Abstract
Introduction
The National Joint Registry of England, Wales, Northern Ireland, and the Isle of Man (NJR) monitors the performance of primary total hip arthroplasty (THA) implants and summarizes usage and outcomes for specific hip systems. The objectives of this study were to 1) determine if survivorship for the PROCOTYL® L acetabular cup, a hemispherical press-fit cup coated with hydroxyapatite and a metal on XLPE articulation, is significantly different from all other cementless cups in the NJR and 2) to analyze patient reported outcomes measures (PROMs) at a minimum five year follow-up for the subject cup.
Methods
The database of the NJR was searched for demographic information and survivorship data for all THAs performed with the PROCOTYL® L cup (metal on XLPE) and all other cementless cups. Survivorship data for both groups was adjusted to exclude metal on metal bearings and compared for all revisions and acetabular revisions only. The Cox Proportional Hazards model for the revision risk ratio of the subject cup to all cementless cups was also calculated. Patients with the subject cup implanted for at least five years were mailed a PROMs program questionnaire consisting of the Oxford Hip, EQ-5D, and EQ VAS scores. No pre-operative PROMs scores were collected.
Results
Patient demographic information for the subject system and all cementless cups is provided in Figure 1. As seen in Figure 2, the six-year survivorship for the 1,172 THAs using the subject system (97.8%) was slightly higher than the survivorship for all cementless cups (97.5%), but the difference was not statistically significant (Figure 3). The 1, 2, and 5 year survivorship for the subject cup also exceeded the survivorship of all cementless cups, but without statistically significant differences. When just the cup was revised, the subject system survivorship was similar to survivorship for all cementless cups for years 1 through 6 (Figure 2). Patients with the subject system implanted for an average of 5.73 – 5.75 years reported average Oxford Hip, EQ-5D, and EQ VAS Scores of 39.13 ± 9.93, 0.775 ± 0.273, and 75.87 ± 17.71, respectively.
Conclusions
The subject acetabular cup was associated with survivorship similar to that of other cementless acetabular cups. Patients implanted with the subject system for at least five years reported what are considered satisfactory Oxford Hip, EQ5D, and EQVAS score outcomes. These results represent the first report of midterm outcomes with the subject system.
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