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Dr Prodromos ACL Blog February 2015

Dr Prodromos ACL Blog February 2015

Each month there are roughly 50 – 75 new scientific journal articles in the world’s peer reviewed literature dealing with the human ACL which we collect and peruse. I will summarize the main point of those few that, in my opinion, say something genuinely new or particularly important in this monthly blog.


Article 1:
from departments in The Netherlands and Germany showed that stretching resulted in transiently increased ACL laxity (looseness), as did playing soccer, although to a lesser degree. Knees had instrumented Lachman testing with an arthrometer before and after stretching and soccer. This finding highlights the underappreciated fact that stretching has never been shown to produce any injury preventative benefits, but has been shown to result in hamstring injury in some studies.

However the finding that stretching can actually increase ACL laxity is completely new and of possibly far greater significance. This finding also casts a potentially new light on the ACL injury prevention programs that use strengthening and stretching to reduce injury. It perhaps suggests that it is the strengthening and not the stretching that may be more important.

It also may help explain why soccer is a high risk sportfor ACL tear. It will be interesting to see the results of similar testing before and after participation in other sports.


Article 2:
compares pull out strength of several tibial fixation devices for ACL grafts. Basically they contrast cortical fixation (Washer loc) simple interference fixation (delta screw and retroscrew) and augmented interference fixation (the intra-fix). The results indicated worse pullout strength for the simple interference devices: the delta screw and the retro screw.

It is not necessarily the case that decreased maximum pullout strength will result in great laxity postoperatively. But it does suggest that with these simple interference fixation devices with less pullout strengths, more cautious rehabilitation in the early postop period is probably advisable. The retroscrew advocates feel that there is less morbidity from the less aggressive tunnels is an advantage which may warrant the less good pullout strengths.

However there is really no compensatory benefit that obtains when using a simple interference screw. This may explain the interest in, and development of, several newer devices such as the Cayenne Aperfix and Medshape Exoshape that, like the intra-fix, augment the simple interference fit for soft tissue grafts. Good clinical results are really all that matters. But for many surgeons it will be appealing to get the greater insurance of greater pullout strengths.

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