Orthopedic Considerations of Early Spay and Neutering

Veterinary Medical Abstracts researched and compiled by
Melody Farquhar Chang

J Am Vet Med Assoc. 1991 Apr 1;198(7):1193-203

Gonadectomy in immature dogs: effects on skeletal, physical, and behavioral development.

Salmeri KR, Bloomberg MS, Scruggs SL, Shille V.
Department of Small Animal Clinical Sciences, University of Florida,
Gainesville 32610-0126.

In a 15-month study, the effects of prepubertal gonadectomy on skeletal growth, weight gain, food intake, body fat, secondary sex characteristics, and behavioral development were investigated in 32 mixed-breed dogs. Male and female pups from 5 litters were randomly allotted to 3 groups: group I, neuter at 7 weeks (n = 14); group II, neuter at 7 months (n = 8); and group III, sexually intact dogs (n = 10). Growth plate closure was delayed (group I vs group III; P less than 0.000001; group II vs group III, P less than 0.000001) in all neutered dogs, as compared with sexually intact dogs. Growth plate closure was delayed longer (group I vs group II, P less than 0.000045) in dogs neutered at 7 weeks old, compared with dogs neutered at 7 months old. The rate of growth was unaffected by gonadectomy, but the extended growth period resulted in greater final radial/ulnar length in all male dogs and bitches neutered at 7 weeks. Gonadectomy did not influence food intake, weight gain, or back-fat depth. Penile development was immature in the adult group-I males (mean +/- SEM diameter of pars glandis = 11.1 +/- 1.0 mm), compared with adult group-II (16.3 +/- 0.5 mm) andgroup-III (21.0 +/- 2.2 mm) males. Subjectively, the prepuce and os penis of the group-I males were immature, compared with those of group-II and group-III males. Vulvar development in group-I and group-II bitches was less mature than vulvar development in the sexually intact bitches. Of 7 behavioral characteristics assessed, only general activity and excitability rated differently among treatment groups. All neutered dogs were judged to be more active (group I, P less than 0.004) than sexually intact dogs. Group-I males were judged to be more excitable (P less than 0.02) than group-III males. It was concluded that with respect to skeletal, physical, and behavioral development, the effect of neutering pups at 7 weeks old was similar to that of neutering pups at 7 months old.

Am J Vet Res. 2005; 66(2):307-12 (ISSN: 0002-9645)
Incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of boxers. van Hagen MA ; Ducro BJ ; van den Broek J ; Knol BW, Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, P.O. Box 80154, 3508 TD Utrecht, The Netherlands.

OBJECTIVE: To determine incidence, risk factors, and heritability estimates of hind limb lameness caused by hip dysplasia in a birth cohort of Boxers.

ANIMALS: 1733 Boxers from 325 litters.

PROCEDURE: Status of Boxers with respect to clinical signs of canine hip dysplasia (cCHD) was registered during an 8-year period. Survival analysis accounted for dogs lost to follow-up. Effective heritability for developing cCHD was estimated by use of a proportional hazard model on the basis of the Weibull distribution. Parametric survival models were developed to identify the influence of potential risk factors. RESULTS: Cumulative hazard rate for cCHD from 7 weeks to 8 years of age was 8.5%. Dogs that were kept on a floor covered with a slippery material were 1.6 times as likely to develop cCHD, compared with dogs kept on a nonslippery floor. Risk of cCHD doubled in dogs from litters with a high preweaning mortality rate. Dogs that were neutered at 6 months prior to a diagnosis of CHD were 1.5 times as likely to develop cCHD, compared with sexually intact dogs. Dogs >5 years of age were 1.8 times as likely to develop cCHD, compared with younger dogs. Estimated effective heritability of cCHD was 0.11. In terms of the risk of cCHD in progeny, mean estimated breeding value (EBV) of the 10 best and 10 worst sires was -0.32 and 0.42, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE: Registration of Boxers that develop cCHD may provide a strategy for disease prevention. In addition to diagnostic evaluation of radiographs, sire EBVs provide useful information for breeding selection decisions.

J Am Vet Med Assoc. 1993; 203(7):1016-9 (ISSN: 0003-1488) Epidemiology of cranial cruciate ligament rupture in dogs. Whitehair JG; Vasseur PB; Willits NH, Veterinary Medical Teaching Hospital, Department of Surgery, School of Veterinary Medicine, University of California, Davis 95616.

Data from 10,769 dogs with rupture of the cranial cruciate ligament (CCL) were compared with data from a control population of 591,548 dogs to determine whether age, breed, gender, or body weight was associated with prevalence of CCL rupture. Prevalence of CCL rupture increased as dogs became older, with peak prevalence in dogs 7 to 10 years old. Among breeds represented by > 1,000 individuals, Rottweilers, Newfoundlands, and Staffordshire Terriers had the highest prevalence of CCL rupture, whereas Dachshunds, Basset Hounds, and Old English Sheepdogs had the lowest. Neutered dogs, whether male or female, had a higher prevalence of CCL rupture than did sexually intact dogs. The dog's age at the time of ovariohysterectomy was not associated with prevalence of CCL rupture. Dogs weighing > 22 kg had a higher prevalence of CCL rupture, compared with dogs weighing < 22 kg, and tended to rupture their CCL at a younger age.

Calcif Tissue Int. 1998; 62(3):237-43 (ISSN: 0171-967X) Ovariectomy-induced changes in aged beagles: histomorphometry of rib cortical bone. WilsonAK ;Bhattacharyya MH; Miller S ;Mani A; Sacco-Gibson N, Center for Mechanistic Biology and Biotechnology, Argonne National Laboratory, Illinois 60439, USA.

Bone loss associated with estrogen depletion is well documented in cancellous bone but less well characterized in cortical bone. The effects of ovariectomy on the aged beagle skeleton were studied by histomorphometric analysis of the cortical bone in sequential rib biopsies. Biopsies were taken from each ovariectomized or sham-operated dog at the time of surgery and at 1, 4, and 8.5 months after surgery. Just prior to each postoperative biopsy, tetracycline, calcein, and xylenol orange, respectively, were administered by a fluorochrome labeling procedure (2d-10d-2d) to provide markers of bone formation. Analysis of sequential rib biopsies provided a means to follow the ovariectomy response over time and to compare each animal against its own baseline. Though ovariectomy did not influence histomorphometric indices at 1 month after surgery, a transient increase in cortical bone formation occurred thereafter, with a sixfold increase over that of sham-operated dogs at 4 months (P < 0.001) and a return to near control levels at 8.5 months. Cortical porosity increased by the fourth month after ovariectomy and remained high at 8.5 months. These data demonstrate for the first time that rib cortical bone is a responsive site for the effects of ovariectomy in aged female dogs.

J Am Vet Med Assoc, 203(7): 1016-9 1993
Epidemiology of cranial cruciate ligament rupture in dogs.
Whitehair JG , Vasseur PB , Willits NH

Data from 10,769 dogs with rupture of the cranial cruciate ligament (CCL) were compared with data from a control population of 591,548 dogs to determine whether age, breed, gender, or body weight was associated with prevalence of CCL rupture. Prevalence of CCL rupture increased as dogs became older, with peak prevalence in dogs 7 to 10 years old. Among breeds represented by > 1,000 individuals, Rottweilers, Newfoundlands, and Staffordshire Terriers had the highest prevalence of CCL rupture, whereas Dachshunds, Basset Hounds, and Old English Sheepdogs had the lowest. Neutered dogs, whether male or female, had a higher prevalence of CCL rupture than did sexually intact dogs. The dog's age at the time of ovariohysterectomy was not associated with prevalence of CCL rupture. Dogs weighing > 22 kg had a higher prevalence of CCL rupture, compared with dogs weighing < 22 kg, and tended to rupture their CCL at a younger age.