A critical analysis of radiographic factors in patients who develop dislocation after elective primary total hip arthroplasty.

PURPOSE: In order to diminish total hip arthroplasty (THA) dislocation rate, surgeons strive to achieve adequate component orientation, offset and limb length. In addition, dislocation rate can theoretically be reduced by increasing head diameter and by choosing implants with favorable head-to-neck and cup-to head ratios. We assessed nine radiographic and implant-related parameters associated with an increased risk of dislocation in patients who sustained a dislocation and in those with a stable arthroplasty. METHODS: A total of 1,487 consecutive elective primary THAs performed by a single surgeon, using a posterolateral approach were reviewed at an average follow-up of 18 months (range, 1-112). Fixation was hybrid in 85 % of hips and non-cemented in 15 %. Thirty-eight patients (38 hips, 2.5 %) sustained at least one dislocation. Thirty-seven patients with good quality, standardized anteroposterior radiographs were selected as a "study group". The study group was matched-paired (1:3) with patients who had a stable arthroplasty based on gender, age, BMI, diagnosis and follow-up. Variables compared between the groups included: head size, cup size, head-to-neck ratio, cup-to-head ratio, leg-length discrepancy, offset, cup inclination, cup version and cup orientation based on the safe zone defined by Lewinnek et al. RESULTS: None of the nine parameters showed a statistically significant difference between the groups. DISCUSSION: In this study, 90 % of patients who developed a dislocation had properly positioned acetabular components. In addition, the vast majority of patients in the study group had adequate restoration of limb length and offset. The results of our study may be useful for the orthopedic surgeons who discuss instability following THA surgery, particularly in patients with radiographically sound reconstructions.

A nationwide analysis of risk factors for in-hospital myocardial infarction after total joint arthroplasty.

PURPOSE: Despite acute myocardial infarction (AMI) being a feared medical complication and currently a major cause of death after total hip and knee arthroplasty (THA/TKA), little is known about its peri-operative associated factors. METHODS: Data for this retrospective cohort study were extracted from the Nationwide Inpatient Sample for 2008-2011. Multivariate logistic regression modeling was performed to determine peri-operative factors associated with the development of inpatient AMI following THA/TKA. RESULTS: An estimated 3,096,791 procedures were identified. Perioperative AMI rates were 0.25 % for THA and 0.18 % for TKA. Patients with AMI had significantly greater comorbidity burden, higher peri-operative mortality rates, longer length of hospital stay and increased complication rates. Independent risk factors for the development of AMI comprised advance age, male gender [odds ratio (OR) 1.4, 95 % confidence interval (CI) 1.4-1.5], THA surgery (OR 1.3, 95 % CI 1.3-1.4), low household income (OR 1.3, 95 % CI 1.2-1.4), history of cardiac disease (coronary artery disease: OR 4.9, 95 % CI 4.6-5.2; congestive heart failure: OR 2.6, 95 % CI 2.4-2.8; valvular disease: OR 1.2, 95 % CI 1.1-1.3), diabetes (OR 1.1, 95 % CI 1.1-1.2), pulmonary circulation disorders (OR 1.4, 95 % CI 1.2-1.6), cerebrovascular disease (OR 2.3, 95 % CI 2.0-2.6), peripheral vascular disorders (OR 1.5, 95 % CI 1.4-1.7), coagulopathy (OR 1.4, 95 % CI 1.2-1.5), AIDS/HIV infection (OR 7.9, 95 % CI 4.5-13.9), deficiency anaemia (OR 1.4, 95 % CI 1.3-1.5), fluid and electrolyte disorders (OR 1.9, 95 % CI 1.8-2.0) and the occurrence of concomitant postoperative complications. CONCLUSION: Our findings can be used to better identify patients at high risk of AMI and to develop strategies aimed at diminishing its incidence, which could in turn translate to improved hospital efficiency and quality of care.