This retrospective cohort study was conducted to evaluate the clinical and radiological outcome after anatomic ACL-R with or without early MCL repair in patients with combined ACL and MCL lesions. The study was approved by the institutional review board of the Technical University of Munich (235/19 S).
Patient cohort
All patients presenting with combined acute ACL and MCL injuries at our institution between February 2014 and February 2019 were included in this study. Inclusion criteria were: subjects aged > 18 years, early ACL-R with autologous hamstring tendon and MCL repair (group 1) in the first two weeks after trauma or non-operative treatment of the MCL (group 2) for six weeks followed by staged ACL-R with autologous hamstring tendon. Diagnosis of combined ACL and MCL injuries were made using magnet resonance imaging and clinical examinations. Indication for MCL treatment was dependent on MCL grading according to Fetto and Marshall [9]. In grade II MCL injuries, an increased laxity at 30 degrees of flexion could be found, whereas in grade III MCL injuries an increased laxity at both, 0 and 30 degrees of flexion was present [9]. Grade II MCL injuries with dislocated tibial or femoral avulsions and grade III MCL injuries underwent ligament repair (group 1) due to the limited capacity to heal non-operatively [2]. Grade II MCL injuries without avulsions (partial ruptures) were treated non-operatively with a brace for six weeks with limited range of motion (ROM) and partial weight bearing on crutches (group 2).
Exclusion criteria for the present study were: further ligamentous or osseous injuries of the affected knee as well as previous injuries and surgical interventions on the other knee, and lack of German language skills.
Clinical notes of all patients were reviewed to collect demographic data.
Operative technique
Prior to surgery all patients had undergone a thorough clinical and radiological (X-rays and MRI) examination to ensure ligament injuries to the ACL and MCL with or without concomitant meniscus lesions.
In case of concomitant meniscus lesions, meniscus suture systems (Arthrex, Naples, USA or Smith&Nephew, London, UK) were used or partial resection of meniscus was performed.
In both groups, an arthroscopic, anatomic single-bundle ACL technique with autologous hamstring graft was performed. The femoral tunnel was drilled via an anteromedial portal according to the diameter of the graft. A cortical suspension device (ACL tight-rope, Arthrex, Naples, USA) was used for femoral graft fixation. A K-wire was then placed in the center of the tibial ACL footprint and was overdrilled according to the diameter of the graft, creating the tibial tunnel. A bio-absorbable interference screw (Arthrex, Naples, USA) was used for tibial fixation.
In group 1, the medial collateral ligamentous structures were repaired by the use of suture anchors (Corkscrew 5,5 mm Biocomposite, Arthrex, Naples, USA) in case of femoral- or tibial-sided injuries with or without suture tape augmentation. Suture tape augmentation (FiberTape, Arthrex, Naples, USA) was used in grade III MCL injuries if medial collateral ligamentous structures were badly damaged resulting in poor tissue quality accompanied by limited success of isolated MCL repair by suture anchors. Additionally, MCL augmentation was performed in case of insufficient ligamentous stability after MCL repair intra-operatively.
Postoperative rehabilitation
The postoperative protocol of group 1 consisted of 6 weeks of partial weight-bearing on crutches with limitation in ROM: in the first two weeks an active extension(ex)/flexion(flex) of 0°/20°/60°, in the next two weeks of 0°/10°/90°, and in the last two weeks of 0°/0°/90° was allowed. After six weeks, ROM was no longer limited. A brace (Medi M4, Medi Bayreuth, Germany) was provided for at least 12 weeks.
In group 2, partial weight bearing on crutches with the same limitations in ROM was allowed in the six weeks of non-operative treatment in a brace. After six weeks, ACL-R was performed. Postoperatively, partial weight bearing on crutches was allowed for two weeks and ROM was only limited if meniscus suturing was performed (ex/flex 0°/0°/90°).
Return to running on the treadmill and front crawl swimming was allowed after 6 weeks, trail running after 3 months, return to sport-specific training in both groups was allowed after 6 months and full return to contact and/or pivoting sports activities after at least 9 months postoperatively.
Radiological evaluation
Functional US examinations were performed by two board-certified radiologists with at least 5 years of experience in musculoskeletal imaging at follow-up. All acquired images of the knees were evaluated on picture archiving and communication system PACS workstations (Sectra Medical Systems, Sweden).
Ultrasound examination
For evaluation of medial ligament laxity, the width of the medial joint space was assessed by ultrasound (ACUSON NX3 Ultrasound System, Siemens Erlangen, Germany) using a linear transducer (4.0–12.0 MHz, Maximum Field of View: 153 mm, Maximum Display Depth: 160 mm), placed in a longitudinal direction over the medial aspect of the knee. Subjects were positioned supine with extended leg in 0° with and without reproducible applied valgus stress (loaded condition) through a fixation device (TELOS, Wölfersheim-Berstadt, Germany) with 15 dekanewton (daN), and in a second step with a 30° bended knee with and without valgus stress [11, 20]. For standardized measurements, the medial epicondyle was palpated and the transducer was placed in the longitudinal direction. Since the presentation of the hyperechoic bony outline of femur and tibia has been considered as an important quality assessment for standardized measurement of medial joint width [42], the medial femoral epicondyle and the proximal tibial plateau were used as bony landmarks, as described in the literature (Fig. 1A and B) [11, 20]. The distance between corresponding points on the femoral and tibial articular margins was measured in millimeters (mm). All measurements were performed by a specifically trained orthopedic sports medicine resident (rater 1). Intra- and interrater reliability was tested in 20 randomly assigned and blinded cases after an interval of six weeks by rater 1 and by one senior orthopedic surgeon (rater 2). Medial joint space width in 0° and 30° knee flexion was then compared between unloaded and standardized loaded conditions for each group. Furthermore, the mean change (delta Δ) of medial joint space width between unloaded and loaded conditions for each state of flexion and side-to-side differences of the average change (delta Δ) were compared between both groups.
Clinical examination and patient-reported outcome measures
All subjects underwent standardized clinical examination of the knee. The International Knee Documentation Committee (IKDC) valgus subscore was used for objective MCL stability assessment. Meniscus was evaluated by joint space tenderness and Steinmann test [35]. Patient-reported outcomes were measured with Visual Analogue Scale for pain (VAS), the subjective knee form of the IKDC, the Lysholm score, and the Tegner activity scale at follow-up [14, 38].
Statistical analysis
Statistical analysis was performed by use of SPSS software (IBM, Armonk, New York, USA) and Microsoft Excel Version 2019 (Microsoft, Redmond, Washington, USA). For all statistical tests, p values less than 0.05 were considered as significant.
Descriptive statistics are presented as mean ± standard deviation (SD) with a measurement accuracy of one decimal. Kolmogorov–Smirnov univariate normality test was used for continuous variables to confirm data normality. Mean change of medial joint space width between unloaded and loaded conditions and side-to-side differences were compared between the two groups using paired t-tests. Group comparison was performed with Mann–Whitney U test and unpaired t-test, as appropriate.
Intraclass correlation coefficients (ICCs) were calculated to determine the intra- and interobserver reproducibility. ICC values > 0.9 were considered excellent, values between 0.8 and 0.9 were considered good and values < 0.8 were considered poor. An a priori power analysis based on the results of Zaffagniniet al. was performed with G*Power (Erdfelder, Faul, Buchner, Lang, HHU Düsseldorf, Düsseldorf, Germany) [41]. The authors reported a mean medial joint space opening (side-to-side difference of medial joint opening with and without stress applied) measured with Telos valgus stress radiographs of 0.9 mm (SD 0.7) after isolated ACL-R, and of 1.7 mm (SD 0.9) after ACL-R combined with non-operative treatment of a grade II MCL lesion [41]. The power analysis revealed a sample size of 20 knees in each group at an assumed effect size of 0.81 in order to achieve a statistical power of 0.8.