Screw Fixation Of Fractures Research Articles

The Functional and Radiological Outcome of Hoffa's Fracture Treated With Cannulated Cancellous Screws.

Introduction: Distal femur AO type 33 B fractures consist of partial articular fractures subdivided into three types namely sagittal lateral condyle fracture, medial condyle fracture, and coronal split fracture. Coronal plane fractures of the distal femur are less frequent compared to sagittal plane fractures and are known as Hoffa fractures. The mechanism of injury is usually a direct anteroposterior force to the flexed and abducted knee for lateral condylar fractures and a direct impact on the medial side of the knee in flexion for a medial condylar fracture. Various approaches like lateral parapatellar for lateral condylar Hoffa's fixation, with or without posterior approach for open reduction of Hoffa's fracture with screw or buttress plate fixation, medial parapatellar approach for medial condylar Hoffa's fracture screw fixation are used.Materials and Methods: This study was conducted at R L Jalappa Hospital and Research Center attached to Sri Devaraj Urs Medical College, Kolar, India, from June 2017 to May 2020 with 17 patients as a sample size.Results: Seventeen patients with Hoffa's fracture were treated with cannulated cancellous screws with lag effect including 12 males and five females with a mean age of 31.1 years. The range of motion ranged from 120 to 135 degrees of flexion with a mean of 125.2 degrees. Three patients had extensor lag ranging from 5 to 10 degrees with an average of 6.3 degrees. Neer scores were excellent in 11, good in four, and fair in two patients. The average fracture union time for the lateral condyle was 16.4 months and for the medial condyle, it was 16.7 months.Conclusion: Restoration of articular anatomy and its congruence is of paramount importance for better surgical outcomes. Closed or open reduction and stable fixation with anteroposterior cannulated cancellous screws are essential. A good post-operative rehabilitation program is required for better outcomes.

BIOMECHANICAL PECULIARITIES OF PLATE OSTEOSYNTHESIS FOR FRACTURES OF UPPER AND LOWER EXTREMITIES

In order to study biomechanics of plate osteosynthesis the review of the literature data about the use of different plates and screws for fracture fixation was done. The focus of the review was on the plate design, the connection interface between the screw head and the plate body, and the relations between the type of a plate and the stability of fracture fixation. The application of different types of plates fixed with locking head screws and non-locking head screws were studied for fractures of upper and lower extremities: humerus, forearm, femur and tibia. The application of plates with bigger section area and 4.5 mm or 5.0 mm screws is needed respecting the biomechanical peculiarities of lower extremity fractures, for which body weight is transferred to the fracture site, causing intensive strains in the components of bone-screws-plate system.

Biomechanical stability of complex coronal plane fracture fixation of the capitellum

IntroductionCoronal plane fractures of the distal humerus are relatively rare and can be challenging to treat due to their complexity and intra-articular nature. There is no gold standard for surgical management of these complex fractures. The purpose of this study was to compare the biomechanical stability and strength of two different internal fixation techniques for complex coronal plane fractures of the capitellum with posterior comminution.Materials and methodsFourteen fresh frozen, age- and gender-matched cadaveric elbows were 3D-navigated osteotomized simulating a Dubberley type IIB fracture. Specimens were randomized into one of two treatment groups and stabilized with an anterior antiglide plate with additional anteroposterior cannulated headless compression screws (group antiGP + HCS) or a posterolateral distal humerus locking plate with lateral extension (group PLP). Cyclic testing was performed with 75 N over 2000 cycles and ultimately until construct failure. Data were analyzed for displacement, construct stiffness, and ultimate load to failure.ResultsThere was no significant difference in displacement during 2000 cycles (p = 0.291), stiffness (310 vs. 347 N/mm; p = 0.612) or ultimate load to failure (649 ± 351 vs. 887 ± 187 N; p = 0.140) between the two groups.ConclusionsPosterolateral distal humerus locking plate achieves equal biomechanical fixation strength as an anterior antiglide plate with additional anteroposterior cannulated headless compression screws for fracture fixation of complex coronal plane fractures of the capitellum. These results support the use of a posterolateral distal humerus locking plate considering the clinical advantages of less invasive surgery and extraarticular metalware.Level of evidenceBiomechanical study.

Design and analysis of biodegradable buttress threaded screws for fracture fixation in orthopedics: a finite element analysis

Screws made up of non-biodegradable materials (Ti-alloy, etc.) have been used since long for temporary joining/fixation in applications involving skeleton damage or bone fracture. These screws need to be removed after complete healing as their sustained presence results in many complications, such as - micro-fracturing, stress shielding, etc. The removal of these screws is a little difficult too as it may result in the healed bone getting broken/damaged again. These problems can be overcome by employing metallic implants (plate, screws, etc.) made up of biodegradable metallic materials (Mg-alloy, etc.). Such implants exhibit optimal mechanical performance, are biocompatible, have adequate biodegradation rates, and rely on a unique design. Internal fracture fixation makes usage of screws with or without an accompanying plate. Buttress-threaded screws are the most frequently used ones. These screws must have the capacity to bear usually occurring loads and hold fractured segments of bone all through the process of healing. Finite element analysis (FEA) is an effective technique used for testing and validation of desired characteristics for Mg-based biodegradable buttress-threaded screw (BBTS). The characteristics of interest include maximum possible pullout resistance to tightly hold segments of bone, torsional ability for tightening or tapping, bending ability during providing plate support by screw head, and resistance to combined loading (tensile/compressive and bending) during the self-support stage using merely the screw(s). According to test results and subsequent validation through discretization error and convergence plot, BBTS made up of Mg-alloy are found safe for regular applications under usually encountered impact loads. Topological optimization and vibration analysis are also performed wherein it is observed that design of BBTS is good enough for possible usage in fracture fixation in orthopaedics.

Diabetes as a Risk Factor for Orthopedic Implant Surface Performance: A Retrieval and In Vitro Study

Orthopedic devices are often associated with increased risk for diabetic patients due to impaired wound healing capabilities. Adverse biological responses for immunocompromised patients at the implant-tissue interface can lead to significant bone resorption that may increase failure rates. The goal of this study was to characterize the surface of implants removed from diabetic patients to determine underlying mechanisms of diabetes-induced impaired osseointegration. Thirty-nine retrieved titanium and stainless-steel orthopedic devices were obtained from diabetic and non-diabetic patients, and compared to non-implanted controls. Optical Microscopy, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, and X-ray Photoelectron Spectroscopy revealed changes in morphology, chemical composition, oxidation state, and oxide thickness of the retrieval specimens, respectively. Additionally, titanium disks were immersed for 28 days in simulated in vitro diabetic conditions followed by Inductively Coupled Plasma-Optical Emission Spectroscopy to quantify metal dissolution. Electrochemical testing was performed on specimens from retrievals and in vitro study. Aside from biological deposits, retrievals demonstrated surface discoloration, pit-like formations and oxide thinning when compared to non-implanted controls, suggesting exposure to unfavorable acidic conditions. Cyclic load bearing areas on fracture-fixation screws and plates depicted cracking and delamination. The corrosion behavior was not significantly different between diabetic and non-diabetic conditions of immersed disks or implant type. However, simulated diabetic conditions elevated aluminum release. This elucidates orthopedic implant failures that potentially arise from diabetic environments at the implant-tissue interface. Design of new implant surfaces should consider specific strategies to induce constructive healing responses in immunocompromised patients while also mitigating corrosion in acidic diabetic environments.

Fixation using Alternative Implants for the Treatment of Hip Fractures (FAITH-2): The Exploratory Health-Related Quality of Life and Patient-Reported Functional Outcomes of a Multi-Centre 2 × 2 Factorial Randomized Controlled Pilot Trial in Young Femoral Neck Fracture Patients

PurposeFemoral neck fractures in young patients are typically managed with internal fixation using either cancellous screws or a sliding hip screw (SHS). Although fixation preserves the hip joint, patients are still at risk of complications and poor clinical outcomes which lead to diminished function and health related quality of life (HRQL). The Fixation using Alternative Implants for the Treatment of Hip Fractures (FAITH-2) pilot randomized controlled factorial trial evaluated the effect of surgical fixation (cancellous screws vs. SHS) and vitamin D supplementation vs. placebo on patient-reported function and HRQL. MethodsPatients between the ages of 18-60 years with a femoral neck fracture requiring surgical fixation were eligible. Eligible patients were randomized to receive either a sliding hip screw or cancellous screws for fracture fixation AND vitamin D3 4,000 IU or placebo daily for 6 months. Patient-reported function (Hip Outcome Score) and HRQL (Short Form-12) were assessed at standardized time points in the 12 months following their fixation surgery. Patient-reported function and HRQL were summarized using means, SD, and 95% confidence intervals (CIs), or percentages and counts. Longitudinal data analysis with mixed models was used to explore the effect of treatment group and time on the patient-reported function and HRQL. Results86 of the 91 patients randomized into the FAITH-2 pilot study were deemed eligible. There were no significant differences in patient-reported function or HRQL between the treatment groups at 12 months post-fracture. At the 6- and 9-month assessments, a potential benefit in hip function was seen in the cancellous screw group. In all treatment groups, participants reported lower function and HRQL at 12 months post-fracture as compared to their pre-injury assessment. ConclusionsFew differences were found in function and HRQL among the treatment groups in the FAITH-2 pilot study. Despite modern implants and vitamin D supplementation, neither function nor HRQL returns to baseline in this population. Additional efforts to improve the outcomes of these challenging injuries are still needed. Level of EvidenceTherapeutic Level II

Comparative study of operative fixation of fracture of medial malleolus by malleolar screw versus tension band wiring

Background: Ankle fractures are common and many require surgical intervention. It has been well documented that type of surgery and a delay in fracture fixation results in increased length of hospital stay and increased complication rate. Initial delay can also allow swelling or blistering to develop which may necessitate a further delay in operative fixation up to 10 days and increase morbidity. Patients and Methods: A prospective study of twenty-one patients presented with displaced closed fracture of medial malleolus and treated surgically at AL-KARKH Hospital from March 2010 to September 2011; the fractures had been fixed by tension-band wiring or by malleolar screw. The patients were then classified into two groups (15 patients in group 1 were treated by tension-band wiring, figure of eight, and 6 patients in group 2 were treated by malleolar screw fixation). The patients were evaluated clinically, radiologically, and functionally with follow-up till complete healing. Results: Radiological union took place in the group 1 patients (mean time 10.2 weeks) earlier than in group 2 patients (mean time 12.2 weeks) with p=0.001. Excellent and good functional results were achieved in 73% in group 1 patients and in 66.7% in group 2 patients with p=0.034. A better range-of-motion (especially for dorsiflexion of ankle) was noticed in the group 2 patients. Conclusions: Tension-band wiring may be more valid and excellent option than the malleolar screw for internal fixation of fracture of medial malleolus, as it is more stable fixation than malleolar screw, and allows early active exercises of the ankle and these results have to be supported by studies of larger number of cases and longer follow-up duration, and application of other methods of internal fixation, before recommending the optimum method for ankle fracture fixation.

Long-term study on the osteogenetic capability and mechanical behavior of a new resorbable biocomposite anchor in a canine model

BackgroundBiodegradable suture anchors are commonly used for repairing torn rotator cuffs, but these biodegradable materials still suffer from low mechanical strength, poor osteointegration, and the generation of acidic degradation byproducts. MethodThe purpose of this study was to evaluate the long-term mechanical behavior and osteogenetic capabilities of a biocomposite anchor injection molded with 30% β-tricalcium phosphate microparticles blended with 70% poly (L-lactide-co-glycolide) (85/15). This study investigated in vitro degradation and in vivo bone formation in a canine model. The initial mechanical behavior, mechanical strength retention with degradation time, and degradation features were investigated. ResultsThe results showed that the biocomposite anchor had sufficient initial mechanical stability confirmed by comparing the initial shear load on the anchor with the minimum shear load borne by an ankle fracture fixation screw, which is considered a worst-case implantation site for mechanical loading. The maximum shear load retention of the biocomposite anchor was 83% at 12 weeks, which is desirable, as it aligns with the rate of bone healing. The β-tricalcium phosphate fillers were evenly dispersed in the polymeric matrix and acted to slow the degradation rate and improve the mechanical strength of the anchor. The interface characteristics between the β-tricalcium phosphate particles and the polymeric matrix changed the degradation behavior of the biocomposite. Phosphate buffer saline was shown to diffuse through the interface into the biocomposite to inhibit the core accelerated degradation rate. In vivo, the addition of β-tricalcium phosphate induced new bone formation. The biocomposite material developed in this study demonstrated improved osteogenesis in comparison to a plain poly (L-lactide-co-glycolide) material. Neither anchor produced adverse tissue reactions, indicating that the biocomposite had favorable biocompatibility following long-term implantation. ConclusionIn summary, the new biocomposite anchor presented in this study had favorable osteogenetic capability, mechanical property, and controlled degradation rate for bone fixation. Translational potential of this articleThe new biocomposite anchor had sufficient initial and long-term fixation stability and bone formation capability in the canine model. It is indicated that the new biocomposite anchor has a ​potential for orthopedic application.

Pre-clinical testing of human size magnesium implants in miniature pigs: Implant degradation and bone fracture healing at multiple implantation sites

Two miniature pig models to assess safety and performance of degradable osteosynthesis implants are presented. Both models provide multiple implantation sites with human size implants. In the first model, different types of magnesium plates and screws for fracture fixation were used to study local and systemic safety aspects in 14 Göttingen minipigs. Implant degradation, gas release and accumulation of alloying elements in organs were assessed for non-coated and plasmaelectrolytic coated magnesium implants and compared to the titanium reference. The observed implant degradation was mostly uniform and did not seem to depend on the implantation site and implant condition. The coating was effective in delaying initial gas release and degradation. No rare earth alloying elements could be detected in local lymph nodes, kidneys, livers or spleens. In the second model with Göttingen und Yucatan minipigs, full osteotomies were inflicted to four different anatomical sites and treated with magnesium plates and screws to assess fracture healing performance. Two Göttingen pilot minipigs showed promising results including a mandible osteosynthesis which healed within 6 weeks. The subsequent study was compromised by the more massive jaws of the used Yucatan minipigs. Three out of seven animals had to be sacrificed within two months as the stability of magnesium and titanium reference implants in the mandible was surpassed. In conclusion, the resorbable magnesium implants showed promising in vivo properties. For the analysis of human standard sized implants under full chewing load conditions, lighter Göttingen minipigs were more suitable than heavier Yucatan minipigs.

Sliding Hip Screw for Fixation of Fracture Through a Previously Arthrodesed Hip

Hip arthrodesis is a treatment option for painful chronic hip conditions. Hip fractures through a previously arthrodesed hip are relatively uncommon as indications for hip arthrodesis are rare. The following case reports on the use of a sliding hip screw and a pelvic reconstruction plate to address arthrodesed hip fracture in an 81-year-old man. The use of a dynamic hip screw in this setting gave us a stable fixed-angle construct with compression across the fracture site, and the addition of a trochanteric side plate added to the stability. The dynamic compression plate with limited bone contact was used to neutralize the construct. This case describes the successful treatment of such an injury in a way not previously described in the literature with the intent of giving the orthopaedic traumatologist another method to approach this rare injury.

Biomechanical Comparison between Preloaded Position Screw and Lag Screw Fixations for Their Compressive Effects in a Porcine Rib Fracture Model.

The aim of this study was to compare the compressive effect between preloaded position screws and lag screws in fracture fixation. Pairs of semi-cylindrical bone fragments were created on a porcine rib model to simulate fractured bones. The compressive forces of fracture fixation generated by preloaded position screws (P group) and conventional lag screws (L group) were recorded by a film stress sensor. In the P group, a pair of Angus bone holding forceps was used to compress the interfragmentary interface until reaching the preloading force of 1.3 MPa. Similar preloading procedure was applied on lag screw fixations to explore its potential of additional compressive force. With 1.3 MPa preloading force and 0.2 Nm screw insertion torque force, the interfragmentary compressive force of P group was similar to that of L group. When the insertion torque force was increased to 0.4 Nm, all screws in the L group failed due to thread stripping. When screws in the P group were installed under 0.4 Nm torque and in the L group under 0.2 Nm torque, the P group generated significantly greater compressive force. With preloading device applied on lag screw installation, it did not further increase the interfragmentary compressive force. Compared with lag screws, preloaded position screws tolerated greater torque in screw installation and provided greater interfragmentary compressive force. The study suggests the applicability of preloaded position screws in fracture fixation requiring interfragmentary compression.

Study on the complications of locking compression plate used for fracture lower end of femur

The tension band & axial compression principles are used frequently while using plate and screws for fracture fixation. Muller, Allgower, and others of the AO group in Switzerland designed a compression plate and equipment to apply compression to fractures. These plates have been modified several times since their introduction in 1963.In our study of 20 lower end of femur fractures, 4 were of Muller’s Type A2.; 5 were of Muller’s Type A3; 1 was of Muller’s Type C1 ; 5 were of Muller’s Type C2; and remaining 5 were Muller’s Type C3. Of all these fractures 4 were open and of these fractures 2 needed prior debridement and primary closure.

Commentary on 'Intramedullary headless screw fixation for fractures of the proximal and middle phalanges in the digits of the hand: a review of 31 consecutive fractures' and 'Treatment of proximal phalangeal fractures with an antegrade intramedullary screw: a cadaver study'.

Commentary on 'Intramedullary headless screw fixation for fractures of the proximal and middle phalanges in the digits of the hand: a review of 31 consecutive fractures' and 'Treatment of proximal phalangeal fractures with an antegrade intramedullary screw: a cadaver study'.

Minimally invasive screw fixation of fractures in the cervical and thoracic spine: CT-controlled pre-surgical guidewire implantation in clinical routine

Minimally invasive screw fixation of fractures in the cervical and thoracic spine: CT-controlled pre-surgical guidewire implantation in clinical routine

Contact Analysis for Coupling of Plates and Screws in Fracture Fixation of Cortical Bone

Internal fixation is a common treatment for bone fracture. Bone fracture occurs due to different reasons such as motor vehicle accidents, falling,...etc. The treatment is performed by fixing plate and screws to the fracture site. Lack of stability of the implants (plates and screws) may lead to delay in healing or failure of treatment. Micro-motion between the implant and the bone may cause formation of fibrous tissue around the screw which will lead to implant loosening. On the other hands, firm fixing of the conventional implants (Dynamic Compression Plates) may lead to delay resorption and delay in healing. Recently, Locked Compression Plates were introduced to get over the shortcomings of the existing Dynamic Plates. In Locked Plates the hole and screw head were threaded to provide more stability and reduce contact with the bone surface. In this communication we conducted computational analysis to compare the stability of both sets of implants. Results have revealed that Locked Plates provide more stable fixation and resistance to micro-motion. However, stress shielding might occur which will delay healing. Future designs of the Locked Plates can focus on improving stability and reducing damage to blood supply which will shorten the Short Research Article Gailani et al.; AIR, 4(2): 94-101, 2015; Article no.AIR.2015.065 95 healing period. Computational analysis (finite element analysis) can be effectively used to guide these future designs.

Metallic Artifacts From Internal Scaphoid Fracture Fixation Screws

The aim of this study was to compare image quality and extent of artifacts from scaphoid fracture fixation screws using different computed tomography (CT) modalities and radiation dose protocols. Imaging of 6 cadaveric wrists with artificial scaphoid fractures and different fixation screws was performed in 2 screw positions (45° and 90° orientation in relation to the x/y-axis) using multidetector CT (MDCT) and 2 flat-panel CT modalities, C-arm flat-panel CT (FPCT) and cone-beam CT (CBCT), the latter 2 with low and standard radiation dose protocols. Mean cartilage attenuation and metal artifact-induced absolute Hounsfield unit changes (= artifact extent) were measured. Two independent radiologists evaluated different image quality criteria using a 5-point Likert-scale. Interreader agreements (Cohen κ) were calculated. Mean absolute Hounsfield unit changes and quality ratings were compared using Friedman and Wilcoxon signed-rank tests. Artifact extent was significantly smaller for MDCT and standard-dose FPCT compared with CBCT low- and standard-dose acquisitions (all P < 0.05). No significant differences in artifact extent among different screw types and scanning positions were noted (P > 0.05). Both MDCT and FPCT standard-dose protocols showed equal ratings for screw bone interface, fracture line, and trabecular bone evaluation (P = 0.06, 0.2, and 0.2, respectively) and performed significantly better than FPCT low- and CBCT low- and standard-dose acquisitions (all P < 0.05). Good interreader agreement was found for image quality comparisons (Cohen κ = 0.76-0.78). Both MDCT and FPCT standard-dose acquisition showed comparatively less metal-induced artifacts and better overall image quality compared with FPCT low-dose and both CBCT acquisitions. Flat-panel CT may provide sufficient image quality to serve as a versatile CT alternative for postoperative imaging of internally fixated wrist fractures.

Dynamic hip screw fixation of fractures of the femoral neck—a useful technique for accurate positioning

Dynamic hip screw fixation of fractures of the femoral neck—a useful technique for accurate positioning

A New Option for Intramedullary Fixation of Jones Fractures: The Charlotte™ Carolina™ Jones Fracture System

A number of different screws are used for Jones fracture fixation in cases in which hastened healing is desirable or nonoperative treatment has failed. None of them were designed for this application, and consequently there is a lack of continuity in screw configuration and sizing that can force the use of a screw that is not optimally size-matched to the metatarsal. This can be particularly problematic in high-demand patients such as athletes, in whom screw fixation failure is more likely to occur. Application-specific screws available in graduated sizes are now an option. This study was designed to compare the bending fatigue resistance of the new screws with that of clinically-proven contemporary Jones fracture fixation screws. The results may provide a basis for judging the probability of successful screw performance relative to the other established screw options. Bending fatigue resistance of the smallest-diameter Wright Medical Technologies Charlotte Carolina screw was compared to that of three commonly used contemporary screws. Cyclic three-point bending was applied to the screw shafts for 2,000,000 cycles or until 5 mm of deflection occurred. Four to six samples of each screw were tested. The number of load cycles withstood by the new screws greatly exceeded the number of cycles tolerated by Acutrak 4/5 screws, Synthes 4.5-mm malleolar screws, and Synthes 4.5 mm cannulated screws. The fatigue resistance of the smallest-diameter Charlotte Carolina screw exceeds that of other contemporary screws known to possess sufficient strength for Jones fracture fixation. It is likely that this system of graduated-size screws may be implemented for treatment of acute Jones fractures without concern for device failure. Patients may benefit from more accurate matching of the screw size to the fractured metatarsal.

Carbon Nanotubes with High Bone‐Tissue Compatibility and Bone‐Formation Acceleration Effects

Carbon nanotubes (CNTs) have been used in various fields as composites with other substances or alone to develop highly functional materials. CNTs hold great interest with respect to biomaterials, particularly those to be positioned in contact with bone such as prostheses for arthroplasty, plates or screws for fracture fixation, drug delivery systems, and scaffolding for bone regeneration. Accordingly, bone-tissue compatibility of CNTs and CNT influence on bone formation are important issues, but the effects of CNTs on bone have not been delineated. Here, it is found that multi-walled CNTs adjoining bone induce little local inflammatory reaction, show high bone-tissue compatibility, permit bone repair, become integrated into new bone, and accelerate bone formation stimulated by recombinant human bone morphogenetic protein-2 (rhBMP-2). This study provides an initial investigational basis for CNTs in biomaterials that are used adjacent to bone, including uses to promote bone regeneration. These findings should encourage development of clinical treatment modalities involving CNTs.

Long-term tissue response to bioabsorbable poly- l-lactide and metallic screws: An experimental study

Late, clinically manifest, adverse inflammatory reactions have sometimes occurred after the use of slowly degrading bioabsorbable poly- l-lactide (PLLA) devices in clinical series of bone fixation. In this study, long-term tissue response to bioabsorbable fracture fixation screws made of poly- l-lactide and to similar metallic screws in cancellous bone was examined and compared with intact bone. The postoperative evaluation of the rabbit femora was performed by using plain radiography, microradiography, histology, histomorphometry, and oxytetracycline labeling studies. The follow-up times were 36 and 51 months in groups of 15 and 14 rabbits, respectively. A walling-off response by formation of trabecular bone which outlined the screw profile was observed in the PLLA and metallic groups both. Connective tissue between this bone front and the implant was seen only in the PLLA group. There was no difference in the thickness of the layer between the two follow-up groups. Between the surgically handled femora and the intact control bone, there was no statistically significant difference in the amount of trabecular bone. The osteoid formation activity in the tissue–implant interface showed no differences between the groups. However, active osteoblasts were visible only in the PLLA group. The amount of birefringent PLLA material diminished between the 36-month and the 51-month follow-up groups. Within the follow-up times of this study, both the PLLA screws and the metallic screws were rather inert. Also, long-term walling-off was a typical response to both PLLA and metallic screws in cancellous bone. PLLA screws did not evoke any osteostimulatory reaction over the long-term follow-up. The findings clearly demonstrated that the overall degradation process of PLLA was very slow and accompanied by fibrous tissue formation. Macrophage activity seemed to be related to the slow degradation process of PLLA and might be associated with the formation of connective tissue replacing the original implant. The results of this study showed no significant differences between the bioabsorbable PLLA screws and the metallic screws in biocompatibility, and no signs of inflammatory foreign-body reactions occurred during the follow-up.