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Indicators of the Effectiveness of Non-Surgical Treatment of Thumb Carpometacarpal Instability: A Prospective Cohort Study
Niek J. Nieuwdorp, MSc
1, Isabel C. Jongen, MD
1, Ruud W. Selles, PhD
1, Robbert M. Wouters, PT, PhD
1, Thybout M. Moojen, MD, PhD
2, Caroline A. Hundepool, MD, PhD
1, The Hand Wrist Study Group, .
1,2; J. Michiel Zuidam, MD, PhD
1(1)Erasmus MC, Rotterdam, Netherlands, (2)Xpert Clinics, Amsterdam, Netherlands
Introduction: Thumb carpometacarpal (CMC) joint instability, typically due to ligament laxity, is most common in young females and causes pain and impaired hand function. Although it resembles early-stage osteoarthritis (Eaton-Glickel stage 1) in clinical presentation, CMC instability occurs without degenerative changes and should be considered a separate condition requiring a distinct treatment strategy, ranging from targeted hand therapy to stabilizing surgery. While non-surgical management is typically the first-line approach, it remains unclear which patients benefit most. Stabilizing surgery is considered if non-surgical treatment fails, but its use is controversial, and predictors of surgical conversion are poorly defined. This study aimed to identify patient, clinical, and mindset factors associated with surgical conversion in CMC instability. Additionally, it examined how these factors relate to changes in pain and function during the initial three months of non-surgical treatment.
Material & Methods: This multicenter prospective cohort study included patients diagnosed with CMC instability who underwent three months of hand therapy with or without an orthosis. Pain and hand function were assessed using the Visual Analogue Scale (VAS, 0-100) at baseline, six weeks, and three months into treatment. Cox regression was used to identify the predictors of surgical conversion, while a linear mixed model evaluated factors influencing pain and function change during non-surgical treatment.
Results: Of the 451 patients included, 58 (13%) underwent surgery after a median follow-up of 6.0 years. There was major variability in conversion rates across surgeons. Patients seeking a second opinion were 2.8 times more likely to convert to surgery (p=0.003). Surgery was also more likely in patients treated on the non-dominant hand (1.7 times; p=0.038) and those who were unemployed (2.1 times; p=0.040). During the first three months of non-surgical treatment, patients with non-traumatic instability improved 4.5 VAS pain points less per month than those with traumatic instability (p=0.031). Unemployed patients improved 5.0 points less per month (p=0.016), and those with a concurrent diagnosis improved 3.8 points less per month (p=0.007).
Conclusions: Surgical conversion rates varied significantly between surgeons, highlighting the need for standardized guidelines. Key predictors of surgery included second-opinion status, unemployment, and involvement of the non-dominant hand. Pain severity and functional impairment did not predict surgery, supporting a conservative-first approach even in severe cases. Poorer outcomes from non-surgical care were linked to non-traumatic instability, unemployment, and concurrent diagnoses. These findings aid clinicians in identifying patients who may benefit from non-surgical care versus those more likely to undergo surgery.
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