Friday, April 29, 2016 From PTJ: Electrodiagnostic Testing Sheds Light on 'Bioscaffolding' Procedure for VML Researchers believe electrodiagnostic testing may be a useful way to predict just what kind of improvement to expect from an experimental approach that uses material from pig bladders and intestines to grow new muscle in patients with severe muscle loss. According to an April 2016 article in Physical Therapy (PTJ), APTA's science journal, presurgical electrodiagnostic testing may help predict increase in muscle strength after a process known as extracellular matrix (ECM) implantation, a procedure that uses pig tissue cells to act as "scaffolding" that draws a patient's own stem cells to the site of volumetric muscle loss (VML). The procedure has been successful in regrowing tissue in preclinical testing, but research has been lacking on patient functional outcomes. In the longitudinal case series, authors wanted to find out how the surgery would change preoperative and postoperative electromyography (EMG) and nerve conduction study (NCS) results, as well as whether these tools could identify the best candidates for ECM implantation. They hypothesized that both electrophysiologic activity and muscle strength would improve. Researchers implanted 8 patients with severe muscle loss due to trauma. Three of the patients had VML in the anterior tibial compartment, 4 in the quadriceps compartment, and 1 in the biceps brachii. The average percentage of muscle loss was 66.1%. All participants completed a preoperative physical therapy program until they reached what authors describe as "a plateau in strength and function." One day prior to surgery, researchers performed needle EMG and NCS testing, and a physical therapist (PT) measured muscle strength using a handheld dynamometer. EMG testing measured muscle recruitment and abnormal spontaneous activity; the latter can indicate instability of muscle fibers. Within 48 hours after surgery, each patient began a 6-month physical therapy regimen, after which the same testing was performed. Four had significant improvement in strength (20% or more), 2 had minor improvement, and 2 experienced no increase in strength. Authors concluded that electrodiagnostic testing could be beneficial in predicting suboptimal outcomes. Five of the participants had improvements in either NCS or EMG results while also showing clinical improvements in muscle strength. Two participants showed no EMG activity or strength at baseline; they had no improvement in strength. "These findings suggest that muscles judged to have no electrical activity at baseline are unlikely to display improved strength following ECM implantation," authors note. The researchers attribute the wide variability in response to ECM implantation in part to degree and type of initial injury causing the muscle loss. For example, 1 participant showed increased compound muscle action potential (CMAP) amplitude of 80% but no increase in strength. Another had a 33.3% improvement in strength but no electrophysiologic improvement. Two others showed a "dramatic increase" in strength but decreased CMAP amplitude. Authors suggest the possibility "that the increased strength was a result of a restoration of mechanical integrity, rather than electrical conductance, of the muscle." However, the improvement in CMAP amplitude in 4 of the participants "is encouraging," they write, because it indicates an increased number of muscle fibers after implantation. These findings, the researchers contend, could not only inform surgical decisions in the future but also help PTs in designing regenerative rehabilitation protocols. Research-related stories featured in PT in Motion News are intended to highlight a topic of interest only and do not constitute an endorsement by APTA. For synthesized research and evidence-based practice information, visit the association's PTNow website.