This paper by Walch and Boileau reports the design rationale and early clinical results of the Aequalis prosthesis — a third-generation modular shoulder implant. Cadaveric data from 65 humeri revealed extreme variability in humeral geometry, motivating a system with interchangeable neck angles and an eccentric offset dial. The study asks whether adapting the implant to individual anatomy produces better fixation and functional outcomes than fixed-geometry predecessors.
Every shoulder arthroplasty case you scrub carries an implicit assumption: the implant system you use can actually match what you find intraoperatively.
Walch and Boileau measured 65 cadaveric humeri and found inclination spanning 33 degrees and retroversion spanning 53 degrees across individuals. That range is why modern shoulder systems offer multiple neck angles and offset options. When you encounter post-traumatic anatomy with an altered neck-shaft angle, or a varus-impacted malunion, the eccentric dial and variable neck of a third-generation system let you adapt the implant rather than osteotomize the patient.
For fixation, the evidence here is unambiguous: cement the humeral component. Zero lucent lines in 91 cemented stems versus subsidence in 3 of 5 press-fit stems, with supporting literature showing press-fit loosening rates 15 times higher. The short stem requires cement — primary stability through cortical engagement is not achievable at 105 mm.
On outcomes, primary OA and AVN are your best candidates for total shoulder arthroplasty. Cuff tear arthropathy and post-traumatic arthritis will achieve meaningful improvement but expect a lower ceiling. Also note the authors' glenoid contraindications: do not implant a glenoid component when there is a two-tendon cuff tear with superior migration, severe erosion preventing keel seating, or intact glenoid cartilage.
This paper by Walch and Boileau reports the design rationale and early clinical results of the Aequalis prosthesis — a third-generation modular shoulder implant. Cadaveric data from 65 humeri revealed extreme variability in humeral geometry, motivating a system with interchangeable neck angles and an eccentric offset dial. The study asks whether adapting the implant to individual anatomy produces better fixation and functional outcomes than fixed-geometry predecessors.
Every shoulder arthroplasty case you scrub carries an implicit assumption: the implant system you use can actually match what you find intraoperatively.
Walch and Boileau measured 65 cadaveric humeri and found inclination spanning 33 degrees and retroversion spanning 53 degrees across individuals. That range is why modern shoulder systems offer multiple neck angles and offset options. When you encounter post-traumatic anatomy with an altered neck-shaft angle, or a varus-impacted malunion, the eccentric dial and variable neck of a third-generation system let you adapt the implant rather than osteotomize the patient.
For fixation, the evidence here is unambiguous: cement the humeral component. Zero lucent lines in 91 cemented stems versus subsidence in 3 of 5 press-fit stems, with supporting literature showing press-fit loosening rates 15 times higher. The short stem requires cement — primary stability through cortical engagement is not achievable at 105 mm.
On outcomes, primary OA and AVN are your best candidates for total shoulder arthroplasty. Cuff tear arthropathy and post-traumatic arthritis will achieve meaningful improvement but expect a lower ceiling. Also note the authors' glenoid contraindications: do not implant a glenoid component when there is a two-tendon cuff tear with superior migration, severe erosion preventing keel seating, or intact glenoid cartilage.