Lisfranc injury: Refined diagnostic methodology using weightbearing and non-weightbearing radiographs.

BACKGROUND: To compare diagnostic parameters for Lisfranc instability on WB and NWB radiographs and to assess the inter-observer reliability of a standardized diagnostic protocol. PATIENTS AND METHODS: Patients who had undergone surgical treatment for subtle, purely ligamentous Lisfranc injury with both WB and NWB post-injury, pre-surgery films (n = 26) were included in this multicentre, retrospective comparative study. Also included was a control group (n = 26) of patients with isolated fifth metatarsal avulsion fractures who similarly had both WB and NWB films. Multiple midfoot distance and alignment measurements were used to evaluate the Lisfranc joint on both WB and NWB views. To evaluate interobserver reliability, measurements were made by two independent observers across a cohort subset. RESULTS: When comparing the NWB views between groups, only C1M2 (medial cuneiform- second metatarsal) distance was found to be significantly larger (∆ = 1.35 mm, p <0.001) for Lisfranc injuries. Most notably, C2M2 (Intermediate cuneiform - second metatarsal) step off-caused by lateral translation of the second metatarsal base-was not significantly different (∆ = 0.39 mm, p = 0.101) between Lisfranc patients and controls. On WB views, Lisfranc patients had significantly larger changes to C1M2 distance and C2M2 step-off as compared to controls (∆ = 2.97 mm, p <0.001 and ∆ =  1.98 mm, p <0.001 respectively). M1M2 (first to second intermetatarsal) distance was not significantly different between patients and controls in WB films. Within the cohort of ligamentous Lisfranc patients, C1M2 distance and C2M2 step-off were significantly larger in WB when compared to NWB films (∆ =  1.77 mm, p <0.001 and ∆ =  1.58 mm, p <0.001 respectively). For these parameters, inter-observer reliability scores (ICC) of >0. 90 were found when interpreting WB radiographs and ICC's ranging between 0.61 and 0.80 were found when interpreting NWB radiographs. CONCLUSION: Using WB imaging for diagnosing subtle Lisfranc instability reveals larger diastasis in the tarsometatarsal joint and has a higher interobserver reliability compared to NWB imaging. Clinical concern for subtle or occult Lisfranc instability in any patient should therefore trigger WB radiographic assessment since such injuries may be missed on NWB views.

Novel values in the radiographic diagnosis of ligamentous Lisfranc injuries.

BACKGROUND: Ligamentous Lisfranc instability is commonly missed on unilateral radiographs. However, measurement protocols for bilateral weightbearing radiographs have not been standardized. The primary aim of this study was to investigate the optimal cut-off values for diagnosing Lisfranc instability by evaluating the side-to-side differences of preoperative bilateral weightbearing radiographs among patients with surgically-confirmed ligamentous Lisfranc instability. A secondary aim was to investigate whether the midfoot measurements for detecting Lisfranc injury could also be used in patients with a pre-existing bilateral Hallux Valgus (HV) deformity by evaluating whether the Lisfranc measurements could be affected by a foot deformity as HV. PATIENTS AND METHODS: Patients who underwent surgical repair of ligamentous Lisfranc instability, as well as a separate cohort with bilateral hallux valgus deformity, were included in this multicenter retrospective cohort study. A standardized radiographic measurement protocol was used to assess the midfoot and a receiver operator correlation (ROC) analysis was used to identify the optimal cut-off value for measurements. Interclass Correlation (ICC) scores were calculated to assess the interrater reliability of the Lisfranc area measurement. RESULTS: Forty-seven patients were included in the Lisfranc group with a mean age of 33 (± 15) years and 25 patients were included in the HV group with a mean age of 51 (± 15) years. For the Lisfranc group, measurements that demonstrated a significant side-to-side difference included; increased C1M2 diastasis of 2.4 mm (± 1.4, P<0.001), increased C1M2 surface area of 24 mm2 (± 15, P<0.001), C2M2 malignment by 1.7 mm (± 1.2, P<0.001), second tarsometatarsal joint dorsal step-off sign by 0.8 mm (± 0.7, P<0.001), and arch height by 2.5 mm (± 6.4, P<0.048), all greater on the injured side. In the HV group, side-to-side measurements were not significantly different. There was no significant difference comparing the M1M2 measurement in the HV group with the injured (P = 0.16) or uninjured (P = 0.08) foot in the Lisfranc group. The optimal cut-off points were between the injured and uninjured foot in the Lisfranc group were 2.1 mm for C1M2 diastasis, 0.7 mm for the C2M2 alignment, and 30 mm2 for the C1M2 surface area. The ICC-score for the second C1M2 area measurement was 0.88. CONCLUSION: Bilateral foot weightbearing radiographs can effectively diagnose ligamentous Lisfranc instability using a standardized measurement protocol. Malalignment of the medial aspect of the second metatarsal base ≥0.3 mm relatively to the intermediate cuneiform offers a high sensitivity, and distance ≥2.1 mm between the second metatarsal base and the medial cuneiform has a high specificity. Intermetatarsal distance between the first and second metatarsal base has a low sensitivity and specificity and should not be used in solitary for diagnosis. LEVEL OF EVIDENCE: Level III, retrospective comparative study.

Early onset albuminuria in Dahl rats is a polygenetic trait that is independent from salt loading.

The aim of the study was to characterize the genetic basis for the early onset of increased urinary albumin excretion (UAE) observed in the salt-sensitive Dahl rat (SS). We first characterized blood pressures and UAE values in adult SS compared with the spontaneously hypertensive rat (SHR) strain. Blood pressure measurements by radiotelemetry at 14 wk demonstrated similar spontaneous hypertension in both strains on a low-sodium diet containing 0.2% NaCl by weight, whereas UAE was markedly increased in SS compared with SHR (253.07 +/- 68.39 vs. 1.65 +/- 1.09 mg/24 h, P < 0.0001). Analysis of UAE in young animals of both strains fed a low-sodium diet demonstrated that UAE is elevated in SS as early as 4 wk of age (P < 0.0001), when ultrastructural evaluation of glomeruli by electron microscopy appears still normal. At 8 wk SS demonstrated a 280-fold elevated UAE compared with SHR (P < 0.0001). Consequently, to identify quantitative trait loci (QTLs) contributing to salt-independent early manifestation of increased UAE in the SS rat, we performed genome-wide linkage and QTL mapping analysis in a young F(2) population derived from the two contrasting strains. UAE was determined in 539 F(2) animals at 8 wk. We identified seven suggestive or significant UAE QTLs on rat chromosomes (RNO) RNO2, RNO6, RNO8, RNO9, RNO10, RNO11, and RNO19, accounting together for 34% of the overall variance of UAE in this F(2) population. Thus early onset albuminuria in the SS rat is under polygenetic influence and independent from salt loading.