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Biomedical subjects

H A Jacob

Publications and source records attributed to H A Jacob.

At least 19 recordsLinked to original sources
PubMed1996

The mobility of the sacroiliac joint in healthy subjects.

A three-dimensional stereophotogrammetric method is described for measuring the mobility of the sacroiliac joint, which was based on preliminary two-dimensional in vitro experiments. The investigations were carried out with intraosseous markers in 24 healthy volunteer male (15) and female (9) subjects having an age range of 20 to 50 years. Considerable intra- and inter-individual variability was found for both the measurements of rotation and translation. The position and direction of the movement axes showed wide variations, but a basic pattern could always be recognized. The average values for rotation and translation were low, being 1.8 degrees / 0.7 mm for the males and 1.9 degrees / 0.9 mm for the females. No statistically significant differences could be demonstrated with respect to either sex or age. On the basis of the measurement results, it is postulated that there is pathological sacroiliac joint movement when rotation is more than 6 degrees and translation more than 2 mm. This increased mobility seems to be of greater clinical significance than reduced mobility.

Adult↗
PubMed1996

The Balgrist hip socket for fixation without cement: analysis of 387 primary total hip replacements.

The results of 387 primary hip arthroplasties in which an uncemented Balgrist hip socket had been used in 346 patients were reviewed after a maximum of six years. The mean age of the patients at the time of operation was 54.3 years. Acetabular deficiency according to the AAOS classification was found in 21% of these primary arthroplasties. Three acetabular components (0.77%) had been revised. Using Kaplan-Meier survivorship analysis, with the use of prosthesis revision as the endpoint of failure, the survival rate at five years was found to be 99%. Four acetabular components (1%) had migrated and lysis of bone around the component in zone III occurred in one patient (0.26%). The data suggest that the unique socket design of the Balgrist hip socket (consisting of two tapered parts: an expansive outer titanium-alloy split ring and an insert of polyethylene) provides very satisfactory clinical results with various acetabular defects.

Adolescent↗
PubMed1995

Physical equilibrium of the normal wrist and its relation to clinically defined "instability".

The rotational stability of the proximal carpal row was tested on six unembalmed human cadaver hand specimens. The physiological load conditions were stimulated by loading the wrist flexor and extensor tendons. Pure torque was introduced to the lunate, scaphoid and triquetrum, one at a time, by means of a dynamometer wrench, forcing the bones loaded to perform a flexion-extension motion. A truly stable state of equilibrium could be found in the normal wrist only under axial load. A uni-directional coupling was observed through the scapho-lunate ligament as a counteraction to a tendency for the lunate to extend and the scaphoid to flex. The triquetrum and lunate moved together, showing close coupling in both directions. As conclusion: a stable wrist can be defined as one which, while being loaded within a physiological range of stress, does not deviate from a stable state of equilibrium (the ability to return to a single position when disturbed) at any point within the whole physiological range of motion.

Carpal Bones↗
PubMed1994

The palmar wrist ligaments revisited, clinical relevance.

In fifteen cadaver wrists and ten foetus wrists palmar ligaments were studied. As a result, the palmar scapho-triquetral ligament was presented by means of gross anatomical study, MR imaging, and histological study. A kinematic study was conducted on three cadaver wrists to analyze patterns of motion on the proximal carpal row bones based on the helical axis concept. Motion analysis showed that the scaphoid has a set of helical axes bundled at the radial side of the wrist. On the contrary, the triquetrum had axes bundled on the ulnar side, approximately in the same position as the lunate. That shows that the lunate and triquetrum are coordinated in motion and opposed to that of the scaphoid. The structure possibly ruling this pattern of motion could be the palmar scapho-triquetral ligament, whose insertions on the scaphoid and triquetrum are close to the crossing-point of the helical axes of the scaphoid and triquetrum/lunate, respectively. In order to study the clinical relevance of our findings, a prospective clinical study on 53 patients after wrist injury was conducted. All patients were clinically examined, simple and semi-stress X-rays were taken, and arthrography and arthroscopy performed. Ligament tears were often found, but any correlation to clinical findings or arthrography could not be found. However, high correlation could be found between the lesion of the palmar scapho-triquetral ligament and a DISI position of the lunate combined with increased scapho-lunate angle. It can be concluded that the tear of the palmar scapho-triquetral ligament causes instability pattern that is radiologically evident at an early stage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

[Foot problems in the elderly].

Foot problems in the geriatric patient are multiple and sometimes complex. The choices in treatment are frequently restricted because of contraindications for surgery. Common foot problems are common in the elderly patient, too, but in addition there is a specific pathology of this group of patients. Inexpensive, but institutionalized routine foot care is an essential medical need of the elderly to improve the quality of life.

Aged↗
PubMed1994

The Balgrist hip socket for cementless fixation in primary total hip replacements and in acetabular revisions.

The results of 532 hip arthroplasties in which an uncemented Balgrist hip socket had been used in 387 primary total hip replacements and in 145 acetabular revisions were reviewed after a maximum of six years. The socket consists of two tapered parts, namely an expansive outer titanium-alloy split ring and an insert of polyethylene. The mean age of the patients at the time of operation was 54.3 years in primary hip replacements, and 64.7 years in acetabular revisions. Acetabular deficiency according to the AAOS classification was found in 21% of the primary arthroplasties, and in 80.7% of the acetabular revisions. Using Kaplan-Meier survivorship analysis, with the use of prosthesis revision as the endpoint of failure, the survival rate at five years was 99% in primary arthroplasties, and 88.7% in acetabular revisions. Our data suggest that the unique socket design of the Balgrist hip socket gives very satisfactory clinical results not only in primary hip replacements but also in acetabular revisions even with various acetabular defects.

Adolescent↗
PubMed1993

Kinematic analysis of relative motion within the proximal carpal row.

The motions of the scaphoid and triquetrum relative to the lunate have been studied on cadaver specimens. The helical axis concept was applied. The wrist motions performed were flexion-extension and radial-ulnar deviation. The results showed increased relative motion of the scaphoid towards terminal extension, and to a lesser amount in the case of the triquetrum, towards terminal flexion. The lunate might be considered as a keystone in the proximal carpal row when wrist stability is considered. It is doubly intercalated: longitudinally and transversely. Wrist ligaments co-ordinate the positioning of the bones in the mid-range of carpal motions, and restrict further motion in extreme positions of the wrist joint.

Cadaver↗
PubMed1993

Kinematics of the wrist and its ligaments.

Precise anatomic dissections of unembalmed physiologically intact cadaver specimens were carried out before proceeding with the kinematic investigations on further specimens. Carpal flexor and extensor tendons were used to move the wrist. The analysis of the carpal bone movements was performed according to the finite helical axis motion concept for increments of 10 degrees for each main carpal motion. Separate axes of rotation for each of the bones in the proximal carpal row were found; however, the axes for the lunate and triquetrum bones were close, and the magnitudes of rotation and translation almost equal. One finding was that the axes of rotation of the bones in the proximal carpal row often cross at some particular point. Because the axes of the scaphoid are differently oriented than those of the lunate and triquetrum, shear might occur during wrist motion. This indicates also that the scaphoid and lunate cannot be considered rigidly coupled elements. We also assume that the individual bones of the proximal carpal row self-align themselves as long as they are not constrained by torsion. Several potential mechanisms of flexion motion of the proximal carpal row during radioulnar deviations of the hand were considered. The ligament function is still an unsolved problem. Compensation mechanisms may mask clear correlations between a lesion and the instability pattern associated with it. The proximal carpal row should be studied as one system.

Cadaver↗
PubMed1993

[Radio-carpal and medio-carpal arthroscopy in instability of the wrist].

Forty-one arthroscopies were performed on previously asymptomatic wrists following trauma. In about 25% of the wrists there was only one specific ligamentous lesion. In 75% however a combination of 2 or several distinct lesions was observed. These lesions, localised on the ulnar aspect of the mid-carpal joint, are more complex than those on the radio-carpal joint on the radial aspect of the carpus. These observations would tend to confirm our present day knowledge of wrist biomechanics but disagree with the currently proposed concepts of instability by several American authors. "Instability" seems to be inadequate to define complex lesions, more adequate would be the simple description of a "dysfunctional state" of the wrist complex. This statement must be related to the position of the carpal bones, which do not show any significant change despite the tears shown. The arthroscopy appears to range first in a series of diagnostic tools. However it concerns mainly the ligamentous layers facing the interior of the joint while lacking information about time elapsed since the actual trauma. We therefore state that arthroscopy may decrease but not exclude diagnostic failures. Type and risk of therapeutic decisions are also appreciated with increased accuracy. No doubt there still remain discrepancies when clinical, arthrographic and arthroscopic examination are compared, which indicates the complementary nature of the technics of investigation, especially in the light of the current state of the biomechanic sciences of the wrist.

Adolescent↗
PubMed1993

The self-locking Balgrist hip socket for cementless fixation: biomechanical principles and clinical results.

The Balgrist hip socket, initially made entirely of HDPE (high molecular weight polyethylene), now made of outer titanium alloy shell that faces the bone of the acetabulum has been in clinical use for 10 years. The purpose of this presentation is to illustrate the biomechanical principles that have governed this unique design and to present the clinical results that we have obtained until the end of 1991 with 717 implants. From 1982 to 1987 Balgrist HDPE sockets had been implanted for 346 hips, from 1984 to 1991 Balgrist Titanium alloy sockets have been implanted for 371 hips. The number of revision are 55 of 717 hips. 48 hips out of 55 were with Balgrist HDPE sockets. On the contrary, only 7 hips were with Balgrist titanium socket. The greatest benefit of Balgrist Titanium socket is the excellent mechanical lock with subchondral bone of the acetabulum.

Biomechanical Phenomena↗
PubMed1993

Long-term results with the uncemented thrust plate prosthesis (TPP).

The long-term clinical results of a novel concept for total joint replacement called the Thrust Plate Prosthesis (TPP) are presented. Only a restricted number of patients were provided with this new prosthesis (115 at the Orthopedic Department, Canton Hospital, Chur, and 47 at the Department of Orthopedic Surgery, University of Zurich). All patients have undergone clinical and radiological follow-up covering a period from 1980 to 1991. The basic feature of the Thrust Plate Prosthesis is the direct load transfer to the medial cortical bone of the femoral neck, and this has been unchanged since 1978. Titanium alloy has been used since 1986. The good clinical and radiological results are confirmed by a histological examination of an 8-year-old implant: In the crucial area of load transfer newly formed bone can be seen in direct contact with the thrust plate without fibrous tissue in between. The clinical results and histological findings have confirmed the validity of the biomechanical principle of the TPP. The TPP is therefore to be considered a true alternative to the conventional hip prosthesis. In contrast to the conventional intramedullary anchored stem prosthesis the TPP requires the removal of a minimum amount of bone stock, which is certainly important in young patients.

Adult↗
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↗