Introduction: Osteoarthritis (OA) of the apophyseal (facet) joints often appears to follow degenerative changes in the adjacent intervertebral discs. We test the hypothesis that facet joint OA is directly related to high compressive load-bearing resulting from disc degeneration. Methods: Thirty six cadaveric thoraco-lumbar “motion segments” consisting of two vertebrae and the intervening disc and ligaments, were obtained from 22 human cadavers aged 64–92 yrs (mean 77 yrs). Each was subjected to a constant compressive load of 1.5 kN while the distribution of compressive stress was measured along the mid-sagittal diameter of the intervertebral disc, using a miniature pressure transducer, side-mounted in a 1.3 mm-diameter needle. Measurements of compressive “stress” were summed over area to give the compressive force resisted by the disc. This was subtracted from the applied 1.5 kN to indicate compressive load-bearing by the neural arch, including the apophyseal joints. After mechanical testing, the cartilage of each apophyseal joint surface was graded for degree of degeneration. Joints were then macerated, and each bony joint surface was scored for the following four degenerative changes, according to established criteria: marginal osteophytes, pitting, bony contour change, and eburnation. The four bone scores were summed and used to represent the severity of OA for that joint surface, and values were then averaged for the two facet joints (four surfaces) of each motion segment. Results: Cartilage degeneration and summed bone scores both increased with age, and with each other (P< 0.01). Neural arch load-bearing ranged from 5%–96% (mean 45%) of the applied 1.5 kN compressive force, with values over 50% being found only in specimens with degenerated intervertebral discs. Facet joint summed bone score increased with neural arch load-bearing (P< 0.01), especially when the latter exceeded 50%. Conclusion: High apophyseal joint load loading, equivalent to neural arch compressive load-bearing above 50%, is strongly associated with severe OA changes in the apophyseal joints. Associations were stronger for bone rather than cartilage changes, possibly because pathological load-bearing by the facet joints can occur between the tip of the inferior articular process and the adjacent lamina, substantially by-passing the articular (cartilage) surfaces

Autologous osteochondral grafting has demonstrated positive outcomes for treating articular cartilage defects by replacing the damaged region with a cylindrical graft consisting of bone with a layer of cartilage, taken from a non-loadbearing region of the knee. Despite positive clinical use, factors that cause graft subsidence or poor integration are relatively unknown. The aim of this study was to develop finite element (FE) models of osteochondral grafts within a tibiofemoral joint and to investigate parameters affecting osteochondral graft stability.

Initial experimental tests on cadaveric femurs were performed to calibrate the bone properties and graft-bone frictional forces for use in corresponding FE models, generated from µCT scan data. The effects of cartilage defects and osteochondral graft repair were measured by examining contact pressure changes using in vitro tests on a single cadaveric human tibiofemoral joint. Six defects were created in the femoral condyles which were subsequently treated with osteochondral autografts or metal pins. Matching µCT scan-based FE models were created, and the contact patches were compared. Sensitivity to graft bone properties was investigated.

The bone material properties and graft-bone frictional forces were successfully calibrated from the initial tests with good resulting levels of agreement (CCC=0.87). The tibiofemoral joint experiment provided a range of cases to model. These cases were well captured experimentally and represented accurately in the FE models. Graft properties relative to host bone had large effects on immediate graft stability despite limited changes to resultant cartilage contact pressure.

Model confidence was built through extensive validation and sensitivity testing, and demonstrated that specimen-specific properties were required to accurately represent graft behaviour. The results indicate that graft bone properties affect the immediate stability, which is important for the selection of allografts and design of future synthetic grafts.

Introduction: Vertebral bodies and intervertebral discs resist most of the compressive force acting on the spine. However, experiments on lumbar spines have shown that apophyseal joints can resist more than 50% of applied compression, and that the proportion varies with spinal level, disc narrowing, and posture. In the cervical spine, the situation is likely to be complicated by the presence of uncovertebral joints on the lateral margins of the disc. Load-sharing is important because it influences injury risk, and predisposition to degenerative changes. The present study aims to characterise compressive load-sharing in the cervical spine.

Methods: Sixteen cervical motion segments, consisting of two vertebrae and the intervening disc and ligaments, were dissected from nine cadaveric spines, aged 48-77 yrs (mean 63 yrs) which had been stored at -17degC. Specimens were subjected to 200N of compression while the distribution of compressive ‘stress’ was measured along the mid-sagittal diameter of the disc, using a pressure transducer side-mounted in a 0.9mm-diameter needle. ‘Stress profiles’ effectively were integrated over area to calculate the total compressive force acting on the disc. Experiments were performed with each specimen in flexion, extension and neutral posture. They were repeated after creep compressive loading (2 hrs at 150N) to simulate diurnal loading in life, and again following removal of the apophyseal joints. Eight specimens were re-tested following bi-lateral removal of the uncovertebral joints.

Results: Creep loading reduced disc height by an average 0.64mm (approximately 12%). Creep reduced overall computed disc loading by 14% and 25% in neutral and extended postures respectively (P< 0.005). Apophyseal joint removal increased disc loading in extension (only) by 14% (P< 0.05). Uncovertebral joint removal further increased disc loading in flexed, neutral and extended postures by 28%, 33% and 21% respectively (P< 0.05).

Conclusion: Creep loading of the cervical spine transfers loading to the apophyseal joints and uncus. The former effect is small, and significant only in extended postures. The latter effect is larger, and is greatest in flexed and neutral postures.

Hip joint biomechanics can be altered by abnormal morphology of the acetabulum and/or femur. This may affect load distribution and contact stresses on the articular surfaces, hence, leading to damage and degradation of the tissue. Experimental hip joint simulators have been used to assess tribology of total hip replacements and recently methods further developed to assess the natural hip joint mechanics. The aim of this study was to evaluate articular surfaces of human cadaveric joints following prolonged experimental simulation under a standard gait cycle.

Four cadaveric male right hips (mean age = 62 years) were dissected, the joint disarticulated and capsule removed. The acetabulum and femoral head were mounted in an anatomical hip simulator (Simulation Solutions, UK). A simplified twin peak gait cycle (peak load of 3kN) was applied. Hips were submerged in Ringers solution (0.04% sodium azide) and testing conducted at 1 Hertz for 32 hours (115,200 cycles). Soft tissue degradation was recorded using photogrammetry at intervals throughout testing.

All four hips were successfully tested. Prior to simulation, two samples exhibited articular surface degradation and one had a minor scalpel cut and a small area of cartilage delamination. The pre-simulation damage got slightly worse as the simulation continued but no new areas of damage were detected upon inspection. The samples without surface degradation, showed no damage during testing and the labral sealing effect was more obvious in these samples.

The fact that no new areas of damage were detected after long simulations, indicates that the loading conditions and positioning of the sample were appropriate, so the simulation can be used as a control to compare mechanical degradation of the natural hip when provoked abnormal conditions or labral tissue repairs are simulated.

Abstract

Purpose: To determine if some subsets of healthy subjects displayed other than a typical gait pattern and to identify which subsets have similar kinematic pattern to patients with knee osteoarthritis.

Methods: The healthy subject dataset consisted of 106 asymptomatic volunteers. These subjects were over 17 years of age, pain-free, had no record of surgery to the lower limb and no evidence or history of arthritic disease at the time of testing. The patient population consisted of 12 patients diagnosed with knee OA, evaluated within 6 months prior to the tests. The 3D movements of right knee joint were recorded using a functional knee analyzer with magnetic sensors while subjects walked on a treadmill at their own preferred speed. The magnetic sensors are non-invasive electromagnetic devices, which track the 3D positions and orientations of sensors relative to a source. The system has been shown to be accurate, especially in the frontal and transversal planes. K-means clustering analysis was chosen to identify the gait patterns among healthy subjects based on three components of the knee joint angles, and analyses of variance were performed to determine which parameters were different between subsets.

Results: Three gait groups or patterns were identified in the healthy subjects. The first group (G1) was characterized by a kinematic profile similar to the OA group. The second group (G2) had the highest external rotation angle, which was significantly different from OA group. The abduction angles were always greater in the G2 and G3 than in the OA group. This might be attributed to a valgus static alignment in G2 and G3 comparing to a varus alignment in the patient with OA.

Conclusions: The newly developed functional knee analyzer provided a non-invasive way to accurately measure 3D kinematic data which enabled cluster analysis to distinguish three gait patterns from 106 healthy subjects. The results suggested a strong correlation between static alignment and dynamic ad-abduction angles during the gait, which need to be investigated. Funding: Other Education Grant Funding Parties: NSERC, CIHR and FCAR

Objectives

Understanding lumbar facet joint involvement and biomechanical changes post spinal fusion is limited. This study aimed to establish an in vitro model assessing mechanical effects of fusion on human lumbar facet joints, employing synchronized motion, pressure, and stiffness analysis.

Aim

The aim of this systematic review was to assess the existing published data on tuberculous arthritis involving native joints in adults aged 18 years and older. The specific research questions focused on the diagnosis and management of the disease.

One assumed function of Total Ankle Replacement (TAR) is that by maintaining ankle joint motion we can protect the other hind foot joints from further degredation¹. However, there is no work to our knowledge that compares hindfoot outcomes between TAR and arthrodesis. Sokolowski et al. found that 68% of TAR patients had no radiological progression of subtalar arthritis after TAR, and 4% went on to fusion². However, no evaluation of the other hindfoot joints was made and no comparison made to other treatment. We performed a retrospective review of all patients at our centre who had had a TAR or ankle arthrodesis since 2002. Case notes and imaging were reviewed and all instances of hindfoot treatment (injections or surgical procedures) noted. Patients were excluded who had no documentation, were followed up at other hospitals, had prior hindfoot fusion, or were having staged surgeries at the time of index treatment. Chi squared analysis was used to compare the cohorts. 214 arthrodesis cases and 302 TAR were eligible. The average age was 57. Average time to follow up was 13 years (4–21). At the time of abstract submission 107 sets of notes had been reviewed fully. Full analysis will be performed by conference. 14% of TAR patients went on to have further procedures to the hindfoot joints while 35% of arthrodesis patients had further procedures (p=0.014). There was also a significant difference in the number of patients progressing to fusion of a further hindfoot joint between groups (TAR- 4%, arthrodesis- 20%, p=0.01). These data suggest that TAR are protective of symptomatic change of hindfoot joints. Patients with TAR had fewer hindfoot fusions than those with arthrodesis and also fewer procedures of any form, including injections.

Aims

To evaluate the effectiveness of an institutionally developed algorithm for evaluation and diagnosis of prosthetic joint injection and to determine the impact of this protocol on overall hospital re-admissions.p

Cobalt chrome-on-cobalt chrome bearing surfaces have been re-introduced despite some concerns regarding potential risks posed by soluble metallic by-products. We have investigated whether there are metal-selective differences between the levels of genetic damage caused to a human cell line when cultured with synovial fluids retrieved from various designs of orthopaedic joint replacement prostheses at the time of revision arthroplasty.

Synovial fluids were retrieved from revision hip and knee arthroplasty patients with bearings made from cobalt chrome-on-cobalt chrome, cobalt chrome-on-polyethylene and stainless steel-on-polyethylene. Control synovial fluids were retrieved from primary arthroplasty cases with osteoarthritis. Synovial fluid was cultured with human primary fibroblasts for 48 hours in a cell culture system under standardised conditions. The “Comet” assay was used with an image analysis system to measure levels of DNA damage caused by the various synovial fluid samples.

Synovial fluids from cobalt chrome-on-cobalt chrome and cobalt chrome-on-polyethylene joint replacements both caused substantial levels of genetic damage as detected by the Comet assay. Synovial fluids retrieved from stainless steel-on-polyethylene joints caused low levels of damage. The difference between these groups was highly statistically significant (p< 0.001). Control synovial fluids from osteoarthritic joints caused minimal changes. Atomic absorption spectroscopy demonstrated that the metal-on-metal synovial fluids contained the highest levels of cobalt and chromium. Different alloys used in orthopaedic implants are associated with different levels of DNA damage to cultured human cells in vitro. We are able to demonstrate that this damage is attributable at least in part to the metal content of the synovial fluid samples. We have no evidence for any long-term health risk to patients with such implants.

Introduction

Untreated hip osteoarthritis is a debilitating condition leading to pain, bone deformation, and limited range of motion. Unfortunately, studies have not been conducted under in vivo conditions to determine progressive kinematics variations to a hip joint from normal to pre-operative and post-operative THA conditions. Therefore, the objective was this study was to quantify normal and degenerative hip kinematics, compared to post-operative hip kinematics.

Aims: To study the levels of genetic damage caused to a cultured human cell line when cultured with synovial ßuid retrieved from revision arthroplasty joints. Methods: Synovial ßuids were retrieved from revision hip and knee arthroplasty patients with bearings made from Cobalt chrome-on-Cobalt chrome, Cobalt chrome-on-polyethylene, Stainless Steel-on-polyethylene and Titanium-onpolyethylene. Control synovial ßuid was retrieved from primary arthroplasty cases. Synovial ßuid was cultured with human primary þbroblasts for 48 hours in a cell culture system under standardised conditions. The ÔCometñ assay was used with an image analysis system to measure levels of DNA damage caused by the various synovial ßu id samples. Results: Synovial ßuids from Cobalt Chrome-on-Cobalt Chrome and Cobalt Chrome-on-polyethylene joint replacements caused signiþcantly (p< 0.05) more genetic damage than synovial ßuids from Stainless Steel-on-polyethylene and Titanium-on-polyethylene cases. Control synovial ßuid caused minimal change. Conclusions: Different alloys used in Orthopaedic implants are associated with different levels of DNA damage to human cells in vitro. We have no evidence for any long-term health risk to patients with such implants. Further research is needed in this þeld.

Abstract

Metal-on-metal joint replacements have been reintroduced despite some concerns regarding the potential risks posed by soluble metallic by-products. We have investigated whether there are metal selective differences between the levels of genetic damage caused to a human cell line when cultured with synovial fluids retrieved from orthopaedic joint replacement prostheses at the time of revision arthroplasty.

Methods: Synovial fluids were retrieved from revision hip and knee arthroplasty patients with bearings made from Cobalt chrome-on-Cobalt chrome, Cobalt chrome-on-polyethylene and Stainless Steel-on-polyethylene. Control synovial fluids were retrieved from primary arthroplasty cases with osteoarthritis and no implant in situ. Synovial fluid was cultured with human primary fibroblasts for 48 hours in a cell culture system under standardised conditions. The ‘Comet’ assay was used with an image analysis system to measure levels of DNA damage caused by the various synovial fluid samples. Metal levels were measured in the synovial fluid samples using atomic absorption spectroscopy.

Results: Synovial fluids from Cobalt Chrome-on-Cobalt Chrome and Cobalt Chrome-on-polyethylene joint replacements both caused substantial levels of genetic damage as detected by the Comet assay. Synovial fluids retrieved from Stainless Steel-on-polyethylene joints caused low levels of damage. The difference between these groups was highly statistically significant (p< 0.001). Control synovial fluids from osteoarthritic joints caused minimal changes. Atomic absorption spectroscopy demonstrated that the metal-on-metal synovial fluids contained substantially more cobalt and chromium than the fluids retrieved from cobalt chrome-on-polyethylene joints. Stainless steel-on-polyethylene synovial fluids contained the least metal.

Conclusions: Different alloys used in Orthopaedic implants are associated with different levels of DNA damage to cultured human cells in vitro. We are able to demonstrate that this damage is attributable at least in part to the metal content of the synovial fluid samples. We have no evidence for any long-term health risk to patients with such implants. Further research is needed in this field.

Background

We identified several opportunities to significantly reduce cost for hip and knee arthroplasty procedures:

Customized instruments: by identifying the essential instruments for arthroplasty cases, we managed to have one universal tray for each case, and 3 specific trays from the implant manufacturing company.

Aim of the study was to measure the cost savings, efficacy, and outcomes associated with primary total hip and knee arthroplasty by implementing these protocol

The fingers and thumb are the second most common site for dislocation of joints following injury (3.9/10,000/year). Unlike fractures, the pattern and patient reported outcomes following dislocations of the hand have not previously been reported.

All patients presenting with a dislocation or subluxation of the fingers or thumb were included in this cohort study (November 2008 and October 2009). Patient demographic and injury data were obtained and dislocation pattern confirmed on radiographs. Patient reported outcomes were obtained using the Michigan Hand Outcome Questionnaire (MHQ).

There were 202 dislocations/subluxations recorded. MHQ scores were obtained at 3–5 years for 74percnt; patients. The average age at injury was 40 years, 76percnt; (146) patients were male and 11percnt; (23) injuries were open. 50percnt; (101) of the dislocations were dorsal, 28percnt; (57) were associated with fractures and 4percnt; (9) were recurrent.

There were significant associations between: 1, Direction of dislocation and finger involved (p=0.03); 2, Joint and mechanism of dislocation (p=0.001); 3, Mechanism and direction of dislocation (p=0.008). Older patients had significantly worse outcomes (p<0.001).

This is the first study to assess the epidemiology and patient reported outcomes following dislocation of the fingers and thumb allowing us to better understand these injuries.

Many recent knee prostheses are designed aiming to the physiological knee kinematics on tibiofemoral joint, which means the femoral rollback and medial pivot motion. However, there have been few studies how to design a patellar component. Since patella and tibia are connected by a patellar tendon, tibiofemoral and patellofemoral motion or contact forces might affect each other. In this study, we aimed to discuss the optimal design of patellar component and simulated the knee flexion using four types of patellar shape during deep knee flexion.

Our simulation model calculates the position/orientation, contact points and contact forces by inputting knee flexion angle, muscle forces and external forces. It can be separated into patellofemoral and tibiofemoral joints. On each joint, calculations are performed using the condition of point contact and force/moment equilibrium. First, patellofemoral was calculated and output patellar tendon force, and tibiofemoral was calculated with patellar tendon force as external force. Then patellofemoral was calculated again, and the calculation was repeated until the position/orientation of tibia converged.

We tried four types of patellar shape, circular dome, cylinder, plate and anatomical. Femoral and tibial surfaces are created from Scorpio NRG PS (Stryker Co.). Condition of knee flexion was passive, with constant muscle forces and varying external force acting on tibia. Knee flexion angle was from 80 to 150 degrees.

As a result, the internal rotation of tibia varied much by using anatomical or plate patella than dome or cylinder shape. Although patellar contact force did not change much, tibial contact balances were better on dome and cylinder patella and the medial contact forces were larger than lateral on anatomical and plate patella. Thus, the results could be divided into two types, dome/cylinder and plate/anatomical. It might be caused by the variations of patellar rotation angle were large on anatomical and plate patella, though patellar tilt angles were similar in all the cases. We have already reported that the anatomical shape of patella would contact in good medial-lateral balance when tibia moved physiologically, therefore we have predicted the anatomical patella might facilitate the physiological tibiofemoral motion. However, the results were not as we predicted. Actually our previous and this study are not in the same condition; we used a posterior-stabilized type of prosthesis, and the post and cam mechanism could not make the femur roll back during deep knee flexion.

It might be better to choose dome or cylinder patella to obtain the stability of tibiofemoral joint, and to choose anatomical or plate to the mobility.

Introduction

Geometric variations of the hip joint can give rise to abnormal joint loading causing increased stress on the articular cartilage, which may ultimately lead to degenerative joint disease. In-vitro simulations of total hip replacements (THRs) have been widely reported in the literature, however, investigations exploring the tribology of two contacting cartilage surfaces, and cartilage against metal surfaces using complete hip joint models are less well reported.

The aim of this study was to develop an in-vitro simulation system for investigating and comparing the tribology of complete natural hip joints and hemiarthroplasties with THR tribology. The simulation system was used to assess natural porcine hip joints and porcine hemiarthroplasty hip joints. Mean friction factor was used as the primary outcome measure to make between-group comparisons, and comparisons with previously published tribological studies.