Amadio, Peter C.

ABSTRACTFlexor tendon injuries are common and pose a clinical challenge for functional restoration. The purpose of our study was to assess the adequacy of the turkey as a large animal model for flexor tendon injuries in vivo. Twenty‐four male turkeys underwent surgical flexor tendon cut and repair. Turkeys were allocated to five groups postoperatively: (1) foot casted in extension and sacrificed after 3 weeks; (2) foot casted in extension and sacrificed after 6 weeks; (3) foot casted in flexion and sacrificed after 3 weeks; (4) foot casted in flexion and sacrificed after 6 weeks; and (5) foot casted in flexion for 6 weeks and then free roaming allowed for an additional 3 weeks before sacrifice. After sacrifice, digits were collected and analyzed for adhesion formation, healing at the macrolevel and histologically, and biomechanical properties—including friction, work of flexion, stiffness, and strength of repair. All turkeys survived anesthesia and surgery. Tendon rupture occurred in all extension casts and in 11% of those casted in flexion. Friction and work of flexion were significantly higher in the repaired digit than the control digit. There was a correlation between duration of immobilization and repair strength. Histologically, the tendon healed with tenocytes migrating into the gap and producing collagen fibers. We have, for the first time, studied flexor tendon injury and repair using turkeys in terms of anesthesia, surgical procedures, postoperative care, and animal husbandry. The findings regarding functional and histological results from this novel avian model were comparable to the most commonly used mammal model. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2497–2505, 2018.

ABSTRACTThis study was to test our hypothesis that flexor tendon reconstruction with an allograft revitalized with bone marrow stromal cells (BMSCs) and synovialized with carbodiimide derivatized autologous synovial fluid (cd‐SYN) would result in better digit functional restoration than the conventional allograft tendon. A total of 32 flexor digital profundus tendons from the second and fifth digit of 16 dogs were created a repair failure model first. Then, failed‐repaired tendons were reconstructed with either a revitalized‐synovialized allograft tendon or a clinical standard autograft tendon (control group). The allograft tendon was seeded with autologous BMSCs in multiple slits and the graft surface was coated with cd‐SYN. A 6 weeks after tendon reconstruction, the digits were harvested and evaluated for digit function, adhesion status, tendon gliding resistance, attachment strength, cell viability, and histologic factors. The allograft group had significantly improved digit function compared with the control group through decreased work of flexion, increased digit range of motion under 2‐Newton force, and less adhesion score (p < .05). However, the distal attachment‐site strength and stiffness in the allograft tendon were significantly weaker than the autografts (p < .05). No significant difference was found for gliding resistance. Histologically, allograft tendons coated with allograft had smoother surfaces and showed tendon‐to‐bone and tendon‐to‐tendon incorporation. Viable BMSCs were found in the tendon slits 6 weeks after the graft. In conclusion, cellular lubricant‐based modification of allograft tendons improved digit function and reduced the adhesions compared with autograft for flexor tendon reconstruction. However, improvement of graft‐to‐host tendon healing is still challenging. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2218–2227, 2018.

Tendon injuries are among the most common and severe hand injuries with a high demand for functional recovery. Stem cells have been identified and isolated from different species and a variety of tissues for the sake of regenerative medicine. Recently, turkey has been suggested as a potential new large animal model for flexor tendon-related research. However, turkey tissue-specific stem cells have not been investigated. Here, we presented the isolation and verification of tendon-derived stem cells (TDSCs) from 6- to 8-month-old heritage-breed turkey. TDSCs were isolated from turkey flexor tendon by plating nucleated cells at the determined optimal density. Approximately 4% of the nucleated cells demonstrated clonogenicity, high proliferation rate, and trilineage differentiation potential after induction culturing. These cells expressed surface antigens CD90, CD105, and CD44, but did not express CD45. There was a high level of gene expression of tenogenic markers in TDSCs, including mohawk, collagen type I, tenascin C, and elastin. Turkey TDSCs also expressed transcription factorsPouV,Nanog, andSox2, which are critically involved in the regulation of stemness. The successful isolation of tendon-derived stem cells from turkey was beneficial for future studies in tendon tissue engineering and would help in the development of new treatment for tendon diseases using this novel animal model.

Background: Flexor tendon injury is common, and tendon reconstruction is indicated clinically if the primary repair fails or cannot be performed immediately after tendon injury. The purpose of the current study was to compare clinically standard extrasynovial autologous graft (EAG) tendon and intrasynovial allogeneic graft (IAG) that had both undergone biolubricant surface modification in a canine in vivo model. Methods: Twenty-four flexor digitorum profundus (FDP) tendons from the second and fifth digits of 12 dogs were used for this study. In the first phase, a model of failed FDP tendon repair was created. After 6 weeks, the ruptured FDP tendons with a scarred digit were reconstructed with the use of either EAG or IAG tendons treated with carbodiimide-derivatized hyaluronic acid and lubricin. At 12 weeks after tendon reconstruction, the digits were harvested for functional, biomechanical, and histologic evaluations. Results: The tendon failure model was a clinically relevant and reproducible model for tendon reconstruction. The IAG group demonstrated improved digit function with decreased adhesion formation, lower digit work of flexion, and improved graft gliding ability compared with the EAG group. However, the IAG group had decreased healing at the distal tendon-bone junction. Our histologic findings verified the biomechanical evaluations and, further, showed that cellular repopulation of allograft at 12 weeks after reconstruction is still challenging. Conclusions: FDP tendon reconstruction using IAG with surface modification has some beneficial effects for reducing adhesions but demonstrated inferior healing at the distal tendon-bone junction compared with EAG. These mixed results indicate that vitalization and turnover acceleration are crucial to reducing failure of reconstruction with allograft. Clinical Relevance: Flexor tendon reconstruction is a common surgical procedure. However, postoperative adhesion formation may lead to unsatisfactory clinical outcomes. In this study, we developed a potential flexor tendon allograft using chemical and tissue-engineering approaches. This technology could improve function following tendon reconstruction.

ABSTRACT Carpal tunnel pressure is a key factor in the etiology of carpal tunnel syndrome. Numerous approaches have been conducted to measure carpal tunnel pressure. However, most techniques are invasive and take time and effort. We have developed an innovative approach to noninvasively assess the tunnel pressure by using the ultrasound surface wave elastography (USWE) technique. In a previous study it was shown that the shear wave speed in a tendon increased linearly with increasing tunnel pressure enclosed the tendon in a simple tendon model. This study aimed to examine the relationship between the carpal tunnel pressure and the shear wave speeds inside and outside the carpal tunnel in a human cadaveric model. The result showed that the shear wave speed inside the carpal tunnel increased linearly with created carpal tunnel pressure, while the shear wave speed outside the carpal tunnel remained constant. These findings suggest that noninvasive measurement of carpal tunnel pressure is possible by measuring the shear wave speed in the tendon. After fully establishing this technology and being applicable in clinic, it would be useful in the diagnosis of carpal tunnel syndrome. For that reason, further validation with this technique in both healthy controls and patients with carpal tunnel syndrome is required. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:477–483, 2018.

ABSTRACTIntroduction: The aim of this study was to assess alterations in median nerve (MN) biomechanics within the carpal tunnel resulting from ultrasound‐guided hydrodissection in a cadaveric model. Methods: Twelve fresh frozen human cadaver hands were used. MN gliding resistance was measured at baseline and posthydrodissection, by pulling the nerve proximally and then returning it to the origin. Six specimens were treated with hydrodissection, and 6 were used as controls. Results: In the hydrodissection group there was a significant reduction in mean peak gliding resistance of 92.9 ± 34.8 mN between baseline and immediately posthydrodissection (21.4% ± 10.5%; P = 0.001). No significant reduction between baseline and the second cycle occurred in the control group: 9.6 ± 29.8 mN (0.4% ± 5.3%; P = 0.467). Discussion: Hydrodissection can decrease the gliding resistance of the MN within the carpal tunnel, at least in wrists unaffected by carpal tunnel syndrome. A clinical trial of hydrodissection seems justified. Muscle Nerve 57: 25–32, 2018

Objectives The present study describes a novel technique for revitalising allogenic intrasynovial tendons by combining cell-based therapy and mechanical stimulation in an ex vivo canine model. Methods Specifically, canine flexor digitorum profundus tendons were used for this study and were divided into the following groups: (1) untreated, unprocessed normal tendon; (2) decellularised tendon; (3) bone marrow stromal cell (BMSC)-seeded tendon; and (4) BMSC-seeded and cyclically stretched tendon. Lateral slits were introduced on the tendon to facilitate cell seeding. Tendons from all four study groups were distracted by a servohydraulic testing machine. Tensile force and displacement data were continuously recorded at a sample rate of 20 Hz until 200 Newton of force was reached. Before testing, the cross-sectional dimensions of each tendon were measured with a digital caliper. Young’s modulus was calculated from the slope of the linear region of the stress-strain curve. The BMSCs were labeled for histological and cell viability evaluation on the decellularized tendon scaffold under a confocal microscope. Gene expression levels of selected extracellular matrix tendon growth factor genes were measured. Results were reported as mean ± SD and data was analyzed with one-way ANOVAs followed by Tukey’s post hoc multiple-comparison test. Results We observed no significant difference in cross-sectional area or in Young’s modulus among the four study groups. In addition, histological sections showed that the BMSCs were aligned well and viable on the tendon slices after two-week culture in groups three and four. Expression levels of several extracellular matrix tendon growth factors, including collagen type I, collagen type III, and matrix metalloproteinase were significantly higher in group four than in group three (p < 0.05). Conclusion Lateral slits introduced into de-cellularised tendon is a promising method of delivery of BMSCs without compromising cell viability and tendon mechanical properties. In addition, mechanical stimulation of a cell-seeded tendon can promote cell proliferation and enhance expression of collagen types I and III in vitro. Cite this article: J. H. Wu, A. R. Thoreson, A. Gingery, K. N. An, S. L. Moran, P. C. Amadio, C. Zhao. The revitalisation of flexor tendon allografts with bone marrow stromal cells and mechanical stimulation: An ex vivo model revitalising flexor tendon allografts. Bone Joint Res 2017;6:179–185. DOI: 10.1302/2046-3758.63.BJR-2016-0207.R1.

Fibrosis of the subsynovial connective tissue (SSCT) in carpal tunnel syndrome (CTS) patients is increasingly recognized as an important aspect of CTS pathophysiology. In this study, we evaluated the effect of blocking profibrotic pathways in fibroblasts from the SSCT in CTS patients. Fibroblasts were stimulated with transforming growth factor β1 (TGF‐β1), and then treated either with a specific fibrosis pathway inhibitor targeting TGF‐β receptor type 1 (TβRI), platelet‐derived growth factor receptor (PDGFR), epidermal growth factor receptor (EGFR), or vascular endothelial growth factor receptor (VEGFR). Fibrosis array and quantitative real‐time polymerase chain reaction of fibrotic genes were evaluated. Array gene expression analysis revealed significant down‐regulation of multiple fibrotic genes after treatment with TβRI, PDGFR, and VEGFR inhibitors. No array fibrotic genes were significantly down‐regulated with EGFR inhibition. Further gene expression analysis of known CTS fibrosis markers collagen type I A2 (Col1), collagen type III A1 (Col3), connective tissue growth factor (CTGF), and SERPINE1 showed significantly down‐regulation after TβRI inhibition. In contrast, VEGFR inhibition significantly down‐regulated CTGF and SERPINE1, whereas, PDGFR and EGFR inhibition significantly down‐regulated Col3. Taken together the inhibition of TβRI appears to be the primary mediator of fibrotic gene expression in fibroblasts from CTS patients. TGF‐β/Smad activity was further evaluated, and as expected inhibition of Smad activity was significantly down‐regulated after inhibition of TβRI, but not with PDGFR, VEGFR, or EGFR inhibition. These results indicate that local therapies specifically targeting TGF‐β signaling alone or in combination offer the potential of a novel local antifibrosis therapy for patients with CTS.