the lower limb positioning

informative documents for radiology students.

1. THE LOWER LIM B 1/6/2016 IHTISHAM SAHIL Bs Radiology 4 th samester HIMS PESHAWAR 0345 9865409 0301 8935492

2. Positioning terminology Rotation of the lower limb occurs at the hip joint. The position of the foot relates to the direction of rotation. • Dorsal surface: the superior surface of the foot is known as the dorsal surface and slopes downwards, at a variable angle, from the ankle to the toes and from medial to lateral. • Plantar aspect: the inferior surface of the foot is known as the plantar aspect. • Medial aspect: the surface nearer the midline of the body is the medial aspect. • Lateral aspect: the surface further from the midline of the body is the lateral aspect. • Medial rotation: the lower limb is rotated inwards, so that the anterior surface faces medially. This will produce internal rotation of the hip joint. • Lateral rotation: the lower limb is rotated outwards, so that the anterior surface faces laterally. This will produce external rotation of the hip joint. • Dorsiflexion : dorsiflexion of the ankle joint occurs when the dorsal surface of the foot is moved in a superior direction. • Plantarflexion : plantarflexion of the ankle joint occurs when the plantar surface of the foot is moved in an inferior direction. • Inversion: inversion of the foot occurs when the plantar surface of the foot is turned to face medially, with the limb extended. • Eversion : eversion of the foot occurs when the plantar surface of the foot is turned to face laterally, with the limb extended. • Flexion of the knee joint: the degree of flexion of the knee joint relates to the angle between the axis of the tibia when the knee is extended and the angle of the axis of the tibia when the knee is flexed.

3. Eversion Inversion Plantarflexion Dorsiflexion Lateral rotation Medial rotation

4. Foot Basic projections Dorsi -plantar (basic) Position of patient and cassette • The patient is seated on the X-ray table, supported if necessary, with the affected hip and knee flexed. • The plantar aspect of the affected foot is placed on the cassette and the lower leg is supported in the vertical position by the other knee. • Alternatively, the cassette can be raised on a 15-degrees foam pad for ease of positioning. Direction and centring of the X-ray beam • The central ray is directed over the cuboid-navicular joint, midway between the palpable navicular tuberosity and the tuberosity of the fifth metatarsal. • The X-ray tube is angled 15 degrees cranially when the cassette is flat on the table. • The X-ray tube is vertical when the cassette is raised on a 15-degree pad. Normal dorsi -plantar radiograph of foot

5. Dorsi -plantar oblique This projection allows the alignment of the metatarsals with the distal row of the tarsus to be assessed. Position of patient and cassette • From the basic dorsi -plantar position, the affected limb is allowed to lean medially to bring the plantar surface of the foot approximately 30–45 degrees to the cassette. • A non-opaque angled pad is placed under the foot to maintain the position, with the opposite limb acting as a support. Direction and centring of the X-ray beam • The vertical central ray is directed over the cuboid-navicular joint. Normal dorsi -plantar oblique radiograph of foot

6. LATERAL Position of patient and cassette • From the dorsi -plantar position, the leg is rotated outwards to bring the lateral aspect of the foot in contact with the cassette. • A pad is placed under the knee for support. • The position of the foot is adjusted slightly to bring the plantar aspect perpendicular to the cassette. Direction and centring of the X-ray beam • The vertical central ray is centred over the navicular cuneiform joint. Normal lateral radiograph of foot Lateral – erect Position of patient and cassette • The patient stands on a low platform with a cassette placed vertically between the feet. • The feet are brought close together The weight of the patient’s body is distributed equally. • To help maintain the position, the patient should rest their forearms on a convenient vertical support, e.g. the vertical Bucky. Direction and centring of the X-ray beam • The horizontal central ray is directed towards the tubercle of the fifth metatarsal.

7. Dorsi -plantar – erect Position of patient and cassette • The patient stands with both feet on the cassette. • The cassette is positioned to include all the metatarsals and phalanges. • The weight of the patient’s body is distributed equally. • To help maintain the position, the patient should rest the forearms on a convenient vertical support, e.g. the vertical Bucky. Direction and centring of the X-ray beam • The vertical ray is centred midway between the feet at the level of the first metatarso-phalangeal joint. Dorsi -plantar erect projection of both feet showing hallux valgus

8. TOES Basic projection Dorsi -plantar – basic Position of patient and cassette • The patient is seated on the X-ray table, supported if necessary, with hips and knees flexed. • The plantar aspect of the affected foot is placed on the cassette This cassette may be supported on a 15-degree pad. • The leg may be supported in the vertical position by the other knee. Direction and centring of the X-ray beam • The vertical central ray is directed over the third metatarsophalangeal joint, perpendicular to the cassette if all the toes are to be imaged. • For single toes, the vertical ray is centred over the metatarsophalangeal joint of the individual toe and collimated to include the toe either side. Normal dorsi -plantar projection of all toes

9. Dorsi -plantar oblique – basic Position of patient and cassette • From the basic dorsi -plantar position, the affected limb is allowed to lean medially to bring the plantar surface of the foot approximately 45 degrees to the cassette. • A 45-degree non-opaque pad is placed under the side of the foot for support, with the opposite leg acting as a support. Direction and centring of the X-ray beam • The vertical ray is centred over the first metatarso-phalangeal joint if all the toes are to be imaged and angled sufficiently to allow the central ray to pass through the third metatarsophalangeal joint. • For single toes, the vertical ray is centred over the metatarsophalangeal joint of the individual toe, perpendicular to the cassette.

10. Lateral (basic) – hallux Position of patient and cassette • From the dorsi -plantar position, the foot is rotated medially until the medial aspect of the hallux is in contact with the cassette. A bandage is placed around the remaining toe (provided that no injury is suspected) and they are gently pulled forwards by the patient to clear the hallux . Alternatively, they may be pulled backwards; this shows the metatarsophalangeal joint more clearly. Direction and centring of the X-ray beam • The vertical ray is centred over the first metatarso-phalangeal joint. First metatarsal- phalangeal sesamoid bones Lateral Position of patient and cassette • The patient lies on the unaffected side, and the medial aspect of the affected leg and foot is placed in contact with the table. • The cassette is placed under the foot to include the phalanges of the hallux and the distal part of the first metatarsal. • The hallux is then dorsiflexed with the aid of a bandage and held by the patient. Direction and centring of the X-ray beam • Centre with the vertical ray perpendicular to the cassette, over the first metatarso-phalangeal joint.

11. Axial Position of patient and cassette There is a choice of two positions for this projection: 1 The patient is positioned as for the lateral projection of the foot. The foot is raised on a support and the cassette is supported vertically and well into the instep. A horizontal beam is used in this case. 2 The patient sits on the X-ray table, with legs extended. The hallux is then dorsiflexed with the aid of a bandage and held by the patient. The cassette is raised on a support and positioned firmly against the instep. Direction and centring of the X-ray beam • Centre to the sesamoid bones with the central ray projected tangentially to the first metatarso-phalangeal joint.

12. Ankle joint Antero-posterior – basic ( Mortice projection) Position of patient and cassette •The patient is either supine or seated on the X-ray table with both legs extended. •A pad may be placed under the knee for comfort. •The affected ankle is supported in dorsiflexion by a firm 90-degree pad placed against the plantar aspect of the foot. The limb is rotated medially (approximately 20 degrees) until the medial and lateral malleoli are equidistant from the cassette. •The lower edge of the cassette is positioned just below the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre midway between the malleoli with the vertical central ray at 90 degrees to an imaginary line joining the malleoli .

13. Lateral (basic) – medio -lateral 15-degree pad is placed under the lateral border of the forefoot and a pad is placed under the knee for support. The lower edge of the cassette is positioned just below the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre over the medial malleolus , with the central ray at right-angles to the axis of the tibia.

14. Alternative projection methods Antero-posterior Position of patient and cassette • From the sitting position, whilst the patient is in a wheelchair, the whole limb is raised and supported on a stool and a pad is placed under the raised knee for support. • The lower limb is rotated medially, approximately 20 degrees, until the medial and lateral malleoli are equidistant from the cassette. A non-opaque angled pad is placed against the medial border of the foot and sandbags are placed at each side of the leg for support. • The lower edge of the cassette is placed just below the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre midway between the malleoli , with the vertical central ray at 90 degrees to the imaginary line joining the malleoli or compensatory angulation of the beam if the foot is straight

15. Lateral (alternate) – latero -medial (horizontal beam) Position of patient and cassette • With the patient maintaining the sitting position or lying on the trauma trolley, the limb is raised and supported on a firm non-opaque pad. • A cassette is placed against the medial aspect of the limb. The lower edge of the cassette is placed just below the plantar aspect of the heel. Direction and centring of the X-ray beam • The horizontal central ray is directed to the lateral malleolus .

16. Stress projections for subluxation Antero-posterior – stress Position of patient and cassette • The patient and cassette are positioned for the routine antero -posterior projection. • The doctor in charge forcibly inverts the foot without internally rotating the leg. Direction and centring of the X-ray beam • Centre midway between the malleolus , with the central ray at right-angles to the imaginary line joining the malleoli . Lateral – stress Position of patient and cassette • The patient lies supine on the table, with the limb extended. • The foot is elevated and supported on a firm pad. • The ankle is dorsiflexed and the limb rotated medially until the malleoli are equidistant from the tabletop. • The film is supported vertically against the medial aspect of the foot. • The doctor applies firm downward pressure on the lower leg. Direction and centring of the X-ray beam • Centre to the lateral malleoli with a horizontal beam.

17. Calcaneum Basic projections Lateral – basic Position of patient and cassette • From the supine position, the patient rotates on to the affected side. • The leg is rotated until the medial and lateral malleoli are superimposed vertically. • A 15-degree pad is placed under the anterior aspect of the knee and the lateral border of the forefoot for support. • The cassette is placed with the lower edge just below the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre 2.5 cm distal to the medial malleolus , with the vertical central ray perpendicular to the cassette. Normal lateral radiograph of calcaneum

18. Normal axial projection of calcaneum Calcaneum Axial – basic Position of patient and cassette • The patient sits or lies supine on the X-ray, table with bot limbs extended. • The affected leg is rotated medially until both malleoli ar equidistant from the film. • The ankle is dorsiflexed The position is maintained by usin a bandage strapped around the forefoot and held in position by the patient. • The cassette is positioned with its lower edge just distal to the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre to the plantar aspect of the heel at the level of the tubercle of the fifth metatarsal. • The central ray is directed cranially at an angle of 40 degrees to the plantar aspect of the heel.

19. Subtalar joints Oblique medial Position of patient and cassette • The patient lies supine on the X-ray table, with the affected limb extended. • The ankle joint is dorsiflexed and the malleoli are equidistant from the film. • The leg is internally rotated through 45 dgr • A pad is placed under the knee for support. • A non-opaque square pad and sandbag may be placed against the plantar aspect of the foot to keep the ankle joint in dorsiflexion . • The lower edge of the cassette is placed at the level of the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre 2.5 cm distal to the lateral malleolus with the following cranial angulations:

20. Subtalar joints .Oblique lateral Position of patient and cassette • The patient lies supine on the X-ray table, with the affected limb extended. • The ankle joint is dorsiflexed and the malleoli are equidistant from the cassette. • The leg is externally rotated through 45 d • A pad is placed under the knee for support. • A non-opaque square pad and sandbag may be placed against the plantar aspect of the foot to keep the ankle joint in dorsiflexion . • The lower edge of the cassette is placed at the level of the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre 2.5 cm distal to the medial malleolus , with the central ray angled 15 degrees cranially.

21. Subtalar joints .Lateral oblique Position of patient and cassette • The patient lies on the affected side. • The opposite limb is flexed and brought in front of the affected limb. • The affected foot and leg are now further rotated laterally until the plantar aspect of the foot is approximately 45 degrees to the cassette. • The lower edge of the cassette is positioned just below the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre to the medial malleolus , with the central ray angled 20 degrees caudally. Radiograph of subtalar joints – lateral oblique projection

22. Tibia and fibula Antero-posterior – basic Position of patient and cassette • The patient is either supine or seated on the X-ray table, with both legs extended • The ankle is supported in dorsiflexion by a firm 90-degree pad placed against the plantar aspect of the foot. The limb is rotated medially until the medial and lateral malleoli are equidistant from the cassette . • The lower edge of the cassette is positioned just below the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre to the middle of the cassette, with the central ray at right-angles to both the long axis of the tibia and an imaginary line joining the malleoli . Lateral – basic Position of patient and cassette • From the supine/seated position, the patient rotates on to the affected side . • The leg is rotated further until the malleoli are superimposed vertically. • The tibia should be parallel to the cassette. • A pad is placed under the knee for support . • The lower edge of the cassette is positioned just below the plantar aspect of the heel. Direction and centring of the X-ray beam • Centre to the middle of the cassette, with the central ray at right-angles to the long axis of the tibia and parallel to an imaginary line joining the malleoli .

23. Antero-posterior Latera

24. Proximal tibio -fibular joint Lateral oblique – basic .Position of patient and cassette • The patient lies on the affected side, with the knee slightly flexed. • The other limb is brought forward in front of the one being examined and supported on a sandbag . • The head of the fibula and the lateral tibial condyle of the affected side are palpated and the limb rotated laterally to project the joint clear of the tibial condyle . • The centre of the cassette is positioned at the level of the head of the fibula. Direction and centring of the X-ray beam • The vertical central ray is directed to the head of the fibula . Antero-posterior oblique .Position of patient and cassette • The patient is either supine or seated on the X-ray table, with both legs extended . • Palpate the head of fibula and the lateral tibial condyle . • Rotate the limb medially to project the tibial condyle clear of the joint . • The limb is supported by pads and sandbags . • The centre of the cassette is positioned at the level of the head of the fibula. Direction and centring of the X-ray beam • The vertical central ray is directed to the head of the fibula .

25. Knee joint Antero-posterior Position of patient and cassette • The patient is either supine or seated on the X-ray table, with both legs extended. The affected limb is rotated to centralize the patella between the femoral condyles , and sandbags are placed against the ankle to help maintain this position. • The cassette should be in close contact with the posterior aspect of the knee joint, with its centre level with the upper borders of the tibial condyles . Direction and centring of the X-ray beam • Centre 2.5 cm below the apex of the patella through the joint space , with the central ray at 90 degrees to the long axis of the tibia. Normal antero -posterior radiograph

26. Knee joint .Lateral – basic Position of patient and cassette • The patient lies on the side to be examined, with the knee flexed at 45 or 90 degrees (see below). • The other limb is brought forward in front of the one being examined and supported on a sandbag. • A sandbag is placed under the ankle of the affected side to bring the long axis of the tibia parallel to the cassette. • The position of the limb is now adjusted to ensure that the femoral condyles are superimposed vertically. • The centre of the cassette is placed level with the medial tibial condyle . Direction and centring of the X-ray beam • Centre to the middle of the superior border of the medial tibial condyle , with the central ray at 90 degrees to the long axis of the tibia. Lateral radiograph of the knee with 90 degrees of flexion

27. Knee joint Lateral – horizontal beam This projection replaces the conventional lateral in all cases of gross injury and suspected fracture of the patella. Position of patient and cassette • The patient remains on the trolley/bed, with the limb gently raised and supported on pads. • If possible, the leg may be rotated slightly to centralize the patella between the femoral condyles . • The film is supported vertically against th medial aspect of the knee. • The centre of the cassette is level with the upper border of the tibial condyle . Direction and centring of the X-ray beam • The horizontal central ray is directed to the upper border of the lateral tibial condyle , at 90 degrees to the long axis of the tibia. Horizontal beam lateral

28. Knee joint . Antero-posterior – standing projections Position of patient and cassette • The cassette is supported in the chest stand . • The patient stands with their back against the vertical Bucky, using it for support if necessary. • The patient’s weight is distributed equally. • The knee is rotated so that the patella lies equally between the femoral condyles . • The limb is rotated slightly medially to compensate for th obliquity of the beam when the central ray is centred midway between the knees. • The centre of the cassette is level with the palpable upper borders of the tibial condyles . Direction and centring of the X-ray beam • The horizontal beam is centred midway between the palpabl upper borders of the tibial condyles . Standing antero -posterior knee radiograph showing loss of height of the medial compartment due to osteoarthritis

29. Stress projections for subluxation Antero-posterior – stress Position of patient and cassette • The patient and cassette are positioned for the routine anteroposterior projection. • The doctor forcibly abducts or adducts the knee, without rotating the leg. Direction and centring of the X-ray beam • Centre midway between the upper borders of the tibial condyles , with the central ray at 90 degrees to the long axis of the tibia. Antero-posterior knee with varus stress Antero-posterior knee with valgus stress

30. Knee joint Patella Postero -anterior Position of patient and cassette • The patient lies prone on the table, with the knee slightly flexed . • Foam pads are placed under the ankle and thigh for support. • The limb is rotated to centralize the patella . • The centre of the cassette is level with the crease of the knee. Direction and centring of the X-ray beam • Centre midway between the upper borders of the tibial condyles at the level of the crease of the knee, with the central ray at 90 degrees to the long axis of the tibia. Postero -anterior radiograph of normal patella

31. Knee joint Skyline projections Conventional infero -superior projection Position of patient and cassette • The patient sits on the X-ray table, with the knee flexed 30–45 degrees and supported on a pad placed below the knee. • A cassette is held by the patient against the anterior distal femur and supported using a non-opaque pad, which rests on the anterior aspect of the thigh. Direction and centring of the X-ray beam • The tube is lowered. Avoiding the feet, the central ray is directed cranially to pass through the apex of the patell parallel to the long axis. • The beam should be closely collimated to the patella and femoral condyles to limit scattered radiation to the trunk and head . Conventional infero -superior projection

32. Knee joint Supero -inferior Position of patient and cassette • The patient sits on the X-ray table, with the affected knee flexed over the side. • Ideally, the leg should be flexed to 45 degrees to reflect a similar knee position to the conventional skyline projection. Too much flexion reduces the retro-patellar spacing . Sitting th patient on a cushion helps to achieve the optimum position. • The cassette is supported horizontally on a stool at the level of the inferior tibial tuberosity border. Direction and centring of the X-ray beam • The vertical beam is directed to the posterior aspect of the proximal border of the patella. The central ray should b parallel to the long axis of the patella. • The beam is collimated to the patella and femoral condyles . Supero -inferior image

33. Knee joint . Infero -superior – patient prone Position of patient and cassette • The patient lies prone on the X-ray table, with the cassette placed under the knee joint and the knee flexed through 90 dgri • A bandage placed around the ankle and either tethered to a vertical support or held by the patient may prevent unnecessary movement. Direction and centring of the X-ray beam • Centre behind the patella, with the vertical central ray angled approximately 15 degrees towards the knee, avoiding the toes Normal infero -superior radiograph of patella, patient prone

34. Knee joint . Postero -anterior oblique Position of patient and cassette • The patient lies prone on the X-ray table. • The trunk is then rotated on to each side in turn to bring either the medial or the lateral aspect of the knee at an angle of approximately 45 degrees to the cassette . • The knee is then flexed slightly. • A sandbag is placed under the ankle for support. • The centre of the cassette is level with the uppermost tibial condyle . Direction and centring of the X-ray beam • The vertical central ray is directed to the uppermost tibial condyle . Antero-posterior oblique Position of patient and cassette • The patient lies supine on the X-ray table . • The trunk is then rotated to allow rotation of th affecte limb either medially or laterally through 45 degrees . • The knee is flexed slightly . • A sandbag is placed under the ankle for support . • The centre of the cassette is level with the upper border of the uppermost tibial condyle . Direction and centring of the X-ray beam • The vertical central ray is directed to the middle of the uppermos tibial condyle .

35. Knee joint Intercondylar notch (tunnel ) Position of patient and cassette • The patient is either supine or seated on the X-ray table, with the affected knee flexed to approximately 60 degrees. • A suitable pad is placed under the knee to help maintain the position . • The limb is rotated to centralize the patella over the femur . • The cassette is placed on top of the pad as close as possible to the posterior aspect of the knee and displaced towards the femur . Direction and centring of the X-ray beam • Centre immediately below the apex of the patella, with the following angulations to demonstrate either the anterior or posterior aspects of the notch: Radiograph of intercondylar notch

36. Shaft of femur Basic projections Antero-posterior Position of patient and cassette • The patient lies supine on the X-ray table, with both legs extended . • The affected limb is rotated to centralize the patella over the femur . • Sandbags are placed below the knee to help maintain the position . • The cassette is positioned in the Bucky tray immediately under the limb, adjacent to the posterior aspect of the thigh to include both the hip and the knee joints. • Alternatively, the cassette is positioned directly under the limb, against the posterior aspect of the thigh to include the knee joint . Direction and centring of the X-ray beam • Centre to the middle of the cassette, with the vertical central ray at 90 degrees to an imaginary line joining both femoral condyles . Antero-posterior radiograph of normal femur, knee up

37. Shaft of femur . Lateral – basic Position of patient and cassette • From the antero -posterior position, the patient rotates on to the affected side, and the knee is slightly flexed. • The pelvis is rotated backwards to separate the thighs. • The position of the limb is then adjusted to vertically superimposethe femoral condyles . • Pads are used to support the opposite lim behind the one being examined. • The cassette is positioned in the Bucky tray under the lateral aspect of the thigh to include the knee joint and as much of the femur as possible. • Alternatively, the cassette is positioned directly under the limb, against the lateral aspect of the thigh, to include the knee joint . Direction and centring of the X-ray beam • Centre to the middle of the cassette, with the vertical central ray parallel to the imaginary line joining the femoral condyles .

38. Additional projection – lateral horizontal beam Position of patient and cassette • The patient remains on the trolley/bed. If possible , the leg may be slightly rotated to centralize the patella between the femoral condyles . • The cassette is supported vertically against the lateral aspect of the thigh, with the lower border of the cassette level with the upper border of the tibial condyle . • The unaffected limb is raised above the injured limb, with the knee flexed and the lower leg supported on a stool or specialized support. Direction and centring of the X-ray beam • Centre to the middle of the cassette, with the beam horizontal.

39. Leg alignment .Conventional film/screen method Position of patient and cassette • The patient stands on a low step, with the posterio aspect of the legs against the long cassette. The arms are folded across the chest. The anterior superior iliac spines should be equidistant from the cassette. The medial sagittal plane should be vertical and coincident with the central longitudinal axis of the cassette . • The legs should be, as far as possible, in a similar relationship to the pelvis, with the feet separated s that the distance between the ankl joints is similar to the distance between the hip joints and with the patella of each knee facing forward . • Ideally, the knees and ankle joints should be in the anteroposterior position . However, if this impossible to achieve, it is more important that the knees rather than the ankle joints are placed in the antero -posterior position . • Foam pads and sandbags are used to stabilize the legs and maintain the position. If necessary, a block may be positioned below a shortened leg to ensure that there is no pelvic tilt and that the limbs are aligned adequately. Direction and centring of the X-ray beam • The horizontal central ray is directed towards a point midway between the knee joints . • The X-ray beam is collimated to include both lower limb from hip joints to ankle joints .

40. IHTISHAM SAHIL Bs Radiology 4 th samester HIMS PESHAWAR 0345 9865409 0301 8935492