Chi-Chien Niu

Surgical treatment of adjacent instability after lumbar spine fusion.

Study Design. This study is a retrospective review of 39 patients with previous instrumented lumbar fusion who underwent secondary spine surgery for lumbar adjacent instability. To the authors’ knowledge, this is the largest study of surgical treatment of lumbar adjacent instability in the literature to date. Object. This study evaluated the feasibility of adjacent instability treated with medial facetectomy, fusion with autologous bone grafting, and pedicle screw instrumentation. Summary of Background Data. The surgical treatment of adjacent instability has seldom been discussed. Revision spine fusions are challenged by high pseudarthrosis rates. Methods. Thirty-nine patients with previous lumbar fusion underwent second lumbar spine surgery for adjacent instability. All were treated with autogenous posterolateral arthrodesis and transpedicle screw fixation in addition to decompressive laminectomy. Medical records, radiographs, and pain scores were obtained. Results. The clinical results were excellent or good in 76.9% of patients, and the radiographic fusion was successful in 37 (94.9%) of patients. Flat back was noted in 8 (20.5%) of patients. In 5 patients (12.8%), neighboring segment breakdown again developed, and 2 of those patients underwent a third lumbar fusion. Dural tear during operation occurred in 2 patients. One patient experienced cauda equina syndrome but recovered bladder function 1 month later. Conclusion. Autogenous posterolateral arthrodesis combined with pedicle screw fixation led to successful radiologic and clinical outcome in patients with lumbar adjacent instability. Adequate decompression of the adjacent stenosis requires medial facetectomy, thus preventing aggressive nerve root manipulation and reducing the incidence of dural tear.

Relation Between Laminectomy and Development of Adjacent Segment Instability After Lumbar Fusion With Pedicle Fixation

Study Design. A retrospective study of 101 patients who had undergone posterolateral lumbar fusion, to analyze the association between adjacent instability and the extent of laminectomy. Objectives. To investigate the hypothesis that the integrity of the posterior complex (spinous process/supraspinous ligament/spinous process) between the fused segments and the neighboring motion segments significantly influences lumbar spine stability. Summary of Background Data. Spinal fusion with pedicle fixation accelerates the degeneration of adjacent motion segments. The lowest cranial motion segment is the most common level for the development of adjacent instability. Laminectomy, including removal of the spinous process, supraspinous ligament, interspinous ligament, lamina and ligamentum flavum, jeopardizes the integrity of the posterior complex of the spine. Methods. This study enrolled 101 patients, followed up for at least 6 years, who had been treated with posterolateral lumbar fusion with pedicle fixation because of lumbar spondylolisthesis. The diagnosis of adjacent instability depended on the dynamic lateral views of the lumbosacral spine during each follow-up. The integrity of the posterior complex was based on the extent of laminectomy and the fusion level. Results. At the cranial adjacent motion segment, 2 of 31 (6.5%) patients with preserved posterior complex integrity between the fused segment and motion segment developed adjacent instability, compared with 17 of 70 (24.3%) without preserved posterior complex integrity. At the caudal adjacent motion segment, none of 13 patients (0%) with preserved integrity developed adjacent instability, compared with 3 of 54 (5.6%) without preserved integrity. Conclusions. Damaging the integrity of the posterior complex between the fused segments and the neighboring motion segments may jeopardize lumbar spine stability. Sacrificing either the supraspinous ligament or the tendon insertion points on the spinous processes leads to an accelerated development of adjacent instability.

Pullout strength for cannulated pedicle screws with bone cement augmentation in severely osteoporotic bone: Influences of radial hole and pilot hole tapping

BACKGROUND Pedicle screw fixation in a severely osteoporotic spine remains a challenge for orthopedic surgeons. The previous literature does not adequately address the effects of radial holes for cannulated screws with cement injection and pilot hole tapping on the bone/screw interfacial strength. METHODS Specially designed cannulated pedicle screws, with or without radial holes, were installed in tapped and untapped pilot holes and then injected with cement. A uniform synthetic bone (test block) was used to provide a platform for each screw design. Specimens with inserted screws were then tested for axial pullout failure. FINDINGS (1) Cannulated screws with cement augmentation significantly increased the pullout strength in comparison to solid screws. Additionally, the amount of cement exuded from the cannulated screws increased with an increasing number of radial holes, leading to an increase in the average ultimate pullout strength for cannulated screws with a large number of radial holes. (2) Radiological examination indicated that the cement was exuded from the most proximal holes at the very beginning of its flow path, whereas no cement exudation was found at the remaining distal holes. (3) Cement exudation from the holes of cannulated screws into the open cell of the test block led to a composite (cement/bone) structure at the area of cement exudation. Observations of the failed specimens indicated that failure occurred at the composite/bone interface, while the composite was well bonded to the screws. This implies that the screw/composite interfacial strength was much higher than the composite/bone interfacial strength. (4) Tapping pilot holes decreased the pullout strength of the screws. Generally, larger standard deviations were found for the tapped cases, implying that untapped cases results are more repeatable than tapped cases results. INTERPRETATION Cannulated pedicle screws with radial holes combined with PMMA cement augmentation but without tapping may be a viable clinical option for achieving fixation in severely osteoporotic bone.

Outcomes of interbody fusion cages used in 1 and 2-levels anterior cervical discectomy and fusion: titanium cages versus polyetheretherketone (PEEK) cages.

Study Design A prospective study was performed in case with cervical spondylosis who underwent anterior cervical discectomy and fusion (ACDF) with titanium or polyetheretherketone (PEEK) cages. Objective To find out which fusion cage yielded better clinical and radiographic results. Summary of Background Data Although use of autogenous iliac-bone grafts in ACDF for cervical disc diseases remain standard surgical procedure, donor site morbidity and graft collapse or breakage are concerns. Cage technology was developed to prevent these complications. However, there is no comparison regarding the efficacy between titanium and PEEK cage. Methods January 2005 to January 2006, 53 patients who had 1 and 2-levels ACDF with titanium or PEEK cages were evaluated. We measured the rate and amount of interspace collapse, segmental sagittal angulations, and the radiographic fusion success rate. Odom criteria were used to assess the clinical results. Results The fusion rate was higher in the PEEK group (100% vs. 86.5%, P=0.0335). There was no significant difference between both groups in loss of cervical lordosis (3.2±2.4 vs. 2.8±3.4, P=0.166). The mean anterior interspace collapse (1.6±1.0 mm) in the titanium group was significantly higher than the collapse of the PEEK group (0.5±0.6 mm) (P<0.0001). The mean posterior interspace collapse was also higher in the titanium group (1.6±0.9 mm vs. 0.5±0.5 mm, P<0.0001). An interspace collapse of 3 mm or greater was observed in 16.2% of the patients in the titanium group, compared with zero patients in the PEEK group (P<0.0001). The PEEK group achieved an 80% rate of successful clinical outcomes, compared with 75% in the titanium group (P=0.6642). Conclusions The PEEK cage is superior to the titanium cage in maintaining cervical interspace height and radiographic fusion after 1 and 2-levels anterior cervical decompression procedures.

The fusion rate of calcium sulfate with local autograft bone compared with autologous iliac bone graft for instrumented short-segment spinal fusion.

Study Design. A prospective study. Objectives. To compare the efficacy of calcium sulfate pellets plus laminectomy bone chips with a fresh autologous iliac bone graft for short-segment lumbar fusion. Summary of Background Data. Bone graft substitute material can be used to expand an existing quantity of available laminectomy bone chips. Methods. Seventy-four patients underwent surgery for instrumented one- or two-segment fusion with decompression. Autologous iliac crest bone graft was placed in one posterolateral gutter, while on the other side, an equal quantity of autogenous laminectomy bone supplemented with calcium sulfate was placed. Radiographic assessment included radiographs alone; this was performed every 3 months (3 months to 12 months), then annually. The status of fusion and the relative size of the fusion bone mass on either side of the vertebra were compared. Results. Using iliac crest bone graft (control side) versus autograft laminectomy bone with calcium sulfate (test side), there was no significant difference between the fusion rate and sizes of the fusion bone mass (P > 0.05). Follow-up periods ranged from 30 months to 34 months, averaging 32.5 months. For the 39 patients who received single-segment fusion, 34 patients (87.2%) exhibited bone fusion on the test side, and 35 patients (89.7%) had evidence of fusion on the control side. For the 35 patients who received two-segment fusion, 29 patients (82.9%) exhibited bone fusion on the test side and 30 patients (85.7%) demonstrated complete fusion on the control side. Conclusions. The fusion rate and fusion size between the two groups are similar. Calcium sulfate pellets may play a role as a bone graft extender in short-segment spinal fusion.

Pullout strength of pedicle screws with cement augmentation in severe osteoporosis: A comparative study between cannulated screws with cement injection and solid screws with cement pre-filling

BackgroundPedicle screws with PMMA cement augmentation have been shown to significantly improve the fixation strength in a severely osteoporotic spine. However, the efficacy of screw fixation for different cement augmentation techniques, namely solid screws with retrograde cement pre-filling versus cannulated screws with cement injection through perforation, remains unknown. This study aimed to determine the difference in pullout strength between conical and cylindrical screws based on the aforementioned cement augmentation techniques. The potential loss of fixation upon partial screw removal after screw insertion was also examined.MethodThe Taguchi method with an L8 array was employed to determine the significance of design factors. Conical and cylindrical pedicle screws with solid or cannulated designs were installed using two different screw augmentation techniques: solid screws with retrograde cement pre-filling and cannulated screws with cement injection through perforation. Uniform synthetic bones (test block) simulating severe osteoporosis were used to provide a platform for each screw design and cement augmentation technique. Pedicle screws at full insertion and after a 360-degree back-out from full insertion were then tested for axial pullout failure using a mechanical testing machine.ResultsThe results revealed the following 1) Regardless of the screw outer geometry (conical or cylindrical), solid screws with retrograde cement pre-filling exhibited significantly higher pullout strength than did cannulated screws with cement injection through perforation (p = 0.0129 for conical screws; p = 0.005 for cylindrical screws). 2) For a given cement augmentation technique (screws without cement augmentation, cannulated screws with cement injection or solid screws with cement pre-filling), no significant difference in pullout strength was found between conical and cylindrical screws (p > 0.05). 3) Cement infiltration into the open cell of the test block led to the formation of a cement/bone composite structure. Observations of the failed specimens indicated that failure occurred at the composite/bone interface, whereas the composite remained well bonded to the screws. This result implies that the screw/composite interfacial strength was much higher than the composite/bone interfacial strength. 4) The back-out of the screw by 360 degrees from full insertion did not decrease the pullout strength in any of the studied cases. 5) Generally, larger standard deviations were found for the screw back-out cases, implying that the results of full insertion cases are more repeatable than those of the back-out cases.ConclusionsSolid screws with retrograde cement pre-filling offer improved initial fixation strength when compared to that of cannulated screws with cement injection through perforation for both the conically and cylindrically shaped screw. Our results also suggest that the fixation screws can be backed out by 360 degrees for intra-operative adjustment without the loss of fixation strength.

Polymethylmethacrylate cement dislodgment following percutaneous vertebroplasty: a case report.

Study Design. A case report is presented. Objectives. To report a rare complication of delayed cement displacement following percutaneous vertebroplasty. Summary of Background Data. Although percutaneous vertebroplasty is considered a minimally invasive procedure, it may result in several complications. To our knowledge, this is the first report of delayed cement displacement after percutaneous vertebroplasty. Methods. A 69-year-old man with T12 osteoporotic compression fracture received percutaneous vertebroplasty. One month after surgery, the patient complained of progressive severe back pain, and roentgenographic image revealed a breakdown of the anterior cortex of the T12 vertebral body with anterior displacement of the bone cement. Results. The complication was solved by one stage anterior and posterior operation: thoracoabdominal approach with removal of the displaced cement and posterior instrumentation from T11 to L1. The severe back pain with associated weakness improved after surgery. Conclusions. This complication is rare and likely to occur in treatment of osteoporotic vertebral fracture with avascular necrosis and anterior cortical defect.

Instrumented posterior lumbar interbody fusion for patients with degenerative lumbar scoliosis.

Objective Surgery for degenerative lumbar scoliosis remains challenging for spine surgeons even with the application of pedicle screw instrumentation. This retrospective study assesses the outcomes of instrumented posterior lumbar interbody fusion (PLIF) for degenerative lumbar scoliosis. Methods From April 2000 to April 2004, 26 patients with degenerative lumbar scoliosis were treated with instrumented PLIF. Mean age of the 15 females and 11 males was 64.2 years (range, 51 to 77 y). Clinical and radiographic outcomes were retrospectively reviewed for each case at a minimum follow-up of 2 years (median follow-up, 3 y; range, 2 to 6 y). At final follow-up, patients were classified as “satisfied” or “dissatisfied” according to self-reported outcomes. Results At most recent follow-up, the average Oswestry Disability Index score was significantly lower than the preoperative score (25.8 vs. 58.0; P<0.001). Twenty (76.9%) patients reported that they were satisfied with their surgical outcomes. The average lumbar scoliosis angles were significantly less than preoperative angles (7.4 vs. 16.5 degrees; P<0.001), resulting in a reduction in mean scoliosis angles of 55.2%. The average angles of lumbar lordosis were significantly higher than preoperative angles (30.1 vs. 22.2 degrees; P=0.001), an increase in mean lumbar lordosis angles of 35.6%. No perioperative deaths or major medical complications occurred. Five patients had adjacent segment degeneration and 4 (80%) of 5 reported dissatisfactory outcomes. Further study is required to identify the etiologies of adjacent segment degeneration and methods for avoiding such degeneration. Conclusions Analytical results demonstrate that instrumented PLIF after laminectomy in patients with degenerative lumbar scoliosis is an effective and safe procedure.

A Comparison of Posterolateral Lumbar Fusion Comparing Autograft, Autogenous Laminectomy Bone With Bone Marrow Aspirate, and Calcium Sulphate With Bone Marrow Aspirate: A Prospective Randomized Study

Study Design. A prospective clinical study. Objective. To evaluate whether the fusion rate of autogenous laminectomy bone chips and calcium sulfate pellets could be augmented by bone marrow aspirate (BMA) in one-level lumbar posterolateral fusion. Summary of Background Data. An in vivo animal study has indicated that BMA augments spinal arthrodesis. Methods. Forty-three patients undergoing surgery for instrumented one-level fusion with decompression were divided into 2 groups. Autologous iliac crest bone graft (ICBG) was placed in 1 posterolateral gutter (control), while on the other side (test), an equal quantity of laminectomy bone chips mixed with BMA while harvesting the iliac bone graft (group 1) or an equal quantity of calcium sulfate pellets soaked in BMA (group 2) was placed. Radiographic assessment was performed every 3 months (3–12 months) and then annually. The statuses of fusion on either side of the vertebra were compared. Results. For the 21 patients in group 1, 18 (85.7%) exhibited bone fusion on the test side, and 19 (90.5%) presented evidence of fusion on the control side. Thus, the test side with laminectomy bone chips and BMA achieved a fusion rate similar to that on the control side (P > 0.05). For the 22 patients in group 2, 20 (90.9%) exhibited bone fusion on the control side whereas only 10 (45.5%) demonstrated complete fusion on the test side (P < 0.05), where calcium sulfate and BMA was applied. Conclusion. ICBG performs as expected with high fusion rates and laminectomy bone with BMA performs equally as well. Osteoset is significantly inferior to ICBG despite the addition of BMA, which is osteoinductive and has improved fusion rates and osteogenesis in other models.

A comparison of three types of postoperative pain control after posterior lumbar spinal surgery.

Study Design. Retrospective, nonrandomized, comparative study. Objective. This study compared the early postoperative analgesic effects and the postoperative nausea and vomiting (PONV) associated with three methods of pain control after posterior lumbar spinal surgery. Summary of Background Data. The use of opioids for postoperative pain control is common after spinal surgery; however, PONV is the most frequently encountered side effect, and it is yet to be overcome. The effectiveness of the use of an absorbable low-dose morphine-soaked microfibrillar collagen hemostatic sponge placed on the surface of the dural sac (epidural MMCHS) was compared to patient-controlled analgesia (PCA) and intermittent intramuscular bolus injection of meperidine for postoperative pain control after spine surgery. Methods. One hundred sixty-five patients who underwent short-segment posterior lumbar spinal decompression and fusion surgery between January 2007 and July 2007 in the orthopedic department of a medical center were enrolled. For postoperative pain control, 40 patients received epidural MMCHS, 48 patients received PCA, and 77 patients received meperidine injection. Patient ratings of pain intensity (visual analog scale score from 0 [no pain] to 10 [most severe pain]), nausea (from 0 [no nausea] to 5 [severe nausea]), and vomiting (from 0 [no vomiting] to 5 [severe vomiting]) were recorded at 4 hours postoperation and on postoperative days 1, 2, and 3. Results. The analgesic effect was enhanced significantly in both epidural MMCHS group and the PCA group as compared with the meperidine group on postoperative days 1 and 2 (P < 0.05). On postoperative days 1, 2, and 3, PONV was more severe in the PCA group than in the other two groups (P < 0.05). The side effects of epidural MMCHS were nausea (25%), pruritus (12.5%), vomiting (5%), and hypotension (2.5%). Conclusion. A single low-dose epidural MMCHS is effective for postoperative pain control and minimizes the occurrence of PONV after posterior lumbar spinal surgery.