Introduction

The vastus medialis has (VM) been the object of much research. There is continuing controversy over whether it should be regarded as a single anatomical structure or if it consists of two separate muscles, the vastus medialis longus (VML) and the vastus me...

Methods

As PFP is more common in young women [5] an all-female cohort of twenty-five participants were recruited for this study. A power calculation indicated a required sample size of twenty-three to achieve statistical significance. All volunteers underwent an...

Result

VMO fiber angle

Table 1: VMO fibre angle change following physiotherapy with and without NMES. The difference between the + NMES and -NMES results was found to be significant (P<0.001).

VMO insertion length

Table 2: Changes in insertion length with and without NMES. The difference between the stimulated and unstimulated limb was found to be not significant (P=0.231).

Insertion ratio

Table 3: Changes in insertion ratio (insertion length relative to patella length expressed as a percentage) with and without NMES. The difference between the +NMES and -NMES results was found to be not significant (P= 0.296).

Intra-rater reliability study

Table 4: Summary of the results of the intra-rater reliability study, indicating a high degree of reliability.

Relationship between initial VMO fiber angle and VMO fiber angle change

There was a negative correlation between initial VMO fiber angle and fiber angle change. With NMES, the correlation was moderate (R2=0.49); without NMES, the correlation was weaker (R2=0.25) (Figure 3).

Relationship between initial insertion length and change in insertion length

With NMES, there was a moderate correlation between initial insertion length and the change in insertion length (R2=0.33); without NMES, the correlation was found to be much weaker (R2=0.034).

Effect of compliance of volunteers and VMO fiber angle change

The average compliance was 82.4% (range 50% - 123.8%) (60% compliance was calculated to be equivalent to using the stimulator for a total of 210 minutes). Some participants completed the exercise regime more often than prescribed, and hence recorded compliance > 100%. A strong positive correlation was found between compliance and VMO angle change in the + NMES limb (R2=0.61871), and a moderate correlation in the -NMES limb (R2=0.28724).

Discussion

Currently, in clinical practice, symptoms of PFPS may be managed by VM strengthening exercises [10] and significant improvements have been reported [22]. The management of PFPS requires long-term VMO strengthening, as the symptoms may return after ce...

Limitations

The main limitation that has to be considered in this study is the recording of the compliance of the volunteers. While the Empi muscle stimulator automatically records usage time cumulatively in hours and minutes, it is not possible to determine on which days the machine was being used, and indeed whether it was actually being used while exercising or was just left switched on. There was, however, a high degree of correlation between compliance and VMO angle change, with no obvious outliers, suggesting that the compliance had been accurately recorded. As with all studies of this type, there may have been an element of subjectivity in recording the insertion levels and fiber angles. This was minimized by having the same investigator carrying out all the measurements, and the intra-rater reliability study suggests that the results have a high degree of reliability.

Conclusion

This study found that there was a significant increase in VMO fiber angle with NMES after a six-week programme of physiotherapy, and that the increase was significantly greater than in the limb without NMES. This study shows that the benefits of exercise, in terms of changes to the architecture of the VMO, can be greatly enhanced by the addition of NMES. This can be particularly helpful for elderly patients and those who may not be able to manage, or be less compliant with, strenuous amounts of exercise. Patients for whom this type of therapy would be of maximal benefit can be easily screened in clinic by an ultrasound scan.

Acknowledgement

The authors would like to thank Donjoy Ltd for the loan of the Empi muscle stimulators.