Elsevier

The Journal of Arthroplasty

Volume 22, Issue 2, February 2007, Pages 235-240
The Journal of Arthroplasty

Original Article
The Clinical Consequences of Flexion Gap Asymmetry in Total Knee Arthroplasty

https://doi.org/10.1016/j.arth.2006.04.024Get rights and content

Abstract

This study was carried out to compare femoral component rotation of 18 knees from 18 patients who suffered from lateral flexion instability after total knee arthroplasty (Western Ontario and McMaster University Osteoarthritis [WOMAC], 6.4 points; International Knee Society [IKS] score, 119 points) with 10 asymptomatic controls (WOMAC, 0.1 points; IKS score, 182 points) after total knee arthroplasty. The symptomatic patients showed increased lateral joint laxity as determined by fluoroscopic stress radiography. Femoral component rotation was determined by computed tomography scans. The femoral component rotation was more internally rotated in symptomatic patients (5.5°) than in controls (1.0°) (P = .04). Varus laxity in flexion was higher in symptomatic patients (11.0°) than in controls (7.0°) (P < .001). Increased lateral flexion laxity is associated with increased internal femoral component rotation and a less favorable clinical outcome.

Section snippets

Recruitment of Patients and Controls

Eighteen consecutive patients (median age, 71.5 years; range 53-80 years; 16 women, 2 men) with a persistent painful knee and clinically identified increased lateral flexion laxity after posterior cruciate retaining fixed-bearing total knee arthroplasty with patellar resurfacing (median postoperative follow-up of 42 months; range, 24-156 months) were included in the study. Exclusion criteria were implant loosening or infection, scar neuroma, patellar maltracking, oversized components, flexion

Results

The results of the fluoroscopic stress radiography are summarized in Table 1. Lateral joint opening in flexion was on average 4° larger in symptomatic patients than in controls, and this finding was statistically significant. Medial joint opening in flexion was not increased in either group. Medial and lateral joint opening in extension was not increased neither in the symptomatic nor in the control group. Joint opening in extension was on average 2° higher on the lateral side compared with the

Discussion

Symmetrically balanced collateral soft tissues in extension and in flexion 22, 23 and alignment of the tibial and femoral components perpendicular to the mechanical axis in the coronal plane [24] are major surgical goals in total knee arthroplasty. Erroneous resection of the tibial plateau and distal femoral condyles or inadequate soft tissue release for varus or valgus contracture will result in an asymmetric extension gap. Extension gap imbalance because of insufficient soft tissue release

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    No benefits or funds were received in support of the study.

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