2015 ISAKOS Biennial Congress ePoster #1617

Intramedullary Tibial Nailing Reduced the Attachment Area and Ultimate Strength of the Anterior Medial Meniscal Root: A Potential Explanation for Anterior Knee Pain in Female and Smaller Patients

Matthew David LaPrade, BS, Vail, CO UNITED STATES
Christopher M. LaPrade, BA, Milwaukee, WI UNITED STATES
Mark Hamming, MD, Durham, NC UNITED STATES
Michael B. Ellman, MD, Chicago, IL UNITED STATES
Travis Lee Turnbull, PhD, Vail, CO UNITED STATES
Matthew T. Rasmussen, BS, Vail, CO UNITED STATES
Coen Abel Wijdicks, PhD, München, Bavaria GERMANY
Robert F. LaPrade, MD, PhD, Chanhassen, MN UNITED STATES

Steadman Philippon Research Institute, Vail, CO, USA

FDA Status Not Applicable

Summary: Biomechanical analysis of the change in anterior medial meniscal root attachment area and ultimate failure strength following intramedullary nailing.

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Abstract:

Introduction

Intramedullary (IM) nailing is the treatment of choice among orthopaedic surgeons for tibial shaft fractures. In order to prevent iatrogenic damage to intra-articular structures during surgery, a “safe zone” for placing the tunnel has been defined as 9 mm lateral to the midline of the tibial plateau, 3 mm lateral to the center of the tibial tubercle and adjacent to the anterior margin of the tibial plateau. However, due to its close proximity to the tibial attachment of the anterior medial (AM) meniscus, it is unknown whether the described “safe zone” for IM nail insertion compromises the structural properties of the AM meniscal root. Therefore, the purpose of this study was to quantify the area of the AM meniscal root footprint damaged by reaming an IM tibial nail and determine the subsequent effects on the ultimate failure strength of the root. It was hypothesized that tibial reaming using currently accepted guidelines for nail insertion would significantly weaken the AM root via a decrease in attachment area and strength in both male and female specimens.

Methods

Twelve matched pairs (6 male; 6 female; average age, 50.2 years) of human cadaveric knees were randomly assigned to native and reamed groups. In the reamed group, knees were reamed within the “safe zone” according to current guidelines for IM tibial nail insertion. The overlap areas of the tunnel and AM meniscal root were quantified using a coordinate measuring device. In addition, the medial-lateral width and anterior-posterior length of the tibial plateau were measured for each specimen. A dynamic tensile testing machine was used to precondition each root from 10 to 50 N at a rate of 0.1 Hz for 10 cycles and subsequently pull to failure at a rate of 0.5 mm/s. The ultimate failure strengths were determined, and a nonparametric Wilcoxon Signed-Rank test was used separately for the male and female groups to determine whether the reamed specimen produced a lower ultimate failure load than its paired intact specimen.

Results

Intra-articular reaming did not affect the AM root attachment areas or significantly decrease ultimate failure strengths in male specimens, as only two of the six knees were damaged by reaming. In contrast, all six of the AM roots in the female knees were damaged by reaming, and on average, reaming decreased the female AM root attachment area and significantly decreased ultimate failure strength by 37% (p = 0.028). There was a negative correlation (R^2 = 0.77) between the reamed tunnel-AM root overlap area and medial-lateral width in females, but not males.

Conclusions

Standard reaming for an IM tibial nail induced significant damage to the AM meniscal root in smaller, female specimens, whereas larger, male specimens were not affected. These findings may suggest that improvements in current guidelines and surgical techniques are warranted to prevent iatrogenic injury to the AM root during reaming for tibial shaft fractures in females and smaller patients.