Hallux Varus

Cadaveric biomechanical studies have revealed that the anatomic restraints to hallux varus, in descending order, are the lateral capsule, the adductor hallucis, and the lateral flexor brevis tendon.

Congenital

Congenital hallux varus may be divided into primary and secondary pathologic deformities.[4] Primary hallux varus is a rare condition that is usually related to an overactive abductor hallucis. Secondary hallux varus is related to other congenital abnormalities, such as metatarsus adductus, great toe polydactyly, longitudinal epiphyseal bracket syndrome, and delta phalanx.

Primary dynamic infantile and acquired adult

Primary dynamic infantile hallux varus is caused by medial insertion of the abductor tendon. Acquired adult hallux varus is described in inflammatory arthropathies, including rheumatoid and psoriatic arthritis. The mechanism of such arthropathies combines destruction of the articular surfaces by pannus, intrinsic muscular contracture, and distention of the joint capsule with subsequent laxity of the collateral ligaments.

Traumatic

Few reports exist of traumatic hallux varus following sports injuries. In the cases that have been reported, hallux varus occurred secondary to rupture of the lateral collateral ligament and conjoined tendon.

Spontaneous idiopathic

Spontaneous idiopathic hallux varus may be noted incidentally and is usually supple (see the images below).[5] An etiologic factor is not always demonstrable.

The initial deforming force is likely overpull of the abductor tendon, which is related to medial insertion into the proximal phalanx; this may be influenced by an inflammatory process or by minor trauma. The imbalance leads to varus deformity and subsequent contracture of the medial capsule, decrease of the IM angle, and medial subluxation of the flexor and extensor mechanisms.

Shoe wear tends to correct the varus deformity rather than exacerbate it, as it does for hallux valgus. Therefore, spontaneous idiopathic hallux varus may be more common than is reported.

Iatrogenic

The classic deformity of hallux varus occurs most frequently after a surgical procedure involving aggressive lateral soft-tissue releases, typically a distal soft-tissue or McBride[6] type of bunionectomy, but it can also be produced after Silver, Chevron, Mitchell, Keller, and Lapidus[7] procedures (see the images below).[8, 9]

Classically, the deformity is characterized by the following:

• Hyperextension of the metatarsophalangeal (MTP) joint
• Flexion of the IP joint
• Medial deviation of the hallux
• Supination of the entire ray

This posture results from muscle imbalance that is brought about by the medial subluxation of the tibial sesamoid. Release or transfer of the adductor hallucis alone is not sufficient to produce dynamic hallux varus; however, when coupled with excision of the fibular sesamoid or transection of the lateral head of the flexor brevis tendon, hallux varus likely results. Other predisposing factors for hallux varus are a small IM angle and a round metatarsal head.

Flexion of the MTP joint is brought about by the flexor hallucis brevis through its pull on the sesamoid sling. If the fibular sesamoid is excised, the metatarsal may buttonhole through the defect and result in hyperextension and medial deviation of the MTP joint. Medial deviation is exacerbated when the adductor tendon is detached and nothing opposes the pull of the abductor hallucis.

Potential contributing factors include overplication of the medial capsular structures, medial displacement of the tibial sesamoid, overpull of the abductor hallucis against an incompetent lateral ligamentous complex, excessive resection of the medial eminence, and overcorrection with a postoperative dressing that holds the MTP joint in a varus position. Another cause of hallux varus is overcorrection of a proximal first metatarsal osteotomy, leading to a negative IM angle.

The incidence of iatrogenic postoperative hallux varus ranges from 0% for distal osteotomies without a lateral release to 15% for proximal osteotomies (specifically, the Lapidus procedure) with distal soft-tissue release.[10, 11] Most reports are of crescentic osteotomies, which have an overall varus rate of 10%. The incidence of idiopathic, congenital/infantile, traumatic, and otherwise acquired hallux varus, however, is unknown.

Surgery is aimed at improving the overall position of the hallux, not necessarily its motion. Preoperatively, surgeons must inform patients that further salvage procedures may be necessary and that most surgical procedures directed at correcting iatrogenic hallux varus are 60-80% effective.[12]  In one series of patients treated with extensor hallucis brevis tenodesis, the American Orthopaedic Foot and Ankle Society (AOFAS) hallux MTP-IP score improved from 61 to 85.[13]

The usual symptoms encountered with hallux varus include the following:

• Deformity
• Pain
• Decreased range of motion (ROM)
• Instability
• Clawing of the great toe
• Weakness with pushoff
• Problems with shoe wear

Clinical examination is important to assess the stiffness of the metatarsophalangeal (MTP) and interphalangeal (IP) joints. Carefully analyze the degree of extension of the first MTP joint, and determine whether weightbearing and the dynamics of ambulation accentuate the deformity. Examine the plantar surface for any callosity under the metatarsal head. Evaluate the ROM of the MTP and IP joints, and note whether there is any pain or crepitation.

Cosmetic alignment of the hallux may not require radiographic congruence of the MTP joint. The literature suggests that some degree of varus is acceptable to patients, appears to be stable, and does not require reconstruction. According to some sources, hallux varus of 8º or less has little clinical significance.[14]  Additionally, hallux varus is better tolerated by the patient if the condition does not include a cockup deformity.

However, over time, a varus deformity becomes fixed, making it difficult to wear shoes. Contracture of the IP joint, coupled with fixed extension of the MTP joint, can produce a painful dorsomedial callosity.

Order laboratory studies that are applicable to the specific patient. If infection is suspected, obtain the following indices:

• Erythrocyte sedimentation rate (ESR)
• C-reactive protein (CRP)
• White blood cell (WBC) count

If inflammatory disease is suspected, test for rheumatoid factor (RF) and antinuclear antibody (ANA). Rheumatology consultation may be warranted.

Joint aspiration may also be indicated to evaluate infectious versus rheumatologic etiologies. 

Weightbearing radiographs of both feet, including anteroposterior (see the first and second images), lateral (see the third and fourth images), and sesamoid views, help clinicians to assess the degree of varus, the intermetatarsal (IM) and interphalangeal (IP) angles, the position of the sesamoids relative to the metatarsal head, and any degenerative changes in the metatarsophalangeal (MTP) or IP joints.

The patient who has hallux varus and is symptomatic despite conservative measures for the condition, such as shoe modification, is a surgical candidate. The treatment options consist of either soft-tissue or bony reconstruction, including arthrodesis.

Relative contraindications for tendon transfer reconstruction for hallux varus include, but are not limited to, degenerative arthrosis, inflammatory arthritides, active infection, peripheral neuropathy, and vascular compromise, in addition to excessive resection of the medial eminence and fixed deformity of the metatarsophalangeal (MTP) joint.

Various authors have described numerous procedures for the treatment and correction of hallux varus.[11, 15, 16]  A sampling of these procedures, which have been used both alone and in conjunction with others, is as follows:

• Lengthening of the medial capsular structures
• Lengthening of the extensor hallucis longus (EHL)
• Relocation of the sesamoid(s)
• Skin resection of the first webspace
• Syndactyly of the great and second toes
• Total joint release
• Abductor hallucis transfer ^[17]
• Ligapro suture/technique (an elastic polyethylene terephthalate device that is not available in the United States)
• Split extensor hallucis brevis (EHB) transfer and reverse Akin procedure
• EHL transfer with interphalangeal (IP) arthrodesis
• EHB transfer
• Keller resection arthroplasty
• Implant arthroplasty
• MTP arthrodesis ^[18]

In 1971, Hawkins described transfer of the abductor hallucis tendon to the lateral aspect of the proximal phalanx with release of the medial capsule and mobilization of the medial sesamoid.[19] Patients demonstrated maintenance of alignment between 5 and 54 months. A few years later, Miller described a proximal phalangeal resection for treatment of early acquired hallux varus (ie, before the deformity became fixed and clawing was present). However, no functional outcome was published.

In 1984, Johnson and Spiegl advocated transfer of the EHL tendon to the proximal phalanx as a dynamic stabilizer, coupled with IP joint arthrodesis for flexible hallux varus without MTP arthrodesis.[20] This improved flexion of the MTP joint from –23° to +6°, and total ROM increased from 38° to 67°. The varus was corrected an average of 18°. Later, modification utilized a split EHL transfer with preservation of the IP joint in the absence of deformity at the IP joint, which resulted in less MTP motion.

Skalley and Myerson reported their experience with EHL transfer and IP arthrodesis in a retrospective study; the split EHL transfer resulted in symptomatic joint stiffness.[21]

Subsequently, Myerson and Komenda described a tenodesis of the EHB tendon in conjunction with a medial soft-tissue release for correction of a flexible hallux varus deformity.[22, 23] The tenodesis was thought to act as a static restraint, as opposed to a dynamic restraint to varus-deforming forces. The authors reported restoration of alignment to an average of 0°, minimal loss of sagittal plane motion, and no stiffness or weakness.

Tourne et al reported a case series of 14 French patients with iatrogenic hallux varus.[24] They performed MTP arthrodesis in nine patients who had stiffness and arthrosis; in five, the lateral ligament complex was reconstructed by using a Ligapro suture. Arthrolysis was performed in all patients. Outcomes were excellent in patients who were younger, had a mobile MTP joint, and had no radiographic evidence of degenerative changes. Results included an average postoperative correction of 20° of plantar flexion and 60-90° of dorsiflexion of the MTP joint.

Resection arthroplasty can decompress the joint at the same time that the tendons and capsule are balanced. Loss of strength and floppiness has been reported postoperatively but may not be bothersome in patients who are elderly or who have significant degenerative disease. Note, however, that implant arthroplasty is ill-advised in light of the soft-tissue imbalance that is present in patients who have hallux varus.

MTP arthrodesis remains a logical salvage technique for patients who have hallux varus deformity with arthrosis and bone loss. Moderate-to-severe degenerative changes should probably be addressed with arthrodesis or osteotomy.

Correction of the first intermetatarsal (IM) angle may require metatarsal osteotomy in addition to a soft-tissue balancing procedure for the MTP joint with or without MTP arthrodesis.[25, 26, 27, 28, 29]

Koboayashi et al described a case in which traumatic hallux varus associated with medial subluxation of the second MTP joint and second metatarsocuneiform (MTC) joint arthrosis was successfully treated with metatarsal hemicallotasis with medial soft-tissue release, a proximal second metatarsal shortening osteotomy, and second MTC joint arthrodesis.[30]  After 1 year and 6 months, suitable correction had been maintained, no discomfort or pain was present, and the patient was satisfied with the results. The authors suggested that this technique should be indicated only for hallux varus with a decreased distal metatarsal articular angle, an angular-type metatarsal head, and good MTP joint congruence.

Piat et al described the use of a reverse scarf-type osteotomy to treat postoperative hallux varus involving an abnormal decrease in the first-second IM (M1M2) angle.[31]  After osteotomy, the average M1M2 angle increased from 3º to 8º, and the average first MTP (M1P1) angle of varus improved from –21º to +9º. The median American Orthopaedic Foot and Ankle Society (AOFAS) score increased from 47 to 79, the visual analogue scale (VAS) score decreased from 6.7 to 2.3, joint mobility lost an average of 9º, and all patients were satisfied with the result. All operated bones healed without secondary displacement.

Surgical repair of a traumatic hallux varus using a suture-and-button fixation device has been described.[32]

Potential complications include the following[33] :

• Overcorrection (ie, hallux valgus)
• Avascular necrosis (AVN) of the metatarsal head
• Stiffness
• Progression of degenerative changes in the MTP joint
• Shortening of the medial column
• Transfer metatarsalgia
• Wound complications