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.

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.

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.

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.

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.

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.

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.

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.

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.

Purpose: Unicompartmental knee arthroplasty remains a viable treatment modality for arthrosis confined to the medial compartment of the knee. Few studies have reported survivorship of this procedure into the second decade. The purpose of this study was to report our long-term experience with this procedure at a mean follow-up of fifteen years.

Method: Between 1989 and 2000, 113 medial unicompartmental knee arthroplasties in 84 patients were performed using the Miller-Galante prosthesis. The 84 patients had an average age of 68 years old at the time of surgery; 45 of which were male and 39 female. At a mean of fifteen-year follow-up, 22 patients (25 arthroplasties) had died, and the remaining 62 patients (88 arthroplasties) were reviewed and evaluated. No patient was lost to follow-up.

Results: The mean Knee Society knee and function scores had an improvement from 53 and 48 points pre-operatively to 77 and 90 points respectively at time of most recent evaluation. Twenty unicompartmental knee arthroplasties were revised, at an average of seven years (one to fourteen) following index procedure. The five, ten and fifteen-year rates of survival were 94%, 90%, and 86% respectively with revision to tricompartmental knee arthroplasty as the end point.

Conclusion: The Miller-Galante medial unicompartmental knee arthroplasty provided excellent pain relief and restoration of function in carefully selected patients and demonstrated durable implant survival at fifteen years. Progression of arthrosis is the primary mode of failure.