Impact of low bone mass and osteoporosis on lower limb alignment and knee function in high tibial osteotomy for varus knee osteoarthritis.

OBJECTIVE

To examine whether low bone mass or osteoporosis was associated with clinical and radiographic outcomes after high tibial osteotomy (HTO) in patients with varus knee osteoarthritis (KOA).

METHODS

This retrospective cohort included 123 patients with varus KOA who underwent medial open-wedge HTO between January 2019 and January 2024. Preoperative dual-energy x-ray absorptiometry classified 60 patients as having osteopenia or osteoporosis (T-score <-1.0; 42 with osteopenia and 18 with osteoporosis) and 63 as having normal bone mass (T-score ≥-1.0). Clinical outcomes included the Visual Analogue Scale (VAS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Lysholm score. Radiographic outcomes included the medial proximal tibial angle (MPTA), femorotibial angle (FTA), hip-knee-ankle angle (HKA), weight-bearing line ratio (WBLR), and posterior tibial slope (PTS). Outcomes were assessed preoperatively and during follow-up to 24 months. Because no primary endpoint or a priori sample-size calculation was prespecified, all analyses were considered exploratory.

RESULTS

Both groups improved from baseline in pain, function, and most alignment measures. At 24 months, no statistically significant between-group differences were detected in VAS, WOMAC, Lysholm, MPTA, FTA, HKA, WBLR, or PTS (all P > 0.05). The unadjusted 24-month mean differences (osteopenia/osteoporosis minus normal bone mass) were 0.07 points for VAS (95% CI, -0.10 to 0.24), 1.56 points for WOMAC (95% CI, -3.10 to 6.22), and -0.78 points for Lysholm (95% CI, -2.65 to 1.09). The excellent/good outcome rates were 88.33% and 90.48%, respectively, and complication rates were 5.00% and 3.17%, respectively. These estimates were imprecise for uncommon complications.

CONCLUSIONS

In this retrospective cohort, low bone mass or osteoporosis was not significantly associated with inferior clinical or radiographic outcomes after HTO at 24 months. The absence of statistically significant differences should not be interpreted as evidence of equivalence. Treatment was completely confounded with bone-status group, and the study was not powered to exclude clinically meaningful differences or uncommon complications. Larger prospective studies with prespecified endpoints and standardized treatment protocols are warranted.