A total of 31 patients with degenerative lumbar scoliosis combined with osteoporosis underwent fusion with pedicle screw instrumentation from December 2000 to December 2006. All patients had Dual Energy X-ray examination for bone mineral density (BMD) in L1-L4 and were diagnosed as osteoporosis according to the WHO criteria (T < -2.5). The mean T-score was -3.03 ± 0.34 (-2.5 to -3.8). All the operations were practised by the same surgery group. There were 14 patients in PMMA group and 17 patients in autogenous bone group (see 2 cases in Figure ). The average age of the patients was 60.9 ± 7.9 years (range 42.3-77.8). There were 6 men and 25 women. The average follow-up period was 3.8 ± 1.4 years (range 2.0-7.6 years). All had a minimum of 2-year follow-up.
Figure 1 Two cases of different screws augmented method. Case 1: 61.6 years old, female, with 3 years back pain and radicular symptoms, post-approach decompression and spine fusion augmented with PMMA. Case 2: 68.1 years old, male, with 5 years back pain and radicular (more ...)
Hospital records were reviewed for patients' medical comorbidities, smoking history, estimated intraoperative blood loss, operative time, and hospital stay. Hypertension, diabetes, heart disease, pulmonary disease, gastrointestinal disease, and kidney disease were considered to have medical comorbidities. The number of levels fused and the number of levels decompressed were measured. Complications were defined as any event for which the patient required specific treatment.
Anteroposterior and lateral radiographs were reviewed preoperatively, postoperatively and in final follow up periods. The Cobb angle and lumbar lordosis were assessed. Lumbar lordosis was measured from the upper endplate of L1 to the lower endplate of L5. Clinical outcomes were assessed with the Oswestry disability index. All patients were asked to fill Oswestry disability index scale perioperative and in the last follow-up.
The statistical analysis was performed using SPSS version 13.0. We used independent sample t-test. The significance was defined as P < 0.05.
Patients had undergone segmental pedicle screw instrumentation and autogenous iliac bone graft augmentation. 14 patients accepted the operation with PMMA augmentation.
For the autogenous bone graft augmentation group, using a burr, the pedicle entry point crossed by the longitudinal lateral edge of bony crest of superior articular process and the horizontal line that bisects the middle of the transverse process was prepared. A blunt tip 1.6 mm Kirschner-wire (K-wire) was gently tapped with mallet through the pedicle to the anterior cortex of vertebral body. The K-wire position was checked with fluoroscope image to make sure the K-wire was properly inside the pedicle and vertebral body, and then the K-wire was removed. A blunt tip 3-mm diameter K-wire was used to dilate the pedicle tract, and then it was removed.
The tract was palpated with a straight sensor probe to make sure the pedicle wall of the tract and the anterior cortex of the vertebral body were not violated. Then all the iliac bone graft were chipped to 2-3 mm and weighed by electronic balance. About 2 g graft was filled in to the pre-drilled pedicle screw tract for per screw. For the PMMA group, the preparation for the pedicel screw tract is the same. A 4 mm diameter bone biopsy needle (Allegiance, Healthcare Co.) was used for cement injection. About 2 ml PMMA was injected per screw with none requiring the use of autogenous iliac crest bone graft. Local bone graft (spinous processes) were used in all cases. Both of the two groups had decompression surgery at the level of spinal stenosis and had posterior or posterolateral fusion. All patients were braced with thoracolumbosacral orthosis for 3 months after surgery.
The autogenous bone group, the average number of levels fused was 6.0 ± 2.5 segments, ranging from 2 to 10 segments. The upper instrumented vertebra was T9 in 1 patient, T10 in 4 patients, T11 in 1 patients, L1 in 4 patients, L2 in 5 patients, and L3 in 2 patients,. The lower instrumented vertebra was L4 in 5 patient, L5 in 8 patients, and the sacrum in 4 patients.
The PMMA group, the average number of levels fused was 5.9 ± 1.9 segments, ranging from 3 to 9 segments. The upper instrumented vertebra was T9 in 1 patient, T10 in 2 patients, T11 in 1 patients, T12 in 1 patient, L1 in 5 patients, L2 in 3 patients, L3 in 1 patients. The lower instrumented vertebra was L4 in 3 patient, L5 in 8 patients, and the sacrum in 3 patients.