The effect of an aiming device on the accuracy of humeral transcondylar screw placement.

OBJECTIVES: (1) To evaluate the accuracy of an aiming device on placement of humeral transcondylar screws compared to fluoroscopic methods. (2) To compare experience level on outcome. STUDY DESIGN: Randomized, match pair, prospective ex-vivo study. SAMPLE POPULATION: A total of 68 dogs. METHODS: Canine cadaveric forelimbs were randomly assigned to either aiming device or fluoroscopic-guided groups, and to diplomate or resident. Digital radiography was used to evaluate screw trajectory deviation and eccentricity on the humeral condyle. Procedure time, outcome based on experience, and complications were recorded. RESULTS: The aiming device screw trajectory angle was decreased in the right limb (1.9 ± 1.1°) compared with the left (3.6 ± 1.1°, p = .0178), and compared to fluoroscopy (3.4 ± 1.1° p = .0128). There was no difference between leg laterality with fluoroscopy (p = .9979). Trajectory angle was increased with resident versus diplomate (3.4 ± 1.1° and 2.5 ± 1.1° respectively, p = .0366). Eccentricity deviation was decreased using fluoroscopy versus aiming device (3.1 ± 0.36 mm, 4.2 ± 0.36 mm, respectively, p = .0017). The risk of joint involvement was 8 times greater in aiming device groups, though not significant (p = .0575). Significant complications included increased drill attempts in fluoroscopic groups (p = .0237). CONCLUSION: The aiming device provided accurate placement of transcondylar screws, in terms of both position on the condyle and trajectory angle. Results were similar to fluoroscopic-guided method. CLINICAL SIGNIFICANCE: An aiming device is an acceptable means of placing humeral transcondylar screws. The use of the aiming device had an eight times increased risk of joint involvement compared to fluoroscopy.

Evaluation of a Fixed-Angle Wedge Osteotomy Guide.

OBJECTIVE: The aim of this study was to evaluate a fixed-angle cutting guide designed to aid in the performance of coplanar wedge osteotomies using a proximal tibial cranial closing wedge ostectomy model. STUDY DESIGN: A 30-degree cranial closing wedge ostectomy was created using canine tibia models with either a standard template (method T) or a wedge osteotomy guide (method G) by two surgeons. One surgeon was experienced with both procedures, and one surgeon had no previous experience with the wedge guide. The ostectomy wedges were evaluated for wedge angle, using a digital protractor, and coplanarity by using digital photographs and screen-measuring software. RESULTS: The mean (standard deviation) wedge angles of the T and G groups were 28.16 (1.33) and 28.4 degrees (1.46) respectively. The mean (standard deviation) divergence angles of the T and G groups were 3.21 (1.86) and 2.22 degrees (1.69) respectively. The measured reference angles of the template and cut guides were 31.27 and 29.60 degrees respectively. Individual and cross-surgeon analysis of outcomes found no significant differences when comparing wedge angle or coplanarity with either method regardless of surgeon experience. However, mean wedge angle of group G was significantly closer to the measured reference angles than group T (p < 0.01). CONCLUSION: Use of a fixed-angle surgical wedge guide was successful in consistently producing accurate closing wedge ostectomies regardless of surgeon experience. These results show that use of the guide is a valid method for performing wedge ostectomies.