Citations

Barbed sutures and connecting devices have been historically described and used in flexor tendon tenorrhaphies. With the improvement in biomaterial, we have witnessed recently the resurgence of this concept. In this article, we review the historical use of barbed devices in repairing flexor tendons and explore the available barbed surgical devices that have been described in recent years.

Clinical results following four-corner arthrodesis vary and suggest that nonunion may be related to certain fixation techniques. The purpose of our study was to examine the displacement between the lunate and capitate following a simulated four-corner arthrodesis with the hypothesis that three types of fixation (Kirschner wires, dorsal circular plate, and a locked dorsal circular plate) would allow different amounts of displacement during simulated wrist flexion and extension. Cadaver wrists with simulated four-corner arthrodeses were loaded cyclically either to implant failure or until the lunocapitate displacement exceeded 1 mm. The locked dorsal circular plate group was significantly more stable than the dorsal circular plate and K-wire groups ( p = 0.018 and p = 0.006). While these locked dorsal circular plates appear to be very stable our results are limited only to the biomechanical behavior of these fixation techniques within a cadaver model.

AbstractPurposeThe purpose of this study is to determine whether the RetroScrew tibial fixation system offers a biomechanical advantage over the Delta screw for anterior cruciate ligament (ACL) reconstruction in cadaveric tibias with low bone mineral density (BMD).MethodsTen matched pairs of osteoporotic cadaveric tibiae underwent simulated ACL reconstruction using quadrupled hamstring grafts with one of the two tibial fixation constructs. Group 1 was fixed with the Delta screw (DS; 35‐mm antegrade biointerference screw), and group 2 was fixed with the RetroScrew system (RSS; 20‐mm retrograde and 17‐mm antegrade biointerference screws). Each construct was cyclically loaded (50–200 N, 1 Hz, 500 cycles) and subsequently loaded to failure (20 mm/s).ResultsAll specimens were osteoporotic without significant segmental (proximal, middle, and distal) BMD differences between groups by quantitative computed tomography (P = n.s.). A trend was noted for more construct failures due to graft slippage in the DS group (n = 3) over the RSS group (n = 1). There were no significant differences in cyclic displacement (P = n.s.), maximum cyclic stiffness (P = n.s.), maximum load at failure (P = n.s.), or pullout stiffness (P = n.s.) between groups.ConclusionsIn an osteoporotic cadaveric model, there was no significant biomechanical advantage of the RetroScrew system versus the Delta screw for tibial fixation in soft tissue graft ACL reconstruction. However, a trend toward lower graft fixation failure to cyclic loading was noted with the RetroScrew system.Level of evidenceBiomechanical comparative study, Level II.

AbstractPurposeThe purpose of this study is to determine the effect of bioabsorbable interference screw (BIS) tibial fixation with the Delta screw (antegrade) and RetroScrew (retrograde) on initial (time zero) intra‐articular graft tension in soft tissue anterior cruciate ligament (ACL) reconstruction in a cadaveric model.MethodsTen matched pairs of cadaveric tibias received one of two tibial fixation constructs using quadrupled hamstring grafts, Delta screw (antegrade) or the RetroScrew (retrograde). Each specimen was mounted to the materials testing device with the displacement force vector in line with the tibial tunnel. The construct was pre‐tensioned (10–30 N, 0.1 Hz, 10 cycles), a baseline tension of 25 N was introduced, and the change in intra‐articular graft tension before and after screw insertion was recorded.ResultsSegmental (proximal, middle, distal) BMD was utilized to assess BMD using quantitative computed tomography (qCT). The Delta screw had a higher maximum insertion torque (P = 0.03) and exhibited a larger increase in intra‐articular graft tension as compared to the RetroScrew (38.3 ± 17.9 N, 7.6 N ± 14.4, P = 0.004), respectively. There were no significant correlations between intra‐articular graft tension increase to maximum insertion torque (P = NS) or corresponding segmental BMD (P = NS).ConclusionsDelta screw tibial fixation (antegrade) in soft tissue ACL reconstruction significantly increases the initial intra‐articular graft tension as compared to RetroScrew screw fixation (retrograde) in this cadaveric model. Delta screw (antegrade) tibial fixation may increase initial quadrupled hamstring graft intra‐articular tension with currently accepted insertion techniques.

Tendon disuse, or stress deprivation, frequently accompanies clinical disorders and treatments, yet the metabolism of tendons subject to stress deprivation has rarely been investigated systematically. The effects of stress deprivation on canine flexor tendon were investigated in this study. One adult canine forepaw was suspended for 21 or 42 days. Control forepaws were collected from dogs that had no intervention on their limbs and paws. The expression of collagen I and III was not significantly altered in the tendons disused for 21 days but was significantly decreased at 42 days ( P < 0.03). The expression of collagen II, aggrecan, decorin, and fibronectin was significantly decreased in the tendons in the suspended limbs at 21 days ( P < 0.002) and further reduced at 42 days. With stress deprivation, the expression of matrix metalloproteinase 2 (MMP2) was significantly increased ( P < 0.004) at 21 and 42 days. The expression of MMP3 was significantly decreased at 21 and 42 days ( P < 0.03). The expression of MMP13 was not altered with stress deprivation at 21 and 42 days. The expression of MMP14 was significantly increased at 21 days ( P = 0.0015) and returned to the control level at 42 days. Tissue inhibitor of metalloproteinase 1 (TIMP1) expression was decreased after the limbs were suspended for 42 days ( P = 0.0043), but not 21 days. However, TIMP2 expression was not significantly different from control at 21 or 42 days. Furthermore, the cross-sectional area of the stress-deprived tendons at 42 days was decreased compared with the control group ( P < 0.01). The intervention method in this study did not result in any alteration of stiffness of the tendon. Our study demonstrated that stress deprivation decreases the anabolic process and increases the catabolic process of extracellular matrix in flexor tendon.

A three-dimensional (3D) geometric model for predicting muscle forces in the shoulder complex is proposed. The model was applied throughout the range of arm elevation in the scapular plan. In vitro testing has been performed on 13 cadaveric shoulders. The objectives were to determine homogeneous values of physiological parameters of shoulder muscles and to locate sites of muscular attachment to any bone of the shoulder complex. Muscular fiber lengths, lengths of contractile element (CE), and muscle volumes were measured, corresponding physiological cross-sectional area (PCSA) were calculated, and force/length muscle relations were found. An in vivo biplanar radiography was performed on five volunteers. The photogrammetric reconstruction of bone axes and landmarks were coupled with a geometric modeling of bones and muscle sites of attachment. Muscular paths were drawn and changes in lengths during movement have been estimated. Directions of muscle forces are the same as that of muscular path at the point of attachment to bone. Magnitudes of muscular forces were found from muscle lengths coupled with force/length relations. Passive forces were directly determined contrary to active muscle forces. A resulting active muscle force is calculated from balancing weight and passive forces at each articular center. Active muscle forces were calculated by distributing the resulting force among active muscles based on the muscular PCSA values.

Background: We performed a laboratory-based study of the ankle-hindfoot complex in normal cadaveric ankles with simulated lateral ankle ligament injuries, utilizing an ankle stability testing device. The ankle stability testing device distinguished between intact, injury to anterior talofibular ligament (ATFL) and combined injury to ATFL and calcaneofibular ligament (CFL). Materials and Methods: Ankles were tested in an ankle stability testing device, with a specified inversion torque applied through the range of sagittal plane motion, then internal rotation torque applied through the entire range of sagittal plane motion. Three-dimensional motion of the calcaneus and talus in relation to the tibia were determined with a magnetic tracking system. The specimens were tested in the intact condition, then after sectioning the ATFL, then the CFL. Results: Upon sectioning the ATFL, there was a significant increase in the internal rotation motion at the tibiotalar joint. Subsequent sectioning of the CFL did not significantly increase ankle-hindfoot internal rotation, but it did significantly increase the motion in inversion testing. This increase occurred primarily at the tibiotalar level. Conclusion: The isolated ATFL injury was clearly distinguished from the intact condition by increased talar-tibial internal rotation, but not inversion. The more severe combined ATFL/CFL injury was distinguished from the ATFL injury condition with inversion torque. Clinical Relevance: Inversion torque may disclose combined ATFL/CFL injury, and internal rotation torque may be the key to distinguish isolated ATFL and combined ATFL/CFL injuries.

Abstract The low efficiency of reprogramming and genomic integration of virus vectors obscure the potential application of induced pluripotent stem (iPS) cells; therefore, identification of chemicals and cooperative factors that may improve the generation of iPS cells will be of great value. Moreover, the cellular mechanisms that limit the reprogramming efficiency need to be investigated. Through screening a chemical library, we found that two chemicals reported to upregulate E-cadherin considerably increase the reprogramming efficiency. Further study of the process indicated that E-cadherin is upregulated during reprogramming and the established iPS cells possess E-cadherin-mediated cell–cell contact, morphologically indistinguishable from embryonic stem (ES) cells. Our experiments also demonstrate that overexpression of E-cadherin significantly enhances reprogramming efficiency, whereas knockdown of endogenous E-cadherin reduces the efficiency. Consistently, abrogation of cell–cell contact by the inhibitory peptide or the neutralizing antibody against the extracellular domain of E-cadherin compromises iPS cell generation. Further mechanistic study reveals that adhesive binding activity of E-cadherin is required. Our results highlight the critical role of E-cadherin-mediated cell–cell contact in reprogramming and suggest new routes for more efficient iPS cell generation.

Radioscapholunate arthrodesis is a salvage procedure indicated for osteoarthritis of the radiocarpal joint involving the lunate facet of the radius. This cadaver study examines changes in wrist motion resulting from radioscapholunate arthrodesis, and the effects of surgical techniques to improve the range of motion. Simulated radioscapholunate arthrodesis, distal scaphoidectomy and triquetrectomy were carried out sequentially on six cadaver forearms and measurements (maximum flexion/extension and radial/ulnar deviation) were taken in the intact situation and after each surgical step using a magnetic tracking device. Radioscapholunate arthrodesis diminishes the amplitudes of movements of the wrist in all directions, but range of motion in the radioscapholunate fused wrist improves after scaphoidectomy and improves further after triquetrectomy (88% of original flexion/extension and 98% of original radial/ulnar deviation). Radioscapholunate arthrodesis causes a significant change in kinematics between the hamate and the triquetrum in flexion/extension.