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App quantifies ACL tibial translation in injured patients during pivot shift testing
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Researchers at the University of Pittsburgh created an iPad application to determine pivot shift grade according to tibial translation measured in patients with ACL deficient knees, according to a study presented at the International Society of Arthroscopy, Knee Surgery & Orthopaedic Sports Medicine Congress.
“The standardized pivot shift test improved clinical measurement accuracy,” presenter Volker Musahl, MD, of the University of Pittsburgh, in Pittsburgh, USA, said. “The quantitative pivot shift application can detect tibial translation due to pivot shift and, compared to previous technologies, the pivot application is noninvasive, standardized and quantitative. A clinical examination can and should be standardized.”
The research by Musahl and colleagues earned them the second place Scientific Research Award at the Congress.
A standardized test
To quantify tibial translation in patients using an application (app), Musahl and the other researchers first developed and tested a standardized pivot shift test. Twelve orthopaedic surgeons from different international centers visited the researchers’ institution and each performed their preferred pivot shift test technique for the study, according to Musahl. Then he and his colleagues formulated a standardized pivot shift test based on previous literature and the translation and acceleration of each surgeon’s technique, the results of which showed less variability of translation and improved accuracy than the standardized tests, Musahl noted.
Images: Musahl V
The researchers also created a simple image analysis to track the lateral knee, but they wrote in the abstract of the study that motion artifacts and time-intense post-hoc seemed to limit the technique.
“We had previously developed a simple image analysis which is based on quantifying translation of the lateral knee with markers on the lateral epicondyle, Gerdy’s tubercle and fibular head,” Musahl said. “The video is recorded and then reported image-by-image into the software and markers then get recorded image-by-image and can produce a translation code. This is labor-intensive and costs a lot to test.”
App in action
Musahl and colleagues designed an iPad (Apple; Cupertino, Calif., USA) app with help from a Pittsburgh-area based software company (TrueFit; Cranberry, Pa., USA) that records video, checks marker motion and calculates translation codes. They tested the software on 34 consecutive patients who underwent anatomic ACL reconstruction for complete ruptures and were participants in the Prospective International Validation of Outcome Technology (PIVOT) study, which is a collaborative effort with surgeons from the Rizzoli Institute, in Bologna Italy, Kobe University, in Kobe, Japan, Sahlgrenska University, in Göteborg, Sweden, and their own institution.
All the patients were examined under anesthesia. Investigators noted the extent of tibial translation during pivot shift testing in the patients’ operated and unoperated knees. They found no pivot shift in 10 knees and too much leg movement, which caused false readings of a reduction, in four knees. Among 20 patients with pivot shift in both knees, 10 patients had grade 1 pivot shift with 2.7 mm average anterior translation compared to 3.6 mm in patients with grade 2 pivot shift, a difference that was statistically significant, Musahl said.
Using the app, he and colleagues measured the contralateral knees as grade 0 in every patient.
“The quantitative pivot shift analysis could be used to define clinical grading of ACL injury and in the future, assess ACL graft function,” Musahl said. – by Renee Blisard Buddle
- References:
- Hoshino Y. Knee Surg Sports Traumatol Arthrosc. 2013; doi: 10.1007/s00167-013-2396-0.
- Musahl V. Paper #40. Presented at: International Society of Arthroscopy, Knee Surgery & Orthopaedic Sports Medicine Congress; May 12-16, 2013; Toronto.
- For more information:
- Volker Musahl, MD, can be reached at University of Pittsburgh Physicians, Department of Orthopaedic Surgery, Center for Sports Medicine, 3200 South Water St., Pittsburgh, PA 15203, USA; email: musahlv@upmc.edu.
Disclosure: Musahl has no relevant financial disclosures.
Perspective
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Orrin I Franko, MD
I applaud the authors of the study and developers of the app for using available technology in a creative way to provide clinically relevant objective data. Although this is a preliminary study and does not necessarily herald the transition to ubiquitous use of the iPad in orthopaedic examination rooms, the proof of concept is a leap forward in the way we think about quantifying our physical exam in the clinical setting. I have no doubt that further research will yield less expensive, less time-consuming and scientifically valid techniques to replace subjective examination findings, such as the pivot shift test. The changing health care climate and the emphasis on efficient and cost-effective treatment and research will require providers to think outside the box in this manner. I look forward to learning more about this app, testing it myself, and welcoming modifications, improvements and related apps to help us safely treat patients.
Perspective
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Philippe Neyret, MD
A soft endpoint when performing a Lachman-Trillat test means there is an ACL insufficiency. Some tools, such as the arthrometer, allow for the measurement of this translation.
The jerk test reproduces the pivot shift. This test is clinically useful, but depends on the examiner (type of movement, forces, etc). It is crucial to standardize the test. The measurement of the lateral translation and reduction of such translation is difficult to evaluate objectively in the absence of sophisticated tools (electrogoniometer).
During the physical exam, a simple assessment using a few markers and an iPad is of great interest in the diagnosis and measurement of the abnormal movement of the lateral compartment.
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