Introduction

Although pelvic tilt does not significantly change after primary total hip arthroplasty (THA) at a short term, can vary over time due to aging and the possible appearence of sagittal spine disorders. Cup positioning relative to the stem can be influenced due to these changes.

Total hip replacement in Germany has been performed in 227293 cases in 2015 and tendency is increasing. Although it is a standard intervention, freehand positioning of cup protheses has frequently poor accuracy. Image-based and image-free navigation systems improve the accuracy but most of them provide target positions as alphanumeric values on large-size screens beneath the patient site. In this case the surgeon always has to move his head frequently to change his eye-focus between incision and display to capture the target values. Already published studies using e.g. IPod-based displays or LED ring displays, show the chance for improvement by alternative approaches. Therefore, we propose a novel solution for an instrument-mounted small display in order to visualise intuitive instructions for instrument guidance directly in the viewing area of the surgeon.

For this purpose a solution consisting of a MicroView OLED display with integrated Arduino microcontroller, equipped with a Bluetooth interface as well as a battery has been developed. We have used an optical tracking system and our custom-designed navigation software to track surgical instruments equipped with reference bodies to acquire the input for the mini-display. The first implementation of the display is adapted to total hip replacement and focuses on assistance while reaming the acetabulum. In this case the reamer has to be centred to the middle point of the acetabular rim circle and its rotation axis must be aligned to the acetabular centre axis by Hakki. By means of these references the actual deviations between instrument and target pose are calculated and indicated. The display contains a cross-hair indicator for current position, two bubble level bars for angular deviation and a square in square indicator for depth control. All display parts are furnished with an adaptive variable scale. Highest possible resolution is 0.5 degrees angular, 1 millimeter for position and depth resolution is set to 2 mm.

Compared to existing approaches for instrument-mounted displays, the small display of our solution offers high flexibility to adjust the mounting position such that it is best visible for the surgeon while not constraining instrument handling. Despite the small size, the proposed visualisation symbols provide all information for instrument positioning in an intuitive way.

Purpose: To describe the clinical outcomes of adolescent patients, treated with hip distraction arthroplasty for avascular necrosis (AVN) of the femoral head. Outcomes were examined in order to better understand the usefulness and indications of performing hip arthrodia-stasis in this patient population.

Method: Retrospective review was performed on thirty-one hips with femoral head AVN treated with hip distraction arthroplasty. Mean age at treatment was 14.2 years. Preoperative and follow-up pain, and physical limitations, as well as follow-up range of motion (ROM) were assessed.

Results: Follow up assessment was obtained at 18.3 years of age. Time of follow up was 55.3 months after distraction. The etiologies of AVN were: 11 Slipped Capital Femoral Epyphysis (SCFE); 5 Idiopathic AVN; 3 with hip dysplasia; and 12 others. There was a significant difference in pain preoperatively and postoperatively (p< .001), the majority of patients (79.5%, n=23) had less pain after the treatment. Multivariate regression model demonstrated that patients with SCFE were likely to have less improvement in pain than patients with other etiologies (odds ratio: 24.8; p=.035). All patients had activity limitations before the treatment; at the postoperative assessment more than half of our patients (n=15) reported no limitations in their activities. Nine patients had minor complications with the fixator. At follow up, 5 (16.1 %) patients converted to total hip replacement or arthrodesis.

Conclusion: Hip distraction arthroplasty in adolescent patients with symptomatic AVN reduces the amount of pain and limitation in daily activities, at a follow up of 4.6 years. Arthrodiastasis is not the final solution to AVN, with longer follow up patient’s symptomatology increases. Patients with AVN secondary to SCFE do not beneficiate of this procedure as much as other patients do. Hip distraction is a safe and appropriate procedure to perform in these patients. The procedure might be able to delay definitive surgical procedures at an early age, restoring function and improving the patient s quality of life.

Introduction and purpose: We present a new decision-making method to assist orthopaedists and radiologists in diagnosing soft-tissue tumours. It can distinguish between benign and malignant characteristics in these lesions and classify them histologically with satisfactory efficiency. The pre-surgical diagnosis of the nature of the tumour and whether it is benign or malignant is crucial to planning surgical procedures.

Materials and methods: We reviewed our cases of soft-tissue tumours (47) studied by MRI over the past year and a half. They are part of a multicentre study involving several European hospitals (430 patients).

We analysed the clinical and MRI data: age, clinical presentation, size, shape, location, edges, image signal, calcification, intratumour fat, dependency, fibrosis, relation to fascias, bone and vessel disorders.

Results: With this method we detected 62% benign tumours and 38% malignant. The system sensitivity and specificity are 86% and 95%, respectively.

Conclusions: It is easy to distinguish between vascular, nerve and cystic lesions. The diagnosis of fibrous, synovial and fatty lesions is complex in all cases.

The method can help orthopaedists make a diagnosis before surgery, which will facilitate planning of surgical procedures.

Introduction: Osteoarthritis is the most common joint disease in the world. Biochemical and genetic factors as well as mechanical stress contribute to lesions in the cartilage. The present study analyses the effect of b-Endorphin on the cells of articular cartilage.

Materials and methods: We used rat articular cartilage for the study. After tripsinizing the cartilage and isolating the chondrocytes the cells were cultured in a culture medium. B-Endorphin was dissolved in the culture medium at concentrations of 1 and 10 mM. Only the culture medium was added to the control wells. Naloxone 1 mM was added for co-treatment with b-Endorphin and naloxone. Thirty minutes later, b-Endorphin was added, thus blocking its receptors.

Results: We studied the effect of this procedure on chondrocytes’ proliferating activity and on the proteoglycan synthesis of the extracellular matrix. An increase was observed in the incorporation of 3H-Thymidine, which in turn reflected an increase in the chondrocytes’ proliferating activity. In addition, 35S incorporation analyses were made of cultures which assessed proteoglycan synthesis which showed an increase in the extracellular-matrix forming activity. Differences between the groups with b-endorphin, b-endorphin + naloxone and the control group were found to be highly significant (p< 0.01).

Conclusions: B-endorphin has a stimulating effect upon chondrocytes and proteoglycans present in the extracellular matrix in culture. These stimulating effects are mediated by the interaction with a specific opioid receptor, present in the articular cartilage cells. It may be conceived that trophic stimulation of cartilage cells in the early stages of the disease might partly mitigate the loss of joint surface.