Reconstruction with a double-constrained implant design after complex shoulder extra-articular resection

Area of Science:

• Orthopedic surgery
• Biomedical engineering
• Oncology

Background:

• Extra-articular resection for proximal humerus tumors often leads to poor functional outcomes and high revision rates.
• Existing implants face challenges: unconstrained types cause instability, while constrained ones risk glenoid component loosening due to bone overload.

Purpose of the Study:

• To develop a constrained implant for extra-articular resection cases with deltoid and rotator cuff function loss.
• The implant aims to provide stability, passive motion, and reduce glenoid component aseptic loosening.

Main Methods:

• A novel implant with two constrained joints in series, connected by a dumbbell piece, was designed in collaboration with Czech Technical University.
• Biomechanical analysis demonstrated significant load reduction on the glenoid component.
• Three patients with extensive tumor resection received the implant, with an average follow-up of 16 months.

Main Results:

• The surgical technique was straightforward, with an average surgery time of 175 minutes and 516 ml blood loss.
• No surgical or implant-related complications occurred in the three patients.
• Patients reported pain-free, stable shoulders, fully functional extremities, and high satisfaction, with an average MSTS score of 70%.

Conclusions:

• The innovative constrained implant design shows potential as an effective reconstruction method for challenging proximal humerus tumor resections.
• This approach addresses limitations of previous implants, offering improved stability and reduced risk of loosening.