Biomedical subjects

F Kandziora

Publications and source records attributed to F Kandziora.

At least 19 recordsLinked to original sources

PubMed2006

Percutaneous balloon kyphoplasty in the treatment of pathological vertebral body fracture and deformity in multiple myeloma: a one-year follow-up.

PURPOSE: To evaluate the clinical and radiographic outcomes of balloon kyphoplasty in patients with fractures of the thoracic and lumbar spine caused by multiple myeloma. MATERIAL AND METHODS: Vertebral fractures due to multiple myeloma were treated by balloon kyphoplasty (20 patients, 48 vertebral bodies). Symptomatic levels were identified by clinical presentation, magnetic resonance imaging (MRI), radiographs, and computed tomography (CT). During the following year, visual analog scale (VAS) and Oswestry disability score were documented. Radiographs were taken pre- and postoperatively at 3, 6, and 12 months. Vertebral height and kyphotic deformity were measured to assess restoration of the sagittal alignment. RESULTS: The median pain scores (VAS) decreased significantly from pre- to posttreatment, as did the Oswestry disability score (p < 0.05). Clinically asymptomatic cement leakage occurred at 5 fracture levels (10.4%). During 1-year follow-up, this surgical technique demonstrated restoration and stabilization of the height of the vertebral body. CONCLUSION: Balloon kyphoplasty is an effective minimally invasive procedure for stabilizing pathological vertebral fractures caused by multiple myeloma and leading to a statistically significant reduction of pain status. Balloon kyphoplasty stabilizes the vertebral body height, but is only partially able to prevent further kyphotic deformities.

Aged↗

PubMed2005

[Vertebroplasty and kyphoplasty in osteoporotic fractures of vertebral bodies -- a prospective 1-year follow-up analysis].

PURPOSE: Kyphoplasty and vertebroplasty offer two minimally invasive operative stabilization procedures for vertebral compression fractures. The purpose of this prospective study was to investigate whether both procedures are able to reduce pain and to preserve postoperative vertebral height during a 1-year follow up. MATERIALS AND METHODS: Osteoporotic vertebral fractures were treated in 42 cases, 20 patients (15 female, 5 male) underwent vertebroplasty, 22 patients (14 female, 8 male) underwent kyphoplasty. 32 vertebral fractures were treated with vertebroplasty and 35 vertebral fractures were treated with kyphoplasty. Symptomatic levels were identified by correlating the clinical presentation with conventional radiographs, CT or/and MRI. During the follow up reduction of pain was determined. Radiographic scans were performed pre- and postoperatively and after 3, 6 and 12 months. The vertebral height and endplate angles were measured to assess the restoration of the sagittal alignment. The effects on pain symptoms were measured on a self-reported Visual Analog Scale (VAS) and the Oswestry score was documented. RESULTS: The median pain scores (VAS) decreased significantly for kyphoplasty and vertebroplasty from pre- to post-treatment, as did the Oswestry score (p < 0.05). No significant differences could be found between both groups for the median pain score (VAS) and the Oswestry score. Kyphoplsty led to a significant restoration of the vertebral height and reduction of kyphosis (p < 0.05). During the 1-year follow up both operation techniques were able to stabilize the height of the vertebral body. CONCLUSION: Kyphoplasty and vertebroplasty are effective minimally invasive procedures for the stabilization of osteoporotic vertebral fractures leading to a statistically significant reduction in pain. Kyphoplasty restores significantly vertebral body height in fresh fractures. The restoration of vertebral height and reduction of kyphosis may have an influence on the long term clinical outcome. This has to be evaluated in a long term prospective study.

Aged↗

PubMed2004

Local and controlled release of growth factors (combination of IGF-I and TGF-beta I, and BMP-2 alone) from a polylactide coating of titanium implants does not lead to ectopic bone formation in sheep muscle.

The osteoinductive potential of growth factors leads not only to a stimulated bone formation in bony tissue but also in extra skeletal tissue. This potential depends on the dosage and potentially on the application method and may limit the clinical use. The aim of the present study was to investigate the potential of IGF-I, TGF-beta1 and BMP-2 released from a newly developed application systems of orthopaedic implants to induce ectopic bone formation in muscles. This bioactive coating showed a stimulating effect on fracture healing in several experimental studies before. Titanium discs were coated on one side with the drug carrier poly(d,l-lactide) (PDLLA), with the carrier plus IGF-I and TGF-beta1 or with the carrier plus BMP-2. The discs were implanted in the Musculus cleidomastoideus of sheep and followed up for 3 months. X-rays were taken after the operation and the day of sacrifice. The muscles plus implant were harvested and prepared for histology. Neither the radiology nor the histology revealed any signs of ectopic ossification in the implant/muscle interface or in a distance to the plate in any group. An influence of the locally applied growth factor, however, was seen in the formation of a soft tissue capsule. Histomorphometric analysis revealed a significantly larger capsule area over the growth factor coated side in comparison to the uncoated side or the pure titanium plate, indicating an effect of the applied growth factors on cells, however, not resulting in osteoinduction in muscle. The result showed that the local and controlled release of growth factors from PDLLA coated implants does not induce ectopic bone formation in sheep muscle and could be used in orthopaedic surgery to increase healing without the risk of ectopic bone formation in the surrounding soft tissue.

Animals↗

PubMed2004

[Expandable cages: biomechanical comparison of different cages for ventral spondylodesis in the thoracolumbar spine].

INTRODUCTION: Due to a recent increase in the commercial availability of expandable cages for vertebral body replacement, this study was designed to gain more information about their biomechanical properties. All three expandable cages evaluated in this study are approved for clinical use, but little knowledge about their biomechanical properties exists. MATERIAL AND METHODS: Human thoracolumbar spines (T11 to L3) ( n=32) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive stiffness method. Three-dimensional displacement was measured using an optical measurement system. All motion segments were tested intact. After L1 corporectomy, cages were implanted and the following groups ( n=8 each) were tested: (1) meshed titanium cage (nonexpandable cage, DePuy Acromed), (2) X-tenz (expandable cage, DePuy Acromed), (3) Synex (expandable Cage, Synthes), and (4) VBR (expandable cage, Ulrich). Finally, posterior stabilization and posterior-anterior stabilization, both using USS (Synthes), and anterior plating (LCDCP, Synthes) was applied. The mean apparent stiffness values, ranges of motion, and neutral and elastic zones were calculated from the corresponding load/displacement curves. RESULTS: No significant differences were found between the in vitro biomechanical properties of expandable and nonexpandable cages. Compared to the intact motion segment, isolated anterior stabilization using cages and anterior plating significantly decreased stiffness and increased range of motion in all directions. Additional posterior stabilization significantly increased stiffness and decreased range of motion in all directions compared to the intact motion segment. Combined anterior-posterior stabilization demonstrated the greatest stiffness results. CONCLUSION: Design variations of expandable cages for vertebral body replacement do not show any significant effect on the biomechanical results. There was no significant difference found, between the biomechanical properties of expandable and non-expandable cages. After corporectomy, isolated implantation of expandable cages plus anterior plating was not able to restore normal stability of the motion segment. As a consequence, isolated anterior stabilization using cages plus LCDCP should not be used for vertebral body replacement in the thoraco-lumbar spine.

Biomechanical Phenomena↗

PubMed2004

[Biodegradable cage. Osteointegration in spondylodesis of the sheep cervical spine].

Bioabsorbable implants are commonplace in knee and shoulder surgery. Bioabsorbable poly(l-lactide-co-D,L-lactide) (PLDLLA) cage devices have potential benefits over autologous tricortical iliac crest bone graft and metallic cages for cervical spine interbody fusion. The purpose of this study was to compare interbody fusion of an autologous tricortical iliac crest bone graft with that of a bioabsorbable cage using a sheep cervical spine interbody fusion model. This study was designed to determine differences in (1) the ability to preserve postoperative distraction, (2) biomechanical stability, and (3) histological characteristics of intervertebral bone matrix formation. Sixteen full-grown Merino sheep underwent C3/4 discectomy and fusion. After 12 weeks, there was no significant difference between the results with the bioabsorbable PLDLLA cages and tricortical bone grafts. The cage also did not show advanced interbody fusion but did, however, show large osteolysis, which allows skepticism regarding the value of this bioabsorbable implant.

Absorbable Implants↗

PubMed2004

[Accuracy of CT-based navitation of pedicle screws in the thoracic spine compared with conventional technique].

The goal of this study was to evaluate the accuracy of CT-based computer-assisted pedicle screw insertion in the thoracic spine in patients with fractures, metastases, and spondylodiscitis compared to a conventional technique. A total of 324 pedicle screws were inserted in the thoracic spines of 85 patients: 211 screws were placed using a CT-based optoelectronic navigation system assisted by an image intensifier and 113 screws were placed with a conventional technique. Screw positions were evaluated with postoperative CT scans by an independent radiologist. In the computer-assisted group, 174 (82.5%) screws were found completely within their pedicles compared with 77 (68.1%) correctly placed screws in the conventional group ( p<0.003). Despite use of the navigation system, 1.9% of the computer-assisted screws perforated the pedicle wall by more than 4 mm. The additional use of the image intensifier helped to identify the correct vertebral body and avoided cranial or caudal pedicle wall perforations.

Adolescent↗

PubMed2004

[Vertebral body replacement in spine surgery].

Autografts and allogeneous bone grafts as well as cages are used for the reconstruction of the anterior column after corpectomy. Recently, expandable cages for vertebral body replacement have been developed. Based on our own experience, the purpose of this study was to summarize the available biomechanical and clinical data of expandable corpectomy cages and to compare it with established fixation techniques. If used correctly, expandable cages offer several surgical advantages in comparison to non-expandable cages. However there were no significant differences between the biomechanical properties of expandable and non-expandable cages. Additionally, design variations of expandable corpectomy cages did not show any significant impact on the biomechanical stability. Currently available mid-term clinical and radiological data on the treatment of fractures, metastasis and infection of the cervical, thoracic and lumbar spine demonstrated no significant difference between expandable and non-expandable cages. However, the increased stress-shielding effect of expandable cages compared to non-expandable cages might result in a deterioration of the long-term clinical outcome.

Bone Plates↗

PubMed2004

Comparison of unreamed nailing and external fixation of tibial diastases--mechanical conditions during healing and biological outcome.

Locked intramedullary nailing and external fixation are alternatives for the stabilization of tibial shaft fractures. The goal of this study was to determine to what extent the mechanical conditions at the fracture site influence the healing process after unreamed tibial nailing compared to external fixation. A standardized tibial diastasis was stabilized with either a locked unreamed tibial nail or a monolateral fixator in a sheep model. Interfragmentary movements and ground reaction parameters were monitored in vivo throughout the healing period. After sacrifice, the tibiae were examined mechanically and histologically. Bending angles and axial torsion at the fracture site were larger in the nail group within the first five weeks post-operatively. Unlike the fixator group, the operated limb in the nail group did not return to full weight bearing during the treatment period. Mechanical and histomorphometrical observations showed significantly inferior bone healing in the nail group compared to the fixator group. In this study, unreamed nailing of a tibial diastasis did not provide rotational stability of the osteosynthesis and resulted in a significant delay in bone healing.

Animals↗

PubMed2003

[Diagnostic value of three-dimensional reconstruction in CT of traumatic spinal fractures].

PURPOSE: Evaluation of the diagnostic value of three-dimensional CT-reconstruction in the pre-operative evaluation of traumatic fractures of the spine, compared with axial slices and two-dimensional reconstruction. MATERIALS AND METHODS: The CT image data of 65 patients with 85 different acute traumatic spine fractures (C 2 through L 5) were collected in a period of 42 months. Retrospectively performed 2D- and 3D-reconstructions were analyzed independently by three CT-experienced readers using the Magerl classification and the readings compared with intraoperative findings or the final diagnoses. RESULTS: The fractures were classified according to the AO-classification as 56 compression, 16 distraction and 13 rotation fractures. Axial slices alone incorrectly classified 2 (1.2 %) of 168 (56 fractures x 3 readers) type A fractures. The CT classification was incorrect in 17 (35.4 %) of 48 (16 fractures x 3 readers) type B fractures and in 31 (79.5 %) of 39 (13 fractures x 3 readers) type C fractures. The 2D-reconstruction increased the percentage of incorrect diagnoses to 13 (7.7 %) type A, to 26 (54.2 %) type B and to 27 (69.2 %) type C fractures. The 3D-mode incorrectly classified 2 of 168 type A fractures (1.2 %), 6 of 48 type B fractures (12.5 %), and 1 of 39 type C fractures (2.6 %). The axial mode was superior to the 2D-reconstructions in type A and type B fractures, but inferior in type C fractures. The percentage of correctly classified type B fractures was significantly higher (p < 0.05) with 3D-reconstruction than with the 2D-mode. In type C fractures, this percentage was significantly higher (p < 0.001) with the 3D-mode than with axial slices or 2D-reconstruction. The interactive monitor analysis of the 3D-reconstructions with additional virtual cutting by the reader improved the analysis, especially the evaluation of the spinal canal. CONCLUSION: The 3D-reconstruction in traumatic spine fractures significantly improves the diagnostic outcome, especially the visualization and classification of rotation fractures. Its disadvantages are a slight increase in artifacts and impaired visualization of small details. Interactive monitor analysis and post-processing of the 3D-mode proved to be advantageous.

Adult↗

PubMed2002

Dose-dependent effects of combined IGF-I and TGF-beta1 application in a sheep cervical spine fusion model.

Combined IGF-I and TGF-beta1 application by a poly-(D,L-lactide) (PDLLA) coated interbody cage has proven to promote spine fusion. The purpose of this study was to determine whether there is a dose-dependent effect of combined IGF-I and TGF-beta1 application on intervertebral bone matrix formation in a sheep cervical spine fusion model. Thirty-two sheep underwent C3/4 discectomy and fusion. Stabilisation was performed using a titanium cage coated with a PDLLA carrier including no growth factors in group 1 ( n=8), 75 micro g IGF-I plus 15 micro g TGF-beta1 in group 2 ( n=8), 150 micro g IGF-I plus 30 micro g TGF-beta1 in group 3 ( n=8) and 300 micro g IGF-I plus 60 micro g TGF-beta1 in group 4 ( n=8). Blood samples, body weight and temperature were analysed. Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8, and 12 weeks. At the same time points, disc space height and intervertebral angle were measured. After 12 weeks, the animals were killed and fusion sites were evaluated using quantitative computed tomographic (CT) scans to assess bone mineral density, bone mineral content and bony callus volume. Biomechanical testing was performed and range of motion, and neutral and elastic zones were determined. Histomorphological and histomorphometrical analysis were carried out and polychrome sequential labelling was used to determine the time frame of new bone formation. In comparison to the group without growth factors (group 1), the medium- and high-dose growth factor groups (groups 3 and 4) demonstrated a significantly higher bony callus volume on CT scans, a higher biomechanical stability, an advanced interbody bone matrix formation in histomorphometrical analysis, and an earlier bone matrix formation on fluorochrome sequence labelling. Additionally, the medium- and high-dose growth factor groups (groups 3 and 4) demonstrated a significantly higher bony callus volume, a higher biomechanical stability in rotation, and an advanced interbody bone matrix formation in comparison to the low-dose growth factor group (group 2). No significant difference could be determined between the medium- and the high-dose growth factor groups (groups 3 and 4, respectively). The local application of IGF-I and TGF-beta1 by a PDLLA-coated cage significantly improved results of interbody bone matrix formation in a dose-dependent manner. The best dose-response relationship was achieved with the medium growth factor dose (150 micro g IGF-I and 30 micro g TGF-beta1). With an increasing dose of these growth factors, no further stimulation of bone matrix formation was observed. Although these results are encouraging, safety issues of combined IGF-I and TGF-beta1 application for spinal fusion still have to be addressed.

Animals↗

PubMed2002

Comparison of BMP-2 and combined IGF-I/TGF-ss1 application in a sheep cervical spine fusion model.

Growth factors have proven to promote spine fusion. However, no comparative evaluation of growth factors in spinal fusion has yet been performed. The purpose of this study was to compare the efficacy and safety of combined IGF-I and TGF-ss1 application with BMP-2 application and autologous cancellous bone graft at an early time point in a sheep cervical spine fusion model. Thirty-two sheep underwent C3/4 discectomy and fusion. They were divided into four groups, according to their treatment: group 1, titanium cage ( n=8); group 2, titanium cage filled with autologous cancellous iliac crest bone grafts ( n=8); group 3, titanium cage coated with a poly-(D,L-lactide) (PDLLA) carrier including BMP-2 (5% w/w) ( n=8); group 4, titanium cage coated with a PDLLA carrier including IGF-I (5% w/w) and TGF-ss1 (1% w/w) ( n=8). Blood samples, body weight and temperature were analysed. Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8 and 12 weeks. At the same time points, disc space height and intervertebral angle were measured. After 12 weeks, the animals were killed and fusion sites were evaluated using functional radiographic views in flexion and extension. Quantitative computed tomographic scans were performed to assess bone mineral density, bone mineral content and bony callus volume. Biomechanical testing was carried out and the values for range of motion, and neutral and elastic zone were determined. Histomorphological and histomorphometrical analysis were performed and polychrome sequential labelling was used to determine the time frame of new bone formation. The results showed that, in comparison to the group treated with the cage alone (group 1), the cage plus BMP-2 group (group 3) and the cage plus IGF-I and TGF-ss1 group (group 4) demonstrated a significantly higher fusion rate in radiographic findings, a higher biomechanical stability, a more advanced interbody fusion in histomorphometrical analysis, and an accelerated interbody fusion on fluorochrome sequence labelling. In comparison to the bone graft group (group 2), the BMP-2 (group 3) and IGF-I/TGF-ss1 group (group 4) showed significantly less residual motion on functional radiographic evaluation, higher bone mineral density of the callus and higher biomechanical stability in extension, rotation and bending. The BMP-2 group showed significantly less residual motion on functional radiographic evaluation and higher intervertebral bone matrix formation on fluorochrome sequence labelling at 9 weeks in comparison to the IGF-I/TGF-ss1 group. In contrast, the IGF-I/TGF-ss1 group showed a significantly higher bone mineral density of the callus than the BMP-2 group. In comparison to the autologous cancellous bone graft group, both growth factors (BMP-2 and combined IGF-I and TGF-ss1) significantly improved the biomechanical results of interbody fusion. No systemic side effects were observed for either growth factor. On the basis of these preliminary results, it would appear that combined IGF-I/TGF-ss1 application yields equivalent results to BMP-2 application at an early time point in anterior sheep cervical spine fusion.

Animals↗

PubMed2002

[Experimental fusion of the sheep cervical spine. Part I: Effect of cage design on interbody fusion].

INTRODUCTION: There has been a rapid increase in the use of interbody fusion cages as an adjunct to spondylodesis, although experimental data are lacking. A sheep cervical spine interbody fusion model was used to determine the effect of different cage design parameters (endplate-implant contact area, maximum contiguous pore) on interbody fusion. MATERIAL AND METHOD: IN VITRO EVALUATION: 24 sheep cadaver specimens (C2-C5) were tested in flexion, extension, axial rotation, and lateral bending with a nondestructive flexibility method using a nonconstrained testing apparatus. Four different groups were examined: (1) control group (intact) ( n=24), (2) autologous tricortical iliac crest bone graft ( n=8), (3) Harms cage ( n=8), and (4) SynCage-C ( n=8). IN VIVO EVALUATION: 24 sheep underwent C3/4 discectomy and fusion: group 1: autologous tricortical iliac crest bone graft ( n=8), group 2: Harms cage filled with autologous cancellous iliac crest bone grafts ( n=8), and group 3: SynCage-C filled with autologous cancellous iliac crest bone grafts ( n=8). Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8, and 12 weeks, respectively. At the same time points, disc space height (DSH), height index (HI), intervertebral angle (IVA), and endplate angle (EA) were measured. After 12 weeks the animals were killed and fusion sites were evaluated using biomechanical testing in flexion, extension, axial rotation, and lateral bending. Additionally, histomorphological and histomorphometrical analyses were performed. RESULTS: Over a 12-week period the cage groups showed significantly higher values for DSH, HI, IVA, and EA compared to the bone graft. In vivo stiffness was significantly higher for the tricortical iliac crest bone graft and Harms cage than in vitro stiffness. However, there was no difference between in vitro and in vivo stiffness of the SynCage-C. Histomorphometrical evaluation showed a more progressed bone matrix formation in the Harms cage group than in both other groups. CONCLUSION: The parameter endplate-implant contact area was not able to determine subsidence of cages. In contrast, the maximum contiguous pore of a cage significantly correlates with interbody bone matrix formation inside the cage. Additionally, there was no correlation between in vitro and in vivo stiffness of interbody fusion cages. Therefore, biomechanical in vitro studies are not able to determine in vivo outcome of fusion cages. Animal experimental evaluations of interbody fusion cages are essential prior to clinical use.

Animals↗

PubMed2002

[Experimental fusion of the sheep cervical spine. Part II: Effect of growth factors and carrier systems on interbody fusion].

INTRODUCTION: A sheep cervical spine interbody fusion model was used to determine the effect of different carriers and growth factors on interbody bone matrix formation. The purpose of this study was to compare the efficacy and safety of combined IGF-I and TGF-beta1 application with BMP-2 application in spinal fusion. Additionally, a new poly (D, L-lactide) carrier system was compared to a collagen sponge carrier. METHOD: Forty sheep underwent C3/4 discectomy and fusion: group 1: titanium cage ( n=8), group 2: titanium cage coated with a PDLLA carrier (n=8), group 3: titanium cage coated with a PDLLA carrier including BMP-2 ( n=8), group 4: titanium cage with a collagen carrier including BMP-2 ( n=8), and group 5: titanium cage coated with a PDLLA carrier including IGF-I and TGF-beta1 ( n=8). Blood samples, body weight, and temperature were analyzed. Radiographic scans were performed pre- and postoperatively and after 1, 2, 4, 8, and 12 weeks, respectively. At the same time points, disc space height (DSH) and intervertebral angle (IVA) were measured. After 12 weeks the animals were killed and fusion sites were evaluated using functional radiographic views in flexion and extension. Quantitative computed tomographic scans (QCT) were performed to assess bone mineral density (BMD), bone mineral content (BMC), and bony callus volume (BCV). Biomechanical testing was carried out in flexion, extension, axial rotation, and lateral bending. Range of motion (ROM), neutral zone (NZ), and elastic zone (EZ) were determined. Histomorphological and histomorphometrical analyses were performed and polychrome sequential labeling was used to determine the time frame of new bone formation. RESULTS: In comparison to the non-coated cages, all PDLLA-coated cages showed significantly higher values for BMD of the callus and bone volume/total volume ratio. In comparison to the cage groups (groups 1 and 2), the cage plus BMP-2 (groups 3 and 4) and the cage plus IGF-I and TGF-beta1 group (group 5) demonstrated a significantly higher fusion rate in radiographic findings, a higher biomechanical stability, an advanced interbody fusion in histomorphometric analysis, and an accelerated interbody fusion on fluorochrome sequence labeling. BMP-2 application by the PDLLA carrier system (group 3) demonstrated significantly higher bony callus volume than BMP-2 application by a collagen sponge carrier (group 4). The BMP-2 group (group 3) showed significantly lower residual motion on functional radiographic evaluation and higher intervertebral bone matrix formation on fluorochrome sequence labeling at 9 weeks in comparison to the IGF-I/TGF-beta1 group (group 5). In contrast, the IGF-I/TGF-beta1 group (group 5) showed a significantly higher bone mineral density of the callus than the BMP-2 group (group 3). CONCLUSION: PDLLA coating of cervical spine interbody fusion cages as a delivery system for growth factors was effective and safe. In comparison to the collagen sponge carrier, the new PDLLA carrier system was able to improve results of interbody bone matrix formation. Both growth factors (BMP-2 and combined IGF-I and TGF-beta1) significantly accelerated results of interbody fusion. Based on these preliminary results, the combined IGF-I/TGF-beta1 application yields results equivalent to BMP-2 application at an early time in anterior sheep cervical spine fusion.

Animals↗

PubMed2002

Bone morphogenetic protein-2 coating of titanium implants increases biomechanical strength and accelerates bone remodeling in fracture treatment: a biomechanical and histological study in rats.

Bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor (TGF)-beta superfamily, is known to be a very potent osteoinductive growth factor. The purpose of this study was to investigate the effect of BMP-2 (5% [w/w], 50 microg on each nail), locally released from poly(D,L-lactide) (PDLLA)-coated intramedullary implants, on fracture healing. A closed fracture of the right tibia of 5-month-old Sprague-Dawley rats (n = 64) was intramedullary stabilized with uncoated vs. BMP-2-coated titanium Kirschner wires. X-ray examinations (posteroanterior and lateral) were performed throughout the experiment. At 28 and 42 days after fracture, the animals were killed and both tibiae were dissected for biomechanical torsional testing. For histological and histomorphometric evaluation, 5 microm sections were obtained, stained with Safranin-O/light green and von Kossa, and examined using an image analysis system. The radiological results demonstrated progressed callus consolidation in the BMP-2-treated groups compared with the uncoated groups at both timepoints. Histomorphometric evaluation showed progressed callus remodeling with significantly increased mineralization and less cartilage of the periosteal callus. Due to the BMP-2 treatment, increased mineralization of the cortices was detected at 28 and 42 days after fracture. Biomechanical testing revealed significantly elevated maximum load and torsional stiffness in the BMP-2-treated groups compared with controls at both timepoints. The results clearly demonstrate that local application of BMP-2 from PDLLA-coated implants is feasible and significantly accelerates fracture healing. Local administration of growth factors from coated implants could reduce clinical problems in fracture treatment without opening of the fracture, implantation of further devices, or injection with the risk of infection or side effects caused by other carriers.

Animals↗

PubMed2001

Biomechanical comparison of cervical spine interbody fusion cages.

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.

Animals↗

PubMed2001

Comparison between sheep and human cervical spines: an anatomic, radiographic, bone mineral density, and biomechanical study.

STUDY DESIGN: The quantitative anatomic, radiographic, computerized tomographic, and biomechanical data of sheep and human cervical spines were evaluated. OBJECTIVES: To compare the anatomic, radiographic, computerized tomographic, and biomechanical data of human and sheep cervical spines to determine whether the sheep spine is a suitable model for human spine research. SUMMARY OF BACKGROUND DATA: Sheep spines have been used in several in vivo and in vitro experiments. Quantitative data of the normal sheep cervical spine are lacking, yet these data are crucial to discussion about the results of such animal studies. METHODS: In this study, 20 fresh adult female Merino sheep cervical spines and 20 fresh human cadaver cervical spines were evaluated anatomically, radiographically, computerized tomographically, and biomechanically. Three linear and two angular parameters were evaluated on four digital radiographic views: anteroposterior, right lateral in neutral position, flexion, and extension. Quantitative computed tomography scans at the center of each vertebral body and 3 mm below both endplates were analyzed for bone mineral density measurements. Biomechanical testing was performed in flexion, extension, axial rotation, and lateral bending by a nondestructive stiffness method using a nonconstrained testing apparatus. Range of motion and stiffness of each motion segment were calculated. Additionally, 10 linear anatomic parameters of each vertebra were measured using a digital ruler. RESULTS: Anterior and mean disc space height in the sheep cervical spine increased constantly from C2-C3 to C6-C7, whereas middle disc space height decreased and posterior disc space height remained unchanged. Anterior and mean disc space height were significantly higher in sheep. In both sheep and human cervical spines, intervertebral angles were not significantly different. Standard deviations of bone mineral density in the human cervical spine were fourfold higher than in the sheep cervical spine, yet no significant differences were found in bone mineral density values between the two species. Range of motion differed significantly between the two species except in flexion-extension of C3-C4, C5-C6, axial rotation of C2-C3, and lateral bending of C2-C3, C3-C4, and C4-C5. Stiffness also was significantly different except in flexion-extension of C2-C3, C4-C5, C5-C6, and lateral bending of C2-C3, C3-C4, and C4-C5. Anatomic evaluation showed no difference in upper endplate parameters for C4 and C5. CONCLUSIONS: Although several differences were found between human and sheep cervical spines, the small intergroup standard deviations and the good comparability with the human spine encourage the use of the sheep cervical spine as a model for cervical spine research. On the basis of the quantitative data obtained in this study, the sheep motion segment C3-C4 seemed to be the most reliable model for the corresponding human motion segment.

Adult↗

PubMed2001

[Mechanical comparison of biodegradable intervertebral lumbar cages].

INTRODUCTION: A biodegradable interbody cage for lumbar spine fusion would be able to solve several problems associated with the use of metallic cages. In a biomechanical in vitro study using human lumbar spines three different biodegradable poly(L-lactide-co-D,L-lacitide)(PLDLLA) cages were compared to metallic cages of the same design. MATERIAL AND METHOD: 40 human cadaver lumbar specimens (L3-S1) were tested in flexion, extension, rotation, and bending with a non-destructive flexibility method using a nonconstrained testing apparatus. Seven different groups were examined: (1) control group (intact) (n = 40); (2) unstable group (after discectomy L4/5) (n = 40), (3) autologous iliac crest bone graft (n = 8), (4) BAK-Cage (n = 8), (5) BIO-Cage 1 (PLDLLA) (n = 8), (6) BIO-Cage 2 (PLD-LLA/hydroxylapatite-buffer) (n = 8) and (7) BIO-Cage 3 (PLDLLA/hydroxylapatite particles of different size) (n = 8). Additionally, destructive compression tests of all implants were performed. RESULTS: In comparison to the intact motion segment all cages showed significantly lower range of motion (ROM) in all test modes (P < 0.01). There was no significant difference in stiffness values and ROM between BIO-Cages and metallic cages. Axial compression stiffness and failure load were significantly highest for metallic BAK-cages (P < 0.05). No significant difference for failure load was observed between BIO-cage 1 and the intact motion segment. However, in comparison to the intact motion segment failure load was significantly lower for BIO-cage 2 and 3 (P < 0.05). CONCLUSION: The results of this study are encouraging, because the biodegradable cages were able to limit lumbar spine motion similar to the metallic cages. Especially, the biodegradable PLDLLA cage consisting of pure polymer (BIO-Cage 1) showed adequate initial compression strength. However, further in vivo animal experiments are essential prior to the clinical application of biodegradable lumbar interbody fusion cages.

Absorbable Implants↗

PubMed2001

[Transoral atlanto-axial plate fixation in the treatment of a malunited dens fracture and secondary atlanto-axial instability].

INTRODUCTION: A case of a 22-year-old patient with a malunited dens fracture and secondary atlanto-axial instability is presented. The significant narrowing of the spinal canal due to the atlanto-axial instability was associated with anterior myelon compression and neurological deficit. METHODS: A transoral approach with odontoid resection and anterior atlanto-axial plate fixation was performed. With this technique the atlanto-axial subluxation was reduced and the myelon was decompressed. RESULTS: The postoperative course was uneventful. The follow-up showed a complete remission of the neurological deficit and a bony fusion of the atlanto-axial joints. CONCLUSIONS: The presented case illustrates the importance of an accurate initial diagnosis of the degree of instability and the need for short-term follow-up examinations. If atlanto-axial pseudarthrosis or malunion with anterior spinal cord compression occurs, a transoral procedure with odontoid resection and atlanto-axial plate fixation seems to be an excellent salvage procedure.

Adult↗