Final instrumentation is then performed with long rods that can bypass the osteotomized levels, allowing for simpler contouring. If desired, a cross connector can be placed between the long rod of the fusion construct and the short rod holding the osteotomy. The rest of the fusion procedure is completed in standard fashion with at least 1 subfascial drain.
Results
Our 17 patients’ results are summarized in the Table. Mean sagittal plumb line improved from 17.7 cm (range, 5.9 to 29 cm) before surgery to 4.5 cm (range, –0.2 to 12.9 cm) after surgery, for a mean improvement of 13.2 cm. At final follow-up, mean sagittal plumb line was 5.1 cm (range, –1.4 to 10.2 cm).
Mean lumbar lordosis improved from 10° (range, –14° to 34°) before surgery to 49° (range, 36° to 63°) after surgery, for a mean improvement of 39°. Mean PSO angle improved from 3° (range, –36° to 23°) before surgery to 41° (range, 25° to 65°) after surgery, for a mean improvement of 38°. At final follow-up, mean lumbar lordosis remained at 47° (range, 26° to 64°), and mean PSO angle was 39° (range, 24° to 59°).
Mean thoracic kyphosis improved from 18° (range, –8° to 52°) before surgery to 30° (range, 3° to 58°) after surgery, for a mean improvement of 12°. At final follow-up, mean thoracic kyphosis was 31° (range, 2° to 57°).
Fourteen patients did not have complications during the study period. Of the 3 patients with complications, 1 had an early infection, treated effectively with irrigation and débridement and intravenous antibiotics; 1 had a late deep infection, treated with multiple débridements, hardware removal, and, eventually, suppressive antibiotics; and 1 had cauda equina syndrome (caused by extensive scar tissue on the dura, which buckled with restoration of lordosis leading to cord compression), treated with duraplasty, which resulted in full neurologic recovery.
Discussion
In the present series of patients, the described technique for facilitating PSO for correction of sagittal imbalance was effective, and complications were similar to those previously reported.
The benefit of the outrigger construct is that it allows controlled compression of the osteotomy site and can be left in place at time of final instrumentation, locking in compression and correction. Other techniques involve removing the temporary rod and replacing it with final instrumentation4,5—an extra step that complicates instrumentation of the additional levels of the fusion construct and possibly adds pedicle screw stress and contributes to loosening when the new rod is reduced to the pedicle screw. The final long rod construct can bypass the osteotomy levels and allow for simpler instrumentation.
Mean age was 58 years in this series versus 52.4 years in the series reported by Bridwell and colleagues.2 Given the higher mean age of our patients, though no objective measures of bone quality were available, this technique is likely applicable to patients with poor bone quality.
The complications we have reported are in line with those reported in previous series, and maintenance of radiographic parameters at final follow-up indicates that this osteotomy technique allows for solid fusion constructs.
The outrigger technique for controlling PSO closure is an effective method that simplifies instrumentation during a complex revision case.