Page 43 - ISAKOS 2018 Newsletter Volume 2

Shorter Stems and Stemless Implants in Shoulder Replacement Surgery
Stephen C. Weber, MD
The Johns Hopkins University School of Medicine
Silver Spring, UNITED STATES
Jorge Rojas Lievano, MD
Division of Shoulder and Elbow Fundacion Santa Fe de Bogotá Bogotá, COLOMBIA
Edward G. McFarland, MD
The Johns Hopkins University School of Medicine Lutherville, UNITED STATES
Uma Srikumaran, MD
The Johns Hopkins University School of Medicine Columbia, UNITED STATES
History Of Stem Length
Shoulder arthroplasty was developed during the middle part of the last century by Dr. Charles Neer. The Neer humeral prosthesis, introduced in 1953, was designed to replace the humeral head in cases of fracture. Neer noted that the stem length was chosen so that the stem would diffuse strain over a 15-cm span; this length was most likely chosen on the basis of the concomitant implant length in the hip. Although the standard prosthesis length has remained the same this day, Neer recognized that the anatomical features of some patients might require the use of a shorter stem. The original Neer device therefore included a short stem option that was “designed for use in small or deformed bones, as in patients with juvenile rheumatoid arthritis or chondrodystrophy.” These short stems were not intended for routine use; in Neer’s original series (n = 356), a short stem was used in only 2 patients, both of whom had epiphyseal dysplasia multiplex.
Recognizing many of the disadvantages of stemmed shoulder arthroplasty, Copeland pioneered the concept of surface replacement arthroplasty. While glenoid resurfacing is technically possible with use of resurfacing implants, it can be difficult because of persistence of the humeral head, which makes direct access to the glenoid difficult. Stemless and short-stemmed arthroplasty have shown advantages over surface replacement in that they may decrease the tendency to overstuff the joint and may offer better exposure to the glenoid for glenoid resurfacing.
The Concept
The use of shorter stems is associated with several potential advantages, including (1) preservation of bone stock in revision situations, (2) the fact that humeral head position is not constrained by the stem (thereby allowing placement of the component independent of alignment with the medullary canal, which can be advantageous in cases of proximal humeral deformity), (3) easier stem removal in the event of revision, (4) less blood loss and shorter operating time, (5) less stress resorption in the proximal part of the humerus, and (6) a requirement for less inventory than is the case with third-generation prostheses (because with shorter stems, and especially, with stemless devices, it is not necessary to reproduce neck angles or offsets with multiple implants or modular implants). In theory, short-stem and stemless devices should be associated with fewer periprosthetic fractures because of avoidance of the diaphyseal stress riser, although clinical data to support this concept are lacking. Fractures around short-stem prostheses can still occur (Fig. 1).
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01 Radiograph showing a fracture through the metaphysis six-months following a short-stem reverse total shoulder replacement.
CURRENT CONCEPTS
ISAKOS NEWSLETTER 2018: VOLUME II 41