8.2 Tendon Injuries, Nerve Compressions & Hand Conditions

Tendon Injuries, Nerve Compressions & Hand Conditions

Hand therapy demands exact anatomical knowledge, meticulous orthotic design, and adherence to evidence-based tissue healing timelines. Premature active tension or improper immobilization can rupture repaired tendons, cause permanent joint contractures, or aggravate peripheral nerve compressions.

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1. Flexor Tendon Repairs & Rehabilitation Protocols

Flexor tendon injuries are categorized into five anatomical zones across the volar hand and wrist. Zone II, extending from the proximal edge of the A1 pulley to the insertion of the flexor digitorum superficialis (FDS), is historically termed 'No Man's Land' because both the FDS and flexor digitorum profundus (FDP) tendons travel within a tight, enclosed fibro-osseous sheath where adhesions readily form post-repair.

+---------------------------------------------------------------------------------------------------+
|                              FLEXOR TENDON ANATOMICAL ZONES                                       |
+----------+------------------------------------------+--------------------------------------------+
| Zone     | Anatomical Boundaries                    | Clinical Characteristics & Vulnerability   |
+----------+------------------------------------------+--------------------------------------------+
| **I**    | Distal to FDS insertion to FDP insertion | 'Jersey Finger' (avulsion of FDP).         |
+----------+------------------------------------------+--------------------------------------------+
| **II**   | A1 pulley (distal palmar crease) to FDS  | 'No Man's Land': High adhesion formation;  |
|          | insertion at middle phalanx              | dual tendon gliding in tight sheath.       |
+----------+------------------------------------------+--------------------------------------------+
| **III**  | Distal carpal ligament to A1 pulley      | Palm region: Lumbrical origin site.        |
+----------+------------------------------------------+--------------------------------------------+
| **IV**   | Transverse carpal ligament (carpal canal)| Tendons enclosed beneath median nerve.     |
+----------+------------------------------------------+--------------------------------------------+
| **V**    | Volar wrist to musculotendinous junction | Forearm: Common neurovascular lacerations. |
+----------+------------------------------------------+--------------------------------------------+

Early Controlled Motion Protocols

To minimize tendon adhesions while protecting the delicate surgical suture line, hand therapists utilize specialized early mobilization protocols within a custom Dorsal Blocking Splint (DBS).

+---------------------------------------------------------------------------------------------------+
|                         DORSAL BLOCKING SPLINT (DBS) SPECIFICATIONS                               |
+-----------------------+---------------------------------------------------------------------------+
| **Joint**             | **Prescribed Splint Position**                                            |
+-----------------------+---------------------------------------------------------------------------+
| **Wrist**             | 20° – 30° of flexion                                                      |
| **MCP Joints**        | 50° – 70° of flexion                                                      |
| **IP Joints (PIP/DIP)**| Full extension (0°) within the protective dorsal hood                     |
+-----------------------+---------------------------------------------------------------------------+

+---------------------------------------------------------------------------------------------------+
|                         KLEINERT vs. MODIFIED DURAN PROTOCOL COMPARISON                           |
+------------------------------------+--------------------------------------------------------------+
| Protocol Feature                   | Kleinert Protocol                 | Modified Duran Protocol  |
+------------------------------------+-----------------------------------+--------------------------+
| **Motion Mechanism**               | **Active Extension / Passive Flex**| **Controlled Passive Motion**|
+------------------------------------+-----------------------------------+--------------------------+
| **Apparatus**                      | Dynamic traction: Rubber bands    | Static dorsal blocking   |
|                                    | attached to fingernails pull digits| splint without dynamic   |
|                                    | into passive flexion at rest.     | rubber bands.            |
+------------------------------------+-----------------------------------+--------------------------+
| **Exercise Execution**             | Client actively extends digits to | Therapist/client performs|
|                                    | splint hood against rubber band,  | passive PIP and DIP      |
|                                    | followed by passive elastic return| flexion and extension    |
|                                    | into full flexion.                | individually in splint.  |
+------------------------------------+-----------------------------------+--------------------------+
| **Strict Rule**                    | • NO active digit flexion         | • NO active digit flexion|
|                                    | • NO passive extension past DBS   | • NO passive extension   |
+------------------------------------+-----------------------------------+--------------------------+

Flexor Tendon Healing Phases and Milestone Timeline

• Weeks 0–4 (Inflammatory / Early Reparative Phase): Dorsal blocking splint worn 24/7. Perform protocol-specific passive flexion and extension exercises within splint hood only. Strict contraindication: No active digit flexion or passive digit extension outside the splint.
• Weeks 4–6 (Fibroblastic Phase): Discontinue dynamic traction. Initiate active composite digit flexion and extension within the splint or out of splint with wrist in flexion. Differential tendon glides (hook, straight fist, composite fist).
• Weeks 6–8 (Remodeling Phase): Discontinue protective splint. Initiate gentle active functional tasks, light passive extension, and blocking exercises (if approved).
• Weeks 8–12 (Maturation Phase): Progressive resistive exercises (PREs), gripping tasks, and return to heavy work/sports at 12 weeks.

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2. Extensor Tendon Repairs & Structural Hand Deformities

Extensor tendons are divided into eight anatomical zones across the dorsal hand and wrist (plus five thumb zones). Extensor tendons are flatter, broader, and have less excursion than flexor tendons, making them vulnerable to stretching and adhesions.

+---------------------------------------------------------------------------------------------------+
|                              STRUCTURAL HAND DEFORMITIES MATRIX                                   |
+-------------------+-----------------------------------+-------------------+-----------------------+
| Deformity Name    | Pathoanatomy / Mechanism          | Clinical Posture  | Orthotic Intervention |
+-------------------+-----------------------------------+-------------------+-----------------------+
| **Mallet Finger** | Disruption or avulsion of terminal| • DIP flexion     | • **DIP extension**   |
| *(Zones I – II)*  | extensor tendon at base of distal |   contracture/lag |   **splint in neutral**|
|                   | phalanx (e.g., hit by baseball).  | • Inability to    |   **or slight hyper-**|
|                   |                                   |   actively extend |   **extension** for   |
|                   |                                   |   DIP joint       |   **6–8 weeks 24/7**  |
|                   |                                   |                   |   **UNINTERRUPTED.**  |
+-------------------+-----------------------------------+-------------------+-----------------------+
| **Boutonnière**   | Rupture or attenuation of the     | • PIP flexion     | • **PIP extension**   |
| **Deformity**     | **central slip** of extensor hood;| • DIP hyper-      |   **splint** with DIP |
| *(Zone III)*      | **lateral bands subluxate volarly**|   extension       |   left free to allow  |
|                   | to the PIP axis.                  |                   |   active DIP flexion  |
|                   |                                   |                   |   (relocates bands).  |
+-------------------+-----------------------------------+-------------------+-----------------------+
| **Swan Neck**     | Laxity of the volar plate;        | • PIP hyper-      | • **Figure-8 splint** |
| **Deformity**     | **lateral bands subluxate**       |   extension       |   or **Silver Ring**  |
|                   | **dorsally** to the PIP axis.     | • DIP flexion     |   splint to block PIP |
|                   |                                   |                   |   hyperextension.     |
+-------------------+-----------------------------------+-------------------+-----------------------+

[!IMPORTANT] Critical Mallet Finger Rule: If the DIP joint flexes even a fraction of a degree during splint removal for skin cleaning, the healing tendon fibers rupture or stretch, and the 6 to 8-week continuous immobilization clock must be reset to Day 1.

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3. Nerve Compressions & Cumulative Trauma Disorders

Cumulative trauma disorders (CTDs) and peripheral nerve entrapments represent major occupational impairments requiring conservative splinting, provocative screening, nerve/tendon glides, and ergonomic workstation modifications.

Carpal Tunnel Syndrome (CTS)

• Pathophysiology: Compression of the median nerve beneath the transverse carpal ligament (flexor retinaculum) within the carpal canal.
• Sensory/Motor Symptoms: Numbness, paresthesia, and burning in the thumb, index, middle, and radial half of the ring finger; nocturnal paresthesia; thenar muscle atrophy (abductor pollicis brevis, opponens pollicis) in chronic cases.
• Provocative Tests:
  • Phalen's Test: Bilateral maximal wrist flexion maintained for 60 seconds reproduces median nerve paresthesias.
  • Tinel's Sign: Percussion over the volar carpal tunnel produces tingling sensation radiating into median nerve digits.
  • Carpal Compression Test (Durkan's Test): Direct sustained thumb pressure over the carpal tunnel reproduces symptoms within 30 seconds (highest sensitivity/specificity).
• Orthosis & Interventions:
  • Wrist Cock-Up Orthosis: Positioned at neutral (0° to 10° extension). Biomechanical studies show this position minimizes intracarpal canal pressure. Worn primarily at night and during aggravating daytime tasks.
  • Nerve and Tendon Gliding Exercises: Six standard tendon gliding positions (straight, hook, straight fist, tabletop, composite fist) to maximize differential excursion.
  • Ergonomics: Neutral keyboard alignment, padded palm rests, alternating tasks.

Cubital Tunnel Syndrome (CuTS)

• Pathophysiology: Compression or traction of the ulnar nerve as it passes behind the medial epicondyle through the cubital tunnel.
• Sensory/Motor Symptoms: Numbness and tingling in the small finger and ulnar half of the ring finger; intrinsic muscle weakness (interossei, hypothenars, adductor pollicis); clawing of digits 4 and 5 in severe cases.
• Provocative Tests:
  • Elbow Flexion Test: Maximal elbow flexion with wrist extension held for 3–5 minutes reproduces ulnar paresthesias.
  • Tinel's Sign: Percussion at the cubital tunnel behind the medial epicondyle.
  • Froment's Sign: Client pinches a piece of paper between the thumb and index finger; weakness of the ulnar-innervated adductor pollicis causes compensatory hyperflexion of the thumb IP joint by the median-innervated flexor pollicis longus (FPL).
  • Wartenberg's Sign: Inability to adduct the 5th digit against the 4th digit due to weakness of the 3rd palmar interosseous muscle.
• Orthosis & Interventions:
  • Elbow Flexion Block Orthosis: Positioned at 30° to 45° of elbow extension (or soft padded sleeve) worn at night to prevent sustained elbow hyperflexion.
  • Activity Modifications: Avoid resting elbows on hard armrests, avoid prolonged cell phone holding against the ear, and use hands-free headsets.

De Quervain's Tenosynovitis

• Pathophysiology: Stenosing tenosynovitis of the first dorsal compartment of the wrist, affecting the Abductor Pollicis Longus (APL) and Extensor Pollicis Brevis (EPB) tendons.
• Clinical Presentation: Pain and swelling over the radial styloid aggravated by thumb abduction and wrist ulnar deviation.
• Provocative Test: Finkelstein's Test (patient tucks thumb inside fist and performs active/passive wrist ulnar deviation; sharp radial styloid pain is positive).
• Orthosis & Interventions:
  • Forearm-Based Thumb Spica Orthosis: Wrist positioned in 15° extension, thumb CMC and MCP immobilized in slight abduction/extension, with the IP joint left completely free for functional pinching.
  • Activity Adaptations: Avoid repetitive ulnar deviation and pinch gripping (e.g., lifting babies by placing hands under the torso/arms rather than pinching with an abducted thumb web space).