Body mass index, hip function and surgeon volume are independent predictors of dislocation: an analysis of 4334 total hip replacements.

The aim of this study was to identify pre-operative and intra-operative factors that are predictive of dislocation following primary total hip replacement (THR). Data were prospectively collected for a consecutive series of 4334 THRs undertaken over a 14-year period. Ninety-eight (2.3%) of the 4334 patients had one or more dislocation post-operatively. A body mass index (BMI) of ≥ 35 (p < 0.001), a Harris Hip Score (HHS) of ≤ 41 (p < 0.001) and a low-volume surgeon (p < 0.001), which was defined as performing fewer than 43 THRs per annum, were identified as independent predictors of dislocation using logistic regression analysis. Using these three variables in differing combinations the risk of dislocation varied from 0.5 to 10.4%. Patients at high risk of dislocation, with a BMI of ≥ 35 and a pre-operative HHS of ≤ 41, undergoing surgery by a low-volume surgeon had a dislocation rate of 10.5%, but this decreased to 2.3% when operated on by a high-volume surgeon. These risk factors could be used to identify patients at high risk of dislocation, and modification of these factors, such as weight loss to achieve a BMI of ≤ 35 or referral to a high-volume surgeon, may decrease the risk of dislocation and the resulting secondary morbidity.

Predicted waiting times for orthopaedic surgery : an urgent need to address the deficit in capacity.

Cite this article: Bone Joint Res 2022;11(12):890-892.

Immune responses in patients with metal-on-metal hip articulations: a long-term follow-up.

Metal-on-metal (MoM) hip bearings are being inserted into ever-younger patients. The effects on the immune system of chronic exposure are unknown. We investigated the immune response of patients with MoM hip bearings. In patients with MoM implants, the expression of antigen-presenting cell (APC) surface molecules (CD86 and HLA-DR) was seen to be significantly higher (P < .05) than control group. High levels of APC surface molecules suggest an activated state and attempts to propagate an immune response. However, in the same group, the expression of T-cell markers (CD3 and CD28) was low, indicating a small T-cell population. This suggests, despite the activation of APCs, that T cells down-regulate immune responses in MoM articulations. Conversely, in metal-on-polyethylene articulations, expression of T-cell molecules was elevated and expression of APC molecules lowered.

Tibiofemoral kinematics of the anterior cruciate ligament (ACL)-deficient weightbearing, living knee employing vertical access open "interventional" multiple resonance imaging.

BACKGROUND: Our current understanding of tibiofemoral kinematics in the anterior cruciate ligament (ACL)-deficient knee is very limited. Using vertical open-access MRI, it is possible to accurately analyze tibiofemoral motion in patients with isolated rupture of the ACL. STUDY: Prospective cohort study. PURPOSE: To assess if ACL rupture alters normal knee weightbearing kinematics. METHODS: Tibiofemoral motion was assessed through the arc of flexion from 0 degrees to 90 degrees in 10 patients with isolated rupture of the ACL in one knee and a normal contralateral knee. Midmedial and midlateral sagittal images were analyzed in all positions of flexion in both knees to assess the tibiofemoral relationship. RESULTS: In the lateral compartment of the knee, the tibial plateau is persistently subluxed anteriorly throughout the arc of flexion from 0 degrees to 90 degrees (flexion facet center to posterior tibial cortex distance of 15.8 mm +/- 2.9 in ACL-deficient knees compared to 21.4 mm +/- 1.4 in normal knees at 0 degrees extension, P <.0001) when compared to normal knees. The medial tibiofemoral relationship is unchanged compared to normal knees. CONCLUSION: Rupture of the ACL changes tibiofemoral kinematics producing anterior subluxation of the lateral tibial plateau. CLINICAL SIGNIFICANCE: Altered kinematics may explain, at least in part, the increased incidence of secondary osteoarthritis in patients with ACL rupture.

Predictors of excellent early outcome after total hip arthroplasty.

BACKGROUND: Not all patients gain the same degree of improvement from total hip replacement and the reasons for this are not clear. Many investigators have assessed predictors of general outcome after hip surgery. This study is unique in its quest for the predictors of the best possible early outcome. METHODS: We prospectively collected data on 1318 total hip replacements. Prior to surgery patient characteristics, demographics and co-morbidities were documented. Hip function and general health was assessed using the Harris Hip score (HHS) and the Short-Form 36 respectively. The HHS was repeated at three years. We took a maximal HHS of 100 to represent an excellent outcome (102 patients). Multiple logistic regression analysis was used to identify independent predictors of excellent outcome. RESULTS: The two strongest predictive factors in achieving an excellent result were young age and a high pre-operative HHS (p = 0.001). CONCLUSIONS: It was the young and those less disabled from their arthritis that excelled at three years. When making a decision about the timing of hip arthroplasty surgery it is important to take into account the age and pre-operative function of the patient. Whether these patients continue to excel however will be the basis of future research.