Introduction

Robotic TKA allows for quantifiable precision performing bone resections for implant realignment within acceptable final component and limb alignments. One of the early steps in this robotic technique is after initial exposure and removal of medial and lateral osteophytes, a “pose-capture” is performed with varus and valgus stress applied to the knee in near full extension and 90° of flexion to assess gaps. Component alignment adjustments can be made on the preoperative plan to balance the gaps. At this point in the procedure any posterior osteophytes will still be present, which could after removal change the flexion and extension gaps by 1–3mm. This must be taken into consideration, or changes in component alignment could result in over-correction of gaps can occur.

Background. Osteophytes in the posterior compartment of the knee pose a challenge in achieving soft tissue balance during total knee arthroplasty (TKA). Previous investigations have demonstrated the importance of various factors involved in obtaining flexion and extension gap balance, including the precision of femoral and tibial bone cuts as well as tensioning of the supporting pericapsular soft tissue structures (ligaments, capsule, etc.). However, the role of posterior compartment osteophytes has not been well studied. We hypothesize that space-occupying posterior structures affect soft tissue balance, especially in lesser degrees of flexion, in a cadaveric TKA model. Methods. Five cadaveric limbs were acquired. CT scans were obtained of each specimen to define the osseous contours. 3D printed specimen-specific synthetic osteophytes were fabricated in two sizes (10mm and 15mm). Posterior-stabilized TKAs were performed. Medial and lateral contact forces were measured during a passive range of motion using OrthoSensor ® (Dania Beach, FL) technology. For each specimen, trials were completed without osteophytes, and with 10mm and 15mm osteophytes applied to the posterior medial femur, with iterations at 0°, 10°, 30°, 45°, 60°, and 90° of flexion. These were recorded across each specimen in each condition for three trials. Tukey post hoc tests were used with a repeated measures ANOVA for statistical data analysis. Results. The presence of posterior medial osteophytes increased asymmetric loading from 0°– 45° of flexion. The 25–75% bounds of variability in the contact force was less than 3.5lbs. Conclusions. In this cadaveric TKA model, posterior femoral osteophytes caused an asymmetric increase in contact forces from full extension continuing into mid-flexion. To avoid unnecessary soft tissue releases, we recommend early removal of posterior femoral osteophytes prior to performing ligament releases to obtain desired soft tissue balance during TKA

INTRODUCTION. In total hip arthroplasty, preoperative planning is almost indispensable. Moreover, 3-dimensional preoperative planning became popular recently. Anteversion management is one of the most important factors in preoperative planning to prevent dislocation and to obtain better function. In arthritic hip patients osteophytes are often seen on both femoral head and acetabulum. Especially on femoral head, osteophytes are often seen at posterior side and its surface creates smooth round contour that assumes new joint surface. (Fig. 1). We can imagine new femoral head center tracing that new joint surface. OBJECTIVES. In the present study, the posterior osteophytes are compared in osteoarthritic patients and other patients. MATERIALS & METHODS. Anteversion and new anteversion which was reduced by osteophyte formation were assessed in 28 hip CAT scans, (22 arthritic hips, 6 avascular necrotic hips). RESULTS. Only in arthritic patients, osteophytes on posterior side were observed. The anteversion was 33.7+/− 13.0 degree in arthritic patients, which was reduce to 29.7+/−13.1 degree. The mean difference was 4.0+/−4.7 degree reduction. In AVN patients the mean anteversion was 21.4 +/− 9.40 in AVN patients. No reduction was observed in AVN patients. DISCUSSION. Osteophytes are often created to make the biomechanical situation better. This phenomenon is possiblly explained that those posterior osteophytes have been formed for proper reduction of excessive anteversion

Purpose. The effects of Acetabular Rim Osteophytes (ARO) in Total Hip Arthroplasty (THA), has not been quantified. During THA their presence and location is variable, and the effect on post-operative Range of Motion (ROM) is unknown. The purpose of this study was to evaluate the ROM of a modern hip implant in five cadaver models utilizing computerized virtual surgery, and to analyze the effect of AROs given their location on the acetabulum, and position of the prosthesis during motion. Method. CT scans of five cadaveric pelvises and femurs were used to create 3-D Models. Surgery, using virtual Stryker components was then performed to restore the natural anatomic offset and leg length. ROM to impingement was evaluated for each model in eight vectors: flexion/extension, internal/external rotation, abduction/adduction, and 90 degrees of flexion with internal/external rotation. An Osteophyte Impingement Model was then created by elevating the natural acetabular rim by 10 millimeters circumferentially in each virtual cadaver pelvis. Using the same THA components, ROM was then evaluated in this pelvic model and compared to the cadaveric models. Results. ROM in the Osteophyte Impingement Model yielded a statistically significant decrease in five of the eight vectors tested, when compared to the Cadaveric Model: Flexion, Extension, External Rotation, Flexion to 90 degrees with Internal Rotation, and Flexion to 90 degrees with External Rotation. Only 3 of these 5 vectors were within normal human physiological ROM: Flexion, External Rotation, and Flexion to 90 degrees with Internal Rotation. The osteophyte model yielded a decrease in absolute ROM in the following: Flexion to 101 vs 113 degrees (p= 0.03), External Rotation to 30.4 vs 49.5 degrees (p= 0.01), and Flexion to 90 degrees with Internal Rotation 16.7 vs 31.6 degrees (p=0.01). When mapped on the acetabulum of right-sided hip, with the 12 o'clock position as the superior pole of the acetabulum, impingement on the osteophyte was noted at the following locations: with Flexion, and Flexion to 90 degrees with Internal Rotation, impinged was noted between 1 and 2 o'clock on the acetabulum. In External Rotation impinged occurred between 7 and 8 o'clock on the acetabulum. Conclusion. This study showed that a 10 millimeter osteophyte can potentially decrease range of motion and lead to impingement in THA in certain planes of motions: Flexion, External Rotation and Flexion to 90 degrees with Internal Rotation. The location of this impingement is between the 1 and 2 o'clock in Flexion, and Flexion to 90 degrees with Internal Rotation. In External Rotation, the impingement will occur between the 7 and 8 o'clock. The above applies to a right-sided acetabulum, the left side will demonstrate the mirror image of this impingement: Between the 10 to 11 o'clock, and 4 to 5 o'clock positions respectively. Osteophytes 10 millimeters or more in height at these positions should be carefully evaluated intra-operatively and removed safely if possible

Aims

Sagittal plane imbalance (SPI), or asymmetry between extension and flexion gaps, is an important issue in total knee arthroplasty (TKA). The purpose of this study was to compare SPI between kinematic alignment (KA), mechanical alignment (MA), and functional alignment (FA) strategies.

While osteophytes are a hallmark feature of knee osteoarthritis (OA), there is limited information regarding their location. In particular, it is unknown whether osteophytes develop in patient-specific locations or if there are consistent osteophyte locations among OA knees. This lack of data mainly stems from the fact that osteophytes have been mostly assessed with scores quantifying their size or severity but not their location. Given the important role that bone could play in OA development and the option it offers for OA treatment, there is a need to better understand the osteophyte locations. This study aimed to develop a method to compare osteophyte locations among knees and determine the overlapping ratio. CT arthrogram of 11 medial-compartment OA tibias (Kellgren-Lawrence grade ≥ 3) were segmented to locate the osteophytes and a bone matching technique was used to report the osteophyte locations of the 11 knees on a single reference tibia. This newly proposed method was highly reproducible (intra-operator ICC = 0.89). When used to compare the 11 tibias, it showed that more than 60% of the overall subosteophytal area, defined as the reference bone area covered by at least one osteophyte from one knee, was common to less than two tibias. Moreover, less than 20% of the overall subosteophytal area was common to five or more tibias. The results of this study suggest that osteophyte locations are specific to each knee. Future work should determine the relationships with mechanical loading, as this could explain the high inter-patient variability.

Introduction: Vertebral body osteophytes are common in elderly spines, but their mechanical function is unclear. Do they act primarily to reduce compressive stress on the vertebral body, or to stabilise the spine in bending? How do they influence estimates of vertebral strength based on bone mineral density (BMD)?

Methods: Spines were obtained from cadavers aged 51–92 yrs (mean 77 yrs) with radiographic evidence of vertebral osteophytes (mostly antero-lateral). Twenty motion segments, from T5-T6 to L3–L4, were dissected and loaded a) in compression to 1.5 kN, and b) in bending to 10–25 Nm. Vertebral movements were tracked at 50 Hz using an optical MacReflex system. Bending tests were performed in random order, in flexion, extension, and lateral bending. Resistance to bending and compression was measured before and after surgical excision of all osteophytes. The bone mineral content (BMC) and density (BMD) of each vertebra was measured in the antero-posterior direction, using DXA. Density measurements were repeated after excision of all osteophytes. ANOVA was used to detect changes after osteophyte excision, and regression was used to examine the influence of osteophyte size and BMC.

Results: Removal of osteophytes reduced-vertebral BMD by 9% (SD 13%). Compressive stiffness was affected rather more, being reduced by an average 17% (p< 0.05). Bending stiffness was reduced in flexion and extension by 50% and 39% respectively (p< 0.01), and in left and right lateral bending by 41% and 49% respectively (p< 0.01). Osteophyte removal increased the neutral zone and range of motion in each mode of bending. Most mechanical changes were proportional to osteophyte mass, and to changes in BMC (p< 0.01).

Conclusions: Vertebral body osteophytes primarily stabilise the spine in bending, and do not play a major role in resisting compression. Animal models show that osteophytes grow in response to experimentally-induced instability, so their formation can be seen as mechanically-adaptive (restoring stability) rather than degenerative. The influence of typical osteophytes on compressive stiffness is greater than their influence on vertebral BMD (17% vs 9%) so predictions of vertebral compressive strength based on BMD measurements are likely to be under-estimates if osteophytes are present.

We present to you a match-controlled study assessing co-existing arthroscopic findings during hip arthroscopy in patients with an intraoperative diagnosis of a central acetabular osteophyte (CAO). We feel that this manuscript is both pertinent and timely.

Recent literature has described the entity of central acetabular impingement, in which an osteophyte of the cotyloid fossa impinges against the superomedial femoral head and fovea. The technique for central acetabular decompression has also been described to treat this entity. The primary purpose of this study was to report the prevalence of femoral head articular damage in a matched cohort of patients with and without central acetabular osteophyte (CAO) that was identified during hip arthroscopy. A secondary purpose was to identify the rates of co-existing intraarticular pathology in both patient groups.

Intraoperative data was collected prospectively on all patients undergoing hip arthroscopy at our institution between February 2008 to March 2015,. The inclusion criteria for this study were the presence of a CAO identified during hip arthroscopy for a labral tear and/or femoroacetabular impingement (FAI). Exclusion criteria were revision surgeries, Tönnis grade 1 and higher, and previous hip conditions such as Legg-Calves-Perthes disease, avascular necrosis, and prior surgical intervention. The matched cohort control group was selected based on gender, age within 5 years, body mass index (BMI), and workers' compensation claim, on a 1:3 ratio to patients who underwent hip arthroscopy for a labral tear and/or FAI and did not have a CAO.

The CAO group consisted of 126 patients, which were matched to 378 patients in the control group. The grades of femoral and acetabular chondral damage were significantly different between the two groups (p<0.01).

This study showed that patients with CAO had a significantly higher prevalence of femoral and acetabular chondral damage, size of articular defects on both surfaces and the prevalence of LT tears compared to matched controls.

Introduction: Vertebral body osteophytes are common in elderly spines, but their mechanical function is unclear. Do they act primarily to reduce compressive stress on the vertebral body, or to stabilise the spine in bending?

Methods: Spines were obtained from cadavers aged 51–92yrs (mean 77yrs) with radiographic evidence of vertebral osteophytes (mostly antero-lateral). Twenty motion segments, from T5-T6 to L3-L4, were dissected and loaded a) in compression to 1.5kN, and b) in bending to 10–25Nm. Vertebral movements were tracked at 50Hz using an optical MacReflex system. Bending tests were performed in random order, in flexion, extension, and lateral bending. Resistance to bending and compression was measured before and after surgical excision of all osteophytes. Bone mineral content (BMC) of osteophytes was measured using DXA. ANOVA was used to detect changes after osteophyte excision, and regression was used to examine the influence of osteophyte size.

Results: Compressive stiffness was reduced by an average 17% following osteophyte removal (p< 0.05). In flexion and extension, bending stiffness was reduced by 60% and 79% respectively (p< 0.01). In left and right lateral bending, stiffness was reduced by 42% and 49% respectively. Osteophyte removal increased the neutral zone and range of motion in each mode of bending, and changes were proportional to osteophyte mass and BMC (p< 0.01).

Conclusion: Vertebral body osteophytes primarily stabilise the spine in bending, and do little to resist compression, despite their considerable BMC. Predictions of vertebral compressive strength based on BMC measurements are likely to be over-estimates if large osteophytes are present.

Aim: To determine the incidence of adjacent level osteophytes in patients who have had anterior cervical fusion using an anterior cervical plate as compared to those who are fused without an anterior cervical plate.

Design: We retrospectively reviewed the lateral radiograms of sixty two patients who have had an anterior cervical fusion with a minimum follow up of twelve months.

Materials and methods: We looked for the development of adjacent level osteophytes in these patients at their final follow up, which was generally at the time radiological fusion. There were 27 patients in the first group who had an anterior cervical plate used to fix the vertebrae in addition to the Cervios cage, while the 35 patients in the second group in whom only a Rabea cage was used for the fusion. The mean follow-up was 20.6 months (range 12–48).

Results: 64.3% of the patients who had an anterior cervical plate developed adjacent level osteophytes while none of the patients who have had the fusion without the cage developed the osteophytes.

Conclusion: We found the patients who had an anterior cervical interbody fusion using a plate had a significant risk of developing adjacent level osteophytes while this is not seen in patients who do not have the plate for the fixation.

Newer prosthetic total knee arthroplasty (TKA) designs as well as unicondylar TKAs spare the anterior cruciate ligament (ACL). Although success of these procedures requires near normal ACL function, little has been written about the arthritic ACL.

This study was designed to evaluate the relationship between cross sections of the intercondylar notch and the macroscopic condition of ACL degeneration. Thirty osteoarthritic patients who underwent TKA as a result of severe osteoarthritis were randomly selected. Occupation rate of the osteophytes to the notch width were measured at the anterior 1/3, middle 1/3, and posterior 1/3 notche images obtained from preoperative tunnel view. Macroscopic conditions of the ACL and PCL were classified into four types of Normal, Frayed, Partial rupture, and Absent.

The macroscopic ACL conditions were Normal: 9 cases, Frayed: 9 cases, Partial rupture: 9 cases, and Absent: 3 cases. The macroscopic PCL conditions were Normal: 24 cases, Frayed: 3 cases, Partial rupture: 3 cases, and Absent: 0 case.

Occupation rate of the osteophytes to the notch correlated to the preoperative femorotibial angle (p< 0.05). In terms of ACL, the occupation rate of the osteophytes to the notch were 22.9%, 28.8%, 46.0%, and 81.8% in Normal, Frayed, partial ruptured, and Absent, respectively. The patients with more than 40% occupation rate showed either partial rupture or absent of the ACL during the surgery.

We conclude that occupation rate of the osteophytes to the notch is a good predictor of evaluating the ACL degeneration in osteoarthritic knee.

The influence of Posterior Cruciate Ligament (PCL) removal and re-establishment of the posterior condylar recess on flexion and extension gaps width during posterior-stabilized Total Knee Arthroplasty (TKA) is still controversial. It has been reported that PCL resection lead to a selective increase of the flexion space of 3–4 mm, creating a potential for instability in flexion. Our hypothesis was that these surgical steps will equally increase both gaps. Measurements of the flexion and extension gaps heights were obtained during different surgical phases in 50 consecutive primary posterior-stabilised TKAs using a tensor device and a calibrated torque wrench. There was a slight symmetrical increase in both gaps after PCL release. In extension the width of the gap increased on average 1.3 mm and 1.0 mm in the medial and lateral compartment respectively. The same pattern was observed in flexion, averaging 1.3 mm medially and 1.3 mm laterally. Another increase of the two gaps was observed after the posterior condylar osteophytes were removed and the posterior recess was re-established. The gaps in extension increased, with respect to the baseline value, on average 1.8 mm medially and 1.8 mm laterally, while in flexion the increase averaged 2.0 mm and 2.2 respectively on the medial and lateral side. Again there were no statistical differences between flexion and extension gaps. No independent differences between the flexion and extension gaps were found in any considered surgical phase. PCL removal and re-establishment of posterior condylar recess does not seem to require any additional consideration in gap balancing during posterior-stabilized TKA.

Objectives. Osteophytes are products of active endochondral and intramembranous ossification, and therefore could theoretically provide significant efficacy as bone grafts. In this study, we compared the bone mineralisation effectiveness of osteophytes and cancellous bone, including their effects on secretion of growth factors and anabolic effects on osteoblasts. Methods. Osteophytes and cancellous bone obtained from human patients were transplanted onto the calvaria of severe combined immunodeficient mice, with Calcein administered intra-peritoneally for fluorescent labelling of bone mineralisation. Conditioned media were prepared using osteophytes and cancellous bone, and growth factor concentration and effects of each graft on proliferation, differentiation and migration of osteoblastic cells were assessed using enzyme-linked immunosorbent assays, MTS ((3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)) assays, quantitative real-time polymerase chain reaction, and migration assays. Results. After six weeks, the area of mineralisation was significantly higher for the transplanted osteophytes than for the cancellous bone (43803 μm. 2. , . sd. 14660 versus 9421 μm. 2. , . sd. 5032, p = 0.0184, one-way analysis of variance). Compared with cancellous bone, the conditioned medium prepared using osteophytes contained a significantly higher amounts of transforming growth factor (TGF)-β1 (471 pg/ml versus 333 pg/ml, p = 0.0001, Wilcoxon rank sum test), bone morphogenetic protein (BMP)-2 (47.75 pg/ml versus 32 pg/ml, p = 0.0214, Wilcoxon rank sum test) and insulin-like growth factor (IGF)-1 (314.5 pg/ml versus 191 pg/ml, p = 0.0418, Wilcoxon rank sum test). The stronger effects of osteophytes towards osteoblasts in terms of a higher proliferation rate, upregulation of gene expression of differentiation markers such as alpha-1 type-1 collagen and alkaline phosphate, and higher migration, compared with cancellous bone, was confirmed. Conclusion. We provide evidence of favourable features of osteophytes for bone mineralisation through a direct effect on osteoblasts. The acceleration in metabolic activity of the osteophyte provides justification for future studies evaluating the clinical use of osteophytes as autologous bone grafts. Cite this article: K. Ishihara, K. Okazaki, T. Akiyama, Y. Akasaki, Y. Nakashima. Characterisation of osteophytes as an autologous bone graft source: An experimental study in vivo and in vitro. Bone Joint Res 2017;6:73–81. DOI: 10.1302/2046-3758.62.BJR-2016-0199.R1

Osteophytes are bony spurs on normal bone that develop as an adaptive reparative process due to excessive stress at/near a joint. As osteophytes develop from normal bone, they are not always well depicted in common imaging techniques (e.g. CT, MRI). This creates a challenge for preoperative planning and image-guided surgical methods that are commonly incorporated in the clinical routine of orthopaedic surgery. The study examined the accuracy of osteophyte detection in clinical CT and MRI scans of varying types of joints. The investigation was performed on fresh-frozen ex-vivo human resected joints identified as having a high potential for presentation of osteophytes. The specimens underwent varying imaging protocols for CT scanning and clinical protocols for MRI. After dissection of the joint, the specimens were subjected to structured 3D light scanning to establish a reference model of the anatomy. Scans from the imaging protocols were segmented and their 3D models were co-registered to the light scanner models. The quality of the osteophyte images were evaluated by determining the Root Mean Square (RMS) error between the segmented osteophyte models and the light scan model. The mean RMS errors for CT and MRI scanning were 1.169mm and 1.419mm, respectively. Comparing the different CT parameters, significance was achieved with scanning at 120kVp and 1.25mm slice thickness to depict osteophytes; significance was also apparent at a lower voltage (100kVp). Preliminary results demonstrate that osteophyte detection may be dependent on the degree of calcification of the osteophyte. They also illustrate that while some imaging parameters were more favourable than others, a more accurate osteophyte depiction may result from the combination of both MRI and CT scanning

The objective of our study is to evaluate the accuracy of an X-ray based image segmentation system for patient specific instrument (PSI) design or any other surgical application that requires 3D modeling of the knee. The process requires two bilateral short film X-ray images of knee and a standing long film image of the leg including the hip and ankle. The short film images are acquired with an X-ray positioner device that is embedded with fiducial markers to correct for setup variation in source and cassette position. An automated image segmentation algorithm, based on a statistical model that couples knee bone shape and radiographic appearance, calculates 3D surface models of the knee from the bi-lateral short films (Imorphics, Manchester UK) (Figure 1). Surface silhouettes are used to inspect and refine the automatically generated segmentation; the femur and tibia mechanical axes are then calculated using automatically generated surface model landmarks combined with user-defined markups of the hip and ankle center from the standing long film (Figure 2). The accuracy of the 2D/3D segmentation system was evaluated using simulated X-ray imagery generated from one-hundred osteoarthritic, lower limb CT image samples using the Insight Toolkit (Kitware, Inc.). Random, normally distributed variations in source and cassette positions were included in the dataset. Surface accuracy was measured using root-mean-square (RMS) point-to-surface (P2S) distance calculations with respect to paired benchmark CT segmentations. Landmark accuracy was calculated by measuring angular differences between the 2D/3D generated femur and tibia mechanical tibia with respect to paired CT-generated landmark data. The paired RMS sample mean and standard deviation of femur P2S errors on the distal quarter of the femur after auto-segmentation was 1.08±0.20mm. The RMS sample mean and standard deviation of tibia P2S errors on the proximal quarter of the tibia after auto-segmentation was 1.16±0.25mm. The paired sample mean and standard deviation of the femur and tibia mechanical axis accuracy with respect to benchmark CT data landmarks were 0.02±0.42[deg] and −0.33±0.56[deg], respectively. Per surface-vertex sample RMS P2S errors are illustrated in Figure 3. Visual inspection of RMS results found the automatically segmented femur to be very accurate in the shaft, distal condyles, and posterior condyles, which are important for PSI guide fit and accurate planning. Similarly, the automatically segmented tibia was very accurate in the shaft and plateaus, which are also important for PSI guide fit. Osteophytes resulted in some RMS differences (Figure 3), as was expected due to the know limitations of osteophyte imaging with X-ray. PSI-type applications that utilize X-ray should account for osteophyte segmentation error. Overall, our results based on simulated radiographic data demonstrate that X-ray based 2D/3D segmentation is a viable tool for use in orthopaedic applications that require accurate 3D segmentations of knee bones

Stiffness after a TKA might be said to be present when reasonable functions of daily living cannot be performed or can only be performed with difficulty or pain. This will certainly be true if flexion is less than 75 degrees and/or there is a 15-degree lack of full extension. The purpose of this presentation is to discuss the causes of a stiff TKA, consider the aspects of surgical technique that are associated with the occurrence of stiffness, present post-surgical management that impacts on the development of stiffness and summarise the results of the surgical treatment of a stiff TKA. Pre-operative stiffness is strongly correlated with post-operative limitation of motion. Therefore, pre-surgical measures to optimise motion should be carried out. These include appropriate physical therapy, adequate pain management and a discussion with the patient of the issues likely to affect post-operative range of motion. It is particularly important to discuss with the patient appropriate expectations with regard to the likely range of motion that will be achieved following TKA surgery. There are a number of steps that can be taken during the performance of a TKA that have an impact on range of motion. Osteophytes must be removed. Correctly sized implants must be used to avoid over-stuffing the tibio-femoral and patello-femoral compartments. Mal-positioning implants and the extremity can adversely affect range of motion. Inadequate bone resection will also lead to a reduced range of motion. Improper soft tissue balancing in both flexion and extension may be associated with post-surgical stiffness. Post-operative management must include adequate pain management as well as appropriate rehabilitation. Close post-surgical surveillance will help identify those patients likely to achieve unsatisfactory range of motion. Manipulation of appropriate patients within the first 6 weeks following surgery is usually associated with a satisfactory final range of motion. When persistent stiffness occurs, an attempt must be made to identifying possible causes, including component mal-alignment or mal-rotation, component mis-sizing or mis-positioning and inadequate soft tissue balancing. The surgical treatment of a stiff total knee include: 1) arthroscopic debridement and manipulation; 2) arthrotomy with debridement; and 3) single or complete component revision. Although surgical intervention often results in improved range of motion, the results are variable and somewhat limited

Tissue engineering is a rapidly expanding field of research. Bone and cartilage engineering are being undertaken in an attempt to treat osteoarthritis and repair bone defects. In spite of extensive research little successful clinical application of this work has been seen. There are however many advances in the field that one day may have therapeutic interest. One particular area of interest is the potential for using osteophyte tissue in repairing osteoarthritic defects. Osteophytes represent an attempt by the body to regenerate bone and cartilage. They present an obvious source of cells for tissue engineering. Research ay QUT has shown that cells within the osteophytes are a better source of bone and cartilage regeneration in the laboratory than matched patient’s bone marrow stem cells. Osteoarthritis remains the ultimate challenge for orthopaedic tissue engineering. Understanding the chemical and mechanical signals occurring in osteoarthritis presents opportunities for targeted drug delivery and potential slowing of disease. We have identified changes within the MMP profile of cells at the osteochondral junction. Subchondral sclerosis appears to be associated with changes in the nature of chondrocytes deep within the cartilage layer. This transformation of chondrocytes into osteoblast-like tissue in many ways mimics the changes seen in the growth plate once maturity is reached. Understanding the parallels between these processes may help answer some of the mechanisms of the development of osteoarthritis. This talk will discuss the above topics as well as other areas of interest to an orthopaedic surgeon working within a group of 10 cell biologists

Aims

The aims of this study were: 1) to describe extended restricted kinematic alignment (E-rKA), a novel alignment strategy during robotic-assisted total knee arthroplasty (RA-TKA); 2) to compare residual medial compartment tightness following virtual surgical planning during RA-TKA using mechanical alignment (MA) and E-rKA, in the same set of osteoarthritic varus knees; 3) to assess the requirement of soft-tissue releases during RA-TKA using E-rKA; and 4) to compare the accuracy of surgical plan execution between knees managed with adjustments in component positioning alone, and those which require additional soft-tissue releases.

Bone Tissue Engineering Program, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD 4059, Australia. Osteophytes are the most remarkable and consistently distinct feature of osteoarthritis (OA). Their formation may be related to pluripotential cells in the periosteum responding to stimulus during OA. This study aimed to isolate stem cells from osteophyte tissues, and characterise their phenotype, proliferation and differentiation potential, and immuno-modulatory properties. Osteophyte derived cells were isolated from five osteophyte tissue samples collected during knee replacement surgery. These cells were characterised by the expression of cell surface antigens, differentiation potential into mesenchymal lineages, growth kinetics and modulation of allo-immune responses. Multipotential stem cells (MSCs) were identified from all osteophyte samples namely osteophyte derived MSCs (oMSCs). The surface antigen expression of oMSCs was consistent with that of mesenchymal stem cells, such as lacking the haematopoietic and common leukocyte markers (CD34, CD45) while expressing those related to adhesion (CD29, CD166, CD44) and stem cells (CD90, CD105, CD73). The longevity of oMSCs in culture was superior to that of bone marrow derived MSC (bMSCs), and they readily differentiated into tissues of the mesenchymal lineages. oMSCs also demonstrated the ability to suppress allogeneic T-cell proliferation, which was associated with the expression of tryptophan degrading enzyme indoleamine 2,3 dioxygenase (IDO). Our results showed that osteophyte derived cells had similar properties to mesenchymal stem cells in the expression of antigen phenotype, differential potential and suppression of allo-immune response. Furthermore, when compared to bMSCs, oMSCs maintained a higher proliferative capacity, which may offer an alternative source for therapeutic stem cell based tissue regeneration

The purpose of this study was to present our experience with femoral neck fractures that occurred after metal-on-metal hybrid surface arthroplasty and to assess their causation. Materials and Methods: A series of 600 metal-on-metal surface arthroplasties was performed from late 1996 to early 2003 by the primary author. Failures during this period were assessed radiographically and with implant retrieval analysis to determine the cause of failure. There were five femoral neck fractures in this series (0.83%). In addition, a review of the femoral neck fracture cases identified from the Conserve+ Multi-Center IDE was performed (19 femoral neck fractures in 1203 cases, 1.6%). Results: Lead Author Series: Four of the five fractures occurred at the component–neck junction in the first five months after surgery (average three months). All were associated with a traumatic episode but they also had structural and or technical risk factors, which weakened the constructs. The most important technical deficiency was failure to cover all of the reamed bone with the component in three of the five. One fracture was associated with histological changes consistent with osteonecrosis of the head in a case of overpenetration of cement in very soft bone. Multi-Center IDE: Additional risk factors were identified among which impingement of the neck with the acetabular component, notching of the lateral femoral neck cortex, and leaving the femoral component proud (not completely seated). Conclusion: It is important to avoid or at least minimize notching the femoral neck by performing the cylindrical reaming at the recommended angle of 140° and to stop reaming before the reamer touches the lateral cortex. Osteophytes should be judiciously removed only if there is a notable impingement when the hip is at 90° of flexion and internally rotated. We believe that understanding the factors that contribute to femoral neck fracture after surface arthroplasty may reduce the already low incidence of this mode of failure