The stabilizing axial spinal pillar in the lumbar spine

A revisitation of distractive-extension injuries of the subaxial cervical spine: a cadaveric and radiographic soft tissue analysis

STUDY DESIGN

A biomechanical cadaveric and radiographic analyses.

OBJECTIVE

To identify and elaborate on specific anatomic soft tissue structures that are injured during various stages of a distractive-extension (DE) injury of the lower cervical spine and their role in angulation and posterior translation.

SUMMARY OF BACKGROUND DATA

Two DE stages (DES) of injury to the cervical spine have been described as follows: DES-1 and DES-2. However, the role of the soft tissue structures involved in such injuries has not been clearly defined. Furthermore, the importance of the facet capsules in DES injuries has not been well-addressed.

METHODS

A total of 15 adult cadaveric motion segments of the lower cervical spine were isolated and tested. Motion segments were mounted, with the cervical spine in extension, such that a distractive load was applied through the cephalad body. Anatomic supporting structures were serially sectioned from anterior to posterior to simulate varying degrees of soft-tissue disruption as occurring with the DE mechanism. Specimens were loaded at each stage of injury and measurements of angulation and posterior translation were recorded from fluoroscopic images by 2 independent observers.

RESULTS

A strong correlation was noted between the 2 sets of independent measurements. A statistical significant difference was noted between the degree of soft-tissue injury to the change in angulation and posterior translation (P < 0.001). The mean change in angulation and posterior translation was significantly greatest following sectioning of the anterior aspect of the facet capsules and to a lesser extent following sectioning of the posterior longitudinal ligament (PLL) (P < 0.001). A greater mean percent change between sequential sectioning of soft tissue structures was largely associated with posterior translation rather than angulation.

CONCLUSION

Sequentially greater angulation and posterior translation was seen after serial sectioning of the anterior facet capsule and to a lesser degree the PLL. This suggests that there are in fact 2 main "tethers" to angulation and posterior translation in the DE injury model, with the anterior facet capsule being the major stabilizer and to a lesser degree the PLL. Thus, based on our findings, it would appear that an expansion of the DE injury classification may be warranted, based on angulation and posterior translation, and regarded as DES-1, DES-2A, DES-2B, and DES-3. Such categorization based on the degree of angulation and posterior translation may prove advantageous in designing appropriate treatment strategies to address DE injuries of the lower cervical spine; however, further studies are needed to validate the clinical applications of such categorization.

Titanium mesh implantation--a method to stabilize the spine and protect the spinal cord following a multilevel laminectomy in the adult rat

The development of clinically relevant larger spinal cord injury models is in part limited by the possibility of a widened or multilevel laminectomy causing a spinal cord injury from an unstable spine or from compression of the spinal cord by adjacent soft tissues. In the adult rat, we have developed a method to protect the spinal cord and stabilize the spinal column using a titanium mesh implant following a bilateral, multilevel lumbar laminectomy. For this purpose, bilateral and expanded L1-4 laminectomies were performed with or without the use of a titanium mesh to protect the spinal cord and stabilize the spine. Without titanium mesh protection, the rats developed a severe paraparesis or paraplegia, urinary retention, gross anatomical signs of cord compression, and motoneuron loss. In the titanium mesh treatment group, the rats typically maintained a normal gait and lower urinary tract function, normal gross anatomical features of the spinal cord, and normal motoneuron counts. We propose that the use of a titanium mesh implant may assist in the development of clinically relevant larger spinal cord injury and repair models.

Classification of spinal injuries based on the essential traumatic spinal mechanisms

STUDY DESIGN

A biomechanical unitary classification of spinal injuries is proposed.

OBJECTIVE

To present an evaluation of spinal injuries based on the essential traumatic spinal mechanisms: axial deformation, torsion, translation and combined mechanisms in connection with the concept of the stabilizing axial spinal pillar.

SETTING

Hospital 'Sf. Treime', Iasi, Romania.

METHODS

The essential mechanisms of spinal injuries are considered: (1) axial deformation with (a) compression (centric or eccentric), most often eccentric, including compression in flexion or extension; (b) spinal elongation with distraction as centric elongation, but frequently axial eccentric elongation and a flexion or extension injury; (2) torsion or axial spinal rotation, (3) segmental translation, with a shearing version for the double translation and (4) combined mechanisms - the most frequent situation. Over 300 patients with spinal injuries were analysed and the spinal instability was determined using the criteria of clinical instability. The cases of spinal instability were studied in connection with the types of lesion of the central axial spinal pillar.

RESULTS

All cases with lesions of the central axial spinal pillar had traumatic spinal instability. The spinal instability was absent in cases of isolated lesions of the anterior or posterior secondary pillar. The X-ray and spinal CT analysis of the traumatic spinal lesions showed the types of lesions and specified the mechanisms of spinal injuries. The combined mechanisms were responsible for the majority of the spinal injuries.

CONCLUSIONS

Spinal instability occurs because of the lesion of the central axial spinal pillar The types of lesions of the central spinal pillar and of the secondary spinal pillars are determined by the essential traumatic spinal mechanisms: axial deformation (with compression or elongation), axial rotation, translation and most frequently the above combined mechanisms.