Research Review: Use of MRI for volume estimation of tibialis posterior and plantar intrinsic foot muscles in healthy and chronic plantar fasciitis limbs
By Lynn Willford, PT, MS, Cert MDT
Edited by Brent Brookbush DPT, PT, MS, PES, CES, CSCS, ACSM H/FS
Original Citation:
Chang, R., Kent-Braun, JA., Hamill, J. Use of MRI for volume estimation of tibialis posterior and plantar intrinsic foot muscles in healthy and chronic plantar fasciitis limbs. Clinical Biomechanics. 27 (2012) 500-505 - ABSTRACT
Some of the Intrinsic Foot Muscles - http://upload.wikimedia.org/wikipedia/commons/a/a3/Gray444.png
Why is this relevant?: Approximately 1 million patient visits per year were made to office-based physicians and hospital outpatient departments for the diagnosis and treatment of plantar fasciitis during 1995-2000 (Riddle DL; Schappert SM 2004). However, the proposed mechanism of injury resulting plantar fasciitis are wide and varied. Additional information related to muscle atrophy in a foot with plantar fasciitis will enable the clinician to provide a more specific corrective exercise plan
Study Summary
| Study Design | Retrospective Cohort |
| Level of Evidence | Level III: Evidence obtained from well-designed controlled trials without randomization, quasi-experimental |
| Subject Demographics |
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| Outcome Measures | Muscle cross-sectional area (CSA) obtained using custom software to quantify MRI images of subject’s lower legs
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| Results | PIFM muscle volume mean (SD
PIFM rearfoot muscle volume
Tibialis Posterior (TP) muscle volume
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| Conclusions | The forefoot muscles volumes were significantly different between the NP feet and PF feet, but no volume differences were detected in the rearfoot, or as a total. Compared to NP feet, the PF feet had a 5.3% reduction of forefoot muscle volume. There was no difference seen in the cross sectional area (CSA) between the non-painful and the plantar fasciitis legs. |
| Conclusions of the Researchers | From this data, if may be concluded that plantar intrinsic foot muscles (PIFM) should not be overlooked in the treatment of plantar fasciitis. The total volume of the PIFM are larger than some muscles commonly addressed in the lower leg, and thus their force producing capabilities cannot be assumed to be negligible. It was found that the PIFM atrophy at the forefoot in the presence of chronic plantar fasciitis is significant. The forefoot muscles include: flexor halluces brevis medialis, flexor hallucis brevis lateralis, adductor hallucis transverse, adductor hallucis oblique and the plantar interossei. Differences in the rearfoot were not significant thus the muscles situated in this area are not implicated in atrophy (however, further research may need to consider psuedo-atrophy, for example, as seen in in achilles tendinosis) These muscle include: flexor digitorum brevis, abductor hallucis, quadratus plantae and abductor digiti minimi. The occurrence of forefoot atrophy in PF feet may bring a greater understanding of the etiology of PF and help to guide intervention. |
Cross section of Lower Leg - http://upload.wikimedia.org/wikipedia/commons/4/4e/Gray440_color.png
Review & Commentary:
The methodology of this study was strong. The use of MRI and custom software to determine muscle volume, as well as comparing results of PF patients to non-painful controls and to the PF patients non-painful side contributes to the validity of findings. The authors of the review would like to see additional research published from this group using the same MRI software, possibly exploring other pathologies.
The researchers focused on determining CSA of muscles most commonly implicated as relevant to PF patients; however, they excluded the the tibialis anterior , an important invertor/supinator of the foot/ankle complex.
The sample size was small (8 total), although my guess is that this is related to funding and the expense of MRI testing. In the future, I hope more funding will lead to a larger study with more subjects, and a larger patient population. Although it may not be possible to create a study with high generalizability and small sample size, the use of only women may have implications regarding the results and whether a clinician may be able to apply the same finding relative to a male patient population. Last, longitudinal studies, and/or follow-up may highlight whether atrophy was the result of plantar fasciitis pain or the cause. Of course, this is an issue that is discussed in many research reviews, and is a gap in the body of research as a whole.
Why is this study important?
This study provides evidence that the plantar intrinsic foot muscles (PIFM) may atrophy significantly due in patients with plantar fasciitis pain. Beyond phalangeal flexion and extension, it is difficult to test the strength of intrinsic foot musculature thus the data from this study provides further evidence that would imply strengthening of the forefoot muscles. Additionally, the use of passive treatment options that contribute to muscle atrophy, such as casting, may be contra-indicated. Human movement professionals may utilize this information to enhance corrective exercise strategies for those with foot/ankle impairment.
How does this affect practice:
There may be need for clinicians to add strengthening for plantar intrinsic foot muscles (PIFM) to their corrective interventions for plantar fasciitis patients. Further, this may be dependent on innovation of simple and effective exercise strategies, which at this time lack the sophistication to target specific muscles or the groups of muscles discussed in this study.
How does it relate to Brookbush Institute Content?
Although often a universally accepted, this article may imply that rest and/or immobilization is not the best option. Although this concept is not specifically addressed in the predictive models of postural dysfunction described by the Brookbush Institute, it is our belief that "rest" is rarely the more beneficial solution when compared to intervention. It is our intent to address dysfunction as soon as possible, and decrease the likelihood of further compensation and progression of the cumulative injury cycle. In essence, rest does little to solve the actual cause of movement impairment. Further, it has been our observation that the atrophy, de-conditioning and loss of motor control observed post casting, splinting, bracing, etc., may be harder to overcome then the initial insult to tissues. (Note: in some cases, casting, splinting, bracing, orthotics, may be necessary - for example, fractures, strains, post-surgical intervention, etc.)
The Brookbush Institute to date, has not completed a "predictive model of foot ankle impairment"; however, some thoughts regarding this segment of the human movement system has been discussed in the Integrated Muscular Anatomy articles regarding those muscles that cross the ankle. Rest assured, we are diligently working on an integrated model of impairment for this segment.
- Tibialis Anterior
- Tibialis Posterior
- Fibularis Muscles (a.k.a. Peroneals)
- Extensor Hallucis Longus and Extensor Digitorum Longus (& Fibularis Tertius)
- Flexor Hallucis Longus and Flexor Digitorum Longus
Bibliography
- Riddle DL , Schappert SM . Volume of ambulatory care visits and patterns of care for patients diagnosed with plantar fasciitis: a national study of medical doctors. Foot Ankle Int. 2004 May;25(5):303-10
© 2015 Brent Brookbush
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