Nickerson DS.  Low recurrence rate of diabetic foot ulcer after nerve decompression. J Am Podiatr Med Assoc.  2010 Mar-Apr; 100(2): 111-5. (PubMed ID: 20237362)

WHY did the authors undertake this study?
Diabetic sensorimotor peripheral neuropathy is a major contributing factor associated with foot ulceration and limb loss.  The author of this study works from the hypothesis that this neuropathy is a treatable entity, as opposed to an irreversible pathology, through surgical nerve decompression.

HOW did they attempt to answer this question?
The primary outcome measure of the study was diabetic foot ulcer recurrence following surgical nerve decompression.  Please note how this is an interesting (and creative) outcome measure.  It is not at all a direct measure of peripheral neuropathy, but it does indirectly and objectively measure a consequence of peripheral neuropathy.   So in effect, the author is not measuring the effect of the surgery on diabetic neuropathy, but the effect of surgery on the effects of diabetic neuropathy!

Inclusion criteria of the population cohort were diabetic patients with a diagnosis of sensorimotor peripheral neuropathy, previous/current neuropathic foot ulceration, and at least one palpable foot pulse who had undergone triple nerve release of the ulcerated extremity.

WHAT were the specific results?
At a mean follow-up of 2.5 years (12-month minimum), the prevalence of ipsilateral foot ulcer recurrence was 4.28% (8 ulcerations in 187 patients).

HOW did the authors interpret these results?
From this result, the author concluded  that surgical nerve decompression may be an option to decrease recurrence of foot ulceration in high-risk feet.  He also implies that this finding may contribute to our understanding of the pathogenesis of diabetic sensorimotor peripheral neuropathy.

Vand den Bekerom MP, van Dijk CN.  Is fibular fracture displacement consistent with tibiotalar displacement?  Clin Orthop Relat Res. 2010 Apr; 468(4): 969-74.  (Pubmed ID#: 19582527)

WHY did the authors undertake this study?
This is a rather profound study that investigates our pre-operative evaluation of SER type II ankle fractures.  It is relatively well accepted that lateral talar displacement of >2mm in the ankle mortise is associated with decreased tibio-talar joint contact area and altered ankle joint mechanics.  What this study questions however, is whether the amount of fracture displacement (as measured between the fracture fragments) is actually providing a measure of “movement” of the talus/fibula within the ankle mortise..

HOW did they attempt to answer this question?
The authors measured three distances between the tibia and fibula on pre- and post-operative mortise radiographs following SER type II ankle fracture open reduction-internal fixation:

• The amount of fracture displacement (as measured between the proximal and distal fibular segments)
• The distance between the tibia and proximal fibular segment
• The distance between the tibia and distal fibular segment

WHAT were the specific results?
The average fracture displacement between the fibular segments was 2.3mm.  What was interesting, however, is that when this 2.3mm of displacement was reduced, the majority of the reduction came between the tibia and the proximal fibular segment (1.8mm), as opposed to the tibia and distal fibular segment (0.6mm).

HOW did the authors interpret these results?
From these results, the authors concluded that the majority of “movement”  or “displacement” from SER type II fibular fractures occurs between the tibia and proximal fibular segment (with the proximal fibula displaced medially), and that the distal fibula/talus are relatively stationary compared to the tibia and ankle mortise.  In other words, 2mm of fibular fracture displacement does not mean that the talus/fibula are laterally displaced 2mm within the ankle mortise.  They instead conclude that the amount of fibular fracture fragment displacement is not a reliable measure for pre-operative planning, and that surgical reduction of any SER type II ankle fracture (without increased medial clear space or deltoid involvement) is called into question.

Let’s take a closer look at the use of comparative statistical tests as it applies to the van den Bekerom and van Dijk article.  First off, this is an open access article meaning that anyone with internet access can download the article through the link, so I invite everyone to do so and follow along.  This was a very interesting article in that it provided absolutely no comparative statistics for their pre- and post-operative measurements.  Instead, they only provided descriptive statistics (means and standard deviations) in one basic table (Table 1 on page 971).  These were the only “numbers” in the whole study!

This table very simply shows that following ORIF, fibular fracture displacement decreased from 2.3mm to 0.1mm, the tibia-distal fibula fragment distance decreased from 5mm to 4.4mm, and the tibia-proximal fibula distance increased from 3mm to 4.8mm.

Was the decrease in fibular fracture displacement statistically significant?  We don’t know….the authors didn’t perform a comparative statistical test to figure this out.  I was curious, so I performed a paired t-test (and a Wilcoxon signed-rank test just to be safe) on the data to see, and found that indeed there was easily a statistically significant difference (p<0.05) between the pre- and post-operative values.   But this statistical significance doesn’t give me any more information than the clinical significance does.  It’s more important to me as a surgeon that they decreased the fracture displacement from >2mm to essentially 0mm.  They ended up with an exact anatomic reduction of the fracture, so what do I care if it was statistically significant difference or not? 

There are a lot of cases where adding complicated comparative statistical tests can confuse the results of an article and really take away from the author’s conclusions.  This is probably the case in this article, and may be the reason that the authors chose not to include comparative statistics.  The finding that the authors really wanted to drive home in this article was that the ankle mortise was essentially unchanged following ORIF of SER type II ankle fractures.  The measurement they used that best illustrated the ankle mortise was the tibia-distal fibula fragment distance.  As per Table 1, this decreased from an average of 5mm pre-operatively to 4.4mm post-operatively.   This change represents less than 1mm and only about 25% (0.6/2.3) of the initial fracture fragment displacement.  Clinically, most people would agree, this is not a big difference.