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C Knop

Publications and source records attributed to C Knop.

At least 19 recordsLinked to original sources
PubMed2007

[An improved vertebral body replacement for the thoracolumbar spine. A biomechanical in vitro test on human lumbar vertebral bodies].

BACKGROUND: In recent years, the use of expandable titanium cages for vertebral body replacement in the thoracolumbar spine has been well established for the treatment of tumors, unstable traumatic lesions, or posttraumatic deformity. Collapse of the implant into the vertebral body remains a point of concern. A biomechanical compression test was designed to assess implant subsidence for a newly developed prototype for vertebral body replacement in the thoracolumbar spine using human cadaveric lumbar vertebrae. The objective of this study was to compare the compressive performance of a new expandable cage with modified end-plate design with three commonly available expandable cages for vertebral body replacement. MATERIALS AND METHODS: The compressive strengths at the implant-vertebral body interface were measured via axial loading of the new prototype (Synex II) in comparison with three different expandable titanium cages: Synex I (Synthes), Obelisc (Ulrich Medical) and X-Tenz (DePuy Spine). Twenty-four intact, fresh frozen human lumbar vertebrae (L1-L4) were distributed into four identical groups according to BMD (determined by quantitative computed tomography) and the vertebral level. Specimens were loaded in the craniocaudal direction with a material testing machine at a constant speed of 5 mm/min. Load displacement curves were continuously recorded for each specimen until failure (diminishment of compressive force (F)/obvious implant migration through the vertebral body endplate). One-way analysis of variance and post-hoc tests (Bonferroni) were applied to detect differences at 1, 2, 3, 4 mm displacement (F1-4 mm), and Fmax between implant groups. RESULTS: The four expandable cages did not show statistically significant biomechanical differences in terms of maximum compression force (Fmax) until failure: Synex II (1,782 N/4.7 mm); Synex I (1,645 N/4.7 mm); Obelisc (1,314 N/4.2 mm); X-Tenz (1,470 N/6.9 mm). However, the mean compression force until 4 mm displacement (F1-4 mm: 300-1,600 N) was highest for Synex II. The difference at 2 mm displacement was significant (p=0.028) between Synex II (F2 mm=879 N) and X-Tenz (F2 mm=339 N). CONCLUSION: The modified endplate design of the new prototype was found to improve its compressive performance under constrained uniaxial loading conditions at the implant-bone interface. The improved compressive behaviour of the new implant might help to reduce the risk of implant subsidence and collapse into the vertebral body in vivo.

Aged↗
PubMed2006

Successful posterior interlaminar fusion at the thoracic spine by sole use of beta-tricalcium phosphate.

We report on a 43-year-old male who sustained an isolated distraction injury of the thoracic spine Th7/Th8 (AO/ASIF B 2.3) with wedge compression Th8 and sagittal split Th10 without neurological injury. A bisegmental posterior stabilisation and a monosegmental interlaminar fusion was the treatment of choice. A synthetic bone substitute, beta-tricalcium phosphate (beta-TCP, Chronos) without additional autogenous bone was used to achieve the monosegmental posterior fusion. The clinical course was favourable and 10 months postoperatively the implant was removed. On implant removal the CT scan showed a fused segment and intraoperatively it was found that the fusion was solidly healed. A biopsy was taken from the fusion mass and histology showed vital bone that was rich with osteocytes. Noncalcified osteoid surrounding the bone marrow cavity could be identified. Several studies and the reported case might indicate that osteoconductive material alone can be sufficient for achieving a solid fusion.

Adult↗
PubMed2006

Improved anchorage in osteoporotic vertebrae with new implant designs.

The goal of our study was to evaluate two newly developed implant designs and their behavior in terms of subsidence in lumbar vertebral bodies under cyclic loading. The new implants were evaluated in two different configurations (two small prototypes vs. one large prototype with similar load-bearing area) in comparison to a conventional screw-based implant (MACS TL). A pool of 13 spines with a total of 65 vertebrae was used to establish five testing groups of similar bone mineral density (BMD) distribution with eight lumbar vertebrae each. In additional to BMD assessment via dual-energy X-ray absorptiometry, cancellous BMD and structural parameters were determined using a new generation in vivo 3D-pQCT. The specimens were loaded sinusoidally in force control at 1 Hz for 1000 cycles at three load levels (100, 200, and 400 N). A survival analysis using the number of cycles until failure (Cox regression with covariates) was applied to reveal differences between implant groups. All new prototype configurations except the large cylinder survived significantly longer than the control group. The number of cycles until failure was significantly correlated with the structural parameter Tb.Sp. and similarly with the cancellous BMD for three of five implants. In both large prototypes the cycle number until failure significantly correlated with the preoperative distance to the upper endplates. Although the direct relationship between bone structure or density and mechanical breakage behavior cannot be conclusively proven, all the prototypes adapted for poor bone structure performed better than the comparable conventional implant.

Aged↗
PubMed2006

[Titanium vertebral body replacement of adjustable size. A prospective clinical trial].

OBJECTIVE: The reconstruction of the anterior column of the thoracolumbar spine is still controversial. METHODS: The clinical notes and radiographs of 50 consecutive patients (29 M, 21 F, 43 years) treated with the Synex implant were reviewed at operation and at 12 and 20 months postoperatively. RESULTS: Of 45 patients, 25 returned to pre-injury activities within 1 year and 29 of 39 within 20 months. Two-thirds of the patients who were followed up returned to their job. After 1 year 25 of 45 patients had no or mild limitations in their back function. Six months later this group decreased to 6 of 39 patients. Visual analog scale (VAS) decreased from 87/100 preoperatively to 65/100 at the 1-year follow-up. The average permanent reduction of the injured vertebrae was 16.9 degrees including 2.3 degrees loss of correction. CONCLUSION: After reconstruction of the anterior column with the Synex implant only a minimal loss of correction or reduction was observed. The clinical outcome after use of the Synex implant appears promising. We recommend this implant as a valuable alternative for reconstruction of the anterior column of the thoracolumbar spine. However, long-term results are still required.

Accidental Falls↗
PubMed2006

[Lower cervical spine trauma: classification and operative treatment].

Injuries to the subaxial cervical spine (C3-7) occur mostly from traffic accidents and in recreational activities. Such lesions that appear on roentgenological or magnetic resonance images must be classified according to stability. Neurologic deficits, accompanying injuries, and the patient's general condition play major roles in the choice of therapy. Fracture and fracture dislocations should be reduced as soon as possible, as neurologic regeneration and successful reduction are closely time related. The classification developed by Magerl et al. for thoracic and lumbar spine can also be used for the lower cervical spine. Stable injuries without neurologic deficits can generally be treated functionally and, sometimes, with external immobilization. Unstable injuries should be stabilized and treated surgically. Ventral intercorporal spondylodesis is a proven, standard surgical technique for open reduction, decompression, and fusion. Disc and whole or partial vertebral resection along with intercorporal fusion with autologous iliac crest bone grafting and plate osteosynthesis enables successful stabilization of almost all mono- and bisegmental lesions. Dorsal surgery is indicated only in case of a compressed spinal canal and/or neuroforamens due to destroyed posterior elements or remaining instability following ventral plate spondylesis.

Accidents, Traffic↗
PubMed2006

[Reduction of traumatic dislocations and facet fracture-dislocations in the lower cervical spine].

BACKGROUND: Traumatic facet dislocations and facet-fracture dislocations in the lower cervical spine (C2/C3 to C7/T1) are frequently associated with devastating neurological symptoms. A good outcome can only be achieved if the operator has wide and sound knowledge of reduction techniques and the best possible strategy is devised for the subsequent treatment of these severe lesions. PATIENTS AND METHODS: Between 1973 and 1997 a total of 117 of our patients met at least one of the following inclusion criteria: unilateral locked facet dislocation (48%), bilateral locked facet dislocations (23%), unilateral "perched" facet subluxation (14%), bilateral perched facet subluxation (12%), uni- or bilateral dislocation/perched subluxation with facet fractures (3%). RESULTS: Most of the lesions were located at the levels of C5/C6 and C6/7 (n=46 for each). Associated neurological deficits were present initially in 65% of patients: 35% had complete or incomplete spinal cord injuries (tetraplegia), 2% were paraplegic, and 28% had cervical radiculopathies. CONCLUSIONS: Closed reduction (e.g. with the aid of a halo ring) should be carried out as soon as possible after lower cervical spine dislocation or facet-fracture dislocation, as both the success rate of reduction and the potential for recovery from neurological deficits are clearly higher when reduction is achieved within the first 4 h after the initial injury.

Adolescent↗
PubMed2006

[Acute diagnosis of spinal trauma].

Most traumatic spinal injuries result from a high-energy process and are accompanied by other injuries. Following the CCSPR study, the presence of all low-risk factors (simple trauma mechanism, fully conscious, ambulatory at any time since trauma, neck rotation exceeding 45 degrees bilaterally) obviates the need to acutely image the cervical spine. Imaging is indicated in all other patients. Emergency spiral CT should be performed as the first imaging method in high-risk and moderate-risk patients; only in low-risk patients should conventional radiography be performed and trusted as the sole modality. The AO classification according to Magerl et al. is used for the subaxial spine, whereas the upper cervical spine should be classified separately because the anatomy is different at each level. Radiological evaluation of traumatic spinal injuries should be done systematically using the "ABCS" scheme.

Acute Disease↗
PubMed2005

Acute traumatic L5-S1 spondylolisthesis: a case report.

STUDY DESIGN: Case report of a patient treated surgically 2 months after sustaining a misdiagnosed acute traumatic lumbosacral dislocation is presented. OBJECTIVES: The aims is to report in full about an uncommon case of anterior traumatic L5-S1 spondylolisthesis treated successfully with combined posterior stabilization and anterior fusion. SUMMARY OF BACKGROUND DATA: Review of literature shows that traumatic lumbosacral dislocations and its treatment by open reduction and internal fixation are rare with only few well-documented case reports. METHODS: We report the case of a 37-year-old man, who sustained a work-related traumatic lumbosacral dislocation. The delayed diagnosis of traumatic L5-S1 spondylolisthesis was initially missed and first treated, when the patient was transferred to the author's institution because of persistent neurological deficits. In the following the patient was successfully reduced and stabilized with posterior internal fixation and anterior interbody fusion. This case is documented in detail with radiographs, CT and MRI scans, as well as clinical pictures. RESULTS: At a 1.5-year follow-up complete fusion was achieved. The patient returned to work on the same job before injury, ambulating pain-free with a good subjective back-function and no limitations carrying out his recreational activities. At follow-up he had persistent sensible S1 nerve root deficits (ASIA grade E). CONCLUSIONS: Traumatic lumbosacral spondylolisthesis is a rare injury pattern. Its diagnosis can be missed initially, therefore computed tomography with biplanar reconstructions is mandatory in addition to good-quality conventional radiographs to plan and carry out such challenging management problems successfully. Surgical treatment for reduction, stabilization and interbody fusion is the method of choice.

Accidents, Occupational↗
PubMed2005

[Ankylosing spondylitis. Therapy and complications of 34 spine fractures].

BACKGROUND: Spine fractures in ankylosing spondylitis (AS) are extremely unstable and associated with a high complication rate. The aim of this retrospective study was to evaluate the therapy and complications of these fractures in AS for a better understanding and management. PATIENTS AND METHODS: A total of 32 patients with 34 traumatic spine fractures were treated from 1981 to 2002. Cause of trauma, fracture site, and neurological examination were assessed. Analyses of the management of the treatment and complications were performed. RESULTS: Banal traumas resulted mostly in spinal fractures at the C 5/6 and C 6/7 level. Two patients were treated conservatively, while the others were stabilized operatively. Before therapy was undertaken, six patients suffered from a cervical radiculopathy, ten patients had an incomplete and two a complete paraplegia. After therapy, neurological status improved in eight patients, but one had a deterioration of neurological symptoms. CONCLUSIONS: Dorsal or combined dorsoventral stabilization of these fractures is necessary for better mobilization of these patients and to avoid further complications.

Adult↗
PubMed2003

[Non-operative treatment of thoracolumbar spinal fractures. Long-term clinical results over 16 years].

Non-operative treatment of thoracolumbar fractures remains the standard treatment option for stable and slightly unstable spinal injuries at the level of the lower thoracic and lumbar spine. The purpose of the present retrospective study was to determine the outcome and long-term results of patients treated conservatively using either one of the two major non-operative treatment modalities: (1) functional, or (2) closed reduction and immobilisation by cast. The average follow-up time for the 43 patients reviewed was 16.3 years. They showed a radiologic increase in the average kyphosis angle of 5.2 degrees compared to the time of injury. No difference was noted between early functional therapy and treatment with closed reduction and immobilisation by cast. Patients with initial neurologic impairment showed a significant improvement ( P<0.05) in their neurologic status during the follow-up period. Results of validated psychometric questionnaires (SF-36, FSR, VAS-Spinescore) showed the characteristic pattern of a population with chronic back pain. In conclusion, a radiologic increase in the traumatic kyphotic deformity in patients with a non-operative treatment protocol has to be expected. Measurable negative physical and social long-term consequences can be anticipated after sustaining a type-A fracture of thoracolumbar vertebral bodies. Any correlation between radiologic and functional results has not been observed.

Adolescent↗
PubMed2002

Complications in surgical treatment of thoracolumbar injuries.

The range of surgical methods for operative treatment of thoracolumbar injuries, with their different ways of approach, grafts and techniques, remains wide. The authors present sources of error and specific complications based on their own experience and on the results of a multicenter study of the Spine Study Group of the German Trauma Association (DGU). A systematic overview of possible mistakes and complications is first presented in anatomical order. A detailed analysis is then presented of the complications reported in a multicenter study, carried out prospectively between 1994 and 1996, on 682 patients operated for acute traumatic injuries of the thoracolumbar spine. In 101 cases (15%) at least one complication occurred intra- or postoperatively. In 41 patients (6%) a revision was performed, and in 60 patients (9%) complications without operative revision were observed. These complications were analysed according to the chosen method of initial treatment.

Humans↗
PubMed2002

Fate of the transpedicular intervertebral bone graft after posterior stabilisation of thoracolumbar fractures.

The authors present a retrospective clinical and radiological study addressing the outcome after posterior stabilisation of thoracolumbar fractures with intervertebral fusion via transpedicular bone grafting. The study included computed tomographic (CT) scan after implant removal for analysis of the intervertebral fusion and incorporation of the intervertebral bone graft and its influence on postoperative re-kyphosing. Twenty-nine patients with acute fractures of the thoracolumbar spine, treated between 1988 and 1995 at the Department of Trauma Surgery, Hannover Medical School, underwent posterior stabilisation and interbody fusion with transpedicular cancellous bone grafting. This study group was followed clinically and radiologically for a mean of 3.5 years. All patients underwent spiral CT scan with sagittal reconstruction after implant removal. Twenty-four type A, four type B, and one type C lesion were posteriorly stabilised and transpedicular intervertebral bone grafting was performed. The operative time averaged 2 h 50 min, the intraoperative fluoroscopy time 4 min 7 s, and the mean intraoperative blood loss was 376 ml. Four patients out of six with an incomplete neurologic lesion (Frankel/ASIA D) improved to Frankel/ASIA grade E. Two complications were observed: one delayed wound healing and one venous thrombosis with secondary pulmonary embolism. Compared to the preoperative status, our follow-up examinations demonstrated permanent social sequelae: the percentage of individuals able to do physical labor was reduced, whereas the proportion of unemployed or retired patients increased. The assessment of complaints and functional outcome with the Hannover Spine Score reflected a significant difference ( P<0.001) between the status before injury (96.6/100 points) and at follow-up (64.4/100 points). The radiographic follow-up revealed a mean loss of correction of 7.8 degrees ( P<0.005). CT scans after implant removal showed an interbody fusion and incorporation of the transpedicular bone graft in ten patients (34%). In another ten patients (34%), the CT scans demonstrated the interbody fusion at the anterior and posterior walls of the vertebral body via direct contact due to collapse of the disc space. In these patients, the bone graft was not incorporated and no central interbody fusion could be found. In nine patients (31%) neither interbody fusion nor incorporation of the transpedicular graft was achieved. A frequent and reliable intervertebral fusion could not be achieved with the described technique of transpedicular bone grafting. The ineffectiveness of the intervertebral graft was found to be a reason for postoperative re-kyphosing.

Adult↗
PubMed2002

[Effect of short-distance spondylodesis of the thoracolumbar transition on neighboring facet joints. A biomechanical study].

This study was performed to investigate the range of motion and the forces on the facet joints that are neighboured to spondylodesis on thoracolumbar spine. We used a special spine testing device for a continuous application of pure moments in each direction. For measuring the ranges of motion we used a magnetic tracking device for measuring forces on facet joints we chose a direct measuring system of quartz crystal and prepared for investigation of the spine. The biomechanical testing was done on 18 human spinal specimen. We investigated the range of motion and the forces on facet joints in T11/12 and L2/3 segment with a maximal loading of 8 Nm in each direction (flexion, extension, lateral bending and rotation). This was done before and after double level dorsal instrumentation T12-L2 with an internal fixateur. Statistical analysis was performed using the paired t-test and the Wilcoxon test (p < 0.05). After double level instrumentation there were significant larger ranges of motion in flexion and extension and significant larger forces on facet joints in left lateral bending in the T11/12 segment. No significant differences were found in the L2/3 segment. Our findings could be an indication for changing in joints loading. This could be an explanation for early degenerative changes in spinal segments adjacent to spondylodesis. The results confirm the demand of short segment instrumentation and early remove of implants to keep influence as low as possible.

Adult↗
PubMed2001

Late results of thoracolumbar fractures after posterior instrumentation and transpedicular bone grafting.

STUDY DESIGN: A retrospective clinical study was performed. OBJECTIVE: To study clinical and radiologic late results after posterior stabilization of thoracolumbar fractures with internal fixator and interbody fusion via transpedicular bone grafting. SUMMARY OF BACKGROUND DATA: The posterior approach, using an internal fixator, is a standard procedure for stabilizing the injured thoracolumbar spine. Transpedicular bone grafting was invented by Daniaux in 1986 for achieving an interbody fusion. Pedicle screw fixation with additional transpedicular fusion has remained controversial because of inconsistent reports and a lack of late results. METHODS: Between January 1989 and July 1992, 76 patients with thoracolumbar fractures were operatively treated, and after a mean of more than 3 years, 56 of 62 patients (90%) still alive who had their implants removed were examined. RESULTS: According to the Magerl classification, 33 patients sustained Type A, 13 Type B, and 10 Type C fractures. Three patients with incomplete paraplegia returned to normal. In one case of complete paraplegia, no change occurred. The mean operative time was 3 hours. In this study, two complications (3.6%) were observed: one iatrogenic vertebral arch fracture without consequences and one deep infection. Compared with the preoperative status, follow-up examinations demonstrated permanent physical and social sequelae: The percentage of individuals able to do physical labor was reduced by half (22 to 11 patients), whereas the share of unemployed or retired patients doubled (4 to 8 patients). At the time of follow-up examination, only 21 of 42 patients continued in sports. The assessment of reported problems and functional outcome with the Hannover spine score reflected a significant difference between the status before injury (96.6/100 points) and at the time of follow-up evaluation (71. 4/100 points) (P < 0.001).The radiographic assessment in the lateral plane (Cobb technique) demonstrated a significant (P < 0.001) mean restoration from an initial angle of -15.6 degrees (kyphosis) to +0. 4 degrees (lordosis). Serial postoperative radiographic follow-up assessment showed progressive loss of correction. At follow-up examination, a mean difference from the postoperative angle of 10.1 degrees was found (P < 0.001). Compared with the preoperative deformity, a mean improvement of 6.1 degrees (average, -9.7 degrees ) at follow-up examination was noted. The addition of transpedicular cancellous bone grafting did not decrease the loss of correction. Computed tomography scans after implant removal were performed in nine cases: Only three of nine patients showed evidence of intervertebral fusion. No correlation could be found between the Magerl classification and radiographic outcome. However, the preoperative wedge angle of the vertebral body correlated significantly with the postoperative loss of reduction. CONCLUSIONS: Because of the disappointing results from this study, the authors cannot recommend the additional transpedicular cancellous bone grafting as an interbody fusion technique after posterior stabilization in cases of complete or incomplete burst injury to the vertebral body.

Accidents, Traffic↗
PubMed2001

[Comparative biomechanical compression trials with a new vertebral prosthetic implant].

UNLABELLED: The authors present a new titanium implant for replacement of the vertebral body (Synex). Possible indications would be fractures or dislocations with destruction of the anterior column, posttraumatic kyphosis as well as tumors in the throracolumbar spine. The construction has to be completed by a stabilizing implant. For best fit and contact to adjacent end-plates Synex is distractable in situ. The possibility of secondary dislocation or loss of correction should thereby be minimised. OBJECTIVES: We performed comparative compression tests with Synex and MOSS ("Harms mesh cage") on human cadaveric specimens of intact vertebrae (L1). The aim of the study was to measure the compressive strength of the vertebral body end-plate in uniaxial loading via both implants to exclude a caving of Synex in vivo. METHODS: 12 human cadaveric specimens of intact vertebrae (L1) were divided in 2 similar groups (matched pairs) according to bone mineral density (BMD), determined using DE-QCT. The specimens were loaded with axial compression force at a constant speed of 5 mm/min to failure and the displacement was recorded with a continuous load-displacement curve. RESULTS: The mean ultimate compression force (Fmax) showed a tendency towards a higher result testing Synex with 3396 N versus 2719 N (non significant). The displacement until Fmax was 2.9 mm in group S (Synex), which was half as long as in group M (5.8 mm). The difference was significant (p < 0.001). The compression force was twice as high and significantly (p < 0.05) higher with Synex at a displacement of 1 mm, 1.5 mm and 2 mm. A significant (p < 0.001) correlation (R = 0.89) between Fmax and BMD was found. CONCLUSIONS: Synex was found to be at least comparable to MOSS for suspensory replacement of the vertebral body at the thoracolumbar spine. A possible consequence of the significantly higher mean compression forces between 1 and 2 mm displacement might be a decreased segmental deformation or loss of correction.

Adult↗