Association between synovial tissue damage and pain in late-stage knee osteoarthritis: a cross-sectional study.

OBJECTIVE: To identify the presence and distribution of histopathological features of synovial inflammation and tissue damage, and to test their associations with US imaging measures of synovitis and patient-reported measures of pain in knee osteoarthritis (OA). DESIGN: In the cross-sectional study of 122 patients undergoing surgery for painful late-stage (Kellgren-Lawrence Grade 3 or 4) knee OA, we compared ultrasound (US) measures of synovitis (n=118) and pain (Knee Injury and Osteoarthritis Outcome Score) to histopathological measures of inflammation vs. synovial tissue damage in synovial tissue biopsies. Associations of histopathological features with US measures of inflammation or pain were assessed using linear or logistic regression, while controlling for covariates. RESULTS: Histopathological features of inflammation were associated with higher odds of moderate/severe US synovitis (OR=1.34 [95%CI 1.04, 1.74), whereas features of synovial tissue damage were associated with lower odds of moderate/severe US synovitis (OR = 0.77 [95%CI 0.57, 1.03]). Worse histopathological scores for synovial tissue damage were associated with more pain (-1.47 [95%CI -2.88, -0.05]), even while adjusting for synovial inflammation (-1.61 [95%CI -3.12, -0.10]). CONCLUSIONS: Synovial tissue damage is associated with pain in late-stage knee OA, independent from inflammation and radiographic damage. These novel findings suggest that preventing synovial tissue damage may be an important goal of disease-modifying OA therapy.

Comparison of the Kinematics and Laxity of Total Knee Arthroplasty Bearing Designs Stabilized With Specimen-Specific Virtual Ligaments on a Joint Motion Simulator.

A variety of total knee arthroplasty (TKA) designs offer increased congruency bearing options, primarily to compensate for a loss of posterior cruciate ligament (PCL) function. However, their efficacy in providing sufficient stability under different circumstances requires further investigation. The preclinical testing of prosthesis components on joint motion simulators is useful for quantifying how design changes affect joint stability. However, this type of testing may not be clinically relevant because surrounding ligaments are either ignored or greatly simplified. This study aimed to assess the kinematics and stability of TKA joints during various motions using condylar-stabilized (CS) bearings without a PCL versus cruciate-retaining (CR) bearings with an intact PCL. TKA prosthetic components were tested on a joint motion simulator while being stabilized with five different sets of specimen-specific virtual ligament envelopes. In comparison to CR knees, CS knees without a PCL exhibited a greater amount of posterior tibial displacement laxity, with a mean increase of 2.7±2.1 mm (p = 0.03). Additionally, significant differences were observed in the anterior-posterior kinematics of the knee joint during activities of daily living (ADL) between the two designs. These results were consistent with previous cadaveric investigations, which indicated that CS knees without a PCL are less resistant to posterior tibial displacement than CR knees with one. This study employing virtual ligaments confirms previous findings that the raised anterior lip of some CS bearings may not completely compensate for the absence of the PCL; however, as both studies used reduced joint contact forces, the contributions of this design feature may be attenuated.

Hip Labral and Capsular Repair Are Unable to Restore Distractive Stability in a Biomechanical Model.

PURPOSE: To evaluate the change in hip distractive stability after a capsulotomy, labral tear, and simultaneous repair of both the capsule and the labrum in a biomechanical model. METHODS: Ten fresh-frozen human cadaveric hips were analyzed using a materials testing system to measure the distractive force and distance required to disrupt the hip suction seal under the following conditions: (1) native intact capsule and labrum, (2) 2- or 4-cm interportal capsulotomy (IPC), (3) labral tear, (4) T extension, (5) labral repair, (6) T extension repair, and (7) IPC repair. Each specimen was retested at 0° of flexion, 45° of flexion, and 45° of flexion with 15° of internal rotation. RESULTS: A significantly higher distractive force was required to rupture the suction seal in the intact condition compared with IPC (P = .012; 95% confidence interval [CI], 4.9-42.4); IPC and labral tear (P = .002; 95% CI, 11.3-49.4); IPC, labral tear, and T extension (P = .001; 95% CI, 13.9-51.5); IPC, labral repair, and T extension (P < .001; 95% CI, 20.8-49.7); IPC, labral repair, and T extension repair (P = .002; 95% CI, 12.5-52.4); and IPC repair, labral repair, and T extension repair (P = .01; 95% CI, 5.8-46.1). The IPC condition required a higher distractive force in isolation than when combined with a labral tear (P = .14; 95% CI, 1.2-12.0), T extension (P = .005; 95% CI, 2.8-15.3), or labral repair (P = .002; 95% CI, 4.4-18.8). CONCLUSIONS: The distractive resistance of an intact hip capsule and labrum was not restored once the soft tissues were violated, despite labral repair with a loop technique and capsular repair with interrupted figure-of-8 sutures. CLINICAL RELEVANCE: Time-zero complete capsular repair with concomitant labral repair may not be adequate to restore distractive hip stability after hip arthroscopy, reinforcing the use of postoperative precautions in the early postoperative period.

Central cone design demonstrates greater micromotion compared to keel design in cementless tibial baseplates: A biomechanical analysis.

PURPOSE: The purpose of this study was to compare micromotion of two new cementless tibial baseplates to a cementless design with well-published clinical success. METHODS: Three cementless tibial baseplate designs (fixed-bearing [FB] with keel and cruciform pegs, rotating-platform with porous central cone and pegs, FB with cruciform keel and scalloped pegs) were evaluated on sawbone models. Loading was applied to the baseplate at a rate of 1 Hz for 10,000 cycles, which represents 6-8 weeks of stair descent. This time frame also represents the approximate time length for the induction of biologic fixation of cementless implants. Compressive and shear micromotion at the sawbone-implant interface were measured. RESULTS: At the end of the loading protocol, the central cone rotating-platform design exhibited greater micromotion at the anterior (p < 0.001), posterior (p < 0.001) and medial locations (p = 0.049) compared to the other two implants. The central cone design also exhibited greater translational micromotion in the sagittal plane at the medial (p = 0.001) and lateral locations (p = 0.034) and in the coronal plane anteriorly (p = 0.007). CONCLUSION: The cementless central cone rotating-platform baseplate demonstrated greater vertical and translational micromotion compared to the two FB baseplates with a keel underloading. This may indicate lower initial mechanical stability in implants without a keel, which possibly affects osseointegration. The implication of this is yet unknown and requires further long-term clinical follow-up to correlate these laboratory findings. LEVEL OF EVIDENCE: V (biomechanical study).

Short-Term (90 Days) Clinical Outcomes Following the Day of Surgery Conversion of Inpatient to Same-Day Hip and Knee Arthroplasty.

BACKGROUND: The incidence of total joint arthroplasty is increasing, with added emphasis on shifting care towards outpatient surgery. This has demonstrated improvements in costs and care; however, safety must be prioritized. Published assessment tools highlight candidates for outpatient surgery; however, they often do not define patients who have a worse prognosis. Limited healthcare resources occasionally force patients to convert to outpatient surgery or risk cancellation, creating a dilemma for both patients and surgeons. We evaluated the short-term (90-day) outcomes of patients converted from planned inpatient admission to same-day discharge on day of surgery outpatients and sought to identify any groups at risk, who may not be appropriate for this conversion. METHODS: We identified all patients undergoing planned inpatient total hip or knee arthroplasty at a tertiary academic medical center over a two-year period. We included patients discharged the day of surgery for analysis, excluding revision procedures and those performed for fracture care. A manual chart review identified demographic factors and primary outcome measures; including re-operation, re-admission, and emergency room visits within a 90-day post-operative period. RESULTS: We identified a total of 80 patients who converted from inpatient to outpatient surgery over a two-year interval. Over the first 90 days post-operatively four (5%) patients were readmitted: two (2.5%) for medical complications and two (2.5%) for re-operation. There were two (2.5%) re-operations; one (1.25%) for manipulation under anesthesia, and one (1.25%) for periprosthetic joint infection. There were five (6.3%) wound complications; however, only one (1.25%) required surgical intervention. A total of five (6.3%) patients returned to an emergency department, leading to a single (1.25%) hospital readmission. CONCLUSIONS: Hospital and healthcare resources are occasionally limited to the extent that patients must convert to outpatient surgery or risk cancellation. At our institution, the same-day conversion of planned inpatient hip and knee arthroplasty patients to outpatient surgery was safe and did not increase short-term clinical outcomes or complications.

Evaluation of the Effectiveness of Canadian Cardiovascular Society Guidelines in Minimizing Cardiac Events After Total Hip Arthroplasty.

INTRODUCTION: The aim of the study was to analyze the Canadian Cardiovascular Society (CCS) guidelines for routine postoperative troponin testing after elective total hip arthroplasty (THA) to reduce the mortality rate resulting from myocardial injury. The purpose of this study was to assess the prognostic relevance of implementing these guidelines to minimize cardiac events in patients undergoing elective THA. METHODS: Patients who underwent THA surgery in 2020 were included in the study. The inclusion criteria were elective THA patients aged ≥ 45 years, while emergency, revision, and simultaneous bilateral THA surgeries were excluded. The patients were categorized into four groups based on the CCS guidelines. RESULTS: The study included 669 patients who had an average age of 67 years. There were forty-three patients (6.4%), who experienced a rise in troponin levels ≥ 30 ng/L and developed myocardial injury after noncardiac surgery (MINS). Among these patients, eight developed cardiac complications, and one experienced a serious cardiac event that resulted in death. Notably, there was a significant increase in the length of hospital stay for patients who received the postoperative screening protocol. CONCLUSION: The implementation of the CCS guidelines for routine postoperative troponin testing in elective THA surgery did not significantly decrease the rate of cardiac events or mortality.

Cementless Total Knee Arthroplasty: Does Age Affect Survivorship and Outcomes?

BACKGROUND: Despite the growing popularity of cementless total knee arthroplasty (TKA) in younger patients, the outcomes are unclear in the elderly population. We aimed to compare the clinical outcomes and survivorship of cementless TKA between different age groups. METHODS: Utilizing our prospectively collected institutional database, we retrospectively reviewed all patients undergoing primary cementless TKAs at a tertiary care institute. We identified 347 TKA, which were divided into 3 groups based on age at the time of surgery. Group A was ≤ 60 years, Group B was 60 to ≤ 70 years, and Group C was > 70 years. We compared clinical outcomes (Knee Society Clinical Rating System [KSCRS], Western Ontario and McMaster University Osteoarthritis Index [WOMAC], and Veterans Rand 12 Item Health Survey [VR-12]) and survivorship between the groups. RESULTS: At final follow-up, range of motion, KSCRS, WOMAC, and VR-12 physical score were comparable (P > .05). The VR-12 Mental score was higher in Group B and Group C than in Group A (P = .003). Compared to preoperative scores, the change in KSCRS, WOMAC, and VR-12 physical and mental scores was comparable at the final follow-up (P > .05). No patient underwent revision for aseptic loosening. CONCLUSIONS: There were no cases of revision surgery for aseptic loosening in our cohort of 347 cementless TKAs. Patients > 70 years of age undergoing cementless TKA can achieve clinical scores equivalent to those of younger patients at short term (2-year) follow-up. Longer-term survivorship is still required, but based on early data, cementless TKA can be a safe option for older patients.

Survivorship and Outcomes of 2-Stage Revision for Infected Total Hip Arthroplasty at a Mean of 7-Year Follow-Up.

BACKGROUND: Periprosthetic joint infection (PJI) continues to be one of the leading causes of failure following total hip arthroplasty (THA). The objectives of the study were to (1) determine the minimum 2-year infection-free survivorship of 2-stage revision THA, (2) determine the causative organisms for repeat 2-stage revision THA, and (3) characterize the results of failed 2-stage revisions and evaluate patient-reported outcome measures (PROMs). METHODS: A retrospective chart review was completed for patients who underwent 2-stage revision THA for PJI. Prospective data were collected on each patient, including demographics, causative organisms, complications, and type of reoperation. The PROMs, including Harris Hip Score, 12-item Short-Form Health Survey, and Western Ontario and McMaster Universities Osteoarthritis Index scores were obtained prior to 2-stage revision THA surgery and annually as part of standard clinical and radiographic follow-up. RESULTS: A total of 328 patients who underwent a 2-stage revision THA for a PJI were included in the study (mean age 67 years [range, 28 to 90], mean body mass index of 30.6 [range, 15 to 57]). The overall infection-free survivorship for 2-stage revision THA was 73.8% at a minimum of 2 years (range, 2 to 20). Overall, 194 (59.1%) patients who had successful infection eradication underwent a 2-revision THA only. The most common single organisms infected were Staphylococcus aureus (12.5%) and Staphylococcus epidermidis (11%). Higher reoperation rates were found in cases with methicillin-resistant Staphylococcus aureus and polymicrobial infections. All PROMs showed statistical improvement from preoperatively to the latest follow-up appointment. CONCLUSIONS: Two-stage revision THA is associated with a good success rate in the treatment of PJIs at mid-term to long-term follow-up. Polymicrobial and methicillin-resistant Staphylococcus aureus infections are poor prognostic factors, making the eradication of infection more difficult. The management of PJIs continues to be one of the most important orthopaedic challenges to treat.

Effect of Surgical Technique, Implant Design, and Time of Examination on Contact Kinematics: A Study of Bicruciate-Stabilized and Posterior-Stabilized Total Knee Arthroplasty.

BACKGROUND: Bicruciate-stabilized (BCS) total knee arthroplasty (TKA) designs attempt to approximate natural knee mechanics. Multiple surgical techniques, including gap balancing (GB) and measured resection (MR), have been developed to provide optimal implant positioning and soft-tissue balance. The goal of this study was to determine the effect of surgical technique on BCS TKA contact kinematics. Secondary goals included investigating the change of kinematics over time and comparing BCS TKA kinematics to a posterior-stabilized (PS) design. METHODS: The study included the BCS-GB, BCS-MR, and PS-MR groups. The BCS-GB and BCS-MR groups underwent weight-bearing radiostereometric analysis for multiple knee flexion angles at 3 months and 1 year postoperatively, whereas the PS-MR group was imaged at 1 year postoperatively. The medial and lateral contact kinematics were determined from implant poses. RESULTS: There were no differences in BCS TKA kinematics between the GB and MR techniques. There were differences in the mid-flexion ranges when comparing the 3-month and 1-year kinematics of the BCS design; however, they were less than 1.5 mm. Differences existed between the kinematics of the BCS and PS designs at all flexion angles for the medial condyle (P < .0006) and at 0° of flexion on the lateral condyle (P < .0001). CONCLUSIONS: Contact kinematics for a BCS design were similar for both surgical techniques, suggesting both are appropriate for this design. Small, likely clinically insignificant differences were found between 3-month and 1-year kinematics. The BCS TKA kinematics differed from the PS design; however, it is unclear whether these differences improve clinical outcomes.

Minimum 2-Year Outcomes of a Modern Monoblock Titanium Fluted Tapered Revision Stem for Complex Primary and Revision Total Hip Arthroplasty.

BACKGROUND: Modular titanium fluted tapered (TFT) stems have demonstrated excellent clinical success for femoral revision total hip arthroplasty (THA) surgery. This study reports the short-term outcomes of a novel modern monoblock TFT stem used for revision and complex primary THA with a minimum of 2 years of follow-up. METHODS: We identified 126 patients who received a single monoblock TFT stem: 26 patients for complex THA (failed fracture fixation) and 100 patients for revision THA. The reasons for revision THA included 40 for previous periprosthetic joint infection, 42 for aseptic loosening, 9 for trunnionosis, and 9 for periprosthetic fractures. The Paprosky grading for femoral bone loss at the time of surgery and the measured subsidence of femoral stems at 3-month follow-up were determined. We evaluated the number and indications for reoperations. RESULTS: The mean time from surgery was 3.9 years (range, 2.0 to 6.9). A paired t-test analysis showed significant improvement from preoperative versus postoperative clinical outcome scores (P < .001) for Harris Hip Score (38.76 ± 15.24 versus 83.42 ± 15.38), Western Ontario and McMaster Universities Arthritis Index (45.6 ± 19.0 versus 69.9 ± 21.3), Veterans RAND 12 Item Health Survey Physical component (31.7 ± 8.1 versus 37.8 ± 11.3), and Veterans RAND 12 Item Health Survey Mental component (48.2 ± 12.2 versus 51.6 ± 12.5). The Paprosky grading for femoral bone loss was Grade 1 (3.9%), Grade 2 (35.7%), Grade 3A (47.6%), Grade 3B (11.1%), and Grade 4 (1.6%) cases. There were 18 reoperations (14.7%), with 13 for periprosthetic joint infection (7 treated with implant retention and 6 treated with a 2-stage revision), 4 for instability, and 1 for acetabular aseptic loosening. There were no aseptic failures of the stem. CONCLUSIONS: This novel modern monoblock TFT stem provided reliable femoral fixation and has increasingly supplanted the use of modular TFT stems for complex primary and revision surgery in our institution.

Predictors of Undergoing Revision Within 5 Years of Total Knee Arthroplasty: A Population-Based Study.

BACKGROUND: The objective of this study was to identify the rate and risk factors for revision total knee arthroplasty (TKA) within the first 5 years postoperative. Our secondary objective was to identify the rate of additional surgical procedures and death. METHODS: We conducted a retrospective cohort study among patients in Ontario, Canada who underwent an elective, primary TKA between April 1, 2007, and March 31, 2014, for osteoarthritis. We excluded patients under 40 years and who had undergone a TKA within the previous 15 years. Our final study cohort included 94,193 patients. We reported the proportion of the study cohort who experienced revision surgery within 2 and 5 years of the primary TKA; secondary surgery within 5 years. We conducted Cochran-Armitage tests for trends to assess changes in the proportion of patients who experienced each of the study outcomes, and multivariable logistic regressions to evaluate predictors of a revision TKA. RESULTS: There were 3,112 (3.3%) patients who had a revision within 5 years, and 1,866 (2.0%) within 2 years of their primary TKA. 3,316 (3.5%) had a secondary surgery (0.6% patellar resurfacing; 1.6% manipulation; 1.3% synovectomy; 0.5% washout; 0.9% debridement). Lower age, men, lower income, higher comorbidity score, depression, previous arthroscopy, lower surgeon volume, and general anesthesia were all significant positive predictors of revision. CONCLUSIONS: In our study cohort, 2.0% of patients had a revision TKA within 2 years, and 3.3% within 5 years of their primary TKA. Preoperative identification of risk factors may reduce the future prevalence of revision TKAs.

Orthopedic surgeons' transition into full-time practice over the last 20 years: an analysis using Ministry of Health billing data.

BACKGROUND: Underemployment is a reality for many new graduates, who accept locum or part-time work as an alternative to unemployment because of lack of opportunities. We sought to analyze orthopedic surgeons' Ontario Health Insurance Program (OHIP) billing data over a 20-year period as a proxy of practice patterns and hypothesized that billing in the first 6 years of practice would be affected by underemployment and locum. METHODS: We analyzed the annual average billing totals of orthopedic surgeons, broken down by year of graduation, year of billings, and number of surgeons billing in that year. We analyzed public census data of the Ontario population size as a proxy of orthopedic demand. RESULTS: A 2019 cross-sectional analysis showed that around 15 surgeons per graduating year were billing in Ontario from the 1995 to 2016 cohorts, while 2017 and 2018 saw an increase to 30 and 36 actively billing surgeons, respectively. The number returned to more historical numbers in 2019, with 20 actively billing surgeons. For those surgeons billing in Ontario, billing trends have been roughly stable, with average billings increasing each year for the first 6 years in practice (p < 0.001). Year of graduation did not have an effect on the first 6 years of billings (p > 0.5). Billings were stable after 6 years in practice (p > 0.09). CONCLUSION: The Ontario health care system has not expanded to support more orthopedic surgeons despite the aging and growing population; despite our growing population, the number of surgeons being trained and retained has not matched this growth. Further research needs to be done to guide optimal health human resource decision-making.

Gap patterns and radiographic follow-up of newer-generation cementless total knee arthroplasty designs.

BACKGROUND: Interest in cementless total knee arthroplasty (TKA) has increased with advancement of biomaterials and implant design and associated improved longevity. We sought to evaluate the gap patterns and radiolucent zones radiographically for 2 newer-generation cementless TKA designs. METHODS: We retrospectively reviewed our single-institution database between January 2017 and December 2019. We identified patients with a porous keeled tibia base-plate with 4-bullet cruciform spikes and peri-apatite coated femoral component (study group 1) and patients who received a cementless porous coated femoral component and rotating platform tibia baseplate with 4 peripheral porous coated pegs around a central cone (study group 2). We identified gap patterns at 6 weeks and at 1 year or more postoperatively on radiographs, noting indications for reoperation. RESULTS: We identified 228 patients in study group 1 and 41 patients in study group 2. At 1-year follow-up, we found evidence of resolved femoral gaps in 52 (72.2%) of 72 patients in study group 1 and 10 (58.8%) of 17 patients in study group 2 (p = 0.124). We identified 27 (84.3%) of 32 patients in study group 1 and 7 (70.0%) of 10 patients in study group 2 with resolved tibia gaps (p = 0.313). After 1 year, there were significantly more Zone 3a femoral zonal radiolucent gaps (p = 0.001) and Zone 8 tibia zonal radiolucent gaps (p = 0.002) in study group 2 than in study group 1. There were 4 reoperations for study group 1 and 0 reoperations for study group 2. CONCLUSION: The modern cementless TKA systems have varied gap patterns in postoperative radiographs, which may be attributed to the implant design. Most radiolucent gaps resolve radiographically on follow-up.

Development of Multibundle Virtual Ligaments to Simulate Knee Mechanics After Total Knee Arthroplasty.

Preclinical evaluation of total knee arthroplasty (TKA) components is essential to understanding their mechanical behavior and developing strategies for improving joint stability. While preclinical testing of TKA components has been useful in quantifying their effectiveness, such testing can be criticized for lacking clinical relevance, as the important contributions of surrounding soft tissues are either neglected or greatly simplified. The purpose of our study was to develop and determine if subject-specific virtual ligaments reproduce a similar behavior as native ligaments surrounding TKA joints. Six TKA knees were mounted to a motion simulator. Each was subjected to tests of anterior-posterior (AP), internal-external (IE), and varus-valgus (VV) laxity. The forces transmitted through major ligaments were measured using a sequential resection technique. By tuning the measured ligament forces and elongations to a generic nonlinear elastic ligament model, virtual ligaments were designed and used to simulate the soft tissue envelope around isolated TKA components. The average root-mean-square error (RMSE) between the laxity results of TKA joints with native versus virtual ligaments was 3.5 ± 1.8 mm during AP translation, 7.5 ± 4.2 deg during IE rotations, and 2.0 ± 1.2 deg during VV rotations. Interclass correlation coefficients (ICCs) indicated a good level of reliability for AP and IE laxity (0.85 and 0.84). To conclude, the advancement of virtual ligament envelopes as a more realistic representation of soft tissue constraint around TKA joints is a valuable approach for obtaining clinically relevant kinematics when testing TKA components on joint motion simulators.

What Patient and Implant Factors Affect Trunnionosis Severity? An Implant Retrieval Analysis of 664 Femoral Stems.

BACKGROUND: Corrosion at the modular head-neck taper interface of total and hemiarthroplasty hip implants (trunnionosis) is a cause of implant failure and thus a clinical concern. Patient and device factors contributing to the occurrence of trunnionosis have been investigated in prior implant retrieval studies but generally with limited sample sizes and a narrow range of models. The purpose of the present investigation was to determine which patient and device factors were associated with corrosion damage on the femoral stem taper across a large collection of different implant models retrieved following revision hip arthroplasty. METHODS: A retrieval study of 664 hip arthroplasty modular stem components was performed. Patient and device information was collected. Trunnions were imaged under digital microscopy and scored for corrosion damage using a scaling system. Damage was related to patient and device factors using regression analyses. RESULTS: Greater duration of implantation (P = .005) and larger head size (P < .001) were associated with an elevated corrosion class. Older age at index surgery (P = .035), stainless steel stem material (P = .022), indication for revision as bone or periprosthetic fracture (P = .017), and infection (P = .018) and certain larger taper geometries were associated with a decreased corrosion class. CONCLUSION: Factors identified as contributing to a higher or lower risk of more severe corrosion are consistent with most prior smaller retrieval studies. Surgeons should be aware of these risk factors when selecting implants for their patients and when diagnosing trunnionosis in symptomatic hip arthroplasty patients.

Axial and Sagittal Rotation of Cementless Tibial Baseplates Occurs in Bone Under Joint Loading.

BACKGROUND: There has been a recent increase in the use of cementless fixation for primary total knee arthroplasty. While the early results of contemporary cementless implants are promising, understanding the behavior of cementless tibial baseplates under loading remains an ongoing interest. The objective of this study was to identify the pattern of displacement that occurred under loading for a single cementless tibial baseplate design at one year post operation for stable and continuously migrating implants. METHODS: There were 28 subjects from a previous trial of a pegged highly porous cementless tibial baseplate evaluated. Subjects underwent supine radiostereometric exams from two weeks through one year after surgery. At one year, subjects also underwent a standing radiostereometric exam. Fictive points on the tibial baseplate model were used to relate translations to anatomical locations. Migration over time was calculated to determine if subjects displayed stable or continuous migration. The magnitude of inducible displacement between the supine and standing exams was calculated. RESULTS: Inducible displacement patterns were similar between stable and continuously migrating tibial baseplates. Displacements were greatest in the anterior-posterior axis followed by the lateral-medial axis. Correlation of displacements between adjacent fictive points in these axes indicated an axial rotation of the baseplate occurred under loading (r2 = 0.689-0.977, P < .001). Less displacement occurred in the superior-inferior axis and correlations indicated an anterior-posterior tilt of the baseplate occurred under loading (r2 = 0.178-0.226, P = .009-.023). DISCUSSION: From supine to standing position the predominant pattern of displacement for this cementless tibial baseplate was axial rotation, with some subjects also displaying an anterior-posterior tilt.

Minimum 2-Year Outcomes of All-Polyethylene Tibial Components in Patients Who Have Body Mass Index of 35 or Greater.

BACKGROUND: Several studies have reported negative results after total knee arthroplasty (TKA) in obese patients. This study aims to analyze the minimum 2-year outcomes in patients who have a body mass index (BMI) > 35 undergoing cemented TKA using an all-polyethylene tibial component (APTC) at a minimum of 2 years of follow-up. METHODS: We retrospectively studied 163 obese patients (192 TKAs) who underwent a primary cemented TKA using an APTC comparing the outcomes of 96 TKA patients who had a BMI > 35 to 39.9 (group A) with 96 patients who a TKA and a BMI ≥40 (group B). Median follow-up of groups A and B were 3.8 years and 3.5 years respectively (P = .02). Multiple regression analyses were performed to evaluate independent risk factors associated with complications. Kaplan-Meier survival curves were estimated, defining failure as the need for any further femoral or tibial revision surgery with implant removal, irrespective of the reason. RESULTS: There was no significant difference at the latest follow-up patient-reported outcomes between both groups. Survivorship, as defined by revision for any reason, was 99% for group A and 99% for group B (P = 1.00). There was 1 aseptic tibial failure in group A, and 1 septic failure in group B. Multiple regression analyses showed no significant associations between age (odds ratio [OR] = 1.00; P = .98; 95% confidence interval (CI) = 0.93 to 1.08), sex (OR = 1.38; P = .70; 95% CI = 0.26 to 7.25), BMI (OR = 1.00; P = .95; 95% CI = 0.87 to 1.16), and complication rate. CONCLUSION: At a median 3.7-year follow-up, the use of an APTC provided excellent outcomes and survivorship in patients who had Class 2 and Class 3 obesity. LEVEL OF EVIDENCE: Level III, therapeutic study.

Correlating Contact Kinematics to Tibial Component Migration Following Cemented Bicruciate Stabilized Total Knee Arthroplasty.

BACKGROUND: Contact kinematics in total knee arthroplasty (TKA) has been shown to affect tibial component migration. However, previous studies correlating kinematic variables to implant migration were completed with older TKA designs. The goal of this study was to determine if there are associations between contact kinematics and tibial component migration for a cemented, bicruciate stabilized (BCS) TKA system. METHODS: A total of 54 knees implanted with a BCS TKA system were analyzed using radiostereometric analysis (RSA). Patients underwent RSA exams at 2 weeks, 6 weeks, 3 months, 6 months, 1 year, and 2 years post operation to measure tibial component migration. At 1 year, contact kinematics was evaluated during a quasi-static deep knee bend. Linear regression analyses were performed between kinematic variables and migration values. RESULTS: Significant correlations were found between contact kinematics and tibial component migration. Excursion on the lateral condyle was the most consistent variable correlating with implant migration. Six patients had > 0.2 mm migrations from 1 to 2 years post operation indicating continuously migrating tibial components, and most had atypical contact kinematics. CONCLUSION: Kinematics was shown to influence tibial component migration. Reduced lateral excursion, suggesting a more constrained lateral condyle, resulted in greater implant migration. The 6 patients who had continuously migrating tibial components had demographic factors that may limit the ability to endure unintended force transmissions caused by abnormal kinematics. These results highlight the importance of restoring knee kinematics with this BCS TKA design to minimize improper force transmissions and resultant increased implant migrations.

No Difference in Subsidence Between Modern Monoblock and Modular Titanium Fluted Tapered Femoral Stems.

BACKGROUND: Subsidence remains a concern when utilizing tapered fluted titanium (TFT) femoral stems and may lead to leg length discrepancy, impingement, instability, and failure to obtain osseointegration. This study aims to compare stem subsidence across 3 modern TFT stems. Our secondary aim was to investigate the influence of bicortical contact or "scratch fit" on subsidence, as well as the role of intraoperative imaging in maximizing bicortical contact and preventing stem subsidence. METHODS: A retrospective review of 271 hip arthroplasties utilizing modern TFT stems at a single institution was performed. Three stem designs were included in the analysis: 1 monoblock TFT stem (n = 91) and 2 modular TFT stems (n = 90; n = 90). Patient demographics, Paprosky femoral bone loss classification, bicortical contact, utilization of intraoperative imaging, and stem subsidence (comparison of initial postoperative radiograph to the latest follow-up radiograph-minimum 3 months) were recorded. RESULTS: There was no statistically significant difference in overall subsidence (P = .191) or the incidence of subsidence >5 millimeters between stems (P = .126). Subgroup analysis based on femoral bone loss grading showed no difference in subsidence between stems. Increased bicortical contact was associated with reduced subsidence (P = .004). Intraoperative imaging was used in 46.5% (126 of 271) of cases; this was not correlated with bicortical contact (P = .673) or subsidence (P = .521). CONCLUSION: All 3 modern TFT stems were highly successful and associated with low rates of subsidence, regardless of modular or monoblock design. Surgeons should select the stem that they feel is most clinically appropriate.

Total Hip Arthroplasty in Patients Aged 40 to 60 Years Old: A Population-Based Study.

BACKGROUND: Contemporary total hip arthroplasty (THA) has resolved many implant longevity concerns in younger patients. Patients in their fourth and fifth decades of life are projected to be the fastest-growing demographic of THA patients. We aimed to assess this demographic to: 1) evaluate the rate of THA over time; 2) evaluate the cumulative incidence of revision; and 3) identify risk factors for revision. METHODS: A retrospective population-based study of patients between 40 and 60 years old undergoing primary THA was conducted using administrative data from a large clinical data repository. A total of 28,414 patients were included for analysis with a mean age of 53 years (range, 40-60 years) and median follow-up of 9 years (range, 0-17 years). Linear regressions were used to assess annual rates of THA in this cohort over time. Kaplan-Meier analysis was used to determine cumulative incidence of revision. Multivariate Cox proportional hazards models were used to determine association of variables with revision risk. RESULTS: The annual rate of THA in our population increased by 60.7% over the study period (P < .0001). Cumulative incidence of revision was 2.9% at 5 years and 4.8% at 10 years. Younger age, women, non-osteoarthritis diagnosis, medical complications, and annual surgeon volume ≤ 60 THA were associated with increased revision risk. CONCLUSION: Demand for THA continues to dramatically increase in this cohort. Risk of revision was low but multiple risk factors were identified. Future studies will help delineate the effect of these variables on revision risk and assess implant survivorship beyond 10 years.