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Thread: Reference on carbon cages for spine surgery

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    Reference on carbon cages for spine surgery

    • Agazzi S, Reverdin A and May D (1999). Posterior lumbar interbody fusion with cages: an independent review of 71 cases. J Neurosurg 91:186-92. Summary: OBJECT: The authors conducted a retrospective study to provide an independent evaluation of posterior lumbar interbody fusion (PLIF) in which impacted carbon cages were used. Interbody cages have been developed to replace tricortical interbody grafts in anterior and PLIF procedures. Superior fusion rates and clinical outcomes have been claimed by the developers. METHODS: In a retrospective study, the authors evaluated 71 consecutive patients in whom surgery was performed between 1995 and 1997. The median follow-up period was 28 months. Clinical outcome was assessed using the Prolo scale. Fusion results were interpreted by an independent radiologist. The fusion rate was 90%. Overall, 67% of the patients were satisfied with their outcome and would undergo the same operation again. Based on the results of the Prolo scale, however, in only 39% of the patients were excellent or good results achieved. Forty-six percent of the work-eligible patients resumed their working activity. Clinical outcome and return-to-work status were significantly associated with socioeconomic factors such as preoperative employment (p = 0.03), compensation issues (p = 0.001), and length of preoperative sick leave (p = 0.01). Radiographically demonstrated fusion was not statistically related to clinical outcome (p = 0.2). CONCLUSIONS: This is one of the largest independent series in which PLIF with cages has been evaluated. The results show that the procedure is safe and effective with a 90% fusion rate and a 66% overall satisfaction rate, which compare favorably with those of traditional fixation techniques but fail to match the higher results claimed by the innovators of the cage techniques. The authors' experience confirms the reports of others that many patients continue to experience incapacitating back pain despite successful fusion and neurological recovery. Department of Neurosurgery, University of Geneva, Switzerland.

    • Agrillo U, Mastronardi L and Puzzilli F (2002). Anterior cervical fusion with carbon fiber cage containing coralline hydroxyapatite: preliminary observations in 45 consecutive cases of soft-disc herniation. J Neurosurg 96:273-6. Summary: OBJECT: The purposes of bone substitutes for anterior cervical fusion (ACF) are immediate biomechanical support and osteointegration of the graft. The authors report their preliminary results in performing ACF in which carbon fiber cages (CFCs) containing coralline hydroxyapatite (HA) are used as bone substitute. METHODS: During a 24-month period, anterior microsurgical discectomy was performed in 45 consecutive patients for soft-disc cervical herniation. In all cases ACF was performed using a CFC containing a core of granulated coralline HA. Fifty-seven CFCs were implanted in 33 single-level and 12 two-level procedures. The mean operative time was 83 minutes for one-level and 97 minutes for two-level procedures. The mean hospital stay was 1.51 days, and there were no permanent complications. At a mean follow up of 22.3 months, the pain had decreased or disappeared in all patients, and the patients' satisfaction rate was very high. Good results were also obtained in patients who smoked cigarettes. Patients underwent radiographic evaluation at Day 1, and 1, 3, 6, and 12 months postoperatively. Implant-related complications were not observed and revision surgeries were not performed. Twelve-month cervical x-ray films demonstrated complete fusion in all cases, without evidence of breakage, collapse, pseudarthrosis, subsidence, angular deformity, or protrusion. Signs of pathological absorption and necrosis were not found in contiguous vertebral bodies, and inflammatory reactions were never seen around cages. CONCLUSIONS: These preliminary results suggest that implants composed of CFC containing granulated coralline HA are promising bone substitutes to be used in ACF, with a good rate of incorporation and no significant complications. Division of Neurosurgery, Sandro Pertini Hospital, Rome, Italy.

    • Arai Y, Takahashi M, Kurosawa H and Shitoto K (2002). Comparative study of iliac bone graft and carbon cage with local bone graft in posterior lumbar interbody fusion. J Orthop Surg (Hong Kong) 10:1-7. Summary: We performed a comparative study of iliac bone graft (the iliac bone group) and carbon cage with local bone graft (the cage group) in PLIF to evaluate the clinical results of both methods. We examined both groups about the operating time, the estimated blood loss, the operative results using the score rating system of Japanese Orthopaedic Association (JOA score), and the presence of bone union on radiography. The operating time and the estimated blood loss of the cage group were statistically less than those of the iliac bone group. There were no significant differences between both groups about the operative results. The radiographic evaluation on bone union showed that half of the iliac bone group had collapsed union, but all cases of the cage group revealed union without collapse. Department of Orthopaedic Surgery, School of Medicine, Juntendo University, Japan. y-arai@med.juntendo.ac.jp

    • Bartels RH, Donk R and van Azn RD (2001). Height of cervical foramina after anterior discectomy and implantation of a carbon fiber cage. J Neurosurg 95:40-2. Summary: OBJECT: The authors evaluate the effects of implantation of a carbon fiber cage after anterior cervical discectomy (ACD) on the height of the foramen and the angulation between endplates of the disc space. METHODS: Thirteen consecutive patients who were scheduled for standard microscopic ACD and interbody fusion underwent thin-slice (1.5 mm) spiral computerized tomography scanning 1 day preoperatively, 1 day postoperatively, and 1 year postoperatively. Oblique sagittal reconstructions were made through both foramina; the height of each foramen and the angle between the endplates were measured. Because 16 cages were implanted, 32 foramina were investigated. Preoperatively, the mean height of the foramina (+/- standard deviation) was 8.1 +/- 1.5 mm (range 5.7-12 mm), and at I day postoperatively it was 9.7 +/- 1.4 mm (range 7.5-12.8 mm). This difference reached statistical significance (p < 0.0005). The mean foraminal height after 1 year was 9.4 +/- 1.4 mm [range 6.9-12.7 mm). In terms of the preoperative value, the 1-year measurement still reached statistical difference [p < 0.005) but not with the direct postoperative mean foraminal height. Preoperatively the mean value of the angle between the two adjacent endplates was 1.3 +/- 2.4 degrees [range 0-8 degrees), and postoperatively it was 7.8 +/- 2.9 degrees [rauge 2-12 degrees), which was statistically significant [p < 0.0005). CONCLUSIONS: The cervical carbon fiber cage effectively increased the height of the foramen even after 1 year, which contributed to decompression of the nerve root. The wedge shape of the device may contribute to restoration of lordosis. Department of Orthopedic Surgery, Center for Surgery of the Spine and Craniospinal Junction, Canisius Wilhelmina Ziekenhuis, Nijmegen, The Netherlands. r.bartels@czzonch.azn.nl

    • Boriani S, Biagini R, Bandiera S, Gasbarrini A and De LF (2002). Reconstruction of the anterior column of the thoracic and lumbar spine with a carbon fiber stackable cage system. Orthopedics 25:37-42. Summary: A carbon fiber stackable cage system is presented to promote the reconstruction of the anterior column after vertebrectomy or corpectomy in tumor and trauma surgery. Modularity, immediate stability, early fusion of the graft, radiolucency, and no risk of disease transmission are the main advantages of this system. Department of Orthopedics and Traumatology, Ospedale Maggiore, Bologna, Italy.

    • Brantigan JW, Steffee AD, Lewis ML, Quinn LM and Persenaire JM (2000). Lumbar interbody fusion using the Brantigan I/F cage for posterior lumbar interbody fusion and the variable pedicle screw placement system: two-year results from a Food and Drug Administration investigational device exemption clinical trial. Spine 25:1437-46. Summary: STUDY DESIGN: A carbon fiber-reinforced polymer cage implant filled with autologous bone was designed to separate the mechanical and biologic functions of posterior lumbar interbody fusion. OBJECTIVES: To test the safety and efficacy of the carbon cage with pedicle screw fixation in a 2-year prospective study performed at six centers under a protocol approved by the Food and Drug Administration, and to present the data supporting the Food and Drug Administration approved indications. SUMMARY OF BACKGROUND DATA: The success of posterior lumbar interbody fusion has been limited by mechanical and biologic deficiencies of the donor bone. Some failures of pedicle screw fixation may be attributable to the absence of adequate load sharing through the anterior column. Combining an interbody fusion device with pedicle screw fixation may address some limitations of posterior lumbar interbody fusion or pedicle screw fixation in cases that are more complex mechanically. METHODS: This clinical study of posterior lumbar interbody fusion with pedicle screw fixation involved a prospective group of 221 patients. RESULTS: Fusion success was achieved in 176 (98.9%) of 178 patients. In the management of degenerative disc disease in patients with prior failed discectomy surgery, clinical success was achieved in 79 (86%) of 92 patients, and radiographic bony arthrodesis in 91 (100%) of 91 patients. Disc space height, averaging 7.9 mm before surgery, was increased to 12.3 mm at surgery and maintained at 11.7 mm at 2 years. Fusion success was notdiminished over multiple fusion levels. These results were significantly better than those reported in prior literature. Although significant surgical complications occurred, those attributable to the implant devices occurred less frequently and generally were minor. CONCLUSIONS: The Brantigan I/F Cage for posterior lumbar interbody fusion and the Variable Screw Placement System are safe and effective for the management of degenerative disc disease. South Texas Orthopaedic and Spinal Surgery Associates, San Antonio, Texas 78240, USA.

    • Brooke NS, Rorke AW, King AT and Gullan RW (1997). Preliminary experience of carbon fibre cage prostheses for treatment of cervical spine disorders. Br J Neurosurg 11:221-7. Summary: The objective of this study was to assess the technical feasibility, and the clinical and radiological results of interbody fusion with a carbon fibre cage following anterior cervical discectomy. Nineteen consecutive patients, eight male and 11 female, with an age range from 28 to 75 years (mean 45) underwent anterior cervical discectomy and interbody fusion with a carbon fibre cage at one or two levels. Subjective assessment of symptomatic improvement and radiological assessment of cervical spine alignment and stability was made. All complications were recorded. The procedure was technically feasible. There was no increased morbidity and the length of procedure was no longer when compared with the similar operation but using tricorticate bone graft. All patients initially lost their radicular symptoms and the patients with myelopathy had subjective improvements of their symptoms. Fourteen of the 17 patients with neck pain showed some improvement. Bony fusion was achieved in all cases. Department of Neurosurgery, Kings College Hospital, London, UK.

    • Christensen FB, Hansen ES, Eiskjaer SP, Hoy K, Helmig P, Neumann P, Niedermann B and Bunger CE (2002). Circumferential lumbar spinal fusion with Brantigan cage versus posterolateral fusion with titanium Cotrel-Dubousset instrumentation: a prospective, randomized clinical study of 146 patients. Spine 27:2674-83. Summary: STUDY DESIGN: A prospective randomized clinical study with a 2-year follow-up period was conducted. OBJECTIVE: To analyze the effects of circumferential fusion using ALIF radiolucent carbon fiber cages and titanium posterior instrumentation on functional outcome, fusion rate, complications, and lumbar lordosis. SUMMARY OF BACKGROUND DATA: Circumferential fusion has become a common procedure in lumbar spine fusion, both as a primary and salvage procedure. However, the claimed advantages of ALIF plus PLF over conventional PLF lack scientific documentation. METHODS: From April 1996 through November 1999, a total of 148 patients with severe chronic low back pain were randomly selected for either posterolateral lumbar fusion with titanium CD-Horizon (posterolateral group) or circumferential fusion with a ALIF Brantigan cage plus posterior instrumentation. The Dallas Pain Questionnaire (DPQ), the Low Back Pain Rating Scale (LBPR), and a questionnaire concerning work status assessed their outcomes. RESULTS: Both groups showed highly significant improvement in all four categories of life quality (DPQ) as well as in the back pain and leg pain index (LBPR), as compared with preoperative status. There was a clear tendency toward better overall functional outcome for patients with the circumferential procedure ( < 0.08), and this patient group also showed significantly less leg pain at the 1-year follow-up evaluation [ < 0.03) and less peak back pain at 2 years [ < 0.04). Sagittal lordosis was restored and maintained in the circumferential group [ < 0.01). The circumferential fusion patients showed a higher posterolateral fusion rate [92%) than the posterolateral group [80%)[ < 0.04). The repeat operation rate including implant removal was significantly lower in the circumferential group [7%) [ < 0.009) than in the posterolateral group [22%). CONCLUSIONS: Circumferential lumbar fusion restored lordosis, provided a higher union rate with significantly fewer repeat operations, showed a tendency toward better functional outcome, and resulted in less peak back pain and leg pain than instrumented posterolateral fusion. The clinical perspective of the current study implies a recommendation to favor circumferential fusion as a definitive surgical procedure in complex lumbar pathology involving major instability, flatback, and previous disc surgery in younger patients, as compared with posterolateral fusion with pedicle screws alone. Spine Section, Department of Orthopedic Surgery, University Hospital of Aarhus, Denmark. fbc@dadlnet.dk

    • Ciappetta P, Boriani S and Fava GP (1997). A carbon fiber reinforced polymer cage for vertebral body replacement: technical note. Neurosurgery 41:1203-6. Summary: OBJECTIVE: We analyzed the surgical technique used for the replacement of damaged vertebral bodies of the thoracolumbar spine and the carbon fiber reinforced polymer (CFRP) cages that are used to replace the pathological vertebral bodies. We also evaluated the biomechanical properties of carbon composite materials used in spinal surgery. TECHNIQUE: The surgical technique of CFRP implants may be divided into two distinct steps, i.e., assembling the components that will replace the pathological vertebral bodies and connecting the cage to an osteosynthetic system to immobilize the cage. INSTRUMENTATION: The CFRP cages, made of Ultrapek polymer and AS-4 pyrolytic carbon fiber (AcroMed, Rotterdam, The Netherlands), are of different sizes and may be placed one on top of the other and fixed together with a titanium rod. These components are hollow to allow fragments of bone to be pressed manually into them and present threaded holes at 15, 30, and 90 degrees on the external surface, permitting the insertion of screws to connect the cage to an anterior or posterior osteosynthetic system. RESULTS: To date, we have used CFRP cages in 13 patients undergoing corporectomies and 10 patients undergoing spondylectomies. None of our patients have reported complications. CONCLUSIONS: CFRP implants offer several advantages compared with titanium or surgical grade stainless steel implants, demonstrating high versatility and outstanding biological and mechanical properties. Furthermore, CFRP implants are radiolucent and do not hinder radiographic evaluation of bone fusion, allowing for better follow-up studies. Department of Neurotraumatology, University of Rome, La Sapienza, Italy.

    • Dewald CJ, Millikan KW, Hammerberg KW, Doolas A and Dewald RL (1999). An open, minimally invasive approach to the lumbar spine. Am Surg 65:61-8. Summary: A minimum 2-year follow-up retrospective review was undertaken to assess our experience with an anterior paramedian muscle-sparing approach to the lumbar spine for anterior spinal fusion (ASF). The records of 28 patients (November 1991 through January 1996) undergoing ASF via a left lower quadrant transverse skin incision (6-10 cm) with a paramedian anterior rectus fascial Z-plasty retroperitoneal approach were reviewed. Diagnosis, number, and level of lumbar interspaces fused, types of fusion, estimated blood loss, length of procedure, length of hospital stay, and complications were analyzed. All cases were completed as either a same-day anterior/posterior (24 of 28) or as a staged procedure at least 1 week after posterior fusion (4 of 28). The General Surgery service performed the muscle-sparing approach, whereas the Orthopedic Spine service performed the ASF. There were 14 men and 14 women, with a mean age of 35.5 years (range, 11-52 years). Diagnoses included spondylolisthesis in 20 cases (including four grade III or IV slips), segmental instability (degenerative or postsurgical) in 7, and 1 flatback deformity. A single level was fused in 20 cases (L4/5 in 4 and L5/S1 in 16), two levels were fused in 5 cases (L4/5 and L5/S1) and three levels were fused in 2 cases (L3/4, L4/5, and L5/S1). The mean length of stay was 7.4 days (range, 5-12 days). The mean estimated blood loss was 300 mL for the anterior procedure alone and 700 ml for both anterior/posterior procedures on the same day. The mean length of operating room time for the anterior approach and fusion was 117 minutes (range, 60-330 minutes). Posterior instrumentation was used in all cases. Anterior interbody struts used included 19 autogenous tricortical grafts, 4 fresh-frozen allografts (2 femoral rings and 2 iliac crests), 3 carbon fiber cages packed with autogenous bone, and a Harms titanium cage with autograft. There was one L5 corpectomy for which a large tricortical allograft strut was utilized. There were no vascular, visceral, or urinary tract injuries. In three cases a mild ileus developed, which resolved spontaneously. We conclude that the anterior paramedian muscle-sparing retroperitoneal approach is safe, uses a small skin incision, avoids cutting abdominal wall musculature, and allows for multiple-level anterior spinal fusions by a variety of interbody fusion techniques. This approach does not require transperitoneal violation or added endoscopic instrumentation, nor does it limit fusion level and technique of fusion, as is the case with the recently popularized laparoscopic approach to the lumbar spine. Department of General Surgery, Rush Medical College, Rush Presbyterian St. Luke's Medical Center, Chicago, Illinois, USA.

    • Diedrich O, Kraft CN, Bertram R, Wagner U and Schmitt O (2000). [Dorsal lumbar interbody implantation of cages for stabilizing segmental spinal instabilities]. Z Orthop Ihre Grenzgeb 138:162-8. Summary: PURPOSE: The technique of posterior lumbar interbody fusion (PLIF) has been critically discussed due to a high degree of complications, including the development of pseudarthrosis. With the recent establishment of intercorporeal implants new aspects have to be contemplated in surgical techniques, especially concerning the posterior approach. In this study we present our first results after intercorporeal stabilisation of segmental spinal instabilities utilising carbon and titanium cages. METHOD: 45 spinal instabilities were surgically stabilised in 42 patients who were evaluated on average for 2.8 years post-operatively. 12 patients had isthmic and 19 patients degenerative instabilities while 11 patients suffered from instabilities resulting from prior spinal surgery. RESULTS: Assessed according to the Hambly-score, 69% of the patients had an excellent or good result; 2 (4.8%) patients were subjectively worse off than before surgical treatment. After implantation of cages precise radiological evaluation of bony ingrowth is frequently impaired by artefacts. We found that three months after implantation of a titanium cage, which had to be removed after incorrect placement, no bony consolidation was visible. Persisting or recurrent instabilities in fused segments were not recorded. CONCLUSION: By means of PLIF and implantation of cages the interbody space is reconstructed and jeopardized neural structures are decompressed. In addition to this, the frequently osteochondrotically degenerated segment is immobilized. The posterior approach allows decompression of neural structures and, with comparable results concerning stability, the considerable risks of the ventral approach are avoided. Klinik und Poliklinik fur Orthopadie, Rheinische Friedrich-Wilhelms-Universitat zu Bonn.

    • Eck KR, Lenke LG, Bridwell KH, Gilula LA, Lashgari CJ and Riew KD (2000). Radiographic assessment of anterior titanium mesh cages. J Spinal Disord 13:501-9; discussion 510. Summary: Carbon fiber and titanium cage implantation for anterior column support during spinal fusions is an alternative to the use of more traditional structural allografts and autografts. The authors report instrumentation and cage failure for patients who underwent spinal fusion with structural titanium mesh cages implanted into the anterior column a minimum of 2 years after surgery. They wanted to determine whether plain radiographic techniques can be used to critically assess disk space and corpectomy fusions after implantation of these radioopaque cages. Fifty patients having undergone spinal fusions using structural titanium mesh cages in the anterior column had 99 anterior levels fused with at least 1 (maximum of 2) titanium mesh cage, resulting in a total of 131 cages used. The cages were examined for evidence of settling, migration, or failure. The anterior and posterior instrumentation was assessed for evidence of failure, and the spine was examined for evidence of successful fusion. Radiographic cage settling (>2 mm) into the vertebral body end plates was observed, but cage migration or failure were not. An average lordotic correction of 10 degrees was observed, with loss of correction into kyphosis from immediately after operation to final follow-up averaging 2 degrees. As an average of all reviewers, using a strict radiographic fusion assessment, definite or probable anterior fusion was graded at 81% of the levels, probably not or no at 5% of the levels, and could not be assessed at 14% of the levels. Definite or probable posterior fusion as an average of all reviewers was graded at 44% of the posterior fusion levels, questionable at 4%, no at 5%, and could not be assessed at 47%. The use of anterior-only, posterior-only, or anterior and posterior instrumentation with structural titanium mesh cages in the anterior spine along with proper autogenous bone grafting techniques provided anterior column support with a low rate of radiographic complications. Acceptable anterior spinal fusion rates, as assessed by a consensus agreement of reviewers, were observed primarily by evaluation of the fusion mass around the cages (extracage fusion), because intracage fusion was difficult to assess. Department of Orthopaedic Surgery, Washington University, St. Louis, Missouri, USA.

    • Hashimoto T, Shigenobu K, Kanayama M, Harada M, Oha F, Ohkoshi Y, Tada H, Yamamoto K and Yamane S (2002). Clinical results of single-level posterior lumbar interbody fusion using the Brantigan I/F carbon cage filled with a mixture of local morselized bone and bioactive ceramic granules. Spine 27:258-62. Summary: STUDY DESIGN: A retrospective study to evaluate the results of single-level posterior lumbar interbody fusion (PLIF) using the Brantigan I/F cage (DePuy AcroMed Corp., Raynham, MA) filled with a mixture of local morselized autologous bone and bioactive ceramic granules. OBJECTIVES: To report the clinical and radiologic results of PLIF using the Brantigan I/F cage for lumbar degenerative pathologies with instability. SUMMARY OF BACKGROUND DATA: The Brantigan I/F cage for PLIF was designed to improve the fusion success of interbody fusion by separating the mechanical and biologic functions of PLIF using an implant device and autologous bone from the iliac crest. Although high fusion rates have been reported, donor site morbidity caused by bone harvest from the iliac crest remains a concern. The possibility of accomplishing cage PLIF using a mixture of local morselized bone and a bone extender was studied. METHODS: A total of 25 patients underwent single-level PLIF using the Brantigan I/F cage filled with a mixture of local morselized bone and bioactive ceramic granules. All patients were observed for more than 2 years (average 2 years 7 months) and evaluated by clinical rating and radiograph. RESULTS: Preoperative Japanese Orthopedic Association clinical scores were significantly improved in all patients at the time of follow-up. The average improvement rate was 83.1%. There were no serious complications. Minor complications included two dural tears and two cases of thrombophlebitis. No patient required blood transfusion. All patients achieved radiographic fusion and radiographic stability, although two patients fused in a collapsed position. Regional alignment of the operated segments was restored at surgery and maintained at the time of final follow-up. There were statistical improvements in percent slip and percent posterior disc height in patients with spondylolisthesis. CONCLUSIONS: Posterior lumbar interbody fusion using the Brantigan I/F cage with a mixture of local morselized bone and bioactive ceramic granules can yield a solid union with satisfactory regional alignment and adequate disc height without harvest of iliac crest bone. Department of Orthopaedic Surgery, Hakodate Central General Hospital, Hakodate City, Hokkaido, Japan. tomhashi@bea.hi-ho.ne.jp

    • Jost B, Cripton PA, Lund T, Oxland TR, Lippuner K, Jaeger P and Nolte LP (1998). Compressive strength of interbody cages in the lumbar spine: the effect of cage shape, posterior instrumentation and bone density. Eur Spine J 7:132-41. Summary: One goal of interbody fusion is to increase the height of the degenerated disc space. Interbody cages in particular have been promoted with the claim that they can maintain the disc space better than other methods. There are many factors that can affect the disc height maintenance, including graft or cage design, the quality of the surrounding bone and the presence of supplementary posterior fixation. The present study is an in vitro biomechanical investigation of the compressive behaviour of three different interbody cage designs in a human cadaveric model. The effect of bone density and posterior instrumentation were assessed. Thirty-six lumbar functional spinal units were instrumented with one of three interbody cages: (1) a porous titanium implant with endplate fit (Stratec), (2) a porous, rectangular carbon-fibre implant (Brantigan) and (3) a porous, cylindrical threaded implant (Ray). Posterior instrumentation (USS) was applied to half of the specimens. All specimens were subjected to axial compression displacement until failure. Correlations between both the failure load and the load at 3 mm displacement with the bone density measurements were observed. Neither the cage design nor the presence of posterior instrumentation had a significant effect on the failure load. The loads at 3 mm were slightly less for the Stratec cage, implying lower axial stiffness, but were not different with posterior instrumentation. The large range of observed failure loads overlaps the potential in vivo compressive loads, implying that failure of the bone-implant interface may occur clinically. Preoperative measurements of bone density may be an effective tool to predict settling around interbody cages. M.E. Muller Institute for Biomechanics, University of Bern, Switzerland.

    • Kandziora F, Pflugmacher R, Schafer J, Born C, Duda G, Haas NP and Mittlmeier T (2001). Biomechanical comparison of cervical spine interbody fusion cages. Spine 26:1850-7. Summary: STUDY DESIGN: An in vitro biomechanical study of cervical spine interbody fusion cages using a sheep model was conducted. OBJECTIVES: To evaluate the biomechanical effects of cervical spine interbody fusion cages, and to compare three different cage design groups. SUMMARY AND BACKGROUND DATA: Recently, there has been a rapid increase in the use of cervical spine interbody fusion cages as an adjunct to spondylodesis. These cages can be classified into three design groups: screw, box, or cylinder designs. Although several comparative biomechanical studies of lumbar interbody fusion cages are available, biomechanical data for cervical spine constructs are lacking. Additionally, only limited data are available concerning comparative evaluation of different cage designs. METHODS: In this study, 80 sheep cervical spines (C2-C5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method using a nonconstrained testing apparatus. Three-dimensional displacement was measured using an optical measurement system (Qualysis). Complete discectomy (C3-C4) was performed. Cervical spine interbody fusion cages were implanted according to manufacturers' information. Eight spines in each of the the following groups were tested: intact, autologous iliac bone graft, two titanium screws (Novus CTTi; Sofamor Danek, Koln, Germany), two titanium screws (BAK-C 8 mm; Sulzer Orthopedics, Baar, Switzerland), one titanium screw (BAK-C 12 mm; Sulzer Orthopedics), carbon box (Novus CSRC; Sofamor Danek), titanium box (Syncage; Synthes, Bochum, Germany), titanium mesh cylinder (Harms; DePuy Acromed, Sulzbach, Germany), titanium cylinder (MSD; Ulrich, Ulm, Germany), and titanium cylinder (Kaden; BiometMerck, Berlin, Germany). The mean apparent stiffness values were calculated from the corresponding load-displacement curves. Additionally, cage volume and volume-related stiffness was determined. RESULTS: After cervical spine interbody fusion cage implantation, flexion stiffness increased, as compared with that of the intact motion segment. On the contrary, rotation stiffness decreased after implantation of a cervical spine interbody fusion cage, except for the Novus CSRC, Syncage, and Kaden-Cage. If two screws were inserted (Novus CTTi and BAK-C 8 mm), there was no significant difference in flexion stiffness between screw and cylinder design groups. If one screw was inserted (BAK-C 12 mm), flexion stiffness was higher for cylinder designs (P < 0.05). Extension and bending stiffness were always higher with cylinder designs [P < 0.05). Volume-related stiffness for flexion extension and bending was highest for the Harms cage [P < 0.05). There was no difference for rotation volume-related stiffness between Harms and Syncage. CONCLUSIONS: The biomechanical results indicate that design variations in screw and cylinder design groups are of little importance. In this study, however, cages with a cylinder design were able to control extension and bending more effectively than cages with a screw design. Unfall- und Wiederherstellungschirurgie, and the Strahlenklinik und Poliklinik Universitatsklinikum Charite der Humboldt Universitat Berlin, Campus Virchow-Klinikum, Berlin, Germany. frank.kandziora@charite.de

    • Lund T, Oxland TR, Jost B, Cripton P, Grassmann S, Etter C and Nolte LP (1998). Interbody cage stabilisation in the lumbar spine: biomechanical evaluation of cage design, posterior instrumentation and bone density. J Bone Joint Surg Br 80:351-9. Summary: We performed a biomechanical study on human cadaver spines to determine the effect of three different interbody cage designs, with and without posterior instrumentation, on the three-dimensional flexibility of the spine. Six lumbar functional spinal units for each cage type were subjected to multidirectional flexibility testing in four different configurations: intact, with interbody cages from a posterior approach, with additional posterior instrumentation, and with cross-bracing. The tests involved the application of flexion and extension, bilateral axial rotation and bilateral lateral bending pure moments. The relative movements between the vertebrae were recorded by an optoelectronic camera system. We found no significant difference in the stabilising potential of the three cage designs. The cages used alone significantly decreased the intervertebral movement in flexion and lateral bending, but no stabilisation was achieved in either extension or axial rotation. For all types of cage, the greatest stabilisation in flexion and extension and lateral bending was achieved by the addition of posterior transpedicular instrumentation. The addition of cross-bracing to the posterior instrumentation had a stabilising effect on axial rotation. The bone density of the adjacent vertebral bodies was a significant factor for stabilisation in flexion and extension and in lateral bending. M. E. Muller Institute for Biomechanics, University of Bern, Switzerland.

    • Markwalder TM, Wenger M, Elsig JP and Laloux E (2003). The Wilhelm tell technique for anterior lumbar interbody fusion. Technical note. J Neurosurg 98:222-5. Summary: Experience indicates that stand-alone cages may lack the necessary stability to secure highly unstable motion segments at the lumbosacral junction. The authors have designed a special carbon fiber composite interbody cage that allows additional screw placement in anterior lumbar interbody fusion procedures performed at the lumbosacral junction. thomasmarc.markwalder@bluewin.ch

    • Pape D, Fritsch E, Kelm J, Muller K, Georg T, Kohn D and Adam F (2002). Lumbosacral stability of consolidated anteroposterior fusion after instrumentation removal determined by roentgen stereophotogrammetric analysis and direct surgical exploration. Spine 27:269-74. Summary: STUDY DESIGN: The intervertebral stability of bony consolidated anteroposterior lumbosacral spondylodesis is evaluated by roentgen stereophotogrammetric analysis and direct surgical exploration before and after removal of the internal fixator. OBJECTIVES: To determine the remaining in vivo stability of spinal arthrodesis solely retained by a bony integrated carbon fiber cage. SUMMARY OF BACKGROUND DATA: Roentgen stereophotogrammetric analysis studies on posterolateral lumbar fusions demonstrate primary spinal stability after additional dorsal instrumentation, which is retained during bony fusion healing. Animal models show a persistent stabilizing effect of the fixator despite the presence of bony fusion. Although direct surgical inspection is the most reliable method to evaluate fused vertebrae, roentgen stereophotogrammetric analysis has also proven to be a highly accurate method to evaluate spinal stability. METHODS: In 10 patients lumbosacral fusion was performed using carbon interbody implants and an internal fixator. Ten months after initial surgery (range 7-15 months) the internal fixation was removed to reduce local soft tissue impingement as soon as bony fusion was achieved. Fusion site exploration in the course of instrumentation removal was performed by applying distraction, compression, and torque to the grafted area under fluoroscopic control. Any motion indicated a pseudarthrosis. Lumbosacral stability was evaluated by serial roentgen stereophotogrammetric analysis after fusion and after instrumentation removal. RESULTS: During instrumentation removal the mechanical stress test under fluoroscopic control did not indicate pseudarthrosis. After instrumentation removal, roentgen stereophotogrammetric analysis measurements revealed a nonsignificant increase in lumbosacral micromotions within the fused segment with 0.14, 0.31, and 0.44 mm in the transverse, vertical, and sagittal axes, respectively. CONCLUSIONS: The internal fixator could be removed without endangering the stability of the fusion. Direct surgical exploration confirmed the adequacy of roentgen stereophotogrammetric analysis as a reliable in vivo method to evaluate lumbosacral stability after anteroposterior fusion. Institute for Medical Biometrics, Epidemiology and Medical Informatics, University of Saarland, Homburg/Saar, Germany. Dr.D-Pape@t-online.de

    • Payer M, May D, Reverdin A and Tessitore E (2003). Implantation of an empty carbon fiber composite frame cage after single-level anterior cervical discectomy in the treatment of cervical disc herniation: preliminary results. J Neurosurg 98:143-8. Summary: OBJECT: The authors sought to evaluate retrospectively the radiological and clinical outcome of anterior cervical discectomy followed by implantation of an empty carbon fiber composite frame cage (CFCF) in the treatment of patients with cervical disc herniation and monoradiculopathy. METHODS: Twenty-five consecutive patients (12 men, 13 women, mean age 45 years) with monoradiculopathy due to cervical disc herniation were treated by anterior cervical discectomy followed by implantation of an empty CFCF cage. On lateral flexion-extension radiographs segmental stability at a mean follow up of 14 months (range 5-31 months) was demonstrated in all 25 patients, and bone fusion was documented in 24 of 25 patients. The mean anterior intervertebral body height was 3.4 mm preoperatively and 3.8 mm at follow up in 20 patients. In these patients the mean segmental angle (angle between lower endplate of lower and upper vertebra) was 0.9 degrees preoperatively and 3.1 degrees at follow up. In the remaining five patients preoperative images were not retrievable. Self-scored neck pain based on a visual analog scale (1, minimum; 10, maximum) changed from a preoperative average of 5.6 to an average of 2 at follow up; radicular pain was reduced from 7.7 to 2.1 postoperatively. Analysis of the SF12 questionnaires showed a significant improvement in both the physical capacity score (preoperative mean 32.4 points; follow up 46 points) and the mental capacity score (preoperative mean 45.8 points; follow up 57.5 points). CONCLUSIONS: Implantation of an empty CFCF cage in the treatment of cervical disc herniation and monoradiculopathy avoids donor site morbidity associated with autologous bone grafting as well as the use of any supplementary material inside the cage. Restoration or maintenance of intervertebral height and thus segmental lordosis and a very high rate of segmental stability and fusion are achieved using this technique. Department of Neurosurgery, University Hospital of Geneva, Geneva, Switzerland. mpayer@hotmail.com

    • Peolsson A, Hedlund R, Vavruch L and Oberg B (2003). Predictive factors for the outcome of anterior cervical decompression and fusion. Eur Spine J 12:274-80. Summary: In a prospective study, 103 patients were randomised to anterior cervical decompression and fusion (ACDF) with a cervical carbon-fibre intervertebral fusion cage or the Cloward procedure. Preoperative background variables, active range of neck motion, handgrip strength, radiological evaluation and subjective variables were used in a multiple regression model to find the strongest predictors of postoperative outcome as measured by current pain intensity and the Neck Disability Index (NDI). Male sex, greater kyphosis at the level operated on, non-smoking, a greater neck mobility in right rotation, low disability on NDI, and older age were predictors of pain reduction and explained 30% of current pain intensity at follow-up. Higher educational level, non-smoking, greater kyphosis at the level operated on, a greater flexion mobility, greater right handgrip strength and lower current pain intensity were predictors of improvement, and explained 28% of the postoperative outcome on NDI. The most important predictor for postoperative pain intensity was the magnitude of the preoperative kyphosis. Preoperative pain intensity was the most important predictor for improved NDI. At follow-up about 70% of the patients still had deficit based on current pain intensity and NDI, and 44% had remaining dysfunction based on Odom's criteria. In conclusion, the multivariate analysis shows that male sex, non-smoking, greater segmental kyphosis and a low pain and disability level are preoperative predictors of a good outcome in ACDF. In addition, the study suggests the importance of other predictive variables than those studied for the outcome of ACDF. Department of Health and Society, Division of Physiotherapy, Faculty of Health Sciences, Linkoping University, 58185 Linkoping, Sweden. Anneli.Peolsson@ihs.liu.se

    • Togawa D, Bauer TW, Brantigan JW and Lowery GL (2001). Bone graft incorporation in radiographically successful human intervertebral body fusion cages. Spine 26:2744-50. Summary: STUDY DESIGN: Biopsies were obtained from within radiographically successful human intervertebral body fusion cages to document the histology of remodeling bone graft. OBJECTIVES: The purpose of this study is to describe the tissue within successful human interbody cages with special reference to the viability of bone and the presence or absence of debris particles. SUMMARY OF BACKGROUND DATA: The use of interbody fusion cages is gaining rapid acceptance, but there is little histologic documentation of the nature of tissue within successful human interbody fusion cages. METHODS: Needle biopsies were obtained of tissue within radiographically successful intervertebral body fusion cages at the time of pedicle screw removal for back pain or fusion of adjacent spinal level in nine spinal levels of eight patients. Preoperative diagnoses of these eight adult patients included disease conditions in the sagittal plane: spondylosis (5), degenerative disc disease (6), failed laminectomy and discectomy (2), radiculopathy (1), and spondylolisthesis (1). In all cases the cages had been packed with autograft (iliac crest 7, local 1) at the time of insertion. Cage implantation was performed with anterior (anterior lumbar interbody fusion 4, corpectomy and plate fixation 1), and posterior (posterior lumbar interbody fusion 4), segmental instrumentation (plate 1, or pedicle screws 8). All cases except one cervical case had posterolateral fusion or bilateral facet fusion. The cages were composed of carbon fiber-reinforced polymer (Brantigan cage; DePuy AcroMed, Raynham, MA, n = 5) or titanium mesh (Harms Cage; DePuy AcroMed, Raynham, MA, n = 4). Cages had been in situ from 8 to 72 months (mean 28 months). All nine biopsies from eight patients were obtained from within the center of the cages. Specimens were decalcified, routinely embedded in paraffin, stained with hematoxylin and eosin, and viewed qualitatively with transmitted and polarized light. RESULTS: All needle biopsies were obtained from within the center of the cages, and no patient developed spinal instability after the biopsy. All nine biopsies showed small fragments of necrotic bone associated with viable bone and restoration of hematopoietic bone marrow. Numerous cement lines demarcated the edges of previous cycles of remodeling. The ratio of necrotic to viable bone varied greatly among cases. Small particles of debris were associated with four of the five carbon-fiber cages and one of the four specimens from titanium cages, but there was no visible bone resorption or inflammation. CONCLUSIONS: Autogenous bone graft was incorporated in these radiographically successful human intervertebral body fusion cages. A few debris particles were observed, but there was no histologic evidence of particle-induced bone resorption or inflammation. Department of Anatomic Pathology, Cleveland Clinic Foundation, Ohio 44195, USA.

    • Tullberg T (1998). Failure of a carbon fiber implant. A case report. Spine 23:1804-6. Summary: STUDY DESIGN: Case report. OBJECTIVES: Failure of a carbon fiber implant. SUMMARY OF BACKGROUND DATA: To simplify the procedure of posterior lumbar interbody fusion, a carbon-fiber-reinforced polymer implant has been developed. The implant has ridges to resist retropulsion, struts to support weight, and a hollow area to allow packing of autologous bone graft. So far, no complications have been reported from the use of carbon implant as a fusion aid in spine surgery. METHODS: A patient with postoperative infection has been followed with computed tomography images and histologic examination from a reoperation. RESULTS: An entire nonunion across the width of the disc space and a clearly broken cage was visualized with computed tomography. The spinal canal was explored during a reoperation and the tissue surrounding the dura and nerves were all black. Microscopic examination showed a large quantity of carbon particulate debris. The authors have operated on approximately 100 patients so far and no other carbon cage has broken, to their knowledge. CONCLUSIONS: Carbon cages can break if a nonunion occurs and as a result free carbon particles move out to the spinal canal. Department of Orthopaedics, St. Gorans Hospital, Stockholm, Sweden.

    • Tullberg T, Brandt B, Rydberg J and Fritzell P (1996). Fusion rate after posterior lumbar interbody fusion with carbon fiber implant: 1-year follow-up of 51 patients. Eur Spine J 5:178-82. Summary: Problems associated with posterior lumbar interbody fusion (PLIF) have traditionally included the need for donor bone, prolonged healing time of donor bone, the difficulty of cutting precise bony channels, the risk of retropulsion of graft, postoperative collapse of the bone graft, and pseudarthrosis. To avoid these problems a carbon fiber reinforced polymer implant cage has been developed to facilitate interbody fusion. The aim of the present study was to evaluate the technical problems and fusion rate associated with these new device for PLIF. Between April 1991 and December 1993, 65 pairs of these implant cages were sold in Sweden. They were traced to six hospitals, where they had been used in the treatment of 51 patients operated on at a total of 65 levels. All PLIF were supplemented with VSP (Variable Screw Placement) instrumentation. All medical records were evaluated and all patients were examined with plain radiographs taken at least 1 year after surgery. If that investigation did not show a clear fusion they were also evaluated with CT (18 patients, 27 levels). No intraoperative problems with the device have been reported; 44 patients (86%) and 58 levels (89%) achieved successful fusion. All patients bar one maintained their immediately obtained postoperative disc height. CT with 1-mm slices and sagittal reconstruction is most helpful if radiographs are difficult to interpret. Department of Orthopedics, St. Gorans Hospital, Stockholm, Sweden.

    • Vahldiek MJ and Panjabi MM (1998). Stability potential of spinal instrumentations in tumor vertebral body replacement surgery. Spine 23:543-50. Summary: STUDY DESIGN: The multidirectional stability potential of anterior, posterior, and combined instrumentations applied at L1-L3 was studied after L2 corpectomy and replacement with a carbon-fiber implant. OBJECTIVES: To evaluate the biomechanical characteristics of short-segment anterior, posterior, and combined instrumentations in lumbar spine tumor vertebral body replacement surgery. SUMMARY OF BACKGROUND DATA: The biomechanical properties of many different spinal instrumentations have been studied in various spinal injury models. Only a few studies, however, investigate the stabilization methods in spinal tumor vertebral body replacement surgery. METHODS: Eight fresh frozen human cadaveric thoracolumbar spine specimens (T12-L4) were prepared for biomechanical testing. Pure moments (2.5 Nm, 5 Nm, and 7.5 Nm) of flexion-extension, left-right axial torsion, and left-right lateral bending were applied to the top vertebra in a flexibility machine, and the motions of the L1 vertebra with respect to L3 were recorded with an optoelectronic motion measurement system after reconditioning. The L2 vertebral body was resected and replaced by a carbon-fiber cage. Different fixation methods were applied to the L1 and L3 vertebrae. One anterior, two posterior, and two combined instrumentations were tested. Load-displacement curves were recorded and neutral zone and range of motion parameters were determined. RESULTS: The anterior instrumentation provided less potential stability than the posterior and combined instrumentations in all motion directions. The anterior instrumentation, after vertebral body replacement, showed greater motion than the intact spine, especially in axial torsion (range of motion, 10.3 degrees vs 5.5 degrees; neutral zone, 2.9 degrees vs. 0.7 degrees; P < 0.05). Posterior instrumentation provided greater rigidity than the anterior instrumentation, especially in flexion-extension [range of motion, 2.1 degrees vs. 12.6 degrees; neutral zone, 0.6 degrees vs. 6.1 degrees; P < 0.05). The combined instrumentation provided superior rigidity in all directions compared with all other instrumentations. CONCLUSIONS: Posterior and combined instrumentations provided greater rigidity than anterior instrumentation. Anterior instrumentation should not be used alone in vertebral body replacement. Department of Orthopaedics, Medizinische Hochschule Hannover, Germany.

    • Vavruch L, Hedlund R, Javid D, Leszniewski W and Shalabi A (2002). A prospective randomized comparison between the cloward procedure and a carbon fiber cage in the cervical spine: a clinical and radiologic study. Spine 27:1694-701. Summary: STUDY DESIGN: A prospective randomized study was conducted. OBJECTIVE: To determine whether the use of a cervical carbon fiber intervertebral fusion cage improves the outcome of anterior cervical decompression and fusion, as compared with the Cloward procedure using autograft. SUMMARY OF BACKGROUND DATA: Despite the theoretical advantages of using intervertebral cages, including reduced donor site morbidity and prevention of graft collapse, an improved clinical outcome has not yet been documented. METHODS: For this study, 103 patients were randomized to anterior cervical decompression and fusion with a carbon fiber intervertebral fusion cage (n = 52) or the Cloward procedure (n = 51). An independent observer quantified pain and functional disability. Fusion rate, segmental kyphosis, and disc height were assessed by radiographs. RESULTS: During a mean follow-up period of 36 months (range, 24-72 months) for 89 patients (86%), the pain and disability were similar for both treatments. Postoperative donor site pain was significantly less in the carbon fiber intervertebral fusion cage group. The fusion rate was 86% in the Cloward procedure group and 62% in the carbon fiber intervertebral fusion cage group (P < 0.05). In the latter group, patients with pseudarthrosis reported more severe pain than fused patients [51 and 33 visual analog scores, respectively), but the difference was not significant. The segmental kyphosis was less and the disc height increased in the carbon fiber intervertebral fusion cage group, as compared with the Cloward procedure group. Disc height was not correlated with outcome. Segmental kyphosis showed a weak [r = -0.3) but significant [P < 0.05) correlation with improvement of the Cervical Spine Functional Score, but not with other outcome variables. CONCLUSIONS: Except for reduced donor site pain, the clinical outcome for the carbon fiber intervertebral fusion cage is the same as for the Cloward procedure. Use of the cage results in a more lordotic alignment and an increased disc height, but in a higher pseudarthrosis rate than use of the Cloward procedure. Department of Neuroorthopedics, Jonkoping, Sweden.

    • Wilke HJ, Kettler A and Claes L (2002). [Stabilizing effect and sintering tendency of 3 different cages and bone cement for fusion of cervical vertebrae segments]. Orthopade 31:472-80. Summary: Important requirement for spinal fusion devices for segment are that they provide sufficient stability and guarantee a low subsidence risk. An important requirement for spinal fusion devices for segments are that they provide sufficient stability and guarantee a low subsidence risk. Therefore, in the following in vitro study, the stabilizing effect and subsidence tendency of cervical fusion cages and bone cement were investigated during cyclic loading. The WING cages (Medinorm AG) and BAK cages (Spinetec) made of titanium, the carbon fiber reinforced PEEK cage from Acromed (DePuy Acromed), and bone cement (PMMA, Sulzer) were tested. Twenty-four human cervical spine specimens were first tested intact with a standardized flexibility test (+/- 2.5 Nm). Then the implants were inserted and the primary stability determined. For the simulation of the postoperative loading of the cervical spine a cyclic loading protocol with 700 loading cycles was performed. In this test pure moments +/- 2.0 Nm in 9 different loading directions in randomized order were applied together with a 50 N preload to simulate the weight of the head. The subsidence and "long term stability" was measured after 50, 100, 200, 300, 500, and 700 cycles. All implants had a stabilizing effect in all directions most obviously in lateral bending. Here the range of motion was between 20.9% (AcroMed Cage), and 62% (BAK Cage) with respect to the intact specimen (100%). In laterial bending, flexion, and axial rotation the AcroMed cage stabilized the most followed by the bone cement, WING and BAK Cage. In extension the specimens treated with bone cement were the most stable. After 700 loading cycles the specimens with the BAK cage lost 1.6 mm in height, with the WING Cage 0.8 mm, with the Acromed 0.7 mm, and with the bone cement 0.5 mm. Two Acromed Cages dislocated during the long term testing. Cages have the potential to stabilize as effectively as bone cement. A smaller contact area, however, causes a higher subsidence risk compared to bone cement but increases the fusion area, thus increasing the chance of obtaining bony fusion. Institut fur Unfallchirurgische Forschung und Biomechanik, Universitat Ulm, Helmholtzstrasse 14, 89081 Ulm. hans-joachim.wilke@medizin.uni-ulm.de

    • Zelle B, Konig F, Enderle A, Bertagnoli R and Dorner J (2002). Circumferential fusion of the lumbar and lumbosacral spine using a carbon fiber ALIF cage implant versus autogenous bone graft: a comparative study. J Spinal Disord Tech 15:369-76. Summary: This study reports on 92 patients treated with circumferential lumbar fusions for degenerative conditions. The elected procedure was a circumferential fusion using transpedicular stabilization. Two groups were examined depending on whether they were stabilized anteriorly with autogenous bicortical iliac crest graft (n = 38) or with an ALIF carbon fiber cage implant (n = 54). The patients were evaluated for clinical and radiographic outcome. The minimum follow-up interval was at least 12 months. Fusion rates, postoperative loss of correction, and clinical results, including pain at the bone donor site, neurologic function, satisfaction, depression, and consumption of analgesics, were not significantly different between patients with autogenous bone graft and patients with carbon cage. This study failed to prove major advantages of the carbon cages in the clinical and radiologic outcome. Department of Trauma Surgery, Medical School of Hannover, Germany. Boris.Zelle@web.de

  2. #2
    any one doing 4 level fusion with good results?
    i saw some 3 level

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