Maskill JD, Florie EE, Pomeroy GC.  A new technique for lesser metatarsal osteotomy in the treatment of metatarsalgia.  Techniques in Foot and Ankle Surgery.  2009 Dec; 8(4): 209-14.

WHY did the authors undertake this study?
Surgical intervention for the treatment of metatarsalgia continues to present an interesting challenge for the foot and ankle reconstructive surgeon.  A multitude of procedures have been described, all with relative benefits and potential complications.  The authors of this study present yet another surgical technique for you to consider, specifically an extra-articular shortening osteotomy with plate fixation.

HOW did they attempt to answer this question?
The authors first present their specific technique in detail, and then analyze a retrospective series of their patients.  Two parallel oblique osteotomies are performed within the distal metatarsal shaft, and a 2-4mm segment of bone is removed.  This accomplishes both a shortening and dorsiflexory correction on the distal metatarsal.  The construct is stabilized with a 3-hole 1/3 tubular plate from a small fragment set.  

Twenty-seven consecutive patients over an 8-year period were retrospectively reviewed.  Pre- and post-operative AOFAS Lesser Metatarsophalangeal-Interphalangeal Forefoot Scale scores were compared following an average follow-up period of 61.5 months.

WHAT were the specific results?
Post-operative AOFAS scores improved to an average of 85.6 which is comparable to other metatarsal osteotomies, as were their overall patient satisfaction scores (77%).

HOW did the authors interpret these results?
From these results, the authors concluded that their lesser metatarsal osteotomy compared favorably to other described techniques.

Goodney PP, Nolan BW, Schanzer A, Eldrup-Jorgensen J, Bertges DJ, Stanley AC, Stone DH, Walsh DB, Powell RJ, Likosky DS, Cronenwett JL.  Factors associated with amputation or graft occlusion one year after lower extremity bypass in northern New England.  Ann Vasc Surg.  2010 Jan; 24(1): 57-68.  (Pubmed ID#: 19748222)

WHY did the authors undertake this study?
Lower extremity bypass revascularization is an extensive surgical intervention with significant associated morbidity and mortality.  Although patient selection has been identified as an important key for procedure success, this selection has in the past been a relatively subjective task.  The aim of this study is to identify risk factors associated with failure (defined as major amputation or graft occlusion) 1 year post-operatively. 

HOW did they attempt to answer this question?
Over 100 demographic and clinical variables from 2,306 lower extremity bypass procedures in 2,031 patients from 60 different surgeons and 11 different New England hospitals were collected over a 4-year period.  Cox proportional hazard ratios were used to identify risk of treatment failure occurring within the first year of surgery.

WHAT were the specific results?
Seventeen percent of bypass procedures resulted in failure in the form of amputation or graft occlusion within the first post-operative year.  Eight characteristics were identified as statistically associated with failure:  age <50, nonambulatory status preoperatively, dialysis dependence, diabetes, critical limb ischemia, need for venovenostomy, tarsal target, and preoperatively coming from a nursing home.  Patients with none of these risk factors had a failure rate of <1%, while patients with three or more of these risk factors had a failure incidence of 30%. 

HOW did the authors interpret these results
The authors concluded that these results can be utilized by surgeons to more fully educate and inform patients about the risks and potential complications of these procedures.  It certainly plays a role when primary amputation versus revascularization with limb salvage is considered.

Most studies will set 0.05 as an alpha (α) level at the beginning of a study.  The alpha level is definitely something that should be determined at the beginning of a study before any statistical test is performed.  It’s comparable to deciding ahead of time what you think is important, before the actual results can cloud your judgment about what is important.  This number represents that chance you are willing to take to make a Type I Error, or the chance of rejecting the null hypothesis of no effect when the null hypothesis of no effect is actually true.  In other words, a type I error would be saying there is a difference between two variables when in actuality there isn’t a difference.  An alpha level of 0.05 means that we are willing to make a type I error 0.05, or 5%, of the time.  There’s not necessarily a “rule” that says we have to set the alpha level of 0.05 as opposed to 0.10 or 0.01 or even 0.001, but it is the value that has been accepted over the years as an acceptable risk for making a Type I error.                

Let’s apply this to the Goodney et al article.  This article is attempting to determine if a given variable (age, type of surgery, co-morbidities, etc) is associated with a given outcome (treatment failure as defined by amputation or graft occlusion).  From our definition of a Type I Error above, what is our “null hypothesis of no effect” in this situation?  It is that the variable has “no effect” or no association with the outcome.  As a plain terms example, the null hypothesis of no effect is that the age of a patient (variable) undergoing a lower extremity bypass will not have an effect on whether or not they have an amputation or graft occlusion (outcome). 

For the age group 70-80, a p-value of approximately 0.7 was calculated.  Since 0.7 is not less than 0.05, there is not statistical significance and we can conclude that an age of 70-80 did not have an effect on outcome in this cohort of patients.  For the age group 40-50, a p-value of approximately 0.001 was calculated.  Since 0.001 is less than 0.05, there is statistical significance and we can conclude that an age of 40-50 had some effect on outcome in this cohort of patients.