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A bunionette deformity is characterized by a painful prominence of the lateral eminence of the fifth metatarsal head. The position of a tailor sitting in a cross-legged position has given rise to the term tailor ' s bunion to describe this prominence. Davies observed that pressure over the lateral condyle of the fifth metatarsal head leads to chronic irritation of the overlying bursa ( Fig. 10-1 ). Friction between an underlying bony prominence and constricting footwear can lead to the development of a keratosis over the lateral aspect ( Fig. 10-2A ) or the plantar lateral aspect of the fifth metatarsal head ( Figs. 10-2B and 10-2C ). The fifth toe deviates in a medial direction at the fifth metatarsophalangeal (MTP) joint ( Fig. 10-3 ), and the fifth metatarsal deviates laterally with respect to the fourth metatarsal.
A painful bursa overlying the fifth metatarsal head is surgically excised.
A , Lateral keratosis combined with lateral fifth toe corn. B , Plantar–lateral keratosis overlying the fifth metatarsal head. This is the most common presentation of a symptomatic bunionette. C , Plantar keratosis associated with bunionette deformity.
Abduction deformity of the fifth toe.
Anatomy
Kelikian described a prominent fifth metatarsal lateral eminence of a bunionette deformity as being “analogous to the medial eminence of the first metatarsal head” in a hallux valgus deformity. DuVries described several anatomic variations in the fifth metatarsal head that can lead to a symptomatic bunionette. Thus the etiology and anatomic variations that occur with a bunionette deformity are much more complex than what was originally described by Kelikian and Davies. Although painful symptoms can be localized to the fifth MTP joint region, an abnormal alignment of the fifth metatarsal may be associated with a bunionette deformity.
Recognition of the specific anatomic variation present is important in the preoperative evaluation and can influence the specific procedure chosen to correct the bunionette deformity. The radiographic analysis of a bunionette deformity is critical in defining the magnitude and type of pathology present.
Clinical Symptoms
The typical complaints of a patient with a symptomatic bunionette deformity are pain and irritation caused by friction between constricting footwear and an underlying bony abnormality. On physical examination, an inflamed bursa, a lateral keratosis, a plantar keratosis, or a combined plantar lateral keratosis may be present (see Fig. 10-2 ). Diebold and Bejjani noted that two thirds of patients had significant pes planus. They reported that a third of patients developed a plantar keratosis, whereas half had a lateral keratotic lesion. 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. It is important to consider the specific location of such lesions, as some osteotomies do not allow elevation of the metatarsal head in conjunction with correction of the bunionette deformity; these procedures should be avoided in the presence of a plantar keratosis.
In general, a bunionette is a static deformity. Repeated irritation due to shoewear or activity may lead to thickening or inflammation of the overlying bursa and increase in symptoms.
Physical Examination
The examination of the patient with a symptomatic bunionette is performed both with the patient sitting and standing. The presence of pes planus, an Achilles tendon contracture, or other forefoot abnormalities must be recognized and treated appropriately if they are symptomatic. A key to preoperative planning is the recognition of a plantar keratosis in combination with a lateral keratosis because this differentiation can affect the choice of surgical procedure. In examining the bunionette deformity, an abducted fifth toe, as well as a digital rotational component to the axial deformity, must be recognized. A hammer toe deformity of the fifth toe may also be present. A bunionette can develop as an isolated deformity, but it can also develop in combination with a hallux valgus deformity. An increased angle between the fourth and fifth metatarsals (4-5 intermetatarsal [IM] angle), in combination with an increased angle between the first and second metatarsals, results in a very wide splayed-foot abnormality. Likewise, the need for other forefoot surgical procedures affects the ambulatory capacity of a patient and must be considered as well. A thorough neurovascular examination is important for determining the suitability of the patient for surgical correction.
Diagnostic and Radiographic Examination
Radiographic evaluation of a symptomatic bunionette deformity includes standing anteroposterior (AP) and lateral radiographs. The significant angular measurements that define a bunionette deformity are the angle of the fifth metatarsophalangeal joint (MTP-5 angle) and the 4-5 IM angle ( Fig. 10-4 ). The MTP-5 angle allows one to calculate the magnitude of medial deviation of the fifth toe in relation to the longitudinal axis of the fifth metatarsal shaft. Nestor et al reported that in normal feet the MTP-5 angle averaged 10.2 degrees, and Steele et al noted that in 90% of normal cases, the angle was 14 degrees or less. Nestor et al and Coughlin have reported that in feet with bunionettes the MTP-5 angle averaged 16 degrees.
The 4-5 IM angle is a measure of the divergence of the fourth and fifth metatarsals and is the angle measured by the intersection of lines bisecting the axis of the fourth and fifth metatarsals. Divergence of the fourth and fifth metatarsals leads to pressure over the lateral eminence of the fifth metatarsal head. Fallat and Buckholz stated that the 4-5 IM angle in normal feet averaged 6.2 degrees (range, 3–11 degrees). Although some have noted that a 4-5 IM angle greater than 8 degrees can be considered abnormal, Fallat and Coughlin have reported the 4-5 IM angle on average to be greater than 9 degrees. In general, however, angular measurements serve only to describe a bunionette deformity and guide surgical planning; it is the symptoms and not the magnitude of deformity that necessitates surgical treatment. The width of the foot is determined by a diagonal line drawn from the medial edge of the medial eminence of the first metatarsal to the lateral aspect of the fifth metatarsal head.
Bunionette deformities are classified based on radiographic measurements ( Box 10-1 ). A prominent lateral condyle of the fifth metatarsal head can lead to a type 1 bunionette deformity ( Fig. 10-5 ). Hypertrophy of the lateral condyle has been reported by DuVries and others. The incidence of a type 1 deformity is reported to vary in incidence from 16% to 33%. Zvijac et al noted a variance in width of the fifth metatarsal from 11 mm at the smallest to 14 mm at the widest, and Fallat stated that the normal width of the fifth metatarsal head was 13 mm. Throckmorton and Bradlee and Fallat and Buckholz both reported that with excessive pronation of the foot, the lateral plantar tubercle of the fifth metatarsal head rotated laterally to create the radiographic impression of an enlarged fifth metatarsal head. Fallat and Buckholz also reported a 3-degree increase in the 4-5 IM angle in the presence of a pes planus deformity. Whether true hypertrophy of the fifth metatarsal head occurs or prominence of the fifth metatarsal head results from pronation of the foot, a prominent lateral condyle of the fifth metatarsal head can become symptomatic without an increase in the 4-5 IM angle.
Box 10-1
Classification of Bunionette Deformities
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Type 1. Prominent fifth metatarsal lateral condyle
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Type 2. Lateral bow of distal fifth metatarsal diaphysis
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Type 3. Widened 4-5 intermetatarsal angle
Lateral bowing of the diaphysis of the fifth metatarsal shaft can lead to the development of a symptomatic prominence of the lateral condyle of the fifth metatarsal head and is classified as a type 2 bunionette deformity ( Fig. 10-6 ). Although the proximal fifth metatarsal shaft maintains a normal IM alignment, a lateral curvature develops in the diaphysis of the fifth metatarsal, which leads to a symptomatic bunionette deformity. Fifth metatarsal bowing or an enlarged fifth metatarsal head were observed to be a cause of symptomatic bunionette in between 10% and 23% of cases.
A prominent lateral condyle of the fifth metatarsal head can also be caused by divergence of the fourth and fifth metatarsals, which is classified as a type 3 bunionette deformity ( Fig. 10-7 ). Kitaoka and Leventen in evaluating a series of patients with a symptomatic bunionette deformity, reported that an increase in the 4-5 IM angle was most often associated with a symptomatic bunionette deformity. Koti has suggested an additional type that involves two or more components of the other three types, but this adds unnecessary complexity without aiding in defining a treatment plan so largely has not been adopted.
Regardless of the underlying MTP joint orientation and fifth metatarsal angulation, the common symptom in all patients with a bunionette deformity is increased pressure over the lateral aspect of the fifth metatarsal head caused by constricting footwear. The female-to-male ratio is reported to vary from 3 : 1 to 10 : 1 in series of patients with symptomatic bunionettes that required surgical intervention. At least part of the increased frequency of occurrence of a bunionette deformity in the female population is likely attributable to differences in shoewear between males and females. With time, the development of a hypertrophic keratosis or a thickened bursa can lead to increased symptoms.
Harris mat or other planar pressure mapping studies can help in the assessment of increased pressure beneath a symptomatic fifth metatarsal head in association with a plantar keratosis ( Fig. 10-8 ).
Conservative Treatment
It is important for a patient to recognize that the use of constricting footwear is a significant cause of symptoms and places increased pressure on a prominent fifth metatarsal head. Chronic irritation, pain, and swelling of the bursa overlying the fifth metatarsal head can be reduced by roomy, well-fitted shoes ( Fig. 10-9 ).
Shaving of a hypertrophic callus ( Fig. 10-10A ) and padding ( Fig. 10-10B–D ) of a prominent fifth metatarsal head can reduce symptoms significantly. A prefabricated or custom orthotic device may be used to diminish pronation and, as a result, reduce discomfort over a prominent fifth metatarsal head (see Chapter 5 ). Additionally, in the instance of more plantar lesions, orthotics may be used to unload the fifth metatarsal head.
Conservative methods can be effective in a large number of patients. However, as painful plantar and lateral keratoses develop, surgical intervention may be necessary to relieve symptoms ( Fig. 10-11 ). Various reported techniques are presented in this section. Preferred surgical methods are noted and discussed later in the chapter.
Author’s Preferred Method of Treatment
Early conservative management of a symptomatic bunionette includes shaving the keratotic lesion, padding the lesion, and wearing roomy footwear. Most patients with symptomatic mild bunionette deformities can be successfully treated with shoe modifications and modified insoles or orthoses that relieve pressure over a painful lateral eminence. Often, conservative methods are effective in reducing symptoms; however, in the presence of chronic bursal thickening, development of symptomatic keratoses, and intractable pain, surgical intervention may be warranted. When a bursa becomes inflamed or infection occurs, a sandal or postoperative shoe may be necessary to completely relieve pressure. Plantar pain associated with an intractable keratotic lesion can often be relieved with a prefabricated or custom insole as well.
Surgical Treatment
Preoperative Evaluation
The preoperative evaluation of a patient with a painful bunionette begins with a comprehensive history and physical examination. An AP weight-bearing radiograph typically demonstrates the characteristics of the deformity, but it also helps the surgeon to assess the status of the MTP joint. Additionally, some patients may present with a prominence lateral to the fifth metatarsal head without radiographic evidence of true bunionette deformity. In these patients, ultrasound or MRI evaluation may help identify soft tissue lesions such as bursal tissue, ganglion cyst, or rheumatoid nodules. Pain and swelling of the fifth MTP joint can be caused by degenerative or inflammatory arthritis. Laboratory evaluation is occasionally helpful in diagnosing such underlying causes as gout, early rheumatoid arthritis, and infection or cellulitis.
The presence of a concomitant hammer toe deformity or a sagittal plane deformity of the MTP joint requires treatment with the correction of the bunionette.
Assessment of both the circulatory status of the involved extremity as well as the neurologic status is important, especially in those with early peripheral vascular disease, diabetes, or neuropathy. Although surgery is not necessarily contraindicated, adequate protective sensation and adequate peripheral circulation are necessary for successful healing.
Preoperative Planning
The preoperative assessment determines the underlying cause of symptoms in the patient with a painful bunionette. Likewise, the radiographic findings help to determine the preferred surgical technique. A plantar–lateral callosity requires a surgical correction that reduces the size of the lateral eminence as well as elevates the fifth metatarsal head. The radiographic findings of a mild deformity or mainly an enlarged fifth metatarsal head make a distal fifth metatarsal osteotomy a feasible alternative. A moderate or severe deformity—typically a curved fifth metatarsal shaft or a widened 4-5 IM angle—makes a midshaft diaphyseal osteotomy preferable. Thus a careful correlation of the physical findings and radiologic information allows the physician to select the appropriate surgical procedure with which to correct a bunionette deformity.
Surgical Techniques
Numerous surgical techniques have been described to correct a symptomatic bunionette deformity. These include lateral condylectomy, fifth metatarsal head resection, fifth metatarsal implant arthoplasty, fifth-ray resection, distal metatarsal osteotomy, diaphyseal osteotomy, and proximal fifth metatarsal osteotomy. More recently, minimally invasive techniques have been described as a method to correct bunionette deformity gained popularity. Regardless of technique, correction of the underlying disorder is necessary for preventing a recurrence of deformity. Likewise, preservation of the function of the fifth MTP joint can prevent such complications as recurrence, subluxation, dislocation, or development of a transfer lesion.
Lateral Condylectomy
With an isolated enlargement of the fifth metatarsal head or a prominent fifth metatarsal lateral condyle without an increased 4-5 IM angle, a lateral condylectomy may be performed. The presence of pes planus or a pronated fifth ray is not necessarily a contraindication to a lateral condylectomy if the prominent lateral condyle is the only symptomatic deformity present.
Indications
The main indication for a lateral condylectomy is an enlarged lateral condyle. In this situation, a condylectomy can produce an adequate repair, although a distal metatarsal osteotomy might still be the procedure of choice. A second indication is for the treatment of localized infection overlying the lateral fifth metatarsal head. Although lateral condylectomy might not achieve MTP joint realignment, it might alleviate the acute or chronic infection. Additionally, a lateral condylectomy may be considered in patients with more significant deformity but who would be poor candidates for osteotomy due to other medical comorbidities or inability to protect the foot postoperatively.
Contraindications
Preoperative radiographs are important in the evaluation of a bunionette deformity. With lateral angulation of the fifth metatarsal shaft in relationship to the fourth metatarsal shaft (increased 4-5 IM angle; type 3 deformity) or with lateral bowing of the fifth metatarsal shaft (type 2 deformity), a condylectomy does not effectively reduce a prominent fifth metatarsal lateral eminence, and a fifth metatarsal osteotomy is necessary to correct the deformity.
The significant recurrence rate after lateral condylectomy is attributable to the use of a lateral condylectomy when a fifth metatarsal osteotomy is indicated. Kelikian noted that “at best a lateral condylectomy is a temporizing measure like simple exostectomy on the medial side of the foot; in time deformity will recur.”
Surgical technique
- 1.
The patient is positioned in a supine position, with a pad under the ipsilateral hip to orient the foot appropriately to allow access to the lateral forefoot.
- 2.
The extremity is cleansed in a normal fashion.
- 3.
A longitudinal skin incision is centered over the lateral condyle of the fifth metatarsal head and extends from the interphalangeal joint to 1 cm proximal to the fifth metatarsal condyle. The dorsal cutaneous nerve of the fifth toe is protected ( Fig. 10-12A and B ).
- 4.
An inverted L-shaped capsular incision is used to detach the dorsal and proximal fifth metatarsal capsule. The weakest portion of the capsule is detached, and the strongest capsular attachments to the proximal phalanx and plantar capsule are maintained ( Fig. 10-12C–E ).
- 5.
A sagittal saw or osteotome is used to resect the lateral condyle of the fifth metatarsal head ( Fig. 10-12F and G ).
- 6.
The fifth metatarsal head is exposed, and with traction placed on the fifth toe, the MTP joint is distracted and the medial capsule is released with a scalpel ( Fig. 10-12H and I ).
- 7.
The MTP capsule is closed by approximating it to the fifth MTP metaphyseal periosteum and to the abductor digiti quinti muscle proximally ( Fig. 10-12J ). (For improved fixation, a drill hole in the fifth metatarsal dorsolateral metaphysis may be used to anchor the capsule repair.) A meticulous capsule repair is necessary to prevent recurrence of the deformity or lateral subluxation of the MTP joint.
- 8.
The skin is closed routinely and a compression dressing is applied.
Postoperative care
A gauze-and-tape compression dressing is applied at surgery and is changed weekly for 6 weeks. Alternatively, after skin healing, a toe spacer may be placed between the fourth and fifth toes. The patient is allowed to ambulate in a postoperative shoe for 3 weeks and in a sandal for 3 weeks. Skin sutures are removed 3 weeks after surgery.
Results and complications
Although a lateral condylar resection is a simple treatment for a bunionette deformity, reported results are based on small clinical series, and authors recognize the significant limitations of the procedure. Reported postoperative complications include recurrence of deformity ( Fig. 10-13 ), subluxation of the MTP joint ( Fig. 10-14 ), and poor weight bearing with excessive resection.
Kitaoka and Holiday reported on 16 patients (21 feet) who had undergone a lateral condylar resection for a symptomatic bunionette with average follow-up of 6.4 years. Seventy-one percent of the patients were satisfied with their result. Twenty-three percent reported some element of forefoot pain, although half these patients considered it mild. The average preoperative 4-5 IM angle measured 12.3 degrees, and postoperatively it measured 11.1 degrees, for an average correction of 1.2 degrees. Much of this correction can be accounted for by the measurement techniques. The metatarsophalangeal-5 angle averaged 17.0 degrees preoperatively and 14.6 degrees postoperatively, but this correction was not significant on statistical analysis. Furthermore, the authors concluded that no correlation existed between the amount of correction and the level of patient satisfaction. In 2 (10%) of 21 feet, the MTP joint subluxated postoperatively as the fifth toe displaced medially. A tight capsule closure with excision of redundant MTP joint capsule was recommended to minimize this postoperative complication. The authors also concluded that although only a limited degree of correction of the deformity was possible with this procedure, a lateral condylectomy was often successful in relieving symptoms. No transfer lesions were reported in this series. With an intractable plantar keratotic lesion beneath the fifth metatarsal head, the authors believed that a simple condylectomy was contraindicated.
A meticulous fifth metatarsal capsule repair can prevent subluxation and recurrence of a bunionette deformity. Attention to repair of the abductor digiti quinti muscle and fifth metatarsal capsule can prevent later dislocation of the MTP joint.
Fifth Metatarsal Head Resection
The failure of a lateral condylectomy as an effective treatment of a bunionette deformity has resulted in the recommendation for more extensive resection procedures. Excision of the fifth metatarsal head ( Fig. 10-15 ), resection of the distal half of the fifth metatarsal ( Fig. 10-16 ), and fifth-ray resection ( Fig. 10-17 ) have all been advocated as treatment for a symptomatic bunionette deformity. McKeever advocated excision of the fifth metatarsal head and one half to two thirds of the fifth metatarsal shaft; Brown found that resection of almost the entire fifth ray and a fifth toe amputation adequately narrowed the foot and relieved symptoms. Kelikian recommended McKeever's technique but syndactylized the fourth and fifth toes to avoid a symptomatic flail fifth toe deformity.
Indications
Ray resection, extensive fifth metatarsal diaphyseal resection, and fifth metatarsal head resection should be reserved as a salvage procedure for intractable ulceration, severe deformity, and infection, as well as in rheumatoid arthritis when multiple metatarsal head resections are performed. Fifth metatarsal head resection may also be considered in the presence of recurrent deformity with a significant soft tissue contracture.
Contraindications
As a primary procedure in the treatment of a bunionette deformity, less radical procedures that preserve function of the fifth ray should be considered instead of resection arthroplasty. Implant arthroplasty is to be discouraged at the fifth MTP joint. No evidence indicates that it offers improved postoperative function over resection arthroplasty, and, on occasion, significant complications are associated with this procedure.
Surgical technique
- 1.
The patient is positioned in a supine position, with a pad under the ipsilateral hip to orient the foot appropriately to allow access to the lateral forefoot.
- 2.
The extremity is cleansed in a normal fashion.
- 3.
A longitudinal incision is centered over the lateral eminence, extending from the midportion of the proximal phalanx to 1 cm above the lateral eminence. (With plantar ulceration, a dorsal incision may be used. With rheumatoid arthritis when multiple metatarsal heads are excised, a longitudinal IM incision may be placed in the fourth IM space.)
- 4.
The capsular structures are released, and the fifth metatarsal head is exposed.
- 5.
The fifth metatarsal shaft is transected in the metaphyseal region with a sagittal saw or a bone-cutting forceps (see Fig. 10-16A and B ).
- 6.
The prominent lateral and plantar aspects of the metatarsal shafts are beveled with a rongeur.
- 7.
A 0.045-inch Kirschner wire is introduced at the base of the proximal phalanx and driven distally through the tip of the toe (see Fig. 10-16C ). It is then driven in a retrograde manner into the metatarsal diaphysis to align and stabilize the fifth toe. With plantar ulceration or infection, Kirschner wire stabilization is contraindicated.
- 8.
The capsule is plicated with interrupted absorbable suture. The skin edges are approximated in a routine manner.
Postoperative care
A gauze-and-tape compression dressing is used for alignment of the fifth toe and changed weekly for 6 weeks. Ambulation is permitted in a postoperative shoe. Sutures and the Kirschner wire are removed 3 weeks after surgery.
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