Healing characteristics of deep digital flexor tenorrhaphy within the digital sheath of horses

Longitudinal In Vivo Ultrasound Observations of the Surgically Repaired Zone II Flexor Digitorum Profundus Tendon

The link between the healing process and functional outcomes in the surgically repaired digital flexor tendon is poorly understood. This clinical note describes those gray-scale and power Doppler (PD) ultrasound parameters that can be used to document longitudinal change in the morphologic and dynamic properties of the surgically repaired zone II flexor digitorum profundus (FDP) tendon. The method is supported by ultrasound data obtained from three participants at five points in time post-surgically (two, four, six, 12 and 18 weeks). Longitudinal documentation of the ultrasound properties of echogenicity, defect size, tendon excursion and power Doppler signal is feasible and has the potential to explore the possible link between changes in the structural status of surgically repaired flexor tendons and associated clinical outcomes.

Microangiographic Comparison of the Effects of 3 Loop Pulley and 6 Strand Savage Tenorrhaphy Techniques on Equine Superficial Digital Flexor Tendon

OBJECTIVE

The 6-strand Savage (SSS) tenorrhaphy pattern is biomechanically superior to the commonly employed 3-loop pulley (3LP); however, its effects on intrinsic tendon vasculature remain unknown. The objective of this study was to compare perfusion of intrinsic vasculature of the equine superficial digital flexor tendon (SDFT) after 3LP and SSS tenorrhaphies. We hypothesized that the SSS technique would significantly decrease vascular perfusion compared to the 3LP technique.

STUDY DESIGN

Ex vivo, randomized, paired design.

ANIMALS

Horses (n = 9) METHODS: Under general anesthesia, 9 pairs of forelimb SDFT were transected. Two tendons served as baseline control, the remainder had either SSS or 3LP tenorrhaphy performed. Horses were heparinized, euthanatized, and forelimbs perfused with barium sulfate solution were then fixed with formalin under tension. Tendons were transected every 5 mm and microangiographic images obtained. Microvascular analysis of sections proximal to, throughout, and distal to the tenorrhaphy was completed using a custom macro. Differences in vascular count were assessed using MANOVA.

RESULTS

A significant reduction in the number of perfused vessels was seen for SSS compared with 3LP at 2 locations within the tenorrhaphy (P = .039 and P = .009). The SSS technique took on average 4.7 ± 0.9 times longer to place.

CONCLUSIONS

The SSS technique causes an acute reduction in tendon perfusion compared to the 3LP, which may limit its clinical use. Further research is required to elucidate the clinical significance of this difference.

The past, present and future in scaffold-based tendon treatments

Tendon injuries represent a significant clinical burden on healthcare systems worldwide. As the human population ages and the life expectancy increases, tendon injuries will become more prevalent, especially among young individuals with long life ahead of them. Advancements in engineering, chemistry and biology have made available an array of three-dimensional scaffold-based intervention strategies, natural or synthetic in origin. Further, functionalisation strategies, based on biophysical, biochemical and biological cues, offer control over cellular functions; localisation and sustained release of therapeutics/biologics; and the ability to positively interact with the host to promote repair and regeneration. Herein, we critically discuss current therapies and emerging technologies that aim to transform tendon treatments in the years to come.

Tenosynoviotomy for sepsis of the digital flexor tendon sheath in 9 horses

OBJECTIVE

To describe a tenosynoviotomy technique for treatment of sepsis of the digital flexor tendon sheath (DFTS) in horses and report long-term outcome.

STUDY DESIGN

Case series.

ANIMALS

Horses (n = 9).

METHODS

Horses were positioned in lateral recumbency with the affected limb uppermost. A linear incision was made just lateral to the mesotenon beginning 5 cm proximal to the apices of the proximal sesamoid bones, extending 2 cm distal to the bifurcation of the superficial digital flexor tendon (SDFT). The incision was continued through the skin, subcutaneous tissue, palmar/plantar annular ligament, and DFTS. Tenotomy of the distal lateral branch of the SDFT was also performed. The site was thoroughly debrided, lavaged, and packed with gauze and allowed to heal by second intention. Follow-up was obtained via owner telephone interview.

RESULTS

Mean surgery time was 32 minutes (range, 10-64 minutes). Systemic antibiotics were administered postoperatively (range, 11-46 days; mean, 23 days). Mean hospitalization was 11 days (range, 0-49 days). Follow-up was available for 7 (70%) horses. One year postoperatively, 5 (71%) horses were serviceable for their intended use, and 2 (29%) had been euthanatized. Of 5 survivors, 3 returned to ridden exercise, 1 was retired as a broodmare, and 1 was a broodmare. All owners were satisfied with the cosmetic appearance of the surgery site.

CONCLUSION

Open drainage via tenosynoviotomy, performed as a salvage procedure, represents a feasible treatment for DFTS sepsis.

Biomechanical testing of a novel suture pattern for repair of equine tendon lacerations

OBJECTIVE

To compare in vitro biomechanical properties of a novel suture pattern to a current standard for primary repair of equine superficial digital flexor tendon (SDFT) laceration.

STUDY DESIGN

In vitro randomized, paired design.

ANIMALS

Cadaveric equine forelimb SDFT (n = 24).

METHODS

The 3-loop pulley (3LP) and 6-strand Savage (SSS) suture patterns were applied to transected equine SDFT. Ultimate failure load, stiffness, mode of failure, and load required to form a 3-mm gap were obtained using a materials testing system and synchronized high-speed video analysis. Statistical comparisons were made using Student's t-test, with significance set at P < .05.

RESULTS

The SSS repair failed at a higher ultimate load (421.1 N ± 47.6) than the 3LP repair (193.7 N ± 43.0; P < .001). There was no significant difference in stiffness (P = .99). Failure mode was suture breakage for all SSS repair and suture pull through for all 3LP repair. The maximum load to create a 3-mm gap in the SSS repair (102.0 N ± 22.4) was not significantly different from the 3LP repair (109.9 N ± 16.0; P = .27).

CONCLUSIONS

SSS tenorrhaphy has improved strength and resistance to pull through compared with 3LP for equine SDFT in a single load-to-failure test. Load required to form a 3-mm gap was not significantly different between SSS and 3LP.

The effects of bone marrow stromal cell transplants on tendon healing in vitro

The purpose of this study was to investigate the effect of bone marrow stromal cells (BMSCs) on tendon healing in a canine ex vivo model. Bone marrow was harvested and BMSCs were isolated and cultured according to established protocols. Cells were seeded into 0.5mg/ml collagen gels and cultured for 24h to allow gel contraction, and then implanted between the lacerated ends of repaired flexor digitorum profundus tendons. Tendons repaired with a gel patch alone and without a gel patch served as control groups. After 2 and 4 weeks in culture, the repaired tendons were evaluated for breaking strength and stiffness. Cell viability was assessed by labeling the cells with PKH26 red fluorescent cell linker. The maximal strength and stiffness of repaired tendons with the BMSC-seeded patch were significantly higher than the repaired tendons without a patch or with a patch without cells, at both 2 and 4 weeks (p<0.05). Viable BMSC were present between the cut tendon ends at both 2 and 4 weeks. We conclude that BMSC-seeded gel patch transplantation has the potential to enhance flexor tendon healing, and we plan to investigate this effect in vivo.

Wounds of the distal limb complicated by involvement of deep structures

The authors describe the clinically relevant structures of the distal limb and the current diagnostic and treatment modalities. Specific problems include tendon laceration, septic tenosynovitis, and sep-tic arthritis of the distal joints. A detailed description of tendon repair, tendon sheath lavage, and postoperative convalescent methodology is provided. This article makes available to the reader information necessary to appropriately diagnose and treat wounds of the distal equine limb involving deep structures. Information on the overall prognosis is also provided.

Biomechanical and Clinical Evaluation of a Modified 3-Loop Pulley Suture Pattern for Reattachment of Canine Tendons to Bone

OBJECTIVE

To describe a modified 3-loop pulley suture pattern for the reattachment of canine tendons to bone along with a biomechanical comparison with the locking-loop suture.

STUDY DESIGN

In vitro biomechanical study and clinical case report.

ANIMALS OR SAMPLE POPULATION

Biomechanical study: 10 paired gastrocnemius tendons and calcaneii harvested from 5 canine cadavers.

CASE REPORT

a Doberman with avulsion of the gastrocnemius tendon of insertion.

METHODS

Biomechanical study: paired tendons were reattached to the calcaneus with either a modified 3-loop pulley pattern or a locking-loop pattern. Tensile loading to failure was performed. A direct, non-contact, method of gap measurement, using digital video, was used to measure gap formation. Load required to initiate gap formation (defined as load at a 1 mm gap) and to produce a 3 mm gap was evaluated in addition to maximum load and gap at failure.

RESULTS

Mean (+/-SEM) 1 mm gap loads were 31.0+/-4.2 and 17.2+/-2.5 N, mean 3 mm gap loads were 49.1+/-2.4 and 28.9+/-3.2 N, and mean maximum loads were 72.9+/-4.3 and 55.8+/-2.2 N for the modified 3-loop pulley suture and the locking-loop suture, respectively. These differences were statistically significant (P<.05). The gap at failure was similar for both repairs. The clinical case remained sound 7 months postoperatively.

CONCLUSIONS

A modified 3-loop pulley pattern is biomechanically superior to a locking-loop pattern for reattachment of the canine gastrocnemius tendon to bone and may be suitable for clinical use.

CLINICAL RELEVANCE

Tendon repairs with a gap >3 mm are reported to be at increased risk of rupture during the first 6 weeks postoperatively. A modified 3-loop pulley pattern resists gap formation better than a locking-loop pattern.