Issue: August 2007
August 01, 2007
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Mechanical study uncovers ideal suture material for zone II flexor tendon repairs

Investigators also recommend six knots for secure suturing these repairs to avoid breaking.

Issue: August 2007
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SAN DIEGO – A mechanical study found what it called the optimal suture material and knot configurations for zone II flexor tendon injuries.

Steve K. Lee, MD, and his colleagues undertook the study to determine the effect of the number of throws on knot volume and the strength of common suture materials.

Steve K. Lee, MD
Steve K. Lee

“We figured that the number of knots that you throw would affect the strength of the repair, but also the bulk of the repair, which is important in a zone II injury,” Lee said.

He presented the study findings at the American Academy of Orthopaedic Surgeons annual meeting.

Study methods

Lee and his colleagues studied two monofilament suture types, including the Ethilon nylon suture and the Prolene polypropylene suture (both Johnson & Johnson); and two braided suture types, the Fiberwire (Arthrex) and Ethibond Excel (Johnson & Johnson) polyester suture.

They evaluated each of the sutures under four-knot configurations, and included two-, three-, four- and six-knot configurations, Lee said.

The two-knot configuration was a surgeon’s knot with a half-hitch and each of the other knot configurations were additional half-hitches.

Investigators measured the knot volume using digital calipers and loupe magnification, and calculated the volume by multiplying pr2 by the height.

“The knotted suture loops were cyclically loaded at 100 cycles at 1.1 Hz,” Lee said. “We increased the load by 10 N then re-cycled until failure.” They performed 10 trials per suture type and knot configuration for a total of 160 trials.

Knot Volume Results
Lee and his colleagues found that Fiberwire (Arthrex) had a significantly lower knot volume at the four-knot and six-knot configurations, while Ethibond (Johnson & Johnson) demonstrated the highest volume.

Source: Lee SK

Knot volumes

“We found that the Fiberwire … at four knots and six knots … had the smallest knot volumes, and this was significant,” Lee said. Knot volumes for Fiberwire were 0.4 mm3 at four knots and 0.66 mm3 at six knots.

“Interestingly the previous very commonly used suture material, Ethibond, had high knot volumes,” Lee said.

Fiberwire and Ethibond were both stiffer than the other materials – a finding shown in past studies.

Investigators found that all two-knot configurations slipped, while most four-knot configurations did not slip, but instead broke, Lee said. “We recommend six knots if you’re going to do this repair.”

Load to failure

At four knots, the ultimate load to failure was under 40 N for most suture materials, with the exception of Fiberwire, which had an ultimate load to failure around 50 N, Lee said. “As has been previously shown, you need at least 50 N to withstand an early and active motion protocol. So only the Fiberwire at six knots exceeded 50 N [and] had the highest strength at 55.8 N.”

He explained that a biomodel is the next necessary step to evaluate the work of flexion, adhesion formation and the effect on healing.

Knife laceration of the Zone II flexor tendon
This 22-year-old cook sustained a knife laceration of the Zone II flexor tendon.

Images: Lee SK

CLC-IHM technique
Lee treated this patient with the CLC-IHM technique – using a cross-locked cruciate core suture with 3-0 Fiberwire and using six knots. He also used the interlocking horizontal mattress circumferential suture with 6-0 Prolene.

Patient showing range of motion
Here is the patient at 3 months postoperatively, showing range of motion.

Patient showing range of motion
This image also shows the patients’ range of motion at 3 months postoperatively.

For more information:
  • Steve K. Lee, MD, associate chief, Division of Hand Surgery, can be reached at the New York University Hospital for Joint Diseases, 301 E. 17th St., Suite 413, New York, NY 10003; 212-598-6697; e-mail: steve.lee@nyumc.org. He has no direct financial interest in the products discussed in this article, nor is he a paid consultant for any companies mentioned.
Reference:
  • Lee SK, Vigler M, Palti R, et al. The effect of number of throws on knot volume and security of common tendon suturing materials. #372. Presented at the American Academy of Orthopaedic Surgeons 74th Annual Meeting. Feb. 14-18, 2007. San Diego.