Factors Affecting the Speed of Recovery After ACL Reconstruction

Anterior cruciate ligament (ACL) tears of the knee are frequently repaired by surgically implanting a tendon graft in place of the torn original cruciate ligament. The graft may be taken from the patient having the repair (an autologous graft) or from a cadaver (an allograft). Complete recovery from surgical repair of an anterior cruciate ligament reconstruction requires that the graft becomes firmly engrafted at the site, surrounding tissues are healed and strength is restored in muscles that control movements at the knee. The recovery process typically requires from six months to one year. Pain in the early phase of recovery is typically moderate to severe and may be a major factor determining patient return to normal activity. It may also be a major factor limiting the patient's ability to cooperate with rehabilitation maneuvers. Traditional methods of treatment for pain include use of opioid pain killers (such as morphine) and/or femoral nerve block at the groin. The potential hazards of opioid pain killers include opioid side effects (nausea, vomiting, constipation, drowsiness, respiratory depression and the potential for developing opioid dependency=addiction). Pain in the early phase of recovery, if severe, can lead to changes in the spinal cord that predispose to amplifying pain sensations, thus intensifying the need for pain killer medicines, a process referred to as "windup" or neuroplasticity. Similarly, the use of opioid pain killers may activate pain amplification systems potentially contributing to persistence of pain and favoring development of chronic pain. For these reasons, there is a belief that early aggressive efforts to treat postoperative pain, and minimize the use of opioid pain killers, can have significant benefits to patients both by improving their comfort level after surgery; facilitating rehabilitation efforts and return to normal activity. Anesthesiologists at the University of Washington may use pain medicines alone and/or perform a nerve block to help patients undergoing ACL repair with their pain control. Patients are given a choice as to their desired methods of pain control. These options are normally discussed by the regional block team with the patient prior to surgery and the merits of each discussed. Approximately 60-70% of patients typically request the use of nerve blocks in the recovery unit to help control their pain. For those patients who choose a nerve block, the anesthesiologist will choose to perform the nerve block at the level of the groin or the mid thigh. This decision varies by provider and is typically random in nature. Both locations for the nerve block appear to work most of the time and each may have small differences: the speed of onset is typically faster when performed at groin level, while quadriceps muscle function may be less affected when performed at mid thigh. Neither method is known to be superior for this type of surgery. Because patients are non-weight bearing for at least the first 24 hours after surgery and must use crutches for mobilization, the weakening of the quadriceps muscles may be relatively unimportant during that time. The investigators hypothesize that pain treatment after ACL reconstruction which includes a nerve block in combination with other pain medications will be associated with better pain control immediately after surgery and will minimize the need for patients to use opioid pain killers and experience common opioid- related side effects. A secondary hypothesis is that the effectiveness of pain control, whether by pain medicines, and/or in combination with nerve blocks will determine the patient's ability to perform routine activities of daily living in the acute phase (0-7 days), and subsequently may affect their ability to perform physical therapy maneuvers that are prescribed for their routine care. STUDY PURPOSE Aim 1: Determine whether pain reported by patients after surgery is related to the type of pain control utilized - (1) either intravenous and oral pain medication alone, (2) combined with nerve block at the groin, or (3) combined with nerve block at the mid thigh. Aim 2: Examine whether pain severity affects the ability of patients to perform activities of daily living in the acute phase (recovery index measured at 7 days), and physical therapy maneuvers in the ensuing 6 months after surgery possibly retarding restoration of muscle function in the affected leg. Aim 3: Determine whether preoperative psychologic tests designed to assess patients' coping skills (Pain Catastrophizing score) and anxiety (Stait anxiety index) predict postoperative pain reported by patients, acute phase recovery scores (recovery index), and rehabilitation endpoints