Both Ultrasound guided Adductor Canal Block ( ACB) and Femoral Nerve Block (FNB) has been used to provide postoperative analgesia for knee surgeries. To the investigators' knowledge, no comparison has been made between those blocks in relation to postoperative quadriceps muscle strength, or duration and quality of postoperative analgesia for arthroscopic ACL reconstruction in pediatrics. If ACB provides postoperative analgesia after arthroscopic knee surgery comparable to FNB, it has the potential to improve the postoperative outcome as it will lead to less quadriceps muscle weakness and early mobilization, both of which are very important in the early postoperative period.

Motor preservation with adequate analgesia has become the optimal postoperative goal in orthopedic surgeries, in particular knee surgeries. This enables earlier physical therapy, faster recovery and shorter hospital stays. Both Ultrasound guided ACB and FNB has been used to provide postoperative analgesia for knee surgeries, including anterior cruciate ligament reconstruction . To the investigators' knowledge, no comparison has been made between both blocks in relation to postoperative quadriceps muscle strength as well as duration and quality of postoperative analgesia for arthroscopic ACL reconstruction. ACB predominantly block the sensory component of the femoral nerve without much effect on the motor component. Hence, it can lead to less quadriceps muscle weakness, early postoperative mobilization and decreases the incidence of postoperative fall . With the advent of ultrasonography, the adductor canal can be easily visualized at the mid-thigh level, allowing performance of ACB with a high success rate . In recent years, ACB has been successfully used for postoperative pain control after knee surgery . Anatomical study of adductor canal demonstrated that the adductor canal may serve as a conduit for more than just the saphenous nerve, possibly including the vastus medialis nerve, medial femoral cutaneous nerve, articular branches from the obturator nerve, as well as the medial retinacular nerve . Thus, the sensory change is not limited to the distribution of the saphenous nerve but includes the medial and anterior aspects of the knee from the superior pole of the patella to the proximal tibia.To the investigators Knowledge there has not been a randomized controlled study comparing ACB with FNB after Arthroscopic Anterior Cruciate Ligament (ACL) reconstruction. This prospective, double-blinded, randomized, controlled study will test the hypothesis that ACB would be associated with less quadriceps motor weakness than FNB at 4 hours after block performance . The investigators also hypothesize that ACB will provide analgesia to the anterior knee that is not inferior to FNB and not different in opioids usage at 4 and 24 hours after Peripheral Nerve Block (PNB) performance .

• Hypothesis ACB would be associated with less quadriceps motor weakness than FNB and provide postoperative analgesia comparable to FNB in quality and duration as determined by Numeric Scale (NS) pain scores and opioid use a 4 and 24 hours after PNB.
• Objectives

To compare FNB and ACB regarding:

1. Quadriceps muscle strength at 4 hours after PNB performance.

2. Pain scores at anterior knee at 4 hours and 24 hours after PNB as assessed by Numeric Scale (NS) pain scoring system. Also pain site other than the anterior knee will be recorded and specified (posterior knee, calf, leg)

3. Total opioid consumption at 4 and 24 hours after PNB.

   • Study Design:

Randomized, double blinded, single center clinical trial. A total of 52 pediatric patients (ASA 1or 2), aged between 8 to 18 years, for elective ACL reconstruction at Akron Children's Hospital ( ACH ) will be enrolled in the study. Patients will be randomly assigned to one of two groups, A or B. Group A (26 patients) will have ultrasound guided ACB performed at mid-thigh level and group B (26 patients) will have ultrasound guided FNB, with nerve stimulator confirmation with the type of motor response (e.g., quadriceps, patellar) and the minimum current needed to be recorded. Both blocks will be performed under general anesthesia. Both group will have ropivacaine 0.2 % ( 0.5 ml/kg, maximum of 30 ml and methylprednisolone acetate 1 mg/kg , maximum of 40 mg ).Both blocks will be performed using a 22-gauge 2-inch Stimuplex A needle; ; B. Braun Medical Inc., Melsungen, Germany).Both blocks will be performed using linear ultrasound transducer, General Electric ( GE). Ultrasound pictures will be obtained to Verify proper local anesthetic placement.Unfortunately, surgeons are not able to determine the type of procedure needed to correct ACL injury, until after knee arthroscopy is performed under general anesthesia. ACL reconstruction using a hamstring graft, which is the surgical procedure used in this study may not always be possible to perform by the surgeon. The surgical alternative of ACL reconstruction , is ACL repair, which seldomely is done by our surgeon. Patient undergoing ACL reconstruction can experience pain in the posterior aspect of the knee, in the distribution of the siatic nerve. This is due to the hamstring graft. In contrast to the anterior knee pain covered by both ACB and FNB, posterior knee pain is controlled with IV/oral analgesic. This is why recording the site of the knee pain is important to determine the PNB success. . Due to the inability to determine beforehand, the type of procedure to be performed, we decided therefore to continue the study procedures and data collection on both ACL reconstruction and ACL repair. The statistical analysis will include only patients that undergo ACL reconstruction. For the other patients that undergo ACL repair , data will be collected but not included in the statistical analysis. The data from these patients may be used as a pilot for future research.

Quadriceps strength of both legs will be assessed by placing the dynamometer on the anterior of the ankle, between the malleoli. Patients will be instructed to extend their legs three times each, with a 30 seconds pause between each attempt as described by Maffiuletti . The assessment will be performed in the pre-operative period and will be repeated postoperatively at 4 hours after PNB. All patients will be observed in the post-operative period by an observer unaware of the technique of analgesia used. Pain will be assessed using the NS. Postoperatively, PCA morphine pumps will be attached to patients. A loading dose of 0.05 mg/kg to a maximum of 5 mg will be administered in the Post Anesthesia Care unit (PACU) as needed, followed by demand interval dosing of 0.015 mg/kg every 10 minutes.as demanded by the patient .Four-hours limits for morphine will be set at 0.35 mg/kg. No continuous infusion and no adjuvant NSAIDs or acetaminophen will be administered. Rescue morphine dosing will be ordered via PCA pump at 0.05 mg/kg ( repeated once as needed) and will be available every two hours as needed by pain assessment ( for a NS ≥ 4 ) or patient request. Diazepam 0.03 mg/kg IV will be available every 4 to6 hours as needed for muscle spasm or anxiety. Patients will be considered ready for discharge from hospital when all the following criteria are met: Child is alert, oriented, stable vital signs, and would tolerate clear liquid, with no nausea or vomiting and good pain control. The evaluation for meeting the discharge criteria will be done after one hour from arrival in PACU and every 30 minutes thereafter till the patient meet all the discharge criteria. After discharge, After discharge, parents will be instructed to give the child oxycodone tablets/elixir 0.1 mg /kg PO q 3 hours as needed for pain. In addition, acetaminophen 10mg/kg q 4 hours PRN up to a maximum of 3 gm and/or ibuprofen 10 mg/kg q 6 hours PRN up to maximum of 2400 mg/24 hours, may be administered for any residual pain. The total dose of oxycodone, ibuprofen and tylenol will be recorded per parents for a total of 24 hours after PNB. Pain scores will be also recorded by parent at rest,24 hours post -block. The data for total opioids use in the first 24 hours after PNB and pain score at 24 hours will be collected from parent by phone call.

• Study Endpoints

  1-Quadriceps muscle strength at 4 after PNB 2- Total morphine/morphine equivalent at 4 and 24 hours after PNB. 3-Pain scores at anterior knee at 4 hours and 24 hours after PNB as assessed by Numeric Scale (NS) pain scoring system. Also pain site other than the anterior knee will be recorded and specified (posterior knee, calf, leg).

• Method for Assigning Subjects to Treatment Regimen Random allocation for one of the two treatments will be achieved using sealed envelope assigned by external third party not involved in the study to ensure allocation concealment.

• Study Monitoring Plan This study will be monitored through a data monitoring committee. The study will be performed over a period of 18-24 months. This study offers minimal risk to the patient. The data monitoring committee will include the PI, at least one of the co-investigators, the principal statistician, and the principal research nurse.

The data monitoring committee will meet when approximately 25%, 50%, 75% and 100% of the primary outcomes are observed. The priority of the data monitoring committee will be to ensure the safety of the participants in the trial and to ensure the integrity of the trial. Also, these meetings will monitor the quality of the collected data to assess for weaknesses and errors. If any weakness and/or errors are identified, feedback will be provided during these meetings .The investigator(s) will allocate adequate time for such monitoring activities. The investigator(s) will also ensure that the monitor or other compliance or quality assurance reviewer is given access to all the above noted study-related documents.

-Summary Statistics: Will be provided for all variables. Examination of continuous data will include normality testing as well as assessment of potential outliers. Statistical testing will be based upon distributional shape, but for purpose of analytical planning and sample size analysis normality of distributions will be assumed.

To examine for potential differences in quadriceps motor strength (QMS) between the two groups (ACB, FNB) quadriceps strength will be assessed at the four hour time point (assuming no evidence in sample of baseline or pre-operative differences). Non-inferiority of ACB to FNB in analgesia provided will be assessed by examination of pain scores. Non-inferiority of ACB compared with FNB is defined as the mean ACB - NRS pain score not higher than the mean FNB - NRS pain score by an amount of 1.6. (Kim, 2014) Pain scores will be individually examined at the 4 hour and 24 hour post - operative time points with appropriate Bonferroni adjusted alpha. In addition, a change in pain score from 4 to 24 hours will be created and evaluated for potential difference between groups.

Total opioid consumption as measured in morphine equivalents will be assessed at the 24 hour post-operative time point to determine whether a difference exists. Opioid consumption will also be examined by creating a change score from 4 to 24 hour consumption and comparing between the groups.

All testing will be completed utilizing SAS 9.4 © software and evaluated at the Type I Error Rate of alpha = 0.05 level for statistical significance unless otherwise noted.

Inclusion Criteria:

• ASA I or II
• Age 8 to 18 years
• All research subjects must have an acceptable legally authorized representative capable of giving consent on the subject's behalf.

Exclusion Criteria:

• Those who were unable to use a standard 0-10 NS
• Infection at the site of the block
• Bleeding disorders
• Allergy to the drugs used to perform the block ( ropivacaine , methylprednisolone)
• Those who refused a nerve block or enrollment in the study.