Osteoarthritis (OA) is a debilitating musculoskeletal disease that causes degeneration of the joint surfaces. One of the most common areas of OA is at the base of the thumb, or the carpometacarpal (CMC) joint. CMC OA has been cited as a common cause of joint pain and disability which affected range of motion and strength of the hand. Due to loss of hand function, individuals had trouble carrying out activities of daily living which has resulted in a decrease in independence. Furthermore, CMC OA disproportionally affected females more than males, especially over the age of 55.

When conservative treatment options failed, surgical intervention was necessary. The most common surgical option, ligament reconstruction with tendon interposition (LRTI), was used to restore function and reduce pain for those that have thumb CMC OA. The effectiveness of surgery was commonly determined via patient questionnaires and clinical measurement devices. Clinical measurement devices to document changes pre- and post-surgery insufficiently captured the threedimensional (3D) movement of the thumb and lacked accurate representation of isolated thumb forces. Relying on these clinical metrics have led to gaps in research associated with the thumb. For the best treatment options and rehabilitation, data and methods associated with thumb function are needed.

The objectives of this work were to:​ 1) identify the most appropriate mathematical method (Euler or body-fixed floating axis joint coordinate system methods) to obtain 3D motion patterns of the thumb, 2) determine and compare the motion abilities of the thumb in healthy males and females split into two groups (older and younger) and of those with CMC OA at three time points (pre-surgery, 3-months and 6-months post-surgery), and 3) compare isolated thumb force generation in healthy males and females (older and younger) and of those with CMC OA at three time points (pre-surgery, 3-months and 6-months post-surgery).

Result highlights of this work are as follows. For goal one, the body-fixed floating axis joint coordinate system method was considered to be the most precise, with fewer disadvantages and was used to determine joint angles of the thumb. For goal two, analysis of motion data suggested there may be premature signs of OA in older healthy females that have not yet experienced pain or visible loss of range of motion. Further, OA individuals appear to have utilized compensatory mechanisms to complete certain motion tasks compared to the healthy groups. For goal three, examination of force data showed that generally, only 50% of CMC OA participants improved at 6-months post-surgery compared to pre-surgery in their force abilities. Further, only one individual reached the level of the older healthy cohort.

Overall, this work presents a novel, detailed method for data collection and a complete analysis of thumb motion and force generation for younger healthy individuals, older healthy individuals and those with CMC OA (pre- and post-surgery). This research provides clinicians with in-depth information to encourage individuals to pursue conservative treatment sooner and hand surgeons with new data that provided insights into surgical outcomes and will foster improved treatment plans for those with thumb CMC OA.