Table 1.

 Details of selected device innovations

Development	Altered design features	Intended biomechanical benefits	Expected clinical benefit	Development-specific potential risks
Total hip replacement
Ceramic-on-ceramic bearing	Material of articulating surfaces (cup liner and head) are alumina based ceramics, larger head sizes possible.	Increased longevity and less wear particles with subsequent less wear-induced osteolysis and lower loosening rates	Improved postoperative functional and patient-reported outcomes, lower dislocation and loosening rates	Material fracture due to vulnerability to point loading, squeaking (audible component related noise), liner chipping or canting
Modular femoral neck	Modularity between the stem and neck of the femoral implant, in addition to potential neck-head modularity; modular neck components come in various sizes, angulation, and lengths	Intraoperative adjustment of dimensions for optimal offset, leg length, and anteversion to reduce dislocation, impingement, and wear and allow better muscle balance	Improved postoperative functional and patient reported outcomes, reduced rates of dislocation and loosening, smaller incisions	Fracture, dissociation, corrosion (fretting, crevice, galvanic) with metal ion generation and potential pseudo-tumour formation, component mismatch
Uncemented monoblock acetebular component	Polyethylene liner is moulded into outer metal shell and the cup is a monoblock (non-modular) component which, additionally, allows thicker polyethylene, hemi-elliptical designs en tantalum trabecular metal designs	Prevention of potential (micro)motion induced backside wear and subsequent acetabular osteolysis and cup loosening, prevention of liner dislocation, longer time to revision for wear, less loosening due to more physiological acetabular bone loading due to hemi-elliptical shape and less rigid metal shells	Lower rates of liner dislocations and less concern about wear, resulting in improved postoperative functional and patient reported outcomes, less liner dislocations, and lower revision rates	More demanding implantation, higher risk of improper seating of cup in acetabular bone, intraoperative dimensional changes (that is, offset liners) not possible, isolated liner exchange not possible when worn out, with subsequent difficult revision procedure
Total knee replacement
High-flexion components	Varies from a combination of extension of the posterior condyle of the femoral component with modifications to the cam and tibial spine and reduced anterior thickness of the polyethylene insert to isolated insert modifications	Increased articular contact during high flexion, improved stability and subluxation resistance, decreased stress on quadriceps mechanism, reduced risk of patellar impingement	Increased flexion and decreased incidence of anterior knee pain resulting in better functional and patient reported outcomes	Decreased stability due to higher stress at the cement-implant interface, increased edge loading and higher polyethylene wear, increased patellar impingement
Gender specific components	Enhanced aspect ratio: narrower medial-lateral dimension for a given anteroposterior dimension, reduced anterior flange, recessed and lateralized patellar sulcus	More close match to female anatomy, decreased rate of patellar (sub)luxations, less soft-tissue irritation or imbalance	Increased range of motion and decreased rates of knee pain and patella (sub)luxations resulting in better functional and patient reported outcomes	Unclear and not (yet) described; at least lack of benefit and cost effectiveness due to absence of evidence that women benefit less from unisex knee replacement than men, unknown risks