Semi-Bone Tunnel Technique Using Double-Row Suture Bridge Combined With Platelet-Rich Plasma Hydrogel for Rotator Cuff Repair in a Rabbit Model

BACKGROUND

The approach to managing the footprint area and reconstructing the tendon-bone interface (TBI) is critical for optimal healing.

PURPOSE

To evaluate the outcomes of the semi-bone tunnel (SBT) technique using a double-row suture bridge combined with platelet-rich plasma (PRP) hydrogel for rotator cuff repair in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 48 New Zealand White rabbits were divided into 4 groups. The supraspinatus tendons were severed at the footprint to create a rotator cuff tear model in the surgical groups. Rabbits were treated with the traditional onto-surface repair (control group), SBT technique (SBT group), and SBT technique combined with PRP hydrogel implantation (SBT+PRP group). The rabbits without surgery were the normal group. At 8 weeks after surgery, macroscopic observation, magnetic resonance imaging (MRI) and micro-computed tomography (μCT) examinations, histological evaluations, and biomechanical tests were performed to assess the curative effects of the given treatments.

RESULTS

The MRI results showed that the repaired supraspinatus tendon presented a uniform signal, minimal inflammatory response, and the lowest signal-to-noise quotient value in the SBT+PRP group. The μCT results suggested that the SBT technique did not reduce the local bone mineral density in the TBI area compared with the onto-surface repair technique. The histological staining results showed that the regenerated TBI in the SBT+PRP group had a 4-layer structure similar to the natural tissue. The highest values for biomechanical properties were observed in the SBT+PRP group, and there was no significant difference between the SBT+PRP group and normal group.

CONCLUSION

The SBT technique presented a better tendon-bone healing effect for rotator cuff tear in the rabbit model compared with the traditional onto-surface repair technique. The specimens in the SBT+PRP group had a similar TBI structure and biomechanical properties to the natural tissue.

CLINICAL RELEVANCE

The SBT technique can be an alternative surgical approach for rotator cuff repair, especially for moderate to large tears and cases requiring scaffold implantation.

Local Administration of Metformin Improves Bone Microarchitecture and Biomechanical Properties During Ruptured Canine Achilles Tendon-Calcaneus Interface Healing

BACKGROUND

Tendon-bone interface (TBI) healing is a clinical dilemma that is closely relevant to new bone formation and remodeling at the repair site. Previous studies showed that metformin is an osteogenic inducer for stem cells in vitro and capable of stimulating bone regeneration in vivo.

HYPOTHESIS

Metformin would be effective for promoting TBI healing by enhancing new bone formation and remodeling.

STUDY DESIGN

Controlled laboratory study.

METHODS

Canine bone marrow stem cells (BMSCs) were cultured with various concentrations of metformin (0, 10, 50, 100, 200 μM). The effect of metformin on the osteogenic differentiation of canine BMSCs was evaluated via alizarin red staining and osteogenic gene expression. Eighteen mature beagles were included in a bilateral Achilles tendon-calcaneus (ATC) interface injury model. The right interface was reattached via surgical repair only, while the left was surgically reattached after implanting a fibrin glue containing metformin. At postoperative week 4 or 8, the healing quality of the wounded ATC interfaces was evaluated.

RESULTS

In vitro experiments determined that metformin was an osteogenic inducer for canine BMSCs. In vivo experiments showed that the metformin-treated ATC interfaces were repaired with significantly greater failure load and stiffness than was the no-metformin control site (P < .05 for all). Micro-computed tomography analysis showed that the metformin-treated specimens presented significantly higher bone volume/total volume and trabecular thickness than did the no-metformin control specimens (P < .05 for all), as confirmed via hematoxylin and eosin staining. Immunohistochemical staining showed that significantly more osteocalcin-positive cells were located at the newly formed bones treated with metformin than at the no-metformin control site at week 4 (P < .05). Masson trichrome staining showed that significantly more oriented collagen fibers anchored into the newly formed bone of the metformin-treated site than the no-metformin control site (P < .05).

CONCLUSION

Metformin induced the osteogenesis of canine BMSCs in vitro, and local administration of metformin provided an improvement of bone microarchitecture at the calcaneus as well as an increase in the tensile properties of the repaired ATC interfaces in canines.

CLINICAL RELEVANCE

Findings of the study indicate that local administration of metformin may be an effective strategy for TBI healing in clinic.