Update - “Big-head”: The solution to the problem of hip implant dislocation?

Background Implant arthroplasties for trapeziometacarpal osteoarthritis are often associated with high complication and revision surgery rates. There are no previous studies reporting revision outcomes of failed interposition implant arthroplasty. Methods A patient register search was done for all implant arthroplasties performed for trapeziometacarpal osteoarthritis during a 10-year period in a single hand surgical unit. Altogether, 32 patients had primary interposition implant arthroplasty (Artelon 22, Pyrosphere 6, Ortosphere 2, and Pyrodisk 2), and 19 of these patients had revision surgery with 23 revision procedures performed. In all, 15 of the revised 19 patients were reexamined clinically (Connolly-Rath score, Quick Disabilities of the Arm Shoulder and Hand, patient evaluation measure, the visual analog score for pain, thumb range of motion and strength measurements) and radiographically. Results The indication for revision surgery was pain alone or implant dislocation accompanied by pain in all cases. Thirteen of the revised 15 patients reported functional deficit and pain after revision. There was no statistically significant difference in the revision outcomes between patients operated on primarily with the Artelon implant versus pyrocarbon/ceramic implants. Compared to previous studies on revision surgery and primary trapeziometacarpal arthroplasty, our results showed slightly higher pain and poorer functional scores. Conclusions Interposition implant arthroplasty may yield high revision rates. The results after revision surgery may be worse than previously described, and there may also be a tendency for worse results than those of primary arthroplasty. Interposition implant arthroplasty should always be thoroughly contemplated.

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Novel concept of a modular hip implant could contribute to less implant failure in THA: a hypothesis

Patient Safety in Surgery ◽

10.1186/s13037-017-0148-7 ◽

2018 ◽

Vol 12 (1) ◽

Author(s):

Ronny Grunert ◽

Stefan Schleifenbaum ◽

Robert Möbius ◽

Michael Kopper ◽

Christian Rotsch ◽

...

Keyword(s):

Implant Failure ◽

Hip Implant ◽

Novel Concept

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Redesign of the Femoral Stem for a Total Hip Arthroplasty for Additive Manufacturing

Volume 2A: 44th Design Automation Conference ◽

10.1115/detc2018-85850 ◽

2018 ◽

Author(s):

Bradley Hanks ◽

Shantanab Dinda ◽

Sanjay Joshi

Keyword(s):

Additive Manufacturing ◽

Total Hip Arthroplasty ◽

Hip Arthroplasty ◽

Lattice Structure ◽

Stress Shielding ◽

Patient Specific ◽

Hip Implants ◽

Hip Implant ◽

Total Hip ◽

Multiple Materials

Total hip arthroplasty (THA) is an increasingly common procedure that replaces all or part of the hip joint. The average age of patients is decreasing, which in turn increases the need for more durable implants. Revisions in hip implants are frequently caused by three primary issues: femoral loading, poor fixation, and stress shielding. First, as the age of hip implant patients decreases, the hip implants are seeing increased loading, beyond what they were traditionally designed for. Second, traditional implants may have roughened surfaces but are not fully porous which would allow bone to grow in and through the implant. Third, traditional implants are too stiff, causing more load to be carried by the implant and shielding the bone from stress. Ultimately this stress shielding leads to bone resorption and implant loosening. Additive manufacturing (AM) presents a unique opportunity for enhanced performance by allowing for personalized medicine and increased functionality through geometrically complex parts. Much research has been devoted to how AM can be used to improve surgical implants through lattice structures. To date, the authors have found no studies that have performed a complete 3D lattice structure optimization in patient specific anatomy. This paper discusses the general design of an AM hip implant that is personalized for patient specific anatomy and proposes a workflow for optimizing a lattice structure within the implant. Using this design workflow, several lattice structured AM hip implants of various unit cell types are optimized. A solid hip implant is compared against the optimized hip implants. It appears the AM hip implant with a tetra lattice outperforms the other implant by reducing stiffness and allowing for greater bone ingrowth. Ultimately it was found that AM software still has many limitations associated with attempting complex optimizations with multiple materials in patient specific anatomy. Though software limitations prevented a full 3D optimization in patient specific anatomy, the challenges associated such an approach and limitations of the current software are discussed.

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