Inferior Radiographic and Functional Outcomes With Modular Stem in Metal-on-Metal Total Hip Arthroplasty

Pinnacle Ultamet metal-on-metal total hip arthroplasty survivorship: average 10-year follow-up

Background

It is unclear whether a connection exists between femoral head size, offset, neck length, and cup abduction angles, and rate of revision in metal-on-metal (MoM) total hip arthroplasty (THA) implant systems.

Methods

A retrospective review of MoM THA completed by a single surgeon with a single implant between 2003 and 2008 was conducted. Patient demographics, implant data, radiographs, and revision details were collected at follow-up. Incidence rates for revision and osteolysis were calculated in regard to the femoral head size, stem offset, neck length, and cup abduction angles.

Results

Six hundred and ninety two THAs were identified, with 79% of patients returning for a median follow-up of 10.3 years (interquartile range = 6.0-12.3). The median time to revision was 7.5 years (interquartile range = 5.3-9.9) among 27 total revision surgeries. The overall incidence rate of revision was 5.4 revisions per 1000 person-years, 3.0 revisions per 1000 person-years for adverse local tissue reaction. Hips with a cup abduction angle of ≤40° had revisions at nearly twice the rate of those with an angle of 41°-50° (incidence rate ratio = 1.98, 95% confidence interval: 0.92, 4.29). Hips with a 9 mm neck length had an increased rate of revision (incidence rate ratio = 5.94, 95% confidence interval: 1.33, 26.55) relative to those with a neck length of 0 mm. Rates of osteolysis were similar between implants of different head sizes, neck lengths and cup abduction angles.

Conclusions

MoM implant systems with longer necks and smaller cup abduction angles may lead to increased need for revision. Results from this study suggest a need for closer long-term follow-up of MoM THA systems.

Midterm Outcomes and Frequency of Osteolysis of Total Hip Arthroplasty Using Cementless Modular Stem for Asian Patients

BACKGROUND

Modular stems are useful for total hip arthroplasty (THA) in anatomically difficult dysplasia. Here, we present mean 6.8-year outcomes of cementless primary THA using S-ROM-A (modified modular stem for Asian patients) femoral prosthesis in anatomically difficult cases.

METHODS

Charts of 373 patients (461 hips) undergoing THA (mean age, 58 years) were reviewed for clinical evaluation of modified Merle d'Aubigné-Postel score and Kaplan-Meier survivorship with revision for any reason as the end point. For radiographic analysis, 331 patients (412 hips) followed up for ≥5 years were included. Bearing couples were metal-on-metal (n = 145), metal-on-polyethylene (n = 120), and ceramic-on-polyethylene (n = 147). Radiography and multiplanar computed tomography were performed.

RESULTS

No postoperative dislocation or deep infection occurred. Mean modified Merle d'Aubigné-Postel score improved significantly (10.9 points preoperatively, 16.7 points at last follow-up; P < .001). Cumulative 5- and 10-year stem survival rates were 100% and 84%, respectively (95% confidence interval, 75%-93%). All stems were classified as bone ingrown fixation. Osteolysis occurred in metal-on-metal (42.8%) and metal-on-polyethylene (15.8%) groups. Mean time to osteolysis was ~3 years, with no significant difference between 3 groups (P = .264). In logistic regression, lower cup inclination angle was significantly associated with osteolysis (odds ratio, 0.914; 95% confidence interval, 0.84-0.99; P = .029).

CONCLUSION

S-ROM-A femoral prosthesis achieved excellent midterm fixation, and the modular system was useful in primary THA with severe deformity. Bearing couples are potentially associated with adverse reactions to metal debris. S-ROM-A with ceramic-on-polyethylene bearing couples may be an option for anatomically difficult THA.