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OR10.1,OR11.1 | Bone Tumours and Peripheral Nerve Injuries — Practice Quiz
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A 15-year-old boy presents with a 3-month history of pain and swelling around the distal femur. X-ray shows a dense metaphyseal lesion with a sunburst pattern and Codman's triangle at the periosteal edge. Which tumour is the most likely diagnosis?
Correct. Osteosarcoma is the most common primary malignant bone tumour in adolescents; its metaphyseal location and characteristic periosteal reactions (sunburst + Codman's triangle) are hallmarks.
Osteosarcoma classically occurs in adolescents at the metaphysis of long bones (distal femur most common), producing a sunburst periosteal reaction and Codman's triangle (periosteum lifted by tumour). Both features together are virtually pathognomonic.
The sunburst periosteal reaction and Codman's triangle in a teenager's metaphysis point strongly to osteosarcoma.
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A 22-year-old man presents with bone pain and a tender swelling in the mid-shaft of the femur. X-ray shows a permeative lytic lesion in the diaphysis with an onion-skin periosteal reaction. A biopsy reveals small round blue cells. Which of the following is the MOST appropriate initial systemic treatment?
Correct. Ewing's sarcoma is treated primarily with multi-agent neoadjuvant chemotherapy (e.g., VDC/IE). Local control with surgery or radiotherapy follows. Chemotherapy is essential because of the high rate of micrometastases.
Ewing's sarcoma (small round blue cell tumour) classically affects the diaphysis with an onion-skin periosteal pattern. Unlike osteosarcoma, Ewing's is highly chemosensitive; neoadjuvant chemotherapy (VAC/IE regimens) is the backbone of treatment, followed by local control.
Ewing's sarcoma is a chemosensitive tumour; systemic chemotherapy is the cornerstone of management, not surgery or radiation alone.
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A 35-year-old woman presents with dull aching knee pain for 4 months. X-ray of the distal femur shows a lytic lesion extending to the articular surface (epiphysis) with a soap-bubble appearance and no periosteal reaction. Which tumour best fits this description?
Correct. GCT is characteristically epiphyseal, occurs in adults 20–40 years, and produces the soap-bubble (trabeculated lytic) radiographic appearance without periosteal reaction.
Giant cell tumour (GCT) occurs in skeletally mature adults, is epiphyseal in location (extending from the closed physis to the articular surface), and appears as a soap-bubble lytic lesion on X-ray. It is locally aggressive (Campanacci grade I–III) but usually benign histologically.
Epiphyseal location + soap-bubble lytic lesion in a skeletally mature adult = giant cell tumour until proven otherwise.
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A 60-year-old man with known carcinoma of the prostate presents with severe pain in the proximal femur. X-ray shows a cortical breach and pathological fracture through a lytic lesion. Which of the following is the MOST appropriate definitive management of the fracture?
Correct. Pathological fractures through metastatic long-bone lesions require surgical stabilisation (IM nail or prosthesis) for durable pain relief and mobility, followed by local radiotherapy to the metastatic focus.
Pathological fractures through metastatic lesions in weight-bearing long bones are best managed by internal fixation (intramedullary nail or endoprosthetic replacement) to restore function quickly, followed by adjuvant radiotherapy. Casting or conservative management is inadequate as bone healing is impaired in malignant tissue.
Conservative immobilisation fails because pathological bone heals poorly. Surgical fixation restores function and palliates pain; radiotherapy targets the metastasis.
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A biopsy of a suspicious bone lesion is planned in a 17-year-old. Which of the following biopsy principles is MOST critical to subsequent limb salvage surgery?
Correct. The biopsy incision/tract must be longitudinal and lie within the resection field of the planned definitive surgery. This is the cardinal rule of bone tumour biopsy (Mankin principle).
The biopsy tract must be placed along the line of the planned surgical resection so the contaminated tract can be excised en bloc with the tumour. A poorly placed biopsy (e.g., transverse incision, wrong compartment) can contaminate planes and convert a limb-salvageable tumour into one requiring amputation.
The placement of the biopsy relative to the resection plan is the most critical principle. A wrongly sited biopsy tract contaminates compartments and can force amputation.
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A 30-year-old man sustains a mid-shaft humeral fracture after a fall. On examination, he cannot extend his wrist (wrist drop) but sensation over the lateral forearm is intact. Which nerve is injured?
Correct. Radial nerve palsy at the humeral shaft level causes wrist drop (loss of wrist and finger extension). It is the classic nerve at risk with humeral shaft fractures.
The radial nerve runs in the spiral groove of the humerus and is vulnerable in mid-shaft humeral fractures. Injury at this level paralyses wrist and finger extensors (wrist drop) but spares the lateral forearm sensation (lateral cutaneous nerve of the forearm = musculocutaneous) because the sensory branch to the dorsal forearm arises proximally.
Wrist drop after a humeral shaft fracture = radial nerve in the spiral groove. This is the most common nerve injury with humeral shaft fractures.
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A patient presents with inability to extend the ring and little fingers at the interphalangeal joints, wasting of the hypothenar muscles, and loss of sensation over the medial one-and-a-half fingers. The index and middle fingers can be fully extended. Which pattern best describes this nerve injury?
Correct. Ulnar nerve palsy causes claw hand affecting ring and little fingers (the 'ulnar two'), hypothenar wasting, and sensory loss over the medial 1.5 fingers.
Ulnar nerve palsy produces the classic claw hand deformity: hyperextension at the MCP joints and flexion at the IP joints of the ring and little fingers (intrinsic minus pattern), because the lumbricals of those digits are denervated while the long flexors remain intact. Index and middle fingers are spared because their lumbricals are supplied by the median nerve.
Clawing of ring and little fingers with hypothenar wasting and medial 1.5-finger sensory loss = ulnar nerve palsy.
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A cyclist falls and sustains an injury at the fibular neck. She now has foot drop and is unable to evert the foot. Sensation is lost over the dorsum of the foot and the lateral leg. Which nerve is injured?
Correct. The common peroneal nerve is injured at the fibular neck. It causes foot drop (loss of dorsiflexion) and eversion weakness with sensory loss over the lateral leg and dorsum of the foot.
The common peroneal (fibular) nerve winds around the neck of the fibula where it is superficial and vulnerable. Injury here causes foot drop (loss of dorsiflexion and eversion via deep and superficial peroneal branches), with sensory loss over the dorsum of the foot and lateral leg. The recommended splint is a foot drop splint (posterior slab or ankle-foot orthosis).
Foot drop after a fibular neck injury = common peroneal nerve. This is the classic site for this nerve's injury due to its superficial position.
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