Current Understanding of Incomplete Ossification of the Humeral Condyle (IOHC)

bloghumeralcondyle

Presenter: Toby Gemmill BVSc MVM DSAS(Orth) DipECVS MRCVS, RCVS Specialist in Small Animal Surgery (Orthopaedics) European Specialist in Small Animal Surgery, Willows Veterinary Centre and Referral Service

Incomplete ossification of the humeral condyle (IOHC) is a condition most commonly encountered within the spaniel breed indicating that genetic factors play an important role in its development. However, Toby Gemmill who led last week’s webinar considers its common name, IOHC, a misnomer as it points towards a particular pathogenesis, which is not correct. Toby explained that this is a condition which has a spectrum of severity with two groups of patients presenting either as young puppies aged three-six months or adult dogs aged between two-six years, both having different underlying pathogenesis. For this reason, Toby believes the name ‘humeral condylar fissure (HCF)’ is a much more appropriate use of terminology and this is how it will be referred to throughout this blog.

So what is the pathogenesis underlying HCF? Toby explained that in the group of young puppies it has been hypothesised that HCF could be another form of OCD leading to a persistent physis where the saggital growth plate persists. However, evidence has shown that the adult group of dogs can have completely normal elbows when X-rayed at a younger age, only to develop fissures at a later stage of life. This group of dogs have an acquired fissure and it is assumed these develop as a result of an insufficiency stress fracture where excessive forces are placed on abnormal bone. Toby explained that understanding the underlying pathogenesis is key to explaining why the techniques used for repairing these fissures have to be robust in order to combat these excessive forces alongside non-healing abnormal bone.

Of course, a diagnosis of HCF has to be achieved prior to providing any treatment and performing X-rays of both elbows is usually where most general practitioners start. Toby explained however, that although good radiography will pick up 70-80% of cases, it is still not sensitive enough to pick up all fissures. This is also true of arthroscopy with some cases potentially being missed. By far the most sensitive method for detecting HCFs is to perform a CT scan where detailed cross sectional images can be fully assessed. These CT images can also be a very useful in the positioning of screws to stabilise these lesions which is discussed later.

The treatment for both humeral condylar fractures and fissures were discussed in depth by Toby within this webinar. Toby explained repairing a condylar fracture by placing a lateral to medial lag screw sounds relatively straightforward but with a complication rate of around 40%, and complications including the intra-articular placement of screws and the development of seromas and infection, there really is no margin for error with these cases. Y fractures can be even more challenging and will require a rigid robust fixation which needs to be over engineered on order to overcome all the pathology and stresses placed upon these diseased joints.

humeralcondyle

Repair of a humeral condylar fissure prior to a fracture developing can also prove challenging, as traditionally the 4.5mm lag screw placed to support the fissure using a lateral to medial approach often leads to seroma formation and infection and on top of this there is a 5-10% chance that this screw will break at some point. Toby’s current technique to try and avoid these complications is to use a thick 5.0mm locking screw in order to reduce the chances of screw fracture and also to use a medial approach at placement in an attempt to avoid seroma formation and infection. The concern with placing such a large screw using the medial approach is that it can prove difficult to place with the correct trajectory thereby risking intra-articular penetration. Toby discussed the variety of options available to place locking screws with the right trajectory, including the utilisation of CT scan images to plan the ideal entry and exit points for placement, the use of intra-operative fluoroscopy, and the use of 3D printing machines to build the perfect guide to deliver the correct trajectory for each individual patient based on data exported from the CT scan.
Of course many of these techniques are not readily available in practice and Toby’s preference is to use a modified aiming device, all of which was fully explained within last week’s webinar.

The take home messages delivered by Toby’s webinar included the fact that there are two groups of HCF dogs, those with a persistent physis and those with an acquired stress fracture. It is also important to remember that radiography only picks up 70-80% of HCF cases and that CT is by far the most sensitive method of diagnosis. Finally, Toby advises always considering HCF as a possible underlying cause where patients present with low trauma condylar fractures.

Being somewhat spatially unaware, orthopaedic surgery is an area of veterinary medicine I tend to steer well clear of in practice, leaving it up to referral surgeons if at all possible. I’m sure this would also be the case with the repair of condylar fractures and fissures and, after listening to Toby’s webinar, I’m in little doubt that this is the right approach to take. However, there may be others out there who are more brave and have the experience, skills and equipment to perform the corrective surgery necessary. If this is the case then this webinar is an absolute must. For those of you a bit more like myself, I would still strongly recommend taking an hour of your time to watch this webinar as it delivers all the necessary information on diagnosing and managing this condition. It will allow you to discuss all treatment options available for the owner so they can make the right choice for their pet which, in the majority of cases, will be referral to an orthopaedic surgeon.

The Stethoscope (MRCVS)

view-here

One response to “Current Understanding of Incomplete Ossification of the Humeral Condyle (IOHC)”

  1. Stacey Blease says:

    Feedback provided by people who attended the live webinar:

    “Brilliant webinar. Full of useful information”

    “Very interesting. Good, practical information”

    “superb subject: v relevant to daily practice. Thankyou”

    Do you agree?

Leave a Reply

Your email address will not be published. Required fields are marked *