The Use of a Rib Vascularized Bone Graft in Revision Vertebral Column Resection for a Complex Pediatric Spine Patient

Abstract

We report a case of a 9-year, 10-month-old female patient who ultimately required a revision vertebral column resection to manage a progressive congenital kyphoscoliosis complicated by postoperative surgical site infection, decubiti and implant exposure, proximal junctional kyphosis, and pseudarthrosis. Definitive surgery consisted of T4-L4 posterior spinal fusion and revision vertebral column resection with a pedicled rib vascular bone graft. At 3-year follow-up, the patient was fully recovered with return to full noncontact activities. The purpose of this case report is to describe the use of a rib vascular bone graft to increase the likelihood of arthrodesis for a complex pediatric spinal fusion patient with deficient posterior elements and multiple failed surgeries.

The technique of rotating a rib vascular bone graft (R-VBG) into the posterolateral space to augment spinal fusion in complex spinal patients has been described.^1,2 Vascularized bone grafts maintain their vascular supply and osteocyte viability, enabling rapid incorporation into a structural fusion mass when compared with nonvascularized bone grafts.² The increased number of viable osteocytes leads to quicker fusion because creeping substitution is not required to form bone as in an allograft or dysvascular graft.³ VBGs are also more resistant to infection than N-VBGs.^2-5 This case demonstrates the successful use of a pedicled R-VBG leveraged to overcome recurrent surgical site infection and pseudarthrosis by spanning a large posterior osseous defect to obtain arthrodesis in a complex pediatric spine patient with a history of multiple failed surgeries.

Case Presentation

A 9-year 10-month-old female patient presented to the emergency department after experiencing multiple falls secondary to left leg weakness. Her surgical history was notable for a T12 posterolateral hemivertebra resection and T10-L2 short segment posterior spinal fusion (PSF) with anterior interbody cortical rib autograft at the age of 2.5 years ultimately requiring removal of implant for persisting Enterobacter cloacae surgical site infection. At the age of 3.5 years, following long-term intravenous antibiotic therapy, normalization of inflammatory markers, and MRI confirmation of infection eradication, the patient underwent revision with staged preoperative halo-gravity traction therapy followed by a revision T12 vertebral column resection (VCR) through the pseudarthrosis of her prior resection site with PSF from T9-L2 and placement of anterior titanium interbody cage. This procedure was complicated again by posterior surgical site infection (SSI) with methicillin-sensitive Staphylococcus aureus, contributing to pseudarthrosis and subsequent development of proximal junctional kyphosis (PJK) with resultant loss of cephalad fixation and decubiti with implant exposure requiring implant removal to enable eradication of SSI at the age of 7 years, 27 months before her presentation for the reported case.

At emergency department presentation the patient reported of frequent falling, incoordination, and vague lower extremity weakness. She denied having bowel or bladder incontinence. Her physical examination revealed skin thinning over a sharp angular kyphosis (Figure 1), and neurologic examination revealed 4/5 strength throughout both lower extremities, 0/5 strength in the left ankle dorsiflexors and plantarflexors, patellar hyperreflexia, and bilateral upgoing Babinski. Radiograph and CT images revealed a progressive recurrence of kyphoscoliosis (55° scoliosis, 104° kyphosis) with a large segmental posterior element osseous defect and severe spinal canal stenosis and spinal cord compression at the deformity's apex (Figures 2 and 3). The patient's leg weakness with worsening kyphosis and spinal canal stenosis suggested a developing myelopathic pattern that would likely proceed to paraplegia without intervention, warranting urgent revision PSF from T4-L4 with anterior Pyramesh cage (Medtronic) removal and revision VCR at T11. The patient's parent consented to submitting this case data for publication.

Figure 1.

Clinical photographs with a posterior view (A) and a side view (B) before revision surgery demonstrating a sharp angular kyphosis.

Figure 2.

Preoperative Posteroanterior (PA) and lateral plain radiographs (A&B), 3D CT reconstructionC), and sagittal CT scan reconstruction (D) demonstrating severe kyphotic gibbus, pseudarthrosis with embedded anterior corpectomy cage, large posterior osseous defect.

Figure 3.

Sagittal T2 MRI image demonstrating focal spinal cord compression and central stenosis before revision surgery (A). Midsagittal axial images cephalad to the focal kyphotic gibbus (B), at the kyphotic gibbus (C), and caudal to the kyphotic gibbus (D) demonstrating severe stenosis.

Two, attending, fellowship-trained, pediatric, orthopaedic spine surgeons performed the case due to its complexity. Prone positioning provided sufficient access. An endotracheal tube, nasogastric tube, and foley catheter supported the patient intraoperatively. The surgery started with dissection of the T4-L4 spinous processes, laminae, and facets. Irrigation & debridement was performed at all levels before reinstrumentation. Upper and lower instrumented vertebrae selection of T4 and L4, respectively, included the last cephalad and caudad vertebrae touched by the sagittal stable vertebrae line terminating in lordotic segments of the upper thoracic and lumbar spine. A freehand, landmark-based approach for pedicle screw insertion was used at T4-T8 and L3-L4. Pedicle screws were placed using O-arm (Medtronic) navigation at T9-T11 and L1-L2 given the complex anatomy at these levels. Intraoperative neurologic monitoring assessed somatosensory and motor-evoked potentials (MEPs). Left lower extremity MEPs were decreased before procedural start and remained unchanged throughout the exposure, instrumentation, and VCR.

Intraoperative findings revealed severe anterior spinal cord impingement at the apex of kyphosis with protrusion of the posterosuperior corner of the cage (Figure 4). After obtaining circumferential exposure of the spine, the spinal cord and exiting nerve roots were mobilized from anterior adhesions from the L1 vertebral defect up to the inferior aspect of T10 using a Penfield elevator for dissection. The Pyramesh cage was palpated protruding from the posterior vertebral body. Following instrumentation and placement of temporary working rods, the revision VCR was performed using O-arm navigation to guide osteotome position cephalad and caudad to the embedded Pyramesh cage, which was extracted in bone through en bloc anterior osteotomy. The kyphotic deformity was corrected using temporary working rods enabling serial, incremental, deformity correction with preservation of anterior spinal length. An expandable vertebral body cage (Small VBR, Ulrich Medical) packed with autogenous bone was placed for anterior column support. Intraoperative imaging revealed drastic improvement in kyphotic impingement of the cord with well-positioned instrumentation. Following resection, decompression, and deformity correction, the spinal cord was confirmed to have anterior decompression and had excellent vascular pulsations and resultant normalization of lower extremity MEP.

Figure 4.

Intraoperative lateral fluoroscopy imaging pre and post revision vertebral column resection (A and B) and immediate postoperative upright lateral imaging (C) demonstrating sagittal deformity correction, en block resection of embedded Pyramesh cage, and placement of expandable vertebral body cage.

Preoperative consultation with plastic surgery enabled collaborative planning to use an R-VBG for posterior arthrodesis of the large segmental posterior column bone defect. Fifteen centimeters of bone was required to span the posterior defect, and rib 8 was chosen for its level of cephalad fixation at T7-T8. Dissection of the eighth rib began at the right transverse process. A Doppler test confirmed adequate arterial signal. The rib was freed from the transverse process and dissection continued laterally. The periosteum was divided at the cephalad aspect of rib 9 with all intercostal muscle and neuromuscular structures bluntly dissected to enable protection of the vascular bundle on the inferior margin of rib 8.

An anterior lateral chest wall incision was made over rib 8 with dissection through latissimus dorsi and serratus anterior to the rib. The rib was measured and dissected anteriorly 15 cm. The neurovascular bundle was ligated, and dissection continued posteromedially while protecting the neurovascular bundle. Dissection then continued from the posterior incision, and the rib was freed and rotated clockwise along its pedicle and flipped into vertical, posterior-central orientation overlying the posterior laminar defect (Figure 5). The right-sided spinal rod was temporarily removed to enable passage of the rib vascular bundle beneath it, and the rod was replaced over the pedicle with Doppler signal reconfirmation of vascularity to the graft. Three monocorticotomies were performed along the rib's convexity to induce greenstick fractures, allowing the rib to be straightened and contoured to fit the posterior elements (Figure 6). Laminotomies were performed at T7 and L4, and the graft was fixed with sublaminar sutures passed under T8 and L3 laminae and tied over the cephalad and caudad graft. The remainder of the posterior elements, including the prior bony fusions at T9, T10, L1, and L2 were decorticated and incorporated into the graft. Final posterior-central fusion mass grafting was performed with morcellized autograft and bone graft substitute (Mastergraft, Medtronic) combined with vancomycin powder. The plastic surgery team closed the incision using paraspinal advancement flaps and applied an incisional vacuum dressing (Prevena) and two Jackson-Pratt drains (Cardinal Health).

Figure 5.

Intraoperative images from a posterior view (A) and a side view (B) demonstrating mobilized rib vascular bone graft (R-VBG) before fixation.

Figure 6.

Intraoperative image demonstrating monocorticotomies (arrows) performed at three areas along the convex aspect of the rib allowing the rib to be straightened.

Postoperative course included pediatric intensive care unit disposition followed by transfer to the floor and rapid mobilization with physical therapy. Upon awakening, the patient experienced complete neurologic recovery and resolution of myelopathy. Examination and radiographs at 37 months of follow-up confirmed clinical union without SSI and satisfactory, stable radiographic deformity correction without evidence of pseudarthrosis (Figure 7). Given the known radiation risk of repeated CT scans in pediatric patients, clinical, and radiographic follow-up was used to infer arthrodesis rather than repeating postoperative advanced imaging. The patient had well-healed surgical incisions and resumed daily and school activities with full return to recreational and noncontact athletic activities (Figure 8).

Figure 7.

Postoperative radiographs demonstrating stable deformity correction from a posterior-anterior view (A) and a lateral view (B) at 37 weeks of follow-up after posterior spinal fusion T4-L4 with replacement of the anterior cage at T11 and incorporation of a rib vascular bone graft from T8-L3.

Figure 8.

Clinical photographs with a posterior view (A), side view (B), and oblique view (C) following final revision surgery demonstrating well-healed surgical incisions and clinical deformity correction.

Discussion

Hemivertebra excision and short-segment PSF is the preferred treatment of progressive kyphoscoliosis in patients younger than 5 years to prevent curve progression and avoid large compensatory curves development, while minimizing iatrogenic growth impairment of the immature spine.^6,7 However, they are often complicated by PJK, especially when the hemivertebra is in the lower spine.⁸ Consequently, revision surgery rates approach 50% following hemivertebra resections.⁹

A VCR involves resection of the entire vertebral body and its associated disks and has notable risk of spinal cord injury, necessitating intraoperative spinal cord neuromonitoring.¹⁰ Performing a VCR at the apex of deformity enables simultaneous decompression of the anterior spinal cord impingement and 3-column mobility of the vertebral column, allowing for correction of angular deformity.¹¹ Anterior column support is required, and anterior strut or cage placement is recommended to enable anterior arthrodesis and prevent anterior spine shortening.¹² Arthrodesis is commonly achieved in these complex pediatric spinal fusions through morcellized graft incorporation.¹³

Despite the use of autogenous bone graft and anterior support in this patient's first two fusion surgeries, she developed infected pseudarthrosis with resultant loss of cephalad fixation and PJK requiring revision surgeries (Figure 2C). Ultimately, a massive posterior column osseous deficiency existed at the site of the two prior VCRs, which was spanned by a R-VBG in the final revision. A R-VBG is created when a rib is rotated while maintaining its blood supply and placed over the length of spine intended to be fused.¹⁴ VBGs have demonstrated superior outcomes to N-VBGs in patients predisposed to recurrent pseudarthrosis or infection with complex posterior column defects. VBGs maintain osteocyte viability, thus providing biologically favorable fusion than N-VBGs.^1,2 In addition, VBGs have shorter times to fusion as osteogenic cell migration is not required, offer excellent mechanical support in the postoperative period, and are more resistant to infection than N-VBGs.^2-5 In this case, the combination of an anterior column expandable vertebral cage packed with autogenous autograft and a posterior R-VBG enabled 360° spinal arthrodesis, which has proven stable without evidence of pseudarthrosis at over 3-year follow-up.

Pediatric spine fusions for congenital deformity incur nonunion rates as high as 25%, increasing risk for neurological complications during high-risk revision surgeries.¹³ Patients undergoing VCR have revision rates of approximately 13% by 5 years postoperatively.¹⁵ With the biological and mechanical advantages of VBGs vs. N-VBGs, a R-VBG was chosen for this patient to ensure a more reliable anterior-posterior arthrodesis and to diminish the risk of pseudarthrosis and need for revision. The viability of a R-VBG in this complex revision case demonstrates a promising option for pediatric spine deformity patients, especially those with large posterior column osseous deficiencies undergoing revision procedures. In this study, we reported the successful use of a R-VBG to establish 360° arthrodesis in a complex pediatric spine patient.

Summary Statement

Rib vascular bone graft is a promising treatment option for large posterior column osseous deficiencies in pediatric patients with complex spinal pathology.