Purpose: The purpose of this study is to evaluate the biomechanical properties and the stability between locking clavicle plate, dynamic compression plate and external fixation systems on an unstable displaced fracture model under torsional and 3 point bending loading.

Materials and Methods: Forty eight human adult formalin fixed clavicles were paired according to their BMD (DEXA) homogeneously into three groups; Group 1: Locking clavicle plate, Group 2: Dynamic compression plate and Group 3: External fixator. Each specimen was then osteotomized in the midshaft; and a 5mm bone segment was removed in order to stimulate a displaced fracture model. Biomechanical tests were applied in a cyclic loading model in MTS, Bionix 2. Torsional and three point bending forces were performed for 1000 cycles in all subgroups, stiffness was recorded at 10 cycles (initial) and periodic every 100 cyclic intervals. Failure load and moment were obtained after 1000 cycles. Initial stiffness, failure loads and the percentage of initial stiffness for each subgroup were compared across each group. One-way ANOVA and Bonferoni post- hoc tests were utilized to determine which were significantly different from one another with the significance level set as p< 0.05.

Results: The mean initial stiffness(Nmm/deg) - mean failure moments(Nmm) for torsional tests were 703.2 – 7671.7 (locking plate), 448.1 – 4370.3 (compression plate), 365.2 – 2999.7 (ex-fix) and the mean initial stiffness(Nmm) – mean failure loads(N) for bending tests were 32.6 – 213.2 (locking plate), 23.4 – 131.1 (compression plate), 20.6 – 102.7 (ex-fix) respectively. ANOVA test confirmed an overall significant difference between the three constructs in terms of both failure loads and a significant difference only between locking plate and others in terms of initial stiffness. At all cyclic intervals after 100 cycles there was significant difference of percentage of initial stiffness between locking plate and others in bending and torsion. There was a significant difference between compression plate and ex-fix after 700 cycles in torsional group and no difference found in bending group between (any of) them at any cyclic interval.

Conclusions: Locking anatomic clavicle plate is significantly more stable than unlocked dynamic compression plate and external fixator under torsional and bending cyclic loading in an unstable displaced fracture or non-union clavicle model.

Background. Although described as a commensal bacterium with low pathogenicity, Cutibacterium acnes involvement has been reported in many clinical entities: infections associated with devices, such as shoulder prosthetic joint infections, osteosynthesis, breast implants or cerebrospinal fluid shunts. Various studies show that C. acnes grows as a biofilm, contributing to its persistence by allowing its escape from the action of the immune system and antibiotics. Purpose. Our aim was to assess the activity of different active substances (erythromycin, clindamycin, doxycycline and Myrtacine. ®. ) on eight different well-characterized C. acnes strains after growth in biofilm mode. Methods. Eight susceptible strains of C. acnes were selected for this study, including two reference strains (ATCC6919 and ATCC11827) and six clinical strains. All C. acnes strains were studied using two different methods to study the biofilm production at different time points: the BioFilm Ring Test. ®. technique (early stages of adhesion) and the Crystal Violet (CV) method (mature biofilm). In a second step, the impact of different active substances (erythromycin, clindamycin, doxycycline and Myrtacine. ®. ) was studied. For the CV technique, two types of tests were performed: preventive tests (addition of active substances and bacteria at the same time) and curative challenge tests (addition of active substances on a biofilm already formed after 48h). Transmission electron microscopy was performed to investigate the morphology modifications. Results. C. acnes isolates from phylotypes IA. 1. and IA. 2. , seem to produce more mature biofilm in the first stages of adhesion than other phylotypes. Curative assays were performed to evaluate the efficacy of antibiotics and Myrtacine. ®. on mature biofilm. Significant efficacy of Myrtacine. ®. at 0.03% was observed for C. acnes strains. Moreover, the combination of Myrtacine. ®. and doxycycline appears to decrease the total biofilm biomass. The effect of doxycycline as a preventive measure was minimal. On the contrary, a similar use of Myrtacine. ®. as early as 0.001% showed significant efficacy with a significant decrease in total biofilm biomass for all C. acnes strains. Transmission electron microscopy revealed a significantly decreased biofilm growth in treated bacteria with Myrtacine. ®. compared to untreated bacteria. Moreover, the total number of bacteria decreased as the concentration of Myrtacine. ®. increased suggesting also an antimicrobial effect. Conclusion. These results confirm the difference in biofilm producing ability depending on C. acnes phylotypes. These results suggest that Myrtacine. ®. may be a promising alternative antibacterial and anti-biofilm agent like peroxide de benzoyle to prevent shoulder prosthetic joint infection involving planktonic and biofilm C. acnes

Magnesium calcium alloys are promising candidates for an application as biodegradable osteosynthesis implants [1,2]. As the success of most internal fracture fixation techniques relies on safe anchorage of bone screws, there is necessity to investigate the holding power of biodegradable magnesium calcium alloy screws. Therefore, the aim of the present study was to compare the holding power of magnesium calcium alloy screws and commonly used surgical steel screws, as a control, by pull-out testing. Magnesium calcium alloy screws with 0.8wt% calcium (MgCa0.8) and conventional surgical steel screws (S316L) of identical geometries (major diameter 4mm, core diameter 3mm, thread pitch 1mm) were implanted into both tibiae of 40 rabbits. The screws were placed into the lateral tibial cortex just proximal of the fibula insertion and tightened with a manual torque gauge (15cNm). For intended pull-out tests a 1.5mm thick silicone washer served as spacer between bone and screw head. Six animals with MgCa0.8 and four animals with S316L were followed up for 2, 4, 6 and 8 weeks, respectively. Thereafter the rabbits were sacrificed. Both tibiae were explanted, adherent soft tissue and new bone was carefully dissected around the screw head. Pull-out tests were carried out with an MTS 858 MiniBionix at a rate of 0.1mm/sec until failure of the screw or the bone. For each trial the maximum pull-out force [N] was determined. Statistical analysis was performed (ANOVA, Student's t-test). Both implant materials were tolerated well. Radiographically, new bone was detected at the implantation site of MgCa0.8 and S316L, which was carefully removed to perform pull-out trials. Furthermore, periimplant accumulations of gas were radiographically detected in MgCa0.8. The pull-out force of MgCa0.8 and S316L did not significantly differ (p = 0.121) after two weeks. From 6 weeks on the pull-out force of MgCa0.8 decreased resulting in significantly lower pull-out values after 8 weeks. Contrary, S316L pull-out force increased throughout the follow up. Thus, S316L showed significantly higher pull-out values than MgCa0.8 after 4, 6 and 8 weeks (p<0.001). MgCa0.8 showed good biocompatibility and pull-out values comparable to S316L in the first weeks of implantation. Thus, its application as biodegradable osteosynthesis implant is conceivable. Further studies are necessary to investigate whether the reduced holding power of MgCa0.8 is sufficient for secure fracture fixation. In addition, not only solitary screws, but also screw-plate-combinations should be examined over a longer time period. Acknowledgements. The study is part of the collaborative research centre 599 funded by the German Research Foundation

Secondary fracture healing processes are strongly influenced by interfragmentary motion. Shear movement is assumed to be more critical than axial movement, however experimental results are controversial. Numerical fracture healing models allow to simulate the fracture healing process with variation of single input parameters and under comparable normalized mechanical conditions. Therefore, a direct comparison of different in vivo scenarios is possible. The aim of this study was to simulate fracture healing under several axial and shear movement scenarios and compare their respective time to heal. We hypothesize that shear movement is always more critical than axial loading. For the presented study, we used a corroborated numerical model for fracture healing in sheep. Numerous variations of the movement amplitude, the fracture gap size and the musculoskeletal loads were simulated for comparable axial compressive and shear load cases. In all simulated cases, axial compressive load had less inhibitory influences on the healing process than shear load. Therefore, shear loading is more critical for the fracture healing outcome in general. Thus, our findings suggest osteosynthesis implants to be optimized to limit shear movements under musculoskeletal loading

Purpose of the study: We report a prospective consecutive series of femoral fractures on prosthesis. The goal was to evaluate mid-term outcome of treatment with a locking plate. Material and methods: From June 2002 to December 2007, we treated 35 patients (1 bilateral), 28 female and 7 male, with a fracture around their total hip arthroplasty (n=21), total knee arthroplasty n=7), unicompartmental knee prosthesis (n=1), between a THA and a TKA (n=2), or between a trochanteric osteosynthesis and a TKA (n=5). Mean age was 76 years (39–93). For the majority, osteosynthesis was achieved via a mini-invasive incision, using a locking plat (Synthes. ®. ) bridging the implant in situ. The rehabilitation protocol consisted in immediate weight-bearing for most of the cases. Results: At revision, one patient was lost to follow-up, one was an early failure, and seven patients had died, including four which were retained for the analysis because data was available for 24, 40, 43 and 67 months respectively. The analysis thus included 30 patients with 31 fractures and mean 26 months follow-up (range 6 – 67 months). The following results were obtained for the initial series: mini-invasive surgery (n=26), access to fracture focus (n=10), total postoperative weight bearing (n=20), partial weight bearing at 20 kg (n=3), no weight-bearing for six weeks (n=13). Complications were: infection (n=2), general (n=2), disassembly (n=3, one femoral stem replacement and two revision ostheosynthesis). Bone healing was obtained in all cases except one. There was a misalignment > 5 in five cases. At review, there was no implant loosening. Discussion: This work shows that locking compression plates inserted via a mini-invasive approach followed by weight-bearing is a feasible option. This technique combines the principles of closed osteosynthesis with preservation of the haematoma and stability of osteosynthesis material. The rehabilitation protocol was developed in consideration of the nature of the material. The locked plate acts like an internal fixator, allowing increased implant stability. Screw hold appeared to be sufficient to allow early weight-bearing. Conclusion: Use of locking compression plates for femoral fractures on osteosynthesis implants is effective. The stability of the assembly allow, despite the age of the patients, early weight-bearing and walking, with a stable outcome over time

Aims

The aim of this meta-analysis is to assess the association between exchange of modular parts in debridement, antibiotics, and implant retention (DAIR) procedure and outcomes for hip and knee periprosthetic joint infection (PJI).

Background: The presence of bacteria forming biofilms or prior antimicrobial use has been shown to reduce the sensitivity of the standard technique (PT cultures) in patients with infection of orthopedic implants. Culturing fluid resulting from sonication (FRS) of prosthesis could improve the microbiologic diagnosis. Objective: To analyze the diagnostic validity of culturing FRS of different orthopedic implants and PT culture. Methods: Between Jan 2007 and Apr 2008, patients undergoing knee or hip prosthesis removal, and those with ostheosyntesis or spinal instrumentation removal, were prospectively included (44 hip prosthesis, 63 knee prosthesis, 91 osteosynthesis and 14 spinal instrumentations). 5 PT specimens were collected for culture. Removed implants were sonicated during 5 min. (40Hz). Both, PT and FRS, were inoculated in aerobic agar (Chocolate Polyvitex), anaerobic agar (Schaedler + 5% blood) and in thioglycolat, for 7 days. Positive culture cut-off was defined as growing of > 5 CFU. Clinical diagnosis of prosthetic-joint infection was made as commonly accepted. Previous antimicrobial therapy was assessed. Diagnostic validity was calculated for both culturing methods. Sensitivity of methods was compared by Chi-square test (SPSS 15.0). Results: 212 cases were included. Diagnostic of infection was made in 17 hip prosthesis (THA), 20 knee prosthesis (TKA), 24 osteosynthesis (OS) and 6 spinal fusions (SI). Tissue culture was positive in 9 THA, 11 TKA 18 OS and 4 SI. Sonication culture was positive in 14 THA, 18TKA, 23 Os and 6 SI. Tissue culture: Sensibility: THA53%, TKA 55%, OS 75% and SI 66%. Specificity: THA 96%, TKA 100%, OS 96%, SI 100%. Sonications: Sensibility: THA 82%, TKA 90%, OS 95% and SI 100%. Specificity: THA 96%, TKA 100%, OS 92%, SI 100%. Statistical differences favoring sonication were found in sensitivity in knee arthroplasty and osteosynthesis implants. 6 patients received antibiotics for > 7 days before implant was removed. Sonication culture was positive in 4 of them whereas only one standard culture yielded positive. Conclusions: FRS cultures are more sensitive than PT cultures. Sensitivity of the method depends on which device is evaluated. Sonication also improves sensitivity of culture after preoperative antimicrobial therapy

Purpose: The diagnosis of chronic bone and joint infections, particularly in patients with implants, can be a difficult task. Among the clinical and laboratory tests proposed for the diagnosis of infection, 99mTc HMPOA labelled leukocyte scintigraphy is one of the least invasive examinations available. We evaluated its efficacy in terms of reliability. Material and methods: Ninety patients with suspected bone and joint infections were included in this study: 53% men and 47% women. Mean age was 56.6 years and 80% had osteosynthesis implants. Mean duration of clinical signs before scintigraphy was 6.5 months. The suspected site was the hip in 49%, the knee in 28% and another in 23%. Physical examination (local aspect, temperature) and laboratory tests (differential count, platelets, CRP, ESR) as well as standard radiographs were performed in addition to labelled scintigraphy. These patients were operated and bone samples were taken for bacteriology studies to confirm or infirm the presence of infection. In this series, 73% of the patients were found to have a real infection (73% staphylococcal, 17% multiple germs, 20% other). Results: The following variables were included in the multivariate analysis: fever, standard radiographs, polynuclear neutrophil count, CRP, ESR, leukocyte-labelled scintigraphy. Sensitivity (Se), specificity (Sp), and odds ratio (OR) were determined. The multivariate analysis showed: fever (Se=0.48; Sp=0.59; OR=1.3); abnormal radiograph (Se=0.71; Sp=0.62; OR=4; p=0.02); polynuclear neutrophil count (OR=1; p=0.19); CRP (OR=1.02; p=0.06); ESR (OR=1.03; p=0.04); leukocyte-labelled scintigraphy (Se=0.71; Sp=0.82; OR=11.6; p< 0.001). Discussion and conclusion: These findings demonstrate the efficacy of 99mTc HMPOA-labelled leukocyte scintigraphy in terms of reliability for the diagnosis of chronic bone infection compared with other clinical (fever), laboratory (ESR, CRP), and radiographic indicators

Proximal humeral fractures account for approximately 4–5% of all fractures seen in the emergency departments. Of all shoulder injuries they account for aproximatelly 53%. In 1970 Neer published his classic study, in which he described a new method of classification, and gave recommendations for treatment. Neer recommended ORIF for three-part fractures, and prosthetic replacement for four-part fractures and fracture-dislocations. However there is still disagreement on the management of the displaced humeral fractures. Diagnosis. Accurate radiographic evaluation, is essential in order to make a correct classification of the proximal humeral fractures. The radiographic examination consists of films from three different views. The anterio-posterior (AP), lateral (Y view of the scapula), and the axillary one. The AP view will assess the fracture position, and by centring it 30 degrees posteriorly and obliquely, clearly image the glenohumeral joint space. The lateral view is taken perpendicular to the scapular plain. The head overlaps the glenoid, and projects on the centre of a “Y“, formed by acromion, the coracoid superiorly, and the scapular body inferiorly. In this projection any large avulsed greater tuberosity fragments are usually easy to visualise posteriorly, and the lesser tuberosity is visualised medialy. The axillary view is the most useful in assessing the relationship between the humeral head and the glenoid. Fracture dislocations, and true posterior dislocations can be easily distinguished in the axial view. Computer tomography, plain or with three dimensional reconstruction-views might also help the surgeon to make an accurate diagnosis and in preoperative planning. Classification. A valid classification system can be useful as a tool to select the optimal treatment. The system should be comprehensive enough to reflect the complex fracture pattern, and specific enough to allow an accurate diagnosis. The classification should be useful as a tool for identifying those fractures which should be operated upon. In 1935, Codman proposed a new classification system based on four different anatomical fragments of the proximal humerus. The anatomical head, the greater tuberosity, the lesser tuberosity and the humeral shaft. Codman stressed that the musculotendinous cuff attachment to each fragment was of major significance to the fracture pattern. In 1970 Neer further developed Codmans classification, stressing the importance of the biomechanical forces, and the degree of displacement for more complex fractures. When any of the four major segments is displaced over 1 cm or angulated more than 45 degrees, the fracture is considered to be displaced: Group 1: all fractures regardless of the level or number of fracture lines, in wich NO segments are displaced. Group 2: a two-part fracture is one in which one fragment is displaced in reference to the other three fragments. Group 3: a three-part fracture is one in which two fragments are displaced in relationship to each other and the other two are undisplaced fragments, but the head remains in contact with the glenoid. Group 4: a four-part fracture is one in which all four fracture fragments are displaced; the articular surface of the head is out of contact with the glenoid and angulated either laterally, anteriorly, posteriorly, inferiorly, or superiorly. Furthermore it is detached from both tuberosities. Neer has also emphasised the term fracture dislocation. It exists when the head is displaced outside the joint space rather than subluxated or rotated and there is, in addition, a fracture. The degree of displacement is directly related to the clinical outcome and the choice of treatment. In the 1970’s the AO group from Switzerland, emphasised the importance of the blood supply to the articular surface of the humeral head. Since the risk for avascular necrosis was high, they based their classification on the vascular anatomy of the proximal humerus. The system classified the fractures into three different categories:. Group A: Extra-articular, unifocal fracture. Group B: Partially extra-articular, bi-focal fracture. Group C: Articular fracture. Each group is sub-divided into three categories, from less to more serious lesions. This gave us 27 different sub-groups to analyse and interpret. The AO system is easy to use for the diaphyseal segments of the femur, tibia and humeral shaft, but applying it to the proximal humerus is confusing, and makes it more difficult to use than the Neer system. Consequently the AO classification system has not gained general acceptance among shoulder surgeons. The reliability and the reproducibility of these classifications have been questioned Unfortunately, we do not have a better classification system on hand and therefore the Neer system is still widely used. Treatment. Many methods of treatment of proximal humeral fractures have been proposed during the past 50 years, creating a great deal of controversy and confusion. There are two main treatment options: Non-operative treatment and operative. Conservative treatment. Approximately 80% of all proximal humeral fractures are non-displaced, or only minimally displaced, and the clinical outcome is satisfactory after conservative treatment. After some days of rest, early mobilisation with gentle physiotherapy is of great importance. Operative treatment. Various types of osteosynthesis have been suggested. Semitubular straight or angulated plates, screws, Rush pins, external fixators, cerclage wires, tension band technique or K-wires with bone grafting have been used. The results reported range from excellent to poor. In cases of three- and four- part fractures, most authors have used open reduction with internal fixation. Because of poor bone quality, and a torn cuff, especially in elderly patients, osteosynthesis is not always the best choice. Hemiarthroplasty is reported to give an excellent outcome in many studies. In fracture dislocations, when closed reduction is not possible, the only way to restore the dislocated shoulder joint is to perform an open reduction and stabilise the fracture with an osteosynthesis implant, or replace the humeral head with a hemiarthroplasty. Scoring systems for evaluation of the end results. There are two rating systems generally used. The Neer system from 1970 has been widely used in a number of studies, all over the world, and the Constant-Murley system from 1987 has been recommended for use in Europe. Neer’s rating system from 1970 is used to assess shoulder function, after fractures, arthroplasty and dislocations. It is based on a 100 units scale, with points for pain (35), function (30), range of motion (25), and anatomy (10). In 1987 Constant and Murley designed a European scoring system, claiming it to be applicable for measuring shoulder function regardless of diagnosis. This system is also based on a 100 point scale. The degree of pain, activities of daily living, strength, and active range of movement are assessed. The results are then related to gender, age and activity level of the patient. Both systems has recently been questioned because of its low reliability. Confusion remains because different authors from the USA and Europe continue to use their own criteria for evaluation. Consequently, it is not unusual that the reported results after fracture treatment vary, depending on which rating system was used

Purpose: The purpose of this study was to analyse mechanical failures involving dismonted osteosynthesis materials implanted to fix pertrochanteric or subtrochanteric fractures with a dynamic hip screw (DHS), a Gamma nail, or a plate nail system (STACA). Material and methods: Our cohort included 16 patients among a series of 350 patients who had been treated with 240 DHS, 80 Staca nailplates, and 30 Gamma nails between 1996 and 1999. We used the Ender classification for the x-ray analysis and the Cuny criteria which describe the most common causes of dismounted material. Results: According to the defined criteria, 70/350 osteosynthesis assemblies (20%) were considered insufficient on the immediate postoperative x-rays and eventually dismounted in 16 patients. Two of these patients had major osteopaenia according to the Singh criteria and ten underwent revision because of poor clinical tolerance. These patients had six DHS (3 “swinging” cervical nails, two dismounted plates, and one screw protruding into the joint space). A protruding screw was the problem for the eight Staca nail-plates. Two Gamma nails had a “swinging” screw. These cases of dismounted material were predominantly observed in patients with Ender grade 5, 7 and 8 pertrochanteric fractures. Discussion: Our analysis of these cases revealed several important factors: 1) the quality of the fracture reduction with restitution of the medial pillar of the per-trochanteric mass; 2) central anchoring in the femoral head essential for stable fixation; 3) superior stability of the DHS in grade 1 and 6 fractures due to the greater projected surface improving hold in cancellous bone. Inversely, for subtrochanteric fractures (grade 7 and 8), centromedulary shaft anchoring with a Gamma nail reduces mechanical stress in varus and thus the risk of “swinging” screws. Finally, the monoblock construct of the Staca nail-plate, which does not have the dynamic potential of the DHS and the Gamma nail, raises a risk of protrusion, particularly in case of “internal rotation” fractures with major metaphyseal comminution (grades 4 and 5). This latter type of fixation is however very effective for simple pertrochanteric fractures with minimal comminution (grades 1 to 3). Conclusion: Material dismounting results from a series of factors related both to the material used and to the operative technique. We thus reserve the Staca nail-plate for grade 1 to 3 fractures in the Ender classification, the DHS for grades 1 to 6 and the nail-screw fixation for subtrochanteric (grade 7 and 8) fractures

Objectives

Implant-related infection is one of the most devastating complications in orthopaedic surgery. Many surface and/or material modifications have been developed in order to minimise this problem; however, most of the in vitro studies did not evaluate bacterial adhesion in the presence of eukaryotic cells, as stated by the ‘race for the surface’ theory. Moreover, the adherence of numerous clinical strains with different initial concentrations has not been studied.