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Biomedical subjects

H J Oestern

Publications and source records attributed to H J Oestern.

At least 19 recordsLinked to original sources
PubMed1992

The relationship of mechanical properties to morphology in patellar tendon autografts after posterior cruciate ligament replacement in sheep.

In a sheep model the posterior cruciate ligament (PCL) was replaced by a patellar tendon autograft (PTAG) using the central one-third of the ipsilateral patellar tendon (PT). The sheep were sacrificed at 16, 26, 52 and 104 weeks postoperation. The PTAG, and, as controls, the contralateral PCL and PT were harvested. These were examined using biomechanical testing as well as light and transmission electron microscopy, including immunohistological techniques. The material properties (maximum stress, elastic modulus) were compared to the morphological features. The cellular distribution, the distribution of glycosaminoglycans (GAGs), the collagen fibril diameter and the occurrence of Type III collagen were studied. Prior to transplantation, the PTAG was shown to be superior in maximum stress (57.2 +/- 5.5 MPa vs 41.3 +/- 1.9 MPa) and elastic modulus (368.8 +/- 49.3 MPa vs 172.3 +/- 14.6 MPa) to the PCL. The early decline in material properties of the PTAG (maximum stress 22% and elastic modulus 42% of the control) after free grafting paralleled a cell- and capillary-rich PTAG tissue with remnants of necrosis and a poorly organized extracellular matrix. Two years after implantation, with progressive alignment of the tissue matrix, maximum stress and elastic modulus acquired approximately 60 and 70% of the control, respectively. However, there was also an evidence of degenerative changes characterized by acellular areas, loss of the normal bundling pattern of collagen fibers and abnormal accumulation of GAGs. Ultrastructurally, there was a predominant shift to thin collagen fibrils in the PTAG compared to PCL and PT, both consisting of thick and thin collagen fibrils. Thin fibrils were demonstrated to be, in part, split thick fibrils as well as newly formed fibrils. Most of these thin fibrils revealed a positive reaction with antibodies to Type III collagen.

Animals↗
PubMed1991

Influence of immobilization on autograft healing in the knee joint. A preliminary study in a sheep knee PCL model.

The influence of immobilization on patellar tendon autograft healing was investigated in 12 sheep with replaced posterior cruciate ligaments of the knee (PCLs). In one group achillotomy immobilized the operated knee joint. In another group initial reduced weight-bearing was obtained by hanging the sheep in a special trapeze. In the third group no protection at all was given to the operated knee. The sheep in this group went within 8 weeks from partial use of the operated leg to unrestricted weightbearing and mobility. Biomechanical testing 16 weeks after the operation demonstrated a considerable decrease in the maximum force, ligament stiffness, and strain values in the achillotomy group, as well as an increase in posterior laxity. The best data were observed in the no-protection group. This study demonstrates the negative effect of immobilization on autograft healing in a sheep PCL model. Even early in the healing process tissue may be extremely sensitive to stress and strain.

Animals↗
PubMed1991

[Compartment syndrome. Definition, etiology, pathophysiology].

A compartment syndrome is a condition in which increased pressure a confined fascial space causes decreased capillary blood flow and tissue function below a level necessary for viability. There are a variety of possible etiologies, such as increased compartment content (hematoma, edema, exertion, intoxication) and decreased compartment size (constrictive dressings and casts, closure of fascial defects). The pathophysiology of compartment syndrome is based on the arteriovenous gradient theory. The high pressure within the compartment leads to a decrease in the arteriovenous gradient, to a lowering of tissue PO2 and finally to a metabolic deficit. The tolerance of increased pressure by nerve and muscle is defined by the relationship of mean arterial pressure to tissue pressure and not by absolute tissue pressure.

Compartment Syndromes↗
PubMed1991

[Age, activity and strength of knee ligaments].

The cruciate ligaments of older persons are thought to have diminished biomechanical properties. On the other hand, joint immobilization also leads to similar functional losses in ligaments. It can be difficult to differentiate between these factors in older and immobile persons. The anterior and posterior cruciate ligaments of six younger (average age 30 years) and six older (average age 64.7 years) donors with similar levels of activity were subjected to biomechanical testing. Each sample had to meet the following conditions: appropriate age, no chronic vascular and cardiopulmonary disease found on autopsy, no signs of osteoarthrosis and no knee injuries. The material properties of maximum stress (e.g. ACL: young/old 24/21N/mm2), elastic modulus (e.g. ACL: young/old 144/129 MPa), and strain (e.g. ACL: young/old 25/28%), did not differ significantly (p less than 0.05). This indicates that older persons who are active do not necessarily show functional losses in the cruciate ligaments. Other data found in the literature can be ascribed to immobilization influences. In this data many of the older test persons had chronic vascular insufficiency, cardiopulmonary disease or malignancies.

Aged↗
PubMed1991

Ultrastructural changes of the patellar tendon as a cruciate ligament substitute (one year and two year results).

In four black-faced sheep, the posterior cruciate ligament was replaced with a free autogenous patellar tendon transplant. Tissue samples from the transplants were investigated by light and electron microscopy 1 year and 2 years after surgery. The normal contralateral posterior cruciate ligament and the normal contralateral patellar tendon were used as controls. The structural differences concerned cells, collagen fibrils, elastic tissue and proteoglycans. Most of the cells of the contralateral patellar tendon were spindle-shaped, whereas those of the transplant were frequently chondroid. In the central region of the transplant as well as in the area far from the bone, cell degenerations, and occasionally hypo- or even acellular zones were found. Measurements of the diameter of collagen fibrils in both contralateral patellar tendon and posterior cruciate ligament showed a more or less pronounced bimodal distribution. A unimodal distribution with mainly thin fibrils (20-60 nm) was demonstrated in the transplant tissue which also revealed some morphological alterations of the collagen fibrils. Thin elastic fibers (microfibrils and amorphous material) were randomly scattered among the collagen fibrils of the control samples, bundles of microfibrils (without amorphous material) characterized the transplant. Staining with Alcian blue in the presence of 0.3 M MgCl2 demonstrated a close relationship between proteoglycans and collagen fibrils as well as elastic components in patellar tendon. This arrangement was lost in the transplant where abundant proteoglycans were revealed which, however, composed a tight irregular network between the collagen fibrils. The results serve as a baseline for understanding the impaired biochemical properties of a free autogenous patellar tendon transplant.

Animals↗
PubMed1990

[Corrective osteotomy of malunited distal radius fractures].

The malunion of the distal radius may result in shortening, radial impaction, volar angulation, dorsal displacement or rotatory deformity. For restoration, the anatomy and kinematics of the distal radioulnar joint and the triangular fibrocartilaginous complex (TFCC) are of importance. This nonunion consists of the articular disk, a meniscus homologue, the ulnar collateral ligament, and the dorsal and palmar radioulnar ligaments. Malunion of the distal radioulnar joint leads to an increase in loading on the individual parts, as well as pain and a decrease in supination and pronation. Osteotomy is indicated if the angulation of the malunion is more than 20 degrees in the frontal or sagittal plane. Corrective osteotomy requires detailed preoperative planning with calculation of the correct position in all planes. The most common operation that has proved to be effective is osteotomy of the radius, insertion of a trapezoidal bone graft in place, and internal fixation with a dorsal or volar plate.

Elbow Joint↗
PubMed1990

[Healing phases in autogenous posterior cruciate ligament replacement. A decision aid for after-care. A biomechanical and histologic study].

In a sheep model for reconstruction of the posterior cruciate ligament using the central one-third of the autogenous patellar tendon and immediate mobilization, the incorporation course was studied biomechanically, histomorphometrically and radiographically at eight different points in time up to 1 year after surgery. Four different phases of autograft healing were demonstrated on the basis of the histological events. The biomechanical data were correlated with the morphological findings. Phase 1--necrosis--was characterized by a maximum of necrotic autograft tissue 2 weeks postoperatively. Initially, graft strength was determined by the surgical fixation strength. During phase 2--revitalization--the autograft showed cellular proliferation and revascularization, starting from the periphery. The autograft was determined to be weakest during this phase. Phase 3--collagen formation--revealed a marked increase in newly formed collagen tissue between weeks 12 and 16. A significant increase in maximum load and stress was measured. In phase 4--remodeling--the longest phase, the collagen tissue appeared more compact and less cellular. The fiber bundles were arranged more longitudinally. However, the biomechanical properties remained clearly below that of a normal posterior cruciate ligament.

Animals↗
PubMed1989

Biological aspects of long-term failure of autografts after cruciate ligament replacement.

The alterations of the ultrastructure of the posterior cruciate ligament autograft of patellar tendon origin were examined in a sheep model 1 year after surgery. The ultrastructure was also compared with that of the normal contralateral posterior cruciate ligament and patellar tendon. The most striking finding was the unimodal distribution of the collagen fibrils, with a predominance of loosely packed thin fibrils in the central portion of the autograft. The results suggested that the remodeled autograft tissue became highly organized but never exhibited the ultrastructural features of a ligament. This could be responsible for the decreased biomechanical properties and the long-term failure of a patellar tendon autograft.

Animals↗
PubMed1989

Healing at graft fixation site under functional conditions in posterior cruciate ligament reconstruction. A morphological study in sheep.

The incorporation course at the fixation sites of a free patellar tendon graft used in posterior cruciate ligament reconstruction was examined in eight adult sheep. After surgery the sheep were functionally treated without any protection of the operated legs. Two, 6, 12, 16, and 26 weeks after surgery the sheep were killed and the character of biological attachment to bone at fixation sites was evaluated using macroradiography, high-resolution radiography, and routine histology. After 6 weeks good osseous incorporation of the bone pegs of free patellar tendon grafts could be demonstrated at the desired position.

Animals↗
PubMed1988

[Distal radius fracture].

The treatment of fractures of the distal radius is in a state of flux, because the results of conservative treatment have so far been unsatisfactory in 20%-30% of cases. Instability resulting from dorsal compression, damaged ligaments (60%) and the presence of débris in the area of the metaphysis means that, while reduction is easy, retention is frequently difficult to achieve. Such fractures are reduced by using the ball of the little finger for extension while the ball of the thumb is positioned under the proximal fragment to provide support. A plaster cast based on the principle of three-point fixation is applied to immobilize the fractured part. The simplest surgical technique for unstable fractures of the distal radius is internal fixation with crossed Kirschner wires. For Smith's fractures [41], and especially those of type II (Thomas [44]), internal fixation with plates fixed to the volar bone surface is the procedure of choice. Comminuted fractures of the metaphysis and a tendency to shortening should be immobilized by external fixation. Early filling of the defect with cancellous bone leads to more rapid consolidation. In our own clinic we treated 409 cases of fracture of the distal radius in 2 years. The procedures applied were: conservative treatment in 39.6% of cases; internal fixation with wires in 55%; internal fixation with plates in 3.7%; and stabilization by means of external fixation in 1.7%.

Fracture Fixation, Internal↗
PubMed1986

[Isolated soft tissue trauma and combination injuries].

The special problem in severe soft tissue injuries of the lower limb are the thin soft tissue coverage and the diminished blood supply of the distal lower limb and foot. For this reason there is a big difficulty in estimating the severity of the injury. We developed a classification for severe lower limb and foot injuries and classified: soft tissue damage. concomitant local injuries. fracture type. classification of multiple injuries. time of treatment. This classification resulted in 4 groups, which have a prognostic value especially towards amputation or preservation of the limb.

Fractures, Bone↗
PubMed1986

Increased lung capillary permeability after trauma: a prospective clinical study.

Pulmonary dysfunction and permeability were prospectively studied in a group of severely traumatized patients. Ventilatory parameters (i.e., PaO2/FiO2, dynamic compliance, per cent shunt, and A-a DO2) and extravascular lung water (EVLW) measurements were compared with scintigraphic determinations of pulmonary albumin extravasation. Albumin extravasation data demonstrated a pulmonary capillary permeability increase occurring shortly following trauma. The median albumin extravasation value in the patients within 24 hours of trauma was 3.6 X 10(-5)/sec, compared to a control value of -0.1 +/- 0.7 X 10(-5)/sec. Intermediate levels of albumin extravasation were found in patients studied within 48 hours of total hip replacement (1.6 +/- 0.9 X 10(-5)/sec). Eighty per cent of patients studied within the first 48 hours of their trauma had albumin extravasation values exceeding the upper limit of normal as determined by the control value + 2 S.D. In contrast to albumin extravasation values, the PaO2/FiO2, dynamic compliance, per cent shunt, A-a DO2, and EVLW did not begin to deteriorate significantly until at least 48 hours after trauma. We conclude that severe multiple trauma induces an early increase in pulmonary capillary permeability as measured by albumin extravasation scintigraphy. This change is not detectable with other commonly used measures.

Adolescent↗
PubMed1985

[Thoracic trauma].

Thoracic trauma in multiple trauma increases mortality threefold, usually due to sepsis. Disturbances of the pulmonary vasculature are seen soon after trauma, as is increased EVLW. This can be due to 3 different mechanisms: 1. High pressure edema due to high intrathoracic pressure. Protein-poor edema. No hypervolemia, therefore no diuresis called for. 2. Hematoma: blood and dead tissue should be removed. Bronchial drainage is important. 3. Capillary permeability damage: areas of direct trauma with protein-rich interstitial edema. Can lead to ARDS. Modern ventilation techniques are helpful. No drug therapy (i.e. steroids) is proven.

Hemodynamics↗
PubMed1985

The German model for rescue of traumatized patients.

Accidents and their sequelae are the main cause of death in Germany among people under 40 years of age. The cost in disability payments and lost work averages $40 000 per injury. The author describes the German system for trauma rescue. The aims of rescue care in Germany are to reduce the interval between injury and hospital admission and to bring the patient to the right hospital, bypassing smaller hospitals if necessary. Ambulance rescue systems are of two types: the stationary, in which the physician travels with the ambulance, and the rendezvous, in which the physician and ambulance, travelling separately, meet at the accident site. At the beginning of the 1970s the air-rescue system was started and now comprises 32 stations and 25 BO-105 helicopters. The Hannover experience shows that of the initial diagnoses made at the accident site by helicopter rescue service, 51.9% of victims had head injuries, 35.5% fractures of extremities, 17.0% thoracic trauma, 10.2% abdominal trauma and 7.6% spinal fractures. Because of respiratory insufficiency or unconsciousness with danger of aspiration, 12.0% of the patients had to be intubated endotracheally. One hundred and twenty-two patients with a clinical diagnosis of death were successfully resuscitated at the accident scene. A study comparing the efficiency of the helicopter and ambulance systems showed that as the severity of the injuries increases, the death rate is greater in the group rescued by ambulance. Of 22 accidents involving rescue helicopters, 7 (32%) resulted in at least one death. Between 1973 and 1983, 16 doctors, pilots or attendants were killed.

Accidents, Traffic↗
PubMed1984

Studies of hemorrhagic and traumatic shock influence on liver oxygen tension: effects of a single large dose of dexamethasone.

Liver surface oxygen tension in response to hemorrhagic shock (hs) and to combined hemorrhagic-traumatic shock (hts) as well as to hemorrhagic-traumatic shock with glucocorticoid application ( htsc ) has been studied using male rats (Wistar strain, 250-300 g b.w.). The animals were anaesthetized by i.p. injection of ketamine/xylazine. All animals were bled through a catheter inserted into the vena jugularis until a hypotension of 40 mm Hg mean arterial blood pressure (MAP) was attained. The hts rats were traumatized by fracturing the left tibia and crushing the adjacent muscle tissue with 45 N/2.25 cm2 for 5 minutes. The htsc animals were traumatized and treated with a single injection of a large pharmacological dose of dexamethasone (6-8 mg/kg b.w.). Initial surface Po2 of the liver was higher than published by others (29 +/- 7 mm Hg) probably due to the narcotic agents. Maximal blood withdrawal was 24.4 +/- 2.2 ml/kg b.w. for hs, 17.9 +/- 3.8 ml/kg b.w. for hts and 20.6 +/- 4.5 ml/kg b.w. for htsc rats. Liver surface Po2 decreased to zero mm Hg in response to hypovolemic hypotension in all rats. Retransfusion of the shed blood caused a MAP and surface Po2 increase to only about half of the initial levels in hts and htsc rats while in hs animals the initial values were approximated. The hts and htsc rats showed signs of progressive hypotension to about 45 mm Hg MAP within 90 minutes post retransfusion. Dexamethasone improved the arterial pH to 7.15 compared with 7.05 of the control. Pao2 was elevated to 60 mm Hg vs. 49 mm Hg of the control animals. The beneficial influence of glucocorticoids on liver surface Po2 has not been substantiated as would have been desirable for the patient. Nevertheless, from a physiological standpoint a positive trend in the liver O2 supply has been evaluated as a small right shift of the surface Po2 histogram as well as the blood gas and pH data.

Animals↗