Since the advent of magnetic resonance imaging (MRI) of acute skeletal injuries, some studies have focused on the detection of occult osseous injury, in which plain radiographic imaging is normal or equivocal.4,21 One MRI finding that has been investigated is that of the bone bruise,4 which has been defined by Mink and Deutsch11 as "a traumatically involved, geographic, and nonlinear area of signal loss involving the subcortical bone" detected on T1-weighted MR images. Attention has been focused mainly on traumatic lesions of bone and cartilage about the knee.21
A case of severe bruises to both calcaneal bones is reported. Pathogenesis, clinical course, and MR findings are discussed.
A 28-year-old man was admitted to the authors' hospital with pain in both heels, severe on the left, that occurred after jumping from a 2-m high wall the day before. On physical examination, no deformity or decreased range of motion of the ankle, subtalar, or metatarsal joints was found, but there was significant and painful swelling under both hindfeet. Weightbearing was not possible. Radiographs of both feet showed no evidence for a fracture. Bone scans showed high technetium uptake of both hindfeet (Fig 1). On T1-weighted MR scans, a signal loss of the plantar subcortical area of both tuber calcanei and the intermediate portion of the calcaneus was found (Fig 2). The signal loss was greater on the left. Corresponding T2-weighted images showed an increased signal in the same areas (Fig 3). A bone bruise in each calcaneus was diagnosed, and the patient was immobilized for 5 days using local and systemic antiinflammatory agents until swelling was reduced.
Within a week, the pain on the right side significantly decreased, and the patient started full weightbearing on the right and partial weightbearing with 15 kg on the left side. After 6 weeks, weightbearing was increased progressively until full weightbearing was achieved after 12 weeks, but crutches still were used for longer distances. Full recovery from pain was late in the fourth month after injury. Six months after trauma, new radiographs and MR scans were obtained. Plain radiographs were still normal, and T1-weighted MR scans showed complete resolution of the signal loss seen directly after trauma.
Attention was drawn to bone bruises through MRI of the knee in association with ligamentous injuries.1,5,8,10,11,14,16-19 In the patient reported here, bone bruises to both calcanei after axial overloading are discussed. To the authors' knowledge, only two cases with a similar location have been reported: Soudry and Mannting reported a unilateral bone bruise to the anterior portion of the calcaneus.15 However, in that case the patient could not recollect experiencing trauma, and pain was persistent for 6 months before bone and MR scans were obtained. Pinar et al13 reported a calcaneal bruise at the anteromedial portion concurrent with a complete rupture of the anterior talofibular and the calcaneofibular ligament.
Bone bruises are considered to be related to trauma.6,11,21 There is no unique mechanism of injury, but they seem to result from direct impact, axial overloading, and impingement.7,9,12 In the current case, axial overloading resulted in blunt trauma to the tubera calcanei. Bone bruises were suspected because radiographs showed no fracture in the cortical bone, and radionuclide bone scanning revealed high tracer uptake of both calcaneal bones. T1-weighted MR images showed the characteristic findings of a bone bruise, as defined by Mink and Deutsch.11 This pattern of MRI abnormalities has been interpreted as microfractures of weightbearing trabeculae.4,18
It has been suggested that location and MR signal intensity can give an indication as to the mechanism of injury and magnitude of the associated axial load.3,5,12,20 In the current case, it appears the moderate signal changes in the right calcaneus and severe changes in the left calcaneus confirmed by MRI are preliminary stages of the joint depression type and tongue type of calcaneal fracture after axial overloading.2 The location and tapering of the signal loss on T1-weighted images to the calcaneal sulcus correspond to the fracture lines in the fracture types mentioned.
Concurrent with the MR findings, pain was located more on the left side, lasting for almost 4 months, whereas resolution on the right side was early in the second week after trauma. The self-limiting and benign course of a bone bruise has been reported by other authors, and similar times for resolution of pain in the knee have been described.4,6,10,11,20,21 However, the intensity of pain leading to partial weightbearing for more than 3 months appears unusual. This may be related to the location of the bone bruise because the mechanism of trauma and loading during walking are similar.
The type of treatment remains a matter of controversy. Whereas Tervonen et al18 saw no need for immobilization, Fowler3 concluded that subcortical infraction is an important variable to consider. In joints, bone bruises are useful indirect signs by which to predict associated ligamentous and cartilage injuries.3,8,12,17,20 Vellet et al20 considered that microtrabecular fractures may heal early, but chondrolysis may occur because of disrupted perforating transcortical vessels. To avoid additional compression at these already weakened trabecular sites, it seems to be important to avoid weight-bearing for a certain time.7,20 Not only may chondrolysis and osteochondral sequelae occur, but trabecular microfracture also may progress to stress fracture and cortical macrofracture.7 As suggested by this case, the possibility of a preliminary state of cortical fracture has to be considered.
Followup MRI showed complete resolution 6 months after trauma. This is concomitant to the findings of other studies in which the medullary component in control MRI showed resolution or negative MRI between 6 weeks and 12 months after trauma.4,10,11,20,21
Bone bruises can occur in other sites than in the knee. They pose a potential risk for chondrolysis and stress fracture, and mobilization and weightbearing should be increased gradually.
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