Thoreson, Andrew R.

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.

Background: The purpose of this study is to determine the effects of proximal hamate transfer for proximal pole scaphoid reconstruction upon carpal kinematics. Methods: Eight fresh-frozen cadaveric wrists underwent evaluation of their radiocarpal and midcarpal motion after proximal hamate osteotomy. A wrist simulator was used to apply cyclical tension to the flexor carpi ulnaris (FCU), flexor carpi radialis (FCR), extensor carpi ulnaris (ECU), and extensor carpi radialis longus and brevis stitched together (ECR). Kinematic motion was captured using Moiré Phase Tracking 3-dimensional motion-tracking sensors (MPT, Metria Innovation, Inc, Milwaukee, Wisconsin) to evaluate the lunocapitate and scapholunate angles for each condition. Results: During wrist flexion-extension and radial-ulnar deviation, there were no statistically significant differences about the lunocapitate or scapholunate axis between the intact and post-hamate osteotomy conditions. Conclusions: The harvest of the proximal hamate for proximal pole scaphoid reconstruction does not appear to adversely affect wrist kinematics.

Background: Anatomic reconstruction techniques are increasingly used to address cases of acromioclavicular (AC) joint chronic instability. These usually involve an additional surgical site for autograft harvesting or an allograft. Purpose: To describe a triple-bundle (TB) anatomic reconstruction using on-site autografts, the semiconjoint tendon (SCT) and the coracoacromial ligament (CAL), and compare its primary stability to the native AC joint ligamentous complex and to a modified Weaver-Dunn (WD) reconstruction. Study Design: Controlled laboratory study. Methods: Intact AC joints of 12 paired cadaveric shoulders were tested for anterior, posterior, and superior translations under cyclic loading with a servo-hydraulic testing system. One shoulder from each pair was randomly assigned to the TB group, where 2 SCT strips were used to reconstruct the coracoclavicular ligaments while the distal end of the CAL was transferred to the distal extremity of the clavicle to reconstruct the AC ligaments; the other shoulder received a modified WD reconstruction. After reconstruction, the same translational testing was performed, with an additional load-to-failure test in the superior direction. Results: In both the TB and the WD groups, no significant differences were found before and after reconstruction in terms of joint displacements after cyclic loading, in all 3 directions. Compared with the WD reconstruction, the TB repair resulted in significantly lower displacements in both the anterior (ie, 2.59 ± 1.08 mm, P = .011) and posterior (ie, 10.17 ± 6.24 mm, P = .014) directions, but not in the superior direction. No significant differences were observed between the 2 reconstructions during the load-to-failure testing, except for the displacement to failure, which was significantly smaller (ie, 5.34 ± 2.97 mm) in the WD group ( P = .037). Conclusion: Anterior, posterior, and superior displacements after an anatomic reconstruction of the AC joint complex using the SCT and CAL as graft material were similar to those of native AC joints and significantly smaller in the axial plane than those of AC joints after a WD repair. Clinical Relevance: An anatomic reconstruction is achievable using the CAL and the SCT as on-site graft materials, providing satisfactory initial stability and thereby allowing earlier mobilization.

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.

ABSTRACTSurgical repair is a common treatment for rotator cuff tear; however, the retear rate is high. A high degree of suture repair strength is important to ensure rotator cuff integrity for healing. The purpose of this study was to compare the mechanical performance of rotator cuffs repaired with a mesh suture versus traditional polydioxanone suture II and FiberWire sutures in a canine in vitro model. Seventy‐two canine shoulders were harvested. An infraspinatus tendon tear was created in each shoulder. Two suture techniques—simple interrupted sutures and two‐row suture bridge—were used to reconnect the infraspinatus tendon to the greater tuberosity, using three different suture types: Mesh suture, polydioxanone suture II, or FiberWire. Shoulders were loaded to failure under displacement control at a rate of 20 mm/min. Failure load was compared between suture types and techniques. Ultimate failure load was significantly higher in the specimens repaired with mesh suture than with polydioxanone suture II or FiberWire, regardless of suture technique. There was no significant difference in stiffness among the six groups, with the exception that FiberWire repairs were stiffer than polydioxanone suture II repairs with the simple interrupted technique. All specimens failed by suture pull‐out from the tendon. Based on our biomechanical findings, rotator cuff repair with the mesh suture might provide superior initial strength against failure compared with the traditional polydioxanone suture II or FiberWire sutures. Use of the mesh suture may provide increased initial fixation strength and decrease gap formation, which could result in improved healing and lower re‐tear rates following rotator cuff repair. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:987–992, 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

The purpose of this study was to assess the correlations of acceleration measurements between an instrumented hockey helmet and the Hybrid III headform and to determine whether collision with a broad surface affects the correlations between these data. A CCM Vector hockey helmet, instrumented with the Head Impact Telemetry System, was fitted onto an instrumented Hybrid III headform and dropped onto an inclined plate to simulate impacts in hockey. The helmet and headform were dropped from 0.15, 0.30, and 0.60 m at different orientations to create impacts to the vertex, occipital, right, left, and forehead surfaces. Peak linear and rotational acceleration magnitudes and head injury criteria were assessed for each system. Correlations were assessed with the Pearson correlation coefficient, and linear regression models were generated. Relative error was assessed, and results were compared with the Wilcoxon signed rank test. Peak acceleration magnitudes generally had strong mathematical correlations, although a 1:1 linear relationship for rotational acceleration data was not observed. Differences between helmet and head peak acceleration magnitudes were significant. The linear relationship varied according to the impact direction. Instrumented helmet and head data demonstrated a strong mathematical correlation, but measures of linear acceleration generally had better 1:1 agreement than rotational acceleration measures. There is some dependence in the relationship between the helmet and head data on the impact direction, with vertex strikes showing the weakest correlation. Although data generated from the helmet may be useful for interpreting head accelerations experienced by on-ice players, additional analysis of the time-series data should be performed to understand its full utility.