Thermographic evaluation of knee osteonecrosis in a patient with systemic lupus erythematosus

Abstract

Osteonecrosis (ON) occurs due to the interruption of blood supply to the bone, causing collapse of bone architecture, cartilage destruction, pain and functional impairment. In most cases, it involves the femoral head and then the knee joint, resulting in the need for surgery to replace the joint, associated with functional impairment and decreased quality of life. In addition, several risk factors for the development of NO in patients with systemic lupus erythematosus (SLE) have been identified. Magnetic resonance imaging is considered the most specific and sensitive diagnostic investigation for ON, however, since the process of ischemia and changes in blood perfusion cause a change in the thermal pattern, medical infrared thermography can be useful in the early diagnosis of abnormalities in the vascularization of this joint. The present study is a case report on thermographic evaluation of knee osteonecrosis in a patient with SLE. For the bibliographic review, a search was carried out in the online databases PUBMED and Scielo, with the descriptors “Osteonecrosis of the knee”, “medical infrared thermography” and “systemic lupus erythematosus”, individually. We selected 4 articles, published between 2017 and 2022, relevant to this study. About the case report, patient female, 45 years old, with chronic pain in both knees and movement limitation. She has a previous diagnosis of SLE and fibromyalgia. On physical examination, he presented pain in flexion and extension of the left and right knee and generalized hyperalgesia. Infrared thermography revealed a low thermal gradient in both knees. Radiographic investigations with MRI showed areas of chronic osteonecrosis in the distal femur and proximal tibia without areas of acute edema in both knees. Infrared thermography is a non-invasive method for determining the infrared radiation or surface heat of an object. Although it is not possible to diagnose specific pathologies, it is possible to detect areas with an increase in temperature in cases of inflammatory processes, as well as a decrease in heat production, due to reduced blood flow, in areas of ischemia. In the thermographic analysis of the lower limbs, the temperature of the knee joint region (ºT = 25.2 ºC) was lower when compared to the distal and fibular portions (ºT > 27 ºC), compatible with the diagnosis of osteonecrosis of the knee, visualized on MRI. Thus, it can be concluded that thermography is an effective option for screening suspected cases of knee osteonecrosis.