PennHip vs OFA

What are they?

OFA and PennHip are the two versions of radiographs accepted by the Orthopedic Foundation for Animals (OFA) Canine Health Information Centre (CHIC) program to certify hips.

The CHIC is the minimum requirement for health testing before breeding a litter. Dalmatians require OFA eyes OR thyroid, BAER hearing testing, and hips. With such a short list of requirements, there is no excuse for breeding a litter without CHIC numbers for both Sire and Dam.

It is important to remember that CHIC merely certifies that the tests have been done. Do your own due diligence to ensure that the results are favourable!

What is the difference?

The primary difference is that OFA radiographs are evaluated by a panel of 3 board-certified radiologists, giving special attention to the craniolateral acetabular rim, cranial acetabular margin, femoral head, fovea capitis, acetabular notch, caudal acetabular rim, dorsal acetabular margin, junction of femoral head and neck, and trochanteric fossa.

After evaluating these regions, the radiologist provides a subjective grade of excellent, good, fair, borderline, or dysplastic (mild, moderate, severe). 

With Pennhip, a distraction index is calculated by dividing the measured distance between the femoral head center and the acetabular center by the radius of the femoral head.

A distraction index of 0 is the tightest possible reading and a distraction index of 1 represents a fully luxated hip. Dogs with a distraction index of >0.4 are at an increased risk of developing hip dysplasia. 

PennHip Pros:

Timing:

PennHip radiographs can be performed on puppies as young as 16 weeks of age

Consistency:

The distraction index remains static, as opposed to OFA scoring which will vary over time

Accuracy:

Given that the PennHip score is calculated off precise measurements AND is static (does not change over time), it could be argued that this is a more accurate representation of overall hip health as opposed to a subjective grading that will change over time.

PennHip radiographs are more sensitive for detecting hip dysplasia than OFA radiographs

PennHip Cons:

Patient Sedation:

Dogs must be fully anaesthetized to obtain proper PennHip radiographs

Cost/Availability:

The veterinarian and veterinary technician taking the radiographs must complete a training program. There are fewer veterinary practices offering PennHip than OFA, a PennHip clinic may require more travel.

PennHip requires 3 radiographs, OFA requires one. These additional views + cost of anaesthesia + limited availability often results in a higher cost vs OFA radiographs.

OFA Pros:

OFA radiographs do not require any specialized training. However, ensuring your practice is familiar with positioning would still be recommended so as not to get inaccurate results.

Cost:

Because any veterinary team can take the necessary radiograph, only one view is necessary, and sedation is not always required, cost can be lower for OFA.

OFA Cons:

Timing:

Final results can not be given until 24 months (prior to then, you can get a preliminary consultation that can give you some insight on hip quality).

OFA grading can not be performed in pregnant females or females in estrus due to the effects of hormones on joint laxity.

Accuracy:

OFA grading is more subjective than PennHip radiographs and an individual dog’s results can change between reviewers and over time.

Viewing the pros and cons, I will always choose PennHip over OFA to get the most accurate results and best information when planning future pairings.

 Info for this blog came in part from VetPrep.