Thursday, January 18, 2018

What does Propionibacterium do to living tissue?

Propionibacterium acnes induces intervertebral disc degeneration by promoting nucleus pulposus cell apoptosis via the TLR2/JNK/mitochondrial-mediated pathway

These authors point out the evidence that intervertebral disc degeneration can be induced by Propionibacterium acnes (P. acnes).

They analyzed the pathological changes in degenerated human intervertebral discs infected with P. acnes, finding that compared with P. acnes-negative samples, P. acnes-positive discs showed increased apoptosis of nucleus pulposus cells concomitant with severe intervertebral disc degeneration. 

They then established a P. acnes inoculated intervertebral disc degeneration animal model, finding that severe intervertebral disc degeneration was induced by P. acnes infection by promoting nucleus pulposus cell apoptosis. 

Their results suggested that P.acnes-induced apoptosis of nucleus pulposus cells via the Toll-like receptor 2 (TLR2)/c-Jun N terminal kinase (JNK) pathway and mitochondrial-mediated cell death. 

Furthermore P. acnes was found to activate autophagy (the orderly degradation and recycling of cellular components), which likely plays a role in apoptosis of nucleus pulposus cells

Overall, these findings further validated the involvement of P. acnes in the pathology of intervertebral disc degeneration and provided evidence that P. acnes-induced apoptosis of nucleus pulposus cells via the TLR2/JNK pathway is likely responsible for the pathology of intervertebral disc degeneration

Comment: While this study concerns intervertebral disc degeneration caused by Propionibacterium, it elucidates the mechanism by which this bacteria can destroy tissue. This same mechanism may be involved in the destruction of bone and soft tissue by this organism in failed arthroplasty and cuff repair.

Wednesday, January 17, 2018

Does implant sonication help in the diagnosis of periprosthetic shoulder infection?

Performance of implant sonication culture for the diagnosis of periprosthetic shoulder infection

These authors performed routine perioperative testing in 53 patients who underwent revision shoulder arthroplasty. In addition to routine tissue and fluid culture, the retrieved shoulder implants underwent sonication with culture of the sonicate fluid.

25 (47%) were classified as infected. Propionibacterium was the identified pathogen in 19 of 25 cases. Other cultured organisms were CNSS (4/25 [16%]), methicillin resistant Staphylococcus aureus (2/25 [8%]), group B streptococcus (1/25 [4%]), and Enterobacter cloacae (1/25 [4%]). Two (8%) cases were polymicrobial, with both CNSS and P. acnes identified in each. 

Using the cutoff value of >20 colony forming units (CFU)/mL to exclude contaminants, implant sonication culture had a low sensitivity (56%) but high specificity (93%) .

Without using a cutoff value, implant sonication culture had a high sensitivity (96%) but low specificity (64%). 

Standard intraoperative cultures (tissue and fluid) had a better overall performance compared with the cutoff and non-cutoff sonication results.
The authors concluded that implant sonication fluid culture in revision shoulder arthroplasty showed no significant improvement in diagnostic utility over standard intraoperative cultures.

Comment: In our laboratory, explanted prosthesis are submitted to vortexing, which is an alternative approach to sonication for shaking loose bacteria that may be encased in a biofilm on the implant. Our experience indicates that implants studied in this way provide an important source of culture positive specimens harvested at the time of revision arthroplasty. In a recent study (see this link) only 32.6% of the fluid cultures were positive in comparison with 66.5% of the soft-tissue cultures and 55.6% of the cultures of the explant specimens.

Reverse total shoulder in the face of glenoid defects

Management of glenoid bone defects with reverse shoulder arthroplasty—surgical technique and clinical outcomes

Between 2001 and 2010, these authors found that 94 of 1074 reverse total shoulders had significant glenoid bone loss. Of these patients, 17% had a centric defect 

 and 83% had an eccentric glenoid defect.



Composite glenoid grafts were required in 12 patients, 9 of whom required a glenoid baseplate with a long central peg.





92.5% (87/94) of the patients could be managed with a single-stage procedure.  If the long central peg did not purchase a minimum of 50% of its length in the native scapula, a single-stage reconstruction was aborted in favor of a 2-stage procedure: the glenoid defect was grafted with a composite graft and fixated using cortical screws as required to attain graft stability. In cases of centric defects, a modular humeral component was used and a hemiarthroplasty performed. In cases in which eccentric defects were reconstructed, a resection arthroplasty was performed. In the authors’ experience, a hemiarthroplasty for an eccentric bone defect led to poor graft incorporation and graft nonunion or resorption.

Comment: The key in such cases is that secure baseplate fixation needs to be achieved before the construct is loaded by completing the reverse total shoulder with a glenosphere and a humeral component.

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The reader may also be interested in these posts:



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 runreverse total shoulderCTA 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.

Grammont-style reverse shoulder arthroplasty - avoiding humeral complications

Long-term humeral complications after Grammont-style reverse shoulder arthroplasty

These authors analyzed humeral complications in follow-up of 1035 reverse total shoulders (RSAs) with a minimum 5-year follow-up (implanted in 7 specialized shoulder centers between 1993 and 2010)

A 3.3% rate of postoperative humeral complications was found:17 cases (1.6%) with postoperative humeral fractures, 15 cases (1.4%) with aseptic humeral loosening, and 3 cases (0.3%) with humeral stem disassembly.

Humeral complications were more frequent in RSAs implanted for tumors, fracture sequelae, and revision for failed arthroplasty. Humeral complications after RSA are not rare, increase with longer follow-up, and have a negative impact on functional outcomes. Postoperative humeral fractures are more frequent in elderly patients, operated on through a superior approach, and after cemented stem implantation. In the absence of associated humeral loosening, conservative treatment should be preferred. Proximal humeral bone loss (due to revisions and tumors) is the most significant risk factor for humeral loosening.

Comment: The risk of some of these complications may be lowered by modifications in technique or in the implant. For example the risk of fracture at the tip of a cemented implant 

can be reduced by fixation with bone preserving impaction grafting, which avoids the distal stress riser.


 The risk of component disassembly





can be lowered by using a monoblock humeral component


Bone quality and bone quantity are often compromised in RSA, especially in elderly patients and in the setting of revision. In such cases, it is important to optimize implant design and surgical technique as well as minimizating of the risk of falls. 

Our technique of reverse total shoulder arthroplasty can be found at this link.

Acetaminophen, naproxen and post arthroplasty pain control

Multimodal analgesia decreases opioid consumption after shoulder arthroplasty: a prospective cohort study

These authors conducted a prospective cohort analysis of patients undergoing elective shoulder arthroplasty who were treated with either a standard opioid-based regimen or a multimodal analgesia regimen perioperatively.

Collection was performed sequentially: the first 75 patients treated with the standard regimen, followed by 75 patients treated with the multimodal regimen. Patients with high preoperative chronic opioid use (defined as >60 mg of oral morphine equivalents taken daily) and patients with active infection undergoing removal of implants were excluded. 

Patients in both groups received a preoperative single-shot interscalene regional nerve block with 15-20 mL of 0.5% ropivacaine.
Patients in the standard group received scheduled doses of an opioid and acetaminophen combination medication postoperatively, with additional opioid medications as needed for pain control.


Multimodal patients received scheduled doses of non-opioid analgesics preoperatively and postoperatively, with additional opioid medications as needed for pain control.



Patients treated with the multimodal analgesia regimen had significantly lower postoperative day 0 pain scores (mean, 1.5 vs 2.2; P = .027).


 Opioid use in the multimodal cohort was lower on all days: 47% lower on postoperative day 0, 37% on day 1, and 44% on day 2 (all P < .01).



The length of inpatient stay was significantly shorter for multimodal patients than for patients treated with the standard regimen (1.44 days vs 1.91 days, P < .01) as shown below. Parenthetically, this chart demonstrates that the cost of the implant is almost half of the hospital costs. 

Comment: This study shows that the multimodal program resulted in less opiate use after surgery. It is not clear which elements of the multimodal program are most important. While we do not use gabapentin or lyrica in our practice because of the potential for side effects, we find, as did the authors, that scheduled Tylenol and Naproxen are most helpful in postoperative pain control.

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The reader may also be interested in these posts:



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 runreverse total shoulderCTA 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.

Tuesday, January 16, 2018

Management of a posterior locked fracture dislocation

A 55 year old triathlete fell while bike riding, landing on his outstretched left hand. He developed posterior instability that was treated with a posterior arthroscopic stabilization at an outside facility. Subsequently it was noted that he had developed a locked posterior fracture dislocation with both an anterior humeral and a posterior glenoid defect as shown by the images below.





He elected an open reduction and humeral hemiarthroplasty with an anteriorly eccentric humeral head and a posterior glenoid bone graft using part of the resected humeral head. At surgery his shoulder was very stable under vigorous posterior loading.

The postoperative films are shown below



The plan is for external rotation isometrics and 6 weeks immobilization in a neutral rotation brace.
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The reader may also be interested in these posts:



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 runreverse total shoulderCTA 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.

A synovial fluid test for infected joint replacements

The Accuracy of the Alpha Defensin Lateral Flow Device for Diagnosis of Periprosthetic Joint Infection Comparison with a Gold Standard

These authors examined the accuracy for the detection of periprosthetic hip and knee infections (i.e. those meeting the criteria established by the Musculoskeletal Infection Society) of a rapid lateral flow version of the alpha defensin test in a aspirate of synovial fluid.

The study group included patients with pain after total hips or total knees. There were 119 joints with an aseptic revision and 76 joints with periprosthetic joint infection according to the MSIS criteria (Clin Orthop Relat Res (2011) 469:2992–2994)




The overall sensitivity of the Synovasure Alpha Defensin Test was 92.1%, the specificity was 100%, the positive predictive value was 100%, and the negative predictive value was 95.2%. The overall accuracy of the Synovasure test was 96.9%.

The culture results of the aspirates are shown below.

The authors conclude that the "Synovasure Alpha Defensin Test with a lateral fl ow device demonstrates encouraging results with high accuracy for diagnosing infection following total hip arthroplasty and total knee arthroplasty. However, the test is associated with high costs, which is a limiting factor. Further cost-benefit studies will determine if the high costs of this new tool are justifiable."

Comment: With respect to the use of such a study in the evaluation of patients with pain after a shoulder arthroplasty, we must recall that a high percentage of these patients have positive deep tissue and explant cultures for Propionibacterium but do not meet the MSIS criteria for a periprosthetic infection. It is well recognized that the stealth presentation of a failed shoulder arthroplasty with positive cultures can occur months or years after the joint replacement. It would be of interest to learn the sensitivity of this new test in the evaluation of these patients.