Changes in bone mineral density at the proximal tibia after total knee arthroplasty: A 2‐year follow‐up of 28 knees using dual energy x‐ray absorptiometry

Abstract

The change in bone mineral density at the proximal tibia during 2 years after total knee arthroplasty was studied in 28 knees (28 patients: 10 men and 18 women; median age: 71 years) with dual energy x-ray absorptiometry. Bone mineral density was measured at the proximal tibia at nine regions of interest below the tibial component within 1 week after the operation (baseline); measurements were repeated at 3, 6, 12, and 24 months. All but one knee was malaligned before the operation, and all but three were corrected to within the normal range of alignment after it. The mean bone mineral density of all nine regions of interest at the proximal tibia temporarily decreased by 13% (p = 0.001) during the initial 3 months, probably due to a general metabolic reaction of the skeleton to the operative trauma combined with the effect of the postoperative immobilization, and then the initial level was regained for as long as 2 years. The overall changes in mean bone mineral density to 2 years were insignificant (p > 0.05); however, a great variation (43.9% decrease to 98.0% increase) was observed on an individual basis. This change over time was significantly associated (R2 = 0.36, p = 0.002) with the level of the baseline bone mineral density, which in turn was partly related (R2 = 0.24, p = 0.009) to the amount of malalignment of the knee before the operation. Knees with high baseline levels (n = 14: 11 with varus and three with valgus alignment) displayed a decrease of 10.0 +/- 14.0% (mean +/- SD, p > 0.05) for as long as 2 years, whereas those with low baseline levels (n = 14: seven with varus and six with valgus alignment and one neutrally aligned) had an increase of 19.1 +/- 38.2% (p = 0.038). In both groups, the mean bone mineral density converged to a level of 0.75-0.95 g/cm2 at 2 years.

Loss of Tibial Bone Density in Patients with Rotating- or Fixed-platform TKA

“…Based on current literature, we expected to see a loss of proximal tibial BMD within 2 years after arthroplasty [1,2,7,9,11,12,21]. We also expected the implant to alter physiologic stress transfer at the plateau, specifically reducing cancellous BMD to a greater degree than cortical BMD by shielding the cancellous bone and transferring stress to the cortical bone.…”

Loss of Cement-bone Interlock in Retrieved Tibial Components from Total Knee Arthroplasties

“…There also is evidence that there are changes in bone density surrounding cemented tibial trays with in vivo service. Bone mineral density (BMD) measured during the initial 3 months after TKA showed a temporary decrease of 13% in BMD under the tibial tray [9]. Further, tibial tray components that have been cemented with a central stem or keel show a greater loss of BMD under the tray when compared with components that do not use a keel [10].…”

Joint area constraint had no influence on bone loss in proximal tibia 5 years after total knee replacement

“…Most bone loss was seen during the first postoperative year in all regions of interest as found in earlier studies. 1,2, 6 Li and Nilsson 1,2 reported that the mean BMD in all ROIs at the proximal tibia temporarily decreased by 13% during the initial 3 months after TKR. A general metabolic reaction of the skeleton to the operative trauma combined with the effect of the postoperative immobilization was speculated to cause this reduction.…”

“…[1][2][3][4][5] Stress shielding is considered the major cause for this bone loss. Several studies have shown that the most pronounced reduction occurs during the first year after implantation.…”

“…Several studies have shown that the most pronounced reduction occurs during the first year after implantation. 1,2,6 According to a finite element study by Van Lenthe et al, 7 the bone resorption will continue in the distal femur for more than 2 years after TKR. Changes of BMD could influence component fixation depending on the quality of the interface.…”