Are Flexible Metaphyseal Femoral Cones Stable and Effective? A Biomechanical Study on Hinged Total Knee Arthroplasty

BACKGROUND

Cones currently available in the market are rigid, and unless they are custom-specific designed, are unable to correctly adapt to the shape of the patient's bone. Therefore, flexible metaphyseal cones have been recently introduced to reduce potential bone trauma during implantation. Even if a preliminary clinical study on their use has shown promising results, no biomechanical study evaluates and quantifies their mechanical efficacy and safety.

METHODS

Two commercial versions of flexible cones were analyzed in this study using finite element analysis, based on a previously validated model. Each cone geometry was modeled both as flexible and as rigid, and implanted following surgical guidelines. Three activities were simulated in this study and compared among configurations: surgical impaction, walking, and chair rise.

RESULTS

During impaction, results showed considerably reduced stress in the flexible cones in comparison with rigid ones; the stress resulted was also better distributed and more homogeneous all over the cortical bone, with lower bone peaks. Considering the 2 different activities, the analysis did not show any remarkable differences between flexible and rigid cones both in terms of bone stress and implant micromotion.

CONCLUSIONS

The findings demonstrate that metaphyseal flexible cones allow macrodeformation during impaction due to their flexibility, and therefore, are safer in comparison with rigid cones. However, for the daily tasks investigated, results showed no major differences between rigid and flexible cones in terms of bone stress, implant stability, and micromotion. Therefore, their mechanical performances can be considered similar to the rigid cone.

Outcomes are Compromised When Revising Patellofemoral Arthroplasties for Patellar Component Failures

BACKGROUND

Outcomes of patellofemoral arthroplasty (PFA) to total knee arthroplasty (TKA) conversion are reported to be similar to primary cases. The purpose of this study was to determine whether the cause for conversion from PFA to TKA correlated to outcomes when compared to a matched cohort.

METHODS

A retrospective chart review was performed to identify aseptic PFA to TKA conversions between 2000 and 2021. A cohort of primary TKAs was matched by patient sex, body mass index, and American Society of Anesthesiology score. Clinical outcomes, including range of motion, complication rates, and patient reported outcomes measurement information systems scores, were compared. Chi-squared, Fisher's Exact, and t-tests were performed. There were 20 PFA to TKA conversions that met inclusion criteria and were matched to 60 primary cases.

RESULTS

There were 7 cases revised for arthritis progression, 5 for femoral component failure, 5 for patellar component failure, and 3 for patellar maltracking. PFA to TKA conversions for patellar failure (fracture, component loosening) had worse postoperative flexion (115 versus 127°, P = .023) and more complications of stiffness (40 versus 0%, P = .046) than primary TKAs. Conversions for failed patellar components had worse patient reported outcomes measurement information systems physical function (32 versus 45, P = .0046), physical health (42 versus 49, P = .0258), and pain scores (45 versus 24, P = .0465). No differences were found in rates of infection, manipulations under anesthesia, or reoperations.

CONCLUSION

PFA to TKA conversion outcomes were similar to primary TKA, except in patients who had failed patellar components and demonstrated worse postoperative range of motion and patient-reported outcomes. Surgeons should avoid thin patellar resections and extensive lateral releases to minimize patellar failures.

Antibiotic Prophylaxis in One-Stage Revision of Septic Total Knee Arthroplasty: A Scoping Review

BACKGROUND

Total knee replacement (TKA) is becoming a routine procedure in orthopedic surgery. One of the possible complications of this surgery is periprosthetic joint infection (PJI). The purpose of this study is to identify, through a literature review, which antibiotic is used as prophylaxis for septic one-stage revision TKA and what is the rationale for its use.

METHODS

We searched: MEDLINE, Embase, PsycINFO on Ovid, the Cochrane Library, and the Google Scholar Database. The searches were limited by date (January 2005 to September 2022) and to the English language. All types of original research were considered, including prospective or retrospective longitudinal studies, cross-sectional studies, and randomized trials. The specific search terms were ((antibiotic [MeSH]) AND (prophylaxis)) and (TKA OR TKR OR "Arthroplasty, Replacement, Knee" [MeSH] OR ((knee) adj2 (replace* OR arthroplasty* OR prosthe*))).

RESULTS

Despite our research efforts, we found no article capable of answering the question of which antibiotic to use as surgical prophylaxis for a septic revision one-stage TKA.

CONCLUSIONS

Although the research results are inconclusive, we would recommend using the same antibiotic prophylaxis as for primary joint replacement, i.e., cefazolin, as it was recommended for its low side effect rate and relative effectiveness.

Outcomes After Revision Total Knee Arthroplasty from a Specific, Now-recalled Implant System

BACKGROUND

A specific total knee arthroplasty (TKA) implant system was recently recalled for high incidence of early polymeric wear and osteolysis. We analyzed the early outcomes of aseptic revision with these implants.

METHODS

We identified 202 aseptic revision TKAs of this implant system performed at a single institution between 2010 and 2020. Revision indications included aseptic loosening (n=120), instability (n=55), and polymeric wear/osteolysis (n=27). In 145 cases (72%) components were revised and 57 cases (28%) were isolated polyethylene insert exchange. Kaplan-Meier and Cox proportional hazards analyses were used to determine survivorship free from all-cause re-revision and re-revision risk factors.

RESULTS

At 2 and 5 years, survivorship free from all-cause re-revision was 89 and 76% in the polyethylene exchange cohort versus 92 and 84% in the component revision cohort (P=0.5). At 2 and 5 years, survivorship in revision with components from the same manufacturer was 89 and 80% compared to 95 and 86% in revision with components from a different manufacturer (P=0.2). Among re-revisions (n=30), cones (37%), sleeves (7%), hinge/distal femoral replacement implants were frequently used (13%). Men had increased risk for re-revision (Hazard Ratio=2.3, P=0.04).

CONCLUSIONS

In this series of aseptic revision TKAs performed on a now-recalled implant system, survivorship free from re-revision was lower than expected when components from the same manufacturer were utilized, but comparable to contemporary reports when both components were revised with an alternative implant system. Metaphyseal fixation with cones and sleeves as well as highly constrained implants were frequently utilized at time of re-revision TKA.

Are Trends in Revision Total Joint Arthroplasty Sustainable? Declining Inflation-Adjusted Medicare Reimbursement for Hospitalizations

BACKGROUND

While the burden of revision total joint arthroplasty (TJA) procedures increases within the United States, it is unclear whether health care resource allocation for these complex cases has kept pace. This study examined the trends in hospital-level reimbursements for revision TJA hospitalizations.

METHODS

The Centers for Medicare and Medicaid Services (CMS) inpatient utilization and payment public use files from 2014 to 2019 were queried for diagnostic-related groups (DRGs) for revision TJA: DRG 467 (revision of hip or knee arthroplasty with complication or comorbidity [CC]) and DRG 468 (revision of hip or knee arthroplasty without CC or major CC). From 2014 to 2019, 170,808 revision TJA hospitalizations were billed to Medicare, and revision TJA procedures increased by 3,121 (10.7%). After adjusting to 2019 US dollars with the consumer price index, a multiple linear mixed-model regression analysis was performed. Analysis of covariance compared regressions from 2014 to 2019 for mean-adjusted Medicare payment and mean- adjusted charge were submitted for these DRGs.

RESULTS

Mean-adjusted average Medicare payment for DRG 467 decreased by $804.37 (-3.5%) from 2014 to 2019, whereas, that for DRG 468 decreased by $647.33 (-3.6%). The average inflation-adjusted Medicare payment for DRG 467 decreased at a greater rate during the study period, compared to that for DRG 468 (P = .02).

CONCLUSION

The decline in reimbursement for DRGs 467 and 468 reveals decreasing incentives for revision TJA hospitalizations. Further research should assess the efficacy of current Medicare payment algorithms and identify modifications which may provide for fair hospital level reimbursements.

Biomechanical Analysis of the Use of Stems in Revision Total Knee Arthroplasty

Adequate fixation is fundamental in revision total knee arthroplasty; consequently, surgeons must determine the correct set-up for each patient, choosing from numerous stem solutions. Several designs are currently available on the market, but there are no evidence-based quantitative biomechanical guideline yet. Therefore, several stems were designed and analyzed using a previously-validated finite-element model. The following parameters were studied: stem design characteristics (length and shape), added features (straight/bowed stem), fixation technique, and effect of slots/flutes. Bone stress and Risk of Fracture (RF) were analyzed in different regions of interest during a squat (up to 120°). For the femoral stem, the results indicated that all parameters influenced the bone stress distribution. The maximum von Mises stress and RF were always located near the tip of the stem. The long stems generated stress-shielding in the distal bone. Regarding the tibial stem, cemented stems showed lower micromotions at the bone-tibial tray interface and at the stem tip compared to press-fit stems, reducing the risk of implant loosening. The results demonstrated that anatomical shapes and slots reduce bone stress and risk of fracture, whereas flutes have the opposite effect; no relevant differences were found in this regard when alternating cemented and press-fit stem configurations. Cemented tibial stems reduce antero-posterior micromotions, preventing implant loosening.

Surgical Management of Tibial Bone Loss in Revision Total Knee Arthroplasty: Clinical Outcomes and Radiographic Analysis of Tantalum Cones, Titanium Cones and Titanium Sleeves

BACKGROUND

The use of metaphyseal cones and sleeves has improved the ability to manage tibial bone loss in revision total knee arthroplasty (TKA). The purpose of this study was to compare the outcomes of three systems used for tibial metaphyseal reconstruction in revision TKA.

METHODS

We performed a retrospective review of a consecutive series of 723 revision TKAs, including 145 (20%) knee revisions using tibial cones or sleeves. We compared porous tantalum (TM) cones, titanium (Ti) cones and titanium sleeves. The mean follow-up was 2.5 years.

RESULTS

The rate of revision for any reason was similar among all groups. Revision-free survival rates were similar among all systems studied at a mean follow-up of 2.5 years (TM cones 93%, Ti cones 94%, titanium sleeves 89%). Ti cones had a lower complication rate (6%) compared to TM cones (24%) and sleeves (29%). TM cones (15%) and titanium sleeves (13%) had higher reoperation rates (for any cause) than Ti cones (2%). Radiographic loosening was higher for sleeves (11%) than TM and Ti cones (2%).

CONCLUSION

Metaphyseal reconstruction for tibial bone loss in revision TKA using tantalum cones, titanium cones and titanium sleeves showed successful and comparable early clinical outcomes at a mean follow-up of 2.5 years with higher rates of radiographic loosening for titanium sleeves. Level of Evidence: III.

Synchronous Periprosthetic Joint Infections: High Mortality, Reinfection, and Reoperation

BACKGROUND

Synchronous periprosthetic joint infections (PJIs) are a catastrophic complication with potentially high mortality. We aimed to report mortality, risk of reinfection, revision, reoperation, and implant survivorship after synchronous PJIs.

METHODS

We identified 34 patients treated for PJI in more than one joint within a single 90-day period from 1990 to 2018. PJIs involved bilateral knee arthroplasty (27), bilateral hip arthroplasty (4), 1 knee arthroplasty and 1 elbow arthroplasty (1), 1 knee arthroplasty and 1 shoulder arthroplasty (1), and bilateral hip and knee arthroplasty (1). Irrigation and debridement with component retention was performed in 23 patients, implant resection in 10 patients, and a combination of irrigation and debridement with component retention and implant resection in 1 patient. A competing risk model was used to analyze implant survivorship, and Kaplan-Meier survival was used for patient mortality. Mean follow-up was 6 years.

RESULTS

Mortality was high at 18% at 30 days and 27% at 1 year. The 1-year cumulative incidence of any reinfection was 13% and 27% at 5 years. The 1-year cumulative incidence of any revision or implant removal was 6% and 20% at 5 years. The 1-year cumulative incidence of unplanned reoperation was 25% and 35% at 5 years. Rheumatoid arthritis was associated with increased risk of mortality (HR 7, P < .01), as was liver disease (HR 4, P = .02).

CONCLUSION

In the largest series to date, patients with synchronous PJIs had a high 30-day mortality rate of 18%, and one-fourth underwent unplanned reoperation within the first year.

Utility and Prognostic Ability of a Diagnostic Injection Before Revision Total Knee Arthroplasty

BACKGROUND

Diagnostic injections are commonly utilized in the workup of painful total knee arthroplasties (TKA), particularly when the diagnosis remains unclear. However, current literature provides limited evidence regarding the utility and prognostic capability of anesthetic injections in this scenario. This study sought to establish the role of diagnostic injections in predicting successful revision TKA.

METHODS

A retrospective review was conducted on 144 consecutive aseptic revision TKAs receiving diagnostic anesthetic injections. Instability (57.6%) and aseptic loosening (33.3%) comprised most revision etiologies. Patient-reported percentage pain relief after the injection was statistically correlated with KOOS JR, Knee Society Score, UCLA Activity Level, and satisfaction scores.

RESULTS

About 74.3% (107/144) of revision TKAs reported >50% pain relief after injection. There were no differences in pain relief based on revision indication (P = .841). Improvement from preoperative activity level was greater in the >50% pain relief group (P = .024). Four-month patient satisfaction did not differ between patients who reported >50% and ≤50% pain relief (67% vs. 66%, P = .130). About 64% of patients who reported >50% pain relief were satisfied at minimum 1-year follow-up, compared with only 47% of those who reported ≤50% pain relief after diagnostic injection (P < .001).

CONCLUSION

Study results show that patients reporting >50% pain relief after diagnostic injection have improvements in activity level and maintain greater satisfaction at minimum 1-year than those reporting ≤50% pain relief. Expectations for improvement after revision TKA should be tempered if diagnostic anesthetic injection yields minimal subjective pain relief.

Cost of Aseptic Revision Total Knee Arthroplasty at a Tertiary Medical Center

BACKGROUND

Revision total knee arthroplasty (TKA) involves varying levels of case complexity and costs depending on the following: (1) number of components revised, (2) duration of operating room time, and (3) length of hospital stay. However, the cost associated with different types of aseptic TKA revisions, based on number and type of components revised, is not well described. We sought to determine differences in cost associated with different revision types, and to correlate this with average national hospital and surgeon reimbursement based on current Centers for Medicare and Medicaid Services data.

METHODS

This is a retrospective review of aseptic revision TKAs performed at a single tertiary referral center from 2015 to 2018. Patient demographic data, operating room time, and direct surgery and total hospital costs obtained from an internal accounting database (Enterprise Performance Systems, Inc) were collected. Patients were stratified by the components revised (polyethylene liner only, tibia only, femur only, or both femur and tibia). We hypothesized that direct surgery and total hospital costs would increase as case complexity increased from poly exchange to single-component revisions and both-component revisions.

RESULTS

In total, 106 patients were included (19 poly exchanges, 10 tibia-only revisions, 13 femur-only revisions, and 64 both-component revisions). Operating room time was significantly lower for poly exchange than all other groups (P < .001). Direct surgery and total hospital costs were significantly lower for poly exchange than all other groups (P < .001), and were significantly lower for tibia-only and femur-only revisions compared to both-component revisions (P < .001). Average national surgeon reimbursement by Medicare decreased as a percentage of direct surgery cost as case complexity increased from poly exchange to tibia-only, femur-only, and both-component revisions. Total hospital cost per average Diagnosis Related Group weight was lowest for single-component revisions and highest for both-component revision.

CONCLUSION

There are significant differences in cost associated with aseptic TKA revisions based on number and type of components revised. These differences may not be accurately reflected in reimbursement, and often represent a burden to those who treat complex revisions.

Is constraint implant with metaphyseal sleeve a viable option for revision TKR with preoperative coronal plane instability and bone defect?

BACKGROUND

Metaphyseal sleeves have been used as metaphyseal filling implants to address bone loss during revision total knee replacements (TKRs). This study aims to compare the 2-year clinical and radiological outcomes of constraint implant with bone defect and constraint implant without or minimal bone defect in revisions TKR with preoperative coronal plane instability.

MATERIALS AND METHODS

Seventeen cases of constraint implants with metaphyseal sleeve matched paired with 34 cases of constrained condylar knee (CCK) prosthesis. Age, gender, body mass index and aetiology for revision surgery were recorded. Clinical outcome measures included Knee Society Knee Score (KSKS), Knee Society Function Score (KSFS), Oxford Knee Score (OKS), physical component summary (PCS) and mental component summary (MCS). Radiological outcome measures included joint line changes, hip-knee-ankle angle (HKA), coronal femoral angle (CFA) and coronal tibial angle (CTA).

RESULT

Patients in sleeve group showed significant improvement in KSKS, KSFS and OKS (38 ± 7, 35 ± 6 and 20 ± 2 points, respectively, p < 0.001), while they were 19 ± 3 and 6 ± 2 points for PCS and MCS, respectively (p < 0.001 and p = 0.021). These postoperative scores after surgery were similar between the two groups at 6 months and 2 years. The sleeve provides comparable result in joint line restoration; the postoperative HKA, CFA and CTA were all comparable between the two groups.

CONCLUSION

Metaphyseal sleeve with constraint implant is a viable option for revision TKR with preoperative coronal plane instability and significant bone defect. It is able to achieve similar clinical outcomes and joint line restoration compared to CCK prosthesis at 2-year follow-up.

Trabecular Metal Cones Combined With Short Cemented Stem Allow Favorable Outcomes in Aseptic Revision Total Knee Arthroplasty

BACKGROUND

The purpose of this study was to compare the functional outcomes and implant survivorship at a minimum of 5 years of follow-up of several reconstruction techniques with or without metaphyseal cone and stems of variable length.

METHODS

A retrospective comparative matched analysis was performed from 2 prospectively collected databases. Only patients who underwent revision total knee arthroplasty procedures for aseptic causes using a single design of rotating hinge knee with a minimum of 5 years of follow-up were analyzed. Patients were separated into 3 groups: trabecular metal (TM) cones + short cemented stems (TM + short stem [SS]), TM cones + long uncemented stems (TM + long stem [LS]), and no cone (NC) + long uncemented stems (NC + LS). A matching process based on age (±5 years) was realized.

RESULTS

About 99 patients were included; 33 in the TM + SS group, 33 in the TM + LS group, and 33 in the NC + LS group. The mean time of follow-up was 9.3 years. A significant difference of the improvement of subscale pain, symptom, activities of daily living, quality of life of the Knee Injury and Osteoarthritis Outcome score and knee, function of the Knee Society Score was observed in favor of TM + SS group compared with the 2 other groups. At 8 years of survivorship, the components free of revision for any cause were 90.9% for the TM + SS group, 84.9% for the TM + LS group, and 90.6% for the NC + LS group.

CONCLUSION

The use of a short cemented tibial stem combined with a TM cone in revision total knee arthroplasty offers identical survival rate with better functional outcome compared with the use of a long uncemented stem associated with TM cones or metallic augments at a minimum of 5 years of follow-up.

Gastrocnemius Muscle Flaps for Soft Tissue Coverage in Periprosthetic Knee Joint Infection

BACKGROUND

Soft tissue deficiency in total knee arthroplasty infection is a potentially devastating complication. Gastrocnemius muscle flaps can be used to address this problem. We aim at reporting survival rates of these reconstructions and identify risk factors for failure.

METHODS

A retrospective evaluation of all flaps performed at a single center between 2006 and 2019 was performed. Clinical and microbiological results were assessed in 43 cases after a median follow-up period of 53 months (25%-75% interquartile range 18-79). Function was assessed using the Oxford Knee Score. We analyzed the infection-free survival and identified risk factors using survival comparison and (non-)parametric testing.

RESULTS

Infection-free survival was 71% at 2 years and 63% at 5 years. The rate of subsequent amputation was 16% with a mortality rate of 26% during follow-up. Four patients did not undergo reimplantation and 11 patients received an arthrodesis implant. There were no failures of the flap itself. The Charlson Comorbidity index was the only relevant risk factor for reinfection. Coagulase-negative staphylococci were most common organisms identified. Postoperative function was limited with a mean Oxford Knee Score of 20.

CONCLUSION

Gastrocnemius flap coverage is a valid option for soft tissue reconstruction in periprosthetic infections to retain a functioning limb despite a high complication rate and the risk of subsequent amputation.

Manipulation Under Anesthesia After Total Knee: Who Still Requires a Revision Arthroplasty?

BACKGROUND

Stiffness after total knee arthroplasty (TKA) is a multifactorial complication involving patient, implant, surgical technique, and rehabilitation, occasionally necessitating manipulation under anesthesia (MUA) or revision. Few modern databases contain sufficient longitudinal information of all factors. We characterized MUA after primary TKA and identified independent risk factors for revision TKA after MUA from the American Joint Replacement Registry.

METHODS

We retrospectively reviewed primary TKAs for American Joint Replacement Registry patients ≥65 years from January 1, 2012 to 31 March, 2019. We linked these to the Centers for Medicare and Medicaid Services database to identify MUA and revision TKA procedure codes. We compared groups with chi-squared testing, identifying independent risk factors for subsequent revision with binary logistic regression presented as odds ratios with 95% confidence intervals.

RESULTS

Of 664,604 primary TKAs, 3918 (0.6%) underwent MUA after a median of 2.0 ± 1.0 months. Revision surgery occurred in 131 (3.4%) MUA patients after a median of 9.0 months. Timing of MUA was not different between revision and no revision patients (P = .09). Patients undergoing MUA compared to no MUA were older (age 71.5 vs 70.7, P < .01), predominantly female (63.9% vs 61.2%, P < .01), current/former tobacco users (24.2% vs 13.3%, P < .01), with osteoarthritis diagnoses (98.0% vs 84.3%, P < .01). Independent risk factors for revision after MUA were male gender (1.56, 1.09-2.22).

CONCLUSION

The incidence of MUA after primary TKA is low (0.6%) in Medicare patients ≥65 years of age; 3.4% progress to revision after a median of 9 months. Being male was significantly associated with revision TKA after MUA.

Estimated Glomerular Filtration Rate as a Risk Stratification Tool for Early Complications in Revision Total Hip and Knee Arthroplasty

BACKGROUND

Establishing an association between postoperative outcomes and the spectrum of renal function would allow for more informed decisions to manage surgical risks and improved patient-specific care. Estimated glomerular filtration rate (eGFR) can be calculated from standard prescreening measurements to gauge renal function. This work investigates the effect of eGFR, as a continuous and categorical variable, on mortality and major and minor complications in patients undergoing revision total knee and hip arthroplasty.

METHODS

25,056 patients having undergone revision total hip and knee arthroplasty from 2013 to 2016 were identified using the National Quality Improvement Program database. The investigated outcomes included 30-day mortality, major complications, and minor complications. Multivariate regression models were created to evaluate the effect of eGFR on the outcomes of interest. Multivariate spline regressions were generated to assess for nonlinear relationships between eGFR as a continuous variable and the outcomes.

RESULTS

Our study revealed that as eGFR decreased <60 mL/min/1.73 m², mortality (P = .0001), any major complication (P < .001), and any minor complication (P < .001) increased. Patients with eGFR 15-30 mL/min/1.73 m² had increased risk for mortality (P = .033). There was an increased risk for any major complication at an eGFR 30-60 and <15 mL/min/1.73 m², (P < .05). There was an increased risk of minor complications for those with hyperfiltration and <60 mL/min/1.73 m².

CONCLUSION

Patients with lower preoperative eGFR generally display an increased risk for complications after revision total hip and knee arthroplasty. Proper consideration should be given to this patient population before surgical intervention to allow for preventative measures to be taken to improve patient outcomes.

Two-Stage Treatment for Total Knee Arthroplasty Infection Utilizing an Articulating Prefabricated Antibiotic Spacer

Periprosthetic joint infection represents a serious complication following total knee arthroplasty. In the setting of chronic or age-indeterminate total knee arthroplasty infection, a 2-staged approach has been traditionally the preferred method of treatment over single-stage debridement and reimplantation debridement or debridement, antibiotics and implant retention. Two-stage is the preferred treatment method in North America and has demonstrated better overall success than the single stage techniques. Additionally, the 2-stage method is the preferred treatment for difficult to treat pathogens as well as in patients who have already undergone a previous revision procedure. An articulating prefabricated antibiotic spacer has entered the armamentarium of 2-stage revision knee surgery, and has demonstrated comparable results to custom and static spacers in terms of the primary goal of infection control. Importantly, the potential for enhanced mobility and function hold promise by safely providing a more "livable" knee during the convalescent period prior to definitive reimplantation.

Do Antibiotic-Impregnated Intramedullary Dowels Assist in Eradicating Infection in Total Knee Arthroplasty? Pro

Antibiotic-loaded bone cement (ALBC) spacer constructs for the treatment of periprosthetic joint infections of the knee continue to evolve from the original hockey puck designs. Countless techniques have since been described for augmentation of ALBC spacers with the use of intramedullary (IM) dowels. The use of IM dowels has become a vital addition to any knee spacer construct. ALBC IM dowels are an excellent vessel to provide targeted local antibiotic treatment to high-risk areas like the medullary canal while increasing the overall therapeutic antibiotic elution. In addition, IM dowels provide needed stabilization to the relatively unstable intra-articular spacer component, thereby reducing spacer-related complications like displacement and fracture. Therefore, we recommend regular use of IM dowel augmentation to ALBC spacer constructs.

Intraoperative Practice Variability in Total Knee Arthroplasty

BACKGROUND

Considerable practice variability exists among orthopedic surgeons performing total knee arthroplasty (TKA). The purpose of this study is to understand what TKA surgical and perioperative techniques are standard among high-volume academic knee arthroplasty surgeons.

METHODS

A written survey with 59 questions regarding management preferences in TKA was distributed by the 2018 John N. Insall Traveling Fellows to all arthroplasty-trained attending physicians at 13 medical centers, with 45 responses recorded.

RESULTS

Surveyed surgeons performed unicompartmental knee arthroplasty (88%) and bilateral TKA (87%). Most surveyed surgeons rarely or never performed outpatient primary TKA (71%). Conventional alignment guides and cemented implants were used by 80% of respondents. Most surgeons used posterior-stabilized implants (67%), followed by cruciate-retaining (20%), ultracongruent (20%), and medial congruent or medial pivot designs (17.8%). Surveyed surgeons frequently or always resurfaced the patella (73%), used a tourniquet for the entire case (73%), and used tranexamic acid for all TKAs (91%). The most common locations for intra-articular anesthetic injection were the arthrotomy (91%), the periosteum (84%), and the medial posterior capsule (82%). Saline (62%) and dilute iodine (47%) were the most common irrigation fluids. The arthrotomy was most commonly closed with running barbed suture (60%) followed by interrupted vicryl (40%). Skin closure was predominantly with running monocryl (60%) followed by staples (29%). Anticoagulation for TKA was primarily aspirin 81 mg BID (60%).

CONCLUSION

There was considerable variability among surgeons polled although a strong preference for more conventional and less developmental techniques prevailed.

Analysis of Biomechanical Differences Between Condylar Constrained Knee and Rotating Hinged Implants: A Numerical Study

BACKGROUND

Different levels of constraint for total knee arthroplasty can be considered for revision surgeries. While prior studies have assessed the clinical impact and patient outcomes of condylar constrained knee (CCK) and rotating hinged (RTH) implants, nowadays little is known about the biomechanical effects induced by different levels of constraint on bone stress and implant micromotions.

METHODS

CCK and RTH implant models were analyzed using a previously validated numerical model. Each system was investigated during a squat and a lunge motor task. The force in the joint, the bone and implant stresses, and micromotions in this latter were analyzed and compared among designs.

RESULTS

Different activities induced similar bone stress distributions in both implants. The RTH implant induces mostly high stress compared to the CCK implant, especially in the region close to tip of the stem. However, in the proximal tibia, the stresses achieved with the CCK implant is higher than the one calculated for the RTH design, due to the presence of the post-cam system. Accordingly, the condylar constrained design shows higher implant micromotions due to the greater torsional constraint.

CONCLUSION

Different levels of constraint in revision arthroplasty were always associated with different biomechanical outputs. RTH implants are characterized by higher tibial stress especially in the region close to the stem tip; condylar implants, instead, increase the proximal tibial stress and therefore implant micromotions, as a result of the presence of the post-cam mechanism. Surgeons will have to consider these findings to guarantee the best outcome for the patient and the related change in the bone stress and implant fixation induced by different levels of constrain in a total knee arthroplasty.

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.

Are Stems Redundant in Times of Metaphyseal Sleeve Fixation?

BACKGROUND

Various options exist for implant fixation in revision total knee arthroplasty. One of it is direct cementless metaphyseal sleeve fixation with stems, which has shown excellent short-term and midterm results. Stemless fixation of sleeves is another fixation option for the treatment of specific bone defects; however, so far no data in larger series exist. The objective of this study was, therefore, to analyze the midterm (3-6.5 years) results of stemless sleeve fixation in a larger revision total knee arthroplasty series.

METHODS

In this prospective study, 85 patients with 109 stemless sleeves have been assessed with a mean follow-up of 58.2 (36-78) months. An exclusion criterion was uncontained type II and type III defects. Analysis included clinical and radiographic assessment.

RESULTS

The results showed a survival rate of sleeves in 96% of the tibia (27/28) and 100% of the femur (81/81). This results in an overall survival rate of sleeves of 99% (108/109). So far, 10 patients (11.8%) underwent rerevision during the follow-up period. The main reason for failure was infection (4/85; 4.7%). Range of motion, Oxford Knee Score, Knee Society Score, and Functional Score improved significantly. Mechanical leg alignment was within the 3° corridor in all patients.

CONCLUSIONS

In cases with type I and contained type II defects, sleeves without stems are a promising option, with a survival rate of sleeves of 99% after 5 years. Also, the clinical improvement and reconstruction of leg alignment showed excellent results. In uncontained defects and type III defects, however, we do recommend using stems for additional fixation in the diaphysis. Although the midterm results are very promising, long-term data are needed.

Metaphyseal Fixation Using Highly Porous Cones in Revision Total Knee Arthroplasty: Minimum Two Year Follow Up Study

BACKGROUND

Highly porous metaphyseal cones have been introduced to restore metaphyseal integrity for improved cement interdigitation to achieve durable fixation in revision total knee arthroplasty (TKA). The purpose of this study is to review the survivorship, clinical results, and complications of revision TKA using highly porous 3-dimensionally printed titanium metaphyseal cones.

METHODS

This is a review of 62 revision TKAs using metaphyseal tibial cones, with 15 cases utilizing both tibial and femoral cones. The mean age of the patients was 66 years (range 32-84) who had a mean follow-up of 27 months (range 24-34). There were 38 women and 24 men, who had a mean body mass index of 33 (range 18.3-62).

RESULTS

Revision-free survival of the cones was 90.2%. If infection was excluded, survivorship was 100%. There were no cases of aseptic loosening. The mean Knee Society Score improved from 51 points preoperatively to 80 points at the time of latest follow-up. The mean Knee Society Functional Score improved from 48 points preoperatively to 68 points. A total of 15 of the 62 patients (24%) required additional surgery: 10 (16%) for infection, 3 (5%) for contracture, 1 for patellar subluxation, and 1 for quadriceps tendon rupture.

CONCLUSION

Metaphyseal fixation is important for survivorship in revision TKA which can be challenging due to cancellous and structural bone loss encountered at the time of revision. Prosthetic joint infection continues to be the leading cause of failure in revision TKA. The use of highly porous titanium metaphyseal cones produced from 3-dimensionally printed technology used in this study demonstrated excellent short-term results with no cases of aseptic loosening. Further follow-up is required to determine if these results can be durable over a longer period.

Ignore the Patella in Revision Total Knee Surgery: A Minimum 5-Year Follow-Up With Patella Component Retention

BACKGROUND

In the setting of aseptic revision, a common question is: what should be done with the previously resurfaced patella? We report on a series of aseptic revision total knee arthroplasties (RTKA) where one or both components were revised and the patella was not.

METHODS

The study group was 147 consecutive RTKA in 137 patients with a mean age of 70.1 ± 9.3 years where the patella was not revised. The average body mass index was 31.0 ± 5.4 kg/m². Follow-up was a minimum of 5 years (range, 5 to 12 years). At final follow-up, 13 patients died and 2 patients were lost to follow-up leaving 122 patients and 130 knees available for review. Mean time from primary surgery to RTKA was 9.2 ± 5.5 years. Both components were revised in 50 knees, the femur only in 11 knees, the tibia only in 12 knees, and 57 had an isolated polyethylene revision. We found 5 patients with a mismatch between the patella and femoral components and 30 cases with patella component wear identified intraoperatively.

RESULTS

At final follow-up, there were no reoperations on any patella and none were at risk of failure. There were 6 knees with a lateral patella tilt beyond 10°, but none were subluxed. Knee Society Scores averaged 85 ± 17.2 points at final follow-up.

CONCLUSION

At midterm follow-up in this group of RTKA where the patella was not revised, we identified no subsequent failures of the patella. This is despite the presence of mild patella polyethylene wear and mismatched shapes in several knees.

LEVEL OF EVIDENCE

III.

Are the Outcomes of Revision Knee Arthroplasty for Flexion Instability the Same as for Other Major Failure Mechanisms?

BACKGROUND

Aseptic loosening, infection, and flexion instability have emerged as the leading etiologies for revision after total knee arthroplasty (TKA). Although studies have reported improved outcomes after revision TKA, the relative functional and clinical outcomes of patients revised for flexion instability and other failure etiologies have not been extensively reported. The aim of the study was to compare the functional and patient-reported outcomes of revision TKA for the common failure etiologies.

METHODS

We retrospectively reviewed records of 228 consecutive cases of revision TKA from 2008 to 2014. Revisions performed for aseptic loosening (n = 53), septic revisions (n = 48), and isolated flexion instability (n = 45) with a minimum of 18 months follow-up were included for analysis. Revision for all other etiologies (n = 82) were excluded. The Modified Knee Society Score (KSS), KSS Function, and Western Ontario and McMaster Universities Osteoarthritis Index were recorded for all cases. A 7-point Likert scale was used to record patient's perception of outcomes after revision surgery and analyzed based on etiology.

RESULTS

Although all groups showed improvement in outcome after revision TKA, the changes in Modified KSS and KSS-Function varied according to the etiology of failure of the primary procedure with the smallest improvement being reported by the flexion instability group.

CONCLUSION

Patients undergoing revision for isolated flexion instability have less improvement in functional outcome as compared with other etiologies. We hypothesize this is due to a higher baseline preoperative knee function in the flexion instability group.

Corrosion Damage and Wear Mechanisms in Long-Term Retrieved CoCr Femoral Components for Total Knee Arthroplasty

BACKGROUND

Metal debris and ion release has raised concerns in joint arthroplasty. The purpose of this study was to characterize the sources of metallic ions and particulate debris released from long-term (in vivo >15 years) total knee arthroplasty femoral components.

METHODS

A total of 52 CoCr femoral condyles were identified as having been implanted for more than 15 years. The femoral components were examined for incidence of 5 types of damage (metal-on-metal wear due to historical polyethylene insert failure, mechanically assisted crevice corrosion at taper interfaces, cement interface corrosion, third-body abrasive wear, and inflammatory cell-induced corrosion [ICIC]). Third-body abrasive wear was evaluated using the Hood method for polyethylene components and a similar method quantifying surface damage of the femoral condyle was used. The total area damaged by ICIC was quantified using digital photogrammetry.

RESULTS

Surface damage associated with corrosion and/or CoCr debris release was identified in 51 (98%) CoCr femoral components. Five types of damage were identified: 98% of femoral components exhibited third-body abrasive wear (mostly observed as scratching, n = 51/52), 29% of femoral components exhibited ICIC damage (n = 15/52), 41% exhibited cement interface damage (n = 11/27), 17% exhibited metal-on-metal wear after wear-through of the polyethylene insert (n = 9/52), and 50% of the modular femoral components exhibited mechanically assisted crevice corrosion taper damage (n = 2/4). The total ICIC-damaged area was an average of 0.11 ± 0.12 mm² (range: 0.01-0.46 mm²).

CONCLUSION

Although implant damage in total knee arthroplasty is typically reported with regard to the polyethylene insert, the results of this study demonstrate that abrasive and corrosive damage occurs on the CoCr femoral condyle in vivo.

Functional Improvement and Expectations Are Diminished in Total Knee Arthroplasty Patients Revised for Flexion Instability Compared to Aseptic Loosening and Infection

BACKGROUND

Instability has emerged as the most common noninfectious cause necessitating early revision after total knee arthroplasty (TKA). Although studies have documented improvement in outcomes with revision for flexion instability, it remains unknown how the outcomes compare to patients revised for other failure etiologies. The study purpose was to compare outcomes after revision TKA based on failure etiology.

METHODS

A retrospective review of our prospectively collected revision TKA database was performed on patients who underwent revision TKA from October 1, 2010 to November 19, 2014. Demographic data; minimum 1-year Knee Society Scores; and University of California, Los Angeles activity level scores were obtained.

RESULTS

One hundred seventy-seven consecutive revision TKAs were evaluated. After exclusion of revisions with confounding variables and diagnosis groups with small numbers, 92 patients with a revision diagnosis of flexion instability, infection, or loosening/osteolysis were compared. There were no group differences in Knee Society objective (P ≥ .460) and satisfaction (P ≥ .112) scores or UCLA activity level scores at final follow-up (P ≥ .118). Preoperative Knee Society function scores were significantly higher in patients with flexion instability (P = .019), but the amount of improvement in function relative to baseline was equivalent in the 3 groups (P = .170). Patients revised for flexion instability were significantly more likely than patients in the other 2 groups to report that their expectations were not met (P = .028).

CONCLUSION

Patients and surgeons can expect that revision for isolated flexion instability may only obtain modest improvement compared with other diagnoses, potentially in part due to a higher preoperative functional level in patients with instability.

Factors Associated With 20-Year Cumulative Risk of Infection After Aseptic Index Revision Total Knee Arthroplasty

BACKGROUND

The purpose of this study was to calculate the cumulative risk of periprosthetic joint infection (PJI) after aseptic index knee revisions and to identify the surgical, perioperative, and medical comorbidity risk factors associated with deep infection.

METHODS

We retrospectively reviewed 1802 aseptic index revision total knee arthroplasties performed at our institution from 1970 to 2000. From this cohort, there were 60 reoperations performed for deep infection.

RESULTS

The cumulative risk of infection at 1, 5, 10, and 20 years after index revision was 1%, 2.4%, 3.3%, and 5.6%, respectively.

CONCLUSIONS

Male gender, use of constrained implants, increased operative times, increased Charlson Comorbidity Index, and a history of liver disease were all significantly associated with PJI. The development of cardiovascular disease, endocrine disorders, and renal disease were also associated with PJI.

Direct, Cementless, Metaphyseal Fixation in Knee Revision Arthroplasty With Sleeves-Short-Term Results

Different options for implant fixation in revision TKA exist. Small series have been published on direct cementless fixation with sleeves. The objective of this study was to analyze the short- and mid-term results of sleeve-fixation in a large revision TKA series. In this prospective study 121 patients with 193 sleeves (119 tibial and 74 femoral) were included. Mean follow-up was 3.6 years (2-6.1 years). Analysis included clinical and radiographic assessment. ROM, KSS and Functional Score improved significantly. Fourteen patients (11.4%) underwent operative re-revision during the follow-up period. Direct cementless fixation in the metaphysis by sleeves is a promising option for implant fixation in revision TKA, both on the tibial and femoral side.

Are Revisions of Unicompartmental Knee Arthroplasties More Like a Primary or Revision TKA?

If revision is required, most unicompartmental arhroplasties (UKAs) are converted to total knee arthroplasties (TKAs) and conflicting results regarding surgical complexity and outcome have been reported in publications. 48 UKAs converted to a TKA between 1998 and 2009 were matched based on age, gender, and body mass index, pre-operative Knee Society Score, length of follow-up, and date of the index surgery to 48 primary TKAs and 48 revision TKAs. Surgical characteristics, clinical outcomes, and complications were compared at a mean follow-up of 7 ± 4 years. Even if a revision of UKA is technically less demanding than a revision TKA, functional scores, quality of life, complications and survival rate after revision UKA are more comparable to a revision than primary TKA.

Clinical & radiographic outcomes of cemented vs. diaphyseal engaging cementless stems in aseptic revision TKA

Modular revision systems have become standard in revision TKAs. However, the type of stem fixation remains controversial. The purpose of this study is to compare the incidence of failure between cemented and diaphyseal engaging cementless stems in aseptic revision TKAs. We performed a multicenter retrospective review of 82 revision TKAs performed for aseptic failure. Follow-up averaged 76 and 121 months for the cemented and cementless groups respectively. Re-revision and radiographic failure rates for both femoral and tibial stems were similar between groups. We found similar improvements in knee society scores between the groups. At midterm follow-up, we found no difference in failure rates between the groups. Both types of stem appear to provide reliable fixation and are viable options in revision TKAs.

Predictors of pain medication use for arthroplasty pain after revision total knee arthroplasty

OBJECTIVE

Our objective was to study the use of pain medications for persistent knee pain and their predictors after revision total knee arthroplasty (TKA).

METHODS

We examined whether demographic (gender, age) and clinical characteristics [BMI, co-morbidity measured by the Deyo-Charlson index (a 5-point increase), anxiety and depression] predict the use of NSAIDs and narcotic pain medications 2 and 5 years after revision TKA. Multivariable logistic regression adjusted for these predictors as well as operative diagnosis, American Society of Anesthesiologists class and distance from the medical centre.

RESULTS

A total of 1533 patients responded to the 2-year questionnaire and 881 responded to the 5-year questionnaire. NSAID use was reported by 13.4% (206/1533) of patients at 2 years and 16.7% (147/881) at 5 years. Narcotic medication use was reported by 5.4% (83/1533) of patients at 2 years and 5.9% (52/881) at 5 years. Significant predictors of the use of NSAIDs for index TKA pain at 2 and 5 years were age >60-70 years [odds ratio (OR) 0.62 (95% CI 0.39, 0.98) and 0.46 (0.25, 0.85)] compared with age ≤60 years and a higher Deyo-Charlson index [OR 0.51 (95% CI 0.28, 0.93)] per 5-point increase at 5-year after revision TKA. Significant predictors of narcotic pain medication use for index TKA pain were age >60-70 years [OR 0.41 (0.21, 0.78)] and >70-80 years [0.40 (95% CI 0.22, 0.73)] at 2 years and depression [OR 4.58 (95% CI 1.58, 13.18)] at 5 years.

CONCLUSION

Younger age and depression were risk factors for the use of NSAIDs and narcotic pain medications for index TKA pain at 2- and 5-years after revision TKA.

Variation of Medicare payments for total knee arthroplasty

We analyzed the 2009 Medicare inpatient claims data and other databases to estimate Medicare payments for primary or revision total knee arthroplasty (TKA). The average Medicare hospital payment per procedure was $13,464 for primary TKA (n=227,587) and $17,331 for revision TKA (n=18,677). For both primary and revision TKAs Medicare payments varied substantially across patients, hospitals and healthcare markets. Less than one percent of primary TKA cases but seven percent of revision TKA cases triggered Medicare "outlier" payments, which were $10,000 or higher per case beyond regular diagnosis-related-group payments. Urban and major teaching hospitals were more likely to treat these unusually expensive cases. Hospitals in the Northeast and West regions tended to receive higher Medicare payments than hospitals in the Midwest.

Revision knee arthroplasty including reconstruction of the lateral collateral ligament by allograft: a case report

A 53-year-old woman presented with an unstable and painful total knee arthroplasty 6 months after the index procedure. Disruption of both collateral ligaments as a young adult and the subsequent development of traumatic arthritis required repeated surgical and extensive conservative treatment before a prosthesis was implanted. Examination disclosed marked instability of the lateral collateral ligament (LCL) and loosening of the tibial and the femoral components. Review of the MRI obtained prior to the total knee replacement revealed discontinuity of the LCL with intense scarring of the posterolateral ligament complex. Definitive management of this twofold problem was not helped by literature review, which failed to reveal a gold standard or a broad consensus as a rationale for treatment. Consequently, an individual approach to the problem was defined: A one-stage revision arthroplasty was performed using a modular non-articulated constrained prosthesis and a bone-tendon-bone allograft to reconstruct the LCL in a one-stage operation. Postoperative rehabilitation included continuous passive motion, which was begun immediately after surgery and was gradually increased to 90° of flexion. The LCL reconstruction was initially protected in a hinged knee brace and weight-bearing was initially limited to toe-touch and gradually increased over 6 weeks. Pain-free motion to 0-115° flexion was achieved at 3 months after surgery and the patient had returned to her normal activities. The 4-year-follow-up displayed a stable and functional knee with no evidence of loosening or wear.