Welcome to a diverse issue of PT Crab and I think the first one that doesn’t really have an article for outpatient PT. Wow. Instead, we have some tangential ones for you, including one about predicting disability after childbirth, and another on vastus medialis. Our King Crab supporters got two more this week, one about long Covid and the lungs, and another on PTs role in treating victims of sexual assault. You can become a supporter for just $10/mo here and the first month is free!
It’s an up, down, and all around edition of PT Crab coming right up.
Let’s dive in!
P.S. This issue of PT Crab is brought to you by Bright Cellars and Fulton Insoles.
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Predicting disability after childbirth is all about ‘dat pelvis. And fear avoidance. And other stuff too. But not IRD.
The Gist - This summary sets the record for the longest ever title in PT Crab (19 words!). So, what’s it about? Inter-recti distance. AKA IRD. Increased IRD is common after childbirth and many attribute post-childbirth disability to this phenomenon. But is it right to do so? This article in PTJ says maybe not. They did a cross-sectional observational study of 141 women with an IRD of at least 2 finger-widths and a youngest child between 1 and 8 years old to see. They did lotsa fancy stats to see how disability (using the PDI) correlated with fear-avoidance beliefs, lumbopelvic pain, emotional distress, BMI, IRD, and physical activity.
In the end, they found that actual IRD didn’t explain disability. Rather, lumbopelvic pain and fear avoidance behaviors were the strongest predictors of disability with regression coefficients of 1.4 and 0.42 respectively. IRD was not correlated at all, with a confidence interval that massively spanned 0 (from -1.15 to +0.89).
Tell Me More - Here’s why this matters. If the actual size of IRD was the problem, that’d be what one ought to focus on in rehab. This work shows that that’s probably not the case. Rather, pain was number one with fear-avoidance well behind and emotional distress taking the third spot. So a focus on reducing lumbopelvic pain may be the PT answer. Still, we’re not completely certain due to the limitations here. This was a volunteer-based study and the mean level of disability was fairly low across the board. So we’re not certain, but it points in the direction that IRD itself isn’t the problem, it’s other factors instead.
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Link? I mean, it’s right up there, but sure, I’ll put it here too.
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What is Vastus Medialis Really Like? Really Weird.
The Gist - Cadaver studies don’t often feature in PT Crab, since there’s rarely anything clinically applicable, but this interesting study may have some clinical nuggets. They assessed 18 cadaveric lower limbs to study the anatomical interaction between VM and VI and came up with some cool stuff. VM is a clamp muscle. Strange, huh? The figures in the paper really make it clear, so I highly recommend checking those out. I’ll try to explain below.
VM originates from the medial surface of the femur and has most of its fibers directed transversely across the bone, then wrapping around the VI aponeurosis “like a clip holding a sheet of paper.” It uses this clipping action to pull the VI medially while it contracts, changing the direction of force on the patella. Cool! VM also has an insertion on the patella, so it doesn’t only pull VI, but that’s a function of it.
Tell Me More - Let’s talk about why this matters. The researchers point out that this is new information about VM and that it digs deeper into how the muscle controls patellar motion. In their words, it “functions as a dynamic medial stabilizer of the patella”, not via direct pull on the patella via the distal, VMO portion, but mostly through its control of VI’s direction of pull. They also note that this study, combined with previous ones, shows that direct force supplied by VM for knee extension is limited. Specifically:
The EMG observations in the literature, together with findings of the present anatomical study, suggest that the VM acts as an indirect extensor at the knee. It can be hypothesized that by pulling the longitudinal components of VI and rectus femoris medially and dorsally, the VM tight- ens and shortens these quadriceps muscles, much like a belt around the waist. Obviously, this shortening of the length of the quadriceps (indirect extensor mechanism) is most important during the terminal phase of extension.
This is some interesting new ground in our understanding of knee extension. Check out the full paper for the figures and more details about their new findings.
Here’s That Paper - And it’s open access! Yay!
And that’s our week. Please share PT Crab and stay spooky this October! And become a supporter here. Supporters get twice as many articles and 100% fewer ads.