[Precise orthormorphia of tibial angulation deformity and shortening deformity by using digital technology combined with circular external fixator].

Objective: To evaluate the effectiveness of precise orthormorphia of tibial angulation deformity and shortening deformity by using digital technology combined with external fixator.

Methods: Twenty-six cases of tibial angulation deformity combined with shortening deformity were treated between June 2012 and August 2016, including 12 males and 14 females aged from 1 to 19 years with an average age of 16.5 years. There were 6 cases of congenital patella pseudoarthrosis, 1 case of fibrous dysplasia of femur and tibia, 3 cases of limb shortening deformity caused by infantile paralysis, 16 cases of fracture malunion. Limb shortening was 1.5-9.5 cm (mean, 6.2 cm) before operation. The deformity from three-dimensional perspective was analysed by digital technology, the surgical procedures of lengthening and osteotomy was simulated, the navigation templates were completed with computer aided design (CAD) and three-dimensional printing, and the external fixator was used to assist the lengthening of the tibia. X-ray films were regularly reviewed after operation to observe the new bone remolding, limb lengthening, load bearing line of lower limb, and recurrences of angulation.

Results: All the patients were followed up 14-48 months (mean, 18.8 months). There was only 1 case of superficial pin site infection which was cured with oral antibiotics and pin site care with mild disinfectants, and no complication such as bone nonunion, equines deformity, or vascular nerve injury occurred. The deformity of tibia and load bearing line of lower limb had been completely recovered according to postoperative X-ray films at 1 week. All the cases achieved perfect limb length as with preoperative design. The bone mineralization time was 12-20 weeks (mean, 11.6 weeks), the external fixator removal time was 18-26 weeks (mean, 14.9 weeks), and the healing index was 21-78 d/cm (mean, 63.4 d/cm). The postoperative flexion range of the injured limb was 15° less than the unaffected extremity in 1 case, and the situation was improved significantly after some physical manipulation and exercise, who completed the limb lengthening and achieved the expected effectiveness finally.

Conclusion: Precise orthormorphia of tibial deformity by using digital technology, and limb lengthening with the aid of external fixator can achieve good effectiveness with good reliability, invasiveness, and precision.