Postoperative dislocations are known to be a big problem in revision surgery. In literature dislocation rates vary from 4.8% to 33% after previous surgery. In revision surgery, impingement of the implant components, the capsular and soft tissue release, muscular weakness and greater trochanter problems can give additional instability. The reason for revision is important, where instability, infection and tumour cases will lead to a higher percentage of dislocations. The use of big metal heads on polyethylene should be avoided because of the higher volumetric wear. With the new developments of metal-on-metal hip resurfacing and the production of big modular metal heads, the metal-on-metal bearing should guarantee a low-wear result without osteolysis. Between November 2000 and December 2003 45 patients requiring a revision were treated with a Birmingham Hip Resurfacing cup (MMT, UK) and a big metal-on-metal modular head. All surgery was done with a posterolateral approach. Cup sizes range from 44 to 66 mm, head sizes range from 38 to 58 mm. The head sizes most often used were 58 mm, 54 mm and 50 mm. All patients were prospective followed using the Orthowave software (CRDA France). In this series of 45 revisions (mean age 56.17) with large modular heads we encountered 2 dislocations, which give us a dislocation rate of 4.4%. One of these dislocations became recurrent and was revised to a full-constrained acetabular component. Our own dislocation rate in revision hip surgery is 13% (21/159) in the anterolateral approach. Dislocations using the posterolateral approach increased this percentage to 14.8% (21/141). Taking in account that 31% of the causes of revision were infection and recurrent dislocation, this trial demonstrates that large diameter ball heads give beside a better range of movement also a statistically proven reduction in the dislocation rate in revision hip surgery.
The difference in outcome after uncemented ceramic-on-ceramic total hip and metal-on-metal resurfacing is looked at in comparable patient groups. Theoretical advantages in resurfacing are less bone resection, normal femoral loading, avoidance of stress shielding and restoration of normal anatomy. In addition, reduced risk of dislocation, less leg lengthening and easier revision should convince us to perform metal-on-metal resurfacing. These advantages of resurfacing, the subjective “better feeling” and having a more “normal” joint is illustrated by objective proof with functional scores and activity. The first 250 cases of 1067 (September 1998 –March 2004) performed Birmingham Hip resurfacings (MMT, UK) (follow up 2–5 years, mean age 49.54) were scored clinically and functionally. In the same period (July 1996 – September 2003) 164 ceramic-on-ceramic Ancafit total uncemented prostheses (Wright Medical, US) were implanted inthe same age and activity group as the resurfacings. The first group of 126 patients (follow up 2 – 6 years, mean age 46.76) was compared with the resurfacing group. All the data were collected intra operatively and postoperatively, mostly in a prospective way. At the most recent follow-up there was a significant statistical difference in Harris Hip Scores (global and total), and activity function between the 2 types of pros-theses. Resurfacing scored a Harris Hip Total of 97.9 (ceramic THA 92.1). Of the resurfacing patients 60.71 had a strenuous activity (ceramic THA 30.43). Dislocation rate in resurfacing group was 0.4% (ceramic THA 3%). The early clinical results in the group of metal-on-metal resurfacing are very satisfactory with Harris and PMA scores indicating early clinical success. The high percentage of strenuous activity in this young patient group satisfies the expectations of the resurfacing. The difference with a normal uncemented hip is stated with a better outcome in Harris Hip Scores and a better activity level.
We present the results of our initial experience with the use of the Birmingham metal-on-metal Hip Resurfacing. The Birmingham Hip Resurfacing(BHR) consists of a high carbon chrome cobalt uncemented hydroxyapatite cupand a cemented femoral component. For patients with severe dysplasia adysplasia cup with screws was used. We utilise this kind of prosthesis for the younger patients (<
65 year). Excellent clinical results are encountered; none of the early problems aswith the old Wagner resurfacing (metal-on-poly) are seen. Our early results are similar to the encouraging results of the series of D.McMinn/R.Treacy. From September 1998 through April 2001, 185 BHR arthroplasties were performed. The mean age was 49.7 year (16–75). More male patients were operated with this method than female patients (64%–36%). The aetiology was osteoarthritis (81%), necrosis (9%), dysplasia (CDH) (6.6%).
The mean length of stay in hospital was six days (range: 2–26). Complications were: One fractured neck of femur, one ischial nerve palsy and one guide pin was left in the femur. All patients were followed on regular basis and the X-rays were studied for angle of preoperative neck of femur, postoperative angle of the femoral component, angle of cup placement and the parallelism of both components.