Association of the Number of Teeth With Physical Function and Length of Hospital Stay After Hip Fracture Surgery: A Prospective Observational Study at a Tertiary Hospital in Japan

Objectives: Although lower-extremity muscle strength is associated with physical function, there are challenges in assessing the muscle strength of patients after hip surgery due to pain or limited cognitive function. The number of teeth is a characteristic that can be easily examined. Although the relationship between the number of teeth and physical function has been reported in recent years, there are no reports examining the relationship with prognosis in patients with hip fractures. Therefore, this study aimed to investigate the relationship between the number of teeth and physical function and length of hospital stay after hip fracture surgery and to evaluate the predictive efficacy of the number of teeth on postoperative prognosis. Methods: This prospective cohort study was conducted in a tertiary clinical care facility. Patients aged ≥65 years who underwent hip surgery were included. A total of 101 patients (mean age: 85.1±8.0 years) were included. The factor analyzed was the number of teeth at admission. Patients were divided into two groups according to the number of teeth: those with ≥20 and those with ≤19 teeth. The outcomes were knee extension muscle strength-to-weight ratio at two weeks postoperatively and the length of hospital stay. A multiple regression analysis was performed to determine the association between the two groups. Results: Of 101 patients, 79 (78.2%) had ≤19 teeth, whereas 22 (21.8%) had ≥20 teeth. The mean muscle strength-to-weight ratio and length of hospital stay were 0.26±0.11 kgf/kg and 57.5±31.4 days, respectively. Multiple regression analysis revealed that the number of teeth was significantly associated with the muscle strength-to-weight ratio (β=-0.26, p=0.04) but not with the duration of hospitalization (β=0.17, p=0.09). Conclusions: We suggest that assessment of the number of teeth at admission may be a useful predictor of patient physical function.