Masanori Izeki

Reduction of atlantoaxial subluxation causes airway stenosis.

Study Design. A cross-sectional study. Objective. The purpose of this study was to investigate the effect of reduction of anterior atlantoaxial subluxation (AAS) on the oropharyngeal airway space. Summary of Background Data. Our previous studies have shown that reduction of the occipito-C2 angle (O-C2A) makes the mandible shift posteriorly, resulting in oropharyngeal airway stenosis, which occasionally causes postoperative dysphagia after occipitocervical fusion. Based on this background, we hypothesized that reduction of AAS would also cause oropharyngeal airway stenosis independent of the O-C2A, because it also shifts the mandible posteriorly. To our knowledge, there are no data demonstrating an association between reduction of AAS and the oropharyngeal airway space. Methods. The authors prospectively evaluated 64 patients with rheumatoid arthritis. We analyzed lateral cervical plain radiographs of 5 different positions (neutral, flexion, extension, retraction, and protrusion), and measured the O-C2A, C2–C6 angle, anterior atlantodental interval, anteroposterior distance of the narrowest oropharyngeal airway space (nPAS), and so on. The subjects were classified into 2 groups: group R comprised patients with a “reducible AAS” in dynamic cervical movement, and group N comprised “patients without AAS” patients. Results. In the multiple regression analysis, the change in the O-C2A was the only significant independent variable related to the percentage change in the nPAS from the neutral position in group N. On the contrary, the change in the anterior atlantodental interval and change in the O-C2A were significantly related to the percentage change in the nPAS in group R. No cases in group N and 7 cases (28%) in group R showed a paradoxical decrease in the nPAS in extension, in which the O-C2A is largest and reduction of AAS is obtained. Conclusion. Reduction of AAS has a negative effect on the oropharyngeal airway space. Therefore, reduction of AAS during occipitocervical fusion may cause postoperative dysphagia despite maintenance of the O-C2A. Level of Evidence: 2

Does the formation of vertebral endplate cysts predict nonunion after lumbar interbody fusion

Study Design. A retrospective study was conducted to investigate the impact of vertebral endplate cyst formation on union status after lumbar interbody fusion. Objective. To assess the impact of cyst formation at the vertebral endplate in the early detection of nonunion after lumbar interbody fusion. The relationship between vertebral endplate cyst formation and subsequent union status was evaluated retrospectively using dynamic x-ray and computed tomography (CT) and multiplanar reconstruction. Summary of Background Data. Although many studies have reported on the assessment of bony union after lumbar interbody fusion, no study has reported on the radiological risk factors for nonunion in the early postoperative period. The meaning and importance of vertebral endplate cyst formation have not been reported and should be clarified. Methods. Radiological vertebral endplate changes at 93 levels were assessed in 76 patients after transforaminal lumbar interbody fusion, using a titanium cage with pedicle screw fixation. Computed tomographic findings for the vertebral endplate at 3 months were compared between nonunion and union cases. The relationship between vertebral endplate cyst formation and union status was tested statistically. Results. Fifty-nine union cases were compared with 17 nonunion cases. The overall union rate was 75.2% at 1 year and 82.8% at 2 years. At 1 year, the sensitivity of cyst formation for subsequent nonunion was 69.6%, specificity was 100%, positive predictive value was 100%, and negative predictive value was 90.9%. Multivariate logistic regression analysis showed that a multioperated back was a significant predictor of cyst formation (odds ratio [OR]: 3.8; 95% confidence interval [CI]: 1.1–13.1) and that cyst formation and multioperated back were significant predictors of nonunion (OR: 12.3; 95% CI: 1.8–133 and OR: 116; 95% CI: 22.4-infinity, respectively). Conclusion. These findings show a relationship between vertebral endplate cyst formation in the early postoperative period and nonunion after lumbar interbody fusion. Endplate cyst formation is a useful early predictor of subsequent nonunion.

Utility of the analysis of intracranial venous sinuses using preoperative computed tomography venography for safe occipital screw insertion.

Study Design. Prospective descriptive study. Objective. To verify the feasibility and utility of evaluating venous sinuses (VSs) using computed tomography venography (CTV) concomitant with preoperative CT angiography (CTA) for safe occipital screw fixation. Summary of Background Data. Preoperative evaluation of the vertebral artery by CTA is indispensable in occipitocervical spinal instrumentation surgery. Despite accumulating evidence showing the potential of CTV, no studies have reported the usefulness of concomitant use of CTV and CTA before placement of occipital plate-screw constructs. Methods. We analyzed 30 consecutive patients who underwent CTV simultaneously with CTA. First, we investigated VS anatomy in individual cases and classified the continuity patterns of relevant VSs. Subsequently, we evaluated the probable risk zones for VS injury, from the viewpoint of occipital screw insertion. Results. VSs can be clearly visualized using CTV simultaneously with CTA examination without significant increase of radiation exposure or extra workload for radiographical technicians. VS continuity was classified into 4 categories: the confluence type (n = 9), bifurcation type (n = 8), transverse type (n = 11), and others (n = 2). The confluence of sinuses and their relevant VSs were greatly variable between individuals, and occasionally, some cases with high-risk morphology for VS injury in occipital screw placement were observed. Conclusion. Our findings indicate that there is no universal position for safe insertion of occipital screws that is applicable to all individuals. It is risky to determine optimal screw placement, only on the basis of traditional cadaveric information such as occipital bone thickness and several external bony landmarks. Spine surgeons must recognize that VS injury may occasionally lead to life-threatening complications. The detailed information on VSs obtained by preoperative CTV examination combined with CTA in individual cases can be useful in preoperative planning and can contribute greatly to the improvement of surgical safety. Level of Evidence: 2

Quantification of changes in gait characteristics associated with intermittent claudication in patients with lumbar spinal stenosis.

Study Design: Cross-sectional observational study. Objective: To quantify changes in gait characteristics associated with claudication after continuous walking, and to investigate the relationship between walking capacity and gait characteristics in patients with lumbar spinal stenosis (LSS). Summary of Background Data: Walking difficulty due to pain or neurological symptoms accompanied by continuous walking may have negative effects on gait characteristics in patients with LSS. However, there are few detailed reports on the association of these changes with intermittent claudication and their relationship with walking capacity. Methods: For this study, 11 LSS patients with intermittent claudication were recruited. The subjects continued walking until they expressed a difficulty in continuing further. Postural sway, autocorrelation peak (AC), stride frequency (SF), and coefficient of variance (CV) were analyzed using accelerometers. To detect changes in gait parameters, we compared acceleration at the start and at the end of the walking task. Results: Walking difficulty during the test increased from 4 (interquartile range, 1–5) to 9 (interquartile range, 7–10). The postural sway significantly increased after the onset of maximum walking difficulty. AC, SF, or CV did not show significant change. Maximum walking distance significantly correlated with postural sway at the cervical sensor (r=−0.64), and CV (&rgr;=−0.66), an index of gait variability, at the beginning of the walking task. Conclusions: The change in gait parameters associated with claudication during continuous walking is detectable using accelerometers. Postural sway increases after the provocation of walking difficulty due to pain or neurological symptoms. In addition, walking capacity correlated with postural sway of the upper trunk and gait variability during walking initiation. This methodology warrants further studies to confirm its usefulness as an assessment tool for patients with LSS.

The reinforcement of a C2 laminar screw by a C2 laminar hook as an anchor of occipito-C2 fusion

Abstract Although a C1–C2 transarticular screw (TAS) or a C2 pedicle screw (PS) is the most rigid anchor for C2, each entails the risk of vertebral artery injury. Although a C2 laminar screw (LS) is often used as an alternative anchor in such cases, its anchoring strength may be inadequate. We introduce a technical tip, in which a C2 LS is reinforced by a C2 infralaminar hook without extending the fusion range. Six patients, for whom a unilateral TAS or C2 PS was risky or impossible, were treated with O-C2 fusion using this technique. The post-operative course of each patient was uneventful. Bone union was achieved in all patients, except one who died of indifferent disease before the confirmation of bone union by computed tomography. This method would be a safe and non-technical-demanding option when the placement of a TAS or PS is risky or impossible.

Cementing Technique for THA Sockets Using Bone Cement and HA Granules: Modified-IBBC

In this report, the middle-term clinical and radiographic results were investigated in total hip arthroplasty (THA) cases using PMMA bone cement and hydroxyapatite (HA) granules (modified interfacial bioactive bone cement technique; M-IBBC). 76 hip joins (69 cases) were operated between June 2010 and September 2012, and followed. The minimum follow-up period was 4.5 years, the average follow-up was 5.5 years and average age at operation was 67.4 years. Revision was not performed. Average Japanese orthopaedic association (JOA) score improved from 45 to 88. Socket loosening was not observed radiographically. X-p findings of sockets demonstrated radiolucent line in the outer part of Zone 1 (designated Zone 1a in this report) in 1.3% immediately after the operation, and 6.6% at 1 year postoperatively. After 2 years progressive changes were not observed. The improvement of radiolucent line was observed in two cases at 3 years postoperatively and radiolucent line in Zone 1a was observed in 3.9%. These findings suggested that osteoconductivity of HA granules was maintained after the operation.

Radiographic Changes Observed in THA Cemented Sockets Using Bone Cement and Hydroxyapatite Granules

The middle-term clinical and radiographic results were investigated in total hip arthroplasty (THA) cases using bone cement and hydroxyapatite (HA) granules (the interfacial bioactive bone cement technique; IBBC). 42 hip joins (39 cases) were operated between October 2005 and July 2007, and followed. The minimum follow-up was 6 years, average follow-up period was 7.0 years and average age at operation was 67 years. One revision was performed due to late infection. Average Japanese orthopaedic association (JOA) score improved from 48 to 87. Socket loosening was not observed radiographically. X-p findings of sockets demonstrated radiolucent line in the outer part of Zone 1 in 12% immediately after the operation, 24% at 2 years postoperatively. After 2 years there was no progressive change, however, improvement of radiolucent line (gap filling) with bone remodeling was observed in three cases after 3 years postoperatively.