Limb salvage of the traumatized lower extremity is predicated on an orthoplastic approach to fracture repair and concomitant soft-tissue reconstruction.1 Improvements in clinical protocol-driven trauma management and microsurgical expertise have led to limb salvage rates approaching 90 percent at tertiary Level I trauma centers.2–6 Bony union and adequate soft-tissue coverage are integrally related, and increasing attention has focused on optimal flap tissue selection to improve functional and aesthetic outcomes. The ideal free flap is one that restores lower extremity form and function, promotes osseous union, recovers sensibility, and minimizes donor-site morbidity.7 The choice of muscle versus fasciocutaneous free flaps for soft-tissue coverage of lower extremity traumatic defects is still debated.
Muscle free flaps have historically been reported to be superior to fasciocutaneous free flaps in the soft-tissue management of open contaminated wounds.8–10 Recent clinical evidence from single-center series suggests that muscle and fasciocutaneous free flaps achieve similar rates of limb salvage and functional recovery,5,6 but few studies have examined the need for secondary flap revisions and staged orthopedic procedures. Increasing enthusiasm for perforator flaps in the past decade has expanded the indications for fasciocutaneous free flaps in microsurgical reconstruction to include open tibial fractures2,5,6 and chronic osteomyelitis.11,12 Further clinical evidence is needed to guide a comprehensive evidence-based approach to lower extremity free flap selection to optimize reconstructive and functional outcomes.
This 17-year multicenter series of lower extremity traumatic free flaps assessed the impact of muscle versus fasciocutaneous free flap coverage on limb salvage, functional recovery, flap success, and primary bone healing. In addition, we examined patterns of secondary free flap procedures to identify key factors in flap selection that should be considered in the multidisciplinary management of lower extremity trauma.
PATIENTS AND METHODS
Following multicenter institutional review board approval, a retrospective review was performed on all patients undergoing muscle or fasciocutaneous free tissue transfer for lower extremity traumatic reconstruction at Duke University Medical Center from 1997 to 2013 (n = 370) and the University of Pennsylvania Health System from 2002 to 2013 (n = 148). Muscle and fasciocutaneous free flaps were compared in two defect subgroups: (1) acute traumatic injuries sustained within 30 days before reconstruction and (2) chronic defects secondary to traumatic sequelae, such as osteomyelitis and nonunion. Acute trauma was defined using a 30-day cutoff to account for variable timing of definitive reconstruction secondary to transfers from outside hospitals, adequate wound débridement, and injury stabilization. Only primary free flap reconstructions were included; second flaps following a failed primary flap were excluded from analysis.
Primary study outcomes included limb salvage, return to ambulation, the occurrence of intraoperative and/or postoperative flap thrombosis, flap salvage in the setting of thrombosis, flap loss, and nonunion requiring bone grafting in Gustilo grade IIIb tibial fractures. Return to ambulation was calculated as the time interval from reconstruction to full weight-bearing status. Intraoperative flap thrombosis was defined as recurrent venous or arterial thrombosis occurring during the primary flap procedure. Postoperative flap thrombosis was defined as any thrombotic event requiring emergent take-back for flap salvage following the conclusion of the primary flap procedure. Take-backs for the planned débridement of a necrotic flap with no salvage attempts initiated were excluded. Flap salvage in the setting of thrombosis was defined as any flap that did not result in total loss following intraoperative or postoperative thrombosis. Our secondary study endpoint was the rate of secondary flap procedures performed following primary reconstruction, including flap elevations for orthopedic procedures, secondary skin grafting, and aesthetic refinement procedures (e.g., complex tissue rearrangement/flap debulking, direct scar excision, suction-assisted lipectomy, and tissue expansion).
Baseline patient variables included sex, age, body mass index, current or past reported tobacco use, and the following comorbidities: hypertension, diabetes mellitus, coronary artery disease, and peripheral vascular disease. Defect variables included wound location (i.e., above knee, ankle to knee, and below ankle), Gustilo grade IIIb injury classification, hardware exposure, and the time interval from acute traumatic injury to flap reconstruction. Provider variables included the institution (Duke University or University of Pennsylvania) and the year of the flap procedure. Operative variables included flap size, split-thickness skin graft coverage, flap nerve coaptation, operative time, and estimated blood loss. All variables were analyzed per patient.
Univariable associations of flap choice with study variables were analyzed using the Fisher’s exact or chi-square test for categorical variables and the Mann-Whitney U and unpaired t-tests for continuous variables. Kaplan-Meier curves for cumulative limb salvage and return to ambulation were compared between flap groups using log-rank tests. Cox proportional hazard regression models were used to examine the possibility that flap choice was associated with limb salvage and functional recovery after adjusting for independent risk factors. First, univariable outcome associations were screened to identify candidate variables for inclusion in multivariable regression models (p < 0.10). Next, flap group was forced into multivariable models containing significant covariates retained by backward stepwise selection to determine covariate-adjusted effects of flap choice on outcomes. All tests were two-sided, with statistical significance assigned to values of p < 0.05. Statistical analyses were performed using R version 3.3.1 (The R Foundation for Statistical Computing, Vienna, Austria).
From 1997 to 2013, a total of 518 lower extremity free flaps were performed for acute traumatic injuries [n = 238 (46 percent)] or chronic traumatic sequelae [n = 280 (54 percent)], with a mean follow-up of 4.2 ± 9.1 years. Figure 1 shows the 307 muscle and 211 fasciocutaneous free flaps performed in this series. Muscle flaps were more commonly used to reconstruct acute rather than chronic traumatic defects (p < 0.01). Workhorse muscle flaps included the latissimus dorsi (n = 149) and gracilis flaps (n = 106). Common fasciocutaneous flaps were the anterolateral thigh (n = 109) and radial forearm flaps (n = 53). The overall rates of flap loss and limb amputation were 8 percent (n = 43) and 6 percent (n = 32), respectively. The mean return time to ambulation was 6.1 ± 9.1 months after flap reconstruction.
Baseline Clinical Characteristics
Table 1 shows a comparison of baseline clinical characteristics by flap type in acute and chronic trauma subgroups. Muscle flaps were preferred for mid-third lower extremity defects (ankle to knee), whereas fasciocutaneous flaps were favored for distal ankle and foot wounds (p < 0.01). Muscle flaps were more commonly used to reconstruct Gustilo grade IIIb injuries (p < 0.01) and acute traumatic defects with exposed hardware (p < 0.01). Intraoperatively, muscle flaps were significantly larger than fasciocutaneous flaps (p < 0.01 for acute trauma; p = 0.02 for chronic trauma) and commonly required split-thickness skin graft coverage (p < 0.01 for both trauma subgroups). Fasciocutaneous flaps were associated with a longer operative time (p = 0.04 for acute trauma; p = 0.02 for chronic trauma). Muscle flaps were associated with greater estimated blood loss during surgery (p = 0.01 for acute trauma; p < 0.01 for chronic trauma). Patterns in flap selection differed significantly by provider institution (p <0.01) and evolved in favor of fasciocutaneous flaps over the 17-year study period (p < 0.01).
Reconstructive and Functional Outcomes
Table 2 shows a comparison of reconstructive outcomes following muscle versus fasciocutaneous free tissue transfer. No significant differences between flap groups were observed in the rates of flap thrombosis (p = 0.34 for acute trauma; p = 0.36 for chronic trauma), flap salvage in the setting of flap thrombosis (p = 1.00 for acute trauma; p = 1.00 for chronic trauma), and flap loss (p = 0.18 for acute trauma; p = 0.33 for chronic trauma). Flap group was not associated with postoperative rates of tibial nonunion requiring bone grafting in patients who sustained Gustilo grade IIIb tibial fractures. In Kaplan-Meier survival curve analysis, muscle and fasciocutaneous flaps achieved similar cumulative limb salvage rates in acute trauma (90 percent versus 94 percent; p = 0.56) and chronic trauma subgroups (90 percent versus 88 percent; p = 0.51) (Fig. 2, above). In addition, flap choice was not associated with functional recovery among acute trauma (median ± SE, 5.0 ± 0.49 months versus 4.33 ± 0.56 months; p = 0.83) and chronic trauma patients (median, 3.47 ± 0.46 months versus 3.70 ± 0.54 months; p = 0.49) (Fig. 2, below).
Cox proportional hazard regression models were used to examine the possibility that flap choice was associated with limb salvage and functional recovery after adjusting for independent risk factors. First, univariable outcome associations were screened to identify candidate variables for inclusion in multivariable regression models (p < 0.10). Next, flap group was introduced into the multivariable models containing significant covariates retained by backward stepwise selection. Tables 3 and 4 show the covariate-adjusted associations of flap choice with cumulative limb salvage and return to ambulation, respectively. Cumulative limb salvage was not associated with the use of fasciocutaneous flaps among acute trauma patients, adjusted for defect hardware exposure and flap size [hazard ratio (HR), 0.67; 95 percent CI, 0.08 to 5.60; p = 0.72] or among chronic trauma patients, adjusted for operative time and provider institution (HR, 1.41; 95 percent CI, 0.42 to 4.74; p = 0.58) (Table 3). Return to ambulation was not associated with the use of fasciocutaneous flaps among acute trauma patients, adjusted for Gustilo grade IIIb injuries and primary split-thickness skin graft coverage (HR, 0.73; 95 percent CI: 0.51 to 1.05; p = 0.09) or among chronic trauma patients, adjusted for defect hardware exposure and reconstruction year (HR, 1.12; 95 percent CI, 0.80 to 1.55; p = 0.51) (Table 4).
Secondary Flap Procedures
Table 5 summarizes the secondary procedures performed after the primary free flap operation. Approximately one-third of all patients underwent a secondary flap refinement procedure, such as complex tissue rearrangement/flap debulking, direct scar excision, suction-assisted lipectomy, and tissue expansion. No differences were noted in the rates of secondary flap refinement between the two flap groups. In patients with Gustilo grade IIIb injuries and/or exposed defect hardware, fasciocutaneous flaps were more commonly reelevated for orthopedic procedures, including staged primary bone grafting, hardware manipulation, and bone grafting for nonunion (p < 0.01 for acute trauma; p = 0.03 for chronic trauma). In addition, muscle flaps more commonly required secondary skin grafting procedures in the acute trauma subgroup (p = 0.01).
This 17-year multicenter study of 518 patients is the largest published outcomes analysis of muscle versus fasciocutaneous free tissue transfer in lower extremity traumatic reconstruction. We found that muscle and fasciocutaneous free flaps achieved similar rates of limb salvage and functional recovery in patients with acute and chronic traumatic wounds, adjusting for defect, flap, and provider characteristics. In addition, flap choice did not differentially impact the rates of flap success, take-backs, salvage, or the rates of bony nonunion in patients who sustained Gustilo grade IIIb tibial fractures. Importantly, fasciocutaneous flaps enabled flap reelevation for subsequent orthopedic procedures and limited the need for secondary skin grafting. Our multicenter experience spanning nearly two decades reflects a fundamental paradigm shift toward fasciocutaneous free flaps as our predominant flap choice in microsurgical lower extremity reconstruction. This study describes important indications for muscle versus fasciocutaneous free flaps and provides level III clinical outcomes evidence to optimize flap selection for acute and chronic traumatic lower extremity defects.
Our findings show that muscle and fasciocutaneous free flaps are similarly effective in restoring lower extremity form and function after traumatic injury, with comparable rates of limb salvage, return to ambulation, flap success, flap salvage, and primary fracture healing. Muscle free flaps have historically been regarded to be superior to fasciocutaneous free flaps for soft-tissue coverage of open lower extremity traumatic wounds.8–10 Our study corroborates recent clinical evidence from smaller scale series suggesting that fasciocutaneous flaps achieve similar reconstructive and functional outcomes in the management of traumatic defects, including open tibial fractures5,6 and chronic osteomyelitis.11,12 Importantly, our multicenter study shows no risk-adjusted effect of flap choice on limb salvage and functional recovery, after controlling for confounding baseline factors independently associated with outcomes. In the acute traumatic setting, defect hardware exposure and flap size were independently predictive of worse cumulative limb salvage, whereas Gustilo grade IIIb fractures were independently associated with lower cumulative rates of return to ambulation. Collectively, our findings show that muscle and fasciocutaneous free flaps are similarly successful in achieving limb salvage and functional recovery. These outcomes remain heavily influenced by the severity of the original defect.
Our analysis of secondary free flap procedures highlights certain advantages of fasciocutaneous flaps that should be considered in the orthoplastic management of lower extremity trauma. First, fasciocutaneous flaps enabled reelevation for subsequent orthopedic procedures in patients who had open fractures and/or exposed wound hardware, such as internal screws and/or metal plates. Bony union and adequate soft-tissue coverage are integrally related, and both orthopedic and plastic surgeons should consider all aspects of fracture repair, soft-tissue management, and rehabilitation when planning a reconstruction.7 In our experience, fasciocutaneous flaps are ideal for soft-tissue coverage of bony defects when staged bone grafting or fixation is required for optimal bony reconstruction and union. Fasciocutaneous flaps can be easily reelevated for such procedures, as the flap has a subcutaneous dermal plexus and heals in a manner that creates a partially avascular plane over the hardware.2,6 Although we did not evaluate flap complications related to reelevation, muscle flaps become indurated as they heal and we have found that they are prone to partial flap necrosis and poor interface healing after reelevation. In addition, our study shows that the use of fasciocutaneous flaps limited the need for secondary skin grafting, which may reduce the number of surgical sites and secondary operations. Although this study did not examine secondary procedures performed at the donor site, fasciocutaneous flaps spare functional muscle units and have been reported to minimize donor-site morbidity.13
Overall, our study reflects a paradigm shift in free flap selection over the past two decades, with the use of fasciocutaneous flaps rising from 25 percent (1997 to 2000) to 65 percent (2009 to 2013) in our multicenter series and up to 73 percent at the institution of the senior author (L.S.L.). Muscle flaps, such as the latissimus dorsi flap, were commonly used for extensive proximal leg injuries and remain our first choice in the reconstruction of massive three-dimensional soft-tissue defects requiring pliable tissue bulk. However, increasing familiarity with perforator flaps has expanded the applicability of fasciocutaneous free flaps for limb salvage and led to the use of chimeric fasciocutaneous flaps to suit individual reconstructive needs.14–18 Fasciocutaneous flaps, such as the anterolateral thigh flap, can be used to fill dead space using a segment of the vastus lateralis muscle,19 restore sensibility by including the lateral cutaneous nerve,20 and serve as a flow-through conduit for limb revascularization.21 Based on our anecdotal experience, fasciocutaneous flaps also provide a superior aesthetic result compared to traditional skin-grafted muscle or myocutaneous flaps. Of note, we found that fasciocutaneous flaps were associated with an increased operative time in agreement with previous reports,2,5 although this was not predictive of limb salvage or functional outcomes. Fasciocutaneous free flaps may have a steeper learning curve,22 and surgeon comfort level with a given flap may also guide flap selection. In summary, our multicenter study provides level III clinical evidence to dispel the notion that muscle free flaps are inherently superior to fasciocutaneous free flaps in the management of open lower extremity wounds. The ideal free flap is one that restores function and form, promotes bony union, recovers sensibility, and limits donor-site morbidity.7 Free flap selection in lower extremity traumatic reconstruction should be based on defect characteristics, such as wound location, size, and deficient tissue components, and the reconstructive needs of the patient.
This retrospective study has limitations. First, patients undergoing muscle versus fasciocutaneous free flap reconstruction may differ in patient, defect, and procedural factors not captured in this study. Clinical patient evaluation and overall fitness status are difficult to discern retrospectively and are critical in preoperative risk assessment and flap selection. Second, we did not collect data on the presence of multiple or contralateral traumatic injuries, American Society of Anesthesiologists status, or donor-site morbidity, which may be related to flap choice and influence the reported cumulative rates of limb salvage and functional recovery. In addition, we did not evaluate flap complications related to flap reelevation in either flap group. Our analysis of flap reelevation has inherent selection bias and reflects our preferential use of fasciocutaneous flaps when staged orthopedic procedures are required. Finally, this multicenter study spans nearly two decades of our experience with a heterogeneous trauma patient population and may be prone to evolving patterns in patient selection, clinical protocol-driven practice, and level of surgeon experience not captured herein. Future prospective studies comparing lower extremity free flap outcomes should consider specific functional assessments, aspects of donor-site morbidity (e.g., sensibility), and aesthetic results to optimize lower extremity reconstructive management.
This 17-year multicenter study demonstrates that muscle and fasciocutaneous lower extremity free flaps achieve similar rates of limb salvage, functional recovery, and flap success. In addition, fasciocutaneous free flaps permitted reelevation for subsequent orthopedic procedures and limited the need for secondary skin grafting. Fasciocutaneous free flaps may be optimal for composite bony and soft-tissue defects that require staged orthopedic procedures. Our study highlights important advantages of fasciocutaneous free flaps that should be considered when planning a lower extremity reconstruction.
The authors thank the following individuals who contributed to the management of patients in this study: Detlev Erdmann, M.D., Ph.D., M.H.Sc., Howard Levinson, M.D., David W. Low, M.D., Joseph M. Serletti, M.D., and Liza C. Wu, M.D. They also thank Jennifer Gallagher and Robyn Broach for assistance in the preparation of the institutional review board for this work.
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