Hallux limitus and hallux rigidus. Clinical examination, radiographic findings, and natural history.

Numerous clinical features of hallux limitus/rigidus have been previously reported as isolated entities based on individual case review or myopic observations. Few attempts have been made to synthesize a comprehensive natural history which correlates the inter-relationship of these findings. Frequently unrecognized or overlooked subtle clinical findings, such as shoe-wear patterns, hyperkeratoses locations, and gait disturbances, precede significant radiographic changes or painful degenerative arthritis by months to years. Recognition of these subtle clinical features will aid in establishing an early and accurate diagnosis, and provide the physician with an opportunity to institute treatment prior to the need for surgical reconstruction. Several conclusions can be made regarding the natural history of hallux rigidus. 1. Predisposing factors (pes planovalgus, uncompensated varus) lead to spastic contracture of the hallux (hallux equinus). 2. A shift in the axis of movement occurs within the first metatarsophalangeal joint, from centrally within the metatarsal head to plantarly at the level of the sesamoidophalangeal ligament. 3. Dorsal articular impingement of the proximal phalangeal base on the metatarsal head leads to either a chronic erosion of the dorsal metatarsal head (chondritis dissecans), or fracture through the subchondral bone plate (osteochondritis dissecans). 4. Progressive degenerative arthritis within the first metatarsophalangeal joint appears as joint space narrowing, dorsal osteophyte proliferation, subchondral cyst formation and sclerosis, and articular flattening. 5. Synovial effusion produces periarticular pain, resulting in chronic splinting of the hallux. 6. Auto-fusion of the metatarsophalangeal joint represents the end-stage progression of hallux rigidus. In addition to degeneration of the metatarsophalangeal joint, sesamoid degeneration further compounds joint immobility. 1. Sesamoid immobility from chronic spasm leads to traction proliferation of the sesamoid bones (hypertrophy). 2. Disuse osteopenia of the sesamoids is an indication of sesamoid-metatarsal degeneration, and parallels degenerative changes of the first metatarsophalangeal joint. 3. Proximal sesamoid retraction reflects the degree of hallux equinus. Metatarsus primus elevatus is a co-existant feature of hallux limitus and hallux rigidus. 1. Primary metatarsus primus elevatus is encountered in patients with a more proximal level of uncompensated varus, with hallux equinus occurring secondarily in an attempt to provide medial column support. 2. Secondary metatarsus primus elevatus results from the retrograde effects of hallux equinus on the first metatarsal, and occurs in patients with pes planovalgus. 3. Flexor stabilization syndrome of the hallux occurs in patients with pes planovalgus, and is analogous to a flexor stabilization hammertoe of the lesser digits. 4. Differentiation between primary and secondary metatarsus primus elevatus is made by evaluation of weight-bearing radiographs, comparing the standard lateral radiograph to a lateral radiograph using a forefoot block test, in which the digits are suspended off of the weight-bearing surface.