Reports cite up to 20% of total knee arthroplasty (TKA) patients are not satisfied. Recent focus on alignment and balance has perhaps overshadowed kinematics as a key determinant of outcomes. Some propose that reproducing the native knee kinematics of lateral-pivot motion in early flexion during walking will enact optimal TKA outcomes. The purpose of this study was to determine if intra-operative kinematic patterns correlate with patient function, pain and satisfaction after TKA. A retrospective review of consecutive TKA's performed by two surgeons was performed. After final components were implanted and balanced, sensor-embedded tibial trials were inserted and kinematic patterns were recorded through range-of-motion. Femoro-tibial contact points were recorded at four distinct flexion points (0°, 45°, 90° and full flexion). Center of rotation kinematic patterns were calculated and categorized as medial pivot, lateral pivot or translation at each measurement range via established criteria. Knees with lateral (L) pivot in early flexion between 0 and 45 ° and medial (M) pivot beyond 90°, regardless of the mid-flexion pivot pattern, formed the experimental group designated as LXM. All other patterns were designated non-LXM and formed the control group. Modern, validated clinical outcome measures (Knee Society Score, EQ5D, UCLA) were obtained preoperatively and at minimum one-year postoperatively.Introduction
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The direct anterior approach (DAA) for total hip arthroplasty (THA) is marketed with claims of superiority over other approaches. Femoral exposure can be technically challenging and potentially lead to early failure. We examined whether surgical approach is associated with early THA failure. A retrospective review of 478 consecutive early revision THAs within five years of primary THA at three academic centers from 2011 through 2014 was performed. Exclusion criteria resulted in a final analysis sample of 341 early failure THAs. Primary surgical approach was documented for each revision, along with time to revision, and failure etiology.Background
Methods
The purpose of TKA is to restore normal kinematics and functioning to diseased knees. The purpose of this study was to determine whether intraoperative kinematic data are correlated with minimum one-year outcomes following primary TKA. We reviewed data on 185 consecutive primary TKAs in which sensor-embedded tibial trials were used to evaluate kinematic patterns following traditional ligament balancing. Procedures were performed by two board-certified arthroplasty surgeons. The same implant design and surgical approach was used for all knees. Contact locations on the medial and lateral condyles were recorded for each patient at 0°, 45° and 90° of flexion, and full flexion. Vector equations were created by contact locations on the medial and lateral sides and the vector intersections determined the center of rotation between each measurement position. Center of rotation was calculated as the average of vector intersections at 0 to 45°, 45 to 90°, and 90° to full flexion. If the average center of rotation was between 16 and 1000 mm of the contact location on the medial side it was considered a medial pivot knee. Knees were also classified as medial (16 to 200 mm on medial side), lateral (16 to 200 mm on lateral side), translating (> 200 mm medially or laterally), and other (< 16 mm on both medial and lateral sides). The new Knee Society Scoring System (KSSO objective score, KSSS satisfaction score, KSSF function score), the EQ-5D™ Health Status Index, and the University of California Los Angeles (UCLA) Activity Level Score were measured preoperatively and at minimum one-year follow-up (average 20.4 months).INTRODUCTION
METHODS
Cementless fixation is the current preferred method for acetabular reconstruction in total hip arthroplasty (THA). Despite promising long-term results among several designs, theoretic concerns regarding the high modulus of elasticity, low friction against bone and low volumetric porosity of contemporary cementless cups have spurred the introduction of novel porous surfaces that are designed to improve osseointegration and decrease aseptic loosening. Although several novel surfaces have been introduced into clinical use over the past decade, very little literature regarding their clinical and radiographic performance exists. The current study investigates the performance of one such novel surface, Tritanium (Stryker, Mahwah, NJ). We prospectively evaluated 121 consecutive THAs performed in 94 patients by a single arthroplasty surgeon using the Tritanium Primary Acetabular Component (Stryker, Mahwah, NJ). 109 hips (90.1%) had adequate clinical and radiological follow-up for analysis. Clinical parameters recorded included implant survivorship, Harris Hip Scores, WOMAC and SF-12. Furthermore, radiographs at the 6-week, 1 year and most recent clinical visit were evaluated by two blinded observers for implant position, evidence of radiolucency, sclerosis and component migration.Introduction
Methods
Medial unicompartmental knee arthroplasty (UKA) restores mechanical alignment and reduces lateral subluxation of the tibia. However, medial compartment translation remains abnormal compared to the native knee in mid-flexion Intra-operative adjustment of implant thickness can modulate ligament tension and may improve knee kinematics. However, the relationship between insert thickness, ligament loads, and knee kinematics is not well understood. Therefore, we used a computational model to assess the sensitivity of knee kinematics, and cruciate and collateral ligament forces to tibial component thickness with fixed bearing medial UKA. A computational model of the knee with subject-specific bone geometries, articular cartilage, and menisci was developed using multibody dynamics software (Fig 1a). The ligaments were represented with multiple non-linear, tension-only force elements, and incorporated mean structural properties. The 3D geometries of the femoral and tibial components of the Stryker Triathlon fixed-bearing UKA were captured using a laser scanner. An arthroplasty surgeon aligned the femoral and tibial components to the articular surfaces within the model (Fig 1b). The intact and UKA models were passively flexed from 0 to 90° under a 10 N compressive load. The tibial polyethylene insert was modeled by the orthopaedic surgeon to create a “balanced” knee. The modeled polyethylene insert thickness was then increased by 2 mm and decreased 2mm (in increments of 1mm) to simulate over- and under-stuffing, respectively. Outcomes were anterior-posterior (AP) translation of the femur on the tibia in the medial compartment, and forces seen by the ACL and MCL during mid-flexion (from 30 to 60° flexion). The mean differences between the intact knee model and all other experimental conditions for each outcome were calculated across mid-flexion.Introduction
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