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Saturday, January 10, 2026

How I perform a kinematic anatomic shoulder arthroplasty : what is the appropriate amount of stuffing?

Overstuffing in anatomic shoulder athroplasty is simply defined as putting too much volume in the limited space of the glenohumeral joint. The capacity of the joint is limited by its soft tissue envelope. While a tight capsule can be surgically released, the excursion of the rotator cuff and subscapularis remain limiting.  Sort of like what Lewis Carroll described in his 1865 children's novel, Alice in Wonderland. After Alice drinks from the bottle labeled "DRINK ME" she expands to where she cannot move.



The authors of a recent article, Humeral Head Reconstruction in Anatomic Shoulder Arthroplasty: How to Assess It, How to Avoid Overstuffing, and Whether It Matters provide an excellent review of factors that can influence overstuffing.

When we perform an anatomic arthroplasty, we add volume: the humeral and the glenoid components.  When we replace a flattened humeral head with a round one, we add volume. When we add a glenoid component to a joint that had no preoperative articular cartilage, we add volume.

Other factors influence the change in volume in shoulder arthroplasty: osteophyte resection, location of the humeral head cut and extent of glenoid reaming. 

Since the goal of shoulder arthroplasty is restoration of mobility and stability, the optimal amount of stuffing for a particular shoulder cannot be determined by preoperative planning but only by intraoperative examination with the trial components in place. For example a shoulder with severe preoperative stiffness may need to be understuffed (i.e. putting in less volume than that suggested by preoperative imaging). Recall that our goal is not "restoring pre-morbid anatomy", but restoring optimal shoulder kinematics for the patient.

Here are some steps that have proven useful in optimizing anatomic shoulder arthroplasty outcomes for the patient while being mindful of stuffing.

(1) Preoperatively, have an in-depth discussion with patient regarding the procedure, emphasizing the importance of adhering to the postoperative rehabilitation. program, precautions, and contacting the surgical team with questions or concerns during the recovery period,

(2) Assess preoperative glenohumeral motion and write it on the white board in the OR.


(3) Review preoperative Grashey and axillary "truth" views to determine the degree of joint space loss, humeral flattening, and humeral centering. Display these images in the OR.



(4) Display the tentative plan on the Grashey view, recognizing that this plan does not consider the thickness of the glenoid component or the preoperative glenohumeral tightness.


(5) Perform a 360 release of the subscapularis to achieve maximal excursion.



(6) Resect osteophytes to reveal the inferior capsular reflection and identify the "hinge point"( the superior-lateral extent of the humeral articular surface) and place baby Hohmann retractor there to assure a complete head resection.



(7) Make humeral head cut at 45 degrees with the long axis of the shaft and in 30 degrees of retroversion, being careful to avoid the cuff insertion posteriorly.



(8) Conservatively ream the glenoid to a single concavity. 



(9) Insert glenoid component making sure it is perfectly seated on the prepared bone without cement between its backside and the glenoid bone.


(10) Insert trial humeral component, making sure that its superior margin is just below the berm.



(11) Verify the desired range of flexion, internal rotation with the arm in 90 degrees of abduction, and external rotation with the subscapularis approximated to its repair site. 


(12) If the range of motion is limited, especially if tight preoperatively, downsize the humeral component thickness.

(13) Examine stability: optimally shoot for 50% translation on posterior loading. If excessive posterior translation, consider anteriorly eccentric humeral head to avoid stiffness from overstuffing by upsizing humeral head thickness.

(14) Securely repair subscapularis and re-examine motion.


(15) Verify range of flexion with a "parting shot" photograph to be included in the operative note along with documentation of final range of motion measurements.


(16) Tailor post operative rehabilitation program, considering early assisted range of motion for shoulders at risk for stiffness. Document plan in operative note.


(17) Share a copy of the operative note with the patient.

(18) Stay in close communication with patient after surgery, inviting them to email photos of their progress in range of motion


until their rehabilitation is complete.



(19) If the outcome is not what was expected, ask the counterfactual : "what could I have done differently for this patient?

(20) Note that this is a Bayesian approach (see How to make good decisions in shoulder (and other) surgery : Bayesian Thinking) in which at each step the "prior" (starting with the preoperative images and the physical exam) is progressively informed by new information to generate a new "posterior" resulting in a kinematic arthroplasty (rather than an attempt at restoring "premorbid anatomy". Furthermore, the outcomes from each case refine the surgeon's priors for future similar patients, creating a continuous learning cycle that improves a surgeon's judgment over time - something that algorithmic or robotic approaches cannot replicate.




Be self-critical

Barred owl
Seattle Arboretum
2024


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).

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