Joint line level in revision total knee replacement: assessment and functional results with an average of seven years follow-up.

INTRODUCTION: It has been shown that the distance between the joint line (JL) and the fibular head is constant in both knees in a given individual. We analysed the influence of the JL level difference between the revised knee and the native knee from the functional outcomes after TKR revision. METHODS: This multicentre study assessed retrospectively a consecutive series of 177 revised total knee replacements. Patients with contralateral knees that had undergone previous major surgery or trauma were excluded. The JL level difference between both knees was measured on Knee's AP standing X-rays and compared to the KSS Knee and Function scores at the final follow-up. RESULTS: Eighty-five cases were analysed at a mean of seven years follow-up. There was a significant increase in KSS Knee and Function scores after surgery. The average elevation of the JL was 2.2 mm (s.d. 2.66 mm) compared with the healthy contralateral knee. When the JL was elevated more than 4 mm this correlated with a decreased KSS Function score and decreased post-operative knee flexion. CONCLUSIONS: Poorer functional results are significantly associated with an elevation in the JL compared to the contralateral healthy knee. In those patients with a suitable contralateral knee the JL level to restore can be assessed by the distance between the femoral condyle and the apex of the fibular head of the contralateral knee.

Obesity is no longer a risk factor for dislocation after total hip arthroplasty with a double-mobility cup.

PURPOSE: Dislocation is one of the most feared complications after total hip arthroplasty (THA). This risk is greater in obese patients compared with the general population. METHODS: We performed a retrospective cohort study in which the main objective was to compare the dislocation rate between obese patients (BMI > 30 kg/m²) (exposed group) and non-obese patients (BMI ≤ 30 kg/m²) (unexposed group) after primary THA with a double-mobility acetabular cup. The patients had a minimum follow-up of 24 months. RESULTS: The 'obese' group consisted of 77 THA cases and the 'non-obese' group of 425 cases; the two groups were similar in terms of age, gender and ASA score. After a mean follow-up of 58.3 ± 27 months (range 27-159), 43 patients had been lost to follow-up and 56 had died; the two groups had similar mean values. One patient in the 'obese' group had suffered a dislocation due to a fall 16 months after the THA. One patient in the 'non-obese' group had suffered a dislocation after a periprosthetic femur fracture with stem subsidence two months after the THA procedure. Both patients underwent surgical revision where the double-mobility cup was preserved; there were no further dislocation events as of the last follow-up. The dislocation rate in the two groups was similar (1.3 % versus 0.23%, p > 0.05). No cases of loosening were found. Revisions were secondary to deep or superficial infection (n = 22), periprosthetic femur fracture (n = 10) or haematoma (n = 3). CONCLUSION: These findings imply that double-mobility cups are a reliable way of reducing the risk of dislocation in obese patients after primary THA.