Grade 2 osteotomy

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SRS-Schwab osteotomy classification

• Indication
• Long, gradual, rounded kyphosis eg Scheuermann kyphosis.
• Apex of a rigid coronal curve to enhance curve flexibility and correction.
• Osteotomy creates a window through which the pedicles can be palpated for more confident screw insertion.

• Degree of kyphotic correction
• 9.3–10.7° per level.
• 1°/mm of bone resected.

• Surgical Principles
• Require a mobile disc space anteriorly.
• Disc space typically compresses posteriorly and expands anteriorly with a fulcrum between
• Uses the disc space as a fulcrum to effect anterior column lengthening and posterior column shortening.
• Removal of the
• Posterior ligaments (supraspinous, intraspinous, and ligamentum flavum) AND
• Facets to produce a posterior release
• For coronal correction and sagittal plane realignment.
• Compression of the osteotomy brings about kyphosis correction.
• Compression leads to contraction of the neural foramina, which necessitates a preceding wide facetectomy to prevent nerve root impingement.

• Outcome
• Cho 2005:
• 3x SPOs = 1x PSO interms of sagittal correction with half the blood loss
• 10.7° of sagittal correction per level.
• Blood loss tends to be less.
• Cho 2005: Average blood loss
• SPO: 1392 ml
• PSO: 2617 ml
• Fusion rates
• Cho 2005: similar between SPO and PSO
• ODI
• Cho 2005: similar between SPO and PSO
• Sagittal plane imbalance correction
• Cho 2005: PSO>SPO
• (≥ 3 SPOs 5.49 ± 4.5 vs PSO 11.19 ± 7.2 [p < 0.01])
• Greater coronal decompensation
• Cho 2005: SPO>PSO

• Complication in SPO>PSO
• Cho 2005:
• Lesser complication with SPO

• In AIS
• Primarily used to improve sagittal plane mobility, especially in cases of hypokyphosis (<20°) or hyperkyphosis (>40°).
• Studies have shown significant improvements in thoracic kyphosis (e.g., from 8.1° to 18.3° for hypokyphosis, or reduced from 45° to 26° for hyperkyphosis).
• Can achieve greater thoracic Cobb angle correction (e.g., 67.1% vs. 61.8%) and better rib prominence correction (e.g., 53.2% vs. 38.4%) compared to Grade 1 osteotomies in some studies.
• Associated with increased surgical complexity, including higher estimated blood loss and longer operative time compared to Grade 1 osteotomies.
• Indications:
• Typically reserved for patients with thoracic sagittal plane deformities (e.g., hypokyphosis < 10° or hyperkyphosis > 40°) or severe, rigid coronal deformities (>70–90°) with limited flexibility (>40° on dynamic imaging).