Introduction This article describes a clinical case of a stress fracture of the distal tibial metaepiphysis following a high-energy tibial shaft fracture stabilized with interlocking intramedullary (IM) nail to identify an underlying cause of the traumatic event. Objective To demonstrate the occurrence of a stress fracture after adequate interlocking IM nailing of a traumatic fracture due to systemic osteoporosis that presented no clinical manifestations prior to injury. Material and methods Magnetic resonance imaging was performed to diagnose the stress fracture. Bone mineral density and laboratory markers of bone metabolism were measured to identify underlying causes of the stress fracture. Consolidation of the traumatic fracture fixed with interlocking IM nail was re-evaluated with a radiograph of the fracture site. Results The stress fracture was seen off the IM nail on MRI scans. Osteoporosis was diagnosed with bone densitometry using dual energy X-ray absorptiometry, and deoxypyridinoline, a bone resorption marker and vitamin D deficiency were identified with laboratory tests. No signs of fracture union were seen radiologically. Conclusion A stress fracture of the distal tibial metaepiphysis detected 3 months after a tibial shaft fracture fixed with interlocking IM nail can be considered an insufficiency fracture caused by primary (idiopathic) systemic osteoporosis that was asymptomatic prior to the high-energy injury.

Phosphaturic mesenchymal tumor can cause osteomalacia due to excessive secretion of fibroblast growth factor 23 (FGF23), which disrupts the metabolism of phosphate and vitamin D. These tumors are predominantly benign, but less than 5% of them are malignant forms. This article presents the first clinical case in the Russian Federation of a 69-year-old patient with severe hypophosphatemia due to metastatic prostate cancer. Increased secretion of FGF23 are described in the androgen-resistent prostate cancer, which led to pronounced disorders of mineral metabolism, accompanied by a clinical symptom of weakness, pain in the bones, immobilization of the patient. The condition was regarded as worsening against the background of the progression of the disease. However, symptomatic therapy aimed at increasing the level of phosphate significantly improved the patient’s general condition. The medical community should be aware of the possibility of developing hypophosphatemia in patients with weakness and bone pain, which are not always associated with the progression of metastatic prostate cancer.

Phosphaturic mesenchymal tumor inducing development of phosphopenic osteomalacia is manifested as deformations and multiple fractures of the bones which decreases patients’ quality of life and leads to disability. Insufficient awareness about this pathology among doctors and absence of symptoms allowing its diagnosis cause late diagnosis of the disease despite application of up-to-date high-tech diagnostic methods. The optimal treatment of phosphaturic mesenchymal tumors is radical resection. However, strong connection of the tumor with the surrounding tissues and, in many cases, absence of a capsule or sclerosis (if located in the bones) complicate surgery leading to high recurrence rate. Radical resection of phosphaturic mesenchymal tumors is especially complicated in cases of localization in complex anatomical areas of the lower limbs.The disease is characterized by long timespan between first clinical signs, diagnosis, and start of treatment (sometimes, several years). Diagnosis confirmation and visualization of the details of phosphaturic mesenchymal tumor requires magnetic resonance imaging. This method allows to examine connection between the tumor and surrounding tissues and the presence of a capsule. Magnetic resonance imaging also allows to accurately determine the area of surgical intervention. Radical tumor resection leads to normalization of blood and urine biochemistry in the span of several weeks. Restoration of bone density and muscle function requires 3–6 months after the operation.

Prospective study of zolendronic acid efficacy was performed in 112 patients with systemic osteoporosis. Study results confirmed the presence of patients who did not response to the treatment: in 15.7 % of observations reduction of mineral bone density (BMD) continued to progress. No significant differences in initial deviations of resorption and bone formation markers, peculiarities of calcium homeostasis were detected in “non respondents”. At the same time by the 12th month after treatment initiation the relationship between BMD increase with preservation of marked decrease of resorption marker (deoxypyridinoline) and bone formation marker (osteocalcin) was noted, that pointed out the expediency of prognostic model creation. Evaluation of the influence of certain risk factors (age, results of blood and urine biochemical tests, data of densitometry including the results of femoral neck BMD in some patients) using discriminant analysis showed that 81.5% of patients were correctly referred to the groups of patients who responded and not responded to treatment. Out of all initially studied parameters the most significant were 7 that in 78.6% of cases (method sensitivity) enabled to identify the patients with negative treatment effect and in 82.1% of cases (method specificity) - with positive treatment effect.