Introduction: Cementless femoral revision has become increasingly popular because the cementless implants provide the potential for long-term biologic implant fixation. The IOTA interlocking femoral stem is a hydroxyapatite-coated stem with the option of interlocking the stem distally. The aim of the current study was to evaluate the short-term results of IOTA interlocking stem.
Materials and methods: We retrospectively reviewed the results of 18 total hip arthroplasties in 17 patients performed between July 2002 and 2004 using the IOTA interlocking stem. In-patient records were retrieved and in addition to demographic data the indication for revision, the preoperative and postoperative Harris Hip scores, need for allografts were noted. The bone deficiency was classified based on the AAOS classification. Intraoperative complications and problems if any were retrieved from the authors' operative notes. Radiographs at the final follow up were evaluated by the criteria described by Engh et al. (Clin Orthop 257:107-128, 1990)
Results: Average age at the time of revision was 57 years. Preoperatively five femora showed type I deficiency, type II deficiency was seen in three, type III in nine and type IV deficiency in one femur. In five hips the calcar replacing prosthesis was implanted to manage the proximal calcar defect, in one hip allograft was used to reconstruct the calcar. One patient sustained intraoperative fracture of the shaft of the femur while implanting the trial prosthesis and one patient had a perforation of the posterior cortex of femur while trying to remove the cement. The mean follow up period was 33.5 months (range 27-45 months). The mean preoperative Harris Hip score was 36 (range 23-50), which improved to 77 (range 68-92) at the time of final follow up. None of the stems required revision and at minimum 27 months follow up, bony ingrowth was noted in 83.33% of the stems.
Conclusion: IOTA interlocking stem has shown promising short-term results for femoral revisions. The advantages are initial axial and rotational stability and consistent bony in growth owing to hydroxyapatite coating. Intraoperative fracture is a potential drawback because of the straight nature of the stem. The calcar replacing option of the stem is especially useful in patients with deficient calcar as a substitute for the allograft.