# Novel Methods to Assess Interfragmentary Motion: Quantifying a Critical Factor in Fracture Healing

> **NIH VA I21** · VA PUGET SOUND HEALTHCARE SYSTEM · 2022 · —

## Abstract

PROJECT SUMMARY/ABSTRACT
We seek to understand how variations in surgical fixation and rehabilitation protocols for distal femur fractures
impact the mechanical environment at the fracture and how this in turn influences healing. The concept of
mechanotransduction, where physical forces are converted into biomechanical signals that guide cellular
responses, is relevant to the healing of all human fractures. Distal femur fractures treated with locked plate
fixation are an excellent model for study given a relatively high rate of healing complications (in up to 32% of
cases) and a range of treatment strategies across a wide variety of mechanical conditions. The challenges faced
when attempting to provide stable, yet biologically friendly (i.e., promoting secondary fracture healing) fixation at
this site typify those encountered for all long bone fractures. Although the clinical importance of
mechanotransduction in bone healing—in particular strain across a fracture site—has been qualitatively
demonstrated, there is a lack of quantitative data. Its specific mechanisms are not fully characterized, and
progress to improve related clinical outcomes [has been stagnant. A lack of quantitative clinical data limits our
ability to design surgical techniques, implants, and rehabilitation protocols to optimize healing outcomes.
Currently, a major obstacle in the field is an inability to assess interfragmentary strain or a clinically useful
surrogate.] To overcome this, we aim to validate two novel, noninvasive, and complementary methods of
quantifying clinical [fracture site motion]. Method 1) A case-specific computational model will be refined to
estimate [fracture site motion] for 10 human subjects recently treated with locked plate fixation for a distal femur
fracture. Method 2) Biplane fluoroscopy will be used to track [the proximal and distal bone fragments] during
standing and walking for these same 10 patients. The proposed research provides two complementary methods
of assessing [fracture site motion] in future translational research. These methods will be validated via cadaveric
testing. Furthermore, unloaded and loaded CT measurements of [fracture site motion] in the test cohort will [allow
in vivo validation]. Computational modeling provides an indirect, scalable method of estimating [fracture site
motion] while biplane fluoroscopy will provide direct in vivo assessment. Both methods will support future
translational research involving heretofore untestable hypotheses. This includes research into optimal fixation
strategies and rehabilitation protocols, as well as the ability to control for confounding factors in studies of other
aspects of fracture healing. This innovative work aims to overcome limitations in current research to develop two
complementary methods of quantifying patient-specific [fracture site motion, which has been shown to be a
clinically relevant surrogate for interfragmentary strain. A quantitative understanding of fracture site...

## Key facts

- **NIH application ID:** 10487818
- **Project number:** 1I21RX003608-01A1
- **Recipient organization:** VA PUGET SOUND HEALTHCARE SYSTEM
- **Principal Investigator:** William Dean Lack
- **Activity code:** I21 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2022
- **Award amount:** —
- **Award type:** 1
- **Project period:** 2022-06-01 → 2024-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10487818

## Citation

> US National Institutes of Health, RePORTER application 10487818, Novel Methods to Assess Interfragmentary Motion: Quantifying a Critical Factor in Fracture Healing (1I21RX003608-01A1). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10487818. Licensed CC0.

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