Patient-Directed Valgus Stress Radiograph of the Knee: A New and Novel Technique
The radiographic investigation of patients with medial-compartment osteoarthritis of the knee is a critical element in the decision-making process of determining whether the patient is a candidate for unicompartmental or total knee arthroplasty. A valgus stress radiograph of the affected knee is an essential part of this radiographic investigation. Historically, this has been performed with manual stress applied by the surgeon or the radiologic technologist; thus, this examination requires 2 individuals to complete. In addition to being inefficient, 1 individual is exposed to radiation, which can be undesirable over many exposures and in a long career.
For these reasons, we instituted a quality improvement project to develop a method of obtaining the valgus stress view with 1 technologist that would obviate these concerns. Of 78 examinations performed, 5 studies did not show complete correction of the varus deformity. Of these, 3 showed complete correction on a manual valgus stress radiograph, and 2 did not. Three patients displayed collapse of the lateral compartment, indicating a nonfunctional lateral compartment. The remaining 70 patients had identical radiographic results with both the manual and patient-directed valgus stress.
Discussion
In total, 73 patients (93.5%) with the patient-directed stress film showed the desired result, either correction of the medial compartment narrowing in conjunction with an intact lateral compartment or narrowing of the lateral compartment. Of the 5 patients (6.5%) whose patient-directed stress films did not show correction of the varus deformity, 3 patients displayed correction with a manually applied stress radiograph and 2 did not. Based on this observation, our recommendation would be for those patients who do not show adequate correction on the patient-directed stress radiograph to have a manual examination to establish the presence or absence of the desired correction.
Performing a valgus stress radiograph is an integral part of the investigation to determine if the patient is an appropriate candidate for partial knee arthroplasty.3 The historical, manually performed valgus stress radiograph requires 2 individuals, 1 to apply the stress with the patient on the table and 1 to shoot the exposure. For the individual or individuals applying this stress, there is an increased radiation exposure that would be undesirable over a long career. The authors developed a new technique using a commercially available spinal positioning wedge and 11-in youth soccer ball wrapped with Coban wrap, as described, which is economical and easy to obtain and use in the clinical setting. We believe this cost-effective method will offer surgeons who perform partial knee arthroplasty a novel method to obtain the important information gleaned from the valgus stress radiograph and to improve surgical outcomes through the preoperative assessment of the lateral compartment. Additionally, as a quality and safety improvement initiative, we believe this technique will reduce radiographic exposure for those performing these studies, and, because the examination can be carried out by a single technologist, it will significantly improve efficiency in the radiology suite.
Conclusion
We have developed a new method of obtaining the important valgus stress radiograph as part of the workup of patients with medial-compartment osteoarthritis of the knee. The technique can be performed with easily obtainable, commercially available products and is reliable 93.5% of the time. It also adds to the efficiency of the radiology suite and reduces radiographic exposure for technologists.
