The goal of this study was to identify the effect of mismatches in the subchondral bone surface at the native:graft interface on cartilage tissue deformation in human patellar osteochondral allografts (OCA). Hypothesis: large mismatches in the subchondral bone surface will result in higher stresses in the overlying and surrounding cartilage, potentially increasing the risk of graft failure. Nano-CT scans of ten 16mm diameter cadaveric patellar OCA transplants were used to develop simplified and 3D finite element (FE) models to quantify the effect of mismatches in the subchondral bone surface. The simplified model consisted of a cylindrical plug with a 16 mm diameter (graft) and a washer with a 16 mm inner diameter and 36 mm outer diameter (surrounding native cartilage). The thickness of the graft cartilage was varied from 0.33x the thickness of native cartilage (proud graft subchondral bone) to 3x the thickness of native cartilage (sunken graft subchondral bone; Fig. 1). The thickness of the native cartilage was set to 2 mm. The surface of the cartilage in the graft was matched to the surrounding native cartilage. A 1 MPa pressure was applied to the fixed patellar cartilage surface. Scans were segmented using Dragonfly and meshed using HyperMesh. FE simulations were conducted in Abaqus 2019. The simplified model demonstrated that a high stress region occurred in the cartilage at the sharp bony edge between the graft and native subchondral bone, localized to the region with thinner cartilage. A 20% increase in applied pressure occurs up to 50μm away from the graft edge (primarily in the graft cartilage) for grafts with proud subchondral bone but varies little based on the graft cartilage thickness. For grafts with sunken subchondral bone, the size of the high stress region decreases as the difference between graft cartilage and native cartilage thickness decreases (Fig. 2-4), with a 200 μm high stress region occurring when graft cartilage was 3x thicker than native cartilage (i.e., greater graft cartilage thickness produces larger areas of stress in the surrounding native cartilage). The 3D models reproduced the key features demonstrated in the simplified model. Larger differences between native and graft cartilage thickness cause larger high stress regions. Differences between the 3D and simplified models are caused by heterogeneous cartilage surface curvature and thickness. Simplified and 3D FE analysis confirmed our hypothesis that greater cartilage thickness mismatches resulted in higher cartilage stresses for sunken subchondral bone. Unexpectedly, cartilage stresses were independent of the cartilage thickness mismatch for proud subchondral bone. These FE findings did not account for tissue remodeling, patient variability in tissue mechanical properties, or complex tissue loading. In vivo experiments with full-thickness strain measurements should be conducted to confirm these findings. Mismatches in the subchondral bone can therefore produce stress increases large enough to cause local chondrocyte death near the subchondral surface. These stress increases can be reduced by (a) reducing the difference in thickness between graft and native cartilage or (b) using a graft with cartilage that is thinner than the native cartilage. For any figures or tables, please contact the authors directly

Purpose. Based on a structure function relationship, bone density distribution has been described as being representative of skeletal loading. As such, computed tomography (CT) may be used to visualize the structure of femoral head subchondral bone to allow in vivo quantification of joint mechanics without the need for implanted hardware. This study aims to characterize the distribution of subchondral bone density in the femoral head. We hypothesize that a non-uniform distribution of bone density will be observed, with correlation between left and right sides for a given patient. Method. Femoral head surfaces were created bilaterally for thirty patients through semi-automatic segmentation of reconstructed CT data and used to map bone density, by shrinking them into the subchondral bone and averaging the grey values (linearly related to bone density) within five millimeters of the articular surface. Density maps were then oriented with the center of the head at the origin, the femoral mechanical axis (FMA) aligned with the vertical, and the posterior condylar axis (PCA) aligned with the horizontal. Twelve regions were created by dividing the density maps into three concentric rings at increments of thirty degrees from the horizontal, then splitting into four quadrants along the anterior-posterior and medial-lateral axes. Average bone density within each region was then calculated using histogram analysis. All analysis was performed with AmriaDEV 5.2.2 image analysis software (Visage Imaging, Carlsbad USA). Results. The regions representing the most-superior medial portion of the femoral head (one and four) were found to have significantly higher densities compared to all other regions (p<0.05). One exception to this was on the left side where region five, on the posteromedial side (adjacent but inferior to region one) was not found to be significantly different from region four (p=0.595). Significant side-to-side correlations were found for all regions (r=0.90 to r=0.40), with very strong correlations for the highest density regions (r=0.85 for region one, r=0.84 for region four). Side-to-side differences in measured bone density were seen for two of the low-density regions in the anterolateral portion of the femoral head (p<0.05). Conclusion. The locations of highest bone density on the femoral head correspond with principal contact areas found in previous investigations of loading in the human hip joint. Regions of the femoral head found to have highest average bone density, correspond well with high-density regions found previously for the acetabulum. The high correlation found between the left and right sides indicates that this tool may be used to detect early differences in bone density caused by unilateral hip pathologies, such as osteonecrosis or osteoarthritis of the femoral head, prior to the presentation of clinical symptoms

Introduction. The degree of cartilage degeneration assessed intraoperatively may not be sufficient as a criterion for patellar resurfacing in total knee arthroplasty (TKA). However, single-photon emission tomography/computed tomography (SPECT/CT) is useful for detecting osteoarthritic involvement deeper in the subchondral bone. The purpose of the study was to determine whether SPECT/CT reflected the cartilage lesion underneath the patella in patients with end-stage osteoarthritis (OA) and whether clinical outcomes after TKA without patellar resurfacing differed according to the severity of patellofemoral (PF) OA determined by visual assessment and SPECT/CT findings. Methods. This study included 206 knees which underwent TKA. The degree of cartilage degeneration was graded intraoperatively according to the International Cartilage Repair Society grading system. Subjects were classified into four groups according to the degree of bone tracer uptake (BTU) on SPECT/CT in the PF joint. The Feller's patella score and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) were assessed preoperatively and postoperative 1 and 2 years. Results. The increased BTU in the PF joint was associated with more severe degenerative cartilage changes underneath the patella (P < 0.001). The risk for the presence of denudated cartilage was greater in the high uptake group (odds ratio = 5.89). There was no association between clinical outcomes and visual grading of patellar cartilage degeneration or the degree of BTU on SPECT/CT. Discussion and Conclusions. The visual assessment of the degree of cartilage degeneration underneath the patella and preoperative SPECT/CT evaluation of the PF joint were not predictive of clinical outcome after TKA with unresurfaced patella

Introduction:. Subchondral bone density (SBD) distribution is an important parameter regarding that may be important when considering implant stability. This parameter is a reflection of the loading experienced by the joint throughout the lifetime and may be useful in pre-surgical planning and implant design. Clinically, the question of the glenoid surface preparation for TSA/RSA remains controversial, despite numerous published studies on glenoid bone morphology. To address this question, there exists a need to develop a 3D quantitative method capable of analyzing the complex glenoid bone morphology at different depths from the surface. Computed tomographic osteoabsoptiomery (CT-OAM) evaluates SBD based on the Housfield Unit (HU) value of each pixel. In this pilot study, we aimed to analyze SBD distribution of the glenoid at different depths by means of CT-OAM in male TSA subjects. Materials and Methods:. A study group of twenty male TSA patients (61–69y.o) were included in this study. Each subject obtained a pre-operative CT scan following a standardized protocol on the same CT scanner (1.25 mm slice thickness). Resultant DICOM 2D images were processed in custom-written program (VC++) and the surface of every glenoid was manually traced from the axial slices. Care was taken during the manual tracing process to exclude osteophytes and cyst formations from the resultant surface. Values of HU at every selected pixel on the surface of the glenoid were recorded. Subsequently, the layer of pixels at a 0.5 mm distance from the previous surface was virtually scraped and the HU values of new layer of pixels were recorded. This routine was repeated up to a depth of 5 mm from the glenoid surface, taking measurements on 11 virtual 3D surfaces with a thickness of 0.5 mm. Mean SBD distribution was reported for each layer and differences were compared using ANOVA and Fisher's post-hoc test. Results:. Apparent differences in mean SBD distribution were identified at every measured depth from the glenoid surface (Fig. 1). Significant differences (Tab.1) were identified between the middle range of studied surfaces (2.5–4.5 mm) when compared to the superficial (0–1.5 mm, p < 0.0001) and deep layers (5 mm, p < 0.0001). The maximum mean value of HU (1635.9 ± 35.5) was measured at 3.5 mm depth and the minimum value of HU was measured on the surface of the glenoid (1445.8 ± 31.3). Discussion:. The stability of the glenoid component in TSA prostheses is highly dependent on the SBD distribution. Controversy among orthopaedic surgeons exists regarding the depth of reaming required to prepare an arthritic glenoid. Extensive reaming may lead to the violation of the support provided by the denser subchondral bone; however, optimal match between the bone and glenoid component undersurface is highly desirable. This study demonstrates that the density of the bone is sustained up to a depth of approximately 4.5 mm from the glenoid surface, suggesting that an increased reaming may be favorable without compromising bony support

Pain and disability following wrist trauma are highly prevalent, however the mechanisms underlying painare highly unknown. Recent studies in the knee have demonstrated that altered joint contact may induce changes to the subchondral bone density and associated pain following trauma, due to the vascularity of the subchondral bone. In order to examine these changes, a depth-specific imaging technique using quantitative computed tomography (QCT) has been used. We've demonstrated the utility of QCT in measuring vBMD according to static jointcontact and found differences invBMD between healthy and previously injured wrists. However, analyzing a static joint in a neutral position is not necessarily indicative of higher or lower vBMD. Therefore, the purposeof this study is to explore the relationship between subchondral vBMDand kinematic joint contact using the same imaging technique. To demonstrate the relationship between kinematic joint contact and subchondral vBMDusing QCT, we analyzed the wrists of n = 10 participants (n = 5 healthy and n = 5 with previous wrist trauma). Participantsunderwent 4DCT scans while performing flexion to extension to estimate radiocarpal (specifically the radiolunate (RL) and radioscaphoid (RS)) joint contact area (JCa) between the articulating surfaces. The participantsalso underwent a static CT scan accompanied by a calibration phantom with known material densities that was used to estimate subchondral vBMDof the distal radius. Joint contact is measured by calculatinginter-bone distances (mm2) using a previously validated algorithm. Subchondral vBMD is presented using mean vBMD (mg/K2HPO4) at three normalized depths from the subchondral surface (0 to 2.5, 2.5 to 5 and 5 to 7.5 mm) of the distal radius. The participants in the healthy cohort demonstrated a larger JCa in the RS joint during both extension and flexion, while the trauma cohort demonstrated a larger JCa in the RL during extension and flexion. With regards to vBMD, the healthy cohort demonstrated a higher vBMD for all three normalized depths from the subchondral surface when compared to the trauma cohort. Results from our preliminary analysis demonstrate that in the RL joint specifically, a larger JCa throughout flexion and extension was associated with an overall lower vBMD across all three normalized layers. Potential reasoning behind this association could be that following wrist trauma, altered joint contact mechanics due to pathological changes (for example, musculoskeletal trauma), has led to overloading in the RL region. The overloading on this specific region may have led to a decrease in the underlying vBMD when compared to a healthy wrist. However, we are unable to conclude if this is a momentary decrease in vBMD that could be associated with the acute healing phase following trauma given that our analysis is cross-sectional. Therefore, future work should aim to analyze kinematic JCa and vBMD longitudinally to better understand how changes in kinematic JCa over time, and how the healing process following wrist trauma, impacts the underlying subchondral bone in the acute and longitudinal phases of recovery

Osteoarthritis (OA) is a chronic degenerative joint disease with cartilage degeneration, subchondral bone sclerosis, synovial inflammation and osteophyte formation. Sensory nerves play an important role in bone metabolism and in the progression of inflammation. This study explored the effects of capsaicin-induced sensory nerve denervation on OA progression in mice. This study was approved by the Institutional Animal Care and Use Committee. OA was induced via destabilization of the medial meniscus (DMM). Sensory denervation was induced by subcutaneous injection of capsaicin (90mg/kg) one week prior to DMM. One week after capsaicin injection, sensory denervation in the tibia was confirmed by immunofluorescent staining with calcitonin gene-related peptide (CGRP)-specific antibodies. Four weeks after DMM, micro-CT scans, histological analysis and RT-PCR tests were performed to evaluate OA progression. Statistical analysis was performed using SPSS 13. P values of less than 0.05 were considered statistically significant. Subcutaneous injection of capsaicin successfully induced tibial sensory denervation (n=3), which aggravated OA by increasing subchondral bone resorption. The Osteoarthritis Research Society International (OARSI) score of the capsaicin+DMM group (n=8) (11.81±2.92) was significantly higher (P=0.003) than the score of the vehicle+DMM group (n=8) (8.31±1.80). The BV/TV of the tibial subchondral bone in the capsaicin+DMM group (n=8) was 55.67%±3.08, which was significantly lower (P < 0 .001) than in the vehicle+DMM group (n=8) (86.22%±1.92). In addition, the level of expression of somatostatin in the capsaicin+DMM group (n=8) was lower than in the vehicle+DMM group (n=8) (P=0.007). Capsaicin-induced sensory denervation increased tibial subchondral bone resorption, reduced the expression of somatostatin and eventually exacerbated the existing cartilage degeneration in mice. Despite capsaicin is often used clinically to relieve OA pain, its safety is still controversial according to the OARSI guidelines for the non-surgical management of knee osteoarthritis. The findings of our study suggest that application of capsaicin, although effective in relieving pain, may accelerate the progression of existing OA

Bone marrow lesions (BMLs), identified by MRI, are defined as a region of cancellous bone with high T2 and low T1 signal intensity. They are associated with various knee pathologies including spontaneous osteonecrosis of the knee (SPONK), AVN, trauma (fracture and bone contusion), following arthroscopy and secondary to overuse (i.e., after completing a marathon). They also are commonly recognised in patients with knee OA (referred to as OA-BMLs) and their substantial importance in knee OA pathogenesis has been recently identified. Depending upon the etiology (i.e., bone contusion, overuse, etc.) of the BML, these lesions can be “acute” in nature and spontaneously resolve over time. However, OA-BMLs generally are considered to be a “chronic” condition and overtime they have been shown to often persist and increase in size. Retrieval studies following THA and TKA, in patients with a preoperatively identified BML, have greatly expanded our understanding of OA – BMLs and these investigations consistently identify the critical role subchondral bone plays in OA disease progression. Histologic, histochemical and mechanical studies of OA-BMLs demonstrate significant alternations from healthy subchondral bone. The effected bone contains regions where fibrous tissue has replaced cancellous bone, microfractures are present and vascularity is increased. There is an increased concentration of inflammatory mediators and the bone structural integrity is compromised. Standard radiographs of the knee correlate only modestly with patient symptoms, but conversely, the presence of an OA-BML is an extremely strong predictor of pain and knee joint dysfunction. Felson et al. reported this relationship. In a large group of patients with painful knee OA, 77.5% of these patients had a BML. Both the presence and size of the BML, following multiregression analysis, were significant predictors of knee pain severity. Additionally, likely secondary to inadequate subchondral bone plate support, the presence of an OA-BML is associated with subchondral bone attrition (SBA). SBA leads to collapse of the subchondral bone plate and progressive joint deformity. Based on the association of an OA-BML with pain, joint dysfunction and deformity, it is not surprising that these lesions are prognostic for patients seeking knee arthroplasty. Several studies have demonstrated that the odds of knee arthroplasty performance are substantially higher in patents with an OA-BML. This enhanced understanding of knee OA pathogenesis and the critical role of subchondral bone in this process creates an opportunity for development of novel prevention and treatment strategies. Prevention of OA-BML formation has been considered and pharmacologic interventions proposed. Recent studies have reported positive results for treatment with bisphosphonates in patients with knee OA. One study reported significant pain and OA-BML size reduction in patients receiving a bisphosphonate for 4 months. A strategy aimed at repairing and/or enhancing subchondral bone compromised by an OA-BML has also been proposed. Early results reported with this intervention are encouraging, but preliminary

The avascular nature of articular cartilage relies on diffusion pathways to obtain essential nutrients and molecules for cellular activity. Understanding these transport pathways is essential to maintaining and improving the health of articular cartilage and ultimately synovial joints. Several studies have shown that joint articulation is associated with fluid and solute uptake although it remains unclear what role sliding motion independently plays. This study investigates the role of sliding with a non-stationary contact area on the uptake of small molecular weight tracers into articular cartilage. Ten-millimeter diameter cartilage-bone plugs were obtained from porcine knee joints and sealed into purpose made diffusion chambers. The chambers were designed to eliminate diffusion from the radial edge and only allow diffusion through the articular surface. The bone side of the chamber was filled with PBS to maintain tissue hydration while the cartilage side was filled with 0.01mg/ml fluorescein sodium salt (FNa) prepared using PBS. Sliding loads with a non-stationary contact area were applied across the articular surface by a custom apparatus using a 4.5 mm diameter spherical indenter. A moving contact area was chosen to represent physiological joint motions. Reciprocal sliding was maintained at a rate of 5 mm/s for 2 and 4 hours. Control samples were subject to passive diffusion for 0, 4, and 88 hours. After diffusion tests, samples were snap frozen and 20 µm cross-sectional cuts were taken perpendicular to the sliding direction. Samples were imaged using a Zeiss AxioImager M2 epifluorescent microscope under 5× magnification with a filter for FNa. Intensity profiles were mapped from the articular surface to the subchondral bone. Unloaded control samples demonstrated minimal solute uptake at 4 hours penetrating less than 5% of the total cartilage depth. By 88 hours solute penetration had reached the subchondral bone although there was minimal accumulation within the cartilage matrix indicated by the relatively low intensity profile values. Samples that had been subjected to reciprocal sliding demonstrated accelerated penetration and solute accumulation compared to unloaded samples. After 1 hour of reciprocal sliding, the solute had reached 40% of the cartilage depth, this increased to approximately 80% at 4 hours, with much higher intensities compared to unloaded controls. Sliding motion plays an important role in the uptake of solutes into the cartilage matrix. Maintaining joint motion both post injury and in the arthritic process is a critical component of cartilage nutrition. Samples that had been subject to reciprocal sliding demonstrated accelerated solute penetration and accumulation in the cartilage matrix, exceeding steady state concentrations achieved by passive diffusion

In this study, a biomimetic triphasic scaffold was constructed to mimic the native cartilage-subchondral bone tissue structure. This scaffold contained chondral layer, calcified zone of cartilage (CZC) and subchondral bone layer. The chondral layer was type II collagen sponge, the CZC and the subchondral bone layer were derived from normal pig knee by decellularization. In order to build separate microenvironment for chondral layer and subchondral bone layer, a dual-chamber bioreactor was designed by computer aided design, manufactured by 3D printer using Poly Lactic Acid, with CZC as the barrier of these two chambers. Culture medium in these two chambers was circulated separately by peristaltic pumps. Amniotic mesenchymal stem cells were seeded in this scaffold, fluorescence labeling was used for cell tracking, total DNA content analysis was used to indicate cell proliferation, and inducing medium was used to direct stem cells differentiation. After 7 days culture, the cells regularly distributed in the scaffold, cell adhesion and proliferation was not affected. No cell migration across CZC occurred. Total DNA content analysis showed that cells in scaffold increased in a time-dependent manner. Chondrogenic and osteogenic medium could induce stem cells in these two chambers to differentiate into chondrocytes and osteocytes, respectively. Our pilot study showed that the dual-chamber culture system with biomimetic triphasic scaffold was feasible, therefore this system will be further modified and tested in vivo

Severe glenoid bone loss in patients with osteoarthritis with intact rotator cuff is associated with posterior glenoid bone loss and posterior humeral subluxation. Management of severe glenoid bone loss during shoulder arthroplasty is controversial and technically challenging and options range from humeral hemiarthroplasty, anatomic shoulder replacement with glenoid bone grafting or augmented glenoid component implantation, to reverse replacement with reaming to correct version or structural bone grafting or metallic augmentation of the bone deficiency. Shoulder replacement with severe glenoid bone loss is technically challenging and characterised by higher rates of complications and revisions. Hemiarthroplasty has limited benefit for pain relief and function especially if eccentric glenoid wear exists. Bone loss with >15 degrees of retroversion likely requires version correction include bone-grafting, augmented glenoid components, or reverse total shoulder replacement. Asymmetric reaming may improve version but is limited to 15 degrees of version correction in order to preserve subchondral bone and glenoid bone vault depth. Bone-grafting of glenoid wear and defects has had mixed results with graft-related complications, periprosthetic radiolucent lines, and glenoid component failure of fixation. Implantation of an augmented wedge or step polyethylene glenoid component improves joint version while preserving subchondral bone, but is technically demanding and with minimal short term clinical follow-up. A Mayo study demonstrated roughly 50% of patients with posteriorly augmented polyethylene had radiolucent lines and 1/3 had posterior subluxation. Another wedge polyethylene design had 66% with bone ingrowth around polyethylene fins at 3 years. Long term outcomes are unknown for these new wedge augmented glenoid components. Reverse shoulder arthroplasty avoids many risks of anatomic replacement glenoid component fixation and stability but is associated with a high complication rate (15%) including neurologic and baseplate loosening and often requires structural bone grafting behind the baseplate with suboptimal outcomes or metallic augmented baseplates with limited evidence and short term outcomes. Reverse replacement with baseplate bone grafting or metal augmentation is technically challenging due to limited native glenoid bone stock available for baseplate component ingrowth and long term fixation. Failure to correct glenoid superior inclination and restore neutral version within 10 degrees increases the risks of reverse baseplate failure of fixation, pull out, and failure of reverse replacement. Reverse baseplate failure rates in patients with severe glenoid bone loss and concomitant glenoid bone grafting range from 5–11%. The minimum native glenoid bony contact with the baseplate is unknown but likely is approximately 1cm of native bone contacting a central ingrowth post and a minority (∼15–25%) of native glenoid contacting the backside of the baseplate. Failure to correct posterior bone loss can lead to retroversion of the baseplate, reduced external rotation, posterior scapular notching, and posteromedial polyethylene wear. In summary, shoulder replacement with severe glenoid bone loss is technically challenging and characterised by higher rates of complication and revision

Introduction. Oriental people habitually adopt formal sitting and squatting postures, the extreme flexion of the knees allowing of this. The influence exercised by pressure and posture are, therefore, found at the posterior side of knee joint. However, we don't have many report about articular cartilage of posterior femoral condyle. Objectives. The purpose of this study was to reveal the accurate prevalence and related factors to the presence of degenerative changing of the articular cartilage of posterior femoral condyle in cadaveric knee joints. Methods. One hundred and thirty two knees from 66 cadavers (42 male knees and 24 female knees, formalin fixed, Japanese anatomical specimens) were included in this study. The average age of the cadavers was 81.4 (56–101) years. Knees were macroscopically evaluated the depth of cartilage degeneration of the patellofemoral joint, medial and lateral femoral condyle, medial and lateral posterior femoral condyle following the Outerbridge's classification. Grading was as follows: Grade 1: normal cartilage or softening and swelling of the cartilage. Grade 2: partial-thickness defect which did not reach the subchondral bone and was less than 1.3 cm in diameter. Grade 3: partial-thickness defect which did not reach the subchondral bone and was more than 1.3 cm in diameter. Grade 4: exposed subchondral bone and visible reactive tissue formation. When there were multiple lesions of different Outerbridge's classification grades, the sizes of the lesions were added up. Lesions with degenerative changes more severe than Outerbridge's classification grade 3 were regarded as OA lesions. Statistical analysis was performed to reveal the correlation between the occurrences of cartilage degeneration of medial and lateral posterior femoral condyle and medial and lateral femoral condyle and gender. Results. The prevalence of OA-positive was 48.5% (64 knees). Analyzing in the prevalence in gender, male was 31% (26 knees) OA-positive, female was 79.2% (38knees) OA-positive. The frequency of OA-positive was significantly higher in females than in males (P < 0.001). The prevalence of OA-positive in posterior condyle was 53.1% (34 knees) in 64 knees of OA-positive. Analyzing in the prevalence in gender, male was 15.4% (4 knees) in 26 knees of OA-positive, female was 78.4% (30knees) in 38 knees of OA-positive. The frequency of OA-positive in posterior condyle was significantly higher in females than in males (P < 0.001). Conclusions. In this study, the prevalence of OA-positive in posterior condyle was evaluated in cadaveric knees. The prevalence of OA-positive in posterior condyle was 53.1% in OA-positive knees, and was significantly correlated with the gender

Osteoarthritic (OA) changes to the bone morphology of the proximal tibia may exhibit load transfer patterns during total knee arthroplasty not predicted in models based on normal tibias. Prior work highlighted increased bone density in transverse sections of OA knees in the proximal-most 10mm tibial cancellous bone. Little is known about coronal plane differences, which could help inform load transfer from the tibial plateau to the tibial metaphysis. Therefore, we compared the cancellous bone density in OA and cadaveric (non-OA) subjects along a common coronal plane. This study included nine OA patients (five women, average age 59.1 ± 9.4 years) and 18 cadaver subjects (four women, average age 39.5 ± 14.4 years). Patients (eight with medial OA and one with lateral OA) received pre-operative CT scans as standard-of-care for a unicompartmental knee replacement. Cadavers were scanned at our institution and had no history of OA which was confirmed by gross inspection during dissection. 3D reconstructions of each proximal tibia were made and an ellipse was drawn on the medial and lateral plateau using a previously published method. A coronal section (Figure 1) to standardize the cohort was created using the medial ellipse center, lateral ellipse center, and the tibial shaft center 71.5mm from the tibial spine. On this section, profile lines were drawn from the medial and lateral ellipse centers, with data collected from the first subchondral bone pixel to a length of 20mm. The Hounsfield Units (HU) along each profile line was recorded for each tibia; a representative graphical distribution is shown in Figure 2. The Area Under the Curve (AUC) was calculated for the medial and lateral sides, which loosely described the stiffness profile through the region of interest. To determine differences between the medial and lateral subchondral bone density, the ratio AUC[medial] / AUC[lateral] was compared between the OA and cadaver cohorts using a two-sample t-test. Data from the sole lateral OA patient was mirror-imaged to be included in the OA cohort. The majority of the OA patients appeared to have higher subchondral bone density on the affected side. Figure 3 compares the medial and laterals sides of each group using the AUC ratio method described above. For the cadaver group the AUC was 1.2 +/− 0.22, with a median of 1.1 [0.9 1.6], smaller than the mean AUC for the OA group, which was 1.4 +/− 0.39, with a median of 1.6 [0.93 2.1]. The p-value was 0.06. The increased density observed in OA patients is consistent with asymmetric loading towards the affected plateau, resulting in localized remodeling of cancellous bone from the epiphysis to metaphysis. From the coronal plane, bone was often observed in OA patients bridging the medial plateau to the metaphyseal cortex. Although the cadaver subjects were normal from history and gross inspection, some subjects exhibited early bone density changes consistent with OA. Future work looks to review more OA scans, extend the work to the distal femur, and convert the HU values to bone elastic moduli for use in finite element modelling

Introduction. Mechanical integrity of patella can be weakened by the technique of removing the articulating surface. The senior author developed the technique of maintaining subchondral bone of the lateral patellar facet in early 1980s. Though laboratory studies have demonstrated deleterious effect of excessive resection of patella on the strains in the remaining bone under load; clinical studies have not shown the importance of strong subchondral bone of lateral facet to have an effect on patellar fracture prevalence. We present the results of our patellar resection technique preserving the subchondral bone of lateral facet. Methods. 393 TKRs were performed between 1989 and 1996 using cruciate substituting modular knee with recessed femoral trochlear groove and congruent patello-femoral articulation. 45 patients with 48 knees died and 37 patients with 41 knees were lost to follow-up. Three hundred and four knees were followed for an average 10 years (range 5 -16 years). Patellar surface was resected with an oscillating saw without the use of cutting guide. The medial facet and most of the articular cartilage of the lateral facet was resected, while preserving the subchondral bone of lateral facet. An all-polyethylene implant with single peg was used in most cases. Results. There have been two fractures in the cohort with prevalence of 0.66%. Eight TKRs were revised for synovitis and osteolysis. Patellar osteolysis was found in 4 of these cases, with loosening of 3 of these patellae, and 1 patellar fracture. Two patellar implants had global radiolucencies and were considered loose. The average knee score in unrevised knees improved from 48.6 to 92.2, while functional scores improved from 50 to 81.1. Conclusion. We believe that maintaining this anatomic landmark allows for preserved patellar strength, and in association with a femoral component with a recessed trochlear groove, has resulted in our low patellar fracture rate in primary TKR and revision cases for patellar osteolysis

Hypothesis. Cartilage defects pretreated with marrow stimulation techniques will have an increased failure rate. The first 321 consecutive patients treated at one institution with autologous chondrocyte implantation for full-thickness cartilage defects that reached more than two years of follow-up were evaluated by prospectively collected data. Patients were grouped based on whether they had undergone prior treatment with a marrow stimulation technique. Outcomes were classified as complete failure if more than 25% of a grafted defect area had to be removed in later procedures because of persistent symptoms. Results. There were 522 defects in 321 patients (325 joints) treated with autologous chondrocyte implantation. On average, there were 1.7 lesions per patient. Of these joints, 111 had previously undergone surgery that penetrated the subchondral bone; 214 joints had no prior treatment that affected the subchondral bone and served as controls. Within the marrow stimulation group, there were 29 (26%) failures, compared with 17 (8%) failures in the control group. Conclusion. Defects that had prior treatment affecting the subchondral bone failed at a rate three times that of nontreated defects. The failure rates for drilling (28%), abrasion arthroplasty (27%), and microfracture (20%) were not significantly different—possibly because of the lower number of microfracture patients in this cohort (25 of 110 marrow-stimulation procedures). The data demonstrate that marrow stimulation techniques have a strong negative effect on subsequent cartilage repair with autologous chondrocyte implantation and, therefore, should be used judiciously in larger cartilage defects that could require future treatment with autologous chondrocyte implantation. Unlike coventional wisdom, MSTs do ‘burn bridges’

Osteoarthritis (OA) is one of the most prevalent joint diseases involving progressive and degenerative changes to cartilage resulting from a variety of etiologies including post-traumatic incident or aging. OA lesions can be treated at its early stages through cell-based tissue engineering therapies using Mesenchymal Stem Cells (MSCs). In vivo models for evaluating these strategies, have described both chondral (impaction) and osteochondral (biopsy punch) defects. The aim of the investigation was to develop a compact and reproducible defect inducing post-traumatic degenerative changes mimicking early OA. Additionally, a pilot study to evaluate the efficacy of MSC-hydrogel treatment was also assessed. Surgery was performed on New Zealand white rabbits (male, 5–8 months old) with defects created on medial femoral condyle. For developing an appropriate defect, three approaches were used for evaluation: a biopsy punch (n = three at six and twelve weeks), an impaction device1 (n = three at six and twelve weeks) and a dental drill model (n = six at six and twelve weeks). At stated time points, condyles were harvested and decalcified in 10% EDTA, then embedded in Tissue-Tek and sectioned using a cryostat. Upon identification of region of interest, sections were stained with Safranin-O/Fast green and scored using OARSI scoring system by two blinded observers2. For the pilot study, autologous bone marrow was harvested from rabbits and used to isolate and expand MSCs. The Dental drill model was applied to both knee condyles, left untreated for six weeks at which stage, PKH26 fluorescently labelled MSCs were seeded into a hyaluronic acid hydrogel (TETEC). Repair tissue was removed from both condyles and MSC-hydrogel was injected into the left knee, whilst right knee was left empty. Rabbits were sacrificed at one (n = 1), six (n = 3) and twelve (n = 3) weeks post-treatment, processed as previously described and cartilage regeneration evaluated using Sellers score3. Impacted condyles exhibited no observed changes histologically (Mean OARSI score = 1 + 1), whereas biopsy punched and dental drilled defects demonstrated equal signs of cartilage erosion (OARSI score = 3 + 1) at assessed time points. However, biopsy punched condyles formed a diffusive defect, whereas dental drilled condyles showed a more defined, compact and reproducible defect. In the pilot study, PKH-labelled MSCs were observed at one and six weeks post-implantation within the defect space where hydrogel was injected. Tissue regeneration assessment indicated no difference between empty (Mean Sellers score = 14 + 2) and MSC treated defects (Sellers score = 16 + 5) at six weeks post-injection. At twelve weeks, MSC treated defects showed improved tissue regeneration with substantial subchondral bone restoration and good integration of regenerative cartilage with surrounding intact tissue (Sellers score = 10 + 1), whereas untreated defects showed no change in regeneration compared to six weeks (Sellers score = 16 + 2). Dental drill model was found to be the appropriate strategy for investigating early OA progression and treatment. Application of MSCs in defects showed good cartilage regeneration after twelve weeks application, indicating their promise in the treatment of early OA defects

Intraosseous pressure measurements (IOP) are not new. Several authors have struggled to interpret static IOP and to understand arthritis and osteonecrosis pathology. This work uses a combination of simple experiments in vivo to reassess bone and joint physiology. Joint replacement needs to take into account the hydrodynamic conditions that are present in bone. Intraosseous pressure measurements were carried out with vascular occlusion, activity and saline injection in experimental conditions and then in man during walking. RESULTS. 1. Basal IOP has a pulse wave and an underlying respiratory wave (RW). 2. IOP closely reflects systemic vascular changes. 3. Proximal arterial occlusion causes loss of IOP (IOPa) and pulse volume (PV). 4. Proximal vein occlusion causes a rise in IOP (IOPv) with preservation of PV and RW. 5. Physical loading raises IOP with preservation of PV and RW. 6. Load with arterial occlusion caused minimal rise in IOP. Loading with venous occlusion caused an augmented rise in IOP with preservation of the PV. 7. Simultaneous recordings from the femoral head, condyle and upper tibia during vascular occlusion and loading show that the same effects occur at all sites. 8. Simultaneous recording from the femoral head, condyle and upper tibia during saline injection shows pressure is transmitted through bone but not across joints. 9. The Ficat bolus test destroys local circulation. Aspiration is better and preserves local perfusion. 10. Bone health at the needle tip is better assessed by IOPv – IOPa, the perfusion ‘bandwidth’. 11. Upper tibial pressure during standing, slow walking and fast walking shows large IOP changes in vivo. 12. There is probably a physiological subchondral bone blood pump. 13. Anatomical features are present which support this idea. CONCLUSIONS. IOP measurement in isolation is meaningless. With arterial and venous occlusion, perfusion at the needle tip can be studied. Compartment syndrome testing should be similar. Subchondral bone is a compressible perfused sponge with a ‘pumped’ microcirculation. Very high pressures arise in subchondral bone during activity. There are protective modifications of the microcirculation. Failure of subchondral circulation causes arthritis. Arthritis is mainly a ‘vasculo-mechanical’ disease. This work explains the spectrum of arthritis and osteonecrosis, and Perthes, caisson and sickle cell disease patterns. It explains why osteoporosis might protect against arthritis

Introduction. Bone marrow stimulation has been a successful treatment option in cartilage repair and microfracture was the procedure of choice since the late 1980s. Despite its success in young and active patients, microfracture has inherent shortcomings such as shallow channels, wall compression, and non-standardized depth and diameter. This in vitro study assessed bone marrow access comparing microfracture, 1 and 2mm K-Wires, 1mm drill, and a recently introduced standardized subchondral bone needling procedure (Nanofracture) that creates 9mm deep and 1mm wide channels. Methods. An adult ovine model was used to assess access to bone the marrow spaces as well as effects on bone following microfracture, nanofracture, K-wire, and drilling following ethical clearance. All bone marrow stimulation techniques were conducted on a full thickness articular cartilage defect on the medial femoral condyles by the same surgeon. The same groups were repeated in vitro in 4 paired ovine distal femurs. MicroCT (Inveon Scanner, Siemens, Germany) was performed using 3D reconstruction and 25 micron slice analysis (MIMICS, Materialise, Belgium). Results. Microfracture elicited shallow depth with bone compression surrounding the channels. Trabecular channel access was limited; the channel depth and diameter were non-standardized and highly user and instrument dependent. Nanofracture demonstrated deep cancellous bone perforation with a high number of open trabecular channels. K-Wire drilling with both diameters resulted in well-defined channel walls, outlined by fine osseous deposits. Trabecular channel access was limited. The diameter of bone perforation is standardized, but depth is defined by visual controls. 1mm drill bit reaming demonstrated better osseous evacuation, but still limited trabecular marrow access. Discussion and Conclusion. Nanofracture resulted in thin, fragmented cancellous bone channels without rotational heat generation. Compared to microfracture, drilling and K-Wire stimulation, nanofracture showed superior bone marrow access with multiple trabecular access channels extending 9mm into subchondral bone

INTRODUCTION. Controversy exists regarding the ability of unicompartmental knee arthroplasty (UKA) to restore native knee kinematics, with some studies suggesting native kinematics are restored in most or all patients after UKA. 1–3. , while others indicate UKA fails to restore native knee kinematics. 4,5. Previous analysis of UKA articular contact kinematics focused on the replaced compartment. 2,5. , neglecting to assess the effects of the arthroplasty on the contralateral compartment which may provide insight to future pathology such as accelerated degeneration due to overload. 6. or a change in the location of cartilage contact. 7. The purpose of this study was to assess the ability of medial UKA to restore native knee kinematics, contact patterns, and lateral compartment dynamic joint space. We hypothesized that medial UKA restores knee kinematics, compartmental contact patterns, and lateral compartment dynamic joint space. METHODS. Six patients who received fixed-bearing medial UKA consented to participate in this IRB-approved study. All patients (4 M, 2 F; average age 62 ± 6 years) completed pre-surgical (3 weeks before) and post-surgical (7±2 months) testing. Synchronized biplane radiographs were collected at 100 images per second during three repetitions of a chair rise movement (Figure 1). Motion of the femur, tibia, and implants were tracked using an automated volumetric model-based tracking process that matches subject-specific 3D models of the bones and prostheses to the biplane radiographs with sub-millimeter accuracy. 8. Anatomic coordinate systems were created within the femur and tibia. 9. and used to calculate tibiofemoral kinematics. 10. Additional outcome measures included the center of contact in the medial and lateral compartments, and the lateral compartment dynamic joint space (i.e. the distance between subchondral bone surfaces). 11. The results of the three movement trials were averaged for each knee in each test session. All outcome measures were interpolated at 5° increments of knee extension (Figure 2). The average differences between knees at corresponding flexion angles were analyzed using paired t-tests with significance set at p < 0.05. RESULTS. The UKA knee was in 5.3° more varus than the contralateral knee prior to surgery (p=0.005). After surgery, the UKA knee was in 4.9° more valgus than before surgery (p=0.005). The UKA knee was 4.3° more externally rotated than the contralateral knee post-surgery (p=0.05) (Table 1). No significant differences were observed between knees or pre- to post-surgery in lateral compartment dynamic joint space or the center of contact in the medial and lateral tibia compartments (Table 1). DISCUSSION. These results suggest that medial UKA can restore native knee varus without significantly altering lateral compartment joint space or contact location during the chair rise movement. For any figures or tables, please contact the authors directly

Reverse total shoulder arthroplasty (RTSA) has a proven track record as an effective treatment for a variety of rotator cuff deficient conditions. However, glenoid erosion associated with the arthritic component of these conditions can present a challenge for the shoulder arthroplasty surgeon. Options for treatment of glenoid wear include partial reaming with incomplete baseplate seating, bony augmentation using structural or impaction grafting techniques, and augmented baseplates. Augmented components have the advantage of accommodating glenoid deformity with a durable material and also ream less subchondral bone; both of which may offer an advantage over traditional bone grafting. Biomechanical and early clinical studies of augmented glenoid baseplates suggest they are a reasonable treatment option, though posteriorly augmented baseplates have shown better performance than superiorly augmented implants. However, there are no mid- or late-term studies comparing augmented baseplates to bone grafting or partial reaming. We present a live surgical demonstration of RTSA for a patient with advanced glenoid erosion being treated with an augmented glenoid baseplate that can be dialed in the direction of any deformity (superior, posterior, etc.). This versatility allows the surgeon to place the augment in any direction and is not confined to the traditional concepts of glenoid wear in a single vector. Clearly, longer term follow up studies are needed to determine the ultimate effectiveness of these devices in treating glenoid deformity in RTSA

Background:. Different surgical approaches have been proposed for the treatment of chondral lesions. However surgical management of osteochondral defects of the knee joint involving subchondral bone are still under debate. Purpose:. The aim of this prospective non-randomized uncontrolled clinical investigation is to confirm the effectiveness of a commercially available biomimetic osteochondral scaffold in regenerating cartilage and subchondral bone of severe osteochondral lesions of the knee joint with one step surgery. Methods:. The biomimetic scaffold has a multilayer structure consisting of a combination of type I collagen and type I collagen/hydroxyapatite, mimicking the osteochondral connective tissue of the knee joint. From 2009 to 2011, sixty-one patients affected by grade III or IV osteochondral lesions of the knee, according to Outerbridge Classification, were admitted to three centers and received the biomimetic scaffold. Four-nine patients were evaluated using the International Knee Documentation Committee (IKDC), Tegner and VAS scores, and MRI at 1-, 2- and 3-year follow-ups. Biopsies were carried out in 5 patients at an average time of 19.2 months to histologically evaluate the quality of the newly-formed tissue. Results:. All patients tolerated the surgery well; no major adverse events were observed in the early postoperative period. Clinical evaluation of the 49 patients showed a statistically significant improvement in all scores at 1- 2- and 3-year follow-ups as compared to preoperative baseline scores. Improvement in the scores and functional recovery seemed to reach a plateau after 2 years; no significant improvement was seen between the 2- and the 3-year follow-up. Conclusions:. A synthetic biomimetic scaffold used in one-step surgery for the treatment of severe osteochondral knee lesions significantly improved symptoms and joint function, as demonstrated by subjective and objective scoring system evaluation. Furthermore, the athletic subpopulation exhibited a significantly better outcome than the non-athletic subpopulation