1. Rationale for real time ultrasound measurements of m. Transversus abdominis thickness; a systematic review Vincent Hoogstad Jan Paul van Wingerden Richard Goossens Annelies Pool-Goudzwaard

2. Introduction The use of RUSI (Rehabilitative Ultrasound Imaging) for the assessment of deep trunk muscle function, particularly TA, becomes increasingly popular. Since normative data are lacking clinical use of RUSI in LBP patients can only inform the clinician about the presence of a contraction and not the quality of a contraction. It seems questionable whether measurements of architectural parameters on RUSI are of any importance when assessing TA muscle activity. After all, not the amount or quality of TA contraction is altered in LBP patients but the timing is delayed. Aim of this study is to search the literature systematically for the rationale to use RUSI measuring TA and to appraise the relevant literature for methodological quality.

3. Methods A systematic search of relevant literature was conducted in February 2012 in the following data bases; Pubmed, Cinahl en Embase. Both reviewers (AP and VH) subsequently screened the selected abstracts independently with regard to the in- and exclusion criteria. In addition, both reviewers conducted a full text screening of the remained articles and finally performed a methodological assessment using the adapted QUADAS tool.

4. Results Despite the increasing popularity of using RUSI for measuring motor control of the TA only a few studies (4) on this matter were conducted, with each a disappointing number of subjects. Non of the 4 included studies met all the quality criteria of the Quadas-tool

5. Conclusion Although different opinions, the timing delay itself can not be held responsible for the differences found with ultrasound In the research there must be searched for a biomechanical, and/or neurophysological declaration for the differences in thickness found. And all different confounders should be taken in account. Thickness changes measured with RUSI cannot be used indiscriminately as a surrogate measure for muscle activity. For detecting differences in timings delay the only golden standard remains EMG and this is not easy accessible for clinicians Using RUSI for creating awareness in the patients can be helpfull. By the visual feedback provided by USI it’s likely that brain area’s on the cortex are more activated, which will help for retraining the muscle’s specific task.

6. Discussion Differences in thickness and/or thickness change between healthy subjects and patients are reported and in some studies change in thickness-change correlates with clinical improvement. The fact that differences were reported, gives a reason for further research. Conclusions about validity should not be based on studies with small populations. From a biomechanical perspective the TA should generate more tension on fascial structures and therefore the thickness and thickness change should not be the only parameter.

7. Thanks to…. V.Hoogstad Advice (www.vincenthoogstad.com) Spine & Joint Centre, Rotterdam, the Netherlands Erasmus University Rotterdam, dept of Neuroscience/Anatomy University of Rotterdam, dept of Physical Therapy Esics Health Service (www.esics.nl)

8. Contact;. Vincent Hoogstad University of RotterdamSpine & Joint Centre Dept. of Physical TherapyWesterlaan 10 Rochussenstraat 1983016 CK Rotterdam 3015 EK Rotterdamthe Netherlands The Netherlands www.vincenthoogstad.com vincehoogstad@gmail.com