UW Shoulder and Elbow Academy: Challenges in removal of a humeral stem

Do preoperative factors and implant design features influence humeral stem extraction efforts?

The authors conducted a retrospective review of 58 patients requiring stem extraction. Their technique consisted of (1) removing scar tissue, (2) hammering upwards on a punch placed under the stem neck or flange, (3) if necessary removing the proximal bone to expose the proximal portion of the stem, and (4) finally, if necessary, performing a "humerotomy".

They classified 26% (15/58) of the study population as having a "difficult" extraction with an 18-minute average stem extraction time and 35 mm of bone removed. By contrast 74% (43/58) of patients had an "easy" extraction, with a 4-minute average extraction time and 10 mm of bone removed.

The likelihood of a cemented stem being difficult to extract is 5 times greater compared to an uncemented stem.

Stems with a proximal coating had twice the likelihood of a difficult stem removal compared to cases with no coating.

Comment: It is frequently necessary to remove an existing humeral stem when revising a prior arthroplasty. Less than 10% of stems were left in place in a recent study of revisions (see Revision of failed shoulder hemiarthroplasty to reverse total arthroplasty: analysis of 157 revision implants). Even with so called "convertible" stems, the height and version of the existing implant is often incompatible with the desired revision. If there is substantial concern for periprosthetic infection, a well-fixed stem may need revision even it is properly positioned.

This study suggests that avoiding the use of cement or implant coating may facilitate stem removal should it become necessary.

The internal anatomy of the humeral canal is not cylindrical and varies substantially among patients.

A safe, effective, and versatile method for fixing a smooth stem in the humeral canal is impaction grafting - a method that avoids the need for cementing or implant coating (see this link). This technique minimizes stress shielding by providing a smaller filling ratio; as well, it facilitates stem removal should it become necessary.

In removing a well fixed implant, it is important to free up the proximal aspect of the implant including bone that may have overgrown the fins. Care with this step minimizes the risk of tuberosity fracture.

For stems that cannot be removed easily, a controlled longitudinal osteotomy can be created with a saw or osteotome and pried open to free the component. The osteotomy is then prepared with side to side sutures to re-establish the integrity or the canal.