Comparison of three types of lumbar osteotomy for ankylosing spondylitis: a case series and evolution of a safe technique for instrumented reduction

The principles of correction of thoraco-lumbar kyphotic deformity (TKLD) in ankylosing spondylitis (AS) are essentially centred on lordosing osteotomies such as pedicle subtraction closing wedge osteotomy (CWO), polysegmental posterior lumbar wedge osteotomies (PWO) and Smith Peterson's open wedge osteotomy (OWO) of the lumbar spine. There have been no studies that compared the results of the three osteotomies performed by a single surgeon with a long-term follow-up. A retrospective review of 31 patients with AS was performed: 12 patients underwent CWO, 10 had OWO, and 9 had PWO. Radiographic assessment was performed at 6, 12, 24, and 52 weeks and annually thereafter. Clinical assessment included blood loss, intensive care unit (ICU) stay, and surgical time recordings. All patients were assessed clinically at regular intervals and outcome measures recorded included Oswestry Disability Index (ODI), Visual Analogue Score (VAS) for pain, and SRS-22 (recorded in 23 patients). The mean age at surgery was 54.7 years (40-74 years) and mean duration of symptoms was 3 years (range, 5-8 years). Mean follow-up was 5 years (range, 2-10 years). There was no statistically significant difference between the three techniques with regard to mean duration of surgery and ICU stay. The mean duration of surgery was 7 h (range, 4-9 h) (OWO cases had shorter period than CWO and PWO cases, and the longest period was for CWO cases). The mean ICU stay was 3 days (range, 2-20 days) (the period of stay was shorter in general for OWO and slightly longer for CWO and PWO). Blood loss was expressed as percentage of estimated blood volume (EBV). The mean blood loss in PWO was 23 +/- A 15.4% (range, 9-36%), CWO was 28 +/- A 4.5% (range, 12-40%) and in OWO was 15 +/- A 11% (range, 13-99%). Mean correction of kyphosis was 38A degrees (range, 25A degrees-49A degrees) with CWO, 28A degrees with OWO (range, 24A degrees-38A degrees) and 30A degrees with PWO (range, 28A degrees-40A degrees). In comparison to preoperative scores, statistically significant improvement was noted in all three groups in the postoperative period with regard to ODI, VAS and SRS-22 (p = 0.001, Wilcoxon signed-rank test). Better radiographic correction was noted in the CWO and PWO groups, although this was associated with increased blood loss, multiple levels of instrumentation, and increased surgical time compared to OWO. A new safe technique of instrumentation using temporary malleable rods to prevent sagittal translation during the reduction manoeuvre is also described.