High Plantar Force Loading After Achilles Tendon Rupture Repair With Early Functional Mobilization.

Background: Mechanical loading is essential for tendon healing and may explain variability in patient outcomes after Achilles tendon rupture (ATR) repair. However, there is no consensus regarding the optimal postoperative regimen, and the actual amount of loading during orthosis immobilization is unknown. Purpose: The primary aim of this study was to assess the number of steps and the amount of loading in a weightbearing orthosis during the first 6 weeks after surgical ATR repair. A secondary purpose was to investigate if the amount of loading was correlated to fear of movement and/or experience of pain. Study Design: Case series; Level of evidence, 4. Methods: Thirty-four patients (mean +/- SD age, 38.8 +/- 8.7 years) with ATR repair were included. Early functional mobilization was allowed postoperatively in an orthosis with adjustable ankle range of motion. During the first postoperative 2 weeks, patient-reported loading and pain were assessed with a visual analog scale and step counts with a pedometer. At the 2- and 6-week follow-up, a mobile force sensor was used for measuring plantar force loading, and the Tampa Scale for Kinesiophobia was used to examine fear of movement. Results: Between the first and second weeks, there was a significant increase in the mean number of daily steps taken (from 2025 to 2753, P < .001) as well as an increase in self-reported loading (from 20% to 53%, P < .001). Patient self-reported loading was significantly associated with the plantar force measurement (rho = 0.719, P < .001). At 6 weeks, loading was 88.2% on the injured limb versus the uninjured limb. Fear of movement was not correlated with pedometer data, subjective loading, pain, or force data. Patients with less pain during activity, however, reported significantly higher subjective load and took more steps (P < .05). Conclusion: This is the first study to demonstrate the actual loading patterns during postoperative functional mobilization among patients with surgically repaired ATR. The quick improvements in loading magnitude and frequency observed may reflect improved tendon loading essential for healing. Pain, rather than fear of movement, was associated with the high variability in loading parameters. The data of this study may be used to improve ATR rehabilitation protocols for future studies. Registration: NCT02318472 (ClinicalTrials.gov).