Abstract
Purpose of Review
The purpose of this review is to provide an up-to-date summary on the most recent literature examining techniques and outcomes in anterior cruciate ligament (ACL) reconstruction using quadriceps tendon (QT) which will enable surgeons to make well informed evidence-based decisions when choosing a particular graft option and technique in ACL reconstruction.
Recent Findings
Several RCTs and systematic reviews have been published recently on this topic, and overall, there were no differences found between the QT, HT, and BPTB groups in patient-reported outcomes, stability testing, or graft re-rupture rates. In terms of strength testing, the QT group did have inferior knee extensor strength on isokinetic testing when compared to the HT group, whereas the HT group had inferior knee flexor strength compared to the QT group. No differences were found on strength testing between the QT and BPTB groups. Currently, two large RCTs, the Stability2 and SQuASH trials, are ongoing examining the effectiveness of the QT vs BPTB with or without LET and QT vs HT in the pediatric population which will help shed further light on the effectiveness of the QT as a graft choice in ACL reconstruction.
Summary
The findings of this scoping review demonstrate that the QT is an excellent graft option in ACL reconstruction both in the primary and revision settings, among adult and pediatric populations. This review provides surgeons with further assurance when selecting QT autograft in ACL reconstruction.
Keywords: ACL, Reconstruction, Quadricep tendon, Graft
Introduction
Anterior cruciate ligament (ACL) rupture is a common orthopedic injury with an incidence of 30–78 per 100 000 person years [1]. ACL reconstruction has proven to be an effective treatment option for this injury, with an estimated return to sport rate of 83% among elite level athletes [2]. Several graft options may be used in ACL reconstruction including hamstring tendon (HT), bone-patellar-tendon-bone (BPTB), and quadriceps tendon (QT), among others. Furthermore, the QT can be harvested both with and without a proximal patellar bone block.
QT for ACL reconstruction was first described in the 1970s but failed to gain popularity due to the high incidence of postoperative knee laxity and extensor mechanism weakness, as well as a rate of positive pivot shift of up to 20% [3, 4]. However, this should not come as a surprise as early techniques involved a large exposure and harvesting an extensive (13 cm) portion of the extensor mechanism that included QT, prepatellar retinaculum, and patellar tendon [5]. As such, the most common graft choices in ACL reconstruction have traditionally been the BPTB and HT autografts. Today, newer techniques with decreased soft tissue dissection yield a more robust and stable graft with comparable outcomes to BPTB and HT autografts. Consequently, the QT is emerging as an effective graft option, and a study by the ACL study group highlights the increase in popularity of the QT since 2014 [6]. In light of the minimally invasive harvesting techniques and superior biomechanical characteristics, a study by the International Quadriceps Tendon Interest Group urged surgeons to increase their use of QT autograft in ACL reconstruction [7].
Therefore, the purpose of this scoping review is to provide an up-to-date summary on the most recent literature examining techniques and outcomes in ACL reconstruction using QT. This research will enable surgeons to make well informed evidence-based decisions when choosing a particular graft option and technique in ACL reconstruction.
Materials and Methods
Identification of Studies
Two reviewers searched the online electronic databases (PubMed, Medline, and Embase) for studies regarding ACL reconstruction with QT. The search encompassed studies published between January 1, 2010, and May 5, 2021. Once it was deemed that greater than 100 articles were published, the search was narrowed to only include articles published within the last 5 years. The search terms used included anterior cruciate ligament (ACL) reconstruction and quadriceps tendon (QT). Studies were eligible if they met the following inclusion criteria: (1) human study, (2) English language study, (3) ACL reconstruction using quadriceps autograft, and (4) discussion on clinical outcomes or reconstruction technique. The exclusion criteria included cadaveric studies, book chapters, and conference papers. Furthermore, when two studies had overlapping patient groups, the most recent study was selected for inclusion.
Two reviewers (D.C, D.S) initially completed the title and abstract review screening for eligible studies independently and in duplicate. Following this, a full text review was conducted, and the references for each article were hand-searched for other eligible studies. Agreement between the reviewers was substantial at the title (κ = 0.73; 95% CI: 0.68–0.82), abstract (κ = 0.77; 95% CI 0.73–0.88), and full text (κ = 1.00; 95% CI 1.00–1.00) stages. Disagreements were resolved through consensus discussions with the senior author. The search strategy is outlined in Fig. 1.
Figure 1.
PRISMA flow diagram demonstrating the search strategy for techniques and outcomes in QT ACL reconstruction
Results/Discussion
Biomechanics
Mechanical testing of the QT is known to be challenging due to the variability of the location of insertion of various parts of the tendon into the proximal pole of the patella, making it difficult to section on the basis of proximal-distal or medial-lateral referencing [8]. Nonetheless, the QT graft has biomechanical properties that make it an attractive option for ACLR.
Ultimate failure loads have been reported in the literature as 1725–2160 N for the native ACL, 2977 N for patellar tendon grafts, 2119-2352 N for quadriceps tendon grafts, and even 4090 N for hamstring tendon autografts [9, 10]. The QT graft is also known to be nearly double the stiffness (466.2 N/mm) than a native ACL (242 N/mm). In fact, it has been shown that the mechanical and microstructural properties differ significantly among BPTB, HT, and QT grafts, with the latter exhibiting the largest stiffness modulus and greatest strength of collagen alignment, while single hamstring tendon had the smallest moduli and least strongly aligned collagen [8]. This is likely attributable to the fact that QT is a composite tissue that forms from the confluence of four musculotendinous units which have shown to have significant variability in fiber orientation, thereby contributing to its strength in variously oriented force vectors.
One study evaluated the femoral fixation of QT versus HT grafts with four different bioabsorbable interference screws (Wolf (W), Storz (S), Mitek (M), Arthrex (A)) in a cadaveric study [10]. All grafts were pretensioned 60 N for 30 s and then underwent cyclic loading of 500 cycles between 60 and 250 N at 1 Hz. The mean ultimate failure load of all four screw subgroups using QT grafts was 481.7 ± 82.2 N which was not significantly different than that of the HT graft of 551.6 ± 103.1 N.
With regard to tibial fixation using QT, another author compared the use of an adjustable length loop cortical button versus interference screw fixation with cadaveric QT grafts [11]. They concluded that tibial fixation using an adjustable length loop cortical button provides for comparable dynamic stabilization of the knee but with significantly increased ultimate failure load (743.3 N vs 606.3 N; P = 0.0027) and decreased stiffness (133.2 N/mm vs 153.5 N/mm; P = 0.0045) compared to screw fixation. Therefore, both methods can tolerate maximal daily loading of 454N.
Additionally, a review by one author demonstrated that both suspensory and aperture fixation are equally efficacious when used on both the femoral and tibial sides in QT ACL reconstruction [12].
Different stitching methods for graft preparation (Krackow locking stitch, whipstitch, and baseball stitch) were also investigated [13]. Their results suggest that a double Krackow stitch with no. 2 braided composite suture exhibits a significantly higher mean maximum load to failure (553 ± 82 N) combined with a lower mean amount of elongation (10.59 ± 2.63 mm) after 500 cycles. Unlike the whipstitch and the baseball stitch, it can reliably prevent suture pullout.
The results above were performed on single-bundle QT grafts; however, it is also possible to split the QT grafts for anatomic double-bundle ACL reconstruction. In fact, one study showed that splitting the QT in either the sagittal or coronal plane leads to comparable results so long as care was taken to preserve fibers as much as possible [14].
Lastly, graft positioning and tensioning also requires special attention when using the QT graft. Using finite element modeling, one study determined that the ideal positioning of the QT graft to restore native knee kinematics is in an isometric position with a fixation tension of 85 N [15]. This in contrast to the patellar tendon and hamstring tendon grafts for which anatomical positioning and a fixation force of 40 N was shown to yield ideal kinematics.
Therefore, the quadriceps tendon autograft displays robust biomechanical properties and microscopic features that allow it to be a safe and reliable autograft option in primary and revision ACL reconstruction surgery.
Clinical Outcomes
The parameters used to measure clinical outcomes in ACL reconstruction include stability tests (Lachman, pivot shift, instrumented laxity testing), functional outcomes and objective strength testing, patient-reported outcomes (PROs, IKDC, Lysholm, Tegner Activity Score), donor site morbidity, and graft re-rupture rates (see Table 1 for a summary of clinical outcomes by individual studies).
Table 1.
Clinical outcomes
| Author (year) | Study design (level of evidence) | Adult vs peds | Primary or revision | Graft type | Number of patients | Summary |
|---|---|---|---|---|---|---|
| Runer (2020) | Cohort (level 3) | Adult | Primary | QT | 217 | (1) Odds of revision surgery were 2.7 times greater in patients receiving HT vs QT. (2) Significantly higher ipsilateral re-rupture vs contralateral graft rupture rate in HT but not QT, even more pronounced in highly active patients. (3) 2 year Lysholm, Tegner, and VAS did not differ between grafts |
| HT | 658 | |||||
| Tirupathi (2018) | Cohort (level 2) | Adult | Primary | QT | 44 | No statistical difference found between HT and QT groups at 2 year follow-up in functional outcomes (IKDC scores) |
| HT | 42 | |||||
| Lind (2019) | Retrospective comparative (level 3) | Adult | Primary | QT | 400 | (1) QT autograft associated with increased laxity compared to HT (P<0.001), more positive pivot shift compared to HT and PT (P<0.05), and higher revision rate compared to PT (P<0.001) and HT (P=0.002). (2) No difference in QT with bone block vs without. (3) Subgroup analysis for young patients, patients with contact sports activity and reduced learning curve cohort showed similar tendency to overall cohort |
| HT | 13436 | |||||
| BPTB | 1761 | |||||
| Galan (2020) | Retrospective (level 4) | Adult | Primary | QT | 291 | (1) Lysholm score improved from 64 (SD 6.09) to 91 (SD 6.05) postoperatively, (2) 60% patients had excellent IKDC, (3) 89% knees has less than 3mm difference on arthrometric analysis, (4) 5% of patients had anterior knee pain |
| Lind + Sinding (2019)* | Randomized controlled trial (level 1) | Adult | Primary | QT | 50 | (1) At 2 years, no difference between 2 groups regarding subjective outcomes, knee stability and reoperations. (2) QT group had significantly lower donor site morbidity while hop test demonstrated lower limp symmetry in QT vs HT (91% vs 97%). (3) Knee extensor strength lower in QT vs HT while knee flexor strength lower in HT vs QT. Compared to controls, knee flexor, and extensor was lower in HT, while only knee extensor was lower in QT |
| HT | 49 | |||||
| Horstmann (2021) | Randomized controlled trial (level 1) | Adult | Primary | QT | 24 | No difference between groups for knee stability, muscle strength, outcome scores (IKDC, Lysholm), or revision rates |
| HT | 27 | |||||
| Barié (2020) | Prospective randomized (level 2) | Adult | Primary | QT-B | 30 | (1) 90% of patients scored very good and good results in the Lysholm score, (2) normal or near normal IKDC score reported in 84% of patients, (3) KT-1000 showed a difference of less than 3mm in 91% of patients, (4) no significant differences in above parameters between groups, (5) significantly more patients in BPTB group complained about kneeling at 1 (P<0.001) and 10 year (P=0.019) and squatting at 1 (P=0.003) and 10 years (P=0.046) |
| BPTB | 30 | |||||
| Lubis (2020) [50] | Prospective cohort (level 2) | Adult | Primary | QT | 15 | (1) Quadricep group showed significant difference in mean difference rolliometer testing (3.12 ± 0.94 vs 3.87 ± 0.61, p=0.015) and side-to-side difference (0.34 ± 0.70 vs 0.84 ± 0.60, P=0.04). (2) Significant difference favoring quadricep in 3- and 6-month IKDC (P=0.002, P=0.004), 3-month Lysholm (P=0.004), and 1-year KOOS pain (P=0.034) and symptoms (P=0.001) |
| HT | 15 | |||||
| Vilchez-Cavazos (2020) | Randomized controlled trial (level 1) | Adult | Primary | QT | 14 | No significant differences found between HT and QT groups for VAS pain, Lysholm score, and IKDC score at any time point |
| HT | 14 | |||||
| Todor (2019) | Retrospective comparative (level 3) | Adult | Primary | QT | 39 | (1) No significant difference between groups for KT-1000 measurements, mean postoperative Lysholm score, modified Cincinnati score, and the general SF-36 score. (2) Less side-to-side thigh diameter difference noted in the quadriceps group (P=0.026) |
| HT | 39 | |||||
| Kwak (2018) | Retrospective comparative (level 3) | Adult | Primary | QTB autograft | 45 | (1) No significant difference between groups in clinical outcomes (IKDC, Tegner, Lysholm, KOOS scores), complication rates including re-rupture rates, or in laxity testing (KT-2000, Lachman). (2) No significant difference found in peak extensior torque except at 60 degrees per second at 6 months favoring the allograft group (P=0.042) |
| QTB allograft | 45 | |||||
| Lee (2016) | Cohort (level 3) | Adult | Primary | QTB | 48 | (1) No differences between groups for manual laxity testing (KT-2000, Lachman, pivot shift). (2) No difference between groups in functional outcomes (Tegner, Lysholm, IKDC). (3) No difference between groups in postoperative anterior knee pain. (4) No difference between groups in extensor muscle strength. (5) Flexor muscle strength was better in the quadriceps group at 180deg/s (P=0.01) |
| HT | 48 | |||||
| Hunnicutt (2019) | Cohort (level 3) | Adult | Primary | QT | 15 | (1) Limb symmetry indices were not significantly different between QT versus BPTB groups (isokinetic strength at 60deg/s and 180deg/s, activation, cross sectional area of vastus medialis, single leg hop test and step length symmetry). (2) Functional outcomes between groups were not significantly different (IKDC, Lysholm, Tegner) |
| BPTB | 15 | |||||
| Cavaignac (2017) | Cohort (level 3) | Adult | Primary | QTB | 45 | (1) The Lysholm, KOOS symptoms and KOOS sport were significantly better in the QT group (P<0.05). (2) Mean side-to-side difference on KT-1000 measurement significantly less stable in the HT vs QT group (P<0.005) and negative Lachman significantly higher in QT vs HT group (P<0.005). (3) No difference between groups in isokinetic strength. (4) No difference between groups in re-rupture or reoperations |
| HT | 41 | |||||
| Letter (2019) [23] | Cohort (level 3) | Adult | Primary | QT | 17 | (1) Significantly lower values were seen between the operative vs non operative extremity for average (P=0.008) and peak torque (P<0.0001) isometric testing with no significant difference between graft types. (2) On EMG testing, no difference was found between limbs or graft types for the rectus femoris/vastus medialis and rectus femoris/vastus lateralis firing ratio |
| BPTB | 17 | |||||
| Martin-Alguacil (2018) | Randomized controlled trial (level 1) | Adult | Primary | QT | 26 | (1) The results of H/Q ratio analysis revealed significant differences at 60, 180 and 300deg/s at 12-month follow-up (P=0.005, 0.004, 0.005 respectively) favoring the QT group. (2) Also there were significant differences at 60 deg/s, 180deg/s, and 300deg/s in peak torque extensor muscle strength favoring the HT group at 3- and 6- but not 12-month follow-up. (3) No significant differences in functional outcomes (Lysholm, Cincinnati score). (4) No differences in KT-2000 arthrometer testing |
| HT | 25 | |||||
| Perez (2019) | Retrospective comparative (level 3) | Adult | Primary | QT | 28 | (1) No difference between groups in functional outcomes (IKDC, Lysholm, Tegner). (2) No difference between groups in re-rupture or other morbidity (arthrofibrosis, kneeling difficulty) |
| BPTB | 22 | |||||
| Mouarbes (2020) | Cohort (level 3) | Adult | Primary | QT | 30 | (1) Concerning QT vs BPTB, QT patients had a more cosmetic scar with a significantly lower POSAS score (P<0.0001), short mean incision (P<0.0001), lower extent of hypoesthesia (P<0.0001), and better Lysholm score (P=0.0156), with no difference in KOOS score. (2) Concerning QT vs HT, no significant difference was found in POSAS, mean length of incision, Lysholm, or KOOS score, but the area of hypoesthesia was significantly higher in HT group (P<0.0001) |
| BPTB | 30 | |||||
| HT | 30 | |||||
| Akoto (2019) | Retrospective comparative (level 3) | Adult | Primary | QT | 41 | No significant difference in Tegner score, subjective or objective IKDC, knee stability (Lachman, pivot shift, side-to-side difference), functional testing (one-leg hop test, thigh circumference), or donor site morbidity observed between the two groups |
| HT | 41 | |||||
| Johnston (2020) [51] | Cohort (level 3) | Adult | Primary | QT | 37 | (1) No difference between groups for PROMs (IKDC, KOOS), (2) HT groups had reduced active and standing knee flexion range compared to QT (P<0.001), (3) significant deficits in the HT group in isokinetic strength testing for peak hamstring torque at 60deg/s (P<0.001) and 180 deg/s (P=0.01), with significantly greater deficits in QT group for quadriceps peak torque at 60deg/s (P<0.001) and 180deg/s (P=0.001) |
| HT | 74 | |||||
| Xerogeanes (2017, abstract) [52] | Prospective cohort (level 2) | Adult | Primary | QT | 353 | ACL reconstruction with all soft tissue QT and aggressive rehab resulted in acceptable short and intermediate functional outcomes (IKDC), and low complication and failure rates (hematoma, arthrofibrosis, graft failure) |
| Karpinski (2020, abstract) | Prospective comparative (level 2) | Adult | Primary | QT | 25 | No significant difference between groups in KT-1000 stability testing, functional outcomes testing (KOOS, Lysholm), and no re-ruptures in either group |
| HT | 25 | |||||
| Gregory (2020, abstract) | Retrospective comparative (level 3) | Adult | Primary | QT, HT, BTB, ITB | 68 total | Overall, 35% of patients “passed” the physical performance tests at 6 months post surgery. QT was a strong predictor of passing the PPTs (P=0.003 compared to BTB) and a strong predictor of the number of PPTs passed (P=0.02 compared to BTB) |
| Pennock (2019) | Cohort (level 3) | Peds | Primary | QT | 27 | No difference between groups in functional or PROs (Lysholm, SANE, pain, satisfaction, and Tegner scores). No physeal complications in either group. Significantly higher graft failure in HT vs QT (P=0.037). Significantly larger graft size QT vs HT (9.6 ±0.6mm vs 7.8 ± 0.7mm, P<0.001) |
| HT | 56 | |||||
| Gagliardi (2019) | Case series (level 4) | Peds | Primary | QT-B | 81 | Cumulative incidence of graft failure was 1.2%. Median Pedi-IKDC score was 94 (IQR 89–98), median Lysholm 99.5 (IQR 89–100). 87.9% returned to play at 36 months after surgery |
| Sherman (2020, abstract) | Retrospective comparative (level 3) | Peds | Primary | QT | 30 | Both groups QT and HT had significant improvement in PROs with no difference between groups (KOOS, IKDC, Tegner). No difference between groups in revisions or re operations |
| BPTB | 41 | |||||
| Barie (2019) | Retrospective comparative (level 3) | Adult | Revision | QT-B | 41 | Overall no difference in functional outcomes between groups (IKDC, Lysholm, satisfaction). HT group performed pivoting sports significantly more often (P=0.03), but had significantly worse pivot shift results compared to the QT group (P=0.003) |
| HT | 37 | |||||
| Hunnicutt (2021) | Case series (level IV) | Adult | Revision | QT | 100 | Mean IKDC scores significantly improved postoperatively (P<0.001), quadriceps LSIs significantly improved for 60 degrees and 180 degree isokinetic testing (P<0.001), and hamstring LSI at 60 degrees (P=0.007) |
| Haner (2016) | Prospective comparative (level 2) | Adult | Revision | QT | 25 | No significant difference between groups in KT1000 arthrometer testing or rate of positive pivot shift tests. No difference between groups in Lysholm score or KOOS pain with kneeling sub score. No re-ruptures in either group at 2-year follow-up |
| HT | 26 |
*These are two separate articles examining the same group of patients from the same RCT
QT vs HT
Four RCTs have been published in the last 5 years all examining clinical outcomes in QT vs HT with no difference being found between groups in functional outcomes, PROs, laxity testing, or revision rates. However, three of these studies were poorly powered with 51 patients or fewer in both groups combined. Moreover, two studies found significantly higher knee flexor strength favoring the QT group and higher knee extensor strength favoring the HT group [16, 17]. It should be noted that this finding was not observed at 12 months in one of the studies [16]. Furthermore, one study found a significantly higher rate of donor site morbidity in the HT group [18••]. These findings demonstrate the importance of a tailored physiotherapy protocol to the specific graft type used based on the corresponding strength deficits seen in the QT vs HT groups. This also demonstrates the need to shift away from “time since surgery” return to sport protocols given the persistent strength deficits that may be seen 12 months postoperatively. Engaging in sporting activity with such deficits present is linked to repeat ACL injuries among other complications [19].
QT vs BPTB
In a prospective randomized study, no differences in functional outcomes, PROs, or stability outcomes between QT-B vs BPTB groups were found, although significantly more patients in the BPTB complained of pain with kneeling and squatting [20]. Moreover, three retrospective comparative studies found no differences between groups in various functional and PROs, while another study also found no difference in re-rupture rates [21–23]. This contradicts an older study that found that the BPTB group was more likely to have a normal IKDC score and patients were overall more satisfied with their knee postoperatively [24]. The findings seen in the more recent literature are highly encouraging, and the improved outcomes compared to prior studies may be explained by increased surgeon experience using the QT graft as it becomes more routinely utilized autograft in many surgeons’ practice. Currently, the Stability2 trial is an ongoing RCT examining patients with BPTB versus QT with or without LET in primary ACL reconstruction and aims to compare clinical failure rates and functional and objective outcomes across participants.
QT vs HT vs BPTB
In a large retrospective study of the Danish Knee Ligament Registry, it was found that QT was associated with increased knee laxity compared to HT, increased pivot shift compared to both HT and BPTB, and higher revision rates compared to HT and BPTB [25•]. However, a subsequent study examining this registry found that untoward outcomes were not observed for QT autograft when reconstructions were performed at higher volume centers compared to lower volume centers [26•]. These results contrast a retrospective study which found that the QT group had a superior Lysholm score, more cosmetic scar, and lower extent of hypoesthesia compared to the BPTB group and also found a lower extent of hypoesthesia with no difference in PROs compared to the HT group [27]. These findings further highlight the equivalent outcomes seen in more recent studies between QT vs other graft types and supports the notion that as surgeons gain more experience with using the graft, outcomes improve accordingly
Systematic Reviews
In a large systematic review and meta-analysis examining 1095 patients with QT vs BPTB and 357 patients with QT vs HT ACL reconstruction, no significant differences between groups were found in postoperative mean side-to-side difference, Lachman test, pivot shift, IKDC score, or graft failure [28••]. The QT group was found to have significantly less donor site pain than the BPTB group (P<0.0001) and a greater mean Lysholm score than the HT group (P=0.03). In terms of knee strength testing, one review examining 1340 patients found significant results favoring the HT vs QT group in knee extensor strength, with no difference found between the QT vs BPTB groups, and increased knee flexor strength when comparing the QT vs HT groups [29] (see Table 2 for a summary of systematic reviews).
Table 2.
Summary of systematic reviews
| Author | Level of evidence | Graft type/details | Number of patients | Results |
|---|---|---|---|---|
| Mouarbes (2019) | Level 2 evidence | QT vs BPTB | 581 vs 514 | No significant differences in mean side-to-side difference, Lachman test, pivot shift grade 0 or 1, Lysholm score, IKDC score or graft failure between groups. QT group was found to have less donor site pain (P<0.0001) |
| QT vs HT | 181 vs 176 | No significant differences in mean side-to-side difference, Lachman test, pivot shift grade 0, IKDC score, donor site pain or graft failure between groups. Significantly better mean Lysholm score in QT group (P=0.03) | ||
| Riaz (2017) [52] | Level 3 evidence | QTB vs BPTB | 354 vs 452 | No significant difference between groups in AP arthrometer testing and percentage of patients with positive pivot shift. Significantly less patients with graft site pain in the QTB group (P=0.002) and pain with kneeling in the QTB group (P<0.001) |
| Mo (2020) [53] | Level 1 evidence | QT vs BPTB vs HT vs others | Total: 3992 | SUCRA analysis showed that QT had the highest probability of being the best intervention concerning pivot shift testing |
| Kanakamedala (2018) [54] | Level 4 | Full vs partial thickness QT | Total: 1212 | Similar results between groups for instrumented laxity testing, postoperative IKDC score, postoperative quadriceps strength, and graft failure rates |
| Migliorini (2020) [55] | Level 3 | QT vs BPTB vs HT | Total: 2603 | On network meta-analysis, similar values for IKDC, Tegner, and Lysholm scores were seen between graft types. QT had a comparable rate of Lachman >3mm, pivot shift >3mm, and instrumental laxity >3mm. QT showed a lower rate of graft failure compared to HT and BPTB and reduced anterior knee pain compared to BPTB |
| Agarwal (2018) [56] | Level 4 | QT, BPTB, HT | Total: 762 | Comparing the correlation of preoperative MRI measurements to intraoperative harvested measures, strength was very highly positive for QT, high positive for patellar tendon, negligible, highly positive for semitendinosus only tendon, and negligible, moderately positive for gracilis only tendon |
| Ajrawat (2019) [57] | Level 4 | QT vs BPTB vs HT | Total: 1398 | No significant difference between groups in revision rates, knee stability and patient-reported functional outcomes. Significantly more anterior knee pain in BPTB vs QT (P<0.001) |
| Hurley (2018) [58] | Level 3 | QT vs BPTB vs HT | Total: 1910 | No difference between groups in graft re-rupture rates. Lower rates of anterior knee pain in QT vs BPTB |
| Crum (2019) [59] | Level 4 | Aperture vs suspensory fixation | Total: 1155 | Suspensory fixation on both sides demonstrated a higher percentage of patients achieving the highest IKDC compared to aperture fixation and also had a lower side-to-side difference in anterior laxity. Overall, both fixation methods equally efficacious |
| Belk (2018) [60] | Level 3 | QT vs BPTB vs HT | 368 vs 225 vs 150 | No significant difference between groups in graft failure rates. Significantly greater knee laxity seen in HT vs QT patients in 2 studies |
| Johnston (2019) | Level 4 | QT vs BPTB vs HT | 952 vs 143 vs 245 | Knee extensor strength LSI following QT ACL reconstruction did not reach 90% even at 24 months post op, whereas knee flexor strength LSI exceeded 90% at 9–15 months post op. Knee extensor strength at 5–8 months following QT reconstruction appears similar to BPTB and weaker than HT, whereas flexor LSI appears significantly greater than HT |
Revision
In a retrospective comparative study examining 78 patients, there was no difference between the QT-B and HT groups in IKDC, Lysholm, or satisfaction scores. However, this study found that the HT group participated in pivoting sports significantly more often but had significantly inferior results on pivot shift testing [30]. In contrast, in a prospective comparative study, no difference was found by the QT and HT groups in stability testing, Lysholm score, or re-rupture rates [31]. In a large case series examining 100 patients undergoing revision surgery with QT autograft, there was a significant improvement in postoperative IKDC scores and quadricep and hamstring isokinetic strength testing with a re-rupture rate of 13.8% [32]. The higher re-rupture rate in this study can possibly be attributed to a younger patient cohort (mean age 22.6 years), as younger patients may be more likely to sustain recurrent ACL rupture [33]. Overall, these studies demonstrate that the QT is an effective alternative graft type in revision ACL reconstruction.
Pediatrics
One study compared QT vs HT reconstruction and found no difference between groups in PROs but did find a significantly higher rate of graft failure in the HT group (4 vs 21%, respectively) [34]. Another study compared QT vs BPTB reconstruction and found no difference between groups in PROs or revision rates [35]. In a case series looking at 81 patients, the cumulative incidence of graft failure for QT was 1.2% and 87.9% of patients returned to sport at 36 months after surgery [36•]. These results demonstrate that the QT is an effective graft type in ACL reconstruction in the pediatric population and may be superior to alternative graft types such as the HT. Currently, the SQuASH trial is an ongoing RCT examining soft tissue quadriceps autograft ACL reconstruction vs hamstrings tendon ACL reconstruction in the skeletally immature patient.
Techniques
For the purposes of homogeneity, the following summary only includes studies describing primary single-bundle QT ACL reconstruction in adult patients [22, 37–47] [16, 18•, 20, 21, 48] (see Tables 3 and 4).
Table 3.
Reporting of surgical techniques
| Reported (%) | Not Reported (%) | ||
|---|---|---|---|
| Use of accessory medial portal | Yes: 35.3% | No: 23.5% | 41.2% |
| Scope prior to graft harvest | Yes: 35.3% | No: 41.2% | 23.5% |
| ACL remnant removed | Yes: 11.8% | No: 35.3% | 52.9% |
| Incision length + orientation | 88.2% | 11.8% | |
| All soft tissue | Yes: 41.2% | No: 58.8% | 0% |
| Harvesting instrument | 58.8% | 41.2% | |
| Graft length | 94% | 6% | |
| Graft width | 88.2% | 11.8% | |
| Graft thickness | 70.6% | 29.4% | |
| Graft harvest closure | Yes: 35.3% | No: 23.5% | 41.2% |
| Patellar bone harvest technique | 80% | 20% | |
| Patellar defect grafting | Yes: 30% | No: 20% | 50% |
| Length of graft in femoral tunnel | 52.9% | 47.1% | |
| Femoral tunnel size | 64.7% | 35.3% | |
| Tibial tunnel size | 52.9% | 47.1% | |
| Visualization of lateral intercondylar or bifurcate ridge | 23.5% | 76.5% | |
| Performing notchplasty | 23.5% | 76.5% | |
| Flexion angle during femoral drilling | 41.2% | 58.8% | |
| Placement of tibial tunnel in ACL footprint | 82.4% | 17.6% | |
| Placement of femoral tunnel in ACL footprint | 70.6% | 29.4% | |
| Placement of tibial tunnel at a fixed distance from another anatomic structure | 17.6% | 82.4% | |
| Tibial tunnel drilling technique | 94.1% | 5.9% | |
| Femoral tunnel drilling technique | 88.2% | 11.8% | |
| Knee angle during tibial graft fixation | 76.5% | 23.5% | |
Table 4.
Graft fixation devices
| Fixation method | Femoral side | Tibial side |
|---|---|---|
| Adjustable suspensory fixation | 38.9% | 16.7% |
| Biointerference screw | 22.2% | 61.1% |
| Metal interference screw | 16.6% | 5.6% |
| Press fit technique | 11.1% | 11.1% |
| NR | 5.6% | 5.6% |
Use of Accessory Medial Portal
Of those that reported, 60% of studies reported use of the accessory medial portal, while 40% reported use of a standard 2-portal approach.
Arthroscopic Details
Of those that reported, 46% of studies reported performing arthroscopy prior to graft harvesting. Furthermore, 25% of studies reported removing the native ACL remnant during diagnostic arthroscopy, while 75% of studies did not. Moreover, 24% of studies reported performing a bony notchplasty in all included patients.
Graft Harvest Details
Eighty percent of studies reported performing a longitudinal skin incision that ranged from 2 to 10cm in length between studies, while the other 20% of studies reported performing a 2–4cm transverse skin incision. Furthermore, 41% of studies harvested an all-soft tissue graft, while the remaining 59% harvested a QT-B graft. The instruments used in graft harvesting varied from different sized blades including 10, 15, and 21 blades to specialized graft harvesters. The all-soft tissue graft length ranged from 6 to 10cm, while the QT-B ranged from 5.5 to 9cm for the soft tissue component and 1.5 to 2cm for the bone block. The graft width ranged from 8 to 12mm, while the graft thickness varied with 25% of studies harvesting a full thickness graft and the remaining 75% harvesting a partial thickness graft ranging from 5 to 8mm in thickness. The most common patellar bone harvest technique was performing longitudinal bone cuts angled 20–40 degrees towards the midline yielding a trapezoidal bone block. Sixty percent of studies performed routine grafting of the patellar bone defect, and 60% of studies performed routine closure of the graft harvest site with the remaining 40% only performing closure if the supra patellar pouch was violated.
Femoral Tunnel Preparation
Most commonly, the femoral tunnel was drilled using an inside out technique using a 6–8mm offset guide aimed towards the native ACL footprint with the knee flexed between 90 and 120 degrees. Twenty-four percent of studies specifically reported visualizing the lateral intercondylar or bifurcate ridges prior to drilling. The tunnel was drilled to a diameter equal to the graft diameter, and the graft length in the femoral tunnel varied from 10 to 25mm in length.
Tibial Tunnel Preparation
The tibial tunnel was most commonly drilled using an outside in technique with the tibial guide set at 45–55 degrees and aimed towards the native ACL footprint. Specifically, the tibial tunnel was placed medial to the anterior horn of the lateral meniscus and lateral to the medial tibial spine with a tunnel diameter equal to the graft diameter. Moreover, the knee angle during tibial graft fixation ranged from 0 to 30 degrees of flexion.
Femoral and Tibial Graft Fixation Methods
The most common device used for femoral sided graft fixation was an adjustable suspensory fixation device in 39% of studies, while the most common device used for tibial sided graft fixation was a biointerference screw in 61% of studies.
Pediatrics
The pediatric population offers a unique challenge in ACL reconstruction given the high risk of physeal injury. Therefore, several techniques have been proposed to attempt to reduce this risk. One author proposed an algorithm using the transphyseal technique for males with open growth plates and a bone age between 13 and 15 years and females with a bone age of 11–13 years [34]. Meanwhile, another author proposed a technique using the transphyseal technique within 6 months of skeletal maturity, using a hybrid femoral epiphyseal and tibial transphyseal technique within 6 months to 3 years of skeletal maturity, and an all-epiphyseal technique if greater than 3 years from skeletal maturity [36•]. For the transphyseal technique, the authors propose drilling the tibial tunnel more vertical at 55–60 degrees and drilling the femoral tunnel at 110–115 degrees in the coronal plane. For the all-epiphyseal technique, one author drills the tibial tunnel at 35 degrees ensuring that the socket depth does not exceed the height of the epiphysis and drills the femoral tunnel at 85 degrees in the coronal plane [36•]. Another author proposed a transtibial transphyseal technique which allows reproduction of the anatomic ACL footprint while still maintaining a more vertical tunnel orientation and therefore decreasing the risk of physeal injury [49]. One author used interference screw fixation in the tibia only if the distance from the cortex to the physis was greater than 23mm [34]. Otherwise, all authors used suspensory fixation or a screw and post for both tibial and femoral fixation to ensure no hardware crosses the physis.
Senior Author’s Preferred Technique
The patient is positioned supine on the operating table with the operative leg held with a Wolff clamp holder and the foot of the bed dropped. The graft harvest is performed first using a double blade knife set to an 8mm width. A full thickness 7–9cm length all soft tissue QT graft is harvested, and the harvest site is subsequently closed using a running number 1 Vicryl suture ensuring any capsular rents or defects are closed as well. Care is taken not to over-tension the quadriceps tendon upon closure. The graft is then brought to the back table and prepared and sized with an adjustable loop fixation device on the femoral side. Diagnostic arthroscopy is then performed, addressing any concurrent meniscal or cartilage pathology. Subsequently the ACL remnant is removed, and the notch is prepared. A 2–3cm skin incision is then made over the anteromedial tibia approximately 4–5cm from the joint line and 2–3cm medial to the tibial tubercle. Care is taken to stay above the insertion of the pes anserine tendons with subsequent drilling of the tibial tunnel. Using a guide, the tibial tunnel is then drilled from outside in at a 45-degree angle aimed towards the native ACL footprint equal to the graft diameter and then dilated 0.5cm larger to aid with graft passage. The femoral tunnel is then drilled from inside out using a long beath pin and an 8mm offset guide with the knee hyper flexed to approximately 110 degrees aiming towards the native ACL footprint and having the beath pin exit 1cm anterior to the posterior border of the IT band and 2–3cm proximal to the lateral femoral condyle. Using a reamer, the tunnel is drilled equal to the graft diameter and a 23mm socket depth, with the remaining tunnel drilled 5mm in diameter for the adjustable loop device passage. Subsequently, a 2-0 Vicryl suture is looped and placed in the proximal portion of the beath pin which is then pulled out the femoral tunnel and the looped end retrieved through the tibial tunnel serving as a shuttling suture for the graft. Under direct arthroscopic visualization, the adjustable loop device attached to the femoral end of the graft is passed through the tibial and then femoral tunnel until the button flips on the lateral femoral cortex. The tibial side is fixed using a biointerference screw that is 0.5–1mm larger than the tunnel diameter with the knee in full extension and a posterior directed force placed over the proximal tibia.
Conclusion
The findings of this scoping review demonstrate that the QT is an excellent graft option in ACL reconstruction both in the primary and revision settings and both in the adult and pediatric populations and should provide surgeons with further assurance when selecting this graft option in ACL reconstruction. Currently, two large RCTs, the Stability2 and SQuASH trials, are ongoing examining the effectiveness of the QT vs BPTB with or without LET and QT vs HT in the pediatric population which will help shed further light on the effectiveness of the QT as a graft choice in ACL reconstruction.
Declarations
Conflict of Interest
Dan Cohen, David Slawaska – Eng, Mahmoud Almasri, Andrew Sheean, and Darren de SA declare that they have no conflicts of interest.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
Footnotes
This article is part of the Topical Collection on Outcomes Research in Orthopedics
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Contributor Information
Dan Cohen, Email: dan.cohen@medportal.ca.
David Slawaska-Eng, Email: david.slawaskaeng@medportal.ca.
Mahmoud Almasri, Email: malmasri@gmail.com.
Andrew Sheean, Email: ajsheean@gmail.com.
Darren de SA, Email: Darren.desa@medportal.ca.
References
Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance
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