Screw Fixation Technique Research Articles

Calcar buttressed screw fixation for femoral neck fracture

<p class="abstract"><strong>Background:</strong> The incidence of neck of femur fracture among elderly population is increasing day by day. Femoral neck fracture has always been an unsolved fracture<strong> </strong>as far as treatment and results are concerned. There are different views regarding the optimal method of internal fixation in femoral neck fractures. Biomechanical data from literature suggest that calcar fixation is superior to central screws placement. This study aims to analyse the functional and radiological outcome of femoral neck fractures treated by calcar buttressed screw fixation described by Filipov as biplane double supported screw fixation.</p><p class="abstract"><strong>Methods:</strong> This is a prospective study conducted in our institution from May 2015 to May 2018.The study included 43 patients (31 male, 12 female) with femoral neck fracture. Three 6.5-mm cannulated screws were laid in two medially diverging oblique planes. The distal and the middle screws were supported on the calcar. The distal screw had additional support on the posterior neck cortex. Patients were followed up for average period of 2 years. Functional outcome was evaluated using Harris Hip score.<strong></strong></p><p class="abstract"><strong>Results:</strong> Bone union occurred in 40 patients (93%) with average period of 3-4 months.<strong> </strong>51.2% of cases had<strong> </strong>excellent outcome. 23.2% of cases had good and 16.3% of cases had fair outcome. 9.3% of cases ended with poor outcome. Non union was reported in 3 patients (7%) and AVN in one patient. Various factors like age, Garden and Pauwel fracture types, time of presentation and time of surgery were statistically significant to the final functional outcome in our study.</p><p><strong>Conclusions:</strong> By providing additional calcar buttress compared to conventional method, this technique of screw fixation enhances femoral neck fracture fixation strength and reduces the fixation failure. </p>

Evaluation of Multi-Slice Spiral Computed Tomography in In vivo Simulation of Individualized Cervical Pedicle Screw Placement at C3-C7 in Chinese Healthy Population.

Background:Cervical pedicle screw fixation through posterior approach has shown greater cervical stability advantage. The cervical pedicle screw fixation technique through posterior approach is demanding. The key to the technique is the choice of point and angle of screw entrance. The angle of screw placement is variable. Morphometric measurements of the cervical pedicle are a prerequisite for individualized screw. CT imaging has become the most reliable and important means to obtain cervical pedicle's measurement data and morphology in vivo. This study explores the feasibility and application of precise in vivo measurements by multi-slice computed tomography (MSCT) for individualized cervical transpedicular screw placement at C3–C7 in Chinese healthy population.Materials and Methods:80 adults who underwent cervical examination by enhanced and nonenhanced computed tomography angiography, respectively, were selected and submitted to bone algorithm reconstruction for slice thickness and interval of 0.75 mm to acquire clear images and detailed bone structures. Simulation of individualized screw placement was performed with a 4.0 mm diameter screw with the help of postprocessing workstation. Pedicle transverse angle (PTA) and sagittal angle (PSA) were measured using the single- and double-line methods (analog nailing, 4.0 mm in diameter) in 160 pairs of C3–C7 pedicles, setting positive and negative values for cranial direction and foot side PSAs, respectively. Comparison of the measured change scope in PTA and PSA between the two methods was carried out; the range was defined as the error range.Results:Significantly, different results (P < 0.05) were obtained between the single- and double-line methods in the error ranges of PTA and PSA in C3–C7 pedicles. Interestingly, the double-line method was better in simulating the actual needs of individualized nailing. The mean values of PTA and PSA were 42.9°, 45.5°, 42.4°, 37.1°, 29.0° and 8.4°, 5.0°, −4.0°, and −7.8°, −8.1°, respectively, with the double-line method.Conclusion:MSCT reconstruction techniques can determine the direction and required parameters for individualized screw placement. In addition, accurate in vivo measurements of PTA and PSA, particularly PSA, provide the orthopedic surgeon with theoretical guidance and reliable basis in screw placement.

Posterior L5-S1 transdiscal screws for high grade spondylolisthesis - a systematic review.

The surgical management of high-grade lumbar spondylolisthesis (HGLS) is complex and aims to achieve both a solid fusion that is able to support the high shear forces of the lumbosacral junction, as well as neural decompression. We performed a systematic literature review of the safety and efficacy of posterior transdiscal (PTD) screw fixation from L5S1 for HGLS and its variations. A systematic literature review following the PRISMA guidelines was performed in the PubMed database of the studies describing the use of PTD screw fixation for HGLS. Clinical and radiological data were extracted and discussed. Study quality was assessed with the Oxford Centre for Evidence-Based Medicine Levels of Evidence. Seven studies were included and reviewed; all of them were level IV of evidence. Two of them had large case series comparing different surgical techniques: one concluded that PTD was associated with better clinical outcomes when compared with standard screw fixation techniques and the other suggesting that the clinical and radiological outcomes of PTD were similar to those when an interbody fusion (TLIF) technique was performed, but PTD was technically less challenging. The remaining five studies included small case series and case reports. All of them reported the successful useful of PTD with or without technical variations. Our review concludes, with limited level of evidence that PTD fixation is a safe and efficient technique for treating HGLS patients. It is technically less demanding than a circumferential fusion, even though proper screw insertion is more demanding than conventional pedicle screw fixation.

Suture Button Versus Syndesmotic Screw for Syndesmosis Injuries: A Meta-analysis of Randomized Controlled Trials

Background: Operative treatment is indicated for unstable syndesmosis injuries, and approximately 20% of all ankle fractures require operative fixation for syndesmosis injuries. Purpose: To perform a meta-analysis of randomized controlled trials evaluating clinical outcomes between suture button (SB) and syndesmotic screw (SS) fixation techniques for syndesmosis injuries of the ankle. Study Design: Meta-analysis. Methods: A literature search was performed according to the PRISMA guidelines to identify randomized controlled trials comparing the SB and SS techniques for syndesmosis injuries. Level of evidence was assessed per the criteria of the Oxford Centre for Evidence-Based Medicine. Statistical analysis was performed with RevMan, and a P value ≤.05 was considered statistically significant. Results: Five clinical studies were identified, allowing comparison of 143 patients in the SB group with 142 patients in the SS group. Patients treated with the SB technique had a higher postoperative American Orthopaedic Foot & Ankle Society score at a mean 20.8 months (95.3 vs 86.7, P < .001). The SB group resulted in a lower rate of broken implants (0.0% vs 25.4%, P < .001), implant removal (6.0% vs 22.4%, P = .01), and joint malreduction (0.8% vs 11.5%, P = .05) as compared with the SS group. Conclusion: The SB technique results in improved functional outcomes as well as lower rates of broken implant and joint malreduction. Based on the findings of this meta-analysis, the SB technique warrants a grade A recommendation by comparison with the SS technique for the treatment of syndesmosis injuries.

Effectiveness of F-shaped screw fixation technique in treatment of Pauwels type Ⅲ femoral neck fractures

To summarize the effectiveness of F-shaped screw fixation technique in treatment of Pauwels type Ⅲ femoral neck fractures. Between January 2013 and December 2016, 43 patients with Pauwels type Ⅲ femoral neck fractures were treated with F-shaped screw fixation technique. There were 32 males and 11 females with an average age of 38.9 years (range, 20-55 years). The fractures located on the left side in 21 patients and on the right side in 22 patients. The cause of injury included traffic accident in 19 patients and falling from height in 24 patients. There were 25 patients of Garden type Ⅲ and 18 of Garden type Ⅳ. The time from injury to operation was 2-3 days (mean, 2.2 days). These data were recorded, including operative time, fluoroscopy time, postoperative hospital stay, quality of reduction, postoperative complications (nonunion, varus deformity, femoral neck shortening, avascular necrosis of femoral head, screws back-out), and Harris scores. The operative time was 28-45 minutes (mean, 37.5 minutes). The fluoroscopy time was 13-20 seconds (mean, 14.7 seconds). The postoperative hospital stay was 2-3 days (mean, 2.7 days). All incisions healed by first intention. All patients were followed up 18-58 months with an average of 38.7 months. All patients have anatomical reduction of fractures. Fracture healing occurred in 42 patients; the union time was 3-5 months with an average of 3.6 months. Nonunion occurred in 1 patient who was treated with total hip arthroplasty. Of the 42 patients with fracture healing, 11 cases had a femoral neck shortening, 9 cases had varus deformity, 3 cases had avascular necrosis of femoral head, and 8 cases had screws back-out. There was no significant difference in complication incidences between Garden type Ⅲ fractures and Garden type Ⅳ fractures ( P>0.05). Treatment of femoral neck fractures by using the F-shaped screw fixation technique, can achieve satisfactory effectiveness with less postoperative complication.

Minimally invasive surgical treatment using 'iliac pillar' screw for isolated iliac wing fractures in geriatric patients: a new challenge.

There have been no prior case series of isolated iliac wing fracture (IIWF) due to low-energy trauma in geriatric patients in the literature. The aim of this study was to describe the characteristics of IIWF in geriatric patients, and to present a case series of IIWF in geriatric patients who underwent our minimally invasive screw fixation technique named 'iliac pillar screw fixation'. We retrospectively reviewed six geriatric patients over 65 years old who had isolated iliac wing fracture treated with minimally invasive screw fixation technique between January 2006 and April 2016. Six geriatric patients received iliac pillar screw fixation for acute IIWFs. The incidence of IIWFs was approximately 3.5% of geriatric patients with any pelvic bone fractures. The main fracture line exists in common; it extends from a point between the anterosuperior iliac spine and the anteroinferior iliac spine to a point located at the dorsal 1/3 of the iliac crest whether fracture was comminuted or not. Regarding the Koval walking ability, patients who underwent iliac pillar screw fixation technique tended to regain their pre-injury walking including one patient in a previously bedridden state. The visual analog scale score for pain at the last follow-up was quite satisfactory. Union was achieved in all patients at the last follow-up. Geriatric patients can have a form of IIWF caused by low-energy trauma that is a type of fragility fracture of the pelvis. Because subsequent deterioration of their walking status followed by a long period of non-weight bearing in geriatric patients could be as threatening as the fracture itself, the treatment paradigm for IIWF due to low-energy trauma in geriatric patients should differ from that due to high-energy trauma in most patients. In these types of fractures, minimally invasive surgical management that includes iliac pillar screw fixation can lead to good outcomes.

A Review of the Historical Evolution, Biomechanical Advantage, Clinical Applications, and Safe Insertion Techniques of Cervical Pedicle Screw Fixation.

Cervical spine instrumentation is evolving with an aim of stabilizing traumatic and non-traumatic cases of the cervical spine with a beneficial reduction, better biomechanical strength, and a strong construct with minimal intraoperative, as well as immediate and late postoperative complications. The evolution from interspinous wiring till cervical pedicle screws has changed the outlook in treating the cervical spine pathologies with maximum 3D stability, decreasing the duration of postoperative immobilization and hospital stay. Some complications associated with the use of cervical pedicle screw can be catastrophic. This review article discusses the morphometry of cervical pedicle; indications, biomechanical superiority, tricks, and pitfalls of cervical pedicle screw; complications and technical advancements in targeting safe surgery; and future directions of cervical pedicle screw instrumentation.

A finite element study on posterior short segment fixation combined with unilateral fixation using pedicle screws for stable thoracolumbar fracture.

The objective of this study was to use finite element models to investigate the biomechanics of stable thoracolumbar burst fracture repair using unilateral short-segment fixation and 4 alternate pedicle screw systems.Four posterior pedicle screw systems were compared for unilateral short-segment fixation using finite element models: intermediate bilateral short pedicle screw fixation, intermediate bilateral long pedicle screw fixation, intermediate unilateral short pedicle screw fixation, and intermediate unilateral long pedicle screw fixation. We compared range of motion (ROM), von Mises stresses on the implants, and stress on the intervertebral discs superior and inferior to the injured vertebra during simulated spinal movements.There were no significant differences in ROM, von Mises stress, or intervertebral disc stress among the 4 intermediate pedicle screw fixation techniques for all spinal movements evaluated. In addition, there were no consolidated trends depicting beneficial differences between the short and long screw models, or between the unilateral and bilateral screw models.ROM, von Mises stress, and intervertebral disc stress are the same across the 4, posterior short-segment fixation techniques evaluated using finite element models. The simplest technique—posterior short segment fixation combined with intermediate unilateral short pedicle screw fixation—is a feasible treatment strategy for stable thoracolumbar fracture.

Is S1 Alar Iliac Screw a Feasible Option for Lumbosacral Fixation?: A Technical Note.

Nonunion at the lumbosacral junction is a classic complication of long construct and deformity corrections. Iliac fixations have been extensively studied in the literature and have demonstrated superior biomechanical proprieties and lower complication rates. S2 alar iliac screws address the drawbacks of classical iliac screws but demonstrate similar biomechanical advantage. The main aim of this paper was to describe the S1 alar iliac (S1AI) screw fixation technique while evaluating our early results. S1AI screw fixation technique has the advantage of being able to achieve pelvic fixation without dissection to the S2 pedicle entry and is therefore a viable option for salvage of a failed S1 promontory screw.

C2 Translaminar Screw Fixation in Children.

Axis (C2) screw fixation has been shown to be effective in treating disorders that necessitate cervical stabilization. Although translaminar C2 screws have demonstrated clinical efficacy in adults, this technique has not yet been thoroughly investigated in children. This study describes the indications, technique, and results of translaminar C2 screw fixation in a case series of pediatric cervical spine disorders. We searched the orthopaedic database at our institution for patients who had undergone a cervical spinal fusion that encompassed C2 between 2007 and 2017. Operative records were reviewed to determine if C2 screw fixation was performed and, if so, the type of C2 screw fixation. Clinical data with regard to patient age at surgery, diagnosis, procedure details, intraoperative complications, and postoperative complications were recorded. Preoperative and postoperative computer tomographic scans were reviewed to determine laminar measurements and containment, respectively. In total, 39 C2 translaminar screws were placed in 23 patients that met our inclusion criteria. The mean age was 12.6 years (range, 5.2 to 17.8 y) with a mean of 2 levels fused (range, 1 to 6). Diagnoses included 7 patients with instability related to skeletal dysplasia, 6 os odontoideum, 4 congenital deformities, 3 basilar invaginations, 2 cervical spine tumors, and 1 fracture. Indications for C2 translaminar screws included 14 cases with distorted anatomy favoring C2 translaminar screws, 6 cases without explicit reasoning for translaminar screw usage in the patient records, and 3 cases with intraoperative vertebral artery injury (1 sacrificed secondary to tumor load and 2 others injured during exposure because of anomalous anatomy). The vertebral artery injuries were not due to placement of any instrumentation. There were no screw-related intraoperative or postoperative complications and no neurological injuries. All patients demonstrated clinical union or healing on follow-up with no episodes of nonunion. Translaminar C2 screw fixation can be reliably used in the pediatric population. Our series contained no screw-related complications, no neurological injuries, and all patients demonstrated clinical union or healing. Level IV-Case series.

Clinical and Radiographic Outcomes of Midfoot Arthrodesis Using Different Fixation Methods

Category: Midfoot/Forefoot Introduction/Purpose: Midfoot arthritis is a disabling condition, causing chronic foot pain and functional disability. The goals of midfoot arthrodesis are to a plantigrade, stable, and pain-free foot. The procedure can be technically demanding and associated with a number of complications. The use of midfoot-specific plate fixation has become more popular as an alternative to screw-only fixation. The purpose of this study was to compare the clinical and radiographic outcomes following midfoot arthrodesis using different fixation methods. Methods: This was a retrospective study of all midfoot arthrodeses performed at a single institution between January 2005 and December 2014. Patients qualified if they had a minimum of 12 months follow-up, specifically with patient-reported outcomes. Demographic and surgical information were collected. Final post-operative outcomes were reviewed and consisted of patient-reported functional measures, union rate, complications, and radiographic outcomes. Patient-reported functional measures included the American Orthopedic Foot and Ankle Score (AOFAS) midfoot scale, Visual Analogue Scale (VAS) for pain, and Lower Extremity Functional Score (LEFS). Radiographic outcomes included alignment in the antero-posterior (AP) and lateral views, as measured by the talo-first metatarsal angle during the pre-operative and final follow-up visits. Outcomes were compared among the following groups: Screw fixation group (SFG), plate fixation group (PFG), and combined fixation group (CFG), which had screw and plate fixation. Results: A total of 79 midfoot fusions in 75 patients had a mean follow-up of 61 months (range 13-122) with patient-reported outcome measures. At final follow-up, the SFG had a higher median LEFS (72.5 versus 53 in the PFG and 56 in the CFG; p&gt;0.1) and a higher mean AOFAS score (87 versus 78 in the PFG and 77 in the CFG; p&gt;0.15). The complication and nonunion rate was highest in the PFG, with 13 (50%) and 4 (50%) cases, respectively; however, the differences were not statistically significant. The talo-first metatarsal angle improved in all three groups from a median of 6.4 degrees pre-operatively to 3.9 degrees on final post-operative imaging. Conclusion: Although not statistically significant, there was a trend towards higher patient-reported outcomes, union rate, and less complication rate in midfoot fusions treated with screw fixation compared to plate fixation and combined fixation. There was no difference in radiographic correction among the difference fixation methods. Although new techniques and implants continue to be introduced, we found no significant difference in outcomes when compared to the traditional technique of screw fixation.

Comparative study on digital orthopedic three-dimensional visualization technology combined with image-based computer navigation and simple image-based computer navigation in percutaneous screw fixation for sacroiliac joint complex injury

Objective To compare the clinical effect of digital orthopedic three-dimensional visualization technology combined with image-based computer navigation and simple image-based computer navigation in percutaneous screw fixation for the treatment of sacroiliac joint complex injury. Methods A retrospective case-control analysis was conducted on 49 cases of sacroiliac complex injury from January 2015 to May 2017. There were 27 males and 22 females, with an average of 39.3 years old (range, 21-66 years). According to AO typing, there were 10 cases of type B1, 19 type B2, and 20 type C1. The duration from injury to operation ranged from 5 to 11 days (mean, 6.5 days). Based on the application of three-dimensiona digital programming, the 49 cases were assigned to Group A (n=24) which used Mimics computer assisted surgery software to simulate screw placement on the healthy side of sacroilic joint before operation and Group B (n=25) without the simulation programming. Screw placement time, intraoperative fluoroscopy frequency, and intraoperative bleeding were compared between two groups. Fracture reduction was evaluated by modified Matta standard score, and the function of hip joint by Majeed pelvic fracture function score at the last follow-up. Fracture healing and complications were observed. Results All patients were followed up for an average of 10.4 months (range, 6-24 months). The time of sacroiliac joint screw placement [(18.4±3.0)min] and the intraoperative fluoroscopy frequency [(12.9±3.8)times] in Group A were significantly less than those [(26.4±3.8) min, (19.4±1.5) times] in Group B (P 0.05). According to the modified Matta reduction standard, the good and excellent rate of Group A was 92% (22/24), and that of Group B was 92% (23/25). At the last follow up, the Majeed pelvic function score was 96% (23/24) in Group A and 92% (23/25) in Group B (P>0.05). Bone healing was seen in all patients 4 months after operation, and no complications such as wound infection, deep venous thrombosis, or screw loosening were observed. Conclusion The digital orthopedic three-dimensiona visualization technology in preoperative planning can reduce the time of sacroiliac screw placement and the intraoperative fluoroscopy frequency. It is an effective adjuvant technique for the percutaneous screw fixation under navigation in the treatment of sacroiliac joint. Key words: Sacroiliac joint; Imaging, three-dimensional; Surgery, computer-assisted; Bone nail

Biomechanical Comparison of Screw Fixation Versus a Cortical Button and Self-tensioning Suture for the Latarjet Procedure.

Background:Metal screws are traditionally used to fix the coracoid process to the glenoid. Despite stable fixation, metal screws have been associated with hardware complications. Therefore, some studies have advocated for suture button fixation during the Latarjet procedure to reduce the complications associated with screw fixation.Purpose:To biomechanically evaluate the ultimate failure load of a cortical button and self-tensioning suture versus metal screws for coracoid graft fixation during the Latarjet procedure.Study Design:Controlled laboratory study.Methods:Eight matched pairs of fresh-frozen, male cadaveric shoulders (N = 16) underwent the Latarjet procedure. The shoulders of each pair were randomly assigned to 1 of 2 groups: fixation using two 3.75-mm cannulated, fully threaded metal screws or fixation using a double suture button construct. Specimens were secured in a dynamic testing machine and cyclically preconditioned from 2 to 10 N at 0.1 Hz for 10 cycles. After preconditioning, specimens were pulled to failure at a normalized displacement rate of 400% of the measured gauge length per minute. The ultimate failure load and mechanism of failure were recorded for each specimen.Results:The mean ultimate load to failure for screw fixation (226 ± 114 N; 95% CI, 147-305 N) was not significantly different from that for suture button fixation (266 ± 73 N; 95% CI, 216-317 N) (P = .257). The mean strain at failure for screw fixation (63% ± 21%; 95% CI, 48%-77%) was not significantly different from that for suture button fixation (86% ± 26%; 95% CI, 69%-104%) (P = .060). The most common mechanism of failure for the screw fixation method was at the bone block drill holes, while an intramuscular rupture at the clamp-muscle interface occurred for the suture button construct.Conclusion:The screw and suture button fixation techniques exhibited comparable biomechanical strength for coracoid bone block fixation of the Latarjet procedure.Clinical Relevance:Metal screws have been reported to be a large contributor to intraoperative and postoperative complications. Therefore, given the results of the current study, a suture button construct may be an alternative to metal screw fixation during the Latarjet procedure. However, further clinical studies are warranted.

Extent and location of fixation affects the biomechanical stability of short- or long-segment pedicle screw technique with screwing of fractured vertebra for the treatment of thoracolumbar burst fractures: An observational study using finite element analysis.

Intermediate screw fixation at the fracture level has been widely accepted to treat thoracolumbar burst fractures, but no study has shown the effect of the extent and location of fixation. The effect of the extent and location of fixation on short- or long-segment pedicle screw fixation through intermediate screw fixation at the fracture level in the treatment of thoracolumbar burst fractures is discussed.Posterior intermediate screw fixation techniques in treating T12 vertebral fracture models were simulated and compared using finite element methods; the fixation techniques included M3-L1 (bilateral 3 monoaxial pedicle screw fixation from L1 to T11), M3-L2, M4-L1 (bilateral 4 monoaxial pedicle screw fixation from L1 to T10), M4-L2, M4-L3, and M5-L2 (bilateral 5 monoaxial pedicle screw fixation from L2 to T10). Range of motion (ROM) and largest von Mises stress (LVMS) of the instrumentations were recorded and analyzed.No significant differences were observed in the mean ROM of all states of motion between the M3-L1 model and the other fixation models except for M5-L2. The LVMS of the pedicle screws and rods all occurred during flexion. The LVMS values of the pedicle screws were larger in the M3-L2 fixation model and M4-L3 fixation model than in the other fixation models. The M3-L1 model presented a significantly smaller mean LVMS of the pedicle screws in all states of motion than the M3-L2 model (P = .026). The LVMS values of the rods were larger in the M3-L2 fixation model, M4-L3 fixation model, and M4-L2 fixation model than in the other fixation models. No significant differences were observed in the mean LVMS of the rods in all states of motion among all the fixation models.When choosing short-segment pedicle screw fixation with the screwing of fractured vertebrae to treat thoracolumbar fractures, we suggest M3-L1 over M3-L2. More severe injuries can be considered to identify an alternative treatment to long-segment monoaxial pedicle fixation constructs such as the M4-L1 and M5-L2 techniques.

Comparative study of 1-year clinical and radiological outcomes using robot-assisted pedicle screw fixation and freehand technique in posterior lumbar interbody fusion: A prospective, randomized controlled trial.

The purpose of this study was to compare the clinical outcome of surgery using robot-assisted posterior interbody fusion with that using freehand posterior interbody fusion in patients with degenerative spinal disease. 78 participants with degenerative spinal disease were randomly allocated (1:1) to the minimally invasive (MIS), posterior lumbar interbody fusion (Robot-PLIF) or conventional, freehand, open-approach, posterior lumbar interbody fusion (Freehand-PLIF). The baseline-adjusted scores on the Oswestry Disability Index (ODI) in both groups at 1year after surgery were not different (P=0.688). However, the decrease in disc height at the proximal adjacent segment was significantly less in the Robot-PLIF group than in the Freehand-PLIF group (P=0.039). One-year surgical outcomes including Visual Analog Scale, ODI and Short Form-36 did not differ between the two groups. The disc height in the proximal adjacent segment was significantly less decreased in the Robot-PLIF group than in the Freehand-PLIF group.

Posterior Subaxial Cervical Spine Screw Fixation: A Review of Techniques.

Study Design:A narrative literature review.Objectives:To review the surgical techniques of posterior screw fixation in the subaxial cervical spine.Methods:A broad literature review on the most common screw fixation techniques including lateral mass, pedicle, intralaminar and transfacet screws was performed on PubMed. The techniques and surgical nuances are summarized.Results:The following techniques were described in detail and presented with illustrative figures, including (1) lateral mass screw insertion: by Roy-Camille, Louis, Magerl, Anderson, An, Riew techniques and also a modified technique for C7 lateral mass fixation; (2) pedicle screw fixation technique as described by Abumi and also a freehand technique description; (3) intralaminar screw fixation; and finally, (4) transfacet screw fixation, as described by Takayasu, DalCanto, Klekamp, and Miyanji.Conclusions:Many different techniques of subaxial screw fixation were described and are available. To know the nuances of each one allows surgeons to choose the best option for each patient, improving the success of the fixation and decrease complications.

Occiput-axis crossing translaminar screw fixation technique using offset connectors: An in vitro biomechanical study

ObjectiveFixation with the axis vertebra (C2) using pedicle screws is commonly used to treat an unstable occipitocervical junction; however, it is accompanied by a risk of vertebral artery injury. The occiput-C2 (OC2) crossing translaminar screw fixation technique may avoid this risk, but rod implantation is difficult. Offset connectors can help facilitate this construct. This study aimed to evaluate the stability of a technique for OC2 crossing translaminar screw fixation using offset connectors (C2LAM + OF) in comparison with other methods. Patients and methodsSix fresh-frozen human cadaveric occipital–cervical spines were tested intact under flexion, extension, lateral bending, and axial rotation. These were then made into a type II odontoid fracture model, instrumented with an occipital plate, and tested in the following modes: C2 bilateral pedicle screws (C2P), a single C2 pedicle screw and bilateral C3 lateral mass screws (C2P + C3M), C2 crossing translaminar screws (C2LAM), and C2LAM + OF. The OC2 range of motion (ROM) for each construct was obtained and compared using a repeated-measures analysis. ResultsThe ROM of the C2LAM + OF construct was found not to be significantly different from that of the C2P and C2P + C3M fixations in every direction (p > 0.05). However, the C2LAM + OF construct was superior to the C2LAM construct in axial rotation (p < 0.05). ConclusionsOC2 crossing translaminar screw fixation using offset connectors offers similar stability to C2 pedicle screw fixation and is an effective alternative method for treating an unstable occipitocervical junction.

A practical 'safe zone' technique for lag screw fixation of the fibula.

Introduction During ankle fracture fixation, iatrogenic trauma to retro fibula structures can result in morbidity and reoperation. We describe a safe zone for lag screw insertion. Materials and methods This study was completed in three sections. We identified the average entry and exit points for the lag screw using 45 Weber B ankle fractures identified from our trauma database. We then analysed 26 sequentially presented ankle magnetic resonance images, concentrating on axial sections at 4, 8, 12 and 16 mm above the ankle joint. Finally, we used 63 sequentially performed magnetic resonance scans to confirm the safe zone from these consistent structures. Results The typical lag screw exit point was 14.2 mm above the ankle joint (95% confidence Interval 11.3-17.1 mm). A safe zone trajectory occurred between 31 and 45 degrees taken from the anterior aspect of the flat fibular surface at this level. The obvious palpable landmark to direct screw trajectory and avoid 'at risk' structures was found to be the medial edge of the Achilles tendon. Our final dataset confirmed in 63 scans, the medial aspect of the Achilles tendon to be a consistent safe zone with a minimum distance of at risk structures of 4 mm. Conclusion This simple method of directing the fibula lag screw towards the palpable medial edge of the Achilles tendon is practical, easy to teach and directs the screw on a safe trajectory away from the most commonly injured structures around the back of the fibula.

C2 Translaminar Screw Fixation (Wright`s Technique) Applicability in Atlantoaxial Instability

Atlantoaxial instability often requires surgical treatment. Several techniques are available to perform antlantoaxial stabilization, and all of these have their different advantages and disadvantages. In 2004, Wright described the C2translaminar screw fixation, which offers rigid fixation but without the technical demands of C2 pars placement and eliminates the risk of vertebral artery injury. The aim of this study is to review the C2 translaminar screw fixation technique, emphasizing operative details, risks and benefits comparing with the others atlantoaxial fixation techniques.

Biomechanical characterization of three iliac screw fixation techniques: A finite element study

We aim to characterize the biomechanical properties of a modified iliac screw fixation method compared with the classic iliac screw fixation and the S2 alar iliac screw (S2AI) fixation using a FEM.A three-dimensional, non-linear FEM of lumbosacral spine and pelvis (L1-pelvis) was modified to simulate 3 different iliac screw fixations based on posterior screw fusion. The peak von Mises stress (PVMS) values of the iliac screws in the 3 different iliac screw fixations were recorded in during flexion/extension/axial rotation/lateral bending. The interaction stress which arose between the screw head and the shaft of iliac screws, was also measured for each case.The PVMS values of the 3 different iliac screw fixation techniques were lower than the fatigue strength levels under physiological loadings. PVMS of iliac screws was observed in the screw shaft for S2AI, in the screw neck for the modified iliac screw technique, and in the offset connectors of the classic iliac screw technique. The interaction between the screw head and the neck was compressed in modified iliac screw fixation technique. On the other hand, distraction force was observed in the S2AI technique between the screw head and the screw shaft.This FEM study supports our previous clinical results, which found that the modified iliac screw fixation technique can be an effective alternative sacropelvic fixation technique comparable to the classic iliac screw and the S2AI technique.