In an earlier post on rotatory atlatoaxial subluxation, we discussed the Fielding and Hawkins classification, and its application to symptomatic patients (e.g., those with torticollis). Here, we discuss the challenge of making a diagnosis of rotatory atlatoaxial subluxation in unselected patients.
That is, what do you do if your neck or c-spine CT scan is obtained with the head turned, and you see what looks like a Type I rotatory atlatoaxial subluxation?
The patient below was referred to our institution in a cervical collar for management of atlantoaxial rotatory subluxation.
30-year-old man: Thick reconstructions centered at C1-C2 from a CTA obtained with the head rotated to the left. There is apparent type I atlantoaxial rotatory subluxation.
Let’s take a look at what we know:
- Normal maximum rotation of the head on body is between 60–80°.
- Normal maximum rotation of C1 on C2 makes up for about half of that: 30–45° (although some sources say it can be up to 50°).
- Cutoff for abnormal C1-C2 rotation: >45° or >56°, depending on source.
Looking at our image above, our rotation of C1 on C2 is about 30 degrees, which puts it in the normal range. But, what if the number was higher? How well do we do as radiologists in correctly identifying this as normal?
One study that was helpful came from the forensic field. Pathologists had noted that CTs of cadavers, which are impossible to position “correctly,” were resulting in a lot of over-calling of atlantoaxial rotatory subluxation. When they looked at their data they found:
- 19 cases where the C-spine was stable on autopsy. In those 19, 13 had suspected rotatory subluxation based on on CT (false positives)
- The C1-C2 angle in those 13 false positives were between 16–47°.
- All false positives were type I.
- 2 cases where the C-spine was unstable at autopsy. In those 2 cases, 1 had suspected rotatory subluxation on CT (true positive).
- The C1-C2 angle in the 1 true positive was 42°.
- There was a significant association between the false positives and degree of head rotation.
Generalizing this cadaveric study suggests that we need to be careful in calling type I atlantoaxial rotatory subluxation in asymptomatic patients who simply happen to have their head turned in the scanner. This supports the conclusions from a study in living, asymptomatic patients, where the authors showed that incomplete rotational facet displacement on CT was not sufficient to define subluxation.
Bisphosphonate-related osteonecrosis of the jaw (BRONJ) is associated with the use of bisphosphonates to treat severe osteoporosis, and metabolic and oncologic bone conditions, including hypercalcemia associated with malignancy. These agents inhibit osteoclasts, reducing bone resorption and osteolysis, and also possess antiangiogenic properties, reducing blood flow and necrosis. Patients with BRONJ present with pain and exposed, nonvital bone involving the maxillofacial structures. The incidence of BRONJ increases with the duration of treatment, especially with the intravenous route and concomitant steroid therapy. The osteonecrosis usually is participated by dental extraction. When spontaneous, it commonly occurs along the mylohyoid ridge. BRONJ can mimic osteomyelitis and osteoradionecrosis. A history of dental caries and the presence of periosteal elevation can help direct one towards the diagnosis of osteomyelitis. Osteoradionecrosis can be excluded if the patient has not received oropharyngeal radiation therapy. Jaw neoplasm, primary or metastatic, can potentially also mimic BRONJ. Treatment of BRONJ consists of cessation of bisphosphonate drug therapy, antibiotics for secondary infection, and surgical debridement of necrotic sequestra.
|Figure 1: Axial CT of the facial bones. There is a mixed sclerotic and lytic lesion within the mandible (Figure 1, arrows) with foci of cortical interruption (Figure 2, arrowheads).
|Figure 2: Sagital CT of the facial bones. There is a mixed sclerotic and lytic lesion within the mandible (Figure 1, arrows) with foci of cortical interruption (Figure 2, arrowheads).
Juvenile idiopathic arthritis (JIA) is an umbrella term for a group of abnormalities characterized by chronic articular inflammation and association with HLA alleles. The International League Against Rheumatism (ILAR) has classified JIA into seven subtypes, including an unclassifiable group. These include:
- Systemic arthritis: Arthritis in one or more joints with or preceded by fever of at least 2 weeks’ duration documented to be daily for at least 3 days, and accompanied by one or more of: evanescent erythematous rash, lymphadenopathy, hepatomegalyor splenomegaly, or both, serositis
- Oligoarthritis: Arthritis in 4 or fewer joints in the first 6 months. Subtypes include persistent (no more than 4 joints throughout the course of the disease) and extended (more than 4 joints after the first 6 months).
- Polyarthritis, RF negative: Arthritis affecting 5 or more joints in the first 6 months of disease. RF is negative
- Polyarthritis, RF positive: Arthritis affecting 5 or more joints in the first 6 months of disease. Two or more tests for RF, conducted at least 3 months apart during the first 6 months, are positive. Considered the pediatric version of adult rheumatoid arthritis.
- Psoriatic: Arthritis plus psoriasis OR Arthritis plus at least two of the following: dactylitis, nail pitting or onycholysis, psoriasis in a first-degree relative.
- Enthesis-related: Arthritis plus enthesitis OR Arthritis or enthesitis, plus at least two of the following: presence of or a history of sacroiliac joint tenderness and/or inflammatory lumbosacral pain‡, presence of HLA-B27 antigen, onset of arthritis in a male over 6 years of age, acute (symptomatic) anterior uveitis, history of AS, ERA, sacroiliitis with IBD, reactive arthritis, or acute anterior uveitis in a first-degree relative
- Unclassified: Arthritis that fulfills criteria in none of the above categories, or fulfills criteria in two or more of the above categories
Petty RE, Southwood TR, Baum J, Bhettay E, Glass DN, Manners P, Maldonado-Cocco J, Suarez-Almazor M, Orozco-Alcala J, Prieur AM. Revision of the proposed classification criteria for juvenile idiopathic arthritis: Durban, 1997. J Rheumatol. 1998 Oct;25(10):1991-4.