Hallux varus is a rare foot deformity due to iatrogenic, post-traumatic, idiopathic, inflammatory, spontaneous, or congenital pathologies. In particular, the iatrogenic type is the most common cause of hallux varus. ^{1 , 2} Multiple studies reported that postsurgical hallux varus was observed in 2%–15.4% of cases. ³

Post-surgically observed hallux varus is attributed to overcorrection of the hallux valgus deformity. This includes excessive removal of the medial osteophyte and over-release of adductor halluces tendons, transmetatarsal ligament, and lateral metatarsophalangeal (MTP) joint capsule. ¹ The incidence of iatrogenic hallux varus after surgery of hallux valgus is not very low, and there is a paucity of reports associated with the treatment strategy.

Herein, we report a novel case of postsurgical hallux varus deformity. We performed revision surgery, i.e., MTP joint arthrodesis for hallucis and shortening oblique osteotomy for the lesser toes. Four years after surgery, the patient was satisfied, functionally good, and experienced no pain upon standing or walking. No postoperative callosity was detected.

A 74-year-old Japanese woman visited our clinic with complaints of left hallucis pain and concerns about medial deviation. Twenty-one years prior, the patient underwent Mann’s procedure with bunionectomy and with fibular sesamoidectomy, a surgical operation for bilateral hallux valgus. After the operation, the MTP joint surface deviated medially in a hyperextended position ( Figure 1A– C). In addition, the second and fourth toes demonstrated hammer toe deformities ( Figure 1A and C). First, an orthosis was applied; however, medial deviation and pain in her MTP joint worsened six months after the orthosis application. Hence, surgical intervention was decided on. Upon physical examination, the left MTP joint of the patient was swollen, tender, and erythematous. Extensor hallucis longus was very tense, the MTP joint was hyperextended, and the interphalangeal (IP) joint was in a flexed position, resulting in the “cock-up deformity” of hallux varus ( Figure 2A– D). Lateral instability of the MTP joint of the hallux was not detected.

The Japanese Society for Surgery of the Foot (JSSF) Rheumatoid Arthritis (RA) foot and ankle scale ⁴ is often used in Japan as a means to evaluate the function of the ankle and foot. In the present case, we evaluated it for the functional outcome because the surgery was performed in not only hallux but also lesser toes. The patient’s scale was 73 out of 100 points (pain, 30 out of 30; deformity, 17 out of 25; range of motion, 13 out of 15; gait, 10 out of 20; and activity of daily life, 3 out of 10).

Regarding the range of motion, the MTP joint was very stiff and showed extension contracture (-90° in extension and -30° in flexion), but the IP joint remained flexible (-20° in extension and 90° in flexion) ( Figure 2A– D).

Radiographs showed that the hallux valgus angle (HVA) was -28° ( Figure 3A). The intermetatarsal angle between the first and the second metatarsus (M1M2A) was 0° (normal range, 6°–9°), which meant that the first and second metatarsal bones were parallel ( Figure 3A). As the tibial sesamoid shifted medially, and the fibular sesamoid was absent, excessive medial eminence resection might have been performed. An oblique view of the foot demonstrated that the proximal phalanx subluxated dorsally ( Figure 3B).

In this case, MTP joint arthrodesis, medial capsular release, and EHL tendon lengthening were performed. For the second and fifth toes, a shortening oblique osteotomy was performed. The intraoperative macroscopic findings revealed that the medial portion or the articular surface was impacted by the severe degenerative change. The degenerative changes were also observed in the capsule ( Figure 4).

A cup and cone type reamer (Wright Medical, Tokyo, Japan) was used to preserve the length of the hallux as much as possible. The metatarsal articular surface was reamed to a cup-shaped surface, and the proximal phalanx articular surface was recreated with a cone-shape.

The hallux valgus angle was fixed at 0°, and the first proximal phalanx axis was dorsally fixed at 15° to the metatarsal bone axis. Two full-thread Acutrak ^® screws (Nihon Medical Next Co. Ltd, Tokyo, Japan) were inserted at the fixed position in a crisscross fashion. For the lesser toes, a shortening oblique osteotomy was performed ( Figure 5A and B). The postoperative radiographs showed that M1M2A was 6° and HVA was 0° ( Figure 5A).

Dorsal curved skin incisions were applied in between the 2 ^nd and the 3 ^rd metatarsals and between the 4 ^th and 5 ^th metatarsals. Wounds were deepened and extensor digitorum brevis tendons were identified and partially resected. Distal metatarsal regions were subperiosteally released and shortening oblique osteotomy were performed with 45-degrees tilted to the metatarsal longitudinal axis for the 2 ^nd through 5 ^th toes. The osteotomized thickness were 7 mm. Then, distal fragment was flipped dorsally and osteophyte in the metatarsal head was totally removed and rasped.

A Kirschner wire of 1.2 mm in diameter was inserted into the metatarsal, and proximal phalanx, mid phalanx, and distal phalanx for each toe.

Three weeks after the insertion, these wires were removed and weight bearing and gait exercises were performed using arch support.

The screws remained intact and in place, and no valgus or varus deformities were apparent four years after surgery ( Figure 6A– C).

Post-operative evaluation of the JSSF score of hallucis was 81 out of 100 (pain, 30 out of 30; deformity, 23 out of 30; range of motion, 5 out of 15; gait, 20 out of 20; and activity of daily life, 3 out of 10), which showed an eight-point increase. A six-point increase in deformity and a 10-point increase in walking abilities were noted; however, an eight-point decrease in range of motion was observed. No deformities were apparent and pain that worsened during movement was relieved.

Hallux varus is a clinical condition characterized by the medial deviation of the great toe at the MTP joint. Iatrogenic hallux varus is caused by an imbalance between the various bone, tendon, and capsule-ligament structures of the first MTP joint, including a progressive medial deviation of the hallux. ⁵

The causes of iatrogenic hallux varus are 1) overstitching of the medial joint capsule, 2) medial deviation of the tibial sesamoid, 3) over-traction by the abductor hallucis muscle due to lateral ligament complex release, 4) postoperative dressing in varus position of the hallux metatarsophalangeal joint, and 5) over-excision of the medial bony protrusion of hallux metatarsus. The patient in our case exhibited the second and fifth causes. ⁶

For procedures of MTP joint preservation, soft tissue release and tendon transfer method using extensor hallucis longus tendon or abductor hallucis longus tendon are used. ⁵

For soft tissue release, medial capsule release or intermetatarsal space release are used. ⁵

For tendon transfers, 2 methods such as a dynamic transfer and a static transfer are known. The dynamic transfer means transfer with muscle body and the static transfer means transfer without muscle body. Both transfers compensate for the incompetent lateral collateral ligament. Extensor hallucis longus tendon transfer is selected for a dynamic transfer with or without interphalangeal joint fusion. Abductor hallucis tendon transfer is also used. ⁵

For static tendon transfer, abductor hallucis tendon or artificial implant (TightRope) is selected. ⁵

When MTP joint is unstable or limited range of motion, MTP joint cannot be preserved, so MTP joint arthrodesis is selected. ^{5 , 7} The present case demonstrated that MTP joint congruity was not so good because of the joint instability and that MTP joint degeneration was clearly detected ( Figure 4). Therefore, MTP joint arthrodesis was performed.

MTP joint arthrodesis for hallux varus also significantly improved both the average 1–2 intermetatarsal angle from 4.8° to 8.4° and HVA from -20.7° to 8.1° in 26 patients (29 feet). ⁸ In our case, M1M2 A improved from 0° to 6° and HVA improved from -28° to 0° postoperatively ( Figures 3A and 5A).

Tourne et al. reported 14 cases of hallux varus. Each case showed medial arthrolysis of the MTP joint. Of 14 patients, five were treated with a reconstruction procedure of the lateral ligament accompanied by the medial release. Thereafter, nine patients were treated with MTP joint arthrodesis in case the MTP joint was stiff and arthrosis was present. According to the 100-point scoring system, the results were excellent in 56% and good in 44% of the patients with MTP joint arthrodesis. ⁹

The guidelines for our cases were as follows: 1) V-shaped incision was used for the dorsal MTP joint capsule. Thereafter, the articular surface was sufficiently exposed and medial tightness was thoroughly released. Tibial sesamoid was also released and relocated; subsequently, the V-shaped flap was tightly repaired after the MTP joint fusion. 2) The MTP joint level of hallucis after the primary surgery was much shorter than those of the lesser toes. To correct the imbalance of the MTP joint line between hallucis and lesser toes, and to prevent postsurgical metatarsalgia, we used a cup and cone reamer to minimize bone excision of the hallux metatarsus. Ball and cup reamer and osteosynthesis with pure titanium staples have been reported to yield good results in 54 patients with hallux valgus. ¹⁰ In addition, we performed shortening oblique osteotomy for lesser toes. 3) EHL elongation was performed because the EHL tendon became shortened due to flexion contracture of hallucis.

In conclusion, MTP joint arthrodesis using a cup and cone reamer minimized the shortening length of the metatarsal bone and proximal phalanx bone of the hallux. Additionally, it enabled stabilization in walking and bearing on the foot, resulting in good functional outcomes for this iatrogenic hallux varus case.

Written informed consent for the publication of their clinical details and clinical images was obtained from the patient.