literature on TMR and outline technical and conceptual pitfalls and pearls based on our local experience. Results: Excessive donor nerve redundancy, kinking, donor–recipient nerve size mismatch, superficial placement of the nerve coaptation, inappropriate target selection, and incomplete target muscle denervation were identified as technical pitfalls of TMR surgery. Techniques to avoid these pitfalls were described. Conclusions: Although TMR has been a major development in amputee care for both pain management and improved myoelectric control, it is important to acknowledge that it is not a foolproof surgery and does not provide a guaranteed result. Failed cases of TMR represent opportunities to learn about factors contributing to unfavorable outcomes and refine our techniques empirically.

High-frequency alternating current (HFAC) can yield a rapid-acting and reversible nerve conduction block. The present study aimed to demonstrate the successful implementation of HFAC block delivery via regenerative macro-sieve electrodes (MSEs). Dual-electrode assemblies in two configurations [dual macro-sieve electrode-1 (DMSE-I), DMSE-II] were fabricated from pairs of MSEs and implanted in the transected and subsequently repaired sciatic nerves of two male Lewis rats. After four months of postoperative nerve regeneration through the MSEs' transit zones, the efficacy of acute HFAC block was tested for both configurations. Frequencies ranging from 10 kHz to 42 kHz, and stimulus amplitudes with peak-to-peak voltages ranging from 2 V to 20 V were tested. Evoked muscle force measurement was used to quantify the nerve conduction block. HFAC stimulation delivered via DMSE assemblies obtained a complete block at frequencies of 14 to 26 kHz and stimulus amplitudes of 12 to 20 V p-p. The threshold voltage for the complete block showed an approximately linear dependence on frequency. The threshold voltage for the partial conduction block was also approximately linear. For those frequencies that displayed both partial and complete block, the partial block thresholds were consistently lower. This study provides a proof of concept that regenerative MSEs can achieve complete and reversible conduction block via HFAC stimulation of regenerated nerve tissue. A chronically interfaced DMSE assembly may thereby facilitate the inactivation of targeted nerves in cases wherein pathologic neuronal hyperactivity is involved.