THE bACK PAgE REsEARCh REVIEW Getting to the root cause of foot drop revieweD by shawn thistle Study titLe: Assessment of hip abductor power in patients with foot drop: A simple and useful test to differentiate lumbar radiculopathy and peroneal neuropathy AuthOrS: Jeon C, Chung N, Lee Y et al. PubLicAtiOn inFOrmAtiOn: Spine 2013; 38(3): 257–263. F oot drop, or dorsiflexion weak-ness, is one area of clinical practice that can sometimes be misleading. This clinical sign can stem from various prob-lems, including a lumbar disc hernia-tion, pressure on the lumbosacral plexus and compression of the fibular (pero-neal) nerve. Weakness of the hip abduc-tors can also stem from several sources, including muscular weakness and neu-rological compromise. The superior gluteal nerve, which is derived from the lumbosacral trunk and the L5 root, supplies the hip abductor muscles (glu-teus medius, gluteus minimus and ten-sor fasciae latae). The L5 nerve root also supplies the ankle dorsiflexors. Weak-ness of these muscles can be produced by the lesions proximal to the division of superior gluteal nerve. This study aimed to determine the di-agnostic validity and reliability of assess-ing hip abductor power for differentiating between lumbar radiculopathy and per-oneal neuropathy as a root cause of foot drop. The authors hypothesized concom-itant weakness of hip abductor power and foot drop would be associated with lumbar radiculopathy. Pertinent result Unilateral foot drop involvement was found in 85.2 per cent of the patients (the remaining patients had bilateral involvement). The most common etiol-ogy of foot drop was peroneal neuropa-thy (45.9 per cent), followed by lumbar radiculopathy (34.4 per cent), lumbosa-cral plexopathy (14.8 per cent) and sciatic nerve disorder (4.9 per cent). When considering all the manual mus-cle tests and sensory outcome measures evaluated, statistically, hip abduction power was the only significantly different measure between the lumbar radiculop-athy and peroneal neuropathy groups (P < 0.001). Among the 21 foot drop patients asso-ciated with lumbar radiculopathy, hip abductor weakness (MRC grade of < 3) was found in 18 patients with three pa-tients showing false-negative results. Meanwhile, among the 28 foot drop pa-tients with peroneal neuropathy, hip ab-ductor weakness (MRC grade of < 3) was found in one patient, while 27 patients showed true negative results. Therefore, the sensitivity and specificity of hip abductor power in the differential diagnosis of foot drop due to lumbar ra-diculopathy and peroneal neuropathy were found to be 85.7 per cent and 96.4 per cent, respectively. The positive and negative predictive values were found to be 94.7 per cent and 90 per cent, respectively. The interobserver reliability of the hip abductor power assessment by the three orthopedic surgeons had kappa values of 0.85 to 0.91, indicating excellent agree-ment. Conclusions and practical applications vague and atypical signs. Clinically, it can be difficult to identify the exact lo-cation of the problem or the pathologi-cal structure involved. In this study, the majority of spontaneous foot drops that were difficult to diagnose were caused by fibular (peroneal) neuropathy and lumbar radiculopathy. Concomitant hip abductor weakness was usually present in foot drop cases that were due to lum-bar radiculopathy, and rarely in those from peroneal neuropathy – this is the take-home message from this study. The electrodiagnostic test is useful and commonly used in the diagnosis of both peroneal neuropathy and lumbar radicu-lopathy. Unfortunately, the crucial find-ings in these tests do not appear until two to three weeks after the initial injury. The results from this study suggest that assessment of hip abductor power is a fast, simple and valid test in determining the etiology of the foot drop when dis-criminating between peroneal neuropa-thy and lumbar radiculopathy as differen-tial diagnoses. Peroneal neuropathy at the fibular head is fairly common due to the proxim-ity of the nerve to the skin with limited protection. Direct trauma, sustained pressure and a mass around the knee joint are common mechanisms of peroneal nerve injury. Lumbar degenerative dis-ease, including herniated nucleus pulpo-sus and spinal stenosis, are very common lumbar related causes of foot drop. Since peroneal neuropathy and lumbar radicu-lopathy are two of the most common causes of foot drop that present in clinical practice, this simple hip abductor muscle test can help speed up the diagnostic and treatment process. The foot drop patient can present with For more on this review, visit www. canadianchiropractor.ca. www.canadianchiropractor.ca dr. ShAwn thiStLe is the founder and president of Research Review Service, an online, subscription-based service to help busy practitioners integrate current, relevant, scientific evidence into their practice (www.researchreviewservice.com). This article was submitted by Dr. Daniel Avrahami for Research Review. 42 Canadian Chiropractor October 2013
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