The Journal of Rheumatology

VOLUME 21: NO. 7

Editorials The ESR — Time Honored and Tradition Bound

A . W e i n s t e i n , J. D e l G i u d i c e 1177 What Can We Learn about Rheumatic Diseases by Studying Pirna Indians?

L T . H . J a c o b s s o n , S . R . P i i l e m e r 1179 Autoantibodies are Central to the Diagnosis and Clinical Manifestations of Lupus

J . B . H a r l e y 1183

Articles Specificity of Antibodies to Type II Collagen in Early RA A . D . C o o k , M . J . R o w l e y , A . S t o c k m a n ,

K . D . M u i r d e n , L R . M a c K a y 1186 Sulfate Metabolism is Abnormal in Patients with RA. Confirmation by I n V i v o Biochemical Findings H. B r a d l e y , A . G o u g h , R . S . S o k h i ,

A . H a s s e i l , R. Waring, P . E m e r y 1192 Increased Capillary Permeability in Systemic Rheumatoid Vasculitis: Detection by Dynamic Fluorescence Nailfold Videomicroscopy

E. H a c h u l l a , M . P e r e z - C o u s i n , R - M . F l i p o , e t a l . . . 1197 Immunization of Patients with RA Against Influenza: A Study of Vaccine Safety and Immunogenicity A . C h a l m e r s , D. S c h e i t e l e ,

C. P a t t e r s o n , et a l 1203 Outcome in Patients with RA Receiving Prednisone Compared to Matched Controls

R. M c D o u g a l l , J. S i b l e y , M . H a g a , A . R u s s e l l . . . . 1207 Expression of Muscarinic Cholinergic Receptors on Lymphocytes in Various Subsets of RA and Their Variabilities Connected with Treatment

H . L a s k o w s k a - B o z e k , A . F i l i p o w i c z - S o s n o w s k a , A . Z u b r z y c k a - S i e n k i e w i c z , J. R y z e w s k i 1214

A Canadian Survey of Current MTX Prescribing Practices in RA

D. C o l l i n s , N . B e l l a m y , J. C a m p b e l l 1220 Underrecognized Postdosing Reactions to MTX in Patients with RA J . T . H a l l a , J . G . H a r d i n 1224 The Clinical and Research Significance of the ESR

F. Wolfe, K. M i c h a u d 1227 RA in Tlingit Indians: Clinical Characterization and HLA Associations D . W . T e m p l i n ,

G. S. B o y e r , A . P . L a n i e r , e t a l 1238

JULY 1994

Evaluation of a German Version of the Physical D imensions of the HAQ in Patients with RA

P. Brühlmann, G. S t u c k i , B . A . M i c h e l 1245 Q uality of Life in RA: Validation of a Spanish V ersion of the AIMS (Spanish-AIMS)

M . A b e l l o - B a n f i , M . H . C a r d i e l , R . R u i z - M e r c a d o , D. Alarcön-Segovia 1250

Osteocalcin in Patients with RA. A One-Year Followup Study H . F r a n c k , T . H . I t t e l ,

O . T a s c h , G . H e r b o r n , R . R a u 1256 Clinical Utility and Serological Connections of Anti-RA33 Antibodies in SLE

D . A . I s e n b e r g , G. S t e i n e r , J . S . S m o l e n 1260 L ipid Profiles in Patients with SLE

K . H . L e o n g , E . T . K o h , P . H . F e n g , M . L B o e y 1264 Localization of Endothelin-1 and its Binding S ites in Scleroderma Skin R . V a n c h e e s w a r a n ,

A . A z a m , C . B l a c k , M . R . D a s h w o o d 1268 Sensitivities of Noninvasive Tests for CNS Vasculitis: A Comparison of Lumbar Puncture, CT, and MRI J . H . S t o n e , M . G . P o m p e r ,

R . R o u b e n o f f , T . J . M i l l e r , D . B . H e l l m a n 1277 A nalysis of Steroid Related Complications and Mortality in TA: A 15-Year Survey of 4 3 Patients G. N e s h e r , M . S o n n e n b l i c k ,

Y. F r i e d l a n d e r 1283 Aspergillus Spondylodiscitis: Successful C onservative Treatment in 9 Cases

B. C o r t e t , R . R i c h a r d , X . D e p r e z , et a l 1287 Hyperprolactinemia in Reiters Syndrome

L . J . J a r a , L H . S i l v e i r a , M . A . C u e l l a r , C. J. P i n e d a , E. S c o p e l i t i s , L R . E s p i n o z a 1292

P atient Utilities in AS and the Association w ith Other Outcome Measures

C. B a k k e r , M . R u t t e n - v a n Mölken, A . H i d d i n g , E. v a n D o o r s l a e r , K. B e n n e t t , S. v a n d e r L i n d e n 1298

T reatment of PsA at the Dead Sea S. S u k e n i k , H . G i r y e s , S. H a l e v y , L. N e u m a n n , D. F l u s s e r , D . B u s k i l a 1305

Factors Affecting Articular Cartilage Thickness in OA and Aging R . L . K a r v o n e n , W.G. N e g e n d a n k ,

R . A . T e i t g e , A . H . R e e d , P . R . M i l l e r , F. F e r n a n d e z - M a d r i d 1310

C o n t e n t s c o n t i n u e d o p p o s i t e i n s i d e b a c k c o v e r . . .

PRINTED IN CANADA — ISSNI 0315-162X

CONTENTS ( c o n t i n u e d f r o m f r o n t c o v e r )

Abnormal Thermoregulatory Responses in Patients with RSDS

A . H e r r i c k , K. E i - H a d i d y , D . M a r s h , M . J a y s o n 1319

Comparison of ACTH and Triamcinolone Acetonide in the Treatment of Acute Gouty Arthritis

L B . S i e g e l , J . A . A I I o w a y , D J . N a s h e l 1325

Capillary Permeability in FM W. G r a s s i , P . C o r e , G . C a r l i n o , F. S a l a f f i , C. C e r v i n i 1328

Somatomedin C (IGF-1) Levels Decrease Düring Acute Changes of Stress Related Hormones. Relevance for FM

G . F e r r a c c i o l i , P . G u e r r a , V. R i z z i , e t a l 1332

FM in FMF P . L a n g e v i t z , D . B u s k i l a , R . F i n k e l s t e i n , e t a l . . . . 1335

Contribution of Neuromuscular Impairment to Physical Functional Status in Patients with Lumbar Spinal Stenosis

G . S t u c k i , M . H . L i a n g , S J . L i p s o n , A . H . F o s s e l , J . N . K a t z 1338

Pediatric Rheumatology aCL in Pediatric Patients with HIV

L C a r r e h o , I. M o n t e a g u d o , F . J . Löpez-Longo, e t a l 1344

Workshop Report: Research in Pediatric Rheumatology

D . N . G I a s s , B . S . N e p o m , P . H . White, L E . S h u l m a n 1347

Case Reports Intravenous Cyclophosphamide Pulses in the Treatment of Pyoderma Gangrenosum Associated with RA

A . Z o n a n a - N a c a c h , F . J . J i m e n e z - B a l d e r a s , P . M a r t i n e z - O s u n a , G . M i n t z 1352

An Association of PMR with Myelodysplastic Syndromes

M . K o h l i , R . M . B e n n e t t 1357

An Association Between Refractory HELLP Syndrome and aPL Düring Pregnancy

M . H . O r n s t e i n , J . H . R a n d 1360

Gout Düring Pregnancy J . T . K e l s a l l , D . P . O ' H a n l o n 1365

Correspondence Factors Predicting Outcome in RA

J . G . J o n e s 1367 Reply D . v a n Z e b e n , F . C . B r e e d v e l d 1367 aPL in Rheumatic Fever Chorea R . E . A . S . D i n i z ,

J. G o l d e n b e r g , L E . C . A n d r a d e , e t a l 1367 Reply F. F i g u e r o a , X . B e r r i o s , M . G u t i e r r e z , e t a l 1368 Primary APS or SLE related APS: From Theory to Practice J - C . P i e t t e 1368 Reply R . A . A s h e r s o n 1369 aCL in Klinefelter's Syndrome

G. B a j o c c h i , G. S a n d r i , F. Trotta 1370 Reply J. M . D u r a n d , G . K a p l a n s k i , J. S o u b e y r a n d . . 1370 Cofactor (ß2-Glycoprotein 1) Dependent aCL and Thrombosis J. K a b u r a k i , M . K u w a n a ,

Y . l k e d a , M . Y a m a m o t o , S . K a w a i , E . M a t s u u r a ... 1371 Reply J. O r d i R o s , A . S e l v a - O ' C a l l a g h a n ,

P . P e r e z - P e m a n , C . F a l g a , E . C u c u r u l l 1371 Recurrent Reflex Sympathetic Dystrophy as a Manifestation of SLE D . H . N e u s t a d t 1372 Reply B . E . O s t r o v 1372 Fat Necrosis from im GTG J . M . S o w a 1372 Reply J. M c C a i n , T Wizda West 1373

Letters TCR Vß Selection from DRB1*401*0101 Patient with RA Complicated by CD8 + T Cell Infiltrated Rheumatoid Pericarditis A . T r a v a g l i o - E n c i n o z a ,

J - M . A n a y a , A . D u p u y d ' A n g e a c , J . S a n y , T . R e m e ..1373 Factors Influencing the Prevalence of APS in SLE U . P i c i l l o , S. M i g l i a r e s i , M . R . M a r c i a l i s ,

F. L a P a l o m b a r a , G. Tirri 1375 Immunomodulatory Therapy of Recurrent Purpura Associated with SS. Effect of Oral Gold Compound /. K a t a y a m a 1376 Chronic Hepatitis C and SS J - L . P o e t ,

I. T o n o l l i - S e r a b i a n , P . P . G a r n i e r 1376 Membranous Nephropathy Developing Düring the Course of DM H . M a k i n o , K. H i r a t a ,

M . M a t s u d a , T. A m a n o , Z . O t a 1377 Orchitis: An Unusual Feature in Relapsing Polychondritis J - F . M a i l l e f e r t , B . D e W a z i e r e s ,

F. M e i g n a n 1378

Book Reviews Antibodies to Endothelial Cells and Vascular Damage 1379 Occupational Musculoskeletal Disorders 1379 Oxford Textbook of Rheumatology 1380 Notices 1381

x v i i i

Contribution of Neuromuscular Impairment to Physical Functional Status in Patients with Lumbar Spinal Stenosis G E R O L D STUCKI , M A T T H E W H . L I A N G , S T E P H E N J. LIPSON, A N N E H . FOSSEL, and J E F F R E Y N . K A T Z

ABSTRACT. Objective. To evaluate the relationship between neuromuscular impairment and physical functional Status in patients with lumbar spinal Stenosis. Methods. Cross sectional analysis of 217 consecutive patients with lumbar spinal Stenosis referred to 3 teaching hospitals. Physical functional Status was measured with the physical dimension of the Sickness Impact Profile (P-SIP). Physical and radiological findings were abstracted from clinical records. The neuromuscular findings included pin Sensation, strength, deep tendon reflexes and Vibra­tion. They were aggregated in a neuromuscular impairment index (NMI). Univariate relationships of the P-SIP and the NMI were analyzed with nonparametric methods. The determinants of physical functional Status were evaluated using multiple linear regression models. Results. In 148 patients with complete clinical data, objective weakness of the lower extremity as measured at rest was not related to physical functional Status in univariate analyses. Decreased Vibration was common and was associated with balance disturbance and reduced physical functional Status, reflecting the importance of proprioception loss. In the multivariate regression analysis, neuromus­cular deficit explained only 2.5% of the variance in physical functional Status. The primary deter­minants of physical functional Status were pain, depression, comorbid conditions and work Status. Conclusion. While neuromuscular impairment is an indispensable feature of the diagnostic evalua-tion, its value in assessing outcome is limited. The decision whether to intervene surgically in patients without cauda equina Syndrome or rapidly progressive neurological deficits should therefore be driven by pain and physical disability rather than the degree of neuromuscular impairment. (J Rhewnatol 7994;21:1338-43)

Key Indexing Terms: LUMBAR SPINAL STENOSIS NEUROMUSCULAR IMPAIRMENT INDEX PHYSICAL FUNCTIONAL STATUS SICKNESS IMPACT PROFILE

Degenerative lumbar Stenosis results from chronic compres-sion of the cauda equina and the exiting nerve roots by a combination of degenerative change in the facet joints, in-tervertebral discs and ligamentum flavum, and is a common cause of discomfort and reduced physical functional Status in the elderly. This condition is now the most common diag-nosis leading to lumbar spinal surgery in adults older than 651 and the associated inpatient costs have been estimated to reach half-billion dollars annually in the United States2.

F r o m the Departments of M e d i c i n e and Rheumatology/Immunology and the Robert B . B r i g h a m M u l t i p u r p o s e A r t h r i t i s and Musculoskeletal Disease Centers, B r i g h a m and Women 's Hospital, and the Department of Orthopedic Surgery, Beth I s r a e l Hospital, H a r v a r d M e d i c a l School, Boston, M A , USA. Supported by NIH G r a n t A R 3 6 3 0 8 . D r . Stucki is a recipient of a

fellowship of the Swiss Science N a t i o n a l F o u n d a t i o n and grants f r o m the E U L A R and the Swiss Associations of Physical M e d i c i n e , R e h a b i l i t a t i o n and Rheumatology. D r . Katz is supported in part by a n A r t h r i t i s Investigator A w a r d f r o m the A r t h r i t i s F o u n d a t i o n . G. Stucki, M D , Research F e l l o w in Rheumatology, H a r v a r d M e d i c a l School; M . H . L i a n g , M D , M P H , Associate Professor of M e d i c i n e , S.J. Lipson, M D , Associate Professor of Orthopedic Surgery, H a r v a r d M e d i c a l School; A . H . Fossel, Research Assistant, M u l t i p u r p o s e A r t h r i t i s Center, J . N . Katz, M D , MS, Assistant Professor of M e d i c i n e , H a r v a r d M e d i c a l School. Address r e p r i n t requests to D r . G. Stucki, M D , R B B M u l t i p u r p o s e A r t h r i t i s Center, B r i g h a m and Women 's Hospital, 75 F r a n c i s St., Boston, M A , USA 0 2 1 1 5 . Submitted M a y 1 1 , 1 9 9 3 revision accepted December 1 9 , 1 9 9 3 .

The diagnosis is based on the clinical Syndrome of neuro-genic claudication, generally defined as radiating pain in the buttocks and lower extremities, which is provoked by Stand­ing or Walking and is relieved by lumbar flexion, along with radiological evidence of spinal Stenosis with cauda equina compression1.

Neuromuscular deficits are common in patients with long-standing Symptoms. Nonoperative treatment with corsets, analgesics, nonsteroidal antiinflammatory agents, epidural corticosteroid injections and physical therapy may occasion-ally ameliorate or relieve the pain, but many patients do not respond to these measures and are candidates for decompres-sive surgery.

There is agreement that cauda equina Syndrome and rapid Progression of neurological deficits are indications for surgery 3 5. However, these phenomena occur rarely in patients with spinal Stenosis6. In the majority of patients, the progression of neurological deficits is insidious and the efficacy of decompression in preventing progression of neurological impairment has been questioned7.

Our goal was thus to evaluate the contribution of neuro­muscular impairment to physical functional disability, the disease dimension of most concern to the patient and the primary endpoint generally used to evaluate the success of surgical decompression. We hypothesized that neuromuscular

1 3 3 8 The J o u r n a l of Rheumatology 1 9 9 4 ; 2 1 : 7

deficit correlates poorly with physical functional disability and that the principal determinants of physical disability in-clude pain, depression and sociodemographic factors, and only to a lesser extent neuromuscular impairment.

MATERIALS AND METHODS Design. The association between neuromuscular impairment and physical functional Status, along with the evaluation of the principal determinants of physical functional Status, were examined in a cross sectional study of patients with spinal Stenosis referred for surgery to 3 teaching hospitals. Patients. Consecutive patients referred to the 5 study surgeons for evalua­tion of spinal Stenosis were eligible. Inclusion criteria were age greater than 50 (to exclude predominantly congenital Stenosis), presence of pain in the low back, buttock and lower extremity exacerbated by lumbar extension, and evidence of central or central lateral compression of the cauda equina by a degenerative lesion of the facet Joint, disc, or ligamentum flavum on computerized axial tomography, magnetic resonance imaging or myelo-graphy. Patients unable to complete questionnaires because of cognitive or language difficulties were excluded.

D a t a collection procedures. The Sickness Impact Profile (SIP)8, and data on disease specific Symptoms, depression and sociodemographic variables were gathered using mailed questionnaires and augmented by phone inter-views. Neuromuscular impairment, radiographic findings and the presence of comorbid conditions were abstracted from medical records using stan-dardized coding forms. The surgeons used a protocolized examination proce-dure as part of their involvement in the study, ensuring fairly uniform data recording.

Measures. Physical functional Status was assessed with the physical dimension of the SIP (P-SIP), a widely used quality of life measure which has been tested for its reliability and validity. The physical dimension of the SIP con-sists of 3 subscales measuring mobility, ambulation and body care and management. The SIP has been previously used in studies of acute9 and chronic low back pain10.

The symptom questions had Likert response scales and asked about overall pain, pain in the back, pain in the leg, numbness, weakness, balance dis-turbance, Walking difficulty and Walking distance. Patient characteristics included age, sex, work, living Status and educational level. Depression was assessed with the Zung self-rated depression scale11. Comorbidity was assessed with the Cumulative Illness Rating Scale proposed and validated by Linn and Linn 1 2.

The physical findings abstracted from clinical records included pin Sensa­tion of the medial and lateral leg and foot, strength of the quadriceps, tibia-lis anterior, extensor hallucis longus, gastrocnemius, deep tendon reflexes of the knee and ankle, and Vibration (recorded only for the medial foot). For purposes of the analysis we created a simple summation index for the neuromuscular findings (Table 2). Each of the eleven physical findings was graded as normal (0 point), reduced (1 point) or absent (2 points) resulting in a worst possible neuromuscular impairment index (NMI) score of 44 (22 each side).

The number of stenotic segments and the presence and degree of spon-dylolisthesis were abstracted from radiology reports. In 11 patients, the pre-cise number of segments involved and degree of spondylolisthesis could not be obtained although they had reportedly radiological involvement. Analysis. The principal dependent variable, P-SIP score, was skewed towards higher (worse) physical functional Status; thus, we used nonparametric methods for the univariate analysis of relationships between P-SIP and covar-iates. Univariate relationships between P-SIP and specific Symptoms were analyzed with the Spearman correlation coefficient. Univariate associations between P-SIP and discrete variables with 2 or 3 categories were evaluated using the Wilcoxon rank sum test and the Kruskal-Wallis test, respectively. Relationships among covariates were assessed similarly. Fisher's exact test was used for the comparison of categorical variables. The reported p values are all 2-tailed.

The determinants of physical functional Status were evaluated using mul­tiple linear regression models including both sociodemographic and disease specific variables. In our cross sectional approach, this analysis was explora-tory and the directionality with respect to cause and effect could not be inferred for most variables. Only patients with a complete neurological exami­nation were included in this analysis. The sociodemographic variables in­cluded age, sex, work Status, educational level and Zung depression scale. Disease specific variables included the NMI, number of segments involved and presence of spondylolisthesis, duration of disease and pain. The model also controlled for comorbidity. Neurogenic claudication, race and prior back surgery were not included since virtually all patients had neurogenic claudication, were white and had no prior back surgery. Missing informa-tion on covariates (18% of the depression scores; less then 5% for the other covariates) were substituted with mean values. For the regression analysis we used a Square root transformation of the outcome variable (P-SIP) to account for skewness towards higher scores. A second analysis using the untransformed variable revealed virtually identical results.

RESULTS Subjects. The demographic, clinical and radiographic charac­teristics of the 217 patients studied are shown in Tables 1, 2, and 3.

Sixty-two percent of this elderly population with a median age of 69.6 years had significant comorbidity (score > 2). The mean (Standard deviation) of the Zung depression scale was 2.0 (0.45), which represents moderate depression. The mean P-SIP score was 16.5 (ränge 0-55) which is compar-able to the physical functional Status of patients with hip Osteoarthritis prior to total hip replacement surgery (mean score 17)13. Twenty-eight percent of the patients were working (50% of the patients under 65), 43.9% had an educa­tional level of high school or higher, 73.4% lived with others whereas 26.6% lived alone.

The median disease duration was 18 months; the duration was > 36 months in 25% and < 9 months in 25%. Seventy-eight percent of the patients experienced severe or very severe pain and two thirds reported balance disturbance. Patients'

Table 1. B a s e l i n e d e m o g r a p h i c v a r i a b l e s , c o m o r b i d i t y i n ­dex a n d p h y s i c a l d i m e n s i o n of SIP

Number (N = 217) %

Age group (years) 50-62 51 23. 62-69 57 26. 69-76 63 29. 76-90 46 21.

Sex Female 135 62. Male 82 37.

Comorbidity score < 2 85 39. 2-4 60 27. 4-6 53 24. >6 19 8.

P-SIP score < 7 51 23. 7-14 60 27, 14-21 44 20. >21 62 28,

Stucki, et al: Spinal Stenosis 1 3 3 9

Table 2. C l i n i c a l Symptoms a n d r a d i o g r a p h i c findings

Number %

Neurogenic claudication (N = 189) Absent 7 3.7 Present 182 96.3

Pain in back, buttock and legs (N = 215)

Mild, very mild, none 9 4.2 Moderate 39 18.1 Severe 114 53.0 Very severe 53 24.7

Balance disturbance (N = 208) Never 71 34.1 Sometimes 97 46.6 Often 40 19.2

Walking distance (N = 216) > 2 miles 12 5.6 < 2 miles, but > 2 blocks 78 36.1 < 2 blocks but > 50' 78 36.1 < 50' 48 22.2

Difficulty Walking (N = 159) None 7 4.4 Mild 16 10.1 Moderate 54 34.0 Severe 65 40.9 Very severe 17 10.7

Numbness or tingling in legs or feet (N = 159)

None 38 23.9 Mild 34 21.4 Moderate 49 30.8 Severe 29 18.2 Very severe 9 5.7

Weakness in legs or feet (N = 157)

None 20 12.7 Mild 45 28.7 Moderate 60 38.2 Severe 28 17.8 Very severe 4 2.5

Number of segments involved radi-ologically (N = 206)

1 43 20.9 2 69 33.5 3 58 28.2 4 or 5 36 17.5

Spondylolisthesis (> 5 mm) (N = 206) Absent 135 65.5 Present 71 34.5

Walking distance was limited to less than 2 blocks in 58%. While 71 % had normal strength by examination, only 13% of the patients perceived no weakness. Spondylolisthesis of at least 5 mm was found in 34.5% of the patients and 43% had involvement of 3 or more stenotic segments.

With respect to neuromuscular impairment we report on 148 out of 217 patients with complete examination data. The demographic and disease specific characteristics of the patients with complete examination and the patients without were similar. The first group (N = 147) was on average 69

Table 3. N e u r o l o g i c a l findings a n d n e u r o m u s c u l a r i m p a i r ­ment i n d e x

Neurological Examination Right Left (N = 148) % Diminished or % Diminished or

Absent Absent

Strength M . quadriceps 4.1 3.4 M. tibialis anterior 6.1 8.8 M . extensor hallucis longus 12.8 20.9 M . gastrocnemius 6.1 4.8

Pin prick sensibility Lateral leg 4.7 6.1 Medial leg 3.4 4.7 Lateral foot 5.4 4.7 Medial foot 12.2 7.4

Reflexes Patellar 66.2 64.8 Ankle 96.6 96.6

Vibration Medial foot 86.4 86.4

Neuromuscular impairment index Number % (score)

< 4 31 20.9 4-8 59 39.9 8-12 37 25.0 > 12 21 14.2

years old, 63.5% female and had a mean comorbidity score of 3.4 and a mean P-SIP score of 17.0. Severe or very severe pain was reported in 78.7%, radiological involvement of 3 or more levels was found in 48.3% and spondylolisthesis in 32.9%. The second group (N = 69) was on average 69 years old, 63.5% female and had a mean comorbidity score of 3.2 and a mean P-SIP score of 15.3. Severe or very severe pain was reported in 75.3%, radiological involvement of 3 or more levels was found in 39.7% and spondylolisthesis in 38.1%.

In the patients with complete examination data, vibratory Sensation and reflexes were more commonly impaired than pin-prick Sensation or strength. Ankle reflexes were absent bilaterally in 64.4% of patients, and were either reduced or absent on at least one side in 96.4%. Reduction in patellar tendon reflexes was detected in two-thirds of the patients. U n i v a r i a t e a s s o c i a t i o n s (Table 4). The relationships between the covariates, the P-SIP and the neuromuscular index are shown in Table 4. Age, sex, work Status and depression score were significant correlates of P-SIP, whereas higher educa-tion and living Status (living alone) were not significantly associated with P-SIP in the univariate analysis. Comorbidity was a strong correlate of P-SIP. Overall pain (r = 0.40) was more strongly correlated with P-SIP than back pain (r = 0.25) and leg pain (r = 0.13). Walking distance, Walking difficulty and balance disturbance were strong correlates of the P-SIP. A weak but significant relationship was found for self-perceived weakness whereas numbness was not related to P-SIP.

1 3 4 0 The J o u r n a l of Rheumatology 1 9 9 4 ; 2 1 : 7

Table 4. U n i v a r i a t e r e l a t i o n s h i p between t h e c o v a r i a t e s a n d P - S I P a n d n e u r o m u s c u l a r i m p a i r m e n t i n d e x

Neuromuscular Index P-SIP (N = 217) (N = 148)

Categorical Variables Mean p Value* Mean p Value*

Sex Female 8.7 0.36 18.5 <0.01 Male 9.5 13.3

Work Status Not working 9.0 0.85 18.8 <0.01 Part/full-time 9.2 11.0

Balance disturbance None 7.9 <0.01 11.6 <0.01 Sometimes 8.6 16.4 Often 11.6 25.9

Spondylolisthesis None 8.7 0.6 16.4 0.71 Present 9.1 17.0

Continuous and interval Spearman r p Value Spearman r p Value variables

Age 0.28 <0.01 0.23 <0.01 Comorbidity score 0.26 <0.01 0.36 <0.01 Disease duration 0.04 0.61 -0.04 0.6 Depression score 0.09 0.31 0.48 <0.01 Segments involved 0.10 0.25 -0.04 0.55 Pain overall 0.12 0.15 0.40 <0.01 Back pain <0.01 0.99 0.25 <0.01 Leg pain 0.09 0.37 0.13 0.10 Numbness 0.10 0.28 0.04 0.62 Subjective weakness 0.26 <0.01 0.24 <0.01 Walk distance 0.16 0.05 0.47 <0.01 Neuromuscular index NA NA 0.21 0.01

NA = not applicable. * Wilcoxon rank sum test for dichotomous, Kruskal-Wallis test for ordinal variables.

The neuromuscular index was significantly but weakly related to the P-SIP. Among the components of the neu­romuscular index, patellar tendon reflexes and vibratory Sen­sation had a significant relationship with the P-SIP. Reduced ankle reflex was not related to P-SIP. Neither pin-prick Sen­sation, nor muscle weakness were related to physical func­tional Status. The number of stenotic segments and spon­dylolisthesis were not related to P-SIP and showed no rela­tionship with pain, neuromusuclar impairment or the socio­demographic variables.

Univariate analysis showed no correlation between sub­jective and objective weakness. Balance disturbance was sig­nificantly related to Vibration (r = 0.25) and reflex deficit (r = 0.18). M u l t i v a r i a t e m o d e l ( T a b l e 5 ) . The multivariate model which included sociodemographic variables, depression score, dis­ease duration, neuromuscular index and anatomical varia­bles explained 40% of the total Variation of physical func­tional Status measured with the P-SIP. The N M I which ex­plained 5.4% of the variance in P-SIP in the univariate analy­sis, remained a significant independent correlate in the multi­variate model explaining 2.5% of the total Variation in

Table 5. P a r a m e t e r estimates of t h e r e g r e s s i o n m o d e l . D e p e n d e n t v a r i a b l e i s p h y s i c a l S I P - s c o r e (N = 1 4 8 )

Variable Parameter 95% p Value** Partial r 2 t

Estimate* Confidence Interval

Intercept -1.9 Age (years) 0.1 (-0.1, 0.3) 0.73 <0.01 Female gender 2.6 (-1.0, 6.2) 0.06 0.015 Education 1.8 (-1.7, 5.3) 0.35 <0.01 Living alone 1.0 (-3.1, 5.1) 0.44 <0.01 Working -5.3 (-9.2, -1.4) <0.01 0.048 Comorbidity score 1.0 (0.2, 1.8) <0.01 0.084 Pain 4.4 (2.1, 6.7) <0.01 0.187 Depression score 6.3 (1.9, 10.7) 0.01 0.038 Disease duration 0 (-0.1, 0.1) 0.97 <0.01 (months) Neuromuscular 0.4 (0.0, 0.8) 0.03 0.025 impairment score Segments 0.1 (-1.6, 1.8) 0.77 <0.01 involved Spondylolisthesis 0.27 (-3.3, 3.8) 0.64 <0.01

** p Values from the model with the Square root of P-SIP. * Parameter estimates from the model with P-SIP. f Partial r2's from the forward selection process. Model r 2 = 0.40; F-Test for the model: < 0.01.

P-SIP. In the stepwise forward selection process, pain was selected first and explained 18.7% of the variance of P-SIP, comorbidity explained an additional 8.4%, work Status 4.8%, depression 3.8%, neuromuscular impairment 2.5% and sex 1.5%. Age, a significant univariate correlate was not in-dependently associated with the P-SIP in the linear regres­sion model. Higher education, living Status (living alone), longer disease duration, greater number of segments involved and the presence of spondylolisthesis were not related to physical functional Status, in either univariate or multivari­ate analyses.

Based on the parameter estimates of this model, the predict-ed difference in the physical SIP score between a patient hav-ing the median observed neuromusuclar impairment score (8 points, representing for example bilateral absence of Vibra­tion and extensor hallucis longus) and a patient having minimal deficit (1 point, representing e.g., unilateral reduced Vibration) was 3.3 points. In contrast, the predicted differ­ence in P-SIP between patients with very severe pain and patients with moderate pain was 8.8 points.

To put these differences in perspective, the mean P-SIP score in our sample was 16.5 points and the mean change in P-SIP score following laminectomy in patients with spinal Stenosis was 6.5 points (Katz JN, unpublished data). Thus, 8.8 points represents an enormous difference and a 3.5 point differ­ence is modest.

DISCUSSION Patients referred with spinal Stenosis experience considera-ble physical disability. However, the degree of objective neu­

ste/:/, et al: S p i n a l Stenosis 1 3 4 1

romuscular impairment explains a relatively small amount of the Variation in physical functional Status and is reminis-cent of the weak relationship between physical signs and reported disability in patients with nonspecific low back pain 1 4.

Consistent with previously reported series, objective muscle weakness is not common 1 5 1 7 . This may be ex­plained in part by the multiple segmental innervation of most muscles. The preservation of strength is also hypothesized to result from effective reinnervation by collateral sprout-ing of surviving motor units18. This compensation is effec­tive until 50-70% of the motor units are lost1 8. It is, how-ever, important to note, that neuromuscular testing was per-formed when patients were at rest in our study. Testing after exertion may reveal more frequent and severe strength deficits1 9. Interestingly, self-perceived weakness, which measures subjective weakness with exertion, was correlated significantly with reported physical functional Status while objective muscle testing was not. This finding suggests that testing of neuromuscular impairment may be more informa­tive if it is performed after exertion.

Pin-prick sensitivity deficits were uncommon compared with Vibration deficits which were noted in 86.9% of the patients. This has been noted anecdotally but has not been well documented in the literature. Also, vibratory deficit was a strong correlate of self-reported balance disturbance. Balance is multifactorial and relates to strength, propriocep-tion and, particularly in patients with spinal Stenosis, to sway of the center of gravity2 0. Our data suggest, that Vibration deficit and, to an even greater extent, balance disturbance are important correlates of perceived physical functional Status.

Reduction in reflexes was a common finding in our patients with the patellar tendon reflex involved in as many as two thirds of patients. The greater physical disability in patients with deficits of patellar tendon reflexes may reflect the in­volvement of L3/L4 in addition to L5/S1.

The degree of anatomical impairment, as shown by imag-ing studies, was not related to physical functional Status at all. Although radiological Stenosis is indispensable in con-firming the clinical diagnosis and planning surgical interven-tion, the number of stenotic segments involved and the presence and extent of spondylolisthesis are of little value in assessing the impact of the disease on the patient.

In a comprehensive multivariable model, neuromuscular impairment was a significant but weak correlate of functional physical Status. The strongest correlate of physical functional Status was pain. Back pain and leg pain were independently associated with physical functional Status. Depression was found to be a strong correlate of physical functional Status in the model. Work Status was an independent correlate of physical functional Status and may be a Surrogate for prog-nostically favorable social and psychologic factors. However, in a cross sectional analysis it is difficult to determine whether

depression and work Status represent cause, effect, or as we suspect, both. As previously noted, women referred for sur­gery have worse physical functional Status (Katz JN, unpub-lished data). This may reflect referral bias, reporting bias or sex differences in preferences for surgical therapy. Women were similar to men with respect to neuromuscular impair­ment, anatomical and sociodemographic variables. However, women reported significantly more pain.

Some limitations of the study require comment. First, the study population consists of patients referred for considera-tion of surgical decompression and therefore represents the severe end of the disease spectrum. Second, neuromuscular impairment data were collected by chart abstraction using physician notes. However, the surgeons utilized a protoco-lized examination procedure as part of their involvement in the study, ensuring fairly uniform data recording. Of more concern is the problem of missing values for neuromuscular data. However, patients with complete neuromuscular data did not differ from the group without complete physical ex­amination data with respect to baseline characteristics (i.e., sex, age, disease specific Symptoms and functional physical Status). To assess deep sensitivity loss, vibratory sense was recorded and served as a Surrogate of Joint position sense which may be more directly relevant for balance disturbance and physical function. Furthermore, in the elderly study population, Vibration and reflexes may be impaired for rea-sons other than the studied disease process. This may explain, why neuromuscular deficit explained an even smaller amount of the Variation in physical functional disability in a multi­variate analysis Controlling for age and comorbidity than in the univariate analysis. Also, electrodiagnostic tests were not available to document the extent of nerve compression: they were not performed routinely but only for differential diag-nostic reasons, since it was feit that the additional informa-tion would not justify costs and bürden for the patient. Finally, the assessment of anatomical impairment was based on radiology reports and included just two variables, spon­dylolisthesis and number of segments involved. The reports were unlikely to introduce bias, as radiologists were unaware of this study. In addition, there is no validated Classification and grading system for radiologic evaluation of spinal Stenosis available. However, a more detailed assessment of radiographic nerve compression might have shown an as-sociation with disease impact.

In conclusion we found that the neurological exam and ana­tomical involvement, as performed in our study, were not important correlates of reported physical functional Status in patients with lumbar spinal Stenosis. While they are in­dispensable features of the diagnostic evaluation, their value in assessing outcome is limited. The decision of whether to intervene surgically in patients without cauda equina Syn­drome or rapidly progressive neurological deficits should therefore be driven by pain and physical disability rather than the degree of neuromuscular impairment.

1 3 4 2 The J o u r n a l of Rheumatology 1 9 9 4 ; 2 1 : 7

REFERENCES 1. Turner JA, Ersek M , Herron L, Deyo R: Surgery for lumbar

spinal Stenosis. Attempted meta-analysis of the literature. Spine 1 9 9 2 ; 17:1-8.

2. Katz JN, Lipson SJ, Larson MG, Mclnnes JM, Fossel A H , Liang M H : The outcome of decompressive laminectomy for degenerative lumbar Stenosis. J Bone Joint Surg /997;73A:809-16.

3. Spengler DM: Lumbar decompression for spinal Stenosis. Surgical indications and technique. In: Frymoyer JW, ed. The A d u l t Spine. New York: Raven Press, 1991:1811-9.

4. Moreland LW, Lopez-Mendez A, Alarcon GS: Spinal Stenosis: A comprehensive review of the literature. Seminars A r t h r i t i s Rheum 7959,19:127-49.

5. Herkowitz HN, Garfin SR: Decompressive surgery for spinal Stenosis. Semin Spine Surg 7989,1:163-7.

6. Blau JN, Logue V: The natural history of intermittent claudication of the cauda equina. B r a i n 7978; 101:211-22.

7. Johnsson K E , Uden A, Rosen I: The effect of decompression on the natural course of spinal Stenosis. A comparison of surgically treated and untreated patients. Spine 7990/16:615-9.

8. Bergner M , Bobbitt RA, Pollar WE, et al: The Sickness Impact Profile: Validation of a health Status measure. M e d C a r e 1 9 7 6 ; 1 4 : 5 1 - 6 1 .

9. Deyo RA, Diehl AK: Measuring physical and psychosocial function in patients with low back pain. Spine 7983;8:635-42.

10. Follick MS, Smith TW, Ahern DK: The Sickness Impact Profile. A global measure of disability in chronic low back pain. P a i n 1985;21.61-16.

11. Zung WWK: Depression in the normal aged. Psychosomatics 7967;8:287-92.

12. Linn BS, Linn MW, Gurel L: C u m u l a t i v e Illness R a t i n g Scale. J A m G e r i a t r Soc 7968; 16:622-6.

13. Katz JN, Larson MG, Phillips CB, Fossel AH, Liang M H : Comparative measurement sensitivity of short and longer health Status instruments. M e d C a r e 1 9 9 2 ; 3 0 : 9 1 1 - 2 5 .

14. Roland M , Morris R: A study of the natural history of back pain. Part I: Development of a reliable and sensitive measure of disability in low-back pain. Spine 1982;%: 141-4.

15. Paine KWE: Clinical features of lumbar spinal Stenosis. C l i n Orthop R 7976; 115:77-82.

16. Hall S, Bartleson JD, Onofrio BM, Baker HL, Okazaki H , O'Duffy JD: Lumbar spinal Stenosis. Clinical features, diagnostic procedures and results of surgical treatment in 68 patients. A n n I n t e r n M e d 7985;103:271-5.

17. Watanabe R, Parke WW: Vascular and neural pathology of lumbosacral spinal Stenosis. J Neurosurg 7986,64:64-70.

18. Daube JR: Electrophysiologic studies in the diagnosis and prognosis of motor neuron diseases. N e u r o l C l i n 7985;3:473.

19. Lipson SJ: Clinical diagnosis. Semin Spine Surg 7989; 1:143-4. 20. Kenji H, Ishii K, Hajime N: Sway of the center of gravity in

patients with spinal canal Stenosis. Spine 7988; 13:1303-6.

Stucki, et al: Spinal Stenosis 1 3 4 3