JBJS Classics: Biomechanics of the Normal Elbow
OrthoBuzz regularly brings you a current commentary on a “classic” article from The Journal of Bone & Joint Surgery. These articles have been selected by the Editor-in-Chief and Deputy Editors of The Journal because of their long-standing significance to the orthopaedic community and the many citations they receive in the literature. Our OrthoBuzz commentators highlight the impact that these JBJS articles have had on the practice of orthopaedics. Please feel free to join the conversation by clicking on the “Leave a Comment” button in the box to the left.
The classic 1981 JBJS article by B.F. Morrey et al. begs to be read carefully, in part because of the name of the lead author. More importantly, this study answers the question that arises with almost every patient with an elbow disorder: Is the achieved range of motion sufficient for activities of daily living? We can answer this question “yes” or “no” after reading this article, and in my own practice, I repeatedly refer to the information provided in it.
Dr. Morrey was an aerospace engineer who worked at NASA for two years before he attended medical school at the University of Texas Medical Branch. After his residency at the Mayo Clinic and after achieving a master’s degree in biomechanics from the University of Minnesota, he joined the staff at Mayo in 1978.
In this article, which integrates Dr. Morrey’s engineering and medical disciplines, he applied a high-tech device of that period (the triaxial electrogoniometer) to answer simple but eternal questions such as what degree of elbow flexion is needed to eat or perform personal hygiene.
It is the nature of human beings to notice particular joint impairments only when they disturb activities of daily living. Patient-reported outcome scores assessing subtle disturbances have recently been published, but we learned from Dr. Morrey’s article that patients with elbow flexion less than 130° will probably be reminded of their elbow problem whenever they try to use a telephone. (With today’s small cellular phones the problem might be even more accentuated.)
There is not much that a contemporary reviewer would criticise if this study were to be submitted today. Yes, the graphics would be nicer, and there would be more than 12 references. Modern computer-aided tools and methods for motion analysis might be more precise (and produce a mass of partially redundant data), but the results would remain essentially the same.
In fact, the question of functional elbow range of motion was revisited in JBJS by Sardelli et al. exactly 30 years after Dr. Morrey’s study appeared. Using modern three-dimensional optical tracking technology, Sardelli et al. found only minimal differences compared to findings in the Morrey et al. study. Only a few contemporary tasks like working on a computer (greater pronation) or using a cellular phone (greater flexion) appeared to require slightly more range of motion than previously reported.
Finally, it is the succinct and pointed results that amaze me whenever I recall the information from Dr. Morrey’s study. All we need to remember are four numbers: 100, 30, 130, and 50. Therein we are reminded that the patient needs to achieve a 100° arc of motion for flexion /extension (from 30° to 130°) and forearm rotation (50° of pronation and 50° of supination).
The authors were able to omit the conclusion sentence we see so often these days: “Further studies are needed…” The question about the minimal range of elbow motion needed to accomplish activities of daily living has been convincingly answered in this article. All residents should read this JBJS classic early, certainly before they examine their first patient with an elbow disorder.
Bernhard Jost, M.D.
JBJS Deputy Editor