UW Shoulder and Elbow Academy: humeral implant

Friday, April 18, 2025

Surgical decision making in shoulder arthroplasty

The surgeon makes critical decisions for each patient, striving for the optimal shoulder comfort and function. These decisions include those involving prosthesis selection and positioning.

As pointed out in preoperative planning for anatomic total shoulder and ream and run arthroplasty, aspects of planning can be accomplished using standardized plain films and the available PACs tools. However, image-based preoperative planning (whether based on plain films or on 3D CT scans) does not predict important characteristics of the shoulder that are only evident intraoperatively after surgical exposure and osteophyte resection.

Let's consider two examples from this week's surgical schedule.

Case 1- a 66 year old active man with a successful ream and run for right shoulder. arthritis who presented for a left sided ream and run because of refractory functional limitations. The shoulder was not especially stiff preoperatively (140 degrees of active elevation).

Preoperative x-rays showed osteoarthritis with mild-moderate posterior decentering seen on the axillary truth view.

Preoperative image-based planning showed the ideal head cut and suggested a concentric humeral head implant with 56 mm diameter and a thickness of 24 mm.

At surgery, however, after glenoid reaming the suggested head size overstuffed his soft tissues such that range of motion was excessively limited. Trialing with a 50 mm diameter 20 mm thick concentric head component provided the desired mobility, but this implant was posteriorly unstable when the arm was lifted into flexion. An anteriorly eccentric 50 20 humeral trial provided both the desired mobility and stability. His postoperative x-rays are shown below.

The learning point here is that preoperative imaging could not have predicted the correct implant - that decision had to rest on intraoperative trialing.

The patient kindly gave us permission to show this video of his assisted motion three days after his ream and run.

Case 2: A 76 year old man, 5 ft 3 in with cuff tear arthropathy, pseudoparalysis and osteoporosis - all placing him at increased risk for instability and acromial/spine stress fractures. His preoperative Grashey view is shown below.

Because of his pseudo paralysis, he was not a candidate for a CTA hemiarthroplasty (see Cuff tear arthropathy-current considerations); he elected to proceed with a reverse total shoulder. The surgical goals were to optimize stability without excessive lateralization or distalization and with glenosphere inferior tilt to match the orientation of the line (yellow) representing the base of the suprascapularis fossa.

Achieving this goal is a challenge: (1) the orientation of this reference line is not discernible at surgery and (3) the inferior prominence of glenoid would confound the use of a guide to orient the drill for the central screw.

In this case a surgically visible landmark was the plane of the central glenoid (black line). A line (red) perpendicular to this plane provides a reference of zero degrees of inferior tilt.

The angle between the red and yellow lines indicates the desired orientation of the drill to achieve the desired inferior tilt of the baseplate.

The superior-inferior position of the baseplate was selected so that after reaming the inferior glenoid would be covered by the glenosphere.

The final reconstruction is shown below using a 36 mm glenosphere (selected intraoperatively because the 32 mm glenosphere did not provide sufficient stability to vigorous testing), a semiconstrained humeral liner both for stability and to minimize humeral lateralization, and a long smooth impaction grafted stem to avoid varus position of the humeral component (see Dislocation of the reverse total shoulder).

In these two cases the combination of preoperative image-based planning and intraoperative trialing led to the final choice of implant components and positioning.

Recognizing that there is more than one way to skin a cat(bird).

it will be interesting to know the readers' thoughts on alternate approaches.

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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).

Saturday, July 29, 2017

Short-stemmed humeral components - do they 'preserve more bone'?

Short-term clinical outcome of an anatomic short-stem humeral component in total shoulder arthroplasty

These authors evaluated the short-term clinical outcomes of an anatomic short-stem humeral

component in total shoulder arthroplasty. They hypothesized that the implant would lead to significant functional improvement with low rates of radiographic loosening at a minimum follow-up of 2 years.

This is the implanted used.

After an anatomic head cut was made, the canal of the humerus was sequentially broached until optimal fit was achieved and rotational stability of the implant was obtained. All humeral implants were impacted with a press-fit technique without the use of cement.

Sixty-four patients with a mean age of 64.1 years were available for follow-up at a mean of 25 months postoperatively. There were significant improvements in the Visual Analog Scale (6 to 2; P < .001), Simple Shoulder Test (4 to 10; P < .001), Single Assessment Numeric Evaluation (32 to 84; P < .001), and American Shoulder and Elbow Surgeons (37 to 80; P < .001) scores. Forward flexion improved from 116° to 148° (P < .001), external rotation improved from 30° to 57° (P < .001), and internal rotation improved from an average spinal level of S1 to L2 (P < .001). 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 one 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.

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.