We have examined the relationship between the size of the flexion gap and the anterior translation of the tibia in flexion during implantation of a posterior cruciate ligament (PCL)-retaining BalanSys total knee replacement (TKR). In 91 knees, the flexion gap and anterior tibial translation were measured intra-operatively using a custom-made, flexible tensor-spacer device.

The results showed that for each increase of 1 mm in the flexion gap in the tensed knee a mean anterior tibial translation of 1.25 mm (SD 0.79, 95% confidence interval 1.13 to 1.37) was produced.

When implanting a PCL-retaining TKR the surgeon should be aware that the tibiofemoral contact point is related to the choice of thickness of the polyethylene insert. An additional thickness of polyethylene insert of 2 mm results in an approximate increase in tibial anterior translation of 2.5 mm while the flexed knee is distracted with a force of between 100 N and 200 N.

Introduction: The aim of introducing mobile-bearing knee replacements was to improve long term survival by maintaining large areas of surface contact, while allowing motion to occur at the bearing-metal interface on the tibial and patellar components. Despite wide use of these implants, there are only a few intermediate or long-term follow-up studies.

Aims: To present the intermediate follow-up results of a cementless, posterior cruciate ligament retaining, low contact-stress, knee replacement system (LCS).

Methods: Between 1987 and 1991 the senior author (U.W.) performed 134 cementless LCS total knee arthroplasties in 121 patients. Twenty of the patients were male, 101 female, with an average age of 70 years (range: 49 years to 91years). In 40% of the cases the patella was resurfaced. The patients were evaluated with clinical knee rating (Insall score) and radiographic analysis, between six and nine years postoperatively.

Results: At the time of the follow-up 94 patients were alive. Twelve patients (10%; 14 prostheses) were contacted by phone after an average of 77 months. Evaluation was possible in 82 patients (68%; 91 prostheses) after an average of 74 months. Ninety percent of these patients had an Insall score of > 80 (good to very good). One patient had a score of < 70 (insufficient). Average flexion was 114 degrees (range: of 70 to 135 degrees). Two patients had flexion of < 90 degrees. There were no radiographic signs of aseptic loosening. The meniscal bearing of four prostheses and one patellar component were replaced. Complications like haematoma, fibrotic arthritis and infection due to endocarditis lenta lead to three revisions.

Conclusion: Our study has shown that the non-cemented posterior cruciate ligament retaining LCS knee replacement system produced very satisfactory results with few complications in the medium term.