Abstract

Upon evaluation of a 4-week-old Bornean orangutan (Pongo pygmaeus pygmaeus) born at Cheyenne Mountain Zoo to a primiparous female who was being hand reared due to maternal neglect, bilateral hyperflexed (plantar flexed) feet were noted. There was no active motion of the ankle, only minimal passive motion (10° range) was present. The peroneal muscles were overstretched but the Achilles tendon and posterior tibialis muscle lacked flexibility. An EMG was completed to evaluate muscle conductivity and prognosis and found to be normal. In comparison to the clinical presentation of the human clubfoot where three consistent variations to the normal anatomy are observed (talonavicular subluxation, calcaneal equinovarus and metatarsus adductus), only the metatarsus adductus was absent in the orangutan. Radiographically, there was also parallelism of the talus and calcaneus in the orangutan as seen in the human condition. Thus, physical examination and radiographs performed correlated to what is seen and found in the human talipes equinovarus. To our knowledge, this medical condition has not been reported in orangutans.

Our goal with this infant was to obtain active plantigrade locomotion with grasping ability as soon as possible in order to allow reintroduction with conspecific. Currently, there are many methods of treatment to make clubfeet functional. In humans, the approach is a conservative method, as was chosen with the orangutan, though surgery was an option if this method did not achieve full function. Conservative treatment consisted of physical therapy (massage, stretching and strengthening of muscles, mobilization of joints involved, functional electrical stimulation) and graduated active splinting. Once functional range was reached, active muscle function was encouraged using an adaptive climbing apparatus. After 5 months of 24-hour care and excellent caregiver compliance with the rehabilitation program, the goals of fully functional feet were attained.