What Factors Influence the Success of Medial Gastrocnemius Flaps in the Treatment of Infected TKAs?

BACKGROUND: Soft tissue defects after TKA are a potentially devastating complication. Medial gastrocnemius flaps occasionally are used to provide soft tissue coverage, most commonly with a periprosthetic joint infection. QUESTIONS/PURPOSES: We asked: (1) What were the rates of persistent or recurrent infection, implant survivorship, flap-related complications, and reoperation for patients who underwent medial gastrocnemius flap reconstruction for soft tissue coverage after TKA? (2) What were the Knee Society clinical and functional scores for patients who underwent medial gastrocnemius flap reconstruction for soft tissue defects after TKA? (3) What were the risk factors for failure of medial gastrocnemius flap reconstruction after TKA, with failure defined as recurrent or new periprosthetic joint infection or inability to reimplant the TKA prosthesis?
METHODS: Between 2003 and 2011, four surgeons at one institution performed 31 medial gastrocnemius flaps for soft tissue coverage over an infected TKA. Of those, 27 (87%) were available for followup at a minimum of 2 years (mean, 4 years; range, 2-6 years), although patients experiencing complications or treatment failures before two years were included. The study group consisted of 15 men and 12 women with a mean age of 61 years at the time of surgery (range, 36-86 years). The general indication for using a gastrocnemius flap in this setting was full-thickness soft tissue deficiency over the anterior knee during the course of treatment for concomitant deep infection. Six flaps were performed at prosthetic explantation and antibiotic spacer placement, eight at a spacer exchange, eight at second-stage TKA prosthesis reimplantation, and five at débridement with polyethylene exchange. The decision regarding when during staged treatment to place the flap was based solely on when the soft tissues were deemed insufficient, and not based on a belief that placement at one stage versus another was advantageous. Failure was defined as inability to undergo reimplantation of a TKA prosthesis or recurrence of periprosthetic joint infection. Patient and procedural characteristics were tested for association with failure. Survivorship was calculated by Cox proportional hazards modeling. Outcomes scores were drawn from a longitudinal institutional registry.
RESULTS: Fourteen of 27 (52%) patients had a persistent or recurrent infection; survivorship of the TKA prosthesis at 4 years was 48% (95% CI, 31%-66%). Although there were no flap-related complications, 12 patients had a total of 19 reoperations during the study period. Overall, the mean (± SD) Knee Society knee (38 ± 18 vs 65 ± 20; p < 0.001) and function (20 ± 22 vs 37 ± 25; p = 0.002) scores were improved at most recent followup. No factors were identified as associated with failure when a Bonferroni correction was applied.
CONCLUSIONS: Gastrocnemius flaps were used to address difficult soft tissue defects in this series, in the presence of deep infections; the high proportion of patients experiencing persistent or recurrent infections reflects the case complexity and not necessarily a problem with the flaps. However, this series highlights the need to continue to explore alternative approaches to managing this difficult clinical problem. Future studies should aim to establish an evidence-based reconstructive algorithm, focusing on host, wound, and timing characteristics that may maximize outcomes. LEVEL OF EVIDENCE: Level IV, therapeutic study.