Low and high risk stress fractures of the lower limb: multimodal imaging and diagnostic algorithm.

Transcription

1 Low and high risk stress fractures of the lower limb: multimodal imaging and diagnostic algorithm. Poster No.: C-0922 Congress: ECR 2017 Type: Educational Exhibit Authors: N. How Kit, L. FOURNIER, L. Florescu, J.-P. Pelage; Caen/FR Keywords: Musculoskeletal system, Bones, Extremities, Conventional radiography, MR, SPECT-CT, Diagnostic procedure, Athletic injuries DOI: /ecr2017/C-0922 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 29

2 Learning objectives To illustrate imaging features of stress fractures of the lower limb with conventional radiography, ultrasonography, CT scan, bone scan/spect-ct scan and MRI. To propose a multimodal imaging diagnostic algorithm for an early clinical management. Background Stress fractures result from an imbalance between the strength of the bone and the exerted constraints in the absence of traumatism or preexisting focal lesions. Common in military recruits and athletes, symptoms consist in progressive mechanical pain and stress fractures are often not initially diagnosed. There are two kinds of stress fractures which have strictly the same clinical and radiological presentation and the same topography: Insufficiency fractures: caused by normal or physiologic stresses upon a weakened bone Fatigue fractures: caused by abnormal stresses on a normal bone Predisposing factors of insufficiency fractures are osteoporotic bone (menstrual disturbance, immobilization, chronic steroid treatment, endocrine pathologies), renal failure, rheumatoid arthritis, radiotherapy, complex regional pain syndrome (type 1). Predisposing factors of fatigue fractures are bone morphological abnormalities and static pathologies of the lower limb. There is a relationship for athletes between the location of the stress fracture and the sport practiced (Table 1). Page 2 of 29

3 Lower limb Sports Femur (neck) Long-distance running, jumping, ballet Femur (shaft) Long-distance running Patella Running, hurdling Tibial (plateau) Running Tibial (shaft) Running, ballet Fibula Running, aerobic, ballet, race-walking Medial malleolus Basketball, running Calcaneus Running, long distance military marching, skydiving Talus Pole-vaulting Tarsal navicular bone Sprint, middle distance running, hurdling, long-jumping, triple jump, football Metatarsal bones Running, ballet, walking Base of the 2 nd metatarsal bone th Ballet Base of the 5 metatarsal bone Basketball, tennis, ballet Hallux sesamoids Running, ballet, basket ball Pelvis Running, ballet Table 1. Fatigue fractures - sports relationship Stress fractures can affect the functional prognosis of the lower limb depending on the risk of fracture. In fact, there are two types of fracture: low and high risk, depending on the location of the lesion on the bone, based on the prognosis, the treatment and the complication rate (Table 2). Low risk fractures will typically heal with rest, they will have a better prognosis and less complications. They usually happen on the compression side of the bone. High risk fractures will need heavier treatments than rest (discharge, casting, surgery) and they will have more complications (complete fracture, non-union), if not managed in time. They usually happen on the tension side of the bone. Page 3 of 29

4 Low risk High risk Tibia (postero-medial cortex) Tibia (anterior cortex) Fibula/lateral malleolus Medial malleolus Femur (shaft) Femur (neck) Calcaneus Tarsal navicular bone nd Metatarsal bones (2 th to 4 shafts) Pelvis Talus Base of the 2 nd rd and 3 metatarsal bones th Base of the 5 metatarsal bone Patella (transversal form) Hallux sesamoids Table 2. Low and high risk stress fractures of the lower limb Thus, an early imaging diagnosis is mandatory although there is currently no consensual multimodal imaging diagnostic algorithm. Findings and procedure details IMAGING OF STRESS FRACTURES 1) Conventional Radiography (CR): (Figure 1) Conventional radiography should be the first-choice investigation for the accessibility, the cost and for the differential diagnosis (bone tumors). Initial radiographs are usually normal and the first radiological abnormalities appear 15 to 21 days after the first symptoms. Thus, we should consider another imaging modality to make an early diagnosis after the first radiographs. We observe 3 forms of stress fractures: cortical form, cancellous form and mixed form Cortical form: thin cortical fracture line, gray cortex sign and the periosteal reaction Cancellous form: cancellous bone callus Page 4 of 29

5 Mixed form: both signs (cortical et cancellous) 2) Ultrasonography (US): (Figure 2) Ultrasound can do early diagnosis of stress fractures when initial radiographs are normal, mainly when the lesion is superficial and reachable with the probe (fibula, metatarsal th bones, base of the 5 metatarsal). In fact, we consider stress fractures when we have 2 of the 3 ultrasonographical signs listed below: Subperiosteal haematoma Cortical disruption Hyperemia in Doppler mode of the soft tissues around the fracture 3) Computed Tomography (CT): (Figure 3) Excellent imaging technique for complex anatomical location of bone stress fractures such as the pelvis and the sacrum. The radiological signs on CT is the same as CR with a better resolution to detect subtle cortical breaks or periosteal/endosteal reaction. 4) Bone scan/single Photon Emission Computed Tomography (SPECT) - CT: (Figure 4) Positive at the onset of symptoms, the tri-phasic uptake of stress fractures is nearly constant. Associated with the CT, this imaging modality increase in spatial resolution. 5) Magnetic Resonance Imaging (MRI): (Figure 5) MRI has a good sensitivity and specificity for the early detection of stress fractures, bone edema and associated soft tissue edema. It can also exclude other diagnosis such as bone tumors, tendonitis and osteomyelitis. Early signs are the fracture line (in low signal in T1-weighted images), periosteal edema and associated bone marrow edema (in high signal in T2-weighted images), which can give a pseudotumoral aspect in MRI. Bone edema can persist 6 months after treatment. The MRI Fredericson's classification optimizes the management of stress fractures: Page 5 of 29

6 Periosteal edema. No abnormality of bone marrow. Periosteal edema with bone marrow edema on T2-weighted images. Periosteal and marrow edema on T1 and T2-weighted images. Periosteal and marrow edema and visible fracture line LOW RISK STRESS FRACTURES (Table 2) 1) Tibia (postero-medial cortex): (Figure 6) It is the first location of stress fractures in long distance runners (25.9% to 49.1% overall) and the second location in the insufficiency fractures. It has a good prognosis and occurs on the compression side of the tibia (postero-medial cortex). Diagnosis on CR is often delayed and early diagnosis can be done with SPECT-CT, CT and MRI. 2) Fibula/lateral malleolus: (Figure 7) Much rarer than the tibial stress fracture, it has an incidence of 5.1% to 9.3%. Stress fracture of the fibula can happen all over the height of the bone but occurs mainly on the distal third in adults. Its mechanism is the muscular torsion or contraction but not the compression forces. 3) Femur (shaft): (Figure 8) Representing 1 to 7.2% of stress fractures, femoral stress fractures (low and high risk) are relatively rare. Every inch of the diaphysis may be affected, but it typically predominates in the proximal third of the medial side of the cortex where compression forces are applied. SPECT-CT or MRI are excellent imaging modalities when initial CR is considered as normal. 4) Calcaneus: (Figure 9) nd The calcaneus is the 2 most frequent site of stress fractures and is the first location concerning the tarsal bone (25.3%). Often bilateral, the cancellous form of the posterior tuberosity is easily diagnosed on CR but the signs are delayed. However, stress fracture Page 6 of 29

7 of the anterior tuberosity is rarer and more difficult to diagnose with CR and the investigation should be completed with SPECT-CT or MRI. nd 5) Metatarsal bones (2 th to 4 shafts): (Figure 10) It counts for 8.8% of all stress fractures and it affects mainly the diaphysis of the middle nd rd third and the neck of the 2 and 3 metatarsal. Initially negative on CR, US is a good alternative if the region of interest is accessible anatomically with the probe. Xrays realized 15 days after the initial CR usually give the diagnosis by highlighting the periosteal reaction and the fracture line. 6) Pelvis (sacrum, acetabulum, iliac, obturator): (Figure 11) Rare in athletes (1.6% to 7.1%), they are typically insufficiency fractures. Difficult to image on CR, SPECT-CT, CT and MRI are good tools to set the early diagnosis. HIGH RISK STRESS FRACTURES (Table 2) 1) Tibia (anterior cortex): (Figure 12) Representing only 4.6% of all stress fractures, it happens preferentially on the anterior cortex of the middle third of the tibia, when most of the tension forces are applied. This form is prone to more complications (non-union, complete fracture) because the anterior cortex is constantly subjected to the tensile stress of the muscles of the posterior compartment of the leg. Moreover, the anterior cortex is less vascularized than the rest of the cortical bone. A positive X-rays (dreaded black line sign) is complemented by CT and a negative Xrays by SPECT-CT or MRI to eliminate a shin splint. 2) Medial malleolus: (Figure 13) Rare and not frequent, it results from the repeated microtrauma of the talus on the medial malleolus during dorsal flexion and medial rotation of the ankle. The fracture line Page 7 of 29

8 originates at the tibial pilon - medial malleolus junction with an upward oblique vertical orientation. Often and initially not seen on CR, SPECT-CT or MRI are good tools for early diagnosis. 3) Femur (neck): (Figure 14) 2 mechanisms with the fracture line perpendicular to the neck: On the compression side of the femoral neck (medial side of the neck), with less complications and more frequent. On the tension side of the femoral neck (lateral side of the neck), with more complications (complete displaced fracture, non-union, aseptic necrosis of the femoral head) but less frequent. MRI is more sensitive to make the diagnosis and to exclude differential diagnosis such as complex regional pain syndrome type 1 and aseptic necrosis of the femoral head. 4) Tarsal navicular bone: (Figure 15) It occurs at the middle third of the bone, where maximum shear forces are exerted. The fracture line is sagittal to the bone and starts at its proximal dorsal face with an extension to its distal plantar face. The middle portion of the tarsal navicular bone is poorly vascularized due to the lateral and medial peripheral vascularization. This characteristic explains the high rate of complications encountered. The navicular bone is difficult to study on CR due to the oblique orientation of the bone. SPECT-CT and CT are good alternatives when stress fracture of the navicular is suspected. The CT shows typically the split target sign. 5) Talus: (Figure 16) Rare and non-frequent (4.4/10000), it affects usually the head and the postero-lateral parts of the body of the talus. X-rays are insufficient to make the diagnosis and MRI is better for early diagnosis. Page 8 of 29

9 6) Base of the 2 nd rd and 3 metatarsal bones: (Figure 17) nd rd Frequent and often misdiagnosed, it results from the locking of the base of the 2 and 3 metatarsals and the intermediate and lateral cuneiforms during extreme plantar flexion. This mechanism switches the center of gravity onwards the diaphysis and causes more charges at the base of the metatarsals. Anatomically, the tarsometatarsal region is poorly explored in CR because of the overlay of the cuneiforms and the proximal portions of the metatarsals. Thus, CT and MRI are better imaging tools to make early diagnosis in this situation. th 7) Base of the 5 metatarsal bone: (Figure 18) th Stress fractures of the base of the 5 metatarsal differ in all post traumatic forms. Indeed, three zones of fractures exist and are classified anatomically: Zone I: avulsion fracture of the styloid and the fracture of the tuberosity Zone II: fracture of Jones Zone III: proximal diaphyseal fracture (stress fracture) It is due to the repeated movement of equine varus placing the superficial plantar th aponeurosis in tension on the base of the 5 metatarsal. Zone II and zone III have nourishing vascularization and any interruption of their blood supply will create an avascular zone, explaining the high rate of non-unions. The combination of CR and US is a good compromise before considering more expensive techniques such as SPECT-CT or MRI. 8) Patella (transversal form): (Figure 19) Extremely rare (22 cases reported in the literature since the 60's), the transversal form results from the repeated stress of the tendons (patellar and quadricipital) on the patella depending on the flexion of the knee. The transverse patellar stress fracture can be Page 9 of 29

10 encountered over the entire height of the patella. It initially settles on its anterior aspect with a predominance in its distal third. CT is enough to make the diagnosis. 9) Sesamoids of hallux: (Figure 20) The hallux sesamoids are contained in the flexor hallucis tendon and belong to the plantar plate. They are articulated with the head of the first metatarsal by their upper articular facet and are covered by a thin layer of the flexor halluces tendon in their lower portion. Their function is to reduce the load on the head of the first metatarsal and to stabilize the first radius of the foot. They also increase the mechanical advantage of the short flexor of the hallux during plantar flexion. The main load during standing and walking is on the medial sesamoid, which explains that the medial sesamoid has a protective role of the plantar plate and the hallux. Thus, stress fractures of the sesamoids most often affect the medial sesamoid with a transverse fracture line as a result of the tension forces during dorsal flexion. Moreover, the vascularization of the sesamoids is poor and asymmetrical between the proximal pole and the distal pole of the bone, explaining the high rate of complications. Difficult to differentiate with a bipartite sesamoid (5% to 30% of the population) on CR, CT and SPECT-CT with sagittal reformatted images are superior to MRI for the diagnosis. MULTIMODAL IMAGING DIAGNOSTIC ALGORITHM With a perfect knowledge of the topography, the imaging modalities and imaging features of low and high risk stress fractures of the lower limb described above, we propose a multimodal imaging diagnostic algorithm for an early clinical management (Table 3). Page 10 of 29

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12 Table 3. Multimodal imaging diagnostic algorithm for an early clinical management of stress fractures of the lower limb. Images for this section: Fig. 1: A: cortical form ; B: cancellous form; C: mixed form Page 12 of 29

13 Fig. 2: X-rays considered as normal. Stress fracture on the ultrasound (subperiosteal haematoma, cortical disruption and hyperemia) Fig. 3: Stress fracture of the 2nd metatarsal shaft on CT Page 13 of 29

14 Fig. 4: Bone scan and SPECT-CT: right tibial stress fracture Fig. 5: MRI of sacral stress fracture (A: T1-weighted with the fracture line in low signal; B: bone edema in T2-weighted images) Page 14 of 29

15 Fig. 6: Tibial (postero-medial cortex) stress fracture (A: bone scan; B: CT; C, D, E: MRI) Fig. 7: Stress fracture of the fibula (A: bone scan and SPECT-CT; B: MRI; C: X-rays and ultrasound) Page 15 of 29

16 Fig. 8: MRI: left femoral stress fracture (shaft) Fig. 9: Calcaneus stress fracture (A, B, C: posterior tuberosity form on X-rays, CT and MRI respectively; D: anterior tuberosity on MRI) Page 16 of 29

17 Fig. 10: A: 3rd metatarsal stress fracture on Xrays; B; metatarsal neck stress fracture on MRI Fig. 11: Pelvic stress fractures: - A: bilateral sacral fractures (CT) - B: pubic ramus fracture (CT) - C: ischiatic ramus fracture (CT) - D: right sacral fracture (MRI) Page 17 of 29

18 Fig. 12: CT of axial stress fracture of tibial anterior cortex. Page 18 of 29

19 Fig. 13: Medial malleolus stress fractures (A: X-rays; B: CT) Jacques Rodineau, MD, PhD, Paris Page 19 of 29

20 Fig. 14: Right femoral neck stress fracture (X-rays and MRI) Page 20 of 29

21 Fig. 15: Right navicular stress fracture (CT, multiplanar reformat) Fig. 16: Talus head stress fracture (X-rays and MRI) Jacques Rodineau, MD, PhD, Paris Page 21 of 29

22 Fig. 17: Stress fracture of the base of the 2nd metatarsal (CT) Jacques Rodineau, MD, PhD, Paris Page 22 of 29

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24 Fig. 18: The 3 different zones of fracture of base of the 5th metatarsal fractures Fig. 19: Transversal stress fractures of the patella Jacques Rodineau, MD, PhD, Paris Page 24 of 29

25 Fig. 20: X-rays of sesamoids stress fractures (A: medial sesamoid; B: lateral sesamoid) Jacques Rodineau, MD, PhD, Paris Page 25 of 29

26 Conclusion A perfect knowledge of the topography and the imaging features of low and high risk stress fractures of the lower limb is required for an optimal imaging evaluation. The diagnostic algorithm may evolve with the improvement of imaging technologies. Personal information Nicolas How Kit, MD Department of Diagnostic Imaging and Interventional Radiology CHU de Caen, Normandie University UNICAEN, France, howkit-n@chu-caen.fr Luc Fournier, MD Department of Diagnostic Imaging and Interventional Radiology CHU de Caen, Normandie University UNICAEN, France, Liviu Florescu, MD Department of Diagnostic Imaging and Interventional Radiology CHU de Caen, Normandie University UNICAEN, France, Jean-Pierre Pelage, MD, PhD Department of Diagnostic Imaging and Interventional Radiology CHU de Caen, Normandie University UNICAEN, France, Page 26 of 29

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