Master of Science
Scaphoid fractures are very common injuries that can have serious sequelae if pathologic healing ensues. Although there is consensus regarding the importance of a non-united scaphoid, the impact of a malunited scaphoid is less clear. This is based on a paucity in the literature and understanding of the natural history of scaphoid malunion. This study aims to elucidate this study but investigating the impact of scaphoid malunion and joint kinetics, as well as the impact of scaphoid malunion on carpal bone kinematics. This was accomplished using a combination of in-silico, as well as in-vivo modelling based of cadaveric results derived from an active motion. Our results showed that increasing scaphoid malunion was associated with increasing joint contact at the radioscaphoid joint. There was no significant relationship between scaphoid motion and scaphoid malunion severity, however, there was a significant change in lunate motion, as well as motion between the scaphoid and lunate.
This work serves as the framework for understanding the complex motion of the carpus and emphasizes the potential importance of establishing a good reduction of the scaphoid following fracture. The clinical importance of this finding has yet to be elucidated, but by understanding this relationship future clinical studies can be target at identifying feature of patients who may benefit from therapy.
Summary for Lay Audience
The wrist is a complex joint made up of eight bones. These bones are uniquely shaped to fit together in a way that allows for many different gripping positions. One of the bones, the scaphoid, is particularly important because it coordinates movement of all the other wrist bones. For this reason, if the shape of the scaphoid is changed by an injury, the entire wrist can be impacted. This leads to painful and limited motion that can result in arthritis. The most common injury that results in a change to a scaphoids shape is when it is broken and heals in the wrong position; this is called a malunion. Some of these injuries heal with standard medical treatment, but others have a difficult recovery. With the number of these injuries being so large in Ontario, numerous individuals who have this injury will go on to have lifelong wrist pain, limited movement, and loss of strength. Currently, the importance of this injury is not known. There have been many reports of patients with this injury having limited painful movement that improves after surgery to correct this. Other reports have argued that this change in shape is not important to normal function. The overall picture is unclear because the changes to wrist motion caused by a scaphoid malunion have never been studied. This makes it difficult for surgeons to decide the best treatment for patient with this injury.
The objective of this project was to investigate how increasing severity of scaphoid malunion changes wrist motion. By understanding this relationship we plan to identify target future clinical research that may eventually help create guidelines to assist surgeons make decisions about the best treatment for a patient with this injury.
Chambers, Spencer B., "The Impact of Scaphoid Malunion on Wrist Kinematics & Kinetics: A Biomechanical Investigation" (2019). Electronic Thesis and Dissertation Repository. 6707.
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