The acetabular index also called acetabular roof angle or Tönnis angle is a radiographic measurement of femoral head bony coverage by the acetabulum. It is useful in assessing for developmental dysplasia of the hip (DDH) as well as pincer morphology in femoroacetabular impingement (FAI).
The Ahlbäck classification is one of many ways to grade knee osteoarthritis.
grade 1: joint space narrowing (less than 3 mm)
grade 2: joint space obliteration
grade 3: minor bone attrition (0-5 mm)
grade 4: moderate bone attrition (5-10 mm)
grade 5: severe bone attrition (mo...
Allen and Ferguson classification is used for research purposes to classify subaxial spine injuries. It is based ofn the mechanism of injury and position of the neck during injury. This classification was proposed by Allen and Ferguson in 19823 and at the time of writing (July 2016) remains the ...
The American Academy of Orthopedic Surgeons classification of periprosthetic hip fractures divides the femur into three separate regions:
level I: proximal femur distally to the lower extent of the lesser trochanter
level II: 10 cm of femur distal to level I
level III: femur distal to level...
The Anderson and D'Alonzo classification is the most commonly used classification of fractures of the odontoid process of C2.
fracture of the upper part of the odontoid peg (generally oblique)
above the level of the transverse band of the cruciform ligament
The Anderson and Montesano classification of occipital condyle fractures is the most widely used scheme for describing occipital condyle fractures and divides injuries into three types based on morphology and mechanism of injury 1,2,3.
type I - comminuted (3-15%)
Ankle fractures account for ~10% of fractures encountered in trauma, preceded only in incidence by proximal femoral fractures in the lower limb. They have a bimodal presentation, involving young males and older females. Ankle injuries play a major part in post multitrauma functional impairment t...
Ankle injection is a general term which can refer to an intra-articular ankle injection but also other injections, particularly by patients, which include:
Achilles hydrodilation and microtenotomy
ankle joint injection
extensor tendon she...
Anterior cruciate ligament (ACL) avulsion fracture or tibial eminence avulsion fracture is a type of avulsion fracture of the knee. This typically involves separation of the tibial attachment of the ACL to variable degrees. Separation at the femoral attachment is rare 5.
It is mor...
The AO classification of clavicular fractures along with the Neer classification system is one of the more frequently used classification systems when assessing distal clavicular fractures.
The classification system, broken into three categories focuses on the displacement and p...
The AO classification of proximal humeral fractures, along with the Neer classification, is one of the most frequently used systems for classifying proximal humeral fractures.
The AO classification divides proximal humeral fractures into three groups, A, B and C, each with subgroups, and place...
The AO Spine classification of subaxial injuries aims to simplify and universalise the classification of subaxial cervical spine fractures and improve interobserver and intraobserver reliability.
Although its existence is widely known among the relevant subspecialty groups, its day-to-da...
The AO/OTA classification is one of the most frequently used systems for classifying distal tibial fractures or tibial distal end segment fractures. Like other fractures, they are divided into three groups subject to the severity and complexity of the respective injury 1:
type A: extraarticular...
The AO/OTA classification of malleolar segment fractures is one of the most frequently used systems for classifying malleolar fractures. It takes the Danis-Weber classification into account and can be correlated to the Lauge-Hansen classification.
Malleolar fractures are divided into three grou...
The AO Spine classification of sacral injuries aims to simplify and universalise the process of classifying sacral injuries and improve interobserver and intraobserver reliability.
The AO Spine sacral classification is broken into three subsections that follow a hierarchical structure similar t...
The AO Spine classification of thoracolumbar injuries is one of the more commonly used thoracolumbar spinal fracture classification systems and aims to simplify and universalise the process of classifying spinal injuries and improve interobserver and intraobserver reliability 3.
Unlike the othe...
The AO Spine classification of upper cervical injuries aims to simplify and universalise the process of classifying upper cervical injuries and improve interobserver and intraobserver reliability.
Although in routine clinical practice, at least in many institutions, injuries will be desc...
The AO Spine classification systems is a group of imaging morphology-based classification system, combined with clinical factors for injury of spinal trauma. It is designed to be a simple and reproducible method of describing injury patterns.
AO Spine has published four injury classification sy...
The ARCO classification (Association Research Circulation Osseous classification) is one of the staging systems used in the assessment of the femoral head osteonecrosis. It was originally created in 1994 and periodically revised. The most recent revision from 20192 includes the use of radiograph...
Arnold-Hilgartner classification is a plain radiograph grading system for haemophilic arthropathy of the knee 1,2:
stage 0: normal joint
stage I: no skeletal abnormalities, soft-tissue swelling is present
stage II: osteoporosis and overgrowth of the epiphysis, no cysts, no narrowing of the ca...
First published in 2009 with a revised consensus in 2016, the Assessment in SpondyloArthritis International Society (ASAS) classification system utilizes imaging features of the sacroiliac joints on MR imaging to assist in characterizing the presence of sacroiliitis.
The ASAS classification is ...
The American Spinal Injury Association Impairment Scale was developed by the American Spinal Injury Association (ASIA) in 2006, was revised in 2011, and remains the most widely used neurologic classification of spinal cord injury.
The scale divides spinal cord injuries into 5 ca...
The Atzei classification of peripheral triangular fibrocartilage complex (TFCC) tears offers a more differentiated approach on a spectrum of peripherally located triangular fibrocartilage complex (TFCC) tears, which are classically summarized as “Palmer 1b” lesions 1-3.
The Bado classification is one of the more widely used classifications for Monteggia fracture-dislocations and mainly focuses on the radial component. Four types are recognized and are generally based on the principle that the direction in which the apex of the ulnar fracture points is the same ...
Bent bone dysplasias are a class of dysplasia included in a 2010 classification of genetic skeletal disorders 1.
kyphomelic dysplasias, a diverse class, including
congenital bowing of the long bones
cartilage-hair hypoplasia (CHH; metaphyseal d...
Berndt and Harty classification is used for osteochondral lesions of the talus.
stage I: subchondral bone compression (marrow edema)
stage IIa: subchondral cyst
stage IIb: incomplete separation of fragment
stage III: complete separation but no displacement
There are a bewildering number of bone tumors with a wide variety of radiological appearances:
Brachydactyly type A1, also known as Farabee type brachydactyly, is a subtype of brachydactyly.
The anomaly is characterized by hypoplasia or aplasia of middle phalanges of the second to fifth digits in hands and feet and proximal phalanges of the thumbs and great toes...
Brachydactyly type A2 or Mohr-Wriedt type is characterized by hypoplasia/aplasia of the second middle phalanx of the index finger, second toe and sometimes little finger. There is radial deviation of the index finger and tibial deviation of the second toe.
Type A2 brachydactyly can b...
Brachydactyly type A3 is characterized by shortening of the middle phalanx of the little finger with radial deviation of distal phalanx. Slanting of the distal articular surface of the middle phalanx leads to radial deflection of the distal phalanx. However, it is not always associated with clin...
Brachydactyly type A4 or Temtamy type is characterized by brachymesophalangy (absent or hypoplastic middle phalanx) of the second and fifth fingers. Other less common features include club foot, clinodactyly, ulnar deviation of the second finger.
Like other brachydactyly, type A4 is ...
Brachydactyly type A5 is characterized by absence of the middle phalanges and nail dysplasia with duplicated terminal phalanx of the thumb with resultant bifid thumb. Inheritance is suggested as autosomal dominant.
The British Athletics muscle injury classification (BAMIC/BAC) is a five-point MRI-based system that is based on extent and site. It has been primarily based on hamstring injuries but is used in other muscle injuries. The classification system has been shown to have moderate inter- and intra-rat...
Capsulolabral insertion classification reflects the variation in the relationship between the glenoid labrum and the anterior shoulder joint capsule.
type 1: capsule inserts into the labrum proper
type 2: capsule inserts into the base of the labrum, or within 1 cm of the base
The Castellvi classification is used for lumbosacral transitional vertebra (LSTV):
type I: enlarged and dysplastic transverse process (at least 19 mm)
type II: pseudoarticulation of the transverse process and sacrum with incomplete lumbarization/sacralization; en...
The Catterall classification of Perthes disease is based on radiographic appearances of the epiphysis and metaphysis visible in osteonecrosis of the femoral head:
bone absorption changes visible in the anterior aspect of the epiphysis of femoral head
changes are visible best in frog l...
Cervical degenerative disease can be graded using a very old but reliable classification given by Kellgren et al. It is based on findings on a lateral cervical spine radiograph although it can also be applied to MRI evaluation of spine.
The key parameters are osteophyte formation, intervertebra...
There are several cervical spine fracture classification systems:
Anderson and D'Alonzo classification (odontoid fracture)
Roy-Camille classification (odontoid fracture)
Levine and Edwards classification (for traumatic injuries to axis)
Allen and Ferguson classification (subaxial spine injur...
This classification of gamekeeper's thumb (also known as skier's thumb) was proposed by Hintermann et al. 1 in 1993 and is based on whether a fracture is present and whether the injury is stable:
fracture present, which is non-displaced and stable in flexion
typically treated with a sp...
Classification of proximal femoral deficiency (PFFD) can be complicated and numerous such classifications have been proposed. For a discussion of the condition refer to the article proximal focal femoral deficiency.
One of the simplest and most widely used is that proposed by Aitken 1 which is ...
There are several classification systems for sacral fractures, but the most commonly employed are the Denis classification and subclassification systems, and the Isler classification system. These classification systems are important to understand as proper classification can impact management.
Closed reduction-internal fixation, abbreviated to CRIF, refers to the orthopedic operative management of a fracture (or fracture-dislocation complex) where closed reduction is performed (manipulation) and internal fixation is applied, usually in the form of K-wires to stabilize the fracture.
The Cooke and Newman classification of periprosthetic hip fractures is a modification of the Bethea classification proposed several years earlier.
explosion type fracture, comminuted around the stem of the implant
the prosthesis is always loose and the fracture is inherently unstable
Fractures of the coronoid process of the ulna are uncommon and often occur in association with elbow dislocation.
Fracture of the coronoid process is thought to result from elbow hyperextension with either avulsion of the brachialis tendon insertion or shearing off by the...
The Coughlin classification is the most widely used to type bunionettes. It relies on simple angle measurements on weight-bearing foot radiographs taken in the dorsoplantar projection 1,2. In 2013 DiDomenico et al added type IV 2.
type I: enlarged lateral surface of the head of ...
The Dameron-Lawrence-Botte classification, or Lawrence-Botte classification, is a commonly used nomenclature for proximal fifth metatarsal fractures, which are categorized into one of three anatomic zones of involvement:
zone 1: tuberosity (styloid process) avulsion fracture
The de Carvalho index is used to measure patellar height and identify patella alta. Similar to the Caton-Deschamps index, it relies upon the length of the patellar articular surface and its distance from the tibia, reducing erroneous measurements in those with long patella bodies, as measured in...
Degloving injuries can refer to a number of conditions:
degloving soft tissue injury
Morel-Lavallée lesion (closed degloving soft tissue injury)
intramuscular degloving injury
degloving bowel injury
The Delbet classification helps predict the risk of avascular necrosis of the femoral head in neck of femur fractures, as well as determine operative vs non-operative management.
type I: trans-epiphyseal separation
fracture through proximal femoral physis, and represents Salte...
Deltoid ligament injuries involve the deltoid ligament that forms the medial part of the ankle joint. It attaches the medial malleolus to multiple tarsal bones.
Mechanism of injury
It occurs due to eversion and/or pronation injury, or can be associated with lateral ankle fractures.
Depositional arthropathy refers to a group of joint disorders caused by the depositional of substances within and/or around joints.
calcium pyrophosphate dihydrate deposition disease (CPPD)
hydroxyapatite crystal deposition disease (HADD)
This is a basic article for medical students and other non-radiologists
Distal fibula fractures are the most common type at the ankle and are usually the result of an inversion injury with or without rotation. They are the extension of a lateral collateral ligament injury.
The Eaton classification was proposed by Eaton and Malerich in 1980, and presently (time of writing, August 2016) along with Keifhaber-Stern classification, is the most widely accepted classification of volar plate avulsion injuries 1.
Knowledge of the orthopedic Eaton classification is practi...
Elbow injection usually refers to an elbow joint injection, but especially to patients, it can be a term used referring to other procedures which include:
common extensor origin microtenotomy
common flexor origin microtenotomy
distal biceps tendon sheath injection
elbow joint injection
Elbow instability refers to as an excessive, usually painful, mobility in the elbow joint, most of the time as a result of a prior traumatic event or overuse and maybe also seen in patients with connective tissue disease 1,2.
Elbow instability can be classified in respect of tim...
The Ficat and Arlet classification uses a combination of plain radiographs, MRI, and clinical features to stage avascular necrosis of the femoral head.
plain radiograph: normal
clinical symptoms: nil
plain radiograph: normal or minor osteopenia
The Ficat classification of osteonecrosis is based on radiographic findings. In 1985 Dr Ficat published a modified version of his initial classification in 1980:
preclinical and preradiographic
diagnosis is suspected in one hip when the other has a definite disease - this is the stage...
Foot injection is a non-specific term, often used by patients, in reference to tarsal or metatarsal joint injections, and to other injections which include:
calcaneocuboid joint injection
metatarsophalangeal joint (MTPJ) injection
naviculocuneiform joint injection
plantar fascia microtenoto...
General rules and nomenclature of fractures should be understood by, and familiar to, anyone involved in the interpretation or management of fractures of the extremities. This article covers basic nomenclature of fractures.
Before the most appropriate treatment for a fr...
The Frykman classification of distal radial fractures is based on the AP appearance and encompasses the eponymous entities of Colles fracture, Smith fracture, Barton fracture, chauffeur fracture. It assesses the pattern of fractures, involvement of the radioulnar joint and presence of a distal u...
The Garden classification of subcapital femoral neck fractures is the most widely used. It is simple and predicts the development of AVN 1,2. Garden described particular femoral neck and acetabular trabeculae patterns which can assist in recognizing differences within this classification system ...
The Gartland classification of supracondylar fractures of the humerus is based on the degree and direction of displacement, and the presence of intact cortex. It applies to extension supracondylar fractures rather than the rare flexion supracondylar fracture.
type I: undisplaced...
The Genant classification of vertebral fractures is based on the vertebral shape, with respect to vertebral height loss involving the anterior, posterior, and/or middle vertebral body.
grade 0: normal
grade 1: mild fracture, <25% loss of height
grade 2: moderate fracture, 25% to 40% loss of h...
The Gertzbein and Robbins classification assesses the position of transpedicular screws.
Transpedicular screw position is graded from A to E based on the extent by which the screw breaches the cortex of the pedicle 1-3:
A: fully intrapedicular position without breach of the ped...
Gilula three carpal arcs refer to the carpal alignment described on posteroanterior or anteroposterior wrist radiographs and are used to assess normal alignment of the carpus:
first arc: is a smooth curve outlining the proximal convexities of the scaphoid, lunate and triquetrum
second arc: tra...
The Goutallier classification is a classification system used to quantify the amount of fatty degeneration of the rotator cuff muscles, particularly in the context of rotator cuff tendon tears. Although originally described in shoulder CT 1, it is applicable and now most commonly used in MR. It ...
According to CT myelography, brachial plexus injuries can be classified into six types 1:
N type: normal root sleeve and nerve roots
A1 type: slightly deformed root sleeves and nerve roots as compared to unaffected site
A2 type: obliteration of the tip of root sleeves and deformed thickened n...
The Graf method for ultrasound classification system for developmental dysplasia of the hip (DDH) in infants, combines both alpha and beta angles. There are a number of additional subdivisions, which are often not used clinically.
As a general rule, the alpha angle determines the type and in s...
The Gustilo Anderson classification, also known as the Gustilo classification, is the most widely accepted classification system of open (or compound) fractures.
The grading system is used to guide management of compound fractures, with higher grade injuries associated with higher risk of compl...
The Harris classification of acetabular fractures is based on definitions of acetabular walls and columns that differ from the Judet and Letournel classification 1.
The Judet and Letournel classification is more widely used and is applicable to both CT and plain radiographs, whereas, the...
Hereditary connective tissue diseases are an enlarging group of connective tissue diseases that have a degree of inheritance risk. They include:
Marfan syndrome: genetic disease causing abnormal fibrillin
Ehlers-Danlos syndrome: progressive deterioration of collagen and affects joints, heart ...
Classification of Legg-Calvè-Perthes disease based on the height of the lateral pillar:
Group A : No involvement of the lateral pillar with no density changes identified.
Group B : at least 50% of the lateral pillar height maintained
Group C: less than 50% of the lateral pillar maintained
Hip injection can refer to an intra-articular injection, but especially to patients, it can be a term used referring to other procedures around the hip which include:
common hamstrings origin microtenotomy
gluteus minimus/ medius calcific tendinopathy barbotage
greater trochanteric bursa inje...
The Ideberg classification system is the most common system used to describe glenoid fossa and rim fractures 1. Glenoid fractures are uncommon fractures of the shoulder but are important to recognize as they are often associated with concomitant injuries to chest, head, brachial plexus and humer...
The International Myeloma Working Group response criteria are consensus definitions used to assess response to treatment of multiple myeloma. With the latest version published in 2016, the criteria have been widely adopted for classifying responses in clinical trials and in routine practice 1. I...
The Johansson classification of periprosthetic hip fractures was the first classification system proposed and is the simplest. It is based on the level of the fracture in relation to the prosthesis.
type I: fracture proximal to the tip of the prosthesis with the stem still in contact with the m...
The Judet and Letournel classification is the most widely used classification system for acetabular fractures. It classifies acetabular fractures into ten major fracture patterns, which consist of five simple patterns and five complex patterns 1,2.
The morphology of fracture pa...
The Keifhaber-Stern classification was proposed originally by Hastings and later modified by Keifhaber and Stern in 1998. This classification, along with the Eaton classification, is the most widely accepted classification at the time of writing (August 2016) for the management of volar plate av...
The Kellgren and Lawrence system is a common method of classifying the severity of osteoarthritis (OA) using five grades.
The original paper 1 graded OA at the following sites and projections:
cervical spine: lateral
lumbar spine (facet joints only): lateral
Knee injection is a general term and can be made in reference, especially by patients, to multiple procedures which include:
common peroneal (fibular) nerve injection
knee joint injection
patella tendon microtenotomy
quadriceps tendon mic...
The Kuwada classification of Achilles tendon tear was proposed in 1990 4 and at the time of writing (July 2016) remains the most widely used system for describing achilles tendon rupture.
Achilles tendon tears may be grouped (according to severity of the tear and degree of retr...
The Langenskiold Classification of Blount disease uses age and severity of deformity as grading parameters.
Six stage radiographic classification of infantile tibia vara, which is based on changes observed as the child matured:
stage I: 2-3 years
irregularity of metaphyseal os...
The Langer Saldino syndrome or achondrogenesis type II is a subtype of achondrogenesis. It is an extremely rare fatal skeletal dysplasia.
Majority of cases are sporadic. Autosomal dominant inheritance is also another mode. There is mutation in the collagen type II gene (COL...
Lateral humeral condyle fractures also referred to simply as lateral condyle fractures (in the appropriate context), are relatively common elbow fractures that predominantly occur in children. They may be subtle but are hugely important to diagnose in a timely manner because if they are missed, ...
The lateral humeral line is used to confirm the alignment of the pediatric radiocapitellar joint in the coronal plane 1. This is particularly important in injuries such as a Monteggia fracture-dislocation or in a radial neck fracture.
The lateral humeral line is drawn on a pediatri...
The Lauge-Hansen classification system is used for the classification of the ankle injuries based on injury mechanisms which have predictable patterns and imaging findings. Along with the Weber classification, these systems are useful tools for describing and classifying ankle injuries.
Le Fort fractures are fractures of the midface, which collectively involve separation of all or a portion of the midface from the skull base. In order to be separated from the skull base, the pterygoid plates of the sphenoid bone need to be involved as these connect the midface to the sphenoid b...
Levine and Edwards classification is used to classify hangman fractures of the C2, which is also known as traumatic spondylolisthesis of the axis. Upper neck hyperextension causes bilateral pars interarticularis fractures and the amount and direction of displacement will guide treatment.
The Lodwick classification is a system for describing the margins of a lytic bone lesion (or lucent bone lesion). The terms used in the description suggest the level of concern for an aggressive, and possibly malignant, process.
type 1: geographic
1A: thin, sclerotic margin
Lumbar foraminal stenosis or lumbar neuroforaminal stenosis is a common cause of back pain and/or radiculopathy, and is assessed for as part of the routine evaluation of lumbar MRI studies to determine what impact, if any, the surrounding structures have on the exiting nerve root.
Several classification systems exist for the lunate morphology 1, 2.
The lunate classification proposed by Viegas et al. is arguably the most relevant 3:
type I lunate: single distal articular facet for the capitate
type II lunate: additional distal articular facet medially f...
The Magerl classification, one of many thoracolumbar spinal fracture classification systems, was adopted as the original AO classification in 1994 but has since then been superseded: see the current AO classification of thoracolumbar injuries.
Although the Magerl classification is based ...
Here is a list of some of the most useful differential diagnoses in musculoskeletal imaging.
lucent/lytic bone lesions (FEGNOMASHIC)
multiple lucent/lytic bone lesions
benign lytic bone lesions in patients under 30 years old
diffuse bony sclerosis
permeative process in bone