The purpose of the study by Drogset et al. was to compare the long-term results of three different operative techniques for treatment of ruptures of the anterior cruciate ligament: acute primary repair, acute repair augmented with a synthetic ligament-augmentation device, and acute repair augmented with autologous bone-patellar tendon-bone graft. This was the third report in a series of patients who were randomized equally to one of three treatment groups1,2. The authors report on an original 150 patients following rupture of the anterior cruciate ligament, of which twenty-one patients (14%) were lost to follow-up and an additional fourteen patients had follow-up by phone interview only. This left a total of 115 (77%) of the 150 original patients with complete follow-up data. Of the remaining 115 patients, twelve patients underwent revision of the anterior cruciate ligament repair or contralateral primary anterior cruciate ligament repair, leaving a total of 103 patients (69% of the original cohort) for comparison study (thirty-three who had primary repair, thirty-four who had repair with a ligament augmentation device, and thirty-six who had repair with a bone-patellar tendon-bone graft).
Group 1 underwent primary anterior cruciate ligament repair. Primary repair was performed through a medial arthrotomy with loop sutures placed through the remnants of the anterior cruciate ligament and then through drill holes in the tibia and the femur and tied over the bone-bridge. The sutures were tied with the knee in 30° of flexion while tension was applied manually.
Group 2 received anterior cruciate ligament repair with a ligament augmentation device. After a primary repair was performed, the ligament augmentation device was passed through a 4-mm tunnel in the tibia to the over-the-top position on the femur. The ligament augmentation device was secured to the periosteum of the anteromedial aspect of the tibia with six to eight interrupted nonabsorbable sutures and, with the knee flexed to 30°, to the lateral femoral condyle with a "belt-buckle staple technique."
Group 3 underwent anterior cruciate ligament repair with bone-patellar tendon-bone graft autograft augmentation. A central-third bone-patellar tendon-bone graft autograft was harvested and placed through a 10-mm tunnel in the tibia placed 5 mm anterior and medial to the center of the tibial insertion of the anterior cruciate ligament. An inside-out technique was used to pass a Steinmann pin into the femoral insertion of the anterior cruciate ligament, and the femoral hole was overdrilled to 10 mm after a notchplasty was performed. The graft was secured (with the knee in 30° of flexion) on the tibia and the femur with interference screws and backed up with sutures tied over screw and washer at both sites. The remnants of the anterior cruciate ligament were then sutured to the autograft.
The method of postoperative rehabilitation was quite conservative, with a long leg cast worn for two weeks and then a brace worn for six additional weeks; weightbearing was prohibited for the entire eight weeks. The findings consisted of a 24.5%, 9.5%, and 2.4% revision rate in the acute primary repair, the acute repair with the ligament augmentation device, and the acute repair with the bone-patellar tendon-bone graft groups, respectively, at sixteen years. The rate of revision was ten times higher in the primary repair group compared with the bone-patellar tendon-bone graft group, although no statistical difference was found in the prevalence of revisions between the primary repair group and the ligament augmentation device group or between the ligament augmentation device group and the bone-patellar tendon-bone graft group.
Subjective knee function was rated as fair or poor in 15% of the primary repair group, 17.6% of the ligament augmentation device group, and 2.7% of the bone-patellar tendon-bone graft group. At sixteen years, 30% of the primary repair, 27% of the ligament augmentation device, and 23% of the bone-patellar tendon-bone graft patients had an extension deficit of >5°. However, all but two of the patients achieved full flexion (total degrees of flexion not given). A 2+ or 3+ result on the pivot shift test was found in 18% of the primary repair group and 17% of the ligament augmentation device group, while only 6% of the bone-patellar tendon-bone graft group demonstrated more than a 1+ pivot shift at sixteen years. The mean anterior laxity, as measured with the KT-1000 arthrometer, was 1.9 mm, 2.3 mm, and 1.4 mm for the respective groups at sixteen years, none of which showed statistical significance. Side-to-side difference was also not significant among the treatment groups.
An important finding of this study was the prevalence of osteoarthritis at sixteen years in these knees. Osteoarthritis developed in 10.6% of the involved knees compared with 3.5% of the contralateral knees, which was statistically significant.
The strengths of this study include its long-term follow-up of patients following anterior cruciate ligament surgery. It also uses well-known objective diagnostic tools, such as KT-1000, Tegner, and Lysholm scores, for comparison. In addition, subjective but not blinded evaluation was performed with use of current methods such as the Lachman, pivot-shift, and range-of-motion tests. This study confirms statistically why procedures such as primary suture repair of the anterior cruciate ligament and anterior cruciate ligament repair with a ligament augmentation device are not currently performed for ruptures of the anterior cruciate ligament.
The weaknesses of this study include comparison of procedures and techniques which are not currently performed during anterior cruciate ligament surgery. The rehabilitation protocol used in this study is quite conservative, and the range of motion achieved in this study is not acceptable by current standards. While it is difficult to maintain a 100% follow-up rate at sixteen years, the rate of return for patients in this study was under 70%. Also, the number of patients in each group seemed to be inconsistent throughout the analysis. Perhaps with the current techniques of anterior cruciate ligament reconstruction, we would hope to see a lower prevalence of subsequent osteoarthritis, but additional long-term studies will need to be performed to determine this. Surprisingly, the laxity values that were measured in this study revealed that some knees became tighter with time rather than undergoing loosening with time. This has not been found in other studies.
The current state of anterior cruciate ligament surgery is in flux. There has been more emphasis on anatomical anterior cruciate ligament reconstruction as we have refocused on the results of older literature that have shown the two different functional bundles of the anterior cruciate ligament3. By recreating the anatomy of the anterior cruciate ligament, it is hoped that we can not only improve the stability of the knee both rotationally and sagittally but also reduce the risk of the development of osteoarthritis in the reconstructed knee. We currently perform anatomic double-bundle anterior cruciate ligament reconstruction for these specific reasons4. Early results have shown improved motion, stability, and return to sports; however, long-term results, such as those reported by Drogset et al., will need to be studied.
The authors are to be commended for their ongoing pursuit to follow their patients in this long-term prospective randomized study. By continuing this study, the authors have provided sound proof that anterior cruciate ligament reconstruction has long-term beneficial effects for patients and knees.
*The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They 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 authors are affiliated or associated.
1. Engebretsen L, Benum P, Fasting O, Molster A, Strand T. A prospective, randomized study of three surgical techniques for treatment of acute ruptures of the anterior cruciate ligament. Am J Sports Med. 1990;18:585-90.
2. Grontvedt T, Engebretsen L, Benum P, Fasting O, Molster A, Strand T. A prospective, randomized study of three operations for acute rupture of the anterior cruciate ligament. Five-year follow-up of one hundred and thirty-one patients. J Bone Joint Surg Am. 1996;78:159-68.
3. Girgis FG, Marshall JL, Monajem A. The cruciate ligaments of the knee joint. Anatomical, functional, and experimental analysis. Clin Orthop Relat Res. 1975;106:216-31.
4. Cha PS, Brucker PU, West RV, Zelle BA, Yagi M, Kurosaka M, Fu FH. Arthroscopic double-bundle anterior cruciate ligament reconstruction: an anatomic approach. Arthroscopy. 2005;21:275.