[Instabilities of the Thumb Carpometacarpal Joint: Our Surgical Outcomes]

PURPOSE OF THE STUDY Carpometacarpal (CMC) instabilities of the thumb joint occur after injuries or due to joint overload in patients with congenital joint hypermobility. They are often undiagnosed and, if left untreated, are the basis for the development of rhizarthrosis in young individuals. The authors present the results of the Eaton-Littler technique. MATERIAL AND METHODS The authors present a set of 53 CMC joints of patients with an average age of 26.8 years (15-43 years) operated on in the years 2005-2017. Post-traumatic conditions were found in 10 patients and in 43 cases instability was caused by hyperlaxity, also demonstrated in other joints. The operation was performed from the Wagner's modified anteroradial approach. After the operation, a plaster splint was applied for 6 weeks, after which rehabilitation (magnetotherapy, warm-up) began. Patients were evaluated using the VAS (pain at rest and during exercise), DASH score in the work module, and subjective evaluation (no difficulties, difficulties not limiting normal activities, and difficulties limiting normal activities) before surgery and 36 months after surgery. RESULTS During the preoperative assessment, the average VAS value was 5.6 at rest and 8.3 during exercise. During the VAS assessment at rest, the values at 6, 12, 24 and 36 months after surgery were 5.6, 2.9, 0.9, 1, 2 and 1.1. When evaluated in the given intervals under load, the detected values were 4.1, 2, 2.2 and 2.4. The DASH score in the work module was 81.2 before surgery, 46.3 at 6 months, 15.2 at 12 months, 17.3 at 24 months, and 18.4 at 36 months after surgery. In the subjective self-assessment made at 36 months after surgery, 39 patients (74%) assessed their condition as having no difficulties, ten patients (19%) reported difficulties that did not limit normal activities, and four patients (7%) reported difficulties limiting normal activities. DISCUSSION Most authors present the results of their surgeries in patients with post-traumatic joint instability, and they report excellent results at two to six years after surgery. There is a negligible number of studies addressing instabilities in patients with instability caused by hypermobility. When using the conventional method described by the authors in 1973, our results of the evaluation performed at 36 months after surgery are comparable to those reported by other authors. We are well aware of the fact that this is a short-term follow-up and that this method does not prevent developing degenerative changes in the case of long-term follow-up, but reduces clinical difficulties and may delay the development of severe rhizarthrosis in young individuals. CONCLUSIONS CMC instability of the thumb joint is a relatively common disorder, although not all individuals experience clinical difficulties. In the case of difficulties, the instability needs to be diagnosed and treated as this is how the development of early rhizarthrosis in the predisposed individuals can be prevented. Our conclusions suggest a possibility of a surgical solution with good results. Key words: carpometacarpal thumb joint, thumb CMC joint, carpometacarpal thumb instability, joint laxity, rhizarthrosis.