Abstract
Background
The present study was aimed to compare the clinical outcomes following double-bundle (DB) ACL reconstruction (ACLR) with the outcomes following single-bundle (SB) ACLR in skeletally mature teenagers.
Methods
A total of 113 skeletally mature teenagers with unilateral ACL injury, who underwent primary ACLR using hamstring autograft with minimum 2 years follow-up, were included. This included 82 DB ACLR (median 16.0 [interquartile range (IQR), 2.0] year-old, male/female: 21/61) and 31 SB ACLR (17.0 [2.0] year-old, male/female: 6/25). At the final follow-up (3.6 [1.9] years), IKDC Subjective Knee Form (IKDC-SKF), Tegner activity scale, the side-to-side difference (SSD) in anterior tibial translation using KT arthrometer were obtained. The rate of residual pivot-shift test, graft rupture rate and contralateral ACL injury rate were also assessed.
Results
The rate of residual pivot-shift test was significantly lower in DB group than SB group (12.0 % vs 33.3 %, P = 0.02). Postoperative Tegner activity scale was significantly greater in DB group (7 [2]) than SB group (4 [4], P = 0.002). No significant differences were observed between two groups in IKDC-SKF (96.6 [10.0] in DB group, 97.7 [9.0] in SB group) and SSD in anterior tibial translation (1.5 [2.0] mm in DB group, 2.0 [2.0] mm in SB group). Graft rupture occurred in seven patients in DB group (8.5 %), and one patient in SB group (3.3 %). Contralateral ACL injury occurred in four patients in DB group (4.9 %), and two patients in SB group (6.5 %). No significant differences were observed between two groups in graft rupture and the contralateral ACL injury rates.
Conclusion
Clinical outcomes following DB ACLR were similar to SB ACLR, but the pivot-shift phenomenon appeared to be better controlled in DB ACLR than SB ACLR. Thus, to better restore rotatory knee stability, DB ACLR may be recommended in the skeletally mature teenagers.
Level of evidence
III.
Keywords: ACL, Anterior cruciate ligament reconstruction, Adolescents, Double-bundle, Single-bundle, Pivot-shift
1. Introduction
Especially in the adolescent population, high graft failure rates (10–29 %) following anterior cruciate ligament reconstruction (ACLR) have been reported,1, 2, 3 compared to the graft failure rate in the adult population.4, 5, 6, 7, 8, 9 Furthermore, younger age has been shown to be one of the predictors of revision ACLR,10,11 and age younger than 20 years has been also shown to be associated with a high-grade pivot-shift test at the time of the surgery.12
Biomechanical studies have shown that double-bundle (DB) ACLR could more closely restore normal knee kinematics, especially during rotatory loads than single-bundle reconstruction.13,14 Furthermore, recent systematic reviews have shown that DB ACLR may provide better postoperative knee stability15, 16, 17 and fewer re-ruptures16 compared to the single-bundle (SB) procedure. However, in the previous reports regarding DB ACLR, the outcomes have been evaluated by including the entire population; thus, clinical outcomes especially in the subpopulation of adolescent patients, who are at high risk for graft failure, remains unclear. Therefore, the purpose of the present study was to investigate the clinical outcomes following anatomic DB ACLR in skeletally mature teenagers, and to compare them to the outcomes following anatomic single-bundle (SB) ACLR. The hypothesis was that the clinical outcomes following DB ACLR would be better than SB ACLR in skeletally mature teenagers.
2. Materials and methods
This study was a retrospective analysis of prospectively collected data of 113 unilateral ACL-injured adolescent patients (male/female: 27/86) with median (interquartile range, IQR) age of 16.5 (2.0) years at the surgery, who underwent primary ACLR using hamstring (HT) autograft at our institution. The median follow-up after the surgery was 3.6 (1.9) years (range: 2–5). This consisted of two groups: 82 DB ACLR (DB group; 16.0 [2.0] years old, male/female: 21/61) and 31 SB ACLR (SB group; 17.0 [2.0] years old, male/female: 6/25) (Table 1). Inclusion criteria were ACL-injured patients who underwent primary ACLR from 2013 through 2017 at our institution younger than 20 years old at the time of surgery. Exclusion criteria were (1) open physis of the knee, (2) technique with one-bundle (anteromedial or posterolateral bundle) augmentation, (3) other graft sources than hamstring autograft, (4) previous contralateral ACLR, (5) other simultaneous ligamentous surgery, (6) previous knee surgery, or (7) less than 2-year follow-up after the index surgery. CONSORT flowchart is shown in Fig. 1.
Table 1.
Demographic data
Continuous variables are shown as median (interquartile range, IQR). DB; double-bundle. SB; single-bundle. MM; medial meniscus. LM; lateral meniscus.
| DB group | SB group | P value | |
|---|---|---|---|
| Patients | 82 | 31 | – |
| Sex (M/F) | 21/61 | 6/25 | 0.48 |
| Age at surgery (years) | 16.0 (2.0) | 17.0 (2.0) | 0.43 |
| Follow-up period (years) | 3.3 (1.5) | 4.1 (2.0) | 0.41 |
| Period from injury to surgery (months) | 2.5 (3.2) | 3.6 (5.3) | 0.27 |
| Tegner activity scale before the injury | 7 (2) | 7 (0) | 0.32 |
| Concomitant meniscal tear at time of surgery (n) | 42 (51.2 %) | 17 (54.3 %) | 0.83 |
| Tear location: MM/LM/both (n) | 19/16/7 | 6/8/3 | 0.77 |
| Procedure: resection, repair, both (n) | 7/33/2 | 2/15/0 | 0.61 |
Fig. 1.
CONSORT flowchart.
The procedure of ACLR (SB or DB) was not randomized, and DB ACLR was the first choice for primary ACLR in our institution. Most of the patients who underwent SB ACLR were those who were enrolled into the prospective multicenter study of SB ACLR (PIVOT Study Group18) during the present study period. In addition, when graft size was not sufficient to perform DB ACLR, SB ACLR was chosen. There were no significant differences in baseline demographics between DB ACLR and SB ACLR. Sports participation at the time of the injury is summarized in Fig. 2.
Fig. 2.
Sports participation at the time of the injury. Other includes American Football, Athletics, Baseball, Dance, Judo, Lacrosse, Ski, and Softball.
2.1. Surgical procedure
Anatomic SB or DB ACLR was performed by experienced four surgeons as previously described.19 Using a 30° arthroscope and a three-portal technique, including anteromedial, anterolateral, and far anteromedial (AM) portals, a complete ACL tear was confirmed by diagnostic arthroscopy. A far AM portal was created above the level of the medial meniscus. Meniscal pathology was addressed by repair or partial meniscectomy prior to commencing with ACLR. The ACL remnant was debrided with an arthroscopic shaver. The femoral footprint was then debrided and examined for osseous landmarks, including the lateral intercondylar and bifurcate ridges. The femoral tunnel was created through the far AM portal. On average, graft diameters of AMB and PLB was 6 mm and 6 mm in double-bundle ACLR, and 8 mm in single-bundle procedure.
2.2. DB ACLR
The femoral tunnels were created through the far AM portal. A 2.4-mm Hewson pin was inserted into the footprint of the posterolateral (PL) bundle and drilled over the guide wire at 120–135 degrees of knee flexion. Femoral AM bundle was created in the same way. To create the tibial tunnel, the tip of the aimer was placed AM to the anterior horn of the lateral meniscus for the PL bundle and lateral to the intercondylar eminence and posterior to the anterior horn of the medial meniscus for the AM bundle. A doubled semitendinosus or gracilis tendon was used for the PL bundle. A doubled or quadrupled semitendinosus tendon was used for the AM bundle. Suspensory button device was used for graft fixation of the femoral side, and a post screw was used for graft fixation of the tibial side. The PL bundle graft was fixed at 0–10 degrees of knee flexion and the AM bundle graft was fixed at 20–30 degrees of knee flexion with the maximum manual load.
2.3. SB ACLR
A 2.4-mm Hewson pin was inserted through the far AM portal into the center of femoral ACL footprint at 120–135 degrees of knee flexion. The guide pin was inserted using the aimer at the center of tibial footprint. A quadrupled semitendinosus or gracilis tendon was used for the graft. Suspensory button device was used for graft fixation of the femoral side, and a post screw was used for graft fixation of the tibial side. The graft was fixed at 10 degrees of knee flexion with the maximum manual load.
2.4. Rehabilitation
A standardized postoperative rehabilitation protocol was provided to all patients. In general, all patients were treated with similar rehabilitation protocols for the first 6 months after the surgery. Progressive range of motion exercises and partial weight bearing with crutches were started as tolerated one day after surgery. Full knee extension and full weight bearing were allowed with a knee brace, starting 2 weeks after the surgery. If concomitant meniscal repair was performed for an incomplete or complete tear, the weight bearing and range of motion exercises were delayed for one to two weeks. The rehabilitation protocol was intended to improve range of motion, lower limb muscle strength, and proprioceptive sensation. Jogging was usually allowed approximately 3–4 months after the surgery. Return to full activity, including sports, was typically allowed at 9 months after surgery.
2.5. Postoperative outcomes
At the final follow-up (3.2 ± 1.2 years on average), Tegner activity scale20 and International Knee Documentation Committee Subjective Knee Form (IKDC-SKF)21 were obtained. The side-to-side difference (SSD, mm) in anterior tibial translation with manual maximum load using the KT-1000/2000 knee ligament arthrometer (MedMetric, San Diego, CA), and rotatory knee laxity by the pivot-shift test were also evaluated at the final follow-up. Anterior knee translation was measured at 30 degrees of knee flexion in both the reconstructed and contralateral knees; the SSD in anterior tibial translation was calculated by subtracting the value of the contralateral knee from that of the reconstructed knee. The pivot-shift test was assessed according to IKDC grade (A, equal; B, glide; C, clunk; D, gross). The rate of residual positive pivot-shift test (%) was calculated. IKDC grade greater than B was defined as a positive pivot-shift test. These measurements were performed by experienced orthopaedic surgeons, and the maneuverers were standardized to minimize inter-examiner variability by the supervision of a senior surgeon. Graft rupture rate (%) and contralateral ACL injury rate (%) were also assessed. Patients who tore the graft were excluded from the postoperative measurements including SSD in anterior tibial translation using arthrometer and pivot-shift test. Sports participation and Tegner Activity Scale were also evaluated at final follow-up. The study was approved by the institutional review board for human research in Kobe University Graduate School of Medicine (IRB# B190055). Informed consent was obtained from all patients.
2.6. Statistical analysis
Statistical analyses were performed using SPSS software v26.0 (IBM Software Group, Chicago, IL, USA). Shapiro-Wilk test was used to assess the normal distribution of the data, and non-parametric test was used when the data were not normally distributed. Mann-Whitney U test was used to explore the differences in Tegner Activity Scale, IKDC-SKF, and SSD in anterior tibial translation between DB and SB group. These variables are expressed as median (IQR). Fisher's exact test was used to determine the difference in residual positive pivot-shift test between DB and SB group. A priori power analysis showed that at least 98 patients (group 1: n = 28, group 2: n = 70) were required to detect a difference in the proportion of 0.10 (group 1) and 0.35 (group 2), with a power of 0.80 and alpha error of 0.05. Significance level was set as P < 0.05.
3. Results
There were no significant differences in ratio of concomitant meniscal tears and procedures for meniscal tears (Table 1). Postoperative clinical outcomes at final follow-up were summarized in Table 2. The rate of residual positive pivot-shift test was significantly smaller in DB group than SB group (12.0 % vs 33.3 %, P = 0.02) at final follow-up. All residual positive pivot-shift tests were glide (IKDC grade B). Postoperative Tegner activity scale was significantly greater in DB group (median, 7 [IQR, 2]) than SB group (median 4 [IQR, 4], P = 0.002). No significant differences were observed between two groups in terms of IKDC-SKF (96.6 [10.0] in DB group, 97.7 [9.0] in SB group) and SSD in anterior tibial translation (1.5 [2.0] mm in DB group, 2.0 [2.0] mm in SB group). Graft rupture occurred in 7 patients in DB group (8.5 %), and one patient in SB group (3.3 %). The contralateral ACL injury occurred in 4 patients in DB group (4.9 %), and 2 patients in SB group (6.5 %). There were no significant differences between two groups in graft rupture rate and contralateral ACL injury rate.
Table 2.
Postoperative clinical outcomes at final follow-up
Continuous variables are shown as median (interquartile range, IQR). DB; double-bundle. SB; single-bundle. SSD; side-to-side difference. ATT; anterior tibial translation. ∗significant difference.
| DB group | SB group | P value | |
|---|---|---|---|
| IKDC-SKF | 96.6 (10.0) | 97.7 (9.0) | 0.34 |
| Tegner activity scale at final follow-up | 7 (2) | 4 (4) | 0.002∗ |
| SSD in ATT w/knee arthrometer (mm) | 1.5 (2.0) | 2.0 (2.0) | 0.24 |
| Pivot-shift test (+/−, positive rate) | 9/66 (12.0 %) | 10/20 (33.3 %) | 0.02∗ |
| Ipsilateral ACL graft rupture (n, rate) | 7 (8.5 %) | 1 (3.3 %) | 0.44 |
| Contralateral ACL rupture (n, rate) | 4 (4.9 %) | 2 (6.5 %) | 0.67 |
| Period from the surgery to second ACL rupture (months) | 22 (range: 8–47) | 18 (range: 8–32) | 0.73 |
| Cause of second ACL rupture | Basketball (n = 6), Soccer, Judo, Volleyball, Lacrosse, Jumping (each n = 1) |
Basketball (n = 2), Judo (n = 1) |
– |
4. Discussion
The main finding of the present study was that the rate of residual pivot-shift test was significantly smaller in DB group than SB group in skeletally mature teenagers who are at high risk of graft re-tear, although SSD in anterior tibial translation and IKDC-SKF were similar between two groups. This finding is supported by previous studies showing that DB ACLR may provide better postoperative knee stability compared to SB procedure.15, 16, 17 These findings suggest that the pivot-shift phenomenon appears to be better controlled in DB ACLR than SB ACLR; hence, in the skeletally mature teenagers, DB ACLR may be recommended to better restore rotatory knee stability when HT autograft is used.
Recent studies have shown that particular attention is needed in teenagers who are at high risk of graft rupture after primary reconstruction.2,3,10,11 In the present study, the rates of ipsilateral and contralateral ACL graft tears were not significantly different between two groups; however, the rate of ipsilateral ACL graft tear tended to be higher in DB group (8.5 %) than SB group (3.3 %) albeit not statistically significant. One possible reason might be that the post-operative activity level in DB group was significantly higher than SB group as shown in the difference in postoperative Tegner activity scale, and thus the patients in DB group might be exposed to higher risk situations than SB group. In the present study, more than three fourth of DB group patients and about two third of SB group patients participated in team ball sports, suggesting that the present population included many high risk teenagers because returning to competitive team ball sports has been shown to be a risk factor for ACL graft rupture in adolescents.10 The high graft failure rates (10–29 %) following ACLR have been reported especially in adolescent populations.1, 2, 3,10 Thus, the graft rupture rate in the present study seems commensurate with rates previously reported in the literature.
Tegner activity scale at the final follow-up was significantly greater in DB ACLR than SB ACLR although postoperative IKDC-SKF was not significantly different between two groups. Postoperative IKDC-SKF were satisfactory in both groups and greater than the patient acceptable symptom state (PASS) threshold (75.9) which was previously reported.22 The difference in postoperative Tegner activity scale was mainly attributable to the fact that many patients who underwent SB ACLR did not continue playing the sports they were playing when they graduated junior high or high school; basically, it was not due to problems related to the operated knee. Importantly, Tegner activity scale at final follow-up was maintained in DB ACLR.
According to the survey from members of the ACL Study Group,23 the preference for HT autograft increased over the study period (1992 through 2020) relative to bone-patellar tendon-bone (BTB) autograft, with quadriceps (QT) autograft gaining popularity in recent years. HT autograft is the most frequently used graft choice, though there are some signs of decline in its use.24 Previous biomechanical studies have shown that DB technique yields kinematics closer to normal than when compared with SB technique.25 The recent systematic reviews have shown that DB procedure may provide better postoperative knee stability compared to SB procedure.15, 16, 17 Another systematic review has shown significant differences favourable to DB reconstruction in the return to preinjury level according to the Lysholm score and the subjective knee function according to the IKDC subjective score.26 However, in the previous reports regarding DB ACLR, the outcomes have been evaluated by including the entire population; thus, the present findings highlight that DB ACLR better restores rotatory knee stability than SB ACLR in skeletally mature teenagers.
Although the present study offers important findings, several limitations should be noted. Firstly, the allocation of the surgical procedure (SB or DB) was not randomized. However, the patients' demographics are similar between two groups, so that the bias would be small. Secondly, the present study was a retrospective data analysis of prospectively collected data, so there is inherent bias from the retrospective nature of the methodological design. Thirdly, the pivot-shift tests were performed by four surgeons. However, these were experienced surgeons using a standardized technique, which reduced inter-examiner variability.27 Fourthly, patients’ factors such as knee hyperextension, generalized joint laxity, and femoral intercondylar notch were not able to be analyzed in the present study, so the influence of these factors on postoperative outcomes were unclear.
5. Conclusion
Clinical outcomes following DB ACLR were similar to SB ACLR, but the pivot-shift phenomenon appeared to be better controlled in DB ACLR than SB ACLR in skeletally mature teenagers. Thus, in the skeletally mature teenagers, DB ACLR may be recommended to better restore rotatory knee stability.
Informed consent
Informed consent was obtained from all patients.
Ethical approval
The institutional review board (IRB) for human subject research in Kobe University Graduate School of Medicine approved the study (ID No. B190055).
Funding
This research does not have any funding sources.
Conflict of interest
The authors declare no conflicts of interest in association with the present study.
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