FRCS Mock Exam #201828-1

Risk of dislocation. As part of a deltopectoral approach, the subscapularis is taken down off the humerus. This may be done trans-tendon, directly off bone, or with a lesser tuberosity osteotomy. In the initial post-operative period passive external rotation is limited to a maximum 30
to allow healing and protect the repair.

Posterior column and posterior hemitransverse. The Judet and Letournel classification describe 10 fracture patterns: Simple fractures posterior wall posterior column anterior wall anterior column transverse Complex/associated fracture both columns posterior wall and transverse T-shaped fracture anterior column and posterior hemitransverse posterior wall and posterior column

Previous formation of heterotopic ossification. Although the exact aetiology is poorly understood, if there is a history of heterotopic ossification, then it is very likely to recur at a new site of surgery. Other factors include: ankylosing spondylitis, hypertrophic osteoarthritis, and diffuse idiopathic skeletal hyperostosis, with weaker evidence for extensive soft tissue handling/stripping, or bone debris from reamings. Although patients with head injuries are found to produce extensive calcific deposits a patient would not have elective total hip replacement so soon after significant head injury. Over-expression of bone morphogenetic protein-4 BMP-4) may be implicated in the pathogenesis of heterotopic ossification.

Decreased risk of re-injury. This patient has an Achilles tendon rupture. Operative and non-operative management are both acceptable options, but the principal advantage of the former is a decreased risk of re-rupture. This benefit has to be balanced against the complications of surgery, which include wound breakdown, infection and nerve injury. Some of these risks may be reduced by performing surgery percutaneously. Pain and speed of recovery are not necessarily improved by surgery. Surgery may allow a shorter immobilization time, but this is not the principal benefit.

Urine cortisol. The opening line of this case may tempt one to consider the diagnosis of Duchenne’s muscular dystrophy for which choice B would be the correct answer. This child has features of Cushing’s syndrome, which can be caused by excess adrenocorticotrophic hormone (ACTH) production or occur independent of ACTH, due to an adrenal adenoma. Obesity, hypertension, bruising and proximal myopathy are all features of Cushing’s syndrome. The first step in establishing this diagnosis is to measure the urinary free cortisol. The cause of the Cushing’s syndrome can then be determined by performing the dexamethasone suppression test, measuring plasma ACTH and obtaining an MRI of the pituitary if appropriate.

Total elbow replacement. The Larsen classification of the rheumatoid elbow is based on plain radiographs and is graded I–V: Grade I – soft tissue swelling and osteoporosis. Grade II – mild narrowing of the joint space and some marginal erosion. Grade III – significant joint space narrowing. Grade IV – integrity of subchondral plates is breached by deep erosions. Grade V – total joint destruction

IIB. The case in this question is of a high-grade tumour (dedifferentiated chondrosarcoma), which has invaded its natural anatomical barrier (periosteum) to become extraosseous and hence extracompartmental, in the absence of metastases, i.e. stage IIB. Stage is determined by three different subcategories: G1: Low grade G2: High grade T1: Intracompartmental T2: Extracompartmental M0: No identifiable skip lesions or distant metastases M1: Any skip lesions, regional lymph nodes or distant metastases Enneking’s and MSTS Staging System of Malignant Bone Tumours: IA Low grade, intracompartmental G1 T1 M0 IB Low grade, extracompartmental G1 T2 M0 IIA High grade, intracompartmental G2 T1 M0 IIB High grade, extracompartmental G2 T2 M0 IIIA Any grade, intracompartmental, with metastases G1/2 T1 M1 IIIB Any grade, extracompartmental, with metastases G1/2 T2 M1

Pain avoidance. Yellow flags are psychological factors shown to be indicative of long-term chronicity and disability which include a negative attitude that back pain is harmful or severely disabling resulting in fear avoidance behaviour and reduced activity levels. There is a tendency to depression, low morale and social withdrawal.

Complete C5. Spinal cord injury levels are defined by the ASIA classification. Complete injuries are defined as: No voluntary anal contraction with a distal power MRC 0 and 0/2 distal sensory score (absent perianal sensation) with an intact bulbocavernous reflex (patient not in spinal shock). This patient is functional at C5 (deltoid and biceps) and not functional at C6 (wrist extensors) and C7 (wrist flexion and triceps). His last functional level is C5 indicating a C5 neurological level. It is complete as his distal motor and sensory function is absent.

Flexion/extension of the C-spine is often reduced. Contrary to the common belief, the classic triad of low posterior hairline, short neck and reduced range of movement is seen in fewer than 50% of patients with Klippel–Feil syndrome. A Sprengel deformity is seen in 33% of cases, congenital scoliosis occurs in 60% and renal abnormalities is encountered in 33% of cases. Lateral side bending is usually limited whilst flexion/extension is often preserved.

Ca10 (PO4)6 (OH)2. Calcium hydroxyapatite (Ca10 (PO4)6 (OH)2) forms part of the inorganic component of the bone matrix and gives it compressive strength.

5º valgus, 10º external rotation, 0º flexion, 5 mm posterior talar translation. It is extremely important to fuse the ankle in the correct position. The position affects knee function and the ability to walk on uneven ground. The ideal position of arthrodesis is neutral flexion, 0–5
valgus of hindfoot valgus, 5–10
of external rotation, and slight posterior displacement of the talus under the tibia (5 mm). Posterior displacement normalizes the gait pattern and decreases the stress on the knee.

A University of Colarado Biomechanics Laboratory orthosis is often effective treatment. Tibialis posterior tendon dysfunction is very common and often misdiagnosed as a ‘sprain’ or ‘arthritis’. Johnson and Strom described three stages and Myerson added a fourth: I – tenosynovitis, normal tendon length, no deformity II – tendon lengthening, flexible planovalgus deformity III – rigid planovalgus deformity IV – valgus ankle tilt The ‘too many toes’ sign refers to the number of toes seen from behind; normally up to three, but with a planovalgus deformity, more may be seen. Treatment is always non- operative in the first instance, and can include a University of California (not Colorado) Biomechanics Laboratory heel cup orthosis. Surgery may include tendon debridement, tendon reconstruction, medial displacement calcaneal osteotomy, lateral column lengthening and triple or pantalar arthrodesis. If the tendon is acutely ruptured, which is rare, the flatfoot develops over time as the static stabilizers fail. Normally the tibialis posterior stabilizes the midtarsal joint, if it is absent or defunctioned the midtarsal joint is overloaded and the static supporters (spring ligament, talonavicular capsule, plantar fascia) fail. The arch eventually collapses and a flatfoot ensues.

Less in ceramic than polyethylene cups. The Swedish Hip Registry reports that deep infections are slightly lower with ceramic components. The exact mechanism is unclear, but may be due to bacterial adhesion being poorer on the smoother surface of ceramic components.

Medial scapular winging. The long thoracic nerve supplies serratus anterior, injury to which can result in medial translation of the scapular and the inferior angle rotated medially. Lateral scapular winging (lateral translation and the inferior angle rotated laterally) can occur as result of spinal accessory nerve palsy which supplies trapezius.

Wrist arthrodesis. The Lichtman classification system essentially divides Kienbock’s disease into types that can be treated with therapeutic operations such as radial shortening or grafting versus those that need salvage operations such as partial or complete wrist arthrodesis. One of the deciding factors in the type of fusion is the degree of fixed deformity. In the presence of fixed deformity radial shortening is not an option. It is also not an option in the more uncommon scenario of the ulnar positive wrist. The Lichtman classification, based on radiographs, is as follows: Stage 1 – normal (may have a linear or a compression fracture) Stage 2 – sclerosis but no collapse Stage 3A – collapse of entire lunate without fixed scaphoid rotation Stage 3B – collapse of entire lunate with fixed scaphoid rotation Stage 4 – stage III with generalized degenerative changes in the carpus 19

Enchondral ossification. Primary healing (also known as Haversian remodelling) is a direct healing process at the cortex requiring anatomical reduction and rigid stability. Secondary bone healing involves responses in the periosteum and external soft tissues. There are two types; enchondral healing which occurs with non-rigid fixation (such as fracture braces, external fixation, bridge plating, intramedullary nailing); and intramembranous healing which occurs with semi-rigid fixation (such as locked plating in a non-absolute stability construct).

Lateral cutaneous nerve of thigh. The ilio-inguinal approach is an exam favourite. It affords exposure to the inner aspect of the pelvis from the sacroiliac joint all the way to pubic symphysis. The lateral cutaneous nerve of thigh often is in the way and must be sacrificed. Although infrequently used by 86 most surgeons, it would be worth memorizing the concepts of this approach, particularly the structures at risk in the three ‘windows’: Lateral – between the iliac wing and the iliopsoas muscle; Middle – between the femoral nerve (iliopsoas muscle) and the external iliac vessels; Medial – between the lymphatics and the rectus abdominus at the level of the pubic tubercle.

It originates underneath the anterior longitudinal ligament and can cause destruction of several contiguous levels. Spinal tuberculosis (TB) originates in the metaphysis of the vertebral body and spreads under the anterior longitudinal ligament causing destruction of several contiguous levels and skip lesions in 15% of the cases. The disc spaces are preserved in the early stages of the infection, which differentiates TB of the spine from pyogenic infection. Contrary to a spinal cord injury occurring as a result of meningomyelitis, a cord injury secondary to direct pressure from the TB abscess or the bony sequestra carries a good prognosis.

Osteofibrous dysplasia. Most orthopaedic oncology centres would agree that there is no role for curettage and grafting in osteofibrous dysplasia. This condition often regresses by the time a child reaches 161 skeletal maturity and therefore observation is all that is required. This line of management is controversial. Osteofibrous dysplasia has been linked to progression to adamantinoma, in which case wide surgical excision is recommended.

Spring. The intertarsal ligaments in the foot are important for stability. The cervical is also termed the interosseous talocalcaneal. The bifurcate is composed of two ligaments, which are also termed calcaneocuboid and calcaneonavicular. The long plantar is also termed calcaneocuboid-metatarsal: it arises from the calcaneum and inserts into the cuboid and all five metatarsals. The short plantar is the plantar calcaneocuboid. The spring ligament is the plantar calcaneonavicular and arises from the sustentaculum tali.

Inwardly displaced parasymphyseal fracture >1 cm. The single biggest predictor of urethral injury is pubic symphysis diastasis, especially of >1 cm, along with medially displaced medial 1/3 fracture. However, inward displacement didn’t result in a large number of patients having urethral injury. It would appear that the traction caused to the urethra is more significant than compression. 87 remains tight laterally in extension. The next most appropriate step is to? a. Carry out a medial release. b. Carry out a medial release and increase the size of the polyethylene insert. c. Release the iliotibial band. d. Release popliteus. e. Decrease the size of the polyethylene insert. is false? a. The maximum load to failure of a patellar tendon graft is approximately 2600 newtons. b. The use of an autologous hamstring graft results in a 50% loss of hamstring strength. c. The maximum load to failure of a quadruple hamstring graft is approximately 4500 newtons. d. Allograft processing does not always alter the mechanical properties of the graft. e. The maximum load to failure of the native ACL is approximately 2100 newtons. rotation? a. Anterior cruciate ligament (ACL). b. Posterior cruciate ligament (PCL). c. Lateral collateral ligament (LCL). d. Medial collateral ligament (MCL). e. Patellar tendon. squat. The most likely diagnosis is? a. Primary osteoarthritis. b. Osteochondral defect. c. Loose body. d. Posterior horn meniscal tear. e. Pigmented villonodular synovitis. 93

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.

Forefoot pronation. Congenital talipes equinovarus (clubfoot) is a deformity of the foot with an incidence of 1 in 250–1000. It is more common in males and is often bilateral. There may be associated 135 musculoskeletal anomalies. A number of deformities are seen: forefoot adduction (tibialis posterior), forefoot supination (tibialis anterior), midfoot cavus (intrinsics, flexor hallucis longus, flexor digitorum longus), hindfoot varus (Achilles tendon, tibialis posterior) and hindfoot equinus (Achilles tendon). Dr Ponseti has revolutionized the treatment of clubfoot from a surgical (posteromedial release) to a non-surgical one (serial casting).

Right L5 perineural fibrosis. Gadolinium-enhanced MRI scans are helpful post discectomy in differentiating between recurrence of disc herniation, which does not enhance with gadolinium, and perineural 61 fibrosis, which shows enhancement around the root. A schwannoma enhances with gadolinium although the root would be enlarged. Systemically the patient is well and there is no evidence of fluid collection on scanning to suggest an infective process.

In the prediction of malunion, the presence or absence of comminution is not an important factor. Important factors in predicting early and late instability and radiographic outcome after distal radial fractures include patient age, metaphyseal comminution of the fracture and ulnar variance. Dorsal angulation has not been shown to be significant in the prediction of radiographic outcome for displaced fractures.

The middle genicular artery. The middle genicular artery supplies the anterior and posterior cruciate ligaments and the synovial membrane. The medial superior genicular supplies the vastus medialis, lower femur and the knee joint. The lateral superior genicular supplies the vastus lateralis, lower femur and the knee joint. The medial inferior genicular supplies the upper end of the tibia and the articulation of the knee.

The pudendal nerve is at risk as it enters the pelvis through the greater sciatic notch. The Kocher–Langenbeck approach provides exposure to the posterior wall of and posterior column of acetabulum. It is considered by some as an extension to the posterior approach to the hip and exposes the greater sciatic notch and lesser sciatic notch. The superior gluteal artery and nerve are at risk of injury here and must be protected. The pudendal nerve is at risk, but it exits the pelvis via the greater sciatic notch and re-enters via the lesser sciatic notch.

Continued as usual. Although there is a higher rate of infection in general in rheumatoid patients, continuing their methotrexate at the normal dose has not been shown to affect their risk of infection. Grennan et al found that methotrexate made no difference to early infection following elective orthopaedic surgery when two groups were compared, one which continued and a group that didn’t; other drugs such as penicillamine, indomethacin, ciclosporin, hydroxychloroquine, chloroquine and prednisolone did increase the early infection risk post-operatively. Conversely, discontinuing their methotrexate may result in disease flare that impedes their post-operative rehabilitation.

Transforming growth factors. Bone morphogenetic proteins (BMPs) are multifunctional growth factors that belong to the transforming growth factor beta (TGF-b) superfamily.

Resect more distal femur. It is important to ensure balanced flexion and extension during total knee replacement. As a general rule, if the knee is tight in flexion and extension, the tibia is addressed. If the knee is tight in either flexion or extension, the femur is addressed. There are different methods which may be used including: Tight in flexion and extension – (i) decrease polyethylene insert size; (ii) resect more proximal tibia Tight in extension only – (i) resect additional distal femur; (ii) posterior capsular release Tight in flexion only – (i) downsize the femoral component; (ii) recess and release the posterior cruciate ligament; (iii) resect a posterior slope on the tibia; (iv) release the posterior capsule

Vertebral fractures may give rise to false low density values. DEXA scanning is used to assess bone mineral density, in particular to diagnose osteoporosis. Vertebral fractures may give rise to falsely elevated bone density values.

A hyperextension injury in a patient with a facet joint hypertrophy and thickened ligamentum flavum. Central cord syndrome is the most common incomplete spinal cord lesion. It is usually seen in patients with cervical spondylosis who sustain a hyperextension injury. The mechanism causes compression of the cord by osteophytes anteriorly and ligamentum flavum posteriorly. 65 avascular necrosis (AVN) and non-union rates are affected in this way? a. No difference between AVN and non-union rates. b. AVN higher, no change in non-union. c. No change in AVN, non-union higher. d. AVN and non-union both higher. e. AVN higher but non-union lower. posterior approach to the hip? a. Inferior gluteal. b. Superior gluteal. c. Pudendal. d. Ascending branch of lateral circumflex femoral. e. Popliteal. a. Wound infection is higher with use of drains. b. Haematoma formation is lower with use of drains. c. Wound dehiscence is more likely without the use of drains. d. Blood transfusion is more likely with the use of drains. e. Bruising is more likely with the use of drains. a. Lateral circumflex artery. b. Obturator artery. c. Medial circumflex artery. d. Descending branch of lateral circumflex artery. e. Superior gluteal artery. a. Gluteus minimus and tensor fascia lata. b. Obturator internus, superior and inferior gemelli. 71

Hydrodynamic. Although the majority of lubrication in total hip replacements is boundary lubrication, hard-on-hard bearing surfaces, such as metal-on-metal, have been found to have hydrodynamic lubrication during the motion phase of the gait cycle, particularly effective when the prosthesis is polar bearing with high conformity.

Young woman, injured hill-running. In general, outcome following operative management of calcaneal fractures relies on the number of intra-articular fragments and the quality of articular reduction. A number of factors have been shown to be associated with a poor outcome and they include age >50, obesity, manual labourers, work insurance cases, smokers, bilateral fractures and vascular disease. In addition, men appear to do worse with surgery than women.

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.

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.

A ligamentous chance fracture should be treated using a compression construct with one level above and one level below the fracture. A chance fracture is the result of a flexion-distraction injury (seatbelt injury). It can be bony, ligamentous or mixed. Gastrointestinal injuries occur in 50% of cases. The bony lesions unite non–operatively with a brace in extension. The ligamentous type may remain unstable and therefore should be treated operatively using a compression construct (restore the tension band) with one level above and one level below the fracture. A chance fracture is seldom associated with a neurological deficit unless translation occurs.

B and C. In 1994, the WHO introduced definitions for osteoporosis and osteopaenia in terms of T score thresholds of –2.5 and –1 respectively. A T score of –2.5 means that the bone mineral density in the lumbar spine (L2–L4) is at least 2.5 standard deviations below the mean of a young (age 25–35), healthy female. A T score of more than –2.5 implies it is more positive and hence could represent either osteopaenia or normal bone density.

A bilateral above knee amputee (AKA) requires 80% increase in energy expenditure for ambulation. Unilateral BKA necessitates a 25–50% increase in energy expenditure. Bilateral AKA requires >200% increase.

Physiotherapy and passive range of motion, 10 days following the injury. Immediate physiotherapy and prolonged immobilization are not appropriate in this situation. Although surgical management is an option, a good result can be achieved with non-operative treatment, if the physiotherapy is started within 2 weeks. 212

Chondroblastoma. Benign skeletal tumours rarely if ever metastasize to lung. The two exceptions to this rule are giant cell tumour (up to 10% metastasize to lung) and chondroblastoma.

10% occur in motorcyclists. Traumatic scapulothoracic dissociation is a high-energy injury, with associated injury to the brachial plexus and subclavian artery. The mechanism of injury is probably traction caused by a blunt force to the shoulder girdle, commonly seen in motorcyclists (up to 60%). The presence of a complete brachial plexus avulsion is predictive of a poor functional outcome in a patient with scapulothoracic dissociation. Treatment may include vascular repair, plexus exploration and fixation of the commonly associated clavicle fracture to instil stability. 213

Marked osteopaenia. The use of locking plates is on the rise. They rely on different mechanical principles compared to conventional plates. Useful indications include osteoporotic bone, bridging severely comminuted fractures, plating of fractures where anatomical constraints prevent plating on the tension side of the bone, and the use of the plate for indirect fracture reduction.

Albright’s hereditary osteodystrophy. Brachydactyly refers to short first, fourth and fifth metacarpals and metatarsals. This is seen in pseudohypoparathyroidism, otherwise known as Albright’s hereditary osteodystrophy. This disorder occurs due to a parathyroid hormone (PTH) receptor abnormality. In addition to the brachydactyly, patients are obese, have reduced intelligence and can present with exostoses.

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.

Supination-adduction. An understanding of the Lauge-Hansen classification of ankle fractures is needed to answer this question. The first word in each type refers to the foot’s position at the time of injury and the second word refers to the direction of the deforming force. A supination-adduction gives rise to the injury described.

Revision to a constrained knee prosthesis. Medial collateral ligament deficiency in a total knee replacement may present with pain, instability or both. A knee brace may provide a temporary solution. Repair or reconstruction of the ligament is unlikely to provide the necessary valgus resistance, and the only sensible option is to revise to a constrained prosthesis. There is some debate as to whether this can be a high posted design (non-linked) or whether it has to be hinged. 112 a. Sural. b. Saphenous. c. Tibial. d. Deep peroneal. e. Superficial peroneal. the most important factor in predicting a satisfactory outcome? a. Severity of initial injury. b. The state of the articular cartilage. c. The age of the patient. d. The smoking status of the patient. e. Whether or not a compensation claim is involved. a. Absent fibula. b. Deficient knee ligaments. c. An equinovarus deformity. d. Talocalcaneal coalition. e. Proximal femoral focal deficiency. a. Oligohydramnios. b. Arthrogryposis. c. Congenital talipes equinovarus. d. Tarsal coalition. e. Developmental dysplasia of the hip. performing. The likely diagnosis is? a. Hallux valgus. b. Hallux rigidus. 119

Left lateral foot numbness. A foraminal or extraforaminal/far lateral disc herniation affects the exiting root (in this case L5), whilst a paracentral or posterolateral disc herniation affects the traversing root (S1). An EHL and EDL weakness would be consistent with an L5 compression. Dorsomedial foot and lateral calf numbness would also be the result of an L5 compression.

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.