Saturday, February 25, 2017

Prevention and treatment of propionibacterium biofilms

Prevention of Propionibacterium acnes biofilm formation in prosthetic infections in vitro

These authors studied biofilm formation on synthetic calcium sulfate (CaSO4) bone void filler beads using scanning electron microscopy (SEM) over a period of 14 days.

Here are some SEM photographs of Propionibacterium biofilm formation on the surface of an unloaded pharmaceutical-grade calcium sulfate alpha-hemihydrate bead over a period of 14 days. Surface colonization was observed at day 3 with evidence of extracellular polymeric substance (EPS) strands  (indicated by arrows), with small microcolonies noted at day 7 with more extensive EPS deposition. At day 14, biofilm was observed across  the bead surface over a matted layer of EPS. Scale bars equal 10 μm.

Beads loaded with vancomycin/tobramycin were able to kill planktonic cultures of 106 colony-forming units/mL, prevent bacterial colonization, and significantly reduce biofilm formation over periods of weeks. 

Here is a graph showing Propionibacterium biofilm formation over a period of 14 days in the presence of antibiotic-loaded pharmaceutical-grade calcium sulfate alpha-hemihydrate (PG-CSH) beads as determined by confocal laser scanning microscopy images and colony-forming unit (CFU) counts (CFUs per square centimeter). Data represent the mean of 3 experimental repeats (15 data points, n = 5 per experimental repeat) with standard deviation bars. Arrows indicate a fresh bacterial challenge of 106 CFU/mL every 72 hours. Scale bars equal 25 μm.

Comment: This is an interesting study showing the effectiveness of local antibiotic elution from calcium sulfate beads in preventing and treating Propionibacterium biofilms in vitro. Future in vivo models and clinical experience will help define the role of this approach for prophylaxis in high risk patients and in treatment for patients suspected of having Propionibacterium infections. 

Failed shoulder arthroplasty

Is reverse total shoulder arthroplasty a feasible treatment option for failed shoulder arthroplasty? A retrospective study of 44 cases with special regards to stemless and stemmed primary implants

Revisions of failed shoulder arthroplasties are on the rise.  From 2010 to 2012 60 failed shoulder arthroplasties were converted to reverse total shoulder arthroplasty by an individual surgeon.

Forty-four of these patients were available for follow-up after a mean of 24 months. Seven (16%) of these revisions had complications:

Comment: We found the two case examples particularly interesting, not because of the revisions, but because of the implants requiring revision.

Here is an unstable total shoulder arthroplasty in which a metal backed, cementless glenoid component had become loose. The ingrowth humeral stem required extensive osteotomy for removal.

And here is a stemless humeral component complicated by a proximal humeral fracture.

 In reading papers on revisions, it is always worthwhile to ask whether revisions might have been (a) less likely and (b) less complex with more conventional implants, such as a non-ingrowth standard stem and an all-polyethylene ingrowth glenoid.

Glenohumeral arthritis - management with a spherical implant.

Pyrocarbon interposition shoulder arthroplasty: preliminary results from a prospective multi center study at 2 years of follow-up

It is asserted that "Pyrocarbon has superior tribologic properties than metal because it can slide against bone and cartilage without causing pain or damage".

These authors explored the concept of a free pyrocarbon-coated interposition shoulder arthroplasty in  67 consecutive patients (mean age at surgery was 51 years). The indications for surgery were primary glenohumeral arthritis in 42, avascular necrosis in 13, and secondary arthritis in 12 patients. The criteria for the use of this implant were similar to those the authors use for hemiarthroplasty, notably young age or high activity level, or both.

In this surgery the humeral head resection was performed at the anatomic neck level then a cavity was then reamed in the center of the humeral metaphysis leaving a 2-mm-thick peripheral bony rim at the equator to accept the graphite sphere coated with pyrocarbon. The implant is freely positioned in the reamed cavity within the proximal humerus, articulating directly against the glenoid. 

Revision surgery was performed in 7 patients (10.4%), 2 (3.0%) were lost to follow-up, and the outcome assessments were incomplete in 3 (4.4%). The indications for revision to anatomic or reverse total shoulders included posterior subluxation, inferior glenohumeral impingement causing pain or stiffness, rotator cuff tears, persistent glenoid pain, stiffness and subsidence from wear related to a metal particle. 

In 55 patients at  26.8 ± 3.4 months, the Constant score improved from 34.1±15.1 preoperatively to 66.1±19.7 postoperatively. Here are the x-rays of stable components at > 2 years after surgery.

Progressive glenoid erosion was observed in 6 shoulders and thinning of the tuberosities in 3.

Here is the x-ray of component at > 2 years after surgery with medial erosion of the glenoid

The authors concluded that pyrocarbon-coated interposition shoulder arthroplasty renders clinical scores and implant survival comparable to those of hemiarthroplasty but remain inferior to those results reported for total shoulder arthroplasty. 

Comment: This is an interesting approach to treating glenohumeral arthritis with a free hemiarthroplasty. This device requires removal of metaphyseal bone that may compromise conversation to or revision to a conventional humeral implant should the sphere not provide the desired stability, motion or comfort and, like other hemiarthroplasties, does not address glenoid pathology that may be present.
We concur with the authors that "Until long-term results are available, this type of innovative implant should remain to be tested in a few specialized shoulder centers."


Can viruses be used to fight Propionibacterium?

Prospects of Phage Application in the Treatment of Acne Caused by Propionibacterium acnes

These authors point out that Propionibacterium are associated with purulent skin and periprosthetic infections and that these organisms are showing increasing resistance to antibiotics.

Bacteriophages are bacterial viruses that naturally control microbial populations. They can multiply only in bacterial (not human) cells. Phages may be thought of as naturally occurring “living drugs” with features that give them advantages over antibiotics, e.g., they are specific to their bacterial host and they multiply at the site of infection, but not elsewhere.

In this article they review the literature on Propionibacterium phages, viruses that can kill Propionibacterium.

The isolation of new phages for therapeutic purposes is an affordable and rapid process compared to research and development of new antibiotics. Phage therapy has the potential to be a safe, effective and less expensive than conventional antibiotic therapy.

There are also some limitations of the potential application of anti-Propionibacterium phages, including their high homogeneity which may cause difficulties in identifying other phages if phage resistance develops.

This is a topic worth following as this novel antibiotic approach is explored.

Shoulder joint replacement - is experience the great teacher?

The influence of patient- and surgeon-specific factors on operative duration and early postoperative outcomes in shoulder arthroplasty

These authors asserted that increased operative duration is associated with an increase risk of adverse outcomes and complications. They sought to determine if patient- and surgeon-specific factors correlated to operative duration in shoulder arthroplasty. They conducted a retrospective review of primary and revision total and reverse shoulder arthroplasties performed at a single institution from 2012 through 2015. Patients with postoperative readmission had a longer mean operative time (163 vs. 107.1 minutes).

They found that high surgeon volume (>30 shoulder arthroplasties/year) was associated with shorter operative duration (105.9 vs. 128.3 minutes; P < .001).

Progression through a fellowship academic year was found to be associated with decreased surgical times (100.7 vs. 116.5 minutes; P < .0001).

Reverse shoulder arthroplasty for sequelae of prior fracture, total shoulder arthroplasty for dysplastic glenoid morphology, revision surgery were also associated with increased operative times.

Comment: Increased annual surgical volume has the potential not only for shortening surgical time, but also for improving patient selection, preoperative preparation, surgical technique, postoperative rehabilitation, and justifying a consistent patient-care team around the high-volume practice - all of which can contribute to improved outcomes.

The challenges for the prospective shoulder arthroplasty patient include:
(1) 'exactly what is a 'high volume surgeon?'
(2) 'how do I find a high volume surgeon?'
(3) 'in a high volume practice, will I get personalized attention?'
(4) 'what is the trade-off between the convenience of a local lower volume surgeon and the experience of a more distant higher volume surgeon'?

Some of these questions can be informed by a recent publication:

Distribution of High-Volume Shoulder Arthroplasty Surgeons in the United States: Data from the 2014 Medicare Provider Utilization and Payment Data Release.

These authors point out that high-volume TSA surgeons are reported to have superior outcomes. They studied patient access to these surgeons using 2012 Medicare Provider Utilization and Payment Data Public Use File (MPUPD-PUF). This data base provided volume and reimbursement data for procedures performed by individual physicians participating in Medicare. They studied surgeon prevalence, surgeon distribution, and factors associated with higher or lower surgeon prevalence in metropolitan areas. Data were extracted for all physicians who performed a minimum of 11 TSA procedures for Medicare beneficiaries

The MPUPD-PUF included 774 surgeons across the United States who performed an annual minimum of 11 TSA procedures covered by Medicare, with a combined total of 19,505 TSA procedures. The median annual number of Medicare service claims for TSA was 19 (range, 11 to 163), and the mean was 25 (SE, 0.7).

Of these surgeons, 45% practiced within major metropolitan areas with a population of >1 million. Surgeons who had completed an ASES fellowship had a higher volume of procedural claims (median, 26; range, 11 to 120) compared with other surgeons (median, 17; range, 11 to 163; p < 0.001). 

The distribution among major metropolitan areas was highly unequal, and more surgeons were present in cities with an ASES fellowship program.

This study points to the challenges that patients in certain geographical areas have in accessing surgeons who perform at least 11 shoulder arthroplasties per year.

An interesting question arises from the use of an annual case volume of ≥11 as the definition of a 'high volume' surgeon. Historically, 'high volume' has been defined arbitrarily:

Surgeon Experience and Clinical and Economic Outcomes for Shoulder Arthroplasty categorized surgeons according to the total number of procedures performed within the total 6 year ( 1994 to 2000) study period  with one to five procedures considered low volume; six to thirty procedures, medium volume; and more than thirty procedures, high volume.

The relationship between surgeon and hospital volume and outcomes for shoulder arthroplasty defined a 'high volume' surgeon as one who performed 5 or more cases per year.

This study defines 'high volume' as ≥ 11 cases per year. The number is creeping up.

Last month this article was published:

Meaningful Thresholds for the Volume-Outcome Relationship in Total Knee Arthroplasty

These authors used a database of 289,976 patients undergoing primary total knee arthroplasty from an administrative database, they applied stratum-specific likelihood ratio (SSLR) analysis of a receiver operating characteristic (ROC) curve to generate sets of volume thresholds most predictive of adverse outcomes. The outcomes considered for surgeon volume included 90-day complication and 2-year revision.

They identified four volume categories: 0 to 12, 13 to 59, 60 to 145, and ≥146 total knee arthroplasties per year. 
Complication rates decreased significantly (p < 0.05) in progressively higher-volume categories without a 'bottom' in sight:

Revision rates followed a similar pattern.  This study supports the use of SSLR analysis of ROC curves for risk-based volume stratification in total knee arthroplasty volume-outcomes research. SSLR analysis established meaningful volume definitions for low, medium, high, and very high-volume total knee arthroplasty surgeons.

The question then arises, 'if a high volume knee arthroplasty surgeon is defined as one performing ≥65 cases per year, shouldn't the same threshold apply to shoulder arthroplasty surgeons?' Is there any reason to believe that the annual number of cases of shoulder arthroplasty necessary to achieve and maintain excellence should be lower than that for knee arthroplasty? Is a shoulder arthroplasty easier to learn and master than a total knee?

It is apparent that the higher the standard for 'high volume', the greater the challenge of finding a high volume surgeon.  

Never the less, there is no denying the benefits of volume. More practice

increases the chances of a good result

What makes a treatment worthwhile?

We recently came across this editorial that pointed out the divergence between evidence and practice. In it the author points out that in spite of the substantial evidence that hyaluronate injections (viscosupplementation) are ineffective, the market value of these products is expected to exceed $2.6 Billion by 2021.

He points to three questions we should ask about any treatment we use: (1) is it effective? (2) is it safe? and (3) is it worth the cost? 

This editorial is recommended reading for all of us who are tempted by 'novel' approaches, drugs, and implants.

We could say that the burden of proof lies with the advocates for a new technology, perhaps restating the author's questions:  (1) is it more effective than what we are currently using? (2) is it safer than what we are currently using? and (3) is it worth the increased cost over what we are currently using?

Revision reverse shoulder arthroplasty

Cement-within-cement technique in revision reverse shoulder arthroplasty

These authors reviewed 38 shoulders in which a cemented humeral component was revised to a cemented reverse humeral component fixed by cementing within the existing cement mantle.

The primary indications for revision surgery were instability or subluxation (21), glenoid  disease (wear or component loosening) (16) , and humeral component loosening within the cement mantle (1). Of those revised for instability, 7 had prior anatomic arthroplasties with rotator cuff tears leading to anterior (n = 2) or posterosuperior (n = 5) instability, 5 had instability associated with a reverse arthroplasty, and 9 had failed hemiarthroplasties associated with rotator cuff tears and superior escape.

There were 7 (18%) nondisplaced intraoperative fractures involving the greater tuberosity that occurred on implant removal; all healed at last follow-up. A second revision surgery was performed in 3 (8%) patients who underwent cement-in-cement humeral component revision for glenoid loosening (n = 1), periprosthetic instability associated with glenoid loosening (n = 1), and periprosthetic humerus fracture (n = 1). There was 1 “at-risk” humeral component (grade 4 or higher humeral lucency, moderate subsidence) that did not undergo revision surgery. There were 2 other humeral components with grade 3 humeral lucency, no subsidence.

The overall implant revision-free survival at 2 and 5 years was 95% and 91%, respectively. 

Of note, 3 of the 17 cases revised for loosening had positive intraoperative cultures.

Comment: From this report one can see that (1) the primary reasons for revision to a reverse were instability and glenoid failure, (2) revision carries the risk of intraperative fracture, and (3) failed arthroplasties can be associated with positive cultures - a potential concern because of the retained cement.

Recementing in an extant cement mantle usually requires the use of a smaller stem.


One of the advantages of humeral stem fixation with impaction grafting is the ease of revision as shown by a recent case of a patient with arthritis after multiple failed attempts at cuff repair but who retained active elevation. 

This patient elected to have an impaction-autografted CTA prosthesis which provided good comfort and function for seven years

A recent fall rendered this shoulder pseudo paralytic and the patient elected to have a revision to a reverse. The CTA prosthesis was removed without difficulty or fracture and the reverse stem was fixed securely with impaction allografting without down-sizing the stem. This approached optimized bone preservation.

When applicable, the impaction grafting approach may help reduce the risk of periprosthetic fractures after revision reverse arthroplasty.