Abstract
Upper instrumented vertebra (UIV) fracture in adult spinal deformity surgery leads serious complications, such as spinal cord injury in 0.5–0.8%. Although tip-apex distance is important for preventing screw cut-out in proximal femoral fracture surgery, this suggest that the screw occupancy rate for bone fragments is also important. The purpose of this study was to investigate how the occupancy rate of pedicle screws (ORPS) affects UIV fracture. Patients with UIV fracture 1 year after surgery were defined as the fracture group (F); others were defined as the no fracture group (NF). ORPS, cut-out of pedicle screw (PS), medications, and bone mineral density were evaluated. Significant differences (P < 0.05) between group F (n = 58) and group NF (n = 260) were observed in age (71 years old in group F and 65 years old in group NF), diabetes medication use (19% in group F and 4% in group NF), steroid drug use (10% in group F and 2% in group NF), and ORPS (70% in group F and 76% in group NF). The cut-off value of ORPS using receiver operator characteristic analysis was 73%. Multiple logistic regression analysis identified diabetes medication use (P = 0.026, odds ratio [OR] 4.0) and ORPS < 73% (P = 0.001, OR 3.6) as significant risk factors for UIV fracture. The surgeon can’t control use of diabetes medication. However, they can replace with longer PS when ORPS < 73% is detected on radiographs taken during surgery. Further studies will be needed to better elucidate it’s use.
Highlights
Upper instrumented vertebra (UIV) fracture in adult spinal deformity surgery leads serious complications, such as spinal cord injury in 0.5–0.8%
We determined that the risk factors of UIV fracture were LIV at the ilium level, use of diabetes medication, use of steroid drugs, absence of preoperative thoracic kyphosis (TK) of 30°–39°, tip-apex distance (TAD), APD, and ORPS
Selection of LIV and decisions regarding the length of the pedicle screw (PS) (TAD and ORPS) are factors that can be controlled by the surgeon
Summary
Upper instrumented vertebra (UIV) fracture in adult spinal deformity surgery leads serious complications, such as spinal cord injury in 0.5–0.8%. Tip-apex distance is important for preventing screw cut-out in proximal femoral fracture surgery, this suggest that the screw occupancy rate for bone fragments is important. Baumgaertner et al.[11] reported that failed fixation with a sliding hip-screw device in patients with proximal femoral fracture was related to the position of the lag screw in the femoral head They concluded that the tip-apex distance (TAD) should be less than 25 mm to prevent cut-out of the lag screw. TAD is the sum of the distance (A + B) from the tip of the lag screw to the apex of the femoral head on the (A) anteroposterior and (B) lateral radiographs This result suggests that the occupancy rate of the lag screw in the bone fragments is important for the prevention of cut-out. The purpose of the present study was to investigate the risk factors of UIV fracture (such as age, bone mineral density, and comorbidity) including the way in which instruments are installed in the UIV
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