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[maximize]

In light of losing the Stryde and having to reconsider options, I think it's worth noting the following:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5654310/

In that case review:

• 46% of PRECICE 2 nails developed bending/breaking/instability
• 12% of PRECICE 1 nails developed bending/breaking/instability

Is the PRECICE 2 actually less stable than PRECICE 1 or is this random sample bias? Who knows. Either way we can clearly see these nails can bend or break very easily.

If I had one I would treat it like it is very fragile because according to these kinds of statistics it sounds like it very much is. All patients in that study were advised to maintain <20 kg weight bearing. Perhaps they were noncompliant. Or perhaps the devices were just so fragile that was still too much.

Most of the cases of bending or even rotational breakage/instability may not cause major problems. But as an alternative example, here is a woman's leg who developed "rotational instability" (device broke and started rotating freely) and they had to fixate externally with a mono-fixator until consolidation:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5654310/bin/BMRI2017-8032510.004.jpg

I am not saying the PRECICE nail is a bad option. The magnets and allowing contraction in case of nonunion are nice. But it seems a lot more fragile from this than many people seem to imply.

[maximize]

For more context on the nature of the issues:

Nail bending in PRECICE2 was observed in smallest diameter nail (8.5 mm) which in only available in PRECICE2 and this occupies 35% of 8.5 diameter nail used (7/20). Small diameter nails are necessary for the patients with narrow intramedullary canal, especially in East Asia. However, it seems to be necessary to have a stronger mechanical character in order to avoid the bending phenomenon, since “bending” may change the alignment and be exposed to the risk of nail breakage. Twelve cases using PRECICE2 (26.1%) showed breakage of rotation coupling without instability (IIa). All of this occurred in femoral lengthening regardless diameter of the nail. This shows the importance of higher stability against the rotational force regarding the femoral lengthening nail.

So maybe if you're using the thicker nails you won't have so many troubles. And they note that although a full 30.4% of the PRECICE 2 nails broke in their rotational stability, and this was irrespective of nail diameter, only 4.3% of the total patients developed a real problem from this. The other 26.1% that had a rotational break were unaffected.

[Michael J. Assayag, MD]

So lets talk about this.

Precice 1 was a modular nail that had to be assembled on the back table . It had weld points as well that were very fragile.

They would break upon removal and cause another set of issues.

Precice 2 (by the way, we just call it PRECICE, as the modular version is not accessible nor manufactured anymore.) is an amazing implant. The most accurate and versatile of the internal lengthening devices. The key part that seemed to be overlooked in this above article is:

In the PRECICE2 group, 7 segments (15.2%) had nail bending without breakage (IIa) (Figure 2)All of this occurred in smallest diameter nail (8.5 mm) which in only available in PRECICE2 and this occupies 35% of 8.5 diameter nail used (7/20) (Table 3).

Experienced surgeons know that the 8.5mm nail is not as strong nor rotationally stable and should never be used for cosmetic lengthenings. We use it for very small pediatric patients or for humeral lengthenings.

Thicker PRECICE and even Stryde also routinely bends, along with all other internal lengthening devices. It is by design as elasticity of a mechanical implant is desired to prevent breakage. I have even brought it up here on the forums when discussing anatomical vs mechanical axis deviations. This elasticity is taken into account by the engineers who design the implants.

Furthermore, all orthopedic implants can fail. From joint replacements to plates and screws to nails used to fix fractures. They're inert objects with mechanical properties. 

That being said, one has to be careful! Even Stryde breaks. Sometimes its not only about the implant, but about the abuse the nail is submitted to.  that's why I always cringe when I see  surgeons advertise normal levels of activities during lengthening. Or patients posting videos of themselves running during active lengthening. IT's deceitful as too much weight bearing or activity can accelerate implant failure.

[maximize]

So lets talk about this.

Precice 1 was a modular nail that had to be assembled on the back table . It had weld points as well that were very fragile.

They would break upon removal and cause another set of issues.

Precice 2 (by the way, we just call it PRECICE, as the modular version is not accessible nor manufactured anymore.) is an amazing implant. The most accurate and versatile of the internal lengthening devices. The key part that seemed to be overlooked in this above article is:

Experienced surgeons know that the 8.5mm nail is not as strong nor rotationally stable and should never be used for cosmetic lengthenings. We use it for very small pediatric patients or for humeral lengthenings.

Thicker PRECICE and even Stryde also routinely bends, along with all other internal lengthening devices. It is by design as elasticity of a mechanical implant is desired to prevent breakage. I have even brought it up here on the forums when discussing anatomical vs mechanical axis deviations. This elasticity is taken into account by the engineers who design the implants.

Furthermore, all orthopedic implants can fail. From joint replacements to plates and screws to nails used to fix fractures. They're inert objects with mechanical properties. 

That being said, one has to be careful! Even Stryde breaks. Sometimes its not only about the implant, but about the abuse the nail is submitted to.  that's why I always cringe when I see  surgeons advertise normal levels of activities during lengthening. Or patients posting videos of themselves running during active lengthening. IT's deceitful as too much weight bearing or activity can accelerate implant failure.

Thanks for your perspective! Pretty cool to have a LL surgeon who is willing to hang out here and reply. Can I ask a few follow up questions?

First I think it's interesting you say even the Stryde can bend. I would think that the steel units (Stryde, Guichet, Betz) should all be pretty stable against bending as long as they are used below their weight tolerances. In principle, that is what the weight tolerances are supposed to determine. If they are bending beneath their weight tolerances, then either as you say people are doing stupid things like jumping up and down, or the weight tolerances are wrong and should be redefined lower.

If someone had a steel unit like these, when would you think it should be considered reasonable to return to basic office work (walking around the office) even once or twice a week?

On a related subject, I also wonder if you can read this study and let me know what you think:

http://www.limblengtheningforum.com/index.php?topic=66326.0

That meta-analysis showed PEMF/LIPUS allowed 25% faster bone healing in distraction osteogenesis. Do you think most LL surgeons are not aware of this finding? Or are they just skeptical for some reason? I would expect most LL surgeons would happily then add these modalities if it means faster consolidation. Faster consolidation = faster lengthening, quicker weightbearing, and less risk of device failure. Yet no one seems to be getting these unless there is a nonunion already presenting itself.

I lastly wondering if you wouldn't mind commenting on what you think about this:

http://www.limblengtheningforum.com/index.php?topic=66332.0

Speaking in general terms (not about any one ortho in general), why do you think some orthopedic surgeons are so careless about the lengths of their screws? I am not an ortho myself but I am also a doctor. I had one patient of mine in chronic pain after a hip fixation post-trauma. Everyone kept saying the xrays were normal. Then I looked at them myself and the screws were similarly jutting out almost an inch into his soft tissue where he had pain.

It should seem obvious having screws digging an inch into your soft tissue every time you move would hurt but yet many orthos don't seem to think twice about it (in LL or general use) and radiologists also report this as "normal." Do you think this is just sloppiness? Rushing? Are orthos taught that this does not matter? Why not just do an extra x-ray in the OR to measure once more when the nail is in place before screwing it?

I don't mean this as a slam against orthos - I just find it puzzling that anyone would put such massively missized screws inside someone, expect to leave them there 2 years, and not expect problems from it. If they could have just taken the extra 5 minutes to pick the right sized hardware they could potentially save that person so much misery.

Thanks again for your participation here and I appreciate any candid thoughts you can provide.

[sprit33]

I read the above paper, in fact, the data of this paper is the statistics of precice nail from 2010 to 2014, p2.1 and p2.2 entered the market after that, and according to Paley's description, the strength of p nail has increased and it is less prone to breakage. I don't know if the current precice2.2 still has this problem.