A Short Distance Between Pedicle Screw Tip and Upper Endplate as a Risk Factor for Upper Instrumented Vertebra...

Area of Science:

• Spine Surgery
• Orthopedic Surgery
• Radiography

Background:

• Adult spinal deformity (ASD) surgery involves instrumentation, with potential complications like upper instrumented vertebra fracture (UIVF).
• Specific pedicle screw characteristics at the upper instrumented vertebra (UIV) may influence UIVF development.

Purpose of the Study:

• To investigate the association between UIV pedicle screw characteristics (screw slope, tip-to-endplate distance [TED], tip-to-anterior cortex distance [TAD]) and UIVF following ASD surgery.
• To identify predictive factors and cutoff values for UIVF.

Main Methods:

• Retrospective cohort study of 132 patients undergoing ASD corrective surgery (2013-2022) with ≥2 years follow-up.
• Analysis of radiographic parameters, including UIV screw characteristics.
• Logistic regression and ROC curve analyses to determine risk factors and cutoff values for UIVF.

Main Results:

• UIVF occurred in 28.8% of patients.
• Postoperative thoracic kyphosis (Post-TK) > 36.5° and upper UIV screw tip-to-endplate distance (Post-TEDupper) < 6.5 mm were independently associated with UIVF.
• A Post-TEDupper < 6.5 mm significantly increased UIVF incidence (HR = 2.417, P = 0.010); UIVF commonly occurred within 3 months postoperatively.

Conclusions:

• Post-TK > 36.5° and Post-TEDupper < 6.5 mm are significant predictors of UIVF in ASD surgery.
• A postoperative TEDupper of ≥ 6.5 mm may be a target to reduce UIVF risk, though further validation is needed.