Combined Percutaneous and Endovascular Treatment of Symptomatic Aneurysmal Bone Cyst of the Spine: Clinical Six Months. Follow-up of Six Cases

We describe the usefulness of endovascular and direct percutaneous treatment as a therapy option for aneurysmal bone cysts (ABCs) of the spine. From January 2007 to December 2008, we treated six consecutive patients with symptomatic ABCs resistant to continuous medical management or with acute clinical onset of paraparesis at cervical, thoracic and lumbar spine level. Two patients were treated after emergency laminectomy. All patients were studied with an MRI protocol and multidetector CT with MPR reconstructions followed by angiographic control before treatment. The procedure was performed under general anaesthesia for all patients. Under CT or fluoroscopy guidance, percutaneous treatment was performed either by direct injection of Glubran(®) diluted at 30% with Lipiodol(®) only, or combined with endovascular treatment by Onyx® injection. Clinical and X-ray follow-up was performed at three and six months. Combined endovascular and percutaneous treatment for ABCs was successful and led to an excellent outcome in five out of six patients with clinical improvement. There were no periprocedural or subsequent clinical complications and the glue resulted in successful selective permanent occlusion with intralesional penetration. Direct sclerotherapy resulted in immediate thrombosis of the malformation with no progression of symptoms. Complete healing was observed in five out of six aggressive lesions. No major complications were noted. At six month follow-up the symptoms had completely resolved and X-ray control showed a partial or total sclerotic reaction of the lesion with stable clinical results (no partial or clinical abnormalities). One patient had a recurrence of the ABC with spinal cord cervical clinical symptomatology. Combined endovascular and percutaneous treatment or direct percutaneous sclerotherapy with glue alone are important, safe, effective therapy options for symptomatic aneurysmal bone cyst. Results are stable and confirmed by clinical and X-ray follow-up six months after treatment.

Narrow band imaging for detecting superficial squamous cell carcinoma of the head and neck in patients with esophageal squamous cell carcinoma

BACKGROUND AND STUDY AIMS

Narrow band imaging combined with magnifying endoscopy (NBI-ME) is useful for the detection of superficial squamous cell carcinoma (SCC) within the oropharynx, hypopharynx, and oral cavity. The risk of a second primary SCC of the head and neck is very high in patients with esophageal SCC. This prospective study evaluated the detection rate of superficial SCC within the head and neck region (superficial SCCHN) with NBI-ME in patients with esophageal SCC.

PATIENTS AND METHODS

Between March 2006 and February 2008, 112 patients with a current or previous diagnosis of esophageal SCC were enrolled. All patients underwent endoscopic screening of the head and neck by NBI-ME. The primary end point was the detection rate for superficial SCCHN. Secondary end points were to compare demographic characteristics between patients with and without superficial SCCHN and to assess the clinical course of patients with superficial SCCHN.

RESULTS

The detection rate for superficial SCCHN was 13 % (15/112). The prevalence of multiple Lugol-voiding lesions, observed endoscopically throughout the esophageal mucosa after application of Lugol dye solution, was significantly higher in patients with superficial SCCHN than in those without (100 % vs. 24 %, P < 0.0001). Minimally invasive curative treatment with organ preservation was feasible without severe complications in patients with superficial SCCHN after curative treatment of esophageal SCC.

CONCLUSIONS

In patients with esophageal SCC, NBI-ME is useful for detecting superficial SCCHN, thereby facilitating minimally invasive treatment.

Vertebroplasty as a Treatment for Primary Benign or Metastatic Cervical Spine Lesions: Up to One Year of Follow-up

This paper illustrates the validity of vertebroplasty (VP) in patients with primary benign or metastatic lesion in the cervical spine. From January 2006 to December 2007, ten consecutive patients were treated with VP for a total of ten vertebral bodies: two symptomatic vertebral haemangiomas at C5 and C4.3, multiple myeloma at C2 (two cases) and one case at C4, five patients with vertebral metastasis from breast or lung cancer at C2, C4 (three cases) and C5. All the patients complained of pain resistant to continuous medical management. All procedures were performed under general anaesthesia by anterolateral approach under CT or fluoroscopy control with manual dislocation of the carotid axis. A transoral approach under fluoroscopy was performed to treat the C2 lesion. Bone biopsy was never performed. VP was performed to prevent fracture after implantation of a double discal prothesis in two patients. For patients with multiple myeloma, VP was performed to prevent new vertebral fracture. VP was performed before of radiotherapy in three patients with metastasis, and just after radiotherapy in two. Two metastatic patients were lost at one year follow-up due to death from systematic diffusion. Results were evaluated on the Visual Analogue Scale (VAS) and the Oswestry Disability Index (ODS). A successful outcome was observed with a complete resolution or partial reduction of pain in 90% of patients 24-72 hours after VP. At 12 months follow-up, we recorded a reduction of four points in the VAS evaluation and a 45% reduction in the ODS score. No extravertebral vascular or discal cement leakage was observed. At 12 months, X-ray follow-up showed a stable result. Percutaneous treatment with VP for benign or malignant cervical spine lesions is a valuable, mini-invasive and quick method that allows a complete and enduring resolution of painful vertebral symptoms without fracture of the adjacent or distal vertebral bodies.

The epidemiology of ovarian granulosa cell tumors: a case-control study

OBJECTIVE

This study identified risk factors for ovarian granulosa cell tumors (GCT) through a case-control study comparing women with GCT to women with epithelial ovarian cancers (OC) and general population (GP) controls.

METHODS

Women with GCT and OC were identified from our hospital tumor board and the Massachusetts and New Hampshire Statewide Cancer Registries between January, 1988 and November, 2008. Age, gender and county matched GP controls were identified through town books in Massachusetts and drivers' license lists in New Hampshire. Epidemiologic factors including age, race, obesity, pregnancy history, smoking, and family history were evaluated. Odds ratio (OR) was calculated and adjusted for race and age.

RESULTS

Seventy-two women with GCT, 1578 GP controls, and 1511 OC controls were identified. Patients with GCT were significantly more likely to be non-white (OR 8.49; 4.07, 17.7), obese with a BMI >30 (OR 5.80; 3.01, 11.2), and have a family history of breast (OR 2.13; 1.19, 3.80) or ovarian cancer (OR 2.89; 1.08, 7.72) than GP controls. The risk of developing GCT was significantly decreased in women who smoked (OR 0.46; 0.27, 0.78), used oral contraceptive pills (OR 0.32; 0.17, 0.63) or were parous with 1-2 (OR 0.30; 0.16-0.56) or greater than 2 births (OR 0.50; 0.27, 0.94) when compared to GP controls.

CONCLUSION

These findings suggest an independent association between non-white race and obesity as a hyperestrogenic state in the development of GCT while parity and OCP use may be protective. An unknown familial predisposition for GCT may exist.

Management of vertebral re-fractures after vertebroplasty in osteoporotic patients

SUMMARY

This study illustrates the usefulness of vertebral biopsy in osteoporotic patients previously treated with vertebroplasty (VP) who present at follow-up with a new fracture in a vertebral soma adjacent or distant from the collapsed vertebral body. Five hundred and fifty patients with osteoporotic vertebral collapse underwent a minimally invasive treatment with vertebroplasty (VP) for a total of 980 vertebral bodies. The approach was unipedicular in 520 patients and bipedicular in 30. Only cases with unclear findings at MR or CT (23 patients) were scheduled for a vertebral biopsy before VP treatment. The biopsy results were positive for haematological disease in only eight patients. A vertebral biopsy was carried out during re-treatment with VP in all patients who presented a vertebral refracture in the three month follow-up at a site adjacent to or distant from the previously treated vertebra (21 patients). We have found new fractures of adjacent vertebrae in 15 patients and new fractures of distant vertebrae in 16 patients at three month follow-up examination. Five of the 31 cases (16%) of spinal refracture, where during vertebroplasty treatment a bone biopsy and a sternal medullary aspiration had been carried out, an anatomopathological response to multiple myeloma was responsible for the refracture. It is useful to perform a spinal bone biopsy during re-treatment of the vertebroplasty procedure to rule out multiple myeloma or other disease as the cause of the new collapse in patients with osteoporotic disease presenting a new vertebral fracture in an adjacent or distant site from the previously collapsed vertebral body.

A comparison of minimally invasive techniques in percutaneous treatment of lumbar herniated discs. A review

Low back pain is the commonest spine disease causing absence from work in developed countries. Low back pain with classical irradiation along the course of the nerve root affected is more frequently due to disc disease. In 60-80% of patients with herniated disc, radicular symptoms disappear with conservative treatment after about six weeks, the remainder are treated surgically with a 2-6% of incidence of true recurrence of herniation post-intervention and with failed back surgery syndrome in 15% of cases. Recently minimally invasive techniques have developed as "alternative" treatments to surgical intervention. This review aimed to assess the pathogenesis of low back pain caused by lumbar disc hernia as a basis for action of minimally invasive techniques; to illustrate the techniques already used or currently in use, to compare them in technical guidance, indications and complications, exposing for each of them the inclusion/exclusion criteria in enrolling patients and the imaging guide technique of choice. Minimally invasive techniques can be a valuable alternative to traditional surgery with low cost, low risk of complications, easy feasibility, and in the event of failure they do not exclude subsequent surgery.

Vertebroplasty as treatment of aggressive and symptomatic vertebral hemangiomas: up to 4 years of follow-up

INTRODUCTION

This study aimed to illustrate the validity of the treatment with vertebroplasty (VP) in patients with aggressive or symptomatic vertebral hemangioma (VH) with or without epidural extension.

METHODS

From January 2003 to December 2007, 24 consecutive patients have been treated with VP, for a total of 36 vertebral bodies affected by VH: two cervical, ten dorsal, 24 lumbar. All the patients complained of a pain syndrome resistant to continuous medical medication; four of 24 patients also presented aggressive magnetic resonance features of the vertebral lesion and two patients showed also epidural extension. A unipedicular approach has been performed in 16 patients; a bipedicular approach has been performed in six, while for the cervical spine an anterior-lateral approach with manual dislocation of the carotid axis has always been performed. Bone biopsy was never done. All procedures have been carried out with local anesthesia, except for the treatment of the cervical hemangiomas which has always been performed under general anesthesia. Four vertebral bodies in the same session have been treated in one case.

RESULTS

Results have been evaluated with the visual analog scale and the Oswestry Disability Index methods. In all the patients, in the following 24-72 h, a successful outcome has been observed with a complete resolution of pain symptom. Extravertebral vascular or discal cement leakage has been observed in four patients, without any onset of clinical radicular syndrome due to epidural diffusion. Clinical and radiological follow-up until 4 years has been performed in 12 patients and it showed stability of the treatment and absence of pain.

CONCLUSIONS

Percutaneous treatment with VP for aggressive and symptomatic vertebral hemangiomas even with epidural extension is a valuable, mini-invasive, and quick method that allows a complete and enduring resolution of the painful vertebral symptoms without findings of fracture of a vertebral body adjacent or distant to the one treated.

Effects of urine pH modification on pharmacokinetics of phenobarbital in healthy dogs

Although pH modification is one of the effective strategies for dissolving or preventing uroliths, little is known about its effects on the pharmacokinetics of phenobarbital in dogs. Five spayed, female Beagles were fed with a twice-daily diet that included potassium citrate and ammonium chloride for urine alkalinization and acidification, respectively. After a stabilizing period of 7 days, a single clinical dose of phenobarbital (3 mg/kg) was orally administered, and time-course changes in its serum and urine concentrations were determined by high-performance liquid chromatography. Total amounts of unchanged phenobarbital excreted into urine for 216 h were decreased by urine acidification and increased by urine alkalinization. The elimination half-life of serum phenobarbital in dogs with urine alkalinization was shortened and Cl(R) increased when compared with dogs with urine acidification. Other pharmacokinetic parameters, including C(max), T(max), AUC(0-216), Cl/F, and A(e0-216) were not changed by modification of the urine pH. These results suggest that the pH of urine is likely to be a determinant of the pharmacokinetics, especially urine excretion rate, of a clinical dose of oral phenobarbital. It is possible that the serum concentration of phenobarbital might be altered when a pH modifying-diet is administered for the purpose of dissolving or preventing uroliths.

Vertebroplasty and kyphoplasty: friends or foes?

PURPOSE

This paper aims to compare vertebroplasty and kyphoplasty by illustrating the two techniques, analysing the results and discussing the indications in relation to the type of fracture.

MATERIALS AND METHODS

Vertebroplasty was performed on 805 vertebral bodies in 485 patients affected by osteoporosis (310), metastasis (160) and vertebral haemangioma (15). The approach was unipedicular in 365 patients and bipedicular in 120 patients. Biopsies were obtained in patients with no known primary cancer (75). Kyphoplasty was performed in 39 patients with Magerl type A1 and A3 fractures within 3 months from the trauma. A bipedicular approach was used in all cases.

RESULTS

Outcomes were assessed on the basis of the visual analogue scale and the Oswestry Disability Index. In patients treated with vertebroplasty, success rates at 24-72 h were 90% for osteoporotic fractures, 100% for vertebral haemangiomas and 77% for metastatic fractures. Extravertebral vascular or discal leakage of cement occurred in 39 patients, but only two of them reported radicular pain due to epidural involvement. Osteoporotic patients developed new vertebral fractures at adjacent levels in 25 cases and at distal levels in 19 cases. In patients treated with kyphoplasty, pain relief was achieved within one month after treatment in 90% of cases. None of the patients wore orthotic braces after treatment, and no vertebral collapse was observed.

CONCLUSIONS

Vertebroplasty and kyphoplasty are both useful in the management of vertebral pain. In light of our experience, vertebroplasty is better indicated for vertebral fractures due to osteoporosis, haemangioma or metastasis on account of its simplicity and minimal invasiveness. Kyphoplasty is suggested in acute traumatic fractures of type A1 and A3 according to Magerl, as it allows recovery of vertebral stability and a better distribution of the cement.

Long-term results of salvage endoscopic mucosal resection in patients with local failure after definitive chemoradiotherapy for esophageal squamous cell carcinoma

BACKGROUND AND STUDY AIMS

Local failure after definitive chemoradiotherapy (CRT) in patients with esophageal cancer remains one of the major problems in finding a cure. Endoscopic mucosal resection (EMR) is one treatment option when failure lesions are superficial. However, there are no relevant long-term survival data. The aim of this study was to clarify the long-term survival of salvage EMR.

PATIENTS AND METHODS

Between January 1998 and March 2004, 289 patients with esophageal squamous cell carcinoma were treated with definitive CRT at the National Cancer Center Hospital East, Japan. Of these 289 patients, 21 patients with local failure without lymph-node or distant metastases were treated with salvage EMR. The technique of salvage EMR involved a strip biopsy method. We retrospectively analyzed the long-term survival data for the patients who underwent salvage EMR.

RESULTS

At a median follow-up period of 54 months (range, 16-108 months), eight of 21 patients (38%) were alive with no recurrence and two patients had died from another disease but with no recurrence of esophageal cancer. Local recurrence after EMR was detected in four patients, with local and lymph-node recurrence in two patients, and lymph-node and/or distant metastases in five patients. The 5-year survival rate from the initiation of salvage EMR was 49.1%. There were no severe complications associated with EMR.

CONCLUSION

EMR is one of the curative salvage treatment options for local failure after definitive CRT, if the failure lesion is superficial and there are no lymph-node or distant metastases.

Narrow band imaging with magnifying colonoscopy as diagnostic tool for predicting histology of early colorectal neoplasia

BACKGROUND

The presence of abnormal microcapillaries detected by narrow band imaging (NBI) with magnifying colonoscopy has been reported to be a marker of colorectal neoplasia.

AIM

To investigate prospectively if NBI with magnification could help predict the histology of early colorectal neoplasia.

METHODS

A series of 104 consecutive patients with 139 colorectal lesions were studied. All lesions were detected by conventional colonoscopy and subsequently evaluated by NBI with magnification. During NBI with magnification, the microvascular architecture observed on the surface of the detected lesions, capillary patterns (CP), was divided into non-neoplastic (CP I) and neoplastic (CP II and CP III) types. Only lesions endoscopically diagnosed as CP II or CP III were included in the study. All of the lesions were resected endoscopically or surgically and examined histologically for comparison.

RESULTS

Ninety-seven per cent (n = 103) of colorectal neoplastic lesions with CP II were histologically diagnosed as low-grade dysplasia. Eighty-seven per cent (n = 31) of the colorectal neoplastic lesions with CP III were high-grade dysplasia or invasive cancer.

CONCLUSION

Capillary patterns observed by NBI with magnification could be used to assess the degree of atypia in early colorectal neoplasia.

Subcortical ischaemic changes in young hypertensive patients: frequency, effect on cognitive performance and relationship with markers of endothelial and haemostatic activation

Information on subcortical ischaemic changes (SIC) in young hypertensive patients is scarce. We evaluated the frequency of SIC at magnetic resonance imaging (MRI), the possible effect on cognition of these patients, and the role of plasma markers known as indicators of endothelial and haemostatic activation. Inclusion criteria were age <or=54 years, hypertension for at least 2 years and absence of cerebrovascular disease or other conditions possibly related to SIC. Patients with SIC at MRI and two control groups (matched for age, sex and education) of hypertensive patients without SIC and non-hypertensive healthy subjects underwent an extensive neuropsychological examination and evaluation of plasma markers. Amongst the 200 patients evaluated, 50 (25%) showed SIC at MRI. Mean age was 48.4 +/- 4.8 years. Compared with both control groups, hypertensive patients with SIC performed significantly worse in general cognition, attention, memory and executive functions. Moreover, they showed significantly more often increased levels of all plasma markers compared with healthy controls, and of von Willebrand factor (vWF) compared with both control groups (P < 0.001). In young hypertensive patients SIC are frequent, related to a worse cognitive performance and endothelial dysfunction. Our findings suggest vWF as marker of end-organ damage, underscoring the relevance of treating hypertension at younger age.

Quantitative analysis of Malassezia in the scale of patients with psoriasis using a real-time polymerase chain reaction assay

BACKGROUND

It has been suggested that Malassezia is associated with the development of skin lesions in psoriasis because of the response of the scalp lesions in psoriasis to antifungal agents. Malassezia restricta and M. globosa are the two major members of the cutaneous Malassezia flora in patients with psoriasis, although they have not been analysed quantitatively.

OBJECTIVES

This study quantified the two major cutaneous Malassezia species in psoriatic scale from different body sites using a real-time polymerase chain reaction (PCR) assay.

METHODS

Scale samples were collected from lesional and nonlesional skin of 20 Japanese patients with psoriasis and fungal DNA was extracted from the samples directly. All the Malassezia species, including the two major species M. globosa and M. restricta, were quantified with high accuracy, using a real-time PCR assay.

RESULTS

Colonization by M. restricta was approximately five times higher at all body sites than colonization by M. globosa. Malassezia colonization was significantly lower in patients with hyperlipidaemia than in patients with normolipidaemia.

CONCLUSIONS

Malassezia restricta is the predominant species in psoriatic scale.

Clinical outcome after endoscopic mucosal resection for esophageal squamous cell carcinoma invading the muscularis mucosae--a multicenter retrospective cohort study

BACKGROUND AND STUDY AIMS

Endoscopic mucosal resection (EMR) is now commonly indicated for esophageal squamous cell carcinoma (ESCC) within the lamina propria mucosa. However, EMR for ESCC that has invaded the muscularis mucosa is controversial because the risk of lymph node metastasis is not negligible. We conducted a multicenter retrospective cohort study to investigate the incidence of lymph node metastasis and survival after EMR for ESCC invading the muscularis mucosa.

PATIENTS AND METHODS

A total of 104 patients with 111 lesions invading the muscularis mucosa, were retrospectively studied at eight institutes. No patients exhibited evidence of metastasis of lymph nodes or distant organs prior to EMR. Overall and cause-specific survival rates were calculated from the date of EMR to the date of death or the most recent follow-up visit. Survival curves were plotted according to the Kaplan-Meier method.

RESULTS

In total, 86 patients (82.7%) who did not receive further treatment such as chemotherapy, irradiation therapy, chemoradiotherapy, or esophagectomy after EMR were followed up. Only two patients (1.9%) developed lymph node metastasis after EMR. With a median follow-up period of 43 months (range, 8-134 months), overall and cause-specific survival rates at 5 years after EMR were 79.5% and 95.0%, respectively.

CONCLUSIONS

EMR for ESCC that invades the muscularis mucosa has curative potential as a minimally invasive treatment option.

Combination of endoscopic mucosal resection and chemoradiotherapy as a nonsurgical treatments for patients with clinical stage I esophageal squamous cell carcinoma

4529

Background: Endoscopic mucosal resection (EMR) has become the standard treatment for mucosal cancer. For the other clinical stage I esophageal squamous cell carcinoma (ESCC), radical surgery is standard and chemoradiotherapy (CRT) is optional but has high locoreginoal failure. If EMR and CRT are combined efficiently, these may improve outcomes with less invasion. A retrospective analysis was conducted to evaluate the efficacy of these combined nonsurgical modalities. Methods: Recruitment criteria were histologically proven SCC, clinically estimated as stage I except for the candidates of the standard EMR, age ≤ 75, PS ≤ 2, no prior therapy, no serious complication and no other active malignancy. Primary EMR was indicated if a tumor was within the focal submucosal (SM) invasion and a width of less than two-thirds of its circumference. EMR was followed by prophylactic CRT (5-FU + cisplatin + RT; 40Gy) for latent node metastasis when SM invasion was present pathologically. The remaining patients (pts) underwent primary CRT (5-FU + cisplatin + RT; 60Gy); salvage EMR was indicated for local residual, recurrent, or metachronous tumors. Results: Between Jan. 1996 and Apr. 2004, 86 pts fulfilled the criteria; median age 60 years (46–75), male/female; 74/12. Forty-one received primary EMR and 45 received primary CRT. Pathological diagnoses of primary EMR revealed eight mucosal cancers of the epithelium and lamina propria, 19 of the musclaris mucosae (MM), and 14 SM cancers. Eleven pts with SM cancers subsequently underwent prophylactic CRT, one with SM cancer underwent surgery, and the remaining 29 pts with mucosal and MM cancers received no additional treatment. Of the 45 CRT pts, 11 (24%) received salvage EMR. Three (3%) (one primary EMR pt and two primary CRT pts) underwent salvage surgery. With a median follow-up of 4.2 years, the 4-year overall survival of all, primary EMR, and primary CRT pts was 76%, 78%, and 72%, respectively; the disease-specific survival was 86%, 91%, and 81%, respectively. Conclusion: The survival of combination treatment with EMR and CRT for clinical stage I ESCC was comparable with that of surgery in Japan. EMR and/or CRT may be highly effective, minimally invasive treatments for stage I ESCC.

No significant financial relationships to disclose.

Association of a novel polymorphism G-133C of thymidylate synthase (TYMS) gene with 5-FU-related severe diarrhea in Japanese patients with colorectal cancer

14108

Background: 5-FU remains a key drug for the treatment of several cancers, including cancers of the colorectum, stomach, and breast. Increasing evidence suggests that genetic polymorphism results in increased toxicity. This prospective study intended to elucidate the relations between 5-FU-related toxicity and polymorphisms of several genes. Methods: Blood for genotyping was obtained before treatment. Blood samples were drawn at 2-week intervals for 8 weeks to assess hematologic toxicity. Adverse events were assessed according to NCI CTC, v2.0. The genes encoding TYMS and thymidine phosphorylase (ECGF1) were analyzed with leukocyte DNA obtained from patients with colorectal cancer who received 5-FU (500 or 600 mg/m2) and leucovorin (LV) (250 mg/m2) weekly for 6 weeks every 8 weeks. Results: Seventy-eight patients with colorectal cancer were enrolled and genotyped. Toxicity was evaluated in all patients. No genetic polymorphisms detected were significantly associated with 5-FU-related hematological toxicity. Only G- 133C located in the 5’-UTR region of the TYMS gene was significantly associated with 5-FU-related grade 3 diarrhea. Conclusions: The TYMS G-133C SNP may be a critical determinant of severe diarrhea in patients treated with 5-FU/LV. [Table: see text]

No significant financial relationships to disclose.

Biomechanics of the Spine III. The Cranio-Cervical Junction

By virtue of its unique anatomy and functions the cranial-cervical junction was excluded in previous reviews on the general biomechanics of the spine, being a world apart. The special design of the cranial-cervical (CCJ) junction responds to seemingly opposed necessities being at same time loose enough to allow a great variety of movements and strong enough to preserve the spinal cord and vertebral arteries and to resist the head weight and muscular action. The primary goal of the CCJ is to ensure the maximal mobility of the head for visual and auditory exploration of space. Like a cardan joint the CCJ allows simultaneous independent movements about three axes in order to repeat and extend eye movements under the control of vestibular receptors. Several muscular groups and a number of ligaments control the movements of the CCJ and ensure its stability. Although composed of two seemingly distinct joints the CCJ forms a unique functional complex whose stability is ensured by ligaments and bony restraints often operating on both joint components: the occipitoatlantal and atlantoaxial joints.