Shin, Alexander Y.

Abstract Background Placement and spacing of skin incisions are important for maintaining soft tissue perfusion and viability, particularly in the setting of local trauma. Question/Purpose The aim of this article is to determine if multiple skin incisions in the surgical management of distal radius fractures result in an increased risk of postoperative wound complications, particularly in the setting of high-energy mechanisms of injury with substantial initial displacement and associated soft-tissue insult that require multiple incisions for distal radius reconstruction. Patients and Methods A multicenter, retrospective chart review was performed for all adult patients who underwent open reduction, internal fixation of a closed distal radius fracture with multiple (≥2) hand, and wrist incisions with minimum follow-up of 6 weeks. Primary outcome measures included wound healing complications such as partial or complete skin necrosis, dehiscence, delayed healing, and superficial or deep infections. Results For 118 wrists, a total of 305 incisions were utilized, averaging 2.6 incisions per patient (range: 2–6) with the flexor carpi radialis and dorsal distal radius approaches occurring in 86 and 78% of cases, respectively. One patient was identified as having a pyogenic granuloma along an incision. However, two patients were identified as having wound concerns, including fracture blisters (n = 1) and wound margin epidermolysis (n = 1) along the incision. There were no cases of skin bridge necrosis, delayed healing, wound dehiscence, or infection. Conclusions There is no increased risk of wound healing complications with the use of multiple skin incisions (≥2) in the surgical management of distal radius fractures, afforded by the abundant and robust angiosomes around the wrist. Surgeons should have the confidence to utilize the necessary number of skin incisions to effectively reconstruct distal radius fractures.

A retrospective review of hospital employees at a single employer institution who underwent ultrasound guided thread carpal tunnel release (TCTR) or open carpal tunnel release (OCTR) between January 2018 and August 2020 was performed to ascertain differences in return-to-work status. Patient age, sex, occupation, handedness, severity of carpal tunnel syndrome, prior treatments and surgical outcomes were reviewed. A total of 18 patients underwent TCTR and 17 patients underwent OCTR. The TCTR group averaged 12 days to return to work without restrictions, as opposed to 33 days for the OCTR group. Resolution of symptoms was afforded in all patients without any complications regardless of surgical technique. While both TCTR and OCTR were effective, our data indicates that TCTR resulted in a shorter return to work. Level of evidence: III

An expert opinion study was designed to query five countries and six brachial plexus surgeons regarding the demographics, mechanisms of injury, evaluation, timing of surgery, reconstructive strategies and controversies in adult traumatic pan brachial plexus injuries. Variations in assessing outcomes, management of neuropathic pain and future considerations were elucidated. Clear differences in regional demographics, mechanisms of injury, patient evaluation and treatment strategies were identified. The role of phrenic nerve and contralateral C7 transfer, acute use of free functioning muscle transfers, root reimplantation and amputation/myoelectric prosthetic fitting were regional/surgeon dependent. Comparison of outcomes across regions requires an understanding of the regional nuances of patient demographics, injury mechanisms, preferred reconstructive strategies and how outcomes are measured. Future studies are required to allow accurate regional comparisons.

AbstractBackgroundThe aim of this study was to investigate the combined effect of mesenchymal stem cells (MSC) and local delivery of tacrolimus (FK506) on nerve regeneration when applied to nerve autografts and decellularized allografts.MethodsA three‐dimensional in vitro compartmented cell culture system consisting of a neonatal dorsal root ganglion adjacent to a nerve graft was used to evaluate the regenerating neurites into the peripheral nerve scaffold. Nerve autografts and allografts were treated with (i) undifferentiated MSCs, (ii) FK506 (100 ng/mL) or (iii) both (N = 9/group). After 48 hours, neurite extension was measured to quantify nerve regeneration and stem cell viability was evaluated.ResultsStem cell viability was confirmed in all MSC‐treated grafts. Neurite extension was superior in autografts treated with FK506, and MSCs and FK506 combined (p < 0.001 and p = 0.0001, respectively), and autografts treated with MSCs (p = 0.12) were comparable to untreated autografts. In allografts, FK506 treatment and combined treatment were superior to controls (p < 0.001 and p = 0.0001, respectively), and treatment with MSCs (p = 0.09) was comparable to controls. All autograft groups were superior compared to their respective allograft treatment group (p < 0.05) in neurite extension.ConclusionsAlone, either MSC or FK506 treatment improved neurite outgrowth, and combined they further enhanced neurite extension in both autografts and allografts.

ABSTRACT We measured the passive mechanical properties of intact, living human gracilis muscles (n=11 individuals, 10 male and 1 female, age: 33±12 years, mass: 89±23 kg, height: 177±8 cm). Measurements were performed in patients undergoing surgery for free-functioning myocutaneous tissue transfer of the gracilis muscle to restore elbow flexion after brachial plexus injury. Whole-muscle force of the gracilis tendon was measured in four joint configurations (JC1–JC4) with a buckle force transducer placed at the distal tendon. Sarcomere length was also measured by biopsy from the proximal gracilis muscle. After the muscle was removed, a three-dimensional volumetric reconstruction of the muscle was created via photogrammetry. Muscle length from JC1 to JC4 increased by 3.3±1.0, 7.7±1.2, 10.5±1.3 and 13.4±1.2 cm, respectively, corresponding to 15%, 34%, 46% and 59% muscle fiber strain, respectively. Muscle volume and an average optimal fiber length of 23.1±0.7 cm yielded an average muscle physiological cross-sectional area of 6.8±0.7 cm2 which is approximately 3 times that measured previously from cadaveric specimens. Absolute passive tension increased from 0.90±0.21 N in JC1 to 16.50±2.64 N in JC4. As expected, sarcomere length also increased from 3.24±0.08 µm at JC1 to 3.63±0.07 µm at JC4, which are on the descending limb of the human sarcomere length–tension curve. Peak passive muscle stress was 27.8±5.5 kPa in JC4 and muscle modulus ranged from 44.8 MPa in JC1 to 125.7 MPa in JC4. Comparison with other mammalian species indicates that human muscle passive mechanical properties are more similar to rodent muscle than to rabbit muscle. These data provide direct measurements of whole-human muscle passive mechanical properties that can be used in modeling studies and for understanding comparative passive mechanical properties among mammalian muscles.

Purpose: Application of mesenchymal stem cells (MSCs) or tacrolimus (FK506), an FDA approved immunosuppressant, to nerve grafts has been a topic of interest to enhance peripheral nerve regeneration. The aim of this study was to investigate the combined effect of MSCs and local delivery of FK506 on nerve regeneration when applied to nerve autografts and decellularized nerve allografts. Methods: A three-dimensional (3D) in vitro compartmented cell culture system, validated by Tajdaran et al (2019), consisted of rat neonatal dorsal root ganglion (DRG) adjacent to rat nerve autograft or decellularized allograft. This model was used to evaluate regenerating neurites from the DRG into the peripheral nerve scaffold. Nerve autografts and decellularized allografts were augmented with (i) dynamic undifferentiated MSC seeding, (ii) local application of FK506 (100 ng/mL) or (iii) both (N=9/group). Local application was ensured by isolating the central system (i.e. DRG side) from the peripheral system (i.e. nerve graft side), where treatment was applied. After 48-hours of incubation, DRG-nerve graft constructs were collected, fixed, sectioned and stained against neurofilament-160 to measure neurite extension. CD90 staining was used to confirm stem cell characterization. Results: All grafts treated with MSCs confirmed CD90 expression. Compared to untreated autografts, neurite extension in autografts treated with FK506 and autografts treated with MSCs and FK506 combined were found superior (P<0.001 and P=0.0001, respectively), and comparable to autografts treated with MSCs (P=0.12). Compared to untreated allografts, allografts treated with FK506, and allografts treated with MSCs and FK506 were found superior (P<0.001 and P=0.0001, respectively), and allografts treated with MSCs were found comparable (P=0.09). All autograft groups were found superior compared to their respective allograft treatment group (P<0.05). Solely allografts receiving combined treatment were found superior to untreated autografts (P<0.05). Conclusion: MSCs or FK506 treatment improved neurite outgrowth and when combined, this resulted in significant synergistic neurite extension in both autografts and allografts in comparable patterns. Schematic overview of 3D compartmented cell culture system for isolated evaluation of treatment with MSCs and local FK506 in vitro. A 3.5 mm autograft or allograft with or without undifferentiated MSC seeding is attached to a DRG. DRG-nerve graft constructs are placed through a silicone isolator in the middle of a 24-wells plate to isolate the DRG from the nerve graft. FK506 containing media was added to the nerve graft side.

Background: Surgical angiogenesis applied to nerve grafts has been suggested to enhance nerve regeneration after nerve injury. The authors hypothesized that surgical angiogenesis to decellularized nerve allografts would improve functional recovery in a rat sciatic nerve defect model. Methods: Sixty Lewis rats were divided in three groups of 20 animals each. Unilateral sciatic nerve defects were repaired with (1) autografts, (2) decellularized allografts, and (3) decellularized allografts wrapped with a superficial inferior epigastric artery fascial flap to add surgical angiogenesis. Twelve and 16 weeks after surgery, nerve regeneration was assessed using functional, electrophysiologic, histologic, and immunofluorescence analyses. Ultrasonography was used during the survival period to noninvasively evaluate muscle atrophy and reinnervation by measuring cross-sectional muscle area. Results: Surgical angiogenesis of allografts demonstrated significantly improved isometric tetanic force recovery at 12 weeks, compared to allograft alone, which normalized between groups at 16 weeks. Cross-sectional muscle areas showed no differences between groups. Electrophysiology showed superiority of autografts at both time points. No differences were found in histologic analysis, besides a significantly inferior N ratio in allografts at 12 weeks. Immunofluorescent expression of CD34, indicating vascularity, was significantly enhanced in the superficial inferior epigastric artery fascial group compared to allografts at 12 weeks, with highest expression at 16 weeks compared to all groups. Conclusion: Surgical angiogenesis with an adipofascial flap to the nerve allograft increases vascularity in the nerve graft, with subsequent improvement of early muscle force recovery, comparable to autografts.

Background: Mesenchymal stem cells have the potential to produce neurotrophic growth factors and establish a supportive microenvironment for neural regeneration. The purpose of this study was to determine the effect of undifferentiated and differentiated mesenchymal stem cells dynamically seeded onto decellularized nerve allografts on functional outcomes when used in peripheral nerve repair. Methods: In 80 Lewis rats, a 10-mm sciatic nerve defect was reconstructed with (1) autograft, (2) decellularized allograft, (3) decellularized allograft seeded with undifferentiated mesenchymal stem cells, or (4) decellularized allograft seeded with mesenchymal stem cells differentiated into Schwann cell–like cells. Nerve regeneration was evaluated over time by cross-sectional tibial muscle ultrasound measurements, and at 12 and 16 weeks by isometric tetanic force measurements, compound muscle action potentials, muscle mass, histology, and immunofluorescence analyses. Results: At 12 weeks, undifferentiated mesenchymal stem cells significantly improved isometric tetanic force measurement and compound muscle action potential outcomes compared to decellularized allograft alone, whereas differentiated mesenchymal stem cells significantly improved compound muscle action potential outcomes. The autografts outperformed both stem cell groups histologically at 12 weeks. At 16 weeks, functional outcomes normalized between groups. At both time points, the effect of undifferentiated versus differentiated mesenchymal stem cells was not significantly different. Conclusions: Undifferentiated and differentiated mesenchymal stem cells significantly improved functional outcomes of decellularized allografts at 12 weeks and were similar to autograft results in the majority of measurements. At 16 weeks, outcomes normalized as expected. Although differences between both cell types were not statistically significant, undifferentiated mesenchymal stem cells improved functional outcomes of decellularized nerve allografts to a greater extent and had practical benefits for clinical translation by limiting preparation time and costs.

» The incidence of brachial plexus birth injury (BPBI) in the United States is declining and now occurs in <1 per 1,000 births. » The gold standard for predicting the need for early intervention remains serial examination. » Early treatment of BPBI with reconstructive surgery requires the ability to perform both interposition nerve grafting and nerve transfers. » Given the heterogeneity of lesions, the evidence is largely limited to retrospective comparative studies and case series.

AbstractThe application of scaffold‐based stem cell transplantation to enhance peripheral nerve regeneration has great potential. Recently, the neuroregenerative potential of tacrolimus (a U.S. Food and Drug Administration‐approved immunosuppressant) has been explored. In this study, a fibrin gel‐based drug delivery system for sustained and localized tacrolimus release was combined with rat adipose‐derived mesenchymal stem cells (MSC) to investigate cell viability in vitro. Tacrolimus was encapsulated in poly(lactic‐co‐glycolic) acid (PLGA) microspheres and suspended in fibrin hydrogel, using concentrations of 0.01 and 100 ng/ml. Drug release over time was measured. MSCs were cultured in drug‐released media collected at various days to mimic systemic exposure. MSCs were combined with (i) hydrogel only, (ii) empty PLGA microspheres in the hydrogel, (iii) 0.01, and (iv) 100 ng/ml of tacrolimus PLGA microspheres in the hydrogel. Stem cell presence and viability were evaluated. A sustained release of 100 ng/ml tacrolimus microspheres was observed for up to 35 days. Stem cell presence was confirmed and cell viability was observed up to 7 days, with no significant differences between groups. This study suggests that combined delivery of 100 ng/ml tacrolimus and MSCs in fibrin hydrogel does not result in cytotoxic effects and could be used to enhance peripheral nerve regeneration.