Extensive pulp (zone 4) defects of the thumb, with the exposure of tendon or bone, are challenging reconstructive problems. Surgical treatment includes the use of local, regional, and free flaps. The first dorsal metacarpal artery flap has been used successfully for defects of the thumb. The innerved first dorsal metacarpal artery flap from the dorsum of the index finger was first described by Hilgenfeldt and refined by Holevich. An island flap carried on a neurovascular pedicle consisting of the first dorsal metacarpal artery was first demonstrated by Foucher and Braun. Seven innervated FDMCA island flaps were performed from May 2005 until July 2007 for thumb reconstruction. There were three women and four men with an average age of 54.9 years (range 28-89 years). The mean follow-up period was 15.4 months (range 4-29 months). The dominant hand was involved in six (85.7%) patients. In a retrospective clinical study, the following criteria were evaluated: (1) etiology of the defect, (2) time of reconstruction (primary vs. delayed), (3) survival rate of flap, (4) sensory function (Semmes-Weinstein monofilaments, static 2-PD, pain, cortical reorientation), (5) TAM measured with the Kapandji index, and (6) subjective patient satisfaction (SF 36). Four patients presented with trauma, two patients with defects after tumor resection and one with infection of the thumb. The flap was used for immediate reconstruction in three (42.9%) patients and for delayed reconstruction in four (57.1%) patients. Delayed reconstruction was performed 4.75 (1-12) months after initial trauma or first surgery. The donor area was grafted with full-thickness skin grafts in all cases. All flaps survived. The mean SWMF was 3.31 g and average statis 2-PD over the flap was 10.57 mm. Pain at the flap scored 3.71 over 10 and at the donor site 2.17 over 10. Paresthesia at the flap scored 0.57 over 4 and at the donor site 0.33 over 4. Complete cortical reorientation was only seen in one patient. The mean Kapandji score of the reconstructed thumb was 7.43 over 10. Using the SF-36, mean physical health of the patients scored 66.88% and mean mental health scored 70.55%. Disturbing pain and paresthesia of the flap are exceptional. The static 2-PD is more than 10 mm, and is clinically over the limit. Cortical reorientation was incomplete in all but one patient. Touch on thumb is felt on the dorsum of the index finger; however, sensation is not disturbing or interfering with the patient's activities. Foucher described the technique débranchement-rébranchement in order to improve this problem. The postoperative total amount of motion of the reconstructed thumb was very good. The results demonstrated that the FDMCA flap has a constant anatomy and easy dissection. It has a low donor site morbidity if FTSG is used. It also shows good functional and aesthetic results. Therefore, the FDMCA flap is a first treatment of choice for defects of the proximal phalanx and proximal part of the distal phalanx of the thumb.