[gemy]

While Dr Chris Zink entitled her article Early Spay Neuter- Considerations for the Canine Athlete, in my opinion this information is important for all dog owners whether you think/plan on doing performance sports or not with your dog.

I have copied what she has to say about the ortho considerations below.

What does this mean in terms of our breed - the Yorkshire Terrier? Is it pertinent to me? After all they are just tiny dogs. There are several key points; a) length of and weight of tibia and b) bone density - c) hip dysplasia

Let us take a look at bone density. Peak bone density the sex hormones are critical in acheiving this - this means intact testicles. This is important for our breed as although tiny the density should help to give "strong" bones, not so easily broken.

Now the length of tibia in relationship to the femur. Given the very high incident rate of LP - luxating patella in our breed, any benefit that would give a better chance for our pup to grow up without LP is a good one.

Hip Dysplasia-Is creeping into our breed and Leggs Perthes is already here. Again the sex hormones are important.

So especially if I've been told by my vet my pup has "loose knees", or I have been given an LP diagnosis of what-ever grade, I would make the decision to withhold neutering until after growth plate closure. Also any competent vet should be able to evaluate LP and give you a grade if they feel it is present.

The great thing about growth plate closure is - You or the vet do Not have to guess. Just take a lateral view of the tibia - one Xray $40 or so, and you will know for sure.

There is very little risk health wise for a male to delay neutering until after one year old.

Orthopedic Considerations

A study by Salmeri et al in1991 found that bitches spayed at 7 weeks grew significantly taller than thosespayed at 7 months, who were taller than those not spayed (or presumably spayedafter the growth plates had closed).(1)

A study of 1444 GoldenRetrievers performed in 1998 and 1999 also found bitches and dogs spayed and

neutered at less thana year of age were significantly taller than those spayed or neutered at morethan a year of age.(2) The sex hormones, by communicating with a number ofother growth-related hormones, promote the closure of the growth plates atpubjerty (3), so the bones of dogs or bitches neutered or spayed before pubertycontinue to grow. Dogs that have been spayed or neutered well before puberty canfrequently be identified by their longer limbs, lighter bone structure, narrowchests and narrow skulls. This abnormal growth frequently results insignificant alterations in body proportions and particularly the lengths (andtherefore weights) of certain bones relative to others. For example, if thefemur has achieved its genetically determined normal length at 8 months when adog gets spayed or neutered, but the tibia, which normally stops growing at 12to 14 months of age continues to grow, then an abnormal angle may develop atthe stifle. In addition, with the extra growth, the lower leg below the stiflelikely becomes heavier (because it is longer), and may cause increased stresseson the cranial cruciate ligament. In addition, sex hormones are critical forachieving peak bone density.(4) These structural and physiological alterationsmay be the reason why at least one recent study showed that spayed and neutereddogs had a higher incidence of CCL rupture.(5) Another recentstudy showed that dogs spayed or neutered before 5 1/2 months had asignificantly higher incidence of hip dysplasia thanthose spayed or neutered

after 5 1/2 months ofage, although it should be noted that in this study there were no standardcriteria for the diagnosis of hip dysplasia.(6) Nonetheless, breeders ofpurebred dogs should be cognizant of these studies and should consider whetheror not pups they bred were spayed or neutered when considering breedingdecisions.