[Assessment of pedicle screws following dorsal instrumentation of the spine: a comparison of conventional radiographs with multidetector CT].
OBJECTIVE
To evaluate the performance of conventional radiographs (CR) for the assessment of pedicle screws in comparison with CT including MPR.


METHODS
Comparison of CR and CT for the evaluation of screw length, extracorporal perforation (grade A: 0 - 2 mm, B: 3 - 4 mm, C: 5 - 6 mm, D: > 6 mm, relevant: grade C and D), screw contact/loosening, and subjective image quality (1: excellent to 4: non-diagnostic). The sensitivity (SE), specificity (SP), positive (PPV) and negative predictive value (NPV), and overall accuracy (OA) were calculated with 4x4 contingency tables. The subjective image quality was evaluated using the Wilcoxon test (p < 0.05).


RESULTS
411 screws were evaluated. The relevant medial perforation was diagnosed with CR/CT in 53(13 %)/ 11(3 %) screws, while the relevant lateral perforation was found in 3(1 %)/ 43(11 %) screws. Pedicle screw contact was diagnosed by CR/CT in 10(2 %)/ 18(4 %) cases and incorrect length was confirmed in 80(20 %)/ 90(22 %) screws. A diagnosis of loosening was established in 10(2 %) screws by CR and in 7(2 %) screws by MDCT. In summary, CR demonstrated SE, SP, PPV, NPV, and OA for the following variables: relevant medial perforation = 64 / 89 / 13 / 99 / 88 %, relevant lateral perforation = 4 / 99 / 67 / 90 / 90 %, screw contact = 11 / 98 / 20 / 96 / 94 %, incorrect screw length = 86 / 58 / 89 / 51 / 81 %, and screw loosening = 71 %/ 99 %/ 50 %/ 100 %/ 98 %. The subjective image quality of CR was significantly lower compared to CT (2.19 A + or - 0.84 and 1.11 A + or - 0.31; p < 0.001).


CONCLUSIONS
CR evaluation of pedicle screws following dorsal instrumentation of the spine demonstrated an OA < or = 90 % for relevant medial and lateral perforation and for incorrect screw length compared to CT. Thus, reliable evaluation of pedicle screws based solely on CR does not seem feasible.
Institut für Diagnostische Radiologie, Interventionelle Radiologie und Nuklearmedizin, Berufsgenossenschaftliches Universitätsklinikum Bergmannsheil.
S
S
Lemburg
A
A
Atta
S
S
Peters
D
D
Roggenland
V
V
Nicolas
J
J
Altenbernd
C M
CM
Heyer
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws; D004868:Equipment Failure; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000293:injuries / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000000981:diagnostic imaging*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016103:Spinal Fractures / Q000000981:diagnostic imaging / Q000601:surgery*; D013123:Spinal Fusion / Q000295:instrumentation*; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging* / Q000293:injuries / Q000601:surgery*; D014025:Titanium; D036542:Tomography, Spiral Computed; D055815:Young Adult
D014025:Titanium