Shin, Alexander Y

Distal radius fractures are one of the most common upper extremity injuries seen by hand surgeons each year. Many of these fractures require reduction and surgical fixation because of displacement, comminution or inherent fracture instability. New hardware is designed and introduced each year to help surgeons manage these injuries. We report a case of a major complication from the use of the Dorsal Nail Plate hardware. The patient presented to our clinic with an extensor pollicis longus attrition rupture, which required tendon transfer for treatment. Intraoperatively, we also found ongoing extensor digitorum communis tendon attrition, myostatic atrophy of the extensor pollicus longus and ultimately a large bony defect following complex hardware removal. This case serves as a reminder to consider the potential complication profile of any hardware or technique you are considering using in your patients and to evaluate donor muscles and tendons when performing grafting or transfers.

AbstractBackgroundIn nerve allograft development, currently used subjective histological scoring systems to evaluate nerve structure in experimental studies are not uniform and have not been validated.The aim of this study was to describe and validate a simple, fast and inexpensive method to compare structural properties of nerve allografts on a histological level.Materials and methodsA total of 113 histological sections of rat (sciatic nerves) and human peripheral nerve segments (thoracodorsal and long thoracic nerve for motor and sural for sensory nerve) treated with various decellularization protocols were analyzed. Slides were stained with Hematoxylin & Eosin (H&E), Toluidine Blue and Laminin. A subjective scoring system using a 5‐point scale was used to score each nerve section by four independent researchers. For validation of this score both inter‐ and intra‐rater reliability were calculated using the Intraclass Correlation Coefficient (ICC).ResultsOverall, an excellent correlation between the different observers was found for the Toluidine Blue (ICC = 0.919, 95% CI: 0.891–0.941), H&E (ICC = 0.9, 95% CI: 0.865–0.927) and Laminin staining (ICC = 0.897, 95% CI: 0.860–0.926). Intra‐rater reliability was good for all three staining techniques (ICC >0.8).ConclusionThis study demonstrates the validity of this simple scoring system to evaluate nerve structure after different processing protocols. All three evaluated staining techniques can reliably be used for both rat and human nerve tissue. We believe this method is suitable to compare different processing techniques to create processed nerve allografts, especially when the average scores of multiple raters are used.

AbstractPurposeAdipose derived mesenchymal stem cells (MSCs) are hypothesized to supplement tissues with growth factors essential for regeneration and neovascularization. The purpose of this study was to determine the effect of MSCs with respect to neoangiogenesis when seeded onto a decellularized nerve allograft in a rat sciatic nerve defect model.MethodsAllograft nerves were harvested from Sprague–Dawley rats and decellularized. MSCs were obtained from Lewis rats. 10 mm sciatic nerve defects in Lewis rats were reconstructed with reversed autograft nerves, decellularized allografts, decellularized allografts seeded with undifferentiated MSC or decellularized allografts seeded with differentiated MSCs. At 16 weeks, the vascular surface area and volume were evaluated.ResultsThe vascular surface area in normal nerves (34.9 ± 5.7%), autografts (29.5 ± 8.7%), allografts seeded with differentiated (38.9 ± 7.0%) and undifferentiated MSCs (29.2 ± 3.4%) did not significantly differ from each other. Unseeded allografts (21.2 ± 6.2%) had a significantly lower vascular surface area percentage than normal nonoperated nerves (13.7%, p = .001) and allografts seeded with differentiated MSCs (17.8%, p = .001). Although the vascular surface area was significantly correlated to the vascular volume (r = .416; p = .008), no significant differences were found between groups concerning vascular volumes. The vascularization pattern in allografts seeded with MSCs consisted of an extensive nonaligned network of microvessels with a centripetal pattern, while the vessels in autografts and normal nerves were more longitudinally aligned with longitudinal inosculation patterns.ConclusionsNeoangiogenesis of decellularized allograft nerves was enhanced by stem cell seeding, in particular by differentiated MSCs. The pattern of vascularization was different between decellularized allograft nerves seeded with MSCs compared to autograft nerves.

Vascularization is an important factor in nerve graft survival and function. The specific molecular regulations and patterns of angiogenesis following peripheral nerve injury are in a broad complex of pathways. This review aims to summarize current knowledge on the role of vascularization in nerve regeneration, including the key regulation molecules, and mechanisms and patterns of revascularization after nerve injury. Angiogenesis, the maturation of pre-existing vessels into new areas, is stimulated through angiogenic factors such as vascular endothelial growth factor and precedes the repair of damaged nerves. Vascular endothelial growth factor administration to nerves has demonstrated to increase revascularization after injury in basic science research. In the clinical setting, vascularized nerve grafts could be used in the reconstruction of large segmental peripheral nerve injuries. Vascularized nerve grafts are postulated to accelerate revascularization and enhance nerve regeneration by providing an optimal nutritional environment, especially in scarred beds, and decrease fibroblast infiltration. This could improve functional recovery after nerve grafting, however, conclusive evidence of the superiority of vascularized nerve grafts is lacking in human studies. A well-designed randomized controlled trial comparing vascularized nerve grafts to non-vascularized nerve grafts involving patients with similar injuries, nerve graft repair and follow-up times is necessary to demonstrate the efficacy of vascularized nerve grafts. Due to technical challenges, composite transfer of a nerve graft along with its adipose tissue has been proposed to provide a healthy tissue bed. Basic science research has shown that a vascularized fascial flap containing adipose tissue and a vascular bundle improves revascularization through excreted angiogenic factors, provided by the stem cells in the adipose tissue as well as by the blood supply and environmental support. While it was previously believed that revascularization occurred from both nerve ends, recent studies propose that revascularization occurs primarily from the proximal nerve coaptation. Fascial flaps or vascularized nerve grafts have limited applicability and future directions could lead towards off-the-shelf alternatives to autografting, such as biodegradable nerve scaffolds which include capillary-like networks to enable vascularization and avoid graft necrosis and ischemia.

AbstractIntroductionNerve regeneration involves multiple processes, which enhance blood supply that can be promoted by growth factors. Currently, tools are lacking to visualize the vascularization patterns in transplanted nerves in vivo. The purpose of this study was to describe three‐dimensional visualization of the vascular system in the rat sciatic nerve and to quantify angiogenesis of nerve reconstruction.Materials and MethodsIn 12 Lewis rats (weighing 250–300 g), 10 mm sciatic nerve gaps were repaired with ipsilateral reversed autologous nerve grafts. At 12 and 16 weeks of sacrifice, Microfil® contrast compound was injected in the aorta. Nerve autografts (N = 12) and contralateral untreated nerves (N = 12) were harvested and cleared while preserving the vasculature. The amount of vascularization was measured by quantifying the vascular surface area using conventional photography (two‐dimensional) and the vascular volume was calculated with microcomputed tomography (three‐dimensional). For each measurement, a vessel/nerve area ratio was calculated and expressed in percentages (vessel%).ResultsThe vascular volume measured 3.53 ± 0.43% in autografts and 4.83 ± 0.45% vessels in controls at 12 weeks and 4.95 ± 0.44% and 6.19 ± 0.29% vessels at 16 weeks, respectively. The vascular surface area measured 25.04 ± 2.77% in autografts and 26.87 ± 2.13% vessels in controls at 12 weeks, and 28.11 ± 3.47% and 33.71 ± 2.60% vessels at 16 weeks, respectively. The correlation between both methods was statistically significant (p = .049).ConclusionsBoth methods are considered to successfully reflect the degree of vascularization. Application of this technique could be used to visualize and objectively quantify angiogenesis of the transplanted nerve graft. Moreover, this simple method is easily reproducible and could be extrapolated to any other desired target organ ex vivo in small animals to investigate the vascular network.

ABSTRACTVascularized composite allotransplantation of bone is a possible alternative treatment for large osseous defects but requires life‐long immunosuppression. Surgical induction of autogenous neo‐angiogenic circulation maintains transplant viability without this requirement, providing encouraging results in small animal models [1–3]. A preliminary feasibility study in a swine tibia model demonstrated similar findings [4, 5]. This study in swine tibial allotransplantation tests its applicability in a pre‐clinical large animal model. Previously, we have demonstrated bone vascularized composite allotransplantation (VCA) survival was not the result of induction of tolerance nor an incompetent immune system [1]. Fourteen tibia vascularized bone allotransplants were microsurgically transplanted orthotopically to reconstruct size‐matched tibial defects in Yucatan miniature swine. Two weeks of immunosuppression was used to maintain allotransplant pedicle patency during angiogenesis from a simultaneously implanted autogenous arteriovenous bundle. The implanted arteriovenous bundle was patent in group 1 and ligated in group 2 (a neo‐angiogenesis control). At twenty weeks, we quantified the neo‐angiogenesis and correlated it with transplant viability, bone remodeling, and gene expression. All patent arteriovenous bundles maintained patency throughout the survival period. Micro‐angiographic, osteocyte cell count and bone remodeling parameters were significantly higher than controls due to the formation of a neo‐angiogenic autogenous circulation. Analysis of gene expression found maintained osteoblastic and osteoclastic activity as well as a significant increase in expression of endothelial growth factor‐like 6 (EGFL‐6) in the patent arteriovenous bundle group. Vascularized composite allotransplants of swine tibia maintained viability and actively remodeled over 20 weeks when short‐term immunosuppression is combined with simultaneous autogenous neo‐angiogenesis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:288‐296, 2020

AbstractIntroductionThere is conflicting anatomic and innervation data regarding the rabbit brachial plexus injury model. This study aims to validate a rabbit brachial plexus injury model. We hypothesize the middle trunk (C6, C7) is the primary innervation of the biceps, and when cut and unrepaired, would demonstrate lack of recovery and when repaired would demonstrate evidence of recovery.Materials and MethodsTwenty two male New Zealand white rabbits (3–4 kg) underwent unilateral surgical division of the middle trunk. Five rabbits were randomly assigned to the “no‐repair” group while the remaining 17 rabbits underwent direct coaptation (“repair” group). Rabbits were followed for 12 weeks, with ultrasound measurement of biceps cross‐sectional area performed preoperatively, and at 4, 8, and 12 weeks postoperatively. At a euthanasia procedure, bilateral compound muscle action potential (CMAP) and isometric tetanic force (ITF) were measured. Bilateral biceps muscles were harvested and wet muscle weight was recorded. The operative side was expressed as a percentage of the non‐operated side, and differences between the no repair and repair rabbits were statistically compared.ResultsThe repair group demonstrated significantly higher CMA (23.3 vs. 0%, p < .05), ITF (25.6 vs. 0%, p < .05), and wet muscle weight (65.8 vs. 52.0%, p < .05) as compared to the unrepaired group. At 4 weeks postoperatively, ultrasound‐measured cross‐sectional area of the biceps demonstrated atrophy in both groups. At 12 weeks, the repair group had a significantly larger cross‐sectional area as compared to the no‐repair group (89.1 vs. 59.3%, p < .05).ConclusionsThis injury model demonstrated recovery with repair and lack of function without repair. Longer survival time is recommended for future investigations.

AbstractPurposeAnimal models can be helpful in evaluating new surgical strategies for brachial plexus reconstruction. While several groups have already used the rabbit brachial plexus to model injury, reports conflict in anatomic detail and do not identify a nerve‐muscle pair to measure motor function recovery after reconstruction. The purpose of the current study is to describe the innervations of the biceps and triceps muscles in rabbits, which are both amenable to study in brachial plexus injury models.Materials and MethodsThirteen rabbits weighing 2–2.5 kg were anesthetized. Six rabbits were sacrificed and dissected using loupe and microscope magnification to understand the overall morphology of the brachial plexus. Seven rabbits underwent electrophysiologic investigation. A bipolar nerve stimulator was used to systematically stimulate the roots, trunks and divisions, and nerve branches of the rabbit brachial plexus and compound muscle action potential was used to record muscle response. Nerve length and width measurements were not recorded.ResultsRoots contributing to the brachial plexus were C5, C6, C7, C8, and T1. In contrast to other anatomical studies, T2 did not contribute to the brachial plexus. The triceps was innervated by the radial nerve, which received contributions from C6 (1.6 mA), C7 (1.9 mA), C8, and T1 (12.2 mA).The biceps had dual innervation (proximally and distally). The proximal branch received contributions from C6 (3.5 mA) and C7 (5mA). The distal portion was innervated by a branch from the median nerve, which received innervation from C6, C7, C8, and T1.ConclusionsThe overall structure of rabbit brachial plexus is described and innervation of the biceps and triceps is described in detail. This anatomic investigation will form the basis of a future brachial plexus model of injury and repair.

* Rates of opioid use and abuse continue to rise in the United States, as do opioid-related deaths. Many patients who misuse opioids receive their first exposure in the perioperative setting. * Postoperative opioid use reduction in patients who have undergone an upper-extremity procedure can be difficult secondary to the often-painful nature of orthopaedic procedures. Postoperative pain can prevent timely discharge from hospitals and is a major cause for emergency medicine visits following outpatient upper-extremity surgical procedures. * Utilization of a multidisciplinary, multimodal, home-going continuous peripheral nerve block catheter protocol may be able to comfortably allow patients to recover in an outpatient setting after an upper-extremity surgical procedure, with a diminished opioid requirement.

Background: Outcomes following revision surgery for scaphoid nonunions with osteonecrosis are guarded. We hypothesized that use of free vascularized medial femoral condyle (MFC) bone grafts can lead to healing of the nonunion, increase vascularity of the proximal pole, and restore scaphoid architecture, resulting in acceptable functional outcomes. Methods: We performed a retrospective review of 49 patients who were treated with an MFC bone graft, between May 2005 and September 2016, after prior failure of operative treatment for scaphoid nonunion. The mean time from the injury to the revision surgery with the MFC bone graft was 24 months, and the mean time from the prior, failed surgery was 15 months. Thirty-six of the 49 patients had had a prior bone graft procedure and 6 patients had had 2 previous surgical procedures for the nonunion. The initial internal fixation of the scaphoid fracture was with a scaphoid screw in 43 patients. All patients had documented osteonecrosis of the proximal pole at the time of our surgery. Carpal indices, time to union, pain scores, functional outcomes, and complications were recorded. Results: Forty-one (84%) of the 49 previously operated on scaphoid nonunions healed at a mean of 16 weeks (range, 9 to 31 weeks) after the MFC bone-grafting as confirmed on computed tomography (CT). Radiographs demonstrated significant improvement in carpal alignment following the surgery with the MFC bone graft. Comparison between preoperative and postoperative values showed a trend toward improved grip strength and no important change in total wrist range of motion. Subsequent procedures were performed in 29 patients, 21 of whom had planned Kirschner wire removal. All 24 patients in whom scaphoid union had been achieved and who were available for follow-up were able to work or attend school full-time, and 88% were satisfied or very satisfied with their wrist function. Age, smoking status, body mass index, time to surgery, and preoperative radiographic findings were not found to be significant predictors of failure. Conclusions: MFC grafts increase vascularity and restore scaphoid architecture, promoting union in most patients with the combination of proximal pole osteonecrosis, carpal collapse, and failed prior scaphoid nonunion surgery. Level of Evidence: Therapeutic Level IV . See Instructions for Authors for a complete description of levels of evidence.