Title: Prognostic factors for poor functional outcomes in knee dislocations treated by multi ligament reconstructions.

Background

Knee dislocation (KD) remains a therapeutic challenge. Current literature promotes multi ligament reconstructions (MLR) rather than repairs. However, little is known on their mid-term functional outcomes and especially their prognostic factors.

Purpose

To identify prognostic factors for Patient Reported Outcomes (PROMs), Return to Sport (RTS) and Return to Work (RTW) in knee dislocations treated by MLR.

Methods

Patients with knee dislocations treated by MLR between 2013 and 2019 were identified in our university hospital registry. They all received a similar procedure: all complete ligament ruptures were reconstructed, starting with the PCL. Realignment osteotomy was performed as a first step if HKA > 5 degrees. Patients with drug dependency and age above 60 years were excluded. Postoperative functional outcomes were assessed with PROMs (IKDC, ACL-RSI, KOOS), RTS and RTW questionnaires. We hypothesized the following factors as possible determinants of poor outcomes: KD severity according Schenck classification, postero medial (PMC) and lateral (PLC) corner injury, age, BMI, gender, OA changes stage =2 according Kellgren Lawrence (KL), and ligament reconstruction failure confirmed under dynamic radiographs.

Results

52 consecutive patients were assessed at 3.8±1.6 years following MLR. Demographics: sex ratio: 3, BMI: 25.7±4.5 kg/m2, age: 35.5±11 years. According Schenck, knee dislocations were classified KD I (40.4%), KD III (40.4%), KD IV (9.6%) and KD V (9.6%). Overall, 76.9 % of these dislocation sustained either complete PMC (n=27) or PLC (n=13) injury. 11.5% suffered from peroneal nerve palsy (fully recovered for two thirds). Mean postoperative PROMs were: IKDC: 68±14.5, ACL-RSI: 55.9±24.5, total KOOS: 74.1±19.7. Return to sports classified as level 1-2 according the IKDC failed in 44.2 % postoperatively. Professional reorientation was more frequent in manual labor (28.5%) than in more sedentary occupations (7.9%, p=0.05).
In Schenck classification, only KD V (intra articular fracture) was associated with lower IKDC (51.9; p=0.007) and KOOS (49.7; p=0.004) scores. In dislocation patterns involving PLC injury (encountered in KD I L and III L), we observed lower IKDC (63.0; p=0.04) and ACL-RSI (43.2; p=0.02), as well as more frequent need for professional reorientation (30.7%, p=0.05). Early medial compartment OA led to lower ACL RSI (47.3; p=0,04), IKDC (62.5; p=0,03), total KOOS (67.1; p=0,03).
Failure to return to sports classified as level 1-2 according the IKDC increased with severity of dislocation according Schenck classification (KD I: 28.6%, KD III: 47.6%; KD IV: 60%; KD V 80%) but differences did not reach significance (p=0.151).

Conclusion

this study describes for the first time injury patterns associated with functional outcomes after knee dislocation treated by MLR. Simultaneous intra articular fracture, dislocation with PLC injuries and early medial compartment OA were identified as poor prognostic factors.