Utility of the MISDEF2 Algorithm and Extent of Fusion in Open Adult Spinal Deformity Surgery With Minimum 2-Year Follow-up

Abstract

Objective: Long-segment fusion in adult spinal deformity (ASD) is often needed, but more focal surgeries may provide significant relief with less morbidity. The minimally invasive spinal deformity surgery (MISDEF2) algorithm guides minimally invasive ASD surgery, but it may be useful in open ASD surgery. We classified ASD patients undergoing focal decompression, limited decompression and fusion, and full correction according to MISDEF2 and correlated outcomes.

Methods: A retrospective study of ASD patients treated by 2 surgeons at our hospital was performed. Inclusion criteria were: age > 50, minimum 2-year follow-up, and open ASD surgery. Tumor, trauma, and infections were excluded. Patients had open surgery including focal decompression, short segment fusion, or full scoliosis correction. All patients were categorized by MISDEF2 into 4 classes based upon spinopelvic parameters. Perioperative metrics were assessed. Radiographic correction, complications and reoperation were recorded.

Results: A total of 136 patients met inclusion criteria. Mean follow-up was 46 ± 15.8 months (range, 24-118 months). Forty-seven underwent full deformity correction, 71 underwent short segment fusion, and 18 underwent decompression alone. There were 24 cases of class I, 66 cases of class II, 23 cases of class III, and 23 cases of class IV patients. Patients in class I and II had perioperative complication rates of 0% and 16.7% and revision rates of 8% and 21.2% when undergoing focal decompression or limited fusion. However, class II patients undergoing full correction had higher perioperative complications rate (p = 0.03) and revision surgery rates (p = 0.047). This difference was not seen in class III patients (p > 0.05). All class IV patients underwent full correction, but they had higher perioperative complication rates (p < 0.019), comparable revision surgery rates (p = 0.27), and better radiographic realignment (p < 0.001). In addition, full deformity correction was associated with longer length of stay, increased blood loss, and longer operative time (p < 0.001).

Conclusion: The MISDEF2 algorithm may help guide ASD surgical decision making even in open surgery, with focal treatment used in class I and II patients as a viable alternative and full correction implemented in class IV patients because of severe malalignment. However, class II patients with ASD undergoing full deformity correction do have higher complication rates.

Keywords: Adult spinal deformity; Complications; MISDEF2; Minimally invasive surgery; Outcomes.

Fig. 1.

MISDEF2 algorithm class I patient with compression alone. Preoperative coronal and sagittal parameters: sagittal vertical axis, 23 mm; Cobb angle, 14°; pelvic incidence (PI), 61°; pelvic tilt, 18°; sacral slope, 43°; lumbar lordosis (LL), -64°; PI–LL, 3°. (A) Preoperative anteroposterior (AP) radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph at 2-year follow-up. (D) Postoperative lateral radiograph at 2-year follow-up.

Fig. 2.

MISDEF2 algorithm class II patient with limited fusion. This was planned as a minimally invasive spinal (MIS) procedure, but converted to open. Because the MIS equipment was ready, the MIS rods were used even though the procedure was open. Preoperative coronal and sagittal parameters: sagittal vertical axis, 20 mm; Cobb angle, 22°; pelvic incidence (PI), 44°; pelvic tilt, 15°; sacral slope, 29°; lumbar lordosis (LL), -40°; PI–LL, 4°. (A) Preoperative anteroposterior (AP) radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph at 1-year follow-up. (D) Postoperative lateral radiograph at 1-year follow-up. (E) Postoperative AP radiograph at 3-year follow-up. (F) Postoperative lateral radiograph at 3-year follow-up.

Fig. 3.

MISDEF algorithm class II patient with full correction. Preoperative coronal and sagittal parameters: sagittal vertical axis, 68 mm; Cobb angle, 31°; pelvic incidence (PI), 45°; pelvic tilt, 24°; sacral slope, 21°; lumbar lordosis (LL), -25°; PI–LL, 20°. (A) Preoperative anteroposterior (AP) radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph at 3-month follow-up. (D) Postoperative lateral radiograph at 3-month follow-up. (E) Postoperative AP radiograph at 1-year follow-up. (F) Postoperative lateral radiograph at 1-year follow-up proximal Junctional Kyphosis.

Fig. 4.

MISDEF algorithm class IV patient with full correction. Preoperative coronal and sagittal parameters: sagittal vertical axis, 145 mm; Cobb angle, 20°; pelvic incidence (PI), 64°; pelvic tilt, 39°; sacral slope, 25°; lumbar lordosis (LL), -15°; PI–LL, 49°. (A) Preoperative anteroposterior (AP) radiograph. (B) Preoperative lateral radiograph. (C) Postoperative AP radiograph at 2-year follow-up. (D) Postoperative lateral radiograph at 2-year follow-up.