Three-Dimensional Scapular Kinematics in Patients with Reverse Total Shoulder Arthroplasty during Arm Motion

BACKGROUND: There have been few reports on altered kinematics of the shoulder after reverse total shoulder arthroplasty (RTSA). We investigated differences in 3-dimensional (3D) scapular motions assessed using an optical tracking system between RTSA treated shoulders and asymptomatic contralateral shoulders during arm motion. METHODS: Thirteen patients who underwent RTSA were assessed for active arm elevation in 2 distinct elevation planes (sagittal plane flexion and scapular plane abduction). Their mean age was 72 years (range, 69 to 79 years) and the mean follow-up was 24.4 months (range, 13 to 48 months). The dominant side was the right side in all the 13 patients, and it was also the side treated with RTSA. Scapular kinematics was recorded with an optical tracking system. The scapular kinematics and the scapulohumeral rhythm (SHR) of the RTSA shoulders and asymptomatic contralateral shoulders were recorded and analyzed during arm elevation. RESULTS: There were no significant differences in internal/external rotation and anterior/posterior tilting of the scapula between shoulders during arm motion (p > 0.05). However, upward rotation of the scapula differed significantly during arm motion (p = 0.035 for sagittal plane flexion; p = 0.046 for scapular plane abduction). There were significant differences in the SHR between the two shoulders (p = 0.016 for sagittal plane flexion; p = 0.021 for scapular plane abduction). CONCLUSIONS: The shoulder kinematics after RTSA showed significant differences from the contralateral asymptomatic shoulders. Increased upward rotation and decreased SHR after RTSA indicate that RTSA shoulders use more scapulothoracic motion and less glenohumeral motion to elevate the arm.

Accuracy Verification of Optical Tracking System for the Maxillary Displacement Estimation by Using of Triangulation

USE OF A COMPUTER NAVIGATION SYSTEM FOR OSTEOTOMIES IN THE ORTHOGNATHIC SURGERY: TECHNICAL NOTE

Development and application of stent-based image guided navigation system for oral and maxillofacial surgery / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study was to develop a stent-based image guided surgery system and to apply it to oral and maxillofacial surgeries for anatomically complex sites. MATERIALS AND METHODS: We devised a patient-specific stent for patient-to-image registration and navigation. Threedimensional positions of the reference probe and the tool probe were tracked by an optical camera system and the relative position of the handpiece drill tip to the reference probe was monitored continuously on the monitor of a PC. Using 8 landmarks for measuring accuracy, the spatial discrepancy between CT image coordinate and physical coordinate was calculated for testing the normality. RESULTS: The accuracy over 8 anatomical landmarks showed an overall mean of 0.56+/-0.16 mm. The developed system was applied to a surgery for a vertical alveolar bone augmentation in right mandibular posterior area and possible interior alveolar nerve injury case of an impacted third molar. The developed system provided continuous monitoring of invisible anatomical structures during operation and 3D information for operation sites. The clinical challenge showed sufficient accuracy and availability of anatomically complex operation sites. CONCLUSION: The developed system showed sufficient accuracy and availability in oral and maxillofacial surgeries for anatomically complex sites.

Quantitative analysis of the TMJ movement with a new mandibular movement tracking and simulation system / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study was to develop a system for the measurement and simulation of the TMJ movement and to analyze the mandibular movement quantitatively. MATERIALS AND METHODS: We devised patient-specific splints and a registration body for the TMJ movement tracking. The mandibular movements of the 12 subjects with facial deformity and 3 controls were obtained by using an optical tracking system and the patient-specific splints. The mandibular part was manually segmented from the CT volume data of a patient. Three-dimensional surface models of the maxilla and the mandible were constructed using the segmented data. The continuous movement of the mandible with respect to the maxilla could be simulated by applying the recorded positions sequentially. Trajectories of the selected reference points were calculated during simulation and analyzed. RESULTS: The selected points were the most superior point of bilateral condyle, lower incisor point, and pogonion. There were significant differences (P<0.05) between control group and pre-surgical group in the maximum displacement of left superior condyle, lower incisor, and pogonion in vertical direction. Differences in the maximum lengths of the right and the left condyle were 0.59+/-0.30 mm in pre-surgical group and 2.69+/-2.63 mm in control group, which showed a significant difference (P<0.005). The maximum of differences between lengths of the right and the left calculated during one cycle also showed a significant difference between two groups (P<0.05). CONCLUSION: Significant differences in mandibular movements between the groups implies that facial deformity have an effect on the movement asymmetry of the mandible.

Development of an Intra-operative Navigation System Using an Optical Tracking System / 대한정형외과연구학회지

PURPOSE: The purposes of this study were to develop an intraoperative navigation system as the first step toward image-guided surgery and robotic surgery, and to evaluate its accuracy. MATERIALS AND METHODS: The navigation system was composed of an optical tracking system (Polaris, Northern Digital) and a personal computer. The registration error and target localization error of fiducial registration and surface registration were measured using a phantom. Each of the errors was measured 30 times, and the average values and the standard deviations were calculated. RESULTS: The registration error was 0.84 +/- 0.28 mm at fiducial registration and 0.81 +/- 0.21 mm at surface registration. The target localization error was 1.54 +/- 0.34 mm at fiducial registration and 1.46 +/- 0.32 mm at surface registration. CONCLUSION: We have developed an intraoperative navigation system using an optical tracker, and could assure ourselves that its accuracy is adequate for many orthopaedic surgeries. However, it still requires improvement in the accuracy and development of specific software and instruments for various operations.