Original researchCan ultrasound measurements of muscle thickness be used to measure the size of individual quadriceps muscles in people with patellofemoral pain?
Introduction
Patellofemoral pain (PFP) is a common source of knee pain experienced by active adolescents and young adults that typically presents as anterior knee pain with squatting, running and stair descent (Witvrouw, Lysens, Bellemans, Cambier, & Vanderstraeten, 2000). Excessive lateral patellar tracking has been associated clinically with PFP (Pal et al., 2013, Song et al., 2011, Souza et al., 2010, Wong et al., 2012), and may be due to dysfunction of the vastus medialis oblique (VMO) relative to the vastus lateralis (VL) (Serrão, Cabral, Bérzin, Candolo, & Monteiro-Pedro, 2005), as these muscles have an opposing role in patellar tracking (Lin, Wang, Koh, Hendrix, & Zhang, 2004). It is impossible to directly assess differences in force production between VMO and VL in PFP, and investigation into the relative size of these muscles may be an appropriate clinical alternative to determine if there is selective VMO dysfunction. Greater atrophy of VMO relative to VL has been speculated in PFP (Al-Hakim et al., 2012, Halabchi et al., 2013, McConnell, 1996, Witvrouw, 2005). Investigation is required into the validity of tools that could detect quadriceps atrophy or selective VMO atrophy in a clinical setting.
The gold standard instrument to measure quadriceps muscle size is magnetic resonance imaging (MRI) (Morse, Degens, & Jones, 2007). However, MRI is time-consuming and expensive, which prevents regular use by clinicians to measure quadriceps muscle size in patient populations. In contrast, real time ultrasound measurements are more readily available in clinical situations and may be a viable alternative clinical measure of muscle size. Ultrasound measurements of quadriceps muscle thickness have good reliability and repeatability (English, Fisher, & Thoirs, 2012), can be performed in a short amount of time, and are strongly correlated to quadriceps strength (Strasser, Draskovits, Praschak, Quittan, & Graf, 2013). Ultrasound measurements of muscle thickness at the mid-thigh are strongly correlated to MRI measurements of rectus femoris (RF) thickness (Thomaes et al., 2012), and whole quadriceps volume (Miyatani, Kanehisa, Kuno, Nishijima, & Fukunaga, 2002). The validity of using ultrasound to measure the thickness of other quadriceps muscles requires investigation.
Real-time ultrasound may be preferable to other commonly used clinical tools to identify which people with PFP have quadriceps atrophy. A systematic review found quadriceps atrophy in unilateral PFP on meta analysis of imaging measurements, but not from thigh girth measurements (Giles, Webster, McClelland, & Cook, 2013). These results suggest that thigh girth measurements are not as sensitive as imaging modalities in detecting quadriceps atrophy, and modalities such as real-time ultrasound could be an appropriate clinical alternative. Findings on clinical assessment of whether selective or general quadriceps atrophy are present could influence physiotherapist treatment selection. In current clinical practice selective VMO atrophy is often inferred subjectively, from visual comparison of the quadriceps bulk between limbs (Blønd and Hansen, 1998, Calmbach and Hutchens, 2003, Halabchi et al., 2013). Alternatively, ultrasound could be used as an objective tool to assess whether selective VMO atrophy is present in unilateral PFP, by comparing VMO and VL size between limbs.
The aim of this study was to investigate the validity of muscle thickness measurements of the quadriceps with real-time ultrasound, by investigating the correlation with MRI measurements of muscle thickness, CSA, and volume. The primary aim was to investigate the validity of measuring the thickness of quadriceps muscles VMO, VL, vastus medialis (VM), vastus intermedius (VI) and RF with ultrasound. The secondary aim was to investigate the validity of measuring the ratios in thickness of VMO and VM relative to VL with ultrasound, as well as whether differences between limbs in these ratios correspond to differences between limbs in MRI measurements. The validity of ultrasound muscle thickness measurements of each quadriceps muscle has not been investigated. Research into the validity of this method could identify an inexpensive alternative to MRI that is available in many physiotherapy clinics and can be operated by the rehabilitation provider.
Section snippets
Participants
Five participants (two men, three women) aged 24–37 years, with unilateral patellofemoral pain for greater than 6 weeks, attended La Trobe University for assessment after responding to recruitment posters placed in medical and physiotherapy clinics. Participants with unilateral PFP were investigated as this is the appropriate population for clinical assessment of quadriceps size in PFP. Participants were examined by a physiotherapist for the presence of patellofemoral pain according to pre
Results
Mean values of the thickness of each quadriceps muscle measured with ultrasound and MRI, as well as MRI muscle CSA and volume measurements are presented (Table 1).
Discussion
Real-time ultrasound may be an adequate substitute for MRI to measure the thickness of the superficial quadriceps muscles. Measurements of muscle thickness from US were strongly correlated with those from MRI for each of the superficial quadriceps muscles. Ultrasound measurement of muscle thickness was also correlated to MRI measurement of CSA and volume for the muscles VM, VL and RF. This suggests that measurement of muscle thickness with ultrasound may be used as a surrogate for measurement
Conclusion
Ultrasound measurement of the thickness of all superficial quadriceps muscles (VM, VMO, VL, RF), and in the proportional thickness of VM and VMO relative to VL are correlated to MRI measurements of muscle thickness. These ultrasound measurements are also correlated to the CSA of all superficial quadriceps muscles, measured with MRI, except for VMO. These findings suggest real time ultrasound measurements of muscle thickness may be suitable for use in the assessment of quadriceps muscle size in
Conflict of Interest
None declared.
Ethical Approval
All procedures described in the manuscript “Can ultrasound measurements of muscle thickness be used to measure the size of individual quadriceps muscles in people with patellofemoral pain?” were approved by La Trobe University Faculty of Human Ethics Committee FHEC12/143.
All participants in this study provided informed consent.
Funding
None declared.
Acknowledgements
Prof Cook was supported by the Australian centre for research into sports injury and its prevention, which is one of the International Research Centres for Prevention of Injury and Protection of Athlete Health supported by the International Olympic Committee (IOC).
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