Load transfer and periprosthetic fractures after total hip arthoplasty: Comparison of periprosthetic fractures of femora implanted with cementless distal-load or proximal-load femoral components and measurement of the femoral strain at the time of implantation.

BACKGROUND: Little is known about the causes and mechanisms underlying periprosthetic fractures around femoral components particularly in relation to the stem design. In an in vitro study 20 pairs of fresh cadaveric femora were loaded to fracture axially and transversally. FINDINGS: When proximal femoral strain was measured at the time of impaction of cementless stems the load transfer was determined by the underlying anatomy rather than by the shape of the stem, so that the so-called "load transfer" properties - proximal or distal - ascribed to stem designs are a myth. The axial-load and the transverse-load model were then exposed to loads to failure (fracture) and showed a biphasic pattern throughout independent of the impact direction. In the second phase, the fracture phase proper, the bone behaved like a brittle solid. Failure occurred very rapidly within less than 5 milliseconds. The forces to failure were between 2 and 11 kN. Most of the fractures (82.5%) occurred above the stem tip. INTERPRETATION: Note that the study was confined to early preosteointegration fractures. Neither the stem design nor the impact direction, i.e. on the knee or on the side of the hip, was related to the fracture morphology.

[Treatment procedure in humeral shaft fractures with primary or secondary radial nerve damage]. / Vorgehen bei Oberarmschaftfrakturen mit primärem oder sekundärem Radialisschaden.

We give an account of 28 patients with fractured humerus diaphysis, suffering from primary and seven patients suffering from secondary lesion of the radialis nerve, all treated by operation. In each case the radialis nerve was exposed and the fracture was treated by fixation with compression plates. In case of primary lesions of the radialis nerve, we found intraoperative damages by traction (six times), contusions (seven times), intraneural hämatomas (six times) and for one time perforation of the nerve by bones. The rest of this group (eight times) did not show any pathological finding. Those patients with secondary lesion of the radialis nerve showed damages by traction (three times) and in two cases the nerve was walled up by callus or connective tissue. Two times we could not find any pathological alteration of the nerve. 23 (six) out of 28 (seven) patients with primary (secondary) lesion of the radialis nerve could be followed up. On this occasion we stated complete neurological restitution 20 times (four times) and incomplete restitution three times (two times). The great number of pathological findings, which necessitate operative treatment, the short duration of remission and the high rate of restitution confirm us to leave the way of conservative treatment in cases of primary or secondary lesion of the radialis nerve and the indication of acute operation is given.

[Therapeutic measures in subluxation and dislocation of the patella]. / Therapeutische Massnahmen bei Subluxation und Luxation der Kniescheibe.

The pathology of patella dislocation is divided into different groups: primary, secondary, recurrent dislocation and patella subluxation. In the diagnosis, in addition to clinical and X-ray investigations a certain computerized tomography extended on the SEG examination. A new examination of the EG tomographs had increased the diagnostic facilities. Our therapeutical program is based on physical therapy. After failure of physiotherapy to achieve satisfactory results the operation technique according to Slocum and Larson is performed.

[Computerized tomography in instability of the femoropatellar joint]. / Computertomographie bei Instabilität des Femoropatellargelenks.

Compared with normal X-ray examination, a CT scan can give more information about patellar alignment, especially close to full extension of the knee-joint. We compared the normal knee-joints of 10 volunteers with the knee-joints of 15 patients (19 recurrent luxations, 5 habitual subluxations). We were able to distinguish between instabilities with and without changes seen on the X-ray pictures, making it possible to develop a systematic concept of treatment. In the case of recurrent dislocation with radiologically visible instability, surgical repair is the treatment of choice, while for habitual subluxation without radiologically visible instability the primary treatment of choice is conservative therapy with physiotherapy and muscle training. This is successful in most cases. If physiotherapy fails surgical repair is the next step in treatment. This dynamic type of investigation (the patella is stabilized by tension of the quadriceps femoris muscle) makes an objective judgement of the result of therapy possible.

[The surgical treatment of humeral shaft fractures]. / Die operative Versorgung von Humerusschaftfrakturen.

This is a study of 84 patients with upper arm fractures who were treated by plate osteosynthesis. The indication was mandatory in 9 patients with open fractures, 23 patients with primary radial nerve palsy on admission, 5 patients with radial nerve palsy after the initial treatment, 22 patients with pseudarthrosis and 7 patients who were polytraumatised. The operation was also indicated in 15 patients, because of the form of the fracture, in 3 patients with brachial plexus lesion, in 3 patients because it involved both upper arms and in 3 patients with segmental fractures. The 4.5 DCP was used in all these cases. All the cases of pseudarthrosis progressed to achieve bony union after the operation. There was no incidence of postoperative pseudarthrosis. We did encounter two cases (2.4%) of radial nerve palsy that required exploration. All the preoperative primary and secondary cases of radial nerve palsy recovered postoperatively. After an average follow-up period of 2.4 years (1-10 years) 90% of the patients could be classified as having very good or good results.

Relationship between design and control of artificial heart for protection of the right/left balance.

Right/left matching in the total artificial heart (TAH) is essential to prevent fatal volume displacement into the pulmonary circuit. Measurements were made with three different sized Rostock pneumatic artificial ventricles incorporated in the Donovan mock circulatory system together with the heart driver AKT 86. First for each ventricle we determined the dependence of the maximum effective stroke volume on the systolic driving pressure and the afterload. The right ventricle (RV) is about 10% more effective than the left ventricle (LV). Control of the TAH permits different or equal frequencies for the RV and LV. For control with equal frequencies and full-to-empty regimen of one ventricle (RV-Master or LV-Master) the ratio of designed stroke volumes between RV and LV is important. This follows from the smaller efficiency of the LV and the left-to-left shunt. Otherwise a control mode with different heart rates must be used.

[Surgical complications following implantation of femur head prostheses in a traumatology patient sample. Prevention and therapy]. / Chirurgische Komplikationen nach Implantation von Hüftkopfprothesen in einem traumatologischen Krankengut. Prophylaxe und Therapie.

At the 1st University-Clinic of Traumatology, Vienna, 420 patients with a medial fracture of the femoral neck received a femoral neck prosthesis (59 male, 361 female, phi age 81.3 years; range: 60-97 years). Severe early complications were fractures of the femoral shaft in 1.19%, that healed without problems after cerclage and plate osteosynthesis, and early infections in 3.1%. The rate of infections can be reduced to 1% prophylactic administration of antibiotics, surgery in an laminar airflow operating theater, and by the use of cement containing antibiotics. Dislocation of the prosthesis was observed in 2 patients (0.47%). the low rate of dislocation appears to be due to the antero-lateral operative approach according to Watson-Jones without osteotomy of the trochanter as well as to the precise technique of implantation of the prosthesis. More frequent late complications were periarticular calcification in 20 cases (4.7%) and protrusion in 18 cases (4.28%). However, only one out of the patients with calcification is restricted in his movements, and only 3 out of the patients with protrusion do complain of symptoms. The low rate of symptomatic protrusions is explained by a correct level of resection, by the implantation of a head prosthesis with appropriate dimensions and by the exclusion of patients with arthrosis of the hip or severe osteoporosis from the implantation of a femoral head prosthesis.

The extensor apparatus of the knee joint and its peripheral vasti: anatomic investigation and clinical relevance.

Anatomic dissections of the vastus medialis m. in 115 fixed thigh specimens always demonstrated a clear separation between a long head of the muscle (VML) inserted at the base of the patella and a short head (VMO) inserted at its medial margin. The plane of separation was identified by a branch of the femoral n. in every case. In 17 instances, the localization of the nerve was superficial; in 57, it was in the areolar fascial plane; and in 41 instances in lay deeply between the muscles. The ramification of the branch of the femoral n. traversing the plane of separation showed 4 types of variation. Dissections of the vastus lateralis m. in 42 specimens always demonstrated a separation into 2 heads: a long head inserted at the base of the patella (VLL) and a short head inserted at its lateral margin (VLO). The directions of the individual heads of the quadriceps femoris m. were angulated in relation to the long axis of the femur. The deviations were between 10 degrees and 17 +/- 8 laterally for the vastus lateralis longus m. (VLL), between 26 degrees and 41 degrees laterally for the vastus lateralis obliquus m. (VLO), between 15 degrees and 18 degrees medially for the vastus medialis longus m. (VML), and between 46 degrees and 52 degrees medially for the vastus medialis obliquus m. (VMO). The results demonstrate great variation in the distal parts of the medial and lateral anterior thigh m.

[Prevention of infection in implantation of femur head prostheses]. / Infektionsprophylaxe bei Implantation von Hüftkopfprothesen.

An account of 581 patients managed with head prosthesis after femoral neck fractures between 1975-1988 revealed that the administration of prophylactic antibiotics coupled with the use of a laminar airflow system in the operating room reduced the infection rate from 5% to 0.75%. The important risk factors which predispose infection are poor physical state, chronic urinary tract infection as well as diabetes mellitus.

[Hemocompatibility testing in the rat model by noninvasive blood flow measurement using an arteriovenous shunt]. / Hämokompatibilitätstest am Tiermodell Ratte mittels a.-v.-Shunt durch nichtinvasive Blutflussmessung.

The flowing periods of blood through biomaterial shunts were measured by means of a noninvasive sensor with sufficient reliability. Falsifications of the measuring results by foreign influences as roller pumps, punctures, changes of the cross section, or the coupling of different materials were avoided extensively. The accomplishment of the test is possible routinely without a great display of apparatus.

[Noninvasive monitoring of pneumatically driven blood pumps based on measurements of air volume flow in the drive hose]. / Nichtinvasive Uberwachung pneumatisch angetriebener Blutpumpen auf der Grundlage von Luftvolumenstrommessungen im Antriebsschlauch.

A computer-assisted measuring system for the noninvasive control of pneumatically driven blood pumps in the artificial total heart replacement and in assist-systems is described. Air volume current measurements with heat wire anemometer in the driving tube underlie as principle. The technique takes into consideration losses of valves, depending upon driving parameters and central circulatory parameters. The dependences established base on measurements at the circulation model. The methods demonstrated allow to qualitatively characterize the signals of the air volume current in the driving tube and approximatively to determine central circulatory parameters on the basis of comparative measurements at the circulation model. Animal-experimental experiences confirm the necessary application of such systems for the measurement of the cardiac output and for the control of the pumping function of pneumatically driven blood pumps. Analyses at the circulation model let expect a measuring error for the volume of output smaller than 20%. By increased measuring exactness of the heat wire anemometer this error can be diminished. For final evidence concerning the measuring exactness animal-experimental investigations and comparisons with reference techniques are provided.

[Catheter problems in the use of ventricular cardiovascular assist systems]. / Zur Kanülenproblematik bei der Applikation von ventrikulären Herz-Kreislauf-Assistsystemen.

The prerequisite for efficient assist-ventricles and impulses in the pulsatile pumping function are sufficiently dimensioned afflux and flowing off connections. In systematic investigations on the hydraulic circulation model the cannulas from an internal parameter of 12 mm with a total length of the connection distance to the inflow and outflow valve, respectively, at the bypass ventricle of 30 cm proved sufficient for performing a volume of output of 5-6 l/min in clinic-relevant filling pressures in a hypodynamic circulatory situation. Connection cannulas for the heart-lung machine used in routine work are not sufficient in periodic filling and ejection processes in the pulsatile pumping function for an effective decompression and effective increase of the cardiac output. In case of an ECG-triggered mode of action of the ventricular assist-system an increase of frequency up to 130/min in after that incomplete filling of the assist-ventricle does not remarkably restrict the effectiveness of the assist-system.

[First results after the use of a Y-plate for the stabilization of supradiacondylar humeral fractures]. / Erste Ergebnisse nach Anwendung der Y-Platte zur Stabilisierung supradiakondylärer Oberarmfrakturen.

A new implant for the stabilisation of supra- and diacondylar fractures of the humerus is assessed. If compared with other implants this y-shaped plate has a considerably better stability. Due to different diameters of the holes 4.5 mm screws may be used for the long part, 3.5 mm screws for the branches of the plate, which in most cases allow good stabilisation and early mobilisation of the limb. Out of twelve patients, operated since 1981, ten were reexamined for follow-up after a mean of 34.1 months. All of the fractures stabilised with the y-plate were healed with normal osseous consolidation. According to the scheme of Cassebaum, the result was excellent in five, good in four and unsatisfactory in one patient. For each of the two available types of plates the dimensions proved to be sufficient with respect to the branches. However, for cases with fractures continuing into the humeral shaft, an additional type with a longer mainpart would seem desirable.

[Experimental testing of the left-ventricular and biventricular assistant systems in dogs]. / Experimentelle Erfahrungen beim Testen des linksventrikulären (LVAD) und biventrikulären Assistsystems (BVAD) am Hund.

The left-ventricular (LVAD) and bi-ventricular assistant system (BVAD) were tested in dogs. Our hitherto existing experiences give information specially for the indication of LVAD and BVAD. The risk of a belated application of the LVAD exists in case of only a clinical control by pressure parameters for the degree of a cardiac insufficiency caused by coronary starvations. An aortic pressure of nearly 150/70 mm Hg could be reached by means BVAD on condition of heart fibrillation and a left-atrial pressure of 20 mm Hg. The aortic pressure and the left-atrial pressure decrease drastically after disconnection of the BVAD and these attain the initial values again very promptly after a new connection with the BVAD.

[Filling behavior of pneumatically driven artificial ventricles of the membrane type in vitro]. / Füllungsverhalten pneumatisch betriebener künstlicher Ventrikel vom Membrantyp in vitro.

The filling behaviour of pneumatically driven artificial hearts is an essential determinant of its pumping function. The artificial ventricles developed in Rostock were investigated by means of a hydraulic circulation model for analysis of the influence of different parameters on the filling time. The filling rate is decided by the flow resistance of the inlet valve. Additional resistances are given by the rigidity of the membrane and the flow resistances of the drive line and the drive.