Objectives Elbow angle (EA) measurement is one of the major procedures in International Paralympic Committee Para Powerlifting (IPC PO) classification. There is a general historic consensus around the relative mechanical instability of the elbow joint associated to the 20° deficit of extension. Therefore in IPC PO athletes with such deficiency were classed as non-eligible to compete for safety reasons. However there is lack of evidence-based approach on measuring EA in sport specific setting.
Methods EA in 60 healthy sedentary individuals aged 19-75 with visually flat arms and no extension deficit at the elbow joints was measured twice: between three bone landmarks (3LM): (1) top of the acromion, (2) lateral epicondyle of the humerus, (3) radial styloid process, and along the bone axes (ABA) with clinical goniometers. Measurements were done between 9 and 11 am, and patients were asked to avoid any physical activity prior to the investigation. EA in 11 patients were also measured with X-Rays goniometry.
Results The study has shown that in a person with a visually flat arm (estimated elbow angle 0°) the angle measured with the 3LM method was 10.42° +/0.49° (p < 0.05) and measured with the ABA method was 1.40° +/0.20° (p < 0.05) No correlations of the EA with either sex or age were found. X-ray data has shown that the acromion is located approx. 11.1° higher than the humerus axis when measured from the lateral epicondyle of the humerus (Figure 1).
Coclusions We presume the EA in a healthy sedentary person with a visually flat arm to be 0° (180°). However, the evidence shows that measured by different methods it could be either 2° (ABA) or 11° (3LM). This shows a need to be explicit and consistent about exactly what is meant by the elbow angle. We suggest that a true elbow angle (TEA), which can be defined as an angle between the axis of the humerus and the axis of the radial bone should be distinguished from an arm curve angle (ACA), which is an angle between three abovementioned landmarks. So the reasonable approach to measure the TEA would be to use the 3LM method to carry out the measurement and find the ACA, and then deduct 11°. However one of the possible limitations for extrapolation of these findings are athletes with achondroplasia. They have severe deformities in the skeleton, thus the acromion cannot be used as a reference point when measuring the TEA or another formula should be applied. Further investigations are needed to define the difference between the ACA and the TEA in this special population. Our findings could be used in the sports specific classification in Paralympic sports for precise measurements of the EA. They also give a better understanding of difference between the TEA and the ACA, which might be useful in medical rehabilitation of patients with musculoskeletal problems and physiotherapy. By the recent decision of IPC PO Sports Technical Committee extension deficit of 20° in elbow joint was excluded from eligibility criteria.
Acknowledgments We would like to thank Dr. Evgeny Shuporin, for his help in conducting the current research and the group of IPC Powerlifting Technical and Classification experts: Derek Groves, Lt Cdr Kadir, Dr. Bassam Qasrawi, Jorge Moreno, Sam Munkley, and others for their support in this work.
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