In the prior post, I reviewed the concept of overstuffing - a limited volume with an excessive volume of stuff put in it.

Once more, it is emphasized that in anatomic shoulder arthroplasty, the volume available in the shoulder joint is not the "premorbid" volume, but rather the volume available at surgery after the osteophytes have been removed and after the soft tissue releases have been carried out. Attempting to restore premorbid anatomy to a shoulder with diminished volume will predictably cause a tight shoulder.

The volume of the components put into this space relates in part to the volume of the implants themselves (the chart below shows the humeral head volume in relation to the diameter of curvature and the thickness of the humeral head in a typical arthroplasty system)

but also to the position in which the component is placed. Shown below is overstuffing related to an insufficient humeral neck cut (red = actual, green = desired).

I found 14 English language articles containing the terms "overstuffing" and "shoulder" published since the original description of overstuffing.

The preponderance of these articles proposed the importance of two-dimensional radiographs to assess postoperative humeral positioning in relation to "premorbild" anatomy, failing to recognize that overstuffing is a three-dimensioinal issue related to the relationship of the intraoperative volume of the glenohumeral joint and the volume of the components added to this space.

However, one article pointed out that "anatomic' reconstruction is less important than good postoperative glenohumeral kinematics. It needs to be read by surgeons performing shoulder arthroplasty.

The authors of How anatomic should anatomic total shoulder arthroplasty be? Evaluation of humeral head reconstruction with the best-fit circle demonstrated that "utilization of the best-fit circle in GHOA may lead to excessive humeral lateralization in aTSA." "This method of guiding humeral reconstruction and the addition of a 4-mm glenoid component resulted in a mean humeral lateralization of approximately 6.4 mm. The humeral lateralization was 7 mm or greater in one-third of cases. This is especially relevant in the context of standard anatomic glenoid preparation, which typically involves minimal bone reaming and the addition of an onlay glenoid which contributes to humeral lateralization. Joint line and humeral lateralization require balancing the benefits of improved stability and deltoid efficiency against the risks of rotator cuff over-tensioning and increased glenoid component loading, which may compromise early subscapularis repair healing and contribute to long-term rotator cuff and glenoid component failure. The available evidence and the findings of our study suggest that efforts to reconstruct the proximal humerus in aTSA performed using the best-fit circle as a guide should be considered with caution. The morphological bone changes and associated soft tissue contracture patterns of advanced GHOA need to be considered on a case by case basis in order to appropriately reconstruct anatomy, restore glenohumeral kinematics and function, and optimize survivorship of aTSA."

While the volume of the glenohumeral joing cannot be directly measured at surgery, the adequacy of the joint volume for a given set of trial implants can be inferred from the range of glenohumeral motion

Here are the rest of the articles that focus on two-dimensional restoration of the "premorbid anatomy".

Geometrical analysis of Copeland surface replacement shoulder arthroplasty in relation to normal anatomy

The Copeland resurfacing humeral head implant does not restore humeral head anatomy. A retrospective study

Radiographic assessment of prosthetic humeral head size after anatomic shoulder arthroplasty

Assessment of the Anatomic Neck as an Accurate Landmark for Humeral Head Resurfacing Implant Height Placement

Results and limitations of humeral head resurfacing: 105 cases at a mean follow-up of 5 years

Low inter-observer agreement among experienced shoulder surgeons assessing overstuffing of glenohumeral resurfacing hemiarthroplasty based on plain radiographs

Overstuffing in resurfacing hemiarthroplasty is a potential risk for failure

Does computerized CT-based 3D planning of the humeral head cut help to restore the anatomy of the proximal humerus after stemless total shoulder arthroplasty? These authors concluded that restoration of proximal humeral anatomy with stemless anatomic total shoulder using computed tomography-based 3D planning was not precise. A poorly performed humeral head cut was the main reason for overstuffing, which was seen in 88% of the cases with inaccurate restoration of premorbid proximal humeral anatomy. Preoperative small humeral head diameter, low humeral head height, and varus-angulated head neck angle were risk factors for poor restoration of premorbid proximal humeral anatomy with stemless TSA.

Extra-short humeral heads reduce glenohumeral joint overstuffing compared with short heads in anatomic total shoulder arthroplasty

Best-Fit Circle for the Replication of Humeral Head Anatomy in Total Shoulder Arthroplasty

The impact of glenoid parameters and implant overstuffing on functional outcomes of shoulder hemiarthroplasty in patients with glenohumeral joint arthritis

Radiographic comparison of eccentric stemmed vs. concentric stemless prosthetic humeral head positioning after anatomic total shoulder arthroplasty

A reproducible method for evaluating the degree and direction of overstuffing of the humeral head component in anatomic total shoulder arthroplasty

The shoulder is not a two dimensional thing in FlatLand with the arm fixed at the side

The Shoulder is a Three-Dimensional Structure that Moves in Three Dimensions

Note the patagial bars on the shoulders of this red tailed hawk.

Montlake

2024

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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).