These authors examined 74 anatomical, reverse or pyrocarbon hemiprostheses using a curved modular short stem with a proximal porous coating at 2-5 years postoperatively (mean 35 months).
No subsidence or shift of the stems occurred.
2 of 74 patients showed 1 zone of periprosthetic lucency of 1mm.
The filling ratio averaged 0.54 (range 0.36-0.75).
30 patients (40.5%) displayed bony resorption, first seen at 16.6 months
22 patients had ≥1 zone with partial resorption and 8 (10.8%) developed full thickness resorption after 32 (range 10-49) months.
Female sex and older age accounted for 51% of the variation of the filling ratio.
A high filling ratio, especially when >0.55, correlated with bone resorption.
Bony sclerosis correlated with a high filling ratio and thereby indirectly with resorption.
RSA had a higher filling ratio than TSA patient resulting indirectly in more bone resorption.
RSA had a higher filling ratio than TSA patient resulting indirectly in more bone resorption.
The authors concluded significant bone loss, linked to a high filling ratio (>0.55), is observed proximally around these stems. The development of sclerotic lines around the stem indicates oversizing. The implantation of stems with a large filling ratio is more common in older females and in patients receiving RSA.
They state that autologous impaction bone grafting could downsize the required stem.
Comment: Short stemmed humeral components are usually described as 'bone preserving". We agree that bone preservation is important, but find that this objective can be achieved with a standard humeral component inserted with impaction grafting - an approach that is at least as bone preserving as with the use of short stemmed implants. Because impaction grafting distributes interface forces over a broad area, a standard length stem without ingrowth surfaces minimizes problems with stress shielding and achieves additional stability through greater bone-prosthesis contact.
Observe the amount of bone preserved and the low filling ratios obtained with this method as used in anatomic arthroplasty
and reverse total shoulder
Here are some other related articles
Clinical and radiographic outcomes after total shoulder arthroplasty with an anatomic press-fit short stem
These authors identified 118 TSAs completed with press-fit short stem and minimum 2-year follow-up; 85 of these patients had a grit-blasted (GB) short stem placed, whereas 33 patients had short stems with proximal porous coating (PPC).
These authors identified 118 TSAs completed with press-fit short stem and minimum 2-year follow-up; 85 of these patients had a grit-blasted (GB) short stem placed, whereas 33 patients had short stems with proximal porous coating (PPC).
Three female patients with GB stems had gross loosening of their humeral components before 1 year, 2 requiring revision. Radiolucent lines around the humeral component were found in 5.9% without evidence of loosening. Osseous resorption at the medial cortex was noted in 9.3%.
Of patients with PPC stems, none were observed to have radiolucent lines compared with 8.2% in the GB group (P = .09).
The figures from this article show some of the issues with short humeral stems
This article can be considered along with a recent post on a similar topic:
Radiographic changes differ between two different short press-fit humeral stem designs in total shoulder arthroplasty
These authors compared the radiographic changes of the humerus in the short term after total shoulder arthroplasty using two different short-stem humeral components,
and here is the x-ray one year after surgery, showing humeral component loosening.
Radiographic changes differ between two different short press-fit humeral stem designs in total shoulder arthroplasty
These authors compared the radiographic changes of the humerus in the short term after total shoulder arthroplasty using two different short-stem humeral components,
(1) a collarless humeral stem with an oval geometry and curved stem (Ascend or Ascend Flex;Wright Medical, Memphis, TN, USA) (42 patients)
and
(2) a humeral stem with a metaphyseal collar, rectangular geometry, and straight stem (Apex; Arthrex, Inc., Naples, FL, USA) (35 patients).
At a minimum of 2 years postoperatively the authors determined that there were greater radiographic changes seen with the Ascend (classified as low in 38% and high in 62%, medial calcar osteolysis in 71% than with the
Apex (classified as low in 77% and high in 23%, medial calcar osteolysis in 28.5%).
The examples they present show a stress shielding effect with both designs.
This study, along with others highlighted in prior posts, point out that humeri with short stems often demonstrate a stress shielding effect. This is in contrast to the findings with smooth, impaction grafted standard stems (see below) that appear to preserve at least as much bone as a short stemmed prosthesis.
Secure fixation may also become an issue with short stemmed components as shown by this case we saw last week. Here is the x-ray soon after surgery
and here is the x-ray one year after surgery, showing humeral component loosening.
Here is another recent post on the topic of short stems.
This is the implanted used in that study:
Sixty-four patients with a mean age of 64.1 years were available for follow-up at a mean of 25 months postoperatively. On radiographic examination, 9% of stems were deemed "at risk" for loosening (defined as the presence of any stem subsidence, varus or valgus tilt, or radiolucent lines ≥2 mm in 3 or more radiographic zones), but there was no gross loosening in any patient.
They reviewed a recent report (see this link) evaluating the clinical and radiographic outcomes of 73 TSAs performed with a collarless press-fit short stem which demonstrated a 71% rate of radiolucent lines. The overall revision rate at a mean of 33 months was 12%, and 8.7% of the remaining stems were considered at risk for loosening. They reviewed another recent report (see this link) that reported radiolucencies in 22% of 49 short-stem TSAs with a press-fit collared design.
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