Ultrasound Confirmation of the Multiple Loci Hypothesis of the Myofascial Trigger Point and the Diagnostic Importance of Specificity in the Elicitation of the Local Twitch Response

Abstract

The literature has hypothesized that a trigger point (TrP) area consists of a hyperperfused contracture knot with smaller hypoperfused TrPs within the contracture knot. By contrast, the only published ultrasound image of a TrP has it labeled hypoechoic (i.e., hyperperfused) with no commentary regarding smaller speckles of hypoperfusion within. Furthermore, the lack of clarity in objective definition of the terms associated with the TrP (namely, the palpable “contracture knot” and smaller nonpalpable “trigger point”) has led to unnecessary communication difficulties between and among clinicians and researchers. In this case series of three muscles across two patients, by using high-definition musculoskeletal ultrasound imaging technology, we present what we believe to be the first reliable capture of palpable hypoechoic (e.g., hypoperfused) contracture knots (previously mislabeled as a hypoechoic TrP), and a visual support of the multiple loci hypothesis first proposed by Hong and Simons—the first reliable confirmation of the hyperechoic (i.e., hypoperfused) TrP within. Initially proposed by a histological study and supported by microdialysis study, this case series lends further support for the multiple loci hypothesis through visual confirmation of palpable hypoechoic contracture knots, with smaller hypoechoic TrPs “speckles” within.

Contracture Knots vs. Trigger Points. Comment on Ball et al. Ultrasound Confirmation of the Multiple Loci Hypothesis of the Myofascial Trigger Point and the Diagnostic Importance of Specificity in the Elicitation of the Local Twitch Response. Diagnostics 2022, 12, 321

“…Ball et al included ultrasound images of “TrP speckles” within contracture knots, based on the apparent assumption that contracture knots would present as larger hypoechoic (hyperperfused) areas and TrPs as small hyperechoic (hypoperfused) spots [ 1 ]. They maintained to have visualized TrP speckles within contracture knots [ 1 ], and postulated that a hypoechoic/hyperperfused area of approximately 1 cm × 1 cm in the vicinity of the palpable nodule represented a contracture with smaller hyperechoic/hypoperfused and nonpalpable TrP speckles of approximately 1 mm × 1 mm within each [ 1 ].…”

“…In our humble opinion, Ball et al did not provide any evidence of an alleged interchangeable use of the terms ‘contracture knot’ and ‘TrPs’ and the communication difficulties this may have caused. Ironically, the authors used the terms interchangeably themselves [ 1 ], e.g., when they referenced a 1999 diagnostic ultrasound study for detecting active TrPs [ 24 ]. Ball et al noted that the study failed to identify contracture knots, but the objective of the study was “to find an objective and reliable tool that could identify TrPs” without ever referring to contracture knots [ 24 ].…”

“…In a recent study published in Diagnostics , Ball et al [ 1 ] attempted to visualize trigger points and contracture knots (foci of segmental sarcomere contraction [ 2 ]) using high-definition sonography. While potentially the study could contribute to a better understanding of myofascial trigger points (TrPs), the paper’s conclusions are not supported by the data provided by the authors.…”

“…While potentially the study could contribute to a better understanding of myofascial trigger points (TrPs), the paper’s conclusions are not supported by the data provided by the authors. Furthermore, the authors claimed that a “lack of clarity in objective definition” of TrPs and contracture knots had resulted in “unnecessary communication difficulties between and among clinicians and researchers” [ 1 ], but they did not include any indication when and where this confusion might have occurred. They may have contributed further to the perceived lack of clarity by not only contradicting themselves, but also by inadvertently redefining the two terms.…”

Intramuscular Electrical Stimulation to Trigger Points: Insights into Mechanisms and Clinical Applications—A Scoping Review

“…A recent study found foci of segmentally contracted sarcomeres, i.e., contracture knots, in the vicinity of a taut band and TrP region [ 19 ]. These focal areas of sustained contraction are suggested to be hypo-perfused in relation to the surrounding area [ 20 ]. Because of reduced blood flow, Shah et al suggest that TrP pain is induced from elevated levels of bioactive substances and acidity accumulating in the TrP region [ 21 , 22 ].…”