Saturday, October 22, 2016

Metal backed glenoid components and failure rate.

The weak link in metal-backed glenoid implants is the polyethylene

These surgeons have authored a most thoughtful letter regarding the metal backed glenoid. We encourage reading of the complete letter (see this link) and their original article (see this link).

Here we paraphrase their letter. "the results this clinical study, showing poor results with metal backed (MB) glenoid implants at medium- to long-term follow-up, are in accordance with other long-term clinical studies reporting on a high number of patients and with a recent systematic review showing that the revision rate with MB glenoid components is 3 times higher than with all-PE components (see this link). Finally, biomechanics studies have demonstrated the problems created by the metallic interface in anatomic TSA on both the plastic side and the bone side. All these are good reasons, published in the literature, that do not encourage the use of MB glenoid components for anatomic TSA. Careful consideration of the inherent risks is warranted if future exploration of MB anatomic glenoid components is undertaken. The success of MB glenoid components for reverse TSA should not lead to confusion of surgeons: the biomechanical environment is very different in reverse TSA, in which a metallic sphere is associated to a metallic baseplate."

Comment: We have posted some informative links on this topic (see here, and here). In a recent post (see here) we point out that in addition to problems of thickness and back side wear, the issue is in large part the mismatch in the material properties of polyethylene and the metal backing.

Additional data on the difficulties associated with metal backed implants can be found from the robust database of the Australian Orthopaedic Association (see here), showing 'higher than anticipated rates of revision' for metal backed glenoid components.

Examples of these components are shown below:

While no prosthetic glenoid component is perfect, the current evidence is that the safest and most durable implants are the pegged all-polyethylene component

 inserted with careful and conservative glenoid bone preparation.


Systemic reaction after a Vancomycin spacer and systemic Vancomycin for treating a periprosthetic infection

Drug eruption secondary to vancomycin-laden spacer in the shoulder: a case report

These authors point out that periprosthetic joint infections (PJIs) after shoulder arthroplasty are often treated with two-stage revisions, involving prosthesis explantation, thorough d├ębridement, and implantation of an antibioticimpregnated cement spacer with a course of IV antibiotics followed by a revision arthroplasty. Antibiotic-impregnated cement spacers containing aminoglycosides or vancomycin are commonly used. Whereas the use of antibiotic spacers is generally considered safe, there have been previous reports of a diffuse desquamating rash from vancomycin-laden cement and cases of hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms after concurrent use of systemic vancomycin and vancomycin laden bone cement in the hip and knee. They report a case of a drug eruption caused by parenteral vancomycin in combination with a vancomycin-impregnated spacer inserted for a shoulder PJI.

The details of the case are interesting.  The patient was a 69-year-old with the diagnosis of rotator cuff arthropathy. He underwent a right reverse total shoulder arthroplasty in December 2012. In November 2014, the patient underwent a revision surgery to manage loose hardware and a broken baseplate screw. No culture specimens were taken at the time of the revision surgery.

The patient continued to have significant pain and was subsequently found to have a Propionibacterium infection diagnosed by aspiration. He then underwent an initial irrigation and d├ębridement with retention of implants and was prescribed a 60-day course of doxycycline.

Six weeks later, the patient was noted to have significant wound site drainage.

He was given a peripherally inserted central catheter line, through which he received multiple infusions of vancomycin 1000 mg during the course of 2 weeks without any adverse reactions. When that failed to eradicate the PJI, he underwent removal of the prosthesis with placement of a vancomycin-impregnated bone cement spacer; he also received vancomycin 1250 mg every 12 hours starting on postoperative day 1.

On postoperative day 4, he noticed swelling of his right arm, forearm, and hand. During the next 48 hours, he developed an erythematous, pruritic, maculopapular rash that spread to his entire torso and extremities.

These symptoms resolved after removal of the vancomycin spacer and a course of systemic steroids. 

Comment: Pharmacokinetic studies of vancomycin-loaded bone cement show that blood vancomycin levels reach peak blood concentration between 6 and 24 hours and fall to undetectable levels by the tenth day (see this link).

The point is that drug eruption reactions can occur after both systemic and local diffusion from antibiotic-laden cement spacers.


Humeral and glenoid component loosening - aseptic or culture positive? What can we learn?

Here are the films of the right shoulder of a man in his late 60s with glenohumeral arthritis

 and a posteriorly biconcave glenoid.

He had a total shoulder with mono block chrome-cobalt humeral component and a Hylamer glenoid.

He did very well after surgery, returning to gym workouts and a wide range of outdoor physical activities. His x-ray at three monte after surgery is shown below.

One year after surgery, he was still doing well. His X-ray at that time is shown below.

Seven years after surgery, his shoulder was becoming somewhat painful, but not so much that he wanted anything done. His x-rays at that time show glenoid component wear and humeral subsidence.

Thirteen years after his surgery, his symptoms were worsening as were the x-ray findings. He elected to give it a bit more time.

 Three months later the symptoms and x-ray changes (see below)

led to a revision surgery. Preoperative blood tests were normal.

At surgery the joint fluid was cloudy, but gram stains showed no neutrophils.

The humeral and glenoid components were loose and there was a thick humeral membrane. Frozen sections showed "Humeral membrane, right shoulder, excision: - Synovial tissue with extensive fibrosis and marked foreign body giant cell reaction with associated polarizable foreign material. - No neutrophils identified." 

The retrieved glenoid component showed substantial wear.

 Based on these findings, we considered the diagnosis of detritic synovitis (see this link).

He had a single stage revision to a hemiarthroplasty using Vancoymycin allograft for humeral fixation.

As a precaution we placed the patient on oral antibiotics (Augmentin) until the culture results were finalized.

In a week after surgery, the culture results came back as shown below

Note that the preoperative culture of his unprepared skin was strongly positive for Propionibacterium.
The humeral and glenoid explants and the membrane deep to the glenoid component were also strongly positive for Propionibacterium, while the humeral membrane specimens and joint fluid were unimpressive.
These findings emphasize that Propionibacterium is not uniformly distributed throughout the shoulder. Had the cultures been limited to the humeral membrane and joint fluid, the presence of Propionibacterium may have been overlooked.

With these culture results he was converted to the red protocol (see this link) of IV Ceftriaxone and Rifampin. 

Clinically, he is doing well with 140 degrees of assisted elevation and minimal shoulder discomfort.

Comment: This case is an excellent example of the complexities of the evaluation and management of a shoulder with delayed loosening of the total shoulder components. It is not possible to know if the Propionibacterium recovered from this shoulder were introduced from the patient's skin at the index surgery 13 years prior to the revision or if they arrived in the shoulder subsequently.

We have so much left to learn.


Thursday, October 20, 2016

Is every shoulder joint surgery contaminated with Propionibacterium? How do we deal with that?

Contamination of the Surgical Field with Propionibacterium acnes in Primary Shoulder Arthroplasty

These authors point out that Propionibacterium are commonly recovered in revision shoulder surgery and that they are also present in specimens from primary shoulder arthroplasty.

The exclusion criteria for this study were a previous shoulder surgical procedure, shoulder infection, previous proximal humeral fracture, use of antibiotics within 2 weeks prior to the surgical procedure, and cortisone injection into the shoulder within 6 months prior to the procedure.

All patients received a general anesthetic and 2 g of intravenous cefazolin at induction prior to skin preparation and draping. The surgical site was prepared with a Betadine-alcohol skin preparation antiseptic, equivalent to 10% povidone-iodine solution and 30% ethyl alcohol

From each of 40 patients (25 female patients and 15 male patients) having primary shoulder arthroplasty they submitted 5 swabs from: (1) the subdermal layer, (2) the tip of the surgeon’s glove, (3) the inside scalpel blade (used for deeper incision), (4) the forceps, and (5) the outside scalpel blade (used for the skin incision).

Swabs were inoculated onto blood agar, prereduced blood agar, and chocolate agar plates. Specimens were incubated at 37C under 5% carbon dioxide aerobic conditions and anaerobic conditions for 14 days. Organisms grown were identified with initial Gram stain and matrix-assisted laser desorption/ionization time-of-flight (MALDI-ToF) mass spectrometry. 

Thirteen (33%) of the 40 patients had at least 1 culture specimen positive for P. acnes. 

Two (8%) of the 25 female patients while 11 (73%) of the 15 male patients had ≥1 culture specimen positive for P. acnes. 

The most common site of growth of Propionibacterium was the subdermal layer (12 positive samples), followed by the forceps (7 positive samples), the tip of the surgeon’s glove (7 positive samples), the outside scalpel blade (4 positive samples), and the inside scalpel blade (1 positive sample). 

27 of 75 swabs that were positive on culture for Propionibacterium in male patients compared with 4 of 125 swabs in female patients; male patients had 66 times higher odds of having a positive culture indicating subdermal colonization compared with female patients (p < 0.001).

The time to positivity ranged from 4 to 10 days. Seventeen (55%) of the 31 specimens that grew P. acnes had growth by day 5, 7 specimens (23%) had growth by day 8, and 7 specimens (23%) had growth between 9 and 10.25 days.

The authors acted on the results of these cultures: the 6 patients with 3 positive cultures were empirically treated with oral amoxicillin (or clindamycin in case of penicillin allergy) for 6 weeks, as they were deemed at high risk of developing a postoperative infection.

None of the patients in this study showed evidence of infection within 6 months of surgery.

One patient having two positive cultures for Propionibacterium at the primary surgery had a revision procedure to remove a prominent suture. The suture removed at the revision procedure was culture positive for Propionibacterium.

They concluded that Propionibacterium commonly contaminates the surgical field in primary shoulder arthroplasty. The subdermal layer may be the source of this contamination.  Propionibacterium is likely to be spread throughout the surgical field from the subdermal layer via soft-tissue handling by the surgeon and instruments. 

Comment:  There are two major conclusions that can be drawn from this work. 

First, the reported rates of positive cultures at the time of revision arthroplassty may be falsely high as a result of specimen contamination from the dermis at the time of revision. In our practice we strive to avoid this contamination by protecting the tissue samples and explants harvested at the time of revision from contact with the skin. Each tissue sample is obtained with a previously unused sterile rongeur. 

Second and more importantly, conventional means of prophylaxis and surgical technique do not prevent the introduction of Propionibacterium into arthroplasty wounds. The fact that some of the swabs were recognized as culture positive within as few as four days indicates that the bacterial load in the sample was large. Taking this result, surgeons and patients need to recognize the reality of wound contamination with Propionibacterium from the sebaceous glands transected at each arthroplasty (and each shoulder procedure) , especially in male patients. This risk remains in spite of standard skin preparation (see this link). The introduction of Propionibacterium into the oxygen poor environment of the medullary canal along with a titanium alloy stem sets up the perfect incubator for the formation of an enduring, bacteria-containing, antibiotic-resistent biofilm on the surface of the implant (see this link). As shown in the present study and others, antibiotic prophylaxis and standard wound preparation does not prevent wound contamination with Propionibacterium.

So what can be done? First, we try to minimize contact of instruments, gloves and implants with the Propionibacterium-containing dermis by applying a Vancomycin impregnated sponge around the periphery of the wound as shown by the arrows in the diagram below.

Second, we try to reduce the number of bacteria in the field prior to implant insertion by copious irrigation with at least 3 liters of antibiotic-containing saline solution, following the adage that 'dilution is the solution to pollution'.

Finally, we apply topical antibiotics (Vancomycin) down the medullary canal just prior to humeral implant insertion in an attempt to 'sterilize the incubator' (see this link). We use additional topical Vancomycin in the wound prior to closure.

Hopefully our long term followup studies will, over time, reveal the effectiveness of these steps.

Wednesday, October 19, 2016

Failed total shoulder: what to do when the glenoid component is loose?

Revisions for aseptic glenoid component loosening after anatomic shoulder arthroplasty

These authors remind us that glenoid component loosening is a common indication for revision shoulder arthroplasty.

They report on 34 revision shoulder arthroplasties performed for aseptic glenoid loosening over two decades between January 1, 1985, and December 31, 2005.

Three patients were lost to follow-up. Treatment included component reimplantation in 20 shoulders (group I) or component removal with bone grafting in 11 shoulders (group II). 

Nine cases demonstrated instability with or without rotator cuff tearing prior to revision. 

The mean follow-up period was 8.3 years.

Pain relief occurred in 26 of 31 shoulders, with no difference between groups (P > .99). Active elevation and external rotation improved in both groups (P = .8). The rate of survival free of reoperation at 10 years was 78.9% in group I (red line) and 83.9% in group II (blue line) (P = .5).  

Five (25%) shoulders with glenoid remimplantation were recognized as having radiographically loose glenoids; two had reoperations. 

Nine shoulders without glenoid reimplantation had medial glenoid erosion, with two requiring reoperation for pain. 

There was a trend toward reoperation in those with preoperative instability (5 of 8 re-revisions).

The case example below shows the revision of a loose glenoid without reimplantation.

 Bone grafting of the defect was used.
 At 15 years after revision, the bone graft had resorbed, but the patient was satisfied with her outcome and had a stable articulation without risk of repeat failure of a prosthetic glenoid.

Comment: The landscape of loose glenoid components is changing. In the 'old days', many cases were truly 'aseptic'. But recent evidence demonstrates that as many as half of these cases will have positive cultures, often for Propionibacterium - which requires special culture protocols and culture observation for at least 2 weeks. The problem is that preoperative data and intraoperative findings (including gram stains and frozen sections) are not sensitive to the presence of this organism. Removing or revising a loose glenoid component and leaving the humeral stem in place in a shoulder that subsequently is found to be culture positive leaves a stem that most likely will have a Propionibacterium containing biofilm on it.

Here are two representative cases of glenoid loosening that were associated with no preoperative or intraoperative evidence of infection (negative blood work, gram stains, frozen sections). In both cases, multiple cultures were sent for Propionibacterium and in both cases >60% were strongly positive for this organism.

Case 1

Case 2

The point is that we cannot be sure whether a shoulder with a failed glenoid component is "aseptic" or not until the results of proper cultures are finalized. Intraoperative decision making about humeral component exchange and immediate post operative decisions regarding antibiotic therapy need to be made in the absence of the final culture results.

In the current era, we are inclined to treat cases of glenoid component loosening as infected until proven otherwise, with glenoid component removal without reimplantation or bone grafting, with humeral component exchange and with antibiotic coverage until the intraoperative cultures are found to have no growth.

Tuesday, October 18, 2016

Topical Vancomycin as infection prophylaxis in shoulder arthroplasty

The cost effectiveness of vancomycin for preventing infections after shoulder arthroplasty: a break-even analysis.

These authors collected cost data for infection-related care of 16 patients treated for deep periprosthetic shoulder infection. They developed and applied an equation to the data to determine how effective vancomycin powder would need to be at reducing a baseline infection rate to make prophylactic use cost effective.

Assuming a 4% baseline infection rate and a cost of vancomycin of $17.15, and the average cost of treating an infection to be $46,745, they found that vancomycin would be cost effective if the initial infection rate decreased by 0.04% (absolute risk reduction, ARR).

Using the current costs of vancomycin reported in the literature (range: $2.50/1000 mg to $44/1000 mg), they determined vancomycin to be cost effective with an ARR range of 0.01% at a cost of $2.50/1000 mg to 0.19% at $44/1000 mg. Baseline infection rate did not influence the ARR obtained at any specific cost of vancomycin or the cost of treating infection.

Comment: While this is an interesting study, we lack data supporting the effectiveness of topical Vancomycin in reducing the rate of Propionibacterium infections in the shoulder. The data to support its use in this article (see below) does not provide this evidence.

A related post of interest shows laboratory evidence in support of topic Vancomycin (see 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'

The failed reverse total shoulder - what can we learn?

Conversion to hemiarthroplasty as a salvage procedure for failed reverse shoulder arthroplasty

These authors report on 16 patients undergoing conversion to hemiarthroplasty after failed reverse total shoulder (RSA). All patients had insufficient bone stock for reimplantation of another RSA.

Glenoid loosening was the primary reason for RSA failure in 11 patients. Three required revision surgery because of infection (Propionibacterium, E Coli, Staph Epidermidis).

The case below shows the case of Propionibacterium presenting 8 years (!) after the index procedure. A two stage reconstruction was performed.

Here is a case of glenoid component failure in a patient with rheumatoid arthritis revised to a hemiarthroplasty. The two year followup show anterosuperior escape.

Postoperative functional outcome for these cases was generally poor at the latest follow-up, with mean Constant, Shoulder Pain and Disability Index, and 11-item version of the Disabilities of the Arm, Shoulder and Hand scores of 25, 37, and 63 points, respectively. Baseline pain also did not improve. Medialization progressed beyond the coracoid in 6 patients, and complete anterosuperior escape was reported in 3 patients. Three postoperative complications were recorded by the final follow-up, including 2 periprosthetic humeral fractures treated conservatively and 1 patient with painful humeral component medialization leading to resection arthroplasty.

Comment: These authors give us some cautionary tales: failed reverse total shoulders can be very difficult to successfully revise, hemiarthroplasty is at best a salvage, and infection is always a consideration - even years after the index surgery. The high incidence of glenoid loosening in this series emphasizes the importance of excellence in glenoid fixation technique and perhaps avoiding RSA when the glenoid bone is of poor quality or quantity. Three cases had scapular fractures, possibly related to weakening of the scapular spine by a superiorly placed screw. The occurrence of periprostheic humeral fractures emphasizes the importance of humeral bone preservation and fixation with impaction grafting rather than cement.

The key seems to be secure fixation of both the glenoid and humeral component with maximal bone preservation on both sides:

To review, there are several important failure modes after reverse total shoulder. Infection is one of the more common and is probably related to the fact that many reverse total shoulders are performed as revisions after multiple prior surgeries coupled with the dead space created when the humerus is displaced distally by the procedure. As with anatomic shoulders, Propionibacterium is a frequently cultured organism from failed reverse total shoulders, which can present with loosening in the absence of the usual clinical signs of infection 

The infection with Propionibacterium in the x-ray on the left was treated with a single stage exchange to a long stem prosthesis. The patient is currently asymptomatic six years after the revision. 

Instability can result from falls, suboptimal component selection, component malposition, bulky tissues in the posterior shoulder, leverage of the humeral component against the glenoid , or lack of sufficient compressive effect by the deltoid. 


Early closed reduction can be successful. Recurrent or chronic instability may require surgical revision. The case below shows a failed anatomic prosthesis for fracture with anterosuperior escape that was treated with a reverse that dislocated recurrently. 


 The prosthesis was revised to a hemiarthroplasty that was unsatisfactory. Finally a successful revision was accomplished by the removal of posterior scar tissue and revision to a reverse with a 40 mm set of components.
Shown below is another example where stability was restored by changing to a larger diameter of curvature and increasing the thickness of the polyethylene and humeral cup.


The risk of humeral fracture is increased in revision surgery, by falls and when the humeral component fixation results in an abrupt transition between a cemented or press fit diaphyseal stem tip and osteopenic bone distal to the prosthetic tip These fractures deserve a trial at closed management.


in that surgical revision can be very complex


Scapular and acromial fractures can result from excessive deltoid tension producing a fatigue fracture or from bone weakened by screw placement. These fractures are preferably treated non-operatively.

Scapular notching is a prominent complication, particularly common in prosthetic designs that medialize the humerus or when the glenoid component is positioned high on the glenoid bone.


The issues with notching are not so much the ‘notch’ in the scapula but the radiographically unseen damage to the polyethylene of the humeral component

 and to glenoid component fixation 

Notching may also be associated with unwanted bone formation that limits the range of motion 

Humeral component failure may result from dissociation of the cup from the stem

Glenoid failure may result from glenosphere-baseplate dissociation,

glenoid fracture,

or failure of fixation

While some cases can be reconstructed, others require salvage conversion to a hemiarthroplasty after glenoid component removal; the clinical results of this conversion are generally poor.

Neurologic lesions can result from dissection, retraction or over lengthening of the arm. Finally, there has been some concern about loss of active external rotation with reverse total designs that medialize the tuberosity, prompting consideration of latissimus dorsi transfers; this problem seems less of an issue with those designs that maintain ‘East-West” tensioning of the residual cuff posteriorly.

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'