Stress-Induced Spiculated Periosteal Reaction Appearing as a Malignant Bone Tumor: A Case Report

Case Report 

A 54-year-old woman had experienced left ankle pain for 1 year. The initial event was described as a mild inversion sprain. The patient did not notice significant pain immediately after the injury. Four months later, the pain gradually worsened, and she presented to her primary care physician for evaluation. Radiographs taken at that time were negative. Several months later, she presented to a chiropractic physician for treatment. The pain was localized to the medial side of the ankle. Physical examination showed pronation of the left foot. The patient had undergone treatment of breast carcinoma 5 years earlier. Radiography of the ankle was again performed and revealed a spiculated periosteal reaction of the distal metadiaphyseal region of the fibula (Fig 1). A solid periosteal reaction with slight undulation was seen on the tibia. The remainder of the radiographic examination was unremarkable. A history of breast carcinoma and the spiculated appearance of the periosteal reaction on the fibula warranted suspicion of metastasis or another aggressive process, such as osteomyelitis.

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Fig 1. The AP radiograph of the ankle (A) shows a spiculated periosteal reaction on the medial margin of the metadiaphyseal region of the distal fibula (arrows). Close-up view showing the spiculation and irregularity of the periosteum (B).

A delayed whole body bone scan revealed radiotracer accumulation surrounding the left ankle, including the distal fibula. The anterior surface of the left tibia showed a nonfocal distribution of accumulation. There were no sites of increased activity elsewhere in the skeleton. The increased accumulation of radioisotope was attributed to prior trauma and altered use of the tibia by the interpreting radiologist. The radionuclide study was consistent with stress reaction and enthesopathy; however, metastatic disease was not fully excluded.

An MRI of the left ankle was ordered and showed normal marrow signal intensity throughout the examination, with no evidence of skeletal metastasis. Gadolinium contrast administration revealed mild enhancement along the insertion of the interosseous membrane (IOM) at the distal fibula (Fig 2). A partial tear and tenosynovitis of the posterior tibial tendon (PTT) were discovered incidentally (Fig 3). The periosteal abnormality was felt to represent a benign, stress-induced lesion of the periosteum related to the IOM.

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Fig 2. A T1-weighted gadolinium-enhanced axial magnetic resonance image through the distal leg (A) shows enhancement of the periosteum (arrow) at the insertion of the IOM. T2-weighted magnetic resonance axial image (B) shows high signal intensity in the same location, which is indicative of inflammation. The bone marrow and cortex are uninvolved.

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Fig 3. Proton-density transverse magnetic resonance image through the level of the talus (A) shows inhomogeneous signal intensity (arrowhead) in the PTT, which is indicative of tendinopathy. Also noted was an increase in fluid in the tendon sheath (arrow), which is indicative of tenosynovitis. T2-weighted transverse magnetic resonance image through the level of the talus (B) shows high signal intensity within the PTT (arrowhead), which is suggestive of a partial tear. An excessive amount of high signal intensity fluid is also observed within the tendon sheath surrounding the PTT indicating tenosynovitis.

After serious pathology was ruled out, the patient was subsequently treated with interferential electrotherapy and therapeutic ultrasound. Long axis traction of the ankle was performed. Orthotics were suggested to correct the pronation of the foot, but the patient did not comply with the recommendation. Because of unforeseen personal circumstances, the patient discontinued care.

Discussion 

Periosteal reactions are important radiographic signs in characterizing lesions of bone. There are 4 basic types of periosteal reactions: solid, lamellated, spiculated (sunburst), and Codman triangle. Solid periosteal reactions are usually associated with benign processes. The remaining types are usually associated with more aggressive processes. Spiculated (or sunburst) periosteal reactions are predominantly caused by aggressive lesions. Common causes of a spiculated reaction include osteosarcoma, Ewing sarcoma, metastasis,4 and infection. Rarely, spiculated periosteal reactions can be caused by trauma or stress.5, 6 A more detailed discussion on periosteal reactions is provided by the review article by Wenaden et al.7

The MRI exam revealed no evidence of metastatic disease. Metastasis causes edema within the medullary space of bone. No such findings were present in this case. We hypothesize that the spiculated periosteal reaction in this case was caused by repetitive stress on the distal fibula by the IOM. It was incidentally discovered that the patient had a partial tear and tenosynovitis of the PTT. Weight bearing was altered in the left lower extremity as a result. This may have caused abnormal stress on the fibula and IOM, which resulted in the spiculated periostitis. Because of the insertion of the IOM on the fibular periosteum, the periostitis took on a spiculated appearance rather than the typical solid appearance. In this case, the pattern of periosteal reaction is similar to the orientation of the fibers of the IOM as they insert on the fibula.

The source of the abnormal stresses on the IOM and the fibula may have been the pronation of the foot and altered weight bearing due to the partial tear of the PTT. The fibula is thought to carry as much as 15% of the load upon the leg.8 The IOM primarily acts as a means to transfer loads from the tibia to fibula and also to resist bowing forces on the fibula and tibia.9 Altered position of the ankle and subtalar joints affects how the weight is transferred through the IOM. Two cases of stress-induced spiculated periosteal reaction have been published.5, 6 In both cases, the lesions were in the ulna and were due to repetitive stresses caused by sports participation. In one case, the spiculated reaction occurred along with evidence of radioulnar IOM stress injury.5 The authors hypothesized that pulling forces of the IOM may have contributed to the spiculated reaction on the ulna.

In addition, PTT tears are not uncommon in this patient population.10 Injuries to the PTT are most frequently seen in females around the fifth to sixth decade. Most tears occur at the musculotendinous junction, approximately 6 cm proximal to its insertion on the tarsal navicular.

Imaging of stress injuries in bone is largely performed by radionuclide scintigraphy and MRI. Scintigraphy has a sensitivity approaching 100% for bone stress injuries.11 False-negative diagnoses have been reported. Increased uptake in a regional or large distribution typically indicates a stress lesion. Asymptomatic stress injuries can also be detected, appearing as clusters of increased uptake.11 The scintigraphic findings must be correlated with the clinical presentation. Metastasis or other lesions of bone, such as osteomyelitis and primary bone tumors, can have a similar appearance on scintigraphy. In some cases, other imaging modalities, such as MRI, are necessary to make an accurate diagnosis.

Magnetic resonance imaging has equal, if not better, sensitivity than radionuclide imaging for bone stress injuries.12 MRI is also more specific than scintigraphy.13 Information about the surrounding soft tissues is obtained in addition to the changes seen in bone. The pulse sequences that best show stress injuries in bone are T2 and short tau inversion recovery techniques.14 High signal areas in cortical bone, periosteum, and bone marrow typically indicate edema. If radiographs are negative and scintigraphy is positive, MRI can provide useful additional information.15 Advantages over 3-phase bone scintigraphy include lack of ionizing radiation and less imaging time.16 As with any diagnostic procedure, there is never 100% sensitivity. Compared with other modalities, such as computed tomography and skeletal scintigraphy, MRI imaging has a high sensitivity for detection of osseous metastasis. The lack of marrow involvement on the MRI and the pattern of uptake on the radionuclide images speak toward a benign etiology.

A radiographic appearance similar to the case presented is seen in acute traumatic injuries to the IOM of the leg. These syndesmosis sprains are uncommon and require a longer recovery period than typical ankle sprains.17, 18 Calcification and ossification of the IOM often follow these sprains and can become symptomatic.19 This ossification can have the appearance of a periosteal reaction along the margins of the distal tibia and fibula.

Conclusion 

Periosteal reactions can be caused by many pathological processes. Stress injury commonly causes a solid periosteal reaction. In rare instances, a spiculated periosteal reaction can be elicited, and advanced imaging should follow. The stress-induced response can mimic a more aggressive process and complicate the diagnostic process. Scintigraphy and MRI are very sensitive in the detection of stress injury. MRI is more specific than scintigraphy and may provide valuable additional information as occurred in this case.