Can bone apposition predict the retention force of a femoral stem? An experimental weight-bearing hip-implant model in goats

Abstract

BackgroundThe increasing incidence of prosthesis revision surgery in the Western world has led to an increased focus on the capacity for stem removal. We previously reported on a femoral stem implanted in goats with an approximate 15% reduction in retention force by drilling longitudinally orientated grooves on the side of the stem. In this current study, we aimed to histologically evaluate the bony apposition towards this stem and correlate this apposition with the pullout force.MethodsWe analyzed the femora of 22 goats after stem removal. All stems remained in place for 6 months, and the goats were allowed regular loading of the hip during this time. For histological evaluation, all femora were immersed in EDTA and decalcified until sufficiently soft for standard technique preparation. We evaluated bone apposition, the presence of foreign particle debris and other factors. The apposition was evaluated with a scoring system based on semi-quantitative bone apposition in four quadrants. Kappa statistics were calculated for the score. We correlated the retention force with the amount of bone apposition.ResultsThe stem drilling was the only significant factor influencing the retention force (p = 0.020). The bone apposition Kappa score comparing poor and good apposition scores was fair (κ = 0.4, 95% CI 0.00–0.88). Signs of foreign body reaction were noted in 5 of 22 goats.ConclusionsBased on the current findings in an experimental goat model, it appears that the effect of drilling tissue/bone out of the longitudinal grooves has a more significant impact on the retention force required to remove the stem than the amount of bone apposition outside the stem grooves. This observation may be further explored in the research of stem designs that are potentially easier to remove.

A New Stem Extractor with Specific Multigrip Pliers for Revision Hip Arthroplasty – A Biomechanical Investigation

“…Second, not much data exists on how much force is needed to extrude a femoral stem with a slap hammer, regardless whether they are cemented or uncemented (3, 4). We therefore chose a pragmatic way to find the amount of torque per cleat needed to fix the stems impossible to extract and considered 50% of this torque to be enough for moderately fixed stems.…”

“…Furthermore, there might be a certain bias as the examiner could not have been blinded for the stem and extractor used during backslapping. Comparable studies are rare, some tested the grip of extractors (2) or extraction of stems (3, 4) with increasing tensile load. However, increasing tensile load does not fully account for the high peak forces during backslapping, which we think is the major cause of grip loosening in vivo.…”

Translational relevance of the goat as a preclinical model of the human labrum and chondrolabral junction—histological study

“…In comparison with sheep, goats are more active animals, therefore this may make an investigation of the hip labrum more applicable to human hip pathology. The caprine model has been previously validated for investigation of the hip arthroplasty procedures due to its high degree of similarity to the human hip . The goal of this study was to advance this validation of the histological characteristics of the caprine acetabular labrum and chondrolabral junction, in comparison to the human hip.…”

Enhancing Osseointegration of Orthopaedic Implants with Titania Nanotube Surfaces

“…The presence or absence of cellular structures, including leukocytes and macrophages, was also evaluated. [146] We propose a study replicating the characterization methods described in Chapter 6, using total hip arthroplasty components developed for use in the canine population (e.g. BioMedtrix Universal Hip CFX).…”

“…At a single, 6-month endpoint, harvested femora would be randomized to either the biomechanical testing cohort or imaging/histologic analysis cohort. Femora randomized to biomechanical would undergo femoral stem pull-out testing, as described by Harboe, et al [144][145][146] Femora in the imaging/histologic analysis cohort would be immersed in 10% neutral buffered formalin for 1 week to fix all tissues, then rinsed with PBS and stored in ethanol. Femora would first be scanned with μCT (vivaCT-80, Scanco USA, Wayne, PA).…”