Effects on Patient Satisfaction and Gait After Loss of Peroneus Longus Function
Conditions: Patient Satisfaction, Gait, Rigid
Sponsor: Anna Sprinchorn

Cover page
Study protocol and statistical analysis plan
2015/428
Effects on Patient Satisfaction and Gait After Loss of Peroneus Longus Function 
A. Sprinchorn, G. Elmgren Frykberg, J. Karlsson,  K. Michaëlsson
1  st   of May 2016

Study plan
Effects on patient satisfaction and gait after loss of peroneus longus function 
A. Sprinchorn, G. Elmgren Frykberg, J. Karlsson,  K. Michaëlsson
This study is one out of four studies that will make up my doctoral thesis. The study has been 
conducted for a bit over two years and is now in its final year. The data collected needs to be 
analysed and time and money set aside for this.
Hypothesis: The gait is minimally impaired by the loss of the peroneus longus function 
BACKGROUND
The peroneus longus muscle is a strong evertor and plantar flexor of the foot. It also plantar flexes 
the first ray and stabilizes the transverse arch (Perry 1992). It is most active during the stance phase 
of the human gait (Hunt et al. 2001). Transfer of the peroneus longus tendon to the peroneus brevis 
has been suggested as a component of the cavus foot reconstruction (Ortiz and Wagner 2014) and in
the case of a damaged peroneus brevis tendon (Redfern and Mayerson 2004). One might 
hypothesise a severe effect on the gait resulting from the loss of this important stabilizer of the foot,
but patients seem to recover well after this tendon transfer (Redfern and Mayerson 2004, Molloy 
and Tisdel 2003). The peroneus longus has been used as an augmentation for anterior crucial 
ligament reconstruction, and in a 5-9 year follow up, all patients have returned to sport with no 
weakness of their ankle (Kerimoglu 2008). There are no prospective studies of the effect on gait of 
a peroneus longus to brevis transfer. 
It has been shown that certain parameters in plantar loading vary significantly between the normal 
foot and the cavo-varus foot: peak pressure, pressure time integral, maximum force, force time 
integral and area (Hillstrom et al. 2013). In the same study there was no significant difference in the
gait pattern between foot types in subjects with healthy feet. In a dynamic study, pressure time 
integrals have been shown to be higher in patients with foot pain than in patients without pain, and 
higher in patients with cavo-varus feet than in normal feet (Burns et al. 2005).
Some studies using dynamic pedobarography have shown a rather poor correlation between the 
distribution of pressure and patient satisfaction (Metaxiotis et al. 2000). There is also indication that
the correction achieved radiographically is not well correlated with the distribution of pressure 
(Chan et al. 2007). 
Aim
In this prospective study we examine foot function (force and pressure) and gait variables of 
patients who have undergone a peroneus longus to brevis transfer, or who have had their peroneus 
longus tendon removed due to injury. We also look at patient satisfaction with a patient reported 
outcome mesure (PROM). The aim of this study is to determine the extent to which the loss of the 
peroneus longus tendon affects the gait and post-operative patient satisfaction. 
METHODS
Patient selection
The patients will be selected mainly from two groups: those undergoing cavo-varus foot 
reconstruction (calcaneal shift, Broströms ligamental reconstruction and a peroneus longus to brevis
transfer) and those having surgery for severe peroneus brevis or longus injuries and instability 
(Broströms ligamental reconstruction and peroneus longus to brevis transfer). These two groups 
have in common that the surgery includes a peroneus longus to brevis transfer. In the second group 

the surgeon will decided to transfer the peroneus longus tendon on the basis of clinical examination 
and/or ultrasound and MRI, indicating a high probability of damage to the peroneus longus tendon. 
When the surgery is planned the patient will be offered to take part in the study. Patients with 
neuro-muscular disorders will be excluded. 
Procedures and outcome measures
The patients will be examined before surgery and follow up examinations will be made at 6 months 
and one year after the surgery. Together with a clinical examination, a weight-bearing X-ray 
including the Saltzman projection (Saltzman and El-Khoury 1995) will be performed before surgery
and at six months follow-up. The Foot and Ankle Outcome Score (FAOS) will be used pre- and 
postoperatively (Roos et al. 2001) in conjunction with the self-reported health questionnaire SF-36. 
A gait analysis of the foot will be performed before and after surgery, using the GAITRite system 
(measuring pressure, force, symmetry and step length), the RsScan mat (measuring pressure) and 
the MoLab system (measuring 3D information about the gait with sensors on abdomen, pelvis, 
thigh, lower leg and foot). The gait analysis will be compared to a standardized normal rectus foot. 
The radiographs in this study will be taken primarily to ensure that all patients have a similar 
skeletal reconstruction.
Power
Sample size:
There are no previous studies of the gait after peroneus longus transfer. We have therefore assumed 
that the foot before surgery has varus hindfoot and after suregery a more neutral hindfoot. In a 
recent study pressure and force of 54 normal feet and 24 varus feet has been measured (Hillstrom et 
al. 2013). In this study there is a significant difference between peak pressure and force in the 
hallux between the two types of feet. The normal rectus foot had a mean peak pressure of 26.39 
N/cm2 (17.31 SD) and the varus foot had mean pressure 29.05 N/cm2 (13.68 SD) with a difference 
of 9.27 N/cm2 (p=0.01). The recuts foot had a mean force in the hallux of 110.1 N (40.91 SD) and 
varus feet had 83.93 N (34.68 SD). The difference between the feet is 10.39 N (p=0.006).
Assuming a standard deviation of 15 for the maximum pressure (N/cm2) and using a paired t-test 
with alpha of 0.05, we need to include 30 patients to have 80% power to detect a paired difference 
of 8 N/cm2.
At the orthopaedic department in Uppsala seven peroneus longus to brevis transfers were performed
during 2013, and in the same year two patients were diagnosed with a primary peroneus longus 
rupture. The study is planned to start in 2016 and to take three years in order to give a statistically 
acceptable sample size.
Data processing
Statistical analysis
Paired differences before and after treatment will be analyzed using a T-test.

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