Introduction: Two-stage revision is the gold standard for chronic periprosthetic joint infection (PJI). The removal of well-fixed implants, especially the femoral component, can be extremely difficult and additional osteotomies may be needed, which is time-consuming and results in bone stock loss. When the femoral stem is osseointegrated, there is no clear indication for the use of partial two-stage revision. The primary objective was to assess infection eradication after surgery. Methods: Retrospective study of specific case series. A total of eight patients with a chronic uncemented PJI, in the setting of complex revision surgeries, were treated with partial two-stage revision, which included selective retention of the well-fixed femoral component and complete acetabular removal. Stem retention was carried out regardless of the bacteria or associated comorbidities. Results: All patients were re-revision cases with at least two previous surgeries (range, 2–4). Complex revisions were performed in five cases (non-articulated spacer) and simple revisions in three cases (articulated spacer). The minimum follow-up time was 24 months (range, 24–132 months). The infection eradication rate at final follow-up was 100%. Conclusion: Partial two-stage reconstruction is a promising technique for the treatment of chronic PJI in patients with a well-fixed stem and complex re-revision acetabular procedures. Further prospective studies and prolonged follow-ups are required to confirm our results.

The phosphaturic mesenchymal tumour (PMT) is a very uncommon cause of oncogenic osteomalacia (OO), which is a paraneoplastic syndrome with severe clinical osteomalacia. The PMT is a neoplasia that produces the fibroblast growth factor FGF23, resulting in reduced proximal tubular phosphate reabsorption leading to hyperphosphaturia and hypophosphatemia. Our aim is to present our experience and complications in diagnosis and treatment of PMT in three patients. We propose an observational, descriptive and retrospective study of three cases of OO secondary to PMT found in our database of bone and soft tissue tumours. The inclusion criteria were: symptoms related with OO, presence of hyperphosphaturic hypophosphatemia, elevated levels of FGF23 in blood and pathological diagnosis of PMT. In all cases, the disease showed asthenia, non-specific bone pain, progressive functional weakness, and pathological fractures. The average delay time in diagnosis was 7 years. All presented with hyperphosphaturic hypophosphatemia, elevated levels of alkaline phosphatase as well as FGF23. The use of Octreoscan and PET-CT were essential to find the producing tumour and its subsequent biopsy. Treatment was surgery in two cases and one case was treated by CT-guided cryotherapy with neurophysiological control. Once the surgery was performed, the blood parameters normalized. There is no recurrence. Phosphaturic mesenchymal tumor is a very rare entity as part of bone and soft tissue tumors, it may occur in both tissues. The phosphate-calcium homeostasis is altered due to high serum levels of FGF23 because of PMT. Delay in diagnosis is usual, leading to renal and skeletal comorbidities. To avoid this, knowledge of this entity together with high diagnostic suspicion are critical. Surgical treatment leads to normalization of serum levels and systemic symptoms.