Always a Diagnostic Puzzle Osteomyelitis Always a Diagnostic Puzzle schreibman.info

Osteomyelitis: Put the Pieces Together HISTORY Clinical Surgical RADIOGRAPHS Recent CT Chronic MRI Active

Osteomyelitis: Put the Pieces Together HISTORY Clinical Surgical RADIOGRAPHS Recent MRI Marrow +Gd Abscess

Osteomyelitis: Topics Definitions Active Chronic Mechanisms Hematogenous Direct spread Imaging Radiographs CT MRI Bone Model Cortex Marrow

Osteomyelitis: Definitions comes from Greek: osteon = bone myelos = marrow itis = inflammation “Inflammation of bone marrow” Infection of bone marrow “Osteomyelitis” High Sensitivity Low Specificity Marrow inflammation from infection looks like inflammation from any other cause MRI Marrow

Osteomyelitis: Definitions Active Osteomyelitis vs Chronic Osteomyelitis

Osteomyelitis: Definitions Active Osteomyelitis “Aggressive” Resembles Tumor Cortex Destruction Periosteal Reaction

Active Osteomyelitis “Aggressive” Cortex Destruction 16yoM distal fibula pain 3w after inversion injury “Aggressive” Cortex Destruction Periosteal Reaction HISTORY Clinical Followup

Osteomyelitis: Definitions Chronic Osteomyelitis “Non-Aggressive” Resembles Callus 3 Characteristics: Involucrum: “wrap” Thick periosteum around infected bone Sequestrum: “set apart” Piece of dead, infected, bone Cloaca: “sewer” Opening in cortex through which pus can escape RADIOGRAPHS Active ≠ Chronic

Active vs Chronic Osteomyelitis RADIOGRAPHS Active ≠ Chronic Active Osteomyelitis Chronic Osteomyelitis

Active Osteomyelitis “Aggressive” Cortex Destruction 16yoM distal fibula pain 3w after inversion injury “Aggressive” Cortex Destruction Periosteal Reaction Active Osteomyelitis

Chronic Osteomyelitis 19yoM fibula pain 2.5years later… RADIOGRAPHS Active ≠ Chronic Chronic Osteomyelitis 2.5 years

Chronic Osteomyelitis 19yoM fibula pain 2.5years later… CT Tibia Involucrum Chronic Osteomyelitis Fibula Sequestrum Cloaca

Chronic Osteomyelitis 42yoM Diabetic Involucrum Developing 6 weeks later 10 more weeks

Chronic Osteomyelitis 27yoM s/p removal Rt Femoral Rod 27yoM s/p removal Rt Femoral Rod Involucrum CT Scout

Chronic Osteomyelitis 27yoM s/p removal Rt Femoral Rod 27yoM s/p removal Rt Femoral Rod Involucrum Sequestrum Axial Slice CT Scout Coronal Reformat

Chronic Osteomyelitis 27yoM s/p removal Rt Femoral Rod 27yoM s/p removal Rt Femoral Rod Involucrum Sequestrum Cloaca Axial Slice CT Scout Oblique Coronal

Osteomyelitis: Mechanisms Direct Spread  adjacent tissues Most common cause Decubitus ulcer Septic arthritis PUS

Decubitus Ulcer  Ischium 52yoM quadriplegic T1  Ischium Ischium  T1

Osteomyelitis: Mechanisms Direct Spread  adjacent tissues Most common cause Decubitus ulcer Septic arthritis Puncture into bone Stepped on nail External fixator Ring sequestrum

Chronic Osteomyelitis Ring Sequestrum Chronic Osteomyelitis Involucrum Sequestrum Cloaca Poor Union RADIOGRAPHS

Osteomyelitis: Mechanisms Direct Spread  adjacent tissues Most common cause Decubitus ulcer Septic arthritis Puncture into bone Stepped on nail External fixator Ring sequestrum Hematogenous Site related to patient age

Hematogenous Osteomyelitis Site related to patient age Epiphysis Physis Metaphysis Arteriole Venule Infection occurs at end of Infection occurs at metaphysis of Septic Emboli Diaphysis Blood Supply Immature Bone Mature Bone

Hematogenous Osteomyelitis 1yoM strep pneumonia

Hematogenous Osteomyelitis 1yoM strep pneumonia 3 months later

Osteomyelitis: Imaging Many Imaging Options: Radiographs CT MR US Nuc Med What to order when?

Osteomyelitis: What to Order When Radiographs ………… ALWAYS! May show evidence of active infection Bone destruction, periosteal reaction May show evidence of chronic infection Involucrum Screen for metal Orthopedic hardware, foreign bodies Unexpected findings Fractures, Delineate current anatomy Surgical resections, RADIOGRAPHS NEED TO BE RECENT vs gas in soft tissues neuropathic deformity

Need for Recent Radiographs Example 66yoM h/o Diabetes Presents in Sept swollen foot MR is requested to “r/o Osteo” Are there radiographs? Yes …3 months ago Repeat radiographs obtained now, prior to MR, reveal… Normal Lisfranc joint Neuropathic destruction of the Lisfranc joint June September

Osteomyelitis: What to Order When Radiographs ………… ALWAYS! CT……………………. Chronic Cases CT best for calcified structures Involucrum Sequestrum Cloaca CT of the extremities is insensitive for: Bone marrow pathology Soft tissue pathology

Osteomyelitis: What to Order When Radiographs ………… ALWAYS! CT……………………. Chronic Cases MRI..…………………. Active Cases Shows extent of soft tissue edema Excellent for demonstrating abscesses and other drainable fluid collections Sensitive for bone marrow pathology Can be overly sensitive at expense of specificity Infected bone marrow resembles marrow edema due to other causes

Osteomyelitis: MR Imaging Bone Model Marrow Cortex T1 T2 X-rays

Osteomyelitis: MR Imaging Bone Model Marrow Marrow Marrow Cortex Cortex Cortex Surrounding Tissues (fat) Surrounding Tissues (fat) T1 T2 X-rays

Osteomyelitis: MR Imaging Bone Model Marrow Marrow Marrow Cortex Cortex Cortex Surrounding Tissues (fat) Surrounding Tissues (fat) T1 T2fs X-rays

Osteomyelitis: MR Imaging   Path=Fluid T1=Dark T2=Bright T1fs+Gd Enhancement Inflamed  Uniform Abscess  Wall Cyst  Not (STIR) T1 T2fs

Osteomyelitis: MR Imaging    Enhancement Inflamed  Uniform Abscess  Wall Cyst  Not (STIR) T1fs T1 T2fs +Gd

Osteomyelitis: MR Imaging Detection of the non-enhancing pus pocket (abscess) is crucial Presence of soft tissue abscess proves the edema in underlying bone marrow is osteomyelitis. Site for aspiration for culture. If IV Gd doesn’t get into abscess, IV antibiotics won’t get in either, abscess may require drainage.

Osteomyelitis: MR Imaging 63yoM Diabetic with heel ulcer Intact cortex T1 Enhancing cellulitis No non-enhancing abscess pocket Minimal Marrow Edema Figure 115: Developing calcaneal osteomyelitis in a 63 year-old diabetic patient. a) Lateral radiograph of the calcaneus shows intact cortex along the plantar surface (white arrowheads). Incidentally seen is mural calcification of the posterior tibial artery. Such arterial calcifications are common in diabetic patients. b) Mid-sagittal T1 image shows no bone destruction. c) Corresponding sagittal Inversion Recovery image shows little if any bone marrow edema. d) Corresponding sagittal post IV contrast T1 fat-suppressed image reveals diffuse enhancement of the plantar soft tissues, indicative of cellulitis, but no non-enhancing abscess pockets. Arterial Ca++ T1fs IVGd IR

Osteomyelitis: MR Imaging 63yoM Diabetic 2 weeks later… 2 weeks earlier Cortical destruction Intact cortex More marrow edema More tissue edema Non-enhancing abscess pocket When the patient’s symptoms did not respond to antibiotics, repeat imaging was obtained 2 weeks later. e) Lateral radiograph now demonstrates loss of cortex along the plantar surface of the calcaneus (black arrowheads). f) Mid-sagittal T1 image reveals infiltration of the fatty heel pad (gray arrows). g) Corresponding sagittal Inversion Recovery image reveals fluid bright signal (white arrows) within the soft tissues adjacent to the calcaneus, as well as bone marrow edema within calcaneus (white arrowheads). h) Corresponding sagittal post IV contrast T1 fat-suppressed image reveals a non-enhancing abscess pocket (black arrows) as well as enhancing bone marrow (white arrowheads). T1fs IVGd IR

Osteomyelitis: MR Imaging 63yoM Diabetic 2 weeks later…    2 weeks earlier Cortical destruction Intact cortex Marrow edema Abscess Pocket Coronal T1 (i), Inversion Recovery (j) and post IV contrast T1 fat-suppressed (k) images through the abscess pocket confirm the findings seen in the sagittal plane: an abscess pocket (white and black arrows) adjacent to the osteomyelitis (white arrowheads) along the planter surface of the calcaneus. T1fs IVGd T1 IR

Decubitus Ulcer  Ischium 52yoM quadriplegic Abscess!  T1fs +Gd  T1 Abscess?   T2fs

Osteomyelitis: MR Imaging 1yoF Swollen left lower leg R L Periosteal Reaction Figure 116: Brodie’s abscess in a young child. a) AP radiograph of the asymptomatic right leg. b) AP radiograph of the swollen left leg reveals a lucency in the distal fibula metaphysis (white arrow in the magnified dashed box). This lucency has a well-defined and sclerotic margin, indicating chronicity. There are also thick, chronic, periosteal reactions (white arrowheads) extending up the diaphysis. Metaphyseal lucency

Osteomyelitis: MR Imaging 1yoF Swollen left lower leg Brodie Abscess Periosteal Reaction c) Coronal T1 image through the distal fibula confirms the radiographic findings of a thick chronic periosteal reaction (white arrowheads), as well as the well-circumscribed dark line (open arrowheads) around the lesion corresponding to the sclerotic margin. d) The corresponding coronal T2 fat-suppressed image shows the well-circumscribed lesion (white arrow) is a bright as fluid and thus probably cystic. e) The corresponding coronal T1 fat-suppressed post IV contrast image not only confirms the lesion (black arrow) is mostly non-enhancing and thus mostly cystic… but also demonstrates peripheral enhancement, in some places thick (black arrowhead), characteristic of an abscess, in this case an intra-osseous or “Brodie’s” abscess. (There is inadequate fat-suppression of the heel pad (gray arrowheads) on both of the fat-suppressed sequences.) Non-enhancing abscess Intra-osseous Metaphyseal T1fs IVGd T1 T2fs

Osteomyelitis: What to Order When Radiographs ………… ALWAYS! CT……………………. Chronic Cases MRI..…………………. Active Cases US……….…………… Fluid/Abscess US guided aspiration for culture Cannot assess bone involvement Nuc Med.……………. Problem Cases Where MR specificity is decreased Neuropathic feet Infected hardware

Infection around metal: MRI T2fs T1fs IVGd We can see soft tissues around bone Enhancing granulation tissue (phlegmon?) We can’t see the marrow within bone Cannot evaluate for “osteomyelitis” T,K 21yoM

Infection around metal: Nuc Med Requires 2 Radiopharmaceuticals Tc-Bone Scan (Active bone metabolism) In-WBC Scan (Areas of WBC accumulation) 1)BS: Sen/Spec 2)WBC:Spec/Sen

Infection around metal: Nuc Med Femur Plate Tc-Bone Scan In-WBC Scan Removed Tibia Plate Femur Femur Tibia Tibia Placed Antibiotic PMM-Beads Tibia Plate S,B 31yoM

Charcot (Neuropathic) Foot T1fs +IV Gd T2fs Abscess Tc99m MDP In111 WBC Infection P,K 65yoF

Osteomyelitis: Put the Pieces Together HISTORY Clinical Surgical RADIOGRAPHS Recent MRI Marrow +Gd Abscess

Osteomyelitis: Put the Pieces Together HISTORY Clinical Surgical RADIOGRAPHS Recent CT Chronic MRI Active