Changes in Bone Density in Metal-Backed and All-Polyethylene Medial Unicompartmental Knee Arthroplasty

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• 作者：Chloe E.H. Scott ; BSc ; MSc ; FRCS(Tr&Orth)^a ; ^b ; ; Frazer A. Wade ; FRCSEd (Orth)^b ; Rajarshi Bhattacharya ; MSc ; FRCS(Tr&Orth)^b ; ¹ ; Deborah MacDonald ; BA(Hons)^b ; Pankaj Pankaj ; PhD^a ; Richard W. Nutton ; MD ; FRCS(Orth)^b
• 关键词：BMD ; bone mineral density ; GSRa ; grayscale ratio a (digital radiodensitometry ratio of medial to lateral proximal tibial condyles) ; GSRb ; Grayscale ratio b (digital radiodensitometry ratio of medial fourth to lateral three fourths proximal tibial condyle)
• 刊名：The Journal of Arthroplasty
• 出版年：2016
• 出版时间：March 2016
• 年：2016
• 卷：31
• 期：3
• 页码：702-709
• 全文大小：824 K

文摘

Proximal tibial strain in medial unicompartmental knee arthroplasty (UKA) may alter bone mineral density and cause pain. The aims of this retrospective cohort study were to quantify and compare changes in proximal tibial bone mineral density in metal-backed and all-polyethylene medial UKAs, correlating these with outcome, particularly ongoing pain.

Methods

Radiographs of 173 metal-backed and 82 all-polyethylene UKAs were analyzed using digital radiograph densitometry at 0, 1, 2, and 5 years. The mean grayscale of 4 proximal tibial regions was measured and converted to a ratio: the GSRb (grayscale ratio b), where GSRb > 1 represents relative medial sclerosis.

Results

In both implants, GSRb reduced significantly to 1 year and stabilized with no differences between implants. Subgroup analysis showed less improvement in Oxford Knee Score in patients whose GSRb increased by more than 10% at 1 year (40/255) compared with patients whose GSRb reduced by more than 10% at both 1 years (8.2 vs 15.8, P = .002) and 5 years (9.6 vs 15.8, P = .022). Patients with persistently painful UKAs (17/255) showed no reduction in GSRb at 1 year compared with a 20% reduction in those without pain (P = .05).

Conclusions

Bone mineral density changes under medial UKAs are independent of metal backing. Medial sclerosis appears to be associated with ongoing pain.