A Cam-Post Mechanism Is No Longer Necessary in Modern Primary Total Knee Arthroplasty.

Conclusive evidence supporting a clinical difference between posterior-stabilized (PS) and cruciate-retaining (CR) designs in total knee arthroplasty (TKA) does not currently exist, despite both designs being used for decades. Proponents of PS designs that employ a cam-and-post mechanism cite in vivo fluoroscopic data that demonstrate improved posterior rollback; however, optimal rollback has never been correlated to superior clinical outcomes. Recently, anterior-lipped and more conforming CR bearings, such as ultracongruent, medial pivot, and dual-pivot designs, have been used to substitute for the posterior cruciate ligament and obviate the need for the cam-post mechanism of a traditional PS design. Advantages of avoiding a PS TKA include eliminating the risk of box cut induced femoral condylar fracture, improving operative efficiency by removing procedural steps, removing the articulation that is a source of wear, postdeformation, breakage, or dislocation, and eliminating patellar clunk. Health care reform efforts mandate cost reduction, and procedural efficiencies and minimizing inventory through the removal of unnecessary bearing options foster that initiative.

Total Hip Arthroplasty Bearing Surface Trends in the United States From 2007 to 2014: The Rise of Ceramic on Polyethylene.

BACKGROUND: Wear of the bearing surface is a critical element in determining the longevity of a total hip arthroplasty (THA). Over the past decade, concerns related to modern metal-on-metal (MoM) bearings and corrosion at the femoral head-neck interface have influenced surgeon selection of bearing surfaces. The purpose of this study is to analyze trends in THA bearing surface selection from 2007 through 2014 using a large national database. METHODS: The Nationwide Inpatient Sample database was used to extract bearing surface data from patients who underwent a primary THA between 2007 and 2014. Patients were grouped by bearing surface type: metal-on-polyethylene (MoP), ceramic-on-polyethylene (CoP), MoM, and ceramic-on-ceramic (CoC) bearings. Descriptive statistics were employed to describe trends. Univariate and multivariate analyses were performed to identify differences between bearing surface groups. RESULTS: During the study period, 2,460,640 THA discharges were identified, of which 1,059,825 (43.1%) had bearing surface data. A total of 496,713 (46.9%) MoP, 307,907 (29.1%) CoP, 210,381 (19.9%) MoM, and 44,823 (4.2%) CoC cases were identified. MoM utilization peaked in 2008 representing 40.1% of THAs implanted that year and steadily declined to 4.0% in 2014. From 2007 to 2014, the use of CoP bearing surfaces increased from 11.1% of cases in 2007 to 50.8% of cases in 2014. In 2014, CoP utilization surpassed MoP which represented 42.1% of bearing surfaces that year. CONCLUSION: During the study period, MoM bearing surfaces decreased precipitously, while CoP surpassed MoP as the most popular bearing surface used in a THA.

Systematic review of literature of cemented femoral components: what is the durability at minimum 20 years followup?

BACKGROUND: Cemented femoral total hip arthroplasty may be one of the most successful surgical interventions of all time. However, although results are very encouraging over the early to mid-term followup, relatively few studies have analyzed the durability of these implants beyond 20 years followup. To evaluate the performance of contemporary implants, it is important to understand how previous implants perform at 20 or more years of followup; one way to do this is to aggregate the available data in the form of a systematic review. QUESTIONS/PURPOSES: (1) How durable is cemented femoral fixation in the long term (minimum 20-year followup) with respect to aseptic loosening? (2) Is the durability of cemented femoral fixation dependent on age of the patient? (3) Are the long-term results of the cemented femoral fixation dependent on any identifiable characteristics of the prosthesis such as surface finish? METHODS: A systematic review was performed to identify long-term studies of cemented femoral components. After application of inclusion and exclusion criteria to 1228 articles found with a search in PubMed and EMBASE, 17 studies with a minimum of 20-year followup on cemented femoral components were thoroughly analyzed in an attempt to answer the questions of this review. The quality of the studies reviewed was assessed with the Methodological Index for Nonrandomized Studies (MINORS) instrument. All studies were case series and cohort sizes ranged from 110 to 2000 hips for patients older than 50 years of age and 41 to 93 hips for patients younger than 50 years at the time of surgery. RESULTS: Among the six case series performed in patients older than 50 years of age, survivorship for aseptic loosening of the femoral component ranged from 86% to 98% at 20 years followup. There were no obvious differences for younger patients when analyzing the five studies in patients younger than age 50 years in which survivorship free from aseptic loosening for these studies ranged from 77% at 20 years in one study and 68% to 94% at 25 years in the other studies. Although data pooling could not be performed because of heterogeneity of the studies included here, it appeared that stems with a rougher surface finish did not perform as well as polished stems; survivorship of stems with rougher surface finishes varied between 86% and 87%, whereas those with smoother finishes ranged between 93.5% and 98% at 20 years. CONCLUSIONS: Excellent long-term fixation in both older and younger patients can be obtained with cemented, polished femoral stems. These results provide material for comparison with procedures performed with newer cementing techniques and newer designs, both cemented and cementless, at this extended duration of followup.

Fixation and wear with a contemporary acetabular component and cross-linked polyethylene at minimum 10-year follow-up.

UNLABELLED: Long term total hip arthroplasty follow-up has demonstrated bearing surface wear and failure of fixation as the major modes of failure. The purpose of this study was to evaluate the minimum 10year results of a third generation cementless acetabular component using moderately cross-linked polyethylene liners. 150 primary THAs were evaluated clinically for need for revision and activity evaluated using accelerometers, WOMAC, Tegner and UCLA activity-level scores. Radiographs were evaluated for wear, osteolysis and loosening. We compared this cohort to three of our previously reported cohorts. The only revision was unrelated to liner wear and all acetabular components were bone ingrown. There were no cases of acetabular osteolysis and one case of femoral osteolysis. Average steps per year were 1.59 million. Mean steady state wear rate averaged 0.04mm/year. At 10-years, excellent fixation and low wear were demonstrated using a cementless acetabular construct and moderately cross-linked polyethylene liner. LEVEL OF EVIDENCE: Therapeutic study, Level III (retrospective comparative study-prospective cohort with historical control).

Primary cementless acetabular fixation at a minimum of twenty years of follow-up: a concise update of a previous report.

The purpose of the present study was to analyze the longer-term results for a previously reported cohort of patients with cementless acetabular fixation and to compare the results with those for historical controls with cement fixation and a comparable follow-up period. One hundred and twenty consecutive nonselected total hip arthroplasties were performed in 108 patients with use of a cementless acetabular component. This series was evaluated at a minimum of twenty years of follow-up and was compared with 330 consecutive hip arthroplasties that had been performed by the same surgeon with use of cemented acetabular components and had been followed for a comparable period of time. Thirty-nine patients (forty-two hips) in the cementless fixation group were living at twenty years of follow-up. In the group of 120 hips with cementless acetabular fixation, twenty-two hips (18.3%) were revised during the follow-up period, but only one hip (0.8%) was revised because of loosening of the acetabular component, with no additional cup loosening since the previous report at thirteen to fifteen years of follow-up. In the group with cemented acetabular fixation with comparable follow-up, thirty-two hips (10%) were revised overall and eighteen hips (6%) were revised because of acetabular loosening. An additional twenty-five hips (8%) had acetabular cups that were loose on radiographs but had not undergone revision. At a minimum of twenty years of follow-up, cementless acetabular components provided superior long-term fixation compared with cemented components but the overall rates of acetabular revision for mechanical reasons were comparable.