Cobalt-chromium femoral components developed scratches and released metal debris in simulated wear whereas ceramic femoral components did not

Oxidized zirconium versus cobalt-chrome femoral heads in total hip arthroplasty: a multicentre prospective randomized controlled trial with ten years' follow-up

AIMS

This study reports the ten-year wear rates, incidence of osteolysis, clinical outcomes, and complications of a multicentre randomized controlled trial comparing oxidized zirconium (OxZr) versus cobalt-chrome (CoCr) femoral heads with ultra-high molecular weight polyethylene (UHMWPE) and highly cross-linked polyethylene (XLPE) liners in total hip arthroplasty (THA).

METHODS

Patients undergoing primary THA were recruited from four institutions and prospectively allocated to the following treatment groups: Group A, CoCr femoral head with XLPE liner; Group B, OxZr femoral head with XLPE liner; and Group C, OxZr femoral head with UHMWPE liner. All study patients and assessors recording outcomes were blinded to the treatment groups. The outcomes of 262 study patients were analyzed at ten years' follow-up.

RESULTS

Patients in Group C were associated with increased mean liner wear rates compared to patients in Group A (0.133 mm/yr (SD 0.21) vs 0.031 mm/yr (SD 0.07), respectively; p < 0.001) and Group B (0.133 mm/yr (SD 0.21) vs 0.022 mm/yr (SD 0.05), respectively; p < 0.001) at ten years' follow-up. Patients in Group C were also associated with increased risk of osteolysis and aseptic loosening requiring revision surgery, compared with patients in Group A (7/133 vs 0/133, respectively; p = 0.007) and Group B (7/133 vs 0/135, respectively; p = 0.007). There was a non-statistically significant trend towards increased mean liner wear rates in Group A compared with Group B (0.031 mm/yr (SD 0.07) vs 0.022 mm/yr (SD 0.05), respectively; p = 0.128). All three groups were statistically comparable preoperatively and at ten years' follow-up when measuring normalized Western Ontario and McMaster Universities Osteoarthritis Index (p = 0.410), 36-Item Short Form Health Survey (p = 0.465 mental, p = 0.713 physical), and pain scale scores (p = 0.451).

CONCLUSION

The use of UHMWPE was associated with progressively increased annual liner wear rates after THA compared to XLPE. At ten years' follow-up, the group receiving UHMWPE demonstrated an increased incidence of osteolysis and aseptic loosening requiring revision surgery compared to XLPE. Femoral heads composed of OxZr were associated with trend towards reduced wear rates compared to CoCr, but this did not reach statistical significance and did not translate to any differences in osteolysis, functional outcomes, or revision surgery between the two femoral head components. Cite this article: Bone Joint J 2022;104-B(7):833-843.

Clinical Results of Revision TKA in Patients With Presumed Metal and Cement Allergy

BACKGROUND

Metal and cement allergy affects a small subset of patients, causing severe pain and often systemic reaction after total knee arthroplasty (TKA). Revision with ceramic-surfaced femoral components has been reported to resolve these symptoms of metal allergy, but no solution currently is available for patients with allergies to metal and bone cement.

METHODS

Five patients (5 knees) with documented metal allergy were revised with custom porous-coated ceramic femoral components (Magnesia-stabilized Zirconia) from January 2007 to January 2013. An additional 23 patients (23 knees) met inclusion criteria from 2007 to 2015, but because the ceramic implant was unavailable, they underwent different treatment based on their underlying allergy to metal, cement, or both. Inclusion criteria included the history of clinically documented severe metal allergy, severe pain, swelling, and effusion >1 year after TKA, negative workup for infection, loosening, and ligament imbalance. Knee Society scores were compared for each cohort.

RESULTS

Mean Knee Society scores for all 5 patients revised with custom cementless ceramic femoral components improved significantly for objective score (preoperative, 39 ± 5; most recent visit, 90 ± 2) and function score (preoperative, 33 ± 8; most recent visit 93 ± 4) (P < .0001). The 12 knees revised with off-the-shelf cemented ceramic-coated femoral components had similar results. The 7 unrevised knees (including 4 knees with allergy to metal and bone cement) and the 4 knees revised with standard CoCr femoral components did not improve and worsened over time.

CONCLUSION

Symptoms resolved in the 5 patients revised with custom ceramic implants and in the 12 patients revised with ceramic-coated components, but did not improve in the patients unrevised or revised with CoCr femoral components. Symptoms presumed to be associated with metal or cement allergy improve with the use of ceramic femoral surfaces, but patients who are allergic both to metals and bone cement would be candidates only for porous-coated ceramic implants fixed without bone cement.