Anatomy TUESDAY – The Crowded Carpal Tunnel

If you take a postage stamp and place it at the base of your hand, you can appreciate the size (or lack thereof) of the carpal tunnel. Within this tunnel lies ten structures: the median nerve, the eight tendons of flexor digitorum superficialis and flexor digitorum profundus and the tendon of flexor pollicis longus, each of which are housed in a tendon sheath. These structures are bordered by the proximal row of carpal bones dorsally and the transverse carpal ligament on the volar side.

Carpal tunnel syndrome involves compression of the median nerve due to chronic inflammation of the tendon structures. An interesting question to answer is what causes the inflammation? Is it just repetitive movement?

Try this:

Sit upright with the scapula relatively neutral and make a strong fist.

Then deliberately protract and anteriorly tilt the scapula, allowing the shoulder to roll forward, and grip again.

Many people perceive a difference.

That’s because grip isn’t an isolated hand function. Strong gripping requires coordinated activity throughout the kinetic chain. Wrist extensors stabilize the wrist so the finger flexors can generate force efficiently, while elbow and shoulder musculature provide proximal stability.

So altered scapular mechanics can change muscle recruitment and grip performance without directly changing tendon excursion through the carpal tunnel.

A creative solution

Restore thoracic rotation – use the thoracic sequence
Correct scapular position – check pec minor for trigger points and then activate lower trapezius with over head pressing or reaching.
Median nerve gliding – Elbow flexion + wrist/finger extension ↔ elbow extension + wrist/finger relaxation
Tendon gliding (5 positions): Start with the wrist in neutral and the forearm supported. Move slowly through these positions:

Straight hand – MCP, PIP, and DIP joints extended.
Hook fist – MCP joints remain relatively extended while the PIP and DIP joints flex. This produces substantial FDP excursion relative to FDS.
Full fist – MCP, PIP, and DIP joints all flex. Both FDS and FDP glide through the carpal tunnel.
Tabletop / intrinsic-plus position – MCP joints flex to about 90° while the IP joints remain extended.
Straight fist – MCP and PIP joints flex while the DIP joints remain relatively extended. This particularly emphasizes FDS excursion relative to FDP.
Typically, the patient moves slowly from one position to the next, holding each for roughly 3–5 seconds, for perhaps 5–10 repetitions, provided the exercise doesn’t provoke or sustain paresthesia.

Why does this matter?

There are a lot of structures squeezing through the carpal tunnel. Understanding the “why?” behind the “what?” can lead to more treatment solutions than just stretching the flexor tendons and bracing to prevent extreme wrist positions at rest. Tendon and nerve gliding should be restored, but more importantly, workload to these tendons can be reduced by restoring thoracic rotation and a normal scapular position.

Check this list the next time you see someone with carpal tunnel syndrome.

Because nobody has time to be in pain.

Until next time…