Analyzing Bony Constraints as a Key Stone of an Integrated Approach Towards Functional THA Planning

5 pages•Published: July 12, 2018

Juliana Hsu, Maximilian C. M. Fischer, Kunihiko Tokunaga, Gildas Esnault and Klaus Radermacher

Abstract

Both, prosthetic design and implantation have a great influence on the impingement and dislocation risk after total hip arthroplasty (THA). Potential impingement risks should be analyzed during THA planning. In order to analyze bony impingement, often 3D meshes of the bony structures have to be transformed and collision between the 3D meshes is calculated which might be complex and time consuming. This work introduces a simplified collision calculation algorithm based on 2D mapping. Possible impingement points on the femur and the pelvis, which are points on a sphere, are extracted and mapped into a 2D plane. Impingement can be calculated using a 2D distance map.
The method was applied for analysing a dislocation case. A 38-year-old female THA patient had a dislocation 3 months after the surgery. The hip dislocated anteriorly in the standing positon while carrying a load in the front (a child) and turning the upper body slightly towards the contralateral side. The cup orientation was within the so called Lewinnek safe zone. The pelvis in standing position was tilted by 11° posteriorly. The impingement analysis revealed that maximal external hip rotation was less than 15° and even less than 10° when the pelvis is tilted more posteriorly which might have been the case during the dislocation. Considering additional soft-tissue involvement, a minor external rotation could in fact be a potential cause for dislocation.
Using the previously introduced prosthetic ROM-based target zone calculation algorithm, optimized THA parameters were determined. This include changing the CCD angle and the stem or neck antetorsion. Using the modified parameters, external rotation of at least 20° would have been possible without bony impingement. The dislocation could have been avoided.

Keyphrases: bony impingement, cup orientation, dislocation, patient specific tha, pre operative planning, range of motion, safe zone, stem orientation, target zone

In: Wei Tian and Ferdinando Rodriguez Y Baena (editors). CAOS 2018. The 18th Annual Meeting of the International Society for Computer Assisted Orthopaedic Surgery, vol 2, pages 74-78.

Links:	https://easychair.org/publications/paper/NSW7
	https://doi.org/10.29007/qrbg

BibTeX entry

@inproceedings{CAOS2018:Analyzing_Bony_Constraints_as,
  author    = {Juliana Hsu and Maximilian C. M. Fischer and Kunihiko Tokunaga and Gildas Esnault and Klaus Radermacher},
  title     = {Analyzing Bony Constraints as a Key Stone of an Integrated Approach Towards Functional THA Planning},
  booktitle = {CAOS 2018. The 18th Annual Meeting of the International Society for Computer Assisted Orthopaedic Surgery},
  editor    = {Wei Tian and Ferdinando Rodriguez Y Baena},
  series    = {EPiC Series in Health Sciences},
  volume    = {2},
  publisher = {EasyChair},
  bibsource = {EasyChair, https://easychair.org},
  issn      = {2398-5305},
  url       = {/publications/paper/NSW7},
  doi       = {10.29007/qrbg},
  pages     = {74-78},
  year      = {2018}}

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