The patterns of loss of correction after posterior wedge osteotomy in ankylosing spondylitis-related thoracolumbar kyphosis: a minimum of five-year follow-up

Abstract

BackgroundShort-term studies have demonstrated good surgical outcomes after pedicle subtraction osteotomy (PSO) in ankylosing spondylitis (AS) patients, but there is a paucity of literature focused on middle-term results, especially regarding patterns of loss of correction. The objective of this study is to assess the durability of surgical outcomes and the patterns of loss of correction in thoracolumbar kyphosis secondary to AS following lumbar PSO with over 5-year follow-up.MethodsWe performed a retrospective review of 155 consecutive AS patients undergoing lumbar PSO from January 2001 to December 2011. Twenty-four patients were included with an average follow-up of 6.9 years (range, 5–15 years). Radiographical evaluations included global kyphosis (GK), lumbar lordosis (LL), sagittal vertical axis, spinal-sacral angle, kyphosis of proximal non-fused segments (KPNS), angle of fused segments (AFS), osteotomized vertebra angle (OVA), distal intervertebral disc wedging (DIDW) and proximal junctional angle. Meanwhile, clinical outcomes were assessed by the Oswestry disability index (ODI) and Numerical rating scale (NRS).ResultsThe average correction per PSO segment was 34.9°. Significant improvement in sagittal parameters were found postoperatively, and no obvious deterioration was noticed during the follow-up. Mild loss of correction in GK (2.82°) and LL (3.77°) were observed at the final follow-up (P < 0.05). The KPNS and DIDW increased from 26° and −5.0° postoperatively to 30° and −2.2° at the final follow-up (P < 0.05), respectively. In contrast, no significant diminishment was identified in OVA and AFS (P > 0.05). The ODI and NRS improved significantly from 20.6 and 6.6 preoperatively to 5.9 and 2.3 at the final follow-up (P < 0.05).ConclusionsPSO is an effective procedure for treating AS-related thoracolumbar kyphosis and can maintain sustained surgical outcomes during the middle-term follow-up. The loss of correction was mainly attributable to non-instrumented segments without fully ossified bridging syndesmophyte in the thoracolumbar region instead of instrumented levels.

Comparison of loss of correction between PSO and VCD technique in treating thoracolumbar kyphosis secondary to ankylosing spondylitis, a minimum 2 years follow-up

“…The SVA decreased from approximately 171–174 mm before the surgery to average 59 mm in the PSO group and 63 mm in the VCD group after surgery and maintained till the final follow-up. Despite the immediate satisfactory surgical results, mild loss of correction of GK was observed in both groups in the long-term follow-up with no significant difference, which was in line with the previous studies [7, 14]. However, different from Qiao’s study [14], no significant changes were observed in the correction loss of lumbar lordosis.…”

“…In Zhu’s study [7], loss of correction in the GK of SPOs technique (3.9°) and PSO technique (2.4°) was identified 2 years after surgery. More recently, Mu [14] conducted a retrospective research in PSO-treated AS patients using comprehensive methods in analyzing the radiographic parameters and found a worsening of GK (2.82°) combined with decreased LL (3.77°) at the last visit of 6.9 years postoperatively. To our best knowledge, it remains unclear of the difference between PSO and VCD techniques on correction loss in long-term follow-up.…”

“…2b); (6) proximal junctional angle (PJA) [11], determined by the angle between the caudal endplate of the upper instrumented vertebra and the cranial end plate of two vertebrae above. Proximal junctional kyphosis (PJK) was defined as a kyphosis of the junctional area which was > 10° and at least 10° greater than the preoperative measurement [12, 13]; (7) kyphotic angle of proximal non-fused segment involved in the GK (KPNS) [14]: the angle between the superior endplate of the preoperative maximally tilted upper end vertebra and the superior endplate of upper end vertebra of the fused segments (Fig. 2b); and (9) the sum of distal non-fused intervertebral disc wedging (DIDW) (Fig.…”

“…2b). The angle is positive if the curve is kyphotic and negative if the curve is lordotic in LL [14]. All of the parameters were measured by an orthopedic resident three times using surgimap software (Nemaris, New York, NY) and the average values were calculated (Fig.…”

The clinical relevance of the presence of bridging syndesmophytes on kyphosis correction and maintenance following pedicle subtraction osteotomy for thoracolumbar kyphotic deformity in ankylosing spondylitis: a comparative cohort study

“…This higher possibility of correction loss for patients in NBG may be due to the fact that patients in this subgroup mostly had earlier forms of AS with underlying active inflammation. And their osteoproliferation process progressed during follow-up, developing collapse of proximal and distal discs, decreasing the mobility of non-fused segments, increasing the kyphotic angle of non-instrumented segments involved in the global kyphosis, and finally detracting from the initial correction [ 24 , 30 ]. This was also mirrored by the fact that 20.5% of the patients in NBG developed bridging syndesmophytes at the neighboring disc level by the ultimate follow up.…”