Cook KD, Clark G, Lui E, Vararia G, Wallace GF.  Strength of braided polyblend polyethylene sutures versus braided polyester sutures in Achilles tendon repair.  J Am Podiatr Med Assoc.  2010 May-Jun; 100(3): 185-8. (PubMed ID: 20479448)

WHY did the authors undertake this study?
There are a variety of potential surgical techniques and materials available to foot and ankle surgeons when considering repair of a ruptured Achilles tendon.  The authors of this study aim to directly compare two specific types of suture material:  2-0 FiberLoop and #2 Ethibond.

HOW did they attempt to answer this question?
The primary outcome measures of the study were two measures of suture failure:  (1) Ultimate tensile strength [defined as the point in which the suture material failed] and (2) Yield load [defined as the point in which the suture material underwent damage).

Rupture was simulated on a total of twelve cadaveric Achilles tendons (6 matched pairs), and repaired with a modified Krackow technique with either 2-0 FiberLoop or #2 Ethibond.  Limbs were then mounted to an Instron materials testing system and loaded to failure.

WHAT were the specific results?
Statistically significant differences were found  between both the ultimate tensile strength (282 ± 52 Newtons (N) versus 135 ± 33N; p <0.001) and yield load (233 ± 48N versus 134 ± 34N; p = 0.002) with the 2-0 Fiberloop being the stronger suture material despite having a 25% smaller diameter (0.21mm2 versus 0.28mm2).

HOW did the authors interpret these results?
From these results, the authors concluded that 2-0 FiberLoop was stronger than #2 Ethibond when considering Achilles tendon repairs with a modified Krackow technique.

Murray O, Holt G, McGrory R, Kay M, Crombie A, Kumar CS.  Efficacy of outpatient bilaterally simultaneous hallux valgus surgery.  Orthopedics.  2010 Jun; 33(6).

WHY did the authors undertake this study?
Hallux abductovalgus often presents as a bilateral patient complaint, but most physicians are hesitant to recommend simultaneous bilateral lower extremity surgical procedures.  The aim of this study was to evaluate patient outcomes following simultaneous bilateral surgical correction of hallux valgus.

HOW did they attempt to answer this question?
The primary outcome measures of this study included several patient clinical outcomes (AOFAS scores, pain scores, etc) as well as radiographic measures (1st intermetatarsal angle and hallux abductus angle).

Inclusion criteria of the population cohort included an ASA score of 1-3, BMI ≤ 35, availability of a responsible caregiver in the first 24 post-operative hours, easy access to emergency care if needed, and no significant mobility impairment.  Forty patients (80 1st MPJs) were included in the analysis and underwent of variety of surgical procedures (mostly Chevrons and Scarfs, but also a couple arthrodesis and Lapidus procedures).  Patients were allowed to weight bear as tolerated to the heels only.

WHAT were the specific results?
All patient-related outcome measures significantly improved from the pre-operative period to the post-operative period, and 85% of patients reported that they would undergo the simultaneous procedures again if given the choice.

HOW did the authors interpret these results?
From these results the authors concluded that simultaneous bilateral hallux valgus surgery can be performed if patients are selected appropriately.  

Let’s take a closer look at the topic of Newtons.  For the second straight PJC session, we have examined an article that attempted to measure the “strength” of a common operative technique.   In PJC#19, Pollard et al found that 3.5mm bicortical screws were “stronger” than 4.0mm unicortical screws when considering operative repair of medial malleolar fractures.  In this edition, Cook et al found that 2-0 FiberLoop was “stronger” than #2 Ethibond when considering surgical repair of Achilles tendon ruptures.  Both studies quantified this “strength” using a unit of measurement called a Newton.  I usually try and spend a lot of time in this space harping on the differences between statistical significance and clinical significance, so let’s try and make the Newton a little more clinically significant for your future critical reading and analysis. 

Put most simply, the Cook et al study found that the FiberLoop suture ultimately broke at around 282 Newtons and that the Ethibond suture ultimately broke at around 135 Newtons.  They found a statistically significant difference between these two numbers, but is there a clinical difference between them?  The answer to that question depends on how much force you expect to pass through your Achilles tendon repairs!  In other words, if you can’t imagine a clinical situation in which more than 100 Newtons of force will pass through your tendon repair, then it really doesn’t matter if the suture breaks at 135 Newtons, 282 Newtons, 500 Newtons or even 1000 Newtons.

The Newton is the most common way that we express force in the orthopedic literature, but what exactly is it?  What does a Newton of force mean in real life?  The answer (of course) is a complicated physics formula, but a general rule of thumb for everyday use is that 10 Newtons are equal to about 1 kilogram, or that 1 Newton is equal to about 0.1kg (or if you prefer the English system, then 1 Newton equals about 0.05 pounds).  This unit of measurement was named after that hack of a physicist Isaac Newton who is credited with “discovering” gravity (I happen to think that gravity is just a theory, but that’s a topic for another time).

So while this is not exactly mathematically correct, it may help to estimate or visualize the FiberLoop suture breaking when approximately 28kg are applied to it, and the Ethibond suture breaking when approximately 14kg are applied to it.  These are weights that we deal with on an everyday basis, and certainly fall within the range of clinical significance.