Aim of the study: Joint infection and infection of arthroplasty is a severe problem and its treatment controversial. Treatment with irrigation-suction-drain is still common. We investigated the outcome of this method.

Patients and method: In a retrospective trial, 129 patients with infection of the hip-, knee- and shoulder joint were included. 28 of these patients had an infected hip, knee or shoulder prosthesis.

The mean follow up was 5 years. Patients with rheumatic disease, tumors or patients under immunosuppressive therapy were excluded. Infectious disease consultants supervised the administration of intravenous antibiotics. No antibiotics were added to the irrigating solution.

Results: In 44, 6% of the patient group with septic arthritis the infection could not be eradicated with open surgical debridement and irrigation-suction drainage treatment. In the arthroplasty group 39, 3% were not cured. In total 55 patients underwent additional surgery once or several times to get the infection under control. In 9 of the 28 patient with arthroplasty, the prosthesis had to be removed. The predominant infectious organisms were gram-positive (Staphylococcus epidermidis, Staphylococcus aureus and Streptococcus Group B). Three percent of the knees that were infected clinically had no organisms that could be identified. In 78, 2% of the patients who had additional surgery the antibiogram showed a change in the resistance or/and a change of the pathogen microorganism. Four patients developed a MRSA. The mean duration in the hospital stay was 36 days.

Conclusion: The treatment with irrigation-suction-drain is not recommended according to these results. Other methods like debridement and local antibiotics in combination with systemic antibiotics seams to be more effective according to the literature. Even the duration of the hospital stay is shorter with other methods. The high rate of microorganism changes and changes in the resistance of the microorganism is not acceptable.

There are nearly no studies which describe the influence of the ileotibial tract (IT) on force distribution in the knee joint in a qunatitative manner. Therfore the aim of this work was to develop a complex 3-D computer model of the lower extremity, consisting of bones, joints and muscle models describing their dynamic behaviour including a special IT model. The computer model provided the possibility to simlate training of the muscular system.

Thus the computer model provided among others the possibility to simulate training of the lateral thigh muscles and vastus lateralis with the aim to tension the IT, with the option to calculate force distribution in the knee and compare it with the effect of a tibial osteotomy.

Patients with varus knees were examined. Kinematic data during walking together with forceplate and EMG data wer collected, before and after tibial osteotomy. The anatomy of the patients was recorded by MRI.

Gait and MRI data were the input in the new developed three dimensional computer model. The scaled geometrical data by Delp (1990) and the MRI data were combined to represent the individuals anatomy.

The model of the lower extremity included 43 muscles with origins/insertions and force-length properties described by Delp (1990). The muscle model was improved by including force-velocity properties and a new muscle tendon parameter (tendon stiffness). A functional scaling method was developed to fit the muscle models to individual anatomy. The IT complex was modelled as a coupled unit of IT, tensor fascia latae and gluteus maximus. Muscle and joint forces were determined using an optimization approach minimizing the cube of the sum of muscle forces divided by their upper bounds.

Simulated muscle training of the lateral thigh muscles and vastus lateralis led to an increased tensioning of the IT. As a result the lateral knee force raised considerably similar to the increase after osteotomy. However the decrease in the medial compartment was small and not comparable with the effect of a valgus osteotomy. Tensioning of the IT leads apparently to an overall larger resulting knee force stabilizing the joint, but is not able to reduce medial knee force to an extent that can avoid osteotomy.