Fetlock (incl P1 and condylar fractures)

Question 1

According to Bryner et al 2020 Vet Surg, what % of short incomplete P1 fractures return to intended use following lag screw fixation in sports horses

How does this compare to the same fracture type return to racing reported by Smith and wright 2017 EVJ

Answer 1

89%

Smith and Wright report 92% return to racing for P1 fissures

Question 2

What % of short incomplete P1 fractures were not radiographically healed at follow up according to Bryner 2020 Vet Surg

Answer 2

68% had fracture line still visible at follow up rads

Question 3

What % of horses remained lame at follow up exam after P1 fissure repair reported by Bryner 2020

Answer 3

40%

This was generally not noted by the owner and was not performance limiting

Question 4

What constitutes ‘optimal screw position’ for the proximal screw in P1 fissure repair according to Bryner 2020

What percentage of horses had optimally positioned screws at follow up rads

Answer 4

Screw centered in the dorsopalmar center of the fracture, and within 5mm of the MCPj, parallel to the articular surface

5/19 were optimally positioned (26%)

Question 5

Reported return to racing following medial condylar fracture repair according to Boorman et al 2020 Vet Surg

What was the difference in return to racing with experienced vs inexperieced horses

Answer 5

49% overall, 54% of those surviving to discharge

64% experienced vs 27% inexperienced returned to racing. Those that had raced previously were 5 times more likely to race vs those that hadn’t

Question 6

Factors associated with increased liklihood of return to racing following P1 fracture repair according to Smith and Wright 2017 EVJ

Answer 6

1) Age at fracture - more likely to return if 2 vs 3 year olds
2) Short incomplete fractures were more likely to race vs other configurations
3) Shorter fracture length
4) 3 or less screws used in fracture repair

Question 7

What % of complete and comminuted P1 fractures returned to racing according to Smith and Wright 2017 EVJ

Answer 7

50% complete

0% comminuted

57% long incomplete

92% short incomplete

Question 8

What is the benefit of triangular screw configuration in repair of complete P1 fractures as reported by Labens et al 2019 Vet Surg

Answer 8

Triangular construct reduced fractures better in both loaded and unloaded states

Loading of linear repairs rx in fracture gap distraction (good agreement between observers) vs triangular where distraction was difficult to detect

Question 9

If P1 fractures have an oblique/spiral component, which direction is this typically?

Answer 9

Dorsolateral to palmar/plantaromedial

ie dorsal cortical fracture line moves laterally, plantar line medially.

Can see 2 separate lines on shallow DLPMO obliques, whereas not visible on DMPLO obliques

Question 10

What direction do spiralling medial condylar fractures usually propagate in?

Answer 10

Dorsal cortical fracture line usually travels medially and plantar cortical line laterally

Ie screws are placed from dorsolateral to plantaromedial

Question 11

Common types of P1 fracture

Answer 11

A) Sagittal/parasagittal

1) Short incomplete
2) Long incomplete
3) Complete uniarticular (lateral cortex)
4) Complete biarticular

B) Frontal

1) Short uniarticular (dorsal frontal fractures)
2) Long biarticular

C) Comminuted

Question 12

4 types of P2 fracture

Answer 12

1) Palmar OC chip fracture from the proximal axial aspect of the bone
2) Uniaxial palmar eminence fractures
3) Bilateral palmar eminence fractures
4) Comminuted fractures

Question 13

Management options for SH type 2 fractures of the distal metacarpus/tarsus

Answer 13

1) Conservative - cast or splinted bandage (with the splint on the opposite side to the metaphyseal spike) +/- palmar splint. Casts require changing q2 weeks in young foals. Heal fast, drop to a bandage in 4 weeks or 8 weeks in older foals
2) Surgical - GA lateral with the metaphyseal spike uppermost. Use 2 4.5mm screws in lag across the metaphyseal spike parallel to the physis, with a transphyseal bridge across the physeal part of the fracture, using unicortical cortex screws (in position) above and below the physis to facillitate figure-8 wire around the screw heads tightened proximally. Simple bandaging usually adequate PO

Question 14

What 3 forms of fixation are required for fetlock arthrodesis and why?

Answer 14

1) Dorsally applied plate (broad LCP preferable, somoe prefer 10 hole, upto 14 hole)
2) Palmar/plantar tension band required or the dorsal plate would be subjected to excessive bending forces
3) Transarticular screw from dorsodistal to palmaroproximal P1 to MC3

Can also place lag screws from MC3 to PSBs depending on injury

Question 15

How to perform the tension band part of fetlock arthrodesis

Answer 15

• Needs to be done before plate applied as done with the joint luxated, but plate needs to be contoured and holes planned first
• Done using 1.2-1.5mm wire (or 1.7mm cable)
• Need lateromedial (frontal plane) 3.2-4mm holes in distal cannon and proximal P1 (junction of proximal and middle 1/3 of the bone) - may want to prepare the 4 plate holes in P1 first so the LM hole doesn’t interfere
• Wire placed with the joint luxated; threaded through the hole in P1, passed through the palmar joint then threaded through hole in the condyle
• 2 wires are passed in opposite directions so that 1 is tightened laterally and 1 medially over P1
• Wires are tightened in 10° dorsiflexion (fetlock angle 180°) so they come under tension when the joint is extended

Question 16

Method of tension band wiring for fetlock arthrodesis reported by Chapman (VS2019)

Answer 16

1) 1.2-1.5mm wire: 4mm transverse holes in MC3 (10cm above MCP) and P1 (junc of prox and middle 1/3). Wire passed through MC3 from lat to medial, then passed into palmar joint and retrieved with wire paser through incision in distal sesamoidean ligs behind the sagittal groove of P1. Then passed from lat to medial through P1 hole. The wire then passed back through the wire passer the opposite way to lie on medial P1. Another wire placed in opposite direction so one tightened medially and 1 laterally on P1

2) 1.7mm cable: as above. Used only 1 cable vs 2 wires and placed so it tightened on the lateral aspect of MC3

Wires or cables tightened at approx 180° joint angle so they are brough under tension once the plate is applied

Question 17

List the steps in the correct order for fetlock arthrodesis

Answer 17

1) GA lateral with the limb uppermost
2) Linear skin incision over the dorsal aspect of the limb through the CDET
3) Transection of lateral CL to disarticulate the joint, leaving skin/SQ intact
4) Cartilage removal (oscillating saw) with 1mm depth cross hatch pattern plus 203mm deep 3.2mm forage holes on all visible surfaces of P1, MC3 and PSBs
5) Application of tension band (tightened approx 180°)
6) Plate application - final joint angle of 195°
7) Application of 2 5.5 cortex screws in lag from distal P1 to MC3
8) Can also apply 5.5 lag screws from MC3 to each PSB dependeing on injury

Question 18

Plate application for fetlock arthrodesis

(as reported by Chapman et al VS 2019, also combines some AO)

Answer 18

1) Applied after tension band in place, athough contouring and planning done before
2) Broad hole LCP ideally. 10 hole preferred by some (Chapman et al VS 2019), upto 14 holes
3) Plate contoured to the dorsl aspect of the limb with 15-20° dorsal flexion (ie joint angle approx 195°)
4) Position plate so that 4 screws are located within P1. 1 5.5mm cortex screw placed in 2nd/3rd most distal hole of P1 (to compress plate to bone), remaining 3 5.0 LHS
5) Drill the 5.5mm glide holes from dorsodistal to palmaropriximal through P1 either side of the plate for the TA scres
6) Attach the tension device to proximal MC3 w unicortical 4.5 cortex screw, tightened maximally
7) 1 or 2 5.5mm cortex screws used in 3rd most proximal hole before removal of tension device
8) Remaining holes filled with 5.0LHS
9) Drill the 4.0 glide holes for the 2 TA screws
10) 5.5mm screw in lag from MC3 to each PSB in most cases (not possible if tx biaxial SB fractures)
11) Half limb WB cast for recovery

Question 19

Recommended joint angle for fetlock arthrodesis

Answer 19

Although the optimal angle hasn’t been determined, 195° seems to be adequate

Question 20

Survival to discharge and long term outcome for fetlock arthrodesis reported by Chapman et al (2019 VS)

Why is the px likely more favourable in this case series vs prev reports

Answer 20

100% STS

All 17 had excellent outcome defined as breeding success or unrestricted pasture exercise

Favourable px reflects case selection - no traumatic disruptions of the suspensory apparatus (TDSA) whereby extensive vascular and soft tissue damage make PO complications much more prevalent - incl infections, implant failure, PIP subluxation (loss of palmar support from suspensory apparatus), and supporting limb laminitis

Question 21

Advantage of orthopaedic cable vs wire for tension band in fetlock arthrodesis

Answer 21

Cable has superior handling characteristics and flexibility during tightening

Multifilament cable is 600% stronger in tension than monofilament wire

Disavantage is increased cost

Question 22

Plate size reported by Chapman et al (VS 2019) for fetlock arthrodesis

Answer 22

Most had 10 hole broad LCP, some 11 and 12

Traditionally used longer 14 hole plates to stop the implant ending mid-diaphysis and creating stress riser. No recovery complicaitons noted in this population and 10 hole plate offers greater flexibility with placement

Question 23

What structure is being demonstrated by numer 2?

Answer 23

Sub-tendinous bursa of the LDET in the hind limb

A bursa of the CDET is also present in the FL, although may also be a separate bursa of the lateral extensor

Question 24

What condition is this described by Iglesias-Garcia 2019 (VS)

Answer 24

Sub-tendinous bursitis of the LDET in the hind limb

Question 25

Outcome reported by Inglacias-Garcia (2019 VS) following medical and sugical tx of sub-tendinous bursitis of the LDET at the hind fetlock

Answer 25

3 medially treated horses all experienced recurrence by 2yrs

Of 3 surgically treated horses (bursoscopic debridement and 2 months bandaging), 2 hadn’t recurred by 3 years. 1 failed to bandage and recurred at 1mo

Question 26

Most common site of origin of lateral condylar fractures

Answer 26

Lateral parasagittal groove of MC/MT3

The majority of lateral condylar fractures originate at 20–50% of the distance from the midpoint of the sagittal ridge to the outer aspect of the condyle (parasagittal groove close to 30% this distance). Fractures very rarely occurred in the outer 50% of the condyle

Question 27

Main findings of Anne-Archard 2019 (EVJ) WRT SCB microarcitecture at the lateral condyle and parasagittal groove of MC3 in neonates, growing and training horses

Answer 27

1. At birth, significant diff in bone qual/quant between lateral parasagittal groove & lateral condyle, w fewer and longer trabeculae & greater spacing between them + lower bone fraction vs the condyle; surmised that there is a weaker SCB in the lateral parasagittal groove at birth
2. Consistent pattern of trabecular orientation in dorsal & palmar MC in neonates → dominant direction approx 45° away from sagittal plane toward abaxial lateral condyle; vs in growing foals/yearlings → progressive shift to sagittal alignment of trabeculae at all sites EXCEPT the palmar parasagittal groove which retained a pattern closer to that of the neonate
3. ∴ lateral parasagittal groove may be inherently weaker than surrounding SCB in the condlye, both at birth & following adaptation to training.

Question 28

General recommendations for transfixation pin casting of comminuted phalangeal fractures

Answer 28

• Place 2-3 horizontal pins diverging 10-15° in a dorsal plane, in the metaphysis or distal diaphysis of MC/MT3
• Variety of pins incl positive profile fully or partially threaded, smooth and ones with thread runout design - generally approx 6.3mm diameter
• Positive profile pins generally preferred because of their higher resistance against extraction forces and pin loosening (although not all literature supports this notion)
• Drill tracts need to be progressively enlarged
• Incorporate pins into fibreglass cast; allows the transfer of the axial weight bearing forces through the pins into the cast

Question 29

List complications of transfixation pin casting

Answer 29

• Pin breakage
• Pin loosening
• Sequestration
• Catastrophic fracture through pin hole
• Pin tract infections

Question 30

What is the diagnosis?

What are the treatment options?

Answer 30

1. Closed reduction and external coaptation alone (cast or splint on the opposite side of the metaphyseal spike). Place in lateral recumbency with the metaphyseal spike uppermost to help with reduction (ie limb down if spike is medial). This is suitable for minimally/non-displaced fractures in young foals
2. Lag screw fixation of the metaphyseal spike with a screw/wire TP bridge on the opposite site. Does carry a risk of ALD in foals <3 mo dt unilateral physeal bridging. If bridging technique is used in young foals with significant growth potential, the implants must be removed as early as possible.
3. Lag screw fixation of the metaphyseal spike combined with cast external coaptation, without a transphyseal bridge (Klopfenstein 2016 VCOT)

Question 31

Normal thickness of the vilonodular pad.

What is considered abnormally thick on sagittal US?

Answer 31

Normal 2-3mm medially & laterall, thinner centrally sagittal ridge. Overlies MC/MT3 in the dorsal fetlock, terminates where articualr cartilage begins. Bone under it has periosteum

>4mm considered abnormal on sagittal US