Predicting Cementless Stem Fixation in Total Hip Arthroplasty Using Radiodensity Mapping

7 pages•Published: September 25, 2020

Teja Cherukuri, Chameka Madurawe, Jim Pierrepont, Jonathan Bare, Stephen McMahon and Andrew Shimmin

Abstract

Femoral component loosening due to poor fixation is a common failure mode in cementless total hip arthroplasty (THA). We sought to develop a technique to predicted femoral stem fixation using pre-operative CT.
Forty-nine patients requiring THA received pre-operative CTs as part of Corin OPSTM 3D dynamic planning. All patients received a taper wedged blade stem (TriFitTM TS, Corin UK) implanted through a posterior approach. Post-operatively, patients received an immediate CT and AP x-ray and a 1-year follow-up x-ray. The distance between the most superior point of the greater trochanter and the shoulder of the stem was measured and scaled using the known cup diameter on both the immediate and 1- year follow-up x-rays. The difference was recorded as stem subsidence. Subsidence greater than 4mm was deemed clinically relevant. The precise placement of the stem determined by registering the known 3D implant geometry to the post-op CT was virtually implanted back into the pre-operative OPSTM planning software. A colour map of the bone density at the stem/bone interface using the Hounsfield Units (HU) of each CT pixel was generated. Blue represents low density bone transitioning through to green and then red.
Mean stem subsidence was 1.8mm (0 to 11.1mm). Five patients had clinically relevant subsidence. Significant areas of blue and green around the proximal portion of the stem was observed in high subsidence stems when compared to the stems with minimal subsidence.
Using the HU of the CT scan as an indicator for bone density, we were able to predict poor implant fixation and subsequent subsidence in a taper wedge stem.

Keyphrases: implant fixation, loosening, pre operative planning, subsidence, total hip arthroplasty

In: Ferdinando Rodriguez Y Baena and Fabio Tatti (editors). CAOS 2020. The 20th Annual Meeting of the International Society for Computer Assisted Orthopaedic Surgery, vol 4, pages 28-34.

Links:	https://easychair.org/publications/paper/QMT6
	https://doi.org/10.29007/dv5n

BibTeX entry

@inproceedings{CAOS2020:Predicting_Cementless_Stem_Fixation,
  author    = {Teja Cherukuri and Chameka Madurawe and Jim Pierrepont and Jonathan Bare and Stephen McMahon and Andrew Shimmin},
  title     = {Predicting Cementless Stem Fixation in Total Hip Arthroplasty Using Radiodensity Mapping},
  booktitle = {CAOS 2020. The 20th Annual Meeting of the International Society for Computer Assisted Orthopaedic Surgery},
  editor    = {Ferdinando Rodriguez Y Baena and Fabio Tatti},
  series    = {EPiC Series in Health Sciences},
  volume    = {4},
  publisher = {EasyChair},
  bibsource = {EasyChair, https://easychair.org},
  issn      = {2398-5305},
  url       = {/publications/paper/QMT6},
  doi       = {10.29007/dv5n},
  pages     = {28-34},
  year      = {2020}}

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