Age / Sex : 25 / F

Chief complaint: Periodic right forefoot pain for 3 years

What is your impression?

Two weeks later, you can see the final diagnosis with a brief discussion of this case.

(답안은 한 개만 보내주시기 바랍니다)

Courtesy: 최자영 (Ja Young Choi), 서울대학교병원 (Seoul National University Hospital)

Osteonecrosis of the Medial Hallucal Sesamoid

Discussion

Findings: 1) heterogeneous sclerosis, multi-fragmentation, and mild collapse of the medial hallucal sesamoid on X-ray

         2) hypointense BM signal of the affected sesamoid with focal dark signal area

Differential Diagnosis: 1) Bipartite sesamoid

2) Sesamoid fracture

                      3) Sesamoiditis

Diagnosis:  Osteonecrosis (Avascular Necrosis) of the Medial Hallucal Sesamoid

Discussion:

1.     Clinical issues

A.     Sx

                         i.         Mechanical pain in the 1^st metatarsal upon weight bearing on the great toe and at the last phase of the walking cycle

                        ii.         Supination of the foot during walking

                       iii.         Pressure on the sesamoid and forced flexion of the great toe: reproduce pain

B.     Most common in adolescents or young adults

C.     F > M

D.     Lateral sesamoid is more vulnerable to AVN d/t greater loading

E.     Predisposing factors: microtrauma, sport activities such as track-and-filed and dancing, and foot alignment disorder (pes cavus and valgus of hindfoot)

2.     Imaging findings

A.     X-ray: changes can take up to 6 months following the initial onset of symptoms.

                         i.         Early fragmentation, irregularity, and cyst formation

                        ii.         Sclerosis, collapse, flattening, and enlargement of the bone

B.     Bone scan

                         i.         Acute: increased uptake d/t hyperemia in the surrounding tissue

                        ii.         Chronic: cold spot

C.     MRI: helpful for early diagnosis

                         i.         Hypointense BM on T1WI and T2WI

                        ii.         Normal BM signal on T1IW may rule out osteonecrosis.

3.     Treatment

A.     Elimination of weight bearing or use of a shoe insert

B.     Partial or total sesamodectomy

References:

1.     Toussirot E, Jeunet L, Michel F, Kantelip B, Wendling D. Avascular necrosis of the hallucal sesamoids update with reference to two case-reports. Joint Bone Spine 2003 Aug;70(4):307-9.

2.     Boike A, Schnirring-Judge M, McMillin S. Sesamoid disorders of the first metatarsophalangeal joint. Clin Podiatr Med Surg. 2011 Apr;28(2):269-85.