View Full Version : Hip surgeries on an animal model

06-24-1996, 01:16 AM
Below is a summary of the responses to my request for information regarding
hip surgeries on sheep. The information has proved very valuable. Many
thanks to those who responded.

The original request .

>We are gearing up to conduct an investigation of a newly designed femoral
>component of a total hip joint in an animal model (sheep). Preferably, we
>would like to conduct bilateral hip surgeries, but are concerned with how
>well the sheep will ambulate after bilaterals. All of the literature I have
>reviewed thus far reported unilateral surgeries. A second concern is pain
>medication post-op. Any guidance regarding ambulation after bilateral
> surgeries and administration of pain medications post-op would be greatly
> appreciated.
The responses were as follows:
Bilateral Surgeries on Sheep

Analgesics in sheep: a variety of techniques can be used. Remember to give
the analgesics during surgery or even before, as a premed, in order to get
the benefits of pre-emptive analgesia.

1) Systemic opiates: sheep do well on most opiates. Morphine is cheap and
effective for immediate post-op pain, for lower grade pain later on
butorphanol and buprenorphine are good.

2) Non-steroidal anti-inflammatories give good analgesia. They can be
mixed with opiates or used on their own for mild to moderate pain. The
combination of NSAIDs and opiates is very effective. Flunixin has been
used a lot in sheep. Carprofen is also popular (less tendency to cause
but difficult to get hold of in NA.

3) Consider epidural analgesia. This, IMHE, is very effective in dogs
undergoing hip replacement. The choices are to use local anaesthetics,
opiates or alpha-2 adrenergic agonists. Local anaesthetics are only of use
during sx as you want the sheep to stand afterwards, but they will reduce
the amount of anaesthetic needed considerably as the whole back end is
blocked out. You will also get useful pre-emptive analgesia. Epidural
opitates (morphine and oxymorphone are the most widely used) give very
good, long-lasting analgesia with no interference with motor control. You
can mix a short-acting local analgesia (e.g. lidocaine) with opiate and give
in one injection. There have been some trials of epidural alpha-2 agonists in
sheep but results are still mixed.

I've attached some recent correspondence on other lists about sheep

Simon Young


Also FYI for sleep analgesia: check out the work by Eisenach and
especlally re: spinal analgesia. may be even better for pregnant ewes and
concerns about fetus due to less systemic and placental transfer of
analgesic. here are a few refs I've seen:

1. Eisenach, J.C., Dewan, D.M., Rose, J.C., and Angelo, J.M. Epidural
clonidine produces antinociception, but not hypotension, in sheep.
Anesthesiology 66:496-501, 1987.

2. Detweiler, D.J., Eisenach, J.C., Tong, C., and Jackson, C. A
interaction in alpha 2 adrenoceptor-mediated antinociception in sheep.
J.Pharmacol.Exp.Ther. 265:536-542, 1993.


Craig W. Stevens, Ph.D. internet: stevens@vms.ocom.okstate.edu
Associate Professor of Pharmacology FAX: 918-561-8412
OSU-College of Osteopath Medicine Ph: 918-561-8234
1111 West 17th Street
Tulsa, OK 74107-1898


We have been using since more than 2 years buprenorphine (Temgesic)
every 8 hrs in pregnant sheep after operations on the foetus and in goats
after cardiac or orthopaedic surgery with apparently good results and no
unwanted side effects.
Sincerely yours,
Ton van den Bogaard

Are bilateral surgeries legal in America? When I was involved with
animal trials in Switzerland, we were only allowed to operate on one
limb. This question is for my own curiosity.

Stephen Ferguson
Queen's University
Kingston, Ontario

I am not an expert; however I've been involved in a ACL reconstruction
study on a sheep model. They tried a bi-lateral surgery on a few animals
but it was a failure. The animals did not walk anymore and some of the
died shortly after; for the others the immobilization invalidated any bone
related study.
Thus they quit the bi-lateral procedure and continued the study with
mono-lateral, which never produced an immobilized sheep.

My two cents ....


MARCO VICECONTI (lk1boq74@icineca.cineca.it)
Laboratorio di Tecnologia dei Materiali tel. 39-51-6366865
Istituti Ortopedici Rizzoli fax.
via di barbiano 1/10, 40136 - Bologna, Italy


I think that bilateral surgeries would be a really bad idea. Bilateral THRs
in dogs are always staged, and in sheep there is the added problem of
recumbency. Sheep that are unable to ambulate will lie down, leading to a
risk of ruminal tympany (gas bloat)..this is potentially fatal. Some people
have advocated the use of slings to support the sheep after surgery, but
this can be a real problem...especially if your sheep are anything other
than tame!
Staged surgeries are possible, but again it might be better to settle for a
good result on one hip rather than risk losing both hips if an animal with
a bilateral replacement becomes infected etc.

>A second concern is pain medication post-op. Any guidance regarding
>ambulation >after bilateral surgeries and administration of pain
>medications post-op would >be greatly appreciated.

We have just finished a large study involving TKRs in sheep (unilateral).
As far as pain control is concerned, we found that flunixine meglumine
(Banamine) and phenylbutazone were adequate. A good option might be
epidural anesthesia via an indwelling catheter. I can point you in the
direction of a veterinary anesthetist who specializes in ovine
anesthesia/analgesia, if that would help.

If you would like further info, please don't hesitate to contact me.

Best wishes


Matthew J Allen MA VetMB PhD MRCVS,
Bone and Articulation Research Section,
School of Veterinary Medicine,
Purdue University,
West Lafayette, IN 47906.

tel: (317) 494-8701
fax: (317) 494-1772
e-mail : mja@vet.purdue.edu

Dogs seem to do well after bilateral surgery. See the literature for
kinetics and kinematics detail as well as post-harvest cortical strains and
inplant-to-bone micromotion.
Sean Kohles, PhD

A you know, typically total hip animal research has been performed in dogs.
If there is literature on the procedure performed in sheep I am not aware of
it though I did not do a lit search. I assume you have a reason for sheep,
but watch the anatomy very closely. Reaming will be very difficult I would
think, but I've never done it. It would be wise to get a DVM with knowledge
of sheep anatomy, handling, anesthsia and THA procedures to get you going.
As far as post op analgesia, I use an epidural of morphine (Duramorph),
followed by butorphenol injections q6h for 72 hours. This does require night
time dosing. Fentanyl patches could be used, but there is little literature
on their use in sheep and they would be expensive. The USDA and IACUCs
recently will not accept prn dosing of post op analgesics. As far as
bilateral procedures, I would strongly discourage performing a bilateral
procedure. You will likely have a recumbant animal for some time and it will

not be able to protect the prosthesis in the 1-2 weeks post op. The prolonged

anesthesia and post op recumbency would likely lead to some deaths, pressure
sores on the incisions, aspiration pneumonia, etc. I would be very surprised

if your IACUC accepted a bilateral protocol for humane reasons. I personally

would not accept such a protocol. Feel free to ask/consult further.

Karl H. Kraus DVM
Associate Professor of Surgery
Tufts University School of Veterinary Medicine
Diplomate, American College of Veterinary Surgeons

How does you animal care committee feel about bilateral surgeries? I once
proposed one and was told that it would take a very strong justification
because it qualified as multiple procedures. I once had someone tell me
that it was more defensible to do a unilateral and then to amputate the
contralateral limb to make sure that the implant got used.

Seriously, if you do bilateral procedures, you need to be careful to
observe whether the animal favors one limb, which can change the results.
If you do a unilateral, you need to make sure the animal walks on it. I
ran across a report (I can't remember where) in which the investigators
did a unilateral hip replacement and then tied the contralalateral leg to
a harness so that the animal could not use it.

************************************************** ******************
Kenneth R. St. John, Assistant Professor Voice: (601) 984-6199
Orthopaedic Research and Biomaterials Fax: (601) 984-6087
University of Mississippi Medical Center
2500 North State Street
Jackson, MS 39216-4505 Internet: stjohn@umsmed.edu
************************************************** ******************


We have done some work on simultaneous total knee replacements in human
subjects. We're still compiling our data, but (anecdotally) they do quite
well, bear weight quickly, and really don't require any more pain meds than
primary unilaterals. Our total joint service does a few simultaneous hips,
not enough to really draw any conclusions from. I took a quick look at my
bibliography for this project and came up with a few references that may help

(you may have these already ):

Bobyn, et al. "The effect of stem stiffness on femoral bone resorption after
canine porous-coated total hip arthroplasty." Clin-Orthop. 1990 Dec (216):
-213 (they did simultaneous tha's)
Ritter, et al. "Single-stage, bilateral cementless total hip arthroplasty." J

Arthroplasty. 1995 Apr; 10 (2): 151-6.
Onsten, et al. "Migration of acetabular components, inserted with and without

cement, in one-stage bilateral hip arthroplasty." J-Bone-Joint-Surg-Am. 1994
Feb; 76 (2) : 185-94.
Bergmann, et al. "Hip joint loading during walking and running, measured in
two patients." J-Biomech. 1993 Aug; 26 (8) : 969-90. (gait analysis -
bilateral vs. unilateral).
Wykman, et al. "Walking ability after total hip replacement. Comparison of
gait analysis in unilateral and bilateral cases." J-Bone-Joint-Surg-Br. 1992
Jan; 74 (1) : 53-6.

Good luck with your study.


David Curd, M.S.
Director of Research
Hughston Sports Medicine Foundation
Columbus, Georgia



About 2 years ago, when I was at Biomedical Engineering, UNSW in Sydney, we
did a series of 10 unilateral total arthroplasties in sheep - again testing
a new design of prosthesis.
We found that the sheep had a remarkable capacity to recover and weight-bear
immediately after the surgery (the stems were cemented).
Pain control was, as I recall, by intra- and post-operative morphine. (I ama
biologist/materials scientist, not a vet...)
My question to you would be - why bilateral? In our studies there was no
sign of the sheep favouring the unoperated leg, at least not after the first
day or so. The use of unilateral procedures may provide an advantage in
that it allows the animal to resume weight bearing gradually as the limb
recovers from the surgery.

Arthur Brandwood.
Arthur Brandwood PhD Arthur.Brandwood@tga.ausgovhhcs.telememo.au
Head, Postmarket Section or Arthur.Brandwood@hcn.net.au
Therapeutic Devices Branch
Therapeutic Goods Administration Tel: +61 (0)6 239 8694
PO Box 100, Woden, ACT 2606, Australia Fax: +61 (0)6 239 8687