Subsidence remains a concern when utilizing modern tapered fluted titanium (TFT) femoral stems and may lead to leg length discrepancy, impingement, instability and failure to obtain stem osseointegration. This study aims to compare stem subsidence across three modern TFT stems. Our secondary aim was to investigate the influence of bicortical contact or ‘scratch fit’ on subsidence, as well as the role of intraoperative imaging in maximizing this bicortical contact and preventing stem subsidence.

A retrospective review of 271 hip arthroplasties utilizing modern TFT stems in a single institution was performed. Three stem designs were included in the analysis: one monoblock TFT stem (n=91) and two modular TFT stems (Modular A [n=90]; Modular B [n=90]). Patient demographics, Paprosky femoral bone loss classification, bi-cortical contact, utilization of intra-operative imaging and stem subsidence (comparison of initial post-operative radiograph to the latest follow up radiograph - minimum three months) were recorded.

There was no statistically significant difference in the amount of subsidence between the three stems (Monoblock: 2.33mm, Modular A: 3.43mm, Modular B: 3.02mm; p=0.191). There was no statistical difference in subsidence >5mm between stems (Monoblock: 9.9%, Modular A: 22.2%, Modular B: 16.7%). Subgroup analysis based on femoral bone loss grading showed no difference in subsidence between stems. Increased bicortical contact was strongly associated with reduced subsidence (p=0.004). Intra-operative imaging was used in 46.5% (126/271) of cases; this was not correlated with bicortical contact (p=0.673) or subsidence (p=0.521). Across all groups, only two stems were revised for subsidence (0.7%).

All three modern TFT stems were highly successful and associated with low rates of subsidence, regardless of modular or monoblock design. Surgeons should select the stem that they feel is most clinically appropriate.

The purpose of this study was to precisely measure the 10-year polyethylene wear rate of primary total hips using Radiostereometric analysis (RSA) comparing Oxidized Zirconium (OxZi) to cobalt chrome (CoCr) femoral heads articulating with highly cross-linked polyethylene (XLPE).

RSA was performed on 46 patients who underwent total hip arthroplasty − 23 who received OxZi femoral heads and 23 who received CoCr heads in combination with XLPE at a minimum of 10 years follow-up. All patients had identical THR systems implanted except for the femoral head utilized. The Centre Index method was utilised to assess total wear rates (from index surgery until final evaluation) using a dedicated RSA Software program (UmRSA Digital Measure v.2.2.1). In addition, the Martell technique was used to subtract head penetration occurring in the first 1–2 years (i.e. bedding-in phase) to allow calculation of the ‘steady state’ wear rates.

There were no significant differences in demographics (i.e age, BMI, gender) between the groups. The average time from surgery of the RSA examinations was 11.7 and 12.6 years for the CoCr and OxZi groups respectively. Using the Centre Index Method to calculate total head penetration, wear rates were slightly higher in the OxZi group (0.048 +/− 0.021mm/year) compared to the CoCr group (0.035 +/− 0.017mm/year) with no statistical difference between the groups (p= 0.02). After correction for the bedding-in period, there was no statistically significant difference in mean ‘steady-state’ wear rate between OxZi (0.031 +/− 0.021mm/year) and CoCr (0.024 +/− 0.019mm/year) at 10 year follow up (p= 0.24). A comparison of preoperative and postoperative SF12, HHS, and WOMAC scores showed no statistical difference between the groups.

RSA demonstrated the 10 year in-vivo wear rates of both bearing combinations to be well below the threshold for osteolysis. There was no significant difference between either the total or ‘steady-state’ wear rates of the OxZi and CoCr groups at 10 years.

Introduction

Current methodologies for designing and validating existing THA systems can be expensive and time-consuming. A validated mathematical model provides an alternative solution with immediate predictions of contact mechanics and an understanding of potential adverse effects. The objective of this study is to demonstrate the value of a validated forward solution mathematical model of the hip that can offer kinematic results similar to fluoroscopy and forces similar to telemetric implants.

With the success of the medial parapatellar approach (MPA) to total knee arthroplasty (TKA), current research is aimed at reducing iatrogenic microneurovascular and soft tissues damage to the knee. In an effort to avoid disruption to the medial structures of the knee, we propose a novel quadriceps-sparing, subvastus lateralis approach (SLA) to TKA. The aim of the present study is to compare if a SLA can provide adequate exposure of the internal compartment of the knee while reducing soft tissue damage, compared to the MPA. Less disruption of these tissues could translate to better patient outcomes, such as reduced post-operative pain, increased range of motion, reduced instances of patellar maltracking or necrosis, and a shorter recovery time.

To determine if adequate exposure could be achieved, the length of the skin incision and perimeter of surgical exposure was compared amongst 22 paired fresh-frozen cadaveric lower limbs (five females/six males) which underwent TKA using the SLA or MPA approach. Additionally, subjective observations which included the percent of visibility of the femoral condyles and tibial plateau, as well as the patellar tracking, were noted in order to qualify adequate exposure. All procedures were conducted by the same surgeon. Subsequently, to determine the extent of soft tissue damage associated with the approaches, an observational assessment of the dynamic and static structures of the knee was performed, in addition to an examination of the microneurovascular structures involved. Dynamic and static structures were assessed by measuring the extent of muscular and ligamentus damage during gross dissection of the internal compartment of the knee. Microneurovascular involvement was evaluated through a microscopic histological examination of the tissue harvested adjacent to the capsular incision.

Comparison of the mean exposure perimeter and length of incision was not significantly different between the SLA and the MPA (p>0.05). In fact, on average, the SLA facilitated a 5 mm larger exposure perimeter to the internal compartment, with an 8 mm smaller incision, compared to the MPA, additional investigation is required to assert the clinical implications of these findings. Preliminary analysis of the total visibility of the femoral condyles were comparable between the SLA and MPA, though the tibial plateau visibility appears slightly reduced in the SLA. Analyses of differences in soft tissue damage are in progress.

Adequate exposure to the internal compartment of the knee can be achieved using an incision of similar length when the SLA to TKA is performed, compared to the standard MPA. Future studies should evaluate the versatility of the SLA through an examination of specimens with a known degree of knee deformity (valgus or varus).

Dexmedetomidine, an alpha 2 agonist, has been approved for providing sedation in the intensive care unit. Along with sedative properties, it has analgesic activity through its highly selective action on alpha 2 receptors. Recent studies have examined the use of dexmedetomidine as an adjuvant to prolong the duration of peripheral nerve blocks. Studies showing effectiveness of dexmedetomidine for adductor canal block in knee surgery are small. Also, its effectiveness has not been compared to Epinephrine which is a strong alpha and beta receptor agonist. In a previous study, we showed that motor sparing knee blocks significantly increased the duration of analgesia compared with periarticular knee infiltration using local anesthetic mixture containing Epinephrine following total knee arthroplasty (TKA). In this study, we compared two local anesthetic mixtures: one containing Dexmedetomidine and the other Epinephrine for prolongation of motor sparing knee block in primary TKA patients.

After local ethics board approval and gaining Notice of Compliance (NOC) from Health Canada for use of Dexmedetomidine perineurally, 70 patients between the ages 18 – 95 of ASA class I to III undergoing unilateral primary total knee arthroplasty were enrolled. Motor sparing knee block − 1) Adductor canal continuous catheter 2) Single shot Lateral Femoral Cutaneous Nerve block 3) Single shot posterior knee infiltration was performed in all patients using 60 ml mixture of 0.5% Ropivacaine, 10 mg Morphine, 30 mg Ketorolac. Patients randomized into the Dexmedetomidine group (D) received, in addition to the mixture, 1mcg/kg Dexmedetomidine and the Epinephrine (E) group received 200mcg in the mixture. The primary outcome was time to first rescue analgesia as a surrogate for duration of analgesia and secondary outcomes were NRS pain scores up to 24 hours and opioid consumption.

The time to first rescue analgesia was not significantly different between Epinephrine and dexmedetomidine groups, Mean and SD 18.45 ± 12.98 hours vs 16.63 ± 11.80 hours with a mean difference of 1.82 hours (95% CI −4.54 to 8.18 hours) and p value of 0.57. Pain scores at 4, 6, 12, 18 and 24 hours were comparable between groups. Mean NRS pain scores Epinephrine vs Dexmedetomidine groups were 1.03 vs 0.80 at 4 hours, 1.48 vs 3.03 at 6 hours, 3.97 vs 4.93 at 12 hours, 5.31 vs 6.18 and 6.59 v 6.12 at 24 hours. Opioid consumption was also not statistically significant between both groups at 6, 12 18, 24 hours (p values 0.18, 0.88, 0.09, 0.64 respectively).

Dexmedetomidine does not prolong the duration of knee motor sparing blocks when compared to Epinephrine for total knee arthroplasty. Pain scores and opioid consumption was also comparable in both groups. Further studies using higher dose of dexmedetomidine are warranted.

While Oxidized Zirconium (OxZr) femoral heads matched with highly cross-linked polyethylene (XLPE) have demonstrated the lowest rate of revision compared to other bearing couples in the Australian National Joint Registry, it has been postulated that these results may, in part, be due to the fact that a single company offers this bearing option with a limited combination of femoral and acetabular prostheses. The purpose of this study was to assess clinical and radiographic outcomes in a matched cohort of total hip replacements (THR) utilizing an identical cementless femoral stem and acetabular component with either an Oxidized Zirconium (OxZr) or Cobalt-Chrome (CoCr) femoral heads at a minimum of 10 years follow-up.

We reviewed our institutional database to identify all patients whom underwent a THR with a single cementless femoral stem, acetabular component, XLPE liner and OxZr femoral head with a minimum of 10 years of follow-up. These were then matched to patients who underwent a THR with identical prosthesis combinations with CoCr femoral head by gender, age and BMI. All patients were prospectively evaluated with WOMAC, SF-12 and Harris Hip Score (HHS) preoperatively and postoperatively at 6 weeks, 3 months, 1 and 2 years and every 2 years thereafter. Charts and radiographs were reviewed to determine the revision rates and survivorship (both all cause and aseptic) at 10 years for both cohorts. Paired analysis was performed to determine if differences exist in patient reported outcomes.

There were 208 OxZr THRs identified which were matched with 208 CoCr THRs. There was no difference in average age (OxZr, 54.58 years, CoCr, 54.75 years), gender (OxZr 47.6% female, CoCr 47.6% female), and average body max index (OxZr, 31.36 kg/m2, CoCr, 31.12 kg/m2) between the two cohorts. There were no significant differences preoperatively in any of the outcome scores between the two groups (WOMAC (p=0.449), SF-12 (p=0.379), HHS(p=0.3718)). Both the SF12 (p=0.446) and the WOMAC (p=0.278) were similar between the two groups, however the OxZr THR cohort had slightly better HHS compared to the CoCr THR cohort (92.6 vs. 89.7, p=0.039). With revision for any reason as the end point, there was no significant difference in 10 years survivorship between groups (OxZr 98.5%, CoCr 96.6%, p=0.08). Similarly, aseptic revisions demonstrated comparable survivorship rates at 10 year between the OxZr (99.5%) and CoCr groups (97.6%)(p=0.15).

Both THR cohorts demonstrated outstanding survivorship and improvement in patient reported outcomes. The only difference was a slightly better HHS score for the OxZr cohort which may represent selection bias, where OxZr implants were perhaps implanted in more active patients. Implant survivorship was excellent and not dissimilar for both the OxZr and CoCr groups at 10 years. Therefore, with respect to implant longevity at the end of the first decade, there appears to be no clear advantage of OxZr heads compared to CoCr heads when paired with XLPE for patients with similar demographics. Further follow-up into the second and third decade may be required to demonstrate if a difference does exist.

At the present time, there is no bearing in total hip arthroplasty that a surgeon can present to a younger and/or more active patient as being the bearing that will necessarily last them a lifetime. This is the driver to offering alternative bearings (crosslinked polyethylene with either a CoCr or ceramic head, resurfacings, and ceramic-on-ceramic) to patients. Each of these bearings has pros and cons, and none has emerged as the clear victor in the ongoing debate.

Ceramic-on-ceramic (CoC) bearings have been available for decades. Earlier generation CoC bearings did encounter problems with rare fractures, however, with a greater understanding and improvement in the material, the fracture incidence has been significantly reduced. However, what has emerged in the past few years is an increasing reporting of significant squeaking. The incidence of squeaking, reported in the literature in various series, has varied from less than 1% to over 20%, depending on the definition used.

The primary reasons that ceramic-on-ceramic is not truly the articulation of choice for younger patients are: 1) There is absolutely no evidence that this bearing has a lower revision rate. Data from the Australian joint registry actually shows that at 15 years it has a significantly increased rate of revision (7.2%) compared with using a highly crosslinked liner with either a ceramic (5.1%) or a CoCr (6.3%) head; 2) This bearing is by far the most costly bearing on the market. In 2017 with significant constraints on health care systems across the globe, this is a significant concern; 3) This bearing has unique complications including squeaking and both liner and head fracturing.

While ceramic-on-ceramic can be considered a viable alternative bearing in total hip arthroplasty, it can be in no way considered the articulation of longevity for the younger patient.

Metal-on-metal bearings (MoM), in both a total hip and resurfacing application, saw an increase in global utilization in the last decade. This peaked in 2008 in the US, with approximately 35% of bearings being hard-on-hard (metal-on-metal or ceramic-on-ceramic). Beginning in 2008, reports in the orthopaedic literature began to surface regrading local soft tissue reactions and hypersensitivity to metal-on-metal bearings. A major implant manufacturer recalled a resurfacing device in 2010 after national joint registries demonstrated higher than expected revision rates.

Patients with painful metal-on-metal bearings presenting to the orthopaedic surgeon are a difficult diagnostic challenge. The surgeon must go back to basic principles, perform a complete history and physical exam, obtain serial radiographs and basic bloodwork (ESR, CRP) to rule out common causes of pain and determine if the pain is, or is not, related to the bearing.

The Asymptomatic MoM Arthroplasty: Patients will present for either routine followup, or because of concerns regarding their bearing. It is important to emphasise that at this point the vast majority of patients with a MoM bearing are indeed asymptomatic and their bearings are performing well. The surgeon must take into account: a) which specific implant are they dealing with and what is its track record; b) what is the cup position; c) when to perform metal ion testing; d) when to perform further soft tissue imaging (MARS MRI, Ultrasound); e) when to discuss possible surgery. A simple algorithm for both painless and painful MoM Arthroplasties has been developed and will be presented.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected knee arthroplasty experts.

The primary cases will include challenges such as patient selection and setting expectations, exposure, alignment correction and balancing difficulties. In the revision knee arthroplasty scenarios issues such as bone stock loss, fixation challenges, instability and infection management will be discussed.

This will be an interactive case-based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

The infection rate after total joint arthroplasty (TJA) has been shown to be 1–2% in multiple series and registry data. Irrigation, debridement, and polyethylene exchange (IDPE) is a common first line treatment in many cases of acute prosthetic joint infection (PJI). The reinfection rate in open IDPE procedures is variable with studies showing reinfection rates of 10–70% depending on various patient and microbial factors. Our pilot study aimed to determine if the bacterial load in infected total joints was sufficiently reduced by IDPE to allow for the use of post-debridement cultures as an independent marker of procedural success.

46 prosthetic joint infections underwent irrigation and debridement using 6L of normal saline and 3L of a normal saline and bacitracin mixture prior to the insertion of a new polyethylene liner. This protocol utilized a single equipment setup with all surgical members donning new gloves prior to polyethylene exchange. Between 3 and 5 intraoperative cultures were obtained both prior to and after debridement as per the surgeon's standard protocol. A two-tailed student's t-test was used to evaluate for any differences in the rate of positive culture between these two groups.

Of all pre- and post-debridement cultures sampled 66.5% and 60.7% of cultures were positive respectively. No significant difference in the rate of positive intraoperative culture was found between pre-debridement and post-debridement groups (p = 0.52). In 32 of 46 (69%) cases there was no difference in the total number of positive cultures despite a thorough debridement.

Our data shows that open debridement of PJI does not provide a sterile environment, and post-debridement cultures should not be used as an independent marker of procedural success. The role of an irrigation and debridement to reduce the bacterial burden and potentiate the clearance of an infection is established but its efficacy is unclear, and the inability to create a post-debridement sterile environment is a concern.

The purpose of this study is to compare 90-day costs and outcomes for primary total hip arthroplasty (THA) patients between a non-obese (BMI 18.5–24.9) versus overweight (25–29.9), obese (30–34.9), severely-obese (35–39.9), morbidly-obese (40–44.9), and super-obese (45+) cohorts.

We conducted a retrospective review of a prospective institutional database of primary THA patients from 2006–2013, including patients with a minimum of three-year follow-up. Thirty-three super-obese patients were identified, and the other five cohorts were randomly selected in a 2:1 ratio (total n = 363). Demographics, 90-day outcomes (costs, reoperations, and readmissions), and outcomes after three years (revisions and change scores for SF12, HHS, and WOMAC) were collected. Costs were determined using unit costs from our institutional administrative data for all in-hospital resource utilization. Comparisons between the non-obese and other groups were made with Kruskal-Wallis tests for non-normal data and chi-square and Fisher's exact test for categorical data.

The 90-day costs in the morbidly-obese ($13,134 ± 7,250 mean ± standard deviation, p <0.01) and super-obese ($15,604 ± 6,783, p <0.01) cohorts were statistically significantly greater than the non-obese cohorts ($10,315 ± 1,848). Only the super-obese cohort had statistically greater 90-day reoperation and readmission rates than the non-obese cohort (18.2% vs 0%, p <0.01 and 21.2% vs 4.5%, p=0.02, respectively). In addition, reoperations and septic revisions after 3 years were greater in the super-obese cohort compared to the non-obese cohort 21.2% vs 3.0% (p = 0.01), and 18.2% vs 1.5% (p= 0.01), respectively. There were no other statistical differences between the other cohorts with the non-obese cohort at 90-days or after 3 years. Improvements in SF12, HHS, and WOMAC were comparable in all cohorts.

The 90-day costs of a primary total hip arthroplasty for morbidly-obese (BMI 40–44.9) and super-obese (BMI>45) are significantly greater than for non-obese patients, yet these patients have comparable improvements in outcome scores. Health care policies, when based purely on the economic impact of health care delivery, may place morbidly-obese and super-obese patients at risk of losing arthroplasty care, thereby denying them access to the comparable quality of life improvements.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected hip arthroplasty experts. The primary cases will include challenges such as hip dysplasia, altered bony anatomy and fixation challenges. In the revision hip arthroplasty scenarios issues such as bone stock loss, leg length discrepancy, instability and infection will be discussed. This will be an interactive case-based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

Patients with painful metal-on-metal bearings presenting to the orthopaedic surgeon are a difficult diagnostic challenge. The surgeon must go back to basic principles, perform a complete history and physical exam, obtain serial radiographs and basic blood work (ESR, CRP) to rule out common causes of pain and determine if the pain is, or is not, related to the bearing.

The Asymptomatic MoM Arthroplasty: Patients will present for either routine follow up, or because of concerns re: their bearing. It is important to emphasise that at this point the vast majority of patients with a MoM bearing are indeed asymptomatic and their bearings are performing well. The surgeon must take into account: a) which specific implant are they dealing with and what is its track record; b) what is the cup position; c) when to perform metal ion testing; d) when to perform further soft tissue imaging (MARS MRI, Ultrasound); e) when to discuss possible surgery.

Painful MoM THA causes not related to the bearing couple: These can be broken down into two broad categories. Causes that are Extrinsic to the hip include: spine, vascular, metabolic and malignancy. Causes that are Intrinsic to the hip can either be Extracapsular (iliopsoas tendonitis and trochanteric bursitis) or Intracapsular (sepsis, loosening, thigh pain, prosthetic failure)

Painful MoM THA causes related to the bearing couple: There are now described a number of possible clinical scenarios and causes of pain that relate to the metal-on-metal bearing couple itself: a) local hypersensitivity reaction without a significant soft tissue reaction; b) local hypersensitivity reaction with a significant soft tissue reaction; c) impingement and soft tissue pain secondary to large head effect.

Metal ions: obtaining serum, or whole blood, cobalt and chromium levels is recommended as a baseline test. However, there is no established cutoff level to determine with certainty if a patient is having a hypersensitivity reaction. A 7 parts per billion cutoff has been suggested. This gives high specificity, but poor sensitivity. Metal ions therefore can be used as a clue, and one more test in the workup, but cannot be relied upon in isolation to make a diagnosis.

MARS MRI: a useful tool for demonstrating soft tissue involvement, but there are many painless, well-functioning MoM implants that have soft tissue reactions, that don't require a revision. In the painful MoM hip an MRI, or ultrasound, is recommended to look for soft tissue destruction or a fluid-filled periprosthetic lesion (pseudotumor). Significant soft tissue involvement is concerning and is commonly an indication for revision in the painful MoM hip.

Treatment: management of the painful MoM hip is directly related to the etiology of the pain. Unique to MoM bearing is the issue of pain secondary to a local hypersensitivity reaction. All above tests should be utilised to help determine the best course of action in any individual patient. The painful MoM bearing, that is demonstrating significant soft tissue involvement is a concerning scenario. Earlier revision, to prevent massive abductor damage, would seem prudent for these patients. The painful MoM bearing with no significant soft tissue changes can probably be followed and reviewed at regular intervals. If the pain persists and is felt to be secondary to a hypersensitivity reaction, then revision is really the only option, although the patient must be cautioned regarding the unpredictable nature of the pain relief.

The use of robotics in total joint arthroplasty is the latest in a long list of expensive technologies that promise multiple positive outcomes, but come with an expensive price tag. In the last decade alone we've seen the same claims for navigation and patient specific instruments and implants. There are various current systems available including a robotic arm, robotic-guided cutting jigs and robotic milling systems.

For robotics to be widely adopted it will need to address the following concerns, which as of 2017 it has not.

1)

Cost - Very clearly the robotic units come with a significant price tag. Perhaps over time, like other technologies, they will reduce, but at present they are prohibitive for most institutions.

As with any new technology one must be wary of the claims superseding the results. In 2017 the jury is still out on the cost vs. benefit of robotic-assisted TKA.

At the present time, there is no bearing in total hip arthroplasty that a surgeon can present to a younger and/or more active patient as being the bearing that will necessarily last them a lifetime. This is the driver to offering alternative bearings (crosslinked polyethylene with either a CoCr or ceramic head, resurfacings, and ceramic-on-ceramic) to patients. Each of these bearings has pros and cons, and none has emerged as the clear victor in the ongoing debate.

Ceramic-on-Ceramic (CoC) bearings have been available for decades. Earlier generation CoC bearings did encounter problems with rare fractures, however, with a greater understanding and improvement in the material, the fracture incidence has been significantly reduced. However, what has emerged in the past few years is an increasing reporting of significant squeaking. The incidence of squeaking, reported in the literature in various series, has varied from less than 1% to over 20%, depending on the definition used.

The primary reasons that Ceramic-on-Ceramic is not truly the articulation of choice for younger patients are:

1)

There is absolutely no evidence that this bearing has a lower revision rate. Data from the Australian joint registry actually shows that at 15 years it has a significantly increased rate of revision (7.2%) compared with using a highly crosslinked liner with either a ceramic (5.1%) or a CoCr (6.3%) head.

While Ceramic-on-Ceramic can be considered a viable alternative bearing in total hip arthroplasty, it can be in no way considered the articulation of longevity for the younger patient.

Lewinnek's safe zone recommendation to minimise dislocations was a target of 5–25° for anteversion angle and 30–50° for inclination angle. Subsequently, it was demonstrated that mal-positioning of the acetabular cup can also lead to edge loading, liner fracture, and greater conventional polyethylene wear. The purpose of this study was to measure the effect of acetabular cup position on highly crosslinked polyethylene wear in total hip arthroplasty (THA) at long-term follow-up.

We identified all patients that underwent primary THA with a minimum of 10 years follow-up using an institutional database in London, Ontario, Canada. Patients with a single implant design consisting of a 28 mm cobalt chromium head and highly crosslinked polyethylene liner (ram extruded, GUR 1050, 100 kGy gamma irradiated, remelted, ethylene oxide sterilised) were selected for inclusion. In total, 85 hips from 79 recruited patients were analysed. Patients underwent a supine radiostereometric analysis (RSA) exam in which the x-ray sources and detectors were positioned to obtain an anterior-posterior and cross-table lateral radiograph. Acetabular cup anteversion angle, inclination angle, and 3D penetration rate (including wear and creep) were measured from the stereo radiograph pairs.

At a mean follow-up of 13 years (range, 10–17 years) the mean penetration rate was 0.059 mm/year (95% CI: 0.045 to 0.073 mm/year). Mean anteversion angle was 18.2° (range, −14 to 40°) and mean inclination angle was 43.6° (range, 27 to 61°). With respect to the Lewinnek safe zone, 67% hips met the target for anteversion angle, 77% met the target for inclination angle, and 51% met the target for both. There was no correlation between anteversion angle and penetration rate (r = −0.14, p = 0.72) or between inclination angle and penetration rate (r = 0.11, p = 0.35). There was also no difference (p = 0.07) in penetration rate between hips located within the Lewinnek safe zone for both anteversion angle and inclination angle (mean 0.057 mm/year, 95% CI: 0.036 to 0.079 mm/year) and those outside the safe zone (mean 0.062 mm/year, 95% CI: 0.042 to 0.083 mm/year).

Acetabular cup position had no effect on the wear rate of highly crosslinked polyethylene at long-term follow-up. Although care should still be taken to correctly position the acetabular cup for stability, highly crosslinked polyethylene is a forgiving bearing material that can withstand a wide range of cup positions without negatively impacting longevity due to wear.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected knee arthroplasty experts.

The primary cases will include challenges such as patient selection and setting expectations, exposure, alignment correction and balancing difficulties. In the revision knee arthroplasty scenarios issues such as bone stock loss, fixation challenges, instability, and infection management will be discussed.

This will be an interactive case based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

The incidence of major complications following total joint arthroplasty is low, however, surgeons often continue to see patients regularly to monitor outcomes and the performance of the implant. The purpose of this study was to assess the feasibility, effectiveness and cost-effectiveness of a web-based follow-up compared to in-person assessment following primary total hip or total knee arthroplasty. We also determined patient satisfaction and preference for follow-up method.

Patients who were at least 12 months post-operative were randomised to complete either a web-based follow-up or to have their appointment at the clinic, as usual. We excluded patients who had revision surgery, osteolysis, or identified radiographic issues. We report the frequency of web-based patients who had an issue missed by using the web-based follow-up. We recorded travel costs and time associated with each follow-up, and any health care resource use for one year following the assessment. We conducted a cost analysis from the health-care payer (Ontario Ministry of Health and Long-Term Care) and societal perspectives. All costs are presented in 2012 Canadian dollars. We used descriptive statistics to summarise the satisfaction and preference results and compared satisfaction between groups using Pearson's chi-square test.

Two-hundred-twenty-nine patients completed the study (111 usual-care, 118 web-based), with a mean age of 69 years (range, 38 – 86 years). There were no patients who had an issue missed by the web-based follow-up. The cost for the web-based assessment was significantly lower from both the societal perspective (mean difference, −$64; 95% confidence interval, −$79 to −$48; p < 0.01) and the health-care payer perspective (mean difference, −$27; 95% CI, −$29 to −$25; p < 0.01). Ninety-one patients (82.0%) in the usual-care group indicated that they were either extremely or very satisfied with the follow-up process compared with 90 patients (75.6%) in the web-based group (p < 0.01; odds ratio = 3.95; 95% CI = 1.79 to 8.76). Similarly, 92.8% of patients in the usual care group were satisfied with the care they received from their surgeon, compared to 73.9% of patients in the web-based group (p < 0.01, OR = 1.37; 95% CI = 0.73 to 2.57). Forty-four percent of patients preferred the web-based method, 36% preferred the usual method, and 16% had no preference (p = 0.01).

Web-based follow-up is a feasible, clinically effective alternative to in-person clinic assessment, with moderate to high patient satisfaction. A web-based follow-up assessment has lower mean costs per person compared to the usual method of in-person follow-up from both a societal and health-care payer perspective. The web-based assessment may introduce additional efficiency by redirecting limited outpatient resources to those awaiting first consultation, patients who have complications, or those who are further post-operative and may require a revision.

Metal-on-metal bearings (MoM) saw an increase in global utilisation in the last decade. This peaked in 2008 in the US, with approximately 35% of bearings being hard-on-hard (metal-on-metal, or ceramic-on-ceramic). Beginning in 2008, reports began to surface regarding local soft tissue reactions and hypersensitivity to MoM bearings. A major implant manufacturer recalled a resurfacing device in 2010 after national joint registries demonstrated higher than expected revision rates. Patients with painful MoM bearings are a difficult diagnostic challenge. The surgeon must go back to basic principles, perform a complete history and physical exam, obtain serial radiographs and basic blood work (ESR, CRP) to rule out common causes of pain and determine if the pain is, or is not, related to the bearing. The Asymptomatic MoM Arthroplasty: Patients will present for either routine follow up, or because of concerns regarding their bearing. It is important to emphasise that at this point the vast majority of patients with a MoM bearing are indeed asymptomatic and their bearings are performing well. The surgeon must take into account: a) which specific implant are they dealing with and what is its track record; b) what is the cup position; c) when to perform metal ion testing; d) when to perform further soft tissue imaging (MARS MRI, Ultrasound); e) when to discuss possible surgery. Painful MoM THA causes not related to the bearing couple: These can be broken down into two broad categories. Causes that are Extrinsic to the hip include spine, vascular, metabolic and malignancy. Causes that are Intrinsic to the hip can either be Extracapsular or Intracapsular. Painful MoM THA causes related to the bearing couple: There are now described a number of possible clinical scenarios and causes of pain that relate to the MoM bearing couple itself: A) Local hypersensitivity reaction without a significant soft tissue reaction; B) Local hypersensitivity reaction with a significant soft tissue reaction; C) Impingement and soft tissue pain secondary to large head effect. Factors related to a hypersensitivity reaction: Some patients, and prostheses, seem to be at a higher risk of developing issues following a MoM bearing, although our understanding of the interplay of these factors is still in evolution: patients at risk include all women and patients with smaller component sizes. Implant factors play a role with some implants having higher wear rates and being more prone to corrosion. Special tests: There is ongoing confusion related to the relative value of the various special tests that patients with a painful MoM undergo. A) Metal Ions - obtaining serum, or whole blood, cobalt and chromium levels is recommended as a baseline test. However, there is no established cutoff level to determine with certainty if a patient is having a hypersensitivity reaction. Metal ions therefore can be used as a clue, but cannot be relied upon in isolation to make a diagnosis. B) MARS MRI - a useful tool for demonstrating soft tissue involvement, but there are many painless, well-functioning MoM implants that have soft tissue reactions, that don't require a revision. In the painful MoM hip an MRI, or ultrasound, is recommended to look for soft tissue destruction or a fluid-filled periprosthetic lesion (pseudotumor). Significant soft tissue involvement is concerning and is commonly an indication for revision in the painful MoM hip. C) CT imaging - can be utilised to help determine cup position and combined anteversion, however, plain radiographs can give a rough estimate of this as well, so routine CT scan evaluations are not currently recommended. The painful MoM bearing, that is demonstrating significant soft tissue involvement is a concerning scenario. Earlier revision, to prevent massive abductor damage, would seem prudent for these patients.

The painful MoM bearing with no significant soft tissue changes can probably be followed and reviewed at regular intervals. If the pain persists and is felt to be secondary to a hypersensitivity reaction, then revision is really the only option, although the patient must be cautioned regarding the unpredictable nature of the pain relief.

Metal-on-metal hip resurfacing enjoyed a period of increased global clinical application beginning in the early to mid-2000's. This tapered off quickly, to the point that it is now a niche surgery. One naturally asks the question, why?

The answers are quite simple: 1) There are no clinical benefits when compared with total hip replacements (THA). While many authors have tried valiantly to demonstrate a benefit clinically to performing a resurfacing over a THA, they have simply been unable to convincingly do so. The procedures produce equivalent clinical results. Many claims, such as allowing a patient greater activity levels and return to sports are clearly heavily biased depending on patient selection. The only credible claim to an advantage over THA that can be made regarding resurfacing implants is indeed there is preservation of host bone of the femoral head and neck. However, this retained bone also reduces the femoral head-to-neck ratio compared to a THA and leads to the potential for bone-on-bone impingement that would not be seen if the neck was resected. Additionally the clinician needs to carefully question the true clinical relevance of this preserved bone. One need only think of all of the isolated acetabular component revisions, or polyethylene liner exchanges, that are performed while retaining solidly ingrown femoral components with good preservation of calcar bone years following the index procedure.

2) Resurfacing implants are much more costly than conventional THA implants. In an era of increased cost constraints, parties are willing to pay more only when there is a proven benefit. Resurfacing implants offer no such benefit.

3) There is a well-documented higher revision rate with resurfacing implants over THA.

While the previous claim was that this wasn't seen in younger males, that too has been disproven. The latest data from the Australian Joint Replacement Registry demonstrates the 15-year cumulative percentage revision rates for conventional total hip at 9.7% and resurfacing at 13.3%.

4) There is the significant risk of metal ions and local hypersensitivity secondary to the metal-on-metal bearing. Again, this risk is significantly limited with the use of a THA with a polyethylene insert.

5) There is a significant incidence of femoral neck fractures.

6) The overall femoral component loosening rates are higher than for total hip replacements.

7) There is a clear learning curve with resurfacing implants with most series showing increased complications in the first fifty cases, and depending on a surgeons overall clinical practice, it may be quite a challenge to ever really overcome this learning curve issue.

8) There is difficulty restoring offset and leg length discrepancies in certain cases when trying to utilise a resurfacing implant.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected hip arthroplasty experts. The primary cases will include challenges such as hip dysplasia, altered bony anatomy and fixation challenges. In the revision hip arthroplasty scenarios issues such as bone stock loss, leg length discrepancy, instability and infection will be discussed. This will be an interactive case-based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

While no one would argue the necessary role for the medical management of patients with early knee arthritis, significant controversy remains regarding the ideal treatment for a patient with bone-on-bone osteoarthritis who could equally be treated with a high tibial osteotomy, a uni-compartmental total knee, potentially a patello-femoral replacement if dealing with isolated patello-femoral disease or lastly, a complete total knee replacement. While clearly to date there has not been consensus on this issue, a review of the arguments, both pro and con, should be used as a guide to the surgeon in making this clinical judgment.

1. Patient Satisfaction.- Many ardent supporters of uni-compartmental knee replacements espouse one of the principle benefits of the uni knee as much greater patient satisfaction. Unfortunately, what is never taken into account is the pre-selection bias that occurs in this patient population. Patients with the most minimal amount of arthritis and those with the greatest range of motion are pre-selected to undergo a uni-compartmental knee replacement compared to the more advanced arthritic knee with mal-alignment and more significant pre-operative disability that will undergo a total knee replacement. Additionally the sources of data to draw the conclusions must be carefully analyzed. We must avoid using data from small series with unblinded patients performed by surgeons expert in the technique. Instead registry data, with its broad based applicability, is a much more logical source of information. Of significance, when over 27,000 patients were assessed regarding satisfaction following knee surgery; there was no difference in proportions of satisfied patients whether they had a total knee or a uni-compartmental knee.

2. Implant Longevity - Once again large prospective cohort data in the form of arthroplasty registries strongly favors total knee arthroplasty over uni-compartmental knee arthroplasty. The Swedish Knee Arthroplasty Registry demonstrated higher revision rates with uni's as compared with total knee replacements. In the Australian Joint Replacement Registry the cumulative 13-year percent revision rate for primary total knee replacements is 6.8% and for uni-compartmental knee replacements is 15.5%. Higher failure rates in uni-compartmental knee replacements seen in Australia has correlated to a significant decrease in the number of uni's being performed, which peaked at 15.1% in 2003 and in 2014 has reduced to 4.7%. There is a direct correlation to age, with younger patients having a significantly higher percentage of revision following uni-compartmental knee replacements (25% failure rate at 11 years if less than 55 years old). There is also tremendous variability in the success rate of the uni in the Australian Registry depending on the implant design (5 year cumulative revision rate range 5.0% to 18.9%), which is simply not seen in the total knee replacement population (5 year cumulative revision rate range 1.6% to 7.7%).

While one can perform the philosophical exercise of debating the merits of a total knee versus uni-compartmental knee, the evidence is overwhelming that in the hands of the masses a total knee replacement patient will have equal satisfaction to a uni-compartmental patient, and will enjoy a much lower probability of revision in the short term and in the long term.

Background

The advent of highly cross-linked polyethylene has resulted in improved wear rates and reduced osteolysis with at least intermediate follow-up when compared to conventional polyethylene. However, the role of alternative femoral head bearing materials in decreasing wear is less clear. The purpose of this study was to determine in-vivo polyethylene wear rates across ceramic, Oxinium, and cobalt chrome femoral head articulations.

Background

Fretting corrosion at the junction of the modular head neck interface in total hip arthroplasty is an area of substantial clinical interest. This fretting corrosion has been associated with adverse patient outcomes, including soft tissue damage around the hip joint. A number of implant characteristics have been identified as risk factors. However, much of the literature has been based on metal on metal total hip arthroplasty or subjective scoring of retrieved implants. The purpose of this study was to isolate specific implant variables and assess for material loss in retrieved implants with a metal on polyethylene bearing surface.

The concept of constitutional varus and controversy regarding placing the total knee arthroplasty (TKA) in a neutral versus physiologic alignment in varus osteoarthritic (OA) patients is an important current discussion. However, the physiologic mechanical alignment of a varus OA knee is unknown and the relative contribution of the femur and tibia to the mechanical axis is unknown. The goal of this study was to determine and analyse the physiologic mechanical axis of medial OA knees.

Plain radiographs of the knee and full-leg standing radiographs of 1558 patients were reviewed for inclusion criteria; 313 patients with a non-arthritic knee and a contralateral varus end-stage OA knee were analysed in the coronal plane. The Hip-Knee-Ankle (HKA), Condylar-Hip (CH)(femoral), Condylar-Plateau (CP) (intra-articular) and Plateau-Ankle (PA)(tibial) angles were measured for both the arthritic and non-arthritic/physiologic knee. The relationship and contribution of all angles was analysed for every 2° degrees of progressive varus: from 4° valgus to 8° varus. The proportion of patients with constitutional varus was also determined for the sample population and correlated with increasing HKA.

The mean CH (femoral) angle was valgus in all groups and decreased with progressive varus alignment (p< 0.0001), ranging from 3.8° ± 1.0° with HKA of 2–4° valgus, to 0.1° ± 1.5° with HKA of 6–8° varus. The mean PA (tibial) angle was varus in all groups and decreased from valgus to progressively varus alignment (p p<0.0001), ranging from 0.78° ± 1.4° with HKA 2–4° valgus, to 5.6° ± 1.9° with HKA 6–8° varus. The CP angle showed no difference between all groups (p=0.3). Forty five percent of males and 22% of females with arthritic HKA in varus alignment were found to have constitutional varus.

Correlation of unilateral arthritic knees to the unaffected, physiologic aligned knee using full-leg radiographs indicates that it may be possible to understand the patient's physiologic, pre-arthritic coronal plane alignment. The mechanical axis of physiologic knees in a unilateral varus OA population demonstrates a variable contribution of the femur (CH) and tibia (PA) from overall valgus to varus alignment. In addition, a significant proportion of the sample population possessed constitutional varus. This may provide important information regarding the placement of physiologic TKA's and direct future research questions.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected hip arthroplasty experts. The primary cases will include challenges such as hip dysplasia, altered bony anatomy and fixation challenges. In the revision hip arthroplasty scenarios issues such as bone stock loss, leg length discrepancy, instability and infection will be discussed. This will be an interactive case-based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

Adequate fixation of implant components is an important goal for all arthroplasty procedures. Aseptic loosening is one of the leading causes of revision surgery in total knee arthroplasty. Radiostereometric analysis (RSA) is an imaging technique to measure implant migration, with established migration thresholds for well-fixed, at risk, and unacceptably migrating components. The purpose of the present study was to examine the long-term fixation of a cemented titanium fixed bearing polished tibial baseplate.

Patients enrolled in a previous two-year prospective trial were recalled at ten years. All patients received a cemented, posterior-stabilised total knee replacement of the same design implanted by one of three surgeons. Of the original 35 patients, 16 were available for long-term follow-up, with one patient lost to follow-up, nine patients deceased, and a further nine patients unwilling to return to the clinic. Each patient underwent RSA imaging in a supine position using a conventional RSA protocol. Migration of the tibial component in all planes as well as maximum total point motion (MTPM) was compared between all time points (baseline, six weeks, three months, six months, one year, two years) up to the ten year follow-up visits. Outcome scores including the Knee Society Score (KSS), WOMAC, SF-12, and UCLA Activity Score were recorded.

At ten years, the mean migrations of the tibial component were less than 0.1 mm and 0.1 degree in all planes relative to the post-operative RSA exam. There was no significant difference in tibial component migration between time points. However, MTPM increased significantly over time (p = 0.002), from 0.23 ± 0.18 mm at six weeks to 0.42 ± 0.20 mm at ten years. At one year, 13 patients had an acceptable MTPM level, three patients had an ‘at risk’ level, and no patient had an ‘unacceptable’ level. No patients were revised at ten years. WOMAC and KSS were significantly improved (p < 0.0001) at the latest follow-up compared to pre-operatively, but there was no difference in SF-12. The median UCLA Activity Score at latest follow-up was six (range, two to eight).

The tibial baseplate demonstrated solid fixation at ten years. No patients had an unacceptable MTPM level at one year and no patients were revised at ten years, supporting the use of RSA to predict long-term loosening risk. The low level of tibial baseplate migration found in the present study correlates to the low rate of revision for this implant as reported in individual studies and in joint replacement registries.

Infection following total hip arthroplasty (THA) represents a devastating complication and is one of the main causes for revision surgery. This complication may be treated by irrigation and debridement with head and polyethylene exchange (IDHPE) or a two-stage revision (2SR). Previous studies have reported on the eradication success rates but few have reported patient outcome scores. The purpose of this study was to report patient outcome scores for both IDHPE and 2SR and compare these to a non-infected matched cohort. We hypothesised that both cohorts would have worse outcomes than the control group, and that those who failed an initial IDHPE and required a 2SR would have a worse outcome than those treated initially with a 2SR.

A retrospective review identified 137 patients from our institutional arthroplasty database who had an infected primary THA between 1986–2013. We excluded patients with less than one-year follow-up. Mean follow-up was 60 months (12–187 months). A control cohort was identified and matched according to age and Charlton Comorbidity Index (CCI). Harris Hip Scores, Short Form 12 and WOMAC scores were compared between our control group and our infected cohort.

Sixty-eight patients were treated with a 2SR and 69 patients were treated with an IDHPE. There was a 59% success rate in eradicating the infection with an IDHPE. All of the 28 patients who failed an IDHPE later went on to a 2SR. Outcome scores for the 2SR cohort were significantly worse than the non-infected controls (p0.05). There was no difference in outcome scores when comparing our 2SR cohort to our failed IDHPE (p>0.05).

Previous studies have focused on eradication rates. However, it is important to consider patient outcome scores when deciding the best treatment. Infected patients treated with a successful IDHPE had similar outcomes to non-infected patients. Patients that failed IDHPE and went onto 2SR had similar outcomes to those that had a 2SR alone. IDHPE should still be considered in the treatment algorithm of infected THA.

While no one would argue the necessary role for the medical management of patients with early knee arthritis, significant controversy remains regarding the ideal treatment for a patient with bone-on-bone osteoarthritis who could equally be treated with a high tibial osteotomy, a uni-compartmental total knee, potentially a patello-femoral replacement if dealing with isolated patello-femoral disease or lastly, a complete total knee replacement. While clearly to date there has not been consensus on this issue, a review of the arguments, both pro and con, should be used as a guide to the surgeon in making this clinical judgment.

Patient Satisfaction: Many ardent supporters of uni-compartmental knee replacements espouse one of the principle benefits of the uni knee as much greater patient satisfaction. Unfortunately, what is never taken into account is the pre-selection bias that occurs in this patient population. Patients with the most minimal amount of arthritis and those with the greatest range of motion are pre-selected to undergo a uni-compartmental knee replacement compared to the more advanced arthritic knee with mal-alignment and more significant preoperative disability that will undergo a total knee replacement. Additionally the sources of data to draw the conclusions must be carefully analyzed. We must avoid using data from small series with unblinded patients performed by surgeons expert in the technique. Instead registry data, with its broad based applicability, is a much more logical source of information. Of significance, when over 27,000 patients were assessed regarding satisfaction following knee surgery; there was no difference in proportions of satisfied patients whether they had a total knee or a uni-compartmental knee.

Implant Longevity: Once again large prospective cohort data in the form of arthroplasty registries strongly favors total knee arthroplasty over uni-compartmental knee arthroplasty. The Swedish Knee Arthroplasty Registry demonstrated higher revision rates with uni's as compared with total knee replacements. In the Australian Joint Replacement Registry the cumulative 13 year percent revision rate for primary total knee replacements is 6.8% and for uni-compartmental knee replacements is 15.5%. Higher failure rates in uni-compartmental knee replacements seen in Australia has correlated to a significant decrease in the number of uni's being performed, which peaked at 15.1% in 2003 and in 2014 has reduced to 4.7%. There is a direct correlation to age, with younger patients having a significantly higher percentage of revision following uni-compartmental knee replacements (25% failure rate at 11 years if less than 55 years old). There is also tremendous variability in the success rate of the uni in the Australian Registry depending on the implant design (5 year cumulative revision rate range 5.0% to 18.9%), which is simply not seen in the total knee replacement population (5 year cumulative revision rate range 1.6% to 7.7%).

While one can perform the philosophical exercise of debating the merits of a total knee versus uni-compartmental knee, the evidence is overwhelming that in the hands of the masses a total knee replacement patient will have equal satisfaction to a uni-compartmental patient, and will enjoy a much lower probability of revision in the short term and in the long term.

Previous retrieval studies demonstrate increased tibial baseplate roughness leads to higher polyethylene backside wear in total knee arthroplasty (TKA). Micromotion between the polyethylene backside and tibial baseplate is affected by the locking mechanism design and can further increase backside wear. The purpose of this study was to examine modern locking mechanisms, in the setting of both roughened and polished tibial baseplates, on backside tibial polyethylene wear.

Five TKA models were selected, all with different tibial baseplate and/or locking mechanism designs. Six retrieval tibial polyethylenes from each TKA model were matched based on time in vivo (TIV), age at TKA revision, BMI, gender, number of times revised, and revision reason. Two observers scored each polyethylene backside according to a visual damage score and individual damage modes. Primary outcomes were mean damage score and individual damage modes. Demographics were compared by one-way ANOVA. Damage scores and modes were analysed by the Kruskal-Wallis test and Dunn's multiple comparisons test.

There were no differences among the groups based on TIV (p=0.962), age (p=0.651), BMI (p=0.951), gender, revision number, or reason for revision. There was a significant difference across groups for mean total damage score (p=0.029). The polished tibial design with a partial peripheral capture locking mechanism and anterior constraint demonstrated a significantly lower score compared to one of the roughened tibial designs with a complete peripheral-rim locking mechanism (13.0 vs. 22.1, p=0.018). Otherwise, mean total damage scores were not significant between groups. As far as modes of wear, there were identifiable differences among the groups based on abrasions (p=0.005). The polished design with a tongue-in-groove locking mechanism demonstrated a significantly higher score compared to both groups with roughened tibial baseplates (5.83 vs. 0.83, p=0.024 and 5.83 vs. 0.92, p=0.033). Only the two designs with roughened tibial baseplates demonstrated dimpling (5.67 and 8.67) which was significant when compared against all other groups (p0.99). No other significant differences were identified when examining burnishing, cold flow, scratching, or pitting. No polyethylene components exhibited embedded debris or delamination.

Total damage scores were similar between all groups except when comparing one of the polished TKA design to one of the roughened designs. The other TKA model with a roughened tibial baseplate had similar damage scores to the polished designs, likely due to its updated locking mechanism. Dimpling wear patterns were specific for roughened tibial baseplates while abrasive wear patterns were identified in the design with a tongue-in-groove locking mechanism. Our study showed even in the setting of a roughened tibial baseplate, modern locking mechanisms decrease backside wear similar to that of other current generation TKA designs.

The incidence of major complications following total joint arthroplasty is low, however, surgeons often continue to see patients regularly to monitor outcomes and the performance of the implant. The purpose of this study was to assess the feasibility, effectiveness and cost-effectiveness of a web-based follow-up compared to in-person assessment following primary total hip or total knee arthroplasty. We also determined patient satisfaction and preference for follow-up method.

Patients who were at least 12 months postoperative were randomised to complete either a web-based follow-up or to have their appointment at the clinic, as usual. We excluded patients who had revision surgery, osteolysis, or identified radiographic issues. We report the frequency of web-based patients who had an issue missed by using the web-based follow-up. We recorded travel costs and time associated with each follow-up, and any health care resource use for one year following the assessment. We conducted a cost analysis from the health-care payer (Ontario Ministry of Health and Long-Term Care) and societal perspectives. All costs are presented in 2012 Canadian dollars. We used descriptive statistics to summarise the satisfaction and preference results and compared satisfaction between groups using Pearson's chi-square test.

Two hundred-twenty nine patients completed the study (111 usual-care, 118 web-based), with a mean age of 69 years (range, 38–86 years). There were no patients who had an issue missed by the web-based follow-up. The cost for the web-based assessment was significantly lower from both the societal perspective (mean difference, $−64; 95% confidence interval, $−79 to $−48; p < 0.01) and the health-care payer perspective (mean difference, $−27; 95% CI, $−29 to $−25; p < 0.01). Ninety-one patients (82.0%) in the usual-care group indicated that they were either extremely or very satisfied with the follow-up process compared with 90 patients (75.6%) in the web-based group (p < 0.01; odds ratio = 3.95; 95% CI = 1.79 to 8.76). Similarly, 92.8% of patients in the usual care group were satisfied with the care they received from their surgeon, compared to 73.9% of patients in the web-based group (p < 0.01, OR = 1.37; 95% CI = 0.73 to 2.57). Forty-four percent of patients preferred the web-based method, 36% preferred the usual method, and 16% had no preference (p = 0.01).

Web-based follow-up is a feasible, clinically effective alternative to in-person clinic assessment, with moderate to high patient satisfaction. A web-based follow-up assessment has lower mean costs per person compared to the usual method of in-person follow-up from both a societal and health-care payer perspective. The web-based assessment may introduce additional efficiency by redirecting limited outpatient resources to those awaiting first consultation, patients who have complications, or those who are further postoperative and may require a revision.

A conceptually new, to the North American market, acetabular design is currently available when performing a total hip arthroplasty – the dual mobility socket. Essentially this is a press-fit acetabular component with a polished surface (either modular or monoblock) that articulates with a large polyethylene head with a 28 mm ball inserted into that polyethylene in a similar fashion to a bipolar design.

Proponents of this design advocate its use to reduce the risk of dislocation, and it is being offered as an alternative to constrained liners and also as a potential prophylactic application in revision and high risk patients.

The concerns regarding this construct include:

Wear - A large polyethylene head articulating against a polished metal surface may have much greater wear than a conventional metal against polyethylene bearing. Hip simulator data has shown this previously. Additionally there are two articulating surfaces, potentially leading to a greater combined wear than one would see with just a singular surface.

There are many options available to both manage and to prevent hip instability. Any new implant must show equivalence to current devices on the many fronts of wear, fixation, mid-term results, complications and costs.

Studies that have previously examined the relationship between inclination angle and polyethylene wear have shown increased wear of conventional polyethylene with high inclination angles. To date, there have been no long term in vivo studies examining the correlation between cup position and polyethylene wear with highly crosslinked polyethylene.

An institutional arthroplasty database was used to identify patients who had metal-on-highly crosslinked polyethylene primary total hip arthroplasty (THA) using the same component design with a minimum follow up of 10 years ago. A modified RSA examination setup was utilised, recreating standard anteroposterior (AP) and cross-table lateral exams in a single biplane RSA acquisition. Three dimensional head penetration was measured using the centre index method. The same radiographs were used to measure inclination angle and anteversion. Spearman correlation was used to show an association between the parameters of acetabular position and wear rate.

A total of 43 hips were included for analysis in this study. Average follow-up was 12.3 ± 1.2 years. The average linear wear rate was calculated to be 0.066 ± 0.066 mm/year. Inclination angle was not correlated with polyethylene wear rate (p=0.82). Anteversion was also not correlated with polyethylene wear rate (p=0.11). There was no statistical difference between wear rates of hips within Lewinnek's “safe zone” and those outside this “safe zone” (p=0.11). Males had a higher wear rate of 0.094 ± 0.089 mm/year compared to females with a wear rate of 0.046 ± 0.032 mm/year (p=0.045).

At long term follow up of greater than 10 years, highly cross linked polyethylene has very low wear rates. This excellent tribology is independent of acetabular position, but gender did impact wear rates. Due to the low wear rates, follow-up of even longer term is suggested to examine variables affecting wear.

The incidence of major complications following total joint arthroplasty is low, however, surgeons often continue to see patients regularly to monitor outcomes and the performance of the implant. The purpose of this study was to assess the feasibility, effectiveness and cost-effectiveness of a web-based follow-up compared to in-person assessment following primary total hip or total knee arthroplasty. We also determined patient satisfaction and preference for follow-up method.

Patients who were at least 12 months post-operative were randomised to complete either a web-based follow-up or to have their appointment at the clinic, as usual. We excluded patients who had revision surgery, osteolysis, or identified radiographic issues. We report the frequency of web-based patients who had an issue missed by using the web-based follow-up. We recorded travel costs and time associated with each follow-up, and any health care resource use for one year following the assessment. We conducted a cost analysis from the health-care payer (Ontario Ministry of Health and Long-Term Care) and societal perspectives. All costs are presented in 2012 Canadian dollars. We used descriptive statistics to summarise the satisfaction and preference results and compared satisfaction between groups using Pearson's chi-square test.

Two hundred-twenty nine patients completed the study (111 usual-care, 118 web-based), with a mean age of 69 years (range, 38–86 years). There were no patients who had an issue missed by the web-based follow-up. The cost for the web-based assessment was significantly lower from both the societal perspective (mean difference, $-64; 95% confidence interval, $-79 to $−48; p < 0.01) and the health-care payer perspective (mean difference, $−27; 95% CI, $−29 to $−25; p < 0.01). Ninety-one patients (82.0%) in the usual-care group indicated that they were either extremely or very satisfied with the follow-up process compared with 90 patients (75.6%) in the web-based group (p < 0.01; odds ratio = 3.95; 95% CI = 1.79 to 8.76). Similarly, 92.8% of patients in the usual-care group were satisfied with the care they received from their surgeon, compared to 73.9% of patients in the web-based group (p < 0.01, OR = 1.37; 95% CI = 0.73 to 2.57). Forty-four percent of patients preferred the web-based method, 36% preferred the usual method, and 16% had no preference (p = 0.01).

Web-based follow-up is a feasible, clinically effective alternative to in-person clinic assessment, with moderate to high patient satisfaction. A web-based follow-up assessment has lower mean costs per person compared to the usual method of in-person follow-up from both a societal and health-care payer perspective. The web-based assessment may introduce additional efficiency by redirecting limited outpatient resources to those awaiting first consultation, patients who have complications, or those who are further post-operative and may require a revision.

While the vast majority of total knee replacements performed throughout the world employ a modular metal-backed tibial tray, and not an all-polyethylene tray, this issue remains controversial.

Proposed advantages to a metal-backed tray include: a) decreased bending strains, b) reduces compressive stresses in the cement and cancellous bone beneath the baseplate (especially in asymmetric loading), c) distributes load more evenly across the interface

Proposed advantages of an all-polyethylene tray include: a) cost reduction, b) reduced polyethylene thickness with the same amount of bone resection, c) increased tensile stresses at the interface during eccentric loading

The challenge is at present we don't know the >10-year track record of current generation tibial components. This debate centers on the <60-year-old. This is the most difficult patient in total knee arthroplasty with higher revision rates than an older cohort.

It makes sense to use an all-polyethylene tibia if the revision rates turn out to be similar and you don't intend to do a polyethylene exchange in the future. It makes sense to do a modular tray if the results are similar, but there is an intention to do a polyethylene exchange in the future. If either one of these implants choices has a lower cumulative revision rate, then that is the implant of choice at present.

However, we need to understand that at present we don't know if the results of current generation all-polyethylene tibial components will indeed be equal to metal-backed components. The most recent data from the Australian registry suggests that in fact all-polyethylene tibial components have a higher failure rate than metal-backed components when looking at the entire class of design. This would be expected to be even more significant in the younger patient.

Complications involving the patellofemoral joint are a source of anterior knee pain, instability, and dysfunction following total knee arthroplasty. “Overstuffing” the patello-femoral joint refers to an increase in the thickness of the patellofemoral joint after a total knee replacement compared to the preoperative thickness. While biomechanical studies have indicated that overstuffing the patellofemoral joint may lead to adverse clinical outcomes, limited clinical evidence exists to support this notion. The purpose of this study is to evaluate the effect of changing the thickness of the patellafemoral joint on functional outcomes following total knee arthroplasty.

Our institutional arthroplasty database was used to identify 1347 patients who underwent a primary total knee arthroplasty between 2006 and 2012 with the same component design. Standard preoperative and postoperative anteroposterior, lateral, and skyline radiographs were collected and measured for patello-femoral overstuffing. These measurements included anterior patellar displacement, anterior femoral offset, and anteroposterior femoral size. These measurements were correlated with patient outcome data using WOMAC, KSS scores, and postoperative range of motion. Multiple linear regression analysis was used to assess the association between stuffing and functional outcomes.

A total of 1031 patients who underwent total knee arthroplasty were included. Increased anterior patellar displacement, a measure of patellofemoral joint thickness, was associated with decreased WOMAC scores (p=0.02). Anterior femoral offset (p=0.210) and anteroposterior femoral size (p=0.091) were not significantly associated with patient functional outcomes. Postoperative range of motion (ROM) was not associated with patellofemoral stuffing (p=0.190).

The current study demonstrated that functional outcomes are adversely affected by patellofemoral overstuffing. Based on these results, caution is encouraged against increasing the thickness of the patellofemoral joint, particularly on the patellar side of the joint.

Pain immediately following total knee arthroplasty (TKA) is often severe and can inhibit patients' rehabilitation. Recently, adductor canal blocks have been shown to provide adequate analgesia and spare quadriceps muscle strength in the early postoperative period. We devised a single injection motor sparing knee block (MSB) by targeting the adductor canal and lateral femoral cutaneous nerve with a posterior knee infiltration under ultrasound. Our primary objective was to evaluate the analgesia duration of the MSB in comparison to a standard periarticular infiltration (PAI) analgesia using patients' first rescue analgesia as the end point. Secondary outcomes measured were quadriceps muscle strength and length of stay.

We randomised 82 patients scheduled for elective TKA to receive either the preoperative MSB (0.5% ropivacaine, 2.5ug/ml epinephrine, 10mg morphine, and 30mg ketorolac) or intraoperative periarticular infiltration (0.3% ropivacaine, 2.5ug/ml epinephrine, 10mg morphine, and 30mg ketorolac). Duration of analgesia, postoperative quadriceps power, and length of stay were evaluated postoperatively.

Analgesic duration was found to be significantly different between groups. The MSB had a mean duration of 18.06 ± 1.68 hours while the PAI group had a mean duration of 9.25 ± 1.68 hours for a mean difference of 8.8 hours (95% CI 3.98 to 13.62), p<0.01. There were no significant differences between groups in quadriceps muscle strength power at 20 minutes (p=0.91) or 6 hours (p=0.66) after block administration. Length of stay was also not significantly different between the groups (p=0.29).

Motor sparing blocks provide longer analgesia than patients receiving periarticular infiltration while not significantly reducing quadriceps muscle strength or increasing length of hospital stay.

The philosophy of cemented total hip arthroplasty (THA) femoral components has become polarised. At one extreme are polished, collarless, tapered devices that are expected to subside; at the other extreme are roughened, non-tapered implants with a collar designed not to subside. Radiostereometric analysis (RSA) allows the accurate measurement of implant movement and has been extensively used for measurement of the in vivo migration of implants. The degree of migration as measured by RSA during the first years after surgery has been shown to correlate with the long-term performance of cemented femoral implants. The purpose of this study was to review the two-year RSA results of two different designs of primary cemented THA stems.

Data from two previous prospective RSA trials with two-year follow-up were pooled. The first group included 36 patients who received a Spectron (Smith & Nephew, Memphis, USA) cemented stem. The second group included 13 patients who received an Exeter (Stryker, Mahwah, USA) cemented stem, and 15 patients who received a CPCS (Smith & Nephew, Memphis, USA) cemented stem. All patients underwent RSA examinations shortly post-operation, at 6 weeks, 3 months, 6 months, 1 years, and 2 years. Migration and rotation of the femoral stems was measured at each time point relative to the post-operative exam, and compared between the two groups.

There was no difference in age at surgery (Spectron 78 ± 6 years, Exeter/CPCS 77 ± 5 years, p = 0.43), BMI (Spectron and Exeter/CPCS 28 ± 5 kg/m2, p = 0.92), or percentage of male patients (Spectron 23% male, Exeter/CPCS 21% male) between the implant groups. Subsidence was significantly greater (p < 0.0001) at all time points from three months to two years for the Exeter and CPCS stems (0.94 ± 0.39 mm at two years) compared to the Spectron stem (0.05 ± 0.16 mm at two years). There was no significant difference between the stem types for medial-lateral translation (p = 0.07) or anterior-posterior translation (p = 0.49), or for anterior-posterior tilt (p = 0.15), internal-external rotation (p = 0.89), or varus-valgus rotation (p = 0.05).

Implant material, design, and surface finish are all factors in the long-term performance of cemented femoral hip implants. In this study, both femoral stem designs had a magnitude of sub-sidence that was within the limits of what is considered to be safe with respect to long-term performance. The continuous subsidence of the Exeter and CPCS stems is consistent with previous reports in the literature.

Trunnionosis in modular hip arthroplasty has recently been recognised to be clinically important. Gaining an understanding of how the material interface at the head-trunnion affects the tribology at the modular junctions has current clinical implications as well as an implication on future implant selection and material choice. This matched-cohort study aims to compare tribocorrosion between ceramic and cobalt-chromium trunnions and to investigate other factors that contribute to the difference in tribocorrosion if present.

All hip prostheses retrieved between 1999 and 2015 at one centre were reviewed. Fifty two ceramic heads were retrieved, and these were matched to a cobalt-chromium cohort according to taper design, head size, neck length and implantation time in that order. The two cohorts were similar in male:female ratio (p=0.32) and body mass index (p=0.15) though the ceramic group was younger than the cobalt-chromium group (56.6 (+/−)13.5 years for ceramic group vs 66.3 (+/−14.4) years for cobalt-chromium group; p=0.001). There was no significant difference in the reasons for revision between the two groups (p=0.42). The femoral head trunnions were examined by two independent observers using a previously published 4-point scoring technique. The trunnions were divided into three zones: apex, middle and base. The observers were blinded to clinical and manufacturing data where possible.

Ceramic head trunnions demonstrated a lower median fretting and corrosion score at the base zone (p<0.001), middle zone (p<0.001) and in the combined score (p<0.001). In a subgroup analysis by head size, ceramic heads had a lower fretting and corrosion score at 28mm head diameter (p<0.001). Within the ceramic group, taper design had a significant effect on fretting and corrosion in the apex zone (p=0.04). Taper design also had a similar effect in the cobalt-chromium group in the apex zone (p=0.03). For the ceramic trunnions, the largest effect was contributed by the difference between the 11/13 taper and the 12/14 taper. For the cobalt-chromium trunnions, the largest effect was contributed by the difference between the 5 degree 38′ 37″ taper and type 1 taper.

Ceramic head trunnions showed a significantly lower fretting and corrosion score as compared to cobalt-chromium trunnions. Ceramic heads had a lower score than cobalt-chromium heads at 28mm head diameter. Taper design had an effect on fretting and corrosion within each cohort.

The advent of highly cross-linked polyethylene has resulted in improved wear rates and reduced osteolysis with at least intermediate follow-up when compared to conventional polyethylene. However, the role of alternative femoral head bearing materials in decreasing wear is less clear. The purpose of this study was to determine in-vivo polyethylene wear rates across ceramic, Oxinium, and cobalt chrome femoral head articulations.

A review of our institutional database was performed to identify patients who underwent a total hip arthroplasty using either ceramic or oxidised zirconium (Oxinium) femoral head components on highly cross-linked polyethylene between 2008 and 2011. These patients were then matched on implant type, age, sex and BMI with patients who had a cobalt chrome bearing implant during the same time period. RSA analysis was performed using the centre index method to measure femoral head penetration (polyethylene wear). Secondary quality of life outcomes were collected using WOMAC and HHS Scores. Paired analyses were performed to detect differences in wear rate (mm/year) between the cobalt chrome cohorts and their matched ceramic and Oxinium cohorts. Additional independent group comparisons were performed by analysis of variance with the control groups collapsed to determine wear rate differences between all three cohorts.

A total of 68 patients underwent RSA analysis. Fifteen patients with a ceramic femoral head component and 14 patients with an Oxinium femoral head component along with the same number of matched patients with cobalt chrome femoral head component were included in the analysis. The time in vivo for the Oxinium (5.17 +/− 0.96 years), Oxinium matched cohort (5.13 +/− 0.72 years), ceramic (5.15 +/− 0.76 years) and ceramic matched cohort (5.36 +/− 0.63 years) were comparable. The demographics of all bearing surface cohorts were similar. The paired comparison between the Oxinium and cobalt chrome cohorts (0.33 vs. 0.29 mm/year, p=0.284) and ceramic vs cobalt chrome cohorts (0.26 vs. 0.20 mm/year, p=0.137) did not demonstrate a significant difference in wear rate. The independent groups analysis revealed a significantly higher wear rate of Oxinium (0.33 mm/year) compared to cobalt chrome (0.24 mm/year) (p = 0. 038). There were no differences in HHS and WOMAC scores between the Oxinium and cobalt chrome cohorts (HHS: p = 0.71, WOMAC: p=0.08) or the ceramic and cobalt chrome cohorts (HHS: p=0.15, WOMAC: p=023).

This study presents evidence of a greater wear rate (mm/year) of the Oxinium femoral head component compared to a cobalt chrome femoral head component. This difference was not demonstrated in the ceramic femoral head component. Despite this difference, there were no clinical differences as measured by the HHS and WOMAC. Future research should focus on factors that may contribute to the higher wear rate seen in the Oxinium cohort.

Total joint arthroplasty is commonly associated with post-operative anemia. Blood conservation programs have been developed to optimise patients prior to surgery. Epoetin Alfa (Eprex) or intravenous (IV) iron transfusions are two modalities that can be used pre-operatively to optimise hemoglobin and ferritin levels. There are, however, potential complications and increased costs associated with their use. Oral iron is a less costly option for those undergoing surgery but requires more time to take effect. There are no studies to date that examine the effects of an early screening program utilising oral iron supplementation prior to total joint arthroplasty. The purpose of this study is to evaluate the effect of implementing early pre-operative oral iron supplementation on patients prior total joint arthroplasty.

A retrospective review of patients undergoing total joint arthroplasty was performed using our institution clinical informatics database. We identified all patients seen in pre-admission clinic (PAC) between Jan 1, 2009 and March 31, 2010 representing our control group. We then identified all patients seen in PAC between October 1, 2012 and December 31, 2013. Patients in this cohort received screening blood work when booked for surgery, and oral iron supplementation was given to patients with hemoglobin of less than 135g/L or ferritin less than 100ug/L, thus representing our treatment group. Patients undergoing revision, uni-compartment knee arthroplasty and bilateral arthroplasties were excluded from the study. Pearson Chi-Square tests were used to calculate significance between groups with main outcomes including pre-admission hemoglobin, and pre-operative requirements for Eprex or IV iron.

In our control group, we identified 354 patients (25.6%) with hemoglobin less than 130 g/L at time of pre-admission clinic. In our treatment group, this number dropped significantly to only 16.4% of patients (p<0.005).

Implementation of an early screening program using oral iron supplementation resulted in a decrease in the number of patients with hemoglobin lower than 130 g/L at the time of pre-admission clinic. There was also a significant decrease in the use of Eprex and IV iron pre-operatively in the patients in the early screening program. These results encourage the use of early oral iron supplementation for patients with hemoglobin less than 135 g/L or ferritin less than 100ug/L in order to optimise patients prior to total joint arthroplasty.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected knee arthroplasty experts.

The primary cases will include challenges such as patient selection and setting expectations, exposure, alignment correction and balancing difficulties. In the revision knee arthroplasty scenarios issues such as bone stock loss, fixation challenges, instability and infection management will be discussed.

This will be an interactive case-based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

We present a case of multifocal infection involving the left total hip replacement and the right total knee replacement of a patient, further complicated by an infected non-union of a periprosthetic fracture of the right knee. This required the unique simultaneous management of both infection eradication and fracture stabilization in the knee.

Both sites were treated with a 2-stage procedure, including the novel use of a stemmed articulating spacer for the right knee. This spacer was made combining a retrograde humeral nail, coated with antibiotic-impregnated cement, and a pre-formed articulating cement spacer. The patient was able to weight-bear on this spacer. The fracture went on to unite, and a second stage was performed with the use of stemmed prosthesis and augments. She remains infection free 2 years after the second stage operation.

The use of a stemmed articulating knee spacer can facilitate infection eradication and fracture stabilization while preserving some motion and weight-bearing ability in the 2 stage management of an infected periprosthetic fracture of the knee.

Introduction

Total knee arthroplasty (TKA) has proven clinical success with reported longterm survivorship of 92% in the elderly population. Concerns regarding increased loosening rates and potential need for multiple revision surgeries in patients younger than 60 years have traditionally discouraged TKA in younger patients. The purpose of this study was to review the longterm clinical and radiographic results of patients under the age of 45 yrs who underwent a total knee replacement.

Objectives

Porous metal surfaces have been a popular option for acetabular component fixation in total hip arthroplasty (THA). New THA component designs are introduced periodically with the expectation of better wear properties and survivorship. Since its approval for use in 2002 there have been few clinical outcome studies published on the Pinnacle acetabular cup system. We hypothesised that the hemispherical porous coated Pinnacle acetabular cup system with a range of cup options and bearing surfaces would give us predictably good fixation and survivorship at five years post implantation.

Summary

The effect of polyethylene wear and lift-off between the tibial and femoral components on the mechanical axis was assessed in primary TKA (Total Knee Arthroplasty) based on retrieval data and full leg radiographs.

Introduction

Coronal plane alignment is one of the contributing factors to polyethylene wear in total knee arthroplasty (TKA). The goal of this study was to evaluate the wear and damage patterns of retrieved tibial polyethylene inserts in relationship to the overall mechanical alignment and to the position of the tibial component.

Only a little over a decade ago the vast majority of primary total hip replacements performed in North America, and indeed globally, employed a conventional polyethylene insert, either in a modular version or in a cemented application. Beginning in the early 2000's there was an explosion in technology and options available for the bearing choice in total hip arthroplasty.

Highly crosslinked polyethylene was introduced in 1998, and within a few short years the vast majority of polyethylene inserts performed in North America were manufactured from this material. Globally there was a mixed picture with variable market penetration. Surgeons had seen historically poor results with attempts at “improving” polyethylene in the past and many were hesitant to use this new technology. Many randomised clinical trials have been performed and all have shown to a greater or lesser degree, that indeed the highly crosslinked polyethylene insert has undergone less linear and volumetric wear than its more conventional counterpart. This replicates well the hip simulator data. The challenge, however, is as we approached mid-term results, orthopaedic manufacturers began altering the polyethylene to improve wear and improve mechanical strength. Therefore while 10-year and greater data will ultimately be published, the actual polyethylene in use at that time will be a different material. Additionally, while wear rates are undoubtedly lower, we are still waiting for long-term results of actual osteolytic lesion development and the effect that highly cross-linked polyethylene will have on this clinical scenario. That being said, with over a decade of clinical experience, unquestionably highly crosslinked polyethylene has truly been a revolution in design, essentially eliminating polyethylene wear as an early failure mode.

The question still remains as to the best material for the femoral ball. Essentially two options exist – cobalt chrome and ceramic (Delta). There are theoretically advantages to ceramic heads; however they come at a cost premium: 1.) To date there have been no published reports that demonstrate any improved clinical outcomes with the use of ceramic heads. In fact, the Australian registry demonstrates that the cumulative revision rate is lowest with CoCr heads (at 10 years, 4.3% with CoCr on XLPE and 4.6% with ceramic on XLPE). 2.) Costs continue to be significantly higher for ceramic heads. A price premium of 2–4× higher cost for ceramic over CoCr heads exists in most global markets. 3.) Trunion issues. An emerging concern is corrosion at the head neck junction in THA. Ceramic heads should theoretically have a lower incidence of taper corrosion. To date this is unproven, as is the actual incidence of this as a significant clinical problem.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected hip arthroplasty experts. The primary cases will include challenges such as hip dysplasia, altered bony anatomy and fixation challenges. In the revision hip arthroplasty scenarios issues such as bone stock loss, leg length discrepancy, instability and infection will be discussed. This will be an interactive case based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

Obesity is clearly a worldwide epidemic with significant social, health care and economic implications.

A clear association between obesity and the need for both hip and knee replacement surgery has been demonstrated. Specifically the presence of class 3 obesity (BMI > 40) increases the incidence of THA by 8.5 times and the incidence of TKA by 32.7 times, compared with patients of normal weight.

Issues related to TJA in the morbidly obese include:

Outcomes - There is a growing body of evidence to support the premise that patients undergoing either THA or TKA who are morbidly obese derive significant benefit from the surgical intervention. Specifically patient and disease specific outcome measures (WOMAC, SF-12, KSCRS, HSS) demonstrate equal change between pre-operative and post-operative scores in those patients of normal weight compared to the morbidly obese cohort.

There is little debate that performing total joint arthroplasty in the morbidly obese is technically challenging and that the potential for increased peri-operative morbidity, particularly in the form of infection is present. That being said, the realised benefit to the patient of the surgical intervention is significant, and denying surgery on the basis of obesity alone is not justified.

Only a little over a decade ago the vast majority of primary total hip replacements performed in North America, and indeed globally, employed a conventional polyethylene insert, either in a modular version or in a cemented application. Beginning in the early 2000's there was an explosion in technology and options available for the bearing choice in total hip arthroplasty.

Highly cross-linked polyethylene was introduced in 1998, and within a few short years the vast majority of polyethylene inserts performed in North America were manufactured from this material. Globally there was a mixed picture with variable market penetration. Surgeons had seen historically poor results with attempts at “improving” polyethylene in the past and many were hesitant to use this new technology. Many randomised clinical trials have been performed and all have shown to a greater or lesser degree, that indeed the highly cross-linked polyethylene insert has undergone less linear and volumetric wear than its more conventional counterpart. This replicates well the hip simulator data. The challenge, however, is as we approached mid-term results, orthopaedic manufacturers began altering the polyethylene to improve wear and improve mechanical strength. Therefore while ten-year and greater data will ultimately be published, the actual polyethylene in use at that time will be a different material. Additionally while wear rates are undoubtedly lower, we are still waiting for long-term results of actual osteolytic lesion development and the effect that highly cross-linked polyethylene will have on this clinical scenario. That being said, with over a decade of clinical experience, unquestionably highly cross-linked polyethylene has truly been a revolution in design, essentially eliminating polyethylene wear as an early failure mode.

The question still remains as to the best material for the femoral ball. Essentially two options exist – cobalt chrome (CoCr) and ceramic. There are theoretically advantages to ceramic heads; however, they come at a cost premium:

To date there have been no published reports that demonstrate any improved clinical outcomes with the use of ceramic heads. In fact, the Australian registry demonstrates that the cumulative revision rate is lowest with CoCr heads (at 10 years, 4.3% with CoCr on XLPE and 4.6% with ceramic on XLPE).

Costs continue to be significantly higher for ceramic heads. A price premium of 2–4x higher cost for ceramic over CoCr heads exists in most global markets.

Trunnion issues. An emerging concern is corrosion at the head neck junction in THA. Ceramic heads should theoretically have a lower incidence of taper corrosion. To date this is unproven, as is the actual incidence of this as a significant clinical problem.

Obesity is clearly a worldwide epidemic with significant social, healthcare and economic implications.

A clear association between obesity and the need for both hip and knee replacement surgery has been demonstrated. Specifically the presence of class 3 obesity (BMI > 40) increases the incidence of THA by 8.5 times, and the incidence of TKA by 32.7 times, compared with patients of normal weight.

Issues related to TJA in the morbidly obese include: Outcomes - There is a growing body of evidence to support the premise that patients undergoing either THA or TKA who are morbidly obese derive significant benefit from the surgical intervention. Specifically patient and disease specific outcome measures (WOMAC, SF-12, KSCRS, HSS) demonstrate equal change between preoperative and postoperative scores in those patients of normal weight compared to the morbidly obese cohort; Complications - It would appear that the rate of deep infection is increased in the morbidly obese, and that the greater the BMI, the greater the risk of infection. This is important to understand and appreciate preoperatively as the surgeon discusses the risk/benefit ratio of the operative intervention.

There is little debate that performing total joint arthroplasty in the morbidly obese is technically challenging and that the potential for increased perioperative morbidity, particularly in the form of infection is present. That being said, the realised benefit to the patient of the surgical intervention is significant, and denying surgery on the basis of obesity alone is not justified.

While no one would argue the necessary role for the medical management of patients with early knee arthritis, significant controversy remains regarding the ideal treatment for a patient with bone-on-bone osteoarthritis who could equally be treated with a high tibial osteotomy, a uni-compartmental total knee, potentially a patello-femoral replacement if dealing with isolated patello-femoral disease or lastly, a complete total knee replacement. While clearly to date there has not been consensus on this issue, a review of the arguments, both pro and con, should be used as a guide to the surgeon in making this clinical judgment.

Patient Satisfaction - Many ardent supporters of uni-compartmental knee replacements espouse one of the principle benefits of the uni knee as much greater patient satisfaction. Unfortunately, what is never taken into account is the pre-selection bias that occurs in this patient population. Patients with the most minimal amount of arthritis and those with the greatest range of motion are pre-selected to undergo a uni-compartmental knee replacement compared to the more advanced arthritic knee with malalignment and more significant preoperative disability that will undergo a total knee replacement. Additionally the sources of data to draw the conclusions must be carefully analyzed. We must avoid using data from small series with unblinded patients performed by surgeons expert in the technique. Instead registry data, with its broad based applicability, is a much more logical source of information. Of significance, when over 27,000 patients were assessed regarding satisfaction following knee surgery; there was no difference in proportions of satisfied patients whether they had a total knee or a uni-compartmental knee.

Implant Longevity - Once again large prospective cohort data in the form of arthroplasty registries strongly favors total knee arthroplasty over uni-compartmental knee arthroplasty. The Swedish Knee Arthroplasty Registry demonstrated higher revision rates with uni's as compared with total knee replacements. In the Australian Joint Replacement Registry the cumulative 13-year percent revision rate for primary total knee replacements is 6.8% and for uni-compartmental knee replacements is 15.5%. Higher failure rates in uni-compartmental knee replacements seen in Australia has correlated to a significant decrease in the number of uni's being performed, which peaked at 15.1% in 2003 and in 2014 has reduced to 4.7%. There is a direct correlation to age, with younger patients having a significantly higher percentage of revision following uni-compartmental knee replacements (25% failure rate at 11 years if less than 55 years old). There is also tremendous variability in the success rate of the uni in the Australian Registry depending on the implant design (5-year cumulative revision rate range 5.0% to 18.9%), which is simply not seen in the total knee replacement population (5-year cumulative revision rate range 1.6% to 7.7%).

While one can perform the philosophical exercise of debating the merits of a total knee versus uni-compartmental knee, the evidence is overwhelming that in the hands of the masses a total knee replacement patient will have equal satisfaction to a uni-compartmental patient, and will enjoy a much lower probability of revision in the short term and in the long term.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected hip arthroplasty experts. The primary cases will include challenges such as hip dysplasia, altered bony anatomy and fixation challenges. In the revision hip arthroplasty scenarios issues such as bone stock loss, leg length discrepancy, instability and infection will be discussed. This will be an interactive case based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

There has been ongoing debate for many years on the relative merits of routine tourniquet use while performing a total knee replacement. Interestingly there have been many retrospective reviews and opinion articles on the topic, but little in the way of well powered prospective randomised clinical trials.

Those that dislike the premise of routine tourniquet use usually cite a list of either very rare complications, or theoretical concerns (nerve damage, muscle function, wound healing issues).

Like most debate topics, however, the issue is usually a shade of grey, rather than black and white, if the pro/con arguments are evaluated individually.

1. Blood Loss

There can be little debate that intra-operative blood loss is less with the use of a tourniquet. This has been demonstrated in multiple studies and is clearly intuitively obvious. Interestingly the overall blood loss (intra-op + post-op) may, however, be the same regardless of tourniquet use. Having a dry operative field, however, is important in achieving adequate cement fixation, and if tourniquet use is not employed, an alternative should be.

2. OR time

There is an overwhelming body of literature that supports the understanding that increased OR time directly correlates to increased infection rates in total joint arthroplasty. Proponents of not using a tourniquet will often have alternates to achieving a dry operative field that clearly add time to the procedure – meticulous hemostasis, air delivery systems, etc. This increased OR time may come at the cost of increased infection risk.

There is clearly a need for well-designed randomised clinical trials evaluating the practice of routine tourniquet use in TKA. Any trial done, however, must look critically at factors such as OR time, costs of alternatives, and potential long-term outcome effects.

Only a little over a decade ago the vast majority of primary total hip replacements performed in North America, and indeed globally, employed a conventional polyethylene insert, either in a modular version or in a cemented application. Beginning in the early 2000's there was an explosion in technology and options available for the bearing choice in total hip arthroplasty.

Highly crosslinked polyethylene was introduced in 1998, and within a few short years the vast majority of polyethylene inserts performed in North America were manufactured from this material. Globally there was a mixed picture with variable market penetration. Surgeons had seen historically poor results with attempts at “improving” polyethylene in the past and many were hesitant to use this new technology. Many randomised clinical trials have been performed and all have shown to a greater or lesser degree, that indeed the highly crosslinked polyethylene insert has undergone less linear and volumetric wear than its more conventional counterpart. The challenge, however, is as we approached mid-term results, orthopaedic manufacturers began altering the polyethylene to improve wear and improve mechanical strength. Therefore while ten-year and greater data will ultimately be published, the actual polyethylene in use at that time will be a different material. Additionally while wear rates are undoubtedly lower, we are still waiting for long-term results of actual osteolytic lesion development and the effect that highly crosslinked polyethylene will have on this clinical scenario. That being said, with over a decade of clinical experience, unquestionably highly crosslinked polyethylene has truly been a revolution in design, essentially eliminating polyethylene wear as an early failure mode.

During this same decade metal-on-metal implants had seen a significant resurgence in use. Metal-on-metal implants had in-vitro advantages with very low wear rates. They allowed the use of large metal heads and articulations, thereby improving range of motion and stability. Concerns always existed regarding the production of metal ions and the potential for metal hypersensitivity, as well as possible systemic effects. Metal hypersensitivity remains a diagnosis of exclusion with no definitive diagnostic tests to either screen for it, or diagnose it, if suspected. Over the past few years metal-on-metal implant use has dropped significantly, to the point now in 2013, where the only remaining application is resurfacing implants in the younger male patient.

Ceramic-on-ceramic bearings enjoy the lowest wear rates of all currently available hip articulations. Historically there has been concern regarding fracturing of both the inserts and the heads, although current generation ceramic-on-ceramic bearings have a much lower reported fracture rate. The phenomenon of a squeaking articulation remains a concern for both patient and surgeon. Conflicting reports exist on whether this is related to implant malposition or is a function of the bearing itself. As with other bearings, improvements in technology continue to evolve and newer ceramics have recently been introduced and are in clinical practice.

The future will continue to see the evolution of the articulation in total hip arthroplasty. Patients are undergoing total hip replacements at younger ages and clearly have higher demands than seen historically. That being said, two factors will have a major influence on future developments. The tremendous clinical success of highly crosslinked polyethylene should have us all question the need for significant changes in bearing material and the current environment following the multiple issues with metal-on-metal is one of evolutionary, rather than revolutionary, design and introduction.

Only a little over a decade ago the vast majority of primary total hip replacements performed in North America, and indeed globally, employed a conventional polyethylene insert, either in a modular version or in a cemented application. Beginning in the early 2000's there was an explosion in technology and options available for the bearing choice in total hip arthroplasty.

Highly cross-linked polyethylene was introduced in 1998, and within a few short years the vast majority of polyethylene inserts performed in North America were manufactured from this material. Globally there was a mixed picture with variable market penetration. Surgeons had seen historically poor results with attempts at “improving” polyethylene in the past and many were hesitant to use this new technology. Many randomised clinical trials have been performed and all have shown to a greater or lesser degree, that indeed the highly cross-linked polyethylene insert has undergone less linear and volumetric wear than its more conventional counterpart. This replicates well the hip simulator data. The challenge however is as we approached mid-term results, orthopaedic manufacturers began altering the polyethylene to improve wear and improve mechanical strength. Therefore while ten-year and greater data will ultimately be published, the actual polyethylene in use at that time will be a different material. Additionally while wear rates are undoubtedly lower, we are still waiting for long-term results of actual osteolytic lesion development and the effect that highly cross-linked polyethylene will have on this clinical scenario. That being said, with over a decade of clinical experience, unquestionably highly cross-linked polyethylene has truly been a revolution in design, essentially eliminating polyethylene wear as an early failure mode.

During this same decade metal-on-metal implants had seen a significant resurgence in use. Most major orthopaedic companies produced a metal-on-metal implant whether in the form of a more conventional modular insert, or a monoblock resurfacing-type implant, or both. Metal-on-metal implants had in-vitro advantages with very low wear rates. They allowed the use of large metal heads and articulations, thereby improving range of motion and stability. Concerns always existed regarding the production of metal ions and the potential for metal hypersensitivity, as well as possible systemic effects. Metal hypersensitivity remains a diagnosis of exclusion with no definitive diagnostic tests to either screen for it, or diagnose it, if suspected. Over the past few years metal-on-metal implant use has dropped significantly, to the point now in 2013, where the only remaining application is resurfacing implants in the younger male patient.

Ceramic-on-ceramic bearings enjoy the lowest wear rates of all currently available hip articulations. Historically there has been concern regarding fracturing of both the inserts and the heads, although current generation ceramic-on-ceramic bearings have a much lower reported fracture rate. The phenomenon of a squeaking articulation remains a concern for both patient and surgeon. Conflicting reports exist on whether this is related to implant mal-position or is a function of the bearing itself. As with other bearings, improvements in technology continue to evolve and newer ceramics have recently been introduced and are in clinical practice.

The future will continue to see the evolution of the articulation in total hip arthroplasty. Patients are undergoing total hip replacements at younger ages and clearly have higher demands than seen historically. That being said, two factors have will have a major influence on future developments. The tremendous clinical success of highly cross-linked polyethylene should have us all question the need for significant changes in bearing material and the current environment following the multiple issues with metal-on-metal is one of evolutionary, rather than revolutionary, design and introduction.

While no one would argue the necessary role for the medical management of patients with early knee arthritis, significant controversy remains regarding the ideal treatment for a patient with bone-on-bone osteoarthritis who could equally be treated with a high tibial osteotomy, a unicompartmental total knee, potentially a patello-femoral replacement if dealing with isolated patello-femoral disease or lastly, a complete total knee replacement. While clearly to date there has not been consensus on this issue, a review of the arguments, both pro and con, should be used as a guide to the surgeon in making this clinical judgment.

Many ardent supporters of unicompartmental knee replacements espouse one of the principle benefits of the uni knee as much greater patient satisfaction. Unfortunately, what is never taken into account is the pre-selection bias that occurs in this patient population. Patients with the most minimal amount of arthritis and those with the greatest range of motion are pre-selected to undergo a unicompartmental knee replacement compared to the more advanced arthritic knee with mal-alignment and more significant pre-operative disability that will undergo a total knee replacement. Additionally the sources of data to draw the conclusions must be carefully analysed. We must avoid using data from small series with unblinded patients performed by surgeons expert in the technique. Instead registry data, with its broad based applicability, is a much more logical source of information. Of significance, when over 27,000 patients were assessed regarding satisfaction following knee surgery; there was no difference in proportions of satisfied patients whether they had a total knee or a unicompartmental knee.

Once again large prospective cohort data in the form of arthroplasty registries strongly favors total knee arthroplasty over unicompartmental knee arthroplasty. The Swedish Knee Arthroplasty Registry demonstrated higher revision rates with uni's as compared with total knee replacements. In the Australian Joint Replacement Registry the cumulative 11 year percent revision rate for primary total knee replacements is 6.1% and for unicompartmental knee replacements is 16.3%. The 10 year cumulative percent revision rate for patella femoral replacements 29.9% and lastly bicompartmental replacements are at 10.3% after only 3 years. Higher failure rates in unicompartmental knee replacements seen in Australia has correlated to a significant decrease in the number of uni's being performed, which peaked at 14.6% in 2003 and in 2012 has reduced to 9.0%. There is a direct correlation to age, with younger patients having a significantly higher percentage of revision following unicompartmental knee replacements (25% failure rate at 11 years if less than 55 years old). There is also tremendous variability in the success rate of the uni in the Australian Registry depending on the implant design (5 year cumulative revision rate range 5.0% to 18.9%), which is simply not seen in the total knee replacement population (5 year cumulative revision rate range 1.6% to 7.7%).

While one can perform the philosophical exercise of debating the merits of a total knee versus unicompartmental knee, the evidence is overwhelming that in the hands of the masses a total knee replacement patient will have equal satisfaction to a unicompartmental patient, and will enjoy a much lower probability of revision in the short term and in the long term.

This session will present a series of challenging and complex primary and revision cases to a panel of internationally respected hip arthroplasty experts. The primary cases will include challenges such as hip dysplasia, altered bony anatomy and fixation challenges. In the revision hip arthroplasty scenarios issues such as bone stock loss, leg length discrepancy, instability and infection will be discussed. This will be an interactive case based session that at its conclusion should leave the attendee with a more thorough approach to these challenging issues.

There has been ongoing debate for many years on the relative merits of routine tourniquet use while performing a total knee replacement. Interestingly there have been many retrospective reviews and opinion articles on the topic, but little in the way of well powered prospective randomised clinical trials.

Those that dislike the premise of routine tourniquet use usually cite a list of either very rare complications, or theoretical concerns (nerve damage, muscle function, wound healing issues).

Like most debate topics however, the issue is usually a shade of grey, rather than black and white, if the pro/con arguments are evaluated individually.

There can be little debate that intraoperative blood loss is less with the use of a tourniquet. This has been demonstrated in multiple studies and is clearly intuitively obvious. Interestingly the overall blood loss (intraop + postop) may however be the same regardless of tourniquet use. Having a dry operative field however is important in achieving adequate cement fixation, and if tourniquet use is not employed, an alternative should be.

There is an overwhelming body of literature that supports the understanding that increased OR time directly correlates to increased infection rates in total joint arthroplasty. Proponents of not using a tourniquet will often have alternates to achieving a dry operative field that clearly add time to the procedure – meticulous hemostasis, air delivery systems, etc. This increased OR time may come at the cost of increased infection risk.

There is clearly a need for well-designed randomised clinical trials evaluating the practice of routine tourniquet use in TKA. Any trial done however must look critically at factors such as OR time, costs of alternatives, and potential long-term outcome effects.

Background:

Varus-valgus constrained (VVC) implants are used in cases of severe valgus deformity, attenuated medial collateral ligament and difficulty in balancing the medial and lateral gaps of the knee. The increased constraint has been postulated to lead to more stress at the bone-implant interface and early loosening. The objective of this study was to compare the wear characteristics of the polyethylene liner in VVC prosthesis with the posterior-stabilized (PS) prosthesis and identify the factors leading to more wear in the VVC tibial inserts.

Purpose

The objective of this study was to compare the wear characteristics and damage scores in highly crosslinked (XLPE) and conventional polyethylene (CPE) acetabular liners.

Background:

Polyethylene wear in total knee arthroplasty (TKA) is influenced by patient, surgeon and implant factors. The objective of this study is to assess the effect of limb alignment, implant position and joint line position on the pattern of wear in posterior stabilized (PS) tibial inserts.

In North America, and for the most part globally, a cementless acetabular component with adjuvant screw fixation is the preferred technique for revision total hip arthroplasty.

However, there are situations that involve massive pelvic bone loss that preclude the use of a cementless cup alone.

Options include: i)

Enhanced fixation components and augments

Complex acetabular revisions present the arthroplasty surgeon with challenges that require an approach with more than one solution for all scenarios. While structural allografts have recently fallen out of favour with the increasing use of enhanced fixation components, there would still appear to be a role in the case in which bone stock restoration is a primary goal. The role of bone graft substitutes remains unclear, with supportive basic science data, but limited clinical experience to date. An algorithm will be discussed to assist in prioritising the multiple goals of acetabular reconstruction and one stock restoration.

A conceptually new acetabular design is currently available when performing a total hip arthroplasty – the dual mobility socket. Essentially this is a press-fit acetabular component with a polished surface that articulates with a large polyethylene head with a 28 mm ball inserted into that polyethylene in a similar fashion to a bipolar design.

Proponents of this design advocate its use to reduce the risk of dislocation, and it is being offered as an alternative to constrained liners and also as a potential prophylactic application in revision and high risk patients.

The concerns regarding this construct include: 1.

Wear

A large polyethylene head articulating against a polished metal surface will have much greater wear than a conventional metal against poly bearing. Hip simulator data has shown this previously. To demonstrate a reduction in wear, one must compare unlike polyethylenes, or extremes in component positioning.

There are many options available to both manage and to prevent hip instability. Any new implant must show equivalence to current devices on the many fronts of wear, fixation, midterm results, complications and costs.

Pain following total hip arthroplasty is a relatively rare event. Several series place the incidence of some degree of pain post THA at approximately 5%.

A systematic approach to determining etiology will direct treatment. Hip pain can be categorised as:

Summary Sentence: Cementless solid tri-spiked titanium shells, with a polished inner surface and improved locking mechanism, demonstrated excellent fixation and survivorship at mid-term (minimum 5 years) follow-up.

Introduction: The tri-spiked Reflection cup (Smith & Nephew, Memphis) is a second-generation solid titanium shell with a polished inner surface, no screw holes and an improved locking mechanism. The purpose of this prospective study was to evaluate the minimum 5-year clinical & radiographic results and survivorship of this second-generation acetabular component.

Methods: Between 1997 and 2003, 659 primary THA were performed using the Reflection tri-spiked socket. None of the shells had adjuvant fixation with screws. The mean follow-up time was 7.0 years (5 to 11 yrs). The patients were followed prospectively using validated clinical outcome scores (WOMAC, SF-12, Harris Hip scores) and yearly radiographs.

Results: Twenty-seven patients had died before the minimum 5-year follow-up period. The mean Harris Hip and WOMAC scores were 89 and 79 respectively at last follow-up. Three sockets (0.6%) had been revised: two for infection, one for component malpositioning. No cup was revised for aseptic loosening. Six liners were exchanged: three for residual instability, 3 for wear associated with aseptic loosening of the stem. Radiographic review of remaining cups in-situ identified no cases of loosening and only a small number of cups (< 3%) with any osteolysis. The KM survivorship analysis with revision for any reason, was 97.5% and 97.4% at 5 and 10 years, while survivorship of the acetabular component was 99.8% at 5 and 10 years.

Conclusions: This second-generation cementless solid tri-spiked titanium shell, with a polished inner surface and improved locking mechanism, demonstrated excellent fixation and survivorship at mid-term follow-up.

Sixty four patients undergoing total hip replacement (THR) were randomized to receive a peri-articular intra-operative multi modal drug injection or to receive no injection. All patients received patient controlled analgesia (PCA) for 24 hours after surgery.

Patients receiving the peri-articular injection showed significantly less PCA consumption 6 hours postoperatively (P< 0.002). The 24 hour PCA requirement post surgery was also less (P< 0.009).

The VAS score for pain on activity in the post anaesthetic care unit (PACU) was significantly less for injected patients (P< 0.04). The VAS satisfaction score for injected patients in the PACU and 4 hours post-operatively showed no statistical difference.

Peri-articular intra-operative injection with multimodal drugs can significantly reduce post-operative patient controlled analgesia requirements and pain on activity in patients undergoing total hip replacement with no apparent increase in risk.

We performed a prospective, randomised, blinded clinical trial comparing metal versus polyethylene bearing surfaces in patients receiving a THA.

Forty-one patients were randomised to receive a metal (twenty-three) or a polyethylene (eighteen) insert with identical femoral and acetabular components. The metal bearing was a 28mm low carbon on high carbon couple. Patients were evaluated pre-operatively, at three, six, twelve months and annually thereafter, including an evaluation of erythrocyte and urine cobalt, chromium, and titanium, outcome measures (WOMAC, SF-12, Harris Hip Score) and radiographs.

No patients were lost to follow-up. At an average 7.2 (range 6.1 – 7.8) years follow-up there were no differences in any outcome measures or radiographic findings. Patients receiving metal liners had significantly elevated metal ion measurements. At most recent follow-up, compared to the polyethylene control group, patients receiving a metal on metal bearing had erythrocyte cobalt levels were eleven times elevated (median 1.4 μg/L (metal) vs 0.12 μg/L (poly), p< .001). Urine cobalt levels were thirty-nine times elevated (median 11.4 μg/L/day (metal) vs 0.29 μg/day (poly), p< .001) and urine chromium levels were twenty-eight times elevated (median 4.75 μg/day (metal) vs 0.17 μg/day (poly), p< .001). Additionally the metal ion levels reached an early steady state level and did not decrease over time. (Erythrocyte Co (μg/L): 1.29 (6 mos), 1.20 (1 yr), 1.0 (2 yr), 1.10 (3 yr), 1.35 (4 yr), 1.40 (5 yr)).

Both cobalt and chromium ion measurements were significantly elevated in the blood and urine of the patients randomised to receive the metal on metal THA at all time intervals. Contrary to previous reports, in 34% of patients with a metal liner, metal ion (erythrocyte cobalt) elevation was still increasing at latest follow-up, and in the overall metal on metal patient cohort, metal ion median levels were not decreasing over time. As in polyethylene wear data, metal ion results are not necessarily generalizable, but are bearing design specific.

There is an increasing trend towards performing a high tibial osteotomy (HTO) with a medial opening wedge technique. Amongst the potential advantages is easier conversion to a total knee replacement (TKR), although literature regarding this is scarce. We report our early clinical and radiological results, along with the technical issues encountered.

From our database, we identified thirty-one patients who had undergone thirty-two TKRs after medial opening wedge HTOs. Clinic and operative records were reviewed, and our database used for knee society scores. Those patients not seen in the last twelve months were reviewed in clinic. All pre- and postoperative radiographs were reviewed. The average age of the patients was fifty-seven years, and the average time from HTO to TKR was 4.5 years.

Difficulties with patella eversion were seen in 12.5%, and the knee balanced easily in 85% of cases. The tibia had minimal deformity in most cases, and all osteotomies were healed at the time of conversion. A stem was used in ten cases, and only if metalwork was removed at the time of conversion (which was done in twenty-three of the thirty-two). Minimum one year follow-up was available for twenty-six patients, with a mean follow-up time of twenty-eight months (range twelve to ninety-three months). The average Knee Society knee score was eighty-eight, function score seventy-five, and total score one hundred and sixty-two. Compared to non-matched group of 1149 primary TKRs (of older average age), the knee score was significantly lower, and there was a higher percentage of patients in the poor category. Poor results correlated strongly to the presence of chronic pain or workers compensation issues, and also to whether the knee had undergone revision HTO prior to TKR.

We conclude that the conversion of a medial opening wedge HTO to a TKR is relatively straightforward technically, and some aspects are easier than performing a TKR after a lateral closing wedge osteotomy (using historical controls). The clinical results appear inferior to that of a TKR performed without a prior osteotomy, although the results in our osteotomy group were skewed by a small group of chronic pain and workers compensation cases.

Attempts have been made to develop standardise guidelines for knee implant wear testing of polyethylene (PE). The current ISO-14243-3 standard recommends the use “calf serum”, without giving ranges on the specific protein constituents and characteristics. In the present study, three types of frequently used calf sera with various protein constituents (albumin, globulins) were utilised. The effect of osmolality and hyaluronic acid (HA) was also assessed. An attempt was made to identify synovial fluid (SF) characteristics that may be responsible for the boundary lubrication in the joint with the goal to develop a more clinically relevant lubricant.

Twenty samples of SF were drawn from twenty patients and analyzed. Specific protein constituents and osmolality were then compared to three calf sera used for wear testing. Test One (six million cycles (Mc)): Bovine calf serum (BCS), newborn calf serum (NCS) and alpha-calf serum (ACS) were diluted with distilled water (DW). Test two (5.5Mc): ACS with an osmolality of 312 ± 1.00 mmol/kg (closest to clinical osmolality; diluted with phosphate buffered saline, PBS) and 145 ± 2.00 mmol/kg (diluted with DW) were consecutively tested. HA was added at a concentration of 1.5g/l. Modular total knee replacements of cruciate retaining design (GUR 1050, 10mm PE insert) were used.

ACS diluted with PBS appeared to be of closest specific protein constituents and osmolality when compared to SF. The wear rate for BCS was 21.81 ± 2.48 mg/Mc, 17.05 ± 3.25 mg/Mc for NCS, and 13.44 ± 0.79 mg/Mc for ACS (p < 0.016). Decreased osmolality amplified the PE wear by a factor of 2.3 (p = 0.020). Adding HA increased the PE wear by a factor of two (p = 0.002).

There was significant difference in PE wear rates between the three calf-sera. BCS and NBC did not have clinically relevant levels of specific protein constituents. This study strongly suggests that current standards for total knee wear testing should be revised to enable more controlled wear testing under more clinically relevant conditions. It is suggested to be of particular importance when new bearing materials, such as cross-linked PE’s, are evaluated and proposed for clinical application.

Patients with moderate to severe osteoarthritis of the knee, on a waiting list for total knearthroplasty, were recruited to a double-blind, randomized clinical trial evaluating neoprene knee braces containing high-power static magnets or sham magnets. Patients wore the brace for a minimum of six hours per day and were evaluated at baseline, two, six, twelve and twenty-four weeks. The subjective outcomes (MACTAR, WOMAC, KOOS, SF-36) and functional outcomes (six minute walk, thirty second stair climb) showed no statistically significant differences between the groups at any of the follow-up time periods.

The purpose of this study was to compare the effectiveness of neoprene knee braces containing high-power static magnets to sham magnets in the management of osteoarthritis of the knee

No statistically significant difference in patient-related quality-of-life and objective functional evaluation was found between groups.

This study provides patients and doctors with evidence as to the efficacy of this type of therapy. It will allow those individuals on fixed incomes to utilize their resources to the best advantage to minimize their symptoms related to osteoarthritis of the knee.

A prospective double-blinded randomized clinical trial was conducted. Ninety-five patients with moderate to severe osteoarthritis of the knee were randomized to receive a Magnet (M) or Sham (S) knee brace. Both groups were equal with regards to age (M = 71.1 yrs, S = 66.8yrs), severity of disease, gender and all baseline measures. No statistically significant difference in patient-related quality-of-life and objective functional evaluation was found between groups at any time interval.

All study patients were recruited from a knee arthroplasty waiting list. At baseline and at two, six, twelve and twenty-four weeks each patient completed a WOMAC, MACTAR, KOOS quality-of-life questionnaire, SF–36 global health measure, and six minute walk and thirty second stair climb after which they were asked to determine their general fatigue, pain and shortness of breath on a 100mm VAS scale. Patients were instructed to wear their brace at least six hours per day and when active (walking, shopping, golfing).

Isolated liner exchange in revision total hip arthroplasty for the treatment of polyethylene wear is an increasingly common surgical procedure. Twenty-four hips underwent this procedure via the direct lateral approach and were prospectively followed clinically and radiographically. Accessible osteolytic lesions were curetted and bone grafted. At a mean follow-up of forty months, a significant clinical improvement was observed. One cup collapsed into an osteolytic lesion postoperatively; all other lesions regressed. No dislocations have occurred. Isolated liner exchange via the direct lateral approach may reduce dislocation rates while avoiding the morbidity associated with the removal of well-fixed components.

The purpose of this study was to evaluate the clinical and radiographic results of isolated liner exchange in revision total hip arthroplasty (THA) for osteolysis and polyethylene wear via the direct lateral surgical approach.

Retention of well-fixed implants avoids unnecessary bone loss at revision surgery. Previous studies report a significant dislocation rate with isolated liner exchange. Revision via the direct lateral surgical approach may reduce the dislocation rate in surgery for acetabular osteolysis.

Twenty-four hips that underwent an isolated liner exchange revision procedure via the direct lateral approach were prospectively followed. Accessible osteolytic lesions were curetted and bone grafted. Harris Hip Score, WOMAC Index, and radiographic analysis were recorded. The area of osteolytic lesions was calculated using a computer imaging technique.

At mean follow-up of forty months, all except one of the osteolytic lesions had regressed in size. Mean Harris Hip scores improved from sixty-nine to eighty-three and WOMAC indices improved from thirty-seven to twenty-four. No dislocations have occurred. One cup collapsed into an osteolytic lesion postoperatively, requiring an acetabular revision procedure.

Isolated liner exchange is a promising technique that avoids the removal of well-fixed acetabular implants. The increased dislocation rate associated with revision THA may be reduced and osteolytic lesions may be debrided and bone grafted through the direct lateral approach.

Isolated liner exchange via the direct lateral approach reduces the dislocation rate in THA. Retention of wellfixed implants and bone grafting is a procedure that preserves bone stock and addresses osteolytic lesions at revision surgery.

The pathogenesis of osteolysis in failed total hip arthroplasty is not fully understood. The purpose of this study is to identify CD4+CD25+ Regulatory T cells in periprosthetic tissues in failed total hip replacements secondary to osteolysis. Intra-operative tissue samples and peripheral blood were collected from patients undergoing revision total hip arthroplasty surgery. Regulatory T cells were present in the tissues, and significantly increased in the peripheral blood in patients with failed total hips compared to normal controls. Further characterization of these regulatory T cells are warranted as they may play a role in osteolysis in loose total hip replacements.

Osteolysis remains the most common complication following total joint arthroplasty. To date, no authors have investigated the role of CD4+CD25+ regulatory T cells (T_REG) participating in the osteolytic pathogenesis. The purpose of this study is to quantitate the presence of T_REG cells in periprosthetic tissues in failed total hip replacements secondary to osteolysis.

Fifteen consecutive patients booked for revision total hip arthroplasty secondary to osteolysis were included. Tissue samples were collected: peripheral blood (PB), synovial fluid (SF), synovial tissue (ST), and interface tissue (IT) between the failed component and the bone defect. Total lymphocytes were isolated and analyzed using fluorescent-tagged antibody cell sorting (FACS) for the presence of T_REG cells. Frozen sections of ST and IT were analyzed with immunohistochemistry for T_REG cells.

T_REG cells were significantly upregulated (p< 0.01) in the PB (68%) of revision hip patients compared to normal controls PB (44%). In the synovial tissue (ST) and interface tissue (IT), 57% of the lymphocytes isolated were TREG cells. The presence of T_REG cells in the ST and IT were confirmed with immunohistochemistry.

T_REG cells are upregulated in the peripheral blood of patients with failed total hips secondary to osteolysis. The TREG cells are also present in the synovial tissue and interface tissue.

Evidence for involvement of regulatory T cells contribute to our understanding of this complex biologic response to artificial wear particles.

Functional studies of these T_REG cells are warranted as they are upregulated in patients with loose total hip replacements.

Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL^® (mobile bearing) versus the AMK^® and Genesis II^® (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System).

The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL^®, Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK^®, Depuy and Genesis II^®, Smith and Nephew).

Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.

No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two year follow up, and one patient was revised for infection at 6 months leaving eighty-seven patients at an average follow-up of 3.37 years (range 2.91 – 4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL - 167, AMK – 158, GenesisII – 166). There were no differences in knee flexion at two years (SAL – 117^°, AMK – 115^°, GenesisII – 118^°).

No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

In this prospective randomized clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.

Funding: London Health Sciences Centre Internal Research Fund

Fixed bearing and mobile bearing knee designs are both currently used in clinical practice with little evidence- based research available to determine superiority of one system. We performed a prospective, randomized, blinded clinical trial to compare a mobile bearing to two standard fixed bearing implants. A single observer was used to measure all range of motion scores. We evaluated the short and long- term outcomes of the SAL^® (mobile bearing) versus the AMK^® and Genesis II^® (fixed bearings) total knee joint replacements. Minimum two- year follow-up revealed no differences in the outcome measures (WOMAC, SF-12, Knee Society Clinical Rating System).

The purpose of this study was to compare the results between a cruciate retaining mobile bearing total knee (SAL^®, Sulzer) and two cruciate retaining fixed bearing total knee prostheses (AMK^®, Depuy and Genesis II^®, Smith and Nephew).

Ninety patients were randomized to receive a SAL, AMK, or GenesisII prostheses. Patients were evaluated pre-operatively, at three, twelve months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated.

No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two year follow up, and one patient was revised for infection at 6 months leaving eighty-seven patients at an average follow-up of 3.37 years (range 2.91 – 4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL - 167, AMK – 158, GenesisII – 166). There were no differences in knee flexion at two years (SAL – 117^°, AMK – 115^°, GenesisII – 118^°).

No differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

In this prospective randomized clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.

Funding: London Health Sciences Centre Internal Research Fund

The Self Aligning (SAL I) total knee prosthesis (Sulzer, Winterthur) is a first generation cruciate retaining mobile bearing implant allowing unrestricted rotation and up to 5 mm. of translation. A consecutive series of two hundred and three SAL I components in one hundred and sixty- seven patients were implanted between 1990 and 1994 and were reviewed clinically and radiographically. Quality of life outcomes (SF-12 and WOMAC) were also reviewed pre-operatively and regular intervals. This first generation mobile bearing knee implant in this series, continues to function well at a minimum ten years follow-up, with a mechanical failure rate (8%) comparable to fixed bearing designs.

A consecutive series of SAL I total knee arthroplasties were performed between 1990 and 1994 and were reviewed clinically, radiographically and with standardized quality of life outcome tools, including the SF-12 and the Western Ontario MacMaster Osteoarthritis Index (WOMAC).

Patient demographics, radiographs, and multiple validated outcome measures (WOMAC, SF12, Knee Society Clinical Rating System) were evaluated pre-operatively, at three, twelve, and twenty-four months and every two years thereafter.

The series included two hundred and three SAL I implants in one hundred and sixy-sevenpatients. There have been sixty-nine patient deaths (eighty-five procedures), nine patients (eleven procedures) now reside in nursing homes and are unable to return due to medical complications, two patients (three procedures) could not be located. Nine-teen patients/procedures have had revision surgery. Therefore, seventy-six patients (ninety-three procedures) were evaluated with over ten year follow-up (average 10.89 years, range 10.03–13.72). Indications for revision included, sepsis (three), aseptic loosening (eight), instability (two) and poly-wear (six). The KSCRS was assessed for all remaining patients at greater than ten years including pain (45.83), function(65.60), range of motion extension(0.13) and flexion(113.82) as well as the results of the WOMAC (pain-4.36, joint stiffness-2.29, function-18.66, total- 15.92) and SF-12 (Mental-55.37 Physical- 34.99).

The SAL I mobile bearing implant continues to perform comparably to fixed bearing cruciate retaining designs.

This first generation mobile bearing knee implant continues to function well at a minimum ten years follow-up, with a mechanical failure rate (8%) comparable to fixed bearing designs.

The Genesis II total knee prosthesis was a successor to the Genesis I TKR in which three degrees of external rotation was built into the femoral component to improve patellofemoral tracking and eliminate rotational incongruity. The midterm (minimum five year) results of three hundred and forty-three Genesis II cemented components were reviewed in three hundred and twenty-four patients. Kaplan-Meier survivorship was 98% at a mean 7.6 years.

The focus of this study was to analyze the minimum five- year results of patients receiving either a cruciate-retaining, posterior stabilizing, or mobile bearing Genesis II TKR. Further analysis was performed to delineate differences between subsets of this population.

Data from a consecutive series of three hundred and twenty-four patients receiving three hundred and sixty-seven Genesis II TKR’s between February 1996 and July 1999 was collected. Patients were evaluated pre-operatively, at six weeks, three months, six months and annually thereafter, using the Knee Society Clinical Rating System and the Western Ontario MacMaster Osteoarthritis Index. A Kaplan-Meier Survivorship was performed on the consecutive series. Statistical analyses were used to delineate significant differences between subsets of patients.

There were three hundred and sixty-seven procedures (one hundred and sixty-nine cruciate-retaining, one hundred and sixty-six posterior stabilized and six mobile bearing designs) performed on three hundred and twenty-four patients. At the time of evaluation, forty-five (13%) patients were deceased, twenty-four (7%) patients were unavailable for evaluation and nine (2%) knees had been revised. A 98% implant survivor-ship was calculated at a mean time of 7.6 years.

These are the first mid-term (minimum five year) clinical results of the Genesis II TKR, which continues to function well. Kaplan-Meier survivorship was 98% at a mean 7.6 years.

The purpose of this study was to determine contact patterns in cementless acetabular cups using a novel computed tomography (CT) scan analysis technique. Eighteen embalmed cadaveric hemipelvis specimens were randomly assigned to receive one of three cup designs. A custom CT platform was designed to optimize imaging of the acetabular cups. After cup implantation, specimens were mounted on the platform and imaged in a spiral CT scanner. Contact analysis was preformed using custom-developed imaging software. The hemisphere, dual geometry and spiked cup designs analyzed using this CT analysis technique demonstrate differences in the amount and distribution of bone pros-thesis contact.

The purpose of this study was to determine contact patterns in cementless acetabular cups using computed tomography (CT) scan analysis.

Eighteen embalmed cadaveric hemipelvis specimens were randomly assigned to receive a hemispherical cup, a dual geometry cup, or a spiked cup. After radiographic templating, an experienced orthopaedic team prepared the specimens and implanted the acetabular cups. A custom CT platform was designed to optimize imaging of the acetabular cups. After cup implantation, specimens were mounted on the platform and imaged in a spiral CT scanner. Contact analysis was preformed using custom-developed imaging software. Contact was defined as a bone-prosthesis distance of 0.5 mm or less.

The mean amount of cup contact was 40.4% (SD=8.2%) in the hemisphere group, 24.7% (SD=2.3%) in the dual geometry group, and 29.7% (SD=9.5%) in the spiked group. Colour mapping of the bone-prosthesis gap was used to identify contact/non-contact regions along the acetabular contour for all cup designs.

Preliminary work with this CT analysis technique demonstrates differences in the amount and distribution of contact in the acetabular cup designs. Future work will involve development of an imaging phantom to clarify error, use of the technique with different cup designs and reaming techniques, and comparison of this technique with conventional CT scan techniques.

This study outlines a novel CT analysis technique for quantitatively determining bone-prosthesis contact for cementless acetabular cups.

The hemisphere, dual geometry and spiked cup designs analyzed using this CT analysis technique demonstrate differences in the amount and distribution of bone prosthesis contact.

Funding: Smith and Nephew

Constrained acetabular components are a useful adjunct for the potentially unstable hip arthroplasty. There have been concerns over implant failure and early acetabular component loosening secondary to the increased implant constraint. We report the results of a constrained ace-tabular component used as treatment for dislocating hips and as prophylaxis against dislocation in high risk primary and revision hip arthroplasty. At average 3.1 years follow-up only one insert of eighty-nine inserted had failed. No cups have demonstrated radiographic or clinical evidence of loosening. We conclude this implant is safe and effective for both the prevention and treatment of hip instability.

To review the effectiveness and durability of a constrained acetabular component used to treat and prevent recurrent dislocation after total hip arthroplasty

Constrained acetabular components of this type provide both an excellent treatment and preventative option in total hip arthroplasty. There is no evidence of accelerated cup loosening and the implant failure rate remains acceptable despite the increased constraint.

Constrained acetabular components have been mainly used as a salvage option for dislocating hip arthroplasty. There have been concerns over implant failure and early acetabular component loosening secondary to the increased implant constraint. Use of this implant can prevent dislocation in high risk patient groups (eg: revision surgery) without compromising implant longevity. This significantly reduces the potential morbidity associated with hip instability.

Eighty-nine patients received the tripolar constrained acetabular component. Fifteen were inserted for recurrent dislocation whilst seventy-two were inserted in patients felt to be at high risk of dislocation (forty-nine for intra-operative instability at revision surgery, twenty-five for primary THA in patients with poor compliance, neurological conditions or deficient abductor mechanism). One implant failed by component dissociation at eighteen months. All other recurrent dislocators remained stable. There was no evidence of accelerated component loosening at medium term review (range twelve – eighty three months, average thirty-seven months)

Radiographic and clinical data was prospectively collected on eighty-nine patients who had the constrained acetabular component inserted.

Funding: The primary author’s fellowship position is partially funded by Smith and Nephew Richards Inc.

Purpose: The young patient with hip arthritis remains one of the biggest challenges to arthroplasty surgeons. The difficulty of providing a long-lasting total hip arthroplasty (THA) has been clearly documented in the literature. The aim of this study was to assess the outcomes of uncemented THA’s performed in our unit in patients aged under 50.

Methods: In our unit information on all patients is recorded prospectively on an arthroplasty database. From this database we identified 273 uncemented THAs in 237 patients under the age of 50 performed in our unit between 1985 and 2000 with a minimum of 5 year follow up. Outcomes were assessed in terms of 10 and 15-year survival with revision for any reason as the endpoint. Hip scores at routine and most recent follow-up were also reviewed. All surviving implants were radiographically assessed for acetabular wear, component loosening and for the presence of osteolysis.

Results: The mean age of patients at the time of surgery was 41.1 years. 36 patients had bilateral THA. The overall 10 and 15 year survival was 88.7 ± 2.4% and 65.6 ± 4.8 % respectively. Femoral stem survival was significantly higher at 100 % and 98.4 ± 1.6% at 10 and 15 years. Acetabular component survival was 88.6 ± 2.5 % at 10 years and 65.9 ± 4.8 % at 15 years. In unrevised THA’s 56.9% had asymmetric polyethylene wear > 2mm. 2% had definite evidence of acetabular loosening. 25.5% had radiographic evidence of femoral cortical hypertrophy or spot-welds. The mean HHS pre–operatively, at 5 and 10-year follow-up was 46.4 ± 13, 90.7 ± 12.2 and 87.9 ± 14.7 respectively.

Conclusions: Uncemented THA is effective even in young active patients. The main challenges remain ace-tabular polyethylene wear and loosening. Femoral uncemented stems provide long-term functional fixation. Contemporary bearing surfaces in association with such stems may provide long lasting THA’s even in young active patients.

One hundred and thirty-one cemented femoral stems inserted during revision total hip arthroplasty were reviewed to determine component survival. Harris Hip scores and complete radiographs were analysed. Survival at 10.5 years was 86.9%. Radiographically, 76.9% of the remaining components were classified as stable or possibly loose. Chi-square analysis of demographic and surgical factors determined age < 60 years, male gender and stems > 200 mm in length contributed significantly to failure (p < 0.05). Contrary to published results, we found that longer stems were more susceptible to failure. Revision femoral THA to a cemented component is an effective procedure that exhibits good long-term survival.

The purpose of this study was to determine the long-term survival of cemented femoral components in revision total hip arthroplasty (THA) and to identify factors significant to implant failure.

Cemented femoral components demonstrate good long-term survival and remain a suitable option for revision THA for hips with an intact cortical tube.

We report high long-term survival for this increasingly popular procedure, and contradict published results regarding the relationship between stem length and failure.

A consecutive series of one hundred and thirty-one THA revisions using a cemented femoral component were reviewed. Ninety-four hips in eighty-five patients alive > six years post-operatively were studied with a mean follow-up of 10.5 years. Hips excluded from analysis were thirty deceased and seven lost to follow-up before six years post-operatively. Implant success was graded radiographically and by comparing pre-operative to recent Harris Hip scores.

Of the ninety-four hips, fifteen (16%) femoral components were subsequently revised; nine (9.6%) for aseptic loosening, three (3.2%) for periprosthetic fracture, and one (1.1%) for each of stem fracture, instability, and sepsis. Survival at 10.5 years was 86.9% for all reasons and 91.0% for aseptic loosening as an endpoint. 76.9% of the retained components were radiologically classified as stable or possibly loose at follow-up. Factors significant for failure included age at revision < sixty years (p = 0.003), male patients (p = 0.036) and stems > 200 mm in length (p = 0.024).

Controversy continues to exist regarding the choice of a cementless femoral component in a primary total hip arthroplasty. Both proximally coated tapered stems and fully coated cylindrical stems have excellent clinical results. The incidence of both thigh pain and proximal femoral stress shielding and multiple validated outcome measures were evaluated in a prospective randomized clinical trial with a minimum of two year follow-up comparing a proximally coated tapered femoral stem to a fully coated cylindrical femoral stem.

A prospective randomized clinical trial (RCT) was performed comparing a cylindrical cobalt chrome fully coated femoral stem (Prodigy, Depuy, Warsaw, IN) to a tapered, titanium, proximally porous coated stem (Synergy, Smith & Nephew,

Memphis, TN) with respect to thigh pain, femoral stress shielding and multiple outcome measures.

One hundred and ninety-four patients were enrolled and evaluations were performed pre-operatively, three months, six months and annually. Multiple outcome measures (Harris Hip Score, SF12, WOMAC, Patient Satisfaction Questionnaire, Thigh Pain Questionnaire) were obtained. Sixty-one of these patients were randomized to receive a bone density scan pre-operatively, two weeks post-operatively, six months and annually.

Twelve patients were unavailable for two-year follow-up, leaving one hundred and eighty-two patients evaluated. No significant differences were demonstrated in thigh pain incidence or the multiple outcome measures. Bone density scans demonstrated significantly greater bone density (p< 0.005) in the tapered stem versus the cylindrical stem patients at two-week evaluations from distal femoral reaming. Both stem designs demonstrated statistically significant bone loss in Gruen zones one, six, seven between the two-week and one and two-year evaluations. There were no differences between stem designs although the Prodigy stem demonstrated trends towards greater bone loss in Gruen zones six and seven.

This prospective RCT demonstrated no difference in thigh pain incidence and multiple outcome measures between patients receiving a proximally coated tapered versus a fully coated cylindrical femoral component. Both stem designs demonstrated statistically significant proximal femoral bone loss between the post-operative and two-year evaluations; however, there were no differences between stem designs.

This Blinded Randomized Clinical Trial outlines: how peri-articular intra-operative multimodal analgesia significantly reduces post-operative analgesia requirement. Sixty-four patients undergoing total knee replacement were randomised to receive a peri-articular intra-operative injection containing ropivacaine, ketorolac, epimorphine and epinephrine or nothing. Patients who received the injection demonstrated greater satisfaction and pain relief. Finally, patients in the injected group did not show any signs of cardio and central nervous system toxicity.

Post-operative analgesia can be associated with troublesome side effects. Good peri-operative analgesia facilitates rehabilitation, improves patient satisfaction and may reduce hospital stay. The purpose of this study was to assess a novel cocktail for peri-articular analgesia after total knee replacement.

Sixty-four patients undergoing total knee replacement were randomised to receive a peri-articular intra-operative injection containing ropivacaine, ketorolac, epimorphine and epinephrine or nothing. The anaesthetic analgesic regime was standardised. All patients received patient controlled analgesia (PCA) for twenty-four hours post surgery, followed by standard analgesia. VAS pain scores during activity and at rest and patient satisfaction scores were recorded pre and post operatively and at six week follow up. PCA consumption and overall analgesic requirement were measured.

PCA use at six, twelve and over twenty-four hours post surgery was significantly less in patients receiving the injection (p< 0.01, p=0.016, p< 0.01). Patient satisfaction in PACU and four hours post operation was greater (p=0.016, p=0.013). VAS for pain during activity in PACU and at four hours were significantly less (p=0.04, p=0.007) in the injected group. The average ROM at six weeks was no different. Overall hospital stay and the incidence of wound complications were not different between the two groups.

Peri-articular intra-operative multimodal analgesia significantly reduces post-operative analgesia requirement. Patient satisfaction and pain relief is greater in the injection group. No cardio and central nervous system toxicity was observed.

Our novel cocktail of ketorolac, epimorphine, epinephrine and ropivacaine provides superior pain relief with no adverse side effects.

Despite favourable wear characteristics of compression molded HMWPE in vitro preliminary data show no statistical difference in wear between RAM extruded HMWPE and compression moulded polyethylene. This study reviews AP and lateral radiographs for wear using the Martell technique at two, five years and maximum follow up (mean 88.2 months).

Reduced implant survivorship due to aseptic loosening has prompted research into alternative bearing materials. Simulator testing is useful but clinical studies are the gold standard to evaluate the wear characteristics of new bearing materials.

On hundred and twelve patients matched for sex, age, body mass index, primary pathology, Charnley grade, and follow up underwent uncemented total hip replacement using an identical implant. Group One (sixty-four patients) had a RAM extruded liner (GUR 4150 HP) and Group Two (forty-eight patients) had a compression molded liner (Montell H 1900). HMWPE sterilisation regimes were identical. AP and lateral radiographs were analysed for wear using the Martell technique at two, five years and maximum follow up (mean 88.2 months).

Preliminary data show a linear and volumetric wear rate in Group One of 0.067 mm/yr and 26 mm3/year respectively between two years to maximum follow up. Similarly, the wear rates for Group Two were 0.132 mm/yr and 45 mm3/year respectively. There was no statistical difference in acetabular osteolysis between Group One (16.3%) and Group Two (15%) patients at maximum follow up.

Despite favourable wear characteristics of compression molded HMWPE in vitro preliminary data show no statistical difference in wear between RAM extruded HMWPE and compression moulded polyethylene. Quality of the wear debris is more likely to be important in producing aseptic loosening than actual wear rate.

T cells have been implicated in the pathogenesis of osteolysis. The goal of this study was to compare the ratios of CD4+ T cell populations in total hip arthroplasty (THA) patients with and without osteolysis. We found no significant differences in the frequency of peripheral blood CD4+CD25+ regulatory and effector T cells, serum IL-10 and TGF-β concentrations, and immuno-suppressive ability of regulatory T cells from patients with osteoarthritis prior to THA, and THA patients with and without radiographic evidence of osteolysis.

CD4+ T cells are critical in regulating immune-mediated conditions. This study compared the frequency of CD4+ T cell subpopulations in the peripheral blood of patients with and without osteolysis following total hip arthroplasty (THA).

Numbers of CD4+CD25hi regulatory T cells, CD4+CD25moderate effector T cells, and CD4+CD25+ T cells in the peripheral blood of thirty patients with osteoarthritis prior to primary THA, thirty patients with asymptomatic THAs and no radiographic evidence of osteolysis, nineteen patients with asymptomatic THAs with radiographic evidence of early osteolysis (not requiring revision surgery) and nine patients scheduled for revision THA for osteolysis were determined by flow cytometry. Serum IL-10 and TGF-β levels were measured using ELISA kits. Results were compared by t-test and rank sum test. CD4+ CD25hi regulatory T cells and CD4+ CD25neg T cells were isolated from blood using a MACS cell isolation kit, co-cultured for three days, and T cell proliferation determined by [3H]-thy-midine uptake.

The frequency of CD4+CD25hi regulatory T cells, CD4+CD25moderate effector T cells, and CD4+CD25+ T cells were similar in each study group. Regulatory T cells from patients with and without osteolysis had a normal functional ability to inhibit CD4+ T cell proliferation. Serum levels of the regulatory T cell-derived cytokines IL-10 and TGF-β were also comparable between groups.

Our data suggests that CD4+ T cell immune responses are normal in THA regardless of the level of osteolysis, in contrast to previous studies that have implicated T cell hypersensitivity in the pathogenesis of osteolysis surrounding THA.

Purpose: Post-operative analgesia using opioids or epidural analgesia can be associated with troublesome side effects. Effective peri-operative analgesia facilitates rehabilitation, improves patient satisfaction and may reduce hospital stay. Locally administered analgesia is effective, avoids systemic drug related side-effects and may be of benefit in minimally invasive joint replacement. This study compares the effects of a peri-articular injection cocktail in patients undergoing total knee and hip replacement surgery

Methods: 128 patients undergoing total knee (TKR) and hip (THR) replacement were randomised to receive a peri-articular intra-operative injection containing ropivacaine, ketorolac, epimorphine and epinephrine or nothing. The anaesthetic analgesic regime was standardised. All patients received patient controlled analgesia (PCA) for 24 hours post surgery, followed by standard analgesia. VAS pain scores during activity and at rest and patient satisfaction scores were recorded pre and post operatively and at 6 week follow up. PCA consumption and overall analgesic requirement were measured.

Results: Both TKR and THR patients used significantly less PCA 6 hours after surgery (p = 0.02 THR, p< 0.01 TKR). TKR patients receiving the injection used significantly less PCA use over 24 hours post surgery (p = 0.013). VAS for pain at 4 hrs post operation was significantly lower in the both groups (p = 0.003 TKR)(p = 0.017 THR). VAS for pain during activity at 24 hours was significantly less (p = 0.001) in the injected TKR group. Overall hospital stay and wound complications were not different between the groups.

Conclusions: Peri-articular analgesia significantly reduces post-operative analgesia requirement in TKR and THR patients. Greater satisfaction and pain relief was seen in TKR patients compared with THR.

Fifty-one prospectively followed Contour_ acetabular reconstruction cages, inserted through the direct lateral approach, were reviewed at three years minimum follow-up (range 3 to 6.4 yrs.). To date, four reoperations were required (two each for sepsis and instability) with no failures due to aseptic loosening. The Kaplan-Meier Survival Rate for any reoperation was 87% at 6.4 years. Short to mid-term follow-up of a single type of acetabular reconstruction cage, inserted through the lateral approach, demonstrated this to be a successful reconstruction option in the management of large acetabular bone defects.

This study reports the mid-term results of a single design of acetabular reconstruction cage inserted through the direct lateral approach.

At minimum three years follow-up (range 3 to 6.4 yrs.), there were no failures due to aseptic loosening with only four of fifty-one cases requiring reoperation (two sepsis, two instability).

This review supports the use of the reconstruction cage, inserted through the lateral approach, for large defects that cannot be managed with a hemispherical porous implant.

The use of the reconstruction cage in our center is reserved for large defects that cannot be managed with a hemispherical porous implant because of insufficient bone stock for initial implant stability and/or host bone contact for in-growth. Fifty-one consecutive prospectively followed Contour_ (Smith and Nephew) acetabular reconstruction cages, inserted through the direct lateral approach, were reviewed at three years minimum follow-up (range 3 to 6.4 yrs.). The majority of cases were AAOS Type Three and Four defects in which morsellized allograft was used in forty-nine cases and structural graft in three cases. Harris hip scores improved from 32.1±17.8 pre-op to 65.3±24.1 at most recent follow-up. Defining any acetabular reoperation as a failure, four of the fifty-one cages were considered to have failed giving a Kaplan-Meier Cumulative Survival Rate of 87% at 6.41 years. Two reoperations were for recurrent dislocation and the other two for sepsis. None of the fifty-one cages have been revised for aseptic loosening to date.

The timing of liner exchange for retroacetabular oste-olysis in THA remains uncertain. Liner exchange should be done before the shell becomes loose. The purpose of this study was to determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell. Osteolytic lesions were quantified radiographically using three different measures. Implant stability was confirmed intraoperatively. Percent of shell circumference with surrounding osteolysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than fifty percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.

The timing of liner exchange for retroacetabular osteolysis in cementless THA remains uncertain. Liner exchange should be done before the shell becomes loose.

To determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell.

Osteolytic areas differ between loose and stable shells.

Between 1992 to 2002, seventy-one cementless shells of the same design were revised at our institution; forty-six were for aseptic retroacetabular osteolysis. Radiographs and a computer-assisted technique were used to quantify osteolytic areas and percent of shell circumference associated with lesions. Implant stability was confirmed intraoperatively.

Of twenty-six stable and twenty loose shells, the average area of osteolysis on AP radiographs showed no significant difference (Stable 591mm², Loose 630 mm², p greater than 0.05); whereas, lateral radiographs demonstrated a significant difference (Stable 546 mm², Loose 837 mm², p 0.05). The percentage of shell circumference with associated osteolysis on AP and lateral films demonstrated a significant difference (AP: Stable 60, Loose 75, p 0.042; LATERAL: Stable 49, Loose73, p 0.016). Diagnostic criteria of fifty percent shell circumference associated with osteolysis on AP films has sensitivity 1, specificity 0.27 while the same criteria on lateral films has sensitivity 0.84, specificity 0.54 for shell loosening.

Percent of shell circumference with surrounding oste-olysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than fifty percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.

Introduction: Post-operative analgesia using parenteral opioids or epidural analgesia can be associated with troublesome side effects. Good peri-operative analgesia facilitates rehabilitation, improves patient satisfaction and may reduce hospital stay. Locally administered pre-emptive analgesia is effective, reduces central hyper-sensitisation and avoids systemic drug related side-effects and may be of benefit in minimally invasive joint replacement.

Materials and methods: 64 patients undergoing total knee replacement were randomised to receive a peri-articular intra-operative injection containing ropiva-caine, ketorolac, epimorphine and epinephrine. The anaesthetic analgesic regime was standardised. All patients received patient controlled analgesia (PCA) for 24 hours post surgery, followed by standard analgesia. VAS pain scores during activity and at rest and patient satisfaction scores were recorded pre and post operatively and at 6 week follow up. PCA consumption and overall analgesic requirement were measured.

Results: PCA use over 24 hours post surgery was significantly less in patients receiving the injection (P=0.013). Patient satisfaction at 4 hrs post operation was greater (P=0.003). VAS for pain during activity at 4 hrs and 24 hours were significantly less (P=0.001) in the injected group. The average ROM at 6 weeks was no different. Overall hospital stay and the incidence of wound complications was not different between the 2 groups.

Discussion: Peri-articular intra-operative multimodal analgesia significantly reduces post-operative analgesia requirement. Patient satisfaction is greater in the injection group. No cardio and central nervous system toxicity was observed.

Introduction and Aims: To compare the results of patients treated with articulating versus static antibiotic-impregnated spacers for infected knee arthroplasty.

Method: All patients undergoing two-stage revision knee arthroplasty for sepsis in the last five years were reviewed. Twenty-six patients had been treated with articulating spacers. This group was compared to 36 patients treated with static spacers. The articulating spacer technique had been adopted more recently than the static technique. Minimum follow-up was 12 months from second stage re-implantation (average 22 months articulating, 40 months static). Patients were compared in terms of the need for extensile exposures required for re-implantation, range of motion at most recent review, eradication of infection and augmentation required on revision implants.

Results: In the articulating group, fewer extensile exposure methods were required at second-stage prosthesis re-implantation (19% vs 36%). No tibial tuberosity osteotomies have been required since using the articulating spacer. The articulating group demonstrated a significantly improved range of flexion compared to the static group (106 vs 97 degrees – p=0.045) and had fewer patients with significant loss of extension or quadriceps lag. Eradication of infection was improved in the articulating group (92% vs 82%) but at shorter average follow-up. The need for augments and stabilised prostheses at revision surgery as a measure of bone loss was no different between the groups but was related to the number of prior surgical procedures.

Conclusion: Articulating cement spacers facilitate reimplantation surgery by maintaining tissue planes and joint mobility without compromising joint stability or eradication rate of infection. Patients demonstrate better range of motion and less complications related to the extensor mechanism with the articulated spacer.

Introduction and Aims: Cemented femoral revision total hip arthroplasty has been associated with early mechanical failure by aseptic loosening. This study was performed to determine the long-term survival of cemented femoral revision arthroplasty and to identify factors predictive of failure.

Method: One hundred and twenty-nine cemented femoral revision cases were reviewed to determine component survival. Ninety-seven hips with a minimum follow-up of five years were included for survival analysis and tests of significance. Harris hip scores were used to quantify clinical outcomes. Complete radiographic series were reviewed. Kaplan-Meier survival curves were calculated. Clinical and surgical factors were analysed to determine if they were predictive of failure.

Results: Individual Harris hip scores improved to a mean of 71 at the most recent follow-up from a mean pre-operative score of 52 (p< 0.001). Kaplan-Meier survival at 10 years was 91%, with revision for aseptic loosening of the femoral component as the endpoint and 71% with mechanical failure as the endpoint. Patients older than 60 years experienced greater long-term component survival and less pain than patients younger than sixty years (p< 0.05). Good quality post-operative cement mantles were associated with better long-term radiographic fixation (p< 0.001). Poor femoral bone quality was significantly associated with an increased rate of re-revision for aseptic loosening (p=0.021).

Conclusion: Revision femoral THA with cement remains an option in selected patients with acceptable 10-year survival and fair radiographic fixation. Patients demonstrated acceptable clinical outcomes at 10 years and few experienced significant pain. The best results may be achieved in older patients with adequate bone stock and modern cementing techniques.

Introduction and Aims: Problem: The timing of liner exchange for retroacetabular osteolysis in THA remains uncertain. Liner exchange should be done before the shell becomes loose.

Purpose: To determine the radiographic quantity of osteolysis that will predict impending loosening of the cementless shell.

Hypothesis: Osteolytic areas differ between loose and stable shells.

Method: Between 1992 and 2002, 71 cementless shells of the same design were revised at our institution; 46 were for aseptic retroacetabular osteolysis. Radiographs and a computer-assisted technique were used to quantify osteolytic areas and percent of shell circumference associated with lesions. Implant stability was confirmed intra-operatively.

Results: Of 26 stable and 20 loose shells, the average area of osteolysis on AP radiographs showed no significant difference (Stable 591mm2, Loose 630 mm2, p greater than 0.05); whereas, lateral radiographs demonstrated a significant difference (Stable 546 mm2, Loose 837 mm2, p 0.05). The percentage of shell circumference with associated osteolysis on AP and lateral films demonstrated a significant difference (AP: Stable 60, Loose 75, p 0.042; LATERAL: Stable 49, Loose 73, p 0.016). Diagnostic criteria of 50 percent shell circumference associated with osteolysis on AP films has sensitivity 1.0, specificity 0.27, while the same criteria on lateral films has sensitivity 0.84, specificity 0.54 for shell loosening.

Conclusion: Percent of shell circumference with surrounding osteolysis appears to be more predictive of cementless shell loosening than the area of osteolysis. When greater than 50 percent of the shell circumference has osteolysis on AP or lateral films, liner exchange is necessary.

Introduction and Aims: The dilemma to retain or sacrifice the posterior cruciate ligament in a primary total knee arthroplasty continues to be an area of discussion. A randomised clinical trial was performed comparing clinical, radiographic and quality of life outcomes between patients receiving a posterior cruciate sparing versus posterior cruciate substituting knee implants.

Method: A multi-centred, prospective, randomised, blinded, clinical trial was performed to compare posterior cruciate retaining (CR) versus posterior cruciate substitution (PS) in osteoarthritic patients with an intact posterior cruciate ligament, undergoing total knee arthroplasty using the AMK^® (Depuy^®, Warsaw, Indiana) component. One hundred and fifty-two patients were randomised to receive one of the two devices. Patients were evaluated pre-operatively, at three, six, 12 months and annually thereafter. Patient demographics, radiographs, and multiple validated, outcome measures (WOMAC, SF-12, the Knee Society Clinical Rating System, and a stair climbing test) were evaluated. Patients and assessors were blinded to the implant design.

Results: One hundred and fifty-two patients were randomised at three centres; 72 in the CR group and 80 in the PS group. One patient was revised due to instability. Average follow-up was 5.14 years (range 2.97–6.99 years). There were no significant differences in baseline patient demographics between groups. There were no significant differences in outcome measures or radiographic findings. There were no significant differences in the Knee Society Clinical Rating System (CR- 159.18 versus PS- 156.49). There were no differences in knee extension at latest follow-up (CR- 1.02) and (PS- 1.10). There were no differences in knee flexion at latest follow-up (CR-111.00 ) and (PS- 113.61). No differences were noted in the WOMAC and SF-12 scores between the two groups.

Conclusion: In this prospective randomised clinical trial no significant differences involving radiographs and multiple outcome measures could be seen between a cruciate retaining versus a posterior stabilised total knee prostheses at a mean follow-up of 5.14 years. Long-term evaluation is necessary to comment on wear, osteolysis and implant longevity.

Introduction and Aims: Polyethylene wear in total hip arthroplasty (THA) is frequently associated with wellfixed cementless implants. Purpose: To evaluate the clinical and radiographic results of the isolated liner exchange (ILE) procedure in revision THA via the direct lateral surgical approach.

Method: A prospective study of 24 hips that underwent an ILE revision procedure via the direct lateral approach was conducted. Accessible osteolytic lesions were managed with curettage and bone grafting. Clinical data including Harris hip score, WOMAC Index, SF-12, and radiographic analysis were recorded. The area of osteolytic lesions was calculated using a new software program.

Results: This is the first study to our knowledge to report on the results of the ILE procedure performed via the direct lateral surgical exposure. Twenty-three patients underwent 24 revisions with an ILE. At mean follow-up of 40 months, all osteolytic lesions had regressed. Harris hip scores improved from 69 to 83. WOMAC indices improved from 37 to 24. No dislocations have occurred. Two patients have required revision. Isolated liner exchange for polyethylene wear is a promising technique that avoids the removal of well-fixed acetabular implants. The increased dislocation rate associated with this revision THA procedure may be reduced and osteolytic lesions may be successfully debrided and bone grafted through the direct lateral approach.

Conclusion: The ILE procedure, when performed via the direct lateral surgical approach, may reduce the dislocation rate commonly reported via the posterolateral exposure with this procedure. Retention of well-fixed implants and bone grafting preserves bone stock and adequately addresses osteolytic lesions at revision surgery through this exposure.

Introduction and Aims: Polyethylene wear continues to be the most significant issue following total hip arthroplasty (THA), leading to the current increase in use of alternative bearing surfaces. We performed a prospective, randomised, blinded clinical trial comparing metal versus polyethylene bearing surfaces in patients receiving THA.

Method: Forty-one patients were randomised to receive a metal (23) or a polyethylene (18) insert with identical femoral and acetabular components. Patients were evaluated pre-operatively at three, six, 12 months and annually thereafter, including an evaluation of erythrocyte and 24-hour urine cobalt, chromium and titanium metal ion levels, validated outcome measures (WOMAC, SF-12, Harris Hip Score) and radiographs.

Results: No patients were lost to follow-up. One patient died of unrelated causes. At an average 4.4 (range 3.3–5.1) years follow-up there were no differences in any outcome measures or radiographic findings. Patients receiving metal liners had significantly elevated metal ion measurements. At the latest follow-up erythrocyte cobalt levels were seven times elevated (median 1.2μg/l (metal) Vs 0.18μg/l (poly), p< .001). Urine cobalt levels were 41 times elevated (median 11.9μg/day (metal) Vs 0.29μg/day (poly), p< .001) and urine chromium levels were 14 times elevated (median 4.9μg/day (metal) Vs 0.36μg/day (poly), p< .001). Erthrocyte chromium, titanium and urine titanium were not significantly different between groups. As well, contrary to previous reports, there was not a significant trend towards decreasing ion levels over time.

Conclusion: In this prospective randomised blinded clinical trail comparing metal to polyethyle bearing surfaces, both cobalt and chromium ion levels were significantly elevated in the blood and urine of the patients randomised to receive the metal on metal THA.

Introduction and Aims: While highly cross-linked polyethylene has achieved widespread clinical use based on laboratory testing showing significant wear reduction, there is little clinical information demonstrating its benefits in vivo. This study reports the early clinical and wear performance of a prospective randomised controlled trial comparing highly cross-linked to standard polyethylene.

Method: One hundred patients were enrolled in a prospective randomised controlled trial in which all patients received a hybrid THR (cemented Versys stem, Triology cementless acetabulum). The two groups were virtually identical in terms of age, weight, male/female ratio and received identical hip implants, except that one half (50 patients) randomly received a highly cross-linked polyethylene liner. Clinical outcomes were determined using Harris hip, WOMAC and SF-12 scores. Two-dimensional (2D) and three-dimensional (3D) wear rates were determined using a validated radiographic technique based on AP and lateral radiographs at six weeks and one, two and three years post-operatively.

Results: At two years minimum follow-up (range two to four years), there were no differences in Harris hip, WOMAC or SF-12 scores. No patients were lost to follow-up, although five patients had died of unrelated causes. There were no infections, dislocations or revisions to date. Wear analysis at one-year post-op showed high penetration rates for both groups (mean 3D wear approximately 0.25 mm/year) consistent with the bedding-in phenomena. At most recent radiographic follow-up (two or three years), there was a statistically significant although modest difference in wear rates between the two groups with a 2D and 3D wear rate of 0.14±0.10 mm/yr and 0.15±0.02 mm/yr respectively for conventional polyethylene compared to 0.09±0.04 mm/yr and 0.11±0.02 mm/yr for cross-linked polyethylene. This represented a 32 and 29 percent reduction in 2D and 3D wear rates respectively with cross-linked polyethylene.

Conclusion: At early follow-up, there were no clinical differences. There was a modest wear reduction (approximately 30%) with highly cross-linked polyethylene, considerably less than expected based on laboratory testing. Longer follow-up, after the bedding-in process is completed, is required to demonstrate the wear reduction afforded by highly cross-linked polyethylene.

Introduction: A review of the concept of metal-on-metal bearings is presented.

Method: The material is based on a review of the literature and personal experience.

Results: The metal-on-metal bearing couple is enjoying a resurgence in clinical applications seen in both total hip and hip resurfacing technologies. The most significant advantage of a metal-on-metal implant is the improved wear characteristics seen both in vitro on wear simulators and in vivo with retrieved implants. All bearings have disadvantages and a metal-on-metal bearing is no exception. Concerns exist regarding the generation of metal ions seen in both the blood and urine of patients with metal-on-metal implants. These elevated metal ions have theoretical, although not proven, risks related to carcinogenic and biological concerns. In addition, concerns exist regarding hypersensitivity, increased incidence of instability and increased costs. As well, specific patient selection issues arise with metal-on-metal implants and with the current generation of implants only early and mid-term results are available, with no long-term series yet published.

Conclusions: Therefore, while a metal-on-metal bearing may be considered a viable alternative to either polyethylene or ceramic implants, outstanding and unresolved issues continue to exist.

Introduction and Aims: Fixed bearing and mobile bearing knee designs are currently used in clinical practice with little evidence based research available to determine superiority of one system. The purpose of this study was to compare the results between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

Method: We performed a prospective, randomised, blinded clinical trial to compare a mobile bearing to two standard fixed-bearing implants. We evaluated the short- and long-term outcomes of the SAL^® (Sulzer) mobile bearing versus the AMK^® (Depuy) and Genesis II^® (Smith & Nephew) fixed bearing, total knee joint replacements. Ninety patients were randomised to receive one of the three prostheses. Patients were evaluated pre-operatively, at three, 12 months and annually thereafter. Patient demographics, radiographs, and multiple outcome measures (WOMAC, SF-12 and the Knee Society Clinical Rating System) were evaluated. A single observer was used to measure range of motion scores.

Results and Discussion: No patients were lost to follow-up. One patient was withdrawn due to dementia before three months, one patient died prior to the two-year follow-up, and one patient was revised for infection at six months, leaving 87 patients at an average follow-up of 3.37 years (range 2.91–4.44 years). There were no significant differences in any outcome measures or radiographic findings. There were no differences in KSCRS at two years (SAL – 167, AMK – 158, GenesisII – 166 ). There were no differences in WOMAC scores or SF-12 survey scores. There were no differences in knee flexion at two years (SAL – 117^°, AMK – 115^°, GenesisII – 118^°). Therefore, no differences in multiple outcome measures were seen between a cruciate retaining mobile bearing and two cruciate retaining fixed bearing total knee prostheses.

Conclusion: In this prospective randomised clinical trial no differences could be seen between a mobile bearing and two fixed bearing designs at a minimum of two years follow-up. Long-term evaluation will be required to comment on differences in polyethylene wear and implant longevity.

Our aim was to evaluate the functional outcome of extensile revision knee exposure techniques.

166 revision total knee arthroplasties requiring an extensile exposure with 2 year minimum follow-up were prospectively studied {81 rectus snips (RS), 42 tibial tubercle osteotomies (TTO), and 43 quadriceps turn-downs (QT)}. Patients were clinically evaluated for knee society score, range of motion (ROM) and extensor lag comparing pre-op and 24 month follow-up appointment findings. Radiological evidence of avascular necrosis (AVN) pre & post operation was recorded. The TTO group was further examined for proximal migration of the tubercle post op.

Pre-operative knee motion (75° & 71°) and knee scores (74 & 70) were lower in revision total knee arthroplasties requiring QT & TTO than those requiring a RS (91° & 84). Post op flexion and knee scores were greater in the RS group (102° & 131) than in the QT (81° & 114) and TTO (84° & 111) groups in whom there was no significant difference. Avascular necrosis of the patella was most commonly seen following QT. In both QT & TTO groups performing a lateral release was significantly associated with AVN of the patella. Extensor lag (> 10°) was seen only in the QT & TTO groups (11% & 8%) in whom there was no significant difference. Tubercle escape (> 2mm) in the TTO group was significantly greater (54%) in those where circlage wires only had been used than in those where a proximal transfixation wire was used (11%).

In conclusion, both QT & TTO groups had similarly poor knee scores & ROM pre & post operation. AVN of the patella for both groups was similar and significantly associated with performing a lateral release. Finally we would conclude that the use of a through wire significantly reduces tubercle escape in TTO fixation.