Wen-Jer Chen

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.

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±1.0u2009mm) in the titanium group was significantly higher than the collapse of the PEEK group (0.5±0.6u2009mm) (P<0.0001). The mean posterior interspace collapse was also higher in the titanium group (1.6±0.9u2009mm vs. 0.5±0.5u2009mm, P<0.0001). An interspace collapse of 3u2009mm 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.

Combined anterior and posterior surgeries in the treatment of spinal tuberculous spondylitis.

Methods for the treatment of tuberculous spondylitis still are controversial. The authors treated 32 consecutive patients with a two-stage surgical technique combined with antituberculous chemotherapy for 1 year. After anterior debridement, fusion with autogenous anterior iliac tricortical strut bone graft was done, and in a second stage, posterior instrumentation and fusion with autogenous posterior iliac corticocancellous bone graft was done 11 days (range, 4–22 days) later. Postoperatively, patients were encouraged to ambulate with brace protection as early as possible. Twenty-nine patients were followed up for a minimum of 2 years (median, 4.7 years; range, 2–10 years) of whom 28 patients achieved solid fusion (97%). All patients had improvement of back pain including the only patient with pseudarthrosis. Neurologic deficits completely recovered in 84% (16 of 19) of patients after 3 months. Kyphotic deformity improved in all 29 patients (34.6° versus 17.3°) with the average correction angle of 17.3°. Clinically, 27 patients had achieved a satisfactory outcome (93%). There were no evident surgical complications. The authors, therefore, recommend a two-stage surgical technique combined with antituberculous chemotherapy to treat patients with severe vertebral body destruction attributable to tuberculosis because of its high success rate and a low complication rate.

Biomechanical comparison between lumbar disc arthroplasty and fusion

The artificial disc is a mobile implant for degenerative disc replacement that attempts to lessen the degeneration of the adjacent elements. However, inconsistent biomechanical results for the neighboring elements have been reported in a number of studies. The present study used finite element (FE) analysis to explore the biomechanical differences at the surgical and both adjacent levels following artificial disc replacement and interbody fusion procedures. First, a three-dimensional FE model of a five-level lumbar spine was established by the commercially available medical imaging software Amira 3.1.1, and FE software ANSYS 9.0. After validating the five-level intact (INT) model with previous in vitro studies, the L3/L4 level of the INT model was modified to either insert an artificial disc (ProDisc II; ADR) or incorporate bilateral posterior lumbar interbody fusion (PLIF) cages with a pedicle screw fixation system. All models were constrained at the bottom of the L5 vertebra and subjected to 150N preload and 10Nm moments under four physiological motions. The ADR model demonstrated higher range of motion (ROM), annulus stress, and facet contact pressure at the surgical level compared to the non-modified INT model. At both adjacent levels, ROM and annulus stress were similar to that of the INT model and varied less than 7%. In addition, the greatest displacement of posterior annulus occurred at the superior-lateral region. Conversely, the PLIF model showed less ROM, less annulus stress, and no facet contact pressure at the surgical level compared to the INT model. The adjacent levels had obviously high ROM, annulus stress, and facet contact pressure, especially at the adjacent L2/3 level. In conclusion, the artificial disc replacement revealed no adjacent-level instability. However, instability was found at the surgical level, which might accelerate degeneration at the highly stressed annulus and facet joint. In contrast to disc replacement results, the posterior interbody fusion procedure revealed possibly accelerative degeneration of the annulus and facet joint at both adjacent levels.

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.

Impact of cement leakage into disks on the development of adjacent vertebral compression fractures.

Study Design A retrospective study assessing new adjacent vertebral compression fracture (VCF) after percutaneous vertebroplasty (PV). Objective To evaluate the relationship between cement leakage into the disk during initial PV and development of subsequent new adjacent VCF. Summary of Background Data Cement leakage outside the vertebral body during PV has been reported and usually responds to conservative treatment. Sometimes bone cement may leak into the intervertebral disk and result in painful new adjacent VCF that usually requires another PV for pain relief. Methods From January 2002 to December 2002, a total of 106 consecutive patients underwent PVs for osteoporotic VCFs. The risk of new fractures of adjacent vertebral bodies, the amount of cement injection, and the duration of development of new adjacent fractures in relation to cement leakage into the disk were retrospectively assessed and statistically compared. Results New adjacent VCFs occurred in 20 (18.9%) of 106 patients at 22 adjacent vertebral bodies after PVs during at least 24 months of follow-up. The difference in number of new adjacent fractures between both patients and vertebral bodies with cement leakage and those without leakage into the disk were statistically significant (P<0.001 and P<0.001). Amounts of cement injected and duration to development of new adjacent fractures differed between patients with or without cement leakage (P<0.001 and P=0.005, respectively). Conclusions PV is a simple and effective, but not risk-free or complication-free procedure for the treatment of osteoporotic VCF. Patients undergoing PV should be informed of the possibility of new adjacent fractures and the higher risk if cement leaks into the disk.

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 77u2009y). Clinical and radiographic outcomes were retrospectively reviewed for each case at a minimum follow-up of 2 years (median follow-up, 3u2009y; range, 2 to 6u2009y). 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.

Long-term Results of Disc Excision for Recurrent Lumbar Disc Herniation With or Without Posterolateral Fusion

Study Design. A retrospective study assessing the long-term outcomes of repeat surgery for recurrent lumbar disc herniation. Objectives. To evaluate the results of repeat surgery for recurrent disc herniation, and compare the results of disc excision with and without posterolateral fusion. Summary of Background Data. The outcomes of revision surgery varied owing to the mixed patient populations. The optimal technique for treating recurrent disc herniation is controversial. Methods. The sample included 41 patients who underwent disc excision with or without posterolateral fusion, with an average follow-up of 88.7 months (range, 60–134 months). Clinical symptoms were assessed based on the Japanese Orthopedic Association Back Scores. All medical and surgical records were examined and analyzed, including pain-free interval, intraoperative blood loss, length of surgery, and postsurgery hospital stay. Results. Clinical outcome was excellent or good in 80.5% of patients, including 78.3% of patients undergoing a discectomy alone, and 83.3% of patients with posterolateral fusion. The recovery rate was 82.2%, and the difference between the fusion and nonfusion groups was insignificant (P = 0.799). The difference in the postoperative back pain score was also insignificant (P = 0.461). These two groups were not different in terms of age, pain-free interval, and follow-up duration. Intraoperative blood loss, length of surgery, and length of hospitalization were significantly less in patients undergoing discectomy alone than in patients with fusion. Conclusions. Repeat surgery for recurrent sciatica is effective in cases of true recurrent disc herniation. Disc excision alone is recommended for managing recurrent disc herniation.