OR10.1,OR11.1 | Bone Tumours and Peripheral Nerve Injuries — Glossary

A serum enzyme elevated in states of active bone formation; markedly raised in osteosarcoma (reflecting tumour osteoid production); used as a disease-activity marker and to monitor response to chemotherapy.

A rigid or semi-rigid plastic splint that holds the ankle at 90° of dorsiflexion (neutral) to prevent equinus contracture in foot drop; worn inside the shoe; the standard splinting device for common peroneal or sciatic nerve injury producing foot drop.

A purely motor branch of the median nerve arising just below the elbow; supplies flexor pollicis longus, FDP to index/middle fingers, and pronator quadratus; AIN palsy presents as inability to form an 'OK' sign (tip-to-tip pinch) between thumb and index, without sensory loss.

A deformity seen in median nerve palsy in which the thenar eminence is wasted and the thumb lies flat in the plane of the palm due to loss of the abductor pollicis brevis and opponens pollicis; the hand resembles the hand of an ape (which lacks thumb opposition).

Seddon grade II peripheral nerve injury in which axon continuity is disrupted but the endoneurial tubes and outer connective tissue sheaths remain intact; Wallerian degeneration occurs distally; recovery proceeds by axon regeneration at 1 mm/day along the intact endoneurial scaffold.

A valveless paravertebral venous network connecting the veins of the thorax, abdomen, and pelvis to the epidural venous plexus; provides a pressure-independent channel for tumour cells to seed the axial skeleton, explaining the predilection of breast, prostate, and lung cancers for spinal and pelvic metastases.

A classification of giant cell tumour aggressiveness: Grade I = latent (well-marginated, intact cortex); Grade II = active (expanded but intact cortex); Grade III = aggressive (cortical breach, soft-tissue extension). Guides extent of surgical resection.

A deformity of the hand in which the ring and little fingers are hyperextended at the metacarpophalangeal joints and flexed at the interphalangeal joints, due to loss of intrinsic muscles (interossei and medial lumbricals) from ulnar nerve palsy; managed with a knuckle-bender lumbrical bar splint.

A dorsal wrist splint that maintains the wrist in 30–40° of extension to compensate for wrist drop (radial nerve palsy); it frees the metacarpophalangeal joints and fingers for active flexion, restoring grip function; prevents flexion contracture of the wrist during nerve recovery.

A triangular zone of reactive periosteal new bone at the junction of elevated periosteum and normal cortex, visible on X-ray as a triangular shadow; a hallmark of aggressive bone tumour growth, particularly osteosarcoma.

Application of liquid nitrogen to the tumour bed after curettage of giant cell tumour; destroys residual microscopic tumour cells by freeze-thaw cycling, reducing local recurrence risk.

A monoclonal antibody against RANKL (receptor activator of NF-κB ligand) that inhibits osteoclast-mediated bone resorption; used as adjuvant therapy for unresectable or recurrent giant cell tumour and for bone protection in skeletal metastases.

An electrophysiological investigation that records electrical activity in muscle at rest and during voluntary contraction; fibrillation potentials and positive sharp waves at rest indicate denervation; nascent polyphasic motor unit action potentials (MUAPs) indicate early reinnervation; performed 3–4 weeks after nerve injury for meaningful results.

The MSTS staging system for musculoskeletal tumours based on histological grade (G1 low-grade / G2 high-grade), compartmental extent (T1 intracompartmental / T2 extracompartmental), and metastases (M0/M1); determines required surgical margins and adjuvant therapy.

A fixed plantar-flexion deformity of the ankle caused by shortening of the Achilles tendon and posterior ankle capsule, which develops when the foot drop is not splinted; prevents heel-toe gait even after neurological recovery and may require serial casting or surgical release.

The second commonest primary malignant bone tumour in young patients, arising from primitive neural ectodermal cells in the diaphysis; histologically shows small round blue cells; highly chemosensitive and radiosensitive.

Inability to dorsiflex the foot at the ankle joint due to paralysis of tibialis anterior and extensor muscles, resulting from common peroneal (lateral popliteal) nerve injury; the patient walks with a high-stepping gait; treated with an ankle-foot orthosis (AFO) to maintain neutral ankle dorsiflexion.

A locally aggressive, epiphyseal bone tumour of skeletally mature adults composed of osteoclast-like multinucleated giant cells; usually benign but approximately 5% are malignant; managed by extended curettage.

A metal rod inserted into the medullary canal of a long bone to provide internal fixation; the preferred method for stabilising pathological fractures through metastatic disease because it spans the entire bone and allows early weight-bearing.

A volar hand splint incorporating a lumbrical bar that blocks hyperextension at the metacarpophalangeal joints of the ring and little fingers in ulnar nerve palsy; allows the intact extrinsic extensors to extend the interphalangeal joints through the redirected lumbrical mechanism, functionally correcting the claw.

Surgical removal of a malignant bone tumour with wide margins while preserving limb function, typically replacing the excised bone with a prosthesis or allograft; now the standard for 80–90% of osteosarcomas.

A radiological classification of bone lesion aggressiveness based on margin characteristics: Grade IA = geographic with sclerotic rim (benign); IB = geographic without sclerotic rim; IC = geographic with endosteal scalloping; II = moth-eaten (aggressive); III = permeative (most aggressive, malignant).

A scoring system (0–12) for assessing fracture risk in long-bone metastases, based on site, pain, lesion type (blastic/mixed/lytic), and cortical destruction; a score ≥9 indicates high fracture risk and recommends prophylactic fixation.

Medical Research Council scale grading muscle power from 0 (no contraction) to 5 (normal power against full resistance); used to document the severity of motor deficit in peripheral nerve injuries and to track recovery over serial assessments.

Chemotherapy given before definitive surgical resection, used in osteosarcoma and Ewing's sarcoma to reduce tumour bulk, treat micrometastases, and assess histological response to guide prognosis.

An electrophysiological test measuring the speed and amplitude of electrical impulse transmission along a nerve; in neurapraxia, conduction is blocked at the injury site but normal distal to it; in axonotmesis and neurotmesis, distal conduction velocity is absent after Wallerian degeneration.

The mildest grade of peripheral nerve injury (Seddon I, Sunderland 1) in which there is a physiological conduction block without axonal disruption; caused by focal demyelination or compression; recovery is complete and spontaneous within 6–12 weeks.

Seddon grade III peripheral nerve injury representing complete division of all nerve elements including axons and connective tissue sheaths; no spontaneous recovery is possible; surgical repair (end-to-end suture or nerve graft) is required.

Concentric layers of periosteal new bone resembling the layers of an onion on X-ray; represents repeated periosteal elevation and re-ossification, classically seen in Ewing's sarcoma of the diaphysis.

The commonest benign bone tumour; a cartilage-capped bony exostosis (outgrowth) from the metaphysis, pointing away from the adjacent joint; usually asymptomatic; risk of malignant transformation is low but monitored by cartilage cap thickness on MRI.

The commonest primary malignant bone tumour, arising from osteoblastic cells in the metaphysis of long bones, peak incidence in adolescents; characterised by production of tumour osteoid.

A fracture occurring through structurally weakened bone (due to tumour, infection, metabolic disease, or osteoporosis) with minimal or no trauma; requires management of both the fracture and the underlying pathology.

A satellite focus of tumour in the same bone as the primary lesion, separated by normal marrow; detectable on MRI and relevant to planning the proximal resection margin, as skip lesions that are not excised lead to local recurrence.

Radiological appearance of thin trabecular septa within a lytic bone lesion giving a multi-loculated bubbly look; characteristic of giant cell tumour at the epiphysis.

Radiological appearance of perpendicular spicules of bone radiating outward from the cortex like sun-rays; produced by tumour bone spicules growing along periosteal vessels, classically seen in osteosarcoma.

A peripheral nerve graft harvested from the posterolateral calf (sural nerve, a sensory nerve from the popliteal fossa), providing up to 30 cm of graft material; the most commonly used donor nerve for bridging gaps in peripheral nerve repair.

A surgical procedure in which the tendon of a functional muscle is detached from its insertion and reattached to a new site to substitute for the function of a paralysed muscle; used when nerve recovery is not expected; for irreversible radial nerve palsy, pronator teres can be transferred to the wrist extensors.

A tingling sensation (paraesthesia) radiating into the sensory territory of a nerve elicited by percussing over the nerve's course; in nerve injury recovery, it marks the most distal site of regenerating axon tips and advances distally at 1 mm/day; a stationary Tinel's sign after 8 weeks suggests incomplete nerve regeneration or neurotmesis.

The observation that ulnar nerve injury at the wrist produces a more severe claw hand than injury at the elbow; at the elbow level, the FDP to ring and little fingers is also paralysed, reducing the flexion component of the claw; at the wrist, FDP is intact and flexes the distal phalanges forcefully, producing a more pronounced claw.

Anterograde degeneration of the axon and myelin distal to a site of nerve transection or axonotmesis, occurring within 3–5 days of injury; characterised by axon fragmentation, myelin breakdown, and Schwann cell proliferation within the endoneurial tubes; detected by EMG fibrillation potentials 3–4 weeks after injury.

En-bloc excision of the tumour with a continuous cuff of normal tissue on all surfaces, including the biopsy tract; the standard required for high-grade (Stage IIA/IIB) bone sarcomas to prevent local recurrence.

Inability to extend the wrist and fingers at the metacarpophalangeal joints due to radial nerve palsy; the wrist adopts a gravity-flexed posture; managed with a cock-up splint to maintain the wrist in extension and prevent contracture.