An, Kai‐Nan

AbstractThis study aimed to compare the clinically established autologous extrasynovial tendon graft to a newly developed tissue‐engineered allograft (Eng‐allograft) in terms of functional outcomes following flexor tendon reconstruction in a canine model. The second and fifth flexor digitorum profundus (FDP) tendons from 16 dogs were transected and repaired in Zone II. After 6 weeks of cage activity, the repaired tendons were intentionally ruptured, creating a clinically relevant model for reconstruction. The re‐ruptured FDP tendons were then reconstructed using either the clinically standard autologous extrasynovial tendon graft or the Eng‐allograft, which had been revitalized with autologous bone marrow‐derived mesenchymal stem cells (BMSCs) and synovialized using carbodiimide derivatized synovial fluid (cd‐SYN). Following 12 weeks of postoperative rehabilitation, the functional outcomes of the surgical digits were evaluated. The Eng‐allograft group exhibited improved digital function, including lower digit work of flexion and reduced adhesion status, while maintaining similar tendon gliding resistance compared to the autograft group. However, the failure load of both the distal and proximal host/graft conjunctions in the Eng‐allograft group was significantly lower than that of the autograft group with higher graft rupture at the host−graft junction. In conclusion, the decellularized allogenic intrasynovial tendon, when revitalized BMSCs and synovialized with cd‐SYN, demonstrates positive effects on digital function improvement and adhesion reduction. However, the healing at both proximal and distal graft/host junctions is far lower than the autograft. Further research is needed to enhance the healing capacity of allograft conjunctions, aiming to achieve a comparable level of healing seen with autografts.

AbstractPurposeAbnormal adherence at functional myofascial interfaces is hypothesized as an important phenomenon in myofascial pain syndrome. This study aimed to investigate the feasibility of MR elastography (MRE)–based slip interface imaging (SII) to visualize and assess myofascial mobility in healthy volunteers.MethodsSII was used to assess local shear strain at functional myofascial interfaces in the flexor digitorum profundus (FDP) and thighs. In the FDP, MRE was performed at 90 Hz vibration to each index, middle, ring, and little finger. Two thigh MRE scans were performed at 40 Hz with knees flexed and extended. The normalized octahedral shear strain (NOSS) maps were calculated to visualize myofascial slip interfaces. The entropy of the probability distribution of the gradient NOSS was computed for the two knee positions at the intermuscular interface between vastus lateralis and vastus intermedius, around rectus femoris, and between vastus intermedius and vastus medialis.ResultsNOSS map depicted distinct functional slip interfaces in the FDP for each finger. Compared to knee flexion, clearer slip interfaces and larger gradient NOSS entropy at the vastus lateralis–vastus intermedius interface were observed during knee extension, where the quadriceps are not passively stretched. This suggests the optimal position for using SII to visualize myofascial slip interface in skeletal muscles is when muscles are not subjected to any additional force.ConclusionThe study demonstrated that MRE‐based SII can visualize and assess myofascial interface mobility in extremities. The results provide a foundation for investigating the hypothesis that myofascial pain syndrome is characterized by changes in the mobility of myofascial interfaces.

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.

AbstractSubstance P (SP), a neurotransmitter released after injury, has been linked to deregulated tissue repair and fibrosis in musculoskeletal tissues and other organs. Although SP inhibition is an effective treatment for nausea, it has not been previously considered as an anti‐fibrotic therapy. Although there are extensive medical records of individuals who have used SP antagonists, our analysis of human registry data revealed that patients receiving these antagonists and arthroplasty are exceedingly rare, thus precluding a clinical evaluation of their potential effects in the context of arthrofibrosis. Therefore, we pursued in vivo studies to assess the effect of SP inhibition early after injury on pro‐fibrotic gene expression and contractures in an animal model of post‐traumatic joint stiffening. Skeletally mature rabbits (n = 24) underwent surgically induced severe joint contracture, while injected with either fosaprepitant (a selective SP antagonist) or saline (control) early after surgery (3, 6, 12, and 24 h). Biomechanical testing revealed that differences in mean contracture angles between the groups were not statistically significant (P = 0.27), suggesting that the drug neither mitigates nor exacerbates joint contracture. However, microarray gene expression analysis revealed that mRNA levels for proteins related to cell signaling, pro‐angiogenic, pro‐inflammatory, and collagen matrix production were significantly different between control and fosaprepitant treated rabbits (P < 0.05). Hence, our study demonstrates that inhibition of SP alters expression of pro‐fibrotic genes in vivo. This finding will motivate future studies to optimize interventions that target SP to reduce the formation of post‐traumatic joint contractures.

ABSTRACTIntroduction: Rotator cuff (RC) tears result in muscle atrophy and fat infiltration within the RC muscles. An estimation of muscle quality and deformation, or extensibility, is useful in selecting the most appropriate surgical procedure. We determined if noninvasive quantitative assessment of intramuscular fat using MRI could be used to predict extensibility of the supraspinatus muscle. Methods: Seventeen cadaveric shoulders were imaged to assess intramuscular fat infiltration. Extensibility and histological evaluations were then performed. Results: Quantitative fat infiltration positively correlated with histological findings and presented a positive correlation with muscle extensibility (r = 0.69; P = 0.002). Extensibility was not significantly different between shoulders graded with a higher fat content versus those with low fat when implementing qualitative methods. Discussion: A noninvasive prediction of whole‐muscle extensibility may directly guide pre‐operative planning to determine if the torn edge could efficiently cover the original footprint while aiding in postoperative evaluation of RC repair. Muscle Nerve 57: 129–135, 2018

AimThe aim of this study was to compare passive muscle stiffness in children with cerebral palsy (CP) and children with typical development using a novel ultrasound technique: ultrasound shear wave elastography (SWE).MethodWe conducted a prospective study of 13 children with CP (six females and seven males, median age 5y 1mo [interquartile range 4y 4mo–7y 8mo]) and 13 children with typical development (six females and seven males, median age 5y 3mo [interquartile range 4y 4mo–9y 4mo]). Demographic information and physical exam measurements were obtained in addition to shear modulus measurements (passive muscle stiffness) of the lateral gastrocnemius muscle at 20° plantar flexion, 10° plantar flexion, and 0° plantar flexion using SWE.ResultsChildren with CP had significantly greater shear modulus measurements at all three foot positions (p<0.050). When the shear modulus values were normalized to the baseline value for each child, there was no significant difference between the two groups.InterpretationPassive muscle stiffness, measured without the influence of spasticity, is greater in children with CP than in children with typical development when a muscle is at slack and at stretch. When shear modulus was normalized, the results indicate that muscle in children in both groups responds similarly to passive stretch. Further work includes evaluating effect of botulinum toxin on passive muscle properties.

ABSTRACTThe purpose of the study was to test a novel treatment that carbodiimide‐derivatized‐hyaluronic acid‐lubricin (cd‐HA‐lubricin) combined cell‐based therapy in an immobilized flexor tendon repair in a canine model. Seventy‐eight flexor tendons from 39 dogs were transected. One tendon was treated with cd‐HA‐lubricin plus an interpositional graft of 8 × 105 BMSCs and GDF‐5. The other tendon was repaired without treatment. After 21 day of immobilization, 19 dogs were sacrificed; the remaining 20 dogs underwent a 21‐day rehabilitation protocol before euthanasia. The work of flexion, tendon gliding resistance, and adhesion score in treated tendons were significantly less than the untreated tendons (p < 0.05). The failure strength of the untreated tendons was higher than the treated tendons at 21 and 42 days (p < 0.05). However, there is no significant difference in stiffness between two groups at day 42. Histologic analysis of treated tendons showed a smooth surface and viable transplanted cells 42 days after the repair, whereas untreated tendons showed severe adhesion formation around the repair site. The combination of lubricant and cell treatment resulted in significantly improved digit function, reduced adhesion formation. This novel treatment can address the unmet needs of patients who are unable to commence an early mobilization protocol after flexor tendon repair. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:154–160, 2016.

ABSTRACTAchilles tendon is one of the most commonly injured tendons. Mechanical force is regarded as a major causative factor. However, the biomechanics of Achilles tendon and mechanical mechanism of the injuries are unclear. Lubricin expresses at regions exposed to sliding motion and shear force in a number of tissues. This study investigated the distribution and concentration of lubricin in human Achilles tendons for better understanding the biomechanics of Achilles tendon. Achilles tendons were harvested from nine cadavers. Lubricin was extracted from various locations proximal to the calcaneal insertion and quantified with ELISA. The distribution of lubricin was investigated with immunohistochemistry. Lubricin was mainly identified at the interfaces of tendon fascicles, especially in the mid‐portion of the tendon. The concentration of lubricin in Achilles tendons varied by individual and the distance from its calcaneal insertion. The distal portion of the tendon had a higher concentration of lubricin than the proximal regions of the tendon. This study suggests the presence of intratendinous sliding motion of fascicles and shear force at interfaces of fascicles in human Achilles tendon. Shear force could be an important mechanical factor for the development of Achilles tendinopathy and rupture. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:932–937, 2015.

ABSTRACTThe purpose of this study was to investigate the biomechanical properties of modified repair techniques for flexor tendon reconstruction and the effects of surface modification using carbodiimide‐derivatized synovial fluid plus gelatin (cd‐SF‐G), compared to the traditional repair techniques. The second and fifth digits from 16 canine forepaws were randomly divided into 4 groups: (1) traditional graft repairs (TGR group) including distal Bunnell repair and proximal Pulvertaft weave repair; (2) modified graft repairs (MGR group) including distal graft bony attachment repair and proximal step‐cut repair; (3) group TGR coated with cd‐SF‐G (TGR‐C group); and (4) group MGR coated with cd‐SF‐G (MGR‐C group). Digit normalized work of flexion (nWOF), ultimate failure strength, and stiffness were measured. The nWOF in MGR group was significantly less than TGR group (p < 0.05). The nWOF in groups treated with cd‐SF‐G was significantly less than their untreated counterparts (p < 0.05). Ultimate load to failure of the MGR‐C group was significantly greater than the TGR‐C group (p < 0.05), but no significant difference in stiffness was found between these two groups. The modified techniques cannot only improve tendon gliding abilities but can also improve breaking strength. Additionally, surface modification with cd‐SF‐G significantly decreased the work of flexion. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:731–737, 2015.

ABSTRACTThe subsynovial connective tissue (SSCT) is a viscoelastic structure connecting the median nerve (MN) and the flexor tendons in the carpal tunnel. Increased strain rates increases stiffness in viscoelastic tissues, and thereby its capacity to transfer shear load. Therefore, tendon excursion velocity may impact the MN displacement. In carpal tunnel syndrome (CTS) the SSCT is fibrotic and may be ruptured, and this may affect MN motion. In this study, ultrasonography was performed on 14 wrists of healthy controls and 25 wrists of CTS patients during controlled finger motions performed at three different velocities. Longitudinal MN and tendon excursion were assessed using a custom speckle tracking algorithm and compared across the three different velocities. CTS patients exhibited significantly less MN motion than controls (p ≤ 0.002). While in general, MN displacement increased with increasing tendon excursion velocity (p ≤ 0.031). These findings are consistent with current knowledge of SSCT mechanics in CTS, in which in some patients the fibrotic SSCT appears to have ruptured from the tendon surface. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:483–487, 2015.