Soft Tissue Coverage of Complex Periprosthetic Defects in Patients With Total Knee Arthroplasty: Analysis of Factors That Influence Reconstructive and Functional Outcomes

Introduction. Wound breakdown following total knee arthroplasty (TKA) increases the risk of device exposure, infection, and major amputation. Although a variety of options to facilitate coverage of compromised knee joint prostheses exist, the relative safety, efficacy, and functional impact of each has not been determined. Objective. This study aims to identify those perioperative factors that influence reconstructive and functional outcomes in patients with periprosthetic TKA defects. Materials and Methods. A 5-year retrospective review of outcomes following surgical management of TKA wounds was undertaken. Data pertaining to the timing of presentation, type and frequency of operative interventions, rates of implant/limb salvage, ambulatory status, visual analogue scores (VAS) for pain, and complications were collected. Results. Thirty patients were identified during the study period with a mean follow-up of 20 months. Rates of limb salvage (66.7% vs. 91.7% vs. 75% vs. 0%, P < .001) and postoperative ambulation (100% vs. 83.3% vs. 75% vs. 54.5%, P = .036) were significantly different between patients who underwent primary closure, local muscle flap coverage, free tissue transfer coverage, and above-the-knee amputation, respectively. The number of debridements prior to definitive closure did not significantly influence rates of limb salvage (P = .21). Active tobacco use (odds ratio [OR], 4; 95% confidence interval [CI], 1.13-14.2; P = .03) and time to initial presentation from the index joint replacement (OR, 0.99; 95% CI, 0.9-1.0; P = .04) adversely impacted device salvage. Both of these factors similarly influenced the overall likelihood of limb salvage (OR, 6.5; 95% CI, 1.5-28.8; P = .01; OR, 0.99; 95% CI, 0.99-1.0; P = .04). The VAS scores were not significantly different between index closure types (P = .77) but were significantly lower for patients who required < 10 debridements prior to definitive closure (P = .02). Conclusions. Early intervention with limited-frequency, and thorough debridement and prompt soft tissue coverage optimizes the chances of functional limb salvage in patients with complex periprosthetic TKA wounds. These findings may inform practice patterns and surgical treatment of patients presenting with compromised TKA and suggest that early involvement by reconstructive surgeons should be advocated to optimize reconstructive and functional outcomes in this difficult patient population.

Wound breakdown and soft tissue defects around the joint following a total knee arthroplasty (TKA) can be catastrophic, with resultant device exposure and/or infection increasing the risk for limb loss. Currently, the literature is abundant with multiple reports attempting to create a simplified treatment algorithm.^1-6 Data derived from these publications, however, are often underpowered, contradictory, and lack generalized consensus regarding the ideal management of such wounds. Periprosthetic soft tissue defects around a TKA are difficult to treat because multiple clinical variables confound their management. These variables include the size, depth, and location of the wound; variations in the surrounding soft tissue quality and availability; presence of infection; and exposure of bone, joint space, and/or prosthesis. Other patient factors such as medical comorbidities, ambulatory capacity, and functional reserve may further limit reconstructive options. Given the multifactorial and complex nature of these wounds, a reliable and reproducible algorithm for soft tissue management in compromised TKA eludes the field. Thus, the burden of treatment is often shared between orthopedic and plastic surgeons who have little published evidence to guide proper management. To date, most series focus primarily on limb or device salvage as the primary endpoint(s), with few investigating perioperative variables that contribute to improved reconstructive outcomes, functional performance, and/or long-term morbidity.⁷

The investigators retrospectively reviewed their experience with periprosthetic wound complications following TKA at a high-volume, tertiary referral center for both total joint arthroplasty and advanced limb salvage.

The aim of this study was to identify those perioperative factors and patient characteristics that most significantly influence limb/device salvage, postoperative ambulation, and patient-centered outcomes following reconstruction of complex periprosthetic wounds in patients with TKA.

Following approval by the MedStar Georgetown University Hospital Institutional Review Board (Washington, DC), the plastic surgery and orthopedic departmental databases were queried to identify patients with a history of periprosthetic complications following TKA between January 2011 and December 2015. Patients were identified using International Classification of Diseases (ICD)-9 codes for knee arthritis (715.16, 715.26, 714.0, 715.96, and/or 905.4) and for periprosthetic infection (996.60 and/or 996.66). Patients were included for review if they presented with a periprosthetic soft tissue complication, such as infection or wound dehiscence, requiring coordinated endoprosthesis and soft tissue management by both an orthopedic arthroplasty specialist and a reconstructive wound care specialist (KKE or CEA). Patients < 18 years of age at the index operation, who required extensor mechanism reconstruction, and with an oncologic diagnosis, autoimmune disease, and/or absence of overlying soft tissue complication were excluded.

Surgical management by the plastic surgery and orthopedic teams was conducted in a coordinated manner, according to the MedStar Georgetown University Hospital institutional algorithm for periprosthetic complications (Figure 1). Each patient underwent serial debridement to the level of the deepest exposed tissue with interval use of negative pressure wound therapy until negative wound cultures and clinical signs of healing (ie, granulation, marginal epithelialization) were evident.

For patients with exposed prostheses, the joint capsule was thoroughly debrided and the device either salvaged or exchanged for an antibiotic spacer, based on the timing of exposure relative to TKA. Staged reconstruction with an antibiotic spacer was performed when infectious and/or exposure-related complications occurred > 4 weeks out from the index operation (ie, TKA). Within 4 weeks, however, device salvage was usually attempted with replacement of the polyethylene liner only. Delayed primary closure was performed whenever possible. If tension-free approximation could not be achieved, a medial gastrocnemius muscle flap with split-thickness skin graft was typically used for coverage (Figure 2). Free tissue transfer (FTT) was reserved for those patients in whom the gastrocnemius muscle was either nonviable or insufficient for reconstruction, as well as those in whom sacrifice of the gastrocnemius muscle would have posed an unacceptable risk of functional compromise (ie, high-performance athletes; Figure 3).

Patients underwent above-the-knee amputation (AKA) if they lacked a salvageable extensor mechanism, presented with a life-threatening infection, or if joint salvage was deemed otherwise futile (ie, intractable pain and stiffness). Patients who lacked an extensor mechanism were initially evaluated for reconstruction with allograft, autograft (ie, fascia lata), or composite FTT (ie, anterolateral thigh flap with vascularized fascia lata). These patients were excluded from review.

Data pertaining to age at initial presentation for soft tissue management, gender, comorbidities, and date of index TKA were collected. Laboratory values including hemoglobin A_1C, white blood cell (WBC) count, erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were recorded at the time of presentation. Types, timing, and frequency of operative interventions were recorded for both the orthopedic and plastic surgery teams. Complications after final closure by the plastic surgery team also were documented.

Primary outcome measures at the final follow-up visit included limb/device salvage, pain, and ambulatory status. Pain was assessed using a 10-point visual analog scale (VAS) for all patients. Secondary outcome measures included complications after definitive closure, such as recurrent infection, wound breakdown, or need for upstaging to a more complex method of wound closure (ie, converting a delayed primary closure to a muscle flap or FTT). The diagnosis of prosthesis infection was made in accordance with the Musculoskeletal Infection Society guidelines for periprosthetic joint infection, defined as the presence of a communicating sinus tract, an identical culture obtained from 2 separate tissue or fluid samples from the joint in question, or by the presence of 4 of 6 minor criteria: (1) elevated CRP or ESR; (2) elevated synovial WBC count; (3) elevated synovial neutrophil percentage; (4) gross purulence within the joint; (5) isolation of a pathogen from a single culture of periprosthetic fluid or tissue; and (6) more than 5 neutrophils per high-power field.⁸

A pooled analysis of all patients included in this study was performed to determine perioperative, patient, and treatment-specific variables that influenced outcomes. Logistic and linear regression models were utilized to determine statistical significance. Stratified analysis between cohorts also was performed using Chi-squared tests for categorical data and Kruskal-Wallis, Student’s t, and Wilcoxon rank sum tests for continuous variables. In addition, polychotomous ordinal logistic regression was used when variables were categorical and ordered. Where appropriate, confidence intervals (CI) were set at 95% and values of P < .05 were considered statistically significant.

Patient demographics and operative characteristics

During the study period, 363 patients with TKA-related complications were managed at the MedStar Georgetown University Hospital tertiary referral center for advanced limb salvage. Of these, 30 patients presented with periprosthetic soft tissue defects requiring coordinated orthoplastic intervention. In all cases, definitive reconstruction was achieved by means of delayed primary closure (n = 3), muscle flap coverage (n = 12), FTT (n = 4), or AKA (n = 11), according to the aforementioned algorithm. Fifteen (50.0%) patients were male, with a mean age of 65 years (range, 46–84 years) and average body mass index of 33 kg/m² (range, 21.7–70.6 kg/m²). Seven patients had diabetes (23.3%), 8 (26.7%) had peripheral vascular disease, and 18 (60.0%) reported tobacco use. Average length of follow-up was 66 months (range, 6–272 months). There were no significant differences in demographic data, comorbidities, smoking status, and follow-up for patients in the various treatment cohorts (Table 1).

The frequencies and characteristics of operative interventions are presented in Table 2. The mean number of operations prior to index closure and mean total operations during a patient’s course were 3.7 (range, 1–11; P = .14) and 8.2 (range, 6–14; P = .15), respectively. These values did not vary significantly across cohorts. Overall, 10% of patients required upstaging to a more sophisticated closure technique or conversion to AKA, with no significant difference across cohorts (P = .4). Mean number of operative revisions (ie, planned/unplanned spacer exchanges, soft tissue debridement, scar revision, debulking) after index closure were similar among delayed primary closure (4.0), muscle flap (6.0), FTT (6.3), and AKA (2.5) as their initial definitive management (P > .05).

Device and limb salvage

The overall rates of device and limb salvage were 79% and 84%, respectively (eTable 3). No significant difference in device (P = .26) or limb salvage (P = .7) was found between closure types. In pooled analysis, active tobacco use (odds ratio [OR], 4; 95% CI, 1.13–14.2; P = .03) and time to initial presentation from the index joint replacement (OR, 0.99; 95% CI, 0.9–1.0; P = .04) were found to adversely impact device salvage (eTable 4a and 4b). Both of these factors similarly influenced the overall likelihood of limb salvage (OR, 6.5; 95% CI, 1.5–28.8; P = .01; OR, 0.99; 95% CI, 0.99–1.0; P = .04; respectively) in the setting of compromised TKA. The number of revision operations after index closure trended toward decreased rates of device and limb salvage; however, this association did not reach statistical significance (P = .08 and P = .09, respectively).

Postoperative pain scores (VAS)

The overall mean postoperative VAS score was 3.1, with no differences across cohorts at final follow-up (eTable 3). Interestingly, when stratified into patients who underwent < 10 operations versus those who underwent > 10 operations, a significant reduction in the postoperative pain score was discovered (42% vs. 37%; P = .02; eTable 5). In other words, postoperative pain levels as measured by VAS scores decreased by 5% more in individuals who underwent < 10 total operations compared with those who underwent > 10 operations, showing a significant difference (P = .02). No other perioperative or patient factors were found to contribute significantly to a reduction in postoperative pain scores (eTable 6).

Ambulation

At final follow-up, the postoperative ambulation rate was 73% across all cohorts, with significantly more patients achieving ambulatory status in the delayed primary closure (3/3; 100.0%), muscle flap coverage (10/12; 83.3%), and FTT (3/4; 75.0%) cohorts when compared with those in the AKA (6/11; 54.5%) cohort (P = .04; eTable 3). No perioperative or patient-related factors were found to contribute significantly to the ambulatory prognosis (eTable 4a and 4b).

Complications

The overall complication rate across all cohorts was 13.3% (eTable 3). The overall rates of recurrent infection and wound breakdown following index closure were each 6.7%. These values did not vary significantly between cohorts (eTable 3). No perioperative or patient-specific factors were found to contribute significantly to recurrent infection or wound breakdown (eTable 6).

Upstaging to higher level closure or conversion to AKA

The rate of upstaging, or need for a more sophisticated reconstructive modality than performed at the index closure, was 10% overall, with no significant difference between closure types (eTable 3). No perioperative or patient factors were found to contribute significantly to the need for upstaging; however, the number of revision operations and total number of operations trended toward increased rates of upstaging (P = .05 and P = .05, respectively; eTable 6).

Total knee arthroplasty is an established operative procedure designed to cure gonarthrosis or permit limb salvage in cases of trauma and bony neoplasm. With an aging population, longer life expectancy, and younger age at index operation, it is projected that by 2030 the number of primary TKA operations will increase by 600% to more than 268 000 procedures per year.^9,10 With such a dramatic increase in the demand for this procedure, a parallel rise in the number of failures and complications may be expected.¹¹ Currently, up to one-fifth of knee joint replacements are complicated by soft tissue breakdown that leaves the prosthesis and surrounding bone susceptible to infection, exposure, and proximal amputation.^12,13 The need for serial debridement, revision implantations, lengthy hospitalizations, and long-term intravenous antibiotic therapy in a growing population leads to inefficient utilization of resources and places undue economic burden on the health care system. The analysis performed here sought to identify perioperative risk factors that are associated with adverse outcomes with an aim toward minimizing the aforementioned sequelae of post-TKA complications.

Treatment algorithm and influence of closure type on outcomes

Previous reports on compromised TKA have sought to determine an ideal treatment regimen for soft tissue management by comparing primary surgical outcomes of various flap types.^14-17 Given the heterogeneity of wounds and complexity involved in treating a prosthetic device in a dynamic, load-bearing joint, a one-size-fits-all approach to the management of periprosthetic defects represents an unrealistic goal. In their series of 29 TKAs, Nahabedian et al¹⁴ proposed a thoughtful algorithm for soft tissue management in both infected and noninfected joints. Their approach takes into account differences in wound size, location, and exposed tissues.¹⁴

At the authors’ institution, they adhere to the principles outlined in that series,¹⁴ whereby reconstruction follows a graduated reconstructive ladder algorithm (Figure 1). Small wounds without tension and/or exposed vital structures are closed primarily, while more extensive wounds and/or those with exposed deeper structures generally undergo local muscle flap coverage (generally gastrocnemius muscle) or FTT for definitive reconstruction. Defects that are not biomechanically stable or those complicated by progressive infection and/or life-threatening sepsis undergo AKA. It is important to note that conversion to AKA is only undertaken when limb salvage is futile. In the circumstance where the extensor mechanism is damaged, all attempts at reconstruction are made with either allograft, autograft (ie, fascia lata), or composite FTT (ie, anterolateral thigh flap with vascularized fascia lata). If these reconstructive attempts fail, arthrodesis is considered prior to amputation.

The investigators’ approach toward reconstruction also aims to optimize postoperative function. As such, they hesitate to offer gastrocnemius muscle flaps to otherwise young, active, and/or athletic patients. For this subpopulation, they prefer local or free fasciocutaneous flap coverage, because the sacrifice of muscle within the posterior compartment of the calf can lead to decreased strength and power of plantar flexion. This is particularly important for ambulatory patients and/or high-performance athletes, where prior reports have shown that harvest of these muscles for wound coverage significantly compromises functional capacity.^18-20

When reviewing the results of this study, it is important to take into account the implicit bias of wound type on outcomes. Other factors notwithstanding, the investigators hypothesized that there would be a bias toward improved outcomes for patients requiring less invasive reconstructions (ie, delayed primary closure), as these patients were more likely to present with smaller and more superficial defects. Similarly, they expected outcomes to gradually worsen as defects became more recalcitrant and as the need for more extensive intervention increased. This assumption was generally true. For instance, device salvage rates were higher in the delayed primary closure cohort, likely due to a lower rate of device exposure among patients who were able to undergo direct approximation, versus those who required flap reconstruction at initial presentation. This assumption is further supported by a 0% rate of recurrent infection following delayed primary closure.

Lastly, although revision operations were equivalent across cohorts, muscle flap and FTT were the only 2 groups with patients who required upstaging to a more complex closure type or conversion to AKA. The management of potential future complications and need for further operative interventions are important to consider when approaching these defects for the first time. Results from pooled analysis demonstrated that more frequent operations during a patient’s course adversely impacted patient-centered outcomes such as ambulation and pain

Perioperative and patient factors influencing successful outcomes

In the present review of patients who had undergone management of compromised TKA, the authors also sought to identify those factors that influenced successful device/limb salvage and patient-centered outcomes in TKA wounds, regardless of the type of soft tissue coverage performed. The results of this review suggest 2 main influences on successful surgical outcomes: (1) a shorter time interval between index joint replacement and presentation with wound, and (2) lack of active tobacco consumption. The ill effects of smoking on wound healing are well known,²¹ and it may be deduced that a longer interval between index joint replacement and presentation with a wound may lead to the development of more extensive defects with greater tissue necrosis, higher infection potential, exposure of prosthesis/bone, and/or wider surface area of involvement. The investigators’ observations suggest early detection and management of wound healing problems are of paramount importance in joint replacements, as rates of both limb and device salvage were significantly improved for patients who presented earlier following index TKA.

Postoperative pain was similarly affected by 2 main factors: (1) total number of operations required during a patient’s course, and (2) total number of revision operations following index closure. Specifically, postoperative pain was found to be adversely affected by more frequent surgical intervention. This observation is not surprising, as it is expected that patients will experience more pain (scarring/stiffness) while undergoing surgery, and this pain may ultimately inhibit their ability to ambulate. Higher pain levels have been shown to correlate with lower patient satisfaction in both primary arthroplasty and lower extremity soft tissue reconstruction.^22,23

Therefore, a natural progression follows that a delay in presentation may lead to more aggressive wounds that require more intensive surgical intervention. In turn, this may lead to not only decreased chances for limb and/or device salvage, but also increased pain and decreased ability to participate successfully in rehabilitation with an aim toward ambulation.

From these data, the investigators may deduce that earlier and more aggressive monitoring, together with close follow-up after initial signs of periprosthetic compromise in TKA, may be the most important steps in improving limb salvage, postoperative pain, and function. It also must be stated that these outcomes are influenced by confounding factors such as access to and participation in physical therapy and rehabilitation, discharge to home versus a long-term care facility, etc.

A multidisciplinary approach involving seamless coordination between plastic surgery, orthopedic surgery, and infectious disease teams at a tertiary care center specializing in salvage of total joint replacements is necessary for intensive surveillance of at-risk joints. Similar to the concept of the golden hour in trauma literature, a window of time may exist for patients with compromised prosthetic joint replacements to achieve optimal recovery. As health care systems move toward further consolidation and regionalization, a coordinated approach may be undertaken to identify those arthroplasty patients who may be at highest risk for wound breakdown or prosthesis failure, in order to refer them to a concentrated care center specializing in orthoplastic management of joint replacements.

This study is limited by its retrospective nature and relatively small sample size, which limited the role of statistical analysis and the authors’ ability to generate meaningful comparisons between closure types and/or identify significant differences in rates of device/limb salvage, ambulation, and pain scores between cohorts. Heterogeneity of indications for joint salvage, various reconstructive modalities, and multiple involved surgeons are potential confounders that also can influence surgical and patient-centered outcomes. Furthermore, incomplete documentation of wound characteristics (ie, size, location, depth of involvement) in the medical record precluded their inclusion in this analysis. Nevertheless, this study provides important initial data on external factors that influence outcomes in this complex patient population. As further research unfolds, a prospective multicenter study will be necessary to thoroughly investigate those factors that contribute to success or failure in periprosthetic limb salvage.

The incidence of TKA-related wound complications may concurrently increase with the rise in index operation as the population ages. As this may pose a burden to the health care system, investigations into factors contributing to limb salvage in periprosthetic wounds will be necessary. These data suggest delays in care decrease the likelihood of limb salvage and may contribute to worse functional and patient-centered outcomes. Future research is necessary and may lead to the creation of concentrated centers specializing in the salvage of joint replacements.

Affiliations: Department of Plastic and Reconstructive Surgery, MedStar Georgetown University Hospital, Washington, DC; and Department of Orthopaedic Surgery, MedStar Georgetown University Hospital

Correspondence: Karen K. Evans, MD, Associate Professor, Department of Plastic Surgery, Center for Wound Healing, MedStar Georgetown University Hospital, 3800 Reservoir Road, 1-PHC, Washington, DC 20007; karen.k.evans@gunet.georgetown.edu

Disclosure: The authors disclose no financial or other conflicts of interest.