In a retrospective study probable etiological factors of rare cases of osteochondritis dissecans of the patella were analyzed. Anamnestic data and data obtained from standardized roentgenography in the anterior-posterior, axial, and lateral views of the patella were evaluated. Anamnestic data provided no evidence of the etiology in addition to the fact that several patients mentioned a single or multiple trauma. In contrast to this, evaluation of the roentgenograms showed that most of the patients with osteochondritis patellae exhibited a flat articular surface of the patella (types I and V in Hertel's classification) and a distinct accumulation of the patellae with greater lateral than medial facet (types II and III in Wiberg's classification). Furthermore, the axial shape of the patellar groove exhibited a distinct accumulation of type III trochleae, representing a hypoplasia of the medial and hyperplasia of the lateral part of the trochlea. Evaluation of the lateromedial patellar alignment revealed in a distinct accumulation of grade II dislocation medially and laterally. Although the data were obtained from a rather small number of patients, in our opinion these results support the theory of biomechanical induction of osteochondritis dissecans patellae. Further dynamic analyses are needed to clarify biodynamic effects on the patella and the patellofemoral joint.

Traumata or repetitive microtraumata, malalignment with varus or valgus deviation, or chronic joint instability are discussed in the aetiology of osteoarthritis and osteochondritis dissecans of the knee. Biomechanical factors influencing the patterns of pressure distribution at the articular surface and the subchondral bone are suggested to be most important in the pathogenesis. Consequently, the patterns of pressure distribution at the femoral condyles of weight-bearing knee joints were investigated in a cadaveric biostatic model. The pressure in the articular joint space was evaluated with pressure-sensitive films of the knee in different joint positions in the coronal plane (10 degrees varus, 10 degrees valgus, and neutral position) without and with medial collateral ligament (MCL), lateral CL (LCL), MCL + anterior cruciate ligament (ACL) or LCL + ACL ligament division. Results demonstrated that the location of the contact area and the peak pressure depended on the joint position and stage of ligamentous division. Without ligament division, a maximum peak pressure was observed at the medial condyle in the neutral and varus positions. Only in the valgus position did the lateral condyle show a higher peak of pressure than the medial condyle. Ligament division of the LCL and LCL + ACL resulted in an increase of peak pressure at the medial condyle, particularly in the varus position. Division of the MCL and MCL + ACL ligament complex reduced the differences between the medial and lateral condyle. In the valgus position, the peak pressure was significantly higher at the lateral condyle. The absolute maximum peak pressure was measured in the varus position at the medial condyle after division of the LCL and ACL.(ABSTRACT TRUNCATED AT 250 WORDS)

We report on our experiences with internal hemipelvectomy followed by an implantation of a endoprosthetic pelvic replacement (EPR) performed in 15 patients over a period of 15 years. Our primary aim was to determine the implications for this procedure because of its high rate of complications. Due to the malignant character of the disease and the biomechanical stress on the anatomical region, the demands on the surgeon are high. The most important factor is a sufficiently wide resection of the primary tumour because most are chondrosarcomata which do not respond to other therapies. In addition, the malignant character of the tumour has the greatest influence on the long-term results. Internal hemipelvectomy and endoprosthetic pelvic replacement are accompanied by a high rate of operative and postoperative complications Nevertheless, nearly full anatomical and functional reconstruction can be obtained provided a medium level of function is accepted. Follow-up results of the remaining six still living patients were evaluated by means of three different scoring systems. All patients had only a medium score but emphasised subjective acceptance of the endoprosthetic pelvic replacement even when removal was necessary later on. Because of the lower functional outcome of alternative operative procedures such as pseudarthroses and arthrodeses and problems with the replantation of autoclaved autografts or implantation of an allograft, internal hemipelvectomy combined with endoprosthetic pelvic replacement is the treatment of choice for these specific acetabular lesions, provided a complete resection is feasible. Otherwise, an external hemipelvectomy is necessary because even alternative limb-salvaging procedures must incorporate the same complete resection of the tumour. In cases of metastatic lesions, internal hemipelvectomy and endoprosthetic pelvic replacement are indicated relatively because of the systemic character of the disease. The procedure should be considered only when resection of a solitary metastasis enables a cure and/or prolongation of life with an improved quality of life.

We report a case of bilateral osteochondritis dissecans of the medial trochlea femoris. Arthroscopic removement of loose bodies in the symptomatic left knee led to an excellent result; the untreated right knee showed effusion and locking one year later. This condition should be considered in the diagnosis of patellofemoral pain.

Biomechanical factors influencing the patterns of pressure distribution at the articular surface and the subchondral bone are suggested to be most important in the pathogenesis of osteoarthritis and osteochondritis dissecans at the knee joint. Besides this, chronic joint instability is another important factor under discussion in the etiology of osteoarthritis of the knee. The patterns of pressure distribution on the femoral condyles of weight-bearing knee joints were investigated in a biostatic cadaver model. The pressure on the femoral condyles was evaluated using pressure-sensitive films with the knee in different physiological joint positions (extension, 15 degrees and 30 degrees flexion) with and without division of either the medial collateral ligament (MCL), the lateral collateral ligament (LCL), the MCL and the anterior cruciate ligament (ACL), or the LCL and the ACL. Results showed that the location of the contact area and peak pressure depended on the joint position and stage of ligament division. Without ligament division the maximum peak pressure was always observed on the medial condyle. Only after MCL and combined MCL + ACL division did the lateral condyle show in extension a higher peak pressure than the medial condyle. Division of the LCL and LCL + ACL resulted in an increase in peak pressure on the medial condyle, particularly in flexion. The highest peak pressure of all was measured in the 30 degrees flexion position on the medial condyle after division of the LCL. The lowest at all was found on the lateral condyle in 15 degrees flexion after LCL division. Additional ACL division resulted in only minor further changes.(ABSTRACT TRUNCATED AT 250 WORDS)