Purpose of the study: Cementless hydroxyapatite-coated prostheses have proven their reliability, but how about their longevity? The intimate contact between the receiver bone and the prosthetic implant, due to the bone ongrowth, allows ‘union’ between the inert and living material. The purpose of this restrospective study was to evaluate the behavior of an anatomic femoral hydroxyapatite-coated stem at long-term follow-up.

Materials and Methods: One hundred and eleven total hip arthroplasties were performed with a ABG 1 HA-Coated hip prosthesis (ABG, Stryker Newbury, England) in 101 patients, by one senior operator. A posterolateral approach was done every time. Average patient age at surgery was 61, 3 years [33–83].

Results: Average follow-up was 13 years [10–17,5]. Seventy five THA were reviewed, 21 were dead and 15 were lost. Clinical outcome have been good. The average preoperative Harris hip score and Postel Merle d’Aubigné score were 56,7 and 11,8, which rose to 87,3 and 16,3 at the longest follow-up. Most patients were satisfied with the outcome, no thigh pain was deplored. There were sixteen revisions: 1 bipolar revision for loosening of both component, 14 cup revisions for osteolysis (11) and loosening (3) and 1 stem revision for periprosthetic fracture. Radiographic changes were consistent with bone remodeling. Osteointegration was achieved in 98,7%. Proximal stress-shielding was noted in 36,4%, osteolysis was developed in 66,7% focused essentially in gruen zones 1a and 7a and never below HA coating. Cancellous densifications were found to be mainly in zones 2, 6, 9 and 13 (92,7%, 94,2%, 91,3% and 85,5%), extending distally in zones 3, 5, 10 and 12 (33,3%, 31,9%, 34,8% and 39,1%). A femoral shaft hypertrophy was noted in 27,5%.

Discussion: In this serie, the global survivorship of ABG 1 THA at 13 years of follow-up was 78,7%. Acetabular cup survivorship was 80%. Failure of acetabular cup was well explained by osteolysis and high wear rate. Stem survivorship was 97,3% and the failure rate of femoral stem due to aseptic loosening was only 1,3%. Excellent results of femoral stem were due to the good osteointegration, cause of the anatomic design of the stem and the hydroxyapatite coating.

Conclusion: The results of our series have proven that anatomic cementless stem with HA coating provide a long term reliability and longevity.

Introduction

Debate continues regarding the relative advantages of ceramic-on-ceramic (CoC) and metal-on-polyethylene (MoP) articulations in total hip arthroplasty (THA). Perceived benefits of CoC include longevity, and low wear - in turn limiting the effects of particulate wear debris. However, CoC bearings cost significantly more, and concern remains over the risk of ceramic fracture; a complication not seen with MoP bearings, which are also cheaper.

Aim: Assessing Polyethylene wear is very important in following up patients after Total hip replacement (THR) and Livermore method (using callipers) is routinely used by clinicians in calculating this wear. Our aim was to assess if ‘Imagika’, a new computer software programme can accurately assess polyethylene wear(PE-wear). We also compared the computer software with the Livermore method in calculating wear. Method: We used 15 different THR X rays of patients who had an ABG total hip replacement done. X rays that were included for the calculations were taken at different time intervals following the operation. Wear was calculated on each X ray by 3 clinicians using both the methods, on 3 separate occasions. We compared the Livermore method and the computer software for consistency of measurements and also calculated the inter and intra observer variability for both. Results: There was a statistically significant difference (at the 5% level) between the measurements taken by the Imagika software and the Livermore method. F(1,88) = 5.38, p< 0.05. There was a statistically significant difference in the inter-observer measurements using the Livermore method. F(2,42) = 4.18, p< 0.05, but there was no significant inter-observer variation using the Imagika computer software. There was no statistically significant difference (at the 5%level) in the intra-observer variability of both groups. Conclusion: The Imagika computer software proved to be better than the Livermore method in calculating wear with regards to inter-observer bias. There was also a significant difference between measurements taken using both methods. We conclude that the computer software may be a more accurate tool in the assessment of PE-wear in the future

Introduction This study was performed to evaluate the wear rates of Zirconia ceramic heads manufactured prior to the introduction of hot isostatic pressing, on a modular cementless polyethylene cup, and to compare this with the wear rate of a cobalt chrome head coupled with the same cup. Methods Radiological analysis of 281 primary uncemented ABG total hip arthroplasties performed between 1991 and 1994 was carried out. Patients were divided into three groups: 203 patients with 28 mm zirconia head/polyethylene bearings, 47 patients with 32 mm zirconia ceramic head/polyethylene bearings, 31 patients with 28 mm cobalt chrome head/polyethylene bearings. Wear analysis was performed using the Martel software after digitising radiographs on a flatbed scanner. Initial radiographs were at a minimum of one year to exclude bedding in, and follow-up radiographs a minimum of two years later. Mean follow-up was 6.5 years. Results The mean linear wear rate of the groups following age and gender matching: for 28 mm Zirconia heads 0.22 mm/yr, for 32 mm Zirconia heads 0.20 mm/yr and for 28 mm metal heads 0.14 mm/yr (p< 0.05). The patients with Zirconia heads had higher rates of osteolysis and revision than those with cobalt chrome heads. Conclusions The reason for this increased wear rate of Zirconia on polyethylene may well be the transformation of the tetragonal stable phase of the Zirconia to the monolithic unstable phase on the surface of the material. This transformation at grain boundaries on the surface results in ceramic grain “pull-out” by the sliding action of the head against the polyethylene cup. This phenomenon may well occur as a result of the Zirconia processing; the ceramic studied was produced prior to hot isostatic pressing, which produces an inherently more stable ceramic i.e. a higher percentage of the tetragonal phase. In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source

Introduction and Aims: This is a prospective randomised trial comparing the ABG uncemented total hip replacement with the Charnley in 243 patients less than 65 years of age. A standardised protocol and anterolateral approach was used. Method: The ABG I cup was used in combination with a polyethylene liner. All stems were templated and a 28mm cobalt chrome head was used. Early mobilisation with partial weightbearing for six weeks was allowed. In the Charnley group, Elite polyethylene cups were used in conjunction with 22mm monoblock stems. All hips were inserted with pressurised CMW cement. Patients were followed up annually. Standardised radiographs were taken at each visit and the Harris hip score and Merle d’Aubigné outcome measures recorded. There were 222 hips available for follow-up, 96 ABG hips and 126 Charnley hips (17 died and 10 were lost to follow-up), with the mean age at surgery and mean length of follow-up comparable. Most hips were replaced due to osteoarthritis. There was no significant difference in the mean Harris hip or Merle d’Aubigné scores at one year and at latest follow-up. Results: Radiographic results demonstrated accelerated polyethylene wear in the ABG hips with mean polyethylene wear at seven years being 2.1mm compared with 0.9mm for Charnley hips. Wear associated lysis around the ABG cup was the major reason for failure, with a total of eight cups (8.3%) undergoing revision. Conclusion: There was no evidence of subsidence of the stem or osteolysis around the stem despite the polyethylene wear. Conversely, in the Charnley group the stem was the major reason for failure with 12 stems (9.5%) being revised for aseptic loosening. The Kaplan Meier Survivorship at 10 years was 66.6% ± 19.1% for the ABG and ± 82% for the Charnley group. This was not significant