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Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft
THEKNE-02304; No of Pages 5 The Knee xxx (2016) xxx–xxx
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The Knee
Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft Yingzhen Niu, Chao Niu, Xiaomeng Wang, Junhang Liu, Pengkai Cao, Fei Wang ⁎, Jinghui Niu Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Hebei, China
a r t i c l e
i n f o
Article history: Received 20 January 2016 Received in revised form 14 June 2016 Accepted 23 June 2016 Available online xxxx Keywords: Anterior cruciate ligament Anterior cruciate ligament reconstruction Bone–patellar tendon–bone graft Hamstring allograft
a b s t r a c t Background: This study compared the clinical outcomes of anterior cruciate ligament reconstruction using double-layer bone–patellar tendon–bone (DBPTB) allografts and four-strand hamstring (4SHS) grafts. Methods: This prospective randomized controlled trial included 101 patients. Of these, 50 patients received DBPTB allografts, and 51 received 4SHS grafts. Evaluations included KT-1000 arthrometer measurements, Lachman tests, pivot-shift tests, the International Knee Documentation Committee (IKDC) classification and Lysholm scores at three year postoperative follow-up. Results: Two DBPTB patients (four percent) and nine 4SHS patients (17.6%) had graft failures, which was significantly different (P = 0.028). The DBPTB group had significantly better Lachman test, IKDC knee score and Lysholm score results than the 4SHS group (P b 0.05). However, these differences were below the threshold for clinical significance. Conclusions: DBPTB allografts had fewer graft failures at three years than 4SHS grafts for anterior cruciate ligament reconstruction; and there were statistically significant differences but not clinically significant differences between DBPTB and 4SHS grafts in terms of the KT1000 test, IKDC and Lysholm scores. © 2016 Elsevier B.V. All rights reserved.
1. Introduction The ideal choice of graft for anterior cruciate ligament (ACL) reconstruction remains controversial. Options include bone–patellar tendon– bone (BPTB) autografts, hamstring tendon (HT) autografts, quadriceps autografts, and various types of allografts [1–9]. Allografts have multiple advantages compared with autografts, such as reduced donor complications, shorter-duration surgery and the ability to retain the structure of the knee extensors and flexors. However, disadvantages of allografts include increased graft re-rupture rates, a slower graft incorporation and increased local immune response [1,3,7,9–11]. The clinical applications of both allografts and autografts have been widely studied. Recent work has shown that irradiated allografts (BPTB allograft, Achilles allograft and hamstring tendon allograft) could achieve similar knee stability and function compared with autografts [12–14]. However, other works suggested that BPTB irradiated allografts had a higher failure rate than BPTB autografts [1,5,6,11,15,16]. Wang et al. [17–20] improved on the traditional BPTB to create a double-layer bone–patellar tendon–bone (DBPTB) allograft, which boasts a larger cross-sectional area and a greater initial strength than BPTB. DBPTB allografts have also been shown to produce better anterior ⁎ Corresponding author at: Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang 050051, Hebei, China. E-mail address: [email protected] (F. Wang).
stability and knee function than BPTB allografts. To the best of our knowledge, there has been no prospective study to date that evaluates DBPTB and four-strand hamstring allografts (4SHS). We therefore designed this study to further assess the clinical outcomes of DBPTB allograft for ACL reconstruction. The purpose of our prospective study was to compare the outcomes of ACL reconstruction with DBPTB versus 4SHS. Our hypothesis was that a single-bundle ACL reconstruction with a modified DBPTB allograft would achieve better overall clinical results than 4SHS reconstructions, measured by success rate, KT-1000 scores, Lachman test measurements, International Knee Documentation Committee (IKDC) scores and Lysholm scores. 2. Materials and methods 2.1. Patients and inclusion criteria Informed consent was obtained from all patients prior to their enrollment in this study. This study was approved by our hospital institutional ethics committee. Inclusion criteria were as follows: (1) no history of previous surgery on the injured knee; (2) no concomitant injury of the other ligaments of the knee; (3) a healthy contralateral knee; (4) chondral lesions no worse than Grade II according to the Outerbridge classification; (5) no meniscus repair or partial meniscectomy that involved more than
http://dx.doi.org/10.1016/j.knee.2016.06.015 0968-0160/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
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Y. Niu et al. / The Knee xxx (2016) xxx–xxx
one-third of the entire meniscus; and (6) patients who wished to participate in the study. A total of 110 patients who needed an ACL reconstruction and had an established diagnosis of an ACL rupture based on clinical and magnetic resonance imaging (MRI) findings from 2010 to 2011 were eligible to participate in this clinical study. Participants were randomly divided into two groups using a coin toss (n = 55 for both DBPTB and 4SHS groups). Based on the inclusion criteria, nine patients were excluded, leaving 101 patients (DBPTB group, n = 50; 4SHS group, n = 51). The demographic data of all participants are presented in Table 1. No statistical differences were observed between the two groups (P N 0.05). All patients had at least three years of clinical follow-up after surgery. 2.2. Allograft preparation All allografts were maintained at a certified tissue bank in China. The process of making a modified BPTB allograft has been described in previous studies [17,19]. In short, the bone blocks of the BPTB were split into two fragments at the midline along its long axis with the ligament intact. Excessive spongy bone on the two fragments was resected and trimmed to permit the folding of the bone into a double layer with the cortices facing each other. The graft was then shaped into a column that was 10 mm in diameter using two to 0 polyester sutures (Ethibond, Ethicon, Johnson & Johnson, New Brunswick, NH, USA) to merge the two layers into one bone plug (Figure 1). The hamstring tendon allograft was prepared as a quadruple graft. The free ends of both tendons were sutured together with two to 0 polyester in a running baseball-style whipstitch. The number of patients who received each graft size is shown in Table 2. The mean diameter of the DBPTB and 4SHS groups was 9.9 ± 0.14 mm and 9.8 ± 0.39 mm, respectively (Table 2; P N 0.05). 2.3. Surgical technique and post-operative management All surgical procedures were performed by a senior author (W.F.). For the DBPTB group, a 50° tibial tunnel located just posterior to the centre of the natural ACL insertion was created with the ACL tibial guide. The femoral tunnel was drilled through the arthroscopic anteromedial (AM) portal between the target points of the AM and posterolateral bundles with the knee in 90° of flexion. The tibial and femoral tunnels (both 10 mm in diameter) were fixed with two 9 × 25 mm bioabsorbable interference screws (Figure 2). The same procedures were performed for the 4SHS group, and the tibial and femoral tunnels were also 10 mm in diameter. Femoral graft fixation was performed with an EndoButton flipped over the lateral femoral cortex. Tibial tunnel fixation was obtained with a 9 × 25 mm bioabsorbable interference screw (Figure 3). A similar rehabilitation regimen was applied to all patients by the same group of physical therapists. The operative knee was immobilized with a hinged brace locked at 0° of flexion for two weeks after surgery.
Table 1 Demographical patient data.
No. of patients Sex (male/female) Side involved (right/left) Age (years) Interval to surgery (weeks) Follow up time (months) Meniscus, n (%) Medial Lateral Both
DBPTB
4SHS
P
50 25/25 24/26 26 ± 5 12 ± 6 43 ± 5
51 27/24 25/26 27 ± 4 13 ± 5 40 ± 4
n.s. n.s. n.s. n.s. n.s. n.s. n.s
13 10 1
15 10 1
DBPTB, double-layer bone–patellar tendon–bone; n.s., not significant; 4SHS, four-strand hamstring.
Quadriceps isometric exercises, gradual knee flexion and partial weight bearing were permitted on the second day after surgery. Full weight bearing and knee flexion up to 90° were permitted four weeks after surgery. Three months post-operatively, jogging, walking and cycling were permitted. Patients could return to sports that involved jumping, pivoting or sidestepping six months after their reconstructions. 2.4. Post-operative assessment All patients were evaluated a minimum of three years after their surgery with Lachman and pivot-shift tests as well as arthrometric measurements of anterior tibial translation with a KT-1000 instrument (MEDmetric, San Diego, CA, USA). All tests were performed by the senior author. Functional changes were assessed using the subjective IKDC and Lysholm scores. Ruptures and side-to-side changes of N5 mm as measured with the KT1000 instrument were considered graft failures. 2.5. Statistical analysis Ad hoc sample size calculations were based on the hypothesis that there was no difference in the anterior knee laxity between the two graft groups. For a confidence level of 95% (α = 0.05) and a power (1-β) of 80%, a sample size of 39 patients per group was required. Statistical analysis was performed using SPSS for Windows (version 13.0; SPSS Inc., Chicago, IL, USA). If the variable was continuous (i.e., IKDC and Lysholm scores), the Kolmogorov–Smirnov goodness-of-fit test was used to satisfy the assumptions of a Student's t-test. If it failed, comparisons were made using the non-parametric Mann–Whitney U test. The Wilcoxon rank sum test was used to compare categorical data, such as the Lachman, pivot-shift and KT-1000 tests. All statistical assessments were two-sided and P b 0.05 was considered significant. 3. Results The overall mean follow-up was 40 months (range 36 to 48). Of the 101 patients in the study, 96 (49 in the DBPTB group and 47 in the 4SHS group) were available for the three year follow-up exam. Five patients (one in the BPTB group and four in the 4SHS group) re-ruptured their grafts after high-energy traumas. Three of these patients underwent a re-operation during the follow-up period. All patients with a re-rupture were removed from the study. Forty-six meniscal repairs or resections were performed at the time of the ACL reconstruction. In the DBPTB group, there were five partial resections and eight repairs of the medial meniscus, and six resections and four repairs of the lateral meniscus. In the 4SHS group, there were nine partial resections and six repairs of the medial meniscus, and three resections and seven repairs of the lateral meniscus. No surgical interventions were required for articular cartilage lesions in either group. All the patients recovered a full range of motion without any surgical complications, such as infections, fractures, or deep vein thromboses during the follow-up period. One patient (two percent) in the DBPTB group and four patients (eight percent) in the 4SHS group ruptured their reconstructed ACL (P = 0.362). Two patients (four percent) from the DBPTB group had graft failures, compared with nine (17.6%) from the 4SHS group, which was significantly different (P = 0.028). The mean side-to-side differences between the DBPTB and 4SHS groups three years after surgery were 1.4 ± 1.5 mm and 1.6 ± 1.7 mm, respectively (P = 0.033). There was a significant difference between the Lachman tests in both groups one year after surgery (P = 0.03). There was no significant difference in the pivot shifts of both groups during the three year follow-up after surgery (P = 0.336). The mean IKDC knee scores three years after surgery of the DBPTB and 4SHS groups were 89.9 ± 5.2 and 87 ± 5.0, respectively (P = 0.041). The mean Lysholm scores of the DBPTB and 4SHS groups three years after surgery were 90.1 ± 5.1 and 87.3 ± 4.6, respectively, which was significant (P = 0.032; Table 3).
4. Discussion The main finding of our study was that arthroscopic ACL reconstruction with DBPTB allografts resulted in fewer graft failures than 4SHS reconstructions. However, differences between DBPTB and 4HT in KT1000 test, IKDC and Lysholm scores were not clinically significant. This prospective randomized study suggests that the DBPTB allograft might be a better graft choice than a 4SHS for ACL reconstructions.
Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
Y. Niu et al. / The Knee xxx (2016) xxx–xxx
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Figure 1. The process of making a modified BPTB allograft. (a–c) The bone blocks of a traditional BPTB were split into two fragments at the midline along its long axis with the ligament intact. The excessive spongy bone on the two fragments was resected and trimmed to allow the graft to be folded into a double layer with the cortices facing each other. (d, e) The graft was then shaped into a 10 mm diameter column and secured with polyester sutures to create one unit to use as the bone plug.
The BPTB allograft has become a more popular choice of allograft. However, the use of BPTB allografts has been restricted due to high failure rates [1,5,6,15,16]. A DBPTB graft, which is created using a modified BPTB technique, has a higher initial strength and a larger cross-sectional area than a BPTB graft [17,19]. In recent studies using DBPTBs, Kang et al. [17] reported that DBPTB allografts were significantly better than monolayer BPTB allografts in the recreation of anterior stability (KT1000 test) and knee function (as measured using the Lysholm and Tegner scores). When single-bundle reconstruction using DBPTB allografts and doublebundle reconstruction using hamstring allografts are compared, it has Table 2 The number of patients per graft size. Graft size (mm)
Mean
DBPTB 4SHS
9.9 9.8
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
2
1 4
6 5
43 40
DBPTB, double-layer bone–patellar tendon–bone; 4SHS, four-strand hamstring.
been shown that DBPTB achieved improved anterior and posterior knee stability and pivot-shift results [21]. In our study, DBPTB allografts had good success rates, with improved anterior knee stability and overall knee function compared with 4SHS reconstructions. In a five year follow-up study, the re-rupture rates of HT reconstructions were found to be seven percent, compared with an eight percent re-rupture rate in the BPTB group [21]. Other work found generally lower re-rupture rates, finding a rate of 5.6% in the hamstring tendon group and 4.2% in the BPTB group [22]. In our study, the re-rupture rate of the DBPTB group was two percent, compared with eight percent for the 4SHS group, which was significant. DBPTB allograft reconstructions also had improved anterior knee stability and knee function compared with 10 mm 4SHS allografts. Some prior studies have noted that the functional outcomes of BPTB and hamstring grafts were not different [1,23,24]. However, ACL reconstructions with hamstring tendon grafts were associated with increased knee laxity, a weakness in deep knee flexion, the development of a flexion deficit and an increased risk of tunnel widening [5,25]. In our study, the modified DBPTB
Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
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Y. Niu et al. / The Knee xxx (2016) xxx–xxx
Figure 2. The fixation devices for a DBPTB tendon. The tunnel was 10 mm in diameter and was fixed with two 9 × 25 mm bioabsorbable interference screws.
allografts were significantly better than the 4SHS group in terms of Lachman test, IKDC knee score and Lysholm score. The reason for the improved benefits of DBPTB compared with 4SHS may be multifactorial. In this study, the traditional BPTB was converted to the improved DBPTB allograft, which is the equivalent of the 20 mm wide BPTB allograft but shaped to fit into a 10 mm diameter bone tunnel. Some studies have shown that wider BPTB grafts have a higher initial strength [26,27]. Others have shown that larger cross-sectional area grafts impart greater ACL stability [28–30]. We doubled the crosssectional area of the monolayer BPTB and consequently attained better anterior translation compared with the BPTB. Additionally, the DBPTB allograft avoided leaving any ‘dead space’ [26]. The DBPTB also avoided the ‘windshield wiper’ effect [26]. These factors are thought to interfere with tendon-to-bone healing and lead to post-operative bone tunnel enlargement [19]. The nature of the DBPTB allograft therefore is justified by the good anterior stability and knee function outcomes observed in our study. Theoretically, bone-to-bone healing in the tunnel creates a more stable graft construct with better graft integration and stability [31,32]. In previous studies, the insertion site of the BPTB allograft was thought to be stronger and easier to create than that of the 4SHS, and bore a closer similarity with the anatomic insertion. Jackson et al. [32] in their study comparing BPTB autografts and allografts found that BPTB allografts had similar insertion sites to autografts six months postoperatively. The structure of this site was also more anatomic than typical hamstring graft sites. In addition, most studies found that the site formed during hamstring tendon attachment unintentionally created a three-tiered structure. This study was a prospective randomized comparison. However, the fixation method, the diameter of the interference screws and the use of
Figure 3. The fixation devices for hamstring tendon. The tunnel was 10 mm in diameter. Femoral fixation was achieved with an EndoButton flipped over the lateral femoral cortex. Tibial tunnel fixation was accomplished with a 9 × 25 mm bioabsorbable interference screw.
sterilized allografts may serve as confounders. A randomized controlled trial with a larger sample size and a longer-term follow-up period should be performed to validate our findings. In addition, most previous studies are based on animal models because of the complexities of tunnel healing. As we do not fully understand graft healing within the human joint, errors may appear in our analysis. Biomechanical studies would also be useful to support our research.
Table 3 Post-operative knee physical examination and function assessment.
Lachman test 0 (b3 mm) 1 + (3–5 mm) 2 + (6–10 mm) 3 + (N10 mm) Pivot-shift test 0 (equal) 1 + (glide) 2 + (clunk) 3 + (gross) Side-to-side difference b3 mm 3–5 mm N5 mm Subjective IKDC Lysholm
DBPTB group
4SHS group
43 (88%) 5 (10%) 1 (2%) 0
33 (70%) 9 (19%) 5 (11%) 0
40 (82%) 8 (16%) 1 (2%) 0
35 (74%) 8 (17%) 4 (9%) 0
42 (86%) 6 (12%) 1 (2.0%) 89.9 ± 5.2 90.1 ± 5.1
32 (68%) 10 (21%) 5 (11%) 87.0 ± 5.0 87.3 ± 4.6
P 0.030
0.336
0.033
0.041 0.032
DBPTB, double-layer bone–patellar tendon–bone; IKDC, International Knee Documentation Committee; 4SHS, four-strand hamstring.
Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
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5. Conclusions After a three year minimum follow-up, this study showed that DBPTB ACL reconstructions could have a higher success rate than 4HT reconstructions. However, further research is needed to understand the subjective scores and anterior knee stability differences we measured between DBPTB and 4HT grafts. Conflict of interest The authors declare no conflicts of interest. References [1] Sherman OH, Banffy MB. Anterior cruciate ligament reconstruction: which graft is best? Arthroscopy 2004;20:974–80. [2] Leong NL, Petrigliano FA, McAllister DR. Current tissue engineering strategies in anterior cruciate ligament reconstruction. J Biomed Mater Res A 2014;102:1614–24. [3] Mascarenhas R, Erickson BJ, Sayegh ET, Verma NN, Cole BJ, Bush-Joseph C, et al. Is there a higher failure rate of allografts compared with autografts in anterior cruciate ligament reconstruction: a systematic review of overlapping meta-analyses. Arthroscopy 2015;31:364–72. http://dx.doi.org/10.1016/j.arthro.2014.07.011. [4] Noh JH, Yang BG, Yi SR, Roh YH, Lee JS. Single-bundle anterior cruciate ligament reconstruction in active young men using bone-tendon Achilles allograft versus free tendon Achilles allograft. Arthroscopy 2013;29:507–13. http://dx.doi.org/10.1016/j. arthro.2012.10.023. [5] Prodromos C, Joyce B, Shi K. A meta-analysis of stability of autografts compared to allografts after anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 2007;15:851–6. http://dx.doi.org/10.1007/s00167-007-0328-6. [6] Romanini E, D Angelo F, De Masi S, Adriani E, Magaletti M, Lacorte E, et al. Graft selection in arthroscopic anterior cruciate ligament reconstruction. J Orthop Traumatol 2010;11:211–9. http://dx.doi.org/10.1007/s10195-010-0124-9. [7] Cvetanovich GL, Mascarenhas R, Saccomanno MF, Verma NN, Cole BJ, Bush-Joseph CA, et al. Hamstring autograft versus soft-tissue allograft in anterior cruciate ligament reconstruction: a systematic review and meta-analysis of randomized controlled trials. Arthroscopy 2014;30:1616–24. http://dx.doi.org/10.1016/j.arthro. 2014.05.040. [8] Biau DJ. Bone–patellar tendon–bone autografts versus hamstring autografts for reconstruction of anterior cruciate ligament: meta-analysis. BMJ 2006;332: 995–1001. http://dx.doi.org/10.1136/bmj.38784.384109.2F. [9] Xie X, Xiao Z, Li Q, Zhu B, Chen J, Chen H, et al. Increased incidence of osteoarthritis of knee joint after ACL reconstruction with –patellar tendon–bone autografts than hamstring autografts: a meta-analysis of 1443 patients at a minimum of 5 years. Eur J Orthop Surg Traumatol 2015;25:149–59. [10] Cohen SB, Sekiya JK. Allograft safety in anterior cruciate ligament reconstruction. Clin Sports Med 2007;26:597–605. [11] Bottoni CR, Smith EL, Shaha J, Shaha SS, Raybin SG, Tokish JM, et al. Autograft versus allograft anterior cruciate ligament reconstruction: a prospective, randomized clinical study with a minimum 10-year follow-up. Am J Sports Med 2015. [12] Barber FA, Cowden CR, Sanders EJ. Revision rates after anterior cruciate ligament reconstruction using bone–patellar tendon–bone allograft or autograft in a population 25 years old and younger. Arthroscopy 2014;30:483–91. [13] Barrett G, Stokes D, White M. Anterior cruciate ligament reconstruction in patients older than 40 years: allograft versus autograft patellar tendon. Am J Sports Med 2005;33:1505–12. [14] Noh JH, Yi SR, Song SJ, Kim SW, Kim W. Comparison between hamstring autograft and free tendon Achilles allograft: minimum 2-year follow-up after anterior cruciate ligament reconstruction using EndoButton and Intrafix. Knee Surg Sports Traumatol Arthrosc 2011;19:816–22. http://dx.doi.org/10.1007/s00167-010-1388-6.
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Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
Contents lists available at ScienceDirect
The Knee
Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft Yingzhen Niu, Chao Niu, Xiaomeng Wang, Junhang Liu, Pengkai Cao, Fei Wang ⁎, Jinghui Niu Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Hebei, China
a r t i c l e
i n f o
Article history: Received 20 January 2016 Received in revised form 14 June 2016 Accepted 23 June 2016 Available online xxxx Keywords: Anterior cruciate ligament Anterior cruciate ligament reconstruction Bone–patellar tendon–bone graft Hamstring allograft
a b s t r a c t Background: This study compared the clinical outcomes of anterior cruciate ligament reconstruction using double-layer bone–patellar tendon–bone (DBPTB) allografts and four-strand hamstring (4SHS) grafts. Methods: This prospective randomized controlled trial included 101 patients. Of these, 50 patients received DBPTB allografts, and 51 received 4SHS grafts. Evaluations included KT-1000 arthrometer measurements, Lachman tests, pivot-shift tests, the International Knee Documentation Committee (IKDC) classification and Lysholm scores at three year postoperative follow-up. Results: Two DBPTB patients (four percent) and nine 4SHS patients (17.6%) had graft failures, which was significantly different (P = 0.028). The DBPTB group had significantly better Lachman test, IKDC knee score and Lysholm score results than the 4SHS group (P b 0.05). However, these differences were below the threshold for clinical significance. Conclusions: DBPTB allografts had fewer graft failures at three years than 4SHS grafts for anterior cruciate ligament reconstruction; and there were statistically significant differences but not clinically significant differences between DBPTB and 4SHS grafts in terms of the KT1000 test, IKDC and Lysholm scores. © 2016 Elsevier B.V. All rights reserved.
1. Introduction The ideal choice of graft for anterior cruciate ligament (ACL) reconstruction remains controversial. Options include bone–patellar tendon– bone (BPTB) autografts, hamstring tendon (HT) autografts, quadriceps autografts, and various types of allografts [1–9]. Allografts have multiple advantages compared with autografts, such as reduced donor complications, shorter-duration surgery and the ability to retain the structure of the knee extensors and flexors. However, disadvantages of allografts include increased graft re-rupture rates, a slower graft incorporation and increased local immune response [1,3,7,9–11]. The clinical applications of both allografts and autografts have been widely studied. Recent work has shown that irradiated allografts (BPTB allograft, Achilles allograft and hamstring tendon allograft) could achieve similar knee stability and function compared with autografts [12–14]. However, other works suggested that BPTB irradiated allografts had a higher failure rate than BPTB autografts [1,5,6,11,15,16]. Wang et al. [17–20] improved on the traditional BPTB to create a double-layer bone–patellar tendon–bone (DBPTB) allograft, which boasts a larger cross-sectional area and a greater initial strength than BPTB. DBPTB allografts have also been shown to produce better anterior ⁎ Corresponding author at: Department of Orthopaedic Surgery, Third Hospital of Hebei Medical University, Shijiazhuang 050051, Hebei, China. E-mail address: [email protected] (F. Wang).
stability and knee function than BPTB allografts. To the best of our knowledge, there has been no prospective study to date that evaluates DBPTB and four-strand hamstring allografts (4SHS). We therefore designed this study to further assess the clinical outcomes of DBPTB allograft for ACL reconstruction. The purpose of our prospective study was to compare the outcomes of ACL reconstruction with DBPTB versus 4SHS. Our hypothesis was that a single-bundle ACL reconstruction with a modified DBPTB allograft would achieve better overall clinical results than 4SHS reconstructions, measured by success rate, KT-1000 scores, Lachman test measurements, International Knee Documentation Committee (IKDC) scores and Lysholm scores. 2. Materials and methods 2.1. Patients and inclusion criteria Informed consent was obtained from all patients prior to their enrollment in this study. This study was approved by our hospital institutional ethics committee. Inclusion criteria were as follows: (1) no history of previous surgery on the injured knee; (2) no concomitant injury of the other ligaments of the knee; (3) a healthy contralateral knee; (4) chondral lesions no worse than Grade II according to the Outerbridge classification; (5) no meniscus repair or partial meniscectomy that involved more than
http://dx.doi.org/10.1016/j.knee.2016.06.015 0968-0160/© 2016 Elsevier B.V. All rights reserved.
Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
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Y. Niu et al. / The Knee xxx (2016) xxx–xxx
one-third of the entire meniscus; and (6) patients who wished to participate in the study. A total of 110 patients who needed an ACL reconstruction and had an established diagnosis of an ACL rupture based on clinical and magnetic resonance imaging (MRI) findings from 2010 to 2011 were eligible to participate in this clinical study. Participants were randomly divided into two groups using a coin toss (n = 55 for both DBPTB and 4SHS groups). Based on the inclusion criteria, nine patients were excluded, leaving 101 patients (DBPTB group, n = 50; 4SHS group, n = 51). The demographic data of all participants are presented in Table 1. No statistical differences were observed between the two groups (P N 0.05). All patients had at least three years of clinical follow-up after surgery. 2.2. Allograft preparation All allografts were maintained at a certified tissue bank in China. The process of making a modified BPTB allograft has been described in previous studies [17,19]. In short, the bone blocks of the BPTB were split into two fragments at the midline along its long axis with the ligament intact. Excessive spongy bone on the two fragments was resected and trimmed to permit the folding of the bone into a double layer with the cortices facing each other. The graft was then shaped into a column that was 10 mm in diameter using two to 0 polyester sutures (Ethibond, Ethicon, Johnson & Johnson, New Brunswick, NH, USA) to merge the two layers into one bone plug (Figure 1). The hamstring tendon allograft was prepared as a quadruple graft. The free ends of both tendons were sutured together with two to 0 polyester in a running baseball-style whipstitch. The number of patients who received each graft size is shown in Table 2. The mean diameter of the DBPTB and 4SHS groups was 9.9 ± 0.14 mm and 9.8 ± 0.39 mm, respectively (Table 2; P N 0.05). 2.3. Surgical technique and post-operative management All surgical procedures were performed by a senior author (W.F.). For the DBPTB group, a 50° tibial tunnel located just posterior to the centre of the natural ACL insertion was created with the ACL tibial guide. The femoral tunnel was drilled through the arthroscopic anteromedial (AM) portal between the target points of the AM and posterolateral bundles with the knee in 90° of flexion. The tibial and femoral tunnels (both 10 mm in diameter) were fixed with two 9 × 25 mm bioabsorbable interference screws (Figure 2). The same procedures were performed for the 4SHS group, and the tibial and femoral tunnels were also 10 mm in diameter. Femoral graft fixation was performed with an EndoButton flipped over the lateral femoral cortex. Tibial tunnel fixation was obtained with a 9 × 25 mm bioabsorbable interference screw (Figure 3). A similar rehabilitation regimen was applied to all patients by the same group of physical therapists. The operative knee was immobilized with a hinged brace locked at 0° of flexion for two weeks after surgery.
Table 1 Demographical patient data.
No. of patients Sex (male/female) Side involved (right/left) Age (years) Interval to surgery (weeks) Follow up time (months) Meniscus, n (%) Medial Lateral Both
DBPTB
4SHS
P
50 25/25 24/26 26 ± 5 12 ± 6 43 ± 5
51 27/24 25/26 27 ± 4 13 ± 5 40 ± 4
n.s. n.s. n.s. n.s. n.s. n.s. n.s
13 10 1
15 10 1
DBPTB, double-layer bone–patellar tendon–bone; n.s., not significant; 4SHS, four-strand hamstring.
Quadriceps isometric exercises, gradual knee flexion and partial weight bearing were permitted on the second day after surgery. Full weight bearing and knee flexion up to 90° were permitted four weeks after surgery. Three months post-operatively, jogging, walking and cycling were permitted. Patients could return to sports that involved jumping, pivoting or sidestepping six months after their reconstructions. 2.4. Post-operative assessment All patients were evaluated a minimum of three years after their surgery with Lachman and pivot-shift tests as well as arthrometric measurements of anterior tibial translation with a KT-1000 instrument (MEDmetric, San Diego, CA, USA). All tests were performed by the senior author. Functional changes were assessed using the subjective IKDC and Lysholm scores. Ruptures and side-to-side changes of N5 mm as measured with the KT1000 instrument were considered graft failures. 2.5. Statistical analysis Ad hoc sample size calculations were based on the hypothesis that there was no difference in the anterior knee laxity between the two graft groups. For a confidence level of 95% (α = 0.05) and a power (1-β) of 80%, a sample size of 39 patients per group was required. Statistical analysis was performed using SPSS for Windows (version 13.0; SPSS Inc., Chicago, IL, USA). If the variable was continuous (i.e., IKDC and Lysholm scores), the Kolmogorov–Smirnov goodness-of-fit test was used to satisfy the assumptions of a Student's t-test. If it failed, comparisons were made using the non-parametric Mann–Whitney U test. The Wilcoxon rank sum test was used to compare categorical data, such as the Lachman, pivot-shift and KT-1000 tests. All statistical assessments were two-sided and P b 0.05 was considered significant. 3. Results The overall mean follow-up was 40 months (range 36 to 48). Of the 101 patients in the study, 96 (49 in the DBPTB group and 47 in the 4SHS group) were available for the three year follow-up exam. Five patients (one in the BPTB group and four in the 4SHS group) re-ruptured their grafts after high-energy traumas. Three of these patients underwent a re-operation during the follow-up period. All patients with a re-rupture were removed from the study. Forty-six meniscal repairs or resections were performed at the time of the ACL reconstruction. In the DBPTB group, there were five partial resections and eight repairs of the medial meniscus, and six resections and four repairs of the lateral meniscus. In the 4SHS group, there were nine partial resections and six repairs of the medial meniscus, and three resections and seven repairs of the lateral meniscus. No surgical interventions were required for articular cartilage lesions in either group. All the patients recovered a full range of motion without any surgical complications, such as infections, fractures, or deep vein thromboses during the follow-up period. One patient (two percent) in the DBPTB group and four patients (eight percent) in the 4SHS group ruptured their reconstructed ACL (P = 0.362). Two patients (four percent) from the DBPTB group had graft failures, compared with nine (17.6%) from the 4SHS group, which was significantly different (P = 0.028). The mean side-to-side differences between the DBPTB and 4SHS groups three years after surgery were 1.4 ± 1.5 mm and 1.6 ± 1.7 mm, respectively (P = 0.033). There was a significant difference between the Lachman tests in both groups one year after surgery (P = 0.03). There was no significant difference in the pivot shifts of both groups during the three year follow-up after surgery (P = 0.336). The mean IKDC knee scores three years after surgery of the DBPTB and 4SHS groups were 89.9 ± 5.2 and 87 ± 5.0, respectively (P = 0.041). The mean Lysholm scores of the DBPTB and 4SHS groups three years after surgery were 90.1 ± 5.1 and 87.3 ± 4.6, respectively, which was significant (P = 0.032; Table 3).
4. Discussion The main finding of our study was that arthroscopic ACL reconstruction with DBPTB allografts resulted in fewer graft failures than 4SHS reconstructions. However, differences between DBPTB and 4HT in KT1000 test, IKDC and Lysholm scores were not clinically significant. This prospective randomized study suggests that the DBPTB allograft might be a better graft choice than a 4SHS for ACL reconstructions.
Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
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Figure 1. The process of making a modified BPTB allograft. (a–c) The bone blocks of a traditional BPTB were split into two fragments at the midline along its long axis with the ligament intact. The excessive spongy bone on the two fragments was resected and trimmed to allow the graft to be folded into a double layer with the cortices facing each other. (d, e) The graft was then shaped into a 10 mm diameter column and secured with polyester sutures to create one unit to use as the bone plug.
The BPTB allograft has become a more popular choice of allograft. However, the use of BPTB allografts has been restricted due to high failure rates [1,5,6,15,16]. A DBPTB graft, which is created using a modified BPTB technique, has a higher initial strength and a larger cross-sectional area than a BPTB graft [17,19]. In recent studies using DBPTBs, Kang et al. [17] reported that DBPTB allografts were significantly better than monolayer BPTB allografts in the recreation of anterior stability (KT1000 test) and knee function (as measured using the Lysholm and Tegner scores). When single-bundle reconstruction using DBPTB allografts and doublebundle reconstruction using hamstring allografts are compared, it has Table 2 The number of patients per graft size. Graft size (mm)
Mean
DBPTB 4SHS
9.9 9.8
6.0
6.5
7.0
7.5
8.0
8.5
9.0
9.5
10.0
2
1 4
6 5
43 40
DBPTB, double-layer bone–patellar tendon–bone; 4SHS, four-strand hamstring.
been shown that DBPTB achieved improved anterior and posterior knee stability and pivot-shift results [21]. In our study, DBPTB allografts had good success rates, with improved anterior knee stability and overall knee function compared with 4SHS reconstructions. In a five year follow-up study, the re-rupture rates of HT reconstructions were found to be seven percent, compared with an eight percent re-rupture rate in the BPTB group [21]. Other work found generally lower re-rupture rates, finding a rate of 5.6% in the hamstring tendon group and 4.2% in the BPTB group [22]. In our study, the re-rupture rate of the DBPTB group was two percent, compared with eight percent for the 4SHS group, which was significant. DBPTB allograft reconstructions also had improved anterior knee stability and knee function compared with 10 mm 4SHS allografts. Some prior studies have noted that the functional outcomes of BPTB and hamstring grafts were not different [1,23,24]. However, ACL reconstructions with hamstring tendon grafts were associated with increased knee laxity, a weakness in deep knee flexion, the development of a flexion deficit and an increased risk of tunnel widening [5,25]. In our study, the modified DBPTB
Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
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Figure 2. The fixation devices for a DBPTB tendon. The tunnel was 10 mm in diameter and was fixed with two 9 × 25 mm bioabsorbable interference screws.
allografts were significantly better than the 4SHS group in terms of Lachman test, IKDC knee score and Lysholm score. The reason for the improved benefits of DBPTB compared with 4SHS may be multifactorial. In this study, the traditional BPTB was converted to the improved DBPTB allograft, which is the equivalent of the 20 mm wide BPTB allograft but shaped to fit into a 10 mm diameter bone tunnel. Some studies have shown that wider BPTB grafts have a higher initial strength [26,27]. Others have shown that larger cross-sectional area grafts impart greater ACL stability [28–30]. We doubled the crosssectional area of the monolayer BPTB and consequently attained better anterior translation compared with the BPTB. Additionally, the DBPTB allograft avoided leaving any ‘dead space’ [26]. The DBPTB also avoided the ‘windshield wiper’ effect [26]. These factors are thought to interfere with tendon-to-bone healing and lead to post-operative bone tunnel enlargement [19]. The nature of the DBPTB allograft therefore is justified by the good anterior stability and knee function outcomes observed in our study. Theoretically, bone-to-bone healing in the tunnel creates a more stable graft construct with better graft integration and stability [31,32]. In previous studies, the insertion site of the BPTB allograft was thought to be stronger and easier to create than that of the 4SHS, and bore a closer similarity with the anatomic insertion. Jackson et al. [32] in their study comparing BPTB autografts and allografts found that BPTB allografts had similar insertion sites to autografts six months postoperatively. The structure of this site was also more anatomic than typical hamstring graft sites. In addition, most studies found that the site formed during hamstring tendon attachment unintentionally created a three-tiered structure. This study was a prospective randomized comparison. However, the fixation method, the diameter of the interference screws and the use of
Figure 3. The fixation devices for hamstring tendon. The tunnel was 10 mm in diameter. Femoral fixation was achieved with an EndoButton flipped over the lateral femoral cortex. Tibial tunnel fixation was accomplished with a 9 × 25 mm bioabsorbable interference screw.
sterilized allografts may serve as confounders. A randomized controlled trial with a larger sample size and a longer-term follow-up period should be performed to validate our findings. In addition, most previous studies are based on animal models because of the complexities of tunnel healing. As we do not fully understand graft healing within the human joint, errors may appear in our analysis. Biomechanical studies would also be useful to support our research.
Table 3 Post-operative knee physical examination and function assessment.
Lachman test 0 (b3 mm) 1 + (3–5 mm) 2 + (6–10 mm) 3 + (N10 mm) Pivot-shift test 0 (equal) 1 + (glide) 2 + (clunk) 3 + (gross) Side-to-side difference b3 mm 3–5 mm N5 mm Subjective IKDC Lysholm
DBPTB group
4SHS group
43 (88%) 5 (10%) 1 (2%) 0
33 (70%) 9 (19%) 5 (11%) 0
40 (82%) 8 (16%) 1 (2%) 0
35 (74%) 8 (17%) 4 (9%) 0
42 (86%) 6 (12%) 1 (2.0%) 89.9 ± 5.2 90.1 ± 5.1
32 (68%) 10 (21%) 5 (11%) 87.0 ± 5.0 87.3 ± 4.6
P 0.030
0.336
0.033
0.041 0.032
DBPTB, double-layer bone–patellar tendon–bone; IKDC, International Knee Documentation Committee; 4SHS, four-strand hamstring.
Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015
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Please cite this article as: Niu Y, et al, Improved ACL reconstruction outcome using double-layer BPTB allograft compared to that using four-strand hamstring tendon allograft, Knee (2016), http://dx.doi.org/10.1016/j.knee.2016.06.015