Objectives

The objective of this study was to compare the early migration characteristics and functional outcome of the Triathlon cemented knee prosthesis with its predecessor, the Duracon cemented knee prosthesis (both Stryker).

Purpose. Total knee replacement is the one of the most performed surgeries. However, patient's satisfaction rate is around 70–90 % only. The sacrifice of cruciate ligament might be the main reason, especially in young and active patients. ACL stabilizes the knee by countering the anterior displacing and pivoting force, absorbs the shock and provides proprioception of the knee. However, CR knees has been plagued by injury of PCL during the surgery and preservation of the ACL is a demanding technique. Stiffness is more common comparing to PS designed knee. To insert a tibial baseplate with PE is usually thicker than 8 mm comparing to 2–4 mm of removed tibial bone. The stuffing of joint space may put undue tension on preserved ACL and PCL. Modern designed BCR has been pushed onto market with more sophisticated design and instrumentation. However, early results showed high early loosening rate. Failure to bring the tibia forward during cementing may be the main cause. The bone island where ACL footprint locates is frequently weak, intraoperative fracture happens frequently. A new design was developed by controlled elevation and reattachment of the ACL footprint to meet all the challenges. Method. A new tibial baseplate with a keel was designed. The central part of the baseplate accommodates elevated bony island with ACL footprint. The fenestrations at the central part is designed for reattachment of bony island under proper tension with heavy sutures and fixed at anterior edge of the baseplate in suture bridge fashion and also for autograft to promote bony healing after reattachment. The suture bridge method has been used by arthroscopists for ACL avulsion fracture without the need of immobilization. The elevation of bony island release the tension in the ACL which come from stuffing of baseplate and PE insert and greatly facilitate cementing of the baseplate. The keel improve the weakness of traditional U shape design of BCR knees. Instead of keeping the bony island intact by separately cutting the medial and lateral tibial plateau in BCR knees in the past, we choose to saw the tibial plateau in one stroke as in PS knees, then removes the two condyles. The bony island includes the footprint both ACL and PCL. The central part of tibial baseplate will push the bony island upward which release the undue tension in the cruciate ligaments. Summary. We proposed a new solution for the kinematic conflict in the present bi-cruciate knee designs by elevation and re- attachment of bony island with ACL footprint at the same time simplify the ACL preservation. The simple tibial cutting procedure also facilitate the process. The technique protects PCL from injury during tibial bone cutting in CR knees. We believe the new BCR design has the potential to replace CR knee in term of function and longevity in the future

Introduction:. For reconstructive surgery of the deteriorated rheumatoid MCP-joints silastic implants are used in general. Though realignment and stability after silastic joint replacement is achieved many disadvantages as reduced ROM, fractures and osteolysis are known. The first study of the cement less, non-constrained MCP-arthroplasty with HM-prosthesis showed a high rate of subluxation and synovitis. Therefore the design of the HM-prosthesis was changed with a PE-head to avoid wear and an increase of the diameter of the phalangeal base of 30% to get more stability. In prospective study we replaced 20 MCP joints in RA with this new designed prosthesis. Material and Methods:. short-time results after a mean Fu-period of 6 month (2–12 month) are now reported. In all cases a total replacement was performed. Clinical and radiographic re-examination could performed in all cases. Results:. In all cases we found an osteo-integration, no infection was seen. A luxation or subluxation as we have seen in the old design was not seen in any new designed prosthesis. In all cases pain-reduction was reported. The range of motion improved in all cases (flexion/extension 70/5/0). Conclusion:. The results after changing the design of the HM-pros-thesis show an improvement of stability and show no wear, luxation or subluxation. The Improvement of mobility and pain-reduction is still seen as published in our studies before. This first results have to be verified by longer FU-periods a higher number of patients

Introduction: Current existing joint designs, principally flexible silastic spacers, satisfy the initial requirements but commonly lack durability. In particular all flexible silastic joints are prone to early breakage due to abrasion against bone and constant loading of the central section of the flexible implants. The aim of our new small joint design is to overcome many of the deficiencies of the flexible silastic designs while maintaining their main advantage of stabilising joint alignment throughout the flexion range. Aim: To investigate the wear properties of the new small joint design in both static and dynamic applied loads using finite element analysis (FEA). Materials: The design is essentially a cross between a flexible spacer and a surface replacement, whereby the spanning flexible spacer is located within the long axes of direct load bearing metacarpal and phalangeal ‘housings’. We have investigated a number of parameters, using finite element analysis (FEA), focussing principally upon the load bearing and wear properties of the new design to both static and dynamic applied loads with reference to the test protocol developed by the Durham group. Results: Detailed FEA of the new joint design has highlighted the extreme potential durability of the housings and the internal flexible spacer. Our results suggest that the wear characteristics of both housings manufactured from PEEK (Polyetheretherketones) may result in the generation of considerably less wear debris compared with conventional alloy/plastic articulations. In addition, polyurethanes would appear to have better load bearing and wear characteristics than existing silastic materials. Conclusions: Clearly, if our FEA findings were to be reproduced with biomechanical testing, we would be well placed to introduce durable and readily affordable small joint arthroplasties that may well resolve our current difficulties of treating patients with moderate joint disease in addition to being a realistic alternative for patients with advanced destructive small joint arthritis

The aim of this study is to evaluate the early results of gleno-humeral reconstruction after tumour excision with a new design of endoprosthesis. The prosthesis is a fixed fulcrum gleno-humeral replacement consisting of a hydroxyapatite (HA) coated glenoid component with a polyethylene liner and a cemented stem with HA coated collar. Between 1997 and 2000 we inserted the prosthesis into 15 patients with primary bone tumours of the proximal humerus. There were nine males and six females with a mean age of 38 years (range: 8–71 years). Twelve stems were cemented and three uncemented. Two skeletally immature patients had an extendible stem inserted, one subsequently having a successful lengthening procedure. The mean follow-up was 28 months (range: 12–41 years). Functional outcome was assessed using the Musculoskeletal Tumour Society (MTS) scoring system. There were two early dislocations and one superficial wound infection. Three patients died of their disease and one underwent forequarter amputation for local recurrence. The remaining eleven had satisfactory functional outcomes with a mean MTS score of 81%. Radiologically there has been no evidence of early loosening. Microscopic analysis of the components in the amputated arm showed excellent osseointegration around the HA coated components

Aims: To study clinical outcome of patients treated with a new design of the patellar tendon-tibial tubercle graft, which has reliable stability for transfer in recurrent dislocation of patella. Methods: 22 dislocations in 19 patients (3 bilateral) operated by this new technique were reviewed. There were 14 female and 5 male patients. Indications for surgery included functional disability due to repeated dislocations and failure of conservative management. Average age of the patient: 26 years (15–39 years). Duration of follow-up: 12–88months. Demographic data was collected by reviewing the case notes. Postoperative evaluation based on subjective pain evaluation score and Lysholm knee score. Surgical approach: limited infrapatellar midline incision, no internal fixation in any of the cases. Results: 75% of the patients had excellent to good result. There was no recurrence of instability/dislocation in any of the cases. Fair & poor (25%) results were graded based on stiffness and pain Conclusions: Multiple surgical procedures have been described for the management of recurrent dislocation of patella ranging from soft tissue realignment to bony procedures with internal fixation. Our results showed good functional improvement in the majority of the patients. This procedure is less extensive compared to the original procedure. Also there is the added advantage of no internal fixation and hence a second surgery for the removal of the implant can be avoided

Pedicle screws fixation to stabilize lumbar spinal fusion has become the gold standard for posterior stabilization. However their positioning remain difficult due to variation in anatomical shape, dimensions and orientation, which can determine the inefficacy of treatment or severe damages to close neurologic structures. Image guided navigation allows to drastically decrease errors in screw placement but it is used only by few surgeons due to its cost and troubles related to its using, like the need of a localizer in the surgical scenario and the need of a registration procedure. An alternative image guided approach, less expensive and less complex, is the using of patient specific templates similar to the ones used for dental implants or knee prosthesis.

Like proposed by other authors we decided to design the templates using CT scans. (slice thickness of 2.0 mm). Template developing is done, for each vertebra, using a modified version of ITK-SNAP 1.5 segmentation software, which allow to insert cylinders (full or empty) in the segmented images. At first we segment the spine bone and then the surgeon chose screw axes using the same software. We design each template with two hollow cylinders aligned with the axes, to guide the insertion in the pedicle, adding contact points that fit on the vertebra, to obtain a template right positioning. Finally we realize the templates in ABS using rapid prototyping. After same in-vitro tests, using a synthetic spine (by Sawbones), we studied a solution to guarantee template stability with simple positioning and minimizing intervention invasiveness. Preliminary ex-vivo animal testing on porcine specimens has been conducted to evaluate template performance in presence of soft-tissue in place, simulating dissection and vertebra exposure. For verification, the surgeon examined post-operative CT-scans to evaluate Kirschner wires positioning.

During the ex-vivo animal test sessions, template alignment resulted easy thanks to the spinous process contact point. Their insertion required no additional tissue removal respect to the traditional approach. The positioning of contact points on vertebra's lamina and articular processes required just to shift the soft tissue under the cylinders bases. The surgeon in some cases evaluated false stable template positions since not each of the 4 contact points were actually in contact with the bone surface and tried the right position. CT evaluation demonstrate a positive results in 96.5% of the Kirschner wires implanted.

Our approach allows to obtain patient specific templates that does not require the complete removal of soft tissue around vertebra. Guide positioning is facilitated thanks to the using of the spinous processes contact point, while false stable positions can be avoided using four redundant contact points. The templates can be used to guide the drill, the insertion of Kirschner in case of use of cannulated screws or to guide directly the screw. After these preliminary ex-vivo animal tests we obtained the authorization of the Italian Health Ministry to start the human study.

Design and materials selection and optimisation are the-factors affecting the performance of the modern TKR. In this study new surface treatments were performed and investigated on CoCrMo with the goal to minimize the wear in a new total knee prosthesis design.

Three surface finishing treatments were considered and applied to cast CoCrMo alloy specimens. A surface polishing treatment performed by mass finishing technique was applied on machined CoCrMo. ACoCrMo coating, obtained by Magnetron Sputtering Physical Vapour Deposition (PVD) technique, was applied on mass finished CoCrMo specimens. Conventional hand polishing performed by silicon carbide papers followed by a final diamond past polishing was considered as reference material. For this study not cross-linked not sterilized UHMWPE was used. Surface morphology obtained by the surface treatments was investigated by SEM, Atomic Force Microscopy, and non contact laser profilometry. The microstructure and micro-hardness of CoCrMo alloy was investigated as well. Wear tests were performed in bovine serum using two screening wear test machines. A final wear test was performed on the new knee pros-thesis design using a knee wear simulator, up to five millions cycles.

CoCrMo PVD coating performed on CoCrMo substrate was capable to eliminate and to fill all the surface defects originated by the casting process of the CoCrMo alloy. Such surface defects could not be eliminated by hand polishing or mass finishing process alone. Vickers micro-hardness was improved by the mass finishing treatment. Although the roughness measured on the mass finished specimens was not the lowest, screening wear test produced for them the best results. Wear simulator test performed on the mass finished knee femoral prostheses sliding against UHMWPE, confirmed very low UHMWPE wear generation.

The mass finishing surface treatment applied to cast CoCrMo alloy specimens and femoral components is capable to polish the surface to the level required by standards. The PVD coating investigated was capable to improve the surface morphology of the alloy and to eliminate all the surface micro defects. Nevertheless, the screening wear tests indicated that the mass finishing treatment generate the lowest wear. The results were confirmed by wear simulator test. This study indicated that the mass finishing surface treatment can be effectively applied for the polishing of the femoral components of knee prosthesis.

Introduction: When introducing new joint replacement designs, it is difficult to predict with any certainty the clinical performance of the new design. Using roentgen stereophotogrammetric analysis (RSA) to evaluate the first two years of follow-up may serve as a predictor of late mechanical loosening for both hip and knee prostheses. This randomized study was designed to evaluate the performance of the new Triathlon total knee system and compare the results to its predecessor design, the Duracon total knee system. Methods: Sixty patients were consecutively randomized to receive either a Duracon (30 patients) or Triathlon total knee (30 patients). All components were cemented, and the posterior Cruciate Retaining version was used for both systems. The study was approved by the Ethical Committee for Lund University. All patients met the inclusion criteria. The mean age was 66 years (Duracon) vs 67 years (Triathlon). The BMI was 29 for both groups. The left knee was operated on in 15 vs 18 patients for the Duracon and for the Triathlon group. There were no statistically significant differences between the demographics for the two groups, except for the number of Ahlbäcks grade III OA, 20 (Duracon) vs 28 (Triathlon). The mean duration of surgery was 64 minutes (Duracon) vs 67 (Triathlon). The hospital stay was 5 days for both groups. The patients were followed up postoperatively at 3, 12 and 24 months. The principal evaluation tool was RSA to measure migration. The clinical results were evaluated using KOOS and KSS. Results: There were no significant differences in rotation or translation for the three coordinal axes. Neither were there any significant differences in the Maximal Total Point Motion (MTPM) during the 2-year follow-up The MTPM for the Duracon and Triathlon groups respectively was 0.5±0.5 vs 0.4±0.3 mm at 3 months, 0.6±0.4 vs 0.6±0.5 mm at 1 year, and 0.8.±5 vs 0.6±0.7 mm at 2 years. There were no significant differences in the clinical results between the groups when using the KSS and the KOOS. Discussion: The results of this study suggest that the new Triathlon total knee system is at least clinically equivalent to the Duracon total knee system. There were no significant differences in the RSA 2-year follow-up data nor in the clinical data (p< 0.05), which suggests the Triathlon knee system may replicate the excellent long-term clinical results achieved by the Duracon knee system

Introduction: Aseptic loosening of the acetabular cup is the commonest cause for revision surgery of total hip replacements (THR). Whereas a sound bone cement micro-interlock is believed to contribute most to the stability, most surgeons prefer to enhance their fixation by adding a macro-interlock. Drilling of additional keyholes creates cement pegs intended to resist rotational forces at the acetabular bone-cement interface. Only a few attempts have been made to investigate the effect of number, configuration and shape of these keyholes. Following the limited experiments by Oh (1983) on beechwood blocks, Mburu (1999) systematically optimised diameter, depth and number of keyholes using the same beechwood model. He subsequently developed a novel drill, bell-shaped in cross-section, aiming to minimise the stress concentration observed at the base of cement pegs.

Methods: This study compares the novel drill against a conventional drill using the same beechwood model and the previously optimised number, diameter and depth of keyholes, the shape of the drills being the only difference. The tests were performed on twenty beechwood blocks, half of the blocks allocated to the novel drill and half to the conventional drill. Since the three keyholes were not equidistant, it was also tested whether the direction of torque had an influence on the results. This was done by applying torque clockwise in half of the specimens and anticlockwise in the other half.

Results: The results showed that the static torque to failure was superior in the novel drill (mean: 163 Nm) compared to the conventional drill (mean: 127 Nm), but this was not statistically significant (p= 0.12) due to the wide variation of results. There was no difference for the direction of torque (p= 0.8) and the type of drill and the direction of torque did not show any interaction (p= 0.5).

Conclusions: Results suggest that there is an improvement with the novel drill in static torque to failure. Further testing appears therefore to be worthwhile. Results also suggest that the difference or improvement achieved with the novel drill is less pronounced than it is for number, depth and position of keyholes (Mburu, 1999). However, more variability than expected was encountered. Despite recognition as a possible model for keyhole testing, beechwood blocks testing three keyholes at the same time may not be appropriate when the load to failure for cement pegs is approximating the load to failure for beechwood as encountered in our experiment. Simplification of the system like testing single pegs should be considered.

The design of the femoral prosthesis in cementless total hip arthroplasty is known to affect the initial strains in the cortex during implantation and in the early postoperative time period. High strains have a direct influence on periprosthetic fracture. This study compares the existing ABGII stem, which is proximally coated with a grit blasted titanium surface with hydroxyapatite coating with a prototype that has a rougher titanium plasma spray proximal coating. The Australian National Joint registry results 2011 reported the ABG2 femoral component cumulative percent revision (CPR) of 6.5 (93.5% survival), which compares favourably with equivalent stems with 10 year CPR data such as the Taperloc 6.6 and Corail 7.3.

Six pairs of fresh-frozen cadaveric femurs were mounted in blocks according to ISO guidelines in single leg stance setup. Five strain gauges were attached around the neck of the femur and then prepared according to routine operative techniques to accept the femoral prosthesis. Cortical strains were measured during insertion of the prosthesis with an instrumented mallet attached to an accelerometer. Subsequently, force-displacement readings were taken during cyclical loading on a servo-hydraulic machine and finally the stems were tested to failure.

Our results showed significantly less strain during cyclical loading of the stem with increased surface roughness (p < 0.05). They also showed no significant differences loads/strains during impaction (p = 0.159), no significant difference in micromotion (p = 0.148) and no significant difference in load-to-failure (p = 0.37).

Purpose and Background

Back pain impinges upon all aspects of life, has a reported UK lifetime prevalence as high as 84% and considering approximately a third of our lives are spent asleep the paucity of research into the effect a mattress has on back pain and sleep is surprising. Mood changes, effecting an increase in pain perception, due to sleep loss may also lead to a downward spiral of increasing back pain and greater sleep loss. A controllable factor in this spiral, affecting both aspects, is the mattress but to the authors' knowledge none currently available on the market have any robust, published research to objectively support any claims made and at best being ‘endorsed’ by experts. This may lead to possible misinterpretation of efficacy and leave professionals at a loss with what to advise when questioned.

Clinical success of prostheses in joint arthroplasty is ultimately determined by survivorship and patient satisfaction. The purpose of this study was to compare (non-inferiority) a new morphometric designed stem for total hip arthroplasty (THA) against an established comparator. A prospective randomised multi-centre study of 144 primary cementless THA performed by nine experienced orthopaedic surgeons was completed (70 received a fully coated collarless tapered stem and 74 received a morphometric designed proximally coated tapered stem). PROMs and blood serum markers were assessed preoperatively and at intervals up to 2-years postoperatively. In addition, measures of femoral stem fit, fill and subsidence at 2-years post-operatively were measured from radiographs by three observers, with an intra-class correlation coefficient of 0.918. A mixed effects model was employed to compare the two prosthesis over the study period. A p-value <0.05 was considered statistically significant. Demographics, Dorr types and blood serum markers were similar between groups. Both stems demonstrated a significant improvement in PROMs between the pre- and post-operative measurements, with no difference at any timepoint (p > 0.05). The fully coated tapered collarless femoral stem had a non-significantly higher intra-operative femoral fracture rate (5.8% vs 1.4%, p = 0.24), with all patients treated with cable fixation and partial weight bearing. The mean subsidence at 2-years was 2.5mm +/- 2.3mm for the morphometric stem and 2.4mm +/- 1.8mm for the fully coated tapered collarless femoral stem (p = 0.879). There was one outlier in each group with increased subsidence (fully coated tapered collarless femoral stem 6.9mm, morphometric wedge stem 7.4mm), with both patients reporting thigh pain at 2 years. When compared with an established stem, the newer designed morphometric wedge stem performed well with comparable radiological and PROM outcomes at 2 year follow up. Continued follow-up is required for long term benchmarking

Clinical success of prostheses in joint arthroplasty is ultimately determined by survivorship and patient satisfaction. The purpose of this study was to compare (non-inferiority) a new morphometric designed stem for total hip arthroplasty (THA) against an established comparator. A prospective randomised multi-centre study of 144 primary cementless THA performed by nine experienced orthopaedic surgeons was completed (70 received a fully coated collarless tapered stem and 70 received a morphometric designed proximally coated tapered stem). PROMs and blood serum markers were assessed preoperatively and at intervals up to 2-years postoperatively. In addition, measures of femoral stem fit, fill and subsidence at 2-years post-operatively were measured from radiographs by three observers, with an intra-class correlation coefficient of 0.918. A mixed effects model was employed to compare the two prostheses over the study period. A p-value <0.05 was considered statistically significant. Demographics and Dorr types were similar between groups. Both stems demonstrated a significant improvement in PROMs between the pre- and post-operative measurements, with no difference at any timepoint (p > 0.05). The fully coated tapered collarless femoral stem had a non-significantly higher intra-operative femoral fracture rate (5.8% vs 1.4%, p = 0.24), with all patients treated with cable fixation and partial weight bearing. The mean subsidence at 2-years was 2.5mm +/- 2.3mm for the morphometric stem and 2.4mm +/- 1.8mm for the fully coated tapered collarless femoral stem (p = 0.879). There was one outlier in each group with increased subsidence (fully coated tapered collarless femoral stem 6.9mm, morphometric wedge stem 7.4mm), with both patients reporting thigh pain at 2 years. When compared with an established stem, the newer designed morphometric wedge stem performed well with comparable radiological and PROM outcomes at 2 year follow up. Continued follow-up is required for long term benchmarking

Hip fractures frequently occur in elderly patients with osteoporosis and are rapidly increasing in prevalence owing to an increase in the elderly population and social activities. We experienced several recent presentations of TFNA nails failed through proximal locking aperture which requires significant revision surgery in often highly co-morbid patient population. The study was done by retrospective data collection from 2013 to 2023 of all the hip fractures which had been fixed with Cephalomedullary nails to review and compare Gamma (2013–2017) and TFNA (2017–2023) failure rates and the timing of the failures. Infected and Elective revision to Arthroplasty cases were excluded. The results are 1034 cases had been included, 784 fixed with TFNA and 250 cases fixed Gamma nails. Out of the 784 patients fixed with TFNA, 19 fixation failed (2.45%). Out of the 250 cases fixed with Gamma nails, 15 fixation failed (6%). Mean days for fixation failure were 323 and 244 days in TFNA and Gamma nails respectively. We conclude that TFNA showed remarkable less failure rates if compared to Gamma nails. At point of launch, testing was limited and no proof of superiority of TFNA over Gamma nail. Several failures identified with proximal locking aperture in TFNA which can be related to the new design which had Substantial reduction in lateral thickness at compression screw aperture

Background. Scapular notching is a complication after reverse shoulder arthroplasty with a high incidence up to 100%. Its clinical relevance remains uncertain; however, some studies have reported that scapular notching is associated with an inferior clinical outcome. There have been no published articles that studied positional relationship between the scapular neck and polyethylene insert in vivo. The purpose of this study was to measure the distance between the scapular neck and polyethylene insert in shoulders with Grammont type reverse shoulder arthroplasty during active external rotation at the side. Methods. Eighteen shoulders with Grammont type prosthesis (Aequalis Reverse, Tornier) were enrolled in this study. There were 13 males and 5 female, and the mean age at surgery was 74 years (range, 63–91). All shoulders used a glenosphere with 36mm diameter, and retroversion of the humeral implant was 10°in 4 shoulders, 15°in 3 shoulders, and 20°in 11 shoulders. Fluoroscopic images were recorded during active external rotation at the side from maximum internal to external rotation at the mean of 14 months (range, 7–24) after surgery. The patients also underwent CT scans, and three-dimensional glenosphere models with screws and scapula neck models were created from CT images. CT-derived models of the glenosphere and computer-aided design humeral implant models were matched with the silhouette of the implants in the fluoroscopic images using model-image registration techniques (Figure 1). Based on the calculated kinematics of the implants, the closest distance between the scapular neck and polyethylene insert was computed using the scapular model and computer-aided design insert models (Figure 2). The distance was computed at each 5° increment of glenohumeral internal/external rotation, and the data from 20°internal rotation to 40°external rotation were used for analyses. One-way repeated-measures analysis of variance was used to examine the change of the distance during the activity, and the level of significance was set at P < 0.05. Results. The mean glenohumeral abduction during the activity was 17°-22°. The mean distance between the neck and insert was approximately 1mm throughout the activity (Figure 3). The distance tended to become smaller with the arm externally rotated, but the change was not significant. Discussion. The reported incidence of scapular notching after Grammont type reverse shoulder arthroplasty is generally higher than the newer design prosthesis with the lateralized center of rotation. This may be associated with the design of the prosthesis, and the results of this study that the distance between the neck and insert was approximately 1mm throughout active external rotation at the side will support the high incidence of notching. We may need to analyze the distance with the newer design reverse shoulder prosthesis to prove the architectural advantage of the newer systems. Conclusion. The distance between the scapular neck and polyethylene insert was approximately 1mm throughout active external rotation activity in shoulders with Grammont type prosthesis

For amputated patients, direct attachment of upper leg prosthesis to the skeletal system by a percutaneous implant is an alternative solution to the traditional socket fixation. Currently available implants, the OPRA system (Integrum AB, Göteborg, Sweden) and the ISP Endo/Exo prosthesis (ESKA Implants AG, Lübeck, Germany) [1-2] allow overcoming common soft tissue problems of conventional socket fixation and provide better control of the prosthetic limb [3], higher mobility and comfort [2, 4]. However, restraining issues such as soft-tissue infections, peri-prosthetic bone fractures [3, 5–8] and considerable bone loss around the stem [9], which might lead to implant's loosening, are present. Finally, a long a residual limb is required for implant fitting. In order to overcome the limiting biomechanical issues of the current designs, a new concept of the direct intramedullary fixation was developed. The aim was to restore the natural load transfer in the femur and allow implantations in short femur remnants (Figure 1). We hypothesize that the new design will reduce the peri-prosthetic bone failure risk and adverse bone remodeling. Generic CT-based finite element models of an intact femoral bone and amputated bones implanted with 3 analyzed implants were created for the study. Models were loaded with two loading cases from a normal walking obtained from the experimental measurements with the OPRA device [10-11]. Periprosthetic bone failure risk was evaluated by considering the von Mises stress criterion [12-14]. Subsequently the strain adaptive bone remodeling theory was used to predict long-term changes in bone mineral density (BMD) around the implants. The bone mineral content (BMC) change was measured around implants and the results were visualized in the form of DXA scans. The OPRA and the ISP implants induced the high stress concentration in the proximal region decreasing in the distal direction to values below physiological levels as compared with the intact bone. The stresses around the new design were more uniformly distributed along the cortex and resembled better the intact case. Consequently, the bone failure risk was reduced as compared to the OPRA and the ISP implants. The adaptive bone remodeling simulations showed high bone resorption around distal parts of the OPRA and the ISP implants in the distal end of the femur (on average −75% ISP to −78% OPRA after 60 months). The bone remodeling simulation did not reveal any bone loss around the new design, but more bone densification was seen (Figure 2). In terms of total bone mineral content (BMC) the OPRA and the ISP implants induced only a short-term bone densification in contrast to the new design, which provoked a steady increase in the BMC over the whole analyzed period (Figure 3). In conclusion, we have seen that the new design offers much better bone maintenance and lower failure probability than the current osseointegrated trans-femoral prostheses. This positive outcome should encourage further developments of the presented concept, which in our opinion has a potential to considerably improve safety of the rehabilitation with the direct fixation implants and allow treatment of patients with short stumps

Suture anchors are widely used to secure tendons and ligaments to bone during both arthroscopic and open surgery. However, single stage insertion suture anchors, i.e. anchors that could be inserted without predrilling of the bone, are not currently available. We aimed to record the impact needed for insertion of the new design single stage suture anchors, and to compare their pull out strength with another range of commercially available suture anchors. The force required to insert the new design of suture anchors was investigated using an impact hammer capable of recording the number and force of each of the hits. The anchors were inserted in a consistent manner into animal (porcine) bone at sites analogous to common anchor sites used in clinical practice. Pull out strength was assessed using a digital force gauge after tying the suture to create a secure loop. Thereafter, force was applied steadily until either the anchor or the suture failed and compared with a popular range of commercially available suture anchors (Mitek). Our initial investigations using prototype designs for small, medium and large anchors compared favourably with the Mini-mitek, GII, and Superanchor range of Mitek anchors. Essentially the most common point of failure for each of the suture anchor families was the suture itself with both suture anchor systems performing similarly. In addition, similar pull out strengths were demonstrated for both the Mitek and new design of suture anchors when loaded parallel, or at 90°, to the line of anchor insertion. The new design single stage suture anchors have an equivalent pull out strength compared with a popular commercially available family of suture anchors, but in addition have the significant advantage of being suitable for single stage insertion in many clinical settings

Implant designs for hip and knee arthroplasty have undergone a continual improvement process, but development of implants for total elbow arthroplasty (TEA) have lagged behind despite the marked mechanical burden placed on these implants. TEA is not as durable with failure rates approaching thirty percent at five years. The Coonrad-Morrey (Zimmer, Warsaw, IN), a linked design, remains the standard-bearer, employing polyethylene bushings through which a metal axle passes. A common failure mode is bushing wear and deformation, causing decreased joint function as the bushing-axle constraint decreases and osteolysis secondary to release of large volumes of wear debris. Improving upon this poor performance requires determining which factors most influence failure, so that failure can be avoided through design improvements. The approach integrates clinical observations of failed TEAs with implant retrieval analysis, followed by measurements of loads across the elbow for use in stress analyses to assess the performance of previous designs, and, finally, new design approaches to improve performance. Examination of the clinical failures of more than seventy Coonrad-Morrey TEAs revealed patterns of decreased constraint and stem loosening. Implant retrieval analysis from more than thirty of these cases showed excessive bushing deformation and wear and burnishing of the fixation stems consistent with varus moments across the joint. To determine loads across the elbow, motion analysis data were collected from eight TEA patients performing various activities of daily living. The kinematic data were input into a computational model to calculate contact forces on the total elbow replacement. The motion that produced the maximum contact force was a feeding motion with the humerus in 90° of abduction. For this motion, the joint reaction forces and moments at the point of maximum contact were determined from a computational model. We applied these loads to numerical models of the articulating bushings and axle of the Coonrad-Morrey to examine polyethylene strains as measures of damage and wear. Strain patterns in response to the large varus moment applied to the elbow during feeding activities showed extensive plastic deformation in the locations at which deformation and wear damage were observed in our retrieved implants (Fig. 1). Finally, we examined a new semi-constrained design concept intended to meet two goals: transfer contact loads away from the center of the joint, thus allowing contact to provide a larger internal moment to resist the large external varus moment; and reduce polyethylene strains by utilizing curved contacting surfaces on both the axle and the bushings (Fig. 2). After a sensitivity analysis to determine optimal dimensional choices (e.g., bushing and axle radii), we compared the resulting polyethylene strains between the Coonrad-Morrey and new design at locations that experienced the largest strains (Fig. 3). Substantial decreases were achieved, suggesting far less deformation and wear, which should relate to marked improvements in performance. Currently, we are incorporating this new design concept, along with alterations in stem design achieved from examination of load transfer at the fixation interfaces based on the same loading conditions, to achieve an implant system intended to improve the performance of TEA

Introduction and Objective. The surgical strategy for acetabular component revision is determined by available host bone stock. Acetabular bone deficiencies vary from cavitary or segmental defects to complete discontinuity. For segmental acetabular defects with more than 50% of the graft supporting the cup it is recommended the application of reinforcement ring or ilioischial antiprotrusio devices. Acetabular reconstruction with the use of the antiprotrusion cage (APC) and allografts represents a reliable procedure to manage severe periprosthetic deficiencies with highly successful long-term outcomes in revision arthroplasty. Objective. We present our experience, results, critical issues and technical innovations aimed at improving survival rates of antiprotrusio cages. Materials and Methods. From 2004 to 2019 we performed 69 revisions of the acetabulum using defrosted morcellized bone graft and the Burch Schneider anti-protrusion cage. The approach was direct lateral in 25 cases, direct anterior in 44. Patients were re-evaluated with standard radiography and clinical examination. Results. Eight patients died from causes not related to surgery, and two patients were not available for follow up. Five patients were reviewed for, respectively, non-osseointegration of the ring, post-traumatic loosening with rupture of the screws preceded by the appearance of supero-medial radiolucency, post-traumatic rupture of the distal flange, post-traumatic rupture of the cemented polyethylene-ceramic insert, and dislocation treated with new dual-mobility insert. Among these cases, the first three did not show macroscopic signs of osseointegration of the ring, and the only areas of stability were represented by the bone-cement contact at the holes in the ring. Although radiographic studies have shown fast remodeling of the bone graft and the implant survival range from 70% to 100% in the 10-year follow up, the actual osseointegration of the ring has yet to be clarified. To improve osseointegration of the currently available APC whose metal surface in contact with the bone is sandblasted, we combined the main features of the APC design long validated by surgical experience with the 3D-Metal Technology for high porosity of the external surface already applied to and validated with the press fit cups. The new APC design is produced with the 3D-Metal technology using Titanium alloy (Ti6Al4V ELI) that Improves fatigue resistance, primary stability and favorable environment for bone graft ingrowth. We preview the results of the first cases with short-term follow up. Conclusions. Acetabular reconstruction with impacted morcellized bone graft and APC is a current and reliable surgical technique that allows the restoration of bone loss with a high survival rate of the implant in the medium to long term. The new 3D Metal Cage is designed to offer high friction for the initial stability. The high porosity of the 3D Metal structure creates a favorable environment for bone growth, thus providing valid secondary fixation reproducing the results achieved with the 3D metal press fit cup