47 Patient-specific aiming device increases precision of guide wire placement in arthritic glenoids – an experimental study
Background: Correct positioning of the glenoid component is crucial for the success of total shoulder arthroplasty. Patient-specific aiming devices may improve the precision of glenoid component positioning. However, there are only few studies comparing a free-hand technique with a patient-specific aiming device.
Aim: The aim of this study was to compare the precision of glenoid guide wire positioning into different glenoid models using free-hand technique or a patient-specific aiming device.
Methods: Three experienced surgeons inserted 2.5 mm K-wires into 30 polyurethane cast glenoid models. There were 10 Walch A, 10 Walch B and 10 Walch C models. The freehand technique involved the use of a standard aiming device. The patient-specific guide was positioned on the “fulcrum axis” (anterior coracoid, posterolateral acromion) and the inferior tip of the glenoid. Precision was defined as deviation from the planned entry point, version and inclination.
Results: Statistically significant (p<0.01) smaller deviations for version and inclination angles were achieved by means of the patient-specific aiming device compared to free-hand in all glenoid types. For glenoid type B, more than 50% of the guide wires placed with the free-hand technique had a deviation of ≥11.9° compared to ≤2.2° with the aiming device. A larger scattering of the entry point was observed within the free-hand group in each glenoid, with a maximum in type C. In the freehand group, the probability of hitting the planned entry point decreased from glenoid types A to C.
Conclusion: In vitro, patient-specific aiming devices substantially enhanced the precision of guide wire placement compared to a free-hand technique. It seems likely that this benefit can be translated to the clinical situation, particularly for B and C type glenoids.