Ulnar Nerve Flashcards
What is the characteristic appearance of claw deformity in ulnar nerve palsy?
Hyperextension of the MCP joints and flexion of the IP joints, primarily affecting the ring and little fingers, due to paralysis of intrinsic muscles (lumbricals and interossei), allowing unopposed action of extrinsic extensors and flexors.
When is the claw deformity in ulnar nerve palsy most apparent?
During active finger extension, as the extrinsic extensors hyperextend the MCP joints while the weakened intrinsics fail to extend the IP joints, resulting in the characteristic claw posture.
How does joint mobility affect the severity of claw deformity in ulnar nerve palsy?
Greater joint mobility leads to a more pronounced deformity because mobile joints can more easily adopt the abnormal hyperextended MCP and flexed IP positions, whereas stiffer joints may limit the deformity.
What is the normal sequence of joint flexion during grasping, and how is it altered in ulnar nerve palsy?
Normally, MCP joints flex before IP joints. In ulnar palsy, IP joints flex first due to intrinsic muscle paralysis, disrupting efficient grasping and leading to an abnormal ‘roll-up’ pattern.
What is the primary functional impact of claw deformity on grasping ability in ulnar nerve palsy?
The reversed flexion sequence (IP before MCP) impairs the hand’s ability to envelop objects, resulting in an inefficient grip and reduced holding strength, as the fingers close prematurely.
What role do intrinsic muscles play in preventing claw deformity?
Intrinsic muscles (lumbricals and interossei) flex the MCP joints and extend the IP joints, balancing the forces of extrinsic muscles. Their paralysis in ulnar palsy leads to unopposed extrinsic muscle action, causing the deformity.
What is the Bouvier maneuver, and why is it important for planning surgical correction of claw hand?
The Bouvier maneuver tests whether PIP joint extension can be achieved when the MCP joint is passively flexed.
A positive test indicates a flexible deformity suitable for procedures like Zancolli’s tenodesis, while a negative test suggests lateral band dysfunction, requiring different approaches.
What happens to the lateral bands of the extensor apparatus in longstanding claw deformity?
In longstanding claw deformity, the lateral bands may displace palmarly due to chronic abnormal joint positioning, losing their extension moment arm and contributing to PIP flexion, complicating correction.
What is the difference in claw deformity presentation between high and low ulnar nerve palsy?
In low ulnar palsy, functional FDP increases IP flexion in the ring and little fingers, making clawing more severe.
In high ulnar palsy, FDP paralysis reduces IP flexion severity, resulting in less pronounced clawing.
What is Froment’s sign and what does it indicate in ulnar nerve palsy?
Froment’s sign is thumb IP joint flexion during pinch, indicating paralysis of adductor pollicis and first dorsal interosseous, with compensatory FPL action, leading to poor pinch strength.
What is Wartenberg’s sign in ulnar nerve palsy?
Wartenberg’s sign is the inability to adduct the extended little finger due to unopposed EDM action and paralysis of the third palmar interosseous, causing abduction of the little finger.
What are the main aims of reconstructive surgery in low ulnar nerve palsy?
The main aims are to improve thumb pinch, correct finger clawing, and restore the normal pattern of finger flexion. In high ulnar palsy, restoring ring and little finger DIP flexion may also be considered.
What is the Zancolli lasso procedure and when is it indicated for claw hand correction?
The Zancolli lasso procedure redirects the FDS tendon around the A1 pulley to prevent MCP hyperextension. It’s indicated when the Bouvier maneuver is positive, suggesting a flexible deformity without fixed contractures.
What is the Stiles-Bunnell procedure for claw hand correction and when is it indicated?
The Stiles-Bunnell procedure transfers the FDS through the lumbrical canals to the lateral bands to restore PIP extension. It’s indicated when lateral bands are displaced or dysfunctional (negative Bouvier test).
What modifications did Littler make to the Stiles-Bunnell procedure for claw hand correction?
Littler used only one FDS tendon (usually middle finger), split into four slips, each passed through the lumbrical canal and sutured to the radial lateral band, reducing complexity and complications.
What are the potential complications of the Stiles-Bunnell procedure for claw hand correction?
Complications include adhesion formation, overcorrection leading to intrinsic-plus deformities, and conversion of FDS into powerful extensors, potentially disrupting finger flexion.
What is the difference between static and dynamic procedures for correcting ulnar claw hand?
Static procedures (e.g., MCP capsulodesis) prevent MCP hyperextension mechanically without active motor function. Dynamic procedures use tendon transfers to provide active control, restoring both mechanical block and active finger positioning.
What is the intrinsic-minus thumb deformity in ulnar nerve palsy and how does it affect function?
The deformity involves thumb MP hyperextension and IP flexion during pinch (Froment’s sign), due to loss of adductor pollicis and FPB function, leading to poor pinch strength and control.
What are the six functional goals of tendon transfers for claw hand correction according to Brand?
Brand’s goals are:
1) Restore transverse metacarpal arch,
2) Correct clawing,
3) Restore abduction-adduction,
4) Restore normal finger flexion sequence,
5) Restore pinch, and
6) Restore individual lumbrical movement.
What is the significance of the Martin-Gruber anastomosis in diagnosing and treating ulnar nerve palsy?
The Martin-Gruber anastomosis is a motor nerve connection between median and ulnar nerves in the forearm (17% prevalence), which can cause anomalous innervation patterns, complicating diagnosis and management of ulnar nerve lesions.
What factors should be considered when selecting a motor for tendon transfer in ulnar nerve palsy?
Factors include:
1) Matching resting muscle fiber length and tension,
2) Expendability,
3) Synergism,
4) Adequate strength and excursion,
5) Direct line of pull, and
6) Whether the transfer crosses the wrist for tenodesis effect.
How does the insertion point of a tendon transfer affect its function in claw hand correction?
Insertion onto the proximal phalanx or A1 pulley provides pure MCP flexion. Insertion onto the radial lateral bands provides MCP flexion, abduction, and IP extension, fine-tuning the transfer’s function.
What is EPL rerouting and when is it indicated in thumb deformity associated with ulnar nerve palsy?
EPL rerouting translocates the EPL tendon radially to enhance thumb abduction and extension. It’s indicated when EPL function is good but thumb abduction is weak, improving the abduction-extension arc by approximately 40 degrees.
What role does postoperative rehab play in tendon transfer success?
Maintains ROM, prevents adhesions, retrains transferred tendon for new role.
What does the DASH score evaluate in radial nerve repair patients?
Degree of disability and symptom severity; lower scores mean better function.
What’s the “donor distal, recipient proximal” principle in nerve transfers?
Use donor nerve distally, recipient proximally to minimize regeneration distance.
What are contraindications for tendon transfers in radial nerve palsy?
Infection, joint contractures, significant scarring, weak donor muscle (<M4), poor rehab compliance.
How is the palmaris longus used in tendon transfers for thumb function?
Transferred to EPL for thumb extension/abduction; alternatives needed if absent (~14% incidence).
How does 70% grip strength recovery affect functional outcomes?
Allows most daily activities despite residual weakness; considered good outcome.
How might clinical setting influence nerve transfer outcomes?
High-volume centers with experts may yield better, less generalizable results.
What are key surgical steps in preparing nerve ends for repair?
Debride to healthy tissue, align fascicles, ensure tension-free repair, use microsurgery.
Why avoid overloading donor muscles in tendon transfers?
Prevents fatigue and reduced force, preserving both original and new functions.
What advantages does the Pulvertaft technique offer in tendon transfers?
Secure, tension-free junction, allows early mobilization, preserves tendon glide.
How do researchers standardize outcomes in radial nerve repair studies?
Propose protocols with objective (ROM, MRC, grip) and subjective (patient-reported) metrics.
List the three connective tissue layers enveloping peripheral nerves?
Endoneurium (axons), perineurium (fascicles), epineurium (entire nerve).
Which nerve roots and brachial plexus cord form the ulnar nerve?
C8 and T1 roots, medial cord.
Describe the ulnar nerve’s course in the arm?
Medial arm, pierces medial septum ~8 cm above medial epicondyle, passes arcade of Struthers, enters cubital tunnel.
What is the arcade of Struthers, and why is it significant?
Aponeurotic band (~5.7 cm) from medial septum to triceps; potential ulnar nerve compression site.
Name the five common ulnar nerve compression sites around the elbow?
Arcade of Struthers,
medial triceps head,
FCU aponeurosis (Osborne’s ligament),
FCU fascia,
intermuscular ligament (FCU-FDS).
Why is the ulnar nerve vulnerable at the elbow?
Runs opposite elbow rotation axis, prone to compression/tension during flexion.
What are the two fascicular bundles of the ulnar nerve at the wrist and their roles?
Sensory (volar/ulnar): sensation; Motor (dorsal/radial): intrinsic hand muscles.
How does the ulnar nerve divide in Guyon’s canal?
Superficial sensory branch (small finger, ulnar ring finger); deep motor branch (intrinsics).
Define Wallerian degeneration and its relevance?
Distal nerve degeneration post-transection, clears path for regenerating axons.
What’s the role of Schwann cells in nerve regeneration?
Dedifferentiate, form Bands of Büngner, secrete trophic factors to guide axons.
How does prolonged axotomy affect regeneration?
Reduces axons, disrupts Schwann cell support, increases inhibitory proteoglycans.
How much functional potential is lost weekly during denervation, and why is it critical?
~1% per week; beyond 18 months, muscle recovery unlikely.
What is a neuroma, and its two main types?
Abnormal nerve thickening from disorganized regrowth;
* end-bulb (proximal stump),
* in-continuity (partial injury).
Define “Bowler’s thumb”?
Neuroma from repetitive trauma to ulnar digital nerve of thumb.
How are ulnar nerve palsies anatomically classified?
High: proximal to dorsal sensory branch;
Low: distal to it.
What sensory deficits occur in low ulnar nerve palsy?
Loss on palmar ulnar hand, entire small finger; radial ring finger often spared (median nerve).
What additional deficits distinguish high ulnar nerve palsy?
Dorso-ulnar sensory loss, FCU and FDP (ring/small fingers) paralysis.
