The foundations of computer assisted surgery

Using navigation systems in general orthopaedic surgery and, in particular, knee replacement is becoming more and more accepted. This paper describes the basic technological concepts of modern computer assisted surgical systems. It explains the variation in currently available systems and outlines research activities that will potentially influence future products. In general, each navigation system is defined by three components: (1) the therapeutic object is the anatomical structure that is operated on using the navigation system, (2) the virtual object represents an image of the therapeutic object, with radiological images or computer generated models potentially being used, and (3) last but not least, the navigator acquires the spatial position and orientation of instruments and anatomy thus providing the necessary data to replay surgical action in real-time on the navigation system's screen.

[Measures for allogeneic blood conservation in surgery]

The aim of all efforts to reduce the need of allogeneic blood transfusions is to avoid associated risks. There should particularly be a favourable effect according to the rate of transfusion-transmitted virus infections and immunological side-effects. The acceptance of an individually adjusted lowest haematocrit level and the minimisation of intra-operative blood loss by the application of optimal surgical techniques are among the most essential strategies to reduce or even avoid allogeneic blood transfusions. In addition the following interventions are generally accepted: Preoperative autologous blood donation, where appropriate supported by erythropoietin Preoperative haemodilution, where appropriate supported by erythropoietin Intra- and postoperative blood salvage Topical or systemic pharmacologic interventions to accelerate haemostasis Controlled hypotension Efficacy and indication of the different measures always depend on the individual circumstances of the specific patient. Therefore one should develop an individual approach for every case. In this context the most important subjects are an optimal coordination and if required an appropriate combination of the discussed methods. Algorithms which preoperatively allow approximate calculation of expected transfusion need may be a meaningful tool to facilitate blood conservation planning. However, at the same time one must consider that all strategies to reduce allogeneic transfusion needs are also associated with particular risks. Therefore one has to weigh carefully the pros and cons prior to their application, including the possible alternative of allogeneic transfusion in one's decision making process.

[Endovascular therapy of an abdominal aortic aneurysm in a renal transplant recipient]

INTRODUCTION: The indications for endovascular aortic aneurysm repair (EVAR) are mainly established in hostile abdomen, in patients with significant comorbidities which affect the general operability of the patient and, given the necessary infrastructure, also in ruptured aneurysm. Along to those, we present another possible indication in the presence of a kidney allograft in patients with aortic aneurysm. METHODS: Based on a case report of aorto-biiliac stent-graft repair of an infrarenal aortic aneurysm in a patient with renal allograft, a systematic review of the literature was performed of all similar cases concerning surgical therapy in this constellation. RESULTS: EVAR was performed using an aorto-biiliac system (Zenith) Trifab, COOK) in a 61-year-old male patient 11 years after heterotopic renal allotransplantation in the right iliac fossa. Preoperative renal function was normal. Because the donor renal artery was anastomosed to the recipient's external iliac artery the stent-graft was implanted from the left common femoral artery to minimize temporary allograft ischemia. The intra- and postoperative course was uneventful with a follow-up of presently 12 months. A primary type-II endoleak (retroleak from a lumbar artery) is being treated conservatively so far with embolization being a future option. At present there are 15 cases of EVAR in renal allograft patients that have been reported, all of them being successful. DISCUSSION: All data existing in the literature reported to date as well as our own experience justify the first choice of EVAR in morphologically suitable cases. One major advantage of EVAR in this constellation is the avoidance of aortic cross clamping which poses the graft at risk of ischemia. Long-term results will be most important for definite assessment of EVAR. However, contrast media application during the operation and for CT surveillance should be considered as a major disadvantage.

Injuries to permanent teeth. Part 3: Therapy of root fractures

Diagnostic and therapeutic interventions following dental injuries are not part of the routine practice in the dental office. Quite often, these patients are emergency cases who seek treatment after normal office hours. The objective of this and the future papers is to present the current treatment concepts in dental traumatology at the School of Dental Medicine, University of Berne. The fruitful cooperation in the field of dental traumatology between the Department of Oral Surgery and Stomatology, and the Department of Conservative Dentistry (including pediatric dentistry and endodontology), is based on the interdisciplinary approach that has been established four years ago. Following discussion and evaluation of such treated cases, and considering current clinical and experimental studies, the said concepts have been worked out. The present paper describes the therapeutic approach for root fractures.

[Efficacy of specific physiotherapy for temporomandibular joint dysfunction of muscular origin]

INTRODUCTION: Little explanation is given to patients with temporomandibular disorders and muscles dysfunction on the mechanism and the expected results of conservative treatment. The purpose of this prospective study was to evaluate the efficacy of specific physical therapy prescribed after this explanation was given and also after using a flat occlusal splint adapted only if muscle pain remained after physical therapy. MATERIAL AND METHOD: Twenty-seven patients with temporomandibular joint dysfunction of muscular origin were evaluated after a mean of six sessions of specialized physical therapy with professionals. Patients were treated by oral and facial massages and were trained for self-reeducation. They were also trained for a specific exercise named the "propulsive/opening maneuver". Every patient was questioned on the subjective evolution of pain and the current maximal pain was evaluated with the Visual Analogical Scale (VAS). Clinical evaluation focused on tenderness of masticator muscles and also assessed the changes in the amplitude of mouth opening. RESULTS: Ninety-three percent of the patients treated by specific physical therapy had a significant reduction of their maximal pain feeling (p<0.05). The recovery of an optimal mouth opening without deviation was also improved as was the protrusion. For 33% of the patients a flat nighttime occlusal splint was necessary as a complementary treatment. Twenty-two percent of the patients decided to change their treatment for alternative therapies (osteopathy, acupuncture, etc.). Fifty percent of the patients were convinced of the efficacy of the prescribed treatment. DISCUSSION: Patients who undertake the specific physical therapy and who regularly practice self-physical therapy succeed in relaxing their masticator muscles and in decreasing the level of pain. Explanations given by the doctor concerning the etiology of pain, during temporomandibular joint dysfunction of muscular origin, and the purpose of specific physical therapy increase the capacity of self-relaxation. A flat occlusal splint is indicated for patients who grind their teeth and for those whose pain resists to physical therapy.