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Objectives: The aim of this study was the determination of complications of posttraumatic radius-ulna synostosis associated with antebrachium fractures in dogs. The characteristics, common complications, and the outcome of canine radius and ulna fractures were described in order to indicate the influence of synostosis in the canine patient population. Incidence, location, risk factors, the center of rotation of angulation (CORA), and outcome of treatment of post-traumatic radius-ulna synostosis in dogs were determined. To demonstrate the function of affected canine forelimbs (pronation and supination) due to synostosis, an experimental study in cadaveric dogs was included.
Study designs: Four separate studies are subject of this dissertation:
Study I: Retrospective study: characteristics, complications, and outcome of canine radius-ulna fractures in 188 cases (1999 to 2009)
Study II: Retrospective study: incidence and correlation factors of post-traumatic radius and ulna synostosis in dogs: 24 cases (1999-2009)
Study III: Experimental study: synostosis between radius and ulna and the function of pronation and supination in cadaveric dogs
Study IV: Case report: outcome of radius ulna synostosis treatment in four dogs including a two year follow- up period Data and Patients: The medical records of 221 cases in 213 dogs with received operations at radius ulna region submitted during 1999 to 2009 at the Small Animal Clinic, Freie Universitӓt Berlin, Berlin, Germany were reviewed. Furthermore, follow-up during 2009 to 2012 was performed in four synostosis patients. Seven cadaveric dogs were used in the experimental study.
Methods: Medical data and radiographs of canine radius and ulna fractures which were caused by traumatic fractures and as well as operative fractures (osteotomy) to correct antebrachial growth deformities were analysed. Post-traumatic synostosis was identified from the radiographs. Over a two years period, follow-up in four synostosis patients was performed. Comparison of pronation and supination of forelimbs before and after surgery to simulate radius and ulna synostosis in cadaveric dogs was investigated. Descriptive statistics, t-test and Pearson’s correlation coefficiency were applied in this dissertation.
Results: 188 cases of traumatic radius ulna fractures in 179 dogs were identified. 53 breeds were presented; the most common breed was large mixed breed (13.83%). The age of the affected dog at the time of treatment varied from 1 to 173 months. The median age was 21 months (1.75 years). The causes of traumatic fracture were road traffic accident (34.57%), falling or jumping from high places (12.76%), biting injuries (6.91%), trauma due to other causes (17.55%), and no information (26.59%). Mean duration of bone healing was 108.11 ± 77.91 days. Revision surgeries were performed in 20 cases (10.64%) which were statistically significant correlated with the presence of an open fracture (R=0.176, p<0.05), the biting injuries (R=0.232, p<0.01), the street accidents (R=0.154, p<0.05), and the bacterial infection (R=0.41, p<0.01). The increasing time of revision surgery had an effect to the alignment of the radius and ulna bone after the bone healing (p< 0.05). An increased lateral distal radial angle (LDRA), is significantly correlated to the presence of radial curvus and carpal valgus, which was shown in the dogs that obtained the revision surgery.
In the study II, 24 cases (10.86%) with radius and ulna synostosis were presented. All synostosis formations occurred at the fractured site and the most common location was distal third of radius and ulna (n=13 cases; 50%). Dogs with high body weights and dogs with the presenting sign of infection had high risk of synostosis (R= 0.17 and R=0.167; respectively, p< 0.05). The degree of the lateral distal radial angle (LDRA) and the frontal plane alignment (FPA), which obtained from radiographs, were also significantly correlated with synostosis (R= 0.216 and R= -0.216; respectively). These parameters indicated the malalignment of the limb (carpal varus) after the bone healing which were caused by the formation of synostosis between radius and ulna. An extended degree of supination (p<0.01), and a reduced degree of pronation (p<0.05) of forelimbs were presented on cadaveric dogs in the experimental study in order to simulate synostosis. Over a two years period, follow-up was performed in four patients. The age of the animal at the time of surgery to correct synostosis varied in a wide range (4 months to 119 months). Recurrence of synostosis after surgical treatment was observed and one case was required a second operation in two years after a first operation.
Conclusions and clinical relevance: Dogs with high bodyweight and/or dogs with signs of bacterial infection (e.g. bite wound fractures or open fractures) have high risk of posttraumatic synostosis formation after healing of the radius-ulna fracture.
To decrease the incidence of synostosis, it is very important to perform careful tissue handling. In order to obtain an accurate bone alignment, trauma of the interosseous membrane shall be prevented and an efficient reduction of both of radius and ulna fragments is required. Synostosis alters the angle of supination and pronation on the affected forelimb, which may lead to short and long term problems.
Recurrence of synostosis after resection of bony bridge and ulna ostectomy can be seen.