Pseudarthrosis at L5-S1 after Posterolateral Lumbar Fusion

STUDY DESIGN: This is a retrospective study. OBJECTIVES: We wanted to investigate the rate of pseudarthrosis at L5-S1 after posterolateral fusion only for degenerative lumbar spinal disease, and to determine the radiological findings that help diagnose pseudarthrosis. SUMMARY OF THE LITERATURE REVIEW: The pseudarthrosis rate at L5-S1 is much higher than that at the other lumbar segments. However, there have been few studies for the rate and risk factors of pseudarthrosis at L5-S1. MATERIALS AND METHODS: A total of 88 patients who underwent pedicle screw instrumentation and posterolateral lumbar fusion were evaluated with a minimum of 1-year follow up. Bony union was evaluated by the bony fusion mass, the angulation on the flexion-extension radiographs and the radiolucent zone around the pedicle screws. The patients' age, bony mineral density, the number of fused segments and lumbar lordosis were evaluated for their association with pseudarthrosis at L5-S1. RESULTS: Pseudarthrosis developed in 22 patients at L5-S1 and in 8 patients at other levels. The change of angulation on the flexion-extension radiographs at the last follow-up was 5.2degrees in the pseudarthrosis group and 1.7degrees in the fusion group (P=0.3). A radiolucent zone of the sacral screws was noted in 10 patients; in 7 of the 22 patients in the pseudarthrosis group and in 3 of the 66 patients in the fusion group. The average age, the mean number of levels fused and the bone mineral density were similar in both groups. Lumbar lordosis was not associated with the development of pseudarthrosis at L5-S1. CONCLUSION: The pseudarthrosis rate was significantly higher at L5-S1 than that at the other lumbar segments following instrumented posterolateral fusion. Pseudarthrosis was closely related to hypermobile angulation (> or =5degrees) on the flexion-extension radiographs and a radiolucent zone around the sacral screws.

Does a Radiolucent Zone Surrounding the Pedicle Screws mean Nonunion? / 대한정형외과학회잡지

PURPOSE: We wanted to retrospectively evaluate the clinical significance of radiolucent zones surrounding the pedicle screws after spinal fusion. MATERIALS AND METHODS: Spinal surgery was performed between May 2003 and December 2005 on elective patients with degenerative lumbar disorders and they underwent transpedicular screw fixation and posterolateral fusion and these patients were the subjects of the study. There were 124 cases with more than 2 years of follow up. Determination of the radiolucent zones around pedicle screws was done using simple x-rays and the cases were divided in to 4 different groups: segmental fixation with short (2 or less segments) or, long (3 or more segments) segmental fixation and those cases with or without sacral fixation. Comparative analysis was done according to osteoporosis, the location of the pedicle screws, the degree of bony-union and fixation of the anterior cortex of the sacrum. RESULTS: Among the 124 cases and 846 pedicle screws, 189 pedicle screws (22%) had radiolucent zones; 151 of the 189 pedicle screws with a radiolucent zone (27%) were in the sacral fixed group, while 38 of the 189 pedicle screws with a radiolucent zone (13%) were in the non-sacral fixed group, and the difference was significant (p=0.001). In the case of anterior cortical fixation in the sacral fixed group and the complete bony-union, the radiolucent zones had a significantly lower incidence, while the group of patients with osteoporosis (a T score lower than -2.5) had a higher incidence of radiolucent zones. CONCLUSION: The radiolucent zones surrounding the pedicle screws after spinal fusion were closely related to spinal fusion with sacral fixation and pseudarthrosis, and these radiolucent zones mostly occurred before complete bony-union. The existence of osteoporosis and the techniques of sacral fixation and many different contributing factors must be considered, and careful monitoring is needed even if the radiolucent zone progressive after complete bony-union.

Clinical Significance of the Radiolucent Zone Around the Pedicle Screws in the Lumbar Degenerative Disease / 대한척추외과학회지

STUDY DESIGN: A retrospective study. OBJECTIVE: To analyze the clinical significance of the radiolucent zones surrounding pedicle screws. SUMMARY OF LITERATURE REVIEW: Clear zones have been suggested in pseudoarthrosis and a loss of fixation. However, few reports have clearly described the long-term course and clinical significance of clear zones. MATERIALS AND METHODS: The clear zones were evaluated in 399 patients with pedicle screw fixation after 6 months, 1 year, 2 years and 3 years. The patient was considered to be clear zone positive when 1 mm or greater circumferential lucency was confirmed around a screw on film from 2 or more directions. The time-course of the clear zones was examined with regard to age, number of levels fused, bone union, fusion method and reoperation. RESULTS: After 6 months, clear zones were observed in 124 patients (31.1%) but the clear zone-positive rate decreased with time. Clear zones were observed in 89 patients(22.3%), 44 patients(11.0%) and 41 patients(10.3%) after 1 year, 2 years and 3 years, respectively. No new clear zones had developed after 6 months. At the final follow-up, pseudoarthrosis was observed in 12 patients(3.0%). Among them, 11 were clear zone-positive and 1 was clear zone-negative. There was a statistically significant relationship between the clear zone-positive rate and multi-levels, older age and nonunion during following up. In addition, there was a relatively lower clear zone-positive rate in posterolateral fusion combined with posterior lumbar interbody fusion than only posterolateral fusion. However, the difference between them was not statistically significant. CONCLUSION: The presence of clear zones does not always mean pseudoarthrosis but clear zones persisting for more than 2 years after surgery have a higher rate of pseudoarthrosis.

Radiolucent Zones Surrounding Transpedicular Screws After Lumbar Spinal Instrumented Fusion / 대한척추외과학회지

STUDY DESIGNS: A retrospective study for radiographic and clinical assessment. OBJECTIVES: To clarify the clinical significance of the radiolucent zones surrounding transpedicular screws that occasionally appears following lumbar spinal instrumented fusion. SUMMARY OF LITERATURE REVIEW: that the formation of radiolucent zones surrounding pedicular screws are significantly frequent after transpedicular fixation. MATERIALS AND METHOD: 88 cases, age 50 or older, which underwent lumbar spinal fusion with transpedicular screws, between January 1999 and December 2002, were included in this investigation. The postoperative radiographs of all patients were analyzed for radiolucent zones around the transpedicular screws. These radiolucent zones were evaluated in relation the number of fusion levels, the existence of osteoporosis, and the fusion status and satisfaction rates. RESULTS: Radiolucent zones were observed in 30 cases (34%, 30/88), 13 (43%, 13/30) of which disappeared during the follow-up period. The average number of fixation levels in the cases with and without radiolucent zones were 2.33 (range 1-4, SD 0.94) and 1.74 (range 1-4, SD 0.82), respectively. Osteoporosis was found to accompany 43.3 and 20.7% of the cases with and without radiolucent zones, with the latter cases showing a statistically significant higher fusion rate and greater patient satisfaction. CONCLUSION: Radiolucent zones, a frequent finding following pedicle screw fixation, resulted in less favorable outcomes. Surgeons should be alert to radiolucent zones and their transformation during follow-up. Methods for improving the stability of the interface between the pedicle screw and vertebral bone will require further research.