These authors reviewed 35 patients presenting with suspected low-grade infection in which biopsy specimens taken at revision surgery. Patients presented with symptoms akin to resistant postoperative frozen shoulder (persistent pain and stiffness, unresponsive to usual treatments).
Positive cultures were identified in 21 cases (60.0%), of which 15 were male patients (71%). Of all patients with low-grade infection, half were male patients between 16 and 35 years of age.
Propionibacterium acnes and coagulase-negative staphylococcus were the most common organisms isolated (81.1% [n = 17] and 23.8% [n = 5], respectively). The mean time from index surgery to diagnosis for P. acnes –positive cases was 1.2 years (60.3 weeks).
Not all patients with clinically suspected low-grade infections presentedwith positive microbiologic cultures, despite use of enhanced culture methods. The authors suggest that the suspect organisms may be nonculturable on routine culture media or that the suspect organism was in an area of the shoulder not sampled. Of 14 negative culture cases, 9 were treated with early empirical antibiotics (64.3%); 7 patients reported symptomatic improvement (77.8%). Of 5 patients treated with late empirical antibiotics, 4 stated improvement. Again, the majority of the patients with negative cultures reported improvement in their pain, stiffness, and range of movement after early empirical antibiotic treatment (doxycycline and amoxicillin, n = 8 [88.9%]; gentamicin and teicoplanin, n = 1 [11.1%]). More than half of these patients (n = 6 [66.7%]) stated that their pain completely resolved
Comment: This series of cases points to the complex and uncertain relationship between cultures and clinical findings. Patients without the characteristic signs of infection can have positive cultures. Patients with negative cultures can respond to antibiotics.
In such cases, we must be careful to use the term "positive cultures" rather than "infection" and to relate the apparent improvement after administration of antibiotics as an "association" rather than a "treatment".
For more, see the below:
In such cases, we must be careful to use the term "positive cultures" rather than "infection" and to relate the apparent improvement after administration of antibiotics as an "association" rather than a "treatment".
For more, see the below:
These authors point out that while as many as 50% of revision shoulder arthroplasties are culture positive, a consistent, clinically useful definition of a "periprosthetic shoulder infection" is lacking. They conducted a systematic review of the published literature with respect to (1) the definition of a "periprosthetic shoulder infection", (2) the pre-operative evaluation for possible infection, and (3) the harvesting and culturing of specimens at the time of surgical revision.
They found a remarkable lack of consistency in the way different authors defined an 'infection', in the way authors evaluated patients with possible infections before surgery and in the way authors obtained and analyzed specimens obtained for culture harvested at the time of the surgical revision of failed shoulder joint replacements.
They found a remarkable lack of consistency in the way different authors defined an 'infection', in the way authors evaluated patients with possible infections before surgery and in the way authors obtained and analyzed specimens obtained for culture harvested at the time of the surgical revision of failed shoulder joint replacements.
This inconsistency makes it very difficult to compare different treatment approaches to failed shoulder joint replacements, recognizing that some of them will have substantial bacteria in the joint, the presence of which may go unrecognized until the culture results are finalized at 2 to 3 weeks after surgery.
Comment: It is critically important not to combine, confuse or commingle data from
Comment: It is critically important not to combine, confuse or commingle data from
"obvious infections" (i.e. those with swelling, redness, drainage, fever, chills, elevated serum markers of inflammation) where the diagnosis of infection is apparent
with cases of
"stealth" presentation (i.e. the unexplained onset of pain and stiffness of the shoulder after a 'honeymoon' of good function in which specimens obtained at revision surgery are strongly positive for organisms such as Propionibacterium).
Here's an example of a stealth presentation:
A 50 year old patient presented desiring a ream and run arthroplasty for severe glenohumeral arthritis
A single stage revision was performed (soft tissue releases, prothesis exchange) without any evidence of inflammation, joint fluid, loosening, or osteolysis. Five explant and tissue cultures were sent. The patient was discharge on the yellow protocol (Augmentin) until the results of the cultures were final.
The culture results were
Humeral head explant: 3+ Propionibacterium
Humeral stem explant: no growth
Collar membrane: 1+ Propionibacterium
Humeral periosteum: 1+ Propionibacterium
Joint capsule: no growth
At this point the red protocol (IV ceftriaxone) was started and continued for 6 weeks followed by a 6 month course of Augmentin. The patient has a comfortable shoulder and has regained most of the lost shoulder motion.
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Here's an example of a stealth presentation:
A 50 year old patient presented desiring a ream and run arthroplasty for severe glenohumeral arthritis
After surgery, the shoulder progressively regained comfort and function. Subsequently, however it started to become stiff and painful without obvious explanation. Eight years after his shoulder arthroplasty, the patient returned to the office with no clinical, laboratory, or radiographic evidence of infection.
The culture results were
Humeral head explant: 3+ Propionibacterium
Humeral stem explant: no growth
Collar membrane: 1+ Propionibacterium
Humeral periosteum: 1+ Propionibacterium
Joint capsule: no growth
At this point the red protocol (IV ceftriaxone) was started and continued for 6 weeks followed by a 6 month course of Augmentin. The patient has a comfortable shoulder and has regained most of the lost shoulder motion.
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