Sunday, February 5, 2017

Shoulder arthroplasty with a mini-stem humeral implant

Proximal ingrowth coating decreases risk of loosening following uncemented shoulder arthroplasty using mini-stem humeral components and lesser tuberosity osteotomy

These authors performed a minimum 2-year (mean follow-up of 27.3 months (range, 24-50 months) review of 68 shoulders that underwent anatomic total shoulder arthroplasty (TSA) using uncoated (below left) or coated (below right) mini-stem humeral components (MSHC) .

The two surgeons used somewhat different combinations of prostheses.  The first surgeon used the Tornier Aequalis Ascend (no proximal porous coating) in 29 cases and the Tornier Aequalis Ascend PTC in 7 (coated).  The second surgeon used the Tornier Aequalis Ascend (no proximal porous coating)  in 5 and Tornier Aequalis Ascend Flex (coated) in 27. 

Both surgeons used a lesser tuberosity osteotomy for subscapularis management during TSA and HHA with 4 sutures around the fragment, through the bone bed and around the bicipital groove. The results as follows:

Comment: In contrast to a conventional stem that distributes the load across a broad surface are of the humeral endosteal surface

the mini-stem humeral components requires a tight fit in the diaphysis.

This study shows that with these implants, added fixation from a coated implant is needed for fixation, especially if a lesser tuberosity osteotomy is used in the surgical approach.

These prostheses will need to be observed over time to determine the stress-shielding effects of the tight diaphyseal fit and the coated surface as indicated in these related posts:

Radiographic evaluation of short-stem press-fit total shoulder arthroplasty: short-term follow-up