Leprosy Orthopaedic Manifestations
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Direct answer
Leprosy orthopaedic manifestations result from Mycobacterium leprae damaging peripheral nerves, so the deformities are neurogenic rather than primary bone disease. The classic pattern is claw hand from ulnar nerve palsy, foot drop from common peroneal palsy and neuropathic plantar ulcers from posterior tibial anaesthesia. Protecting the anaesthetic limb always comes before reconstructive surgery.
What you must remember
- Causative organism: Mycobacterium leprae, which has a predilection for cooler superficial nerves and skin, so joint and bone changes are secondary to nerve damage.
- Nerve predilection: the ulnar nerve at the elbow, the common peroneal nerve at the fibular neck and the posterior tibial nerve behind the medial malleolus, with the median and radial nerves also involved.
- Claw hand: ulnar palsy paralyses the interossei and medial lumbricals, so the ring and little fingers claw, and Froment's sign reveals adductor pollicis weakness.
- Foot drop: common peroneal palsy gives a steppage gait, while posterior tibial anaesthesia produces painless ulcers on the heel and metatarsal heads.
- Reactions: type 1 reversal reactions cause acute neuritis and need corticosteroids, whereas type 2 erythema nodosum leprosum causes painful nodules with systemic upset.
- Classification: WHO paucibacillary disease has up to five skin lesions and multibacillary disease has more, and India's National Leprosy Eradication Programme uses multidrug therapy matched to this grouping.
- Neuropathic damage: painless burns, resorption of digits, neuropathic arthropathy and lagophthalmos from facial nerve palsy.
- Surgical principle: the Brand principle is to protect the anaesthetic limb first and reconstruct only once the disease is quiescent.
Mapping nerve palsy to deformity
Each leprosy deformity follows from the specific nerve that is paralysed or anaesthetised, so examiners often test the link in a short vignette. The table below pairs each nerve with its deformity, its clinical clue and the usual reconstructive option once the disease is quiet.
| Nerve | Deformity or ulcer | Clinical clue | Usual reconstruction |
|---|---|---|---|
| Ulnar | Claw hand, ring and little fingers | Hypothenar and interosseous wasting, Froment's sign | Tendon transfers to restore grip and finger control |
| Median | Ape hand, thumb in the plane of the palm | Thenar wasting, loss of thumb opposition | Opposition transfer |
| Radial | Wrist drop | Inability to extend wrist and fingers | Tendon transfers for extension |
| Common peroneal | Foot drop, steppage gait | Weak ankle dorsiflexion, numb dorsum of foot | Tibialis posterior transfer |
| Posterior tibial | Plantar ulcers, neuropathic foot | Painless sole ulcers at heel and metatarsal heads | Offloading and protective footwear, surgery rarely needed |
Lesions in the ulnar and median nerves produce hand deformities, while peroneal and posterior tibial lesions dominate the foot. Sensory loss usually precedes motor loss, so a thickened, tender nerve with anaesthesia is the earliest clue to an evolving deformity.
Where the exam tries to catch you
Marks are usually lost by confusing nerve damage with bone disease, or by operating during an active phase.
- Trap: calling claw hand a bony or tendon disorder. Correct: the clawing comes from ulnar palsy, with unopposed extensor action at the knuckles and unopposed long flexors at the finger joints, so nerve assessment makes the diagnosis.
- Trap: treating an anaesthetic plantar ulcer as a routine wound and ignoring pressure. Correct: the ulcer arises from repeated pressure the patient cannot feel, so offloading, protective footwear and debridement form the core treatment.
- Trap: planning tendon transfers during an active reaction. Correct: reconstruction follows quiescence and a settled reaction, because surgery during active disease risks poor results and recurrence.
Frequently asked questions
Which nerve causes claw hand in leprosy?
The ulnar nerve causes claw hand in leprosy, with the ring and little fingers clawing because the intrinsic muscles are paralysed. Thickening of the ulnar nerve at the elbow and numbness over the little finger are common early clues in leprosy.
What is the main cause of plantar ulcers in leprosy?
Plantar ulcers in leprosy result from anaesthesia of the sole, usually from posterior tibial nerve involvement, so repeated unnoticed pressure breaks the skin. The heel and metatarsal heads are typical sites, and treatment combines debridement, offloading and protective footwear.
How do type 1 and type 2 leprosy reactions differ?
Type 1 reactions, or reversal reactions, cause acute neuritis and loss of nerve function, and corticosteroids are the mainstay of treatment. Type 2 reactions, or erythema nodosum leprosum, cause painful skin nodules with fever and systemic upset, and they typically occur in multibacillary disease.
When is reconstructive surgery done in leprosy?
Reconstructive surgery in leprosy is deferred until the disease is quiescent, the nerve reaction has settled and the anaesthetic limb has been protected. Tendon transfers are then planned to restore function, because operating during an active phase risks poor results and recurrence.