Sunday, August 20, 2017
Tornier BluePrint
The Aequalis shoulder replacement (Tornier) is a popular, reliable system with runs on the board. Tornier have now developed a computerised tool called BluePrint that allows the surgeon to play with CT scans in two and three dimensions to best position the glenoid component within the bone
Why?
Two main reasons: minimisation of the glenoid face ream and optimisation of bone stock volume in the glenoid vault. Both have proven (or at least generally agreed) implications on longevity/ survivorship of the implant. Given that approximately 40% of osteoarthritic glenoids show posterior wear (Walch B or C - noting that the classification has recently been refined) means that a significant proportion of patients will require some adjustment in the “angle of attack” to correct for this when placing the critical guide pin that determines how the glenoid is prepared. This is much harder to do on the table with CT scans illuminated in the background than it is with a computerised system set up to make a custom guide (custom guides for guide pins being the most prominent of the set of “patient specific instrumentation” which has become the rage in arthroplasty surgery). Ultimately shoulder replacement surgery will progress to on-table computer guidance systems (Exactech provides the only navigated system currently available) but Tornier does not (yet) provide this option.
Although I feel compelled to follow the advice of the development team that researches, reports, and advances the shoulder system I use I think there are two counterarguments against a full-hearted adoption of BluePrint in its current guise. The first is obvious: BluePrint (and all the other competing systems out there) only takes data from CT scans to create patient-specific bone models but does not take account of the surrounding soft tissue. Soft tissue tension is critical for stability and function in shoulder replacements (more so in anatomic TSR than reverse TSR). Soft tissue restraints also play a role in the exposure of the glenoid which influences how the glenoid is attacked. I’ve seen enough live surgery events from experienced surgeons to know that I’m not the only one who (occasionally) modifies their angle of attack to accommodate for this (especially in the elderly patient with osteoporotic bone). To say that shoulder replacement surgery is a balance of getting the best compromise given a number of suboptimal variables would not be far off the truth. BluePrint is a tool that optimises bony variables but does not take into account soft tissue variables.
The second problem is that BluePrint does not account for how the scapula sits in relation to the chest wall. In BluePrint the scapula and its articulation with the proximal humerus is taken in isolation for modelling purposes. How that articulation sits on the chest wall also has implications that we are only now starting to understand (eg glenoid notching in reverse TSR).
Another thing lurks in the background. The surgeon - and the orthopod in particular - prides himself on his spatial orientation, his technical ability. and the mastery of his tools. Years of practice hones what natural talent (or lack thereof) preceded it. Guided systems diminishes that role and takes away a skillset that future surgeons may never develop to full potential.
Surgeons have bodged shoulder replacements into patients with generally good results since the mid 1970’s. If there is adequate bone stock, an active deltoid, and an intact rotator cuff then we’re good to go. Even better when the patient is elderly with low physical demands. The developments in shoulder arthroplasty over the past forty years have refined our approach (surgical technique and hardware configuration) based on a growing dataset of long term outcomes. There remain problem areas such as glenoid volume and wear patterns which programs like BluePrint attempt to address.
It is fair to say that orthopaedic surgery with its plethora of ever-evolving tools and hardware has a proclivity to yield to market forces that are not necessarily in the interest of the patient (or society which ultimately bears the cost of such developments). But it’s also fair to say that using a computer to create virtual models of a patient’s anatomy/ pathology, though still unproven, gives us a better handle of the task at hand.
Another example of the endless march of the machine? Well, computers are more exacting when posed with a problem where there are known and quantifiable parameters.
No doubt computerised systems (with on-table navigation and robotic assistance as we are starting to see in knee replacement surgery) will become gold-standard practice in the not so distant future where people live longer, in better health, and with greater demands. Machine learning AI may account for - and teach us about - areas we currently have difficulty quantifying: optimal soft tissue balance, joint stability, and humeral version. The question is not whether we will see semi-autonomous (or even fully autonomous) robots in the surgical theatre but when.
End of the Anthropocene.
Computerised modelling like the Tornier’s Blueprint is a step in the right direction. But for now, the human brain, with all its foibles and fallibility, remains best placed to process the optimal (compromised) solution to accomodate all the (perceived) suboptimal variables.
Watch this space.
Sunday, July 23, 2017
Sunday, July 2, 2017
Sunday, June 18, 2017
Breathe
Him: “Would you rather your child be smart or good?”
Her: “Can’t she be a bit of both?”
Him: “No. The distinction therein is the crux of the question.”
Her: “Well, it’s a stupid question.”
I felt sick in the stomach.
Dilip had just convinced me of the need to return to India. Or rather, of the need for me to be part of the team heading back to India. And that we would do it again over the Christmas break. Maybe it was the hot chocolate. I always get a bit bloated when I drink too much milk. And I did have a bowl of cereal a little earlier. I must be lactose intolerant. It could be that. But I also hadn’t planned on going back. Not anytime soon. In any case I felt sick. Or bloaty.
India. I do not see her as part of my identity. She does not define me. Certainly not any more than anything else in my life. I prefer to see my identity in the routine of daily life. My work defines me. That’s expected for something that takes up so much of my time. And I would take offence if someone tells me that I do not do a good job. I am a cyclist and I enjoy riding my bicycle. It is my most fun regular activity. Sure, I'm not as fast as I used to be, but I stepped up to A-grade and not everyone can say that. Races are faster now. But I was - and still am - a cyclist. And I’m a runner. A slow runner who would be lucky to run 4min k’s. But I identify as a runner. And I’m a brother. A son. An uncle to two beautiful children. A friend. A person who believes in the power of reason. And a votary of the Marvel Cinematic Universe.
Not everyone has to sail an ocean to find themselves.
And not everyone needs to know the meaning of life to be happy. But if you live long enough then that question is bound to come up.
So once a year I go to India. That’s seven years now. Seven camps with Dilip in exhausting, exasperating India. Any measure of productivity would see that much activity is inefficient. And sometimes ineffective. But some good gets done. The good is very, very good.
India's a problem I don't need.
It’s just before 5AM on the Jinker Track. The stars are out. My breath fogs the air and the chill stings my arms. I rub my ears to get some blood into them. I pull my gloves on, drop the saddle, and hit the trails with lights blazing. Those that have tried it will know that night riding pares down the choice of available lines. Today I'm on point. I feel faster and more agile than I know I am. Focus. And pure joy. In a couple of hours I will be telling jokes and doing what I am paid to do. I get great satisfaction from the work and the mingling. I am part of a great team. In the meantime I have a clear run of the tracks. Solitude. I might be the luckiest guy in the world.
And yet I can be better than that.
Life can be guided by a few simple rules. Be curious. Ask questions. Have a bit of self doubt and reflection but not too much to be crippling. Breathe. Tell your own story. And never tell another person theirs.
Him: “I’m not saying that being smart or good are mutually exclusive. Rather, I’m asking which you value more.”
Her: “I value both. You cannot measure between the two.”
Him: “But if you had to?”
Her: “But I don’t.. You really have some silly ideas.”
Sunday, June 4, 2017
Sunday, May 14, 2017
Evolution
2002 On One Inbred (size 16”)
Steel, 1070mm wheelbase, 40mm BB drop, 71º HT angle
1x1, lock-on grips, clipless pedals
26” wheelset with chainring guard
Rider’s fitness & strength rating: 7/10
Height & weight: 173cm, 64kg
Riding style (timid - aggressive): timid
Natural habitat: Brisbane Forest Park, Bunyaville, Daisy Hill, Tewantin, Nerang
Was it fun to ride? Yep
2012 Santa Cruz Chameleon (medium)
Aluminium, 1074mm wheelbase, 0-20mm BB drop (eccentric BB), 68º HT angle
2x10, 120-150mm front suspension, disc brakes, lock-on grips, clipless pedals
26” wheelset
Rider’s fitness & strength rating: 5/10
Height & weight: 173cm, 66kg
Riding style (timid - aggressive): timid
Natural habitat: Brisbane Forest Park, Bunyaville, Tewantin
Was it fun to ride? Well.. it's complicated
Do you dance?
Do you dance?
If ever a bicycle chooses its rider then this (the 26” all-mountain hardtail) is it. Takes skill and confidence to shred on a bike like this. One day I’ll drop that post, screw on flat pedals, relax my grip, and harden the f*** up. #BBdropmatters
2014 Scott Scale 700SL (small)
Carbon fibre, 1074mm wheelbase, 40mm BB drop, 69º HT angle
1x11, 100mm front suspension, disc brakes, ESI grips, clipless pedals
27.5” wheelset
Rider’s fitness & strength rating: 6/10
Height & weight: 173cm, 63kg
Riding style (timid - aggressive): timid
Natural habitat: Mt Cootha, Daisy Hill
Was it fun to ride? Yep
2016 Trek Fuel EX 9.8 (17.5”)
Carbon fibre, 1137mm wheelbase, 17mm BB drop (excl suspension sag), 68º HT angle
2x11, 120mm dual suspension, disc brakes, dropper post, flat pedals, lock-on grips
27.5” wheelset
Rider’s fitness & strength rating: 6/10
Height & weight: 173cm, 63kg
Riding style (timid - aggressive): timid
Natural habitat: Brisbane Forest Park, Bunyaville, Daisy Hill, Tewantin
Was it fun to ride? Yep
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