Why did Anterior Dislocation Occur During Dandling her Baby in front of her in Standing Position after THA?

4 pages•Published: July 12, 2018

Kunihiko Tokunaga, Juliana Hsu, Maximilian C. M. Fischer, Masashi Okamoto and Klaus Radermacher

Abstract

We experienced an anterior dislocation of a lady after THA in standing position during dandling her baby in front of her. The orientations of acetabular cup and femoral stem, measured by 3D image analysis and post-operative CT images, were within the so called safe zone. As it happened, the moment of this dislocation was captured in a smart phone movie. Surface 3D models were created from pre- and post-operative CT images. The pelvic sagittal tilt angle was measured using pre-operative EOS image in standing position and landmark-based 2D/3D registration. The pelvic tilt and the post-operative THA parameters served as input to calculate the cup orientation relative to the prosthetic ROM-based target zone, the bone stock-based target zone, and maximal amount of external rotation until “bony impingement”. The prosthetic ROM- based target zone algorithm calculates impingement free cup orientations dependent on the stem orientation, neck shaft angle and pelvic orientation. The system clearly showed that impingements occurred during the slight hip external rotation and leaning back motions of the patient in standing position as shown in the smart phone movie. This system demonstrated the neck shaft angle of the stem should be reduced from 135° to 130°, and the stem antetorsion should be reduced from 35° to 20° to get optimum target zone without impingements. In addition, the cup should be placed at 6mm posteriorly to get maximum bony coverage. This patient-specific target zone calculation is a powerful tool to decide the optimum orientation and position of THA implants.

Keyphrases: dislocation, patient specific, standing position, target zone, tha

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 219-222.

Links:	https://easychair.org/publications/paper/qJSR
	https://doi.org/10.29007/f4p2

BibTeX entry

@inproceedings{CAOS2018:Why_did_Anterior_Dislocation,
  author    = {Kunihiko Tokunaga and Juliana Hsu and Maximilian C. M. Fischer and Masashi Okamoto and Klaus Radermacher},
  title     = {Why did Anterior Dislocation Occur During Dandling her Baby in front of her in Standing Position after THA?},
  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/qJSR},
  doi       = {10.29007/f4p2},
  pages     = {219-222},
  year      = {2018}}

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