Chealon Miller, HMS IV Gillian Lieberman, MD. November Stress Fractures. Chealon Miller, Harvard Medical School Year IV Gillian Lieberman, MD

Transcription

1 November 2005 Stress Fractures Chealon Miller, Harvard Medical School Year IV

2 Our Patient G.F. 29 year old female runner c/o left shin pain and swelling Evaluated at OSH with MRI showing a mass Referred to BIDMC for further evaluation 2

3 Initial Referral Workup History and Physical Exam Plain Radiograph 3

4 History & Physical Exam PMH/PSH: Right ACL allograft repair Medications: OCP, Bactrim, Ciprofloxacin Allergies: PCN Angioedema Physical Exam: Patient has FROM; TTP at proximal tibia; neurovascularly intact; no palpable mass felt at left leg 4

5 After the initial physical exam, a plain radiograph was obtained 5

6 Plain Radiograph* Findings: No evidence of fracture line Indistinctness of the outer periosteum Impression: Possible subtle stress fracture at the medial cortical surface of the tibia at point of tenderness Recommendation: Bone scan if needed 6 * Radiograph not available on PACS

7 Let s Review the Anatomy of Long Bone and The Lower Extremity 7

8 Anatomy of Long Bone 8 pharyngula.org/ index/weblog/2003/11

9 Anatomy of Lower Extremity anatomy.uams.edu/.../ xrays/xra_atlas42.html 9

10 Menu of Tests for Stress Fractures Plain Film MRI Nuclear Imaging 10

11 Let s review the characteristics of various tests and look at them in different patients with stress fractures 11

12 Stress Fracture Imaging: Plain Film Advantages: inexpensive first modality used in the evaluation of a possible fracture Disadvantage: may not demonstrate nondisplaced fractures and microfractures Appearance: dark streak within the bone 12

13 Companion Patient One-Plain Film of Stress Fracture injuries/shin_&_calf/... Arrows indicate fracture line 13

14 Stress Fracture Imaging: MRI Advantages: better spatial resolution better specificity detects bone contusions Disadvantages: more expensive requires patient cooperation can be difficult to differentiate stress fracture from bone contusion Appearance: Bone contusion: low T1 signal, high T2 signal intensity Stress Fracture: low T1 signal, low T2 signal intensity 14

15 Companion Patient Two-MRI of Stress Fracture Logan and Hardy, cfm?pg=how_to&fn=bonestim 15

16 Stress Fracture Imaging: Nuclear Imaging 3 phase skeletal scintigraphy with 99mTc Advantages: The entire skeleton can be imaged Scintigraphy changes can precede plain film changes by weeks Disadvantage: Specificity is poor Appearance: Increased tracer uptake at affected site in the third phase 16

17 Companion Patient Three-Bone Scan of Stress Fracture Oliphant, aidil/lowerextremity.htm 17 Arrow (left image) and circle indicate increased tracer uptake

18 Let s return to our patient 18

19 Our Patient G.F.: Revisited Interpretation of plain films taken at initial presentation: Indistinctness of the outer periosteum Possible stress fracture Subsequent MRI (10 days later) Anterior Tibia: Increased intramedullary signal in the anterior aspect of the proximal tibia Compatible with early stress reaction Posterior Tibia: Abnormal enhancement in the posterior cortex of the proximal tibia Surrounding enhancement in the soft tissues Not typical for stress fracture 19

20 Initial plain film unavailable, but let s review the MRI findings 20

21 MRI Anterior Lesion Arrows indicate increased signal intensity PACS, BIDMC Coronal STIR 21

22 Differential Diagnoses: Anterior Lesion Stress Fracture Stress Reaction (Bone Contusion) Bone Metastases Osteomyelitis Probable Diagnosis: History: Long Distance Runner Radiology: No linear lucency indicative of fracture ***Stress Reaction*** 22

23 MRI Posterior Lesion Normal Bone on T2 weighted image Abnormal T2 weighted image PACS, BIDMC 23

24 MRI Posterior Lesion Increased signal intensity (bone) Increased signal intensity (soft tissue) PACS, BIDMC 24

25 Differential Diagnoses: Posterior Lesion Scar of a prior stress fracture Sessile osteochondroma Periosteal chondroma Non-ossifying fibroma Definitive Diagnosis: non-ossifying fibroma based on radiologic appearance Follow Up: X-rays in 2 months 25

26 Follow Up X-rays were obtained at 2 and 5 months 26

27 Follow Up X-Rays: 2 months Later 27 PACS, BIDMC

28 Follow Up X-ray: 2 Months Later Anterior No soft tissue masses No bone lesions Posterior Focally sclerotic, slightly expansile area in the posterior upper tibia Not changed when compared with previous films Non-aggressive appearance 28 PACS, BIDMC

29 Follow Up X-ray: 5 months later 29 PACS, BIDMC

30 Follow Up X-ray: 5 Months Later Anterior No soft tissue masses No bony lesions Posterior Focal density in proximal tibia posteriorly Density abuts the posterior cortex 30 PACS, BIDMC

31 Let s review information about stress fractures 31

32 Stress Fractures: General Information Definition: Failure of the skeleton to withstand submaximal forces over time Two Types: Fatigue Fracture: normal bone is exposed to repeated abnormal stresses Insufficiency Fracture: normal stress is applied to abnormal bone Epidemiology Most are located in the tibia Distal Tibia: long distance runners Proximal Tibia: children and elderly 32

33 Stress Fractures: Radiologic Considerations MRI with diffuse edema, but without dark fracture line Bone contusion: microfracture of cancellous bone Could also be osteonecrosis or transient osteoporosis Best modality for follow up of stress fractures Plain radiographs Computed Tomography High rate of false negatives Often skipped with preference for MRI or bone scan 33 pharyngula.org/ index/weblog/2003/11

34 Final comments about our patient 34

35 Our Patient G.F.: Revisited Patient s follow-up X-rays show no abnormalities in the region of the anterior tibial cortex Posterior cortex shows non-ossifying fibroma Stress fractures have occurred in non-ossifying fibromas Patient no longer experiences pain in left lower extremity; however, clinical change should be investigated 35

36 References Groves et al. 16-Detector multislice CT in the detection of stress fractures: a comparison with skeletal scintigraphy. Clin Radiol Oct;60(10): Novelline, R. Squire s Fundamentals of Radiology: Sixth Edition, 2004; 362 Pretorius, E, Solomon, J. Radiology Secrets: 2 nd Edition, 2006; Reeder, M. Gamuts in Radiology: Comprehensive Lists of Roentgen Differential Diagnosis: 4 th edition, 2003; 331 Reeser, J. Alice Fisher, MD Eric Stein, MD 36

37 Acknowledgments Larry Barbaras our Webmaster Pamela Lepkowski 37