BackgroundIt has been propagated that patients with Klippel-Feil syndrome (KFS) exhibit “clinical triad” findings (CTFs), known as a short neck, low posterior hairline, and limited cervical range of motion (ROM). However, the literature has noted that up to 50 % of KFS cases may not present with such findings and the reasoning behind such assertions remains speculative. As such, the following study addressed the association between CTFs to that of congenitally-fused cervical segments and other risk factors in KFS patients.MethodsWe conducted a retrospective clinical study based on prospectively collected radiographic data. Thirty-one KFS patients at a single institution were assessed. Radiographs were used to evaluate the location and extent of congenitally-fused segments (spanning the occiput (O) to the first thoracic vertebra (T1)), as well as examining coronal and sagittal cervical alignments based on the Samartzis et al. KFS classification. Clinical records were evaluated to account for the initial clinical assessment of CTFs. Patients were further stratified into two groups: Group 1 included patients noted to have any CTFs, while Group 2 included patients who had no such findings.ResultsThere were 12 males and 19 females (mean age at initial consultation: 9.7 years). No evidence of any of the CTFs was shown in 35.5 % of patients, whereas 38.7, 16.2 and 9.7 % were determined to have one, two or all three criteria, respectively. Limited cervical ROM was the most common finding (64.5 % of patients). In Group 1, 25 % had a short neck, 30 % a low posterior hairline, and 100 % exhibited limited cervical ROM. Group 1 had a mean of 3.9 fused cervical segments, whereas Group 2 had a mean of 2.5 fused cervical segments (p = 0.028). Age, sex-type, occipitalization and alignment parameters did not significantly differ to Group-type (p > 0.05). In Group 1, based on the Samartzis et al. Types I, II, and III, 16.7, 73.3, and 80.0 % of the patients, respectively, had at least one CTF.ConclusionsComplete CTFs were not highly associated during the clinical assessment of young KFS patients. However, KFS patients with extensive, congenitally-fused segments (i.e. Samartzis et al. Type III) were significantly more likely to exhibit one of the components of the CTF, which was predominantly a limited cervical ROM. Clinicians managing young pediatric patients should not rely on the full spectrum of CTFs and should maintain a high-index of suspicion for KFS, in particular in individuals that exhibit associated spinal findings, such as congenital scoliosis.

The study noted a prevalence of cervical scoliosis to occur in 53.3% of young KFS patients. Such patients that exhibited congenital fusion of the mid and lower cervical spine region, had multiple, contiguous congenitally fused segments (Type III), and associated vertebral malformations (e.g., hemivertebrae) were highly associated with the presence of cervical scoliosis. However, in young KFS patients, the presence of cervical scoliosis may not be associated with the manifestation of cervical spine-related symptoms.

A hypermobile segment in the pediatric KFS patient is a risk factor that may lead to cord compression. A symptomatic herniated cervical disc may develop from an excessive mechanical load stress in a pediatric KFS patient with multiple fused segments. In such a patient, a same-day combined posterior-anterior procedure provides cord decompression and stabilizes the spine with a favorable outcome.

Klippel-Feil syndrome (KFS) is an uncommon condition noted primarily as congenital fusion of two or more cervical vertebrae. Superior odontoid migration (SOM) has been noted in various skeletal deformities and entails an upward/vertical migration of the odontoid process into the foramen magnum with depression of the cranium. Excessive SOM could potentially threaten neurologic integrity. Risk factors associated with the amount of SOM in the KFS patient are based on conjecture and have not been addressed in the literature. Therefore, this study evaluated the presence and extent of SOM and the various risk factors and clinical manifestations associated therein in patients with KFS. Twenty-seven KFS patients with no prior history of surgical intervention of the cervical spine were included for a prospective radiographic and retrospective clinical review. Radiographically, McGregor's line was utilized to evaluate the degree of SOM. Anterior and posterior atlantodens intervals (AADI/PADI), number of fused segments (C1-T1), presence of occipitalization, classification-type, and lateral and coronal cervical alignments were also evaluated. Clinically, patient demographics and presence of cervical symptoms were assessed. Radiographic and clinical evaluations were conducted by two independent blinded observers. There were 8 males and 19 females with a mean age of 13.5 years at the time of radiographic and clinical assessment. An overall mean SOM of 5.0 mm (range = -1.0 to 19.0 mm) was noted. C2-C3 (74.1%) was the most commonly fused segment. A statistically significant difference was not found between the amount of SOM to age, sex-type, classification-type, AADI, PADI, and lateral cervical alignment (P > 0.05). A statistically significant greater amount of SOM was found as the number of fused segments increased (r = 0.589; P = 0.001) and if such levels included occipitalization (r = 0.616; P = 0.001). A statistically significant greater amount of SOM was also found with an increase in coronal cervical alignment (r = 0.413; P = 0.036). Linear regression modeling further supported these findings as the strongest predictive variables contributing to an increase in SOM. A 7.20 crude relative risk (RR) ratio [95% confidence interval (CI) = 1.05-49.18; risk differences (RD) = 0.52] was noted in contributing to a SOM greater than 4.5 mm if four or more segments were fused. Adjusting for coronal cervical alignment greater than 10°, five or more fused segments were found to significantly increase the RR of a SOM greater than 4.5 mm (RR = 4.54; 95% CI = 1.07-19.50; RD = 0.48). The RR of a SOM greater than 4.5 mm was more pronounced in females -006-0280-z (RR = 1.68; 95% CI = 0.45-6.25; RD = 0.17) than in males. Eight patients (29.6%) were symptomatic, of which symptoms in two of these patients stemmed from a traumatic event. However, a statistically significant difference was not found between the presence of symptoms to the amount of SOM and other exploratory variables (P > 0.05). A mean SOM of 5.0 mm was found in our ...

This study provides some insight into the potential developmental aspects of the extent of segmental fusion of the cervical spine in patients with KFS. In older patients, complete fusion of involved fused segments was more prevalent in regards to C2-T1; however, such an observation was not noted for segments from O-C2. In the absence of complete segmental fusion, fusion of the posterior elements was more often noted than fusion of the anterior elements. Awareness of the varied phenotypic expression of segmental fusion patterns of the cervical spine in patients with KFS underlines theimportance of thorough evaluation of the cervical spine to assess the presence and extent of segmental fusion to facilitate in the identification of neurologic risk factors.