Small-head metal on metal total hip arthroplasty is associated with a high rate of complication and reoperation at mid-term follow-up

Abstract

Background: Adverse reactions to metal debris are significant complications after metal-on-metal total hip arthroplasty. Recently, late appearances of adverse reactions to metal debris and subsequent need for reoperations have been reported with small-diameter head metal-on-metal devices. We retrospectively investigated mid-term clinical outcomes of small-head metal-on-metal total hip arthroplasty.

Methods: We reviewed 159 hips in 139 patients who had a small-head metal-on-metal total hip arthroplasty (M2a Taper; Biomet, Warsaw, IN) with a minimum 5-year follow-up and documented postoperative complications.

Results: Focal osteolysis in either the femur or acetabulum was observed in 12 hips (7.5%, 44 months after surgery on average), with pseudotumor observed in 8 hips (5%, 120 months after surgery on average). Four hips (2.5%) had dislocations (84 months after surgery on average) and six hips (3.8%, 122 months after surgery on average) underwent reoperation.

Conclusion: Small-head metal-on-metal total hip arthroplasty is associated with a high degree of complications at mid-term follow-up period. Considering this, we discourage the use of metal-on-metal total hip arthroplasty regardless of head size.

Keywords: Metal on metal; adverse reactions to metal debris; complication; focal osteolysis; reoperation; total hip arthroplasty.

Figure 1.

Osteolysis-free survival rate. Osteolysis-free survival rate was 91.6% (95% CI, 86.9–96.3) at 168 months after THA.

Figure 2.

Revision-free survival rate. Revision-free survival rate was 82.9% (95% CI, 68.1–97.7) at 168 months after THA.

Figure 3.

Postoperative radiography of a 68-year-old female patient who underwent MoM THA of the left hip using M2a Taper with head-size of 32 mm. The patient experienced no complications until 8 years postoperatively, when she developed left hip pain. At that time, focal osteolysis at the femur and the acetabulum were recognized by radiography (Figure 3(a) and (b)). A CT scan and radiography at 9 years postoperatively showed a pseudotumor around the stem and further advanced osteolysis at the femur (Figure 3(c) and (d)). The patient subsequently underwent reoperation changing the bearing surface to highly cross-linked polyethylene, and intraoperative findings were consistent with ARMD. (a) Postoperative X-ray. (b) X-ray performed 8 years postoperatively shows osteolysis (yellow circle) of the femur and acetabulum. (c) A CT scan performed 9 years postoperatively shows a pseudotumor (yellow circle) around the proximal stem. (d) X-ray performed 9 years postoperatively shows further advanced osteolysis at the femur.

Figure 4.

Postoperative radiography of a 59-year-old female patient who underwent MoM THA of the right hip using M2a Taper with head-size of 28 mm (a). The patient experienced no complications until 6 years postoperatively, when she developed right hip pain. At that time, focal osteolysis of the femur and the acetabulum were observed on radiography. A CT scan and radiography at 12 years postoperatively showed a pseudotumor around the stem and further advanced osteolysis at the femur (b) and (c). The patient subsequently underwent reoperation by changing the bearing surface to highly cross-linked polyethylene, and intraoperative findings were consistent with ARMD (d)–(h). (a) Postoperative X-ray. (b) X-ray performed 12 years postoperatively shows osteolysis (yellow circle) at the femur and acetabulum. (c) A CT scan performed 12 years postoperatively shows a pseudotumor (yellow circle) that developed around the proximal stem. (d) X-ray after revision surgery at 12 years from the THA. Intraoperative findings: (e) the capsule was filled with yellow-colored liquid; (f) a pseudotumor was filled with viscous debris inside; (g) the cup was filled with debris; and (h) after removing the debris, a highly cross-linked polyethylene liner was fixed with cement to the original metal cup, and the metal head was replaced to new one of the same-size.