The majority of conversion total hip arthroplasties can be considered primary replacements - a matched cohort study

The success of conversion Total Hip Arthroplasty (THA) among primary THA and revision THA re- mains unclear. We hypothesized that most conversion THAss can be performed using primary implants and will have an uncomplicated post-operative course. Thirty-six patients (23 females, mean age 68,0y) who underwent conversion THA for failed interventions for proximal femur fractures in the period 2006-2018 were matched sequentially against patients of the same sex and age who underwent primary THA or revision THA. Data was collected on implants used, major complications, and mortality. PROMs used included the Western Ontario and McMaster Osteoarthritis Index, Harris Hip Score, Visual Analogue Scale and the EQ-5D Health Questionnaire. Seventy- two percent of patients who underwent conversion THA were treated with primary implants and never suffered from a major complication. PROMs were excellent for this group of patients. The distinction primary / conversion / revision THA could not explain differences in outcomes, however the necessity of using revision implants and the development of major complications could. The majority of conversion total hip arthroplasties can be considered a primary replacement. Predicting outcomes for THA should focus on patient frailty and technical difficulties dealing with infection, stability and loss of bone stock and should discard the conversion versus revision terminology.