Initial stability of a highly porous titanium cup in an acetabular bone defect model

A novel primary stability test method for artificial acetabular shells considering vertical load during level walking and shell position

Uncemented acetabular shell primary stability is essential for optimal clinical outcomes. Push-out testing, rotation testing, and lever-out testing are major evaluation methods of primary stability between the shell and bone. However, these test methods do not consider shell loads during daily activity and shell installation angle. This study proposes a novel evaluation method of acetabular shell primary stability considering load during level walking and acetabular installation angles such as inclination and anteversion. To achieve this, a novel primary stability test apparatus was designed with a shell position of 40° acetabular inclination and 20° anteversion. The vertical load, corresponding to walking load, was set to 3 kN according to ISO 14242-1, which is the wear test standard for artificial hip joints. The vertical load was applied by an air cylinder controlled by a pressure-type electro-pneumatic proportional valve, with the vertical load value monitored by a load cell. Torque was measured when angular displacement was applied in the direction of extension during the application of vertical load. For comparison, we also measured torque using the traditional lever-out test. The novel primary stability test yielded significantly higher primary stabilities; 5.4 times greater than the lever-out test results. The novel primary stability test failure mode was more similar to the clinical failure than the traditional lever-out test. It is suggested that this novel primary stability test method, applying physiological walking loads and extension motions to the acetabular shell, better reflects in vivo primary stability than the traditional lever-out test.

Initial stability of cementless acetabular cups using robotic-assisted total hip arthroplasty compared with the conventional manual technique: An in vitro biomechanical study

BACKGROUND

The aim of this study is to determine whether the initial stability of a cementless cup with the Mako system is superior to that of a conventional manual technique using bone models.

METHODS

The bone models were prepared using a polyurethane foam block. Two hemispherical cementless cups (highly porous titanium cup [Trident II Tritanium, Stryker] and hydroxyapatite-coated titanium cup [Trident HA, Stryker]) were implanted using the Mako system. The torque of the cups was measured by rotational and lever-out torque testing and compared with that of a conventional manual technique.

RESULTS

The two types of cups that were implanted using the Mako system demonstrated significantly higher mean rotational torque than that of the manual technique (p < 0.01, p = 0.01, respectively).

CONCLUSIONS

This study provides the advantage of the initial stability of a cementless hemispherical cup implanted by the Mako system compared with that of the conventional manual technique.

Clinical and radiological outcomes of total hip arthroplasty in octogenarian patients using a three-dimensional porous titanium cup: a retrospective analysis in Japanese patients

PURPOSE

Osteointegration of a three-dimensional (3D) porous titanium material has been experimentally proven, but only a few studies have shown the clinical outcomes of a 3D porous titanium cup in the Japanese elderly population. The purpose of this study was to compare the short-and-medium term clinical and radiographic results of total hip arthroplasty (THA) using a 3D porous titanium cup in patients aged ≥ 80 (octogenarians) versus those aged < 80 (younger controls).

METHODS

A total of 104 hips that underwent THA using a 3D porous titanium cup (SQRUM TT, Kyocera Medical) were enrolled in the study and were divided into two groups according to age: the octogenarian group (≥ 80, n = 42) and the younger control group (< 80, n = 62). Furthermore, we evaluated patient characteristics, clinical outcomes determined by the Japanese Orthopedic Association score, cup alignment, and incidence of radiolucent lines around the cup.

RESULTS

The mean follow-up period was 4.2 and 4.0 years (p = 0.29) for octogenarians and younger controls, respectively. The clinical outcomes were excellent, and no revision surgery occurred until the last follow-up in both groups. The number of patients with radiolucent lines at the final evaluation was 21 of 62 (33.9%) in younger controls and 16 of 42 (38.1%) in octogenarians.

CONCLUSION

THA with 3D porous titanium cup for octogenarians had similar clinical outcomes and incidence of radiolucent lines as those of younger controls, suggesting that the 3D porous titanium cup may be useful in THA for octogenarians. Further investigations will confirm its long-term outcomes.

The Diagnosis and Treatment of Acetabular Bone Loss in Revision Hip Arthroplasty: An International Consensus Symposium

Despite growing evidence supporting the evaluation, classification, and treatment of acetabular bone loss in revision hip replacement, advancements have not been systematically incorporated into a single document, and therefore, a comprehensive review of the treatment of severe acetabular bone loss is needed. The Stavros Niarchos Foundation Complex Joint Reconstruction Center at Hospital for Special Surgery held an Acetabular Bone Loss Symposium on June 21, 2019, to answer the following questions: What are the trends, emerging technologies, and areas of future research related to the evaluation and management of acetabular bone loss in revision hip replacement? What constitutes the optimal workup and management strategies for acetabular bone loss? The 36 international experts convened were divided into groups, each assigned to discuss 1 of 4 topics: (1) preoperative planning and postoperative assessment; (2) implant selection, management of osteolysis, and management of massive bone loss; (3) the treatment challenges of pelvic discontinuity, periprosthetic joint infection, instability, and poor bone biology; and (4) the principles of reconstruction and classification of acetabular bone loss. Each group came to consensus, when possible, based on an extensive literature review. This document provides an overview of these 4 areas, the consensus each group arrived at, and directions for future research.

In vitro and in vivo evaluations of the fully porous Ti6Al4V acetabular cups fabricated by a sintering technique

A type of canine fully porous Ti6Al4V acetabular cup was fabricated by a well-controlled powder sintering technique. The traditional hydroxyapatite-coated (HA-coated) cups were also prepared as the control. The characteristics, mechanical and biological properties of the two types of cups were evaluated by scanning electron microscopy, mechanical tests, finite element analysis and canine total hip arthroplasty (THA). Results showed that the porous cup had high porosity and large pore size with good mechanical properties without obvious stress shielding, and it had sufficient safety for implantation according to the finite element analysis. Both groups showed good biocompatibility and osteogenic ability after the THA surgeries, but the porous group had more bone ingrowth and higher bone-implant contact rate according to the micro-CT and histopathologic results. Therefore, the canine fully porous Ti6Al4V acetabular cup fabricated by the sintering technique could provide sufficient space and adequate mechanical support without obvious stress shielding effect for bone ingrowth. Compared with the traditional HA-coated cup, the porous cup may be more effective in achieving in vivo stability, which could contribute to reducing the risk of aseptic loosening.