Muthuuri-2 FIGURE 1.jpg
Muthuuri-2 FIGURE 2.jpg
Developmental Lumbar Spinal Canal Stenosis and Severity of Radiculopathy

Muthuuri Jamlick
The Mombasa Hospital
Correspondence to: Dr. Jamlick Muthuuri, The Mombasa Hospital, PO Box 84074–80100, Mombasa, Kenya;
email: michenimuthuuri@yahoo.com

Abstract

Background: The severity of radiculopathy is varied and may not concur with MRI findings. Large disc bulges may elicit fewer symptoms than smaller bulges. This was postulated to be due to the size of the canal. Objective: To assess the severity of radiculopathy in individuals with developmental lumbar spinal canal stenosis (DLSS) and in those without. Methods: This cross-sectional survey compared two groups: those with DLSS and those without. 597 participants were recruited and screened for DLSS, creating two groups: a group with DLSS and a group without. Severity and duration of symptoms were assessed with visual analogue scale, Oswestry Disability Index and duration of symptoms. Results: Prevalence of DLSS in the study population was 19%. 90% of those with DLSS had radiculopathy with longer duration of symptoms (mean 20.8±21.8 months against 12.3±15.9 months, p<0.0001), higher ODI scores (32.9±15.2 against 17.2±16.5, p<0.0001), and a higher VAS score (5.1±2.9 vs 4.7±1.3, p=0.068). Conclusions: Patients with DLSS have increased prevalence of radiculopathy and symptoms are more severe than in those without.

Key words: Developmental, Lumbar spinal canal, Radiculopathy, Chronicity, Disability, Severity

Ann Afr Surg. 2019; 16(2):64–68

DOI: http://dx.doi.org/10.4314/aas.v16i2.5

Conflicts of Interest: None

Funding: None

© 2019 Author. This work is licensed under the Creative Commons Attributon 4.0 International License

Muthuuri-3 table1.jpg
Muthuuri-4 table 2.jpg

Introduction

Lumbar spinal stenosis is defined as a narrowing of the spinal canal that results in compression of the neurovascular tissues before their exit or as they exit the spinal canal. Arnoldi et al. presented an etiological classification that attempted to distinguish congenital, developmental and acquired forms of spinal stenosis (1, 2). Congenitally undeveloped vertebral canals tend to be syndromic, particularly associated with dwarfism and achondroplasia (3). Developmentally narrow canals are characterized by narrowed spinal canals when compared with fully developed canals in the same population. The cause is unknown but it is thought to be part of generalized osseous stunting. Because the depth of the canal or the anteroposterior diameter (AP diameter) is fully completed by 5 years of age and has no chance of catching up, it is vulnerable to early life stresses such as malnutrition (4). Malnutrition may be caused by food shortage, placenta disorders and various maternal factors; these all may potentially influence development of the spinal canal (5). The width of the spinal canal diameter (transverse diameter) continues to grow until around 17 years (6), giving it room to grow when nutritional circumstances change. In developmentally narrow canals, the depth is more affected, and therefore statistical developmental lumbar spinal canal stenosis (DLSS) is narrowness of -2 SD from the population mean of depth of the vertebral canal. The resultant canal is either ovoid or shows trefoilness. In this study, the prevalence of DLSS (in the study population) was found to be 19%. Lumbar spinal canal stenosis is an important etiological factor in chronic low back pain syndromes (3, 7-9). Using ultrasound scanning, Porter et al. examined thousands of patients attending low back pain clinic and found a significant difference in the canal size of symptomatic individuals than in asymptomatic volunteers. They also found that most patients requiring surgery have smaller spinal canal cross-sectional areas (10). It can be concluded that canal size is a crucial determinant of neurological outcome in symptomatic individuals.

Various methods have been used to measure the dimensions of the spinal canal including ultrasonography, plain X-ray, CT scan and MRI, but the radiological method of choice for evaluating spinal canal stenosis and its pathology is MRI (11). Advantages of MRI over other methods include: non-invasiveness, non -radiation, high sensitivity and high soft tissue contrast that clearly shows nervous tissue, ligaments and other paraspinal soft tissues (11, 12). Except for the CT scan radiating, which is a major disadvantage, CT axial views are an accurate method of measuring canal dimensions. In both CT and MRI scans, measurements are taken at the interpedicular level where the canal is spared the degenerative processes that generally affect the junctional levels, particularly the disc level (13). This study used CT and MRI scans.

The visual analogue scale (VAS) and the Oswestry Disability Index (ODI) have been validated to measure the health-related quality of life outcomes. VAS evaluates severity of pain while ODI evaluates a patient’s functional disability. Duration of symptoms is an unspecific measure of chronicity of the disease condition.

Methods

The study was a cross-sectional survey (all data collected in a single short period) and was part of a larger research study with multiple objectives. Data were collected between 2 October 2017 and 13 January 2018 in seven radiological centres in the coastal region of Kenya. Permission was sought from the Ethics Review Committee (ERC) of Mount Kenya University and the study permit was granted by the National Commission for Science, Technology and Innovation. Written informed consent was sought from each participant, who joined the study freely without coercion or monetary inducement. Confidentiality was maintained and patient information de-identified. All study participants were mature adults who had a CT or MRI scan of the lumbosacral spine to allow measurement of the spinal canal. The study used a semi-structured questionnaire that was administered by a researcher to collect data. All necessary observations and measurements were collected simultaneously on the spot. The questionnaire had sections for VAS enquiry, longevity of symptoms, and an ODI questionnaire attached.

All participants were indigenous adult black Africans who were born in and and spent their first 5 years of life in the coast region (this was hoped to eliminate genetic confounders). The sample was meant to represent an impoverished population because poverty levels in the coastal region are higher than the national average for the country (46.5% vs. 42%) (24). The individuals were required to be between 18 and 60 years of age and have had a CT or MRI scan with clear magnification of the lumbosacral spine. Those excluded were people of non-African race, those with musculoskeletal disorders such as hip dysplasia or scoliosis, those who were syndromic (Downs syndrome, dwarfism and achondroplasia), and those with prior spine surgery, spine fractures, infection or tumors. Using Fisher’s formula, the sample size was predetermined as 436. The recruitment obtained 597 participants and the study sample was obtained from this group by systematic sampling method, where every 5th participant was eliminated beginning from a random number. Lumbar spinal canal dimensions were measured prospectively using a Siemens sixteen- slice multi-detector CT scanner or a GE 1.5T MRI scanner (General Electric, USA). Measurements of the spinal canal were taken at the interpedicular level on the axial scans of each lumbar vertebra from LV1 to LV5. All measurements were done manually by study assistants and counterchecked by the principal researcher. The true value of the measurement was recorded after factoring in the magnification.

The dimensions of the spinal canal were marked anteriorly by the posterior edge of the vertebral body, posteriorly by the anterior edge of the spinous process, and laterally by the medial borders of the pedicles. Measurements used those landmarks on the axial scans of each lumbar vertebra from LV1 to LV5 at the pedicular level (Fig. 1).

Click to view Figure 1

 

The anteroposterior diameter (APD) and the transverse diameter (TRD) were taken for each segment of the lumbar spine in each participant. These dimensions were used to calculate the cross-sectional area (CSA) using the mathematical formula for calculating the area of an oblong as follows: A = πxy, where A is the cross-sectional area, x the transverse diameter and y the anteroposterior diameter (Fig. 2). 

Click to view Figure 2

 

After the spinal canal measurements, two groups were created: Group1 consisted of individuals with DLSS and Group2 of individuals without DLSS. Comparisons were made within these groups to determine the severity of radic