بسم االله الرحمن الرحيم
DEXA LATERAL LUMBAR IS IT IMPORTANT? By S. Tantawy,, M.D.
Osteopenia,, bone mineral deficiency in the absence of fracture, is an indicator of the bone structural integrity and compared with osteoporosis Osteopenia has a greater potential i.e it is possible to improve bone mass and associated bone strength, as well as prevent fracture.
Three degrees of vertebral deformation are recognized: 1 End plate deformity. 2 Anterior wedge deformity. 3 Compression deformity.
A vertebral deformation score is quantified objectively to study the condition and/or response to treatment (at least 14 vertebrae)... L4 should be roentgenographed. T4 through The anterior, middle and posterior heights of the vertebrae are measured and fracture can be then classified as follow:
Mildly depressed (Grade I): 20% to 25% decrease in anterior, middle and/or posterior height and/or reduction in 10% to 20% of the area. Moderately deformed (Grade II) 25% to 40% reduction in the height and/or a reduction in the area of 20% to 40%. Severely deformed (Grade III) 40% reduction in any height and area.
Using previous criteria CLINICIANS are frequently surprised to find that many pts who seems to have obvious obvious osteoporosis and clinically apparent dorsal kyphosis have normal X ray. X Scheurman s kyphosis for example is associated with relatively sharp curvature of the dorsal spine but with normal vertebral bodies and bone mineral.. Also,
There are no currently available practical methods of assessing microfractures and/or disruption of microarchitecture of the plates in the vertebral bone. Supine lateral DEXA exam. Is a promising technique and is better index of vertebral bone strength and the potential risk for future fracture than AP DEXA and lateral X ray. X
Difficulty with patient positioning is also a potential limiting factor and this disadvantage has been resolved by improved positioning technology in newer densitomter. Roentgenograms serve two useful clinical purposes : 1 Disc degeneration. 2 Osteoarthritis. As a cause of low back pain and they are helpful in clarifying why some pts with known osteoporosis can have relatively normal bone mineral density.
Diagnosis of Osteoporosis: Bone Density Assessment Technique Dual energy X ray absorptiometry (DXA) Sites measured Lumbar spine Proximal femur Total body Forearm Calcaneus Phalanges Advantages Diagnostic test of choice High accuracy, precision, resolution Measures all areas Short scan time, low radiation dose Disadvantages AP spine measurement influenced by degenerative sclerosis, other artifacts Combined trabecular and cortical measure ment
Diagnosis of Osteoporosis: Bone Density Assessment (cont d) Technique Sites measured Advantages Disadvantages Quantitative computed tomography (QCT) Lumbar spine Allows assessment of trabecular bone alone Greater radiation exposure than DXA Less precise & less accurate in spine than DXA Quantitative ultrasonography Calcaneus Patella Tibia Portable Uses no radiation Effectiveness in predicting fracture risk is controversial Less precise & less accurate than DXA
Sources of errors in PA DEXA of the lumbar spine is an areal density of the integral bone which include : both the vertebral body and neural arches (cortical/trabecular trabecular) bone ratio is (50%:50%) all mineral with in the path of photon beam contributes to BMD.
Factors affecting BMD in AP DEXA of lumbar spine: Calcification in the aorta or abdominal lymph nodes. Degenerative disc. Large lumbar body osteophytes. Osteo arthretic changes of the posterior apophyseal joints with consequent hyperostosis Vertebral wedging Paget s disease. Sclerotic metastasis. Vertebral haemangioma. Residual myodil in the spinal canal and previous spinal surgery with metallic fixation.
Also difficulty in DEXA PA of the lumbar spine may be due to spinal scoliosis, kyphosis or vertebral segmentation all may result in inaccurate or overestimated values of BMD (Frank et al., 98).
Indication For Bone Mass Measurement In estrogen deficient women, to diagnose significantly low bone mass to make decisions about hormone replacement therapy. In patient with vertebral abnormalities or radiographic osteopenia,, to diagnose spinal osteoporosis to make decision about further diagnostic evaluation and therapy.
In patient receiving long term gluco corticoid therapy, to diagnose low bone mass to adjust therapy. In patient with primary asymptomatic hyperparathyroidism to diagnose low bone mass to identify those at risk of severe skeletal disease who may be candidate for surgical intervention.
Other potential Indications Universal screening for osteoporosis prophylaxis. Monitoring bone mass to assess efficacy of therapy. Identifying women who are fast bone losers for more aggressive therapy.
Ensherah Mohamed 72 y
Thoraya Mohamed 54 y
Nahed Abd El Aziz 75 y
Amal Ahmed 40 y
Fatma Abd El Mageed 56 y
Fatma Mohamed 41 y
Kamelya Sadeek 65 y
Fareda Ahmed 62 y
Amal Ahmed 50 y
Conclusion LASTLY WE CAN CONLUDE THAT DEXA OF THE LATERAL LUMBAR SPINE MUST BE DONE IN THE FOLLOWINGS : *OLD PATIENTS WITH POSSIBLE DEGENERATIVE CHANGES TO OVERCOME POSTERIOR ELEMENTS AND LARGE OSTEOPHYTS.
Continue *IN Pts WITH CALCIFIEC ABD. AORTA OR CALCIFIED ABDOMINAL L.Ns. *IN Pts SUFFERING FROM PAGET S S DISEASE LYMPHOMA, SCLEROTIC METASTASIS OR HAEMANGIOMA. *IF THE ONLY SCREENING METHOD IS LUMBAR SPINE ESP. IN OLD PATIENTS LATERAL DEXA MUST BE DONE AND FOLLOW UP WILL BE BY THE SAME MANNER.
Continue *IN PATIENT EXAMINED ROUTINLY BY DEXA FOR THREE SITES; FOREARM PA LUMBAR SPINE HIP JOINT *AND THERE IS DECREASE IN BMD IN BOTH FOREARM AND HIP JOINT WITH NORMAL PA LUMBAR SPINE SO DEXA OF LATERAL LUMBAR SPINE MUST BE DONE FOR ACTUAL MEASUREMENT OF BMD OF LUMBAR SPINE AND TO GARD AGAINST FRACTURE RISK
Thank you