Achilles, Pascal, Occam, TUNC and Bonini

In the world of eponyms in surgery - Monteggia, Fournier, Chiari etc - I actually prefer the non-medical ones.

There is, for example, Achilles' Dilemma in hip resurfacing  ("to choose whether to live a short and glorious life or live a long and boring life"); Occam's Razor in diagnostics; Pascal's Wager in avoiding hip dislocation (just use an elevated lip - there is no down side). In case you're wondering, TUNC theory is an acronym not an eponym, for any confused readers.

Here, though, is a new one for me. Bonini's Paradox (courtesy of Kevin Williamson, writing on US politics).

Let us consider hip replacement first. A sphere sits within a hemisphere, as a near perfect fit. It can move freely in any direction for everyday function. It has intrinsic stability by nature of its shape. It is a fairly accurate facsimile of a real hip in many ways. It is a simple design philosophy, if subject to highly sophisticated manufacturing. It is very forgiving in practice, if you put it in slightly askew.

Not so knee replacement. Here there are several radii of curvature in coronal and sagittal planes, not one. A highly complex ligamentous arrangement ensures stability and translational movement. The lateral tibial plateau is smaller in life than the medial side. The lateral plateau has convexity. The shock absorption from the menisci varies between the two sides. Yet the knee prosthesis has a symmetrical biconcave tibial plateau with no difference in impact resistance, no benefit from the cruciates (except in those cruciate retaining cases with a pristine PCL), and relies on a difficult-to-consistently-get-right 'balancing' of the intact collaterals. It is a very unforgiving scenario, so no wonder that pretty much everyone admits these days that knee outcomes are poorer overall than those from hip replacement, particularly in high activity patients.

Attempts to make more complex knee replacements incorporating these issues have generally failed, with either poorer results or at best, unpredictable ones. It's not been for lack of trying by implant companies (1, 2).

Back to Bonini, who is a business professor at Stanford University, looking at reproducing complex systems, for example, a computer model of the brain:

And this is Bonini's Paradox: The less information a model carries about its subject, the less useful it's going to be in helping someone understand that subject. And yet, the more information a model carries about its subject, the less useful it's going to be in helping someone understand any single point of that subject. Any sufficiently detailed map of a region is going to be just as dense and difficult as the region itself. Any sufficiently detailed model of a brain is going to be a brain.

...and any sufficiently detailed model of a knee is going to be a knee. Wikipedia quotes French poet and philosopher Paul Valery, with a similar take, from years earlier in 1937: "Everything simple is false. Everything which is complex is unusable."

Indeed, a hip replacement is undoubtedly 'false', but it nearly always works. A more complex knee replacement is also false, but it just edges a little bit along the spectrum towards unusable.

Another quote from the Gizmodo article already cited: Any model, of anything, is in an act of editing. It picks out what we think is important regarding the subject, and directs our attention to how that important thing can be manipulated.

Even orthopaedic surgeons aren't gods. I suppose

...OK, everybody got that?

The best hip fracture ever?

Taken from Twitter. No comment required:

Country music meets total joint replacement

Nobody closes over an actively bleeding surgical site. Do they?

In my handwritten operation note it says 'haemostasis' followed by a tick symbol. In the dictated note I use the authoritative phrase 'haemostasis secured', which has a nice feel to it. Obviously I won't get any postoperative haematoma, and if I did, which I won't, it wouldn't be my fault. Or something.

So I will never have to use the phrase  'it was dry when I closed'.

In this matrix lesson, Leo Gordon notes the unusually fruitful use of Country & Western lyrics as applied to surgery, thus creating a new composition: 'Don't the Fields All Get Drier at Closing Time'. It's true that near the end of a big case you often just want to get out of there.  Songwise, one might add 'Does My Ring Hurt Your Finger' by Charley Pride, when examining for anal tone in a patient with a spinal presentation, or 'Life Has Its Little Ups and Downs' for when the MMC results come out (which has just happened)....



....I digress. Basically, not all complications are preventable, but bleeding is one that certainly can be. It doesn't help that in orthopaedics we've been trapped by what Gus Sarmiento aptly called 'the orthopaedic-industrial complex' as a variation on the medical-industrial complex theme (AKA Big Pharma), such that we dose all our arthroplasties with chemicals of extremely dubious value on the recommendation of physicians who are, to put it politely, remote from the consequences for the patient who has a bleeding complication.

Leo also describes the dreaded 'knee-jerk suspicion of surgical sloppiness' that we cannot banish from our mind when we confront the offending haematoma. Our own suspicion, and inevitably that of our friends and peers.

I blame Big Pharma, it was definitely dry when I closed.

An orthopaedic Christmas Carol, sort of

With a nod to Charles Dickens, this is about the ghosts of Orthopaedics Past, Orthopaedics Present and Orthopaedics Future. The reminiscences and reflections of surgeons late in their career or at retirement are a regular feature of this blog (label: wise surgeon). They really are  fascinating, and a treasure trove of useful thoughts.

This is Gordon Bannister, one of the best known British orthopods of the past 30 years, a very fine trainer and researcher, and generally a good guy, part of the Bristol centre of excellence.

He is no Luddite, but I draw your attention to a few things:

1. In the old days "senior consultant staff..had long since delegated acute trauma to their registrars. As a result, registrars acquired a wealth of experience". That's what happened to me much of the time. It doesn't happen now, which is both good and bad.

2. "At that time (the 80's) a 1:2 rota was common, occasionally tiredness ensued. The number of trainees increased whilst their experience declined". There is no way round this fact - you have to do the operations (and see the acute presentations) to get good. Most of my rotas were actually 1:3.  The promotion of the surrogate experience of 'simulated surgery' tells you how far things have gone. Note this from the former president of the RCS, Norman Williams. My view is that the New Deal has been even more damaging to training, morale and running a unit than the EWTD.

3. It was (and still should be) a lot of fun. If it consistently is not, then you may be in the wrong job.

4. I could not agree more that the demise of the true generalist to be replaced by self-anointed 'superspecialists' has been both stupid and damaging. It will be interesting to see what all the hip arthroscopy specialists will be doing in 10 years time.

Lastly, I would highlight the segment on NHS management and the conclusion. It's actually surprising how many empathetic and quality managers you encounter, but the long lasting damage wrought by the bad ones (and their political masters) is quite something.




(Thanks to BJJ News, September 2015)

Celebrity orthopaedics: Paul Stanley

Post THR exercise routine

One of my occasional pleasures is seeing how once youthful rockers grow old, get ill etc. I remember a picture of Rod Stewart coming out of a New York pharmacy clutching a large box of anti-inflammatories. A few weeks ago we had Joe Perry with his walking stick.

Well, here's Paul Stanley (65 last month), the guitarist with the star on his face from Kiss. He's an orthopaedic case history:

"What I do has taken its toll. I've had both my rotator cuffs surgically repaired. They're all similar to sport injuries. I've torn my meniscus in both knees and had a hip replacement. This is all from onstage performances. It's like doing a triathlon with a guitar around my neck. You have to jump, sing, swing your arm and play the right chord. With that combination, anything can go wrong. I used to jump up in the air and land on my knees. It didn't hurt then, but it does now."

He was 52 when he had his hip done. Last year he had a torn biceps fixed, with all the vital technical details:

Not only that, he identified the difficulty deciding whether to undergo a hip replacement in a tweet after bandmate Gene Simmons was critical following Prince's OD on analgesics for his hip disease (keep up):

As he said about his own decision:

"I wound up postponing my hip surgery and, you know, it's like reading in the newspaper your own death, you know, when you keep reading about your hip surgery, and I haven't done it, but I'm just postponing it for awhile. I have, you know, every intention of continuing doing what I've been doing, but little by little I'm turning bionic."

Interestingly Paul did have a complication - recurrent dislocation. Money can't guarantee that you avoid it. When I did private medicine I always felt my complication rate was slightly higher in the private sector. . It would be interesting to know what the salvage procedure was, because he looks like he's functioning at a pretty high level. Although...

"You know things did not go as well as they could have or perhaps should have. Hip replacement is major surgery yet it's fairly routine. It's done so often. The actual procedure has changed so much that you basically have the surgery and are walking that day. But there's a saying, minor surgery is what somebody else is having. This clearly was not minor surgery and the first one did not go well and kept pulling out or dislocating almost immediately. So within two months I went back and had it done again, which seemed to fix one problem and start others. The recovery has taken way longer and been more painful than I expected. It will never be great."


And that fits with the evidence that although patient satisfaction after dislocation soon catches up - if the hip is stabilised - the functional scores are frequently less than in the uncomplicated hip arthroplasty. 

I'm not a huge fan of Kiss, though I kind of like the whole trashy metal showbiz thing. Here they are in 2014. That's a 10 year old revision hip in a 62 year old you're looking at. Not bad.

But I like doing uncemented...

The title of one of the worst films ever to achieve fame is the same as one of the best papers I've read in the last few years. It's in Bone & Joint 360, and it takes a careful, evidence based and pragmatic look at the use of uncemented total hip replacement in the NHS. It's not particularly pretty reading.

Put simply, it's not possible for uncemented hips to achieve better survivorship than the Charnley or Exeter, partly for statistical reasons (you could never have a study with adequate statistical power, unless we all start living to be 130). There is no evidence of better function - unlike, say, the much maligned resurfacings. There is evidence of higher complication rates - pain, leg length discrepancy, dislocation, periprosthetic fracture. Generally speaking they cost more. There is no consistent evidence that because you can in theory do them more quickly, you'll do more on a list. Not in the NHS anyway.

So why do them at all? Obviously they're great for many revisions, and there are specific cases - awkward anatomy, femoral shortening, the very young - where they make sense. There are quite a few uncemented stems with great survivorship, although not better than the cemented rivals.

If they're not being done for clinical reasons, or because they're cheaper, then it must be because the surgeon says so. Not ideal really. The UK still has a predominance of cemented stems, because of hybrids, but the commonest single combination is uncemented, albeit it's coming down slightly. Bizarre. Here's the NJR data:

And here's the Inconvenient Truth, followed by a short film on how to put them in:

The science of walking sticks and related matters

Joe Perry of Aerosmith genuinely uses a walking stick!

A minority of orthopaedic surgeons are entirely at ease with biomechanics, I would say. I am in the slightly perturbed majority. However, all orthopaedic 'exit exams' of which I'm aware will include it, reasonably enough. Drawing free body diagrams, explaining joint reaction forces, discussing the rationale of prosthetic design etc

Happily, as Isaac Newton has amply demonstrated, the principles have been established for centuries, and so the two papers here, from 1959 and 1997, seem bang up to date.

The first, by Robin Denham, one of the relatively unsung heroes of British orthopaedics, is as nice an exposition of basic hip mechanics as you could wish for. He references Blount's classic JBJS article "Don't Throw Away the Cane", and the end of Denham's piece has a great little exposition of the use of a walking stick (cane), which includes why patients will intuitively hold it in the opposite hand from the affected hip. The final 9 points in the summary are in a way all you need to understand for both clinical practice and exams.




The second paper, from Richard Brand in Iowa, is more about osteotomies, and relating the mechanics to the biology. Proximal tibial osteotomy for knee arthritis is definitely on the way up again, and periacetabular osteotomy in adults is an essential part of the hip repertoire now. Proximal femoral osteotomy in adults though is not really on the same page. There seem to be very few patients in whom it would be a better bet than a hip replacement. The last one I did was for a varus proximal femur causing stress fractures, ages ago (it did work). The bottom line is, if you absorb these two papers you know a lot about hip mechanics. if you're like me, and you get most of the content, that's enough to function perfectly well.

If you add in Charnley's stuff on wear and head size, you're almost an expert. Almost

What have the Americans ever done for us?

Jasper Johns, Flag, 1954. MoMA

It's true that the greatest advances in skeletal trauma and orthopaedics are predominantly European in origin (and many of them are British), but our friends in the States catch up quickly. I remember being at the American Academy meeting about 15 years ago, having been doing a lot of MIPPO fixation for damage control for about 3 years, after the Hannover trauma stars like Krettek had published really wonderful papers on it. At the AAOS meeting they had one guy presenting about 10 femoral MIPPO's to a sceptical audience. Now they're completely on top of it.

Areas where they do have a great track record of innovation include spines and an interest of mine, lower limb revision arthroplasty. Kelly Vince on knees, for example, is a truly great surgeon and educator, one of many North Americans (I know he's Canadian) in that field, and there are lots of revision hip stars like Paprosky, the Mayo guys, lots of them.

Which brings me to Charlie Engh, who has graced numerous CCJR meetings. He is the man behind the AML cementless fully porous coated stem, which like Paprosky's Solution stem really cracked the problem of the difficult femoral revision. There are now quite a few imitations. I can't stand modularity on revision femoral stems - I regard it primarily as a marketing ploy for companies, and it pushes the price up - as it's nearly always unnecessary and complicates matters. The AML had a modular head and that was it, although there a couple of variants now. This is not an advert - I use one of its competitors, I'm just paying homage to Charlie.

Anyway, here is a great reminiscence by the man himself, on his career and the development of orthopaedics in the USA over that period. It's followed by a minimum of 10 year follow up on the fully porous coated femoral revision stem - a landmark paper in my view.




That piece mentions the other Engh brother, Gerry, also an orthopaedic surgeon. I once saw him present a case - with videos - of a patient with no arms who drove a car with their feet on the wheel. Gerry did an ACL reconstruction (I think on both knees) followed by medial AND lateral unicompartmental knee arthroplasties. The end of the talk showed a new video - back driving the car. I'm not making this up. Wonderful.


Here's the 10 year outcome paper. Relatively few cases, but difficult ones, and a long follow up. Most surgeons and patients would be happy to get a good 10 years (and more) in cases like this.

The problem with big heads

*

The only thing that John Charnley did in orthopaedics that I don’t like is when he designed those big ugly forceps – I prefer a Lane’s any day. All his other instruments convey the message that he must have been a master surgeon and a gifted engineer. When I started orthopaedics his hip was still THE prosthesis in the UK, although back then the Exeter was already catching up. Now the Exeter and its lookalikes rule supreme and Depuy have incredibly pretty much abandoned the original Charnley, the most studied and successful implant of them all.

Back then the McKee had a 35mm head, the Exeter was 26mm (still a pitfall for today’s revision surgeon who hasn’t checked it properly), the dreaded Ring implant was 32mm, there were quite a few 28mm prostheses about, and the Charnley was 22mm. Why 22?

The simple answer is that with the materials available, Charnley saw it as the best trade off between reducing volumetric wear and the associated creation of polyethylene debris in large amounts, and linear wear eroding the superolateral part of the socket.

Not many people now have Charnley’s landmark book Low Friction Arthroplasty of the Hip, currently trading at upward of £150 on eBay, and fewer have actually read his 1969 paper on head size in a bioengineering journal, but here it is! (The second paper is a very handy review from HSS on the modern thinking on head size issues.)

It’s not a great read in a way, but it contains lots of key thinking. I believe that the main problem with those metal on metal articulations which fail in the present era is lubrication failure. Charnley spotted this as a major issue, hence he wanted inherently low friction materials in contact with each other. As he put it in the paper: “in the absence of a fluid film a good theoretical argument can be made out for using the smallest ball which the load bearing capacity of the plastic will tolerate”. Which was obviously not going to be 32mm.

The paper is based on experiments with polytetrafluoroethylene (PTFE), commonly called Teflon (as in various dodgy politicians), which is not the still useful ultra high molecular weight polyethylene (UHMWPE). This stuff seemed to behave differently in the lab compared to in the human body. It famously failed badly in a large early series of Charnley’s patients which in the current climate would have ended with a visit to the GMC and we would never have enjoyed the amazingness of total hip replacement. Possibly.

But I digress. Remarkably, even as early as 1969, Charnley had intuited that it was the microscopic plastic wear particles that were creating a biological reaction and implant loosening, and it was therefore his mission to reduce the overall volume of wear as much as possible. He ended up with the view that a head diameter half of the outer diameter of the socket was the right balance – see his relatively simple calculations. If the average socket is around 52mm, that makes the Exeter cult about right with 26mm. Which is now virtually abandoned too. As the great man admitted however “little is lost if the diameter lies between 21 and 31mm” 

The old myth that 22mm was chosen for manufacturing reasons is not borne out. It was purely to do with reducing volumetric wear, and Charnley reckoned that going below 22mm meant too high a risk of dislocation, and of ‘boring’ into the socket. The truth is, 22mm worked brilliantly.

The current vogue for large heads of 36 and 40mm is genuinely worrying. There could still be lubrication concerns and idiosyncratic wear problems, however low friction the coupling theoretically is with the latest hard bearing materials.

Finally, all the best orthopods come from the North West of England.

Joel Matta on being excellent

Many years ago the great Gus Sarmiento (read his excellent memoir) told me how, when he was running the Los Angeles orthopaedic residency programme, he first noticed Joel Matta. He said that whenever they had a postgraduate educational event, Matta who was apparently a fairly self effacing young surgeon, was always the guy who asked the most penetrating and apposite questions, not the usual 'in my experience' guff that you get, which is grandstanding disguised as a question. Sarmiento said that it was most unusual in a resident to have this quality consistently - Matta went on to study with Letournel in Paris and a star of pelvic and acetabular surgery was born.

There are many many pelvic fracture surgeons about now, and much of Matta's more recent published work has been about pelvic osteotomy and the anterior approach to hip replacement. If you've heard him speak then you'll know how good he is.

This is a superb piece on 'how to be good'. It may not turn you into another Joel Matta, but it's great. And yes, speed is not an end in itself, but it's not a bad thing either