Comparison of 3D-printed titanium-alloy,standard titanium-alloy,and PEEK interbody spacers in an ovine model

BACKGROUND CONTEXTOsseointegration is a pivotal process in achieving a rigid fusion and ultimately a successful clinical outcome following interbody fusion surgery. Advancements in 3D printing technology permit commonly used titanium interbody spacers to be designed with unique architectures, such as a highly interconnected and specific porous structure that mimics the architecture of trabecular bone. Interbody implants with a microscale surface roughness and biomimetic porosity may improve bony ongrowth and ingrowth compared to traditional materials.PURPOSEThe purpose of this study was to compare the osseointegration of lumbar interbody fusion devices composed of surgical-grade polyetheretherketone (PEEK), titanium-alloy (TAV), and 3D-printed porous, biomimetic TAV (3DP) using an in vivo ovine model.STUDY DESIGNIn Vivo Preclinical Animal StudyMETHODSEighteen sheep underwent two-level lateral lumbar interbody fusion randomized with either 3DP, PEEK, or TAV interbody spacers (n=6 levels for each spacer per time point). Postoperative time points were 6 and 12 weeks. Microcomputed tomography and histomorphometry were used to quantify bone volume (BV) within the spacers (ingrowth) and the surface bone apposition ratio (BAR) (ongrowth), respectively.RESULTSThe 3DP-treatment group demonstrated significantly higher BV than the PEEK and TAV groups at 6 weeks (77.3±44.1 mm³, 116.9±43.0 mm³, and 108.7±15.2 mm³, respectively) (p<.05). At 12 weeks, there were no BV differences between groups (p>.05). BV increased in all groups from the 6- to 12-week time points (p<.05). At both time points, the 3DP-treated group (6w: 23.6±10.9%; 12w: 36.5±10.9%) had significantly greater BAR than the PEEK (6w: 8.6±2.1%; 12w: 14.0±5.0%) and TAV (6w: 6.0±5.7%; 12w: 4.1±3.3%) groups (p<.05).CONCLUSIONS3DP interbody spacers facilitated greater total bony ingrowth at 6 weeks, and greater bony ongrowth postoperatively at both 6 and 12 weeks, in comparison to solid PEEK and TAV implants.CLINICAL SIGNIFICANCEBased on these findings, the 3DP spacers may be a reasonable alternative to traditional PEEK and TAV spacers in various clinical applications of interbody fusion.     

Outcomes of the use of cement-augmented cannulated pedicle screws in lumbar spinal fusion

BACKGROUND CONTEXTThere are few studies of the radio-clinical outcomes of cement-augmented cannulated pedicle screw (CPS) fixation in osteoporotic patients.PURPOSETo compare the radiological and clinical outcomes between groups receiving cement-augmented CPS and solid pedicle screws (SPS) in lumbar fusion surgery.STUDY DESIGN/SETTINGRetrospective comparative studyPATIENT SAMPLEA total of 187 patients who underwent lumbar fusion surgery for degenerative spinal stenosis or spondylolisthesis from 2014 to 2019.OUTCOME MEASURESRadiological evaluation included screw failure, cage failure, rod breakage, and fusion grade at postoperative 6 months and 1 year. Pre- and postoperative visual analog scales for back pain (VAS-BP), leg pain (VAS-LP), Korean Oswestry disability index (K-ODI), and postoperative complications were also compared.METHODSOutcomes of patients with high risk factors for implant failure [old age, osteoporosis, autoimmune disease or chronic kidney disease (CKD)] who underwent open transforaminal lumbar interbody fusion with cement-augmented CPS fixation (Group C, n=55) or SPS fixation (Group S, n=132) were compared.RESULTS324 pedicle screws in Group C and 775 pedicle screws in Group S were analyzed. Group C had a significantly higher average age and lower T-score, and included more patients with autoimmune disease and CKD than group S (all p<.05). Clear zones, screw migration and loss of correction were significantly less frequent in Group C (all p<.05). Thirteen screw breakages were observed; they were only in Group C (4.0%) and all were in the proximal of the two holes. Interbody and posterolateral fusion rates were not significantly different. At last follow-up, all clinical parameters including VAS-BP, VAS-LP, and K-ODI scores had improved significantly in both groups. Postoperative complications were not significantly different in the two groups.CONCLUSIONIn lumbar fusion surgery, using cement-augmented CPS in high-risk groups for implant failure could be a useful technical option for reducing acute radiological complications and obtaining clinical results comparable to those obtained using SPS in patients with low risk of implant failure.LEVEL OF EVIDENCELevel 4     

Internal Fixation of the Cervical Spine: Current Indications and Techniques

Numerous techniques for the internal fixation of the cervical spine have been developed in recent years. The indications for surgery must be strictly defined before the optimal type of implant can be selected on the basis of the advantages and potential risks. Wiring techniques are still commonly used for posterior stabilization. Anterior fusion can be accomplished without internal fixation in most cases. The halo vest is still widely used for the conservative management of cervical fractures and for postoperative external immobilization. Posteriorly, traditional wiring methods are still used, as well as newer techniques, such as C1-C2 screw fixation, occipitocervical plate fixation, and lateral-mass lower cervical plating. Anteriorly, meticulous Smith-Robinson surgical approach and grafting techniques are essential. Further studies are needed to define the exact indications for various new techniques, such as anterior odontoid screw fixation and anterior plating. The surgeon must choose an appropriate device on the basis of the mechanism of injury, the pathoanatomy of the lesion, and familiarity with the device, keeping in mind the goals of internal fixation-stabilization, reduction and maintenance of alignment, early rehabilitation, and perhaps enhancement of fusion and avoidance of the need to use an external halo vest.     

How do lateral hinge and distraction affect three-dimensional rotation in open wedge high tibial osteotomy?

BackgroundOpen-wedge high tibial osteotomy (OWHTO) has extensively been used for the correction of medial knee osteoarthritis. The proximal tibia is osteotomized and distracted to enable the rotation of tibial fragments around the lateral hinge. Both, wedge inclination on the medial side and saw progression near the lateral cortex determine the hinge orientation. This study focused on the interaction between hinge orientation and distraction sites on the coronal, sagittal, and horizontal planes of the distracted plateau.MethodsThree parameters of wedge inclination, saw progression, and distraction site (i.e., posterior, middle, and anterior) were systematically varied. Using a three-dimensional (3D)-printing technique, the osteotomized tibiae were manufactured as the specimens for the in vitro experiments. In total, 27 variations (3 × 3 × 3) were tested. After distraction, the specimens were scanned by computed tomography and spatially registered with the original tibia to compare the 3D angles of the distracted plateaus.ResultsCoronal rotation is the main purpose of OWHTO; therefore, all the values of the coronal angles were positive and significantly higher than the other two. The sagittal and horizontal angles had relatively similar values. Distraction in the middle site seems to have the least impact on sagittal rotation. Large angles of hinge orientation show the superior ability in adjusting the sagittal rotation than small angles. However, the larger the horizontal angles the greater the wedge inclination.ConclusionsThe wedge inclination, saw progression, and distraction site constitute a complex mechanism that affects 3D rotations of the distracted plateau. The coronal angles are sensitive to hinge orientation and distraction site. The intraoperative planning of manipulating hinge orientation is an effective method to adjust sagittal rotation. A large angle of wedge inclination is an indicator of horizontal rotation, and it should be carefully mitigated to reduce the risk of cracking in the lateral hinge.     

Increased torsional stability by a novel femoral neck locking plate. The role of plate design and pin configuration in a synthetic bone block model

BackgroundIn undisplaced femoral neck fractures, internal fixation remains the main treatment, with mechanical failure as a frequent complication. As torsional stable fixation promotes femoral neck fracture healing, the Hansson Pinloc® System with a plate interlocking pins, was developed from the original hook pins. Since its effect on torsional stability is undocumented, the novel implant was compared with the original configurations.MethodsForty-two proximal femur models custom made of two blocks of polyurethane foam were tested. The medial block simulated the cancellous head, while the lateral was laminated with a glass fiber filled epoxy sheet simulating trochanteric cortical bone. Two hollow metal cylinders with a circumferential ball bearing in between mimicked the neck, with a perpendicular fracture in the middle. Fractures were fixated by two or three independent pins or by five configurations involving the interlocking plate (two pins with an optional peg in a small plate, or three pins in a small, medium or large plate). Six torsional tests were performed on each configuration to calculate torsional stiffness, torque at failure and failure energy.FindingsThe novel configurations improved parameters up to an average of 12.0 (stiffness), 19.3 (torque) and 19.9 (energy) times higher than the original two pins (P < 0.001). The plate, its size and its triangular configuration improved all parameters (P = 0.03), the plate being most effective, also preventing permanent failure (P < 0.001).InterpretationThe novel plate design with its pin configuration enhanced torsional stability. To reveal clinical relevance a clinical study is planned.     

The Patient Acceptable Symptom State for the Harris Hip Score Following Total Hip Arthroplasty: Validated Thresholds at 3-Month, 1-, 3-, 5-, and 7-Year Follow-Up

BackgroundThe Patient Acceptable Symptom State (PASS) represents the value on a patient-reported outcome measure scale beyond which patients consider themselves well or in a satisfactory state. The aim of this study is to define and validate the PASS threshold for the HHS at 3 months, 1, 3, 5, and 7 years after THA.MethodsA total of 976 patients from 14 centers in 7 countries were enrolled into a prospective study. Patients completed the HHS and a numerical rating scale for satisfaction at each follow-up. PASS thresholds for the HHS were calculated at each follow-up interval using the anchor-based, 80% specificity method. A bootstrapping method was used to internally validate the primary PASS thresholds. A patient sample sourced from an institutional registry was used for external validation.ResultsThe HHS was an excellent predictor of satisfaction at each time point (area under the curve > 0.8; P < .001). PASS thresholds for the HHS were 76 points at 3 months, 89 points at 1 year, 93 points at 3 years, 94 points at 5 years, and 93 points at 7 years. When applied to the internal and external validation cohorts, all PASS thresholds showed acceptable or excellent ability to predict satisfaction (area under the curve = 0.73-80; P < .001).ConclusionThe present study is the first to present validated PASS thresholds for the HHS following THA. These findings will serve as a useful reference for future THA outcome studies and as benchmarks for surgeons in their assessment of their patients’ clinical success.