Overview
This lecture covers plain-film radiographic anatomy and common fracture patterns of the lower limb, worked through region by region (hip, knee, ankle, foot) via a series of unlabelled teaching cases. For each region it pairs labelled anatomy diagrams and x-ray landmarks with a case-based introduction to fracture description and classification, including SUFE and neck of femur fracture at the hip, fracture terminology and a tibial fracture at the knee/leg, the Weber classification and Salter-Harris fracture classification at the ankle, and stress and base-of-5th-metatarsal fractures at the foot. Radiographic positioning technique is also introduced for the pelvis and foot. (Note: the lecture deck contains a second, six-slides-per-page handout copy of most of the same material appended after the main deck; its content duplicates the sections below and is not treated separately.)
Imaging Modalities
The lecture opens with a composite slide of lower-limb images representing different imaging modalities without naming them individually: a plain AP knee x-ray, a CT/MR angiogram of lower-limb vasculature, a fluoroscopic/intra-operative image showing a guidewire or catheter, a bilateral paediatric pelvis/hip x-ray, a cross-sectional (CT or MRI) image through the hip, a sagittal cross-sectional (CT or MRI) image of the ankle, and a longitudinal strip image resembling an ultrasound or nuclear-medicine bone scan. [slide does not label or name these modalities explicitly]
Hip Anatomy and Radiographic Assessment
The acetabulum is formed from the ilium, ischium and pubis. Key bony landmarks include the anterior superior and anterior inferior iliac spines, the acetabulum, pubic tubercle, obturator canal and membrane, greater and lesser sciatic notches, ischial spine and ischial tuberosity.
At the proximal femur, the fibrous (iliofemoral ligament) and synovial capsule surround the joint. Blood supply is via the medial and lateral circumflex femoral arteries (the latter with ascending, transverse and descending branches), the deep artery of the thigh, the obturator artery, and the acetabular and retinacular arteries; the acetabular branch runs within the ligament of the head of femur to supply the femoral head. The epiphyseal plate is also identified.
On an AP pelvis film, four acetabular reference lines are drawn: the iliopectineal line, the roof and medial wall of the acetabulum, the posterior wall of the acetabulum, and the ilioischial line. > [!warning] A fourth line (for the anterior wall of the acetabulum) is also drawn on this slide but its label is obscured in the source file. Other landmarks marked on the AP pelvis film are the fovea capitis, femoral head, superior and inferior pubic rami, Shenton’s line, greater trochanter, femoral neck and lesser trochanter. [slide does not elaborate on the clinical significance of Shenton’s line]
Standard pelvis radiographic technique: patient supine, feet internally rotated, with the x-ray tube at a 120 cm focus-film distance; the pubic symphysis and ASIS are used as centring/reference points; angled views are also taken at 45 degrees and 15 degrees. A paediatric pelvis film shows symmetric immature hip joints with visible growth plates and ossification centres.
Hip Pathology: SUFE and Neck of Femur Fracture
SUFE (slipped upper, or capital, femoral epiphysis) typically affects girls aged 8-15 and boys aged 10-17; obesity is the major risk factor. It is assessed on an AP pelvis film by drawing Klein’s lines along both femoral necks and comparing the two sides. Treatment is a single cannulated screw fixed across the affected proximal femoral epiphysis.
Neck of femur fracture (NOF) is described by anatomical location: capital, subcapital, transcervical, intertrochanteric, or subtrochanteric. Treatment shown in the lecture is an angled plate-and-screw (dynamic-hip-screw type) construct fixed across the proximal femur.
Knee Anatomy and Imaging
Knee anatomy: quadriceps, hamstrings, femur, tibia, fibula, patella, articular cartilage, anterior and posterior cruciate ligaments (ACL, PCL), medial collateral ligament (MCL), meniscus and patellar ligament. In cross-section: tendon of quadriceps femoris, suprapatellar bursa, prepatellar bursa, infrapatellar bursa, synovial cavity and infrapatellar fat pad.
On a labelled sagittal knee MRI, structures identified include the prefemoral fat body, quadriceps tendon, patella, patellar ligament, infrapatellar fat, the anterior and posterior horns of the lateral meniscus, popliteus tendon, superior tibiofibular joint, soleus and biceps femoris muscles, and the lateral superior genicular artery.
Knee and Leg Trauma
A 45-year-old woman who fell while skiing (knee pain) had an AP and lateral knee x-ray. The lateral view showed a horizontal fluid level at the suprapatellar region, consistent with a lipohaemarthrosis. [slide does not elaborate on the underlying mechanism or clinical significance]
A 20-year-old man struck in the leg during rugby had a tibial fracture, described using the lecture’s fracture terminology as a moderately displaced, comminuted, transverse fracture of the mid to distal tibial diaphysis, with no angulation.
Fracture Description Terminology
Fractures are described on x-ray using seven descriptors: location, comminution, displacement, angulation, shortening, rotation, and joint involvement (or epiphyseal involvement). Long bone anatomy used in this description includes the proximal and distal epiphyses, physes (growth plates) and apophyses, the metaphyses, the diaphysis, periosteum, cortical (compact) bone, endosteum, and the medullary (spongy) bone and marrow.
Ankle Anatomy and Imaging
The ankle joint comprises the tibia, fibula, talus and calcaneus. On an AP ankle x-ray the joint space, tibial plafond, talar dome, and the lateral and medial malleoli are identified. A standard ankle series consists of three views: AP, Mortise and Lateral.
Ankle Fractures: Weber and Salter-Harris Classifications
A 25-year-old woman with an inversion ankle injury is used to introduce the Weber classification (Danis-Weber classification) of ankle fractures, based on the level of the fibular fracture relative to the syndesmosis:
- Type A: fracture below the syndesmosis
- Type B: fracture at the level of the syndesmosis
- Type C: fracture above the syndesmosis
Her fracture was treated with ORIF: a plate and screws fixing the distal fibula.
A 15-year-old boy with a twisted ankle is used to introduce the Salter-Harris fracture classification of paediatric growth-plate injuries, covering five types (I-V), with the mnemonic given in the lecture: S = Separated, A = Above, L = Below (growth plate), T = Through, ER = Erasure.
Foot Anatomy and Imaging
Foot anatomy: phalanges (distal, middle, proximal), metatarsals 1-5, and the tarsals, comprising the talus, calcaneus, navicular, cuboid, and the medial, intermediate and lateral cuneiforms. On a lateral foot x-ray, additional structures identified are the tibiotalar joint, sinus tarsi, and sesamoid bones.
Three standard foot projections are used: DP (beam angled at 15 degrees), oblique, and lateral.
Foot Fractures
A 40-year-old male runner with foot pain (Case 7) had a second metatarsal stress fracture. A 10-year-old girl who hurt her foot at school (Case 8) is presented as an unanswered “where is the abnormality” case; the slide immediately following it in the deck shows a base of 5th metatarsal fracture, presented as the diagnosis for this case.
Self-test
- Name the three bones that fuse to form the acetabulum.
- List the acetabular reference lines drawn on an AP pelvis x-ray.
- Describe the standard positioning technique for a pelvis x-ray, including focus-film distance and centring points.
- In which age groups does SUFE typically occur, and what is its major risk factor?
- Describe how SUFE is assessed on an AP pelvis x-ray, and how it is treated.
- List the five anatomical descriptors used to classify a neck of femur fracture.
- How was the neck of femur fracture case in this lecture treated?
- Name four structures identifiable on a sagittal knee MRI.
- Describe the radiographic finding on the lateral knee x-ray in the skiing case, and where it was located.
- List the seven descriptors used to describe a fracture on x-ray.
- Using the fracture-description terminology, describe the tibial fracture from the rugby case.
- Name the three standard ankle x-ray views.
- Describe the Danis-Weber classification of ankle fractures, types A to C.
- How was the Weber-classified ankle fracture case in this lecture treated?
- What does the Salter-Harris classification describe, and what does the mnemonic given in the lecture stand for?
- List the tarsal bones of the foot.
- Name the three standard foot x-ray projections and the beam angle used for one of them.
- For each of the hip, knee, ankle and foot, name the fracture or pathology case discussed and any classification system given for it.
Answers
Reveal answers
- Ilium, ischium and pubis.
- The iliopectineal line, the roof and medial wall of the acetabulum, the posterior wall of the acetabulum, and the ilioischial line (a fourth line for the anterior wall is also drawn but its label is obscured in the source).
- Patient supine, feet internally rotated, tube at 120 cm focus-film distance; pubic symphysis and ASIS used as centring/reference points; additional angled views taken at 45 degrees and 15 degrees.
- Girls aged 8-15 and boys aged 10-17; the major risk factor is obesity.
- Klein’s lines are drawn along both femoral necks on an AP pelvis film and compared side to side; treatment is a single cannulated screw fixed across the affected proximal femoral epiphysis.
- Capital, subcapital, transcervical, intertrochanteric, subtrochanteric.
- With an angled plate-and-screw (dynamic-hip-screw type) construct fixed across the proximal femur.
- Any four of: prefemoral fat body, quadriceps tendon, patella, patellar ligament, infrapatellar fat, anterior/posterior horns of the lateral meniscus, popliteus tendon, superior tibiofibular joint, soleus muscle, biceps femoris muscle, lateral superior genicular artery.
- A horizontal fluid level at the suprapatellar region on the lateral view, consistent with a lipohaemarthrosis.
- Location, comminution, displacement, angulation, shortening, rotation, and joint involvement (or epiphyseal involvement).
- A moderately displaced, comminuted, transverse fracture of the mid to distal tibial diaphysis, with no angulation.
- AP, Mortise and Lateral.
- Type A: fracture below the syndesmosis. Type B: fracture at the level of the syndesmosis. Type C: fracture above the syndesmosis.
- With ORIF: a plate and screws fixing the distal fibula.
- It describes paediatric growth-plate (physeal) fracture injuries across five types (I-V). The lecture’s mnemonic: S = Separated, A = Above, L = Below (growth plate), T = Through, ER = Erasure.
- Talus, calcaneus, navicular, cuboid, medial cuneiform, intermediate cuneiform, lateral cuneiform.
- DP, oblique and lateral; the DP view uses a 15 degree beam angle.
- Hip: SUFE (age/risk-factor based, assessed with Klein’s lines, no formal x-ray classification given) and neck of femur fracture (five anatomical-location descriptors). Knee: lipohaemarthrosis on the skiing case (no classification given) and the tibial fracture from the rugby case (described with the seven-descriptor terminology, not a named classification). Ankle: Weber classification (types A-C) and Salter-Harris classification (types I-V) for growth-plate injuries. Foot: second metatarsal stress fracture and a base of 5th metatarsal fracture (neither with a formal classification given).