Prospective investigation of the relationship between dorsal tilt, carpal malalignment and capitate shift in distal radial fractures

Listen to Mr Andrew Duckworth interview Dr Joe Dias and Dr Nick Johnson about their paper 'Prospective investigation of the relationship between dorsal tilt, carpal malalignment and capitate shift in distal radial fractures', published in the January 2020 issue of The Bone and Joint Journal.

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[00:00:00] Welcome everyone to this month's BJJ podcast. I am Andrew Duckworth and a warm welcome to our first podcast of 2020 from your team here at The Bone & Joint Journal. As always, we would like to thank our readers and listeners for the comments and support we have received so far as well as to our many authors and guest interviewers who have taken part. 

Over the upcoming year we hope to build on the range of topics we covered last year with our continuing aim to improve the accessibility and visibility of the studies we publish at The Journal, for both you as our listeners and readers, as well as for our many authors.

For this months study, as you know, over the next 15 to 20 minutes or so we will cover a range of aspects for the chosen work, emphasizing the important points of how the study has been designed, as well as the key findings from the data and how these potentially fit into each of your day-to-day clinical practices.

We also hope to give you a behind-the-scenes insight, should we say, into how the authors have developed the study and give them an opportunity to put forward the key findings of their work. 

So today I have the pleasure of being joined by Mr. Nick Johnson and Professor Joe Dias from the academic team of musculoskeletal surgery in Leicester to [00:01:00] discuss their study, entitled Prospective investigation of the relationship between dorsal tilt, carpal malalignment, and capitate shift in distal radial fractures, which were published in the January edition of The BJJ.

Welcome both and a big thank you to both of you for taking the time to join us today. 

Thank you. Thanks. 

So if we move straight onto the paper as you state, carpal malalignment, after a distal radial fracture occurs due to loss of volatility with the relationship between the radiological parameters, following a fracture and functional outcomes, still very unclear in the literature.

So the aim of your study was to investigate the magnitude of dorsal tilt that leads to carpal malalignment, whether reduction of that dorsal tilt corrects the malalignment and which measure of malalignment is the most useful. So Prof, if I could start with you, can you give our listeners a brief introduction to the paper and maybe some information on the large international Delfi study you discussed that looked at the important radiological parameters for distal radius fractures.

Andrew, thank you very much for inviting us to present on this paper. [00:02:00] And it's good to be the first of this decade. Distal radial fractures are the commonest fractures that we see in fracture  clinics, where the treatment is done in outpatients or in as an inpatient. Across the hospitals in England, there is a nine-fold variation in surgery or treatments offered to patients with distal radius fractures. This suggests that fracture displacement threshold at which we offer treatment in the UK reflects clinical preferences rather than an absolute agreed threshold. 

In January of last year, we published the international Delfi consensus study, which captured 614 years of experience of 43 senior [00:03:00] clinicians, both within the UK and internationally. Trying to investigate whether there was a consensus displacement threshold at which we would offer intervention. This Delphi consensus established that three millimeters of shortening or a dorsal tilt of 10 degrees, is the point at which most offered treatment. But three out of four of our experts also pointed out that although we were focusing in the Delphi about the thresholds of displacement, that coupled malalignment may be an important, additional factor, which they take into consideration.

 Many colleagues and Nick will elaborate on this, but many colleagues over the years have observed the association, including, Margaret McQueen from Edinburgh and, and the team there. Carpal [00:04:00] malalignment and outcome following a distal radius fracture. 

However, there's very little information of  carpal malalignment per se, because we are focusing on how the distal radius looks rather than how the carpus overall sets after a distal radius fracture. And this is what led us to investigate more on carpal malalignment.

That's great. Well, thank you very much. That's a very interesting summary of the Delphi study that was performed. So if I move to you Nick, so as we've already alluded to, what do we really already know about carpal malalignment and outcome for our patients? 

Well, actually carpal malalignment was initially noted just over a hundred years ago, in a paper from 1919 by Jean Mouchet that it caused wrist pain and instability. Following that there is there's little else in the literature about it. Apart from there's a few [00:05:00] papers in the eighties, actually one from Leicester and Prof Dias here, that reported that carpal malalignment was related to dorsal tilt after a distal radius fracture. And there was a small series from Tolesnik and Watson when they found that dorsal displacement of the longitudinal axis of the capitate in relation to the access of the radius led to pain and instability.

Well, the interesting thing was they did corrective osteotomies for this and they found that the symptoms improved. It was only a small series about 13 patients, but nevertheless, they had noted this. And as we've just mentioned, there was a Margaret Mcqueen RCT looking at four different treatment methods for distal radius fracture. And in that they found that carpal malalignment was a major predictor of function following the distal radius fracture. And in our literature review for this paper, we actually only found seven papers, which had investigated the importance of carpal [00:06:00] malalignment. So the knowledge base about this is varse.

It's interesting that isn't it, because it's one of these things that you would think there'd be more out there, but there really isn't is there? No, I agree. So Prof, I suppose with that in mind, what was the aim and hypothesis of your study and how did you hope to sort of address these limitations of the current literature with your work. 

The previous papers as Nick has summarized had observed or suggested an association between carpal malalignment and dorsal tilt. And had suggested this as an explanation for persistent pain or weakness, and hence gave that as an indication for a corrective osteotomy. However, we did not know the strength of the association. We do not know how best to evaluate it and whether the alignment or the change in alignment was restored after the tilt was corrected when we [00:07:00] reduce the fracture.

We also don't know what the normal ranges of capitate shift were either without a fracture or within an acceptably displaced fracture. That was what led us to raise these set of questions. And pick up on one of the strands that came out of the Delphi study. 

That's great. That's a great way to sort of summarize the aim of the study. So if we sort of move on to how it was sort of performed and how it's put together, it was obviously a prospective study. It had 250 consecutive patients who had 252 fractures. They were 16 years and they presented with a distal radius fracture to your service over roughly a four month period.

So Prof just for our listeners, can you give a brief overview of how the patients were identified and the inclusion, exclusion criteria, more importantly for the study? That is quite simple, Andrew. This was an observational study. So we set out to define a cohort of adult patients. As you [00:08:00] said, we had 250, participants with a distal radius fracture who presented to our hospital consecutively and these 250 participants had 252 fractures.

Most were dorsally displaced. It wasn't exclusive some of them were button fractures or Smith's factors because we wanted a range of displacements on which to check carpal malalignment. We did not exclude patients as this was an observational study and it is based on radiographs taken for routine care so therefore there were no exclusion criteria. So the whole set was consecutive. 

Excellent. Yeah. Yeah, absolutely. And in terms of, I suppose, moving on to, which is more, the crux that the detail of the study is. With regards to the radiographic measurements, what and how were collected. And  how was the former, I suppose quality control, performed to ensure the accuracy of that. Obviously that's such a key part of the [00:09:00] study.

Firstly we got the 576 sets of posterior, anterior and lateral radiographs of the injured wrist, taken before and after treatment. And we exported these into open access software called Veserex, which is commonly used and is easily available, but it has got a great set of measurement tools. So it's used  for instance in radiology research, by our radiology teams. For this particular study, we assessed four attributes. The first is we looked at fracture factors, for example, intraarticular extension comminution variance and aspects of the, not the primary focus of our assessment, but could be core factors that changed our observations.

For [00:10:00] example, the position of the wrist wasn't measured. So we knew whether the wrist x-ray, the lateral x-ray was taken in extension of flexion, which would alter some of our measurements. The second thing we measured was the tilt of the distal radius. So we did all the usual measurements for fracture assessment itself. The principle one being dorsal tilt.

The third set was to assess carpal malalignment, which we assessed on lateral radiographs by measuring the tilt of the lunate on the radius in degrees or the capitate on the lunette in degrees,  which are well described in the literature. And we just followed their methods by defining the access of the radius, the access of each of these bones and then measuring the angle between them.

The capitate shift, we then [00:11:00] measured and we did this and we described it specifically because it has not been clearly described before. What we did was we firstly identified the centre of the head of the capitate by putting a circle on the capitate head and therefore marking out the center.

We defined the access of the radius by using an access tube within the cervix which is a reproducible tool to find out the axis of a bone. And then the perpendicular distance of the center of the capitate from the axis gave us the shift of the capitate from the axis of the radius. And this was negative if it was dorsal to the access.

We set the fourth element that we assessed was the signs of other explanations for carpal malalignment, principally ligament injury. And we assess this by [00:12:00] measuring gaps between the scaphoid and lunate or between the lunate and *inaudible* and noting breaks and gilula lines and those were all recorded. 

As far as quality control goes, all these x-rays were measured by Rachel checked by Rachel and finalized by Rachel. So that was our first author who did all the hard graft of research, the police work type of stuff. Yeah. Then all the measurements, were then checked by me. Each and every measurement was checked by me. The data was completed, but there were tiny gaps. The signs were checked - the negative signs, the positive signs were checked. 

We looked at the outliers and confirmed or corrected the outliers. And then we came to the data lock. So the data was then locked [00:13:00] for analysis and no data was then changed after it was locked. And no analysis was conducted before the data was locked. 

The team had agreed analysis plan before we completed collection of the data so I think that should give our listeners an outline on how we collected and checked on our data. 

Absolutely, Prof that was really interesting, actually a really nice overview of the, obviously quite a complex analysis was performed, but very, very robust clearly. So Nick, if I come to you next, obviously the analysis performed in the study in terms of the statistical analysis, are very nicely laid out, but for our listeners, could you give us a simple, concise overview of what was actually done? 

Yeah. So, I mean, initially we did some scatter plots, which showed a clear linear relationship between the different measures of carpal alignment and dorsal tilt. So we chose to use the near regression to [00:14:00] assess the relationship. And for each measurement of carpal alignment, we created individual linear regression models, to assess the relationship with dorsal tilt. And we did that at three timepoints. So that was the initial radiograph. So that was the first xray after injury basically. We did it if they'd had a manipulation, we did it again following reduction and also the last available radiograph. And then we also did further regression models where we added in different variables, including age, gender, and risk position to see how these affected the results. 

Separately as you've heard, we also wanted to find out what was the actual normal value of capitate shift cause no one knows that. It would be unethical to take radiographs of 50 normal wrists so we weren't able to do that, but we had a series of patients who'd had a wrist x-ray [00:15:00] for a possible injury, but were reported as completely normal. So we used a random sample of 50 of these patients and measured the capitate shift on those as you've heard, to give us a normal sample. 

And then we also wanted to know what was capitate shift likely to be within a population of patients who had a distal radius fracture that had  been determined to be within an acceptable position. And we defined that as a dorsal tilt of naught to 11 degrees. 

Okay. Yep. 

And this was then used to determine the cook point. So we were looking at the capitate shift in that group, and then to find a cook point of when dorsal tilt would lead to an abnormal capitate shift in these patients with a wrist fracture.

That's great. 

We used rock curves, sorry to analyse that. 

No, absolutely. [00:16:00] That's a really good summary because honestly there's a lot of analyses there, but I think that summarizes them really nicely and obviously moves onto the results of the study quite well. So just to reiterate for our listeners, obviously there's 252 fractures, as we've already said, the mean age was 58 years and just over 70% were female, which is very in keeping with the normal  epidemiological data for these injuries.

As you've already said, Prof three quarters were displaced fracture. And just over a quarter were intra-articular and in terms of management, almost 80% were managed nonoperatively. And also, in terms of the quality of the gradient, which you graded the vast majority were good, with about 92% with a small spattering of fair and only two cases, they were poor, but all were included. So Prof, to summarize, what do you feel that the key findings of your study in terms of the results were in relation to the primary analysis performed to address your aims? 

Yeah. The two hands, the right and left hands were equally represented as well. 

Of course. Yeah. 

[00:17:00] And the first important thing was that we were unable to identify significant ligament injury, which could explain carpal malalignment. So then, having excluded that as a cause of carpal malalignment our key observations were that the capitate shifts dorsally as the distal radius tilts after the fracture. And that this shift is reversed by reducing the fracture. 

The mean capitate shift in our population was three millimeters dorsal to the access of the distal radius. Although we measured radio donated and capital donated in addition to the capitate shift to assess carpal malalignment, we found a weaker association of the angle measurements with the tilt than we found with capitate shift. We found that the mean tilt of the lunate in our population was 11 degrees [00:18:00] tilting back and the capitate seems to compensate for this by moving forward seven degrees.

 So this raised the question of what capitate shift we may accept and we adjust this as Nick has pointed out by defining a probable normal range of capita shift in 50 wrists, which had no evidence of bone or ligament injury. And we found that the normal capitate shift was two millimetres in front of the access of the radius and the range was from two millimetres behind the access to seven millimetres in the front. And the mean was four millimetres in front of the axis. So the centre of the capitate seems to line up with the palmar cortex of the distal radius, which is an easy visual clue without in fact doing measurements. 

Yeah. 

It is usual in clinical practice to be unconcerned of [00:19:00] the dorsal tilt of the distal radius is at least zero. And we start getting more and more concerned when it gets back. So we looked at the capitate shift in the population, random, a separate population of distal radius fractures, which were zero or palmar tilted and therefore the normal acceptable range. And for these the mean location of the capitate centre was two millimetres in front of the access of the radius and the dorsal limit, the 95% confidence limit was six millimetres behind the act. And that is the one that we used as a cut point. 

As a cut-point. Yeah, absolutely. And Nick with regards to the regression analysis and the ROC analysis, what did you find for those? 

Well, the regression analysis showed that all measures of carpal alignment were associated with dorsal tilt up to each timepoint that we [00:20:00] measured them. It was very clear that capitate shift had the strongest relationship with dorsal tilt. So on the initial x-rays the R-squared value for capitate shift and regression calculation was 0.8 compared to 0.27 for the capitate lunate angle and 0.3 for the radial lunate angle. And it was similar values throughout. So on the final x-ray the capitate shift was 0.65. Whereas capitate lunate was 0.09 radial lunate 0.18 and as I'm sure you've seen on the figures, this can be clearly seen where the spread around the regression line is quite tight for capitate shift. And then in the additional regression where we added in the other variables capitate shift was the only parameter not affected by age or risk position.

Yeah. 

And our ROC analysis showed that the cut-point of dorsal tilt to [00:21:00] maintain the capitate shift within the 99th percentile following a distal radius fracture was nine degrees of dorsal tilt. And this is interesting because it corresponds with what our Delphi palmar said that, that is the amount that most people would accept nine degrees of dorsal tilt.

Absolutely. It's very, it's, remarkable how close that is. Isn't it really? And, I just said those R-squared values are quite stark in terms of, in relation to the capitate shift. Very interesting finding, I think that. So if we move on to the implications of the work, I mean, I think the strengths are without question, it's a very large perspective data set. Very robust analysis performed. And I think without doubt as clearly provides us with very new and useful information regarding carpal realignment to distal radial fractures, you know, the analysis has been performed well. The review has been performed blinded to outcome and very sound overall. But what do you feel really the key findings of the work considering any potential limitations of the data? 

[00:22:00] I mean, I would say the main thing we've done is we've confirmed that previous impression that dorsal tilt is related to carpal malalignment. It's been hinted at- people have suggested it before, but this clearly demonstrates that. We've also shown that if you correct the tilt by reducing the fracture well then you will improve the alignment.

 In terms of the measures of carpal malalignment we've shown that captive shift is the best measure. It's got the strongest association at all timepoints, and it's not related to the position of the wrist or the other variable such as gender or age.

I think the paper is also useful because we've defined how to measure capitate shift. And as you've heard, it is quite a simple method. It's easy to do visually and it will aid people clinically. 

The other parts of the study, we have attempted to establish the normal values of the capitate shift on the amount of tilt, which can be accepted to keep it [00:23:00] within acceptable parameters. I suppose the main limitation is we don't have a true normal sample but as we've said, ethically, that's very difficult to do at present. 

Yeah, I would agree with all of that, Nick, I think, like you say, it's impossible to get that data otherwise, but I think it's been very nicely laid out and like you said, a very relatively simple method to use.

And in terms of the findings of the study, though, how do you feel they fit into the overall literature or the topic area currently? 

I think a similar answer to the previous question really. I mean, I think the main thing to me though, is that we have actually confirmed a significant relationship between carpal malalignment and dorsal tilt.

Yeah, no, I agree. I agree. And Prof, sort of probably just finishing up finally, what do you feel, I mean, I think it's a really interesting study and redefining it in some ways how, or maybe defining almost, how we measure carpal malalignment. What do you feel the implications are moving forward in terms of the measurements, but also for [00:24:00] future studies in the distal radius?

I think about focus so, the last hundred odd years has been on the alignment of the distal radius. And this study will hopefully make doctors aware that how the risk changes after the fracture of the distal radius may have an impact. And that may be where our focus should be rather than just looking at the tilting of the distal radius. And to understand that when the radius  tilts the carpal bones buckle, so a very subtle mechanism of stabilizing the wrist changes by changing the tilt of the distal  radius. So a capitate shifts dorsally and low transmission across the wrist shifts backwards. 

 We have shown how this can be easily assessed without needing to [00:25:00] do any measurements. So doctors can just look at the image and say whether the centre of the capitate lines up in front of the access of the radius or at least is aligned with the palmar cortex of the radius on a lateral view. 

The aim of reducing the fracture should be to get the capitate aligned with the radius rather than to correct the tilt of the radius. So you're now suddenly thinking differently about the distal radius. And when you assess whether it is stable or not, you are actually saying you've achieved restoration or the best situation to transmit low across the broken wrist. 

The study also establishes that the Delphi consensus of an acceptable tilt of 10 degrees dorsally would keep the capitate shift within [00:26:00] acceptable limits. So I think all those are benefits and hopefully the outcome of this will be useful to clinicians treating these common injuries.

 I'm sure it will Prof. No, I totally agree. Well, both I'm afraid that is all we have time for today. So thank you so much for taking the time to join us and congratulations on a really excellent study that is without doubt an invaluable addition to the literature in this area. Thank you very much to both of you. 

And to our listeners we do hope you've enjoyed joining us, and we encourage you to share your thoughts and comments through Twitter, Facebook, and a like. Feel free to post or tweet about anything we have discussed here today. And thanks again for joining us.