Sándor Manó

Ex vivo and in vitro determination of the axial rotational axis of the human thoracic spine.

Study Design. Different geometrical and biomechanical evaluations were performed to determine the axial rotational axis of the thoracic spine. Objective. Our research group has been dealing with the determination of the axial rotational axis of the thoracic spine. Here, we would like to present the geometrical and experimental results of our trials. With our experiments, we are trying to evaluate the contradictions of the related literature. Summary of Background Data. In the present state, we know quite a lot about the biomechanics of healthy and pathologic spines. Nevertheless, for a seemingly simple question like the position of the axial rotation of the thoracic spine, the literature gives contradicting results. During correction of a scoliotic deformity, when trying to correct the pathologic rotation, not knowing the physiologic rotation can be hazardous. Methods. We wanted to clarify this question, so we examined the thoracic spine in many different ways. First, we examined the problem from a geometrical point of view then we modeled the different rotational axes by studying the change in volume of the spinal canal. Finally, we used cadaver spines that we rotated and examined with radiographs and digital pictures. Results. Based on the results, we made the following establishments: most of the center points fell on the anterior half of the vertebral body or into the spinal canal, basically on the midsagittal axis of the vertebra. The rib cage has a significant effect on the place of the axis. After removing the ribs, the axis of axial rotation moved forward. Conclusions. After evaluating the results, we determined that the most likely place for the rotational axis is on the median-sagittal plane, in the anterior portion of the spinal canal.

Biomechanical examination of the thoracic spine—the axial rotation moment and vertical loading capacity of the transverse process

Our objective was to examine the load‐bearing capacity of the transverse processes of human cadaveric thoracic vertebrae to vertical loads and axial rotation moments (i.e., moment applied in the transverse plane). A secondary objective was to examine the effect of the attached rib stumps. We wanted to demonstrate that the transverse process is durable enough to support the CAB hook—a complementary hook to the CD system—and can handle the vertical load or axial rotation moment during correction of scoliosis. We used 107 thoracic vertebrae removed from 10 cadavers. They were prepared in vertebral pairs, and were fixed into a material testing apparatus. Superoinferior vertical loads and axial rotation moments were applied to the transverse process using the CAB hooks at a rate of 30 mm/min and 8.5°/s respectively until it fractured. We recorded 142 measurements, 99 were for vertical load and 43 for axial rotation moment. The average ultimate vertical load was 338 (SD = 128) N and the average ultimate axial rotation moment was 14.4 (SD = 4.52) Nm. The ultimate axial rotation moment for specimens with rib stumps attached was significantly greater than for specimens without rib stumps 15.9 (SD = 4.1) Nm versus 12.5 (SD = 4.4) Nm. Our results showed that both the vertical and axial rotation loading capability of the transverse process are large enough to withstand significant correctional forces, without fracture, through the CAB hooks.

Retrograde stem removal in revision hip surgery: removing a loose or broken femoral component with a retrograde nail

IntroductionRemoval of a cemented femoral stem during revision total hip arthroplasty is a technically demanding procedure that requires a multitude of surgical techniques and tools. To gain full access to the cement and the stem, distal fenestration or a transfemoral approach is often required. This paper presents a technique of retrograde removal of femoral stems and cement from the distal femur.Materials and methodsThe authors present five clinical cases. In two cases the femoral component and the surrounding cement was removed using this technique. In the other three cases, due to femoral component fracture, the distal fragment of the femoral component with its cement mantle was removed using the same technique. In an experimental study, we simulated the above technique and compared it with a windowing technique on six, paired cadaveric femora (12 femurs in all).ResultsIn all of the clinical cases the stem and the cement were removed completely without any complications. The cadaveric experiments clearly showed that the biomechanical resistance of the femur against compression and torsion forces is greatly decreased by using a window to access the proximal femur, compared with the retrograde technique, which shows no significant change.ConclusionRetrograde component removal provides a simple, rapid, and less invasive technique for stem and cement extraction in elective revision hip arthroplasty.

The influence of lateral knee X-ray positioning on the accuracy of full extension level measurements: an in vitro study

The inaccuracy of full extension measurements can lead to errors, especially in reconstructive surgery of the knee and in the rehabilitation period following total knee replacement. The goal of this study was to first determine whether plain lateral X-rays of the knee can be used to measure the axis of the bones of the lower limb. The second goal was to determine whether the angle from which the X-ray is taken influences the true angle of the knee. We analyzed 620 digital photographs of cadaver knees to measure the difference between the true axis of the femur and tibia compared with lines drawn on the anterior and posterior cortex of the femur and tibia. We also analyzed 150 photographs of cadaver lower limbs to determine how the true flexion angle compares to the angles measured if the picture was taken from different rotated positions (maximum of 30°). Our results concluded that lines drawn onto the distal anterior cortex of the femur and proximal posterior cortex of the tibia can determine the true flexion angle with 2° of accuracy. We also concluded that lateral X-rays of the knee taken within ±30° of the true lateral position only causes a maximum of a 2% discrepancy in the true flexion angle.

A new technique of wedge osteotomy to diminish undesirable fractures

Opening and closing wedge osteotomy is a frequent procedure in orthopedics. Interestingly, the technique did not considerably change over the years. In this paper, we would like to introduce a new technique to make the cut easier and to decrease the fracture at the opposite cortex. Our proposal is that by making a juxtacortical drill hole on the opposite side and performing the osteotomy after, decreases the stress on the cortex therefore making it safer and easier to open or close. We demonstrate our idea through three cases.

The biological and biomechanical comparison of two bulk bone graft techniques used in case of dysplastic acetabulum.

BackgroundThe incorporation of bulk bone grafts in the replacement of dysplastic acetabulum is determined by the biological environment of the recipient site, the size of the contact surface, and the stability of the osteosynthesis used. Based on these, the present study compares the Harris acetabular plasty used routinely by us with the Radojević L-shaped graft technique.MethodsFor our measurements, we used 20 hemi-pelvises removed from 10 cadavers. In 10 cases, acetabular plasty according to Harris, in 10 cases Radojević L-plasty, was performed. The biological environment was analyzed; with geometric calculations, the contact surface was determined, and with a material testing apparatus, the primary stability of the osetosynthesis was measured. For the measurements, a new method was developed.ResultsThe Radojević technique provides a better biological environment for graft ingrowth. The contact surface is nearly twice as much as in Harris plasty. No significant difference was found in the primary stability of the osteosynthesis used. The deviation on the value of the stability measurements is explained by the differences in the bone quality of the cadavers used.ConclusionsBased on the 3 aspects examined, the Radojević L-shaped graft technique has similar stability when compared to the Harris acetabular plasty, but provides better biological circumstances and larger graft host bone contact. Based on this, we started using the L-shaped technique in our department.

Multilevel callus distraction: a novel idea to shorten the lengthening time

Lower extremity inequality is a common problem in everyday orthopaedic practice. The leg discrepancy can lead to variety of other problems, i.e., spinal problems. Surgical intervention is very demanding and requires patient compliance. Wagners and Ilizarovs elongation technique are most commonly used worldwide, but it gives satisfactory results only in a long period of time and as we know there could be several inconvenient outcomes. Our idea aims at shortening this time period, and avoiding some of the inconvenient outcomes. Unfortunately we do not have the opportunity to go further in our investigations, but we hope that someone interested in this field will have an idea which would make continuation possible.

STRUCTURAL ANALYSIS AND ITS STATISTICAL EVALUATION OF A CLOSED-CELL METAL FOAM

The development of an efficient procedure for 3d modeling and finite element simulation of metal foams is one of the greatest challenges for engineer researchers nowadays. Creating 3d CAD model is alone a demanding engineering task due to its extremely complex geometry, and the proper finite element analysis process is still in the center of the research. The increasingly widespread application of the metal foams, e.g. in vehicle and medical industry, requires this knowledge in the design phase. A closed-cell metal foam is studied using different analyzing methods where the aim is to collect information about the composition and geometry (structure) that is satisfactory for the later research. Using statistical methods microscopic, X-ray and surface analyzing studies on the specimens produced according to the concerning standard are evaluated. The main goal of this part of the project is to obtain structural information and to determine the homogeneity or the in-homogeneity property of the metal foam spec...

Intraosseous structural graft technique: a new surgical concept in the treatment of superolateral defects in case of dysplastic acetabulum, during hip replacement surgery biomechanical and cadaver experimentations

AbstractPurposeThe replacement of the dysplastic hip, despite the numerous available surgical techniques, is not entirely solved. One of the reasons for this is the relative lack of bone in the acetabulum. In this study, we present a new concept (intraosseous structural graft technique), with the aim to improve the primary stability and biological environment of the graft.MethodsDuring the procedure in the cranial quadrant of the acetabulum, a proximally hinged cortico-spongious plate is fashioned that is opened laterally and a wedge-shaped graft made from the femoral head is impacted. The precisely fitted graft has good primary rotational and cranial stability which is further improved by a bicortical screw.ResultsThe hypothesis is supported by examination on 3D models. Cadaver experimentations were performed on 19 hips of 10 cadavers, and stability testing was done on a further 20 hips of 10 cadavers with a material testing apparatus. Also the analysis of the biological and mechanical properties of the graft and the implant were examined.ConclusionBased on our results, it can be concluded that our technique provides good primary stability with a more favorable biological condition for bony incorporation compared to other bulk bone graft techniques.

Development and characterization of a new measurement technique for monitoring changes in acceleration during hippotherapy

Abstract The beneficial effects of hippotherapy lie in the transmission of the horses movements to the patient. The aim of our work was to create a measurement method for objective evaluation that can be used in natural settings without interfering with therapy. Methodology/Principal findings Our measurement system consists of three treble axis accelerometers connected to a data logger. Software was developed for data analysis and post processing. A commercial DVD recording camera was used to document the hippotherapy session. In this paper we present the results obtained in pilot measurements on ten children with cerebral palsy. For reference, a skilled rider was measured on the same horse using a passive following seat. Conclusions The acceleration diagrams show common characteristics useful to the interpretation of the movement transfer during hippotherapy as well as individual patterns indicating alterations in the movement reactions of different patients.