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[tacoma94]

Hi,

I was wondering currently about the differences in nail size and how it could relate to medical risks. Some of them may be:
1. Fat embolism
2. Bone breakage
3. Bone healing

I know stryde is off the market, but I will use it as an example. From a paper from Paley (https://paleyinstitute.org/wp-content/uploads/Stryde-Weight-bearing-Internal-Lengthening-Nail.pdf),
The Stryde nail comes in 10, 11.5, and 13 mm diameters, with 5, 6.5, and 8 cm lengthening stroke corresponding to minimal lengths of 235, 250, and 265 mm. The 8 cm stroke nail is available in longer lengths (280, 305, 335, and 365 mm).

Theoretically, the smallest nail (10mm/235mm) would be (5^2 x 235)/(6.5^2 x 285) = 0.488 in volume compared with 13mm 8cm stroke nail.

Would this imply 1) less reaming and 2) less displacement of marrow and 3) less pressure in the intramedullary canal and 4) increased reduction of bone thickness and hence lower risk of fracture?

I am going for a conservative 5cm and am a rather lightweght individual, so I was interested in seeing whether my nail choice could derisk some of the medical risks.

[tacoma94]

Apologies, should be 265 in above denominator.

[SuchLL]

I don’t have answers but I know Paley likes to use largest nail that fits you. My guess is larger nails are stronger and are less likely to have bending or rotation problems. (There’s risk of nail bending with stryde despite it’s weight bearing.

[two]

I have the same question. I feel a little taken aback when I see a very fat nail in someone's xrays. Won't the bone become flimsy?

[Masteryourlife]

From a logic standpoint a smaller nail is better for the reasons u mentioned up there .
I think the surgeons feel safer with a larger one but it comes down to a "worst" experience for ur bones .
So I guess if you are scared of nail issues u ask for a larger one , if u care more about the health of ur bone you ask for the smallest one and u will have to be little more carefull.
As with everything in this surgery , we have to choose between the less invasive one according to our concerns .
Everyone is scared of different aspects of this surgery .
This is my opinion at least

[Michael J. Assayag, MD]

The real answer to that question is always: what is the best nail to accommodate both your bone, and your lengthening goal.

Every year at the Baltimore Limb Deformity Course, I teach international surgeons about the best way to pick an implant and plan an internal lengthening.

The nail diameter should be chosen by taking into account both inner and outer bone diameters.

The nail length or Shortest nail length (SNL!!) should be a function of the level of osteotomy and lengthening goal. here is the quick formula i use.

SNL = Distance between entry point and osteotomy + lengthening goal + 8 (sometimes 7)

where the constant 8 is dictated by the length of the telescopic portion sticking out (3cm) + 5 which represents the thick part of the nail beyond the lengthening at the end of the distraction phase.

I hope that helped!