Clinical and Functional Outcome After Lateral Trochlear Lengthening Osteotomy Lateral Trochlear Lengthening Osteotomy

presence of a recurrent patellar dislocation postoperative by plain radiograph of the knee/ lateral view:

• crossing sign: The sign is positive when the trochlear groove lies in same plane as anterior border of lateral condyle. It represents a flattened trochlear groove
• double contour sign: The sign is positive when the anterior border of lateral condyle lies anterior to anterior border of medial condyle. It represents a convex trochlear groove/hypoplastic medial condyle
• presence of a lateral trochlear bump prominence
• the patellar height will be evaluated according to Insall-Salvati method (normal between 0.8 and 1.2) and Caton Deschamps method (normal between 0.6 and 1.3)

The trochlea form will be assessed, the existence of trochlear dysplasia will be confirmed and classified according to Dejour

Lateral condyle index assessed by MRI of the knee (preoperative (always conducted) and in the cases where they are available postoperative MRIs). The lateral condyle index was designed to measure the lateral trochlea by comparing the anterior cartilaginous trochlea (a) and the posterior aspect (p) [(a:p)× 100].

The patients will be asked to subjectively evaluate the outcome of the operation according to the following options:

• Excellent: Patient is fully recovered and has resumed all activity without restrictions
• Somewhat Improved: Patient is mostly recovered and has resumed a majority of activities
• Unchanged: Patient outcome is equivalent to pre-operative complaints
• Somewhat Worse: Patient is experiencing symptoms worse than pre-operative complaints
• Significantly Worse: Patient outcome is worse than pre-operative complaints with significantly worse symptoms

The Kujala AKPS is a 13-item screening instrument designed to assess patellofemoral pain in adolescents and young adults, with a variable ordinal response format. For example, a 'Limp' score would be scored as follows: none (5), slight/periodic (3), constant (0). Total scores range from 0 to 100.

The Lysholm Knee Score consists of eight items that measure: pain (25 points), instability (25 points), locking (15 points), swelling (10 points), limp (5 points), stair climbing (10 points), squatting (5 points), and need for support (5 points). Every question response has been assigned an arbitrary score on an increasing scale. The total score is the sum of each response to the eight questions, and may range from 0-100. Higher scores indicate a better outcome with fewer symptoms or disability.

The visual analogue scale (VAS) is 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.

The Tegner activity scale is a one-item score that graded activity based on work and sports activities on a scale of 0 to 10. Zero represents disability because of knee problems and 10 represents national or international level soccer.