Assessment of sagittal spinopelvic parameters in a Taiwanese population with spondylolysis by the EOS imaging system: a retrospective radiological analysis

The Importance of Spinopelvic Parameters in Recurrent Lumbar Disk Herniation

STUDY DESIGN

Retrospective clinical study.

OBJECTIVES

We aimed to investigate preoperative spinopelvic mismatch as a risk factor for recurrent lumbar disk herniation (RLDH) in patients undergoing lumbar disk herniation (LDH) surgery.

SUMMARY OF BACKGROUND DATA

Spinopelvic parameters have been associated with lumbar degenerative diseases, particularly LDH. However, the relationship between these parameters and RLDH has yet to be studied.

MATERIALS AND METHODS

Data of 1453 patients aged ≥18 who underwent single-level, unilateral fenestration microdiscectomy for the first time in our hospital between 2013 and 2019 were reviewed. The study group comprised 88 patients who underwent surgery for RLDH. The control group comprised 101 randomly selected patients who underwent surgery for LDH but not RLDH. Age, sex, body mass index, occupational activity level, operative level, Roussouly classification type, and time to recurrence were recorded. Moreover, pelvic incidence, lumbar lordosis (LL), interverteberal disk height (IDH), segmental lordosis, sacral slope (SS), pelvic tilt (PT), and sacral table angle (ST) were measured for each patient. Pelvic mismatch was calculated.

RESULTS

Mean age was 46.5±11.4 y (range, 20-70). Both groups were similar concerning age, sex, body mass index, occupational activity level, and level of surgery. The mean time to recurrence was 167.3±36.6 d (range, 62-363). Measurements in the RLDH group were as follows: IDH=7.6±1.5 mm, pelvic incidence =54.4°±10.1°, LL=47.3°±13°, segmental lordosis =9.3°±5°, SS=35.1°±9.9°, and PT=19.3°±7.3°. Mean IDH was significantly lower in the RLDH group ( P =0.02). Less LL and lower PT at L3-4 level and increased SS at L5-S1 level were considered risk factors for RLDH.

CONCLUSION

This study showed that preoperative low IDH is at higher risk for RLDH in patients undergoing LDH surgery. LL, PT, and SS may be risk factors for specific levels.

Associations between femoral 3D curvature and sagittal imbalance of spine

Background

The sagittal imbalance (SI) of spine triggers compensatory mechanisms (CMs) of lower extremity (LE) to restore trunk balance. These CMs can cause long-period stress on the femur and may possibly alter the femoral morphology. This cross-sectional observational study aimed to answer the following questions: (a) Do SI subjects exhibit greater femoral bowing compared to subjects with sagittal balance? (b) Are there associations between femoral bowing and CMs of LE in SI subjects?

Methods

Subjects who underwent biplanar full body radiographs with the EOS imaging system between January 2016 and September 2021 were recruited. Sagittal parameters included T1-pelvic angle (TPA), pelvic incidence (PI), pelvic tilt (PT), sacral slope, lumbar lordosis (LL), PI-LL, and PT/PI ratio. LE parameters were femoral obliquity angle (FOA), knee flexion angle (KA), and ankle dorsiflexion angle. Femoral bowing was quantified as 3D radius of femoral curvature (RFC). Associations between 3D RFC and the radiographic parameters were analyzed.

Results

A total of 105 subjects were included, classified into balance group (TPA < 14°, n = 40), SI group (TPA ≥ 14° and KA <5°, n = 30), and SI with knee flexion group (TPA ≥ 14° and KA ≥ 5°, n = 35). 3D RFC was significantly lower in SI with knee flexion group compared to the other two groups (both p < 0.001). Stepwise linear regression showed that age, SI and knee flexion, femoral length (FL), FOA, and KA were independent predictors for 3D RFC.

Conclusion

Greater femoral bowing is observed in subjects with SI and knee flexion compared to the balanced population. CM parameters, including KA and FOA, are associated with 3D RFC. Further longitudinal study is needed to investigate the cause-and-effect relationship between SI, CMs of LE, and femoral bowing.