Describe the motion of the radial head during forearm pronation and supination using real-time ultrasound (US) imaging and determine the immediate effects of joint mobilization.

NUMBER OF SUBJECTS:

Forty-three subjects (32 female, 11 male; mean age, 29 years) with normal upper extremity (UE) range of motion.

The experimental UE was randomly selected and assessed in full elbow extension and 90° of elbow flexion. An adjustable height table was used to standardize positioning while the glenohumeral joint was stabilized. Subjects performed pronation and supination from neutral synchronized to a metronome at 60 bpm. Ultrasound (US) cineloops were recorded using a linear transducer oriented in the transverse plane over the radial head. Subjects were then randomized to receive an anterior or posterior radial head mobilization the rate of which was standardized at 2 Hz (120 bpm) with a metronome. Range of motion (ROM) measurements were taken pre-mobilization and post-mobilization.

RESULTS:

US showed the radial head rolled in an anteromedial direction during pronation and a posterolateral direction during supination. No translation was evident on US imaging in the transverse plane. Multivariate analysis revealed significant interaction effects (P = .02; power, 0.66) between direction of mobilization and ROM and elbow position and ROM (P = .03; power, 0.60). Post hoc ROM analysis revealed anterior mobilization significantly increased passive pronation (P = .040) while significantly decreasing active supination (P = .045) when assessed in full extension but significantly increased active supination (P = .037) when assessed in 90° of flexion. Posterior mobilization significantly increased ROM for active supination (P = .028) while significantly decreasing pronation (P = .044) in 90° of flexion.

Studies have reported translatory motion of the radius that contrasts with that opined by the convex-concave rule which therapists frequently use to determine the direction of joint mobilization. Our findings appear to support previous findings which question the application of the convex-concave rule, albeit we did not note any translation which may be a consequence of imaging in 1 plane and the magnitude of translation. Neumann has postulated that the rule is not flawed but misinterpreted as it was not intended for use to enhance joint motion but merely to describe physiological joint motion. The motion in pathological joints by definition may be different. Should we now reconsider application of the convex-concave rule as a means of improving joint motion or just mobilize

based on where the restrictions are?

CLINICAL RELEVANCE:

Elbow trauma often leads to deficits in PRUJ motion which can be difficult to treat given the complexity of the joints involved. This study is in agreement with others which have reported inconsistencies which are paradoxical to the convex-concave rule. Further study is required to determine if current mobilizations are efficacious and if the technique should be changed given recent findings.