It has been speculated that 50 to 75 percent of weightbearing forces are transmitted through the first metatarsophalangeal joint (MTPJ) complex during weightbearing and these forces can account for up to three times one’s body weight.1,2 Anatomical location of the hallucal sesamoids predisposes them to significant shear, pressure and ground reactive forces during weightbearing activities. As a result, sesamoids are a site for potential injury. Sesamoid pathology is not uncommon in a typical podiatric sports medicine practice. In a study of 1,000 running injuries, the sesamoids were involved 12 times (1.2 percent incidence).3 Sesamoid injuries accounted for 12 percent (12/100) of great toe complex injuries and four percent of all foot and ankle injuries (12/300).3 Theoretically, the hallucal sesamoids protect the flexor hallucis longus during the push-off phase of gait, absorb shock, increase FHB lever action across the first MTPJ and elevate the first metatarsal to evenly distribute weightbearing forces to the lesser metatarsal heads. In two in vitro laboratory studies on hallucal sesamoid function, Aper, et. al., concluded the prime functions of the sesamoids are maintaining a constant FHL tendon leverage across the first MTPJ and allowing the FHB muscle to stabilize the hallux during stance for controlled and levered propulsion.4,5 Reviewing Potential Etiologies Direct and indirect macrotrauma as well as recurrent microtrauma can contribute to sesamoid pathology. Direct trauma includes contusions and crushing injuries. Indirect traumatic injury occurs with forced dorsiflexion. One may see this with or without hallux abduction with resulting sesamoid compression against the metatarsal head (i.e., “turf” toe). During toe off at maximal hallux dorsiflexion, the sesamoids are in their most distal position, moving up 1 cm from their proximal resting position. Being fixed in this distal position subjects the sesamoids to significant ground reactive and tendon forces. Given this position at toe-off, recurrent microtrauma has been implicated in sesamoid pathology and this likely represents most of the sesamoid injuries one would see in a sports medicine practice. Any sport or activity involving sudden starting and stopping with repetitive first MTPJ extension can predispose patients to sesamoid injuries. There are also certain foot types and conditions, such as excessively pronated or severe cavus feet, a plantarflexed and/or long first ray, ankle equinus deformities and bunion deformities with deviated sesamoids that can increase the risk for sesamoid disorders. What To Look For In The History And Physical Exam A complete history, thorough physical exam and timely diagnostic testing are required to differentiate sesamoid pathology from other great toe joint pathology. For the patient history, one should ascertain the duration of the problem, the mechanism of injury, aggravating factors (i.e., pain with propulsion), and any type or change in activity. One should also assess footwear, consider any sport-specific demands and obtain a summary of previous self- or professional treatment. A general, lower extremity physical examination and focal physical examination of the sesamoid apparatus should then be performed. This should include inspection, range of motion, muscle testing, direct palpation and provocative maneuvers. You must also evaluate the patient’s gait and inspect the patient’s footwear. For the gait evaluation, one should look for any asymmetry, antalgia or compensation. During the physical exam, these patients will commonly experience pain upon direct palpation of the involved sesamoid, pain with maximum hallux dorsiflexion, and have pain or a loss of strength when testing for hallux flexion. Hallux dorsiflexion is the most reproducible provocative maneuver as it involves stabilizing the sesamoid in its most distal position and then plantarflexing the hallux while maintaining pressure on the sesamoid.6 You may note edema, warmth, erythema, ecchymosis and crepitus but they are not specific for sesamoid dysfunction. Pertinent Insights On Diagnostic Testing At this point, the clinician should develop a broad differential diagnosis including potential sesamoid and non-sesamoid pathology (see “Differential Diagnosis Of Sesamoid Pathology” below). Diagnostic testing usually involves imaging studies including plain radiographs, triphasic bone scan, computed tomography (CT) and/or magnetic resonance imaging (MRI). Laboratory testing may include joint fluid analysis, CBC and/or serum uric acid. One can also consider differential local anesthetic injections including intraarticular first MTPJ, extraarticular peri-sesamoid injection, and selective nerve blocks of the first MTPJ complex. The differential local anesthetic injection is an excellent method for differentiating sesamoid pathology from other great toe joint complex pathology. When it comes to imaging, initial evaluation should include radiographs, consisting of AP, MO (fibular sesamoid visualization), LO (tibial sesamoid visualization), lateral and axial sesamoid views. When radiographs are negative or equivocal, and sesamoid pathology is suspected, the best screening test is a triphasic bone scan. Obtaining a three phase (12 to 24 delayed images) bone scan may be helpful. Sesamoid pathology will be hot on bone scan with few exceptions. Unfortunately, a positive bone scan does not necessarily mean there is pathology. Chisin, et al., found a 29 percent positive bone scan rate in physically active people and only one of 86 patients studied had sesamoid pain.7 Therefore, a positive bone scan without clinical correlation does not necessarily implicate sesamoid pathology. When there is pain, dysfunction and a positive bone scan, a CT scan is indicated. Computed tomography is excellent because it provides a more detailed assessment of pathology and can, along with the bone scan, shorten the amount of time between the appearance of symptoms and determination of a definitive diagnosis. An example of sesamoid pathology with a normal or equivocal bone scan is early avascular necrosis (AVN). A bone scan in this case could be normal or “cold.” When one has a high index of suspicion for sesamoid injury and the bone scan is normal, we recommend proceeding with an MRI, which is useful in elucidating AVN and other subtle pathology. While changes on MRI T1 and T2 sequencing can vary depending on the stage of the disease process, characteristic MRI changes of AVN are a decreased signal on T1 and an increased signal on T2 of the avascular area. Recommendations For Conservative Treatment Once a diagnosis is established, a treatment plan can be formulated including both medical and mechanical treatments. There are a variety of options when it comes to the initial treatment of sesamoid injuries. They include: avoidance of precipitating activity; icing; NSAIDs (which are more effective for acute, subacute or less chronic cases); offloading/immobilization; footwear modifications; corticosteroid injection; orthoses/accommodative padding; taping/strapping hallux into plantarflexion; and/or physical therapy. For sesamoiditis, modified activity is recommended until the patient is symptom-free. We emphasize an accommodative insole or orthosis, and a hiking shoe with a stiff, rocker sole. The initial orthosis we recommend is an over-the-counter arch support with a modified topcover. This includes a Vylite® dancer’s pad (sesamoid cut-out) with soft, plastazote backfill of the cutout area to offweight the involved area. Taping the hallux in a plantarflexed position can also be helpful during loading activities. When treating a sesamoid stress fracture, we recommend up to six weeks of nonweightbearing immobilization depending on the symptoms. We re-evaluate patients at two and four weeks. When they are symptom-free, patients can progress to protected weightbearing for two additional weeks. Once patients can walk without pain, we transition the patients into an athletic shoe and an accommodative orthosis as mentioned previously. Patients may progress to normal athletic activity as tolerable. We tell them to refrain from increasing their activity level until they can function at their current level without pain. For an occult fracture, we recommend six weeks of nonweightbearing immobilization followed by two to four weeks of protected weightbearing in a removable walking cast. When it comes to a progression to protected weightbearing, it is a clinical decision, but we rarely allow early protected weightbearing. When the patients are symptom-free after the aforementioned period of protected weightbearing, we transition them into normal shoes and activities as mentioned above. If a delayed or non-union becomes evident, one may consider bone stimulation. For cases involving chronic symptomatic AVN or arthritis, we recommend an aggressive trial of symptomatic treatment that includes: an initial period of physiologic rest with cast or SLW boot immobilization; a tapered 10-day course of an oral steroid, an injectable local/steroid into the involved area; and cessation of the inciting activity. This is followed by the aforementioned progression to an appropriate shoe and an accommodative orthosis. Unfortunately, we have found that prolonged conservative therapy is minimally effective in completely relieving symptoms and allowing athletes to return to their pre-injury level of activity. At this point, patients need to consider two options: live with the problem and avoid inciting athletic activities or consider surgical intervention. What About Nerve Entrapment Or Neuritis? One should also consider the possibility of entrapment or neuritis of the first proper digital plantar nerve coursing below tibial sesamoid and/or second proper digital plantar nerve coursing below fibular sesamoid. This is a common cause of sesamoid pain. Diagnostic imaging for this problem is negative with relief from a diagnostic injection being pathognomonic. Treatment of this condition involves accommodative padding, footwear modifications (i.e., shoes with a wider toe box) and neurontin (starting at 100 mg tid and titrating the dosage up to 400 mg tid to give relief. If the problem is well localized, one may administer two to four local/steroid injections with dexamethasone phosphate. If the patient fails conservative therapy, one can consider surgical intervention. Options include performing a sesamoid excision to decompress involved nerve branch. However, this is not recommended if both nerve branches (the tibial and fibular sesamoid region respectively) are affected. Another surgical option is the nerve excision, which one can consider as a last resort. With nerve excision, you must resect the involved nerve branch(s) well proximal to the first MTPJ in order to ensure the nerve “rests” in a nonweightbearing area. When One Must Consider Surgical Intervention Regardless of conservative treatment, sesamoid injuries can result in a “sick” sesamoid condition. The senior author has coined the term “sick” sesamoids to describe any chronic sesamoid condition that is unresponsive to conservative therapy and characterized by intractable pain and dysfunction. This term was developed to identify patients who are unlikely to respond to conservative treatment. These patients present with intractable sesamoid pain and the exact diagnosis in these cases becomes a moot point as further conservative treatment is usually futile and surgical intervention becomes the treatment of choice. The decision to consider surgical treatment depends on the patient’s symptoms, level of dysfunction and specific goals. There are a variety of procedures to choose from with no consensus on the best procedure. Surgical intervention in the acute setting is reserved for traumatic injuries or osteomyelitis. Sesamoidectomy is the most common surgical procedure but remains one of the most controversial. We reviewed 157 cases of sesamoidectomy and found little information as to the description of operative procedure, postoperative care, subjective/objective results and postoperative complications.8-29 Most long-term reports on sesamoidectomy are favorable. However, reported results are frequently anecdotal, and evidence-based support of the procedure is lacking, if not absent. Theoretically, complete excision of a sesamoid should weaken FHB and could weaken FHL as well. In two separate studies on partial versus total sesamoid excision and its effect on FHB and FHL moment arms, Aper, et. al., found only total excision of both sesamoids led to a decrease in the moment arm of FHB. They also found that total excision of fibular, tibial or both sesamoids significantly weakened FHL.4,5 Partial excision of either sesamoid resulted in no significant decrease in the moment arm of FHB or FHL.4,5 The authors concluded that when one performs a singular total sesamoid excision with tendon repair, all attachments of FHB to the joint capsule and ligaments remain intact. Therefore, one can preserve FHB function.4 The authors make no conclusion about what, if any, deformity could occur over time, but hallux hammertoe is possible with loss of FHB and weakening of FHL. In our experience, the sesamoidectomy is one of the best surgical procedures for alleviating symptoms of chronic sesamoid disorders. However, one must consider the possibility of specific complications related to this surgery (see “Common Complications Of Sesamoid Excision” below). Treating Sick Sesamoids: What We Recommend When addressing sick sesamoid conditions, we generally prefer a total excision as opposed to a partial excision. The partial sesamoid excision remains controversial. Our experience with partial excision is limited and indications would need to be very specific. Biedert and Hintermann relate good/excellent results in a limited number of patients (five patients, six feet), removing the proximal portion of tibial sesamoid for stress fracture.30 We feel it can be difficult to differentiate which fractured sesamoid fragment is responsible for symptoms but if clinical evaluation localizes the problem to one of the sesamoid fragments then one can consider a hemi-sesamoidectomy of the offending fragment. Partial excision may also require a patient to undergo a second surgery to remove the remaining fragment should symptoms persist and this facts needs to be underscored to the patient. We feel many complications associated with total sesamoid excision are the result of not preserving and not balancing vital soft tissue structures that envelop the sesamoids. This is probably due to the fact that traditional surgical approaches have not allowed adequate exposure to allow preservation of these structures. For example, in cases of tibial and fibular sesamoid excision without preservation of flexor hallucis brevis tendon slips, a predictable complication of hallux hammertoe will likely result, prompting many surgeons to perform a prophylactic interphalangeal joint arthrodesis procedure. In our experience, if one can preserve flexor hallucis brevis slips with a sesamoidectomy, hallux hammertoe should not occur. In cases involving isolated tibial or fibular sesamoidectomy, if one preserves the medial or lateral slips of flexor hallucis brevis respectively, complications will be unlikely. In cases of isolated tibial sesamoidectomy and low intermetatarsal angle (< 8 degrees), hallux abductus will be unlikely if one performs medial augmentation and lateral release of soft tissue structures. Medial augmentation would include plication of medial capsule and abductor hallucis. A lateral release would include an adductor hallucis and extensor hallucis brevis tenotomy, and possibly a lateral capsulotomy. When considering sesamoid excision, the primary issue of importance should be blood supply to the sesamoids. The sesamoids are well and equally vascularized, possessing a multifocal blood supply. Blood enters the sesamoids at the proximal and distal nonarticular surfaces with a majority of blood flow entering proximally.31 The proximal origin of the vessels which supply the hallucal sesamoids are the medial plantar artery (MPA) and plantar arch (PA) of the lateral plantar artery (LPA). The MPA and PA give rise to plantar hallucal arteries, the medial proper plantar artery (MPPA) and the first plantar metatarsal artery (FPMA). The MPPA supplies the tibial sesamoid and the FPMA supplies the fibular sesamoid.32 Researchers have identified three distinct patterns of vascularization.32 Type A vascularization, the most common pattern with a 52 percent incidence, occurs when plantar hallucal arteries take their origin equally from both MPA and PA. Type B vascularization, with a 24 percent incidence, occurs when plantar hallucal arteries arise from primarily PA. Type C vascularization, also with a 24 percent incidence, occurs when plantar hallucal arteries arise primarily from MPA. These findings imply that when excising a pathological sesamoid, if one does not perform the procedure through a well-vascularized soft tissue envelope, then inadvertent disruption of blood supply to the healthy sesamoid can occur. Based on the vascular study by Pretterkleiber, et. al., we recommend a medial-central longitudinal incision for a tibial sesamoidectomy and a plantar-central longitudinal incision (between sesamoids) for an isolated fibular or combined tibial and fibular sesamoidectomy.32 Other incisional approaches (i.e., dorsal, medial-plantar, and plantar-lateral incisions) may interrupt sesamoidal blood supply.32 Repairing the flexor hallucis brevis tendon slip(s) after sesamoid excision is highly recommended to limit potential complications.1,4,5,9,11,12,23,25,30,33-37 When an isolated tibial sesamoidectomy is indicated, we recommend using a medial-central longitudinal incision between the first dorsal and plantar digital proper nerves. Advantages of this approach include avoiding a plantar incision, good exposure, limited potential for first MTPJ contracture, the ability to preserve medial slip of FHB, and avoidance of plantar digital nerves, which one can easily identify and protect. This approach also faciltates good exposure for any medial soft tissue augmentation. Disadvantages of this incision are its proximity to the plantarmedial neurovascular bundle and the possibility of a painful scar that may become irritated by shoe pressure. Plantar forefoot incisions are the most controversial because they involve a weightbearing surface. Making a plantar-central longitudinal incision between sesamoids is recommended when it comes to excising an isolated fibular or both sesamoids. Advantages of this incision are better exposure, easier access to sesamoids, direct visualization of FHL tendon and avoidance of the neurovascular bundle. Disadvantages include the possibility of a hypertrophic scar, the need for postoperative nonweightbearing up to four weeks, and violation of plantar fat pad. The senior author has found that as long as incisions do not extend perpendicular to plantar MPJ crease, a painful hypertrophic scar is unlikely. In Conclusion Although sesamoid pathology in the athlete is common, correct evaluation, diagnosis, treatment and surgical approach remain enigmatic because of small patient samples, anecdotal evidence and a lack of consistent terminology. Clinicians must have a high index of suspicion for sick sesamoids when patients do not respond to long-term conservative therapy. There is much disagreement as to the best management of sesamoid pathology, both conservative and surgical. Surgical procedures and possible complications of these procedures, including biomechanical imbalances created by sesamoidectomy, continue to be a point of debate. With this article, we have provided a guideline for managing sesamoid pathology based on our clinical experience. Hopefully this article will stimulate further study and research which is sorely needed. Dr. Bouché is a Fellow of the American College of Foot And Ankle Surgeons, a Diplomate of the American Board of Podiatric Surgery and is a Past President of the American Academy of Podiatric Sports Medicine. He is a staff podiatrist at The Sports Medicine Clinic (at Northwest Hospital) in Seattle. Dr. Heit is an Associate of the American College of Foot And Ankle Surgeons. CE Exam #118 Choose the single best response to each question listed below. 1. The function of the hallucal sesamoids is to: a) Absorb shock. b) Increase the FHB lever arm. c) Protect the FHL during the push-off phase of gait. d) Elevate the first metatarsal head to evenly distribute weightbearing forces across the forefoot. e) All of the above 2. Which of the following statements most accurately represents the mechanism of hallucal sesamoid injuries? a) Hallucal sesamoid injuries are most commonly associated with long-distance running. b) Direct and indirect macrotrauma as well as recurrent microtrauma have all been implicated in sesamoid injuries. c) Patients with a pes cavus foot type have the highest incidence of hallucal sesamoid injuries. d) Athletes who excessively pronate do not develop hallucal sesamoid injuries because the pronated foot is better able to absorb shock. 3. The initial evaluation of the athlete who presents with medial plantar forefoot pain includes: a) Bone scan followed by an MRI and diagnostic injection. b) Developing a comprehensive differential diagnosis list including sesamoid and nonsesamoid pathology. c) Surgical extirpation of the sesamoid if it is tender to palpation. d) A careful history, general lower extremity exam, focal exam of the painful area, gait analysis and footwear evaluation. 4. The simplest and most reliable diagnostic test to differentiate sesamoid pain from nerve pain is: a) MRI b) Sesamoid axial X-ray c) Differential local anesthetic injection d) Range of motion testing of the first MTPJ 5. You have carefully evaluated an athlete who you feel has sustained a tibial sesamoid injury 48 hours prior to his or her visit. The initial X-rays show no definite pathology and the bone scan is normal. The next diagnostic test to order is: a) MRI b) CT scan c) Follow-up radiographs in two weeks d) No test needed because there is no sesamoid injury e) Diagnostic injection 6. Conservative therapy of a hallucal sesamoid injury may consist of all of the following except: a) NSAIDs b) Off- or unweighting the affected area c) Oral or injectable steroid d) Taping the hallux into plantarflexion e) Continuation of normal exercise routine 7. Which of the following statements about the blood supply to the hallucal sesamoids is true? a) The hallucal sesamoids are well and equally vascularized, possessing a multifocal blood supply. b) The hallucal sesamoids are primarily supplied by the medial plantar artery. c) If sesamoidectomy is not carried out through a well-vascularized soft-tissue envelope, inadvertent disruption of the blood supply to the healthy sesamoid may occur. d) All of the above e) a and c only 8. Advantages of the medial incision for tibial sesamoidectomy include all of the following except: a) Avoiding a plantar incision b) Good exposure c) No possibility of a painful scar d) Limited possibility for a first MTPJ contracture e) Ability to preserve the medial slip of the FHB 9. The major disadvantage to the plantar-central incisional approach is a) Proximity to the first plantar interspace nerve b) The need for lengthy nonweightbearing to prevent hypertrophic scar and to recover from violation of the plantar fat pad c) Inability to visualize the FHL d) Limited surgical exposure of the hallucal sesamoids Instructions for Submitting Exams Fill out the postage-paid card that appears on the following page or log on to www.podiatrytoday.com and respond electronically. Within 60 days, you will be advised that you have passed or failed the exam. A score of 70 percent or above will comprise a passing grade. A certificate will be awarded to participants who successfully complete the exam. Responses will be accepted up to 12 months from the publication date.
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