The Results and Complications of Pedicle Subtraction Osteotomies for the Treatment of Fixed Sagittal Imbalance

Lewis SJ,
Bridwell KH,
Lenke LG,
Baldus C,
Blanke K
St Louis, MO, USA

INTRODUCTION:
The 2 most common surgical options for fixed sagittal in balance include a pedicle subtraction osteotomy (PSO) or multiple Smith–Petersen osteotomies (SPOs). To–date only 1 North American series has been presented reporting the results of ³ 10 patients (pts) undergoing PSO. Its feasibility in pts with previous decompressions has not been reported.

PURPOSE:
To report operative, radiographic and functional outcome results on pts undergoing lumbar PSO for positive sagittal imbalance.

METHODS:
The radiographic findings and clinical course of 33 consecutive pts undergoing PSO by 2 surgeons at 1 institution between 1995 and 1999 were studied with 100% follow–up. The data presented represent early radiographic results and perioperative course of all pts. 14 of the 33 pts have been followed >2 years (yrs) and completed a functional outcome questionnaire based on SRS and AAOS questions (Spine 1999;24:1712). Preop and postop gait testing was performed on 5 pts.

RESULTS:
There were 27 females, 6 males with varying diagnoses. The mean age was 53.5 (range 32–72) yrs at the time of the surgery. The pts had undergone a mean 2.4 (range 0–7) operative procedures with a mean of 6.1 (range 0–13) levels involved prior to the PSO. Total mean OR time was 14.4 (range 7.1–18.8) hours. There was a mean of 11.3 (range 4– 16) levels involved with the procedures. 13 osteotomies were performed through previous laminectomies, 13 through rotated vertebrae (Nash–Moe ³1.5) at the apex of a residual scoliosis, and 21 through a previous fusion mass. The osteotomy was performed at L1 (1 pt), L2 (11 pts), or L3 (21 pts). Mean EBL was 2250 cc (range 950–6650 cc). Early complications for the 33 pts included 2 anterior gapping of the osteotomy, and 1 each of delayed cauda equina, MI requiring CABG, hand and abdominal compartment syndromes. There was 1 implant failure at 4 yrs postop in a PSO done proximal to a previous fusion. The sagittal plumb line measured from the center of C7 to the posterior aspect of the L5–S1 disc improved from a mean of 15.9+/–1.4 cm preop to 2.5+/–1.6 cm immediately postop. The mean lumbar lordosis measured from T12 to S1 improved from 15.2°+/–3.9° preop to 50.0°+/–2.8° postop. The correction obtained through the osteotomy was a mean of 35.1°+/–2.2° and did not change in the 14 pts with >2 yr follow–up. There were no cases of coronal decompensation as had been observed in pts undergoing SPOs through rotated vertebrae (Spine 1999;24:1712). Graded treadmill testing was performed on 5 pts pre and postop. These pts reached 70% of their maximal heart rate at a mean of 4.8 (range 3–12) minutes preop and at a mean of 18 (range 9–30) minutes postop. Based on the SRS/AAOS pt questionnaire ³2 yrs postop (14 pts), activity level improved in 6 pts and was the same in 8 others. All but 1 pt felt they had improved their functional ADLs. The mean pain score improved from 8.6/10 preop to 3.6/10 postop. Only 1 pt with ankylosing spondylitis who has recently sustained compression fractures proximal to the instrumented levels complained of increased pain at 4 yrs postop. 12 reported an improvement in their self–image. All 14 were satisfied with the surgery and all but 1 would undergo the procedure again.

CONCLUSIONS:
PSO can be accomplished in the multi–operated pt with improved clinical and radiographic results. The osteotomy can be performed safely through rotated apical segments with less risk of significant coronal decompensation when compared with SPOs. There were no adverse effects from performing the osteotomy through previously decompressed levels. The mean correction through the osteotomy was approximately 35° and the C7 sagittal plumb line improved a mean of 13.5 cm. Walking endurance and efficiency is significantly improved in pts undergoing PSO. Pt satisfaction was high in this group of pts at >2 yr follow–up.

Portions of this study were funded by the Scoliosis Research Society.