Constrained arthroplasty of the shoulder

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Prosthetic Joint Replacement

Background:

• Constrained shoulder arthroplasty is an evolving prosthetic replacement technique.
• It is indicated for patients with a non-functional rotator cuff mechanism, particularly those with acromial fulcrum and deltoid deficiency.
• This procedure is considered a salvage option, distinct from standard unconstrained arthroplasty.

Purpose of the Study:

• To evaluate the role and considerations of constrained shoulder arthroplasty.
• To discuss the advantages and disadvantages of specific constrained devices, like the MRTS.
• To highlight factors influencing functional outcomes, such as deltoid muscle power.

Main Methods:

• Review of current literature and clinical experience with constrained shoulder arthroplasty.
• Analysis of device-specific features, including dislocation mechanisms and glenoid component fixation.
• Assessment of patient selection criteria and potential complications.

Main Results:

• Constrained arthroplasty is less durable than unconstrained options but offers benefits when indicated.
• The MRTS (Modular Reverse Total Shoulder) system's dislocation feature may reduce scapular fracture risk but requires open revision for reduction.
• Surface mounting of the metal glenoid component aims to decrease loosening or pull-out risks.

Conclusions:

• Constrained shoulder arthroplasty is a valuable salvage procedure when risks are understood.
• Patient selection is critical, with outcomes dependent on residual deltoid muscle function.
• While providing pain relief and functional improvement, device failure can lead to loss of these benefits.