Safe, bone preserving fixation of the humeral component in reverse total shoulder arthroplasty.

 Reverse total shoulders are often indicated for patients with poor bone quality. In such patients, the risk of additional bone loss from stress shielding (below left) and the risk of periprosthetic fracture (below right) are substantial.

We have found that the risks of these two complications can be minimized using impaction cancellous autograft to secure the stem in the prepared humeral canal. The use of a smaller stem with impaction autografting also facilitates secure positioning of the humeral cup in the prepared proximal humerus. 

Some of the important technical steps are:

(1) avoiding reaming the diaphysis, the "reamers" are only used to size the canal. This prevents weakening the diaphyseal bone.

(2) selecting a humeral component with a stem diameter that fits loosely in the canal.

(3) using a "juicer" to create a concavity for the cup of the humeral component exactly in the center of the proximal humerus

(4) using a trial humeral component and cancellous bone harvested from the resected humeral head, impaction graft the humeral canal until secure rotational stability is achieved. The relative softness of the cancellous bone eliminates the risk of fracture when the prosthesis is inserted. 

(5) fully seating the component in the prepared proximal humerus; if fixation is not secure, additional cancellous bone is added

(6) the thinner stem allows for the critical fit of the component at the proximal humerus, allowing the stem to find its own position (rather than having a large stem dictate the position of the proximal component).

(7) impaction grafting of a smaller stem avoids a stress riser at the distal end of the prosthesis that would increase the risk of diaphyseal fracture

 The full details of our reverse total shoulder arthroplasty technique are shown in this link.

A recent publication is relevant, Humeral stem with low filling ratio reduces stress shielding in primary reverse shoulder arthroplasty, investigated the amount of humeral bone stress shielding with press-fit humeral stems, comparing those with high and low filling ratios (HFR and LFR).

The illustration below shows the measurement of metaphyseal and diaphyseal filling ratios. 

During surgery with the HFR stem, humeral canal rasping was performed to accept large press-fit humeral stems. 

During surgery using the LFR stem, humeral canal rasping was performed using the smallest rasp (7 mm). The inside of the humeral canal was then filled with autogenous cancellous bone from the humeral head until rotational stability was achieved.

At one year after surgery, no stress shielding was observed in 27 of the 50 shoulders (54.0%) with low filling ratios and in  5 of the 53 (9.4%) with high filling ratios.  

High-stress shielding was found in 3 of the 50 (6%) shoulders with low filling ratios and 19 of the 53 (35.8%) shoulders with high filling ratios. 

Greater tuberosity and medial calcar bone resorption were more common in the HFR group.

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Here are some videos that are of shoulder interest

Shoulder arthritis - what you need to know (see this link).

How to x-ray the shoulder (see this link).

The ream and run procedure (see this link).

The total shoulder arthroplasty (see this link).

The cuff tear arthropathy arthroplasty (see this link).

The reverse total shoulder arthroplasty (see this link).

The smooth and move procedure for irreparable rotator cuff tears (see this link).

Shoulder rehabilitation exercises (see this link).