Commentary & Perspective

Commentary & Perspective on
"Posterior Cruciate Ligament Replacement with a Two-Strand Quadriceps Tendon-Patellar Bone Autograft and Tibial Inlay Technique"
by Frank R. Noyes, MD, and Sue Barber-Westin, BS

Commentary & Perspective by
Christopher D. Harner, MD*,
University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania

Over the last five years there have been numerous new surgical techniques advocated for posterior cruciate ligament injuries, including single-bundle, double-bundle, inlay, on-lay, allograft, autograft, quadriceps tendon, patellar tendon, and Achilles tendon. Although it would appear that posterior cruciate ligament surgery is in a total state of chaos, I would contend that the experts are becoming more unified in their approaches to these complex injuries, and that common themes, such as the importance of proper placement of the anatomical graft and the need to address all deficient structures resulting from associated ligamentous injuries, can be found despite individual differences with regard to surgical technique and graft selection.

In their article, Noyes and Barber-Westin present a series of patients who had either a chronic isolated type or a combination type of posterior cruciate ligament laxity, which they addressed with a tibial inlay technique. The strengths of this article are that it involved one surgeon, one technique for posterior cruciate ligament reconstruction, and an extensive data-collection process to follow the patients. The weaknesses, as pointed out by the authors, include the retrospective (Level IV) study design and a small patient population.

Patient Population

This series initially included twenty patients with a variety of different patterns of posterior cruciate ligament injury. A minimum two-year follow-up was attained in nineteen patients. This in itself is an excellent achievement. What was difficult to determine was the specific pattern of injury involved. I discerned that eleven of these patients had an isolated posterior cruciate ligament deficiency and eight had various combinations of combined ligament injuries. Eight of these procedures were revisions of failed procedures, although we do not know the cause of graft failure or the type of previous surgical techniques that were used. I suspect that this subgroup will be presented in detail in the future. Because we do not know the patterns of injury, it is difficult to interpret the authors' approach to chronic posterior cruciate ligament injuries. It is important to point out that most posterior cruciate ligament surgery is done in combination with other procedures¹. In this particular series, eleven of nineteen patients had an isolated posterior cruciate ligament injury. I was particularly interested to know if there would be differences between isolated and combined injuries, but this was difficult to discern from the paper. The authors presented the overall International Knee Documentation Committee (IKDC) results in the isolated posterior cruciate ligament group (seven in group B, three in group C, and one in group D), but the breakdown for combined injuries was not reported. This information (i.e., the IKDC groups C and D) would be useful when looking at potential causes of failure.

It is important to note that the results for return to work and sports in the study by Noyes and Barber-Westin are similar to the results reported by others² for complex injuries of the knee ligament and that successful return to sports is not as predictable as is a successful return to activities of daily living and work. This is a very important message that seems to repeat itself in the literature regardless of the author and surgical technique².

Surgical Technique

The authors give a brief description of their surgical technique and cite two references for additional detail. I would strongly encourage anyone who is going to undertake this procedure to study those referenced works. The tibial inlay procedure has some attractive theoretical advantages, but it presents the surgeon with substantial challenges. These include patient positioning, proximity to neurovascular structures (with substantial anatomical variations) a technical challenge of placing two 4.5-mm "cannulated" screws in a 12 × 20-mm bone block, a separate arthrotomy incision, and follow-up arthroscopic evaluation. I have used this procedure for a few primary posterior cruciate ligament procedures and for revision posterior cruciate ligament surgery in selected patients. As an experienced knee surgeon, I can confirm that it is a technical challenge. I do believe that there may be a role for tibial inlay in certain revision procedures. Nonetheless, I have not continued to pursue this technique for use in primary posterior cruciate ligament reconstruction because I do not believe the added time and technical difficulties are worth the theoretical advantages of the inlay. Noyes and Barber-Westin point out that there are biomechanical cadaveric studies that demonstrate the superiority of the total inlay technique over the transtibial technique in repetitive loading studies³. However, in studies that quantitated graft in-situ forces and knee kinematics, there were no significant differences between the two techniques⁴.

I found it interesting that the author split the graft in half, thereby creating two 6-mm bundles, one of which was placed in the anterolateral and the other in the posteromedial femoral insertion site. It is well known that the anterolateral component is biomechanically more important than the posteromedial component^5,6. This information emphasizes the necessity of using the anterolateral component in the reconstruction. In addition, both grafts were tensioned at the same angle of knee flexion. Biomechanically, the anterolateral component is relatively lax in extension and taut in flexion and the posteromedial component has a reciprocal tensioning pattern⁶. This implies that the anterolateral graft should be tensioned in flexion and the posteromedial graft should be tensioned more toward extension, which was not done in this series. In the transtibial double-bundle technique, the anterolateral component is reconstructed with an 11-mm allograft and tensioned at 90°, while the posteromedial component is reconstructed with a smaller allograft (6 to 7 mm in diameter) and is tensioned and fixed in extension^5,7.

Finally, with respect to this inlay technique, it would have been helpful to know the tourniquet and/or operative times. It is important to remember that the senior author (F.R.N.) is one of the most experienced surgeons in the world with regard to posterior cruciate ligament reconstruction and states in the final sentence of the article, "The disadvantages of the tibial inlay technique include increased operative time and added risks due to the proximity of the posterior neurovascular structures."

Data Reporting

The major strength of this article is the detailed data collection by the authors. In addition to using the Cincinnati Knee Rating System and the IKDC knee rating scale, they have gone a step further by including stress radiography. The authors point out that a traditional knee arthrometer (such as the KT-2000) "…underestimates the true amount of residual posterior translation…" They present a comparison of two techniques and report overall averages of 5.5 ± 2.8 mm versus 2.3 ± 2.2 mm. It is unclear in their study if this difference was significant. In addition the question is whether this approximately 3.0-mm difference in the two tests is clinically significant. I would contend that stress radiography may overestimate the true functional instability of the knee. We must remember that all laxity tests are performed in the unloaded/unweighted knee. With weight-bearing, there is a natural movement of the tibia anteriorly due to its sagittal slope⁸. This basic principal of functional biomechanics of the knee is not taken into account with stress radiography. Therefore the laxity detected may not reflect the true joint position during weight-bearing.

Summary

The posterior cruciate ligament tibial inlay technique is a technically demanding procedure. It presents the surgeon with many challenges, including patient positioning, balancing of incisions, proximity to the neurovascular structures (with anatomical variation) and tibial graft fixation. In addition to these challenges, the inlay technique necessitates the removal of all remaining posterior cruciate ligament tissue. For these reasons, it is not my procedure of choice for primary posterior cruciate ligament reconstruction. I continue to use the arthroscopic transtibial tunnel technique (single bundle in most acute cases, and double bundle in most chronic cases). We have found that, in many patients, there are substantial posterior cruciate ligament and meniscal femoral ligament attachments that can be preserved and used during the arthroscopic reconstruction.

Finally, I believe that this technique does have a role in certain posterior cruciate ligament revision procedures in which the transtibial tunnel is found to be poorly positioned. Drs. Noyes and Barber-Westin are to be commended for their continuing pursuit to improve the surgical treatment of these complex injuries.

*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. Harner CD, Hoher J. Evaluation and treatment of posterior cruciate ligament injuries. Am J Sports Med. 1998;26:471-82.
2. Harner CD, Waltrip RL, Bennett CH, Francis KA, Cole B, Irrgang JJ. Surgical management of knee dislocations. J Bone Joint Surg Am. 2004;86:262-73.
3. McAllister DR, Markolf KL, Oakes DA, Young CR, McWilliams J. A biomechanical comparison of tibial inlay and tibial tunnel posterior cruciate ligament reconstruction techniques: graft pretension and knee laxity. Am J Sports Med. 2002;30:312-7.
4. Margheritini F, Mauro CS, Rihn JA, Stabile KJ, Woo SL, Harner CD. Biomechanical comparison of tibial inlay versus transtibial techniques for posterior cruciate ligament reconstruction: analysis of knee kinematics and graft in situ forces. Am J Sports Med. 2004;32:587-93.
5. Harner CD, Xerogeanes JW, Livesay GA, Carlin GJ, Smith BA, Kusayama T, Kashiwaguchi S, Woo SL. The human posterior cruciate ligament complex: an interdisciplinary study. Ligament morphology and biomechanical evaluation. Am J Sports Med. 1995;23:736-45.
6. Race A, Amis AA. The mechanical properties of the two bundles of the human posterior cruciate ligament. J Biomech. 1994;27:13-24.
7. Petrie RS, Harner CD. Double bundle posterior cruciate ligament reconstruction technique: University of Pittsburgh Approach. Oper Tech Sports Med. 1999;7:118-26.
8. Giffin JR, Vogrin TM, Zantop T, Woo SL, Harner CD. Effects of increasing tibial slope on the biomechanics of the knee. Am J Sports Med. 2004;32:376-82.

Copyright © 2005 by the The Journal of Bone and Joint Surgery, Inc.