Bunionette Deformity

Introduction

Bunionette (Tailor’s bunion) is the lateral prominence of the fifth metatarsal head. It consists of an abnormal (varus) fifth metatarsal and overlying soft tissues due to chronic irritation of the overlying bursa. Focal pressure and frequent friction by the shoe wear can lead to keratosis.

​It is important to understand that bunionette deformity is not an analogous to hallux valgus deformity. The head of 5th Metatarsal is usually broader than its shaft. Bunionette can have underlying anatomical or biomechanical causes.

​Anatomical causes include prominent 5th metatarsal head, abnormal foot position during gait, hypertrophy of the overlying soft tissues and increased 4th-5th intermetatarsal angle.

​Biomechanical causes include lateral deviation of the fifth metatarsal, congenital plantar or dorsiflexed fifth ray deformities, excessive pronation (hypermobility) and pes planus (hindfoot eversion leads to a more laterally pronounced fifth metatarsal).

 

Clinical Presentation

​Bunionette deformity is often an incidental finding but can present with persistent symptoms. It is common in adolescents and the incidence is suggested to be up to ten times more in females than in males.

​The major subjective complaints of a patient are pain and irritation caused by friction between constricting footwear and an underlying bony abnormality. An inflamed bursa, a lateral keratosis, a plantar keratosis or a combined plantar lateral keratosis may be present. 

Bunionette is a static deformity. However, repeated activities such as running or jogging can lead to thickening or inflammation of the overlying bursa.

​Diebold and Bejjani noted that two thirds of the patients in their series had significant pes planus. They reported that a third of the patients in their series developed a plantar keratosis, whereas half had a lateral keratosis. The remaining had a combined plantar and lateral keratosis.

​Coughlin noted that 10% of the patients in his series had developed a plantar keratosis, 70% had developed a lateral keratosis, and 20% had developed a combined plantar and lateral keratosis. 

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Imaging

​Weight-bearing plain radiographs (AP, oblique and lateral) are recommended as a baseline imaging modality. Divergence of the fourth and fifth metatarsals may help to assess the deformity. The normal 4th–5th IM angle is 6.5° (3–11°) in patients without a bunionette and 9.6° in feet with a symptomatic bunionette. Coughlin noted the preoperative 4th–5th IM angle in symptomatic patients to be 10.6°. In patients with pes planus, the 4th–5th IM angle may be increased by up to 3°.

​The fifth metatarsophalangeal angle indicates the magnitude of medial deviation of the 5th toe in relation to the axis of the 5th metatarsal. In 90% of normal feet, this angle is 14° or less. The mean fifth metatarsophalangeal angle in patients with symptomatic bunionette is 16°.

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Classification

​Coughlin described 3 types of bunionette deformity, based on weight-bearing AP radiographs:

​Type I -  enlargement of the lateral surface of the fifth metatarsal. This could be secondary to an exostosis; a prominent lateral condyle; or a round, or dumbbell-shaped, metatarsal head.

​Type II - secondary to abnormal lateral bowing of the distal fifth metatarsal with a normal 4th–5th IM angle. This is not usually associated hypertrophy of the fifth metatarsal head.

​Type III - the most common type, characterized by an increased 4th–5th IM angle with divergence of the 4th and 5th metatarsals.

Type IV - Not described originally by Coughlin, consists of a combination of the above deformities.

 

Treatment​

Conservative Treatment

​Always the first line of managing symptoms and is often successful. There are no evidence-based guidelines for conservative management of bunionette; however, there are several agreed upon recommendations.

​Initial management should include wearing shoes with a wider toe-box, as most patients have pain only with shoe wear. Shoes can also be custom-made or altered to accommodate the lateral deformity (cutouts or stretching). Inflamed soft tissues overlying a bunionette deformity may be managed with silicone gel pads. Hyperkeratotic lesions can be periodically pared down and padded to help alleviate pain. If the bunionette is associated with other deformities, including pes planus, orthotic devices may be helpful in reducing pronation. Nonsteroidal oral analgesics and corticosteroid injections have been reportedly used in patients with an acutely inflamed bursa overlying the fifth metatarsal head without adverse side effects.

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Surgical Treatment

Surgical treatment has been reported to be required in 10%-23% cases with failed conservative treatment or high-performing athletes. The aim of surgery is to decrease the width of the forefoot, identify and correct the underlying anatomical variation and maintain the 5th metatarsal length and 5th MTPJ function.

​The range of surgical procedures includes exostectomies, resections, and various metatarsal osteotomies. Metatarsal osteotomies can be divided based on the anatomic location: proximal, diaphyseal, or distal. Other options that have been described but are of limited usefulness are metatarsal head resection, fifth metatarsal ray amputation, and isolated soft tissue procedures.

​Various osteotomies described in literature include:

  • Lateral exostectomy/condylectomy

  • Metatarsal head resection

  • Distal metatarsal osteotomy

  • Distal transverse medializing osteotomy with fixation

  • Distal chevron osteotomy

  • Distal oblique osteotomy

  • Midshaft scarf osteotomy

  • Midshaft (diaphyseal) osteotomies

  • Proximal metatarsal osteotomy

 

Simple Exostectomy

In some cases, the prominent dorsal or dorsolateral aspect of the fifth metatarsal head is the symptomatic area and the IMA is normal. In these cases, without large bunionette deformity, a simple dorsolateral cheilectomy is sufficient to alleviate symptoms and an osteotomy is not needed. It is most often indicated for type I deformities.

The reported problems with simple exostectomy include recurrence of deformity, joint instability, and production of an incongruous joint with possible lateral dislocation of the 5th MTP joint. Preservation of function of the fifth metatarsophalangeal joint may prevent such complications as recurrence, subluxation, dislocation, or the development of a transfer lesion.

The significant recurrence rate following lateral exostectomy is due to the use of this procedure when a fifth metatarsal osteotomy is indicated. Kitaoko et al. reported the only long-term outcome study of lateral exostectomy for bunionette deformity. They performed 21 lateral condylar resections in 16 patients with a symptomatic bunionette with an average follow-up of 6.4 years and 71% patient satisfaction rates. 23% patients had mild residual pain and 2 patients had subluxation of the MTP joint. They suggested that lateral exostectomy was limited in correcting the deformity but helpful in improving symptoms.

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Osteotomies

​The location of the osteotomy and the surgical technique performed have a significant effect on the ultimate success of a metatarsal osteotomy. Distal, diaphyseal, and proximal metatarsal osteotomies have all been recommended in the treatment of symptomatic bunionette deformities. The choice of a specific type of osteotomy depends on the experience of the surgeon and the anatomic variation present

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Distal Osteotomies

​Weil osteotomy is commonly recommended because of its inherent stability in the sagittal plane, technical ease, and rapid healing. . Internal fixation is preferable. Hohmann and later Steinke described a distal fifth metatarsal osteotomy, reporting on the use of a transverse osteotomy of the 5th metatarsal neck.

Kaplan et al. advocated a distal closing-wedge osteotomy internally fixed with a K-wire. They suggested internal fixation because the osteotomy was unstable and might rotate postoperatively, resulting in loss of correction.

Haber and Kraft used a distal metatarsal crescentic osteotomy. They did not use internal fixation and reported excessive callus formation at the osteotomy site and delayed healing.

Catanzariti et al. performed a distal oblique osteotomy without internal fixation and reported a 26% recurrence rate and transfer lesions in 35% of cases.

Weitzel et al. reported on 21 patients (30 feet) who were noted to have 81% good and excellent results at an average follow-up of more than 7 years with improvements in AOFAS and VAS scores. Complications with this limited fixation included 8 of 30 patients with dorsal displacement, 3 pintract infections, and 1 transfer lesion.

Giannini et al. reported on 32 patients (50 feet) at almost 5-years follow-up. Two patients developed transfer lesions, but overall, 90% good and excellent results were reported.

​Sponsel advocated an oblique distal fifth metatarsal osteotomy. The capital fragment was allowed to float because internal fixation was not used. An 11% delayed union rate was reported.

Keating et al. also used an oblique distal fifth metatarsal osteotomy without internal fixation. Transfer lesions were reported in 75% of patients, and a 12% recurrence rate was noted.

​Pontious et al. compared distal 5th metatarsal osteotomies that were internally fixed to those not fixed and concluded that osteotomies that were internally fixed healed more predictably and that fixation prevented displacement, making it possible to maintain the corrected osteotomy position. In a report on 46 patients (56 feet), they noted that the average healing time was 8 weeks in osteotomies that were internally fixed and 11 weeks in those that were not.

​Kitaoka and Holiday and Frankel et al. concluded that floating fifth metatarsal osteotomies that seek their own level in an uncontrolled manner have a significant incidence of transfer metatarsalgia. Kitaoka and Leventen performed a distal oblique osteotomy in 16 patients (23 feet). The orientation of this osteotomy was proximal–lateral to distal–medial.

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Distal Chevron Osteotomy

​Throckmorton and Bradlee initially reported the use of a chevron osteotomy to correct a bunionette deformity. No long-term series were reported. Campbell reported on 9 patients (12 feet) and noted that all patients were satisfied postoperatively.

​Kitaoka et al. reported on the results of a distal chevron osteotomy in 13 patients (19 feet)at an average follow-up of 7.1 years, 12 of 19 feet (63%) were reported to have good or excellent results. Complications included a postoperative keratosis over the bunionette in 1 patient and transfer metatarsalgia in another. The average forefoot width was decreased by 3 mm. The authors concluded that although a limited degree of correction is possible with a chevron osteotomy, it can achieve subjective relief of symptoms.

​Pontious et al. reported on 8 chevron osteotomies and noted no dorsal displacement, indicating that this was a very stable osteotomy. Excessive soft tissue stripping on the dorsal and plantar aspect of the distal metatarsal osteotomy does, however, increase the risk of instability at the osteotomy site and also predisposes to non-union or avascular necrosis of the metatarsal head.

Reporting on 12 patients (16 feet), Moran and Claridge stressed that there was a low margin of error with this osteotomy but also a risk of recurrence or overcorrection. They suggested that the osteotomy site be stabilized with K-wire internal fixation.​

Boyer and DeOrio reported the results of 10 patients with 12 osteotomies fixed with an absorbable pin. At an average follow-up of 48 months, there was no evidence of avascular necrosis, displacement of the osteotomy, or osteolysis. All osteotomies healed by 6 weeks with improvement in AOFAS.

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Scarfette Osteotomy

In cases of an intractable plantar keratosis, a Scarfette osteotomy is the procedure of choice because of its ability to correct the deformity and elevate the head, diminish plantar pressure, and remain stable during healing. As the IMA and bowing of the fifth metatarsal increase, the Scarfette is carried more proximal, allowing for greater surface area for bony healing and stability. In cases of a plantar flexed fifth metatarsal head, as seen in a cavus foot, the long Scarfette allows for dorsal as well as medial translation to render a more favorable position.

​Weil et al. reported the outcomes of 50 patients after Scarfette osteotomy at an average of 12 months, average age 50 years and 44 female patients. Nineteen (38%) patients had a type 2 deformity and 31 (62%) patients had a type 3 deformity. Postoperative correction of the 4th–5th IMA and fifth MTPJ angles were statistically significant. Complications included one undercorrection and seven hardware removals.

​Kilmartin et al. reported on 63 patients (77 feet) who underwent scarfette osteotomy. 86% were completely satisfied, 11.4% were satisfied with reservations, and 3% were dissatisfied. 91% considered themselves better than before their surgery whereas 8.6% felt they were no better. The clinical improvement was maintained, with the AOFAS score at final review 36 months of 88.1.

​Coughlin et al. reported a series of 30 feet (20 patients) who underwent oblique diaphyseal osteotomy with 31 months follow-up. 93% patients had excellent or good clinical results. The mean 4th–5th IMA corrected from 10.6° preoperatively to 0.8° postoperatively. All osteotomies healed within 8 weeks, with only one case of a mild transfer lesion.

​These findings were reproduced in another series by Vienne and co-workers on 33 patients for 24 months. 91% patients had excellent or good clinical outcomes, with similar radiographic correction to Coughlin’s original series. They noted no instances of delayed union or non-union. Both series did note a relatively high rate of the need for hardware removal, likely due to the subcutaneous position of the fifth metatarsal and screws.

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Midshaft (Diaphyseal) Osteotomies

​An osteotomy in the diaphyseal region of the 5th metatarsal also has been recommended for the correction of a bunionette deformity. Yancy described a double transverse closing-wedge osteotomy in the diaphysis to correct a type 2 bunionette deformity characterized by lateral bowing of the metatarsal.

Okuda et al. described a crescentic osteotomy in the diaphyseal region. Vouteyalso advocated a transverse diaphyseal osteotomy but reported several complications, including delayed union, pseudarthrosis, and angulation at the osteotomy site. The transverse nature of this osteotomy rendered it relativelyunstable.

​Gerbert et al. and Shrum et al. described a closing wedge diaphyseal osteotomy that was internally fixed with a cerclage wire. They suggested that with a plantar or plantar–lateral keratotic lesion, a biplanar osteotomy might be advisable to achieve medial and dorsal displacement of the distal fragment. Unfortunately, no long-term follow-up was reported in either study.

​Mann initially described an oblique fifth metatarsal diaphyseal osteotomy for the treatment of bunionette deformities characterized by diffuse keratotic lesions on the plantar or plantar lateral aspect of the 5th metatarsal head. The oblique nature of the metatarsal osteotomy allowed not only medial but also dorsal translation of the distal fragment, with rotation at the osteotomy site. He advocated internal fixation with a wire loop, K-wire, or small-fragment screw, or all three. The 5th MTP joint was not realigned in this procedure. Although no series was reported, Mann did report a case of non-union.

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Proximal Metatarsal Osteotomy​

The rationale for a proximal metatarsal osteotomy is that it achieves correction at the actual site of the deformity, not unlike a first-ray bunion deformity. It has been advocated as a means to correct a widened 4th-5th IMA, however, there are some controversies about its use.

Diebold and Bejjani noted that there was an increased “risk of disruption of the transverse metatarsal joint” with a proximally placed 5th metatarsal osteotomy.

​Gerbert et al. stated that the anastomosing arterial branches in the fourth IM space may be vulnerable to injury with a proximal fifth metatarsal osteotomy. This observation is consistent with delayed healing of Jones type fractures within the proximal 2 cm of the fifth metatarsal.

Estersohn et al. emphasized the importance of the metaphyseal branch to the proximal fifth metatarsal region that enters on the medial aspect of the fifth metatarsal, and they cautioned that this important vascular supply should not be interrupted at surgery.

​In a series of 72 patients who underwent an opening wedge osteotomy of the proximal metatarsal, Bishop et al. reported a diminished 4th-5th IMA. Estersohn et al. performed a similar procedure in four cases. No long-term results were reported regarding the correction of the IMA or the complications. Regnauld performed a proximal closing-wedge osteotomy and stabilized it with a cerclage wire between the 4th and 5th metatarsals. Again, no results were reported.

​In the only series in which significant follow-up study was reported after a proximal metatarsal osteotomy, Diebold and Bejjani performed a horizontal chevron osteotomy 1 cm distal to the base of the 5th metatarsal. In 12 patients (average follow-up, 1 year), they reported excellent results in 90% of cases. No non-unions were reported. The 4th-5th IMA was decreased from 17 to 7 degrees. Later in a follow-up report, Diebold and Bejjani reported on 22 osteotomies that all successfully healed.

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Minimally-Invasive Osteotomy

​The Kramer technique utilizes a percutaneous distal oblique osteotomy on the fifth metatarsal, allowing for bony translation and K-wire fixation to correct for angular deformity. Lee et al. published their results on 38 patients (43 feet, type II and type III deformities, average age 51 years) using this minimally invasive technique. They concluded that this was an effective and safe treatment option in patients with painful bunionette achieving significant correction of the 4th-5th IMA and MTPJ angles, without significant shortening and with few associated complications. However larger series with longer follow ups are needed to support the use of minimally invasive techniques.

In a recently published meta-analysis Martijn et al. reported the results of 28 studies on bunionette (21 retrospective and 7 prospective) including a total number of 733 feet (608 patients, age 12-80 years) receiving surgical intervention (16 studies reviewed distal osteotomies, 10 reviewed diaphyseal osteotomies, and 2 reviewed proximal osteotomies). Fixation was used in 21 studies, of which 7 used K-wires and 13 used 1 or 2 screws. The overall success (satisfaction) rates were 100% for proximal osteotomies and 92% for both distal and diaphyseal osteotomies with highest complication rate in proximal oeteotomies (19%) compared to diaphyseal (7%) and distal osteotomies (6%). Proximal osteotomies were found to enable a large degree of correction and therefore should be considered for patients with severe bunionette deformity while the revision surgery rates were highest in distal osteotomies (2%).

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