Carpal tunnel syndrome (CTS) leads to distortion of axonal architecture, demyelination and fibrosis within the median nerve. Diffusion tensor imaging (DTI) characterises tissue microstructure and generates reproducible proxy measures of nerve ‘health’ which are sensitive to myelination, axon diameter, fiber density and organisation. This meta-analysis summarises the normal DTI values of the median nerve, and how they change in CTS. This systematic review included studies reporting DTI of the median nerve at the level of the wrist in adults. The primary outcome was to determine the normal fractional anisotropy (FA) and mean diffusivity (MD) of the median nerve. Secondarily, we show how the FA and MD differ between asymptomatic adults and patients with CTS, and how these differences are independent of the acquisition methods. We included 32 studies of 2643 wrists, belonging to 1575 asymptomatic adults and 1068 patients with CTS. The normal FA was 0.58 (95% CI 0.56, 0.59) and the normal MD was 1.138 × 10–3 mm2/s (95% CI 1.101, 1.174). Patients with CTS had a significantly lower FA than controls (mean difference 0.12 [95% CI 0.09, 0.16]). Similarly, the median nerve of patients with CTS had a significantly higher mean diffusivity (mean difference 0.16 × 10–3 mm2/s [95% CI 0.05, 0.27]). The differences were independent of experimental factors. We provide summary estimates of the normal FA and MD of the median nerve in asymptomatic adults. Furthermore, we show that diffusion throughout the length of the median nerve becomes more isotropic in patients with CTS.
BackgroundAnkle injuries are common presentations to the emergency department and may lead to syndesmotic instability. These have a high socioeconomic burden due to prolonged rehabilitation, chronic pain, and posttraumatic arthritis. Early diagnosis is essential to minimize these complications, and the assessment of instability in the clinical setting is often limited by pain and clinician experience. Cross-sectional imaging of the distal syndesmosis accurately evaluates the syndesmosis through abnormal bony relationships, which in the presence of instability, worsens during physiological loading. Cone-beam CT (CBCT) has gained popularity in the diagnosis of these injuries because it enables syndesmotic assessment under weightbearing conditions, it mitigates the high radiation dose, and it is time-efficient.Questions/purposesThe purposes of this systematic review were: (1) to establish normal values for weightbearing CBCT of the syndesmosis in uninjured ankles and ascertain interobserver reliability and (2) to identify the impact of weightbearing on the syndesmosis in patients with occult ankle injuries and assess the effect of patient demographics on these metrics.MethodsThis systematic review was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered in PROSPERO (ID CRD42021248623). MEDLINE, PubMed, Embase, and Emcare databases were searched for studies assessing for syndesmotic instability, of which 307 studies were screened and 11 studies with 559 ankles in 408 uninjured patients and 151 patients with syndesmotic instability were included. All patients 18 years of age or older presenting with unilateral ankle injuries who underwent weightbearing CBCT for the diagnosis of an occult fracture or syndesmotic instability compared with the uninjured contralateral side were included. A control group of uninjured ankles was identified during weightbearing CBCT performed for other indications such as forefoot or midfoot injuries. Methodological assessment of the studies was performed using the Risk of Bias In Non-randomized Studies (ROBINS-1) tool and most included studies had a low risk of bias. Thus, a random-effects restricted maximum likelihood ratio model was used.ResultsIn the uninjured ankle, the mean area of the tibiofibular syndesmosis was 112.5 ± 7.1 mm2, which increased to 157.5 ± 9.6 mm2 after injury when compared with uninjured ankles with a standardized mean difference of 29.5 (95% confidence interval 19.5 to 39.5; p < 0.01), and an excellent interobserver agreement (κ = 1.0 [95% CI 0.9 to 1.0]). However, syndesmosis volume decreased with age (β = -0.76; p = 0.04), and therefore, has a negative association with increasing age.ConclusionOur study has shown that the syndesmotic area is the most reliable parameter in the assessment of syndesmotic injuries because it increases in the presence of instability during weightbearing status. It is a composite measurement that could potentially allow clinicians to use weightbearin...
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