RetroBRACE - Clinical and Functional Outcomes 2 Years After Primary ACL Repair (Internal Bracing)

Primary outcomes

1. joint position sense Analysis (proprioception)

   Time frame: single time point assessment (2 years after surgery)

   Proprioception will be assessed bilaterally using a dynamometer (Biodex System 4 Pro: Biodex Medical Systems, Shirley, NY, USA) with an active joint position sense protocol. Participants will be positioned with hips and knees flexed at 90°. The subjects will then actively extend their knee to the target angles of 60° or 20° flexion, respectively. The subjects will be asked to remember this position. Starting from 90° flexion they will then be asked to extend their knee and reproduce the remembered target flexion angle pressing a stop button when they think they reached the angle. The difference between the perceived angle and the initial target angle will be calculated.

2. muscle strength

   Time frame: single time point assessment (2 years after surgery)

   Muscle strength will be measured bilaterally using a dynamometer (Biodex System 4 Pro: Biodex Medical Systems, Shirley, NY, USA).

3. gait analysis

   Time frame: single time point assessment (2 years after surgery)

   Instrumented gait analysis on treadmill with embedded plantar pressure plate (h/p/cosmos, Zebris FDM-T, Isny, Germany; 7168 sensors; area, 1.5 * 0.5 m; range, 1-120 N/cm2; precision, 1-120 N/cm2 ± 5%; sampling rate, 120 Hz) and on an overground walkway with two embedded force plates (Kistler force plate 9260AA6, Kistler AG, Winterthur, Switzerland; sampling rate 2400 Hz). Patients walk barefoot for 2 minutes at 0% slope at their preferred walking speed and at 1 m/s followed by walking at preferred walking speed. The treadmill speed will be increased to preferred running speed, and data for 2 minutes running will be recorded. Maximum flexion and extension angles and joint moments will be computed using the Biomove software (Stanford University).

4. maximum jump height (cm)

   Time frame: single time point assessment (2 years after surgery)

   Participants will perform three single leg hops on each leg. Maximum jump height will be determined as the highest position of the pelvis marker compared to a standing trial

5. Euroquol 5 Dimensions (EQ-5D-5L)

   Time frame: single time point assessment (2 years after surgery)

   EQ-5D-5L questionnaire measuring generic health Status; descriptive system comprises five dimensions: mobility, self-care, usual activities, pain/discomfort and anxiety/depression. Each dimension has 5 levels: no problems, slight problems, moderate problems, severe problems and extreme problems. The patient is asked to indicate his/her health state by ticking the box next to the most appropriate statement in each of the five dimensions. This decision results in a 1-digit number that expresses the level selected for that dimension. The digits for the five dimensions can be combined into a 5-digit number that describes the patient's health state. As a result, a person's health status can be defined by a 5-digit number, ranging from 11111 (having no problems in all dimensions) to 55555 (having extreme problems in all dimensions).