Biomedical subjects

H A Jacob

Publications and source records attributed to H A Jacob.

At least 19 recordsLinked to original sources

PubMed2001

[Functional anatomy and kinematics of the femorotibial joint. Results of research 1836-1950].

Ever since the investigations of the Weber brothers in 1836, on the mechanics of the walking implements of humans, several others, like von Meyer (1853), Langer (1858), Robert (1855), Albert (1878), Bougnion (1892), Fischer (1907), Zuppinger (1904), A.E. Fick (1877), R. Fick (1911), Strasser (1917), Tretter (1944), and Knese (1959), have presented a vast amount of literature on the kinematics and functional anatomy of the knee joint which continue to be a source of inspiration even for contemporary international research work. This literature has been reviewed and is now presented in short form, not only because of its historical value, but to stimulate further research activity in this field. Furthermore, possible application of the kinematics of the physiological knee joint in orthotics and prosthetics is indicated.

Biomechanical Phenomena↗

PubMed2001

[Significance of 3 dimensional motion of the femurotibial joint for design of knee support orthoses].

Stimulated by investigations on the kinematics of the human knee joint conducted during the nineteenth and early twentieth centuries, we have determined the spatial motion of this articulation, describing it by means of the helical axis concept, as obtained with the assistance of modern tools. As expected, there are similarities with the results of other recent investigators. Some details of the photogrammetrical method employed are unique. We have now related our findings to unsolved problems in orthotics and prosthetics. The presentation also describes a technique to align the movement of a brace with that of the knee joint. This work serves as a basis on which criteria for the fitting of braces could be determined.

Adult↗

PubMed2001

[Clubfoot orthosis with integrated dynamic cuff for retention and redressing].

Conservative treatment of clubfoot deformities with braces and bandages is traditionally several hundred years old. The clubfoot braces of Venel, Scarpa, and Schulthess, as well as the redressing bandage of Cheselden, are reviewed as typical examples. The treatment of clubfoot deformities was initiated in the Balgrist Hospital for Orthopedic Surgery by W. Schulthess. Recently, in Balgrist, we developed a brace that retains and redresses the foot. This brace is described, and early clinical results are reported.

Bandages↗

PubMed2001

Forces acting in the forefoot during normal gait--an estimate.

OBJECTIVE: To estimate forces acting along tendons and across the joints of the first and second rays of the forefoot during gait. DESIGN: Using recently published data on force distribution under the forefoot and relevant anthropometrical data, internal forces are calculated. BACKGROUND: It is of paramount importance to know the magnitude and direction of the forces acting within the most heavily loaded structures of the forefoot, especially when surgical treatment is envisaged. It can also be of major value in understanding the pathomechanics of certain disorders of the foot. As far as the author is aware, there is no such information presently available. METHODS: The ground force distribution during the second force peak of the stance phase was used with anthropometrical data (including lengths of lever arms of the tendons that cross the joints investigated) to determine conditions of equilibrium in the sagittal plane for each joint of the first and second rays. RESULTS: The flexor hallucis longus and brevis tendons exert about 52% and 36% body weight, respectively, and the peroneus longus muscle more than 58% body weight. The resultant force on the first metatarsal head amounts to about 119% body weight. The second metatarsal bone is subjected to a high bending moment with a resultant force of about 45% body weight acting on its head. The flexor digitorum longus and brevis forces are about 9% and 13% body weight, respectively. CONCLUSIONS: The high forces acting along the flexor tendons of the heavily loaded first ray support the so-called longitudinal arch of the foot. The second metatarsal bone is also heavily loaded, but more in bending. If the first ray with its powerful toe be deprived of its function, be it through muscular fatigue, disease, or trauma, the second metatarsal bone will probably also fail. RELEVANCE: Such information is necessary to understand the physiological function of the foot. It might also explain the development and manifestation of certain foot pathologies. Furthermore, it is of importance when considering surgical procedures in the treatment of forefoot disorders.

Biomechanical Phenomena↗

PubMed2001

Palmar tilt of the distal radius: influence of off-lateral projection initial observations.

PURPOSE: To evaluate the effect of slight off-lateral positioning of the wrist on measurements of the palmar tilt of the distal radius on lateral views and to determine how this effect can be corrected quantitatively. MATERIALS AND METHODS: Seven cadaveric forearms in neutral and various oblique positions (5 degrees, 10 degrees, 15 degrees, 20 degrees ) of supination and pronation were examined with lateral radiography. The palmar tilt of the distal radius measured on the radiographs was correlated with each position of the wrist and the distance between the position of the palmar cortex of the pisiform bone (P) and a reference point (point 0), which was defined as the midpoint within the interval between palmar cortices of the distal scaphoid pole and of the capitate head (P0 distance). The same measurements were performed on 11 wrists during arthrography. RESULTS: The apparent palmar tilt of the distal radius increased with supination of the forearm. Regression analysis with the P0 distance as independent and palmar tilt as dependent variables resulted in a slope of 0.95 in the seven cadaveric wrists and of 0.92 in the 11 wrist arthrograms. The squares of the correlation coefficients (R(2)) were 0.89 in cadaveric wrists and 0.69 in 11 wrist arthrograms. CONCLUSION: Differences in the palmar tilt produced by off-lateral projections of the wrist can be estimated from the measured difference of the P0 distance. A 1-mm difference in the P0 distance corresponds to a difference in the palmar tilt of approximately 1 degrees.

Adult↗

PubMed1999

8-year survivorship analysis and subjective results of 687 primary Balgrist hip sockets.

The Balgrist hip socket consists of an outer split ring in the form of a truncated cone, made of titanium, which is expanded by a tapered HDPE insert during implantation, thus ensuring firm primary press-fit and the possibility of retightening in the postoperative remodelling phase. Between November 1987 and October 1996, 687 primary Balgrist hip sockets were implanted in 555 patients. Five hundred and thirty-seven patients were investigated. Of these patients, 71.1% never had pain in the operated hip, 88.1% had no problems putting on their shoes, 76.2% were able to walk one or more hours. Furthermore, 91.7% are very or mostly content with the postoperative result. Nineteen hip sockets had to be revised until April 1997. With a 92.1% Kaplan-Meier survivorship rate after 8 years the Balgrist hip socket ranks among the most successful noncemented acetabular components.

Arthroplasty, Replacement, Hip↗

PubMed1998

Reconstruction of the first and second metatarsals with free microvascular fibular bone graft after resection of a Ewing sarcoma.

We report the case of a 12-year-old girl with a Ewing sarcoma originating from the first metatarsal of one foot. Because the girl and her parents refused amputation of the foot, we resorted to complete local resection and to reconstruction of the first and second metatarsals with a free microvascular fibular bone graft. At 3 1/2 years after surgery, the patient continues to walk without a limp, and the mechanical function of the forefoot has been largely restored, although considerable loss of function of the big toe is apparent. Details of the surgical technique and tumor management are described.

Bone Neoplasms↗

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↗