DOS 2018

64 · DOS Abstracts Bone remodeling around a short femoral neck stem - 5 years follow up of the Primoris® Janus Duus Christiansen, Poul Torben Nielsen, Mogens Laursen, Gordon Blunn Northern Ortopaedic Division, Aalborg University Hospital; University College London RNOHT, Stanmore, United Kingdom Background: The use of conventional stems in total hip arthroplasty gives a non- physiological load pattern. In case of revision, the bone stock left for reim- plantation may be compromised. The Primoris ® stem is a development of earlier conceived bone-saving prosthesis in order to preserve bone stock maintaining normal stress to the proximal femur. Purpose / Aim of Study: This study includes postoperative changes in bone mineral densities (BMD) in the proximal femur and evaluation of bone stock preservation in patients operated with the Primoris ® stem. Materials and Methods: A prospective cohort study of 52 patients scheduled for surgery with the femoral neck-preserving Primoris ® stem was carried out. Patients were studied with DXA-scans to evaluate BMD around the implant. Results from DXA-scanner were measured in 4 specific regions of interest (ROI) – the area of the greater trochanter (ROI1), a lateral area below the greater trochanter (ROI2), a distal area of the diaphysis (ROI3) and a medial region of calcar and trochanter minor (ROI4). Postoperative BMD results from day one, 6 weeks, 6 months, 1 year, 2 years and 5 years were analyzed including double measurements at 1 year FU. Findings / Results: 3 patients were excluded, leaving 49 patients for BMD- analysis. A slightly non significant decrease was found at 5 years FU compared to day 1 in ROI1. A significant decrease was found at 5 year FU compared to day 1 in ROI2. A non significant gain of BMD was found at 5 years FU compared to day 1 in ROI3 and ROI4. Conclusions: As to bone preservation, the results are encouraging supporting the rationale of the Primoris® implant. With special regard to the calcar area (ROI4), bone stock has remained stable throughout the follow up period. If the proximal femoral bone stock is preserved, the potential for successful future revision is maximized. 7.