Anterior cruciate ligament reconstruction: Which graft is best?

Anterior cruciate ligament (ACL) injury accounts for more than 50% of knee injuries occurring during sports, with an estimated annual incidence of 30-78 injuries per 100 000 people, with particular emphasis on adolescents [9, 33].

ACL rupture is indicated for surgery when symptomatic in patients with moderate to high functional demand, in order to enhance rehabilitation, return to sports and reduce the risk of associated long-term intra-articular lesions (meniscal and chondral lesions and early osteoarthritis).

Available graft types include autografts, including hamstring (IT), patellar/rotator tendon (OTO) and quadriceps tendon, allografts and synthetic grafts.

According to the ACL registry, in both Europe and the United States of America, more than 95% of reconstructions use autologous IT or patellar tendons [43]. This text will focus only on these two types of graft.

Although the patellar tendon (OTO) is considered the gold standard In primary ACL reconstruction, particularly in athletes [8, 18, 23], several factors should be considered in graft selection. These include age, gender, activity level, associated injuries, the risk of donor site morbidity, the aesthetics of the harvest site scar and the type of graft fixation [5, 18].

The ideal graft should have similar properties to the native ligament, not cause donor site morbidity and allow rapid fixation and incorporation [4].

There are numerous studies comparing IT tendons with OTO in ACL reconstruction. However, it should be kept in mind that many of the meta-analyses include studies with multibundle IT (2-5) and do not restrict the comparison to 4-bundle IT. Another methodological limitation is the inclusion and non-distinction of single-beam and double-beam reconstructions with TI.

A summary review of the comparison between the two main graft types used in ACL ligamentoplasty is presented below.

BIOMECHANICS

The biomechanical characteristics of each graft type vary during the embedding process, so the values presented reflect only time zero after reconstruction. In terms of ultimate load failureBoth OTO and IT appear to be viable substitutes for native ACL.

Table 1. Comparison of the biomechanical characteristics of different graft types. Adapted from [4]

GRAFT INCORPORATION

The incorporation of the patellar tendon (bone-on-bone) is faster than that of the IT tendon (tendon-on-bone), taking 8 and 12 weeks respectively A ultimate load failure of IT is lower at 3 (45.8%) and 6 (85%) weeks than OTO [1, 20, 26, 29, 38]. A recently published study contradicts this classical theory, showing similar graft displacement values in the bone tunnel between the two graft types at 6 weeks and 12 months. Given the biological plausibility of a bone-bone interface achieving superior results in short-term incorporation, we continue to suggest greater caution in increasing the intensity, volume and complexity of rehabilitation exercises in the context of IT grafts.

GRAFT FAILURE/REVISION

In a meta-analysis including 1272 elite athletes, the failure rate of ACL ligamentoplasty was estimated at 5.2 % (2.8-19.3%) [6], increased to up to 30-40% in cohorts of young athletes [10, 39].

Recent studies point to a higher revision rate with IT tendons. [11, 22, 27, 28]. A meta-analysis including more than 45,000 ACL reconstructions confirms this finding [31]. The rate of traumatic re-rupture is higher in IT.

In summary, the failure rate in both grafts is low and practically equivalent, with a slight advantage for the patellar tendon (OTO) (2.8 vs 4.2%, OTO and IT respectively). The graft failure rate is significantly higher in young athletes (<25 years) [10], and is mitigated by the association of extra-articular lateral tenodesis [10] (or anterolateral ligament reconstruction) [36].

STABILITY

Recent systematic reviews (SR) show no differences in anteroposterior stability (test Lachman or instrumented measurement) between the two grafts [31, 40, 44]. In terms of rotatory instability (test pivot shift or instrumented measurement), some studies do not detect differences [31, 44], while a meta-analysis shows that OTO has a lower rate of injury. pivot shift positive [40].

MUSCLE STRENGTH

Patients who underwent patellar tendon reconstruction (PTO) had higher deficit extensor and flexor minor, and these deficits may persist up to 2 to 5 years after surgery.

Regarding the use of IT, the deficits depend on the number of tendons harvested, with the deficit strength more pronounced at higher flexion angles [35, 42]. The Gracilis tendon should be preserved whenever possible and the use of IT tendons should be avoided in sports involving maximal flexion and flexion. sprint.

Rehabilitation protocols should focus on the type of graft used, particularly on specific muscle strength training.

RETURN TO PRE-INJURY ACTIVITY LEVEL

There are multiple factors that influence the return to pre-injury level and it is not clear that the type of graft is determinant. There is no consensus in the literature [24, 40, 44].

CLINICAL SCORES - Patient-reported outcome measures (PROM)

Multiple SRs and meta-analyses have concluded that there is no difference in IKDC scores and Lysholm [37, 37, 44]. Studies using KOOS also found no differences [12, 34].

OSTEOARTHROSIS

The long-term incidence of OA after ACL reconstruction can reach 40% [25]. Although a recent SR revealed a higher incidence of OA with OTO [21, 25, 41], the remaining studies do not confirm this association [17]. Many non-anatomical OTO reconstructions are included in these studies, according to the evolution of the surgical technique over time.

There are a number of confounding variables on this topic, so more studies are needed to determine the role of the graft in the risk of developing OA in anatomical reconstructions.

DONOR SITE MORBIDITY

Anterior knee pain and pain on kneeling are more frequent complications with patellar tendon harvest[19, 21, 37, 40, 44]. When considering the use of OTO, harvest site morbidity and the deficit extensor strength should be considered, particularly in athletes who need to kneel frequently. Regarding the aesthetics of the surgical scar at the harvest site, the incision for IT harvesting is smaller (1.5-2 cm).

Table 2. Comparison of morbidity between patellar tendon and IT [15, 30]

INFECTION

Although the overall risk of infection (0.48%) is reduced in both graft types, several studies show an increased risk (8x) of infection with IT compared to patellar tendon [2, 3, 45].

TUNNEL WIDENING

Tunnel widening is greater with IT tendons than with OTO [13, 32]. However, there appears to be no correlation between widening and clinical outcomes [32].

RATIONALE FOR GRAFT CHOICE

Personalized graft type selection is recommended in ACL reconstruction surgery. There is no single graft that is appropriate for all patients. In choosing the ideal graft for each patient, the surgeon should consider multiple factors related to the patient, the graft and the surgeon's experience.

The ideal graft should have low harvest morbidity, rapid integration and structural and biomechanical properties similar to the native ACL. Nevertheless, each type of graft has its own specific characteristics with consequent advantages and disadvantages.