[Dynamic stability of the glenohumeral joint. A biomechanical study]. / Die dynamische Stabilität des Glenohumeralgelenks. Eine biomechanische Untersuchung.

Stability of the glenohumeral joint with an anterior, posterior and inferior displacement force of 50 Newton was measured in a dynamic shoulder model. Controlled hydrodynamic actuator forces were applied to the deltoid muscle and to the rotator cuff in seven anatomic specimens. During elevation of the arm, the position of the humerus was measured with a six-degree-of-freedom ultrasonic sensor device. The rotational center of the humeral head was used as reference point for translation. A displacement force of 50N led to significant humeral head displacement anteriorly and posteriorly, but not inferiorly. A 50% reduction of rotator cuff forces increased anterior displacement by 46% and posterior displacement by 31%. Venting of the glenohumeral joint space and of the subacromial bursa resulted in a 50% increase of anterior displacement, a 19% increase of posterior displacement and in significant inferior displacement. This study demonstrates that, in addition to passive stabilizers and negative intraarticular pressure, rotator cuff force significantly contributes to stabilization of the glenohumeral joint during arm motion. Muscle strength and coordination should gain more emphasis in the diagnosis and treatment of shoulder instability.

[Improved radiological imaging of acetabular screw socket]. / Verbesserte radiologische Darstellung von Hüftschraubpfannen.

The improved radiological representation of the cementless acetabular screw-socket at two levels is of fundamental importance for the postoperative determination of position as well as for the judgement of an aseptic loosening. To improve the radiological representation two special radiographic techniques in the anterior-posterior as well as in the axial view have been examined on a human preparation of pelvis and have been scrutinized on a great number of clinical patients. The a.-p. radiography with twenty degrees cranio-caudal prone view in the sagittal plane and the axial radiography with forty-five degrees caudo-cranial prone view in the coronal plane shows the best and fewest overlayed representation of the screw-socket. The position of inclination and anteversion could have been directly determined out of these two radiographs. Malpositions of the screw-socket, especially with regard to the anteversion are easily identifiable due to the special axial radiographic technique. Overprojection of adjoining bone areas, which were possible should be considered at the judgment of the implant-bone-contact. Radiographic technical and positioning problems were not observed in patients. Out of these examinations the a.-p. radiography with twenty degrees cranio-caudal prone view in the sagittal plane and the axial radiography with forty-five degrees caudo-cranial prone view in the coronal plane could be recommended to the radiological diagnosis after implantations of hip prosthesis.

[Intertrochanteric flexion osteotomy and allo-arthroplasty in femur head necrosis. A comparative retrospective study]. / Intertrochantäre Flexionsosteotomie und Alloarthroplastik bei Femurkopfnekrose. Eine vergleichende retrospektive Untersuchung.

Intertrochanteric flexion osteotomy and total hip arthroplasty are the most frequent operative treatments of advanced osteonecrosis of the femoral head in adults. In a retrospective study the postoperative results of intertrochanteric osteotomy and total hip arthroplasty were determined in 68 cases. The evaluation was based on the modified Harris-Hip-Score, the clinical examination and the radiological classification of the ARCO. The patients after osteotomy showed significantly worse subjective results. After osteotomy an increase of the stage of osteonecrosis was found in 73% of the patients. There was no correlation between clinical result and radiological stage of osteonecrosis. In spite of a better preoperative situation the results after osteotomy compared to hip arthroplasty were disappointing in many cases. The postoperative result did not depend on the preoperative stage of the osteonecrosis. The new classification system of the ARCO, which includes the very important MRI, proved to be very suitable and practicable. Based on our results it seems to be reasonable, to restrict the indication for intertrochanteric flexion osteotomy to cases of low stage osteonecrosis and carry out cementless total hip arthroplasty primarily in all others.

[Ultrasound imaging of congenital knee joint dislocation. Value in diagnosis and therapy]. / Die sonographische Darstellung der kongenitalen Kniegelenksluxation. Stellenwert in Diagnostik und Therapie.

Congenital dislocation of the knee is a uncommon malformation. Frequently there is an association with other congenital deformities including congenital dislocation of the hip. The classification of Leveuf and Pais into three separate groups (Type A, Type B, Type C) is now widely accepted. Between October 1989 and April 1995 we evaluated ten children (five girls and five boys) with twelve dislocated knees. Clinical, radiographic and different ultrasonography examinations were carried out on both knees. The sonographic classification showed Type A in 3, Type B in 5 and Type C in 4 cases. The sonographic examination revealed the essential anatomic structures and their pathomorphology. The anterior and the posterior cruciate ligament could be demonstrated in the majority of the cases. Three dislocated knees showed an obliteration of the recessus suprapatellaris and fibrotic changes in the m. quadriceps. These cases required operative treatment. With conservative treatment we achieved a satisfactory result in eight children with nine disease knees. There was a good functional result with an average flexion of 106 degrees. Early conservative treatment recommend as the therapy of choice. Ultrasonography imaging offers the possibility of reliable differentiation into one of the three groups of the classification of Leveuf and Pais. Radiographic documentation during the therapy has become the exception. Ultrasonography imaging helped substantially in the decision making and the timing of operative treatment.

A comparative study of two cerclage systems.

Intraoperative femoral fracture is a well recognized technical complication of cementless total hip arthroplasty (THA). The aim of this study was to establish an in vitro model for initiation of fractures of the femur in cementless THA and to assess the effect of fracture fixation by cerclage wiring. An in vitro comparison of two methods of cerclage fixation was performed using steel wire (Protasul) versus multifilament Vitallium alloy cable. Ten fresh human femur specimens were studied. Longitudinal fractures were created on a material testing machine. The force to create a longitudinal fracture in the femur was 1915 N to 9288 N (median 6531 N). This force corresponds 3 to 15 times (median 11 times) the body weight. The femoral cortex was fractured in 5 cases ventrally, in 6 cases medially and in 1 case laterally. After monofile cerclage wire application, the force required to press the prosthesis 5 mm deeper into the medullary canal was 0.3-2.7 times body weight. After Vitallium alloy cable application in other specimens, the force was 1.3-2.7 times body weight. The difference was not statistically significant. After monofile cerclage wire application, a force of 1.8-8.1 times body weight was necessary to press the prosthesis 30 mm deeper into the medullary canal. After polyfile Vitallium alloy cable application in other specimens, the force was 7.7-12 times body weight. The difference was statistically significant (U-test, alpha < 0.025).

[Ultrasound hip joint screening in newborn infants. Is twin pregnancy a risk factor for dysplasia?]. / Sonographisches Hüftgelenk-Screening bei Neugeborenen. Ist die Zwillingsschwangerschaft ein Dysplasie-Risikofactor?

PURPOSE: This study aimed at investigating whether twin pregnancy is a risk factor for congenital dysplasia of the hip. METHOD: From 1987 until 1994 the hips of 3739 (1902 male, 1837 female) newborn were examined by ultrasound (screening) according to Graf's technique. We compared the results of twins and the other newborn (non-twins). The examinations were performed by 19 physicians. 73 (2%) of the newborn were twins (29 male, 44 female). RESULTS: In the group of 3666 non-twins we found the types of hip IIa (alpha < 55 degrees) to IV (Graf's classification) in 237 (6.5%) newborn: 136 (3.7%) right side/183 (5.0%) left side. Only 2 (2.7%) of the 73 twins showed these types of hip. We found 4% (149/3739) breech presentations at birth in the entire group. 3.9% (141/3666) in the group of non-twins and 11% (8/73) cases in the twin group. 5.2% (190/3666) of the non-twins and 2.7% (2/73) of the twins required a treatment with abduction orthosis or Pavlik harness. CONCLUSION: This report shows that the types of hip IIa (alpha < 55 degrees); IIc; D; IIa, IIb and IV according to Graf and a required treatment in twins was significantly not more frequent than in the other newborn (non-twins), although twins showed more often a breech presentation at birth. The different kind of breech position in twins (hips and knees in flexion, legs and feet parallel) and non-twins (hips in flexion, knees in extension) could be one reason for these results. Besides, non-twins assume their breech position earlier than twins with a consecutively longer period of time of mechanical stress on the hips.

[Biomechanic results in impingement syndrome of the shoulder]. / Biomechanische Ergebnisse zum Impingement-Syndrom der Schulter.

Forces underneath the coraco-acromial vault during elevation of the arm were evaluated with a dynamic shoulder model. The deltoid muscle and the rotator cuff muscles were simulated with a hydrodynamic device, in ten autopsy specimens. Controlled cycles of glenohumeral joint motion were initiated with computerised regulation. An ultrasonic device measured the position of the arm in all spatial orientations. Capacitive sensors recorded forces underneath the coraco-acromial vault. The mean force during one cycle of elevation averaged 13.9 Newton +/- 12.5 Newton underneath the coraco-acromial ligament and 3.44 Newton +/- 4.37 Newton underneath the coracoid process. The peak force averaged 37.8 Newton +/- 33.2 Newton underneath the acromion, 3.03 Newton +/- 2.62 Newton underneath the coraco-acromial ligament and 6.93 Newton +/- 7.38 Newton underneath the coracoid process. The force markedly increased at the final stage of arm elevation and during early reverse-elevation in most specimens, corresponding to the painful arc sign. In some specimens, the force under the coracoid process exceeded the force under the acromion. Osteophytes protruding into the subacromial space may lead to a concentration of force and to high regional pressures.