9.70. Radiographic examination:
(b) Edinburgh method: An AP film is taken with the child's legs held parallel, with slight traction and no external rotation. Centre the beam at a standard distance of 100 cm. Measure the gap between the most medial part of the femur and the lateral edge of the ischium. This is normally 4 mm; over 5 mm is suspicious: 6 mm is regarded as diagnostic of DDH. Proximal migration can also be measured in the same film.
9.71. Developmental dislocation of the hip (DDH): The older child (1):
Appearance: (A) The affected leg in a case of unilateral dislocation of the hip may appear slightly shorter, and lie in external rotation. (B) There may be asymmetry of the skin folds in the thigh, although this sign is of limited reliability.
9.72. Developmental dislocation of the hip (DDH): The older child (2): If both hips are involved there is usually widening of the perineum owing to the hip displacement. If the child has been walking, there will be a compensatory increase in lumbar lordosis.
9.73. Developmental dislocation of the hip (DDH): The older child (3):
Trendelenburg's test will be positive and the gait will be abnormal, with excessive shoulder sway. In unilateral cases the child will dip on the affected side; in bilateral cases the child will have a waddling gait.
9.74. Developmental dislocation of the hip (DDH): The older child (4): Test the range of abduction from a position of 90° flexion of the hip. In DDH abduction is restricted in this position, and of course is most obvious in the unilateral case. A 20° difference between the sides, or less than 60° of abduction, is regarded as highly significant, and further investigation is essential. The test should be performed routinely at 3 months, especially in a high-risk case.
9.75. Developmental dislocation of the hip (DDH): The older child (5): Attempt to elicit telescoping in the affected limb. Steady the pelvis with one hand, and push and pull along the axis of the femur with the other. Abnormal excursion of the limb is suggestive of DDH. Always compare the sides.
9.77. Radiographs: Normal lateral hip in the adult.
9.76. Radiographs: Normal anteroposterior projection of the pelvis in the adult.
9.78. Radiographs: An anteroposterior view showing both hips (A) is the most useful single screening film, as it allows both sides to be compared. If the joint is strongly suspect, an additional lateral projection (B) and an anteroposterior (C), centred on the suspect hip, are essential. Note first in the films any disturbance of bone texture (e.g. in Paget's disease, osteoporosis, tumour). Now note the joint space (which indicates the depth of articular cartilage and interposing fluid), which may be (D) increased in Perthes' disease, synovitis and infection, and (E) decreased in the later stages of infection and arthritis. Note the relative density of the femoral head, which may be decreased, e.g. in rheumatoid arthritis, infection and osteoporosis, and increased in avascular necrosis (F), segmental avascular necrosis (G) and Perthes' disease (H).
9.79. Radiographs ctd: Now note the shape of the femoral head, which may, for example, be (A) buffer-shaped after Perthes' disease. (B) flattened after avascular necrosis (total or segmental), (C) irregular or destroyed after infection. (D) atrophic in persistent developmental dislocation of the hip. Note Shenton's line, which normally forms a smooth curve flowing from the superior pubic ramus to the femoral neck (E). Compare the sides if possible. Distortion occurs in many conditions involving the femoral neck and head, particularly fractures (F) and subluxations. Note the neck-shaft angle. This is decreased in congenital coxa vara (G), and coxa vara secondary to rickets, Paget's disease, osteomalacia, fracture etc. It is increased in coxa valga secondary to polio (H) and other neurological disturbances.
9.80. The neck-shaft angle may be measured from lines drawn through the shaft and along the centre of the neck into the centre of the head.
Normal neck-shaft angle in males = 128°. Normal neck-shaft angle in females = 127°.
The centre of the head may be easily found with the aid of an orthopaedic rule or similar transparent drawing template inscribed with concentric circles of different radii.
9.81. Pelvic distortion: This may be localized and of the pattern fdlind in protrusio acetabuli (A), which is often hereditary and frequently associated with osteoarthritis; or it may be generalized (B). leading to deformity of the pelvic inlet (triradiate pelvis): this is found in osteomalacia and other diseases accompanied by bone softening, such as rickets and Paget's disease.
9.82. Osteoarthritis: Note the presence of any of the changes commonly seen in osteoarthritis, such as (A) joint space narrowing, (B) marginal osteophytes, (C) marginal sclerosis, (D) cystic changes in the head of the femur and in the acetabulum.
9.83. Complete obliteration of the hip joint (bony ankylosis) is seen in ankylosing spondylitis (where there is invariably involvement of the sacroiliac joints). It is also seen as a late result of tuberculous and other infections, and after surgical fusion.
9.84. Perthes' disease (1): The earliest radiographic sign is an increase in joint space. (Note, however, that this is also seen in synovitis of the hip and in infective arthritis). Minor degrees of joint space widening may be detected by measuring the distance between (A) 'the tear drop' and the capital epiphysis on both sides.
9.85. Perthes' disease (2): If the tear drop' (formed by the anterior acetabular floor) is not clear, note (A) the overlap shadows of the head and neck on the acetabulum, comparing one hip with the other. Alteration (B) occurs in Perthes' disease, synovitis and infection.
9.86. Perthes' disease (4): Cattemll Grading (a): This is the commonest method used to assess the severity of the bone changes when they appear. Grade I: Cyst formation occurs in the anterolateral aspect of the capital epiphysis. Revascularization may be completed without bone collapse, and the prognosis without treatment is good. Grade 2: A little more of the head is involved, and bony collapse is inevitable.
9.87. Perthes' disease (5): Carte/all grading (b): Grade 3: Most of the head is involved. Grade 4: The whole head is affected. Bony collapse is inevitable in grades 3 and 4, and the prognosis is consequently poorer.
9.88. Perthes' disease (6): The so-called 'frog' lateral (Loewenstein projection, (L)) is routine in assessing these cases. Apart from the cystic changes that appear in the capital epiphysis, the acetabulum may be similarly affected (A); cystic changes may also occur in the metaphysis, which may widen (M). The femoral head may flatten and extrude laterally (H). MR1 scanning allows more accurate grading.
9.89. Perthes' disease (7): Lateral extrusion may be expressed as a percentage of the diameter of the metaphysis on the normal side (N): if ab/cd x 100 > 20%, then the prognosis is poor. An accurate assessment of the amount of avascular bone may be made by radionuclide bone scanning. Prognosis is mainly dependent on the mass and degree of epiphyseal involvement (assessed, for example, by Catterall grading).
9.90. Perthes' disease (8): Other adverse factors placing the case in the 'head-at-risk' category include (a) presentation above the age of 4, (b) calcification seen lateral to the epiphysis or other evidence of major extrusion, (c) lateral subluxation (S). (d) a positive Gage sign (a sequestrum surrounded by a 'V' of viable epiphysis (G).
9.91. Perthes' disease (9): Herring lateral pillar classification: Divide the head into three columns during the fragmentation stage: then, if the lateral part is of normal height (Herring A), the prognosis is excellent. If the lateral part is depressed up to 50% (even with the central column involved) (Herring B), the results are generally good under age 9. In Herring C the lateral pillar is less than 50% and all develop permanent deformity.
9.92. Slipped femoral epiphysis (1):
The earliest changes are seen in the lateral projection. A line drawn up through the centre of the neck fails to meet the midpoint of the base of the epiphysis. The distance between the centre of the base of the epiphysis (x) compared with the width of the base of the epiphysis may be used to calculate the degree of slip. Less than 1/3 may be classified as grade 2; grade 3 = 1/3 to 1/2; grade 4 = more than 1/2. (Grade 1 is used for pre-slip cases.)
9.93. Slipped femoral epiphysis (2):
Soittlnvick's method of quantifying the severity of any slip: In the frog lateral draw a perpendicular (p) from a line (ab) drawn across the base of the epiphysis. Note the angle (A) between this and a line (e) drawn through the centre of the femoral shaft, and compare the sides. (If the condition is unilateral, subtract 12° to allow for the normal-shaft angle in this projection.) 30° is regarded as mild; 30-60° is moderate, and more than 60° severe.
9.94. Slipped femoral epiphysis (3):
Although the earliest radiographic changes are seen in the lateral, greater degrees of slip become detectable in the AP projections. The first sign is that a tangential line drawn on the upper femoral neck fails to strike the epiphysis (A), whereas in a normal well-centred view such a tangent (B) includes part of the epiphysis.
9.95. Slipped femoral epiphysis (4): In 9.96. Slipped femoral epiphysis (5):
the later stages, some weeks after the initial Physeal separation: the frog lateral slip (now the so-called 'chronic slip' stage) radiograph is again used. The distance there is distortion of the inferior part of the between the anterior lip of epiphysis and the femoral neck, with new bone formation closest point of the metaphysis is measured,
('buttressing'). In the majority of cases of slipped femoral epiphysis there is in fact no physeal separation. If separation is present, it is seldom detected unless it exceeds 4 mm. Detected separations normally lie in the 4-12 mm range. Separation is a significant finding, as it tends to be associated with a high incidence of avascular necrosis.
9.97. Radiographs in the child (1): Interpretation of hip radiographs in the older child is dependent on the presence of ossification in the epiphysis of the femoral head. This normally appears between 2 and 8 months, but is often delayed in DDH. The position of the capital epiphysis in relation to the other pelvic elements must be determined. First draw a horizontal line (Hilgenreimer line) across the pelvis. On each side this should touch the downward-pointing apex of the acetabular element of the ilium. Vertical lines (Perkins' lines) should then be drawn from the lateral limits of the acetabula. These lines divide the region of each hip into four areas. The epiphysis of the femoral head should normally lie within the lower and inner quadrant (A), but in DDH the head moves upwards and outwards (as at B). Shenton's line (C) may be disturbed. Dysplasia of the acetabulum alters its slope (E), which decreases with growth (it usually does not exceed 30° at 6 months). There are a number of other measurements of a specialized nature that may be made (and compared with tables detailing average values relating to age and sex) when a more detailed assessment of hip dysplasia is required.
9.98. Radiographs (2): To assess joint development after treatment for DDH the following may be noted (a) the centre-edge angle (CE, of Wiberg); and (b) the acetabular index (AI angle). (V is a vertical, C the centre of the femoral head, T an acetabular edge tangent. M is the midpoint of a line joining the acetabular margins, P a vertical drawn from it.) Additional information regarding the head, acetabulum and limbus may be obtained by MRI scans or contrast arthrography.
9.99. Component loosening after total hip replacement: The cup (C): The wire marker (1) sunk within the radiolucent cup aids the analysis of any radiographic series. The plane (2) of the sockct lies at an angle (3) to the plane of the pelvis (4), shown by a line drawn between the ischial tuberosities. This angle may be altered (5) by rotation of the cup if it loosens. The cup may also migrate proximally: look for any disturbance in the relationship between the wire marker and the fixed landmarks of the pelvis. An increase in the distance (6) between the centre of the cup and the ischium may be suggestive of migration, although errors of positioning and tube/film distances make this a little unreliable. Development of a radiolucent zone (7) (between cement and bone) exceeding 1 mm and extending right round the cup is a strong indicator of loosening. (Note that the appearance of a radiolucent line between the cement and a component is diagnostic of loosening.) The stem (S): Look for a radiolucent zone of more than 1 mm between cement and bone (8) or between the stem and the cement. Note any change in the angle between the axes of the femur and prosthetic stem (9). or any local bone disturbance (10). Check for sinking of the prosthesis, by noting the distance between the upper edge of the acetabulum and the greater trochanter (11). Non-union of the greater trochanter (12) and wire fracture and fragmentation (13) should also be recorded.
9.101. Radiographs: In this (normal) Charnley total hip replacement, the stem of the prosthesis is well placed. The greater trochanter is uniting in good position, and the wires are intact. The head of the femoral component is concentric with the acetabular wire marker.
9.102. Hip radiographs: examples of pathology (1 ): After a total hip replacement the floor of the acetabulum has given way and the cup is becoming centrally displaced.
9.100. Component wear: This is posing less of a problem than was originally anticipated by both surgeons and patients, but should be assessed. Wear involves the softer acetabular component: head wear is negligible. To determine wear, measure the gap between the prosthetic head and the wire marker at their upper and lower limits. Half the difference between these is a measure of wear in the wall of the cup, 3 mm or more being an appreciable amount.
9.103. Pathology (2): After a total hip replacement the prosthetic stem has fractured, with loss of the ability to weightbear. Note the cement, which has extruded into the pelvis during the insertion of the device. There is some evidence of loosening of both the cup and the stem.
9.104. Pathology (3): In this case of total hip replacement the trochanteric wires have broken; the trochanter has displaced proximally and failed to unite. The stem has loosened, and its distal end is in danger of broaching the femoral cortex. Note the extensive translucency at the bone-cement interface.
9.105. Pathology (4): Following a dislocation of the hip which was successfully reduced, this patient complained of great stiffness in the hip. Note the extensive new bone formation around the joint. Diagnosis: myositis ossificans.
9.107. Pathology (6): In the left hip (right of the illustration) the femoral epiphysis is smaller than on the other side, and the slope of the acetabulum greater. Shenton's line is disrupted. If Perkins' squares are constructed, the epiphysis of the femoral head will be seen to lie in the upper and outer quadrant. (Compare these findings with the other side.) There is some atrophy of the femoral shaft, suggesting a long-standing lesion.
Diagnosis: developmental dislocation of the left hip.
9.108. Pathology (7): There is distortion of both femoral heads, which have become buffer shaped, and there is alteration of the neck-shaft angles. Diagnosis: congenital coxa vara.
9.109. Pathology (8): The left the hip is dislocated and the femoral head atrophic; on the right the femoral head is poorly contained in the acetabulum, and there are early osteoarthritic changes in the joint. Both acetabula are poorly developed, and their slope is markedly increased.
Diagnosis: untreated developmental dislocation of the hip.
9.110. Pathology (9): There are widespread cystic changes in both femora and the pelvis.
Diagnosis: in this case the abnormal appearances are due to hyperparathyroidism.
9.111. Pathology (10): This radiograph of the pelvis of an adolescent boy shows gross destruction of the right hip joint, with changes in both the head of the femur and the acetabulum. Diagnosis: the appearances are typical of an infective arthritis. In this case the organism was the tubercle bacillus.
9.112. Pathology (11): This lateral projection of the hip shows displacement of the proximal femoral epiphysis relative to the femoral neck.
Diagnosis: slipped femoral epiphysis.
9.112. Pathology (11): This lateral projection of the hip shows displacement of the proximal femoral epiphysis relative to the femoral neck.
Diagnosis: slipped femoral epiphysis.
9.113. Pathology (12): The pointer marks a ringed area of bone in the femoral neck with a central nidus. This was the source of chronic, niggling bone pain. Diagnosis: the history and X-ray appearance are typical of osteoid osteoma.
9.114. Pathology (13): The complaint is of pain and stiffness of the hip following a hip fracture 2 years previously. The fracture was treated by nailing: the internal fixation device was subsequently removed, and there are some very minor changes only in bone texture to show its previous presence. Diagnosis: collapse of the femoral head due to avascular necrosis. There are secondary osteoarthritie changes in the hip.
9.115. Pathology (14): There is marked disturbance of the bony texture, mainly involving the right hemipelvis. There is a degree of protrusio acetabuli, and there is disturbance of the architecture of the hemipelvis, which is becoming centrally displaced. Diagnosis: Paget's disease.
9.116. Pathology (15): The epiphysis of the right femoral head is small and of increased density. There is some broadening of the metaphysis, and there are some cystic changes in the roof of the acetabulum.
Diagnosis: Perthes' disease.
9.117. Pathology (16): There is increased density of the capital epiphysis and some cystic change in the metaphysis, which is showing signs of broadening. There are also some cystic changes in the outer half of the acetabulum.. The area of sclerosis along the inferior margin of the cyst is sometimes referred to as the 'sagging rope' sign. Diagnosis: Perthes' disease.
9.118. Pathology (17): There is fragmentation of the capital epiphysis, with the presence of Gage's sign. Diagnosis: Perthes' disease.
9.119. Pathology (18): There is separation and collapse of the lateral part of the epiphysis, with distortion of the epiphyseal plate and cystic changes in the metaphysis, which is broadened. The bone density, which was previously increased, is returning to normal. Diagnosis: long-established Perthes' disease. This would be described as grade C in the Herring classification of Perthes' disease.
9.120. Pathology (19): There are widespread changes in bone texture in the femur and pelvis, both having a motheaten appearance.
Diagnosis: metastatic bone disease.
9.121. Pathology (20): The floor of the acetabulum is projecting into the pelvis. There is narrowing of the joint space, and a minor degree of marginal exostosis formation. Diagnosis: osteoarthritis with protrusio acetabuli.
9.122. Pathology (20): There is gross narrowing of the hip joint space. Diagnosis: osteoarthritis.
Anatomical features 202-204
Causes of knee swelling 204-205
Extensor mechanism of the knee 205-206
Ligaments of the knee 206-208
Rotatory instability of the knee 208
Patellofemoral instability 209
Anterior knee pain syndromes 210
Osteochondritis dissecans, fat pad injuries and loose bodies 21 1
Osteoarthritis, rheumatoid arthritis, Reiters syndrome, ankylosing spondylitis 21 2
Disturbances of knee alignment
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