Workbook questions 11 & 12 Flashcards
Young people transmit transient forces as high as 2000 kg/cm sq. through their Achilles tendons, yet rupture of the tendon tends to only occur after middle age. Hence, what pathological changes occur in tendons during ageing? (2 X ½ marks)
The injury may be due to age-related degeneration of the tendon or poorly conditioned middle-aged persons with a history of calcaneal tendonitis. It is known that the lower part of the tendon has a poor blood supply is often a point of weakness.
With her foot in the neutral position, the woman had normal plantar flexion power when she pushed against the SHO’s hand. Pushing upwards against his hand, she could manage no more than a flicker of dorsiflexion. She could extend all her toes but the SHO could easily push them into flexion again. Similarly, she could evert her foot quite well, but he could easily overcome it with his hand around her foot.
Which muscle groups are weak in this lady’s left leg?
Dorsiflexors (or extensors) – tibialis anterior, extensor hallucis longus & extensor digitorum longus - & everters (peroneus longus & brevis) of the foot.
Pinprick testing showed she had impaired sensation along the lateral side of the leg extending on to the dorsum of the foot. The area of the skin over the lateral side of the big toe and the medial side of the adjoining toe and the inter-digital cleft felt numb.
Which nerve(s) supply the areas of impaired sensation and numbness?
Deep fibular (peroneal) nerve; this area may also receive sensory nerve fibres from the superficial fibular (peroneal) nerve.
From (i) and (ii) which nerve has been damaged, what has caused it and what is the name of this particular disability?
Common fibular (peroneal) nerve has been damaged due to pressure from the plaster cast causing foot drop.
A 17 year-old complained of the first few days of having a plaster cast on her leg which went away after a few more days. Explain why did she have tingling for a few days, which then stopped?
Compression or pressure on the nerve results in paraesthesia (numbness and tingling); compression affects nerve conduction and its effects are time-dependent. With prolonged compression, may lead to local conduction block lasting longer; the nerve myelin sheath will be damaged but axonal continuity is preserved.
What will be the ultimate outcome in terms of sensation and motor function and why?
Since axonal continuity is preserved, removal of the compression forces leads to nerve recovery within a few weeks (usually 10 –12 weeks).
Give one other common cause of foot drop?
Bumper Injuries
Explain why after a peripheral nerve lesion, the area of skin which loses its innervation may become red then dry and scaly?
A peripheral nerve contains afferent (sensory), motor (efferent) and often autonomic fibres. Loss of sympathetic nerves to bloody vessels will remove peripheral vasoconstrictor fibres (1). Hence, loss of the latter will lead to initially, vasodilation (reddening). Heat loss and loss of innervation to sweat glands, will produce dry, scaly skin.
List the common sites of the ‘perforators’ in the leg.
Around the ankle
On the medial side of the calf
Around the popliteal fossa
Explain why people who suffer from varicose veins in the lower limb have skin ulcers in the leg?
Stagnation of blood in the skin of the lower limb results in the skin being poorly nourished. As a consequence, it breaks down into a varicose ulcer if subjected to even minor trauma. Skin ulcers are common over the subcutaneous antero-medial surface of the tibia where cutaneous blood supply is relatively poor.
Explain the occurrence of oedema around the ankle in persons with varicose veins with reference to Starlings-Landis capillary forces.
Disturbances in the venous drainage of the lower limb (e.g. in cases of varicose veins) results in the build up of tissue fluid. Hydrostatic pressure increases in the veins distal to the varicosity, which increases hydrostatic pressure at the venous end of the capillaries feeding into these veins. This pressure rise means there is less tissue fluid (interstitial fluid) resorption back into the capillaries. Accumulation of this tissue fluid is seen as oedema in the patient. Revise Starlings-Landis capillary forces covered in the CVS unit.
Why might stripping the short saphenous vein for varicose veins leave the patient with a tingling in his little toe?
The sural nerve (formed by the union of the medial sural cutaneous branch of the tibial nerve and the fibular communicating branch of the common fibular nerve) running alongside the short saphenous vein supplies the skin on the posterior and lateral aspects of the leg and on the lateral side of the foot.
Where would you hope to find the great (long) saphenous vein in a patient who requires an intravenous line inserted urgently because all the other veins have collapsed?
The great (long) saphenous vein runs in front of the medial malleolus – the anatomical positioning of this vein in the body is relatively constant. Another site of location of the vein is one hand’s breadth posterior to the patella.
What is the possible cause of venous stasis and blood clotting in the so-called “economy class syndrome”?
Venous stasis (stagnation) which is an important cause of thrombus formation (thrombosis – blood clotting) is aggravated by muscular inactivity. Look up mechanism in the Mechanism of Disease Unit
Which muscles are involved in dorsiflexion and in plantarflexion at the ankle joint?
Dorsiflexion – Tibialis anterior, extensor hallucis longus, extensor digitorum longus & peroneus (fibularis) tertius
Plantarflexion – Gastrocnemius, soleus, plantaris, flexor hallucis longus, flexor digitorum longus & tibialis posterior
