SLR - July 2015 - Khoa D. Vuong

Second Toe Systolic Pressure Measurements are Valid Substitutes for First Toe Systolic Pressure Measurements in Diabetic Patients: A Prospective Study

Reference:  Bhamidipaty V, Dean A, Yap SL, Firth J, Barron M, Allard B, Chan ST. Second Toe Systolic Pressure Measurements are Valid Substitutes for First Toe Systolic Pressure Measurements in Diabetic Patients: A Prospective Study. Eur J Vasc Endovasc Surg. 2014 Nov 3.  

Scientific Literature Review

Reviewed By: Khoa D. Vuong, DPM
Residency Program: Pinnacle Health Hospital System- Harrisburg, PA

Podiatric Relevance:
Toe pressures are used to help assess healing capability in both vascular and podiatric settings.  Currently, studies have used the hallux primarily as a means of measurement for toe pressure.  Hallux measurements may not always be feasible due to associated ulceration or amputation, this study would allow the second toe as an alternative that could potentially provide an additional measurement opportunity. The purpose of this prospective review was to determine if there was a correlation in toe pressures of the 2nd toe with comparison of the hallux.  

Methods: A prospective study was performed on 100 individuals affected by diabetes mellitus with confirmed diagnosis via both HbA1c>6.5% and fasting glucose > 7mmol/L.  Individuals were required to have both a hallux and 2nd toe. Duplicate systolic toe pressures were measured with the hallux and its adjacent 2nd toe via the Systoe Automated Toe Pressure System, Systoe Photophlethymsograph Sensor Cuff and occlusion cuffs (120x22mm for hallux and 90x15mm for 2nd toe).  Correlation analysis was followed by Ordinary Least Products regression to detect if there was a relationship between the adjacent toe measurements.  The acceptable limits that were considered interchangeable were defined as between 5-10mmHg.

Results: 69 patients had systolic toe pressures bilaterally whereas 31 patients had one foot measured in this prospective study. The acceptable limit of interchangeable results was defined as between 5-10mmHg. The Ordinary Least Products regression showed no fixed or proportional bias between the two different methods of measurement in regards to the different cuff sizes.  Repeatability analysis showed 0.5% variation between duplicate measurements.   Variance of second toe pressures was constant across all values of hallux pressures.  The correlation coefficient r= 0.908 with p<0.001, which implied that 82% of the variation of the 2nd toe measurements is accounted for by knowing the first toe measurements.

Conclusions:
Systolic measurements of the 2nd toe in comparison of the hallux were considered interchangeable with a limit of 5-10mmHg difference.  Prior literature measuring the second toe systolic pressures, but no comparison was made to the hallux.  These prior studies had questionable accuracy in regards to the questionable measurement criteria (color changes of digit, Doppler sound, untested bladder cuffs, etc.)   This is the first known study which demonstrates that systolic toe pressures of the hallux in comparison to an adjacent 2nd digit can be interchangeable.  Limitations to the study include the heterogeneous population (diabetics) and the different size of the cuffs used to measure the hallux and the 2nd toe.  Due to the fact that there are some individuals who cannot have a hallux toe systolic pressure taken, the 2nd digit could be used as a viable alternative.

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