The addition of an anti-rotation screw to the dynamic hip screw.

The aim of this study is to assess if there is a difference in outcomes between a dynamic hip screw with or without an anti-rotation screw in the treatment of hip fractures. All patients with an intracapsular hip fracture who underwent dynamic hip screw osteosynthesis between January 2010 and December 2013 in three Dutch hospitals were reviewed. Minimal follow-up was one year. The study included a total of 364 patients. 24 patients were lost to follow-up and excluded. 297 (87.4%) were in the dynamic hip screw group and 43 (12.6%) in the dynamic hip with anti-rotation screw group. Direct comparison of patient characteristics of the two groups showed significant differences in age, sex, Garden classification and Pauwels classification. Patients operated with a dynamic hip screw and anti-rotation screw are significantly younger and their fractures are significantly more dislocated and steeper. To draw conclusions about differences in outcome, a randomised clinical trial should be performed.

Sequential fluoroscopic rollover images reliably identify "in-out-in" posterosuperior screws during percutaneous fixation of femoral neck fractures.

INTRODUCTION: Percutaneous screws placed into the posterosuperior femoral neck are frequently extraosseous or "in-out-in" (IOI). These IOI screws are not readily identifiable on anteroposterior (AP) and lateral fluoroscopic images. The purpose of this study was to examine the ability of surgeons to identify IOI guide pins using sequential fluoroscopic rollover images. MATERIALS AND METHODS: A 3.2-mm guide pin was placed into the posterosuperior quadrant of eleven synthetic femur models. Five samples were "all-in" (AI), and six were IOI. Sequential fluoroscopic rollover images were obtained starting with an AP image, then images at 10-degree rollover intervals ending with a direct lateral image. Images were reviewed in a blinded fashion by five attending orthopedic trauma surgeons and 20 resident surgeons to determine whether guide pins were AI or IOI. Accuracy, interobserver reliability, sensitivity, and specificity were assessed. RESULTS: The overall accuracy of responses was 86% with no difference between attending trauma surgeons and residents (p = 0.5). The sensitivity and specificity for an IOI guide pin were 98.0% and 71.2%, respectively. Interobserver reliability among surgeons was good (κ = 0.703). CONCLUSION: The use of the sequential fluoroscopic rollover images after placement of the posterosuperior guide pin into the femoral neck was highly sensitive for detecting an IOI position. The 40-degree rollover image was the best view to evaluate the proximity of the guide pin to the posterior cortex.

Pullout strength of 2.0 mm cancellous and cortical screws in synthetic bone.

OBJECTIVE: To determine whether 2.0 mm cancellous screws are superior to 2.0 mm cortical screws when inserted into cancellous and bicortical bone. STUDY DESIGN: Biomechanical study. METHODS: The 2.0 mm cancellous screws and 2.0 mm cortical screws were inserted according to the recommended guidelines in synthetic cancellous and bicortical blocks. Fifteen screw-block constructs per group were tested to failure in axial pullout. Axial pullout strength and yield strength were calculated. Data were analyzed using a one-way ANOVA. RESULTS: The 2.0 mm cortical screws achieved lower axial pullout strength than 2.0 mm cancellous screws in cancellous blocks. The 2.0 mm cortical screws achieved greater pullout strength than 2.0 mm cancellous screws in bicortical blocks. CONCLUSION: The 2.0 mm cancellous screws may offer a biomechanical advantage in bone with thin cortices (<1 mm thick), whereas 2.0 mm cortical screws may be preferred in cortical bone with cortices measuring at least 1 mm in thickness.

Nuts and bolts: dimensions of commonly utilized screws in upper extremity surgery.

A plethora of screw designs and sizes are available from multiple companies for use in upper extremity surgery. Knowing the dimensions of screws is critical in the treatment of bone of varying dimensions for fractures, osteotomies, or arthrodeses. Although many screws are named by their major thread diameter, this is not always true. Because of this confusing nomenclature and vast number of options, we sought to review the most commonly used screws and codify their dimensions into a readily available article and reference chart. This article highlights the basic dimensions of commonly used headless screws, stand-alone lag screws, non-locking and locking screws for plating, and biocomposite screws. Commonly described treatments using these screws include fixation of elbow, wrist, carpal, metacarpal, and phalangeal fractures and osteotomies, as well as arthrodeses of upper extremity joints. This article and its tables are by no means exhaustive of all commercially available implants. The focus is on the most commonly used implants in the United States as of 2014.

How to prevent cut-out and cut-through in biaxial proximal femoral nails: is there anything beyond lag screw positioning and tip-apex distance?

PURPOSE: Hip perforation is a major complication in proximal femoral nailing. For biaxial nails, knowledge of their biomechanics is limited. Besides re-evaluation of accepted risk factors like the tip-apex distance (TAD), we analysed the influence of anti-rotational pin length. METHODS: We compared 22 hip perforation cases to 50 randomly chosen controls. TAD, lag-screw position, angle between lag-screw and femoral neck axis, lag-screw gliding capacity, displacement and anti-rotational pin length were investigated. RESULTS: Hip perforation was associated with a higher angle of deviation between lag-screw and femoral neck axis (p = 0.001), a lower telescoping capacity of the lag screw (p = 0.02), and higher TAD (p = 0.048). If the anti-rotational pin exceeded a line connecting the tip of the nail and the lag screw (NS line), hip perforation incidence was increased (p = 0.009). Inadequate pin length resulted in an odds ratio of 10.8 for hip perforation (p = 0.001). CONCLUSIONS: In biaxial nails anti-rotational element positioning is underestimated, however, crucial.

Miniscrew implants as temporary anchorage devices in orthodontics: a comprehensive review.

In recent times, the use of miniscrew implants to obtain absolute anchorage has gained momentum in clinical orthodontics as rigid anchorage modality. Miniscrew implants offers many advantages when used as temporary anchorage devices like, easy placement and removal, immediate loading, can be used in a variety of locations, provide absolute anchorage, economic and requires less patient cooperation. This makes them as a necessary treatment option in cases with critical anchorage that would have otherwise resulted in anchorage loss if treated with conventional means of anchorage. The aim of this comprehensive review is to highlight the gradual evolution, clinical use, advantages and disadvantages of the miniscrew implants when used to obtain a temporary but absolute skeletal anchorage for orthodontic applications.

Anterior approach for fixation of isolated type III coronoid process fracture.

Authors chose anterior approach through the antecubital fossa for better exposure in that case of isolated coronoid process fracture. The objective of the study was to report validity of anterior approach for the Regan and Morrey type III, isolated fracture of the coronoid process of the ulna without residual valgus or varus instability. From January 2007 and January 2010, we evaluated eleven consecutive patients (7 men, 4 women; mean age 44 years; range 25-67 years) who underwent surgical fixation through the anterior approach. The mean follow-up period was 21 months (range 15-34 months). Preoperative and follow-up roentgenograms were evaluated for assessment of the fracture configuration and confirmation of fracture union. Clinical evaluation included an analysis of surgical complication, range of motion, Mayo elbow performance score, and DASH (disability of the arm, shoulder, and hand) score. Fractures were mainly fixed with plate and screws in 8 cases, cannulated screws in 3 cases. There was no residual joint instability after fracture fragment fixation. All fractures were united, and the average union time was 15.2 weeks with a range of 11-20 weeks. Mean flexion contracture of the elbow was 3.6° (range 0°-10°), and further flexion was 130.9° (range 125°-140°) at the last follow-up. Mean Mayo elbow performance score was 92.3 (range 80-100 points), and mean DASH score was 5.9 (range 1.6-8.3 points). In conclusion, Primary fixation of the coronoid process fractures through the anterior approach could be particularly useful in the Regan and Morrey type III isolated coronoid process fractures.

Evaluation of intersegmental displacement according to osteosynthesis method for mandibular setback sagittal split ramus osteotomy using cone-beam computed tomographic superimposition.

PURPOSE: To compare intersegmental displacements after mandibular setback sagittal split ramus osteotomy with reference to the fixation system applied: miniplate with monocortical screw, 3 bicortical screws, and 1 bicortical screw and 2 resorbable screws. MATERIALS AND METHODS: The 42 subjects were divided into 3 groups according to the osteosynthesis method applied. To evaluate the intersegmental displacements from immediately after surgery (T0) to 6 months after surgery (T1), 2 cone-beam computed tomographic data sets were superimposed on the symphyseal area and the lower part of the mandible below the root apex. On the superimposed 3-dimensional images, the mean and standard deviation of the differences of the coordinates (x, y, z) between T0 and T1 were calculated. RESULTS: From T0 to T1, group B (bicortical screws) manifested the greatest condylion (Cd) and coronoid process (Cp) displacements (P < .05). In group A, the right Cd moved anteriorly and the left Cd moved anteriorly and inferiorly, whereas the right and left Cps moved anteriorly. In group B, the right and left Cps moved laterally and inferiorly. In group C, the right Cd moved anteriorly and inferiorly, the left Cd changed laterally and anteriorly, the right Cp moved anteriorly, and the left Cp moved anteriorly and inferiorly. CONCLUSIONS: In the present study, group B (bicortical screws) showed the greatest displacement after the healing period. In view of these findings, surgeons should consider carefully their choice of osteosynthesis method to effectively decrease intersegmental displacement.

[Contribution and limitations of MIS(®) screwed expanders in the jaws: illustration from clinical cases and comparison of the osseous volume from three-dimensional radiographic pictures]. / Intérêts et limites des expanseurs vissés de MIS(®) aux maxillaires : illustration à partir de cas cliniques et comparaison du volume osseux à partir de clichés radiographiques tridimensionnels.

INTRODUCTION: Implanting on an atrophic maxilla alveolar ridge may require bone augmentation. Screwed expanders may sometimes be used, thus avoiding a more invasive bone graft. It allows bone density to increase and results in alveolar ridge expansion, by using bone elasticity and adaptation, allows the optimization of the available bone volume, with low morbidity. TECHNICAL NOTE: Despite its apparent simple implementation, the technique should be adapted to each type of bone so as to optimize results. We present two clinical cases, use of screwed expanders, their action on the crestal bone, and the limitations of this technique depending on ridge configuration. DISCUSSION: Screwed expanders are non-traumatic easy-to-use tools. They can be inserted like implants because they have a good self-tapping effect. Their use is more secure in narrow spaces; they are more comfortable for the patient than impacted expanders use. They allow increase of cancellous bone density, which improves primary stability in case of low density bone. Bone volume preservation and avoiding bone grafts can shorten the implant treatment procedure and decrease costs for the patient. Unfortunately, this technique does not allow alveolar ridge height increase. If this is required, onlay graft or guided tissue generation are the best alternatives.

Multiple screws versus sliding hip screws in femoral neck fractures: A protocol of cohort study.

BACKGROUND: There has been a paucity of cohort trials directly comparing multiple cannulated screws (MCS) and sliding hip screws (SHS) in femoral neck fractures at any level. Thus, a well-conducted clinical trial with an adequate sample size is urgently needed. We undertake a retrospective study to compare outcomes in patients who undertake MCS or SHS fixation for femoral neck fractures. METHODS: A retrospective review of femoral neck fractures performed with SHS or MCS between February 2016 and June 2018 was conducted with Institutional Review Board approval in the First Affiliated Hospital of Dali University of Orthopedic Trauma. All cases were performed by a single surgeon. Of these, we included 180 patients (90 hips) that were performed surgery in treatment of femoral neck fractures. All patients received the same standardized postoperative multimodal pain protocol and the same postoperative rehabilitation program. The primary endpoint was Harris Hip Score. Secondary outcome measures include operation time, length of hospital stay, incision length, patient satisfaction, and postoperative complications. Multivariate linear and regression analyses was used to identify independent predictors of outcome. A P-value of <.05 was defined as statistical significance. RESULTS: We hypothesize that both treatments provide comparable outcomes. TRIAL REGISTRATION: This study protocol was registered in Research Registry (researchregistry5638).

[Comparison of bioabsorbable screw and metallic screw for Maisonneuve fracture].

OBJECTIVE: To compare the clinical and radiographic outcomes of bioabsorbable screw and metallic screw for Maisonneuve fracture. METHODS: The clinical data of 68 patients of Maisonneuve fracture treated with open reduction and internal fixation between October 2012 and October 2016 were retrospectively analyzed. Metallic screw fixation was used in 37 cases (group A) and absorbable screw fixation was used in 31 cases (group B). There was no significant difference in age, gender, weight, operated side, cause of injury, time from injury to operation, and complications between the two groups ( P>0.05). At last follow-up, the tibiafibular clear space (TFCS), tibiafibular overlap (TFO), medial clear space (MCS), and syndesmotic malreduction rate were recorded. And the dorsiflexion and plantar-flexion range of motion, pain visual analogue scale (VAS) score, ankle and hind foot score of American Orthopaedic Foot and Ankle Society (AOFAS), and Olerud-Molander (OM) score were recorded. RESULTS: All patients were followed up 25-43 months, with an average of 32.3 months. There was no significant difference in the operation time between the two groups ( t=1.229, P=0.282). All the fractures healed, and there was no significant difference in fracture healing time between the two groups ( t=1.367, P=0.413). At last follow-up, the syndesmotic malreduction rate of group A was 16.2% (6/37), showing no significant difference when compared with group B [6.2% (2/31)] ( χ 2=1.549, P=0.213). There were 3 complications in group A, 1 was superficial wound infection, 1 was local heterotopic ossification due to failure to remove the screws in time, 1 was local heterotopic ossification of the screws; and there were 2 complications in group B, 1 was rejection and 1 was local heterotopic ossification of the screws. There was no significant difference in the incidence of complications between the two groups ( χ 2=0.068, P=0.794). There was no significant difference in TFCS, MCS, TFO, ankle dorsiflexion and plantar-flexion range of motion, AOFAS score, OM score, and VAS score between the two groups at last follow-up ( P>0.05). CONCLUSION: Compared with metallic screw, absorbable screws provide adequate fixation and functional recovery with avoiding screw removal and lower syndesmotic malreduction.

Comparison of dynamic hip screw and antirotation screw with cannulated screw in the treatment of transcervical collum femoris fractures.

OBJECTIVES: This study aims to compare the results of internal fixation with dynamic hip screw (DHS)/antirotation screw and conventional cannulated screw (CS) for femoral neck fracture. PATIENTS AND METHODS: This retrospective study included a total of 78 patients (57 males, 21 females) with collum femoris fractures treated with internal fixation between January 2015 and January 2019. Group 1 comprised 41 patients with a mean age of 45.7 years (range, 19 to 62 years) treated with DHSs/antirotation screws, while group 2 comprised 37 patients with a mean age of 41.9 years (range, 17 to 75 years) treated with CSs. The patients were evaluated for union, avascular necrosis (AVN), femoral neck shortness, operation time, duration of fluoroscopy exposure, and functional outcomes. RESULTS: Age, gender, and Garden classification stages were similar in both groups. No significant difference was found between the groups in respect of AVN and non-union rates. The non-union rate was 12.2% in group 1 and 21.6% in group 2 (p>0.05). The duration of fluoroscopy exposure was statistically significantly higher in group 2 (p=0.001) and the operation time was statistically significantly longer in group 1 (p=0.001). In group 2, femoral neck shortness stature was significantly higher (p=0.007). At the final follow-up examination, the Harris hip score was statistically significantly higher in group 1 (p=0.04). CONCLUSION: Dynamic hip screw/antirotation screw was a more relevant treatment method for transcervical femoral neck fractures compared to CS with more favorable functional outcomes and less fluoroscopy exposure.

Self-tapping and self-drilling screws for intermaxillary fixation in management of mandibular fractures.

The current study evaluated the success and the possible complication of intermaxillary fixation with self-tapping and self-drilling screws (STSDSs) in nondislocated or slightly dislocated mandibular fractures.Forty patients with mandibular fractures, treated with intermaxillary fixation using STSDSs, were clinically assessed by means of a dental vitality test and evaluation of tooth mobility adjacent to the cortical screw holes, and radiologically by means of a panoramic dental radiograph upon removal of the screws.The main complication was screw loss in 4.4% of cases, followed by coverage by oral mucosa in 1.2% of cases. However, no dental root damage, screw breakage, malocclusion, or poor consolidation of mandibular fractures was observed.The use of STSDSs for intermaxillary fixation is a useful alternative to the use of arch bars in the treatment of some types of mandibular fractures. In addition, there is no risk of dental lesions as with self-tapping screws.

Comparative Stiffness of an Equine Distal Sesamoid Bone Fracture Model Stabilized with 3.5-mm versus 4.5-mm Cortical Bone Screws in Lag Fashion.

OBJECTIVE: The aim of this study was to to determine the comparative stiffness following repair of an axial sagittal fracture model in equine distal sesamoid bones using either a single 3.5-mm or 4.5-mm cortical bone screw placed in lag fashion. STUDY DESIGN: The present study was an in vitro biomechanical study. RESULTS: The mean (±standard deviation) stiffness value for the 4.5-mm screw-bone construct (522.49 N/mm ± 168.21) was significantly greater than the 3.5-mm screw-bone construct (408.46 N/mm ± 131.13) (p = 0.047). This represents a 28% difference in mean stiffness. CONCLUSIONS: In vitro, the 4.5-mm screw-bone construct creates a stiffer repair of fractured distal sesamoid bones by a margin of 28%. The 4.5-mm cortical bone screw may better withstand forces imparted on the distal sesamoid bone sustained during anaesthetic recovery, normal weight bearing and athletic exercise, thereby minimizing the risk of implant failure.

Mechanical aspects of a multidirectional, angular stable osteosynthesis system and comparison with four conventional systems.

BACKGROUND: Following open reduction, internal fixation of fractures of the mandible is predominantly achieved using plates and screws. Today, a multitude of osteosynthesis systems are available on the market. One therapy modality, primarily developed for orthopaedic surgery, is using angular stable osteosynthesis plate systems. The dominating principle of these is the bond between screw and plate following insertion. This principle of an "internal fixateur" results in a more stable fixation of the fragments associated with less compression of the bone surfaces. MATERIAL: A new multidirectional osteosynthesis system (TiFix=Smartlock, Hamburg - Germany) was modified to fit the maxillofacial region and compared with four other well established osteosynthesis systems developed by Mondial, Medicon, Synthes, Leibinger-Stryker, one of these (Unilock by Synthes) being also angular stable. The resistance to deformation in varying directions was investigated following fixation in four different materials. RESULTS: The TiFix system proved more resistant to deformation even when mounted with fewer screws than the non-angular stable systems. CONCLUSION: This system results in greater stability even when fewer screws are used. For the clinician this means smaller access incisions, less soft tissue trauma, better aesthetic results, decreased duration of operation and a reduction of costs.

A novel nail providing more biomechanical rotational and axial stability than conventional interlocking nail in femur complex fracture model.

PURPOSE: Inter-fragmentary rotational and axial instabilities are major challenges in nailing of complex or comminuted fractures. We aimed to compare the inter-fragmentary rotational and axial stability of novel anti-rotation interlocking nail and the conventional interlocking nail in complex or comminuted femur shaft fractures. METHODS: Twenty composite femurs were divided into two groups, 30 mm was resected from the mid-portion of all composite femurs. The inter-fragmentary rotational and axial stabilities were assessed. RESULTS: Between 10-N m external and 6-N m internal rotation torques, mean maximum inter-fragmentary rotational arc motion in the novel nails was 1.63 mm and 291 % less than that of the conventional nails (6.38 mm, P = 0.000). Between 150 N distraction and 2300 N compression, mean axial motion in the novel nails was 0.8 mm and 257 % less than that of the conventional nails (2.86 mm, p = 0.000). CONCLUSION: An anti-rotational novel nail is superior to the conventional interlocking nail in terms of maximum inter-fragmentary rotational and axial stabilities in complex and comminuted femur shaft fractures.

Biomechanical Evaluation of the Femoral Neck System in Unstable Pauwels III Femoral Neck Fractures: A Comparison with the Dynamic Hip Screw and Cannulated Screws.

OBJECTIVES: To evaluate the biomechanical performance of femoral neck system (FNS) in comparison with established methods for fixation of femoral neck fractures in a cadaveric model. METHODS: Twenty pairs of fresh-frozen human cadaveric femora were instrumented either with dynamic hip screw and antirotation screw (DHS-screw), DHS-blade, 3 cannulated screws (3CS) or with FNS in a partially paired design. The specimens were randomized to 2 paired treatment groups based on the bone mineral density (BMD), namely DHS-screw/DHS-blade and FNS/3CS. A reduced unstable femoral neck fracture with postero-caudal comminution, OTA/AO 31-B2.3, 70 degrees Pauwels III, was simulated by cutting 30 degrees distal and 15 degrees posterior wedges. Cyclic axial loading was applied in 16 degrees adduction, starting at 500 N and with progressive peak force increase of 0.1 N/cycle until construct failure. Axial stiffness was measured in the third loading cycle. Femoral neck and leg shortening, and varus tilting and implant migration were calculated by means of optical motion tracking. RESULTS: Mean axial stiffness was 688.8 ± 132.6 N/mm for DHS-screw, 629.1 ± 94.1 N/mm for DHS-blade, 748.9 ± 211.4 N/mm for FNS, and 584.1 ± 156.6 N/mm for 3CS, with no statistical significances. Cycles until 15-mm leg shortening were comparable for DHS-Screw (20,542 ± 7465), DHS-blade (19,161 ± 3793) and FNS (17,372 ± 2996), however significantly higher than for 3CS (7293 ± 2819), P < 0.001. Similarly, cycles until 15 mm femoral neck shortening were comparable between DHS-screw (20,846 ± 7339), DHS-blade (18,974 ± 4032) and FNS (18,171 ± 2585), and significantly higher than 3CS (8039 ± 2778), P < 0.001. CONCLUSIONS: From a biomechanical point of view, the femoral neck system is a valid alternative to treat unstable femoral neck fractures, representing the advantages of a minimally invasive implant with comparable stability to the 2 DHS systems and superior to cannulated screws.

Numerical Optimization of the Position in Femoral Head of Proximal Locking Screws of Proximal Femoral Nail System; Biomechanical Study.

BACKGROUND: Proximal femoral fracture rates are increasing due to osteoporosis and traffic accidents. Proximal femoral nails are routinely used in the treatment of these fractures in the proximal femur. AIMS: To compare various combinations and to determine the ideal proximal lag screw position in pertrochanteric fractures (Arbeitsgemeinschaft für Osteosynthesefragen classification 31-A1) of the femur by using optimized finite element analysis. STUDY DESIGN: Biomechanical study. METHODS: Computed tomography images of patients' right femurs were processed with Mimics. Afterwards a solid femur model was created with SolidWorks 2015 and transferred to ANSYS Workbench 16.0 for response surface optimization analysis which was carried out according to anterior-posterior (-10°0) and posterior-anterior directions of the femur neck significantly increased these stresses. The most suitable position of the proximal lag screw was confirmed as the middle of the femoral neck by using optimized finite element analysis.

Radiographic Review of Helical Blade Versus Lag Screw Fixation for Cephalomedullary Nailing of Low-Energy Peritrochanteric Femur Fractures: There is a Difference in Cutout.

OBJECTIVES: To compare the rate of cutout of helical blades and lag screws in low-energy peritrochanteric femur fractures treated with a cephalomedullary nail (CMN). DESIGN: Retrospective review. SETTING: Academic medical center. PATIENTS: Overall, this study included 362 patients with an average age of 83 year old, a majority of whom were women, and had sustained a low-energy peritrochanteric femur fracture treated with a CMN. All patients had at least 3 months of clinical and radiographic follow, with an average follow-up of 11 months and a range of 3-88 months follow-up. INTERVENTION: Cephalomedullary nailing with the use of a helical blade or single lag screw for proximal fixation. MAIN OUTCOME MEASUREMENTS: Cutout of the helical blade or lag screw. RESULTS: Twenty-two cutouts occurred, 14 (15.1%) of 93 patients with helical blades and 8 (3.0%) of 269 patients with lag screws. Cutout with the helical blade was significantly more frequent than with the lag screw (P = 0.0001). The average tip-apex distance (TAD) was significantly greater for those patients who experienced cutout both for the helical blades (23.5 vs. 19.7 mm; P = 0.0194) and lag screws (24.5 vs. 20.0 mm; P = 0.0197). An absolute TAD predictive of cutout could not be determined. CONCLUSIONS: When the helical blade was used, implant cutout occurred at a significantly higher rate compared with lag screw fixation. There was not a threshold TAD that was predictive of cutout for either implant. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

A novel classification of screw placement accuracy in the cervical spine.

BACKGROUND: Goal of this study is to present an easily reproducible and reliable measurement to evaluate accuracy of screw placement in cervical spine. METHODS: Accuracy of cervical screw position was assessed in 52 patients treated with 163 screws. Each patient receiving pedicle, transarticular C1/2, lateral mass, or laminar screws and postoperative CT scan was included. Placement position was categorized in 5 grades: Grade 1 is ideal with pedicle wall perforation < 1 mm, grade 2 < 2 mm, grade 3 < 3 mm, and grade 4 < 4 mm. Grade 5 > 4 mm and/or obstruction of transverse foramen by more than half a screw diameter. Intraclass correlation coefficient (ICC) values were assessed for inter- and intraobserver reliability. RESULTS: The mode of individual evaluations was calculated to assign a single value to each screw. This yielded 89 grade 1 (54.6%), 48 grade 2 (29.4%), 14 grade 3 (8.6%), 3 grade 4 (1.8%), and 9 grade 5 (5.5%) screws. Intraobserver reliability ICC was 0.966 and 0.959 for measurements. Interobserver reliability ICC was 0.938. CONCLUSION: This study introduces a reliable classification of cervical spine instrumentation with various screw types. This should enable the use of a uniform and reproducible, and thus comparable classification for screw position in cervical spine.