Faculty Bibliography

BACKGROUND:Prolonged retention of antibiotic-loaded articulating spacers after the first stage of a two-stage revision for periprosthetic joint infection (PJI) can occur because of patient preference, surgeon preference, or medical reasons that prevent the planned second stage. Little is known about the frequency of persistent infections, mechanical complications, and functional results in patients with retained spacers. QUESTIONS/PURPOSES/OBJECTIVE:At a minimum follow-up of 2 years after spacer placement, among patients who do not undergo the second stage revision (replacement of the spacer with a definitive prosthesis of the hip or knee): (1) What was the survival of the spacer free from unplanned reoperation or removal, the cumulative incidence of symptomatic infection, and the overall (Kaplan-Meier) survivorship of the patients? (2) What is the cumulative incidence of mechanical complications (spacer fracture or dislocation)? (3) What is the ambulatory status of patients who have retained their spacers? METHODS:Between March 2011 and July 2023, a total of 111 and 152 patients underwent first-stage revision with an articulating spacer placement as part of a planned two-stage procedure for chronic PJI after THA and TKA at our institution, respectively. Of these, 21% (23 of 111) in the THA group and 24% (37 of 152) in the TKA group did not undergo the anticipated second-stage reimplantation at our institution at least 1 year after spacer placement. Among the original cohorts, 2% (2 of 111) of patients who underwent THA and 3% (4 of 152) of patients who underwent TKA subsequently underwent second-stage reimplantation at outside institutions when reviewed, leaving 19% (21 of 111) in the THA group and 22% (33 of 152) in the TKA group with retained spacers. Of the original cohorts, 7% (8 of 111) in the THA group and 5% (8 of 152) in the TKA group did not have a 2-year follow-up, leaving 12% (13 of 111) of patients with THA and 16% (25 of 152) of patients with TKA available for analysis with a minimum of 2 years of follow-up or death in this retrospective study. The median (range) follow-up from spacer placement to the latest follow-up was 5 years (2 to 11) for patients with THA and 4 years (2 to 8) for patients with TKA. In the THA cohort, the median (range) age was 72 years (59 to 86), and eight patients were female; the median BMI was 32 kg/m2, and the median Charlson comorbidity index (CCI) was 3.5. In the TKA cohort, the median (range) age was 69 years (45 to 83), 13 patients were female, the median BMI was 31 kg/m2, and the median CCI was 4. Complication data following spacer placement were obtained from the electronic medical record and by telephone follow-up when needed. Clinical symptoms (swelling, erythema, warmth, fever, drainage, sinus tract, and pain), inflammatory markers (C-reactive protein and erythrocyte sedimentation rate), available radiographic findings, and laboratory test results (including synovial fluid analysis when obtained) were reviewed for evidence of infection or spacer-related mechanical failure. Infection after the spacer placement was defined as failure when the treating surgeon determined that an unplanned return to the operating room or spacer removal was warranted, acknowledging that postoperative evaluation thresholds varied among surgeons. Spacer-related mechanical failure was defined as spacer fracture or dislocation leading to reoperation or spacer removal. Patients were classified based on whether they underwent an unplanned reoperation or spacer removal. Patients who did not undergo unplanned reoperation or spacer removal were further categorized based on use of chronic suppressive antibiotics (decisions regarding chronic antibiotic therapy were made by the treating surgeon and/or infectious disease team). Patients who underwent reoperation were those who returned to the operating room because of concerning clinical, imaging, and/or laboratory findings of infection or mechanical complications, and the treating surgeon decided to proceed with revision surgery. All reoperation decisions were made by fellowship-trained arthroplasty surgeons with high-volume experience in two-stage revision. We used a competing-risks model to estimate survival of the spacer free from unplanned reoperation or removal attributable to infection or mechanical complications (calculated as 1 minus the corresponding cumulative incidence), with death treated as a competing event. Kaplan-Meier analysis was used to estimate patient survivorship, with death as the endpoint. Mortality data were obtained from medical records and hospital databases and were confirmed by telephone follow-up with family members and public records when needed. Ambulatory status before and after spacer placement was summarized descriptively and reported only for patients with both prespacer and postspacer data available (10 THAs and 25 TKAs); no formal hypothesis testing was performed for ambulatory or functional measures. RESULTS:At 2 years of follow-up, the survival of the spacer free from unplanned reoperation or removal was 89% (95% confidence interval [CI] 80% to 99%) for patients with THA and TKA combined, the cumulative incidence of infection was 5% (95% CI 0% to 12%), and the Kaplan-Meier survivorship of the patients was 92% (95% CI 84% to 100%). The cumulative incidence of mechanical complications (spacer fracture or dislocation) was 5% (95% CI 0% to 13%). In the THA cohort (10 patients), ambulatory status before the first stage included two patients using a wheelchair, two using a walker, one using crutches, two using a cane, and three walking without assistive devices. At latest follow-up, four patients used a wheelchair, two used a walker, two used a cane, and two walked without assistive devices. In the knee cohort (25 patients), ambulatory status before the first stage included two patients using a wheelchair, five using a walker, 13 using a cane, and five walking without assistive devices. At latest follow-up, two patients used a wheelchair, five used a walker, 13 used a cane, and five walked without assistive devices. CONCLUSION/CONCLUSIONS:Retained articulating spacers can provide infection control in selected patients who do not proceed to reimplantation after first-stage spacer placement for PJI. Although infection-free spacer survival is achievable, these patients remain at risk for mechanical complications, including dislocation and fracture, as well as progressive functional decline. These risks should be clearly discussed during preoperative counseling to align expectations and support informed decision-making. Further studies are needed to refine patient selection, improve spacer durability, and standardize definitions of treatment success in PJI. LEVEL OF EVIDENCE/METHODS:Level III, case series.

The multiply revised total knee arthroplasty (TKA) poses unique surgical challenges. Patients who present to the office with a failed TKA or revision TKA expect durable, long-term fixation and improved function, yet bone loss and extensor mechanism insufficiency can easily complicate the reconstruction. The aim of this American Association of Hip and Knee Surgeons symposium is to provide up-to-date guidance for re-revision TKA with a specific focus on 1) safe exposure; 2) improved fixation with impaction grafting; 3) improved fixation using porous metal structural augmentation; and 4) managing the patella. After reviewing this paper, the reader should feel comfortable with standard and extensile exposures of a revision knee arthroplasty, understand the technique and outcomes for impaction bone grafting and the use of porous metal augmentation, and develop an algorithm for treating and optimizing patellofemoral kinematics through augmentation and reconstruction techniques.

BACKGROUND:This study compares clinical and functional outcomes between simultaneous hardware removal during total knee arthroplasty (TKA) and staged TKA after prior hardware removal. METHODS:We retrospectively reviewed 155 patients who had prior knee hardware and underwent elective primary TKA between 2012 and 2024 at an urban academic institution. Patients were categorized into "simultaneous" removal during TKA (n = 127) or "staged" TKA after removal (n = 28), and stratified by hardware type (minor/moderate/major). RESULTS:Simultaneous procedures involved significantly less "major hardware," single incisions, and tibial stem extensions than staged procedures (32.3 versus 78.6%, P < 0.001; 81.9 versus 100%, P = 0.007; and 0.8 versus 10.7%, P = 0.019, respectively). Hardware, particularly the major type, was more often retained or partially retained in the simultaneous group (48.0 versus 21.4%, P = 0.008). Reoperation, revision, and infection rates did not significantly differ based on timing or hardware location. Simultaneous patients had smaller 3-month Patient-Reported Outcomes Measurement Information System (PROMIS) Pain Intensity and Interference score reductions (-1.6 versus -9.9, P = 0.006 and +0.4 versus - 7.2, P = 0.007, respectively), but greater 2-year Knee Injury and Osteoarthritis Outcome Score for Joint Replacement improvements (+25.0 versus - 1.1, P = 0.006) compared to staged patients. Simultaneous major hardware removal demonstrated significantly greater 2-year Knee Injury and Osteoarthritis Outcome Score for Joint Replacement and PROMIS Pain Interference improvement (+32.0 versus -5.5, P = 0.001, and -6.2 versus +5.8, P = 0.027, respectively), but smaller 2-week PROMIS Pain Intensity score reduction (+2.2 versus -4.9, P = 0.050) compared to staged procedures. CONCLUSIONS:Simultaneous hardware removal during TKA led to higher retained major hardware rates and fewer single incisions than staged procedures, without increased reoperation or revision risks. Despite higher 3-month pain scores, simultaneous surgery achieved greater 2-year functional improvement, suggesting it offers advantages for select patients.

BACKGROUND:The Centers for Medicare and Medicaid Services now mandates the collection of patient-reported outcome measures (PROMs) before and after total knee arthroplasty (TKA), though their utility in predicting clinical outcomes remains unclear. This study compared the power of preoperative PROMs to predict clinical outcomes after TKA to established indices, including the Charlson Comorbidity Index and the Risk Assessment and Prediction Tool (RAPT). METHODS:We retrospectively reviewed 2,923 patients undergoing elective, primary, unilateral TKA who completed the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement and four Patient-Reported Outcomes Measurement Information System (PROMIS) domains within 90 days preoperatively. Outcomes included same-day discharge (SDD) rate, prolonged length of stay (LOS ≥ 48 hours), nonhome discharge, 90-day readmission, and revision surgery. Predictive utility was assessed using receiver operating characteristic curves (area under the curve [AUC]) and multivariable logistic regressions. RESULTS:The RAPT was the strongest predictor of SDD (AUC = 0.697), extended LOS (AUC = 0.703), and nonhome discharge (AUC = 0.877). The PROMIS Physical Health (AUC = 0.609 for SDD; 0.607 for LOS; 0.696 for discharge) and PROMIS Mental Health (AUC = 0.613; 0.610; 0.655) demonstrated modest predictive value. In adjusted models, higher PROMIS Mental Health was associated with greater odds of SDD (odds ratio (OR) = 1.027, P = 0.003) and lower odds of extended LOS (OR = 0.975, P < 0.001). Higher PROMIS Physical Health was associated with decreased odds of nonhome discharge (OR = 0.935, P = 0.017). The Charlson Comorbidity Index was the strongest predictor of 90-day readmission (AUC = 0.604) and the only significant variable in adjusted models. There were no PROMs that were significant predictors of readmission or revision. CONCLUSIONS:Preoperative PROMs are associated with some clinical outcomes following TKA, but demonstrate limited predictive power compared to established tools like the RAPT score. These findings underscore the need for more robust, outcome-aligned PROMs to improve surgical planning in a value-based care model.

INTRODUCTION/BACKGROUND:Periprosthetic patellar fracture (PPPF) after total knee arthroplasty (TKA) is a rare complication, but can significantly affect patient function and implant survival. This study sought to better identify radiographic and anatomical risk factors for PPPF compared to a propensity-matched cohort. METHODS:We retrospectively queried 22,092 TKAs from January 2011 to December 2024 with patellar resurfacing at a single, urban, academic institution, yielding 44 (0.2%) verified cases of PPPF after TKA. Using propensity score matching on the basis of age, sex, body mass index (BMI), race, and Charlson Comorbidity Index, 44 control TKA patients who had patellar resurfacing without fracture were identified and analyzed using the same methods. RESULTS:The mean time to PPPF was two years after TKA (range, 10 days to 10 years), and 46% were atraumatic. A decreased native lateral patellar tilt (20.0 versus 22.6°, P = 0.039) and thinner native patellar thickness (22.6 versus 24.0 mm, P = 0.018) were associated with increased PPPF risk. Lateralization of the patella during resurfacing also increased risk (P = 0.011), as well as increased patellar component size (P = 0.034). On Receiver Operating Characteristic analysis, thinner native patella thickness was the most predictive of fracture risk (Area Under the Curve = 0.621); however, this result was underpowered, thus an optimal cutoff value could not be meaningfully established. CONCLUSION/CONCLUSIONS:The PPPFs are rare complications following TKA and may occur with or without trauma. Native patellar thickness was inversely correlated with fracture risk, and lateral positioning during resurfacing and increased component size were associated with increased risk. Patients who had PPPFs also demonstrated lesser lateral patellar tilt compared to non-fractured controls. Further investigation with a larger cohort may enable more precise risk factor stratification.

BACKGROUND:Robotic-assisted total knee arthroplasty (RA-TKA) allows for intraoperative component positioning to personalize alignment and gaps. However, traditional trochlear designs not optimized for patellar tracking in kinematic alignment result in femoral internal rotation relative to the surgical transepicondylar axis (TEA). We sought to determine the femoral component alignment's effect on patellar tracking in RA-TKA. METHODS:We retrospectively reviewed 932 RA-TKA cases performed from January 2023 to August 2024 using a computed tomography (CT)-based robotic platform with a single radius femoral component with a 6° trochlear sulcus angle. Femoral rotation was defined as internal (IR) and external (ER) relative to TEA. Femoral coronal alignment was defined as varus (Var) or valgus (Val) relative to the mechanical axis. Patient-reported outcomes were collected at six weeks, three months, and one year postoperatively. Outcomes were analyzed using one-way analyses of variance and Chi-square tests. RESULTS:There were 445 (48%) Var-ER, 242 (26%) Val-ER, 105 (11%) Var-IR, and 141 (15%) Val-IR cases. Mean femoral component rotation (° external) was Var-ER: 2.8° (range, 0.2 to 6.5); Val-ER: 2.4° (range, 0.1 to 5.0); Var-IR: -0.6° (range, -3.4 to 0); and Val-IR: -1.0° (range, -4.2 to 0). There were three patella-related complications, two of which had further reoperations, all of which occurred in the Val-IR cohort (P < 0.001). Knee Injury and Osteoarthritis Outcome for Joint Replacement (KOOS, JR) at six weeks was lowest in the Var-ER cohort (52.3, P < 0.039). Planned femoral IR had no statistically significant impact on three-month and one-year KOOS, JR scores; there were no differences in Patient-Reported Outcomes Measurement Information System (PROMIS) scores at postoperative intervals studied. CONCLUSION/CONCLUSIONS:Planned femoral IR was not associated with statistically significant differences in patient-reported outcomes beyond six weeks postoperatively. However, all patella-related complications occurred in the Val-IR cohort. We caution surgeons against placing excessive combined valgus and IR with femoral implants designed with narrower trochlear sulcus angles.

For femoral reconstruction in revision total hip arthroplasty (rTHA), cementless, diaphyseal engaging femoral components are the most commonly-used implants. At present, there are no reviews that directly compare the design features of these implants. We performed a manual review of the designs of commercially available diaphyseal engaging femoral stems. We compiled and compared the design features of these implants. Clinical outcomes of modular and monoblock stems were also compared. We identified five modular and four monoblock stems in the manual review of commercial companies manufacturing these stems. Distal stem taper varied from 2° to 3.5°, and the number of splines varied from 8 to 16. The stems varied in their stem lengths, offsets, and surface finish. Although there are no clinically significant differences in the restoration of leg length between monoblock compared to modular stems. The modular stems appear to perform slightly better with respect to subsidence and restoration of leg length. A source of concern for modular stems are mechanical implant failures that occur almost exclusively at modular junctions. Current evidence does not support any difference in dislocation rate, intraoperative or postoperative fracture, aseptic loosening, re-revision rates, or clinical outcomes between monoblock and modular stems. With the knowledge of the distinct features of implants, surgeons must make choices associated with specific design characteristics that could be pivotal to the success of the operation. Our understanding of design differences will help us minimize chances of failure and choose patient-specific implants that will lead to a high rate of success.

BACKGROUND:Tranexamic acid (TXA) has reduced, but not eliminated, blood transfusions surrounding total knee arthroplasty (TKA). Identifying risk factors for transfusion remains important for risk reduction and type and screen (T and S) optimization. METHODS:We retrospectively reviewed 7,254 patients who underwent primary, unilateral TKA and 307 patients who underwent primary bilateral TKA between January 2014 and January 2023, who received perioperative TXA and had preoperative hemoglobin (Hgb) values. We compared demographics, baseline Hgb levels, and surgical details between patients who were and were not transfused. Data were analyzed utilizing multivariate regressions and receiver operating characteristic (ROC) analyses. A total of 172 unilateral TKA patients (2.4%) received perioperative transfusions, with 170 (2.3%) receiving postoperative transfusions and two (0.03%) receiving intraoperative transfusions. There were 26 bilateral TKA patients (8.5%) who received postoperative transfusions with no documented intraoperative transfusions. RESULTS:For unilateral TKA, the risk of transfusion demonstrated an inverse correlation with preoperative Hgb levels, a bimodal association with body mass index (BMI), and a direct correlation with American Society of Anesthesiologists (ASA) class and estimated blood loss (EBL) on multivariate testing. The ROC analyses demonstrated an optimal Hgb cutoff of 12.1 g/dL for predicting transfusion. The transfusion rate below Hgb of 12.1 g/dL was 6.6%, compared to a rate of 1.4% above this Hgb threshold. Below Hgb of 11 g/dL, the transfusion rate was 11.1%, while for Hgb between 11 and 12 g/dL, the transfusion rate was 4.6%. CONCLUSION/CONCLUSIONS:Transfusion is rare in unilateral TKA when TXA is used and preoperative Hgb is ≥ 12.1 g/dL, challenging universal T and S. Patients who have Hgb less than 11.0 g/dL and bilateral TKA patients remain at higher risk. Risk factors such as Hgb between 11 and 12 g/dL, BMI, ASA and EBL may predict transfusion risk and need for T and S.