Aliaa Rehan Youssef, PhD

PURPOSE: To cross-culturally adapt the Core Outcome Measures Index for the back (COMI-back) for the Arabic language and to test its reliability and validity in Egyptian patients with non-specific low back pain (LBP).

METHODS: COMI-back was translated and cross-culturally adapted into Arabic according to standard guidelines. Its construct validity was assessed in 85 patients with chronic LBP (mean (± SD) age, 41.1 (± 10.4) years and 65/85 (76.5%) female) who completed a booklet of questionnaires including the Arabic versions of COMI-back, Roland Morris disability questionnaire, Oswestry disability index, the short form health survey 36, and the visual analogue scale for back pain. Test-retest reliability was assessed in 52 participants who completed the booklet again within 7 days.

RESULTS: Floor effects (worst status; 1.2-10.6%) and ceiling effects (best status; 1.2-11.8%) for COMI-back were acceptable, except for symptom-specific well-being (18.8%, floor), leg pain (23.5%, ceiling), and work disability (31.8%, ceiling). The COMI item scores correlated with those of the reference questionnaires (ρ = 0.45-0.88) to the hypothesized extent, except for the COMI symptom-specific well-being (ρ = 0.16-0.17) and quality of life (ρ = 0.38). The intra-class correlation coefficient for the summary score was 0.90, whereas that of the individual items ranged from 0.71-0.92. The standard error of measurement and minimal detectable change for the summary score were 0.51 and 1.41 points, respectively. The predefined hypotheses for construct validity and reliability were largely confirmed.

CONCLUSION: The Arabic version of COMI-back represents a valid and reliable instrument for use in Arabic-speaking patients with non-specific LBP.

Botulinum toxin type A (BTX-A) is a frequently used therapeutic tool to denervate muscles in the treatment of neuromuscular disorders. Although considered safe by the US Food and Drug Administration, BTX-A can produce adverse effects in target and non-target muscles. With an increased use of BTX-A for neuromuscular disorders, the effects of repeat injections of BTX-A on strength, muscle mass and structure need to be known. Therefore, the purpose of this study was to investigate the changes in strength, muscle mass and contractile material in New Zealand White (NZW) rabbits. Twenty NZW rabbits were divided into 4 groups: control and 1, 3 and 6 months of unilateral, repeat injections of BTX-A into the quadriceps femoris. Outcome measures included knee extensor torque, muscle mass and the percentage of contractile material in the quadriceps muscles of the target and non-injected contralateral hindlimbs. Strength in the injected muscles was reduced by 88%, 89% and 95% in the 1, 3 and 6 months BTX-A injected hindlimbs compared to controls. Muscle mass was reduced by 50%, 42% and 31% for the vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM), respectively, at 1 month, by 68%, 51% and 50% at 3 months and by 76%, 44% and 13% at 6 months. The percentage of contractile material was reduced for the 3 and 6 months animals to 80-64%, respectively, and was replaced primarily by fat. Similar, but less pronounced results were also observed for the quadriceps muscles of the contralateral hindlimbs, suggesting that repeat BTX-A injections cause muscle atrophy and loss of contractile tissue in target muscles and also in non-target muscles that are far removed from the injection site.