HSS Journal ®

, Volume 10, Issue 1, pp 6–12

Minimum Distraction Gap: How Much Ankle Joint Space Is Enough in Ankle Distraction Arthroplasty?

  • Austin T. Fragomen
  • Thomas H. McCoy
  • Kathleen N. Meyers
  • S. Robert Rozbruch
Original Article



The success of ankle distraction arthroplasty relies on the separation of the tibiotalar articular surfaces.


The purpose of this study was to find the minimum distraction gap needed to ensure that the tibiotalar joint surfaces would not contact each other with full weight-bearing while under distraction.


Circular external fixators were mounted to nine cadaver ankle specimens. Each specimen was then placed into a custom-designed load chamber. Loads of 0, 350, and 700N were applied to the specimen. Radiographic joint space was measured and joint contact pressure was monitored under each load. The external fixator was then sequentially distracted, and the radiographic joint space was measured under the three different loads. The experiment was stopped when there was no joint contact under 700N of load. The radiographic joint space was measured and the initial (undistracted) radiographic joint space was subtracted from it yielding the distraction gap. The minimum distraction gap (mDG) that would provide total unloading was calculated.


The average mDG was 2.4 mm (range, 1.6 to 4.0 mm) at 700N of load, 4.4 mm (range, 3.7 to 5.8 mm) at 350N of load, and 4.9 mm (range, 3.7 to 7.0 mm) at 0N of load.


These results suggest that if the radiographic joint space of on a standing X-ray of an ankle undergoing distraction arthroplasty shows a minimum of 5.8 mm of DG, then there will be no contact between joint surfaces during full weight-bearing. Therefore, 5 mm of radiographic joint space, as recommended historically, may not be adequate to prevent contact of the articular surfaces during weight-bearing.


ankle distraction arthrodiastasis ankle arthritis joint preservation external fixation Ilizarov RAD 

Supplementary material

11420_2013_9359_MOESM1_ESM.pdf (511 kb)
ESM 1(PDF 510 kb)
11420_2013_9359_MOESM2_ESM.pdf (511 kb)
ESM 2(PDF 510 kb)
11420_2013_9359_MOESM3_ESM.pdf (511 kb)
ESM 3(PDF 510 kb)
11420_2013_9359_MOESM4_ESM.pdf (510 kb)
ESM 4(PDF 510 kb)

Copyright information

© Hospital for Special Surgery 2013

Authors and Affiliations

  • Austin T. Fragomen
    • 1
    • 3
  • Thomas H. McCoy
    • 2
  • Kathleen N. Meyers
    • 3
  • S. Robert Rozbruch
    • 1
    • 3
  1. 1.Orthopaedic Surgery, Weill Cornell Medical CollegeNew YorkUSA
  2. 2.Harvard Medical SchoolBostonUSA
  3. 3.Hospital for Special SurgeryNew YorkUSA

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