Achilles Tendon Rupture: A Biomechanical Evaluation of

Varying the Number of Loops in a Physiological Model

Qais Naziri, MD; Preston Grieco, BA; Westley Hayes, MS;

Maxwell Weinberg, BS; and Jaime Uribe, MD

SUNY Downstate Medical Center, Department of Orthopaedic Surgery and Rehabilitation

Achilles Tendon Rupture: A Biomechanical Evaluation of Varying the Number of Loops in a Physiological Model

2

Our disclosure is in the Final AOFAS Program Book. None of the authors have any potential

conflicts with this presentation

Introduction Achilles tendon Ruptures

The Achilles tendon is the most frequently ruptured tendon in the body despite being the largest and strongest

Management tends to be controversial and decided on a case by case basis

Treatment methods include:

- Non-operative

- Percutaneous methods

- Open repair – Krackow technique

Krackow Repair

Previous studies have shown that an augmented Krackow repair with an epitendinous weave both more resistant to gapping and stronger than percutaneous methods 1

Risk of wound complication, with reports up to 21%, due to the poor blood supply to the skin overlying the incision site2

There is controversy over the number of loops that should be placed

Purpose of Study

To create a physiologic model representative of Achilles tendon ruptures seen clinically - not done in prior studies

Biomechanical study to see how the number of Krackow loops alters the repairs resistance to gapping and overall strength.

See if the physiologic model changes the strength of repair when compared to the model used in previous studies

Creating the Physiologic Model

32 Fresh frozen Bovine Achilles tendons

Transected with scalpel 5cm from calcaneal tuberosity

To create fraying we:

Made 2 cm long longitudinal cuts perpendicular to the original transection

Incisions were spaced 2mm apart

Repair

Tendons were repaired using Krackow technique with Orthocord No#2

2 sutures were used with varying number of loops based on group assignment

Augmentation weave with Ethibond 2.0

Pitch of 1cm3

Group Assignment

1 2 3 4

Three Phases of Biomechanical Testing

Cyclic Loading (Adopted from Lee et al., 2009)

1000 cycles oscillating between 20N and 100N

1000 cycles oscillating between 20N and 190N

Gap formation was measured after each phase

If repair failed, specimen would not advance to next phase

Repair failure set as gapping of 15mm

Load to Failure (if sample did not fail on cyclic loading)

Groups 2 3 4 # of failures after cyclical loading

0 0 0 1

1 2 2 3

Phase 1

Phase 2

Discussion Gapping/Max Load

Increasing the number of loops did not statistically change the overall strength of the repair

– Agrees with McKeon et al., 2006,

Increasing the number of loops lead to decrease in gapping

Frayed vs Unfrayed

Group 1 and 2 both had 3 loops in healthy, unfrayed tendon

There was no significant difference in load to failure

Group 2 was more prone to gapping

We believe that the frayed ends forces the surgeon to put the load bearing loops further from both the rupture site and knot and may decrease the repair’s gap resistance

vs

Clinical Relevance

The current trend is to accelerate rehabilitation protocol after Achilles tendon repairs (shorter immobilization, return to sports sooner)

Repair gapping leads to tendon elongation and delayed healing

Need for repairs that are more gap resistant to the cyclic stressing that would be seen in rehabilitation

Limitations

Bovine tendons

Small sample size

In-vitro nature only accounts for suture strength and not biological healing

Frayed ends were created with the use of a scalpel instead of by tendon rupture – different biomechanical stresses

Conclusion and Future Studies Increasing the number of loops did not increase overall load to failure but did increase resistance to gapping

Repairs with more loops requiring larger incisions may not necessarily lead to stronger repairs

Further studies with more loops to see if this trend continues

Maffulli, N., Rupture of the Achilles tendon. J Bone Joint Surg Am, 1999. 81(7): p. 1019-36. Khan, R.J., et al., Treatment of acute achilles tendon ruptures.

Kellam, J.F., G.A. Hunter, and J.P. McElwain, Review of the operative treatment of Achilles tendon rupture. Clin Orthop Relat Res, 1985(201): p. 80-3.

Pajala, A., et al., Rerupture and deep infection following treatment of total Achilles tendon rupture. J Bone Joint Surg Am, 2002. 84-A(11): p. 2016-21.

Lee, S.J., et al., Cyclic loading of 3 Achilles tendon repairs simulating early postoperative forces. Am J Sports Med, 2009. 37(4): p. 786-90.

McKeon, B.P., et al., The Krackow stitch: a biomechanical evaluation of changing the number of loops versus the number of sutures. Arthroscopy, 2006. 22(1): p. 33-7.

Jassem, M., et al., Biomechanical analysis of the effect of varying suture pitch in tendon graft fixation. Am J Sports Med, 2001. 29(6): p. 734-7.

References