[Comparative tribological studies of Chirulen, Hylamer and Enduron combined with A1203]

The creep and wear behaviour of Chirulen, Hylamer and Enduron, materials which differ only in their manufacturing procedures, was examined and compared. Chirulen is manufactured by being pressed into form by plates, whereas Hylamer and Enduron are shaped by tubes. Hylamer differs from Enduron in that intermediate material processing is undertaken with the goal of improving the initial material. The wear and deformation rate was determined by means of the ring-on-disc testing device after 360,000 cycles and after 1.0 x 10(6) cycles, respectively. The static tests for the determination of wear were carried out at a contact stress of 5.62 MPa and a testing time of 100 h in analogy to the ring-on-disc tests. Chirulen and Hylamer demonstrated comparable wear with a tendency toward a lower wear rate in Hylamer, while Enduron presented a clearly higher wear rate.

[Experimental studies of metal-metal slide combinations and their value in relation to expected in-vivo behavior]

A simulator test was carried out in the hip joint simulator on a metal-on-metal coupling of a modified CoCrMo alloy. The test was run up to 1.9 million cycles and the tribological behaviour of the coupling was documented by means of roundness measurements and scanning electron microscopy. It is seen that the tribological system metal on metal is characterized by mixed friction in the artificial hip joint, thus generating material contacts that are documented by the roundness variation and by the SEM contact zone analysis, showing "three-body" wear of this system. The roundness variations indicate that running-in wear is to be noticed at first with a decreasing tendency over the 1.9 million cycles. Nevertheless, this observation does not allow any prognosis as to the wear rates in the case of a higher number of cycles. It must be taken into consideration that aqua destillata had to be used as a lubricant for technical reasons; the use of serum/Ringer solution might have produced different results. Further investigations in the hip joint simulator and on revised metal-on-metal couplings will be carried out in this respect.

[Primary leiomyosarcoma of the bone]

In a 52-year-old female patient and a 50-year-old patient with a malign tumor of the right distal femur (stage IIIb) respectively the left distal tibia (stage Ia according to Enneking), the extremely rare primary leiomyosarcoma of the bone was diagnosed. The mortality of the primary leiomyosarcoma of the bone is 50%, the mean survival time after diagnosis is 3.4 years. Diagnosis of a primary leiomyosarcoma of the bone is only possible after a secondary leiomyosarcoma has been excluded as well as by histopathological including immunohistochemical examination. The operative procedure is the therapy of choice. A neoadjuvant and/or adjuvant radio- or chemotherapy can be useful.

Primary leiomyosarcoma affecting the ankle joint

In a 50-year-old patient with a malignant tumor of the left distal tibia (stage la, according to Enneking) undermining the cartilage of the ankle joint, an extremely rare primary leiomyosarcoma of bone was diagnosed. The diagnosis of a primary leiomyosarcoma of bone is possible only after a secondary (metastatic) leiomyosarcoma has been excluded. Furthermore, typical histopathological features, including immunohistochemical staining results, are required for the diagnosis. Surgery is the therapy of choice. An R0 resection should always be attempted.

[Alloplastic replacement of the proximal femur--indications, results and experiences]

The aim of this follow-up study was to see if, by the application of a special endoprosthesis for the replacement of the proximal femur, a radical tumour resection could be achieved and/or the function of the lower limb could be preserved or restored respectively. Between 11/1986 and 12/1992 a proximal femoral endoprosthesis was implanted in 9 patients with metastases in the proximal femur. In 21 cases this special endoprosthesis was used in the revision of conventional cemented total hip arthroplasties with loosening of the implant and extreme bone loss at the proximal femur. Twenty-three patients were seen for a follow-up examination with an average follow-up period of 20 months. In all cases the walking ability was preserved or restored respectively. The majority (22/23) of the patients had complete or, nearly complete pain relief. In those patients with skeletal metastases, were no cases of local reoccurrence. The majority problem of this endoprosthesis was the increased risk of dislocation. There is a clear indication for such a special endoprosthesis in the treatment of primary and secondary bone tumours in the proximal femur. For revision of cemented total hip prostheses with loosening and bony defects a revision prosthesis with uncemented distal fixation should be used.

[Effect of surface energy on wear characteristics of material combinations for the artificial hip joint]

One of the factors determining the wear of UHMWPE used as acetabular cup material is the lubricating properties of the head materials. In order to determine the lubricating properties, the wettability of Al2O3, ZrO2, CoCrMo and N-coated TiAl6V4 was established. Wettability is determined by the surface energy of the head material (solid-state material), which was measured via the contact angle of drops of fluid. As head material, appropriate rings from the Ring-on-Disc Test as per International Standard 6474 were used. The poorest wettability was associated with CoCrMo. The wettability of Al2O3 and ZrO2 was comparable. Worthy of note is the tendentially good wettability of N-coated TiAl6V4.

[Clarification of the concept humeroscapular periarthritis]

Shoulder pain may be due to various reasons. It is primarily produced by changes in the periarticular structures of the shoulder joint. The term "periarthritis humeroscapularis" (PHS), often used at diagnosis, is unsuitable however because it prevents differentiation of the various clinical pictures related to the anatomical structures. Among the anatomical structures concerned, above all the rotator cuff and here especially the suprasinatus muscle must be mentioned. Also the long biceps tendon and the shoulder joint capsule are, according to Welfling, locations of painful processes, not to forget the subacromial bursa. The pathology responsible for the clinical symptoms and signs is primarily produced by degenerative changes. They lead to tendopathy, as well as to tendon rupture, and also seem to be of importance in connection with calcifying tendopathy. Capsule shrinkage in shoulder stiffness can also be influenced by neighboring degenerative processes. This also applies to isolated bursitis. Today thorough clinical and radiological clarification makes a differentiated diagnosis possible so that the vague term "periarthritis humeroscapularis" can be dropped.

Long tendon of the biceps brachii: sites of predilection for degenerative lesions

The extreme stress on the long head of the biceps tendon is defined by its specific anatomic course, with its proximity to the rotator cuff, the intertubercular groove and the acromion. We studied the morphologic and cross-sectional anatomy of the long head of the biceps tendon in 104 cadavers to analyze degenerative lesions. Degenerative changes in the tendon (disorganized collagen fibers and large mucoid deposits) occurred mainly in the distal bicipital groove and near the origin of the tendon from the superior part of the glenoid labrum. The results of histologic examination identified sites that possibly have a predilection for tendon rupture.

[Preferential sites for rupture of the long head of the biceps tendon]

The extreme stress on the long head of the biceps tendon is defined by its specific anatomical situation with near contact to the rotator cuff, to the sulcus intertubercularis and to the acromion. We took 74 specimens from cadavera and studied the macromorphological and cross-sectional anatomy to analyze changes preceding rupture of the biceps tendon. Degenerative tendon alterations with disorganized collagen fibers and large mucoid deposits occurred especially at the distal sulcus bicipitalis and near the origin of the tendon at the superior part of the glenoid labrum. The found degenerative histological alterations are possibly precursor of tendon rupture near to the distal sulcus or precursor of the so called "SLAP"-lesions.

[Thermo-elastic stress analysis of human bones]

The Thermoelastic Stress Analysis (THESA) is a widely used procedure in motorcar- and airplane engineering. This study investigated the reliability of THESA for stress analysis of human bone. A human femur was cyclic stressed and the resulting stress pattern was scanned from the surface of the bone by means of the thermoelastic stress measuring instrument SPATE 9000. To proof whether the scan of SPATE 9000 is equivalent to the stress distribution of human femur surface, strain gauges are used to control the results at two different regions of the femur diaphysis under equal but static conditions. It could be shown, that both measuring methods lead to corresponding results of stress pattern on human femur surface.

[Effect of the manufacturing process on creep and wear properties of UHMWPE (ultra-high molecular weight polyethylene)]

The creep and wear behaviour of pressed UHMWPE and extruded UHMWPE was compared, taking Chirulen and extruded UHMWPE of the Lennite type as examples. Using the ring-on-disc test, the wear and deformation volumes per 360,000 cycles were determined. The static tests were performed at surface pressures of 5.62 MPa and 9.37 MPa, while the test duration was 41.86 and 100 hours, respectively. The surface pressures result from the axial forces of 900 N and 1500 N, respectively, and a ring surface analogous to the DIN 58,835 and ISO 6474 standards. Between conventionally pressed and the extruded UHMWPE material differences of up to 350% in the sums of wear and deformation were found. It was noted that already at low surface pressures the extruded UHMWPE is more susceptible to creep deformation than is the conventionally pressed material, and that this effect dramatically increases at high surface pressures.

Prevalence of cyclic changes in limb volume (volumotion) of male patients with knee injury and the effects of ischemia/reperfusion due to tourniquet

During surgery of limbs tourniquet up to a maximum of 2 h is frequently applied which may cause ischemia/reperfusion injury (IRI). During this condition the presence of vasomotion may have consequences for the perfusion and nutritive state of the tissues. We used a noninvasive plethysmographic method to investigate periodic changes in limb circumference (volumotion) in healthy male patients (n = 24) undergoing surgery for knee injury. To facilitate surgery a tourniquet was applied to the thigh, which caused an IRI of the leg. Results are given as mean of all values +/- SEM. Immediately after tourniquet release (duration 57.75 +/- 5.19 min) blood lactate levels in the femoral vein increased significantly from 1.40 +/- 0.08 to 2.59 +/- 0.20 mmol/l (p < 0.001) and pH fell from 7.39 +/- 0.01 to 7.32 +/- 0.01 (p < 0.001). Preoperatively 10 out of 24 patients (42%) showed signs of volumotion on the injured leg with a periodicity ranging from 0.8 to 6.9 cycles/min, whereas none showed volumotion in the control leg (p < 0.001). In the second measurement, taken after surgery and reperfusion while peripheral sympathetic nerves were blocked, 7 out of 18 patients (39%) showed volumotion on the injured leg and 0 on the control leg (p < 0.004). 6 h after IRI, volumotion was observed in 11 out of 17 patients (65%) on the injured leg and in 1 patient (6%) on the control leg (p < 0.001). The mean volume change in the patients with volumotion on the injured leg was 0.057 +/- 0.007 ml/100 ml tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

[MRI in orthopedics: diagnosis of joint disorders]

For the visualization of joint structures, magnetic resonance imaging (MRI) has definite advantages over other imaging modalities. High soft tissue contrast and multiplanar capabilities contribute to adequate representation of the joints. With surface and special coils as well as high gradient field strengths, superior spatial resolution can be achieved, thus allowing for depiction of fine anatomical details. Newly developed pulse sequences, especially with fat suppression techniques and utilization of paramagnetic contrast agents (gadolinium complexes) have improved image contrast. Examination techniques, results and diagnostic value of MRI in various joints are discussed. Close cooperation between orthopaedic surgeons and radiologists is mandatory for effective and economically acceptable use of MRI in the diagnosis of joint disorders.

[Results of surgical treatment of posterior knee instability]

A retrospective study was performed to evaluate the outcome of operative treatment of posterior cruciate ligament (PCL) lesions in 115 patients operated on between 1980 and 1989. Follow-up was possible in 89 patients at 18-124 months postoperatively (average 76 months). In 65 re-examination was possible, while 24 patients returned a questionnaire. The results of patients who were operated on in the acute state were superior to those with chronic instabilities (Lysholm 79.9 +/- 18.5 vs 64.3 +/- 22.1; Tegner 5.7 +/- 2.3 vs 4.2 +/- 2.2; instrumented posterior drawer 5.3 +/- 3.5 mm vs 5.9 +/- 3.8 mm). On the other hand, the preoperative scores of symptomatic patients with chronic instabilities (Lysholm 38.8 +/- 22.0; Tegner 2.1 +/- 1.7) were clearly lower. Extraarticular procedures (Hughston) slightly improved symptoms in posterolateral instabilities. Olecranization of the patella had no influence on the results. Interpretation of the data is difficult as there was no matched group of patients with nonoperative treatment. A reviews of the literature suggests that isolated PCL tears are best treated with conservative management. Only in cases where associated ligamentous injuries require operative treatment should PCL reconstruction be performed. Chronic posterior instabilities should be treated operatively only if the patients are severely symptomatic. However, complete restoration of knee stability was usually not achieved with the techniques presented in this paper.

[Initial clinical results with heat-treated homologous bone transplants]

Several ways for HIV inactivation in bone allografts are being discussed. These methods must be efficient, but they must not compromise biologic properties of the allografts. According to animal studies, moderate heat treatment of bone allografts in a 65 degrees C waterbath has no adverse effects on osseointegration. A clinical follow-up study of 49 patients with heat treated bone allografts was conducted. 37 patients with conventional cryopreserved allografts were included in the study as controls. Average follow-up time was 27 months. Results were evaluated by clinical and X-ray examination, using a modified radiologic score. No significant differences in the two groups were detected, except for a slight retardation in bony integration of the heat treated allografts between week 39 and 52 postoperatively. Complication rates were 11.4% vs. 10.7%. In conclusion, moderate heat treatment of bone allografts appears to be a practicable and safe method to improve safety in bone transplantation in clinical practice. In addition to the known guide lines for bone banking heat treating of allografts should be further improved in order to minimize the low remaining risk of infection which exists despite of the three months test.

Surgical treatment of acromioclavicular dislocation

Sixty-five patients were operated on for acromioclavicular dislocation between 1980 and 1991. Seventeen type II and 48 type III dislocations according to the criteria of Tossy et al. were treated. Three different surgical techniques were employed. (1) tension band wiring, (2) a modification of the Bosworth repair, (3) reconstruction of the ligaments with augmentation by a PDS (polydioxanon) cord. Forty-four patients could be investigated retrospectively, and an additional 12 were recorded by questionnaire. The Taft score was used, representing self-assessment, clinical statements and radiological findings. Of all investigated patients 87.5% had a normal range of motion without any loss of strength, and 32% suffered an osteoarthritis of the acromioclavicular joint. The average Taft score was 9.8. With respect to the three surgical techniques, reconstruction of the ligaments augmented by a PDS cord produced the best result, an average Taft score of 10.8.

[Possibilities for HIV inactivation in homologous bone transplants]

Recently, the availability of bone allografts has declined dramatically, due to the three-month HIV test which is often difficult to obtain. Accordingly, there is a search for methods to inactivate HIV in bone allografts without compromising the biologic quality of the grafts. Chemical substances require long exposure and desorption times, to ensure that no toxic agents remain within the bone before actual transplantation. X-ray inactivation leads to complete loss of any osteoinductive properties of the allografts, according to some authors. In addition, the high doses that are necessary are difficult to apply. Autoclaving has been practiced in some instances, but all experimental results and some more recent clinical observations warn that osteoinductive properties of the allografts are lost during the autoclaving process. Lower temperatures (56 degrees C) are sufficient to warrant inactivation of HIV, and some experimental results and preliminary clinical observations indicate that moderate heat treatment of bone allografts in a water bath may become a useful method for virus inactivation of bone allografts.

[Primary suture of the anterior cruciate ligament. A critical analysis]

Recently some authors have claimed that primary repair of an acute tear in the anterior cruciate ligament will fail in the long run. A review of the literature reveals that this opinion is mainly based on an American study in 1976. However, the poor results presented in this study were never reproduced. The study is critically analyzed, and 14 more papers presenting successful primary reconstructions of the anterior cruciate ligament are discussed. Preserving proprioceptive structures may be an important advantage of this technique, as it is hypothesized that the anterior cruciate ligament functions as a significant sensory organ, not only providing proprioceptive information, but also initiating protective and stabilizing muscular reflexes. In conclusion, it is recommended that primary suture be used combined with intra-articular semitendinosus tendon augmentation for rapid rehabilitation in cases of acute tears in the anterior cruciate ligament.

The importance of arthroscopy in sports injuries in children and adolescents

Within a 3-year period (1985-1988), 60 children and adolescents with knee injuries sustained mainly while skiing or playing football (soccer) underwent clinical examination, X-radiography and arthroscopy. Nearly all the patients still had open epiphyseal plates in the knee region. Arthroscopy revealed more severe intra-articular trauma than had been suspected on the basis of clinical findings. The skiing injuries most commonly involved anterior cruciate ligament tears, whereas injuries of the patellar retinaculum and medial meniscus lesions predominated in soccer injuries. On comparison with arthroscopic diagnosis, clinical diagnosis was erroneous in about 45%. The most common mistaken clinical diagnosis was "medial meniscus tear". Of the 60 knee joints subjected to arthroscopy, 40 were severely enough injured to warrant surgery. Only one had normal intra-articular findings. The study demonstrates that children and adolescents can suffer knee trauma requiring surgery, despite open growth plates. Downhill skiing and soccer are particularly risky sports in this respect. Therefore, sports injuries involving haemarthrosis are clearly an indication for arthroscopy, even in childhood and adolescence. Arthroscopy enables early identification of the type and extent of intra-articular trauma and subsequent early initiation of appropriate therapy.

Mechanical failure of the femoral component in cemented total hip replacement--a finite element evaluation

The quality of cementation is of paramount importance for the long-term clinical outcome in cemented total hip replacement. Four "modes of failure" have been differentiated by various authors and correlated with the clinical findings. A finite element analysis was performed to simulate an ideally cemented femoral stem-type prosthesis as well as failure modes III (proximal anchorage of implant only) and IV (Distal anchorage of implant only). While failure mode III produces a stress distribution at the bone/acrylic cement interface, which is similar to the ideally cemented prosthesis, failure mode type IV leads to a hazardous rise of the interface stresses. This correlates well with the clinical findings given in the literature, thus validating the computer simulation used. Distal cementation only of a stem-type femoral component in total hip replacement should definitely be avoided.

[Proprioception in the anterior cruciate ligament of the human knee joint--morphological bases. A light, scanning and transmission electron microscopy study]

In 21 human anterior cruciate ligaments removed with their synovial sheaths during autopsy and operation, nerves and nerve endings were demonstrated by light microscopy, scanning electron microscopy and transmission electron microscopy. Ultrastructural examination allowed a classification of nerve endings into three types: Ruffinian corpuscles, Pacinian corpuscles and free (afferent and efferent) nerve endings. The nerve endings corresponded to those characteristic of articular capsules. The anterior cruciate ligament shows evidence of a proprioceptive function besides its stabilizing function, which is based on its collagenous structure. Together, they probably represent the most important factor in the dynamic stabilization of the knee joint. At present it is only possible to speculate on the potential clinical significance of these findings, for example in development of rehabilitation programs and prevention strategies offering protection against anterior cruciate tears. This also applies to the question of whether to preserve the ligament during surgery for ruptures and knee-joint prostheses.

[Results of surgical treatment of proximal biceps tendon rupture]

During a 9-year period we operated on 19 patients in whom the proximal tendon of the biceps brachii muscle had been disruptured. Various surgical techniques were employed, such as refixation at the processus coracoideus, tenodesis in the sulcus intertubercularis, keyhole operation, in combination with an intraarticular inspection, revision, or if necessary widening of a narrow passage ("defile"). Follow-up was possible in 15 patients for an average period of 3 years after the operation, in respect of clinical, roentgenological and isokinetic findings. Results were mainly good while employing a variety of different surgical techniques; in only 3 patients the shoulder function remained restricted, painful and/or weakened. The isokinetic maximum torque was either increased on the operated side (after coracoid refixation) or reduced (after tenodesis in the sulcus). The underlying biomechanical causes are explained. Good results can be obtained in surgical treatment of the rupture of the proximal biceps tendon provided the procedure is accurately executed while taking into consideration, at the same operation stage, the associated pathology of the rotatory cuff. For biomechanical reasons, preference should be given to the operations according to Hitchcock and Bechtol in respect of refixation, and to the keyhole operation method.

[Results of the surgical therapy of distal biceps tendon rupture]

The rupture of the distal tendon of the biceps brachii is a relatively uncommon but severe injury of the upper extremity. Different techniques for surgical reattachment are described with a small number of patients. The purpose of this study was to show whether the surgical technique modified after Max Lange leads to good clinical results in the number of eleven patients who underwent physical examination between six months and eight years after surgical repair. Three patients showed a small deficit in the range of motion. Six patients had ossifications in the distal tendon, no patient had an osteoarthritis of the elbow. Strength and endurance, tested by the Cybex-II isokinetic dynamometer, showed no significant difference between operated and healthy extremity. The surgical technique modified after Max Lange is a safe and effective way for reattaching the distal tendon of the biceps brachii.

[Rupture of the distal tendon of the biceps--diagnosis and results]

The rupture of the distal tendon of the biceps brachii is a uncommon injury of the upper extremity. For this reason, the clinical patterns are quite unknown. Between 1980 and 1989 14 patients were treated operatively because of a distal biceps tendon rupture. Aetiology, diagnostic efforts and operative treatment are demonstrated as well as the results of a follow-up of 12 patients. The results of operative treatment are quite good and point out the need for operative treatment.