Bringing the Below-Knee amputation out of the Civil War era: Utilization of the neurovascularized lateral compartment flap, TMR, and RPNI

Background

The Below-Knee amputation (BKA) remains a viable reconstructive option for threatened limb loss due to trauma, oncology, and vascular disease. However, the current procedural gold standard of simple osteotomy, traction neurectomy, and closure with a long posterior myocutanoeus flap can lead to less-than-optimal outcomes. Traction neurectomy is often associated with disorganized nerve growth, resulting in both residual limb pain (RLP) and phantom limb pain (PLP). The long posterior flap may result in residual limb widening, edema, muscle atrophy, and need for revisions to optimize prosthetic fit. With recent literature describing the benefits of both targeted muscle reinnervation (TMR) and/or regenerative peripheral nerve interfaces (RPNI) at the time of amputation, we describe a new approach for the reconstruction of the residual limb after BKA via the utilization of these peripheral nerve techniques and a lateral compartment rotational muscle flap that remains innervated by the superficial peroneal nerve.

Methods

Survey data from 25 consecutive patients who had below-knee amputation from October 2019 through October, 2021 with peripheral nerve preparation using TMR or RPNI and innervated vascularized rotational lateral compartment flap closure were analyzed retrospectively using a novel, graphic patient reported outcome pain interface. Patients were excluded from the pain interface if they had active residual limb wounds or their survey was not complete.

Results

Satisfactory results were achieved in 21 patients with this combination of TMR/RPNI and an innervated, vascularized lateral compartment rotational flap. 67% (n ​= ​14) of the patients were completely pain free, with 33% (n ​= ​7) reporting residual limb pain (RLP), 21% (n ​= ​4) reporting phantom limb sensation, and 5.3% (n ​= ​1) reporting PLP. 76% (n ​= ​16) of patients opted for a prosthetic limb and completed fitting in a median average of 82.5 days (IQR ​= ​52) or 11.7 weeks. Of those sixteen, 81% (n ​= ​13) were ambulating in a median average of 185 days (IQR ​= ​28) or 6 months. Only two patients reported associated residual limb wounds that inhibited them from achieving optimal prosthetic use. The residual limb region that correlated with the underlying superficial peroneal nerve within the lateral compartment flap was only indicated as a cause of RLP in two patients (9.52%).

Conclusion

The reconstructive amputation technique described provides for preservation of additional functional muscle, additional soft tissue coverage over the distal residual limb, and integration of TMR and RPNI for mitigation of post amputation neuropathic pain. Performing the BKA with an innervated, vascularized lateral compartment flap provides reliable soft tissue coverage, resulting in a lower incidence of wound dehiscence, residual limb revision, and time to prosthetic fitting.