The Nuts and Bolts of Broken Bones

Jill E. Parker, VMD, DACVS &: Karen I. Timm, DVM, PhD
College of Veterinary Medicine, Oregon State University

Llamas seem to sustain fracture of the bones in their legs relatively commonly, and some of the breaks occur after fairly minimal trauma. For example, one llama that had a fracture repaired at the Veterinary Teaching Hospital had been startled and jumped to the side, breaking his leg as he landed. On the other hand, some fractures occur after a major accident, like the llama that was kicked by a pony.

Regardless of the cause, long-bone fractures are obviously very serious injuries. If you have the unfortunate experience of having a llama sustain a fracture, one of the most important things to do is to prevent a “closed” fracture from becoming “open.” An open fracture is one in which there is a break in the skin, usually from the bone ends protruding through. This can allow infection to occur and can make successful treatment much more difficult. Conversely, a closed fracture is one in which there is no opening in the skin. Many times fractures become open when the llama tries to use the leg after the incident or while it is being transported to a veterinary hospital.

The best way to prevent a closed fracture from becoming open is to apply a bandage with a splint to the leg as soon as possible after the fracture occurs. Keeping the animal quiet while waiting for a veterinarian to treat the llama may be the best way, particularly with llamas that have not learned to tolerate having their legs handled. The veterinarian can give sedation that will make applying the splint less stressful and painful for the llama.

At the Veterinary Teaching Hospital, we commonly use PVC pipe to make splints. A strip about a third of the circumference of 4- or 6-inch diameter pipe, cut the appropriate length, can be placed on the back surface of the leg over a heavy bandage. (For temporary support, the splint could be applied without padding if bandage material isn’t available, but this should be replaced as soon as possible to prevent pressure sores.) We usually use Elastikon bandage material to hold the splint on the leg, but duct tape often works well, especially in an emergency. Other materials that can be used for splints include broom handles placed on either side of the leg, or other strong rigid material that can be cut to the correct length.

To be able to stabilize the fracture, the splint needs to extend a joint above and a joint below the break. Applying a splint that stops at the site of the fracture will make it more likely that the fracture will become open by creating a pivot point at the break. For this reason, splints are rarely helpful for fractures above the elbow or stifle joints. Fortunately, there is a lot more muscle in the leg above the elbow or stifle, so open fractures are less likely. A good rule-of-thumb is that if it is not pretty obvious which bone is broken by looking at the leg, you should not apply a splint. There is a chance you will place it incorrectly and worsen the break, the fracture may be high enough that a splint will not add effective support, or there may be another reason the animal is not using the leg other than a fracture.

A veterinary examination is important to determine the severity and type of fracture, and radiographs, or X-rays, are an essential part of this exam. In fact, any llama with a sudden onset of severe lameness should have a veterinary exam, even if a fracture is not obvious. Fractures and infection are the most common causes of severe lameness in llamas, and either may require emergency treatment.

Fortunately many if not most fractures in llamas can be repaired. Llamas tend to have a good healing response in their bones and soft tissues. They’re fairly lightweight with a calm temperament, and they are comfortable lying down for much of the day. The method of repair varies with the location and type of fracture, but there are two general categories of repair methods: external fixation or internal fixation.

With external fixation, materials placed on the outside of the leg support the fracture. The most common form of external fixation used to repair llama leg fractures involves applying a cast with “transfixation pins.” Transfixation pins are stainless steel pins placed all the way through the leg, from side to side. These are incorporated into the cast as it is applied. The pins are placed above and below the fracture site, or sometimes just above the fracture, to help keep the fracture stable inside the cast as it is healing. The cast, just like a splint, needs to extend at least a joint above and a joint below the fracture.

The transfixation cast technique works well for most fractures of the cannon bones – the bones just below the knee or the hock, which are the joints in the middle of the legs. It also works well for many fractures of the radius or tibia. These are the bones directly above the knee in the front leg or hock in the rear leg. This is a technique that is relatively easy to perform, less expensive than internal fixation, has minimal risk of infection at the fracture site in a closed fracture, and is generally successful even for fractures in many pieces. Principle disadvantages include having the leg in a cast for a fairly long time, which can lead to a dropped fetlock or reduced range of motion of the joints. Casts can also cause pressure sores on the leg, although these are not common in llamas and generally heal well if they occur.

Most llamas wear casts very comfortably for several weeks. The cast is usually changed in about 4 weeks, and the pins are removed. The second cast stays on for a similar length of time. Young, growing llamas may need the cast changed sooner because they can outgrow the cast, but their fractures also tend to heal faster. Once the cast is removed, the llama will need to wear a splinted bandage for a week or two as the muscles, tendons, and ligaments in the leg regain their strength. Overall, it takes about 4-6 months for most fractures to heal, although the leg does not need to be in a cast or splint for this entire time. The llama does need to be in a stall where the cast can stay clean and dry and the llama’s activity limited.

With internal fixation, fractures are repaired by implants placed directly on or within the bone. The type of internal fixation most commonly used to fix fractures in llamas involves applying a stainless steel plate and screws. The plate is applied through a surgical incision, after the fractured pieces are realigned. The plate is held on the broken bone with bone screws placed after drilling holes in the bone. This is an effective method of repair for closed fractures, with a small number of large pieces, toward the center of the bone. It is not a good choice for fractures in many pieces, most open fractures, or fractures very close to the top or bottom of the bone, which would limit the placement of the screws. Plate and screw fixation also allows the llama to use the leg normally sooner than other repair techniques. On the other hand, it is expensive and has a risk of infection associated with it because of the surgical approach made through already injured soft tissues.

Clearly, long-bone fractures are better prevented than treated, and we are currently trying to determine if some fractures occur because of seasonal changes in bone density. It is possible that vitamin D plays a role in this. As you may know, adequate levels of vitamin D is very important in young growing llamas because vitamin D is essential for calcium absorption in the intestines. Without adequate vitamin D, young llamas can develop hypophosphatemic rickets. This is a condition characterized by pain in the limbs, weak bones, and crooked legs. In very severe cases of hypophosphatemic rickets, bones can break without any traumatic incident.

Young growing animals, with high requirements for calcium and phosphorus, are the ones that typically show clinical signs. However, it is possible that less severe and less obvious changes occur in young adult and older llamas with inadequate vitamin D levels, which could cause insufficient calcium absorption from the intestine. If this occurs, calcium is mobilized from bone, because calcium is critical for many functions in the body. If enough calcium is leached from the bone, bone density is decrease, and fractures could occur with less trauma than it would normally take for a bone to break.

Six mature male alpacas from the OSU Camelid research herd were included in a study led by Dr. Karen Timm and funded by Morris Animal Foundation to measure seasonal changes in bone density. Mature animals were used to decrease the potential changes in vitamin D associated with growth and development, and males were used to avoid variability associated with pregnancy and lactation.

Their bone density was measured using dual-energy X-ray absoptiometry (Hologic Dual-energy X-ray Absorptiometer, Hologic Inc., Waltham, MA), which is a noninvasive way of measuring bone mineral density and bone mineral content. This is the same technique used in people to determine if they are developing osteoporosis. Scans were performed four times over a 1-year period. In addition to measurement of bone density and mineral content, calcium, phosphorus, and vitamin D levels were measured in the serum the day of each scan.

Data for this project are still under analysis; however, preliminary findings show there was a seasonal change in bone density and vitamin D levels in the alpacas, with the lowest levels measured in May. This correlates well with the previous studies of seasonal changes in vitamin D and phosphorus in unsupplemented animals.

A related study funded by the Willamette Valley Llama Association is in progress at the College of Veterinary Medicine at OSU to evaluate bone density and vitamin D levels in llamas and alpacas with naturally occurring long-bone fractures. The study involves measurement of bone density using the same technique as in the previous study (dual-energy X-ray absorptiometry), and vitamin D, calcium and phosphorus will also be measured.

Completion of the study requires additional animals, and we would appreciate any assistance in this. There is funding to perform the serum tests and bone density measurements, but unfortunately not to perform fracture repairs. Measurement of bone density can be performed in alpacas and immature llamas with fracture repairs without adversely affecting treatment. (Unfortunately, most adult llamas are too large to fit on the densiometer, which is designed for people.)

With these studies we hope to clarify the association between naturally occurring long-bone fractures, vitamin D levels, and bone density - with the ultimate goal of preventing fractures. If the final data analysis supports our theory, vitamin D supplementation could be helpful in young adult and mature animals (in addition to crias) in maintaining bone density and, consequently, preventing some of the fractures that occur.

Reproduced from www.orst.edu with permission of Susan Tornquist. Copyright © Oregon State University