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Nicholas U Ahn

Publications and source records attributed to Nicholas U Ahn.

15 recordsLinked to original sources
PubMed2007

Mechanical neck pain and cervicogenic headache.

Mechanical neck pain is a very common symptom that may occur with cervical spondylosis. It can be associated with cervical radiculopathy and myelopathy or can occur in isolation. Neck pain can result from a variety of causes, including trauma, tumor, infection, and degeneration. The presentation of axial neck pain varies. This article highlights the presentation, differential diagnosis, and appropriate work-up for the patient who presents with mechanical neck pain.

Cervical Vertebrae↗
PubMed2006

Anatomic considerations for the placement of C2 laminar screws.

STUDY DESIGN: Cadaveric study. OBJECTIVE: To study the applicability of C2 laminar screw placement in the general adult population and to provide useful guidelines for their safe placement. SUMMARY OF BACKGROUND DATA: Laminar screws for fixation into the second cervical vertebra are becoming an increasingly used technique since they eliminate the risk of vertebral artery injury. Although it is being used clinically, there are no published data that describe the anatomic considerations and potential limitations of this technique in the general population. METHODS: The C2 vertebrae of 420 adult specimens were studied. Laminar thickness, spinolaminar angle, and the length from the spinolaminar junction to the contralateral lamina/lateral mass junction were measured. Statistical analysis was performed using unpaired Student t tests and regression analysis (P < 0.05). RESULTS: Mean laminar thickness was 5.77 +/- 1.31 mm; 70.6% of specimens had a laminar thickness > or =5 mm; 92.6% had a thickness > or =4.0 mm. The spinolaminar angle was 48.59 degrees +/- 5.42 degrees. The mean screw length that could be used was 2.46 +/- 0.23 cm. More than 99% of specimens had an estimated screw length of at least 20 mm. Gender had a significant effect on all of the measurements studied, but race, height, and weight did not. CONCLUSION: The majority of specimens can safely accept placement of a laminar screw. This study establishes anatomic guidelines to allow for accurate screw selection and insertion. Preoperative planning is essential for safe screw placement via this technique.

Adult↗
PubMed2006

Protrusio acetabuli in Marfan syndrome: age-related prevalence and associated hip function.

BACKGROUND: Protrusio acetabuli is known to occur in patients with Marfan syndrome, but its prevalence, its effects on hip function, and its possible association with the subsequent development of degenerative hip disease have not been studied in a large population. Nevertheless, some clinicians have recommended prophylactic hip surgery for preadolescents with Marfan syndrome and protrusio acetabuli. METHODS: We performed a cross-sectional study of 173 patients (346 hips) with Marfan syndrome who were interviewed and examined for calculation of the Iowa hip score. Anteroposterior radiographs of the pelvis were made, and two radiographic indices of acetabular depth were measured: (1) the center-edge angle of Wiberg and (2) the acetabular-ilioischial distance. The presence of protrusio was defined with use of two extant definitions: (1) a center-edge angle of >50 degrees or (2) an acetabular-ilioischial distance of >/=3 mm in male patients or >/=6 mm in female patients. Linear regression analyses were performed between these radiographic indices of acetabular depth and patient age, Iowa hip scores, the magnitude of the radiographic joint space, and range of motion. RESULTS: The prevalence of protrusio acetabuli was 27% according to the center-edge angle criterion and 16% according to the acetabular-ilioischial distance criterion. The prevalence of protrusio increased until the age of twenty years and remained stable after the age of twenty years. Slight but significant negative correlations were detected between the two radiographic indices of acetabular depth and both the Iowa hip score and the summed range of motion (p < 0.02 for all). No significant relationship was found between the two radiographic indices and pain scores. In patients with Marfan syndrome who were more than forty years old, the Iowa hip scores for hips with protrusio were not significantly lower than those for hips without protrusio. CONCLUSIONS: In patients with Marfan syndrome, the prevalence of protrusio acetabuli increases during the first two decades of life and then plateaus in terms of both population-wide prevalence and radiographic severity. In this population, protrusio generally is not associated with severely problematic hip function but it is associated with slightly decreased range of motion of the hip. We concluded that prophylactic surgical intervention is not indicated for most patients with Marfan syndrome who have a radiographic diagnosis of protrusio.

Acetabulum↗
PubMed2003

Operative treatment of the patient with neck pain.

Most patients with axial neck pain and cervical radiculopathy can be managed conservatively. Surgical intervention for radiculopathy is considered only when conservative management has failed unless the neurologic deficits are very significant. In cases of myelopathy, surgery may be considered earlier, but if the myelopathy is mild, conservative treatment and close observation are still appropriate. For patients with axial neck pain, surgery is generally not considered except for rare cases caused by single- or two-level degenerative disk disease with severe and unrelenting pain. There are many surgical options for the patients with the degenerative cervical spine, but the indications are different. Surgical intervention involves a complete understanding of the disease process both from physical examination and from radiographic studies. If surgery is undertaken without appropriate clinical correlation, poor results often occur. Although the operative planning is the responsibility of the surgeon. the referring physician should also have some awareness of the basic principles behind the different surgeries.

Cervical Vertebrae↗
PubMed2003

Evaluation of registration methods used in frameless stereotactic surgery for the lumbar and cervical regions of the spine.

Computer-assisted pedicle screw insertion is feasible but has proved to be problematic. The purpose of this study was to detail the accuracy of registration techniques and pedicle screw insertion using a frameless stereotactic system. Two registration techniques were evaluated on a model spine. The frameless stereotactic system was then used to insert 26 pedicle and 8 lateral mass screws in human cadavers. For posterior vertebral elements, trajectory accuracy was 2.5 +/- 1.0 mm between T12 and L5 and 2.2 +/- 0.9 mm between C2 and T1. Registration of the anterior elements, however, was less accurate. Despite this flaw, all screws were inserted without penetrating the cortex. Screw trajectory was accurate to 2 degrees. The main limitation of frameless stereotactic surgery in the spine stems from the fact that only the posterior vertebral elements are used during registration. Despite this flaw, the system placed all screws correctly. Given these limitations, we believe that this system is most useful for locating the screw insertion point and providing a trajectory in the pedicle.

Bone Screws↗
PubMed2003

Posterior decompressive procedures for the cervical spine.

Cervical degenerative disease encompasses a complex array of pathologies. Before considering surgical intervention, the surgeon should have a complete understanding of the indications for surgery and should have conducted a thorough physical examination and evaluation of radiologic studies. In general, unless myelopathy is present, surgery should be the treatment of last resort, used only after conservative measures have failed. The indications for posterior cervical decompression include both radiculopathy and myelopathy. However, these conditions alone are not sufficient to indicate that a posterior procedure is appropriate. Other factors, such as bilaterality of symptoms, presence or absence of cervical lordosis, number of levels involved, and presence of axial neck pain, should also be considered when deciding whether an anterior procedure or posterior decompression is more appropriate.

Cervical Vertebrae↗
PubMed2003

Microsurgery for degenerative conditions of the cervical spine.

Although the operating microscope has been used for spine surgery for more than 20 years, its use is still not widely accepted by orthopaedic spine surgeons. Nevertheless, surgeons who have used the operating microscope are well aware of its many advantages in performing spine surgery. Most notably, the superior visualization it provides allows for faster, safer, and more extensive decompressions. The reluctance of many surgeons to use the operating microscope often has to do with trepidation regarding new technology. The use of the operating microscope when performing anterior and posterior cervical spine surgery makes these procedures easier to carry out and decreases the risk of complications during decompression of the spinal cord.

Cervical Vertebrae↗
PubMed2002

Functional outcome and radiographic correction after spinal osteotomy.

STUDY DESIGN: A prospective clinical trial to study the radiographic parameters and functional outcome in patients undergoing spinal osteotomy. OBJECTIVES: To determine whether correction of specific radiographic parameters is associated with improved functional outcome. SUMMARY OF BACKGROUND DATA: Although vertebral osteotomies have been shown to improve functional outcome in patients with spinal deformity, no prospective reports have studied whether correction of specific radiographic parameters is associated with improvement in functional outcome. METHODS: Eighty-three patients with fixed sagittal and/or coronal deformity were followed over a 7-year period. Patients were evaluated clinically and radiographically and completed a SF-36 Health Survey and American Academy of Orthopedic Surgeons Modems Instrument questionnaire. Spearman correlation analysis was used to determine the association between correction of radiographic parameters and functional outcome. RESULTS: Mean preoperative lumbar lordosis measured -14.2 degrees (i.e., kyphosis) with an average postoperative correction of 27.9 degrees. Mean preoperative lumbar scoliosis measured 40.1 degrees with an average postoperative correction of 15.1 degrees. Mean preoperative plumb sagittal and coronal plane alignment was 8.37 cm and 4.22 cm, respectively; after surgery they improved to 3.33 cm and 2.31 cm, respectively. A significant association was found between sagittal angular correction and physical function (P = 0.034) and role-physical (P = 0.01) when postoperative lumbar lordosis was >25 degrees. A significant association was also found between plumb coronal correction and physical function (P = 0.041), vitality (P = 0.05), and social function (P = 0.047) when postoperative plumb coronal alignment was <2.5 cm. CONCLUSIONS: Correction of sagittal and coronal deformity is important in the treatment of spinal deformity. A significant association was found between outcomes and radiographic correction of coronal and/or sagittal deformity if postoperative sagittal lordosis was >25 degrees and if postoperative plumb coronal alignment was <2.5 cm. Therefore, these radiographic parameters should be the goal of a spinal osteotomy. The surgery has a relatively high complication rate.

Adult↗
PubMed2002

Dural ectasia and back pain: review of the literature and case report.

Dural ectasia is defined as a ballooning of the dural sac which is more common in patients with connective tissue disorders such as the Marfan syndrome. Several studies have shown that dural ectasia may be associated with such conditions as back pain, headaches, radiculopathies, or incontinence. We present a case of a 52 year old woman with Marfan syndrome who presented with a significantly large anterior sacral meningocele without having associated symptoms. In light of this case, we recommend that asymptomatic Marfan patients with dural ectasia should be closely observed without need for immediate surgical intervention.

Back Pain↗
PubMed2002

The etiology of adolescent idiopathic scoliosis.

The etiology of adolescent idiopathic scoliosis (AIS), the most common form of scoliosis, is unclear. Researchers with divergent perspectives have tried to better define this etiology. Genetics, growth hormone secretion, connective tissue structure, muscle structure, vestibular dysfunction, melatonin secretion, and platelet microstructure are major areas of focus. In this article, we review the literature in these areas and present the consensus on proposed hypotheses. Studies that simplify the etiology to a single factor have been inconclusive or unsuccessful. Most likely, the etiology is multifactorial, and reported associations are links in pathogenesis rather than etiologic factors. Research is needed to better define the role of all factors in AIS development.

Adolescent↗
PubMedDate not supplied

Septic arthritis of the hip following cortisone injection: case report and review of the literature.

Septic arthritis of the hip is a serious medical condition that can result in permanent joint dysfunction. This is a case of a 65-year-old woman who underwent therapeutic intraarticular steroid/lidocaine injection for hip pain and subsequently developed septic arthritis. It is critical that radiologists performing these procedures maintain a high index of suspicion in symptomatic patients following intraarticular injections to prevent destruction of the joint.

Anti-Inflammatory Agents↗
PubMedDate not supplied

Plain radiography of the lumbosacral spine in Marfan syndrome.

BACKGROUND CONTEXT: Marfan syndrome is a connective tissue disorder that results from a defect in the production of fibrillin. These patients tend to have several osseous anomalies of the lumbosacral spine. PURPOSE: This study examines the effectiveness of plain radiographic findings in predicting Marfan syndrome. STUDY DESIGN/SETTING: Case-control study. PATIENT SAMPLE: Fourteen height-matched controls and 33 patients with Marfan syndrome were obtained from our genetics clinic or through the National Marfan Foundation. OUTCOME MEASURES: Determined using measurements taken on plain radiographs. METHODS: Five measurements were acquired of the lumbosacral spine from the radiographs of both groups: interpedicular distance, scalloping value, sagittal canal diameter, vertebral body width and transverse process width. RESULTS: The following measurements were significantly larger in patients with Marfan syndrome: interpedicular distance at L1-L5 (p<.0001); sagittal diameters of the vertebral canal at L4-S2 (p<.01); transverse process to vertebral body width ratio at L2-L5 (p<.01). There was no significant difference in the scalloping values from L1-L5 between the patients with Marfan syndrome and the controls. A multivariate regression analysis generated the following criteria for plain film diagnosis of Marfan syndrome (two criteria need to be met for diagnosis): interpedicular distance at L5 greater than or equal to 36.0 mm, sagittal diameter at L5 greater than or equal to 13.5 mm or transverse process to vertebral width ratio at L3 greater than or equal to 2.25. CONCLUSION: Based on this criteria, patients can be diagnosed with Marfan syndrome with a high sensitivity (81.8%) but a low specificity (58.3%). Thus, plain radiography can be a useful means of screening patients with Marfan syndrome.

Adult↗