Total Knee Arthroplasty Kinematics Predict Patient-Reported Outcome Measures: Implications for Clinical Kinematic Examinations.

BACKGROUND: A core tenet of total knee arthroplasty (TKA) is that achieving more natural kinematics will lead to superior patient outcomes. Yet this relationship has not been proven for large representative cohorts of TKA patients because accurately measuring 3-dimensional TKA kinematics is time-consuming and expensive. But advanced imaging systems and machine learning-enhanced analysis software will soon make it practical to measure knee kinematics preoperatively and postoperatively in the clinic using radiographic methods. The purpose of this study was to assess the reported relationships between TKA kinematics and outcomes and distill those findings into a proposal for a clinically practical protocol for a clinical kinematic exam. METHODS: This study reviewed the recent literature relating TKA kinematics to patient outcomes. There were 10 studies that reported statistical associations between TKA kinematics and patient outcome scores utilizing a range of functional activities. We stratified these activities by the complexity of the radiographic examination to create a proposed examination protocol, and we generated a list of requirements and characteristics for a practical TKA clinical kinematic examination. RESULTS: Given considerations for a clinically practical kinematic exam, including equipment, time and other resources, we propose 3 exam levels. With basic radiographs, we suggest studying single-leg stance in extension, lunge or squat, and kneeling. For fluoroscopic systems with X-ray pulses up to 20 ms, we propose chair-rise or stair ascent to provide additional dynamic information. For fluoroscopic systems with X-ray pulses of less than 10 ms, we propose rapid open-chain knee flexion-extension to simulate the highly dynamic swing phase of gait. CONCLUSIONS: It is our hope that this proposed examination protocol spurs discussion and debate so that there can be a consensus approach to clinical examination of knee and TKA kinematics when the rapidly advancing hardware and software capabilities are in place to do so.

Time Required for Planned and Unplanned Episodes of Care in Aseptic Hip and Knee Revision Arthroplasty.

BACKGROUND: Studies indicate aseptic revision total hip arthroplasty (rTHA) and revision total knee arthroplasty (rTKA) requires much more effort but is reimbursed less than primary procedures per minute work time. This study quantified planned and unplanned work performed by the surgeon and/or their team during the entire episode of care "reimbursement window" and compared it to allowed reimbursement times by Centers for Medicare and Medicaid Services (CMS). METHODS: Between October, 2010, and December, 2020, all unilateral aseptic rTHA and rTKA procedures performed by a single surgeon at a single institution were retrospectively reviewed. Time dedicated to planned work was calculated from surgery scheduling to 90 days postoperative. Impromptu patient inquiries and treatments after discharge but within the episode of care, involving the surgeon/surgeon team constituted unplanned work. Planned and unplanned work minutes were summed and divided by the number of patients reviewed to obtain average minutes of work per patient. Work time was compared to CMS allowable times for rTHA (617 minutes) and rTKA (520 minutes). RESULTS: There were 292 Aseptic rTKA and 63 aseptic rTHA procedures included. Based upon CMS allowable times per patient there were a mean of 4.4 hours (267 minutes) of uncompensated care time per rTKA patient and a mean of 2.4 hours (141 minutes) of uncompensated care time per rTHA patient. CONCLUSION: Aseptic revisions are substantially more complex than primaries, requiring work effort that is not commensurate with current reimbursements. Financially disincentivizing surgeons to care for patients requiring revision surgery could reduce patient access to care when high quality care is needed the most.

Cementless Tapered Wedge Femoral Stems Decrease Subsidence in Obese Patients Compared to Traditional Fit-and-Fill Stems.

BACKGROUND: Femoral component stability and resistance to subsidence is critical for osseointegration and clinical success in cementless total hip arthroplasty. The purpose of this study was to radiographically evaluate the anatomic fit and subsidence of 2 different proximally tapered, porous-coated modern cementless femoral component designs. METHODS: A retrospective cohort study of 126 consecutive cementless total hip arthroplasties was performed. Traditional fit-and-fill stems were implanted in the first 61 hips with the remaining 65 receiving morphometric tapered wedge stems. Preoperative bone morphology was radiographically assessed by the canal flare index. Canal fill in the coronal plane, subsidence, and the sagittal alignment of stems was measured digitally on immediate and 1-month postoperative radiographs. RESULTS: Demographics and canal flare indices were similar between groups. The percentage of femoral canal fill was greater in the tapered wedge compared to the fit-and-fill stem (P = .001). There was significantly less subsidence in the tapered wedge design (0.3 mm) compared to the fit-and-fill design (1.1 mm) (P = .001). Subsidence significantly increased as body mass index (BMI) increased in the fit-and-fill stems, a finding not observed in the tapered wedge design (P = .013). CONCLUSION: An anatomically designed morphometric tapered wedge femoral stem demonstrated greater axial stability and decreased subsidence with increasing BMI than a traditional fit-and-fill stem. The resistance to subsidence, irrespective of BMI, is likely due to the inherent axial stability of a tapered wedge design and may be the optimal stem design for obese patients.

How to Approach a Recalled Dual Modular Hip Implant: An Update.

BACKGROUND: The aim of this study was to provide an update on the "Modular taper junction corrosion and failure: how to approach a recalled total hip arthroplasty implant" (Pivec et al JOA 2014) publication. METHODS: We performed a comprehensive review of the literature in English, with search terms referencing to the diagnosis, management, and outcomes of patients who underwent total hip arthroplasty with a recalled dual modular hip implant. RESULTS: Based on this review and the new guidelines by the American Academy of Orthopedic Surgeons and the Hip Society, we propose an updated algorithm for the diagnosis and management of patients with these recalled implants. CONCLUSION: When encountering patients with these prostheses, it is imperative to take a step-by-step approach to evaluate whether patients are having potential complications. We hope that this has further clarified the appropriate steps that need to be carried out when confronted with these recalled devices.

Can Intraoperative Sensors Determine the "Target" Ligament Balance? Early Outcomes in Total Knee Arthroplasty.

BACKGROUND: The optimal "target" ligament balance for each patient undergoing total knee arthroplasty (TKA) remains unknown. The study purpose was to determine if patient outcomes are affected by intraoperative ligament balance measured with force-sensing implant trials and if an optimal "target" balance exists. METHODS: A multicenter, retrospective study reviewed consecutive TKAs performed by 3 surgeons. TKA's were performed with standard surgical techniques and ligament releases. After final implants were made, sensor-embedded smart tibial trials were inserted, and compartment forces recorded throughout the range of motion. Clinical outcome measures were obtained preoperatively and at 4 months. Statistical analysis correlated ligament balance with clinical outcomes. RESULTS: One hundred eighty-nine consecutive TKAs were analyzed. Patients were grouped by average medial and lateral compartment force differences. Twenty-nine TKAs (15%) were balanced within 15 lbs and 53 (28%) were "balanced" greater than 75 lbs. Greater improvement in University of California Los Angeles activity level was associated with a mediolateral force difference <60 lbs. (P = .006). Knee Society objective, function, and satisfaction scores, and self-reported health state were unrelated to mediolateral balance in the knee. CONCLUSION: Intraoperative force-sensing has potential in providing real-time objective data to optimize TKA outcomes. These data support some early outcomes may improve by balancing TKAs within 60 lbs difference. Close follow-up is warranted to determine if gait pattern adaptations affect longer term outcomes with greater or less ligament "imbalance."