Shape of the Spinal Canal Is Not Associated with Success Rates of Microsurgical Unilateral Laminotomy and Bilateral Decompression for Lumbar Spinal Canal Stenosis

Effect of L5 spinal canal type on pedicle screw placement based on CT imaging: a retrospective clinical study

PURPOSE

The objective of this study was to investigate the optimal entry point and pedicle camber angle for L5 pedicle screws of different canal types.

METHODS

CT imaging data were processed by Mimics for simulated pedicle screw placement, and PD (Pedicle diameter), PCA (Pedicle camber angle), LD (Longitudinal distance), TD (Transverse distance), and PBG (Pedicle screw breach grade) were measured. Then they were divided into the Round group and Trefoil group according to the type of spinal canal. When comparing PD, PCA, LD, TD, and PBG, the two sides of the pedicle were compared separately, so they were first divided into the round-type pedicle group and the trefoil-type pedicle group.

RESULTS

In the round-type pedicle group (n = 134) and the trefoil-type pedicle group (n = 264), there was no significant difference in PD and LD, but there was a significant difference in PCA between the two groups (t = - 4.072, P < 0.05). A statistically significant difference in the distance of the Magerl point relative to the optimal entry point (t = - 3.792, P < 0.05), and the distance of the Magerl point relative to the optimal entry point was greater in the trefoil-type pedicle group than in the round-type pedicle group.

CONCLUSION

The optimal entry point for L5 is more outward than the Magerl point, and the Trefoil spinal canal L5 is more outwardly oriented than the Round spinal canal L5, with a greater angle of abduction during pedicle screw placement.

Lumbar Thecal Sac Dimensions and Axial Spinal Cord Areas on Magnetic Resosnace Imaging in 626 Healthy Subjects

STUDY DESIGN

A cross-sectional study.

OBJECTIVE

The aim of this study was to investigate the lumbar thecal sac dimensions and spinal cord area on magnetic resonance (MR) imaging in healthy volunteers.

SUMMARY OF BACKGROUND DATA

There are few reports regarding lumbar spine MRI in healthy subjects, and the difference in spinal canal dimensions by age remains unclear.

METHODS

A total of 629 healthy volunteers were enrolled, including ≥50 males, females, and subjects in each of the 20s to 70s age decades. The anteroposterior and transverse diameters of the thecal sac and axial areas of the thecal sac and spinal cord were measured at the disc levels on T2-weighted axial MR images. The anteroposterior-to-transverse ratio of the thecal sac (APTR) was calculated.

RESULTS

The thecal sac area from T12/L1 to L4/5 was reduced in older age group, but there was no significant difference in L5/S1. The thecal sac area was significantly reduced in older age group: 89.9%, 86.0%, 84.6%, 80.3% at T12/L1, L1/2, L2/3, and L3/4, respectively, and 79.9% at L4/5 in subjects in their 70 s relative to that in subjects in their 20 s. The APTR was significantly reduced in older age group from T11/12 to L2/L3 in males and at T10/11, L3/4 and from T11/12 to L2/3 in females. Narrow thecal sac areas <80 mm2 were found in 10 subjects. The spinal cord area was significantly reduced in older age group at T10/11 in males and at T9/10, T10/11, and T11/12 in females. The area was 92.0% at T10/11 in subjects in their 70s relative to the area of subjects in their 20s.

CONCLUSION

The thecal sac area was reduced in older age group from T12/L1 to L4/5, and the thecal sac area was reduced in the anteroposterior and all directions in the upper and lower lumbar area in age group, respectively. Approximately, 3.0% of healthy population in their 50s or older will have severe asymptomatic stenosis.Level of Evidence: 2.

[Degenerative lumbar spine stenosis: minimally invasive microsurgical methods of treatment]

Degenerative lumbar spine stenosis is one of the main causes of chronic pain and radiculopathy in advanced age people. Along with increase in average life expectancy, degenerative lumbar spine stenosis becomes the most common indication for spinal surgery. There is still no consensus regarding the most optimal surgical approach due to the variety of modern surgical methods. In recent years, minimally invasive spinal surgery has become a more advisable alternative to open surgery due to its advanced technical features combined with less soft tissue damage, lower risk of complications and shorter postoperative recovery.