Case study
Comparative study of risk factors of SSI following spinal fusion in two cases.
Introduction:
SSIs are divided into the categories of superficial incisional SSI, deep incisional SSI, and
organ/space SSI. Superficial incisional SSIs involve only the subcutaneous space,
between the skin and underlying muscular fascia, occur within 30 days of the index opera
and are documented with at least 1 of the following findings: (1) purulent incisional
drainage; (2) positive results of culture of aseptically obtained fluid or tissue from the
superficial wound; (3) local signs and symptoms of pain or tenderness, swelling, and
erythema, with the incision opened by the surgeon (unless culture results are negative);
or (4) diagnosis of SSI by the attending surgeon or physician.
A deep incisional infection involves the deep layers of soft tissue (e.g., fascia and muscle)
in the incision and occurs within 30 days after the operation or within 1 year after the
operation if a prosthesis was inserted and has the same findings as described for a
superficial incisional SSI.
At least one of the following criteria:
Purulent drainage from the incision but not from the organ/space of the surgical site
A deep incision spontaneously dehisces or is deliberately opened by a surgeon when the
patient has at least one of the following signs or symptoms - fever (>38°C), localized pain
or tenderness - unless the culture is negative
An abscess or other evidence of infection involving the incision is found on direct
examination or by histopathology or radiological examination diagnosis of a deep
incisional SSI by a surgeon or attending physician.
An organ/space SSI has the same time constraints and evidence for infection as a deep
incisional SSI and involves any part of the anatomy (organs or spaces) other than the
incision opened during the operation.Any deep SSI that does not resolve in the expected
manner after treatment should be investigated as a possible superficial manifestation of a
deeper
organ/space
infection.
Literature
review showed
the
following
flow chart with
factors leading
to SSI which
are observed in
this study.
Results and discussion:
Patient factors in Case 1 and Case 2
Non modifiable
Case -1
Case-2
Advanced Age
77yrs
68yrs
Development delay
NA
NA
Immunosupression
No
No
Spinal trauma
NO
NO
Diabetes
YES 203-300 HbA1c -7.3
YES Hba1c -5.9 >200
Perioperative-161-179
122-157
No
urea/creatinine raised
rheumatoid arthritis , low
CD4 counts
cancer patients on
chemotherapy
Radiotherapy
Chronic Renal failure
High rates of infection have been observed in elderly patients and spine trauma patients.
Insensate patients with spinal dysraphism and developmental delay undergoing scoliosis surgery
have also been found to have higher rates of postoperative infection. Operating through
previously irradiated tissue or previously operated tissue has also shown an increased risk for
surgical site infection. Diabetes mellitus, especially when it is uncontrolled with blood glucose
levels greater than 200 mg/dL is shown to impede chemo taxis and phagocytosis, hence
diminishing immune response to bacteria/infections
Modifiable
Case 1
Case-2
Obesity
BMI 23 WT58 HEIGHT 159.5CM
BMI
25
HEIGHT162CM
Smoking/Alcoholism
No
no
Indwelling catheter
Yes
Yes( recatheterisation)
Extended hospitalization
Yes(3days)
No
Malnutrition
Hb 13gm Albumin 3.9(6.7)
HB-10.1gm
1.8(4.8)
L 27.3%
WT-65
albumin-
L3.8%
Biophysical alterations in obesity and technical issues with surgery. Tissue dissection in these
patients can be extensive. Wide retraction and use of electro cautery can lead to fat necrosis and
large devitalized areas promoting bacterial proliferation.
Klein and Garfin reported preoperative malnourishment in 25% of 114 patients undergoing
elective lumbar fusion and 11 of 13 reported complications in this series occurred in this
malnourished group. Paradoxically, obesity also can be a risk factor for malnutrition, especially in
those patients undergoing rapid weight reduction.
Malnutrition, objectively defined by a serum albumin level <3.5 g/dL, a total lymphocyte count less
than 1,500 to 2,000 cells/mm3 and a serum transferrin level of 150 μg/dL is another documented
risk factor.
Most surgeons will attempt to address modifiable factors preoperatively to minimize the risk of
postoperative infection. Patients should be counseled to quit smoking both for reducing risk of
infection and preventing pseudarthrosis. All active infections should be identified and treated
before undertaking elective spine surgery Systemic conditions such as diabetes, rheumatoid
arthritis, HIV, and malnutrition should be optimized preoperatively. Furthermore, patients with a
prolonged hospital course may be considered for discharge and return as a same-day admission
for elective spinal surgery to minimize nosocomial/iatrogenic infections.
Surgical factors in case 1 and case 2:
Keller and Pappas reported a dramatic decrease in infection rates from 2.7% to 0% with the use
of preoperative prophylactic antibiotics. Infection rates after lumbar diskectomies dropped from
9.3% to 1% with the use of preoperative antibiotics. Another study showed that infection rates
were significantly lower (4.3%) in patients treated with preoperative antibiotics vs those treated
with placebo (12.7%) before undergoing clean lumbar surgery.
Surgical Factors
Case1
Case 2
Preoperative
infection
Negative
HCV+
local/ Systemic
Prophylactic Antibiotics
Supacef
750mg
Surgery classification
L2 to S1 transpedicular screw
and rod fixation and L2 to L5
laminectomy
L2 to S1 Trans pedicular screw
and
rod
fixation,
L3-L5
Laminectomy
Clean
clean
Short segment fusion
Short segment fusion
Implant
Medtronics M8 spinal system
Medtronics M8 spinal system
Sterilization
Implant sticker
Implant sticker
Duration of surgery >2hours
61/2 hours
5hours
Electro cautery/Retraction
Used
Used
Bone graft /Tessel glue
No
Yes
Romovac drain malfunction
No
Yes
Hematoma
No
Yes
Complexity of surgery
Yes
Yes
Intraoperative CF leak
No
Yes
Osteoporosis
Osteoporosis of high risk of
fracture
Radiology
suggestive
osteoporosis/ Vit- D-31
H/O of postoperative wound
drainage Before discharge
No
Yes
Suture material/Re-exploration
Vicryl / Ethel one/no
Vicryl/ Ethel one/ vicryl sutures
were removed
Inspection of the
postoperative period
Regular healthy
Regular healthy
Diagnosis of SSI
wound
1.5gm
Amikacin
Follow up OPD visit
Attending neurosurgeon
Case 1 Bone densitometry-Osteoporosis of high risk for fracture.
by
Magnex 1gm
Follow up OPD Visit
attending neurosurgeon
of
by
Radiology evidence of disease/Surgery
•
Short Segment Fusion
Indications
•
Cobb’s angle
•
Sagittal imbalance
•
Coronal imbalance
•
Lordosis
•
Rigid fixation is doubtful as bone are osteoporotic.
Fusion without instrumentation has been associated with infection rates from 0.4% to
4.3%. The use of internal fixation raises the risk significantly (6.6–8.7%) . Several theories
attempt to explain this increase likelihood of infection. It is suggested that instrumentation
can cause local soft tissue irritation leading to inflammation and seroma formation with
subsequent infection. The implants provide an avascular surface for bacteria to lay down
a glycocalyx, which in turn protects them from antibiotic penetration. Finally, metallosis
from micromotion of the instrumentation leads to granuloma formation and yet another
medium for bacterial colonization Long segment fusion has higher immediate
postoperative complication s than short segment fusion.
Case 2 Short Segment Fusion Indications are Cobb’s angle,Saggittal imbalance,Coronal
imbalance,Lordosis
 Right L4 pedicle could not be tapped due to being narrow and breach of medial wall (few
drops of CSF seen coming – controlled by waxing of entry point may be additional factor.
 Radiology evidence of disease/surgery
Rigid fixation as no evidence of osteoporosis.
Anaesthetic factors of SSI in case 1 and case 2.
Factors
Case 1
Case2
Pain
Low back ache ,Pain
radiating to B/L lower limb.
Low backache ,Left lower
limb radicular pain
History of neck and left
shoulder pain.
VAS-6/10,Discharged VAS 3/10
VAS 6/10, Discharged VAS3/10
Crocin
pain
relief
(Gabapentin stopped)
Combination analgesia
Perioperative
250mg
Perioperative Fentanyl 250
mcg
Fentanyl
Perfalgan 1gm
Perfalgan 1GM
Normovolumic/ hypovolemic
Blood transfusion
Normovolumic
?Hypovolemic
Urine output -460ml
Urine Output 280ml
1Autologous (1200ML)
1PRBC(300ML)
1PRBC
Hb-9.2-8.4
Hb 11.6-8.6-8.5
Peroperative
temperature
body
35 degree F
No record
FIO2
100-0.45-0.5
0.5-0.5
Tissue perfusion(MAP at 4
hour of surgery)
>70 mm Hg
>70 mm Hg
Clinical presentation of SSI.
Worsening pain 1 to 4 weeks after a spinal procedure is the most common symptom suggestive
of infection . Pain may or may not follow a period of initial relief. The patients often confuse this
pain as a recurrence of their original back pain, thus confusing the diagnosis with that of a
mechanical cause. The back pain is generally out of proportion to the physical findings and may
be referred to the buttock, thigh, leg, groin, perineum, or abdomen Constitutional symptoms have
also been reported but are less common than pain. A floridly septic picture with high fevers, chills,
and sweats is a rare, but dramatic, presentation In the setting of superficial infections, local wound
changes, such as erythema or drainage, may be present .
Persistent progressive pain is once again the hallmark of a developing infection. Occasional
drainage is noted and frank sepsis is uncommon. The patients, however, may complain of malaise
and night sweats.
Significant pain with lumbar range of motion is the sine qua non for post procedural diskitis. The
incision is usually unremarkable, and in fact, less than 10% of surgical incisions show signs of
purulent infection with erythema, drainage, or dehiscence. The presence of a neurological deficit
(motor/sensory involvement or bowel/bladder changes) should raise the suspicion for an epidural
abscess. Sixteen percent of epidural abscess are postoperative complications.
Clinical presentation
Case 1
Case 2
Yes
Yes
Postoperative
wound
drainage within one week
No
Yes
Postoperative fever/Malaise
with 1 week of postoperative
period
yes
Yes
Postoperative confusion
No
Yes
Preop
weakness
present
Nil
Benign appearing wound
Yes
Yes
Significant
postoperative
Drainage
beyond
1st
postoperative week
Serous
Purulent
Dermal necrosis/ Ecthyma
gangrenosum
No
Yes
Postoperative
pain/Neuralgic pain
back
neurological
Investigations
The white blood cell (WBC) count may, or may not, be elevated, depending on host and pathogen
factors. Thus, this parameter is unreliable, when used in isolation, for the diagnosis of infection.
Less than 50% of the cases of infective spondylodiskitis had an elevated WBC count according
to a recent report.
The ESR alone is not very specific for infection, Relatively sensitive marker for an inflammatory
process and can be reliably followed during the treatment course of a patient to assist with clinical
decision making such as cessation of antibiotics.
In the setting of infection, the ESR is 78% to 82% sensitive and 38% to 62% specific as a
laboratory marker. When interpreting ESR values, it is paramount to understand that the ESR is
routinely elevated in the first 1 or 2 weeks after a procedure/operation of the spine.
Several authors have attempted to delineate the ESR trend in the postoperative period. Kapp and
Sybers reported that the ESR was rarely elevated greater than 25 mm/h and that it generally
returned to baseline by the third week of an uncomplicated spine surgery. Jonsson et al ( reported
a higher postoperative peak in ESR in more extensive spine procedures (102 mm/h) compared
with the limited procedures (75 mm/h).
Case 1
Case2
CBC
HB9.2,TLC5800-8600
Hb7-9TLC 9600(13000)
ESR
NO
NO
CRP
NO
18.025 very high
Procalcitonin
NO
2.71 high risk of sepsis
Wound swab culture
No growth
E-coli/Enterococcus faecalis
Furthermore, they reported that the ESR peaked on the fourth postoperative day and returned to
baseline after 2 weeks in most patients. A study conducted by Thelander and Larsson showed an
even longer postoperative period (6 weeks) during which the ESR was elevated. In light of these
data, the ESR is not thought to be useful as a definitive marker for infection.
CRP, an acute-phase reactant, is possibly the most sensitive indicator of postoperative infection
Both, CRP elevation and its return to baseline after surgery are more rapid compared with the
ESR values. CRP levels usually peak on the second or third postoperative day and normalize
within 2 weeks after surgery/procedure.
A rise in CRP values after the aforementioned timeframe correlates highly with the presence of
an infection. Some authors recommend obtaining preoperative ESR and CRP values as a
baseline for comparison with postoperative measurements. In the future, other laboratory markers
such as interleukin-6 (IL-6) may provide us with the most accurate and reliable means of
diagnosing surgical site infection
Postoperative Radiology:
Plain radiographs are the first imaging modality, there are no changes in the first 3 weeks. In
cases of diskitis, disk space narrowing and endplate changes are the earliest findings, seen from
the fourth to the sixth postoperative week.
Paravertebral soft tissue shadows may be visible on plain films and might signify a paravertebral
abscess. Plain radiographs are also helpful in inspecting surgical implants. Lysis around the
implants (suggestive of loosening) and overall alignment can be readily assessed from the x-rays.
Computed tomography (CT) scans show areas of early bony destruction and soft tissue
collections with better anatomical detail than plain radiographs. Similar to plain films, early
changes include that of erosive and destructive changes at the endplates and disk space
narrowing .The image quality and the level of detail may be compromised in the presence of
instrumentation-related scatter/artifact, particularly if stainless steel implants were used. CT
guidance can also be used to obtain a tissue biopsy of postoperative diskitis/osteomyelitis or
needle aspiration of pus from abscess cavities to provide a microbiological diagnosis.The
specimens should be sent for Gram stain and cultures to identify the organism and its
susceptibilities before starting antimicrobial therapy.
Nuclear medicine studies have been used as part of the diagnostic workup of spinal infections,
but usually show nonspecific increased uptake in the majority of cases. Gallium 67 often identifies
the presence of a postoperative disk space infection earlier than techne-tium-99m scans or plain
films.The results are less accurate and predictive than they are for appendicular infections. A
sequential technetium-99m study followed by a gallium-67 study increases the cumulative
accuracy of these studies Indium 111-labeled WBC scans may also be useful in establishing the
diagnosis but are infrequently used secondary to suboptimal specificity.
Magnetic resonance imaging (MRI) with gadolinium enhancement is the imaging modality of
choice to delineate post procedural spine infections. MRI is shown to have the highest sensitivity
and specificity in the diagnosis of post procedural diskitis, superior to both technetium-99 and
gallium-67 scans reported sensitivity of 93% and a specificity of 97%. ), contrast enhancement of
the disk space/ paraspinal tissues in the absence of Modic I changes is suggestive of infection
when comparing MRI scans of asymptomatic individuals with those with biopsy proven diskitis.
An epidural abscess is seen as an area isointense with the cord or cauda equina on T1-weighted
images that may cause effacement of the neural structures, and on the T2-weighted images,
these lesions reveal a high signal expression. Gadolinium-enhanced T1-weighted images provide
additional evidence of infection, as enhancement of the collection is typically quite apparent
Gram negative organisms:
Historically, the primary gram-negative pathogens have been E. coli, Klebsiella species, and P.
aeruginosa, but there is wide variability in the pathogens isolated in different treatment centers].
The relative incidence of gram-negative bacilli as causes of initial infections has decreased
significantly during the past 2 decades, but they remain important pathogens for patients with
profound neutropenia (<100 polymorphonuclear leukocytes/µL) with a prolonged duration (7–10
days) or for patients who have not received antibacterial prophylaxis during their period of
neutropenia.
Dermatologic manifestations of gram-negative skin and soft-tissue infections include
erythematous maculopapular lesions, focal or progressive cellulitis, cutaneous nodules and
ecthyma gangrenosum. Ecthyma gangrenosum begins as painless, erythematous, macules that
rapidly become painful and necrotic during a 12–24-h period. They may be discrete or multiple;
are found preferentially in the groin, axilla, or trunk; and can increase in size from 1 cm to >10 cm
in <24 h.
Ecthyma gangrenosum is a cutaneous vasculitis caused by bacterial invasion of the media and
adventitia of the vessel wall. Progression of the lesion leads to dermal necrosis, and bacteria are
often visible during microscopic analysis of biopsy specimens.
Ecthyma gangrenosum has classically been reported to occur with P. aeruginosa infections, but
similar lesions can occur with disseminated infections caused by other Pseudomonas species,
Aeromonas species, Serratia species, S. aureus, Stenotrophomonas maltophilia, Candida
species, and fungi, including Aspergillus, Mucor, and Fusarium species
Case 1Incision site
Case2 Incision site
Case -2 Gr IIID
A deep incision spontaneously dehisces or is deliberately opened by a surgeon when the patient
has at least one of the following signs or symptoms - fever (>38°C), localized pain or tenderness
- unless the culture is negative
Practice Guidelines for the Diagnosis and Management of Skin and Soft-Tissue Infections
Incidence of SSIs following closure/delayed closure of an infected wound
Opening and re-closure times
Reinfection rate
Opening and re-closure at once
50%
Opening and re-closure after two days
20%
Opening and re-closure after four days
5%
Opening and re-closure after nine days
10%
Classification of postoperative wound and scoring system.
Conclusion:Major factors has beed analysed with review of the literature.Patient factors,surgical factors
are major cause of SSI in case I and Case 2.Malnutrition ,Diabetes and renal impairement is associated
with Case2.CRP is strong marker of infection in case 2 associated with evidence of infection and culture
positivity.Modifiable risk factors should corrected before surgery.