Bone density of the humeral condyle in Labrador retrievers with medial coronoid process disease.

OBJECTIVES: To estimate, using CT imaging, differences in the regional bone density of the humeral condyle in Labrador retriever elbows with and without medial coronoid process disease. MATERIALS AND METHODS: The elbows of Labrador Retrievers that had undergone CT were reviewed. Scans were divided into three categories: elbows without medial coronoid process disease; elbows with medial coronoid process disease involving fragmentation of the radial incisure; elbows with medial coronoid process disease involving fragmentation of the medial coronoid apex. A templating technique was employed to define the weight-bearing regions of the medial and lateral portion of the humeral condyle and estimates of volumetric bone density (defined by Hounsfield unit measurement) were compared across the three groups. RESULTS: CT evaluation was performed on 122 elbows in 81 dogs. There was a higher mean Hounsfield unit measurement in the medial and lateral portions of the humeral condyles in elbows with medial coronoid process disease involving fragmentation of the medial coronoid apex compared with elbows with medial coronoid process disease involving fragmentation of the radial incisure. CLINICAL SIGNIFICANCE: Dogs with apical fragmentation of the medial coronoid process exhibited significantly higher estimated bone mineral density within the medial portion of the humeral condyle when compared to dogs with radial incisure fragmentation. The medial portion of the humeral condyle may be associated with the pathogenesis of apical but not radial incisure medial coronoid process fragmentation in Labrador Retrievers.

Outcomes, complications and risk factors following fluoroscopically guided transcondylar screw placement for humeral intracondylar fissure.

OBJECTIVES: To describe the surgical technique and complications for fluoroscopically guided transcondylar screw placement for humeral intracondylar fissure in dogs. MATERIALS AND METHODS: A retrospective review was undertaken of cases from two hospitals where identical surgical technique was employed. Factors were analysed for any association with postoperative complications. RESULTS: Sixty-two dogs (82 elbows) were reviewed for which the postoperative complication rate was 45%; a total of 15% of cases required revision surgery. Complications were more likely in cases operated on earlier in the case series and with increasing dog bodyweight. Both increasing surgical time and being a neutered female were protective against postoperative complications. CLINICAL SIGNIFICANCE: Fluoroscopically guided transcondylar screw placement for humeral intracondylar fissure is associated with a high postoperative complication rate (45%) with 15% of cases requiring revision surgery.

CT evaluation of elbow congruity in dogs: radial incisure versus apical medial coronoid process fragmentation.

OBJECTIVES: To compare elbow congruity in two cohorts of Labrador retrievers affected with either radial incisure or apex fragmentation of the medial coronoid process. MATERIALS AND METHODS: Dogs were included if they had elbow lameness and a CT diagnosis of a fissure or fragmentation of the medial coronoid process occurring either along the radial incisure or at the coronoid apex. Radioulnar joint space was measured incrementally from the lateral to the medial coronoid process on transverse slice images. Axial radioulnar congruency was also measured at the apex and mid-coronoid in the dorsal plane and at the base of the coronoid in the sagittal plane. RESULTS: We studied 99 elbows (in 66 dogs) of which 56 had a fissure or fragmentation along the radial incisure and 43 had an apical fragment. No difference was found between the two groups at the different measuring points - with the exception of a transverse plane radioulnar joint space measurement in the radial incisure group that was smaller adjacent to the lateral coronoid process. CLINICAL SIGNIFICANCE: Abnormal ulnar morphology in the radial incisure group could result in a fulcrum effect within the radioulnar joint, overloading the radial incisure and predisposing to osteochondral damage at this site.

Reliability of CT measurement of induced radioulnar step in dogs using a circle superimposition technique.

OBJECTIVES: To evaluate the reliability of CT measurement of canine elbow axial radioulnar congruence using a duplicated circle superimposition technique. MATERIALS AND METHODS: CT of six cadaveric canine elbows was performed following either: (1) placement of an external fixator on the radius with ostectomy and radial shortening of 1 to 5 mm; (2) radial lengthening of 1 to 5 mm using a radial lengthening system; or, (3) no axial length adjustment. Four observers, on two occasions, blinded to the amount of radial adjustment, placed a circle of best fit of the ulnar trochlear notch on a sagittal image that was duplicated and transposed to the articular contour of the radial head; then the axial distance between circles relative to the dorsal radius was measured. Statistical analysis assessed differences between actual and observer-assessed radial length adjustment; inter-/intra-observer interclass correlation coefficients and sensitivity/specificity were calculated to evaluate measurement reliability. RESULTS: There was not a significant difference between actual and observer measures of radioulnar congruence. Inter- (intraclass correlation coefficient=0.98) and intra-observer reliability (intraclass correlation coefficient=0.94 to 0.99) were almost perfect for measurement of radioulnar incongruence when compared to the actual radial adjustment. A Bland-Altman plot revealed a 95% confidence interval range of -1.31 to 1.16 mm. Sensitivity and specificity were high for correct identification of congruent elbows and elbows with 1 or 2 mm incongruency. CLINICAL SIGNIFICANCE: The duplicated circle superimposition technique provides a simple and accurate means of assessing radioulnar axial incongruence.

Inter- and intraobserver agreement in interpretation of CT features of medial coronoid process disease.

OBJECTIVES: To evaluate inter- and intraobserver reliability of the assessment of computed tomography features commonly used in the identification and classification of medial coronoid process disease and to assess inter- and intraobserver variability in the identification of the percentage ulna sclerosis from single transverse computed tomography images. METHODS: Eight observers, on two occasions, reviewed 84 standardised single transverse computed tomography images acquired at the level of the apex of the medial coronoid process. Observers assessed: medial coronoid process disease, coronoid process fragmentation, osteophytes, sclerosis grade and sclerosis delineation with normal bone defined using a sclerometer. Cohen's kappa and intraclass correlation coefficient were calculated. RESULTS: Inter-observer agreement was fair to moderate for identification of computed tomography changes consistent with medial coronoid process disease, moderate to almost perfect for fragmentation, and moderate for osteophyte detection. Agreement was poor for sclerosis grading. Percentage sclerosis measured with a sclerometer had moderate to almost perfect inter- and intraobserver agreement. CLINICAL SIGNIFICANCE: These findings suggest that subjective assessment of computed tomography images is less repeatable than more quantitative methods.

Computed tomographic evaluation of elbow congruity during arthroscopy in a canine cadaveric model.

OBJECTIVE: To assess the effect of arthroscope insertion, using a carbon-fibre rod model, on humero-radial, humero-ulnar and radio-ulnar congruity, as assessed by computed tomography (CT). METHODS: Cadaveric Greyhound elbow joints were assessed at a flexion angle of 135 ± 5° using CT. For condition 1, a 36 mm fulcrum induced cubital valgus, as used to aid arthroscope insertion. For conditions 2 and 3, a single 1.8 or 2.5 mm diameter rod was inserted under arthroscopic guidance to simulate arthroscope position for assessment of the medial coronoid process. Repeat CT scans were obtained for all conditions and parasagittal sections were reconstructed to evaluate medial, axial and lateral positions within the elbow. Humero-radial, humero-ulnar, and radio-ulnar congruity measurements were obtained. Differences between groups were assessed using repeated measures analysis of variance. RESULTS: Mean (±SD) change in radio-ulnar step between conditions 1 and 3 was 0.6 ± 0.3 mm (axial), 0.8 ± 0.6 mm (medial), and 0.5 ± 0.1 mm (lateral). Insertion of rods induced a significant decrease in radio-ulnar step in all planes. Significant differences were also identified between groups for humero-radial, humero-ulnar, and radio-ulnar congruity. CLINICAL SIGNIFICANCE: Insertion of carbon-fibre rods as a model for elbow arthroscope insertion induces elbow incongruity. Changes in radio-ulnar congruity are small but the effect of arthroscope diameter should be considered when assessing elbow congruity.

Patellar ligament rupture in the dog: repair methods and patient outcomes in 43 cases.

The medical records of dogs receiving surgery for unilateral patellar ligament rupture between 1999 and 2012 at 12 multidisciplinary referral centres were reviewed. Forty-three cases were identified; 26 were traumatic in origin; almost one-third were iatrogenic, of which over three-quarters occurred as a complication following surgical stabilisation of patellar luxation. Treatment involved primary reapposition of the ligament (36 cases). The repair was protected by circumpatellar and/or transpatellar loop(s) of orthopaedic wire, nylon, polypropylene or polydioxanone suture (34 cases). Wire loops were more likely to require surgical removal compared with loops of other materials (P=0.0014). The stifle joint was immobilised postoperatively by the applications of a transarticular external skeletal fixator (taESF) in 17 cases and by external coaptation (EC) in 8 cases; in 18 cases, no postoperative joint immobilisation was provided. Complications specific to the method of immobilisation occurred in seven of the cases with taESF and six of the cases with EC. Revision surgery to address failure of repair was required in five cases. Outcome was classified as acceptable or good in over three-quarters of the cases (31/40) and poor in less than a quarter (9/40). These data highlight patellar ligament rupture as a complication of surgical stabilisation of patellar luxation.

Total knee replacement in a dog with a non-union type B3 tibial plateau fracture.

A six-year-old German Shorthaired Pointer was presented with a 12 month history of left pelvic limb lameness following trauma. Clinical examination revealed marked thickening and reduced range-of-motion of the left stifle and radiographs were suggestive of a non-union type B3 tibial plateau fracture with severe secondary osteoarthritis. Total knee replacement was performed with adjunctive stabilization of the proximal tibial fracture fragment. Clinical follow-up at six and 12 months with quantitative gait analysis revealed significant improvement in limb function.

CT assessment of the influence of dynamic loading on physiological incongruency of the canine elbow.

OBJECTIVES: To present a novel technique for loading of the canine elbow joint and to quantify changes in congruency with increasing load using computed tomography. MATERIALS AND METHODS: Five pairs of thoracic limbs were mounted at a mid stance angle in a custom made jig. Elbow joints were loaded to 0, 33, 66 and 100% of total individual cadaver bodyweight. At each load computed tomography of the elbow was performed. Joint space measurement was performed on sagittal plane central, lateral and medial compartment images at humero-radial (R1 , R2 , R3 ), humero-ulnar (U1 , U2 ) and radio-ulnar loci. The effect of loading on joint spaces was assessed (P<0.05). RESULTS: With increasing load; for central an increase in R1 and radio-ulnar distance and decreased R3 occurred; for medial R1 increased; and for lateral R1 and radio-ulnar distance increased. The largest increases were seen in the lateral compartment. CLINICAL SIGNIFICANCE: Significant changes in humero-radio-ulnar congruency occurred suggesting pronation of the radius with respect to the ulna was induced during loading. This movement may influence the load experienced by the medial coronoid process and could play a role in the aetiopathogenesis of medial coronoid process disease.

An ex vivo investigation of the effect of the TATE canine elbow arthroplasty system on kinematics of the elbow.

OBJECTIVE: To devise a kinematic technique to objectively ascertain the location and orientation of the centre of rotation of the canine elbow and to compare this axis following arthroplasty with the first generation TATE™ prosthesis in an ex vivo model. METHODS: Five pairs of cadaveric forelimbs were obtained and proximal limb soft tissues removed. Pin-mounted reflective markers were applied to the humerus and ulna. Limbs were mounted on a frame and six trials of the elbow manually cycled through its sagittal range of motion captured using 4 Qualisys cameras at 120 Hz. Radiography was performed to identify marker position. TATE™ cartridges were implanted and kinematic analysis repeated. Kinematic data were imported into custom software and the three-dimensional joint centre of rotation defined using a closed-form solution for absolute orientation. Paired t tests were performed to determine if the centre of rotation of the elbow differed significantly (P<0·05) pre- and postoperatively and between left and right limbs. RESULTS: There was no significant difference in three-dimensional orientation of the elbow axis between pre and postoperative measurements or between left and right limbs. CLINICAL SIGNIFICANCE: A critical factor in obtaining a successful functional outcome following elbow arthroplasty in humans is accurate reconstruction of the anatomic centre of rotation. The first generation TATE canine elbow arthroplasty cartridge and its instrumentation accurately reconstructed the anatomic centre of rotation in 8 of the 10 elbows assessed in this ex vivo model.

Biomechanical comparison of a novel castless arthrodesis plate with T-plate and cross pin techniques for canine partial carpal arthrodesis.

OBJECTIVES: To describe a novel canine castless partial carpal arthrodesis plate (par-CA) and its ex vivo biomechanical comparison with T-plate and cross pinning techniques for canine partial carpal arthrodesis. METHODS: The three implant systems were applied to three cohorts of six forelimbs from Greyhounds euthanatized for reasons unrelated to the study. Intercarpal and carpometacarpal palmar fibrocartilage and ligaments were sectioned. Potentiometers were applied between the radial carpal and third metacarpal bones to measure micromotion, and limbs were loaded at 30% of bodyweight at 1 Hertz for 10,000 cycles on a servo-hydraulic universal testing machine. Following assessment of micromotion, limbs were loaded to failure at 20 mm/s and ultimate strength, ultimate displacement, and stiffness were measured. RESULTS: The T-plate (p <0.01) and par-CA (p <0.01) had reduced micromotion relative to the cross pin constructs but there was no significant difference between the control, T-plate and par-CA constructs. There was no significant difference in ultimate strength between constructs. Ultimate displacement was reduced in the plated constructs. Stiffness did not differ between constructs. CLINICAL SIGNIFICANCE: The novel par-CA construct was biomechanically similar to the T-plate and both were superior to cross pins in resisting micromotion. There was no difference in load at failure between constructs. The par-CA plate permits radial and ulnar carpal bone compression, a more distal location of the plate to limit impingement, and placement of screws in two metacarpal bones; features which may offer clinical benefits over T-plate fixation.

Ex vivo evaluation of the biomechanical effect of varying monocortical screw numbers on a plate-rod canine femoral gap model.

OBJECTIVE: To compare the biomechanical behaviour of plate-rod constructs with varying numbers of monocortical screws applied to an ex vivo canine femoral-gap ostectomy model. SAMPLE POPULATION: Twenty Greyhound dog cadaveric femurs. METHODS: Bone mineral density (BMD) was assessed with dual x-ray absorptiometry. Bones were assigned to four groups. Bones had a 12-hole 3.5 mm locking compression plate with one bicortical non-locking cortical screw in the most proximal and distal plate holes and an intramedullary Steinmann pin applied across a 20 mm mid-diaphyseal ostectomy. Additionally, one to four monocortical non-locking cortical screws were then placed (Groups 1-4 respectively) in the proximal and distal fragments. Stiffness and axial collapse were determined before and after cyclic axial loading (6000 cycles at 20%, 40%, and 60% of mean bodyweight [total: 18000 cycles]). Constructs subsequently underwent an additional 45000 cycles at 60% of bodyweight (total: 63000 cycles). Loading to failure was then performed and ultimate load and mode of failure recorded. RESULTS: The BMD did not differ significantly between groups. Construct stiffness for group 1 was significantly less than group 4 (p = 0.008). Stiffness showed a linear increase with an increasing number of monocortical screws (p = 0.001). All constructs survived fatigue loading. Load-to-failure was not significantly different between groups. Mean load- to-failure of all groups was >1350N. CLINICAL RELEVANCE: Ex vivo canine large-breed femurs showed adequate stability biomechanically and gradually increasing stiffness with increasing monocortical screw numbers.

Can owners and clinicians assess outcome in dogs with fragmented medial coronoid process?

OBJECTIVES: To investigate the long term reliability of clinician and owner visual analogue score (VAS) for dogs with unilateral forelimb lameness attributable to fragmented medial coronoid process (FMCP) when compared to objective gait analysis. METHODS: Nine dogs with unilateral thoracic limb lameness due to FMCP underwent inverse dynamics gait analysis at initial presentation, and at one, two, six and 12 months following diagnosis. Total support moments were calculated and a total support moment ratio (TSMR) derived as an objective assessment of thoracic limb asymmetry. A VAS questionnaire for lameness was completed by the owner of each dog for each visit. Video footage of each dog walking and trotting at each visit was compiled, assigned to random order and subjected to VAS for lameness by a specialist in small animal surgery. Data from owner and clinician VAS lameness questionnaires were compared to the thoracic limb TSMR. RESULTS: Statistical analysis demonstrated a significant negative correlation between TSMR and owner VAS at four weeks post treatment but at no other period of evaluation. There was no significant correlation between TSMR and clinician VAS score at any evaluation period. CLINICAL SIGNIFICANCE: Assessments by owner and clinicians using VAS appear to be of limited use as a long term outcome measure for dogs with unilateral lameness due to FMCP when compared to objective gait analysis. There is a tendency for owners to underestimate forelimb lameness with increasing time which is not supported by quantitative measures of gait.

Reliability of radiological assessment of ulnar trochlear notch sclerosis in dysplastic canine elbows.

OBJECTIVES: The objectives of this study were to quantify the sensitivity and specificity of visual assessment of radiographs of the canine elbow in detecting ulnar trochlear notch sclerosis, to establish interobserver and intra-observer variation for the presence and grade of sclerosis and to quantify the effect of radiographic exposure on observer grading. METHODS: Mediolateral elbow radiographs were obtained from Labrador retrievers (n=34) aged between six and 18 months. Radiographs from dogs with an arthroscopic diagnosis of fragmented medial coronoid process (n=17) and those from a control population (n=17) were subjected to observer grading for the presence or absence of and the grade of ulnar trochlear notch sclerosis. Interobserver and intra-observer variation and observer sensitivity and specificity were calculated. Digital data from the ulnar trochlear notch were correlated with mean observer grade to quantify the effect of radiographic exposure on observer grade. RESULTS: Interobserver agreement was "fair" (kappa=0.251 to 0.369) and intra-observer agreement was "moderate" to "substantial" (kappa=0.462 to 0.667). The sensitivity of observer assessment was 72 per cent with a specificity of 22 per cent. Mean observer grade was not significantly correlated with the degree of radiographic exposure (P=0.70). CLINICAL SIGNIFICANCE: Ulnar trochlear notch sclerosis is a phenomenon associated with fragmented medial coronoid process. However, interobserver agreement in grading this feature is only fair, being identified by observers with moderate sensitivity but with relatively poor specificity. This low specificity may predispose to overdiagnosis in clinical cases. Intra-observer agreement is moderate to substantial, suggesting that individuals can reliably quantify this radiological feature on multiple occasions. The ability of observers to assess the degree of sclerotic change is not significantly affected by radiographic exposure.

Joint angle, moment and power compensations in dogs with fragmented medial coronoid process.

Fragmented medial coronoid process (FMCP) is the most common cause of forelimb lameness in juvenile medium and large breed dogs; however methods of assessing the disruption to their gait remain subjective. The purpose of this study was to objectively quantify the mechanical disruptions to gait in dogs with arthroscopically confirmed unilateral FMCP. Seven dogs underwent full inverse dynamic analysis at the time of diagnosis. Kinematic and force data were collected from both forelimbs at trot. Stance phase joint angles, net joint moments and net joint powers were calculated using custom software. There were gross differences in kinetic and kinematic patterns between FMCP affected and compensating forelimbs. Stance time was 0.24 sec on the lame side and 0.26 sec on the compensating side. The shoulder and the elbow were more flexed at ground contact, and elbow, carpal and MCP joints had smaller ranges of motion on the lame side. Net joint moments were significantly reduced (P < 0.05) in the elbow, carpal and MCP joints of the FMCP affected limb. Net joint powers were likewise significantly smaller (P < 0.05). However, the overall moment and power patterns persisted. Total limb support moment was significantly smaller on the affected side (P < 0.05). Total limb power was significantly reduced on the affected side (P < 0.05) being most affected in its propulsive phase in the second half of stance. Inverse dynamic analysis of this clinical condition is an objective means by which to assess the mechanical disruption to gait.

Limb alignment of pes valgus in a giant breed dog by plate-rod fixation.

A 2-year-old, female, neutered Newfoundland presented with pelvic limb lameness due to a distal tibial valgus deformity. A left distal fibula ostectomy and disto-medial tibial cuneiform ostectomy were performed with reduction and stabilisation using plate-rod internal fixation. Following surgical correction of the deformity the dog regained good functional mobility of the limb.

Treatment of a shoulder luxation in a forelimb amputee dog.

An eight-year-old, male, thoracic limb amputee Whippet presented with a traumatic lateral luxation of the scapulohumeral joint. Surgical reduction and stabilisation of the shoulder joint by means of a modified Campbell scapulohumeral prosthesis and capsulorrhaphy was unsuccessful and reluxation of the shoulder joint occurred. Subsequent surgical stabilisation using bicipital tendon transposition and a modified Campbell scapulohumeral encircling prosthesis in combination with a novel body cast / Spica splint resulted in a return to satisfactory function of this limb.

Digital analysis of ulnar trochlear notch sclerosis in Labrador retrievers.

OBJECTIVES: To compare ulnar trochlear notch bone radiopacity in Labrador retrievers with and without fragmented medial coronoid process using quantitative analysis of film density on digitised radiographs. METHODS: Mediolateral view elbow radiographs from Labrador retrievers (n=34) aged between six and 18 months were obtained and digitised. Images from dogs with an arthroscopic diagnosis of fragmentation of the medial coronoid process (n=17) were compared with that of a control population (n=17), and this data subject to statistical analysis. RESULTS: A statistically significant relationship between the presence of increased trochlear notch radiopacity and a fragmented medial coronoid process was identified. Fractional analysis of this area shows the region of greatest difference in radiopacity between normal and fragmented medial coronoid process cohorts to be in the trochlear region of the medial coronoid process of the ulna. A decrease in radiopacity values in the dysplastic group versus the normal cohort was observed for the region of the proximo-caudal ulnar trochlear notch. CLINICAL SIGNIFICANCE: An increase in ulnar trochlear notch radiopacity is a finding associated with fragmentation of the medial coronoid process in Labrador retrievers.