We recently performed a clinical trial comparing motor sparing blocks (MSB) to periarticular infiltration (PAI) following total knee arthroplasty (TKA). We found that MSBs provided longer analgesia (8.8 hours) than PAI with retention of quadriceps strength, and with similar function, satisfaction, and length of hospital stay. However, its potential increased cost could serve as a barrier to its adoption. Therefore, our aim was to compare the costs of MSBs to PAI following TKA.

We conducted a retrospective review of data from our previous RCT. There were 82 patients included in the RCT (n=41 MSB group, n=41 PAI group). We compared the mean total costs associated with each group until hospital discharge including intervention costs, healthcare professional service fees, intraoperative medications, length of stay, and postoperative opioid use.

Seventy patients were included (n=35 MSB group, n=35 PAI group). The mean total costs for the MSB group was significantly higher ($1959.46 ± 755.4) compared to the PAI group ($1616.25 ± 488.33), with a mean difference of $343.21 (95% CI = $73.28 to $664.11, p = 0.03). The total perioperative intervention costs for performing the MSB was also significantly higher however postoperative inpatient costs including length of stay and total opioid use did not differ significatnly.

Motor sparing blocks had significantly higher mean total and perioperative costs compared to PAI with no significant difference in postoperative inpatient costs. However, its quadricep sparing nature and previously demonstrated prolonged postoperative analgesia can be used to facilitate an outpatient TKA pathway thereby offsetting its increased costs.

Total knee arthroplasty is a successful procedure that reduces knee pain and improves function in most patients with knee osteoarthritis. Patient dissatisfaction however remains high, and along with implant longevity, may be affected by component positioning. Surgery in obese patients is more technically challenging with difficulty identifying appropriate landmarks for alignment and more difficult exposure of the joint. Patient specific instrumentation (PSI) has been introduced with the goal to increase accuracy of component positioning by custom fitting cutting guides to the patient using advanced imaging. A strong criticism of this new technology however, is the cost associated. The purpose of this study was to determine, using a prospective, randomized-controlled trial, the cost-effectiveness of PSI compared to standard instrumentation for total knee arthroplasty in an obese patient population.

Patients with a body mass index greater than 30 with osteoarthritis and undergoing a primary total knee arthroplasty were included in this study. We randomized patients to have their procedure with either standard instrumentation (SOC) or PSI. At 12-weeks post-surgery patients completed a self-reported cost questionnaire and the Western Ontario and McMaster Osteoarthritis Index (WOMAC). We performed a cost-effectiveness analyses from a public health payer and societal perspective. As we do not know the true cost of the PSI instrumentation, we estimated a value of $100 for our base case analysis and used one-way sensitivity analyses to determine the effect of different values (ranging from $0 to $500) would have on our conclusions.

A total of 173 patients were enrolled in the study with 86 patients randomized to the PSI group and 87 to the SOC group. We found the PSI group to be both less effective and more costly than SOC when using a public payer perspective, regardless of the cost of the PSI. From a societal perspective, PSI was both less costly, but also less effective, regardless of the cost of the PSI. The mean difference in effect between the two groups was −1.61 (95% CI −3.48, 026, p=0.091). The incremental cost-effectiveness ratio was $485.71 per point increase in the WOMAC, or $7285.58 per clinically meaningful difference (15 points) in the WOMAC.

Overall, our results suggest that PSI is not cost-effective compared to standard of care from a public payer perspective. From a societal perspective, there is some question as to whether the decreased effect found with the PSI group is worth the reduced cost. The main driver of the cost difference appears to be time off of volunteer work, which will need to be investigated further. In future, we will continue to follow these patients out to one year to collect cost and effectiveness data to investigate whether these results remain past 12 weeks post-surgery.

Increasing pressure to use rapid recovery care pathways when treating patients undergoing total hip arthroplasty (THA) is evident in current health care systems for numerous reasons. Patient autonomy and health care economics has challenged the ability of THA implants to maintain functional integrity before achieving bony union. Although collared stems have been shown to provide improved axial stability, it is unclear if this stability correlates with activity levels or results in improved early function to patients compared to collarless stems. This study aims to examine the role of implant design on patient activity and implant fixation. The early follow-up period was examined as the majority of variation between implants is expected during this time-frame.

Patients (n=100) with unilateral hip OA who were undergoing primary THA surgery were recruited pre-operatively to participate in this prospective randomized controlled trial. All patients were randomized to receive either a collared (n=50) or collarless (n=50) cementless femoral stem. Patients will be seen at nine appointments (pre-operative, < 2 4 hours post-operation, two-, four-, six-weeks, three-, six-months, one-, and two-years). Patients completed an instrumented timed up-and-go (TUG) test using wearable sensors at each visit, excluding the day of their surgery. Participants logged their steps using Fitbit activity trackers and a seven-day average prior to each visit was recorded. Patients also underwent supine radiostereometric analysis (RSA) imaging < 2 4 hours post-operation prior to leaving the hospital, and at all follow-up appointments.

Nineteen collared stem patients and 20 collarless stem patients have been assessed. There were no demographic differences between groups. From < 2 4 hours to two weeks the collared implant subsided 0.90 ± 1.20 mm and the collarless implant subsided 3.32 ± 3.10 mm (p=0.014). From two weeks to three months the collared implant subsided 0.65 ± 1.54 mm and the collarless implant subsided 0.45 ± 0.52 mm (p=0.673). Subsidence following two weeks was lower than prior to two weeks in the collarless group (p=0.02) but not different in the collared group. Step count was reduced at two weeks compared to pre-operatively by 4078 ± 2959 steps for collared patients and 4282 ± 3187 steps for collarless patients (p=0.872). Step count increased from two weeks to three months by 6652 ± 4822 steps for collared patients and 4557 ± 2636 steps for collarless patients (p=0.289). TUG test time was increased at two weeks compared to pre-operatively by 4.71 ± 5.13 s for collared patients and 6.54 ± 10.18 s for collarless patients (p=0.551). TUG test time decreased from two weeks to three months by 7.21 ± 5.56 s for collared patients and 8.38 ± 7.20 s for collarless patients (p=0.685). There was no correlation between subsidence and step count or TUG test time.

Collared implants subsided less in the first two weeks compared to collarless implants but subsequent subsidence after two weeks was not significantly different. The presence of a collar on the stem did not affect patient activity and function and these factors were not correlated to subsidence, suggesting that initial fixation is instead primarily related to implant design.

HXLPE acetabular liners were introduced to reduce wear-related complications in THA. However, post-irradiation thermal free radical stabilization can compromise mechanical properties, leave oxidation-prone residual free radicals, or both. Reports of mechanical failure of HXLPE acetabular liner rims raise concerns about thermal free radical stabilization and in vivo oxidization on implant properties. The purpose of this study is to explore the differences in the mechanical, physical and chemical properties of HXLPE acetabular liner rims after extended time in vivo between liners manufactured with different thermal free radical stabilization techniques.

Remelted, single annealed and sequentially annealed retrieved HXLPE acetabular liners with in vivo times greater than 4.5 years were obtained from our implant retrieval laboratory. All retrieved liners underwent an identical sanitation and storage protocol. For mechanical testing, a total of 55 explants and 13 control liners were tested. Explant in vivo time ranged from 4.6 – 14 years and ex vivo time ranged from 0 – 11.6 years. Rim mechanical properties were tested by microindentation hardness testing using a Micromet II Vickers microhardness tester following ASTM standards. A subset of 16 explants with ex vivo time under one year along with five control liners were assessed for oxidation by FTIR, crystallinity by Raman spectroscopy, and evidence of microcracking by SEM.

No significant difference in in vivo or ex vivo was found between thermal stabilization groups in either set of explants studied. In the mechanically tested explants, there was no significant correlation between in vivo time and Vickers hardness in any thermal stabilization group. A significant correlation was found between ex vivo time and hardness in remelted liners (r=.520, p = .011), but not in either annealed cohort. ANCOVA with ex vivo time as a covariate found a significant difference in hardness between the thermal free radical stabilization groups (p 0.1) was found in retrieved remelted (25%), single annealed (100%) and sequentially annealed (75%) liner rims. Crystallinity was increased in the subsurface region relative to control liners for both annealed, but not remelted, liner rims. Hardness was increased in oxidized rims for both annealed cohorts but not in the remelted cohort. Microcracking was only found along the surface of one unoxidized remelted liner rim.

Mechanical properties were reduced at baseline and worsened after in vivo time for remelted HXLPE liner rims. Rim oxidation was detected in all groups. Oxidation was associated with increased crystallinity and hardness in annealed cohorts, but not remelted liners. Increased crystallinity and oxidation do not appear to be directly causing the worsened mechanical behavior of remelted HXLPE liner rims after extended in vivo time.

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).

Closed ankle fractures have been reported to account for 10% off all fractures presenting to the Emergency Department. Many of these injuries require acute surgical management either via direct admission or through defined outpatient surgical pathways. While both methods have been shown to be safe, few studies have examined the cost effectiveness of each clinical scenario. The purpose of this study is to compare cost and resource utilization associated with inpatient and outpatient ankle fracture surgery at a Canadian academic institution.

This is a retrospective chart review of patients who underwent acute ankle fracture surgery at London Health Sciences Centre between 2016 and 2018. Thirty patients who underwent inpatient ankle surgery for closed, isolated ankle fractures at University Hospital were compared to 30 consecutive patients who underwent outpatient ankle surgery for similar fractures at Victoria hospital. Data pertaining to age at time of surgery, sex, BMI, fracture type, operating/recovery room time, and length of hospital stay were collected. All emergency room visits, readmissions and complications within 30 days of surgery were also recorded.

Inpatient and outpatient cohorts were similar with respect to average age (48 vs. 44, P=0.326) and body mass index (29.8 vs. 29.1, P=0.741). There was a greater proportion of patients with an American Society of Anesthesia (ASA) Classification of 3 or greater in the inpatient surgery group (48% vs. 23%). The inpatient group spent an average of 1.2 days in hospital while waiting for surgery and a average of 72 hours in hospital for their entire surgical encounter. The outpatient group spent an average of eight days (at home) waiting for surgery while spending an average of 7.4 hours in hospital during their entire surgical encounter. Outpatient ankle fracture surgery was associated with a cost savings of 35.9% in comparison to inpatient ankle fracture surgery (P < 0 .001). There were no significant differences in the rates of emergency room visits, readmissions, or complications between cohorts.

Preliminary findings suggest that outpatient ankle fracture surgery is appropriate for most patients, requires less hospital resources and is associated with similar rates of readmission and complications as inpatient surgery. An established outpatient surgical pathway may offer significant cost savings in the treatment of the common closed ankle fracture that requires surgical intervention.

During revision total knee arthroplasty (rTKA), proximal tibial bone loss is frequently encountered and can result in a less-stable bone-implant fixation. A 3D printed titanium alloy (Ti6Al4V) revision augment that conforms to the irregular shape of the proximal tibia was recently developed. The purpose of this study was to evaluate the fixation stability of rTKA with this augment in comparison to conventional cemented rTKA.

Eleven pairs of thawed fresh-frozen cadaveric tibias (22 tibias) were potted in custom fixtures. Primary total knee arthroplasty (pTKA) surgery was performed on all tibias. Fixation stability testing was conducted using a three-stage eccentric loading protocol. Static eccentric (70% medial/ 30% lateral) loading of 2100 N was applied to the implants before and after subjecting them to 5×103 loading cycles of 700 N at 2 Hz using a joint motion simulator. Bone-implant micromotion was measured using a high-resolution optical system. The pTKA were removed. The proximal tibial bone defect was measured. One tibia from each pair was randomly allocated to the experimental group, and rTKA was performed with a titanium augment printed using selective laser melting. The contralateral side was assigned to the control group (revision with fully cemented stems). The three-stage eccentric loading protocol was used to test the revision TKAs. Independent t-tests were used to compare the micromotion between the two groups.

After revision TKA, the mean micromotion was 23.1μm ± 26.2μm in the control group and 12.9μm ± 22.2μm in the experimental group. There was significantly less micromotion in the experimental group (p= 0.04). Prior to revision surgery, the control and experimental group had no significant difference in primary TKA micromotion (p= 0.19) and tibial bone loss (p= 0.37).

This study suggests that early fixation stability of revision TKA with the novel 3D printed titanium augment is significantly better then the conventional fully cemented rTKA. The early press-fit fixation of the augment is likely sufficient for promoting bony ingrowth of the augment in vivo. Further studies are needed to investigate the long-term in-vivo fixation of the novel 3D printed augment.

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.

Introduction

Surgeons performing a total knee replacement (TKR) have two available techniques available to help them achieve the proper bone resections and ligament tension – gap balancing (GB) and measured resection (MR). GB relies on balancing ligaments prior to bony resections whereas bony resections are made based on anatomical landmarks in MR. Many studies have been done to compare the joint kinematics between the two techniques, however the results have been varied. These studies were not done with anatomically designed prostheses. The Journey II (Smith & Nephew, Memphis, TN) is one such design which attempts to mimic the normal knee joint structure to return more natural kinematics to the joint, with emphasis on eliminating both paradoxical anterior motion and reduced posterior femoral rollback. Given the design differences between anatomical and non-anatomical prostheses, it is important to investigate whether one technique provides superior kinematics when an anatomical design is used. We hypothesize that there will be no difference between the two techniques.

Objective

Wearable sensors have enabled objective functional data collection from patients before total knee replacement (TKR) and at clinical follow-ups post-surgery whereas traditional evaluation has solely relied on self-reported subjective measures. The timed-up-and-go (TUG) test has been used to evaluate function but is commonly measured using only total completion time, which does not assess joint function or test completion strategy. The current work employs machine learning techniques to distinguish patient groups based on derived functional metrics from the TUG test and expose clinically important functional parameters that are predictive of patient recovery.

Introduction

Infections affect 1–3% of Total Knee Arthroplasty (TKA) patients with severe ramifications to mobility. Unfortunately, reinfection rates are high (∼15%) suggesting improved diagnostics are required. A common strategy to treat TKA infection in North America is the two-stage revision procedure involving the installation of a temporary spacer in the joint while the infection is treated for 6–12 weeks before permanent revision. Subdermal temperature increases during infection by 1–4°C providing a potential indicator for when the infection has been cleared. We propose an implantable temperature sensor integrated into a tibial spacer for telemetric use. We hypothesized that suitable sensing performance for infection monitoring regarding precision and relative accuracy can be attained using a low power, compact, analog sensor with <0.1ºC resolution.

Introduction

HXLPE acetabular liners were introduced to reduce wear-related complications in THA. However, post-irradiation thermal free radical stabilization can compromise mechanical properties, leave oxidation-prone residual free radicals, or both. Reports of mechanical failure of HXLPE acetabular liner rims raise concerns about thermal free radical stabilization and in vivo oxidization on implant properties. The purpose of this study is to explore the differences in the mechanical, physical and chemical properties of HXLPE acetabular liner rims after extended time in vivo between liners manufactured with different thermal free radical stabilization techniques.

Introduction

A total knee arthroplasty (TKA) is the standard of care treatment for end-stage osteoarthritis (OA) of the knee. Over the last decade, we have observed a change in TKA patient population to include younger patients. This cohort tends to be more active and thus places more stress on the implanted prothesis. Bone cement has historically been used to establish fixation between the implant and host bone, resulting in two interfaces where loosening may occur. Uncemented fixation methods provide a promising alternative to cemented fixation. While vulnerable during the early post-operative period, cementless implants may be better suited to long-term stability in younger patient cohorts. It is currently unknown whether the surgical technique used to implant the cementless prostheses impacts the longevity of the implant. Two different surgical techniques are commonly used by surgeons and may result in different load distribution across the joint, which will affect bone ingrowth. The overall objective of the study is to assess implant migration and in vivo kinematics following cementless TKA.

Background

There is increasing impetus to use rapid recovery care pathways when treating patients undergoing total hip arthroplasty (THA). The direct anterior (DA) approach is a muscle sparing technique that is believed to support these new pathways. Implants designed for these approaches are available in both collared and collarless variations and understanding the impact each has is important for providing the best treatment to patients.

Introduction

Despite improvements in the survivorship of total knee replacements (TKR) over the years, patient satisfaction following TKR has not improved, with approximately 20% of patients recording dissatisfaction with their new knee joint. It is unclear why many patients feel this way, but it may relate in part to implant designs that do not provide a “natural” feeling knee. Implant manufacturers continue to introduce new concepts for implant design, which are essential for reaching the goal of a “normal” knee after TKR surgery. The Journey II TKR (Smith & Nephew) was developed with this goal in mind. Its anatomical design attempts to mimic the normal knee joint structure to return more natural kinematics to the joint, with emphasis on eliminating both paradoxical anterior motion and reduced posterior femoral rollback. Our objective is to examine patients receiving the Journey II TKR to measure the knee joint contact kinematics of the Journey II TKR compared to a non-anatomically designed implant by the same manufacturer. We hypothesize that the Journey II TKR will have more natural contact kinematics that differ from the non-anatomically designed implant.

Introduction

Total hip arthroplasty (THA) is the most effective treatment modality for severe arthritis of the hip. Patients report excellent clinical and functional outcomes following THA, including subjective improvement in gait mechanics. However, few studies in the literature have outlined the impact of THA, as well as surgical approach, on gait kinetics and kinematics.

Purpose

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 baseplate is affected by the locking mechanism design and can further increase backside wear. This study's purpose was to examine modern locking mechanisms influence, in the setting of both polished and non-polished tibial baseplates, on backside tibial polyethylene damage and wear.

Background

Surgeons generally perform total knee replacement using either a gap balancing or measured resection approach. In gap balancing, ligamentous releases are performed first to create an equal joint space before any bony resections are performed. In measured resection, bony resections are performed first to match anatomical landmarks, and soft tissue releases are subsequently performed to balance the joint space. Previous studies have found a greater rate of coronal instability and femoral component lift-off using the measured resection technique, but it is unknown how potential differences in loading translate into component stability and fixation.

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.

Introduction

Anterior knee pain following total knee arthroplasty continues to be prevalent and may result from abnormal loading of the patellofemoral joint. The kinematics and biomechanics of the patellofemoral joint are complex, and trochlear design likely plays a principle role in affecting patellofemoral contact. As such, understanding the implications of trochlear design on patellofemoral contact remains important. The goal of the present study was to characterize trochlear wear of retrieved femoral components, which may help elucidate the details regarding patellofemoral kinematics and contact properties in relation to design features.

Introduction

Complications related to the patellofemoral joint continue to be a substantial source of patient morbidity, causing anterior knee pain, instability, and dysfunction following total knee arthroplasty. One of the principle factors affecting patellofemoral outcomes may be trochlear design. The optimal design is currently unknown. The purpose of the present study was to study patellofemoral joint contact by analysing areas of wear in retrieved femoral components of three modern designs.

Background

Total hip arthroplasty (THA) has become one of the most commonly performed elective procedures. Today, there are nearly 50 000 annual hospitalizations for hip replacement surgery in Canada. This number is projected to increase significantly with the aging population. Periprosthetic joint infection (PJI) is the 3rd leading cause of failure following THA and is reported to occur at an incidence of 1–3%. A two-stage revision THA is the current gold standard treatment and this has a tremendous economic impact on the healthcare system. The purpose of this study is to create an accurate cost estimate of two-stage revision THA and, in turn, evaluate the economic burden of PJI as it compares to primary THA in a Canadian healthcare context.

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.

The purpose of our study was to prospectively examine early functional differences in gait between the direct anterior and direct lateral surgical approaches for total hip arthroplasty over the first three months postoperatively.

Forty participants were prospectively enrolled to either the direct anterior (20 patients) or direct lateral group (20 patients) based on their surgeon's expertise. Outcome measures were collected preoperatively at their preadmission appointment and postoperatively at discharge from the hospital, two weeks, six weeks and three months. We used the GAITRite® system to measure gait velocity, stride length, single-limb support and single-limb support symmetry. We also had participants complete the Timed Up and Go test and a series of questionnaires at each visit: WOMAC, SF-12, Harris Hip Score, and pain VAS.

Our primary outcome, gait velocity, was significantly greater in the direct anterior group at discharge and six weeks postoperatively with adjusted mean differences of 0.12m/s and 0.17m/s respectively. Single-limb support symmetry was also significantly better in the direct anterior group at two weeks, six weeks and three months with adjusted mean differences of 0.10, 0.09 and 0.04 respectively. The direct anterior group also had significantly shorter times to complete the Timed Up and Go test at two and six weeks with adjusted mean differences of −9.02s and −2.64s. There were no differences between the groups at any time point for the WOMAC, SF-12, Harris Hip Score, or pain VAS.

Preliminary results of our expertise-based study have found the direct anterior approach to total hip arthroplasty offers better early functional outcomes than the direct lateral approach.

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.

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.

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.

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 purpose of this study was to determine the effect of sectioning the relevant soft tissues and a TKA on the medial and lateral knee joint gap.

Twelve intact lower extremity cadaveric specimens (mean (SD) age 76.5 (11.6) years) were tested. A custom designed knee tensioner was developed that allowed the separate application of forces to the medial and lateral components of the knee. The distance between the bottom of the load cell and the top of a compression rod was measured with digital calipers (precision = 0.1mm). Loads of 100N and 200N were then applied to each compartment and the resulting displacement was measured. The two loads were applied to the knee in the following conditions: i) All soft tissues intact; ii) an arthrotomy; iii) ACL sectioned; iv) PCL sectioned; v) release of the mid-coronal tissues; and vi) TKA. Finally, tensions were applied for all conditions from 90° to 0° of knee flexion in 30° increments.

There was a significant effect of soft tissue release on the magnitude of the gap at the 100N load application, such that there was an increase in the when the mid-coronal MCL release was performed compared to the intact (2.2mm) and arthrotomy (1.75mm) conditions. With respect to the 200N load application there was a statistically significant tissue release effect, where differences were detected between the mid-coronal MCL release and intact (3.04mm) and arthrotomy conditions (2.31mm). At the 100N load there was a significance increase in the gap compared to the intact knee. There was also a significant condition by knee angle interaction where the gap was approximately 4mm larger following the TKA compared to the intact condition when the knee was flexed at 90°. Furthermore, there was a statistically significant 4.8mm and 3.8mm difference between 90° and 0° and 60° and 0° of knee flexion respectively, for the TKA condition only. At the 200N load application the gap width increased significantly by 2.5mm following the TKA. Finally, there was a significant condition by knee angle interaction where the change in gap width increased significantly from the intact (7.54mm) to the TKA condition (13.88mm) at 90° of knee flexion. There was a statistically significant difference in the TKA condition between 60° and 0° of knee flexion.

Releasing the soft tissues increases the gap between the tibia and femur, when compared to the intact condition, with significance occurring only following the mid-coronal release. Furthermore, the TKA did not return the knee to its intact state as was evident by the significant difference between the TKA and intact conditions. This suggests that the resulting kinematics may not accurately match those pre-surgery resulting in un-physiological motion patterns and the possibility of early failure and revision.

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.

Radiostereometric analysis (RSA) has become the gold standard technique for measuring implant migration and wear following joint replacement due to its high measurement precision and accuracy. However, RSA is conventionally performed using two oblique radiographic views with the presence of a calibration cage. Thus, a second set of radiographs must be acquired for clinical interpretation, for example anterior-posterior and cross-table lateral views following total hip arthroplasty (THA). We propose a modification to the RSA setup for examining THA, in which RSA measurements are performed from anterior-posterior and lateral views, with the calibration cage images acquired separately from the patient images. The objective of the current study was to compare the accuracy and precision of the novel technique to the conventional technique using a phantom.

X-ray cassette holders were developed to enable simultaneous acquisition of anterior-posterior and cross-table lateral radiographs with the patient in a supine position in the RSA suite. A Sawbones phantom with total hip implant components was attached to a micrometer-driven stage. The femoral component was translated known distances relative to the acetabular cup in all planes, mimicking head penetration due to wear. Double RSA examinations were acquired for each increment using the traditional and novel radiograph orientations. Translations were measured from the radiographic images using RSA software. For both techniques, accuracy was calculated by comparing the measured translations to the known translation from the micrometer, and reported as the 95% confidence interval. Precision was measured by comparing the measured translations between the double exams, and reported as the standard deviation.

Accuracy was greater for the conventional technique in the inferior-superior axis (p = 0.03), greater for the novel technique in the anterior-posterior axis (p = 0.01), and equivalent in the medial-lateral axis (p = 0.06). Overall accuracy for both the conventional and novel techniques was identical at ±0.022 mm. Precision was equivalent between both techniques for the medial-lateral (p = 0.68), inferior-superior (p = 0.14), and anterior-posterior axes (p = 0.86). Overall precision for the conventional technique was ±0.127 mm and for the novel technique was ±0.095 mm.

Utilising standard clinical radiograph view angles within an RSA exam had no detrimental effect on wear measurement accuracy or precision. This reduces the barriers to implementing RSA imaging in routine follow-up of arthroplasty patients, potentially greatly increasing the numbers of patients that can have quantitative data on implant performance. Future applications can involve applying more clinically relevant radiograph view angles to RSA exams of the knee and shoulder.

Total hip arthroplasty (THA) is the most effective treatment modality for severe arthritis of the hip. Patients report excellent clinical and functional outcomes following THA, including subjective improvement in gait mechanics. However, few studies in the literature have outlined the impact of surgical approach on gait kinetics and kinematics. The purpose of this study was to determine the impact of surgical approach for THA on quantitative gait analysis.

Thirty patients undergoing THA for primary osteoarthritis of the hip were assigned to one of three surgical approaches (10 anterior, 10 posterior, and 10 lateral). A single surgeon performed each individual approach. Each patient received standardised implants at the time of surgery (cementless stem and acetabular component, cobalt chrome femoral head, highly cross-linked liner). Patients underwent 3D gait analysis pre-operatively, and at 6- and 12-weeks following the procedure. At each time point, temporal gait parameters, kinetics, and kinematics were compared. Statistical analysis was performed using one-way analysis of variance.

All three groups were similar with respect to age (p=0.27), body mass index (p=0.16), and the Charlson Comorbidity Index (p=0.66). Temporal parameters including step length, stride length, gait velocity, and percent stance and swing phase were similar between the groups at all time points. The lateral cohort had higher pelvic tilt during stance on the affected leg than the anterior cohort at 6-weeks (p=0.033). Affected leg ipsilateral trunk lean during stance was higher in the lateral group at 6-weeks (p=0.006) and 12-weeks (p=0.037) compared to the other cohorts. The anterior and posterior groups demonstrated an increased external rotation moment at 6-weeks (p=0.001) and 12-weeks (p=0.005) compared to the lateral group.

Although temporal parameters were similar across all groups, some differences in gait kinematics and kinetics exist following THA using different surgical approaches. However, the clinical relevance based on the small magnitude of the differences remains in question.

The direct anterior (DA) approach for total hip arthroplasty (THA) has become increasingly popular in North America. With experience, exposure of both the acetabulum and femur can be achieved similar to those in other approaches. In cases of difficult femoral exposure, the conjoint tendon of the short external rotators can be released to improve visualisation. The effect of conjoint tendon release has not been previously explored in regards to overall outcomes, or postoperative pain. The goal of this study was to evaluate 1) the length of stay and inpatient pain medication requirements of patients undergoing DA THA on the basis of conjoint tendon release, and 2) whether conjoint tendon release influenced functional outcomes.

We conducted a retrospective chart review of all cases of primary DA THAs conducted by single surgeon at LHSC University between August 2012 and July 2015. Patient demographics, bilateral THA cases, intraoperative conjoint tendon or other soft tissue releases, intra-operative complications, and length of stay (LOS) were evaluated for all cases. Inpatient pain medication data was available for all cases from Apr 2014 onwards. One year functional outcome scores, including WOMAC and Harris Hip Scores (HHS), were evaluated for all cases before August 2014. Six-week and three-month functional outcome scores were available and evaluated for a subset of cases. All data was analysed with multiple linear regression.

Three hundred and twelve cases of primary DA THAs were identified, of which 29 were concurrent bilateral THAs. One hundred and eighty cases included a conjoint tendon release, while 29 cases had other soft tissue releases (tensor fascia lata). Mean age and BMI were 64.9±11.5 years and 29.0±5.3 respectively. Mean LOS was 1.3±1.1 days, with age, bilateral THA, non-conjoint tendon soft tissue release, and intra-operative complications being predictive of LOS (p<0.05). Pain medication data was available for 107 cases, of which 11 were concurrent bilateral THAs. Sixty four cases included a conjoint tendon release, while one case had other soft tissue releases. Mean daily morphine equivalent dose (MED) narcotic use was 43.2±48.2mg, with age being a negative predictor of narcotic use (p<0.05). BMI was a negative predictor of one year HHS pain, HHS total, and all WOMAC subcategory scores, while age was a negative predictor of one year HHS function and HHS total scores (p<0.05). None of the variables were predictive of six-week and three-month functional outcome scores. Conjoint tendon release was not predictive of LOS, inpatient pain medication requirements, or outcome scores.

Conjoint tendon release did not affect postoperative pain, LOS, or functional outcomes. Given that conjoint release improves femoral exposure, intraoperative thresholds for conjoint release should be low. The effect of intraoperative release of other soft tissues is uncertain, as this increased LOS but not postoperative pain.

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.

Total hip arthroplasty (THA) has become one of the most commonly performed elective procedures. Today, there are nearly 50 000 annual hospitalisations for hip replacement surgery in Canada. This number is projected to increase significantly with the aging population. Periprosthetic joint infection (PJI) is the 3rd leading cause of failure following THA and is reported to occur at an incidence of 1–3%. A two-stage re-vision THA is the current gold standard treatment and this has a tremendous economic impact on the healthcare system. The purpose of this study is to create an accurate cost estimate of two-stage revision THA and, in turn, evaluate the economic burden of PJI as it compares to primary THA in a Canadian healthcare context.

We conducted a retrospective review of primary THA cases and two-stage revision THA for PJI at our institution. Patients were matched for age and BMI. We recorded all costs associated with each procedure, including: OR time, equipment, length of hospital stay, readmission rates, and any other inpatient resource use. Unit costs were obtained using administrative data from the case costing department at London Health Sciences Centre. Billing fees associated with the procedure were obtained from the Ontario Schedule of Benefits. Descriptive statistics were used to summarise the demographic characteristics of patients, hospital costs and resource use data. Patients with PJI were compared to the matched cohort of primary THA using the t-test (for continuous variables), and the chi-square test (for categorical variables).

Twenty consecutive cases of revision THA were matched to 20 patients who underwent uncomplicated primary THA between 2006 and 2014. Periprosthetic infection was associated with a significant increase in hospital stay (26.5 vs. 2.0; p<0.001), clinic visits (9.5 vs. 3.8; p<0.001), readmission rates (12 vs. 1; p<0.001) and overall cost ($39 953 vs. $7 460; p<0.001) in comparison to the primary arthroplasty cohort.

Two-stage revision for infected THA is a significant economic burden to the healthcare system. Our data suggests a 5-fold increase in healthcare cost when compared to primary THA. This may be an important consideration when distributing resources among Canadian tertiary care centres.

Introduction

Total hip arthroplasty (THA) is a commonly performed surgical procedure for the treatment of hip arthritis. Approximately 50,000 THAs are performed annually in Canada. The costs incurred to the healthcare system are tremendous, amounting to anywhere between 4.3 and 7.3 billion dollars each year. Despite the substantial financial burden of THA to the Canadian healthcare system, few studies have provided accurate cost estimations of this procedure.

Background

Fractures of the femoral component are well reported complications that present a challenging task in revision total hip arthroplasty. Albeit being uncommon, with an incidence of 0.23–11%, the consequences can be devastating. Its extraction being a demanding undertaking that is potentially detrimental to the remaining host bone. Several techniques have been described to address this complex issue prior to revision: drilling of the exposed part of the femoral stem and attaching a threaded extraction device, surface undercutting with an extraction device wedged in, femoral trephine techniques, creation of a femoral cortical window, an extended femoral osteotomy procedure, as well as extraction by means of retrograde nail impaction. Here we present the modified technique we employed in the revision of a failed cementless extensively porous coated femoral component that had fractured at the neck-stem interface.

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.

Increased modularity of total hip arthroplasty components has occurred, with theoretical advantages and disadvantages. Recent literature indicates the potential for elevated revision rates of modular neck systems and the potential for metallosis and ALVAL (Aseptic Lymphocyte dominated Vasculitis Associated Lesion) formation at the modular neck/stem site. Retrieval analysis of one modular neck implant design including SEM (Scanning Electron Microscopy) assessment was done and correlated to FEA (Finite Element Analysis) as well as clinical features of patient demographics, implant and laboratory analysis. Correlation of the consistent corrosion locations to FEA indicates that the material and design features of this system may result in a biomechanical reason for failure. The stem aspect of the modular neck/stem junction may be at particular risk.

Introduction

Fast track arthroplasty regimens require preservation of motor power to perform early rehabilitation and ensure early discharge (1). Commonly performed nerve blocks like femoral and Sciatic nerve blocks results in motor weakness thereby interfering with early rehabilitation and may also predispose to patient falls (2, 3). Hence, targeting the terminal branches of the femoral and sciatic nerves around the knee joint under ultrasound is an attractive strategy. The nerve supply of interest for knee analgesia are the terminal branches of the femoral nerve, the genicular branches of the lateral cutaneous nerve of thigh, obturator and sciatic nerves (4).

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.