Monday, May 25, 2015

Cuff tear arthropathy - the use of a CTA prosthesis


The cuff tear arthropathy prosthesis is considered for individuals with active elevation of 90 or more degrees without anterosuperior escape – especially those who desire higher levels of physical activity or those who are at increased risk of falls. It is important to realize that this prosthesis has an extended lateral joint surface for articulation with the undersurface of the coracoacromial arch, thus it is distinct from the usual hemiarthroplasty prosthesis. The implant system should allow selection of the appropriate diameter of curvature and should enable fixation by impaction grafting.

 

The surgical keys to a successful CTA arthroplasty are (1) optimizing stability and (2) matching the prosthetic diameter of curvature to that of the resected humeral head. The patient positioning, anesthetic, prophylactic antibiotics, skin preparation, and skin incision are identical to that for an anatomic arthroplasty. 

 

In exposing the humeral head, we retain as much as possible of the clavipectoral fascia attached to the coracoacromial ligament (the “CA+”) as an additional barrier to anterosuperior instability. 



The subscapularis is carefully incised from the lesser tuberosity taking care to keep the subjacent capsule attached to its deep side. The humerus is exposed by gentle external rotation allowing for debridement of cuff tendon remnants and osteophytes as well as sectioning of the long head tendon of the biceps if it remains intact. The humeral head height and diameter of curvature are measured, ideally before the head is resected.


The medullary canal is entered and progressively larger reamers inserted as sizers until the diaphyseal endosteal cortex is encountered at a depth corresponding to the length of the prosthetic stem (‘love at first bite’); this reamer defines the orthopaedic axis. The humeral head is resected at an angle of 45 degrees with the orthopaedic axis; the proximal humerus is prepared as for a standard humeral arthroplasty. The lateral tuberosity is resected. The humeral head diameter of curvature is chosen to match that of the resected head. Trial reduction is carried out. The height of the prosthesis is selected so that the deltoid is under mild-moderate tension when the arm is adducted. Impaction grafting is carried out using bone from the resected humeral head. If the biceps tendon is available, an in-and-out biceps tenodesis is performed. Drill holes are placed for reattachment of the subscapularis. The is prosthesis assembled and inserted and the subscapularis is securely repaired.

 


Here's a video showing the function two years after this procedure (see link)

video
Rehabilitation is as for an anatomic arthroplasty with special emphasis on subscapularis protection..



Be sure to click on this link to the Shoulder Arthritis Book.

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