Background. Osteophytes in the posterior compartment of the knee pose a challenge in achieving soft tissue balance during total knee arthroplasty (TKA). Previous investigations have demonstrated the importance of various factors involved in obtaining flexion and extension gap balance, including the precision of femoral and tibial bone cuts as well as tensioning of the supporting pericapsular soft tissue structures (ligaments, capsule, etc.). However, the role of posterior compartment osteophytes has not been well studied. We hypothesize that space-occupying posterior structures affect soft tissue balance, especially in lesser degrees of flexion, in a cadaveric TKA model. Methods. Five cadaveric limbs were acquired. CT scans were obtained of each specimen to define the osseous contours. 3D printed specimen-specific synthetic osteophytes were fabricated in two sizes (10mm and 15mm). Posterior-stabilized TKAs were performed. Medial and lateral contact forces were measured during a passive range of motion using OrthoSensor ® (Dania Beach, FL) technology. For each specimen, trials were completed without osteophytes, and with 10mm and 15mm osteophytes applied to the posterior medial femur, with iterations at 0°, 10°, 30°, 45°, 60°, and 90° of flexion. These were recorded across each specimen in each condition for three trials. Tukey post hoc tests were used with a repeated measures ANOVA for statistical data analysis. Results. The presence of posterior medial osteophytes increased
Osteoarthritic (OA) changes to the bone morphology of the proximal tibia may exhibit load transfer patterns during total knee arthroplasty not predicted in models based on normal tibias. Prior work highlighted increased bone density in transverse sections of OA knees in the proximal-most 10mm tibial cancellous bone. Little is known about coronal plane differences, which could help inform load transfer from the tibial plateau to the tibial metaphysis. Therefore, we compared the cancellous bone density in OA and cadaveric (non-OA) subjects along a common coronal plane. This study included nine OA patients (five women, average age 59.1 ± 9.4 years) and 18 cadaver subjects (four women, average age 39.5 ± 14.4 years). Patients (eight with medial OA and one with lateral OA) received pre-operative CT scans as standard-of-care for a unicompartmental knee replacement. Cadavers were scanned at our institution and had no history of OA which was confirmed by gross inspection during dissection. 3D reconstructions of each proximal tibia were made and an ellipse was drawn on the medial and lateral plateau using a previously published method. A coronal section (Figure 1) to standardize the cohort was created using the medial ellipse center, lateral ellipse center, and the tibial shaft center 71.5mm from the tibial spine. On this section, profile lines were drawn from the medial and lateral ellipse centers, with data collected from the first subchondral bone pixel to a length of 20mm. The Hounsfield Units (HU) along each profile line was recorded for each tibia; a representative graphical distribution is shown in Figure 2. The Area Under the Curve (AUC) was calculated for the medial and lateral sides, which loosely described the stiffness profile through the region of interest. To determine differences between the medial and lateral subchondral bone density, the ratio AUC[medial] / AUC[lateral] was compared between the OA and cadaver cohorts using a two-sample t-test. Data from the sole lateral OA patient was mirror-imaged to be included in the OA cohort. The majority of the OA patients appeared to have higher subchondral bone density on the affected side. Figure 3 compares the medial and laterals sides of each group using the AUC ratio method described above. For the cadaver group the AUC was 1.2 +/− 0.22, with a median of 1.1 [0.9 1.6], smaller than the mean AUC for the OA group, which was 1.4 +/− 0.39, with a median of 1.6 [0.93 2.1]. The p-value was 0.06. The increased density observed in OA patients is consistent with
