Extensor Tendon Injuries Flashcards
Extensor Tendons in the Digits
- Extensor digitorum communis
- Extensor indicis proprius
- Extensor digiti minimi
Thumb
- Extensor pollicis longus- extends the tip
- Extensor pollicis brevis- extends the mp
*primary ones without the dorsal expansion piece
Extensor Digitorum Communis
Innervation
-Posterior interosseous nerve (a deep motor branch of the radial nerve)
Action
- Extends the MCP joints of the medial four digits
- In conjunction with the lumbricals, extends the IP joints.
- Weakly extend the wrist.
*Helps extend the IPs through the dorsal expansions with the lumbricals (primary job is to extend the IPs)
EDC
- Inserts at the base of the middle phalanx in extensor zone 3.
- this area is called the central slip- name of insertion point of the EDC on the middle phalanx just as it crosses the middle phalanx.
*Is a secondary mover of the wrist. Not a primary. Can be a problem after coming out of a cast because it thinks that it can lift the heavy wrist
Central Slip
Dorsal expansion- lateral bands are fibers that come from the lumbricals and the interossei and join together to insert on the dorsal phalanx
Extensor Hood Mechanism
- The “extensor hood”, Also called “extensor expansion mechanism” or “extensor aponeurosis” is made up of a combination of tendinous fibers coming from the palmer and dorsal interossei, the lumbricals and the EDC proximal to insertion.
- Job is too extend the DIP and PIP of the finger while the MCPs are flexed. They work together.
Extensor Hood Mechanism
- Lateral bands connect the middle phalanx and the distal phalanx.
- When the extensor muscle contracts it shortens and pulls on these attachments to straighten the finger.
-EDC doesn’t go past the DIP joint but through its fibrous connections it extends on up with help from the lumbricals and the interossei.
Terminal tendon
end of dorsal expansion mechanism
Lateral bands
- don’t have the EDC fibers in it.
- lumbricals only come up the radial side.
Tension on the lateral bands fully straightens the PIPJ and the terminal insertion is the only means by which the distal phalanx extends.
-this allows us to flex at the MCPJ and extend at the IPs
Extensor hood mechanism cont’d
-Keep the EDC on top of the metacarpal head on the back (kind of like a pulley) to help keep things in place/ a sheath- sagittal fibers. Keep the EDC staying on top..
(RA, lupus can effect its ability to stay on top)
Triangular ligament
- keeps terminal components of lateral bands from migrating downward. Injury to the triangular ligament can lead to a Boutonniere deformity.
- top distal portion of the dorsal expansion ligament
Transverse retinacular ligament.
Keeps the lateral bands from migrating up or dorsally. An injury in this area would result in swan neck deformity.
-keeps the lateral bands from moving.
Superior Oblique retinacular ligament (SORL)- ligament of landsmere
- gets tight with immobilization.
- It is located at the distal end of the middle phalanx and extends across the DIP and inserts on the distal phalanx. If tight it will limit DIP flexion.
-Also on the very top and goes over the entire expansion mechanism. Can get tight and prevent the system from expanding.
Sagittal bands
-at the MCP level and keep the EDC on a track over the dorsal MP joint. When a sagittal band is loose or ruptured the tendon can sublux. RA attacks the soft tissues and can affect all of these structures which results in hand deformity.
Extensor tendon zones
I- DIP joint II- Middle Phalanx III- PIP joint IV- Proximal Phalanx V- MCP joint VI- Metacarpal VII- Dorsal retinaculum VIII- Distal forearm
thumb I- IP joint II- Proximal Phalanx III- MCP joint IV- Metacarpal V- CMC joint/radial styloid
Treatment Goals
- Prevent tendon rupture
- Protect the tendon
- Promote tendon healing
- Encourage tendon gliding
- Prevent flexion contractures
- Control edema
- Restore PROM and AROM
- Maintain ROM of uninvolved joints
- Return to previous level of function
Extensor Tendon Injury: Zone 1 and 2
Mallet Finger
-lesion of the terminal extensor tendon results in a mallet finger (zone 1 or 2)
- inability to extend the DIP due to lesion of the terminal extensor tendon.
- Lag– inability to go through the full ROM
VERY COMMON
Mallet Finger
- Most common injury to the extensor tendon
- Lesions may be open or closed and may have an associated fracture
- Also known as baseball finger
- Could be a traumatic laceration, or they could have fallen and put force on it and ruptured it. It is common in baseball.
Mallet finger Treatment
Stax splints
- maceration- breakdown of the skin
- don’t fit well, person is usually swollen and then eventually are too big.
*Just about 10 degrees of hyperextension so that they are not stuck with a lag. It could stretch while it is healing and become too long and not be able to pull them through full ROM when healed.
Too much extension can prevent blood flow- no more than 10 degrees of hyper extension.
If lateral band is torn
- 30 degrees of flexion at PIP and 10 degrees hyper-extension at DIP if lateral band is torn
- They can do full flexion but cannot extend beyond the limit set in the splint.
Mallet Finger progression
-0-6 weeks: splint DIP in about 10 D of hyperextension. More than that cuts off the blood flow.
- 6-8 weeks: Splint is removed for exercises, then worn again day and night
- Active DIP flexion to 20-30 Degrees
*6 weeks is the magic number- how long it takes for tendons to heal in a healthy person.
Some limitations to motions- gentle gliding, get tip to move, no resistance exercises.
- 8 Weeks: If not extension lag, splint is removed during the day, Continue night splint until week 12 (don’t get into a weird posture at night).
- AROM program
- Light gripping and isolated resistive strengthening exercises. Monitor for lag.
-Week 12: Begin unrestricted use.
ZONE 2 IS WHEN THE LATERAL BANDS ARE INVOLVED!!!!!!!!
Extensor Tendon Injury: Zone 3 and 4
Boutonniere Deformity- EDC cannot extend the PIP but the lateral bands are often intact on the side and they pull on the distal phalanx and pulls DIP into flexion.
- Occurs after rupture of the central slip or triangular ligament.
- effects the central slip (zone 3)
Boutonniere Therapy
0 to 4-6 weeks: Splint the PIP joint in 0 degrees extension.
- The MCP and DIP joints are left free
- Splint is NOT removed for 4-6 weeks.
- DIP flexion 20 reps every hour.
- active DIP flexion prevents SORL contracture and lateral bands from migrating volarly.
- keep the PIP joint straight- allow the EDC to tact back down and heal. One that we try to heal nd fix without surgery.
- If the lateral bands drop down it will reinforce the boutonniere deformity.
Boutonniere therapy cont’d
- 6-8 weeks: Gentle AROM for PIP flexion and extension
- Continue to wear the splint between exercises and at night.
10-12 weeks: Gentle strengthening for full fist.
- Continue to wear the splint between exercises and at night for up to 4 months.
- Zone 3 and 4 strengthening doesn’t start until 10 weeks.
Zone 4
- adhesions are common
- Might consider a short arc motion protocol
- Zone 4 is the proximal phalanx- bad for adhesions on extensor side, Zone 2 for the flexor side.
- EDC often becomes adherent to the bone below.
