Optimal Timing and Duration of Flap-Frame Immobilization: A Podoplastic Case Series

Flap-based and podoplastic limb salvage in the foot and ankle is difficult due to the presence of biomechanical forces that can impact flap healing and complication rates and, in turn, limb salvage rates. For this reason, external fixation is indicated to neutralize forces across the flap interface and allow for optimal flap take and healing. Although external fixation for flap immobilization is the current standard of care, not much is known about how duration and timing may impact complication and salvage rates.

We retrospectively identified and analyzed complication and limb salvage rates in 18 patients who underwent flap-frame immobilization with a multiplanar external fixator during a 4.75-year period.

Patients ranged in age from 40 to 75 years (mean, 55.5 years). Sixteen patients (88.9%) had diabetes mellitus, and all had defects that were a mean of 110.9 cm2 (range, 36-500 cm2) and required the use of a local or free flap. Thirteen defects (72.2%) were in the plantar region, with the remaining five (27.8%) in nonplantar regions. Eleven flaps (61.1%) were fasciocutaneous, and the remaining seven (38.9%) were vascularized muscle flaps. All of the flaps were immobilized with either a three- or four-ring circular external fixator. Overall, a 66.7% limb salvage rate (12 of 18) was observed with mean follow-up of 2.4 years, or 892.6 days (range, 222-1,555 days). Seven minor flap complications (38.9%) required a return to the operating room.

External fixation is an essential tool in flap-based limb salvage. These findings hint that the "Goldilocks zone" of duration is approximately 28 to 35 days. Furthermore, we believe that risk factors such as open amputation, increased defect size, and presence of Charcot's neuroarthropathy impact limb salvage rates regardless of duration and timing of flap-frame immobilization.