The main findings of this study is that the use of FQT for ACL reconstruction showed a good functional outcome, as well as successful stability assessments, similar to those reported with other grafts such as BPTB [12, 21, 28, 40]. However, patients had less anterior knee pain. The outcome is also comparable to the results reported with the use of hamstrings for ACL reconstruction [6, 22], but with less flexor force deficit.
There are multiple reports on how to perform an ACL reconstruction with Quad Tendon: a) with bone block [2, 6, 7, 12, 13, 15, 19,20,21,22, 24,25,26, 28, 36, 41, 42] or b) without bone block [10, 23, 36]. Regarding fixation in cases with bone block, some authors prefer fixing the bone block to the femur [7, 26], while others, to the tibia [6, 41]. Most importantly, some authors prefer partial thickness [15, 21, 26] others full thickness [6, 41]. All these variables render assessment and comparison of results difficult. Ajay C. Kanakamedala et al.  conducted a systematic review in which no differences were found between the use of full-thickness versus partial-thickness quadriceps tendon; a result which is difficult to understand because in a hamstring graft, for instance, a 7 mm vs 10 mm thickness shows differences regarding rerupture risk . This may be one of the explanations of the results regarding rerupture on the Danish Registry report  that does not differentiate between partial and full harvesting.
To our knowledge, the present report is one of the few that includes a large group of patients (291) with 5 year results, which is longer than the 48-month follow-up reported by Chen et al. , the 2, 8 years of Cavaignac et al. , or the 24 month minimum of Geib  or others. Furthermore, this is a young cohort of patients, younger than that reported by Chen et al. , which was 26 years old, and that reported by Kim et al. . Another point to highlight is previous sporting level of the patients. In this study, patients who were operated had a higher level of sporting activity if compared to the rest of the publications such as Lee  (Tegner score of 4.7), or that of Cavaignac  (Tegner score of 7). Compared to other series, we obtained similar results in terms of Lysholm, IKDC, Lachman, percentage of tendinopathy and anterior knee pain.
The KT-1000 was used for the objective evaluation of the stability of the operated knee in relation to the non-operated knee. In this work we found that 89% of patients had a side-to-side difference of less than 3 mm; and that only 4% of the patients had a side-to-side difference of more than 5 mm. Results are similar to those described by Geib and Shelton , who reported 88.6% of patients with less than a 3 mm difference, and 5.3% of patients with a difference greater than 5 mm. Similar to reports from Kim et al. , Lund et al.  and Cavaignac .
Regarding IKDC, Chen reports  more patients in the normal group than this report (80% vs 59%), but with a shorter follow-up and without a description of the type of sports practiced. Our IKDC results are also in range with other studies.
We evaluated percentage of comorbidities, such as anterior knee pain, with the ability to walk on knees, as described by Kartus et al. . We observed that, at the final follow-up visit, 5.15% of patients had anterior knee pain, but it did not prevent them from carrying out their daily life and sports activities. Same percentage is in the lower range reported in the literature ; these findings are probably influenced by the long follow-up period. It is important to emphasize the low incidence of this postoperative morbidity comparing to BPTB in literature. There are series of BPTB reconstructions that report up to 44% of anterior knee pain, and 48.1% of pain when kneeling [9, 21, 28, 40]. However, we reported a larger percentage of failures (10.7%) than the Danish report , probably the younger population (23 vs 28 years); very active (Postoperative Tegner Median 8) and the follow up (5 years vs 2 years), could explain this difference.
Something to keep in mind is that among patients undergoing revision, highest percentage of reruptures occurred in the tibia, where the tendon-bone block is fixed. This pattern of rerupture has been shown on biomechanical testing literature [37, 43]. As there are no other clinical reports in the literature about this subject, we cannot assure that this zone is the weak link, or that rerupture may be caused by use of a retrograde fixation or the placement of a bone block in the tibial zone.
One of the weaknesses of this study is the lack of a comparison group. Another weak point to take into account is the chronological time dispersion of patients from 2009 to 2014. In addition, there is a loss of (11.67%) follow-up, and the evaluation was not performed by an independent observer.
Although this “All Inside” FQT reports knee stability, complication rates and comorbidities, similar to other types of reconstructions technique, however our study is performed in a younger, more active sports involved population with a longer follow up. Nevertheless, we think that future prospective types comparing different quad reconstructions types are needed.