Vitamin D status and index representing the detrimental mechanical loading across the knee joint in end-stage knee osteoarthritis representing the detrimental mechanical loading across the knee joint in end-stage knee osteoarthritis
M. Kinoshita Osteoarthritis and Cartilage VOLUME 25, SUPPLEMENT 1, S362, APRIL 01, 2017
Purpose: Osteoarthritis of the knee (knee OA) is a slowly progressive joint disease and a leading cause of impaired mobility in the elderly. Although only a small population among the patients proceeds to end-stage knee OA, activity of daily life (ADL) and, presumably, quality of life of patients with end-stage knee OA are severely disturbed. Detrimental mechanical loading across the knee joint is speculated to be one of the main factors in the pathophysiology of knee OA. The alignment of the lower limb, which may be closely related to the detrimental mechanical loading across the knee joint has been reported to associate with pain in knee OA. The malalignment of the lower limb has been considered to be risk factors for the progression of knee OA, due to the association between these factors and the joint load. Vitamin D insufficiency and deficiency are common in the elderly women. Vitamin D plays an important role in bone mineralization and remodeling. It has been speculated whether there are any associations between vitamin D status and pathogenesis and progression of the knee OA, as the bone metabolism, in addition to the cartilage metabolism, is also involved in the pathophysiology of knee OA, especially end-stage knee OA due to their severe disability. In this study, we focused on the vitamin D status of end-stage knee OA, because the effect of disability, in addition to bone metabolism, may affect the vitamin D status in patients with end-stage knee OA. The aim of this study is to investigate the vitamin D status, and the association between the vitamin D status and the indexes representing the detrimental mechanical loading across the knee joint in patients with end-stage knee OA.
Methods: Study design was a cross-sectional study. 94 female patients with end-stage knee OA who underwent total knee arthroplasty (TKA) at our hospital from 2013 to 2016 were enrolled. Patients with rheumatoid arthritis (n = 22), history of trauma and tumor (n = 5), lateral knee OA (n = 5) and patients had used active vitamin D analog (n = 7) were excluded. Total 55 patients with medial knee OA were included. Blood samples were taken from the patients at the one day before operation. Serum 25-hydroxy vitamin D (25(OH)D) level was assessed by ELISA method and concentrations less than 15 ng/ml was considered sever deficiency and concentrations 30 ng/ml and over was considered sufficiency. Preoperative and postero-anterior long-leg standing X-ray was conducted in the patients with measuring femoro-tibial angle (FTA) and % mechanical axis of the femur (%MA) as the knee joint alignments. The clinical manifestations were evaluated by the visual analog scale (VAS; 0–100) for pain and the Japanese Knee Osteoarthritis Measure (JKOM) score which is a patient-based, self-answered evaluation score that includes 4 subcategories (J Rheumatol, 32, 1524–32, 2005). All subjects were divided into 2 groups according to their 25(OH)D levels; the vitamin D deficient group: 25(OH)D < 15 ng/ml and the vitamin D insufficient or sufficient group: 25(OH)≧15 ng/ml and analyzed each alignments, VAS and JKOM score by using t-test. A p-value less than 5% was considered to be statistically significant. All analyses were undertaken using the statistical package SPSS for Windows.
Results: A total of 55 subjects (mean age of 74.5 ± 6.4 years old) were analyzed. Total mean serum 25(OH)D level was 22.3 ± 7.7 mg/dL, FTA was 185.6 ± 5.1° and %MA was 4.98 ± 20.8 %. 11 of 55 subjects (20%) were classified as the vitamin D deficient group, while remaining 44 subjects (80%) were classified as the vitamin D insufficient or sufficient group. There was no significant difference in VAS, JKOM total score and several subcategories of the JKOM between both groups. There was also no significant difference in FTA between both groups, whereas %MA of the vitamin D deficient group (−8.6°) was significantly lower than that of the vitamin D insufficient or sufficient group (9.0°, p = 0.017). The Odds ratio for < 0 of %MA in vitamin D deficient group was 2.8 (95%CI: 1.57–5.05, p < 0.01).
Conclusions: The serum 25(OH)D levels of the patients with postmenopausal osteoporosis (67.5 years of age on average) who have visited our university hospital without any walking disability were 22.5 mg/ml on average (Calcif Tissue Int, 85, 398–404, 2009). Based on these results, the vitamin D status of the patients with end-stage knee OA underwent TKA is not likely to be under special circumstances. Although many other possible predisposing factors for OA should be taken into consideration, the results of the present study suggest that vitamin D deficiency is involved in the worsening of detrimental mechanical loading across the knee joint in the pathophysiology of knee OA.