Do Lordotic Cages Provide Better Segmental Lordosis Versus Nonlordotic Cages in Lateral Lumbar Interbody Fusion (LLIF)?

STUDY DESIGN: A retrospective comparative radiographic review. OBJECTIVE: To evaluate the radiographic changes brought about by lordotic and nonlordotic cages on segmental and regional lumbar sagittal alignment and disk height in lateral lumbar interbody fusion (LLIF). SUMMARY OF BACKGROUND DATA: The effects of cage design on operative level segmental lordosis in posterior interbody fusion procedures have been reported. However, there are no studies comparing the effect of sagittal implant geometry in LLIF. METHODS: This is a comparative radiographic analysis of consecutive LLIF procedures performed with use of lordotic and nonlordotic interbody cages. Forty patients (61 levels) underwent LLIF. Average age was 57 years (range, 30-83 y). Ten-degree lordotic PEEK cages were used at 31 lumbar interbody levels, and nonlordotic cages were used at 30 levels. The following parameters were measured on preoperative and postoperative radiographs: segmental lordosis; anterior and posterior disk heights at operative level; segmental lordosis at supra-level and subjacent level; and overall lumbar (L1-S1) lordosis. Measurement changes for each cage group were compared using paired t test analysis. RESULTS: The use of lordotic cages in LLIF resulted in a significant increase in lordosis at operative levels (2.8 degrees; P=0.01), whereas nonlordotic cages did not (0.6 degrees; P=0.71) when compared with preoperative segmental lordosis. Anterior and posterior disk heights were significantly increased in both groups (P<0.01). Neither cage group showed significant change in overall lumbar lordosis (lordotic P=0.86 vs. nonlordotic P=0.25). CONCLUSIONS: Lordotic cages provided significant increase in operative level segmental lordosis compared with nonlordotic cages although overall lumbar lordosis remained unchanged. Anterior and posterior disk heights were significantly increased by both cages, providing basis for indirect spinal decompression.

Comparison of nonnavigated and 3-dimensional image-based computer navigated balloon kyphoplasty.

Balloon kyphoplasty is a common treatment for osteoporotic and pathologic compression fractures. Advantages include minimal tissue disruption, quick recovery, pain relief, and in some cases prevention of progressive sagittal deformity. The benefit of image-based navigation in kyphoplasty has not been established. The goal of this study was to determine whether there is a difference between fluoroscopy-guided balloon kyphoplasty and 3-dimensional image-based navigation in terms of needle malposition rate, cement leakage rate, and radiation exposure time. The authors compared navigated and nonnavigated needle placement in 30 balloon kyphoplasty procedures (47 levels). Intraoperative 3-dimensional image-based navigation was used for needle placement in 21 cases (36 levels); conventional 2-dimensional fluoroscopy was used in the other 9 cases (11 levels). The 2 groups were compared for rates of needle malposition and cement leakage as well as radiation exposure time. Three of 11 (27%) nonnavigated cases were complicated by a malpositioned needle, and 2 of these had to be repositioned. The navigated group had a significantly lower malposition rate (1 of 36; 3%; P=.04). The overall rate of cement leakage was also similar in both groups (P=.29). Radiation exposure time was similar in both groups (navigated, 98 s/level; nonnavigated, 125 s/level; P=.10). Navigated kyphoplasty procedures did not differ significantly from nonnavigated procedures except in terms of needle malposition rate, where navigation may have decreased the need for needle repositioning.

Does prone repositioning before posterior fixation produce greater lordosis in lateral lumbar interbody fusion (LLIF)?

STUDY DESIGN: Retrospective comparative radiographic review. OBJECTIVE: To determine if lateral to prone repositioning before posterior fixation confers additional operative level lordosis in lateral lumbar interbody fusion (LLIF) procedures. SUMMARY OF BACKGROUND DATA: In a review of 56 consecutive patients who underwent LLIF, there was no statistically significant change in segmental lordosis from lateral to prone once a cage is in place. The greatest lordosis increase was observed after cage insertion. METHODS: We reviewed 56 consecutive patients who underwent LLIF in the lateral position followed by posterior fixation in the prone position. Eighty-eight levels were fused. Disk space angle was measured on intraoperative C-arm images, and change in operative level segmental lordosis brought about by each of the following was determined: (1) cage insertion, (2) prone repositioning, and (3) posterior instrumentation. Paired t test was used to determine significance (α=0.05). RESULTS: Mean lordosis improvement brought about by cage insertion was 2.6 degrees (P=0.00005). There was a 0.1 degree mean lordosis change brought about by lateral to prone positioning (P=0.47). Mean lordosis improvement brought about by posterior fixation, including rod compression, was 1.0 degree (P=0.03). CONCLUSIONS: In LLIF procedures, the largest increase in operative level segmental lordosis is brought about by cage insertion. Further lordosis may be gained by placing posterior fixation, including compressive maneuvers. Prone repositioning after cage placement does not produce any incremental lordosis change. Therefore, posterior fixation may be performed in the lateral position without compromising operative level sagittal alignment.

Adult Degenerative Scoliosis Surgical Outcomes: A Systematic Review and Meta-analysis.

INTRODUCTION: There is increasing awareness of adult degenerative or de novo scoliosis, and its surgical treatment when indicated can be challenging and resource intense. Surgical randomized controlled trials are rare, and observational studies pose limitations because of the heterogeneity of surgical practices, techniques, and patient populations. Pooled analysis of current literature may identify effective treatment strategies and guide future efforts at prospective clinical research. This study aimed to synthesize existing data on the outcomes of surgical intervention for adult degenerative scoliosis. METHODS: PubMed, Medline, Cochrane, and Web of Science databases were searched using key words and were limited to the English language. Spine surgeons reviewed abstracts and evaluated whether they contained surgically treated cohorts of adults (more than 18 years of age) with degenerative scoliosis. Full-text articles were reviewed in detail and data were abstracted. All meta-analyses were conducted using random effects models and heterogeneity was estimated with I2. Random-effects meta-regression models were used to investigate the association of treatment effects with baseline levels of each outcome. RESULTS: Of 482 articles, 24 (n = 805) met inclusion criteria Available outcomes included Cobb angle correction, coronal and sagittal balance, visual analog scale for pain (VAS), and Oswestry Disability Index. Despite significant heterogeneity among studies, random-effects meta-analysis showed significant improvements in Cobb angle (-11.1°; 95% confidence interval [CI], -13.86° to -8.40°), coronal balance (7.674 mm; 95% CI, -10.5 to -4.9), VAS (-3.24; 95% CI, -4.5 to -1.98), and Oswestry Disability Index (-27.18%; 95% CI, -34.22 to -20.15) postoperative treatment (p < .001). Meta-regression models showed that preoperative values for Cobb angle, coronal balance, and VAS were significantly associated with surgical treatment effect (p < .05). Changes in sagittal balance did not reach statistical significance although only 6 articles were included. CONCLUSIONS: Exhaustive literature review yielded 24 studies reporting preoperative and postoperative data regarding the surgical treatment of adult degenerative scoliosis. No randomized clinical trials (RCTs) were identified. Despite heterogeneity, a limited meta-analysis showed significant improvement in Cobb angle, coronal balance, and VAS after surgical treatment of adult degenerative scoliosis.

The accuracy of navigation and 3D image-guided placement for the placement of pedicle screws in congenital spine deformity.

BACKGROUND: Treatment of congenital spine deformity has high surgical risk due to abnormal anatomy and dysmorphic pedicles. We hypothesized that an image-guided navigation system would result in a low rate of screw revision due to malposition. METHODS: From 2007 to 2010, 142 screws were placed in 14 consecutive patients with congenital spine deformity using an intraoperative computer tomography (CT) (O-arm) and image-guided navigation system (Stealth). Mean age was 8.8 years (range, 1 to 18 y). Deformities included scoliosis (12), kyphosis (1), and spinal dysgenesis (1). Screws were placed from T2 to S1. An intraoperative CT verified screw position. Need for intraoperative screw revision is the primary outcome measure. RESULTS: Of the 142 screws placed, 1 required revision intraoperatively due to malposition (99.3% screw accuracy rate). The screw was at L3 and was successfully redirected. There were no complications due to screw malposition. This navigated congenital screw accuracy rate (99.3%) is higher than the 94.9% accuracy rate reported for non-navigated screws in all children undergoing pedicle screw fixation in a recent systematic literature review and higher than the reported 96.4% accuracy rate for navigated pedicle screws in children. Kosmopoulos and colleagues found a lower accuracy rate (86.6%) in adult non-navigated screws (P<0.0001) and adult navigated screws (93.7%). Of note, 9 pedicles were noted on navigation to be absent. Despite the goal of bilateral screw placement at each fusion level, 31 of 173 pedicles were left unfilled due to technical impossibility based on intraoperative CT imaging. This represents an 18% screw dropout rate. CONCLUSIONS: CT-guided navigation resulted in the successful placement of 142 pedicle screws in patients with congenital deformity and altered anatomy, which represents a 99.3% screw accuracy rate. This is comparable with the screw accuracy rate of 93.7% reported for adult navigated pedicle screws. Further, navigation prevented attempts of screw placement at levels with absent or impassable pedicles. Image-guided navigation and intraoperative CT are valuable tools for the safe placement of pedicle screws in patients with significant congenital spine deformity and altered anatomy. LEVEL OF EVIDENCE: IV, Case Series.

The accuracy of intraoperative O-arm images for the assessment of pedicle screw postion.

STUDY DESIGN: Human cadaveric study. OBJECTIVE: The objective of the study was to determine the accuracy of intraoperative O-arm images in determining pedicle screw position using open dissection as the gold standard. SUMMARY OF BACKGROUND DATA: Pedicle screws are widely used in the treatment of various spinal disorders. Postoperative computed tomographic scans are the imaging gold standard to detect pedicle screw malposition. However, a second procedure is necessary if such malpositioned screws have to be revised. The O-arm is an intraoperative scanner that allows revision of a screw without having to return the patient to the operating room for a separate procedure. No previous studies have looked at the accuracy of intraoperative O-arm images in determining pedicle screw position. METHODS: This factorial validation study utilized 9 cadavers in a comparison of intraoperative O-arm images and the dissection gold standard. Four hundred sixteen screws were inserted using 3-dimensional image (O-arm) guidance from C2 to S1. The screw positions were randomized into 3 groups: "IN" (fully contained within the pedicle), "OUT-lateral," or "OUT-medial." After screw insertion, O-arm images were obtained and reviewed in a blinded fashion by 3 independent observers. Dissection identified the true position of the screws. Specificity, sensitivity, positive predictive value (PPV), and negative predictive value (NPV) were calculated using dissection results as the gold standard. The interobserver reliability was also determined. RESULTS: The overall accuracy, specificity, sensitivity, PPV, and NPV of O-arm images for the thoracic and lumbar spine were 73%, 76%, 71%, 74%, and 72%, respectively. Accuracy of surgeon perception in the cervical spine was significantly less than in the thoracic and lumbosacral spine. There was substantial interobserver agreement between the 3 readers. CONCLUSION: Intraoperative O-arm images accurately detect significant pedicle screw violations in the thoracic and lumbosacral spine but are less accurate for the cervical spine.

Pediatric pedicle screw placement using intraoperative computed tomography and 3-dimensional image-guided navigation.

STUDY DESIGN: A retrospective cohort study reporting the use of intraoperative computed tomography (CT) and image-guided navigation system for the placement of pedicle screws in pediatric compared with adult patients. OBJECTIVE: To evaluate the accuracy of open pedicle screw placement in pediatric patients using intraoperative CT and 3-dimensional (3D) image-guided navigation. SUMMARY OF BACKGROUND DATA: Pedicle screws are widely used in children for the correction of spinal deformity. Navigation systems and intraoperative CT are now available as an adjunct to fluoroscopy and anatomic techniques for placing pedicle screws and verifying screw position. METHODS: From 2007 to 2010, 984 pedicle screws were placed in a consecutive series cohort of 50 pediatric patients for spinal deformity correction with the use of intraoperative CT (O-arm, Medtronic, Inc, Louisville, CO) and a computerized navigation system (Stealth, Medtronic, Inc, Louisville, CO). The primary outcome measure for this study is redirection or removal of screw on the basis of the intraoperative CT imaging. During the study period, 1511 screws were placed in adult patients using the same image guidance system. RESULTS: A total of 984 pedicle screws were implanted using real-time navigation, with a mean of 20 screws per patient (range: 2-34). On the basis of intraoperative CT, 35 screws (3.6%) were revised (27 redirected and 8 removed), representing a 96.4% accuracy rate. No patients returned to the operating room because of screw malposition.Of the 1511 screws placed in adult patients, 28 (1.8%) were revised intraoperatively for malposition on CT imaging, for an overall 98.2% accuracy rate. Screw revision thus was more common in the pediatric population (P = 0.008). However, the pediatric screw accuracy rate is significantly higher than the findings from a recent meta-analysis of predominantly nonnavigated screws in children, reporting a 94.9% accuracy rate (P = 0.03). CONCLUSION: We report 96.4% accuracy in pediatric pedicle screw placement using intraoperative CT and a 3D navigation system. This is similar to other reports and has better accuracy than a recent meta-analysis of nonnavigated screws in children.

Mobile and fixed-bearing (all-polyethylene tibial component) total knee arthroplasty designs. A prospective randomized trial.

BACKGROUND: Proponents of mobile-bearing total knee arthroplasty believe that it has potential advantages over a fixed-bearing design in terms of diminished wear and improved motion and/or function, but these advantages have not been demonstrated in a randomized clinical comparison to our knowledge. We conducted a patient-blinded, prospective, randomized clinical trial to compare mobile-bearing and fixed-bearing cruciate-substituting total knee arthroplasties of the same design. METHODS: Patients between the ages of sixty and eighty-five years were prospectively randomized to receive a cruciate-substituting rotating-platform design or a fixed-bearing design with an all-polyethylene tibial component. There were no significant differences in the demographic characteristics (mean age, 72.2 years; mean American Society of Anesthesiologists score, 2.7; mean body mass index, 31.8 kg/m(2)) or preoperative clinical or radiographic measures between the groups. Routine clinical and radiographic follow-up measures included the Knee Society score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Short Form-36 (SF-36) outcome measures. RESULTS: The results of 312 arthroplasties (136 with an all-polyethylene tibial component and 176 rotating-platform designs) in 273 patients were analyzed at a minimum of two years (mean, forty-two months) postoperatively. Although there was significant improvement in both groups, there was no significant difference between the groups with regard to the mean postoperative range of motion (110.9 degrees and 109.1 degrees, respectively; p = 0.21), the mean KSS clinical score (90.4 and 88.2 points; p = 0.168), or the mean KSS pain score (44.9 and 43.1 points; p = 0.108) at this follow-up point. There were ten revisions: seven because of infection, one because of patellar fracture, one because of instability, and one because of aseptic loosening. CONCLUSIONS: The two designs functioned equivalently at the time of early follow-up in this low-to-moderate-demand patient group. The rotating-platform design had no significant clinical advantage over the design with the all-polyethylene tibial component.

Revision lumbar arthrodesis for the treatment of lumbar cage pseudoarthrosis: complications.

STUDY DESIGN: A study documenting major complications encountered in revision procedures for lumbar cage pseudoarthrosis. OBJECTIVE: To document the perioperative complications associated with revision surgery for threaded cylindrical cage pseudoarthrosis. SUMMARY OF BACKGROUND DATA: Pseudoarthrosis after cylindrical cage placement manifests as persistent or recurrent pain and disability after surgery. Revision strategies include isolated posterior stabilization and posterior bone grafting, versus circumferential revision where an attempt is made to remove the cages anteriorly, followed by posterior stabilization and fusion. Potential complications associated with these revision procedures have not been adequately documented in the past. METHODS: Forty-seven consecutive patients with the diagnosis of cylindrical cage pseudoarthrosis were surgically treated with either a circumferential revision (AP) or an isolated posterior instrumented fusion (P). All intraoperative and postoperative complications were documented. Radiographic interbody fusion rates and preoperative and postoperative visual analog scale (VAS) scores were documented. RESULTS: Three of the AP patients, all with anterior cage placement at L5-S1, had iliac vein lacerations requiring repair. A fourth patient had a ureteral injury requiring subsequent nephrectomy. Three patients who underwent circumferential revision and 2 patients who had an isolated posterior procedure had postoperative complications, including 2 infections (1 AP and 1 P), 1 radiculopathy (P), and 2 patients with prolonged ileus (both AP). There was a statistically significant decrease in overall VAS scores postoperatively for the 2 groups using the paired t test (P<0.0001). There was no difference in either the preoperative (P=0.22) or 2-year postoperative (P=0.30) VAS scores between the AP and P groups [rank-sum (Mann-Whitney) t tests]. Interbody fusion was achieved in 79% (30 of 38 levels) in the AP group. The interbody fusion rate was 37% (8 of 22) for the P group. CONCLUSIONS: Circumferential revision including cage removal, structural allograft placement, and posterior stabilization is associated with increased perioperative complications. Although an anterior approach showed increased interbody fusion rates, this technique did not lead to more superior clinical outcomes based on VAS scores. It remains to be shown by larger prospective studies if there is a true difference in outcome between these 2 groups that will justify the increased perioperative morbidity associated with attempted cage removal.

Spinopelvic fixation in deformity: a review.

Spinopelvic fixation techniques are evolving and now seem to be converging. Good S1 pedicle fixation is the initial key anchor point. The tricortical technique tests out as the best. Supplemental fixation options are available. The most efficacious seems to be iliac fixation, followed by two-level structural interbody support. Achieving appropriate global sagittal balance also lessens the likelihood of implant pullout and places the fusion mass under relatively more compressive forces than tension forces. Regardless of the method of fixation, the ultimate determinant of long-term implant survival is the achievement of adequate biologic fusion.

All-polyethylene and metal-backed tibias have similar outcomes at 10 years: a randomized level I [corrected] evidence study.

The advantages of a monoblock design and lower cost have generated renewed interest in all-polyethylene tibial components for total knee arthroplasty (TKA). We hypothesized an all-polyethylene design would function equivalently to a metal-backed modular design at lower cost and at long-term followup. We report the 8- to 12-year followup of our earlier reported prospective randomized comparison of a modern congruent all-polyethylene tibial component with a modular metal-backed tibial component of the same design. The mean age of the patients was 69 years and 92% were diagnosed with osteoarthritis. Of 290 patients (316 total knee arthroplasties) enrolled, 120 patients died, 22 had revision surgery, and one was lost to followup. We followed the remaining 147 patients (167 TKAs: 97 all-polyethylene/70 metal-backed) clinically and radiographically. There were no differences in knee function (Knee Society clinical score, range of motion, stability) or radiographic parameters between the groups. Of the 22 revisions, only three were performed for tibial aseptic loosening (three metal-backed). Ten-year survivorship of the all-polyethylene tibial component was 91.6% with revision for any reason and 100% for aseptic loosening. The metal-backed tibial component survivorship was 88.9% with revision for any reason and 94.3% for aseptic loosening. The contemporary all-polyethylene tibial component functioned equivalently to its monoblock counterpart and was less costly.

Magnetic resonance imaging 20 years after anterior lumbar interbody fusion.

STUDY DESIGN: A 20-year magnetic resonance imaging (MRI) and functional outcome follow-up study was performed on patients who had undergone anterior lumbar interbody fusion. OBJECTIVES: The objectives of the present study are to determine whether or not degeneration is related to adjacent level fusion and the clinical significance of this degeneration. SUMMARY OF BACKGROUND DATA: There are concerns that lumbar fusion leads to increase stress at the adjacent levels. However, the clinical significance of this remains unclear. METHODS: Thirty-nine patients who underwent lower lumbar anterior lumbar interbody fusion and who had normal preoperative discograms at the level adjacent level were evaluated with a minimum of a 20-year follow-up. MRI scans were performed and independently evaluated for any evidence of degeneration. Functional status was assessed using the Low Back Outcome Scale. RESULTS: Twenty-nine (74.3%) patients had some evidence of degeneration in their lumbar spine and advanced degeneration was identified in 12 (30.7%) patients. Nine (23.1%) patients had advanced degeneration isolated to the adjacent level and 7 (17.9%) patients had evidence of advanced degeneration with preservation at the level adjacent to the fusion. There was no association between function and radiographic degeneration. Only 3 patients required additional surgery as a result of adjacent level degeneration. CONCLUSION: The prevalence of degenerative changes is similar to other studies involving normal asymptomatic subjects. Furthermore, the majority of degenerative changes seen occurred over multiple levels or at levels not adjacent to the fusion, suggesting that changes seen may be more likely related to constitutional factors as opposed to the increased stresses arising from the original fusion.

Surgical treatment for the painful motion segment: matching technology with the indications: posterior lumbar fusion.

STUDY DESIGN: A convenience literature-based review of the different techniques of posterior lumbar fusion. OBJECTIVE: To describe the history, specific techniques, and outcomes of different methods of posterior lumbar fusion. The specific methods that were described include 1) uninstrumented posterior, posterolateral, and facet fusion, and 2) instrumented fusion using pedicle screws or facet screws. SUMMARY OF BACKGROUND DATA: There are various posterior fusion techniques available for the treatment of degenerative lumbar spine conditions. Each individual technique has specific technical demands, indications, advantages, and disadvantages which should be taken into consideration when performing these procedures. METHODS: The published scientific literature on the different methods of posterior lumbar fusion was reviewed. The history, indications, advantages, disadvantages, and clinical and radiographic outcomes were described based on the literature search. RESULTS/CONCLUSIONS: Posterior fusion techniques have been and will continue to be among the most commonly performed procedures in lumbar spine surgery. The different methods of fusion are well defined, as are the possible complications and outcomes. They are effective techniques when performed on appropriately selected patients by a surgeon knowledgeable in the techniques and indications. Further studies are needed regarding promising but relatively unproven developments such as minimally invasive surgery and the use of osteoinductive agents.

Total knee arthroplasty in juvenile rheumatoid arthritis.

BACKGROUND: There is a paucity of reports regarding the long-term results of total knee arthroplasty in patients with juvenile rheumatoid arthritis. The purpose of this study was to evaluate the outcome of total knee arthroplasty in patients with juvenile rheumatoid arthritis who had been followed for a minimum of twelve years. METHODS: Eight consecutive patients (fifteen knees) with juvenile rheumatoid arthritis underwent total knee arthroplasty at an average age of 16.8 years. Clinical evaluation of pain status, range of motion, and the ability to walk and radiographic evaluation of the alignment of the knees and component loosening were performed preoperatively and at a mean of 15.5 years postoperatively. RESULTS: All patients had substantial pain and functional limitation before the surgery, and seven of the eight patients used a wheelchair. At the time of the latest follow-up, which was after revision surgery in three patients, all of the knees were pain-free and six patients were able to walk about the community. The mean arc of motion had increased from 36 degrees to 79 degrees . The final radiographic evaluation showed that thirteen of the fifteen knees were in neutral alignment and two were in valgus. Failure, defined as revision of any of the components or definite loosening as seen radiographically, occurred in three knees. CONCLUSIONS: Good results, in terms of pain relief and restoration of function, were seen at a minimum of twelve years following total knee arthroplasty in our series of patients with juvenile rheumatoid arthritis. This procedure is a reasonable option when nonoperative therapy has been inadequate for patients with severe disability and pain in this relatively young population.

Radiologic assessment of interbody fusion using carbon fiber cages.

STUDY DESIGN: A comparative study investigated the use of plain static radiographs, flexion-extension radiographs, and thin-section helical computed tomography (CT) scanning in the assessment of anterior lumbar interbody fusion using carbon fiber cages. OBJECTIVE: To compare plain static radiographs, flexion-extension radiographs, and thin-section helical computed tomography scans in the assessment of lumbar interbody fusion using carbon fiber cages. SUMMARY OF BACKGROUND DATA: Lumbar interbody fusion has become a popular procedure for the treatment of discogenic back pain. However, there currently is no universally accepted radiologic assessment tool for determining fusion, and the definitive criteria for diagnosing a successful interbody fusion in the lumbar spine remains controversial. METHODS: Plain static radiographs, flexion-extension radiographs, and helical computed tomography scans were performed on 32 patients (49 levels) 5 years after anterior lumbar interbody fusion using carbon fiber cages and autologous bone. A radiologist assessed fusion using the Hutter method to detect movement, whereas a spinal surgeon measured movement in degrees using the Simmons method. Helical computed tomography scans were assessed for the presence of bridging trabecular bone. RESULTS: The fusion rate was 86% on plain radiographs and 84% with the Hutter method. The fusion rate was 74% with the 2 degrees cutoff, and 96% with the 5 degrees cutoff prescribed by the Food and Drug Administration. Fusion on helical computed tomography scans was observed in 65% of the patients. CONCLUSIONS: In the radiologic assessment of interbody fusion using carbon fiber cages, the use of plain radiographs and flexion-extension radiographs produced much higher fusion rates than assessment with thin-section helical computed tomography scans. The thin-section helical computed tomography studies clearly demonstrated the radiographic presence or absence of bridging bone, a property that was not seen with plain static radiographs or flexion-extension radiographs.