Axial spondylectomy and circumferential reconstruction via a posterior approach

Abstract

Background: Spinal metastases of the second cervical vertebra are a subset of tumors that are particularly difficult to address surgically. Previously described techniques require highly morbid circumferential dissection posterior to the pharynx for resection and reconstruction.

Objective: To perform a biomechanical analysis of instrumented reconstruction configurations used after axial spondylectomy and to demonstrate safe use of a novel construct in a patient case report.

Methods: Several different published and novel reconstruction configurations were inserted into 7 occipitocervical spines that underwent axial spondylectomy. A biomechanical analysis of the stiffness of the constructs in flexion and extension, lateral bending, and rotation was performed. A patient then underwent a posterior-only approach for axial spondylectomy and circumferential reconstruction.

Results: Biomechanical analysis of different constructs demonstrated that anterior column reconstruction with bilateral cages spanning the C1 lateral mass to the C3 facet in combination with occipitocervical instrumentation was superior in flexion-extension and equivalent in lateral bending and rotation to currently used constructs. The patient in whom this construct was placed via a posterior-only approach for axial spondylectomy and instrumentation remained at neurological baseline and demonstrated no recurrence of local disease or failure of instrumentation to date.

Conclusion: When C1 lateral mass to C3 facet bilateral cage plus occipitocervical instrumentation is compared with existing anterior and posterior constructs, this novel reconstruction is biomechanically equivalent if not superior in performance. In a patient, the posterior-only approach for C2 spondylectomy with the novel reconstruction was safe and durable and avoided the morbidity of the anterior approach.

Figure 1

Photographs of cadaveric occipitocervical constructs tested. (A) C2 corpectomy with cage spanning from anterior arch of C1 to the body of C3, posterior view and anterior view, (B) Complete spondylectomy of C2 with Steinman pins and methylmethacrylate spanning from C1 lateral masses to the body of C3, (C) Complete spondylectomy of C2 with cages spanning from the C1 lateral masses to the C3 facets (D) Complete spondylectomy of C2 and resection of anterior arch of C1 with cage spanning from the clivus to C3 body, (E) Posterior occipitocervical fixation without any other reconstruction after C2 spondylectomy and C1 anterior arch resection.

Figure 2

Corresponding radiographs of the constructs created for biomechanical testing. (A) C2 corpectomy with cage spanning from anterior arch of C1 to the body of C3, posterior view and anterior view, (B) Complete spondylectomy of C2 with Steinman pins and methylmethacrylate spanning from C1 lateral masses to the body of C3, (C) Complete spondylectomy of C2 with cages spanning from the C1 lateral masses to the C3 facets (D) Complete spondylectomy of C2 and resection of anterior arch of C1 with cage spanning from the clivus to C3 body, (E) Posterior occipitocervical fixation without any other reconstruction after C2 spondylectomy and C1 anterior arch resection.

Figure 3

Results of cadaveric testing. The stiffness of each construct in (A) flexion-extension, (B) lateral bending and (C) axial rotation is depicted in the graphs. Significant differences (p<0.05) are noted (“*”). Though superior in some aspects, the overall performance of the C1 lateral mass to C3 facet construct was generally equivalent to previously used constructs for C2 reconstruction.

Figure 4

Preoperative sagittal images demonstrated the tumor involvement and pathological fracture of the C2 vertebra. T2 weighted (A) T1 weighted post contrast (B) and computed tomography images (C).

Figure 5

Technique for posterior decompression of C2. An intraoperative lateral cervical spine radiograph is shown (A) Temporary fixation is achieved with a unilateral C1-3 screw and rod construct. The vertebral arteries have been mobilized. An axial corpectomy via the transpedicular corridor is performed using the pneumatic drill. An artist’s depiction of the same (B).

Figure 6

Artist’s rendition of the expandable cages spanning the C1 lateral masses to C3 facets. (A) Lateral image of left cage placement between left C1 lateral mass and left C3 superior facet. (B) Posterior view of bilateral cage construct. Note the C3 superior facet needs to be trimmed to facilitate flush surface contact of the endplates of the cage to the surfaces of C1 and C3. The C1 and C3 screws and temporary rods were excluded in this illustration to clearly demonstrate the cage construct.

Figure 7

Postoperative images demonstrating Occiput to C5 fusion with cages spanning the C1 lateral masses to C3 facets. Sagittal (A) and coronal (B) computed tomography reconstructions with patent vertebrobasilar flow on coronal views. Lateral cervical (C) anteroposterior (D) and spine radiographs taken two years post-operatively.