Predictors of post-hip fracture knee pain in hospitalized older adults with intertrochanteric femoral fracture.

BACKGROUND

Post-hip fracture knee pain (PHFKP) is an important issue that contributes to reduced gait speed and prolonged hospitalization. Femoral morphology has been reported to contribute to the development of PHFKP, but an independent association has not been confirmed and clinically applicable cutoffs for predicting the development of PHFKP remain unclear.

OBJECTIVE

To determine whether femoral morphology and knee extension range of motion limitation are independent factors in PHFKP and to determine cutoffs for predicting the development of PHFKP.

DESIGN

Retrospective chart review study.

SETTING

Convalescent inpatient rehabilitation hospital.

PARTICIPANTS

Patients in a convalescent ward after intertrochanteric femoral fracture surgery.

MAIN OUTCOME MEASURES: PHFKP development, radiographic femoral morphology (leg length discrepancy and neck-shaft angle), and knee extension range of motion limitation.

RESULTS

PHFKP developed in 36 (35%) of the 103 patients enrolled. The PHFKP group had a longer hospital stay (p = .029), greater weight (p = .031), greater knee extension range of motion limitation (p = .001), and more varus neck-shaft angle (p < .001) compared to the non-PHFKP group. Varus neck-shaft angle (odds ratio, 0.85; 95% confidence interval [CI], 0.78-0.92; p < .001) and knee extension range of motion limitation (odds ratio, 1.18; 95% CI, 1.07-1.30; p = .001) were significant factors for PHFKP development. Neck-shaft angle discrepancy and knee extension range of motion limitation demonstrated moderate accuracy in discriminating development of PHFKP according to receiver operating characteristic analysis, with cutoffs of 9.6° and 7.5°, respectively. Areas under the receiver operating characteristic curve were 0.77 (95% CI, 0.66-0.88; p < .001) for neck-shaft angle discrepancy and 0.67 (95% CI, 0.56-0.79; p = .004) for knee extension range of motion limitation.

CONCLUSIONS

Varus neck-shaft angle and knee extension range of motion limitation were identified as independent predictors of PHFKP. The cutoff for neck-shaft angle may be useful for predicting PHFKP development and to define an acceptable angle of fracture reduction to prevent PHFKP.