AbstractHip resurfacing arthroplasty has become an attractive treatment option for young, active patients with femoral head necrosis. However, little information is available about the potential thermal damage to the remaining femoral head when a cemented component is used. We used an experimental model to measure the temperature profile at the cement–bone interface during hip resurfacing. We compared four simulated lesion sizes—15, 25, 33, and 50%—of the femoral head, and a control group with no cystic lesion. Temperatures were measured with the specimens in a 37°C saline bath or with copious pulsed lavage. With specimens tested in the bath, peak temperatures were higher, and durations of temperatures above 50°C were longer, in femoral heads with necrotic lesions (88.8 ± 7.5°C; 17.6 ± 1.1 min for a 15% lesion; 96.2 ± 7.2°C; 22.86 ± 1.3 min for a 25% lesion; 99.7 © 200 ± 9.4°C; 28.6 ± 2.0 min for a 33% lesion; and 97.2 ± 4.2°C; 35.6 ± 2.4 min for a 50% lesion) than those in the control group (65.8 ± 4.9°C; 10.0 ± 1.3 min). The larger the cement‐filled cysts, the longer the temperatures remained above 50°C. Although copious lavage reduced the temperature profile in each group, the temperatures remained above 50°C for 7 to 17 min in specimens with necrotic cysts. The measured temperatures during surface replacement are sufficiently high in magnitude and long in duration to cause thermal damage to the remaining bone in femoral heads with preexisting necrotic lesions. Hip resurfacing for femoral head necrosis should be performed with caution. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:1206–1209, 2008