Application of 3D printing in treatment of traumatic knee varus deformity: a pilot study

Abstract

Objective To explore the clinical effect of using 3D printing in the treatment of genua varus deformity. Methods From September 2010 to April 2013, 27 cases of genua varus were admitted. They were 15 men and 12 women, with an average age of 37.8 years. The deformity affected the left side in 10 cases and the right in 17, with an average angle of 20.1°. All patients were examined by lamellar CT scan to harvest the original data of lower limbs. Three dimensional reconstruction of bone models was performed by software Materialise Mimics 10.01. 3D models were imported into software 3-matic 6.1 to measure the angles of varus, femorotibial angle, and the medial interspace of knee joint. The position and angle of osteotomy were precisely determined according to the results of computer-aided measurement. The cloud data of surface points were collected to design individual osteotomy-assisting templates by software Geomagic Studio 11.0, and the virtual procedures of the osteotomy and reconstruction of genua varus were simulated in software Magics 9.55. Physical templates were manufactured using 3D printing technology. In the actual operation, the best location of tibial osteotomy was determined according to the template. After osteotomy, internal fixation was performed using a steel plate and screws. X-ray examinations of bilateral lower limbs were conducted preoperation, 3 and 12 months postoperation. The femorotibial angles and the medial interspaces of knee joint were measured on postoperative X-ray films of lower limbs. The Hospital for Special Surgery (HSS) knee score was used to evaluate the preoperative and postoperative functions of the knee joint. Results All 27 patients were followed up from 7 to 36 months (average, 23.4 months). The bony union time was 3 to 5 months (average, 3.3 months). The femorotibial angles and the medial interspaces of knee joint at 3 and 12 months postoperation were significantly greater than those at preoperation, the average HSS score at 12 months postoperation was significantly higher than that at preoperation and 3 months postoperation, and the average HSS score at 3 months postoperation was significantly higher than that at preoperation (P < 0.05). According to the HSS scores at the last follow-up, 21 cases were excellent, 4 cases good, and 2 cases fair, giving an excellent to good rate of 92.6%. Conclusion 3D printing technology can be used along with computer-aided design to manufacture an individualized osteotomy-assisting template which greatly improves the accuracy of bone cutting and ensures better lines of force at the lower limb in the treatment of traumatic knee varus deformity. Key words: Surgery, computer-assisted; Knee joint; Abnormalities; Osteotomy; 3D printing technology