Ultrasonographic evaluation of pennation angle in canine tibialis cranialis muscle in South Korea: an observational study

Abstract

In human, ultrasonography is used to measure the pennation angle in various muscles to identify muscle functions such as force production, and to study alterations of the pennation angle during muscle contraction, hypertrophy, and atrophy. However, assessments of the pennation angle have not yet been conducted in dogs. This study aims to assess the normal pennation angle of the tibialis cranialis muscle in dogs using ultrasound and to detect changes in this angle in dogs with muscular atrophy. Sixty-eight healthy dogs were examined to establish normal values, while 12 ataxic and 12 lame dogs with suspected hindlimb muscle atrophy were also included. The pennation angle was measured using ultrasound at the midpoint between the proximal end of the tibia and the malleolus, measuring the angle between the muscle bundle and the deep aponeurosis. To confirm the significance between the 5 breeds and to identify a difference between normal and atrophied muscles, statistical analysis was conducted. The study found no significant difference in pennation angle between breeds, with mean values (± standard deviation) of 4.97° (± 1.88) in neutral, 7.25° (± 2.68) in flexion, and 3.31° (± 1.33) in extension positions. Decrease of the pennation angle was identified in muscle atrophy and the flexion position was determined to be the most appropriate for pennation angle measurement of tibialis cranialis muscle. We recommend considering the pennation angle as a valuable indicator of muscle health in dogs, as it demonstrates significant potential for diagnosing and monitoring muscular conditions.