Three-dimensional volumetric evaluation of root resorption in maxillary anteriors following en-masse retraction with varying force vectors - a randomized control trial.

BACKGROUND: Root resorption in orthodontics is associated with direction and magnitude of force application as primary etiological factors. Well-controlled trials that utilize three-dimensional segmentation to detect volumetric changes in tooth structure are required to assess the quantitative nature of root resorption. OBJECTIVE: To assess the severity of root resorption (RR) during retraction of maxillary anteriors with three different force vectors (with and without skeletal anchorage) via cone-beam computed tomography (CBCT) superimpositions. TRIAL DESIGN: Three-arm parallel randomized clinical trial (RCT). MATERIALS AND METHODS: Forty-two (16 males, 26 females) patients, (17-28 years), in permanent dentition with bimaxillary protrusion were randomly allocated to three groups of 14 patients each using block randomization (1:1:1 ratio) and allocation concealment. En-masse anterior retraction post first premolar extractions was carried out with modified force vectors in the three groups based on anchorage type [Molar, Mini-implant and Infrazygomatic crest (IZC) bone screws]. Volumetric root loss and linear dimensional changes were blindly assessed on initial (T0) and final (T1, end of space closure) CBCT scans. Normality distribution of values was done using Shapiro-Wilk's test. ANOVA and Post-hoc Tukey HSD test were done to compare measurements between groups at significance levels (P < .05). RESULTS: Forty patients were analysed (14, 14, and 12 in three groups). Significant volumetric loss was noted in all groups. Central incisors demonstrated a significant reduction in IZC group (81.5 ± 21.1 mm3 ) compared to conventional (50.1 ± 26.5 mm3 ) and mini-implant groups (76.1 ± 27.6 mm3 ). Canines demonstrated a significant reduction in mini-implant group (108.9 ± 33.9 mm3 ) compared to conventional (68.8 ± 42.5 mm3 ) and IZC groups (103.1 ± 29.1 mm3 ). Regarding linear parameters, central incisors and canines revealed significant root length reduction in both skeletal anchorage groups. Lateral incisors showed no significant changes between groups. CONCLUSIONS: Intrusive force vectors generated during skeletally anchored retraction can predispose anteriors to an increased risk of resorption. Greater loss of root volume was noted in the centrals and canines when retracted with skeletal anchorage. LIMITATIONS: Small sample size and variations during CBCT acquisition. HARMS: Low-dose CBCT scans were taken at T0 and T1 treatment intervals.

Cancellous bone graft from the distal radius and headless screw fixation for unstable scaphoid waist nonunion.

PURPOSE: Cancellous bone harvested from the distal radius has been used in various hand surgeries, but studies on its use in scaphoid waist nonunions are insufficient. We investigated the usefulness of cancellous bone graft from the distal radius and headless screw fixation in unstable scaphoid waist nonunion. METHODS: Thirty-one patients who underwent cancellous bone graft from the distal radius and headless screw fixation for unstable scaphoid waist nonunion with follow-up for at least 1 year were included. Bone union time, the number of patients with bone union at six and 12 weeks, total number of patients with bone union at last follow-up, and bone union on the computed tomography (CT) image at postoperative six weeks were evaluated. Further, pre- and postoperative radiological measurements, such as scaphoid length and height, lateral intra-scaphoid angle, and height-to-length ratio, and functional outcomes were compared. Additionally, inter-observer reliability of radiologic parameters was checked. RESULTS: Bone union was achieved in 29 patients. There were two nonunions (6.5%). Bone union time was 10.7 (range, 6-26) weeks. Eighteen (58%) and 25 patients (80.6%) were diagnosed with bone union on the plain radiographs at six and 12 weeks, respectively. Twenty-two patients (71%) were diagnosed with bone union on CT performed at six weeks. Radiological measurements and functional outcomes improved postoperatively. The scaphoid length showed good inter-observer agreement. CONCLUSIONS: In treating unstable scaphoid waist nonunion, cancellous bone graft from the distal radius and headless screw fixation achieved 93.5% union and improved radiological measurements as well as functional outcomes.

Relationship between thread depth and fixation strength in cancellous bone screw.

BACKGROUND: Clarifying the effect of each parameter of screw design on its fixation strength is critical in the development of any type of screw. The purpose of this study was to clarify the relationship between the thread depth and fixation strength of metal screws for cancellous bone. METHODS: Nine types of custom-made screws with the only changed variable being the thread depth were manufactured. Other elements were fixed at a major diameter of 4.5 mm, a thread region length of 15 mm, a pitch of 1.6 mm, and a thread width of 0.20 mm. The pull-out strength and insertion torque of each screw were measured for each of two foam-block densities (10 or 20 pcf). The correlation between the thread depth of the screw and the mechanical findings were investigated with single regression analysis. RESULTS: Regardless of the foam-block density, the pull-out strength significantly increased as the thread depth increased from 0.1 mm to 0.4 mm; after that, the increase was more gradual (p < 0.01, respectively). The relationship between the thread depth and insertion torque was similar. In addition, the insertion torque tended to be more strongly affected by screw depth than the pull-out strength (2.6 times at 20 pcf and 1.4 times at 10 pcf). CONCLUSIONS: The pull-out strength of 4.5-mm-diameter metal screws in a cancellous bone model was found to be biphasic, although linearly correlated with the change in screw depth in both phases. The boundary of the correlation was 0.4 mm regardless of the density of the bone model, with the effect of screw depth on pull-out strength beyond that being small in comparison.

Topographic localization of the sacroiliac joint and superior gluteal artery branches on the posterolateral ilium.

Latrogenic vascular injuries at the posterior ilium during sacroiliac screw placements are not uncommon. Though intra-operative imaging reduces the risk of such injuries, anatomical localization of the sacral segments using discrete topographical landmarks is not currently available. This descriptive study proposes the use of an anatomical grid system to localize the sacroiliac articulation on the posterolateral ilium. It also investigates the positional variability of the branches of the superior gluteal artery (SGA) within areas defined by the grid. 48 dried adult hip bones were examined to determine the position of the sacral articular surface on the posterolateral surface of the ilium. A novel grid-system was defined and used to map the positions of the articulation of the first two sacral segments on the posterolateral ilium. Superficial and deep branches of the SGA were dissected in donor cadavers and their courses were virtually overlayed on the grid system. The grid system localized the sacral articular surfaces within a defined area on the posterior ilium. Arterial distributions indicated the presence of the superficial branch of SGA more frequently over the screw insertion area (at an intermuscular plane), while the deep branch ran closer to the ilium but antero-inferior to the screw placement areas. This study proposes a new topographical perspective of visualizing SGA branches with respect to the cranial sacral segments. Precise localization of vascular anatomy may help to reduce potential risk of injury during sacroiliac screw placements.

A human, allogeneic cortical bone screw for distal interphalangeal joint (DIP) arthrodesis: a retrospective cohort study with at least 10 months follow-up.

INTRODUCTION: The prime requisites of a good digital arthrodesis are a painless and stable union in a proper position. Arthrodesis of the distal interphalangeal joint of the fingers is not without potential complications including nonunion, malunion, and deep tissue infections. The Shark Screw® is a human, cortical bone allograft for osteosynthesis and an alternative to metal or bioabsorbable devices in orthopedics and trauma surgery. The primary hypothesis is that the fusion and complication rate, using the Shark Screw®, is at least similar to those reported in the literature, using metal or bioabsorbable screws. MATERIAL AND METHODS: This retrospective cohort study analyzes the fusion and complication rate and the patient satisfaction of distal interphalangeal joint arthrodesis of 27 fingers with the human allogeneic cortical bone screw. Complications, Disabilities of Arm, Shoulder, and Hand Questionnaire (Quick-DASH) score and Michigan Hand Outcomes Questionnaire (MHQ) score, grip and pinch strength and fusion angle were investigated. RESULTS: The mean follow-up was 23 months. At 6 weeks after surgery, fusion was obtained for all fingers. There was no surgical complication that required revision surgery. An average fusion angle of 13.6° ± 10.7° was measured. VAS pain score decreased significantly from 6.9 before surgery to 0.14 after surgery. The Quick-DASH score decreased from 10.7 to 7.8. The MHQ score improved in all sub-scores. CONCLUSION: The complication rates, using the Shark Screw® for DIP joint arthrodesis, are lower compared to the results reported in the literature for other surgical techniques. Complications related to the human allograft cortical bone screw itself were not observed. The bone screw is completely remodeled into the host bone and further hardware removal is not necessary. LEVEL OF EVIDENCE: IV.

Treatment of scaphoid fractures and pseudarthroses with the human allogeneic cortical bone screw. A multicentric retrospective study.

BACKGROUND: Allograft bone screws are rarely described for the fixation of the scaphoid. When fresh fractures are treated, metal screws are mainly used; when pseudarthrosis is the indication, plates in combination with vascularized or non-vascularized bone grafts are mainly used. The necessity of metallic screw removal is under debate, but it is mandatory for plates because of movement restrictions due to the plate. The use of biomaterials in scaphoid fracture fixation was described as leading to union rates of between 64 and 100%. Brcic showed the incorporation of an allogeneic cortical bone screw at 10 weeks postoperative, along with revascularization and stable osteosynthesis with primary bone healing, without any signs of immunological rejection. The purpose of this retrospective study was to explore the results obtained using an allogenic cortical bone screw (Shark Screw®) in patients with fresh scaphoid fracture fixation and pseudarthroses with respect to union rates and time to union. PATIENTS AND METHODS: We retrospectively analyzed 75 patients: 31 with fresh fractures and 44 pseudarthrosis patients. The Shark Screw® was used for the fixation of the scaphoid in the fresh-fracture and pseudarthrosis patients. We evaluated the union rate, complication rate and time to union. RESULTS: Using the human allogeneic cortical bone screw for scaphoid fracture fixation led to a high union rate (94-96%). There were two nonunions in the fresh fracture group and two nonunions in the pseudarthrosis group. The complication rate was 1.3% (1 patient). Median time to union was 16, 18 and 29 weeks for the fresh-fracture, pseudarthrosis and delayed-union patients, respectively. The treatment of fresh scaphoid fractures and pseudarthroses showed similar union rates to those described in the literature, uses a shorter and less invasive surgical method with no need for hardware removal, and has a low complication rate. CONCLUSION: Using the human allogenic cortical bone screw (Shark Screw®) led to similar union rates in fresh fractures-but better union rates in pseudarthrosis patients-compared to those presented in the literature for other scaphoid fracture fixation techniques, and it enabled a short and low-invasive procedure without any donor site morbidity and without the necessity to remove the hardware in a second surgery. The pseudarthrosis patient group showed a particularly strong benefit from this new procedure. The physiological bone metabolism remodels the cortical bone screw without scars. LEVEL OF EVIDENCE: III: retrospective cohort study, therapeutic investigation of a treatment.

Tomographic assessment of infrazygomatic crest bone depth for extra-alveolar miniscrew insertion in subjects with different vertical and sagittal skeletal patterns.

OBJECTIVE: To evaluate bone availability at the infrazygomatic crest for extra-alveolar bone miniscrew insertion in subjects with different vertical and sagittal skeletal patterns. SETTING AND SAMPLE POPULATION: Measurements of the infrazygomatic crest were performed on multislice computed tomography scans from 58 adults with different skeletal patterns. MATERIALS AND METHODS: Infrazygomatic crest bone depth was measured at 4, 5 and 6 mm from the cementoenamel junction (CEJ) of the maxillary first molar at three different angles (60°, 70° and 80°) in the first molar occlusal plane. The sagittal and vertical skeletal patterns were determined. Analysis of variance followed by Tukey's post hoc test was used (P ≤ .05). RESULTS: Bone depth was greater near the CEJ (8.7 ± 3.1 mm) and lower in the apical area (5.8 ± 2.7 mm). In Class II subjects, considering 6 mm from the CEJ, there was a significantly lower depth at the 80° angle (5.4 ± 2.5 mm) than at 60° (8.6 ± 3.5 mm; P = .007). In mesofacial subjects, considering 5 and 6 mm from the CEJ, bone depth was lower at 80° (5.7 ± 3.2 mm and 5.3 ± 2.5 mm) than at 60° considering 4 mm from the CEJ (P ≤ .019). CONCLUSION: Bone availability was lower at the apical level, especially in Class II and mesofacial subjects. Therefore, when the planned insertion site is located in the apical direction, it is recommended to choose shorter miniscrews (2.0 x 12mm) and a smaller insertion angle (60°) and/or to plan a miniscrew bone insertion deep enough to allow bicortical fixation.

Fixation stability comparison of bone screws based on thread design: buttress thread, triangle thread, and square thread.

BACKGROUND: The influence of thread profile on the fixation stability of bone screws remains unclear. This study aimed to compare the fixation stability of screws with different thread profiles under several loading conditions. METHODS: Bone screws that differed in thread profile (buttress, triangle, and square thread) only were made of stainless steel. Their fixation stabilities were evaluated individually by the axial pullout test and lateral migration test, besides, they were also evaluated in pairs together with a dynamic compression plate and a locking plate in polyurethane foam blocks under cyclic craniocaudal and torsional loadings. RESULTS: The triangle-threaded and square-threaded screws had the highest pullout forces and lateral migration resistance. When being applied to a dynamic compression plate, higher forces and more cycles were required for both triangle- and square-threaded screws to reach the same displacement under cyclic craniocaudal loading. On the other hand, the triangle-threaded screws required a higher torque and more cycles to reach the same angular displacement under cyclic torsional loading. When being applied to a locking plate, the square-threaded screws needed higher load, torque, and more cycles to reach the same displacement under both cyclic craniocaudal and torsion loadings. CONCLUSIONS: The triangle-threaded screws had superior pullout strength, while square-threaded screws demonstrated the highest lateral migration resistance. Moreover, dynamic compression plate fixation with triangle- and square-threaded screws achieved more favorable fixation stability under craniocaudal loading, while triangle-threaded screws demonstrated superior fixation stability under torsional loading. Locking plate fixation with a square-threaded screw achieved better fixation stability under both loading types.

Treatment of the Hoffa fracture of the lateral femoral condyle with cannulated screws in combination with an anti-gliding steel plate, a retrospective observational study.

BACKGROUND: The stability of the Hoffa fracture fixed with a cannulated screw is limited. In the present work, we adopted two cannulated screws from anterior to posterior and posteriorly anti-gliding plate to treat 12 cases with Hoffa fracture of the lateral femoral condyle. METHODS: Open reduction and internal fixation were performed in 12 patients with Hoffa fractures of the lateral femoral condyle. The Hoffa fracture end was fixed with an anti-gliding steel plate based on cannulated screw fixation in the rear of the distal femur. All patients were followed for 12-24 months, with a median of 15.3 ± 4.6 months. RESULTS: All fractures were bony union, with a healing time of 3-6 months (median, 4.5 months). The Letenneur evaluation system was used to assess efficacy. Four indexes were observed, including knee range of motion (ROM), stability, pain, and dependent ambulation. The results revealed that eight cases were excellent and four cases good, with a good rate of 100%. CONCLUSION: The surgical treatment with cannulated screws in combination with an anti-gliding steel plate could fix the end of the Hoffa fracture, which could acquire strong internal fixation and a good curative effect.

The application of an allogeneic bone screw for osteosynthesis in hand and foot surgery: a case series.

INTRODUCTION: The allogeneic bone screw transplant is a new osteosynthesis device making the use of foreign fixation material obsolete for various kinds of indications. Moreover, it is integrated into the recipient bone by natural bone remodeling without harming the surrounding tissue. The aim of this study was to determine the efficacy and safety of the transplant for osteotomy and arthrodesis in hand and foot surgery and to evaluate the clinical importance of the device. MATERIALS AND METHODS: A single-surgeon case series of 32 patients who had undergone hand or foot surgery with the application of an allogeneic bone screw with an average follow-up time of 1 year is reported. Clinical data were reviewed to evaluate the pain levels and satisfaction of the patients and the frequency and type of complications occurring during the healing process. Routine radiography and computed tomography were reviewed to determine the fusion rate, the ingrowth behavior of the transplant and the possible occurrence of transplant failure. RESULTS: High patient satisfaction was paired with low postoperative pain levels and a low complication rate. 97% of the patients were free of pain at the timepoint of the second follow-up examination, the mean time of recovery of full mobility was 50.1 ± 26.1 days after surgery. Wound healing disturbance occurred only in two cases. Bony consolidation of the osteotomy or arthrodesis gap as well as osseointegration of the transplant was seen in all cases. No transplant failure or transplant loosening occurred. CONCLUSIONS: The application of the allogeneic bone screw resulted in a 100% fusion rate while the patient burden was low. The transplant is safe and suited for various kinds of osteosynthesis in hand and foot surgery.

[Research on Self-tapping Performance Test of Self-tapping Bone Screws].

OBJECTIVE: To study the self-tapping performance test method of self-tapping bone screws based on the YY/T 1505 standard. METHODS: With reference to the method of YY/T 1505, various factors affecting the self-tapping force test was optimised, and the self-tapping force judgment method was improved. RESULTS: The experimental results showed that the self-tapping force obtained by the improved self-tapping force judgment method has good repeatability and high stability of the experimental data. At the same time, the test results of other influencing factors indicated that the manufacturer should fully consider the test material and the size of the pre-drilled hole. CONCLUSIONS: An improved method for judging the self-tapping force is helpful for the repeatability and stability of the test data. This study has certain significance referring to the self-tapping performance test of self-tapping bone screws.

Defining a Safe Zone for Percutaneous Screw Fixation of Posterior Malleolar Fractures.

Posterior malleolar fractures require fixation to confer stability to the ankle. Although some have suggested that fractures involving less than 25% of the articular surface require no intervention, estimation of malleolar size on plain imaging is inaccurate. Some posterior malleolar fractures may be particularly suitable for posterior-to-anterior percutaneous screw fixation of the posterior malleolus via a posterolateral approach. We hypothesized that there may be a safe zone in the posterolateral ankle, identifiable with reliable anatomic landmarks, that might allow safe percutaneous screw placement for fracture fixation. The study protocol involved Step 1, in which multiple Kirschner wires were used in a single cadaveric specimen to attempt to identify a safe zone entry point in the posterior ankle, and Step 2, in which a single wire was used in each of six additional cadaveric specimens to test the ability to safely replicate the use of that entry point. In Step 1, a safe zone entry point was identified, located immediately lateral to the Achilles tendon and 1 cm above the level of the tip of the medial malleolus, when visualizing the posterior ankle. In Step 2, using these landmarks and an image intensifier, single wires were then successfully placed in the other six specimens without injury to any significant structure. If confirmed in clinical studies, the safe zone entry point that we have identified could potentially be used to facilitate posterior-to-anterior percutaneous fixation in patients with posterior malleolar fractures for whom open reduction may not be required or may be contraindicated.

Interradicular distance and alveolar bone thickness for miniscrew insertion: a CBCT study of Persian adults with different sagittal skeletal patterns.

BACKGROUND: This study aimed to assess the interradicular distance and alveolar bone thickness of Persian adults with different sagittal skeletal patterns for miniscrew insertion using cone-beam computed tomography (CBCT). METHODS: This cross-sectional study was conducted on maxillary and mandibular CBCT scans of 60 patients (18-35 years) in three groups (n = 20) of class I, II and III sagittal skeletal pattern. Anatomical and skeletal parameters were measured at 2, 4 and 6 mm apical to the cementoenamel junction (CEJ) by one examiner. The intra- and inter-class correlation coefficients were calculated to assess the intra, and interobserver reliability. Data were analyzed by ANOVA and Tukey's test (alpha = 0.05). RESULTS: The intra- and interobserver reliability were > 0.9 for all parameters. The largest inter-radicular distance in the maxilla was between the central incisors (1-1) in classes I and III, and between premolars (4-5) in class II patients. The largest inter-radicular distance in the mandible was between molar teeth (6-7) in all three classes. The buccal cortical plate thickness was maximum at the site of mandibular first and second molars (6-7). The posterior maxilla and mandible showed the maximum thickness of cancellous bone and alveolar process. Wide variations were noted in this respect between class I, II and III patients. CONCLUSIONS: The area with maximum inter-radicular distance and optimal alveolar bone thickness for miniscrew insertion varies in different individuals, depending on their sagittal skeletal pattern.

Diagnostic accuracy of perioperative electromyography in the positioning of pedicle screws in adolescent idiopathic scoliosis treatment: a cross-sectional diagnostic study.

BACKGROUND: To investigate in the conventional techniques of the pedicle screws using triggered screw electromyography (t-EMG), considering different threshold cutoffs: 10, 15, 20 25 mA, for predicting pedicle screw positioning during surgery of the adolescent with idiopathic scoliosis (AIS). METHODS: Sixteen patients (4 males, 12 females, average age 16.6 years) were included, with an average curve magnitude of 50 degrees and placement of 226 pedicle screws. Each screw was classified as "at risk for nerve injury" (ARNI) or "no risk for nerve injury" (NRNI) using CT and the diagnostic accuracy of EMG considering different threshold cutoffs (10,15, 20 and 25 mA) in the axial and Sagittal planes for predicting screw positions ARNI was investigated. RESULTS: The EMG exam accuracy, in the axial plane, 90.3% screws were considered NRNI. In the sagittal plane, 81% pedicle screws were considered NRNI. A 1-mA decrease in the EMG threshold was associated with a 12% increase in the odds of the screw position ARNI. In the axial and sagittal planes, the ORs were 1.09 and 1.12, respectively. At every threshold cutoff evaluated, the PPV of EMG for predicting screws ARNI was very low in the different threshold cutoff (10 and 15); the highest PPV was 18% with a threshold cutoff of 25 mA. The PPV was always slightly higher for predicting screws ARNI in the sagittal plane than in the axial plane. In contrast, there was a moderate to high NPV (78-93%) for every cutoff analyzed. CONCLUSIONS: EMG had a moderate to high accuracy for positive predicting value screws ARNI with increase threshold cutoffs of 20 and 25 mA. In addition, showed to be effective for minimizing false-negative screws ARNI in the different threshold cutoffs of the EMG in adolescent with idiopathic scoliosis (AIS).

Can implants move in bone? A longitudinal in vivo micro-CT analysis of implants under constant forces in rat vertebrae.

OBJECTIVES: Whereas stationary stability of implants has been postulated for decades, recent studies suggested a phenomenon termed implant migration. This describes a change in position of implants as a reaction to applied forces. The present study aims at employing image registration of in vivo micro-CT scans from different time points and to assess (a) if migration of continuously loaded implants is possible and (b) migration correlates with the force magnitude. MATERIAL AND METHODS: Two customized machined implants were placed in the dorsal portion of caudal vertebrae in n = 61 rats and exposed to standardized forces (0.5 N, 1.0 N, and 1.5 N) applied through a flat nickel-titanium contraction spring, or no forces (control). Micro-CT scans were performed at 0, 1, 2, 4, 6, and 8 weeks after surgery. The baseline image was registered with the forthcoming scans. Implant migration was measured as the Euclidean distance between implant tips. Bone remodeling was assessed between the baseline and the forthcoming scans. RESULTS: The findings confirmed a positional change of the implants at 2 and 8 weeks of healing, and a linear association between applied force and velocity of movement (anterior implant: χ2  = 12.12, df = 3, and p = .007 and posterior implant: χ2  = 20.35, df = 3, and p < .001). Bone apposition was observed around the implants and accompanied by formation of load-bearing trabeculae and a general cortical thickening close and also distant to the implants. CONCLUSION: The present analysis confirmed that implants can migrate in bone. The applied forces seemed to stimulate bone thickening, which could explain why implants migrate without affecting stability.

Morphometric Analysis of the Lumbar Vertebrae Concerning the Optimal Screw Selection for Transpedicular Stabilization.

Transpedicular stabilization is a frequently used spinal surgery for fractures, degenerative changes, or neoplastic processes. Improper screw fixation may cause substantial vascular or neurological complications. This study seeks to define detailed morphometric measurements of the pedicle (height, width, and surface area) in the aspects of screw length and girth selection and the trajectory of its implantation, i.e., sagittal and transverse angle of placement. The study was based on CT examinations of 100 Caucasian patients (51 women and 49 men) aged 27-75 with no anatomical, degenerative, or post-traumatic spine changes. The results were stratified by gender and body side, and they were counter compared with the available literature database. Pedicle height decreased from L1 to L4, ranging from 15.9 to 13.3 mm. Pedicle width increased from L1 to L5, extending from 6.1 to 13.2 mm. Pedicle surface area increased from L1 to L5, ranging from 63 to 140 mm2. Distance from the point of entry into the pedicle to the anterior surface of the vertebral body, defining the maximum length of a transpedicular screw, varied from 54.0 to 50.2 mm. Variations concerning body sides were inappreciable. A transverse angle of screw trajectory extended from 20° to 32°, shifting caudally from L1 to L5, with statistical differences in the L3-L5 segments. A sagittal angle varied from 10° to 12°, without such definite relations. We conclude that the L1 and L2 segments display the most distinct morphometric similarities, while the greatest differences, in both genders, are noted for L3, L4, and L5. The findings enable the recommendation of the following screw diameters: 4 mm for L1-L2, 5 mm for L3, 6 mm for L4-L5, and the length of 50 mm. We believe the study has extended clinical knowledge on lumbar spine morphometry, essential in the training physicians engaged in transpedicular stabilization.

Extra-Alveolar Bone Screws for Conservative Correction of Severe Malocclusion Without Extractions or Orthognathic Surgery.

PURPOSE OF REVIEW: Evaluate management of challenging malocclusions conservatively (no extractions or orthognathic surgery). RECENT FINDINGS: Most malocclusions have a predominately environmental etiology. Optimal esthetics and function are restored by aligning the dentition over the apical base of bone at the appropriate vertical dimension of occlusion (VDO). Extra-alveolar (E-A) anchorage is achieved at three intraoral sites: mandibular buccal shelf (MBS), infrazygomatic crest (IZC), and anterior ramus. MBS and IZC bone screws effectively anchor the conservative correction of severe dental and skeletal malocclusions. All bone screw sites are effective for anchoring lever arms to recover impacted teeth. Rather than extracting teeth, E-A anchorage corrects crowding by retracting the posterior segments to increase arch length. Skeletal malocclusion is corrected by aligning teeth over the apical base of bone and restoring the VDO by retracting and posteriorly rotating the dental arches as segments. Challenging dental and skeletal malocclusions can be treated routinely via determinate mechanics anchored with E-A bone screws.

Arthroscopic Subtalar Arthrodesis: Does the Type of Fixation Modify Outcomes?

The goal of the present study was to analyze a modified American Orthopaedic Foot and Ankle Society (AOFAS) ankle-hindfoot scale score, time to union, and the incidence of fusion after isolated arthroscopic posterior subtalar arthrodesis using either 1 or 2 screws of different diameters. We reviewed a consecutive series of 65 patients, mean age 50.0 ± 15.6 years, including 38 males (58.5%) and 27 females (41.5%), who had undergone arthrodesis from May 2004 to February 2011. The mean follow-up duration was 57.5 (range 24 to 105) months. The patients were divided into 3 groups according to the fixation method used: group 1 (n = 12; 18.5%) underwent fixation with one 6.5-mm screw; group 2 (n = 40; 61.5%) with one 7.3-mm screw; and group 3 (n = 13; 20%) with two 7.3-mm screws. An overall statistically significant (p <.0001) improvement was seen in the modified AOFAS scale score for all 3 fixation groups; however, the difference was not statistically significant (p = .79) among the fixation groups. Fusion was achieved in 62 patients (95.4%) after a mean of 12.1 (range 9 to 16) weeks. The difference in the time to union was not statistically significant (p = .781) among the fixation groups. Nine patients (13.8%) experienced complications, and nonunion was significantly (p = .005) more prevalent in the single 6.5-mm screw group. In conclusion, all 3 screw configurations led to improved modified AOFAS scale scores, although nonunion was more common among patients fixed with a single 6.5-mm screw.

Computer-assisted Patient-specific Prototype Template for Thoracolumbar Cortical Bone Trajectory Screw Placement: A Cadaveric Study.

The cortical bone trajectory (CBT) screw technique yields effective mechanical and clinical results, improving the holding screw strength with a less invasive exposure. Accurate and safe screw placement is crucial. A patient-specific drill template with a preplanned trajectory was considered a promising solution; however, it is critical to assess the efficacy and safety of this technique. This study aims to evaluate the accuracy of patient-specific computed tomography (CT)-based rapid prototype drill guide templates for the CBT technique. CT scanning was performed in 7 cadaveric thoracolumbar spines, and a 3-dimensional reconstruction model was generated. By using computer software, we constructed drill templates that fit onto the posterior surface of thoracolumbar vertebrae with drill guides to match the CBT. In total, 80 guide templates from T11 to L5 were created from the computer models by using rapid prototyping. The drill templates were used to guide the drilling of CBT screws without any fluoroscopic control, and CT images were obtained after fixation. The entry point and direction of the planned and inserted screws were measured and compared. In total, 80 screws were inserted from T11 to L5. No misplacement or bony perforation was observed on postoperative CT scan. The patient-specific prototype template system showed the advantage of safe and accurate cortical screw placement in the thoracolumbar spine. This method showed its ability to customize the patient-specific trajectory of the spine, based on the unique morphology of the spine. The potential use of drill templates to place CBT screws is promising.

Analysis of Locking Self-Taping Bone Screws for Angularly Stable Plates.

Paper focuses on biomechanics, specifically on locking cortical bone screws in angularly stable plates used for the treatment of bone fractures in the medical fields of traumatology and orthopaedics. During extraction of titanium-alloy implants, problems are encountered in an effort to loosen some locking bone screws from the locking holes of an angularly stable plate and the subsequent stripping of the internal hexagon of the screw head. The self-locking of the screw-plate threaded joint was verified by calculation and the effect of the angle of the thread on the head of the locking cortical bone screw on self-locking was evaluated. The magnitude of the torque, causing the stripping of the internal hexagon (the Inbus type head) of a locking cortical bone screw with a shank diameter of 3.5 mm from Ti6Al4 V titanium alloy to ISO 5832-3, was determined experimentally. Also, it was experimentally found that the rotation of the screwdriver end with a hexagonal tip inside the locking cortical bone screw head during stripping of the internal hexagon causes strain of the screw head perimeter and thereby an increase of thread friction. The effect of tightening torque on the possibility of loosening of the locking cortical bone screw from the locking hole of an angularly stable plate was assessed experimentally. From the evaluation of five alternative shapes of locking cortical bone screw heads in terms of the acting stress and generated strains, it follows that the best screw is the screw with the Torx type head, which demonstrates the lowest values of reduced stress and equivalent plastic strain. Based on experiments and simulations the authors recommend that all global producers of locking cortical bone screws for locking holes of angularly stable plates use the Torx type heads, and not heads of the Inbus type or the Square, PH, PZ types.