A Surgical Method for Determining Proper Screw Length in ACDF

OBJECTIVE: We describe a surgical tool that uses the distractor pin as a reference for determining proper screw length in ACDF. It is critical that screw purchase depth be as deep as possible without violating or penetrating the posterior cortical wall, which ensures strong pull out strength. METHODS: We enrolled 81 adult patients who underwent ACDF using an anterior cervical plate from 2010 to 2012. Patients were categorized into Groups A (42 patients: retractor pin used as a reference for screw length) and B (39 patients: control group). Intraoperative lateral x-rays were taken after screwing the retractor pin to confirm the approaching vertebral level. The ratio of retractor pin length to body anteroposterior (A-P) diameter was measured as a reference. Proper screw length was determined by comparison to the reference. RESULTS: The average distance from screw tip to posterior wall was 3.0+/-1.4mm in Group A and 4.1+/-2.3mm in Group B. The ratio of screw length to body sagittal diameter was 86.2+/-5.7% in Group A and 80.8+/-9.0% in Group B. Screw length to body sagittal diameter ratios higher than 4/5 occurred in 33 patients (90%) in Group A and 23 patients (59%) in Group B. No cases violated the posterior cortical wall. CONCLUSION: We introduce a useful surgical method for determining proper screw length in ACDF using the ratio of retractor pin length to body A-P diameter as a reference. This method allows for deeper screw purchase depth without violation of the posterior cortical wall.

Anterior Lumbar Interbody Fusion for the Treatment of Postoperative Spondylodiscitis

OBJECTIVE: To analyze the clinical courses and outcomes after anterior lumbar interbody fusion (ALIF) for the treatment of postoperative spondylodiscitis. METHODS: A total of 13 consecutive patients with postoperative spondylodiscitis treated with ALIF at our institute from January, 1994 to August, 2013 were included (92.3% male, mean age 54.5 years old). The outcome data including inflammatory markers (leukocyte count, C-reactive protein, erythrocyte sedimentation rate), the Oswestry Disability Index (ODI), the modified Visual Analogue Scale (VAS), and bony fusion rate using spine X-ray were obtained before and 6 months after ALIF. RESULTS: All of the cases were effectively treated with combination of systemic antibiotics and ALIF with normalization of the inflammatory markers. The mean VAS for back and leg pain before ALIF was 6.8+/-1.1, which improved to 3.2+/-2.2 at 6 months after ALIF. The mean ODI score before ALIF was 70.0+/-14.8, which improved to 34.2+/-27.0 at 6 months after ALIF. Successful bony fusion rate was 84.6% (11/13) and the remaining two patients were also asymptomatic. CONCLUSION: Our results suggest that ALIF is an effective treatment option for postoperative spondylodiscitis.

Diagnosis of Cervical OPLL in Lateral Radiograph and MRI: Is it Reliable?

OBJECTIVE: Cervical OPLL is a relatively common cause of developing cervical myelopathy or radiculopathy in Asians. Cervical OPLL is sometimes missed in lateral radiography or MRI. In the present study, we analyzed the diagnostic accuracy of cervical OPLL in lateral radiography and MRI compared to CT scan. METHODS: This is a retrospective study of forty-six patients who underwent decompressive surgery anteriorly or posteriorly in our institute. All patients were diagnosed with cervical OPLL by CT scan. The patients were grouped into continuous type, segmental type, mixed type, and localized type. We then evaluated lateral radiographs and MRI compared to CT scans. The diagnostic accuracy and false negative rates in lateral radiograph and MRI were evaluated. RESULTS: In a total of 46 patients diagnosed with cervical OPLL in CT scans, diagnostic accuracy using lateral radiograph and MRI were 52.2%(24/46) and 58.7%(27/46), respectively. In the continuous type group, diagnostic accuracy using lateral radiograph and MRI were 85.7%(6/7) and 100.0%(7/7). In the segmental type group, diagnostic accuracy using lateral radiograph and MRI were 27.3%(6/22) and 31.8%(7/22). In the mixed type group, diagnostic accuracy was 91.7%(11/12) in lateral radiograph and 83.3%(10/12) in MRI. In the localized group, diagnostic accuracy was 20.0%(1/5) in lateral radiograph and 60.0%(3/5) in MRI. CONCLUSION: The diagnostic accuracy of cervical OPLL using lateral radiograph and MRI was less than using CT scan. For the best treatment plan, preoperative CT scan should be performed to detect conditions of ossifications such as cervical OPLL.

A PET/CT-based Morphometric Study of Spinal Canal in Korean Young Adults: Anteroposterior Diameter from Cervical Vertebra to Sacrum

OBJECTIVE: To establish normative data for spinal canal AP diameter from cervical vertebra to sacrum in the Korean young and to assess the exposed spinal canal after laminectomy which was related with restenosis by post-laminectomy membrane formation. METHODS: From PET/CT, axial bone-window CT of 83 young adults (20-29 years) were obtained, and we measured AP diameters of C3, C5, C7, T1, T4, T8, T12, L1, L3, L5 and S1. We also measured exposed AP diameter of C3, C5, C7, T1 and T2 above imaginary line for laminectomy. RESULTS: The shortest mean AP diameter was at C5 (14.5+/-1.5 mm), and the longest was at S1 (17.4+/-2.3 mm). AP diameter increased from C3 (14.6+/-1.1 mm) to T1 (16.1+/-1.2 mm) at cervical spine. In the thoracic spine, the diameter gradually decreased from T1 (16.1+/-1.2 mm) to T8 (14.6+/-1.3 mm) and increased to T12 (16.7+/-1.2 mm). The diameter decreased from L1 (16.7+/-1.3 mm) to L3 (15.7+/-1.9 mm), and it increased to S1 (17.4+/-2.3 mm) at lumbar spine. Exposed AP diameter above imaginary line for laminectomy was the longest at C3 (4.8+/-1.2 mm) and gradually decreased to T1 (3.3+/-0.9 mm) and T2 (0 mm). CONCLUSIONS: Spinal AP diameter was the shortest in the mid-cervical area (C5) and increased to the upper thoracic area. From the upper thoracic vertebra, the diameter gradually decreased to the mid-thoracic vertebra (T8) and then increased to the lower thoracic vertebra. Lumbar vertebra also was similar with thoracic vertebra. Below T2, there was no exposed dural sac after laminectomy. This means that restenosis by post-laminectomy membrane formation can occur above T1.