Conservative Versus Arthroscopic Management For Medial Coronoid Process Disease In Dogs: A...

L E T T E R T O T H E E D I T O R

Conservative Versus Arthroscopic Management For MedialCoronoid Process Disease In Dogs: A Prospective GaitEvaluation

To the Editor: We read with interest the article by Burtonet al (Vet Surg 2011; 40: 972–980). As stated, the precisecause and the best treatment for elbow dysplasia remainelusive. We welcome high-quality, well-controlled prospec-tive studies with objective outcome measures, such as this.The scientific merit of this study is without question; how-ever, some very robust conclusions were made, which webelieve should be tempered in light of some potentially im-portant limitations.

The authors were careful to acknowledge the poten-tially important problem of the lack of controlled velocityduring the measurement of ground reaction forces. If veloc-ity is not limited to a narrow range, it becomes unclear ifchanges in ground reaction forces are a result of gait differ-ences or velocity variation.1, 2 Two other important limita-tions were not mentioned, but we believe that they warrantfurther discussion. These two limitations are the lack ofcontrol for the nature and severity of elbow pathology, andthe potential for type II error.

Both the conservatively and arthroscopically treatedgroups had medial coronoid process (MCP) pathology de-fined in terms of the International Elbow Working Group(IEWG) score for periarticular osteophytes. Apart from thepresence of lameness localized to the elbow joint, this wasthe only criterion listed to support the presence of MCPpathology for the conservatively managed group. Othershave demonstrated that free fragmentation is often not vis-ible on standard radiographic projections,3–5 and that thecorrelation between radiographic osteophytosis and arthro-scopic pathology is, at best, ill defined.6 Thus, although thedogs treated arthroscopically had well-defined pathologylocalized to the MCP, it is not possible to tell if the con-servatively treated group were suffering from pathology ofan equivalent nature or severity. In a recent retrospectivestudy examining patterns of arthroscopic pathology in 594elbows from Labrador retrievers affected by medial com-partment disease, 143 different patterns of elbow pathologywere identified.7 For elbows with equivalent radiographicosteophytosis according to the IEWG scheme, the severityof arthroscopic pathology can vary from mild focal pathol-ogy affecting the MCP to full thickness cartilage erosion

affecting the entire medial compartment. Thus, it can bevery challenging to appropriately match treatment groupswhen considering therapeutic intervention.

The second important limitation, which the authorsmay be able to clarify, is the potential for type II error. Thestudy demonstrated a lack of significant difference betweentreatment groups, and this lack of difference could eitherbe a real finding or a consequence of small group size. Thedefinitive conclusion that “there is no therapeutic benefitto arthroscopic removal of fragmented coronoid processesor chondroplasty of the MCP” suggests that power anal-ysis ruled out the possibility of type II error (ie, insuffi-cient group size to demonstrate a significant difference).We understand that there is a trend to suggest that recov-ery is delayed after arthroscopic surgery (ie, fragment re-moval and chondroplasty). It was postulated by the authorsthat a deleterious effect should be expected after arthro-scopic surgery because of surgically induced exposure ofsubchondral bone to synovial fluid; however, it was alsostated that all elbows had overt fragmentation of the coro-noid apex, in which case subchondral bone was alreadyexposed. We agree with the authors that fragmented coro-noid process probably represents a specific lesion within awide spectrum of pathology affecting the medial compart-ment of the elbow joint. Consequently, surgical manage-ment of a focal coronoid lesion cannot possibly addressevery aspect of this complex condition. However, it is alsotrue that abrasion arthroplasty and fragment removal donot constitute the only currently available surgical optionsfor the treatment of medial compartment disease of theelbow joint. The closing statement in the discussion con-cludes, “Until a therapeutic modality is created which canaddress incongruence, cartilage and subchondral bone de-generative change concurrently, it is unlikely that surgicalintervention will improve outcomes in this disease beyondthose achieved with medical management alone.” Over-all, while this paper offers some useful and very objec-tive information regarding the medium-term outcome ofa small number of dogs with elbow pain and lameness, wedo not feel that there is sufficient evidence to justify thisconclusion.

Veterinary Surgery 41 (2012) 541–543 C© Copyright 2012 by The American College of Veterinary Surgeons 541

Letter to the Editor Farrell et al.

Once again, we thank the authors for their valuablecontribution to the current veterinary literature.

Michael Farrell BvetMed, CertVA,CertSAS, Diplomate ECVSNoel Fitzpatrick DUniv, CertVR, CertSAO, MVBFitzpatrick Referrals, Godalming, Surrey, UK

REFERENCES

1. McLaughlin RM, Roush JK: Effects of increasing velocityon braking and propulsion contact times during force plategait analysis in Greyhounds. Am J Vet Res1994;55:1666–1671

2. Riggs CM, DeCamp CE, Soutas-Little RW, et al: Effects ofsubject velocity on force plate measured ground reactionforces in clinically normal Greyhounds at the trot. Am J VetRes 1993;54:1523–1526

3. Olsson SE: The early diagnosis of fragmented coronoidprocess and osteochondritis dissecans of the canine elbowjoint. J Am Anim Hosp Assoc 1983;19:616–626

4. Haudiquet PR, Marcellin-Little DJ, Stebbins ME: Use ofthe distomedial-proximolateral oblique radiographic view ofthe elbow joint for examination of the medial coronoidprocess in dogs. Am J Vet Res 2002;63:1000–1005

5. Moores AP, Benigni L, Lamb CR: Computed tomographyversus arthroscopy for detection of canine elbow dysplasialesions. Vet Surg 2008;37:390–398

6. Fitzpatrick N, Smith TJ, Evans RB, Yeadon R:Radiographic and arthroscopic findings in the elbow jointsof 263 dogs with medial coronoid disease. Vet Surg2009;38:213–223

7. Fitzpatrick N: Subtotal coronoid ostectomy: indications andoutcome. Proceedings of the 2011 ACVS VeterinarySymposium, Chicago. pp 113–118

The author’s reply: We appreciate the opportunity for fur-ther discussion of our study. First, with regards to the com-ments on the influence of velocity on ground reaction force,from our Figure 1, velocity did not change much over the12 months of the study. On average, in the arthroscopicallytreated (AT) group, velocity changed by <0.1 m/s and inthe conservatively managed (CM) group, by 0.12 m/s (andonly at the 4-week point). Typically, studies attempting tocontrol velocity set a “velocity window” of about 0.1–0.2m/s.1–4 Examination of the following velocity table (seebelow) from which our Figure 1 was constructed revealsthere were individual dogs whose velocity varied by slightly>0.2m/s, but on average, most were reasonably consistentthroughout the study. Velocity is a thorny issue; on theone hand, there are arguments for constraining velocity tobaseline level in subsequent tests per dog. This would helpto keep the vertical ground reaction forces similar betweentests, as suggested, and these make a major contribution tothe joint moment calculation. On the other hand, if we wanteach dog’s gait at each time point to represent its functionalability, then we should allow the dog to trot at its own, self-selected speed, which is the way we approached our study.

But then there is the trade-off between contributions by allthe limbs (and individual muscle groups) to the measuredvelocity, and there are many degrees of freedom in how thedog accomplishes this. So, we elected to have the dogs trotat their own speeds at each time point, which for the mostpart, were reasonably consistent throughout the study.

Pre-Treat 4 weeks 8 weeks 26 weeks 56 weeks

Conservative Group1 1.98 1.694 1.775 2.184 2.3332 2.001 2.260 2.244 2.21 2.2233 1.698 1.697 2.344 2.215 2.5154 2.152 1.934 1.876 1.979 1.8545 2.352 1.874 1.989 2.4 2.1466 2.212 1.936 2.16 2.0737 2.383 2.201 2.084 2.02 2.5678 2.305 2.181 2.279 2.014 2.0689 1.981 2.202 2.085 2.238 1.851Average 2.118222 1.997667 2.092889 2.148111 2.194625

Arthroscopic Group1 2.221 2.322 2.294 2.421 2.2322 1.777 2.167 2.184 2.365 1.9813 1.921 1.9 2.011 1.837 2.0544 1.957 1.749 1.789 1.8175 2.159 2.157 2.092 1.92 1.8576 2.484 1.995 2.043 2.266 2.4827 2.472 2.638 2.497 2.343 2.9728 1.895 2.173 2.189 2.045 2.179 1.952 1.98 2.358 1.994 2.02110 2.161 2.077 2.356 2.462 2.4311 2.18 2.298 2.187 2.378 1.885Average 2.107182 2.1707 2.178182 2.165455 2.172818

Throughout the study, there were no differences betweenthe CM and AT groups in the pattern of improvement ofthe affected limb, notwithstanding the small velocity differ-ences. Figures 3 and 4 show a gradually increasing momentin the affected limb across the 5 measurement periods inboth CM and AT groups, and comparison of the affectedand unaffected limbs indicates that asymmetry between theaffected and unaffected limb moments and power profileswere almost identical between groups at 26 and 52 weekswhen velocity was the same between groups. Given thisobservation, there is no way one could argue that one treat-ment had a superior outcome to the other.

Second, we fully acknowledge that the CM group wasnot characterized in terms of the arthroscopic appearanceof the medial compartment of the elbow joint at the time ofenrolment into the study. Although arthroscopic evaluationis generally regarded (in concert with CT evaluation) the“gold standard” for the assessment of medial compartmentpathology,7 arthroscopic assessment of the elbow joint inour CM group would have comprised a surgical interven-tion with the potential to seriously confound the reliabilityof the gait analysis of the CM group. All CM dogs had ev-idence of osteophytes on orthogonal radiographic assess-ment of the elbow. We did not use definitive radiologicalidentification of an overtly fragmented coronoid process asan inclusion criterion for the CM group as we are simi-

542 Veterinary Surgery 41 (2012) 541–543 C© Copyright 2012 by The American College of Veterinary Surgeons

Farrell et al. Letter to the Editor

larly aware of the studies cited by Messrs. Farrell and Fitz-patrick state that identification of a fragment is an incon-sistent finding, and not synonymous with, nor indicative ofthe extent of medial coronoid pathology.5–7 We are unclearwhy this latter point has been raised, as we did not statethis was an inclusion criterion for the CM group. Althoughthe severity of the articular pathology was not definitive inthe CM group, and there remains the possibility of varia-tion in pathology in terms of arthroscopic appearance be-tween CM and AT groups, there is to date and to the bestof our knowledge, no robust objective evidence showing acorrelation between the arthroscopic appearance of elbowdysplasia affected elbows and the clinical response to treat-ment (CM or AT) over the time period we studied. Further,there was no significant difference in the total support mo-ment, elbow moment, or elbow power between CM andAT groups at the start of the study, thus, no one group wassignificantly more lame than the other.

Third, we acknowledge that the potential for a TypeII error warrants consideration because our study is of acohort of only 20 dogs. However, and in the interests ofproviding a balanced consideration for the reader, a TypeII error could equally have resulted in the AT group havingan erroneously good outcome, or the CM group havingan erroneously poor outcome. Thus, it would be of limitedviewpoint to assume, should a Type II error be present, thatthis is synonymous with a disaccreditation of the results wehave presented. Such an error could, for example, equallymask that outcomes for CM are superior to AT.

We acknowledge Messrs. For Farrell and Fitzpatrick’scontention that in our Discussion we have not providedsufficient evidence to justify a definitive conclusion regard-ing likely outcomes of surgical interventions for elbow dys-plasia; however, we wish to emphasize that we expressedan opinion that it was unlikely that until a therapeuticmodality is created that can address incongruence, cartilageand subchondral bone degenerative change concurrently,that surgical intervention will improve outcomes in thisdisease beyond those achieved with medical managementalone. Although we recognize that therapeutic interven-tions for medial compartment disease of the elbow continueto emerge (biceps release,8 sliding humeral osteotomy,9 ro-tational humeral osteotomy,10 etc) to our knowledge, noneof the reported outcomes of these procedures have been ob-jectively compared with a control group treated medically.We know only too well how challenging it is to conducta study that compares a treatment intervention to medicaltreatment and the paucity of studies of similar robustnessto our study is testament to the difficulty other workers ex-perience in conducting studies of similar quality. Hence, inthe spirit of advancing the understanding of the treatmentof elbow dysplasia, rather than raising counter challengesto Messrs, Farrell, and Fitzpatrick’s letter regarding ourstudy, we would respectfully challenge clinicians and scien-tists with an interest in canine elbow dysplasia to take thebold step of participating and collaborating in multicenterstudies, agreeing and sticking to set protocols and havingthe integrity of scientists who are willing to compare the

outcomes of their surgical interventions to noninterven-tional medical treatment such that we can honestly claim tobe working toward “at least doing no harm” in our clinicalmanagement of this disease. We would be willing to collabo-rate in future studies with colleagues who share our interest.

Neil Burton BVSc, DSAS(Orth), CertSASLangford Veterinary Services, University of Bristol,Langford, UK

Martin Owen BVSc, PhD, DSAS(Orth), Diplomate ECVSDick White Referrals, Six Mile Bottom, UK

Bob Colborne PhD and Mike Toscano PhDCentre for Comparative and Clinical Anatomy,Faculty of Medical and Veterinary Sciences,University of Bristol, Avon, UK

REFERENCES

1. Al-Nadaf S, Torres BT, Budsberg SC: Comparison of twomethods for analyzing kinetic gait data in dogs. Am J VetRes 2012;73:189–193

2. Boddeker J, Druen S, Meyer-Lindenberg A, et al:Computer-assisted gait analysis of the dog: comparison oftwo surgical techniques for the ruptured cranial cruciateligament. Vet Comp Orthop Traumatol 2012;25:11–21

3. Gordon-Evans WJ, Dunning D, Johnson AL, et al: Effect ofthe use of carprofen in dogs undergoing intenserehabilitation after lateral fabellar suture stabilization. J AmVet Med Assoc 2011;239:75–80

4. Oosterlinck M, Bosmans T, Gasthuys F, et al: Accuracy ofpressure plate kinetic asymmetry indices and theircorrelation with visual gait assessment scores in lame andnon-lame dogs. Am J Vet Res 2011;72:820–825

5. Olsson SE: The early diagnosis of fragmented coronoidprocess and osteochondritis dissecans of the canine elbowjoint. J Am Anim Hosp Assoc 1983;19:616–626

6. Haudiquet PR, Marcellin-Little DJ, Stebbins ME: Use ofthe distomedialproximolateral oblique radiographic view ofthe elbow joint for examination of the medial coronoidprocess in dogs. Am J Vet Res 2002;63:1000–1005

7. Moores AP, Benigni L, Lamb CR: Computed tomographyversus arthroscopy for detection of canine elbow dysplasialesions. Vet Surg 2008;37:390–398

8. Fitzpatrick N, Danielski A: Biceps ulnar release procedurefor the treatment of medial coronoid disease in 164 elbows.Proceedings of the BVOA Autumn meeting, Croke Park,Dublin 2010, p 71(abstr)

9. Fitzpatrick N, Teadon R, Smith T, et al: Techniques ofapplication and initial clinical experience with slidinghumeral osteotomy for treatment of medialcompartment disease of the canine elbow. Vet Surg2009;38:261–78

10. Gutbrod A Montavon PM, Haessig M, et al: Effects ofhumeral rotational osteotomy on contact mechanism of thecanine elbow joint: an ex vivo study. Proceedings of the 28thAnnual conference of the veterinary orthopaedic society,Snowmass, CO, March 5–12, 2011, p 31 (abstr)

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