Pericollapse Stage of Osteonecrosis of the Femoral Head: A Last Chance for Joint Preservation

Zhang, Qing-Yu; Li, Zi-Rong; Gao, Fu-Qiang; Sun, Wei

The three most commonly used grading systems for the evaluation of ONFH include the Ficat system, ARCO system, and Steinberg system. [12] The Ficat classification system mainly considers collapse observed on standard radiographs, making it impossible to quantify the lesion size and assess disease progression. [13] The classification system proposed by the ARCO consists of four stages with comprehensive reference to X-ray, magnetic resonance imaging (MRI), computed tomography (CT), bone scintigraphy, and histologic findings. [14] In the ARCO system, Stage III indicates evidence of subchondral fracture, and the modified Nijmegen ARCO system further subdivides this stage into an early and late phase according to the existence of femoral head collapse. [15] Mont et al. [16] defined the stages of ONFH as precollapse, early collapse (head depression ≤2 mm), late collapse (head depression >2 mm), and acetabular changes. [1] However, to evaluate the status of ONFH, these classification systems are apparently not sufficient. The pericollapse stage is a conception that is first recommended in an attempt to assess a continuous period before and after head collapse as a whole. [17] At first, this term refers to ARCO Stage II ONFH with necrotic lesions located at the anterolateral part of the femoral head as well as ARCO Stage III ONFH with head depression <4 mm observed on an anteroposterior film, a faint sclerotic band, and a pain history of <6 months. It reflects a gray area lasting from the extensive trabecular fracture to early collapse of ONFH. [17] However, this definition has several flaws in its application of clinical diagnosis and treatment guidance. First, ARCO Stage II ONFH is normally asymptomatic and has a variable development process according to this classification system. [3, 9, 10] Second, by searching related electronic databases, we found that currently, there were no clinical reports regarding the treatment of pericollapse ONFH according to this definition. Therefore, authors of review articles tend to use Ficat Stages II-III or ARCO Stages II-III ONFH to approximately evaluate the pericollapse period, which may impose a big selection bias. [17] Last but not least, the complexity of this definition prevents it from broadly popularizing.