Biomechanical Evaluation of Impaction Fractures of the... : Journal of Orthopaedic Trauma (original) (raw)

Original Articles

Konrath, Gregory A.; Hamel, Andrew J.*; Guerin, Justin†; Olson, Steve A.†; Bay, Brian†; Sharkey, Neil A.*

Lafayette Orthopedic Clinic, Lafayette, Indiana, U.S.A.; *Pennsylvania State University, University Park, Pennsylvania, U.S.A.; and †Department of Orthopaedic Surgery, University of California-Davis Medical Center, Sacramento, California, U.S.A.

Accepted March 1, 1999.

Address correspondence and reprint requests to Dr. Steve A. Olson, Department of Orthopaedic Surgery, UCDMC, 4860 Y Street, Suite 3800, Sacramento, CA 95817, U.S.A.

No financial support of this project has occurred. The authors have received nothing of value.

This manuscript does not contain information about medical devices.

Abstract

Objectives:

To measure the effect of an impaction fracture of the femoral head on load transmission in the hip joint.

Design:

We measured the contact areas and pressure between the acetabulum and femoral head of cadaveric pelves in four different conditions: intact, with an operatively created one-square-centimeter defect in the superior femoral head, with a two-square-centimeter defect, and with a four-square-centimeter defect. All defects were uniformly three millimeters deep.

Setting:

Hips were loaded in a simulated single-limb stance. Pressure and area measurements were made with Fuji pressure-sensitive film.

Specimens:

Seven hip joints in seven whole pelves were tested.

Main Outcome Measurements:

Contact area, load, and mean and maximum pressures were measured.

Results:

Peripheral loading was seen in the intact acetabulum. This was not disrupted after impaction fractures of any size. A significant increase in mean maximum pressures in the superior acetabulum was seen with two-square-centimeter and four-square-centimeter defects.

Conclusions:

In contrast to prior biomechanical studies of acetabular fractures, our investigation revealed that disruption of the peripheral distribution of load does not occur with impaction fractures of the femoral head. Clinical series indicate that impaction injuries to the femoral head are associated with a poor prognosis. Previous biomechanical data on acetabular fracture patterns associated with a poor prognosis have shown increases in mean and peak pressures in the superior acetabulum. This was seen with two-square-centimeter and four-square-centimeter impaction injuries. Other factors, such as wear of the articular cartilage during joint motion or associated microscopic damage to the remainder of the joint surface at the time of injury, may also contribute to the rapid joint deterioration seen in these injuries. Further study is indicated.