Schlüsselwort: ulna

Retrospective analysis of diaphyseal and distal metaphyseal radius/ulna fractures in dogs after plate osteosynthesis and osteosynthesis with external fixator The aim of the retrospective study was to analyse the treatment of diaphyseal and distal metaphyseal antebrachial fractures with angle-stable and non-angle-stable methods of osteosynthesis, their healing and possible complications, taking into account patient- and fracture-dependent influencing factors. A total of 91 diaphyseal or distal metaphyseal radius/ulna fractures (88 dogs, 3 of them with bilateral fractures) were evaluated. The fractures were stabilized with plate osteosynthesis or external fixator in the Small Animal Clinic of the Free University of Berlin in the years 2009-2015. The 88 dogs belonged to 39 different breeds or hybrids of these breeds. The age of the dogs varied between 2 and 186 months and corresponded to an average age of 3.17 years. 52.3% of the dogs were female and 47.7% male. Light-weight breeds (< 5 kg; toy breeds) were represented with 31.8%, low- (5-15 kg) with 23.9%, medium- (> 15-30 kg) with 26.1% and heavy-weight (> 30 kg) with 18.2%. Fractures were caused by road traffic accidents (42.9%), falls from low heights (24.2%), minor trauma (getting stuck, trapped or playing, kicking; 9.9% each), dog bite (5.5%) or wild boar injuries (2.2%). In 5.5% of the dogs the cause was unknown. In 96.7% of cases both radius and ulna were fractured, in 3.3% only the radius was fractured. A total of 74.7% of the fractures affected the diaphysis and 25.3% affected the distal metaphysis. The distal metaphysis was fractured more frequently (46.7%) in the lightweight dogs (< 5 kg) than in the heavier dogs (6.3-18.2%). Overall, transverse fractures (79.1%) were the most common fracture type, followed by comminuted (12.1%) and oblique fractures (8.8%). Even when considering the localization separately, transverse fractures accounted for the largest share in each case (diaphysis: 77.9%; distal metaphysis: 82.6%). 14.3% of fractures were open. The fractures were treated after an average of 1.07 days. The average duration of surgery was 67.7 minutes. 46.2% of the operations were performed by highly experienced surgeons and 53.8% by less experienced surgeons. 83.5% of the fractures were stabilized angle-stable (73.6% NCP; 9.9% external fixator) and 16.5% non-angle-stable (DCP). Plate osteosynthesis (90.1%) was overall more common than external skeletal fixation (9.9%). The external fixator (17.4%) was used more frequently in the distal metaphyseal region than in the diaphyseal region (7.4%). 78% of the fractures were radiographed at least once at the clinic after the day of surgery. Fracture healing was confirmed radiographically for 52 fractures, at an average time of 15.58 ± 7.9 weeks post-operatively. Patient- (age, gender, body weight) and fracture-dependent (fracture localization, type, open vs. closed) factors did not significantly influence healing time. Fractures treated with external fixator tended to heal faster (11.33 ± 7.89 weeks) than after plate osteosynthesis (16.13 ± 7.87 weeks), but this difference was not significant. No significant differences in healing time were observed between fractures treated with nonangle-stable (DCP) and angle-stable plate osteosynthesis (NCP). This also applied to the comparison of non-angle-stable osteosynthesis (DCP) with angle-stable osteosynthesis (NCP and external fixator). The implants were removed from 54 fractures at the clinic. The calculated times until implant removal were significantly shorter for the external fixator cases (10.88 ± 5.08 weeks; p =0.036) than for plate osteosynthesis cases (16.69 ± 8.58 weeks). The detailed analyses did not reveal any significant differences in time until implant removal for non-angle-stable vs. angle-stable plate osteosynthesis and non-angle-stable vs. angle-stable osteosynthesis. The healing process was checked in 84 dogs (95.5%) with 84 fractures (92.3%) in the clinic. In 33 (39.3%) fractures (= patients), healing was accompanied by complications (some of them with multiple complications; 57 complications). The most common complications were osteomyelitis and bone resorption (13.1% each; n = 11), followed by fracture healing disorders (malunion, nonunion, delayed union; 10.7%; n = 9), implant failure (8.3%; n = 7), ankylosis of the carpal joint (2.4%; n = 2) and transient radial paralysis (1.2%; n = 1). In cases with osteomyelitis, antibiotic treatment was administered (n = 11), loose implants were removed (n = 2), autologous cancellous bone graft was packed into the fracture site and/or the construct was modified (n = 1). To treat bone resorption and non- or delayed union, the fractures were dynamized (n = 6), the construct was modified (n =1) and/or a cast bandage was applied after implant removal (n = 2). Wound infections were treated with antibiotics. In cases with implant failure, the construct was modified (n = 3), loose implants were removed (n = 2) or refixed (n = 1). For refractures after implant removal a new osteosynthesis procedure (n = 6) was performed. Ankylosis of the carpal joint and radial nerve paralysis were treated with physiotherapy. Malunions (all minor axial deviations) were not treated with corrective osteotomy and synostoses were not resected, as they did not cause any functional impairment. No significant correlations were found between patient-dependent factors (breed, age, gender, body weight) and the general risk of complications. However, the weight of the patients had a significant effect on the risk of developing osteomyelitis (p = < 0.001). Fracture-dependent (fracture localization, fracture type, open vs. closed) and treatmentdependent factors (time interval between trauma and osteosynthesis, duration of surgery, level of experience of the surgeon) were not significantly correlated with the complication rate. Likewise no significant differences in the risk of complication could be found in the analysis of the osteosynthesis procedures (plate vs. external fixator; DCP vs. NCP; DCP vs. NCP / external fixator) This also applied to dogs < 5 kg with distal metaphyseal fractures, which have previously been described in the literature as being particularly prone to complications. The functional outcome was evaluated for 88.6% of the dogs with 85.7% of the fractures. Limb function was evaluated as good (93.6%), satisfactory (5.1%) or unsatisfactory (1.3%) based on the degree of lameness (no lameness, low-, medium-, high-grade lameness). A good functional result was achieved in 92.8% of the plate osteosyntheses and in 100% of the external fixator osteosyntheses. In conclusion, angle-stable (NCP / fixator external) and non-angle-stable (DCP) osteosyntheses are ideally suited for the treatment of diaphyseal and distal metaphyseal radius/ulna fractures. However, decision making with regards to the most appropriate repair must be made individually on the basis of already available recommendations in the literature and the results of the present study, taking into account as many influencing factors as possible (patient, fracture, surgeon, owner compliance, costs), and any complications must be detected and treated early on if possible.