Background. Sequentially annealed, highly crosslinked polyethylene (HXLPE) has been used clinically in total knee arthroplasty (TKA) for over a decade[1]. However, little is known about the reasons for HXLPE revision, its surface damage mechanisms, or its in vivo oxidative stability relative to conventional polyethylene. We asked whether retrieved sequentially annealed HLXPE tibial inserts exhibited: (1) similar reasons for revision; (2) enhanced resistance to surface damage; and (3) enhanced oxidative stability, when compared with tibial inserts fabricated from conventional gamma inert sterilized polyethylene (control). Methods. Four hundred and fifty-six revised tibial inserts in two cohorts (sequentially annealed and conventional UHMWPE control) were collected in a multicenter retrieval program between 2000 and 2016. We controlled for implantation time between the two cohorts by excluding tibial inserts with a greater implantation time than the longest term sequentially annealed retrieval (9.5 years). The mean implantation time (± standard deviation) for the sequentially annealed components was 1.9 ± 1.7 years, and for the control inserts, 3.4 ± 2.7 years (Figure 1). Reasons for HXLPE revision were assessed based on medical records, radiographs, and examinations of the retrieved components. Surface damage mechanisms were assessed using the Hood method[2]. Oxidation was measured at the bearing surface, the backside surface, the anterior and posterior faces, as well as the post (when available) using FTIR (ASTM F2102). Surface damage and oxidation analyses were available for 338 of the components. We used nonparametric statistical testing to analyze for differences in oxidation and surface damage when adjusting for polyethylene formulation as a function of implantation time. Results. The tibial inserts in both cohorts were revised most frequently for loosening, infection, and instability. Instability was observed more frequently in inserts without a stabilizing post. In both cohorts, the most commonly observed surface damage mechanisms were burnishing, pitting, and scratching. Delamination was rare and only observed in 2 sequentially annealed inserts and 7 inserts in the control cohort. We observed six cases of posterior condyle fracture, which was always associated with instability (Figure 2). 5/6 of the fracture cases did not have a stabilizing post. Oxidation indices of the sequentially annealed inserts were, on average, low (ASTM oxidation index < 1) and not significantly different than the control inserts on the bearing surface and anterior/posterior face (Figure 3). Discussion. The findings of this study document the reasons for revision, surface damage mechanisms, and oxidative behavior of sequentially annealed HXLPE for TKA. We observed evidence of low in vivo oxidation in both retrieved sequentially annealed HXLPE and control tibial inserts. We found no association between the levels of oxidation and clinical performance of the HXLPE tibial components. However, because of the short-term follow-up, analysis of longer-term retrievals may be appropriate

Source of the study: University of Auckland, Auckland, New Zealand

Unicompartmental knee arthroplasty (UKA) is effective for patients with isolated compartment osteoarthritis, however the procedure has higher revision rates. Long-term survivorship and accurate characterisation of revision reasons are limited by a lack of long-term data and standardised revision definitions. We aimed to identify survivorship, risk factors and revision reasons in a large UKA cohort with up to 20 years follow-up.

Patient, implant and revision details were recorded through clinical and radiological review for 2,137 consecutive patients undergoing primary medial UKA across Auckland, Canterbury, Counties Manukau and Waitematā DHB between 2000 and 2017. Revision reasons were determined from review of clinical, laboratory, and radiological records for each patient using a standardised protocol. To ensure complete follow-up data was cross-referenced with the New Zealand Joint Registry to identify patients undergoing subsequent revision outside the hospitals. Implant survival, revision risk and revision reasons were analysed using Cox proportional-hazards and competing risk analyses.

Implant survivorship at 15 years was comparable for cemented fixed-bearing (cemFB; 91%) and uncemented mobile-bearing (uncemMB; 91%), but lower for cemented mobile-bearing (cemMB; 80%) implants. There was higher incidence of aseptic loosening with cemented implants (3–4% vs. 0.4% uncemented, p<0.01), osteoarthritis (OA) progression with cemMB implants (9% vs. 3% cemFB/uncemMB; p<0.05) and bearing dislocations with uncemMB implants (3% vs. 2% cemMB, p=0.02). Compared with the oldest patients (≥75 years), there was a nearly two-fold increase in risk for those aged 55–64 (hazard ratio 1.9; confidence interval 1.1-3.3, p=0.03). No association was found with gender, BMI or ASA.

Cemented mobile-bearing implants and younger age were linked to lower implant survivorship. These were associated with disease progression and bearing dislocations. The use of cemented fixed-bearing and uncemented mobile-bearing designs have superior comparable long-term survivorship.

Introduction

A key outcome measured by national joint registries are revision events. This informs best practice and identifies poor-performing surgical devices. Although registry data often record reasons for revision arthroplasty, interpretation is limited by lack of standardised definitions of revision reasons and objective assessment of radiologic and laboratory parameters. Our study aim was to compare reasons for unicompartmental knee arthroplasty (UKA) revision reported to the New Zealand Joint Registry (NZJR) with reasons identified by independent clinical review.

The 2021 Australian Orthopaedic Association National Joint Replacement Registry report indicated that total shoulder replacement using both mid head (TMH) length humeral components and reverse arthroplasty (RTSA) had a lower revision rate than stemmed humeral components in anatomical total shoulder arthroplasty (aTSA) - for all prosthesis types and diagnoses. The aim of this study was to assess the impact of component variables in the various primary total arthroplasty alternatives for osteoarthritis in the shoulder. Data from a large national arthroplasty registry were analysed for the period April 2004 to December 2020. The study population included all primary aTSA, RTSA, and TMH shoulder arthroplasty procedures undertaken for osteoarthritis (OA) using either cross-linked polyethylene (XLPE) or non-cross-linked polyethylene (non XLPE). Due to the previously documented and reported higher revision rate compared to other anatomical total shoulder replacement options, those using a cementless metal backed glenoid components were excluded. The rate of revision was determined by Kaplan-Meir estimates, with comparisons by Cox proportional hazard models. Reasons for revision were also assessed. For a primary diagnosis of OA, aTSA with a cemented XLPE glenoid component had the lowest revision rate with a 12-year cumulative revision rate of 4.7%, compared to aTSA with cemented non-XLPE glenoid component of 8.7%, and RTSA of 6.8%. The revision rate for TMH was lower than aTSA with cemented non-XLPE, but was similar to the other implants at the same length of follow-up. The reason for revision for cemented aTSR was most commonly component loosening, not rotator cuff deficiency. Long stem humeral components matched with XLPE in aTSA achieve a lower revision rate compared to shorter stems, long stems with conventional polyethylene, and RTSA when used to treat shoulder OA. In all these cohorts, loosening, not rotator cuff failure was the most common diagnosis for revision

Source of the study: University of Auckland, Auckland, New Zealand and University of Otago, Christchurch, New Zealand. Outcomes following knee arthroplasty are typically defined as implant survivorship at defined timepoints, or revision incidence over time. These estimates are difficult to conceptualise, and lack context for younger patients with more remaining years of life. We therefore aimed to determine a ‘lifetime’ risk of revision as a more useful metric for total (TKA) and unicompartmental knee arthroplasty (UKA). The New Zealand Joint Registry was used to identify 96,497 primary TKAs and 13,481 primary UKAs performed between 1999 and 2019. Patient mortality and revision incidence were also extracted. Estimates of lifetime risk were calculated using an actuarial lifetable method. The estimates were stratified by age and gender. Reasons for revision were categorised using previously published standardised definitions. The lifetime risk of UKA revision was two-fold higher than TKA across all age groups (range 3.7-40.4% UKA, 1.6-22.4% TKA). Revision risk was higher for males with TKA (range 3.4%-25.2% males, 1.1%-20% females), but higher for females with UKA (range 4.3%-43.4% vs. 2.9%-37.4% for males). Revision due to infections were higher for TKA (1.5% males, 0.7% females) compared with UKA (0.4% males, 0.1% females). The increased risk in younger UKA patients was associated with higher incidence of aseptic loosening (UKA 2%, TKA 1%) and ‘unexplained pain’ (UKA 2%, TKA 0.2%). The risk for UKA was two-fold higher than TKA, and this was partially explained by a higher proportion of revisions due to ‘unexplained pain’. For TKA, males had higher risk of revision, in contrast to UKA where females had higher risk; this gender difference was associated with higher incidence of infections with TKA. Younger age, gender and higher ASA status were also associated with increased lifetime risk of UKA revision. Lifetime risk of revision can provide a meaningful measure of arthroplasty outcomes to aid patient counselling

Introduction. Dual mobility (DM) total hip arthroplasty (THA) prostheses are designed to increase stability. In the setting of primary and revision THA, DM THA are used most frequently for dysplasia and instability diagnoses, respectively. As the use of DM THA continues to increase, with 8,031 cases logged in the American Joint Replacement Registry from 2012–2018, characterizing in vivo damage and clinical failure modes are important to report. Methods. Under IRB-approved implant retrieval protocol, 43 DM THA systems from 41 patients were included. Each DM THA component was macroscopically examined for standard damage modes. Clinically-relevant data, including patient demographics and surgical elements, were collected from medical records. Fretting and corrosion damage grading is planned, according to the Goldberg et al. classification system. Results. In this 43-retrieved implant series, there were 23 female and 17 male patients (n=1, unknown), with an average body mass index of 29 (range, 19–49), and average ages at index and revision of 63 years (range, 34–80) and 64 years (range, 38–88), respectively. The average duration of implantation was 12.9 months (range, 0.1–72.0). Reasons for revision included infection (n=11, 26%), mechanical complication (n=10, 23%), intraprosthetic dislocation (n=6, 14%), periprosthetic fracture (n=5, 12%), pain (n=4, 9%), acetabular-associated loosening (n=3, 7%), unknown (n=3, 7%), hematoma (n=2, 5%), leg length discrepancy (n=1, 2%), and inflammatory reaction (n=1, 2%); some cases included multiple reasons for revision. On articular surfaces, scratching was the most commonly observed damage mode on all components, with more than 40% of acetabular cup and femoral heads showing scratching damage (Figure 1A). Abrasion, burnishing, and pitting damage were also observed in more than 10% of acetabular cup and acetabular liner components; further, approximately 20% of polyethylene acetabular liners exhibited edge deformation damage. On backside surfaces, polyethylene acetabular liners showed the greatest damage, with more than 60% of components exhibiting abrasion, scratching, or pitting damage (Figure 1B). Conclusion. This series showed various reasons for revision as well as in vivo damage of retrieved DM systems following short-to-midterm implantation. Damage was observed on both articular and backside surfaces of the five components of DM THA. Modularity of DM THA prostheses may amplify rates of in vivo damage. Future studies are needed to confirm these results and clinical significance. For any figures or tables, please contact the authors directly

Aim. Aim of the study was to find out whether patients with positive minor criteria but without meeting the MSIS definition have a difference in the outcome after revision-surgery compared to patients without any MSIS-criteria? And does the reason for revision-surgery (eg. loosening) have an additional influence on the outcome parameters in patients with positive minor criteria?. Method. A retrospective matched-pair analysis with 98 patients who had undergone revision-surgery after TJA was performed. Forty-nine patients who showed 1 to 3 positive minor criteria (PMC) whereas 49 patients without any positive minor criteria (aseptic complications control group) were compared regarding re-revision-rate and revision-free survival. Patients were matched regarding sex, age, joint and comorbidities using the classification system by McPherson et al. Reasons for revisions were categorized in loosening, body wear, periprosthetic fracture/mechanical failure and soft-tissue complication. Endpoints were defined as re-revision for any cases. Results. In the group of patients with PMC 30.6% (n=15) had to undergo re-revision compared to 6.12% (n=3) in the true aseptic complication (AC) control group. The overall-survival in the PMC-group was 69.4% (95% CI: 47–69 months) and in the AC-group 93.9% (95% CI: 82–94 months) (p=0.001). In patients with PMC but not exchange of the implant the overall-survival was 94.1% (95%CI survival time: 71–88 months) and in comparison the cohort with exchange of the prosthesis showed an overall-survival of 56.25% (95% CI survival time: 29–53 months) (p=0.008). Conclusions. Our findings suggest that in dependence of the occurrence of prosthetic loosening even single positive minor-criteria may have an impact on the outcome after THA- and TKA revision-surgeries

Introduction. A modern total knee replacement system was introduced in 2012 in order to improve the mechanics of total knee replacement (TKR). The purpose of this study was to assess the early clinical and radiographic outcomes of patients who have been treated with this modern TKR system at two years postoperatively. Methods. Patients who received this TKR system between June of 2012 and September of 2014 were included in this prospective registry-based follow-up study. Demographics, component, and surgical data were collected. Radiographic outcomes were also assessed. Patient reported outcome measures (PROMs) of all patients with 2-year follow-up data were collected. Reasons for revision and overall survival at 2-years were evaluated. Results. The study population consisted of 290 patients (307 knees). The mean age was 66 years and 61% were women. 250 patients received cruciate retaining and 57 patients posterior stabilized implants. The median tibiofemoral axis was in 4° valgus and the femoral component was in 5° valgus and 2° flexion. The median coronal and sagittal alignment of the tibial component was −1° varus and −5° slope, respectively. Most patients had tibial components that fit the tibial resection. At one year, 7 of 80 knees had a radiolucency in the tibia or femur. At two years, two of 30 knees had a radiolucency in the tibia or femur. Mean PROMs for thirty-six patients at two years were: EQ-5D WHI 0.76 (range 0.31–1.00), EQ-5D VAS 82 (range 48–98), UCLA activity score 5.3 (range 2–10), KOOS pain 70.9 (22–100), symptoms 69 (14–96), ADL 74.2 (18–100), sports 51.4 (0–100), and QoL 59.8 (0–90). Cumulative 2-year implant survival was 97.1%. There were 7 revisions for infection and 2 revisions due to an unsatisfactory clinical outcome. Conclusion. Clinical and radiographic outcomes at two years were good, and overall implant survival was excellent

The inmate population is a unique cohort with several healthcare-related challenges. International studies have demonstrated higher rates of infectious diseases, chronic diseases and psychiatric disorders in inmates when compared to general population. However, little is known about the outcomes following total joint arthroplasty in this population. This retrospective chart review aims to outline the differences in clinical outcomes after hip and knee total joint arthroplasty in the Kingston inmate population compared to the national population standard. A list of all inmate inpatient hospital visits with diagnostic/procedure codes pertaining to total joint arthroplasty within the last ten years was obtained through a computer-based search of the Kingston General Hospital Discharge Abstract Database(DAD). The patient charts were reviewed and demographic and outcome data pertinent to our study was collected. Data was compiled using Excel and imported into IBM SPSS for descriptive analysis. Twenty male inmate patients underwent 24 primary Total Hip Arthroplasties(THA) or Total Knee Arthroplasties(TKA) and one medial unicompartmental knee arthroplasty from May 2003 to January 2013. The average age was 58 with mean Body Mass Index(BMI) of 34. Median American Society of Anesthesiologist(ASA) score was 3 and mean Charlston Comorbidity Index was 3.92. The rates of HCV and HIV were 35%(n=5) and 0%, respectively. Average length of stay from time of initial procedure was 4.2 days. The overall revision rate was 24% (n=6). Reasons for revision included deep prosthetic infection (50%, n=3), aseptic loosening (17%, n=1), arthrofibrosis (17%, n=1) and late periprosthetic fracture (17%, n=1). Infection rates were reported at 16% (n=4); 75% of which were deep prosthetic infections requiring revision surgery. Other complications included ST-elevation myocardial infarction(STEMI) (n=1), and postoperative knee stiffness requiring manipulation under anesthesia(MUA) (n=1). Compared to Correctional Services Canada(CSC) data on male inmate health in 2012, our study population demonstrated a higher rate of HCV (35% vs. 9.4%), diabetes (30% vs. 4.2%) and overall cardiovascular and respiratory comorbidities. This may reflect the higher rate of comorbidities associated with osteoarthritis, such as BMI>25, which was evident in 95% of our study population vs. 64.5% in Canadian inmates. Total joint revision rates in our inmate study population was 24%, which is higher than the 2014 Canadian Joint Replacement Registry's yearly revision rate of 8.7% in THA and 5.2% in TKA. Our study population also demonstrated infection as the leading cause for revision at 50%, compared to 14.5% for THA and 19.6% for TKA in the general Canadian population. Further study of the complex biopsychosocial risk factors in the inmate population is warranted to better define pre-surgical risk assessment criteria

Purpose. Traditional total knee arthoplasty techniques have involved implantation of diaphyseal stems to aid in fixation expecially when using constrained polyethylene inserts. While the debate over cemented vs uncemented stems continues, the actual use of stems is considered routine. The authors' experience with cemented stemmed knee revisions in older patients with osteoporotic bone has been favorable. Our younger patients with press-fit stems from varying manufacturers have been plagued with a relatively high incidence of component loosening and stem tip pain in the tibia and occasionally thigh. We report the early results of the first 20 total knee revisions using press-fit metaphyseal filling sleeved stemless implants with constrained bearings. Methods. Twenty three patients with failed primary or revision total knees were assigned to receive stemless sleeved revision knee designs using the DePuy MBT/TC3 system. Reasons for revision included loosening, implant fracture, stiffness, instability, and stem pain. Twenty patients (ages ranging from 42–73) were successfully reconstructed without stems. Six knees with significant uncontained cavitary defects were included. Three patients with unexpectedly osteoporotic metaphyseal bone were revised with cemented stemmed implants and excluded. All cases used cement for initial fixation on the cut bone surface and fully constrained mobile bearing inserts. Results. Follow up ranged from six months to three years. All patients had radiographic evidence of well fixed stable implants on most recent examination. All four cases of revision for “end of stem pain” had complete resolution of symptoms within two weeks of revision surgery. Long leg anterior posterior mechanical alignment x-rays measured within two degrees of neutral in all cases. Knee Society Scores improved an average of 34 points. Clinical results for revision for stiffness had the lowest final scores post operatively. Conclusion. Stemmed total knee arthroplasty revision implants with or without cement are considered the standard for most revision reconstructions. Recently, primary total hip replacements using newer short metaphyseal stems have shown promising early clinical results. This case series of twenty total knee revisions using stemless press-fit metaphyseal sleeves shows similarly favorable outcomes. The complications of stemmed implants such as stem tip pain and difficulty of cemented stem removal can be avoided successfully in non-osteporotic bone reconstructions. With stable bony ingrowth visible on early post-operatyive radiographs, long term stable fixation even with constrained bearings is expected. Longer follow up will be needed to validate this technique for routine use

Introduction. Total hip arthroplasties in younger patients often requires revision because these patients frequently have acetabular deficiencies, which hamper proper implantation of the cup essential for good long-term prosthesis survival. For 30 years, we have used a biological acetabular-reconstruction technique with bone-impaction grafting in all patients <50 years with an acetabular deficiency at surgery, always in combination with a cemented total hip implant. Methods. We evaluated all 150 consecutive patients (177 hips) < 50 years with an acetabular reconstruction by bone-impaction grafting surgically-treated from 1978–2004 at our clinic. Mean follow-up was 10.3 (range, 2.0–28.3) years with no patient lost to follow-up. Mean index surgery age was 38.1 (range, 16–49) years. Clinical, radiological, and statistical analysis of all patients was performed. Results. Twenty-eight of 177 hips were revised at a mean of 10.5 years (range, 5 days to 23.2 years). Reasons for revision were: aseptic loosening (n=17), septic loosening (n=3), recurrent dislocations (n=3), traumatic loosening (n=2), neuropathy (n=1), wear (n=1), and fracture (n=1). Ten-year and 15-year survival with endpoint revision of any component for any reason was 91% and 78%. Ten-year survival with endpoint aseptic loosening was 96% for the cup and 97% for the stem. Conclusion. Performing a total hip implant in combination with acetabular bone impaction grafting in younger patients with acetabular bone stock loss seems to be an attractive approach as the long-term results are acceptable and fulfill the NICE-criteria, showing a ten -year survival of more than 90% with endpoint revisions for any reason

Current evidence suggests that we should be moving away from Thompson's hemiarthroplasties for patients with intracapsular hip fractures. Furthermore, the use of cement when inserting these prostheses is controversial. This study aims to show the Inverness experience. We performed a retrospective review of all NHS Highland patients who underwent a hemiarthroplasty for an intracapsular neck of femur fracture over the last 15 years. Demographics and the use of cement were documented. Further analysis of this group was performed to identify any of these patients who required revision of their prosthesis. Patients requiring revision had their case-notes reviewed to identify the cause for further surgery. From 1996 until present 2221 patients from the Highland area had a hemiarthroplasty for an intracapsular neck of femur fracture. 1708 where female (77%) and 513 male (23%). The ages ranged from 28 years to 104 years (mean 80 years, median 81). 2180 of this group had their operations in Raigmore Hospital with the remaining 41 at various centres throughout Scotland. 623 (28%)had a cemented hemiarthroplasty, with the remaining 1578 (72%) having an uncemented Thompson's hemiarthroplasty. The revision rate for the cemented group was 2% (13 of 623 patients). In the uncemented group it was 0.4% (6 of 1578). Reasons from revision included dislocation, periprosthetic fracture, infection and pain. Current evidence from some joint registers regarding the use of Thompson's hemiarthroplasty in the elderly is discouraging. The use of bone cement in this group with multiple co-morbidities is not without it's risks. Our data suggests that uncemented Thompson's hemiarthroplasties in low demand elderly patients with multiple co-morbidities can yield excellent results with less risk to the patients

Background. Reasons for revision of metal-on-metal hip resurfacing arthroplasty (MoMHRA) have evolved with improving surgical experience and techniques. Early revisions were often due to fracture of the femoral neck while later revisions are associated with loosening and/or adverse local tissue reactions (ALTR) to wear debris. In some studies, revisions of MoMHRA with ALTR have been complicated by an increased risk of rerevision and poor outcome. The purpose of this study was to investigate the causes of failure and to identify factors that improve outcome following revision of a failed HRA. Methods. From 2001 to May 2015, 180 consecutive HRA revisions were performed in 172 patients. Ninety-nine primary surgeries were done at a HRA specialist centre (99/4211, revision rate: 2.4%), 81 elsewhere. Eight different HRA designs were revised mainly in females (60%). Components’ orientation was measured from radiographs using EBRA. Ion levels were used as a diagnostic tool since 2006 (n=153). Harris-Hip-Score (HHS) was obtained prerevision and at latest follow-up. The initial experience of the first 42 cases (Initial Group) was compared to cases 43–180 (Later Group). Patients of the Later group were noted to have less soft tissue damage, had significantly bigger THA heads implanted at surgery, were educated of the increased complication risk and some wore an abduction brace for 6 weeks. Results. All patients presented with some pain/discomfort. Mean time to revision was 38 months (0–160). Eight HRAs were revised for fracture and 8 for infection. The most common reason for revision was component malpositioning (acetabular 48%, excessive abduction and/or anteversion; femoral 10%) usually associated with high metal ions (62%). The most common intra-operative finding was ALTR (48%) followed by metallosis (36%) and impingement (29%). Metal sensitivity was suspected in 8 patients (6F/2M). There were gender-specific differences in component sizes and causes of failure, with a higher incidence of component malpositioning, osteolysis and elevated metal ions in women. Time to revision in patients with high metal ion levels was shorter with the ASR (21 months, SD:10) in comparison to the BHR (38 months, SD: 25) (p=0.05). For the whole cohort, HHS significantly improved post revision (93, 42–100) (p<0.001). Fourteen complications (9 dislocations; 5 infections) and 9 re-revisions occurred. Outcome {HHSpost-op (p=0.04), complication and re-revision rates (p=0.005)} was significantly better in the Later Group compared to the Initial group. The incidence of complications/re-revisions significantly reduced since the introduction of metal ions (p=0.004). The presence of ALTR did not significantly affect outcome (p=0.65). However, patients with ALTR in the Later group (n=51) had significant reduced complication(p=0.005) and re-revision(p=0.016) rates in comparison to those in the Initial Group. Conclusion. Component malpositioning is the most common cause of HRA failure. Metal ion measurements are an excellent tool to detect wear at an early stage. The revision analysis highlights the importance of surgical experience, indications and prosthesis design. Use of ion levels, big THA-heads and patient education/compliance were identified as factors improving outcome following HRA revision. Patients with soft tissue reactions can have good outcome if operated prior to extensive soft tissue destruction

Background. Unicompartmental knee arthroplasty provides a good alternative to total knee arthroplasty in patients with isolated medial compartment osteoarthritis. Reported ten-year survival for the Oxford medial unicompartmental knee arthroplasty is variable, ranging from 80.2% to 97.7% in the originator series. The aim of this study was to determine the survival and reasons for revision of the Oxford medial unicompartmental knee arthroplasty when performed at a specialist orthopaedic centre. Methods. Details of consecutive patients undergoing Oxford unicompartmental knee arthroplasty at our centre between January 2000 and December 2009 were collected prospectively. Failure of the implant was defined as conversion to total knee arthroplasty. Survival was determined using the Kaplan-Meier method. Results. There were 494 Oxford unicompartmental knee arthroplasties implanted in 425 patients for isolated medial compartment osteoarthritis. Mean age was 62.8 yrs (range 34.6-90.1 yrs) and 53.4% were female. During a mean follow-up time of 3.0 yrs (range 0.5-9.2 yrs), twenty-two knees (4.5%) were revised to a total knee arthroplasty. Reasons for revision were aseptic loosening of the femoral (n=8) or tibial component (n=2), undiagnosed pain (n=5), patellofemoral pain (n=2), infection (n=1), lateral meniscus tear (n=1), periprosthetic fracture (n=1), joint instability (n=1), and dislocation of meniscal bearing (n=1). Mean time to revision surgery from the primary procedure was 3.0 yrs. Eight-year survival for the cohort was 87.4%. The median pre-operative Oxford knee score was 62.5% which reduced to 27.7% at four years post-operatively. Conclusion. This study has demonstrated our revision rate for the Oxford unicompartmental knee replacement is comparable to independent series and national registry data. Post-operative function in patients not revised was good. The commonest reason for failure was aseptic component loosening which usually occurred within two to four years. Extended follow-up may therefore be beneficial in these patients so these cases are identified early and subsequently revised

Introduction. Modularity is being increasingly used throughout the world for both primary and revision total hip arthroplasty. Recently there have been concerns of increased corrosion and fretting at the modular junctions. In the SROM® modular hip system, two modular junctions are the head-neck taper junction and the stem-sleeve taper junction. The aim of this study was to investigate corrosion at these junctions with the use of different bearing materials. Methods. Between 1994 and 2012, fourty-two patients were revised with SROM® stems. Reasons for revision included aseptic loosening of the cup or stem (11), periprosthetic fracture (2), osteolysis (8), dislocation (13) and other reasons (7). One was revised for stem breakage, and this was excluded from this study. We examined 41 retrieved S-ROM® comprised of 6 metal-on-metal (MOM), 12 metal-on-polyethylene (MOP), 7 ceramic-on-polyethylene (COP) and 16 ceramic-on-ceramic (COC). The orientation for all components was marked at the time of revision surgery. Both the proximal sleeve/stem and the femoral head-neck modular junctions were examined under 10X magnification, and graded by two independent observers. The head tapers were divided into 4 regions, and graded using a previously published 3 point scoring system for fretting and corrosion damage (Goldberg et al, Kop et al), for a total corrosion damage score of 12. The SROM stems were also assessed at the sleeve/stem taper junction. Each stem was divided into 8 quadrants, and graded for corrosion and fretting using the same system as the taper. In addition to severity, we also quantified area of corrosion damage of the stem at the sleeve-stem junction from 0–3, which was multiplied by the severity of damage, to give a score out of 9 for each quadrant (maximum total score of 72 for the stem). The bearing type was unknown to the investigators, so the grading was done in a blinded fashion. Corrosion scores were divided by time to account for differences in time to revision. Results. Corrosion at the head-neck taper junction was higher for 17 stems with metal heads compared to 23 stems with ceramic heads (p=0.008). The average corrosion rate at the stem-sleeve taper junction in hips with hard-on-hard bearings (COC and MOM) was higher than polyethylene (MOP and COP) bearings, but this was not significant (p=0.07). Conclusions. Corrosion at the head-neck modular junction of hips with metal heads was greater than ceramic heads, likely due to galvanic corrosion in a mixed-metal system. Greater corrosion was found at the stem-sleeve taper junction in stems with hard-on-hard bearings. This may be related to friction in the bearings

Wear of the polyethylene (PE) insert in total knee replacements can lead to wear-particle and fluid-pressure induced osteolysis. One major factor affecting the wear behaviour of the PE insert in-vivo is the surface characteristics of the articulating femoral components. Contemporary femoral components available in Canada are either made of cast Cobalt Chromium (CoCr) alloy or have an oxidized zirconium surface (Oxinium). The latter type of femoral components have shown to have increased abrasive wear resistance and increased surface wettability, thus leading to reduced PE wear in-vitro compared with conventional cast CoCr components. Although surface damage has been reported on femoral components in general, there have been no reports in the literature as to what extent the recommended operating techniques affect the surface tribology of either type of femoral component. Twenty-two retrieved total knee replacements were identified with profound surface damage on the posterior aspect of the femoral condyles. The femoral components were of three different knee systems: five retrievals from the NexGen(r) total knee system (Zimmer Inc., Warsaw, IN), twelve retrievals from the Genesis II(r) total knee system (CoCr alloy or Oxinium; Smith & Nephew Inc., Memphis, TN), and five retrievals from the Duracon(r) total knee system (Stryker Inc., Mahwah, NJ). Reasons for revision were all non-wear-related and included aseptic loosening in two cases, painful flexion instability, and chronic infection. All retrieved femoral components showed evidence of surface damage on the condyles, at an average of 99° flexion (range, 43° – 135° flexion). Titanium (Ti) alloy transfer and abrasive surface damage were evident on all retrieved CoCr alloy femoral components that came in contact with Ti alloy tibial trays. Surface damage on the retrieved Oxinium femoral components was gouging, associated with the removal and cracking of the oxide and exposure of the zirconium alloy substrate material. CoCr alloy femoral components that had unintended contact with CoCr alloy tibial trays also showed evidence of gouging and abrasive wear. All femoral components showed severe surface damage in the posterior aspect of the condyles. The femoral surface was heavily scratched and the oxidized zirconium coating surface appeared removed. The surface analysis suggested that the surface damage most likely occurred during the time of initial implantation. In particular, it appeared that the femoral condyles were resting on the posterior aspect of the tibial tray in flexion, thus scratching the femoral components. Such scratches could potentially lead to accelerated PE insert wear and reduced implant longevity, thus making expensive revisions surgery necessary. The authors strongly suggest a revision of the current operating techniques recommended by the implant manufacturer to prevent this type of surface damage from occurring

Purpose:. Acetabular bone loss during revision total hip arthroplasty (THA) poses a challenge for reconstruction as segmental and extensive cavitary defects require structural support to achieve prosthesis stability. Trabecular metal (TM) acetabular augments structurally support hemispherical cups. Positive short-term results have been encouraging, but mid- to long-term results are largely unknown. The purpose of this study was to determine the continued efficacy of TM augments in THA revisions with significant pelvic bone loss. Methods:. Radiographs and medical records of 51 patients who had undergone THA revision with the use of a TM augment were retrospectively reviewed. Acetabular defects were graded according to the Paprosky classification of acetabular deficiencies based on preoperative radiographs and operative findings. Loosening was defined radiographically as a gross change in cup position, change in the abduction angle (>5°), or change in the vertical position of the acetabular component (>8 mm) between initial postoperative and most recent follow-up radiographs (Figure 1). Results:. Eleven patients had incomplete radiographic follow-up and were excluded. The study population included 17 men and 23 women, averaging 68.1 ± 14.1 years of age (range, 37–91), with average radiographic follow-up of 19.0 months (range, 2.4–97.4). Reasons for revision included osteolysis (n = 20, 38.5%), component loosening (n = 18, 15.4%), and periprosthetic fracture (n = 6, 11.5%). All patients underwent revision THA using a TM multi-hole revision acetabular cup and TM acetabular augment(s) to fill bony defects. Morcellized allograft was used in 9 patients. There were 33 Paprosky Type IIIA and seven Paprosky Type IIIB defects. One patient with Paprosky Type IIIB had catastrophic failure of the reconstructive construct three months postoperatively. The remaining 39 acetabular revisions demonstrated signs of bony ingrowth at the latest follow-up. There were no radiolucent lines suggestive of loosening, and no significant differences in abduction angle (p = 0.78), vertical distance between the superolateral edge of the cup and the trans-ischial reference line (p = 0.96), or the vertical distance between the center of the femoral head and trans-ischial reference line (p = 0.75) between the initial postoperative and most recent follow-up radiographs (Figure 2). Discussion and Conclusion:. Achieving fixation and long-term stability in THA revisions with segmental and/or cavitary bone loss is challenging. TM augments provide a modular structural system to achieve bony ingrowth, while avoiding large structural allografts, cages, and custom implants. At latest follow-up, 39 revision hips remained well-fixed with no evidence of loosening. One patient with a significant surgical history of infection, periprosthetic femur fracture, and 2 prior revision surgeries before acetabular reconstruction had an early clinical failure. Trabecular metal augments can be used for reconstruction of acetabular bone loss with good mid-term results. Continued follow-up is warranted for radiographic evaluation of bony integration and implant stability to determine long-term survivorship of these implants