Biomedical subjects

T Pitzen

Publications and source records attributed to T Pitzen.

23 records · Page 2Linked to original sources

PubMed1998

Anterior cervical plate stabilization in one- and two-level degenerative disease: overtreatment or benefit?

This consecutive case retrospective chart review of 356 patients compares the reoperation rate of one- and two-level anterior cervical discectomies for degenerative disease with and without anterior cervical plate stabilization (ACPS). A total of 210 patients underwent surgery without ACPS (bone alone) and 146 patients underwent surgery with the addition of ACPS. Follow-up ranged from 1 to 9 years. A total of 22 patients with one- or two-level cervical arthrodesis required a second surgical intervention (19 bone alone, 3 with ACPS). Reoperations were performed in the bone-alone group for pseudarthrosis in 12 cases and for progression of degenerative disease in 7 cases. The reoperations in the ACPS group were performed for pseudarthrosis in one case and settling of the graft with screw fracture before fusion in two cases. The log-rank test, which uses all patients and their total follow-up periods, was statistically significant in favoring ACPS (p = 0.05). Furthermore, the reoperation rate after 1 year was also significantly lower when ACPS was utilized compared with bone alone (p = 0.0308, Fisher's exact test, two tailed). These data provide evidence that the addition of ACPS in one- and two-level cervical degenerative disease does not constitute overtreatment but rather supplements the internal stabilization initially provided by the bone graft and yields a lower reoperation rate.

Adult↗

PubMed1994

[Dens fracture in elderly patients and surgical management].

The problems of surgical therapy in seven patients aged over 70 years are discussed. Clinical and radiological findings as well as operative treatment (anterior transaxial screw osteosynthesis or posterior atlanto-axial arthrodesis) are analysed in detail. Five out of 7 patients treated in this way could be early mobilised. Two patients died on multiorgan failure after an initial uneventful postoperative course (28.6% mortality rate). A stable osteosynthesis was obtained in all cases; a complete bony fusion as could be radiologically demonstrated, occurred in four out of the five survivors. We feel that despite this relatively high mortality rate surgical treatment provides better recovery chances and a higher quality of life to such patients.

Aged↗

PubMedDate not supplied

[Effect of spongiosa density on load bearing of the lumbar spine.A finite element analysis].

OBJECTIVE: Different parts of the human spine have to accomplish different functions. But little is known about the exact distribution of forces within the spine and whether this is influenced by bone quality. The purpose of this study was to predict fields and extent of greatest load in compression in a human lumbar spine motion segment using a finite element model. METHODS: A three dimensional isotrophic finite element model was generated using the software ANSYS 5.4. Spinal loading was performed in axial compression (600 N). The model was validated by biomechanical analysis using 12 human spinal segments that were loaded with the same forces. Prediction was done with different E-modulus for cancellous bone, representing a wide range of bone quality between osteoporotic and strong bone quality. RESULTS: Load-sharing was influenced by bone quality: the weaker bone quality is, the higher is the extent of load that is passed through the posterior part of the spine. CONCLUSION: This finite element model predicts that load-sharing in a lumbar spine segment with decreased bone mineral density is different from that in healthy segments. A decrease of bone mineral density is resulting in an increase of load that is passed through the posterior part of the lumbar spine. Keeping in mind the simplifications of this model, the results may influence surgical treatment of patients suffering from osteoporosis or osteolytic destructions of the lumbar spine.

Adult↗

PubMedDate not supplied

[A validated finite element model of the human spine--description of the model and initial application].

AIM: To generate a finite-element model of the human cervical spine and evaluate the first application of the model to the analysis of new c-spine implants. METHODS: CT-data were used to generate a three-dimensional, anisotrophic, linear model of the human C4-C7 motion segments using the software ANSYS 5.4. As a next step, anterior cervical fusion and plate fixation using mono- and bicortical screws was simulated in the model. Loading of the finite-element models was simulated using pure moments of +/- 2.5 Nm in flexion/extension, axial left/right rotation, and left/right lateral bending. The range of motion was calculated. The results were compared to the results of an in vitro study using human cadaveric c-spine segments C4-C7, with the same implants and moments on both the intact and surgically treated specimens. RESULTS: The results obtained by the finite-element model were always within one standard deviation of the results of the in vitro study. CONCLUSION: Keeping in mind the simplifications of such a mathematical model, it may be used for a first analysis of the shape of new c-spine implants or to predict the initial stability of a new device.

Adult↗

PubMedDate not supplied

[Primary stability of 2 PLIF (posterior lumbar interbody fusion)--a biomechanical in vitro comparison].

OBJECTIVE: The purpose of this biomechanical in-vitro-study was to compare two different PLIF-techniques with two types of implants on human lumbar spine: PLIF with threaded cages, (Bagby and Kuslich, Spinetech, Minneapolis, USA) and PLIF with the Moss-Miami-implants, (DePuy International Limited, Leeds, Great Britain). METHODS: Six cadaveric human lumbar spine segments L2-5 were explanted, frozen at -20 degrees C and thawed before preparation. They were cut in two parts by discectomie and arthrotomie L3/4, so six specimen L2/3 and six specimen L4/5 were obtained and used in a crossover-trial. Analysis included testing in a tension-torsion-machine under axial compression with 600 N, rotation (left-right) with 25 Nm and shearing forces with 250 N without preload. This was first done in the intact and then in the fused specimen. RESULTS: Stiffness before treatment was comparable in both groups irrespective of location. Posttreatment stiffness was higher with MOSS-MIAMI-implants as compared to PLIF with BAK-cages. Average relative superiority (and 95%-confidence intervall) were 1.98 (1.01-3.69) for compression, 2.30 (0.85-6.24) for rotation and 1.73 (0.78-3.84) for shearing. Statistical comparison of log posttreatment stiffness was significant for compression but not for rotation and shearing (2-sided independent crossover t-test). CONCLUSION: This biomechanical in-vitro-study demonstrates the higher initial stability of PLIF with titanium surgical mesh and posterior instrumentation when compared to PLIF with threaded cages alone.

Biomechanical Phenomena↗