Clinical diagnosis

Case 61

1. a, b, c Based on MRI findings and symptoms, he was diagnosed sesamoisitis and stress fracture of the sesamoid bone

【Treatment】
Our orthopedist advised him not to play handball but keep rest. He was treated by brace covering his right forefoot. He did not want non-steroidal anti-inflammatory drugs (NSAIDs).

【Progress】
Sesamoids (or sesamoid bones) are focal ossification areas within tendons as they pass over joints (1-3). The term of “sesamoid bone” seemed to be named as an alternative of a small bone or a round-shaped bone probably looking like a sesame seed. A sesamoid bone usually exists at the site of the joint and embedded in the tendon where it crosses over a joint (1-3). The largest sesamoid bone is a knee cap or patella. A hyoid bone does not belong to a sesamoid bone because it forms from cartilage and exists not relevant with a joint. The sesamoid bone is not present at birth. Ossification of the sesamoid bone of the thumb presents at the age of 10 to 12 (4).
Sesamoids bones act like fulcrum points of tendon and function such as pulleys. In short, a sesamoid bone makes the tendon or the ligament goes slightly further away from the joint, inducing to increase the smooth movement of the tendon and to inhibit the tendon from flattering into the joint as tension increases (Figs 3, 4). In case of the forefoot, sesamoid bones form the bump at the underside of the big toe (Figs 3, 4). The toe flexor muscle (flexor hacillus longus tendon) contacts sesamoid bone and pass underneath the first metacarpo-pharyngeal (MP) joint (Fig. 5). When this muscle bends the big toe, the sesamoid bone functions as a fulcrum point for the flexor muscle with gliding over MP joint, helps to absorb pressure from under the foot during standing and walking, and eases friction between MP joint and toe flexor muscle when the big toe moves (Figs 3 – 5).

Sesamoid pain is caused by sesamoiditis, stress fracture and traumatic fracture. Hyperextension of the big toe is the possible cause of sesamoid damage (5 – 7). Sesamoiditis of the inflamed soft tissue around sesamoid bones is caused by the repeated activity or the same toe movements over and over again such as running and dancing. Stress fracture is caused by strain of the soft tissue and often found in athletes due to repetitive load bearing activities such as running or dancing (Fig. 6). People with high arches in the feet are susceptible to sesamoiditis or stress fracture, inducing the MP joint of the big toe becomes rigid. Traumatic fracture is caused when a person fell down from the height place and the bumping of the big toe hit the ground.

In general, two sesamoid bones of fore foot usually exist: medial sesamoid bone and lateral sesamoid bone. Medial sesamoid bone sometimes is occasionally found to be two parts, which is called a bi-partite sesamoid bone – usually congenital or related to a history of trauma (8, 9) (Fig. 7). When a patient has a painful symptom on the big toe, it is hard to differentiate on radiograph between a bi-partite sesamoid bone and sesamoid bone fracture. MRI with fat depression T2 weighted image might be useful for differentiation between them (7 – 9). In our case, he was a hand-ball player and fat suppression T2 weighted images and T1 weighted images of MRI showed high signal intensity and low signal intensity respectively on the medial sesamoid bone, implying sesamoid bone injury, probably stress fracture.

As several conservative treatments for sesamoid bone fracture are listed (10); a stiff-soled shoe or a short leg-fracture brace; tape the joint to limit movements of the big toe; J-shaped pad or cushioning pad around the sesamoid area to relieve pressure: non-steroid anti-inflammatory drugs. It takes several months for the discomfort to subside. Surgical fixation or removal might be needed when sesamoid bone fractured into pieces, but orthopedists usually try to avoid both sesamoids out. In our case, he accepted to our offer of a short leg-fracture brace, although he refused to take NSAIDs.

【Summary】
We present a sixty nine-year-old male with stress fracture of right medial sesamoid bone which was visualized on fat-suppression T2WI and T1WI. He was an athlete of handball that long-standing and repeated weight loading to the big toe was considered to cause the sesamoid bone injury. We should keep in mind that sesamoid bones is present at the joint and is embedded in the tendon and act such as fulcrum points of tendon and pulleys for the purpose of the tendon going slightly further away from the joint, inducing to increase the movement of the tendon and to inhibit the tendon from flattering into the joint as tension increases, inducing the flexor muscle glides over MP joint smoothly and eases friction between MP joint and toe flexor muscle when the big toe moves.

【References】
1.Boike A, Schnirring Judge M, McMillin S. Sesamoid disorders of the first metatarsophalangeal joint. Clin Podiatry Med Surg. 2011;28(2):269–85. [PubMed]
2.Lee DK, Mulder GD, Schwartz AK. Hallux, sesamoid, and first metatarsal injuries. Clin Podiatry Med Surg. 2011;28(1):43–56. [PubMed]
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4.Chaumoître K, et al. Value of the sesamoid bone of the thumb in the determination of bone age J Radiol. 2008 Dec;89(12):1921-4.
5.Biedert R, Hintermann B. Stress fractures of the medial great toe sesamoids in athletes. Foot Ankle Int. 2003;24(2):137–41. [PubMed]
6.Parra E. Stress fractures of the sesamoid. Clin Orthop. 1960;18:281–85.
7.Kalantari BN, Seeger LL, Motamedi K, Chow K. Accessory ossicles and sesamoid bones: Spectrum of pathology and imaging evaluation. Appl Radiol. 2007;36(10):28-37. Appl Radiol (full text)
8.Dobas DC, Silver MD. The frequency of the bipartite sesamoids of the first metatarsophalangeal joint. J Am Podiatry Assoc. 1977;67(12):880–82. [PubMed]
9.Frankel J, Harrington J. Symptomatic bipartite sesamoids. J Foot Surg. 1990;29:318–23. [PubMed]
10.Blundell CM, Nicholson P, Blackney MW. Percutaneous screw fixation for fractures of the sesamoid bones of the hallux. J Bone Joint Surg Br. 2002;84(8):1138–41

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