High body mass index is associated with increased risk of implant dislocation following primary total hip replacement: 2,106 patients followed for up to 8 years.

BACKGROUND AND PURPOSE: Implant dislocation is one of the commonest complications following primary total hip replacement (THR). We investigated the effect of body mass index (BMI) and tobacco use on the risk of this complication. SUBJECTS AND METHODS: Through linkage between the Swedish Construction Workers' cohort and the Swedish Inpatient Register, 2,106 male patients who had undergone primary THR between 1997 and 2004 were identified. We used Cox multivariable regression analysis to study the association between BMI and tobacco use and the risk of implant dislocation. RESULTS: 53 patients (2.5%) developed implant dislocation during a mean of 2 (0-3) years of follow-up. We found overweight and obesity to be associated with increased risk of implant dislocation (HR = 2.5,95% CI: 1.1-5.5 and HR = 3.7, 95% CI: 1.5-9.3, respectively as compared to those of normal weight). There was no statistically significant association between tobacco use and the risk of dislocation. INTERPRETATION: Greater attention should be given to high BMI as a risk factor for implant dislocation following THR.

MRI-negative bucket-handle tears of the lateral meniscus in athletes: a case series.

Magnetic resonance imaging (MRI) is the most widely used non-invasive test for assessing intra-articular injuries of the knee. It has been suggested that a negative MRI can be useful in avoiding the need for diagnostic arthroscopy in cases where clinical examination is equivocal. However, the sensitivity and specificity of MRI is not 100%, particularly for tears of the lateral meniscus. Furthermore, a false negative MRI scan may result in premature return to play in athletes, resulting in increased risk of further damage to a torn meniscus. To illustrate this issue, we present a case series of eight elite athletes who all presented with mechanical knee symptoms and where MRI scans revealed no significant intra-articular pathology. Five of the athletes were allowed to return to sport on the basis of a negative MRI. All patients were subsequently found to have a bucket-handle tear of their lateral meniscus at arthroscopy. Two independent, experienced musculoskeletal radiologists were asked to review the MRI films without being given any clinical history of the cases. Although injuries to the popliteus tendon were noted in two of the athletes who had sustained a recent acute injury to their knee, no meniscal tears were identified. Thus arthroscopy remains the gold standard for the assessment and management of high-demand patients with a clinical suspicion of meniscal pathology.