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Biomedical subjects

H A Jacob

Publications and source records attributed to H A Jacob.

At least 37 records · Page 2Linked to original sources
PubMed1993

[Arthrosis of the wrist joint due to carpal instability. Therapeutic alternatives].

A kinematic analysis of the movement of the scaphoid, the lunatum and the triquetrum has shown that their turning axes do not correspond with each other. Without arthritis, and within the range of normal motion, the bones move without imposing any appreciable load on the ligaments. They merely guide the bones and hold them together. In the case of arthritic disorders and in states where abnormal frictional resistance occurs, or following trauma, the ligaments are highly loaded. This could lead to increased wear and ruptured ligaments. A series of 20 arthroscopies has shown that LT and SC ligaments are very prone to this, and are often affected simultaneously. Therefore, there may be certain predisposed sites or "weak points", which should definitely not be further aggravated by inappropriate therapeutic measures. The clinician can classify the carpal dysfunction into five main groups; however, the therapy options cannot be classified in the same way. On the basis of clinical experience and the kinematic study, the following statements can be made: scapho-lunatum (SC) arthrodesis can be considered kinematically unsuitable, while scapho-capitatum (SC) and lunato-capitatum (LC) arthrodeses are both clinically and kinematically acceptable. LC arthrodesis has given good results in cases with advanced carpal collapse. From a mechanical point of view, SC arthrodesis is probably better than scapho-trapezo-trapezoid arthrodesis. In the case of ulnar translocation, radio-ulna-to-scaphoid arthrodesis could be an acceptable alternative to total fusion. Proximal row carpectomy can only be a temporary solution, as can prostheses. Partial prostheses, whether of Silastic or titanium, are also not suitable for permanent use.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

[Biomechanics of the foot--forces in the forefoot during walking and their clinical relevance].

Pathologic conditions of the toe and metatarsophalangeal (MP) joints, such as the commonly encountered hallux valgus but also the relatively rare idiopathic necrosis of the metatarsal heads (Freiberg-Koehler's disease) and many other disorders of the foot, call for precise investigation of the kinematic and dynamic behavior of the foot during walking. The success of surgery performed on bone or soft tissues in the forefoot depends on an understanding of the biomechanics of the region. Therefore, the plantar forces acting under the metatarsal heads of the 1st, 2nd and 5th rays and under the pads of the 1st and 2nd toes were measured during walking, so that with the aid of anthropometric information pertaining to the forefoot, reaction forces in the flexor tendons and in the joints could be estimated. Particularly evident was the large share of the load taken by the big toe. This necessitates correspondingly high tension forces in the flexor tendons of the 1st ray, which simultaneously have the function of supporting the longitudinal arch of the foot. Because of this, the 1st metatarsal bone is loaded mainly in compression. In sharp contrast to this, the 2nd metatarsal bone is heavily loaded in bending, similar to a cantilever that is firmly held at its base. The high bending stress, especially when the 1st ray is no longer taking its share of the total load, leads to fatigue or march fractures, typically in the shank of the bone. A possible explanation for the pathogenesis of locally restricted necrosis of the metatarsal heads (Freiberg-Koehler's disease) is suggested and, finally, the question of dislocation of the base of the 2nd toe in the MP joint is discussed.

Adult↗
PubMed1992

[Biomechanics of the carpus--functional anatomy and movement analysis of the carpal bones].

The often unsatisfactory outcome of attempts to reconstruct ligaments and perform partial arthrodeses of the wrist bones has prompted us to investigate the kinematic behavior of the proximal row of carpal bones in their immediate environment. The movements of the individual bones were observed on fresh autopsy specimens before they were dissected to study the exact location of the interconnecting ligaments. Finally, a special model of epoxy resin was made in which the exact form of the joint surfaces (cartilage surfaces) was maintained. The ligaments were simulated by means of stout threads and, according to the observations recorded in the previous study, attached to the model bones. In this manner a working model resulted that not only proved the correct positioning of the ligaments, but also enabled their function in controlling the movements of the bones during dorsal-palmar flexion and radial-ulnar abduction of the wrist to be established. It was seen that movement of the proximal row of carpal bones is caused primarily by the orientation of the adjoining articular surfaces and limited by the ligaments. Therefore, it is of paramount importance that the friction at the joint surfaces remains as low as possible. If the friction increases, the "floating" bones can no longer slide under load and movement of the hand becomes limited.

Biomechanical Phenomena↗
PubMed1991

The effects of morphology and histopathologic findings on the mobility of the sacroiliac joint.

The sacroiliac joints of seven pelvic specimens were examined to determine functional, morphologic, and histopathologic aspects. The movements were measured in four intact pelvises (from two men and two women). The joint surfaces of all pelvises (from three men and four women) then were examined topographically by means of a photogrammetric method. After this, they were examined histologically to characterize any effects on function. The morphologic investigation revealed sex-specific differences. All joint surfaces from the female pelvises showed circular contours, the centers of which coincided with the iliac tuberosities. These morphologic characteristics were not discernible in the joint surfaces from the male pelvises; these had interlocking irregularities without a topographic pattern. As expected, this configuration involved distinct differences in mobility. Rotation of the sacrum was markedly less in the sacroiliac joints of men than in those of women.

Cadaver↗
PubMed1989

[Experiences with the "Balgrist" cement-free, self-anchoring conical acetabular prosthesis--March 1982 to September 1988].

The advantage over other acetabular sockets for cementless fixation lies in the easier preparation of the acetabulum without endangering neighbouring structures, and in its self-locking ability which ensures firm fixation in the surrounding bone during the critical period of bone-remodelling which occurs during the first three months postoperatively. In over 90% of the 414 sockets, implanted over 6.5 years, with an average follow-up period of four years (3 to 78 months), we have had, clinically and radiologically, good results. Loosened sockets (3.6%) were observed with those made of polyethylene during the early stages mainly due to inadequate experience in implanting them. The titanium model which has been exclusively used from november 1987 has shown no signs of instability neither in the case of primary or revision sockets.

Acetabulum↗
PubMed1989

[Could biomechanical factors affect the etiology of Morton's neuralgia?].

In the literature mechanical factors are considered as the most frequent etiology of Morton's disease. The pathology is a classical progressive fibrosis with rupture of nerve "fascicules" and/of arterioli, without nerve proliferation and without specific inflammatory factors. The deep intermetatarsal ligament and the bursae between the metatarsal heads are probably the most important factors in nerve irritation. In the literature there are few precise descriptions of the mechanism of irritation of the nerve, either by the bursae between the metatarsal heads, by the deep intermetatarsal ligament, or by the tendons of the lumbrical muscles which are close to the nerve. The aim of this study is an analysis of the mobility of these structures in both planes, by radiological evaluation in the erect position, after implantation of radiopaque pellets. The authors also present an hypothesis on the mechanism of the lesion.

Biomechanical Phenomena↗
PubMed1986

Percutaneous nucleotomy. An alternative to spinal surgery.

As an alternative to the well-established surgical procedures for the treatment of disk herniation, percutaneous nucleotomy has proved to be very satisfactory. In several cases this approach has brought complete relief to the patient without sacrifice of bone and without causing soft tissue damage as would have been inevitable with the usual surgical methods. Percutaneous nucleotomy is also a true alternative to chemical nucleolysis when leakage of contrast agent into the spinal canal has already been observed during diskography. Furthermore, this method avoids disagreeable complications encountered in chemical nucleotomy, for example, anaphylactic shock or the escape of the nucleolytic agent into the spinal canal. The method basically consists of removing the nucleus pulposus (or a major part of it) by means of a forceps that is introduced to the site through a cannula. In this manner a reduction of volume of the disk is achieved. The procedure can easily be carried out under local anesthesia. This method should be avoided in the case of prolapse within the spinal canal and especially when displacement beyond the level of the disk has occurred. In the period between 1979 and 1985 we carried out percutaneous nucleotomies in 51 patients with herniation mostly combined with a narrow spinal canal or spondylolisthesis. The clinical results from 32 of 51 patients can be assessed as very good, good, or satisfactory. We consider the proportion of patients showing good clinical results to be high, bearing in mind that the indication was not just disk herniation alone but, in most cases, combined with other lumbar pathologies as well.

Adult↗
PubMed1986

Lumbar and thoracic spinal fusion with transpedicular fixation (including a novel distraction and compression device). A preliminary report.

Experience with three different systems of transpedicular fixation in fusion of the lumbar and thoracic spine over 4 years is reported. The Roy-Camille plates, Louis plates, and the Balgrist turn-buckle arrangement are compared. The Balgrist device allows both extension and compression, and affords better stability. Far better clinical results were obtained with transpedicular fixation in general than with the Harrington method.

Adolescent↗
PubMed1984

Loosening of the femoral component of the ICLH double cup hip prosthesis. A biomechanical investigation with reference to clinical results.

The cancellous bone in the proximity of the rim of the ICLH femoral cup may not only be subjected to an axial stress that is about three times the value physiologically encountered, but the cup also tends to move transversally away from the medial bone margin in this area. Hence, fracture of the trabecular structure in this area can occur, accompanied by cleavage formation. Across the gap which thus forms between cement and bone, the mating surfaces that are now no longer joined, probably move relative to each other with every subsequent walking cycle. This relative motion leads to bone resorption and the development of a thick intermediate layer of fibrous connective tissue that spreads until eventually the whole cup becomes loosened. In the meantime the bone further proximal probably undergoes atrophy due to mechanical inactivity. This presentation includes a biomechanical analysis which might explain the discouraging observations made in a series of forty-three implantations carried out between 1976 and 1979 in our clinic.

Adult↗
PubMed1983

Surface replacement hip arthroplasty with the Freeman double cup.

The authors report their clinical experience with 43 hip arthroplasties using Freeman's double femoral cup. The patients were followed up from 3 to 6 years after operation. At that time, only 44% were totally free from pain, while migration of the femoral cup, which was severe and progressive, was observed radiographically in almost half the cases. In 3 cases it was possible to study histologically the stump of the neck of the femur and the zone of contact between femoral bone and cement. Biomechanical studies were also performed with photo-elastic models, using the technique of finite elements. These studies indicated overloading on contact between the edge of the femoral cup and the cortical bone (especially medially), but without any load over the whole of the spongy bone. Consequently there was bone resorption in the overload zone and osteoporosis in the spongy bone. The femoral cup rapidly became unstable, and this produced progressive migration, thus constituting a vicious circle.

Biomechanical Phenomena↗
PubMed1981

A comparison of the long term results of three types of posterior fusion of the lumbar spine for spondylolisthesis.

Between 1923 and 1976, 312 posterior spinal fusions using the methods of Albee, Bosworth and Hibbs were performed on patients with spondylolisthesis at the Orthopaedic University Hospital Balgrist, Zurich. Long-term clinical results were rated as good in 80% of all patients operated on with the Albee method. The results after the Hibbs procedure on the other hand was good in only 65%. Progressive vertebral slipping after operation was seen in about 60% of all patients operated on by Albee's method, particularly in cases with severe spondylolisthesis. This slipping stops as soon as the intervertebral space had fused. Relief of the subjective symptoms also occured at this time. This phenomenon was only rarely seen after the Hibbs operation, in which the better postoperative stability leads to sclerosis of the discs indicating degenerative changes without a significant decrease in the disc height. The greater stability of the Hibb's fusion is more easily overstressed by body movements which can cause persistent symptoms and later lead to fatigue fractures.

Adult↗
PubMed1981

[Wear measurements of hip prostheses with UHMW polyethylene (RCH-1000) socket and chromium plated protasul-10 head (author's transl)].

An estimation of wear was carried out on 100 of 340 UHMW polyethylene sockets (RCH 1000) that were implanted with Protasul-10 prostheses furnished with a chromium plated head. This was effected by measuring the position of the head relative to the socket as seen on radiographs during a follow-up period of 4 years. The method employed was verified in 3 cases (in which the socket had been removed) by measurements on silastic casts of the bearing surface. Practically no difference in the results was observed. The average wear rate amounted to 0.16 mm/year over an observation period of 4 years. Furthermore, it has been observed that para-articular calcification seems to be independent of the amount of abrasive debris present. It seems rather to depend on other factors, such as the size of the haematom, degree of muscle necrosis, etc.

Aged↗
PubMed1981

[Biomechanical examination of stress distribution in the femoral neck for varus-implanted and valgus-implanted cups (author's transl)].

The contents of this contribution pertain to the above mentioned article of Gerngross et al. The problem of fracture propagation is indeed of very local character, limited either to the discontinuity in the immediate neighbourhood of the cup lip or to the notch accidentally formed in the femoral neck by the milling cutter during surgery. Strain measurements performed far removed from the area of stress concentration do not bear sufficient evidence to support the conclusions drawn. The presentation of results is misleading because a comparison of stress or strain within the bone at chosen moments during the walking cycle is valid only if the relevant loading conditions, with respect to direction as well as magnitude, are applied. Finally, the description of the strain measurement and evaluation procedure is inadequate and questionable.

Biomechanical Phenomena↗