Acetabular cup failure after total hip replacement

Configuration of anchorage holes affects fixation of the acetabular component in cemented total hip replacement--a finite element study

Our survey of current practice among UK orthopaedic surgeons shows wide variations in fixation techniques. The aim of this study, is to investigate the effect of drilling different configurations of anchorage holes in the acetabulum on implant stability. To avoid variables that could incur during in vitro testing, we used commercially available COSMOS finite element analysis package to investigate the stress distributions, deformations, and strains on the cement mantle when drilling three large anchorage holes and six smaller ones, with straight and rounded cement pegs. The results, which are in line with our in vitro studies on simulated reconstructed acetabulae, indicate better stability of the acetabular component when three larger holes than six smaller holes are drilled and when the necks of the anchorage holes are rounded. The longevity of total hip replacements could be improved by drilling three large anchorage holes, rather than many smaller ones, as initially proposed by Charnley.

Wear and fracture of the acetabular cup in Charnley low-friction arthroplasty

Seven cases of progressive wear-out and fracture of the cemented high-density polyethylene cup in Charnley low-friction arthroplasty were identified in a group of 1,815 revisions of failed total hip arthroplasties. Normal function, rapid wear in the superolateral direction, and localized superolateral loss of bone-cement interface support with perfect medial cup fixation but, above all, asymptomatic nature of the problem until the moment of sudden failure were the characteristic features. The time to failure ranged from 11 to 20 years. Stem fixation remained unaffected. The findings suggest that the problem was wear-out without any changes that could have been attributed to the volume of high-density wear particles shed into the tissues.

Prosthetic component failures in hip arthroplasty surgery

A survey was conducted of the entire membership of the American Association of Hip and Knee Surgeons to determine their experience with total hip arthroplasty (THA) device-related failures. Forty-seven percent of the membership reviewed their preceding 5-year clinical experience and returned the survey instrument. The aggregate 5-year volume encompassed experience with more than 60,000 hip arthroplasties. The median 5-year experience per respondent was 200 metal-based sockets and 214 metal stems. The frequency distribution of the number of hip arthroplasties per respondent was skewed to the right, with fewer surgeons reporting the higher volumes of arthroplasties. In aggregate, 60,115 of the acetabular components used were metal backed. Nonmetal acetabular component usage totaled 3,219. Complete polyethylene failure was defined as fracture or complete wear through of the polyethylene portion of the component. Complete polyethylene failure was seen in 172 metal-backed sockets (29/10,000). Seventy-seven all-polyethylene sockets had complete polyethylene failure (239/10,100). A total of 87 THAs were revised for modular acetabular dissociations for a dissociation rate of 15/10,000. In aggregate, 64,483 metal-stemmed components were used. Femoral stem fractures occurred in 172 for a rate of 27/10,000. A total of 56,965 metallic femoral components were reported as being modular. Dissociation between the femoral head and neck was uncommonly seen (3/10,000). Use of ceramic femoral heads was low (5,023); however, a total of 11 ceramic head fractures were revised in the 5-year period for a failure rate of 22/10,000. The risks of catastrophic prosthetic THA failure are low but vary according to hip component and the manufacturer of the part.

Thermal expansion modular femoral head extractor for revision total hip arthroplasty

Removal of a prosthetic modular femoral head is sometimes desirable during revision hip arthroplasty. A femoral head extractor was designed to heat and expand the prosthetic femoral head, apply a gentle distraction load, and remove the femoral head without injury to the femoral neck, taper, or bone-prosthesis interface. The device was used clinically in six hip revision cases. In five hips with cobalt-chrome heads and titanium alloy tapers, femoral heads were removed successfully; femoral fixation was maintained and femoral components were not visibly damaged. In the sixth case, the female portion of the taper junction was contained in a long femoral head sleeve. Heating the ball did not adequately expand the sleeve to allow easy ball removal.

Late disassembly of modular acetabular components. A report of two cases

We report two cases of late disassembly of modular acetabular components, 4 and 5 years after implantation. One was revised immediately after the disassembly and one after 4 months, the latter demonstrating excessive wear of metal and polyethylene. Radiographs showing eccentric displacement of the femoral head in the cup associated with a dark, curved shadow representing the displaced polyethylene insert identify this type of implant failure.

The biologic responses to orthopedic implants and their wear debris

The use of artificial materials in the treatment of orthopaedic conditions, most notably arthritis, over the past few decades has been increasing dramatically. Such use makes an understanding of the tissue responses to the various materials necessary to determine their effectiveness and acceptability. This review concentrates on the studies of the biological responses to the materials that are used mainly in joint replacements and fixation of fractures. In-vivo and in-vitro experimental studies of various metals, polymers and ceramics and their constituents are first presented with discussions regarding their clinical importance. Studies of clinically successful implants are then presented to illustrate the expected morphological features of incorporation and acceptance by the host tissues. The local and systemic effects complicating the use of the implanted materials as well as the failure of the implant are then presented.

Fracture of the ceramic head in total hip arthroplasty. Report of two cases

This article reports two cases of fracture of the ceramic head component in total cementless hip arthroplasty. There was no history of difficulty prior to the component fracture, neither during the operation nor during daily use, and in one of the patients, no history of trauma was observed.

Modified rotational acetabular osteotomy (RAO) for advanced osteoarthritis of the hip joint in the middle-aged person. First report

Classical methods for pelvic osteotomy, such as those of Salter, Pemberton, Chiari, and Wagner, have been developed for reconstruction of the subluxed hip joint in children and young adults. Regarding pelvic osteotomy involving a middle-aged patient, however, there are not as many operation methods to consider, and it is difficult to choose the most suitable technique for alleviating advanced osteoarthritis. Based on current practice, total hip replacement (THR) seems the accepted method, though it presents problems such as loosening, sinking, and infections; because of these factors physicians hesitate to recommend THR surgery, particularly if the patient is otherwise healthy and appears to have many good years ahead of him. As an alternative, we have been developing and improving the acetabular osteotomy, based on Tagawa's rotational acetabular osteotomy (RAO) and Wagner's acetabular osteotomy (type II). In this paper we present the results of a modified RAO operation performed on 50 middle-aged patients with an average age of 42 years and 2 months (31-61). The average follow-up was 3 years and 3 months (1-9 years). In 82% of patients the result was satisfactory (41 of 50 cases). A similar osteotomy technique has been used by Eppright and Wagner. We feel that our method achieves a more favorable result for an older patient with severe osteoarthritis, since both the surgery and the follow-up rehabilitation are more comprehensive. A modified acetabular osteotomy should not be regarded as merely an alternative to total hip replacement, but as the preferred choice for hip-joint reconstruction.

Fracture of a metal-backed acetabular cup. A case report

In this case of fracture of a metal-backed polyethylene acetabular component after a total hip arthroplasty, there was no history of difficulties prior to the component fracture and no history of trauma.