Smith-Petersen Osteotomy

Despite different origins, the terms Smith Petersen osteotomy and Ponte osteotomies are often used interchangeably.

• The Smith-Petersen osteotomy (SPO) was first described in 1945 for patients with a kyphotic deformity and an ankylosed spine secondary to rheumatic conditions (ie, ankylosing spondylitis).¹ The technique utilized the posterior vertebral body (middle column) as the fulcrum to obtain deformity correction through the fused disc spaces. Consequently, the anterior column was lengthened and the posterior column shortened in the treatment of "flexion"-type deformity. This method essentially created a fracture through the fused discs, violating the anterior longitudinal ligament with a high associated incidence of vascular injuries.

• The Ponte-type osteotomy was first described by Ponte et al in 1984 for Scheuermann’s kyphosis;² the terminology first entered the U.S. literature in 2007.³ The Ponte osteotomy was described as wide segmental osteotomies followed by posterior compression along unfused regions of the kyphotic deformity in patients with Scheuermann’s kyphosis.

Although today the terms are often used interchangeably, the current technique more closely resembles the release as described by Alberto Ponte. In addition, SPOs have become a mainstay in correction of coronal deformities, such as adolescent idiopathic scoliosis; however, this was not an originally described indication for this release.

What Is It?

The SPO and Ponte osteotomy is a release of the posterior spinal articulations, in the presence of a mobile disc, to increase flexibility and reduceability of spinal deformity, such as scoliosis and kyphosis.

What Is Resected?

Supra-spinous ligament, Intra-spinous ligament, ligamentum flavum, and superior and inferior articular processes

Indications

• Deformity with a mobile anterior column
• Sagittal plane deformity, such as kyphosis
  • Symmetric shortening of the posterior column
  • Sagittal correction obtained per level
    • 10 to 15 degrees per level
    • 1 degree/mm of bone resected
• Scoliotic deformity
  • Shorten the concavity, lengthen the convexity, and displace the patient towards the concavity
• Deformity correction is required over multiple segments
• Fixed angular deformity a relative contraindication

Preoperative Planning

• Must have good baseline neuro-monitoring (tcMEP and SSEP)
• Our institutional preference for SPO
  • Coronal deformity: Perform from cobb-to-cobb of deformity
  • Sagittal deformity: Perform from end-to-end of vertebrae

Positioning

• Standard prone positioning on a Jackson Spine Frame, with hips extended if significant contractures are not present. Maintain a free abdomen to decrease epidural bleeding.

Approach

• Standard sub-periosteal posterior spinal exposure
  • Past tips of transverse process

Techniques

• Objective in native spine: Removal of the posterior ligaments (supraspinous, intraspinous, and ligamentum flavum) and superior and inferior facets
• Objective in fused spine: An osteotomy through the foramen bilaterally, between the pedicles above and the pedicles below
• Technique in "virgin” thoracic spine
• Perform inferior facetectomy
  • May be performed with osteotome or round bur
• Using a rongeur resect the supra-spinous and inter-spinous ligaments, exposing the ligamentum flavum
• Dissect the ligamentum flavum to expose underlying epidural fat
• Under-cut and resect the remainder of the ligamentum flavum with Kerrisons
• Resect the superior articular facet and underlying joint capsule

Pearls and Pitfalls

• Osteotomies should be performed with good baseline neuro-monitoring whenever possible
• Use osteotomy site to palpate medial wall of pedicle to aid in placement of pedicle screws
• In prior fusion, use the transverse process, if present, to identify pedicle location
• In the absence of relevant anatomic landmarks, use fluoroscopy to identify pedicle location and place pedicle markers to guide osteotomy
• Clearly identifying the location of the pedicle on the concavity of a severe coronal deformity is critical for performing a Ponte osteotomy. This will prevent resection of the medial wall of the pedicle or resecting across the lamina to the neighboring foramen.

Outcome

• 3 SPOs achieve degree of correction comparable to a single PSO
• No difference noted in fusion rates
• No difference in the Oswestry Disability Index
• Pedicle subtraction osteotomy experienced greater sagittal plane imbalance correction
• Pedicle subtraction osteotomies had a reduced risk of coronal decompensation ⁴
• Ponte is fast, safe, and effective vs. more complex and destabilizing 3-column osteotomy (ie, pedicle subtraction osteotomy)
  • Decreased blood loss
  • Decreased OR time
  • Decreased neurologic risk

References

1. Smith-Petersen MN, Larson CB, Aufranc OE: Osteotomy of the spine for correction of flexion deformity in rheumatoid arthritis. J Bone Joint Surg 1945;27: 1-11.
2. Ponte A, Vero B, Siccardi GL (eds): Surgical Treatment of Scheuermann’s Hyperkyphosis. Bologna: Aulo Gaggi,1984.
3. Shufflebarger HL, Clark CE: Thoracolumbar osteotomy for postsurgical sagittal imbalance. Spine 1992;17(8S):S287-90.
4. Cho KJ, Bridwell KH, Lenke LG, Berra A, Baldus C: Comparison of Smith-Petersen versus pedicle subtraction osteotomy for the correction of fixed sagittal imbalance. Spine (Phila Pa 1976) 30:2030--2038, 2005.

Additional Reading

Bridwell KH: Decision-making regarding Smith-Petersen vs. pedicle subtraction osteotomy vs. vertebral column resection for spinal deformity. Spine (Phila Pa 1976) 31 (19 Suppl): S171--S178, 2006.

Geck MJ, Macagno A, Ponte A, Shufflebarger HL: The Ponte procedure: posterior only treatment of Scheuermann’s kyphosis using segmental posterior shortening and pedicle screw instrumentation. J Spinal Disord Tech 20:586--593, 2007.

Lichtblau PO, Wilson PD: Possible mechanism of aortic rupture in orthopaedic correction of rheumatoid spondylitis. J Bone Joint Surg Am 38-A:123--127, 1956.