Silent soft tissue pathology is common with a modern metal-on-metal hip arthroplasty

Abstract

Background and purpose: Adverse reactions to metal debris have been reported to be a cause of pain in metal-on-metal hip arthroplasty. We assessed the incidence of both symptomatic and asymptomatic adverse reactions in a consecutive series of patients with a modern large-head metal-on-metal hip arthroplasty.

Methods: We studied the early clinical results and results of routine metal artifact-reduction MRI screening in a series of 79 large-head metal-on-metal hip arthroplasties (ASR; DePuy, Leeds, UK) in 68 patients. 75 hips were MRI scanned at mean 31 (12-52) months after surgery.

Results: 27 of 75 hips had MRI-detected metal debris-related abnormalities, of which 5 were mild, 18 moderate, and 4 severe. 8 of these hips have been revised, 6 of which were revised for an adverse reaction to metal debris, diagnosed preoperatively with MRI and confirmed histologically. The mean Oxford hip score (OHS) for the whole cohort was 21. It was mean 23 for patients with no MRI-based evidence of adverse reactions and 19 for those with adverse reactions detected by MRI. 6 of 12 patients with a best possible OHS of 12 had MRI-based evidence of an adverse reaction.

Interpretation: We have found a high early revision rate with a modern, large-head metal-on-metal hip arthroplasty. MRI-detected adverse rections to metal debris was common and often clinically "silent". We recommend that patients with this implant should be closely followed up and undergo routine metal artifact-reduction MRI screening.

Figure 1.

Mild adverse reaction to metal debris. Sagittal T2W MR through the femoral stem (S) of a Corail total hip replacement demonstrating mild periprosthetic disease. A small fluid-filled cavity (asterisk) surrounding the neck of the prosthesis is encapsulated by a thick, ragged low-signal rim (white arrow).

Figure 2.

Moderate adverse reaction to metal debris. A sagittal T2W MR positioned just medial to the acetabular cup demonstrates moderate periprosthetic disease with a large cystic collection, demarcated by a low signal wall (black arrow), and filled with debris (white arrow) extending proximally in the line of the iliopsoas bursa. The relatively thick low signal wall and the debris are not typical of conventional iliopsoas bursae.

Figure 3.

Severe adverse reaction to metal debris. Coronal T1W MR through the mid-coronal plane of the femoral head (black arrows indicate the medial wall of the acetabulum), demonstrating severe periprosthetic disease with bone marrow replacement in the acetabular roof (white arrow).