J Korean Orthop Assoc.  2007 Oct;42(5):571-577. 10.4055/jkoa.2007.42.5.571.

Spontaneous Osteonecrosis of the Knee in the Elderly over 60 Years Old

• Lim HC
• Noh KS
• Yang JH
• Jang KM

• KMID: 2186462
• DOI: http://doi.org/10.4055/jkoa.2007.42.5.571

Abstract

PURPOSE: This study examined the results of treatment according to the stage and size of a spontaneous osteonecrosis lesion of the knee (SONK) in the patients over 60 years of age.
MATERIALS AND METHODS
Twenty-two knees from 19 patients over 60 years of age were treated for spontaneous osteonecrosis of the knee at our institution between January, 2000, and June, 2004. The mean follow time was 20.7 months. The condylar ratios, proportion of the lesion size to the condyle were measured. The size was obtained by multiplying the values from the anteroposterior and lateral radiographs. The stages were classified radiographically, and the treatment results were analyzed according to the size and stage. Conservative treatment was performed if the ratio and size were <40% and 5.0 cm2, respectively. Arthroplasty was performed if the ratio or size was >40% or 5.0 cm2. A paired T-test, Spearman correlation test and Wilcoxon test were used for the statistical evaluation.
RESULTS
There was a higher prevalence in females (15 patients, 79%), and the mean age was 65 years (46-77 years). Bilateral involvement was observed in 3 patients. The lesions involved mainly the medial femoral condyle (21 cases, 95%). Seven cases (31%) had a condylar ratio <40% and 15 cases (69%) had a condylar ratio >40%. Conservative treatments were performed in 5 cases staged radiographically as I or II and there were no significant changes in the knee scores (p=0.931). Of the 17 cases staged III and IV radiographically, conservative treatment and arthroplasty were performed in 7 and 10 cases, respectively. Seven cases, in whom conservative treatments had been performed, showed a decreased in the knee scores compared with the increased knee scores in 10 patients treated with arthroplasty (p=0.943).
CONCLUSION
An accurate diagnosis and measurement of the size and staging of spontaneous osteonecrosis of knee in patients over 60 years of age is important for proper treatment. Clinically, no further progression of symptoms is visible on grade I and II spontaneous osteonecrosis of the knee after conservative treatment. However, arthroplasty improves the clinical results in patients with radiological grade III and IV osteonecrosis compared with conservative treatment.

Keyword

Knee; Spontaneous osteonecrosis; Arthroplasty

MeSH Terms

Aged*
Arthroplasty
Diagnosis
Female
Humans
Knee*
Middle Aged*
Osteonecrosis*
Prevalence

Figure

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  Fig. 1 (A) Simple radiography for measuring the size of the lesion on the anterior-posterior view. The condylar ratio and transverse diameter can be measured. (B) Simple radiography for measuring the size of the lesion on the lateral view. The depth can also be measured. *a: Maximum transverse width of the medial femoral condyle on the anteriorposterior radiography, b: Transverse width of the lesion on anteriorposterior radiography, c: The greatest length of the lesion on lateral radiography.

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  Fig. 2 Outcome of conservative treatment in stages I and II. There is a strong correlation in the outcome of conservative treatment (ρ=0.931). *AKSS: American Knee Society Score.

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  Fig. 3 (A) On the initial simple radiography we cannot identify the lesion in the medial condyle of the femur (stage I). (B) After conservative treatment (12 months), the follow-up radiography showed a collapse of the medial femoral condyle (arrow).

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  Fig. 4 Outcome of conservative and surgical treatment in stages III and IV. There is a statistical difference between the outcomes of conservative treatment and surgical treatment (p<0.005). *AKSS: American Knee Society Score

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  Fig. 5 Outcome of surgical treatment (UKA vs. TKA). There is a strong correlation between the outcomes of UKA and TKA (ρ=0.943). *AKSS, American Knee Society Score, UKA: Uni-Knee Arthroplasty, TKA: Total Knee Arthroplasty.

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