| dc.description.abstract | Experimental surgical curettage of the left lateral metacarpophalangeal ( LLMCP ) joints of calves was performed in an attempt to develop and describe a suitable surgical and post-operative management protocol for creating pseudoarthrosis of the curetted joints, in order to obtain clinical and radiological data with respect to function of curetted joints, to determine the macroscopic and microscopic features of and the repair tissue resurfacing the articular cartilage defects and to evaluate the ability of dexamethasone and phenylbutazone to modulate body temperature, pain and limping after joint surgery in calves.
Six to twelve months old male Friesian calves weighing 50-70kg were obtained from established farms. On acquisition, physical clinical and radiographic examination was done on each calf. Only calves free from disease, blood parasites, gastrointestinal parasites, gait or conformational defect and with clinically and radiologically normal metacarpophalangea1 joints were included in the study .
Thirty of the disease free calves were randomly divided into three ( I , 11 & III) groups of ten. Under general anaesthesia and standard surgical conditions
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left-lateral metacarpophalangeal arthrotomy and curettage were performed on group I and group II. Only arthrotomy incisions without curettage (sham operations) was performed on group III calves. The operated joints were then partially immobilized by application of a plaster of Paris cast and the operated limbs immediately after surgery but before recovery from general anaesthesia.
One hour after recovery from general anaesthesia each calf in group I was given phenylbutazone intramuscularly at the dosage rate of 4.4mg/kg; while each group II calf was given 0.2mg/kg dexamethazone intramuscularly. Group III calves were given 0.5ml of isotonic solution (Water for Injection, Infusion, Kenya Ltd., Nairobi) intramuscularly. These treatments were repeated on the third and the seventh day after surgery and plaster of Paris casts were removed on the 21st post-operative day.
Post-operative recordings of the degree of limping and rectal temperatures were taken in the mornings of day 1 to 7 days 10, 14, 21 and from then on weekly until the 135 post-operative day. Weekly recordings of pain and joint mobility were taken starting from the 21st post-operative day up to the 135th post-operative day. The degree of limping of each calf was assessed by the surgeon and marked on a 5mm visual anolog scale ( OAS ) running from 'no
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limping’ (Omm) to limping 'cannot be worse’ (5mm). The surgeon assessed the intensity of pain felt by the calves by exerting digital pressure on the operated joints. The pain estimate was marked on a VAS running from 'no pain’ (Omm) to 'pain cannot be worse’ (5mm). Joint healing was assessed by evaluation of radiographs of the operated joints taken 3, 6, 9, and 15 weeks after surgery. The
healing was evaluated on the basis of "radiographic union" and graded against a semi- quantitative scale from 0 to 4:-
0 - No evidence of union. A radioluscent line where
the joint space originally was (intercondylar space ).
1 - Callus bridging the intercondylar space is
partially ossified.
2 - Intercondylar
space is filled
with
ossi fi
ed
t i ssue whose
radio-opacity does
not
match t
he
remaining cortex.
3 - Most of the osseous tissue in the intercondy1er
space has the same radio-opacity as the rest of the cortex .
4 - Intercondylar space is undecernible as it is
completely filled with radio-opaque bone.
Joint mobility was assessed by subjectively evaluating the angles of flexion through palpation and visual examination of operated joints and scored
as a percentage of the normal angle of flexion of the contra-1 atera 1 joint.
Rectal temperatures were recorded in degrees celcius (#C) for each calf using a mercury thermometer .
All the calves were euthanatized on the 135th post operative day. The operated joints were then cut out and dissected open for macroscopic examination. The repair tissue resurfacing the articular cartilage defects was harvested, fixed in 5% formalin embedded in paraffin wax and standard histological sections prepared and stained with Hematoxylin and Eosin (H/E ) stain. The cellular composition of the repair tissue was assessed by viewing the sections under a light microscope and assigning one of three categories:-
1. Fibrous tissue containing predominantly spindle shaped fibroblasts.
2. Incomplete differentiated mesenchymal tissue composed of cells beginning to differentiate towards chondrocytes.
3. "Hy1ine-1ike" articular cartilage containing chondrocytes in lacunae.
Data collected were analysed and assessed for normality and the t-test used for comparing means.
Blood samples collected from all the calves on the 14 and 2 days before surgery, on the day of
surgery and on the 1st, 3rd, 5th, 7th, 9th, 11th and the 13th post-operative days. Serum from the blood samples collected was analysed for gamma- glutamyl transpeptidase.
The arthrotomy and surgical curettage of the metacarpophalangeal joints in the thirty calves was well tolerated and did not impair the general well being of the calves. When the calves recovered from anaesthesia associated with initial surgery they walked well having only minor gait changes. The calves remained bright and alert and had a good appet i te.
Temperatures above the pre-operative cut-off of 38.7°C were recorded on the days of surgery and cast removal in all calves. However in the two groups the temperatures went down within 24hrs of surgery or cast removal. Calves treated with dexamethasone had a mean peak temperature reading of 39#C and 39.1°C on the first and the second post-operat i ve days respectively. From then on there was a sharp decline in temperature readings by the third day after surgery until day 21 when there was another peak of 39.7°C. Temperature readings for calves treated with phenylbutazone followed a similar trend to that recorded for the calves treated with dexamethasone. The mean peak reading on the first day of surgery was 40.0° C whereas the peak on day 21 was 39.4°C. The
temperature readings of sham operated calves described similar trends to those recorded for calves treated with dexamethazone and those treated with phenylbutazone. The mean peak reading on the first day of surgery was 39.9°C whereas the peak on day 21 was 39.7° C.
In the three groups there was a sharp decrease to pre-operative levels in the temperature readings after the 21st post-operative day. There was no significant difference in the ability of dexamethazone and phenylbutazone to reduce rectal temperatures in these calves (p<0.05).
Peak recordings for limping were recorded on the first day after surgery but there was a steady decrease until the 21st post-operat i ve day when there was another peak recording.
On the first day after surgery the mean peak recording for the phenylbutazone treated calves was
4.1 compared with 3.5 and 2.2 for the dexamethasone treated and sham operated calves respectively. On the 21st day after surgery the mean peak recordings were 3.4, 3.1 and 2.0 for the phenylbutazone treated, dexamethasone treated and sham operated calves respectively. The mean recordings for all the calves diminished steadily after cast removal 21 days after surgery and reached zero by day 48 in dexamethasone treated calves, day 68 in pneylbutazone treated
calves and day 35 in sham operated calves
There was moderate pain on palpation of the operated joints of group 1 and group II calves on the 21st post-operative day (day of cast removal ). There was however a steady reduction in this parameter such that “no pain" was assessed on palpation of the joints by day 70 in the phenylbutazone treated group and the dexamethasone treated group. A pain estimate of 1 was recorded on day 21 for group 3 calves. Similar to group I and II the pain diminished steadily and an estimate of *0* (no pain) was recorded on day 35. Overall there was no significant difference in the reduction of pain between the two treatment groups (p<0.5) but there was a general tendancy for dexamethasone to be more potent than phenylbutazone.
The lowest mean scores for joint mobility were assessed on the 21st day after surgery. The mean mobility on this day (21st post-operative day) was assessed at 90* for the dexamethasone treated group, at 76* for the phenylbutazone treated and 90* for the sham opereated calves. There was tremendous individual variation and a progressive increase in the joint mobility in all the calves to a maximum possible mobility of 100* on the 49 post-operative day for the dexamethasone treated calves. The mean maximum mobility for the phenylbutazone treated
calves was 92% and was reached 77 days after the curettage. The maximum joint mobility of 100% was reached on the 49 post operative day for the sham operated calves.
Three weeks after curettage there was marked soft tissue swelling at the site of surgery in all treatment groups. The joints of group I and II calves had a widened radioluscent area where the joint space originally was (intercondylar space) while there was no other detectable change in the operated joints of group III calves. Six weeks post- operatively, the intercondylar spaces of the joints of group T and II calves were further widened but remained radioluscent. At nine weeks, some joints showed wide radioluscent intercondylar spaces while in other joints the widened intercondylar spaces had a barely detectable radiodensity.
Fifteen weeks after surgery some of the intercondylar spaces in group 1 and II had greater radiodensity than seen at nine weeks, but this radiodensity did not match that of the surrounding cortex. In other joints the intercondylar spaces were still radioluscent at fifteen weeks after joint curettage. There was no significant difference in the scores recorded for the joint healing between the phenylbutazone treated and dexamethasone treated calves. Soft tissue swelling was present at the
surgical sites of all the operated joints. There was no evidence of union and a radioluscent line was apparent in the intercondylar spaces of sham operated joints upto 15 weeks after surgery.
When the joints were opened 135 days after surgery there was fibrous tissue reaction involving the subcutaneous tissue and the joint capsule at the surgical site of the calves in the three groups. The articular cartilage of sham operated (group III) joints was pink, entire and glistening and the joints contained straw-coloured, viscous and stickly synovial fluid.
Contrastingly, there was no articular cartilage in any of the curetted joints (groups I and II) except near the proximal sessamoid bones, laterally and medially. In each joint the distal end of the third metacarpal bone and the proximal end of the first phalanx were covered by a dark brown repair tissue with thick fibrous bands joining the central parts of the distal end of the third metacarpal bone and the opposing surface on the proximal end of the first phalanx. A synovial membrane like tissue joined these fibrous bands to the joint capsule. The synovia1-1ike fluid of the curetted joints was similar to that of sham operated joints but blood tinged. The interosseous ligament between the left medial and the left lateral metacarpophalangeal
joints was very tough and thicker than that of the opposite limb of the same calves. No adhesions or repair tissue were detected in the sham operated joints.
Histologically the repair tissue in curetted joints (groups I and II) was mainly made up of predominantly spindle shaped fibroblasts. No significant difference was detected between the scores recorded for joints of the calves treated with phenylbutazone and those treated with dexamethasone. The trabecular pattern of the subchondral bone beneath the repair tissue was disrupted and a few osteoclast-like cells were seen near the areas of bone destruction. The synovium and articular cartilage adjacent to the repair tissue were inflammed and hypertrophied. There was an increase in the number of vascular channels in the subchondral bone.
No obvious changes were detected in the histology of the articular cartilage of sham operated joints. In each section, the articular cartilage surface was smooth and formed the four layers typical of cartilage. The superficial layer was composed of flattened chondrocytes which were parallel to the articular surface; deeper, the cartilage cells were round and arranged in columns at right angles to the surface; adjacent to the subchondral bone, columns of
chondrocytes were evident. There was a dark line crossing from one side to the other indicating the junction of calcified and non-calcified intercellular substance (tide-mark). Deep to the tide-mark, cartilage was replaced by bone with well developed haversian systems. Examination of the growth plates revealed four distinct zones. A zone of moderately- sized, irregularly-arranged cartilage cells lay immediately below the epiphysis. Deeper, there was a zone of thin, wedge-shaped chondrocytes, stacked together in columns at right angles to the axis of the bone below which was another zone of rounded cells which were also in columns. Adjacent to the diaphysis, a thin, flat layer of rounded cells merged directly into the bone.
The mean pre-operative values for serum gamma- glutamyl transpeptidase ( Y-GT ) were 30.2 I.U. for the dexamethazone treated, 29.9 I.U. for the phenylbutazone treated and 30.9 for the sham operated calves. The post-operative Y-GT values were 30.1
I.U., 29.4 I.U. and 30.5 I.U. for the dexamethazone treated, phenylbutazone treated and the sham operated calves respectively. There was no significant difference between the pre-operative and post-operative levels of serum Y-GT in all the three groups (p<0.05).
Based on the results of this study the
following conclusions were made:-
1. A surgical procedure and post-operative
management protocol for recreating curetted
bovine metacarpophalangeal joints (surgical pseudoarthrosis) has been developed and descr ibed.
2. The protocol for surgical pseudoarthrosis
developed in this study could be usefully
adopted for the surgical management of bovine arthritides when curettage is indicated.
3. The surgical removal of the articular cartilage
and subchondral bone of the bovine
metacarpophalangeal joints (curettage) with subsequent three weeks partial immobilization of the operated joints is well tolerated and does not impair the general well being of the animals.
4. Curetted and partially immobilized bovine
metacarpophalangeal (MCP ) joints remain functional with joint mobility of more than 92% being maintained upto the 135th post-operative day .
5. Deep articular cartilage defects created by
curettage of the bovine MCP joints heal by metaplasia of the connective tissue and 135 days old defects of partially immobilized joints are
resurfaced by fibrous tissue which unites the distal metacarpal condyles to the proximal first phalangeal condyles of the curetted joints. However, further studies are warranted to determine whether or not the repair tissue remains static or modulates to other forms of tissue later in the repair process.
6. Both dexamethazone and phenylbutazone are effective in reducing pain, limping and body temperature subsequent to radical joint surgery in cattle with a tendency for dexamethazone to be more potent than phenylbutazone.
7. Serum gamma-glutamyltranspeptidase may not be a good indicator of inflammation in young calves aged 6-12 months. | |
