Successful treatment of a radioulnar synostosis in a Mississippi kite (Ictinia mississippiensis)

Characteristics of antebrachial fractures associated with a successful outcome among free-ranging birds of prey that received treatment in a rehabilitation program

OBJECTIVE

To identify characteristics of antebrachial fractures associated with a successful outcome (ie, bird released back into the wild after regaining normal flight ability, without being returned to the rehabilitation program within 1 month afterward) for free-ranging birds of prey admitted to a rehabilitation program.

ANIMALS

620 birds of prey (representing 24 species) with antebrachial fractures admitted alive to a rehabilitation program from August 1986 through December 2015.

PROCEDURES

The medical record of each bird was reviewed to obtain information on species, age, sex, year of admission, fracture characteristics, and treatments administered. Outcome was classified as successful or unsuccessful on the basis of available data. Multivariable logistic regression was used to identify fracture characteristics associated with outcome.

RESULTS

519 of 620 (84%) birds received treatment, and a successful outcome was recorded for 245 (47%) treated birds. Birds with closed (vs open) fractures were significantly more likely to have a successful outcome. Birds with concomitant radial and ulnar fractures involving the same third of the antebrachium (vs other types of antebrachial fractures) were significantly less likely to have a successful outcome, although birds with this type of fracture were significantly more likely to have a successful outcome when the fracture was localized to the middle or distal (vs proximal) third of the antebrachium.

CONCLUSIONS AND CLINICAL RELEVANCE

The characteristics of antebrachial fractures associated with a successful or unsuccessful outcome in this study may be useful in the development of triage protocols for birds of prey in other rehabilitation centers.

Release Rates and Complications for Birds of Prey With Antebrachial Fractures at a Veterinary Teaching Hospital

A retrospective case series that included 253 free-ranging birds of prey admitted to a rehabilitation center was conducted to describe the treatment and outcome of antebrachial fractures. Medical records from birds of prey belonging to 21 species admitted with antebrachial fracture between 1989 and 2015 at the University of California, Davis, were reviewed. Species distribution on admission, treatment, outcome, and complications were described by fracture category and species. Among 134 birds treated after initial triage on the day of admission, 4 bone/ wing categories were identified: 83 birds had an ulnar fracture only; 18 birds had a radial fracture only; 28 birds had a concomitant fracture of the radius and ulna on the same wing; and 5 birds had bilateral antebrachial fractures. Logistic regressions were performed to determine which factors were associated with a positive outcome within each of these 4 categories. Among birds having only an ulnar fracture, those with a closed fracture were significantly more likely to be released than birds with open fractures (P = .03; odds ratio = 5.43, 95% confidence interval: 1.29-28.12). In addition, birds with a fracture of the middle third of the ulna were significantly more likely to be released than birds diagnosed with a single fracture of the proximal third of the ulna (P = .02; odds ratio = 4.54, 95% confidence interval: 1.35-16.64). No significant prognostic factor was detected in other fracture categories.

Evaluation of Goniometry and Electrogoniometry of Carpus and Elbow Joints in the Barred Owl (Strix varia)

The motion of wing joints is a critical factor for successful flight in avian patients, but little information is available about goniometry in birds. Elbow and carpus joints in flexed and extended positions from 10 orthopedically normal wings of 6 adult wild barred owls (Strix varia) were evaluated with the animals under general anesthesia using a modified universal plastic goniometer and an electrogoniometer. These measurements were compared to those obtained using radiographic assessment. Intra- and interobserver reliability was calculated. Measurements in live animals were compared to those obtained from frozen-thawed carcasses. Results showed that the modified universal plastic goniometer can be used to obtain accurate results for elbow flexion and extension and for carpal flexion with good to excellent reliability compared to measurements collected from radiographic assessment. Measurements obtained using an electrogoniometer were less accurate and less reliable than those obtained with a plastic goniometer, possibly because of the size and configuration of the model used. Comparison of measurements from live animals and carcasses revealed no significant differences between mean measurements and suggested that further evaluation of carcasses as a model for study of goniometry measurements in avian wing joints should be considered.

How pigeons couple three-dimensional elbow and wrist motion to morph their wings

Birds change the shape and area of their wings to an exceptional degree, surpassing insects, bats and aircraft in their ability to morph their wings for a variety of tasks. This morphing is governed by a musculoskeletal system, which couples elbow and wrist motion. Since the discovery of this effect in 1839, the planar 'drawing parallels' mechanism has been used to explain the coupling. Remarkably, this mechanism has never been corroborated from quantitative motion data. Therefore, we measured how the wing skeleton of a pigeon (Columba livia) moves during morphing. Despite earlier planar assumptions, we found that the skeletal motion paths are highly three-dimensional and do not lie in the anatomical plane, ruling out the 'drawing parallels' mechanism. Furthermore, micro-computed tomography scans in seven consecutive poses show how the two wrist bones contribute to morphing, particularly the sliding ulnare. From these data, we infer the joint types for all six bones that form the wing morphing mechanism and corroborate the most parsimonious mechanism based on least-squares error minimization. Remarkably, the algorithm shows that all optimal four-bar mechanisms either lock, are unable to track the highly three-dimensional bone motion paths, or require the radius and ulna to cross for accuracy, which is anatomically unrealistic. In contrast, the algorithm finds that a six-bar mechanism recreates the measured motion accurately with a parallel radius and ulna and a sliding ulnare. This revises our mechanistic understanding of how birds morph their wings, and offers quantitative inspiration for engineering morphing wings.