Saturday, December 20, 2014

Propionibacterium in the shoulder: the Strange Case of Dr Jekyll and Mr Hyde


Presence of Propionibacterium acnes in primary shoulder arthroscopy: results of aspiration and tissue cultures

This is a great study.

These authors collected control, 2 skin swabs, synovial fluid, and 3 tissue samples were obtained from 57 patients (mean age 51 years) undergoing first-time shoulder arthroscopy. None of these patients had prior surgery or antibiotic treatment within the prior month. Demographic data and medical comorbidities were collected.

Patients received pre-arthroscopy cefazolin or clindamycin. The skin was scrubbed with chloroxylenol cleansing solution and then prepared with  2% ChloraPrep. The skin of the anterior deltoid at the site of the anterior arthroscopic portal was then swabbed with a skin swab for culture. The glenohumeral joint was then aspirated for culture. If no fluid was available, the glenohumeral joint was flushed with 5 mL of saline, which was then collected in a sterile specimen container. Three samples of debrided tissue were collected through a cannula. The first tissue sample was collected  from the middle glenohumeral ligament. The second tissue sample came from the rotator interval and the third tissue sample from the bursa. A sample of the cuff was taken instead of the bursa in  patients with torn rotator cuffs. For a patient undergoing a labrum repair, the second tissue sample was collected from the high rotator interval and the third tissue sample from the low rotator interval

All samples were placed on aerobic plates, on anaerobic plates, and in thioglycolate broth and held for 28 days. Two of 39 control air samples cultured positive for Priopionibacterium.

Eighty-one samples (21.8%) were positive for P. acnes when cultures were held 14 days. From 4 to 27 days were required for the cultures to become positive (overall average 8.4).



32 subjects (56%) had at least 1 culture that grew P. acnes. Thirteen patients (22.8%) had more than 3 cultures positive. The rate of positive cultures was not different for those shoulders with prior injections.

Positive skin cultures for P. acnes increased from 15.8% before incision to 40.4% at closure. In men positive skin cultures increased from 31.3% before incision to 63.0% at closure. 

None of the patients in this study have had signs or symptoms to suggest clinical P. acnes infection.

Comment: This is a very well done and important study in that it suggests that surgical wounds - even those without any prior procedure - are commonly culture positive for Priopionibacterium. While the authors opine that these these positive cultures are "a consequence of true positive cultures from imperfect skin preparation and dermal contamination," there is another hypothesis: that Priopionibacterium can inhabit normal shoulders (perhaps in a manner similar to the inhabitance of the normal gut with E Coli). We have previously shown that Priopionibacterium live in normal skin, so it is not a big stretch to imagine their presence in normal shoulders. It may be the case that when the internal environment of the shoulder is disturbed by a procedure that implants prosthetic components (creating an anaerobic niche in a biofilm), an opportunity is created for these bacteria to turn from benign to potentially problematic. 


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Friday, December 19, 2014

Shoulder joint replacement arthroplasty - revisions for failure on the rise

The contribution of reverse shoulder arthroplasty to utilization of primary shoulder arthroplasty.

These authors assessed the trends in shoulder arthroplasty using the Nationwide Inpatient Samples for 2009 through 2011.

They estimated that 52,397 primary shoulder arthroplasties (anatomic total shoulder arthroplasty, hemiarthroplasty, and reverse shoulder arthroplasty) were performed in 2009 increasing to 67,184 cases in 2011.

Reverse shoulder arthroplasty accounted for 42% of all primary shoulder arthroplasty procedures in 2011. The concomitant diagnosis of osteoarthritis and rotator cuff impairment was found in only 29.8% of reverse shoulder arthroplasty cases. The highest rate of reverse shoulder arthroplasty was in the 75- to 84-year-old female subgroup. 

Revision cases comprised 8.8% and 8.2% of all shoulder arthroplasties in 2009 and 2011, respectively, and 35% of revision cases were because of mechanical complications/loosening whereas 18% were because of dislocation.

Comment: One of the most important conclusions that can be derived from this study is that the number of revisions for shoulder arthroplasty is on the rise as shown in the plot of their data showing number of revision cases/year by year.

Their observation that over half of these revisions are for mechanical problems, suggests that better surgeon training may help curb the rate of rise of these complications. It also suggests that as a specialty we need to help decide how to best manage these revisions. Frequently, we are referred a failed arthroplasty by a surgeon who states that he/she is comfortable with doing a primary but not a revision.

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Thursday, December 18, 2014

Anterosuperior rotator cuff tears - does repair technique matter?

Arthroscopic Repair of Anterosuperior Rotator Cuff Tears: In-Continuity Technique Vs. Disruption of Subscapularis-Supraspinatus Tear Margin


The defined an anterosuperior rotator cuff tear as a full-thickness subscapularis tear combined with a full-thickness supraspinatus tear, involving a medial biceps sling and formation of a tear margin between the two tendons.

In this series the patient age averaged 60 years and the time between symptom onset and surgery averaged 22 years. 22 were men and 37 women. 92% of the patients had a biceps lesion.

These authors compared the clinical outcomes and structural integrity after arthroscopic repair of the anterosuperior rotator cuff - either in continuity or with disruption of the tear margin.

At the two-year follow-up evaluation, VAS pain scores, SSVs, ASES scores, UCLA shoulder scores, subscapularis strength, and active range of motion were significantly improved in both groups compared, but there were no significant differences between groups for any of these follow-up measurements. 

The overall retear rate (by MRI or CT arthrogram)  did not differ significantly different between the group with marginal disruption (22%; five of twenty-three) and without marginal disruption (19%; six of thirty-two). Five patients did not have followup imaging.

Comment: This paper again shows (as we've noted before here) that the details of surgical technique seem to have little effect on the clinical or anatomic outcomes of rotator cuff repair.

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Wednesday, December 17, 2014

Cuff repairs and patch reinforcement

Long-term successful arthroscopic repair of large and massive rotator cuff tears with a functional and degradable reinforcement device.

This author reports a small series of 18 patients with repairs of large to massive rotator cuff tears reinforced with a poly-l-lactic acid synthetic patch.

The ultrasound examination targeted the supraspinatus, infraspinatus, and subscapularis to detect the presence of the tendons and their attachment to the bone. The shoulder was observed while the patient moved the arm to determine attachment and functionality of the graft. This examination showed that 15 of 18 patients had intact rotator cuff repair at 12 months; at 42 months, an additional patient had a failed repair. 

Overall, patients showed improvement in the ASES shoulder score from 25 preoperatively to 70 at 42 months after surgery. Patients with intact rotator cuff (n = 14) at 42 months had an ASES shoulder score of 82.

Comment: While these results seem encouraging, the experience of the sonographer and the ability of the technique to determine the integrity of a repair after grafting is not stated. 

At this time the reported results with patch reinforcement are not universally favorable as shown here, and here, and here. At present we have not found the evidence supporting the use of patches in cuff repair to be compelling.

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Chronic rotator cuff tears - it's not just about the tendon

Reduced muscle fiber force production and disrupted myofibril architecture in patients with chronic rotator cuff tears.

These authors studied the contractility of muscle fibers from biopsy specimens of supraspinatus muscles of 13 patients with chronic full-thickness posterosuperior rotator cuff tears, comparing the results to healthy vastus lateralis muscle fibers.

They found that chronically torn supraspinatus muscles had a 30% reduction in maximum isometric force production and a 29% reduction in normalized force compared with controls. They identified disordered sarcomeres along with an accumulation of lipid-laden macrophages in the extracellular matrix surrounding supraspinatus muscle fibers.

Comment: The figures in this paper are quite striking. These results show that in addition to the re-estabishment of a durable tendon attachment to bone, recovery from the repair of a chronic rotator cuff tear would hopefully include reversion of the muscle force generation and sarcomere architecture towards normal.

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Is it a good idea to remove axillary hair before shoulder surgery?

The effect of axillary hair on surgical antisepsis around the shoulder

These authors studied the effect of clipping axillary hair (with commercially available surgical clippers) on the aerobic and anaerobic cultures taken from the axillae of 85 healthy male volunteers. 

All subjects with clipped axillae and most of those with unclipped axillae had positive cultures.

Coagulase negative staph was found in 73%, Propionibacterirum in 72%, and Corynebacterium in 17%. 

The overall bacterial burden was higher in the clipped axilla, but removal of axillary hair had no effect on the burden of P. acnes in the axilla.

Each shoulder was then prepared with 2% chlorhexidine gluconate and 70% isopropyl alcohol. Repeated culture specimens were then taken from both axillae apparently immediately after the preparation.There was a significant reduction in total bacterial load and P. acnes load for both axillae immediately after surgical preparation (P < .001 for all).

Comment: This work does not support the practice of clipping axillary hair prior to shoulder surgery.

The conclusion that a "2% chlorhexidine gluconate surgical preparation is effective at removal of all bacteria and specifically P. acnes from the axilla" is not that comforting in that it has been shown that Propionibacterium live in and not on the skin. Furthermore it has been previously shown that skin preparation does not eliminate Propionibacterium from the shoulder region, especially if the cultures are obtained a while after the skin preparation is applied.

So our current practice is to avoid clipping the axillary hair, to use a standard skin preparation after intravenous administration of Ceftriaxone and Vancomycin, to irrigate the wound with three liters of antibiotic saline and to avoid as much as possible contact of the prosthesis with the wound edge - all of this is based on the assumption that every shoulder incision is likely to be contaminated with Propionibacterium because the skin incision transects the dermal organs in which they reside.

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Rotator cuff repair - what patient and surgical factors matter in the outcome?

Specific patient-related prognostic factors for rotator cuff repair: a systematic review.

These authors conducted a literature search up to July 2013 for prospective studies that describe prognostic factors affecting outcome in primary open or arthroscopic repair of a full-thickness supraspinatus or infraspinatus tear.

Included outcome measures were shoulder function and cuff integrity; 12 studies met the inclusion criteria..

They defined a 'moderate' effect as one supported by by statistically significant findings in outcome measures in at least 1 high-quality prognostic cohort study or supported by consistently statistically significant findings in outcome measures in at least 2 medium quality prognostic cohort studies.

We tabulated the results of this carefully done study below, showing the strength of the relationships between different variables and (1) shoulder function and (2) repair integrity



Comment: This study again shows the difference in the factors associated with poorer function and those associated with failure of the repair to achieve tendon integrity. It also reminds us that the characteristics of the tear and the patient's age are the dominant factors in determining the chances of achieving a durable repair integrity.

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