Saturday, April 29, 2017

Re-revision shoulder arthroplasty and Propionibacterium

Recently we encountered multiple positive cultures for Propionibacterium in three male shoulders that had had prior revisions, but no other clinical or laboratory evidence of infection. In each case we suspected a mechanical rather than an inflammatory cause of the patient's problem. In every revision we obtain cultures and the results are often of interest.

Case 1: Prior revision for glenosphere dissociation. Clinically excellent result for 4 years. Dislocated shoulder while extending arm 3 months prior to revision and desired revision because of persistent pain. Surgical findings benign except for mild poly wear. Pre revision x-ray below.

Case 2: Prior hemiarthroplasty for anchor arthropathy. Initial clinical result for 1 year. Recurrent pain thought to be due to prominent suture anchors. Surgical findings benign except for prominent anchors. Pre revision x-ray below.

Case 3: Prior single stage revision loose glenoid. Positive cultures treated with IV antibiotics. Initially excellent result for two years. Surgical findings benign except for humeral membrane in distal canal. Recurrent pain and stiffness. Pre revision x-ray below.

 The Specimen Propi Values (see this link) for the three cases are shown below.

Comment: These cases again illustrate that cultures for Propionibacterium are not infrequently strongly positive even though there is low clinical suspicion for infection.

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Friday, April 28, 2017

What does an infected biofilm on a titanium implant look like?

Quantification of Peri-Implant Bacterial Load and in Vivo Biofilm Formation in an Innovative, Clinically Representative Mouse Model of Periprosthetic Joint Infection

These authors developed a murine PJI model involving a Ti-6Al-4V implant capable of bearing weight and permitting quantitative analysis of periprosthetic bacterial load and evaluation of biofilm.

Twenty-five mice received a unilateral proximal tibial implant and intra-articular injection of either Staphylococcus aureus containing saline or saline solution alone.

In contrast to the control mice, infected mice had difficulty walking over time, exhibited radiographic findings of septic implant loosening, and had significantly elevated inflammatory markers. Periprosthetic tissues and implant surfaces contained viable S. aureus.

Images of a pristine implant, showing the smooth tibial baseplate that resides in the articular space and the stem that resides in the intramedullary space, roughened with sintered titanium beads (arrows).


Below left - an implant retrieved from an infected animal 2 weeks following surgery, with bacteria visible adjacent to a titanium bead (star). Below right - magnified view of the boxed region of interest, showing clusters of S. aureus bacteria covered in biofilm consisting of several fibrin-like shapes, including straight fibers connecting bacteria (arrows).

Below left - an implant retrieved from an infected animal 6 weeks following surgery, showing adherent material consisting of cellular and fibrinous content. Below right - magnified view of the implant, showing a cluster of S. aureus bacteria covered in biofilm in the middle of the image, as well as a wall of fibrinous tissue filled with multiple layers of bacteria (arrows).

Below left - image from an infected implant 6 weeks following surgery, showing multiple host cells (arrowheads) covering titanium beads (stars) and the fibrin coating. Below right - magnified view of the same implant showing 3 S. aureus bacteria (arrows) surrounded by host leukocytes (yellow asterisks). A red blood cell is also noted in the field (red asterisk).

Comment: While these images are from an animal model infected with S. aureus, they are helpful reminders of how adherent bacteria can be to a Titanium implant surface. It is no wonder that such colonization cannot be resolved with systemic or local antibiotics. Implant exchange is the key.

==
Consultation for those who live a distance away from Seattle.

Click here to see the new Shoulder Arthritis Book.

Click here to see the new Rotator Cuff Book

Information about shoulder exercises can be found at this link.

Use the "Search" box to the right to find other topics of interest to you.

You may be interested in some of our most visited web pages including:shoulder arthritis, total shoulder, ream and run, reverse total shoulder, reverse total shoulder patient information, CTA arthroplasty, and rotator cuff surgery as well as the 'ream and run essentials'

See from which cities our patients come.

See the countries from which our readers come on this post.

Complications of reverse total shoulder arthroplasty

Prevalence of Early Minor and Major Complications After Reverse Shoulder Arthroplasty According to the Pathology in Treatment and Comorbidities: A Multicenter Study

These authors assessed the prevalence of early minor and major complications of reverse shoulder arthroplasty in 75 shoulders operated between August 2009 and September 2015.

Revision surgeries and patients with less than 2 months of follow-up were excluded leaving 72 shoulders. The indication for surgery was cuff tear arthropathy in 56.9% of cases and proximal humeral 4-part fractures in 13.8%.

Minor complications were found in 14 patients (19.4%) and major complications in 29 patients (40.3%).




Example: prosthetic fracture at 10 months after the reverse


Example: dissociation of the glenosphere from the base plate 



Comment: This article shows a high rate of complications. It is unclear how many surgeons were involved in this relatively small series or what the level of experience of the surgeons might have been. Of particular concern was the high incidence of neuropraxias in this series. In any event, this paper shows that complications are not infrequent after reverse total shoulder arthroplasty.

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Monday, April 24, 2017

Outpatient shoulder arthroplasty - risk factors

Ambulatory Total Shoulder Arthroplasty: A Comprehensive Analysis of Current Trends, Complications, Readmissions, and Costs

These authors queried a national insurance database for patients who underwent anatomic total shoulder arthroplasty between the fourth quarter of 2010 and 2014, comparing 706 patients undergoing ambulatory total shoulder arthroplasty to a matched group of patients undergoing inpatient total shoulder arthroplasty.

They found no statistically different complication rates or rates of readmission between the two groups. The patients undergoing ambulatory total shoulder arthroplasty had significantly lower costs (p <0.0001) at $14,722 compared with the matched controls at $18,336 in numerous itemized cost categories as well as costs related to diagnosis-related groups.

Comments: While this retrospective study of an insurance database demonstrated that ambulatory shoulder arthroplasty can result in cost savings, this study did not clarify the selection criteria for such procedures nor the particular infrastructure elements necessary to support patients having outpatient arthroplasty. The safe conduct of ambulatory shoulder arthroplasty would seem to depend on the 24/7 availability of qualified support for patients in the event of bleeding, unexpected pain, urinary retention and other medical and surgical complications.

Of interest is the factors associated with readmission after either inpatient or ambulatory arthroplasty.
It is clear that patient safety and economics are more dependent on these factors than in which setting the surgery is done.






Metal sensitivity - do we know enough to alter our practice?

Females with Unexplained Joint Pain Following Total Joint Arthroplasty Exhibit a Higher Rate and Severity of Hypersensitivity to Implant Metals Compared with Males Implications of Sex-Based Bioreactivity Differences

It has been reported that the prevalence of metal hypersensitivity in 10% of the general population, in 20% of people with well-performing implants, and in 60% of those with failing implants (Metal sensitivity in patients with orthopaedic implants. J Bone Joint Surg Am. 2001 Mar;83(3):428-36.). 

These authors conducted a retrospective study of the rates and levels of metal sensitization in a selected group of 1,038 male and 1,575 female subjects with idiopathic joint pain following total joint arthroplasty (TJA) who were referred for sensitivity testing for cobalt, chromium and nickel.

A “no pain” control group consisted of age-matched control subjects who were tested prior to TJA implantation and had no reported history of metal allergy (n = 318).

Females demonstrated a significantly higher rate and severity of metal sensitization compared with males (median lymphocyte stimulation index (SI) among males was 2.8 (mean, 5.4; 95% confidence interval [CI], 4.9 to 6.0) compared with 3.5 (mean, 8.2; 95% CI, 7.4 to 9.0) among females (p < 0.05). Forty-nine percent of females had an SI equal to or greater than 4 (reactive) compared with 38% of males, and the implant-related level of pain was also significantly (p < 0.0001) higher among females (mean, 6.8; 95% CI, 6.6 to 6.9) compared with males (mean, 6.1; 95% CI, 6.0 to 6.3).

Interestingly, a positive sensitivity test was much more common than a positive self-reported history.

While the patients with painful joints had higher mean simulation indices, many had values in the normal range.



Comment: The place of metal sensitivity testing in the evaluation of the painful arthroplasty, the cause/effect relationship of metal sensitivity to implant failure, and the success of revision to implants with different material compositions remain to be determined.

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Sunday, April 23, 2017

Glenohumeral pathoanatomy - are we making its evaluation too complicated?

Interest in the glenoid hull method for analyzing humeral subluxation in primary glenohumeral osteoarthritis

These authors opine that "humeral subluxation is the main cause of failure of total shoulder arthroplasty". They set out to compare humeral head subluxation in various reference planes and to search for a correlation with retroversion, inclination, and glenoid wear using reconstructions of 109 computed tomography scans of primary glenohumeral osteoarthritis and 97 of shoulder problems unrelated to shoulder osteoarthritis (controls) in (a) the scapular plane and (b) the glenoid hull plane
(a line perpendicular to the line joining the center of the glenoid and the tip of the hull (where the anterior and posterior cortical regions meet)).

They concluded that posterior subluxation of the humeral head may be defined in terms of the  glenohumeral offset or the scapulohumeral offset. They prefer measuring subluxation in the glenoid hull plane because it is less affected by the shape of the scapular body.

Comment: It is of interest that many new and increasingly complex methods for assessing glenohumeral pathoanatomy continue to surface monthly. To reduce the resulting confusion, we need to consider several points:

(1) As stated in this link, we need to ask "what information is needed" before a shoulder arthroplasty is performed. Do we need CT scans at all (see this link and this link) in most cases?

(3) While the term "static posterior subluxation of the humeral head" is in common use, the anteroposterior position of the humeral head on the glenoid is not 'static', but rather changes from when the arm is at the side to when the arm is flexed - a phenomenon known as functional decentering. Of course what is most important is not the preoperative posterior subluxation, but rather that noted at surgery as reported recently (see this link).

(3) We need to be clear on the definition of 'subluxation' (see this link). Some authors use the term subluxation to refer to the position of the humeral head in relation to all or part of the the body of the scapula. However, "subluxation" actually means separation of the joint surfaces as in incomplete or partial dislocation of the joint.

Basically, there are three important pieces of information we can obtain from preoperative imaging, each of which can be assessed by an axillary view taken with the arm in the functional position of elevation in the plane of the scapula (rather than with the arm adducted as is the case for CT scans).

First is the shape of the glenoid face. This film shows that the posterior 25% of the glenoid has a pathological concavity.

Second is the retroversion of the glenoid face as shown by the angle between G and S (S is a line drawn along the 'hull' as the authors of this article describe.


Third is the amount of posterior decentering of the head on the face of the glenoid when the arm is elevated in the plane of the scapua, which can be characterized as the ratio of C (the distance from the anterior lip of the glenoid) to G (the distance from the anterior to the posterior lip of the glenoid). 
In over 98% of our cases, these key elements of glenohumeral pathoanatomy can be gained from a single axillary view, avoiding the expense and radiation of a CT scan.

Monday, April 17, 2017

After a total shoulder, when is glenoid loosening aseptic?

A man in his mid sixties had a total shoulder for arthritis. Five years afterwards he noted a feeling of instability in his shoulder on active motion. Eight years after the arthroplasty he presented to us for a revision. On exam his shoulder was painful on active and passive motion. A distinct "clunk" could be felt when he flexed his arm. His AP views show a large humeral stem with the head sitting a bit high and perhaps a suspicion of lucency around the glenoid.


His axillary "truth" view showed obvious radiolucent lines around the cement of the keeled glenoid.


At his revision the humeral component was removed; the glenoid was grossly loose. The residual glenoid was smoothed. No glenoid bone grafting was performed. A new humeral component with an anteriorly eccentric humber head was inserted with impaction allografting. The residual glenoid defect is seen on the post operative x-ray.


His culture results, particularly from the glenoid, were positive for Propionibacterium (Cutibacterium) as shown below

Humeral head - 0.1
Humeral stem - no growth
Capsule - no growth
Collar memberane - 1.1
Glenoid cement #1 - 1
Glenoid cement #2 - 1
Glenoid component - 2

He was managed with the red protocol.

Ten months after surgery his shoulder was comfortable and stable, his active range of motion was progressing with PT. His x-rays showed apparent filling-in of the glenoid defect.





Comment: This case suggests the possibility of a Propionibacterium infection localized primarily to the glenoid.  In our practice of revision arthroplasty we usually avoid grafting the glenoid defect. It is of interest that in this case the glenoid surface appears to have reconstituted without grafting.


Our current management of apparently aseptic shoulder arthroplasty failure can be seen in this link

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