Specific foraminal changes originate from degenerative spondylolisthesis on computed tomographic images

PURPOSE

Operative treatment for degenerative spondylolisthesis (DS) is accompanied by the high incidence of nerve injury. Foraminal structures, especially the hypertrophied facet joints, have significant impacts on the adjacent nerve. This study aims to identify the specific foraminal changes relating to DS and nerve injury.

METHODS

The CT images of 70 patients with DS and 50 patients without lumbar disease were collected. The length and height of the foraminal structure were measured horizontally and vertically on sagittally reconstructed images. Horizontal stenosis, meaning to pending compression to nerve root after complete reduction, was evaluated on the image located to the middle of the foramen. Chi-square test or T-test were carried out using SPSS 26.0.

RESULTS

The hyperplasia of the superior articular process (SAP) and articular capsule (Ac) incidence rates in DS group was significantly more common than that of the control group (9.2 vs 0.0%, 42.9 vs 2.0%). The height and width of the SAP and Ac in vertical and horizontal directions were significantly greater than those in the control group (4.95 mm vs - 0.47 mm, P < 0.0001; 3.28 vs 0.02 mm, P < 0.0001; 5.27 vs3.44 mm, P < 0.0001; 2.60 vs 0.37 mm, P < 0.0001). In the DS group, hyperplasia of the SAP and Ac accounted for 9 and 43% respectively, 85 and 45% of which were accompanied by horizontal stenosis of the intervertebral foramen.

CONCLUSION

DS is usually characterized of excessive hyperplasia of the SAP and Ac, both of which are possible elements of nerve root injury after complete reduction in operation and should be focused on during surgery.

A superior articular process morphology of 5th lumbar vertebra prone to screws placement failure: an anatomical study of 299 patients

PURPOSES

This study aimed to investigate whether the morphology of the superior articular processes of L5 vertebra affected the accuracy of pedicle screw placement by reviewing 299 patients who had undergone L5 pedicle screw fixation over the past 12 months and measuring relevant parameters.

METHODS

We retrospectively analyzed patients who underwent L5 vertebra fixation at our spine surgery department from October 20, 2020 to October 20, 2021. Patients with spondylolisthesis, spondylolysis, and scoliosis were excluded. Parameters associated with the superior articular process were analyzed, including Mammillary process-Spinal canal Distance (MCD), Inter-Facet Distance (IFD), Inter-Pedicle Distance (IPD), Zygapophysial Joints Angle (ZJA), Superior Articular Width, and Lateral Recess Transverse Diameter. The L5 vertebral body was reconstructed by Mimics 21.0, and the simulated L5 screws were inserted at multiple entry points to measure the Maximum Safe Transverse Angle (STA^max).

RESULTS

A total of 299 patients who underwent L5 vertebra fixation with 556 pedicle screws were analyzed. An MCD < 6 mm was associated with a significant increase in screw placement failure rate and decrease in ZJA. The MCD was positively correlated with IFD. No significant change in IPD was observed. Mimics software analysis showed that the STA^max decreased with a decrease of MCD. When WBV < 6 mm, 93% of the trans-mammillary vertical line was located within 50% of the pedicle.

CONCLUSIONS

The superior articular process tended to narrow the spinal canal and exhibit a steep and a "cloverleaf" morphology when the MCD was < 6 mm. This morphology increased the risk of operator mis-judgement resulting in screw placement failure. Assessment of the relationship between the trans-mammillary vertical line and the pedicle represents a simple method to predict abnormal morphology of the superior articular process before surgery.

The Endoscopic Trans-Superior Articular Process Approach: A Novel Minimally Invasive Surgical Corridor to the Lateral Recess

BACKGROUND

Transforaminal approaches to the lumbar spine are typically performed utilizing Kambin's triangle as approach corridor; however, degenerative changes can distort anatomy and expose the exiting nerve root to inadvertent injury.

OBJECTIVE

To describe the surgical technique of a novel full-endoscopic approach to access the lateral recess and report clinical outcomes.

METHODS

The trans-superior articular process (SAP) approach involves partial resection of the SAP, allowing access to the lateral recess both ventral and dorsal to the traversing nerve root. A retrospective review of 40 patients who had undergone a trans-SAP approach for decompression of lateral recess pathology was conducted. Outcomes were measured using visual analog scores (VAS) and Oswestry Disability Index (ODI) at 2 wk, 3 mo, and at last follow-up.

RESULTS

At a mean follow-up of 24 mo, patients experienced statistically significant improvement of the VAS for ipsilateral leg pain, VAS for back pain, and ODI when comparing preoperative values to all postoperative time points. The percentage of patients reaching a minimally clinically important difference for VAS leg pain and ODI was approximately 90% and 88%, respectively. The complication profile was favorable with no dural tears and no postoperative motor or sensory deficits. One patient required revision, with a total reoperation rate of 3%.

CONCLUSION

The trans-SAP approach is a novel approach that utilizes a safe surgical corridor via the SAP to access lateral recess pathology. Our initial clinical experience suggests that the trans-SAP approach allows for treatment of lateral recess and foraminal pathology with low complication rates.

Management of Root-Level Double Crush: Case Report with Technical Notes on Contralateral Interlaminar Foraminotomy with Full Endoscopic Uniportal Approach

BACKGROUND

Double crush of a nerve at the root level is not common. We describe here a double crush of the right L4 nerve with foramina to far lateral disk (ventral) and extraforaminal (dorsal) compression. The double crush was managed by endoscopy with a contralateral uniportal approach from the left interlaminar space. Right lateral recess stenosis at the same level was subsequently managed with the same approach.

CASE DESCRIPTION

A 79-year-old lady presented to our clinic with a low backache, right leg pain, and weakness. On her right side, the straight leg raise test was 70 degrees, great toe dorsiflexion was grade 3/5, and hypoesthesia was present in the L4 dermatome. Her preoperative visual analog scale score was 9. Magnetic resonance imaging showed right lateral recess stenosis and a double compression of L4 nerve root from the dorsal and ventral sides. A diagnosis of right lateral recess stenosis with double crush of the right L4 nerve root was made. The patient was managed with percutaneous endoscopic contralateral interlaminar foraminotomy from the left interlaminar approach. She got relief for the symptoms and her postoperative visual analog scale score was 2. Magnetic resonance imaging and computed tomography showed nerve root decompression and well-preserved facet joints.

CONCLUSIONS

We conclude that the management of double crush at the nerve root level with interlaminar contralateral approach endoscopy (percutaneous endoscopic contralateral interlaminar foraminotomy) can deal with the issue effectively with facet joint preservation and other benefits of the minimally invasive spine procedure.

Is the Superior Articular Process a Reliable Landmark for Determining the Transverse Plane Angulation of Thoracic Pedicles in Patients With Adolescent Idiopathic Scoliosis?

PURPOSE

To analyze the usefulness of the superior articular process (SAP) as an external landmark for determining the transverse plane angulation of thoracic pedicles in scoliotic spines.

METHODS

Two investigators reviewed thoracic spine CT scans of 60 patients with adolescent idiopathic scoliosis. The gantry was adjusted to obtain axial images parallel to the superior endplate. Each investigator measured the Cobb angle of the thoracic curve and identified the apical vertebra. This vertebra as well as the vertebrae bordering it superiorly and inferiorly was examined. A line was subtended at a 90° angle to the surface of the SAP, with a starting point at the midpoint of the lateral half of the SAP. It was documented whether the line was contained within the pedicle or breeched it medially or laterally. Breeches were corrected to an ideal projection, and the degree and direction of correction was recorded. Curves of 50°-60° were then compared to curves ≥70°.

RESULTS

Four subjects in our cohort were excluded as a result of inadequate imaging. Of 336 measurements, 89.3% were contained in bone, resulting in a breech rate of 10.7%. A majority of wall violations were on the lateral side (94.4%), with the average degree of correction being 6.1°. Interobserver agreement was calculated to be 95%, 87.5%, and 89.3% for superior, apical, and inferior vertebral measurements, respectively. On further stratification of the patients based on a Cobb angle of 50°-60° and ≥70°, we found that patients with curves ≥70° have a greater incidence of wall breech at the apical vertebra (10% vs. 5.6%) (p = .02).

CONCLUSION

The SAP can serve as a reliable external landmark for determining the transverse plane angulation of thoracic pedicles in scoliotic spines.

LEVEL OF EVIDENCE

Level 3.

The Superior Articular Process as an External Landmark for Determining the Transverse Plane Angulation of Thoracic Pedicles

STUDY DESIGN

Computed tomographic (CT) study of thoracic spine pedicles.

OBJECTIVE

To analyze the usefulness of the superior articular process (SAP) as an external landmark for determining the transverse plane angulation of thoracic pedicles.

SUMMARY OF BACKGROUND DATA

The use of thoracic pedicle screws has become commonplace. Although most authors report them to be safe, their use poses a risk to neurovascular structures. Previous studies have provided useful information regarding thoracic pedicle anatomy, but this information is difficult to apply intra-operatively. To avoid neurovascular injury, it is important to determine the correct transverse plane angulation of screw insertion.

METHODS

Two separate investigators reviewed thoracic spine CT scans of 53 patients, 26 years of age or younger. Measurements were taken of the angular relationship of the pedicle and the SAP of T4-T11. A 90° angle was subtended from a line parallel to the SAP with a starting point at the midpoint of the lateral half of the SAP. Measurements were then adjusted laterally for medial breeches and medially for lateral breeches, to align the trajectory down the middle of the pedicle. The degree of correction was recorded. Each investigator made 3 sets of measurements. We calculated kappa values to assess intra-observer/interobserver agreement.

RESULTS

Of the 4,008 measurements, 95.2% were contained within bone, leaving 4.8% pedicle violations. The average correction made for medial and lateral breeches was 6.3% and 6.7%, respectively. The first rater had 92.6% agreement, and an intra-observer kappa value of 0.57. The second rater had a 95.3% agreement and an intra-observer kappa value of 0.40.

CONCLUSIONS

The results support the hypothesis that the SAP can be a useful external landmark for determining the transverse plane angulation of thoracic pedicle screw insertion.