EDITOR'S NOTE: The authors were invited to respond to the letter, but to date, have not done so.

To the Editor:

I read with great interest the paper by Williams,III, et al., in which the authors present the endoscopic surgical technique of anterior cruciate ligament reconstruction using the Endobutton CL (Smith & Nephew, Inc., Endoscopy Division, Andover, Massachusetts) for femoral fixation of the four-strand hamstring tendon autograft (1). I wish to comment on aspects of the technique of drilling the femoral tunnel with this fixation device.

While the authors state that the primary femoral tunnel, “should measure between 25 and 30 mm in length”, they also state that the loop of the Endobutton CL should allow, “at least 25 mm of the hamstring graft within the femoral tunnel” (1). With the numbers provided, a turning radius of only 0-5 mm would be available for the Endobutton; this would make flipping it over the anterolateral femoral cortex very difficult, if not impossible, technically.

Authors of previous reports on the use of the Endobutton have recommended overdrilling the femoral socket by 6 mm (2-4) or just short of the anterolateral femoral cortex (5,6). While the latter option has been reported to increase the risk for the Endobutton to deploy outside the vastus lateralis muscle (2), overdrilling by only 6 mm is just sufficient to allow it to deploy. Therefore, overdrilling by about 10 mm appears a reasonable compromise because it provides ample space for the Endobutton to flip while simultaneously limiting its potential excursion once outside the femur. Indeed, the manufacturer now recommends overdrilling of the femoral socket by 9-10 mm (7). It has also been my experience that this works well in clinical practice.

Consequently, for a minimum of 25 mm of graft to rest in the femoral tunnel, reaming to 35-40 mm, rather than 25-30 mm, appears advantageous.

The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

References

1. Williams RJ 3rd, Hyman J, Petrigliano F, Rozental T, Wickiewicz TL. Anterior cruciate ligament reconstruction with a four-strand hamstring tendon autograft. Surgical technique. J Bone Joint Surg Am. 2005;87 Suppl 1:51-66.

2. Simonian PT, Behr CT, Stechschulte DJ Jr, Wickiewicz TL, Warren RF. Potential pitfall of the EndoButton. Arthroscopy. 1998;14:66-9.

3. Karaoglu S, Halici M, Baktir A. An unidentified pitfall of Endobutton use: case report. Knee Surg Sports Traumatol Arthrosc. 2002;10:247-9.

4. Chen L, Cooley V, Rosenberg T. ACL reconstruction with hamstring tendon. Orthop Clin North Am. 2003;34:9-18.

5. Barrett GR, Papendick L, Miller C. Endobutton button endoscopic fixation technique in anterior cruciate ligament reconstruction. Arthroscopy. 1995;11:340-3.

6. Treme GP, Miller MD. Single-bundle ACL reconstruction technique: hamstring autograft. In: Fu FH, Cohen SB, editors. Current concepts in ACL reconstruction. Thorofare, NJ: SLACK Incorporated; 2008. p 201-212.

7. Rosenberg TD. ACL reconstruction with the ACUFEX director drill guide and ENDOBUTTON CL fixation system. http://www.global.smith-nephew.com/us. Accessed May 1, 2009.

My co-authors and I would like to thank Dr. Narvani for his astute observation of this error. He is correct in pointing out that the femoral tunnel during ACL reconstruction should be in the eleven o'clock position for left knees and in the one o'clock position for right knees.

Riley J. Williams III, MD

To The Editor:

It was with great interest that I read the March 2005 JBJS Surgical Techniques Supplement. On the cover of that issue, there is a schematic drawing of a knee joint during ACL single-bundle reconstruction. This illustration also depicts the position of the tibial and the femoral bone tunnels (Figure 1).

Since I have been performing anatomic ACL double-bundle reconstructions as my preferred technique for the past 18 months, I have learned a great deal about the anatomy of the tibial and femoral ACL insertion sites. In fact, the femoral insertion site of the ACL covers a broad area on the lateral femoral condyle. Below, is a picture of a cadaveric specimen that illustrates the broad insertion areas of the anteromedial (AM) and the posterolateral (PL) bundles of the ACL on the femoral side (Figure 2).

In addition, I have observed that the position of the femoral insertion of the PL bundle changes throughout flexion and extension of the knee joint. Figure 3a (left, below) shows the femoral insertion sites of the AM and the PL bundle in the extended knee position, with the PL insertion distal to the AM insertion. However, arthroscopic ACL reconstruction procedures are usually performed in 90 degrees of knee flexion. Flexing the knee joint to 90 degrees changes the position of the femoral PL insertion site and brings it more to the front, as illustrated in Figure 3b(below,right).

For that reason, the clock system is of limited value for the choice of the tunnel position since the insertion sites of the AM bundle and the PL bundle are not in the same coronal plane. I had not realized this phenomenon until I started performing anatomic ACL double-bundle reconstructions. I believe that this three-dimensional concept needs to be understood by knee surgeons who perform either ACL single-bundle or anatomic ACL double- bundle reconstructions.

Sincerely,

Freddie H. Fu, MD, DSc (Hon), DPs (Hon)

To The Editor:

We would like to thank Williams, et al, for their very informative and clear “Surgical Technique” article titled “Anterior Cruciate Ligament Reconstruction with a Four-Stranded Hamstring Tendon Autograft” (2005; 87- A: S(1): 51-66). Do the authors really mean eleven o’clock position for the right knee and one o’clock position for the left knee instead of the published “one o’clock position for the right knee and eleven o’clock position for the left knee” for femoral tunnel placement (pages 59 & 61)?

-Amir Ali Narvani, MRCS

-Elefterios Tsirisdis, FRCS

69A Frognal

London NW3 6YA

alinarvani@hotmail.com