Magnetic resonance imaging of spondylolysis and isthmic spondylolisthesis Pascal Niggemann – Johannes Kuchta –Dieter Grosskurth– Hans-Konrad Beyer Janine Höffer – Karl Stefan Delank XIX Symposium Neuroradiologicum iWiZ

Part I: Static magnetic resonance imaging Incidence of vertebral hypoplasia Impact of vertebral hypoplasia on measurement and classification Part II: Positional magnetic resonance imaging Positional MRI findings Clinical implication of positional MR findings

Static magnetic resonance imaging

Spondylolysis and isthmic spondylolisthesis: - multi-factorial common disorder (prevalence 2.5 to 10.5 %) - high prevalence in specific populations and in certain families - aquired disorder => acquired disorder with a genetic predisposition Pathogenesis: - facture of the pars interarticularis => spondylolysis - Vertebra looses dorsal “hock” => isthmic spondylolisthesis - Hypoplasia is common in patients with spondylolysis and isthmic spondylolisthesis

Material: 181 patients with 184 levels of spondylolysis - 53 women /128 men 176 bilateral / 8 unilateral mean age: 50.5 ± 13.5 years - Level of spondylolysis: - L5/S1:157 patients85 % - L4/L5:20 patients11 % - L3/L4: 6 patients 3 % - L2/3: 1 patient 1 % Positional MRI using the Fonar Upright MRI Scans in flexion, extension, supine and sitting position

Methods I: S agittal T2 weighted scan of the midline A B C Line A: dorsal margin of L5 Line B: parallel to line A at the dorsal edge of S1 Line C: distance between A and B

Methods II: MRI in seated position using the FONAR Upright MRI = > sagittal T2 weighted scan D E Line D: lower margin of L5 Line E: upper margin of S1 Difference in size between Line A and line B in mm

Methods III: C E Grade Meyerding: C divided by E in % Hypoplasia: E minus D in mm Real Spondylolisthesis: C – Hypoplasia Real Slip (Meyerding): C- Hypoplasia / E Control: Group of 526 patients without spondylolysis or spondylolisthesis = > Is L4 smaller than L5 or L5 smaller than S1? => Dorsal alignment? D

Results I: Hypoplasia was found in 62 levels out of 184 (L5: 61, L4: 1) Range of hypoplasia: 3 to 13 mm (5 +/- 2 mm) Hypoplasia (classic): Grade 0: 0Adjusted: Grade 0: 24 Grade I: 37Grade I: 31 Grade II: 24Grade II: 7 Grade III: 1 In 41 patients the grade of slip had to be adjusted! 24 patients were reclassified as spondylolysis!

Results II: Hypoplasia was found in 10 levels in 526 controls (p<0.001). -L5 was hypoplastic in 8 patients (8 out of 526) -L4 was hypoplastic in 2 patients (2 out of 526) Hypoplasia was 3 to 4 mm in the controls.  Not taken into account were other hypoplasia (S1, combined hypoplasia, ventral hypoplasia)

Conclusion I: Hypoplasia is common in spondylolysis 34 % of all segments, 39 % of level L5 - Hypoplasia might mimic spondylolisthesis - Grading after Meyerding takes not into account hypoplasia  Careful not to misdiagnose spondylolysis as spondylolisthesis, when hypoplasia is present  Measure the hypoplasia and grade accordingly

Conclusion II: Pathogenetic implications Is the shortening acquired or inborn? Hypoplasia exists in non spondylolytic vertebrae, but is rare => Hypoplasia is predisposition? Inborn: - might explain family predisposition - is found in patients without spondylolysis Acquired: - might be acquired during growth -bone overgrowth at the fracture site - growth of the vertebral body hindered

Positional magnetic resonance imaging

Stability of the lumbar spine - Panjabi (1980) defines spinal instability as ”the loss of the ability of the spine under physiological loads to maintain relationships between the vertebrae in such way that there is neither damage nor subsequent irritation to the spinal cord or nerve roots”. Cross-sectional imagingfunctional X-Ray Positional MRI

Methods IV: Classification of the complaints into radicular vs. non radicular - according to pain / numbness / paralysis - solely with the clinical neurological findings Positional Imaging: - Unstable anterior slip - Increased angular movement - Movement in the spondylolytic defect

Movement ≥ 3 mm Unstable anterior slip: => Anterior Instability Supine Flexion

Increased angular movement : => Angular Instability Angular change ≥ 6º

Movement in the spondylolytic defect: => Posterior Instability

Results III: Anterior Instability:21 patients(max: 7 mm) Angular Instability:46 patients(max: 18 degrees) Posterior Instability:48 patients Anterior and angular instability: 3 patient Anterior and posterior instability: 5 patients Angular and posterior instability:15 patients All three forms together: 3 patient No Instability:98 patients

Results IV: Patients with radicular symptoms:69 (of 184) patients No instability and radicular symptoms:17 patients (of 98) Anterior instability and radicular symptoms: 15 patients (of 21) Angular instability and radicular symptoms: 30 patients (of 46 ) Posterior instability and radicular symptoms: 28 patients (of 48) All forms of instability are statistically more often associated with radicular symptoms. (χ2 –Test: p < )

Conclusion III: Positional MRI: - different forms of instability as described usually on X-Ray - three common forms associated with radicular symptoms - new insights into pathomechanisms - therapeutic implications are not clear yet, but might help to choose appropriate treatment - valuable addition to plan treatment

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