Erschienen in:
01.09.2005 | Knee
Assessment of posterior stability in total knee replacement by stress radiographs
Prospective comparison of two different types of mobile bearing implants
verfasst von:
S. Louisia, R. Siebold, J. Canty, R. J. Bartlett
Erschienen in:
Knee Surgery, Sports Traumatology, Arthroscopy
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Ausgabe 6/2005
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Abstract
The aim of this study was to assess the posterior stability of two different designs of total knee replacement (TKR) with deep-dished mobile bearing (MB) implants using stress X-rays. In a prospective non-randomized consecutive study, 34 patients with primary osteoarthritis of the knee underwent TKR. In group A (17 knees), they received a MB insert with a Duracon prosthesis and in group B (18 knees), a Genesis prosthesis. In all cases the posterior cruciate ligament (PCL) was resected. All patients had pre- and post-operative kneeling X-rays and were clinically evaluated with the Knee Society Score. Measurements on the radiographs were taken by tracing a line along the posterior cortex of the tibia and then measuring the perpendicular distance to a point marked at the posterior corner of Blumensaat’s line. The average follow up was 10.7 months for group A and 5.4 months for group B. No statistical difference could be found in terms of clinical results and pre- and post-operative kneeling X-rays between the two groups. In each group, all knees demonstrated a significant posterior tibial translation postoperatively compare to their pre-operative status (p<0.0001). There are advantages in resecting the PCL in TKR: mobile flexion gap, correction of fixed deformity, more flexibility to adjust the joint line. The use of a deep dished polyethylene (PE) insert provides stability and use of MB insert reduces PE wear whilst retaining congruity. Two designs of deep-dished MB inserts showed significant posterior tibial translation on stress X-rays. It remains to be determined what amount of laxity is optimal for clinical function and polyethylene longevity.