Hallux varus is a clinical condition characterized by medial deviation of the great toe at metatarsophalangeal (MTP) joint. This condition may present with varying degrees of severity, causes, and symptoms. Adult acquired hallux varus deformity is commonly iatrogenic, commonly resulting from surgery for hallux valgus.
A patient may have difficulty in walking and wearing shoes. Mild hallux varus can be managed with stretching exercises and splints. However, if the symptoms become significant and affect daily activities, then surgery should be considered.
Rarely, hallux varus is congenital. Flexible hallux varus may be found in newborns and reflects their intrauterine positioning. It corrects to valgus in early childhood when walking begins.
More frequently this deformity develops after a surgical procedure for hallux valgus because of overcorrection, excessive lateral release, over-resection of medial eminence, over-plication of the medial capsule, zero-degree or negative intermetatarsal angle, or immobilization of the toe in excessive varus after surgery. Other causes include trauma and certain systemic inflammatory diseases such as psoriasis and rheumatoid arthritis.
Spontaneous idiopathic hallux varus is noted incidentally, and the cause is not usually demonstrable.
Congenital hallux varus is typically due to connective tissue disorders (i.e., Marfan syndrome and Ehlers-Danlos syndrome) or is associated with Down syndrome and neuromuscular disorders (i.e., cerebral palsy).
The incidence of iatrogenic postoperative hallux varus varies from 2% to 14% after corrective surgery for hallux valgus deformity. Crescentic osteotomies have an overall varus rate of 10%. However, the incidence of idiopathic, congenital/infantile, traumatic, and otherwise acquired hallux varus is unknown.
With a chevron osteotomy, if the capital fragment is excessively displaced lateralward, a hallux varus deformity can develop. Likewise, with a proximal osteotomy, the distal segment can be translated too far laterally. For classical McBride procedure, the fibular sesamoid is excised which causes MTP joint hyperextension, interphalangeal (IP) joint flexion and medial deviation of the hallux.
With time, the deformity becomes fixed, and it is difficult for the patient to obtain comfortable footwear. The deformity usually manifests itself as the medial deviation of the great toe, supination of the phalanx and claw tow deformity.
Anatomically, cadaveric biomechanical studies reveal the restraints in descending order are the lateral capsule, the adductor hallucis, and the lateral flexor brevis tendon.
The hallux varus deformity if often asymptomatic. Some patients complain of the deformity and have difficulty in wearing shoes, instability, decreased the range of movement, and weakness with push-off. Pain indicates an underlying arthritic process. Patients may present with chronic pain, difficulty walking and standing for long, foot weakness, ingrowing toenails, limited MTP joint range of motion, swelling of the foot and occasionally redness/ulceration of the big toe. The symptoms become worse when the patients wear closed-toe shoes which crowd the toes. The most common cause of pain in hallux varus is irritation of the deformed toe due to a poorly fitting shoe
On physical examination, one can identify varus orientation of the great toe. There may be dorsal contracture of the MTP joint with or without IP joint contracture. The extensor hallucis longus may be displaced medially creating a bowstring deformity. Medial sesamoid may be medially displaced. Analyze the degree of extension of the first MTP joint and determine whether weight-bearing and the dynamics of ambulation increase the deformity. Also, a clinician should examine the plantar surface for any callosity under the metatarsal head.
Blood tests are only needed if one is expecting an infective or inflammatory process.
Weightbearing radiographs of both feet, including anteroposterior, lateral, and sesamoid, assess the degree of varus, the intermetatarsal and interphalangeal angles, absent lateral sesamoid, excessive medial eminence resection, the position of the sesamoids relative to the metatarsal head, and degenerative changes in the metatarsophalangeal or interphalangeal joints.
Non-operative treatment includes shoe stretching and modification. Shoes with wide toe boxes and padding over bony prominences should be recommended. For early postoperative varus deformities after hallux valgus correction surgery, taping or splinting the toes can be effective. If there is persistent pain or inability to wear shoes, surgery is indicated.
Aims of surgery include restoring and/or maintaining normal gait pattern and weight bearing mechanism, realigning of sesamoids, correcting of deformity in the sagittal and transverse plane, and preserving the first MTP joint range of motion, if possible.
Operative treatment depends upon whether the deformity is flexible or rigid. As a rule, the flexible deformity can be corrected with a soft tissue procedure. Lengthening of the medial capsular structures may be sufficient if the deformity is not too advanced. For advanced but flexible deformities treatment recommendations include:
In cases with rigid deformity, deformity with limited first MTP joint motion, or presence of arthritic changes in the first MTP joint, arthrodesis of first MTP joint is considered.
Surgery improves the overall position of the hallux but not necessarily its motion. Salvage procedures may be necessary and corrective iatrogenic hallux varus procedures are 60% to 80% effective.
Potential complications of hallux varus surgery include the following: