Given an abstract of a paper, generate a title for this paper such that conveys the key focus of the paper.

Ex Input:
Abstract: The authors present an in-depth clinical, radiographic, and pathologic analysis of a 62-year-old man with massive bone reabsorption around the proximal femur in a total hip arthroplasty (THA). The THA was revised 13 years after implantation. Thirty millimeters of calcar resorption was noted radiographically. Evidence of stem bending was present on examination of the femoral implant, and marked wear of the acetabular cup was noted. The pathologic evaluation of removed calcar bone and cement revealed a histiocytic mass invading the bone. Intracellular and extracellular polymethylene debris was noted within the invasive mass. Evidence of fragmented methylmethacrylate cement was also present. The bone-cement interface in the excised calcar region contained segments that showed active bone remodelling around the cement without an interposed membrane. It is possible that this case of calcar resorption began with histiocytic activation and recruitment by polyethylene wear debris followed by active bone lysis. The process may be perpetuated by the fragmentation of cement, as motion occurred at the calcar bone-cement interface, and may represent an extreme example of a process occurring in cases of calcar resorption in general.

Ex Output:
14-year follow-up study of a patient with massive calcar resorption. A case report.

Ex Input:
Abstract: The paper describes physical examination of the knee and some of the knowledge functional anatomy necessary for diagnosis and management of knee disorders that occur in children. It includes brief descriptions of the diagnostic features of these conditions, as well as principles of conservative and surgical management.

Ex Output:
Knee problems in children.

Ex Input:
Abstract: Seven dog lower left lung lobes were statically inflated and perfused at a constant rate for each lobe with a perfusate in which the hematocrit was altered over a wide range. The permeability-surface area of urea was calculated from multiple indicator dilution curves using two separate injectates for each hematocrit level. One injectate contained only 125I-albumin as the vascular reference tracer and the other contained both 51Cr-erythrocytes and 125I-albumin as the vascular reference tracers; both contained [14C]urea as the permeating tracer. The results strongly indicate that the phenomenon of "erythrocyte trapping" of urea does not affect the calculation of urea permeability-surface area product provided the appropriate albumin-erythrocyte composite reference tracer is utilized in its calculation.

Ex Output:
Effect of perfusate hematocrit on urea permeability-surface area in isolated dog lung.