Functional elbow range of motion on positional and functional tasks has been reported previously by Morrey et al.5. With use of a triaxial goniometer, it was determined that 30° to 130° of flexion, 50° of pronation, and 50° of supination were required for personal hygiene and sedentary tasks. These numbers have often been quoted as the standard for functional range of motion about the elbow and have been used to formulate surgical indications regarding elbow stiffness, arthrodesis positioning, and validating outcomes in total elbow arthroplasty.
Despite this report, various other studies that have disputed these findings have emerged over the years7-10. With the advent of three-dimensional motion capture technology, which includes electromagnetic and optical tracking methods, several studies have found greater motion arcs for pronation and supination as well as flexion and extension compared with those in the original article by Morrey et al. These models are able to track and measure motion in three different planes simultaneously with a high degree of accuracy, and the measurements are not affected by soft-tissue impingement as potentially seen with the triaxial goniometer.
Safaee-Rad et al.6, in 1990, were the first, to our knowledge, to report elbow range of motion with use of three-dimensional optical tracking methods. Examining three feeding activities, they found drinking from a cup, eating with a fork, and eating with a spoon all required an arc of flexion from 70° to 130° and 40° of pronation to 60° of supination. These findings were limited by only studying feeding activity, although they were important in that the range of motion confirmed previous data of feeding-related tasks in the study by Morrey et al.
In 2005, Magermans et al.7 used electromagnetic three-dimensional tracking to evaluate six functional tasks. Electromagnetic tracking and digital optical tracking techniques have been shown to be within 2° of each other in direct comparison studies15. Twenty-four female subjects performed simulated tasks of combing their hair, perineal care, eating with a spoon, reaching, washing the axilla, and lifting a 4-kg bag. Flexion values ranged from 61° to 135.7°, and pronation ranged from 71° to 120°. Although flexion values were similar to those found by Morrey et al., there was a marked increase in the amount of pronation required compared with that found by Morrey et al.5. In comparison with the results described by Safaee-Rad et al., with use of a three-dimensional optical tracking method, the inclusion of tasks other than feeding markedly increased the required arc of motion6.
In 2005, standards for defining motion axes were implemented by the International Society for Biomechanics16. It is important to understand that three-dimensional motion tracking relies on Euler angles to determine axes of motion and joint centers. The precise definition of joint centers and various axes about them is required if comparisons among studies are to be reliably made. After these guidelines were published, three other studies (one in 2006 and two in 2007) described the range of motion of the upper extremity with use of an optical tracking setup8-10. Pieniazek et al.9 used a system similar to the one used in the present study to evaluate combing one’s hair, closing a “zip fastener,” and answering a telephone. Eight subjects participated in the study, and maximum flexion values for picking up a telephone and combing one’s hair were reported as 140°. Raiss et al.10, in a study of eight subjects, used an optical tracking system to evaluate ten activities of daily living. A motion arc for flexion of a mean of 110° (range, 36° to 146°) and a mean pronation-supination arc of 117° (range, 55° of pronation to 72° of supination) were found. Henmi et al.8 evaluated five subjects for three functional tasks. Eating a meal, shampooing one’s hair, and washing one’s face were all evaluated with use of an optical tracking system with a similar marker setup. Flexion values ranged from a mean (and standard deviation) of 140° ± 5° for washing one’s face to 151° ± 9° for shampooing one’s hair. Mean pronation was reported as 75° and mean supination as 100°. These motion arcs and positional values are more consistent with the findings in the present study. Nevertheless, none of those authors replicated all of the tasks evaluated in the study by Morrey et al.5.
Possible explanations for the differences between the results reported by Morrey et al., with use of the triaxial goniometer, compared with the results with use of optical motion tracking include soft-tissue impingement with the device and/or inadequate alignment of the goniometer along the arm during elbow motion, subsequently altering motion axes. Both of these were identified as potential weaknesses in the original study by Morrey et al.5. Three-dimensional motion tracking offers the advantage of not needing to have the subjects to wear a linkage and wires, and potentially allows individuals to perform the tasks more naturally.
Varus and valgus elbow positioning in a normal group of individuals has not been previously reported as far as we know. These data may prove useful, especially when total elbow arthroplasty is considered. The degree to which the varus-valgus motion is coupled with flexion due to axis alignment and Euler angle specifications versus true motion laxity is uncertain. O’Driscoll et al. reported on electromagnetic tracking of eleven cadaveric elbows before and after implantation of a semiconstrained Coonrad-Morrey elbow prosthesis17. Varus-valgus laxity was evaluated throughout the flexion arc with the muscles loaded. A mean (and standard deviation) of 6.9° ± 3.7° of varus and valgus laxity was found prior to implantation, while 10.8° ± 1.8° of each was found after implantation. This information suggested that the prosthesis behaved as a “semi-constrained” joint. The authors suggested that because the Coonrad-Morrey prosthesis has more allowable varus-valgus motion than commonly seen in the intact elbow, the implant should never achieve the maximal varus-valgus positions allowed by the design, thereby limiting the development of early wear. That study was the first, as far as we know, to report on the kinematics of the elbow after total elbow arthroplasty, confirming that angular changes are present at the prosthesis with regard to varus and valgus positioning. Our study confirms these in vitro data as we found that, within a normal group of individuals, there is varus and valgus motion of the elbow while performing activities of daily living. Similarly, our in vivo data of 7.0° ± 1.7° of varus and 9.0° ± 2.9° of valgus is close to the 6.9° ± 3.7° determined by O’Driscoll et al. in cadaveric elbows. Further study would include in vivo analysis of varus and valgus motion arcs in patients after undergoing total elbow arthroplasty.
We found supination was much greater than previously reported, particularly for the task of touching the sacrum. While this finding is new and different from the results in the study by Morrey et al., increased supination of greater than 80° or 90° has been previously reported with higher levels of elbow flexion (as in the increased elbow flexion required to touch the sacrum in the present study). Shaaban et al.18 reported maximum pronation and supination to be greater than previously measured, and related this increase to the flexion and extension position of the elbow. With use of a custom jig and goniometer that fit the arm at the elbow and distal radioulnar joint, fifty volunteers held a grip and moved their forearms from full supination to full pronation with the elbow at full extension, 45° of flexion, 90° of flexion, and full flexion. The forearm supinated fully to 47.4° with the elbow in full extension and to 115.3° with the elbow in full flexion. With greater flexion, there was an increase in supination motion. A possible anatomic explanation for the increased supination with greater amounts of elbow flexion, as reported by Shaaban et al., is secondary to the shape of the proximal radioulnar joint and the known translation of the radial head inside this joint. The proximal aspect of the proximal radioulnar joint is wider than the distal part. The radial head translates volarly with pronation and dorsally with supination as well as distally with extension and proximally with flexion. The amount of forearm rotation depends on the amount of volar-dorsal translation allowed. With flexion, the radial head translates proximally into the wider portion of the joint, allowing greater volar-dorsal translation and, as a consequence, more forearm supination than is typically found at lesser degrees of elbow flexion. This anatomic finding may explain why the maximal supination values of 105° (at flexion angles of >90°) in our study are larger than those typically reported for maximal allowable supination.
The strengths of the present study include the large number of subjects evaluated compared with previous motion analysis studies. With twenty-five subjects, we were able to achieve flexion confidence intervals for each task within 5°. Additionally, a model utilizing a functionally determined elbow axis location and orientation and a glenohumeral joint center may offer improved accuracy over previous methods (as described in our previous study14). Another improvement of the current study compared with prior investigations is the fact that we replicated all of the tasks evaluated in Morrey et al., the current standard used to define functional elbow range of motion, with the addition of contemporary tasks not previously evaluated. Finally, the optical tracking system allowed us to determine varus and valgus ranges of motion for subjects with normal elbows, which had not been previously reported.
Limitations of the study can be categorized as those inherent to studying the upper extremity with motion analysis and those specific to our study design and rationale. Unlike gait, upper extremity tasks can be performed in a variety of ways. Repeatability of testing was an issue with this study, as it has been for all previous studies. For example, when a subject is asked to pick up a pitcher and pour into a glass, there is a great deal of individual variation in the execution of the task, which alters the mean and standard deviation values for the given task. Another disadvantage similar to the variety in execution strategies among individuals is the varying amounts of compensatory motions from the other joints of the spine and upper extremity used to complete a task. Vasen et al. demonstrated this in their study of functional elbow range of motion19. They had forty-nine subjects wear a Bledsoe brace, which sequentially limited their range of flexion and extension by 15°, and asked them to perform tasks as outlined by Morrey et al.5. They used “completion of the task” as their primary end point and found that subjects could complete most tasks within a range of 75° to 120°. Completion of tasks was facilitated through compensatory motion at other joints. A limitation of any optical motion capture measurement is soft-tissue artifact. Skin motion across the bones, along with movement between markers, is a source of error that cannot be ignored. It is most pronounced in the forearm affecting rotation, but could also affect joint centers and motion axes as markers change position relative to one another through each movement. In this study, a calibration, described in our previous study14, was applied to adjust for skin motion artifact in supination-pronation.
Investigation performed at Shriners Hospitals for Children, Salt Lake City, and the Department of Orthopaedics, University of Utah, Salt Lake City, Utah
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.
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