This perennial issue has come up again with the publication of another study. I have done a previous rant elsewhere on this issue: The Redundancy of Research on Custom Made vs Prefabricated Foot Orthotics. The alleged evidence to date from most studies so far is that there are no differences in outcomes between custom made and prefabricated foot orthotics, but both are better than a placebo (ie they work). Third party funders like these studies as they can use the data to question the reimbursement for custom made devices. However most experienced clinicians call ‘foul’ over these studies as when you look closely at the type of custom made device used in the study and the prescription protocol followed, it bears no relationship to what most clinicians actually do in clinical practice. So how fair are these studies if they do not follow good clinical practice?. All they really showed was that there was no difference between prefabricated foot orthotics and custom made foot orthotics of the type used in the study that bear no relationship to what actually happens in clinical practice. That does not mean that the results would or would not have been different if a different prescription protocol was followed. It means we just do not know if the results would have been different. The most recent study does not help to resolve this issue:
Clinical Efficacy and Cost-Effectiveness of Bespoke and Prefabricated Foot Orthoses for Plantar Heel Pain: A Prospective Cohort Study.
Ring K, Otter S.
Musculoskeletal Care. 2013 Jun 25
Plantar heel pain is a common reason for referral to podiatric practice, and one of the key interventions is the use of orthoses. The aim of the present study was to compare the clinical efficacy of bespoke, casted foot orthoses and prefabricated foot orthoses for plantar heel pain.
People with plantar heel pain were included if, following initial assessment, foot orthoses were indicated and participants received either bespoke, casted foot orthoses or prefabricated semi-rigid orthoses (Powerstep™). Clinical efficacy was assessed at eight weeks using the Manchester Foot Pain and Disability Questionnaire (MFPDQ).
A total of 67 patients completed the trial and at baseline there were no appreciable differences in the two groups of patients in terms of the MFPDQ score; however, at eight weeks post-treatment both had significantly reduced foot pain and disability (both p < 0.0001). There was no significant difference in effectiveness between the bespoke or prefabricated orthoses. However, prefabricated devices were 38% cheaper per patient compared with the average costs of casted devices.
For most patients with plantar heel pain, prefabricated semi-rigid insoles such as the Powerstep™ devices used in the present trial provide short-term benefit equivalent to that of bespoke, casted foot orthoses, but at considerably reduced costs.
Overall this was a generally well done study (and NB it wasn’t on runners) with a number of shortcomings. The sample size was adequate; inclusion criteria was good; and a validated outcome measure was used. There was no no-intervention control group to know if the two foot orthotics were better than a placebo, but the research question was to compare two different devices to each other and not if they were better than a placebo. Interestingly, the lack of control group appears to be a requirement of the ethics committee: “At the specific behest of the Research Ethics Committee, a true control group (i.e. receiving no treatment) was excluded from the study, as there is considerable evidence that foot orthoses are an effective treatment for heel pain and therefore it would be inappropriate to withhold such treatment.”
A number of negatives: There was no data presented on the baseline characteristics of the the two groups, so that can not be evaluated. The subjects were not randomly allocated to the groups; they were allocated on an alternating basis. They should have been randomly allocated. There was no blinding of the participants as to which group they were in. The custom made group had a cast taken of the feet and the prefabricated group did not. The study would have been strengthened if a cast was taken of the feet of those in the prefabricated group to at least give them the impression that they could be in the custom group. The authors claim that “Blinding of the researchers was not included, as this is particularly difficult, if not impossible, to achieve with different mechanical therapies such as foot orthoses“. The researcher doing the follow up assessments and administrating the outcome measure should have been blinded to which intervention was used to avoid any potential biases. That is easy to do. There is no information provided on when the foot orthotics were issued. Did the custom made group have to wait two weeks for them to be manufactured and did the prefabricated group get given them immediately or did they have to wait as long as the custom made group?
The really big issue that clinicians are going to have is the nature of the custom made devices:
for the casted orthoses, a foam casting box was used to take an impression of the foot in the sub-talar neutral position defined by Root et al. (1971), described by Guldemond et al. (2006). Dimensions of the cast were compared with the subject’s foot while held in a neutral sub-talar joint position, as recommended by Tollafield and Merriman (2004). The impression was filled with plaster of Paris and prepared as described in detail elsewhere (Philps, 1990) Comparable, medium-density (Shore A 50 durometer) EVA was heated (170 °C for 12 minutes) and vacuum formed to the cast, then shaped to fit according to an individual prescription for each subject, based on a routine musculoskeletal assessment carried out in the department.
Most clinicians do not do it that way! The researchers used a semi-weightbearing foam box for the impression (cast) rather than the more commonly used non-weightbeairng plaster cast (as was described by Root et al 1971; Root never used foam impression boxes!). Most clinicians use plastic for the orthotic shell and not a medium density EVA. Given that it was a Shore A of 50, that is pretty soft and given the mean BMI was 26.2, most clinicians would probably consider it not close to being firm enough, even though it worked (but no better than the prefabricated). Would they have got a different result if the more commonly used plastic device was used or a higher density EVA was used? We do not know, so to tarnish all custom made foot orthotics based on the type of custom made device used in this study, is not appropriate (but is going to happen anyway!).
This study suffers from what all studies that have compared custom made to prefabricated foot orthoses fall short on: a true custom made foot orthotic will have different density EVA or thickness of plastic depending on the weight of the subject (all the studies used the same density of EVA or same thickness of plastic; given that bodyweight is an issue in plantar fasciitis, then a custom made orthotic should vary to accommodate that and not be a one size fits all); a true custom made orthotic will have, for example, a first ray cut-out, if functional hallux limitus is present (none of the studies did that and not be a one size fits all); a true custom made foot orthotic will have, for example, a temporary heel raise if the calf muscles were tight (none of the studies did that and not be a one size fits all); a true custom made foot orthotic will have, for example, a grove in them if the plantar fascia is prominent (none of the studies did that and not be a one size fits all);a true custom made foot orthotic will have, for example, more medial wedging and be more rigid if supination resistance is higher (none of the studies did that and not be a one size fits all); and so on… Can you see where I am heading with this? None of the devices in the studies were ‘true’ custom prescribed devices, but were a one-size-fits-all prescription with custom molding to the foot. Who in clinical practice would accept that or do that? Who in the third party funder’s office sitting behind a computer would accept that? Will the company that manufacturers the prefabricated devices accept that? This does not mean that if all this one done that the results would or would not be different – it means we can not use studies like this to jump to conclusions based on the nature of the “custom” foot orthotics that were used in each study.
In plantar fasciitis, the short term aim of foot orthotics is to reduce the load in the plantar fascia so that it can get better. We do now have experimental data on what those design features probably should be for plantar fasciitis. The study above did not use those design features. Again, that does not mean the results would have been any different if they had. It just means that we don’t know. Personally, I have no preference for one type of device over another – I use a wide range of custom and prefabricated. It will all depend on delivering the design feature that are needed to reduce the load in the specific tissue in specific individuals. Often a modified prefabricated device is all that is needed; also you often need a custom made device to deliver them – its all going to be specific to the individual. The design features are going to be different for each individual and different for each pathology, and not a one size fits all (regardless of it being a prefabricated design or custom made). What is needed are clinical trials on plantar fasciitis that compares foot orthotics that the experiments have shown to reduce the load in the plantar fascia to foot orthotics that do not reduce the load. Who cares if it is custom made or prefabricated? The plantar fascia does not care as long as the load in its reduced. Can you now see why I did that previous rant?
As always: I go where the evidence takes me until convinced otherwise, and the evidence from this study, in the context of the shortcomings tells me that custom foot orthotics of the type that are not often used in clinical practice are just as effective in plantar fasciitis as a commercial prefabricated foot orthoses.
Kate Ring, Simon Otter (2013). Clinical Efficacy and Cost-Effectiveness of Bespoke and Prefabricated Foot Orthoses for Plantar Heel Pain: A Prospective Cohort Study Musculoskeletal Care DOI: 10.1002/msc.1053