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Autogenous iliac crest bone graft (ICBG) is the gold standard of materials for spinal fusion. We conducted a prospective observational study of posterior autogenous ICBG harvesting and used process measures to establish a normative database of bone harvesting for future comparative studies and analyses of bone graft substitutes. Between August 2000 and March 2002, we obtained posterior autogenous ICBG from 36 consecutive patients (29 men, 7 women). Mean age was 39 years (range, 22-62 years). For harvesting, the "trephine curettage" technique was performed through a skin incision separate from that of the primary surgery. Mean estimated blood loss (EBL) for harvesting was 71 mL (range, 20-200 mL). The index procedure consisted of transforaminal lumbar interbody fusion (27 patients), posterior spinal fusion (3), combined anterior and posterior spinal fusion (5), or anterior spinal fusion (1). Mean EBL for the index procedure was 790 mL (range, 150-1500 mL). Mean harvest time was 37 minutes (range, 20-51 minutes). Mean harvest volume was 38 mL (range, 25-65 mL). Donor site and sacroiliac (SI) joint were clearly visualized in 29 (81%) of the 36 patients; the SI joint (ligamentous portion) was violated in 1 patient (3%). With the emergence of bone graft substitutes, costs and benefits of autogenous ICBG harvesting will be scrutinized. This database establishes a prospective benchmark for additional EBL, harvest time, harvest volume, and SI joint violation for ICBG harvesting. To our knowledge at the time of manuscript preparation, this is the first report of routine use of postoperative computed tomography to determine incidence of SI joint violation after ICBG harvesting.

Iliac screw fixation is often used for long fusions to the sacropelvis. Maximum iliac screw purchase is obtained both by placing the screws within 1.5 cm of the greater sciatic notch and by extending them anterior to the axis of rotation in flexion-extension. Screw insertion is "blinded" or dependent on tactile feedback, and hence extreme care is necessary to avoid incorrect placement and damage to vital neurovascular structures in the pelvis and sciatic notch. Long screws may violate the hip joint while medial placement may injure the lumbosacral plexus and the nearby vessels. To explore the best intraoperative fluoroscopic method of determining optimal iliac screw placement, we used a synthetic pelvis model to investigate screw placement conditions: (1) optimal anatomic placement, (2) violation of the sciatic notch, (3) hip joint violation, (4) medial wall violation, and (5) lateral wall violation. Each condition was examined utilizing fluoroscopy with posteroanterior, inlet, outlet, lateral, iliac oblique, and obturator oblique Judet views to simulate operative conditions. These views were obtained to evaluate critical malposition of iliac screws. We found that, for a sciatic notch violation, the obturator oblique view best demonstrated the cortical breech, while for a hip joint violation, the inlet and outlet views were best. For a medial wall violation, the iliac oblique view best showed the violation. For a lateral wall violation, we were unable to demonstrate the cortical breech using these fluoroscopic views. Fluoroscopy is an effective method to determine sciatic notch, hip joint, and medial wall violations after iliac screw placement; however, it is not effective in identifying a lateral wall violation.

We report on a prospective randomized study of coralline hydroxyapatite (CH) used as backfill for iliac-crest donor sites. Autogenous iliac-crest bone graft is routinely harvested for spinal fusion. Donor-site morbidity is underappreciated; the presumption is that donor sites regenerate. In this study, we assessed the biological viability of the backfill CH (Pro OsteonTM Implant 500 Hydroxyapatite Bone Void Filler; Interpore, Irvine, Calif) and compared donor-site morbidity after harvest. Twelve patients (11 men, 1 woman) were enrolled: 5 in the backfill group and 7 in the no-backfill group. As part of routine evaluations done preoperatively and 6 weeks, 3 months, 6 months, and 1 year postoperatively, plain radiographs and computed tomography (CT) scans were used to assess bone ingrowth, and technetium bone scans were used to assess biological activity. Postoperative pain analysis was also done. Ten patients (9 men, 1 woman) completed the study. Of the 4 completers in the backfill group, 3 (75%) showed bony ingrowth on plain radiographs and CT scans at 1 year; the fourth patient showed bony ingrowth only on plain radiographs. All 4 patients showed biological activity on bone scans and reported mild pain to no pain. Of the 6 completers in the no-backfill group, 1 (17%) showed bony ingrowth on plain radiographs and CT scans. No patient showed biological activity on bone scans at 1 year. CH aids in iliac-crest healing after bone-graft harvesting by acting as a biological osteoconductive matrix. Postoperative pain at the bone-graft site is potentially reduced. More studies of larger numbers of patients are needed to assess the true long-term benefits of this material in a clinical setting.

We conducted a study to quantify the attainable cross-sectional area available for fusion and the mean volume of disk removed with a unilateral transforaminal lumbar interbody fusion (TLIF). Starting with the unilateral approach and completing the procedure with a bilateral approach, we removed the maximal amount of disk material. Postoperative computed tomography (CT) images were used to estimate the cross-sectional area/vertebral endplate available for bone grafting and fusion. Results showed that, using the unilateral approach, we removed 11.8 cm3 (range, 7-25 cm3) of disk material--or more than 69% of the total volume of resected disk. Postoperative CT images confirmed that more than 56% of the endplate cross-sectional area is available for fusion using the unilateral approach. We conclude that unilateral TLIF removes sufficient disk material for achieving a solid and stable arthrodesis while minimizing neural retraction and dural exposure.

This is a consecutive study of patients with adolescent idiopathic scoliosis requiring surgical intervention. The purpose was to determine the best radiographic method of evaluating the flexibility of the proximal thoracic (PT) curve in patients with a double thoracic curve pattern. The PT curve averaged 40 degrees (range, 27 degrees-67 degrees) on posteroanterior (PA) radiographs, 30 degrees (range, 12 degrees60 degrees) on supine side-bending radiographs, and 24 degrees (range, 8 degrees -55 degrees) on traction radiographs. The flexibility index (FI) for the PT curve was 0.72 (range, 0.40-0.96) on side-bending and 0.58 (range, 0.29-0.82) on traction. The main thoracic (MT) curve averaged 62 degrees (range, 45 degrees-102 degrees) on PA, 40 degrees (range, 19 degrees-88 degrees) on supine side-bending, and 35 degrees (range, 17 degrees-76 degrees) on traction radiographs. The FI for the MT curve was 0.62 (range, 0.30-0.89) on side bending and 0.56 (range, 0.32-0.81) on traction. There was a statistically significant difference between the flexibility of the PT curve on supine traction as compared with the side-bending films (P0.0005). Comparison of the MT curve flexibility with the PT curve demonstrated the PT curve to be less flexible in 11 of 15 cases (P = 0.16). The authors conclude that for double thoracic curve patterns, the PT curve is usually the smaller, yet often the stiffer curve. Furthermore, the supine traction radiograph demonstrates greater flexibility of the PT curve than does the supine side-bending radiograph. Clinically, this may assist scoliosis surgeons in assessing the PT curve and achieving a stable, balanced spine.