THE EFFECT OF ELBOW POSITION ON THE RANGE OF SUPINATION AND PRONATION OF THE FOREARM

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1 THE EFFECT OF ELBOW POSITION ON THE RANGE OF SUPINATION AND PRONATION OF THE FOREARM H. SHAABAN, C. PEREIRA, R. WILLIAMS and V. C. LEES From the Wythenshawe Hospital, Wythenshawe, Manchester, UK A kinematic study was performed to examine the influence of elbow position on the range of supination and pronation of the forearm. The ranges of supination and pronation were measured in 5 volunteers (25 men and 25 women) using a custom-designed jig which constrained unwanted and confounding movements of the limb. Measurements were taken with the elbow in full extension, 451 flexion, 91 flexion and full flexion. The data showed a reciprocal relationship between the range of supination and the range of pronation of the forearm which depended on the degree of elbow flexion. As the elbow is flexed, the maximum angle of supination increases while the maximum angle of pronation decreases (po.1). The converse is true as the elbow is extended (po.1). The Journal of Hand Surgery (European Volume, 28) 33E: 1: 3 8 Keywords: supination, pronation, forearm, elbow Clinical observation that elbow position appears to alter the maximum angle of supination and pronation led us to formulate the hypothesis that the position of the elbow joint has a significant effect on the range of supination and pronation. The range of forearm rotation has been assessed in a number of studies, albeit with different objectives in mind (Table 1). There appears to be considerable variation in the reported normative data, with no particular explanation offered for the differences in the data sets. Furthermore, none of the studies to date have addressed the effect of position of the elbow joint on range of supination and pronation, despite the potential relevance to function and design of elbow joint prostheses. This kinematic study was performed to examine the influence of elbow position on the ranges of supination and pronation of the forearm. MATERIALS AND METHODS Volunteers Fifty healthy volunteers (25 men and 25 women) with a mean age of 31 (range 21 44) years were recruited. Seven of the volunteers (four men and three women) were left-handed (L-handed) and 43 (21 men and 22 women) were right-handed (R-handed). Ethical approval for the study was obtained from the Trust Local Research Ethics Committee. Volunteers below 18 and above 5 years of age were excluded. Exclusion criteria also included volunteers with a history of injury or pathology to the upper extremity. This paper was presented at the meeting of British Society for Surgery of the Hand, November 25. The Experimental Jig A custom-designed jig (Fig 1), designed to constrain the unclothed upper limb and eliminate unwanted movements, was used in the study. The upper arm was held within a gutter and a pneumatic cuff was used to eliminate rotatory movement that would, otherwise, occur at the shoulder. The distal forearm was secured by a plastic clamp incorporating a goniometer, to allow a true reading of forearm rotation and eliminate any confounding rotatory movements of the radiocarpal, carpal or carpometacarpal joints which could occur from a clamp attached more distally. The jig was fully adjustable to accommodate arms of different sizes. With the arm fitted into the jig, the volunteer could, freely, demonstrate active rotation of the forearm and flex and extend the elbow. Once any movement was made, the apparatus could be locked so that accurate readings could be taken from the goniometer. Passive movements were achieved using a calibrated force applied to the goniometer clamp through a twisting torque. Measurements A single observer (the first author) undertook the measurements on all volunteers. Reliability of intraobserver reproducibility was tested by repetition of measurements in the case of the first ten volunteers. An almost constant measurement was taken for each volunteer. Elbow flexion and extension were first measured out of the apparatus. The arm was then fitted to the jig, as described above, and measurements were undertaken to the right and left forearms of each volunteer. For each elbow position of extension, 451 flexion, 91 flexion and full flexion, the active and passive ranges of supination and pronation were determined as follows: the volunteer was asked to pass his/her hand through the goniometer 3

2 4 THE JOURNAL OF HAND SURGERY VOL. 33E No. 1 FEBRUARY 28 Table 1 Previous studies showing different degrees of rotation of forearm Study Result of the study Silver (1923) Pronation and supination are equal and measure 81 Cyriaz (1926) The difference between passive rotation of the hand and that of the DRUJ is 451 Glanville and Kreezer (1937) Passive rotation of the hand is 2221 Active rotation of the hand is 1921 Darcus and Salter (1953) Average rotation of the hand is 1831 Average rotation of the DRUJ is 1561 King et al. (1986) Average rotation of the hand is 261 (range ) Average rotation of the DRUJ is (range ) Askew et al. (1987) Supination is approximately 15% greater than pronation Weiler and Bogoch (1995) Active supination is 71 Active pronation is 631 Manson et al. (2) Supination is 771 Pronation is 611 Fig 1 The jig showing the arm position, goniometers and twisting torque. to grip the handle of the jig. The pneumatic cuff was inflated around the upper arm. The forearm was rotated into full active supination and the angle recorded. The passive range of supination was subsequently recorded by adding a calibrated force through the goniometer clamp to rotate the forearm further, just to the point of reported discomfort. Then, the forearm was rotated into pronation and the angles of full active and passive pronation were recorded similarly. The pneumatic cuff was then deflated. Statistics A three-factor repeated measures analysis of variance was used to analyse the data. The elbow position, position of forearm rotation and hand side (dominant/non-dominant) were considered as within-subject factors. A simple t-test was used to analyse the effect of gender and hand dominance (R-handed/L-handed) on the maximum range of supination and pronation. A p value p.5 was judged to denote statistical significance.

3 THE EFFECT OF ELBOW POSITION ON THE RANGE OF SUPINATION 5 RESULTS Fifty volunteers were chosen for the study. Both sexes were equally represented. The percentage of L-handed volunteers (14%) represented that of normal population. The study showed that the elbow position has a significant effect on the range of supination/pronation of the forearm. The principal findings of the study were as follows. As the elbow flexed, the range of supination increased significantly, while the range of pronation decreased significantly (po.1) (Table 2). Extension of the elbow joint had the opposite effect on the range of both supination and pronation (po.1) (Fig 2). This pattern was demonstrated for both the active and passive ranges of forearm rotation. The total range of forearm rotation (supination and pronation) was greatest in the mid-range of elbow flexion i.e. the most functional part of the range of motion of the elbow joint. Total range increased significantly between 1 and 451 (po.1), remained unchanged between 451 and 91 (p ¼ 1.) and decreased significantly between 91 and full flexion (po.1) (Table 3). In all positions of the elbow joint, the range of passive total rotation was significantly higher than that of active rotation (po.1) (Fig 3). There was an additional 111 each Table 2 Active supination and active pronation in different positions of the elbow joint of the right forearm Supination Pronation FE, full extension; 45F, 451 flexion; 9F, 91 flexion; FF, full flexion. Supination Pronation Fig 2 The relationship between active supination and active pronation in different positions of the elbow joint of the right forearm (FE, full extension; 45F, 451 flexion; 9F, 91 flexion; FF, full flexion). Table 3 Active and passive rotation in different positions of the elbow joint of the right forearm Active Passive FE, full extension; 45F, 451 flexion; 9F, 91 flexion; FF, full flexion Active Passive Fig 3 The relationship between active and passive rotation in different positions of the elbow joint (FE, full extension; 45F, 451 flexion; 9F, 91 flexion; FF, full flexion). Table 4 The degrees of active supination and pronation in the dominant and non-dominant forearms Supin-D Supin-N Pron-D Pron-N Supin-D, supination in the dominant forearm; Supin-N, supination in the non-dominant forearm; Pron-D, pronation in the dominant forearm; Pron-N, pronation in the non-dominant forearm. of passive supination and passive pronation over the active ranges. Interestingly, the range of supination in the nondominant arm was significantly higher than that of the dominant arm (po.1). In contrast, there was no significant difference in the range of pronation between the dominant and non-dominant forearms (p ¼.27) (Table 4) (Fig 4). The range of supination was significantly greater in the female group with the elbow flexed to 91 (p ¼.23) and with full (maximal) flexion (p ¼.24). Also, the range of pronation was significantly greater in the female group with the elbow fully extended (p ¼.39) (Table 5) (Fig 5).

4 6 THE JOURNAL OF HAND SURGERY VOL. 33E No. 1 FEBRUARY Supin-D Supin-N Pron-D Pron-N Supin F Supin M Pron F Pron M Fig 4 Active supination and pronation in the dominant and nondominant forearm (Supin-D, supination in the dominant forearm; Supin-N, supination in the non-dominant forearm; Pron-D, pronation in the dominant forearm; Pron-N, pronation in the non-dominant forearm). Fig 5 Active supination and pronation in male and female forearm (Supin-F, supination in the female group; Supin-M, supination in the male group; Pron-F, pronation in the female group; Pron- M, pronation in the male group) Table 5 The degrees of active supination and pronation in the right forearm of the male and female groups Supin-F Supin-M Pron-F Pron-M Supin-F, supination in the female group; Supin-M, supination in the male group; Pron-F, pronation in the female group; Pron-M, pronation in the male group; FE, full extension; 45F, 451 flexion; 9F, 91 flexion; FF, full flexion R Sup L Sup R Pro L Pro Fig 6 Active supination and pronation in R-handed and L-handed forearms (R-Sup, supination in the R-handed group; L-Sup, supination in the L-handed group; R-Pro, pronation in the R-handed group; L-Pro, pronation in the L-handed group). The range of supination and pronation significantly changed with different positions of the elbow in the dominant arm, of the L-handed group (n ¼ 7) compared to that of the R-handed group (n ¼ 43, po.1). The greatest difference between the two groups arose with full flexion of the elbow. The L-handed group showed greater range of supination in the dominant arm, while the R-handed group showed greater range of pronation in the dominant arm (Fig 6). The average angle of hyperextension of the elbow joint was similar in the right and left arms. It was 2 (range minus 1 - plus 7)1 in the right arm and 2 (range minus 7 - plus 4)1 in the left arm. The average angle of full flexion was similar in the right and left arms. It was 138 (range )1 in the right arm and 138 (range )1 in the left arm. One constraint of our measuring system was that the measured angle of full flexion in the jig was 71 less than the anatomical angle of full flexion of the elbow as the bulky size of the pneumatic cuff and goniometer did not allow the volunteer to fully flex the elbow. The average angle of hyperextension of the elbow was slightly greater in the men, 2.11 compared to 1.91 in the women. The average angle of full flexion of the elbow was greater in the women, 141 compared to 1361 in the men. However, the difference was not statistically significant. DISCUSSION The principle finding of this study is that the position of the elbow joint has a significant effect on the range of supination and pronation. There would appear to be a reciprocal relationship between the range of supination and that of pronation. With flexion of the elbow, the range of supination increases, while that of pronation decreases. Extension of the elbow has the opposite effect; the range of supination decreases, while that of pronation increases. The study also shows that max-

5 THE EFFECT OF ELBOW POSITION ON THE RANGE OF SUPINATION 7 imum rotation of the forearm (combined supination/ pronation) occurs at mid-flexion of the elbow (45 91 flexion). There may be physiological reasons for the observed phenomena. Facilitation of the greatest range of supination when the elbow is fully flexed assists in the action of feeding by approximation of the fingers to the mouth. The ability to pronate with the elbow extended is necessary for personal and perineal care. With the elbow in its mid-range of flexion/extension, the range of rotation is greatest and this mobility may assist in performing many activities of daily living and technical manoeuvres which require accurate and flexible placement of the hand relative to its target object. Such tasks are assisted by the ability to readily rotate the forearm. Previously published normative data report differences in the recorded ranges of supination, pronation and total rotation of the forearm (Table 1). The differences can be explained by the variety of methods used to undertake the measurements and the aim of each study. Some studies measured active rotation, while others measured passive rotation. In addition, some studies included rotation of the hand, while other studies measured rotation of the distal radioulnar joint (DRUJ), rotation of the forearm. However, none of the previous studies has recorded the position of the elbow joint when measurements were taken. Our study shows that, unless the position of the elbow is defined, measurements of forearm rotation are of limited use. This fact probably explains some of the reported differences in forearm rotation in previous studies. All of the previously reported figures for rotation of the forearm lie within the range of figures obtained in our study. This study showed that the range of supination and total rotation is significantly higher in women and in the non-dominant arms. This may be explained by the greater flexibility of the female but may also be impacted by anatomical differences at the elbow joint such as the greater carrying angle. It is not known whether there are additional male/female differences in the configuration of the articulating surfaces of the proximal and distal radioulnar joints. The observed phenomena described in this study must have an anatomical explanation that is yet to be defined definitively. The authors offer the suggestion, based on reading of the literature, that the trapezoidal configuration of the articular surface of the radial notch of the ulna and the known intraarticular translation of the radial head inside the proximal radioulnar joint could explain the study findings. Anatomically, the proximal part of the proximal radioulnar joint is wider than its distal part as a result of sloping of the anterior margin of the radial notch of ulna. Also, the annular ligament gets tighter around the head of radius distally as the diameter of the annular ligament gets narrower. Biomechanically, the head of the radius translates inside the proximal radioulnar joint in two different planes with flexion of the elbow and rotation of the forearm. It translates volarly with pronation and dorsally with supination (Weiss and Hastings, 1992). It also moves distally with extension of the elbow and proximally with flexion of the elbow (Palastanga et al., 1989). Our hypothesis is that the ranges of supination and pronation of the forearm depend on the range of volar-dorsal translation of the head of radius inside the proximal radioulnar joint. With flexion of the elbow, the head of the radius translates proximally to occupy the wider proximal part of the proximal radioulnar joint, with greater volardorsal translation as a consequence. With extension of the elbow, the head of the radius translates distally to occupy the narrower distal part of the proximal radioulnar joint, with less volar-dorsal translation as a consequence. The difference in position of the head of radius inside the proximal radioulnar joint results in differences in the range of volar-dorsal translation and, consequently, the range of supination and pronation. The importance of stating the degree of elbow flexion when reporting measurements of forearm rotation has been delineated in this study. This will, for the future, lead to better comparability between relevant data sets from different authors. There are also applications of this work to research, most notably in the future design of elbow and DRUJ prostheses. In addition, this work impacts on medicolegal work in the form of personal injury reporting. The model presented here may also be of assistance in conceptualising the proximal and radioulnar joints as two halves of a single functional couple facilitating the action of forearm rotation. Acknowledgements We are grateful to the Hand Surgery Research Fund, Wythenshawe Hospital, for a grant and to Ms Julie Morris for help and advice with statistical analysis. References Askew LJ, An KN, Morrey BF, Chao EY (1987). Isometric elbow strength in normal individuals. Clinical Orthopaedics and Related Research, 222: Cyriaz EF (1926). On the rotatory movements of the wrist. Journal of Anatomy, 6: Darcus HD, Salter N (1953). The amplitude of pronation and supination with the elbow flexed to a right angle. Journal of Anatomy, 87: Glanville AD, Kreezer G (1937). The maximum amplitude and velocity of joint movements in normal male human adults. Human Biology, 9: King GJ, McMurtry RY, Rubenstein JD, Gertzbein SD (1986). Kinematics of the distal radioulnar joint. Journal of Hand Surgery, 11A: Manson TT, Pfaeffle HJ, Herndon JH, Tomaino MM, Fischer KJ (2). alters interosseous ligament strain distribution. Journal of Hand Surgery, 25A: Palastanga N, Field D, Soames R. Anatomy and human movement: structure and function, Oxford, Heinemann Medical Books, Silver D (1923). Measurement of the range of motion in joints. Journal of Bone and Joint Surgery, 5:

6 8 Weiler PJ, Bogoch ER (1995). Kinematics of the distal radioulnar joint in rheumatoid-arthritis an in-vivo study using centrode analysis. Journal of Hand Surgery, 2A: Weiss APC, Hastings H (1992). The anatomy of the proximal radioulnar joint. Journal of Shoulder and Elbow Surgery, 1: THE JOURNAL OF HAND SURGERY VOL. 33E No. 1 FEBRUARY 28 Dr V.C. Lees, Department of Plastic Surgery, Acute Block, Wythenshawe Hospital, Southmoor Road, Wythenshawe, Manchester M23 9LT, UK. Tel.: ; fax: vlees@dsl.pipex.com. r 28 The British Society for Surgery of the Hand. Published by SAGE. All rights reserved. doi:1.1177/ available online at Received: 9 August 26 Accepted after revision: 5 July 27