Femoral interference screw divergence as a result of anteromedial portal insertion and outside-in FlipCutter femoral tunnel drilling: A cadaveric study

Aims and objectives

To investigate whether interference screw fixation through an anteromedial portal into an outside-in drilled femoral tunnel via a flip cutter results in acceptable hardware position.

Materials & methods

10 cadaveric knees underwent ACL-reconstruction with patellar BTB autograft. Femoral tunnel drilling was performed utilizing an outside-in flip cutter drill and interference screws for femoral fixation. Lateral and anterior-posterior (AP) fluoroscopic images were taken to measure screw divergence within the femoral tunnel. The means of AP and lateral divergence angles were compared using two-tailed t-tests.

Results

Using the flip cutter, the AP and lateral divergence angles were 7.3° ± 4.5° and 9.3° ± 9.3°, respectively, while the total divergence angles were 16.6° ± 11.8°. Divergence angles using a cannulated reamer were found to be 14.4° ± 2.5° and 6.8° ± 2.8° for AP and lateral, respectively and 21.1° ± 5.2° for the total divergence. The AP divergence angles using the flip cutter were significantly less than those reported using a cannulated reamer (p = 0.001).

Conclusions

The flip cutter method resulted in significantly reduced divergence angle between the screw and graft when compared to previous cadaveric studies in the coronal plane. There was no significant difference in divergence angle in the sagittal plane. Both methods appear to result in divergence angles below the threshold which would be considered to significantly decrease pull-out strength. Large standard deviations also reflect limited sample size but may also suggest more variability in divergence when compared to historical control set. This study clearly establishes the outside-in technique using a retrograde reamer as a viable independent femoral drilling solution for ACL reconstruction when using a BTB autograft with a femoral interference screw.

Spinolaminar locking plates improve fixation strength compared to pedicle screws: a biomechanical analysis

INTRODUCTION

Pedicle screw loosening is a significant complication of posterior spinal fixation, particularly among osteoporotic patients and in deformity constructs. In orthopedic trauma surgery, locking plates and screws have revolutionized the fixation of osteoporotic fractures. We have combined the traumatology principle of fixed-angle locking plate fixation with the spine principles of segmental instrumentation.

METHODS

A novel spinolaminar locking plate was designed based on morphometric studies of human thoracolumbar vertebrae. The plates were fixed to cadaveric human lumbar spines and connected to form 1-level L1-L2 or L4-L5 constructs and compared to similar pedicle screw constructs. Pure moment testing was performed to assess range of motion before and after 30,000 cycles of cyclic fatigue. Post-fatigue fixture pullout strength was assessed by applying a continuous axial tensile force oriented to the principal axis of the pedicle until pullout was observed.

RESULTS

Spinolaminar plate fixation resulted in superior pullout strength compared to pedicle screws (1,065 ± 400N vs. 714 ± 284N, p = 0.028). Spinolaminar plates performed equivalently to pedicle screws in range of motion reduction during flexion/extension and axial rotation. Pedicle screws outperformed the spinolaminar plates in lateral bending. Finally, no spinolaminar constructs failed during cyclic fatigue testing, whereas one pedicle screw construct did.

CONCLUSIONS

The spinolaminar locking plate maintained adequate fixation post-fatigue, particularly in flexion/extension and axial rotation compared to pedicle screws. Moreover, spinolaminar plates were superior to pedicle screw fixation with respect to cyclic fatiguing and pullout strength. The spinolaminar plates offer a viable option for posterior lumbar instrumentation in the adult spine.

Predictive approach for post-covid 19 evolution study of the pavement surface deterioration based on visual inspection results

This study proposes a statistical approach to examine pavement surface deterioration tendencies resulting from the COVID-19 pandemic. The road inspection results, the historical road databases, and the condition analysis make pavement management a major challenge for managers in Morocco as well as around the world. The decrease in traffic, the maintenance stoppages, the difficulties in obtaining field information, all these imperative ingredients are a consequence of the covid-19 pandemic. In this respect, historical analysis, remote monitoring and damage prediction have become increasingly important. In collaboration with the Moroccan National Center for Road Research, this study examines the impact of pandemic-induced lockup on the variation of three important pathologies: pullouts, cracks and potholes, based on the results of a visual inspection and the results of deflection and evenness performed in 2020 on a 50 km long section connecting Meknes and Khemisset cities. First, the reduction of data based on deterioration represented in four levels (A, B, C and D), second, the comparison of the different pathologies before and after the pandemic, the impact of the pandemic on the pavement quality, and finally, a prediction of the progression of the pathology using the linear regression method. This study will help decision makers to take into account pandemics and health failures in their pavement management approaches, and especially to prevent future damage for budget allocation.

Novel press-fit technique of patellar bone plug in anterior cruciate ligament reconstruction is comparable to interference screw fixation

PURPOSE

Conventional press-fit technique for anterior cruciate ligament reconstruction (ACLR) is performed with extraction drilling of the femoral bone tunnel and manual shaping of the patellar bone plug. However, the disadvantages of this technique include variation in bone plug size and, thus, the strength of the press-fit fixation, bone loss with debris distribution within the knee joint, potential heat necrosis, and metal wear debris due to abrasion of the guide wire. To overcome these disadvantages, a novel technique involving punching of the femoral bone tunnel and standardized compression of the bone plug was introduced. In this study, the fixation strength and apparent stiffness were tested and compared to that of the gold-standard interference screw fixation technique in three flexion angle configurations (0°/45°/90°) in a porcine model. We hypothesized that the newly developed standardized press fit fixation would not be inferior to the gold standard method.

METHODS

Sixty skeletally mature porcine knees (30 pairs) were used. Full-thickness central third patellar tendon strips were harvested, including a patellar bone cylinder of 9.5 mm in diameter. The specimens were randomly assigned to 10 pairs per loading angle (0°, 45°, 90°). One side of each pair was prepared with the press-fit technique, and the contra-lateral side was prepared with interference screw fixation. Equivalent numbers of left- and right-sided samples were used for both fixation systems. A three-way multifactor ANOVA was carried out to check for the influence of (a) fixation type, (b) flexion angle, and (c) side of the bone pair.

RESULTS

The primary fixation strength of femoral press-fit graft fixation with punched tunnels and standardized bone plug compression did not differ significantly from that of interference screw fixation (p = 0.51), which had mean loads to failure of 422.4 ± 134.6 N and 445.4 ± 135.8 N, respectively. The flexion angle had a significant influence on the maximal load to failure (p = 0.01). Load values were highest in 45° flexion for both fixations. The anatomical side R/L was not a statistically significant factor (p = 0.79).

CONCLUSION

The primary fixation strength of femoral press-fit graft fixation with punched femoral tunnels and standardized bone plug compression is equivalent to that of interference screw fixation in a porcine model. Therefore, the procedure represents an effective method for ACL reconstruction with patellar or quadriceps tendon autografts including a patellar bone plug.

Augmenting a dynamic hip screw with a calcium sulfate/hydroxyapatite biomaterial

Internal fixation failure in hip fractures can lead to reoperation. Calcium sulfate/hydroxyapatite (CaS/HA) is a biomaterial that can be used for augmenting fracture fixation. We aimed to determine whether an injection of 2 ml CaS/HA increases the fixation of a dynamic hip screw inserted in synthetic and human trabecular bone. The study consists of two parts: 1) synthetic bone blocks (n = 74), with three subgroups: empty (cannulated screw, no injection), cannulated, and fenestrated; and 2) osteoporotic human femoral heads (n = 29), with the same subgroups. The heads were imaged using µCT. Bone volume fraction, insertion angle, and head diameter were measured. Pullout tests were performed and peak force, stiffness, and work were measured. The fenestrated group showed increases in pullout strength compared to no injection in the synthetic blocks. The cannulated group showed a higher pullout strength in low-density blocks. In the femoral heads, the variation was larger and there were no significant differences between groups. The bone volume fraction correlated with the peak force and work, and the insertion angle correlated with the stiffness. CaS/HA can improve the fixation of a dynamic hip screw. For clinical use, spreading of the material around the threads of the screw must be ensured.

All-suture anchor pullout results in decreased bone damage and depends on cortical thickness

PURPOSE

To evaluate the influence of cortical and cancellous bone structure on the biomechanical properties of all-suture and conventional anchors and compare the morphological bone damage after their failure. The hypothesis of the study is that all-suture anchor pullout is less invasive and that the pullout force is influenced by the cortical thickness.

METHODS

Thirty human humeri were biomechanically tested as follows: starting with a load cycle from 20 to 50 N, a stepwise increase of the upper peak force by 0.05 N for each cycle at a rate of 1 Hz was performed. Analysis included maximum pullout strength for three different anchor implantation angles (45°, 90°, 110°) of the two anchor types. After anchor pullout, every sample underwent micro-CT analysis. Bone mineral density (BMD) and cortical thickness were determined at the anchor implantation site. Furthermore, the diameter of the cortical defect and the volume of the bone cavity were identified.

RESULTS

The maximum pullout strength of all-suture anchors demonstrates a strong correlation to the adjacent cortical thickness (r = 0.82, p ≤ 0.05) with at least 0.4 mm needed to withstand 200 N. No correlation could be seen in conventional anchors. Moreover, no correlation could be detected for local BMD in both anchors. All-suture anchors show a significantly narrower cortical defect as well as a smaller bone cavity following pullout (4.3 ± 1.3 mm vs. 5.3 ± 0.9 mm, p = 0.037; 141 mm³ vs. 212 mm³; p = 0.009). The cortical defect is largest if the anchors are placed at a 45° angle.

CONCLUSION

In contrast to conventional anchors, the pullout force of all-suture anchors depends on the thickness of the humeral cortex. Furthermore, all-suture anchors show a significantly smaller cortical defect as well as decreased bone damage in the case of pullout. Therefore, the clinical implication of this study is that all-suture anchors are advantageous due to their bone preserving ability. Also, intraoperative decortication should not be performed and cortical thickness should be preoperatively evaluated to decrease the risk of anchor failure.

Securing CSF catheters to the skin: from sutures and bolt system to subcutaneous anchoring device towards zero complications

INTRODUCTION

Securing the catheter to the skin either with sutures or staples and to the skull with bolt system still represents the most common options in the management of CSF external drainage. However, these options bear an unavoidable risk of complications. This problem is common to vascular accesses and has been successfully overcome with the introduction of device for subcutaneous anchoring (SecurAcath®, Interrad Medical, Inc., Plymouth, Minnesota), which has rapidly become the standard of care in this field.

METHODS

We report our experience with the use of SecurAcath® to secure CSF drainage, either ventricular or spinal. Results were compared with literature data.

RESULTS

Since 2015, SecurAcath® was used in 209 patients (mean age 7 years) to secure 195 external cranial catheters (either ventricular or subdural or intralesional) and 16 spinal drainages. Indwell time ranged from 5 to 30 days. No complication related to the use of the device was observed. In particular, there was no case of dislocation or accidental pullout of the catheter. Rate of infection, or superinfection in case of ventricular catheter implanted for CSF infection, was null.

CONCLUSIONS

SecurAcath® is a safe and effective device to secure CSF external catheters, with several relevant advantages, including easy placement and maintenance. Moreover, it may stay in place for the whole duration of the catheter without any skin tissue trauma and allows a complete antisepsis of the exit site, thus reducing local skin complications. This factor has significant impact on the reduction of infection rate of external CSF catheters.

Contribution of postoperative ultrasound to early detection of anchor pullout after rotator cuff tendon repair: Report of 3 cases

INTRODUCTION

Rotator cuff repair by suture bridge is now widely used. Few studies reported secondary pullout of radiotransparent anchors. The aim of the present prospective study was to demonstrate the contribution of in-office ultrasonography to detect pullout, and to describe the examination procedure.

MATERIAL AND METHOD

A total of 102 patients underwent arthroscopic rotator cuff repair by suture bridge, with impacted second-row anchors. Ultrasonography was performed by the surgeon in postoperative consultations.

RESULTS

At 6 weeks' follow-up, 3 patients showed mean 2nd-row implant pullout of 8.3mm. All underwent arthroscopic revision to extract the implant, which was mobile within its tunnel in all cases. Clinical progression was good, with mean Constant score 72 and no aggravation of the lesion on ultrasound at 3 months' follow-up.

DISCUSSION

The present series would seem to be the first to report: early radiotransparent in-vivo pullout 6 weeks after suture bridge cuff repair; ultrasound detection of pullout in consultation by the orthopedic surgeon; a description of the ultrasound technique for screening this rare and specific problem.

CONCLUSION

Ultrasound now enables radiotransparent anchor positioning to be monitored following rotator cuff repair as of the first postoperative days, without compromising tendon healing.

LEVEL OF EVIDENCE

II.

Pullout Strength Predictor: A Machine Learning Approach

Study Design

A biomechanical study.

Purpose

To develop a predictive model for pullout strength.

Overview of Literature

Spine fusion surgeries are performed to correct joint deformities by restricting motion between two or more unstable vertebrae. The pedicle screw provides a corrective force to the unstable spinal segment and arrests motions at the unit that are being fused. To determine the hold of a screw, surgeons depend on a subjective perioperative feeling of insertion torque. The objective of the paper was to develop a machine learning based model using density of foam, insertion angle, insertion depth, and reinsertion to predict the pullout strength of pedicle screw.

Methods

To predict the pullout strength of pedicle screw, an experimental dataset of 48 data points was used as training data to construct a model based on different machine learning algorithms. A total of five algorithms were tested in the Weka environment and the performance was evaluated based on correlation coefficient and error matrix. A sensitive study of various parameters for obtaining the best combination of parameters for predicting the pullout strength was also preformed using the L9 orthogonal array of Taguchi Design of Experiments.

Results

Random forest performed the best with a correlation coefficient of 0.96, relative absolute error of 0.28, and root relative squared error of 0.29. The difference between the experimental and predicted value for the six test cases was not significant (p >0.05).

Conclusions

This model can be used clinically for understanding the failure of pedicle screw pullout and pre-surgical planning for spine surgeon.

A Novel C2 Screw Trajectory: Preliminary Anatomic Feasibility and Biomechanical Comparison

BACKGROUND

Pedicle screw and translaminar screw fixation in C2 may not be applicable in many patients with anatomic abnormalities or narrow laminar thickness and spinous process height. The aim of this study was to assess morphometric and mechanical feasibilities of a novel alternative screw trajectory that pierces the bifid base of C2.

METHODS

Anatomic measurements that determined the feasibility of spinous process bifid base (SPB) screw fixation were assessed in 14 cadaveric C2 vertebrae. Pullout tests to assess ultimate fixation strength for 3 screw trajectories (transpedicular, translaminar, and SPB) were performed in cadaveric vertebrae for comparison.

RESULTS

Anatomic measurements included mean spinous process height (10.4 ± 4.2 mm) and mean bilateral bifid base length (10.1 ± 2.2 mm) and thickness (left, 4.4 ± 1.0 mm; right, 4.3 ± 0.9 mm). In 64% (9/14) of specimens, bifid base length was ≥9 mm. Mean pullout strength for transpedicle, translaminar, and SPB screws in 9 viable specimens was 648 ± 305 N, 628 ± 417 N, and 755 ± 279 N.

CONCLUSIONS

SPB screw fixation may be viable anatomically and mechanically for C2 fixation. Feasibility of SPB screw fixation is determined by length, thickness, and mutual angle of the bilateral bifid bases. Patients with thin (<4 mm) and short (<9 mm) bifid bases are not likely to be suitable candidates. SPB screw fixation shows potential as an alternative approach or a salvage technique for patients with high-riding vertebral arteries or severely thin C2 lamina and warrants further investigation.

Biomechanical Performance of Various Cement-Augmented Cannulated Pedicle Screw Designs for Osteoporotic Bones

INTRODUCTION

Early-stage pullout is a common problem for surgeons during the fixation of osteoporotic bones. Poor bone quality limits the use of pedicle screws for patients with osteoporosis. In this study, the researchers investigated the effects of hole and gap position and type on the pullout strength of cannulated screws.

METHODS

Seven different designs were tested, including a control group. All cannula diameters were 2 mm and holes were drilled with a diameter of 1.5 mm. Gaps were milled with a 2-mm-diameter tool with 2-mm displacement proximally. All holes and gaps were drilled or opened unilaterally and bilaterally. Grade 40 and 10 polyurethane foam was used to simulate healthy and osteoporotic bones, respectively. For pullout tests, insertion depth was 30 mm and 2-mm-diameter pilot holes were drilled into blocks before screws were inserted. The cross-head speed was 2 mm/min. For torsion tests, 1 side of the screw was fixed and other was twisted clockwise.

RESULTS

For torsion tests, the maximum torque value exhibited by the control group (non-cannulated) was 14.94 Nm. The highest torsional strength among tested cannulated screws was 13.54 Nm for Single side two holes including design (S2H) (p < .0001). The minimum torsional strength was 9.45 Nm with a breaking angle of 39° (p < .005). Comparing results for samples pulled out from grade 40 polyurethane foam, single side slot including design (SS) samples exhibited the highest pullout strength with a maximum force of 3,104 N.

CONCLUSIONS

The unilateral, sequential, 3-radial hole, drilled, cannulated screw was the optimal alternative when considering pullout and torsional strength as criteria.

Biomechanical Comparison of 2 Different Pedicle Screw Systems During the Surgical Correction of Adult Spinal Deformities

STUDY DESIGN

A biomechanical spine model was used to evaluate the impact of screw design on screw-vertebra interface loading during simulated surgical corrections of adult scoliosis.

OBJECTIVES

To evaluate differences in screw-vertebra interface forces during adult scoliosis correction between favored angle (FA) screws with extension tabs and standard polyaxial screws while varying deformity severity and curve rigidity.

SUMMARY OF BACKGROUND DATA

Pedicle screws enable surgeons to safely and effectively realign spinal deformities. The risk of perioperative screw pullout increases when presented with adult deformities that have less flexible spines and lower bone mineral density. An FA screw with reduction tabs is believed to enable surgical techniques permitting load distribution on multiple screws, thereby reducing screw pullout potential.

METHODS

The researchers constructed 3 finite element spine models from adult scoliosis patients. Mechanical properties of intervertebral discs were modeled to reflect less flexible adult spines and their stiffness was varied to evaluate impact on screw-vertebra forces. Models simulated scoliosis surgery according to clinical data using FA or polyaxial screws. Forces measured at the screw-vertebra interface were monitored and compared for each patient with FA and then polyaxial screws.

RESULTS

Simulations using FA screws reduced screw-vertebra interface forces significantly compared with polyaxial screws. Favored angle screws caused 18%, 14%, and 16% reductions in peak forces and 29%, 35%, and 22% reductions in average forces compared with polyaxial screws for patients 1, 2, and 3, respectively. Favored angle screws also provided consistent relative reduction in average forces by 28% when varying properties of intervertebral discs among 8, 10, and 12 MPa.

CONCLUSIONS

Using a virtual finite element platform, FA screws reduced screw-vertebra interface forces encountered during simulated correction of less flexible adult scoliosis compared with standard polyaxial screws. These results show a potential benefit of using this modified screw design to reduce screw-vertebra forces and potential intraoperative pullout failures.

Primary stability of pedicle screws depends on the screw positioning and alignment

BACKGROUND CONTEXT

There is no universal consensus regarding the biomechanical aspects and relevance on the primary stability of misplaced pedicle screws.

PURPOSE

The study is aimed to the determination of the correlation between axial pullout forces of pedicle screws with the possible screw misplacement, including mild and severe cortical violations.

METHODS

Eighty-eight monoaxial pedicle screws were implanted into 44 porcine lumbar vertebral bodies, paying attention on trying to obtain a wide range of placement accuracy. After screw implantation, all specimens underwent a spiral computed tomography scan, and the screw placements were graded following the scales of Laine et al. and Abul Kasim et al. Axial pullout tests were then performed on a servohydraulic material testing system.

RESULTS

Decreasing pullout forces were determined for screws implanted with increasing cortical violation. A smaller influence of cortical violations in the medial direction with respect to the lateral direction was observed. Screws implanted with a large cortical violation and misplacement in the craniocaudal direction were found to be significantly less stable than screws having comparable cortical violation but in a centered sagittal position.

CONCLUSIONS

These results provide adjunctive criteria to evaluate more accurately the fate of a spine instrumentation. Particular care should be placed in the screw evaluation regarding the craniocaudal positioning and alignment.

Calcium Triglyceride Versus Polymethylmethacrylate Augmentation: A Biomechanical Analysis of Pullout Strength

STUDY DESIGN

Biomechanical pullout study using calcium triglyceride (CTG) and polymethylmethacrylate (PMMA) for screw augmentation.

OBJECTIVE

Compare the biomechanical performance of CTG augmentation versus the gold standard, PMMA, in primary and revision models, using a pedicle screw pullout model.

BACKGROUND SUMMARY

CTG is a novel form of bone augmentation with several reported biocompatible properties compared with PMMA. PMMA is the standard of care for pedicle screw augmentation in osteoporotic spine.

METHODS

Blocks of closed-cell rigid polyurethane foam of uniform density, representing subcortical layer in osteoporotic pedicle, were prepared according to ASTM standards. After the components of PMMA (n = 11) and CTG (n = 11) were individually mixed in a standardized fashion, 0.2 ml was injected from deep to superficial along a predrilled pilot hole followed by immediate insertion of the pedicle screw. An unaugmented group (n = 10) was also prepared. Blocks cured for 24 hrs, and screws were pulled out at a rate of 5 mm/min on materials testing equipment. For the revision model, the unaugmented group, after screw pullout, was augmented with 0.8 ml of PMMA (n = 5) or CTG (n = 5) as detailed above and screw pullout performed similarly.

RESULTS

The mean pullout strengths (SD) for the intact models were as follows: unaugmented, 976.6 N (94.2 N); PMMA, 1,218.1 N (66.8 N); and CTG, 1,841.6 N (57.4 N). A one-way analysis of variance indicated a significant difference among the primary models (p < .0001). For the revision models, the pullout strength for PMMA was 1,939.2 N (108.9 N) and for CTG, 2,513.0 N (149.1 N), which were statistically different from each other (p < .0003). Stiffness of the constructs was increased with both PMMA and CTG augmentation over no augmentation (p < .0001) although no significant difference in stiffness was detected between the 2 forms of augmentation.

CONCLUSION

We conclude that CTG augmentation of pedicle screws resulted in significantly higher axial pullout strength in primary (p < .0001) and revision (p < .0003) models compared with PMMA.

Pullout of a lumbar plate with varying screw lengths

Background

Screw length pertains to stability in various orthopedic fixation devices. There is little or no information on the relationship between plate pullout strength and screw length in anterior lumbar interbody fusion (ALIF) plate constructs in the literature. Such a description may prove useful, especially in the treatment of osteoporotic patients where maximizing construct stability is of utmost importance. Our purpose is to describe the influence of screw length on ALIF plate stability in severely and mildly osteoporotic bone foam models.

Methods

Testing was performed on polyurethane foam blocks with densities of 0.08 g/cm³ and 0.16 g/cm³. Four-screw, single-level ALIF plate constructs were secured to the polyurethane foam blocks by use of sets of self-tapping cancellous bone screws that were 20, 24, 28, 32, and 36 mm in length and 6.0 mm in diameter. Plates were pulled out at 1 mm/min to failure, as defined by consistently decreasing load despite increasing displacement.

Results

Pullout loads in 0.08-g/cm³ foam for 20-, 24-, 28-, 32-, and 36-mm screws averaged 303, 388, 479, 586, and 708 N, respectively, increasing at a mean of 25.2 N/mm. In 0.16-g/cm³ foam, pullout loads for 20-, 24-, 28-, 32-, and 36-mm screws averaged 1004, 1335, 1569, 1907, and 2162 N, respectively, increasing at a mean of 72.2 N/mm.

Conclusions

The use of longer screws in ALIF plate installation is expected to increase construct stability. Stabilization from screw length in osteoporotic patients, however, is limited.