Biomechanical behavior analysis of four types of short implants with different placement depths using the finite element method.

STATEMENT OF PROBLEM: The clinical application of short implants has been increasing. However, studies on the marginal bone loss of short implants are sparse, and clinicians often choose short implants based on their own experience rather than on scientific information. PURPOSE: The purpose of this finite element analysis study was to evaluate the microstrain-stress distribution in the peri-implant bone and implant components for 4 types of short implants at different placement depths of platform switching. MATERIAL AND METHODS: By using short implants as prototypes, 4 short implant models were 1:1 modeled. The diameter and length of the implants were 5×5, 5×6, 6×5, and 6×6 mm. The restoration was identical for all implants. Three different depths of implant platform switching were set: equicrestal, 0.5-mm subcrestal, and 1-mm subcrestal. The models were then assembled and assigned an occlusal force of 200 N (vertical or 30-degree oblique). A finite element analysis was carried out to evaluate the maximum equivalent elastic strain and von Mises stress in the bone and the stress distribution in the implant components. RESULTS: The 5×5 implant group showed the largest intraosseous strain (21.921×103 µÎµ). A 1-mm increase in implant diameter resulted in a 17.1% to 37.4% reduction in maximum intraosseous strain when loaded with oblique forces. The strain in the bone tended to be much smaller than the placement depth at the equicrestal and 0.5-mm subcrestal positions than that at the 1-mm subcrestal position, especially under oblique force loading, with an increase of approximately 37.4% to 81.8%. In addition, when the cortical bone thickness was less than 4 mm, 5×6 implants caused significantly higher intraosseous stresses than 6×6 implants. CONCLUSIONS: Large implant diameters, rather than long implants, led to reduced intraosseous strain, especially under oblique loading. Regarding the implant platform switching depth, the short implant showed small intraosseous strains when the platform switching depth was equicrestal or 0.5-mm subcrestal.

An implant-supported overdenture for a mandibular defect after tumor resection guided by 3-dimensional finite element analysis: A clinical report.

This clinical report describes the rehabilitation of a mandibular defect after tumor resection with an implant-supported overdenture and the attachment selection as guided by 3-dimensional finite element analysis. Autologous bone grafting was declined by the patient who demanded the restoration of lateral appearance and mastication function. Three implants were placed based on the condition of the bone, and a satisfactory definitive prosthesis was provided that corresponded with the results of the finite element analysis.

Single-stage debridement via autogenous iliac bone graft through the OLIF corridor and lateral fixation in treating spontaneous single-level lumbar pyogenic spondylodiscitis.

BACKGROUND: The aim of the present study was to investigate the efficacy and safety of mini-open oblique debridement and lumbar interbody fusion combined with lateral screw fixation for treating single-level pyogenic spondylodiscitis. METHODS: Twelve patients with single-level lumbar pyogenic spondylodiscitis underwent OLIF combined with lateral screw fixation were analyzed. Patients underwent follow-up for 12 to 24 months. The clinical characteristics, etiological examinations, operative time, intraoperative blood loss, Oswestry Disability Index (ODI), visual analog scale score (VAS), postoperative complications, and the bony fusion rate were recorded. RESULTS: The mean follow-up period of time was 14.8 months. The average operative time and intra-operative blood loss were 129.0 ± 19.76 min and 309.2 ± 92.96 mL, respectively. No severe intra-operative complications were observed during surgery, except in 1 case that develops abdominal pain and distension after surgery, 2 cases that develop left-sided transient thigh pain/numbness and 8 cases that complains of donor site (iliac crest) pain. All of these symptoms disappeared 8 weeks after surgery. Tissue sample cultures were obtained from all patients intraoperatively and four (33.3%) were positive, including 2 with Staphylococcus aureus, 1 with Staphylococcus epidermidis, and 1 with Escherichia coli. During an average of 22.5 ± 2.1 days (range, 14-29 days) after surgery, WBC, CPR, and ESR levels in all patients had returned to normal. All patients were pain free with no recurring infection. Solid bony fusions were observed in all cases within 6 months, including 10 with I grade fusion, 2 with II grade fusion according to the classification suggested by Burkus et al. No fixation failure was observed during follow up and solid bony fusions were observed in all 12 patients at finally follow-up. A significant postoperative increase was also observed in the mean segmental height and lordosis (P < 0.05), followed by a slight decrease of segmental height and lordosis at final follow-up. At the final follow up, the mean VAS (1.5 ± 0.6) and ODI (18.9 ± 7.6) were significantly lower than VAS (8.4 ± 2.7) and ODI (71.2 ± 16.5) before surgery (P < 0.01). CONCLUSION: Single-stage debridement with autogenous iliac bone graft through the OLIF corridor and lateral fixation was a feasible surgical approach in our consecutive 12 cases of pyogenic spondylitis.

Spinal Metastatic Melanoma with Unknown Primary Lesions Presenting as Radiculopathy: Case Report and Literature Review.

BACKGROUND: Metastatic malignant melanoma of the spine is rare, while the spinal metastatic melanoma with unknown primary lesions presenting as radiculopathy is even rarer. Summarizing and analyzing this disease can provide insight into disease development and allow optimization of clinical management. CASE DESCRIPTION: A 55-year-old male patient was admitted to our institution presenting with lower back pain that had persisted for 3 years. It was aggravated, with radiating pain in bilateral lower extremities lasting 2 weeks. Neurologic examination revealed bilateral L5 motor deficit with paresis. Radiologic findings showed an irregularly destructive lesion of the L5 vertebral body, and the lesion extended dorsally, obstructing the spinal canal. The patient underwent complete resection of the L5 vertebral tumor with titanium mesh implantation and posterior fusion and instrumentation from L3-S2. The pathologic diagnosis after surgery was malignant melanoma. No obvious primary lesion was detected anywhere on the skin surface, mucosa, and retina. A postoperative positron emission tomography-computed tomography scan of the whole body displayed no abnormal uptake in other parts of the body. However, the patient didn't receive any chemotherapy or radiotherapy. Five months after operation, the tumor recurred and metastasis was detected in other sites. CONCLUSIONS: Although spinal metastatic melanoma with unknown primary lesions presenting as radiculopathy is rare, effective management and treatment of these patients remains an important challenge for surgeons. Surgical resection can alleviate patients' chief complaints and improve their quality of life. However, it may not prolong the survival period and improve the prognosis. Postoperative radiotherapy and/or chemotherapy may be needed.

Laparoscopic Acetabular Fracture Fixation after Three-dimensional Modelling and Printing.

Current surgical treatment of acetabular fractures is open reduction and internal fixation and requires a large incision resulting in considerable blood loss and a potentially long duration of recovery. We report a case of an acetabular fracture that received laparoscopic internal fixation after three-dimensional (3D) modelling and printing of the acetabulum. A 43 year old male fell from a height of 3 m resulting in a right acetabulum anterior column fracture. Thin section computed tomography scanning with 0.6 mm increments and subsequent 3D reconstruction was performed, and a 3D model of the acetabulum and fracture was printed. The steel reconstruction plate was prebent in vivo and placed into the optimized position based on the 3D modelling and the optimized insert orientation and measured screw length were determined. The fracture was reduced and the plate placed laparoscopically without complications, and the patient had excellent functional recovery. Acetabular fractures are complex injuries, and while minimally invasive surgical techniques are used in many fields, they are not common for the treatment of acetabular fractures. 3D modelling is commonly used in medicine, and although 3D printing is used in some fields, it has not found widespread use in orthopedics.

A combination of three-dimensional printing and computer-assisted virtual surgical procedure for preoperative planning of acetabular fracture reduction.

OBJECTIVE: Treatment of acetabular fractures remains one of the most challenging tasks that orthopaedic surgeons face. An accurate assessment of the injuries and preoperative planning are essential for an excellent reduction. The purpose of this study was to evaluate the feasibility, accuracy and effectiveness of performing 3D printing technology and computer-assisted virtual surgical procedures for preoperative planning in acetabular fractures. We hypothesised that more accurate preoperative planning using 3D printing models will reduce the operation time and significantly improve the outcome of acetabular fracture repair. METHODS: Ten patients with acetabular fractures were recruited prospectively and examined by CT scanning. A 3-D model of each acetabular fracture was reconstructed with MIMICS14.0 software from the DICOM file of the CT data. Bone fragments were moved and rotated to simulate fracture reduction and restore the pelvic integrity with virtual fixation. The computer-assisted 3D image of the reduced acetabula was printed for surgery simulation and plate pre-bending. The postoperative CT scan was performed to compare the consistency of the preoperative planning with the surgical implants by 3D-superimposition in MIMICS14.0, and evaluated by Matta's method. RESULTS: Computer-based pre-operations were precisely mimicked and consistent with the actual operations in all cases. The pre-bent fixation plates had an anatomical shape specifically fit to the individual pelvis without further bending or adjustment at the time of surgery and fracture reductions were significantly improved. Seven out of 10 patients had a displacement of fracture reduction of less than 1mm; 3 cases had a displacement of fracture reduction between 1 and 2mm. CONCLUSIONS: The 3D printing technology combined with virtual surgery for acetabular fractures is feasible, accurate, and effective leading to improved patient-specific preoperative planning and outcome of real surgery. The results provide useful technical tips in planning pelvic surgeries.

Evaluation of three-dimensional printing for internal fixation of unstable pelvic fracture from minimal invasive para-rectus abdominis approach: a preliminary report.

OBJECTIVE: The aim of this study is to evaluate the efficacy and feasibility of three-dimensional printing (3D printing) assisted internal fixation of unstable pelvic fracture from minimal invasive para-rectus abdominis approach. METHODS: A total of 38 patients with unstable pelvic fractures were analyzed retrospectively from August 2012 to February 2014. All cases were treated operatively with internal fixation assisted by three-dimensional printing from minimal invasive para-rectus abdominis approach. Both preoperative CT and three-dimensional reconstruction were performed. Pelvic model was created by 3D printing. Data including the best entry points, plate position and direction and length of screw were obtained from simulated operation based on 3D printing pelvic model. The diaplasis and internal fixation were performed by minimal invasive para-rectus abdominis approach according to the optimized dada in real surgical procedure. Matta and Majeed score were used to evaluate currative effects after operation. RESULTS: According to the Matta standard, the outcome of the diaplasis achieved 97.37% with excellent and good. Majeed assessment showed 94.4% with excellent and good. The imageological examination showed consistency of internal fixation and simulated operation. The mean operation time was 110 minutes, mean intraoperative blood loss 320 ml, and mean incision length 6.5 cm. All patients have achieved clinical healing, with mean healing time of 8 weeks. CONCLUSION: Three-dimensional printing assisted internal fixation of unstable pelvic fracture from minimal invasive para-rectus abdominis approach is feasible and effective. This method has the advantages of trauma minimally, bleeding less, healing rapidly and satisfactory reduction, and worthwhile for spreading in clinical practice.

[Internal fixation surgery planning for complex tibial plateau fracture based on digital design and 3D printing].

OBJECTIVE: To investigate the application of 3D printing and digital technology in preoperative assessment and planning of internal fixation surgery for complex tibial plateau fracture. METHODS: Complex tibial plateau fractures and commonly used plates for tibial plateau were imaged using computed tomography (CT) to reconstruct the 3D fracture and plate models. The 3D models were used to perform virtual reduction and preoperative planning of internal fixation surgery with the most appropriate plates assisted by the 3D library of plates. According to the optimal plan, the 3D physical models of tibial plateau fractures and plates were 3D printed to simulate internal fixation operation. The effects of internal fixation were compared between the virtual surgery and the simulated surgery based on the 3D models. RESULTS: The effects of internal fixation in the simulated surgery based on the 3D models were consistent with those of the virtual surgery. No significant difference was found in the screw length between the two surgeries. CONCLUSION: The combination of 3D printing and digital design can improve the effects of internal fixation for complex tibial plateau fractures.

Improved accuracy of 3D-printed navigational template during complicated tibial plateau fracture surgery.

This study was aimed to improve the surgical accuracy of plating and screwing for complicated tibial plateau fracture assisted by 3D implants library and 3D-printed navigational template. Clinical cases were performed whereby complicated tibial plateau fractures were imaged using computed tomography and reconstructed into 3D fracture prototypes. The preoperative planning of anatomic matching plate with appropriate screw trajectories was performed with the help of the library of 3D models of implants. According to the optimal planning, patient-specific navigational templates produced by 3D printer were used to accurately guide the real surgical implantation. The fixation outcomes in term of the deviations of screw placement between preoperative and postoperative screw trajectories were measured and compared, including the screw lengths, entry point locations and screw directions. With virtual preoperative planning, we have achieved optimal and accurate fixation outcomes in the real clinical surgeries. The deviations of screw length was 1.57 ± 5.77 mm, P > 0.05. The displacements of the entry points in the x-, y-, and z-axis were 0.23 ± 0.62, 0.83 ± 1.91, and 0.46 ± 0.67 mm, respectively, P > 0.05. The deviations of projection angle in the coronal (x-y) and transverse (x-z) planes were 6.34 ± 3.42° and 4.68 ± 3.94°, respectively, P > 0.05. There was no significant difference in the deviations of screw length, entry point and projection angle between the ideal and real screw trajectories. The ideal and accurate preoperative planning of plating and screwing can be achieved in the real surgery assisted by the 3D models library of implants and the patient-specific navigational template. This technology improves the accuracy and efficiency of personalized internal fixation surgery and we have proved this in our clinical applications.