Risk factors analyasis of instrument complication after posterior asymmetric vertebral column resection of collapsed tuberculous kyphosis of lumbosacral spine

English Keywords:Collapsed tuberculous kyphosis  Lumbosacral  Instrument complication  Asymmetric vertebral column resection

English Abstract:

  【Abstract】 Objectives: To analyse the risk factors and preventions of instrument complication after posterior asymmetric vertebral column resection(PAVCR) of collapsed tuberculous kyphosis of lumbosacral spine. Methods: 45 patients with collapsed tuberculous kyphosis of lumbosacral spine received posterior asymmetric vertebral column resection from January 2012 to December 2016 in our medical center were analyzed. There were 27 males and 18 females with an average age of 38.6±17.4(22-65) years old, and the average follow up was 36.4±9.8(24-66) months. Oswestry disability index(ODI), general epidemiological data including age, gender, osteotomy segment, fusion segments, bone mineral density(BMD), lower instrumented vertebra(LIV), and radiologic parameters of coronal and sagittal standing full spine X ray including local kyphosis cobb angle, coronal scoliosis cobb angle at preoperative, postoperative and final follow up were collected. All patients were categorized into rod fracture group, screw loosening group and non-complication group according to the diagnosis criteria of instrument complication. Results: 9 cases occurred instrument complication with an average time at 25.4±7.3 months, including simple distal screw loosening in 5 cases, simple rod fracture in 3 cases, screw loosening accompanied with rod fracture in 1 case. The incidence was 20%. There were significant differences between non-complication group and screw loosening group in postoperative local kyphosis Cobb angle(19.2°±6.3° vs 24.5°±8.7°, P<0.05), final follow up local kyphosis Cobb angle(21.2°±6.1° vs 28.4°±8.4°, P<0.05), final follow up ODI(11.1±3.6 vs 17.3±4.3, P<005), distal scew numbers ratio(P<0.05) and BMD ratio(P<0.05). There were significant differences between non-complication group and rod fracture group in postoperative local kyphosis Cobb angle(19.2°±6.3° vs 25.6°±7.3°, P<0.05)， final follow up local kyphosis Cobb angle(21.2°±6.1° vs 30.2°±7.9°, P<0.05) and final follow up ODI(11.1±3.6 vs 19.5±5.8, P<0.05), distal screw numbers ratio(P<0.05). There were no significant difference among those three groups in preoperative local kyohosis Cobb angle, preoperative scoliosis Cobb angle, postoperative scoliosis Cobb angle, final follow up scoliosis Cobb angle, preoperative ODI and postoperative ODI(P>0.05). Conclusions: There are risks of screw loosening and rod fracture after posterior asymmetric vertebral column resection(PAVCR) of collapsed tuberculous kyphosis of lumbosacral spine. The risk factors of screw loosening could be postoperative residual local kyphosis, less distal screws, nonunion and osteoporosis. The risk factors of rod fracture could be postoperative residual local kyphosis, absence of middle screws, and nonunion.