Orthopedics

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The Krackow Suture: How, When, and Why

Kenneth A. Krackow, MD

Abstract

One of the reasons I chose orthopedic surgery as a field was my expectation that orthopedics was a discipline in which I could invent. Within this context, my participation in orthopedic invention started with the association of Robert V. Kenna, David S. Hungerford, and a group of approximately 10 other surgeons, all working on knee instrumentation and prosthesis design. The project involved the development of instrumentation to accompany a new press-fit porous-coated uncemented knee. The instrumentation and associated first modern fully porous-coated, bone-ingrowth, 3-component total knee system were released in 1979 and 1980, respectively, by Howmedica (Rutherford, New Jersey).

One particular instrument, the spacer-tensor, distracted the tibia from the femur after the distal femoral cut had been made, and we saw frequently the relatively large residual asymmetry or imbalance of the extension gap. This finding was particularly clear after the properly aligned proximal tibial cut was made and the extension gap was seen to be sometimes grossly asymmetric, even after routine soft tissue release to achieve balance. David Hungerford first proposed performing collateral ligament advancement to achieve the desired balance. And in the case of severe valgus deformity, the first method used involved advancing distally the entire capsular, ligamentous, and periosteal flap at the medial tibia.

This capsular-ligamentous advancement posed 2 problems regarding the fixation security for the flap. Bone staples seemed an obvious method. However, due to what I called the differential density of deformity,1 osteoporotic bone at the convex, relatively unloaded, medial side of a valgus deformity would not hold such staples securely. It was even difficult to grasp the tissue and effect a secure pull to get it out to enduring, adequate tension to function as a ligamentous reconstruction.

I saw this sleeve as having a largely longitudinal fibrous structure and wanted a stitch that would grasp the fibers and pull them distally while the grasping mechanism itself enhanced the hold of the suture material on the tissue. In addition, the new method needed to avoid the purse-stringing effect of a Bunnell suture.

I can recall specifically the scene and time, although not the date, when the solution came to mind: driving to work, approximately 3 or 4 blocks from Good Samaritan Hospital, Loch Raven Boulevard and Belvedere Avenue, Baltimore, Maryland. A series of locking loops up one side of the tissue, then down the other, would leave 2 tails of suture that could be secured in many ways (Figure 1).

I practiced the suture on paper and many types of tissue and began using it in a number of settings. With the help of Lynn Jones, our laboratory director, and a senior medical student, Steven C. Thomas, now an orthopedist in Las Vegas, we performed comparative strength testing of the suture in many configurations (Figure 2).2-4 In addition, post-mortem injection studies were done in a few rabbits to show that the suture was not strangulating the tissue, ie, thwarting circulation.

When the chosen suture material is appropriately size-matched to the tissue, this locking loop configuration fails always at the tails of the suture, rather than by pulling out or through the tissue. This observation indicates that the failure mechanism is not loss of grasp on the tissue but rather overpowering of the tensile strength of the suture material itself. Figure 2 indicates the failure strengths with various configurations.

Figures courtesy of Kenneth A. Krackow, MD.

The important conclusions here are 1) the limiting feature is the number of strands and the tensile strength of each strand; 2) individual simple sutures of the same grade of material taken through rigid holes in bone are not strong, because…

Kenneth A. Krackow, MD
Kenneth A. Krackow

One of the reasons I chose orthopedic surgery as a field was my expectation that orthopedics was a discipline in which I could invent. Within this context, my participation in orthopedic invention started with the association of Robert V. Kenna, David S. Hungerford, and a group of approximately 10 other surgeons, all working on knee instrumentation and prosthesis design. The project involved the development of instrumentation to accompany a new press-fit porous-coated uncemented knee. The instrumentation and associated first modern fully porous-coated, bone-ingrowth, 3-component total knee system were released in 1979 and 1980, respectively, by Howmedica (Rutherford, New Jersey).

One particular instrument, the spacer-tensor, distracted the tibia from the femur after the distal femoral cut had been made, and we saw frequently the relatively large residual asymmetry or imbalance of the extension gap. This finding was particularly clear after the properly aligned proximal tibial cut was made and the extension gap was seen to be sometimes grossly asymmetric, even after routine soft tissue release to achieve balance. David Hungerford first proposed performing collateral ligament advancement to achieve the desired balance. And in the case of severe valgus deformity, the first method used involved advancing distally the entire capsular, ligamentous, and periosteal flap at the medial tibia.

Underlying Concept

This capsular-ligamentous advancement posed 2 problems regarding the fixation security for the flap. Bone staples seemed an obvious method. However, due to what I called the differential density of deformity,1 osteoporotic bone at the convex, relatively unloaded, medial side of a valgus deformity would not hold such staples securely. It was even difficult to grasp the tissue and effect a secure pull to get it out to enduring, adequate tension to function as a ligamentous reconstruction.

Figure 1: First artist’s rendering of the Krackow suture with a generic muscle-tendon application
Figure 1: First artist’s rendering of the Krackow suture with a generic muscle-tendon application (1983).
Figure courtesy of Kenneth A. Krackow, MD.

I saw this sleeve as having a largely longitudinal fibrous structure and wanted a stitch that would grasp the fibers and pull them distally while the grasping mechanism itself enhanced the hold of the suture material on the tissue. In addition, the new method needed to avoid the purse-stringing effect of a Bunnell suture.

I can recall specifically the scene and time, although not the date, when the solution came to mind: driving to work, approximately 3 or 4 blocks from Good Samaritan Hospital, Loch Raven Boulevard and Belvedere Avenue, Baltimore, Maryland. A series of locking loops up one side of the tissue, then down the other, would leave 2 tails of suture that could be secured in many ways (Figure 1).

Application, Study, and Publication

I practiced the suture on paper and many types of tissue and began using it in a number of settings. With the help of Lynn Jones, our laboratory director, and a senior medical student, Steven C. Thomas, now an orthopedist in Las Vegas, we performed comparative strength testing of the suture in many configurations (Figure 2).2-4 In addition, post-mortem injection studies were done in a few rabbits to show that the suture was not strangulating the tissue, ie, thwarting circulation.

When the chosen suture material is appropriately size-matched to the tissue, this locking loop configuration fails always at the tails of the suture, rather than by pulling out or through the tissue. This observation indicates that the failure mechanism is not loss of grasp on the tissue but rather overpowering of the tensile strength of the suture material itself. Figure 2 indicates the failure strengths with various configurations.

Figure 2: Graph showing the pull-out strengths of different constructs for tendon fixationFigure 3: Bovine xenograft material used in fixation testing
Figure 3: Bovine xenograft material used in fixation testing
Figure 2: Graph showing the pull-out strengths of different constructs for tendon fixation. Figure 3: Bovine xenograft material used in fixation testing. The tendon has a Krackow suture on the left end while the right end is firmly fixed to wood with a chrome-cobalt soft tissue staple (A). After pulling the tendon by the Krackow suture strands, the tendon is pulled through the staple as the spikes underneath the staple fail to grasp it (B).

Figures courtesy of Kenneth A. Krackow, MD.

The important conclusions here are 1) the limiting feature is the number of strands and the tensile strength of each strand; 2) individual simple sutures of the same grade of material taken through rigid holes in bone are not strong, because they simply cut through the fibrous aspects of the soft tissue or any other weak features; and 3) even good staples can have similar failure mechanisms (Figure 3).

Technical Points

Figure 4 shows the step-by-step technique for constructing the suture. The needle holder is held the same way and the needle moved similarly for both limbs of the locking loops. Upon finishing the third locking loop on the first row, as one moves over to start the first loop on the second row, the trailing suture is held as if it is not intended to lock. One will understand this on trying the suture for the first time. The second and third loops for the second side involve handling the trailing suture so that it is deliberately locked.

In some applications the strength may be enhanced, not by using ≥2 separate Krackow sutures, but by increasing the number of strands per suture. It is relatively easy to use a threadable small needle that has 2 to 5 strands of suture as large as No. 5 Ethibond (Ethicon Inc, Somerville, New Jersey). However, technical points here are important. All of the strands should be adjusted and cut to equal length on each side of the needle. Also, it will be difficult to get the needle, together with the folded double thickness of ≥2 strands of heavy suture material, through the soft tissue.

The proper technique involves pausing with the needle 75% to 80% of the way through the thick soft tissue, and then with a needle holder grabbing the pointed portion of the needle 50% to 75% of the way behind the tip, supporting the soft tissue with one’s nondominant hand, and giving a firm pull to get the combined needle and suture through the tissue without creating any unusual disarray. Lastly, it is important to be ready to pinch the suture material, the doubled strands, behind the eye of the needle as the needle clears the sewn soft tissue. In so doing, the suture material can be advanced as far as necessary to position it properly and tighten it if this is a loop. This is the key maneuver that keeps the suture material in proper relationship to the needle and makes things go smoothly.

It was obvious in the early experience with the stitch that 2 well-functioning locking loops would provide maximum fixation in the soft tissue, and that 4 loops would be excessive. I routinely use 3 loops up 1 direction and 3 down the other, as shown in all of my illustrations. This choice derives from the fact that the first loop and/or last loop may be close to the edge or end of the tissue and therefore pull out. If one starts with 2 loops per limb and loses fixation of 1 or 2 of the end loops, the strength will be compromised, ie, the third loop on each limb is insurance.

Many illustrations show the suture used at one end of a discrete tendinous structure (Figure 1). Some do not realize that the lateral edges are not necessary. When making each locking loop, the surgeon puts the needle through the near side and brings it back out, deep to superficial, at the same level just a few millimeters to the right or left, easily sewing a sheet of tissue with the same results regarding the locking loop features.

Figure 4A: Step-by-step construction of the Krackow suture Figure 4B: Step-by-step construction of the Krackow suture Figure 4C: Step-by-step construction of the Krackow suture Figure 4D: Step-by-step construction of the Krackow suture
Figure 4E: Step-by-step construction of the Krackow sutureFigure 4F: Step-by-step construction of the Krackow sutureFigure 4G: Step-by-step construction of the Krackow sutureFigure 4: Step-by-step construction of the Krackow suture. Step C is the first loop of the descending row and at first appears not to lock.
Figures courtesy of Kenneth A. Krackow, MD.

Current Applications

Possibly the widest single application of this suture is for the acute or delayed repair of the Achilles tendon. More than 80% to 90% of the operative reports and descriptions indicate its use. I use the suture at every primary total hip arthroplasty for reattachment of the gluteus medius tendon at the anterior greater trochanter.

Quadriceps tendon and patellar tendon repairs seem to be common applications, and I use the suture to reinforce any patellar tendon peel resulting from an exceptionally tight anteromedial knee arthrotomy. Aside from quadriceps and patellar tendon applications is a wide array of applications in sports medicine.

Many large tendon repairs and reconstructions find applications for this suture; however, it works just as well with small tendons—for certain types of applications. I used it years ago doing rheumatoid foot surgery to fixate a tendon graft for reconstruction of the medial collateral ligament at the first metatarsal phalangeal joint after a Keller resection arthroplasty. Somewhat similarly, it has been used in my unpublished small series of lateral ankle ligament reconstructions.

I never expected the suture to be adopted for flexor tendon repair or reconstruction because of its surface roughness. In many ways my suture has certain similarities to a modified Kessler tendon repair suture. However, I had never seen the Kessler stitch until many years after mine was conceived, and the Kessler method would not be suitable for many of the applications that use my locking loop variation. The Kessler suture is more internal to the flexor tendon and better suited to that application.

Conclusion

Despite fairly early capture and republication in Campbell’s Operative Orthopaedics, the suture was not widely known for at least 10 years. The technique seems more widely known and used today, approximately 25 years after its development in 1983. The concept behind it is simple—grasping either a tendon, a sheet of fascia, or many other forms of principally soft tissue via parallel running locked sutures. The locking loops tighten and stabilize their grasp on the tissue as the strands of the suture are pulled to remove slack, and later as the repair or reconstruction is stressed.

References

  1. Krackow, KA. Deformity. In: Krackow, KA. The Technique of Total Knee Arthroplasty. St. Louis, MO: CV Mosby; 1990:249-372.
  2. Krackow KA, Thomas SC, Jones LC. A new stitch for ligament-tendon fixation. Brief note. J Bone Joint Surg Am. 1986; 68(5):764-766.
  3. Krackow KA, Thomas SC, Jones LC. Ligament-tendon fixation: analysis of a new stitch and comparison with standard techniques. Orthopedics. 1988; 11(6):909-917.
  4. Krackow KA, Jones LC, Thomas SC. Soft tissue fixation to bone: a review of experimental and clinical experience with a new stitch. The Journal of Orthopaedic Surgical Techniques. 1989; 4(1-2):47-58.

Author

Dr Krackow is from the Department of Orthopedic Surgery, Kaleida Health/Buffalo General Hospital, Buffalo, New York.

Dr Krackow is a consultant for Stryker.

Correspondence should be addressed to: Kenneth A. Krackow, MD, Buffalo General Hospital B-2, 100 High St, Buffalo, New York 14203.

10.3928/01477447-20080901-19

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