Screw Motion Used in Semiconstrained Rotational Plate Systems for Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: Retrospective observational study. OBJECTIVE: To scrutinize screw motion used in semiconstrained rotational plate systems for anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Semiconstrained rotational plate systems are supposed to control graft subsidence and facilitate lordosis acquisition and maintenance by toggling the instrumented vertebrae via variable-angle screws. However, their benefits may be unrealized if the screws move within the vertebrae. METHODS: We reviewed medical records of 119 patients who underwent 1-level, 2-level, 3-level, or 4-level ACDF, divided them into the short-segment (n=62, 1-level or 2-level ACDF) and long-segment (n=59, 3- level or 4-level ACDF) groups, and investigated their immediate and 1-year postoperative lateral radiographs. We measured the fused segmental angle, screw angles at the upper-instrumented vertebra (UIV) and lower-instrumented vertebra (LIV), distance from the screw base to the endplate of UIV/LIV (SBE), and distance from the screw tip to the endplate of UIV/LIV (STE) to analyze the screw motion used in these plate systems. The differences between the immediate and 1-year postoperative values were statistically analyzed. The nonunion level was also investigated. RESULTS: Screw angle and SBE at the LIV significantly decreased in the long-segment group (-14.5±9.8 degrees and -2.8±1.8 mm, respectively) compared with those in the short-segment group (-4.6±6.0 degrees and -1.0±1.5 mm, respectively). Thus, the long-segment group could not maintain the immediate-postoperative segmental angle. Overall, 27 patients developed nonunion, with 19 (70.4%) in the long-segment group and 21 (77.8%) at the lowest fused level. CONCLUSIONS: Semiconstrained rotational plate systems provide only vertical forces to the fused segment rather than toggling the instrumented vertebrae. Postoperatively in multilevel ACDF, LIV screws migrate caudally, suggesting that these plate systems are not always effective in maintaining lordosis. Moreover, LIV screws and the anterior wall of the LIV are subject to overloading, resulting in a high rate of nonunion at the lowest fused level. LEVEL OF EVIDENCE: Level III.

Navigation-Assisted Micro-Window Excision of Thoracic Ossification of Ligamentum Flavum (Mishima Surgery) in Professional Baseball Pitchers: A Case Report and Technical Note.

Background and Objectives: Thoracic ossification of the ligamentum flavum (OLF) often causes myelopathy and/or radiculopathy. The disease is frequently observed in East Asian populations. Although thoracic OLF in young athletes who have underwent decompression surgery has been reported, the removal of posterior spinal bony elements and ligamentous complex may often cause postoperative thoracolumbar instability. We established a novel surgical technique that preserves the posterior spinal elements, including the spinous processes, facet joints, and supraspinous and interspinous ligaments for thoracic OLF. This is the first case report to describe a navigation-assisted micro-window excision of thoracic OLF. Case: A 32-year-old male right-handed professional baseball pitcher with significant weakness and numbness in the left leg was referred to our hospital. The patient was diagnosed with thoracic OLF at T10-11 based on radiographic and magnetic resonance images in August 2022. After exposure of the left T10-11 laminae via a small unilateral incision, the location of T10-11 OLF was detected over the lamina by O-arm navigation. Then, the micro-window was made directly above the OLF using a navigated air drill, and the OLF was removed on the ipsilateral side. The contralateral side of OLF was also resected through the same micro-window, achieving complete spinal cord decompression. Results: The next day of the surgery, his leg weakness and numbness were significantly improved. Six weeks after the surgery, he started pitching. Three months after surgery, his symptoms had gone completely, and he pitched from the mound. Approximately 6 months after surgery, he successfully pitched in a professional baseball game. Conclusions: A navigation-assisted micro-window excision of thoracic OLF effectively preserved the spinal posterior bony elements and ligamentous complex. However, long-term clinical outcomes should be evaluated in future studies.

Optimum Vertebral Level of Castellvi Type III or Higher Lumbosacral Transitional Vertebrae When Measuring Spinopelvic Parameters.

BACKGROUND: Castellvi type III and IV lumbosacral transitional vertebrae (LSTVs) are fused to the sacrum. In these cases, the pelvic incidence (PI) and pelvic tilt (PT) may vary according to the selected "S1." This study aimed to determine the optimum vertebral level of these LSTVs when measuring PI and PT. METHODS: PI and PT were measured twice in 56 patients with type III and IV LSTVs with a balanced spine, with LSTV considered as the lowest lumbar vertebra (LLV) or S1. PI and PT measured with LSTV as LLV were denoted as LLV_PI and LLV_PT, and those measured as S1 were denoted as S_PI and S_PT. Reference ranges (mean -2 SD to +2 SD) of PI and PT were derived from 183 non-LSTV patients with a balanced spine as 35.5° to 68.8° (PI) and 2.5° to 29.6° (PT). If S_PI, S_PT, or both were below the reference range, the LSTV was interpreted as LLV. If LLV_PI, LLV_PT, or both were above the reference range, it was interpreted as S1. If all parameters were within the respective reference range, it was interpreted as an intermediate type. RESULTS: The optimum vertebral level of LSTV was S1 (n = 29, 51.8%), most frequently due to high LLV_PT (35.4°±4.7), followed by LLV (n = 14, 25%) due to low S_PI (31.5°±5.2) and intermediate type (n = 13, 23.2%). CONCLUSIONS: If PI is too small or PT is too large to represent the actual sagittal alignment in patients with Castellvi type III and IV LSTVs, the selected S1 should be reconsidered. CLINICAL RELEVANCE: PI and PT measurements can be used to determine whether the optimum vertebral level of Castellvi type III and IV LSTV should be considered LLV or S1.

Changes in Lumbosacral Anatomy and Vertebral Numbering in Patients with Thoracolumbar and/or Lumbosacral Transitional Vertebrae.

The presence of a thoracolumbar transitional vertebra (TLTV) and/or lumbosacral transitional vertebra (LSTV) may cause wrong-site surgery and problems while measuring spinopelvic parameters, including pelvic incidence and lumbar lordosis. The Castellvi classification of LSTV addresses coronal images but not sagittal or axial images. Therefore, it is unclear how LSTV differs from the normal lumbosacral anatomy. We aimed to investigate the lumbosacral anatomy and vertebral numbering in patients with TLTV and/or LSTV. We performed computed tomography (CT) to identify TLTV, to number presacral vertebrae accurately, and to analyze morphological differences in each LSTV type. METHODS: The medical records of 880 patients who underwent spinopelvic fixation between July 2014 and March 2020 were evaluated for TLTV and LSTV. Castellvi LSTVs (above the promontory on the arcuate line of the ilium) and our newly proposed LSTV ("S6 LSTV," with 6 sacral vertebrae and 5 foramina below the promontory) were analyzed. The anatomical location of the lowest thoracic vertebra was defined, and TLTV with dysplastic ribs was identified. Each LSTV type was examined for its morphological features on sagittal and axial CT images. RESULTS: LSTV was observed in 111 (12.6%) of 880 patients. Castellvi type-III LSTV was the most common (42 [37.8%] of 111), followed by S6 LSTV (37 [33.3%] of 111). TLTV was associated with LSTV (87 [78.4%] of 111) and was commonly identified at T13 (59 [67.8%] of 87). On sagittal CT images, the lumbosacral transitional anatomy of Castellvi LSTVs resembled that of normal L5-S1, and the lumbosacral transitional anatomy of S6 LSTV resembled that of normal S1-S2. When comparing the S1 upper segments on axial CT images, most Castellvi LSTVs exhibited S2-like appearances and most S6 LSTVs exhibited L5-like appearances. CONCLUSIONS: Although LSTV possesses L5 and S1 features, Castellvi LSTVs have more L5 elements than S1 elements. The converse is true for S6 LSTV. At least for the Castellvi type-IIIb LSTV, the vertebra below the Castellvi type-IIIb LSTV should be recognized as S1, but clinically it is better to recognize it as S2. Overlooking TLTV may cause problems in vertebral numbering due to coexisting LSTV. CLINICAL RELEVANCE: Three-dimensional CT images are suitable for detecting transitional vertebrae. This study reveals their morphological features on axial CT images and their lumbosacral anatomy on sagittal CT images.

Intraoperative Neural Mobility and Postoperative Neurological Recovery in Anterior Cervical Decompression Surgery: Evaluation With Intraoperative Sonography.

STUDY DESIGN: A study using intraoperative sonography (IOS) was conducted for evaluating neural mobility in anterior cervical decompression surgery. OBJECTIVES: To analyze decompression status and mobility of the spinal cord and the nerve root during anterior cervical decompression and to clarify its relevance to the postoperative neurological recovery. SUMMARY OF BACKGROUND DATA: Several papers introduced the usefulness of IOS assessments; however, there have been no reports systematically evaluating the neural mobility in anterior cervical decompression surgery. METHODS: Eighty-four consecutive patients with compressive myelopathy who underwent anterior cervical decompression procedures were studied. The decompression status of the spinal cord was evaluated with IOS and classified into 3 grades according to the restoration pattern of the space ventral to the cord. Pulsatile motion of the spinal cord in cranio-caudal direction was named "sliding pulsation" and graded into 3 groups. The nerve root pulsation was also assessed using the IOS short-axis views. This study analyzed whether those neural mobility in anterior cervical decompression surgery had relevance to postoperative neurological recovery, which was assessed by the Japan Orthopaedic Association score. RESULTS: The mean recovery rate of the Japan Orthopaedic Association score was 59.1% in total. According to the decompression status in IOS, 67 patients who acquired space ventral to the spinal cord indicated 64.3% of the recovery rate which was significantly higher than 36.6% of the other patients on an average. As to the sliding pulsation of the cord, 10 patients who failed to show this particular motion indicated significantly lower recovery rate as 36.9%. In addition, 6 patients who did not exhibit nerve root pulsation indicated just 29.3% of recovery rate, and 4 of them failed to show the cord sliding motion. CONCLUSIONS: Sonographic evaluation during anterior cervical decompression surgery provided very useful information of neural decompression status that had significant correlation with postoperative neurological recovery.

A new performance test for cervical myelopathy: the triangle step test.

STUDY DESIGN: Our original performance test for evaluating the severity of cervical myelopathy, the triangle step test (TST), was introduced along with an assessment of its validity. OBJECTIVE: The TST was designed to evaluate the lower extremity motor function objectively and quantitatively. This study aimed to assess the validity of the test by analyzing the relation to the other analytic methods. SUMMARY OF BACKGROUND DATA: Several rating scales and performance tests have been proposed to evaluate the severity of cervical myelopathy. Simple walking test is useful; however, the test is limited for the patients who can walk safely. METHODS: Each subject sitting on a chair was instructed to step on marks at each apex of a triangular board and the number of steps in 10 seconds was counted for each foot. The subjects were 270 cervical myelopathy patients who had visited our hospital since 2002. As a control group, 60 healthy adults also underwent this test. All subjects were simultaneously evaluated by the Nurick score, the Japan Orthopedic Association score and the finger grip and release test. An assessment of the effect of surgery was analyzed for 94 patients who underwent surgical treatments. RESULTS: The mean of the lower count for each subject (TST score) in the control group was 25.4 +/- 3.7 steps, which was superior to 18.4 +/- 5.2 steps for myelopathy patients. TST score significantly correlated to the other analytic measures for cervical myelopathy. Regarding the effect of surgery, a performance of 16.7 +/- 4.5 steps before surgery improved to 21.2 +/- 4.9 steps at follow-up. Patients who could step more than 20 times before surgery, showed greater neurologic recovery. CONCLUSION: TST score correlated with other analytic methods for cervical myelopathy. This test is very useful to quantitatively evaluate lower extremity function and its improvement following surgical intervention.

Clinical results of intrapedicular partial pediculectomy for lumbar foraminal stenosis.

DESIGN: A retrospective case study of the use of intrapedicular partial pediculectomy (IPPP) to treat lumbar foraminal stenosis. OBJECTIVE: To evaluate the clinical results of lumbar foraminal stenosis treated with IPPP. SUMMARY OF BACKGROUND DATA: There is no gold standard for the surgical treatment of foraminal stenosis, which occurs in 8% of surgical cases of lumbar degenerative diseases. METHODS: A total of 26 patients who were followed up for a minimum of 2 years after IPPP for foraminal stenosis, were included in this study. The study group consisted of 20 men and 6 women with an average age at surgery of 63.3 years (range: 42 to 83) and a mean follow-up of 5.5 years (range: 2 to 11). The affected levels were L3/4 in 1 patient, L4/5 in 7, and L5/S1 in 18. Bilateral IPPP at L5/S1 was performed in 2 patients. The clinical results were evaluated according to the Japanese Orthopedic Association (JOA) scoring system. RESULTS: Two patients required revision surgery to correct insufficient decompression. In the remaining 24 patients, the average JOA scores were 6.7 (range: -1 to 10) before surgery, 12.4 (range: 9 to 15) 3 months after surgery, 12.3 (range: 9 to 15) 1 year after surgery, and 11.7 (range: 5 to 15) at the final follow-up. The average recovery rate was 62.1% (range: 40.0% to 81.3%). CONCLUSIONS: This follow-up study confirms that IPPP affords long-lasting improvements in leg symptoms for patients with lumbar foraminal stenosis.

Combined anterior-posterior fusion for cervical spondylotic myelopathy in patients with athetoid cerebral palsy.

OBJECT: Cervical spondylotic myelopathy (CSM) or myeloradiculopathy, frequent in adults with athetoid cerebral palsy, is a serious secondary disability in patients with an existing congenital handicap. Although several surgical procedures have been described for CSM in adults with athetoid cerebral palsy, none has had satisfying long-term results. The object of this study was to evaluate the effectiveness and safety of combined anterior-posterior fusion with wave-shaped rods and its influence on the stability of other spinal segments. METHODS: Twenty-three patients with CSM and athetoid cerebral palsy underwent posterior fusion with wave-shaped rods combined with anterior interbody fusion with internal fixation; 20 patients, 17 men and three women, were followed for more than 5 years. This procedure yielded good results. The mean follow-up period was 8.7 years (range 5-17 years). At 1-year follow-up examination, ambulation had improved in 12 patients. Upper-extremity pain, deltoid muscle weakness, and ability to self-feed improved in almost all patients. Myelopathy recurred in one patient 8.5 years after surgery. The mean motion angle at the adjacent level to the fixed segment did not change postoperatively, but the mean motion between C-1 and C-2 increased and slight atlantoaxial subluxation occurred postoperatively in five patients. CONCLUSIONS: Combined anterior-posterior fusion can effectively improve neurological function in patients with CSM and athetoid cerebral palsy, even in those with severe involuntary movements. Postoperative rigid external fixation is not required.