Bone quality is probably important for the survival of knee arthroplasty (KA), but little is known about systemic bone mineral density and bone turnover in patients prior to KA surgery. The aim of this study was to explore the prevalence of osteoporosis and bone turnover in relation to knee osteoarthritis (OA) grade in patients scheduled for KA surgery. Prospective preoperative evaluation of 450 patients (259 females) prior to KA between 2014 and 2016 with standing knee radiography, Dual-energy X-ray absorptiometry (DXA), biomarkers for bone turnover (CTX, P1NP), and vitamin D. Grading of knee OA was done with the Altman Atlas and Kellgren Lawrence (KL). Adjustments for age and BMI were made. The mean age was 67.9 years (range 39-94), and mean BMI was 28.8 (SD 4.8). The prevalence of osteoporosis was 9.6% (CI 95% 7.2; 12.7), while the proportion of patients with osteopenia was 36.0%. T score was similar between KL OA grade 3 and 4 (p = 0.06); however, T score was lower (p = 0.02) with the worst knee OA grade (attrition). The median serum Vitamin D level was 78.5 nmol/L (range 10-196), and there was no association between serum vitamin D and the grade of OA (p > 0.88). P1NP was significantly higher in KL grade 4 compared to KL grade 3 (p = 0.03), but there was no association between KL grade and CTX (p = 0.21). 10% had osteoporosis, which is similar to the age-matched background population. Bone mineral density was lower with severe knee osteoarthritis (attrition), and P1NP was higher with worse osteoarthritis grading.

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Purpose Cementless tibial components migrate initially until osseointegration and preserve periprosthetic bone. Cemented tibial components are ixed from surgery but loose periprosthetic bone. Little is known about bone formation and resorption biomarkers in relation to component ixation and bone mineral density (BMD) changes of cementless and cemented total knee arthroplasty. We hypothesize a similar migration of cemented and cementless tibial components between 1-and 2-year follow-up indicating a stable long-term ixation. MethodsIn a prospective patient-blinded randomized study, we compared cementless (n = 27) and cemented (n = 26) tibial components with radiostereometry measured migration (MTPM = Maximum Total Point Motion: point of component that migrates the most) and changes in BMD and biochemical bone turnover markers (BTMs) until 24 months after surgery. ResultsThe mean MTPM between 12 and 24 months were similar between groups with − 0.06 mm (95% CI − 0.23; 0.11) in the cementless group compared to 0.02 mm (95% CI − 0.07; 0.11) in the cemented group. However, there was a higher proportion of cementless components (16/25) than cemented components (7/24) with continuous migration (MTPM > 0.2 mm) (p = 0.02). In the medial and anterior region below the tibial components, the BMD increased by mean 1.8% and 7.4% for cementless components and decreased by mean 8.6% and 4.2% for cemented components until 24-month follow-up. In both groups, BTMs initially showed increased bone resorption (CTx) and bone formation (P1NP) followed by normalization to preoperative levels at 6 months post-surgery. ConclusionMore cementless components than cemented components showed continues migration which suggest a higher risk of early revision. Bone turnover increased post-surgery in both groups, but did not explain the diference in change in periprosthetic BMD. Level of evidence I. KeywordsKnee arthroplasty • Radiostereometry analysis • Bone mineral density • Bone turnover markers Abbreviations TKA Total Knee Arthroplasty OA Knee osteoarthritis RSA Radiostereometric analysis MTPM Maximum total point motion BMD Bone mineral density DXA Dual-energy X-ray absorptiometry BTMs Bone turnover markers CTx Collagen type 1 cross-linked C-telepeptide P1NP Type 1 procollagen N-terminal CR Cruciate retaining * Karina Nørgaard Linde