Healthcare associated infections (HAI) pose a major threat to patients admitted to hospitals, and infection rates following orthopaedic arthroplasty surgery are as high as 4%, while the infection rates are even higher after revision surgery. 405 nm High-Intensity Narrow Spectrum (HINS) light has been proven to reduce environmental contamination in hospital isolation rooms, and there is potential to develop this technology for application in orthopaedic surgery.

Cultured rat osteoblasts were exposed to 405 nm light to investigate if bactericidal doses of light could be used safely in the presence of mammalian cells. Cell viability was measured by MTT reduction and microscopy techniques, function by alkaline phosphatase activity, and proliferation by the BrdU assay. Exposures of up to a dose of 36 J/cm² had no significant effect on osteoblast cell viability, whilst exposure of a variety of clinically relevant bacteria, to 36 J/cm² resulted in up to 100% kill. Exposure to a higher dose of 54 J/cm² significantly affected the osteoblast cell viability, indicating dose dependency.

Work also demonstrated that 405 nm light exposure induces reactive oxygen species (ROS) production in both mammalian and bacterial cells, as shown by fluorescence generated from 6-carboxy-2′,7′-dichlorodihydrofluorescein diacetate dye. The mammalian cells were significantly protected from dying at 54 J/cm² by catalase, which detoxifies H₂O₂. Bacterial cells were significantly protected by sodium pyruvate (H₂O₂ scavenger) and by a combination of free radical scavengers (sodium pyruvate, dimethyl thiourea (·OH scavenger), catalase) at 162 and 324 J/cm². Thus the cytotoxic mechanism of 405 nm light in mammalian cells and bacteria is likely oxidative stress involving predominantly H₂O₂ generation, with other ROS contributing to the damage.

Additional work describing the potential for incorporation of this antimicrobial light within operating theatre lighting systems will also be discussed, and this, coupled with the cell viability and cytotoxicity results, suggests that 405 nm light could have great potential for continual patient safe decontamination during orthopaedic replacement surgeries and thereby reduce the incidence of infections.

Wear particles produced by alumina ceramic-on-ceramic (CoC) bearings cause a minimal immunological response with low cytotoxicity and inflammatory potential^{1, 2}. However, more comprehensive immunological studies are yet to be completed for the composite CoC (zirconia-toughened, platelet reinforced alumina) hip replacements due to difficulties in isolating the very low volume of clinically relevant wear debris generated by such materials in vitro. The aim of this study was to compare the cytotoxic effects of clinically relevant cobalt chromium (CoCr) nano-particles with commercial composite ceramic particles.

Composite ceramic particles (commercial BIOLOX® delta powder) were obtained from CeramTec, Germany and clinically relevant CoCr wear particles were generated using a six station pin-on-plate wear simulator. L929 fibroblast cells were cultured with 50µm³ of CoCr wear debris or composite ceramic particles at low to high volumes ranging from 500µm³–0.5µm³ per cell and the cyctotoxic effects of the particles were assessed over a period of 6 days using the ATP-Lite™ cell viability assay.

The composite ceramic particles were bimodal in size (0.1–2µm & 30–100nm) and showed mild cytotoxic effects when compared with equivalent particle volumes (50µm³) of clinically relevant CoCr nano-particles (10–120nm). The CoCr nano-particles had significant cytotoxic effects from day 1, whereas the composite ceramic particles only showed cytotoxic effects at particle concentrations of 50 and 500µm³ after 6 days. The increased cytotoxicity of the clinically relevant CoCr nano-particles may have been attributed to the release of Co and Cr ions.

This study demonstrated the potential cytotoxic effects of model ceramic particles at very high volume concentrations, but it is unlikely that such high particle volumes will be experienced routinely in vivo in such low wearing bearing materials. Future work will investigate the longer-term effects on genotoxicity and oxidative stress of low volumes of clinically-relevant generated BIOLOX® delta ceramic wear particles.

Introduction

The rate of technological innovation in procedural total knee arthroplasty has left little time for critical evaluation of a new technology before the adoption of even newer modalities. With more drastic financial restrictions being placed on operating room spending, orthopaedic surgeons are now required to provide excellent results on a budget.

It is integral that both clinical efficacy and cost-effectiveness of these intraoperative technologies be fully understood in order to provide patients with effectual, economically conscious care. The purpose of this qualitative analysis of literature was to evaluate clinical and economic efficacy of the three most prominent technologies currently used in TKA: computer navigation, patient-specific instrumentation, and kinetic sensors.

Introduction

Instability after total knee arthroplasty (TKA) represents, in excess of, 7% of reasons for implant failure. This mode of failure is correlated with soft-tissue imbalance, and has continued to be problematic despite advances in implant technology. Thus, understanding the options available to execute safe and effective soft-tissue release is critical to mitigating future complications due to instability. This study aimed to use intraoperative sensors to evaluate a multiple needle puncturing technique (MNPT), in comparison with traditional transection-based release, to determine its biomechanical and clinical efficacy.

Introduction

Improper soft-tissue balancing can result in postoperative complications after total knee arthroplasty (TKA) and may lead to early revision. A single-use tibial insert trial with embedded sensor technology (VERASENSE from OrthoSensor Inc., Dania Beach, FL) was designed to provide feedback to the surgeon intraoperatively, with the goal to achieve a “well-balanced” knee throughout the range of motion (Roche et al. 2014). The purpose of this study was to quantify the effects of common soft-tissue releases as they related to sensor measured joint reactions and kinematics.

Avascular necrosis of the femoral head (AVN) is associated with collapse of the femoral head and arthritic degeneration of the joint. The combination of an implant inserted into the femoral head that provides mechanical support and bone grafting to promote bone formation may offer a possible joint-preserving solution1. Seventeen such procedures were performed between November 2012 and March 2014 during an IRB approved clinical trial. Thirteen out of 18 patients remained unrevised at a minimum of 12 months; the results of radiographic and histological analysis of four revisions are presented.

The investigational device (Figure 1) was developed as a joint preserving treatment for AVN with a clinical grade of IIC or less according to the ARCO grading system2.

The device consisted of a braided spherical Nitinol cage with a Titanium / Nitinol orientation feature. It was implanted using fluoroscopic navigation into a spherical cavity cut into the femoral head via an 11mm diameter access tunnel. Once deployed, the implant was filled with a lightly impacted mixture of autologous bone graft and bone marrow soaked Conduit TCP (DePuy CMW, Blackpool, UK). The implant's purpose was to provide mechanical support to the weakened subchondral surface while the bone graft mixture re-integrated with the host bone.

The retrieved femoral heads were trimmed to leave approximately 3mm of bone around the implant, dehydrated, embedded in methacrylate resin, sectioned and thinned into 50–70µm coronal slices for histological analysis. The following observations were made (Figure 2):

Case 1 (Female, age 70, ARCO IIB, revised after 2 days): The patient was revised for spontaneous sub-trochanteric fracture secondary to osteoporosis. Contact between the native bone and bone graft was observed. Marrow elements and repair tissue were visible within the pores in the graft (Figure 2a).

Case 2 (Male, age 67, ARCO IIIC, revised after 82 days): Two wires were broken but retained within the braided structure. A radiolucent gap caused by the presence of fibrous tissue between the graft mixture and native bone was evident suggesting that the implant was unable to prevent progression in this case.

Case 3 (Female, age 70, ARCO IIC, revised after 482 days): The cavity penetrated the subchondral surface; at revision the implant was found to have breached the articular cartilage. There was partial separation of the proximal osteonecrotic fragment and no evidence of graft revascularisation or remodelling within the implant.

Case 4 (Male, age 42, ARCO IIC, revised after 469 days): There was no indication of bone graft re-integration. Collapse of the necrotic bone and deformation of the implant was diagnosed from 1 year follow-up x-rays.

Introduction

Aseptic loosening has been reported to be the most common, contemporary mode of total knee arthroplasty failure. It has been suggested that the etiology of revision due to loosening can be attributed, in part, to joint imbalance and the variability inherent in standard surgical techniques. Due to the high prevalence of revision, the purpose of this study was to quantify the change in kinetic loading of the knee joint before versus after the application of the final cement-component complex.

INTRODUCTION

Understanding the relationship between knee specific tissue behavior and joint contact mechanics remains an area of focus. Seminal work from 1990's established the possibility to optimize tissue properties for recreation of laxity driven kinematics (Mommersteeg et al., 1996). Yet, the uniqueness and validity of such predictions could be strengthened, especially as they relate to joint contact conditions. Understanding this interplay has implications for the long term performance of joint replacements.

Development of instrumented knee implants, highlighted by a single use tibial insert trial with embedded sensor technology (VERASENSE, Orthosensor Inc.), may offer an avenue to establish the relationship between tissue state and joint mechanics. Utilization of related data also has the potential to confirm computational predictions, where both rigid body motions and associated reactions are explicitly accounted for. Hence, the goal of this work was to evaluate an approach for optimization of ligament properties using joint mechanics data from an instrumented implant during laxity style testing. Such a framework could be used to inform joint balancing techniques, improve long term implant performance, and alternatively, qualify factors that may lead to poor outcomes

Objectives

“Virtual fracture clinics” have been reported as a safe and effective alternative to the traditional fracture clinic. Robust protocols are used to identify cases that do not require further review, with the remainder triaged to the most appropriate subspecialist at the optimum time for review. The objective of this study was to perform a “top-down” analysis of the cost effectiveness of this virtual fracture clinic pathway.

Objectives

The objective of this study was to determine if combining variations in mixing technique of antibiotic-impregnated polymethylmethacrylate (PMMA) cement with low frequency ultrasound (LFUS) improves antibiotic elution during the initial high phase (Phase I) and subsequent low phase (Phase II) while not diminishing mechanical strength.

INTRODUCTION

Achieving balance in TKA is critical in assuring favorable outcomes. But, in order to achieve quantifiably balanced loading values, is it more advantageous to make bony corrections or release soft-tissue? The answer to this question will be paramount in evaluating the most appropriate surgical techniques for use with new dynamic technology, thereby maximizing favorable clinical outcomes. Therefore, the purpose of this investigation was to evaluate a possible quantitative loading threshold, using intraoperative sensors, which may dictate surgical correction of bone versus soft-tissue release.

INTRODUCTION

Patient-reported satisfaction is a critical measure in understanding the clinical success of total knee arthroplasty. Yet, satisfaction levels in TKA patients are generally lower than THA patients; and surgeon-patient agreeability regarding clinical success is typically in discordance. Thus, the purpose of this evaluation was to report on the one-year satisfaction data of a group of sensor-assisted TKA patients, and compare that data to the average satisfaction reported in literature, as measured by a meta-analysis.

INTRODUCTION

The cost associated with the TKA revision burden is projected to reach 13 billion dollars, annually. Complications reported by post-TKA patients include: pain (44%, multilocational), sensation of instability (21% reason for revision), and joint stiffness (17% reason for revision); problems that may be attributed to soft-tissue imbalance. One of the possible reasons for the substantial prevalence of such complications is the subjectivity associated with defining soft-tissue balance. A priority must be placed on developing new objective methods with which to avoid costly post-operative complications, including the integration of intraoperative sensing technology. The purpose of this evaluation was to report on the disparity between the patient-reported outcomes scores of quantitatively balanced versus unbalanced patients, at 1-year, using a group of 135 multicenter patients.

High-intensity narrow-spectrum (HINS) light is a novel violet-blue light inactivation technology which kills bacteria through a photodynamic process, and has been shown to have bactericidal activity against a wide range of species. Specimens from patients with infected hip and knee arthroplasties were collected over a one-year period (1 May 2009 to 30 April 2010). A range of these microbial isolates were tested for sensitivity to HINS-light. During testing, suspensions of the pathogens were exposed to increasing doses of HINS-light (of 123mW/cm² irradiance). Non-light exposed control samples were also used. The samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration. Complete inactivation (greater than 4-log₁₀ reduction) was achieved for all of the isolates. The typical inactivation curve showed a slow initial reaction followed by a rapid period of inactivation. The doses of HINS-light required ranged between 118 and 2214 J/cm². Gram-positive bacteria were generally found to be more susceptible than Gram-negative.

As HINS-light uses visible wavelengths, it can be safely used in the presence of patients and staff. This unique feature could lead to its possible use in the prevention of infection during surgery and post-operative dressing changes.

Cite this article: Bone Joint J 2015;97-B:283–8.

The aim of this prospective multicentre study was to report the patient satisfaction after total knee replacement (TKR), undertaken with the aid of intra-operative sensors, and to compare these results with previous studies. A total of 135 patients undergoing TKR were included in the study. The soft-tissue balance of each TKR was quantified intra-operatively by the sensor, and 18 (13%) were found to be unbalanced. A total of 113 patients (96.7%) in the balanced group and 15 (82.1%) in the unbalanced group were satisfied or very satisfied one year post-operatively (p = 0.043).

A review of the literature identified no previous study with a mean level of satisfaction that was greater than the reported level of satisfaction of the balanced TKR group in this study. Ensuring soft-tissue balance by using intra-operative sensors during TKR may improve satisfaction.

Cite this article: Bone Joint J 2014;96-B:1333–8

Cubitus varus is the most frequent complication following the treatment of supracondylar humeral fractures in children. We investigated data from publications reporting on the surgical management of cubitus varus found in electronic searches of Ovid/MEDLINE and Cochrane Library databases. In 894 children from 40 included studies, the mean age at initial injury was 5.7 years (3 to 8.6) and 9.8 years (4 to 15.7) at the time of secondary correction. The four osteotomy techniques were classified as lateral closing wedge, dome, complex (multiplanar) and distraction osteogenesis. A mean angular correction of 27.6º (18.5° to 37.0°) was achieved across all classes of osteotomy. The meta-analytical summary estimate for overall rate of good to excellent results was 87.8% (95% CI 84.4 to 91.2). No technique was shown to significantly affect the surgical outcome, and the risk of complications across all osteotomy classes was 14.5% (95% CI 10.6 to 18.5). Nerve palsies occurred in 2.53% of cases (95% CI 1.4 to 3.6), although 78.4% were transient. No one technique was found to be statistically safer or more effective than any other.

Cite this article: Bone Joint J 2014;96-B:691–700.

We determined the short-term clinical outcome and migration within the bone of the humeral cementless component of the Instrumented Bone Preserving (IBP) total elbow replacement in a series of 16 patients. There were four men and 12 women with a mean age at operation of 63 years (40 to 81). Migration was calculated using radiostereometric analysis. There were no intra-operative complications and no revisions. At two-year follow-up, all patients showed a significant reduction in pain and functional improvement of the elbow (both p < 0.001). Although ten components (63%) showed movement or micromovement during the first six weeks, 14 (88%) were stable at one year post-operatively. Translation was primarily found in the proximal direction (median 0.3 mm (interquartile range (IQR) -0.09 to 0.8); the major rotational movement was an anterior tilt (median 0.7° (IQR 0.4° to 1.6°)). One malaligned component continued to migrate during the second year, and one component could not be followed beyond three months because migration had caused the markers to break off the prosthesis.

This study shows promising early results for the cementless humeral component of the IBP total elbow replacement. All patients had a good clinical outcome, and most components stabilised within six months of the operation.

Cite this article: Bone Joint J 2014;96-B:229–36.

Introduction

During primary total knee arthroplasty, the surgeon may encounter excessive medial collateral ligament tension while addressing a varus knee. This may be due to medial ligament/capsular complex contractures, and/or, due to the creation of a 0 degree mechanical axis in a varus knee. This tension leads to increased loading in the medial compartment, which contributes to an unbalanced extension and flexion gap. If uncorrected, this imbalance can lead to unfavorable clinical outcomes, including: pain, accelerated polyethylene degradation, joint instability, and limited ROM. Currently, intercompartmental soft-tissue balance is obtained by a subjective surgeon's “feel”. However, this method of judging soft-tissue tension is both variable and unreliable. Most surgeons can detect gross instability, but judging ligament tension is difficult. The following technique describes the integration of intraoperative microelectronic tibial inserts to assess and modify ligament tension, utilizing real-time dynamic sensor feedback

Introduction

Post-operative clinical outcomes of TKA are dependent on a multitude of surgical and patient-specific factors. Malrotation of the femoral and/or tibial component is associated with pain, accelerated wear of the tibial insert, joint instability, and unfavorable patellar tracking and dislocation. Using the transepicondylar axis to guide implantation of the femoral component is considered to be an accurate anatomical reference and is widely used. However, no gold standard currently exists with respect to ensuring optimal rotation of the tibial tray. Literature has suggested that implantation methods, which reference the tibial tubercle, reduce positioning outliers with more consistency than other anatomical landmarks. Therefore, the purpose of this evaluation is to use data collected from intraoperative sensors to assess the true rotational accuracy of using the mid-medial third of the tibial tubercle in 98 TKAs.

Introduction:

Most cases of hip osteoarthritis (OA) are believed to be caused by alterations in joint contact mechanics resulting from pathomorphologies such as acetabular dysplasia and acetabular retroversion. Over the past 13 years, our research group has focused on developing approaches for patient-specific modeling of cartilage and labrum in the human hip, and applying these approaches to study hip pathomorphology. The long term objective is to improve the understanding of the etiology of OA related to hip pathomorphology, and to improve diagnosis and treatment. The objectives of this presentation are to provide a summary of our subject-specific modeling approach, and to describe the results of our analysis of hips from three populations of subjects: normal, traditional dysplastic, and retroverted.

Background:

A large percentage of the patients who present for unilateral TKA have bilateral disease. Performing simultaneous, bilateral TKA has been debated and currently there is no consensus on the risks and benefit of this approach. In addition, specific selection criteria have not been defined to more accurately identify which patients are potentially appropriate candidates for this approach.

This presentation will provide an overview of the interdisciplinary research program on hip pathomorphology at the University of Utah, including studies of dysplasia and femoracetabular impingement. The discussion will emphasize the implications of the research findings for hip preserving surgery

Introduction

Flexion instability of the knee accounts for, up to, 22% of reported revisions following TKA. It can present in the early post-operative phase or present— secondary to a rupture of the PCL— in the late post-operative phase. While most reports of instability occur in conjunction with cruciate retaining implants, instability in a posterior-stabilized knee is not uncommon. Due to the prevalence of revision due to instability, the purpose of constructing the following techniques is to utilize intraoperative sensors to quantify flexion gap stability.

Infection rates following arthroplasty surgery are between 1–4%, with higher rates in revision surgery. The associated costs of treating infected arthroplasty cases are considerable, with significantly worse functional outcomes reported. New methods of infection prevention are required. HINS-light is a novel blue light inactivation technology which kills bacteria through a photodynamic process. The aim of this study was to investigate the efficacy of HINS-light for the inactivation of bacteria isolated from infected arthoplasty cases.

Specimens from hip and knee arthroplasty infections are routinely collected to identify causative organisms. This study tested a range of these isolates for sensitivity to HINS-light. During testing, bacterial suspensions were exposed to increasing doses of HINS-light of (123mW/cm² irradiance). Non-light exposed control samples were also set-up. Bacterial samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration.

Complete inactivation was achieved for all Gram positive and negative microorganisms

More than a 4-log reduction in Staphylococcus epidermidis and Staphylococcus aureus populations were achieved after exposure to HINS-light for doses of 48 and 55 J/cm², respectively. Current investigations using Escherichia coli and Klebsiella pneumoniae show that gram-negative organisms are also susceptible, though higher doses are required.

This study has demonstrated that HINS-light successfully inactivated all clinical isolates from infected arthroplasty cases. As HINS-light utilises visible-light wavelengths it can be safely used in the presence of patients and staff. This unique feature could lead to possible applications such as use as an infection prevention tool during surgery and post-operative dressing changes.

Acetabular component positioning is highly correlated with total hip arthroplasty (THA) outcomes. Multiple reports however indicate that less than 50% of acetabular cups are placed within surgeon-desired ranges for abduction and anteversion angles when using conventional cup positioning techniques. Issues with improper placement include instability-dislocation, impingement and impact on range of motion, polyethylene wear, leg length discrepancy, and gait mechanics. Accuracy in placement of the acetabular component is complicated by the need to estimate cup impactor angles to create desired cup position. A low cost approach to THA using Image-based Ultrasonic Guidance (IUG) (Orthosensor, Sunrise, FL) coupled to existing surgical tools is presented. IUG utilises acoustic measurement techniques for achieving optimal component positioning and leg length. A precisely machined Hip Test Fixture (HTF) has been built to simulate the anatomical pelvis, acetabular cup, and femur to validate system accuracy.

The IUG was affixed to the HTF to demonstrate placement of the cup during THA. The HTF was loaded onto a 27-inch Graphic User Interface (GUI) providing three-dimensional CAD data of the HTF. Registration points included the Iliac Crest and 10 points around the acetabular cup. These points were mapped to the CAD data by the GUI. The HTF was set to 45° of abduction and 0° of version to begin testing. Abduction and version were measured over a +15° range in 1-degree increments while leg length and offset were measured over a +5mm range in 2mm increments. A high-resolution coordinate measurement machine (FaroArm EDGE) verified the accuracy and margin of error for inclination, version, leg length and offset at each increment.

The HTF provided a precise means for evaluating IUG system accuracy of simulated THA in a controlled environment. Acceptable margins of error were reported on the HTF: mean error for version was 0.36° (SD 0.02°; 0.25° to 0.38°); mean error for inclination was 1.04° (SD 0.52°; 0.48° to 1.66°); mean error for leg length and offset were respectively 0.36mm (SD 0.86mm; −0.65 to 1.55mm) and 0.41mm (SD 0.28; 0.05 to 0.80mm).

IUG provides a means for achieving acceptable precision and accuracy in component placement during THA as evaluated with the HTF. Further study is however necessary to correlate accuracy of IUG with clinical utility and short-term clinical outcomes.

Infection rates following arthroplasty surgery are between 1–4%, with higher rates in revision surgery. The associated costs of treating infected arthroplasty cases are considerable, with significantly worse functional outcomes reported. New methods of infection prevention are required. HINS-light is a novel blue light inactivation technology which kills bacteria through a photodynamic process. The aim of this study was to investigate the efficacy of HINS-light for the inactivation of bacteria isolated from infected arthroplasty cases.

Specimens from hip and knee arthroplasty infections are routinely collected to identify causative organisms. This study tested a range of these isolates for sensitivity to HINS-light. During testing, bacterial suspensions were exposed to increasing doses of HINS-light of (123 mW/cm² irradiance). Non-light exposed control samples were also set-up. Bacterial samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration.

Complete inactivation (greater than a 4-log reduction) was achieved for all of the clinical isolates from infected arthroplasty cases. The typical inactivation curve showed a slow initial reaction followed by a period of rapid inactivation. The doses of HINS-light exposure required ranged from 118–2214 J/cm² respectively. Gram-positive bacteria were generally found to be more susceptible than Gram-negative.

This study has demonstrated that HINS-light successfully inactivated all clinical isolates from infected arthroplasty cases. As HINS-light utilises visible-light wavelengths it can be safely used in the presence of patients and staff. This unique feature could lead to possible applications such as use as an infection prevention tool during surgery and post-operative dressing changes.

In a time of limited resources, the debate continues over which types of hip prosthesis are clinically superior and more cost-effective. Orthopaedic surgeons increasingly need robust economic evidence to understand the full value of the operation, and to aid decision making on the ‘package’ of procedures that are available and to justify their practice beyond traditional clinical preference.

In this paper we explore the current economic debate about the merits of cemented and cementless total hip replacement, an issue that continues to divide the orthopaedic community.

Cite this article: Bone Joint J 2013;95-B:874–6.

At our institution surgical correction of symptomatic flat foot deformities in children has been guided by a paradigm in which radiographs and pedobarography are used in the assessment of outcome following treatment. Retrospective review of children with symptomatic flat feet who had undergone surgical correction was performed to assess the outcome and establish the relationship between the static alignment and the dynamic loading of the foot.

A total of 17 children (21 feet) were assessed before and after correction of soft-tissue contractures and lateral column lengthening, using standardised radiological and pedobarographic techniques for which normative data were available.

We found significantly improved static segmental alignment of the foot, significantly improved mediolateral dimension foot loading, and worsened fore-aft foot loading, following surgical treatment. Only four significant associations were found between radiological measures of static segmental alignment and dynamic loading of the foot.

Weakness of the plantar flexors of the ankle was a common post-operative finding. Surgeons should be judicious in the magnitude of lengthening of the plantar flexors that is undertaken and use techniques that minimise subsequent weakening of this muscle group.

Cite this article: Bone Joint J 2013;95-B:706–13.

Introduction

Optimized tibial tray rotation during a total knee replacement (TKR) is critical for tibiofemoral congruency through full range of motion, as it affects soft tissue tension, stability and patellar tracking. Surgeons commonly reference the tibial tubercle, or the “floating tibial tray,” while testing the knee in flexion and extension. Utilization of embedded sensors may enable the surgeon to more accurately assess tibiofemoral contact points during surgery.

Infection rates following arthroplasty surgery are between 1–4%, with higher rates in revision surgery. The associated costs of treating infected arthroplasty cases are considerable, with significantly worse functional outcomes reported. New methods of infection prevention are required. HINS-light is a novel blue light inactivation technology which kills bacteria through a photodynamic process. The aim of this study was to investigate the efficacy of HINS-light for the inactivation of bacteria isolated from infected arthoplasty cases.

Specimens from hip and knee arthroplasty infections are routinely collected to identify causative organisms. This study tested a range of these isolates for sensitivity to HINS-light. During testing, bacterial suspensions were exposed to increasing doses of HINS-light of (123mW/cm2 irradiance). Non-light exposed control samples were also set-up. Bacterial samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration.

Complete inactivation was achieved for all Gram positive and negative microorganisms More than a 4-log reduction in Staphylococcus epidermidis and Staphylococcus aureus populations were achieved after exposure to HINS-light for doses of 48 and 55 J/cm2, respectively. Current investigations using Escherichia coli and Klebsiella pneumoniae show that gram-negative organisms are also susceptible, though higher doses are required.

This study has demonstrated that HINS-light successfully inactivated all clinical isolates from infected arthroplasty cases. As HINS-light utilises visible-light wavelengths it can be safely used in the presence of patients and staff. This unique feature could lead to possible applications such as use as an infection prevention tool during surgery and post-operative dressing changes.

Introduction

Infection rates following arthroplasty surgery are reported between 1–4%, with considerably higher rates in revision surgery. The associated costs of treating infected arthroplasty cases are over 4 times the cost of primary arthroplasties, with significantly worse functional and satisfaction outcomes. In addition, multiple antibiotic resistant bacteria are developing, so to reduce the infection rates and costs associated with arthroplasty surgery, new preventative methods are required. HINS-light is a novel blue light inactivation technology which kills bacteria through a photodynamic process, and is proven to have bactericidal activity against a wide range of species. The aim of this study was to investigate the efficacy of HINS-light for the inactivation of bacteria isolated from infected arthoplasty cases.

Skills simulation is increasingly used as a training tool in postgraduate surgical training. Trainee's perception of the value of this experience has not previously been investigated. The aim of this investigation was to investigate the value of surgical simulation training delivered by an arthroscopy skills course.

We constructed a subject-specific, self-assessment questionnaire based around the ISCP Peer Assessment Tool. The questionnaire was administered to candidates before and after attending the Plymouth Arthroscopy Skills Course. Participant demographic data was recorded. Questionnaire data was interrogated to give an overview of the course, as well as the benefit of site-specific skills stations. Statistical analysis showed the data to be normally distributed. The paired T-test was used to compare mean values.

Twelve surgical trainees attended the course – CT2 trainees (n=4); ST3 trainees (n=7); ST4 trainee (n=1). 11 candidates completed both administered questionnaires giving a 92% response rate. The global mean score at the beginning of the course was 2.39. The global mean score at the end of the course was 3.90. The mean improvement was 1.51 (p<0.01; 95% CI= 0.96-2.07). Skill station specific scores all showed improvement with the greatest effect in wrist arthroscopy. CT trainees had a lower mean score compared to ST trainees. Both groups completed the course with similar mean scores.

This study shows that arthroscopy simulation improves trainee-reported ratings of surgical skill. It also shows that less experienced candidates derived the greatest benefit from the training. Further research is required to compare self-assessed performance against objective benchmarks using validated assessment tools.

Military patients have high functional requirements of the upper limb and may have lower pre-operative PROM scores than civilian patients i.e. their function is high when benchmarked, but still insufficient to perform their military role thereby mandating surgery. Our aim was to compare the pre-operative Oxford Shoulder Instability Scores in military and civilian patients undergoing shoulder stabilisation surgery.

We undertook a prospective, blinded cohort-controlled study (OCEBM Level 3b). The null hypothesis was that there was no difference in the Oxford Shoulder Instability Scores between military and civilian groups. A power calculation showed that 40 patients were required in each group to give 95% power with 5% significance. A clinical database (iParrot, ByResults Ltd., Oxford, UK) was interrogated for consecutive patients undergoing shoulder stabilisation surgery at a single centre. The senior author - blinded to the outcome score - matched patients according to age, gender and diagnosis. Statistical analysis showed the data to be normally distributed so a paired samples t-test was used to compare the two groups. 110 patients were required to provide a matched cohort of 80 patients.

There were 70 males and 10 females. Age at the time of surgery was 16-19yrs (n=6); 20-24yrs (n=28); 25-29 (n=16); 30-34(n=12); 35-49(n=12); 40-44(n=6). 72 patients (90%) had polar group one and 8 patients (10%) had polar group two instability. The mean Oxford Shoulder Instability Score in the civilian group was 17 and the in military group was 18. There was no statistical difference between the two groups (p=0.395).

This study supports the use the Oxford Shoulder Instability Score to assess military patients with shoulder instability.

Regional anaesthetic for foot surgery has been discussed as a method of post operative analgesia. Ankle block as the sole anaesthetic for foot surgery has not been extensively reviewed in the literature. We aimed to describe our experience of forefoot surgery under ankle block.

Sixty-six consecutive forefoot procedures (59 patients) were carried out under ankle block. Patients were contacted post operatively and completed a standardised questionnaire including an incremental pain assessment ranging from 0-10 (0 no pain, 10 severe pain).

Forty nine female and 10 male patients (age range 20-85y) were included. Procedures included 33 first metatarsal osteotomies, 15 cheilectomies, 3 first MTP joint replacements, 5 fusions, 4 excision of neuroma and 6 other procedures. 22 patients (33% of cases) reported discomfort during the block procedure (average pain score 1.5). 6 patients reported pain during their operation(s), average score 0.26. Average pain scores at 6, 12, 24 and 48 hours following surgery were 2.0, 3.2, 2.7 and 2.1 respectively. All patients were discharged home and walking on the same day. There were no readmissions. Each patient confirmed they would have surgery under regional block rather than general anaesthesia and would recommend this technique to family and friends.

There are many advantages in being able to perform these relatively small procedures under regional anaesthesia. The anaesthesia obtained permits the majority of forefoot procedures and provides lasting post-operative analgesia. Combined with intra-operative sedation, use of ankle tourniquet and same day discharge; it has very high patient acceptance and satisfaction.

Regional anaesthetic for foot surgery has been discussed as a method of post operative analgesia. Ankle block as the sole anaesthetic for foot surgery has not been extensively reviewed in the literature.

Regional anaesthetic for foot surgery has been discussed as a method of post operative analgesia. Ankle block as the sole anaesthetic for foot surgery has not been extensively reviewed in the literature.

We aimed to describe our experience of forefoot surgery under ankle block alone. 21 consecutive forefoot procedures (18 patients) were carried out under ankle block. The blocks were performed by the senior authors. A mixture of 10ml 2% Lidocaine with 10ml 0.5 % Bupivacaine was administered to the superficial peroneal, deep peroneal, sural and saphenous nerves. Ankle tourniquet was employed in all procedures. The patients were contacted post operatively and completed a standardised questionnaire including an incremented pain assessment ranging from 0-10 (0 no pain, 10 severe pain). 17 female and 1 male patients were contacted (age range 33-67y). Procedures included 13 first metatarsal osteotomies, 3 cheilectomies, 2 first MTP joint replacements, and 5 fusions. 14 patients requested a short acting sedative (midazolam). 5 patients (27 %) reported some discomfort during the block procedure (average pain score 1.2). No patients reported any pain during their operation(s). 4 patients (22%) required supplementation of the block. Average pain score at 6, 12, 24 and 48 hours following surgery were 0.66, 2.9, 2.4 and 1.3 respectively. All patients were discharged home and walking on the same day. None complained of nausea or required parenteral analgesia; there were no readmissions. Each patient confirmed they would have surgery under local block rather than general anaesthesia and would recommend this technique to family and friends.

Forefoot surgery under ankle block alone is safe and effective. Anaesthesia obtained permits the majority of forefoot procedures and provides lasting post-operative analgesia. Combined with intraoperative sedation, use of ankle tourniquet and same day discharge, it has very high patient acceptance and satisfaction.

To assess whether prosthetic femoral stem centralisers have a detrimental effect on the macroporosity of the cement mantle, and if so, whether this is independent of their design and the rate of implantation, 30 identically cast moulded prosthetic femora were divided into 3 groups. Group 1: no centraliser (control), Group 2: centraliser A and Group 3: centraliser B. Using third generation cementation techniques and pressure monitoring, Charnley C-stems +/− the appropriate centraliser were implanted to a constant depth. Half in each group were implanted as rapidly as possible and the other half over 90 seconds. The stems were removed and the cement mantle then underwent a preliminary arthroscopic examination prior to being sectioned transversely at 3 constant levels. Each level was then photographed and digitally enlarged to a known scale to allow examination and determination of any cement voids (macropores) surface area.

There were no significant pressure fluctuations between the groups. Preliminary arthroscopic examination revealed that cement voids appeared more common when a centraliser was used. This difference was confirmed (p=0.002) following sectioning of the specimens, with cement voids found in 85% of femora when a centraliser was used and only 20% in the control group. Centraliser B performed worst with cement voids of a larger volume and more frequent occurrence (p=0.002). The macroporosity of the cement mantle was independent of the rate of implantation (p=0.39).

The use of femoral stem centralisers is helpful in preventing malposition of the implant but results in increased macroporosity of the cement mantle. This may have implications regarding the longevity of an implant in terms of early loosening and therefore their design and use must always be carefully considered.

This study evaluated the biologic fixation of two different titanium porous coatings: a clinically successful sintered spherical bead coating [1] and a new sintered asymmetric particle coating (STIKTITE™, Smith & Nephew). The spherical bead coating has a porosity of about 50% and an average pore size of about 220 μm, whereas the STIKTITE coating has greater porosity (about 62%) and slightly smaller average pore size (about 200 μm). Biologic fixation was assessed using a load-bearing ovine model in which coated semi-circular disc implants were inserted into a defect created in the cancellous bone parallel to and approximately 3 mm below the medial tibial plateau [2] similar to the method reported by Ignatius [3]. The implants were slightly thicker than the defect created, producing a 0.2-mm overall pressfit. Initial implant stability was assessed using mechanical push-out (n = 3) immediately after implantation into cadaveric ovine bone. Quantitative mechanical push-out testing and qualitative histology (n = 9 and n = 2, respectively, per group per time point) was performed after six and 26 weeks in vivo.

The time-zero average peak push-out load (±S.D.) of the STIKTITE group (95±3 N) was found to be significantly greater (p < 0.02) than that of the spherical bead group (36±5 N). By six weeks in vivo, the average peak push-out load for the STIKTITE group was up to 1001±362 N, and that for the spherical bead group was up to 985±425 N, both representing a significant increase compared to their time-zero results (p < 0.0005). From six to twenty-six weeks in vivo, there was again a significant increase in the peak push-out load irrespective of group (p < 0.0005), with the average peak push-out loads up to 1620±406 N and 1444±446 N for the STIK-TITE and spherical bead groups, respectively. Histology revealed bone ingrowth in both groups that confirmed the findings of the mechanical push-out testing. While the STIKTITE group showed a trend toward greater biologic fixation, overall there was insufficient evidence to support differences between the two groups (p = 0.47) irrespective of the amount of time in vivo.

The results of this study confirm the ability of the STIK-TITE coating to achieve superior initial stability. This improved initial stability reduces the reliance on adjunct fixation (such as screws) or large amounts of press-fit to prevent micromotion and create an environment suitable for long-term bone ingrowth. The results also suggest that the STIKTITE coating had a tendency to initiate and maintain bone ingrowth under load-bearing conditions to a level greater than that of a clinically successful sintered bead coating. Because loading of the implant can cause micromotion at the bone/implant interface, models like the one used in this study likely provide a more challenging and realistic representation of anticipated clinical conditions than models with minimal implant loading.

Aseptic loosening is the leading cause for revision in total hip arthroplasty. Retro-acetabular lysis is often a silent process until severe bone loss causes catastrophic failure. This presents a technically difficult problem for the surgeon and a poorer result for the patient compared to primary arthroplasty. While the major cause of osteolysis is reaction to polyethylene particles, there is little data on the initiation and progression of such lesions. Further, alterations in the mechanical environment caused by such pathology is unclear. We present our use of 3D, finite element (FE) models of retro-acetabular pathology to investigate the biomechanical effects of osteolysis in total hip arthroplasty. Axial CT scan slices from a patient with cystic osteolysis were selected. Areas of cortical bone, cancellous bone, the cup and the cyst are accurately identified. The axial images are matched to a predetermined grid and used to build a complex finte element model. In this way complex anatomy can be built into the FE model and used to map cystic lesions. Force is then applied to the acetabulum.

Initial analysis shows similar stress transmission in cystic disease compared to the post operative pelvis. Pelvic bone still behaves as a sandwich construct with transmission from the acetabulum to the SI joints, pubic symphysis and medial wall. In the setting of pelvic medial wall deficiency, stress transmission is altered with areas of low stress around the defect.

The FE models containing pathology can be compared to models with generic bone density values immediately after total hip arthroplasty. The presence of a cyst in cancellous bone with intact cortical bone, demonstrates strain patterns similar to the post operative pelvis. Once cortical bone loss occurs strain patterns begin to change. This may mark a critical point in osteolytic progression. We present a developing new tool to be used in the assessment of a patient population with retroacetabular cystic disease.

Correct positioning of the femoral component in resurfacing hip arthroplasty (RHA) is an important factor in successful long-term patient outcomes. Computer-assisted navigation (CAS) shows potential to improve implant positioning and possibly prolong survivorship in total hip and knee arthroplasty. The purposes of CAS systems in resurfacing the femoral head are to insert the femoral head and neck guide wire with greater accuracy and to help in sizing the femoral component, thus reducing the risk of notching of the head and neck junction. Several recent studies reported satisfactory precision and accuracy of CAS in RHA. However, there is little evidence that computer navigation is useful in the presence of anatomical deformities of the proximal femur, which is frequently observed in young patients with secondary degenerative joint disease.

The purpose of this in-vitro study was to determine the accuracy of an image-free resurfacing hip arthroplasty navigation system in the presence of two femoral deformities: pistol grip deformity of the head and femoral neck junction and slipped upper femoral epiphysis deformity. An artificial phantom leg with a simulated hip and knee joint was constructed from machined aluminum. Implant-shaft angles for the guide wire of the femoral component reamer were calculated, in frontal and lateral planes, with both a computer navigation system and an electronic caliper combined with micro-CT.

With normal anatomy we found close agreement between the CAS system and our measurement system. However, there was a consistent disagreement in both the frontal and lateral planes for the pistol grip deformity. Close agreement was found only on the frontal plane angle calculation in the presence of the slipped upper femoral epiphysis deformity, but calculation of the femoral head size was inaccurate.

This is the first study designed to assess the accuracy of a femoral navigation system for resurfacing hip arthroplasty in the presence of severe anatomical deformity of the proximal femur. Our data suggests CAS technology should not be used to expand the range of utilisation of resurfacing surgery, but rather to improve the surgical outcome in those with suitable anatomy.

Purpose: Reducing wait times for total hip (THA) or knee (TKA) joint arthroplasty is a Canadian health care priority. Models that maximise the capacity of advanced practice clinicians (nurses, physical therapists, sports medicine specialists) have been established to streamline care. Hospitals across the Hamilton Niagara Haldimand Brant Local Health Integration Network in Ontario collaborated to establish a Regional Joint Assessment Centre (RJAC). This study was designed to profile patients deemed suitable for surgical review, and to examine wait times for THA or TKA in RJAC patients compared to those referred directly to an orthopaedic surgeon’s office.

Method: Patients referred to the RJAC between July 2007 and August 2008 with knee or hip OA were included. Self-reported function was evaluated using the Oxford Hip and Knee Score that is scored out of 60 (higher scores reflect greater disability). Time to surgery was measured as the number of days from initial review to surgery. Group one consisted of patients that were referred to the RJAC while group two was comprised of patients who were referred directly to a surgeon’s office. Patient characteristics were examined using univariate analyses. Independent t-tests were used to examine between group differences.

Results: One hundred thirty-six patients (mean±sd: 68±2 years, body mass index 31±6 kg/m2, 83 females) with 150 hip and/or knee joint problems were reviewed in the RJAC. Of those, only 33% (45/136 patients) were deemed suitable for surgical review. Self-reported function (Oxford Scores) in the group requiring surgical review was significantly worse (40±7, p=0.03) than in those patients deemed unsuitable for surgical review (37±9). The RJAC group waited on average 130 days for THA and 129 days for TKA (below the provincial target of 182 days) while those referred directly to the surgeons’ offices waited significantly longer (194 days for THA and 206 days for TKA, p< 0.001).

Conclusion: Patients with hip and knee OA who require surgical review have worse self-reported function than those triaged to conservative care. Wait times for THA or TKA were significantly shorter for patients referred to the RJAC under the new model of care than for those referred directly to an orthopaedic surgeon’s office.

Objective: To determine patient characteristics and outcomes for extremity rhabdomyosarcoma (RMS) utilizing an international cohort of prospectively treated patients.

Methods: Data were collected from 566 patients (1984 through 2003) treated on cooperative protocols : US IRS III, IV Pilot, IV studies – SIOP 84, 89, 95 studies – Italian ICG 79, 88, 96 studies – German CWS81, 86, 91, 96 studies.

Results: 29 % of the patients were < 3 year old, 36 % were 3 to 10 year old and 35 % > 10 year old. 350 (63%) patients had alveolar RMS and 116 (22%) had regional nodes.

The overall survival and EFS were 65% and 51% at 5 years respectively and 59% and 48% at 10 years respectively.

By univariate analysis, EFS was influenced by age below 3 years but not by age over 10 years (EFS were 61%, 49% and 46% for patients below 3 years, from 3 to 10 and 10 years or more respectively). It was also influenced by tumor invasiveness, tumor size, lymph node involvement, histology, completeness of surgery at diagnosis and cooperative groups. In multivariate analysis of EFS, size, lymph nodes, quality of surgery, cooperative groups had independent impact. Age and histology had no more impact.

OS (univariate analysis) was influenced by age below 3 years but not by age over 10 years (OS were 77%, 61% and 58% for patients below 3 years, from 3 to 10 and 10 years or more respectively). In multivariate analysis, age, lymph nodes, tumour invasiveness, quality of surgery at diagnosis had independent impact. Histology, tumour size and cooperative groups had no more impact.

Conclusion: This analysis shows that significant cut-point for age is 3 years, that histology per se has no impact on OS and EFS. It also underscores the impact of initial surgery on outcome.

Aim: To assess the safety and efficacy of a mini-incision surgical (MIS) approach to knee arthroplasty (TKA) compared to a traditional standard approach.

Background: TKA through less invasive approaches have become increasingly popular in recent years. These range from smaller skin incisions to the ‘quadriceps-sparing’ procedures. Claims of improved recovery time and other clinical/economic advantages have been tempered by concerns about the safety of such procedures. This study was designed to evaluate any potential advantages of a specific approach (MIS) whilst studying peri-operative, radiological and outcome data to examine procedural safety.

Patients and Methods: 80 patients undergoing TKA were randomised to a standard or MIS (mini-midvastus) approach. The latter involved patella subluxation, rather than eversion. The operative, anaesthetic and post-operative treatments were standardised including rehabilitation protocols. Strict discharge criteria were established and independently verified and patients were discharged directly to their homes capable of independent care. Specifically the study evaluated patient demographics, operative time, blood loss and hospital stay. Outcome data including Knee Society Scores, Oxford Knee Scores and SF36 were recorded regularly in the early recovery period and up to 1 year post-operatively. Independent radiological review of implant positioning and alignment was obtained.

Results: There were no significant differences in operative time, blood loss, or other intra-operative data. Accelerated discharge was achieved in both groups (compared to historic data), however the length of stay (LOS) was significantly shorter in the MIS patients (mean – 3.5 days compared with 4.4 days in the standard patients). There was no statistical difference in clinical outcome analyses between the groups.

Discussion: Less invasive approaches to TKA have been reported over recent years but most studies have been anecdotal comparing patient recovery with historic controls which potentially can exaggerate clinical and economic benefits. Concerns have also been raised regarding the safety of these modified procedures. This study demonstrates a reduction in hospital stay and recovery in all patients as a result of accelerated rehabilitation. The MIS patients benefited from an additional significant reduction length of stay compared to controls with no evidence of compromise in terms of safety or efficacy.

Conclusions: This study has demonstrated the safety of the MIS mini-midvastus approach and a clear reduction in hospital length of stay. MIS surgery can offer substantial clinical and economic benefits but procedures must be closely evaluated to ensure equivalent or enhanced outcomes are achieved.

Purpose: In patients with pelvic trauma, the need to quickly and accurately rule out sources of bleeding is paramount. We sought to determine the predictive value of CT angiography in determining the need for therapeutic angiography and to ascertain if definable arterial bleeding correlated with anatomic injury.

Method: Over a 2 year period 58 patients with a high-energy mechanism and pelvic injury underwent pelvic CT angiography as part of their initial trauma CT scan. This was performed as a 25 second delayed scan (after contrast introduction) using a GE light speed VCT64 scanner. The decision to proceed to therapeutic angiography was made on clinical grounds and was later compared with the CT angiographic findings. The anatomic location of bleeding on CT angio and interventional angio were compared.

Results: There were 36 male and 22 female patients, aged 43 (17 – 86), with average ISS of 18.6. The 18 (31%) patients with positive extravasation on CT angiography had higher initial blood requirements compared to those without extravasation. Two of the CT(+) group died prior to therapeutic angiography being performed. 11 of the remaining 16 had interventional angiography; 8 had (+) findings, including 7 major vessels coiled and 1 cutoff vessel observed. 1 patient of 40 with negative CT angiogram met clinical criteria had an interventional angiography; no arterial bleeding was discovered. The negative predictive value of CT angiography for pelvic arterial bleeding requiring therapeutic angiography was 100%; the positive predictive value of angiographically treatable bleeding was 70% (counting the two early deaths). The vessel location on CT angio and therapeutic angio was consistent in all cases. The CT angio (+) group had a higher percentage of unstable pelvic injuries (67% vs. 40%).

Conclusion: In this pilot study, CT angiography added to the initial trauma scan in patients with pelvic trauma demonstrated a 100% NPV for arterial bleeding that required therapeutic angiography on clinical grounds. Positive findings correlated well with the anatomic location of pelvic injury and had a 70% PPV for angio-graphically treatable bleeding. Further study of this technique is warranted.

Patient- specific orthopaedic models are currently used in computer navigation. They provide realistic 3-D geometries for assessment of device placement (e.g. tibial trays, hip implants). Models are generated at time of operation by the surgeon. But patient-specific models have other uses. We envisage a future in which realistic 3-D patient models are routinely used for predicting the outcome of surgical procedures and new devices and for general patient health monitoring.

We are currently developing accurate 3-D models directly from CT scan post-operation. They are being used in investigations of the progress of bone remodeling. Such work can provide valuable feedback on the outcome of new procedures and how bone remodels under load. Such models would eventually include other tissue such as muscles and skin.

But there are a number of research and development challenges associated with the creation of patient-specific models. They include

minimal use of radiation for data collection;

We are working to meet these challenges. They include the use of generic data to supplement patient data, efficient ways of morphing models to fit the patient, and multi-scale modeling strategies. Work in progress at the Auckland Bio-engineering Institute will be presented in this talk.

Purpose: To evaluate the functional outcome of operatively treated Lisfranc injuries.

Method: Over a 7-year interval from 1998 to 2005, 184 skeletally mature patients were identified retrospectively with operatively treated Lisfranc injuries. 85 patients had prospectively measured SMFA functional outcomes and satisfaction surveys. The gender was 37 males and 48 females. Mean age was 39 years (range 17–93).

Results: The mechanism was fall (31), MVA (24), crush (15), equestrian (5), or twisting (10). Patients were operatively treated with open reduction internal fixation (ORIF, 53) or primary arthrodesis (PA, 32). The SMFA reliability for this patient sample was 0.892. The function and bother outcomes were 19.4 and 15.8, respectively. The function (21.5 vs. 16.0, p=.11) and bother (17.5 vs. 13.0, p=.25) outcomes were not significantly different for ORIF vs. PA, respectively. In the ORIF group, HW removal (40 of 53) performed better than HW retention (13 of 53) with outcome bother but not function measures of (14.7 vs. 26.1, p< 0.05).

Conclusion: If performed well, either ORIF or PA technique function well. Patients are more satisfied with the results and appearance of PA over ORIF. HW removal compared to HW retention positively affect bother not function measures. Secondary surgeries negatively affect both bother and function measures. Patients with pain, associated foot or polytrauma injuries function worse.

Purpose: 2 orthopaedic surgeons identified 18 patients who developed glenohumeral chondrolysis following arthroscopic shoulder surgery. The index surgery for all 18 patients occurred over an 18 month period. We sought to find any common factors among the 18 cases.

Method: A retrospective chart review of all 18 patients was performed. We gathered information on patient demographics, type of surgical procedure, nature of shoulder instability, post-operative complications such as infection, the use of radiofrequency energy, the type/number of suture anchors, the use of an IAPPC and the type of local anaesthetic used. We compared pre-operative radiographs and MRI scans to the intra-operative findings from the operative report to confirm that no chondrolysis was present pre-operatively. We examined post-operative radiographs and MRI scans to document the extent of chondrolysis

Results: Of the 18 patients who developed chondrolysis, we had 15 males and 3 females with an average age of 23 years (range 16–39). 17 patients had shoulder instability due to a definitive traumatic event while 1 patient had an atraumatic etiology. No radiofrequency energy was used in any of the cases. No post-operative infections were diagnosed and many had work-ups for infection which included ESR, CRP, bone & gallium/WBC scans. All patients had labral stabilization procedures, 15 anterior (Bankart), 1 posterior, and 2 combinations. All patients received suture anchors, 13 patients had 2 anchors and 5 had 3 anchors. 2 different manufacturer’s suture anchors were used, 10 patients received Smith & Nephew anchors while 8 patients received Linvatec anchors. 10 patients received bioabsorbable anchors and 8 patients received metal anchors. All patients received an IAPPC loaded with 0.5% bupivacaine with epinephrine for post-operative pain control. 15 of the IAPPC’s were considered large with an infusion rate of 5 mL/hr and a fill volume of 275 mL’s. 3 IAPPC’s were considered small with an infusion rate of 2 mL/hr and a fill volume of 100 mL’s.

Conclusion: We suspect a continuous intra-articular infusion of bupivacaine with epinephrine may have contributed to the development of chondrolysis. We caution against the use of IAPPC’s until their safety has been proven.

Intramedullary nailing is acknowledged as a safe and effective mode of treatment for many tibial fractures. Implant removal is frequently indicated either as an elective procedure following union or because of problems such as infection or delayed fracture union. It is therefore essential that intramedullary rod removal should be reasonably straightforward and atraumatic.

We describe three cases in which bony growth into the implant has made rod removal either difficult or impossible. We include photographs of two removed implants with clearly visible areas of osseo-integration with bony growth into the cannulation through the interlocking holes as well as radiographs demonstrating the same phenomenon.

The average time between insertion and removal was 16 months. In all cases an end cap had been used such that insertion of the extraction device was straightforward but for two patients nail removal was extremely difficult due to bone ingrowth and in the third patient the nail had to be left in-situ. All three implants were made of titanium and the patients were all active young males. The authors have never encountered this problem with steel rods and speculate that the osteointegrative property of titanium is the major causative factor.

We suggest that unremoved intramedullary rods represent a major risk in fracture management and that close monitoring of these implants should be undertaken.

FDA approval of metal-on-metal (MOM: 28, 32mm) bearings has provided 10 years of clinical experiences in USA. However there has been no detailed mapping of wear phenomena in retrieval cases. We present an analysis of 28 cases, MOM retrievals with 1 to 10 years follow-up, radiographic reviews and metal ion studies. Ball diameters ranged from 28mm to 42mm. Two balls were the early design with skirts. Main indicators for revision were the progressive radiographic changes indicative of osteolysis, with associated hip pain. Approximately 54% of patients were males and ages ranged from 36 to 76 years of age. Only 7 femoral stems were recovered but all had impingement marks. Only three cases lacked any evidence of stripe wear and these were in very elderly patients. Approximately 85% of these cases showed some evidence of stripe wear and multiple stripes were clearly visible on 50% of the femoral balls. The medial ball stripes were twice as common as lateral. Stripe wear was identified in 25% of CoCr liners.

In the hip simulator studies generally show ‘run-in’ wear rates of 1–7mm3 per million cycles (Mc). We noted that above the 5mm3/Mc threshold, the serum generally appeared black. In contrast, the ‘steady-state’ wear rates of 0.1–1.6 mm3/Mc showed the true potential of MOM bearings. However there were often examples of higher wear (7–20 mm3/Mc), which gave confounding trends in published studies. Our studies of metal ions in the simulator lubricant provided a very accurate representation of MOM wear.

There are many limitations in comparing in-vitro to in-vivo wear performance. Our retrieval data are biased to cases that failed due to hip pain, had radiographic signs of progressive osteolysis and some showed high levels of metal ions. There was also the bias of having predominantly a CoCr sandwich design (polyethylene adaptor). Use of the small ball added the well-known risks of impingement, subluxation and dislocation with rigid cups. Using the ‘damage modes’ from McKellop, we found only normal Mode-1 wear to be rare in these cases, whereas Modes# 2–4 had an incidence approaching 30% each. Signs of impingement were evident in 85% of our cases. Thus summarizing these MOM wear phenomena in retrieved 28mm sandwich cups, the evidence implicated impingement and 3rd-body wear modes (#2–4) as the clinical risk for adverse wear effects at 10 years follow-up. The in-vitro wear studies have not yet simulated such adverse clinical effects.

From 1985 metal-on-metal (MOM) designs of resurfacing (RSA) and total hip arthroplasties (THR) have been available over a large diameter range (28–60mm). In-vitro studies indicated satisfactory low wear performance for all designs and diameters tested (wear = 0.1 to 7 mm3). While reports from many centers have been encouraging, some have reported adverse effects. We reviewed clinical and metal ion studies in large diameter retrievals and compared these to 28mm MOM cases. Patients with the latter THR ranged 36–76 years of age and were followed 9–11 years. Main finding in our revisions was osteolysis and pain. The 28mm ball was represented 86% of cases; 71% balls had stripe wear. For liners, 25% had circumferential stripe wear and impingement was evident in 64% cases. Seven cemented stems were recovered with impingement marks; 26 stems were undamaged and therefore not revised. Using the concept of ‘damage modes’ from McKellop, normal wear mode #1 was evident in only 14% of 28mm retrievals whereas incidence of ‘abnormal’ modes #2-4 approached 30% each. Thus the 28mm MOM appeared susceptible to impingement risks with CoCr liners. Summarizing MOM retrievals, damage modes 2–4 were most likely implicated in revisions. The performance of such ‘small diameter’ THRs will be contrasted to our large diameter THR and RSA experience. The questions to be reviewed include, how much of the reported MOM adversity was predictable and how much risk was due to

wear of small diameter MOM,