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Biomedical subjects

K Klaue

Publications and source records attributed to K Klaue.

At least 19 recordsLinked to original sources
PubMed2003

[Talus fractures].

Explore the source record for details and available documents.

Ankle Injuries↗
PubMed2000

Development and testing of a new self-locking intramedullary nail system: testing of handling aspects and mechanical properties.

A distal interlocking system has been developed which is easy to use, carries out an aligning effect on the distal fracture fragment, reduces the exposure to radiation for the surgeon and the patient, and allows for a decrease in operating time. The goal of this study was to develop and test the handling and mechanical properties of two prototype nails in comparison to a conventional interlocking nail concept (Unreamed Femoral Nail system). It was shown that the prototype designs represent an improvement over this system. Both designs were easy to use. The prototype with the asymmetrically offset interlocking bolts exhibited an exemplary aligning effect on the distal fracture fragment. Both designs showed mechanical stability comparable or superior to that of the standard contralateral control in four-point-bending and axial compression. Given the handling advantages afforded by the new self-locking intramedullary implant system, it would be expected that use of this system would reduce exposure to radiation for the surgeon as well as the patient and allow for a decrease in operating time. This new development may be of particular interest for clinics without access to fluoroscopes in the operating theatre (e.g. in the Third World).

Aged↗
PubMed2000

Functional load of plates in fracture fixation in vivo and its correlate in bone healing.

In clinical practice efforts are made to apply a fixation plate on the side opposite the strongest muscle pull. This achieves an optimal distribution of compression between the fragment ends (principle of tension band plating). This is however frequently impossible for anatomical or surgical reasons. In an 'in vivo' study lasting 8 weeks a standardized oblique osteotomy was performed on the tibia of 16 sheep in four different models of tension band plating (a contoured and an overbent plate with or without an interfragmentary lag screw) were assessed. Tension on the plate surface was recorded by strain gauges for different gait speeds on the treadmill. These measurements were performed throughout the experiment. Radiographs were taken at regular intervals in order to assess stability and polychrome sequential labelling and microradiographs served to investigate the healing process. Possible relationships and/or interactions between plate tension and bone healing were investigated. Implant loading under bending strain was reduced the most for the combination of plate overbending with a lag screw. The insertion of a lag screw reduces the surface strain on the plate whether it is contoured or overbent. The bending and torsional forces are greatest if a straight plate is used alone and the principle of tension band plating is not applied. Direct bone healing was only observed in the group with contoured plate and lag screw. Overbending combined with a lag screw provided only a relatively unstable fixation. A residual gap immediately beneath the plate permits "dynamic compression" since the screws slide towards the osteotomy when loaded producing bone resorption under the plate and signs of screw loosening. The models with contoured and overbent plates without a lag screw were histologically assessed as very unstable with signs of secondary fragment displacement, obvious callus formation, resorption at the fragment ends and under the plate, delayed and diminished Haversian remodelling and corrosion sites at the screw heads and at the adjacent site on the plate hole. In all groups, stripping of the periosteum under the plate was associated with porosis of the corresponding cortex as a sign of temporarily impaired blood supply. A relationship between implant loading and/or unloading (stress shielding) could not be demonstrated. Callus formation, measured quantitatively on the radiographs, is directly related to the strain on the plate. Direct bone healing is rapid and is seen histologically three weeks postoperatively, particularly for fixations with contoured plate and lag screw. The early appearance of fixation callus in the presence of an intact blood supply indicates a primary instability of the osteosynthesis. Later, it may be an indication of secondary instability. The time at which osteons appear, their number and location provides information on the stability of the osteosynthesis. At a time when indirect fracture reduction and stabilization using minimally invasive techniques and implants is being propagated, additional ways and means must be sought to assess clinically the load on the implants and the risk of implant failure.

Animals↗
PubMed2000

Long-term effects of plate osteosynthesis: comparison of four different plates.

Various phenomena have been observed subsequent to plate osteosynthesis, for example, refracture after plate removal. Experimental research has shown that changes in the cortex occur within the first three months after plating and again several months later. These changes are independent of the fracture and take the form of porosis under the plate and excessive bone growth around the plate. Porosis under the plate was regarded until recently as being due to unloading of the bone by the plate, also known as stress shielding. Investigations of the relationship between bone porosis and the changes in periosteal blood supply due to its compression by the plate, however, have been neglected. In this study, the effect of plate properties such as structural stiffness ('unloading'), implant material, and plate contact surface (altered periosteal blood supply) on bone after osteosynthesis were investigated. This was done by comparative histomorphometry of the altered bone in sheep after application of four plates differing in the above-mentioned properties. After plating the sheep tibia with a trapezoid plate with narrow contact surface, significantly larger bone cross sections were observed one year after the operation and considerable bone growth around the plate. The area of early temporary porosis in the cortex under the plate as observed in the first nine weeks and after one year was not significantly different for any particular plate, all of which were applied subperiosteally. The trapezoid plates were easier to remove, thus causing less damage to the bone lamellae along the sides of the plate. The marked increase in bone cross section after one year and the larger areas of bone growth around the trapezoid plates with smaller contact surface can be attributed to the larger grooves cut along the sides of the plates. Cortical porosis was mainly the result of impaired periosteal blood supply which was of equal size in all groups as a result of careful periosteal stripping and subperiosteal plate insertion. It was assumed that applying the plate onto the periosteum would be associated with effects on periosteal blood supply directly related to the plate and consequently cortical porosis. Plate related stress shielding and the implant material had no significant effect on the extent of cortical porosis.

Animals↗
PubMed1999

Retroversion of the acetabulum. A cause of hip pain.

We describe a little-known variety of hip dysplasia, termed 'acetabular retroversion', in which the alignment of the mouth of the acetabulum does not face the normal anterolateral direction, but inclines more posterolaterally. The condition may be part of a complex dysplasia or a single entity. Other than its retroversion, the acetabulum is sited normally on the side wall of the pelvis, and its articular surface is of normal extent and configuration. The retroverted orientation may give rise to problems of impingement between the femoral neck and anterior acetabular edge. We define the clinical and radiological parameters and discuss pathological changes which may occur in the untreated condition. A technique of management is proposed.

Acetabulum↗
PubMed1994

Clinical, quantitative assessment of first tarsometatarsal mobility in the sagittal plane and its relation to hallux valgus deformity.

Today, bunion surgery is still controversial. Considering that a bunion deformity in fact may be a result of multiple causes, the rationale of the currently applied techniques of surgical treatment has not been conclusively demonstrated. In view of the known hypermobility syndrome of the first ray that results in insufficient weightbearing beneath the first metatarsal head, the relationship between this syndrome and hallux valgus deformity has been investigated. The results suggest a direct relationship between painful hallux valgus deformity and hypermobility in extension of the first tarsometatarsal joint. A pathological mechanism of symptomatic hallux valgus is proposed that relates this pathology with primary weightbearing disturbances in the forefoot where angulation of the first metatarsophalangeal joint is one of the consequences. The alignment of the metatarsal heads within the sagittal plane seems to be a main concern in many hallux valgus deformities. As a consequence, treatment includes reestablishing stable sagittal alignment in addition to the horizontal reposition of the metatarsal over the sesamoid complex. As an example, first tarsometatarsal reorientation arthrodesis regulates the elasticity of the multiarticular first ray within the sagittal plane and may be the treatment of choice in many hallux valgus deformities.

Adult↗
PubMed1993

Extra-articular augmentation for residual hip dysplasia. Radiological assessment after Chiari osteotomies and shelf procedures.

The Chiari osteotomy and various shelf procedures are used to augment the weight-bearing area in dysplastic acetabula. The new articular surface derives by metaplasia from the acetabular rim and joint capsule, and is therefore of poorer quality than congruous hyaline cartilage. We reviewed 32 patients after augmentation procedures, using conventional radiographs and three-dimensional reconstruction from CT scans. We showed that Chiari osteotomy and shelf procedures generally achieve less than complete cover, especially over the posterolateral quadrant of the femoral head. Our results suggest that alternative methods which reorientate the whole of the acetabulum are the treatment of choice. Augmentation procedures remain as a salvage option when reorientation is inappropriate or the original hyaline cartilage surface is absent, as in subluxed joints with a secondary acetabulum. Computerised assessment is recommended before operation to assess existing cover and the possible extent of provision of new cover.

Adolescent↗
PubMed1991

Internal fixation with a self-compressing plate and lag screw: improvements of the plate hole and screw design. 1. Mechanical investigation.

For a number of years, self-compressing plates, with oval holes and using special drill guides, have been in use. Recently, the advantages offered by lag screw interfragmentary compression inserted through the plate have gained prominence. Often such screws are inserted in an inclined position toward the fracture plane for better efficiency. It has also become evident that inclined screws placed into oval holes undergo a displacement toward the fracture. Efforts to improve the effect of this technique have led to a new plate and screw interaction that is described herein. The result is versatility and efficiency of the fracture fixation.

Biomechanical Phenomena↗
PubMed1991

Internal fixation with a self-compressing plate and lag screw: improvements of the plate hole and screw design. 2. In vivo investigations.

A mechanically improved design of bone plate and screw was compared in vivo with conventional plate fixation. This method was investigated biologically in a standardized osteotomy model on sheep tibiae. It was found that maintenance of reduction of an osteotomy was facilitated and there was no adverse effect of this fracture fixation system on bone remodeling. The modified implant permits the reduced surgical approach to the bone through one plane and optimal fixation of the fracture or osteotomy.

Animals↗
PubMed1991

The acetabular rim syndrome. A clinical presentation of dysplasia of the hip.

The acetabular rim syndrome is a pathological entity which we illustrate by reference to 29 cases. The syndrome is a precursor of osteoarthritis of the hip secondary to acetabular dysplasia. The symptoms are pain and impaired function. All our cases were treated by operation which consisted in most instances of re-orientation of the acetabulum by peri-acetabular osteotomy and arthrotomy of the hip. In all cases, the limbus was found to be detached from the bony rim of the acetabulum. In several instances there was a separated bone fragment, or 'os acetabuli' as well. In acetabular dysplasia, the acetabular rim is subject to abnormal stress which may cause the limbus to rupture, and a fragment of bone to separate from the adjacent bone margin. Dysplastic acetabuli may be classified into two radiological types. In type I there is an incongruent shallow acetabulum. In type II the acetabulum is congruent but the coverage of the femoral head is deficient.

Acetabulum↗