PROspective Minimally Invasive Surgery of the toes
A prospective cohort study

The results of traditional open claw toe surgery, in which large incisions are
used, are reasonably satisfying, but complication rates are high. In response,
minimally invasive surgery (MIS) techniques have been developed that are aimed
to do as little damage as possible to the surrounding tissues. The results of
minimally invasive foot surgery look promising: good functional outcome and low
complication rates are reported. However, most studies that advocate minimally
invasive foot surgery techniques are small retrospective case series.
Regardless of this serious lack of knowledge, more and more patients in the
Netherlands request to be treated with this technique, and an increasing number
of orthopedic surgeons have adopted MIS claw toe surgery into their daily
practice. This is problematic - even potentially dangerous - because it is
currently unknown how the results of the MIS technique are compared to the
results of the traditional technique. The few small retrospective studies
provide no reliable evidence on the safety and efficacy of this technique.
Furthermore, there is no data that provides any insight into what the
indications for this technique should be, and for which patients the MIS
technique might not be suitable. From the surgeons* point of view, there is a
serious lack of knowledge regarding a potential learning curve and what
pitfalls should be avoided when this technique is adopted into standard care.
In summary: MIS-techniques are currently being implemented as standard
treatment without being backed by proper scientific evidence.
The PROMIS-Trial is designed to solve these very important problems and provide
the necessary evidence that we desperately need to decide if and how we should
start using this technique for the treatment of rigid claw toes. The
PROMIS-Trial consists of two parts and is aimed to answer three important
questions:
• What is the outcome and foot function after minimally invasive claw toe
surgery?
• For which patients should minimally invasive claw toe surgery be used (can we
predict what patients are likely to have a good outcome)?
• Is there a learning curve for minimally invasive claw toe surgery?

The primary objective is to assess the outcome of treatment of rigid claw toes
with the MIS technique in terms of the Foot Function Index (FFI), measured two
years postoperatively.
The secondary objective of this study is to assess the outcome of treatment of
rigid claw toes with the MIS technique in terms of AOFAS score, NRS pain score,
NRS satisfaction score and return to work/activities, measured at four weeks,
three months, one year, two years and five years postoperatively. Additionally,
the FFI will be measured after four weeks, three months, one year and five
years postoperatively. Another objective is to create a prediction model
(multiple linear regression model) for FFI outcome two years postoperatively
after MIS surgery, based on preoperative variables.

Furthermore, we assess to what extent a learning curve exists for surgeons
during the first 10 surgeries after completing the GRECMIP courses by
curve-fitting of the two years postoperative FFI scores (plotted per #
performed surgeries) in comparison to a predefined level of expertise (the FFI
scores of the experienced surgeons), and to assess individual learning curves
using CUSUM analysis and by assessing mean FFI scores per 5 subsequent
surgeries (surgery 1-5, 6-10, +11)
Furthermore, we assess treatment effect of MIS surgery (measured using PROMs).

The PROMIS-Trial is a multicenter prospective cohort study in which 100
patiënts will be prospectively enrolled who will undergo minimally invasive
claw toe surgery.
The inclusion period is estimated at 4 years. Follow-up appointments will be
after 4 weeks, 3 months, 1 year, 2 years and 5 years. Therefore, the total
duration of the study is approximately 9 years.

For patients in Part I the study group will be treated according to the
minimally invasive technique as described by De Prado et al., the control group
will be treated with traditional open surgery.
Patients in Part II will all be treated with the MIS technique as described by
De Prado et al.

Patients fill out questionnaires at every standard follow-up appointment, which
will take approximately 10 minutes. Two extra appointments (after 2 and 5
years) are planned as follow-up in this study. This is a minor burden compared
to the relevance of this study.

Although there is an absence of high-quality evidence on the efficacy and
safety of this technique, MIS aims to do as little damage as possible to avoid
complications of traditional open surgery by performing the established
treatment concepts (such as tenotomies and osteotomies) through smaller
incisions and less traumatic procedures. Especially potentially damaging
complications such as infections, DVT, nerve damage and necrosis are rare
compared to open surgery.

Compared to patients that are treated with the MIS technique outside of this
study, there is no extra risk associated with study participation, and perhaps
even a slight risk reduction. When patiënts do not participate, they'll recieve
the same treatment.
Patients in Part II are exposed to a minor risk compared to patients that are
treated with the traditional technique, due to the absence of high-quality
evidence on the efficacy and safety of this technique. However, all
participating surgeons are guaranteed to have received adequate training (all
experienced foot- and ankle surgeons in Dutch hospitals and clinics), which
certainly cannot be guaranteed outside this study, expecially in foreign
clinics that many patients currently go to for their MIS surgery.
The researchers believe that the risks of this study are negligible, and
justified.

The PROMIS-Trial is essential to study the outcome of the MIS technique because
these techniques are being implemented everywhere without being backed by
proper evidence from large trials. The value of this study is very high and
more than justifies the minor possible extra risks.