Visualization of Knee Joint Degeneration after Non-invasive ACL Injury in Rats

Overview

Source: Lindsey K. Lepley¹^,², Steven M. Davi¹, Timothy A. Butterfield³^,⁴ and Sina Shahbazmohamadi⁵,

¹Department of Kinesiology, University of Connecticut, Storrs, CT; ²Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, CT;³Department of Rehabilitation Sciences, University of Kentucky, Lexington, KY;⁴Center for Muscle Biology, Department of Physiology, University of Kentucky, Lexington, KY; ⁵Biomedical Engineering Department, University of Connecticut, Storrs, CT

Anterior cruciate ligament (ACL) injury to the knee dramatically increases the risk of post-traumatic osteoarthritis (PTOA), as approximately one-third of individuals will demonstrate radiographic PTOA within the first decade following ACL injury. Though ACL reconstruction (ACLR) successfully restores knee joint stability, ACLR and current rehabilitation techniques do not prevent the onset of PTOA. Therefore, ACL injury represents the ideal model to study the development of PTOA after traumatic joint injury.

Rat models have been used extensively to study the onset and effect of ACL injury on PTOA. The most widely used model of ACL injury is ACL transection, which is an acute model that surgically destabilizes the joint. Though practical, this model does not faithfully mimic human ACL injury due to the invasive and non-physiological injury procedures that mask the native biological response to injury. To improve the clinical translation of our results, we have recently developed a novel non-invasive model of ACL injury where the ACL is ruptured through a single load of tibial compression. This injury closely replicates injury conditions relevant to humans and is highly reproducible.

Visualization of joint degeneration through micro-computed tomography (µCT) provides several major advancements over traditional OA staining techniques, including rapid, high-resolution, non-destructive 3D imaging of whole joint degeneration. The goal of this demonstration is to introduce the state of the art non-invasive ACL injury in a rodent model and use µCT to quantify knee joint degeneration.

Procedure

Non-invasive ACL Injury

Wear proper personal protection equipment. You may use a respiratory mask, but it is not mandatory for this protocol.
Anesthetize the rats using an induction chamber with 5% isoflurane and 1 L/min oxygen. Maintain the flow of anesthesia using via a nose cone with 1 - 3% isoflurane and 500 mL/min of oxygen. If the apparatus is not set up on a backdraft or downdraft table, ensure that waste gas is scavenged using a tabletop system and charcoal filters.
Perform a toe-p

Results

Smaller trabecular number, reduced trabecular thickness and greater trabecular spacing, all hallmark characteristics of PTOA onset, were evident 4 weeks after the non-invasive ACL tear (Table 1 and Figure 3). An image of a dissected ACL of healthy limb versus an acute injured limb is shown in Figure 5. The novel non-invasive model of ACL injury, where the ACL is ruptured through a single load of tibial compressio

Application and Summary

This video demonstrates how a linear actuator can be used to produce an isolated non-invasive ACL rupture in rats. This injury closely replicates injury conditions relevant to humans and is highly reproducible. To overcome several of the major limitations of traditional OA staining techniques, this method uses µCT to quantify whole joint degeneration and trabecular structure.

Evidence-based interventions to improve musculoskeletal rehabilitative outcomes is a highly significant area that

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