Neil J. Burton

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.

Conservative Versus Arthroscopic Management for Medial Coronoid Process Disease in Dogs: A Prospective Gait Evaluation

OBJECTIVE To investigate, using objective gait analysis, the long-term outcome of dogs with medial coronoid process disease (MCPD) treated with conservative management (CM) versus arthroscopic treatment (AT). STUDY DESIGN Prospective clinical trial. ANIMALS Dogs (n = 20) with unilaterally confirmed MCPD. METHODS Eleven dogs were treated arthroscopically with removal of coronoid fragments and burring of any associated chondromalacic cartridge and 9 dogs were managed conservatively. All dogs were administered a 6-week course of oral tepoxalin on enrollment. Inverse dynamics gait analysis was performed at initial presentation and at 4, 8, 26, and 52 weeks. The gait variables analyzed were elbow moment (EM), elbow power (EP), total support moment (TSM), and total support moment ratio (TSMR) as a measure of forelimb asymmetry. RESULTS Affected peak EM increased from 0.58 to 0.76 Nm/kg in the AT dogs, and from 0.66 to 0.81 Nm/kg in the CM dogs and there was no significant difference between groups. Affected peak EP increased marginally in the AT dogs, but was unchanged in the CM dogs and there was no significant difference between groups. TSM increased from 1.49 to 1.92 Nm/kg in the AT dogs and from 1.52 to 2.06 Nm/kg in the CM dogs and there was no significant difference between groups. TSMR was statistically different between treatment groups at 1 (P = .003) and 2 months (P = .048) with the AT group more asymmetric and hence more lame. TSMR at 12 months was 0.83 (AT) and 0.86 (CM) implying a failure of return to soundness by either group. CONCLUSIONS AT dogs had increased mechanical asymmetry at 4 and 8 weeks compared to the CM group revealing surgery worsened limb function. There was no significant difference in mechanical symmetry between groups at 26 and 52 weeks.

Comparison of bone mineral density in medial coronoid processes of dogs with and without medial coronoid process fragmentation

OBJECTIVE To quantify bone mineral density (BMD) in the medial coronoid process (MCP) of dogs with and without fragmented medial coronoid processes (FMCPs) by use of dualenergy x-ray absorptiometry. SAMPLE POPULATION 50 osteochondral samples from 31 dogs that underwent subtotal coronoid ostectomy for unilateral or bilateral FMCP and 10 control osteochondral samples of the MCP collected from forelimbs of 5 cadaveric Greyhounds. PROCEDURES Each sample was mounted in proximodistal and mediolateral orientations for BMD determinations via dual-energy x-ray absorptiometry, and area-of-interest data (0.03-cm(2) increments) were obtained. Values of BMD were compared between left and right limb control samples, between control and FMCP samples, and between axial and abaxial regions of the control or FMCP samples. RESULTS The BMD in control and FMCP samples in both proximodistal and mediolateral orientations differed significantly. Mean BMD throughout the MCP was decreased in FMCP samples, compared with control sample findings. In both control and FMCP samples, BMD of the abaxial half of the MCP was 50% higher than that of the axial portion. CONCLUSIONS AND CLINICAL RELEVANCE The similar pattern of BMD in osteochondral samples of the MCP in dogs with and without FMCP indicated that the MCP was eccentrically loaded during weight bearing. Topographic variation in BMD in the MCP, and hence tolerance to compressive loading, suggested that the abaxial portion of the MCP in dogs was more resistant to compressive load than was the axial edge. This difference may predispose the coronoid process to microcrack formation and fragmentation at that juxtaposition.

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.

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.

Composite fixation of comminuted ilial wing fractures in cats: three cases

Clinical summary The surgical repair of comminuted ilial wing fractures (comprising a long oblique fracture with ventral multiple fragmentation) in three cats using composite internal fixation is reported. The technique comprised the use of pins, screws, wire and polymethylmethacrylate. All cases had an excellent outcome with uneventful bone healing. One case had a very mild reduction in pelvic canal diameter postoperatively. There was no evidence of implant loosening or migration in any cat on follow-up radiographs. Practical relevance This technique provided a quick and highly adaptable means of stabilising this fracture configuration, as well as restoring pelvic symmetry, when limited buttressing support and bone stock were available cranial and ventral to the acetabulum. This method of fixation may have biomechanical advantages over lateral or dorsal plating techniques for this particular type of fracture configuration.

Canine elbow dysplasia 1. Aetiopathogenesis and diagnosis

CANINE elbow dysplasia is a term encompassing multiple developmental anomalies of the cubital joint, including elbow incongruity, a fragmented medial coronoid process, an ununited anconeal process, osteochondrosis of the humeral condyle and an ununited medial epicondyle. Collectively, these lesions are a common cause of thoracic limb lameness in juvenile medium‐ and large‐breed dogs. However, the precise mechanisms by which these anomalies arise are still unknown. Diagnosis in some cases can be challenging, as can be determining the most appropriate course of treatment. This article reviews current understanding of the aetiopathogenesis of canine elbow dysplasia and outlines the approach to diagnosing the most common developmental anomalies associated with this condition. An article in the next issue will discuss the treatment and prognosis.

Effect of Osteotomy Position and Tibial Plateau Rotation on the Tensile Force Required for Failure of the Canine Quadriceps Mechanism

OBJECTIVE To measure the tensile force required for failure of the quadriceps mechanism with different tibial tuberosity widths and different degrees of rotation of the tibial plateau after radial osteotomy of the proximal tibia. STUDY DESIGN Ex vivo study, randomized unblocked design ANIMALS Thirty-five hind limbs from 18 adult Greyhound cadavers. METHODS Part 1 (15 limbs)--The center of rotation of the proximal tibial radial osteotomy was advanced craniodistally, progressively reducing absolute tibial tuberosity width (ATTW) for 5 different widths. Part 2 (21 limbs)-Tibial plateau rotation was performed at a set ATTW. Rotation was varied as a function of tibial tuberosity position with rotation proximal, level with, or distal to the tuberosity. All 35 limbs were tested with force applied via the quadriceps mechanism until construct failure occurred. RESULTS All but 2 limbs failed by fracture of the tibial tuberosity. The tensile force required for failure of the quadriceps mechanism increased linearly with increasing ATTW. Significantly less force (P = .016) was required for failure of the quadriceps mechanism when the rotation of the tibial plateau was distal to the level of the patella tendon (mean 1,877 N) compared to when it was above the level of the patella tendon (mean 2,533 N). Rotation of the tibial plateau distal to the level of the patella tendon insertion point resulted in fracture at the base of the tibial tuberosity, level with the tibial plateau buttress. CONCLUSION The overwhelming mode of failure of the quadriceps mechanism was by tibial tuberosity fracture, thus this was the weakest part of the construct. Reducing the tibial tuberosity width and rotation of the tibial plateau segment below the patella tendon insertion decreased the force required for tibial tuberosity fracture. These results support the idea of a safe point with the tibial plateau segment providing buttress to the tibial tuberosity.

Colored Indicator Undergloves Increase the Detection of Glove Perforations by Surgeons During Small Animal Orthopedic Surgery: A Randomized Controlled Trial

Objective To determine whether use of colored indicator gloves affects perforation detection rate and to identify risk factors for glove perforation during veterinary orthopedic surgery. Study Design Prospective randomized controlled trial. Sample Population 574 double pairs of gloves worn during 300 orthopedic surgical procedures (2,296 gloves). Methods Primary and assistant surgeons double‐gloved for all orthopedic surgical procedures. Type of inner glove (standard or colored indicator) was randomized for the first 360 double pairs of gloves worn by surgeons during 180 procedures. Perforations detected by surgeons were recorded and gloves changed if requested. For a further 120 procedures, indicator gloves were used exclusively. All gloves were leak‐tested after surgery to identify perforations. Association between potential risk factors and perforation was explored using multivariate logistical regression analysis. Results Glove perforations occurred during 43% of surgeries with a mean of 2.3 holes/surgery. Inner gloves were intact in 63% of glove pairs where an outer perforation occurred. Intraoperative perforation detection was improved when colored indicator gloves were worn (83% sensitivity) vs. standard gloves (34% sensitivity; P<.001). Independent risk factors for perforation were placement of plates and/or screws (P=.001; OR=2.4; 95% CI, 1.4–4.0), placement of an external skeletal fixator (P=.002; OR=7.0; 95% CI, 2.1–23.8), use of orthopedic wire (P=.011; OR=2.4; 95% CI, 1.2–4.7), and primary surgeon being board‐certified (P=.016; OR=1.9; 95% CI, 1.1–3.1). Conclusion Increased surgeon recognition of glove perforations through use of colored indicator gloves enables prompt change of gloves if perforation occurs and may reduce potential contamination of the surgical site.

Topographic Bone Density of the Radius and Ulna in Greyhounds and Labrador Retrievers With and Without Medial Coronoid Process Disease

OBJECTIVE To quantify, using computed tomography (CT), cross-sectional ulnar bone density (UBD), and regional radial bone density (RRBD) at the level of the medial coronoid process (MCP) in elbows with and without medial coronoid process disease (MCPD) and with and without fragmentation of MCP (FCP). STUDY DESIGN Retrospective clinical case-control and ex vivo study. SAMPLE POPULATION Labrador Retriever elbows (n = 54) and normal cadaveric Greyhound elbows (11) undergoing elbow CT. MATERIALS AND METHODS Labrador Retriever elbows were divided into 2 groups: (1) clinically unaffected and (2) MCPD-affected elbows. This 2nd group was subdivided based on the presence of a displaced FCP. UBD was measured linearly, in Hounsfield units (HU) across the widest part of the ulna incorporating the MCP. The radial head was divided into 6 zones, with mean RRBD (HU) calculated for each group. RESULTS MCPD-affected Labrador Retriever elbows had significantly lower UBD within the MCP with a higher UBD in the cranial ulnar medulla. Lower RRBD was also seen in the radial head adjacent to the MCP in MCPD-affected Labrador Retriever elbows with FCP compared with Labrador Retriever elbows without FCP. Greyhounds had consistently lower RRBD and UBD at the apex of the MCP compared with clinically unaffected Labrador Retriever elbows. CONCLUSIONS Our results suggest a caudolateral load-transfer shift through the ulna in MCPD-affected elbow joints, unloading the MCP. Changes in regional radial head bone density suggest that the radial head is involved in the pathogenesis of MCPD.