Abstract
Introduction
The Primoris® femoral stem was designed to preserve bone and maintain normal stress to the proximal femur, thereby minimizing stress-shielding. The implant is anchored in the femoral neck and metaphysis without diaphysial involvement and differs from other neck prothesis by: a) Elliptical shape to fit the inner neck dimensions. b) On top of Ti– porous-coating electrochemically deposited hydroxy apatite (Bonemaster®) c) The surgical technique aims to enhance initial implant stability by compaction of neck and metaphyseal cancellous bone.
Objectives
As part of stepwise introduction to monitor bone remodeling, RSA data and clinical results.
Methods
A prospective cohort study of 52 patients (Female = 55 years or younger, Male = 65 years or younger) with end stage non inflammatory osteoarthritis and no anatomical abnormality was carried out. Clinical data (HHS score, UCLA, and verbal satisfaction score) were collected regularly and compared with patients who in a previous study had a conventional femoral stem (Bimetric®). Furthermore serial DXA scans and RSA analysis were performed.
Results
Two patients were excluded during surgery (one major neck deformity, one insufficient bony support). One neck fracture (not compromising implant stability). One was revised in the follow period (aseptic loosening). The mean HHS score increased from 54 (median) preoperatively to 95 at one year and 95 at two years. These results favourably compared with the Bimetric group. DXA scans revealed no bone loss in femoral diaphysis and minimum bone loss at the area of calcar. RSA revealed stable bone implant bond.
Conclusions
The early clinical results are encouraging and favourably comparable to the clinical results with a conventional uncemented femoral implant. As part of the stepwise introduction process this clinical step I study justifies further clinical evaluation before the implant is introduced in a wider population.
