Keywords medial coronoid process disease - dogs - arthroscopy - conservative management - clinical
metrology instrument
Introduction
Elbow dysplasia is a major cause of osteoarthritis in the canine elbow.[1 ] Elbow dysplasia is a collective term describing several inheritable diseases, of
which medial coronoid process disease (MCPD) is the most prevalent form and most common
cause of thoracic limb lameness in medium, large and giant breed dogs.[1 ]
[2 ] While the underlying aetiopathogenesis of MCPD is not fully elucidated, various
pathophysiological mechanisms have been postulated including failure of endochondral
ossification,[3 ] repetitive mechanical overloading of the medial compartment leading to microdamage
of subchondral bone,[4 ] fragmentation of bone and destruction of articular cartilage[5 ] and radioulnar incongruency causing mechanical overload within the medial compartment.[6 ]
The veterinary literature contains many treatment options for MCPD including medical
and surgical interventions, which are aimed at ameliorating pain and slowing progression
of osteoarthritis.[7 ]
[8 ]
[9 ]
[10 ]
[11 ]
[12 ]
[13 ] Historically, gait analysis[14 ] or activity monitoring[15 ] has been used to measure the efficacy of interventions aimed at decreasing chronic
pain in dogs with osteoarthritis. While gait analysis is a gold standard measurement
for lameness, it is time consuming and requires specialized equipment. Collection
of kinetic data also relies on strict inclusion criteria including control of velocity
and acceleration to limit variability of the gait and acquisition of valid trials.
Gait analysis evaluates a dog contemporaneously, and weight bearing on an affected
limb is only one part of chronic pain in dogs with osteoarthritis.[16 ] Methods of assessing chronic pain by owners are limited to clinical metrology instruments,
which include Liverpool Osteoarthritis in Dogs (LOAD) and Canine Brief Pain Inventory
(CBPI), hence their use in this study. The CBPI was designed to measure pain severity
specifically related to osteoarthritis in dogs[17 ] and its impact on function, whereas LOAD evaluates pain related to osteoarthritis
and ascertains a dog's ability and eagerness to exercise as well as function and stiffness.[18 ]
Both LOAD and CBPI have been validated for use in the assessment of canine osteoarthritis.[17 ]
[18 ] They are cost-effective and quantify the owners' behaviour-based assessment of pain,
function and stiffness in their pets over extended periods of time.[17 ]
There are currently no studies that have used both LOAD and CBPI as clinical outcome
measures for dogs undergoing arthroscopic intervention (AI) or conservative management
(CM) for MCPD. The only study to directly compare long-term outcomes up to 12 months,
of dogs with MCPD following AI with CM, used objective methods (inverse dynamic analysis).
No difference was found between treatment groups.[19 ]
The purpose of our study was to evaluate owner-assessed long-term outcome of dogs
with MCPD treated with AI or CM alone using a combined LOAD and CBPI questionnaire.
We hypothesized that there would be no difference in long-term outcome between treatment
groups.
Materials and Methods
Inclusion and Exclusion Criteria
The study was approved by the local institutional veterinary research ethics Committee
(Veterinary Research Ethics Committee 108). Clinical records of the database of the
Small Animal Teaching Hospital at the University of Liverpool were reviewed from January
2007 to January 2015 to identify dogs diagnosed with MCPD. Cases with incomplete medical
records, dogs that had died since their treatment for MCPD or dogs with concurrent
elbow joint pathology (ununited anconeal process, osteochondritis of the medial humeral
condyle and flexor tendon enthesiopathy), were excluded. Dogs were eligible for participation
in the study if their lameness was localized to one or both thoracic limbs based on
subjective gait assessment, or the orthopaedic examination revealed signs of elbow
pain, or there was a combination of these findings. In addition to this, computed
tomography (CT) of the elbows supported a diagnosis of MCPD.[20 ] Inclusion into the study required a complete data entry for each patient and a completed
combined owner questionnaire for LOAD and CBPI at least 12 months post-treatment.
The data were entered into an electronic spreadsheet (Excel 2013, Microsoft), including
patient identification number, age, breed, sex, weight, age at diagnosis of MCPD,
clinically affected limb based on examination of the elbow joint and subjective gait
assessment, lameness score out of 10 and grade of lameness at presentation. Treatment
intervention (arthroscopy and type of intervention [inspection only, chondroplasty,
fragment removal] or CM) was also included.
Computed Tomography
Computed tomography images of both elbow joints from each dog that met the inclusion
criteria were scored retrospectively by a board-certified radiologist (T.W.M) who
was blinded to the clinically affected elbow. Images were obtained (4-slice Siemens
SOMATOM; Siemens Healthcare Diagnostics, Deerfield, Illinois, United States or 80-slice
Toshiba Aquilion Prime; Toshiba Medical Systems, Japan) while the dogs were positioned
in sternal recumbency.[21 ] Scanning parameters varied depending on bodyweight, but most images were obtained
using 0.5-mm slice thickness, 120 kVp and 100 to 120 mAs. All images were reconstructed
using sharp bone and smooth soft-tissue algorithms. The images were viewed using proprietary
DICOM software (OsiriX Pixmeo, Geneva, Switzerland [versions 7.0]) in standard bone
and soft-tissue display windows (soft tissue window level 50 HU/ window width 350
HU; bone window level 700 HU/window width 4000 HU). A scoring system modified from
the International Elbow Working Group[22 ]
[23 ] was used to score both elbows on CT images ([Supplementary Table 1 ], available in online version only.). There were four variables measured in each
elbow joint (conformation of the medial coronoid process, the size of the largest
osteophyte in the joint on any reconstructed view, congruity by means of measurement
of any step between the radius and ulna on the sagittal view and ulnar sclerosis ratio
measured at the mid-medial coronoid process on the sagittal view). Each variable had
a sub-score 0 to 3, with a total score of 12 per elbow.
Treatment Groups
All dogs had either AI (inspection only, chondroplasty of the MCP or fragment removal)
or CM for MCPD. The decision whether AI was undertaken was due to surgeon preference,
owner choice or financial considerations.
Arthoscopy[24 ] was performed by a board-certified surgeon or resident in-training under direct
supervision. Conservative management consisted of weight reduction in dogs with a
body condition score of 6/9 and above, a non-steroidal anti-inflammatory drug for
6 weeks, in some cases paracetamol/codeine for 1 to 2 weeks and increasing lead-restricted
exercise for 8 weeks. Advice on long-term management was given via a telephone conversation
or reassessment with the referral clinician after 6 weeks. Postoperative care of the
AI group was identical to the CM group.
Questionnaire
Owners were sent an email summarizing the study aims and methodology with a link to
the online questionnaire. A duplicate hard copy of the questionnaire was sent by mail
if a completed online questionnaire had not been returned within 4 weeks of the original
contact. The questionnaire comprised details on current medication, current type and
average exercise per day, LOAD and CBPI scores—Pain Severity Score (PSS), Pain Interference
Score (PIS) and quality of life score (QOL) ([Supplementary Figs. 1 ] and [2 ], available in online version only).
Statistical Analysis
Statistical analysis was performed using dedicated statistical software (SPSS 22.0,
SPSS Inc, Chicago, Illinois, United States). Independent variables were derived from
the signalment data, CT scores, arthroscopic records and patient follow-up. Variables
assessed included those related to the dog (weight, breed, sex, age at diagnosis,
lameness score at presentation, age at questionnaire completion), CT data (total score
and individual sub-scores) and arthroscopic procedure (whether arthroscopy was performed
and type of intervention [inspection only, chondroplasty, fragment removal]).
In dogs with bilateral lameness based on subjective gait assessment, only data relating
to the elbow of the more severely lame thoracic limb were included in the analysis.
If the more severely lame thoracic limb could not be ascertained in dogs with bilateral
lameness on subjective assessment, then the elbow with the highest CT score was used.
In dogs that were sound on the day of assessment, the clinically affected limb for
analysis was based on a combination of findings from elbow examination or the documented
lame limb in the referring veterinarians' and owners' history.
Medical treatment (no treatment, non-steroidal anti-inflammatory drug only, non-steroidal
anti-inflammatory drug plus another drug) and average amount and type of exercise
(mostly on or off lead, mostly walking gait or more active gait at exercise) at the
time the owner completed the questionnaire were also assessed in the statistical analysis.
Descriptive statistics were generated for all variables; continuous data were summarized
as median values with interquartile ranges (IQR), and categorical data were amalgamated
into appropriate groups if required (due to small group sizes) and expressed as frequencies
with 95% confidence intervals. For continuous variables (age, weight, LOAD, CBPI and
CT scores), graphical assessment and a test for departure from linear trend were applied
to determine the validity of assuming a linear association. Normality of distribution
for continuous variables was also assessed via the Kolmogorov–Smirnov test. Difference
in weight, age, age at questionnaire completion, CT score and initial lameness score
between those dogs in the AI and CM groups were assessed using the Mann–Whitney U
Test. The main dependent (outcome) variables considered for the main analyses were
LOAD, PSS and PIS. Correlations between LOAD, total CBPI, PSS and PIS were assessed
using the Spearman rank correlation coefficient. Initial univariable and subsequent
multivariable linear regression analyses were performed to identify association between
these outcomes and independent variables. All variables that showed some association
with LOAD, PSS or PIS on initial univariable analysis (p < 0.20) were considered for incorporation into a final multivariable model. For any
pair of variables with a correlation coefficient of ≥ 0.70, the variable with the
smallest p -value was considered for further analysis. The models were constructed by manual
backward stepwise procedures where variables with p < 0.05 were retained in the model. Potential confounding factors were assessed by
examining parameter estimates for substantial changes following their removal.
Results
Altogether 149 dogs met the inclusion criteria, but 82 dogs were excluded due to failure
of the owners to return the questionnaire leaving 67 dogs for the final analysis.
Arthroscopic Intervention Group
There were 44 dogs in the AI group. The Labrador Retriever was the most frequent breed
(28 dogs) followed by the German Shepherd (6 dogs) with a total of 9 breeds ([Table 1 ]). There were 14 males, 12 males neutered, 1 female and 17 females neutered dogs.
Bodyweight ranged from 16.5 to 65.5 kg (median: 31.2 kg, IQR: 26.7–34.4). Age at diagnosis
ranged from 5 to 64 months (median: 17 months, IQR: 10–33.2) and age at time of completion
of the questionnaire ranged from 24 to 148 months (median: 87.5 months, IQR: 71–104).
Two dogs were sound on both thoracic limbs at presentation, 5 dogs displayed bilateral
lameness, 20 dogs were lame on the right and 17 dogs were lame on the left thoracic
limb. Forty-one dogs presented with mild-to-moderate lameness and 1 dog was presented
with severe lameness of the affected limb.
Table 1
Number of breeds affected with MCPD in the arthroscopic intervention and conservative
management groups
Breed of dog
No. of dogs with MCPD
Arthroscopic intervention group
(n = 44)
No. of dogs with MCPD
Conservative management
group
(n = 23)
Labrador Retriever
28
12
German Shepherd
6
0
Rottweiler
1
3
Labrador cross-breed
2
1
Boxer
3
0
Golden Retriever
1
1
English Springer Spaniel
0
2
Bull Mastiff
1
1
Bernese Mountain Dog
1
0
Staffordshire Bull Terrier
0
1
Shetland Sheepdog
1
0
Border Collie
0
1
Other Crossbreeds
0
1
Abbreviation: MCPD, medial coronoid process disease.
The majority of dogs (34/44) in the AI group were diagnosed with bilateral disease,
6 dogs had MCPD in the right elbow only and 4 dogs had MCPD in the left elbow only
diagnosed on CT. The median total CT score for elbows at time of diagnosis for the
AI group was 7/12 (IQR 6–8).
Forty-four clinically affected elbow joints in 44 dogs had AI and fragments were removed
in 30 elbows, chondroplasty of the medial coronoid process only was performed in 10
elbows and 4 elbows had inspection only (medial coronoid process was probed and there
were no loose cartilage or fragments). Twenty-four dogs had AI of both elbows. The
most clinically lame elbow from each dog was analysed in our study.
Conservative Management Group
There were 23 dogs in the CM group. The Labrador Retriever was the most frequent breed
(12 dogs) followed by the Rottweiler (3 dogs) with a total of nine breeds ([Table 1 ]). There were 6 males, 5 males neutered, 2 females and 10 females neutered dogs.
Bodyweight ranged from 15.3 to 70.2kg (median 31.1kg, IQR 24.3–33.9). Age at diagnosis
ranged from 6 to 81 months (median 31 months, IQR 13–58) and age at the time of completion
of the questionnaire ranged from 25 to 124 months (median 63 months, IQR 44–85.5).
Seven dogs were sound on both thoracic limbs at presentation, 10 dogs were lame on
the right and 6 dogs were lame on the left thoracic limb. Sixteen dogs presented with
mild-to-moderate lameness of the affected limb.
The majority of dogs (16/23) in the CM group were diagnosed with bilateral disease,
6 dogs had MCPD in the right elbow only and 1 dog had MCPD in the left elbow only
diagnosed on CT. The median total CT score for elbows at time of diagnosis for the
CM group was 7/12 (IQR 6–8).
There was no significant difference in weight (p = 0.99), age (p = 0.08) or lameness score (p = 0.17) between dogs in the AI and CM groups at presentation. There was no significant
difference between median total CT scores for elbows in the AI and CM groups (p = 0.23).
Questionnaires
The questionnaires were completed at a median of 56 months (IQR 23–71) post diagnosis.
Dogs in the AI group were significantly older (p = 0.004) than the CM group at the time of questionnaire completion. At the time the
questionnaire was completed, a larger proportion of dogs in the CM group were off
lead (82.6% vs. 77.3%) and displayed a more active gait versus the AI group (69.6%
vs. 63.6%) ([Table 2 ]). A larger proportion of dogs in the CM group were no longer receiving medication
(52.2% vs. 36.4%) and the median average distance covered per day was greater (2.5
miles vs. 1.5 miles). There was no significant difference between the AI and CM groups
as to whether dogs were receiving any type of medication versus no medication (p = 0.285). There was no significant difference between the AI and CM groups for the
average amount of exercise per day (p = 0.058), whether dogs were exercised on or off lead (p = 0.505) or whether the gait at exercise was mainly a walking gait or more active
gait, that is, trotting, running or combination of gaits (p = 0.547). In both groups, owners were the main limiting factor for their dogs' willingness
to exercise, accounting for 56.8 and 65.2% of the AI and CM groups respectively.
Overall for both groups, the median LOAD score was 14/52 (IQR 6–20) and median total
CBPI was 11/100 (IQR 1–27). The median LOAD, PSS and PIS for dogs in the AI group
(14/52, 4/40 and 5.5/60 respectively) were higher than the CM group (9/52, 3/40 and
3/60 respectively) ([Fig. 1A–C ]). This difference was not significant on linear regression for LOAD or PSS (p = 0.066 and p = 0.10 respectively) but was for PIS (p = 0.028). The specific type of AI (inspection, chondroplasty or fragment removal)
undertaken was not significant for LOAD (p = 0.32), PIS (p = 0.097) or PSS (p = 0.36).
Fig. 1 (A–C ) Box and whiskers plots comparing median Liverpool Osteoarthritis in Dogs score (LOAD),
median Canine Brief Pain Inventory (CBPI) Pain Severity Score (PSS), and median Canine
Brief Pain Inventory (CBPI) Pain Interference Score (PIS) for the conservative management
of conservative management (CM) (no arthroscopy) and arthroscopic intervention (AI)
groups. Each box represents the interquartile range, the horizontal line within each
box represents the median, the whiskers represent the range and circles represent
outliers. The median LOAD score was not significantly higher for the AI group versus
the CM group, p = 0.066. The median CBPI PSS was not significantly higher for the AI group versus
the CM group, p = 0.10. The median CBPI PIS was significantly higher for the AI group versus the
CM group, p = 0.02.
The type of medication the dog was being treated with at the time of completion of
the questionnaire was not significantly associated with LOAD or PSS for both treatment
groups (p = 0.073 and p = 0.15 respectively) but was significantly associated with PIS (p = 0.016), with dogs being treated with a non-steroidal anti-inflammatory drug (p = 0.033) or non-steroidal anti-inflammatory drug plus other drugs (p = 0.014) having lower scores.
In the AI group, owners rated their dog's QOL as 18 (40.9%) excellent, 18 (40.9%)
very good and 8 (18.1%) as good. In the CM group, owners rated their dog's QOL as
12 (52.1%) excellent, 6 (26.0%) very good and (5) 21.7% good.
Correlation between LOAD and CBPI, PSS and PIS
There was good correlation between LOAD and total CBPI scores (Spearman rank correlation
coefficient [ρs ] = 0.86, p < 0.001), LOAD and PIS (ρs = 0.87, p < 0.001) and LOAD and PSS (ρs = 0.76, p < 0.001).
Univariable Analysis
Univariable linear regression did not identify any significant associations between
LOAD, PSS or PIS and breed, sex or weight ([Table 3 ]). For LOAD, PSS and PIS, older age at diagnosis was all significantly associated
with higher scores (p = 0.048, p = 0.026 and p = 0.046 respectively); however, for all of these, older age at time of questionnaire
completion showed a stronger association with the scores (p ≤ 0.001 for all).
Table 2
Descriptive data for current medication, amount and type of exercise dogs with MCPD
were receiving and limiting factors for exercise at the time the questionnaire was
completed
Variable
Arthroscopic intervention (AI) group
(n = 44)
Conservative management (CM) group
(n = 23)
No. of dogs receiving NSAID plus another medication (paracetamol/codeine, gabapentin,
tramadol, amantadine, nutraceutical)
12
3
No. of dogs receiving NSAID only
9
5
No. of dogs receiving another medication only (paracetamol/codeine, gabapentin, tramadol,
amantadine, nutraceutical)
7
3
No. of dogs receiving no medication
16
12
Median (mean) exercise per day in miles
1.5
2.5
No. of dogs exercised mostly off lead
34
19
No. of dogs exercised mostly on lead
10
4
No. of dogs with mainly a walking gait at exercise
16
7
No. of dogs with mainly a trotting gait at exercise
3
3
No. of dogs with mainly a running gait at exercise
13
7
No. of dogs with a combination of gaits at exercise
12
6
No. of dogs where the owners are the main limiting factor to exercise
25
15
No. of dogs where they are the main limiting factor to exercise
18
6
No. of dogs where the owner and dog are both limiting factors to exercise
1
2
Abbreviation: NSAID, non-steroidal anti-inflammatory drug.
Table 3
Results of univariable analysis showing variables and their association with LOAD,
CBPI PIS and CBPI PSS in 67 dogs with medial coronoid process disease
Variable
Category (units)
LOAD
CBPI pain interference score
CBPI pain severity score
β (95% CI)
p -Value
β (95% CI)
p -Value
β (95% CI)
p -Value
Age at diagnosis
(months)
0.11 (0 to 0.23)
0.048
0.16 (0.003 to 0.31)
0.046
0.11 (0.01 to 0.2)
0.026
Age at questionnaire completion
(months)
0.17 (0.11 to 0.23)
<0.001
0.21 (0.12 to 0.29)
<0.001
0.12 (0.07 to 0.17)
<0.001
Weight
(kg)
0.01 (–0.22 to 0.24)
0.92
0.02 (−0. 29 to 0.34)
0.88
−0.11 (−0.29 to 0.08)
0.27
Sex
MN
(Ref)
−
−
−
−
−
M
0.23 (–5.89 to 6.35)
0.94
2.6 (−5.2 to 10)
0.50
0.43 (−4.3 to 5.1)
0.86
FN
1.8 (–3.9 to 7.6)
0.52
−0.89 (−9.2 to 7.4)
0.83
−0.60 (−5.7 to 4.5)
0.81
F
–7.1 (–19 to 4.5)
0.23
−5.0 (−21 to 10)
0.53
−4.3 (−14 to 5.3)
0.37
Breed
Labrador Retriever
(Ref)
–
−
−
−
−
Crossbreed
6.6 (–3.1 to 16)
0.18
9.2 (−3.9 to 22)
0.17
2.7 (−5.2 to 10)
0.50
German Shepherd dog
–6.3 (–14 to 1.8)
0.12
−0.97 (−8.9 to 7.0)
0.81
−2.8 (−7.5 to 2.0)
0.25
Rottweiler
–0.45 (–10 to 9.2)
0.93
−6.7 (−18 to 4.2)
0.22
−5.8 (−12 to 0.78)
0.083
Other breeds
–0.72 (–6.6 to 5.2)
0.81
−4.1 (−17 to 8.9)
0.53
−4.4 (−12 to 3.5)
0.27
Arthroscopy performed
4.3 (–0.29 to 8.9)
0.066
6.9 (0.78 to 13)
0.028
3.1 (−0.63 to 6.9)
0.10
Arthroscopic intervention
None
(Ref)
−
−
−
−
−
Inspection
6.1 (–7.5 to 20)
0.37
−3.6 (−21 to 14)
0.69
1.0 (−10 to 12)
0.86
Debridement
5.1 (–1.8 to 12)
0.15
7.5 (−1.5 to 17)
0.10
4.5 (−1.1 to 10)
0.12
Arthroscopic intervention
Fragment removal
3.9 (–1.1 to 8.9)
0.12
7.3 (0.78 to 13)
0.029
2.8 (−1.3 to 6.9)
0.17
CT score
–0.12 (–1.4 to 1.1)
0.84
−0.16 (−1.8 to 1.5)
0.85
−0.37 (−1.4 to 0.63)
0.47
Medical treatment
None
(Ref)
−
−
−
−
−
NSAID only
–5.0 (–11 to 0.91)
0.095
−8.5 (−16 to −0.7)
0.033
−3.4 (−8.3 to 1.5)
0.17
NSAID and another drug
–5.4 (–11 to 0.0)
0.05
−8.9 (−15 to −1.9)
0.014
−3.9 (−8.3 to 0.57)
0.087
Abbreviations: CBPI PIS, Canine Brief Pain Inventory Pain Interference Score; CBPI
PSS, CBPI pain severity score; CI, confidence interval; CT, computed tomography; F,
female; FN, female neutered; M, male; MN, male neutered; LOAD, Liverpool Osteoarthritis
in Dogs; NSAID, non-steroidal anti-inflammatory drug; Ref, reference category.
Multivariable Analysis
Age, age at questionnaire, arthroscopy, type of AI and type of medication were all
included in the initial multivariable models. However, for LOAD, PSS and PIS, only
age at questionnaire completion remained significant in the final models, with none
of the other variables being significant when controlling for age at questionnaire
completion.
Discussion
We failed to reject our hypothesis that there was no overall difference in owner-assessed
long-term outcomes, in dogs with MCPD treated either by AI or CM. LOAD scores, PSS
and PIS for the AI group were higher than the CM group with the difference significantly
higher for PIS but not for LOAD or PSS. No significant difference remained after controlling
for age at questionnaire completion. This is currently the longest follow-up of dogs
treated with AI versus CM for MCPD (median 56 months) and only one other study directly
compares these two treatment modalities.[19 ] The long-term impact of various treatment modalities for dogs with MCPD is vital
to establishing the best way forward to treat patients. Clinical metrology instruments
are a useful tool for behaviour-based assessment of pain, function and stiffness of
dogs in their home environment and during exercise over extended periods of time[17 ] in comparison to clinical evaluations based on ‘a snapshot in time’.
Our results concur with that of a previous study directly comparing arthroscopy and
CM,[19 ] which concluded there was no long-term benefit up to 52 weeks to removal of fragmented
medial coronoid process or chondroplasty, using inverse dynamic analysis as an outcome
measure. Other studies using force plate analysis and goniometry[25 ]
[26 ] found arthrotomy was not superior to medical treatment.[26 ] Despite AI, osteoarthritis progressed after 6 months.[25 ] An earlier meta-analysis[27 ] suggested arthroscopy was superior to medial arthrotomy and medical management,
but arthrotomy was inferior to medical management with a follow-up of 6 to 9 months.[7 ]
[26 ]
[28 ]
[29 ] In our study, the type of AI, that is, whether a fragment was removed or not, was
not significant for long-term outcome and is not reported in other studies.
The median age of 21 months of dogs at diagnosis and median weight of 31.1kg were
similar to other studies.[23 ]
[30 ]
[31 ] Labrador Retrievers[8 ]
[23 ]
[31 ] and male dogs[6 ]
[8 ]
[23 ] were over-represented which is mirrored in other studies. Bodyweight was not associated
with long-term outcome; however, body condition score may have been a better measure
of actual obesity. This was not consistently entered in the records and so could not
be included in the analysis. Obesity is an etiological factor for osteoarthritis in
people by increasing load on the joint and altering joint alignment.[32 ] A subclinical proinflammatory state with increased concentrations of adipokines
leading to cartilage degradation is associated with obesity.[33 ]
Computed tomography is the imaging modality of choice for detecting fragmented medial
coronoid process with a sensitivity and specificity of 71 to 100% and 85 to 93% reported
respectively, when compared with arthroscopy or arthrotomy.[34 ]
[35 ]
[36 ] In our study, the CT scoring system was used as an attempt to establish that the
degree of osteoarthritis was similar for the AI and CM groups at time of diagnosis
and the initial management decision.
For LOAD, PSS and PIS, increasing age at diagnosis and questionnaire completion was
significantly associated with higher scores, likely due to progressive osteoarthritis.
Several studies have shown a correlation between radiographic arthrosis and cartilage
pathology[8 ]
[35 ]
[37 ]
[38 ] and increasing age to be associated with more severe cartilage disease in MCPD.[37 ]
[39 ] Osteophytes signal significant joint morbidity in dogs affecting cartilage, synovium
and subchondral bone.[8 ]
[38 ] Their formation with joint capsule fibrosis interferes with joint motion and function
and is a source of pain in people.[40 ]
There were no significant differences between the AI and CM groups for dogs receiving
any type of medication versus no medication or the average amount and type of exercise
per day. Hence, no benefit of one treatment intervention over the other in the long
term was supported. Some of these variables are owner dependent, which is supported
by the questionnaire data that a larger proportion of owners in both groups influence
their dogs exercise more than the dogs themselves. In the AI group, dogs were significantly
older at the time of completion of the questionnaire and progression of osteoarthritis
may have had an impact on their mobility. Across both treatment groups, the type of
medication the dog was on at the time of questionnaire completion was significantly
associated with PIS with dogs receiving non-steroidal anti-inflammatory drug plus
other drugs having significantly lower scores, suggesting a benefit of analgesia in
dogs with osteoarthritis secondary to MCPD. Despite progressive osteoarthritis, 81.8%
of owners in the AI group and 78.3% in the CM group perceived their dogs to maintain
a very good to excellent quality of life.
Limitations of the present study included a lack of an objective measurement as the
primary outcome, although LOAD and CBPI have been validated with gait analysis. As
our study was retrospective, there were no LOAD scores, PSS, or PIS available at time
of diagnosis, which could have been compared with the follow-up scores. The retrospective
nature of the data prohibited randomization of dogs into groups and therefore some
selection bias is possible, although the similar distribution of variables across
groups suggests that this may not have been a major factor. Small group sample sizes
especially in the CM group could also lead to type II error.
Variability in experience and skill of the surgeon in performing the arthroscopy may
have contributed to the outcome. Experienced surgeons may be better at differentiating
between intact cartilage, chondromalacia or between superficial and deep cartilage
lesions which have been found in human studies.[37 ] Experienced surgeons may also be more practiced with their intervention leading
to better outcomes. However, residents were fully supervised by board-certified surgeons
when performing arthroscopy to avoid this possibility. One veterinary study showed
almost perfect interobserver agreement for grading cartilage arthroscopically.[37 ]
Another limitation was that there was no standardized arthroscopic grading system
to assess the severity of cartilage lesions such as the modified Outerbridge scoring
system[41 ] which is the ‘gold standard’ in veterinary medicine. This would have been interesting
to compare severity of cartilage lesions to long-term outcome.
Dogs in the AI group were significantly older at the time of questionnaire completion.
This may have resulted from surgeons choosing to treat patients with MCPD conservatively
instead of arthroscopically in later years. Older age could impact the results due
to progression of osteoarthritis, leading to higher outcome scores in the AI group.
However, the multivariable analysis attempted to control for this.
Owner-assessed outcome scores observed the dog's overall function, rather than at
the ‘elbow level’. In our study, measurements and interventions were focused at the
elbow joint. This is still relevant and important to the owner as LOAD and CBPI have
been validated as clinical metrology instruments.[17 ]
[18 ]
Medial coronoid process disease is complex and the presentation of symptoms can be
intermittent or constant. The functional deficit can range from mild stiffness but
weight bearing through to severe non-weight bearing lameness. It is recognized that
while bilateral changes may be seen radiographically with MCPD, radiographic findings
may not correlate with clinical manifestations of musculoskeletal disease[25 ]
[29 ] and dogs most often present with unilateral symptoms, which were evident in our
study. For consistency, we decided to use the clinically most affected limb in the
data analysis. Our methodology in using a single limb for data analysis for those
dogs with bilateral disease may have confounded our results. In those dogs with bilateral
disease, the owner-assessed outcome scores may have been worse. One of the challenges
when designing and interpreting any studies on the subject of MCPD is how to navigate
the bilateral nature of the disease.
Conclusion
A general consensus of opinion is that the best prognosis is early surgical treatment
in young dogs with MCPD, with minimal to mild osteoarthritis combined with postoperative
rehabilitation and preventative measures against osteoarthritis.[42 ] More studies comparing treatment groups are required to identify whether younger
dogs and those where osteoarthritis is minimally established benefit from AI, even
if the discomfort is alleviated for a short period of time.
Our study has shown no significant benefit in long-term outcome for AI of dogs with
MCPD compared with CM. Prospective randomized studies including larger populations
of different ages of dogs, addressing subjective and objective parameters at diagnosis
and long-term follow-up at standardized time intervals from treatment, are warranted.
Without these studies, the decision-making process for the management of MCPD will
remain, to a large extent, a matter of opinion and therefore of controversy.[42 ]
