Biomechanical Comparison of the Roof Step Cut Technique with the Bulk Bone Graft Technique During Total Hip Arthroplasty for Hip Dysplasia: a Finite Element Analysis.

PURPOSE OF THE STUDY Different techniques have been reported to reconstruct the defi cient acetabulum during total hip arthroplasty (THA). The purpose of this study was to compare the biomechanical features of the bulk bone graft (BBG) technique (Harris acetabular plasty) and the Roof Step Cut (RSC) technique using fi nite element analysis. MATERIAL AND METHODS Based on a female patient's dysplastic hip CT scan, 3D models were assembled according to the two techniques. For the Harris technique, an irregular BBG was sculpted from a solid sphere, while for the RSC technique, the graft was sculpted into a step-cut shape with a similar size. Each graft was fi xed with two compression screws at two different angles (0° and 45°). Four fi nite element models were used to compare the von Mises stress distribution and total deformation of the grafts and the screws. The pressure and sliding distances of the contacts between the bone graft, metal cup and acetabular host bone were also analyzed. RESULTS For both of the bone grafts and the screws, compared to the Harris models, the maximum stress of the RSC models was signifi cantly lower (16.56 MPa, 25.50 MPa vs 97.13 MPa, 112.72 MPa) and the total deformation was signifi cantly smaller (0.0096 mm, 0.0089 mm vs 0.022 mm, 0.018 mm). 45° inserted screws generated higher stress at the end of the screws and on the outside of the bone graft. In case of 0° inserted screws, the maximum value was mainly located in the middle of the screws, inside the screw channel as well as at the contact area between the graft and the host bone. At all analyzed contacts, the RSC technique shows signifi cantly lower pressure and sliding distances, irrelevant to the screw's insertion angle. In comparison, the model of BBG with 45° screws showed a signifi cant sliding effect and higher contact pressure. CONCLUSIONS Compared with the BBG technique, the step-shaped graft of the RSC technique could signifi cantly reduce the maximum stress and deformation of the graft and the screws, and decrease the pressure and sliding distance between the bone graft, metal cup and the acetabular host bone. The angle of screw placement affects the location of stress and deformation. Key words: developmental dysplasia of the hip, total hip arthroplasty, acetabular reconstruction, bone graft, fi nite element analysis.

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.

PURPOSE: The 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. METHODS: During 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. RESULTS: The 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. CONCLUSION: Based 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.

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

INTRODUCTION: Removal 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 METHODS: The 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). RESULTS: In 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. CONCLUSION: Retrograde component removal provides a simple, rapid, and less invasive technique for stem and cement extraction in elective revision hip arthroplasty.

The most severe forms of Perthes' disease associated with the homozygous Factor V Leiden mutation.

It has recently been postulated that thrombophilia may have a role in the aetiology of Perthes' disease. The published reports, however, remain conflicting. In this study a retrospective analysis of the coagulation parameters was made in 47 patients with Perthes' disease and the results compared with the clinical data. Five patients with Factor V Leiden mutation were found (10.6%) and surprisingly four of them had a homozygous pattern. These four patients showed the most severe form of the disease, Catterall group IV, with flattening of the entire epiphysis, involvement of the metaphysis, shortening and broadening of the femoral neck, trochanteric overgrowth and developed mushroom-shaped aspherical laterally displaced femoral heads in dysplastic acetabula. We would like to suggest that the homozygous form of Factor V Leiden mutation has some role in the clinical course of Perthes' disease and particularly its most severe form.

Contradictions of derotation in scoliosis surgery using the CD principle.

Current literature has increasingly emphasized the problem of derotation in scoliotic deformities. The Cotrel-Dubousset (CD) principle as a means of correcting rotation has been questioned by various authors. This paper aims to draw attention, using algebraic methods, to the importance of the remaining rotational deformities, and to suggest the introduction of the notion 'rotational balance'.

The 'rotational preconstraint'.

This model provides a novel view of the etiology of some scolioses and can answer some of the biomechanical questions regarding pathogenesis of dorsal curves. According to our findings, paravertebral muscular imbalance is likely to favour such a pathological condition which, with the interference of the postural reflexes and the body weight-related vertical loading, might lead to the formation of a true scoliotic curve. Review of earlier research studies in the light of our findings reveals controversy in some authors' reported results and their own interpretations and seems to generally support our theory.

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. Wagner's and Ilizarov's 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.

[Results in Miacalcic therapy in the analgesic treatment of patients with bone metastases]. / Miacalcic kezeléssel elért eredményeink a csontmetastasisos betegek fájdalomcsillapításában.

Authors have administered between 1984--87 in 30 patients with bone metastasis weekly 3 X 100 iu Miacalcic injections to relieve pain. The literature dealing with the pain relieving effect of calcitonin is summarized and their own results are assessed from more viewpoints. The use of Miacalcic injection is suggested as it was found a modern and very effective palliative medicine for pain relieving.

[Experience with the implantation of porous coated hip endoprostheses and primary stability of implantation]. / Tapaztalataink porosus bevonatú csípöprothesis beültetési technikájával és a beültetés primer stabilitásával.

The use of porous coated cementless prosthesis, shows a worldwide spread in consequence of the advantages given by the "live" connection between the implant and the bone. Based on 40 implantations of prostheses of this type (Duraloc 1200 acetabulum, AML shaft) authors report on the technique of the implantation and the primary stability reached. In consequence of the formation, the variety of size and the properly usable instruments for implantation, the prostheses could be used for every kind of deformed, dysplastic hips and good primary stability was reached in every case operated.

[Synovial chondromatosis of the knee joint]. / Térdízületi synovialis chondromatosis.

Authors removed more than hundred free bodies from the knee joint of a young female patient. In connection with their case the criteria of the synovial chondromatosis, the theories concerning the pathogenesis and the therapy to be chosen are described, based on literary data.

Acute arthroscopy.

The role and significance of acute arthroscopy have been evaluated in the treatment of knee joint injuries on the basis of findings during 59 arthroscopic operations which were conducted within two weeks after the accident. The injuries developed isolated in more than half of the cases (65%) whereas they appeared in a combination of two or more in 26% and in 9%, respectively. Injuries requiring operation were found in 91.5%, most of which were ruptures of the ACL (33 cases) and menisci (23 cases). In the case of ACL rupture, in the acute phase on sportsmen and physical workers primary arthroscopically assisted transligamental replacement was performed with patellar graft while in the case of proximal rupture of the ACL reinsertion and augmentation were carried out with semitendinosus tendon. The ruptures of dislocated eminentia were refixed in each case. In the case of the rupture of meniscus the refixation of the meniscus of resection of the ruptured part was attempted. By means of acute arthroscopy the lesion of the intraarticular structures or that of their combinations can be exactly diagnosed. Depending on the findings of arthroscopy the injuries can be treated immediately or operated on at a later time, thus preventing the joint from further deterioration.

Therapeutic value of continuous passive motion after anterior cruciate replacement.

The aim of this study is the evaluation of the therapeutic value of continuous passive motion after ACL replacement. After 41 ACL reconstruction in 13 cases only active motion, in 28 cases active motion and CPM were used postoperatively. Stability, the range of motion and complications were evaluated at the time of discharge, 3 and 6 months after the operation. The flexion-extension in the CPM group was significantly greater at the time of discharge, but this difference was practically eliminated in 6 months after the operation. There were not any other significant difference between the two groups. The CPM gives only a little advantage in the rehabilitation after the ACL replacement.

Functional improvement after knee arthroplasty without resurfacing of patella.

There has been no universal agreement so far regarding the necessity of patellar resurfacing in total knee arthroplasty. As resurfacing has been reported to be associated with high incidence of complications, this practice has been avoided in our Department. A report is given on the analysis of the functional outcome of 60 knee arthroplasties without patellar resurfacing in 53 patients (7 bilateral) followed up for twelve to thirty months, with special regard to the functions closely related to patelloformal articulation. The underlying diagnosis was osteoarthritis in 78.3%, rheumatoid arthritis in 13.3%, and posttraumatic arthritis in 8.3% of the patients. Graded according to the modified knee-rating system of the Hospital for Special Surgery, excellent or good results were obtained in the case of 55 knees (91.6%) and the mean score improved from 53.6 points preoperatively to 82.6 points following arthroplasty. Subjective and objective functional assessment of stair climbing and transfer activities have shown no functional deficit attributed to the patellofemoral joint of the replaced knee.

Experimental studies for the surgical correction and fixation of dorsal spine deformities.

One of the specific features of the scoliosis operations with a posterior approach is that both the correction of the deformity and then the maintaining of the corrected situation are carried out with the help of the implants. With the currently applied systems based on the CD principle it is still difficult to control the rotational component of the scoliotic curve. To complement the systems based on the CD principle, we have developed an implant family whose application makes the correction of the dorsal deformity generally simplier and derotation more effective. Our method is based on the application of such hooks which, linked to the longitudinal rods and hooked on both transverse processes of the instrumented vertebrae, transmit the concerted forces exerting their influence in the direction of the correction. Depending on their symmetrical relations, the hooks are capable of tilting in the frontal plane and derotating in the horizontal plane simultaneously, in the direction of our choice. The stability and applicability of the hooks were tested in implants into cadavers, and then the intimate relations of the implants were examined by means of radiological tests and dissection on instrumented specimens. On the basis of our results, the implants can already be used in clinical practice.