Prophylactic Antibiotics

                                Dr. KS Dhillon

Introduction

Wound infections are the commonest hospital-acquired infections in patients undergoing surgery [1]. Such infections lead to increased antibiotic usage, increased costs, and prolonged hospitalization [2]. Prophylactic antibiotics can reduce the risk of postoperative wound infections. Inapprioate antibiotic use can increase the risk of emergence of antimicrobial resistance. Hence, judicious use of antibiotics in the hospital is essential.

The original surgical antibiotic prophylaxis experiments were performed in pigs about 40 years ago. The results concluded that the most effective period for prophylaxis begins the moment bacteria gain access to the tissues and the antibiotic are not effective after the bacteria has been in the tissues for more than three hours [3]. Since then there have been several other studies in animals and in humans. Now the principles of antibiotic prophylaxis have become an accepted part of surgical practice [4].

About 30-50% of antibiotics used in hospital practice are for surgical prophylaxis. However, between 30% and 90% of this antibiotic prophylaxis use is inappropriate. Most often the antibiotic is either given at the wrong time or continued for too long [5]. There, however, remains controversy as to the duration of prophylaxis needed and also as to which specific surgical procedures should receive prophylaxis [4].

Indications

Preoperative antibiotic prophylaxis involves the administration of antibiotics prior to performing surgery to decrease the risk of postoperative infections. The evidence that supports the routine use of preoperative prophylactic antibiotics continues to grow. A 2008 study highlighted the effectiveness of prophylactic antibiotics in patients undergoing total hip and knee replacement. It showed an 8% reduction in the absolute risk of wound infection and an 81% relative risk reduction as compared to patients who had no prophylaxis [6]. In patients undergoing, artificial implant or foreign body implantation as part of the procedure, bone grafting procedures, and other surgeries with extensive dissections, prophylactic antibiotics are routinely used.

The timing of antibiotic administration varies. The goal of preoperative systemic prophylactic antibiotics administration is to have a high concentration in the tissues at the start of the operation and during surgery [7,8]. 

The antibiotic must be given at least 30 minutes, but no greater than 60 minutes before the skin incision is made [7,9,10]. The antibiotic must be given 15-45 min before the inflation of a tourniquet [11].

The most common organisms that cause surgical site infections include [12]:

• Staphylococcus aureus

• Staphylococcus epidermidis

• Aerobic streptococci

• Anaerobic cocci

Other organisms, such as Cutibacterium acnes, are often isolated in the postoperative infections following shoulder surgery.

Preoperative antibiotic selection is usually based on the anatomic region where the surgical procedure is to be carried out. When determining appropriate antibiotic selection, the goal is to ensure that the most common organisms are targeted. Several factors are taken into consideration when selecting the preoperative antibiotic. These include: 

• Cost

• Safety

• Ease of administration

• Pharmacokinetic profile

• Bacteriocidal activity

• Hospital resistance patterns

 By addressing these factors during antibiotic selection, surgical site infections are minimized. Surgical site infections constitute a significant factor that drives negative patient-reported outcomes and independent risk factors for increasing the financial burden [13].

Cefazolin is most often used for surgical prophylaxis in patients who have no history of beta-lactam allergy. It is not used for operation at surgical sites in which the most probable organisms are not covered by cefazolin. 

Patients who are allergic to cefazolin are given clindamycin or vancomycin for prophylaxis. Most patients who are allergic to beta-lactam are able to tolerate cefazolin. 

In patients with MRSA colonization, vancomycin is the alternative unless additional antibiotics are required for gram-negative or anaerobic organisms [14]. Multiple options are available for patients requiring additional microbe coverage, including cefazolin plus metronidazole, cefoxitin, or ertapenem. These additional antibiotic options are based on specific surgical sites and patient-specific antibiotic resistance [15].

Weight-based dosing is followed as per standardized protocol. The antibiotic administration should be done within 1 hour of skin incision and continue for 24 hours postoperatively. Patients in whom the surgical duration is greater than 4 hours and in patients with estimated blood loss of over 1,500 ml, intraoperative dosing of antibiotics would be required [16]. The weight-based guidelines include the following [17]:

• Cefazolin: 2 g (3 g for weight >120 kg) -- adult surgical prophylaxis guidelines.

• Vancomycin: 15 mg/kg

Wound Classifications 

Wound types can be classified as clean, clean-contaminated, contaminated, or dirty/infected [18]. Clean wounds are not infected, without inflammation, and are primarily closed. Clean-contaminated wounds involve the genital, respiratory, alimentary, and urinary tract.  Contaminated wounds include open, fresh accidental wounds, and those with non-purulent inflammation. Contaminated wounds also include procedures with breaks in sterile technique or gross spillage from the gastrointestinal tract. Dirty or infected wounds are old traumatic wounds with devitalized tissue, existing clinical infection, and those with perforated viscera.

During clean procedures, skin florae such as coagulase-negative staphylococci (Staphylococcus epidermidis or Staphylococcus aureus) are the predominant pathogens in the infection site. In the clean-contaminated procedures, the most commonly found organisms causing surgical site infections are skin flora, gram-negative rods, and Enterococci [19].

Skin Preparation 

Preoperatively basic infection control strategies have to be followed. The instruments have to be sterilized, and skin preparation is done. Methicillin resistant Staphylococcus aureus [MRSA] decolonization, appropriate hair removal, and skin antiseptic preparation done [20].  Regarding the latter, it is recommended that patients about to undergo surgery perform a combination of a standard soap and water shower and chlorhexidine gluconate cloth wash before surgery.

Murray et al [21] in a study showed that the combined protocol of soap and water shower and chlorhexidine gluconate cloth wash resulted in a 3-fold reduction in colony count for coagulase-negative Staphylococcus (CNS), a significant decrease in positive cultures for CNS and Corynebacterium, as well as a significant decrease in bacterial burden compared to soap and water shower alone.

Some hospitals carry out nasal swab screening for MRSA weeks before

elective arthroplasty procedures and treat those who are positive. Positive MRSA culture can be treated with either 2% mupirocin to the nares twice daily for five days preoperatively or they can be treated with 5% povidone-iodine solution to each nostril for 10 seconds per nostril, 1 hour prior to surgery, in addition to vancomycin administration at the time of the surgery [22,23].

Splenectomized Patients

Infection control in splenectomized patients requires special attention.  

In 1996, the British Committee for Standards in Haematology published Guidelines for the prevention and treatment of infection in patients with an absent or dysfunctional spleen [24], that are considered to reflect best-practice. These recommendations were updated in 2002 [25], and

consist of the following key elements:

1. All splenectomized patients should receive pneumococcal immunization and revaccination. If not previously immunized they should also receive Haemophilus influenzae type B and meningococcal C vaccine. Yearly influenza immunization is recommended.

2. Lifelong prophylactic antibiotics are recommended, or at least the first two years after splenectomy. In case of suspected or proven infection patients should be given systemic antibiotics and be admitted to a hospital.

3. All patients should be educated about the risks of infection and the risk associated with traveling (such as becoming infected by Plasmodium falciparum) and unusual infections (i.e. dog bites). Patient records should be labeled to indicate the risk.

Mechanism of Action

Multiple antibiotic classes are used in preoperative antibiotic prophylaxis. The antibiotics utilized are bactericidal. Bacteriostatic drugs are usually not used. Bactericidal drugs kill the targeted organisms instead of just preventing the multiplication of the bacteria. Certain antibiotics can exhibit bacteriostatic or bactericidal properties depending on bacterial sensitivity and antibiotic concentration. Clindamycin for example is bacteriostatic at lower doses, but at higher doses, it has bactericidal properties. For surgery, the intent is to ensure the bactericidal concentration has been reached in the blood and tissues before the incision is made.

Antibiotic Administration

Most of the preoperative prophylactic antibiotics are administered intravenously (IV). The timing of administration, redosing, duration of prophylactic therapy, and dosing in obese patients are important components in the prevention of surgical site infections [26]. The unnecessary use of antibiotics should be avoided to diminish adverse effects and antibiotic resistance. 

Antibiotics are given within 30 to 60 minutes of a surgical incision. There are exceptions to this rule and these include vancomycin and levofloxacin, which require administration within 120 minutes of the incision due to longer administration times. If a patient is already on an antibiotic for another infection before surgery and that antibiotic is appropriate for surgical prophylaxis, an extra dose of the antibiotic can be administered within 60 minutes of the incision. If the patient is already receiving vancomycin and has renal failure, cefazolin should be used before the surgery instead of an extra vancomycin dose [27].

Redosing of antibiotics is important depending on the half-life of the particular antibiotic used. Renal dysfunction and extensive burns can impact the half-life of an antibiotic. Cefazolin and cefoxitin would have to be administered more than once, depending on the length of the procedure. A perioperative dose of cefazolin has to be administered again four hours after the initial preoperative dose. Cefoxitin should be administered again two hours later. Redosing antibiotics have to be considered in patients with significant blood loss or dilution during surgery. 

Prophylactic antibiotics should be discontinued within 24 hours unless there is an infection. There is some controversy regarding the duration of therapy postoperatively following cardiothoracic surgery. There are two meta-analyses that compared 24 hours versus 48 hours as the cut-off in patients undergoing cardiac surgeries. They found that there was a significant decrease in surgical site infections with the extended duration [28].

The most recent CDC guidelines state that additional prophylactic antibiotics should not be administered after the surgical incision is closed in patients undergoing clean and clean-contaminated procedures. This recommendation applies to patients with or without a drain after the surgical site is closed.

Weight-based dosing is recommended when cefazolin, vancomycin, and gentamicin are used in adult surgical prophylaxis. Cefazolin 2 g is the current recommended dose for prophylaxis except for patients weighing greater than or equal to 120 kg, who should receive 3 g. There is some literature which states that cefazolin 2 g  should be sufficient for an adult of any weight.

The vancomycin dose is 15 mg/kg, and the gentamicin dose is 5 mg/kg. Other prophylactic antibiotic dosing regimens in adults are clindamycin 900 mg, cefoxitin 2 gm, and ertapenem 1 gm. All prophylactic antibiotics for children are dosed based on mg per kg of body weight. Pediatric dose for cefazolin is 30 mg/kg and for vancomycin, it is 15 mg/kg. 

Adverse Effects

Limiting the duration of antibiotics usage is important. Antimicrobial usage can alter the hospital and patient's bacterial flora. This can lead to colonization and the development of resistance. The excessive use of vancomycin can increase the risk of developing vancomycin-resistant enterococcus.

Contraindications

Beta-lactam antibiotics are commonly used for surgical prophylaxis. It is crucial to identify when such antibiotics are contraindicated. If a patient has an immunoglobulin (IgE) mediated allergy to penicillin, then penicillins, cephalosporins, and carbapenems cannot be used for prophylaxis. A type 1 reaction would include anaphylaxis, urticaria, or bronchospasm that occurs 30 to 60 minutes following the administration of the antibiotic. Carbapenems and cephalosporins are considered safe in patients who have not had a type-1 reaction, Stevens-Johnson syndrome, or toxic epidermal necrolysis. Obtaining a good allergy history from each patient is vital to determine whether the patient's allergy is real. 

Monitoring

Surgical site infections can occur for various reasons, including incorrect antibiotic usage. The correct antibiotic dosage, timing of the initial dose, and timing of any applicable redosing are major factors to keep in mind to ensure best practices are followed when considering antibiotic prophylaxis practices.

Monitoring should ensure no surgical site infections occur due to increasing local antibiotic resistance. Antibiotic selection should be reviewed to avoid using antibiotics that result in new or worsening resistance patterns. An institution can choose to use cefoxitin instead of ertapenem in colorectal surgeries so as to avoid excessive usage of the carbapenem class especially if there is an escalating number of carbapenem-resistant organisms [29].

Toxicity

No apparent toxicities are known with the recommended doses of antibiotics. This is mainly due to the limited duration of antibiotic exposure in surgical prophylaxis.

Conclusion

Antibiotic prophylaxis for surgery is an effective management strategy for reducing postoperative infections. This is on condition that appropriate antibiotics are given at the correct time for appropriate durations and for appropriate surgical procedures. Most often surgical antibiotic prophylaxis is given as a single intravenous dose as soon as the patient is stabilized under anesthesia, prior to skin incision. It is important to use a narrow spectrum antibiotic that is appropriate for the type of surgery to be carried out. Hospital surgical antibiotic prophylaxis protocols should be regularly reviewed, as the endemicity of multi-resistant bacteria in certain units or hospitals are subject to frequent change.

References

1. Horan TC, Culver DH, Gaynes RP, Jarvis WR, Edwards JR, Reid CR. Nosocomial infections in surgical patients in the United States, January 1986 - June 1992. Infect Control Hosp Epidemiol 1993; 14:73-80.

2. McGowan JE Jr. Cost and benefit of perioperative antimicrobial prophylaxis: methods for economic analysis. Rev Infect Dis 1991;13(Suppl 10): S879-89.

3. Burke JF. The effective period of preventative antibiotic action in experimental incisions and dermal lesions. Surgery 1961;50:161-8.

4. Patchen Dellinger E, Gross PA, Barrett TL, Krause PJ, Martone WJ, McGowan JE Jr, et al. Quality standard for antimicrobial prophylaxis in surgical procedures. Clin Infect Dis 1994;18:422-7.

5. Dettenkofer M, Forster DH, Ebner W, Gastmeier P, Ruden H, Daschner FD. The practice of perioperative antibiotic prophylaxis in eight German hospitals. Infection 2002;30:164-7.

6. AlBuhairan B, Hind D, Hutchinson A. Antibiotic prophylaxis for wound infections in total joint arthroplasty: a systematic review. J Bone Joint Surg Br. 2008 Jul;90(7):915-9.

7. Tarchini G, Liau KH, Solomkin JS. Antimicrobial Stewardship in Surgery: Challenges and Opportunities. Clin Infect Dis. 2017 May 15;64(suppl_2): S112-S114. 

8. W-Dahl A, Robertsson O, Stefánsdóttir A, Gustafson P, Lidgren L. Timing of preoperative antibiotics for knee arthroplasties: Improving the routines in Sweden. Patient Saf Surg. 2011 Sep 19;5:22.

9. Gyssens IC. Preventing postoperative infections: current treatment recommendations. Drugs. 1999 Feb;57(2):175-85.

10. Galandiuk S, Polk HC, Jagelman DG, Fazio VW. Re-emphasis of priorities in surgical antibiotic prophylaxis. Surg Gynecol Obstet. 1989 Sep;169(3):219-22.

11. Stefánsdóttir A, Robertsson O, W-Dahl A, Kiernan S, Gustafson P, Lidgren L. Inadequate timing of prophylactic antibiotics in orthopedic surgery. We can do better. Acta Orthop. 2009 Dec;80(6):633-8.

12. Tan TL, Gomez MM, Kheir MM, Maltenfort MG, Chen AF. Should Preoperative Antibiotics Be Tailored According to Patient's Comorbidities and Susceptibility to Organisms? J Arthroplasty. 2017 Apr;32(4):1089-1094.e3. 

13. Varacallo MA, Mattern P, Acosta J, Toossi N, Denehy KM, Harding SP. Cost Determinants in the 90-Day Management of Isolated Ankle Fractures at a Large Urban Academic Hospital. J Orthop Trauma. 2018 Jul;32(7):338-343.

14. Bosco JA, Slover JD, Haas JP. Perioperative strategies for decreasing infection: a comprehensive evidence-based approach. Instr Course Lect. 2010;59:619-28.

15. Bratzler DW, Dellinger EP, Olsen KM, Perl TM, Auwaerter PG, Bolon MK, Fish DN, Napolitano LM, Sawyer RG, Slain D, Steinberg JP, Weinstein RA., American Society of Health-System Pharmacists. Infectious Disease Society of America. Surgical Infection Society. Society for Healthcare Epidemiology of America. Clinical practice guidelines for antimicrobial prophylaxis in surgery. Am J Health Syst Pharm. 2013 Feb 01;70(3):195-283.

16. Dehne MG, Mühling J, Sablotzki A, Nopens H, Hempelmann G. Pharmacokinetics of antibiotic prophylaxis in major orthopedic surgery and blood-saving techniques. Orthopedics. 2001 Jul;24(7):665-9. 

17. Clark JJC, Abildgaard JT, Backes J, Hawkins RJ. Preventing infection in shoulder surgery. J Shoulder Elbow Surg. 2018 Jul;27(7):1333-1341.

18. Berríos-Torres SI, Umscheid CA, Bratzler DW, Leas B, Stone EC, Kelz RR, Reinke CE, Morgan S, Solomkin JS, Mazuski JE, Dellinger EP, Itani KMF, Berbari EF, Segreti J, Parvizi J, Blanchard J, Allen G, Kluytmans JAJW, Donlan R, Schecter WP., Healthcare Infection Control Practices Advisory Committee. Centers for Disease Control and Prevention Guideline for the Prevention of Surgical Site Infection, 2017. JAMA Surg. 2017 Aug 01;152(8):784-791.

19. Pfeffer I, Zemel M, Kariv Y, Mishali H, Adler A, Braun T, Klein A, Matalon MK, Klausner J, Carmeli Y, Schwaber MJ. Prevalence and risk factors for carriage of extended-spectrum β-lactamase-producing Enterobacteriaceae among patients prior to bowel surgery. Diagn Microbiol Infect Dis. 2016 Jul;85(3):377-380.

20. Chauveaux D. Preventing surgical-site infections: measures other than antibiotics. Orthop Traumatol Surg Res. 2015 Feb;101(1 Suppl): S77-83.

21. Murray MR, Saltzman MD, Gryzlo SM, Terry MA, Woodward CC, Nuber GW. Efficacy of preoperative home use of 2% chlorhexidine gluconate cloth before shoulder surgery. J Shoulder Elbow Surg. 2011 Sep;20(6):928-33.

22. Phillips M, Rosenberg A, Shopsin B, Cuff G, Skeete F, Foti A, Kraemer K, Inglima K, Press R, Bosco J. Preventing surgical site infections: a randomized, open-label trial of nasal mupirocin ointment and nasal povidone-iodine solution. Infect Control Hosp Epidemiol. 2014 Jul;35(7):826-32. 

23. Campbell KA, Stein S, Looze C, Bosco JA. Antibiotic stewardship in orthopaedic surgery: principles and practice. J Am Acad Orthop Surg. 2014 Dec;22(12):772-81.

24. (1996) Guidelines for the prevention and treatment of infection in patients with an absent or dysfunctional spleen. Working Party of the British Committee for Standards in Haematology Clinical Haematology Task Force. BMJ. 312:430-434.

25. Davies JM, Barnes R, Milligan D (2002) Update of guidelines for the prevention and treatment of infection in patients with an absent or dysfunctional spleen. Clin Med 2:440-3.

26. Chen X, Brathwaite CE, Barkan A, Hall K, Chu G, Cherasard P, Wang S, Nicolau DP, Islam S, Cunha BA. Optimal Cefazolin Prophylactic Dosing for Bariatric Surgery: No Need for Higher Doses or Intraoperative Redosing. Obes Surg. 2017 Mar;27(3):626-629.

27. Unger NR, Stein BJ. Effectiveness of pre-operative cefazolin in obese patients. Surg Infect (Larchmt). 2014 Aug;15(4):412-6.

28. Mertz D, Johnstone J, Loeb M. Does duration of perioperative antibiotic prophylaxis matter in cardiac surgery? A systematic review and meta-analysis. Ann Surg. 2011 Jul;254(1):48-54. doi: 10.1097/SLA.0b013e318214b7e4. PMID: 21412147.

29. Deierhoi RJ, Dawes LG, Vick C, Itani KM, Hawn MT. Choice of intravenous antibiotic prophylaxis for colorectal surgery does matter. J Am Coll Surg. 2013 Nov;217(5):763-9.

 

         Occipitocervical Instability

                                Dr. KS Dhillon

Introduction

The occipitocervical junction is a unique, complex, biomechanical interface between the cranium and the upper cervical spine [1]. Craniocervical instability can be congenital or due to trauma, infections, tumors, and inflammatory conditions [2-5].

Occipitocervical instability can present with disabling pain, cranial nerve palsy, paralysis, or even sudden death. Stabilization with fusion is needed to prevent these complications. Occipitocervical fusion can be a technically challenging procedure. Occipitocervical fixation is carried out to avoid injuring the nerve root, the spinal cord, and the vertebral artery and to obtain rigid fusion [6]. Hypoplasia or absence of the occipital bone and co-morbidities that would prevent the operative procedure or the prone positioning are contraindications for occipitocervical fusion [7].

There have been advances in operative techniques and instrumentation techniques for occipitocervical fusion. The procedure has evolved from simple autograft on lay fusion techniques to sublaminar wiring techniques and, recently to rigid occipital plating with bicortical screws [8-15].

Anatomy and biomechanics

There are 2 separate groups of ligaments that play a vital role in maintaining the stability of the occipitocervical junction. The first group consists of the anterior and posterior atlanto-occipital ligaments, the articular capsule ligaments, and two lateral atlanto-occipital ligaments that attach the cranium to the atlas (Fig. 1) [16,17]. 

The anterior atlanto-occipital ligament is a continuation of the anterior longitudinal ligament. The posterior atlanto-occipital ligament extends from the posterior border of the foramen magnum to the posterior atlantal arch. The cruciate ligament also contributes to the stability of this joint.

Fig 1.

The second groups of ligaments include the apical ligament, the alar ligaments, the tectorial membrane, and the ligamentum nuchae (Fig. 1) [16-18]. They also provide craniocervical stability. The alar ligaments are paired structures. They consist of two components: the atlanto alar and the occipital alar. They connect the tip of the odontoid to the occipital condyles and the lateral masses of the atlas. They are the main restraints for axial rotation. The tectorial membrane is a continuation of the posterior longitudinal ligament. It runs from the dorsal surface of the odontoid to the ventral surface of the foramen magnum and resists hyperextension [16-18].

Occipitocervical dissociation (OCD) occurs following complete or near complete disruption of the ligamentous structures between the occiput and the upper cervical spine. Extreme forces in hyperflexion, hyperextension, and lateral flexion alone or in combination can result in this injury. The prominent force responsible for producing OCD is usually hyperextension which results in the rupture of the tectorial membrane. Incompetence of the alar ligaments and tectorial membrane allows anterior dislocation of the cranium on the upper cervical spine. 

Epidemiology

About 15-30% of cervical spine injuries occur at the occipitocervical junction. Traumatic occipitocervical instability has been identified in 19% of fatal cervical injuries.

Acquired occipitocervical instability is seen most frequently in patients with Down syndrome. It is usually asymptomatic and identified while screening for surgery or screening for special olympic participation.

Etiology 

Occipitocervical instability is also known as atlanto-occipital dissociation (AOD) and occipitocervical dislocation. There are 2 types of occipitocervical instability i.e traumatic and acquired.

The traumatic type results from high-energy trauma leading to translation or distraction injuries that destabilize the occipitocervical junction. The head most often displaces anteriorly. 

The acquired type is due to bony dysplasia or ligament and soft-tissue laxity. There can be associated atlantoaxial instability as seen in Down syndrome patients. There can be associated neurologic deficit and vertebral or carotid artery injuries.

Classification

There are 2 types of classification for occipitocervical instability namely the Traynelis classification and the Harbourview classification. The Traynelis classification is based on the direction of displacement and the Harbourview classification is based on the degree of instability.

Traynelis Classification

Type 1- Anterior occiput dislocation

Type II- Longitudinal dislocation

Type III- Posterior occiput dislocation

Harbourview Classification System 

Stage I- Minimal or non-displaced, unilateral injury to craniocervical ligaments- stable.

Stage II- Minimally displaced, but MRI demonstrates significant soft-tissue injuries. Stability may be based on traction test- Stable or Unstable

Stage III- Gross craniocervical misalignment- Harris lines >2 mm beyond acceptable limits- Unstable

Clinical presentation

The most common cause of OCD is high-speed motor vehicle accidents and striking of pedestrians by motor vehicles [19,20]. OCD is more common among children. The injury is three times more common in children than in adults [21]. A horizontal articular surface and laxity of the ligamentous structures, combined with the presence of a relatively large head and a higher effective fulcrum in the pediatric cervical spine may account for these differences. There is often concurrent head, spinal cord, or multisystem traumatic injuries in patients with OCD because of the severe force involved in producing the injury. Neurological injury from AOD can often lead to sudden death secondary to brainstem injury [22]. Neural injury may be direct due to traction or compression, or indirect, secondary to cerebrovascular injury leading to ischemia [23-26]. 

Patients who have vertebral artery insufficiency at this level may exhibit Wallenberg syndrome which consists of ipsilateral defects of cranial nerves V, IX, X, and XI; ipsilateral Horner syndrome; dysphagia; and cerebellar dysfunction [23-26]. Respiratory compromise resulting from brainstem compression often makes mechanical ventilation necessary and this can make definitive neurologic assessment difficult.

Survivors of OCD often have neurological impairment including lower cranial nerve deficits, and unilateral or bilateral sensory and motor deficits, cruciate paralysis, or even quadriplegia [23-26]. Neurogenic shock may also be present. It should be appropriately recognized and managed to ensure hemodynamic stability. 

Up to 20 % of patients with AOD may have a normal neurological examination at presentation with severe neck pain as the only symptom [23-26]. Any patient involved in high-energy trauma should be suspected of having OCD, irrespective of clinical findings. Appropriate precautionary measures should be taken until the diagnosis is ruled out.

Diagnosis

Plain films of the cervical spine are the first imaging ordered in patients with cervical trauma. The recommended views include AP, lateral, and odontoid views. Injuries to the upper cervical spine are difficult to detect with plain radiographs for several reasons. These include the parallax effect at the occipitocervical junction and obscuration due to mastoid air cells [27]. 

Lateral cervical X-rays when performed should be evaluated to determine instability such as Powers’ ratio, X-line method, condylar gap method, basion-dens interval (BDI), and basion-axial interval (BAI) [28,29].

The Powers ratio (fig 1) is equal to A-B/CD where A-B is the distance from the basion to the posterior arch and C-D is the distance from the anterior arch to the opisthion (median point on the posterior margin of the foramen magnum). A ratio of 1 is normal. If it is more than 1.0 there is anterior dislocation. If the ratio is less than 1.0 there is posterior atlanto-occipital dislocation, odontoid fracture, or a ring of atlas fracture.

Fig 1.

In Harris's rule of 12 the basion-dens interval and basion-posterior axial interval are measured. A distance of more than 12 mm suggests occipitocervical dissociation (fig 2).

Fig 2.

The radiographic findings in patients with OCD may be subtle or even absent on initial films [30-33]. The use of Harris lines on plain X-rays is often recommended for the diagnosis of OCD. The presence of MRI findings such as signal abnormalities affecting the tectorial membrane, alar and transverse ligaments, or occipitoatlantal joint capsule may also indicate the presence of OCD. Further evaluation with a CT scan can be carried out [23,24,34,35].

Multidetector computed tomography (MDCT) is the imaging modality of choice in an awake symptomatic patient. It is proven to be more sensitive and specific than cervical spine radiographs in detecting spinal cord injury [36]. MDCT of the spine is commonly used as a routine screening test for cervical spine injury and allows for more accurate Harris line measurements. The relevant anatomy is visualized 99.75 % of the time with CT as compared to 39 to 84 % of the time with plain films [27]. It also enables the examiner to visualize the occipitocervical and atlantoaxial joints directly to assess for subluxation. 

Direct assessment of condyle to C1 interval (CCI) on a sagittal and coronal CT scan may be more reliable than other radiological measurements to diagnose OCD [27,35,37,38]. Earlier studies suggested a cutoff of ≥2 mm [27] and 2.5 mm [38] as abnormal in adults. Martinez-del-Campo et al [37] proposed a cutoff for the CCI of 1.5 mm and the condylar sum of 3.0 mm as more accurate with 100 % sensitivity and specificity and no false negatives. The study also showed that the cutoff of 2.0 and 2.5 mm had higher false-negative rates of 13.6 and 22.7 %, respectively.

A study by Pang et al [35] found that the normal CCI was 1.28 ± 0.26 mm and they proposed a CCI ≥4 mm as diagnostic for AOD with a sensitivity and specificity of 100 % compared with other standard diagnostic tests. 

In children CCI determined on CT has the highest diagnostic specificity and sensitivity for AOD and should be considered the investigation of choice for diagnosing OCD [35].

An MRI will show increased T2-weighted signal intensity within the occiput-C1 and C1-C2 articulations [23,24,35]. Definitive evidence of disruption of the alar and tectorial ligaments can sometimes be seen on the MRI. Evaluation of the spinal cord and brainstem parenchyma can reveal injuries ranging from mild edema to the presence of intraspinal hematoma or even transection. Epidural fluid collections are commonly seen, as is the presence of subdural hematoma. 

Treatment and outcomes

Improvement in the maintenance of hemodynamic and respiratory stability at the scene of injury and stabilization of the neck with the proper application of a rigid cervical collar at the scene of injury and during transfer to the hospital had led to an increasing number of these patients surviving this injury that was once considered fatal [21,23,24,37]. More recent series have reported mortality rates as low as 0% in patients who were diagnosed and appropriately treated [25]. If the diagnosis of OCD is delayed by a mean of 2 days (range 1–15 days), almost 40 % of the patients suffer from profound neurological deterioration [24]. 

Once the diagnosis has been confirmed, neck immobilization with a rigid collar should be maintained until definitive surgical intervention can be performed. The use of cervical traction in the treatment of patients with OCD is controversial with contradictory opinions in various studies. There is a 10% risk of neurological deterioration in patients on cervical traction [32,39-42]. The most appropriate form of provisional stabilization is also controversial and it depends on several factors such as the timing of surgery, the degree of initial displacement, and the patient’s neurologic status, body habitus, and associated injuries. The possible options include rigid cervical collar immobilization, use of halo immobilization, and taping of the head to sandbags [39]. With nonoperative treatment, neurological worsening can occur in upto 50 % of the patients [39]. 

Cranio-cervical fixation is the treatment of choice in most cases of traumatic OCD [39]. Posterior occipitocervical fusion is the procedure of choice. This can be achieved by using a variety of techniques such as posterior wiring and structural grafting, Ransford loop fixation with wiring or plate/rod, and screw fixation with structural grafting [43,44]. Electrodiagnostic monitoring and continued provisional stabilization are necessary for turning patients with this highly unstable injury into a prone position. The development of rigid fixation has led to increasingly successful outcomes [43-45]. Wire or cable fixed rods or loops only provided semi-rigid fixation. With modern segmental screw-based constructs successful fusion can be obtained in over 90 % of patients [43,45]. 

Occipitocervical fusion is carried out through a posterior midline incision with the patient in a prone position. Mayfield retractor is used to obtain proper craniocervical alignment. Preoperative O-C2 angle is established with lateral fluoroscopy prior to draping. Deep dissection is then carried out.

If performing C1 lateral mass screw fixation it is proper to work within the safe zone and not to dissect above the posterior arch of C1 more than 1 cm lateral to the midline to avoid injury to the vertebral artery. The posterior instrumented fusion is usually performed from the occiput to C3. The occipital plates usually allow for 3 or 4 total screws with adjustable rod holders. The occipital screws are unicortical to avoid injury to the venous sinus. Major dural venous sinuses are located just below the external occipital protuberance. The safe zone for occipital screws is located within an area measuring 2 cm lateral and 1 cm inferior to the external occipital protuberance along the superior nuchal line. C1 lateral mass screws often skipped due to angle at the base of the skull which makes it more difficult to place a rod. A unilateral screw may be inserted to provide some rotational stability to the C1 ring. C2 fixation can be carried out with a screw in the pars, pedicle, or lamina. For C3 fixation standard lateral mass screws are aimed cephalad and lateral to avoid the vertebral artery. Bone grafting and removal of boney fragments compressing neurovascular structures will be required. Complications include nonunion and bleeding from the internal carotid artery or vertebral artery injury.

Treatment outcomes in survivors of occipitocervical dissociation depend on the following [23,24,25,27]:

• Type and severity of associated injuries especially intracranial injuries and cerebrovascular injury.

• The severity of neurologic deficit.

• The timeline with which the diagnosis of craniocervical dissociation is recognized.

Missed diagnosis of OCD is the most important factor associated with poor outcomes in patients sustaining this injury and is higher in patients with other associated significant injuries and reliance on X-rays alone for initial diagnosis of OCD [24,25,27,46]. 

Conclusion

OCD is a devastating injury. It is more prevalent than was originally thought. It produces significant morbidity and mortality if left unrecognized. The availability of high-resolution CT has facilitated the diagnosis due to better visualization of the craniocervical junction. Recognition of newer diagnostic criteria for OCD, especially abnormal condylar separation on a high-resolution MDCT, has made it easier to recognize and reduce the incidence of missed diagnosis and its untoward sequel. A high index of suspicion following high-impact trauma with early recognition and prompt surgical intervention can lead to good clinical outcomes. Posterior occipitocervical fusion and instrumentation remains the treatment of choice.

References

1. J.R. Vender, P.J. Houle, S. Harrison, et al. Occipital-cervical fusion using the Locksley intersegmental tie bar technique: long-term experience with 19 patients Spine J, 2 (2002), pp. 134-141.

2. C.A. Dickman, S.M. Papadopoulos, V.K.H. Sonntag, et al. Traumatic occipitoatlantal dislocations J Spinal Disor, 6 (1993), pp. 300-313. 

3. F.H. Shen, D. Samartzis, L.G. Jenis, et al. Rheumatoid arthritis: evaluation, surgical management of the cervical spine Spine J, 689 (2004), p. 700.

4. L. Labler, K. Eid, A. Platz, et al. Atlanto-occipital dislocation: four case reports of survival in adults and review of the literature Eur Spine J, 13 (2) (2004), pp. 172-180. 

5. H. Koller, U. Holz, A. Assuncao, et al. Traumatic Atlantooccipital Dislocation Critical Review: Diagnosis, Classification and Treatment, and Explanative Case Report. European J of Trauma 2006; 32: 271–9. 3- Abumi K, Avadhani A, Manu A, et al. Occipitocervical fusion Eur Spine J, 19 (2010), pp. 355-356.

6. A. Vaccaro, M. Lim, J. Lee Indications for surgery and stabilization techniques of the occipito-cervical junction Injury Int J Care Injured, 36 (2005), pp. SB44-SB53.

7. C.G. Randazzo, B. LeBude, J. Ratliff, et al. Occiput–Cervical Fixation Spine Trauma, Part 1, 119 (2010), p. 127.

8. K. Abumi, A. Avadhani, A. Manu, et al. Occipitocervical fusion Eur Spine J, 19 (2010), pp. 355-356.

9. J.J. Baskin, C.A. Dickman, V.K.H. Sonntag. Occipitocervical fusion H.R. Winn, R.G. Dacey (Eds.), Youmans Neurological Surgery, Saunders, Philadelphia (2004), pp. 4655-4670.

10. N.A. Ebraheim, H. Elgafy, R. Xu. Bone graft harvesting from iliac and fibular donor sites: techniques and complications J Am Acad Orthop Surg, 9 (2001), pp. 210-218.

11. K. Abumi, T. Takada, Y. Shono, et al. Posterior occipitocervical reconstruction using cervical pedicle screws and plate-rod systems Spine, 24 (1999), pp. 1425-1434.

12. A. Faure, E. Bord, R. Monteiro da Silva, et al. Occipitocervical fixation with a single occipital clamp using inverted hooks Eur Spine J, 7 (1998), pp. 80-83.

13. V. Heidecke, N.G. Rainov, W. Burkert Occipito-cervical fusion with the cervical Cotrel-Dubousset rod system Acta Neurochir, 140 (1998), pp. 969-976.

14. P. Korovessis, P. Katonis, A. Aligizakis, et al. Posterior compact Cotrel-Dubousset instrumentation for occipitocervical, cervical and cervicothoracic fusion Eur Spine J, 10 (1998), pp. 385-394.

15. P. Paquis, V. Breuil, M. Lonjon, et al. Occipitocervical fixation using hooks and screws for upper cervical instability Neurosurgery, 44 (1999), pp. 324-331.

16. Martin MD, Bruner HJ, Maiman DJ. Anatomic and biomechanical considerations of the craniovertebral junction. Neurosurgery. 2010;66:2–6. doi: 10.1227/01.NEU.0000365830.10052.87.

17. Tubbs RS, Hallock JD, Radcliff V, et al. Ligaments of the craniocervical junction. J Neurosurg Spine. 2011;14:697–709. doi: 10.3171/2011.1.SPINE10612. 

18. Yuksel M, Heiserman JE, Sonntag VK. Magnetic resonance imaging of the craniocervical junction at 3-T: observation of the accessory atlantoaxial ligaments. Neurosurgery. 2006;59:888–92.

19. Traynelis VC, Marano GD, Dunker RO, Kaufman HH. Traumatic atlanto-occipital dislocation. Case report. J Neurosurg. 1986;65:863–70. doi: 10.3171/jns.1986.65.6.0863.

20. Werne S. Studies in spontaneous atlas dislocation. Acta Orthop Scand Suppl. 1957;23:1–150.

21. Bucholz RW, Burkhead WZ. The pathological anatomy of fatal atlanto-occipital dislocations. J Bone Joint Surg Am. 1979;61:248–50.

22. Fisher CG, Sun JC, Dvorak M. Recognition and management of atlanto-occipital dislocation: improving survival from an often fatal condition. Can J Surg J Can de Chir. 2001;44:412–20.

23. Horn EM, Feiz-Erfan I, Lekovic GP, Dickman CA, Sonntag VK, Theodore N. Survivors of occipitoatlantal dislocation injuries: imaging and clinical correlates. J Neurosurg Spine. 2007;6:113–20. doi: 10.3171/spi.2007.6.2.113.

24. Bellabarba C, Mirza SK, West GA, et al. Diagnosis and treatment of craniocervical dislocation in a series of 17 consecutive survivors during an 8-year period. J Neurosurg Spine. 2006;4:429–40. doi: 10.3171/spi.2006.4.6.429.

25. Mendenhall SK, Sivaganesan A, Mistry A, Sivasubramaniam P, McGirt MJ, Devin CJ. Traumatic atlantooccipital dislocation: comprehensive assessment of mortality, neurologic improvement, and patient-reported outcomes at a Level 1 trauma center over 15 years. Spine J : Off J N Am Spine Soc. 2015;15:2385–95.

26. Sweet J, Ammerman J, Deshmukh V, White J. Cruciate paralysis secondary to traumatic atlantooccipital dislocation. J Neurosurg Spine. 2010;12:19–21. doi: 10.3171/2009.8.SPINE08496.

27. Dziurzynski K, Anderson PA, Bean DB, et al. A blinded assessment of radiographic criteria for atlanto-occipital dislocation. Spine. 2005;30:1427–32. doi: 10.1097/01.brs.0000166524.88394.b3.

28. Lee C, Woodring JH, Goldstein SJ, Daniel TL, Young AB, Tibbs PA. Evaluation of traumatic atlantooccipital dislocations. AJNR Am J Neuroradiol. 1987;8:19–26.

29. Rojas CA, Bertozzi JC, Martinez CR, Whitlow J. Reassessment of the craniocervical junction: normal values on CT. AJNR Am J Neuroradiol. 2007;28:1819–23. doi: 10.3174/ajnr.A0660.

30. Eismont FJ, Bohlman HH. Posterior atlanto-occipital dislocation with fractures of the atlas and odontoid process. J Bone Joint Surg Am. 1978;60:397–9. 

31. Gabrielsen TO, Maxwell JA. Traumatic atlanto-occipital dislocation; with case report of a patient who survived. Am J Roentgenol Radium Therapy, Nucl Med. 1966;97:624–9. doi: 10.2214/ajr.97.3.624. 

32. Pang D, Wilberger JE., Jr Traumatic atlanto-occipital dislocation with survival: case report and review. Neurosurgery. 1980;7:503–8. doi: 10.1227/00006123-198011000-00017. 

33. Woodring JH, Selke AC, Jr, Duff DE. Traumatic atlantooccipital dislocation with survival. AJR Am J Roentgenol. 1981;137:21–4. doi: 10.2214/ajr.137.1.21.

34. Garrett M, Consiglieri G, Kakarla UK, Chang SW, Dickman CA. Occipitoatlantal dislocation. Neurosurgery. 2010;66:48–55. doi: 10.1227/01.NEU.0000365802.02410.C5. 

35. Pang D, Nemzek WR, Zovickian J. Atlanto-occipital dislocation—part 2: the clinical use of (occipital) condyle-C1 interval, comparison with other diagnostic methods, and the manifestation, management, and outcome of atlanto-occipital dislocation in children. Neurosurgery. 2007;61:995–1015.

36. Ryken TC, Hadley MN, Walters BC, et al. Radiographic assessment. Neurosurgery. 2013;72(Suppl 2):54–72. doi: 10.1227/NEU.0b013e318276edee.

37. Martinez-Del-Campo E, Kalb S, Soriano-Baron H, et al. Computed tomography parameters for atlantooccipital dislocation in adult patients: the occipital condyle-C1 interval. J Neurosurg Spine. 2016;24(4):535–45.

38. Gire JD, Roberto RF, Bobinski M, Klineberg EO, Durbin-Johnson B. The utility and accuracy of computed tomography in the diagnosis of occipitocervical dissociation. Spine J : Off J N Am Spine Soc. 2013;13:510–9. doi: 10.1016/j.spinee.2013.01.023.

39. Theodore N, Aarabi B, Dhall SS, et al. The diagnosis and management of traumatic atlanto-occipital dislocation injuries. Neurosurgery. 2013;72 Suppl 2:114–26. 

40. Evarts CM. Traumatic occipito-atlantal dislocation. J Bone Joint Surg Am. 1970;52:1653–60. 

41. Levine AM, Edwards CC. Traumatic lesions of the occipitoatthop Relat Res. 1989;(239):53–68. 

42. Watridge CB, Orrison WW, Arnold H, Woods GA. Lateral atlantooccipital dislocation: case report. Neurosurgery. 1985; 17:345–7. doi: 10.1227/00006123-198508000-00021.

43. Garrido BJ, Puschak TJ, Anderson PA, Sasso RC. Occipitocervical fusion using contoured rods and medial offset connectors: description of a new technique. Orthopedics. 2009;32. doi:10.3928/01477447-20090818-11. 

44. Lu DC, Roeser AC, Mummaneni VP, Mummaneni PV. Nuances of occipitocervical fixation. Neurosurgery. 2010;66:141–6. doi: 10. 1227/01.NEU.0000365744.54102.B9.

45. Abumi K, Takada T, Shono Y, Kaneda K, Fujiya M. Posterior occipitocervical reconstruction using cervical pedicle screws and plate-rod systems. Spine. 1999;24:1425–34. doi: 10. 1097/00007632-199907150-00007.

46. Blackwood NJ., III Atlo-occipital dislocation: a case of fracture of the atlas and axis, and forward dislocation of the occiput on the spinal column, life being maintained for thirty-four hours and forty minutes by artificial respiration, during which a laminectomy was performed upon the third cervical vertebra. Ann Surg. 1908;47:654–8. doi: 10.1097/00000658-190805000-00003.