Imaging of the Hip. Objectives. Objectives. Anatomy Bones of the hip (lateral) Anatomy Bones of the hip (anterior) Seite 1.

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1 Imaging of the Hip Robert Stahl, MD Thomas M. Link, MD Musculoskeletal and Quantitative Imaging Research, Department of Radiology, UCSF Disclaimer Parts of this presentation are composed of material (figures and text information) from free available web resources This presentation is only for educational purposes and may not be distributed beyond UCSF Objectives Objectives Anatomy of the hip and normal findings Pathologies at the hip Anatomy of the hip and normal findings Pathologies at the hip Anatomy Bones of the hip (anterior) hip joint: articulation of the hip bone (os coxae) with the femur hip bone: fusion of the ilium, ischium, and pubis. two hip bones combine with the sacrum and coccyx to form the bony pelvis femur: longest and strongest bone in the body important insertion site of many of the muscles acting on the hip joint Anatomy Bones of the hip (lateral) demarcation of the three original (embryological) hip bones: Ilium Ischium Pubis all contribute to the formation of the acetabulum acetabular notch: at the inferior margin of the acetabulum Seite 1

2 Anatomy Bones of the hip (lateral) Anatomy Bones of the hip (posterior) Important landmarks: Important landmarks: Ilium Ilium Ala of ilium: origin for the gluteal muscles Ala of ilium: origin for the gluteal muscles Anterior superior iliac spine origin of the sartorius muscle Ischium: ischial tuberosity: origin of the hamstrings insertion for the sacrotuberous ligament Ischium: ischial tuberosity origin of the hamstrings insertion for the sacrotuberous ligament ischial spine: separates greater and lesser sciatic notches Anatomy Bones of the hip (anterior) Anatomy Bones of the hip (anterior) Important landmarks: Important landmarks: Pubis: Ischium: superior ramus: forms the anterior portion of the acetabulum origin of the pectineus muscle inferior ramus: joins the ischial ramus origin of the adductor longus body origin of the adductor brevis and the gracilis medial aspect articulates with the contralateral pubic body at the pubic symphysis ramus of ischium: joins the inferior pubic ramus. origin of many of the adductor muscles of the thigh Ilium: iliac crest / tubercle of iliac crest: palpable surface landmarks Anatomy Bones of the hip (posterior) Anatomy Bones of the hip (posterior) Important landmarks: Important landmarks: Femur: Femur: linea aspera: attachment of intermuscular septa and numerous muscles greater trochanter insertion site for the gluteus medius and minimus muscles,piriformis and obturator internus muscles gluteal tuberosity: receives the distal half of the gluteus maximus and the pubic fibers (adductor portion) of the adductor magnus lesser trochanter: distal attachment of the iliopsoas muscles, a powerful hip flexor intertrochanteric line (anterior) / intertrochanteric crest (posterior): located between the trochanters Important for the classification of hip fractures femoral neck: angle of 115 to 140 degrees relative to the shaft of the femur Seite 2

3 Anatomy Bones of the hip (medial) Anatomy Muscles of the hip (anterior) Important landmarks: Femur: fovea capitis femoris: slight depression in the articular surface of the head of the femur ligament of the head of the femur attaches here. Anterior compartment of the thigh: flexors of the hip and extensors of the knee M. tensor fascia latae M. sartorius M. quadriceps femoris rectus femoris vastus lateralis vastus intermedialis vastus medialis Anatomy Muscles of the hip (anterior) Medial compartment of the thigh: adductors of the thigh M. gracilis M. pectineus M. adductor longus M. adductor brevis M. adductor magnus Anatomy Muscles of the hip (posterior) Posterior compartment of the thigh: extensors of the thigh and flexors of the leg Hamstring muscles: M. biceps femoris M. semitendinosus M. semimembranosus Anatomy Ligaments of the hip Anatomy Ligaments of the hip Hip joint: ball-and-socket type synovial joint between the head of the femur and the acetabulum of the os coxae labrum, fibrous capsule and capsular ligaments (iliofemoral, ischiofemoral, and pubofemoral ligaments): keep the femoral head in the joint and limit the range of motion of the joint Labrum: not actually a ligament (comprised of fibrocartilage) arises from the acetabular rim together with the transverse acetabular ligament, it creates a deep spherical "cup" which the femoral head resides in ligament of the head of the femur: plays only a minor role in stability important because the artery of the head of the femur travels through it Seite 3

4 Acetabulum Anatomy Ligaments of the hip Fibrous Capsule: acetab. lig. lig. teres encloses part of the head and the majority of the neck of the femur forms a collar around the neck constricts the synovial capsule retains the femoral head in the acetabulum pubofemoral, iliofemoral and ischiofemoral ligaments: reinforce the capsule externally lig. teres Radiographs Pelvis/Hip Xray Iliofemoral ligament pubofemoral lig ischiofemoral lig evaluate hip fractures / following trauma bone lesions arthritis. initial imaging modality for hip pain AP projection of the pelvis and upper femora: patient is lying supine feet are inverted 15 degrees places long axes of the femoral neck parallel with the plane of the film Hip Xray AP Lateral ("frog-leg"): Hip Xray frog leg patient resting in supine position externally rotating, flexing and abducting the hip hip has now rotated such that the view of the femur has been altered 90 degrees lesser trochanter will be clearly visible anteriorly and the greater trochanter has been rotated posteriorly Seite 4

5 assessment of symmetry: the general architecture and symmetry of the pelvic bones, the acetabulum and its relations to pelvic landmarks hip joint articulations and the angle of the femoral necks as they enter the acetabula pubic symphysis (normal interpubic distance?) Pelvis Xray AP Pelvis Xray Arthrography evaluates joint anatomy: acetabular labrum articular cartilage ligaments the sacroiliac joint spaces (visible?) Pelvis/Hip CT can be helpful for complex fractures and dislocations Pelvis/Hip MRI modality of choice for: identifying occult fractures hip pain of unknown etiology infection tumor osteonecrosis Labrum perilabral recess labrum axial M. tensor fasciae latae M. rectus femoris M. sartorius M. iliopsoas M. pectineus labrum lig. teres M. gluteus medius minimus perilabral sulcus axial coronal transverse ligament M. gluteus maximus M. quadratus femoris M. gemellus inf. Sciatic nerve Seite 5

6 coronal Objectives M. gluteus medius and maximus M. gluteus minimus Iliofemoral ligament M. obt. internus Anatomy of the hip and normal findings Pathologies at the hip tensor fascia lata M. obt. externus Adductormuscles Iliopsoastendon circumflexa femoris artery Osteoarthritis The most prevalent disorders of the joint Degeneration of articular hyaline cartilage Affects most joint tissues: bone, synovial Heterogeneous and varying in expression Clinical Symptoms Stiffness and pain in affected joints Loss of joint mobility and stability Crepitus Bony swelling or deformity of joints Joint tenderness on palpation Clinical Scoring: WOMAC (Western Ontario and McMaster University) What causes osteoarthritis? exact cause of OA is not known It is believed that joint damage begins in response to physical stress (such as an injury or repetitive movement) this stress can erode the cartilage that normally encases the ends of the bones in a joint As cartilage breaks down, the ends of the bones thicken and the joint may lose its normal shape With further cartilage breakdown, the ends of the bones may begin to rub together causing pain In addition, damaged joint tissue can cause the release of certain substances called prostaglandins, which can also contribute to the pain and swelling characteristic of the disease Risk Factors Age Genetic predisposition (gene defects) Abnormal Biomechanics (joint alignement) Obesity Being female Occupation Joint injury/(trauma or overuse) Certain diseases (e.g. rheumatoid arthritis) Diagnosis of OA Articular cartilage damage (indirectly assessed radiographically by JSN) subchondral sclerosis osteophytes (or bone spurs) subchondral cysts loose bone fragments within the joints radiological features typically occur later in the disease process Seite 6

7 Osteoarthritis Osteoarthritis Ankylosing Spondylitis Ankylosing Spondylitis Bechterew s disease form of arthritis that primarily affects the spine also cause inflammation, pain and stiffness in other areas of the body such as the shoulders, hips, ribs, heels and small joints of the hands and feet hallmark feature: involvement of the sacroiliac (SI) joints exact cause of AS is unknown genetics play a key role in AS. Most individuals who have AS also have a gene that produces a "genetic marker" - in this case, a protein - called HLA-B27 Risk factors: Testing positive for the HLA-B27 marker A family history of AS Frequent gastrointestinal infections Ankylosing Spondylitis Perthes disease Legg-Calvé-Perthes disease (LCPD) avascular necrosis of the proximal femoral head resulting from compromise of the tenuous blood supply to this area usually occurs in children aged 4-10 years occurs more commonly in boys than in girls, with a male-to-female ratio of 4:1 The cause is not known, may be idiopathic, or it may result from a slipped capital femoral epiphysis, trauma, steroid use, sickle-cell crisis, toxic synovitis, or congenital dislocation of the hip Pathophysiology: Rapid growth occurs in relation to development of the blood supply of the secondary ossification centers in the epiphyses, creating an interruption of adequate blood flow and making these areas prone to avascular necrosis. Interruption of the blood supply to the bone results in necrosis, removal of the necrotic tissue, and its replacement with new bone. Bone replacement may be so complete and perfect that completely normal bone may result Seite 7

8 Perthes disease Perthes disease Initial radiographs can be normal, but radiographic changes can be divided into 5 distinct stages representing a continuum of the disease process: MRI More sensitive than X-ray Stage 1: reveals cessation of femoral epiphyseal growth Stage 2: subchondral fracture Stage 3: shows resorption Stage 4: demonstrates reossification Stage 5: healed or residual stage Avascular necrosis (AVN) represents an inability to supply adequate oxygen to underlying bone is extremely rare in healthy individuals is characterized by areas of dead trabecular bone and marrow extending to involve the subchondral plate In the adult, the involved segment usually never fully revascularizes and, once detected radiographically, collapse of the femoral head usually occurs later Avascular necrosis (AVN) Etiologies: - Trauma - Corticosteroids - Idiopathic - Alcoholism - Vasculitis - Sickle cell anemia only occurs in fatty marrow, which contains a sparse vascular supply femoral head is the most vulnerable site for development of AVN Avascular necrosis (AVN) Avascular necrosis (AVN) Minimal disease: patient may be asymptomatic heal spontaneously More severe disease: repair begins at interface between viable and necrotic bone Dead bone is reabsorbed only partially. results in a mixed sclerotic and cystic appearance on radiographs Mechanical failure: microfractures in the subchondral regions Progression of the microfractures => diffuse flattening of the outer portion of the right femoral head from avascular necrosis adjacent joint space narrowing, juxta-articular sclerosis, osteophytes Seite 8

9 Avascular necrosis (AVN) AVN CT: clumping and distortion of the central trabeculae T1 T1+Gd Modified Arlet-Ficat staging Modified Arlet-Ficat staging MRI Therapy MRI Therapy I II Low signal, inhomogenous in T1 More wedgeshaped, Double line - sign in T2 conservative, core decompression, electrostimulation III IV subchondral fracture secondary osteoarthritis operation rotational osteotomy, hemiarthroplasty, total joint replacement Slipped capital femoral epiphysis (SCFE) Slipped capital femoral epiphysis (SCFE) most common hip abnormality presenting in adolescence (11-16 yo) and a primary cause of early osteoarthritis, M>F Pathophysiology: fracture through the proximal femoral physis Stress around the hip causes a shear force to be applied at the growth plate epiphysis moves posteriorly and medially Seite 9

10 Slipped capital femoral epiphysis (SCFE) Slipped capital femoral epiphysis (SCFE) MRI: viability of epiphysis (necrosis in up to 15%) depicts growth plate T1 treatment of a SCFE usually consists of in situ (just as it is) pinning using a cannulated screw Hip dysplasia Hip dysplasia spectrum of disorders affecting the proximal femur and acetabulum hips are subluxatable, dislocatable, and dislocated Early diagnosis and treatment important failure to diagnose can result in significant morbidity result of a disruption in the normal relationship between the acetabulum and femoral head Without adequate contact between them, neither develops normally Acetabular angle: Between Hilgenreiner line (horizontal line between the 2 triradiate or Y-Y cartilages And a second line connecting the superolateral and inferomedial margins of the acetabular roof approximately 28 at birth, decreases gradually with age Hip dysplasia Hip dysplasia Shenton line: Perkins line: at the outer acetabular margin perpendicular to the Hilgenreiner line divides the hip into quadrants femoral head normally is centered in the inferomedial quadrant smooth unbroken arc bridges the medial femoral metaphysis and the inferior edge of the superior pubic ramus Displacement of the femoral head out of the joint space and disruption of the Shenton line is suggestive of DDH Seite 10

11 Hip dysplasia Total hip replacement hip joint may be replaced with a variety of material, including metal, polyethylene, and ceramic A joint prosthesis is identified as a total hip arthroplasty if both the articular surfaces of the acetabulum and femur are replaced If the femoral head is replaced and the acetabulum is not altered, the prosthesis may be considered a hemiarthroplasty Osteopenia occurring in bone as the result of removal of normal stress from the bone by an implant usually indicates that the femoral component is secure Stress shielding Abnormal lucency about acetabular and femoral prosthetic components localized areas of bone resorption around joint prostheses Either polymethylmethacrylate cement or polyethylene can incite a giant cell response well-defined focal areas of bone resorption that do not conform to the shape of the prosthesis. Particle disease Hardware failure Femoral neck fractures: Trauma serious injuries associated with high mortality rates and significant icant morbidity in the geriatric population most commonly occur after falls Osteoporosis is the most important risk factor contributing to hip fractures. It decreases bone strength and bone's ability to resist trauma Radiography remains the first-line modality for imaging and classifying femoral neck fractures can be broadly described according to their location along the femoral neck where the fracture line is located descriptive terms such as subcapital, midcervical, and basicervical fractures of the neck are sometimes used Seite 11

12 Trauma Trauma Trauma Trauma Garden classification of subcapital femoral fractures is the most widely used today describe fractures on the basis of the distortions of the principal (medial) compressive trabeculae prior to reduction, as seen on radiographs Trauma Trauma I II III IV I: incomplete subcapital fracture II: complete but nondisplaced fracture III: complete, partially displaced subcapital fracture IV: complete and fully displaced fracture Seite 12

13 Trauma Stress fracture pubic bone Occult proximal femur and pelvic fractures in osteopenic patients 37% occult hip fractures 23% occult pelvic fractures STIR T1-w Bogost et al. Radiology :263-7 T1-w STIR Sacral insufficiency fracture How many fractures? Fs-T1 + Gd Muscle/tendon injuries = strains Ligamentous injuries = sprain Grade 1 clinical findings: spasm,cramp MRI: edema, hemorrhage, preservation of muscle morphology Grade 2 clinical findings: overuse, discomfort during sporting activity, resolves with rest MRI: hemorrhage (bright in T1), tearing of up to 50% of muscle fibers Grade 3 clinical findings: acute trauma -> pain, palpable mass, hematoma MRI: complete tear with or without muscle retraction Muscle injuries/ strains Grade 1 - left gluteus medius MRI: edema, preservation of muscle morphology STIR fs T2 Seite 13

14 fs T2 Muscle and tendon injuries Muscle and tendon injuries fs T1 + Gd STIR Grade 1-21 muscle strain rectus femoris muscle semimembranosus Hamstring rupture grade 3 Muscle and tendon injuries fs T2 T1 Hamstring rupture Grade 3 muscle injury semimembranosus Full thickness tears semitendinosus and biceps tendons Hematoma vastus lateralis muscle Arthritis T1 STIR fs T1 Gd Infectious arthritis - Edemain theboneand the surrounding tissues - Joint effusion - Synovial enhancement - Cartilage and osseous destruction DD: r.a., ankylosing spondylitis, PVNS, Osteoarthritis fs T1 Gd STIR STIR fs T1 Gd 18 yo female 2 weeks post-partum - hip pain Septic hip - joint effusion - synovitis Seite 14

15 80 yo immunosuppressed female Osteomyelitis due to decubitus - osseous destruction - fluid collection - rim enhancement fs T1 Gd Tendinosis and bursitis - greater trochanter gluteus medius and maximus T1 fs T1 Gd Dermatomyositis Dermatomyositis» idiopathic inflammatory myopathy with characteristic cutaneous findings» systemic disorder that frequently affects the joints, the esophagus, the lungs, and, less commonly, the heart Fibrous dysplasia Tumor T1 skeletal developmental anomaly of the bone-forming mesenchyme that manifests as a defect in osteoblastic differentiation and maturation Virtually any bone in the body can be affected a nonhereditary disorder of unknown cause Pathophysiology: medullary bone is replaced by fibrous tissue, which appears radiolucent on radiographs Benign bone tumors Fibrous dysplasia fs T1 Gd STIR Seite 15

16 Eosinophilic granuloma Eosinophilic granuloma (EG) is the benign form of the 3 clinical variants of Langerhans cell histiocytosis single or multiple skeletal lesions, and it predominantly affects children, adolescents, or young adults Symptoms include localized pain, tenderness, swelling, fever, and leukocytosis morphologic lesions of the entire group of Langerhans histiocytosis disorders consist of expanding erosive accumulations of histiocytes, usually within the medullary cavity Histiocytes: macrophages (cells of the immune system) A wide variety of bone lesions may mimic EG; these include infections, traumatic lesions, and neoplasms Eosinophilic granuloma Multiple Myeloma malignancy that is part of a spectrum of diseases ranging from monoclonal gammopathy of unknown significance (MGUS) to plasma cell leukemia proliferation of malignant plasma cells and a subsequent overabundance of monoclonal paraprotein cause a wide variety of problems: proliferation of plasma cells may interfere with the normal production of blood cells, resulting in leukopenia, anemia, and thrombocytopenia Imaging: Diffuse osteopenia may suggest myelomatous involvement before discrete lytic lesions are apparent Multiple myeloma Pigmented Villonodular Synovitis (PVNS) benign proliferative disorder of uncertain etiology that affects synovial lined joints, bursae, and tendon sheaths. Gross pathologic features include thickened synovium, with a combination of villous and nodular proliferation depending on the site of involvement MRI images demonstrate various appearances ranging from low signal through iso-intense to hyper-intense signals Multiple myeloma Seite 16

17 fs T1 Gd fs T1 Gd Anterior Impingement groin pain in active young people pain in internal rotation/flexion MR signs*: - deformity at head neck junction - labral abnormalities tear/hypertrophy - cartilage defects T2 *Kassarjian et al. Radiology Aug;236(2): Cam - type Anterior Impingement pain in internal rotation/flexion Cam type -deformity at head neck junction - labral abnormalities -os acetabuli - synovial herniation pit Pincer type - protrusio - deepened acetabular fossa - middle aged females Seite 17