Vitamin D deficiency and functional outcomes after total knee arthroplasty in postmenopausal women

The retrospective study in the journal Menopause also concluded that vitamin D deficiency, smoking, and high body mass index (BMI) were independent risk factors for moderate-to-severe knee pain after surgery.

Despite TKA being a safe and dependable therapy for advanced knee osteoarthritis, anywhere from 10% to 44% of women develop persistent postsurgical pain, according to the authors.

The study recruited 226 postmenopausal women diagnosed with primary knee osteoarthritis and treated with primary unilateral TKA at the Shanghai Tenth People’s Hospital, which is affiliated with Tongji University School of Medicine, in Shanghai, China, from April 2017 to December 2019.

The women were divided into 2 groups, based on their preoperative serum 25-hydroxyvitamin D levels: a vitamin D-sufficient group (30 ng/mL) (n = 74; average age 69.2 years) and a vitamin D-deficient group (<30 ng/mL) (n = 152; average age 67.5 years). All the women were recruited at least 12 months after their last menstrual period.

Evaluations were conducted the day before surgery and 3 months postoperation.

The difference in the postoperative Western Ontario and McMaster Arthritis Index (WOMAC) score at 3 months after surgery between the 2 groups was statistically significant: 15.3 for sufficient vitamin D vs. 15.6 for deficient vitamin D (P = 0.02).

However, the differences in the postoperative visual analog scale (VAS) and Knee Society Score (KSS) between the two groups were not significant (P> 0.05).

The incidence of postoperative moderate-to-severe pain for the two groups combined at 3 months postoperation was 16.4% (95% confidence interval [CI]: 11.8% to 21.9%).

In addition, smoking (odds ratio [OR] = 4.741) and high BMI (OR = 1.383) were potential risk factors for moderate-to-severe knee pain occurring early after TKA (P<.05).

“Serum vitamin D levels are associated with osteoporosis, knee extension intensity, and functional ability in postmenopausal women, suggesting that vitamin D possibly affects neuromuscular delivery,” wrote the authors.

Previous studies have shown that vitamin D supplementation can lead to functional recovery in women with knee osteoarthritis, according to the authors.

A limitation of the study is that the investigators did not evaluate the effects of bone mineral density, bone turnover markers and postoperative vitamin D levels. They also did not assess postoperative vitamin D status changes, including increased sunlight exposure and nutritional intake.

“The failure to evaluate these factors may have affected the accuracy of our assessment of the impact of vitamin D levels on postoperative outcomes,” wrote the authors.

Furthermore, despite excluding patients who actively used analgesics, some patients who occasionally used analgesics before and a few days after surgery may have been included. Consequently, the risk of developing moderate-to-severe pain after TKA may have been underestimated.

Regardless, the authors recommend that clinicians “carefully screen preoperative vitamin D levels in postmenopausal women scheduled for TKA to identify high-risk women before surgery and improve prognosis.”

Additional prospective studies with large samples and more stringent measures are needed as well, according to the authors.

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Reference

Song Y, Liu SF, Wu Z, et al. Effects of preoperative serum vitamin D levels on early clinical function outcomes and the moderate-to-severe pain prevalence in postmenopausal women after primary total knee arthroplasty. Menopause. Published online May 3, 2021. doi:10.1097/GME.0000000000001789