We recently developed a clinical decision support tool, capable of estimating the likelihood of survival at 3 and 12 months following surgery for patients with operable skeletal metastases. After making it publicly available on www.PATHFx.org , we attempted to externally validate it using independent, international data. We collected data from patients treated at 13 Italian orthopaedic oncology referral centers between 2010 and 2013, then applied to PATHFx, which generated a probability of survival at three and 12-months for each patient. We assessed accuracy using the area under the receiver-operating characteristic curve (AUC), clinical utility using Decision Curve Analysis (DCA), and compared the Italian patient data to the training set (United States) and first external validation set (Scandinavia). The Italian dataset contained 287 records with at least 12 months follow-up information. The AUCs for the three-month and 12-month estimates was 0.80 and 0.77, respectively. There were missing data, including the surgeon’s estimate of survival that was missing in the majority of records. Physiologically, Italian patients were similar to patients in the training and first validation sets. However notable differences were observed in the proportion of those surviving three and 12-months, suggesting differences in referral patterns and perhaps indications for surgery. PATHFx was successfully validated in an Italian dataset containing missing data. This study demonstrates its broad applicability to European patients, even in centers with differing treatment philosophies from those previously studied.

INTRODUCTION: Metallosis is a condition characterized by an infiltration of periprosthetic soft tissues and bone by metallic debris resulting from wear or failure of joint arthroplasties. PRESENTATION OF CASE: Authors describe a case of a 45-year-old man treated for an osteosarcoma of the distal femur with a modular prosthesis when he was 18 years old, he developed massive metallosis with skin dyspigmentation after 17 years. His medical\surgical history was remarkable for a left tumoral knee prosthesis implanted 21 years ago. Two years before revision, the patient had a car accident with a two-points prosthesis breakage and despite the surgeon’s advice, the patient refused surgery. In two years, prosthesis malfunction caused a progressive catastrophic soft tissues infiltration of metallic debris. DISCUSSION AND CONCLUSION: Authors suggest that if prosthesis fracture is detected, revision surgery should be attempted as earlier as possible. Highlights:

We report the case of a parosteal osteosarcoma of the distal ulna, treated with wide resection without reconstruction. The patient developed lung metastasis and a mass in the interosseus membrane of the forearm proximally to the osteotomy. The lung mass was found to be a metastasis from parosteal osteosarcoma and the biopsy of the forearm mass revealed a myositis ossificans. The suspicion of a recurrence of parosteal osteosarcoma, already metastatic, led to a second wide resection with no reconstruction. A slice of the radial cortex was taken during this second procedure. From a histological point of view, good margins were achieved and diagnosis of myositis ossificans was confirmed. Two months later, a radius fracture occurred and a synthesis, with plate and screws, as added with poly(methyl methacrylate) (PMMA) to reconstruct the bone loss, was performed. Indication of the reconstructive technique and the complication after distal ulna resection in oncologic surgery are discussed in this paper.