Atlantoaxial Rotatory Dislocation: Delayed Diagnose Will Result in More Invasive Treatment Options.

PURPOSE: The atlantoaxial joint represents the most mobile joint complex within the spine, secured by ligaments and capsules. Integrity of the atlantoaxial joint is crucial with respect to the mobility of the head and the upper spine. Atlantoaxial rotatory dislocation is the most common type of injury within this joint in children and is characterized by a typical position of the head (cock robin position). Nevertheless, this type of injury is frequently overlooked. The purpose of the current study was threefold. First, the characteristics of the patients with atlantoaxial dislocation were identified. Next, we checked if the time to treatment did influence the type of treatment. Finally, we checked if the age of the child at the time of treatment influenced the type of treatment. METHODS: Forty-four children, who were treated consecutively due to atlantoaxial dislocation at a single spine center between September 1993 and October 2018, are analyzed retrospectively regarding age, sex, symptoms, etiology, time to diagnosis, time to treatment, and outcome. RESULTS: Forty-four children (30 girls, mean age 8.9 years) were included in the study. The cock robin head position was found in all of them, but neurological deficits were not found in any of them. In 21 patients, dislocation was caused by previous infection (Grisel's syndrome), whereas in 19 patients, dislocation was due to minor trauma. In 4 cases, etiology remained unknown. Mean time to sufficient treatment was 178 days. Eighteen patients received closed reduction and immobilization after 57 days at mean. Open reduction followed by temporary fixation was done in 12 patients after a mean time gap of 188 days. Bony atlantoaxial fusion was necessary in 14 children, who were diagnosed after 319 days on average. Invasiveness of treatment was dependent on the time delay between development of dislocation and treatment; a significant difference was found between invasiveness of treatment and time to treatment (Kruskal-Wallis test, p < 0,05). Moreover, older children were treated significantly more often with fusion than younger ones (χ 2, p = 0,002). CONCLUSION: Young girls are predisposed to incur an atlantoaxial rotatory dislocation, which usually occurs due to minor trauma or infection. The cock robin position is characteristic, but neurological deficits are not common. There is a need for early and sufficient treatment because delayed treatment necessitates more invasive treatment, thus leading to a complete loss of function of the most mobile joint within the spine. Finally, older children are predisposed to more invasive treatment strategies.

Changes in Swallowing After Anterior Cervical Discectomy and Fusion With Instrumentation: A Presurgical Versus Postsurgical Videofluoroscopic Comparison.

Purpose: The purpose of this study was to explore the impact of anterior cervical discectomy and fusion (ACDF) with anterior instrumentation on swallowing function and physiology as measured on videofluoroscopic swallowing studies. Method: We retrospectively analyzed both functional measures (penetration-aspiration, residue) and physiological/anatomical measures (hyoid excursion, posterior pharyngeal wall thickness) in a series of 17 patients (8 men, 9 women, mean age 54 years). These measures were extracted from calibrated 5-ml boluses of thin radio-opaque liquids on both pre-ACDF and post-ACDF videofluoroscopies, thus controlling for individual variation and protocol variation. Results: After ACDF surgery, we found significant within-subject worsening of Penetration-Aspiration Scale (Rosenbek, Robbins, Roecker, Coyle, & Wood, 1996) scores, vallecular (but not piriform sinus) residue, superior (but not anterior) hyoid excursion, and posterior pharyngeal wall thickness. Results are discussed in the context of previous literature. Conclusions: ACDF surgery can affect both physiological/anatomical and functional measures of swallowing. Future research should expand to other biomechanical and temporal variables, as well as greater bolus volumes and a wider array of viscosities and textures.

C1-C2 Instrumentation According to Harms/Goel in Case of Vertebral Artery below the Arch of C1: A Case Report.

Study Design Case report. Background and Study Aims For stabilizing surgery of the atlantoaxial region, a precise evaluation of the course of the vertebral artery (VA) is essential to avoid vessel injury and life threatening complications. In patients with aberrant VA course, an appropriate way for fusion needs to be found. This article presents a case of an unusual VA course and illuminates the importance of surgical planning with computed tomography angiography identifying VA variations at the atlantoaxial region. Case Report A 71-year-old woman with atlantoaxial arthrosis had a VA variation (persistent first intersegmental artery). She underwent C1-C2 posterior fixation according to Harms/Goel using the typical entry points, requiring VA dissection in caudal direction. The postoperative clinical as well as radiographic result was excellent. Angiography 6 months postoperatively showed the VAs below the C1 screws with normal blood flow. Conclusions Placement of C1 screws in a patient with a persistent first intersegmental VA is possible. Careful VA dissection is the key step for safe screw placement, screw anchoring, and clinical success.

Implant complications, fusion, loss of lordosis, and outcome after anterior cervical plating with dynamic or rigid plates: two-year results of a multi-centric, randomized, controlled study.

STUDY DESIGN: Prospective, controlled, randomized, multicenter study. OBJECTIVE: To analyze implant complications and speed. SUMMARY OF BACKGROUND DATA: Rigid plate designs, in which the screws are locked to the plate, are in common use and thought to provide more fixation than dynamic designs, in which the screws may glide when the graft is settling. The aim of the study is to analyze (1) implant complications, (2) speed of fusion, (3) loss of lordosis, and (4) clinical outcome in both types of plates. METHODS: One hundred thirty-two patients were included and assigned by randomization to one of the groups in which they received a routine anterior cervical discectomy and autograft fusion with either a dynamic plate (ABC, study group) or a rigid plate (CSLP, control group). At discharge, after 3 and 6 months and finally after 2 years, implant complications, segmental mobility, absence of radiolucencies, absence of bone sclerosis, evidence of bridging trabecular bone, loss of lordosis, Visual Analog Scale (VAS) and Neck Disability Score were recorded. All radiographic measurements were performed by an independent radiologist. RESULTS: There have been 4 patients with implant complications within the control group and no implant complications within the study group, P = 0.045. Mean segmental mobility before discharge for the study group was 1.7 mm, 1.4 mm after 3 months, 0.8 mm after 6 months, and 0.4 mm after 2 years. For the control group, these values were 1.0, 1.8, 1.6, and 0.5 mm. The difference at 6 months between both groups was significant (P = 0.024). Neither absence of radiolucencies, nor absence of sclerosis, nor evidence of bridging bone showed significant differences between the 2 groups through the postoperative follow-up (P > 0.05). The loss of segmental lordosis for the study group with respect to intraoperative radiograph was 1.3 degrees at discharge and 4.3 degrees after 2 years. For the control group, these values were 0.9 degrees , 0.7 degrees . The difference at 2 years was significant (P = 0.003). Clinical postoperative outcome (VAS and ODI) was not different between the 2 groups through the postoperative follow-up (P > 0.05). CONCLUSION: Dynamic cervical plate designs provide less implant complications (no patient) compared with rigid plate designs (4 patients). Speed of fusion was faster in the presence of a dynamic plate. However, loss of segmental lordosis is significantly higher if dynamic plates are used, which did not result in differences regarding clinical outcome between dynamic and constrained plates after 2 years. Thus, dynamic plates should be considered to be the preferred treatment option because of the lower risk for implant failure-related revision surgery.

Application of a calibration method provides more realistic results for a finite element model of a lumbar spinal segment.

BACKGROUND: An important step in finite element modeling is the process of validation to derive clinical relevant data. It can be assumed that defect states of a finite element model, which have not been validated before, may predict wrong results. The purpose of this study was to show the differences in accuracy between a calibrated and a non-calibrated finite element model of a lumbar spinal segment for different clinical defects. METHODS: For this study, two geometrically identical finite element models were used. An in vitro experiment was designed, deriving data for the calibration. Frequently used material properties were obtained from the literature and transferred into the non-calibrated model. Both models were validated on three clinical defects: bilateral hemifacetectomy, nucleotomy and interspinous defects, whereas in vitro range of motion data served as control points. Predictability and accuracy of the calibrated and non-calibrated finite element model were evaluated and compared. FINDINGS: Both finite element models could mimic the intact situation with a good agreement. In the defects, the calibrated model predicted motion behavior with excellent agreement, whereas the non-calibrated model diverged greatly. INTERPRETATION: Investigating the biomechanical performance of implants and load distribution of different spinal structures by numerical analysis requires not only good agreement with the intact segment, but also with the defect states, which are initiated prior to implant insertion. Because of more realistic results the calibration method may be recommended, however, it is more time consuming.

Cervical spine disc prosthesis: radiographic, biomechanical and morphological post mortal findings 12 weeks after implantation. A retrieval example.

There is a gap between in vitro and clinical studies concerning performance of spinal disc prosthesis. Retrieval studies may help to bridge this gap by providing more detailed information about motion characteristics, wear properties and osseous integration. Here, we report on the radiographic, mechanical, histological properties of a cervical spine segment treated with a cervical spine disc prosthesis (Prodisc C, Synthes Spine, Paoli, USA) for 3 months. A 48-year-old male received the device due to symptomatic degenerative disc disease within C5-C6. The patient recovered completely from his symptoms. Twelve weeks later, he died from a subarachnoid hemorrhage. During routine autopsy, C3-T1 was removed with all attached muscles and ligaments and subjected to plain X-rays and computed tomography, three dimensional flexibility tests, shear test as well as histological and electronic microscopic investigations. We detected radiolucencies mainly at the cranial interface between bone and implant. The flexibility of the segment under pure bending moments of +/-2.5 Nm applied in flexion/extension, axial rotation and lateral bending was preserved, with, however, reduced lateral bending and enlarged neutral zone compared to the adjacent segments C4-C5, and C6-C7. Stepwise increase of loading in flexion/extension up to +/-9.5 Nm did not result in segmental destruction. A postero-anterior force of 146 N was necessary to detach the lower half of the prosthesis from the vertebra. At the polyethylene (PE) core, signs of wear were observed compared to an unused core using electronic microscopy. Metal and PE debris without signs of severe inflammatory reaction was found within the surrounding soft tissue shell of the segment. A thin layer of soft connective tissue covered the major part of the implant endplate. Despite the limits of such a case report, the results show: that such implants are able to preserve at least a certain degree of segmental flexibility, that direct bone implant contact is probably rare, and that debris may be found after 12 weeks.