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Statement of problem. Polyetheretherketone (PEEK) has been advocated to replace metal components in dentistry. Although PEEK is a high-performance polymer with a white color, adequate biological response, and resistance to fracture, data to support PEEK as an alternative material for implant abutments are lacking. Purpose. The purpose of this in vitro study was to assess the mechanical and functional properties of PEEK implant abutments as a nonmetallic alternative to titanium abutments, which presents esthetic limitations and greater difficulty to customize clinically. Material and methods. Implant abutments manufactured by using PEEK (n=24) or titanium grade 5 (n=24) were attached to MIS Implants type M4 3.75×16 mm with an internal screw tightened to 25 Ncm. Screw loosening and microleakage was assessed by submersion in a 2% methylene blue solution for 48 hours at 37 C. Both groups were compared with and without applying dynamic loading; fatigue testing was performed following the International Organization for Standardization (ISO) 14801:2016 standard. All specimens were observed under a stereomicroscope at ×8 magnification. Statistically significant differences among the PEEK and titanium implant abutments were tested with 2-factor ANOVA and the chi-square analysis for nonpaired and paired data, respectively (a=.05). Results. The implant abutments made of titanium were better in all mechanical tests. The torque loss of titanium abutments was approximately 10%, while PEEK showed a significantly higher (P

A mandibular continuity defect can be repaired using either a prosthetic device or autogenous bone. A titanium reconstruction plate can be used with a localized or vascularized flap over the defect of the mandible. Unfortunately, the plate may fail due to plate exposure, screw loosening, fracture, or infection, and will need to be removed. Plate exposure though the skin or mucosa is one of the main reasons for failure. In the present work, the authors introduced a lingually positioned reconstruction plate fabricated via three-dimensional printed bending support. This custom reconstruction plate can avoid plate re-exposure as well as reduce surgical errors and operation time.

BACKGROUND Pedicle screw loosening (PSL) is a postsurgical complication of spinal fusion surgery that can result in morbidity. The aim of this study was to evaluate the efficacy and safety of percutaneous parapedicle screw vertebroplasty (PPSV) for pain reduction and motility improvement in patients with PSL. METHODS The postsurgical solid inter-body fusion with inter-body bone mass formation of 32 patients who underwent lumbar-sacrum spinal fusion surgery was confirmed with plain films and CT scans. Each patient had one or two screws with symptomatic PSL and was treated with PPSV. All the patients were then followed up for 12 to 24 months. The visual analog scale (VAS) and Roland-Morris Disability Questionnaire (RMDQ) were used to evaluate each patient before the operation, after the operation, and during the follow-up period. RESULTS A total of 32 patients with a total of 47 screws with PSL were treated with PPSV and experienced different results in terms of pain reduction (with the mean VAS score dropping from 7.97 ± 0.74 to 2.34 ± 1.59, p < 0.001) and motility improvement (with the mean RMDQ score dropping from 16.75 ± 1.84 to 7.21 ± 4.08, p < 0.001). The motility improvement was significantly correlated with pain reduction (r = 0.42, p = 0.018), with the mean follow-up period being 19.3 ± 6.2 months (range: 8-36 months). However, five patients who experienced moderate improvements had eventually received a revision operation after undergoing PPSV. CONCLUSION The PPSV procedure is effective and safe for the reduction of pain and improvement of life quality in patients with PSL. It can thus be considered as a possible option for the revision of spinal fusion surgery.

Pedicle bone screws are one of the most critical materials used in spinal orthopaedic operations. Screw loosening and pull-out (PO) are basic complications encountered during or after surgery. Pull-out Strength (POS) of the bone is one of the significant parameters to understand the mechanical behaviour of a screw fixed to poor quality or osteoporotic bone. This study investigates how the POS of a pedicle screw is affected by the factors of the screw diameter and the polyurethane (PU) foam density by experimental analysis. In the experiments, two different diameter (5.5 and 6.5 mm) of conical pedicle screws and five different density (0.08, 0.16, 0.24, 0.32 and 0.48 g·cm−3) PU foams were used. According to the force-displacement curves obtained from experimental results, the POS increased with the increases in screw diameter and PU foam density.

One of the chronic problems with traditional cement or screw retention of crowns to implants is the development of biologic and technical complications, including soft tissue complications, bone loss, screw loosening, loss of retention, and veneering material fractures. The purpose of this case series report is to document preliminary results, specifically crown retention, using a friction-fit connection of crown to abutment. A sample composed of patients who had one or more implants restored between July 1, 2019, and October 30, 2019, were enrolled in this retrospective case-control series. Each patient had their crown connected to the implant abutment using a friction-fit system. Patients were seen for routine follow-up for documentation of crown retention, and 24 crowns were followed. After 6 months of follow-up, 100% of the crowns retained retention and did not become loose under normal masticatory function. The use of a friction-fit connection provided excellent retention of the crown to the abutment over the 6-month follow-up period.

We developed a new cranioplasty method that utilizes artificial bone made of ultra-high-molecular-weight polyethylene, with a wedge-shaped edge (UHMWPE Wing). This study shows the methods and data of case series and finite element analyses with the UHMWPE Wing. A circumferential wing was preoperatively designed for a custom-made artificial bone made of UHMWPE to achieve high fixed power and to minimize the usage of cranial implants. Here, we present 4 years of follow-up data and finite element analyses for patients treated with the UHMWPE Wing between February 2015 and February 2019. Eighteen consecutive patients underwent cranioplasty using our UHMWPE Wing design. There were no postoperative adverse events in 17 of the patients for at least 18 months. One case of hydrocephalus experienced screw loosening and graft uplift due to shunt malfunction. Placement of a ventriculo-peritoneal shunt immediately returned the artificial bone to normal position. Finite element analyses revealed that a model using the UHMWPE Wing had the highest withstand load and lowest deformation. This is the first report on the UHMWPE Wing method. This method may enable clinicians to minimize dead space and achieve high strength in cranioplasty.

It is difficult for clinical dentists to keep up with the rapid development of dental implant systems. The surgical issues ofimplantation are mostly clarified, and no surgical revolution is expected in the near future. However, the implant-abutmentconnection (IAC) types are permanently being modified. Advantages and disadvantages of the most importantIACs – external hex, tapered hex, external octagon, spline implant, 3-point internal tripod, 6-point internal hex, internaloctagon, 12-point internal hex, Morse taper – are discussed and biological, mechanical and aesthetic aspects of IACsare detailed in the article. The article can serve as a guide to decide which connection type to use in a certain indication.Following Branemark’s protocol, original external hexagonal implants are excellent alternatives for the treatment of anodontouspatients. However, as the indications were broadened, it became necessary to modify the traditional externalhexagon design, and to develop the internal connections. The increased incidence of screw loosening and fracture inthe new indications has been significantly reduced by the modifications and the introduction of internal connections. Inexternal connections the micro-motion and microleakage are more common between the components, that is why bacterialseal is less satisfactory. Conical structures provide the best mechanical and biological seal. Conical structures do nothave anti-rotation properties, and therefore the insertion of a polygon or spline into the system is required. The 6-point,12-point, 3-point internal connections are suitable for this purpose, as are Morse tapers supplemented by hexagonal oroctagonal structures. In the case of angled abutments or single missing tooth is being replaced these structures are recommended.The force distribution of the internal connections is more favourable for the screw and the implant body, butit is unfavourable to the bone. In contrast to the external connections, the load on the bone is less, so this must also beconsidered when choosing the most suitable type. From the aesthetic point of view, internal connections provide muchbetter results in terms of the emergence profile, the anatomical accuracy of the replacement, and the potential exposureof the metal parts.

OBJECTIVENonunion after posterior lumbar interbody fusion (PLIF) is associated with poor long-term outcomes in terms of health-related quality of life. Biomechanical factors in the fusion segment may influence spinal fusion rates. There are no reports on the relationship between intervertebral union and the absorption of autografts or vertebral endplates. Therefore, the purpose of this retrospective study was to evaluate the risk factors of nonunion after PLIF and identify preventive measures.METHODSThe authors analyzed 138 patients who underwent 1-level PLIF between 2016 and 2018 (75 males, 63 females; mean age 67 years; minimum follow-up period 12 months). Lumbar CT images obtained soon after the surgery and at 6 and 12 months of follow-up were examined for the mean total occupancy rate of the autograft, presence of a translucent zone between the autograft and endplate (more than 50% of vertebral diameter), cage subsidence, and screw loosening. Complete intervertebral union was defined as the presence of both upper and lower complete fusion in the center cage regions on coronal and sagittal CT slices at 12 months postoperatively. Patients were classified into either union or nonunion groups.RESULTSComplete union after PLIF was observed in 62 patients (45%), while nonunion was observed in 76 patients (55%). The mean total occupancy rate of the autograft immediately after the surgery was higher in the union group than in the nonunion group (59% vs 53%; p = 0.046). At 12 months postoperatively, the total occupancy rate of the autograft had decreased by 5.4% in the union group and by 11.9% in the nonunion group (p = 0.020). A translucent zone between the autograft and endplate immediately after the surgery was observed in 14 and 38 patients (23% and 50%) in the union and nonunion groups, respectively (p = 0.001). The nonunion group had a significantly higher proportion of cases with cage subsidence and screw loosening at 12 months postoperatively in comparison to the union group (p = 0.010 and p = 0.009, respectively).CONCLUSIONSA lower occupancy rate of the autograft and the presence of a translucent zone between the autograft and endplate immediately after the surgery were associated with nonunion at 12 months after PLIF. It may be important to achieve sufficient contact between the autograft and endplate intraoperatively for osseous union enhancement and to avoid excessive absorption of the autograft. The achievement of complete intervertebral union may decrease the incidence of cage subsidence or screw loosening.

Study Design: Retrospective study.Purpose: To determine the risk factors for S2 alar iliac (S2AI) screw loosening and its association with lumbosacral fusion in patients with adult spinal deformity (ASD).Overview of Literature: S2AI screws have been widely used for ASD surgery in recent years. However, no studies have analyzed the risk factors for loosening of S2AI screws and its association with lumbosacral fusion.Methods: Cases of 50 patients with ASD who underwent long spinal fusion (>9 levels) with S2AI screws were retrospectively reviewed. Loosening of S2AI screws and S1 pedicle screws and bone fusion at the level of L5–S1 at 2 years after surgery were investigated using computed tomography. In addition, risk factors for loosening of S2AI screws were determined in patients with ASD. Results: At 2 years after surgery, 33 cases (66%) of S2AI screw loosening and six cases (12%) of S1 pedicle screw loosening were observed. In 40 of 47 cases (85%), bone fusion at L5–S1 was found. Pseudarthrosis at L5–S1 was not significantly associated with S2AI screw loosening (19.3% vs. 6.3%, p=0.23), but significantly higher in patients with S1 screw loosening (83.3% vs. 4.9%, pp=0.045) and obesity (OR, 11.4; 95% CI, 1.2–107.2; p=0.033) were independent risk factors for S2AI screw loosening.Conclusions: High UIV level (T5 or above) and obesity were independent risk factors for S2AI screw loosening in patients with lumbosacral fixation in surgery for ASD. The incidence of lumbosacral fusion is associated with S1 screw loosening, but not S2AI screw loosening.

Introduction: Erich arch bar used for maxillomandibular fixation (MMF) since decades has several disadvantages such as risks of injury, additional operating room time, and gingival trauma. To overcome these downsides, modified Erich arch bar was introduced; however, there is not much available literature, indicating the efficacy of modified Erich arch bar over that of conventional arch bar wire. Therefore, the present study focuses on comparing efficiency of modified arch bar with conventional arch bar. Materials and Methods: This comparative randomized study was conducted on 32 patients that required MMF and were divided into Group A patients who received intermaxillary fixation (IMF) with modified Erich arch bars and Group B patients with conventional Erich arch bars. The parameters recorded were average surgical time required, wire prick injuries, IMF stability, occlusal stability, screw loosening, oral hygiene status, and vitality response of the teeth. The variables were statistically analyzed using Student's t-test and Wilcoxon signed-rank test. Results: The wire prick injury, intraoperative time noted in Group A was significantly reduced in comparison to Group B (P < 0.0001). Debris indices were significantly good in Group A in comparison to Group B (P < 0.0001). Nonvitality response of tooth was significantly more in Group B than in Group A patients (P < 0.05). Discussion: The efficiency of modified Erich arch bar group was superior to the conventional arch bar with very limited restrictions.

Objective. Long-term clinical data on the success and complication rates of monolithic or minimally veneered zirconia implant-supported restorations are lacking. Hence, the purpose of this retrospective clinical study was to analyze the complications of monolithic or partially veneered zirconia implant-supported restorations up to 5 years follow-up. Material and Methods. Single crowns, bridges, and full-arch rehabilitations were included. The selection process was achieved by reviewing data from the prosthetic laboratory and excluding cases in which zirconium and full-ceramic coating restorations were used. A total of 154 restorations were included (82 monolithic and 72 with buccal ceramic stratification). All the complications encountered, and the solutions applied, were explained. Results. A total of 93 restorative units had a follow-up of between 24 and 60 months, and 61 restoration units had a follow-up of between 12 and 24 months. A total of 7 complications were encountered (14.58% of cases; 95.45% per prosthetic unit). The technical complication rate was 2.08% (one case of minor chipping in one prosthetic unit); regarding the mechanical complications, four decementations (8.33% of the cases) and two screw loosening (4.17% of the cases) were encountered. Conclusions. Considering the limitations of this study, it can be concluded that monolithic or partially veneered zirconia implant-supported restorations have a good clinical behavior during a follow-up period of up to 5 years.

Screw loosening is amongst the most prevalent mechanical problems in dental implant prosthetics. Clinicians will know if the reverse Detorque values are compromised by contamination of the implant abutment screw hole either by blood , saliva or saline. Research have shown that the drying of the implant cavity may decrease the preload value when the abutment screw is closed and thereafter increase the likelihood of abutment screw loosening. Mobility of the prosthesis, or screw fracture and increase the risk of peri-implant soft-tissue inflammation. This study aims to assess and compare the effect of wet and dry fields while torqueing the abutment screws on the DE torque values. 40 Nobel bio care implant analogues mounted in plaster models were used in this study. The samples were divided into four groups dry abutment screws, artificial saliva, blood and normal saline. All the abutment screws were tightened till 20 Ncm and left aside for 15 minutes. After 15 minutes the abutment screw were DE torqued, and the DE torque values were noted for tall the groups. When analysed using paired sample t-test there was no significant difference with artificial saliva (p=0.269). There was statistical difference with blood (p=0.00) and with saline (p=0.00). Based on this study, the presence of saliva decreases the DE torque values of the abutment screws, whereas Blood and saline increase the DE torque values of the abutment screws. The presence of blood clot might be the reason for the increase in DE torque values which might decrease once the clot disintegrates. Clinicians should prevent contamination of the screw hole by blood and saliva; if contamination arises, sanitation of the infected screw and also the screw hole until final tightening is advised.

Lumbosacral instrumentation continues to be challenging due to complex biomechanical force distributions and poor sacral bone quality. Various techniques have therefore been established. The aim of this study was to investigate the outcome of patients treated with S2-alar-iliac (S2AI), S2-alar (S2A), and iliac (I) instrumentation as the most caudal level. Sixty patients underwent one of the 3 techniques between January 2012 and June 2017 (S2AI 18 patients, S2A 20 patients, I 22 patients). Mean age was 70.4 ± 8.5 years. Screw loosening (SL) and sacroiliac joint (SIJ) pain were evaluated during the course at 3-month and maximum follow-up (FU). All patients completed 3-month FU, the mean FU period was 2.5 ± 1.5 years (p = 0.38), and a median of 5 segments was operated on (p = 0.26), respectively. Bone mineral density (BMD), derived opportunistically from computed tomography (CT), did not significantly differ between the groups (p = 0.66), but cages were more frequently implanted in patients of the S2A group (p = 0.04). SL of sacral or iliac screws was more common in patients of the S2A and I groups compared with the S2AI group (S2AI 16.7%, S2A 55.0%, I 27.3% of patients; p = 0.03). SIJ pain was more often improved in the S2AI group not only after 3 months but also at maximum FU (S2AI 61.1%, S2A 25.0%, I 22.7% of patients showing improvement; p = 0.02). Even in shorter or mid-length lumbar or thoracolumbar constructs, S2AI might be considered superior to S2A and I instrumentation due to showing lower incidences of caudal SL and SIJ pain.

Introduction Recent literature has associated pseudarthrosis and pedicle screw loosening with subchronic infection at the pedicle of the vertebra. The positive culture results of a previous retrieval analysis show that such patients have a high frequency of bacterial contamination. The objective of this study is to visually capture the architecture of these undiagnosed infections, which have been described in other studies as biofilms on supposedly "aseptic" screw loosening. Methods Explants from 10 consecutive patients undergoing revision spine surgery for pseudarthrosis were collected and fixed in glutaraldehyde solution. Each of these implants was imaged thoroughly by using scanning electron microscopy and x-ray spectroscopy to evaluate the architecture of the biofilm. Additionally, eight patient swabs from tissues around the implants were sent for cultures to assess bacterial infiltration in tissues beyond the biofilm. The implants were also analyzed using energy dispersive x-ray spectroscopy. The exclusion criteria included clinically diagnosed infection (current or previous) and/or mechanical failure of the implant due to falls/accidents. Results The study was successful in capturing the visual architecture of the biofilm on retrieved implants. A total of 77% of pseudarthrosis cases presented with loose pedicle screws, which were diagnosed by a preoperative computed tomography scan showing radiolucency along the screw track and were confirmed intraoperatively, and 72% of the cases showed biofilm on explants. Conclusions In the absence of the clinical presentation of infection, impregnated bacteria could form a biofilm around an implant, and this biofilm can remain undetected via contemporary diagnostic methods, including swabbing. Implant biofilm is frequently present in "aseptic" pseudarthrosis cases.

OBJECTIVE This study aimed to investigate the strength of a novel micro-dynamic pedicle screw by comparing it to the traditional pedicle screw. METHODS Forty-five lumbar vertebrae received a traditional pedicle screw on one side and a micro-dynamic pedicle screw on the other side as follows (traditional group vs micro-dynamic group): 15 vertebrae underwent instant pull-out testing; 15 vertebrae underwent 5000-cyclic fatigue loading testing; and 15 vertebrae underwent 10,000-cyclic fatigue loading testing and micro-computed tomography (micro-CT) scanning. The peek pull-out force and normalized peek pull-out force after instant pull-out testing, 5000-cyclic and 10,000-cyclic fatigue loading testing were recorded to estimate the resistance of two types of screws. Bone mineral density was recorded to investigate the strength of the different screws in osteoporotic patients. And the semidiameter of the screw insertion area on micro-CT images after fatigue were compared to describe the performance between screw and bone surface. RESULTS The bone mineral density showed a weak correlation with peek pull-out force (r = 0.252, P = 0.024). The peek pull-out force of traditional pedicle screw after 10,000-cyclic fatigue loading were smaller than that of instant pull-out test in both osteoporotic (P = 0.017) and healthy group (P = 0.029), the peek pull-out force of micro-dynamic pedicle screw after 10,000-cyclic fatigue loading was smaller than that in instant pull-out test in osteoporotic group (P = 0.033), but no significant difference in healthy group (P = 0.853). The peek pull-out force in traditional group and micro-dynamic group underwent instant pull-out testing (P = 0.485), and pull-out testing after 5000-cyclic fatigue loading testing (P = 0.184) did not show significant difference. However, the peek pull-out force in micro-dynamic group underwent pull-test after 10,000-cyclic fatigue loading testing was significantly greater than that measured in traditional group (P = 0.005). The normalized peek pull-out force of traditional groups underwent instant pull-out testing, pull-out test after 5000-cyclic and 10,000-cyclic fatigue loading testing significantly decreased as the number of cycles increased (P

Objectives In this study, we determined the incidence and pattern of screw loosening in patients who received dental implants. Materials and Methods Patients who received implants between January 2008 and October 2013 and completed their prosthetic rehabilitation were evaluated for the incidence, frequency, and onset of screw loosening using dental charts and radiographs. The association between each factor and screw loosening was analyzed using the chi-square test and a multivariate analysis with binary logistic regression models (P

Study Design: Self-tapping and self-drilling screws are two modalities available for plate fixation. When compared to self-drilling, self-tapping screws have a few drawbacks like screw loosening, thermal osteolysis, equipment dependent, and time-consuming. Aim: The aim of this study was to compare the efficacy of self-tapping and self-drilling screws with relation to plate retention and stability in internal fixation of mandibular fractures using 3D finite element analysis (FEA). Objectives: The objective of this study was to determine the influence of screw placement technique on stress concentration and deformation occurring at the screw–bone interface in self-drilling and self-tapping screws. Materials and Methods: A 3D computer-aided design modeling system was used to build a trilaminate mandibular bone, self-tapping screw and self-drilling screw, and a 2-holed miniplate with gap that were converted into finite element models using Hypermesh 13.0 software. Material properties and boundary conditions were assigned to these models. Pullout, torque, and torsional forces were applied to evaluate the stress concentration and deformation at the screw–bone interface. Results: The comparison of stress concentration and deformation values between the two types of screws was interpreted using ANSYS software version 14.5. Results of torque test, pullout test, and torsional test showed maximum Von Mises stress, and deformation around the screw–bone interface was higher in self-tapping screw than in self-drilling screw. Conclusion: Within the limitations of the 3D FEA, the findings provided significant evidence to suggest that self-tapping screws have a greater incidence of fatigue when compared to self-drilling screws as there was more stress distribution and deformation at their screw–bone interface.

Study Design: A retrospective cohort study.Purpose: The purpose of this study was to investigate the prevalence and risk factors for S2 alar-iliac (SAI) screw loosening following lumbosacral fixation, with a minimum 2-year follow-up.Overview of Literature: Although SAI screws allow surgeons to perform lumbosacral fixation with a low profile and enhanced biomechanical strength, screw loosening following surgery can occur in some cases. However, few studies have investigated the prevalence and risk factors for SAI screw loosening.Methods: This retrospective study included 35 patients (mean age, 72.8±8.0 years; male, 10; female, 25) who underwent lumbosacral fixation using SAI screws with at least 2 years of follow-up. SAI screw loosening and L5–S bony fusion were assessed using computed tomography. The period for which the screws appeared loose and the risk factors for SAI screw loosening were investigated 2 years after surgery.Results: A total of 70 SAI screws and 70 S1 pedicle screws were inserted. Loosening was observed 0.5, 1, and 2 years after surgery in 17 (24.3%), 35 (50.0%), and 35 (50.0%) SAI screws, respectively. Bony fusion rate at L5–S was significantly lower in patients with SAI screw loosening than in those without screw loosening (65.0% vs. 93.3%, p =0.048). The score for SAI screw contact with the iliac cortical bone and the bony fusion rate at L5–S were significantly lower in the loosening group than in the non-loosening group (1.8±0.5 vs. 2.2±0.3, p

OBJECTIVEThe goal of this study was to evaluate the radiographic and clinical results of instrumentation surgery without fusion for metastases to the spine.METHODSBetween 2010 and 2017, patients with spinal tumors who underwent instrumentation without fusion surgery were consecutively evaluated. Preoperative and postoperative clinical data were evaluated. Data were inclusive for last follow-up and just prior to death if the patient died. Instrumentation-related complications included screw migration, screw or rod breakage, cage migration, and screw loosening.RESULTSExcluding patients who died within 6 months, a total of 136 patients (140 operations) were recruited. The average follow-up duration was 16.5 months (median 12.4 months). The pain visual analog scale score decreased from 6.4 to 2.5 (p < 0.001) and the Eastern Cooperative Oncology Group scale score improved (p < 0.001). There were only 3 cases (2.1%) of symptomatic instrumentation-related complications that resulted in revisions. There were 6 cases of nonsymptomatic complications. The most common complication was screw migration or pull-out (5 cases). There were 3 cases of screw or rod breakage and 1 case of cage migration. Two-thirds of the cases of instrumentation-related complications occurred after 6 months, with a mean postoperative period of 1 year.CONCLUSIONSThe current study reported successful outcomes with very low complication rates after nonfusion surgery for patients with spinal metastases, even among those who survived for more than 6 months. More than half of the instrumentation-related complications were asymptomatic and did not require revision. The results suggest that nonfusion surgery might be sufficient for a majority of patients with spinal metastases.

Since pseudoarthrosis or screw loosening is frequently seen in lumbosacral stabilizations ending in S1, S2 screws are used more frequently to support S1 screws. This study aims to describe a new screw placement technique and location from S2. Revision surgery was applied to the patient who had previously undergone surgery with the rigid instrumentation system and encountered pseudoarthrosis during the follow-up period. Instrumentation was performed from S2 to the promontorium. The patient’s chronic low back pain arising due to pseudoarthrosis was reduced and a strong lumbosacral dynamic instrumentation was performed to the patient. Dual screw placement from S2 and/or screw placement in the S2-promontorium direction is a new alternative to provide a powerful instrumentation.

Total alloplastic temporomandibular joint replacement (TMJ-TJR) has once again become the focus of therapy for end-stage destroyed joints. Although material quality has increased significantly in terms of service life and wear, problems occur even with patient-specific (PSI) prostheses. Here, mainly the ramus components are affected and an occurrence of screw loosening or fractures in the area of the fossa of stock joints is rare and has not yet been described for patient-specific (PSI) components. Although very rare, such events pose a great challenge to both practitioners and affected patients, especially in the case of PSI components, not least due to the long time required for new fabrication. The case report shows a non-described screw fracture of a PSI-TMJ fossa and the first description of a temporary revision using a PSI-TMJ fossa made of bone cement.

Study Design: Systematic literature review with meta-analysis. Objective: Osteoporosis is common in elderly patients, who frequently suffer from spinal fractures or degenerative diseases and often require surgical treatment with spinal instrumentation. Diminished bone quality impairs primary screw purchase, which may lead to loosening and its sequelae, in the worst case, revision surgery. Information about the incidence of spinal instrumentation-related complications in osteoporotic patients is currently limited to individual reports. We conducted a systematic literature review with the aim of quantifying the incidence of screw loosening in osteoporotic spines. Methods: Publications on spinal instrumentation of osteoporotic patients reporting screw-related complications were identified in 3 databases. Data on screw loosening and other local complications was collected. Pooled risks of experiencing such complications were estimated with random effects models. Risk of bias in the individual studies was assessed with an adapted McHarm Scale. Results: From 1831 initial matches, 32 were eligible and 19 reported screw loosening rates. Studies were heterogeneous concerning procedures performed and risk of bias. Screw loosening incidences were variable with a pooled risk of 22.5% (95% CI 10.8%-36.6%, 95% prediction interval [PI] 0%-81.2%) in reports on nonaugmented screws and 2.2% (95% CI 0.0%-7.2%, 95% PI 0%-25.1%) in reports on augmented screws. Conclusions: The findings of this meta-analysis suggest that screw loosening incidences may be considerably higher in osteoporotic spines than with normal bone mineral density. Screw augmentation may reduce loosening rates; however, this requires confirmation through clinical studies. Standardized reporting of prespecified complications should be enforced by publishers.

Sacropelvic fixation is frequently used in combination with thoracolumbar instrumentation for complex deformity correction and is commonly associated with pseudoarthrosis, implant failure and loosening. This study compared pedicle screw fixation (PED) with three different sacropelvic fixation techniques, namely iliac screws (IL), S2 alar-iliac screws (S2AI) and laterally placed triangular titanium implants (SI), all in combination with lumbosacral instrumentation, accounting for implant micromotion. Existing finite element models of pelvis-L5 of three patients including lumbopelvic instrumentation were utilized. Moments of 7.5 Nm in the three directions combined with a 500 N compressive load were simulated. Measured metrics included flexibility, instrumentation stresses and bone–implant interface loads. Fixation effectively reduced the sacroiliac flexibility. Compared to PED, IL and S2AI induced a reduction in peak stresses in the S1 pedicle screws. Rod stresses were mostly unaffected by S2AI and SI, but IL demonstrated a stress increase. In comparison with a previous work depicting full osteointegration, SI was found to have similar instrumentation stresses as those due to PED. Fixation with triangular implants did not result in stress increase on the lumbosacral instrumentation, likely due to the lack of connection with the posterior rods. IL and S2AI had a mild protective effect on S1 pedicle screws in terms of stresses and bone–implant loads. IL resulted in an increase in the rod stresses. A comparison between this study and previous work incorporating full osteointegration demonstrates how these results may be applied clinically to better understand the effects of different treatments on patient outcomes. These slides can be retrieved under Electronic Supplementary Material.

Systematic review of comparative studies.Partially threaded (PT) cancellous screws are a common method to fix medial malleolar fractures but with reported complications due to the hardware. Fully threaded (FT) screws have been advanced as an alternative yielding similar union results with less implant-related complications.The aim of this study is to systematically collate comparative clinical and biomechanical evidence on the effectiveness and complications of the PT versus FT screw constructs in the treatment of medial malleolar fractures.Based on 7 studies (8 subgroups), similar weighted healing rates were found from pooling 3 clinical studies with the time to heal outcome significantly shorter following FT compared to FT screws. Complication rates in the form of screw loosening (1.97% vs. 13.4%, p = 0.008) and screw removal surgery (0% vs. 15.7%, p 0.0001) were significantly higher after using PT screws. The five biomechanical studies demonstrated that FT screw constructs had significantly superior properties than the PT constructs and that for all outcomes.Fully threaded screws seem to offer significantly better clinical and biomechanical outcomes when compared to the partially threaded screws in treating medial malleolar fractures. The use of headless FT screws could contribute to reduce the implant-related complications.Therapy, level 3.

Study Design: Retrospective cohort study. Objective: Screw loosening in spinal fusion is poorly defined. Accordingly, its prevalence rates range from 1% to 60%, and its risk factors remain undefined. The goal of this study was to assess the prevalence of screw loosening, according to precise definitions, and to identify factors associated with it. Methods: We retrospectively reviewed records for 166 patients who underwent a posterior spinal fusion in our institution between 2011 and 2016. We recorded demographic data, osteoporosis, pelvic balance, surgery-related information, and postoperative radiographic data at a minimum follow-up of 6 months. Univariable and multivariable logistic regression models were used. Significance was defined by P < .05. Results: When loosening was defined by partial pull-out, its prevalence was 9.6% (95% CI 5.6-15); thoracic localization, the use of CrCo (chromium-cobalt) rods, osteoporosis, PI/LL (pelvic incidence/lumbar lordosis) mismatch (preoperative), and frontal imbalance (preoperative) were significant risk factors. When loosening was defined by osteolysis (radiolucent rim) >1 mm around at least 1 screw, its prevalence was 40.4% (95% CI 33-48) and age, scoliosis as indication for fusion, ASA (American Society of Anesthesiologists) 2 or 3, the use of CrCo rods, more than 5 levels fused, no circumferential arthrodesis, postoperative bracing, and sacrum or ilium as the inferior level of instrumentation were also significant risk factors. Conclusions: A clear definition of screw loosening seems essential for a useful analysis of the literature. Osteoporosis, sagittal imbalance, and rigid material appear to be risk factors, regardless of the definition.

Study design A retrospective study. Purpose To investigate the incidence of iliac screw loosening with a two-rod vs. multi-rod construct and the effect on clinical and radiographic outcomes after surgery for adult spinal deformity (ASD). Overview of literature Multi-rod construct is useful for preventing rod fracture in ASD surgery. However, limited information is available regarding the incidence of iliac screw loosening after corrective fusion surgery using a multi-rod construct. Methods Total 106 patients with ASD (24 men and 82 women; mean age, 68 years) who underwent corrective fusion surgery using bilateral iliac screws and were followed up for at least 1 year were reviewed. The following variables were compared between patients who underwent surgery with a two-rod and multi-rod construct: age, sex, bone mineral density (BMD), fusion level, high-grade osteotomy, L5/S interbody fusion, screw loosening (upper instrumented vertebra [UIV], S1, and iliac), rod fracture, proximal junctional kyphosis, spinopelvic parameters, and Oswestry Disability Index (ODI) score. We also compared patients with and without iliac screw loosening in the multi-rod construct group. Results Of the 106 patients, 55 underwent surgery with a conventional two-rod construct and 51 with a multi-rod construct (three rods in 16, four rods in 35). Iliac and UIV screw loosening was observed in 24 patients (21%) and 35 patients (33%), respectively. The multi-rod group showed significantly higher incidence of iliac and UIV screw loosening and lower incidence of rod fracture. Patients with iliac screw loosening had a lower BMD than those without screw loosening; however, no significant differences were observed in the spinopelvic parameters or the ODI score. Conclusions The use of multi-rod constructs led to a higher incidence of junctional screw loosening than the use of conventional two-rod constructs, especially in patients with osteoporosis. Iliac screw loosening did not affect sagittal alignment or clinical outcome in the short term.

Background Cement augmentation is a technique used to increase the stability and purchase of pedicle screws in poor quality bone. Various methods can be applied for cement delivery, such as cement injection before screw placement and the use of fenestrated screws. However, potential problems can arise with the use of cement augmentation. Case presentation A 66-year-old man with a lower trunk deformity, severe kyphosis, and sagittal imbalance following fusion (L2-5 ), with minimal comorbidities, was referred to our unit 9 months after surgery. Pain and progressive kyphosis were investigated clinically and radiographically with computed tomography (CT) scans to assess the status of the hardware and fusion. CT imaging revealed that cement was present only at the distal tip of the fenestrated screws at the L4 vertebral level. A non-union was present along with loosening and a halo around the body of the pedicle screws, and there was evidence of pullout of inferior screws. Conclusion Single-level cement augmentation of pedicle screw in a posterior construct and distal tip cement augmentation of the screw results in a fixed pivot point. Micromotion in cranio-caudal loading during flexion and extension may result in screw toggling with the single-level cement-augmented tip as a fulcrum. This may cause screw loosening, which can lead to pullout and loss of construct stability. The halo around the screw suggests bone loss and/or a fibrous tissue interface, which further complicates revision surgery. Stress shielding and polymethylmethacrylate cement present additional difficulties. The findings of this technical note question the risks and benefits of cement-augmented fenestrated pedicle screw fixation for spinal fusion. Although incidences of such cases are uncommon, surgeons should perform this technique with caution. Accurate restoration of lumbar lordosis during index procedures is important to minimize the risk of construct failure.

Objective In thoracolumbar spinal instrumentation surgery, pedicle screw fixation is widely used, whereas screw loosening occurs only occasionally over time. It is common to evaluate screw loosening by the radiographic lucent zone around screws, which can neither evaluate loosening quantitatively nor detect slight screw loosening. In the present technical note, we describe a novel assessment technique of screw loosening by generating 3-dimensional screw images from computed tomography data and superposing them in time series. Methods Computed tomography data were exported in digital imaging and communications in medicine dataset and imported to the 3-dimensional computer-aided designing software, by which screws and rods were segmented and outputted in stereolithography (STL) format. The STL files were imported to the software, and registration based on iterative closest point algorithm was performed to assess screw position changes. Results Positional changes on STL in time series were classified into 3 types: 1) no position changes existed in the entire system of screws and rods; 2) position changes existed in the entire system of screws and rods, but no position changes were shown when the left-sided and right-sided screws and rod were separately evaluated; and 3) position changes existed in the left and/or right-sided screws and rods even when evaluated separately. Conclusions This technique enables the quantitative evaluation of screw loosening and loosening between screws and rods. In conjunction with conventional methods of assessing radiographic lucent zone, we are able to obtain more accurate information regarding screw loosening after spinal instrumentation surgery.

Background Cement augmentation of pedicle screws to prevent screw loosening is associated with significant complications, such as cement leakage or bone necrosis. Therefore, an alternative strategy to improve pedicle screw anchorage has been recently developed: Polymer reinforcement of pedicle screws uses an in situ melted polymer sleeve in order to enhance screw anchorage. This biomechanical study evaluated the effect of polymer-reinforcement by comparing polymer-reinforced pedicle screws to non-augmented as well as cement-augmented screws under cyclic loading. Methods For each of the two comparisons (polymer-reinforced vs. non-augmented screws and polymer-reinforced vs. cement-augmented screws), polymer-reinforced screws and control screws were placed into the left and right pedicle of seven vertebrae (mean age: 74.0 (SD 9.3) years) to allow for pairwise left–right comparisons. Each screw was subjected to cyclic cranio-caudal loading with an initial load ranging from −50 N to +50 N and with stepwise increasing compressive loads (5 N every 100 cycles) until screw loosening. Findings Polymer-reinforced pedicle screws resisted a higher number of load cycles until loosening than the contralateral non-augmented control screws (4300 SD 2018 vs. 2457 SD 1116 load cycles, p = 0.015). Screw anchorage of polymer-reinforced pedicle screws was comparable to that of cement augmented control screws (3857 (SD2085) vs. 4300 (SD1257) load cycles until failure, p = 0.64). Interpretation Our findings indicate that polymer-reinforcement significantly enhances pedicle screw anchorage in low quality bone and that its effect is similar in size than that of cement augmentation.

Purpose: The purpose of this study was to survey practicing clinicians and determine if differences existed concerning their use of torque-limiting devices (TLDs) and screw-tightening protocols, comparing this with existing universal industry standards. Materials and methods: A nine-question survey was administered with 428 dentists providing data for three specific areas: (1) demographic information-TLD ownership, device age, frequency of use, and observations of screw loosening; (2) recognition information-calibration, reading measurements of the TLD, and the meaning of preload; (3) usage information-screw-tightening protocols and effect of speed during actioning of the TLD. Data collection was compared with industry standards for use of hand torque tools including ISO-6789 1,2:2017 and related texts pertaining to screw fastener protocols. Results: The beam-type TLD was the most popular; however, 33% surveyed used it incorrectly. Most TLDs being used were older than 1 year, with only 6% calibrated. Forty-eight percent observed screw loosening less than once per year, while 44% reported three or more occurrences per year. A similar number used the TLD for implant placement and abutment screw tightening. Screw-tightening protocols varied. Preload was not understood by the majority of those surveyed. Conclusion: Dentistry does not appear to adhere to the protocols and standards recommended by other industries that also rely on screw-fastening mechanisms and TLDs. Further education and training appears to be warranted in this area of implant dentistry to reduce the risks of screw-associated complications.

BACKGROUND AND PURPOSE The internal screw has an essential role in carrying abutment and prosthesis loading. Some dental implant patients such as scuba divers, mineworkers, and hyperbaric oxygen patients are exposed to hyperbaric atmospheres. The aim of this study was to investigate internal screw loosening under hyperbaric conditions. MATERIALS AND METHODS Forty-two dental implants were placed into plexiglass blocks. Abutments were fixed with internal screws by 25 Ncm torque force. Groups were set as control, 2.8-bar air pressure, and 4-bar air pressure groups. Hyperbaric groups were subdivided and exposed to either one or six cycles. Removal torque values were measured with a digital torque meter. Data were analyzed statistically using analysis of variance and Tamhane's T2 tests, considering p

Background The treatment of mallet fracture using hook plate fixation was first introduced in 2007 and has subsequently shown excellent outcomes. Common complications, such as nail deformity and screw loosening, have also been reported. Very few studies have focused on these common complications or their prevention. In this study, we present the clinical outcomes and complications of our case series and describe the pitfalls and detailed solution of surgical tips to avoid common complications related to this procedure. Methods The retrospective case series of 16 patients with mallet fractures who underwent open reduction and hook plate fixation in our hospital from 2015 to 2020 were retrospectively reviewed. Data on extension lag, range-of-motion (ROM) of the distal interphalangeal joint (DIP) joint, the Disabilities of the Arm, Shoulder, and Hand (DASH) score, and surgical complications were collected and analysed. The clinical outcome was graded according to the Crawford mallet finger criteria. Results Sixteen patients were included in our analysis. The median DIP extension lag was 0° (range, 0° to 30°) and the median active DIP flexion angle was 60° (range, 40° to 90°). The median DASH score was 0 (range, 0–11.3). Fourteen patients with good and excellent results were satisfied with this treatment. The Complication rate in our patient series was 18%. Common complications reported in articles included wound necrosis, extension lag, nail deformity, and plate loosening. Conclusions Despite the fact that the treatment of mallet fracture with hook plate fixation has satisfactory functional outcomes, pitfalls, including iatrogenic nail germinal matrix injury, unnecessary soft tissue dissection, and insufficient screw purchase, were still reported. To avoid complications, we suggest modifications of the skin incision, soft tissue dissection, and screw position.

Study Design: Animal experiment. Objective: To evaluate whether the use of polyetheretherketone (PEEK) rods for posterior spinal fixation can improve screw stability. Methods: Sheep models of anterior-posterior cervical fusion were used in this study. Six sheep were randomly assigned to the PEEK rod group and titanium alloy group. A total of 8 screws and 2 fixing rods were implanted in each sheep. At 24 weeks postoperatively, a computed tomography (CT) evaluation, pull-out test, micro-CT evaluation and histological evaluation were conducted to evaluate screw stability in the harvested surgical segments. Result: According to the CT evaluation, there were no signs of screw loosening in either group. The pull-out force and energy of the PEEK rod group were significantly higher than those of the titanium alloy rod group. Denser and thicker trabecular bone around the screw was observed in the PEEK rod group according to the micro-CT reconstructed images, and quantitative analysis of the micro-CT data confirmed this finding. In the histological evaluation, more abundant and denser bone trabeculae were also observed in the PEEK rod group. However, there was no significant difference in the bone-screw interface between the 2 groups. Conclusion: Posterior spinal fixation with PEEK rods can increase screw stability by promoting bone growth around the screw but cannot promote bone integration at the bone-screw interface in an animal model study. This finding presents a new idea for clinical practices to reduce screw loosening rate.

Background: This study aimed to evaluate the risk factors of cover screw loosening (CSL) and its influence on peri-implant marginal bone during early bone healing process.Methods: A total of 91 implants in 90 patients (75 normal patients and 15 patients with CSL) were included in this study. Panoramic radiographs were taken for the measurement of peri-implant marginal bone loss (MBL). A piece of soft tissue above the cover screw during the second-stage surgery was taken for pathological examination. The differences between the two groups were evaluated and the possible risk factors associated with CSL were analyzed.Results: Increased frequency of CSL showed significant association with maxillary region (p=0.038). The mean MBL at implants with CSL was 0.82 ± 0.56 mm, and it was 0.22 ± 0.20 mm at normal implants (pConclusions: CSL during healing process is associated with early peri-implant MBL. The location of the maxilla is considered as a significant risk factor for CSL.

Objective Decreased bone mineral density (BMD) impairs screw purchase in trabecular bone and can cause screw loosening following spinal instrumentation. Existing computed tomography (CT) scans could be used for opportunistic osteoporosis screening for decreased BMD. Purpose of this case-control study was to investigate the association of opportunistically assessed BMD with the outcome after spinal surgery with semi-rigid instrumentation for lumbar degenerative instability. Methods We reviewed consecutive patients that had primary surgery with semi-rigid instrumentation in our hospital. Patients that showed screw loosening in follow-up imaging qualified as cases. Patients that did not show screw loosening or—if no follow-up imaging was available (n = 8)—reported benefit from surgery ≥ 6 months after primary surgery qualified as controls. Matching criteria were sex, age, and surgical construct. Opportunistic BMD screening was performed at L1 to L4 in perioperative CT scans by automatic spine segmentation and using asynchronous calibration. Processing steps of this deep learning-driven approach can be reproduced using the freely available online-tool Anduin (https://anduin.bonescreen.de). Area under the curve (AUC) was calculated for BMD as a predictor of screw loosening. Results Forty-six elderly patients (69.9 ± 9.1 years)—23 cases and 23 controls—were included. The majority of surgeries involved three spinal motion segments (n = 34). Twenty patients had low bone mass and 13 had osteoporotic BMD. Cases had significantly lower mean BMD (86.5 ± 29.5 mg/cm³) compared to controls (118.2 ± 32.9 mg/cm³, p = 0.001), i.e. patients with screw loosening showed reduced BMD. Screw loosening was best predicted by a BMD < 81.8 mg/cm³ (sensitivity = 91.3%, specificity = 56.5%, AUC = 0.769, p = 0.002). Conclusion Prevalence of osteoporosis or low bone mass (BMD ≤ 120 mg/cm³) was relatively high in this group of elderly patients undergoing spinal surgery. Screw loosening was associated with BMD close to the threshold for osteoporosis (< 80 mg/cm³). Opportunistic BMD screening is feasible using the presented approach and can guide the surgeon to take measures to prevent screw loosening and to increase favorable outcomes., publishedVersion

Purpose There is paucity in the studies that assess dental implants replacing failed dental implants due to peri-implantitis. This study aims to evaluate the clinical outcomes of these implants in terms of implant survival and marginal bone loss. Methods Patients in this retrospective study were selected if having one or more implants removed due to peri-implantitis and the placement and loading of dental implants in the same region from April 2010 to December 2019. Information was collected about the patient's demographic data, implant dimensions, surgical and prosthetic variables. Changes in peri-implant bone level, cumulative implant survival rate and technical complications were assessed. Results Three hundred and eighty one dental implants in 146 patients that were placed in the same position or one-tooth position mesially/distally to the site of explantation were included. The patients' mean age was 63 ± 10 years. Ninety seven patients were females and 49 were males. After a mean follow-up of 34 ± 17 months, two implants failed. The cumulative survival rate was 99%. The marginal bone loss was −0.1 ± 0.6. Immediate or delay replacement of the failed implant did not affect implant survival or marginal bone stability. All the prostheses were screw-retained and presented the following complications: ceramic chipping (3 events), resin tooth fracture (1 event) and prosthetic screw loosening (1 event). Conclusions Dental implants replacing failed implants due to peri-implantitis would be an option in the management of peri-implantitis. They showed high survival rate and marginal bone stability.

Osteoporosis is one of the most prevalent bone diseases and is associated with age. Vertebral fractures are the most common manifestation of osteoporosis. Vertebral and hip fractures are associated with excess mortality. A previous spine fracture increases the risk of next vertebral fracture by fivefold during the following year, with almost 20% of women developing a vertebral fracture (VF) within the next 12 months. Low bone mineral density (BMD) is a major risk factor for poor screw fixation, screw loosening, and fixation failure since the ability of screws to resist pullout from bone is directly related to BMD. The anti-osteoporosis medications, pharmacological and non-pharmacological osteoporosis management, and bone-targeted therapy for selected malignancies are described in the chapter.

This study aimed to analyze a novel technique to make screws with greater untightening resistance and to solve screw loosening in implant-supported single crowns. Thirty grade IV titanium straight abutments were screwed onto 30 external hex implants using grade IV titanium screws (30 Ncm). They were exposed to cyclic loading (300,000 cycles, 200 N). Samples were divided into 4 groups (15 samples per group): new screws (SCREW group) (control), reused screws (rSCREW group), new screws wrapped with polytetrafluoroethylene (PTFE) tape (PTFE group), and reused screws wrapped with PTFE tape (rPTFE group). Reverse torque values (RTVs) were recorded with a digitally calibrated implant motor. Mean RTVs observed were 14.46 N (&plusmn, 1.10 N) for the control group, 14.42 N (&plusmn, 1.22 N) for the rSCREW group, 19.97 N (&plusmn, 1.16 N) for the PTFE group, and 19.13 N (&plusmn, 2.38 N) for the rPTFE group. Statistically significant differences were found between RTVs of both groups employing screws without PTFE tape (SCREW and rSCREW groups) compared with those using screws wrapped with PTFE tape (PTFE and rPTFE) (p &lt, 0.001). These results suggest that wrapping the implant&ndash, abutment screw with PTFE tape may effectively lower the risk of loosening and even constitute a solution when this complication occurs in implant single crowns.

Purpose Narrow dental implants are commonly used to restore narrow alveolar ridges. Although the good performance of narrow dental implants supporting multiple prostheses has been repeatedly demonstrated, there are few studies analyzing their performance in a long-term follow-up together with the influence of the loading protocol. Thus, the objective was to assess the influence of implant loading protocol (immediate vs delayed) on the long-term outcomes of 3.0-mm-diameter dental implants supporting fixed multiple prostheses. Materials and methods This retrospective cohort study included 202 3.0-mm-diameter dental implants supporting multiple prostheses placed between January 2006 and April 2009. Immediate loading was performed when the implants were inserted in bone types I, II, and III and achieved an insertion torque ≥ 25 Ncm; otherwise, delayed loading was performed. The survival of the dental implants was recorded together with clinical and demographic information of the participants. The prosthetic complications (ceramic chipping, screw loosening, screw fracture, decementation, prosthesis failure) were also recorded. The marginal bone loss since insertion and the marginal bone loss since loading were calculated. Results Delayed implant loading was performed in 131 implants and immediate loading in 71 implants. The follow-up time was 106 ± 40 months and 117 ± 38 months in the delayed and immediately loaded implants, respectively. The implant loading protocol (delayed vs immediate) showed no influence on the implant survival rate (96.2% vs 97.2%) and the marginal bone loss since insertion (1.2 ± 1.0 mm vs 1.2 ± 1.0 mm). Conclusion The implant loading protocol (immediate vs delayed) did not influence the long-term outcomes (survival and marginal bone loss) of 3.0-mm-diameter dental implants supporting fixed multiple prostheses. These results are in favor of considering immediately loaded narrow dental implants as a viable treatment alternative for horizontally resorbed ridges. Nevertheless, future randomized clinical trials are needed to confirm these observations.

This study aimed to verify the relationship between the number of fusion level and the risk of screw loosening by using cortical bone trajectory (CBT) screws in patients with lumbar degenerative disease. We retrospectively reviewed the serial plain radiograph images of lumbar degenerative disease patients who had undergone posterior fixation and fusion surgery with CBT from 2014. All included patients should have been followed-up with computed tomography scan or plain radiograph for at least 6 months after operation. We individually evaluated the prevalence of screw loosening according to each vertebral level. We also determined whether the number of screw fixation affected the prevalence of screw loosening and whether S1 fixation increased the risk of screw loosening. The screw-loosening rates were high at the S1 level. Moreover, although fixation involved to S1, the loosening rates evidently increased (Fisher exact test, P = .002∗∗). The screw-loosening rate was 6.56% in 2 level fusion. However, it increased with the number of fusion levels (3 level: 25.00%, 4 level: 51.16%, and 5 level: 62.50%). To investigate if the number of fusion level affected the S1 screw loosening, we classified the cohort of patients into either involving S1 (S1+ group) or not (S1– group) according to different fusion levels (Table 3). The screw loosening between 2 group in 2 (5.56% vs 6.98%) and 3 fusion level (26.32% vs 22.73%) did not exhibit any significant difference. Interestingly, significantly high screw loosening was found in 4 fusion level (60.00% vs 15.38%), indicating that the higher fusion level (4 level) can directly increase the risk of S1 screw loosening. Our data confirmed that the screw-loosening rate increases rate when long segment CBT fixation involves to S1. Therefore, in case of long-segment fixation by using CBT screw, surgeons should be aware of the fusion level of S1.

This review was intended on major factors contributing to abutment screw loosening. A search of Pubmed and Google Scholar, as well as a manual search, was conducted. Publications and articles accepted for publication up to February 2020 were included. Out of 150 studies retrieved, a total of 57 were selected for this review. Dental implants are associated with a complexity of abutment screw loosening. Implantologists and prosthodontists should be aware of factors that contribute to this problem. In this review previously identified factors were collected, the consideration of which can help to reduce the frequency of abutment screw loosening.

The purpose of the study was to evaluate the different fracture pattern of patients being treated with trapezoidal plate fixation of condylar base and neck fractures using the AOCMF Classification System to determine specific fracture pattern that are associated with failure of trapezoidal plate fixation. Ten patients with mandibular condylar base and neck fractures underwent internal fixation using trapezoidal plates. Fractures of the condylar process were classified according to the AOCMF Classification System using computed tomography data. The fracture pattern was compared to complications according to hardware failure such as plate or screw loosening and plate fracture. Plate and screw loosening of trapezoidal plates for fixation of condylar base and neck fractures was associated with fracture location in the neck region and major fragment displacement with contact loss between the proximal and distal fragment of the fracture. Further investigations such as finite-element analysis of different plating systems for fixation of condylar neck fractures are necessary to establish the optimal fixation technique for condylar neck fractures.

Introduction (1) To evaluate the influence of pedicle screw loosening on clinical outcomes; (2) to clarify the association between the pull-out length and screw loosening 1 year after surgery; and (3) to determine radiographically which screw parameters predominantly influence the pull-out resistance of screws. Methods We analyzed 32 consecutive patients who underwent minimally invasive lumbar or thoracic spinal stabilization by intraoperative three-dimensional computed tomography (CT)-guided navigation without anterior reconstruction and were followed up for 1 year. The screw pull-out length was measured on axial CT images obtained both immediately after screw insertion and postoperatively. Loosening of screws and clinical outcomes were evaluated radiographically, clinically, and by CT 1 year after surgery. Results There were no significant differences in the mean age, sex, bone mineral density, mean stabilized length, and smoking habits of patients with (+) or without (-) loosening. The Oswestry Disability Index and the lumbar visual analog scale 1 year after surgery were significantly higher in patients with loosening (+) than in those without (-). The overall pedicle screw pull-out rate was 16.2% (47/290) of screws and the overall screw loosening rate was 15.2% (44/290) of screws. Screws with loosening (+) had significantly lower (axial) trajectory angles and higher screw pull-out lengths than those without (-). Approximately 82% of loosened screws had been pulled out during rod connection. Conclusions A lower axial trajectory and an increased screw pull-out length after rod reduction are crucial risk factors for screw loosening.

The primary goal of this study was to conduct a systematic review and meta-analysis of articles focused on odontoid screw fixation (OSF) and screw-related complications or non-union rates.We conducted a systematic review of the PubMed and Crossref databases between January 1982 and December 2019. Inclusion criteria comprised detailed descriptions of the surgical technique and screw-related complications (screw cut-out, loosening, breakage, malposition) or fusion rates.The initial selection consisted of 683 abstracts. A total of 150 full texts were chosen for detailed study, and 83 articles were included in the analysis. The point estimates for screw-related complications were as follows: 1. screw malposition frequency-4.8%; 2. screw cut-out rate-5.0%; 3. screw loosening/pull-out-3.8%; and 4. screw fracture rate-3.1%. The point estimate for the non-union rate was 9.7%. Statistical analysis of the screw-related complications rate based on surgical technique details was also performed CONCLUSIONS: Double-screw OSF performance in elder patients resulted in a higher risk of post-operative screw cut-out. In other cases, the development of screw-related complications did not depend on the method of intraoperative head fixation, selection of the implant entry point for OSF, type of the used screws, or cannulated instruments application. The outcomes of single-screw fixation through the anterior lip of the C2 vertebra were comparable to other techniques of OSF. Further, statistically reliable studies should be carried out to identify the optimal technique of OSF.

OBJECTIVEThe authors aimed to compare the efficacy of lumbar vertebral body Hounsfield units (HUs) and pedicle HUs at predicting pedicle screw loosening.METHODSThe authors retrospectively assessed 143 patients with L3–5 instrumentation. The patients were classified into one of two groups based on the status of their L3 screws (a screw loosening group or a control group). The pedicle HUs and vertebral HUs of L3 were measured using preoperative lumbar CT scans, and the pedicle HUs were measured in two ways: by excluding or by including cortical bone.RESULTSThe screw loosening rate was 20.3% (n = 29/143) at the 12-month follow-up. The vertebral body HUs and pedicle HUs in the screw loosening group were lower than those in the control group (vertebral body group: 98.6 HUs vs 121.4 HUs, p < 0.001; pedicle excluding cortical bone: 208.9 HUs vs 290.5 HUs, p = 0.002; pedicle including cortical bone: 249.4 HUs vs 337.5 HUs, p < 0.001). The pedicle HUs tended to have a higher area under the receiver operating characteristic curve value in predicting screw loosening, compared with that of vertebral body HUs, but the difference was not statistically significant (p > 0.05). Among patients with low vertebral body HUs of ≤ 130, the loosening rate was much lower in patients with pedicle HUs of ≤ 340 than in those with pedicle HUs of > 340 (31.0% vs 13.0%, respectively; p < 0.05).CONCLUSIONSVertebral body HUs alone are insufficient to accurately evaluate the risk of pedicle screw loosening. Therefore, it is important to collect both the pedicle HU and vertebral body HU measurements for surgical planning.

Patellar luxation and associated pelvic limb lameness were treated with polyethylene sulcal ridge augmentation prostheses in four cats. In all cases, the lameness resolved within weeks of a single surgery. No important complications were encountered. On radiographs obtained at least 2 years postoperatively, three cases showed radiographic progression of degenerative joint disease, and one showed evidence of screw loosening, but these were not reflected in apparent lameness and no case required revision.

Background Surgery for adult spinal deformity requires optimal patient-specific spino-pelvic-lower extremity alignment. Distal fixation in thoracolumbar spinal deformity surgery is crucial when arthrodesis to the sacrum is indicated. Although we had performed sacro-pelvic fixation with bilateral S1 and bilateral single iliac screws previously, iliac screw loosening and/or S1 screw loosening occurred frequently. So, the authors attempted to fuse spino-pelvic lesions with the dual iliac screws and S1 pedicle screws. Methods Twenty-seven consecutive adult spinal deformity patients underwent thoracolumbar-pelvic correction surgery with bilateral double iliac screws between May 2014 and September 2015. Sagittal vertical axis, lumbar lordosis, pelvic tilt, sacral slope, T1 pelvic angle, and global tilt were assessed radiographically and by computed tomography both preoperatively and 24 months postoperatively. Iliac screw loosening, S1 pedicle screw loosening, and screw penetration of the ilium were evaluated 2 years postoperatively. Results Only two patients (7.4%) at 1 year and three patients (11.1%) at 2 years presented with iliac screw loosening postoperatively. Loosening of the S1 screw occurred in three cases (11.1%) 2 years postoperatively. Displacement of the iliac screw occurred in eight cases (25%). Internal and external perforation of the ilium by the iliac screw occurred in six (22.2%) and three (11.1%) cases respectively. One reoperation was performed due to back-out of the iliac screw and rod breakage. Conclusion Bilateral dual iliac screws and an S1 pedicle screw system achieve longer stability for spinal and pelvic fusion in adult spinal deformity patients, with few severe complications.

OBJECTIVES The objective of this systematic review was to assess the influence of implant-abutment connection and abutment material on the outcome of implant-supported single crowns (SCs) and fixed dental prostheses (FDPs). METHODS An electronic Medline search complemented by manual searching was conducted to identify randomized controlled clinical trials, prospective and retrospective studies with a mean follow-up time of at least 3 years. Patients had to have been examined clinically at the follow-up visit. Failure and complication rates were analyzed using robust Poisson regression, and comparisons were made with multivariable Poisson regression models. RESULTS The search provided 1511 titles and 177 abstracts. Full-text analysis was performed for 147 articles resulting in 60 studies meeting the inclusion criteria. Meta-analysis of these studies indicated an estimated 5-year survival rate of 97.6% for SCs and 97.0% for FDPs supported by implants with internal implant-abutment connection and 95.7% for SCs and 95.8% for FDPs supported by implants with external connection. The 5-year abutment failure rate ranged from 0.7% to 2.8% for different connections with no differences between the types of connections. The total number of complications was similar between the two connections, yet, at external connections, abutment or occlusal screw loosening was more predominant. Ceramic abutments, both internally and externally connected, demonstrated a significantly higher incidence of abutment fractures compared with metal abutments. CONCLUSION For implant-supported SCs, both metal and ceramic abutments with internal and external connections exhibited high survival rates. Moreover, implant-supported FDPs with metal abutments with internal and external connections for also showed high survival rates.