In 2011 Mulford et al. evaluated the efficacy of PET artificial ligaments in the ACL reconstruction [22]. A total of 23 papers published between 1970 and 2010 were included. Twelve papers were related to the LARS, and the remaining 11 focused on the long-term outcomes of other PET ligaments. In studies of the LARS, the mean follow-up period was 28 months (range 4–60 months). In 655 cases, documented graft rupture occurred in 14 cases (2 %). However, the poor methodological quality of the included studies was of concern.

In a 2013 systematic review that included many of the papers included in the review by Mulford et al., Newman et al. evaluated studies related to the ACL reconstruction with the LARS device [24]. There were nine papers, including one randomized control trial, and all were published between 1990 and 2010. The outcome demonstrated a similar failure rate of 2.5 %. Most failures were attributed to tunnel malposition. Again, only one case of synovitis was reported. Return to sports took 2–6 months, earlier than that for patients having an autograft procedure. However, the poor methodological quality of the papers and the need for high-quality longer-term studies were once again highlighted.

More recently, Batty et al. systematically reviewed the reports related to the clinical application of artificial ligaments in the cruciate ligament surgery [3]. With regard to the ACL, the highest failure rate was observed with the Dacron device with a cumulative failure rate of 33.6 %. Noninfective synovitis and effusion were most frequently seen with the Gore-Tex artificial ligament (up to 27.6 %). In contrast, the reported outcomes of the LARS device appeared encouraging.

Thirteen LARS ACL patient cohorts were identified, with 19 documented failures in 736 patients (2.6 %). In those studies, which reported Lysholm scores, the mean postoperative score was 88, compared to a mean preoperative score of 54. KT-1000 arthrometer side-to-side difference was measured in seven studies in 394 knees with a mean side-to-side difference of 2.2 mm (range, 1.2–4.2 mm). Pivot shift was recorded for 497 patients in four studies with a grade 2 pivot (clear shift and visible reduction) present in 6.4 %. There was only one reported case noninfective effusion or synovitis (Figs. 31.3, 31.4, 31.5, and 31.6).

In terms of comparative studies, the one RCT compared 26 LARS devices with 27 patellar tendon autografts. At 24 months there was no significant difference between the groups in terms of IKDC or KOOS scores. One retrospective study compared 30 patellar tendon autografts with 32 LARS reconstructions with a minimum follow-up of 4 years. There was no difference between the groups in terms of Lysholm, Tegner, IKDC, and KT-1000 assessments. In a second retrospective study, 32 four-strand hamstring ACL reconstructions were compared with 28 LARS ACL reconstructions, also with a minimum follow-up of 4 years. Again, there was no difference in Lysholm, IKDC, or Tegner scores, but the LARS group had significantly less anterior displacement as measured by KT-1000.

In the Batty et al. review, the MINORS score was used to assess the methodological quality of included studies. The ideal score was 16 points for non-comparative studies and case series and 24 points for comparative studies. The mean MINORS score for the included non-comparative LARS studies was only 7.6 points (SD, 1.2 points) and 17.3 points (SD, 1.5 points) for the comparative studies. The authors noted that in view of the low levels of evidence, the findings of the systematic review should be interpreted with caution. In addition, the potential for publication bias – whereby poor outcomes are less likely to be reported – should also be noted.

In spite of the generally satisfactory results reported for the LARS in the above systematic reviews, questions remain about its role. Indeed, in many countries it has either not been approved for use, is not available, or has fallen from favor. In the following section, selected longer-term studies of the LARS are critically evaluated to highlight the varied results.

Parchi et al. reported on 26 of 29 patients a mean follow-up of 7.9 years [26]. The mean age of the patients at the time of follow-up was 38.5 years. Joint stability and range of motion were reported to be satisfactory in 24 patients. For the KOOS score, 11 patients (42.3 %) rated optimal (>90) and 13 (50 %) good [25–33]. However, there was a wide range of scores, from 10 to 100. Similar findings were found for the Cincinnati knee-rating scale with 92.3 % rating optimal (61.5 %) or good (30.8 %). Again, there was a wide range from 22 to 100.

The salient points for this study are that there was no control group; the patients were relatively older compared to the usual group reported in the follow-up of ACL reconstruction and elected to have a LARS procedure (potential for selection bias); despite generally satisfactory outcomes, some patients did badly, and no data regarding return to pre-injury activities was provided. It is to be noted that the authors conservatively concluded that the LARS device might be a “suitable option for ACL reconstruction in carefully selected cases, especially for older patients needing a fast functional recovery.”

However, in a more recent study, Tiefenboeck et al. came to the conclusion that the LARS device should “not be suggested as a potential graft for the primary reconstruction of the ACL” [33]. Twenty-six patients underwent primary isolated ACL reconstruction with the LARS between 2000 and 2004. The final evaluation was completed in 18 at the mean age of 29 years, with a mean follow-up period of 151 months. The high failure rate was the authors’ principal source of concern. Eleven patients had either KT-2000 side-to-side difference in anterior knee laxity of more than 5 mm (four patients) or a revision procedure due to reinjury (five patients) or revision due to deep infection (two patients).

Hamido et al. reported on the use of the LARS as an augmentation for small diameter or short-hamstring tendon autografts in 112 patients with a mean age of 26 years at the time of surgery [12]. The follow-up period was 45 months. Relatively little detail about postoperative assessment is provided. However, on IKDC evaluation 67 % patients rated normal and 28.6 % rated nearly normal. Eighty-two percent of patients returned to their pre-injury sports activities. No patient had a graft rupture, synovitis, screw loosening, or bone tunnel enlargement on radiological examination.

Synovitis was a major concern with earlier synthetic grafts and was associated with osteoarthritis in the longer term [27, 31, 34] Klein. It was attributed to abrasion and breakage of the synthetic devices resulting in free debris and particles within the joint [Greis, Olsen]. It was felt that malposition of bone tunnels would hasten this process [Olsen]. There was a concern that because of the nonabsorbable nature of the synthetic ligaments, there was an increased risk of developing osteoarthritis.

It is therefore important to note that many studies of the LARS device report minimal or no problems with synovitis [3]. However, some instances of disabling synovitis have nonetheless been reported [10].

Chinese surgeons did not experience the wave of enthusiasm for nor the subsequent failures and complications of the early synthetic ligaments. In China the LARS device was approved by the State Food and Drug Administration (SFDA) in 2004, and it has since been used on an ongoing basis. It has been estimated that more than 10,000 cases were performed. More than 100 papers on the results of LARS ACL reconstruction have been published in Chinese, with some studies also being published in English in international journals. Some of these studies are discussed in the following section.