Congenital hypoplastic thumbs treated by staged nonvascularized MTP joint transfer for absent MCP joints and abductor digiti minimi tendon transfer for opposition: a case series study

BACKGROUND: We developed a 2-stage, MTP (metatarsophalangeal) joint- plus ADM (abductor digiti minimi) tendon-transfer, procedure for treatment of hypoplastic thumb. This method is intended to achieve both structural and functional goals of reconstruction. Structurally, it preserves a five-digit hand with minimal donor site complications. Functionally, it provides a functioning opposable thumb. CASE PRESENTATION: The case series included 7 patients with type IV hypoplastic thumb. At the first stage non-vascularized joint (not bone) was transplanted. In the second stage abductor digiti minimi tendon was transferred. Patients were followed for a median 5-yr period (range: 37–79 months). Functional outcome was assessed using a modified Percival assessment tool. Participants aged 17 to 36 months at the time of surgery with (2 male, 4 female). All patients were able to grasp large and small objects after the procedure. The thumb tip could actively move to touch the tips of index (2 patients) middle, ring, and little fingers (all patients) in an ulnar ward sequence and vice versa. All patients attained the ability to do lateral, palmar, and tripod pinch. As for donor site complications, none of the patients were found to have difficulty walking or keeping their balance. CONCLUSIONS: An alternative surgical procedure was developed to reconstruct a hypoplastic thumb. We obtained a good functional and cosmetic outcome with few donor site complications. Future studies will be needed to determine the long-term outcomes, to refine the selection criteria and to examine the necessity of additional procedure at the older ages. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12891-023-06165-8.