I was able to access the following online article about the effect of spaying and neutering on the incidence of ACL injury:

Canine Ovariohysterectomy and Orchiectomy Increases the Prev... : Clinical Orthopaedics and Related Research

Here's a table from the article (sorry for the formatting):

TABLE 1. Prevalence of ACL Injuries
Gender, Number in Sample, Number of ACL Injuries, Prevalence (%)

Female
Sexually intact, 742, 18, 2.43
Spayed, 1067, 55, 5.15
Total, 1809, 73, 4.04

Male
Sexually intact, 861, 18, 2.09
Neutered, 548, 21, 3.83
Total, 1409, 39, 2.77

Male and female
Sexually intact, 1603, 36, 2.25
Spayed or neutered, 1615, 76, 4.71
Total, 3218, 112, 3.48

It looks like the rate of ACL injury is approximately doubled in neutered males and females. Note, however, that the rate of injury is still low, and that one cannot prove that neutering was the cause of ACL injury in any particular animal. Also, these are the rates in dogs that were seen by an orthopedic specialist, so they are prescreened for having some sort of orthopedic issue.

I will look further into this article and post any additional findings about the rates in small dogs, if I can find any.

Yes, the article does discuss the human factor.

Gail did indicate that these studies were large breed dogs and that she would like to see them done for small breeds, Yorkies in particular.

Info from the article about size of dog:

"Furthermore, dog size contributed to the probability of ACL rupture. In particular, compared with large dogs, medium (OR 0.38; p 0.001) and small dogs (OR 0.38; p 0.001) were less likely to sustain ACL injuries."

So in conclusion, neutering does increase the rate of ACL injury in small dogs, but it's not as large an effect as it is in larger breed dogs.

This says nothing about time of neutering.

Once again, what evidence is there that points to causation vs correlation? I think there are environmental/human factors that would be very difficult to measure, especially for small breeds.

You're right about that. The article is still a good read. I'll send you a copy.

This is my issue with trying to link it together. The research is pretty broad and almost always done on large breed dogs. I think we also need to take into consideration the idea that when a Yorkie jumps off the couch it would be equivalent in high to a GSD jumping off the top of (picking a piece of furniture) the chest in my bedroom.

The article addresses these issues in the conclusions section:

One potential source of bias in this study is that only dogs whose owners sought care for lameness were included. This potential source of bias is inherent in all retrospective studies of clinic records. Of particular concern is the possibility that some dogs in our region (e.g., strays or pets of negligent owners) never receive veterinary care of any kind, including for spaying, neutering, or treatment for lameness. If such animals were a large segment of the dog population in our region, it would tend to exaggerate the apparent prevalence of ACL injury in spayed and neutered animals in our study because a population of nonspayed, nonneutered, lame dogs was not represented. However, one also must consider that our region includes a substantial population of highly prized, nonspayed, nonneutered dogs specifically bred for show and for working, especially hunting. Owners of such animals typically seek veterinary care routinely, and especially for conditions that are highly symptomatic, such as ACL injury. Consequently, this population might be over- represented in our study, and thereby would tend to exaggerate the apparent prevalence of ACL injury in nonspayed, nonneutered animals, in opposition to the effects of the stray and neglected population. Regardless, both of these populations are likely to be small in comparison to the overall dog population in our region, and therefore unlikely to affect significantly the conclusions of this study.

Comparisons of mechanism of injury between the dog and human are difficult. The anatomy of the dog knee (stifle joint) is different from that of the human knee. The active range of motion of the dog stifle is 46°–142°,14 whereas that of the human knee is 0°–160°. Dogs have a four-legged gait, so the dynamics of running and cutting are different from humans. These differences suggest the mechanism of injury in dogs is not the same as in humans. Nevertheless, the mechanism of injury is likely to be similar, and most, or all, of the external biases affecting ACL injury introduced by human behavior are minimized in the dog.

The effect of ovariohysterectomy and orchiectomy on the dog is complex and results in various body changes in the animal far greater than an effect seen solely from the absence of one sex hormone. For example, bone density decreases secondary to the reduction of the influences of sex hormones on calcium deposition into the skeleton. Despite the effect on bone, none of the injured animals had a ligament-bone avulsion at the time of surgery. Whether ovariohysterectomy or orchiectomy affect weight gain is controversial, but one study showed no significant increase.21,22 Additionally, ovariohysterectomy or orchiectomy could affect the behavior of the dog.21,22 However, an ovariohysterectomized or orchiectomized dog most likely would become less aggressive, less active, or both, probably decreasing the risk for ACL injury.21,22 Although we cannot predict all of the effects that could result from canine ovariohysterectomies or orchiectomies, many of the effects are likely to decrease injury risk.

The effect of decreased sex hormones on the ACL of the dog is not known. However, alterations in sex hor- mones may affect the size, shape, or material properties of the ACL. Anterior cruciate ligament remodeling is affected by loads placed on the ligament (Wolff’s Law). The remodeling of many soft tissues, including the ACL,1,5,7,13,15,16 also is influenced by sex hormones. In humans, elevated levels of estrogen decrease collagen pro- duction of the ACL in tissue culture. Additionally, expres- sion of an ACL remodeling gene is increased, on average, in human females. Gender differences in ligament remod- eling presumably would affect the size, shape, or internal structure of the ACL, thereby affecting its ability to sustain loads without rupturing. Therefore, it is possible that by altering ligament remodeling, a decrease in sex hormones would affect the predisposition of the ACL to injury.

Ovariohysterectomy and orchiectomy increased the prevalence of ACL injuries across sizes and breeds of dogs. These findings have established an alternative model by which the effect of gonadal gender on ACL injury can be studied, and are consistent with the view that ACL injury in humans is, in part, related to gender differences in hormone production and presentation.

Nearly 50% of the dogs in this study were small breed:

"When dogs were controlled for size, 229 (7.12%) were large, 1053 (32.72%) were medium, 1509 (46.89%) were small, and 427 (13.27%) had an undetermined size."

Shoot looks like it is behind a pay firewall. Awh well. Thanks for posting Phil.

Let us all keep in mind that most of the time CCL injuries are due to luxating patellas which are considered to be genetic. Some of these examples and comparisons are misleading if you ask me.

The bottom line is that someone said that MOST owners should not have intact dogs and I could not agree more. The vast numbers of unwanted dogs in this county is beyond comprehension; and I think it is irresponsible for anyone who truly loves animals to advocate that ALL pet owners worry about altering their pets. Of course those are just my thoughts....and yes, I know people will spout their opinions just as I will spout mine. :)

Phil does the study look at or researched activity levels prior to injury, weight, other osteo presenting conditions, and or other medical conditions, did it look at breed type at all? Age of dog at injury? Subsequent other legs ACL problem?

EDITED TO ADD THIS

Let us all keep in mind that most of the time CCL injuries are due to luxating patellas which are considered to be genetic. Some of these examples and comparisons are misleading if you ask me.

The bottom line is that someone said that MOST owners should not have intact dogs and I could not agree more. The vast numbers of unwanted dogs in this county is beyond comprehension; and I think it is irresponsible for anyone who truly loves animals to advocate that ALL pet owners worry about altering their pets. Of course those are just my thoughts....and yes, I know people will spout their opinions just as I will spout mine. :)

Of interest to me is that every time someone tries to keep the numbers of homeless pets down, people who breed them go out of their way to stop it. The very people who profess to love them so much. Try to limit breeding and you hear all the fear mongering about how there won't be any more dogs. Since around 2006 (when I first became aware of this issue that is being discussed) , breeders have used this hormonal issue to try to stop the push for spay/neuter. Again, the same people who are providing irresponsible pet owners with more pets to abuse and discard, speak up to try to stop people from bringing more into the world. It disgusts me....it really does. The first time I became aware of this little "movement" was in 2005 or 2006 when someone gave me the link to that NAIA article. Note it is breeders doing this. In my opinion they are only protecting their cash cows.

Hi Gemy, if you private message me your email address, I'll email you a PDF copy of the article. But the short answer to your question is no. They divided dogs by breed size: large, medium, and small, but didn't look at individual breeds. Here is the first part of the Materials and Methods:

MATERIALS AND METHODS

The records of all dogs seen and evaluated during a 2-year period in a one-surgeon orthopaedic veterinary practice were reviewed retrospectively. Each dog was identified and was counted as one unit of observation regardless of the number of visits. No dogs were excluded from the general population in the clinic. Inclusion criteria for the ACL-injured group were a history of hind-limb lameness, a positive anterior drawer examination by the orthopaedic veterinarian, and an observed torn ACL at the time of surgery. Breed, gender, ovariohysterectomy status, and orchiectomy status were recorded for all dogs.

I agree with everything you say here. That's why I wish there were a science forum on Yorkietalk where we could dispassionately discuss the science behind these articles without fear of someone taking a single sentence out of context and reaching the conclusion that because there are *some* bad health effects of neutering, they therefore should not have their dog neutered. I agree that overall, the benefits of neutering far outweigh the drawbacks for all dogs except for breeding stock and perhaps a few sporting dogs who have extremely conscientious owners.

I am sure there are such forums somewhere. I honestly don't understand why it must be discussed here on YT like this. It pops up every time someone asks about spay/neuter and it is worrisome to me. Way too many oopsies on this forum as it is....why encourage more?

Well, Yorkietalk is the premier cream-of-the-crop discussion forum for all things Yorkie. We REALLY need a science forum, just like there is a breeder forum. It's not my intention to confuse people who are struggling with the question of whether or not they should get their dog neutered. The answer is clearly yes in 99+% of the instances. But we need a place to discuss cutting edge science without fear of encouraging people to do the wrong thing. And if science ever does give a definitive answer on the health effects of neutering Yorkies in particular, that is something that should be of interest to everyone.

I would agree that de-sexing at the right time for the breed of dog you have is likely overall okay for most females of "most" breeds, according to the research I have read. But not for all female breeds.

I would agree that for ease of ownership issues, for most males, de-sexing at the optimal time is and can be done for ease of ownership. I do not think there is again according to the research I have read, an obvious health advantage and for many breeds there are some very concerning health dis-advantages particularly by breed type.

Yes, well we are discussing Yorkshire Terriers on this forum who have been sadly overbred to a point of ruining the breed imho.

Sadly, many people are going to see threads like this and allow it to feed into their fears and there will be even more oopsies....something this breed does not need. Oh, and never mind that sometimes it is putting the lives of their pets at risk .... and all they were doing was reading something that made them think that altering their pets was just so horribly wrong. You can sit and harp about the right time and all but let us also keep in mind that it will also put the females at a higher risk for mammary tumors. They should worry about a CCL tear over that? I think not. This is just mind boggling to me.

Let us keep in mind that many people don't even know the difference between their and there and your and your're and all of this scientific jargon is being flooded here .. I don't mean to say anyone is dumb....just trying to think about the people who really do not understand all of this. I totally believe in keeping things simple. I try always to explain things in a way that all people will understand. We cannot always assume that the audience can wade through the muck, so to speak.

Well yes, definitely at the right time for the breed of dog in question. The reason I added the caveat about conscientious owners is that even for breeds where spaying is a health concern, if the owner is not responsible and keeping their female dogs in heat on lockdown, it would still be better to spay than have an unplanned pregnancy (in my opinion).

There are a couple of people who believe we "need" it...I am not one of them; but it is not my forum. If they create a forum for that, it's all good in my book.

I personally don't understand the "need" but that does not mean it is not needed.

If it is confusing to people as you acknowledge it could be, then why do it? That is honestly my question.

Yes, if science does come up with a definitive answer, I agree all should be made aware; but the fact is there is no definitive answer for yorkies and IMHO people need to do what has been recommended until there is.

Those are the key words, Phil; and I can promise you there are more irresponsible than responsible pet owners in this world.

Golden REtreiver Life Time Study is Launched!
 

Golden Retriever Lifetime Study takes off - VIN


Please see the article. Linked above. A very interesting read.


And from the Morris Foundation Site.

A Golden Opportunity to Fight Cancer
We’re looking for a few good pups—3,000 to be exact—to be part of the most groundbreaking study ever undertaken to improve the lives of dogs. Morris Animal Foundation’s Golden Retriever Lifetime Study tracks volunteer dogs’ health for life in order to gain insights into preventing and treating cancer and other canine diseases.
Be Part of History
This is the largest and longest study ever conducted to advance veterinary medicine for dogs.
Help Determine Risk Factors for Canine Diseases
The genetic, environmental and nutritional data from participating dogs will help us learn how to prevent cancer and other canine diseases.
Improve the Health of Future Generations
What is learned from the Golden Retrievers in the study will give all dogs a brighter, healthier future.


And interesting enough one of their sponsoring $$ partners is the Golden Retreiver Foundation. And they receive their support from:..
The Foundation has received exceptional support from several sources including:

Annual giving as an option through the GRCA membership renewals.

Proceeds from the annual Art Auction at the GRCA National Specialty.

Funding from generous donors who have offered tributes and memorials to favorite dogs, human friends, celebration of new litters, etc.

GRCA member clubs holding special fund raisers or sharing profits from other events.

Bequests from people wanting to continue their support of Golden Retrievers.

Challenges in which one or more persons has matched contributions up to a specified amount

This looks to be a landmark study that is long awaited and quite frankly long overdue.

:thumbup::thumbup::thumbup: I agree with you on that, and believe me, I do see where you are coming from. I wish people had to take dog parenting classes before they could own a dog :(.

So do I !!! I also wish they would face the same penalties for neglect that people do when they neglect their children.

I could not agree with you more. There is so much more that goes into it then just what size the dog was or if they where fixed.

I don't get why posting studies of larger breed dogs are on topic here and why we are even talking about it because this is a Yorkshire Terrier post bored. Lets see the studies and talk of small breed dogs if not why is it being posted here?

Great point! There are so many health concerns that are truly relevant to Yorkies. Those issues make the case for spay/neuter!!

And those equations and balancing of risks/benefits must be discussed by a) a knowledgeable about their breed pet owner, and their own vet.

Quite frankly with the "huge" risk of hemangiosarcoma in both female and male GR's that were neutered either early or late, some studies are showing 1 in 5 GR's are dying of this at anywhere from 5-7 yrs old.
If you see one of my posts or links below, it is why there is huge support for the Lifetime GR study, which btw, the results of which should benefit many many breeds.

Great point Taylor :thumbup: