A comparative study on the accuracy of pedicle screw placement assisted by personalized rapid prototyping template between pre- and post-operation in patients with relatively normal mid-upper thoracic spine.

PURPOSE: The aim of this study was to assess the accuracy of rapid prototyping drill template technique for placing pedicle screws in the mid-upper thoracic vertebrae in clinics. METHODS: 151 consecutive patients underwent thoracic instrumentation and fusion for a total of 582 pedicle screws placed in the mid-upper thoracic vertebrae. Using computer software, the authors constructed drill templates that fit onto the posterior elements of the mid-upper thoracic vertebrae with drill guides designed to instrument the pedicles. The start point and three dimensional location of the planned and inserted screws were measured and compared. RESULTS: Grading of the CT scans revealed 559 (96.1 %) out of 582 screws completely within the desired pedicle. The direction of pedicle violation included 5 medial, 2 airball, and 16 lateral. The paired t test suggested that these results were statistically significant in more than half of the locations (T1-left-TA(P = 0.024), T2-left-SA(P = 0.031), T3-left-SA(P = 0.014), T4-left-TA(P = 0.004), T5-left-TA(P = 0.034), T7-left-TA(P = 0.000). T1-right-TA(P = 0.049), T2-right-TA(P = 0.044), T3-right-TA(P = 0.014), T5-right-TA(P = 0.013)). The paired t-test suggested that these results were statistically significant at several locations (T4-left-Δy(P = 0.041), T5-left-Δx(P = 0.016), T3-right-Δy(P = 0.015)). CONCLUSION: Use of a rapid prototyping drill template to assist in the placement of mid and upper thoracic pedicle screws may lead to increased accuracy. This patient specific technology must be combined with an understanding of the patients' anatomy and carefully secured to the posterior elements intraoperatively to avoid nerve or vascular complications.

[Application of three-dimensional virtual technology in mandibular defects reconstruction with free fibular flap].

PURPOSE: To present a method for mandibular defects reconstruction with free fibular flap by three-dimensional virtual technology. METHODS: In 11 patients (8 with ameloblastomas, 1 with ossifying fibroma, 2 with carcinoma of the mandibular gingiva ), three-dimensional virtual technology was simulated with software. The osteotomies were translated into rapid prototyping guides. The solid model of the mandible and the surgical guides were the same as the full size and the shape, and made by using rapid prototyping machine. During operation, the bridging plate could be pre-bended on the repaired mandibular model. One group resected the diseased mandibular according to the model of the osteotomy which was planned before operation, the other group used auxiliary guide for accurate osteotomy of the fibula bone with contact pedicle. The fibular segments were reshaped and fixed with prefabricated titanium plate, and transplanted into the defect for vascular anastomosis. RESULTS: All the bone flaps and osteocutaneous flaps survived. During operation, the fibula flap could be cut in appropriate length. Cutting, remodeling and reposition of the fibula could be accelerated by surgery guides. Postoperative follow-up was 1 to 24 months. Imaging examination showed that the shape of mandible and mandibular angle were good, and the temporomandibular joint and occlusion returned to normal. CONCLUSIONS: Three-dimensional virtual technology is useful in reconstruction of mandibular defect with vascularized fibular flap.

Deviation analysis of atlantoaxial pedicle screws assisted by a drill template.

Although C1-C2 pedicle screw fixation provides an excellent fusion rate and rigid fixation, this technique has a potential risk. It is essential to develop an accurate screwing method to avoid this neurovascular injury. To develop and validate the accuracy of a novel navigational template for C1-C2 pedicle screw placement in cadaveric specimens, computed tomography scans with 1-mm-wide cuts were obtained of 32 cadaveric cervical specimens. The authors developed 64 three-dimensional full-scale templates that were created by computer modeling with a rapid prototyping technique from the computed tomography data. Drill templates were constructed with a custom trajectory for each level and side. The drill templates were used to guide the establishment of a pilot hole for screw placement. The average distances between ideal and actual entry points of the C1 pedicle screws in the x, y, and z axes were 0.16±0.46 mm, 0.11±0.52 mm, and -0.01±0.54 mm, respectively, on the left side and 0.11±0.49 mm, 0.01±0.56 mm, and -0.09±0.59 mm, respectively, on the right side. The average distances between ideal and actual entry points of the C2 pedicle screws in the x, y, and z axes were 0.05±0.54 mm, 0.20±0.59 mm, and -0.06±0.58 mm, respectively, on the left side and 0.17±0.55 mm, 0.1±0.58 mm, and -0.01±0.49 mm, respectively, on the right side. Factors related to human error and imprecision are responsible for most malpositioning of instrumentation. The rapid prototyping drill template for C1-C2 screw placement is described to minimize human error, although it introduces error related to computer software and variation in manufacturing.

Deviation analysis of C1-C2 transarticular screw placement assisted by a novel rapid prototyping drill template: a cadaveric study.

STUDY DESIGN: Cadaveric study. OBJECTIVE: The aim of this study was to develop and validate the accuracy of a novel navigational template for C1-C2 transarticular screw (C1C2TAS) placement in cadaveric specimens. SUMMARY OF BACKGROUND DATA: Currently, C1C2TASs are primarily positioned using a free-hand technique or under fluoroscopic guidance. Screw placement is challenging owing to the small size of the C2 isthmus, which places technical demands on the surgeon. Screw insertion carries a potential risk of neurovascular injury, magnifying the importance of using a precise technique for screw insertion. MATERIALS AND METHODS: Computed tomography (CT) scans with 0.625-mm wide cuts were obtained from the 32 cadaveric cervical specimens. The CT data were imported into a computer navigation system. We developed 32 three-dimensional drill templates, which were created by computer modeling using a rapid prototyping technique based on the CT data. We constructed drill templates using a custom trajectory for each level and side based on specimen anatomy. The drill templates were used to guide establishment of a pilot hole for screw placement. The entry point and angular direction of the intended screw positions and inserted screw positions were measured by comparing postoperative and preoperative images after the coordinate axes were synchronized. RESULTS: The average displacement of the entry point of the left and right C1C2TAS in the x-, y-, and z-axis was 0.13±0.90 mm, 0.50±1.50 mm, and -0.22±0.71 mm on the left, and 0.21±1.03 mm, 0.46±1.55 mm, and -0.29±0.58 mm on the right. There was no statistically significant difference in entry point and direction between the intended and actual screw trajectory. CONCLUSIONS: The small deviations seen are likely due to human error in the form of small variations in the surgical technique and use of software to design the prototype. This technology improves the safety profile of this fixation technique and should be further studied in clinical applications.

[A novel computer-assisted drill template for atlantoaxial pedicle screw placement:a cadaveric experimental study].

OBJECTIVE: To validate the accuracy of atlanto-axial pedicle screw placement with a rapid prototyping drill guide template and analyze the factors of screw deviations. METHODS: Computed tomography (CT) scan was performed in 16 cervical specimens. And three-dimension cervical vertebrae was reconstructed by Mimics software. The ideal trajectory for atlanto-axial pedicle screws was designed with a complementary basal template for posterior surface of atlanto-axial corresponding anatomical structure. Then drill guide template was materialized in a rapid prototyping machine. These templates were used during operation. The entry point and ideal and actual trajectories were measured after matching the positions of preoperative and postoperative specimens at designated coordinate axis. RESULTS: The average displacement of entry point of left and right C1 pedicle screw in x, y, z axis was (0.14 ± 0.59),(0.31 ± 1.32), (0.27 ± 0.68), (0.23 ± 0.55), (0.43 ± 1.21) and (0.30 ± 0.72) mm. And the average displacement of entry point of left and right C2 pedicle screw in m, n, p axis was (0.25 ± 0.85), (0.52 ± 1.52), (-0.27 ± 0.67), (0.44 ± 0.87), (0.38 ± 1.48), (-0.14 ± 0.62) mm.No statistically significant difference existed (P > 0.05) in deviation of entry point and between ideal and actual trajectories. CONCLUSION: Both human handling and inherent hardware and software factors are main reasons for a deviation of C1-C2 pedicle screw placement assisted by a rapid prototyping drill guide template.Ease of operation and individualized design are the advantages of drill guide template so as to greatly improve the precision of screw placement and reduce screw deviation.

Deviation analysis of C2 translaminar screw placement assisted by a novel rapid prototyping drill template: a cadaveric study.

PURPOSE: The goal of this study is to evaluate the accuracy of patient-specific CT-based rapid prototype drill templates for C2 translaminar screw insertion. METHODS: Volumetric CT scanning was performed in 32 cadaveric cervical spines. Using computer software, the authors constructed drill templates that fit onto the posterior surface of the C2 vertebrae with drill guides to match the slope of the patient's lamina. Thirty-two physical templates were created from the computer models using a rapid prototyping machine. The drill templates were used to guide drilling of the lamina and post-operative CT images were obtained. The entry point and direction of the planned and inserted screws were measured and compared. RESULTS: Sixty-four C2 translaminar screws were placed without violating the cortical bone of a single lamina. The bilateral average transverse angle of intended and actual screw for C2TLS was 56.60 ± 2.22°, 56.38 ± 2.51°, 56.65 ± 2.24°, 56.39 ± 2.45°. The bilateral mean coronal angle of the planned and actual screw for C2TLS was 0°, 0°, -0.07 ± 0.32°, 0.12 ± 0.57°. The average displacement of the entry point of the superior and inferior C2TLS in the x, y, z axis was 0.27 ± 0.85, 0.49 ± 1.46, -0.28 ± 0.69, 0.43 ± 0.88, 0.38 ± 1.51, 0.23 ± 0.64 mm. CONCLUSION: The small deviations seen are likely due to human error in the form of small variations in the surgical technique and use of software to design the prototype. This technology improves the safety profile of this fixation technique and should be further studied in clinical applications.

Dermatoglyphics from all Chinese ethnic groups reveal geographic patterning.

Completion of a survey of dermatoglyphic variables for all ethnic groups in an ethnically diverse country like China is a huge research project, and an achievement that anthropological and dermatoglyphic scholars in the country could once only dream of. However, through the endeavors of scientists in China over the last 30 years, the dream has become reality. This paper reports the results of a comprehensive analysis of dermatoglyphics from all ethnic groups in China. Using cluster analysis and principal component analysis of dermatoglyphics, it has been found that Chinese populations can be generally divided into a southern group and a northern group. Furthermore, there has been considerable debate about the origins of many Chinese populations and about proper assignment of these peoples to larger ethnic groups. In this paper, we suggest that dermatoglyphic data can inform these debates by helping to classify a Chinese population as a northern or southern group, using selected reference populations and quantitative methods. This study is the first to assemble and investigate dermatoglyphics from all 56 Chinese ethnic groups. It is fortunate that data on population dermatoglyphics, a field of physical anthropology, have now been collected for all 56 Chinese ethnic groups, because intermarriage between individuals from different Chinese ethnic groups occurs more frequently in recent times, making population dermatoglyphic research an ever more challenging field of inquiry.