Introduction
This condition was first described in 1887 by Davies-Colley,1 who used the term Hallux flexus in referring to the planter flexed posture of the phalanx relative to the metatarsal head. In 1888, Cotterill 2 used the term “Hallux Rigidus” to describe a degenerative disease of the first metatarsophalangeal joint with stiffness and deformity. There have been several descriptions of this condition by other authors. Functional Hallux limitus 3 describes biomechanical features of the joint, which effectively limits dorsiflexion, with no degenerative changes present.
Biomechanics of the 1st MTP Joint
In the neutral position the average surface contact area is 0.38 cm2. 4 The average joint surface area of contact decreases as the proximal phalanx dorsiflexes on the 1st metatarsal head. At full dorsiflexion it decreases to 0.04cm2.4 The contact point on the 1st metatarsal head shifts dorsally, with increasing toe dorsiflexion, but the contact point on the proximal phalanx articular cartilage remains the same. 4 This fits with the chondral erosion and degeneration that are described on the dorsal aspect of the joint in Hallux Rigidus in adolescents.5
Epidemiology
It is the second most common condition affecting the 1st MTP joint but is associated with greater pain than Hallux valgus.5 Hallux rigidus has been described in two different age groups. The adolescent form is associated with osteochondritis dessicans. 6 The cause of the adult form is elusive but is thought to be a continuum of the adolescent form by some authors.7 The mean age of occurrence is 43 years (from adolescence to the ninth decade).7
Eighty percent of the first presentations are unilateral. 8 At first presentation, the patients have an asymptomatic dorsal osteophyte and/or reduced dorsiflexion of the Hallux. A higher male involvement has been reported in those over 30 years complaining of Hallux Rigidus, but most studies have shown an overwhelming higher incidence of female involvement in those seeking surgical repair.8 A history of trauma is more common in females with 78% of unilateral HR associated with trauma. 8 The risk of bilateral disease increases with a positive family history.9 It is thought that family history may predispose to early onset9. There is no association with footwear or occupation.
Aetiology
Trauma
A single traumatic episode (intra-articular fracture, crush injury) or repetitive micro-trauma may be at the origin of osteoarthritic changes. Forced planter flexion or dorsiflexion may result in jamming and development of an acute chondral or osteo-chondral injury. 10 In the adolescent patient there is often a dorsal osteo-chondral lesion, which may only be diagnosed on MRI scan. 10
Biomechanical
A number of biomechanical causes had been identified and these include Functional Hallux Limitus, Functional hypermobility, Gastrocnemius-soleus equinus, compensated forefoot valgus. 11 Tendo-Achilles, or gastrocnemius tightness, has been reported in 25% of patients with Hallux Rigidus but there does not appear to be different from the normal population. 11
There are three variations in the shape of the metatarsal head, (the oval, the chevron and the flat). The flat type is associated with resistance of lateral pressure and increased incidence of Hallux Rigidus.12
Structural
Structural causes include: Metatarsus primus elevates (MTPE); Long first metatarsal and long proximal phalanx of Hallux. Lumbrinudi first proposed a hypermobile first metatarsal, with an excess range of dorsiflexion. In 1938, Roukis13 showed that as the first ray moves from neutral to dorsiflexion, the amount of dorsiflexion of the first MTPJ decreases by 19% with 4mm dorsiflexion, and 35% with 8mm dorsiflexion. 13 However, no serious study has demonstrated that hypermobile first ray or metatarsus primus elevatus predisposes to Hallux Rigidus compared to people with normal rays. Roukis found a slight increase of this condition in patients with Hallux Rigidus compared with other foot diagnoses, but did not include a control group.14 Although MTPE is more common in Hallux rigidus, it has not been proven that planter flexion osteotomies, correcting this condition are of any value. 14
Latrogenic
These include: post-surgical excessive elevation of the 1st M, excessive lengthening of the 1st MT, misalignment of the 1st MTPJ, excess fibrosis and seasamoid dysfunction and prolonged immobilisation.
Others causes
It is also worth mentioning, gouty arthritis, septic arthritis, muscle imbalance affecting first ray.
Pathogenesis Diagram
The cause of HR has not been determined although many predisposing factors have been cited. It may be secondary to trauma, gout, infection or other inflammatory arthropathy. Degeneration may begin dorsally with limitation of dorsiflexion and impingement as the predominant features or begin as a central crater spreading to the whole joint.
Clinical presentation
History
The commonest features are pain and stiffness. In the early period, pain is mainly felt dorsally and is provoked by dorsal impingement. It is later situated in the joint and provoked by movement at any point in the range. It may present as mainly planter pain, probably due to seasamoid-metatarsal osteoarthritis. A prominent dorsal osteophyte may cause rubbing in shoes. There is usually a bursa and skin may have abrasions causing pain. Few patients complain of stiffness and compensatory hyperextension of the IP joint, which often develops with increased stiffness of the MTPJ.16 A feeling of “locking” due to synovial impingement or osteo-chondral lesions. There may be nerve symptoms due to irritation of the digital nerve.
The patient may have functional demands, which could have a major influence on his management: A labourer needs a pain-free toe even if stiff. An athlete needs mobility and may be ready to put up with residual pain. We should look out for systemic conditions such as gout or rheumatoid arthritis.
Clinical examination
The patient usually walks with a gait avoiding toe-off, and walking mainly on the lateral aspect of the foot. There is an antalgic component with hurrying the toe-off component of the gait, due to pain on the lateral metatarsals and the lateral border of the foot. Look for any prominences, s