This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Orthopaedics
[{'content': "Trendelenburg's test positive in all EXCEPT - \nSelect and explain. \nA. Posterior dislocation of hip, B. Poliomyelitis, C. # Neck of femur, D. Tuberculosis of hip joint", 'role': 'user'}, {'content': "Answer: D \nExplanation: Trendelenberg test\xa0:\n\nIt tests the stability of the hip and particularly of the abductor mechanism of the limb on which the patient is standing.\n\nThe principle of the test :\n\nNormally when one leg is raised from the ground the pelvis tilts upwards on that side, through the action of the hip abductors of the standing limb.\nIf the abductors are inefficient they are unable to sustain the pelvis against the body weight and it tilts downwards instead of rising up on the side of the lifted leg.\nNote that the test is performed with the patients standing on the affected leg.\n\nAbductor mechanism :\n\nIt can be compared with the lever, with the body weight is trying to tilt the pelvis down; the hip joint being the fulcrum and the abductor muscles being the power acting through the lever arm (from the head of the femur to attachment of the abductor's muscles on the greater trochanter - the neck of the femur)\n\nCauses of the positive Trendelenburg test :\n\nAny failure of the abductor mechanism causes\xa0dipping\xa0of the\xa0pelvic\xa0(ASIS) on the normal side.\n\nThere are three fundamental causes :\n1)\xa0\xa0\xa0Paralysis of the abductor's muscles\n\neg. Polio.\nParalysis of superior\xa0gluteral\xa0nerve (Supplies gluteus medius & minimus)\n\n2) Marked approximation of the insertion of the abductor muscles to their origin by upward displacement of the greater\xa0trochanter ;\xa0so that the muscles are slack.\n\neg. Severe coxa vara,\ndislocation of hip\n\n3)\xa0The absence of stable fulcrum & lever arm about which the abductor muscles can act\n\nNeck femur fracture\nDislocation of hip,\nDestructruction\xa0of\xa0head\xa0as in Perthe's diseases.", 'role': 'assistant'}]