title: Analysis of risk factors for poor prognosis in conservatively managed early-stage spontaneous osteonecrosis of the knee.
abstract: BACKGROUND
  Management guidelines for early-stage spontaneous osteonecrosis of the knee (SONK) have not been established. The purposes of this study were to review the outcome of conservative treatment for patients with early-stage SONK and to examine clinical factors affecting the prognosis.
  
  
  METHODS
  Diagnosis of early-stage SONK was made based on the criteria consisting of specific clinical features including magnetic resonance imaging (MRI) findings. During the study period, all patients with this diagnosis underwent standardized conservative treatment. The study population comprised 38 knees in 36 patients with a mean age at presentation of 66.4years. The mean follow-up period was 34.9months. During the treatment course, progressive joint space narrowing or collapse of bony contours identified in serial follow-up radiographs was regarded as indicating a poor prognosis. The significance of potential prognostic factors such as age, gender, obesity, coronal alignment, lesion size, and MRI findings was analyzed using a multivariate logistic regression analysis.
  
  
  RESULTS
  The prognosis was defined to be poor in eight knees (21.1%). The multivariate logistic regression analysis for potential risk factors revealed that only varus alignment with a femorotibial angle (FTA) of 180° or more on the initial radiograph was significantly associated with the poor prognosis (P=0.01, odds ratio 28.1) while no other factors significantly correlated with the prognosis.
  
  
  CONCLUSIONS
  Approximately 80% of patients with early-stage SONK could be managed successfully with conservative treatment without progression of the disease process. The presence of varus deformity (FTA of 180° or more) was significantly associated with poor prognosis complicated with progressive deformity and prolonged disability.
  
  
  METHODS
  Level IV, case series.
authors: Department of Orthopaedic Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan. Electronic address: hiroshi0273@mac.com.
authors: Hiroshi
authors: H
authors: Nakayama
authors: Department of Orthopaedic Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan.
authors: Tomoya
authors: T
authors: Iseki
authors: Department of Orthopaedic Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan.
authors: Ryo
authors: R
authors: Kanto
authors: Division of Biostatistics, Department of Mathematics, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan.
authors: Takashi
authors: T
authors: Daimon
authors: Department of Orthopaedic Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan.
authors: Kaori
authors: K
authors: Kashiwa
authors: Department of Orthopaedic Surgery, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo 663-8501, Japan.
authors: Shinichi
authors: S
authors: Yoshiya
mesh_terms: D000276:Adjuvants, Immunologic / Q000008:administration & dosage; D000368:Aged; D000369:Aged, 80 and over; D000890:Anti-Infective Agents / Q000627:therapeutic use*; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D006820:Hyaluronic Acid / Q000008:administration & dosage*; D007270:Injections, Intra-Articular; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010020:Osteonecrosis / Q000175:diagnosis / Q000628:therapy*; D026741:Physical Therapy Modalities; D011379:Prognosis; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors
chemical_list: D000276:Adjuvants, Immunologic; D000890:Anti-Infective Agents; D006820:Hyaluronic Acid
keywords: Conservative treatment; Knee; Risk factor; Spontaneous osteonecrosis