Literature Talk

Shoe-stiffening inserts for first metatarsophalangeal joint osteoarthritis: a randomised trial (2021, Osteoarthritis and Cartilage)

S.E. Munteanu y z, K.B. Landorf y z, J.A. McClelland z x, E. Roddy k , F.M. Cicuttini , A. Shiell yy, M. Auhl y z, J.J. Allan y z, A.K. Buldt y z, H.B. Menz yzk

This paper was quite a joy to read and an important one. In my short career as a podiatrist now, one of the many issues that I see from patients that come in are due to inadequate functions of the 1st metatarsal phalangeal joint. So it was quite a blessing to chance upon this RCT about conservative insole treatment for 1st metatarsal joint osteoarthritis. It was also nice to see a collaboration between La Trobe and certain institutions in the UK which was refreshing to see.

Theory Behind

As we toe-off, the 1st MTPJ has to dorsiflex to get the joint on the ground, activate the windlass mechanism and use it as a lever to propel the foot forward. However, that is a problem for patients with 1st MTPJ OA, where the dorsiflexion here already causes the compression in a very much reduced joint space between the 1st shaft and the phalanx. Especially with the force required for forward motion, that could cause subsequent discomfort. So the idea here, through the use of a stiff carbon plated inserts, was to reduce the angle needed for the 1st MTPJ to dorsiflex while still allowing sagittal plane motion.

Using the CONSORT STATEMENT:

Honestly, from the initial glance, I could not see any portion that really strayed away from the statement. It is a well done paper and it was a joy to read and learn from.

Good points:

1. A strict study methodology and criteria

• A great blinding protocol, thorough inclusion/exclusion criteria, randomization through minimization stratification, well differentiated control and sham orthosis, sample size calculation, defined primary and secondary outcome variables, mentioning of sub-analysis outcomes and diagrams provided (Always a bonus!)

2. Good collection of baseline characteristics with corresponding use of randomization to reduce confounding effects. Use of a mixture of qualitative and quantitative data.

3. Strong follow-up and protocol in RCT

4. Outcomes used multiple validated questionnaires

But of course, there were some points that I picked up that raised some questions in me:

1. I’m not really sure why they decided to use risk ratios to describe dichotomous values instead of using the Mann- Whitney U. Maybe because the distribution of results wasn’t in the same distribution for the 2 randomized groups but I thought it might have been a better fit in comparing the median scores of the questionnaire used for outcomes
2. The outcomes were a little clouded and I could feel that there might be some researcher subconscious bias in here. The original primary outcomes weren’t significant but there were other outcomes mentioned around this which sort of did not make this as stark as it should be.
3. The use of rehabilitation in the study. There was not an explanation on why this was included in both the intervention and control group and what the intention was.

Interesting points that could have added more robust

1. Static measurements that could have added to additional data. However, there was already a robust look into clinical features
2. It would have been nice to see dorsiflexion angles and other kinematics in gait of all participants. So that there was a some dynamic data before the start of the trial
3. Some other musculoskeletal data would have also been beneficial, such as calf tightness using the lunge test or measuring forefoot supinatus in prone.

Results

The research reported

in individuals with first MTP joint OA, shoe stiffening inserts are more effective than sham inserts at reducing joint pain, and are cost-effective from a health service perspective.

Although that is true, it has some caveats:

1. There is a statistical significance on the FHSQ pain domain score of 6.66 points in 12 weeks. However, it is not in the range of a clinically worthwhile change of score which is 11 points. Moreover, the range of clinical significance is pretty large, so it also tells us that although on average there could be a positive difference of 6.66 but some patients might be a 1 or a 2 or even a 11 or 12 (However, the range is still largely below the clinical significant change in score)
2. There was then a reported mean difference of 11 points after the 4 weeks follow up, but the research does not say whether it is statistically significant.
3. There was a statistically significant global significance score but I’m not sure what we can really learn from that.

So essentially, there is evidence in saying that using shoe stiffening inserts is better than using sham inserts but it isn’t enough to label it as a gold standard. More of, for consideration. They did explain this by stating a possible explanation for this which was due to the decreased time that the subjects used the insole which was 177 hours to 155 hours in 4 weeks. This would hence have translated to 5.5 hours a day.

My Thoughts

Essentially, this RCT does not give the green light in using a shoe-stiffening insert for shoes for patients with 1st MTPJ OA change. Although the authors had tried to come up with a possible explanation for why they see some positives in 4 weeks and not in 12 weeks. However, personally I think I would expect patients to wear insoles for 5.5 hours a day so it does seem that the results uncovered does it really support using shoe-stiffening inserts strongly. Which is a shame, because it would be really beneficial to have some good evidence to back this particular treatment option.

However, with that being said, it is a particular brand and design of shoe-stiffening insert that was being investigated. Also, the use of such a design could be beneficial for a particular patient group. It would be interesting to have before and after kinematic data for the subjects that have seen benefits from the pain score questionnaire and come up with explanations why this was observed. Moreover, although the authors do not think that rocker bottom footwear is the convenient option, this can be circumvented by using more ubiquitous models such as the Endorphin Shift 2, New balance Vongo V5 or other shoe models that have a stiff midsole base and well designed toe-spring angle and location. Because, all we want is to encourage the forefoot rocker while also incorporating a stiff platform. More research can be done in this aspect to use such shoes and also, open possibilities in using stiff-soled inserts in such sports shoes with specific footwear designs.

There is one thing I am still perplexed about, which was the use of rehabilitation. I am a big supporter of using rehabilitation but this might have influenced the results in trying to discern the differences gained from using shoe inserts. Because if both groups were improving with rehabilitation, it would be hard to get the difference between the use of the insert. Although, this might also tell us that the use of the insert pales in comparison when rehabilitation techniques are used.

Conclusion

A good well done RCT and a joy to read. Something to learn from in terms of methodology and planning. Results were a little disappointing and I could tell that the authors were as well too which might have led to the blurring of the conclusion. I look forward to more work from this team! In regards to shoe-stiffening inserts for 1st MTPJ OA, a possible treatment option but something for consideration rather than iron clad.