Abstract
Introduction
The aim of this study was to analyze the results of our series of female patients treated with <48 mm MOMHR devices at a minimum follow-up of 5 years, to understand which is the most important aspects affecting the results and to define if the metal ions dosage has to be indicated as a routinely follow-up.
Methods
This is a retrospective clinical study; the cohort included 198 consecutive MOMHR implanted in 181 female patients (17 bilateral procedures). All operations were performed between 2002 and 2011. All operations were performed by the senior surgeon. Indications to MOMHR included primary or secondary osteoarthritis (OA), rheumatoid arthritis and avascular necrosis. Contraindications included poor proximal femoral bone stock (T-score<−2.5sd in BMD of the femoral neck) or severely distorted hip anatomy. All patients were advised to underwent clinical and radiological review with the operating surgeon at 5 weeks, 3, 6 and 12 months postoperatively and then every subsequent 2 years.182 patients answered to our phone calls; 4 patients died (one of them was operated bilaterally) for causes not related to the study, and in 11 cases the phone number was expired. The minimum follow-up was 5.0 years (mean 7.5, maximum 13.2, sd 0.11).
Results
Fourteen devices were revised (7%) in 14 patients: 2 of them were operated bilaterally and the controlateral implant is still fine; thus, the Kaplan-Meier survival rate with revision for any reason as the end point was 92.7% at 13 years (95% confidence interval (CI) 0.9 to 1.0). Revisions data are resumed in table 2.
Main OHS was 44 points (4–48, sd 7); no statistical relations were found about any aspect about relation between OHS and metal ions dosage (eg Chi Square Analysis p-value = 0.147>0,05 for Score and CR).
Metal ions dosage was performed in only 2 cases before and after the revision (14%); in one case, the Cr dosage was 20 µg/L before and 8 µg/L after surgery; in the other case, the Cr dosage was 100 µg/L before and 10 µg/L after surgery, and the Co dosage was 70 µg/L before and 0.2 µg/L after surgery.
Metal ions dosage was performed in 64 cases of the survived implants (35%). Main Cr dosage was 1.50 µg/L (0.09–7.00, sd 1.70) and main Co dosage was 1.30 µg/L (0.09–9.00, sd 1.60), at a main follow-up from surgery of 5.7 years (0.2–11.0, sd 3.1), in 14 different laboratories. No statistical relation were found between clinical outcomes and metal ions increase.
Conclusions
MOMHR is a good choice for treating severe hip arthritis also in female patients with <48 mm devices. The results are affected especially by surgical technique and indications. The metal ions dosage has to be performed every year for the first two years and then at a larger follow-up.
We believe that additional imaging, such as CT scanning to measure anteversion may better identify the ideal candidate, and specific training with largely experienced surgeons would be mandatory; the metal ions dosage would be used as a monitor of failures.
