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Biomedical subjects

T Hopf

Publications and source records attributed to T Hopf.

At least 37 records · Page 2Linked to original sources
PubMed1994

Lateral tibial avulsion fractures and disruptions to the anterior cruciate ligament. A clinical study of their incidence and correlation.

Avulsion fractures of the lateral tibial plateau, known as the lateral capsular sign, are increasingly associated with anterior cruciate ligament (ACL) ruptures. This phenomenon, known as the Ségond fracture, is a bony avulsion of the menisco-tibial ligament. Stress, which can lead to an avulsion of this kind, almost always occurs during knee flexion and internal tibial rotation, and in most cases only after damage to the primary ACL stabilizer. Examination of 151 ACL ruptures revealed a Ségond fracture in 9% of patients. Nearly all were caused by sports injuries and, understandably, the accident mechanism always included knee flexion and internal rotation of the tibial. In a similarly large number of other knee injuries without damage to the ACL, only one case of a Ségond fracture was found. This phenomenon, which is easy to detect by radiograph, can thus be regarded as a strong indication of the presence of a ligament injury.

Anterior Cruciate Ligament Injuries↗
PubMed1993

Clonal chromosome aberrations in cell cultures of synovial tissue from patients with rheumatoid arthritis.

Cytogenetic analysis of primary cell cultures and/or passages 1-3 of synovial tissue from seven patients with rheumatoid arthritis was performed. As the only recurrent chromosome aberration, trisomy 7 was found in six of seven cultures. In four cultures, trisomy 7 occurred as a clonal change in up to 20% of the analyzed cells, with an increase of the proportion of cells with +7 with the duration of the in vitro culture. Apart from this recurrent change, a variety of partly clonal, partly nonclonal numerical and structural chromosome aberrations were observed in all cases. These findings support the view that clonal chromosome aberrations may play a role in the pathogenesis of invasive growth of the synovial tissue in rheumatoid arthritis although the localized synovial hyperproliferation is not a true neoplastic process.

Arthritis, Rheumatoid↗
PubMed1991

[The importance and form of the collar in hip joint endoprosthesis. Theoretical analysis and biomechanical study].

Flat contact of the collar of the stem with the resection area of the femur in total hip replacement can often not be achieved even when the operation technique is very precise. Uneven bone patches or deviations in the resection angle lead to points of contact. If this contact area is localized to the lateral part of the collar, considerable varus torque acts on the prosthesis stem. By a simple modification, removal of the lateral area of the collar, medical bone - collar contact is achieved. It is independent from deviations in the operative procedure. In biomechanical experiments, drastic reduction in harmful torque was demonstrated by this modification. Thus, more "physiological" force transmission from the prosthesis to the bone can be expected.

Biomechanical Phenomena↗
PubMed1990

[Comparative studies on the radioactivity of bone cements containing x-ray contrast media and of the contrast media].

Various PMMA bone cements containing zirconium oxide (ZrO2) as an X-ray contrast medium and zirconium oxides of several manufacturers were tested for their radioactivity by means of a gamma spectrometer. All the bone cements tested (Implast, Palacos R, and Sulfix-6) showed a certain degree of radioactivity. The radiation source in the bone cement is the added zirconium oxide, which is polluted by radioactive elements. The examination of various zirconium oxides showed some high radioactive emissions. The risk of radiation-induced cancer seems to be small, because the cements are normally implanted in humans older than 60 years. In view of the fact that these X-ray contrast media remain in the body for decades as components of the bone cement, the radioactive zirconium oxides should be replaced by high-purity radiation-free zirconium oxide or barium sulphate as soon as possible.

Bone Cements↗
PubMed1990

[Tensile strength of plate osteosynthesis. Comparative biomechanical study of the original autocompression plate and a functional modification using the ZESPOL principle].

In order to overcome the problems of stress protection and pressure atrophy of bone, which are associated with the traditional plating technique, in Poland a modified type of plating, ZESPOL has been, developed. In this procedure, the plate is not screwed onto the surface of the bone, but is fixed above the bone by special platform screw bolts in a comblike construction. This paper describes an experimental biomechanical investigation, using cadaver tibia, which compares the stability of the ZESPOL principle with that of the traditionally applied autocompression plate (ACP). In order to make the system biomechanically comparable, instead of the original ZESPOL plates, which are different in dimension, an ACP was used that was specially adapted to fit the ZESPOL criteria. Compared to the ACP, the bending stability of the ZESPOL osteosynthesis was found to be significantly less. When the same stress was applied, the total bending capacity of the ZESPOL system was found to be between 9% and 1348% higher, depending on the position of the plate and the direction of the force applied. In addition, the gap of the osteotomy site was between 6% and 923% greater with the ZESPOL system. Deformation of the bone adjacent to the osteotomy site was more closely approximate to intact bone with ACP than with ZESPOL plate. Our evaluations show that the ZESPOL system has less bending stability than ACP, without having the advantage of a more physiological bone-bending curve. However, the stability of the new system can be regarded as being overall sufficient.

Biomechanical Phenomena↗
PubMed1989

Creatine-kinase-BB after severe head-injury as an index of prognosis in relation to nature of trauma and patients age.

Creatine-Kinase-BB (CK-BB) is a brain specific enzyme, with a prognostic value for the patient's outcome after head-injury. We have investigated 76 brain injured patients and attempted to show a correlation of the concentrations of CK-BB and the Glasgow-Outcome-Scale (GOS). Patients with a CK-BB concentration of more than 50 ng/ml died. Patients, who had a CK-BB concentration less than 25 ng/ml showed only minimal neurological deficits. Intracerebral contusions and acute subdural haematomas showed the highest CK-BB concentration, indicating a high degree of braintissue-damage. CK-BB seems to have no correlation with the age of patients. Normalisation of elevated CK-BB levels do not correlate with recovery from neurological deficit.

Adolescent↗
PubMed1989

[Spongiosa formation in plate osteosynthesis--a comparative animal experiment study of current and auto-compression plates using the Zespol principle].

Osteosynthesis with modern self-contracting plates has a few fundamental drawbacks apart from its undisputably good points. Among these drawbacks we have the pressure strain on the bone surface; the traction strain exercised by the screw thread in the bone; and, chiefly, spongiotisation and bone atrophy due to so-called stress protection. A new modification of this process, called Zespol, in which the plate is no longer fastened direct to the bone but is fastened floating over the bone surface to so-called platform screws, tries to solve these problems. In a comparative animal experiment tibial transverse osteotomies in the rabbit were treated by osteosynthesis using small fragmentary ACP and Zespol plates. In respect of healing of the fracture none of the two methods showed any advantage. Histological evaluation of the plated bone sections were characterised in both plate systems by increasing spongiotisation and bone atrophy that increased with the length of application. Degradation processes were about equal with both systems. A special feature with the Zespol animals was that the cleft originally existing between the plate and the bone was filled up with newly formed spongy and later cortical bone. Due to this process the original cortex layer lost its function and atrophied severely. After 12 to 18 weeks the bone surface had reached the lower side of the Zespol plate and there was contact by touch. This restored similar biomechanical conditions as those existing in conventional plates after this period.

Animals↗
PubMed1986

[Biomechanical studies of the role of the interfragmentary traction screw in plate osteosynthesis exemplified by a short oblique tibial shaft fracture].

In oblique fractures of the shaft of the tibia, plate osteosynthesis is combined with an interfragmentary traction screw to enhance the stability. Depending on the position of the fracture, the screw is introduced separately or via a plate hole near to the fracture. The maximum resistance to bending and the plastic deformation of plate osteosyntheses were studied in the tibiae of human corpses, with or without traction screw; in some cases, pure traction screw osteosyntheses were used in this study. It was found that the additional traction screw enhanced the stability by 52%, whereas plastic deformation was markedly reduced. Furthermore, the traction screw more than doubled the rigidity of the osteosynthesis, facilitating early healing of the fracture. Theoretical considerations show that a traction screw will greatly reduce the harmful shear stress of the fracture and increase interfragmentary compression, depending on the direction of the screw. If the screw is introduced, as recommended by Danis, in the bisector of the angle between the perpendicular on the fracture fissure and the perpendicular on the bone axis, one obtains high interfragmentar compression and reduction of shear stress by one-half. If the traction screw progresses perpendicularly to the bone axis, however, interfragmentary compression will be less, whereas the shear forces are fully compensated. Hence, the procedure according to Danis is meaningful in low-tension plate osteosyntheses (e.g. neutralisation plates), whereas transverse positioning of the screw appears to yield more favourable results in osteosyntheses applied under high tension.

Biomechanical Phenomena↗
PubMedDate not supplied

[Cruciate ligament injuries with knee joint effusion--why can the Lachman sign not be elicited?].

In acute anterior cruciate ligament (ACL) lesions with effusion of the knee joint it is often difficult to realize a positive Lachman sign. It was suggested that the tension of the joint capsule may reduce tibial displacement although the ACL is completely disrupted. In 10 cadaver knee joints the ACL was dissected and the capsule was closed again. By a canula the knee joints were filled with isotonic saline solution in steps of 20 ml up to 100 ml. Before and after dissection of the ACL and during filling the joint we measured the anterior tibial displacement by use of the MEDmetric KT 1000 arthrometer. In a second series we examined 5 patients with acute effusion of the knee joint before and after puncture of the effusion. We detected the electromyographic activity of the quadriceps muscle end and the hamstrings during the KT 1000 test and patellar reflex. In the cadaver tests we found no reduction of the anterior tibial translation while filling the joint with saline solution. The electromyographic examinations showed a reflectory action in the quadriceps muscle and in the hamstrings when the Lachman test was performed. In the quadriceps muscle the electromyographic amplitude was reduced after puncture; the hamstrings showed a drastically reduced amplitude and duration of the signal. When patellar reflex was performed we recorded an electromyographic action in both muscle groups, too. Puncture could only reduce the signals of the hamstrings. Our results suggest that the reduction of the anterior drawer and the Lachman test in acute effusion is caused not mechanically by the tension of the capsule but by a reflectory muscle action of the hamstrings.

Anterior Cruciate Ligament↗
PubMedDate not supplied

[The surgical repositioning of spondylolisthesis using the internal fixator and a new simple repositioning instrument].

A simple aid for reposition of spondylolisthesis with the Fixateur interne is presented. The modification consists of a metric thread, which is cut in the end of the SCHANZ screw, a fitting butterfly nut and a distance tube. This instrument allows a well-dosed and controlled extension and reposition of the dislocated vertebra in all planes. No other instruments or implants, which may hinder the operation, are necessary. After the reposition the bone graft may be inserted from ventral or from dorsal. The dorsal intercorporal spondylodesis saves time, means a lower trauma for the patient and has the possibility for interfragmental compression.

Bone Transplantation↗
PubMedDate not supplied

[Experimental studies on the role of intramedullary alignment rods in the etiology of fat embolisms in knee endoprostheses].

Fat embolism syndrome (FES) during implantation of an uncemented resurfacing type of total knee replacement is the leading cause of postoperative mortality. A possible explanation might be the insertion of a solid intramedullary alignment rod, resulting in an intrafemoral pressure increase. On 45 cadaveric human femora we measured the resulting intramedullary pressure during insertion of three different alignment rods: a solid rod and a hollow shaped guiding rod, both 10 mm in diameter, and a fluted alignment rod of 8.5 mm in diameter. The highest intramedullary pressures occurred after placement of a solid 10 mm alignment rod (3.77 +/- 0.44 bar), followed by a fluted 8.5 mm rod (2.53 +/- 0.28 bar). In both cases, the increased pressure led to an extrusion of bone marrow contents through the venous system of the proximal femur. The least increase occurred after insertion of a hollow shaped alignment rod (0.26 +/- 0.03 bar) without any fat extrusion. Our study confirms the hypothesis that insertion of solid intramedullary alignment rods during preparation of the femoral shaft results in a dangerous pressure increase, so that embolization can occur. To minimize the risk of a FES, instruments should be modified in a manner, that only hollow shaped alignment rods are used.

Bone Marrow↗
PubMedDate not supplied

[Proprioceptive deficit following cruciate lesions--afferent disorder or compensatory mechanism?].

It was suggested that the ACL has not only mechanical functions but also acts as proprioceptive organ. In cruciate deficient knees pathological patterns of muscle control were found. These findings could be caused by a disturbed afferent signal from the disrupted ACL or by secondary changes in muscle innervation, which shall protect the instable knee against subluxation. 33 patients with unilateral operative ACL repair (21 cases with primary suture, 12 cases with autogenous ligamentum-patellae-reconstruction; average post op 36.5 yr) were examined clinically and with the KT 1000 arthrometer (MEDMETRIC Inc.). Patients history was evaluated by using the LYSHOLM score. During a cycling task the electromyographic activity was monitored from the thigh muscles (M. vastus lat. and med., lat. and med. hamstrings). In comparison to the ACL deficient patients, we tested 25 healthy subjects of same age and activity level. In the ACL group the following differences to the normals were found: the M. vastus lat. showed a significantly delayed onset, earlier end and shorter duration. M. vastus med. had the same pattern; the delayed begin of activity and the shorter duration were statistically significant. M. biceps femoris showed a significant later onset and shorter duration. So did the medial hamstrings; the differences, however, were not statistically significant. There was no significant difference between operated and healthy leg in the ACL group. By comparing the primary sutures and the ligamentum-patellae-reconstructions no significant differences were found. The instable patients (KT 1000 > 3 mm) of the ACL group showed more distinct differences in the EMG pattern than the patients with stable knee joints.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

[Comparative biomechanical studies of conventional and self-tapping cortical bone screws].

In normal cortical screws the thread must be cut by a separate thread-cutter. So a high stability of the connection is achieved. On the other hand thread cutting needs time, which may be assumed to several minutes during a plate osteosynthesis. To avoid thread-cutting, self-tapping screws were used 20 years ago. These old self-tapping screws had a reduced stability and a lower torque at the final screw driving so that they tended to destroy the thread. By a modification of the cutting edges at the tip of the screw the tapping quality is increased decisively. The microscopic examination showed a better cutting of the new screws with little difference to a thread-cutter. In biomechanical tests the final torque and the maximum tension force of the self-tapping screws were at the same level as in usual pre-cut screws. In the practical use the new self-tapping screws have a good handling and save time during operation. In osteoporosis, they should be used carefully in order to meet the opposite corticalis' hole and not to destroy the ipsilateral corticalis' thread.

Biomechanical Phenomena↗
PubMedDate not supplied

[Comparative animal experiments on tissue compatibility and measurement of radioactivity of various roentgen contrast media].

In a comparative study the tissue reaction of several X-ray contrast materials was examined by subcutaneous and intraperitoneal application on rats. There were tested Bariumsulphate (BaSO4) and three Zircondioxyde (ZrO2) samples of several manufactures (cubic and monocline ZrO2-Feldmühle; Optipur-Merck). In the histologic evaluation no inflammatory signs could be seen. In case of BaSO4 the tissue reaction was more distinct than in the ZrO2 samples. Within the tested ZrO2 samples the differences were small; the cubic ZrO2 showed the slightest, the monocline one the relatively strongest cellular reaction. We also measured the radioactive emission by the contrast media. Here the monocline and--first of all--the cubic ZrO2 showed an alarming radioactive emission (radium 3000-11,500 Bq/kg). Only the Optipur (Merck) was free of radiation and can so be recommended for human implantation. Also the BaSO4 had no measurable radioactive Emission. Therefore only these two X-ray contrast media can be recommended for human implantation.

Animals↗