title: A modified straight leg raise test to differentiate between sural nerve pathology and Achilles tendinopathy. A cross-sectional cadaver study.
abstract: BACKGROUND
  A modified straight leg raise test for the sural nerve (SLRSURAL) has been proposed to assist in the differential diagnosis of sural nerve pathology in people with posterior calf or ankle pain, or lateral foot pain. The biomechanical rationale is that strain in the dorsolateral ankle and foot structures following dorsiflexion-inversion can be selectively increased in the sural nerve with hip flexion. There are however no studies which have investigated whether hip flexion can increase strain in the sural nerve at the ankle.
  
  
  OBJECTIVE
  To measure strain and longitudinal excursion of the sural nerve and Achilles tendon during a modified SLR.
  
  
  METHODS
  Cross-sectional cadaver study, with a repeated-measures design.
  
  
  METHODS
  Strain and excursion were measured unilaterally in seven embalmed cadavers using differential transducers and a digital calliper. Data were analysed with repeated-measures ANOVAs (p < 0.05).
  
  
  RESULTS
  With hip flexion (mean (SD): 54.6 (10.6) degrees), strain increased in the sural nerve (0.9 (0.5)%; p = 0.008), but not in the Achilles tendon (0.3 (0.3)%; p = 0.16). The sural nerve moved 1.0 (0.5) mm proximally with hip flexion (p = 0.02).
  
  
  CONCLUSIONS
  The load placed on the sciatic nerve following hip flexion is transmitted distally to the sural nerve. These findings provide biomechanical support for the SLRSURAL. The relatively small changes in strain and excursion were most likely due to limited available ankle mobility in the tested cadavers. Further research is required to establish the diagnostic accuracy of SLRSURAL in a clinical setting.
authors: Faculty of Behavioural and Movement Sciences, MOVE Research Institute Amsterdam, VU University Amsterdam, Amsterdam, The Netherlands; Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia. Electronic address: m.coppieters@vu.nl.
authors: Michel W
authors: MW
authors: Coppieters
authors: Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia. Electronic address: Jennifer.L.Crooke@gmail.com.
authors: Jennifer L
authors: JL
authors: Crooke
authors: Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia. Electronic address: peterlawrenson@hotmail.com.
authors: Peter R
authors: PR
authors: Lawrenson
authors: Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia. Electronic address: khoo.shin.jiun@sgh.com.sg.
authors: Shin Jiun
authors: SJ
authors: Khoo
authors: Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia. Electronic address: terje.skulstad@gmail.com.
authors: Terje
authors: T
authors: Skulstad
authors: Physiotherapy, School of Health and Rehabilitation Sciences, The University of Queensland, Brisbane, Australia. Electronic address: y.betor@uq.edu.au.
authors: Yaheli
authors: Y
authors: Bet-Or
mesh_terms: D000125:Achilles Tendon / Q000473:pathology*; D001696:Biomechanical Phenomena; D002102:Cadaver; D003430:Cross-Sectional Studies; D006801:Humans; D035002:Lower Extremity / Q000502:physiology*; D016059:Range of Motion, Articular; D052256:Tendinopathy / Q000473:pathology*; D013979:Tibial Nerve / Q000502:physiology; D016474:Weight-Bearing
keywords: Achilles tendinopathy; Ankle pain; Differential diagnosis; Neurodynamics; Neuropathy; Structural differentiation