Initial clinical experience with the IMEX (TM) circular external skeletal fixation system - Part II: Use in bone lengthening and correction of angular and rotational deformities

The IMEX(TM) Circular External Skeletal Fixation (CESF) System was used to treat 10 antebrachial deformities in nine dogs. The mandible of one dog wit h prognathism was also lengthened. Dogs ranged in age from four to 18 month s (mean +/- SD: 9 +/- four months; median: eight months) and body weight fr om 2.6 to 46.0 kg (mean +/- SD: 23.9 +/- 11.2 kg; median: 24.2 kg). Linear distractions were performed with linear motors or threaded rods with paired nylon nuts securing the connecting rods to rings placed between ring block s. Hinges and angular motors were used to correct angular deformities. A la tency period of two to six days and a distraction rate of 1 mm/day, with a twice daily rhythm, were used. Distraction periods ranged from 12 to 32 day s (mean +/- SD: 21 +/- 8 days; median: 25 days). Lengthening achieved range d from 11 to 40 mm (mean +/- SD: 20 +/- 9 mm: median: 18 mm) or 6 to 30% (m ean +/- SD: 15 +/- 8%; median: 13%) of the distracted bone's initial length . All dogs had substantial improvement of their deformity and effective reg enerate bone formation. Flexure contracture and wire and pin track inflamma tion were common complications during the convalescent period. Functional a nd cosmetic results (direct examination: mean +/- SD: 130 +/- 65 days; medi an: 123 days; telephone communication: mean +/- SD: 351 +/- 133 days; media n: 324 days) were assessed as excellent in six, good in three and fair in t wo dogs and excellent in five, good in four and fair in one dog, respective ly. The IMEX(TM) CESF system allowed precise deformity correction with mini mal morbidity which was attributable to the system's zero tolerance, zero m otion properties.