27 Stemless Humeral Technology in Reverse Shoulder Arthroplasty: Is It the Next Frontier?
Stemless reverse shoulder arthroplasties are newly developed system in order to reduce stem-related complications such as periprosthetic fractures or a difficult revision. Their main advantage is preserving the humeral medullary canal. They should be easy to revise later on. A press-fit impaction and a secondary bone integration to the proximal humerus of a reverse implant is achieved by preserving the bone stock with a minimal bone removal. Little literature is available with relatively short follow-up, but these prostheses seem to give similar clinical results as stemmed ones. Poor bone quality in the metaphyseal humerus is associated with loosening of the prostheses. Further investigations may demonstrate the advantages of the stemless reverse shoulder arthroplasty.
An increasing number of reverse shoulder arthroplasties are being performed each year. Reverse shoulder arthroplasty is associated with a complication rate ranging from 4.8 to 68%.1 The stem might be behind many of these complications2 (up to 20%). Resurfacing of the proximal humerus was the initial step of the development of the stemless shoulder prostheses. They were first developed in the early 1980s by Steve Copeland.3,4 Nowadays, many stemless or stem-free anatomical prostheses exist such as the Sidus (Zimmer Biomet—Warsaw, IN; ► Fig. 27.1). They are being used in glenohumeral osteoarthritis in the presence of a normal rotator cuff. The proximal metaphysis has to be intact or with a sufficient bone stock. Evaluation of bone quality is crucial, as it is highly correlated to the initial stability of the implant. These prostheses seem to give similar results on the shoulder function with numerous advantages compared to the stemmed implants, such as a shorter operating time, a more anatomical placement, less intraoperative complications and blood loss, less periprosthetic fractures, and an easier revision.5,6,7 The purpose of these stem-free prostheses is to be easy to revise compared to a convertible stemmed system.
The emergence of the stemless reverse shoulder prostheses is very recent and very little literature is available. However, some of the advantages demonstrated on the anatomical stemless prostheses might be found in their reverse equivalent.
27.2 Stemless Reverse Shoulder Arthroplasty Systems and Operative Technique
Many stemless reverse shoulder arthroplasties are being developed. They rely on the same basic principles. They are based on the Grammont’s concept, they need a minimal humeral resection, and the metaphyseal fixation is cementless. The glenoid base plate is uncemented too. Results of the TESS prosthesis (Total Evolutive Shoulder System; Biomet; ► Fig. 27.2a, b) were the first to be reported, but other implants exist such as the Verso (Innovative Design Orthopaedics, Worcestershire, United Kingdom; ► Fig. 27.2c), the Easytech Reversed (FX Solutions; Viriat, France), or the SMR (Sistema Multiplana Randelli; Lima Corporate, Udine, Italy). The Nano (Zimmer Biomet) is an evolution of the TESS.
27.2.1 Humeral Preparation
The humeral resection is minimal to preserve the bone stock. Nevertheless, the head resection is larger than a shoulder resurfacing and therefore allows easier access to the glenoid. The humeral head is cut using an intramedullary guide (Verso, Easytech Reversed, TESS) or an extramedullary alignment guidance (SMR, Nano). After the head resection, a base plate is implanted inside the metaphysis. Fixation is cementless and it is obtained inside the metaphyseal bone and then it does not need a stem or a diaphyseal preparation. Primary stability is achieved with fins and press-fit impaction inside the spongious bone. To avoid secondary displacement, the bone quality needs to be sufficient. Osteoporosis or a severe osteopenia or large cysts are contraindications to stemless implants (► Fig. 27.3a). Perioperative evaluation of the bone quality is therefore of great importance. During the surgery, after the head is cut, the compaction of the metaphyseal bone under a light pressure of the thumb is a simple test to detect poor bone quality. This “Thumb Test” (► Fig. 27.3b) arises from our personal experience and was not evaluated. Bone autograft from the cut head augments the metaphyseal bone stock. Most of the available implants are convertible to a stemmed reverse arthroplasty if needed. A hydroxyapatite coating with titanium porous or trabecular metal permits secondary osteointegration.
27.2.2 Glenoid Preparation
There is no particularity in glenoid preparation. Lateralized glenoid baseplates and inferior tilt are used to reduce scapular notching. The Verso’s liner has a low medial edge that reduces inferior impingement with the glenoid.