Alignment of the medial tibial plateau affects the rate of joint space narrowing in the osteoarthritic knee.
OBJECTIVE
To determine, in serial fixed-flexion (FF) radiographs of subjects with knee osteoarthritis (KOA), the importance of, and basis for, the effect of alignment of the medial tibial plateau (MTP), as determined by the inter-margin distance (IMD), on joint space narrowing (JSN).


METHODS
Baseline and 12-month X-rays of 590 knees with Kellgren and Lawrence grade (KLG) 2/3 OA from the public-release dataset of the Osteoarthritis Initiative (OAI) were assigned to subgroups based upon IMD at baseline (IMD(BL)) and the difference between IMD(BL) and IMD(12 mos). Relationships of JSN to IMD(BL) and to the difference between IMD(BL and) IMD(12 mos) were evaluated.


RESULTS
In all 590 knees, mean JSN was 0.13 ± 0.51 mm (P<0.0001) and MTP alignment and replication of IMD(BL) in the 12-month film were, in general, poor. JSN was significantly (P=0.012) more rapid in Subgroup A (IMD≤1.70 mm at both time points) than in Subgroup B (both IMDs>1.70 mm): 0.15 ± 0.43; 0.08 ± 0.47. Within Subgroup B we identified a subset, Subgroup B1, in which, although alignment was poor at both time points, the large IMD(BL) was, by chance, highly reproduced by IMD(12 mos) (difference between the two IMDs=0.01 ± 0.27 mm, NS). JSN in Subgroup B1 was 0.06 ± 0.41 mm and did not differ from that in other knees of Subgroup B (P=0.87). The standardized response mean (SRM) in all 590 knees and Subgroups A, B and B1 was 0.25, 0.34, 0.17 and 0.06, respectively. Independent of IMD(BL), JSN correlated significantly with the difference between the IMDs in the two radiographs (r=0.17, P=0.0001).


CONCLUSIONS
Skewed MTP alignment in serial films and poor replication of IMD(BL) in the follow-up exam affect JSN measurement. The magnitude of change in joint space width (JSW) related to the poor quality of alignment that is common with the FF view jeopardizes accurate evaluation of JSN.
Vignon
E
E
Université Claude Bernard Lyon 1, Lyon, France. eric.vignon@chu-lyon.fr
Brandt
K D
KD
Mercier
C
C
Hochberg
M
M
Hunter
D
D
Mazzuca
S
S
Powell
K
K
Wyman
B
B
Le Graverand
M-P Hellio
MP
D000368:Aged; D018450:Disease Progression; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000473:pathology; D011859:Radiography; D013977:Tibia / Q000000981:diagnostic imaging*
Skeletal Radiol. 2003 Mar;32(3):128-32
12605275
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7492235
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8581752
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18515156
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17074511
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12571847
Arthritis Rheum. 2005 Jul;52(7):2015-25
15986343
Ann Rheum Dis. 2008 Nov;67(11):1562-6
18258709
Osteoarthritis Cartilage. 2006;14 Suppl A:A37-43
16785057
Arthritis Rheum. 2007 May;56(5):1512-20
17469126
J Rheumatol. 2002 Jun;29(6):1308-20
12064851