Sesamoids and Accessory Bones of the Foot

Galen is reported to have first coined the term sesamoid because of the resemblance of these small rounded bones to the sesame seed.⁴⁴ The anatomic location of several of the sesamoids is constant, but the frequency of occurrence of other sesamoids is quite variable.⁴⁰

The sesamoids function to alter the direction of muscle pull, diminish friction, and modify pressure. Sesamoids occur in the substance of their corresponding tendon. They may be totally or partially contained within the tendinous structure. Some sesamoids totally ossify, some remain entirely cartilaginous, and some partially ossify with a fibrocartilaginous interface between the ossified fragments. This variability in ossification might explain the radiographic absence or presence of various sesamoids, as well as the incidence of bipartism of sesamoids.⁹¹

The sesamoids in the foot and ankle region are contained within the plantar plates of the interphalangeal and metatarsophalangeal (MTP) joints and in the tendons of the flexor hallucis brevis, the intrinsic tendons of the lesser toes, the tibialis anterior tendon, the tibialis posterior tendon, and the peroneus longus tendon.

The importance of this chapter is to assist the physician in recognizing both normal and pathologic variants, which may present as an uncommon or rare accessory bone of the foot and ankle, or which, on the other hand, may have developed because of trauma or an event that has caused a bony fragment to appear as an accessory bone.

Sesamoids of the First Metatarsophalangeal Joint

The sesamoids of the first MTP joint play an important role in the function of the hallux. Contained within the tendons of the flexor hallucis brevis, the sesamoids of the first MTP joint have many functions: to absorb the majority of the weight of the first ray; to protect the tendon of the flexor hallucis longus, which courses over the rather exposed plantar surface of the first metatarsal head; and to help increase the mechanical advantage of the intrinsic musculature of the first ray. Although sesamoid dysfunction is uncommon, it can occur with arthritis, trauma, infection, osteochondritis, and sesamoiditis.

First MTP sesamoid abnormalities are uncommon, but degeneration or isolated injury can cause pain and significant dysfunction. To understand the nature of the clinical problems and to appreciate appropriate indications for surgical intervention, an understanding of the function of the sesamoid mechanism and of the pertinent anatomy is necessary.

The sesamoid mechanism and intrinsic musculature of the hallux differentiate the first ray from the lateral toes. The hallucal sesamoids, enveloped within the double tendon of the flexor hallucis brevis (Fig. 10-1), articulate on their dorsal surface with the plantar facets of the first metatarsal head. A crista, or intersesamoid ridge (Fig. 10-2), separates the medial and lateral metatarsal facets. This intersesamoid ridge provides intrinsic stability to the sesamoid complex. In severe cases of hallux valgus, with substantial subluxation of the sesamoid complex in relation to the first metatarsal head, the intersesamoid ridge atrophies and at times is obliterated (Fig. 10-3). Close inspection of the plantar articular surface of the first metatarsal frequently reveals substantial cartilage erosion and degenerative arthritis in this area (Fig. 10-4).¹⁰

Figure 10-1 The sesamoids are enveloped within the double tendon of the flexor hallucis brevis.

Figure 10-2 A cross section of the first metatarsal head demonstrates the sesamoid and the intersesamoidal ridge.

Figure 10-3 A, Normal axial position of the sesamoids centered on either aspect of the cristae. An anteroposterior (AP) radiograph demonstrates the normal position of the sesamoids. B, Mild hallux valgus deformity with mild subluxation. C, Moderate hallux valgus deformity associated with moderate sesamoid subluxation. AP radiograph demonstrates moderate sesamoid subluxation. D, Severe hallux valgus associated with severe subluxation of the sesamoids. AP radiograph demonstrates a hallux valgus angle of 60 degrees.

Figure 10-4 Avascular necrosis of the lateral sesamoid. A, Axial view demonsrating fragmented sesamoid. B, Computed tomography scan. C, Magnetic resonance imaging of lateral sesamoid fragmentation. D, Excised specimen. E, Histology section demonstrating eosinophilic infiltration of the marrow fat and necrosis of the bone trabeculae with absence of the osteocytes. (From Toussirot E, Jeunet L, Michel F, et al: Avascular necrosis of the hallucal sesamoids update with reference to two case-reports, Joint Bone Spine 70:307–309, 2003.)

The sesamoids are connected to the plantar base of the proximal phalanx through the plantar plate (Fig. 10-5), which is an extension of the flexor hallucis brevis tendon. The inferior surface of the sesamoids is covered by a thin layer of the flexor hallucis brevis tendon, whereas the superior surface is articular in nature. These sesamoids are entirely intratendinous, except dorsally, where they articulate with the first metatarsal head. The sesamoids are suspended by a slinglike mechanism composed of the collateral ligaments of the MTP joint and the sesamoid ligaments (Fig. 10-6) on both the medial and lateral aspects of the MTP joint. The flexor hallucis brevis, through its sesamoid mechanism, provides a significant plantar flexion force at the MTP joint. The sesamoids also have an insertion into the joint capsule and the plantar aponeurosis; this provides both stabilization and a static plantar flexion force at the MTP joint.

Figure 10-5 Metatarsophalangeal joint from a dorsal exposure showing the intersesamoidal ligament (1), the lateral sesamoid (2), medial sesamoid (3), lateral metatarsosesamoid ligament (plantar plate) (4), medial metatarsosesamoid ligament (plantar plate) (5), lateral joint capsule (6), and medial joint capsule with extension into the distal plantar plate (7).

Figure 10-6 The sesamoids and collateral ligaments provide medial and lateral stability to the metatarsophalangeal joint.

On the medial aspect of the MTP joint, the abductor hallucis tendon (Fig. 10-7) inserts into the plantar-medial base of the proximal phalanx as well as the medial sesamoid and functions to stabilize the sesamoid mechanism medially. On the lateral aspect, the adductor hallucis tendon inserts into the lateral base of the proximal phalanx and into the lateral sesamoid to stabilize the sesamoid mechanism laterally. The medial and lateral sesamoids are connected by the intersesamoidal ligament, which forms the base of the tendinous canal enveloping the tendon of the flexor hallucis longus.

Figure 10-7 The abductor hallucis inserts into the plantar-medial base of the proximal phalanx, while the adductor hallucis inserts into the plantar-lateral base of the proximal phalanx. Both these intrinsic muscles also insert into their respective sesamoids.

Distal to the sesamoids, the phalangeal-sesamoid ligament is a thin-layered structure that interdigitates with the collateral ligaments, extension of the plantar aponeurosis, and tendons of the flexor hallucis brevis to form the plantar plate. These structures are not individually distinguishable but, rather, coalesce to form the plantar plate. Complete or partial rupture of the plantar plate attachement may lead to a turf toe deformity with retraction of the sesamoids, restricted motion, and degenerative arthritis of the first metatarsophalangeal joint.¹⁸

When a person is in a standing position, the sesamoids are located posterior to the metatarsal head; however, with dorsiflexion of the hallux, the sesamoids move distally, thereby protecting the otherwise exposed plantar surface of the first metatarsal head. When a person rises onto the toes, the sesamoids (especially the medial sesamoid) act as the main weight-bearing focus for the medial forefoot (Fig. 10-8).

Figure 10-8 A, Anteroposterior (AP) radiograph immediately after hyperextension injury of the first metatarsophalangeal joint. B, AP radiograph of both feet 1 year later, demonstrating retraction of the sesamoid complex after disruption of the plantar plate.

Kewenter 54,214 noted that the medial sesamoid is located slightly more distal than the lateral sesamoid and is slightly larger. Orr⁷³ quantitated sesamoid size and reported that the tibial sesamoid averaged 9 to 11 mm in width and 12 to 15 mm in length. The fibular sesamoid was noted to have an average width of 7 to 9 mm and an average length of 9 to 10 mm.

Ossification

Although ossification of the hallucial sesamoids is variable, Kewenter reported that ossification usually occurs between the sixth and seventh years. Ossification of the sesamoids often occurs from multiple centers, and this may be the reason for the development of multipartite sesamoids.54,214

Circulation

The arterial anatomy of the first ray was evaluated in 22 anatomic specimens by Rath et al.⁷⁸ They found that the first plantar metatarsal artery provided the main arterial supply to the medial and lateral sesamoids. It anastomosed with a branch of the medial plantar artery in 90% of cases they dissected. They demonstrated both proximal and distal vessels branching off the two major arteries. Pretterklieber and Wanivenhaus,⁷⁷ in dissections of 29 cadavers, reported three different types of arterial circulation. The most common type (type A, 52%), was characterized by arterial circulation derived from the medial plantar artery and the plantar arch. In the less common types, circulation was derived mainly from either the plantar arch or only from the medial plantar artery (Fig. 10-9). Both authors concluded that the course and distribution of the arterial circulation to the sesamoids might have a significant bearing on the development of avascular necrosis after injury and possible inadvertent injury during surgical exploration of this area.

Figure 10-9 Circulation to the sesamoids. A, The most common pattern of arterial circulation to the sesamoids (52% of cases) involves a direct branch from both the medial plantar artery and the plantar arch. B, In 24% of cases, the sesamoid arterial supply is predominantly from the plantar arch. C, In 24% of cases, the major arterial supply is from only the medial plantar artery. When there is only one blood vessel supplying a sesamoid, a fracture may be at greater risk for avascular necrosis or nonunion. (Courtesy Michael L. Pretterklieber, MD, and Axel Wanivenhaus, MD.)

The number of arterial branches can affect healing of fractures as well as the incidence of avascular necrosis after trauma.¹³ Multiple arterial branches can protect an injured sesamoid, whereas a single arterial branch to a damaged sesamoid may be interrupted by a fracture or injury and lead to delayed healing or a nonunion.

Sobel et al ⁹⁷ and Rath et al,⁷⁸ in their evaluation of sesamoid vascularity, mapped the vascular supply as well of both the medial and lateral sesamoids. The major vascular supply enters the sesamoids from the proximal and plantar aspect, with a minor arterial supply entering through the distal pole of the sesamoids (Fig. 10-10A). The distal vascular supply originates through distal capsular attachments providing, in most cases, a limited arterial supply. The proximal arterial supply, through the flexor hallucis brevis, supplies one third to two thirds of the proximal sesamoid. Vascular anastomoses occur between the proximal supply and that derived from the plantar surface to the body of the sesamoid (Fig. 10-10B). The distal portion of the sesamoid has the most tenuous vascular supply, and this can lead to delayed or unsuccessful healing after injury.

Figure 10-10 A, The major vascular supply enters the sesamoid proximally. An anastomosis occurs between the distal and proximal surface. B, The plantar vascular supply to the sesamoid is significant. (Modified from Sobel M, Hashimoto J, Amoczky SP, Bohne WH: The microvasculature of the sesamoid complex: its clinical significance, Foot Ankle 13:359–363, 1992.)

The sesamoids not only absorb weight-bearing forces on the medial aspect of the forefoot but also increase the mechanical advantage of the intrinsic musculature in plantar-flexing the proximal phalanx. The tendon of the flexor hallucis longus is protected in its tendon sheath by the medial and lateral sesamoids and provides a plantar flexion force to the distal phalanx of the great toe.

Preoperative Evaluation

Physical Examination

Patients with a symptomatic sesamoid often complain of pain and discomfort during the toe-off phase of gait. Objective clinical findings include restricted range of MTP motion, pain on direct palpation, pain with motion of the first MTP joint, swelling of the first MTP joint, and diminished plantar or dorsiflexion strength. Synovitis of the first MTP joint may be noted as well on physical examination. Occasionally, an intractable plantar keratotic lesion develops beneath either the tibial or fibular sesamoid.

The orientation of the hallux must be inspected for lateral (hallux valgus) or medial (hallux varus) deviation or for clawing of the hallux. Progressive insidious deviation of the hallux can develop with sesamoid disruption caused by trauma or fracture. Progressive hallux valgus or hallux varus can also develop as a result of a previous sesamoid resection. Hyperextension of the hallux because of discontinuity of the sesamoid complex can occur after traumatic rupture of the plantar plate (see Fig. 10-8).

Examination of the sensory nerves of the first ray is important in diagnosing a compressed digital nerve,³⁹ which can manifest with isolated neuritic symptoms or numbness. With compression of either the medial or lateral digital nerve by either the tibial or fibular sesamoid, a Tinel sign can be elicited along the border of the sesamoid.

Radiographic Examination

Routine dorsoplantar and lateral radiographs (Fig. 10-11A and 10-11B) can provide limited information in the evaluation of a painful sesamoid. On the dorsoplantar view, the metatarsal head overlies both the medial and lateral sesamoid and often obscures detail; on the lateral projection, the medial and lateral sesamoids overlap each other. The fibular sesamoid is best demonstrated in a lateral oblique radiograph (Fig. 10-11C), where it can be seen between the first and second metatarsal heads. The tibial sesamoid is best seen on a medial oblique radiograph (Fig. 10-11D).⁸¹ With the MTP joint dorsiflexed approximately 50 degrees, the roentgen beam is directed 15 degrees cephalad from a lateral position and is centered over the first metatarsal head. Often, however, the most useful radiograph is the axial sesamoid view (Fig. 10-11E).^43,63 Where radiographs appear normal in spite of a patient’s subjective symptoms, a technetium-99m (^99mTc) bone scan may be useful (Fig. 10-12A, B, and C). A bone scan can demonstrate increased uptake before the development of any significant radiographic change, such as sclerosis, fragmentation, or disintegration. Computed tomography (CT) examination can define osseous changes, such as acute fracture or fragmentation, and magnetic resonance imaging (MRI) examination may demonstrate bone edema, avascular regions, fragmentation or degeneration of a sesamoid early before radiographic changes are demonstrated on plain radiographs (see Fig. 10-4A).

Figure 10-11 A, Dorsoplantar radiograph demonstrating the metatarsophalangeal sesamoids. The view is partially obstructed by the overlying metatarsal head. B, Lateral radiograph of the sesamoids. The medial and lateral sesamoids overlie one another and somewhat obscure the view of each individual sesamoid. C, A lateral oblique radiograph can best visualize the fibular sesamoid. D, A medial oblique radiograph shows more clearly the tibial sesamoid. E, An axial sesamoid radiograph presents the sesamoids without being obstructed by the overlying first metatarsal.

Figure 10-12 Anteroposterior (A) and lateral (B) technetium-99m (^99mTc) bone scan demonstrating increased uptake in the lateral sesamoid. A fractured medial sesamoid (arrow) is demonstrated. C, A bone scan may be helpful in diagnosing an abnormality when a routine radiograph appears normal.

Bipartite Sesamoids and Fractures

The incidence of partite sesamoids as well as their cause has been the subject of substantial discussion in the literature (Table 10-1). Kewenter^54,214 examined 800 feet and found a 31% incidence of bipartite tibial sesamoids (Fig. 10-13), and Dobas and Silvers²⁴ examined radiographs of 1000 feet and found a 19% incidence of combined tibial and fibular sesamoid bipartism (Fig. 10-14). Dobas and Silvers reported that 80% of bipartite sesamoids involve the tibial sesamoid. Rowe⁸⁷ noted a 6% to 8% frequency of bipartite sesamoids and stated that 90% of these were bilateral. Dobas and Silvers²⁴ stated that approximately 25% of partite tibial sesamoids had an identical bipartite tibial sesamoid on the contralateral side, whereas the remaining sesamoids were asymmetric when division was concerned. Jahss⁴⁶ noted that bipartism was 10 times more common in the medial sesamoid. Giannestras³² stated that the occurrence of bipartite sesamoids was typically symmetric, but this is obviously not the case. The medial sesamoid is often divided into two, three, or four parts, whereas the lateral sesamoid is rarely divided into more than two parts (Fig. 10-15).

Table 10-1

Proportion of Tibial and Fibular Division in Representative Series of Cases

Figure 10-13 Many variations can occur in ossification of sesamoids of the metatarsophalangeal joint of the hallux. A, Various shapes of medial and lateral sesamoids. B, An anteroposterior radiograph demonstrates a bipartite medial sesamoid. C, An axial radiograph demonstrates a longitudinal bipartite medial sesamoid. D, Hyperextension injury mechanism resulting in disruption of the sesamoid complex. E, Computed tomography scan of multipartite sesamoid demonstrating oblique separation of medial sesamoid (arrow).

Figure 10-14 Anteroposterior radiograph demonstrating asymptomatic bipartite medial and lateral sesamoids.

Figure 10-15 A, An anteroposterior radiograph demonstrates a painful bipartite sesamoid. B, An axial radiograph does not show evidence of a fracture or bipartite sesamoid. C, Radiograph of a pathology specimen showing rounded edges pathognomonic of a bipartite sesamoid. D, Axial view after excision of medial sesamoid. E, Gross pathology of a specimen. F and G, Immediately after surgery. H, At 19-year follow-up after medial sesamoid excision. Alignment of the first metatarsophalangeal joint is well maintained.

Inge and Ferguson ⁴⁴ reported that 85% of the bilateral partite sesamoids had asymmetric divisions. They also reported that the incidence of division decreased with time, thus implying that osseous union occurs with time in the divided sesamoid. They further reported that histologic evaluation of congenital bipartite sesamoids demonstrated that articular cartilage tended to dip down between the two osseous fragments. This can predispose a bipartite sesamoid to fracture or disruption of the synchondrosis with minimal injury (see Fig. 10-13D). They speculated that the medial sesamoid has a higher frequency of bipartism than the lateral sesamoid because it is more often traumatized, a result of its greater weight-bearing capacity. It has not been determined whether continued trauma with ambulation prevents the union of divided sesamoids or whether some of these partite sesamoids are actually nonunions of fractures.

The incidence of irregular ossification with bipartism in the medial sesamoid is well recognized. Kewenter 54,214 examined a series of sesamoids in cadavers and found that congenitally divided sesamoids fracture with much less force than normal sesamoids when experimental trauma was introduced. Although fractures of sesamoids are relatively rare, numerous cases have been reported in the literature.* Substantial trauma with MTP joint dislocation and simultaneous fractures of both sesamoids have been reported^23,103; in general, the most frequently reported mechanism of injury is a fall onto the forefoot, sudden loading of the forefoot, or a crush injury.

It can be difficult to distinguish between a fractured sesamoid (see Fig. 10-15) and a symptomatic bipartite sesamoid.^30,104 With a divisionary line between two segments of a sesamoid, a careful physical examination and history must be correlated with radiographic findings to differentiate between a partite sesamoid and a superimposed fracture.³⁰ With a sesamoid fracture, pain is localized to the region of the specific sesamoid. Symptoms are typically exacerbated with ambulation and reduced with rest. Often, the patient ambulates with weight bearing on the lateral aspect of the foot to avoid motion and loading of the sesamoid complex.

On physical examination, forced passive dorsiflexion and plantar flexion can cause discomfort. Synovitis or nonspecific swelling on the plantar aspect of the sesamoid complex may be observed. The development of pain after minimal trauma in the presence of a bipartite sesamoid should alert the examiner to the possibility of a superimposed fracture of a bipartite sesamoid. An acute fracture may be noted on a radiograph with a sharp radiolucent line (Fig. 10-16); however, Inge and Ferguson⁴⁴ suggested that a fracture should not be diagnosed unless callus is present. Delay in diagnosis of a sesamoid fracture is therefore common because of the difficulty of confirming the fracture by radiography.^102,110

Figure 10-16 A, Oblique radiograph demonstrating an acute fracture of the medial sesamoid. B, Axial radiograph demonstrating a longitudinal fracture (arrow) of the lateral sesamoid. This fracture was only demonstrated on this particular view. C, Anteroposterior radiograph demonstrating a comminuted fracture of the lateral sesamoid. D, Axial radiograph demonstrating a comminuted fracture of the medial sesamoid.

Although rarely is a preinjury film available to help differentiate a partite sesamoid and a fracture, increased separation between fragments can be a definitive finding in the presence of a disruption of a partite sesamoid (Fig. 10-17). Richardson⁸¹ recommends a bone scan to aid in diagnosis of a fracture in the presence of a bipartite sesamoid. MRIs may demonstrate increased vascularity, bone edema, or acute changes, indicating a disruption of a partite sesamoid⁴⁹ (see Fig. 10-37D). Hobart⁴⁰ recommended non–weight bearing and casting until the sesamoid fracture had healed, which usually occurred in 6 to 8 weeks (Fig. 10-18). Anderson and McBryde² reported on 21 patients treated with bone grafting for symptomatic tibial sesamoid nonunions (Fig. 10-19). They curetted and bone grafted the diastasis, which was typically 1 mm wide. All patients were noted to have a positive bone scan before surgery. In two cases in which articular surface deterioration was noted, a sesamoidectomy was performed. Three other patients had excessive motion at the diastasis site and were not considered candidates for bone grafting. Through an inferior extraarticular approach, they curetted and bone grafted the diastasis “nonunion site.” No internal fixation was used. The patients were placed in a below-knee cast and kept non–weight bearing for 4 weeks. At final follow-up, 19 of 21 sesamoids had healed. Two patients had a persistent nonunion. Reports in which internal fixation has been used for acute sesamoid fracture⁷⁵ or chronic nonunions^9,82 have noted success. Riley and Selner⁸² used a circlage wire and bone grafting in one case, and Blundell et al⁹ used a percutaneous screw in nine cases and reported successful union. Pagenstert et al⁷⁵ reported two cases in which simultaneous correction of a hallux valgus deformity was combined with open reduction and internal fixation of a nonunion of a medial sesamoid.

Figure 10-17 A, Anteroposterior radiograph demonstrating a multipartite medial sesamoid. B, Axial view demonstrating defect. C, Lateral radiograph demonstrating alignment of proximal and distal fragments. D, With dorsiflexion of the hallux, the alignment of the fragments changes, demonstrating motion consistent with a fracture of a partite sesamoid.

Figure 10-18 A, Anteroposterior (AP) radiograph of normal contralateral foot. B, AP radiograph of symptomatic bipartite medial sesamoid. C, Axial view. The patient was treated with a below-knee cast for 6 weeks, unweighting the sesamoids, and symptoms resolved. D and E, Fifteen-year follow-up. AP radiograph (D) and axial view (E) demonstrating no radiographic changes. Patient remains completely asymptomatic.

Figure 10-19 Anteroposterior radiograph (A1), computed tomography scan (A2), and lateral radiograph (A3) demonstrating nondisplaced fracture of tibial sesamoid. B, Incision used to approach metatarsal sesamoid articulation for bone grafting. C, Extraarticular approach exposing plantar surface of sesamoid. After curettage, the nonunion is identified, debrided (D), and bone grafted (E). (Courtesy R. Anderson, MD, Charlotte, N.C.)

Rodeo et al ⁸³ reported on four cases of injuries to the hallux with progressive diastasis of bipartite sesamoids. The patients were treated with a distal resection of a smaller fragment and repair of the sesamoid mechanism.

Biedert and Hintermann ⁷ reported on five athletes who developed stress fractures of the medial sesamoids. Surgical excision of the proximal fragment and repair of the flexor hallucis brevis were performed. After casting for 6 weeks after surgery, full return to sports activity was allowed at 8 weeks.

Kuo et al ⁵⁷ reported a case of nonunion of the fibular sesamoid in association with chronic gout that required surgical excision.

Brodsky et al ¹³ retrospectively reviewed a series of 37 patients with fractured sesamoids. Avascular necrosis secondary to fracture was noted in 9 cases, 16 cases were diagnosed as stress fractures, and 12 cases were related to direct trauma. After surgical excision of the fractured sesamoid, an average postoperative American Orthopaedic Foot and Ankle Society (AOFAS) score of 93 was achieved.

Saxena and Krisdakumtorn ⁹³ reported on 24 patients at a mean follow-up of 86 months after sesamoidectomy. There were 10 fibular and 16 tibial sesamoidectomies. Eleven patients were professional or varsity athletes and returned to activity in 7.5 weeks. The other patients returned to normal activities in 12 weeks. Complications included one varus deformity, one valgus deformity, and two cases of neuroma formation associated with fibular sesamoidectomy. Patients took longer to recover from surgery for tibial sesamoidectomy, which the authors surmised was probably due to increased weight bearing. Patients with fibular sesamoidectomies had an earlier return to activity. They noted that a dorsolateral approach may be more difficult for fibular sesamoidectomy and that the two nerve problems both occurred with a dorsolateral approach.

Custom and prefabricated orthotics and scaphoid and metatarsal pads can relieve pressure in the sesamoid region, diminishing symptoms. Taping of the toe to reduce dorsiflexion can also relieve symptoms. If conservative methods fail, surgical removal of the involved sesamoid may be necessary (see Fig. 10-20).

Figure 10-20 A, Intractable plantar keratotic lesion directly beneath the tibial sesamoid. B1-B5, Insoles and shoe inserts. B1, Insole with Hapad placed just proximal to the sesamoids, relieving pressure. B2, Plastazote insert with proximal Hapad and area beneath sesamoid relieved. B3, Custom insert with proximal Hapad. B4 and B5, Custom inserts with sesamoid region molded to diminish pressure. C, Insert shown from plantar aspect, with area beneath sesamoids decompressed. D, An extra-depth shoe might be necessary to accommodate the specific insert used to relieve sesamoid pain.

Rosenfield and Trepman ⁸⁵ have described the use of a rocker-soled walking shoe with a full-length steel shank. An orthotic insole is added with a recess beneath the sesamoid region (Fig. 10-21).

Figure 10-21 A, Rocker-soled walking shoe with a full-length steel shank and a custom orthotic insole may be used to relieve sesamoid pain. B, Commercially available rocker-type shoe. C, Custom cork insole with recessed area for sesamoids. D, and E, Graphite insole can diminish metatarsophalangeal joint motion. Top and side views. F, Prefabricated insert with graphite insole to stiffen the toe-box area of the shoe. G, Custom insole with graphite and gel-layered insole. (Courtesy Hansen Orthotics, Sun Valley, Idaho.)

Congenital Absence of the Sesamoids

Congenital variations in regard to ossification of the tibial and fibular sesamoids are common. Congenital absence of a sesamoid has been infrequently reported; however, it is probably more prevalent than is realized.48,58 Patients are typically asymptomatic with absent sesamoids. Inge and Ferguson⁴⁴ reported two cases of congenital absence of the tibial sesamoid. Goez and DeLauro,³⁵ Zinsmeister and Edelman,¹¹¹ and others^21,52 have reported absence of the tibial sesamoids as well. Jeng et al⁴⁸ and others^60,108 have reported cases of an absent fibular sesamoid (Fig. 10-22).

Figure 10-22 Absence of fibular sesamoid. A, Anteroposterior radiograph of absent fibular sesamoid with bipartite medial sesamoid. B, Axial view. C, Magnetic resonance image demonstrating absent lateral sesamoid. D, Axial views demonstrating congenital absence of both fibular sesamoids. (B, From Yildirim Y, Saygi B: Congenital absence of the lateral sesamoid, J Am Podiatr Med Assoc 96:78–81, 2006. Used with permission. D, From Jahss MS, editor: Disorders of the foot and ankle: medical and surgical management, ed 2, Philadelphia, 1991, WB Saunders.)

Although absence of a sesamoid can be asymptomatic, removal of a sesamoid for painful plantar keratosis can cause postoperative pain beneath the remaining sesamoid. The absence of a tibial sesamoid can produce a clawing of the hallux or development of a progressive postoperative hallux valgus deformity (see Fig. 10-22D).^35,108

Jahss ⁴⁷ has reported that congenital absence of both sesamoids is extremely rare (Fig. 10-23DE). Wright¹⁰⁷ reported one case of bilateral absence of both sesamoids associated with hallux varus deformity, and Williams et al¹⁰⁶ reported a case of bilateral congenitl absence with associated metatarsalgia (Fig. 10-23A, B, and C).