2015 ISAKOS Biennial Congress ePoster #1903

Cortical Button Suspensory Fixation: A Better Patellar Tendon Repair?

Gabriella Ode, MD, Charlotte, NC UNITED STATES
Dana P. Piasecki, MD, Charlotte, NC UNITED STATES
Nahir A. Habet, MS, Charlotte, NC UNITED STATES
Richard Peindl, PhD, Charlotte, NC UNITED STATES

Carolinas Medical Center, Charlotte, NC, USA

The FDA has not cleared the following pharmaceuticals and/or medical device for the use described in this presentation. The following pharmaceuticals and/or medical device are being discussed for an off-label use: Arthrex, Inc, ACL Tightrope

Summary: Patellar tendon repair using cortical button devices has some mechanical advantages over suture repair and suture anchor repair which may allow for earlier mobilization and greater resistance to catastrophic failure.

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Abstract:

Introduction

Patella tendon rupture requires surgical repair for optimal outcomes yet there is no consensus regarding appropriate repair technique or duration of post-operative immobilization. Cortical button fixation is a secure method for tendon repair but has not been studied in patellar tendons. This study evaluates a novel patellar tendon repair technique using cortical button fixation.

Methods

Twenty-­two fresh­ frozen cadaveric knees compared three techniques of patellar tendon repair following a simulated rupture at the inferior pole of the patella. Specimens were divided into three groups such that mean donor age, weight and height were closely matched. Repairs were performed at 45 degrees of flexion using either a standard suture only (SO) repair (n=7), PEEK suture anchor (SA) repair (n=7) or cortical button (CB) repair (n=8) (ACL Tightrope, Arthrex Inc, Naples FL). A standard suture size and type (#2 Fiberwire, Arthrex Inc, Naples, FL) and suture technique (Krackow) was used for each repair. The CB repair was performed by first looping suture tape through the mid­substance of the proximal edge of the patellar tendon on either side. Each CB construct was passed through the suture tape loop, buried within the tendon edge and then augmented with suture. The CB constructs were passed through drilled trans-patellar tunnels and tethered to the superior pole of the patella. All specimens were tested on a custom apparatus based on an established biomechanical protocol, which simulated cyclic open kinetic chain quadriceps contraction from extension to 90 degrees flexion. Outcomes of interest were gap formation up to 250 cycles, maximum load to failure and mode of failure. Secondary analysis evaluated the effect of bone volume on construct failure. All patellae were CT scanned and the bone volume was estimated in mean Hounsfield units (HU) using MIMICS Software (Materialise, Leuven, Belgium).

Results

CB had significantly less gap formation than SA after 1 cycle (p<0.001) and 20 cycles (p<0.01) and significantly less gap formation than SO from 1-250 cycles (p<0.05). CB repairs sustained significantly higher loads to failure (1530N + 59N) than SA (648N + 53N) and SO (662N + 31N) (p <0.001). All SO repairs failed through the suture. SA repairs failed at the suture ­anchor eyelet interface (n= 4) or by anchor pullout (n=3). Direct construct failure of the CB could not be demonstrated. In all CB repairs, maximum attainable load was limited by failure of the sutured attachment of the quad tendon to the servohydraulic mechanical testing machine. For each group, there was no significant difference between failure load and bone volume. However, SA specimens that failed by anchor pullout had three of the four lowest bone volumes for that group.

Conclusions

Patellar tendon repair using CB fixation has mechanical advantages over suture and anchor repair in cadaveric specimens. CB fixation showed less cyclic gap formation and withstood at least twice the load to catastrophic failure of the construct. This may translate to clinical advantages in accelerated rehabilitation or with ensuring adequate fixation in patients with poor bone density. SA patellar tendon repair in osteoporotic patients may be suboptimal due to risk of anchor pullout.