Posterior Lumbar Pedicle Subtraction Osteotomy/Decancellation for Fixed Post-Surgical Sagittal Imbalance Syndrome

Introduction: Fixed sagittal imbalance leads to a disabling crouched posture with compensatory hip and knee flexion. Treatment requires rebalancing the spine with one or more osteotomies. There are few reports documenting results and complications for correction of fixed sagittal imbalance.

Study Design: This is a retrospective analysis of consecutive cases involving fixed post-surgical sagittal imbalance syndrome treated with three-column pedicle subtraction osteotomy/decancellation by one surgeon at a university hospital.

Objective: Evaluate the radiographic and functional outcomes of a reconstructive realignment procedure for fixed sagittal imbalance, and discuss complications.

Methods: Twenty of twenty-five patients were eligible for 2-year minimum follow-up. Patients were evaluated by standardized upright radiographs, chart review, and questionnaire.

Results: All patients underwent posterior pedicle subtraction/decancellation osteotomy with modern bilateral pedicle screw-hook-rod construct. Seven of twenty were augmented with anterior interbody grafting for associated pseudarthrosis, scoliosis or coronal decompensation. The majority of osteotomies were performed at L3 (thirteen); others included L2 (four), L4 (two), and L5 (one). There were five male and 15 female patients with average age 49.0 years (range, 33-74). Average length of follow-up was 4.0 years (range, 2.0-8.2 years). All patients had at least one prior operative procedure. Diagnostic categories included 15 patients with postoperative iatrogenic flatback, three with post-traumatic deformities, one with congenital scoliosis, and one with severe lumbar spondylosis leading to sagittal decompensation. All patients complained of back pain with deformity, and ten of 20 patients had a preoperative neurological deficit. Standardized lateral upright radiographs demonstrated mean preoperative thoracic kyphosis of 27º which improved to 41º (P = 0.006). Lumbar lordosis preoperatively averaged 10º (range, 55º to -65º (kyphosis)) and improved to 51º (range, 20-99º). Average lumbar lordosis correction was 41º (P <0 .0001). Coronal balance did not change significantly. The sagittal vertical axis (SVA) measured from C7-S1 demonstrated a preoperative decompensation averaging 10.7 cm (range, 6-23 cm) with correction to 2.0 (8.7 average correction, P < 0.0001). Intraoperative complications included three dural tears and one nerve root injury. Early- late-postoperative were relatively common. Ten patients required revision surgery including pseudarthroses instability, coronal treated reinstrumentation, two epidural hematomas, painful spinal implants, deep infection, residual stenosis. One patient had superficial wound infection successfully antibiotics, another pedicle screw pull-out managed nonoperatively. Outcome was reviewed simple questionnaire of satisfaction. majority either satisfied or somewhat satisfied, would elect undergo the same procedure.

Conclusions: Pedicle subtraction osteotomy/decancellation procedure is an effective method for restoring fixed sagittal imbalance and providing biomechanical stability. Most patients are satisfied, particularly when balance is achieved. The high complication rate mandates a careful assessment of the potential risks and benefits before undertaking a major reconstructive procedure.