Femoral Neck Stress Fracture. Can MRI Grade Help Predict Return-to-Running Time?, Ramey LN et al., Am J Sports Med.(2016) Preview

Femoral Neck Stress Fracture. Can MRI Grade Help Predict Return-to-Running Time?, Ramey LN et al., Am J Sports Med.(2016) Preview

Femoral Neck Stress Fracture. Can MRI Grade Help Predict Return-to-Running Time?

Ramey LN et al. http://www.ncbi.nlm.nih.gov/m/pubmed/27261475/

Am J Sports Med.(2016) Preview

Re-post by Andy Franklyn Miller

Har Idag kigget lidt på skader omkring lårbenet og retur til sport tider og fik så tilsendt dette nye studie af Andy Franklyn Miller.

Studiet beskriver Stress fraktur af den øvre lårbensknogle (Femoral Neck Stress Fractures / FNSF), som opstår når gentagne / overdreven stress / load er større end evne til at opretholde tolerancekravet.

Formålet med denne undersøgelse er at fastslå, hvis MRI-grade af skade korrelerer med Return to Running timer efter FNSF.


A retrospective review was performed on patients diagnosed with FNSF at a single sports medicine clinic from January 2009 to December 2015. A total of 27 FNSFs occurring in 24 patients were included. The mean age was 32.9 ± 9.2 years (range, 18-51 years). All patients but one were self-identified runners, with an average weekly mileage of 29.6 ± 20.2 miles (range, 10-75 miles). The average symptom duration before medical evaluation by a specialist was 6.3 ± 6.4 weeks (range, 1.5-33 weeks). The rate of low bone mineral density (BMD) for all patients was 41.0%; by grade, the rate of low BMD was 0% for grade 1, 60% for grade 2, 50% for grade 3, and 44.4% for grade 4. The mean body mass index (BMI) was 23.0 ± 4.6 (range, 15.06-32.92). Only 3 patients were classified as underweight by BMI, and all suffered from grade 4 injuries.
All fractures were compression sided and were treated nonoperatively. A nonoperative approach, with a standard, graduated return-to-play protocol guided by pain, was used for all FNSFs. All patients were required to remain nonweightbearing for a minimum of 4 to 6 weeks. Once pain free, they were upgraded to partial weightbearing and then full weightbearing. They gradually began nonimpact exercise and, if free of pain, progressed to low-impact exercise and, finally, running. All patients were enrolled in a standard physical therapy regimen to address deficits in strength throughout the kinetic chain (particularly hip abductors) and range of motion. The medical record of each injury case was reviewed for RTR time.
The MRIs in all cases were reviewed and the Arendt grading scale was used to grade each stress fracture. Short tau inversion recovery (STIR) and T1- and T2-weighted images were reviewed and graded based on the presence or absence of periosteal or bone marrow edema and/or a fracture line. Grade 1 injuries were defined as having signal change representing periosteal or marrow edema on STIR imaging only. Grade 2 injuries involved signal change in STIR and T2 images. Grade 3 injuries involved signal change on all imaging sequences (STIR, T2, and T1) without fracture line. Grade 4 injuries were defined as having signal change on all imaging sequences with fracture line.

Statistical analysis was performed using survival analysis and Cox proportional hazard model to compare the RTR time between grades. Cox regression was repeated, adjusted for age, BMD, and BMI.
The mean RTR time in weeks was 7.4 ± 2.7 (range, 4-11) for grade 1, 13.8 ± 3.8 (range, 6-21) for grade 2, 14.7 ± 3.5 (range, 8.5-24) for grade 3, and 17.5 ± 3.4 (range, 10-32) for grade 4 injuries. Using survival analysis, grade was found to have a significant effect on RTR time (P = .0065). Using the Cox proportion hazard model, a statistically significant difference in RTR time was found between grade 1 injuries and all other grades (P = .036 for grade 2, P = .014 for grade 3, and P = .002 for grade 4). The hazard ratio was significant (P = .037). Age (P = .71) and BMD (P = .81) did not have an effect on RTR time. After adjusting for age and BMD, the Cox analysis was not significantly changed, and the adjusted hazard ratio remained significant (P = .05). BMI tended to have an effect on RTR time (P = .09). Inclusion of BMI as a third covariate in the Cox model resulted in a loss of statistical significance of the hazard ratio (P = .13), although the difference between grades
2 to 4 and grade 1 injuries remained significant (P = .062 for grade 2, P = .065 for grade 3, and P = .045 for grade 4). There was no significant difference found between grades 2 and 3 ( P = .82), grades 2 and 4 (P = .37), and grades 3 and 4 (P = .31).
The study demonstrates that grade 2 to 4 FNSFs require a significantly longer time to RTR than do grade 1 injuries, averaging a 6- to 10-week increase, respectively. MRI can provide accurate diagnostic information for FNSFs, as well as important prognostic information regarding time to RTR. This study also suggests that patients with low BMI are more likely to have grade 4 injuries and require a longer RTR time. Additional work is needed to fully define RTR guidelines.

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Andreas Bjerregaard
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