Case: Lateral condyle fracture of the humerus
29th December 2013
Fractures of the humerus (the bone in the upper forelimb) are common in young dogs. The condyle of the humerus is the bottom part of the humerus that makes up part of the elbow joint. This condyle is made up of an medial (inner) hemicondyle and a lateral (outer) hemicondyle. Fracture often occurs after relatively low energy trauma, when a pup is accidentally dropped or jumps down from a height. Humeral condylar fractures are also often seen in older Spaniels which often have a breed related weakness in the humeral condyle, called Incomplete Ossification of the Humeral Condyle (IOHC).
Humeral condylar fractures usually occur when energy is transmitted up the bones of the forearm, especially the radius, which buts up against the lateral hemicondyle of the humerus at the elbow. This may just result in the lateral hemicondyle breaking off from the rest of the humerus. Less commonly, just the medial hemicondyle breaks off. If the pup is unlucky, both hemicondyles separate from each other and from the shaft. This gives a fracture made up of three or more pieces. This more complicated fracture is called a “Y” or a “T” fracture and is covered in a separate article in this section of orthopaedic case studies.
Lateral condyle fractures in pups are usually fixed with a transcondylar screw (one that crosses the condyle) and one or more pins. In older, larger patients we often use locking plates to make the repair stronger. Occasionally some of the implants, most often the pins, need removal in the future once the fracture has healed. Sometimes they loosen and migrate causing swelling under skin. Removal is usually very straightforwards and any swelling then resolves.
The key aim of surgery is to accurately reconstruct the joint surface to give the elbow a smooth, congruent, comfortable range of motion to maximise function and to minimise the development of degenerative joint disease (DJD). Left untreated, the healing of a displaced articular (joint) fracture is expected to result in a crippling disability. Even with surgical reconstruction, all articular fractures carry the risk of DJD developing to a greater or lesser extent in the future, and this might require future action (see our information sheet on DJD). With surgical reconstruction of humeral condyle fractures there is still sometimes reduced range of elbow flexion.
The transcondylar screw is often left protruding by a few threads on the far side of the bone and it can be felt coming through on the far side of the bone as it is tightened. It can often be felt under the skin in the long term in this position, but this isn’t a problem. Leaving the the screw a little too long ensures that the screw is gripping in as much bone as possible. It is far better for the screw to be a few mm too long than a few mm too short! We use big, strong screws in the transcondylar position but even so screw breakage in the future can occasionally occur from metal fatigue. When this happens screw retrieval and replacement is much easier if the non-head end of the screw is protruding a little way from the bone. It can then be felt, and it easy to expose and grasp it with instruments without us having to “dig it out” from the bone! These implants are often placed in growing pups and as the pups grow, the screws don’t! So the relative screw protrusion often seems to diminish with time!
IOHC can be hard to spot on plain x-rays because of other bone features that overlie the area of interest. When breed related IOHC is suspected, the ideal course of action is to get a CT scan of the suspect elbow done to confirm if IOHC is present. If it is, that side will be at increased risk of future fracture. If IOHC is confirmed, then a “prophylactic” transcondylar screw can be placed to reinforce the humeral condyle and to help protect it against future fracture. This prophylactic screw placement is usually a straightforward procedure and only requires a tiny wound. Recently, reports from a number of experienced surgeons working at multiple centres have suggested that these screw placements carry increased risk of post-operative infection. This has not been our experience based on dozens of cases, but we recognise the reported risk and consequently we now advise extended courses of antibiotics post-operatively. Some owners struggle to fund CT scans and request a prophylactic screw screw placement in the opposite humeral condyle without the advanced imaging on the assumption that there is IOHC present. Some of these patients will have a grumbling forelimb lameness and often will show signs of pain on elbow extension. These signs often disappear after screw placement, strongly suggesting that IOHC was the reason for these signs.