Vascular tumor in metal-on-polyethylene THA requiring hemipelvectomy.

Total hip arthroplasty with metal-on-polyethylene implants and metal-on-metal articulations have been an area of recent interest. This article describes a patient with a persistent small soft tissue mass on the anterior groin following total hip arthroplasty with negative findings on infection workup, including blood work and aspiration. Subsequent biopsy findings were consistent with organizing thrombus and necrosis. It then developed into an expansile soft tissue groin mass with significant femoral and pelvic bony destruction and soft tissue infiltration. Metallosis, the formation of a pseudocapsule, and aseptic lymphocyte vasculitis-associated lesions have also been an area of interest following adult hip reconstruction. Occasionally, the formation of subsequent lesions make revision surgery impossible to perform due to bony destruction and soft tissue limitations. Although few in number, most studies or cases that have linked metal-on-metal implants to pseudotumors have been treated with revision surgery and replacement of articulating surfaces. This case highlights a metal-on-polyethylene total hip arthroplasty with a mass presenting with pseudotumor-like characteristics. However, final histology demonstrated fibroadipose tissue with fat necrosis and fibrosis, thickened vascular vessels, and diffuse chronic inflammation with lymphocytic infiltrates, which are more consistent with an atypical inflammatory vascular tumor. The current case illustrates treatment difficulties and provides surgical options for when this event occurs. Although aseptic lymphocyte vasculitis-associated lesions have been observed with metal-on-polyethylene articulations, the multiorgan involvement in this case is unique. In this case, radical excision with hemipelvectomy and complex flap closure was a last resort treatment solution that staved off the prospect of patient mortality.

Treatment of a supratentorial primitive neuroectodermal tumor using magnetic resonance-guided laser-induced thermal therapy.

Supratentorial primitive neuroectodermal tumors (PNETs) are rare tumors that carry a poorer prognosis than those arising from the infratentorial compartment (such as medulloblastoma). The overall prognosis for these patients depends on several factors including the extent of resection, age at diagnosis, CSF dissemination, and site in the supratentorial space. The authors present the first case of a patient with a newly diagnosed supratentorial PNET in which cytoreduction was achieved with MR-guided laser-induced thermal therapy. A 10-year-old girl presented with left-sided facial weakness and a large right thalamic mass extending into the right midbrain. The diagnosis of supratentorial PNET was made after stereotactic biopsy. Therapeutic options for this lesion were limited because of the risks of postoperative neurological deficits with resection. The patient underwent MR-guided laser-induced thermal ablation of her tumor. Under real-time MR thermometry, thermal energy was delivered to the tumor at a core temperature of 90°C for a total of 960 seconds. The patient underwent follow-up MR imaging at regular intervals to evaluate the tumor response to the thermal ablation procedure. Initial postoperative scans showed an increase in the size of the lesion as well as the amount of the associated edema. Both the size of the lesion and the edema stabilized by 1 week and then decreased below preablation levels at the 3-month postsurgical follow-up. There was a slight increase in the size of the lesion and associated edema at the 6-month follow-up scan, presumably due to concomitant radiation she received as part of her postoperative care. The patient tolerated the procedure well and has had resolution of her symptoms since surgery. Further study is needed to assess the role of laser-induced thermal therapy for the treatment of intracranial tumors. As such, it is a promising tool in the neurosurgical armamentarium. Postoperative imaging has shown no evidence of definitive recurrence at the 6-month follow-up period, but longer-term follow-up is required to assess for late recurrence.