Introduction

Arthrodesis of the 1st metatarso-phalangeal joint (MTPJ) is a common procedure in forefoot surgery for hallux rigidus and severe hallux valgus. Debate persists on two issues - the best preparation method for the articular surfaces, and the optimal technique for operative stabilisation of the joint.

Hybrid fixation of total joint arthroplasty has been an accepted form of surgical approach in multiple joints. Principles of implant fixation should focus on durability providing secure long-term function. To date there is no conclusive evidence that pressed fit humeral stem fixation has an advantage over well-secured cemented humeral fixation. In fact, need for revision arthroplasty due to inadequate implant fixation has almost universally revolved around failure of cement fixation and loosening of the glenoid component. A case will be made based on 30 years of experience of one surgeon performing total shoulder arthroplasty using secure modern cement fixation techniques of humeral components. More recently, over the last 10 years, extremely high rate of durable secure glenoid implant fixation has been achieved using tantalum porous anchorage with polyethylene glenoid components. This has resulted in no cases of loosening of glenoid fixation and only 1 case of glenoid component fracture with greater than 95% survivorship over a 10 year period. A combination of well cemented humeral stem and trabecular metal anchorage of the glenoid has provided durable lasting function in primary total shoulder arthroplasty

This study was performed to compare the mechanism of bone-implant integration and mechanical stability among three popularly used cementless implant surfaces. Plasma sprayed porous surface (TiPL), grit-blasted rough surface (TiGB), and hydroxyapatite coated implant surface (HA) were tested in a sheep model at 4 and 12 weeks. The integration patterns were investigated using histology, histomorphometry, and mechanical strength by push-out test. All three groups demonstrated early bone ongrowth on their surfaces, with much of the ongrowth resembling contact osteogenesis. TiPL group showed bone anchorage into porous coating with new bone ingrowth into the pores. HA group revealed small cracks at its coating at 12 weeks time point. Plasma sprayed porous surface also demonstrated its superior mechanical stability maybe reinforced by its bone anchorage, whearas, HA surface exhibited higher osteoconductivity with highest ongrowth rate

Introduction:. Total hip arthroplasty has became one of the most successful standard procedures in the orthopaedic surgery. With a more frequent use in young and active patients bone saving procedures become more important. On the other hand, the ever increasing trend toward minimal excision of the healthy bone during implantation of the total hip replacement has led to a range of implants that can be classified according their means of anchorage in the various anatomic segments. The Nanos-short-stem endoprothesis presented here requires metaphyseal anchorage. Material and methods:. From juli 2005 to march 2009 a total of 112 (70 males, 52 female) uncemented Nanos-short-stem prothesis were implanted in 111 patients in Westpfalz academic hospital –University Mainz. The patiens average age was 53 years (33–73). The indication for this procedure was predominantly coxarthrosis. In all cases dorsal approach was used. The mean follow up period was 2,5 years (range 6 months–4,5 years). The patients were assessed using Harris Hip Score and radiologically to detect any bone changes, the stand of the prothesis and peri-articular ossifications. Results:. The perioperative Harris Hip Score was 53 (28–77), postoperative was 94 (86–100). We did not have discovered any prothesis specific complications. Radiological follow up examinations showed the development of increasing trabecular reinforciment of the femoral neck and pertrachanteric regions. There is no evidence of any loosing or migration of the prothesis. Conclusion:. the stem design of Nanos-short-stem prothesis allowed a metaphyseal intertrochanteric multipoint primary fixation. The surgical technique is simple. It offers alternative to convenential total hip arthroplasty especially in young patients and save bone stock for later revision (1–2). Long term studies still be needed

Introduction. Direct skeletal attachment of prosthetic limbs, commonly known as osseointegration (“OI”), is being investigated by our team with the goal of safely introducing this technology into the United States for human use. OI technology allows for anchorage of prosthetic devices directly to bone using an intramedullary stem. For OI to be effective and secure, bone ingrowth and remodeling around the implant must be achieved. Physicians need an effective way to measure bone remodeling in order to make informed decisions on prescribed loading. This work describes methodology that was developed that utilizes computed tomography (CT) imaging as a tool for analyzing bone remodeling around an osseointegrated implant. Method. A subject implanted with a new Percutaneous Osseointegrated Prosthesis (POP) (DJO Surgical, Austin, TX) had CTs taken of their residual femur at 6-weeks and 12-months post-op in a FDA Early Feasibility Study with Institutional Review Board approval. Three-dimensional models of the femur were created from dicom files of the CT slices using Mimics (v21.0, Materialise, Leuven, Belgium). Each scan was segmented into four objects: cortical bone, medullary cavity, total volume (cortical bone plus the medullary cavity) and endoprosthetic stem (Fig. 1). Following segmentation, models were uploaded to 3-Matic Research (v13.0, Materialise, Leuven, Blegium) in STL format for alignment to a common world coordinate system (Fig. 2). A common origin was set by taking the average distance between planes of the femoral head and the greater trochanter. Once aligned to the coordinate system, biomechanical length (BML) was calculated from the proximal origin to the distal end of the amputated femur. BML and STLs of the aligned medullary cavity and femur volume were entered into custom Matlab code designed to measure cortical and medullary morphology in transverse cross sections of the femur. Morphology data from 6-weeks and 12-month time points were compared in order to determine if bone remodeling around the POP implant could be detected using these methods. Results. Comparing longitudinal data from post-operative visits suggests that important indicators of bone remodeling around the device could be detected (Fig 3). One year after implantation of the POP device the medullary perimeter and area had minimal % differences (−1.5 and 2.2) from the 6-week visit, validating that consistent alignment of the femoral model was achieved between scans from different time points. The cortical area, cortical perimeter, and cortical thickness around the POP implant showed positive percent changes at the 12-months of 19.44%, 4.04% and 14.36% respectively, with the largest increases observed at the the distal end for each parameter. These increases in cortex morphology values indicate bone changes were identified around the endoprosthetic stem of the implant. Discussion/Conclusion. This pilot study utilized CT imaging as a tool for analyzing bone remodeling around a new osseointegrated device. These methods can be performed quickly and accurately and have the potential for use in monitoring bone remodeling. CT scans from additional subjects are being analyzed to further validate and optimize these methods for clinical use. This study described an investigational device, limited by federal law to investigational use. No long-term data exists about its performance. For any figures or tables, please contact the authors directly

Aim. Cementless prosthesis is one of the major bone-implant interface fixation methods in total joint replacement. Grit blasted surface, hydroxyapatite coated surface and plasma sprayed metallic porous coating have been popularly used. The latter has demonstrated higher bone implant mechanical stability in previous laboratory study in early and middle stages. However, question remains what the mechanism is to make it performing better and how to improve them further. This study is designed to examine the mode of failure in bone-implant interface in a sheep model. Method. Plasma sprayed porous coated (TiPL); hydroxyapatite (HA) coated and and grit blasted (TiGB) titanium implants were examined in the study. Each type has 36 specimens. Implants were inserted into cortical bones in a press-fit fashion in a total of 22 sheep bilateral hind limbs. Specimens were retrieved at 4 weeks and 12 weeks. Push- out testing was performed to just reach ultimate failure. Failed bone-implant interface were investigated by histology and BSEM. The percentage of failure at bone-coating interface, bone itself fracture, coating itself failure, and coating-substrate dissociation were measured by BSEM. Results. In TiPL group, failure occurred mainly at new bone itself on ingrowing new bone and adjacent bone, with 74% at 4 weeks, and 82% at 12 weeks. The percentages were significantly higher than that of the failure at bone-porous coating dissociation. Furthermore, the percentage of failure occurred at bone was also higher in TiPS group than in the other groups at both time points. In HA group, the main proportion of failure, 69%, occurred at bone-HA dissociation at 4 weeks, higher than the 25% at bone itself fracture. 57% of failure occurred at HA-substrate dissociation at 12 weeks, which was followed by HA coating itself breakage (Figure 1). Bone itself fracture has the lowest proportion of only 4% breakage at 12 weeks. HA coating revealed micro cracks at some area although not all of them were failed. In TiGB group, failure mainly occurred at bone-implant surface dissociation at both time points. Conclusion. The failure mode at the HA and TiGB groups demonstrate that new bone was less likely to break, or stronger, than bone-implant surface interface at early stage, and new bone at middle stage was stronger than the other interfaces. The bone ingrowth to metallic porous coating results in that major proportion failure has to occur at bone anchorage, either at the entry level or at adjacent bone. The anchorage is the reason why TiPS has higher mechanical shear strength in previous study. Improving bone itself remodelling or maturing process may increase the porous coated implant in vivo mechanical strength; improving HA quality and HA-substrate adhesion may enhance HA coated implant performance; and improving bone implant surface bonding may strengthen grit blasted implant mechanical stability

The charateristic of Brexis short stem are:. -Minimal bone loss. -Physiologic load transmission. -Solid anchorage. -Biocompatibility and osteointegration. -Polished brilliant in use

Aims

Safety concerns surrounding osseointegration are a significant barrier to replacing socket prosthesis as the standard of care following limb amputation. While implanted osseointegrated prostheses traditionally occur in two stages, a one-stage approach has emerged. Currently, there is no existing comparison of the outcomes of these different approaches. To address safety concerns, this study sought to determine whether a one-stage osseointegration procedure is associated with fewer adverse events than the two-staged approach.

Aim. To assess the clinical characteristics, diagnostic tests and treatment strategies in orthopedic implant-associated infections (OIAI) caused by Cutibacterium spp. Method. We retrospectively included consecutive patients with OIAI caused by Cutibacterium spp. treated at our institution from January 2012 to January 2017. OIAI was diagnosed when: (i) macroscopic purulence, sinus tract or exposed implant was present; (ii) acute inflammation in peri-implant-tissue was documented; (iii) Cutibacterium spp. grew in joint aspirate, ≥2 intraoperative peri-implant tissue samples or in sonication fluid of the removed implant (>50 CFU/ml). Results. Of 67 patients with Cutibacterium OIAI, 42 (63%) had an infected joint prosthesis (21 hip, 12 shoulder, 9 knee) and 25 (37%) an infected fixation device (10 spinal hardware, 11 osteosynthesis, 2 anchorages after rotator cuff reparation, 2 cruciate ligament grafts). 53 (84%) presented with a delayed (3–24 months) or late (>24months) infection. 62 infections were caused by C. acnes and 5 by C. avidum, all being susceptible to levofloxacin and rifampin. Among non-culture-based diagnostic tests, tissue histology had the highest sensitivity (68%), followed by increased synovial fluid leukocyte count/differential (59%). Of culture-based tests, sonication fluid culture showed the highest sensitivity (83%), followed by tissue culture (71%) and synovial fluid culture (61%). Culture positivity rates of synovial fluid, peri-implant tissue and sonication fluid were 20%, 41% and 40%, respectively, after 7 days of incubation and 58%, 74% and 78%, respectively, after 14 days. Most patients were treated with one-stage (24%) or two-stage (55%) implant exchange of the implant. The majority of patients received oral levofloxacin and rifampin for 6–12 weeks. Conclusions. Cutibacterium spp. affected various types of orthopaedic implants in different anatomic locations (lower and upper limbs and spine). Conventional diagnostic tests showed limited sensitivity of Cutibacterium OIAI and can be easily missed when cultures are incubated less than 10–14 days. All Cutibacterium isolates were susceptible to levofloxacin and rifampin

Introduction. In total hip arthroplasty, press-fit anchorage is one of the most common fixation methods for acetabular cups and mostly ensures sufficient primary stability. Nevertheless, implants may fail due to aseptic loosening over time, especially when the surrounding bone is affected by stress-shielding. The use of acetabular cups made of isoelastic materials might help to avoid stress-shielding and osteolysis. The aim of the present numerical study was to determine whether a modular acetabular cup with a shell made of polyetheretherketone (PEEK) may be an alternative to conventional titanium shells (Ti6Al4V). For this purpose, a 3D finite element analysis was performed, in which the implantation of modular acetabular cups into an artificial bone stock using shells made of either PEEK or Ti6Al4V, was simulated with respect to stresses and deformations within the implants. Methods. The implantation of a modular cup, consisting of a shell made of PEEK or Ti6Al4V and an insert made of either ceramic or polyethylene (PE), into a bone cavity made of polyurethane foam (20 pcf), was analysed by 3D finite element simulation. A two-point clamping cavity was chosen to represent a worst-case situation in terms of shell deformation. Five materials were considered; with Ti6Al4V and ceramic being defined as linear elastic and PE and PEEK as plastic materials. The artificial bone stock was simulated as a crushable foam. Contacts were generated between the cavity and shell (μ = 0.5) and between the shell and insert (μ = 0.16). In total, the FE models consisted of 45,282 linear hexahedron elements and the implantation process was simulated in four steps: 1. Displacement driven insertion of the cup; 2. Relief of the cup; 3. Displacement driven placement of the insert; 4. Load driven insertion of the insert (maximum push-in force of 500 N). The FE model was evaluated with respect to the radial deformations of the shell and insert as well as the principal stresses in case of the ceramic inserts. The model was experimentally validated via comparison of nominal strains of the titanium shells. Results. The maximum radial deformation of the shell made of PEEK was 581 μm (insertion) and 470 μm (relief) and therefore multiple times higher compared to the Ti6Al4V shell (42 μm and 21 μm). As a result, larger deformations occurred at the PE and ceramic inserts in combination with the PEEK shell. Partially, the deformations were above an usual clearance of 100 μm. When the ceramic insert was combined with the shell made of PEEK, maximum principal stresses in the ceramic insert amounted to 30 MPa and were clearly lower than approved bending strength of the ceramic material (948 MPa). Conclusion. The examined acetabular shell made of PEEK was intensively deformed during insertion compared to the geometrically identical Ti6Al4V shell and is therefore not suitable for modular acetabular cups. In future studies it should be clarified to what extent acetabular cups with shells made of carbon fiber reinforced PEEK materials with higher stiffness lead to reduced deformations during the insertion procedure

Aim. To introduce and promote a new technic and a new component using the 3D technology in the extreme acetabular revisions. Method. Since 2012, 13 patients, nine women and four men, were treated, 12 for a chronic complex PJI and one for an aseptic loosening. The average age was 75 years old (60 -90 years), the average follow-up 18,6 months (7–36 months). The revisions were bipolar in 12 cases and unipolar in one case for the oldest patient. For the septic cases, we performed 7 one stage procedure and 5 two stages. The femoral components were in 7 cases a modular stem, in 5 cases a massive component and a total femur. All these massive components were combined with a cemented double cup. The bone loss was evaluated with the AAOS, the Praposky and the Saleh classifications. A preoperative and postoperative Oxford score was used. Results. The bone loss are major; 9 stades III, 4 IV for the AAOS classification, 7 III A, 6 III B for the Praposky and 3 III, 6 IV, 4 V for the Saleh classification. The classifications weren't change by the component removal. 10 components were implanted without using cement. For the three cemented implants, the bone loss interested the columns and the roof. An acetabular disruption isn't a contrindication of an uncemented option. We report one early failure, in relation with no surgical postoperative complications. A good preoperative anchorage had never failed in the follow-up. The preoperative Oxford score was on average 8,9 (4–15) and the postoperative 33,6 (16–44). We report one early failure f a two stage procedure. Two patients underwent a recovery for partial change with no custom made implant involvement. In doing so, we have found that these cement less implants were well integrated and stable two months after the implantation. The most significant events are skin complications always after an extensive debridement, treated systematically by an iterative debridement. None of these complications appear to be related to the use of these implants. Conclusions. It's the first series which reports the use of the powder technology for a custom made component. In our series, it interests specific situations; elderly patients failing conventional medico-surgical strategies in complex functional and PJI. First results are really promising. This technology simplifies the complex acetabular reconstructions. It's a key point for the immediate postoperative functional management and to limit complications

A large number of short stem prosthesis for hip arthroplasty has been introduced in the last years. The main aim of this device is to preserve the proximal bone stock in order to facilitate revisions in the future. Furthermore there is an increase in young and active patients in total hip arthroplasty that's why it's important to consider minimally invasive, muscle-considering procedures. Short stems allow to make minimal invasive approaches easier and improve the biomechanical reconstruction. However, there is a large increase of publication about short stems there is still little data about survival and revision rates. We report about the outcome of 81 patients, who have recieved NANOS short stem prosthesis between October 2012 and April 2014. The average age of the patient was 61,6. The oldest patient was 78 years old and our youngest patient was 41 years old. The main diagnoses were osteoarthritis in 67 patients, dysplastic osteoarthritis in 8 patients and avascular necrosis of the femoral head in 6 patients. We have included 37 female patients and 44 male patients. 3 patients had the surgery on both sides. The average operating time was 75,2 min ± 20,1 min and the average grading of patients for surgical procedures of the American Society of Anesthesiologists was 1,8±0,7. The patients were hospitalized 9,6 days ± 2,9 days. The average BMI was 28,2±5,2. Along with demographic data and co-morbidities, the Harris Hip Score was recorded pre-operatively and at follow-up. The Harris Hip Score increased from 36,6 ± 14,5 pre-operatively to 94,5 ± 8,8 at the final follow-up. None of the 81 stems were revised this corresponds to a to a survival rate of 100%. Two of the patients suffered from a hip dislocation which was treated in both cases conservative. In further consequence unfortunately one of those patients thrombosed and suffered from a pulmonary embolism. The x-rays haven't shown any radiolucent lines in any patients. All in all our patients reported about an high post-operative satisfaction. The clinical and radiographic results encouraged us to continue to use short stems with metaphyseal anchorage. However, there must be more long-term results to confirm our excellent mid term results

Background. Open-wedge high tibial osteotomy (OWHTO) is an operation involving proper load re-distribution in the treatment for medial uni-compartmental arthritis of the knee joint. Therefore, stable fixation is mandatory for safe healing of this additive type of osteotomy to minimize the risk of non-union and loss of correction. For stability, screws provide optimal support and anchorage of the fixator in the condylar area without risking penetration of either the articulating surface. The purpose of the study was to evaluate the screw insertion angle and orientation with an anatomical plate that is post-contoured to the surface geometry of the proximal tibia after OWHTO. Methods. From March 2012 to June 2014, 31 uni-planar and 38 bi-planar osteotomies were evaluated. Postoperative computed tomography data obtained after open wedge high tibial osteotomy using a locking plate were used for reconstruction of the 3 dimensional model with Mimics v.16.0 of the proximal tibia and locking plate. Measurement data were compared between 2 groups (gap lesser than or equal to 10 mm (Group 1) and gap greater than 10 mm(Group 2)). These data were also compared between the uniplanar (Group 3) and bi-planar (Group 4) osteotomy groups. Result. The dimensions of ‘L1’, ‘L2’, and ‘a’ were not statistically different, regardless of the correction degree and operative technique. Also, X1 and X3 were not statistically different, regardless of the correction degree and operative technique. In the axial plane, the angles ‘A_θ1, A_θ2, A_θ3, and A_θ4’ of screw insertion to the lateral hinge point were not statistically different, regardless of the correction degree and surgical technique(Figure 1). Also, the angles ‘C_θ1, C_θ2, C_θ3, and C_θ4’ of screw insertion to the lateral hinge point were not statistically different in the coronal plane, regardless of the correction degree and surgical technique in the coronal plane(Figure 1). Angles of screw insertion, based on quantitative assessment of the tibial bony surface to the lateral hinge point were larger at the A_θ1 and A_θ4 than A_θ2 and A_θ3 in the axial plane. Angle of the C_θ1 was smallest in the coronal plane and it was less than 90°. Angles of C_θ2, C_θ3, and C_θ4 were larger than 90°(Table 1). Discussion & Conclusion. Dimensions of the medial proximal tibia of the sagittal plane, positions of the screw hole in the sagittal plane, and angles of screw insertion of all planes were not statistically different, regardless of the correction degree and operative technique. Additionally, angles of screw insertion were larger at the most anterior and posterior screw in the axial plane and most inferior screw showed smallest angle in the coronal plane. Using a post-contoured plate, the position and angle of the screw insertion were not different in the direction of the lateral hinge, regardless of the correction degree and operative technique. In our study, we evaluated the coronal insertion angle with targeting the lowest portion of the safe zone. Therefore, most screws of the proximal fragment could be inserted in the superior oblique direction if they are targeted to the ‘Safe Zone’. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Failure of the femoral component after a primary or revision THA is commonly associated with some degree of femoral bone loss. Depending on the quantity and quality of the remaining host bone, femoral stem revision can be challenging. Twenty patients with severe proximal femoral bone loss due to prosthetic loosening were treated by Wagner cementless self-locking revision stems with a mean follow up of 24 months (range 18–36 months). The indication of revision surgery was aseptic loosening in 16 patients and septic loosening in 4 cases. At the end of the follow up the mean Harris hip score increased from 35 to 86 points. Definite radiographic evidence of bone regeneration in the bony defects was achieved within 3 months in all patients. Implantation of a Wagner cementless selflocking revision stem provided satisfactory results. The Wagner SL Revision prosthesis, firmly and rotationally stable fixed in the medullary cavity of the healthy bone distal from the original prosthetic bed, with its conical longitudinal ribs and cementless anchorage, bridges the defective prosthetic bed and hereby leads to a condition of relative mechanical stability. With time, there is active ossification in the old prosthetic bed, replacing lost bone

Introduction. Habitual dislocation of the patella is rare in children. Several procedures have been described to stabilise the patella by lateral release and medial check-reins. The results are unpredictable. The failure is probably due to passive stretching of the static stabilisers of the patella ie. tendons and capsule. The aim of this paper is to describe the outcome of Pes Anserinus transfer for habitual dislocation of the patella in children. Methods. Eleven children (13 knees) were reviewed retrospectively between 1990 and 2008 following surgical realignment. The age ranged between 5-13 years. Two had ligamentous laxity. Nine dislocated in flexion and 2 in extension. Through a lateral incision the iliotibial band, vastus lateralis and lateral capsule were released. Through a medial incision the capsule was reefed and the pes anserinus insertion was transferred to the medial side of the patella and its tendon. The vastus lateralis was reattached more proximally to the rectus. Quadriceps rehabilitation was started 4 weeks following plaster immobilisation. Results. The wounds healed well. Scar thickening was seen in 2 children. Extensor lag of 20°-30° improved by 4-6 months. Squatting was possible in all at 1-8 year follow-up. One recurrence occurred following a fall. The results were graded satisfactory in 12 knees and poor in 1. Conclusion. Static stabilisers have been shown to stretch when used as check reins in habitual dislocations of the patella. The pes anserinus transposition is a broad base anchorage providing dynamic stability. It acts as a physiological, non-stretchable sling as its neurovascular supply is intact compared to severed tendon or capsules used as medial check reins

The introduction of a new implant material is not without risk. A series of worst-case scenarios were developed and tested accordingly to answer questions such as: what will happen if the implant is not placed in a good orientation? What will happen to the material after a long implantation time, e.g. 20 or more years?. To reach a higher level of safety, a new approach for the preclinical testing has been taken. The vitamys® material (a novel vitamin-doped HXLPE) followed a severe pre-clinical testing protocol, including mechanical, tribological and biocompatibility testing. The testing includes a comparison of vitamys® vs. standard-UHMWPE and other HXLPE after accelerated ageing for periods equivalent to 20 and 40 years in-vivo. Hip simulator testing was done at inclination angles from 35° to 65° to assess the “forgiveness” of the material for mal-orientation. Comparing the test results to published data, it becomes evident that the vitamin addition and the sequence of the manufacturing steps both have a significant effect of the resulting mechanical, ageing and wear properties. In contrast to UHMWPE or HXLPE without antioxidant, the vitamys material behaves in a very “forgiving” manner: Hip simulator testing of vitamys at high inclination angles and even with severely aged material revealed no increase of wear rates. The vitamys material was first introduced in a monoblock polyethylene cup with a thin Ti-particle coating, the RM-Pressfit vitamys® acetabular cup (Mathys Ltd Bettlach, Switzerland). Its first implantation occurred in Sept. 2009. Since then, a total of nearly 500 implantations have been documented in a prospective multi-centre clinical study involving 11 clinics in 5 countries (CH, DE, FR, NL and NZ). Based on the pre-clinical testing and its first clinical experience, we have reason to believe that the RM-Pressfit vitamys® possesses interesting and unique features such as high elasticity (no stress-shielding), high ageing and wear resistance combined with clinically proven biological anchorage – making it theoretically suitable for a whole range of patients, including the young and active

The spinal motion segment relies critically on there being a mechanically robust integration between the compliant disc tissues and the rigid vertebral bone. Achieving such integration represents a major structural challenge. This study explores in detail the microstructural mechanisms involved in both the nucleus-endplate and annulus-endplate regions. Vertebra-nucleus-vertebra samples were obtained from mature ovine lumbar motion segments and subjected to a novel ring-severing technique designed to eliminate the strain-limiting influence of any remaining annular elements. These samples were loaded in tension and then chemically fixed in order to preserve the stretched fibre arrangement, and then decalcified. Annulus-vertebra samples were similarly treated but without any loading prior to fixation. Differential interference contrast optical microscopy was then used to image at high resolution cryosectioned slices of the still integrated disc-vertebral endplate regions while maintained in their fully hydrated state. Structural continuity across the nucleus-endplate junction was sufficient for the samples to support, on average, 20 N before tensile failure occurred. Microscopic examination revealed fibres inserting into the endplates and extending continuously from vertebra to vertebra in the central nuclear region. While the fibres in the nucleus possess a significant level of structural integration with the endplates their role is not primarily a tensile one: rather, in combination with their convoluted geometry, they confer on the nucleus a form of ‘tethered’ mobility. This permits a high degree of shape change in the nucleus during normal disc function in which hydrostatic loading plays an essential role. The annular fibre bundles on entering the endplate are shown to subdivide into sub-bundles to form a 3-D multi-leaf morphology with each leaf separated by cartilaginous endplate matrix. This branched morphology increases the interface area between bundle and matrix in proportion to the number of sub-bundles formed. Our study challenges previously published views on nucleus-endplate relationships. We also show that the robust integration of the annular fibres in the endplate is achieved via a branched morphology exploiting a mechanism of shear-stress transfer, with the anchorage strength optimised over a relatively short endplate insertion depth

Introduction. As population grows older, and patients receive primary joint replacements at younger age, more and more patients receive a total hip prosthesis nowadays. Ten-year failure rates of revision hip replacements are estimated at 25.6%. The acetabular component is involved in over 58% of those failures. From the second revision on, the pelvic bone stock is significantly reduced and any standard device proves inadequate in the long term [Villanueva et al. 2008]. To deal with these challenges, a custom approach could prove valuable [Deboer et al. 2007]. Materials and methods. A new and innovative CT-based methodology allows creating a biomechanically justified and defect-filling personalized implant for acetabular revision surgery [Figure 1]. Bone defects are filled with patient-specific porous structures, while thin porous layers at the implant-bone interface facilitate long-term fixation. Pre-operative planning of screw positions and lengths according to patient-specific bone quality allow for optimal fixation and accurate transfer to surgery using jigs. Implant cup orientation is anatomically analyzed for required inclination and anteversion angles. The implant is patient-specifically analyzed for mechanical integrity and interaction with the bone based upon fully individualized muscle modeling and finite element simulation. Results. Ten clinical severe pelvic bone defects, classified Parosky IIIb, have benefited from this methodology so far. Implant outline, thickness, fixation and cup orientation was adapted to the anatomical situation. Stress shielding of the bone was eliminated by taking into account personalized muscle anatomy, bone quality and patient weight while evaluating the design performance. All implants were applied smoothly intra-operatively because of personalized case documentation provided and jig technology for accurate pre-drilling of screw holes. Postoperative imaging showed excellent results. Short term follow-up indicates good outcome for the patients treated, restoring mobility and functionality, and showing solid anchorage to the bone. Conclusion. Complex acetabular bone defects can be treated adequately and efficiently, using a personalized solution which addresses both patient's and surgeon's needs

The foot and ankle are very commonly affected in various paralytic conditions. Paralysis of different muscles acting on the foot results in characteristic gait aberrations. The gait abnormalities are a result of one or more of the consequences of paralysis including: loss of function, muscle imbalance, deformity and instability of joints. The aims of treatment of the paralysed foot and ankle are to: make the foot plantigrade, restore active dorsiflexion during the swing phase of gait (if this is not possible then prevent the foot from ‘dropping’ into plantar flexion during swing), ensure that the ankle and subtalar joints are stable throughout the stance phase of gait, facilitate a powerful push-off at the terminal part of the stance phase (if this is not possible, at least prevent a calcaneal hitch in terminal stance). The specific aims of treatment in each patient depend on the pattern and the severity of paralysis that is present and hence the aims are likely to vary. In order to determine what treatment options are available in a particular patient, it is imperative that a careful clinical assessment of the foot is done. Based on the clinical assessment, these questions need to be answered before planning treatment: What are the muscles that are paralysed What is the power of each muscle that is functioning? Is there muscle imbalance at the ankle, subtalar or midtarsal joints that has either already produced a deformity or has the potential to produce a deformity in future? Are there any muscles of grade V power that can be spared for a tendon transfer without producing a fresh imbalance or instability. To facilitate responses to these questions, the muscle power of each muscle can be charted on a template that facilitates graphic representation of the muscle balance around the axes of the ankle and subtalar joints. This assessment clarifies whether a tendon transfer is a feasible option. If a tendon transfer is considered feasible, then the following questions also need to be answered: Is there a fixed, static deformity that needs to be corrected prior to a tendon transfer? If a tendon transfer was performed, would the child be capable of comprehending and cooperating with the post-operative muscle re-education programme?. The decision-making process will be outlined and the use of the template in choosing the tendon transfer and deciding the site of anchorage of the transferred tendon will be explained. With suitable examples the choice of tendon transfers in different patterns of paralysis would be illustrated

Introduction:. Leg length and offset discrepancy resulting from Total Hip Replacement (THR) is a major cause of concern for the orthopaedic community. The inability to substitute the proximal portion of the native femur with a device that suitably mimics the pre-operative offset and head height can lead to loss of abductor power, instability, lower back pain and the need for orthodoses (1). Contemporary devices are manufactured based on predicate studies (2–4) to cater for the variations within the patient demographic. Stem variants, modular necks and heads are often provided to meet this requirement. The number of components and instruments that manufacturers are prepared to supply however is limited by cost and an unwillingness to introduce unnecessary complexity. This can restrict their ability to achieve the pre-osteoarthritic head centre for all patient morphologies. Corin has developed bone conserving prosthesis (MiniHip™) to better replicate the physiological load distribution in the femur. This study assesses whether the MiniHip™ prosthesis can better match the pre-osteoarthritic head centre for patient demographics when compared to contemporary long stem devices. Method:. The Dorr classification is a well accepted clinical method for defining femoral endosteal morphology (5). This is often used by the surgeon to select the appropriate type and size of stem for the individual patient. It is accepted that a strong correlation exists between Flare Index (FI), characterising the thinning of cortical walls and development of ‘stove-pipe’ morphology, and age, in particular for females (Table 1) (3). A statistical model of the proximal femur was built from 30 full length femoral scans (Imorphics, UK). Minimum and maximum intramedullary measurements calculated from the statistical model were applied to relationships produced by combining Corins work with that of prior authors (Table 2) (2; 3; 6). This data was then used to generate 2D CAD models into which implants were inserted to compare the head centres achievable with a MiniHip™ device compared to those of a contemporary long stem. Results:. Results for the CAD overlay indicated the MiniHip prosthesis is better suited to restoring head centre for a range of morphological variations (Figure 1). In contrast, the long stem prosthesis requires a larger size range and increased inventory in terms of stem variants and modular components to achieve the same array of head centres. The disparity between the Corin FI and that of prior authors can be accounted for by the methods employed; the greyscale-based edge detection (Imorphics, UK) compared to a manual identification method. Discussion:. By overlaying the Corin MiniHip™ over the CAD representation of anticipated flare index, it is evident that the MiniHip™ stem is more suitable for the anticipated range of morphologies. The versatility of this design enables the restoration of head height and offset regardless of canal geometry, degree of offset and or CCD angle. This is not the case for contemporary long stem devices which rely on a more diaphyseal region for anchorage and stability and therefore depend on stem variants and modularity to cater for morphology changes