Abstract
Purpose
To evaluate the reliability of an instrumented patellofemoral (PF) stress-testing—the Porto Patellofemoral Testing Device (PPTD)—and validate the instrumented assessment method comparing to manual physical examination.
Methods
Eight asymptomatic volunteers underwent bilateral PF-instrumented examination with the PPTD and magnetic resonance imaging (MRI) to assess intra-rater reliability of the instrumented assessment methodology. Six patients with unilateral PF instability underwent physical examination and PPTD concomitantly with MRI. Manual examination was performed by two blinded surgeons and compared with PPTD test. Ligament stiffness was calculated and compared between injured and non-injured lower limbs.
Results
PPTD showed a pre-determined and reproducible stress-force application with excellent intra-rater agreement (intra-class correlation coefficient 0.83–0.98). The manual exam was imprecise with variable examiner-dependent stress-force application. The PPTD resulted in greater lateral patellar translation (converted in quadrants) than manual exam for patients that have reached maximum translation force. Measurement of patellar position and displacement using PPTD was more accurate and precise than the visual estimation of translated quadrants by manual exam. Ligament stiffness curves showed no relevant changes in patellar displacement after 62 N.
Conclusion
The PPTD instrumented stress-testing is a valid device to quantify PF position and displacement with high intra-rater reliability, showing more accuracy, more precision and less variability than physical examination. This device provides an accurate and objective measure to quantify the patellar movement which can augment the physical examination procedures and assist clinicians in the management of decision-making and in the assessment of post-treatment outcomes of PF pathological conditions.
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Abbreviations
- PPTD:
-
Porto Patellofemoral Testing Device
- MRI:
-
Magnetic resonance imaging
- PF:
-
Patellofemoral
- MPFL:
-
Medial patellofemoral ligament
- PP:
-
Patellar position
- ICC:
-
Intra-class coefficient
- SEM:
-
Standard error of measurement
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Acknowledgements
The authors would like to sincerely acknowledge: the Clinical Director of SMIC Dragão (Dr. Rui Aguiar) and the Head of the CMRR (Juta Ellerman) and their teams for the technical support in the imaging study; the University of Minnesota Professors Joan Bechtold and Jack Lewis for their valuable discussions on the validity study approach and the Department of Orthopedics Research Fund from University of Minnesota for the financial support for the validity study.
Funding
One author (AL) reports funding from FCT—Fundação para a Ciência e a Tecnologia and FLAD—Fundação Luso-Americana para o Desenvolvimento, for the Ph.D. Studentship in Industry (SFRH/BDE/51821/2012) and Internship grant (Proj.16/2015).
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AL, PF, FSS, JEM developed the PPTD device and protocol; AL carried out the PPTD procedure and measurements; BH, MT, EA, JEM validated and interpreted the PPTD measurements. AL and RA drafted the manuscript and performed the statistical analysis. AL, MT, EA, JEM designed the study. BH, MT, PF, FS, EA, JEM validated and critically reviewed the scientific content of the manuscript. All authors read and approved the final manuscript.
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No financial or non-financial competing interest exists for this manuscript. The manuscript was not influenced by personal or financial relationship with other people or organizations.
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Reliability study approval by the Institutional Review Board of Clínica do Dragão, Espregueira-Mendes Sports Centre—FIFA Medical Centre of Excellence: protocol number #003/0015. Validity study approval by the University of Minnesota Institutional Review Board: protocol number #1507M7652.
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Leal, A., Andrade, R., Hinckel, B.B. et al. A new device for patellofemoral instrumented stress-testing provides good reliability and validity. Knee Surg Sports Traumatol Arthrosc 28, 389–397 (2020). https://doi.org/10.1007/s00167-019-05601-4
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DOI: https://doi.org/10.1007/s00167-019-05601-4