How To Address Sesamoidsin Hallux Valgus Surgery

The surgical correction of hallux valgus (aka bunion) is one of the most common operations a foot and ankle surgeon will face. With over 130 procedures described to date, no one procedure has proven to be the definitive solution for every bunion situation. However, the common denominators for success remain osseous realignment and soft tissue balancing. The location of the sesamoid complex in relationship to the first metatarsal plays an integral part in determining whether one has achieved this realignment and balancing act.

The exact etiology of hallux valgus still remains rather controversial. Research has determined that both intrinsic and extrinsic factors have been implicated in the development of bunions. Intrinsic etiologies may include pes plano valgus, hypermobility, metatarsus primus varus, rheumatoid arthritis, collagen and neuromuscular disorders as well as hereditary predispositions. Coughlin and Roger reported the presence of hallux valgus in 29 of 31 mothers (94 percent) whose children were also affected.1 A similar study by Hardy and Clapham found that 57 of 91 patients (63 percent) in their series had a parent with hallux valgus.2

Although pronation, heredity and other intrinsic factors play a key role in the development of hallux valgus, extrinsic factors such as shoegear may prove to be equally as important. Hallux valgus has proven to occur predominantly in shoe-wearing populations. Fashionable footwear worn by many women is more constraining than those worn by men and many authors feel these shoes are a leading factor behind hallux valgus development. This may explain the 4:1 ratio of females to males who present with bunion deformities. Coughlin and Thompson reported a higher incidence of hallux valgus in females between their 30s and 50s. They suggested that constricting footwear was the causative agent.3

Likewise, Sim-Fook and Hodgson found a 33.9 percent incidence of hallux valgus among shoe-wearing populations in comparison to a 1.9 percent incidence in non-shoe-wearing populations.4 However, when it comes to juvenile hallux valgus, researchers showed that constricting footwear played a leading role in hallux valgus development in only 24 percent of the patients they evaluated.5

A combination of intrinsic and extrinsic factors is probably the most logical explanation of hallux valgus development. The combination ultimately leads to a progressive deformity with an increase in the first intermetatarsal angle (IM) and lateral deviation of the hallux. As the deformity progresses, soft tissue imbalance perpetuates the hallux valgus development, creating a retrograde buckling effect at the level of the metatarsophalangeal joint. Incidentally, as the metatarsal shifts medially, the sesamoid complex becomes degenerative as these structures are subluxed from their respective grooves formed by the plantar crista.

This “lateral transposition” of the sesamoid complex renders a distinct mechanical advantage, lending itself to be one of the primary deforming forces in hallux valgus development. It is important to realize that this subluxation process is the direct effect of the medial migration of the first metatarsal rather than movement by the sesamoids themselves. This concept is particularly important when it comes to addressing the hallux valgus via surgical intervention.

Keys To Evaluating Hallux Valgus Deformities
Accurate evaluation of the hallux valgus deformity prior to surgery helps to ensure proper procedure selection for the best possible outcome. Physicians should utilize clinical and radiographic parameters in this decision process. Clinically, it is critical to evaluate the patient in a weightbearing and non-weightbearing manner. Often, the hallux valgus deformity will be accentuated by the faulty mechanics one possesses upon weightbearing. Notably, the treating physician should observe the hallux position, apparent intermetatarsal angle and the presence of EHL contracture.6 An increase in the hallux valgus angle and splaying of the metatarsals may indicate a higher degree of hypermobility than the physician would previously see in a non-weightbearing exam.6

One should assess the patient’s range of motion at the first metatarsophalangeal joint (MPJ) during the non-weightbearing portion of the clinical exam. This exam should determine the maximum amount of dorsiflexion, plantarflexion and quality of motion available. The physician should also evaluate the axis of motion concomitantly. This is helpful in determining joint structure and adaptations.6 Reducibility of the deformity in the transverse plane may prove helpful in determining the level of correction needed. By coupling these findings with the first ray range of motion exam, the surgeon can evaluate the degree of hypermobility involved.

The radiographic evaluation should consist of weightbearing dorsoplantar (DP), lateral (LAT) and plantar axial projections (tangential view) of the foot. One should also pay attention to bone quality, angular relationships, metatarsal lengths as well as the sesamoid position. Successful correction of the hallux valgus deformity is often depicted as improvement in the radiographic parameters such as the intermetatarsal angle, hallux valgus angle and realignment of the sesamoid apparatus.7

Assessing The Impact Of The Sesamoid Apparatus On Hallux Valgus Development
The position and function of the sesamoid apparatus in its relationship to hallux valgus development has long been debated. The phrase “lateral shift of the sesamoids” is often heard when it comes to the development of hallux valgus and many believe it is one of the primary etiologies of hallux valgus. Indeed, surgeons often perform lateral sesamoid releases to ensure relocation of the sesamoid apparatus “back under” the first metatarsal during the surgical correction of this deformity.

In regard to evaluating the sesamoid position, physicians often use standard DP radiographs. However, recent research has now indicated that one should utilize plantar axial projections (tangential view) over standard DP radiographs when evaluating the sesamoid position.8,9,10 Utilizing the tangential sesamoidal view, Kuwano, et al., looked at 54 feet in 29 patients with hallux valgus and 64 feet in 32 normal individuals. The authors concluded that using a 45-degree tangential view of the sesamoid rotation angle provides better assessment of the position of the sesamoids on the four-grade system and seven-point scale than the standard DP radiographs.8

However, the position of the hallux is important when it comes to the accuracy of this evaluation. With this particular view, various degrees of dorsiflexion will alter consistency and position of the sesamoids. Yildirim, et al., utilized computed tomography (CT) to assess the sesamoid position with the hallux in 0, 35 and 70 degrees of dorsiflexion. Their results showed that approximation of the sesamoids to reduction was apparent as dorsiflexion of the hallux increased. When obtaining tangential views, different degrees of hallux dorsiflexion modulate the position of the sesamoids and may lead to misclassifications or grading, according to the study authors.9

Hass described a seven-position rating system for lateral displacement of the sesamoid apparatus based on the tibial sesamoid position.11 A 4 or greater position of the tibial sesamoid classically indicated the need for removal of the fibular sesamoid. Similarly, orthopedic literature describes sesamoid position based on a four-grade system rather than the seven-position system previously described by Hass. However, both systems depend on the longitudinal bisection of the first metatarsal as the reference point for the tibial sesamoid. Yet the need for sesamoid excision has decreased over the years as surgeons are placing more emphasis on lateral releases and osteotomies. Now research has surgeons beginning to question the importance of the lateral releases and their relationship to sesamoid position as it relates to hallux valgus surgery.7,12,13

The question arises as to whether lateral release of the sesamoid apparatus plays any role in the correction of hallux valgus surgery. Although the majority of foot and ankle surgeons today perform the release as an adjunctive procedure to their operation, the release itself probably plays a smaller role than its osseous counterpart. The assumption comes from basic anatomy and research demonstrated by Judge, et al., who evaluated 75 feet that underwent hallux valgus surgery. The authors found no change in the tibial sesamoid-second metatarsal distance when they compared preoperative views and postoperative results. The study authors concluded that the correction in sesamoid position gained with hallux valgus surgery is a direct result of lateral transposition of the metatarsal head with no change in the position of the sesamoid apparatus relative to the foot.7

Similar findings were found by Esemenli, Yildirim and Bezer, who evaluated 30 feet with hallux valgus with grade 2 or 3 sesamoid positions on AP radiographs. They performed distal metaphyseal osteotomies for all 30 corrections with no lateral releases. At 12 months, 20 (67 percent) of the corrections showed sesamoid reduction with only 10 (33 percent) patients having no correction postoperatively. The study authors concluded that sesamoid release is redundant for metatarsosesamoidal reduction if one achieves adequate lateral shift of the first metatarsal head over the sesamoid.12

Rethinking The Role Of Lateral Releases In Sesamoid Reduction
If lateral releases play such a little role in sesamoid position, then why is it foot and ankle surgeons continue to place such emphasis on the lateral releases as part of their correction? It may be best understood if one has a strong grasp of the systematic approach to a lateral release and what structures contribute to the deforming forces.

Historically, releasing the plantar-lateral periarticular structures begins with identifying and sectioning the deep transverse ligament. One would follow this with an arthrotomy of the lateral MPJ capsule with concomitant release of the conjoined tendon of the oblique and transverse heads of the adductor hallucis tendon at the proximal phalanx insertion. Evaluation of hallux range of motion at the MPJ before and after the release of the adductor tendon will give the surgeon a good indication of how the contracture influences joint function.

With longstanding deformities, surgeons typically incise the fibular sesamoidal ligament and lateral collateral ligaments, completely freeing them from any sesamoidal attachments. Some believe this release is critical for relocating the sesamoids back underneath the first metatarsal head as these structures often become contracted in longstanding deformities and prevent such displacement. If a significant contracture remains, one should release the short flexor and extensor tendon as well as the plicae that attaches the proximal surface of the sesamoid apparatus to the inferior surface of the neck of the metatarsal and joint capsule. In certain circumstances in which the sesamoids are bound down to the undersurface of the metatarsal due to arthrosis, the surgeon may use an elevator to break these adhesions.

Based on recent literature and experience, I feel surgeons can modify the lateral release and, in some cases, avoid it altogether. The release of the deep transverse ligament as well the lateral collateral sesamoidal ligaments seem to be less critical in the relocation of the sesamoid apparatus and can often be omitted. However, the lateral arthrotomy and adductor tendon release appear to have a greater influence than the aforementioned soft tissue releases on the deformity, and will typically show a more favorable benefit in the osseous portion of the surgery.

The osteotomy has the greatest influence of all. Whether one utilizes a distal metaphyseal osteotomy or basilar procedure, the surgeon should base the osseous correction on the clinical and radiographic findings, and should address all the critical angles of the deformity.

A Closer Look At The Pros And Cons Of The Fibular Sesamoidectomy
McBride and DuVries popularized the excision of the fibular sesamoid and its benefit in correcting hallux valgus deformities.14,15 Surgeons have long utilized this procedure. McBride and DuVries both understood the importance of sesamoids and their relationship to bunion development as well as their contribution to reoccurrences following a simple bunionectomy. Although one may enhance the reduction of a bunion by excising the fibular sesamoid, particularly in longstanding deformities in which arthrosis of the sesamoid complex has developed, the procedure does have the potential for complications.

The complication of hallux varus following a fibular sesamoidectomy has been well documented.16,17 Likewise, hallux valgus may be accentuated in the likelihood that the surgeon removes the tibial sesamoid as one might see in the treatment of recalcitrant sesamoidal fractures and intractable plantar keratomas. However, employing meticulous dissection and a systematic approach to the lateral release has significantly reduced the risk of complications. With more surgeons relying on the osteotomy and realignment of the first metatarsal as the primary corrective measure in hallux valgus surgery, there is less need for the fibular sesamoidectomy.

However, in severe cases, such as a neglected geriatric bunion with an IM angle approaching 20 degrees and a degenerative sesamoid complex, excision of the fibular sesamoid may seem appropriate. Surgeons often use this procedure when the individual is not a perfect candidate for a more aggressive non-weightbearing base wedge osteotomy or a Lapidus type of bunionectomy, and are looking to perform a less invasive form of correction such as a Keller or a distal metaphyseal osteotomy.

I suggest performing a fibular sesamoidectomy if hypertrophic changes have occurred and significant arthrosis of the sesamoid complex has prevented adequate reduction during a bunionectomy. One may also use this procedure if the surgeon is implementing a joint destructive procedure and must address a large hallux valgus angle with this procedure.

The relationship between the sesamoid apparatus and hallux valgus surgery is of particular value when it comes to assessing correction and the possibility of recurrence. The incidence of recurrence has proven to be higher when there is a failure to relocate the first metatarsal head back over the sesamoid complex. One typically sees this when a surgeon has attempted a distal metaphyseal osteotomy to reduce a large IM angle. Furthermore, soft tissue balancing procedures, such as capsular reefing, capsulotomies and tendon transfers, without proper osseous realignment have typically proven to fail with time.

A Pertinent Review Of Two Case Studies
The following are case studies of patients who have undergone surgery for hallux valgus correction. These cases serve as examples of how proper and improper use of osseous realignment and soft tissue balancing can affect a desirable long-term correction. The position of the sesamoid apparatus in relation to the first metatarsal head helps determine if one has achieved realignment and soft tissue balancing.

A 51-year-old female presents with a painful bunion deformity that she has had for over two years. Preoperatively, the patient has a 14-degree intermetatarsal angle (IM) with an approximate 28-degree hallux valgus angle (HAV). She has a #5 sesamoid position as per the Hass classification.

We performed a long dorsal arm Chevron distal metaphyseal osteotomy with standard sequential lateral release. Postoperative radiographs at seven months revealed a reduction in the IM and HAV angle to 7 and 8 degrees respectively. We had reduced the sesamoid apparatus to approximately a #1 position.

In another case, a 48-year-old male presents with a painful bunion deformity greater than three years in duration. Preoperative radiographs reveal a 15-degree IM angle with a 35-degree HAV angle. He has a #6 sesamoid position.

We performed a long dorsal arm Chevron distal metaphyseal osteotomy with standard sequential lateral release. Postoperatively, the patient had an 11-degree IM angle and a 23-degree HAV angle. There was little change with the sesamoid apparatus as the surgery reduced it to a #4 position.

The case studies demonstrated two different patients with moderately severe hallux valgus deformities. Although both patients underwent the exact same procedure, the outcomes varied greatly. One can extrapolate from these two examples the importance of osseous realignment and sesamoid position in the correction of hallux valgus deformities. As the IM angle increases, so does the tibial sesamoid position. This places greater demand on the importance of osseous realignment for adequate reduction.

Retrospectively, one may criticize the use of a distal metaphyseal osteotomy with the second patient. Surgeons may feel a basilar procedure may have been more appropriate given the larger IM angle. One may have also suggested that adding a fibular sesamoidectomy may have allowed for better reduction of the deformity as well. Regardless of the procedure selection, the reduction of the sesamoid apparatus should be a primary focus for osseous realignment, an important factor that the author failed to achieve.

Final Notes
Foot and ankle surgeons correcting hallux valgus have long appreciated the effect sesamoids have on the reduction of this deformity. The advent of the sesamoidectomy and lateral release has continued to remain popular among adjunctive procedures in hallux valgus correction. Despite this popularity, recent research has placed a greater emphasis on osseous realignment, making the lateral release debatable. Nonetheless, the reduction of the sesamoid apparatus plays an integral part in determining whether one can achieve this osseous realignment and soft tissue balancing.

References:

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