Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-015-3569-9
KNEE
Arthroscopic single‑bundle anterior cruciate ligament reconstruction with six‑strand hamstring tendon allograft versus bone‑patellar tendon‑bone allograft Chengliang Dai1 · Fei Wang1 · Xiaomeng Wang1 · Ruipeng Wang1 · Shengjie Wang1 · Shiyu Tang1
Received: 30 July 2014 / Accepted: 3 March 2015 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2015
Abstract Purpose The aim of this study was to compare the clinical outcomes of arthroscopic single-bundle anterior cruciate ligament (ACL) reconstruction with six-strand hamstring tendon (HT) allograft versus bone-patellar tendon-bone (BPTB) allograft. Methods The prospective randomized controlled trial was included 129 patients. Sixty-nine patients received reconstruction with six-strand HT allografts (HT group), whereas 60 patients with BPTB allografts (BPTB group). Outcome assessment included re-rupture findings, International Knee Documentation Committee (IKDC) scores, Lysholm scores, KT-1000 arthrometer, Lachman test, pivot-shift test, range of motion (ROM) and single-leg hop test. Results At a mean follow-up of 52 months, 113 patients (HT group, 61 patients; BPTB group, 52 patients) completed a minimum 4-year follow-up. Four patients in HT group and six in BPTB group experienced ACL re-rupture (6.2 vs. 10.3 %) and received revision surgery. Significant between-group differences were observed in KT-1000 outcomes and pivot-shift test 1 (1.2 ± 1.5 vs. 1.8 ± 1.3, p = 0.025; positive rate 6.5 vs. 18.9 %, p = 0.036), 2 (1.1 ± 1.4 vs. 1.6 ± 1.2, p = 0.044; 8.1 vs. 20.7 %, p = 0.039), 4 (1.1 ± 1.5 vs. 1.7 ± 1.4, p = 0.031; 9.7 vs. 25 %, p = 0.012) years postoperatively. The outcomes between the two groups were comparable in terms of IKDC scores, Lysholm scores, Lachman test, ROM and single-leg hop test.
* Fei Wang [email protected] 1
Department of Joint Surgery, Third Hospital of Hebei Medical University, 139 Ziqiang Road, Shijiazhuang 050051, Hebei, People’s Republic of China
Conclusions Six-strand HT allograft achieved superior anteroposterior and rotational stability after single-bundle ACL reconstruction. It is a reasonable graft substitute for ACL reconstruction. Level of evidence II. Keywords Anterior cruciate ligament · Single-bundle reconstruction · Bone-patellar tendon-bone · Hamstring tendon · Allograft
Introduction Advances in endoscopic techniques have made arthroscopic reconstruction of the injured anterior cruciate ligament (ACL) a standard surgical intervention, but there is still controversy over graft choice. ACL reconstruction with allograft has been promoted over the past decade because it avoids relative donor site morbidity and surgical trauma arsing from the harvesting process and because of the availability of larger grafts [31]. Allografts including bonepatellar tendon-bone (BPTB) and hamstring tendon (HT) are now widely used. An estimated 20–30 % of ACL reconstructions in 2007 were performed using allografts [6]. Different graft configurations are required depending on their properties. The patellar tendon is normally used as a single strand, whereas two or more hamstring tendons (semitendinosus and/or gracilis) are usually combined by folding into a single multi-strand graft. In a study by Beynnon et al. [4], patients who underwent ACL reconstruction with a two-strand HT graft had a significant decrease in knee stability. Indeed, a two-strand HT graft cannot provide sufficient biomechanical properties. Hamner et al. [12] performed biomechanical measurements of HT grafts and determined that maximum load to failure, stiffness
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and cross-sectional area are proportional to the number of strands, and concluded that multi-strand HT is a reasonable graft alternative from a biomechanical standpoint. Though a number of studies compare the gold-standard BPTB graft to the four-strand HT graft, no significant differences in knee stability were observed [8, 13]. Magnussen et al. [24] showed that, in patients younger than 20 years, the use of an HT graft ≤8 mm in diameter is associated with a higher rate of revision. The mean diameter of the four-strand HT graft reported was 8.1 mm in males and 7.5 mm in females [22]. Therefore, it is necessary to triple HT grafts to achieve sufficient size and biomechanical properties. To the best of our knowledge, no study has compared postoperative knee stability of six-strand HT and BPTB allografts for ACL reconstruction. The purpose of this study was to compare clinical outcomes between six-strand HT and BPTB allografts for arthroscopic single-bundle ACL reconstruction in a prospective manner. The hypothesis was that ACL reconstruction with six-strand HT allograft was superior to that employing BPTB allograft in restoring anteroposterior and rotational stability of the knee joint.
Materials and methods From 2007 to 2009, 191 patients with ACL rupture underwent reconstruction with either a six-strand HT or a BPTB allograft in the Department of Joint Surgery of Third Hospital of Hebei Medical University. Patients between the ages of 17 and 50 who had an established diagnosis based on clinical and radiographic features were eligible to participate in this clinical study. Patients were excluded if they had bilateral ACL injuries, multi-ligament injuries or articular cartilage lesions greater than Outerbridge grade II; if they required meniscal repair, total meniscectomy or more than one-third partial meniscectomy; or if they had had previous articular injury to, or surgery on, the affected knee. Twenty-seven patients declined to participate, and 31 patients failed to meet our criteria. At the time of surgery, four patients were excluded. Ultimately, 129 patients were prospectively randomized to receive either a six-strand HT allograft (HT group, 69 patients) or a BPTB allograft (BPTB group, 60 patients) for ACL reconstruction. Randomization was done by coin toss. Figure 1 provides a flowchart of the participant. Surgical technique All patients were operated on by the same senior surgeon assisted by his colleagues. All cryopreserved allografts were obtained from the same certified tissue bank. Before surgery, the grafts were thawed in room temperature normal saline solution containing 240,000 IU of gentamicin.
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Fig. 1 Participant flowchart. Four patients in the HT group and two in the BPTB group were lost to follow-up. Among these patients, two (one in each group) relocated and lost contact with us, and three in the HT group and one in the BPTB group were satisfied with their outcomes and declined to continue to participate in follow-up. Ten patients experienced ACL re-rupture. Six of the re-ruptures, three in each group, were caused by injury during sports. Another re-rupture in the HT group occurred 41 months after reconstruction, and the other three, in the BPTB group, occurred at 15, 19 and 20 months postoperatively
Six-strand HT grafts were prepared using two semitendinosus tendons and one gracilis tendon. To minimize the error caused by individual differences in grafts and to improve accuracy, we used the same combination of tendons for each graft. Limbs of the tendons were whipstitched together with No. 2 nonabsorbable braided sutures, and the three tendons were looped over an EndoButton CL (Smith & Nephew Endoscopy, Andover, MA, USA). The graft was pulled through a series of calibrated cylinders, and the diameter measured 9–10 mm. In the BPTB group, a 10-mm-wide patellar tendon was prepared with bone plugs at each end. The two bone plugs were trimmed into cylinders 25 mm in length and 10 mm in diameter. All the grafts were pre-tensioned using the Graft-master board (Arthrex, Naples, FL, USA). Diagnosis was reconfirmed and meniscal or chondral pathology was addressed as necessary. After debriding the ruptured ACL, the tibial tunnel was drilled via the medial arthroscopic portal using a tibial guide at an angle of 50° to the tibial plateau. It was placed just posterior to the native tibial ACL footprint and about 7 mm anterior to the native tibial posterior cruciate ligament footprint. The femoral tunnel was drilled via the anteromedial arthroscopic portal with the knee in 90° of flexion. It was positioned about 6 mm in front of the over-the-top position,
Knee Surg Sports Traumatol Arthrosc
at 10 o’clock for the right knee and at 2 o’clock for the left knee. The diameters of the tibial and femoral tunnels were equal to the measured diameter of the HT graft but were all set at 10 mm in the BPTB group. After the graft was pulled through the tunnels and positioned temporarily, femoral fixation was achieved with the knee flexed to 90° using the EndoButton CL in the HT group and an 8-mm × 23-mm bioabsorbable interference screw (Linvatec, Largo, FL, USA) in the BPTB group. On the tibial side, the graft was secured with the knee flexed to 20° using a 10-mm × 28-mm bioabsorbable interference screw reinforced with extracortical fixation in the HT group and a 9-mm × 28-mm bioabsorbable interference screw in the BPTB group. After fixation, the knee was taken through a full range of motion (ROM).
Functional tests included ROM of the knee and single-leg hop test. ROM was measured with a standard goniometer. Single-leg hop test was performed three times on each leg. The distance covered in one hop was measured, and the operated and contralateral legs were compared (grade A, ≥90 % the distance hopped on the contralateral limb; grade B, 75–89 %; grade C, 5.0° in extension or >10.0° in flexion.
Discussion with a re-rupture were excluded from the following assessment and final analysis. No complications, such as wound infection, deep vein thrombosis, vascular or nerve injuries, symptoms of tissue rejection or viral infectious diseases, occurred during the follow-up period. Table 2 details the results of subjective assessment. Both groups demonstrated a great deal of improvement with respect to IKDC scores and Lysholm scores. No significant between-group differences were observed in subjective assessment outcomes 1, 2 and 4 years postoperatively. Details of postoperative stability are shown in Table 3.
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The most important finding of the present study was that the HT group demonstrated greater anteroposterior and rotational stability, as judged by KT-1000 arthrometer and pivot-shift test outcomes. Significant between-group differences were observed in KT-1000 outcomes, which indicated that superior anteroposterior stability could be yielded using the six-stranded HT allograft over time. The pivot-shift test is a standard method for evaluating rotational stability. However, results of the pivot-shift test vary greatly. Positive rates in single-bundle ACL reconstruction using autografts have been reported to be range from 0 to
Knee Surg Sports Traumatol Arthrosc Table 3 Postoperative stability assessment of operated knee 1 Year Postop.
KT-1000 (mm) Lachman test, n (%) 0 1+ 2+ 3+ Pivot-shift test, n (%) 0 1+ 2+ 3+
2 Year Postop.
4 Year Postop.
HT group (n = 62)
BPBT group (n = 53)
p value HT group (n = 62)
BPBT group (n = 53)
p value HT group (n = 61)
BPBT group (n = 52)
p value
1.2 ± 1.5
1.8 ± 1.3
0.025 n.s.
1.1 ± 1.4
1.6 ± 1.2
0.044 n.s.
1.1 ± 1.5
1.7 ± 1.4
0.031 n.s.
59 (95.2) 3 (4.8) 0 (0) 0 (0)
49 (92.5) 2 (3.7) 2 (3.8) 0 (0)
58 (93.5) 4 (6.5) 0 (0) 0 (0)
48 (90.6) 2 (3.8) 3 (5.6) 0 (0)
57 (93.4) 4 (6.6) 0 (0) 0 (0)
46 (88.5) 3 (5.7) 3 (5.8) 0 (0)
0.036 58 (93.5) 4 (6.5) 0 (0) 0 (0)
6.5 Positive rate of pivot-shift test (%)
0.039
0.012
43 (81.1) 6 (11.3) 4 (7.6) 0 (0)
57 (91.9) 5 (8.1) 0 (0) 0 (0)
42 (79.3) 6 (11.3) 5 (9.4) 0 (0)
56 (90.3) 5 (9.7) 0 (0) 0 (0)
39 (75.0) 8 (15.4) 5 (9.6) 0 (0)
18.9
8.1
20.7
9.7
25
Table 4 Postoperative function assessment of operated knee 1 Year Postop.
Extension deficit (°) Flexion deficit (°) Single-leg hop test, n (%) Grade A Grade B Grade C
2 Year Postop.
4 Year Postop.
HT group (n = 62)
BPTB group (n = 53)
p value HT group (n = 62)
BPTB group (n = 53)
p value HT group (n = 61)
BPTB group (n = 52)
p value
1.1 ± 0.7
1.3 ± 0.8
n.s.
1.2 ± 0.6
1.4 ± 0.7
n.s.
1.2 ± 0.5
1.4 ± 0.7
n.s.
1.4 ± 0.7
1.2 ± 0.6
n.s.
1.3 ± 0.7
1.2 ± 0.5
n.s.
1.3 ± 0.6
1.2 ± 0.5
n.s.
n.s.
n.s.
n.s.
59 (95.2) 3 (4.8)
47 (88.7) 6 (11.3)
58 (93.5) 4 (6.5)
48 (90.6) 5 (9.4)
59 (96.7) 2 (3.3)
48 (92.3) 4 (7.7)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
30 % [23]. Zaffagnini et al. [50] reported that the positive rates after reconstruction using BPTB and HT autografts were 12 and 36 %, with significant differences. Mascarenhas et al. [26] found that positive pivot-shift tests occurred less often after HT autograft (17 %) than after BPTB autograft (39 %). Leys et al. [20] reported a rate of 12 % positive in the HT autograft group and 9 % in the BPTB autograft group, a difference that was not statistically significant. Moreover, some studies have reported positive rates to be higher for allografts than for autografts [19, 38], some [25] have been significantly higher in autografts, and some [33, 42] have identified no significant difference. No agreement has reached. As far as we know, no studies have compared the rates of positive pivot-shift tests between
BPTB and six-strand HT allograft, or even four-strand HT allograft. In the present study, there were significantly more positive pivot-shift test results in the BPTB group than in the HT group, suggesting that single-bundle ACL reconstruction using a six-strand allograft may achieve better rotational stability. The rates of re-rupture in the present study were 6.2 % in the HT group and 10.3 % in BPTB group, which were similar to those reported by Goddard et al. [10] and Benjamin et al. [3], respectively. Because of differences in graft choice, fixation method and surgical technique, rates of re-rupture vary (range 0–14 %) [16]. The re-rupture rates reported by Sajovic et al. [39] were 7 % of the HT group and 8 % of the BPTB group at 5-year follow-up. Those
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reported by Wagner et al. [44] were 5.6 % of HT group and 4.2 % of BPTB group. Gerhard et al. [9] reported a rerupture rate of 1.5 % after ACL reconstruction with patellar tendon autograft. Matthew et al. [25] did a meta-analysis and found that graft rupture was significantly higher for allograft patients. It might be attributed to the allogenous nature of the graft material. It is reported that allografts are inferior in initial strength and require more time to undergo ligamentization. Moreover, return to full athletic activities was allowed beginning 6 months postoperatively in the present study, which was a risk factor for graft re-rupture. ACL reconstruction is currently performed using a variety of ligament substitutes. Although the use of BPTB autograft is considered the gold standard, HT autograft has been determined to be comparable [8, 13] and used as the most popular graft choice [28]. Autografts are superior in initial strength [15], time to incorporation [26] and avoidance of disease transmission but may be associated with donor site morbidity, increased operative duration [31] and unavailability of larger grafts. As a result, reconstruction using allograft has grown in popularity. Several reports have indicated that allograft is a viable alternative to autograft, with no significant differences in postoperative symptoms, knee function, activity level or results of physical examination [2, 19]. Factors contributing to the superior outcomes of the six-stranded HT allograft compared with BPTB allograft include initial strength and stiffness, which are particularly important for patients with high demand of activities. Grafts undergo an acute decrease in strength during the process of ligamentization [27]. Moreover, the current aggressive rehabilitation protocol creates a higher demand on the initial strength and stiffness. The mean load to failure and stiffness for four-strand grafts have been reported to be 4,090 ± 295 N and 776 ± 204 N/mm, respectively [12], which exceed those reported for a 10.0-mm-diameter patellar tendon (2,977 N and 455 N/mm, respectively) [7, 12] and for the native ACL (2,160 ± 157 N and 306 N/mm, respectively) [49]. According to Hamner et al. [12], the biomechanical properties are proportional to the number of strands. The six-strand HT graft, with theoretically higher initial strength and stiffness, is better able to withstand the initial weakness without compromise of graft integrity [47]. Furthermore, preservation of mechanical properties with increasing age is seen with HT grafts but not with patellar tendon grafts [47]. Studies have proved statistically significant inverse correlations between the amount of anteroposterior translation and cross-sectional area [11, 18]. The cross-sectional area of six-strand HT graft reached 63.0–78.5 mm2, which exceeded the 41.0 ± 9.8 [30] and 44.4 ± 4.0 mm2 [35] reported for a 10.0-mm-diameter patellar tendon. Moreover, a thicker graft will provide more collagen for the
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ligamentization process to enhance biomechanical stability after reconstruction [5]. The larger size of a six-strand HT graft has been shown in biomechanical studies to provide better knee stability [12, 47]. The flat shape of the patellar tendon makes its width much greater than its thickness and causes graft-tunnel mismatch, in which large, empty lacunae will form within the cylindrical tibial bone tunnel. Synovial fluid leakage into the empty lacunae and graft-tunnel motions (windshieldwiper effect) play influential roles in tunnel enlargement [14]. It results in a broadened fibrous interzone between the bone and graft tissue, leading to a prolonged or impaired healing [46]. In contrast, the cylindrical shape of the sixstrand HT allograft matches that of the bone tunnel. A larger graft-tunnel contact area facilitates the formation of collagen fibres resembling Sharpey fibres at the tendon– tunnel interface and improves osteointegration [43]. Literature has provided a description of the complex anatomical nature of ACL in detail, theorizing that different fibres are recruited to resist loads and maintain stability at different flexion and extension angles [1, 34]. Some studies have indicated that the distribution of load is highly nonuniform among the ligament fibres and that strain gradients could be generated even along the direction of fibres [21, 40]. Moreover, elongation of each ligament fibre has been shown to be inhomogeneous [36]. Livesay et al. [21] stated that the ACL did not function as a uniaxial structure and that the magnitudes of force supported by different portions of ACL differ. That is, the ACL is most likely to be a functional complex with multiple fibres that undergo changes in length and shifts in load distribution. Thus, reconstruction of the ACL with a single-strand structure graft may be inadequate to meet the functional requirements. Wallace et al. [45] measured the tensile stress of each strand of the four-strand HT graft after ACL reconstruction and found them to be unequal during knee motion. Radford et al. [37] stated that a multi-strand graft would provide a closer approximation of normal knee behaviour, with structure moving in a way that is analogous to the fibre bundles of the native ACL. In the present study, tendons were tripled to obtain a larger, multi-stranded graft. During knee motion, the distribution of load between these strands is less consistent [17], but they work in a coordinated manner. As numerous studies have shown, stress can stimulate collagen synthesis and enhance granulation tissue to regain mechanical properties [41, 48]. The unequal stresses on each strand of graft lead to varying performance during the ligamentization process, which may help to reproduce different functional bundles and closely mimic the anisotropic mechanical properties of the native ACL [15, 32]. These will do good to the restoration of knee kinematics and rotational stability.
Knee Surg Sports Traumatol Arthrosc
The clinical relevance of this study is that six-strand hamstring tendon allograft is a reasonable option for ACL reconstruction as it provided superior anteroposterior and rotational stability, allowing the patients to return to activities in demanding environments. We are not stating that BPTB allograft is inadequate for ACL reconstruction. However, surgeons should know the material properties of each graft substitute and choose the optimal one for ACL reconstruction. This study had several limitations. First, participants in both groups who were lost to follow-up or experienced ACL re-rupture were excluded from the final analysis. Their exclusion may have introduced bias into the outcomes. Second, although same postoperative rehabilitation protocol was prescribed to all patients, the quality and consistency of rehabilitation may have varied without strict supervision. Furthermore, the date of postoperative activity level was not validated. The fact that most patients did not participate in strenuous activities may explain the similarity in subjective assessment. Third, incomplete follow-up radiographic data may limit our ability to draw significant conclusions. Fourth, although no significant differences were observed in preoperative parameters, it was difficult to control for clinical and individual factors. Finally, the sample size was relatively small, which limited statistical power. Studies with larger sample sizes, longer follow-up periods and additional assessment, especially for rotational stability, are necessary in the future. Moreover, more biomechanical works are needed to confirm and clarify the results presented.
Conclusions As a result of this study with a mean follow-up of 52 months, single-bundle ACL reconstruction with a sixstrand HT allograft was technically feasible and achieved anteroposterior and rotational stability superior to that of BPTB graft reconstruction. Conflict of interest None.
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22. Ma CB, Keifa E, Dunn W et al (2010) Can pre-operative measures predict quadruple hamstring graft diameter. Knee 17:81–83 23. Magnussen RA, Carey JL, Spindler KP (2011) Does autograft choice determine intermediate-term outcome of ACL reconstruction? Knee Surg Sports Traumatol Arthrosc 19:462–472 24. Magnussen RA, Lawrence TR, West RL, Toth AP, Taylor DC, Garrett WE (2012) Graft size and patient age are predictors of early revision after anterior cruciate ligament reconstruction with hamstring autograft. Arthroscopy 28:526–531 25. Kraeutler Matthew J, Bravman Jonathan T, McCarty Eric C (2013) Bone-patellar tendon-bone autograft versus allograft in outcomes of anterior cruciate ligament reconstruction: a metaanalysis of 5182 patients. Am J Sports Med 41:2439–2448 26. Mascarenhas R, Tranovich MJ, Kropf KL, Fu FH, Harner CD (2012) Bone-patellar tendon-bone autograft versus hamstring autograft anterior cruciate ligament reconstruction in the young athlete: a retrospective matched analysis with 2–10 year followup. Knee Surg Sports Traumatol Arthrosc 20:1520–1527 27. Ménétrey J, Duthon VB, Laumonier T, Fritschy D (2008) Biological failure of the anterior cruciate ligament graft. Knee Surg Sports Traumatol Arthrosc 16:224–231 28. Middleton KK, Hamilton T, Irrgang JJ, Karlsson J, Harner CD, Fu FH (2014) Anatomic anterior cruciate ligament (ACL) reconstruction: a global perspective. Part 1. Knee Surg Sports Traumatol Arthrosc 22:1467–1482 29. Muneta T, Hara K, Ju YJ, Mochizuki T, Morito T, Yagishita K, Sekiya I (2010) Revision anterior cruciate ligament reconstruction by double-bundle technique using multi-strand semitendinosus tendon. Arthroscopy 26:461–476 30. Muneta T, Takakuda K, Yamamoto H (1997) Intercondylar notch width and its relation to the configuration and cross-sectional area of the anterior cruciate ligament: a cadaveric knee study. Am J Sports Med 25:69–72 31. Nakamura N, Horibe S, Sasaki S, Kitaguchi T, Tagami M et al (2002) Evaluation of active knee flexion and hamstring strength after anterior cruciate ligament reconstruction using hamstring tendons. Arthroscopy 18:598–602 32. Nin JR, Leyes M, Schweitzer D (1996) Anterior cruciate ligament reconstruction with fresh-frozen patellar tendon allografts: sixty cases with 2 years minimum follow-up. Knee Surg Sports Traumatol Arthrosc 4:137–142 33. Noh JH, Yi SR, Song SJ, Kim SW, Kim W (2011) 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 19:816–822 34. Norwood LA, Cross MJ (1997) Anterior cruciate ligament: functional anatomy of its bundles in rotatory instabilities. Am J Sports Med 1:23–26 35. Noyes FR, Grood ES (1996) The strength of the anterior cruciate ligament in humans and Rhesus monkeys. J Bone Joint Surg Am 58:1074–1082 36. Pioletti DP, Heegaard JH, Rakotomanana RL, Leyvraz PF, Blankevoort L (1995) Experimental and mathematical methods for representing relative surface elongation of the ACL. J Biomech 28:1123–1126
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Knee Surg Sports Traumatol Arthrosc 37. Radford WJR, Amis AA (1990) Biomechanical properties of a double prosthetic ligament in the anterior cruciate deficient knee. J Bone Joint Surg [Br] 72:1038–1043 38. Romanini E, D’Angelo F, De Masi S et al (2010) Graft selection in arthroscopic anterior cruciate ligament reconstruction. J Orthop Traumatol 11:211–219 39. Sajovic M, Vengust V, Komadina R, Tavcar R, Skaza K (2006) A prospective, randomized comparison of semitendinosus and gracilis tendon versus patellar tendon autografts for anterior cruciate ligament reconstruction: five-year follow-up. Am J Sports Med 34:1933–1940 40. Shunji H, Kouji Y, Takashi K (2001) Circumferential measurement and analysis of strain distribution in the human ACL using a photoelastic coating method. J Biomech 34:1135–1143 41. Stuker BD, Lester GE, Banes AJ et al (1990) Cyclic strain stimulates DNA and collagen synthesis in fibroblasts cultured from rat medial collateral ligaments. Trans Orthop Res Soc 15:130 42. Sun K, Zhang J, Wang Y et al (2011) Arthroscopic reconstruction of the anterior cruciate ligament with hamstring tendon autograft and fresh-frozen allograft: a prospective, randomized controlled study. Am J Sports Med 39:1430–1438 43. Tomita F, Yasuda K, Mikami S et al (2001) Comparisons of intraosseous graft healing between the doubled flexor tendon graft and the bone-patellar tendon-bone graft in anterior cruciate ligament reconstruction. Arthroscopy 17:461–476 44. Wagner M, Kaab MJ, Schallock J, Haas NP, Weiler A (2005) Hamstring tendon versus patellar tendon anterior cruciate ligament reconstruction using biodegradable interference fit fixation: a prospective matched-group analysis. Am J Sports Med 33:1327–1336 45. Wallace MP, Howell SM, Hull ML (1997) In vivo tensile behavior of a four-bundle hamstring graft as a replacement for the anterior cruciate ligament. J Orthop Res 15:539–545 46. Weiler A, Hoffmann RF, Bail HJ, Rehm O, Sudkamp NP (2002) Tendon healing in a bone tunnel. Part II: histologic analysis after biodegradable interference fit fixation in a model of anterior cruciate ligament reconstruction in sheep. Arthroscopy 18:124–135 47. Wilson TW, Zafuta MP, Zobitz MA (1999) Biomechanical analysis of matched bone-patellar tendon-bone and double-looped semitendinosus and gracilis tendon grafts. Am J Sports Med 27:202–207 48. Woo SL, Gomez MA, Sites TJ et al (1987) The biomechanical and morphological changes in the medial collateral ligament of the rabbit after immobilization and remobilization. J Bone Joint Surg Am 69:1200–1211 49. Woo SL, Hollis JM, Adams DJ, Lyon RM, Takai S (1991) Tensile properties of the human femur-anterior cruciate ligamenttibia complex: the effects of specimen age and orientation. Am J Sports Med 19:217–225 50. Zaffagnini S, Marcacci M, Lo Presti M, Giordano G, Iacono F, Neri MP (2006) Prospective and randomized evaluation of ACL reconstruction with three techniques: a clinical and radiographic evaluation at 5 years follow-up. Knee Surg Sports Traumatol Arthrosc 14:1060–1069
KNEE
Arthroscopic single‑bundle anterior cruciate ligament reconstruction with six‑strand hamstring tendon allograft versus bone‑patellar tendon‑bone allograft Chengliang Dai1 · Fei Wang1 · Xiaomeng Wang1 · Ruipeng Wang1 · Shengjie Wang1 · Shiyu Tang1
Received: 30 July 2014 / Accepted: 3 March 2015 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2015
Abstract Purpose The aim of this study was to compare the clinical outcomes of arthroscopic single-bundle anterior cruciate ligament (ACL) reconstruction with six-strand hamstring tendon (HT) allograft versus bone-patellar tendon-bone (BPTB) allograft. Methods The prospective randomized controlled trial was included 129 patients. Sixty-nine patients received reconstruction with six-strand HT allografts (HT group), whereas 60 patients with BPTB allografts (BPTB group). Outcome assessment included re-rupture findings, International Knee Documentation Committee (IKDC) scores, Lysholm scores, KT-1000 arthrometer, Lachman test, pivot-shift test, range of motion (ROM) and single-leg hop test. Results At a mean follow-up of 52 months, 113 patients (HT group, 61 patients; BPTB group, 52 patients) completed a minimum 4-year follow-up. Four patients in HT group and six in BPTB group experienced ACL re-rupture (6.2 vs. 10.3 %) and received revision surgery. Significant between-group differences were observed in KT-1000 outcomes and pivot-shift test 1 (1.2 ± 1.5 vs. 1.8 ± 1.3, p = 0.025; positive rate 6.5 vs. 18.9 %, p = 0.036), 2 (1.1 ± 1.4 vs. 1.6 ± 1.2, p = 0.044; 8.1 vs. 20.7 %, p = 0.039), 4 (1.1 ± 1.5 vs. 1.7 ± 1.4, p = 0.031; 9.7 vs. 25 %, p = 0.012) years postoperatively. The outcomes between the two groups were comparable in terms of IKDC scores, Lysholm scores, Lachman test, ROM and single-leg hop test.
* Fei Wang [email protected] 1
Department of Joint Surgery, Third Hospital of Hebei Medical University, 139 Ziqiang Road, Shijiazhuang 050051, Hebei, People’s Republic of China
Conclusions Six-strand HT allograft achieved superior anteroposterior and rotational stability after single-bundle ACL reconstruction. It is a reasonable graft substitute for ACL reconstruction. Level of evidence II. Keywords Anterior cruciate ligament · Single-bundle reconstruction · Bone-patellar tendon-bone · Hamstring tendon · Allograft
Introduction Advances in endoscopic techniques have made arthroscopic reconstruction of the injured anterior cruciate ligament (ACL) a standard surgical intervention, but there is still controversy over graft choice. ACL reconstruction with allograft has been promoted over the past decade because it avoids relative donor site morbidity and surgical trauma arsing from the harvesting process and because of the availability of larger grafts [31]. Allografts including bonepatellar tendon-bone (BPTB) and hamstring tendon (HT) are now widely used. An estimated 20–30 % of ACL reconstructions in 2007 were performed using allografts [6]. Different graft configurations are required depending on their properties. The patellar tendon is normally used as a single strand, whereas two or more hamstring tendons (semitendinosus and/or gracilis) are usually combined by folding into a single multi-strand graft. In a study by Beynnon et al. [4], patients who underwent ACL reconstruction with a two-strand HT graft had a significant decrease in knee stability. Indeed, a two-strand HT graft cannot provide sufficient biomechanical properties. Hamner et al. [12] performed biomechanical measurements of HT grafts and determined that maximum load to failure, stiffness
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and cross-sectional area are proportional to the number of strands, and concluded that multi-strand HT is a reasonable graft alternative from a biomechanical standpoint. Though a number of studies compare the gold-standard BPTB graft to the four-strand HT graft, no significant differences in knee stability were observed [8, 13]. Magnussen et al. [24] showed that, in patients younger than 20 years, the use of an HT graft ≤8 mm in diameter is associated with a higher rate of revision. The mean diameter of the four-strand HT graft reported was 8.1 mm in males and 7.5 mm in females [22]. Therefore, it is necessary to triple HT grafts to achieve sufficient size and biomechanical properties. To the best of our knowledge, no study has compared postoperative knee stability of six-strand HT and BPTB allografts for ACL reconstruction. The purpose of this study was to compare clinical outcomes between six-strand HT and BPTB allografts for arthroscopic single-bundle ACL reconstruction in a prospective manner. The hypothesis was that ACL reconstruction with six-strand HT allograft was superior to that employing BPTB allograft in restoring anteroposterior and rotational stability of the knee joint.
Materials and methods From 2007 to 2009, 191 patients with ACL rupture underwent reconstruction with either a six-strand HT or a BPTB allograft in the Department of Joint Surgery of Third Hospital of Hebei Medical University. Patients between the ages of 17 and 50 who had an established diagnosis based on clinical and radiographic features were eligible to participate in this clinical study. Patients were excluded if they had bilateral ACL injuries, multi-ligament injuries or articular cartilage lesions greater than Outerbridge grade II; if they required meniscal repair, total meniscectomy or more than one-third partial meniscectomy; or if they had had previous articular injury to, or surgery on, the affected knee. Twenty-seven patients declined to participate, and 31 patients failed to meet our criteria. At the time of surgery, four patients were excluded. Ultimately, 129 patients were prospectively randomized to receive either a six-strand HT allograft (HT group, 69 patients) or a BPTB allograft (BPTB group, 60 patients) for ACL reconstruction. Randomization was done by coin toss. Figure 1 provides a flowchart of the participant. Surgical technique All patients were operated on by the same senior surgeon assisted by his colleagues. All cryopreserved allografts were obtained from the same certified tissue bank. Before surgery, the grafts were thawed in room temperature normal saline solution containing 240,000 IU of gentamicin.
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Fig. 1 Participant flowchart. Four patients in the HT group and two in the BPTB group were lost to follow-up. Among these patients, two (one in each group) relocated and lost contact with us, and three in the HT group and one in the BPTB group were satisfied with their outcomes and declined to continue to participate in follow-up. Ten patients experienced ACL re-rupture. Six of the re-ruptures, three in each group, were caused by injury during sports. Another re-rupture in the HT group occurred 41 months after reconstruction, and the other three, in the BPTB group, occurred at 15, 19 and 20 months postoperatively
Six-strand HT grafts were prepared using two semitendinosus tendons and one gracilis tendon. To minimize the error caused by individual differences in grafts and to improve accuracy, we used the same combination of tendons for each graft. Limbs of the tendons were whipstitched together with No. 2 nonabsorbable braided sutures, and the three tendons were looped over an EndoButton CL (Smith & Nephew Endoscopy, Andover, MA, USA). The graft was pulled through a series of calibrated cylinders, and the diameter measured 9–10 mm. In the BPTB group, a 10-mm-wide patellar tendon was prepared with bone plugs at each end. The two bone plugs were trimmed into cylinders 25 mm in length and 10 mm in diameter. All the grafts were pre-tensioned using the Graft-master board (Arthrex, Naples, FL, USA). Diagnosis was reconfirmed and meniscal or chondral pathology was addressed as necessary. After debriding the ruptured ACL, the tibial tunnel was drilled via the medial arthroscopic portal using a tibial guide at an angle of 50° to the tibial plateau. It was placed just posterior to the native tibial ACL footprint and about 7 mm anterior to the native tibial posterior cruciate ligament footprint. The femoral tunnel was drilled via the anteromedial arthroscopic portal with the knee in 90° of flexion. It was positioned about 6 mm in front of the over-the-top position,
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at 10 o’clock for the right knee and at 2 o’clock for the left knee. The diameters of the tibial and femoral tunnels were equal to the measured diameter of the HT graft but were all set at 10 mm in the BPTB group. After the graft was pulled through the tunnels and positioned temporarily, femoral fixation was achieved with the knee flexed to 90° using the EndoButton CL in the HT group and an 8-mm × 23-mm bioabsorbable interference screw (Linvatec, Largo, FL, USA) in the BPTB group. On the tibial side, the graft was secured with the knee flexed to 20° using a 10-mm × 28-mm bioabsorbable interference screw reinforced with extracortical fixation in the HT group and a 9-mm × 28-mm bioabsorbable interference screw in the BPTB group. After fixation, the knee was taken through a full range of motion (ROM).
Functional tests included ROM of the knee and single-leg hop test. ROM was measured with a standard goniometer. Single-leg hop test was performed three times on each leg. The distance covered in one hop was measured, and the operated and contralateral legs were compared (grade A, ≥90 % the distance hopped on the contralateral limb; grade B, 75–89 %; grade C, 5.0° in extension or >10.0° in flexion.
Discussion with a re-rupture were excluded from the following assessment and final analysis. No complications, such as wound infection, deep vein thrombosis, vascular or nerve injuries, symptoms of tissue rejection or viral infectious diseases, occurred during the follow-up period. Table 2 details the results of subjective assessment. Both groups demonstrated a great deal of improvement with respect to IKDC scores and Lysholm scores. No significant between-group differences were observed in subjective assessment outcomes 1, 2 and 4 years postoperatively. Details of postoperative stability are shown in Table 3.
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The most important finding of the present study was that the HT group demonstrated greater anteroposterior and rotational stability, as judged by KT-1000 arthrometer and pivot-shift test outcomes. Significant between-group differences were observed in KT-1000 outcomes, which indicated that superior anteroposterior stability could be yielded using the six-stranded HT allograft over time. The pivot-shift test is a standard method for evaluating rotational stability. However, results of the pivot-shift test vary greatly. Positive rates in single-bundle ACL reconstruction using autografts have been reported to be range from 0 to
Knee Surg Sports Traumatol Arthrosc Table 3 Postoperative stability assessment of operated knee 1 Year Postop.
KT-1000 (mm) Lachman test, n (%) 0 1+ 2+ 3+ Pivot-shift test, n (%) 0 1+ 2+ 3+
2 Year Postop.
4 Year Postop.
HT group (n = 62)
BPBT group (n = 53)
p value HT group (n = 62)
BPBT group (n = 53)
p value HT group (n = 61)
BPBT group (n = 52)
p value
1.2 ± 1.5
1.8 ± 1.3
0.025 n.s.
1.1 ± 1.4
1.6 ± 1.2
0.044 n.s.
1.1 ± 1.5
1.7 ± 1.4
0.031 n.s.
59 (95.2) 3 (4.8) 0 (0) 0 (0)
49 (92.5) 2 (3.7) 2 (3.8) 0 (0)
58 (93.5) 4 (6.5) 0 (0) 0 (0)
48 (90.6) 2 (3.8) 3 (5.6) 0 (0)
57 (93.4) 4 (6.6) 0 (0) 0 (0)
46 (88.5) 3 (5.7) 3 (5.8) 0 (0)
0.036 58 (93.5) 4 (6.5) 0 (0) 0 (0)
6.5 Positive rate of pivot-shift test (%)
0.039
0.012
43 (81.1) 6 (11.3) 4 (7.6) 0 (0)
57 (91.9) 5 (8.1) 0 (0) 0 (0)
42 (79.3) 6 (11.3) 5 (9.4) 0 (0)
56 (90.3) 5 (9.7) 0 (0) 0 (0)
39 (75.0) 8 (15.4) 5 (9.6) 0 (0)
18.9
8.1
20.7
9.7
25
Table 4 Postoperative function assessment of operated knee 1 Year Postop.
Extension deficit (°) Flexion deficit (°) Single-leg hop test, n (%) Grade A Grade B Grade C
2 Year Postop.
4 Year Postop.
HT group (n = 62)
BPTB group (n = 53)
p value HT group (n = 62)
BPTB group (n = 53)
p value HT group (n = 61)
BPTB group (n = 52)
p value
1.1 ± 0.7
1.3 ± 0.8
n.s.
1.2 ± 0.6
1.4 ± 0.7
n.s.
1.2 ± 0.5
1.4 ± 0.7
n.s.
1.4 ± 0.7
1.2 ± 0.6
n.s.
1.3 ± 0.7
1.2 ± 0.5
n.s.
1.3 ± 0.6
1.2 ± 0.5
n.s.
n.s.
n.s.
n.s.
59 (95.2) 3 (4.8)
47 (88.7) 6 (11.3)
58 (93.5) 4 (6.5)
48 (90.6) 5 (9.4)
59 (96.7) 2 (3.3)
48 (92.3) 4 (7.7)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
0 (0)
30 % [23]. Zaffagnini et al. [50] reported that the positive rates after reconstruction using BPTB and HT autografts were 12 and 36 %, with significant differences. Mascarenhas et al. [26] found that positive pivot-shift tests occurred less often after HT autograft (17 %) than after BPTB autograft (39 %). Leys et al. [20] reported a rate of 12 % positive in the HT autograft group and 9 % in the BPTB autograft group, a difference that was not statistically significant. Moreover, some studies have reported positive rates to be higher for allografts than for autografts [19, 38], some [25] have been significantly higher in autografts, and some [33, 42] have identified no significant difference. No agreement has reached. As far as we know, no studies have compared the rates of positive pivot-shift tests between
BPTB and six-strand HT allograft, or even four-strand HT allograft. In the present study, there were significantly more positive pivot-shift test results in the BPTB group than in the HT group, suggesting that single-bundle ACL reconstruction using a six-strand allograft may achieve better rotational stability. The rates of re-rupture in the present study were 6.2 % in the HT group and 10.3 % in BPTB group, which were similar to those reported by Goddard et al. [10] and Benjamin et al. [3], respectively. Because of differences in graft choice, fixation method and surgical technique, rates of re-rupture vary (range 0–14 %) [16]. The re-rupture rates reported by Sajovic et al. [39] were 7 % of the HT group and 8 % of the BPTB group at 5-year follow-up. Those
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reported by Wagner et al. [44] were 5.6 % of HT group and 4.2 % of BPTB group. Gerhard et al. [9] reported a rerupture rate of 1.5 % after ACL reconstruction with patellar tendon autograft. Matthew et al. [25] did a meta-analysis and found that graft rupture was significantly higher for allograft patients. It might be attributed to the allogenous nature of the graft material. It is reported that allografts are inferior in initial strength and require more time to undergo ligamentization. Moreover, return to full athletic activities was allowed beginning 6 months postoperatively in the present study, which was a risk factor for graft re-rupture. ACL reconstruction is currently performed using a variety of ligament substitutes. Although the use of BPTB autograft is considered the gold standard, HT autograft has been determined to be comparable [8, 13] and used as the most popular graft choice [28]. Autografts are superior in initial strength [15], time to incorporation [26] and avoidance of disease transmission but may be associated with donor site morbidity, increased operative duration [31] and unavailability of larger grafts. As a result, reconstruction using allograft has grown in popularity. Several reports have indicated that allograft is a viable alternative to autograft, with no significant differences in postoperative symptoms, knee function, activity level or results of physical examination [2, 19]. Factors contributing to the superior outcomes of the six-stranded HT allograft compared with BPTB allograft include initial strength and stiffness, which are particularly important for patients with high demand of activities. Grafts undergo an acute decrease in strength during the process of ligamentization [27]. Moreover, the current aggressive rehabilitation protocol creates a higher demand on the initial strength and stiffness. The mean load to failure and stiffness for four-strand grafts have been reported to be 4,090 ± 295 N and 776 ± 204 N/mm, respectively [12], which exceed those reported for a 10.0-mm-diameter patellar tendon (2,977 N and 455 N/mm, respectively) [7, 12] and for the native ACL (2,160 ± 157 N and 306 N/mm, respectively) [49]. According to Hamner et al. [12], the biomechanical properties are proportional to the number of strands. The six-strand HT graft, with theoretically higher initial strength and stiffness, is better able to withstand the initial weakness without compromise of graft integrity [47]. Furthermore, preservation of mechanical properties with increasing age is seen with HT grafts but not with patellar tendon grafts [47]. Studies have proved statistically significant inverse correlations between the amount of anteroposterior translation and cross-sectional area [11, 18]. The cross-sectional area of six-strand HT graft reached 63.0–78.5 mm2, which exceeded the 41.0 ± 9.8 [30] and 44.4 ± 4.0 mm2 [35] reported for a 10.0-mm-diameter patellar tendon. Moreover, a thicker graft will provide more collagen for the
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ligamentization process to enhance biomechanical stability after reconstruction [5]. The larger size of a six-strand HT graft has been shown in biomechanical studies to provide better knee stability [12, 47]. The flat shape of the patellar tendon makes its width much greater than its thickness and causes graft-tunnel mismatch, in which large, empty lacunae will form within the cylindrical tibial bone tunnel. Synovial fluid leakage into the empty lacunae and graft-tunnel motions (windshieldwiper effect) play influential roles in tunnel enlargement [14]. It results in a broadened fibrous interzone between the bone and graft tissue, leading to a prolonged or impaired healing [46]. In contrast, the cylindrical shape of the sixstrand HT allograft matches that of the bone tunnel. A larger graft-tunnel contact area facilitates the formation of collagen fibres resembling Sharpey fibres at the tendon– tunnel interface and improves osteointegration [43]. Literature has provided a description of the complex anatomical nature of ACL in detail, theorizing that different fibres are recruited to resist loads and maintain stability at different flexion and extension angles [1, 34]. Some studies have indicated that the distribution of load is highly nonuniform among the ligament fibres and that strain gradients could be generated even along the direction of fibres [21, 40]. Moreover, elongation of each ligament fibre has been shown to be inhomogeneous [36]. Livesay et al. [21] stated that the ACL did not function as a uniaxial structure and that the magnitudes of force supported by different portions of ACL differ. That is, the ACL is most likely to be a functional complex with multiple fibres that undergo changes in length and shifts in load distribution. Thus, reconstruction of the ACL with a single-strand structure graft may be inadequate to meet the functional requirements. Wallace et al. [45] measured the tensile stress of each strand of the four-strand HT graft after ACL reconstruction and found them to be unequal during knee motion. Radford et al. [37] stated that a multi-strand graft would provide a closer approximation of normal knee behaviour, with structure moving in a way that is analogous to the fibre bundles of the native ACL. In the present study, tendons were tripled to obtain a larger, multi-stranded graft. During knee motion, the distribution of load between these strands is less consistent [17], but they work in a coordinated manner. As numerous studies have shown, stress can stimulate collagen synthesis and enhance granulation tissue to regain mechanical properties [41, 48]. The unequal stresses on each strand of graft lead to varying performance during the ligamentization process, which may help to reproduce different functional bundles and closely mimic the anisotropic mechanical properties of the native ACL [15, 32]. These will do good to the restoration of knee kinematics and rotational stability.
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The clinical relevance of this study is that six-strand hamstring tendon allograft is a reasonable option for ACL reconstruction as it provided superior anteroposterior and rotational stability, allowing the patients to return to activities in demanding environments. We are not stating that BPTB allograft is inadequate for ACL reconstruction. However, surgeons should know the material properties of each graft substitute and choose the optimal one for ACL reconstruction. This study had several limitations. First, participants in both groups who were lost to follow-up or experienced ACL re-rupture were excluded from the final analysis. Their exclusion may have introduced bias into the outcomes. Second, although same postoperative rehabilitation protocol was prescribed to all patients, the quality and consistency of rehabilitation may have varied without strict supervision. Furthermore, the date of postoperative activity level was not validated. The fact that most patients did not participate in strenuous activities may explain the similarity in subjective assessment. Third, incomplete follow-up radiographic data may limit our ability to draw significant conclusions. Fourth, although no significant differences were observed in preoperative parameters, it was difficult to control for clinical and individual factors. Finally, the sample size was relatively small, which limited statistical power. Studies with larger sample sizes, longer follow-up periods and additional assessment, especially for rotational stability, are necessary in the future. Moreover, more biomechanical works are needed to confirm and clarify the results presented.
Conclusions As a result of this study with a mean follow-up of 52 months, single-bundle ACL reconstruction with a sixstrand HT allograft was technically feasible and achieved anteroposterior and rotational stability superior to that of BPTB graft reconstruction. Conflict of interest None.
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