Pullout strength of pedicle screws using cadaveric vertebrae with or without artificial demineralization

Comparison of midline lumbar interbody fusion and minimally invasive transforaminal lumbar interbody fusion for treatment of lumbar degeneration disease

Midline lumbar interbody fusion (MIDLIF) and minimally invasive transforaminal interbody fusion (MIS-TLIF) are two minimally invasive lumbar fusion methods that have gained popularity in the past two decades. MIDLIF involves the use of cortical bone trajectory screws, whereas MIS-TLIF uses traditional pedicle screws. However, there is a significant lack of research directly examining the clinical efficacy of these two methods in treating single-segment lumbar degenerative diseases. Hence, the objective of our retrospective study is to assess and contrast the surgical and clinical results of MIDLIF and MIS-TLIF. The study population comprised 133 patients diagnosed with single-segment lumbar degenerative disease that received treatment using either MIDLIF (n = 65) or MIS-TLIF (n = 68) in our department from January 2017 to January 2019. The fusion rates for MIDLIF were consistently lower than MID-TLIF at all post-operative time periods of follow-up, however, the differences between the two groups were not statistically significant. The 1-year fusion rates were 81.5% (MIDLIF) and 83.8% (MIS-TLIF) (P = 0.728), and the 2-year fusion rates were 87.7% (MIDLIF) and 91.2% (MIS-TLIF) (P = 0.513). The final follow-up fusion rates were 93.8% (MIDLIF) and 95.6% (MIS-TLIF) (P = 0.653). MIDLIF had several advantages over MIS-TLIF, including a shorter operative time (135.2 ± 15.70 vs. 160.1 ± 17.2 min, P < 0.001), decreased intraoperative blood loss (147.9 ± 36.4 vs. 169.5 ± 24.7 mL, P < 0.001), and a shorter length of hospital stay (10.8 ± 3.1 vs. 12.4 ± 4.1d; P = 0.014). No significant differences were seen between the groups in terms of the postoperative day of ambulation, Oswestry dysfunction index (ODI) scores, and visual analog scale (VAS) scores for leg and lower back pain (P > 0.05). Although not significant (P = 0.707), MIDLIF (13.8%) had fewer overall complications than MIS-TLIF (16.2%). Therefore, compared to MIS-TLIF, MIDLIF provides perioperative benefits while achieving the same outcomes as MIS-TLIF in terms of fusion rate, pain relief, functional improvement, and complication rate.

Design of a new detachable pedicle screw based on medical optical imaging inspection to improve osteoporosis and enhance vertebral body revision effect

Osteoporosis is a common bone disease that often leads to difficulty in vertebrae revision. Traditional pedicle screws are often complicated to operate and have poor visibility during implantation. A new detachable pedicle screw is needed to improve the revision effect. The aim of this study was to design a new detachable pedicle screw based on medical optical imaging to improve the outcome of vertebral revision in osteoporosis, and to improve operational feasibility and visibility. In this study, the parameters related to the degree of osteoporosis were obtained by optical imaging detection of the osteoporotic vertebral body. Then a new detachable pedicle screw was designed according to the test results to improve the effect of vertebral body revision. By preparing and optimizing the material and structure of the screw, it is ensured that it has sufficient mechanical strength and stability. Finally, the visibility and operability of the improved screw during implantation were verified by medical optical imaging. Compared with traditional screws, the new detachable pedicle screw can improve the vertebral body revision in the case of osteoporosis. The optical imaging test results show that the new screw has good visibility and maneuverability, providing more accurate guidance and positioning for the vertebral body revision operation.

Biomechanical Computational Study of Pedicle Screw Position and Density in Adolescent Idiopathic Scoliosis Instrumentation

STUDY DESIGN

Computer simulation of adolescent idiopathic scoliosis instrumentation.

OBJECTIVE

To test the hypothesis that different screw densities would result in different apical vertebral rotation (AVR) corrections and bone-screw forces in adolescent idiopathic scoliosis instrumentation.

SUMMARY OF BACKGROUND DATA

The "Minimize Implants Maximize Outcomes" Clinical Trial revealed that the use of more versus fewer screws resulted in similar coronal plane correction for Lenke 1A curves. However, the biomechanical impact of screw density on transverse plane correction is still unclear. Further investigation is needed to determine if and how transverse plane correction is correlated with screw density.

PATIENTS AND METHODS

We simulated apical vertebral derotation after segmental translation using patient-specific computer models of 30 patients from the "Minimize Implants Maximize Outcomes" Trial. For each case, 10 alternative screw patterns were tested with overall densities ranging between 1.2 and 2 screws per level fused, and local density at the 3 apical levels ranging between 0.7 and 2 (total: 600 simulations). Main thoracic (MT) Cobb angle, thoracic kyphosis (TK), AVR, and bone-screw forces were computed and compared.

RESULTS

The presenting MT (62 ± 11°; range: 45° to 86°), TK (27 ± 20°; -5° to 81°), and AVR (14±7°; -2° to 25°) were corrected through segmental translation to 22 ± 7° (10° to 41°), 26 ± 5° (18° to 45°), and 14 ± 7° (-4° to 26°). After apical vertebral derotation, they became 16 ± 8° (1° to 41°), 24 ± 4° (13° to 40°), and 4 ± 5° (-12° to 18°). There was no significant difference in MT among screw patterns; higher screw density had lower bone-screw forces ( P < 0.05). The apical vertebral derotation maneuver reduced AVR by an average of 70%, positively correlated with apical screw density ( r = 0.825, P < 0.05). There was no significant difference in TK.

CONCLUSION

Screw density had no significant effect on 3-dimensional correction through the primary segmental translation maneuver. Transverse plane correction through subsequent apical vertebral derotation was positively correlated with screw density at the apical levels ( r = 0.825, P < 0.05). Bone-screw forces were negatively correlated with overall screw density ( P < 0.05).

Anterior cervical plating combined with zero-profile anchored spacer for the treatment of cervical facet dislocation in elderly patients

OBJECTIVE

The purpose of this study was to evaluate the efficacy of anterior cervical plating combined with zero-profile (Z-P) anchored spacer for the treatment of cervical facet dislocation in elderly patients.

METHODS

This is a retrospective study. Twelve elderly patients (from 57 to 77 years old, averaged 65 years) with unilateral or bilateral facet dislocation of sub-axial cervical spine from September 2015 to September 2019 surgically treated at the authors' hospital were enrolled in this study. The patients with osteoporosis or osteopenia were all surgically treated by anterior-only procedure using cervical plating combined with zero-profile anchored spacer after closed manual reduction under general anesthesia and spinal cord monitoring. The operation times (OT), estimated blood loss (EBL), perioperative complications, were recorded. The clinical evaluation included visual analogue scales (VAS) and the American Spinal Injury Association (ASIA) scale. The radiographic evaluation included kyphotic angle (KA) and disc height (DH) and the fusion rate.

RESULTS

Anterior discectomy, interbody fusion and fixation were performed in all patients after the disloctions were reduced by manual maneuver. The average OT was 66 minutes, with a range from 45 to 110 minutes. The EBL averaged 42 ml per surgical procedure, with a range from 20 to 60 ml. The VAS, ASIA, KA were improved significantly after surgery (P<0.05). The average follow-up time was 24.2 months, with a range from 12 to 38 months. There were no statistical differences between the immediately post-op KA and KA at the last follow-up (P>0.05). No disc space subsidence was observed statistically (P<0.05) Interbody fusion was obtained in all patients. Two patient experienced slight difficulty in swallowing, which were improved 6 weeks later. There were no hardware failure, no segmental instability, no wound infection or other complications.

CONCLUSIONS

Manual reduction with spinal cord monitoring under general anesthesia is a safe and efficient option and the anterior cervical plating combined with Z-P spacer could achieve reliable fixation for the patients with cervical facet dislocation in the elderly patients with osteoporosis or osteopenia.