Age / Sex : 69 / F

Age / Sex : 19/ female

Chief complaint : Right thigh pain for 1 month

adductor insertion avulsion syndrome(thigh splint)

Discussion

Findings:

 Periosteal new bone in the medial aspect of the femur, as shown on a plain radiograph (A) of right femur, corresponds in location to the tendinous insertion of the adductor longus muscle. This area of periostitis is also seen on a transverse CT scan (B). Coronal fat suppressed T2-weighted MR image (C) reveals high signal intensity along periosteum of proximal to mid femur with associated medullary signal intensity abnormality. Contrast enhanced axial T1-weighted image with fat-suppression (D) shows periosteal signal intensity abnormality. Anteroposterior radiograph of right femur (E) obtained one month after MR examination shows mild cortical thickening along medial femoral shaft at site of prior MR imaging abnormalities.

Differential Diagnosis: Benign periosteal bone tumor, Osteomyelitis

Diagnosis: Stress avulsion fracture at insertion site of adductor muscle

Discussion:

 Osseous fatigue injuries are common and result from increased or unaccustomed activities leading to abnormal stresses on a bone. A different type of stress injury is thought to be related to repetitive avulsive stresses at tendinous insertion on a bone, leading to a traction periostitis at these sites. Stress-related injury occurring in the anteromedial portion of the cortex in the upper or middle region of the femur, corresponding in location to the insertion site or sites of one or more adductor muscle groups, has been designated a thigh splint, also known as adductor insertion avulsion syndrome. Thigh splint has been described in the proximal to mid femur. These patients present with activity-related groin pain that is relieved with rest. Findings on physical examination include increased adductor tone and tenderness over the adductor muscles, as well as severe pain with active resistance to hip adduction and external rotation. Radiographs may show periosteal reaction along the proximal third of the medial femoral shaft near the insertions of the adductor brevis and longus muscles. MR imaging of patients presenting with acute thigh splints shows a spectrum of findings ranging from periosteal edema or fluid to abnormal signal intensity in the medullary cavity or cortex, which correspond to stress reactions and stress fractures, respectively. The abnormal signal intensity in the underlying marrow is compatible with an area of stress reaction rather than a traction periostitis, and the cortical signal abnormality seen in two patients is consistent with a developing stress fracture. The differential diagnosis for this MR appearance includes tumor and osteomyelitis. However, the absence of an abnormal signal intensity in the medullary cavity in many cases, especially on T1-weighted images, and the absence of a soft-tissue mass, argue against these entities.

References:

1.  Resnick D, Kang HS, Pretterklieber ML. Traumatic disorder of bone. In: Resnick D, ed. Internal derangements of joints. 2^nd ed. Philadelphia, Pa: Saunders Elsevier, 2007;259-370