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Splint Bone Fractures


Splint bone fracture usually results from one of the following:

Excessive weightbearing stress

Excessive load can result in considerable movement between the splint bone and the parent (cannon) bone. These bones are attached via a ligament (known as the interosseous ligament).

Excessive weightbearing load can result in excessive relative movement between the bones which in turn results in increased pull from the interosseous ligament. In some cases, this increased ligament tension can result in fracture of the splint bone. In almost all cases involving this type of fracture, the splint bone breaks at it thinnest-most aspect, which is approximately 1-2 inches above the "button" (located at the distal aspect/ bottom of the bone). This type of fracture is more commonly associated with the medial (inside) splint bones and is usually "closed" (i.e. it is not associated with an open wound).


External trauma/ injury

Most traumatic fractures occur secondary kicking a hard object or receiving a kick from another horse. With this type of fracture, the bone can break anywhere along its length and involve a varying number of resulting fragments. A simple fracture consists of 2 fragments, a comminuted fracture consists of 3 or more fragments. These fractures are most commonly "open" (i.e. are associated with an open wound) and therefore involve some degree of contamination/ infection.

Click HERE to learn about BONE SEQUESTRAE that can develop within open (infected) wounds.



Clinical Examination

Most splint bone fractures will result in some degree of lameness which is evident during clinical examination. Swelling and pain associated with the fracture site is usually present. In severe cases of open fracture, bone fragments within the wound may be visible to the naked eye.

Radiographic Examination

Most veterinarians elect to confirm a suspicion of splint bone fracture through radiographic examination (i.e. by taking “x-rays”) of the affected limb. A tangential view (which highlights the area in question independently of surrounding bone) is generally diagnostic.

Ultrasonographic Examination

At The Atlanta Equine Clinic, we prefer to diagnose splint bone fractures via ultrasonographic examination, because associated soft tissue damage is better assessed through this method. Although the ultrasound waves cannot penetrate the bone structure, a very detailed (and clear) picture of the bone surface(s) is visible, thereby allowing for quick and accurate diagnosis.


Ultrasonographic Diagnosis of a Splint Fracture

Ultrasonographically, the surfaces of splint bones are discerned as bright white (reflective) lines. A discrepancy, angle change or separation in the white line(s) can indicate fracture.

Each suspicious area designated by a "break" in the white line is imaged in two planes (transverse and longitudinal).

Small fracture fragments are often demonstrated by local repositioning of the bone surface (white line).

Each fragment is measured and its location is "mapped-out".

Surrounding soft tissue structures (subcutaneous, ligamentous, tendinous, etc.) and the surface of the adjacent cannon bone is also evaluated during the exam.


In all cases of ultrasonographic examination of splint bone fractures, the status and integrity of the adjacent suspensory ligament is assessed carefully. The results of this assessment will play a major part in formulating the horse’s prognosis for future soundness.

Treatment Considerations

A fractured (broken) splint bone is unstable because the length of the supporting lever-arm has been reduced. We have to remember that the proximal (uppermost) fragment is still required to bear some degree of weight from the bones above.

Splint bone fracture results in 2 or more fragments. Regardless of the number of fragments, there is usually just one proximal fragment (i.e. one piece that still communicates with the joint above). In lieu of the relationship between proximal fragment size and future prognosis (see above), the size of the proximal fragment becomes the primary point of concern when dealing with splint bone fracture.

The second point of concern is with regard to the specific splint bone that is involved. As mentioned in THIS ARTICLE, some splint bones are more important than others.

With all splint bones excluding MT4, preservation of the articular component on the bone is usually necessary to maintain soundness in the limb. Although the fourth metatarsal bone (i.e. the lateral pelvic splint bone or MT4) is the largest of the splint bones, it actually has the smallest articular component and is therefore considered the least important of the four. In fact, this bone has been completely removed in many cases with no resulting long-term lameness.

Of course, the more functional (i.e. more important) the splint bone, the larger the remaining proximal fragment must be to maintain limb soundness. If there is not enough proximal splint bone fragment size to maintain joint stability, then the bone must be stabilized surgically (via internal fixation). This can be a challenging endeavor, especially when working with an open (infected) wound.

In cases in which there exists ample (intact) proximal splint bone, the distal fragment(s) are simply removed. Again, when considering MT4, very little if any splint bone is required to maintain overlying joint stability.



In many cases of closed (uncontaminated) splint bone fracture, the distal fragments maintain partial or complete vascularity (blood supply). Spontaneous (osteoclastic) resorption of these fracture fragments often occurs without surgical intervention by the veterinarian. This process may take several months up to several years. Unfortunately, the horse’s lameness usually persists while the fragments remain present within the tissue.


Spontaneous Resorption of Distal Splint Bone Fracture Fragments within the Same Year
20 January 31 March


In most cases of splint bone fracture, surgical removal of the distal fragment is recommended. In cases of open (contaminated) splint bone fracture, surgery is usually required to resolve the problem and reestablish the horse’s soundness. The sooner that surgery is performed, the less irreversible damage that occurs to the surrounding tissues (including the adjacent suspensory ligament).

This procedure is performed with the horse under general anesthesia and in lateral recumbency (on his/ her side).


Surgical Removal of Splint Bone Fracture Fragments

Most preoperative preparative work is conducted with the horse standing, so that time spent under general anesthesia is minimized. The surgical site is clipped to prevent hair contamination of the incision during the procedure.

Contact time between the scrub (bacteriocidal soap) and skin surface is maximized by applying the first layer early. This reduces the chance for postoperative infection.

The skin and subcutaneous tissues along the incision site are locally anesthetized (blocked). This allows the surgery to be performed using less general anesthetics, which is healthier and safer for the horse. Moreover, local anesthesia allows for preoperative "marking" of the underlying bone fragments (see below).

While the scrub and local anesthetic are working, an intravenous catheter is placed to allow for easy and immediate access to the horse's vascular (systemic) system during surgery. The catheter is always placed on the same side as the limb containing the fracture(s); that way it will be facing upward during the horse's recovery.

Skin staples are placed in the skin and spaced along the length of the fractured splint bone.

These staples can be used to ascertain the specific location of each fragment along the length of the limb through follow-up radiographic examination. In this case, the lower two staples lie directly over individual bone fragments.

Once the exact position of each fragment has been determined, the horse is placed under general anesthesia and the limb is further prepped and draped.

Following incision, the distal aspect of the splint bone (the button) is identified.

The button is grasped with forceps, which are used to apply upward traction on the distal bone fragment. This exposes the interosseous ligament, which resides between the fracture fragment and underlying cannon bone.

An osteotome (like a chisel) and mallet (hammer) are used to transect the interosseous ligament, thereby freeing the distal bone fragment from its attachment to the underlying cannon bone.

Once the distal fragment is removed, any middle fragments are identified and resected in similar fashion.

After all middle and distal bone fragments have been removed, the scalpel and osteotome are used to expose the lower (bottom) end of the proximal (intact) bone fragment. The majority of this fragment will remain with the horse following surgery.

Once adequately exposed, the lower end of the proximal fragment is resected at an angle (i.e. tapered) to eliminate future interference of sharp bone edges with adjacent soft tissues.

Once freed, the lower end of the proximal (intact) fragment is removed.

The incision is inspected and cleansed of persistent hemorrhage, abnormal (infected) soft tissues and any residual debris prior to closure.

Closure is performed in two layers; Subcutaneous tissue and skin are apposed separately.

The incision is covered with a sterile wrap and a heavy, well-padded distal limb bandage is carefully applied prior to the horse's recovery. Click HERE to learn about complications that can occur with bandaging.

Postoperative radiographic examination (rarely performed) confirms complete removal of the middle and lower splint bone fragments as well as appropriate tapering of the lower end of the remaining fragment.



Pre- and Post- Operative Views of Splint Bone Fragments
Preoperative Radiographic View Postoperative Gross View


If you have any questions regarding Splint Bone Fractures in the Horse please call our office at (678) 867-2577. We look forward to serving you!
THE ATLANTA EQUINE CLINIC: 1665 Ward Road, Hoschton, Georgia 30548 - ph. 678-867-2577

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