The MOXFQ patient-reported questionnaire: Assessment of data quality, reliability and validity in relation to foot and ankle surgery

Abstract

Previously validated for hallux valgus surgery, the Manchester-Oxford Foot Questionnaire (MOXFQ) is here evaluated for use with different regions of the foot and ankle. The study recruited 671 consecutive patients (87.8% of those eligible), mean age 52.8 years, 64% female, who completed the MOXFQ and SF-36 general health survey before foot or ankle surgery. Surgeons completed the American Orthopaedic Foot & Ankle Society (AOFAS) scales and indicated that the patients’ main regions for surgery were: Hallux 210 (31.3%), Lesser toes 119 (17.7%), Mid foot 22 (3.3%), Ankle/hind foot 311 (46.3%), Multiple/whole foot 9 (1.3%). Individual MOXFQ items were assessed in terms of response rate and floor/ceiling effects, with the validity of the three MOXFQ scales (Walking/standing, Pain, and Social interaction) being assessed in terms of item-total correlations, internal and test–retest reliability, and construct validity. MOXFQ item response rates were high (all >98%). Cronbach's alphas of >0.7 confirmed internal consistency of all three scales. Test–retest ICCs were all ≥0.89. Correlations of >0.4 obtained with related SF-36 and AOFAS scales supported a priori hypotheses.

Good measurement properties are confirmed for the MOXFQ in the context of baseline assessment of patients receiving surgery for a variety of foot or ankle problems.

Introduction

A wide range of foot and ankle disorders are treated surgically constituting around one fifth of orthopaedic practice [1]. Foot and ankle surgery is associated with a high level of patient dissatisfaction which translates into considerable litigious activity [2], [3]. There is therefore an urgent need for scientific evaluation of foot and ankle surgery, which in turn requires the employment of appropriate (patient-focused) standard methods of outcomes assessment [4], [5], [6], [7], [8]. Outcome measures need to be validated in the context in which they are to be used.

There is also a need for an outcome measure that is suitable for assessing interventions to all regions of the foot and ankle. There are many reasons for this: because feet and ankles are complex weight-bearing structures with numerous interconnected moving parts, a problem in one area can generate problems elsewhere in the foot or ankle [9]; likewise, treatment to one region can potentially have an affect on another region. It is also common for people to have more than one foot and ankle problem concurrently, particularly if they have a condition (such as various types of arthritis or congenital deformities), that affects – or requires correction of – more than one structure in the foot or ankle. In the surgical context, the precise form or number of surgical procedures – and regions of the foot that they will involve – may not be known before surgery commences and reveals the full extent of the problem, while baseline measures need to be obtained prior to surgery.

Devised with input from patients representing a variety of foot problems [10], [11], the Manchester-Oxford Foot Questionnaire (MOXFQ) was first evaluated in the context of patients (95% females) undergoing surgery for hallux valgus. In this context it was shown to be acceptable, reliable, valid and responsive [10], [12]. It has since been translated into Italian, in which study the reliability and validity of the instrument was reconfirmed in the context of hallux valgus surgery [13]. It has also been applied in the context of surgery for hallux rigidus [14].¹

This paper reports results from a study to evaluate the MOXFQ in patients undergoing, at a regional surgical centre, a wide variety of operations on the foot and ankle. Here we examine MOXFQ item response rates, distribution (floor/ceiling effects) and item to total scale correlations; and for the 3 MOXFQ subscales, we examine internal consistency and test–retest reliability, convergent and divergent validity. Results are presented for all patients scheduled for foot or ankle surgery and separately (where appropriate), for patients having surgery on different regions of the foot and ankle.