gms | German Medical Science

Objectives/Interrogation: We have developed a novel two-stage reconstruction for a severe hypoplastic thumb: transplantation of a non-vascularized metatarsal head with epiphysis or metatarsophalangeal (MTP) joint for the first stage and tendon transfers for the second stage. The purpose of this study was to assess the biological attachment, the bone union and the growth of reconstructed first metacarpal bone.

Methods: We retrospectively reviewed the biological attachment and the bone union of 57 hypoplastic thumbs (27 Blauth III B and 30 Blauth IV) that underwent the two-staged reconstruction after 1992. The mean age at the first stage of surgery was 3.3 years. Bone union and growth of reconstructed first metacarpal was reviewed up to 5 years after surgery. The length of the reconstructed first metacarpal bone was measured on the AP view of plain radiographs every year. It was compared with the length of the ipsilateral second metacarpal bone.

Results and Conclusions: 42 hands obtained biological attachment. 32 hands obtained bone union without complication and a mean period of bone union was 8.8 weeks. Nine hands needed additional surgeries, and one hand with a bone graft from paralyzed side of the spina bifida had fallen into severe bone absorption. 27 hands (13 Blauth IIIB and 14 Blauth IV) reconstructed after 2000, which excluded these complications, were evaluated up to 5 years after surgery for bone growth of the reconstructed first metacarpal. The mean length of the first metacarpal bone was 23.8 mm at surgery and 29 mm at 5 years after surgery. On the contrary, the second metacarpal bone was 33.8 mm at surgery and 44.6 mm respectively. Growth of the reconstructed first metacarpal bone was recognized; however, the growth rate was lower than that of the second metacarpal bone. Subgroup analyses were performed according to the Blauth classification and the type of bone graft (metacarpal head or MTP joint). The growth rate of the first metacarpal bone was 129 % for Blauth III B and 118% for Blauth IV cases. There was a statistically significant difference between the two groups. The growth rate of the first metacarpal bone with the MTP joint was inferior to that with the metatarsal head, but there were no significant differences between the two groups.

In our study, the biological attachment and the long-diameter growth of the bone graft were confirmed for 5 years after surgery, although it was transplanted in a non-vascularized fashion. Further long-term follow-up study until epiphyseal closure is necessary.