Warping of cross sections in the torsion of long bones with internal fracture fixation plates

Torsion of noncircular beams results in warping of each cross section. When noncircular cross sections are constrained to remain plane, the resulting shear stress distribution is different from what Saint Venant torsion (with warping) would predict. This has practical implications to the stress analysis of plated long bones subjected to torsional loadings. Analyses in which warping is not allowed predict incorrect stress fields in the plate and bone and overpredict the amount of stress shielding associated with fracture plate fixation.     

Petrous internal carotid aneurysm causing epistaxis: balloon embolization with preservation of the parent vessel

Summary A patient with severe, recurrent posterior epistaxis was shown at angiography to have an aneurysm of the petrous portion of the internal carotid artery (ICA). Since childhood, she had had pain related to eustachian tube blockage by the aneurysm. An endovascular balloon embolization of the aneurysm was successful with preservation of the parent artery. The treatment resulted in resolution of the symtpoms. The report confirms the usefulness of an angiographic protocol in evaluating vascular problems.     

肱骨干骨折--髓内钉与钢板固定的比较

总体而言，这些报道提示：采用髓内钉治疗肱骨干骨折较采用钢板带来更多的并发症，尤其是采用顺行人路。同时，这些报道没有提供确切的证据证明何种方法在骨折愈合、减少感染或上肢总体功能上优于另一种。     

Skull base surgery for malignancy: when not to operate

The purpose of this paper is to detail the contraindications for surgery, with curative intent for those patients who suffer from a head and neck malignancy that invades the intracranial space. This is based on a 30-year experience of over 250 patients. The most important contraindications are anatomical. Surgery is not done if the following structures are invaded: brain stem, eloquent portions of the cerebrum, superior sagittal sinus, both internal carotid arteries, both cavernous sinuses and certain vital bridging veins. Certain tumor factors are absolute but are occasionally relative contraindications: such as distant metastatic disease especially if multiple and at multiple anatomic sites. Some tumors that behave in a particularly virulent fashion that defy complete resection but are often difficult to predict preoperatively. Lack of patient medical fitness or absence of patient commitment to the operative procedure is make-up two serious contraindications to surgery. Presented at the 77th Annual Meeting of the German Society for Oto-Rhino-Laryngology, Head and Neck Surgery, 24–28 May 2006, Mannheim, Germany.     

Chronic occupational exposure to organic solvents

Summary Twenty-two persons (20 men and 2 women) were examined for their external and internal exposure to the glycol ether 1-methoxypropan-2-ol (PGME) during the production, leak testing and mounting of brake-hoses. For the measurement of external exposure, personal air monitoring was the method of choice. Average concentrations of PGME of 82.2 mg/m³ (22.3 ppm), 68.6 mg/m³ (18.6 ppm) and 11.3 mg/m³ (3.1 ppm) were found in the air of the brakehose production, leak test and mounting areas, respectively. For the estimation of internal exposure to PGME, this glycol ether was measured in both urine and blood. The biological samples were taken post-shift. The highest internal exposure levels were found in the brakehose production section and in the leak test area. The average post-shift concentrations for PGME in workers in the brakehose production section were 4.6 mg/l in urine and 13.5 mg/l in blood; the corresponding figures for workers in the leak test area were 4.2 mg/l in urine and 11.0 mg/l in blood. In blood and urine samples of workers engaged in the mounting area, PGME levels were below the detection limits. The elimination kinetics of PGME were also studied in three highly exposed persons, and mean excretion half-lives of PGME of approximately 4.4 h were found. On the basis of our results we made a rough calculation of a future biological tolerance value: we would except that concentrations of 38-109 mg per litre of blood and 10–31 mg per litre of urine would correspond to the German MAK value for PGME (375 mg/m³).     

Segmental fixation with U-shaped rod in the treatment of spondylolisthesis

Summary From 1987 to 1990 the authors treated 20 cases of spondylolisthesis by an improved operative procedure including excision of the medial part of the superior articular processes of the slipped vertebra, excision of the soft tissue between the ununited isthmi, and excision of the ligamentum flavum between the intervertebral space above the slipped segment. In some instances the lower portion of the lamina over the slipped vertebra should be resected. A U-shaped rod was used to hold sublaminar fixation of two segments above and below the slipped vertebra, with the slipped vertebra spared. Utilizing the U-shaped rod as support, bone strips were placed along the lateral and anterior sides of the rod to bridge the gap between the laminae of the displaced vertebra. Other bone grafts were focused on the facet joints. The patients were allowed ambulation early postoperatively. 19 cases could be evaluated at preliminary follow-up. All showed satisfactory results.     

How four and twelve weeks of implantation affect the strength and stiffness of a tendon graft securely fixed in a bone tunnel: a study of Evolgate fixation in an extra-articular model ovine model

Healing of a tendon graft to a bone tunnel is slower than the healing of a bone plug. Therefore, the device chosen for hamstring fixation may need to maintain its strength and stiffness longer than the device chosen for bone-tendon-bone fixation. We evaluated, in an extraarticular ovine model, how 4 and 12 weeks of implantation affect the strength of a tendon graft fixed to bone with the Evolgate. The long digital extensor tendon was transplanted and fixed with the Evolgate into a 30-mm long, 8 mm diameter bone tunnel drilled in the tibial metaphysis of both posterior limbs of 15 skeletally mature Suffolk sheep. Immediately after implantation, and 4 and 12 weeks later, biomechanical cyclic load tests in 50 N increments were performed until failure to evaluate the ultimate failure load (UFL). Histological analysis was also performed at 4 and 12 weeks. Biomechanical tests revealed a UFL of 339±120 N at time 0, and increases to 635±19 N (4 weeks) and to 867±80 N (12 weeks). The differences between all 3 groups were significant (p<0.001, paired t test). The histological evaluation showed a layer of cellular, fibrous tissue between the tendon and the bone, along the length of the bone tunnel; this layer progressively matured and reorganized during the healing process. The collagen fibers that attached the tendon to the bone resembled Sharpey’s fibers. The strength of the interface significantly and progressively increased between weeks 4 and 12 after transplantation, and was associated with a degree of bone ingrowth noted histologically. The use of the Evolgate seems not to interfere with the bone ingrowth after implantation, allowing an improvement in strength of the bonetendon- device complex.     

External fixation of unstable pelvic ring fractures: comparative rigidity of some current frame configurations

The effectiveness of external fixation in the stabilisation of pelvic ring fractures was studied in a laboratory cadaveric series. Shearing displacements occurring at sacroiliac joint and symphysis pubis dislocation sites, due to simplified longitudinal loading of the sacrum in an Instron unit, were monitored using variable-impedence transducers. The rigidity of fixation was compared for the Slätis and the Bonnel single anterior frames, for coupled and uncoupled double anterior frames, and for combined anterior-plus-posterior fixation achieved with separate transfixation pin clusters, with through-and-through pin clusters, or with a posterior screw plate. The data showed that the use of posterior fixation provided greatly enhanced stabilisation compared to that achieved with anterior fixation alone. The complex double anterior frames performed only slightly better than did the simpler single anterior frames. In no case, however, was it possible to recover rigidity levels approaching those of the intact pelvis. The results suggest that the transfixation pin arrangement is the most important determinant of pelvic fixation stability, and that further investigation of posterior screw-plate fixation is warranted.     

The effect of a series of fixatives on the AgNOR technique

With increasing interest being shown in nucleolar organizer regions (NORs) in pathology, it was considered of great importance to evaluate the effect of some of the more commonly used and more specialized fixatives on the demonstration of these moieties. NORs can be demonstrated in paraffin sections by a silver technique (AgNOR method) which was developed from a method used by cytogeneticists for the demonstration of NORs in chromosome spreads. The degree of staining is dependent on the fixation regime employed and results may vary greatly from one fixative to another. The fixative schedules and post-treatments used in this study were based on standard sequences from the literature. We have shown that, in general, alcohol-based fixatives give optimal results, Carnoy's fluid being especially recommended. Mercurial and dichromate-containing fixatives were found to have highly detrimental effects on NOR staining. 'Routine' 10 per cent formol saline fixation gave adequate results whereas 10 per cent neutral buffered formalin gave optimal staining, similar to alcohol-based fixation.     

股骨颈骨折不同角度固定的生物力学比较研究

本文通过测量２０个股骨上段标本，Ｘ线片的压力骨小梁系统，按照其骨小梁系统采用低角度固定其股骨颈骨折标本，以临床常用角度固定的股骨颈骨折标本作为对照组，进行静力学测定。股骨上段骨小梁系统与股骨纵轴线所成角度均数为１５４．７±１．９度，骨小梁系统与股骨外侧骨皮质交点到大转子距离均数为７．３±１．０ｃｍ。低角度固定组承载力及最大承载力明显大于对照组（Ｐ＜０．０５），且有更小的旋转移位（Ｐ＜０．０５）。本研究将低角度固定概念量化，对股骨颈骨折内固定的使用有显著的临床指导意义。