HIF / IOHC - Humeral Intracondylar Fissure / Incomplete Ossification of the Humeral Condyle
What is HIF / IOHC?
Humeral Intracondylar Fissure (HIF), also known as Incomplete Ossification of the Humeral Condyle (IOHC), is a condition in which there is a weakness in the humeral condyle (the bottom end of the humerus - the long bone in the foreleg running from the shoulder to the elbow) that forms part of the elbow joint in the forelimb. It is most commonly seen in Spaniels, particularly English Springer, Cocker and Brittany Spaniels, although other medium and large breed dogs may also be affected.
The condition predisposes dogs to fractures (breaks) of the humeral condyle and can also cause lameness in its own right without fracture. However, in some dogs it does not cause clinical signs and so an owner may not know their dog has the condition. There is likely to be a genetic basis to HIF, but as yet, this has not been determined.
HIF/IOHC is an important cause of persistent forelimb lameness and subsequent elbow fractures that are not caused by direct damage or trauma. The condition often affects both elbows (i.e. it is bilateral). Early detection is important, with surgical management currently the treatment of choice. Unfortunately, the surgical management of elbow fractures caused by HIF carries a higher complication rate than fractures caused by conventional trauma.
Until fairly recently, the condition was more commonly known as IOHC as it was thought to be caused by the cartilage plates of the humeral condyle failing to ossify (solidify or harden) completely in young dogs - i.e. incomplete ossification - at the vertical physis (part of the long bone where growth bone occurs from), leaving a fissure (fracture, split or crack) through the humeral condyle, which is a line of weakness. However, cases have emerged of humeral intracondylar fissures being discovered later on in some dogs' lives which weren't there when they were younger and therefore can't be explained by incomplete ossification. Hence nowadays the condition is more commonly referred to as HIF.
What are the symptoms?
HIF/IOHC can produce clinical signs of forelimb lameness and elbow pain. Lameness may be intermittent and can range from mild to severe.
Some dogs with the condition do not show any clinical signs until a fracture occurs in the weak spot in the humeral condyle (intracondylar fracture). Fractures tend to separate the condyle (knuckle joint) in two fragments and extend upwards in one of four ways: lateral intracondylar, medial intracondylar, “Y” fracture and “T” fracture (see illustrations below).
What is the treatment?
Fractures of the humeral condyle require surgery and the surgery must be performed well to minimise the likelihood of osteoarthritis (‘arthritis’) developing in the elbow. These fractures can be problematic to manage since the fissure in the condyle will often not heal and will remain as a point of weakness. Therefore the condyle often never returns to full strength, and the implants (plates and screws) used for the fracture repair will be under a lot of stress indefinitely. If undersized implants are used they may break at some point after surgery. If your dog suffers one of these fractures, you should insist that they are treated by a surgeon experienced in treating fractures associated with HIF. Since ‘Y’ fractures are so complex you should certainly consider referral to a specialist orthopaedic surgeon.
The aftercare after fracture repair is as important as the surgery itself. Strict rest will be required for at least 6 weeks. Typically this means confinement to a cage/small room and dogs must be prevented from running, jumping (including on/off furniture) and going up/down stairs. Short walks out to the garden on a lead are allowed for toileting only.
Physiotherapy and hydrotherapy are highly recommended during convalescence and your Vet will able to direct you to a facility for this purpose as near to you as possible, if he/she does not have his/her own facility on the premises. Physiotherapy with a chartered physiotherapist with additional veterinary training, i.e. a member of ACPAT (Association of Chartered Physiotherapists in Animal Therapy) is strongly recommended.
When HIF/IOHC causes lameness in its own right, without fracture, this is usually managed by placing a large screw across the humeral condyle to strengthen the elbow joint. For reasons that remain unclear, this surgery has been reported to be associated with a relatively high rate of complications including infection and seroma formation (a seroma is an accumulation of fluid at a surgery site). However, in those cases that don’t have complications, this surgery is associated with a good prognosis for improvement, although not all dogs will return to normal with no lameness at all.
When HIF/IOHC is discovered as an incidental finding (i.e. without any associated symptoms) it is less clear if surgery should be performed or not. The advantage of placing a screw across the condyle is that it reduces the risk of fracture in the future. However, since we currently do not know the risk of fracture in dogs with HIF it is difficult to advise owners whether the risk of fracture outweighs the risks of surgery. At the end of the day every owner has their own attitude to risk. For some owners the deciding factor will be the relative costs of surgery; it is a lot cheaper to treat HIF with a single screw placed across the condyle than it is to treat a complex ‘Y’ fracture.
Are English Springers more at risk of HIF/IOHC than other breeds?
summary of hif/iohc RESEARCH
A pivotal research project is currently ongoing at The Ralph Veterinary Referral Centre, led by Dr. Alan Danielski DVM MRCVS Dipl ECVS (European and RCVS Specialist in Small Animal Surgery), which aims to identify the cause of HIF and improve treatment outcomes for affected dogs. In September 2021, the first part of this study was published in the Veterinary Surgery journal. You can read the full paper here. The study provides an in-depth look at the possible cause of HIF that has never been identified before. Through arthroscopy (a miniature camera placed inside the elbow joint) the study found that all the Spaniels that were suffering from HIF had a lesion in the cartilage at the back of the humerus (the bottom end of the humerus bone, one of the three bones that are part of the elbow joint), which was caused by the hook/tip of the ulna (the bone at the back of the forearm) being slightly shorter than it should be, causing it to impinge (push against) the humeral condyle (which sits right in front of it) - see photo 1 below. This continuous pushing force against the humeral condyle is what is believed to be the cause of the formation of the fissure (i.e. stress fracture phenomenon) - see photo 2 below.
This would also explain why so many screws break after a few years from being placed to strengthen the elbow joint - if constant force is applied to the humeral condyle by the hook/tip of the ulna thousands and thousands of times (by the dog simply running around like a normal Spaniel would do), the screw can deform and then break (a phenomenon called cyclic fatigue).
Looking at improving this misfit between bones could be the solution to achieving healing of the HIF (which is well renowned for not healing even after a screw has been placed). Hopefully the next year or so may give the answer to this question once the second part of the study being performed at The Ralph reaches conclusion.
A study at Anderson Moores Veterinary Referrals provided an estimate of the incidence of IOHC in non-lame English Springer Spaniels (see link 1 below). Fifty English Springer Spaniels had their elbows imaged with a CT (or ‘CAT’) scan to identify IOHC fissures. Seven dogs (14%) had IOHC although the fissures seen were small in every dog. Ongoing work includes the assessment of a specialist implant for treating IOHC/HIF and associated fractures as well as studies into the risk of fracture in dogs with IOHC/HIF.
Orthopaedic referral specialist Andy Moores has published a Summary of Intracondylar Fissure In Dogs (2020) (see link 2 below).
A new surgical repair system designed for the management of humeral intracondylar fissures and humeral condylar fractures is reported in a paper by Ben Walton & John Innes (Movement Referrals) published in the BSAVA Journal of Small Animal Practice (October 2020) (see link 3 below). Ben Walton has also worked with Fusion Implants to produce the 'lateral epicondylar anatomical plate' (LEAP) which has been developed for the anatomy of Springer Spaniels with lateral condylar fractures.
Although a great deal of research has been carried out over many years to improve surgical techniques and treatment outcomes, sadly the genetics of HIF/IOHC remain unclear. Work in the USA (ref Marcellin-Little and others 1994) has suggested that there is a recessive mode of inheritance and, on this basis, it is advisable not to breed from dogs with confirmed HIF. We can only hope that in future years, research will also aim to identify the genetic risks for this condition.
Click on the links below for published research studies and further reading:
1. Moores, A.P., Agthe, P., Schaafsma, I.A. (2012):