Addressing complex primary THAs with acetabular implant innovation 

Message from Walter B. Beaver Jr., MD 

OrthoCarolina, North Carolina 

Among our peers, I commonly hear in discussions that hip instability is the number one concern when it comes to Total Hip Arthroplasty (THA). The potential for instability is often complicated when we are presented with difficult cases that may be further compromised by spinal deformities, dysplasia, femoral neck fractures or other post-traumatic defects. The reconstruction of the joint remains a great challenge for us as surgeons, not only because of the anatomical defects presented, but also because of what I perceive to be an unmet clinical need. 

When approaching a complex primary THA, what solutions do you consider before making the first incision? Here are three common thoughts—and one potential solution—that I take into consideration when addressing challenging patient anatomy.

1. How can I meet the potential for instability head on?

Dislocation following THA is one of the most common reasons for a revision procedure1. Among patients with spinal challenges, such as spinal fusion, the rate of revision is even higher1. Therefore, enhancing hip stability is always one of my top objectives. In my practice, I’ve found that the new Trident II Tritanium acetabular implants, which feature a slim shell wall, allow for large femoral head size options2 and optimal poly thickness to potentially aid in greater range of motion3, joint stability3 and lower risk of dislocation4. To my knowledge, the new Trident II Tritanium is the only highly porous shell on the market to offer a 36/48 mm head-to-shell size ratio2.

2. When might I need an advanced bearing option?

Additionally, I like to know I have options at my disposal during surgery, particularly when it comes to having multiple liner and bearing options. When appropriate, Modular Dual Mobility (MDM) is my choice to address stability concerns along with Trident II Tritanium. There is a strong case to use MDM; multiple studies have demonstrated strong clinical results in primary and revision arthroplasty5,6.   

3. How can I achieve both good biologic and adjunct fixation? 

While cementless shells generally achieve good cementless fixation, in cases with compromised anatomy, fixation may still be a concern. Since I started using Trident II Tritanium over a year ago, I have confidence in the fixation of its additive manufactured Tritanium surface and have seen excellent 1-year post-op x-rays.

Particularly in these complex cases, I’ve found that screws are often recommended given the anatomical challenges of each patient. The screw hole pattern for Trident II Tritanium has been SOMA-verified* to help achieve multiple screws in the safe zone in the acetabulum7 and offer an average screw angulation of 37 degrees8. This angulation helps me to access my targeted bone region for adjunct screw fixation in these difficult cases.   

Finding solutions for our complex primary THAs will continue to be an on-going discussion. Innovative advancements in acetabular implant design—particularly with the use of additive manufacturing techniques and the engineering design capabilities afforded with this technology—may help to address these needs. 

*Based on 520+ CT scans

  1. Buckland AJ, et al. Dislocation of a primary total hip arthroplasty is more common in patients with a lumber spinal fusion. Bone Joint Journal, 99-B (5) 2017 pp. 585-591. 
  2. Internal memo: Market Analysis of Poly Bearing Options - Trident II Versus Competitors.October 18, 2017.
  3. Burroughs B, et al. Range of Motion and Stability in Total Hip Arthroplasty with 28-, 32-,38- and 44-mm Femoral Head Sizes In Vitro Study. The Journal of Arthorplasty, Vol. 20, No.1, 2005 pp. 11-19.
  4. Berry D.J., et al. Effect of Femoral Head Diameter and Operative Approach on Risk of Dislocation After Primary Total Hip Arthroplasty. J of Bone and Joint Surgery Vol. 87-A, No.11 (2005); pp. 2456-2463.
  5. Epinette J, et al. Early experience with dual mobility acetabular systems featuring highly crosslinked polyethylene liners for primary hip arthroplasty in patients under fifty-five years of age: an international multi-centre preliminary study.
  6. International orthopaedics(SICOT). Sept. 2016 DOI 10.1007/s00264-016-3367-0.6. Abdel M, et al. Dual-Mobility Constructs in Revision THA Reduced Dislocation, Re-Revision & Reoperation Compared to Large Femoral Heads. Hip Society 2017 Otto Aufranc Award.
  7. SOMA Screw Engagement. Stryker R&D Test Report - A0026638. October, 2017. SOMA verification at 45° inclination/20° anteversion.
  8. Stryker R&D Technical Report: Trident II Screw Angulation Memo. December 7, 2017.A0026941