Distal phalangeal and distal sesamoidean fractures Flashcards
What are the possible causes and types of fractures in the pedal and navicular bones?
Causes – acute onset trauma, developmental / osteochondral fragments, and repetitive wear and tear / chronic disease
Types of fracture – small fragments, large complete fractures, stable or unstable, articular and non-articular
What clinical signs are associated with navicular and P3 fractures?
- Both these bones are enclosed within the hoof capsule – this means there is often minimal displacement of the fractures, and identification on physical examination is difficult but important
- Careful palpation of the hoof and pastern region for heat, pain and swelling (including synovial effusions)
- Use of hoof testers to identify site of pain
- Clinical signs depend on fracture site and severity
- Small extra articular fragments – low grade lameness with minimal localising signs
- Significant / complete fractures – acute onset, severe lameness with localising signs (bounding digital pulses, heat in hoof, positive response to hoof testers)
- Articular fragments – Distal interphalangeal joint effusion (pedal bone and navicular bone)
- Tendon involvement – digital flexor tendon sheath effusion (navicular bone)
What is the diagnostic approach for navicular and P3 fractures?
- Radiography – anatomy and technique in subsequent slides
- MRI
- CT
- Gamma scintigraphy
- Nerve and joint blocks – only for mild / chronic cases – avoid in severe / significant fractures
What are the challenges of radiographing P3 and navicular fractures?
- The hoof structure holds the bones together so fractures may not be visible initially, until some bone resorption has occurred (7-10 days)
- Some fractures only heal with a fibrous union (fracture line remains on radiographs, but are stable) – chronic fractures may need additional tests to confirm if clinically significant
What are the key aspects of the navicular bone we should assess on xray?
Key aspects
proximal and distal border, dorsal surface (articular), palmar surface (deep digital flexor tendon and navicular bursa), wings and body
What are the key aspects of the pedal bone we should assess on x-ray?
Key aspects
articular surface, extensor process (site of extensor tendon attachment), sole or distal surface, wings and body, vascular channels
What are reasons for the presence of a fragment at the site of the extensor process?
- Recent fracture
- Previous fracture, now healed and stabilised
- Separate centre of ossification
- Dystrophic mineralisation in the extensor tendon
What views are standard in a foot series?
- Lateromedial
- Dorsopalmar
- Dorsoproximal Palmarodistal 60o oblique centered on pedal bone (upright pedal)
- Dorsoproximal Palmarodistal 60o oblique centered on navicular bone (upright navicular)
- Palmaroproximal Palmarodistal 45o oblique (flexor navicular)
Of both feet!
Plus additional oblique views of the pedal bone..
Describe the steps to take a lateromedial xray of a foot
- Feet on blocks – Even when X-ray machine on floor the light beam diaphragm cannot open to floor- so need to raise the horse! They are more comfy with both feet on blocks at the same time.
- Use heel bulbs to help you – line something straight along them (as long as they are symmetrical). Then align side of X-ray machine to that- this helps prevent rotation of image by aligning the primary beam perpendicular to the sagittal plane of P3.
- Dorsal wall marker/Frog marker if clinical signs require measurements
- Check horizontal beam (use spirit level or X-ray machine may have ball baring at side)
- Set exposures (exposure book/chart)
- Check focal film distance
- Centre 1cm below coronary band half way between dorsal and palmar
- Collimate- tight as possible
Describe the steps to take a DP xray of a foot
- Foot on block
- Make sure limb is straight – or may cause image to look like horse has foot imbalance when it doesn’t!
- Check horizontal beam
- Centre on the middle of the coronary band
Describe the steps to take an upright pedal/D60Pr-PaDi oblique xray of a foot
- Upright - leg positioned against block, beam horizontal. Better image, but need/expose extra person (wear gloves!!)… (a)
- Tunnel – foot positioned on top of block, xray machine angled down 60o, needs less people, but get some image distortion (b)
- Both: Center on coronary band and open out to include all of pedal bone
- Pack foot with play doh to avoid air artefact!
Describe the steps to take an upright Navicular/D60Pr-PaDi oblique xray
- Same approach as for pedal bone views
- If upright in block, tip foot over slightly so dorsal hoof wall about 85 degrees from horizontal
- Tunnel as for P3 view
- Centre 1-2 cm above the coronary band (red arrow on images, black arrow= pedal bone centering)
- Collimate right down to reduce scatter
- Pack the foot with play doh
Describe how to position the horse for a Flexor Navicular / Pa45Pr-PaDi oblique view
- Foot on tunnel
- Foot caudal on block
- Access: Toe in/ block out
- Not always at 45°
- steepest angle possible without hitting back of fetlock
- Centre between heel bulbs
- Collimate, and check your film focal distance
- For safety, try and sort film focal distance, angle and collimation away from horse beforehand
How would you treat this fracture? Remember the principles of fractures
Based on your assessment of this fracture, which treatment option would you recommend:
A. Conservative – box rest only
B. External coaptation – foot cast
C. Fragment removal – bursoscopy surgery
D. Internal fixation – screw placement
- This is a complete transverse fracture – the fracture line will extend into the articular surface with the distal interphalangeal joint, and onto the palmar surface where the deep digital flexor tendon lies
- There are two complete separate fracture fragments, which will remain unstable and move unless stabilised.
- The best option for this horse will be internal fixation
