Introduction: Uncemented total hip arthroplasty has evolved significantly over the past two decades. During this period many implants with different shapes, designs and coatings have developed and are being used with variable results. We present a series of 100 uncemented hip arthroplasties using the Duraloc 100 series cup and Corail stems which have been in use at Merlin Park for the past 5 years and 1 year respectively. The CORAIL stem first introduced in 1986 has a triplanar wedge design for optimal metaphyseal fixation. The prosthesis is pointed in its distal part to allow centering in the medullary canal without cortical locking. The titanium stem is fully coated with a 150 micron thick layer of hydroyapatite. According to the Norwegian arthroplasty register the stem has 99.5% survival at 4.5 years (Havelin L1, Espheaug B, Vollset SE, Engesaeter LB).
The Duraloc 100 series acetabular cups are hemispherical, porous-coated implants that are press fitted to a cavity reamed 2mm smaller than the cup diameter.
Material and methods: Between January 2002 and September 2003 we carried out 100 uncemented THRs in 65 males and 35 female patients. Patients were deemed fit for uncemented hip replacement if they had good bone stock and had no co-morbid condition which might compromise bone quality. Preoperative work up was carried out to exclude any generalised diseases that might compromise bone quality, including bone density measurements where appropriate. Baseline WOMAC scores and Harris hip scores were performed pre-operatively and at latest follow up. Operative details were recorded along with post-operative complications. Patients were followed up clinically and radiologically for a period of 6 to 26 months.
Results: There were 65 male patients and 35 female patients. Average age in men was 62.5 years (range 40 to 85 years) and in women was 65 years (range 48 to 86 years). Four patients had rheumatoid arthritis, the rest had osteoarthritis. The average post-op hospital stay was 12 days. The mean WOMAC score increased from 45 pre-op to 87 at the latest follow up. The average Harris hip score also increased from 52 pre-op to 92 at latest follow up.
All procedures were either performed or directly supervised by the senior authors. Operations were performed through an antero-lateral approach, the femur was prepared first and a trial reamer was left in the femoral canal to minimise blood loss while the acetabulum was reamed. The average duration of surgery was 65 minutes (range 45 to 100 mins) and average intra-operative blood loss was 300mls (range 125 to 750mls). Intra-operative complications included 2 proximal femur stable split fractures, they were identified on table and fixed with circlage cables. Patients were allowed to mobilise partial weight bearing as tolerated. Complications included 4 deep venous thromboses, three superficial wound infections, one respiratory tract infection and one myocardial infarction. At the latest follow up there are no dislocations, no deep infections and no loosening of the cup or the stem.
Discussion: When considering new implants and techniques in arthroplasty long term outcome of studies are necessary before any firm conclusions can be drawn regarding ultimate efficacy. This study however confirms that uncemented THRs using Duraloc cups and Corail stems is safe, involves minimal blood loss and gives good short term results. As there is no cement used, the duration of surgery is at least 15 to 20 mins less than an average cemented THR, which may be important when access to theatre is limited. The procedure is easy to learn and has well designed instrumentation. While there is no substitute for long term studies we feel that these early results are encouraging and justify continued work with the procedure in the context of a well designed prospective randomised trial comparing cemented and uncemented femoral components.
