Biomedical subjects

J Kühle

Publications and source records attributed to J Kühle.

3 recordsLinked to original sources

PubMed1994

[Biomechanical prerequisites for examining the stability of osteosynthesis procedures of the spine].

Basic reflections on biomechanical tests of spinal implants are reviewed. Four different pedicle screw systems are compared during loading in extension, flexion, side-bending, and rotation. The thoracolumbar and the lumbar spine were tested. Stability against rotation forces was lowest in all systems. Because of this, a cross-connector is recommended in highly unstable situations. All tests were done in cadaver spines with normal bone mineral density (measured before the tests). The first series of tests was done without destroying the cadavers. A second series was done with maximal load until the implants or the bony bed of the screws failed. The results show that rigid implants more often led to pedicle fractures. An unstable screw rod interface led to implant failure. Cadaver tests can provide answers about the primary stability characteristic only. Fatigue tests are not possible in cadaver spines because they become autolytic before enough cycles can be applied.

Adult↗

PubMedDate not supplied

[Mechanical versus drug prevention of thrombosis after total hip endoprosthesis implantation. A randomized, controlled clinical study].

Pharmacological prophylaxis is routinely applied after total hip replacement. Although it effectively reduces deep-vein thrombosis, side effects (bleeding, haematoma, swelling, thrombocytopenia) are not infrequent. Since in Germany use of foot pumps as only means of prophylaxis is unpopular, we investigated their efficacy and safety in a randomized study. 106 patients used either low molecular weight heparin (Fraxiparin, Sanofi-Synthelabo, Germany) or the foot-pump (A-V Impulse System, Orthofix, Mühltal, Germany), and were monitored for deep-vein thrombosis using serial duplex sonography on postoperative days 4, 12 and 45. Clinical observations included daily measurements of thigh circumference, recording of postoperative drainage amounts, and monitoring of wound healing. None of the 50 patients treated with the foot-pump developed deep-vein thrombosis, while 4 of the 50 patients (8 per cent) on pharmacological prophylaxis did so. Six patients stopped using the foot-pump during the study. One patient developed heparin-induced thrombocytopenia. Patients on mechanical prophylaxis had smaller amounts of drainage (mean 247 ml vs. 272 ml, p = 0.485) and significantly less swelling of the thigh (10 mm compared with 15 mm, p or = < 0.001), The good results in terms of prevention of thromboembolic complications and soft tissue swelling favour the general use of foot pumps as mechanical prophylaxis.

Adult↗

PubMedDate not supplied

[Stability of pedicle screws. 2: Maximum pullout force with reference to bone density].

Maximum pullout strength of pedicle screws in osteoporotic cadaver spines are tested. Bone mineral density was measured before by two noninvasive methods (QCT, DRA). Pullout direction was axial to screw axis. 210 N to 920 N were reached from D1-S1. There is a high correlation between bone mineral density and pullout strength (r = 0, 8-0.9). Augmentation of osteoporotic pedicles with bone cement increases screw stability nearly to that one of non-osteoporotic spines.

Adult↗