Wednesday, March 19, 2014

Reverse total shoulder - optimizing surgical technique

We've been asked to present our current technique for primary reverse total shoulder arthroplasty using a mono block humeral component with impaction grafting and minimal cement proximally for rotational control.

Here it is in a nutshell.

Low beach chair position
Skin prep with Chlorhexidine
IV prophylaxis with Cephtriaxone and Vancomycin X 24 h.
Long anterior deltopectoral incision.
Careful subscapularis incision from lesser tuberosity.
Gentle dislocation of humeral head by external rotation.
Resection of humeral head at the anatomic neck respecting the native retroversion of the head.
Curettage of the cartilage from the glenoid.
Removal of inferior bony lip of the glenoid.
Drill hole 14 mm up from the inferior bony margin of the glenoid angled down 10 degrees.
Tapping of this hole.
Conservative reaming of the glenoid bone to prepare a smooth surface for the baseplate (using a reamer of sufficient diameter to ream the diameter of the glenopshere).
Fixation of the baseplate using the central screw. In that this is not a locking screw, one can be sure of the quality of the fixation of the medial aspect of the fixation to the strong bone at the glenoid neck. Addition of the four peripheral screws.
Removal of all bone and soft tissue from around the baseplate.
Insertion of the glenoid trial (typically 36 mm for males, 32 mm for females).
Conservative medullary reaming just to the point where the reamer engages the endosteum. 
Insertion of humeral broach 2 mm smaller than the largest medullary reamer that fit the canal.
Reaming of the metaphysis so that it fits the metal humeral cup.
Trial reduction using the mono block prosthesis trial.
Removal of glenosphere trial.
Insertion of definitive glenosphere, making sure after it is impacted in place that the glenosphere cannot be pulled off the baseplate or rotated on the baseplate by traction or rotation applied to the insertion handle.
Securing the set screw.
Impaction grafting using Vancomycin soaked humeral head autograft until a tight press fit is obtained - the definitive stem (2 mm smaller than the largest medullary reamer) is used as the impactor.
Placement of 6 drill holes in the lesser tuberosity for subscapularis repair.
Insertion of humeral prosthesis with cement only in the metaphysis.
Careful examination for contact between the proximal medial humeral prosthesis and the scapula.
Careful examination for stability and absence of other unwanted humeroscapular contact.
Irrigation of wound with 3 liters of antibiotic containing saline (Cephtriaxone and Vancomycin)
Subscapularis repair with six non-absorbable sutures.
Skin closure with staples.

Here's a case from yesterday - the patient had a massive cuff tear and pseudo paralysis.

Here are the post operative films showing densely impacted bone in the diaphysis and a small amount of cement in the metaphysis. 

This approach minimizes the risk of periprosthetic fracture and allows for easier revision of the stem in comparison to trabecular metal or cement fixation.

By coincidence, our first patient in the office today had a similar procedure 6 weeks ago. He came in today because he took a hard fall on the side of his reverse.  The good news is that his arthroplasty and humerus remained intact after this episode. Note again the presence of impacted bone and the absence of cement in the diaphysis.

The axillary view shows his fixation screws securely in the dense bone of the scapular neck.

Note that the lateral offset of the glenosphere with this particular prosthesis minimizes the risk of notching without using a bone graft.


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