Early Radiological Observations May Predict the Long-Term Survival of Femoral Hip Prostheses

Abstract

We reviewed a consecutive series of 527 uninfected hip replacements in patients resident in the UK which had been implanted from 1981 to 1993. All had the same basic design of femoral prosthesis, but four fixation techniques had been used: two press-fit, one HA-coated and one cemented. Review and radiography were planned prospectively. For assessment the components were retrospectively placed into two groups: those which had failed from two years onwards by aseptic femoral loosening and those in which the femoral component had survived without revision or recommendation for revision.All available radiographs in both groups were measured to determine vertical migration and examined by two observers to agree the presence of radiolucent lines (RLLs), lytic lesions, resorption of the neck, proximal osteopenia and distal intramedullary and distal subperiosteal formation of new bone. We then related the presence or absence of these features and the rate of migration at two years to the outcome with regard to aseptic loosening and determined the predictive value of each of these variables.Migration of ≥2 mm at two years, the presence of an RLL of 2 mm occupying one-third of any one zone, and subperiosteal formation of new bone at the tip of the stem were predictors of aseptic loosening after two years. There were too few lytic lesions to assess at two years, but at five years a lytic lesion ≥2 mm also predicted failure. We discuss the use of these variables as predictors of femoral aseptic loosening for groups of hips and for individual hips.We conclude that if a group of about 50 total hip replacements, perhaps with a new design of femoral stem, were studied in this way at two years, a mean migration of <0.4 mm and an incidence of <10% of RLLs of 2 mm in any one zone would predict 95% survival at ten years.For an individual prosthesis, migration of <2 mm and the absence of an RLL of ≤2 mm at two years predict a 6% chance of revision over approximately ten years. If either 2 mm of migration or an RLL of 2 mm is present, the chances of revision rise to 27%, and if both radiological signs are present they are 50%. If at five years a lytic lesion has developed, whatever the situation at two years, there is approximately a 50% chance of failure in the following five years.Our findings suggest that replacements using a limited number of any new design of femoral prosthesis should be screened radiologically at two years before they are generally introduced. We also suggest that radiographs of individual patients at two years and perhaps at five years should be studied to help to decide whether or not the patient should remain under close review or be discharged from specialist follow-up.

High Incidence of Migration with Poor Initial Fixation of the Accolade® Stem

“…Although we did not observe these stems migrating, they were obviously exhibiting some lack of stability, which may be rotational [40]. Previous reported studies have suggested a positive predictive value of 50% for failure in patients with radiographic loosening [25]. We found the Accolade 1 stem demonstrated poor initial fixation in more than 1 . 3 of our patients, with continued progression of migration being a concern for its overall long-term clinical performance, especially for larger stems.…”

“…Initial implant fixation is one of the key elements for a successful THA [21,35]. Consequently, migration analysis presents an early objective assessment of the predicted medium-to long-term performance and minimizes the risk of unexpectedly higher rates of later failure with early identification of at-risk components [10,13,25,28,29]. Having observed some early revisions for aseptic loosening of the Accolade 1 stem at our center, we set out to investigate the potential causes by evaluating initial implant stability using migration analysis.…”

“…Later, Mjoberg et al [36] hypothesized early implant instability and micromotion were associated with aseptic loosening of the femoral component. Similarly, Freeman and Plante-Bordeneuve [13] and Kobayashi et al [25] demonstrated the subsidence of a femoral stem at 2 years could predict failure at long-term followup. The association between early implant stability and long-term survivorship is well established for a variety of stem designs [23,28,38,43], with the gold standard in evaluating initial implant stability being radiostereometric analysis (RSA) [8,39].…”

No increased stem subsidence after arthroplasty in young patients with femoral head osteonecrosis:41 patients followed for 1–9 years

“…Subsidence of 2 mm or more in 2 years has been found to be predictive of implant failure within 5 years in hip surface arthroplasties (Beaule et al 2005). Several studies using the EBRA have demonstrated clearly that early migration predicts implant failure with high accuracy (Walker et al 1995, Kobayashi et al 1997, Biedermann et al 1999. In order to evaluate the fixation of cementless porous-coated stems in patients with osteonecrosis, we investigated 41 patients (41 hips) and compared our results with those of previously published studies dealing with cementless stems over a comparable follow-up time (Fye et al 1998, Hartley et al 2000, Kim et al 2003, Radl et al 2005.…”

“…Another explanation may be that etiological factors of the osteonecrosis, such as steroid use and alcohol abuse, are associated with poor bone stock and potentially poor device fixation (Sarmiento et al 1990, Brinker et al 1994, Radl et al 2005. Measurement of stem subsidence is an accepted tool for evaluation of the quality of implant fixation whereas early migration indicates subsequent implant failure (Kobayashi et al 1997, Biedermann et al 1999). …”