This paper discusses the indications for spinal ultrasound, including its advantages and disadvantages compared with spinal MRI. The features and ultrasound findings both in normal infants and in those with spinal dysraphism are reviewed.

Adult skeletal muscle can regenerate effectively after mild physical or chemical insult. Muscle trauma or disease can overwhelm this innate capacity for regeneration and result in heightened inflammation and fibrotic tissue deposition resulting in loss of structure and function. Recent studies have focused on biomaterial and stem cell‐based therapies to promote skeletal muscle regeneration following injury and disease. Many stem cell populations besides satellite cells are implicated in muscle regeneration. These stem cells include but are not limited to mesenchymal stem cells, adipose‐derived stem cells, hematopoietic stem cells, pericytes, fibroadipogenic progenitors, side population cells, and CD133+ stem cells. However, several challenges associated with their isolation, availability, delivery, survival, engraftment, and differentiation have been reported in recent studies. While acellular scaffolds offer a relatively safe and potentially off‐the‐shelf solution to cell‐based therapies, they are often unable to stimulate host cell migration and activity to a level that would result in clinically meaningful regeneration of traumatized muscle. Combining stem cells and biomaterials may offer a viable therapeutic strategy that may overcome the limitations associated with these therapies when they are used in isolation. In this article, we review the stem cell populations that can stimulate muscle regeneration in vitro and in vivo. We also discuss the regenerative potential of combination therapies that utilize both stem cell and biomaterials for the treatment of skeletal muscle injury and disease. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1246–1262, 2019.

Volumetric muscle loss (VML) is a loss of over ∼10% of muscle mass that results in functional impairment. Although skeletal muscle possesses the ability to repair and regenerate itself following minor injuries, VML injuries are irrecoverable. Currently, there are no successful clinical therapies for the treatment of VML. Previous studies have treated VML defects with decellularized extracellular matrix (D-ECM) scaffolds derived from either pig urinary bladder or small intestinal submucosa. These therapies were unsuccessful due to the poor mechanical stability of D-ECM leading to quick degradation in vivo. To circumvent these issues, in this manuscript aligned nanofibers of D-ECM were created using electrospinning that mimicked native muscle architecture and provided topographical cues to primary satellite cells. Additionally, combining D-ECM with polycaprolactone (PCL) improved the tensile mechanical properties of the electrospun scaffold. In vitro testing shows that the electrospun scaffold with aligned nanofibers of PCL and D-ECM supports satellite cell growth, myogenic protein expression, and myokine production.

Volumetric muscle loss (VML) is a traumatic loss of muscle tissue that results in chronic functional impairment. When injured, skeletal muscle is capable of small‐scale repair; however, regenerative capacities are lost with VML due to a critical loss stem cells and extracellular matrix (ECM). Consequences of VML include either long‐term disability or delayed amputations of the affected limb. While the prevalence of VML is substantial, currently a successful clinical therapy has not been identified. In a previous study, an electrospun composed of polycaprolactone (PCL) and decellularized‐ECM (D‐ECM) supported satellite cell‐mediated myogenic activity in vitro. In this study, we investigate the extent to which this electrospun scaffold can support functional muscle regeneration in a murine model of VML. Experimental groups included no treatment, pure PCL treated, and PCL:D‐ECM (50:50 blend) treated VML defects. The PCL:D‐ECM scaffold treated VML muscles supported increased activity of anti‐inflammatory M2 macrophages (arginase+) at Day 28, compared to other experimental groups. Increased myofiber (MHC+) regeneration was observed histologically at both Days 7 and 28 post‐trauma in blend scaffold treated group compared to PCL treated and untreated groups. However, improvements in muscle weights and force production were not observed. Future studies would evaluate muscle function at longer time‐points post‐VML injury to allow sufficient time for reinnervation of regenerated muscle fibers.