Background: The successful correction of flatfoot in children through lengthening of the lateral column, osteotomy of the medial cuneiform, and advancement of the posterior tibial tendon led to the introduction of similar procedures to treat acquired pes planovalgus secondary to attrition or rupture of the posterior tibial tendon in adults. However, to our knowledge, no study has been published documenting whether these procedures are effective treatment for acquired flatfoot in adults.Methods: The functional and radiographic results of complex reconstruction of a painful, flexible flatfoot associated with attrition or rupture of the posterior tibial tendon were evaluated in thirty-six patients (forty-one feet) with use of a detailed questionnaire, a comprehensive physical examination, and a review of the radiographs and the medical record.Results: At a mean of thirty-four months (range, twenty-four to fifty months) postoperatively, thirty-six feet (88 percent) were less painful compared with the preoperative status or were pain-free and five of the six parameters that had been used to assess correction of the deformity radiographically had improved significantly (p < 0.0001). Eight feet (20 percent) had a nonunion at the calcaneocuboid joint, and thirteen feet (32 percent) had anesthesia or paresthesia of the sural nerve. Twenty-nine feet (71 percent) had had additional operations, including removal of hardware from twenty feet; bone-grafting to treat a nonunion at the site of the calcaneocuboid arthrodesis and revision of the internal fixation in four feet; a medial displacement calcaneal osteotomy because of recurrent valgus angulation of the hindfoot in two feet; and a Lapidus procedure because of a hypermobile tarsometatarsal joint with hallux valgus, a triple arthrodesis because of a nonunion at the site of the calcaneocuboid arthrodesis associated with loss of correction, and a dorsiflexion-abduction wedge osteotomy through the site of the calcaneocuboid arthrodesis (which had healed) for alignment of an overcorrected foot in one foot each. The outcomes of the procedures in thirty-five feet (85 percent) were rated by the patients as satisfactory, and thirty-three (92 percent) of the thirty-six patients (thirty-eight [93 percent] of the forty-one feet) stated that they would have the procedure again if the circumstances were similar.Conclusions: Despite the high prevalence of postoperative complications, most of our patients were satisfied with the result of the procedure after the short duration of follow-up. We believe that the relief of pain and the restoration of function achieved through effective correction of the severe pes planovalgus deformity account for the satisfactory outcomes in our patients.