Survival and performance of a dual tapered-wedge fully HA-coated press fit femoral stem.

INTRODUCTION: Fully hydroxyapatite-coated titanium alloy double-tapered stems have been successful implant designs for THA. The Novation Element Stem (Exactech, Gainesville, FL) is one of several of these implants following a modified Corail design philosophy. Although a great deal is known about the results of the Corail stem, little is known about the more recent Corail-inspired implants. The authors evaluated the clinical outcomes, radiographic findings and survival statistics of the collarless version of the Element Stem when used routinely in a diverse patient population. METHODS: A retrospective review was performed for all primary THR cases from 2010 to 2018. Patient demographics and HHS/OHS/patient satisfaction scores were obtained. Radiographs were evaluated for stem subsidence, radiolucencies, and bone responses to the implant. RESULTS: One hundred and fifty seven Element Stems were implanted with greater than 2 years of radiographic follow-up, while 105 Element Stems implanted during the study period had a survival of 5 years or more. Average HHS was 91.7 and average OHS was 44.0. 54 of 157 hips had radiolucencies, all of which included a proximal zonal radiolucency. Average subsidence was 3.33 mm; 18 hips had subsidence > 4 mm. There were 8 revisions for: aseptic loosening (4), trauma-related peri-prosthetic fractures, and early proximal-medial fractures. At 5 years, the all-cause survival rate is 92.4%, 96.2% based only on aseptic loosening and 98.1% based only on proximal medial fractures. CONCLUSION: Clinical outcomes using the collarless Novation Element Stem are good, but early proximal medial fracture is still a factor in patients with poor-quality bone. Proximal radiolucencies progressing to aseptic loosening post-operatively are also a concern. The 11.5% rate of subsidence is comparable to other fully HA-coated collarless stems. This study provides a thorough critical analysis of outcomes and midterm survival data of this dual tapered-wedge fully HA-coated collarless stem used routinely in a diverse patient population.

Survivorship and Outcomes of Femoral Neck Preserving Stems in Primary Total Hip Arthroplasty.

BACKGROUND: Short-stem femoral implants (SSFIs) promote the preservation of bone in the femoral neck, reduce soft tissue disruption, and facilitate minimally invasive surgical techniques. The purpose of this study was to report the revision rate, complication rate, patient satisfaction, patient-reported outcomes, and radiographic outcomes of patients who underwent total hip arthroplasty (THA) with the Alteon Neck Preserving Femoral Stem (ANPS). METHODS: A prospectively maintained database was reviewed which analyzed 92 THAs between the years 2016 and 2018. Patient-reported outcomes, patient satisfaction, complication rates, and radiographic outcomes were assessed at 2-5 years postoperatively. RESULTS: The final cohort consisted of 63 hips. Five patients (7.9%) underwent revision surgery and 2 (3.2%) had other complications not requiring revision. Survivorship when considering only the femoral component was 93.7% at an average of 41.4 months of follow-up. The average postoperative Oxford Hip Score (41.5 ± 8.3) and Harris Hip Score (77.9 ± 16.6) demonstrated significant improvement among our nonrevised patients, respectively (P < .001). Radiographs demonstrated spot welding in 56% of arthroplasties most commonly in Gruen Zones 2, 3, and 13 and that femur radiolucencies were visualized in 58% predominantly along the distal aspect of the stem. Radiographic femoral component subsidence was present in 9.7% of patients. CONCLUSION: The ANPS may be less reliable than previously reported. Our cohort's revision rate was unacceptably high with 6.3% requiring revision surgery for femoral component loosening in less than 5 years. Surgeons should consider the challenges and prohibitive failure rate associated with SSFIs before routine usage in THA.

Unexpected Wear of a Uniquely Designed Moderately Cross-Linked Polyethylene in Total Hip Arthroplasty.

BACKGROUND: A uniquely designed, non-heat-treated moderately cross-linked acetabular polyethylene liner used in total hip arthroplasty (THA) demonstrated excessive wear during routine follow-up, prompting an evaluation of the linear wear rate. METHODS: All THAs were performed by the senior author. The study group included 38 THAs using the uniquely designed polyethylene in question, compared to a control group of 21 THAs using another moderately cross-linked polyethylene with good 10-year outcomes. Two-dimensional linear head penetration wear measurements were obtained using the Martell Hip Analysis Suite, and retrieval analysis was performed on two liners. RESULTS: The study group had a significantly higher average penetration rate of 0.089 mm/y than the control group average rate of 0.047 mm/y (P = .04). Forty-five percent of the study group had a wear rate above the osteolysis threshold (0.1 mm/y), compared to 24% in the control group. Macroscopic analysis of two retrieved liners validated the radiographic findings. CONCLUSION: The data suggest unexpectedly higher wear rates for a moderately cross-linked polyethylene design, with nearly half of the study group at risk for osteolysis. Further registry or database analyses of this particular moderately cross-linked polyethylene are warranted.

High-Viscosity Versus a Lower-Viscosity Cement Penetration at Dough Phase In Vivo in Primary Total Knee Arthroplasty.

BACKGROUND: Previous studies have shown that the depth of cement penetration and the presence of radiolucent lines (RLLs) correspond with the risk of aseptic loosening in total knee arthroplasty, while others have found a correlation between the viscosity of the cement and the depth of cement penetration. We compared cement marketed as high-viscosity cement (HVC) with one marketed by the same manufacturer as low-viscosity cement (LVC). We hypothesized that no significant difference would be found in depth of penetration or presence of RLLs between the two cohorts. METHODS: The HVC (n = 50) and LVC cohorts (n = 50) were gathered from two sequential series of primary total knee arthroplasties using the same implants and cementing techniques. Depth of cement penetration and presence of RLL were measured in four tibial zones and were compared between cohorts. RESULTS: There were no cases of aseptic loosening in either cohort at a mean of 29 months. Mean maximum cement penetration in 3 of the 4 zones was >3 mm with both cements. There was no significant difference in maximum penetration in any zone between the two cements. There were fewer tibial radiolucencies with HVC than LVC. CONCLUSION: These findings suggest that the marketing description of HVC or LVC is not necessarily a factor in cement penetration. The term high viscosity should not be used as a descriptor of cement that reaches dough phase more quickly, but rather cement that has a higher viscosity at its dough phase when it is typically applied.

The effect of viscosity on cement penetration in total knee arthroplasty, an application of the squeeze film effect.

The authors present a prospective randomized blinded cadaver study designed to evaluate the engineering concept of a squeeze film effect and the effect of cement viscosity on cement penetration in total knee arthroplasty. This was done in response to an earlier clinical study demonstrating inferior tibial cement penetration using early, often liquid, phase cement. Paired cadaver tibias were implanted with the tibial component using either liquid or dough phase cement. Based on an AP fluoroscopic image, the dough phase cement penetrated deeper than liquid in all four zones. This was statistically significant in zones 1, 2 and 3. Deeper cement penetration has been shown to provide a stronger cement-bone interphase. As a result dough phase cement is recommended to obtain optimal cement penetration.

Eleven-year implant survival rates of the all-polyethylene and metal-backed modular Optetrak posterior stabilized knee in bilateral simultaneous cases.

A prospective randomized study was conducted to determine if a design change in the articular surface geometry introduced in the Optetrak total knee to increase prosthetic joint conformity and further reduce polyethylene stress had any impact on implant survival, particularly when the all-polyethylene version of the implant was used. Forty-seven patients undergoing bilateral simultaneous total knee arthroplasties were randomized for the side, receiving an all-polyethylene tibial component and followed up for a mean 11.6 years. Survival rates for the all-polyethylene and metal-backed modular versions of the implant were both 98%, excluding a single case of deep infection. Survival rates with revision for aseptic loosening as an end point were 100%. The increase in tibial and femoral radii in the coronal plane of the Optetrak posterior stabilized knee did not result in a reduced implant survival rate in either the metal-backed modular or all-polyethylene versions of the implant.

The impact of resident teaching on total hip arthroplasty.

The author asked whether THA cases performed with major resident participation in a private practice setting were associated with greater use of health care resources, higher rates of technical errors, or a reduction in quality of outcome compared to THA cases performed without major resident involvement. Eighty-eight primary THA cases performed with major resident participation were compared to 61 cases without major resident participation. Resident cases took 20 minutes longer, required a second assistant more frequently (92% versus 23%) but did not have higher transfusion rates or result in a longer hospital stay. Resident cases did not have more complications or increased technical errors. Resident cases also did not have lower Harris hip scores or inferior Short Form SF-12 physical ratings at minimum 1-year followup.

Five-year follow-up of primary Optetrak Posterior Stabilized total knee arthroplasties in osteoarthritis.

A series of 66 primary Optetrak Posterior Stabilized total knees with modular tibial components were followed prospectively for a minimum of 5 years in patients with osteoarthritis. Fifty-one percent of the patients were obese based on body mass index greater than 30. There was a statistically significant negative correlation between body mass index and both Hospital for Special Surgery and Knee Society scores. Despite reduced ratings due to obesity, 90% of the patients were rated good or excellent. Patellofemoral design changes nearly eliminated patellofemoral crepitation and soft tissue entrapment. Design changes did not compromise implant survival. Predicted implant survival at 93 months using reoperation for any reason as an end point was 97%.

The early innovators of today's resurfacing condylar knees.

The 1970s saw an explosion of ideas in the field of prosthetic knee arthroplasty. This paper is an effort to identify the innovators who contributed to the development of today's condylar total knee prostheses and the surgical techniques used to insert them. The 1970s were selected because most innovations occurred during those years. Two different design approaches were undertaken simultaneously. One was a functional approach whereas the other was a strictly anatomical approach. Initially, these 2 approaches led to very different designs. But the common goal of recreating human knee function eventually led to more similarities than differences. The author describes how, when, and why these dedicated individuals came to their ideas. The work is largely based on interviews and correspondence with those involved as well as on reviews of patents and papers pertaining to their work.