Blunt injuries to the patellofemoral joint

resulting from transarticular loading are

influenced by impactor energy and mass.

J. Biomechanical Engineering. 123(3):293-295, 2001.

Atkinson, PJ, Ewers, BJ, Haut, RC.

ABSTRACT:

Various impact models have been used to study the injury mechanics of blunt trauma to diarthrodial joints, as well as a variety of treatment protocols. Past studies have used a variety of experimental methods to deliver the impact and have documented a range of injuries (gross bone fracture, occult osteochondral injury, cartilage fissures). The current study was designed to study the relationship between several independent experimental (impactor mass and energy) variables and their effect on the impact biomechanics and injury modalities. 48 isolated canine knees were impacted once with one of three free flight inertial masses (0.7, 1.5, or 4.8 kg) at one of three different energy levels (2, 11, 22 J). For a given animal, the impacts were pair-matched such that both limbs were impacted at one of the energy values using different masses. Histological analyses of the patellae revealed that fissures (as the sole injury) are most common with high masses at low energies or with light masses at moderate energies; occult microfractures (with fissures, but without gross fractures) are most common with high masses at moderate energy levels; and gross fractures (concomitant with fissures and collateral occult microfractures) are most common with high masses at high energies. Joint impact biomechanics (peak load, loading rate, contact area) generally increased with increasing energy, and were insensitive to mass. In conclusion, the current study suggests that experimental impact studies need to carefully design the impact protocol to accurately produce the desired acute injuries for chronic studies.

Orthopaedic Biomechanics Laboratories,

College of Osteopathic Medicine,

Michigan State University,

East Lansing, Michigan 48824

Please address correspondence to:

Roger C. Haut, Ph.D.,

Orthopaedic Biomechanics Laboratory,

College of Osteopathic Medicine,

A414 East Fee Hall,

Michigan State University,

East Lansing, MI 48824,

Tel: (517)355-0320,

Fax: (517)353-0789,

E-mail: haut@msu.edu