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T Pitzen

Publications and source records attributed to T Pitzen.

At least 19 recordsLinked to original sources
PubMed2006

Disc replacement using Pro-Disc C versus fusion: a prospective randomised and controlled radiographic and clinical study.

Anterior cervical discectomy and fusion (ACDF) may be considered to be the gold standard for treatment of symptomatic degenerative disc disease within the cervical spine. However, fusion of the segment may result in progressive degeneration of the adjacent segments. Therefore, dynamic stabilization procedures have been introduced. Among these, artificial disc replacement by disc prosthesis seems to be promising. However, to be so, segmental motion must be preserved. This, again, is very difficult to judge and has not yet been proven. The aim of the current study was to first analyse the segmental motion following artificial disc replacement using a disc prosthesis. A second aim was to compare both segmental motion as well as clinical result to the current gold standard (ACDF). This is a prospective controlled study. Twenty-five patients with cervical disc herniation were enrolled and assigned to either study group (receiving a disc prosthesis) or control group (receiving ACDF, using a cage with bone graft and an anterior plate.) Radiostereometric analysis was used to quantify intervertebral motion immediately as well as 3, 6, 12 and 24 weeks postoperatively. Further, clinical results were judged using visual analogue scale and neuro-examination. Cervical spine segmental motion decreased over time in the presence of disc prosthesis or ACDF. However, the loss of segmental motion is significantly higher in the ACDF group, when looked at 3, 6, 12 and 24 weeks after surgery. We observed significant pain reduction in neck and arm postoperatively, without significant difference between both groups (P > 0.05). Cervical spine disc prosthesis preserves cervical spine segmental motion within the first 6 months after surgery. The clinical results are the same when compared to the early results following ACDF.

Adult↗
PubMed2006

[Cervical disc prostheses].

Endoprosthetic replacement for spinal cord disorders represents an attractive alternative to fusion in those cases where surgery appears necessary for degenerative disc disease. At least in theory it has been proven that placement of an endoprosthesis minimizes undue stress on the adjoining segments and its possible negative consequences. Furthermore, cervical endoprostheses facilitate speedier rehabilitation and the problems involved in removal of the bone chip become irrelevant. Clinical results reported to date for the cervical spine are very encouraging and indicate that endoprosthetic replacement has been quite successful particularly for difficulties in multilevel approaches. However, long-term results for cervical endoprostheses have not yet been published and therefore at present there are no reference values for the viability of the prosthesis with regard to the aseptic loosening rate. There are also no findings available on how the implanted cervical prosthesis will behave when bone quality diminishes at an advanced age.

Biomechanical Phenomena↗
PubMed2006

Filling a cervical spine cage with local autograft: change of bone density and assessment of bony fusion.

To date, it remains debatable whether cervical spine fusion cages should be filled with any kind of bone or bone substitute. Using a bone substitute would produce additional costs, using an autologous bone graft from the iliac crest would make the use of the cage at least questionable. As an alternative, cortical and subcortical bone from the anterior osteophytes of the segment in which the disc has been removed could be used to fill the cage: higher costs and complications at the iliac crest could both be avoided and the cage could be filled. However, the fate of these bone chips made from the anterior osteophytes is unclear as well as whether fusion will occur using this technique. The objective of the current study was to investigate possible changes in the bone density of this local autograft in the cage within the first 12 months after surgery by means of computed tomography. A second objective was to assess segmental bony fusion using this technique. 21 patients, suffering from degenerative disc disease of the cervical spine, were included into this prospective study. They all underwent anterior decompression, cage insertion and plate stabilisation. The cage (Rabea, Signus Medizintechnik, Alzenau, Germany), was filled with bone chips made from the anterior osteophytes of the segment that underwent discectomy. On the third day after surgery as well as three, six and 12 months after surgery, an axial computed tomography scan through the cage was taken and density within the apertures of the cage was measured in a standardised manner. Flexion-extension lateral radiographs were taken to investigate segmental fusion. Statistical significance was assumed to be at a 95 % level of significance. 23 cages were implanted. The mean value of the bone density obtained by computed tomography was 505 (+/- 119) HU on day three, 635 (+/- 156) HU after three months, 769 (+/- 162) HU after six months, and 814 (+/- 198) after 12 months. There was a significant difference when the values after 12 months were compared to those obtained after three days (p < 0.001) and after three months (p = 0.004). Bony fusion was seen in 21 out of 23 segments (91.3 %) after 12 months. It may be concluded that this technique could be an alternative to the current treatment options.

Bone Density↗
PubMed2004

Variation of endplate thickness in the cervical spine.

The purpose of the study was to investigate possible variation of thickness of the cervical spine endplate with respect to endplate orientation (superior or inferior endplate) and level distribution (C4-C7). Six human cervical spine segments C4-C7 were used to create six specimen of C4, C5, C6, and C7, respectively. The bony endplates of each vertebra were cleaned carefully from disc tissue without damaging the endplates. Six endplates with severe degenerative changes were excluded from the study. The posterior elements were removed, and a midaxial cut using a bone saw was performed through each vertebral body, thus producing a superior and inferior half. Each half-vertebra was then glued onto a piece of wood with the endplate oriented upwards and horizontally. For each specimen, four computed tomography scans were taken and thickness of the endplate was measured at five points on each scan perpendicular to the midaxial cut. Factorial analysis of variance (ANOVA) and Scheffe-test were used to detect significant differences. All peripheral regions were significantly thicker than the central point of the endplate if all measuring points were considered for statistical analysis, regardless of scan, endplate orientation or level (Scheffe-test, P<0.001). In both superior and inferior endplates, peripheral areas were thicker than the central region (Scheffe-test, P<0.001). For all levels, the endplate within the peripheral regions was thicker than within the central region and the difference reached significance for the superior and inferior endplate of C4, C5, and C6 and the inferior endplate of C7 (Scheffe-test, P<0.05). The peripheral regions of the cervical spine endplate are usually thicker than its central region, regardless of endplate orientation and level (C4, C5, C6, C7) distribution.

Aged↗
PubMed2004

[Complaints and findings at the iliac crest donor site following anterior cervical fusion].

A high rate of donor site complications has been described following bone graft harvesting at the anterior iliac crest for anterior cervical fusion. However, no prospective study exists dealing with this topic. The objectives of the study presented were to evaluate minor and major donor site complications following graft harvesting at the anterior iliac crest, to investigate postoperative changes at the donor site using computed tomography and ultrasound imaging and to judge the patients satisfaction. 67 patients were included in a clinical prospective study. All patients underwent anterior cervical discectomy and fusion using an autologous iliac crest graft. Clinical examination was performed three and ten days and two and three months after the operation. Computed tomography and ultrasound imaging of the donor site were performed 10 days after surgery. Complications were classified as "minor" and "major" complications. Minor complications were found in 62.7%. A significant decrease of minor complication rate was seen between the first and second examination after surgery. At the last follow-up, 80.5% of all patients were free from pain concerning the donor site. Haematomas and seromas were detected by ultrasound in 67.2% and donor site fractures in 6% using computed tomography. Major complications were seen in 11.9% of all patients. The current study revealed a high rate of minor complications and haematomas at the graft donor site. However, the majority of all patients is free of pain at the donor site three months after surgery and satisfied with the surgical result. Techniques without the need of bone grafting may help to avoid these complications and to ameliorate the initial postoperative status.

Adult↗
PubMed2004

Regional variations in the thickness of cervical spine endplates as measured by computed tomography.

PURPOSE: To determine regional variations in the thickness of human cervical spine endplates with high spatial resolution. MATERIAL AND METHODS: Six explanted human cadaveric spine specimens underwent computed tomography (CT) scanning. Measurement of endplate thickness was done fully automatically at every point of the endplate using a computer program written specifically for this purpose. Variations in thickness along sagittal and coronal lines were determined and statistical parametric mapping was used to test for significant regional variations at every point. RESULTS: Anterior and medial aspects of superior endplates were shown to be significantly thinner than lateral and dorsal parts. Superior endplates were found to be thicker than inferior endplates. CONCLUSION: Fully automatic assessment of endplate thickness from CT data is feasible. Central regions of the cervical spine endplates are thinner than peripheral parts of the endplates. This distribution is more pronounced in superior than in inferior endplates.

Algorithms↗
PubMed2002

Screw fixation to the posterior cortical shell does not influence peak torque and pullout in anterior cervical plating.

There is no consensus over whether screw fixation for anterior cervical plating should include the posterior cortical shell of the vertebral bodies or not. Thus, the purpose of this study was to investigate the function of the posterior cortical shell with respect to maximal screw torque and pullout force. Twenty-four fresh frozen human cervical vertebrae coming from six spinal segments C4-C7 were used. They were scanned for bone mineral density (BMD) and then assigned to two groups with comparable bone density and segmental distribution. The posterior longitudinal ligament was resected carefully and two parallel burr holes were drilled into each vertebral body. The posterior cortical shell was removed in one burr hole, using a 6-mm steel burr, producing a shallow excavation with a depth of approximately 2 mm. An ABC screw was inserted into each burr hole. The screw to be inserted into the hole with the posterior excavation was called "monocortical". In contrast, the contralateral screw was called "bicortical". Peak torque was measured in one group, while pullout force was analyzed using the specimens of the second group. Mean value and standard deviation were calculated for peak torque and pullout force with respect to the type of fixation. A paired t-test was used to determine the effect of fixation type on peak torque and pullout force. Pearson moment correlation coefficients were calculated to determine the effect of BMD on peak torque and pullout force with respect to whether the screw was "mono- or bicortical". A 95% level of significance was used for all tests. No significant differences for peak torque and pullout force could be found comparing monocortical and bicortical screw fixation. However, for both monocortical and bicortical screw fixation, a positive correlation was seen for peak torque versus BMD and for pullout force versus bone mineral density, respectively. The importance of the posterior cortical shell for screw pullout force and screw peak torque seems to be negligible. In constrast, BMD greatly influences both peak torque and pullout force for both types of fixation.

Bone Density↗
PubMed2002

The effect of posterior instrumentation following PLIF with BAK cages is most pronounced in weak bone.

BACKGROUND: The use of BAK-cages for lumbar fusion has become very popular but complications such as cage subsidence and settling occurred. To treat these complications posterior instrumentation was used to improve segmental stability. It is, however, poorly understood, why some patients require additional posterior instrumentation, whereas the majority do not. The objectives of the study presented were first to determine the influence of bone mineral density (BMD) to the initial compressive stiffness of a segment that underwent posterior lumbar interbody fusion (PLIF) with two BAK-cages. Second, to estimate the importance of additional posterior instrumentation for compressive stiffness with respect to bone mineral density. METHODS: A validated finite element model (FEM) including posterior decompression and stabilisation by two BAK-cages (BAK_FEM) was used to predict the initial compression stiffness in axial loading of 600 N. This model was used to predict the influence of various grades of BMD on compression stiffness. A second FEM was generated in which additional posterior screw-rod instrumentation was simulated (BAK+PI_FEM) and this model used to predict the influence of BMD in axial loading. FINDINGS: The responses of all FEM suggested that initial compressive stiffness will increase if there is an increase of BMD. The stiffness as predicted by BAK+PI_FEM was always superior to FEM_BAK. This difference was most pronounced for weak bone quality. INTERPRETATION: Compression stiffness following PLIF with BAK-cages depends on BMD. Additional posterior instrumentation results in an additional increase of compression stiffness. This effect is most pronounced in simulated soft bone quality. These results may help to select patients for combined stabilisation.

Adult↗
PubMed2001

The influence of cancellous bone density on load sharing in human lumbar spine: a comparison between an intact and a surgically altered motion segment.

The aim of the current study is twofold: first, to compare load sharing in compression between an intact and a surgically repaired lumbar spine motion segment L3/4 using a biomechanically validated finite element approach; second, to analyse the influence of bone mineral density on load sharing. Six cadaveric human lumbar spine segments (three segments L2/3 and three segments L4/5) were taken from fresh human cadavers. The intact segments were tested under axial compression of 600 N, first without preload and then following instrumented stabilisation. These results were compared to a finite element model simulating the effect of identical force on the intact segments and the segments with constructs. The predictions of both the intact and the surgically altered finite element model were always within one standard deviation of the mean stiffness as analysed by the biomechanical study. Thus, the finite element model was used to analyse load sharing under compression in an intact and a surgically repaired human lumbar spine segment model, using a variety of E moduli for cancellous bone of the vertebral bodies. In both the intact and the surgically altered model, 89% of the applied load passed through the vertebral bodies and the disc if an E modulus of 25 MPa was used for cancellous bone density. Using 10 MPa--representing soft, osteoporotic bone--this percentage decreased, but it increased using 100 MPa in both the intact and the altered segment. Thus, it is concluded that reconstruction of both the disc and the posterior elements with the implants used in the study recreates the ability of the spine to act as a load-sharing construction in compression. The similarity in load sharing between normal and instrumented spines appears to depend on assumed bone density, and it may also depend on applied load and loading history.

Biomechanical Phenomena↗
PubMed2000

[Initial stability of two PLIF-techniques. A biomechanical comparison using a finite element model].

The purpose of this study was to compare the initial stiffness of two techniques for posterior interbody lumbar fusion (PLIF) by a finite element approach. Thus a finite element model of a human L3/4 spinal segment was generated. Stiffness of the intact model was tested under compression (600 N), torsion (25 Nm) and shearing forces (250 N) without preload. The results were compared to the stiffness following simulation of PLIF with two BAK-Cages and PLIF with two Harms-Cages and additional posterior screw-rod-osteosynthesis. PLIF with two BAK-Cages resulted in a loss of stiffness in compression, torsion and shearing. PLIF with two Harms-Cages and posterior osteosynthesis resulted in an increase of stiffness in compression, torsion and shearing.

Biomechanical Phenomena↗
PubMed2000

Motion of threaded cages in posterior lumbar interbody fusion.

A high rate of pseudarthrosis and a high overall rate of implant migration requiring surgical revision has been reported following posterior lumbar interbody fusion using BAK threaded cages. The high rate of both pseudarthrosis and implant migration may be due to poor fixation of the implant. The purpose of this study was to analyse the motion of threaded cages in posterior lumbar interbody fusion. Six cadaveric human lumbar spine segments (three L2/3 and three L4/5 segments) were prepared for biomechanical testing. The segments were tested, without preload, under forces of axial compression (600 N), torsion (25 Nm) and shearing force (250 N). The tests were performed first with the segments in an intact state, and subsequently following instrumented stabilisation with two BAK cages via a posterior approach. These results were compared with those of a finite element model simulating the effects of identical forces on the segments with constructs. As the results were comparable, the finite element model was used for analysing the motion of BAK cages within the disc space. Motion of the implants was not seen in compression. In torsion, a rolling motion was noted, with a range of motion of 10.6 degrees around the central axis of the implant when left/right torsion (25 Nm) was applied. The way the implants move within the segment may be due to their special shape: the thread of the implants can not prevent the BAK cages rolling within the disc space.

Adult↗
PubMed2000

[Is the prediction of initial stability of cervical spinal osteo-synthesis possible using a finite element model?].

The study is dealing with a three segmental (C4-C7) finite element model of the intact human cervical spine. Additionally, anterior cervical fusion and plating (ACFP) with Caspar-plate and bicortical screws in C5/6 was simulated. The models were loaded using pure moments of 2.5 Nm in flexion-extension, axial rotation and lateral bending. The range of motion in C5/6 was calculated and compared to the results of a biomechanical in vitro study, that used six cadaveric human spinal segments C4-C7 for analysing range of motion C5/6 in the intact state and following ACFP. The predictions of the finite element models were always within one standard deviation of the results of the in vitro study. Thus, the current model could be used for first analysis on new C-spine implants. However, the results should be interpreted as a trend and the limitations of these models should be kept in mind.

Biomechanical Phenomena↗
PubMed1999

Evaluation of a new monocortical screw for anterior cervical fusion and plating by a combined biomechanical and clinical study.

The purpose of this combined study was to evaluate the stability and safety of a new monocortical screw-plate system for anterior cervical fusion and plating (ACFP) according to Caspar in comparison with classical bicortical fixation. In the biomechanical part of the study two groups, each comprising six fresh human cadaveric spines (C4-C7), matched for bone mineral density, additionally resulting in almost the same mean age, were used. Range of motion and neutral zone were analyzed in flexion-extension, rotation (left, right) and lateral bending (left, right) using pure moments of +/- 2.5 Nm for each specimen in the intact state, after discectomy at C5/6 and after discectomy at C 5/6 followed by bone grafting plus plating (Caspar plates), with either monocortical or bicortical screws. For all three motion planes, no significant difference could be found between the new monocortical and the bicortical fixation techniques. The clinical part of the study was performed as a prospective study on 30 patients suffering from symptomatic degenerative cervical disc disease in one segment. At the latest follow-up, no hardware- or graft-related complications were seen in any of the patients. Following these findings monocortical screw fixation can be recommended for the majority of anterior cervical fusion and plating procedures in degenerative disease, making the procedure quicker, easier, and safer. Bicortical screw fixation still has specific indications for multilevel stabilization, poor bone quality (osteoporosis, rheumatoid disease - as bicortical oversized rescue screw), unstable spines (trauma, tumour) and in particular for the realignment of kyphotic deformities (restoration of the normal lordotic curve). Due to the design of the study the results apply only to surgical treatment of monosegmental degenerative disc disease at the time.

Adult↗
PubMed1999

Anterior cervical fusion and trapezoidal plate stabilization for re-do surgery.

BACKGROUND: Pseudarthrosis, graft fracture or dislocation, and kyphotic angulations are highly undesired complications after surgery of the cervical spine. The purpose of this retrospective study was to evaluate the effect of anterior cervical fusion and plating in cases of failed cervical spine surgery. METHODS: From January 1980 to December 1993 41 patients (25 male, 16 female, mean age 46.8 years, range 30-66 years) underwent corrective surgery of the cervical spine in our department. A total of 33 patients had one, 7 patients had two, and one patient had three previous cervical operations. Re-do surgery was most frequently indicated because of intractable head-neck-shoulder-arm-pain corresponding with radiological findings. Corrective surgery consisted of anterior cervical decompression, realignment, autologous iliac crest bone graft fusion, and trapezoidal plate stabilization. Clinical and radiological follow-up examinations were performed, ranging from 20 to 112 months with a mean of 24.7 months, in 37 patients. Epidemiological, clinical, and radiological data were collected and used for this retrospective study. RESULTS: Of 37 patients 21 showed complete alleviation of head-neck-shoulder pain, 10 improved, and six remained unchanged. Of 15 myelopathy patients, one showed further progress, two were unchanged, four were normal, and eight showed only mild signs of medullary irritation, e.g., hyperreflexia or minimal spasticity. Radiological examinations showed a stable bony fusion in optimal alignment in all 37 patients. CONCLUSION: Based on these findings, anterior cervical decompression, fusion, and plating is a rational treatment in cases of failed cervical fusion.

Adult↗
PubMed1999

Anterior cervical plating for the treatment of neoplasms in the cervical vertebrae.

OBJECT: To assess clinical outcome and survival in patients with cervical vertebral spinal neoplasms after they have undergone anterior decompression and cervical plate stabilization (ACPS) by using either autologous bone graft or polymethylmethacrylate (PMMA) as the anterior load-bearing support structure. METHODS: This was a retrospective case study composed of 30 patients harboring cervical spinal vertebral neoplasms who underwent anterior cervical decompression and (ACPS) within a 7-year period. Postoperative immobilization included treatment in a halo brace in two cases and in a hard cervical collar for the remaining patients. Postoperatively most patients underwent radio- and/or chemotherapy. All patients except one benefited from a significantly improved quality of life with decreased pain and/or improved neurological status. The mean Kaplan-Meier survivoral estimate was 35.8 months (range 8 days-11.3 years, with 10 patients alive at most recent follow-up contact). Patients achieved long-term or lifelong mechanical stability in the cervical spine, and only one patient required a repeated posterior stabilization procedure. No hardware-related complications occurred. One patient died 8 days postoperatively of pneumonia. A nonsignificant difference in survival (p = 0.2164) was observed between patients harboring metastatic neoplasms (26.8 months) and those harboring lymphomatous and multiple myeloma neoplasms (54 months). CONCLUSIONS: Favorable clinical outcome of both neurological symptoms and pain can be achieved using ACPS after surgery for neoplasms in the cervical vertebrae. Furthermore, long-term or lifelong cervical spine mechanical stability with bone fusion is achieved using this technique even when radiation therapy is delivered to the site of the bone graft.

Adult↗
PubMed1999

[Primary stability of 2 PLIF (posterior lumbar interbody fusion) techniques--a biomechanical and finite element analysis].

The purpose of this study was to compare the initial stiffness of two techniques for posterior interbody lumbar fusion by biomechanical and finite element analysis. Initial stiffness was tested under compression, torsion and shearing forces. The effect of an increasing initial stability by additional posterior instrumentation is proven by the biomechanical analysis and the finite element method.

Biomechanical Phenomena↗
PubMed1998

Reoperation in patients after anterior cervical plate stabilization in degenerative disease.

STUDY DESIGN: Consecutive case retrospective chart review. OBJECTIVES: First, to assess whether the number of' patients requiring a second cervical surgical intervention was changed as a result of using anterior cervical plate stabilization, and second, to determine the additional risks and/or benefits associated with the hardware implantation. SUMMARY OF BACKGROUND DATA: The optimal technique of performing stabilization, arthrodesis, and alignment of a cervical segment after discectomy with neural decompression in degenerative disease has yet to be determined. METHODS: The charts of 402 patients who had undergone an anterior cervical discectomy and arthrodesis for degenerative disease performed both with and without anterior cervical plate stabilization were reviewed, and reoperation data were compiled. The average follow-up time was 3.8 years (range, 1.5-9.4 years). RESULTS: Of 365 patients with 1- or 2-level cervical arthrodesis, 22 required a second surgical intervention (20 bone alone, 2 with anterior cervical plate stabilization). The Log-Rank test, which uses all patients and their total follow-up periods, was statistically significant favoring anterior cervical plate stabilization at one and two levels (P = 0.015). CONCLUSIONS: The addition of anterior cervical plate stabilization in one- and two-level cervical degenerative disease supplements the internal stabilization initially provided by the bone graft, and yields a lower reoperation rate.

Adult↗