The effect of adipose-derived stem cells on enthesis healing after repair of acute and chronic massive rotator cuff tears in rats.

BACKGROUND: Chronic massive rotator cuff tears heal poorly and often retear. This study investigated the effect of adipose-derived stem cells (ADSCs) and transforming growth factor-ß3 (TGF-ß3) delivered in 1 of 2 hydrogels (fibrin or gelatin methacrylate [GelMA]) on enthesis healing after repair of acute or chronic massive rotator cuff tears in rats. METHODS: Adult male Lewis rats underwent bilateral transection of the supraspinatus and infraspinatus tendons with intramuscular injection of botulinum toxin A (n = 48 rats). After 8 weeks, animals received 1 of 8 interventions (n = 12 shoulders/group): (1) no repair, (2) repair only, or repair augmented with (3) fibrin, (4) GelMA, (5) fibrin + ADSCs, (6) GelMA + ADSCs, (7) fibrin + ADSCs + TGF-ß3, or (8) GelMA + ADSCs + TGF-ß3. An equal number of animals underwent acute tendon transection and immediate application of 1 of 8 interventions. Enthesis healing was evaluated 4 weeks after the repair by microcomputed tomography, histology, and mechanical testing. RESULTS: Increased bone loss and reduced structural properties were seen in chronic compared with acute tears. Bone mineral density of the proximal humerus was higher in repairs of chronic tears augmented with fibrin + ADSCs and GelMA + ADSCs than in unrepaired chronic tears. Similar improvement was not seen in acute tears. No intervention enhanced histologic appearance or structural properties in acute or chronic tears. CONCLUSIONS: Surgical repair augmented with ADSCs may provide more benefit in chronic tears compared with acute tears, although there was no added benefit to supplementing ADSCs with TGF-ß3.

The use of Achilles tendon allograft for latissimus dorsi tendon reconstruction: a minimally invasive technique.

Treatment of subacute, retracted latissimus dorsi and teres major tendon ruptures in young overhead athletes is challenging. This case report describes management of a subacute retracted latissimus dorsi and teres major rupture with Achilles tendon allograft reconstruction using a two-incision minimally invasive technique. Level of evidence V.

Matrix metalloproteinase 3 deletion preserves denervated motor endplates after traumatic nerve injury.

OBJECTIVE: Traumatic peripheral nerve injuries often produce permanent functional deficits despite optimal surgical and medical management. One reason for the impaired target organ reinnervation is degradation of motor endplates during prolonged denervation. Here we investigate the effect of preserving agrin on the stability of denervated endplates. Because matrix metalloproteinase 3 (MMP3) is known to degrade agrin, we examined the changes in endplate structure following traumatic nerve injury in MMP3 knockout mice. METHODS: After creation of a critical size nerve defect to preclude reinnervation, we characterized receptor area, receptor density, and endplate morphology in denervated plantaris muscles in wild-type and MMP3 null mice. The level of agrin and muscle-specific kinase (MuSK) was assessed at denervated endplates. In addition, denervated muscles were subjected to ex vivo stimulation with acetylcholine. Finally, reinnervation potential was compared after long-term denervation. RESULTS: In wild-type mice, the endplates demonstrated time-dependent decreases in area and receptor density and conversion to an immature receptor phenotype. In striking contrast, all denervation-induced changes were attenuated in MMP3 null mice, with endplates retaining their differentiated form. Agrin and MuSK were preserved in endplates from denervated MMP3 null animals. Furthermore, denervated muscles from MMP3 null mice demonstrated greater endplate efficacy and reinnervation. INTERPRETATION: These results demonstrate a critical role for MMP3 in motor endplate remodeling, and reveal a potential target for therapeutic intervention to prevent motor endplate degradation following nerve injury.

From a Machine Saw to a Case of Mycobacterium Fortuitum Pyomyositis.

Pyomyositis is a bacterial infection occurring mainly in skeletal muscles. It is most commonly caused by Staphylococcus aureus with initial symptoms including muscle pain, swelling, and site tenderness. When available, the most accurate technique to determine the extent and the specific location of disease is the magnetic resonance imaging. Successful management includes early recognition, timely surgical debridement or drainage, and appropriate antibiotic therapy. This case report describes a case of Mycobacterium fortuitum pyomyositis in an elderly male associated with challenges of successful diagnosis.

Chronic nerve compression injury induces a phenotypic switch of neurons within the dorsal root ganglia.

Chronic nerve compression (CNC) injury initiates a series of pathological changes within the peripheral nerve at the site of injury. However, to date, little work has been performed to explore neuronal cell body responses to CNC injury. Here we show a preferential upregulation of growth-associated protein-43 (GAP-43) and enhanced Fluoro Ruby uptake by the small-diameter calcitonin gene-related protein (CGRP) and isolectin B4 (IB4)-positive neurons in the L4 and L5 ipsilateral dorsal root ganglion (DRG) 2 weeks and 1 month post injury. Furthermore, L4 and L5 DRGs ipsilateral to CNC injury also demonstrated a marked reduction in neurofilament 200 (NF-200) neurons and an increase in CGRP and IB4 neurons at early time points. All numbers normalized to values comparable to those of control when the DRG was evaluated 6 months post injury. Quantification of glial-derived neurotrophic factor (GDNF) protein revealed an upregulation in L4 and L5 DRG followed by a return to baseline values at later stages following injury. Upregulation of GDNF expression by Schwann cells was also readily apparent with both immunohistochemistry and Western blot analysis of 1 month compressed sciatic nerve specimens. Thus, CNC induces a phenotypic change in the DRG that appears to be temporally associated with increases in GDNF protein expression at and near the site of the compression injury in the nerve.

Gross, Arthroscopic, and Radiographic Anatomies of the Anterior Cruciate Ligament: Foundations for Anterior Cruciate Ligament Surgery.

The anterior cruciate ligament (ACL) is one of the more studied structures in the knee joint. It is not a tubular structure, but is much narrower in its midsubstance and broader at its ends, producing an hourglass shape. The ACL is composed of 2 functional bundles, the anteromedial and posterolateral bundles, that are named for their location of insertion on the anterior surface of the tibial plateau. Although the relative contribution in terms of total cross-sectional area of the ACL has been noted to be equal in regards to each bundle, dynamically these bundles demonstrate different properties for knee function.

The Morel-Lavallée Lesion: Diagnosis and Management.

The Morel-Lavallée lesion is a closed soft-tissue degloving injury commonly associated with high-energy trauma. The thigh, hip, and pelvic region are the most commonly affected locations. Timely identification and management of a Morel-Lavallée lesion is crucial because distracting injuries in the polytraumatized patient can result in a missed or delayed diagnosis. Bacterial colonization of these closed soft-tissue injuries has resulted in their association with high rates of perioperative infection. Recently, MRI has been used to characterize and classify these lesions. Definitive management is dictated by the size, location, and age of the injury and ranges from percutaneous drainage to open débridement and irrigation. Chronic lesions may lead to the development of pseudocysts and contour deformities of the extremity.

Kinematic outcomes following ACL reconstruction.

Anterior cruciate ligament (ACL) reconstruction aims to restore the translational and rotational motion to the knee joint that is lost after injury. However, despite technical advancements, clinical outcomes are less than ideal, particularly in return to previous activity level. A major issue is the inability to standardize treatment protocols due to variations in materials and approaches used to accomplish ACL reconstruction. These include surgical techniques such as the transtibial and anteromedial portal methods that are currently under use and the wide availability of graft types that will be used to reconstruct the ACL. In addition, concomitant soft tissue injuries to the menisci and capsule are frequently present after ACL injury and, if left unaddressed, can lead to persistent instability even after the ACL has been reconstructed. Advances in the field of biomechanics that help to objectively measure motion of the knee joint may provide more precise data than current subjective clinical measurements. These technologies include extra-articular motion capture systems that measure the movement of the tibia in relation to the femur. With data gathered from these devices, a threshold for satisfactory knee stability may be established in order to correctly identify a successful reconstruction following ACL injury.

Anatomical Individualized ACL Reconstruction.

The anterior cruciate ligament (ACL) is composed of two bundles, which work together to provide both antero-posterior and rotatory stability of the knee. Understanding the anatomy and function of the ACL plays a key role in management of patients with ACL injury. Anatomic ACL reconstruction aims to restore the function of the native ACL. Femoral and tibial tunnels should be placed in their anatomical location accounting for both the native ACL insertion site and bony landmarks. One main component of anatomical individualized ACL reconstruction is customizing the treatment according to each patient's individual characteristics, considering preoperative and intraoperative evaluation of the native ACL and knee bony anatomy. Anatomical individualized reconstruction surgery should also aim to restore the size of the native ACL insertion as well. Using this concept, while single bundle ACL reconstruction can restore the function of the ACL in some patients, double bundle reconstruction is indicated in others to achieve optimal outcome.

Macrophage recruitment follows the pattern of inducible nitric oxide synthase expression in a model for carpal tunnel syndrome.

Chronic nerve compression (CNC) induces a permeability change in neural vasculature. As recent evidence has shown that an alteration in reactive oxidative species (ROS) is related to neural degradation and regeneration, we evaluated whether inducible nitric oxide synthase (iNOS) plays a role in a rat model for CNC. Semi-quantitative analysis of iNOS mRNA and protein were performed with in situ hybridization and immunohistochemistry, respectively, at 3, 5, and 9 months post-operatively. At 3 months, iNOS mRNA was up-regulated in the perineurium of the proximal nerve with detectable changes in compressed and distal nerve segments. This expression continued to increase in the perineurium of 5-month proximal and compressed nerve segments with distal nerve demonstrating only a slight up-regulation of iNOS mRNA. At 9 months, iNOS mRNA expression was observed in both compressed and distal nerve. iNOS protein expression followed the same pattern of iNOS mRNA. As the perineurium is the blood-nerve barrier, the data suggests that these changes maybe mediated at the level of the perineurium. As macrophages release iNOS, we also evaluated whether macrophage recruitment followed the same pattern as iNOS expression. The results of ED-1 immunostaining for macrophages indicate that macrophages were localized to the outer one-third of cross sections during early time points. At later time points, macrophages were distributed diffusely throughout the nerve sections. Contrary to Wallerian degeneration, which elicits a relatively immediate signal for macrophage recruitment, CNC provides a slow, sustained stimulus for macrophage recruitment, which may be responsible for the up-regulation of iNOS gene expression.

Local down-regulation of myelin-associated glycoprotein permits axonal sprouting with chronic nerve compression injury.

Chronic nerve compression (CNC) injuries induce a robust Schwann cell proliferation in a distinct spatial and temporal pattern, which is accompanied by an increase in the number of small un-myelinated axons in the area of the injury. These findings suggest that this local proliferation of Schwann cells may induce local axonal sprouting. Here, we use quantitative electron microscopic techniques to define the nature of this sprouting response, and explore whether the local sprouting is in response to down-regulation of expression of myelin-associated glycoprotein (MAG) by proliferating Schwann cells. Axonal sprouting was observed without evidence of Wallerian degeneration in the outer region of CNC-injured nerves with a noticeable increase in Remak bundles within this region of injury. Immunolabeling of teased nerve fibers and Western blot analysis of nerves from CNC-injured animals revealed a local down-regulation of MAG protein within the zone of injury. Moreover, local delivery of purified MAG protein intraneurally at the time of CNC model creation abrogates the axonal sprouting response. These data demonstrate that CNC injury triggers axonal sprouting and suggests that a local down-regulation of MAG within the peripheral nerve secondary to CNC injury is the critical signal for the sprouting response.

Schwann cells upregulate vascular endothelial growth factor secondary to chronic nerve compression injury.

To better understand the pathogenesis of chronic nerve compression injuries, we investigated the possibility that Schwann cell production of vascular endothelial growth factor (VEGF) is responsible for the increased vascularity and Schwann cell proliferation associated with chronic nerve injury. In situ hybridization was used to evaluate VEGF mRNA production with immunohistochemistry to further localize the production of VEGF and its receptor proteins in an animal model of chronic nerve compression injury. VEGF mRNA and protein expression increased within Schwann cells as early as 2 weeks after compression and peaked by 1 month with a subsequent marked increase in the number of blood vessels. Thus, chronic nerve compression injury induces Schwann cells to increase VEGF production, which may be responsible for changes in neural vasculature secondary to chronic nerve compression injury. With a better understanding of these nerve injuries, more effective treatments may be developed to help patients with these impairments.

Chronic nerve compression induces local demyelination and remyelination in a rat model of carpal tunnel syndrome.

In a previous study, we demonstrated that chronic compression of rat sciatic nerve, a model of compressive neuropathies, triggered dramatic Schwann cell proliferation and concurrent apoptosis. Importantly, this Schwann cell response occurred before there are signs of overt axonal pathology, raising the question of whether there are alterations in axonal myelination in the areas of the nerve in which Schwann cell apoptosis and proliferation occur. Here, we use nerve teasing techniques and unbiased stereology to assess myelination in nerves after 1 and 8 months of compression. Evaluations of myelin thickness and axonal diameter (AD) using design-based, unbiased stereology revealed alterations in myelin structure that indicate remyelination, specifically a dramatic decrease in the average internodal length (IL) and an increase in the proportion of axons with thin myelin sheaths. The mean IL was reduced after 1 month of chronic nerve injury with no further decrease in IL at 8 months. There was limited change in average axonal diameter at both 1 and 8 months. Measures of myelin thickness revealed not only a greater than 6-fold increase in the number of axons with very thin (<5 microm thickness) myelin sheaths, but also a proportional decrease in the number of axons with the thick myelin sheaths characteristic of normal nerve. These results confirm that an early consequence of chronic nerve compression (CNC) is local demyelination and remyelination, which may be the primary cause of alterations in nerve function during the early period post-compression.