Hardware Complication of Short-Segmental Instrumentation in Low Back Surgery

Kim, Nam Hyun; Lee, Hwan Mo; Hong, Kyung Pyo; Lee, Jin Woo

Abstract

Recently, the use of internal fixation device in spine is popular due to several advantages. The advantages are to make short segmental fusion possible, to obtain early stability, and to reduce the needs of external immobilization. But, we can easily observe the hardware failures such as screw breakage and loosening. The purpose of this study is to evaluate the contributing factors to hardware complications through analysis of the problem cases. The authors reviewed complicated 17 (6.7%) cases out of 271 patients who was done posterior decompression and spinal fusion with transpedicular screws for spinal stenosis or spondylolisthesis from Jan. 1986 to Dec. 1994. We reviewed the clinical data, radiograph, and bone mineralo-densitometry. Seventeen patients (6.7%) had hardware complications: breakage of the screw in 5 cases, loosening of the screw in 11 cases, displacement of the rod in 1 case. The duration from the operation to the onset of complications was 1.3 years (4 month-6 years). More complications were occurred in the distal segments (13 cases) than in the proximal segments (4 cases). In 6 cases of 17 cases, we could observe the incomplete spinal fusion. We performed the bone mineralodensitometry (BMD, DEXA) in 30 patients. Among them, 6 cases had hardware complications-5 cases of screw loosening and 1 case of screw breakage. The average BMD (1.048g/cm2) of 24 patients without hardware complications was higher than that (0.890g/cm2) of 6 patients with complications (p<0.05). The duration of wearing the external support after surgery was also checked. Removal of hardware was performed in 5 cases due to pain, but the others were treated conservatively because of no symptom. Hardware complications were found mainly in the distal segment and was related to bone mineral density. Checking the bone mineral density in preoperative state helps to decide on the indication of surgical intervention. Through follow-up X-ray, spinal fusions can be carefully observed, and the duration of external support can be decided.