Journal:  The Journal of Foot and Ankle Surgery
2009 Sep-Oct; 48 (5) Follow this link to the table of contents.

Article for review:  Krannitz KW, Fong HW, Fallat LM, Kish J.  The effect of cigarette smoking on radiographic bone healing after elective foot surgery.  J Foot Ankle Surg.  2009 Sep-Oct; 48(5): 525-7.   (PubMed ID: 19700113)

WHY did the authors undertake this study? 
Although the detrimental effects of cigarette smoking have been well established in terms of the pathophysiologic mechanisms, the clinical effect on elective forefoot surgery has not been studied.  In this investigation, the authors attempt to answer the clinical question:  What is the effect of cigarette smoke on bone healing following elective distal first metatarsal osteotomy for the surgical correction of hallux abductovalgus surgery?

HOW did they attempt to answer this question?
The primary outcome measure of the study was radiographic bone healing of the first metatarsal osteotomy site.   Sequential post-operative radiographs (at 3-week intervals) were presented to blinded evaluators attempting to determine "cortical bridging consistent with consolidation of the osteotomy".   Three secondary outcome measures were recorded in an attempt to quantify the patient’s level of nicotine dependence.  First, patients were grouped as to whether they were active cigarette smokers, secondhand smokers or non-smokers. Second, the Fagerström test is a patient self-reported evaluation of nicotine dependence that was recorded the morning of surgery.  And finally, urine cotinine levels were measured pre-operatively and throughout the postsurgical healing period to quantify a metabolite of nicotine in the urine.

Inclusion criteria of the population cohort were patients undergoing Austin bunionectomy with internal screw fixation.  Exclusion criteria were those <18 years old, >70 years old, with previous HAV surgery on the same foot, with a radiographic appearance of osteoporosis, or with a diagnosis of either osteoporosis, diabetes or another immunocompromising condition.

WHAT were the specific results? 
Statistically significant differences were found with each of the primary and secondary outcome measures.   One-way analyses of variance demonstrated increased bone healing times between the smoking versus nonsmoking groups (120 days versus 69 days; P < 0.001).  Statically significant correlations were also found with the Pearson correlation when associating both the Fagerström score (P < .05) and urine cotinine levels (P < .01) to the time until radiographic bone healing.

HOW did the authors interpret these results?
From these results, the authors concluded that it took smokers 1.73 times longer to reach radiographic bone healing compared to nonsmokers following distal first metatarsal osteotomy for the surgical correction of HAV.  They warned that both the surgeon and the patient should be aware of this delay in the perioperative period.

Journal: Anesthesia and Analgesia
2009 Sep; 109 (3): 943-50.  Follow this link to the table of contents.

Article for review:  Beloeil H, Gentili M, Benhamou D, Mazoit JX.  The effect of a peripheral block on inflammation-induced prostaglandin E2 and cyclooxygenase expression in rats.  Anesth Analg.  2009 Sep; 109 (3): 943-50.

WHY did the authors undertake this study?
Over the last several decades, the normal physiology and abnormal pathophysiology associated with post-operative pain have become increasingly well understood.  Active surgeons are now able to directly intervene into these processes both peripherally and centrally to improve post-operative patient outcomes.  The authors of this study attempt to answer the clinical question:  Can a peripheral local anesthetic block decrease the inflammation associated with surgical trauma centrally at the spinal cord?

HOW did they attempt to answer this question?
The outcome measures of this study included measures of peripheral edema (paw circumference), pathologic peripheral sensitization (withdrawal latencies), and pathologic central sensitization (prostaglandin E2, COX-1 and COX-2 levels in the cerebral spinal fluid).

Sprague-Dawley rats were divided into six groups varying in the peripheral stimulus (injection of saline or carrageenan [CARR] which mimics surgical trauma), peripheral sciatic nerve block (saline or bupivacaine) and a systemic injection (saline or bupivacaine).

WHAT were the specific results?
Of the groups of rats that received the peripheral trauma mimicking surgical intervention, those who also received the local anesthetic peripheral nerve block did significantly better in terms of peripheral pain, peripheral inflammation and central inflammation.

HOW did the authors interpret these results?
Based on these results, the authors concluded that peripheral local anesthetic nerve blocks are an important component in an attempt to control the inflammation associated with post-operative pain.  Peripheral local anesthetic nerve blocks are unique among pain management interventions in that they act both peripherally and centrally to inhibit the normal physiology and abnormal pathophysiology associated with operative trauma.

Let’s take a closer look at the topic of outcome measures.  I like to think of outcome measures as the specific way in which the authors attempt to answer their clinical question or hypothesis.   As critical readers, it is important to appreciate what an outcome measure is really telling us.  In our Krannitz study for example, they asked the question: What is the effect of cigarette smoke on bone healing following elective distal first metatarsal osteotomy for the surgical correction of hallux abductovalgus surgery?  Based on this question, they had to come up with several outcome measures to quantify the variables "bone healing" and "cigarette smoke".  

They quantified "bone healing" as plain film radiographic evidence of "cortical bridging consistent with consolidation of the osteotomy site" at 3-week intervals.  As critical readers, we should first ask ourselves, "Is this a valid way to measure the question?".   I think that most of us would agree that it is.  Although there is certainly a subjective component to this measure (as the authors freely acknowledged) and there are perhaps some more specific tests (like a CT, which is of course more specific, but less practical), the way that we typically clinically determine whether or not an osteotomy has healed is to take an x-ray.

We should then ask ourselves, "What exactly is this outcome measure telling us?"  Because the radiographs were taken at 3-week intervals, the study did not actually measure when the osteotomy had healed, but really whether it had healed by the 6-week mark, 9-week mark, 12-week mark, etc.   So when the authors reported that the average time to osteotomy healing in non-smokers was 69 days (9.9 weeks), what they are probably saying is that the majority of nonsmoking patients were healed closer to the 9-week mark.  And when they reported that the average time to osteotomy healing in smokers was 120 days (17.1 weeks), what they are probably saying is that the majority of smoking patients were healed closer to the 18-week mark.

If this assumption is correct, then it is important because it may help explain part of the reason why there was no statistically significant difference found between the nonsmokers (69 days or 9.9 weeks) and the secondhand smokers (78 days or 11.1 weeks). These two averages, 9.9 weeks and 11.1 weeks, fall right between two of the study radiographic intervals, 9-weeks and 12-weeks.  Both are closer to and equidistant from the halfway mark of this range (10.5 weeks) than they are to either of the extremes.  If the authors had taken radiographic measurements every week, then they might have been more likely to find a statistically significant difference between these two groups (of course this would be less clinically practical).  They would also probably be more likely to find a statistically significant difference between these two groups if they had studied more patients and decreased the standard deviation of the means. And of course on the other hand, there really might not be a statistically significant difference between nonsmokers and secondhand smokers. 

This seemingly small difference is part of the reason why statistics are at the same time both so important, but also so frustrating, when it comes to critical evaluation of the medical literature.  It’s also one of the reasons why I think this will be an important section as we move forward with this eZine.  Each issue we’ll try and tackle one small statistical finding to help you keep your eyes open in the future.

Please join us for an online discussion of these articles:
-How do you approach the perioperative management of smoking patients?
-What’s different about your consent in these situations?
-Is anyone prescribing Chantix?

What about peripheral nerve blockades?
-Anyone routinely using popliteal nerve blocks for elective forefoot cases?
-Anyone performing their own popliteal nerve blocks?
-What about compounding? Anyone using anything else besides straight local perioperatively (opioids, corticosteroids, NSAIDs, etc.)?