Commentary & Perspective

Commentary & Perspective on
"Transepiphyseal Replacement of the Anterior Cruciate Ligament in Skeletally Immature Patients. A Preliminary Report"
by Allen F. Anderson, MD

Commentary & Perspective by
Christopher D. Harner, MD*, Medical Director, Center for Sports Medicine, University of Pennsylvania Medical Center, Pittsburgh, PA

This article presents a novel approach to physeal sparing procedures for replacement of the anterior cruciate ligament. Unlike most of the subjects in reports of anterior cruciate ligament replacement, the patients in this study were skeletally immature and so had a substantial amount of remaining growth about the knee. It is important to note that the author has stated that this is a technically demanding procedure that should not be attempted by the surgeon who only occasionally performs anterior cruciate replacement. The major weakness of this study concerns its single authorship, so that the issue of observer bias must be raised.

Some aspects of the surgical technique, as described by Anderson, concern me. In particular, I am uncertain how the author was able to place at least 2 cm of the quadruple hamstring tendon graft into the femoral tunnel with use of a 2 to 3 cm Endobutton continuous loop. This would require a lateral femoral condyle with a minimum width of 4 cm, which anatomically is not possible in adults, let alone in prepubescent children. There is also no mention of the total length of the femoral tunnel that was drilled.

In the Discussion, the author cited a study¹ to show that "the distance between the superior margin of the anterior cruciate ligament and the femoral physis was only 3 mm in children and adolescents." The figures reveal that the femoral tunnel is quite close to the physis, which raises a concern about the possibility of iatrogenic injury to the physis. With the graft placed in the over-the-top femoral position, this complication obviously is avoided. It should also be noted that despite a laboratory study showing that placement of the graft in the over-the-top femoral position renders it less "isometric" than does placement achieved with use of a femoral tunnel, there have been no clinical studies comparing the two techniques of graft placement. With respect to the tibial tunnel, I would expect that in many cases there would be a substantial amount of tendon graft on the physis distal to the tunnel exit , and I would like to know how the author dealt with this.

Finally, it is unclear to me why the author elected to use a number-5 non-absorbable suture in the free ends of the graft. The number-5 Ethibond is a very large suture to place through the relatively small tendon grafts used in these patients, and I am concerned about the viability of the tendon ends.

I also have a theoretical concern about tunnel expansion. In numerous studies, expansion of the tunnel has been shown to be a problem on both the femoral and the tibial side^2-5. In most of these reports, the amount of expansion ranges from 5 to 10 mm, which theoretically could injure the growth plate. It would be interesting to plot the possible range of expansion of the tunnels from the data in this study.

In summary, I believe that Anderson has provided a carefully thought out, well presented, and novel approach to physeal sparing anterior cruciate ligament reconstruction. However, because of the several concerns that I have mentioned, when performing anterior cruciate ligament replacement, the placement of the graft in the over-the-top femoral position still remains my choice of technique because of its simplicity and the predictable outcome⁶.

*The author did not receive grants or outside funding in support of the research or preparation of this manuscript. He did not receive 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, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.

References

1. Behr CT, Potter HG, Paletta GA Jr. The relationship of the femoral origin of the anterior cruciate ligament and the distal femoral physeal plate in the skeletally immature knee. An anatomic study. Am J Sports Med. 2001;29:781-7.
2. L'Insalata JC, Klatt B, Fu FH, Harner CD. Tunnel expansion following anterior cruciate ligament reconstruction: a comparison of hamstring and patellar tendon autografts. Knee Surg Sports Traumatol Arthrosc. 1997;5:234-8.
3. Clatworthy MG, Annear P, Bulow JU, Bartlett RJ. Tunnel widening in anterior cruciate ligament reconstruction: a prospective evaluation of hamstring and patella tendon grafts. Knee Surg Sports Traumatol Arthrosc. 1999;7:138-45.
4. Fink C, Zapp M, Benedetto KP, Hackl W, Hoser C, Rieger M. Tibial tunnel enlargement following anterior cruciate ligament reconstruction with patellar tendon autograft. Arthroscopy. 2001;17:138-43.
5. Klein JP, Lintner DM, Downs D, Vavrenka K. The incidence and significance of femoral tunnel widening after quadrupled hamstring anterior cruciate ligament reconstruction using femoral cross pin fixation. Arthroscopy. 2003;19:470-6.
6. Lo IK, Kirkley A, Fowler PJ, Miniaci A. The outcome of operatively treated anterior cruciate ligament disruptions in the skeletally immature child. Arthroscopy. 1997:13;627-34.