The purpose of this investigation was to determine the relationship between height, weight, and sex with implant size in total knee arthroplasty (TKA) using a multivariate linear regression model and a Bayesian model. A retrospective review of an institutional registry was performed of primary TKAs performed between January 2005 and December 2016. Patient demographics including patient age, sex, height, weight, and body mass index (BMI) were obtained from registry and medical record review. In total, 8,100 primary TKAs were included. The mean age was 67.3 years (SD 9.5) with a mean BMI of 30.4 kg/m2 (SD 6.3). The TKAs were randomly split into a training cohort (n = 4,022) and a testing cohort (n = 4,078). A multivariate linear regression model was created on the training cohort and then applied to the testing cohort . A Bayesian model was created based on the frequencies of implant sizes in the training cohort. The model was then applied to the testing cohort to determine the accuracy of the model at 1%, 5%, and 10% tolerance of inaccuracy.Aims
Methods
Obesity has been shown to be an independent risk factor for aseptic loosening of the tibia and smaller implant size has been correlated with increased risk of failure of tibial components in obese patients [1,2]. Many surgeons have noted that obese patients, especially females, not uncommonly will have small implant sizes. As such, we hypothesized that obesity was not directly correlated with total knee arthroplasty (TKA) implant sizes. The purpose of this study was to determine if increasing body mass index (BMI), height, and/or weight is associated with implant size in primary TKA. The institutional registry of a single academic center was reviewed to identify all primary TKAs performed between 2005 and 2016. Those without minimum 2-year follow-up or with incomplete implant data were excluded. The different manufacturer's implant designs were categorized based on anteroposterior and mediolateral dimensions of the femoral and tibial component sizes and cross sectional area was determined. BMI was categorized by the World Health Organization (WHO) obesity scale (Class I: BMI 30 to <35, Class II: BMI 35 to <40, Class III: BMI 40 kg/m2 or greater). Patient demographics including sex, height, weight, and BMI were analyzed to evaluate correlations with implant size using Pearson correlation coefficients.Background
Methods
Dislocation of the distal radioulnar joint (DRUJ) in association with fractures of both bones of the forearm has received relatively little attention in the literature. The purpose of this study was to evaluate the integrity of DRUJ and evaluate the association between the level of fracture and instability of DRUJ following fracture both bones of forearm. This was a prospective study of 65 patients, over 3 years followed up for 12 months. All patients were treated with open reduction and internal fixation of radius and ulna. The mean age of the patients was 34.8 years (15–68 yrs). There were 51 males and 14 females. There were 18 fractures involving distal third of forearm, 42 fractures in the middle third and 5 fractures of the proximal third. 38 fractures (58.4%) had subluxation of the DRUJ and 27 had no DRUJ subluxation. All subluxations were dorsal. Post-operatively, 30 of the 38 fractures (78.9%) had persistent DRUJ subluxation. Of the 27 fractures, which had no pre-operative DRUJ subluxation, 10 fractures (37%) revealed dorsal subluxation in the post-operative radiographs. All fractures were immobilised in above elbow plaster casts for 6 weeks. All patients were followed up at 3, 6 and 12 months. Patients were assessed clinically, radiologically with standardised radiographs and functional assessment of grip and pinch strength using Jamar dynamometer. At 12 months, 12 patients had significant symptoms associated with DRUJ. Of these, 4 had functional restriction, which were related to complex DRUJ dislocations. DRUJ dislocations are more common in fractures, which are in the direction of the interosseous membrane (p<
0.002). They are commonly associated in fractures involving the middle and distal third of the forearm. There is a tendency for under-reporting of DRUJ dislocations in fractures of both bones of forearm and hence, more attention should be paid to this entity.
We describe a patient with multiple sclerosis (MS), who developed recurrent dislocations after total knee arthroplasty. She had both knees replaced using similar mobile-bearing knee prostheses, but the outcome was worse in the leg which was more severely affected with MS.
