Faculty Bibliography

Hip dislocation remains a major concern following total hip arthroplasty due to its high frequency and economic burden. This article evaluates the cost-effectiveness regarding dual mobility as an alternative to standard implant designs. A review of literature analyzing the PubMed Central database was undertaken using the following terms in the primary query: dual mobility, cost-effectiveness, cost-analysis, or economic analysis. Dual mobility systems may be a cost-effective alternative when the price of the implant does not exceed the traditional system by $1023. Dual mobility cups may be an essential component for the future success of value-based total hip arthroplasty.

Proper ligament tension in knee flexion within cruciate-retaining (CR) total knee arthroplasty has long been associated with clinical success; however, traditional balancing principles have assumed that the distal femoral joint line (DFJL) affects only extension. The purpose of this study was to determine the effect DFJL may have on ligament strains and tibiofemoral kinematics of CR knee designs in flexion. A computational analysis was performed using a musculoskeletal modeling system for two different knee implants, the high-flex CR (HFCR) and guided-motion CR (GMCR). Tibiofemoral kinematics and ligament strain were measured at 90-degree knee flexion while the implants' DFJL was incrementally shifted proximally. Femoral implant position and kinematics were used to determine the femur's anteroposterior position relative to the tibia. The change in the femoral medial condyle position relative to the tibia was 0.33 mm and 0.53 mm more anterior per each 1-mm elevation of the DFJL for HFCR and GMCR, respectively. The change in the lateral condyle position was 0.20 mm more anterior and 0.06 mm more posterior for HFCR and GMCR, respectively. The strain in the lateral and medial collateral ligaments changed minimally with elevation of the DFJL. In both implants, strain increased in the anterior lateral and posterior medial bundles of the posterior collateral ligament with elevation of the DFJL, whereas strain decreased in the iliotibial band and iliotibial patellar band. Our findings suggest that DFJL affects ligament tension at 90-degree knee flexion and therefore flexion balance for CR implants. Elevating the DFJL to address tight extension space in a CR knee while flexion space is well balanced could result in increased flexion tension especially when the flexion-extension mismatch is large. To achieve balanced flexion and extension, the amount of DFJL elevation may need to be reduced.

BACKGROUND:Advancements in the management of human immunodeficiency virus (HIV) now permit HIV-positive patients to have longer life spans, increasing their cumulative risk of developing an advanced degenerative joint disease, necessitating total hip arthroplasty (THA). The purpose of this study was to provide an extended follow-up on a previously published study on a cohort of HIV-positive THA recipients in an effort to confirm the safety and longevity of THA in this population. METHODS:This study is a follow-up on a previous study comprised of 41 hips in 31 HIV-positive THA recipients. At this follow-up, 5 patients from the original cohort required contralateral THA. Postoperative complications were recorded up to the patient's last follow-up date. A survivorship analysis was performed using the Kaplan-Meier method with revision THA as the end point. RESULTS:Since the last report, 2 additional hips were revised (one for aseptic loosening and one for a periprosthetic fracture), and 5 patients underwent contralateral THA. This resulted in a total of 5 (13.8%) hips requiring revision THA at the latest follow-up. The mean follow-up interval for the original cohort and for the contralateral 5 hips was 78.9 ± 50.2 months and 54.6 ± 45.3 months, respectively. Kaplan-Meier survivorship analysis with revision THA for any reason as the end point demonstrated survivorship of 93% (2 years), 90% (5 years), and 81% (10 and 14 years) after primary THA, respectively. CONCLUSION/CONCLUSIONS:Our study suggests that it is possible to achieve a low incidence of postoperative infection in HIV-positive THA recipients. In addition, our study demonstrates that non-hemophiliac HIV-positive patients have comparable revision rates to previously published reports on HIV-negative patients of similar age, underscoring the clinical efficacy of highly active antiretroviral therapy.

BACKGROUND:Although preoperative risk assessment tools have been effective in predicting discharge disposition after total joint arthroplasty (TJA), studies reporting on discharge planning in extended length of stay (ELOS), >3 days, patients are lacking. The purpose of this study was to describe the predictive utility of the Risk Assessment and Prediction Tool (RAPT) for discharge disposition in ELOS patients. METHODS:Our study included 260 patients with LOS >3 days who underwent primary TJA between 2014 and 2016. Patients were separated into 3 cohorts, based on their RAPT score: low risk (9-12), medium risk (6-9), and high risk for discharge to a facility (1-6). Scores were compared among cohorts and correlated with discharge disposition for patients who stayed beyond 3 days. RESULTS:In ELOS, RAPT had a higher utility in predicting discharge disposition in the low-risk (76.5% to home) and high-risk (62.9% to facility) patient cohorts, while medium-risk patients (56.5% to home) were the least accurate. Responses that significantly correlated with discharge home included male gender (odds ratio [OR], 1.81; P < .05), ambulation without walking aids (OR, 2.94; P < .01) or a single-point cane (OR, 2.95; P < .0001), <1 community support visit per week preoperatively (OR, 1.86; P < .05), and having support from someone at home (OR, 3.43; P < .0001). CONCLUSION/CONCLUSIONS:The RAPT score in ELOS patients is better correlated with the low-risk and high-risk cohorts than in medium-risk patients. Conversely, medium-risk ELOS patients constituted 56.8% of our sample size, but only predicted 56.5% of discharge dispositions correctly. Future discharge disposition risk assessment tools are needed to stratify medium-risk patients.

Background/UNASSIGNED:There is a paucity of literature assessing whether payer type has an impact on postoperative patient-reported outcomes (PROs) after total knee arthroplasty (TKA). The aim of this study was to comparatively evaluate TKA PROs among patients with commercial and Medicare insurance. Methods/UNASSIGNED:We conducted a single-center, retrospective review of patients operated between January 2017 and March 2018. Knee Disability and Osteoarthritis Outcome Score Junior (KOOS-Jr) and Veterans RAND 12 Health Survey (VR-12) Physical Component (VR-12 PCS) and Mental Component (VR-12 MCS) PRO scores were collected prospectively at baseline and 12 weeks postoperatively via an electronic patient rehabilitation application. Univariable and multivariable linear regressions were utilized to assess the effects of patient insurance type on PRO. Results/UNASSIGNED:> .05). Conclusions/UNASSIGNED:After adjusting for patient-specific variables, PROs are similar at baseline and 12 weeks postoperatively between commercial and Medicare cohorts. For TKA candidates with similar baseline demographics, surgeons can expect similar perioperative PROs regardless of insurance type.

Oxinium is an alternative bearing surface designed to emulate the superior wear and scratch properties of ceramic femoral heads in total hip arthroplasty while minimizing the risk for brittle fracturing. However, recent studies have indicated that hip dislocation following total hip arthroplasty may be a risk factor for catastrophic failure of the femoral head. Here, we report on a novel case of a catastrophic Oxinium head and polyethylene liner failure in the absence of previous hip dislocation or trauma and review the probable failure mechanism. This report underscores the need to be vigilant about proper acetabular cup and liner seating, particularly in the setting of Oxinium femoral head use. In the event of Oxinium head failure, metallosis may compromise stabilizing soft tissues including the abductors. Dual-mobility articulation, which was successful in this case, is one option to consider when the risk for chronic redislocation is elevated.

The number of total knee arthroplasties performed in the United States is growing, and a leading cause of failure is postoperative knee instability from suboptimal coronal or sagittal balancing. This article reviews native knee anatomy as well as several guiding principles of total knee arthroplasty such as limb axis, femoral referencing, and implant constraint. Next, techniques that can be used by the surgeon to achieve ideal sagittal balance and coronal balance are discussed in detail. Finally, due to the growing use of computer and robotic technologies in knee replacement, the impact of advanced technologies on total knee arthroplasty balancing and alignment is reviewed. An in-depth understanding of these topics will enable surgeons to optimize the outcome of their total knee arthroplasty patients.

Despite the overall successful outcomes following primary total knee arthroplasty (TKA) and the concept that a well-balanced TKA yields a more successful result, concerns still remain in the reported literature regarding the patellofemoral joint. Diminished outcomes have been associated with poorly balanced or placed patella implants. The effect of different techniques to achieve flexion-extension balance and the use of posterior stabilized (PS) versus cruciate retaining (CR) implant designs on patellofemoral balancing has not been previously studied. The purpose of this study is to utilize a validated computational analysis software to simulate the effects of varying implant positions and sizes of femoral components. The patellofemoral retinaculum (PFR) load was significantly affected by some conditions, while others did not reach significance. The proximal-distal implant position with knee flexion angle (p < 0.001), the implant size (p < 0.001), and the implant bearing type (CR/PS) (p < 0.05) were significant. For the proximal-distal implant position and knee flexion angle, a more proximal implant position (elevating the joint line) increased the PFR load from 15 to 30°, and a more proximal implant position reduced retinaculum load from 60 to 135°. However, at 45°, implant position does not affect retinaculum load. Achieving the appropriate balance between the dynamic nature of both the tibiofemoral and the patellofemoral interaction in TKA has proven to be complex and challenging to manage. Balancing of a TKA is essential to the proper functioning and overall longevity of the implant. These results demonstrate that patellofemoral balance is affected by implant size and position during flexion-extension gap balancing.