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Balancing of total knee arthroplasty by bone cuts achieves accurately balanced soft tissues without the need for soft tissue releases
  1. Ponky Firer1,
  2. Brad Gelbart1,2
  1. 1 Linksfield Park Knee and Orthopaedic Sports Medicine Clinic, Johannesburg, South Africa
  2. 2 Department of Orthopaedic Surgery, University of the Witwatersrand Johannesburg, Johannesburg, South Africa
  1. Correspondence to Professor Ponky Firer, Department of Orthopaedic Surgery, University of the Witwatersrand Johannesburg, Johannesburg 2050, South Africa; ponky{at}icon.co.za

Abstract

Introduction Patient satisfaction, after mechanically aligned Total Knee Arthroplasty (TKA) is only 80%-85%. There is an inabilty to consistently get perfect soft tissue balance with this technique. It is postulated that soft tissue balance within 2° can be achieved by the boney cuts (Bone Balancing) without soft tissue releases, accepting whatever coronal mechanical alignment (CMA) this produces; that the alignment produced would be similar to natural (constitutional) alignment and that balanced knees would improve patient satisfaction.

Methods We report on 914 consecutive TKAs using Bone Balancing: the femoral rotation for the flexion gap; the distal femoral cut and valgus angle for the extension gap are adjusted to give equal gap sizes with soft tissue balanced within 2° of medio-lateral laxity. Long leg X-rays were used to measure post-operative coronal alignment. Satisfaction beyond 1 year post operation was assessed by an independent researcher, using a question on satisfaction and a VAS score.

Results 782(85.5%) TKAs with satisfactory x-rays were available at 2-7 years follow up. Their CMA had a similar distribution profile to reported natural alignment studies. Of these, 672 (86%) had a CMA of 0°±3° (’aligned' group). Overall patient satisfaction was 92.8%, with satisfied patients having a mean (range) VAS score of 9.53 (7.3-10.0) and the dissatisfied patients 3.78 (0.0-6.3) (p<0.0001). There was no difference in satisfaction between ’aligned' knees (92.7%) and those ’outliers', whose CMA was >±3° (93.6%) (p=0.853). All balance measurements were within 3° with 92.2% being ≤2°. Gap size difference between extension and 90° flexion was ≤2mm in 98.7% of cases. Midflexion (45° flexion) balance was within 3° in all cases and the gap size difference was ≤2mm in 89%.

Conclusion Balancing by bone cuts is able to achieve accurately balanced soft tissues without the need for soft tissue releases. The coronal alignment profile produced matches that of the normal population. This technique improves satisfaction compared to the literature for mechanically aligned TKAs. Acurate and measured soft tissue balancing needs further consideration in TKAs.

Level of Evidence Level IV.

  • knee
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Footnotes

  • Contributors Both authors were involved in the follow-up data collection, measurements of X-rays and reviewing the article. PF did all the surgery with the assistance of BG.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent Not required.

  • Ethics approval Ethics approval for this study was granted by the Linksfield Park Clinic Physicians Advisory Board (December 2006).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement All unpublished or awaiting publication data mentioned in this paper can be obtained from the corresponding author PF via email.

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