Weakness in end-range plantar flexion after Achilles tendon repair

Background: Separation of tendon ends after Achilles tendon repair may affect the tendon repair process and lead to postoperative end-range plantarflexion weakness. Hypothesis: Patients will have disproportionate end-range plantarflexion weakness after Achilles tendon repair. Study Design: Descriptive laboratory study. Methods: Four-strand core suture repairs of Achilles tendon were performed on 1 female and 19 male patients. Postoperatively, patients were nonweightbearing with the ankle immobilized for 4 weeks. Plantarflexion torque, dorsiflexion range of motion, passive joint stiffness, toe walking, and standing single-legged heel rise (on an incline, decline, and level surface) were assessed after surgery (mean, 1.8 years postoperative; range, 6 months-9 years). Maximum isometric plantarflexion torque was measured at 20 degrees and 10 degrees of dorsiflexion, neutral, and 101 and 200 of plantar flexion. Percentage strength deficit (relative to noninvolved leg) was computed at each angle. Passive dorsiflexion range of motion was measured goniometrically. Passive joint stiffness was computed from increase in passive torque between 100 and 201 of dorsiflexion, before isometric contractions. Results: Significant plantarflexion weakness was evident on the involved side at 200 and 100 of plantar flexion (34% and 20% deficits, respectively; P < .001), with no torque deficits evident at other angles (6% at neutral, 3% at 100 of dorsiflexion, 0% at 200 of dorsiflexion). Dorsiflexion range of motion was not different between involved and noninvolved sides (P = .7). Passive joint stiffness was 34% lower on the involved side (P < .01). All patients could perform an incline heel rise; 14 patients could not perform a decline heel rise (P < .01). Conclusion: Disproportionate weakness in end-range plantar flexion, decreased passive stiffness in clorsiflexion, and inability to perform a decline heel rise are evident after Achilles tendon repair. Possible causes include anatomical lengthening, increased tendon compliance, and insufficient rehabilitation after Achilles tendon repair. Clinical Relevance: Impairments will have functional implications for activities leg, descending stairs and landing from a jump). Weakness in end-range plantar flexion may be an unrecognized problem after Achilles tendon repair.