Long-term outcomes of revision total hip arthroplasty with the Zimmer Modular Revision hip system

Aims

There are limited long-term studies reporting on outcomes of the Zimmer Modular Revision (ZMR) stem, and concerns remain regarding failure. Our primary aim was to determine long-term survival free from all-cause revision and stem-related failure for this modular revision stem in revision total hip arthroplasty (THA). Secondary aims included evaluating radiological and functional outcomes.

Methods

We retrospectively identified all patients in our institutional database who underwent revision THA using the ZMR system from January 2000 to December 2007. We included 106 patients (108 hips) with a mean follow-up of 14.5 years (2.3 to 22.3). Mean patient age was 69.2 years (37.0 to 89.4), and 51.9% were female (n = 55). Indications for index revision included aseptic loosening (73.1%), infection (16.7%), fracture (9.3%), and stem fracture (0.9%). Kaplan-Meier analysis was used to determine the all-cause and stem-related failure revision-free survival. At most recent follow-up, Oxford Hip Scores (OHS) were collected, and radiological stem stability was determined using the Engh classification.

Results

A total of 17 hips (15.7%) underwent re-revision of any component. Indications for re-revision were stem failure (35.3%; n = 6), infection (29.4%; n = 5), instability (29.4%; n = 5), and acetabular aseptic loosening (5.9%; n = 1). The five- and 15-year all-cause survival was 89.7% (95% confidence interval (CI) 86.7 to 92.7) and 83.3% (95% CI 79.6 to 87.0), respectively. There were six re-revisions (5.6%) for stem failure; five for stem fracture and one for aseptic loosening. The five- and 15-year survival free from stem-related failure was 97.2% (95% CI 95.6 to 98.8) and 94.0% (95% CI 91.6 to 96.4), respectively. At final follow-up, the mean OHS was 36.9 (8.0 to 48.0) and 95.7% (n = 66) of surviving modular revision stems were well-fixed in available radiographs.

Conclusion

Femoral revision with the ZMR offers satisfactory long-term all-cause revision-free survival, good survival free of stem-related failure, and favourable clinical outcomes. Stem fracture was the most common reason for stem-related failure and occurred both early and late. This highlights the importance of both early and long-term surveillance for stem-related failure.

Navigated Versus Conventional Total Knee Arthroplasty: A Systematic Review and Meta-analysis of Prospective Randomized Controlled Trials

Background

Recent evidence on the cost-effectiveness of technology in total knee arthroplasty (TKA) demonstrated that navigated computer-assisted methods (N-TKA) is likely to be most cost-effective in the clinical setting. The aim of the current meta-analysis is to compare radiographic, clinical and functional outcomes between conventional TKA (C-TKA) and N-TKA methods.

Methods

All prospective randomized controlled trials (pRCTs) comparing primary TKA performed using C-TKA and N-TKA techniques were eligible for inclusion. Radiographic outcomes included postoperative coronal, sagittal and axial component alignment. Clinical outcomes included all-cause revision and aseptic revision. Functional outcomes were analyzed when reported. A random-effects meta-analysis of all available cases was performed. This allowed for all missing data.

Results

Normal coronal mechanical alignment of the tibial (p < 0.001) and femoral (p = 0.001) components was achieved more frequently with N-TKA. Normal sagittal mechanical alignment of the tibial component was achieved significantly more with N-TKA (p < 0.010). There was no difference in short-term clinical survivorship (all-cause, p = 0.649; aseptic, p = 0.79) or in functional outcomes reported between groups. There was a clinically significant reduction in the mean C-TKA operative time (87 min, σ = 16.6, 95% CI 76.4-98.8) compared N-TKA (97.6 min, σ = 16.9, 95% CI 86.2-109.1) (p = 0.17).

Conclusion

Navigated TKA achieves superior radiographic alignment for femoral and tibial components in both the coronal and sagittal plane. Operative times are 10 min longer in the N-TKA group. Functional outcomes are similar between navigated and conventional groups. Clinical outcomes reported in Level I studies are limited to short-term follow-up so future prospective studies are required.

Articulating Spacers in Total Hip Arthroplasty: Surgical Technique and Outcomes

Although one-stage exchange arthroplasty is gaining popularity, two-stage exchange arthroplasty remains the gold standard for the treatment of periprosthetic joint infections. Use of an articulating spacer for this procedure offers an avenue for maintaining hip motion and controlled weight-bearing, allowing local antibiotic elution. However, there is no uniform consensus on the optimal surgical protocol for using articulating spacers. This review describes the surgical technique for undertaking a first-stage exchange arthroplasty using an articulating spacer and discusses the pertinent literature on key concepts relating to periprosthetic joint infections in total hip arthroplasty to guide effective surgical decision making in these patients.

Porous Tantalum Metaphyseal Cones for Severe Femoral and Tibial Bone Defects in Revision Total Knee Arthroplasty are Reliable for Fixation at Mean 5-Year Follow-Up

BACKGROUND

Porous tantalum metaphyseal cones may facilitate reconstructions of severe bone defects during revision total knee arthroplasty (TKA), but there remains a paucity of data on their outcomes at mean 5 years of follow-up. This study reports the component survivorship, patient satisfaction, functional outcomes, radiographic osseointegration, and complications of revision TKA with porous tantalum metaphyseal cones at mid-term (mean 5-year) follow-up.

METHODS

This study included 152 patients who had a mean age of 66 years (range, 33 to 86 years) undergoing revision TKA with porous tantalum metaphyseal cones. Indications for surgery included aseptic loosening (n = 87, 57.3%), second-stage reimplantation for infection (n = 42, 27.6%), osteolysis with well-fixed components (n = 20, 13.2%), and periprosthetic fracture (n = 3, 2.0%). Component survivorship, clinical outcomes, radiographic outcomes, and any complications were recorded. The mean follow-up time was 5.6 years (range, 2.2 to 13.7).

RESULTS

Survivorship was 100% when the end point was revision of the metaphyseal cone (no cones were revised) and 83.8% (95% confidence interval: 77.9 to 90.2%) when the end point was reoperation for any reason at 5-year follow-up. Reoperations were performed for infection (n = 10), instability (n = 4), periprosthetic fracture (n = 2), and quadriceps rupture/dehiscence (n = 3). The mean patient satisfaction score was 78.8 ± 11.3 and the mean Forgotten Joint Score was 62.2 ± 16.7 at the final follow-up. The preoperative median University of California at Los Angeles score improved from 2 (interquartile range 2 to 3) to 6 points (interquartile range 5 to 6) (P < .001), and the preoperative Oxford knee score improved from 15.2 ± 3.8 to 39.4 ± 5.1 points (P < .001) at the final follow-up. All metaphyseal cones showed radiographic evidence of osteointegration without any subsidence or loosening.

CONCLUSIONS

Porous tantalum metaphyseal cones enabled robust reconstructions of severe femoral and tibial bone defects during revision TKA. These reconstructions were associated with excellent survivorship, improvements in functional outcomes, and reproducible radiographic osseointegration at mean 5-year follow-up. The most common reasons for reoperation were infection and instability.

Clinical Outcomes and Risk Factors for Re-Revision Due to Trunnion Corrosion in Primary Metal-on-Polyethylene Total Hip Arthroplasty

BACKGROUND

There is a paucity of literature regarding the mid-term (greater than 2 years) outcomes of revision for adverse local tissue reaction (ALTR) to metal debris due to corrosion at the head-neck junction (trunnionosis) in metal-on-polyethylene (MoP) total hip arthroplasty (THA), and risk factors for re-revision remain largely unknown. We aimed to report the re-revision-free survival and functional outcomes for this patient population and to identify risk factors for re-revision.

METHODS

A total of 80 hips (79 patients) with a MoP THA who had undergone revision for trunnionosis at our institution were included. The mean study follow-up from index trunnionosis revision was 4.6 years (range, 2.0 to 9.4). Kaplan-Meier survival analysis was performed with all-cause re-revision as the endpoint, and multivariate logistic regression was used to identify risk factors for re-revision.

RESULTS

We saw that twenty-one hips (26%) underwent re-revision at a mean of 8.0 months (range, 0.03 to 36.3) after the index trunnionosis revision, most commonly for instability and infection. The two- and five-year all-cause re-revision-free survival rates were 75.0 and 73.2%, respectively. The mean Oxford Hip Score was 33.7 (range, 11 to 48); 76% were satisfied, and 24% were dissatisfied with their hip. Multivariate analysis identified not undergoing a cup revision (Odds Ratio (OR) 4.5, 95% Confidence Interval (CI) 1.03 to 19.7) and time from primary THA to the index trunnionosis revision (OR 0.77, 95% CI 0.62 to 0.97) as risk factors for undergoing re-revision.

CONCLUSION

The risk of early re-revision for these patients is high (26%), mostly due to infection and instability, and functional outcomes are fair. Not performing a cup revision appears to be a risk factor for re-revision, as is the shorter time from primary THA to trunnionosis revision.

Treatment of femoral bone loss in revision total hip arthroplasty: a clinical practice review

Patient and implant selection is essential to optimize outcome. Femoral bone loss classifications such as the American Academy of Orthopaedic Surgeons, Gross, and Paprosky classifications permit surgeons to systematically manage bone stock deficiencies and guide implant selection. Here we provide a comprehensive report on the pitfalls and management of this reconstructive challenge. Preoperative planning remains vital to the treatment of femoral bone loss in revision hip arthroplasty and the authors believe it is essential and should include the entire femur. This commonly includes imaging for bone loss such as Judet views or computed tomography scan and must include the entire femur though additional radiographs such as Judet views apply more for acetabular bone loss as opposed to femoral bone loss. All patients should have pre-operative work up to exclude infection. If any of these results area elevated, an aspirate and sampling is required to guide microbiological management. Classically with regards femoral revision surgery, uncemented fixation has proven to give the best outcomes but surgeons must remain flexible and use cemented fixation when necessary. Adequate proximal bone stock permits the use of implants used in primary joint surgery. Implants with proximal modularity can be used in cases where bone stock allows for superb proximal bone support. The vast majority of femoral revisions have inadequate proximal bone stock, thus distally fixed stems should be used and have been shown to provide both axial and rotational stability provided there is an intact isthmus. Taper fluted stems can provide good outcomes even in cases of major bone loss. However, with severe bony loss, impaction grating or the use of a megaprotsthesis is sometimes necessary and is down to surgeon choice and preference. This article has been written as a guide for management and summarises the best evidence available.

The Diagnostic Utility of Serum Metal Ion Markers for High-Grade Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions (ALVALs) in Revision Hip and Knee Arthroplasty: An International Multicenter Study

BACKGROUND

Aseptic lymphocyte-dominated vasculitis-associated lesions (ALVALs) are typically described in the context of metal-on-metal (MoM) hip bearings. This study explores the diagnostic utility of preoperative serum cobalt and chromium ion levels in determining the histological grade of ALVAL in revision hip and knee arthroplasty.

METHODS

This was a multicenter retrospective review of 26 hips and 13 knees assessing the correlation between preoperative ion levels (mg/L (ppb)) and the histological grade of ALVAL from intraoperative specimens. The diagnostic ability of preoperative serum cobalt and chromium levels to determine high-grade ALVAL was assessed using a receiver operating characteristic (ROC) curve.

RESULTS

In the knee cohort, there was a higher serum cobalt level in high-grade ALVAL cases (10.2 mg/L (ppb) versus 3.1 mg/L (ppb)) (P = .0002). The Area Under the Curve (AUC) was 1.00 (95% confidence interval (CI) 1.00 to 1.00). There was a higher serum chromium level in high-grade ALVAL cases (12.25 mg/L (ppb) versus 7.77 mg/L (ppb)) (P = .0002). The AUC was 0.806 (95% CI 0.555 to 1.00). In the hip cohort, there was a higher serum cobalt level in high-grade ALVAL cases (333.5 mg/L (ppb) versus 119.9 mg/L (ppb)) (P = .0831). The AUC was 0.619 (95% CI 0.388 to 0.849). There was a higher serum chromium level in high-grade ALVAL cases (186.4 mg/L (ppb) versus 79.3 mg/L (ppb)) (P = .183). The AUC was 0.595 (95% CI 0.365 to 0.824).

CONCLUSIONS

Histologically, high-grade ALVAL has significantly higher preoperative serum cobalt and chromium ion levels in revision TKA. Preoperative serum ion levels have excellent diagnostic utility in revision TKA. Cobalt levels in revision THA have a fair diagnostic ability and chromium levels had a poor diagnostic ability.

International primary hip arthroplasty registry review: findings from current reports

We present key information from international registries in relation to primary total hip arthroplasty. The specific questions of interest include which bearings are superior in total hip arthroplasty (THA), which fixation types are optimal, do any specific implants perform better than others, and what is the latest update in the hip fracture setting? This is a comprehensive review of the major English-speaking hip arthroplasty registries across the globe. Key trends and developments in implant performance are identified and presented in the current article. Key points from review of all registries confirm that ceramic-on-polyethylene and metal-on-polyethylene continue to be the commonest bearings. The use of cemented femoral stems is increasing across most regions. Hybrid fixation is now the commonest fixation method in the UK for the first time in registry history. Uncemented femoral stems have a higher early revision rate for periprosthetic fracture than cemented stems across most regions. Dual mobility (DM) bearings are increasing in use and show higher early revision rates than unipolar bearings-they tend to be used for more complex indications (fracture/tumor/revision) and show similar revision rates to unipolar bearings when used exclusively in primary elective THA for osteoarthritis. We present current trends in THA based on current registry data from across the globe. Clinical signals of concern are emerging for THA uncemented femoral stem fixation and DM bearings in specific clinical contexts. These signals should be monitored across the literature in order to reduce the overall revision burden.

Periprosthetic Fractures After a Total Knee Arthroplasty

As the number of total knee arthroplasties performed continues to increase, complications such as postoperative periprosthetic fractures are becoming increasingly more common. Femoral periprosthetic fractures are the most common type of fractures around a total knee arthroplasty, whereas tibial and patellar periprosthetic fractures are infrequent. Treatment principles depend on the bone the fracture is located, the status of the implant fixation, bone stock, and the type of implants available. The Vancouver classification allows for a standardized system to describe and manage these injuries, incorporating these factors. A systematic approach is vital in obtaining the best possible outcomes because complications and mortality rates mimic those of hip fractures.

International primary knee arthroplasty registry review: findings from current reports

INTRODUCTION

International joint registries provide high volumes of information in relation to the performance of total knee arthroplasty on a global scale. Distillation of this data can be challenging, particularly with the establishment of more arthroplasty registries on a yearly basis. We therefore aim to present key information from these registries in relation to primary total knee arthroplasty. The specific questions of interest include: Which fixation type is superior in TKA? Does the level of constraint impact on clinical performance? How do partial knee replacements perform in the registries? Does patellar resurfacing lead to superior results? Are there any specific implants which perform particularly well or poorly?

METHODS

A comprehensive review of the major English-speaking knee arthroplasty registries across the globe was performed. Given the expanding large number of registries worldwide, it was not possible to perform a comprehensive review of all registries and so, a detailed review of the major English-speaking knee arthroplasty registries was included. Key trends and developments in implant performance were identified and presented in the current article.

RESULTS

Total knee replacements have lower revision rates than both unicompartmental and patellofemoral joint replacement procedures. Patellofemoral joint replacements have the highest failure rate of all knee replacement procedures. Cruciate-Retaining (CR) TKR designs have superior outcomes to Posterior-Stabilized (PS) designs across all registries. Patellar resurfacing appears to confer an advantage over non-resurfaced patellas in primary TKR.

CONCLUSION

We present current global trends in the utility and performance of TKA based on data from English-speaking arthroplasty registries.

Cannabis and Pain Control After Total Hip and Knee Arthroplasty

Cannabis use among the elderly has increased over the previous 2 decades. This has translated to a greater proportion of orthopedic procedures being undertaken on these patients. This review provides clinicians with evidence-based information on the effects of cannabis on pain control in THA and TKA, to help counsel these patients and facilitate their perioperative management. The review specifically focuses on the following: origins of cannabis; biochemistry of cannabis; medical versus recreational cannabis; pharmacology of cannabis; effects of cannabis on bone metabolism; preoperative pain control; preoperative systemic considerations; intraoperative considerations; postoperative pain control, postoperative systemic considerations; and scope for future work.

A Sarcoma Masquerading as a Pseudotumor After Total Hip Arthroplasty: A Case Report

CASE

There is an increasing emphasis on adverse reactions to metal debris around prosthetic hip implants. We present a case report of a patient with increasing pain around a previous total hip arthroplasty and magnetic resonance imaging findings consistent with a pseudotumor. Serum metal ion levels were not elevated and initial biopsy findings inconclusive. The patient was diagnosed with an extraskeletal chondrosarcoma after revision total hip arthroplasty and subsequently underwent external hemipelvectomy with negative margins.

CONCLUSION

This report highlights the importance of remaining vigilant for malignant sarcomas presenting as pseudotumors around hip replacements, particularly in the absence of abnormal metal ion levels or definitive biopsy results.

Comparison of Clinical and Functional Outcomes in One versus Two Component Revision for Total Knee Arthroplasty

BACKGROUND

Revisions of total knee arthroplasties (TKAs) may require revision of one or both tibial and femoral components. Our purpose was to examine the clinical and functional outcomes in 1- versus 2-component TKA revisions.

METHODS

We identified 92 1-component (tibial or femoral) revisions at a single center. Our inclusion criteria were isolated revision of the tibial or femoral components with a minimum 2-year follow-up. The included cases were matched 1:2 with a control group of 2-component revisions (tibial and femoral) by age, body mass index, American Society of Anesthesiologists score, and indication for revision. We collected demographics, complications, operative times, any subsequent rerevisions, and functional outcome scores.

RESULTS

The median follow-up time for the 1- and 2-component revision groups were 10 years (range, 3 to 17) and 8 years (range, 2 to 18), respectively. The most common complication after rerevision in both groups was stiffness at 9 of 92 (9.8%) and 9 of 170 (5.3%) in the 1- and 2-component groups, respectively (P = .20). The overall complication prevalence in the 1- and 2- component revision groups was similar 20 of 92 (22%) and 35 of 170 (21%), respectively (P = .87). Subsequent rerevisions for any indication were encountered in 12 of 92 (13.0%) of the 1-component and 18 of 170 (11%) in the 2-component groups (P = .69). There was no statistical difference in survivorship or functional outcomes scores between the groups.

CONCLUSION

Our results showed that isolated revision of a single TKA component is an acceptable option, with comparable functional outcomes, complications, and survivorships when compared with both-component revision. As such, a 1-component revision should be considered where appropriate.

Identification of protective and 'at risk' HLA genotypes for the development of pseudotumours around metal-on-metal hip resurfacings

Hip resurfacing remains a potentially valuable surgical procedure for appropriately-selected patients with optimised implant choices. However, concern regarding high early failure rates continues to undermine confidence in use. A large contributor to failure is adverse local tissue reactions around metal-on-metal (MoM) bearing surfaces. Such phenomena have been well-explored around MoM total hip arthroplasties, but comparable data in equivalent hip resurfacing procedures is lacking. In order to define genetic predisposition, we performed a case-control study investigating the role of human leucocyte antigen (HLA) genotype in the development of pseudotumours around MoM hip resurfacings. A matched case-control study was performed using the prospectively-collected database at the host institution. In all, 16 MoM hip resurfacing 'cases' were identified as having symptomatic periprosthetic pseudotumours on preoperative metal artefact reduction sequence (MARS) MRI, and were subsequently histologically confirmed as high-grade aseptic lymphocyte-dominated vasculitis-associated lesions (ALVALs) at revision surgery. 'Controls' were matched by implant type in the absence of evidence of pseudotumour. Blood samples from all cases and controls were collected prospectively for high resolution genetic a nalysis targeting 11 separate HLA loci. Statistical significance was set at 0.10 a priori to determine the association between HLA genotype and pseudotumour formation, given the small sample size. Using a previously-reported ALVAL classification, the majority of pseudotumour-positive caseswere found to have intermediate-grade group 2 (n = 10; 63%) or group 3 (n = 4; 25%) histological findings. Two further patients (13%) had high-grade group 4 lesions. HLA-DQB1*05:03:01 (p = 0.0676) and HLA-DRB1*14:54:01 (p = 0.0676) alleles were significantly associated with a higher risk of pseudotumour formation, while HLA-DQA1*03:01:01 (p = 0.0240), HLA-DRB1*04:04:01 (p = 0.0453), HLA-C*01:02:01 (p = 0.0453), and HLA-B*27:05:02 (p = 0.0855) were noted to confer risk reduction. These findings confirm the association between specific HLA genotypes and the risk of pseudotumour development around MoM hip resurfacings. Specifically, the two 'at risk' alleles (DQB1*05:03:01 and DRB1*14:54:01) may hold clinical value in preoperative screening and prospective surgical decision-making.

Optimization of surgical tourniquet usage to improve patient outcomes: Translational cross-disciplinary implications of a surgical practice survey

Tourniquet use is common practice in many millions of orthopaedic procedures annually. Recent reviews of risks and benefits of surgical tourniquet use have primarily involved meta-analyses, many of which have forgone a comprehensive risk-benefit analysis to simply question whether "tourniquet or no tourniquet" use produces improved patient outcomes, often leading to limited, inconclusive, or conflicting results. To investigate further, a pilot survey was undertaken to determine current practices, opinions, and understandings among orthopaedic surgeons in Canada regarding use of surgical tourniquets in total knee arthroplasties (TKAs). Results of the pilot survey showed a wide range of understanding and practice associated with tourniquet use in TKAs, especially regarding tourniquet pressures and tourniquet times, two key factors known from basic research and clinical studies to impact the safety and efficacy of tourniquet use. The wide variation of use indicated by the survey results reveals important implications for surgeons, researchers, educators, and biomedical engineers, to better understand the association between key tourniquet parameters and outcomes assessed in research, which may be factors leading to their often limited, inconclusive, and conflicting results. Lastly, we provide an overview of the overly simplified assessments of tourniquet use in meta-analyses, whose conclusions may not provide an understanding of how or whether key tourniquet parameters might be optimized to retain the benefits of tourniquet use while mitigating the associated real or perceived risks.

Can Technology Assistance be Cost Effective in TKA? A Simulation-Based Analysis of a Risk-prioritized, Practice-specific Framework

BACKGROUND

Robotic, navigated, and patient-specific instrumentation (PSI) TKA procedures have been introduced to improve component placement precision and improve implant survivorship and other clinical outcomes. However, the best available evidence has shown that these technologies are ineffective in reducing revision rates in the general TKA patient population. Nonetheless, it seems plausible that these technologies could be an effective and cost-effective means of reducing revision risk in clinical populations that are at an elevated risk of revision because of patient-specific demographics (such as older age at index surgery, elevated BMI, and being a man). Since clinical trials on this topic would need to be very large, a simulation approach could provide insight on which clinical populations would be the most promising for analysis.

QUESTIONS/PURPOSES

We conducted a simulation-based analysis and asked: (1) Given key demographic parameters characterizing a patient population, together with estimates of the precision achievable with selected forms of technology assistance in TKA, can we estimate the expected distributions of anticipated reductions in lifetime revision risk for that population and the associated improvements in quality-adjusted life years (QALYs) that would be expected to result? (2) Are there realistic practice characteristics (such as combinations of local patient demographics and capital and per-procedure costs) for which applying a per-patient risk-prioritized policy for using technology-assisted TKA could be considered cost-effective based on projected cost savings from reductions in revision rates?

METHODS

We designed simulations of hypothetical practice-specific clinical scenarios, each characterized by patient volume, patient demographics, and technology-assisted surgical technique, using demographic information drawn from other studies to characterize two contrasting simulated clinical scenarios in which the distributions of factors describing patients undergoing TKA place one population at a comparatively elevated risk of revision (elevated-risk population) and the second at a comparatively reduced risk of revision (lower-risk population). We used results from previous systematic reviews and meta-analyses to estimate the implant precision in coronal plane alignment for patient-specific instrumentation, navigated, and robotic technology. We generated simulated TKA patient populations based on risk estimates from large clinical studies, structured reviews, and meta-analyses and calculated the patient-specific reduction in the revision risk and the change in QALYs attributable to the technology-assisted intervention in each of the two simulated clinical scenarios. We also incorporated a sensitivity analysis, incorporating variations in the effect size of deviations from overall coronal alignment on revision risk and difference in health state utilities acquired through a structured review process. We then simulated the outcomes of 25,000 operations per patient using the precisions associated with the conventional TKA technique, the three technology-assisted techniques, and a hypothetical technology-assisted intervention that could consistently deliver perfectly neutral overall coronal alignment, which is unachievable in practice. A risk-prioritized treatment policy was emulated by ordering the simulated patients from the highest to lowest predicted increase in QALYs, such that simulated patients who would see the greatest increase in the QALYs (and therefore the greatest reduction in lifetime revision risk) were the patients to receive technology-assisted TKA intervention in a practice. We used cost estimates acquired through a structured review process and calculated the net added costs of each of the three technology-assisted techniques as a function of the percent utilization (proportion of patients treated with technology assistance in a practice), factoring in fixed costs, per-procedure variable costs, and savings occurring from the prevention of future revision surgery. Finally, we calculated the incremental cost-effectiveness ratio (ICER) and marginal cost-effectiveness ratio (MCER) for each technology-assisted technique for the two clinical scenarios. We then used a Monte Carlo approach to simulate variations in key patient risk, health state, and economic factors as well as to obtain a distribution of estimates for cost-effectiveness. We considered an intervention to be cost effective if either the ICER or MCER values were below USD/QALY 63,000.

RESULTS

For the lower-risk population, the median reduction in the revision risk was 0.9% (0.4% to 2.2%, extrema from the sensitivity analysis) and 1.8% (0.9% to 4.4%) for PSI and robotic TKA, respectively, and 1.9% (1.0% to 4.6%) for ideal TKA. In contrast, the median reduction in the revision risk in the elevated-risk clinical scenario was 2.0% (1.2% to 3.4%) and 4.6% (2.7% to 8.5%) for PSI and robotic TKA and 5.1% (3.0% to 9.4%) for ideal TKA. Estimated differences in the cumulative gain in QALYs attributable to technology-assisted TKA ranged from 0.6 (0.2 to 1.8) to 4.0 (1.8 to 10.0) QALYs per 100 patients, depending on the intervention type and clinical scenario. For PSI, we found treating 15% of patients in the lower-risk population and 77% in the elevated-risk population could meet the threshold for being considered cost effective. For navigated TKA systems offering high alignment precision, we found the intervention could meet this threshold for practice sizes of at least 300 patients per year and a percent utilization of 27% in the lower-risk population. In the elevated-risk population, cost-effectiveness could be achieved in practice volumes as small as 100 patients per year with a percent utilization of at least 6%, and cost savings could be achieved with a percent utilization of at least 45%. We found that robotic TKA could only meet the threshold for being considered cost-effectiveness in the lower-risk population if yearly patient volumes exceeded 600 and for a limited range of percent utilization (27% to 32%). However, in the elevated-risk patient population, robotic TKA with high alignment precision could potentially be cost effective for practice sizes as small as 100 patients per year and a percent utilization of at least 20% if a risk-prioritized treatment protocol were used.

CONCLUSION

Based on these simulations, a selective-use policy for technology-assisted TKA that prioritizes using technology assistance for those patients at a higher risk of revision based on patient-specific factors could potentially meet the cost-effectiveness threshold in selected circumstances (for example, primarily in elevated-risk populations and larger practice sizes). Whether it does meet that threshold would depend significantly on the surgical precision that can be achieved in practice for a given proposed technology as well as on the true local costs of using the proposed technology. We further recommend that any future randomized trials seeking to demonstrate possible effects of technology assistance on revision risk focus on clinical populations that are at higher risk of revision (such as, patient populations that are relatively younger, have higher BMIs, and higher proportions of men).

CLINICAL RELEVANCE

This study suggests that technology assistance is only likely to prove cost effective in selected circumstances rather than in all clinical populations and practice settings. In general, we project that surgical navigation is most likely to prove cost effective in the widest range of circumstances, that PSI may be cost effective or cost neutral in a moderate range of circumstances, and that robotic surgery is only likely to be cost effective in moderately large practices containing patients who are on average at an intrinsically elevated risk of revision.

Postoperative Inpatient Rehabilitation Does Not Increase Knee Function after Primary Total Knee Arthroplasty

Inpatient rehabilitation (IR) is a common postoperative protocol after total knee replacement (TKA). Because IR is expensive and should therefore be justified, this study determined the difference in knee function one year after TKA in patients treated with IR or outpatient rehabilitation, fast-track rehabilitation (FTR) in particular, which also entails a reduced hospital length of stay. A total of 205 patients were included in this multi-center prospective cohort study. Of the patients, 104 had primary TKA at a German university hospital and received IR, while 101 had primary TKA at a Canadian university hospital and received FTR. Patients receiving IR or FTR were matched by pre-operative demographics and knee function. Oxford Knee Score (OKS), Western Ontario and McMaster Universities Arthritis Index (WOMAC), and EuroQol visual analogue scale (EQ-VAS) determined knee function one year after surgery. Patients receiving IR had a 2.8-point lower improvement in OKS (p = 0.001), a 6.7-point lower improvement in WOMAC (p = 0.063), and a 12.3-point higher improvement in EQ-VAS (p = 0.281) than patients receiving FTR. IR does not provide long-term benefits to patient recovery after primary uncomplicated TKA under the current rehabilitation regime.

Short-term results of the uncemented triathlon total knee arthroplasty: a large cohort single-centre comparative study

BACKGROUND

The purpose of this study is to assess the short-term survivorship of a new uncemented TKA design in a high-volume centre to evaluate the safety of this design prior to widespread adoption.

METHODS

We performed a retrospective cohort study of all primary TKAs (cemented and uncemented) between May 2018 and May 2019. Primary outcome variables included aseptic revision, all-cause revision, time to revision, operative time and radiological outcomes. Predictor variables considered included age, gender, BMI, ASA, implant type (cruciate-retaining, posterior-stabilised or totally-stabilised) and the use of cemented or uncemented implants.

RESULTS

There were 300 cemented TKAs and 249 uncemented TKAs (Triathlon, Stryker Inc., Mahwah, NJ) implanted. The mean follow-up for all cases was 31.6 months (minimum follow-up 2 years). Of the entire 549 implants only 4 were revised. Two of these were for infection, 1 was for patellar maltracking and 1 was for knee stiffness. All 4 revisions occurred in the cemented cohort. The aseptic revision rate in the cemented cohort was 0.7% compared to 0.0% in the uncemented cohort (p = 0.298). Operative times were significantly reduced in the uncemented cohort from 57.9 to 51.7 min (p < 0.001). There were 8/300 (2.6%) patients with RLLs in the cemented cohort and 4/249 (1.6%) patients with RLLs in the uncemented cohort (p = 0.56).

CONCLUSION

The uncemented Triathlon TKA demonstrates excellent survivorship at short-term follow-up when compared to the cemented Triathlon TKA, thus eliminating any potential clinical concerns with this novel implant in the early post-operative phase.

The Impact of Changing Total Knee Arthroplasty Implants at a High-Volume Institution

BACKGROUND

The ability of a group of high-volume arthroplasty surgeons to simultaneously change their preferred primary total knee arthroplasty (TKA) implant of choice to another, has not been explored in the literature to date. The main hypothesis was that such a change could be made with no significant impact on clinical outcomes.

METHODS

This is a retrospective cohort study comparing the last 500 consecutive TKAs implanted of a routinely used TKA implant (NexGen; Zimmer, Warsaw, IN) with the first 500 consecutive TKAs implanted of a newly adopted TKA implant (Triathlon; Stryker, Mahwah, NJ) at an institutional level. Primary outcomes of importance included all complications that occurred either intraoperatively or early postoperatively, early all-cause revision rate, and early reintervention rate.

RESULTS

There was a 1.2% (n = 6) complication rate in the NexGen cohort compared to 0.8% (n = 4) in the newly adopted Triathlon cohort (P = .75). The rate of intraoperative fracture was 1% in the NexGen cohort and 0.6% in the Triathlon cohort (P = .72). The early all-cause revision rate for the NexGen TKA was 1% (n = 5) compared to 0.8% (n = 4) in the Triathlon cohort (P = 1.0). The manipulation under anesthesia (MUA) rate in the NexGen cohort was 2.4% compared to 4.6% in the Triathlon cohort (P = .058). The only predictor variable associated with MUA rate was American Society of Anesthesiologists grade, where there was a significantly lower rate of MUA with a higher American Society of Anesthesiologists grade (P = .042).

CONCLUSION

It is possible to implement the institution-wide adoption of an established, high-performing TKA implant without any negative implications in relation to early revision rates, perioperative complication rates, and reintervention rates. This study is the first of its kind to be reported in the literature.

Soft Tissue Procedures in the Multiply Operated on Knee Replacement Patient

In the multiply operated on knee replacement, no one soft tissue procedure is vastly superior to another. The most extensive literature available is in relation to muscle flaps, which will continue to be the workhorse technique for orthopedic and plastic reconstructive surgeons for the foreseeable future. Closed incision negative pressure wound therapy may prove to be a superior method in time but further large-scale studies are required to expand our understanding of this technique. The continued use of a combination of these techniques, tailored to the specific patient, is likely to be the best approach to the multiply operated on knee into the future.

Effect of posture and femoral neck osteochondroplasty on femur-acetabulum clearance in patients with cam-type femoroacetabular impingement

It is not clear whether femoral neck osteochondroplasty achieves its objective of increasing femoroacetabular clearance. We used an upright open magnetic resonance imaging scanner to image the hip joint in multiple postures to explore the effect of posture and femoral neck osteochondroplasty on femur-acetabulum clearance in patients with cam-type femoroacetabular impingement. We recruited 13 consecutive patients scheduled to undergo arthroscopic femoral neck osteochondroplasty and completed assessments on 10 patients. We scanned each subject before surgery and at 6 months post-op in supine and 3 other physiological postures: supine 90° flexion with adduction and internal rotation (FADIR), sitting deep (maximal flexion with internal rotation and adduction), and sitting crossed leg (maximal adduction with flexion and internal rotation). We measured the alpha angle, which describes the severity of cam deformity, and the beta angle, which defines joint clearance. We also evaluated hip flexion, internal rotation, and adduction before and after surgery. Femoral neck osteochondroplasty significantly decreased alpha angle by 23.9° ± 4.6° (p = 0.001) and increased beta angle across all postures by 28.1° ± 6.3° (p = 0.002). An increase in beta angle represented a decreased chance of impingement. Femoral neck osteochondroplasty significantly increased flexion by an average of 8.6° in the sitting deep posture after surgery (p = 0.007) which might indicate an improvement of joint function. These findings lend support to the hypothesis that arthroscopic osteochondroplasty accomplishes its stated goals of increasing bone-bone clearance in the hip joint and improving joint mechanics for the static postures assessed.

Simultaneous bilateral total knee arthroplasty : similar outcomes for trainees and trainers

Aims

Simultaneous bilateral total knee arthroplasty (TKA) has been used due to its financial advantages, overall resource usage, and convenience for the patient. The training model where a trainee performs the first TKA, followed by the trainer surgeon performing the second TKA, is a unique model to our institution. This study aims to analyze the functional and clinical outcomes of bilateral simultaneous TKA when performed by a trainee or a supervising surgeon, and also to assess these outcomes based on which side was done by the trainee or by the surgeon.

Methods

This was a retrospective cohort study of all simultaneous bilateral TKAs performed by a single surgeon in an academic institution between May 2003 and November 2017. Exclusion criteria were the use of partial knee arthroplasty procedures, staged bilateral procedures, and procedures not performed by the senior author on one side and the trainee on another. Primary clinical outcomes of interest included revision and re-revision. Primary functional outcomes included the Oxford Knee Score (OKS) and patient satisfaction scores.

Results

In total, 315 patients (630 knees) were included for analysis. Of these, functional scores were available for 189 patients (378 knees). There was a 1.9% (n = 12) all-cause revision rate for all knees. Overall, 12 knees in ten patients were revised, and both right and left knees were revised in two patients. The OKS and patient satisfaction scores were comparable for trainees and supervising surgeons. A majority of patients (88%, n = 166) were either highly likely (67%, n = 127) or likely (21%, n = 39) to recommend bilateral TKAs to a friend.

Conclusion

Simultaneous bilateral TKA can be used as an effective teaching model for trainees without any significant impact on patient clinical or functional outcomes. Excellent functional and clinical outcomes in both knees, regardless of whether the performing surgeon is a trainee or supervising surgeon, can be achieved with simultaneous bilateral TKA.

Cite this article: Bone Jt Open 2022;3(1):29–34.

Compartment Syndrome After Hip and Knee Arthroplasty

Early diagnosis and prompt definitive management of acute compartment syndrome (ACS) are paramount in preventing the significant morbidity associated with compartment syndrome. The diagnosis of compartment syndrome can be difficult, given the pain associated with the procedure in the immediate postoperative period. Obesity, anticoagulation, postoperative epidural infusion, and prolonged operative time have been reported as risk factors for ACS. In addition to maintaining high clinical suspicion in patient with risk factors for ACS after joint replacement, emphasis on limiting modifiable risk factors should be practiced, including meticulous hemostasis, careful patient positioning, and limiting prolonged postoperative regional anesthesia when not required.

Perivascular lymphocytic aggregates in hip prosthesis-associated adverse local tissue reactions demonstrate Th1 and Th2 activity and exhausted CD8+ cell responses

Hip implants are a successful solution for osteoarthritis; however, some individuals with metal-on-metal (MoM) and metal-on-polyethylene (MoP) prosthetics develop adverse local tissue reactions (ALTRs). While MoM and MoP ALTRs are presumed to be delayed hypersensitivity reactions to corrosion products, MoM- and MoP-associated ALTRs present with different histological characteristics. We compared MoM- and MoP-associated ALTRs histopathology with cobalt and chromium levels in serum and synovial fluid. We analyzed the gene expression levels of leukocyte aggregates and synovial fluid chemokines/cytokines to resolve potential pathophysiologic differences. In addition, we classified ALTRs from 79 patients according to their leukocyte infiltrates as macrophage-dominant, mixed, and lymphocyte-dominant. Immune-related transcript profiles from lymphocyte-dominant MoM- and MoP-associated ALTR patients with perivascular lymphocytic aggregates were similar. Cell signatures indicated predominantly macrophage, Th1 and Th2 lymphocytic infiltrate, with strong exhausted CD8⁺ signature, and low Th17 and B cell, relative to healthy lymph nodes. Lymphocyte-dominant ALTR-associated synovial fluid contained higher levels of induced protein 10 (IP-10), interleukin-1 receptor antagonist (IL-1RN), IL-8, IL-6, IL-16, macrophage inflammatory protein 1 (MIP-1α), IL-18, MCP-2, and lower cell-attracting chemokine levels, when compared with prosthetic revisions lacking ALTRs. In addition, the higher levels of IP-10, IL-8, IL-6, MIP-1α, and MCP-2 were observed within the synovial fluid of the lymphocyte-dominant ALTRs relative to the macrophage-dominant ALTRs. Not all cytokines/chemokines were detected in the perivascular aggregate transcripts, suggesting the existence of other sources in the affected synovia. Our results support the hypothesis of common hypersensitivity pathogenesis in lymphocyte-dominant MoM and MoP ALTRs. The exhausted lymphocyte signature indicates chronic processes and an impaired immune response, although the cause of the persistent T-cell activation remains unclear. The cytokine/chemokine signature of lymphocyte-dominant-associated ATLRs may be of utility for diagnosing this more aggressive pathogenesis.

Highly cross-linked polyethylene (HXLPE) is equivalent to conventional polyethylene (CPE) in total knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

The benefits of HXLPE in total knee arthroplasty (TKA) have not been as evident as total hip arthroplasty (THA). A systematic review and meta-analysis to assess the impact of highly-crosslinked polyethylene (HXLPE) on TKA outcomes compared to conventional polyethylene (CPE) is described.

METHODS

All studies comparing HXLPE with CPE for primary TKA were included for analysis. The minimum dataset included revision rates, indication for revision, aseptic component loosening and follow-up time. The primary outcome variables were all-cause revision, aseptic revision, revision for loosening, radiographic component loosening, osteolysis and incidence of radiolucent lines. Secondary outcome measures included postoperative functional knee scores. A random-effects meta-analysis allowing for all missing data was performed for all primary outcome variables.

RESULTS

Six studies met the inclusion criteria. In total, there were 2,234 knees (1,105 HXLPE and 1,129 CPE). The combined mean follow-up for all studies was 6 years. The aseptic revision rate in the HXLPE group was 1.02% compared to 1.97% in the CPE group. There was no difference in the rate of all-cause revision (p = 0.131), aseptic revision (p = 0.298) or revision for component loosening (p = 0.206) between the two groups. Radiographic loosening (p = 0.200), radiolucent lines (p = 0.123) and osteolysis (p = 0.604) was similar between both groups. Functional outcomes were similar between groups.

CONCLUSION

The use of HXLPE in TKA yields similar results for clinical and radiographic outcomes when compared to CPE at midterm follow-up. HXLPE does not confer the same advantages to TKA as seen in THA.

Treatment of B1 Distal Periprosthetic Femur Fractures

The burden of periprosthetic distal femoral fractures is projected to increase accordingly with the increase in total knee arthroplasties (TKAs) performed globally in the future. Less invasive plating and intramedullary (IM) nailing techniques still seem to provide similar outcomes based on current literature. Double-plating and combination techniques may prove to be beneficial in the future pending further large-scale studies but currently have not demonstrated superiority over single plating and IM nailing based on current evidence. Distal femoral replacement may provide a useful option for future treatment, provided it is performed by a trained knee arthroplasty surgeon.

Tibiofemoral contact and alignment in patients with anterior cruciate ligament rupture treated nonoperatively versus reconstruction : an upright, open MRI study

AIMS

Anterior cruciate ligament (ACL) rupture commonly leads to post-traumatic osteoarthritis, regardless of surgical reconstruction. This study uses standing MRI to investigate changes in contact area, contact centroid location, and tibiofemoral alignment between ACL-injured knees and healthy controls, to examine the effect of ACL reconstruction on these parameters.

METHODS

An upright, open MRI was used to directly measure tibiofemoral contact area, centroid location, and alignment in 18 individuals with unilateral ACL rupture within the last five years. Eight participants had been treated nonoperatively and ten had ACL reconstruction performed within one year of injury. All participants were high-functioning and had returned to sport or recreational activities. Healthy contralateral knees served as controls. Participants were imaged in a standing posture with knees fully extended.

RESULTS

Participants' mean age was 28.4 years (SD 7.3), the mean time since injury was 2.7 years (SD 1.6), and the mean International Knee Documentation Subjective Knee Form score was 84.4 (SD 13.5). ACL injury was associated with a 10% increase (p = 0.001) in contact area, controlling for compartment, sex, posture, age, body mass, and time since injury. ACL injury was associated with a 5.2% more posteriorly translated medial centroid (p = 0.001), equivalent to a 2.6 mm posterior translation on a representative tibia with mean posteroanterior width of 49.4 mm. Relative to the femur, the tibiae of ACL ruptured knees were 2.3 mm more anteriorly translated (p = 0.003) and 2.6° less externally rotated (p = 0.010) than healthy controls. ACL reconstruction was not associated with an improvement in any measure.

CONCLUSION

ACL rupture was associated with an increased contact area, posteriorly translated medial centroid, anterior tibial translation, and reduced tibial external rotation in full extension. These changes were present 2.7 years post-injury regardless of ACL reconstruction status. Cite this article: Bone Joint J 2021;103-B(9):1505-1513.

Mid-term results of a prospective randomised controlled trial comparing large-head metal-on-metal hip replacement to hip resurfacing using patient-reported outcome measures and objective functional task-based outcomes

BACKGROUND

The early outcomes of large head-metal-on-metal total hip arthroplasty (MoM THA) are compromised by adverse local tissue reaction to metal debris. This study is the mid-term follow-up of a prospective randomised control trial (pRCT) comparing MoM THA to MoM HR. We sought to answer whether there was a difference between MoM THA and MoM HR at mid-term follow-up in the implant survival; patient-reported outcome measures (PROMs); and when performing objective functional tasks?

METHODS

A total of 104 patients were studied. Of these 56 had MoM THA (50 male) and 48 had HR (43 male). Mean age at surgery was 52 years in both groups.We reviewed this cohort at mid-term follow-up [minimum 8 years (mean 9 years; range 8-10; SD 0.7)]. PROMs that were completed were OHS, WOMAC, SF-12, and the UCLA. For objective functional task-based outcomes, gait parameters for operated legs were assessed in a subgroup of 17 patients with high UCLA.

RESULTS

Revision rate in MoM THA group was 7/56 (12.5%) and in the HR group was 1/48 (2.1%). Overall revision rate at minimum 8-year follow-up was 7.7% (8 of 104 patients). PROMs data comparing MoM THA versus HR showed no difference between the groups. 4 (8.5%) of the non-revised (47) HR patients had WOMAC function or pain score below 70. 3 (6.4%) patients had both pain and function scores <70. In the THA group, 5 (10.2%) of the non-revised (49) patients had WOMAC pain or function scores <70. 3 (6.1%) patients had both pain and function scores <70. The comparison of HA versus THA showed several gait parameters in the HR group to be better but not statistically significant (p > 0.05 Mann-Whitney U-test).

CONCLUSIONS

At mid-term follow-up, the revision rate of MoM articulation for THA is high (7.7%), being higher in large head MoM total hips versus resurfacing. Overall probability of 10-year survival is 92.3% (KM analysis, 95% for MoM THA and 98% for HR). The HR group had better functional parameters on gait-based tasks compared to THA group but this difference did not reach statistical significance.

Cobalt ions induce metabolic stress in synovial fibroblasts and secretion of cytokines/chemokines that may be diagnostic markers for adverse local tissue reactions to hip implants

Adverse local tissue reactions (ALTRs) are a prominent cause of hip implant failure. ALTRs are characterized by aseptic necrosis and leukocyte infiltration of synovial tissue. The prevalence of ALTRs in hips with failing metal implants, with highest rates occurring in patients with metal-on-metal articulations, suggests a role for CoCrMo corrosion in ALTR formation. Although hypersensitivity reactions are the most accepted etiology, the precise cellular mechanism driving ALTR pathogenesis remains enigmatic. Here we show that cobalt ions released by failing hip implants induce mitochondrial stress and cytokine secretion by synovial fibroblasts: the presumptive initiators of ALTR pathogenesis. We found that in-vitro treatment of synovial fibroblasts with cobalt, but not chromium, generated gene expression changes indicative of hypoxia and mitophagy responses also observed in ALTRs biopsies. Inflammatory factors secreted by cobalt-exposed synovial fibroblasts were among those most concentrated in ALTR synovial fluid. Furthermore, both conditioned media from cobalt-exposed synovial fibroblasts, and synovial fluid from ALTRs patients, elicit endothelial activation and monocyte migration. Finally, we identify the IL16/CTACK ratio in synovial fluid as a possible diagnostic marker of ALTRs. Our results provide evidence suggesting that metal ions induce cell stress in synovial fibroblasts that promote an inflammatory response consistent with initiating ALTR formation. STATEMENT OF SIGNIFICANCE: We demonstrate that the cytotoxic effects of cobalt ions on the synovial cells (fibroblast) is sufficient to trigger inflammation on hip joints with metal implants. Cobalt ions affect mitochondrial function, leading to the auto phagocytosis of mitochondria and trigger a hypoxic response. The cell's hypoxic response includes secretion of cytokines that are capable of trigger inflammation by activating blood vessels and enhancing leukocyte migration. Among the secreted cytokines is IL-16, which is highly concentrated in the synovial fluid of the patients with adverse local tissue reactions and could be use as diagnostic marker. In conclusion we define the cells of the hip joint as key players in triggering the adverse reactions to hip implants and providing biomarkers for early diagnosis of adverse reactions to hip implants.

Total Hip Replacements in Patients with Rare Pathologic Conditions Affecting Bone

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As a result of the advances in surgical technique and implant design, total hip arthroplasty (THA) is increasingly offered for the management of osteoarthritis of the hip in patients with fragile or pathologic bone.

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Posttraumatic or congenital deformities associated with fragile or pathologic bone are frequently encountered and necessitate diligent preoperative planning.

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Surgeons should be prepared to evaluate and manage intraoperative iatrogenic fracture.

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While there is limited evidence to date, components made with computer-assisted design can be considered, given the unique and highly variable patient population.

Development and Implementation of International Curricula for Joint Replacement and Preservation

The number of patients undergoing joint replacement and preservation procedures continues to increase worldwide. Globally, there is no standardized educational pathway, training program, or recognized certification program for surgeons in these procedures. Development and implementation of new competency-based curricula to deliver specific educational events and resources may help trainees and practicing surgeons be able to perform these procedures more effectively and therefore improve patient outcomes in their respective countries. Ideally, a curriculum would be globally standardized and professionally designed to interactively meet the needs of surgeons. A competency-based approach with built-in assessment and evaluation processes is today's educational standard.

Surgical Skills Training Using Simulation for Basic and Complex Hip and Knee Arthroplasty

Skills training is important in an arthroplasty curriculum and can focus either on "part tasks" or on full procedures. The most commonly used simulations in orthopedics including arthroplasty are anatomic specimens, dry bone models, and virtual or other technology-enhanced systems. A course curriculum planning committee must identify the gaps to address, define what learners need to be able to do, and select the most appropriate simulation modality and assessment for delivery. Each simulation must have a clear structure with learning objectives, steps, and take-home messages. Feedback from learners and faculty must be integrated to improve processes and models for future learning.

Reliability of tibiofemoral contact area and centroid location in upright, open MRI

BACKGROUND

Imaging cannot be performed during natural weightbearing in biomechanical studies using conventional closed-bore MRI, which has necessitated simulating weightbearing load on the joint. Upright, open MRI (UO-MRI) allows for joint imaging during natural weightbearing and may have the potential to better characterize the biomechanical effect of tibiofemoral pathology involving soft tissues. However open MRI scanners have lower field strengths than closed-bore scanners, which limits the image quality that can be obtained. Thus, there is a need to establish the reliability of measurements in upright weightbearing postures obtained using UO-MRI.

METHODS

Knees of five participants with prior anterior cruciate ligament (ACL) rupture were scanned standing in a 0.5 T upright open MRI scanner using a 3D DESS sequence. Manual segmentation of cartilage regions in contact was performed and centroids of these contact areas were automatically determined for the medial and lateral tibiofemoral compartments. Inter-rater, test-retest, and intra-rater reliability were determined and quantified using intra-class correlation (ICC_3,1), standard error of measurement (SEM), and smallest detectable change with 95% confidence (SDC₉₅). Accuracy was assessed by using a high-resolution 7 T MRI as a reference.

RESULTS

Contact area and centroid location reliability (inter-rater, test-retest, and intra-rater) for sagittal scans in the medial compartment had ICC_3,1 values from 0.95-0.99 and 0.98-0.99 respectively. In the lateral compartment, contact area and centroid location reliability ICC_3,1 values ranged from 0.83-0.91 and 0.95-1.00 respectively. The smallest detectable change in contact area was 1.28% in the medial compartment and 0.95% in the lateral compartment. Contact area and centroid location reliability for coronal scans in the medial compartment had ICC_3,1 values from 0.90-0.98 and 0.98-1.00 respectively, and in the lateral compartment ICC_3,1 ranged from 0.76-0.94 and 0.93-1.00 respectively. The smallest detectable change in contact area was 0.65% in the medial compartment and 1.41% in the lateral compartment. Contact area was accurate to within a mean absolute error of 11.0 mm².

CONCLUSIONS

Knee contact area and contact centroid location can be assessed in upright weightbearing MRI with good to excellent reliability. The lower field strength used in upright, weightbearing MRI does not compromise the reliability of tibiofemoral contact area and centroid location measures.

Allowed Activities After Primary Total Knee Arthroplasty and Total Hip Arthroplasty

It is essential for total knee arthroplasty patients to return to their previous level of activity to maintain a healthy lifestyle. This article reviews the current recommendations regarding return to physical activity after total knee arthroplasty and trying to find the balance between levels of activity and prosthetic joint preservation. In general, most total joint replacement patients are able to return to their previous level of activity and to a lesser extent to sports. This article discuss patients' actual levels of activity including their return to work and sport and the factors that influence meeting their expectations for surgery.

Short-Term Tibial Baseplate Fracture After Total Knee Arthroplasty in the Absence of Osteolysis and Implant Loosening: A Case Report

CASE

The patient is a 62-year-old man with early tibial baseplate failure involving fracture and subsidence of the posteromedial metal implant, only 3 years after primary total knee replacement. Although this mode of failure is frequently observed secondary to polyethylene wear and osteolysis, this case was likely because of suboptimal tibial baseplate size and positioning with lack of cortical support that underwent accelerated fatigue, given the high activity level of the patient.

CONCLUSION

This case demonstrates rare sequelae of inadequate tibial coverage and cortical structural support of the baseplate. Tibial coverage is influenced by implant sizing, implant positioning, and variations in patient anthropometrics.

Hybrid stems are superior to cemented stems in revision total knee arthroplasty: a systematic review and meta-analysis of recent comparative studies

INTRODUCTION

The demand for revision total knee arthroplasty (TKA) has grown significantly in recent years. The two major fixation methods for stems in revision TKA include cemented and 'hybrid' fixation. We explore the optimal fixation method using data from recent, well-designed comparative studies.

METHODS

We performed a systematic review of comparative studies published within the last 10 years with a minimum follow-up of 24 months. To allow for missing data, a random-effects meta-analysis of all available cases was performed. The odds ratio (OR) for the relevant outcome was calculated with 95% confidence intervals. The effects of small studies were analyzed using a funnel plot, and asymmetry was assessed using Egger's test. The primary outcome measure was all-cause failure. Secondary outcome measures included all-cause revision, aseptic revision and radiographic failure.

RESULTS

There was a significantly lower failure rate for hybrid stems when compared to cemented stems (p = 0.006) (OR 0.61, 95% CI 0.42-0.87). Heterogeneity was 4.3% and insignificant (p = 0.39). There was a trend toward superior hybrid performance for all other outcome measures including all-cause re-revision, aseptic re-revision and radiographic failure.

CONCLUSION

Recent evidence suggests a significantly lower failure rate for hybrid stems in revision TKA. There is also a trend favoring the use of hybrid stems for all outcome variables assessed in this study. This is the first time a significant difference in outcome has been demonstrated through systematic review of these two modes of stem fixation. We therefore recommend the use, where possible, of hybrid stems in revision TKA.

Safety of a ‘swing room’ surgery model at a high-volume hip and knee arthroplasty centre

Aims

The practice of overlapping surgery has been increasing in the delivery of orthopaedic surgery, aiming to provide efficient, high-quality care. However, there are concerns about the safety of this practice. The purpose of this study was to examine the safety and efficacy of a model of partially overlapping surgery that we termed ‘swing room’ in the practice of primary total hip (THA) and knee arthroplasty (TKA).

Methods

A retrospective review of prospectively collected data was carried out on patients who underwent primary THA and TKA between 2006 and 2017 in two academic centres. Cases were stratified as partially overlapping (swing room), in which the surgeon is in one operating room (OR) while the next patient is being prepared in another, or nonoverlapping surgery. The demographic details of the patients which were collected included operating time, length of stay (LOS), postoperative complications within six weeks of the procedure, unplanned hospital readmissions, and unplanned reoperations. Fisher's exact, Wilcoxon rank-sum tests, chi-squared tests, and logistic regression analysis were used for statistical analysis.

Results

A total of 12,225 cases performed at our institution were included in the study, of which 10,596 (86.6%) were partially overlapping (swing room) and 1,629 (13.3%) were nonoverlapping. There was no significant difference in the mean age, sex, body mass index (BMI), side, and LOS between the two groups. The mean operating time was significantly shorter in the swing room group (58.2 minutes) compared with the nonoverlapping group (62.8 minutes; p < 0.001). There was no significant difference in the rates of complications, readmission and reoperations (p = 0.801 and p = 0.300, respectively) after adjusting for baseline American Society of Anesthesiologists scores.

Conclusion

The new ‘swing room’ model yields similar short-term outcomes without an increase in complication rates compared with routine single OR surgery in patients undergoing primary THA or TKA. Cite this article: Bone Joint J 2020;102-B(7 Supple B):112–115.

An articulated spacer made of new primary implants in two-stage exchange for infected total knee arthroplasty may provide durable results

Aims

Our objective is to describe our early and mid-term results with the use of a new simple primary knee prosthesis as an articulating spacer in planned two-stage management for infected knee arthroplasty. As a second objective, we compared outcomes between the group with a retained first stage and those with a complete two-stage revision.

Methods

We included 47 patients (48 knees) with positive criteria for infection, with a minimum two-year follow-up, in which a two-stage approach with an articulating spacer with new implants was used. Patients with infection control, and a stable and functional knee were allowed to retain the initial first-stage components. Outcomes recorded included: infection control rate, reoperations, final range of motion (ROM), and quality of life assessment (QoL) including Western Ontario and McMaster Universities osteoarthritis index, Knee Injury and Osteoarthritis Outcome Score, Oxford Knee Score, 12-Item Short-Form Health Survey questionnaire, and University of California Los Angeles (UCLA) activity score and satisfaction score. These outcomes were evaluated and compared to additional cohorts of patients with retained first-stage interventions and those with a complete two-stage revision. Mean follow-up was 3.7 years (2.0 to 6.5).

Results

Eight knees failed directly related to lack of infection control (16%), and two patients (two knees) died within the first year for causes not directly related, giving an initial success rate of 79% (38/48). Secondary success rate after a subsequent procedure was 91% (44/48 knees). From the initially retained spacers, four knees (22%) required a second-stage revision for continuous symptoms and one (5%) for an acute infection. There were no significant differences regarding the failure rate due to infection, ROM, and QoL assessment between patients with a retained first-stage procedure and those who underwent a second-stage operation.

Conclusion

Our protocol of two-stage exchange for infected knee arthroplasties with an articulating spacer and using new primary knee implants achieves adequate infection control. Retained first-stage operations achieve comparable results in selected cases, with no difference in infection control, ROM, and QoL assessment in comparison to patients with completed two-stage revision surgery. Cite this article: Bone Joint J 2020;102-B(7):852–860.

Tourniquet-induced nerve compression injuries are caused by high pressure levels and gradients - a review of the evidence to guide safe surgical, pre-hospital and blood flow restriction usage

Tourniquets in orthopaedic surgery safely provide blood free surgical fields, but their use is not without risk. Tourniquets can result in temporary or permanent injury to underlying nerves, muscles, blood vessels and soft tissues. Advances in safety, accuracy and reliability of surgical tourniquet systems have reduced nerve-related injuries by reducing pressure levels and pressure gradients, but that may have resulted in reduced awareness of potential injury mechanisms. Short-term use of pre-hospital tourniquets is effective in preventing life-threatening blood loss, but a better understanding of the differences between tourniquets designed for pre-hospital vs surgical use will provide a framework around which to develop guidelines for admitting to hospital individuals with pre-applied tourniquets. Recent evidence supports the application of tourniquets for blood flow restriction (BFR) therapy to reduce muscular atrophy, increase muscle strength, and stimulate bone growth. BFR therapy when appropriately prescribed can augment a surgeon’s treatment plan, improving patient outcomes and reducing recovery time. Key risks, hazards, and mechanisms of injury for surgical, BFR therapy, and pre-hospital tourniquet use are identified, and a description is given of how advances in personalized tourniquet systems have reduced tourniquet-related injuries in these broader settings, increasing patient safety and how these advances are improving treatment outcomes.

Revision total hip arthroplasty: An analysis of the quality and readability of information on the internet

The demand for revision total hip arthroplasty (THA) is increasing. Information quality on the internet has been extensively analysed in relation to primary THA but no such analysis has ever been performed for revision THA. Our aim was to assess the quality and readability of this information. Three major internet search engines were searched for information on revision THA. All websites were assessed for quality of information using the DISCERN score, the Journal of the American Medical Association benchmark criteria and a novel scoring system specific to revision THA [Vancouver Revision Arthroplasty Information (VRAI) score]. Website readability was assessed, as was presence of the Health On the Net Foundation (HON) seal. The majority of websites (52%) were academic with a post-graduate reading level. Only 6.5% of websites had the HON seal. Twenty-eight percent of websites had a ‘good’ DISCERN score and only 28% had a ‘good’ score with the novel VRAI scoring system. Health information websites had significantly higher rates of ‘good’ VRAI scores (P = 0.008). Websites with the HON seal had significantly higher DISCERN scores (P = 0.01). All governmental websites were at a reading level suitable for patient review. Information on the internet relating to revision THA is of low quality, much lower than the quality of information on primary THA. We recommend governmental websites for their readability and health information websites for their quality of information specific to revision THA. Websites with the HON seal provide higher quality information and should be recommended to patients as reading material regarding revision THA.

Multivariate analysis of risk factors for re-dislocation after revision for dislocation after total hip arthroplasty

BACKGROUND

The treatment for recurrent dislocation of a total hip arthroplasty is surgical using varied techniques and technologies to reduce the chances of re-dislocation and re-revision. The goal of this study is to compare operative techniques to reduce re-dislocation and re-revision in revision hip arthroplasty due to recurrent dislocations.

METHODS

A retrospective study of revision hip arthroplasties done due to recurrent dislocation prior to 01 January 2014. Electronic physician and provincial health records were used to collect patients' initial and follow-up data. Treatment failure was defined as either aseptic re-revision or re-dislocation without revision. Time to event was considered as the re-revision date or the date of second dislocation when the latter endpoint was used.

RESULTS

Of 379 operations, 88 (23.2%) had aseptic repeat revision or recurrent dislocation. Of these: 66 (75.0%) due to dislocation with re-revision; 10 (11.4%) due to dislocation with no re-revision surgery; 5 (5.7%) due to aseptic loosening of components; 3 (3.4%) due to osteolysis; 3 (3.4%) due to pseudotumour; and 1 (1.1%) due to periprosthetic fracture. The following factors increase risk of failure: the use of augmented-liners (lipped, oblique and high-offset liners; HR = 1.68, 95% CI, 1.05-2.69), periprosthetic femur fracture (HR = 2.80, 95% CI, 1.39-8.21) and pelvic discontinuity (HR = 3.69, 95% CI, 1.66-8.21). Femur head sizes 36-40 mm are protective (HR = 0.54, 95% CI, 0.31-0.86). In abductor dysfunction the use of focal constrained liners decreases the risk of failure (HR = 0.13, 95% CI, 0.018-0.973).

CONCLUSIONS

Larger head sizes and focal constrained liners (abductors dysfunction) should be used and fully constrained liners and augmented-liners should be avoided in a revision hip arthroplasty due to recurrent dislocations.

Pseudotumors and High-Grade Aseptic Lymphocyte-Dominated Vasculitis-Associated Lesions Around Total Knee Replacements Identified at Aseptic Revision Surgery: Findings of a Large-Scale Histologic Review

BACKGROUND

Aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) development (including pseudotumors) secondary to metal debris generation around total hip arthroplasties is a well-recognized histopathologic phenomenon. Emerging data have highlighted a similar potential concern around TKAs although the body-of-knowledge has largely been limited to individual case reports or small retrospective case series. This study sought to establish the prevalence of pseudotumors or high-grade ALVALs seen at the revision of primary TKAs and to establish the correlation between histologic ALVAL grade and patient-reported functional outcome measures.

METHODS

The findings of 321 non-infective (aseptic) patients undergoing unilateral revision knee surgery, at a high-volume tertiary referral center, were reviewed. Each case was independently histologically classified. Complete patient-reported functional outcome measures were available for 134 patients (42%) allowing correlation between functional performance and histopathology results.

RESULTS

Five distinct pseudotumors and a further 18 high-grade ALVALs were histologically identified representing 1.6% and 5.6% of the cohort, respectively. When compared by histologic grade, Oxford Knee Score and Western Ontario and McMaster University's Osteoarthritis Index suggested a high correlation between ALVAL grade and functional knee scores.

CONCLUSION

These findings suggest a prevalence of pseudotumors or high-grade ALVALs at revision TKA surgery of >7%. This unexpectedly high result may contribute insight into the previously under-appreciated significance of metal debris-related local tissue reactions around TKAs. The findings also demonstrate a strong near-linear inverse relationship between patient-reported clinical knee performance and the underlying histologic grade of local tissue reaction. These results have potential management implications for patients with underperforming TKAs and should prompt consideration of an ALVAL secondary to metallosis in the differential diagnosis.

LEVEL OF EVIDENCE

This is a retrospective cohort study with Level III evidence.

Classic Markers for Infection Perform Poorly in Predicting Residual Infection Prior to Reimplantation

Two-stage exchange arthroplasty remains the treatment of choice for chronic periprosthetic joint infections. This retrospective study conducted between 2009 and 2015 examined the diagnostic value of biomarkers for residual infection between stages. The biomarkers evaluated included C-reactive protein prior to reimplantation, preimplantation synovial fluid white blood cell count and percent neutrophils, and the intraoperative histologic synovial white blood cell count per high-power field (×400) on permanent sections. Residual infection was defined as either positive cultures (more than 1) at second stage, any further surgery (eg, amputation, arthrodesis, or another 2-stage revision), or the need for infection suppression with antibiotics. Sensitivity, specificity, positive and negative predictive values, and likelihood ratios were calculated accordingly. A total of 182 two-stage exchange operations that included 109 (59.9%) prosthetic hips and 73 (40.1%) prosthetic knees met the inclusion criteria. Residual infection was present in 38 (20.9%) of the procedures. The area under the curve-receiver operating characteristic values were 0.677 for C-reactive protein (P=.002), 0.506 for aspiration white blood cell count (P=.944), 0.623 for aspiration percent neutrophils (P=.200), and 0.524 for white blood cell count per high-power field (P=.801). Positive and negative predictive values were poor and ranged between 26% and 57% and 78% and 85%, respectively. Analyses using specific combinations of biomarkers did not significantly improve predictive values. This study showed that classic markers perform poorly in identifying residual infection prior to second-stage revision. Further research is necessary to evaluate the diagnostic utility of other, more recently introduced biomarkers to determine whether infection has been eradicated between stages. [Orthopedics. 2019; 42(1):34-40.].

Contrast-enhanced computed tomography (CECT) attenuation is associated with stiffness of intact knee cartilage

Contrast-enhanced computed tomography (CECT) using charged contrast-agents enables quantification of cartilage glycosaminoglycan content. Since glycosaminoglycan content is a key determinant of cartilage compressive stiffness, CECT measurements have the potential to non-invasively assess cartilage stiffness. The objective of this study was to determine whether CECT attenuation, using a cationic contrast-agent (CA4+), correlates with the stiffness of intact cartilage. Six fresh femoral and six fresh tibial compartments with intact cartilage were obtained from patients undergoing total knee replacement surgery. The instantaneous stiffness was determined for 25-50 points on the surface of each compartment using an established indentation technique. The samples were then immersed in CA4+ solution for 48 h, scanned in a micro-CT scanner, and the average CECT attenuation at each indentation site was found for the superficial cartilage. A significant (p < 0.01) and positive correlation was observed between stiffness and CECT attenuation for sites from each individual cartilage surface, with correlation coefficients ranging from r = 0.37-0.57 and r = 0.48-0.69 (p < 0.01) for the tibia and femur, respectively. When data for each type of cartilage surface were pooled together, the correlation coefficients were r = 0.73 for femoral condyle data points and r = 0.49 for tibial plateau data points. CECT provided a map of cartilage stiffness across each surface, which allows regions of low stiffness to be identified. These findings support continued evaluation and development of quantitative imaging techniques to assess the functional properties of cartilage. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2641-2647, 2018.

One- and two-stage surgical revision of peri-prosthetic joint infection of the hip: a pooled individual participant data analysis of 44 cohort studies

One-stage and two-stage revision strategies are the two main options for treating established chronic peri-prosthetic joint infection (PJI) of the hip; however, there is uncertainty regarding which is the best treatment option. We aimed to compare the risk of re-infection between the two revision strategies using pooled individual participant data (IPD). Observational cohort studies with PJI of the hip treated exclusively by one- or two-stage revision and reporting re-infection outcomes were retrieved by searching MEDLINE, EMBASE, Web of Science, The Cochrane Library, and the WHO International Clinical Trials Registry Platform; as well as email contact with investigators. We analysed IPD of 1856 participants with PJI of the hip from 44 cohorts across four continents. The primary outcome was re-infection (recurrence of infection by the same organism(s) and/or re-infection with a new organism(s)). Hazard ratios (HRs) for re-infection were calculated using Cox proportional frailty hazards models. After a median follow-up of 3.7 years, 222 re-infections were recorded. Re-infection rates per 1000 person-years of follow-up were 16.8 (95% CI 13.6-20.7) and 32.3 (95% CI 27.3-38.3) for one-stage and two-stage strategies respectively. The age- and sex-adjusted HR of re-infection for two-stage revision was 1.70 (0.58-5.00) when compared with one-stage revision. The association remained consistently absent after further adjustment for potential confounders. The HRs did not vary importantly in clinically relevant subgroups. Analysis of pooled individual patient data suggest that a one-stage revision strategy may be as effective as a two-stage revision strategy in treating PJI of the hip.

Revision for adverse local tissue reaction following metal-on-polyethylene total hip arthroplasty is associated with a high risk of early major complications

Aims

Fretting and corrosion at the modular head/neck junction, known as trunnionosis, in total hip arthroplasty (THA) is a cause of adverse reaction to metal debris (ARMD). We describe the outcome of revision of metal-on-polyethylene (MoP) THA for ARMD due to trunnionosis with emphasis on the risk of major complications.

Patients and Methods

A total of 36 patients with a MoP THA who underwent revision for ARMD due to trunnionosis were identified. Three were excluded as their revision had been to another metal head. The remaining 33 were revised to a ceramic head with a titanium sleeve. We describe the presentation, revision findings, and risk of complications in these patients.

Results

The patients presented with pain, swelling, stiffness, or instability and an inflammatory mass was confirmed radiologically. Macroscopic material deposition on the trunnion was seen in all patients, associated with ARMD. Following revision, six (18.2%) dislocated, requiring further revision in four. Three (9.1%) developed a deep infection and six (18.2%) had significant persistent pain without an obvious cause. One developed a femoral artery thrombosis after excision of an iliofemoral pseudotumor, requiring a thrombectomy.

Conclusion

The risk of serious complications following revision MoP THA for ARMD associated with trunnionosis is high. In the presence of extensive tissue damage, a constrained liner or dual mobility construct is recommended in these patients. Cite this article: Bone Joint J 2018;100-B:720-4.

A Comparison of Mobile and Fixed-Bearing Unicompartmental Knee Arthroplasty at a Minimum 10-Year Follow-up

BACKGROUND

The long-term survivorship and functional outcomes of the mobile-bearing (MB) compared to the fixed-bearing (FB) unicompartmental knee arthroplasty (UKA) implant design remain a topic of debate. The aim of the current study was to compare the survivorship and functional outcomes of MB and FB UKA at a minimum 10-year follow-up.

METHODS

We retrospectively reviewed 106 consecutive medial UKAs (89 patients) from our institution with a minimum 10-year follow-up. The 38 MB and 68 FB knees had follow-up of 14.2 years (12.9-15.5) and 11.5 years (10.2-15.1), respectively. Validated patient-reported outcomes and radiographs were evaluated as were etiology, timing, and complexity of revision. Kaplan-Meier 10-year survival was calculated with revision to total knee arthroplasty as the end point.

RESULTS

The 10-year survival was 82.9% (95% confidence interval [CI] 65.8-91.9) for MB and 90.9% (95% CI 79.4-96.2) for FB UKA (P = .102), and 88.0% (95% CI 79.3-93.2) for the entire cohort. Patient outcomes were similar between groups, as were timing and etiologies for revision to total knee arthroplasty. One-third of revisions required either stems or tibial augments, and of these, all were of MB design.

CONCLUSION

Survival and functional outcomes were similar between MB and FB designs. One-third of revisions required either stems or augments, all were of MB design.