Free FRCS (Tr & Orth) practice questions

This tests the area moment of inertia. For a solid cylinder the area moment of inertia is πr⁴/4, so bending rigidity (and, through the polar moment, torsional rigidity) rises with the fourth power of the radius: moving from a 10 mm to a 12 mm nail roughly doubles rigidity. The third power describes how the bending stiffness of a plate changes with its thickness, which is the usual source of confusion. Linear and squared relationships describe axial stiffness, which depends on cross-sectional area. Hollow nails follow the same principle using outer and inner radii. Reference: Ramachandran, Basic Orthopaedic Sciences 2e.

Bioabsorbable implants are made of alpha-hydroxy acid polyesters such as polyglycolic acid and poly-L-lactic acid. Their ester bonds are split by hydrolysis, without the need for enzymes or cells, into lactic or glycolic acid, which enters the citric acid cycle and is excreted as carbon dioxide and water; macrophages then clear the remaining fragments. Polyglycolic acid degrades within months and is associated with sterile effusions and sinus formation, whereas poly-L-lactic acid takes years. Osteoclasts resorb calcium phosphate ceramics, not polymers. Proteolysis breaks down collagen-based materials. Oxidation degrades polyethylene, and ionic dissolution describes calcium sulphate and metals. Reference: Miller's Review of Orthopaedics 8e.

This tests the RANK, RANKL and osteoprotegerin axis. Osteoblasts and osteocytes express RANKL, which binds RANK on osteoclast precursors and drives their differentiation, activation and survival. Osteoprotegerin is a soluble decoy receptor, also made by osteoblasts, that binds RANKL and prevents it from reaching RANK; denosumab is a monoclonal antibody to RANKL and so does the same job. Macrophage colony-stimulating factor is the other signal needed for osteoclast formation and promotes resorption. Sclerostin and Dickkopf-1 inhibit Wnt signalling in osteoblasts and restrain formation, not resorption. Osteocalcin is a matrix protein and a marker of bone formation. Reference: Miller's Review of Orthopaedics 8e.

The choice of test depends on the type of data, its distribution, the number of groups and whether they are paired. Here an ordinal, skewed outcome is compared between two independent groups, which calls for the Mann–Whitney U test, the non-parametric counterpart of the unpaired t-test. The unpaired t-test assumes a normally distributed continuous variable and is unreliable with skewed data in small samples. The Wilcoxon signed-rank test is the closest distractor but is for paired observations, such as scores before and after surgery in the same patients. Kruskal–Wallis compares three or more independent groups, and chi-squared compares proportions of categorical data. Reference: Ramachandran, Basic Orthopaedic Sciences 2e.

Local staging should precede biopsy. MRI of the whole bone defines the intraosseous and soft-tissue extent, the relationship to the neurovascular bundle and joint, and any skip lesions; it shows which part of the tumour is viable and most representative, and allows the track to be placed where it can be excised. After a biopsy, haematoma and oedema alter the signal and exaggerate the apparent extent. CT of the chest and whole-body imaging complete systemic staging and are needed before treatment starts, but they are not changed by a biopsy. CT of the lesion shows matrix and cortex well but stages the marrow and soft tissue poorly. Reference: Gerrand C et al., UK guidelines for the management of bone sarcomas, Clin Sarcoma Res 2016.

Severe hypercalcaemia of malignancy, here above 3.5 mmol/L with symptoms, is an emergency. Hypercalcaemia causes a nephrogenic diuresis and vomiting, so patients are profoundly volume depleted, which in turn reduces renal calcium excretion. The first step is vigorous rehydration with intravenous 0.9% sodium chloride, typically 4–6 litres over 24 hours with attention to cardiac and renal function. An intravenous bisphosphonate, usually zoledronic acid, follows once the patient is rehydrated: it is nephrotoxic in a dry patient and takes two to four days to act. Furosemide worsens dehydration and is used only for fluid overload. Calcitonin acts quickly but weakly and briefly. Steroids help in lymphoma and myeloma, not in breast cancer. Denosumab is used for refractory cases. Reference: Walsh J et al., Society for Endocrinology emergency guidance on acute hypercalcaemia, Endocr Connect 2016.

This is an unstable, under-resuscitated polytrauma patient: hypothermic, coagulopathic and acidotic, with chest injury and bilateral femoral fractures, all markers of high risk for acute respiratory distress syndrome and multi-organ failure after prolonged surgery. Damage control orthopaedics applies: rapid external fixation to control pain, bleeding and ongoing soft-tissue injury while limiting the surgical second hit, with conversion to nails once physiology has recovered. Reamed or unreamed nailing and plating are definitive procedures that add blood loss and embolic load. Traction does not stabilise the fractures adequately, prevents upright nursing and prolongs the inflammatory stimulus. Reference: Pape HC et al., J Orthop Trauma 2005; Rockwood and Green's Fractures in Adults 9e.

Early antibiotic administration is the intervention most consistently shown to reduce infection after open fracture. The BOAST standard is that intravenous prophylactic antibiotics are given as soon as possible, ideally within one hour of injury, which in practice often means by the pre-hospital team; the agent follows local policy, commonly co-amoxiclav or a cephalosporin. A 3-hour threshold comes from older observational work and is no longer the standard. The 6-hour figure is the historical rule for debridement, which has not been supported by evidence, and 12 and 24 hours are the current BOAST limits for surgical debridement, not for antibiotics. Reference: BOAST, Open Fractures (2017); NICE NG37.

The type II odontoid fracture, through the waist of the dens, is the most common cervical fracture in the elderly and has a high non-union rate because of its small watershed surface. In a frail, low-demand patient the aim is comfort and safety, not bony union: a rigid collar is tolerated best, and a stable fibrous union gives an acceptable result in most. Halo vests are poorly tolerated in the elderly, with high rates of aspiration, pneumonia and death, and are avoided. Surgery improves union and may be offered to fit older patients, but the anaesthetic risk is not justified here, and osteoporotic bone holds an anterior screw poorly. Traction means prolonged recumbency. Reference: Rockwood and Green's Fractures in Adults 9e; Tashjian RZ et al., J Trauma 2006.

The concern is a Rockwood type IV acromioclavicular dislocation, in which the lateral clavicle is displaced posteriorly into or through trapezius. Because the displacement is in the axial plane, anteroposterior films can look almost normal, and the diagnosis is made on an axillary lateral view, which shows the clavicle lying posterior to the acromion. Type IV injuries are painful, usually irreducible and are treated surgically. The Zanca view, with 10–15° of cephalic tilt, improves the anteroposterior picture of the joint but shows only vertical displacement. The Stryker notch view profiles a Hill-Sachs lesion, the West Point view the anteroinferior glenoid rim, and the serendipity view the sternoclavicular joints. Reference: Rockwood and Green's Fractures in Adults 9e.

NICE NG226 advises referral for consideration of joint replacement when joint symptoms substantially affect quality of life and non-surgical management has been ineffective or is unsuitable, and that referral should come before prolonged, established functional limitation and severe pain. It states explicitly that people should not be excluded from referral because of age, sex or gender, smoking, comorbidities, or overweight or obesity, and that scoring tools should not be used to set thresholds. Body mass index limits are therefore not a reason to delay referral, although weight and smoking are then addressed as risks during shared decision making. A steroid injection gives only short-term relief and is not a required step. Reference: NICE NG226, Osteoarthritis in over 16s (2022).

This is cam-type femoroacetabular impingement. In flexion and internal rotation the aspherical head-neck junction is forced under the anterosuperior acetabular rim, producing an outside-in shear that separates the labrum from the cartilage and peels the acetabular cartilage from the subchondral bone as a carpet delamination; the labrum itself is relatively preserved at first, and the damage may extend deep into the joint. Primary crushing, degeneration and ossification of the labrum with a narrow circumferential strip of cartilage damage is the pincer pattern. Posterior labral and posterior wall damage suggests posterior instability, ligamentum teres rupture follows a twisting injury or dysplasia, and inferomedial head wear is not an impingement lesion. Reference: Beck M et al., J Bone Joint Surg Br 2005; Ganz R et al., Clin Orthop Relat Res 2003.

NICE NG157 recommends offering resurfacing of the patella to people having primary elective total knee replacement. The committee's analysis found that routine resurfacing was cost-effective, mainly because it avoids later operations for anterior knee pain: secondary resurfacing is needed in a proportion of knees left unresurfaced and often gives disappointing relief. Selective resurfacing, guided by the state of the cartilage at operation, by pre-operative anterior knee pain or by an inflammatory diagnosis, is widely practised but was not found to be better value than resurfacing every patella. Denervation with patelloplasty is an adjunct for the retained patella and is not recommended in its place. Reference: NICE NG157, Joint replacement (primary): hip, knee and shoulder (2020).

This is the pivot shift, the most specific test for anterior cruciate ligament deficiency and the one that best matches the symptom of giving way. In extension the iliotibial band lies anterior to the axis of flexion and, with the valgus and axial load, holds the lateral plateau subluxed forwards. At 20–30° of flexion the band passes behind the axis, becomes a flexor and pulls the plateau back into place. The test is therefore unreliable when the iliotibial band or the medial collateral ligament is torn, and when a displaced meniscal tear blocks motion. Biceps, popliteus, gastrocnemius and semimembranosus are dynamic stabilisers that are relaxed under anaesthesia and do not cross the axis in this way. Reference: Galway HR and MacIntosh DL, Clin Orthop Relat Res 1980; Miller's Review of Orthopaedics 8e.

In hallux valgus the sesamoids do not sublux: the metatarsal head moves medially off the sesamoid apparatus once the medial capsule and medial sesamoid ligament attenuate and the crista erodes. The fibular sesamoid stays anchored to the second ray by the adductor hallucis and the deep transverse metatarsal ligament, which is why these are divided in a lateral release. Abductor hallucis migrates plantarwards and loses its abducting action, allowing pronation, but it is a medial structure. Flexor hallucis longus bowstrings laterally with the sesamoids as a deforming force and is not the tether. The medial sesamoid ligament is the structure that fails. Extensor hallucis brevis is dorsal. Reference: Coughlin and Mann's Surgery of the Foot and Ankle 9e; Miller's Review of Orthopaedics 8e.

The accepted position for ankle arthrodesis is neutral in the sagittal plane, about 5° of hindfoot valgus and 5–10° of external rotation matching the other side, with the talus translated slightly posteriorly under the tibia to shorten the lever arm of the foot and ease roll-over. Equinus produces a vaulting gait, a recurvatum thrust at the knee and midfoot overload. Varus locks the transverse tarsal joint, giving a rigid foot that bears weight on its lateral border. Internal rotation is poorly tolerated because the foot trips the swing leg, and excessive external rotation strains the knee and medial foot. Anterior translation lengthens the lever arm. Fixed dorsiflexion overloads the heel. Reference: Buck P, Morrey BF, Chao EY, J Bone Joint Surg Am 1987; Miller's Review of Orthopaedics 8e.

Cervical roots leave above the pedicle of the vertebra of the same number, so a foraminal lesion at C4/5 compresses the C5 root. C5 radiculopathy mimics shoulder disease: the deltoid and the external rotators are weak, the biceps reflex is diminished and sensation is reduced over the regimental badge area, while passive shoulder movement stays full. Weak wrist extension with a diminished brachioradialis reflex is C6, from a C5/6 lesion. Weak elbow extension with a reduced triceps reflex is C7, from C6/7. Weak finger flexion with little finger numbness is C8, from C7/T1, because there are eight cervical roots and seven vertebrae. A weak shrug with supraclavicular numbness would be C4. Reference: Miller's Review of Orthopaedics 8e.

This is presumed idiopathic scoliosis with atypical features that suggest a neural axis abnormality such as a Chiari I malformation with a syrinx, a tethered cord or an intraspinal tumour. Typical adolescent idiopathic curves are right thoracic in a girl, painless and neurologically normal. Indications for MRI of the whole neural axis include a left thoracic curve, an asymmetrical abdominal reflex, other neurological signs, significant pain, rapid progression, onset before 10 years of age, a short angular curve, foot deformity and apical hyperkyphosis. Bracing or observation before imaging would miss a treatable cause whose treatment may halt the curve. CT shows bone but not the cord, and evoked potentials do not provide a diagnosis. Reference: Miller's Review of Orthopaedics 8e.

This is a functional cuff tear, explained by Burkhart's suspension-bridge model. The rotator cable is a thick band of fibres, an extension of the coracohumeral ligament, running perpendicular to the tendon fibres from the anterior supraspinatus insertion to the inferior infraspinatus. It stress-shields the thin, relatively avascular crescent lateral to it. A tear confined to the crescent leaves the cable attachments intact, so cuff force still reaches the tuberosity through the cable, as load passes through the cable of a suspension bridge. Deltoid alone produces superior shear without a centred head. Biceps is at most a weak depressor, a fulcrum on the arch is the mechanism of cuff tear arthropathy, and teres minor does not abduct. Reference: Burkhart SS et al., Arthroscopy 1993; Miller's Review of Orthopaedics 8e.

Uhthoff described calcific tendinitis as a cell-mediated cycle. In the pre-calcific stage tenocytes undergo fibrocartilaginous metaplasia. In the calcific stage, the formative and resting phases produce a dense, chalky, well-defined deposit of carbonated apatite that causes little or only chronic, impingement-type pain. The resorptive phase follows: vascular channels and macrophages invade, the deposit becomes toothpaste-like and under pressure, and may rupture into the bursa. This is the most painful phase, and radiographs show a fluffy, ill-defined deposit of reduced density. In the post-calcific stage fibroblasts remodel the defect with new collagen and the calcification has gone. The acute attack is self-limiting, which is why treatment is supportive. Reference: Uhthoff HK and Loehr JW, J Am Acad Orthop Surg 1997.