The Exeter femoral stem continues to migrate during its first decade after implantation

Abstract

Background Due to its collarless, double-tapered polished design, the Exeter femoral stem is known to migrate distally in the first 5 years after implantation. However, its long-term migration pattern has not been investigated.Patients and methods 39 consecutive patients (41 total hip arthroplasties) received a cemented Exeter stem and had prospective clinical and RSA follow-up. Patients were evaluated postoperatively at 6, 12, 26, and 52 weeks, and annually thereafter. Short-term results have been reported. In this study, the mean length of follow-up was 9.4 years (SD 3.2 years). No patients were lost to follow-up. 15 patients died during follow-up.Results No stems were revised. In 4 stems, fractures of the cement mantle were noted within the first 3 postoperative years. In 3 stems, this resulted in a complete circumferential cement mantle discontinuity. For the 37 well-performing stems, continuous but small migration was measured between 2 and 12 years of follow-up. Continued subsidence of 0.08 mm/year (95% CI: 0.05–0.12, p < 0.001) was seen in combination with continued rotation in retroversion of 0.07°/year (95% CI: 0.02–0.12, p = 0.01). At 10 years of follow-up, mean subsidence was 2.1 (SD 1.2) mm and mean retroversion was 1.8° (SD 2.0). Two-thirds of this occurred during the first 2 postoperative years. In the 3 stems with a complete circumferential cement fracture, a sudden and disproportionately high increase in subsidence was measured in the time period of occurrence.Interpretation The Exeter femoral stem continues to migrate during the first decade after implantation. Absolute stability is not required for good long-term survival if this is compatible with the design of the implant.

Early Migration Predicts Aseptic Loosening of Cementless Femoral Stems: A Long-term Study

“…First, EBRA-FCA is able to measure only distal implant migration and differences in the stem axis to varus position, whereas RSA is able to measure 3-D migration, notably posterior head migration, and it has a higher accuracy. However, when compared with the RSA-based migration data published on the CLS 1 stem [23,24], our mean migration found at 1 and 2 years compares well with that from RSA studies using the CLS 1 stem; therefore, we believe our measurements are accurate. Second, the high dropout rate is a limitation of our study.…”

“…Continuing rapid early migration is said to be predictive of loosening [22]. However, the absolute early migration is different depending on the stem design [6,22,23,29,[34][35][36][37]. We found that early migration, as measured by EBRA-FCA at 2 years postoperatively, can identify uncemented femoral components at risk for aseptic loosening during early and mid-term followup, but did not predict aseptic loosening in the late second and third decades.…”

“…Each millimeter of distal migration at 2 years postoperatively was associated with an approximately twofold greater risk for aseptic loosening. The prognostic value of excessive early migration within 1 to 2 years postoperatively for early aseptic loosening and mid-term survival has been shown for different cemented stems and cups using different measurement methods [11,14,17,19,23,24,26]. Krismer et al [19] reported an association between early migration and loosening during the first decade after surgery in a mixed study combining cemented and uncemented stems.…”

“…The prognostic value of excessive early migration within 1 to 2 years postoperatively for early aseptic loosening and mid-term survival has been shown for different cemented stems and cups using different measurement methods [11,14,17,19,23,24]. However, there are only a few studies regarding the diagnostic performance of early migration as a predictor for aseptic loosening using uncemented femoral components [11,17,19] and, as shown in a recent review by van der Voort et al [36], the published research is insufficient to support robust conclusions.…”

Radiostereometric analysis

“…Orthopaedic applications for the system are many and RSA is commonly used in joint arthroplasty to establish features such as wear, 1 component subsidence (as a surrogate for fi xation) 2 and even to establish relative motion of fracture fragments. 3 In this edition of 360 we report on the use of RSA to establish the quality fi xation in thumb arthroplasty.…”