Abstract
The purpose of this study was to determine the survivorship for a single MOM implant series and create an affordable clinical follow-up model. A retrospective cohort of 104 primary MOM THA procedures (94 patients) were all performed by one surgeon at three local hospitals and have reached 7–12 years follow-up. Fifteen patients are now deceased and 16 patients have been lost to follow-up. In the remaining 63 patients, 8 are bilateral providing a total of 71 THA for study. The clinical follow-up model included: hip score, X-rays, ultrasound, and metal ion testing. Due to the diversity of patient location, a variety of clinical labs were utilized for metal ion analysis. Statistical methods included a Kaplan-Meier survival curve. Hip scores were available for all 71 THA and of these 61 had a hip score (HHS) above 80 (86%). Fifty-three X-rays were available and of these 42 (79%) were in the safe zone (inclination ≤55 and anteversion ≤35). Thirty-six ultrasounds were performed and of these two yielded fluid collections (6%). Metal ion concentrations in either whole blood or serum have been documented for 32 of 63 patients (51%). Three outliers were identified within the metal ion concentrations; Co ranged 0.3–71.1 ppb (average 7.9, median 3.6), Cr ranged 0–26.9 ppb (average 4, median 2.1) and Ti ranged 2–100 ppb (average 51.8, median 52). Three patients have been revised by the original surgeon and two patients are currently scheduled to undergo revision surgery. Of the three patients revised, only one had a documented wear problem resulting from anterior subluxation, while the other two were revised for femur fracture and infection. These results represent survivorship of 94.7% at 9 years and may be a result of anterior lateral approach performed by one surgeon in which 79% of cups were well placed.
