Paper of the Month #7: Davids JR et al

Isokinetic testing serves as a principal outcome measure for a new surgical intervention.

Prof. Dvir’s Commentary:

I have chosen this paper as PoM #7 for two reasons:

First, using isokinetic dynamometry (ISD) for assessing surgical outcomes is not new, especially with respect to orthopedic surgery. Perhaps the most common example is the use of the quadriceps for reconstruction of the ACL. Although on a much more limited scale, the effect of surgical procedures relating to other joint systems like the shoulder and the ankle has also been explored. Plastic surgery is another instance where muscles are used. For example, to restore the shape of the breast following mastectomy, a TRAM flap uses donor muscle, fat and skin from a woman’s lower abdomen. A latissimus dorsi flap uses muscle, fat and skin from the back tunneled to the mastectomy site. For assessing the impact of such interventions on muscle strength, isokinetic analysis has been performed. However in both of the above applications, the muscle served as a means for achieving the goal – joint stability or body cosmesis.

In this new paper the muscle itself (medial hamstring) was the target while its strength after the intervention served as a main outcome measure. It is widely believed that operations to correct contractures in children afflicted with cerebral palsy (CP), often end up with weakening of the involved muscle. Using a new operative and rehabilitative approach, Davids et al were able to show, using ISD, that the strength of the knee flexors actually increased significantly following surgery. This is an important finding, albeit limited to those patients that met with the inclusion criteria. Inasmuch as this concerns ISD, it vindicates its major role in assessing muscular function in operations that target muscles. In that respect, this paper provides yet another support for viewing ISD as a standard assessment tool for pertinent surgical outcomes.

The second reason relates to the finding that isometric assessment (in this case using ISD), did not reveal a change in the medial hamstring strength following the procedure, in contrast to the isokinetic findings. The question whether isometric evaluation can provide information that is equivalent to its isokinetic counterpart has been the subject, directly or incidentally, of a number of studies. This paper clearly supports the notion that the answer is most probably negative. In other words, the two methods should not be considered as interchangeable. In fact, for a clear-cut answer to issues that relate to muscle strength variations due to clinical intervention, ISD should be regarded and employed as the reference or the standard tool.

Read the complete study of Davids et al here
The paper may be purchased directly from the publisher.

More information on CON-TREX® units

Davids JR, Cung NQ, Sattler K, Boakes JL, Bagley AM (2018): Quantitative Assessment of Muscle Strength Following “Slow” Surgical Lengthening of the Medial Hamstring Muscles in Children With Cerebral Palsy. Journal of Pediatric Orthopedics, Dec 18. doi: 10.1097/BPO.0000000000001313. [Epub ahead of print].

Paper of the Month – the initiative

The main objective of the PoM initiative is to serve as an update forum for users of isokinetic dynamometry. Recent papers, generally of the last 3 preceding months, relating to this technology and its applications will be reviewed regularly by Prof. Zeevi Dvir, who will select those that in his opinion present an important/relevant contribution to the science of isokinetic testing and conditioning. The selection will consider the novelty, scientific rigor and possible applicability of the study without any prejudice, reflecting PHYSIOMED’s commitment to the highest standards the company stands for as a world leader in isokinetic technology.

Based at the Dept. of Physical Therapy, the Sackler Faculty of Medicine, Tel Aviv University, Prof. Dvir serves also as a Non-teaching Adjunct Professor at the Biomechanics and Ergonomics Lab, School of Kinesiology and Health Studies (SKHS), Queen’s University, Canada.

Prof Dvir is an international leader in isokinetics. He is the author of the widely recognized leading title in the field “Isokinetics: Muscle Testing, Interpretation and Clinical Applications” (Churchill Livingstone, 1st ed., 1995; Elsevier 2nd ed., 2004). He is also the Editor-in-Chief of Isokinetics and Exercise Science (IOS Press, Amsterdam, Holland) since 1998, the only international journal dedicated to the science and practical aspects of this technology. Prof. Dvir has published more than 60 papers on isokinetics. He coined the terms Dynamic Control Ratio (DCR), which is also known as the functional ratio. The DCR has mostly been applied in the context of muscular balance around the knee especially with respect to ACL deficiency and reconstruction and is expressed as the ratio: Hecc/Qcon. Prof. Dvir was also the first to describe the DCE (the Difference between the high and low velocity Ecc/Con ratios) to assess submaximal effort, a core concept in medicolegal analysis of muscular weakness. A US patent he owns paved the way to a series of papers describing the utilization of Short Range of Motion isokinetic testing and conditioning.