First metatarsophalangeal joint osteoarthritis

Osteoarthritis (OA) of the first metatarsophalangeal joint (1st MTPJ) occurs frequently and causes significant pain and functional impairment. However, there has been very little research particularly in large population-based cohorts. This PhD studentship proposes to investigate the whether there are different radiographic presentations of OA in the 1st MTPJ and examine how these are associated with different clinical signs and symptoms. It will determine to identify potential risk factors for developing OA in this joint, and examine the course of self-reported symptoms over time for the different presentations of 1st MTPJ OA.

BACKGROUND

Osteoarthritis (OA) is the most common form of arthritis and leading cause of disability worldwide. OA predominantly affects the hands, knees, hips and feet and is estimated to affect 10% of people aged over 60 years[3]. The 1st MTPJ of the foot is one of the most commonly affected joints, estimated to be present in 35-65% of the population aged over 65[4]. The 1st metatarsal phalangeal articulation is described as an ellipsoid joint between the rounded head of the metatarsal and the shallow cavity of the phalangeal bone base. The plantar aspect of the joint has two longitudinal grooves which are separated by a ridge and each articulates with a seasmoid bone embedded in the joint capsule, which is formed by the tendons of the hallucial muscles[5]. The joint allows sagittal plane motion, primarily of dorsiflexion which ranges from 60-90 degrees and is believed to be the required value to obtain effective ‘toe-off’ during the propulsive phase of gait [6;7].

The terms hallux limitus and hallux rigidus describe the pathological degeneration of the 1st MTPJ. Hallux limitus refers to a limited range of motion at the joint during functional use (e.g walking). Hallux rigidus is used when structural degeneration progresses to the point where there is an absence of motion and fusion at the joint[8]. OA is a major cause of degeneration at the joint and patients present with clinical symptoms that include pain, stiffness, reduced range of motion, deformity and functional impairment[9;10].

The 1st MTPJ joint is frequently affected by OA along with other weight-bearing affected joints such as the hip and knee[11]. However, this joint has received relatively little research attention. This is confirmed by a review of radiographic definitions of foot OA which shows that whilst studies of the foot tend to focus on the 1st MTPJ[11], the majority concentrate on examining the prevalence of OA with only one study examining the association with localised pain[12]. The recent publication of a validated atlas for scoring radiographic OA at the 1st MTPJ[9] has provided a basis for further investigating patterns of radiographic OA at this joint. Following this only one study has examined the prevalence of individual radiographic features of OA in the 1st MTPJ including joint space narrowing and osteophytes[12] but no research has yet been undertaken to examine if there are different patterns of the occurrence and severity of these features are whether they are associated with different signs and symptoms and how they may affect pain and functional outcomes over a period of time. There has been limited research investigating risk factors for the development of 1st MTPJ OA[13], and changes in plantar pressure as a result of 1st MTPJ OA[14]. Hindfoot valgus deformity has been found to be associated with the development of 1st MTPJ OA[13] but other potential risk factors including other foot deformities and previous joint injuries have not been investigated. Differences in plantar pressure have been seen in the forefoot in those individuals with 1st MTPJ OA and it has been hypothesized that these may lead to secondary pathological changes such as plantar callus formation and hyperextension in the hallux interphalangeal joint[8]. However, it may also be possible that changes in plantar pressure could indicate the early development of OA in this joint.

There is consensus in the literature that further studies investigating 1st MTPJ OA are required to study the aetiology and diagnosis of this condition[11-13]. Therefore the aim of this thesis is to undertake a comprehensive and systematic study in a large community-dwelling cohort of individuals to investigate the radiographic presentation of 1st MTPJ OA, determine the clinical impact of radiographic 1st MTPJ OA upon pain, deformity and gait, to identify potential localised risk factors of 1st MTPJ OA and determine whether baseline radiographic phenotypes of 1st MTPJ OA differ in the course of self-reported outcomes over a period of time.