LAUSR

Dermal embolization associated with peroneal mononeuropathy: an unusual complication after hyaluronic acid intra-articular injections Dear Editor, Intra-articular injection of hyaluronic acid (HA) has been advocated to treat patients with refractory gonarthrosis (GA) who cannot tolerate other treatments. Adverse effects have been reported in 2–5% of injections and 5–10% of patients, usually mild, temporary, and likely associated with the HA injection. Some serious problems, including severe acute inflammatory reactions, infections, allergic reactions, and anaphylaxis, have been reported. Skin necrosis is an extremely unusual complication, described in only two patients. A 72-year-old woman with bilateral GA had been treated for the last 6 years with biannual intra-articular HA infiltrations. Injections were made using a lateral suprapatellar approach. With the patient supine and the knee extended, an 18-gauge needle was positioned perpendicular to the skin on the suprapatellar bursa 1 cm above the proximal patellar margin. Twentyfour hours after the last bilateral infiltration, she complained of intense pain on the proximal surface of her left leg. Physical examination revealed an extensive, livedoid, erythematous lesion with some nonpalpable, purpuric areas (Fig. 1). The patient was treated symptomatically with nonsteroidal anti-inflammatory drugs (NSAIDs), but 1 week later, the lesion persisted with associated paresthesia on the lower third of the leg and distal strength loss. Electromyography (Fig. 2) confirmed a mononeuropathy of the left peroneal nerve, with decreased nerve excitability and sensorial response, and denervation of the dependent musculature. A punch biopsy was taken, and histopathological examination revealed slightly basophilic, amorphous, intraluminal material in some small vessels located in the subcutaneous fat tissue as well as in the surrounding interstitium (Fig. 3). It stained with Alcian blue, and it failed to show refringence under polarized light. Thrombosis or inflammatory signs were not noted. In addition, there was mild dilatation of the superficial dermal vessels, some showing telangiectatic appearance with minimal lymphoid infiltrate. Findings were considered consistent with HA embolism, and symptomatic treatment with NSAIDs was continued. After 7 months, skin lesions had almost completely disappeared and muscular function returned to normal. Only mild hypoesthesia on the involved area persisted for 10 months. Our patient experienced a highly unusual complication of HA intra-articular injection, with livedo reticularis lesions, pain, and neuropathy, which started in the first 24 hours after the procedure. Skin biopsy demonstrated HA embolism in dermal vessels as the etiological factor. Only two similar cases are available in the literature, but this is the first patient with associated neuropathy. It is reasonable to admit that neural damage is related to the involvement of vasa nervorum by HA embolism, similar to that demonstrated in skin vessels. Spontaneous resolution of the cutaneous lesions in parallel to neural function recovery without specific treatment also favors considering HA as the only cause of the patient’s complications, for it is expected HA to be reabsorbed in about 6 months. This complication is likely associated with incorrect injection technique: hyaluronic acid was either injected into the wrong anatomic site or it leaked from the joint due to direct injury with subsequent embolization. Histopathologically, HA is seen in the dermis as basophilic amorphous material which stains positively for Alcian blue but is negative when examined under polarized light, features present Figure 1 Patient presented with extensive livedoid and purpuric lesions involving the lateral aspect of her left leg