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Week 3 Report: Ankle Joint Functionality
Generated Jan 26, 2018 by rosemary.plapp1

Introduction: Breaking an ankle can lead to problems with mobility throughout one's lifetime. Many patients with broken ankles undergo surgery, which sometimes includes the placement of hardware to aid functionality. The current standard is to later remove this hardware after the patient heals. However, according to Wagoner, Creech, Nolan, and Meyr, there are many complications associated with the hardware extraction surgery, including pain, intra-articular fixation, and carcinogenesis (Wagoner, Creech, Nolan, & Meyr 2015). This study looks if there are differences in ankle functionality between patients who undergo hardware extraction and those that retain their hardware. 

Methods: We followed an orthopedist who performed surgery on 19 patients with broken ankles. 9 of these patients had their hardware removed after healing, while 10 of them retained their hardware. We then obtained the percentage of functionality from all 19 patients, yielding interval ratio data. A QQ test was used to determine if normality conditions were satisfied. Because the sample size of 19 was small (>30) and normality conditions were not satisfied, a Mann Whitney test was used to compare group medians. 

Analysis:

<result1>

The QQ plot above depicts the data values for the percentage of functionality of the group with hardware removed and the group with hardware retained. As the data values did not fall on the 45 degree line, normality conditions were not satisfied. Thus, a Mann Whitney Test was used to determine if the median percentage of functionality for the group with hardware removed was greater than the median percentage of functionality for the group with hardware retained. The p-value of 0.9727 rejected our research hypothesis, indicating that those with hardware removed do not experience greater functionality compared to those with hardware retained. 

<result2>

With 95% confidence, we can determine that the median difference in functionality between the hardware removed group and the hardware retained group is between -30 and 1. 

<result3>

Conclusion: There are differences in functionality between the hardware removed group and the hardware retained group, and there does not appear to be greater functionality for the hardware removed group. Because of the small sample size and lack of normality, a Mann Whitney test was the best choice to depict the findings. The small sample size would make these results difficult to generalize for the entire population. It is unfortunate that confounding factors were not accounted for, as other comorbidities and factors can affect ankle functionality. For example, obesity, history of multiple prior injuries, etc. can all negatively impact ankle functionality. Future studies should include larger, stratified samples in order to be able to generalize results for the population and account for confounding factors. 

References:

Wagoner, M.R., Creech, C.L., Nolan, C.K., & Meyr, A.J. (2015). Pictorial Review and Basic Principles of Foot and Ankle Hardware Extraction. Foot & Ankle Specialist, 8(4), 305-313. doi:10.1177/1938640015585964 

 


 

Result 1: Ankle Joint Functionality QQ Plot   [Info]
Right click to copy



Result 2: Mann-Whitney Ankle Joint Functionality   [Info]
Hypothesis test results:
m1 = median of Hardware Removed
m2 = median of Hardware Retained
m1-m2 : m1 - m2
H0 : m1-m2 = 0
HA : m1-m2 > 0
Differencen1n2Diff. Est.Test Stat.P-valueMethod
m1 - m22910-17670.9727Norm. Approx.



Result 3: Confidence interval ankle joint   [Info]
95% confidence interval results:
m1 = median of Hardware Removed
m2 = median of Hardware Retained
m1-m2 : m1 - m2
Differencen1n2Diff. Est.L. LimitU. LimitMethod
m1 - m2910-17-301Exact (95.652645)