Anatomic Ligament Repair Restores Ankle and Syndesmotic Rotational Stability as Much as Syndesmotic Screw Fixation

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Abstract

Objectives:

To compare the external rotation stability of 3 different syndesmotic stabilization techniques in a cadaveric ankle fracture model.

Methods:

Nondestructive external rotation stresses of 4 N·m were applied to 8 cadaveric limbs using a hydraulic loading frame. Four conditions were tested using a repeated-measures design: intact and 3 repair conditions after a destabilizing ligamentous ankle injury with syndesmotic disruption. The 3 repair conditions were tricortical trans-syndesmotic screw fixation, posterior inferior tibiofibular ligament (PITFL) repair, and combined PITFL and deltoid ligament repair. External rotation of the ankle joint and syndesmosis was measured using a motion capture system and compared for each test condition. Repeated-measures 1-way analyses of variance statistical tests were performed to compare the ankle and syndesmotic rotation findings between the 3 repair conditions and intact condition.

Results:

Rotational ankle stability was not fully restored by any of the 3 repair constructs. The intact ankle joint externally rotated approximately half as many degrees as the 3 repair conditions (intact: 10.9; trans-syndesmotic screw: 17.0; PITFL: 21.4; and PITFL/deltoid: 15.6). The intact condition also demonstrated significantly fewer degrees of syndesmotic rotation than the repair constructs (intact 2.4; trans-syndesmotic screw 5.2; PITFL 8.5; and PITFL/deltoid 6.9). Each of the repair conditions resulted in an externally rotated fibula when no loads were applied. The ligamentous repairs externally rotated the fibula twice as much as the trans-syndesmotic screw (P < 0.016).

Conclusions:

We found that combined repair of the PITFL and deltoid ligament restores an equivalent amount of ankle and syndesmotic rotational stability when compared to trans-syndesmotic screw fixation. Based on our findings, ligamentous repair can potentially be a viable treatment alternative in unstable ankle fracture patients with syndesmotic disruption.

Level of Evidence:

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

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