Size of Medial Knee Osteophytes Correlates With Knee Alignment But Not With Coronal Laxity in Patients With Medial Knee Osteoarthritis.

The severity of osteoarthritis (OA) has been related to osteophyte size. However, the effects on osteophyte size of repeated and increased loading associated with joint laxity and varus misalignment remain unclear. We investigated these relationships in patients with medial knee OA and compared the performances of computed tomography (CT) and radiography for assessing osteophyte parameters. We examined knee joint alignment on radiographs and knee laxity using arthrometry in 191 patients with medial knee OA who were undergoing total knee arthroplasty. We also measured femur and tibia osteophyte distance (largest perpendicular distance from the cortical line to outer margin of the osteophyte) using radiography and CT, osteophyte areas (largest area surrounded by the outer margin of an osteophyte) by CT and determined the locations of the osteophytes in the femur and tibia by CT. We then analyzed the correlations between the variables using Spearman's rank correlation tests. Osteophyte sizes in the femur and tibia as determined by radiography (distance) or CT (distance and area) were positively correlated with the degree of varus alignment but not with medial or lateral laxity. There was also a significant correlation between maximum osteophyte distances measured by radiography and CT. The greatest number and the largest osteophytes were located in the posterior third of the femur and middle third of the tibia, respectively. Osteophyte size was correlated with preoperative knee alignment but not with knee laxity in patients with medial knee OA. Osteophyte size can be evaluated using conventional radiography, without the need for CT. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:639-644, 2020.

Insall-Salvati ratio stabilizes one year after mobile-bearing total knee arthroplasty and does not correlate with mid-to-long-term clinical outcomes.

PURPOSE: It has not been established whether changes in the length of the patellar tendon (LPT) after total knee arthroplasty (TKA) affect clinical outcomes. Therefore, this prospective cohort study aimed to evaluate changes in the LPT over time postoperatively and clarify their impact on clinical outcomes after bilateral TKA, performed with differently designed mobile-bearing (meniscal-bearing and rotating-platform) implants on contralateral knees. METHODS: 51 patients who required staged bilateral mobile-bearing TKA were recruited. LPT was evaluated by measuring the Insall-Salvati ratio (ISR) preoperatively and at 1 week, 6 months, and 1, 2, and ≥ 5 years postoperatively. Hospital for Special Surgery score and range of motion were assessed at the final follow-up. RESULTS: Based on the ISR, there were no differences in the patterns of change between the two types of implant (n.s.). At the 6-month follow-up, the ISRs of both implants had significantly decreased (p = 0.002). Throughout the follow-up, the ISR was significantly lower (p < 0.001) for the meniscal-bearing knees than for the rotating-platform knees. After the 1-year follow-up, there were no further substantial changes in the ISR in either group. There was also no significant correlation between the ISR and clinical outcomes. CONCLUSIONS: LPT decreased after both mobile-bearing TKAs for up to 1 year postoperatively, although the decrease was more significant for the meniscal-bearing knees than the rotating-platform knees. After 1 year postoperatively, however, these conditions had stabilized, with no further changes. Thus, LPT plays a minimal role in mid-to-long-term clinical outcomes after TKA. LEVEL OF EVIDENCE: Therapeutic prospective study, Level II.

Preoperative Periarticular Knee Bone Mineral Density in Osteoarthritic Patients Undergoing TKA.

BACKGROUND: Preoperative periarticular bone quality is affected by joint loading. The purpose of this study was to determine the periarticular bone mineral density of the knee joint of patients undergoing total knee arthroplasty, and whether the location of the load-bearing axis correlates with the measured bone mineral density. MATERIALS AND METHODS: The bone mineral densities of the medial and lateral femoral condyles and the medial and lateral tibial condyles were analyzed in consecutive 116 osteoarthritic patients (130 knees) by dual energy x-ray absorptiometry. RESULTS: The median bone mineral density values in the condyles were 1.138 in femoral medial, 0.767 in femoral lateral, 1.056 in tibial medial, and 0.714 in tibial lateral. The medial condyles showed significantly higher bone mineral densities than the lateral condyles in both the femur and tibia. In addition, the femoral medial showed significantly higher bone mineral density levels than the tibial medial, and the femoral lateral condyle had higher bone mineral density levels than the tibial lateral. The bone mineral density Medial/Lateral ratio was significantly negatively correlated with the location (tibial medial edge 0%, lateral edge 100%) of the load-bearing axis in the femur and tibia. CONCLUSION: Preoperative bone mineral density values may provide against the changes in bone mineral density after total knee arthroplasty by reflecting the correlation with joint loading axis. These results help explain why total knee arthroplasty has such good long-term clinical outcomes with a low frequency of component loosening and periarticular fractures despite a high degree of postoperative bone loss.

Changes in the three-dimensional load-bearing axis after mobile-bearing total knee arthroplasty.

BACKGROUND: The purpose of this study was to assess changes in the three-dimensional (3D) load-bearing mechanical axis (LBMA) preoperatively and at 3 weeks and more than 1-year follow-up after total knee arthroplasty (TKA), and effects of the degree of constraint in the anteroposterior (AP) direction because of the retention of the posterior cruciate ligament (PCL) and the implant design on the changes in LBMA. METHODS: We evaluated 157 knees from 131 patients, including 79 knees that received meniscal-bearing-type (PCL-retaining) and 78 knees that received rotating-platform-type (PCL-substituting) prostheses. Quantitative 3D computed tomography was used to assess changes in the location of the pre- and postoperative LBMA at the tibial plateau level. RESULTS: Changes in the 3D axis were mainly found from medial to lateral and posterior to anterior in both implant designs with no significant differences. Change in the mediolateral (ML) direction was improved soon after TKA, but change in the AP direction improved more gradually over time. The different constraints in the AP direction because of the retention of the PCL and different implant designs did not affect the changes in the LBMA. CONCLUSIONS: The LBMA in the AP direction more than 1 year postoperatively, as well as the LBMA in the ML direction at 3 weeks, appears to shift toward the location found in normal knees after TKA, regardless of the type of prosthetic constraint. These changes may be an important factor that influences the periarticular knee bone mineral density which load bearing may be related to. LEVEL OF EVIDENCE: Level II, Prognostic study.

Changes in lower extremity 3-dimensional load-bearing axes before and after mobile-bearing total knee arthroplasty.

This study evaluated changes in the lower extremity 3-dimensional load-bearing mechanical axes in the anteroposterior and mediolateral directions before and at 3 weeks after mobile-bearing total knee arthroplasty. The effects of the degrees of anteroposterior constraint of the designs on the location of the load-bearing mechanical axis at the knee joint level were also assessed. We evaluated 151 knees from 134 patients with 74 knees receiving meniscal bearing-type and 77 knees receiving rotating platform-type prostheses. In the mediolateral direction, both designs showed significant improvements, whereas in the anteroposterior direction, they revealed no improvements postoperatively and were worsened significantly in meniscal bearing type. Differences in the degree of bone and soft tissue involvement for the correction of alignment may explain the findings.