Total Shoulder Arthroplasty Using a Bone-Sparing, Precision Multiplanar Humeral Prosthesis
TAKE-HOME POINTS
- Bone-preserving shoulder arthroplasty is now available and rapidly growing in the US.
- The calibrated, multiplanar instruments and prosthesis shown here allow surgeons to recreate the normal humerus shape with high precision.
- The elliptical, non-spherical design of the humerus prosthesis has shown improved shoulder kinematics compared to standard spherical prostheses.
- The implant rests on dense bone proximal to the anatomic neck where bone support is strong.
- Glenoid implant insertion is routinely performed using this technique and access is facilitated by the angled bone resections.
The implant respects the relationship of the rotator cuff insertion and has a recessed superior margin to keep both the implant and the saw blade 3 mm to 5 mm away from the supraspinatus fibers to protect the rotator cuff from iatrogenic injury.
TECHNIQUE
The technique described in this article uses the Catalyst CSR Total Shoulder System (Catalyst OrthoScience), which was cleared to treat arthritis of the shoulder by the US Food and Drug Administration in May 2016.
A standard deltopectoral incision is made, and the surgeon dissects the interval between the pectoralis major medially and the deltoid laterally. The subscapularis can be incised by tenotomy; alternatively, the surgeon can perform a subscapularis peel or a lesser tuberosity osteotomy using this technique.
Once the glenohumeral joint is exposed, the surgeon delivers the humeral head anteriorly. A preferred method is to place a Darrach retractor between the humeral head and the glenoid, and a cobra or a second Darrach retractor behind the superolateral humeral head superficial to the supraspinatus tendon. By simultaneously pressing on both retractors and externally rotating the patient’s arm, the humeral head is delivered anteriorly. Osteophytes on the anterior and inferior edge of the humeral head are generously removed at this time using a rongeur.
Using a pin guide, the long 3.2-mm guidewire pin is drilled under power into the center of the articular surface. The pin guide is then removed, leaving the pin in the center of the humerus (Figure 3).
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