title: Histopathologic findings of spontaneous osteonecrosis of the knee at an early stage: a case report.
abstract: We histopathologically examined a surgically resected full specimen obtained from an early-stage spontaneous osteonecrosis of the knee (SPONK). On a mid-coronal cut section of the resected medial femoral condyle, a linear fracture line paralleling the subchondral bone endplate was found. Histopathologically, prominent callus formation was seen comprising of reactive woven bone and granulation tissue on both sides of the fracture. Fracture-related bone debris was focally observed at the osteochondral side of the fracture. Definitive features of antecedent bone infarction such as creeping substitution and bone marrow necrosis were not detected. These findings suggested that SPONK was the result of a subchondral fracture rather than primary osteonecrosis.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Hatanaka
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. yamataku@ortho.med.kyushu-u.ac.jp.
authors.forename: Takuaki
authors.initials: T
authors.lastname: Yamamoto
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Goro
authors.initials: G
authors.lastname: Motomura
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Sonoda
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Yukihide
authors.initials: Y
authors.lastname: Iwamoto
mesh_terms: D000368:Aged; D003937:Diagnosis, Differential; D018450:Disease Progression; D042241:Early Diagnosis; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D010020:Osteonecrosis / Q000000981:diagnostic imaging* / Q000473:pathology*
keywords: Etiology; Histopathology; Spontaneous osteonecrosis of the knee; Subchondral fracture