The main finding in this retrospective examination of acute knee dislocations was a superior anterior stability following ACL reconstruction compared to ACL repair, which was accompanied by a trend for improved patient-reported outcome scores. Clinical failure was observed in one patient of each group considering that a highly active patients were studied. A considerable rate of re-operation due to postoperative knee stiffness was noted in both groups with a higher remaining flexion deficit following ACL reconstruction. The treatment concept of the torn ACL in the setting of a multiligament knee injury has been a controversy since a long time [
12,
25,
43]. Only a few studies reported about ACL reconstruction in acute knee dislocation using an early total repair strategy [
10,
18,
32]. However, none of these studies performed a precise comparative analysis between ACL reconstruction and repair. It is known that in isolated ACL repair there is a considerable failure rate, especially when treating highly active patients with type III and IV ACL injuries according to Sherman classification [
24,
36,
37]. In accordance, increased instrumented anterior–posterior laxity was reported in multiligamentary injuries compared to isolated ACL reconstruction [
1‐
3,
11,
19,
23,
38]. Although correlation between PROMS and arthrometric results has been discussed controversially in isolated ACL reconstruction, an SSD of > 3 mm would be considered as an unsatisfactory result [
14,
15,
40,
41]. Follow-up examinations in multiligament knee injuries frequently report SSD > 2 mm with a considerable trend towards higher values [
8,
17‐
19]. In comparison to other studies, this study revealed lower laxity with ACL reconstruction, which was accompanied by a trend for improved clinical outcome scores without reaching significance. In line with our results, Hirschmann et al. reported a positive correlation of ACL reconstruction and clinical outcome [
18]. Variance may be explained by additional bracing techniques and different types of ACL injury patterns as proximal tears seem to perform superior to midsubstance or distal tears [
37,
42]. Single ACL repair and dynamic bracing resulted in 43% positive pivot-shift test and 2.5 mm SSD, but good Lysholm scores [
23]. Internal bracing using a rigid suture augmentation resulted in 3.3 mm anterior–posterior SSD for the ACL and IKDC and Lysholm score > 80 [
19], which was also reported by Rosteius et al. in close similarity [
33]. These results are very similar to the outcomes using ACL repair in our study. Only few studies reported Lysholm scores > 85 as seen with ACL reconstruction in our study [
12,
18,
19,
33]. In terms of graft failure 1/11 ACL graft rupture was observed in both groups, with the failure in both cases being due a traumatic event after return to sports. Both, graft failure and clinical outcome scores strongly depend on the patient age and activity level [
22,
31,
34]. Average age of our study population was mid-age but with high active demands. Recent studies in isolated ACL reconstruction have shown higher graft failure rates in young and highly active patients, who perform high risk pivoting sports [
34]. Therefore, the concept of ACL treatment in cases of acute KD may be chosen depending on the individual patient demand, with highly active and young patients having an advantage from ACL reconstruction. Included patients reported a preinjury Tegner level of 6, which can be considered as highly active. In line with previous reports, patients can return to a highly active sports level following acute knee dislocation [
17].
From a biomechanical point of view less laxity of the cruciates may improve healing of the collaterals, which might explain the poorer results of staged surgery with peripheral fixation first and delayed cruciate reconstructions [
21]. Rosteius reported about a considerable rate of residual laxity of the collaterals using the ACL repair strategy [
33]. Animal models of combined ACL/MCL injuries using a robotic testing system have shown that initially high in situ forces within the ACL graft were transferred to the healing MCL during the early healing phase [
26]. These excessive high loads likely contributed to a decrease in the structural properties of the MCL complex when compared to isolated MCL injuries [
21].
Nevertheless, a considerable rate of stiffness and subsequent LOA in both groups has to be acknowledged. In comparison to a recently published systematic review [
9], the rate of LOA was higher in our study as the indication for early LOA was made generous in this study. This decision was based on a recent study that revealed significantly improved range of motion and functional scores of early LOA (within 6 month) compared to late LOA (> 6 month) [
7]. Although a postoperative flexion deficit of 10–15° has been reported before [
27], a more progressive rehabilitation with unlimited range of motion may be necessary in future rehabilitation protocols.
Conclusions based on this study are limited by the relatively small case number and inhomogenous injury patterns. Improved comparability was tried to achieve by exclusion of obese patients, accompanying fractures of the tibial plateau, major nerve and vascular injuries. Decision for ACL treatment was not randomized, but changed during the study time with ACL reconstructions performed in the second half of the study period. In addition, no matched-pair analysis was feasible given the great rarity of acute KD. Long-term follow-up is necessary to validate the concept of primary ACL reconstruction as recent studies have shown the increase of graft failure during the observation time.