A Comparative Study on the Biomechanical and Histological Properties of Bone-to-Bone, Bone-to-Tendon, and Tendon-to-Tendon Healing: An Achilles Tendon-Calcaneus Model in Goats

Background: Surgical repair around the bone-tendon insertion (BTI) may involve bone-to-bone (BB), bone-to-tendon (BT), or tendon-to-tendon (TT) reattachment with varying healing outcome.

Hypothesis: The repair of Achilles tendon-calcaneus (ATC) by reattachment of homogeneous tissue (BB or TT) would heal faster, with respect to tensile properties at the healing complex, than those of reattachment of heterogeneous tissues (BT) over time.

Study design: Controlled laboratory study.

Methods: Forty-seven adolescent male Chinese goats were divided into BB, BT, and TT groups. Osteotomy of the calcaneus, reattachment of Achilles tendon to the calcaneus after removal of the insertion, and tenotomy of the Achilles tendon were performed to simulate BB, BT, and TT repair, respectively. The ATC healing complexes were harvested at 6, 12, or 24 weeks postoperatively. Mechanical and morphological properties of the healing ATC complexes were assessed by tensile testing and qualitative histology, respectively. The contralateral intact ATC complex was used as the control.

Results: Failure load of BT was 33.4% lower than that of TT (P = .0243) at week 12. Ultimate strength of BT was 50.2% and 45.3% lower than that of TT at weeks 12 (P = .0002) and 24 (P = .0001), respectively. Tissue morphological characteristics of the BB and TT groups showed faster remodeling. The BT group showed limited regeneration of fibrocartilage zone and excessive formation of fibrous tissue at the healing interface.

Conclusion: BTI repair between homogeneous tissues (BB and TT healing) showed better healing quality with respect to mechanical and histological assessments than did healing between heterogeneous tissues (BT healing).

Clinical relevance: Anatomic reconstruction of ATC complex injury may be a primary concern when selecting the proper surgical approach. However, it is recommended to select fracture fixation (BB) or tendon repair (TT) instead of bone-tendon reattachment (BT) if possible to ensure better outcome at the healing interface.