Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Input: Consider Input: Abstract: Twenty patients were examined by standard radiography and roentgen stereophotogrammetric analysis (RSA) during a two-year period after total hip arthroplasty. Eleven of the acetabular components migrated cranially and three femoral components migrated distally. This migration was most rapid during the first four months after operation. Our findings support the possibility that mechanical loosening is initiated by thermal injury during polymerisation of the cement; the less frequent migration of the metallic femoral component compared with the polyethylene acetabular component may be because the metal acts as a heat sink. Standard radiographs were inadequate for assessment of early mechanical loosening, whereas RSA could reveal migration within four months of the arthroplasty.

Output: Follow-Up Studies

Input: Consider Input: Abstract: Magnetic resonance imaging (MRI) is a powerful new tool for the study of human anatomy and pathology. By various MRI techniques, the structure of the middle and inner ears of aborted 20-week fetuses is defined and compared to gross anatomic sections. MRI's potential for evaluating temporal bone development and diseases of the ear is discussed.

Output: Ear, Middle

Input: Consider Input: Abstract: We did complete histologic study on 148 gravid tubes and found that nearly 90% showed chronic lesions. CS was the most frequent lesion encountered (95.5%), followed by SIN (32.6%). Most frequently the lesions were extensive and both the ampulla and isthmus were involved. We therefore question the conservative approach in the treatment of certain TPs.
Output: Chronic Disease