Static Non-articulating Knee Spacers Are Associated with a High Degree of Morbidity in Challenging Clinical Scenarios.

The morbidity associated with the use of static non-articulating knee spacers for the treatment of periprosthetic joint infection (PJI) in challenging clinical scenarios has not been well described. From 2011-2019, 63 molded block static spacers were utilized at two academic institutions for the treatment of PJI with associated severe soft tissue compromise (59%), collateral ligament deficiency (49%), extensor mechanism compromise (48%), or type 3 bone defects (44%). Complications and outcomes were assessed. Complications with the use of static spacers were common and included further bone loss (46%), spacer migration (16%), extensor mechanism compromise (16%), cast or related soft tissue injuries (16%), fracture (13%), and spacer breakage (3%). Ultimately, 22% of patients underwent amputation. Patient variables such as age and body mass index were not associated with outcomes. Static knee spacers are associated with substantial morbidity in challenging clinical scenarios and alternatives may need to be considered. (Journal of Surgical Orthopaedic Advances 32(2):122-126, 2023).

Optimizing Asymmetric Native Knee Flexion Gap Balance Promotes Superior Outcomes in Primary Total Knee Arthroplasty.

INTRODUCTION: Replicating native knee kinematics remains the ultimate goal of total knee arthroplasty (TKA). Technology, such as robotics, provides robust intraoperative data; however, no evidence-based targets currently exist for improved clinical outcomes. Furthermore, some surgeons target a rectangular flexion space in TKA unlike the native knee. This study evaluated the effect of in vivo flexion gap asymmetry on patient-reported outcome measures (PROMs) in contemporary TKA. METHODS: In vivo tibiofemoral joint space dimensions were measured during 129 TKAs using a calibrated tension device before and after complete posterior cruciate ligament resection. PROMs were compared based on the final dimensions and the change in flexion gap dimensions at 90° of flexion: (1) equal laxity, (2) lateral laxity, and (3) medial laxity. Groups did not differ by demographics ( P ≥ 0.347), clinical follow-up ( P = 0.134), tibiofemoral alignment ( P = 0.498), or preoperative PROMs ( P ≥ 0.093). Mean follow-up for the cohort was 1.5 years (range, 1-3). RESULTS: Pain with climbing stairs, pain while standing upright, and knees "always feeling normal" scores were superior for patients with equal or lateral laxity compared with medial laxity ( P ≤ 0.064). Pain with level walking, University of California Los Angeles activity level, KOOS JR, and satisfaction scores also tended to be superior for patients with equal or lateral laxity, although it lacked statistical significance ( P ≥ 0.111). DISCUSSION: Results of this study suggest that patients with either an equally tensioned rectangular flexion space or with later-flexion lateral laxity after posterior cruciate ligament resection may achieve superior PROMs. Findings support the clinical benefit of facilitating posterolateral femoral roll back in flexion, which mimics native knee kinematics and further helps define targets for advanced technology.

Patellar tilt does not affect patient reported outcomes after modern total knee arthroplasty.

BACKGROUND: The focus of patella maltracking after total knee arthroplasty (TKA) has traditionally been on patella polyethylene damage and failure mechanisms rather than functional outcomes. The purpose of this study was to evaluate the effect of patellar tilt on patient reported outcomes (PROMS) after primary TKA performed with patellar resurfacing. METHODS: A retrospective review using a single implant design was performed. Patella tilt was radiographically measured according to a standardized protocol. PROMS related to pain, function, and satisfaction were evaluated preoperatively and at minimum 1-year follow-up. RESULTS: A total of 468 TKAs were included for analysis. Mean age and BMI were 64 years and 35 kg/m2; respectively while 63% of patients were female. The median follow-up period was 12.7 months. Overall, patellar tilt was corrected from a median of 5.0 degrees preoperatively to a median of 3.0 degrees postoperatively. Preoperative, postoperative, and the change in patellar tilt had no significant effects on PROMS at minimum 1-year follow-up (p ≥ 0.092). Satisfaction in knee function while getting out of bed was higher for patients with approximately the same patellar tilt before and after TKA compared to patients with an increase in lateral patellar tilt (95% vs 80%, p = 0.025). CONCLUSIONS: The range of patellar tilt studied in this cohort had little to no effect on PROMS. However, suboptimal patellar tracking may potentiate edge loading of the polyethylene and contribute to implant damage in the long-term. These results are helpful to focus efforts on the tibiofemoral articulation as the predominant determinant of patient outcomes.

Posterior Cruciate Ligament Resection Does Not Consistently Increase the Flexion Space in Contemporary Total Knee Arthroplasty.

INTRODUCTION: It is accepted dogma in total knee arthroplasty (TKA) that resecting the posterior cruciate ligament (PCL) increases the flexion-space by approximately 4mm. Unfortunately, this doctrine is based on historical studies of limited size with variable technique. The aim of this study was to determine the effect of PCL-resection on in vivo tibiofemoral joint space dimensions in a cohort of modern TKAs. METHODS: Tibiofemoral joint space measurements were made during 129 standardized TKAs by two arthroplasty surgeons. A medial parapatellar approach, computer navigation and provisional bone cuts were performed in all cases with particular attention to preserving PCL integrity. The tibiofemoral gap was measured with a calibrated tension device at extension, 45-degrees, and 90-degrees before and after complete PCL-resection. RESULTS: 51% of patients were female (66/129) with mean age and BMI of 69.5 years and 34.2 kg/m2, respectively. After PCL-resection, mean change in center joint space dimension increased 0.33mm at extension, 0.95mm at 45-degrees, and 1.71mm at 90-degrees (P < .001). The 90-degree flexion-space opened ≥4mm in only 10% of patients. Dividing the flexion-space change by femoral implant dimension to account for patient size, the flexion-space at 90-degrees significantly increased more in females compared to males (P = .020). CONCLUSION: The tibiofemoral joint space increased progressively from extension to mid-flexion through deep-flexion after PCL-resection, yet was substantially less than reported in historical studies. However, large variation in flexion-space opening was observed with some patients failing to increase the flexion-space whatsoever with PCL-resection. This runs counter to conventional TKA understanding and should be considered in modern surgical education. LEVEL OF EVIDENCE: Therapeutic Level III.

Intra-articular Injections of the Hip and Knee With Triamcinolone vs Ketorolac: A Randomized Controlled Trial.

BACKGROUND: Clinicians commonly utilize intra-articular injections to treat symptomatic primary arthritis. Steroid injections are common yet have immune-modulating effects and can alter gene expression which may delay definitive arthroplasty and further damage cartilage. Nonsteroidal anti-inflammatory injections may offer a safer profile due to their differing mechanism of action; however, there is a relative dearth of information regarding their efficacy. This noninferiority study compares the effectiveness of triamcinolone vs ketorolac in treating symptoms of moderate to advanced primary osteoarthritis of the hip and knee. METHODS: In total, 110 patients (52 hips and 58 knees) with moderate to severe radiographic primary osteoarthritis of the hip or knee were randomized in a double-blinded study to receive an ultrasound-guided intra-articular injection of ketorolac or triamcinolone. Patient-reported outcome measures were collected pre-injection and at 1 week, 1 month, and 3 months. RESULTS: For hips and knees, intra-articular injections with either ketorolac or triamcinolone led to statistically significant improvements in patient-reported outcome measures. The treatment effect size was largest at 1 week and decreased over time. Primary analysis of variance comparisons revealed no significant differences between ketorolac and triamcinolone. For knee injections, post hoc secondary analysis suggests slight added durability in the triamcinolone group. Adverse effects were minimal with both interventions. CONCLUSION: Intra-articular ketorolac injections provide comparable improvement to triamcinolone for primary hip and knee osteoarthritis. Ketorolac is an additional low-cost option for conservative management of primary osteoarthritis, and due to its differing mechanism of action, it may not propagate additional cartilage damage or preclude from early surgical intervention if unsuccessful. TRIAL REGISTRATION NUMBER: NCT04441112.

Extensor Mechanism Reconstruction Using Marlex Mesh: Is Postoperative Casting Mandatory?

BACKGROUND: Extensor mechanism (EM) disruption after total knee arthroplasty is a catastrophic complication. Reconstruction using monofilament polypropylene mesh (Marlex Mesh; CR Bard, Franklin Lakes, NJ) has emerged as the preferred treatment, but reports are limited to the designing institution. This study describes a nondesigner experience and compares 2 postoperative immobilization strategies: long leg cast vs knee immobilizer. METHODS: A retrospective review of consecutive EM reconstructions between 2012 and 2019 was performed. Primary repairs and allograft reconstructions were excluded, leaving 33 knees (30 patients) who underwent Marlex reconstruction. Mean time from disruption to reconstruction was 14 months, and 14 of 33 (42%) had previous repair or reconstruction attempts. The mean age was 69 years, and mean body mass index was 35 kg/m2. Postoperatively, extension was maintained using a knee immobilizer in 19 of 33 (58%) patients, whereas 14 of 33 (42%) patients were long leg casted. Kaplan-Meier analysis determined all-cause survivorship free of mesh failure. RESULTS: At mean 25-month follow-up, 19 of 33 (58%) EM reconstructions were functioning. Excluding explanted infections (5 recurrent and 2 new), 19 of 26 (73%) EM reconstructions were in situ. Six-year survivorship was 69% and not influenced by immobilization type (cast: 67%, immobilizer: 71%; P = .74). Extensor lag was not associated with immobilization type, improving from a mean preoperative lag of 43° to a mean postoperative lag of 9°. Among successes, University of California at Los Angeles activity and Knee Injury and Osteoarthritis Outcome Score - Joint Replacement score improvements exceeded minimal clinically important difference (2.2-3.3 and 52.5-64.0, respectively). CONCLUSION: Marlex mesh EM reconstruction is a durable and reliable treatment with acceptable clinical results achievable outside the designer institution. Provided sufficient duration and compliance with postoperative immobilization, similar outcomes can be obtained with either a cast immobilizer or a knee immobilizer.

How Has COVID-19 Affected Our Orthopedic Implant Industry Partners? Implications for the Surgeon-Industry Relationship in 2020 and Beyond.

BACKGROUND: The COVID-19 pandemic has had far-reaching societal and financial consequences. The purpose of this study was to evaluate how COVID-19 has affected AAHKS industry partners and the surgeon-industry relationship, emphasizing education, resource allocation, and strategic direction for the second half of 2020. METHODS: AAHKS industry partners were contacted to participate in a blinded survey and optional interview with the AAHKS Industry Relations Committee. Based on the results, a group of AAHKS member surgeons with disparate practice types were asked to postulate on how the COVID-19 pandemic has and will affect their practice and relationship with Industry. RESULTS: AAHKS industry partner responses indicated decreased resource allocation for regional, "other national," and AAHKS annual meetings (67%, 55%, and 30%, respectively). Web-based educational content was expected to increase in 2020 and will likely remain a point of emphasis in 2021 (100% and 70% of responders). For Q3/Q4 2020, a significant emphasis was placed on site of service/outpatient TJA and COVID-19-related safety measures (70% and 90% of responders), as well as increased availability of instrumentation and implants (40% and 60%, respectively). CONCLUSION: The COVID-19 pandemic has altered the orthopedic landscape for the foreseeable future. Survey responses by AAHKS industry partners demonstrate a continued commitment to surgeon education with an increasing shift to a web-based platform. Increased resource allocation for outpatient TJA and COVID-19-related safety measures were significant. Articulating optimal mechanisms to aid industry in supporting surgeons with different practice models to meet demand during the second half of fiscal year 2020 will be critical.

Inadequate Metadiaphyseal Fill of a Modern Taper-Wedge Stem Increases Subsidence and Risk of Aseptic Loosening: Technique and Distal Canal Fill Matter!

BACKGROUND: Adequate interference fit and mechanical stability through optimal surgical technique are essential to prevent subsidence and loosening in cementless total hip arthroplasty. The purpose of this study is to determine the effect of surgical technique on radiographic subsidence and subsequent stability of a modern taper-wedge cementless stem. METHODS: A retrospective review of 250 consecutive cementless primary total hip arthroplasties performed by 2 surgeons was completed. Surgeon A vigorously broached, maximizing the mediolateral stem dimension and confirmed final broach stability with a torsional test, whereas Surgeon B did not. All patients received identical taper-wedge stems. Preoperative bone morphology (canal flare index), postoperative subsidence, and canal fill were radiographically assessed. RESULTS: Canal flare index was not different between groups (P = .747). There was significantly less subsidence at 1 month for Surgeon A (0.3 vs 1.3 mm, P < .001). Additional subsidence at 1 year occurred in only 0.8% of Surgeon A (1/119) compared to 51.6% of Surgeon B stems (33/64, P < .001). Surgeon technique and canal fill measured at 60 mm below the lesser trochanter were the only variables predictive for subsidence, where Surgeon A and B had a mean canal fill of 95% and 86%, respectively. Surgeon B had 2 cases of aseptic loosening (2%) at 2 and 3 years postoperatively. CONCLUSION: These observations support that maximizing mediolateral canal fill and avoiding under-sizing the femoral implant with meticulous broaching technique minimizes subsidence and optimizes stability of modern cementless taper-wedge stems. Failure to optimize canal fill with appropriate broaching and surgical technique may predispose femoral components to failure from aseptic loosening.

Does the h-index and self-citation affect external funding of orthopedic surgery research? An analysis of fellowship directors and their subspecialties.

PURPOSE: Determine the impact of self-citation on external funding for orthopedic fellowship directors. METHODS: The San Francisco Match's website identified directors encompassing 8 subspecialties. The Scopus database identified the number of publications, citations, and h-index for each director. H-index was assessed with/without self-citation. RESULTS: Mean publications, citations, self-citation rate, and h-index for the 446 directors were 71.2, 1816, 3.86%, and 18.3, respectively. Excluding self-citations reduces mean h-index to 18.0; and h-index changed by ≤ 1 integer in 95% of directors. CONCLUSIONS: Self-citation has minimal impact among fellowship directors and should not be adjusted for when considering external funding.

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 Intramedullary Dowels Assist in Eradicating Infection in Two-Stage Resection for Septic Total Knee Arthroplasty?

BACKGROUND: Evidence suggests approximately 40% of intramedullary (IM) canals are culture positive at resection for infected knee arthroplasty. While commonly utilized, no clinical data on the efficacy of antibiotic-eluding IM dowels exist. We quantified treatment success with and without the use of antibiotic-eluding IM dowels in two-stage treatment of periprosthetic knee infection using static and articulating antibiotic cement spacers. METHODS: 109 consecutive patients who underwent two-stage treatment for periprosthetic knee infection were reviewed. Treatment failure, defined as repeat resection before reimplantation or recurrent infection within 6 months of reimplantation, was evaluated based on spacer type and use of IM dowels, accounting for infection type and systemic host and local extremity grade. RESULTS: After exclusions for confounds, articulating spacers without IM dowels were used in 49 (57.7%) cases, articulating spacers with IM dowels in 14 cases (16.5%), and static spacers with IM dowels in 22 (25.9%) cases. Treatment success regardless of infection classification was 85.7% for articulating spacers with IM dowels, 89.8% for articulating spacers without IM dowels, and 68.2% for static spacers with IM dowels (P = .074). In chronically infected poor hosts with compromised extremities, treatment success remained highest in patients with articulating spacers with (90.9%) or without (92.9%) IM dowels compared with static spacers with IM dowels (68.4%) (P = .061). CONCLUSION: Findings suggest that the use of IM dowels did not enhance infection eradication above and beyond that observed for articulating spacers alone, including in the worst cases involving chronically infected poor hosts with compromised extremities.

Screw fixation of the syndesmosis alters joint contact characteristics in an axially loaded cadaveric model.

BACKGROUND: The purpose of this study was to quantify the effects of rigid syndesmotic fixation on functional talar position and cartilage contact mechanics. METHODS: Twelve below-knee cadaveric specimens with an intact distal syndesmosis were mechanically loaded in four flexion positions (20° plantar flexion, 10° plantar flexion, neutral, 10° dorsiflexion) with zero, one, or two 3.5-mm syndesmotic screws. Rigid clusters of reflective markers were used to track bony movement and ankle-specific pressure sensors were used to measure talar dome and medial/lateral gutter contact mechanics. RESULTS: Screw fixation caused negligible anterior and inferior shifts of the talus within the mortise. Relative to no fixation, mean peak contact pressure decreased by 6%-32% on the talar dome and increased 2.4- to 6.6-fold in the medial and lateral gutters, respectively, depending on ankle position and number of screws. CONCLUSIONS: Two-way ANOVA indicated syndesmotic screw fixation significantly increased contact pressure in the medial/lateral gutters and decreased talar dome contact pressure while minimally altering talar position.

Extended Oral Antibiotic Prophylaxis in High-Risk Patients Substantially Reduces Primary Total Hip and Knee Arthroplasty 90-Day Infection Rate.

BACKGROUND: Total joint arthroplasty (TJA) episodic payment models shift risk and cost of periprosthetic joint infection (PJI) to surgeons and hospitals, causing some to avoid treating high-risk patients. Furthermore, there are little data to support optimization of host factors preoperatively to decrease PJI, and recent literature supports using extended antibiotic prophylaxis following reimplantation TJA. The purpose of this study was to evaluate whether extended oral antibiotic prophylaxis minimized PJI after primary TJA in high-risk patients. METHODS: A retrospective cohort study was performed of 2,181 primary total knee arthroplasties (TKAs) and primary total hip arthroplasties (THAs) carried out from 2011 through 2016 at a suburban academic hospital with modern perioperative and infection-prevention protocols. Beginning in January 2015, extended oral antibiotic prophylaxis for 7 days after discharge was implemented for patients at high risk for PJI. The percentages of patients diagnosed with PJI within 90 days were identified and compared between groups that did and did not receive extended oral antibiotic prophylaxis, with p ≤ 0.05 indicating significance. RESULTS: The 90-day infection rates were 1.0% and 2.2% after the TKAs and THAs, respectively. High-risk patients without extended antibiotic prophylaxis were 4.9 (p = 0.009) and 4.0 (p = 0.037) times more likely to develop PJI after TKA and THA, respectively, than high-risk patients with extended antibiotic prophylaxis. CONCLUSIONS: Extended postoperative antibiotic prophylaxis led to a statistically significant and clinically meaningful reduction in the 90-day infection rate of selected patients at high risk for infection. We encourage further study and deliberation prior to adoption of a protocol involving extended oral antibiotic prophylaxis after high-risk TJA, with the benefits weighed appropriately against potential adverse consequences such as increasing the development of antimicrobial resistance. LEVEL OF EVIDENCE: Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Internet Promotion of Direct Anterior Approach Total Hip Arthroplasty by Members of the American Association of Hip and Knee Surgeons.

BACKGROUND: The direct anterior approach (DAA) in total hip arthroplasty is of significant interest to both patients and surgeons, largely due to intense marketing. This study addressed the question, "What is the level of promotion of DAA total hip arthroplasty on the internet by American Association of Hip and Knee Surgeons (AAHKS) members?" METHODS: An internet search was performed to identify surgeon-specific websites for each member of the AAHKS using the members' full name and a previously published set of criteria. Each website was evaluated utilizing a questionnaire to systematically identify claims made regarding proposed DAA-specific risks, benefits, as well as the presence/absence of supporting data. RESULTS: We identified 1855 qualified websites. The DAA was referenced on 22.8% (423/1855) of these websites. Claims regarding DAA-specific benefits included less invasive/muscle sparing (46.3%), quicker recovery (45.2%), decreased pain (28.1%), decreased hospital stay (22.0%), and decreased dislocation risk (16.3%). Potential DAA risks including lateral femoral cutaneous nerve injury, periprosthetic/greater trochanteric fracture, and wound complication/hematoma were addressed on only 4.7%, 3.1%, and 1.7% of websites, respectively. Supporting peer-reviewed literature was identified on only 3.6% of DAA websites. CONCLUSION: Over one-fifth of AAHKS members promoted the DAA on the internet. Member websites claimed DAA benefits such as faster recovery and decreased pain approximately 9 times more frequently than any potential risk of the procedure (P < .001). While AAHKS policy does not regulate member marketing, it is the responsibility of all orthopedic surgeons to disseminate accurate, validated information concerning the procedures we perform.

Fixed-bearing medial unicompartmental knee arthroplasty restores neither the medial pivoting behavior nor the ligament forces of the intact knee in passive flexion.

Medial unicompartmental knee arthroplasty (UKA) is an accepted treatment for isolated medial osteoarthritis. However, using an improper thickness for the tibial component may contribute to early failure of the prosthesis or disease progression in the unreplaced lateral compartment. Little is known of the effect of insert thickness on both knee kinematics and ligament forces. Therefore, a computational model of the tibiofemoral joint was used to determine how non-conforming, fixed bearing medial UKA affects tibiofemoral kinematics, and tension in the medial collateral ligament (MCL) and the anterior cruciate ligament (ACL) during passive knee flexion. Fixed bearing medial UKA could not maintain the medial pivoting that occurred in the intact knee from 0° to 30° of passive flexion. Abnormal anterior-posterior (AP) translations of the femoral condyles relative to the tibia delayed coupled internal tibial rotation, which occurred in the intact knee from 0° to 30° of flexion, but occurred from 30° to 90° of flexion following UKA. Increasing or decreasing tibial insert thickness following medial UKA also failed to restore the medial pivoting behavior of the intact knee despite modulating MCL and ACL forces. Reduced AP constraint in non-conforming medial UKA relative to the intact knee leads to abnormal condylar translations regardless of insert thickness even with intact cruciate and collateral ligaments. This finding suggests that the conformity of the medial compartment as driven by the medial meniscus and articular morphology plays an important role in controlling AP condylar translations in the intact tibiofemoral joint during passive flexion. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1868-1875, 2018.

Results of Porous-Coated Anatomic Total Hip Arthroplasty without Cement at 25 to 30 Years: A Concise Follow-up of a Previous Report.

The purpose of this study was to update the results of a prospective series of 100 primary cementless total hip arthroplasty (THA) procedures that were performed between 1983 and 1986 with use of the Porous Coated Anatomic (PCA) system. This is one of the first prospective studies of cementless primary THA with a minimum of 25 years of follow-up. Twenty-one patients (22 hips) of the original series were alive and had clinical and radiographic follow-up at a minimum of 25 years postoperatively. Twenty-three percent (23) of all hips and 50% (11) of the hips among the living cohort had undergone revision for loosening and/or osteolysis of the acetabular component, and 7% (7) of all hips and 4.5% (1) of the hips among the living cohort were revised for loosening and/or osteolysis of the femoral component. Only 4 femoral stems were revised for isolated loosening (without osteolysis). The PCA femoral component proved to be durable at a minimum of 25 years postoperatively, while the acetabular component was less durable. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Do Medial Pivot Kinematics Correlate With Patient-Reported Outcomes After Total Knee Arthroplasty?

BACKGROUND: Many total knee arthroplasty (TKA) implants are designed to facilitate a medial pivot kinematic pattern. The purpose of this study was to determine whether intraoperative medial pivot kinematic patterns are associated with improved patient outcomes. METHODS: A retrospective review of consecutive primary TKAs was performed. Sensor-embedded tibial trials determined kinematic patterns intraoperatively. The center of rotation (COR) was identified from 0° to 90° and from 0° to terminal flexion, and designated medial-pivot or non-medial pivot based on accepted criteria. Patient-reported outcomes were measured preoperatively and at minimum one-year follow-up. RESULTS: The analysis cohort consisted of 141 TKAs. Mean age and median BMI were 63.7 years and 33.8 kg/m2, respectively. Forty-percent of TKAs demonstrated a medial pivot kinematic pattern intraoperatively. A medial pivot pattern was more common with posterior cruciate-retaining (CR) and posterior cruciate-substituting/anterior lipped (CS) implants when compared to posterior stabilized (PS) TKAs (P ≤.0150). Regardless of bearing type, minimum one-year Knee Society scores and UCLA activity level did not significantly differ based on medial vs non-medial pivot patterns (P ≥.292). For patients with posterior cruciate-sacrificing implants, there were trends for greater median improvement in Knee Society objective (46 vs 31.5 points, P =.057) and satisfaction (23 vs 14 points, P =.067) scores in medial pivot knees. CONCLUSION: A medial pivot pattern may not significantly govern clinical success after TKA based on intraoperative kinematics and modern outcome measures. Further research is warranted to determine if a particular kinematic pattern promotes optimal clinical outcomes.

Cementless Tapered Wedge Femoral Stems Decrease Subsidence in Obese Patients Compared to Traditional Fit-and-Fill Stems.

BACKGROUND: Femoral component stability and resistance to subsidence is critical for osseointegration and clinical success in cementless total hip arthroplasty. The purpose of this study was to radiographically evaluate the anatomic fit and subsidence of 2 different proximally tapered, porous-coated modern cementless femoral component designs. METHODS: A retrospective cohort study of 126 consecutive cementless total hip arthroplasties was performed. Traditional fit-and-fill stems were implanted in the first 61 hips with the remaining 65 receiving morphometric tapered wedge stems. Preoperative bone morphology was radiographically assessed by the canal flare index. Canal fill in the coronal plane, subsidence, and the sagittal alignment of stems was measured digitally on immediate and 1-month postoperative radiographs. RESULTS: Demographics and canal flare indices were similar between groups. The percentage of femoral canal fill was greater in the tapered wedge compared to the fit-and-fill stem (P = .001). There was significantly less subsidence in the tapered wedge design (0.3 mm) compared to the fit-and-fill design (1.1 mm) (P = .001). Subsidence significantly increased as body mass index (BMI) increased in the fit-and-fill stems, a finding not observed in the tapered wedge design (P = .013). CONCLUSION: An anatomically designed morphometric tapered wedge femoral stem demonstrated greater axial stability and decreased subsidence with increasing BMI than a traditional fit-and-fill stem. The resistance to subsidence, irrespective of BMI, is likely due to the inherent axial stability of a tapered wedge design and may be the optimal stem design for obese patients.