Measuring femoral neck loads in healthy young and older adults during stair ascent and descent

The effect of distal locking mode on postoperative mechanical complications in intertrochanteric fractures: a retrospective cohort study of five hundred and seven patients

PURPOSE

The optimal choice of distal locking modes remains a subject due to limited available data, and therefore, this study aims to investigate the relationship between distal locking mode and postoperative mechanical complications in an intertrochanteric fracture (ITF) population who underwent closed reduction and intramedullary fixation with a PFNA-II.

METHODS

Patients aged 65 years or older who underwent surgery with PFNA-II fixation in a university teaching hospital between January 2020 and December 2021 were potentially eligible. Based on the distal locking mode, patients were classified into static, dynamic, and limited dynamic groups, among which the differences were tested using univariate analysis. Multivariate logistic regression was used to examine whether the distal locking mode was independently associated with the risk of postoperative one year mechanical complications, adjusting for covariates and potential confounders. Subgroup analyses were performed to evaluate the robustness of the findings.

RESULT

Among 507 eligible patients, 33 (6.5%) developed postoperative mechanical complications. In the univariate analysis, sex (P = 0.007), fracture type (P = 0.020), LAT Parker ratio (P = 0.023), and lateral femoral (P = 0.003) wall showed that the differences were significant. Compared to the static group, the limited dynamic group and the dynamic group showed higher odds of postoperative mechanical complications (OR = 3.314, 95% CI: 1.215-9.041; and OR = 3.652, 95% CI: 1.451-9.191, respectively). These associations were robust across a series of analyses, including adjusting for confounders and subgroup analyses.

CONCLUSION

Using a distal non-static locking mode significantly increases the risk of postoperative mechanical complications, and static locking could be a preferable option when treating an intertrochanteric fracture.

Effect of gait types and external weight carrying strategies on the femoral neck strains during stair descent

Gait and weight carrying method may change the femoral neck load during stair descent. Applying specific gait and weight carrying methods may reduce the femoral neck load during stair descent, which may reduce hip pain, hip pain related falls and fall related fractures for the older population. The purpose of this study was to test the effect of different gait types (step-over-step v.s. step-by-step) and external weight carrying strategies (ipsilateral v.s. contralateral side) on the femoral neck load, discover which method could reduce the femoral neck load effectively. Seventeen healthy adults from 50 to 70 yrs old were recruited. The kinematic and kinetic analysis, musculoskeletal modelling method were used to estimate the joint and muscle loads for the lower extremities. Finite element analysis was used with the femur model to calculate the femoral neck strains during stair descent with different gait types and weight carrying strategies. The compressive strains were reduced for step-by-step gait method than step-over-step (p<0.015, 12.3-17.4% decrease of strains), the tensile strains were significantly increased for the trailing leg of step-by-step than the leading leg (p<0.001, 24.7% increase of strains). Contralateral weight carrying increased compressive and tensile strains than ipsilateral (p<0.001, 9.9-24.5% increase of strains) in most conditions. Applying step-by-step method and avoiding contralateral side weight carrying could be effective to reduce femoral neck strains. These outcomes could be helpful for the older population to reduce the risks of hip pain, femoral neck pain or pain related falls and fractures.