CT-based Morphometric Analysis of Approach of Percutaneous Transforaminal Endoscopic Lumbar Interbody Fusion

Transforaminal posterior lumbar interbody fusion microscopic safe operating area: a three-dimensional model study based on computed tomography imaging

BACKGROUND

Endoscopic spine lumbar interbody fusion (Endo-LIF) is well-regarded within the academic community. However, it presents challenges such as intraoperative disorientation, high rates of nerve damage, a steep learning curve, and prolonged surgical times, often occurring during the creation of the operative channel. Furthermore, the undefined safe operational zones under endoscopy continue to pose risks to surgical safety. We aimed to analyse the anatomical data of Kambin's triangle via CT imaging to define the parameters of the safe operating area for transforaminal posterior lumbar interbody fusion (TPLIF), providing crucial insights for clinical practice.

METHODS

We selected the L4-L5 intervertebral space. Using three-dimensional (3D), we identified Kambin's triangle and the endocircle within it, and recorded the position of point 'J' on the adjacent facet joint as the centre 'O' of the circle shifts by angle 'β.' The diameter of the inscribed circle 'd,' the abduction angle 'β,' and the distances 'L1' and 'L2' were measured from the trephine's edge to the exiting and traversing nerve roots, respectively.

RESULTS

Using a trephine with a diameter of 8 mm in TPLIF has a significant safety distance. The safe operating area under the TPLIF microscope was also clarified.

CONCLUSIONS

Through CT imaging research, combined with 3D simulation, we identified the anatomical data of the L4-L5 segment Kambin's triangle, to clarify the safe operation area under TPLIF. We propose a simple and easy positioning method and provide a novel surgical technique to establish working channels faster and reduce nerve damage rates. At the same time, according to this method, the Kambin's triangle anatomical data of the patient's lumbar spine diseased segments can be measured through CT 3D reconstruction of the lumbar spine, and individualised preoperative design can be conducted to select the appropriate specifications of visible trephine and supporting tools. This may effectively reduce the learning curve, shorten the time operation time, and improve surgical safety.

Evaluation and analysis of surgical treatment for single-level or multi-level lumbar degenerative disease based on radiography

Background

Radiography has a low level of radiation exposure while providing valuable information. Due to its cost effectiveness and widespread availability, the preoperative radiographic imaging examination is a valuable approach for assessing patients with spinal disease. This study aimed to examine the influence of preoperative X-ray evaluation on the surgical treatment of patients with single- or multi-level lumbar degenerative disease (LDD).

Methods

A retrospective cohort analysis was conducted of 172 patients diagnosed with LDD who underwent transforaminal lumbar interbody fusion (TLIF) or posterior lumbar interbody fusion (PLIF) surgery between December 2021 and February 2023 at the Shanghai Changzheng Hospital. Various parameters were measured on preoperative radiographs, including the iliac crest height, median iliac angle (MIA), lumbar lordosis (LL), intervertebral facet joint degeneration, lumbosacral angle (LSA), intervertebral foramen height (IFH), and surgical segment. The surgical treatment was evaluated based on the operative time, intraoperative blood loss, and postoperative complications. A correlation analysis and independent sample t-tests were used to assess the relationship between preoperative radiographic variables and surgical treatments. Further, a multivariate linear regression analysis was employed to identify the risk factors affecting the clinical outcomes.

Results

The correlation analysis and t-test results showed that the MIA, height of the iliac crest, intervertebral facet joint degeneration, and surgical segment were significantly correlated with the surgical treatments (P<0.05). Specifically, the height of the iliac crest, intervertebral facet joint degeneration, and surgical segment were positively correlated with the surgical treatments. Conversely, the MIA was negatively correlated with the surgical treatments. However, no significant differences were observed between the IFH, LSA, and LL in relation to posterior lumbar surgery (P>0.05). The multiple linear regression analysis showed that the height of the iliac crest, MIA, intervertebral facet joint degeneration, and surgical segment were independent factors affecting the surgical treatments of patients with single- or multi-level LDD. These findings highlight the importance of considering these factors when planning and performing lumbar surgery.

Conclusions

The measurements taken from radiographs, including the height of the iliac crest, MIA, intervertebral facet joint degeneration, and surgical segment, demonstrate potential influences on the treatment of single- and multi-level lumbar spine surgery. These variables can be captured in plain film imaging and can provide valuable insights into the surgical procedure and offer guidance for the operation. By analyzing these radiographic measurements, surgeons can gain a better understanding of a patient's condition and tailor the surgical approach accordingly, thus optimizing the outcomes of the surgery.

Three-dimensional analysis of puncture needle path through safety triangle approach PLD and design of puncture positioning guide plate

OBJECTIVE

In this study, the three-dimensional relationship between the optimal puncture needle path and the lumbar spinous process was discussed using digital technology. Additionally, the positioning guide plate was designed and 3D printed in order to simulate the surgical puncture of specimens. This plate served as an important reference for the preoperative simulation and clinical application of percutaneous laser decompression (PLD).

METHOD

The CT data were imported into the Mimics program, the 3D model was rebuilt, the ideal puncture line N and the associated central axis M were developed, and the required data were measured. All of these steps were completed. A total of five adult specimens were chosen for CT scanning; the data were imported into the Mimics program; positioning guide plates were generated and 3D printed; a simulated surgical puncture of the specimens was carried out; an X-ray inspection was carried out; and an analysis of the puncture accuracy was carried out.

RESULTS

(1) The angle between line N and line M was 42°~55°, and the angles between the line M and 3D plane were 1°~2°, 5°~12°, and 78°~84°, respectively; (2) As the level of the lumbar intervertebral disc decreases, the distance from point to line and point to surface changes regularly; (3) The positioning guide was designed with the end of the lumbar spinous process and the posterior superior iliac spine on both sides as supporting points. (4) Five specimens were punctured 40 times by using the guide to simulate surgical puncture, and the success rate was 97.5%.

CONCLUSION

By analyzing the three-dimensional relationship between the optimal puncture needle path and the lumbar spinous process, the guide plate was designed to simulate surgical puncture, and the individualized safety positioning of percutaneous puncture was obtained.

Pro-Con Debate: Superior Versus Inferior Triangle Needle Placement in Transforaminal Epidural Injections

Although transforaminal epidural injections have long been used for radicular pain, there is no universal standard injection approach to the neural foramen. The intervertebral foramen and its surrounding structures comprise an anatomically sensitive area that includes bone and joint structures, the intervertebral disk, blood vessels (in particular, the radicular arteries), the epidural sheath, and the spinal nerve root. Given the relatively high risk of inadvertent injury or injection to these nearby structures, image guidance for transforaminal epidural steroid injections (TFESIs) is standard of care. However, there is a lack of consensus regarding the optimal approach to the neural foramen: from the traditional superior ("safe") triangle or from the inferior (Kambin's) triangle. In this Pro-Con commentary article, we discuss the relative advantages and disadvantages of each approach for TFESIs.

Current and Future Applications of the Kambin’s Triangle in Lumbar Spine Surgery

Kambin’s triangle has become the anatomical location of choice when accessing the lumbar spine to treat degenerative spinal disorders. Currently, lumbar interbody fusion is the most common procedure utilizing this space; however, with the advent of the Kambin’s prism definition, advanced imaging modalities, and robotic-assisted techniques, lumbar spine surgery has become increasingly precise and less invasive. These technological and procedural advances have drastically reduced the rate of complications, improved patient outcomes, and expanded the use of the Kambin’s triangle to treat different pathologies utilizing cutting-edge techniques. In this review, the authors present the current uses of the Kambin’s triangle and the future application of this anatomical corridor in lumbar spine surgery.

Cadaveric anatomy of the lumbar triangular safe zone of Kambin's in North West Indian population

A three dimensional triangular space ‘the Kambin’s triangle (KT)’ present on the dorsolateral aspect of the intervertebral disc, is considered to be a safe area for transforaminal approaches. It allows access to the exiting and traversing nerve roots, the thecal sac and to the intervertebral disc spaces. Our aim was to calculate the area of the triangle by measuring the height and base at all the intervertebral spaces bilaterally in the lumbar region in North West Indian cadavers and to assess the diameter of circle inscribed within this triangle which will correspond to the size of cannula inserted for the minimally invasive transforaminal approaches in this population. Five randomly chosen adult cadavers were used for this study. After clearing the area, the exiting nerve was identified. The height and base of the bony KTs (n=40) were measured with the help of digital Vernier’s calliper (accuracy 0.02 mm) to calculate the area of the KT. There is a steady increase in the area of the bony KT reaching maximum at the level of L4-5 intervertebral space. Statistically there were no differences in the calculated areas between right and left side. The mean diameter of inscribed circle within the triangle also showed gradual increase from 5.82 mm at L1-2 level, reaching maximum value of 7.26 mm at L4-5 level on the right side while on the left side the values were 5.66 mm and 8.16 mm respectively. Careful anatomical consideration is of utmost importance in transforaminal approaches during surgical or interventional procedures in this region. Cannula having external diameter ranging 6–8 mm is recommended for any interventional approach through Kambin’s space.

Three-dimensional architecture of the neurovascular and adipose zones of the upper and lower lumbar intervertebral foramina: an epoxy sheet plastination study

OBJECTIVE

Kambin's triangle and the safe triangle are common posterolateral approaches for lumbar transforaminal endoscopic surgery and epidural injection. To date, no consensus has been reached on the optimal transforaminal approach, in particular its underlying anatomical mechanism. The aim of this study was to investigate the 3D architecture of the neurovascular and adipose zones in the upper and lower lumbar intervertebral foramina (IVFs).

METHODS

Using the epoxy sheet plastination technology, 22 cadaveric lumbar spines (12 female and 10 male, age range 46-89 years) were prepared as a series of transverse (11 sets), sagittal (8 sets), and coronal (3 sets) slices with a thickness of 0.25 mm (6 sets) or 2.5 mm (16 sets). The high-resolution images of the slices were scanned and analyzed. The height, area, and volume of 30 IVFs from T12-L1 to L4-5 were estimated and compared. This study was performed in accord with the authors' institutional ethical guidelines and approved by the institutional ethics committees.

RESULTS

The findings were as follows. 1) The 3D boundaries of the lumbar IVF and its subdivisions were precisely defined. 2) The 3D configuration of the neurovascular and adipose zones was different between the upper and lower lumbar IVFs; zoning in the upper lumbar IVFs was much more complex than that in the lower lumbar IVFs. 3) In general, the infraneural adipose zone gradually tapered and rotated from the inferoposterolateral aspect to the superoanteromedial aspect. 4) The average height, area, and volume of the IVF gradually increased from the upper to the lower lumbar spine. Within a lumbar IVF, the volumes below and above the inferior border of the dorsal root ganglia were similar.

CONCLUSIONS

This study highlights differences of fine 3D architecture of neurovascular and adipose tissues between the upper and lower lumbar IVFs, with related effects on the transforaminal approaches. The findings may contribute to optimization of the surgical approaches to and through the IVF at different lumbar spinal levels and also may help to shorten the learning curve for the transforminal techniques.