One of the most common conditions of the first metatarsophalangeal joint (MPJ) is a condition known as hallux limitus. This is defined as a less than normal range of motion of the joint. Normal range of motion is generally considered to be upwards of 65 degrees of dorsiflexion, with some references stating numbers even higher than that. Symptoms of hallux limitus may include achy, throbbing, or dull pain in the first metatarsophalangeal joint, exacerbated by activity. It may also cause compensatory changes in the other joints of the foot, which can lead to the development of pain or arthritis in adjacent joints. A palpable bump may be present on the top of the foot at the joint level, sometimes referred to as a dorsal bunion. When the range of motion is measured at less than 10 degrees of dorsiflexion, the condition may be called hallux rigidus.
Over the years, many investigators have postulated the causes of hallux limitus. Excessive length of the first metatarsal has been considered to be a causative factor in the past, which would theoretically decrease the amount of joint space at the first MPJ, thus limiting the motion at the joint. However, researchers have disproven this as a causative factor, and it may simply be an incidental finding.
Another biomechanical etiology of hallux limitus that has been cited in the literature is the presence of a hypermobile first ray and metatarsus primus elevatus. Hypermobility of the first ray means that the first ray, which consists of the hallux (big toe), the first metatarsal and the first cuneiform, is moving during the midstance and propulsive phases of the gait cycle. This erratic movement creates instability, which leads to jamming at the first MPJ, thus decreasing the range of motion available at the joint. Metatarsus primus elevatus is a related finding, which refers to a relative elevation of the first metatarsal on the rest of the foot, which would also decrease the amount of motion available.
Other causes of hallux limitus/rigidus that have come into question over the years include osteoarthritis, direct trauma to the joint, biomechanical malalignment such as hallux valgus, and various forms of inflammatory arthritis such as rheumatoid arthritis. Regardless of the cause of hallux limitus, however, the progression of the condition is rather predictable.
Typically the condition begins with a functional decrease in range of motion, characterized by a joint that has a decreased range of motion when weight-bearing. The progresses to a structural deformity with decreased range of motion in non-weight bearing situations, and the development of cartilage damage to the joint and eventually significant pain and disability. A number of authors have attempted to categorize this progression with classification systems, which take into account both the clinical picture and the radiographic analysis of the joint.
Perhaps the most widely used classification system used for describing hallux limitus is the Regnauld classification described in 1986. This classification system involves grades I-III, and helps to communicate the destruction and limitation involved. Grade I describes a first MPJ that shows a mild limitation of dorsiflexion with a mild dorsal bump, and early evidence of osteoarthritis apparent on x-ray. In grade II hallux limitus, there is evidence of more advanced arthritis development, as well as involvement of the sesamoids apparent on x-ray. There is a greater restriction in motion, and further narrowing of the joint space. Grade III describes severe limitation of motion, extensive development of osteoarthritis include significant osteophyte formation, and possibly loose bodies within the joint known as joint mice.
Conservative treatment should always be attempted before surgical intervention for hallux limitus. Only when conservative therapy has failed does surgery become an option. Conservative therapy may include the use of non-steroidal anti-inflammatory drugs (NSAID’s) in either oral or topical forms. Some doctors will use cortisone injections as well, while others prefer to avoid the use of injectable steroids due to side effects such as atrophy of skin and soft tissues and damage to the surrounding tissues. Orthotics are typically used as well, with a modification known as the Morton’s extension, which serves to protect and accommodate the first MPJ.
Once conservative treatment has failed, surgery may be an option explored by some patients along with the treating physician. A popular option for many foot and ankle surgeons is the cheilectomy. A cheilectomy is the removal of any osteophytes from the joint. Osteophytes develop as a part of cortical hypertrophy, which results from increased pressure through the bone from jamming of the joint. The cheilectomy serves to remove these redundant pieces of bone, which typically block the hallux from moving normally over the first metatarsal head. A cheilectomy will typically double the range of motion of the joint, and serves to alleviate pain as well.
A number of modifications exist for the cheilectomy, including how much to take off of the bone, or to peroform an osteotomy (bone cut) in the first metatarsal to create a larger joint space. Some surgeons will perform a cheilectomy at both ends of the joint, removing osteophytes from the proximal phalanx of the hallux if necessary. With or without these modifications, the cheilectomy has had good results reported for early stages of hallux limitus.
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