2015 ISAKOS Biennial Congress ePoster #1438
Effects of Soft Tissue Balancing with Lateral Loose in the Flexion Position on 3D Kinematics in a Posterior-Stabilized TKA
Eiichi Nakamura, MD, PhD, Kashimashiki-Gun, Kumamoto JAPAN
Nobukazu Okamoto, MD, PhD, Kumamoto, Kumamoto JAPAN
Hiroaki Nishioka, MD, PhD, Kumamoto City JAPAN
Hiroshi Mizuta, MD, PhD, Kumamoto City JAPAN
Department of Orthopaedic Surgery, Faculty of Life Sciences, Kumamoto University, 1-1-1, Honjo, Chuoku, Kumamoto-City, Kumamoto, JAPAN
FDA Status Cleared
Summary: We investigated the relationship between the intraoperative soft tissue balancing and the 3D kinematics at 1 year after surgery in 20 knees implanted a posterior-stabilized fixed-bearing TKA, and Our results suggest that the soft tissue balancing with lateral loose from 2 to 5 mm in the flexed position appears to be more advantageous in order to acquire the postoperative medial pivot motion.
Abstract:
Introduction
In total knee arthroplasty (TKA), to acquire the proper soft tissue balancing is an essential procedure for good clinical outcome. In general, the agreement that flexion and extension gaps should be equal and symmetrical has been recommended. However, how the intraoperative balancing affects on the postoperative kinematics of the implanted knee is not clear. Based on our previous analysis, we have
Hypothesis
that lateral loose in the flexion position in soft tissue balancing leads to acquire the postoperative medial pivot motion. The purpose of this study is to clarify this hypothesis.
[Patients & Methods] Twenty knees of 16 consecutive patients who required a unilateral TKA for osteoarthritis were enrolled in this prospective study.
Surgical Procedure: All patients were implanted with a posterior-stabilized fixed-bearing prosthesis. As for the soft tissue balancing, after the resection of bone, and the step by step medial release, we measured the joint component gap (mm) and ligament balance (lateral loose as positive: º), with the knee at 0º and 90º of flexion with the patella reduced under the joint distraction force of 40 lbs using the offset tensor. After the setting of the proper polyethylene insert, the medial and lateral edge distance from the femoral condyle to the articular surface of insert were calculated
Evaluation: According to the amount of the differences in the edge distance between both sides at 90º of flexion (ED90), the patients were divided into the group A less than 2 mm and the group B more than 2 mm. At one year after surgery, all patients were evaluated clinically and radiographically. In addition, a fluoroscopic analysis was performed during a lunge activity. Using a 3-D/2-D registration technique, the amount of rollback of the femoral condyle and the tibial rotational angle relative to the femur were measured. These parameters were compared between both groups.
Results
The mean ED90 were 1.2 mm (0 - 2.0) in the group A of 8 knees and 3.7 mm (2.3 - 5.2) in the group B of 12 knees. There were no differences in the other parameters between both groups.
The mean posterior translation of the lateral condyle and the tibial internal rotational angle in the group B were significantly larger than those in the group A (p=0.003 and 0.018, respectively). The frequencies of medial pivot pattern were 2 knees (25%) in the group A while 11 knees (92%) in the group B (p<0.001).
Discussion
In normal subjects, during squatting or kneeling, the femoral motion pattern is a medial pivot. Recently, the relationship between the postoperative kinematics and clinical outcome becomes to be addressed but it is not completely understood. Nishio et al. showed that the medial pivot pattern positively influences the flexion angle and patient-reported outcomes after TKA.
Our results suggest that the soft tissue balancing with lateral loose from 2 to 5 mm in the flexed position appears to be more advantageous in order to acquire the postoperative medial pivot motion.