2015 ISAKOS Biennial Congress ePoster #1447

Medial Pivot Pattern of Knee Kinematics Decrese Patello-Femoral Contact Pressure in Total Knee Arthroplasty

Tokifumi Majima, MD, PhD, Tokyo JAPAN
Takuya Konno, MD, Sapporo, Hokkaido JAPAN
Naoki Seito, MD, PhD, Sapporo, Hokkaido JAPAN
Tomohiro Onodera, MD, PhD, Sapporo, Hokkaido JAPAN
Yasuhiko Kasahara, MD, PhD, Sapporo, Hokkaido JAPAN
Dept. of Orthop. Surg, Hokkaido University Graduate School of Medicine, Sapporo, Hokkaido, JAPAN

FDA Status Cleared

Summary: Intraoperative medial pivot kinematic patterns resulted in significant reduction of PF contact pressure compared with knees demonstrating non-medial pivot kinematic patterns even in the conventional TKA prosthesis.

Abstract:

Introduction

Patello-femoral (PF) complications are among the most frequently observed adverse events (6.6% to 12%) after total knee arthroplasty (TKA). However, the etiology of these complications with patellar resurfacing is yet to be clearly established.
Low PF pressure was considered to be advantageous as high pressures might account for anterior knee pain. There is no study of the relationship between tibio-femoral kinematic patterns after TKA and PF contact stress. We hypothesized that tibio-femoral kinematic patterns after TKA will impact PF contact stress. The aim of this study was to evaluate the relationship between knee kinematics and PF contact stress in mobile bearing prosthesis with navigated TKA procedures.

Methods

Thirty-nine patients (46 knees, average age 73.3) with medial compartment osteoarthritis that underwent posterior stabilized mobile-bearing TKA using identical prostheses (PFC Sigma RPF; Depuy) under a CT-based navigation system (Vector Vision 1.61; Brain Lab) were enrolled in the present study. The real-time assessment of femoral rotation, medial shift, and lateral patellar tilt from knee extension to flexion was measured using the navigation system in the kinematic mode. All knees were divided into the medial pivot group (M group, n = 19) or the non-medial pivot group (N group, n = 27) according to previous reported methods using navigation system. In vivo PF contact stress was measured intraoperatively.

Results

The mean maximum PF stress in the M group was significantly lower than that of the N group (1.7 ± 1.7 MPa vs. 3.2 ± 2.7 MPa, P = 0.03). The mean medial patellar shift from knee extension to flexion demonstrated no significant difference between the M group and the N group (11.7 ± 12.4 mm vs. 8.9 ± 8.9 mm, P = 0.48). The mean lateral patellar tilt also revealed no significant difference between the M group and the N group (9.4° ± 5.2° vs. 11.6° ± 4.1°) (p = 0.33). The femoral component rotation (FCR) was 0.58° internal rotation in the M group and 1.97° internal rotation in the N group (p = 0.14) .

Discussion

Our findings showed a large variation in tibio-femoral mechanics similar to the previous reports. Medial-pivot kinematics reduced PF contact pressure, suggesting that restoring normal tibio-femoral kinematics possibly results in a decreased risk of PF problems such as anterior knee pain after TKA.
We have been reported that the functional activities, patient satisfaction and the knee flexion angle of the medial pivot group were significantly better than those of the non-medial pivot group. The present results may be attributable for these good clinical results. Medial pivot kinematics presumably disperses and equalizes PF contact stress due to direct a femoral groove at a tibial tuberosity in knee flexion.
Our study had several limitations. First, the sample size was small. Second, there is a possibility that knee kinematic measurements during surgery are different from measurements under an outpatient visit. We have previously reported that intraoperative kinematic measurement in TKA strongly correlates with postoperative kinematics.