DEFINITION

Posterior vertebral column resection (VCR) entails the removal of the anterior, middle, and posterior columns of the vertebra(e) through a posterior-alone approach.

VCR is often performed at the apex of a deformity for severe, rigid scoliotic and kyphotic spinal deformities.

 

 

ANATOMY

 

A thorough understanding of the anatomy of the vertebral segment and spinal cord is needed to safely perform this procedure. This includes understanding the peculiarities of rotated vertebral segments in severe scoliotic deformities. The morphologic and iatrogenic changes of the posterior elements must be appreciated, as must the course of the spinal cord and nerve roots.

PATHOGENESIS

 

The origins of these deformities are multiple and varied, including congenital, idiopathic, neoplastic, traumatic, and iatrogenic causes.

NATURAL HISTORY

 

The natural history of the diseases leading to severe scoliotic, kyphotic, or combined deformities are variable.

 

Those that do progress to severe, rigid deformities may present with intolerable deformity, severe pain, decreased ability to perform activities of daily living, myelopathy/spinal cord compression, and pulmonary dysfunction.

 

Those fixed deformities that are asymptomatic (ie, a wellbalanced patient without complaint) may be managed nonoperatively. However, one must obtain careful follow-up to assess for possible deformity progression over time.

PATIENT HISTORY AND PHYSICAL FINDINGS

 

The overall coronal and sagittal plane balance should be observed with the patient standing upright.

 

The deformity should be assessed for any flexibility by placing the patient prone and supine on the examination table. Several minutes of supine positioning will allow one to assess the flexibility of a kyphotic deformity. Often, we will have the patient lie supine on the examining table, turn the lights off, and return in 15 to 20 minutes for repeat evaluation.

 

The history should include a careful assessment of current pain medication usage as preoperative narcotic usage may complicate the perioperative care. Additionally, any medications that may confer a risk of increased bleeding (eg, aspirin) should be noted and the patient cautioned to stop them prior to surgery.

 

The use of nicotine-containing products, particularly cigarettes, is a relative contraindication to this procedure as the risk of pseudarthrosis is increased as well as perioperative complications.

 

Those patients with diabetes mellitus must have well-controlled blood glucose levels before surgery as

uncontrolled blood glucose levels are associated with increased risk of perioperative infection.

 

A patient's nutritional status should be assessed and optimized prior to surgery. In addition, a bone density test should be performed to diagnose presence of osteoporosis and initiate preoperative treatment of any deficiencies.

 

The patient's gait should be assessed for evidence of myelopathy (eg, wide based, shuffling gait).

 

A detailed neurologic examination must be performed and documented, including examination for pathologic reflexes such as asymmetric abdominal reflexes, Babinski response, and sustained clonus. Pathologic reflexes must alert the surgeon to possible intraspinal pathologies (eg, Chiari II, syrinx, tethered cord) that may need to be addressed prior to the deformity correction.

 

Preoperative examinations by a primary care physician, a cardiologist (including stress testing as indicated), and an anesthesiologist is mandatory to mitigate any risks of perioperative morbidity and mortality.

 

A review of systems should include a review of the respiratory system and any history of respiratory compromise or distress. Preoperative pulmonary function tests should be obtained in all patients with a deformity severe enough to be considered for a VCR procedure.

IMAGING AND OTHER DIAGNOSTIC STUDIES

 

A radiographic spinal deformity series is obtained, which includes standing anteroposterior (AP) and lateral long-cassette radiographs, left and right side bending, full AP, and lateral supine or prone images (FIG 1).

 

Flexibility radiographs include push-prone and axial traction x-rays and help assess coronal plane rigidity.

 

Hyperextension radiographs (bolster placed at apex of kyphosis) and hyperflexion radiographs (bolster at apex of lordosis) help assess sagittal plane rigidity.

 

A three-dimensional (3-D) computed tomography (CT) scan is obtained to evaluate the entire anterior and posterior spinal column. This aids in the identification of important vertebral landmarks (FIG 2).

 

Skull to sacrum magnetic resonance imaging (MRI) is necessary to evaluate the entire neural axis (eg, Chiari malformation, syringomyelia, tethered spinal cord) (FIG 3).

 

DIFFERENTIAL DIAGNOSIS

Severe scoliosis Global kyphosis

49

 

 

 

 

FIG 1 • A-D. Case 1. Fifty-eight-year-old woman with adult idiopathic thoracic kyphoscoliosis. E,F. Case 2. Six-year-old boy with severe congenital kyphoscoliosis. G-J. Case 3. Seven-year-old girl with a severe 153-degree postlaminectomy kyphosis with myelopathy. She was placed in preoperative halo-gravity traction.

 

 

50

 

 

 

FIG 2 • A,B. Posterior and anterior 3-D CT scans, respectively, of a patient with severe idiopathic scoliosis.

C. Case 3. Preoperative sagittal MRI scan shows postlaminectomy kyphosis with draping of the spinal cord.

D. Case 3. Preoperative 3-D CT scan shows the laminectomy defect.

 

Angular kyphosis Kyphoscoliosis

Fixed coronal and sagittal imbalance syndrome (eg, status post-Harrington rod instrumentation)

 

 

NONOPERATIVE MANAGEMENT

 

Patients with static deformities and only mild pain or physical impairment should be managed with a trial of nonoperative therapy.

 

 

 

 

FIG 3 • A-C. Case 2. Patient's total spine MRI demonstrated a syringomyelia, diplomyelia, and a tethered spinal cord.

 

 

This includes a directed physical therapy program, to include cardiovascular conditioning, postural training, and abdominal strengthening.

 

For those patients with moderate to severe pain, a referral to a pain specialist, most notably for those patients with complaints of pain not consistent with their presenting pathology or other signs of nonorganic causes of pain

 

As with nerve root compression, epidural and transforaminal steroid injections offer a less invasive, potentially diagnostic and/or therapeutic intervention.

 

 

 

SURGICAL MANAGEMENT

51

 

Classically, rigid deformities were treated with staged anterior and posterior procedures to resect and reconstruct the spine through the rigid segment.2,3,4 The posterior VCR allows a similar correction of deformity, with the benefits of shorter total operative time and lower blood loss.6

 

Location of the deformity often determines whether a VCR (thoracic) or pedicle subtraction osteotomy (lumbar) will assist in correction of sagittal imbalance. For less severe and flexible deformity with mobile disc spaces, multilevel

Ponté/Smith-Petersen osteotomies may be adequate for deformity correction.1

 

Flexibility films will help determine whether a three-column osteotomy is needed versus posterior column osteotomies alone. Posterior column osteotomies may on average correct 10 degrees of kyphosis per level of osteotomy dependent on the spinal level being osteotomized. For large, angular deformities, a three-column osteotomy allows for greater correction in the coronal and sagittal planes.

 

We perform VCR in place of anterior and posterior procedures, electing to perform the correction through one single approach.

 

The VCR is almost invariably performed at the apex of the deformity.

 

Preoperative Planning

 

A multidisciplinary team approach is often necessary in the treatment of patients with complex deformity that requires a VCR.

 

Preoperative assessment of the patient's cardiovascular, pulmonary, nutritional, hematologic, and metabolic systems is required to maximize the patient's preoperative reserve.

 

Careful examination of the preoperative CT scan should alert the surgeon to areas of bony deficiency in the posterior elements to prevent incidental durotomies (see FIG 2C,D).

 

Positioning

 

The patient is positioned prone on an OSI Jackson frame with six pads, which are placed strategically to allow the abdomen to rest free, reducing intra-abdominal pressure and intraoperative bleeding.

 

We prefer to place a halo or Gardner-Wells tongs with 5 to 15 pounds of traction that allows for rigid positioning of the skull with the face free.

 

The arms are placed in a 90-90 position with care to position the axillae free and elbows well padded to decrease the risk of brachial plexopathy or ulnar nerve neuropathy.

 

Pressure areas are carefully padded as the length of the procedure increases the risk of position-related complications (eg, skin macerations, plexopathies).

 

The hips are gently extended and the knees slightly flexed with the use of multiple pillows.

 

Spinal cord monitoring leads are placed to monitor the sensory and motor function of the lower extremities.

 

Approach

 

The standard posterior, subperiosteal approach is used.

TECHNIQUES

• Exposure

A subperiosteal approach is undertaken from the transverse processes of the most superior instrumented

 

level to the most distal vertebra or ilium to be instrumented/fused (TECH FIG 1).

 

 

 

TECH FIG 1 • A. Schematic of posterior exposure. B. Intraoperative view of posterior exposure of fusion mass in preparation for VCR.

 

 

Thoracoplasties may be necessary at apical vertebrae to obtain adequate exposure of the transverse processes at the apex of a severe scoliosis or kyphoscoliosis deformity.

 

 

 

Intraoperative radiographs or fluoroscopy should always be used to confirm vertebral levels. An efficient, meticulous exposure is necessary to minimize blood loss.

 

• Facet Osteotomies

   

  52

   

  Inferior facetectomies are performed at every level where motion exists, resecting approximately 3 to 4 mm of the inferior facet joint.

   

  Ponté or Smith-Petersen osteotomies are performed around the apex of the deformity, usually from the upper end vertebra to one level below the lower end vertebra. The ligamentum flavum and facet joints are excised.

   

  These osteotomies allow for more harmonious correction of the deformity as well as offering access to the medial pedicle to aid in screw placement at the concavity of the deformity.

   

  In those patients with severe apical kyphosis, we will place pedicle screws prior to any osteotomies. A temporary rod is placed prior to any osteotomy to prevent sagging of the vertebral column, which can put the spinal cord at risk of neurologic impairment.

  Pedicle Screw Placement

   

  We employ a modified anatomic freehand technique with a straight-ahead screw trajectory to increase pedicle

  pullout strength.5 Assessment of preoperative imaging allows for assessment of pedicle screw diameter and length at each vertebra (TECH FIG 2).

   

   

  Pedicle screw placement is performed in a sequential fashion from distal to proximal. Placement of segmental apical screws is important to ensure rigid stabilization of the VCR site.

   

   

   

  TECH FIG 2 • A. Pedicle screws placed segmentally except at shaded apical level where resection is planned. B-D. Freehand pedicle screw placement.

   

   

  Intraoperative use of fluoroscopy, CT scan, or navigation may be used in assisting the placement of screws, especially through areas of prior fusion with distorted anatomy.

   

  Multiaxial screws (or multiaxial reduction screws) are most commonly used.

   

  Reduction screws are used when cantilever bending is needed for reduction of the rod and deformity. This is often at the distal end of a construct and in areas of hyperlordosis, where rod reduction may be difficult.

   

   

  53

• Vertebral Column Resection

Costotransversectomy and Laminectomy

 

In the thoracic spine, bilateral costotransversectomies are performed at the level of resection (TECH FIG 3A).

 

Five to 6 cm of medial rib is resected prior to the laminectomy to minimize the risk of canal intrusion.

 

After subperiosteal dissection, the medial rib fragment is removed, ideally with the rib head attached. Often, however, the rib head remains attached at the vertebral body and can be removed later during the

corpectomy.

 

The ribs are kept intact, not morselized, and are used as structural grafts to bridge the laminectomy site after osteotomy closure. Next, a wide laminectomy is performed extending from the cranial vertebral pedicles of the level(s) of resection to the caudal vertebra pedicles (TECH FIG 3B,C).

 

A thorough central decompression is necessary to prevent dorsal dural compression with osteotomy closure. Exiting nerve roots are isolated by removing the facet joints and pedicles bilaterally.

 

The nerve roots at the level of the osteotomy are temporarily clamped with a bulldog-type vascular clamp for 5 to 10 minutes and attention is turned to any spinal cord, monitoring data changes.

 

In the thoracic spine, we prefer to ligate the nerve roots medial to the dorsal root ganglion.

 

If spinal cord monitoring data remains stable, then the nerve root is ligated with two 2-0 silk sutures.

 

In our experience, two or three contiguous, unilateral thoracic roots can be sacrificed without neurologic deficits, except for occasional chest wall numbness.

 

In the lumbar spine, the nerve roots are preserved.

 

 

 

TECH FIG 3 • A. Shaded area on ribs adjoining to vertebra to be resected via bilateral costotransversectomy. B. Laminectomy and nerve root ligation. C. Laminectomy and undercutting of ventral aspect of fusion mass.

 

Stabilizing Rod Placement

 

In preparation for the vertebral body resection, a unilateral stabilizing rod is placed with pedicle screws two or three levels above and below the level of resection (TECH FIG 4).

 

For extreme angular kyphotic or kyphoscoliotic deformities, bilateral rods are used to prevent subluxation of the vertebral column.

Vertebral Body Removal and Discectomy

 

The cancellous bone of the vertebral body is accessed via a lateral pedicle body window. Subperiosteal dissection on the lateral vertebral body is done with a combination of blunt dissection tools and electrocautery. The paraspinal structures are carefully peeled away until access to the anterior vertebral body is gained. Special retractors may help protect these structures during the corpectomy (TECH FIG 5A).

 

The cancellous bone is then curetted and saved for use as local bone graft.

 

Resecting the concave pedicle poses a challenge, as it is very cortical.

 

In a pure scoliosis deformity, the dural sac and cord rest on the medial pedicle, with no ventral body due to rotation.

 

We prefer to use a matchstick burr to remove this cortical bone in these situations.

 

In these deformities, most of the vertebral body will be removed from the convexity.

 

The concave pedicle is removed first as blood may obscure the field if the convexity is removed first. This also allows the cord to drift medially, away from the majority of the resection.

 

54

 

 

 

TECH FIG 4 • Stabilizing rod placement.

 

 

 

TECH FIG 5 • A. Lateral vertebral body access. B. Vertebral body removal beginning at posterolateral edge of vertebra. C. Vertebral body removal continued. (continued)

 

 

The entire vertebral body is removed except for a thin section preserving the anterior longitudinal ligament (ALL) (TECH FIG 5B,C).

 

Discectomies are performed at the levels above and below the vertebral body resection (TECH FIG 5D,E).

 

Care must be taken to preserve the endplates for cage placement.

 

The last section of the vertebral body, which is removed by impaction, is the posterior vertebral body wall or ventral spinal canal (TECH FIG 5F).

 

The dural sac must be freed from the posterior longitudinal ligament.

 

The posterior body wall is removed with reverse-angled curettes, Woodson elevators, or a specialized posterior wall resector (PSO tool set; Medtronic Spinal and Biologics, Memphis, TN).

 

Care must be taken to remove any posterior osteophytes to prevent cord impingement during the correction.

 

 

55

 

 

 

TECH FIG 5 • (continued) D. Discectomy is performed above and below corpectomy level. E. Intraoperative view of discectomy. F. Posterior vertebral body wall impaction in final aspect of body removal.

• Closure of Resection Site

 

Closure of the resected area is now performed with compression (TECH FIG 6A). Compression of the convexity allows for shortening of the spinal column. Sequential compression on the convexity and distraction of the concavity, performed in an alternating fashion, allows for safe reduction of the deformity through a shortening procedure. Distraction is not an initial technique as this may put traction on the spinal cord and cause a neurologic deficit.

 

In cases with large degrees of kyphosis, a structural cage is placed anteriorly. This prevents overshortening and acts as a hinge for greater correction of the kyphotic deformity (TECH FIG 6B,C).

 

To choose the cage height, close the osteotomy approximately 50%. Ensure that no excessive dural buckling has occurred and that neurological monitoring data are unchanged. After using trial sizers, place a cage that fits approximately endplate to endplate and compress around the cage.

 

In cases with good pedicular fixation, compression is applied through the screws.

 

In cases with less rigid pedicular fixation, a closure is performed, with dominoes at the level of the resection.

 

Care must be taken to watch for subluxation or dural sac impingement during closure.

 

To create a configuration, rods are cut and contoured to fit the deformity above and below the level of resection. These rods are then fixed in place with set screws, which are tightened. The rods are connected to each other via domino connectors. Thus, compression and distraction forces are applied to

the rods through the domino and a rod gripper, with the forces distributed across the multiple pedicle screws above or below the domino connector.

 

After the closure is performed, a contralateral rod is placed. The temporary stabilization rod is removed, and a final rod is placed (TECH FIG 6D,E).

 

In situ contouring of the rods is performed, again with care taken to watch for subluxation at the resection or dural sac impingement.

 

Intraoperative radiographs are obtained to check alignment.

 

Decortication of dorsal laminae and transverse processes is performed with a matchstick burr.

 

The laminectomy defect at the site of resection is covered with the resected rib sections (from the previously performed costotransversectomy) (TECH FIG 6F).

 

The ribs are split longitudinally, and placed, cancellous side down, from the lamina above to the lamina below.

 

The ribs may be secured with sutures or a cross-link, if space allows.

 

A final circumferential check of the dura is performed to ensure no dural sac impingement.

 

 

56

 

 

 

TECH FIG 6 • A. Posterior shortening is always the initial corrective maneuver. B,C. Cage placement is performed before final closure. D,E. Final correction with both rods placed. F. Rib grafts placed over laminectomy defect.

• Wound Closure

Deep drains are placed, and the fascial layer closed using 0 Vicryl (Ethicon, Somerville, NJ). A suprafascial drain is placed and the subcutaneous layer closed using 2-0 Vicryl suture. The skin is closed using absorbable 3-0 Vicryl suture.

A rehearsed wake-up test is performed prior to extubation. Deleting an intraoperative wake-up test is performed.

Final radiographs are obtained to confirm implant position and overall alignment.

 

 

57

 

PEARLS AND PITFALLS

 

Preoperative planning

• A multispecialty approach to preoperative surgical clearance should include cardiac, pulmonary, hematologic, and bone mineral density workups.

• Use of neuromonitoring of motor and sensory pathways is mandatory.

   

  Vertebral column resection

  • Prior to starting VCR, mean arterial pressure should be kept at 80 mm Hg to help with spinal cord perfusion, hemoglobin should be close to 30, and room should be warmed.

  • Subperiosteal dissection of lateral vertebral body wall with careful attention to save segmental vessels will minimize blood loss.

  • Temporary rod placement prior to decompression to prevent subluxation

  • Wide laminectomy from superior to inferior level pedicles with complete facetectomies

  • Identification of bilateral nerve roots. In the thoracic spine, often, only one nerve root needs to be sacrificed. Tieing off nerve root should be done medial to dorsal root ganglion.

  • Resection of vertebral body should be accomplished as much as possible from one side to minimize the number or exchanges necessary of the temporary rods.

  • The spinal cord should be free from the posterior longitudinal ligament/dorsal vertebral body prior to removal of the posterior vertebral body wall.

  • Osteotomy closure should be done slowly with constant neuromonitoring.

  • Limit osteotomy closure to approximately 2.0-2.5 cm to prevent overshortening of spinal cord.

  • Use of an anterior intervertebral cage will limit amount of spine shortening and should be placed after initial round of osteotomy closure.

     

    After resection complete

  • Neuromonitoring is followed for up to 1 hour after final osteotomy compression, and a formal neurologic examination is performed prior to leaving the operating room.

  • Rib autograft should be used as a bridge over osteotomy site to protect neural elements.

  • Deep and superficial drains may reduce postoperative hematoma/seroma formation.

 

POSTOPERATIVE CARE

 

 

Patients are often sent to the intensive care unit for close monitoring (for 24 to 48 hours as needed), then transitioned to the hospital ward.

 

Patients are mobilized on postoperative day 1.

 

 

Drains are retained until recorded output is less than 30 mL per 8-hour shift. Diet is advanced slowly with the return of bowel sounds.

 

Deep vein thrombosis prophylaxis is provided with sequential compressive devices and thromboembolic deterrent hose.

 

 

 

 

FIG 4 • A-D. Case 1. Patient underwent a posterior spinal fusion T2-L4 with a T10 VCR with radiographs demonstrating excellent alignment at 3 years postoperatively. (continued)

 

 

OUTCOMES

FIGS 4 and 5 show postoperative results in two of the patients in FIG 1. One of the authors (L.G.L.) has performed 107 consecutive posterior VCRs:

Sixty-three pediatric and 44 adult Forty-seven primary and 60 revision

Ninety-nine in the spinal cord region and 8 in the lumbar spine

Seventy-three were one-level, 28 were two-level, and 6 were three-level

58

 

 

 

 

FIG 4 • (continued) E-J. Preoperative and postoperative clinical photos.

 

 

 

FIG 5 • A-D. Case 3. Patient underwent a two-level posterior VCR and posterior spinal fusion T1-T11 with complete relief of her myelopathy (continued).

 

 

59

 

FIG 5 • (continued) E-G. Preoperative, traction, and 1-year postoperative clinical photos, respectively. Diagnoses: severe scoliosis (29), global kyphosis (16), angular kyphosis (25), kyphoscoliosis (37)

Average correction: severe scoliosis (69%), global kyphosis (54%), angular kyphosis (63%), kyphoscoliosis (56%)

Mean estimated blood loss: 1300 mL; mean operative time: 9 hours, 37 minutes

 

 

 

COMPLICATIONS

Twelve spinal cord monitoring changes: All reversed with intraoperative measures to restore spinal cord blood flow (increased mean arterial pressure, wider decompression, larger interbody cage, reduced subluxation). No neurologic deficits upon wake up.

Two neurologic deficits: Spinal cord monitoring is not available on either because of preexisting severe myelopathic disease. Both awoke paraplegic with intact sensation. Both have improved and are able to walk.

 

 

REFERENCES

1. Cho KJ, Bridwell KH, Lenke LG, et al. Comparison of Smith-Petersen versus pedicle subtraction osteotomy for the correction of fixed sagittal imbalance. Spine 2005;30(18):2030-2037.

    

    

2. Dick J, Boachie-Adjei O, Wilson M. One-stage versus two-stage anterior and posterior spinal reconstruction in adults. Comparison of outcomes including nutritional status, complications rates, hospital costs, and other factors. Spine 1992;17(8 suppl):S310-S316.

    

    

3. Johnson JR, Holt RT. Combined use of anterior and posterior surgery for adult scoliosis. Orthop Clin North Am

   1988;19(2):361-370.

    

    

4. Leatherman KD, Dickson RA. Two-stage corrective surgery for congenital deformities of the spine. J Bone Joint Surg Br 1979;61-B(3): 324-328.

    

    

5. Lehman RA Jr, Polly DW Jr, Kuklo TR, et al. Straight-forward versus anatomic trajectory technique of thoracic pedicle screw fixation: a biomechanical analysis. Spine 2003;28(18):2058-2065.

    

    

6. Lenke LG, Sides BA, Koester LA, et al. Vertebral column resection for the treatment of severe spinal deformity. Clin Orthop Relat Res 2010;468(3):687-699.