STUDY DESIGN: Experimental.
SAMPLE POPULATION: Fourteen equine cadaver limbs/horses.
METHODS: Simulated fractures were repaired with 2 lag screws under 4-Nm insertion torque (linear repair). Computed tomography (CT) imaging was performed with the leg unloaded and loaded to forces generated while walking. The fracture repair was revised to include 3 lag screws placed with the same insertion torque (triangular repair) prior to CT. The width of the fracture gap was assessed qualitatively by 2 observers and graded on the basis of gap measurements relative to the average voxel size at dorsal, mid, and palmar P1 sites. Interobserver agreement was assessed with Cohen's κ. The effect of repair type, loading condition, and measurement site on fracture gap grades was evaluated by using Kendall's τ-b correlation coefficients and paired nonparametric tests. Significance was set at P ≤ .05.
RESULTS: Agreement between loading and fracture gap widening was fair in triangular (κ = 0.53) and excellent in linear (κ = 0.81) repairs. Loading resulted in fracture gap distraction in linear repairs (Plinear = .008). Triangular repairs reduced fractures better irrespective of loading (Punloaded = .003; Ploaded
OBJECTIVE: The aim of this study was to assess the safety and pullout strength of medial, partial nonthreaded thoracic pedicle screws compared with conventional screws.
SUMMARY OF BACKGROUND DATA: The perforation rate of the pedicle screws has been reported as high as 41%. Nerve injury and irritation can result from the compression of malpositioned screw on neural structures.
METHODS: Ten fresh cadavers were studied. Screws, 5.0 and 6.0 mm, were inserted from T1 to T6 and T7 to T12, respectively. Pedicle perforations and fractures were recorded upon screw insertion and final positioning (nonthreaded portion facing medially) after a wide laminectomy. Pullout strength of novel and conventional screws were then tested using an Instron machine in an artificial bone substitute.
RESULTS: A total of 240 thoracic pedicle screws were inserted. Of them, 88.8% (213 screws) were fully contained during screw insertion. There were 5.0% (12 screws) grade 1 medial perforations and 6.2% (15 screws) grade 1 lateral perforations during screw insertion. Upon final positioning, 93.8% (225 screws) were fully contained. All grade 1 medial perforations, which occurred during insertion, were converted to grade 0. No dural or nerve root injuries occurred. Pedicle split fractures were noted in 6.7% (16 screws). The use of medial, partial nonthreaded screws reduced the overall perforation rate from 11.2% to 6.2%. The mean pullout load for the 5 mm fully threaded screw versus medial, partial nonthreaded was 1419.3±106.1 N (1275.8-1538.8 N) and 1336.6±44.2 N (1293.0-1405.1 N) respectively, whereas 6 mm pullout load averaged 2126.0±134.8 N (1986.3-2338.3 N) and 2036.5±210.0 N (1818.4-2355.9 N). The difference was not statistically significant.
CONCLUSIONS: The use of medial, partial nonthreaded pedicle screws reduced the medial perforation rate from 5.0% to 0%; however, the pullout strength was not significantly reduced. The use of this novel screw can potentially reduce the incidence of nerve injury or irritation after medial pedicle perforations.
METHODS: Twenty six donkey cadavers of mixed, age, sex and use presented for reasons unrelated to disease of the guttural pouch were subjected to carotid and cerebral angiography using rotational angiography. Rotational angiographic and 3 dimensional multiplanar reconstructive (3D-MPR) findings were verified with an arterial latex casting technique followed by dissection and photography.
RESULTS: The following variations of the carotid arterial tree were identified: [1] the internal carotid and occipital arteries shared a common trunk, [2] the linguofacial trunk originated from the common carotid artery causing the common carotid artery to terminate as four branches, [3] the external carotid artery was reduced in length before giving rise to the linguofacial trunk, mimicking the appearance of the common carotid artery terminating in four branches, [4] the internal carotid artery originated at a more caudal position from the common carotid artery termination.
CONCLUSION: Veterinarians should be aware that considerable variation exists in the carotid arterial tree of donkeys and that this variation may differ markedly from that described in the horse.