Autologous Fat Transfer for Thumb Carpometacarpal Joint Osteoarthritis: A Prospective Study

Sir: The publication “Autologous Fat Transfer for Thumb Carpometacarpal Joint Osteoarthritis: A Prospective Study”1 presents a new surgical treatment for base-of-thumb osteoarthritis. The associated commentary hails it as a potential breakthrough. Although this presents an interesting technique, we believe there are methodologic flaws of the study that warrant attention. First, it was presented as a “pilot study,” building on a previous case series of five patients. However, there was no a priori sample size calculation, statistical analysis plan, or published protocol. The authors themselves acknowledge that it was not powered for statistical analysis but go on to statistically analyze the data and draw conclusions from the results. It would be better described as an Idea, Development, Exploration, Assessment, Long-term study Collaboration stage 2A development study.2 As a nonrandomized study, there were also inherent risks of bias. Additional risk of bias came from the small sample sizes, particularly for the Eaton-Glickel stage IV patient group, and lack of intention-to-treat analysis. Patients who failed the fat grafting were excluded from analysis. The lack of a comparator and use of subjective pain scores puts the study at high risk of the placebo effect. Although the authors mention a previous study demonstrating the effect, they do not adequately address the problem. There are relatively few placebo-controlled trials in surgery, but they can be both feasible and ethical.3 The authors state that it is unethical to subject patients to placebo liposuction, but they are currently subjecting patients to fat injections without a plausible mechanism of action or robust clinical evidence of efficacy. The natural history of osteoarthritis will often have a painful phase, which subsequently settles. Patients with stage II disease might have been earlier in this phase, explaining their apparent greater benefit. As time progressed, they might have improved irrespective of the surgical intervention. Furthermore, the authors suggest the fat might act as a “spacer.” We agree that mechanical factors play a significant role in joint homeostasis and the development of osteoarthritis. This is established in a mouse model of osteoarthritis, and joint distraction of the first carpometacarpal joint in humans is in a pilot phase.4 However, it is unlikely that fat would survive in the joint space to produce this effect. Artificial phosphatidylcholine liposomes show promise as ultraefficient boundary lubricants that are able to withstand the highest physiologic pressures experienced in synovial joints.5 However, it is again unclear whether components of adipose fat would create this effect. Finally, Osteoarthritis Research Society International guidelines recommend the use of outcome measures validated for osteoarthritis, such as the Australian/Canadian Score. These provide validated outcome measures that are then comparable across studies. For this technique, we believe a three-arm placebo-controlled trial is feasible and urge caution in the adoption of this procedure before a plausible mechanism and robust clinical data are available. DISCLOSURE The authors have no financial interest to declare in relation to the content of this communication. Dimitris Reissis, M.R.C.S.(Eng.)Department of Plastic and Reconstructive SurgeryImperial College Healthcare NHS TrustLondon, United Kingdom Matthew D. Gardiner, M.A., Ph.D., F.R.C.S.(Plast.)Department of Plastic and Reconstructive SurgeryImperial College Healthcare NHS TrustLondon, United KingdomKennedy Institute of RheumatologyNuffield Department of OrthopaedicsUniversity of OxfordOxford, United Kingdom