Objectives. Cement augmentation of pedicle screws could be used to improve screw stability, especially in osteoporotic vertebrae. However, little is known concerning the influence of different screw types and amount of cement applied. Therefore, the aim of this biomechanical in vitro study was to evaluate the effect of cement augmentation on the screw pull-out force in osteoporotic vertebrae, comparing different pedicle screws (solid and fenestrated) and cement volumes (0 mL, 1 mL or 3 mL). Materials and Methods. A total of 54 osteoporotic human cadaver thoracic and lumbar vertebrae were instrumented with pedicle screws (uncemented, solid cemented or fenestrated cemented) and augmented with high-viscosity PMMA cement (0 mL, 1 mL or 3 mL). The insertion torque and bone mineral density were determined. Radiographs and CT scans were undertaken to evaluate cement distribution and cement leakage. Pull-out testing was performed with a material testing machine to measure failure load and stiffness. The paired t-test was used to compare the two screws within each vertebra. Results. Mean failure load was significantly greater for fenestrated cemented screws (+622 N; p ⩽ 0.001) and solid cemented screws (+460 N; p ⩽ 0.001) than for uncemented screws. There was no significant difference between the solid and fenestrated cemented screws (p = 0.5). In the lower thoracic vertebrae, 1 mL cement was enough to significantly increase failure load, while 3 mL led to further significant improvement in the upper thoracic, lower thoracic and lumbar regions. Conclusion. Conventional, solid pedicle screws augmented with high-viscosity cement provided comparable screw stability in pull-out testing to that of sophisticated and more expensive fenestrated screws. In terms of cement volume, we recommend the use of at least 1 mL in the thoracic and 3 mL in the lumbar spine. Cite this article: C. I. Leichtle, A. Lorenz, S. Rothstock, J. Happel, F. Walter, T. Shiozawa, U. G. Leichtle. Pull-out strength of cemented solid versus fenestrated pedicle screws in osteoporotic vertebrae. Bone Joint Res 2016;5:419–426

Introduction: Conventional cancellous screws have proven purchase in healthy bone, but may be prone to loosening in osteoporotic bone. Locking screws have become a popular choice to combat loosening. A new screw design has optimized thread form to gain better purchase into poor quality bone. The purpose of this study was to evaluate the maximum stripping torque and pull-out strength of the PERI-LOCTM 5.0mm Osteopenia Bone Screw using an osteopenic model. Methods: Stripping Torque: PERI-LOCTM 5.0mm Osteopenia Bone Screws were inserted through a One-Third Tubular B-plate into a pre-drilled pilot hole to a depth of 20mm. Rotational loading was applied manually using a hex driver until torque reached a peak value. The maximum torque value due to screw head contact with the plate was measured using a torque-meter and denoted as the stripping torque. This same procedure was used for TC-100TM 4.0mm Cancellous Bone Screws, which were inserted through a TC-100TM Standard Tubular Plate. Pull-Out Strength: PERI-LOCTM 5.0mm Osteopenia Bone Screws were inserted to a depth of 20 mm into an osteopenic model. Axial pull-out was then conducted on a MTS testing frame by applying a tensile load along its longitudinal axis at a rate of 0.2 in/min. The maximum pull-out force was recorded. This same procedure was used for TC-100TM 4.0mm Cancellous Bone Screws. The test set-up is shown in Figure 1. Discussion: The PERI-LOCTM 5.0mm Osteopenia Bone Screws showed a 34% increase in stripping torque and a 40% increase in pull-out strength (p < < 0.01 at á = 0.05 in both instances) as compared to clinically successful bone screws. Conclusions: When tested in an osteopenic bone model, the PERI-LOCTM 5.0mm Osteopenia Bone Screw provided superior stripping torque and pull-out strength as compared to conventional cancellous bone screws. The increased torque generation during insertion of PERI-LOCTM 5.0mm Osteopenia Bone Screws provides better fracture reduction, as compared to conventional screws. These findings indicate that the use of the improved thread design is advantageous in poor quality bone

Introduction: There has been a renewed interest in metal-on-metal bearing for total hip replacement with the benefit of a larger head size and decreased incidence of dislocation. In the revision hip scenario cementation of a polyethylene liner, for a previously compromised liner fixation mechanism into a preexisting well-fixed shell or a cage, has become an accepted method to decrease the morbidity of the procedure. Perhaps Bir-mingham cementless cups could be used as cemented devices in primary and revision hip surgery where a cementless cup is not possible. Aim: To study the pull-out strength of cemented Bir-mingham sockets in an experimental model. Materials and Methods: Eight Birmingham cups were cemented into wooden blocks after they were reamed to the appropriate size allowing for a 3mm cement mantle, multiple holes drilled into the reamed sockets and cement vacuum-mixed. Cable was then threaded through the holes on the rim of the cup and the wooden block was then mounted on a metal plate and secured. Linear tension was then gradually applied on the cup through the cable. Results: The pull-out strength of the cemented Birming-ham cups was higher than the failure of the cable. The tensile load to failure for the cables ranged from 3642.6 N to 4960 N with an average load of 4286.9 N. Conclusion: The average tensile load of 4286.9 is very high compared to previous studies with cemented poly-ethylene and metal liners. This finding is very promising and might support clinical application in complex primary and revision total hip replacement

The effect of screw geometry on the pullout strength of Anterior Cruciate Ligament [ACL] reconstruction is well documented. Most research has looked at the effect of screw length and diameter, however other factors such as the degree of taper may also be important. Tapered screws should in theory be associated with increased pullout strength. This has not been demonstrated either clinically or in vitro before. The aim of this study was to compare the pullout strength of ACL reconstruction with a parallel against a tapered screw. A parallel and tapered screw were manufactured which were identical in all other respects. Sixty superficial digital flexors from the hind legs of sheep were harvested. The tendons were paired and combined to form a quadruple tendon reconstruction of approximately 7mm diameter as measured with graft sizer. An ACL reconstruction was performed on the proximal tibia of 30 bovine knees, which had been harvested in right and left knee pairs, using the quadruple tendon. Fifteen reconstructions were fixed using tapered screws and fifteen with non-tapered screws. The insertion torque of both tapered and non tapered screws were recorded using an instrumented torque screwdriver. The reconstructions were mounted in an Instron materials testing machine with an x-ray bearing system to eliminate horizontal forces, to ensure that the forces were all directed along the line of the tibial tunnel. The maximum pullout strengths were recorded in each case. Five knee pairs were subjected to bone densitometry scanning to ensure that any difference in pull out strength was not due to changes in bone density between right and left knee pairs. Results indicated that there was no difference between right and left knee pairs [p = 0.58] and that tapered screws were associated with significantly higher pull-out strengths [p=0.007] and insertion torques [p = 0.001]

Introduction: Knotless Suture Anchors provide numerous advantages in arthroscopic rotator-cuff (RC) repair such as, reducing the difficulties of knot tying, reducing surgical exposure, thus decreasing morbidity. The purpose of this in-vitro study was to compare the pull-out strength of three new knotless suture anchors in correlation with bone quality using the following anchors: Opus Magnum 2 -ArthroCare Co., USA; Push Lock and Swivel Lock -Arthrex Inc., USA. Material & Methods: Ten healthy and ten osteopenic macroscopically intact humeri with an average age of 51.7 and 79.5 years, respectively, were loaded with the three knotless suture anchors according to the manufacturers’ description. The healthy humeri had a mean trabecular BMD of 152.77 mgCa-HA/ml. The osteopenic humeri had a mean trabecular bone mineral density of 54.02 mgCa-HA/ml. The humeri were positioned in a custom - engineered adjustable fixation device, stabilising the direction of the pull of the sutures at an angle of 135° to the axis of the humeral shaft (Universal testing device Z010/TN2A – Zwick GmbH, Ulm, Germany). The anchors were cyclically loaded to simulate postoperative conditions. The ultimate pull-out strenngth, the initial displacement in millimeters after the first pull with 75 N and the modes of failure were recorded. Results: The mean ultimate failure loads of the Opus Magnum 2, PushLock and SwiveLock anchors in osteopenic humeri were 135.0, 102.5 and 130.0 N (p> 0.05), respectively, and in healthy humeri 142.5 N, 182.5 N and 202.5 N (p> 0.05), respectively. The initial system displacement in osteopenic humeri of the Opus Magnum 2, PushLock and SwiveLock anchors were 3.53 mm, 16.11 mm and 3.23 mm (p< 0.01), respectively, and in healthy humeri 3.71 mm, 1.98 mm, and 1.96 mm (p> 0.05), respectively. Discussion: The results of this study show that in osteopenic humeri, the Opus Magnum 2 and SwiveLock anchors display significant superiority in system displacement with an initial pull of 75N compared to the PushLock anchor in osteopenic bone, but all three anchors fail to provide significance in the ultimate failure load. PushLock anchor might cause a greater gap formation between the RC-tendon and greater tubercle interface in osteopenic humeri due to inferior gripping and therefore should not be used solely for RC repair. Due to a manufacturing flaw the suture holding fixture of the Opus Magnum 2 anchor “breaks” when a mean force of 138.75 N is applied to the system, regardless of the bone quality, thus disabling the anchor to unfold it’s properties in healthy bone. Whereas the results in osteopenic bone are comparable to the other two anchors. SwiveLock provides the best support of all three anchors in healthy humeri

Aims. Anchorage of pedicle screw rod instrumentation in the elderly spine with poor bone quality remains challenging. Our study aims to evaluate how the screw bone anchorage is affected by screw design, bone quality, loading conditions, and cementing techniques. Methods. Micro-finite element (µFE) models were created from micro-CT (μCT) scans of vertebrae implanted with two types of pedicle screws (L: Ennovate and R: S. 4. ). Simulations were conducted for a 10 mm radius region of interest (ROI) around each screw and for a full vertebra (FV) where different cementing scenarios were simulated around the screw tips. Stiffness was calculated in pull-out and anterior bending loads. Results. Experimental pull-out strengths were excellently correlated to the µFE pull-out stiffness of the ROI (R. 2. > 0.87) and FV (R. 2. > 0.84) models. No significant difference due to screw design was observed. Cement augmentation increased pull-out stiffness by up to 94% and 48% for L and R screws, respectively, but only increased bending stiffness by up to 6.9% and 1.5%, respectively. Cementing involving only one screw tip resulted in lower stiffness increases in all tested screw designs and loading cases. The stiffening effect of cement augmentation on pull-out and bending stiffness was strongly and negatively correlated to local bone density around the screw (correlation coefficient (R) = -0.95). Conclusion. This combined experimental, µCT and µFE study showed that regional analyses may be sufficient to predict fixation strength in pull-out and that full analyses could show that cement augmentation around pedicle screws increased fixation stiffness in both pull-out and bending, especially for low-density bone. Cite this article: Bone Joint Res 2021;10(12):797–806

Complications after spinal fusion surgery are common, with implant loosening occurring in up to 50% of osteoporotic patients. Pedicle screw fixation strength reduces as a result of decreased trabecular bone density, whereas sublaminar wiring is less affected by these changes. Therefore, pedicle screw augmentation with radiopaque sublaminar wires (made with Dyneema Purity® Radiapque fibers, DSM Biomedical, Geleen, the Netherlands) may improve fixation strength. Furthermore, sublaminar tape could result in a gradual motion transition to distribute stress over multiple levels and thereby reduce implant loosening. The objective of this study is to test this hypothesis in a novel experimental setup in which a cantilever bending moment is applied to individual human vertebrae. Thirty-eight human cadaver vertebrae were stratified into four different groups: ultra-high molecular weight polyethylene sublaminar tape (ST), pedicle screw (PS), metal sublaminar wire (SW) and pedicle screw reinforced with sublaminar tape (PS+ST). The vertebrae were individually embedded in resin, and a cantilever bending moment was applied bilaterally through the spinal rods using a universal material testing machine. This cantilever bending setup closely resembles the loading of fixators at transitional levels of spinal instrumentation. The pull-out strength of the ST (3563 ± 476N) was not significantly different compared to PS, SW or PS+ST. The PS+ST group had a significantly higher pull-out strength (4522 ± 826N) compared to PS (2678 ± 292N) as well as SW (2931 ± 250N). The higher failure strength of PS + ST compared to PS indicates that PS augmentation with ST may be an effective measure to reduce the incidence of screw pullout, even in osteoporotic vertebrae. Moreover, the lower stiffness of sublaminar fixation techniques and the absence of damage to the cortices in the ST group suggest that ST as a stand-alone fixation technique in adult spinal deformity surgery may also be clinically feasible and offer clinical benefits

Aims. To develop an early implant instability murine model and explore the use of intermittent parathyroid hormone (iPTH) treatment for initially unstable implants. Methods. 3D-printed titanium implants were inserted into an oversized drill-hole in the tibiae of C57Bl/6 mice (n = 54). After implantation, the mice were randomly divided into three treatment groups (phosphate buffered saline (PBS)-control, iPTH, and delayed iPTH). Radiological analysis, micro-CT (µCT), and biomechanical pull-out testing were performed to assess implant loosening, bone formation, and osseointegration. Peri-implant tissue formation and cellular composition were evaluated by histology. Results. iPTH reduced radiological signs of loosening and led to an increase in peri-implant bone formation over the course of four weeks (timepoints: one week, two weeks, and four weeks). Observational histological analysis shows that iPTH prohibits the progression of fibrosis. Delaying iPTH treatment until after onset of peri-implant fibrosis still resulted in enhanced osseointegration and implant stability. Despite initial instability, iPTH increased the mean pull-out strength of the implant from 8.41 N (SD 8.15) in the PBS-control group to 21.49 N (SD 10.45) and 23.68 N (SD 8.99) in the immediate and delayed iPTH groups, respectively. Immediate and delayed iPTH increased mean peri-implant bone volume fraction (BV/TV) to 0.46 (SD 0.07) and 0.34 (SD 0.10), respectively, compared to PBS-control mean BV/TV of 0.23 (SD 0.03) (PBS-control vs immediate iPTH, p < 0.001; PBS-control vs delayed iPTH, p = 0.048; immediate iPTH vs delayed iPTH, p = 0.111). Conclusion. iPTH treatment mediated successful osseointegration and increased bone mechanical strength, despite initial implant instability. Clinically, this suggests that initially unstable implants may be osseointegrated with iPTH treatment. Cite this article: Bone Joint Res 2022;11(5):260–269

Surgeons treating fractures with many small osteochondral fragments have often expressed the clinical need for an adhesive to join such fragments, as an adjunct to standard implants. If an adhesive would maintain alignment of the articular surfaces and subsequently heal it could result in improved clinical outcomes. However, there are no bone adhesives available for clinical indications and few pre-clinical models to assess safety and efficacy of adhesive biomaterial candidates. A bone adhesive candidate based on water, α-TCP and an amino acid phosphoserine was evaluated in-vivo in a novel murine bone core model (preliminary results presented EORS 2019) in which excised bone cores were glued back in place and harvested @ 0, 3, 7, 14, 28 and 42days. Adhesive pull-out strength was demonstrated 0–28 days, with a dip at 14 days increasing to 11.3N maximum. Histology 0–42 days showed the adhesive progressively remodelling to bone in both cancellous and cortical compartments with no signs of either undesirable inflammation or peripheral ectopic bone formation. These favourable results suggested translation to a large animal model. A porcine dental extraction socket model was subsequently developed where dental implants were affixed only with the adhesive. Biomechanical data was collected @ 1, 14, 28 and 56 days, and histology at 1,14,28 and 56 days. Adhesive strength assessed by implant pull-out force increased out to 28 days and maintained out to 56 days (282N maximum) with failure only occurring at the adhesive bone interface. Histology confirmed the adhesive's biocompatibility and osteoconductive behavior. Additionally, remodelling was demonstrated at the adhesive-bone interface with resorption by osteoclast-like cells and followed by new bone apposition and substitution by bone. Whilst the in-vivo dental implant data is encouraging, a large animal preclinical model is needed (under development) to confirm the adhesive is capable of healing, for example, loaded osteochondral bone fragments. Acknowledgements: The murine study was supported, in part, by the Swedish Foundation for Strategic Research (#RMA15-0110)

Purpose: The purpose of our work was to assess sutures, suturing techniques, and suture anchors used in rotator cuff surgery in order to explore weak parts in our repair. Material and Methods: Ten types of sutures, four types of suturing techniques and eight types of sutures anchors commonly used in shoulder surgery were tested. Vicryl, Ticron, Dexon, PDS, Panacryl, Ethibond, Durabraid, Fiberwire, HiFi and Orthocord sutures were tested. Simple, mattress, massive cuff tear (MCT) technique and modified Mason Allen. (MMA) suturing technique in ex-vivo ovine healthy rotator cuff were tested. Four metallic and four bioabsorbable anchors: Arthrex, Smith+Nephew, Linvatec, Mitek and bio respectively were tested. Their pull-out strength and failure mode was determined in ex-vivo ovine humeral heads. Materials Testing Machine and attached load cell run with Emperor Software (MEC-MESIN, UK) was used for the tests with application of tensile load(60mm/min). Load and displacement were recorded at a sampling rate of 100 Hz and breaking load and stiffness were recorded. Results: The suture mean breaking strength (N) was: Vicryl 89.0, Ticron 70.9, Dexon 111.7, PDS 92.9, Panacryl 52.9, Ethibond 64.5, Durabraid 72.6, Fiber-wire 127.2, HiFi 163.0 and Orthocord 141.8. The mean suture stiffness (N/mm) was: Vicryl 3.4, Ticron 3.0, Dexon 2.4, PDS 1.2, Panacryl 0.7, Ethibond 2.5, Durabraid 3.1, Fiberwire 9.7, HiFi 11.1, and Orthocord 6.9. The technique’s mean breaking strength (N) was: simple 54.1, mattress 102.8, MCT 194.0, MMA 227.7 and their mean stiffness (N/mm) was: simple 10.4, mattress 13.1, MCT 26.0 and MMA 18.9. The anchors had mean pull-out strength (N): Arthrex 534.0 and Smith & Nephew 574.0, Linvatec 707.2N, Mitek 736.4N and Arthrex Bio 257.4, Linvatec Bio 305.2, Mitek Bio 359.6, S& N Bio 330.6. Often either in metallic (10/20) or in bioabsorbable anchors (11/20) the eyelet fails first. Conclusion: Modern non absorbable sutures (HiFi Orthocord Fiberwire) have higher breaking strength and stiffness than absorbable ones (p< 0.05). MCT suturing technique, arthroscopically applicable, and MMA technique, which is most commonly used in open surgery have no great differences in strength and stiffness (p=0.046 and p=0.352 respectively). Both of them have higher strength and stiffness than simple and mattress technique (p< 0.05). Metallic anchors have a higher pull-out strength than bioabsorbable ones (p< 0.05) and the eyelet is a weak point in both

Currently available fracture fixation devices that were originally developed for healthy bone are often not effective for patients with osteoporosis. Resulting outcomes are unsatisfactory, with longer recovery times, often requiring re-surgery for failed cases. One major issue is the design of bone screws, which can loosen or pull-out from osteoporotic bone. Design improvements are possible, but the development of new screws is a lengthy and expensive process due to the manufacture of the complex geometry involved. The aim of this research was to validate our currently available 3D printing technology in the design, manufacture and testing of screws. Three standard wood screw designs were reverse-engineered using computational modelling and then fabricated in polymeric resin using 3D rapid prototyping on a Stereolithography (SLA) machine. The original metal screws and the 3D screws (n=5 of each) were then inserted into a synthetic bone block (Sawbones, PCF5) representing the mechanical properties of severely osteoporotic cancellous bone. Pull-out tests were conducted in accordance with ASTM 543-13. The three metal screws exhibited pull-out strengths of 125, 74 and 118 N respectively. The 3D printed screws by comparison showed pull-out strengths approximately 15–20 % lower than their metal counterparts. However, when the results were normalised to the material tested, showing the relative changes to the first design, the pattern of results in the metal and 3D printed groups were almost identical (within 3 % of each other), showing excellent correlation. This study is the first to show that 3D Rapid Prototyping can be used in the pre-clinical testing of orthopaedic screws. The methodology provides a cheaper, faster development process for screws, allowing huge scope for development and improvement. Future work will include expanding the study to include more screw configurations as well as testing in higher density foams to compare performance in healthier bone

Introduction: The use of self-tapping screws has become increasingly popular since it allows for a rapid screw placement avoiding the tapping step during ORIF of fractures.. While sharing the same basic principle of cutting flutes and partial threads at the tip, at least four types of screw design is currently available, varying in the number and shape of cutting flutes. The purpose of this biomechanical study was to research for any significant difference between the various self-tapping screws. Material and Methods: Three different designs of 4.5-mm self-tapping screws and one standard 4.5 screw serving as control were compared for pull-out strength after insertion into an adult human non-embalmed cadaveric humeri. All specimens were machined to a 5 mm uniform cortical thickness. Four equidistant 3.2 mm holes were drilled into each specimen by an MTS mounted drill. All screws were inserted randomly in one of the four positions using a hand screwdriver. The cortical bone specimen was secured between two metal plates to the base of a MTS machine while a uniaxial tensile force was applied to the jig for screw removal at a rate of 0.833 mm/sec until holding power had decreased to 25 % of the maximum. Load displacement curves were recorded. Resulting data was analyzed using paired student-t tests. P values of less then 0.05 were considered statistically significant. Results: The mean load-to-failure was 97.4167N (S.D. 13.29924) for the Synthes control screw, 69.2333N (S.D. 4.48360) for the Synthes self-tapping screw, 67.15 (S.D. 11.23864) for the Stryker self-tapping screw, and 55.0667 (S.D. 8.59271) for the ODI self-tapping screw. A significant difference was found between the mean pull-out strength of the Synthes control screw when compared to each of the three self-tapping screws (Pairs 1–3, P < 0.05). Furthermore, the mean pull-out strength of the ODI self-tapping screw was found to be significantly less than Stryker self-tapping screw (Pair 6, P < 0.05). There was no significant difference between Synthes self-tapping screws and Stryker self-tapping screws (Pair 5, P < 0.05). Discussion and conclusion: Self tapping screws with three short cutting flutes performed better than those with two long cutting flutes. Despite of the different designs and length of the cutting flutes in self-tapping screws, they all have less pull out strength than regular screws

The menisci function within the knee as load distributors, shock absorbers and secondary stabilisers. The medial meniscus has been shown to carry as much as 50% of the load across the medial compartment, and the lateral meniscus 70% of its compartmental load. After total meniscectomy, joint contact areas decrease by approximately 75%, and peak local contact stresses increase by as much as 235%. Meniscectomy may lead to a 14 times increase in the risk of arthritis at 20 years. Axial load across the knee is converted into hoop stresses along the circumferential collagen fibres within the meniscus. Strong and stiff attachment of both meniscal horns, via the insertional ligaments, to the tibia is essential. Disruption of the circumferential fibre arrangement will defunction the meniscus. Preservation of meniscal tissue, where possible and appropriate, is now accepted practice. Most techniques for meniscal repair have been validated in vitro by testing radial pull-out strengths. However, meniscal tissue is highly anisotropic, with little strength in the radial direction, perpendicular to the circumferential collagen fibres. Physiological forces in the radial direction, across the menisci, are probably only very small. Therefore, mechanical evaluation of radial pull-out strengths is probably of little clinical significance. The role of different repair techniques, and the significance of gapping across repair sites under cyclical loading will be discussed

Clinically applied methods of assessing implant fixation and implant loosening are of sub-optimal precision, leading to the risk of unsecure indication of revision surgery and late recognition of bone defects. Loosening diagnosis involving measuring the eigenfrequencies of implants has its roots in the field of dentistry. The changing of the eigenfrequencies of the implant-bone-system due to the loosening state can be measured as vibrations or structure-borne sound. In research, vibrometry was studied using an external shaker to excite the femur-stem-system of total hip replacements and to measure the resulting frequencies by integrated accelerometers or by ultrasound. Since proper excitation of implant components seems a major challenge in vibrometry, we developed a non-invasive method of internal excitation creating an acoustic source directly inside the implant. In the concept proposed for clinical use, an oscillator is integrated in the implant, e.g. the femoral stem of a total hip replacement. The oscillator consists of a magnetic or magnetisable spherical body which is fixed on a flat steel spring and is excited electromagnetically by a coil placed outside the patient. The oscillator impinges inside the implant and excites this to vibrate in its eigenfrequency. The excitation within the bending modes of the implant leads to a sound emission to the surrounding bone and soft tissue. The sound waves are detected by an acoustic sensor which is applied on the patient's skin. Differences in the signal generated result from varying level of implant fixation. The sensor principle was tested in porcine foreleg specimens with a custom-made implant. Influence of the measurement location at the porcine skin and different levels of fixation were investigated (press-fit, slight loosening, advanced loosening) and compared to the pull-out strength of the implant. Evaluation of different parameters, especially the frequency spectrum resulted in differences of up to 12% for the comparison between press-fit and slight loosening, and 30% between press-fit and advanced loosening. A significant correlation between the measured frequency and the pull-out strength for different levels of fixation was found. Based on these findings, an animal study with sensor-equipped bone implants was initiated using a rabbit model. The implants comprised an octagonal cross-section and were implanted into a circular drill hole at the distal femur. Thereby, definite gaps were realized between bone and implant initially. After implantation, the bone growth around the implant started and the gaps were successively closed over postoperative period. Consequently, since the tests had been started with a loose implant followed by its bony integration, a reverse loosening situation was simulated. In weekly measurements of the eigenfrequencies using the excitation and sensor system, the acoustic signals were followed up. Finally, after periods of 4 and 12 weeks after implantation, the animals were sacrificed and pull-out tests of the implants were performed to measure the implant fixation. The measured implant fixation strengths at the endpoint of each animal trial were correlated with the acoustic signals recorded

There are several different ways of preparing the femoral canal prior to cementing a hip prosthesis. This study investigated the mechanical strength of the cement-bone interface of four different types of preparation determined by the maximum tensile force required to separate a cemented prosthesis from its cancellous bone origin. Forty-eight fresh-frozen ox femora were prepared for hip arthroplasty, In a four-way comparison, groups of eleven femora were prepared by irrigation using. syringe injected normal saline;. hydrogen-peroxide soaked gauze;. pulse-lavage brushing; and. pulse-lavage brushing and hydrogen-peroxide soaked gauze combination. Specimens were secured to a Material-test System (MTS), and the femoral implant pulled from the femur uni-axially at a rate of 5mm/min. The ‘pull-out strength’ was defined as the maximum tension recorded by the MTS during separation. Cement interdigitation was also inspected for each technique by microscopy of eight bone-implant transverse sections taken from prepared specimens. Following an analysis of variance and pair-wise Fisher comparison, the average pull-out strength of the cemented prosthesis was significantly higher (P< 0.001) using pulse-lavage brushing (mean 8049.2 N), and pulse-lavage brushing in combination with hydrogen-peroxide soaked gauze (mean 8489.1 N), than with normal saline irrigation (mean 947.1 N) or hydrogen-peroxide soaked gauze preparation (mean 1832.6 N). Prosthesis pull-out strength following pulse-lavage brushing in combination with hydrogen-peroxide soaked gauze was not significantly different (P> 0.05) than preparing with pulse-lavage brushing alone. Low and high power microscopy of specimen transverse sections revealed the greatest levels of cement penetration in specimens prepared using pulse-lavage brushing. This study demonstrated that one of the most effective preparations of the femoral canal for optimal mechanical fixation between cement and cancellous bone is pulse- lavage brushing. The use of hydrogen-peroxide soaked gauze in femoral canal preparation, either alone or in combination with pulse-lavage brushing, may not significantly improve prosthesis fixation

To assess the current literature on suture anchor placement for the purpose of identifying factors that lead to suture anchor perforation and techniques that reduce the likelihood of complications. Three databases (PubMed, Ovid MEDLINE, EMBASE) were searched, and two reviewers independently screened the resulting literature. Methodological quality of all included papers was assessed using Methodological Index for Non-Randomized Studies criteria and the Cochrane Risk of Bias Assessment tool. Results are presented in a narrative summary fashion using descriptive statistics. Fourteen studies were included in this review. Four case series (491 patients, 56.6% female, mean age 33.9 years), nine controlled cadaveric/laboratory studies (111 cadaveric hips and 12 sawbones, 42.2% female, mean age 60.0 years), and one randomized controlled trial (37 hips, 55.6% female, mean age 34.2 years) were included. Anterior cortical perforation by suture anchors led to pain and impingement of pelvic neurovascular structures. The anterior acetabular positions (three to four o'clock) had the thinnest bone, smallest rim angles, and highest incidence of articular perforation. Drilling angles from 10° to 20° measured off the coronal plane were acceptable. The mid-anterior (MA) and distal anterolateral (DALA) portals were used successfully, with some studies reporting difficulty placing anchors at anterior locations via the DALA portal. Small-diameter (< 1 .8-mm) suture anchors had a lower in vivo incidence of articular perforation with similar stability and pull-out strength in biomechanical studies. Suture anchors at anterior acetabular rim positions (3–4 o'clock) should be inserted with caution. Large-diameter (>2.3-mm) suture anchors increase the likelihood of articular perforation without increasing labral stability. Inserting small-diameter (< 1 .8-mm) all-suture suture anchors (ASAs) from 10° to 20° using curved suture anchor drill guides, may increase safe insertion angles from all cutaneous portals. Direct arthroscopic visualization, use of fluoroscopy, distal-proximal insertion, and the use of nitinol wire can help prevent articular violation

Recent clinical data suggest improvement in the fixation of tibia trays for total knee arthroplasty when the trays are additive manufactured with highly porous bone ingrowth structures. Currently, press-fit TKA is less common than press-fit THA. This is partly because the loads on the relatively flat, porous, bony apposition area of a tibial tray are more demanding than those same porous materials surrounding a hip stem. Even the most advanced additive manufactured (AM) highly porous structures have bone ingrowth limitations clinically as aseptic loosening still remains more common in press-fit TKA vs. THA implants. Osseointegration and antibacterial properties have been shown in vitro and in vivo to improve when implants have modified surfaces that have biomimetic nanostructures designed to mimic and interact with biological structures on the nano-scale. Pre-clinical evaluations show that TiO. 2. nanotubes (TNT), produced by anodization, on Ti6Al4V surfaces positively enhance the rate at which osseointegration occurs and TNT nano-texturization enhances the antibacterial properties of the implant surface. 2. In this in vivo sheep study, identical Direct Metal laser Sintered (DMLS) highly porous Ti6Al4V specimens with and without TNT surface treatment are compared to sintered bead specimens with plasma sprayed hydroxyapatite-coated surface treatment. Identical DMLS specimens made from CoCrMo were also implanted in sheep tibia bi-cortically (3 per tibia) and in the cancellous bone of the distal femur and proximal tibia (1 per site). Animals were injected with fluorochrome labels at weeks 1, 2 and 3 after surgery to assess the rate of bone integration. The cortical specimens were mechanically tested and processed for PMMA histology and histomorphometry after 4 or 12 weeks. The cancellous samples were also processed for PMMA histology and histomorphometry. The three types of bone labels were visualized under UV light to examine the rate of new bony integration. At 4 weeks, a 42% increase in average pull-out shear strength between nanotube treated specimens and non-nanotube treated specimens was shown. A 21% increase in average pull-out shear strength between nanotube treated specimens and hydroxyapatite-coated specimens was shown. At 12 weeks, all specimens had statistically similar pull-out values. Bone labels demonstrated new bone formation into the porous domains on the materials as early as 2 weeks. A separate in vivo study on 8 rabbits infected with methicillin-resistant Staphylococcus aureus showed bacterial colonization reduction on the surface of the implants treated with TNT. In vitro and in vivo evidence suggests that nanoscale surfaces have an antibacterial effect due to surface energy changes that reduce the ability of bacteria to adhere. These in vivo studies show that TNT on highly porous AM specimens made from Ti6Al4V enhances new bone integration and also reduce microbial attachment

Summary. Optimum position of pedicle screws can be determined preoperatively by CT based planning. We conducted a comparative study in order to analyse manually determined pedicle screw plans and those that were obtained automatically by a computer software and found an agreement in plans between both methods, yet an increase in fastening strengths was observed for automatically obtained plans. Hypothesys. Automatic planning of pedicle screw positions and sizing is not inferior to manual planning. Design. Prospective comparative study. Introduction. Preoperative planning in spinal deformity surgery starts by a proper selection of implant anchors throughout the instrumented spine, where pedicle screws provide the optimum choice for bone fixation. In the case of severe spinal deformities, dysplastic pedicles can limit screw usage, and therefore studying the anatomy of vertebrae from preoperative images can aid in achieving the safest screw position through optimal fastening strength. The purpose of this study is to compare manually and automatically obtained preoperative pedicle screw plans. Materials and Methods. CT scans of 17 deformed thoracic spines were studied by two experienced spine deformity surgeons, who placed 316 pedicle screws in 3D using a software positioning tool by aiming for the safest trajectory that permitted the largest possible screw sizes. The resulting manually obtained screw sizes, trajectory angles, entry points and normalised fastening strengths were compared to those obtained automatically by a dedicated computer software that, basing on vertebral anatomy and bone density in 3D, determined optimal screw sizes and trajectories. Results. Statistically significant differences were observed between manually and automatically obtained plans for screw sizes (p < 0.05) and trajectory angles (p < 0.001). However, for automatically obtained plans, screws were not smaller in diameter (p < 0.05) or shorter in length (p < 0.001), while screw normalised fastening strengths were higher (p < 0.001). Conclusions. In comparison to manual planning, automatically obtained plans did not result in smaller screw diameters or shorter screw lengths, which is in agreement with the definition of the pull-out strength, but in different screw trajectory angles, which is reflected by higher normalised fastening strengths. Captions. Fig. 1. Visual comparison among automatically obtained (green colour) and manually defined pedicle screw placement plans by two experienced spine surgeons (red and blue colour) for three different patients with adolescent idiopathic scoliosis, shown from top to bottom in a three-dimensional view, left sagittal, right sagittal and coronal view. Fig. 2. Histograms of differences between observers and (left column), between observer and automated method (middle column), and between observer and automated method (right column), shown from top to bottom for differences in pedicle screw pedicle screw diameter, sagittal inclination, and normalised fastening strength. For figures/tables, please contact authors directly.

During the development and early use of the First Generation of Universal Total Knee Replacement Instruments, those instruments supplied with the PCA knee and also available for use with the Kinematic and Total Condylar knees, David Hungerford and I noticed our imperfection in balancing some varus and valgus deformed total knee patients. We decided to start ligament tightening procedures to address this problem. I became impressed with the potential difficulty simply of grasping the medial capsular ligamentous sleeve and pulling it distally on the proximal tibia so that it could be stapled in place. I thought that use of a suture and then incorporation of that suture with a staple or screw could enhance the fixation. The tissue we were working with and are now talking about is rather thin, one to two millimeters, flat and broad with longitudinal fibers running in a caudad-cephalad direction. I wanted some way to grab these longitudinal fibers and exert a distal pull without having the suture material pull through. This suggested the use of a locking loop, analogous to what I had seen in my training when locking stitches were commonly used on different layers of wound closure. I developed in my head the picture of a row of locking loops and then saw the cross-over to the other side which revealed the entire structure with trailing tails. At this writing, I am uncertain of the year, but I am thinking it was 1982. Soon after that I illustrated it with OR suture thru paper and then began using it in surgery. I felt that publication would require studies of relative pull-out strength, and we added an injection study to look at possible influence of the tissue vascularity. For tensile strength we used #5 Ethibond in bovine Xenograft material, stapled and sewn to wood. In summary, different from individual stitches or stapling without stitching, The K-stitch fails at the suture material and not buy pulling the tissue. This statement is true when the suture reasonably matches the heft or thickness and strength of the soft tissue. Otherwise one is dealing with suture that is overpoweringly stronger than the tissues being fixed or held

We compared initial fixation strength of two commonly used tibial side hamstring ACL reconstruction fixation implants – the RCI interference screw and the Intrafix device. Using a sheep model 36 hamstring grafts were prepared and implanted into the distal femoral metaphyseal bone using either a RCI screw or an Intrafix device. They were then pulled out until failure using an Instron Materials Testing Machine. Maximum strength of graft fixation and mode of failure were recorded. The average strength of the graft was 48kg using the RCI screw and 90 kg using the Intrafix device. This difference was statistically significant. The maximum pull-out strength was 91kg for the RCI screw and 130 kg for the Intrafix device. The most common mode of failure in the RCI screw fixation was graft shredding on the screw and whole graft pullout whereas in the Intrafix device it was intratendinous failure. The Intrafix device demonstrated a clear strength advantage over the RCI screw with regard to initial fixation strength. The Intrafix device may reduce tibial side graft creep which is a problem with hamstring ACL reconstruction