The quantitative anatomy of the thoracic facet and the posterior projection of its inferior facet

Ultrasound-guided procedures for the management of chronic thoracic back pain: a technical review

Pain arising from the thoracic region has been reported to be potentially as debilitating as cervical or lumbar back pain, and may stem from a vast number of spinal sources, including zygapophysial, costovertebral and costotransverse joints, intervertebral discs, ligaments, fascia, muscles, and nerve roots. Over the last two decades, the use of ultrasound in interventional spinal procedures has been rapidly evolving, due to the ultrasound capabilities of visualizing soft tissues, including muscle layers, pleura, nerves, and blood vessels, allowing for real-time needle tracking, while also reducing radiation exposure to both patient and physician, when compared to traditional fluoroscopy guidance. However, its limitations still preclude it from being the imaging modality of choice for some thoracic spinal procedures, notably epidural (interlaminar and transforaminal approaches) and intradiscal injections. In this technical review, we provide an overview of five thoracic spinal injections that are amenable to ultrasound guidance. We start by discussing their clinical utility, followed by the relevant topographic anatomy, and then provide an illustrated technical description of each of the procedures discussed: (1) erector spinae plane block; (2) intra-articular thoracic zygapophyseal (facet) joint injection; (3) thoracic medial branch block; (4) costotransverse joint injection; and (5) costovertebral joint injection.

Shape variation of the neural arch in the thoracic and lumbar spine: characterization and relationship with the vertebral body shape

Quantifying the human vertebral geometry is important for accurate medical procedures. We aimed to characterize the neural arch (NA) shape at T1-L5. All T1-L5 dry vertebrae (N = 4,080) of 240 individuals were measured and analyzed by age, gender, and ethnicity. A 3D digitizer was used to measure the dimensions of the spinous (SP) and transverse (TP) processes, vertebral canal (VC), laminae, and isthmus. Most parameters were independent of age and ethnicity, yet greater in males than in females. Isthmus length increases from T1 (9.8 mm) to T12 (19.87 mm) and decreases from T12 to L5 (9.68 mm) with right > left in the thorax and oppositely in the lumbar region. The SP is longer than its thickness both decreasing in the upper thorax (by ca. 4mm), increasing in the lower thoracic and upper lumbar vertebrae (by 7 mm for length and ca. 14.5 mm for thickness) and decreasing again along the lower lumbar vertebrae (both by 8 mm). The TP length decreases at T1-T12 (by 13 mm) and increases at L1-L5 with left > right at T1-L5 (P < 0.003). The laminar length decreases from T1 (8.72 mm) through T5 (4.76 mm) and increases toward L5 (8.4 mm) with right > left at T1-L5 (P < 0.003). The VC is oval-shaped at T1 and T11-L5 (width > length), rounded-shape at T2 and T10 (width = length), and inverted oval-shaped at T3-T9 (length > width). In conclusion, the NA is systematically asymmetrical and dynamic in shape along the thoracic and lumbar spine. The inter-relationship with the vertebral body and articular facets is discussed.

Prediction of the human thoracic and lumbar articular facet joint morphometry from radiographic images

The articular facet joints (AFJ) play an important role in the biomechanics of the spine. Although it is well known that some AFJ dimensions (e.g. facet height/width or facet angles) play a major role in spinal deformities such as scoliosis, little is known about statistical correlations between these dimensions and the size of the vertebral bodies. Such relations could allow patient-specific prediction of AFJ morphometry from a few dimensions measurable by X-ray. This would be of clinical interest and could also provide parameters for mathematical modeling of the spine. Our purpose in this study was to generate prediction equations for 20 parameters of the human thoracic and lumbar AFJ from T1 to L4 as a function of only one given parameter, the vertebral body height posterior (VBHP). Linear and nonlinear regression analyses were performed with published anatomical data, including linear and angular dimensions of the AFJ and vertebral body heights, to find the best functions to describe the correlations between these parameters. Third-order polynomial regressions, in contrast to the linear, exponential and logarithmic regressions, provided moderate to high correlations between the AFJ parameters and vertebral body heights; e.g. facet height superior and interfacet width (R², 0.605-0.880); facet height inferior, interfacet height and sagittal/transverse angle superior (R², 0.875-0.973). Different correlations were found for facet width and transverse angle inferior in the thoracic (R², 0.703-0.930) and lumbar (R², 0.457-0.892) regions. A set of 20 prediction equations for AFJ parameters was generated (P-values < 0.005, anova). Comparison of the AFJ predictions with experimental data indicated mean percent errors <13%, with the exception of the thoracolumbar junction (T12-L1). It was possible to establish useful predictions for human thoracic and lumbar AFJ dimensions based on the size of the vertebral bodies. The generated set of equations allows the prediction of 20 AFJ parameters per vertebral level from the measurement of the parameter VBHP, which is easily performed on lateral X-rays. As the vertebral body height is unique for each person and vertebral level, the predicted AFJ parameters are also specific to an individual. This approach could be used for parameterized patient-specific modeling of the spine to explore the clinically important mechanical roles of the articular facets in pathological conditions, such as scoliosis.

Ex vivo and in vitro determination of the axial rotational axis of the human thoracic spine

STUDY DESIGN

Different geometrical and biomechanical evaluations were performed to determine the axial rotational axis of the thoracic spine.

OBJECTIVE

Our research group has been dealing with the determination of the axial rotational axis of the thoracic spine. Here, we would like to present the geometrical and experimental results of our trials. With our experiments, we are trying to evaluate the contradictions of the related literature.

SUMMARY OF BACKGROUND DATA

In the present state, we know quite a lot about the biomechanics of healthy and pathologic spines. Nevertheless, for a seemingly simple question like the position of the axial rotation of the thoracic spine, the literature gives contradicting results. During correction of a scoliotic deformity, when trying to correct the pathologic rotation, not knowing the physiologic rotation can be hazardous.

METHODS

We wanted to clarify this question, so we examined the thoracic spine in many different ways. First, we examined the problem from a geometrical point of view then we modeled the different rotational axes by studying the change in volume of the spinal canal. Finally, we used cadaver spines that we rotated and examined with radiographs and digital pictures.

RESULTS

Based on the results, we made the following establishments: most of the center points fell on the anterior half of the vertebral body or into the spinal canal, basically on the midsagittal axis of the vertebra. The rib cage has a significant effect on the place of the axis. After removing the ribs, the axis of axial rotation moved forward.

CONCLUSIONS

After evaluating the results, we determined that the most likely place for the rotational axis is on the median-sagittal plane, in the anterior portion of the spinal canal.

Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited

OBJECTIVE

The objectives of this white paper are to review and summarize the basic science literature relevant to spinal fixation (subluxation) and spinal adjusting procedures and to make specific recommendations for future research.

METHODS

PubMed, CINAHL, ICL, OSTMED, and MANTIS databases were searched by a multidisciplinary team for reports of basic science research (since 1995) related to spinal fixation (subluxation) and spinal adjusting (spinal manipulation). In addition, hand searches of the reference sections of studies judged to be important by the authors were also obtained. Each author used key words they determined to be most important to their field in designing their individual search strategy. Both animal and human studies were included in the literature searches, summaries, and recommendations for future research produced in this project.

DISCUSSION

The following topic areas were identified: anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system. A relevant summary of each topic area and specific recommendations for future research in each area were the primary objectives of this project.

CONCLUSIONS

The summaries of the literature for the 6 topic sections (anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system) indicated that a significant body of basic science research evaluating chiropractic spinal adjusting has been completed and published since the 1997 basic science white paper. Much more basic science research in these fields needs to be accomplished, and the recommendations at the end of each topic section should help researchers, funding agencies, and other decision makers develop specific research priorities.

Thoracic transfacet pedicle screw fixation: a new instrumentation technique

Object.Pedicle screw instrumentation of the thoracic spine remains technically challenging. Transverse process and costotransverse screw fixation techniques have been described as alternatives to pedicle screw fixation (PSF). In this study, the authors introduce thoracic transfacet PSF and compare its experimental biomechanical results with those of standard PSF in short-term cyclic loading in cadaveric thoracic specimens.

Methods.Specimens were tested intact for six cycles at compressive loads of 250 N offset by 1 cm along appropriate axes to induce flexion, extension, and left and right lateral bending. The specimens were then fixed with either a pedicle screw/rod construct or transfacet pedicle screws and retested in the same fashion. After this sequence, specimens were loaded until failure in flexion mode at a rate of 5 mm/minute was observed.

Both fixation constructs provided significantly greater stiffnesses than that demonstrated when the specimen was intact (p < 0.05, two-way analysis of variance). Additionally, the two constructs were statistically equivalent in terms of stiffness and load-to-failure values (p < 0.05, two-tailed nonpaired t-test). The only difference observed was that the low midthoracic region (T7–9) was biomechanically weaker than the upper midthoracic and lower thoracic areas in flexion after the destabilization and instrumentation-augmented stabilization procedures.

Conclusions.In selected thoracic surgical procedures, transfacet PSF may, after analysis of long-term biomechanical data, potentially become a reasonable alternative to conventional PSF.

Morphometric analysis of the thoracic and lumbar spine in Japanese on the use of pedicle screws

The pedicle screw and hook have become popular instruments in treating spinal deformity and disease. This study gathered morphological data on thoracic and lumbar spines in a Japanese population that should serve as useful reference for posterior instrumentation surgery. One hundred and three dry bones were used to investigate the morphology of pedicle and facet in thoracic and lumbar spines. Measurements included the diameter and axial length of pedicle from T8 to L5, height and width of facets and thickness of articular processes from T1 to T12, and axial angle of pedicle from T1 to L5. The diameter and axial length of pedicle were smallest at T8, diameter was largest at L5 and axial length was largest at L3. Height of facets and thickness of articular processes were largest at T12. Men tended to have larger pedicles and facets than women. Transverse angle of pedicle was smallest at T12. These precise data may provide useful information when performing posterior instrumentation surgery and when developing new spinal implant systems for Asians.

Facet orientation in the thoracolumbar spine: three-dimensional anatomic and biomechanical analysis

STUDY DESIGN

Thoracolumbar facet orientations were measured and analyzed.

OBJECTIVES

To establish a comprehensive database for facet orientation in the thoracolumbar vertebrae and to determine the normal human condition.

SUMMARY OF BACKGROUND DATA

Most studies on facet orientation have based their conclusions on two-dimensional measurements, in small samples or isolated vertebrae. The amount of normal asymmetry in facet orientation is poorly addressed.

METHODS

Transverse and longitudinal facet angles were measured directly from 240 human vertebral columns (males/females, blacks/whites). The specimens' osteologic material is part of the Hamann-Todd Osteological Collection housed at the Cleveland Museum of Natural History (Cleveland, OH). A total of 4,080 vertebrae (T1-L5) from the vertebral columns of individuals 20 to 80 years of age were measured, using a Microscribe three-dimensional apparatus (Immersion Co., San Jose, CA). Data were recorded directly on computer software. Statistical analysis included paired t tests and analysis of variance. RESULTS.: Facet orientation is independent of gender, age, and ethnic group. Asymmetry in facet orientation is found in the thorax. All thoracolumbar facets are positioned in an oblique plane. In the transverse plane, all facets from T1 to T11 are positioned with an anterior inclination of approximately 25 degrees to 30 degrees from the frontal plane. The facets of T12-L2 are oriented closer to the midsagittal plane of the vertebral body (mean range, 25.89 degrees-33.87 degrees), while the facets of L3-L5 are oriented away from that plane (mean range, 40.40 degrees-56.30 degrees). Facet transverse orientation at the thoracolumbar junction is highly variable (approximately 80% with approximately 101 degrees and approximately 20% with 35 degrees). All facets are oriented more vertically from T1 (approximately 150 degrees) to L5 (approximately 170 degrees). The facet sagittal orientations of the lumbar zygoapophyseal joints are not equivalent. CONCLUSIONS.: Asymmetry in facet orientation is a normal characteristic in the thorax.

The quantitative anatomy of the laminas of the spine

STUDY DESIGN

This study evaluated the dimensions of the laminas from C2 to L5 using adult spine specimens.

OBJECTIVES

To provide a set of quantitative data for the laminas from C2 to L5.

SUMMARY OF BACKGROUND DATA

Anatomic evaluation of the pedicle and facet joint in the spine has been extensively reported. No detailed studies of the laminas from the cervical to the lumbar spines exist.

METHODS

Thirty-seven spines from C2 to L5 were directly evaluated for this study. Anatomic evaluation of the laminas included the laminar height, width, thickness, and angulation.

RESULTS

In general, the measurements were greater in male specimens than in female specimens, although significant differences (P < 0.05) between male and female specimens were noted in only three measurements. The greatest laminar height was at T11 (25.1 +/- 2.5 mm), and the least was at C4 (10.4 +/- 1.1 mm). The greatest laminar width was at L5 (15.7 +/- 2.0 mm), and the least was at T4 (5.8 +/- 0.8 mm). Laminar widths in the cervical region were slightly more than those in the thoracic region. The greatest laminar thickness was at T2 (5.0 +/- 0.2 mm), whereas the least was at C5 (1.9 +/- 0.6 mm). Laminar thickness tended to increase in the upper thoracic region and to decrease slightly in the lower thoracic region. The mean laminar thickness of the lower cervical region was least in the whole spine. The widest angle was at C3 (116.1 +/- 8.8 degrees) and T7 (112.3 +/- 8.0 degrees) and the narrowest was at C2 (99.1 +/- 8.0 degrees) and L3 (99.9 +/- 6.3 degrees). The slope angles of the laminas varied from 97.8 +/- 3.0 degrees at T9 to 129.0 +/- 7.5 degrees at L3.

CONCLUSIONS

Surgical placement of sublaminar instruments may benefit from this quantitative study through the use of the provided anatomic parameters of the laminas.