Tsai-Sheng Fu

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.

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.

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.

Pedicle screw insertion: computed tomography versus fluoroscopic image guidance

Computed tomography image-guided surgery (CTGS) clearly improves the accuracy of pedicle screw insertion. Recent reports claim that a fluoroscopy-guided system (FGS) offered high accuracy and easy application. However, the superiority of either technique remains unclear in clinical application. This study compares the accuracy of pedicle screws installed using CTGS with that of screws installed using FGS. Seventy-four screws inserted using FGS in 13 patients and 76 screws inserted using CTGS in 11 patients were compared. The study population included ten cases of vertebral fracture, five cases of degenerative spondylolisthesis, three cases of spondylolytic spondylolisthesis, two cases of tuberculous spondylitis, two cases of failed earlier back surgery and two case of ankylosing spondylitis with pseudarthrosis. The installed vertebral levels ranged from T8 to S1. Screw positions were assessed with postoperative radiographs and computed tomography. Sixty-nine (93.2%) screws were correctly placed in the FGS group, and seventy-three (96.1%) screws were correctly placed in the CTGS group (P = 0.491). The results indicated that both image-guided systems offer high accuracy. However, the fluoroscope image-guided system could be considered the primary tool for lower thoracic and lumbosacral pedicle placement because it enables real-time navigation and does not require a preoperative CT scan.RésuméLa chirurgie assistée par imagerie (CTGS) permet d’avoir une meilleure sécurité lors de l’implantation de vis pediculaires. Des articles récents montrent que le système avec amplificateur de brillance (fluoroscopie FGS) permet également cette implantation. Cependant, la supériorité d’une technique ou d’une autre n’apparaît pas clairement. Le but de cette étude est de comparer la bonne implantation des vis pediculaires en utilisant les deux systèmes. 74 vis ont été insérées avec le système FGS chez 13 patients et 66 vis avec le système CTGS chez 11 patients. Ces deux séries ont été comparées. Cette étude inclut 10 cas de fractures vertébrales, 5 cas de spondylolisthésis dégénératifs, 3 cas de spondylolisthésis avec spondylolyse, à 2 cas d’atteintes tuberculeuses, 2 cas d’échec de chirurgie par voie postérieure et 2 cas de spondylarthrite ankylosante avec pseudarthrose. Les niveaux d’instrumentation se sont échelonnés de T8 à S1. 69 (93.2%) vis ont été correctement mises en place dans le groupe FGS et, 73 (96.1%) avec le groupe CTGS (P = 0.491). Les résultats montrent que le système d’images guidées CTGS offre beaucoup plus de sécurité dans l’implantation des vis tant au niveau lombaire qu’au niveau thoracique ou lombosacré ceci ne nécessite pas par ailleurs un scanner pré opératoire.

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.

Computer-assisted fluoroscopic navigation of pedicle screw insertion An in vivo feasibility study

Background Accurate placement of pedicle screws is difficult. Patients and methods We evaluated the feasibility and accuracy of pedicle screw insertion assisted by a real-time, 2-dimensional (2D) image-guided navigation system in 12 patients who underwent thoraco-lumbar and/or lumbar stabilization. 66 pedicle screws were inserted either by senior spine surgeons or residents. The accuracy of positioning of the screws was evaluated using postoperative plain radiographs and thin-cut CT. Results 61 of the 66 screws were inserted successfully. 5 screw insertions showed structural violations: 4 on the medial and 1 on the lateral pedicle wall. The accuracy was higher in the sagittal plane than in the axial plain. There was no difference between the surgical error rates caused by the senior surgeons and the residents. Interpretation Using computer-assisted 2D fluoroscopic image navigation, it is possible to achieve reliable and accurate pedicle screw insertion during low thoracic and lumbar spinal surgery.

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.

Identifying Pathogens of Spondylodiscitis: Percutaneous Endoscopy or CT-guided Biopsy

AbstractIdentifying offending pathogens is crucial for appropriate antibiotic administration for infectious spondylitis. Although computed tomography (CT)-guided biopsy for bacteriologic diagnosis is a standard procedure, it has a variable success rate. Some reports claim percutaneous endoscopic discectomy and drainage offer a sufficient amount of tissue for microbiologic examination and easy application. We therefore compared the diagnostic value of CT guidance with that of endoscope guidance in 52 patients with suspected infectious spondylitis. Twenty patients underwent percutaneous endoscopic discectomy and drainage by an orthopaedic surgeon and the other 32 patients underwent CT-guided biopsies by a radiologist. Patients were followed a minimum of 12 months after treatment. Culture results of the biopsy specimens were recorded. Causative bacteria were identified more frequently with percutaneous endoscopy than in CT-guided biopsy (18 of 20 [90%] versus 15 of 32 [47%]). We observed no biopsy-related complications or side effects in either group. The data suggest percutaneous endoscopic discectomy and drainage yield higher bacterial recovery rates than CT-guided spinal biopsy. Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.