What is a shoulder infection?

While the diagnosis of obvious shoulder infection is easy: the patient has local and systemic signs of inflammation, abnormal joint fluid and serum lab tests, and positive cultures for indisputable pathogens. 

On the other hand, the diagnosis of a stealth shoulder infection is complicated: the most frequently implicated bacteria (Cutibacterium) is a commensal organism commonly isolated from normal skin, normal deep tissues and healthy shoulder joints. In a stealth infection the usual clinical evidence of infection is absent.

A pragmatic definition of bacterial infection is "bacteria doing harm". That is, the presence of bacteria in and of itself is not sufficient to prove infection. Bacteria in the large intestine; bacteria in sebaceous glands; bacteria recovered from normal joints would not meet the definition whereas E. coli colitis, acne, and joint sepsis would. 

A recent paper,The incidence of subclinical infection in patients undergoing revision shoulder stabilization surgery: a retrospective chart review, exemplifies the challenge. The authors sought to identify the incidence of subclinical infection in 107 patients undergoing revision shoulder stabilization surgery by an experienced shoulder surgeon. Notably the average time from the instability repair to revision was 8 years. The reasons for revision were not provided. Surgical findings (synovitis, purulence, gram stain results) were not given. 

Twenty-nine patients (27.1%) had positive cultures. Patients had multiple specimens sent for culture; the average and range for the number of cultures submitted is not provided. Thirteen patients had only1 positive culture (11 for Cutibacterium). 9 patients had two positive cultures Eight had 3 or more positive cultures (all for Cutibacterium). 

 The paper does not state whether the patients were given antibiotic coverage for the several weeks while the culture results were pending rather than waiting until the results were finalized. The treatment for those patients with positive cultures is not provided.

Twenty-six of these patients (90%) had positive Cutibacterium cultures. The average time to culture positivity was 11 days.

The paper does not state whether any patients developed clinical manifestations of infection.

Comment: It is difficult to know whether these positive cultures obtained on average 8 years after surgery in the absence of other supporting evidence actually represent an infection, i.e. did the bacteria cause harm?

If the surgeon is suspicious of an infection, a reasonable strategy would be to perform a thorough debridement and irrigation at the time of revision, take cultures for Cutibacterium, consider topical antibiotics, and postoperative antibiotics to be continued until the culture results are finalized.     Bases covered.

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

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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).

Stump water - a risk factor for failure of rotator cuff repair

The authors of Tendon stump type on magnetic resonance imaging is a predictive factor for retear after arthroscopic rotator cuff repair investigated the tear size, Goutallier stage, and global fatty degeneration index, seeking factors associated with retear after cuff repair. They also classified the rotator cuff tendon stump (yellow circle) by preoperative oblique coronal image plane T2-weighted fat-suppressed magnetic resonance imaging (MRI), comparing its signal intensity to that of the nearby deltoid muscle (red circle) in 305 patients having arthroscopic cuff repair. 

The authors classified the value of the rotator cuff stump signal intensity (C) divided by the deltoid signal intensity (D) into 3 types defining the stump classification in terms of the C/D ratio.The stump was classified as type 1 if the stump appeared darker than the deltoid, with a C/D ratio less than 0.8; as type 2 if the stump was similar in darkness to the deltoid, with a C/D ratio of 0.8 to 1.3; and as type 3 if the stump appeared whiter than the deltoid, with a C/D ratio greater than 1.3.

The retear rates were 3.4% for type 1 stumps, 4.9% for type 2, and 17.7% for type 3. As shown below, the stump type did not appear to correlate with age, Goutallier stage, GFDI or tear size.

As shown below, multiple regression analysis identified stump type as having the strongest association with retear (odds ratio [OR], 4.28), followed by global fatty degeneration index (OR, 2.99), and anteroposterior tear size (OR, 1.06).

A more recent paper, Re-tear after arthroscopic rotator cuff tear surgery: risk analysis using machine learning found that the most important features predicting re-tears after cuff repair were age, stump type, tear size, and Goutallier grade. 

1. Comment: As these studies demonstrate, the failure risk of rotator cuff repair is influenced by the quality and quantity of cuff tissue available for repair. Stump type is a relatively newly described characteristic.

   The signal intensity on T2-weighted tendon stump images is increased by three factors, each of which can affect the ability of tendon to resist cuff repair suture pull through:

   Water Content: Tissues with higher water content generally have longer T2 relaxation times and appear brighter on T2-weighted images. 

   Protein Content: Tissues with lower protein content tend to have longer T2 relaxation times and appear brighter on T2-weighted images.

   Tissue Structure: Tissues with more disorganized structures, such as muscle, exhibit longer T2 relaxation times and appear brighter compared to tissues with highly organized structures, such as normal tendons or ligaments.

   You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.
   
   Follow on twitter: https://twitter.com/RickMatsen or https://twitter.com/shoulderarth
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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).
   
   
   
   
   
   

Osteoarthritis: Hemiarthroplasty vs Total Shoulder. A pitfall of propensity score matched analysis

Randomization enables unbiased estimation of treatment effects; randomization attempts to assure that treatment-groups are balanced with respect to the important covariates. Unfortunately for us shoulder surgeons, surgical treatments are rarely assigned randomly.

Propensity matching is an attempt to use observational data to compare two treatment groups by accounting for the covariates that are associated with the outcome. 

The possibility of bias arises because a difference in the outcome between treatment groups may be caused by factors that predict which treatment the patient receives rather than the effectiveness of each treatment. For example if an observational study matching patients for age and sex alone retrospectively compared the recurrence rates after Bankart repair and after the Latarjet procedure, it would be at risk for an incorrect conclusion because it did not match for the size of the glenoid defect which may have affected the choice of treatment.

With that background let's look at Shoulder Hemiarthroplasty Is Associated With Higher 30-Day Complication Rates Compared With Total Shoulder Arthroplasty for Glenohumeral Osteoarthritis: A Propensity Score Matched Analysis. So, everyone with OA should get a TSA rather than an HA, right? 

However, the title itself gives pause: why should a smaller operation (hemiarthroplasty) have a higher short term postoperative complication rate than a more involved procedure (total shoulder arthroplasty)? Sounds like a fundamental attribution error.

Let's take a deeper dive. The authors searched the American College of Surgeons National Surgical Quality Improvement Program database for records of patients who underwent either TSA or HA for glenohumeral osteoarthritis of the glenohumeral joint. 

Patients in each group underwent a 1:1 propensity match for age, sex, BMI, ASA classification, diabetes mellitus, hypertension requiring medication, congestive heart failure, chronic obstructive pulmonary disease, inpatient/outpatient status, smoking status, and bleeding disorders.  2188 received TSA and 2188 received HA. The question is, "among these supposedly similar patients, what determined whether they wound up getting HA or TSA? We'll get back to that question shortly.

The HA patients had a higher rate of any adverse event (7.18% vs 4.8%), death (0.69% vs 0.1%), sepsis (0.46% vs 0.1%), postoperative transfusion (4.62% vs 2.2%), postoperative intubation (0.5% vs 0.1%), and extended length of stay (23.77% vs 13.1%). 

Comment: While these differences are striking, it is apparent that putting in a plastic glenoid does not reduce the risk of death, sepsis, transfusion, intubation or extended length of stay.

As stated above, the possibility of bias arises because a difference in the outcome between treatment groups may be caused by factors that predict which treatment the patient receives rather than the effectiveness of each treatment. HA patients had a statistically significantly higher mortality probability (0.004±0.010 vs 0.002±0.003 and morbidity probability (0.027±0.015 vs 0.021±0.011) at baseline compared with the TSA cohort, even after propensity score matching.  Surgeons may prefer to perform HA for high-risk patients and those with more complex pathology. Less experienced surgeons may elect to perform HA because of its simplicity. Surgeons may be more likely to perform HA on patients that have worse social determinants of health (Economic Stability, Education Access and Quality, Health Care Access and Quality, Neighborhood and Built Environment, and Social and Community Context), which are known to be associated with inferior outcomes.

Thus, while the authors state 

"HA was found to increase the odds of developing these complications when baseline demographics were controlled",

 perhaps a more accurate statement would be 

"Patients for whom the surgeons chose HA were found have increased odds of developing these complications when the selected baseline demographics were controlled."

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

Follow on twitter: https://twitter.com/RickMatsen or https://twitter.com/shoulderarth
Follow on facebook: click on this link
Follow on facebook: https://www.facebook.com/frederick.matsen
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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).

Where should we put the glenoid component in shoulder arthroplasty?

Currently many surgeons find it interesting to use CT-based 3D software to help plan shoulder arthroplasty. The planning software program requires a defined target that specifies the desired values for six degrees of glenoid component freedom: version, inclination, rotation, superior-inferior position, anteroposterior-postion and medial-lateral position. The software then suggests the size and position of the glenoid component, as well as the amount of bone removal and the augments or bone graft that might be used to achieve the target position.

So the question becomes, how should the target for the glenoid be determined?

Premorbid Glenoid Anatomy Reconstruction from Contralateral Shoulders 3D-measurements: A CT scan analysis of 260 shoulders suggests that "Total shoulder arthroplasty (TSA) aims to reconstruct the premorbid anatomy of a pathologic shoulder". In the Introduction, it states that "It seems clear that the objective after anatomic TSA is to restore the preoperative anatomy of the patient". One notes that for most arthritic shoulders, premorbid anatomy and preoperative anatomy are not the same.

The paper goes on to suggest that one way to determine the premorbid anatomic of the glenoid is using a reconstruction of the CT of the contralateral shoulder. To support this concept they compared the 3D anatomy of the right and left shoulders of patients without shoulder pathology or injury. From this study they found that paired right and left scapulae were similar but not statistically symmetrical regarding glenoid version, inclination and width. Yet they concluded that "healthy contralateral shoulders can be a useful template in TSA preoperative planning."  One notes that most patients having shoulder arthroplasty on one side do not have a normal shoulder on the contralateral side for comparison.

Furthermore as explained in Glenoid version: acceptors and correctors, the clinical benefit to the patient of "correcting" glenoid version has get to be rigorously demonstrated. 

In the example below an arthritic shoulder in which the humeral head was nearly centered on the face of a retroverted glenoid was 3D planned to "correct" glenoid retroversion with posterior bone removal and insertion of a posteriorly augmented glenoid component.

Is this approach to reconstruction more effective and robust than the example below of a posteriorly decentered humeral head on a retroverted biconcave glenoid treated with a bone conserving standard glenoid component inserted with "accepting" the glenoid retroversion?

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

Follow on twitter: https://twitter.com/RickMatsen or https://twitter.com/shoulderarth
Follow on facebook: click on this link
Follow on facebook: https://www.facebook.com/frederick.matsen
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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).

Where's the wear, where's the osteolysis? 17 year ream and run followup

 A 55 year old active man with limiting pain and stiffness of the left shoulder presented with these x-rays.

Wishing to avoid the risks and limitations associated with the plastic glenoid component used in conventional total shoulder arthroplasty, he elected to proceed with a ream and run procedure.

At followup 17 years after his procedure, he demonstrated excellent comfortable range of motion. 

X-rays showed stable fixation of the impaction autografted humeral component along with healing of the reamed glenoid without evidence of glenoid wear and no humeral osteolysis.

Comment: While glenoid erosion can occur after hemiarthroplasty with a chrome cobalt humeral head, in many cases, as in this one, the reamed glenoid heals to a stable surface. Additional clinical research is needed to determine the factors associated with glenoid wear.

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

Follow on twitter: https://twitter.com/RickMatsen or https://twitter.com/shoulderarth
Follow on facebook: click on this link
Follow on facebook: https://www.facebook.com/frederick.matsen
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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).

How to overstuff an anatomic arthroplasty

Achieving the correct geometry of an anatomic total shoulder is important to the outcome.

The concept of overstuffing in shoulder arthroplasty was introduced over 30 years ago (Practical Evaluation and Management of the Shoulder p181-184): "in many conditions requiring shoulder arthroplasty, the capsule and ligaments are contracted and therefore excessively limit the range of motion. Shoulder arthroplasty tends to further tighten the capsule because the degenerated humeral head is replaced by a larger one, and because a glenoid component is added to the surface of the glenoid bone, consuming more space than the degenerated cartilage it replaces. Thus, the components "stuff" the joint. Unless sufficient capsular releases have been performed to accommodate this stuffing, the joint is "overstuffed" so that the motion is restricted."

As always, credit is due to Steve Lippitt for his amazing illustrations and who kindly provided new drawings for this post.

Adding volume to the joint tightens the soft tissues and restricts range of motion.

How to overstuff the arthroplasty

Overstuffing #1:  the glenoid

While much attention is being paid to the humeral side of the arthroplasty, it is noteworthy that the thickness of the glenoid component also plays a role, particularly with metal backed components.

Overstuffing #2: inadequate humeral head cut

Influence of humeral position of the Affinis short® stemless shoulder arthroplasty system on long-term survival and clinical outcome that assessed the restoration of the center of rotation in patients having anatomic arthroplasty.  75 % (n = 60) of all implants were found to be anatomical and 25 % (n = 20) to be non-anatomical ( postoperative COR deviation of 2.7 ± 1.8 mm vs. 5.1 ± 3.2 mm, respectively).The reason for the non-anatomic reconstruction in all these cases were an improper humeral head resection resulting in an overstuffing with a medial-superior COR deviation of the postoperative COR from the anatomic COR Although the humeral  component position did not affect the functional outcome,  two of twenty shoulders with non-anatomic positioning had glenoid component loosening; none of the 60 anatomically positioned shoulders had glenoid loosening. Two patients with non anatomic positioning and one patient with anatomic positioning had cuff failure

Overstuffing #3:  too thick humeral head component

Overstuffing #4: humeral head component with too large diameter of curvature

Overstuffing #5: humeral component in varus

Overstuffing #6: humeral head component too high

Overstuffing #7: medial positioning of humeral component

These causes of overstuffing relate to the glenoid, humeral head selection, humeral stem position, and the humeral neck cut. With respect to the latter, a number of jigs are marketed to guide the cut

however, it seems that most surgeons prefer to make the humeral cut freehand. This requires (1) complete resection of all osteophytes to expose the anatomic neck, (2) exposure of the cuff insertion superiorly and posteriorly,  (3) drawing a line for the cut from the cuff insertion superiorly to the capsular reflection at the inferior humeral neck, and (4) simultaneously controlling four elements of the cut: (a) the depth of the cut, (b) the varus/valgus angle, (c) the degree of retroversion, and (d) the anteroposterior angulation.

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

Follow on twitter: https://twitter.com/RickMatsen or https://twitter.com/shoulderarth
Follow on facebook: click on this link
Follow on facebook: https://www.facebook.com/frederick.matsen
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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).

Mental toughness - how does it relate to longer term ream and run and total shoulder arthroplasty outcomes?

Shoulder arthroplasty provides a great opportunity for patients with arthritis to recover lost shoulder comfort and function. However, recovery from the operation may challenge the patients' mental as well as their physical toughness. There is evidence that resilience may be an important attribute in the recovery from shoulder surgery.

Several scales have been validated for assessing a person's resilience, including the Brief Resilence Scale

and the The Connor-Davidson Resilience Scale, which assesses the ability to adapt to change, to deal with whatever comes, to see the humorous side of things, to cope with stress, to bounce back after illness or hardship, to achieve goals despite obstacles, to stay focused under pressure, to avoid being discouraged by failure, to think of oneself as being a strong person, and to handle unpleasant feelings.

The authors of Anatomic Shoulder Arthroplasty: The Correlation between Patient Resilience, Mental Health, and Outcome studied 399 patients (195 ream and run (RnR) and 204 anatomic total shoulder (aTSA)) at a mean follow-up of 6.3 ± 3.3 years. 

In this study of anatomic arthroplasties, increased resilience and better mental health were correlated with better outcomes.

In univariable analysis, the Connor Davidson Resilience Scale-10 (CD RISC-10) at latest follow-up was positively correlated with postoperative Simple Shoulder Test (SST), American Shoulder and Elbow Surgeons Score (ASES) and satisfaction after both RnR and aTSA. Mean CD RISC-10 scores were higher in the RnR cohort (34.3 ± 4.8 vs. 32.5 ± 6.2 for aTSA, p<0.001). 

In the multivariable linear regression analysis, greater resilience was associated with better outcomes after anatomic total shoulder arthroplasty: CD RISC-10 was independently associated with postoperative SST, ASES and satisfaction scores in aTSA patients. 

Better mental health was associated with superior outcomes after the ream and run procedure: CD RISC-10 was correlated with satisfaction.Veteran’s RAND-12 Mental Component Score (VR-12 MCS) was correlated with ASES and satisfaction after RnR.

Comment: It may be useful for surgeons to get a sense of the patient's mental toughness before proceeding with surgery and to be sure that appropriate support is in place for those whose resilience may be challenged during post-arthroplasty recovery. 

see also

Is resilience a predictor of the outcomes of total shoulder arthroplasty?

Resiliency Influences Post-Operative Outcomes Following Rotator Cuff Repair

You can support cutting edge shoulder research that is leading to better care for patients with shoulder problems, click on this link.

Follow on twitter: https://twitter.com/RickMatsen or https://twitter.com/shoulderarth
Follow on facebook: click on this link
Follow on facebook: https://www.facebook.com/frederick.matsen
Follow on LinkedIn: https://www.linkedin.com/in/rick-matsen-88b1a8133/

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).