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Biomedical subjects

L Claes

Publications and source records attributed to L Claes.

210 records · Page 12Linked to original sources
PubMed1975

[Torque load and types of fractures of threaded holes in cortical bone by lag screw. Mechanic and histological studies (author's transl)].

For the better understanding of fracture fixation by means of screws the torque load and types of fractures from threaded screw holes in cortical bone were studied. The experiments were performed on sheep tibia and femora in vitro and in vivo. We applied the 4.5 mm cortical bone screw (AISF) as lag screw. The screw was threaded in until total destruction of the thread occurred. The process of torque load was registered as a torque-angle of twist curve with 4 typical parts. Histologically in most cases shear fractures with different geometry occurred. In some cases we found conical geometric, and in others cylindrical geometric fragments in the threaded screw holes. The value of the torque at which destruction of a threaded hole occurs is a linear function of the thickness of the cortical bone. The gradient of this linear function is 6.6 kpcm/mm. In practical case, the insertional torque may be estimated by multiplying the cortical bone thickness in mm (if known) by a factor 4.

Animals↗
PubMedDate not supplied

Glans ischemia after penis revascularization: therapeutic embolization.

A case of hypervascularization of the penis with glans ischemia after venous leakage procedure followed by revascularization of the penis is reported. The venous bypass between the inferior epigastric artery and the dorsal penile artery was misplaced on the deep dorsal vein leading to venous hypertension of the glans. Transcatheter embolization of the venous bypass cured this complication.

Adult↗
PubMedDate not supplied

[The impact of bone morphogenetic protein-2 (BMP-2), vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (b-FGF) on osseointegration, degradation and biomechanical properties of a synthetic bone substitute].

INTRODUCTION: It was the purpose of this investigation to test the osteointegrative capacity and the degradation rate of a neutralized glass ceramic within an animal model after loading with different growth factors. MATERIALS AND METHODS: The glass ceramic GB9N was implanted in the medial tibial head of mature merino sheep (n = 48) after being loaded with either Bone Morphogenetic Protein-2 (BMP-2, 100 micro g/100 micro l), Vascular Endothelial Growth Factor (VEGF, 100 micro g/100 micro l), basic Fibroblast Growth Factor (b-FGF, 60 micro g/100 micro l) or unloaded. At 4 weeks (n = 24) and 9 months (n = 24) after operation histomorphological, histomorphometrical and biomechanical investigations were performed. RESULTS: The amount of newly formed bone was different within the study groups after 4 weeks. BMP-2 induced a significant increase in bone formation and a significant decrease of residual substitute. b-FGF and VEGF induced no such effects in comparison to the controls. Biomechanical investigations could only demonstrate slight increases of the maximal fracture load in the BMP-2 group after 4 weeks in comparison to the others. At 9 months after operation no differences concerning newly formed bone could be found in the study groups comparing to the controls. Only the amount of residual substitute was still significantly lower in the BMP-2 group. Biomechanical data could demonstrate maximal fracture loads of all study samples achieving the level of the controls. CONCLUSION: This investigation has demonstrated that by combining synthetic bone substitutes with growth factors certain parameters of the bone remodelling process can intitially be influenced in a positive way.

Animals↗
PubMedDate not supplied

[The potential for training of proprioceptive and coordinative parameters in patients with chronic ankle instability].

AIM: This study was aimed at assessing the outcome of physical therapy based on both subjective patient's satisfaction and objective measurement of peroneal reaction time in patients with chronic ankle instability. METHOD: 25 patients with chronic ankle instability based on functional deficits were included. Physical therapy consisted in a 6 weeklong program with muscle strengthening and coordination exercises for one hour, three times a week. Before starting physical therapy as well as two weeks after finishing the program, patients underwent both a clinical exam as well as measurement of their peroneal reaction time. RESULTS: Following physical therapy peroneal reaction time of the long (p = 0.0001) and short (p = 0.0003) peroneal muscles significantly decreased. Prior to physical therapy the Kitaoka score was calculated to be 72.2 (+/- 18.7), the post treatment value was 93.3 (+/- 11.7) with a p-value of < 0.001. As for subjective patient's assessment on a scale of 1-10 with 1 being the least and 10 the most satisfied with therapeutical outcome, patients gave an average post treatment score of 8.3 (+/- 1.9). CONCLUSION: Measurement of PRT can be used as a helpful diagnostic parameter, as a parameter for quality control and for verification of therapy results. Specific physiotherapy leads to good clinical results and increased PRT.

Adolescent↗
PubMedDate not supplied

[In vivo measurement of 3-dimensional movement of the iliosacral joint].

The purpose of this study was to quantify in vivo the three-dimensional motion patterns of the sacroiliac joint during passive manipulations as the opinions about the extent of motion of this joint are varied. 12 sacroiliac joints of 6 patients with clinically and radiologically normal joints were investigated. All patients were treated with an external fixator for diagnostic purposes of low back pain unrelated of this study. The motion of the sacroiliac joint was measured continuously with a three-dimensional goniometric system, which was mounted at the end of Schanz screws implanted in S1 and the ilium. All measurements showed relatively small rotation angles around the three main axis to the body between the ilium and the sacrum (< 2 degrees) and very small translations between the screw entry points into the bones (< 1 mm). The maximum rotation angle in the sagittal plane was 1.3 degrees on the right joint and 1.6 degrees on the left joint for flexion plus extension. It is questionable whether this motion can be quantified during manual manipulation. Extension of the hip always produced the largest motion in the sacroiliac joint.

Adult↗
PubMedDate not supplied

[Effect of shock waves on the strength of connection between bone and polymethylmethacrylate. An in vitro study of human femur segments].

The increasing number of revision surgery for failed total arthroplasty including the most difficult aspects of cement removal has lead to various developments of new instruments and techniques to facilitate this procedure. In this in vitro study the effect of extracorporeal shockwaves on the bone-cement interface under this view was investigated. At first the pressure reduction of bounding shockwaves in their progress through compounds consisting of cortical bone-PMMA and cancellous bone-PMMA by means of a needle pressure probe was measured. In the second part of the experiments the mechanical and morphological effects of ESW on the PMMA-Bone-Interface of human femoral segments was tested. Using bone cement cadaveric femoral segments were implanted with stainless steel rods within the medullary canal and the PMMA-Bone-interface was treated with ESW. After treatment the segments were examined mechanically, radiologically and by microscopy. Between the treated and the control group no difference was found which could give any a reference to the disruption of the Cement-Bone-Interface caused by ESW. However, there were observations which indicated that ESW induces a increasing risk of intravasation of bone marrow. Considering these facts ESW seems not to be a good clinical adjunct in revision surgery.

Biomechanical Phenomena↗
PubMedDate not supplied

The influence of muscle forces and external loads on cruciate ligament strain.

We know it is important to avoid excessive strain on reconstructed ligaments, but we do not know how individual muscles affect cruciate ligament strain. To answer this, we studied the effect of muscle forces and external loads on cruciate ligament strain. Nine cadaveric knee joints were tested in an apparatus that allowed unconstrained knee joint motion. Quadriceps, hamstring, and gastrocnemius muscle forces were simulated. Additionally, external loads were applied such as varus-internal or valgus-external rotation forces. Cruciate ligament strain was recorded at different knee flexion angles. Activation of the gastrocnemius muscle significantly (P < 0.05) strained the posterior cruciate ligament at flexion angles larger than 40 degrees. Quadriceps muscle activation significantly strained the anterior cruciate ligament when the knee was flexed 20 degrees to 60 degrees (P < 0.01) and reduced the strain on the posterior cruciate ligament in the same flexion range (P < 0.05). Activation of the hamstring muscles strained the posterior cruciate ligament when the knee was flexed 70 degrees to 110 degrees (P < 0.05). Combined varus and internal rotation forces significantly increased anterior cruciate ligament strain throughout the flexion range (P < 0.05). The results suggest that to minimize strain on the ligament after posterior cruciate ligament surgery, strong gastrocnemius muscle contractions should be avoided beyond 30 degrees of knee flexion. The study also calls into question the use of vigorous quadriceps exercises in the range of 20 degrees to 60 degrees of knee flexion after anterior cruciate ligament reconstruction.

Adult↗
PubMedDate not supplied

Suitability of external fixators for use in the tropics.

External fixation systems proved to decrease the osteomyelitis rate in patients in the tropics compared with internal stabilization. This study was designed to show how external fixators being used for treatment of patients in industrial countries compare with cheap alternatives regarding their suitability for the application in tropical countries. Eleven external fixation systems were compared for stability, cost, weight, variability, handling, and capability of being produced locally. Stiffness, slipping moment, and irreversible deformation were determined in material testing machines. The technically best fixators are expensive and cannot be manufactured locally. The inexpensive constructs lack variability and stability. When cost is not a problem, the Synthes model is recommended. With some restrictions in mechanical stability and variability, the Pfeifer Fixator II and a wooden model offer inexpensive and locally producible alternatives. These results may help to select an external fixation device to meet local needs and possibilities in tropical countries.

Biomechanical Phenomena↗
PubMedDate not supplied

[Biomechanical studies on the pathogenesis of ochronotic arthropathy].

The enzymatic defect leading to alcaptonuria is well known. However, the pathogenesis of the associated arthropathy is poorly understood. From clinical and morphological observations it is assumed that the breakdown of ochronotic cartilage is due to an increased fragility. To test the hypothesis that polymerisation products of homogentisic acid change the biomechanical behaviour of hyalin cartilage, investigations on natural ochronotic cartilage and tissues following in vitro incubation with homogentisic acid were performed. It could be demonstrated that the "ochronotic situation" is associated with an increased hardness and a decreased elasticity of the hyalin cartilage. For the pathogenesis of ochronotic arthropathy it is assumed that these alterations, in association with mechanical stress to the joints, lead to cartilage destruction.

Adolescent↗
PubMedDate not supplied

Surgical treatment of benign tumours of the salivary glands.

In this multicentre retrospective study 30 patients with benign salivary gland tumours are reviewed. Initial operation consisted of total parotidectomy in 6 patients, superficial lobectomy in 13 and tumour enucleation in 11. There were 5 recurrences, treated by enucleation in 1, superficial lobectomy in 2 and extensive total resection in 2 patients. In 18 cases a typical facial nerve dissection was performed. The resected specimens showed a pleiomorph adenoma in 24 cases and monomorph adenoma's in 6 cases. Complications were haematoma formation, Frey syndrome and facial nerve paresis. Recurrences were related to incomplete resection or fragmentation during operation. In this study benign tumours of the salivary glands proved to have a good prognosis, provided a total tumour excision with nerve dissection is performed; the excision should consist of a superficial lobectomy or total parotidectomy depending on the location of the tumour in the lateral or medial part of the gland.

Adenoma↗