FRCS: Paediatric orthopaedics

Fracture type and patient age. Paediatric hip trauma is uncommon (<1% of all paediatric fractures) and is associated with poor outcomes if complicated by AVN (or malunion). Because of its rarity, identifying the best method of treatment and those factors which truly predict AVN has been difficult to prove scientifically. Although the factors mentioned in this question may be associated with AVN, a meta-analysis of 360 cases shows only patient age and fracture type to be predictive of AVN. The older patient has less potential for revascularization and remodelling of the proximal femur and the more proximal intracapsular fractures are more sensitive to vascular disruption. Fractures are classified according to Delbet and Colonna; type I is transphyseal suffixed A if an associated dislocation is present and suffixed B if no dislocation. Type 2 is transcervical, type 3 cervico-trochanteric and type 4 intertrochanteric. Types 1–3 are intracapsular with type 1A carrying the highest risk of AVN at almost 100%. Type IV is extracapsular with the lowest risk of AVN.

Varus – Extension – Supination. All supracondylar fractures should be reduced by correcting the coronal plane deformity first, followed by the sagittal plane and lastly the axial plane. The exact manoeuvres are determined by the direction of displacement and the location of the periosteal hinge. The more common posteromedial fractures have an intact medial periosteal hinge which aids fracture reduction when the forearm is pronated. The same manoeuvre performed for the less common posterolateral fracture will displace the distal fragment further owing to the lateral periosteal hinge and supination is therefore required to aid fracture reduction.

Forefoot adduction. Forefoot adduction is the commonest residual (as distinct from recurrent) deformity in the treated clubfoot and results either from residual talonavicular subluxation or residual metatarsus varus. Radiographs show a short medial column and longer lateral column. The typical ‘bean-shaped’ foot may also be a product of an associated forefoot supination which is the second commonest residual deformity. Treatment may involve medial column 185 lengthening and lateral column shortening osteotomies in the absence of other contributing factors. When evaluating forefoot deformity, it is essential that the hindfoot is examined to ensure that hindfoot deformity is not giving the false impression of a forefoot problem. Residual forefoot adduction is much less of a problem following Ponseti treatment of the congenital talipes equinovarus (CTEV) deformity.

Forearm supination. The typical hip deformities are flexion, adduction and internal rotation with this latter secondary to excessive femoral anteversion. Collectively, these contribute to a scissoring gait. The ‘windswept deformity’ may occur particularly in non-ambulatory patients where one hip is abducted and the other adducted. Typically, the knee is flexed. The common foot abnormalities are secondary to the tendency to toe walk and they include equinovalgus and equinovarus deformities. The upper limb tends to be affected by flexion of the elbow, wrist and fingers with or without the ‘thumb in palm’ deformity. Swan-necking of the fingers is also seen commonly. The forearm is usually pronated. The spine may demonstrate an increased lumbar lordosis, scoliosis or a kyphosis: often dependent on the predominant muscle tone (low or high). A ‘wide-based gait’ is seen in ataxic cerebral palsy.

C-reactive protein (CRP) >20. Due to the rapid chondrolytic effect of pus within the joint, pyogenic septic arthritis of the hip in children represents a surgical emergency. It can be difficult to distinguish a septic hip from other causes of hip pain in children. In such cases, whilst clinical suspicion remains of paramount importance, Kocher’s diagnostic algorithm is a useful tool. The four diagnostic criteria are non-weight-bearing, ESR >40, WBC >12 and fever. The predicted risk of a septic arthritis varies with the number of positive criteria. The algorithm has been tested retrospectively and prospectively. In the prospective validation study the probabilities were lower: Number of criteria met Chance of septic arthritis (original study) Chance of septic arthritis (validation study) 1 3% 9.5% 2 40% 35% 3 93% 73% 4 99.6% 93%

Posteromedial tibial bowing. Fibular hemimelia is a postaxial deficiency or dysplasia in which there is aplasia or variable hypoplasia of the fibula. There are a number of associated features comprising from distal to proximal: absent lateral rays and/or tarsal bones, tarsal coalition, ball and socket ankle, valgus ankle, anteromedial tibial bowing, flattened tibial spine, absent anterior cruciate ligament (ACL), genu valgum, hypoplastic lateral femoral condyle, lateral patellar subluxation, femoral hypoplasia, coxa vara and possibly a true proximal femoral focal deficiency (PFFD). Congenital posteromedial bowing of the infantile tibia is considered ‘benign’ in that the deformity improves with growth. However, there is often a significant residual leg length discrepancy. 186

3.0 cm. Epiphysiodesis of the longer limb is used to treat predicted leg length discrepancies of 2–5 cm. The ‘rule of thumb’ serves as an estimate of remaining growth and therefore guides the surgeon when to perform epiphysiodesis. Lower limb growth occurs from four main physes: most growth occurs around the knee with the greatest contribution from the distal femoral physis at 10 mm per year. The proximal tibial physis contributes a further 6 mm per year with lesser contributions from the proximal femoral and the distal tibial physes (3–4 mm each). Physes are expected to close at approximately age 14 in girls (or 18 months after menarche) and age 16 in boys. Therefore, in this example, physeal closure is expected after 2 years giving a total of 32 mm [(10 2) þ (6 2)]. However, the rule of thumb must be used with caution as bone age and the non-linear growth pattern of bones needs to be taken into account. Aguilar et al have devised and validated a multiplier method for predicting growth and limb length discrepancy which may be more accurate but a little more time consuming and difficult to calculate.

Medial circumflex vessels. The blood supply to the proximal femoral epiphysis is reported to change with age. Until age 4, the supply to the femoral head is derived equally from medial and lateral circumflex vessels as well as the ligamentum teres. The physis acts as a mechanical barrier with virtually no traversing metaphyseal vessels reaching the epiphysis. After age 4, supply from the ligamentum teres diminishes and the distribution of supply from the circumflex vessels changes; the lateral circumflex system supplies predominantly the metaphysis whilst the medial circumflex system becomes the predominant supply to the proximal femoral epiphysis via its posterosuperior branch. After age 10 years, supply by the ligamentum teres diminishes further and the femoral epiphysis relies upon the end arterial supply of the retinacular vessels. With the closure of the physis at skeletal maturity, anastamoses develop between the vessels of the ligamentum teres, epiphyseal and metaphyseal systems and there is less reliance on end arteries.

Isolated rib fractures. The high incidence of fractures in NAI means that one-third of cases are eventually reviewed by an orthopaedic surgeon. Injury patterns vary with age and mobility of the child and an injury out of keeping with the child’s developmental stage or where the mechanism does not fit should raise suspicion. No fracture is pathognomonic and the diagnosis is made on the basis of all the information available from the history, examination and investigation findings. However, certain fractures and patterns of injuries are associated with NAI. Isolated or multiple rib fractures are the most specific. Other associated fractures include those of the scapular, lateral clavicle, vertebrae and complex skull fractures (not linear fractures). Transphyseal fractures through the proximal femoral physis are commonly due to NAI in the non-ambulatory child. The pattern of injury is also important – soft tissue injuries accompanying fractures such as bruises, bites or burns are characteristic of NAI as are multiple fractures at different stages of healing and metaphyseal corner or bucket handle fractures.

Gestational diabetes. The two most important risk factors for developmental dysplasia of the hip are a positive family history and breech position. The other important risk factors are first 187 born children and female sex. Gestational diabetes is not particularly associated with developmental dysplasia of the hip.

Chemoresistance. Rhabdomyosarcoma is the commonest soft tissue sarcoma in children particularly under age 5. It is a highly malignant tumour formed from muscle cell progenitors. It can occur in regions with little skeletal muscle and most commonly presents as a tumour of the head and neck (40%) with a lower incidence in the extremities (20%). It is associated with persistence of the embryonal protein myoD1 that usually vanishes when normal muscle matures and becomes innervated. Histologically, the characteristic findings are spindle cells, giant cells and racquet cells. The rhabdomyoblasts are recognizable by their cross striations. These tumours are difficult to treat surgically but are both chemo- and radiosensitive. Patients commonly receive neoadjuvant chemotherapy followed by wide local excision and post-operative radiotherapy.

Central – medial – lateral; posterior – anterior. A Tillaux fracture is a Salter–Harris III avulsion injury of the anterolateral distal tibial physis by the anterior tibiofibular ligament (ATFL). It occurs following a low energy external rotation injury mechanism between the ages of 11 and 15 more commonly in girls and during sporting activities. It is the sequence of physeal closure at the distal tibia which accounts for this pattern of injury. Physeal closure begins with the central third, followed by the medial third and lastly the lateral third. Closure also occurs in a posterior to anterior direction and therefore, with injury, the strong ATFL avulses the relatively weak anterolateral portion of the epiphysis. The fragment is usually displaced anterolaterally and there may be associated diastasis. The Tillaux fragment should be fixed if displacement is >2 mm.

Risser 3. Risser staging 1–5 depends on the amount of ossification of the iliac apophysis visible on the anteroposterior (AP) radiograph. Ossification begins anterolaterally and proceeds posteromedially. The first 25% equates to Risser 1 and grade 4 equates to 100% ossification. Grade 5 is signified by fusion of the apophysis. The relevance of Risser staging is in predicting the progression of scoliotic curves. Small curves and greater skeletal maturity according to the Risser stage predicts a smaller likelihood of curve progression compared to larger curves and skeletal immaturity.

Proliferative. Fibroblast growth factors (FGFs) affect the growth of long bones through stimulation of the proliferative zone. In achondroplasia, a defective FGF receptor gene (FGFR3) is responsible for the characteristic limb shortening.

Coxa vara. Achondroplasia is a type of rhizomelic dwarfism caused by an autosomal dominant genetic defect in the FGFR3 gene that is responsible for long bone growth. Therefore, individuals may have a normal sitting height with a reduced standing height. Progressively short pedicles in the distal spine predispose the child to problems with spinal stenosis. There is often an excessive lumbar lordosis and a junctional kyphosis in the non-ambulant child. 188 Achondroplasia is associated with coxa valga and genu varum with a disproportionately long fibula whereas spondyloepiphyseal dysplasia congenita is associated with the opposite deformities of coxa vara and genu valgum. Other features of achondroplasia comprise frontal bossing, trident hands, radial bowing, radial head subluxation, a champagne glass pelvis, inverted V-shaped distal femoral physes and tibial bowing.

Budd–Chiari syndrome. Neural tube defects (NTDs) are a spectrum of disorders caused by failure of the posterior neural elements to fuse at around 3–4 weeks’ gestation. The causes are multifactorial although a raised level of homocysteine, a consequence of folate deficiency, is strongly implicated. NTDs are either open or closed. Open lesions usually involve the entire central nervous system (CNS) with leakage of cerebrospinal fluid (CSF) and result from failure of primary neurulation. Closed lesions are usually localized to the spine and result from failure of secondary neurulation. Closed types are covered by an epithelial layer and neural elements are therefore not exposed. However, any overlying skin may be dysplastic and cutaneous stigamata such as a pit or a hairy patch may be noticeable. The effects of NTDs depend on their location and severity although paralysis (flaccid and/or spastic) and bowel and bladder incontinence are characteristic. A type II Arnold–Chiari malformation is the commonest associated condition: downwards displacement of the cerebellar tonsils through the foramen magnum which can lead to hydrocephalus and mental retardation. Budd–Chiari syndrome is occlusion of the hepatic veins and is unrelated to NTDs.

More difficult cord visualization in neutral position. When providing airway management to the paediatric trauma patient, the anatomical differences between children and adults must be considered. A relatively large occiput naturally flexes the C-spine causing buckling of the pharynx. A neutral position with the midface parallel to the spinal board is recommended. As the larynx is more anterior and cephalad, this position also improves visualization of the cords although a larger tongue and tonsils may interfere with this. The larynx is also funnel shaped allowing greater accumulation of secretions. A shorter trachea means a greater risk of right main bronchus intubation, tube displacement, inadequate ventilation and barotrauma.

Elmslie–Trillat procedure. Surgical procedures for chronic patellofemoral instability are often used in combination and include soft tissue or bony procedures performed proximally, at the level of the joint or distal to it. A TT-TG distance of greater than 15 mm on CT suggests an increased Q-angle necessitating medial tibial tubercle transfer (Elmslie–Trillat). Unlike the Hauser technique, the Elmslie–Trillat does not involve posterior displacement which increases patellofemoral contact pressures contributing to pain and degeneration. Patellar alta is an indication for distal TT transfer. Trochlear dyplasia is recognized on lateral radiographs by the presence of the ‘crossing sign’ and may require a trochleoplasty to deepen and lateralize the trochlear groove. Lateral release is only indicated for isolated lateral patellar tilt and should be combined with another procedure if other factors are present. In the presence of a normal Q-angle, proximal soft tissue realignment procedures should be considered such as MPFL reconstruction and vastus medialis oblique (VMO) advancement. 189

Homeobox genes. Limb buds are formed from mesoderm covered with surface ectoderm. The upper limb bud appears at 4 weeks post-fertilization and the lower limb bud appears two days later. Two areas form within the mesoderm – the lateral mesoderm which forms bone, cartilage and connective tissues and the somite which forms the muscular elements. Homeobox (Hox) genes via fibroblast growth factors (FGFs) influence development of the apical ectodermal ridge (AER), which is responsible for proximal to distal growth. Hox gene abnormalities therefore lead to proximal/distal losses. The AER is a transient region of activity from which the digits develop. Separation of the digits occurs at around 50 days. Apoptosis under the influence of BMPs allows digits to separate and prevents webbing whereas noggins block apoptosis thereby preserving the webbing of the digits. The Sonic hedgehog genes control the zone of proliferating activity (ZPA) in the mesoderm that is responsible for radial to ulnar growth and differentiation, i.e. the little (fifth) finger from the thumb.

There is an accepted and effective treatment. Neonatal hip instability is common; if instability persists, particularly when associated with anatomical dysplasia, true DDH develops. Clinical examination is less than 100% sensitive/specific and a missed diagnosis of DDH can lead to multiple invasive procedures and lifelong disability. Ultrasound screening in the neonatal period may therefore improve the accuracy of diagnosis leading to the provision of early treatment which is less invasive and of shorter duration with a greater likelihood of normal hip development. Although hip instability is commonly detectable in the newborn, most will resolve spontaneously without the need for treatment. However, there is no evidence proving the accuracy of ultrasound as a screening tool. Although ultrasound tends to lead to less invasive treatment of shorter duration, screening may lead to overtreatment. Not only is the evidence of the effectiveness of early non-invasive treatment lacking but non-invasive treatments such as the Pavlik harness are not without morbidity and carry a risk of AVN. Therefore, although ultrasound examination is a useful tool for assessing the infant hip prior to ossification, its use for screening remains controversial. It does not meet some of the criteria for a good screening test in that information on the natural history of the disease and the optimal treatment of DDH is lacking. Some countries provide generalized screening although this is not the case in the UK where selective screening of at-risk infants is performed.

Presentation at 12–16 years. Tarsal coalition is due to failure of segmentation of the tarsal bones of the hind- and midfoot and can be partial or complete, fibrous, cartilaginous or bony. It is an autosomal dominant condition with a 20% incidence of multiple coalitions. Although congenital, symptoms occur when the coalition ossifies explaining why each type of coalition presents during a particular age range. Calcaneonavicular coalitions tend to present earlier between 8 and 12 years whereas talocalcaneal coalitions present later, at 12–16 years. Ossification causes loss of subtalar motion, adaptive shortening of the peronei and flatfeet; hence the term ‘spastic peroneal flatfoot’. The typical presentation comprises recurrent ankle sprains, calf pain and flatfeet. The radiographic ‘anteater sign’ represents the elongated anterior process of the calcaneum in calcaneonavicular coalition whereas talar beaking can be seen whenever there is stiffness of the subtalar joint complex. Middle facet talocalcaneal coalition 190 produces the greatest subtalar stiffness, with a valgus hindfoot. Over time, the adaptive shortening of the peroneal tendons contributes to posterior facet arthrosis in the subtalar joint regardless of the type of coalition.

Clinodactyly. The causes of congenital hand anomalies may be classified according to Swanson and the IFSSH (International Federation for Societies for Surgery of the Hand) system: failure of formation, failure of differentiation, duplication, hyperplasia, hypoplasia, amniotic bands, generalized dysplasias or combinations thereof. Clinodactyly (failure of differentiation) is a fixed ulna bowing usually of the little finger. Brachysyndactyly (failure of differentiation) means short digits with webbing between. Camptodactyly (failure of differentiation) is characterized by fixed flexion deformity usually of the interphalangeal joints of the little fingers. Acrosyndactyly is a form of constriction band syndrome which joins digits previously separated. Symphalangism (failure of differentiation) is a congenital ankylosis usually affecting the proximal interphalangeal joints.

Ischial tuberosity. The pelvic apophyses appear in early adolescence and fuse around age 14–16. Avulsions therefore occur most commonly in teenagers during sporting activities. Football and gymnastics are commonly associated with these injuries. Avulsion of the ischial tuberosity is the commonest type caused by sudden hip flexion with knee extension such as striking a football. The diagnosis is usually apparent on plain radiographs. Avulsion injuries are best treated conservatively with a gradual return to sporting activity after 3 months. Unrecognized avulsions may heal with abundant callus and can be misdiagnosed as bone tumours. The situation can be clarified with CT or MR imaging.

Sharp’s All of these lines on the anteroposterior (AP) pelvic radiograph are used to assess the degree of hip dysplasia/incongruence. Hilgenreiner’s line is made horizontally through the superior triradiate cartilage and serves as a reference for Perkin’s line and for measuring the acetabular index. Perkin’s line is perpendicular to Hilgenreiner’s at the superior edge of the ossified acetabulum. Normally, the femoral head should sit in the inferomedial quadrant at the intersection of these lines. Shenton’s line traces the lower edge of the pubis and the inferior aspect of the femoral neck. Any disruption to this line implies joint subluxation. Wiberg’s angle, known as the centre edge angle, is formed by the intersection of a line passing vertically upwards from the centre of the femoral head and a second line again passing from the centre of the head to the superior edge of the ossified acetabulum. This calculation is most reliable after age 5 due to increased ossification. A normal Wiberg’s angle is >25
. Sharps’s line is an alternative method of measuring the acetabular angle. The more common method is to use Caffey’s line drawn from the superior ossified acetabulum which forms an angle with Hilgenreiner’s line at the superior margin of the triradiate cartilage. This method measures the superior acetabular angle that should be <30
under age 2 191 and <20
after age 2. Sharp’s angle measures the inclination of the entire acetabulum. Sharp’s angle is formed by the intersection of a horizontal line at the inferior teardrop and a line passing through it that joins the superolateral and inferomedial aspects of the bony socket. It is used after 9 months when the teardrop becomes visible radiologically. Normal infants should have a value of <50
reducing to <38
in adolescence.

Anterior shoulder dislocation. Erb’s palsy is the most common obstetric brachial plexus injury and the one with the best prognosis. It is caused by a traction injury at Erb’s point: the union of the C5 and C6 nerve roots. The most commonly affected nerves are the axillary (supplying deltoid and teres minor), the suprascapular nerve (supplying the supraspinatus and infraspinatus muscles) and the musculocutaneous nerve (supplying biceps and brachialis muscles). Erb’s palsy gives rise to the characteristic ‘waiter’s tip’ deformity of shoulder adduction and internal rotation, elbow extension, forearm pronation and wrist flexion. Like other neuromuscular conditions in children, soft tissue contractures lead to secondary bony deformity and joint incongruence. In Erb’s palsy, internal rotation of the shoulder caused by relative overactivity of subscapularis leads to dysplasia of the posterior glenoid and posterior (rather than anterior) instability.

Epiphyseal hyperplasia Rubin classifies skeletal dysplasias according to their location of origin within the bone and whether due to over- or underactivity. Trevor’s disease is also known as ‘dysplasia epiphysealis hemimelica’ and is due to hyperplasia within the epiphysis (epiphyseal osteochondroma). It is now more common for dysplasias to be diagnosed genetically rather than radiologically. Hypoplasia Hyperplasia Epiphysis Spondyloepiphyseal dysplasia/multiple epiphyseal dysplasia Trevor’s disease Physis Achondroplasia Enchondromatosis Metaphysis Osteopetrosis Multiple hereditary exostoses Diaphysis Osteogenesis Diaphyseal dysplasia 192 1. Concerning Pipkin’s classification of femoral head and neck fractures, which of the following is not true? a. Posterior dislocation of the hip with fracture of the femoral head caudal to the fovea centralis is a type I fracture. b. A type III fracture is rare, in conjunction with femoral neck fracture. c. Posterior dislocation of the hip with fracture of the femoral head cephalad to the fovea centralis is a type II fracture. d. A femoral head fracture with associated fracture of the acetabulum is a type III fracture. e. A and D. 2. Considering Schatzker’s classification of fractures of the tibial plateau, which of the following statements is false? a. Type I fractures are wedge fractures of the lateral plateau, displaced or undisplaced. b. Type III fractures show depression of the lateral plateau without an associated wedge fracture. c. Type II fractures are often seen in patients whose average age is over 50. d. Anterior cruciate ligament injuries are commonly seen in type V and VI injuries. e. A type V fracture consists of a wedge fracture of the medial and lateral plateaux with metaphyseal–diaphyseal discontinuity. 3. Which of the following statements is incorrect regarding ankle fractures? a. On a mortise view, the tibiofibular overlap should normally be more than 4 mm. b. A Maisonneuve fracture is a high fibular fracture and involves disruption of syndesmosis. c. A Dupuytren’s fracture is a fracture-dislocation with a high fibular fracture. d. On an anteroposterior (AP) radiograph, the medial clear space should be less than 4 mm. e. The talocrural angle can be used to assess shortening. # Cambridge University Press 2012. 198