Risk prevention and treatment of implant-supported central screw fracture / 口腔医学

@#In the complications of dental implant treatment, the mechanical complications, such as central screw breakage, are often complex and serious. This article analyzes factors that affect the loosening of the central screw. Understanding relevant risk factors can prompt doctors to take corresponding strategies to reduce the possibility of complications in clinical operations. After encountering broken cases, this paper also gives some ideas and methods of treatment, and finally summarizes clinical suggestions for preventing the central screw fracture.

Failure Analysis on Interface Stress in Unicompartmental Knee Arthroplasty / 医用生物力学

Objective To analyze interface stress of cemented tibial prosthesis platform and determine the interface stress damage area, so as to provide references for stress failure of tibial platform in clinical single condylar replacement. Methods The full cycle gait was simulated by human dynamics software to obtain the load-bearing condition of knee joint. A complete model of the knee joint was established by medical imaging and three-dimensional (3D) reconstruction software, and unicompartmental replacement was performed. The distribution of interfacial stress of tibial prosthesis platform after single condylar replacement was analyzed by finite element method. ResultsIn gait, force and angle of the knee joint changed periodically with time, a cycle lasted 1.3 s, and the peak of knee joint resultant force was 760 N. The maximum shear stress of the interface was 11.82 MPa and the maximum tensile stress was 6.849 MPa, both occurred at inner front end of the corner of prosthesis cement interface. The maximum interface stress of titanium alloy prosthesis was lower than that of stainless steel prosthesis. Conclusions The decrease in elastic modulus of prosthesis can reduce the maximum principal stress at the interface. Considering the interface stress, titanium alloy prosthesis is better than stainless steel prosthesis. The area of tibial prosthetic platform interface damage is mainly at the medial anterior and posterior corners and lateral middle ends,so improving the ability of prosthesis cement bonding in this area can prevent the loosening of tibial prosthesis of unicompartmental knee joint.The findings have practical implications for the prevention of tibial prosthetic platform loosening after unicompartmental knee arthroplasty in clinic.

Revision for Aseptic Loosening of Tumor Prosthesis in Lower Limbs / 肿瘤防治研究

Objective To determine the prosthesis survival and limb function after revision of global modular replacement system (GMRS) tumor prosthesis. Methods We retrospectively analyzed the clinical data of 16 patients who developed aseptic loosening of lower extremity tumor prosthesis and subsequently received revision with GMRS from 2009 to 2012. Kaplan-Meier method was used to calculate the 5- and 8-year survival rates of the prosthesis. The MSTS function scale was used to evaluate the functional outcomes. Results The average follow-up time was 90 months (52-118 months). The 5- and 8-year survival rates of GMRS prosthesis were both 94%. After revision, two patients failed, including one case of infection and one case of repeated aseptic loosening. The average interval between the first joint replacement and revision surgery was 81 months (27-187 months). Until the last follow-up, 93.3%(14/15) of the patients did not develop repeated aseptic loosening, 85.7%(12/14) of the patients who underwent GMRS revision had a longer loosening-free survival than those with the primary joint replacement (90.6±19.3 vs. 43.4±29.7 months, P=0.001). The average MSTS functional score was 27.7(24-30). Conclusion The incidence of repeated aseptic loosening for GMRS prosthesis is low and the limb function is good. The reported technique is satisfactory in the middle and long term.

Comparing Torque Loss in Standard Implants and Short Implants with Increased Vertical Cantilever Abutments: an In Vitro Study / Comparação da perda de torque em implantes padrão e implantes curtos com pilares cantilever verticais aumentados (in vitro)

Objectives: With regard to the prevalence of abutment screw loosening (SL) and bone height reduction, particularly in the posterior regions of the jaws, as well as the contradictory issue of applying short implants instead of surgeries, along with all preparations associated with longer implants, the present study aimed to compare the amount of torque loss in short implants with increased vertical cantilever abutments and standard ones. Material and Methods: In this experimental study, a total number of 20 implants (MegaGen Implant Co., Ltd, South Korea) with 4.5 mm diameter including 10 short implants (7 mm) and 10 standard ones (10 mm) were utilized. Using a surveyor, fixtures were perpendicularly mounted in 13×34 mm resin for short implants and 19×34 mm resin for standard ones. The abutments of the same height but different cuff heights (2.5 mm for the standard implants and 5.5 mm for the short ones) were then tightened with 30 N.cm, via a digital torque meter. To compensate the settling effect, the abutment screw was re-tightened with 30 N.cm after 10 min. Upon applying 500,000 cycles at 75 N.cm and 1 Hz along the longitudinal axis on each sample, blind reverse torque value (RTV) was measured with a digital torque meter. The data were finally analyzed using Student's t-test. Results:Both groups experienced torque loss, but there was no statistically significant difference between the case and control groups in terms of abutment SL (p = 0451). Conclusion: Short implants seem to be a good mechanical alternative in emergencies with respect to torque loss and abutment SL. (AU)

Objetivos: Considerando a prevalência de afrouxamento de parafuso dos pilares, redução da altura óssea especialmente nas regiões posteriores, a questão contraditória da aplicação de implantes curtos em vez de cirurgias e todos os preparos associados a implantes mais longos, este estudo buscou comparar implantes curtos com pilares cantilever verticais aumentados e implantes padrão na quantidade de perda de torque. Material e métodos: Neste estudo experimental, foram utilizados 20 implantes (Megagen, Coreia do Sul) com diâmetro de 4,5 mm, incluindo 10 implantes curtos (7 mm) e 10 implantes padrão (10 mm). A fixação foi realizada perpendicularmente em uma resina 13 × 34 mm para implantes curtos e uma resina 19 × 34 mm para implantes padrão, usando um topógrafo. Os pilares da mesma altura, mas com diferentes comprimentos de manguito (2,5 mm para os implantes padrão e 5,5 mm para os implantes curtos) foram apertados com 30 N, utilizando um torquímetro digital. Para compensar o efeito de sedimentação, o parafuso do pilar foi reapertado com 30 N após 10 min. Depois de aplicar 500.000 ciclos a 75 N e 1 Hz ao longo do eixo longitudinal em cada amostra, o valor de torque reverso cego foi medido com um medidor de torque digital. Os dados foram analisados pelo teste t de Student. Resultados: Todos os grupos tiveram perda de torque, mas não houve diferença estatisticamente significativa entre os grupos caso e controle em termos de afrouxamento do parafuso do pilar (p = 0451). Conclusão: Os implantes curtos parecem ser uma boa alternativa mecânica em emergências em termos de perda de torque e afrouxamento do parafuso do pilar. (AU)

Establishment of artificial joint aseptic loosening mouse model by cobalt-chromium particles stimulation / 中国修复重建外科杂志

Objective: To explore the feasibility of establishment of a artificial joint aseptic loosening mouse model by cobalt-chromium particles stimulation. Methods: Twenty-four 8-week-old male severe combined immunodeficient (SCID) mice were divided into experimental group ( n=12) and control group ( n=12). The titanium nail was inserted into the tibial medullary cavity of mouse in the two groups to simulate artificial joint prosthesis replacement. And the cobalt-chromium particles were injected into the tibial medullary cavity of mouse in experimental group. The survival of the mouse was observed after operation; the position of the titanium nail and the bone mineral density of proximal femur were observed by X-ray film, CT, and Micro-CT bone scanning; and the degree of dissolution of the bone tissue around the tibia was detected by biomechanical test and histological staining. Results: Two mice in experimental group died, and the rest of the mice survived until the experiment was completed. Postoperative imaging examination showed that there was no obvious displacement of titanium nails in control group, and there were new callus around the titanium nails. In experimental group, there was obvious osteolysis around the titanium nails. The bone mineral density of the proximal tibia was 91.25%±0.67%, and the maximum shear force at the tibial nail-bone interface was (5.93±0.85) N in experimental group, which were significantly lower than those in control group [102.07%±1.87% and (16.76±3.09) N] ( t=5.462, P=0.041; t=3.760, P=0.046). Histological observation showed that a large number of inflammatory cells could be seen around the titanium nails in experimental group, while there was no inflammatory cells, and obvious bone tissue formation was observed in control group. Conclusion: The artificial joint aseptic loosening mouse model can be successfully established by cobalt-chromium particles stimulation.

Systematic evaluation of the efficacy and safety of collum femoris preserving prosthesis in total hip arthroplasty / 中国组织工程研究

BACKGROUND: Total hip arthroplasty with femoral neck prosthesis is being accepted by more and more doctors, but the effect of femoral neck prosthesis preservation or not on total hip arthroplasty is still uncertain. OBJECTIVE: To systematically evaluate the efficacy and safety of collum femoris preserving prosthesis in total hip arthroplasty. METHODS: CBM, CNKI, VIP, WanFang, PubMed, Embase and The Cochrane Library databases were searched systematically. The deadline was March 1,2018. All clinical controlled trials collum femoris preserving prosthesis in total hip arthroplasty were collected and methodological quality was evaluated one by one. RevMan 4.2 software was used for systematic evaluation. RESULTS AND CONCLUSION: (1) Four studies were included, involoing 302 patients. Because there were few studies and patients involved, and the outcome evaluation indicators were quite different, meta-analysis cannot be conducted, only descriptive systematic evaluation was performed. (2) Three studies compared the efficacy of two surgical methods in improving Harris score. Two of them considered that total hip arthroplasty with collum femoris preserving prosthesis was significantly better than total hip arthroplasty with non-collum femoris preserving prosthesis (P 0.05). (3) Two studies compared the efficacy of two surgical methods in improving the range of motion of the joint. One study showed that total hip arthroplasty with collum femoris preserving prosthesis was significantly better than total hip arthroplasty with non-prosthesis (P 0.05). (4) One study showed that bone loss around the prosthesis in the total hip arthroplasty group with prosthesis was significantly less than that in the total hip arthroplasty group without collum femoris preserving prosthesis at 1 year postoperatively (P 0.05). (8) One study found that the total amount of bleeding in total hip arthroplasty group with collum femoris preserving prosthesis was higher than that in total hip arthroplasty group without collum femoris preserving prosthesis (P < 0.05). (9) In summary, total hip arthroplasty with collum femoris preserving prosthesis has advantages in improving Harris score, decreasing the Visual Analogue Scale score and that bone loss around the prosthesis. More rigorous research is needed to increase the intensity of evidence.

Effects of femoral prosthetic materials on artificial knee arthroplasty performance / 中国组织工程研究

BACKGROUND: Aseptic loosening of the femoral prosthesis is one of the important issues affecting the life of knee joint replacement. Particles from tibial polyethylene component wear and stress shielding are the main causes of this loosening, which are all related to the femoral prosthesis materials. OBJECTIVE: To study the effects of femoral prosthesis materials on the stress of the distal femur of the knee joint and the contact pressure on the polyethylene component by finite element method. METHODS: Knee arthroplasty models with four materials, titanium alloy, cobalt-chromium alloy, titanium-hydroxyapatite functional gradient biomaterial (FGBM I), titanium-bioactive glass functional gradient biomaterial (FGBM II), were established; the prosthesis was endowed with different material properties in the Abaqus finite element software. The stress distribution of the important vulnerable path in the femur and the changes of contact pressure on the polyethylene component under different materials were studied. RESULTS AND CONCLUSION: (1) Compared with the currently used titanium alloy and cobalt-chromium alloy, functional gradient biomaterials could significantly increase the stress at the femoral-prosthetic interface and the stress in the pathway of an important vulnerable region of the femur. In those materials, FGBM I increased most significantly. (2) Maximum stress of FGBM I and FGBM II prostheses on polyethylene insert was 20.41% and 19.98% lower than cobalt-chromium alloy, 20.07% and 19.63% lower than titanium alloy. (3) The results showed that functionally gradient biomaterials could produce higher stress at the distal end of the femur and lower contact pressure on the polyethylene insert, reducing the wear and stress shield on polyethylene insert, and FGBM I has significant effects.

Platelet count as a novel potential predictor of periprosthetic joint infection / 中国组织工程研究

BACKGROUND: Obtaining synovial fluid for diagnostic test of periprosthetic joint infection is invasive and painful to patients. Platelet count is a regular blood test which has been used as a possible predictor of several infectious diseases. Presumably, it could be one of the indicators of periprosthetic joint infection. OBJECTIVE: To identify the accuracies of platelet combined with white blood cell, erythrocyte sedimentation rate or C-reactive protein in the diagnosis of periprosthetic joint infection. METHODS: Patients undergoing revision arthroplasty from March 2013 to December 2018 in the First Affiliated Hospital of Guangzhou University of Chinese Medicine were retrospectively enrolled. A diagnosis of periprosthetic joint infection was confirmed in 77 patients according to the criterions from the Musculoskeletal Infection Society; the remaining 137 patients were confirmed as aseptic cases. White blood cell, erythrocyte sedimentation rate, or C-reactive protein and platelet count were compared between the two groups. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated. RESULTS AND CONCLUSION: The platelet values were significantly increased in periprosthetic joint infection cases. Sensitivity and specificity of the platelet for periprosthetic joint infection were 64.94% and 86.13%, respectively. Platelet demonstrated a higher accuracy when compared to erythrocyte sedimentation rate and C-reactive protein. In such cases, the platelet shows a certain reference value in confirming the diagnosis of periprosthetic joint infection. Platelet was enough used as adjunct diagnostic tool in patients suspected with periprosthetic joint infection.

Platelet count as a novel potential predictor of periprosthetic joint infection / 中国组织工程研究

BACKGROUND: Obtaining synovial fluid for diagnostic test of periprosthetic joint infection is invasive and painful to patients. Platelet count is a regular blood test which has been used as a possible predictor of several infectious diseases. Presumably, it could be one of the indicators of periprosthetic joint infection. OBJECTIVE: To identify the accuracies of platelet combined with white blood cell, erythrocyte sedimentation rate or C-reactive protein in the diagnosis of periprosthetic joint infection. METHODS: Patients undergoing revision arthroplasty from March 2013 to December 2018 in the First Affiliated Hospital of Guangzhou University of Chinese Medicine were retrospectively enrolled. A diagnosis of periprosthetic joint infection was confirmed in 77 patients according to the criterions from the Musculoskeletal Infection Society; the remaining 137 patients were confirmed as aseptic cases. White blood cell, erythrocyte sedimentation rate, or C-reactive protein and platelet count were compared between the two groups. The sensitivity, specificity, positive predictive value, and negative predictive value were calculated. RESULTS AND CONCLUSION: The platelet values were significantly increased in periprosthetic joint infection cases. Sensitivity and specificity of the platelet for periprosthetic joint infection were 64.94％ and 86.13％, respectively. Platelet demonstrated a higher accuracy when compared to erythrocyte sedimentation rate and C-reactive protein. In such cases, the platelet shows a certain reference value in confirming the diagnosis of periprosthetic joint infection. Platelet was enough used as adjunct diagnostic tool in patients suspected with periprosthetic joint infection.

Clinical Efficacy of Magui Wenjingtang Combined with Shoulder Joint Loosening Operation in Treating Periarthritis of Shoulder with Syndrome of Blood Deficiency and Cold Coagulation / 中国实验方剂学杂志

Objective::To explore the clinical efficacy of Magui Wenjingtang combined with joint mobilization in the treatment of periarthritis of the shoulder and the effect on hemodynamics and serum pain media. Method::A total of 120 patients with scapulohumeral periarthritis were enrolled in Tianjin Ninghe Hospital from July 2016 to July 2018.All cases were divided into control group and observation group, with 60 patients in each group. The control group received shoulder joint loosening operation (qd), and celecoxib capsules for oral administration. The observation group was treated with Magui Wenjingtang in addition to the shoulder joint loosening operation, 1 dose/d, 2 times/d. After 4 weeks of continuous treatment, the subjects were compared for the subjective pain level McGill Pain Questionnaire (SF-MPQ) score, shoulder mobility hemodynamic changes, and serum prostaglandin E2 (PGE2), substance P (SP), serotonin (5-HT) level and clinical efficacy. Result::Compared with before treatment, visual pain score (VAS), current pain status (PPI), and pain rating index (PRI) scores of the two groups were significantly lower after 4 weeks of treatment, and those of the observation group was significantly lower than the control group (P<0.01). The range of shoulder joint activity was significantly higher than that of the control group (P<0.01), erythrocyte sedimentation rate (ESR), fibrinogen (Fb), whole blood viscosity and serum were compared between the two groups after 4 weeks of treatment and before treatment. The levels of PGE2, SP and 5-HT were significantly lower (P<0.01), and the observation group was significantly better than the control group (P<0.01). The total effective rate of the observation group was 96.61%(57/59), which was significantly higher than 82.76% (48/58) of the control group(χ2=4.685, P<0.05). Conclusion::Magui Wenjingtang combined with shoulder joint loosening operation in treating periarthritis of shoulder with syndrome of blood deficiency and cold coagulation can effectively improve the pain and shoulder joint mobility, increase the curative effect, and improve the hemodynamics, and down-regulatie pain mediator of PGE2, SP, 5-HT, which may be related to the curative effect.

Failure probability, stress distribution and fracture analysis of experimental screw for micro conical abutment

Abstract The aim of this study was to evaluate the failure probability of two types of abutment screws after compressive load and to analyze the stress distribution with finite element method. Sixty (60) single-tooth implant restorations were assembled on titanium implants (e-fix, A.S. Technology - Titanium Fix). The groups were divided into Conventional screw (Screw neck 1.5 ø mm) and Experimental screw (Screw neck constricted with 1.2 ø mm). Specimens were subjected to single load to failure with compressive test according ISO 14801. The fractured specimens were subjected to stereomicroscopy for measurement of remaining screws inside the implant and characterization of fracture origin. Representative specimens were analyzed by scanning electronic microscopy. For finite element method (FEM), an identical 3D model of the two in vitro test groups were used with similar conditions (30º, 100 N load). The stress in the abutment screw was analyzed by von-Mises criteria. The results of strength means were 4132.5 ± 76 MPa and 4528.2 ± 127.2 for conventional and experimental groups, respectively. During microscopy, the mean (mm) of the remaining screw piece inside the implants were 0.97 ± 0.23 and 1.32 ± 0.12 for conventional and experimental groups, respectively. In FEM, the conventional group showed stress concentered in an unfavorable region (peak of 39.23 MPa), while the experimental group showed more stress areas but less concentration than the conventional group (36.6 MPa). In using the tested experimental geometry, the abutment screw can have its strength improved, and the origin of failure can be more favorable to clinical resolution.

Resumo O objetivo deste estudo foi avaliar a probabilidade de falha de dois tipos de parafusos para pilar protético após a compressão e analisar a distribuição da tensão com o método dos elementos finitos. Sessenta (60) restaurações unitárias foram montadas em implantes de titânio (e-fix, A.S. Technology - Titanium Fix). Os grupos foram divididos em parafusos convencionais (parafuso de pescoço 1,5 ø mm) e parafuso experimental (parafuso de pescoço estreitado com 1,2 ø mm). As amostras foram sujeitas ao teste de compressão de acordo com ISO 14801. Os espécimes fraturados foram submetidos a estereomicroscopia para a mensuração dos parafusos restantes dentro do implante e caracterização da origem da fratura. Os espécimes representativos foram analisados ​​por microscopia eletrônica de varredura. Para o método de elementos finitos (FEM), utilizou-se um modelo 3D idêntico dos dois grupos de teste in vitro com condições semelhantes (30º, 100 N). A tensão no parafuso do pilar foi analisada pelo critério de von-Mises. Os resultados de resistência a compressão foram 4132,5 ± 76 MPa e 4528,2 ± 127,2 para grupos convencionais e experimentais, respectivamente. Durante a microscopia, a média do remanescente do parafuso restante dentro dos implantes foi de 0,97 ± 0,23 e 1,32 ± 0,12 mm para os grupos convencionais e experimentais, respectivamente. Em FEM, o grupo convencional mostrou tensão concentrada em uma região desfavorável (pico de 39,23 MPa), enquanto o grupo experimental apresentou mais áreas de tensão, porém menor concentração do que o grupo convencional (36,6 MPa). Ao usar a geometria experimental testada, o parafuso do pilar pode ter sua resistência melhorada e a origem da falha pode ser mais favorável à resolução clínica.

Finite element analysis of the effect of novel Lock Screw system preventing abutment screw loosening

PURPOSE: The purpose of this finite element analysis study is to introduce the novel Lock screw system and analyze its mechanical property to see if it can prevent abutment screw loosening. MATERIALS AND METHODS: The Lock screw is a component tightened on the inside of the implant abutment which applies compressive force to the abutment screw head. To investigate the effect, modeling was done using CAD program and it was analyzed by finite element analysis under various load conditions. First, the preload was measured according to the tightening torque of the abutment screw then it was compared with the theoretical value to verify the analytical model. The validated analytical model was then divided into those with no external load and those with 178 N, and the tightening torque of the lock screw was changed to 10, 20, 30 Ncm respectively to examine the property of stress distribution on the implant components. RESULTS: Using Lock screw under various loading conditions did not produce equivalent stresses beyond the yield strength of the implant components. In addition, the axial load was increased at the abutment-abutment screw interface. CONCLUSION: The use of Lock screw does not exert excessive stress on the implant components and may increase the frictional force between the abutment-abutment screw interface, thus it is considered to prevent loosening of the abutment screw.

Conversion of Failed Reverse Total Shoulder Arthroplasty to Hemiarthroplasty: Three Cases of Instability and Three Cases of Glenoid Loosening

BACKGROUND: Glenoid loosening and postoperative instability are common causes of failed reverse total shoulder arthroplasty (RTSA). When soft-tissue problems or large glenoid bone defect interferes with reimplantation in revision RTSA, conversion to hemiarthroplasty can be considered. We present a case series of patients who underwent conversion to hemiarthroplasty due to glenoid loosening and early instability after RTSAs, along with clinical results. METHODS: A total of 72 primary RTSAs using the Aequalis prosthesis were performed at our institution from May 2009 to December 2016. Of these, five patients, including one with humeral neck fracture and absent rotator cuff and four with cuff tear arthropathy, underwent conversion to hemiarthroplasty. Another patient who had RTSA at a local clinic underwent hemiarthroplasty at our institution for unresolved postoperative anterior dislocation. The mean age of the six patients was 71.7 years (range, 62 to 76 years), and the mean follow-up period was 24.4 months (range, 18 to 30 months). Clinical assessments were conducted by using the visual analog scale (VAS), American Shoulder and Elbow Surgery (ASES) score, and University of California at Los Angeles (UCLA) shoulder score at the last follow-up. RESULTS: The conversion to hemiarthroplasty in the six patients dramatically improved the mean VAS score (preoperative, 8.1; postoperative, 2.5), ASES score (preoperative, 22.1; postoperative, 56.5), and UCLA score (preoperative, 12; postoperative, 18.1). However, the range of motion was almost unchanged after surgery. CONCLUSIONS: Conversion to hemiarthroplasty can be a good alternative to revision RTSA in patients with serious complications (such as unresolved instability and glenoid loosening) difficult to treat with revision RTSA.

Accuracy of different electronic torque drivers: A comparative evaluation

PURPOSE: This study aims to evaluate the loosening torque on the implant fixture, and to assess the accuracy of difference electronic torque drivers.MATERIALS AND METHODS: Three electronic torque drivers were used to measure the loosening torque on the implant system (AnyOne; MegaGen). The implant fixtures were divided among the 3 electronic torque driver types (W&H, SAESHIN, and NSK group) and 9 for each group. The screws were fastened at the implant fixture by three electronic torque drivers using the tightening torques recommended by the manufacturers of the drivers. After 10 minutes, the screws were again fastened at the implant fixture with equal torque. Then, the loosening torques were measured with an MGT12 torque gauge (MARK-10, Inc.). This measurement procedure was repeated 10 times under loosening torques of 15 Ncm, 25 Ncm, and 35 Ncm. In the statistical analysis, all values of loosening torque were analyzed with the one-way ANOVA and Kruskal-Wallis test (α=.05) for comparative evaluation.RESULTS: There were significant inter-group differences at loosening torques of 15 Ncm and 25 Ncm (P<.05). The accuracy of the NSK driver was the highest, followed by SAESHIN and W&H. There was no significant difference between NSK and W&H at 35 Ncm (P>.05). The SAESHIN driver showed the closest loosening torque at 35 Ncm.CONCLUSION: The most accurate loosening torques were SAESHIN at 35 Ncm, and NSK at 15 Ncm and 25 Ncm. Since the loosening torque may vary depending on the tightening torques and electronic torque drivers, periodic calibration of the electronic torque driver is recommended.

Utility of radiolabeled leukocyte and bone marrow scintigraphy with SPECT/CT in the diagnostic work-up- of the painful prosthetic joint: A single-institution experience

@#In tbhe assessment of prosthetic joint pains, differentiating between aseptic loosening and infection can be challenging due to their similarities in clinical presentation and histopathology. Combined radiolabeled leukocyte and bone marrow scintigraphy and SPECT/CT is considered the most suitable nuclear imaging modality for this purpose. However, this is infrequently performed in our local setting. We present two cases where these studies were appropriately performed with different scan outcomes. The first case involved a 67-year-old male with painful right knee prosthesis and an alleged history of recurrent periprosthetic joint infection (PJI). The leukocyte tagging scan and marrow scan images were found to be congruent, which was more compatible with aseptic loosening. No emergent surgical intervention was done in our hospital, and the patient returned to this home territory for further management. The second case was a 72-year-old male with progressive pain in his left prosthetic hiip which began after surgery a year prior. Scan images were incongruent, suggestive of PJI; this was confired on joint aspiration and eventual surgical revision. Despite this imaging study's high sensitvity and high specificity, it has not been well-received in management algorihms of PJI. Collaboration between clinicans and nuclear imaging specilists is key in increasing the general use of these procedures.

Multi-Rod Constructs Can Increase the Incidence of Iliac Screw Loosening after Surgery for Adult Spinal Deformity

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.

Risk Factors for Cement Loosening after Vertebroplasty for Osteoporotic Vertebral Fracture with Intravertebral Cleft: A Retrospective Analysis

STUDY DESIGN: Retrospective case-control study. PURPOSE: To evaluate the primary outcomes and radiographic results of percutaneous vertebroplasty (PVP) in patients with singlelevel osteoporotic vertebral fracture (OVF) with intravertebral cleft (IVC) to identify the risk factors for cement loosening after PVP. OVERVIEW OF LITERATURE: PVP is a widely accepted method for managing painful OVF; however, cement loosening occasionally occurs with poor outcomes. METHODS: This retrospective study involved 195 patients treated with PVP for single-level OVF with IVC. Six months thereafter, the primary outcomes were evaluated using the Visual Analog Scale (VAS) for back pain and the modified Oswestry Disability Index. Computed tomography was conducted to detect cement loosening. Possible risk factors, such as age, sex, wedging angle, intravertebral instability, Parkinson’s disease, spinous process fracture, ankylosing spinal hyperostosis, split vertebrae, and adjacent intervertebral vacuum, were assessed. RESULTS: Forty-nine patients (25%) experienced cement loosening 6 months after PVP. The mean VAS scores were significantly higher in patients with cement loosening than in those without (50 vs. 26 mm, respectively; p < 0.01). Cement loosening was closely associated with intravertebral instability (odds ratio [OR], 1.20; 95% confidence interval [CI], 1.04–1.40; p =0.015), Parkinson’s disease (OR, 54.31; 95% CI, 4.47–659.53; p =0.002), spinous process fracture (OR, 7.11; 95% CI, 1.65–30.60; p =0.009), and split vertebrae (OR, 11.59; 95% CI, 1.64–82.02; p =0.014). CONCLUSIONS: Patients with cement loosening experienced worse back pain than those without cement loosening. The important risk factors that influenced cement loosening after PVP were high intravertebral instability, Parkinson’s disease, spinous process fracture, and split vertebrae.

Comparison of Revision Rates Due to Aseptic Loosening between High-Flex and Conventional Knee Prostheses

PURPOSE: The purpose was to evaluate and compare the revision rate due to aseptic loosening between a high-flex prosthesis and a conventional prosthesis. MATERIALS AND METHODS: Two thousand seventy-eight knees (1,377 patients) with at least 2 years of follow-up after total knee arthroplasty were reviewed. Two types of implants were selected (LPS-Flex and LPS, Zimmer) to compare revision and survival rates and sites of loosened prosthesis component. RESULTS: The revision rate of the LPS-Flex (4.9%) was significantly higher than that of the conventional prosthesis (0.6%) (p<0.001). The 5-, 10-, and 15-year survival rates were 98.9%, 96.2% and 92.0%, respectively, for the LPS-Flex and 99.8%, 98.5% and 93.5%, respectively, for the LPS. The survival rate of the high-flex prosthesis was significantly lower than that of the conventional prosthesis, especially in the mid-term period (range, 5 to 10 years; p=0.002). The loosening rate of the femoral component was significantly higher in the LPS-Flex prosthesis (p=0.001). CONCLUSIONS: The LPS-Flex had a higher revision rate due to aseptic loosening than the LPS prosthesis in the large population series with a long follow-up. The LPS-Flex should be used carefully considering the risk of femoral component aseptic loosening in the mid-term (range, 5 to 10 years) follow-up period after initial operation.

Screw loosening and changes in removal torque relative to abutment screw length in a dental implant with external abutment connection after oblique cyclic loading

PURPOSE: This study investigated the effects of abutment screw lengths on screw loosening and removal torque in external connection implants after oblique cyclic loading. MATERIALS AND METHODS: External connection implants were secured with abutment screws to straight abutments. The abutment-implant assemblies were classified into seven groups based on the abutment screw length, with each group consisting of five assemblies. A cyclic load of 300 N was applied at a 30° angle to the loading axis until one million cycles were achieved. Removal torque values (RTVs) before and after loading, and RTV differences were evaluated. The measured values were analyzed using repeated measures of analysis of variance with the Student-Newman-Keuls multiple comparisons. RESULTS: All assemblies survived the oblique cyclic loading test without screw loosening. There was a significant decrease in the RTVs throughout the observed abutment screw lengths when the abutment-implant assemblies were loaded repeatedly (P < .001). However, the abutment screw length did not show significant difference on the RTVs before and after the experiment when the abutment screw length ranged from 1.4 to 3.8 mm (P=.647). CONCLUSION: Within the limit of this experiment, our results indicate that the abutment screw length did not significantly affect RTV differences after oblique cyclic loading when a minimum length of 1.4 mm (3.5 threads) was engaged. These findings suggest that short abutment screws may yield stable clinical outcomes comparable to long screws in terms of load resistance.

Monitoring osseointegrated prosthesis loosening and fracture using electrical capacitance tomography

A noncontact, noninvasive, electrical permittivity imaging technique is proposed for monitoring loosening of osseointegrated prostheses and bone fracture. The proposed method utilizes electrical capacitance tomography (ECT), which employs a set of noncontact electrodes, arranged in a circular fashion around the imaging area, for electrical excitations and measurements. An inverse reconstruction algorithm was developed and implemented to reconstruct the electrical permittivity distribution of the interrogated region from boundary capacitance measurements. In this study, osseointegrated prosthesis phantoms were prepared using plastic rods and Sawbone femur specimens, which were subjected to prosthesis loosening and fracture monitoring tests. The results demonstrated that the spatial location and extent of prosthesis loosening and bone fracture could be estimated from the ECT reconstructed permittivity maps. The resolution of the reconstructed images was further enhanced by a limited region tomography algorithm, and its accuracy in terms of identifying the severity, location, and shape of bone fracture was also investigated and compared with conventional full region tomography.