Saturday, December 9, 2017

CTA arthroplasty rather than a reverse total shoulder for rotator cuff tear arthropathy

Many of our patients with classical cuff tear arthropathy want to lead active lives. They wish to avoid a reverse total shoulder because of concerns about activity limitations, dislocation, screw breakage or humeral shaft fracture should they fall. If these individuals have active elevation > 90 degrees and have no evidence of anterior superior instability, we discuss the option of a CTA prosthesis.

Here's the example of a 71year old lady with a history of prior failed cuff surgery. At the time of presentation to us she could not perform any of the 12 functions of the Simple Shoulder Test. Her x-rays at the time are shown below.



Because of her desired activity levels, she elected a CTA arthroplasty rather than a reverse total shoulder. At surgery she had an irreparable cuff defect involving her supraspinatus and infraspinatus and her subscapularis had detached from her lesser tuberosity.

She worked very hard at her rehabilitation and by 6 weeks after surgery she had regained active elevation of her arm.

At two years after surgery, she could perform all 12 of the SST functions, including tucking in her shirt behind her. Her x-rays show firm support of her CTA prosthesis by the acromion.



Comment:  From our standpoint, the CTA arthroplasty is a most attractive option for consideration by active individuals with cuff tear arthropathy and the ability to actively elevate the arm above 90 degrees without manifesting anterosuperior instability.  Inserting the prosthesis with impaction grafting makes for an easy conversion to a reverse should that be necessary, fortunately this is rarely the case. 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 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 present, 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 mobilized subscapularis is securely repaired.

Active assisted motion is started immediately after surgery. Progressive strengthening exercises are started at 6 weeks.
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