Aplasia of both cruciate ligaments is a rare congenital disorder. A 28-year-old male presented with pain and the feeling of instability of his right knee after trauma. The provided MRI and previous arthroscopy reports did not indicate any abnormalities except cruciate ligament tears. He was referred to us for reconstruction of both cruciate ligaments. The patient again underwent arthroscopy which revealed a hypoplasia of the medial trochlea and an extremely narrow intercondylar notch. The tibia revealed a missing anterior cruciate ligament (ACL) footprint and a single bump with a complete coverage with articular cartilage. There was no room for an ACL graft. A posterior cruciate ligament could not be identified. The procedure was ended since a ligament reconstruction did not appear reasonable. A significant notch plasty if not a partial resection of the condyles would have been necessary to implant a ligament graft. It is most likely that this would not lead to good knee stability. If the surgeon would have retrieved the contralateral hamstrings at the beginning of the planned ligament reconstruction a significant damage would have occurred to the patient. Even in seemingly clear diagnostic findings the arthroscopic surgeon should take this rare abdnormality into consideration and be familiar with the respective radiological findings. We refer the abnormal finding of only one tibial spine to as the "dromedar-sign" as opposed to the two (medial and a lateral) tibial spines in a normal knee. This may be used as a hint for aplasia of the cruciate ligaments.

A 56-year-old man presented with a two month history of increasing anterior knee pain without previous trauma. As usual we recommended physiotherapy with stretching exercises of the quadriceps muscle. Since symptoms did not improve after 6 weeks MRI was performed. Surprisingly a hyperintense lobulated mass of the patella with small fluid-filled cavities at the inferior pole was revealed. We performed an open biopsy to exclude any malignancy and diagnosed an aneurysmal bone cyst. Further examination with CT scans showed an aggressive behaviour with cortical breakthrough.We performed an intralesional curettage with additional high-speed burring and bone cement packing. Sixteen months later the patient was free from any complaints and without signs of local recurrence.Primary bone tumors of the patella are extremely rare and occurrence of aneurysmal bone cysts in this localization is very uncommon. This case report indicates that although anterior knee pain is a very frequent and usually harmless symptom, it is essential to consider that it might also be caused by more severe disorders such as bone tumors.

e22114 Background: Due to chronic hypoxia cancer cells are growing in a more acidic environment compared to physiological tissue. Recent preclinical in vitro and in vivo data have shown direct pH-sensitive anti-tumor activity by pore formation and apoptosis when synergistically acting combinations of Diflunisal, Paraaminosalicylic acid (PAS) and Aspirin were applied. Therefore, a pilot study was performed to evaluate its clinical relevance and its update is presented. Methods: A total of 65 patients (n=65) with advanced solid tumors and the lack of standard treatments were treated with a protocol consisting of 3-5 weeks with 2 daily i.v. infusions of Diflunisal and Aspirin for 4 days per week after they had signed an informed consent form. Response evaluation was assessed by PET/CT differentiating in metabolic and metric (RECIST) response and tumor marker where available. Results: Out of 65 patients treated 8 patients suffered from colorectal cancer, 17 from breast cancer, 6 from ovarian cancer, 3 from lung cancer, 3 from gastric cancer, 3 from glioblastoma, 3 from CUP, 1 from hemangioendothelioma, 1 from pleuramesothelioma, 1 from non-Hodgkin lymphoma, 2 from pancreatic cancer, 1 from choledochus cancer, 3 from prostate cancer, 5 from sarcomas, 2 from head and neck cancer, 1 from melanoma, 1 from cervical cancer, and 1 from thyroid cancer, respectively. Side effects related to the therapy have been fatigue grade I (30%), nausea grade I (13,3%), tinnitus (25%), hypertension (2,5%), dyspnea (3,3%) and burning sensation in tumor areas (65%). 33 patients were evaluable for metric response, 20 for metabolic and 19 for tumor marker response assessment. For tumor marker follow up 11 % had a CR, 53 % a PR, 26 % a SD of > 3 month and 11 % a PD. For metric follow up 3 % had a CR, 33 % a PR, 39 % a SD of > 3 month and 24 % a PD. For metabolic follow up 10 % had a CR, 35 % a PR, 35 % a SD of > 3 month and 20 % a PD. Conclusions: This continuing pilot study confirms a direct pH-sensitive synergistic anti-tumor activity of intravenous Diflunisal, PAS and Aspirin in patients with advanced solid tumors. Therefore, a further evaluation in a controlled clinical phase II study should be performed.

e13508 Background: Due to chronic hypoxia cancer cells are growing in a more acidic environment compared to physiological tissue. Using this differentiation a new therapy method has been developed for targeted chemotherapy. Recent preclinical in vitro and in vivo data have shown direct pH-sensitive anti-tumor activity by pore formation and apoptosis when synergistically acting combinations of diflunisal, paraaminosalicylic acid (PAS) and aspirin were applied. Therefore, a pilot study was performed to evaluate its clinical relevance. Methods: A total of 30 patients (n=30) with advanced solid tumors and the lack of standard treatments were treated with a protocol consisting of 3-5 weeks with 2 daily i.v. infusions of diflunisal and aspirin for 4 days per week after they had signed an informed consent form. Response evaluation was assessed by PET/CT differentiating in metabolic and metric (RECIST) response. Results: Out of 30 patients treated 4 patients suffered from colorectal cancer, 11 from breast cancer, 2 from ovarian cancer, 2 from lung cancer, 2 from gastric cancer, 2 from glioblastoma, 1 from CUP, 1 from hemangioendothelioma, 1 from pleuramesothelioma, 1 from non-Hodgkin lymphoma, 1 from pancreatic cancer, 1 from choledochus cancer, 1 from prostate cancer, respectively. Side effects related to the therapy have been fatigue (6,7%), nausea (13,3%), tinnitus (10%), hypertension (6,7%), dyspnea (3,3%) and burning sensation in tumor areas (3,3%). Out of 30 patients treated, until today 14 were evaluable for metric response, 12 for metabolic and 13 for tumor marker response assessment. For tumor marker follow up 2 patientis (6,7 %) had a CR, 6 (20 %) a PR, 4 (13,3 %) a SD of > 3 month and 1 (3,3 %) a PD. For metric follow up 0 patients (0 %) had a CR, 6 (20 %) a PR, 5 (16,7 %) a SD of > 3 month and 3 (10 %) a PD. For metabolic follow up 1 patients (3,3 %) had a CR, 3 (10 %) a PR, 5 (16,7 %) a SD of > 3 month and 3 (10 %) a PD. Conclusions: This pilot study confirms a direct pH-sensitive synergistic anti-tumor activity of intravenous salicylic acids in patients with advanced solid tumors. Therefore, a further evaluation in a controlled clinical phase II study will be performed.