Carpus 95 - Carpus ACB fx and other pathologies Flashcards
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What could have happened?
Figure 7.8 Displaced dorsal plane fracture of the accessory carpal bone with distension of the carpal sheath (arrows) and
dorsopalmar foreshortening produced by axial rotation of the palmar fragment (dashed arrow).
dx and projection
FIGURE 1 Lateromedial (a) and dorsopalmar (b) radiograph taken after the injury. Note the closed, minimally dislocated, vertical,
comminuted fracture of the accessory carpal bone. Arrow showing the dorsoproximal fracture fragment.
(a) (b)
ABman EVJ 2023
how do you immobilize?
Fractures of the accessory carpal bone do not cause
instability, but unstable dorsal (frontal) plane fractures are displaced by carpal flexion. This is most easily controlled with a dorsal splint extending from proximal antebrachium to distal metacarpus (Figure 7.24a). Bandage bulk should be sufficient only to avoid point contact between the leg and splint. A splinted Robert Jones bandage with a lateral
splint extending from elbow to ground and cranial
splint from elbow to distal metacarpus (Figure 7.24b) or incorporating a caudally placed elbow to ground splint of half or one-third diameter piece of PVC piping are less effective alternatives.
Which breed of horse is most commonly associated with accessory carpal bone fractures?
Thoroughbred
Accessory carpal bone fractures represent what percentage of all carpal fractures in horses?
2%
In a survey, what percentage of Thoroughbred yearlings radiographed prior to sale had accessory carpal bone fractures?
0.4%
*
A displaced fracture of the accessory carpal bone can lead to injuries of which structure?
DDFT
What is a common cause of frontal plane fractures in the accessory carpal bone?
Avulsion by palmar attachments
Which imaging technique is NOT typically used to confirm the diagnosis of accessory carpal bone fractures?
MRI
What is the recommended initial step in nonsurgical management for accessory carpal bone fractures?
Stall rest for 3 months
In cases of nonsurgical treatment of accessory carpal bone fractures, what was the outcome for horses available for follow-up?
All were sound and some returned to racing
What happens to the fracture edges in chronic accessory carpal bone fractures?
They become rounded off
What type of accessory carpal bone fractures is most commonly treated with surgical repair using bone screws?
Simple vertical fractures
Figure 95-18. (A) Lateromedial radiographic view of a 6-year-old Warmblood horse with a frontal plane fracture of the accessory carpal bone sustained 2 weeks previously when the horse was jumping against an obstacle and fell. (B) Postoperative lateromedial radiograph of the same patient after repair with two narrow 4-hole 2.7-mm LCPs applied to the lateral aspect of the bone.
Why is surgical repair of the accessory carpal bone challenging?
Due to its location and the concave shape of the bone
What was the condition of horses treated nonsurgically for experimentally created vertical fractures after 6 months?
All were still lame
In a case report, which surgical technique was successful for treating vertical fractures?
Application of dynamic compression plates
What can be the prognosis for nonsurgical management of AC bone fractures?
Although nonsurgical management of accessory carpal bone fractures can result in complete return to athletic soundness in fractures, complete bone union is usually not present.
What potential issue should be evaluated in chronic accessory carpal bone fractures?
In chronic fractures, the potential for carpal canal syndrome exists and should be evaluated during the examination. friction to the DDFT (lateral)
ACB it forms the palmarolateral aspect of antebrachiocarpal joint and articulates with __________________ and _________________bones
The accessory carpal bone (ACB) forms the palmarolateral aspect of the antebrachiocarpal joint and articulates with the caudal radius and ulnar carpal bone
what are the 4 ligaments to which teh ACB is anchored?
The ACB is anchored axiolaterally by four
ligaments:
1- the accessorioulnar-,
2- accessoriocarpoulnar-,
3- accessorioquartal-
and
4- accessoriometacarpal ligament
The 4 ligaments of ACB transmit the forces generated by flecor carpi ulnaris muscle and the ulnaris lateralis muscle
The 4 ligaments of ACB transmit the forces generated by flecor carpi ulnaris muscle and the ulnaris lateralis muscle
What types of ACB fractures are described?
Open vs closed
Vertical vs horizontal
Simple vs comminuted
displaced vs non displaced
Fractures usually occur in a vertical plane along the groove formed by the long **tendon of the ulnaris lateralis **muscle and may be simple or comminuted in nature Rarely, ACB fractures have also been described in a **horizontal fracture **configuration
In most comminuted cases a dorsoproximal fragment
involving the antebrachiocarpal joint can be seen
Does the ACB have periosteum?
no, it doesn’t have periosteum neither bone marrow and it has poor blood supply
Conservative tx has been associated with good outcome but why Furst 2022 describes that has unfavourable healing?
- ACB has no periosteum or bone marrow and has a poor blood supply. Conservative management
- fails to provide compression of the fracture ends in conservative management, which is
exacerbated by the constant pull of the various tendons and ligaments on the bone, creating an unfavourable environment for healing.
Fig 3: Illustration of the lateral aspect of the accessory carpal
bone with the two tendons of the ulnaris lateralis muscle. Ca,
accessory carpal bone; S, insertion of one of the tendon of the
ulnaris lateralis muscle; L, second tendon of the ulnaris lateralis muscle.
Note the 2 branches of the ulnaris lateralis muscle and the presence of the groove where the fracture occurs
what is happening?
The typical hyperextension observed in race horses or eventing with opposing forces of the tendons leads to the fracture. ACB compression between the third metacarpal bone and
the radius when the horse falls with the carpus in flexion
what are the 2 tendons involved in the flexion of ACB?
Number 7 - ulnaris lateralis muscle
Number 8 - flexor carpi ulnaris muscle
According to the technique of Preux 2023 a piece of hardwood was incorporated in the cast. What type of cast and the wood was medial or lat?
Fig 2: Photographs of the preoperatively placed fibreglass cast utilised to facilitate the computer-assisted surgical repair of the
accessory carpal bone (ACB) fracture. (a) The cast was placed prior to induction and with the horse standing to ensure immobilisation
of the carpus in a fully extended position. Note: a piece of hardwood has been incorporated to allow the placement of the patient
tracker. (b) Fenestration of the cast over the palmar aspect of the carpus to allow for surgical access to the ACB. (c) Intraoperative
photograph showing the patient tracker anchored to the cast with two 3.2mm pins. The operating surgeon utilises the navigated pointer
to determine the appropriate site for placing the skin incisions. The patient tracker and the pointer are both equipped with lightreflecting
spheres, which are detected by an infrared optical digitiser and camera array (not shown).
Preux et al describe the placement of screws with CAOS system. How?
Fig 1: Lateromedial radiograph (a) of the right carpus showing a zigzag shaped, complete and mildly comminuted fracture
(arrowheads) in the dorsal third of the accessory carpal bone (ACB), with minimal palmar displacement. An additional thin radiolucent line (arrow), originating from the main fracture, is present in the proximal fourth of the dorsal fragment, suspected to represent an incomplete fracture.
Given the lack of displacement and the interdigitation of the fragments, the surgeons hoped to stabilise these fragments in situ with the planned lag screw repair. With the aid of the navigated pointer
For each cortex screw, a 1.5 cm longitudinal incision was
made through the skin reaching the palmar surface of the
ACB, followed by drilling a 2.5mm pilot hole.
they were
enlarged for the placement of a 4.5mm cortex screw (48mm
in length) proximally and a 3.5mm cortex screw (50mm in
length) distally. The proximal pilot hole was over-drilled with a
navigated 4.5mm drill bit to create the glide hole and then a
navigated 3.2mm drill bit to create the thread hole of appropriate width and depth
After countersinking, screw length measurement and tapping, the two cortex screws were placed in lag fashion and tightened
with the maximal strength achieved by holding the
screwdriver with thumb, index and middle finger
According to Preux et al 2022 was the dorsoproximal fragment removed?
6 weeks after srugery the surgical incisions were healed without complications and the horse was sound at walk. Since the fragment was deemed to be mainly extra-articular
and difficult to reach by arthroscopy, its removal was
performed through a navigated cut-down procedure guided
by the navigated pointer
why is advised to remove the dorsoproximal fragments in ACB fracture?
Because osteoarthritis of the antebrachiocarpal joint can happen due to continued synovial irritation because of the unstable articular fragment.
Aßmann et al 2023 describes the use of a special plate for humans in the ACB bone. Describe the name of the plate and screw and the good advantage
The 6-hole APTUS® 3.5 Talonavicular Fusion Plate with TriLock© self-tapping screws can be re-locked
in the same plate hole at different angles up to three times, without loss of stability of the locking mechanism
dx and projection
closed, mildly displaced, mainly vertical comminuted fracture of the ACB with involvement of the antebrachiocarpal joint was diagnosed Lateromedial (a) and dorsopalmar (b) radiograph
name the instrument
APTUS® 3.5 talonavicular fusion plate (a) and the olive pin (b). Note the prefabricated hole in the plate for the application of
the olive pin (*).
what is this?
name the instrument
3.5-mm
APTUS TriLock© screw
The olive pin included in the set is used similarly to
a push–pull
device for the LCPs to fix the plate to the bone.
In contrast to the push–pull device, the olive pin is smaller and is not attached in a screw hole, but in a hole prefabricated for this purpose in the plate centre (Figures 2c and 3).
why the dorsoproximal fragment was not removed according to the author Aßmann et al 2023?
The small dorsoproximal avulsion fragment was not removed intraoperatively in a standing scenario for several reasons: The fragment was firmly attached to the accessorioulnar-,
accessoriocarpoulnar ligaments and the surrounding fascia. As described in the literature and in the author’s experience in some cases it is difficult or even impossible to remove avulsion fragments, because they can be buried within the soft tissue structures and under the synovial membrane (McIwraith 2020). disadvantage. The authors opted to leave the
dorsoproximal fragment in place, which despite mild antebrachiocarpal
osteoarthritis, did not negatively impact the outcome of the
case. Aßmann et al 2023
Flexed lateral radiographic view of the carpus of a 7-year-old Thoroughbred with an exostosis of the caudal aspect of the distal radial physis (arrows). When these lesions extend more than 1 cm into the canal, they frequently are a cause of lameness.
Caudal radial physeal exostoses. A, A lateromedial radiograph of the distal radius of a horse with persistentcarpal sheath effusion and lameness. The exostoses appear as sharp bony (arrow) spikes that protrude a variabledistance toward the carpal sheath.
A radial osteochondroma. A, Lateromedial radiographdemonstrating a sharply pointed osteochondroma on the distalcaudal metaphysis of the radius.
What typically causes Coronation in horses?
A fall and teh tendons are the extensor carpi radialis and the co,,on digital extensor tendons
Figure 95-24. Treatment of a coronation injury. (A) Appearance of the injury. (B) A 1- to 2-mm rim is sharply removed around the skin defect. (C) Careful débridement of the subcutaneous tissues aids in determining if the joint is involved as well. (D) Needles placed from the palmar aspect of the carpus into the joints for joint lavage allow verification of any potential joint involvement. (E) Alternatively, the needles may also be inserted from the dorsolateral or dorsomedial aspect of the carpus. (F) After placing one or two drains, the skin is closed in routine fashion.
Figure 95-25. Synovial osteochondromatosis. Flexed lateral (A) and dorsomedial-palmarolateral 45-degree (B) radiograph of a mineralized mass within the radial carpal joint in a 2-year-old Standardbred filly. Arthroscopic (C) view of the mass within the radial carpal joint.
