[Collected data on freehand technique instrumentation and literature comparison on fluoroscopic and CT-assisted navigation]

Correlation of CT-based bone mineralization with drilling-force measurements in anatomical specimens is suitable to investigate planning of trans-pedicular spine interventions

This interdisciplinary study examined the relationship between bone density and drilling forces required during trans-pedicular access to the vertebra using fresh-frozen thoraco-lumbar vertebrae from two female body donors (A, B). Before and after biomechanical examination, samples underwent high-resolution CT-quantification of total bone density followed by software-based evaluation and processing. CT density measurements (n = 4818) were calculated as gray values (GV), which were highest in T12 for both subjects (GVmaxA = 3483.24, GVmaxB = 3160.33). Trans-pedicular drilling forces F (Newton N) were highest in L3 (FmaxB = 5.67 N) and L4 (FmaxA = 5.65 N). In 12 out of 13 specimens, GVs significantly (p < 0.001) correlated with force measurements. Among these, Spearman correlations r were poor in two lumbar vertebrae, fair in five specimens, and moderately strong in another five specimens, and highest for T11 (rA = 0.721) and L5 (rB = 0.690). Our results indicate that CT-based analysis of vertebral bone density acquired in anatomical specimens is a promising approach to predict the drilling force appearance as surrogate parameter of its biomechanical properties by e.g., linear regression analysis. The study may be of value as basis for biomechanical investigations to improve planning of the optimal trajectory and to define safety margins for drilling forces during robotic-assisted trans-pedicular interventions on the spine in the future.

Correlation of radiographic parameters and patient satisfaction in adolescent idiopathic scoliosis treated with posterior screw-dual-rod instrumentation

PURPOSE

In surgical treatment of adolescent idiopathic scoliosis (AIS), only a few studies measure both, radiological parameters and PROMs and correlate them.

METHODS

Prospectively collected AIS-data of one scoliosis-center within a multicenter German-Spine-Society-Study. All patients underwent instrumented posterior spinal correction and fusion with pedicle-screw-dual-rod-systems from 05/2019 to 01/2021. The data were retrospectively analyzed.

INCLUSION CRITERIA

age 11-17 years, follow-up (FU) at least 12 months. Clinical data, radiographic parameters, and PROMs (SRS-30-questionnaire) were collected. 100% of patients had X-ray images, 88.2% completed SRS-30. Parameters were given as mean ± SD. Differences and subdivision by lower instrumented vertebra (LIV) were analyzed by students t-test (significancy a = 0.05), associations by Pearson's correlation.

RESULT

Total of 51 patients: 15 ± 1.4 years, BMI 20.7 ± 3.7 kg/m2, FU 16.6 ± 6.1 months, fusion length 9.2 ± 2.3 segments, implant density 93 ± 9%, surgical time 215 ± 71 min, mean blood loss 504 ± 360 ml. Mean preoperative Cobb angle of main curve 64 ± 14°, of secondary main curve 46 ± 12°, corrected by 68 ± 11%, 56 ± 17%, respectively. Mean thoracic rib and lumbar hump significantly decreased by - 8.5 ± 7.0° and - 7.7 ± 8.9° (p < 0.5). High thoracic rib hump almost unchanged, - 0.4 ± 2.8° (p = 0.3). Thoracic kyphosis (- 0.9 ± 12.8°, p = 0.6), lumbar lordosis (1.5 ± 10.1°, p = 0.3), clavicle angle (- 0.5 ± 2.7°) and spinopelvic parameters (p > 0.5) did not significantly change, only LIV-tilt from 24.5 ± 6.7° to 6.5 ± 4.3° (p < 0.05). PROMs significantly improved (p < 0.05), no significant improvement for function/activity (p = 0.4). Preoperative mean total-score was 3.6 ± 0.5, 4.2 ± 0.3 at FU(p < 0.05). Self-image improved in 67%. Moderately strong correlation for PROMs: the better LIV-tilt (r = - 0.5) correction and the shorter surgery time (r = - 0.4), the better SRS-30 total-score. No correlation for curve correction and patient's satisfaction.

CONCLUSION

In summary, results of this study demonstrate good surgical correction and significant improvement of most PROMs.