Commentary & Perspective

Commentary & Perspective on
"Knee Injury in Patients Experiencing a High-Energy Traumatic Ipsilateral Hip Dislocation"
by Gary L. Schmidt, MD, et al.

Commentary & Perspective by
J. Lawrence Marsh, MD*,
University of Iowa Hospitals and Clinics, Iowa City, Iowa

Since posterior dislocation of the hip commonly occurs as a result of an impact originating at the knee and directed through the femur, it is not surprising that the knee may also be injured. In this study, the authors have provided additional information about this associated injury by performing magnetic resonance imaging of the knee. The results of most of these examinations (25 of 27 patients) were abnormal, with findings ranging from soft-tissue and bone contusions only to major meniscal and ligament injuries. Unfortunately, the follow-up was limited and provided little meaningful information on the outcomes of these knees. None of the seven patients with a diagnosis of cruciate ligament injuries based on magnetic resonance imaging examination required surgery or planned to have surgery, although two complained of instability.

Soft-tissue injuries of the knee on magnetic resonance imaging examinations have been associated with other lower extremity injuries. Dickson et al.¹ found that over two-thirds of patients with femoral fractures had detectable knee injuries on magnetic resonance imaging. Shepherd et al.² found that patients with even minimally displaced tibial plateau fractures who were treated nonoperatively also had a substantial prevalence of meniscal injuries (80%) and ligament injuries (40%). Although the authors of both studies recommended the use of magnetic resonance imaging or arthroscopy in patients with femoral fractures or minimally displaced tibial plateau fractures, I do not think that the use of these imaging tools has been widely incorporated into routine practice.

The clinical significance of these findings is uncertain because the vast majority of patients with femoral fractures and minimally displaced tibial plateau fractures have excellent outcomes without having the soft-tissue injuries addressed or even detected. The detection of an abnormality on a complex imaging study does not indicate that treatment is necessary and increases the possibility of instituting unnecessary or even harmful interventions on the basis of findings for which the prognosis is excellent. The patients who have clinical knee symptoms can be assessed and managed on a delayed basis.

The authors of the current study imply that all patients with hip dislocation should undergo a magnetic resonance imaging scan of the ipsilateral knee, which is not a conclusion that I would make on the basis of their data. When I look at the list of magnetic resonance imaging findings in Appendix 2 compared with the findings at the clinical examinations, I do not see examples of knee injuries for which an important opportunity for immediate or early treatment would be missed were a magnetic resonance image not obtained. Patients with the type of soft-tissue injuries that the authors have found will most likely recover and do not require treatment in the early weeks or months after injury. The few possible exceptions were detectable on physical examination.

Therefore, this study indicates to me that magnetic resonance imaging is not necessary in all or even in most patients with hip dislocations; rather, it should serve to heighten the awareness of the examining physician with regard to the possibility of associated knee injuries and lead to more careful clinical assessment and follow-up of the knee in patients with posterior hip dislocation. Knowing the extent and range of injuries will be important for clinicians who are assessing patients with knee pain after hip dislocation. For these reasons, the authors should be congratulated on an important study.

*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Dickson KF, Galland MW, Barrack RL, Neitzschman HR, Harris MB, Myers L, Vrahas MS. Magnetic resonance imaging of the knee after ipsilateral femur fracture. J Orthop Trauma. 2002;16:567-71.
2. Shepherd L, Abdollahi K, Lee J, Vangsness CT Jr. The prevalence of soft tissue injuries in nonoperative tibial plateau fractures as determined by magnetic resonance imaging. J Orthop Trauma. 2002;16:628-31.

Copyright © 2005 by the The Journal of Bone and Joint Surgery, Inc.