The Bagby and Kuslich method of lumbar interbody fusion. History, techniques, and 2-year follow-up results of a United States prospective, multicenter trial

STUDY DESIGN: A prospective, multicenter trial of the Bagby and Kuslich method of lumbar interbody stabilization for chronic discogenic low back pain, with follow-up evaluation at 3 months, 6 months, and yearly thereafter, with independent radiographic analysis. OBJECTIVES: To report the history of development, the surgical techniques, and results of the Bagby and Kuslich method when used to manage discogenic pain of the lumbar spine in humans. SUMMARY OF BACKGROUND DATA: Disabling chronic low back pain frequently is resistant to conservative management. The "Bagby Basket" effectively has fused the equine and baboon spine. The results of biomechanical and animal studies performed over the last 20 years have suggested that a similar but improved design--the Bagby and Kuslich device--would be useful in stabilizing the human spine. METHODS: From 1992 to 1995, 947 patients with chronic discogenic low back pain were treated by Bagby and Kuslich interbody fusion in a strict, multicenter, prospective clinical trial by using either the open anterior or open posterior approach. The study involved 42 surgeons at 19 medical centers. The authors of the current report analyzed the fusion rates, pain relief, functional status, and complications occurring in patients who underwent long-term follow-up observation. RESULTS: The Bagby and Kuslich method is safe and effective when compared with methods described in previous reports of posterior and anterior lumbar interbody arthrodesis performed by using bone graft alone. Fusion occurred in 91% of patients at 24 months after surgery, and pain was eliminated or reduced in 84%. Function was improved in 91%. There were no device-related deaths, cases of major paralyses, device failures, or deep infections. CONCLUSIONS: Carefully selected middle-aged patients with chronic low back pain secondary to degenerative disc disease can be treated effectively and safely by skilled surgeons using the Bagby and Kuslich device for one- and two-level interbody fusion.     

A biomechanical comparison of open and thoracoscopic anterior spinal release in a goat model

STUDY DESIGN: A biomechanical assessment of anterior release and discectomy in the thoracic spine was performed on an animal model using thoracoscopic and open thoracotomy techniques. OBJECTIVES: To compare the relative efficacy of these two techniques of release in achieving increased spinal mobility. BACKGROUND DATA: The clinical use of video-assisted thoracoscopy in the correction of spinal deformity is increasing. The effectiveness of thoracoscopic anterior spinal release with discectomy has not been evaluated biomechanically. METHODS: Anterior release with discectomy was performed on six midthoracic motion segments in five mature goats. The thoracoscopic technique was used for three levels on one side, and an open thoracotomy was used for the alternating three levels of the contralateral side. The duration of surgery for disc excision and the amount of blood loss for each technique were recorded. The intact cranial and caudal motion segments served as controls. The motion segments were individually subjected to nondestructive biomechanical testing. Torsional, sagittal, and coronal bending torques were applied, and the resulting angular displacement was measured. RESULTS: The duration of surgery to remove a disc thoracoscopically decreased as experience was gained by the surgeon. The amount of intraoperative blood loss was comparable using the two methods. There was significantly increased flexibility in the released segments with both techniques, compared with the flexibility in the intact levels for all three loading directions. There was no difference in the motion obtained after release between the two techniques. CONCLUSION: Open and thoracoscopic anterior release and discectomy have been demonstrated, through biomechanical in vitro testing, to increase the flexibility of the spine to a similar extent.     

Comparison of thoracoscopic and open thoracic discectomy in a live ovine model for anterior spinal fusion

STUDY DESIGN: The authors undertook a randomized comparison of 30 thoracoscopic and 30 open thoracic discectomies for anterior spinal fusion in a live sheep model. OBJECTIVES: To compare in a live sheep model discectomies performed using a thoracoscopic technique with those using an open thoracotomy technique to validate the efficacy of thoracoscopic disc and end plate removal for potential fusion. SUMMARY OF BACKGROUND DATA: In 1993, Mack and Regan described a technique for video-assisted thoracic surgery that resulted in less morbidity than open techniques. Subsequent reports support the finding that thoracoscopic spinal surgery results in less morbidity. METHODS: Sixty discectomies were performed in 10 live sheep. In each sheep, three randomly selected discectomies were performed thoracoscopically, and, subsequently, three open discectomies were performed. The animal then was killed, and the spine was sectioned and analyzed by computer imaging. RESULTS: Statistical analysis found no significant difference in the amount of disc resected (t' = 1.9639, t0.025, 60 = 2.000, alpha = 0.05). The mean percentage of disc resected was 67.8% (range, 0-92.2%) in the thoracoscopic group and 76.1% (range, 44.9-95.4%) in the open group. More than 50% of the disc was excised in 27 of 30 spines (90%) in the thoracoscopic group and in 29 of 30 (96.7%) in the open group. This difference was not statistically significant (theta 2(0.05, 1) = 3.84, theta 2' = 1.07). CONCLUSION: The findings in this study indicate that the thoracoscopic discectomy technique is equivalent to the open technique in the amount of disc and end plate resected. In addition, these findings suggest that thoracoscopic discectomies provide adequate disc resection to provide for an acceptable fusion rate according to the criteria demonstrated by Bunnell in 1982 and therefore support the efficacy of a thoracoscopic technique for anterior spinal fusion.     

Video-assisted thoracoscopic surgery to the upper thoracic spine

BACKGROUND: The standard open technique for exposure of the upper thoracic spine, T1-T4, usually requires a difficult thoracotomy. From November 1, 1995 to June 30, 1997, eight patients underwent video-assisted thoracoscopic spinal surgery in our institute to treat their upper thoracic spinal lesions endoscopically. METHODS: A new approach, the so-called "extended manipulating channel method," was used in this series that allows the combined use of video-assisted thoracoscopy and conventional spinal instruments to enter the chest cavity freely for the procedures. Patients' ages ranged from 44 to 89 years (average, 60 years). Definitive diagnoses included two pyogenic spondylitis and six spinal metastases. Five patients presented initially with myelopathy. RESULTS: There were no deaths or neurologic injuries associated with this technique. The mean surgical time was 3.1 h. The mean duration of chest tube retention was 3.3 days. The mean total blood loss was 1,038 ml, and two patients had a blood loss of more than 2,000 ml owing to bleeding from epidural veins or raw osseous surfaces. Complications included one superficial wound infection and one subcutaneous emphysema that resolved spontaneously. In this series, there was no need of conversion to open thoracotomy for the patients. CONCLUSIONS: The thoracoscopy-assisted spinal technique using the extended manipulating channels, usually 2.5-3.5 cm, allows variable instrument angulations for manipulation. The mean surgical time (3.1 h) was considered no longer than for an open technique for the equivalent anterior procedure. Such an approach can achieve less procedure-related trauma and has proved to be a good alternative to other treatment modalities.     

Minimally invasive anterior retroperitoneal approach to the lumbar spine. Emphasis on the lateral BAK

STUDY DESIGN: Eighteen patients with lumbar instability from fractures, postlaminectomy syndrome, or infection were treated prospectively with minimally invasive retroperitoneal lumbar fusions. OBJECTIVES: To determine if interbody Bagby and Kuslich fusion cages and femoral allograft bone dowels can be inserted in a transverse direction via a lateral endoscopic retroperitoneal approach to achieve spinal stability. SUMMARY OF BACKGROUND DATA: Endoscopic spinal approaches have been used to achieve lower lumbar fusion when instrumentation is placed through a laparoscopic, transperitoneal route. However, complications of using this approach include postoperative intra-abdominal adhesions, retrograde ejaculation, great vessel injury, and implant migration. This study is the first clinical series investigating the use of the lateral retroperitoneal minimally invasive approach for lumbar fusions from L1 to L5. METHODS: Eighteen patients underwent anterior interbody decompression and/or stabilization via endoscopic retroperitoneal approaches. In most cases, three 12-mm portals were used. Two parallel transverse interbody cages restored the neuroforaminal height and the desired amount of lumbar lordosis was achieved by inserting a larger anterior cage, distraction plug, or bone dowel. RESULTS: The overall morbidity of the procedure was lower than that associated with traditional "open" retroperitoneal or laparotomy techniques, with a mean length of hospital stay of 2.9 days (range, outpatient procedure to 5 days). The mean estimated intraoperative blood loss was 205 cc (range, 25-1000 cc). There were no cases of implant migration, significant subsidence, or pseudoarthrosis at mean follow-up examination of 24.3 months (range, 12-40 months) after surgery. CONCLUSIONS: This preliminary study of 18 patients illustrates that endoscopic techniques can be applied effectively through a retroperitoneal approach with the patient in the lateral position. Unlike the patients who had undergone transperitoneal procedures described in previous reports, in these preliminary 18 patients, there were no cases of retrograde ejaculation, injury to the great vessels, or implant migration.     

Video-assisted lateral intertransverse process arthrodesis. Validation of a new minimally invasive lumbar spinal fusion technique in the rabbit and nonhuman primate (rhesus) models

STUDY DESIGN: Cadaveric anatomic and in vivo survival animal studies were performed to develop a new arthrodesis technique for the lumbar spine. OBJECTIVES: To examine the feasibility, efficacy, and safety of a minimally invasive lumbar intertransverse process arthrodesis technique using an osteoinductive growth factor (rhBMP-2) delivered in a collagen sponge carrier. The technique was first developed using a rabbit model and modified for the nonhuman primate (rhesus monkey), a larger animal with the most similar bone biology to humans. SUMMARY OF BACKGROUND DATA: The morbidity of conventional posterolateral lumbar intertransverse process arthrodesis includes graft donor site morbidity; paraspinal muscle devascularization, denervation, and scarring and nonunion in up to 36% of patients. Minimally invasive anterior lumbar interbody arthrodesis techniques have been developed, but these often require a metal implant and carry risks to major vessels and development of retrograde ejaculation. A minimally invasive technique for posterolateral intertransverse process arthrodesis has not been described previously. METHODS: In Part 1, we examined seven New Zealand white rabbits and five rhesus monkeys at necropsy and during nonsurvival surgeries to determine the best access routes and to develop special instruments for video-assisted lateral intertransverse process arthrodesis. In Part 2, 38 New Zealand white rabbits underwent L4-L5 intertransverse process arthrodesis: the "OPEN" group (n = 16) underwent a standard open muscle-splitting approach using rhBMP-2 (bone morphogenetic protein) and collagen as a bone graft substitute; the "video-assisted control" group (n = 6) underwent video-assisted lateral intertransverse process arthrodesis with the collagen implant only (no growth factor); and the "video-assisted-BMP" group (n = 16) underwent video-assisted lateral intertransverse process arthrodesis with rhBMP-2 and collagen as the graft material. In Part 3, rhesus monkeys (n = 4) underwent video-assisted lateral intertransverse process arthrodesis using rhBMP-2 and collagen after laminectomy of L4-L5. RESULTS: In Part 1, we identified expedient, minimally invasive routes to the intertransverse process interval appropriate for each species: an intermuscular approach for the rabbit and a lateral, extramuscular approach for the rhesus monkey. In Part 2, all rabbits in the OPEN and video-assisted-BMP groups achieved solid intertransverse process lumbar fusions when assessed at 10 weeks. There were no neurologic impairments nor any difference between the two groups in the frequency of postoperative infection or other complications. None of the animals in the video-assisted control group showed evidence of fusion. In Part 3, exposure, decortication and grafting with rh-BMP-2 and collagen was accomplished successfully in all four monkeys through the video-assisted minimally invasive approach without complications. CONCLUSION: Video-assisted lateral intertransverse process arthrodesis is a feasible, effective, and safe method of lumbar spinal fusion in the rabbit and rhesus monkey. Use of this arthrodesis procedure will minimize the morbidity of paraspinal muscle denervation and devascularization seen with open intertransverse process fusion techniques, and the use of an osteoinductive growth factor will eliminate the problem of graft donor site morbidity and possibly increase the chances for successful fusion.     

Reversing the inhibitory effect of nicotine on spinal fusion using an osteoinductive protein extract

STUDY DESIGN: The effect on spinal fusion of an osteoinductive bone protein extract in the presence of a known inhibitor of spinal fusion (systemic nicotine) was studied prospectively in an animal model of posterolateral lumbar fusion. OBJECTIVES: To evaluate the ability of a bovine-derived osteoinductive bone protein extract to overcome the inhibitory effect of nicotine in a rabbit spine fusion model. SUMMARY OF BACKGROUND DATA: Multiple studies have demonstrated the ability of a variety of osteoinductive growth factors to serve as a bone graft substitute for lumbar spinal fusion under "normal" healing conditions. METHODS: Forty-eight adult female New Zealand white rabbits underwent spine arthrodesis at L5-L6 while receiving systemic nicotine through a subcutaneous miniosmotic pump. Arthrodesis was performed using one of the following three graft materials: 1) autogenous iliac crest, 2) osteoinductive bone protein delivered in an allogeneic demineralized bone matrix/ collagen carrier, or 3) osteoinductive bone protein delivered with autogenous iliac crest. Fusions were assessed by blinded manual palpation, radiography, and biomechanical testing. RESULTS: Of the 44 rabbits manually tested by blinded observers, all 14 in the osteoinductive bone protein plus autogenous iliac crest bone group had solid fusions (14 of 14), whereas the fusion rate was less in the osteoinductive bone protein plus demineralized bone matrix group (nine of 14, 64%; P = 0.02), and there were no fusions in the autogenous iliac crest only group (0 of 16, 0%; P = 0.000001). The use of osteoinductive bone protein with autogenous bone produced stronger and stiffer fusions compared with those using autogenous bone alone or osteoinductive bone protein with allograft bone. CONCLUSIONS: Cigarette smoking and nicotine are inhibitory factors in the healing of fractures and spine fusions. This study shows that the inhibitory effect of nicotine can be overcome with an osteoinductive bone growth factor in an animal model.     

Video-assisted thoracoscopic closure of the delayed bronchial rupture after thoracoscopic resection of mediastinal bronchogenic cyst

Video-assisted thoracoscopic surgery (VATS) is an effective and less invasive modality for management of mediastinal disorders, but various complications can result from the procedure. This report describes a case of delayed rupture of the bronchus intermedius which occurred on postoperative day 1 after the patient underwent complete thoracoscopic removal of a mediastinal bronchogenic cyst (BC) with pericystic adhesions to the bronchus. The bronchial rupture was successfully treated by conventional surgical instruments through limited thoracotomy with video-assisted thoracoscopic guidance. In recognition of this possibility, VATS for a BC with adhesions should be carefully performed. Additionally, the role of VATS in bronchial repair is beneficial.     

New technology in diagnosis and treatment of diseases of the pleural space

Recent developments in video camera technology, new instruments, and advanced surgical techniques have increased the importance of video-assisted thoracoscopic surgery (VATS). Currently, VATS offers a new approach in the diagnosis and treatment of many thoracic conditions previously treated only by standard thoracotomy. In our experience, VATS is a safe, reliable, and effective alternative to thoracic surgery. With further improvements and refinements in video imaging and endoscopic instruments, more procedures will be technically feasible. The long-term results of VATS compared to open thoracotomy will require extensive follow up and prospective trials to determine its true value.     

Video-assisted thoracoscopic surgery (VATS). Endoscopic thoracoplasty technique

STUDY DESIGN: The study of two patients whose rib deformity was treated using a new endoscopic thoracoplasty technique is reported. OBJECTIVES: To report a new endoscopic thoracoplasty technique for the treatment of rib deformities associated with idiopathic scoliosis. SUMMARY OF BACKGROUND DATA: Thoracoplasty has traditionally been performed as an open procedure, often necessitating additional incisions and/or tissue dissection. METHODS: Two children with significant rib humps associated with idiopathic scoliosis were treated with a new endoscopic thoracoplasty technique. RESULTS: Both children showed dramatic cosmetic improvement of their rib deformity. CONCLUSIONS: The indications for the use of video-assisted thoracoscopic surgery in the treatment of pediatric spinal deformity are expanding. We have extended our video-assisted thoracoscopic surgery repertoire to include endoscopic thoracoplasty for treatment of rib deformities associated with idiopathic scoliosis. The technique for endoscopic thoracoplasty is discussed, and illustrative cases are presented.     

Shigella gastroenteritis: clinical and epidemiological aspects, and antibiotic susceptibility

We present a case of video-assisted partial resection of the right lower lobe for a pulmonary tumor. A 67 year-old woman was admitted because of an abnormal shadow on a chest roentgenogram. The operation was carried out via a small lateral thoracotomy incision and two surgical ports, by video-assisted thoracotomy with intraoperative ultrasonographic detection of the tumor. Pathologic examination of the specimen revealed a carcinoid tumor and showed no tumor cells remaining in the stump. As the postoperative course was uneventful, we describe the usefulness of video-assisted thoracoscopic surgery combined with intraoperative ultrasonography.     

The intubating laryngeal mask: use of a new ventilating-intubating device in the emergency department

OBJECTIVE: Despite modern diagnostic methods and appropriate treatment, pleural empyema remains a serious problem. Our purpose was to assess the feasibility and efficacy of the video-assisted thoracoscopic surgery in the management of nontuberculous fibrinopurulent pleural empyema after chest tube drainage treatment had failed to achieve the proper results. METHODS: We present a prospective selected single institution series including 45 patients with pleural empyema who underwent an operation between March 1993 and December 1996. Mean preoperative length of conservative management was 37 days (range, 8-82 days). All patients were assessed by chest computed tomography and ultrasonography and underwent video-assisted thoracoscopic debridement of the empyema and postoperative irrigation of the pleural cavity. RESULTS: In 37 patients (82%), video-assisted thoracoscopic debridement was successful. In 8 cases, decortication by standard thoracotomy was necessary. There were no complications during video-assisted thoracic operations. The mean duration of chest tube drainage was 7. 1 days (range, 4-140 days). At follow-up (n = 35) with pulmonary function tests, 86% of the patients treated by video-assisted thoracic operation showed normal values; 14% had a moderate obstruction and restriction without impairment of exercise capacity, and no relapse of empyema was observed. CONCLUSIONS: Video-assisted thoracoscopic debridement represents a suitable treatment for fibrinopurulent empyema when chest tube drainage and fibrinolytics have failed to achieve the proper results. In an early organizing phase, indication for video-assisted thoracic operation should be considered in due time to ensure a definitive therapy with a minimally invasive intervention. For pleural empyema in a later organizing phase, full thoracotomy with decortication remains the treatment of choice.     

Application of thoracoscopy for diseases of the spine

For anterior approaches to the thoracic spine, a posterolateral thoracotomy has been the standard approach. Recent expanded experience with video-assisted thoracic surgical techniques has allowed us to perform many thoracic spine procedures that previously required open approaches. These procedures include drainage of spinal abscesses, biopsy of vertebral bodies, discectomy for a herniated nucleus pulposus, and anterior releases for kyphoscoliosis. All procedures were successful, but experience is limited and follow-up still short. It is hoped that further experience will prove that this less invasive approach can be widely applied in the practice of thoracic spinal surgery.     

Optimal selection and preparation of fresh frozen corticocancellous allografts for cervical interbody spinal fusion

STUDY DESIGN: Iliac crest corticocancellous allografts for anterior interbody fusion were harvested from six cadavers. The grafts were cut sequentially from left and right crests and randomly assigned to tricortical or bicortical preparations. Their compression strengths then were determined and compared by matched pair analysis. OBJECTIVES: To quantify the failure strength of the grafts from different iliac locations and determine the optimal type of preparation of the grafts for anterior interbody fusion. SUMMARY OF BACKGROUND DATA: Iliac crest corticocancellous autografts and allografts commonly are used for interbody cervical fusions. However, graft strengths for specific sites have not been determined fully. METHODS: Six paired, fresh frozen, iliac crests were sectioned using a customized miter box into multiple 1-cm-thick grafts 1.5 cm in depth to simulate cervical interbody grafts. The left and right sides of each pair were randomly assigned to tricortical and bicortical preparations. The samples were tested by applying a compressive load to failure using a specialized fixture to simulate vertebral body loading. RESULTS: The grafts closer to the anterosuperior iliac spine had significantly higher failure loads and failure strengths than those closer to the posterosuperior iliac spine. The strengths of the bicortical grafts were 72 +/- 14% of the strengths of the tricortical grafts (P < 0.001). CONCLUSIONS: Anterior iliac crest grafts were stronger in compression, even after removal of one cortical surface, than posterior iliac crest grafts.     

Video-assisted thoracoscopic treatment of spontaneous pneumothorax: technique and results of one hundred cases

OBJECTIVE: This article describes the technique and results for an initial series of 100 pneumothoraces treated by video-assisted thoracoscopy. METHODS: From May 1991 to November 1994, 97 patients (78 male and 19 female patients) aged 37.2 +/- 17 years (range 14 to 92 years) underwent video-assisted thoracoscopy for treatment of spontaneous pneumothorax (primary in 75 patients, secondary in 22 patients). RESULTS: The procedure was unilateral in 94 patients and bilateral in three patients (total 100 cases). Pleural bullae were resected with an endoscopic linear stapler; a lung biopsy was performed in the absence of any identifiable lesion. Pleurodesis was achieved by electrocoagulation of the pleura (n = 3), "patch" pleurectomy (n = 3), subtotal pleurectomy (n = 20), or pleural abrasion (n = 74), including conversion to standard thoracotomy in five. One of these five patients had primary pneumothorax and four had secondary pneumothorax. There were no postoperative deaths. A complication developed in 10 patients: five patients with a primary pneumothorax (6.6%) and five with a secondary pneumothorax (27.7%). The mean postoperative hospital stay was 8.25 +/- 3.2 days. Mean follow-up is 30 months (range 7 to 49 months). Pneumothorax recurred in 3% of patients, all of whom were operated on at the start of our experience. Three percent of the patients had chronic postoperative chest pain. CONCLUSIONS: Video-assisted thoracoscopy is a valid alternative to open thoracotomy for the treatment of spontaneous primary pneumothorax. Its role for the management of secondary pneumothorax remains to be defined. In the long term, the efficacy of video-assisted thoracoscopic pleurodesis and surgeon experience should yield the same results as standard operative therapy.     

The role of veterinary research laboratories in the provision of veterinary services

Minimally invasive techniques for treatment of pneumothorax should yield the standard of results set with open procedures: the operative morbidity should remain less than 15%, and the recurrence rate less than 1%. In the era before video-assisted thoracic surgery, two minimally invasive variants were used. Chemical pleurodesis resulted in an unsatisfactory recurrence rate of at least 15%. In contrast, pleurectomy and apical stapling performed through a transaxillary minithoracotomy compared favorably with larger thoracotomy approaches, and allowed a reduced hospital stay. Evaluation of video-assisted thoracic surgical operations for spontaneous pneumothorax is hampered by a lack of controlled studies. The general impression is that morbidity did not decline significantly; the main determinant of complications is the patient's underlying health status. However, published recurrence rates range from 5% to 10%, in spite of a shorter follow-up time span. Optimized results are achieved when classic principles combining apical wedge resection and pleurodesis are applied. Reduction of hospital stay is not only a result of the new technology, but also changing drainage and discharge policies. Reduction of cost is debatable, because many studies do not consider the cost of video equipment. The main advantage when compared with open thoracotomy is reduction of postoperative pain. The only two available controlled studies conclude that there is no obvious advantage of video-assisted thoracic surgery when compared with conventional limited-access surgery. The future role of video-assisted thoracic surgery in this disease remains to be determined by a large-scale prospective evaluation.     

Ethylene oxide-protein adduct formation in humans: influence of glutathione-S-transferase polymorphisms

Autogenous cancellous bone fragments can be compressed rapidly during surgery to create reproducible load-bearing grafts. Of the 32 grafts tested, 10 were constructed of composite cortical-cancellous bovine bone and 22 of cancellous human bone. Compressed composite bovine grafts and compressed human cancellous grafts supported average axial compressive loads of 2148 N and 960 N, respectively. Compared to iliac crest grafts, compression grafts may have better load-bearing capabilities and greater reproducibility. Potential applications include trauma, delayed unions, arthrodesis, and spinal fusions.     

Abdominal sonography for the diagnosis of bowel obstruction

Minimally invasive thoracoscopic staging for lung cancer was compared with re-staging by open thoracotomy in seventeen patients to evaluate whether videoimaged thoracoscopic staging was accurate. Seventeen patients underwent thoracoscopic staging initially with a closed videoimaged technique. These same patients then underwent an open thoracotomy and re-staging with a therapeutic resection for lung cancer. All patients underwent pleural evaluation and biopsy if indicated, thoracic hilar and mediastinal lymph node sampling, and then resection of the parenchymal lesion via a wedge resection, lobectomy or pneumonectomy. There was complete TMN stage correlation between the closed videoimaged thoracoscopic and open thoracotomy techniques. This preliminary study suggests minimally invasive videoimaged thoracoscopic staging is an accurate method to assess the stage of lung cancer to guide rational management.     

Use of ultrasound in spinal arthrodesis. A rabbit model

STUDY DESIGN: The biomechanical and histologic characteristics of posterolateral spinal fusion in a rabbit model with and without the application of low-intensity ultrasound were analyzed. OBJECTIVES: To evaluate the use of ultrasound to improve the spinal fusion rate and biomechanical characteristics of the fusion mass in a rabbit model. SUMMARY OF BACKGROUND DATA: This is the first study in which the benefits of ultrasound in spinal fusion have been assessed. Posterolateral intertransverse process fusion in the rabbit has a pseudarthrosis rate similar to that recorded in humans (5-40%). METHODS: Fourteen New Zealand White rabbits were randomly assigned to each of two groups to undergo spinal fusion using autologous bone with ultrasound or autologous bone without ultrasound. A specially designed plastic constraint was used to focus the ultrasound over the rabbits' lumbar spine 20 minutes per day. Animals were killed at 6 weeks for biomechanical and histologic testing. RESULTS: The rate of pseudarthrosis, evaluated radiographically and manually in a blinded fashion, decreased at a statistically significant rate (from 35% to 7%) with ultrasound. Biomechanical analysis of the fusion mass showed that ultrasound resulted in statistically significant increases in stiffness (33%; P = 0.03), area under the load displacement curve (25%; P = 0.05), and load to failure of the fusion mass (24%; P = 0.04). Qualitative histologic assessment showed increased bone formation in those fusions exposed to ultrasound. CONCLUSIONS: Lumbar spinal fusion is a complex biologic process. The results of the current study demonstrate the reproducibility of a rabbit fusion model and the ability of ultrasound to induce a statistically significant increase in fusion rate, stiffness, area under the load displacement curve, and load to failure of the fusion mass. These results provide a basis for continued evaluation of biologic improvement of spinal arthrodesis with the use of ultrasound.     

In vivo evaluation of recombinant human osteogenic protein (rhOP-1) implants as a bone graft substitute for spinal fusions

STUDY DESIGN: Posterior spinal fusion segments were evaluated in adult mongrel dogs at 6, 12, and 26 weeks post-implantation. Four sites on each animal received implants consisting of recombinant human osteogenic protein-1 on a bone collagen carrier, bone collagen carrier alone, autogenous iliac crest bone, or no implant material. OBJECTIVE: To determine the efficacy of recombinant human osteogenic protein-1 as a bone graft substitute in achieving posterior spinal fusion and compare the results to those obtained using autogenous bone graft. SUMMARY OF BACKGROUND DATA: Posterior spinal fusion generally includes onlay grafting of autogenous or allogeneic bone after decortication of bony surfaces of the vertebral elements. The search for an acceptable bone graft substitute material has in recent years centered upon proteins capable of inducing bone in vivo. Recombinant human osteogenic protein-1 has demonstrated efficacy in healing large segmental osteoperiosteal defects in rabbits, dogs, and monkeys and appears ideally suited as a bone graft substitute for spinal fusions. METHODS: The quality of fusion and new bone formation was evaluated using plain films, computed tomography, and magnetic resonance imaging. RESULTS: Radiographic and histologic studies demonstrated that recombinant human osteogenic protein-1-treated fusion segments attained a stable fusion by 6 weeks post-implantation and were completely fused by 12 weeks. The autograft sites demonstrated fusion at 26 weeks post-implantation. CONCLUSIONS: The results indicated that recombinant human osteogenic protein-1 is an effective bone graft substitute for achieving stable posterior spinal fusions in a significantly more rapid fashion than can be achieved with autogenous bone graft.