38: Hemivertebrae Resection

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Procedure 38 Hemivertebrae Resection

Rani Nasser, Matías G. Petracchi, Oheneba Boachie-Adjei, John K. Ratliff

Indications

image The primary objective in surgical treatment of hemivertebrae is to prevent the progression to severe spinal deformity.

image Ideal surgical candidates should have their deformity addressed before the development of compensatory curves.

• Progressive curve greater than 40 degrees
• Pelvic obliquity with deviation generating spinal imbalance

image Single, fully segmented hemivertebrae located at the thoracolumbar junction can deteriorate at a rate of 2 to 3.5 degrees per year.

image Hemivertebrae may lead to a rapidly progressing torsional deformity.

• Anatomic convex compression can transform into a concave mechanical compression.

Indications Pitfalls

• During the adolescent growth spurt, patients with congenital kyphoscoliosis may incur a rapid deterioration because of compression of the spinal cord.

• Adolescent growth spurt occurs at a mean age of 13.7 years.

• Hemivertebrae located higher up in the spine (cervical or thoracic) have a higher risk of intraspinal abnormalities.

Examination/Imaging

image History and physical (Figure 38-1)

image Routine history and physical with special attention to progression of deformity

• Hemivertebrae deformities do not follow any clear genetic inheritance patterns.
• Consider anomalies associated with the spectrum of spine deformity.
♦ VACTERL syndrome: vertebral anomalies, anal atresia, cardiovascular anomalies, tracheoesophageal fistula, esophageal atresia, renal and/or radial anomalies, and/or limb defects (1 in 10,000-40,000 live births)
♦ Genitourinary tract anomalies (26%)
♦ Cardiac defects (26%)

image Imaging

• Radiographs
♦ Anteroposterior (AP) (Figure 38-2, A and C) and (Figure 38-2, B) lateral
♦ Dynamic bending and traction films
• Computer tomography
♦ Coronal, sagittal, and three-dimensional reconstructions
• Magnetic resonance imaging (sagittal, Figure 38-3, A; and coronal, Figure 38-3, B)
♦ Evaluate for possible associated cord abnormalities.

• Arnold-Chiari malformation, syringomyelia, diastematomyelia, diplomyelia, or a tethered cord

image

FIGURE 38-1

image image image

FIGURE 38-2, A-C

image image

FIGURE 38-3, A-B

Treatment Options

• In situ posterior fusion

• The technique is not indicated in patients who are skeletally immature.
• Isolated posterior fusion is not preferred in young children, because of the reduced potential for correction.
• Thirty-six percent of young children by age 4 years could develop lordosis and bending of the fusion mass as the unfused anterior vertebral bodies continue to grow.
• Known as the crankshaft phenomenon
• Treatment goal is preventative and does not primarily address correction.

• Combined anterior and posterior fusion

• More substantial correction with diskectomies, combined anterior and posterior reconstruction of spinal deformity
• No crankshaft complications
• Decreased risk of pseudarthrosis
• May leave a residual curve, loss of growth potential in fused segments

• Epiphysiodesis

• Growth arrest on the convex side is indicated in patients with growth potential remaining only on the concave side.
• Concave growth is unpredictable and kyphosis may develop with growth of the posterior elements.
• Convex hemiepiphysiodesis performed across the entire measurable curve
• Optimized in patients less than 5 years old whose curve deformity has not progressed beyond 60 degrees.

• Hemivertebrae resection

• Eliminates potential for curve progression and potential to correct 60% to 70% of deformity
• Adjacent segments not involved and have no restriction on growth
• Decreases risk of pseudarthrosis and crankshaft phenomenon
• Could be performed as a combined anterior/posterior (single session or staged by 10 days) or posterior approach

Surgical Anatomy

image Expose the convex and anterior side of the hemivertebrae.

Positioning

image Lateral decubitus position

• Use lateral-posterior or simultaneous anterior/posterior approaches.
• Special attention should be paid to position the convex side up.

image Prone position

• For single posterior approaches or sequential anterior-posterior approaches
• Relton-Hall four-poster frame (or similar device)

Positioning Pearls

• Abdomen relieved of all pressure while prone

Positioning Equipment

• Relton-Hall four-poster frame for prone cases

Portals/Exposures

image In thoracic or thoracolumbar approaches, the rib that is one or two levels above the hemivertebrae is removed.

image Subperiosteal dissection of posterior elements is performed at the level of the hemivertebrae.

Portals/Exposures Pitfalls

• A wake-up test after reducing maneuvers and stabilization if intraoperative monitoring is not reliable.

Portals/Exposures Equipment

• Fluoroscopy

• Cell Saver

• Somatosensory and motor evoked potentials during the procedure

Procedure A: Lateral-Posterior Lumbar Hemivertebra Resection and Correction with Segmental Anterior Instrumentation

Step 1

image The patient is placed in the lateral decubitus position on the concave side.

image Make an L-shaped lateral/longitudinal incision 3.5 cm lateral from the spinous processes, above and below the hemivertebrae (Figure 38-4, A).

image The posterior elements of the convexity are exposed subperiosteally.

image Perform excision of the lamina, facets, pedicle, transverse process, and the posterior part of the hemivertebrae.

• Disk material on both sides of hemivertebrae is excised completely.
• Excise the vertebral epiphyseal plates.
image image

FIGURE 38-4, A-B

Step 1 Pearls

• Directly excising the hemivertebrae and appended structures will provide immediate correction of the existing deformity.

• Perform intraoperative monitoring of evoked potentials.

• Dissect hemivertebrae from the convex aspect toward the concave.

• Place thrombin-soaked gelatin over the dura if it is exposed.

• The dissected hemivertebrae is cut into morsels and is later used as a graft in filling the cavity created from the resection.

Step 1 Pitfalls

• To prevent neurologic injury consider temporary stabilization with laminar hooks.

Step 1 Instrumentation/Implantation

• Laminar hooks

Step 2

image An anterior incision is performed.

image The remainder of the hemivertebrae is excised anteriorly.

image Stabilization and compression may be performed with the use of baby Cotrel–Dubousset (CD) Horizon or mini-Harrington instrumentation.

Step 2 Pearls

• The fibular graft is used as a strut between the two adjacent vertebral bodies to prevent further kyphotic deformity.

• The laminae and facets above and below the hemivertebrae are decorticated on the convex side.

Step 2 Pitfalls

• Hemivertebrae resection may create a posterior gap.

Step 2 Instrumentation/Implantation

• Baby Cotrel–Dubousset (CD)

• Mini-Harrington

• Medtronic Sofamor Danek Company

Procedure B: Hemivertebra Resection and Fusion: Anterior and Posterior Approach

Step 1

image Anterior approach

• Make a linear incision from the approach side to the opposite side.
• Retract the psoas muscle and pleura from the vertebral bodies.
• Perform diskectomies caudal and cephalad from the hemivertebrae.

image Resect vertebral body (Figure 38-4, B).

Step 1 Pearls

• Place thrombin-soaked gelatin over dura if it is exposed.

• A hinge consisting of a small portion of the annulus is preserved on the concave side to avoid lateral translation of the adjacent structures.

• The dissected hemivertebrae is cut into morsels and is later used as a graft in filling the cavity created from the resection.

Step 1 Pitfalls

• Avoid damage to nerve roots exiting from underneath the pedicle.

• If bleeding from epidural veins is encountered:

• Use bipolar cautery if the site of epidural hemorrhage can be localized.
• Thrombin-soaked gelatin or other hemostatic agents may be used.

• Temporary stabilization is recommended before posterior approach to prevent potential neurologic injury.

Step 2

image Expose the posterior elements subperiosteally.

• Excise the lamina, facets, transverse process, and pedicle remnants.

image Definitive stabilization is achieved by compressing the convex side.

image Stabilization may also be attained by casting.

• Pantaloon spica casting keeps the patient toward the convexity.

Step 2 Pitfalls

• The initial part of the stabilization may be performed during the posterior hemivertebrae resection.

Step 2 Instrumentation/Implantation

• A wide range of instrumentation should be available in the operating room, including screws (pedicle, iliac), hooks, and cables or wires.

• Pantaloon spica casting may be used.

Procedure C: Posterior Hemivertebra Resection and Correction

Step 1

image Make a longitudinal incision along the entire scoliotic curvature (see Figure 38-2, C).

image Expose the lateral tip of the transverse processes subperiosteally.

image Resect the spinous process, lamina, and facet of the hemivertebrae.

image Pedicle resection is performed anteriorly until the lateral and anterior cortex of the vertebral body is reached.

image Disk material and end plates are removed.

Step 1 Pearls

• Resection of the pedicle and transverse process is performed under direct visualization of the spinal cord.

• In the thoracic hemivertebrae, the attached rib is excised up to a 3-cm length.

• Cortex removal is not necessary because of the compressive forces applied to the convex side.

• Residual cortical shell is crushed and closes the osteotomy gap.

Step 1 Pitfalls

• Excising disk material on the concave side may be problematic.

• These far lateral disk components are beneficial during the correction.
• This remnant disk and annulus serve as a hinge to prevent translation of the vertebral body.

Step 2

image After hemivertebrae resection, hooks and pedicle screws are placed (Figure 38-5 A [AP view] and B [lateral view]).

image Rods are bent to accommodate the convex side.

image Crushing the osteotomy gap with compression force will correct the kyphotic deformity as well as the scoliotic curvature.

image Transverse processes and posterior elements are decorticated.

image image

FIGURE 38-5, A-B

Step 2 Pearls

• Placement of anchors should be designed to allow compression force application to the convex side.

• Distraction forces should be directed toward the concave side.

• A second rod could be applied to the concave side to provide extra stability.

Step 2 Pitfalls

• A bony gap often remains at the site of the resected hemivertebrae.

Step 2 Instrumentation/Implantation

• A wide range of instrumentation should be available in the operating room, including screws (pedicle, iliac), hooks, and cables or wires (see Figure 38-5).

Postoperative Care and Expected Outcomes

image Standing AP and lateral views of the full spine should be attained postoperatively before hospital discharge, with the patient wearing the brace.

• The same studies should be repeated before the follow-up visit.

Postoperative Pearls

• Obtain cell blood counts to analyze hematocrit and hemoglobin postoperatively.

Postoperative Instrumentation/Implantation

• Custom-molded rigid brace should be worn to protect the instrumentation for 6 months.

Evidence

Bollini G, Docquier PL, Viehweger E, Launay F, Jouve JL. Lumbar hemivertebra resection. J Bone Joint Surg Am. 2006;88:1043-1052.

This study demonstrated that excision of a lumbar hemivertebra is safe and provides stable correction when combined with a short-segment fusion and when performed as early as possible.

Bollini G, Docquier PL, Viehweger E, Launay F, Jouve JL. Thoracolumbar hemivertebrae resection by double approach in a single procedure: long-term follow-up. Spine. 2006;31:1745-1757.

This study demonstrated that thoracolumbar hemivertebrae resection by double approach is safe and offers a persistent correction with a short-segment fusion.

Hedequist DJ, Emans JB. Congenital scoliosis. J Am Acad Orthop Surg. 2004;12:266-275.

This article reviewed congenital scoliosis, embryologic errors in vertebral column formation, predicting the natural history, and applying the correct treatment.

Hedequist DJ, Emans JB. The correlation of preoperative three-dimensional computed tomography reconstructions with operative findings in congenital scoliosis. Spine. 2003;28:2531-2534.

The data demonstrated three-dimensional reconstructions of computed tomography scans and the utlility of visualizing posterior vertebral anomalies associated with hemivertebra.

Hedequist DJ, Hall JE, Emans JB. Hemivertebra excision in children via simultaneous anterior and posterior exposures. J Pediatr Orthop. 2005;25:60-63.

This study reported that hemivertebra excision by simultaneous anterior/posterior exposure is effective and safe in managing congenital hemivertebra. Correction results were comparable to posterior-only procedures and staged anterior-posterior procedures.

Lazar RD, Hall JE. Simultaneous anterior and posterior hemivertebra excision. Clin Orthop Relat Res. 1999;364:76-84.

This report described simultaneous anterior/posterior resection of the hemivertebra and correction of deformity with posterior instrumentation in 11 patients, with immediate postoperative curves averaging 13 degrees (range, 1 to 40 degrees). At a mean of 28 months follow-up, the curves averaged 14 degrees (range, 1 to 47 degrees).

McMaster MJ, Ohtsuka K. The natural history of congenital scoliosis: a study of two hundred and fifty-one patients. J Bone Joint Surg Am. 1982;64:1128-1147.

This study described the natural history of congenital scoliosis in 251 patients.

Nasca RJ, Stilling FHIII, Stell HH. Progression of congenital scoliosis due to hemivertebrae and hemivertebrae with bars. J Bone Joint Surg Am. 1975;57:456-466.

This study reported that the rate of progression of the scoliosis was variable, ranging from 1 to 33 degrees per year (average, 4 degrees per year).

Ruf M, Harms J. Posterior hemivertebra resection with transpedicular instrumentation: early correction in children aged 1 to 6 years. Spine. 2003;28:2132-2138.

This study advocated early correction surgery of congenital scoliosis, before the development of severe local deformities and secondary structural changes.

Shono Y, Abumi K, Kaneda K. One-stage posterior hemivertebra resection and correction using segmental posterior instrumentation. Spine. 2001;26:752-757.

The results of this paper indicate that correction of kyphoscoliosis caused by a single hemivertebra can be treated by one-stage posterior hemivertebra resection and correction using segmental posterior instrumentation.

Solomon BD. VACTERL/VATER Association. Drphanet J Rare Dis. 2011;6:56.

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