Early failure of the Ultima metal-on-metal total hip replacement in the presence of normal plain radiographs

Abstract

Metal-on-metal total hip replacement has been targeted at younger patients with anticipated long-term survival, but the effect of the production of metal ions is a concern because of their possible toxicity to cells. We have reviewed the results of the use of the Ultima hybrid metal-on-metal total hip replacement, with a cemented polished tapered femoral component with a 28 mm diameter and a cobalt-chrome (CoCr) modular head, articulating with a 28 mm CoCr acetabular bearing surface secured in a titanium alloy uncemented shell. Between 1997 and 2004, 545 patients with 652 affected hips underwent replacement using this system. Up to 31 January 2008, 90 (13.8%) hips in 82 patients had been revised. Pain was the sole reason for revision in 44 hips (48.9%) of which 35 had normal plain radiographs. Peri-prosthetic fractures occurred in 17 hips (18.9%) with early dislocation in three (3.3%) and late dislocation in 16 (17.8%). Infection was found in nine hips (10.0%). At operation, a range of changes was noted including cavities containing cloudy fluid under pressure, necrotic soft tissues with avulsed tendons and denuded osteonecrotic upper femora. Corrosion was frequently observed on the retrieved cemented part of the femoral component. Typically, the peri-operative findings confirmed those found on pre-operative metal artefact reduction sequence MRI and histological examination showed severe necrosis. Metal artefact reduction sequence MRI proved to be useful when investigating these patients with pain in the absence of adverse plain radiological features.

Pseudotumors Are Common in Well-positioned Low-wearing Metal-on-Metal Hips

“…This was unexpected given that the literature suggests that steep cup inclination is associated with increased release of metal wear debris [7,27,30,31] and increased wear is associated with pseudotumor formation [15,22]. However, there is some recent evidence of high rates of devastating soft tissue reactions in patients with well-positioned MOM hip prostheses [8], which supports our findings. Importantly, our results were unlikely due to the low validity of radiographic measurement of cup position [13,21] because we used three-dimensional CT to measure cup position in all cases.…”

“…Some authors suggested that pseudotumors occurred as a result of an adverse reaction to metal wear debris and raised metal ion levels [15,17,35,36], with several small studies finding a direct association with increased component wear rates [22,25] and raised levels of chromium and cobalt ions [15,35]. However, recent evidence suggests pseudotumors are common in patients with asymptomatic MOM THA [23] and in patients with low metal ion levels and a well-positioned cup [8]. The roles of excess wear and patient-specific sensitivity to metal wear debris in the pathogenesis of pseudotumors remains unclear.…”

“…Given that the pathogenesis of pseudotumors remains unclear and that several recent studies have shown cases in well-functioning, well-positioned, and low-wearing prostheses [8,23], it is important to confirm the roles of component position and wear in larger series of patients.…”

Revisions of Monoblock Metal-on-metal THAs Have High Early Complication Rates

“…Although initial reports were satisfactory [5,14,22,28,29], subsequent research demonstrated unacceptable early failure rates of monoblock MoM THAs, resulting in a substantial revision burden [2-4, 6, 7, 10, 12, 13, 15, 18, 19, 21, 24, 25, 27, 30, 32, 33, 36]. These revisions can be complicated by extensive soft tissue and bony defects, persistence of adverse local tissue reaction as well as problems associated with the general need to reduce the head size at the time of revision, perhaps increasing the likelihood of dislocation [1,3,7,10,13,18,19,23,25,31,33]. Previous studies reporting on the early complications after these revisions are limited and generally of small number [3,10,31,35].…”

How Have New Bearing Surfaces Altered the Local Biological Reactions to Byproducts of Wear and Modularity?

“…First, by confining our review to studies that included quantitative or semiquantitative grading of the histologic findings, we excluded many publications that have used only qualitative descriptions of periarticular findings [5,12,29,35,42,44,46] or that have focused on particle quantitation [13,30,45], cytokine detection [9,21], or lymphocyte subsets [29]. Among the studies that have graded morphologic features of periprosthetic tissues, many have not included conventional metal-on-PE or ceramic-on-polyethylene cases as controls, and differences in grading criteria among studies preclude pooling the data into larger groups.…”