On August 31, 2022, the German news magazine Focus online quoted a meta-analysis by Saueressig et al. recently published in the British Journal of Sports Medicine (BJSM) [9]: “A new study shows that surgical treatment after anterior cruciate ligament (ACL) injury does not automatically have better chances of recovery. Instead, non-surgical therapies can also lead to similarly good results.” In the original BJSM article, however, the following conclusion was drawn based on an analysis of three controlled randomized studies: “There is low to very low certainty of evidence that primary rehabilitation with optional surgical reconstruction results in similar outcome measures as early surgical reconstruction for ACL rupture.” As one can see, the Focus message is more a very broad interpretation than a citation of the article’s scientific conclusion.

The replacement of surgical techniques with non-surgical methods is a topic that always attracts attention in the press. Unfortunately, such coverage-oriented reports often reveal deficits in the processing of scientific information. Attempts are sometimes made to polarize different medical interest groups against each other. This article in Focus is a nice example of this stylistic method. Here, the “new groundbreaking” discovery by authors whose institutes essentially have a physiotherapeutic background is compared with the “old” doctrine of a guideline of the German Society for Orthopedics and Trauma Surgery (DGOU). In the said Focus article, for example, it is distorted that the DGOU guideline always recommends immediate knee surgery, in which the ACL is surgically reconstructed, especially for young patients and competitive athletes [12]. The referenced passage in the DGOU guideline, however, reads as follows: “Surgical therapy is the more common treatment method, which is particularly necessary in young and active patients in order to enable a safe return to activity while reducing the risk of consequential damage” (see also https://www.awmf.org/uploads/tx_szleitlinien/012-005l_S1_Vordere_Kreuzbandruptur_2019-02_01.pdf).

Both statements sound similar. In science and medicine, however, certain nuances in the choice of words often make a big difference. The protective value of cruciate ligament surgery regarding secondary meniscus and cartilage damage is documented in the DGOU guideline by quoting several systematic reviews and meta-analyses, and the various indication criteria for surgical or non-surgical therapy are presented [3, 8]. Here we can also refer to a recently published consensus project by the Ligament Injury Committee of the German Knee Society (DKG), which was also able to show in a differentiated manner that primary and secondary injuries to the menisci and cartilage are responsible for the development of post-traumatic gonarthrosis and that ACL reconstruction is only suitable to prevent secondary damage (Fig. 1; [5]). The DGOU guideline shows, based on evidence, that various criteria must be weighed up against the risks associated with the indication for surgical intervention [12]. A treatment algorithm for the treatment of acute ACL injuries, published in 2020 by the Committee on Ligament Injuries of the German Knee Society, also recommends early surgery only in patients with a repairable meniscal lesion, distal collateral ligament rupture, or competitive athletes (Fig. 2; [6]). For all other patients, primary physiotherapy with optional secondary surgery is recommended for patients with persistent functional instability (e.g., giving way). This recommendation is supported by a recent controlled randomized study that was able to show that ACL reconstruction as a treatment strategy for patients with non-acute ACL injuries with persistent symptoms of instability is clinically superior and more cost effective compared to conservative therapy [1].

Fig. 1
figure 1

Scientific infographic to illustrate the development of post-traumatic gonarthrosis after anterior cruciate ligament (ACL) rupture and to clarify the significance of primary and secondary concomitant injuries. (From [5])

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Fig. 2
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QR code to the treatment algorithm: management of acute anterior cruciate ligament rupture [6]

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Replacement of surgical techniques with non-surgical methods is a topic that always attracts attention

Back to the systematic review by Saueressig et al. [9]. Again, the conclusion that primary rehabilitation with optional surgical reconstruction yielded similar outcomes (patient-reported outcome measures, PROMs) to early ACL reconstruction is surprising, as two of the three studies analyzed conclude that functional outcomes in patients with early ACL reconstruction are better than in patients after primary non-operative therapy [7, 10]. Only in the KANON study by Frobell et al. were functional outcomes equivalent after primary surgery and primary rehabilitation with optional surgical treatment [2]. A primarily non-surgical therapy with the option of surgery can only be justified in terms of possible surgical risks.

Against this background, the advantages and disadvantages of evidence-based medicine (EBM), with its focus on randomized, controlled, double-blind clinical studies, with regard to surgical procedures must also be discussed [4]. These are viewed as top in the vertical hierarchy of evidence. A key problem here is that surgical procedures cannot be standardized as easily as, for example, medication. However, many randomized controlled trials (RCTs) on surgical procedures lack standardization of the surgical procedure (e.g., Frobell et al.: “All reconstructions were single bundle, done by using either a patella tendon or hamstrings tendon procedure depending on the surgeon’s preference”) [2]. One of the cofounders of EBM, Alvan R. Feinstein, has already pointed out the problem of heterogeneity of the complex objects under investigation [11].

The so-called intention-to-treat principle, which makes sense when comparing two diets or pills, must also be questioned when comparing an operative procedure with non-operative therapy, since patients regularly switch from the non-operative group to the operative group. The postoperative results of these patients, however, are counted in the non-surgical therapy group. In the KANON trial, for example, 30 out of 59 patients originally assigned to non-surgical treatment changed to the surgical group [2]. This crossover rate of almost 50% should be considered as an outcome, since this also represents an important result of the study. In addition, more attention should be paid to the “as-treated” analysis, and thus to the result of the therapy that was carried out.

Another risk of RCTs in surgical medicine is selection bias. As a result, the ability to generalize the findings to clinical reality is significantly restricted.

A rethink should take place regarding evidence-based medicine assessment of surgical procedures

Due to the outlined risks, a rethink should take place regarding EBM assessment of surgical procedures. Other study designs should also be taken into account, in order to better do justice to the complexity of the decision regarding whether to operate (e.g., long-term studies, register results, consensus processes, etc.). Here, we see a need for scientific effort.

In conclusion, we would like to state that the indication for a surgical intervention is a complex process in which the patient should be included as far as possible in terms of participatory decision-making. Various risk factors and criteria must be carefully weighed against each other. Regarding ACL surgery, these are the functional gain, the preventive effect of secondary joint damage, and the operative risks. Again, we would like to refer to the treatment algorithm already mentioned and the DGOU guideline [6, 12]. This is the only way we can advise our patients responsibly.