Radioulnar Step Research Articles

Radiographic determination of humeroradial, humeroulnar, and radioulnar subluxation indices to quantify elbow incongruence in dogs confirmed to have medial coronoid disease

Medial coronoid disease and elbow incongruence are common orthopedic problems causing forelimb lameness in large breed dogs. Therefore, the objective of this retrospective clinical study is to radiographically quantify the incongruity of humeroradial, humeroulnar, and radioulnar joints in dogs with confirmed medial coronoid disease compared to controls. Sixty-six (93 elbows) control and 73 (113 elbows) diseased Labrador and Golden Retrievers were enrolled. Our objective was achieved by measuring the central humeroradial, humeroulnar, and radioulnar distances and calculating the corresponding subluxation index of each joint on the extended mediolateral elbow radiograph. The traditional radioulnar step was also measured on the same mediolateral projection. Variables were compared between control and diseased groups, and the significance level was P < .05. The central humeroradial, humeroulnar, and radioulnar distances and corresponding subluxation indices increased significantly (P ≤ .007) in elbows with confirmed medial coronoid disease compared to controls. Radioulnar step increased significantly (P < .0001) in diseased elbows. Elbow incongruence, manifested by increased humeroradial, humeroulnar, and radioulnar subluxation indices, appeared to be consistent with medial coronoid disease in Labrador and Golden Retrievers. An elbow with a humeroradial, humeroulnar, or radioulnar subluxation index >0.15, 0.10, or 0.14, respectively, or radioulnar step >1.4 mm, is more likely to be incongruent and may have a concomitant coronoid disease. However, future validation of the reported measurements is still warranted.

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

To evaluate the reliability of CT measurement of canine elbow axial radioulnar congruence using a duplicated circle superimposition technique. 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. 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. The duplicated circle superimposition technique provides a simple and accurate means of assessing radioulnar axial incongruence.

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

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). 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. 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. 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.

Arthroscopic treatment of fragmented coronoid process with severe elbow incongruity

The purpose of this study was to investigate the long-term treatment results of fragmented coronoid process (FCP) in joints with a radio-ulnar step greater than 3 mm. Treatment of these patients only consisted of fragment removal, without correction of the incongruity. The eight Bernese Mountain Dogs (11 joints) included in this study showed obvious clinical signs of elbow disease and were diagnosed with severe elbow incongruity and concomitant FCP in the time period from 1999-2003. At that time, elbow radiography, computed tomography, and arthroscopy were performed. The mean follow-up period was 5.6 years. The follow-up consisted of a telephone questionnaire combined with a clinical and radiographic re-evaluation at our clinic. The questionnaire revealed that all dogs were either free of lameness or only lame following heavy exercise. One dog sporadically required medication after heavy exercise. The owner satisfaction rate was 100%. The clinical re-evaluation did not reveal any signs of pain or lameness in all cases. Range-of- motion was decreased in nine of the 11 elbows. Radiographs revealed an increase in severity of osteoarthritis in every case.In this case series, arthroscopic fragment removal without treatment of incongruity was demonstrated to be a valuable treatment option and may provide a satisfactory long-term outcome.

Computed Tomography Findings in 32 Joints Affected with Severe Elbow Incongruity and Fragmented Medial Coronoid Process

To describe the computed tomography (CT) findings in dogs with severe elbow incongruity combined with a fragmented medial coronoid process (FCP) and compare these with normal joints and congruent joints affected by FCP. Clinical study. Client-owned dogs with elbow lameness (n = 40) and purpose bred dogs (n = 5; controls). The CT features of 32 severely incongruent joints with concomitant FCP were compared with those of 32 congruent elbow joints affected with FCP and 10 normal joints. In severely incongruent elbow joints, a radioulnar step and widened joint spaces were visible on each CT plane. Additional features typically seen in severely incongruent elbows were a cyst at the radioulnar transition and fragmentation of the axial border of the medial coronoid incisure. None of these features appeared in normal or in congruent FCP joints. On CT, several features associated with severe elbow incongruity and concomitant FCP were detected, which were not found in normal joints or congruent joints affected by FCP.

Arthroscopic Findings in 32 Joints Affected by Severe Elbow Incongruity with Concomitant Fragmented Medial Coronoid Process

To report arthroscopic findings in dogs with severe elbow incongruity combined with fragmented medial coronoid process (FCP) and compare these findings in normal joints and congruent joints affected by FCP. Clinical study. Dogs with elbow lameness (n = 40) and purpose bred dogs (5; controls). Arthroscopic features of 32 severely incongruent joints with concomitant FCP were compared with 32 congruent elbow joints affected with FCP and 10 normal joints. A radioulnar step of ≥ 3 mm on radiographs and computed tomography (CT) scans was the selection criterion for a severely incongruent joint. Intraarticular structures were visually assessed at various sites within the joint. Regions of interest were: the radioulnar transition, humeroradial and humeroulnar joint space, trochlear notch, primary and secondary lesions of the medial coronoid process, and radial head. Incongruent joints had a radioulnar step and changes at the cartilage in the center of the trochlear notch, an irregular radioulnar transition, and an abnormal surface of the radial head. Coronoid pathology was present in every pathologic joint. Arthroscopy allowed detection of several features that were signs or consequences of severe elbow incongruity or accompanying inflammation. After a prominent radioulnar step, cartilage changes involving the radial head and trochlear notch were most frequently seen.

SENSITIVITY AND SPECIFICITY OF RADIOGRAPHY FOR DETECTION OF ELBOW INCONGRUITY IN CLINICAL PATIENTS

Elbow incongruity is an important factor regarding the treatment and prognosis of elbow dysplasia. Our purpose was to determine the sensitivity and specificity for radiographic detection of elbow incongruity in clinical patients, to establish inter- and intraobserver variation for different parameters, and to evaluate the possibility of radiographic grading of incongruity. Standard radiographic projections were acquired from 29 incongruent and nine congruent elbows of dogs of various ages and breeds. Computed tomography (CT) was used to diagnose and grade the incongruity. All radiographs were evaluated by four observers for detection and grading of elbow incongruity. Sensitivity, specificity, inter- and intraobserver variability were calculated. The mean sensitivity for detection of incongruity was very good (88.8%) with a mean specificity of 91.7%. Correct grading of incongruity was difficult. The radioulnar step and the widening of the humeroulnar and humeroradial joint space were seen most frequently. Intraobserver and interobserver variability were fair to excellent (Kappa = 0.372-0.809), depending on the investigated parameters. Radiography is valuable to screen for elbow incongruity. In over 91% of the patients, a clear distinction could be made between a congruent and an incongruent joint grading was not possible.

Quantification of Humeroulnar Incongruity inLabradorRetrievers with and without Medial Coronoid Disease

To quantify humeroulnar incongruity on elbow radiographs in Labrador Retrievers with or without medial coronoid disease (MCD). Retrospective study of 92 elbows. Radiographic projections of elbow joints from Labrador Retrievers with MCD (n = 42 elbows; 26 dogs) and without MCD (n = 50 elbows; 25 dogs). The congruity of the humeroulnar joint was measured using an index of subluxation (SI) for each elbow. SI was defined as the distance between the centers of 2 circles drawn along the margins of the incisura trochlearis and the trochlea of humerus on mediolateral digital radiographic projections, normalized by the radius of the circle circumscribing the humeral trochlea. SI was compared between right and left elbows with and without pathology using a Wilcoxon test for paired data, and between normal and abnormal groups with a Wilcoxon test for unpaired data. Mismatch between ulnar curvature and curvature of humeral trochlea and radioulnar incongruency were also noted (Wilcoxon test). The intraobserver repeatability, correlation between SI and radioulnar incongruency, and between SI and mismatch elbow curvature were estimated with a Pearson's correlation coefficient. Intraobserver repeatability of SI measurement was high (r = 0.97). Mean ± SD humeroulnar incongruity (SI) was greater in elbows with MCD (18.5 ± 6.6) than in the normal elbows (1.7 ± 2.0, P < 0.001). The difference between the diameters of the curvatures of the ulnar and humeral trochlea was greater in elbows with MCD (12.5 ± 4.4) than in the normal group (10.7 ± 4.1, P < 0.05). A moderate correlation was found between the degree of humeroulnar incongruity and a radioulnar step (r = 0.63); however, no correlation was identified between SI and the difference between the diameters of the curvatures of the ulnar and humeral trochleae (r = 0.14). We propose a radiographic index to measure humeroulnar incongruity on mediolateral digital radiographic projections. This index (SI) supports the presence of humeroulnar incongruity in Labrador Retrievers with MCD. Further evaluation of its reproducibility and clinical importance are warranted. Although there is a moderate correlation between humeroulnar incongruity and radioulnar incongruency, causation has not been established.

Visual Estimation of Radioulnar Incongruence in Dogs Using Three‐Dimensional Image Rendering: An In Vitro Study Based on Computed Tomographic Imaging

To determine the sensitivity and specificity of visual estimation of radioulnar incongruence (RUI) in the canine elbow by use of 3-dimensional (3D) image rendering. Experimentally induced negative and positive RUI. Canine (>20 kg) cadaveric right thoracic limbs (n=8). Radial shortening and lengthening of 1 and 2 mm were performed extending an established surgical in vitro model of RUI. Based on transverse computed tomographic (CT) scans of each radioulnar conformation, the subchondral radioulnar joint surface was reconstructed and visualized. A total of 64 3D models of RUI were blindly evaluated in a random manner by 3 independent observers. RUI was estimated subjectively at 1 mm precisely (-2, -1, 0, +1, +2) by visual inspection of the 3D models. Median sensitivity for identifying an incongruent joint was 0.86. Median specificity for identification of a congruent joint was 0.77. Analyzing the data only in respect to a congruent joint versus one with a shortened radius (positive RUI) resulted in a median sensitivity of 0.82, and a median specificity of 1.00. Interobserver agreement was 0.87. Repeatability was 0.96. Estimation of positive and negative RUI based on 3D surface models of the radioulnar articulation mimics gross inspection in a noninvasive manner, the latter being the ultimate gold standard for definitive diagnosis of any radioulnar step. The proposed technique is precise, reliable, and repeatable in vitro. Preoperative estimation of the type and degree of RUI is the basis for deciding which type of corrective or modifying osteotomy might be best suited to restore normal joint loads in vivo.