Abstract
Introduction
Studies have documented encouraging results with the use of fluted, tapered, modular, titanium stems in revision hip arthroplasty with bone loss. However, radiographic signs of osseointegration and patterns of reconstitution have not been previously categorized.
Materials and Methods
64 consecutive hips with index femoral revision using a particular stem of this design formed the study cohort. Serial radiographs were retrospectively reviewed by an independent observer. Bone loss was determined by Paprosky's classification. Osseointegration was assessed by a slight modification of the criteria of Engh et al. Femoral restoration was classified according to Kolstad et al. Pain and function was documented using Harris Hip Score (HHS).
Results
Mean patient age was 68.3 years and radiographic follow-up 6.2 years. 74% femora had type 3 or 4 bone loss. All distal segments were radiographically osseointegrated. Proximal segment radiolucent lines were frequent (40%). Early minor subsidence occured in 4 (6.2%) hips. Definite bony regeneration was documented in 73% femora and stress-shielding in 26%. HHS improved from a pre-operative mean of 50.1 points to 86.2 at most recent follow-up.
Discussion
A consistent pattern of bony remodeling and osseointegration occurred which could be applied for assessment of fixation and stability of this stem. The well established criteria of osseointegration for cylindrical cobalt-chrome stems may have to be altered for application to these stems as the mechanism of load transfer is entirely different. Stems with diameter of 18mm or greater are clearly predisposed to stress shielding, predominantly at the mid-shaft region.
