Biomedical subjects
N Wülker
Publications and source records attributed to N Wülker.
[Hindfoot arthrodesis].
Arthrodesis of the hindfoot is indicated in congenital foot deformity of young adults, in posttraumatic arthrosis of the subtalar joint following calcaneus fractures, in idiopathic, isolated arthroses of hindfoot joints, in rheumatoid arthritis and in deformities of the longitudinal arch of the foot. Common and useful combinations are the triple-arthrodesis and the arthrodesis of the subtalar and the calcaneocuboid joint, in particular if both joints are affected by calcaneus fractures. Arthrodesis of the subtalar and the talonavicular joint are often performed as isolated procedures. The three-dimensional structure of the hindfoot articulations may impede perfect contact of the bone surfaces in combined arthrodeses. Various fixation methods are in use. Follow-up examination of 52 arthrodeses after 11.1 years revealed good, symptomatic improvement in most patients. However, complete bony union was achieved in only 47 percent, and this was due to insufficient stabilization of the arthrodesis in many cases. In view of comparable rates of pseudarthroses in the literature, we advocate stable internal fixation with screws or bone staples.
[Arthrodesis of the metatarsophalangeal joint of the large toe].
Arthrodesis of the first metatarsophalangeal joint is the procedure of choice in hallux rigidus with advanced destruction of the joint surfaces. It is also indicated after failed resection arthroplasty in hallux valgus. A dorsal skin incision is used. Flat osteotomy surfaces are created at the first metatarsal head and at the proximal phalanx with a saw. The angle between the great toe and the bottom of the foot should be ten to 15 degrees of dorsal extension. The great toe should be aligned in ten degrees of valgus relative to the first metatarsal bone, and in neutral rotation. Fixation with a dorsal one-third or one-quarter tubular plate and an interfragmentary lag screw is most stable. Interposition of a bone graft may be necessary in cases of undue shortening of the great toe, as in revision surgery following resection arthroplasty. Full weightbearing in a postoperative shoe with a rigid sole is allowed immediately postoperatively. Results with this technique are good and excellent in approximately 80 percent. The incidence of pseudarthroses is between three and 13 percent, depending on the operative technique. Symptomatic degeneration of the interphalangeal joint occurs in approximately 10 percent of patients at long-term follow-up.
[Dynamic stability of the glenohumeral joint. A biomechanical study].
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.
[Passive stabilizers of the glenohumeral joint. A biomechanical study].
Passive glenohumeral joint stability was tested in ten cadaveric shoulder specimens, before and after venting of the intra-articular space. Force-displacement diagrams were measured with anterior, posterior and inferior excursion, in the neutral position, in 90 degrees of abduction and in a combination of 90 degrees of abduction and 90 degrees of external rotation. Displacement at 50 N prior to venting averaged 11.17 +/- 6.48 mm posteriorly, 7.15 +/- 5.51 mm anteriorly and 3.41 +/- 3.73 mm inferiorly. Venting of the joint increased displacement by 47% anteriorly, 49% posteriorly and 61% inferiorly. In addition, mathematical model calculation was used to estimate the destabilizing force present at the glenohumeral joint capsule during physiological arm motion. This force approximated 970 N, clearly more than passive stabilizers alone can provide. It is therefore assumed that in addition to passive glenohumeral joint stabilization, significant active forces are effective during arm motion.
[The status of the direct magnifying x-ray technique in orthopedics].
22 patients suffering from different orthopaedic disease patterns were x-rayed with direct x-ray magnification with focus diameters between 0.012 and 0.100 mm. This yielded improved resolution of detail structures, especially in tumours and aseptic bone necroses. Due to the relatively low efficiency of the x-ray tube (conditioned by the physics of the x-ray equipment), however, exposure times of several seconds were required, and the voltage had to be higher than in conventional x-ray procedure. This resulted in lack of sharpness due to movement and to a loss in contrast. Hence, the clinical use of focus diameters below 0.1 mm does not seem to be meaningful.
[The value of dynamic examination methods in instability of the shoulder joint].
We prospectively examined 25 patients with shoulder instability by clinical examination and by fluoroscopic and sonographic imaging. 14 patients were classified as recurrent, posttraumatic instabilities, 12 of these anterior and two posterior. Clinical examination revealed the direction of instability in 5 patients, fluoroscopy in 5 and sonography in 3 patients. 11 patients had non-traumatic recurrent instabilities. Of these, clinical examination and fluoroscopy demonstrated identical directions of laxity in 8. Sonography concurred with the other techniques in only three cases. We recommend manual instability testing followed by fluoroscopy for evaluation and documentation of patients with non-traumatic, recurrent shoulder instability. Posttraumatic instabilities should be diagnosed with other, static procedures.
Medial meniscus replacement by a tendon autograft. Experiments in sheep.
In 20 skeletally mature female merino sheep, divided into four groups, we performed total medial meniscectomy, removal of the middle third of the patellar tendon, and tenotomy of the calcaneal tendon of the right hind leg. Group I (control) had no additional procedures. In the other three groups the medial meniscus was replaced by the middle third of the patellar tendon from the ipsilateral knee. The animals were killed at three (group II), six (group III), or 12 months (group IV) and the tendon-meniscus examined macroscopically, by light and scanning electron microscopy, and biomechanically. Remodelling of the tissue had taken place by 12 months but the failure stress and tensile modulus for the tendon-meniscus were lower than for the normal meniscus. Our evidence suggests that, in sheep, replacement of a meniscus by a tendon autograft may decrease the severity of the degenerative changes that occur after meniscectomy.
[Routine ultrasound diagnosis of the shoulder. A simplified examination procedure].
With increasing use of ultrasonography at the shoulder, a confusing number of transducer positions have been recommended. At the shoulder, however, dynamic examination yields more information than fixed transducer orientations. In our examination routine, the transducer is guided across the shoulder following the shape of a triangle. Orientation is secured by palpable, bony structures. The clinically relevant parts of the rotator cuff and the long biceps tendon are investigated, first medially and laterally in a transverse projection and then longitudinally. Dynamic examination is provided by moving the transducer as well as the shoulder joint. In a time-saving examination routine, all important soft tissue structures of the shoulder are visualized.
[The significance of the activity score in evaluating knee ligament reconstructions].
In a follow-up study of 156 patients after knee ligament reconstruction for chronic instability, the results of subjective Lysholm score grading and of Tegner activity grading were compared. The postoperative Lysholm score averaged 85 +/- 13.2 points, the activity scores 6.9 +/- 0.9 points prior to instability, 1.7 +/- 0.9 points preoperatively and 5.9 +/- 1.2 points postoperatively. 89 patients reached their preinjury activity level, the average improvement through surgery was 4.2 +/- 1.6 points. Non-active patients regularly returned to their original activity-level, competitive athletes were less likely to regain their previous activity. The subjective results of athletes and non-athletes showed no significant differences. The postoperative activity level clearly correlated to subjective grading by the patient. For scoring results after knee ligament surgery, we use the subjective Lysholm score and an activity score based on average German sports activities.
Shoulder surgery for rotator cuff tears. Ultrasonographic 3-year follow-up of 97 cases.
We reexamined 97 of 116 shoulders operated on for rotator cuff lesions after an average follow-up time of 37 months. Seventy percent had a good or excellent clinical result, and 14 percent were graded as poor. Upon ultrasonographic examination of the 97 shoulders, 37 had a normal rotator cuff, 31 had thinning and/or hyperdensity, and 29 had a complete rupture of the cuff. Patients with concomitant anterior acromioplasties did better than those without. There was a poor correlation between clinical and ultrasonographic results. We recommend that rotator cuff tears should be closed only if this can be achieved without undue tension. If extensive tissue mobilization or coverage with alloplastic material or with regional muscle flaps is required, the lesion should be debrided and left open, and only an anterior acromioplasty should be performed.
[Experimental study of the classification of intra-articular calcaneus fractures].
Improvement of the diagnostic techniques applied in calcaneus fractures, particularly the increased use of computed tomography, calls for a detailed fracture classification. Thirty lower leg cadaver specimens were submitted to axial loading. Fracture lines could be divided into a relatively constant primary fracture, running from the posterior subtalar joint surface to the tuber calcanei, and highly variable secondary fractures. In order to classify the fracture specimens, the calcaneus was divided into four segments: the sustentacular segment, the posterior subtalar joint segment, the segment of the anterior process, and the tuberosity segment. In addition, the following joints were identified at the calcaneus: the posterior subtalar joint, the anterior subtalar joint, and the calcaneo-cuboid joint. Each specimen was classified by the number of segments (x) and the number of joints (y) affected, and accordingly labelled as x-segment, y-joint fracture. The addition of both numbers was used to grade the severity of the fracture. This classification was easily applicable to all 25 experimental fracture specimens, and also to 33 clinical cases.
Madura foot. A report of two cases.
Two cases of Madura foot which originated in the Middle East are described. This so-called maduramycosis is a chronic progressive infection caused by thread fungi or actinomycetes. The diagnosis is confirmed when the grains of mycetoplaits are demonstrated in the discharge from a sinus. Clinical findings and treatment are discussed. Medical treatment may be needed for several months, but operation is indicated for infections caused by the true fungi (eumycetoma).
Potential mistakes in hip-joint sonography.
The growing propagation of hip-joint sonography and its increasing use as a screening method make it important to point out some potential mistakes. Good image quality, three-dimensional evaluation with real-time technique, consideration of form variants, correct estimation of angle parameters, consideration of medical history, and clinical evaluation as well as the necessity of follow-up examinations are inevitable requirements for reliable diagnostic sonography of the hip joint.
[Intra-articular fracture of the calcaneus. Classification, assessment and surgical procedures].
Our experience with open reduction of calcaneus fractures and internal stabilization without joint transfixation (n = 83) has shown us that the following features are mandatory in order to obtain normal postoperative foot statics and dynamics, normal joint mobility, and normal foot function: (1) restoration of the normal height, length and width of the calcaneus; (2) reduction of all joint surfaces and (3) stable screw- or H-plate osteosynthesis, allowing functional treatment later. Our own fracture classification (X-fragment/Y-joint fracture) allowed us to determine the type of fracture, its severity, and the prognosis, as well as the choice of operative treatment. A detailed +/- 200-point follow-up scoring system assured operative quality control and comparability of results. The complications were: 9 cases of superficial wound-edge necrosis (8%), 2 hematomas requiring revision, and 1 deep bone infection (1.2%). During our first operative period (1983-1985, mostly unilateral medial approach and trans-articular K-wire fixation), we had only 50% good-to-excellent results. During the second period (1986-1988, bilateral, extended lateral approach and stable screw/H-plate osteosynthesis), 76.5% (29 of 51 patients) had good-to-excellent results. Our experience thus indicates that our operative treatment principles can be recommended for patients who are either professionally active or active in sports.
[Osteosynthesis of dislocated intra-articular calcaneus fractures].
Explore the source record for details and available documents.
[Quantification and visualization of the influence of pelvic tilt upon measurement of acetabular inclination and anteversion].
AIM: The indication of acetabular inclination and anteversion not only depends on definition but also on a correctly aligned patient. Determination of anteversion and inclination according to Sven-Johannsson and Visser were simulated with 3D calculations. The influence of pelvic tilt in relation to the frontal plane was evaluated and visualized. METHOD: With 3D calculations of planar X-ray photographs for artificial hip cups the normal vector of the acetabular cup was used to calculate anteversion and inclination. RESULTS: The main axis of the projected acetabular rim is equally suited to determine the cup orientation as the normal vector of the cup plane. Pelvic tilt of about 10 degrees causes measuring errors of about 8 degrees when measured with conventionally used techniques. CONCLUSION: For the correct determination of cup orientation pelvic tilt in relation to the frontal plane has to be accounted for.