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Musculoskeletal > LA MS 10: Navicular Syndrome > Flashcards

LA MS 10: Navicular Syndrome Flashcards

1
Q

Navicular Bone Anatomy

A

Palmar or plantar aspect of P2 and P3 - coffin jt
Has 2 articulating surfaces - distal surface w/ P3, dorsal w/ P2

Lined with synovial fluid - synovial invaginations
Covered with hyaline cartilage
Flexor surface = fibrocartilage –> smooth surface for the tendon to run over

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2
Q

Fxn of the navicular bursa

A

Provides smooth surface for the DDFT to run over
Bursa Does not communicate with the coffin jt
2 collateral sesamoidinal ligaments - attach on the wings of the navicular bone

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3
Q

Blood supply, innervation

A

Medial and lateral palmar digital artery, vein, and nerve

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4
Q

Navicular Syndrome

A 
Common FL lameness
Syndrome vs disease 
Higher incidence in QH, WB, TB - rare in mules, donkeys 
M>F (not supported by research)
Inherited???
--possibly DT conformation
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5
Q

Etiology

A

Poorly understood
2 theories
1- vascular
2 - biomechanical

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6
Q

Vascular Theory

A

Altered blood flow to navicular region

Theory lacks proof of concept support
In vivo data to support increased rate of bone remodeling and increased vascularization
Further in vivo data suggests active arterial hyperemia and passive venous congestion

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7
Q

Biomechanical theory

A

More accepted
Degen changes result from increased mechanical forces on the navicular bone and its supporting ligaments
–tension from DDFT
–tension from supporting ligaments

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8
Q

Origin of navicular pain

A

Intraosseous pressure
Damaged supporting ST structures
–collateral tears and DDFT tears often misdx’d as navicular
Bursa - bursitis

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9
Q

Predisposing Factores

A 
Excessive body weight
Small feet 
Upright pastern angles 
Hoof imbalances 
Work on hard surface --> concussion
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10
Q

Dx

A 
Hx, CS
Localization of lameness to palmar 1/3 of foot 
--perineural blocks - PD blocks 
--coffin jt 
--navicular bursa 
Imaging 
--RADS
--Bone scan, CT, MRI
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11
Q

Hx, CS

A

Progressive, chronic unilat/bilat forelimb lameness
95% have asymmetric lameness
75% had extensor m atrophy
–chronic cases
–don’t want to extend all the way so decrease concussion on heel

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12
Q

CS: gait

A

Stiff, shuffling gait
Refuses leads, not willing to stride out
Lameness more obvious in a circle
Pointing of forelimb

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13
Q

Dx: hoof testers

A

+/- sensitive across heels, frog, possibly toe

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14
Q

Hoof abN

A 
Low, under run, contracted or sheared heels 
Broken-back hoof pastern axis 
Medial-lateral hoof imbalance 
Small, upright foot 
Narrow foot
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15
Q

Dx Lameness Exam

A 
Lameness variable 
Typically bilat but asymmetric - one limb more severely affected 
Stiff, shuffling, choppy gait 
Short cranial phase 
***tend to land on toe***
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16
Q

Dx Lameness Exam: Lameness exacerbated when -

A 
Hard surfaces 
Lower limb flexion
Wedge test 
Frog pressure 
Worked in circle
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17
Q

Dx PD Nerve Block*

A 
Small vol, small gauge needle 
--avoid block diffusing up the leg 
Desensitizes cd 1/3 of foot and ole 
Show marked improvement --> 80-90%
Majority switch over to being lame on the other side
18
Q

Dx Navicular bursa block

A

Aseptic technique

RADS control

19
Q

Dx Coffin Jt Block*

A

IA ax of coffin jt NOT helpful in differentiating problems of coffin jt and navicular region

20
Q

Dx RADS

A

Remove shoes
Clean feet
Pack feet - remove air artifacts
Bilateral

21
Q

Dx RADS - views

A

Lateral
Dorsoprox-palmarodistal (60 degrees)
Palmaroproximal-palmarodistal: tangential or skyline view
Flat dorsopalmar

22
Q

RADS findings: lat projection

A

Palmar, plantar angle
Bone production - prox and distal margins
Eval how P1, P2 and P3 line up
Normally toe should be tipped down just a bit

23
Q

Rad findings: 60 degree dorsopalmar oblique

A

Increase in number, sz, abN shape of synovial invaginations - distal margin

24
Q

RAD findings: skyline

A

(Aka palmaroprox-palmarodistal oblique)
Flexor cortex: erosions, roughening
Corticomedullary distinction - cortex should be more radioopaque than medullary cavity
–If hard to tell where medullary cavity ends and cortex begins, have sclerosis

25
Q

RAD findings: flat DP projection

A

Eval whether have balance medial to lateral hoof

26
Q

Other RAD findings

A
  • loss of corticomedullary distinction
  • medullary sclerosis
  • mineralization of DDFT
  • enthesophytes
27
Q

Lameness with “toe up”

A

Fracture of navicular bone
–lost some of space so DDFT looser
Rupture of DDFT

28
Q

Additional Imaging Modalities

A

Bone Scan
CT
MRI

29
Q

MRI

A

Mainstay of dx problems in foot because presence of so many ST structures

If blocks out to the foot and RADS are inconclusive, move onto an MRI

30
Q

3 mainstays of navicular tx

A
  1. Corrective shoeing
  2. Rest
  3. Bute
31
Q

Treatment

A 
Numerous tx modalities 
Usually combo 
--rest esp after shoeing 
--light work 
--corrective trimming/shoeing 
--drugs designed for tx of OA 
--Meds that improve blood flow 
Sx
32
Q

Corrective shoeing

A 
Basis for tx
Goals 
--restore natural hoof balance 
--reduce biomechanical forces on the navicular region 
Egg Bars
Shorten the toe 
--rolling, rockering, squaring of the toe and setting it slightly back on the front enhances breakover of the foot 
Raise the heel: shoe, wedge pads 
Reverse shoe - easier to bring leg back
33
Q

Med Tx

A

NSAIDS
CS
HA
PSGAG

34
Q

NSAIDS

A

Bute = best

35
Q

CS

A

DIT jt, navicular bursa

36
Q

Hyaluronic acid

A

IA, intramural, IV

37
Q

PSGAG

A

PO, IM

38
Q

Isoxsuprine hydroCl

A

Beta-adrenergic agent
VD/rheologic properties

Poorly proven - low SE so worth trying

39
Q

Pentoxifylline

A 
Synthetic xanthine derivate 
Increases erythrocyte flexibility 
Decreases fibrinogen 
Prevents aggregation of RBCs and platelets 
Inhibits action of IFM cytokines
40
Q

Bisphosphonates

A 
Ex: tildren, osphos 
Causes intracelluler, intercellular mediated cell death of osteoclasts --> decreased bone resorption 
Anti-IFM properties 
--decreased NO and cytokines released 
--Inhibits activity of MMPs 
SE: mild transient colic, renal failure 
No data on efficacy of Tildren as RLP
41
Q

Palmar Digital Neurectomy

A

Not first line of defense
Performed in conjunction with corrective trimming, shoeing
Degree of response to pre-op block will predict response to neurectomy
Only lasts approx 2yr before nerve grows back

42
Q

Tx Suspensory Branch (aka collateral ligament) desmotomy

A

Rationale - reduces forces on the navicular bone during WB phase of stride

Musculoskeletal (10 decks)

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