Nonunion of Pathologic Fracture after Radiation Therapy

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Abstract
Pathologic fractures treated solely with irradiation show retardation of the healing process and subsequent permanent nonunion. In contrast, irradiation of bone metastases results in substantial new bone formation. Analysis of this striking clinical disparity is the basis of this study. A review of clinical material from our experience yields results similar to those of other large studies: 1. Breast cancer and lymphoma are the most common primary tumors that metastasize to bone. 2. The spine and pelvis are most often affected; that is, in about 70 per cent of the cases. 3. Metastases to the long bones occur in approximately 10 per cent of the cases. The effects of radiations on bone metastases, pathologic fracture, and the mechanisms of pain relief have been sketchily studied and are little understood. Tumor which is metastatic to bone may result in bone deposition or bone destruction. Clinically, the results of radiation therapy are evaluated with follow-up serial radiographs and by the degree of subjective improvement. Radiation therapy is most often involved in the treatment of lytic metastases. Presentation of Clinical Cases Lytic Metastases In the treatment of lytic metastases, it is generally thought that radiation inhibits the growth of tumor, permitting partial restoration of the normal balance of absorption and deposition with resultant filling-in by dense sclerotic bone and concurrent pain relief. Cases I and II are characteristic examples (Figs. 1 and 2). The results of therapy for lytic and blas-temic metastases are excellent, with early pain relief being a frequent and enduring effect. In the majority of instances, serial radiologic examinations show reconstruction of destroyed areas. Pathologic Fracture Review of the literature and textbook material elicits the commonly accepted opinion that radiation therapy is useful in the treatment of pathologic fracture. It is stated that radiations will destroy the tumor cells and allow normal fracture healing to progress. We purposely exclude in this group the fracture of vertebral bodies. In actuality this results from compression, the result of weight-bearing on weakened bone. The sequence of healing in these cases appears very much like the filling-in of lytic metastases after radiation. In through-and-through fracture of a long bone the pattern of healing takes a definite course which can be followed radiographically. The pathologic fracture in these cases is usually the result of a physiologic stress on a markedly weakened bone. The bone is not compressed but commonly undergoes complete break and separation of fragments. In the therapy of treated cases of pathologic fracture it is important to note that the aim of treatment is to destroy tumor and allow fracture healing. Cases III and IV exemplify the nonunion that results after treatment of pathologic fractures (Figs. 3 and 4).

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