Introduction. Pedicle subtraction osteotomy is a powerful technique for correcting sagittal imbalance in ankylosing spondylitis. There has been significant perioperative morbidity associated with this technique in the peer review literature. We present the Royal National Orthopaedic Hospital experience with a single surgeon retrospective study that was conducted to evaluate the outcomes in patients who underwent lumbar pedicle subtraction osteotomy for the correction of thoracolumbar kyphotic deformity in ankylosing spondylitis. Method. Twenty seven patients underwent a lumbar pedicle subtraction osteotomy and adjacent level posterior instrumentation between 1995 and 2010. There were 18 males and 9 females in the study. Events during the peri-operative course and post-operative complications were recorded. The radiological outcome and patient satisfaction were analysed with mean follow-up of one and a half years. Results. The mean operative time was three and half hours and the mean blood loss was 2290mls. Final follow-up radiograph showed an increase in lumbar lordosis angle from 17 degrees to 45 degrees. The sagittal imbalance improved by 85mm with the operation. Complications included loosening in two patients, one transient neurologic deficit and one infective non-union occurred overall. There were no mortalities from the surgery. Two patients developed junctional kyphosis and required a repeat operation. There was an improvement in the Oswestry Disability Score from a mean of 29 to 16 after the surgey. All (100%) of the patients were satisfied with the results of the procedure and would recommend the surgey to others. Conclusion. The study shows that pedicle subtraction extension osteotomy is effective for the correction of kyphotic deformity in ankylosing spondylitis

Introduction. Pedicle Subtraction osteotomy (PRO) in correction of severe spinal deformities is well established. Prospective analysis of its efficacy in complex spinal deformities is sparse in literature. Aims and objectives. To assess the role of PRO in correction of uniplanar and multiplanar spinal deformity and to assess the role of revision PRO in failed corrections. Material and methods. 50 patients were operated between 1996-2007 and followed up for 2 years (2-6). 27 had uniplanar kyphosis (60-128 degrees) and kyphoscoliosis was seen in 10. Failed corrections were seen in 11 uniplanar and 2 multiplanar deformities. The average pre-operative kyphosis and sagittal balance was 78.7 degrees and 22 mm (7-30) respectively. Scoliotic deformity ranged from 97-138 (average 108 degrees) and the coronal imbalance from 10-55 (average 24mm). Deformity distribution was upper dorsal 5, mid dorsal 22, dorso-lumbar 18 and lumbar 5. A single posterior approach sufficed in 47 cases while 3 required an anterior approach for reconstruction. 13 patients had pre-operative neurological deficit (bedridden 10, ambulatory 3). The average surgical time required was 300 minutes and blood loss was 800cc. The anterior defect reconstructed averaged 16.5mm (5-28). Results. Pulmonary complications occurred in 8 (21%), (embolism 1, pneumonia 2, hypoxia 5). Wound infection required debridement in 3 (8%). Failed corrections were seen in 10 (3 out of 37 in our series, 8%) due to failure of construct 2, severe disease 2, infection (active 2, quiescent 4). Neurological deterioration occurred in 1(2%), medial pedicle wall perforation. 12 patients regained ambulation (independent 7, support 5). Post-operative kyphosis and sagittal balance was 36.5 (10-108) and 10mm (5-20) respectively. Average correction was: sagittal 46.4%, coronal 37.5% and revisions 58%. The correction of kyphosis and sagittal balance was statistically comparable between primary and revision cases (p >0.05). Conclusions. PRO offers an excellent single stage decompression and controlled correction of kyphosis

In posterior fixation for deformity correction and spinal fusion, there is increasing discussion around auxiliary rods secured to the pedicle screws, sharing the loads, and reducing stresses in the primary rods. Dual-rod, multiaxial screws (DRMAS) provide two rod mounting points on a single screw shaft to allow unique constructs and load-sharing at specific vertebrae. These implants provide surgical flexibility to add auxiliary rods across a pedicle subtraction osteotomy (PSO) or over multiple vertebral levels where higher bending loads are anticipated in primary rods. Other options include fixed-angle devices as multiple rod connectors (MRC) and variable-angle dominoes (VAD) with a single-axis rotation in the connection. The objective in this simulation study was to assess rod bending in adult spinal instrumentation across an osteotomy using constructs with DRMAS, MRC, or VAD multi-rod connections. The study was performed using computer biomechanical models of two adult patients having undergone posterior instrumented spinal fusion for deformity. The models were patient-specific, incorporating the biomechanics of the spine, have been calibrated to assess deformity correction and intra- and postoperative loads across the instrumented spine. One traditional bilateral-rod construct was used as a control for six multi-rod configurations. Spinal fixation scenarios from T10 through S1 with the PSO at L4 were simulated on each patient-specific model. The multi-rod configurations were bilateral and unilateral DRMAS at L2 through S1 (B-DRMAS and U-DRMAS), bilateral DRMAS at L3 and L5 (Hybrid), bilateral MRC over L3-L5, bilateral and unilateral VAD over L3-L5 (B-VAD and U-VAD). Postoperative gravity plus 8-Nm flexion and extension loads were simulated and bending moments in the rods were computed and compared. In the simulated control for each case (#1 & #2), average rod bending moments (of the right and left rods) at the PSO level were 6.7Nm & 5.5Nm, respectively, in upright position, 8.8Nm & 7.3Nm in 8-Nm flexion, and 4.6Nm & 3.7Nm in 8-Nm extension. When the primary rods of the multi-rod constructs were normalized to this control, the bending moments in the primary rods of Case #1 & #2 were respectively 57% & 58% (B-DRMAS), 54% & 62% (B-VAD), 60% & 61% (MRC), 72% & 69% (Hybrid), 81% & 70% (U-DRMAS), and 81% & 73% (U-VAD). Overall, the reduction in primary rod bending moments ranged from 19–46% for standing loads. Under simulated 8-Nm functional moments, the primary rod moments were reduced by 18–46% in flexion and 17–48% in extension. More rods and stiffer connections produced the largest reductions for the primary rods, but auxiliary rods had bending moments that varied from 49% lower to 13% higher than the primary ones. Additional rods through DRMAS, MRC, and VAD connections noticeably reduced the bending loads in the primary rods compared with a standard bilateral-rod construct. Yet, bending loads in the auxiliary rods were higher or lower than those in the primary rods depending on the 3D spinal deformity and stiffness of the auxiliary rod connections. Additional studies and patient-specific analyses are needed to optimize instrumentation parameters that may improve load-sharing in these constructs

Purpose. To review the outcome of multilevel (≥4) instrumented lumbar fusion to sacrum / pelvis performed for degenerative conditions. Methods. Clinical data of 47 consecutive patients from 2002 to 2012 were reviewed retrospectively. Inclusion criteria included fusion from at least L2 to S1 / pelvis, i.e. minimum of 4 levels. Imaging was assessed for restoration of normal sagittal profile as well as subsequent fusion. EQ5D, OSD and VAS scores pre-op and at 6 months post op were analysed. Average age at surgery was 64 years (50–78). Thirteen cases were primary and 34 revisions. Indications were axial back pain either associated with sagittal imbalance (40%) or leg pain (36%) and leg pain alone in 10%. Results. The intra-operative blood loss averaged 2222 (250–7000) ml with 40% re-infusion from cell-saver. The average surgical duration was 268 minutes. Proximal extent of instrumentation was T2 (1), T3 (1), T4 (2), T8 (1), T9 (1), T10 (17), T11 (2), T12 (5), L1 (4) and L2 (13). TLIF's were done in 20 cases mostly at the base of the construct. Pedicle subtraction osteotomies were performed in 14 revision cases. Dural tears occurred in 14 cases, all revision cases except one. Wound infection occurred in 3 cases. Except for transient quadriceps weakness related to osteotomy, no neurological complications occurred. One patient deceased peri-operatively. Subsequent revision was required in 13 cases for instrumentation failure. OSD score improved by 15.3 points on average, which is clinically and statistically significant. Conclusion. Long lumbar fusions remain technically demanding with a high incidence of adverse events. This is due to the nature of revision surgery and high biomechanical demands on constructs. Surgical intervention can however be justified by the desperation of the cohort in terms of pain and poor function which can be modestly improved with this intervention. NO DISCLOSURES