Abstract

Abstract

The National Health Service produces over 500,000 tonnes of waste and 25 mega tonnes of CO2 annually. Operating room waste is segregated into different streams which are recycled, disposed of in landfill sites, or undergo costly and energy-intensive incineration processes.

By assessing the quantity and recyclability of waste from primary hip and knee arthroplasty cases, we aim to identify strategies to reduce the carbon footprint of arthroplasty surgery.

Data was collected prospectively at a tertiary orthopaedic hospital, in the theatres of six arthroplasty surgeons between April – July 2022. Fifteen primary total hip arthroplasty (THA) and 16 primary total knee arthroplasty (TKA) cases were included; revision and complex primary cases were excluded.

Waste was categorised into non-hazardous waste, hazardous waste, recycling, sharps, and linens. Each waste category was weighed. Items disposed as non-hazardous waste were catalogued for a sample of 10 TKA and 10 THA cases. Recyclability of items was determined from packaging.

Average total waste generated for THA and TKA were 14.46kg and 17.16kg respectively, with TKA generating significantly greater waste (p < 0.05).

On average only 5.4% of waste was recycled in TKA and just 2.9% in THA cases. The mean recycled waste was significantly greater in TKA cases compared to THA, 0.93kg and 0.42kg respectively (p < 0.05).

Hazardous waste represented the largest proportion of the waste streams for both TKA (69.2%) and THA (73.4%). On average TKA generated a significantly greater amount (11.87kg) compared to THA (10.61kg), p < 0.05.

Non-hazardous waste made up 15.1% and 11.3% of total waste for TKA and THA respectively.

In the non-hazardous waste, only two items (scrub brush packaging and sterile towel packaging) were identified as recyclable based on packaging.

We estimate that annually total hip and knee arthroplasty generates over 2.7 million kg of waste in the UK. Through increased use of recyclable plastics for packaging, combined with clear labelling of items as recyclable, medical suppliers can significantly reduce the carbon footprint of arthroplasty. Our data highlight only a very small percentage of waste is recycled in total hip and knee arthroplasty cases.

Abstract

Surgical site infections following spinal surgery profoundly influence continued treatment, significantly impacting psychological and economic dimensions and clinical outcomes. Its reported incidence varies up to 20%, with the highest incidence amongst neuromuscular scoliosis and metastatic cord compression patients.

We describe the first reported biphasic osteoconductive scaffold (Cerament G) with a logarithmic elution profile as a cumulative strategic treatment modality for adjacent spinal surgery infections.

All patients who developed surgical site infections following instrumented fusion (May 2021-December 2021) had their demographics (age, sex), type and number of procedures, isolated organism, antibiotics given, comorbidities, and WHO performance status analysed.

The infected wound was debrided to healthy planes, samples taken, and Cerament g applied.

Thirteen patients were treated for deep SSI following spinal instrumentation and fusion procedures with intraoperative Cerament G application. There were four males and nine females with an average age of 40 ranging between 12 and 87. Nine patients underwent initial surgery for spinal deformity, and four were treated for fractures as index procedure.

77% of infections were attributable to MSSA and Cutibacteriousm acnes; others included Klebsiella, Pseudomonas and Streptococcus and targeted with multimodal cumulative therapy. A WHO performance score improved in 11 patients. In addition, there was no wound leak, and infection was eradicated successfully in 12/13 with a single procedure.

This series shows the successful eradication of the infection and improved functional outcomes with Cerament G. However, the low numbers of patients in our series are an essential consideration for the broader applicability of this device.

Aims

The COVID-19 pandemic posed significant challenges to healthcare systems across the globe in 2020. There were concerns surrounding early reports of increased mortality among patients undergoing emergency or non-urgent surgery. We report the morbidity and mortality in patients who underwent arthroplasty procedures during the UK first stage of the pandemic.

Background

There remains a paucity of clinical studies on the effects of coronavirus on perioperative outcomes, with no existing trials reporting on risk factors associated with increased risk of postoperative mortality in these patients. The objectives of this study were to assess perioperative complications and identify risk factors for increased mortality in patients with coronavirus undergoing surgery.

Total knee arthroplasty (TKA) is the most commonly performed elective orthopaedic procedure. With an increasingly aging population, the number of TKAs performed is expected to be ∼2,900 per 100,000 by 2050. Surgical Site Infections (SSI) after TKA can have significant morbidity and mortality. The purpose of this study was to construct a risk prediction model for acute SSI (classified as either superficial, deep and overall) within 30 days of a TKA based on commonly ordered pre-operative blood markers and using audited administrative data from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database.

All adult patients undergoing an elective unilateral TKA for osteoarthritis from 2011–2016 were identified from the NSQIP database using Current Procedural Terminology (CPT) codes. Patients with active or chronic, local or systemic infection/sepsis or disseminated cancer were excluded. Multivariate logistic regression was conducted to estimate coefficients, with manual stepwise reduction to construct models. Bootstrap estimation was administered to measure internal validity. The SSI prediction model included the following co-variates: body mass index (BMI) and sex, comorbidities such as congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD), smoking, current/previous steroid use, as well as pre-operative blood markers, albumin, alkaline phosphatase, blood urea nitrogen (BUN), creatinine, hematocrit, international normalized ratio (INR), platelets, prothrombin time (PT), sodium and white blood cell (WBC) levels. To compare clinical models, areas under the receiver operating characteristic (ROC) curves and McFadden's R-squared values were reported.

The total number of patients undergoing TKA were 210,524 with a median age of 67 years (mean age of 66.6 + 9.6 years) and the majority being females (61.9%, N=130,314). A total of 1,674 patients (0.8%) had a SSI within 30 days of the index TKA, of which N=546 patients (33.2%) had a deep SSI and N=1,128 patients (67.4%) had a superficial SSI. The annual incidence rate of overall SSI decreased from 1.60% in 2011 to 0.68% in 2016. The final risk prediction model for SSI contained, smoking (OR=1.69, 95% CI: 1.31 – 2.18), previous/current steroid use (OR=1.66, 95% CI: 1.23 – 2.23), as well as the pre-operative lab markers, albumin (OR=0.46, 95% CI: 0.37 – 0.56), blood urea nitrogen (BUN, OR=1.01, 95% CI: 1 – 1.02), international normalized ratio (INR, OR=1.22, 95% CI:1.05 – 1.41), and sodium levels (OR=0.94, 95% CI: 0.91 – 0.98;). Area under the ROC curve for the final model of overall SSI was 0.64. Models for deep and superficial SSI had ROC areas of 0.68 and 0.63, respectively. Albumin (OR=0.46, 95% CI: 0.37 – 0.56, OR=0.33, 95% CI: 0.27 – 0.40, OR=0.75, 95% CI: 0.59 – 0.95) and sodium levels (OR=0.94, 95% CI: 0.91 – 0.98, OR=0.96, 95% CI: 0.93 – 0.99, OR=0.97, 95% CI: 0.96 – 0.99) levels were consistently significant in all prediction models for superficial, deep and overall SSI, respectively. Overall, hypoalbuminemia and hyponatremia are both significant risk factors for superficial, deep and overall SSI.

To our knowledge, this is the first prediction model for acute SSI post TKA whereby hyponatremia (and hypoalbuminemia) are predictive of SSI. This prediction model can help fill an important gap for predicting risk factors for SSI after TKA and can help physicians better optimize patients prior to TKA.

Background

Bone preservation is desired for future revision in any knee arthroplasty. There is no study comparing the difference in the amount of bone resection when soft tissue balance is performed with or without computer navigation.

To determine the effect on bony cuts when soft tissue balance is performed with or without use of computer software by standard manual technique in total knee arthroplasty.

One hundred patients aged 50 to 88 years underwent navigated TKR for primary osteoarthritis. In group A, 50 patients had both soft tissue release and bone cuts done using computer-assisted navigation. In group B, 50 patients had soft tissue release by standard manual technique first and then bone cuts were guided by computer-assisted navigation.

In group A the mean medial tibial resection was 5 ± 2.3 mm and lateral was 8 ± 1 mm compared to 5 ± 2 mm (P = 0.100) and 8 ± 1 mm respectively in group B (P = 0.860). In group A the mean medial femoral bone cut was 9 ± 2.9 mm and lateral was 8 ± 2 mm as compared to 9.5 ± 2.9 mm (P = 0.316) and 10 ± 2.2 mm respectively in group B (P = 0.001). Average prosthesis size was 6 (range 3 to 8) in group A as compared to size 5 (range 2 to 7) in group B. Average navigation time in group A was 102 minutes (range 45 to 172) and in group B was 83 minutes (range 42 to 165, P = 0.031).

Our results show that performing soft tissue release and bone cuts using computer- assisted navigation is more bone conserving as compared to manual soft tissue release and bone cuts using computer navigation for TKR, thus preserving bone for possible future revision surgery.

Introduction

Aim was to compare the functional outcome of anterior cervical decompression and fusion (ACDF) with stand-alone tricotical iliac crest auto graft verses stand-alone PEEK cage.

Background

Stress fractures at tracker after computer navigated total knee replacement are rare. Periprosthetic fracture after Minimally Invasive Plate Osteosynthesis (MIPO) of stress fracture through femoral tracker is unique in orthopaedic literature. We are reporting this unique presentation of periprosthetic fractures after MIPO for stress fracture involving femoral pin site track in computer assisted total knee arthroplasty, treated by reconstruction nail (PFNA).

During the preoperative examination, surgeons determine whether a patient, with a degenerative hip, is a candidate for total hip arthroplasty (THA). Although research studies have been conducted to investigate in vivo kinematics of degenerative hips using fluoroscopy, surgeons do not have assessment tools they can use in their practice to further understand patient assessment. Ideally, if a surgeon could have a theoretical tool that efficiently allows for predictive post-operative assessment after virtual surgery and implantation, they would have a better understanding of joint conditions before surgery.

The objectives of this study were (1) to use a validated forward solution hip model to theoretically predict the in vivo kinematics of degenerative hip joints, gaining a better understanding joint conditions leading to THA and (2) compare the predicted kinematic patterns with those derived using fluoroscopy for each subject.

A theoretical model, previously evaluated using THA kinematics and telemetry, was used for this study, incorporating numerous muscles and ligaments, including the quadriceps, hamstring, gluteus, iliopsoas, tensor fasciae latae, an adductor muscle groups, and hip capsular ligaments. Ten subjects having a pre-operative degenerative hip were asked to perform gait while under surveillance using a mobile fluoroscopy unit. The hip joint kinematics for ten subjects were initially assessed using in vivo fluoroscopy, and then compared to the predicted kinematics determined using the model. Further evaluations were then conducted varying implanted component position to assess variability.

The fluoroscopic evaluation revealed that 33% of the degenerative hips experienced abnormal hip kinematics known as “hip separation” where the femoral head slides within the acetabulum, resulting in a decrease in contact area. Interestingly, the mathematical model produced similar kinematic profiles, where the femoral head was sliding within the acetabulum (Figure 1).

During swing phase, it was determined that this femoral head sliding (FHS) is caused by hip capsular laxity resulting in reducing joint tension. At the point of maximum velocity of the foot, the momentum of the lower leg becomes too great for capsule to properly constrain the hip, leading to the femoral component pistoning outwards.

During stance phase, kinematics of degenerative hips were similar to kinematics of a THA subject with mal-positioning of the acetabular cup. Further evaluation revealed that if the cup was placed at a position other than its native, anatomical center, abnormal forces and torques acting within the joint lead to the femoral component sliding within the acetabular cup. It was hypothesized that in degenerative hips, similar to THA, the altered center of rotation is a leading influence of FHS (Figure 2).

The theoretical model has now been validated for subjects having a THA and degenerative subjects. The model has successfully derived kinematic patterns similar to subjects evaluated using fluoroscopy. The results in this study revealed that altering the native joint center is the most influential factor leading to FHS, or more commonly known as hip separation. A new module for the mathematical model is being implemented to simulate virtual surgery so that the surgery can pre- operatively plan and then simulate post-operative results.

Introduction

Many fluoroscopic studies on total knee arthroplasty (TKA) have identified kinematic variabilities compared to the normal knee, with many subjects experiencing paradoxical motion patterns. The intent of this research study was to investigate the results of customized-individual-made (CIM) and off-the-shelf (OTS) PS and PCR TKA to determine kinematic variabilities and to assess these kinematic patterns with those previously documented for the normal knee.

Introduction

Aim was to compare the functional outcome of anterior cervical decompression and fusion (ACDF) with stand-alone tricotical iliac crest auto graft verses stand-alone PEEK cage.

Introduction

Hip osteoarthritis can be debilitating, often leading to pain, poor kinematics and limiting range of motion. While the in vivo kinematics of a total hip arthroplasty (THA) are well documented, there is limited information pertaining to the kinematics of native, non-arthritic (normal) hips and degenerative hips requiring a THA.

The objective of this study is to evaluate and compare the in vivo kinematics of the normal hip with pre-operative, degenerative hips and post-operative THA.

Currently, hip implant designs are evaluated experimentally using mechanical simulators or cadavers, and total hip arthroplasty (THA) postoperative outcomes are evaluated clinically using long-term follow-up. However, these evaluation techniques can be both costly and time-consuming. Neither can provide an assessment of post-operative results at the onset of implant development. More recently, a forward-solution mathematical model was developed that functions as theoretical joint simulator, providing instant feedback to designers and surgeons alike. This model has been validated by comparing the model predictions with kinematic results from fluoroscopy for both implanted and non-implanted hips and kinetics from a telemetric hip. The model allows surgical technique modifications and implant component placement under in vivo conditions.

The objective of this study was to further expand the capabilities of the model to function as an intraoperative virtual surgical tool (Figure 1). This new module allows the surgeon to simulate surgery, then predict, compare, and optimize postoperative THA outcomes based on component placement, sizing choices, reaming and cutting locations, and surgical methods.

This virtual surgery tool simulates the quadriceps, hamstring, gluteus, iliopsoas, tensor fasciae latae, and an adductor muscle groups, as well as the hip capsular ligament groups. The model can simulate resecting, weakening, loosening, or tightening of soft tissues based on surgical techniques. Additionally, the model can analyze a variety of activities, including gait and deep flexion activities.

Initially, the virtual surgery module offers theoretical surgery tools that allow surgeons to alter surgical alignments, component designs, offsets, as well as reaming and cutting simulations. The virtual model incorporates a built-in CT scan bone database which will assist in determining muscle and ligament attachment sites as well as bony landmarks. The virtual model can be used to assist in the placement of both the femoral component and the acetabular cup (Figure 2).

Moreover, once the surgeon has decided on the placements of the components, they can use the simulation capabilities to run virtual human body maneuvers based on the chosen parameters. The simulations will reveal force, contact stress, and motion predictions of the hip joint (Figure 3). The surgeon can then choose to modify the positions accordingly or proceed with the surgery.

This new virtual surgical tool will allow surgeons to gain a better understanding of possible post-operative outcomes under pre-operative conditions or intra-operatively. Simulations using the virtual surgery model has revealed that improper component placement may lead to non-ideal post-operative function, which has been simulated using the model. Further evaluation is ongoing so that this new module can reveal more information pre-operatively, allowing a surgeon to gain ample information before surgery, especially with difficult and revision cases.

Introduction

Previous fluoroscopic studies of total knee arthroplasty (TKA) have revealed significant kinematic differences compared to the normal knee. Often, subjects having a TKA experienced kinematic patterns opposite of the normal knee. Therefore, the objective of this study was to determine the in vivo kinematics of subjects implanted with either a customized-individual-made (CIM) or the traditional (OTS) PS TKA to determine if customization offers a distinct advantage to the patient.

Background

The overall goal of total knee arthroplasty (TKA) is to facilitate the restoration of native function following late stage osteoarthritis and for this reason it is important to develop a thorough understanding of the mechanics of a normal healthy knee.

While there are several methods for assessing TKA mechanics, these methods have limitations that make them prohibitive to both replicating physiological systems and evaluating non-implanted knees. These limitations can be circumvented through the development of mathematical models that use anatomical and physiological inputs to computationally simulate joint mechanics. This can be done in an inverse or forward manner to solve for either joint forces or motions respectively. The purpose of this study is to evaluate one such forward model and determine the accuracy of the predicted motions using fluoroscopy.

Background

Extensive research has previously been conducted analyzing the biomechanical effects of rotational changes (i.e. version and inclination) of the acetabular cup. Many sources, citing diverse dislocation statistics, encourage surgeons to strive for various “safe zones” during the THA operation. However, minimal research has been conducted, especially under in vivo conditions, to assess the consequences of cup translational shifting (i.e. offsets, medial and superior reaming, etc.). While it is often the practice to medialize the acetabular cup intraoperatively, there is still a lack of information regarding the biomechanical consequences of such cup medializations and medial/superior malpositionings.

Background

In vivo fluoroscopic studies have proven that femoral head sliding and separation from within the acetabular cup during gait frequently occur for subjects implanted with a total hip arthroplasty. It is hypothesized that these atypical kinematic patterns are due to component malalignments that yield uncharacteristically higher forces on the hip joint that are not present in the native hip. This in vivo joint instability can lead to edge loading, increased stresses, and premature wear on the acetabular component.

Background

Previous in vivo fluoroscopic studies have documented that subjects having a PS TKA experience a more posterior condylar contact position at full extension, a high incidence of reverse axial rotation and mid flexion instability. More recently, a PS TKA was designed with a Gradually Reducing Radius (Gradius) curved condylar geometry to offer patients greater mid flexion stability while reducing the incidence of reverse axial rotation and maintaining posterior condylar rollback. Therefore, the objective of this study was to assess the in vivo kinematics for subjects implanted with a Gradius curved condylar geometry to determine if these subjects experience an advantage over previously designed TKA.

Background

The Bi-Cruciate Stabilized (BCS) total knee arthroplasty (TKA) incorporates two cam-post mechanisms in order to replicate the functionality and stability provided by the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) in the native knee. Recently (2012), a second generation BCS design has introduced femur and tibial bearing modifications that are intended to delay lateral femoral condyle rollback and encourage more stable positioning of the medial femoral condyle to more closely replicate normal knee kinematics. The purpose of this study was to compare the kinematics of this TKA to the normal knee during a weight bearing flexion activity.

Background

Currently, hip implant designs are evaluated experimentally using mechanical simulators or cadavers, and total hip arthroplasty (THA) postoperative outcomes are evaluated clinically using long-term follow-up. However, these evaluation techniques can be both costly and time-consuming. Fortunately, forward solution mathematical models can function as theoretical joint simulators, providing instant feedback to designers and surgeons alike. Recently, a validated forward solution model of the hip has been developed that can theoretically simulate new implant designs and surgical technique modifications under in vivo conditions.

Introduction

The Bi-Cruciate Stabilized (BCS) total knee arthroplasty (TKA) incorporates two cam-post mechanisms to reproduce the functionality and stability provided by the anterior cruciate ligament and posterior cruciate ligament in the native knee. The anterior cam-post mechanism provides stability in full extension and early flexion (≤20°) while the posterior cam-post mechanism prevents anterior sliding of the femur during deeper flexion (≥60°). Recently (2012), a second generation BCS design introduced more normal shapes to the femur and tibial bearing geometries that provides delayed lateral femoral condyle rollback and encourages more stable positioning of the medial femoral condyle. The purpose of this study was to compare the in vivo kinematics exhibited by the two generations during weight bearing flexion.

Background

While not common in the native hip, occurrences of femoral head separation from the acetabular cup during gait are well documented after total hip arthroplasty. Although the effects of this phenomenon are not well understood, we hypothesize that these atypical kinematics are due to component misalignments that yield uncharacteristic forces on the hip joint that are not present in the native hip.

In addition to mechanical stresses, an inflammatory mediated association between obesity and knee osteoarthritis (OA) is increasingly being recognised. Adipokines, such as adiponectin and leptin, have been postulated as likely mediators. Clinical and epidemiological differences in OA by race have been reported. What contributes to these differences is not well understood. In this study, we examined the profile of adipokines in knee synovial fluid (SF) and the gene expression profile of the infra-patellar fat pad (IFP) by race among patients with end-stage knee OA scheduled for knee arthroplasty.

Age, sex, weight and height (used to derive body mass index (BMI)) and race (White, Asian and Black) were elicited through self-report questionnaire prior to surgery. SF and IFP samples were collected at the time of surgery. Adipokines (adiponectin and leptin) were examined in the SF using MAGPIX Multiplex platform. IFP was profiled using Human Adipogenesis PCRArray and genes of interest were further validated via quantitative relative RT-PCR using Student's t-test. Overall differences in adiponectin and leptin concentrations were tested across race. Linear regression modeling was used to investigate the association between adiponectin and leptin concentrations (outcomes) and race (predictor; referent group: White), adjusting for age, sex and BMI.

67 patients (18 White, 33 Asian, 16 Black) were included. Mean SF adiponectin concentration was greatest in Whites (1175.05 ng/mL), followed by Blacks (868.53 ng/mL) and Asians (702.23 ng/mL) (p=0.034). The mean SF leptin concentration was highest in Blacks (44.88 ng/mL), followed by Whites (29.86 ng/mL) and Asians (20.18 ng/mL) (p=0.021). Regression analysis showed Asians had significantly lower adiponectin concentrations compared to Whites (p<0.05). However, leptin concentrations did not differ significantly by race after adjusting for covariates. Testing of the IFP, using the Adipogenesis PCRArray, showed significant higher expression of LEP gene (leptin, p=0.03) in Asians (n=4) compared to Whites (n=4).

There appears to be important racial differences in the SF adiponectin profile among individuals with end-stage knee OA. Differential gene expression in the IFP across racial groups could be a potential contributory source for the noted SF variations. Further work to determine the source and function of adipokines in knee OA pathophysiology across racial groups is warranted.

Osteoarthritis (OA) is the most common form of arthritis worldwide. It is a major cause of disability in the adult population with its prevalence expected to increase dramatically over the next 20 years. Although current therapies can alleviate symptoms and improve function in early course of the disease, OA inevitably progresses to end-stage disease requiring total joint arthroplasty. Mesenchymal stromal cells (MSCs) have emerged as a candidate cell type with great potential for intra-articular (IA) repair therapy. However, there is still a considerable lack of knowledge concerning their behaviour, biology and therapeutic effects. To start addressing this, we explored the secretory profile of bone marrow derived MSCs in early and end-stage knee OA synovial fluid (SF).

Subjects were recruited and categorised into early [Kellgren-Lawrence (KL) grade I and II, n=12] and end-stage (KL grade III and IV, n=11) knee OA groups. The SF proteome of early and end-stage OA was tested before and three days after the addition of bone marrow MSCs (16.5×10^3, single donor) using multiplex ELISA (64 cytokines) and mass spectrometry (302 proteins detected). Non parametric Wilcoxon-signed rank test for paired samples was used to compare the levels of proteins before and after addition of MSCs in early and end-stage knee OA SF. Significant differences were determined after multiple comparisons correction (FDR) with a p<0.05.

Gender distribution and BMI were not statistically different between the two cohorts (p>0.05). However, patients in early knee OA cohort were significantly younger (44.7 years, SD=7.1) than patients in the end-stage cohort (58.6 years, SD=4.4; p<0.05). In both early and end-stage knee OA, MSCs increased the levels of VEGF-A (by 320.24 pg/mL), IL-6 (by 826.78 pg/mL) and IL-8 (by 128.85 pg/mL), factors involved in angiogenesis; CXCL1/2/3 (by 103.35 pg/mL), CCL2 (by 1187.27 pg/mL), CCL3 (by 15.82 pg/mL) and CCL7 (by 10.43 pg/mL), growth factors and chemokines. However, CXCL5 (by 48.61 pg/mL) levels increased only in early knee OA, whereas PDGF-AA (by 15.36 pg/mL) and CXCL12 (by 497.19 pg/mL) levels increased only in end-stage knee OA.

This study demonstrates that bone marrow derived MSCs secrete angiogenic and chemotactic factors both in early and end-stage knee OA. More importantly, MSCs show a differential reaction between early and end-stage OA. Functional assays are required to further understand on how the therapeutic effect of MSCs is modulated when exposed to OA SF.

Introduction

Recently, a mobile-fluoroscopy unit was developed which can capture subjects performing unconstrained motions, more accurately replicating everyday demands that patients place on their TKA. The objective of this study was to analyze normal knee and various TKA while subjects perform both traditional and more challenging activities while under surveillance of a mobile fluoroscopy unit.

Introduction

Currently, knee and hip implants are evaluated experimentally using mechanical simulators or clinically using long-term follow-up. Unfortunately, it is not practical to mechanically evaluate all patient and surgical variables and predict the viability of implant success and/or performance. More recently, a validated mathematical model has been developed that can theoretically simulate new implant designs under in vivo conditions to predict joint forces kinematics and performance. Therefore, the objective of this study was to use a validated forward solution model (FSM) to evaluate new and existing implant designs, predicting mechanics of the hip and knee joints.

Introduction

Acetabular revision for cavitary defects in failed total hip replacement remains a challenge for the orthopaedic surgeon. Bone graft with cemented or uncemented revision is the primary solution; however, there are cases where structural defects are too large. Cup cage constructs have been successful in treating these defects but they do have their problems with early loosening and metalwork failure.

Recently, highly porous cups that incorporate metal augments have been developed to achieve greater intra-operative stability showing encouraging results.

Previously more femoral rollback has been reported in posterior-stabilized implants, but so far the kinematic change after post-cam engagement has been still unknown. The tri-condylar implants were developed to fit a life style requiring frequent deep flexion activities, which have the ball and socket third condyle as post-cam mechanism. The purpose of the current study was to examine the kinematic effects of the ball and socket third condyle during deep knee flexion.

The tri-condylar implant analyzed in the current study is the Bi-Surface Knee System developed by Kyocera Medical (Osaka, Japan). Seventeen knees implanted with a tri-condylar implant were analyzed using 3D to 2D registration approach. Each patient was asked to perform a weight-bearing deep knee bend from full extension to maximum flexion under fluoroscopic surveillance. During this activity, individual fluoroscopic video frames were digitized at 10°increments of knee flexion. A distance of less than 1 mm initially was considered to signify the ball and socket contact. The translation rate as well as the amount of translation of medial and lateral AP contact points and the axial rotation was compared before and after the ball and socket joint contact.

The average angle of ball and socket joint contact were 64.7° (SD = 8.7), in which no separation was observed after initial contact. The medial contact position stayed from full extension to ball and socket joint contact and then moved posteriorly with knee flexion. The lateral contact position showed posterior translation from full extension to ball and socket joint contact, and then greater posterior translation after contact (Figure 1). Translation and translation rate of contact positions were significantly greater at both condyles after ball and socket joint contact. The femoral component rotated externally from full extension to ball and socket joint contact, and then remained after ball and socket joint contact (Figure 2). There was no statistical significance in the angular rotation between ball and socket joint contact and maximum flexion. Translation of angular rotation was significantly greater before ball and socket joint contact, however, there was no significance in translation rate before and after ball and socket joint contact.

The ball and socket joint was proved to induce posterior rollback intensively. In terms of axial rotation, the ball and socket joint did not induce reverse rotation, but had slightly negative effects after contact. The ball and socket provided enough functions as a posterior stabilizing post-cam mechanism and did not prevent axial rotation.

Mathematical modeling provides an efficient and easily reproducible method for the determination of joint forces under in vivo conditions. The need for these new modeling methodologies is needed in the lumbar spine, where an understanding of the loading environment is limited. Few studies using telemetry and pressure sensors have directly measured forces borne by the spine; however, only a very small number of subjects have been studied and experimental conditions were not ideal for giving total forces acting in the spine. As a result, alternative approaches for investigating the lumbar spine across different clinical pathologies are essential. Therefore, the objective of this study was to develop of an inverse dynamic mathematical model for theoretically deriving in-vivo contact forces as well as musculotendon forces in patients having healthy, symptomatic, pathological and post-operative conditions of the lumbar spine.

Fluoroscopy and 3D-to-2D image registration were used to obtain kinematic data for patients performing flexion-extension of the lumbar spine. This data served as input into the multi-body, mathematical model. Other inputs included patient-specific bone geometries, recreated from CT, and ground reaction forces. Vertebral bones were represented as rigid bodies, while massless frames symbolized the lower body, torso and abdominal wall (Figure 1). In addition, ligaments were selected and modeled as linear spring elements, along with relevant muscle groups. The muscles were divided into individual fascicles and solved for using a pseudo-inverse algorithm which enabled for decoupling of the derived resultant torques defining the desired kinetic trajectory for the muscles.

The largest average contact forces in the model for healthy, symptomatic, pathological, and post-operative lumbar spine conditions occurred at maximum flexion at L4L5 level and were predicted to be 2.47 BW, 2.33 BW, 3.08 BW, and 1.60 BW, respectively. The FE rotation associated with these theoretical force values was 43.0° in healthy, 40.5° in symptomatic, 44.4° in pathological, and 22.8° in post-operative patients. The smallest forces occurred as patients approached the upright, standing position, followed by slight increases in the contact force at full extension. The theoretically derived muscle forces exhibited similar contributory force profiles in the intact spine (healthy, symptomatic, and pathologic); however, surgically implanted spines experienced an increase in the contribution of the external oblique muscles accompanied with decreased slope gradients in the muscle force profiles (Figure 2).

These altered force patterns may be associated with the decrease in the predicted contact forces in post-operative patients. In addition, the decreased slope gradients in surgically implanted patients corresponds with the observed difficulty of performing the prescribed motion, possibly due to improper muscle firing, thereby leading to slower motion cycles and less ranges-of-motion. On the contrary, patients having an intact spine performed the activity at a faster speed and to greater ranges-of-motion, which corresponds with the higher contact forces derived in the model. In conclusion, this research study presented the development of a mathematical modeling approach utilizing patient-specific data to generate theoretical in-vivo joint forces. This may serve to help progress the understanding for the kinetic characteristics of the native and surgically implanted lumbar spine.

Telemetric knee implants have provided invaluable insight into the forces occurring in the knee during various activities. However, due to the high amount of cost involved only a few of them have been developed. Mathematical modeling of the knee provides an alternative that can be easily applied to study high number of patients. However, in order to ensure accuracy these models need to be validated with in vivo force data. Previously, mathematical models have been developed and validated to study only specific activities. Therefore, the objective of this study was compare the knee force predictions from the same model with that obtained using telemetry for multiple activities.

Kinematics of a telemetric patient was collected using fluoroscopy and 2D to 3D image registration for gait, deep knee bend (DKB), chair rise, step up and step down activities. Along with telemetric forces obtained from the implant, synchronized ground reaction forces (GRF) were also collected from a force plate. The relevant kinematics and the GRF were input into an inverse dynamic model of the human leg starting from the foot and ending at the pelvis (Figure 1). All major ligaments and muscles affecting the knee joint were included in the model. The pelvis and the foot were incorporated into the system so as to provide realistic boundary conditions at the hip and the ankle and also to provide reference geometry for the attachment sites of relevant muscles. The muscle redundancy problem was solved using the pseudo-inverse technique which has been shown to automatically optimize muscle forces based on the Crowninshield-Brand cost function. The same model, without any additional changes, was applied for all activities and the predicted knee force results were compared with the data obtained from telemetry.

Comparison of the model predictions for the tibiofemoral contact forces with the telemetric implant data revealed a high degree of correlation both in the nature of variation of forces and the magnitudes of the forces obtained. Interestingly, the model predicted forces with a high level of accuracy for activities in which the flexion of the knee do not vary monotonically (increases and decreases or vice-versa) with the activity cycle (gait, step up and step down). During these activities, the difference between the model predictions with the telemetric data was less than 5% (Figure 2). For activities where flexion varies monotonically (either increases or decreases) with activity (DKB and chair rise) the difference between the forces was less than 10% (Figure 3).

The results from this study show that inverse dynamic computational models of the knee can be robust enough to predict forces occurring at the knee with a high amount of accuracy for multiple activities. While this study was conducted only on one patient with a telemetric implant, the required inputs to the model are generic enough so that it is applicable for any TKA patient with the mobility to conduct the desired activity. This allows kinetic data to be provided for the improvement of implant design and surgical techniques accessibly and relatively inexpensively.

INTRODUCTION:

Stationary fluoroscopy has been a viable resource for determining in vivo knee kinematics, but limitations have restricted the use of this technology. Patients can only perform certain normal daily living activities while using stationary fluoroscopy and must conduct the activities at speeds that are slower than normal to avoid ghosting of the images. More recently, a Mobile Tracking Fluoroscopic (MTF) unit has been developed that can track patients in real-time as he/she performs various activities at normal speeds (Figure 1). Therefore, the objective of this study was to compare in vivo kinematics for patient's evaluated using stationary and mobile fluoroscopy to determine potential advantages and disadvantages for use of these technologies.

INTRODUCTION:

Previous modalities such as static x-rays, MRI scans, CT scans and fluoroscopy have been used to diagnosis both soft-tissue clinical conditions and bone abnormalities. Each of these diagnostic tools has definite strengths, but each has significant weaknesses. The objective of this study is to introduce two new diagnostic, ultrasound and sound/vibration sensing, techniques that could be utilized by orthopaedic surgeons to diagnose injuries, defects and other clinical conditions that may not be detected using the previous mentioned modalities.

Introduction

While fluoroscopic techniques have been widely utilized to study in vivo kinematic behavior of total knee arthroplasties, determination of the contact forces of large population sizes has proven a challenge to the biomedical engineering community. This investigation utilizes computational modeling to predict these forces and validates these with independent telemetric data for multiple patients, implants, and activities.

INTRODUCTION

In-vivo data pertaining to the actual cam-post engagement mechanism in PS and Bi-Cruciate Stabilized (BCS) knees is still very limited. Therefore, the objective of this study was to determine the cam-post mechanism interaction under in-vivo, weight-bearing conditions for subjects implanted with either a Rotating Platform (RP) PS TKA, a Fixed Bearing (FB) PS TKA or a FB BCS TKA.

Orthopaedic companies spend years and millions of dollars developing and verifying new total knee arthroplasty (TKA) designs. Recently, computational models have been used in the hopes of increasing the efficiency of the design process. The most popular predictive models simulate a cadaveric rig. Simulations of these rigs, although useful, do not predict in vivo behavior. Therefore, in this current study, the development of a physiological forward solution, or predictive, rigid body model of the knee is described.

The models simulate a non-weight bearing extension activity or a weight-bearing deep knee bend (DKB) activity. They solve for both joint forces and kinematics simultaneously and were developed from the ground up. The models are rigid body and use Kane's dynamical equations. The model began with a simple two dimensional non-weight bearing extension activity model of the tibiofemoral joint. Step by step the model was expanded. Quadriceps and hamstring muscles were added to drive the motion. Ligaments were added represented by multiple non-linear spring elements. The model was expanded to three-dimensions (3D) allowing out of plane motions and calculation of medial and lateral condylar forces. The patella was added as its own body allowing for simulation of the patellofemoral joint. The model was then converted to a weight bearing deep knee bend activity. A pelvis and trunk were added and muscles were given physiological origin and insertion points. A modified proportional-integral-derivative (PID) controller was implemented to control the rate of flexion and also to assist in joint stability by adjusting the force in individual quadriceps muscles. A method for representing articulating geometry was developed. Once the deep knee bend model was fully developed (Figure 1) it was converted back to a non-weight bearing extension model (Figure 2) resulting in simulations of a normal knee performing a weight bearing and non-weight bearing activity. The tibiofemoral kinematic results were compared to in vivo kinematics obtained from a fluoroscopy study of five normal subjects. Parameters from the CT models of one of these subjects (Subject 3) were used in the model.

The model kinematics behave as the normal knee does in vivo. The kinetic results were within reasonable ranges with a maximum total quadriceps force of 0.86 BW and 4.73 BW for extension and DKB simulations, respectively (Figure 3 and Figure 4). The maximum total tibiofemoral forces were 1.26 BW and 3.70 BW for extension and DKB, respectively. The relationship between the quadriceps force, patella ligament force and patellofemoral forces are consistent with how the extensor mechanism behaves (Figure 3 and Figure 4). The patellofemoral forces are low between 0 and 20 degrees flexion and the patella ligament and quadriceps forces are close in magnitude from 0 to around 70 degrees flexion when the patellofemoral forces increase and the quadriceps forces increase relative to the patella ligament force. The model allows for virtual implantation of TKA geometry and after kinematic and kinetic validation from in vivo TKA data can be used to predict the behavior of TKA in vivo.

Purpose

Shoulder dislocations account for 50 % of all dislocations, of which 98% are anterior dislocations. Different techniques have been described in literature with variable success, which depends upon type of dislocation, technique used and muscle relaxation.

INTRODUCTION

Knee simulators are being used to evaluate wear. The current international standards have been developed from clinical investigations of the normal knee [1, 2] or from a single TKA patient [3, 4]. However, the forces and motions in a TKA patient differ from a normal knee and, furthermore, the resulting kinematic outcomes after TKA will depend on the design of the device [5]. Consequently, these standard tests may not recreate in-vivo conditions; therefore, the goal of this study was to perform a novel wear simulation using design-specific inputs that have been derived from fluoroscopic images of a deep knee bend.

INTRODUCTION

Telemetric implants have provided us with invaluable data as to the in vivo forces occurring in implanted knee joints. However, only a few of them exists. The knee is one of the most studied joints in the human body and various mathematical knee models have been used in the past to predict forces. However, these simulation studies have also been carried out on a small group of patients limiting their general usefulness in understanding overall trends of knee behavior. Therefore, it is the purpose of this research to study the implant forces experienced by a large group of patients so as to have a better understanding of the overall magnitudes and their variability with knee flexion.

INTRODUCTION

Total shoulder arthroplasty (TSA) implants are used to restore function to individuals whose shoulder motions are impaired by osteoarthritis. To improve TSA implant designs, it is crucial to understand the kinematics of healthy, osteoarthritic (OA), and post-TSA shoulders. Hence, this study will determine in vivo kinematic trends of the glenohumeral joints of healthy, OA, and post-TSA shoulders.

Introduction

Numerous studies have been conducted to investigate the kinematics of the lumbar spine, and while many have documented its intricacies, few have analyzed the complex coupled out-of-plane rotations inherent in the low back. Some studies have suggested a possible relationship between patients having low back pain (LBP) or degenerative conditions in the lumbar region and various degrees of restricted, excessive, or poorly-controlled lumbar motion. Conversely, others in the orthopedic community maintain there has been no distinct correlation found between spinal mobility and clinical symptoms. The objective of this study was to evaluate both the in-plane and coupled out-of-plane rotational magnitudes about all three motion axes in both symptomatic and asymptomatic patients.

Objectives

There is increasing application of bone morphogenetic proteins (BMPs) owing to their role in promoting fracture healing and bone fusion. However, an optimal delivery system has yet to be identified. The aims of this study were to synthesise bioactive BMP-2, combine it with a novel α-tricalcium phosphate/poly(D,L-lactide-co-glycolide) (α-TCP/PLGA) nanocomposite and study its release from the composite.

Introduction

The annual incidence of fractures in the UK is almost 4%. Bone grafting procedures and segmental bone transport have been employed for bone tissue regeneration. However, their limited availability, donor site morbidity and increased cost mean that there is still a large requirement for alternative methods and there is considerable research into regeneration using bone morphogenetic proteins (BMPs). The aims of this study are to synthesise and combine BMP-2 with a novel nanocomposite and study its release.

A literature review of bone graft substitutes for spinal fusion was undertaken from peer reviewed journals to form a basis for guidelines on their clinical use.

A PubMed search of peer reviewed journals between Jan 1960 and Dec 2009 for clinical trials of bone graft substitutes in spinal fusion was performed. Emphasis was placed on RCTs. Small and duplicated RCTs were excluded. If no RCTs were available the next best clinical evidence was assessed. Data were extracted for fusion rates and complications.

Of 929 potential spinal fusion studies, 7 RCTs met the inclusion criteria for BMP-2, 3 for BMP-7, 2 for Tricalcium Phosphate and 1 for Tricalcium Phosphate/Hydroxyapatite (TCP/HA). No clinical RCTs were found for Demineralised Bone Matrix (DBM), Calcium Sulphate or Calcium Silicate. There is strong evidence that BMP-2 with TCP/HA achieves similar or higher spinal fusion rates than autograft alone. BMP-7 achieved similar results to autograft. 3 RCTs support the use of TCP or TCP/HA and autograft as a graft extender with similar results to autograft alone. The best clinical evidence to support the use of DBMs are case control studies. The osteoinductive potential of DBM appears to be very low however. There are no clinical studies to support the use of Calcium Silicate.

The current literature supports the use of BMP-2 with HA/TCP as a graft substitute. TCP or HA/TCP with Autograft is supported as a graft extender. There is not enough clinical evidence to support other bone graft substitutes.

This study did not require ethics approval and no financial support was received.

Radial head fractures with fragment displacement should be reduced and fixed, when classified as Mason II type injuries. We describe a method of arthroscopic fixation which is performed as a day case trauma surgery, and compare the results with a more traditional fixation approach, in a case controlled manner.

We prospectively reviewed six Mason II radial head fractures which were treated using an arthroscopic reduction and fixation technique. The technique allows the fracture to be mobilised, reduced, and anatomically fixed using headless screws. All arthroscopic surgeries were conducted as day-cases. We retrospectively collected age and sex matched cases of open reduction and fixation of Mason II fractures using headless screws.

The arthroscopic cases required less analgesia, shorter hospital admissions, and had fewer complications. The averaged final range of follow-up, at 1 year post-operation was 15 to 140 degrees in the arthroscopic group and 35 to 120 degrees in the open group. The Mayo Elbow Performance Score was 95/100 and 90/100 respectively. No acute complications were noted in the arthroscopic group, and a radial nerve neuropraxia [n=1], superficial wound infection [n=1], and loose screw [n=1]. Two patients of the arthroscopic group required secondary motion gaining operations [n=1 arthroscopic anterior capsulectomy for a fixed flexion contracture of 35 degrees, and n=1 loss of supination requiring and arthroscopic radial scar excision]. Three patients in the open group required secondary surgery [n=2 arthroscopic anterior capsulectomy for fixed flexion deformities, and n=1 arthroscopic anterior capsulectomy for fixed flexion deformities, and n=1 arthroscopic radial head excision for prominent screws, loss of forearm rotation, and radiocapitellar arthrosis pain].

The technique of arthroscopic fixation of Mason II radial head fractures appears to be valid, with respect to anatomical restoration of the fracture, minimal hospital admission, reduction in analgesia requirement, fewer complications, and a decreased need for secondary surgery.

At present, long-term follow-up studies are used to assess the performance and longevity of an implant, but the downside is that designers must wait 5–10 years before they receive this feedback. Therefore, the objective of this study was to develop a theoretical simulator that will allow for prediction of kinematic patterns based on implant shape and prediction of implant longevity based on the implant’s ability to adapt to in vivo conditions.

A model of the normal lower leg, including muscles and all ligament structures, was developed using Kane’s theory of dynamics. All muscles and ligaments were modeled as distributed loads and included wrapping points to follow the true path of soft-tissue structures.

Currently, two activities are available to the user: leg extension and deep flexion. 3D shapes, pertaining to the implant designs are input to the model.

A validation of the model was conducted using an initial force prediction for each muscle. The predicted kinematics were compared to a library of in vivo kinematics from over 2000 knees obtained using fluoroscopy and a 3-D model fitting technique. If the kinematic patterns from the model were incorrect, an optimization feedback algorithm induced a change in the muscle force. This process continued until the proper muscle force profiles were determined.

Then, using muscle forces which achieve observed motion in TKA previously implanted and analyzed, evaluation of various new implant designs could be assessed.

Altering designs or constraints in TKA lead to quite different kinematic profiles, even when the same muscle force profiles are used. Further research needs to be conducted using more design profiles before multiple implant designs could be evaluated and compared.

An institution of the authors (Center for Musculoskeletal Research) and one author (DAD) have received funding from DePuy, Inc. (Warsaw, IN).

Each author certifies that his or her institution has approved the reporting of these cases, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.

This work was performed at Center for Musculoskeletal Research, University of Tennessee, Knoxville, TN and the Rocky Mountain Musculoskeletal Research Laboratory, Denver, CO.

Background: The mechanisms underlying the increased prevalence of arterial calcification in diabetes are not understood. An association with distal neuropathy has been reported and a particularly high prevalence was found in patients with Charcot’s disease.

Aim: The aim of this study was to confirm this high prevalence and to determine whether it is specific to that disorder by comparing the results to patients with other types of foot disease.

Methods: A retrospective survey was conducted in three groups of patients with X-rays managed by a specialist service for the diabetic foot between 2002 and 2005. Group A (n=34) comprised patients with an acute Charcot foot, Group B (n=53) included patients with osteomyelitis and Group C (n=35) consisted of patients who had neither osteomyelitis nor Charcot’s disease. All X-rays were independently examined by three observers blinded to the underlying diagnosis, with films from each group being mixed.

Results: No differences existed (p> 0.05) in the mean age of the patients (60, 72 and 68 years, respectively), the proportion of men (68%, 64% and 51%) and the prevalence of nephropathy (41%, 30% and 14%). 100% patients in Group A, 94% in Group B and 80% of Group C had evidence of neuropathy. The overall prevalence of calcification in the three groups was 53%, 66% and 54% (p> 0.05). With all three groups combined, the only factor associated with calcification was disease duration (p=0.004). The prevalence of calcification was higher than the 40% previously reported in patients with neuropathy, but lower than that reported in patients with Charcot.

Conclusion: As there was no difference in the prevalence of calcification between the three groups, it is concluded that the increase is not specific to Charcot’s disease. It is possible that the increase in calcification in each group reflects the effect of local inflammation, possibly by activation of the RANKL/OPG signalling system.

Background: Venous thromboembolism (VTE) remains a significant cause of morbidity and mortality of patients following hip fracture. It is not known preoperatively which patients are at greater risk of developing VTE complications following their surgery. This study reports the incidence of VTE following neck of femur fracture, the timing of the diagnosis of VTE and any risk factors associated with VTE development.

Materials and Methods: We analysed the prospectively recorded complications of patients that presented with a neck of femur fracture. Those patients that developed VTE were compared to those with no complications and their risk factors compared.

Results: A total of 5300 patients were analysed. The incidence of VTE was 2% despite thromboprophylaxis. The significant risk factors for VTE were poor pre operative mobility (p< 0.01), those preoperatively living in their own home (p< 0.01), low mental test score (p< 0.01), high postoperative haemoglobin (p< 0.03), intertrochanteric fractures and fixation with a dynamic hip screw (p< 0.01).

Conclusions: This is the largest group of patients to be prospectively analysed for risk factors for developing VTE following surgery for neck of femur fractures. There were a number of groups that were at a significantly higher risk of developing VTE than others. Orthopaedic surgeons should be aware of these groups in the management of these vulnerable patients.

Introduction: Cervical kyphosis is failure of posterior osteo-ligamento-muscular restraint secondary to a deficient anterior column. Prospective studies of stand-alone anterior construct in correction and maintainence of cervical column that would otherwise require combined ant & post surgeries is sparse.

Objectives: To evaluate the role of stand-alone anterior surgery for cervical kyphosis, determine its efficacy and analyse complications.

Methods: 42 consecutive patients aged 6 – 70 yrs (Av 31.4 yrs) who had a Kyphosis angle of more than 100 with its apex between lower end-plate of C2 and C7 on a lateral x-ray and underwent anterior only surgery for cervical kyphosis over 6 yrs (2000–06) formed the population for this prospective study. The average follow-up was 2.2 yrs (1 – 5 yrs). The mean pre-op kyphosis was 20.820 (100 – 780). Etiology was tuberculosis in 25, dysplasia in 7, trauma in 6 and tumors in 4 cases respectively. 39 of the 42 patients had myelopathic signs. Mean pre-op mJOA score was 7.4 (0–11). A left anterior cervical approach was used in all cases. Modified manubriotomy was required in 5 cases to instrument the caudal vertebra. Tricortical iliac crest strut graft was used in 40 and cylindrical mesh cage in 2 cases. Correction of kyphosis was achieved by intra-op adjustment of the head assembly & controlled distraction. Post-operatively all wore cervical orthosis for 3 mo.

Results: 41 patients were available for analysis (1 lost for f/u). The average number of corpectomies required were 2.5 (1–4) and the mean anterior column defect reconstructed was 27.3mm (22–42mm). The average graft subsidence was 3mm (0–10mm). 2 patients required revision surgery within 6 weeks for implant failure/graft resorption. Fusion occurred in rest of 39 patients. No further graft subsidence was noticed at 4 years in 17 patients. Spontaneous fusion at 3 mo was seen in normal adjacent segment due to plate overlapping in 2 cases. The average correction achieved was 15.220 (−40–730). The mortality rate was 2.12% (1 case). Visceral complications occurred in 3 cases (esophageal perforation in 1 and recurrent laryngeal nerve palsy in 2). The mean post-operative mJOA score was 14 (9 – 17). There was 1 deep and 1 superficial infection.

Conclusion: Ant decompression & reconstruction with instrumentation facilitates neurological recovery restoring alignment. Intra-op maneuvering allows the graft to be placed in an optimal position that allows fusion under compression.

Introduction: Formulation of surgical protocol in CSM is marred by the diversity in clinico-radiological presentation. Prospective data that assigns a specific surgery with identifiable similarities in clinico-radiological attributes is sparse.

Objectives:

To identify radiological patterns of compression (POC) of the spinal cord

Methods: 135 consecutive patients aged 32–75 yrs (mean 48.1yr) operated for CSM from 1999–2005 formed the study group for this prospective series. The objectives were to identify radiological patterns of compression (POC), develop a surgical algorithm based on POC and evaluate outcome. Four POC were identified on MRI.

Pattern I – predominant one/two level compression in normal/narrow canal

Mean follow-up was 3 yrs (2–8). ACDF was performed for patterns I, II & III and posterior decompression for pattern IV and III(A). For pattern IV(A), a two stage primary posterior decompression followed by targeted ACDF at the site of maximal compression was performed. The clinical outcome was measured by modified JOA (mJOA) score, Hirayabashi Recovery Rate (HRR) and functional outcome by modified Neck Disability Index (NDI).

Results: The mean pre & post-op mJOA score was 10.40±3.33 & 15.76±1.45 respectively with average HRR of 80.10 ± 26.38. The difference in the mJOA scores was statistically significant (unpaired t test) for each POC. In multilevel CSM, anterior surgery in POC type III had statistically better post op mJOA as compared to those who underwent posterior surgery viz POC types IV and III & IV variants although the difference in their HRR and NDI were not statistically significant.

Conclusion: Anterior surgery has better neurological outcome in judiciously selected patients with multilevel CSM. Surgical decision-making guided by patterns of compression (POC) is pivotal for optimal functional outcome.

Introduction: Avulsion fractures of the anterior tibial spine are not so common. The best form of treatment for displaced fractures is still debatable.

Aims: We aimed to analyze the results of different forms of internal fixation for avulsion fractures of the anterior tibial spine.

Material and Methods: Twenty-five patients with avulsion fractures of the anterior tibial spine had open reduction and internal fixation with different implants (AO screw, Herbert screw, stainless steel wire loop and absorbable stitch) and techniques. The mean follow up period was 3.66 years. They were evaluated clinically and radiologically, using KT 1000 arthrometer for ACL laxity and goniometer for range of movements. The outcome was measured using Lysholm Knee Score.

Results: Significant residual anterior laxity despite adequate fracture union was a common finding. Maximum ACL laxity was seen in adults in whom absorbable stitches had been used and they had a corresponding lower Lysholm score. Significant migration of the Herbert screws was noted in two of five patients in which it was used. Five of the eight patients with higher Lysholm score had AO screw fixation. Three patients with steel wire loop for stabilization of the fracture also had better results comparatively. Three individuals who had their knee immobilised in 25°–50° of flexion developed fixed flexion deformities, which took 12–18 months to recover.

Conclusions: The use of absorbable stitches as the primary method of fixation for avulsion fractures of the tibial spine should be avoided in adults. Herbert screw in this situation has a tendency to migrate. AO screws and non-absorbable loop yields better functional outcome. Immobilization of the knee in excessive flexion leads to prolonged fixed flexion deformity. Early range of movements can be achieved by replacing cast with a brace allowing flexion up to 90 degrees.

At present, contact stress analyses of TKA involve in vitro experimental testing. The objective of this project was to develop a parametric mathematical model that determines in vivo contact stresses for subjects implanted with a TKA, under in vivo, dynamic conditions. It is hypothesized that the results from this model will be more representative of in vivo conditions, thus leading to more accurate prediction of TKA bearing surface stresses.

In vivo kinematics were determined for ten subjects implanted with a posterior stabilized TKA during gait and a deep knee bend under fluoroscopic surveillance. Three-dimensional contact positions, determined between the femoral component and the polyethylene insert, were entered into a complicated mathematical model to determine bearing surface forces. In vivo kinematics and kinetics were entered into a deformation model to predict in vivo contact areas between the medial and lateral condyles and tibial insert. The orientation of the femoral and tibial components, the predicted in vivo contact areas, and vectoral information of soft-tissue derived from MRI images were then entered into a mathematical model that predicted in vivo contact stresses between the femoral component and the tibial insert.

This is the first computational model that utilizes fluoroscopy, MRI, deformation characteristics and Kane’s theory of Dynamics to predict in vivo contact stresses. Although previous models have not been validated, this model was validated by comparing the predicted foot/ ground force with the experimentally derived force. This study demonstrates that patellar motion influences forces throughout the lower extremity. The in vivo contact stress values predicted in this initial study were less than the yield strength of polyethylene.

The objective of this study was to determine the location of polyethylene post position and/or axis of polyethylene (PE) bearing rotation in order to maximize the rotational freedom of the PE bearing in a posterior-stabilized mobile-bearing TKA.

Kinematic data obtained in a previous study involving subjects implanted with the PFC Sigma RP (PS) was used in two mathematical models to determine the optimal configuration of the implant’s features. An inverse dynamics mathematical model used the kinematic input to calculate interactive forces between the implant components. The second mathematical model used the femur-polyethylene and polyethylene-tibial plate interactive forces in a forward solution giving the amount of polyethylene bearing rotation. Researchers altered the location of cam/post interaction and/or bearing rotation to determine the criteria for optimal bearing rotation.

During flexion, the maximum femur-polyethylene contact force calculated by the inverse model was 1.9 x BW, at maximum flexion. Maximum quadriceps, patello-femoral, and patellar ligament forces were approx. 2.9 x BW, 2.8 x BW, and 1.5 x BW at maximum flexion, respectively. We determined that the sample group experienced an average maximum bearing rotation of approximately 3.5°. Maximum bearing rotation reached approx 12.5° (10°–15°) with a 5mm lateral shift in cam/post engagement. Bearing rotation reached approximately 17.5° (15°–20°) by shifting the bearing axis 5mm posterior to that of the current design. Shifting the cam/post mechanism or bearing axis by greater than 5mm in any direction produced undesirable results.

The mathematical models used in this study were verified by comparing kinematic results obtained from a 3-D model-fitting program whereby models are matched to their respective silhouettes in a 2-D fluoroscopic image. Results from this study show that the rotational freedom of the PE bearing can be optimized by shifting its axis of rotation posterior to its present location.

Purpose Of The Study: Avulsion fractures of the anterior tibial spine are uncommon injury and we have evaluated the results in-patients who have undergone arthrotomy and fixation of the fracture.

Material & Method: Twenty five patients were followed up between 21–108 months (mean 44 months) after the operation. They were evaluated clinically, radiologically and the residual ACL laxity was measured with KT 1000. Lysholm scoring scale has been used to assess the outcome.

Eight fractures were fixed with a single AO screw; 5 with Herbert screws; 4 with a steel wire loop and 8 with absorbable stitch.

Results: Significant residual anterior laxity despite adequate fracture union was a common finding. The ACL laxity was maximum in adults in whom absorbable stitch had been used to fix the fracture and they had a corresponding lower Lysholm score.

In 2 out of the 5 patients where Herbert screws had been used there was significant migration of the screws.

Additional articular damage was observed in 3 patients who were pedestrians hit by a car. All 3 ended up with restricted knee movements and poor results. Three individuals who had their knee immobilised in 250–500 of flexion developed flexion deformities, which took 12–18 months to recover.

Conclusions: We recommend that use of absorbable stitches as a method of fixation be avoided in adults. Herbert screws in this situation have a tendency to migrate. AO screws or a non-absorbable loop should be used were possible. Immobilisation of the knee in excessive flexion leads to prolonged flexion deformity and we recommend immobilising the knee in no more than 100 of flexion.

Background: Autologous blood from reinfusion drains are commonly used after major joint arthroplasties with a view to decrease the heterologous blood transfusion requirement. The aim of this study is to find the effect of reinfusion drains on the difference in haemoglobin (Hb) level before and after total knee arthroplasties.

Material and Methods: Between January 2001 and October 2003, 158 patients had total knee arthroplasty on one side. The type of thromboprophylaxis used was the same in all the patients. 74 patients had autologous blood transfusion through reinfusion drains (Group I) while 84 patients had no autologous blood transfusion and ordinary suction drains were used to drain the wound in the immediate postoperative period (Group II). The mean age was 72.1 +/− 8.5 in group I and 69.3 +/− 9.1 in group II. In each patient the preoperative Hb level, the amount of autologous blood transfusion, the postoperative Hb level and the amount of heterologous bleed transfusion requirement were noted.

Results: The mean preoperative Hb level was 13.6 +/− 1.4 g/dL (10.4–18.1) in group I and 13.7 +/− 1.3 g/dL (7.9–16.5) in group II. The mean postoperative Hb level was 10.7 +/− 1.5 g/dL (10.4–18.1) in group I and 10.7 + 1.6 g/dL (5.4 +/− 13.6) in group II. The difference in Hb level between the two groups was analysed using t-test and found to be not significant (p = 0.76), with the mean difference between the groups being 0.05 and the 95% CI to the mean difference includes zero (range −0.3 to +0.4). The difference in Hb level before and after surgery was plotted against the amount of autologous blood transfused and it was observed that there was no significant improvement with increased amount of autologous blood transfusion. The cost of reinfusion drain is 36.43 (~ 53.37 Euros) more than the suction drain.

Conclusion: Autologous blood from reinfusion drains did not significantly improve the postoperative Hb level. Further usage of reinfusion drain is not cost-beneficial.

Background Non-weight bearing hip is a common problem in the elderly population after a minor fall. Magnetic reasonance imaging (MRI) is used to diagnose occult fractures in the hip and the pelvic ring in these individuals. The aim of this study is to find the relationship between the incidence of occult fractures in the hip and that in the pelvic ring following low velocity trauma in the elderly.

Material and Methods Between January 2000 and February 2004, 106 elderly patients (mean age = 81.4 years; range = 67–101 years), underwent an MRI scan of the pelvis and hip to rule out fracture neck of femur. All of them presented with a non-weight bearing hip after a history of low velocity injury. All had standard radiographs of the pelvis and the hip which did not reveal a fracture of the femoral neck. However, eight patients had fracture of the pubic rami visible on plain radiographs. MRI scans were subsequently performed in all of them to rule out an occult fracture of the femoral neck.

Results Out of the 106 patients, 17 (16%) had intracapsular neck of femur fracture, 26 (24.5%) had extracapsular neck of femur fracture, 26 (24.5%) had pubic rami fracture, 17 (16%) had sacral fractures, and 37 (34.9%) had no fractures. All the sacral fractures occurred in patients with pubic rami fractures. Further except in one patient where the pubic rami fracture and the sacral fracture were contralateral, the remaining 16 patients had ipsilateral pubic rami and sacral fractures. None of the patients with pelvic ring fracture had associated femoral neck fracture.

Conclusion Inability to weight bear after a fall is a common presentation in the elderly population. Falls can lead to fracture neck of femur or a fracture of the pelvic ring but seldom both. We can also conclude that in an elderly patient with low velocity injury, if a pelvic ring fracture is detected in the plain radiograph there is no indication for further MRI to rule out femoral neck fracture. Further, the fracture in the anterior and posterior pelvic ring commonly involves the same side than the contralateral side, in the elderly after trivial trauma.