Influence of the anterior-posterior femoral translation on the range of motion in cruciate-retaining total knee arthroplasty

Comparison of intraoperative kinematics between cruciate-retaining and medial-stabilized inserts in total knee arthroplasty using a CT-free navigation system

BACKGROUND

The kinematics of total knee arthroplasty (TKA) have been shown to affect postoperative function and patient satisfaction. A medial stabilized (MS) insert was designed to improve kinematics by enhancing medial stability and inducing lateral rollback in comparison to cruciate-retaining (CR) inserts. This study aimed to compare the intraoperative kinematic patterns between CR and MS inserts in TKA using a CT-free navigation system.

METHODS

A total of 23 knees from 21 patients who underwent primary TKA for osteoarthritis were included. A CT-free navigation system (BrainLab KNEE3) was used to record intraoperative kinematics during the CR and MS insert trials. Kinematic parameters, including kinematic patterns, such as anteroposterior (AP) translation of the medial and lateral condyles and rotational angles, were analyzed based on range of motion.

RESULTS

The MS insert exhibited significantly less medial AP translation compared to the CR insert (7.0 ± 5.0 vs. 10.3 ± 5.1 mm, p = 0.04). No significant differences were observed in the lateral AP translation (11.5 ± 6.2 vs. 12.8 ± 5.2 mm, p = 0.41), rotational angle (6.3 ± 4.5 vs. 4.7 ± 4.4, p = 0.20), or kinematic patterns.

CONCLUSION

MS inserts may enhance stability by reducing medial translation. Their effect on reproducing medial pivot kinematics is comparable to that of the CR inserts.

High range of motion in the first ten postoperative days after TKA does not predict superior outcome in the long run

INTRODUCTION

To retrospectively investigate the early postoperative range of motion (ROM) (days 4, 7, 10) after total knee arthroplasty (TKA) and to test for associations (a) with long-term outcome in terms of ROM and (b) with a disease-specific knee score.

MATERIALS AND METHODS

A retrospective analysis was performed in patients with previous primary TKA. Data taken from the medical records were ROM from preoperative and postoperative days 4, 7 and 10 and 1 year. As patient-reported outcome the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC Score) was taken from preoperative and one year after TKA.

RESULTS

316 patients (330 knees) were available. Only negligible correlations were determined between ROM at twelve months postoperative and ROM in the early postoperative days (days 4, 7, 10). Similarly, only negligible correlations were determined between ROM in the early postoperative days (days 4, 7, 10) and the 1-year WOMAC.

CONCLUSION

From the main findings it would seem that steepness of ROM ascent in the early postoperative days is of minor importance for (a) long-term ROM and (b) long-term knee score outcome after TKA.

Flexion gap stabilization by oversizing posterior condylar offset in deep-dished total knee replacement does not compromise flexion: A single-surgeon, retrospective, observational, mid-term series

INTRODUCTION

In total knee replacement surgery, medio-lateral knee balancing is recognized as the key to achieving satisfactory functional results. But it may not be enough to stabilize the flexion gap using deep-dished implants. We achieved flexion gap balance by oversizing the femoral component, thus increasing the posterior condylar offset (PCO). The purpose of this study was to describe the applicability of this technique and to test whether it produced adverse effects on medium-term outcomes. We hypothesized that it would not compromise the results if used properly. We therefore asked: (1) at how many cases of flexion gap balance would require oversizing the femoral component; (2) if femoral components oversizing would modify the mid-term results as per forgotten joint score (FJS) scores and whether flexion gain would be comparable to patients in whom it was not increased.

MATERIALS AND METHODS

Ninety-four patients (120 knees) were operated between September 2009 and 2011 (age 68±9 years) using the cementless Hyperflex version of the Natural Knees (Zimmer, Warsaw, IN, USA). Postero stabilization was achieved using deep-dished inserts. The Gender configuration has provided narrow inserts to better adapt the female anatomy. A special navigation system measured the displacement of the lateral and medial femoro-tibial contact points with infra-millimetric precision. Adopting a tibial cut first, gap-balancing technique with anterior referencing, the decision to oversize the femoral component relied on the 90° flexion drawer test, which showed more than 6mm sagittal laxity before the femoral bone cuts. Eighty-one (105 knees) patients were reviewed with average 63±27-month follow-up.

RESULTS

Femoral components were augmented by 1 size in 60 cases and by 2 sizes in 7 cases. At final review, knees with an oversized femoral component (60) achieved the same results as those implanted with a non-oversized femoral component (n=45) in terms of mean flexion gain (-5°±34 versus -4°±23, p=0.78), mean FJS (63±26 versus 61±23; p=0.56).

CONCLUSION

Balancing the Flexion gap by oversizing the femoral component did not compromise flexion range and functional results.

LEVEL OF EVIDENCE

IV, Retrospective cohort study.