Weight-bearing Region Research Articles

Change in Knee Cartilage Volume in Individuals Completing a Therapeutic Exercise Program for Knee Osteoarthritis

Prospective cohort study. To characterize knee cartilage change in individuals with knee osteoarthritis (KOA) who have completed a therapeutic exercise program. While therapeutic exercise is frequently used successfully to improve pain and function in individuals with KOA, no studies have reported the volume of cartilage change or individual factors that may impact volume of cartilage change in those completing an exercise program for KOA. Thirteen individuals with KOA underwent magnetic resonance imaging to quantify cartilage volume change in the weight-bearing regions of the medial and lateral femoral condyles and the entire surface of the tibial plateaus from baseline to 1-year follow-up. Body structure and function measures were taken for body mass index, knee axis alignment, knee motion, and knee strength. Activity limitations and activity levels were also measured prior to the therapeutic exercise program, using the Western Ontario and McMaster Universities Osteoarthritis Index and the Physical Activity Scale for the Elderly. At 6 months from baseline, follow-up clinical measurements of knee strength and motion were performed. At 1 year from baseline, imaging of the knee cartilage and knee alignment were performed, and participants completed the Western Ontario and McMaster Universities Osteoarthritis Index and Physical Activity Scale for the Elderly. The central region of the medial femoral condyle (cMF) had a median volume of cartilage loss of 3.8%. The other 3 knee tibiofemoral articular surfaces had minimal median cartilage volume change. Individuals were dichotomized into progressors (n = 6) and nonprogressors (n = 7), based on the standard error of measurement of cartilage volume change for the cMF. Progressors were younger, had a larger body mass index, had a higher Kellgren-Lawrence grade in the medial compartment of the knee, and had a greater increase in knee varus alignment from baseline to 1-year follow-up. The progressors also had frontal plane hip and knee kinetics during baseline gait analysis that potentially increased medial knee joint loading. The loss of cMF cartilage volume was highly variable and the median loss of cartilage was within the range previously reported. Seven of the 13 individuals did not have cMF cartilage volume loss greater than the standard error of measurement. Change in cartilage volume of the cMF may be influenced to a greater extent by personal factors than by completion of a therapeutic exercise program. Additional research is needed to decipher the interactions among therapeutic exercise and personal characteristics that impact knee cartilage loss.

Abnormal tibiofemoral kinematics following ACL reconstruction are associated with early cartilage matrix degeneration measured by MRI T1rho

PurposeAltered kinematics following ACL-reconstruction may be a cause of post-traumatic osteoarthritis. T1ρ MRI is a technique that detects early cartilage matrix degeneration. Our study aimed to evaluate kinematics following ACL-reconstruction, cartilage health (using T1ρ MRI), and assess whether altered kinematics following ACL-reconstruction are associated with early cartilage degeneration. MethodsEleven patients (average age: 33±9years) underwent 3T MRI 18±5months following ACL-reconstruction. Images were obtained at extension and 30° flexion under simulated loading (125N). Tibial rotation (TR) and anterior tibial translation (ATT) between flexion and extension, and T1ρ relaxation times of the knee cartilage were analyzed. Cartilage was divided into five compartments: medial and lateral femoral condyles (MFC/LFC), medial and lateral tibias (MT/LT), and patella. A sub-analysis of the femoral weight-bearing (wb) regions was also performed. Patients were categorized as having “abnormal” or “restored” ATT and TR, and T1ρ percentage increase was compared between these two groups of patients. ResultsAs a group, there were no significant differences between ACL-reconstructed and contralateral knee kinematics, however, there were individual variations. T1ρ relaxation times of the MFC and MFC-wb region were elevated (p≤0.05) in the ACL-reconstructed knees compared to the uninjured contralateral knees. There were increases (p≤0.05) in the MFC-wb, MT, patella and overall average cartilage T1ρ values of the “abnormal” ATT group compared to “restored” ATT group. The percentage increase in the T1ρ relaxation time in the MFC-wb cartilage approached significance (p=0.08) in the “abnormal” versus “restored” TR patients. ConclusionsAbnormal kinematics following ACL-reconstruction appear to lead to cartilage degeneration, particularly in the medial compartment.

Effect of heel height on in-shoe localized triaxial stresses

Abnormal and excessive plantar pressure and shear are potential risk factors for high-heeled related foot problems, such as forefoot pain, hallux valgus deformity and calluses. Plantar shear stresses could be of particular importance with an inclined supporting surface of high-heeled shoe. This study aimed to investigate the contact pressures and shear stresses simultaneously between plantar foot and high-heeled shoe over five major weightbearing regions: hallux, heel, first, second and fourth metatarsal heads, using in-shoe triaxial force transducers. During both standing and walking, peak pressure and shear stress shifted from the lateral to the medial forefoot as the heel height increased from 30 to 70mm. Heel height elevation had a greater influence on peak shear than peak pressure. The increase in peak shear was up to 119% during walking, which was about five times that of peak pressure. With increasing heel height, peak posterolateral shear over the hallux at midstance increased, whereas peak pressure at push-off decreased. The increased posterolateral shear could be a contributing factor to hallux deformity. It was found that there were differences in the location and time of occurrence between in-shoe peak pressure and peak shear. In addition, there were significant differences in time of occurrence for the double-peak loading pattern between the resultant horizontal ground reaction force peaks and in-shoe localized peak shears. The abnormal and drastic increase of in-shoe shear stresses might be a critical risk factor for shoe-related foot disorders. In-shoe triaxial stresses should therefore be considered to help in designing proper footwear.

Subchondral bone remodeling is related to clinical improvement after joint distraction in the treatment of ankle osteoarthritis

In osteoarthritis (OA), subchondral bone changes alter the joint's mechanical environment and potentially influence progression of cartilage degeneration. Joint distraction as a treatment for OA has been shown to provide pain relief and functional improvement through mechanisms that are not well understood. This study evaluated whether subchondral bone remodeling was associated with clinical improvement in OA patients treated with joint distraction. Twenty-six patients with advanced post-traumatic ankle OA were treated with joint distraction for 3 months using an Ilizarov frame in a referral center. Primary outcome measure was bone density change analyzed on computed tomography (CT) scans. Longitudinal, manually segmented CT datasets for a given patient were brought into a common spatial alignment. Changes in bone density (Hounsfield Units (HU), relative to baseline) were calculated at the weight-bearing region, extending subchondrally to a depth of 8mm. Clinical outcome was assessed using the ankle OA scale. Baseline scans demonstrated subchondral sclerosis with local cysts. At 1 and 2 years of follow-up, an overall decrease in bone density (-23% and -21%, respectively) was observed. Interestingly, density in originally low-density (cystic) areas increased. Joint distraction resulted in a decrease in pain (from 60 to 35, scale of 100) and functional deficit (from 67 to 36). Improvements in clinical outcomes were best correlated with disappearance of low-density (cystic) areas (r=0.69). Treatment of advanced post-traumatic ankle OA with 3 months of joint distraction resulted in bone density normalization that was associated with clinical improvement.

Subchondral cysts create increased intra-osseous stress in early knee OA: A finite element analysis using simulated lesions

Aim of study To investigate the role of intra-osseous lesions in advancing the pathogenesis of Osteoarthritis (OA) of the knee, using Finite Element Modeling (FEM) in conjunction with high-resolution imaging techniques. Methods Twenty early stage OA patients (≤ Grade 2 radiographic score) were scanned with a prototype, cone-beam CT system. Scans encompassed the mid-shaft of the femur to the diaphysis of the proximal tibia. Individual bones were segmented to create 3D geometric models that were transferred to FE software for loading experiments. Patient-specific, inhomogeneous material properties were derived from the CT images and mapped directly to the FE models. Duplicate models were also created, with a 3D sphere (range 3–12 mm) introduced into a weight-bearing region of the joint, mimicking the size, location, and composition of a subchondral bone cyst (SBC). A spherical shell extending 1 mm radially around the SBC served as the sample volume for measurements of von Mises equivalent stress. Both models were vertically loaded with 750 N, or approximately 1 body weight during a single-leg stance. Results All FE models exhibited a physiologically realistic weight-bearing distribution of stress, which initiated at the joint surface and extended to the cortical bone. Models that contained the SBC experienced a nearly two-fold increase in stress (0.934 ± 0.073 and 1.69 ± 0.159 MPa, for the non-SBC and SBC models, respectively) within the bone adjacent to the SBC. In addition, there was a positive correlation found between the diameter of the SBC and the resultant intra-osseous stress under load (p = 0.004). Conclusions Our results provide insights into the mechanism by which SBC may accelerate OA, leading to greater pain and disability. Based on these findings, we feel that patient-derived FE models of the OA knee – utilizing in vivo imaging data – present a tremendous potential for monitoring joint mechanics under physiological loads.

UTE-T2∗ mapping of human articular cartilage in vivo: a repeatability assessment

Ultrashort echo-time enhanced T2∗ (UTE-T2∗) mapping of articular cartilage is a novel quantitative MRI technique with the potential to visualize deep cartilage characteristics better than standard T2 mapping. The feasibility and intersession repeatability of UTE-T2∗ mapping of cartilage in vivo has not previously been evaluated. Eleven asymptomatic subjects underwent repeat UTE-T2∗ imaging on a whole-body 3T MRI scanner on three consecutive days. Full-thickness, superficial and deep regions of interest (ROIs) were evaluated in the central weight-bearing zones of the medial femoral condyle (cMFC) and tibial plateau (cMTP). Intersession precision error across subjects was evaluated by the root-mean-square average coefficients of variation (RMSA-CV) and by the median of intra-subject standard deviations (SDs) of UTE-T2∗ values in each ROI. UTE-T2∗ values in vivo were found to be repeatable with relative (RMSA-CV) intersession precision errors of 8%, 6%, 16% for full-thickness, superficial and deep cMFC ROIs, corresponding to absolute errors (SD) of 1.2, 1.5, 1.5 ms, respectively. In cMTP tissue, UTE-T2∗ relative repeatability was 8%, 8%, 13%, corresponding to absolute repeatability of 1.0, 1.5, 2.1 ms (full-thickness, superficial, deep). UTE-T2∗ values were higher in superficial cartilage compared to deep in both cMFC (P≪0.001) and cMTP (P=0.0004) regions. In vivo 3D UTE-T2∗ mapping at 3T is feasible and can be implemented using a standard clinical MRI scanner and knee coil. Intersession precision error of UTE-T2∗ values in full-thickness ROIs in the weight-bearing regions of asymptomatic subjects is under 1.2 ms or 8% (RMSA-CV). Significant zonal and regional variations of UTE-T2∗ were seen.

β‐catenin, cartilage, and osteoarthritis

The early cellular events during the development of osteoarthritis (OA) are accelerated articular chondrocyte maturation and extracellular matrix degradation, which are usually seen in the weight-bearing region of articular cartilage. The results of our recent studies from transgenic OA mouse models indicate that upregulation of beta-catenin signaling in articular chondrocytes is most likely responsible for the conversion of normal articular chondrocytes into maturing (arthritic) chondrocytes, which is associated with activation of chondrocyte maturational genes and matrix degradation. Conditional activation of the beta-catenin gene in articular chondrocytes leads to an OA-like phenotype. Overexpression of Smurf2, an E3 ubiquitin ligase, also induces an OA-like phenotype through upregulation of beta-catenin signaling. In addition, beta-catenin upregulation was also found in articular cartilage tissues in patients with OA. These findings indicate that beta-catenin plays a central role in articular cartilage function and that activation of beta-catenin signaling may represent a pathologic mechanism for OA development.

Interleukin-1α treatment of meniscal explants stimulates the production and release of aggrecanase-generated, GAG-substituted aggrecan products and also the release of pre-formed, aggrecanase-generated G1 and m-calpain-generated G1-G2

Pro-inflammatory cytokines induce meniscal matrix degradation and inhibition of endogenous repair mechanisms, but the pathogenic mechanisms behind this are mostly unknown. Therefore, we investigated details of interleukin-1 (IL-1alpha)-induced aggrecan turnover in mature meniscal tissue explants. Fibro-cartilagenous disks (3 mm diameter x 1 mm thickness) were isolated from the central, weight-bearing region of menisci from 2-year-old cattle. After 3 or 6 days of IL-1alpha-treatment, GAG loss (DMMB assay), biosynthetic activity ([(35)SO(4)]-sulfate and [(3)H]-proline incorporation), gene expression (quantitative RT-PCR) and the abundance (zymography, Western blot) of matrix-degrading enzymes and specific aggrecan products were determined. Meniscal fibrocartilage had a 4-fold lower GAG content (per wet weight) than adjacent articular cartilage, and expressed MMPs-1, -2, -3 and ADAMTS4 constitutively, whereas ADAMTS5 m-RNA was essentially undetectable. Significant IL-1 effects were a decrease in biosynthetic activity, an increase in GAG release and in the expression/abundance of MMP-2, MMP-3 and ADAMTS4. Fresh tissue contained aggrecan core protein products similar to those previously described for bovine articular cartilage of this age. IL-1 induced the release of aggrecanase-generated CS-substituted products including both high (>250 kDa) and low molecular weight (about 75 kDa) species. TIMP-3 (but not TIMP-1 and -2 or a broad spectrum MMP inhibitor) inhibited IL-1-dependent GAG loss. In addition, IL-1 induced the release of preformed pools of three known G1-bearing products. We conclude that aggrecanases are responsible for IL-1-stimulated GAG release from meniscal explants, and that IL-1 also stimulates release of G1-bearing products, by a process possibly involving hyaluronan fragmentation.

Arthroscopic controlled reduction of femoral condyle fractures using a retrograde navigated approach

Isolated depression fractures of the femoral condyle are rare, but severe injuries due the destroyed congruency of the articular surface in the weight-bearing region of the joint. In most cases, an arthrotomy with fragment reduction and internal fixation by screws buttress or plates is performed. Disadvantages of this procedure are the approach-related complications. Furthermore, an implant removal is necessary, if a secondary osteoarthrosis develops. We present a female patient with a hyperflexion trauma of her right knee, resulting in an isolated depression fracture of the medial femoral condyle. To avoid arthrotomy-related morbidity, the impressed fragment was retrograde addressed using navigated guidance and reduced indirectly under arthroscopic control. Via the retrograde intraosseous tunnel a biodegradable screw was used as a buttress against the fragment to prevent a re-dislocation. The fracture healed without any complications and the patient re-administered her sports activities at 10weeks follow-up. This procedure enables an accurate reduction and stable fixation of joint depression fragments via a minimal invasive approach.

Comparison of 3T MR scanners in regional cartilage-thickness analysis in osteoarthritis: a cross-sectional multicenter, multivendor study

IntroductionCartilage thickness from MR images has been identified as a possible biomarker in knee osteoarthritis (OA) research. The ability to acquire MR data at multiple centers by using different vendors' scanners would facilitate patient recruitment and shorten the duration of OA trials. Several vendors manufacture 3T MR scanners, including Siemens, Philips Medical Systems, and GE Healthcare. This study investigates whether quantitative MR assessments of cartilage morphology are comparable between scanners of three different vendors.MethodsTwelve subjects with symptoms of knee OA and one or more risk factors had their symptomatic knee scanned on each of the three vendor's scanners located in three sites in the UK: Manchester (Philips), York (GE), and Liverpool (Siemens). The NIH OAI study protocol was used for the Siemens scanner, and equivalent protocols were developed for the Philips and GE scanners with vendors' advice. Cartilage was segmented manually from sagittal 3D images. By using recently described techniques for Anatomically Corresponded Regional Analysis of Cartilage (ACRAC), a statistical model was used anatomically to align all the images and to produce detailed maps of mean differences in cartilage-thickness measures between scanners. Measures of cartilage mean thickness were computed in anatomically equivalent regions for each subject and scanner image.ResultsThe ranges of mean cartilage-thickness measures for this cohort were similar for all regions and across all scanners. Philips intrascanner root-mean-square coefficients of variation were low in the range from 2.6% to 4.6%. No significant differences were found for thickness measures of the weight-bearing femorotibial regions from the Philips and Siemens images except for the central medial femur compartment (P = 0.04). Compared with the other two scanners, the GE scanner provided consistently lower mean thickness measures in the central femoral regions (mean difference, -0.16 mm) and higher measures in the tibial compartments (mean difference, +0.19 mm).ConclusionsThe OAI knee-imaging protocol, developed on the Siemens platform, can be applied to research and trials by using other vendors' 3T scanners giving comparable morphologic results. Accurate sequence optimization, differences in image postprocessing, and extremity coil type are critical factors for interscanner precision of quantitative analysis of cartilage morphology. It is still recommended that longitudinal observations on individuals should be performed on the same scanner and that assessment of intra- and interscanner precision errors is undertaken before commencement of the main study.

Static Measure of Foot Loading

Static and dynamic loading of the foot are important characteristics for understanding human walking in both health and disease. The goal of this investigation was to determine whether an objective measure of normal midstance loading of the foot could reliably be recorded using readily available disposable qualitative recording devices. Ten randomly selected normal volunteers were trained to step on Harris mat and Pressure Stat recording devices during normal walking. Each of the recordings was divided into 5 weight-bearing regions by 2 separate examiners. After outlining each foot, the recordings were digitized and compared. Interobserver reliability ranged from 0.81 to 0.96 for the Harris mat technique and 0.94 to 0.97 for the Pressure Stat technique. Data from a linear regression plot indicate high precision of calculations of the foot masks between the 2 examiners based on an R(2) value of 0.966 using the Pressure Stat method. These data plus a linear regression plot suggest that both qualitative recording devices, when digitized using a standardized format, appear to obtain a reliable objective measure of midstance loading during normal gait. The Pressure Stat device may be slightly more reliable. It is planned to use this standardized experimental model to compare objectively patterns of midstance loading in patients with injury or disease that is capable of altering normal walking.

Vibration training intervention to maintain cartilage thickness and serum concentrations of cartilage oligometric matrix protein (COMP) during immobilization

To test the hypotheses that 1) 14-days of immobilization of young healthy subjects using a 6 degrees -"head-down-tilt-bed-rest"-model (6 degrees -HDT) would reduce cartilage thickness in the knee and serum Cartilage oligometric matrix protein (COMP) concentration and 2) isolated whole body vibration training would counteract the bed rest effects. The study was performed and designed in compliance with the Declaration of Helsinki and is registered as trial DRKS00000140 in the German Clinical Trial Register (register.germanctr.de). Eight male healthy subjects (78.0+/-9.5kg; 179+/-0.96cm, 26+/-5 years) performed 14 days of 6 degrees -HDT. The study was designed as a cross-over-design with two study phases: a training and a control intervention. During the training intervention, subjects underwent 2x5-min whole body vibration training/day (Frequency: 20Hz; amplitude: 2-4mm). Magnetic resonance (MR) images (slice thickness: 2mm; in-plane resolution: 0.35x0.35mm; pixels: 448x512) were taken before and after the 6 degrees -HDT periods. Average cartilage thicknesses were calculated for the load bearing regions on the medial and lateral articulating surfaces in the femur and tibia. While the control intervention resulted in an overall loss in average cartilage thickness of -8% (pre: 3.08mm+/-0.6mm post: 2.82mm+/-0.6mm) in the weight-bearing regions of the tibia, average cartilage thickness increased by 21.9% (pre: 2.66mm+/-0.45mm post: 3.24mm+/-0.63mm) with the vibration intervention. No significant differences were found in the weight-bearing regions of the femur. During both interventions, reduced serum COMP concentrations were observed (control intervention: -13.6+/-8.4%; vibration intervention: -9.9+/-3.3%). The results of this study suggest that articular cartilage thickness is sensitive to unloading and that vibration training may be a potent countermeasure against these effects. The sensitivity of cartilage to physical training is of high relevance for training methods in space flight, elite and sport and rehabilitation after illness or injury.

Foreign-Body Giant-Cell Reaction at the Donor Site After Autologous Osteochondral Transplant for Cartilaginous Lesion

The management of chondral and osteochondral defects in weight-bearing regions of the knee is challenging, particularly in athletes. Articular cartilage has a limited capacity for regeneration, and the difficulties are magnified in the presence of full-thickness cartilage defects1. Osteochondral autograft transfer procedures involve taking small cylindrical grafts from areas of decreased weight-bearing in the knee and transferring them to accurately prepared recipient defect sites2,3. These techniques have the advantages of ready availability of donor cartilage and use of native hyaline cartilage containing active, mature chondrocytes4. Because of a lack of consistency in the amount of long-term follow-up in the published literature, no definitive conclusions have yet been drawn on the effectiveness of the osteochondral autograft transfer procedures5. Furthermore, concerns exist related to the morbidity that ensues at the donor cartilage harvest sites6,7. Morbidity of the donor sites, which are selected at the periphery of the articular surfaces from areas of relatively low load per unit area8, has been poorly studied. Even when an osteochondral graft is technically well executed, we do not know what can happen at the donor sites. We report on a competitive athlete who underwent autologous osteochondral transplantation for treatment of a full-thickness osteochondral defect of the right medial femoral condyle. Substantial morbidity developed at the donor site. During arthroscopic revision surgery, biopsy of the donor site showed a foreign-body giant-cell reaction. A revision autologous osteochondral transplantation was performed, and this procedure was associated with a good outcome. To the best of our knowledge, this is the first reported case of foreign-body giant-cell reaction at the donor site after autologous osteochondral transplantation. The patient was informed that data concerning the case would be submitted for publication, and he consented. In September …

Akuter, traumatischer versus chronischer Knorpelschaden unter gutachterlichen Gesichtspunkten

Have chondral lesions been found in the course of an articular injury? Are these lesions of traumatic or degenerative origin? Is it possible to differentiate traumatic from pre-existing pathology with the help of history, clinical findings and imaging features? The answers to these questions are of paramount importance in the setting of legal expert assessment. The diagnosis of an acute traumatic chondral injury is based on arthroscopic and/or MRI findings. MRI is the diagnostic method of choice in a suspected isolated chondral injury. The method yields high accuracy in detecting chondral and osteochondral lesions. The MRI finding of a concomitant subchondral bone contusion ("bone bruise") adjacent to a cartilage lesion helps in the diagnosis of acute chondral lesions. Traumatic bone marrow alterations regress in most cases over the course of 6 months. For this reason the initial MRI should be performed within 1 to 6 weeks after trauma. A follow-up study should be undertaken not prior to 3 months after injury. Osteoarthritic cartilage lesions show a distinct regional pattern on MRI usually affecting the weight-bearing regions. In advanced stages, regularly concomitant osseous reactions such as osteophytes, subchondral sclerosis and bone attrition are observed. Subchondral bone marrow lesions in osteoarthritis show a tendency to progress. The direct inspection and probing of the joint during arthroscopy allows for a detailed assessment of the chondral surface and the diagnosis of possible cartilage softening. An arthroscopic differentiation between acute traumatic chondral lesions and chronic cartilage alterations is possible in most cases within the first 6 to 12 weeks after injury.

Examining the influence of short-term implantation on oxidative degradation in retrieved highly crosslinked polyethylene tibial components

Concerns remain regarding the oxidative resistance of highly crosslinked polyethylene (PE). The study investigated the in vivo performance of Durasul highly crosslinked PE by comparing the oxidation index, density, and percent crystallinity in the weightbearing and nonweightbearing region of retrieved components with unused time zero tibial components. Retrieved and unused Sulene conventional PE tibial components were examined for comparison and the effects of shelf age, in vivo duration, and ex vivo duration were also investigated. The oxidation index was not significantly different between unused time zero and retrieved Durasul PE components. Regression analysis data supported these findings in that neither shelf age, in vivo duration, nor ex vivo duration was a significant predictor of oxidation index in the retrieved Durasul PE components. In contrast, the retrieved conventional PE components had significantly greater oxidation index, density, and percent crystallinity compared with unused time zero PE components. Regression data suggested that in vivo and ex vivo duration, but not shelf aging, influenced the changes observed in the conventional PE components. These data also showed that in vivo loading did not significantly affect the oxidation index, density, or percent crystallinity in either the retrieved Durasul or conventional PE tibial components. This investigation demonstrates that changes in oxidation index, density, and percent crystallinity of retrieved Durasul PE components after short-term in vivo durations are likely not a clinical concern. These data should be used as a benchmark to compare with future studies examining the long-term oxidative resistance of Durasul highly crosslinked PE tibial components.

Osteonecrosis after chemotherapy in children

The application of modern chemotherapy protocols has improved healing and survival rates significantly in pediatric malignancies. As a result, the long-term drug-related side effects are becoming increasingly apparent. Avascular osteonecrosis (AVN) occurs in up to 40% of all patients who have undergone chemotherapy, the average time of onset being 12-18 months after chemotherapy. Compared to other bones, the weight-bearing regions of hip and knee joints are most commonly affected. Incidentally and in early stages, AVN may show only mild symptoms or may not be clinical apparent. Typical risk factors for AVN after chemotherapy are the application of glucocorticoids and an age of 10 ys. and older. The etiology remains unclear. In early stages, AVN can be detected by magnetic resonance imaging (MRI). Evidence-based, standardized therapeutic concepts or orthopedic guidelines are not available for these patients to date. The range of treatment options includes several operative and non-operative treatment alternatives.

Hemiarthroplasty of the hip for fracture—What is the appropriate sized femoral head?

Caliper measurement of the excised femoral head is a standard technique for determination of prosthetic head size during hemiarthroplasty for displaced femoral neck fractures. To evaluate the accuracy of the caliper method of hemiarthroplasty head sizing by comparing it to the native joint congruency (JC) at the weight bearing surface. The diameters of femoral heads in 10 cadaver hip joints were measured by using a caliper at the head equator. Cast moulds were prepared from both the acetabulum and the femoral head in each joint. Every mould's exact spherical diameter at the weight bearing region was measured by a computerised coordinate measuring machine (MNC B231 MITUTOYO). All specimens were coded to ensure that future examination was carried out in a blind manner. Native JC mismatch was determined by subtracting the diameter of the femoral cement mould from that of the acetabular one. Similarly, JC mismatch was calculated for the caliper measurements. The average native JC mismatch (0.36+/-0.29mm, range 0.03-0.82mm, median 0.29mm) was found significantly smaller (p=0.03) than following caliper measurements (0.72+/-0.37mm, range 0.37-1.46mm, median 0.6mm). Routine caliper measured downward size rounding enhanced (p=0.004) this mismatch (0.98+/-0.44mm, range 0.37-1.96mm, median 1.01mm), while upward rounding (0.48+/-0.46mm, range -0.06 to 1.15mm, median 0.41mm) helped mitigate this tendency. Caliper measurements tend to undersize the actual sphere diameter of the femoral head at the weight bearing region. Upward rounded prosthesis should be selected in order to compensate for this propensity.

Influence of surgical preparation on the in-vivo response of osteochondral defects

Cartilage has an extremely poor capacity to heal, which has lead to intensive research into biomaterials and tissue engineering for the purpose of regenerating cartilage in vivo. Many of these techniques have shown great promise in vitro; however, the results do not always carry across to the in-vivo scenario. Healthy cartilage autografts often do not integrate with the adjacent cartilage, suggesting that cartilage is rarely capable of healing even under ideal conditions. It is hypothesized in this study that the surgical creation of defects in cartilage causes significant damage to the adjacent tissues, leading to further degradation of the cartilage and poor outcome for the repair in general. This study compares the healing response of osteochondral defects created with either a punch or a drill in the weight-bearing region of the sheep knee at 4 and 26 weeks following surgery. The use of a drill to create the defect creates a more aggressive inflammatory response at 4 weeks compared with a punch. However, by 26 weeks, defects created with a punch scored higher on the O'Driscoll cartilage grading scale. Tissue damage at the time of surgery plays an important part in the sequence of events for healing of cartilage defects. This knowledge will help to characterize and refine the ovine model for cartilage regeneration and may have an influence on surgical technique and instrumentation for clinical cartilage repair.

The surgical destabilization of the medial meniscus (DMM) model of osteoarthritis in the 129/SvEv mouse

To evaluate anterior cruciate ligament transection (ACLT) and destabilization of the medial meniscus (DMM) surgical instability models of osteoarthritis (OA) in the 129/SvEv mouse knee joint. Micro-surgical techniques were used to perform ACLT or DMM under direct visualization. Histological scoring was performed on multiple sections to assess cartilage damage across the entire joint. The ACLT model gave severe OA, chondrogenesis of the joint capsule and, in some cases, severe subchondral erosion of the posterior tibial plateau. Surgical DMM was less invasive than the ACLT procedure and resulted in lesions primarily on the central weight-bearing region of the medial tibial plateau and medial femoral condyles. Lesions in the DMM model progressed from mild-to-moderate OA at 4 weeks, to moderate-to-severe OA at 8 weeks post-surgery. Destruction of the subchondral bone was never observed in the DMM model. ACLT is not recommended in the mouse due to the high surgical proficiency required and the development of severe OA that may involve subchondral bone erosion. The severity and location of lesions following DMM are consistent with lesions observed in aged spontaneous mouse models of OA. The DMM model has sufficient sensitivity to show disease modification, as observed with the ADAMTS-5 knock out (KO) mouse. The DMM model should be a first choice to challenge mice with gene deletions of potential targets in OA.

The coverage of skin defects over the foot and ankle using the distally based sural neurocutaneous flaps: Experience of 21 cases

Skin defects over the foot and ankle remain a challenge to plastic surgeons. The distally based sural neurocutaneous flap is a reliable and effective procedure. The authors have performed 21 cases (22 flaps) since 2000. Twenty-one flaps survived uneventfully. The recipient range included the dorsum of the foot, heel and forefoot. The texture, thickness and colour were satisfactory although pressure ulcers occurred on flaps over the weight-bearing region, such as sole. The factors that influence the survival of the flap are the width of the pedicle, ligation of the lesser saphenous vein and complete vascular network around the ankle.