Measurement of pectoralis minor muscle length: validation and clinical application.

STUDY
DESIGN: Clinical measurement validity study.
OBJECTIVES: To validate the measurement of the pectoralis minor muscle length using palpable landmarks and to explore the accuracy of the measurement using a clinical instrument.
BACKGROUND: The pectoralis minor is believed to adaptively shorten. Individuals with a relatively short pectoralis minor demonstrate scapular kinematic alterations that have been associated with shoulder impingement. METHODS AND MEASURES: A 3-dimensional electromagnetic motion capture system was used to calculate the length of the pectoralis minor in 11 cadavers, using 2 measurement techniques. In addition, a measurement with the electromagnetic system using palpable landmarks was compared to a measurement with both a caliper and tape measure in vivo.
RESULTS: In cadavers, a measurement using palpable landmarks was determined to be a valid measure of the actual muscle length visualized and measured following dissection. There was a high intraclass correlation coefficient and a small root-mean-square error between these 2 measures. High intraclass correlation coefficients were also calculated in vivo when measurements with the clinical instruments were compared with the electromagnetic device measures.
CONCLUSION: A measurement using palpable landmarks for pectoralis minor length validly represents the muscle length in cadavers. A caliper or tape measure may be used clinically with high accuracy and may help clinicians determine the need for and the effectiveness of interventions for lengthening this muscle.