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

Considering these specific manifestations and high possibility for further collapse, the pericollapse stage should begin with the occurrence of the subchondral fracture instead of with the classification of ARCO Stage II. However, from the onset of femoral head necrosis, how long does it take to progress to the pericollapse stage? How long will the pericollapse stage last? sIze and locatIon of osteonecRosIs and PRogRessIon of the PeRIcollaPse stage It has been widely acknowledged that a large-sized necrotic lesion is a crucial risk factor for the prevalence of collapse. [37, 40] Meanwhile, when the lesions extend laterally to the acetabular edge, which is considered as the weight-bearing portion, head depression often becomes unavoidable. [37, [40] [41] [42] Several classification systems such as the Steinberg classification, modified Kerboul classification, and Japanese Investigation Committee (JIC) classification attempt to quantify and categorize ONFH lesions and therefore predict collapse and prognosis. [14] The lesion volume is the primary reference index of the Steinberg classification system while Kerboul et al.'s [14, 43] modified method calculates an angle by considering the necrotic portion in both the mid-coronal image and mid-sagittal image of the MRI. The JIC classification considers the location of the necrotic lesion first, and the lesion size is also involved because it is reported that large lesions are prone to locate laterally. [44, 45] The CJFH classification system is based on the three-pillar structure theory, in which the medial pillar, central pillar, and lateral pillar represent 30%, 40%, and 30% of the femoral head, respectively. According to the involved site of the necrotic lesion, ONFH can be classified as a medial (M) type (only medial pillar involved), central (C) type (medial and central pillars involved), and lateral (L) type (lateral pillar involved). The L type is further divided into an L1 type (partial lateral pillar preserved [sublateral]), L2 type (the lateral pillar involved only [extralateral]), and L3 type (all three pillars involved) [ Figure 3 ]. Preservation of the lateral pillar is the keystone for forestalling the collapse of the femoral head. [46] The duration of the pericollapse stage and the average intervals from the onset of ONFH to the pericollapse stage varies across the published literature. In the majority of patients who reach the pericollapse stage, head collapse appears within a short period of time. Min reported that for 31 asymptomatic ONFH hips that finally progressed to symptomatic ones, 26 (83.8%) of them collapsed with a mean time of 8 months (range, 1-36 months). [37] In Iida et al.'s study, [24] approximately a 4-month interval (range, 1-7 months) existed from the onset of pain to head collapse. However, Theruvath et al. [18] described 14 patients with subchondral fracture, and 12 patients experienced collapse with a mean follow-up of 2.6 years. The duration of the pericollapse stage should be further confirmed by long-term follow-up. The time needed from the onset of ONFH to the pericollapse stage is mainly determined by the classification, which is consistent with the occurrence of head collapse. [1] [2] [3] 12] Concerning the data about the natural progression of severe acute respiratory syndrome patients with ONFH, it was observed that no CJFH type M lesions, 6 of 45 (13.3%) CJFH type C lesions, and 20 of 89 (22.5%) CJFH type L1 lesions progressed to the pericollapse