Standard ACL Reconstruction vs ACL + Lateral Extra-Articular Tenodesis Study (STAbiLiTY)

• symptomatic instability requiring revision ACL surgery
• positive pivot shift or asymmetrical pivot shift greater than other contralateral side

We will determine the absolute risk of graft failure in each group, calculate a relative risk (RR) and risk difference (RD) of graft failure with 95% confidence intervals around the estimate and use a Mantel Haentzel Test (random effect of surgeon) to determine the significance of the association between the addition of LET and graft failure rates. We will calculate the number needed to treat (NNT) to describe the number of patients who need to receive LET to prevent one graft failure over the first two postoperative years.

The ACL-QOL has five domains that query physical symptoms, occupational concerns, recreational activities, lifestyle, and social and emotional aspects. Each item has one 100 mm visual analogue scale response option, with labeled anchors at 0 mm (e.g., extremely difficult) and 100 mm (e.g., not difficult at all). Scores are calculated by converting the average of each of the five domain scores to a total average score out of 100% where 100% represents the best possible score.

The KOOS is a 42-item knee-specific questionnaire with five separately reported domains, including pain (9 items), other symptoms (7 items), function in daily living (17 items), function in sports/recreation (5 items) and knee-related quality of life (4 items). Domain scores represent the average of all items in the domain standardized to a score from 0 to 100 (worst to best). This instrument has face validity and has demonstrated construct validity, excellent test-retest reliability for each domain (range, 0.75 to 0.93) and has been shown to be responsive to change in patients with knee OA and following HTO surgery.

The MARX Activity Rating Scale is a four-item activity rating scale. The patient is asked to rate how often they were able to perform each activity (e.g. running, cutting, decelerating, and pivoting) in their most healthy and active state. The patient is provided with five categories of frequency of each functional activity, ranging from less than one time in a month to four or more times in a week. One point is allocated for each category of frequency and a maximum score of 16 points can be awarded.

For passive knee extension, the patient is seated with both legs extended on a table, heel propped so that the calf and upper thigh clear treatment table. The patient will be instructed to relax both quadriceps and hamstrings to assure passive measurement. For active-assisted knee flexion, the patient is seated with both legs extended on a table. They will be instructed to perform active-assisted knee flexion by placing one hand under their thigh to initiate flexion and then clasp both hands just below the tibial tuberosity. This is measured as distance in centimeters of heel lift from the couch in passive hyperextension, and distance in centimeters of heel to buttock in flexion, both compared to the uninvolved side.

The EuroQoL comprises two sections, the EQ-5D index and the EQ-5D visual analogue scale (VAS). The EQ-5D index is a 5 item standardized generic measure of HRQOL that includes domains of mobility, self-care, usual activities, pain and discomfort and anxiety and depression. Each item is score using a 3 point response scale and each combination of response choices describes a health state (243 unique health states). Each health state can be converted to a utility value from 0 (worst) to 1.0 (best) using a scoring formula. The EQ-5D VAS is a 0 (worst) to 100 (best) scale that assesses patient-perceived health status. The EQ-5D index and VAS have demonstrated good test retest reliability (0.73 and 0.70 respectively) and good cross-sectional construct validity in patients with rheumatoid arthritis and those with osteoarthritis of the knee, and is able to discriminate between functional classes in patients with arthritis.

Radiographic Evidence of osteoarthritis will also be evaluated with plain antero-posterior, Rosenberg and lateral view radiographs at 1 and 2 years.

The International Knee Documentation Committee (IKDC) Subjective Knee Form is an 18-item region specific, patient-important questionnaire containing the domains of symptoms, function and sports activities. The instrument measures subjective pain, stiffness and swelling, joint locking and instability. Function is assessed through comparing current knee function with knee function prior to injury. It evaluates sports activities based on ability to run, jump and land, stop and start quickly, ascend and descend stairs, stand, kneel on the front of the knee, squat, sit with the knee bent, and rise from a chair. Response types include 5-point Likert scales, 11-point Likert scales and dichotomous "yes or no" responses. The IKDC has been proven to be a valid and reliable instrument for patients suffering from knee injury and disability.