Comparison of Dynamic and Static Medial Patellofemoral Ligament Operation Technique for Recurrent Patellar Dislocation

Patient reported knee function and anterior knee pain as assessed with the Kujala score at preoperative screening, at the hospitalization time and four postoperative follow ups . The Kujala scale consists of 13 questions covering a range of physical symptoms and limitations that are presented in a multiple choice answer format, with a different point value assigned to each answer. The maximum score is 100, with higher scores indicating better function.

Surgical outcome: recurrent patella dislocation.

Surgical outcome: revision surgery.

Surgical outcome: complications (other than revision surgery, e.g. infection, wound healing disorder).

The Banff Patella Instability Instrument (BPII) is a disease-specific health-related quality of life score. It is a patient-reported, disease-specific QOL score that consists of 23 questions across five domains covering symptoms/physical complains, work-related concerns, recreational activity and sport participation/competition, lifestyle, and social/emotional. Patients mark their answers on a visual analogue scale measuring 100 mm in length. Each item is equally weighted with the final score calculated as an average of the scores from all answered items. A higher score reflects a higher QOL.

The IKDC includes 18 questions covering three domains: symptoms, physical activity, and function. The items are answered on Likert scales of varying values. IKDC scores are calculated by dividing the total score by the highest possible score for the items answered, and multiplying by 100, with higher scores indicating better function.

The EQ-5D descriptive system comprises five dimensions: mobility, self-care, usual activities, pain and discomfort, and anxiety and depression. The five levels in each dimension are worded as (1) 'not /no problems', (2) 'slight problems', (3) 'moderate problems', (4) 'severe problems', and (5) 'unable to' (mobility, self-care, usual activities), 'extreme' (pain/depression), or 'extremely' (anxiety/depression).

It is usually presented as a 100-mm horizontal line on which the patient's pain intensity is represented by a point between the extremes of "no pain at all" and "worst pain imaginable."

Operation time

Length of hospital stay Length of hospital stay

Instrumented gait analysis (by EMG) on a treadmill with an embedded plantar pressure plate and on an overground walkway with two embedded force plates.

Muscle strength will be measured bilaterally using a dynamometer.

Timing of the gracilis muscle will be assessed as on- and offset relative to the gait cycle. Gracilis onset will be determined as the time when the processed EMG signal exceeded a threshold of three standard deviations above a baseline mean and as offset, when the processed EMG signal falls below a threshold of three standard deviations above a baseline mean.

Standing erect upon only the tested leg with the foot in neutral position, participants will step off a 30 cm high platform placed 11 cm from the edge of the force-plate. Participants will be instructed to land in the centre of the force-plate on the tested leg only.