Introduction: Osteoarthritis is an irreversible and debilitating disease process that arises from degradation of articular cartilage secondary to joint instability, trauma or a developmental abnormality. It is estimated to affect approximately 20% of adult dogs over the age of 1.1 While there are many methods to assess outcome measurements in dog with osteoarthritis, very few of these outcome measurements have been validated. Commonly employed outcome measures for osteoarthritis in small animals include assessment of lameness, pain, joint mobility, kinetic data, serum inflammatory markers, arthroscopic evaluation, and different imaging modalities like radiographs, ultrasound, CT and MRI.2 In a systemic review of outcome measures in canine osteoarthritis, kinetic data and radiographs were most commonly used when only 1 outcome measure was evaluated. In this same study, only 10 validated outcome measures from 7/117 eligible publications for inclusion in the review were found, which included muscle atrophy, weight bearing and range of motion amongst others.3
While there are many studies that utilize goniometry as an outcome measure, there are few studies that evaluate the relationship of goniometry and radiographic osteoarthritis in small animals.4-7 In a study of osteoarthritic cats, goniometry and orthopedic findings could not predict radiographic osteoarthritis with confidence, but the lack of findings and increased ROM of joints was useful screening tool to rule out degenerative joint disease.7 In contrast, a study of cranial cruciate rupture in dogs that were stabilized with a tibial plateau leveling osteotomy found that ≥ 10° loss of stifle flexion or extension after surgery was associated with a significant increase in lameness, and that loss of stifle extension was significantly correlated with radiographic osteoarthrosis in the cranial femorotibial joint that may have constrained mechanical extension of the stifle.6 Moreover, a study of dogs with hip dysplasia could not find an association between extension loss and the presence of radiographic osteoarthrosis.4
The relationship of limb function through objective evaluation with kinetic gait analysis and radiographic evidence of osteoarthrosis has been evaluated in several joints and have been consistently reported.8-10 These studies have found that presence of osteoarthrosis did not necessarily correlate with limb function9, and furthermore, progressive radiographic osteoarthrosis was observed in dogs with medial coronoid process disease and cranial cruciate rupture despite improvement in limb function with surgical intervention.8,10
While there are studies evaluating the relationship of goniometry and kinetic gait analysis with radiographic degenerative joint disease, there is no agreement in the changes of goniometry with radiographic osteoarthrosis, and furthermore there are no studies that the authors’ are aware of evaluating the relationship of goniometry with kinetic gait analysis. The aim of our study was to 1) evaluate the relationship of goniometry and radiographic evidence of degenerative joint disease in several different joints (elbow, stifle, and hip), 2) confirm that limb function through measurement of kinetic variables using a pressure sensitive walkway was not influenced by the presence or severity of radiographic osteoarthrosis, and 3) determine the influence of passive range of motion measured with universal goniometry on limb function through measurement of kinetic variables. We hypothesize that motion loss measured through goniometry would correlate with radiographic osteoarthrosis, while limb function measured through gait analysis would not. Furthermore, we hypothesize that motion loss can be used to predict limb function.
Materials and Methods:
Dog population:
Data collected and analyzed in the current publication was part of a larger study of evaluating the short-term effects of a certain dietary supplement on gait, joint range of motion, serum inflammatory markers, and pain in dogs with osteoarthritic impairment. An institutional animal care and use committee approved all the procedures and informed owner consent was obtained. Records of 59 dogs of various breeds with osteoarthritic impairment based on clinical signs, history and orthopedic exam were reviewed retrospectively. Dogs were excluded if they received corticosteroids, non-steroidal anti-inflammatory drugs, or a nutraceutical within 14 days of examination and data collection, or had evidence of neurologic disease or joint instability. The same ACVS diplomate performed all orthopedic and neurologic examinations on the study population. The most affected joint (elbow, stifle, hip) was determined based on orthopedic evaluation. Patient signalment, weight, BCS, orthopedic findings, goniometry measurements, and results of gait analysis using a pressure sensing walking were recorded.
Goniometry:
Measurements of flexion and extension of the most affected joint (elbow, stifle, hip) and the contralateral joint were collected as described previously by Jaeger et al.11 A standard clinical goniometer with 1° gradations was used. Prior to measurement, the joint of interest was placed in a full range of motion to determine the axis of joint rotation. The center of the goniometer was placed on the axis of joint rotation and the arms of the goniometer were placed proximally and distally over the long axis of the bones that centered the joint of interest. Maximal comfortable measurements of flexion and extension in conscious dogs were recorded for the both the joint of interest and contralateral joint. Measurements were recorded to the nearest 5° increment. Range of motion (ROM) was determined by subtracting the flexion angle from the extension angle.
Radiographic evaluation:
Radiographs concentrating on the joint of interest, as determined by orthopedic examination, were taken and scored. All radiographs were taken under sedation using a combination of dexmedetomidine hydrochloride (3.3 to 4.4 ug/kg) and butorphanol (0.2 mg/kg). Elbow joints were evaluated cranio-caudal and flexed medio-lateral projections with a 45° opening angle between the radius and humerus and were assigned scores from 0-3 based on the International Elbow Working Group protocol.12 Stifle joints were evaluated with cranio-caudal and medio-lateral projections and were assigned a score from 0-3 based on a radiographic scoring system described by Innes et al.13 Coxofemoral joints were evaluated with lateral and extended ventro-dorsal projections of the pelvis and were assigned a scored from 0-6 based on guidelines established by the British Veterinary Association/Kennel Club.14 All radiographs were reviewed and scored by the same ACVR diplomate.
Kinetic gait analysis:
Gait analysis was performed on a pressure sensing system (7100 QL Virtual Sensor 4 Mat System, Tekscan, Boston, MA). Dogs were walked with a consistent pace of ± 1.50 m/s and acceleration of ± 0.50 m/s2. An average of 5 footfalls was used obtain kinetic information (vertical impulse and peak vertical force). Vertical impulse (VI) and peak vertical force (PVF) were expressed as a percentage of body weight and those values were utilized in data analysis. The percentage of body weight distribution among the 4 limbs was calculated using PVF with the following equation: Distribution of BW(%) = (PVF of the limb/Total PVF of all 4 limbs) x 100.15 Asymmetry index was calculated for PVF using the following equation: SI% = 200 x [(PVFL – PVFR)/(PVFL + PVFR)].16 A SI of 0% indicates a perfect symmetrical gait, while a positive or negative value indicates right limb or left limb lameness.