Equine Tendon and Ligament Injuries

Question 1

What is the difference between a strain and a sprain?

Answer 1

Sprain is ligamentous, strain is tendonous.
Tendon (and suspensory ligament) strain caused by overstretching, often bilateral.
- palmar metacarpus more commonly than plantar metatarsus.
- SDFT > suspensory ligament > inferior check ligament > DDFT.
Sprain usually an inciting acute traumatic event.
- MAY occur in any ligament and joint capsule.
- predominantly collateral ligaments of joints.

Question 2

Investigating potential tendon and ligament injuries.

Answer 2

Hx.
CS:
- visual appearance.
- response to palpation.
- lameness.
- DFTS effusion.
- MCP joint hyperextension w/ suspensory ligament.
Investigation:
- dynamic exam w/ blocking.
- U/S.
- radiography.
- MRI.
- nuclear scintigraphy.
– ST phase.

Question 3

Dx analgesia.

Answer 3

Nerve blocks:
- response depends upon level of tendon which is damaged.
– palmar digital –> distal DDFT.
– abaxial sesamoids:
–> distal DDFT and SDFT.
–> (oblique and straight sesamoidean ligaments).
–> annular ligament —> round back fetlock.
– low 4 point –> fetlock region.
– high 4 point –> palmar metacarpal region or palmar metatarsal region (SDFT, DDFT, CL, SL.
– deep branch of lateral palmar/plantar nerve –> just medial to the accessory carpal bone
Intrasynovial (thecal/bursal) blocks:
- DFTS – desensitises surface of structures that run within it.
- Also:
– carpal canal.
– bicipital bursa.
– tarsal canal.
– calcaneal / gastrocnemius bursae.

Question 4

What structures run through or border the DFTS, suck=h that they might be affected by local aneasthetic infiltration?

Answer 4

DDFT run right through the middle.
Intersesamoidean liagament (dorsal surface).
Manica flexoria.
SDFT.

Question 5

Deep branch of lateral plantar nerve block.

Answer 5

Blocks the entire suspensory origin.
Good and specific block for suspensory ligament.
But note some cross over between this and tarsometatarsal joint.
- diffusion can occur.
– likely to affect lateral plantar nerve too.
Performed w/ leg up.
In and up behind splint bone.
Requires good handling and confidence.

Question 6

Digital flexor tendon sheath block.

Answer 6

4 common entry portals.
- proximal.
- axial sesamoidean.
- basilar.
- distal.
Runs from lower 1/3 cannon (half on rear) on palmar aspect of limb into hoof capsule.
Observe/palpate effusion at these points.

Question 7

Ultrasonography.

Answer 7

High frequency linear probe.
- 10-12MHz.
Standoff to visualise superficial structures.
Doppler to evidence vascularisation associated w/ healing.
Clip, clean, spirit, gel.
Marker conventions:
- lateral on transverse.
- proximal on longitudinal.
- use zones or distance from ACB.

Question 8

Ultrasound views.

Answer 8

2 primary views.
- longitudinal.
- transverse.
- plus off-incidence.
– allows visualisation of tendons that are not running truly vertical e.g. check ligament.
Should achieve a view of all structures between skin and cannon bone.

Question 9

On transverse ultrasonography, what structures are top to bottom?

Answer 9

SDFT.
DDFT.
Inferior check ligament / accessory ligament of DDFT.
Suspensory ligament.
3rd metacarpal bone (white line on U/S).

Question 10

Which soft tissue structure is the most dorsal in the palmar metacarpus?

Answer 10

Suspensory ligament.

Question 11

MRI imaging.

Answer 11

Allows 3 views (3D).
- frontal, transverse, sagittal.
GOLD standard.
BEST for distal DDFT lesions.
- where hoof prevents easy U/S access.

Question 12

Superficial digital flexor tendonitis.

Answer 12

Frequently seen in racing TBs and other performance horses.
Career limiting/ending potentially.
Core lesion:
- most zone 2b (halfway down cannon)-3b (just above distal cannon) FLs.
Risk factors:
- conformation (impacts loading).
- ground surface.
- training.
- fitness.

Question 13

Aetiopathogenesis of “Strain”.

Answer 13

Overstretching during fast exercise.
Initial mechanical disruption, fibre slippage and tearing w/ haemorrhage.
Subsequent inflammation; debrided by enzymes and macrophages.
Repair by fibroblasts and capillary buds.
Remodelling:
- reduced collagen content.
- type III tendon fibres (type I is healthy tendon).
- less collagen cross linking.
- loss of crimp pattern.
- excessive interfibrillar matrix persists.
Prone to recurrence:
- within repaired tissue.
- at margin of repair and healthy tissue.

Question 14

How does a Strain lesion appear on U/S?

Answer 14

Anechoic patch.
Becomes more echoic w/ healing.
Once healed, use off-incidence scanning to view scarring.
- may remain a little hyperechoic once healing complete.

Question 15

Diffuse swelling of SDFT on U/S.

Answer 15

SDFT (top of screen on transverse) can be double its normal size when swollen.
Comparison between left and right limbs.
Comparison between lateral and medial.

Question 16

Proximal suspensory desmitis.

Answer 16

Persistent low-grade lameness of performance horses, esp. warmbloods.
HLs predominantly.
Severe changes drop fetlock.
Risk factor:
- larger hock angle (straighter).
Dx:
- blocking pattern (deep branch lateral plantar nerve).
– hopefully desensitise medial and lateral metacarpal nerves.
- U/S.
- radiographs (MTIII sclerosis).
- scintigraphy.

Question 17

Proximal suspensory desmitis tx option.

Answer 17

Fasciotomy and neurectomy.
- denervates proximal suspensory ligament.
– removes pain comms.
– ?neurogenic atrophy?
- opens fascia.
– reduces pain and pathology associated w/ pressure.
- often poor post op cosmesis.
- horse cannot compete at elite level if neurectomy performed.

Question 18

Where is the suspensory ligament origin?
Where is the suspensory ligament insertion?

Answer 18

Origin at palmar metacarpal region.
Insertion at dorsal P1 and sesamoid bones.

Question 19

Suspensory ligament branch lesion.

Answer 19

Common in sports horses.
Medial or lateral.
Poss. associated w/ fetlock effusion.
Foot imbalance may predispose.
In branch or insertional.
Usually uniaxial, poss. bilateral.
Core or peripheral lesions.

Question 20

SL branch lesions on U/S.

Answer 20

Can have echoic bone lesions or can have sclerosis of bone associated with it that causes irregularity (insertional).

Question 21

Inferior check ligament desmitis.

Answer 21

FL problem.
Mature adult horses.
Ponies and pleasure horses.
U/S:
- off-incidence scanning.
- care of interpretation at insertion.
Conservative management usually successful.
- seen as anechoic space where the check ligament should be visualised.
- care w/ large vasculature.
– check w/ orthogonal imaging.

Question 22

DDFT desmitis.

Answer 22

Lesions located:
- hoof/distal pastern (heel bulbs).
- within DFTS.
- proximal to DFTS (rare).
Investigation, blocking and tx options change w/ DFTS involvement – can perform tenoscopy on these.
Dorsal fibrillation.
Splits and tears.
Don’t tend to be core lesions.
- more generalised.

Question 23

DFTS problems.

Answer 23

Septic tenosynovitis.
- as septic joints.
Annular ligament syndrome.
Tenosynovitis.
DDFT/SDFT/Manica flexoria injuries.
Adhesions.

Question 24

DFTS tenosynovitis.

Answer 24

Associated w/ DDFT more commonly than SDFT.
Lateral more common than medial.
Lots of inflammatory material - may need flush.
Prognosis is fair.
Chronic:
- synovial proliferation.
- adhesions in sheath.
- masses in sheath.

Question 25

What is the manica flexoria?

Answer 25

Part of SDFT that wraps around the DDFT.

Question 26

Manica flexoria damage.

Answer 26

MF originates from SDFT and wraps around DDFT in DFTS.
Continuous with sheath.
Prone to tears, which can then form adhesions.
Tx:
- resection and removal of entire manica.
- px good.

Question 27

Palmar/plantar annular ligament injury.

Answer 27

Causes thickening of ligament.
- palpable step if not effused.
- U/S.
Transection PAL desmotomy to release the constriction and pressure on tendons beneath it and allow more free movement.
- tenoscopic.
– improves access around sheath.
- open.
- care post op to avoid sepsis.

Question 28

Inter and distal sesamoidean ligaments.

Answer 28

Intersesamoidean ligaments are between proximal sesamoid bones.
Distal sesamoidean ligaments are functional continuation of suspensory ligament in palmar pastern.
- straight sesamoidean ligament.
- oblique sesamoidean ligaments.
- cruciate sesamoidean ligaments.
- short sesamoidean ligaments.

Question 29

How can tendons be split?

Answer 29

Sagittally split.
Transected.
*like a cheese string can be bitten or peeled apart.

Question 30

Repair of severed tendons.

Answer 30

Repair w/ permanent or long-lasting resorbable monofilament suture material.
Use suture pattern to give good holding power in tendon end e.g. locking loop.
Cast for post-op support.
- heel elevation to take weight off tendon.
Complete transections will carry guarded to poor px.
Athletics not poss. following this.

Question 31

Tendon rupture management.

Answer 31

Acute injury:
- cryotherapy.
- bandaging.
- NSAIDs.
- ?intralesional steroids.
- ?PSGAGs (polysulfated glycose aminoglycans).
U/S changes will become evident over several days.
In repair phase/when chronic:
- regenerative meds.
– autologous bone marrow derived stem cells.
– platelet rich plasma.
– IRAP (Interleukin-1 Receptor Antagonist Protein).
- CONTROLLED REHABILITATION PROGRAM.
- Monitor U/S.

Question 32

Rehabilitation.

Answer 32

Box rest and CONTROLLED exercise best.
- 71% return to race w/ rehab vs 25% if just turned out.
Movement vital to regain correct fibre alignment.
Likely recovery times:
- ICLDDFT 6w.
- SL 6m.
- SDFT 12-24m.
Incremental time periods.
SID-TID (little and often best).
Increasing gaits.
U/S before each sig. increase.
Allow turnout as exercise increases.
Consider in hand vs walker.

Question 33

Other tx options for tendon rupture.

Answer 33

Regenerative meds:
- improved quality of healing.
– growth factors.
– platelet rich plasma.
– mesenchymal stem cells.
– Autologous mesenchymal stem cells.
– IRAP.