Post-hip-fracture knee pain in older adults prolongs their hospital stays: A retrospective analysis using propensity score matching.

BACKGROUND AND PURPOSE: Post-hip-fracture knee pain (PHFKP) occurs in ∼28%-37% of patients and contributes to a prolonged length of hospital stay (LOS). Analyses of LOS prolongation due to PHFKP have been limited to univariate analyses that do not consider important confounding factors. After adjusting for important confounding factors, we investigated whether the presence or absence of PHFKP makes a difference in LOS in patients with hip fractures.

METHODS: We conducted a retrospective review of the medical records of patients who had undergone postoperative rehabilitation after surgery for a hip fracture. Demographic and clinical information, discharge parameters, and PHFKP development information were collected from the medical records. Using propensity score matching, we performed a two-group comparison of LOS, the functional independence measure (FIM) motor score (FIMm), FIMm gain, and FIMm effectiveness in patients with and without PHFKP. Six variables were included in the calculation of propensity scores: age, sex, body mass index, fracture type, American Society of Anesthesiologists physical status, and independence in activities of daily living at discharge. One-way analysis of variance was used to examine the details of the relationships between LOS and (i) the time of PHFKP development and (ii) pain intensity.

RESULTS: We analyzed the cases of 261 patients, of whom 87 (33.3%) developed PHFKP. In propensity score matching, 80 patients were each matched to a patient in the PHFKP or non-PHFKP group. After propensity score matching, a between-group comparison revealed that the PHFKP group had a longer LOS (+11 days) than the non-PHFKP group, and there were no differences in FIMm gain or FIMm effectiveness. The timing of PHFKP development and pain intensity were not related to the LOS.

DISCUSSION: Even after adjusting for confounders, the development of PHFKP was found to prolong LOS. Clinicians should be aware of possible LOS prolongation in hip fracture patients with PHFKP.