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Low bone mineral density is associated with the onset of spontaneous osteonecrosis of the knee.

Akamatsu Y, Mitsugi N, Hayashi T, Kobayashi H, Saito T - Acta Orthop (2012)

Bottom Line: The BMDs measured at the lumbar spine, ipsilateral femoral neck, and knee condyles and the ratios of medial condyle BMD to lateral condyle BMD (medial-lateral ratios) in the femur and tibia were compared between the two groups.The mean femoral and tibial medial-lateral ratios were statistically significantly higher in the SONK patients than in the OA patients.A proportion of women over 60 years of age have low BMD that progresses rapidly after menopause and can precipitate a microfracture.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Yokohama City University Medical Center, Yokohama City, Kanagawa, Japan. akamatsu@yokohama-cu.ac.jp

ABSTRACT

Background and purpose: The primary event preceding the onset of symptoms in spontaneous osteonecrosis in the medial femoral condyle (SONK) may be a subchondral insufficiency fracture, which may be associated with underlying low bone mineral density (BMD). However, the pathogenesis of SONK is considered to be multifactorial. Women over 60 years of age tend to have higher incidence of SONK and low BMD. We investigated whether there may be an association between low BMD and SONK in women who are more than 60 years old.

Methods: We compared the BMD of 26 women with SONK within 3 months after the onset of symptoms to that of 26 control women with medial knee osteoarthritis (OA). All the SONK patients had typical clinical presentations and met specified criteria on MRI. The BMDs measured at the lumbar spine, ipsilateral femoral neck, and knee condyles and the ratios of medial condyle BMD to lateral condyle BMD (medial-lateral ratios) in the femur and tibia were compared between the two groups. The medial-lateral ratios were used as parameters for comparisons of the BMDs at both condyles.

Results: The mean femoral neck, lateral femoral condyle, and lateral tibial condyle BMDs were between x% and y% lower in the SONK patients than in the OA patients (p < 0.001). The mean femoral and tibial medial-lateral ratios were statistically significantly higher in the SONK patients than in the OA patients.

Interpretation: A proportion of women over 60 years of age have low BMD that progresses rapidly after menopause and can precipitate a microfracture. These findings support the subchondral insufficiency fracture theory for the onset of SONK based on low BMD.

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Flow diagram for identifying patients with SONK who were eligible.
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Figure 1: Flow diagram for identifying patients with SONK who were eligible.

Mentions: Between April 2005 and March 2009, we treated 89 consecutive patients with SONK. To target women over 60 years, we excluded 14 men and 10 women who were aged 60 years or less. To minimize the influence of disuse osteoporosis, women with SONK were only enrolled if no more than 3 months had elapsed between the onset of SONK and the time of the BMD measurements. Consequently, of the 65 patients remaining, we excluded 33 women because more than 3 months had elapsed since the onset of symptoms. In addition, we excluded 4 women for having a history of trauma and 2 women for previous arthroscopic treatment. None of the patients with SONK who were included in the study had corticosteroid injections, oral corticosteroid medication, or alcohol abuse. 26 patients remained (Figure 1). All patients were examined by radiography of the knee, knee MRI (Figures 2 and 3), and dual X-ray absorptiometry examinations of the lumbar spine, proximal femur, and knee condyles.


Low bone mineral density is associated with the onset of spontaneous osteonecrosis of the knee.

Akamatsu Y, Mitsugi N, Hayashi T, Kobayashi H, Saito T - Acta Orthop (2012)

Flow diagram for identifying patients with SONK who were eligible.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3369150&req=5

Figure 1: Flow diagram for identifying patients with SONK who were eligible.
Mentions: Between April 2005 and March 2009, we treated 89 consecutive patients with SONK. To target women over 60 years, we excluded 14 men and 10 women who were aged 60 years or less. To minimize the influence of disuse osteoporosis, women with SONK were only enrolled if no more than 3 months had elapsed between the onset of SONK and the time of the BMD measurements. Consequently, of the 65 patients remaining, we excluded 33 women because more than 3 months had elapsed since the onset of symptoms. In addition, we excluded 4 women for having a history of trauma and 2 women for previous arthroscopic treatment. None of the patients with SONK who were included in the study had corticosteroid injections, oral corticosteroid medication, or alcohol abuse. 26 patients remained (Figure 1). All patients were examined by radiography of the knee, knee MRI (Figures 2 and 3), and dual X-ray absorptiometry examinations of the lumbar spine, proximal femur, and knee condyles.

Bottom Line: The BMDs measured at the lumbar spine, ipsilateral femoral neck, and knee condyles and the ratios of medial condyle BMD to lateral condyle BMD (medial-lateral ratios) in the femur and tibia were compared between the two groups.The mean femoral and tibial medial-lateral ratios were statistically significantly higher in the SONK patients than in the OA patients.A proportion of women over 60 years of age have low BMD that progresses rapidly after menopause and can precipitate a microfracture.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, Yokohama City University Medical Center, Yokohama City, Kanagawa, Japan. akamatsu@yokohama-cu.ac.jp

ABSTRACT

Background and purpose: The primary event preceding the onset of symptoms in spontaneous osteonecrosis in the medial femoral condyle (SONK) may be a subchondral insufficiency fracture, which may be associated with underlying low bone mineral density (BMD). However, the pathogenesis of SONK is considered to be multifactorial. Women over 60 years of age tend to have higher incidence of SONK and low BMD. We investigated whether there may be an association between low BMD and SONK in women who are more than 60 years old.

Methods: We compared the BMD of 26 women with SONK within 3 months after the onset of symptoms to that of 26 control women with medial knee osteoarthritis (OA). All the SONK patients had typical clinical presentations and met specified criteria on MRI. The BMDs measured at the lumbar spine, ipsilateral femoral neck, and knee condyles and the ratios of medial condyle BMD to lateral condyle BMD (medial-lateral ratios) in the femur and tibia were compared between the two groups. The medial-lateral ratios were used as parameters for comparisons of the BMDs at both condyles.

Results: The mean femoral neck, lateral femoral condyle, and lateral tibial condyle BMDs were between x% and y% lower in the SONK patients than in the OA patients (p < 0.001). The mean femoral and tibial medial-lateral ratios were statistically significantly higher in the SONK patients than in the OA patients.

Interpretation: A proportion of women over 60 years of age have low BMD that progresses rapidly after menopause and can precipitate a microfracture. These findings support the subchondral insufficiency fracture theory for the onset of SONK based on low BMD.

Show MeSH
Related in: MedlinePlus