Neuraxial anesthesia, either spinal or epidural, may be utilized for ACL reconstruction surgery, although the duration of action in these ambulatory procedures is necessarily limited to the period of surgical intervention, in contrast to procedures carried out in the inpatient setting, for which long-acting opioids may be added or an epidural catheter may be utilized for 24 h (or longer) of pain relief. These central blocks allow for rapid onset, minimal patient discomfort during the procedures, and improved immediate postoperative pain relief [52]. Avoiding general anesthesia for simple and complex knee procedures by utilizing neuraxial blockade and incorporating peripheral nerve blockade for the more painful surgeries has been shown to reduce postoperative pain and nausea and reduce unexpected admission [74].

Most data related to subarachnoid block (spinal block) and ambulatory knee surgery are derived from studies of knee arthroscopy. In general, these have demonstrated that the subarachnoid block provided superior immediate postoperative pain control, reduced requirements for opioids in the early postoperative phase, a higher ability to “bypass” the PACU, and lower rates of postoperative nausea and vomiting (PONV) [33, 38] in comparison to the use of general anesthesia. However, a meta-analysis [42] did not support lower PONV rates for spinal anesthetics. Most of these studies did not reveal earlier discharge from the hospital with spinal block, despite the noted advantages. However, lower-dose spinals, particularly when utilized in a “unilateral” application (which can be accomplished by placing patients in lateral position during block administration), do allow for more rapid resolution and earlier ambulation [54] than conventional doses, especially when they affect both legs. Inclusion of opioids, such as fentanyl, in the spinal block allows for lower doses and faster return of function [55], but this may come at the cost of side effects such as nausea and pruritus [54]. In addition, when compared to peripheral nerve blockade, such as femoral and sciatic nerve blocks, spinal anesthesia may result in prolonged times to urination and recovery of ambulation, adversely affecting discharge times for ambulatory procedures [13].

In 2003, Williams et al. summarized the experience at a major university hospital’s sports orthopedics program, over a 4-year period, accounting for 1,200 ambulatory knee procedures [72]. In this observational study, the authors evaluated the experience of patients for whom a specified perioperative management pathway, incorporating neuraxial anesthesia and/or peripheral nerve blocks of various types, had been utilized, for simple knee arthroscopy or one of six complex procedures. Patients undergoing the complex procedures were more at risk for pain and benefitted to a greater degree from the use of either neuraxial anesthesia or peripheral nerve blockade, with better control of pain and a markedly decreased risk of unexpected hospital admission, when compared to similar patients who did not receive blocks.

In summary, subarachnoid block as a primary anesthetic technique has been well studied in ambulatory knee procedures and offers potential advantages over standardized general anesthetic techniques, including improved early pain control, reduced PONV (in some studies), and improved ability to bypass the PACU, all of which may have a favorable impact on patient satisfaction. However, there is less literature available comparing this type of neuraxial anesthetic to general anesthesia when optimized with multimodal analgesia and complementary peripheral nerve blockade for postoperative analgesia.

Regional anesthesia has many potential benefits and should be considered as a component of a multimodal treatment plan for the ACLR patient, in order to minimize the side effect burden of opioid medications (Tables 9.2). Peripheral nerve blockade is practical and effective for pain control in the perioperative setting, for orthopedic procedures and other painful surgeries [22, 61]. In a meta-analysis, Liu et al. found that both neuraxial and peripheral nerve blockade reduced postoperative pain scores and reduced PACU analgesic administration compared to general anesthesia [42]. However, in this analysis, only peripheral blocks reduced postoperative nausea and vomiting.

Peripheral nerve block (PNB) techniques have been shown to be quite efficacious in controlling the pain of ACL reconstruction. In general, PNB offers a variety of desirable effects in ambulatory orthopedic surgery. These include reduced pain scores in the immediate aftermath of surgery, reduced opioid use as well as reduced side effects from opioids (such as nausea and dizziness), diminished time in the postanesthesia care unit (PACU), higher likelihood of bypassing the PACU completely, and earlier discharge from the hospital [24, 25, 49]. Patient satisfaction is also improved [24, 25], in comparison to the use of general anesthesia without PNB. In addition, patients are able to take oral fluid and food and walk sooner than with general anesthesia alone, and patient satisfaction scores are increased [24].

For ACLR, femoral nerve block is most commonly employed (Fig. 9.1a, b). As noted above, the femoral nerve provides capsular innervation to the knee, as well as innervation of the skin over the patella, the medial aspect of the knee (in some patients), and the infrapatellar region, via the saphenous nerve’s infrapatellar branch [15]. In 2006, Williams et al. conducted a randomized, controlled trial of single injection and continuous PNB compared to multimodal pharmacologic analgesic techniques, utilizing intraoperative ketamine with postoperative oral immediate- and gradual-release opioids as well as nonsteroidal anti-inflammatory agents [75]. Both of the PNB groups reported lower pain scores than the control group at 24 h after surgery, and there were no functional sequelae at the 6-month postoperative evaluation. In a comprehensive review, Stein et al. noted the reported benefits of FNB in ACLR as improved early postoperative pain control, reduced use of opioids, and fewer opioid side effects [65].

Other studies have shown substantial improvements in pain control with femoral nerve block in ACLR as well. Wulf et al. evaluated several different types and concentrations of local anesthetics for analgesia in ACLR. Compared to placebo, all of the FNB groups had significantly lower pain scores and opioid requirements in the immediate postoperative period, up to 4 h [76]. In a retrospective review of 376 pediatric cases of ACLR, in which 35 % of patients had received femoral block, Schloss et al. reported a reduction in postoperative pain scores, lower opioid requirements, a shorter hospital stay, and reduced admission rate in those who had received the nerve blocks [60]. Williams et al. in an assessment of the impact of a perioperative analgesia pathway in 1,200 patients undergoing ambulatory knee surgery reported better pain control, reduced opioid use, and earlier discharge from the PACU in those with complex procedures (including ACLR) when nerve blocks were included in the anesthetic management [72]. In a later observational study of 948 patients undergoing ACL reconstruction, Williams et al. reported that the use of femoral and sciatic nerve blocks was associated with a markedly reduced requirement for admissions to the phase I recovery (vs. direct admission to phase II recovery) and also a more than 75 % reduction in unexpected hospital admission, with an attendant drop in hospital costs of 12 % [73]. Other trials evaluating the impact of femoral nerve block in ACLR have resulted in similar findings [31, 53].

Adductor canal block (ACB) (Fig. 9.2a, b) has taken on increasing importance and popularity as a means of providing analgesia in total knee arthroplasty (TKA), with minimal or no quadriceps weakness, thus allowing earlier participation in rehabilitation [32], with a lower likelihood of falls [23]. In an early assessment of the use of ACB, this block did not appear to be as effective for analgesia for ACLR as it has for TKA [16]. However, in a more recent evaluation of ACB for ACLR, Espelund et al. found that pain was significantly better controlled compared to the use of general anesthesia, with sparing of quadriceps strength compared to the group which received a block of the femoral nerve [17].

More distal approaches to saphenous nerve branches have been utilized in an attempt to provide analgesia while sparing quadriceps function. Lundblad et al. in a randomized trial of 64 patients compared a standard multimodal regimen to infrapatellar nerve block, provided just above the level at which the saphenous nerve divides [43]. Compared to a sham block, this reduced pain significantly at 16–24 h (as the medications provided for multimodal analgesia were resolving) and improved the ability of patients to sleep in the first postoperative night.

When the semitendinosus tendon is utilized as an autograft for ACLR, femoral nerve blockade will not provide analgesia to the region of the harvest. This may be addressed with pharmacologic methods, or with sciatic nerve blockade, either proximally, in the gluteal region, or distally, in the proximal popliteal fossa (Fig. 9.3a, b) [1]. In many regional anesthesia-oriented practices, a supplement sciatic block is provided routinely for this situation [72]. In addition, drilling and tunneling through the proximal tibia for ACLR occur in an area in which the sciatic nerve may also play a role in innervation and postoperative pain. Finally, as noted above, the anterior capsule of the knee receives significant innervation in its inferior and lateral aspects from the common peroneal nerve [19]. For all of these reasons, sciatic nerve block may be necessary to complement FNB, even when the ACLR utilized allograft or patellar- or quadriceps-tendon autograft. Hibbard et al. evaluated 50 such patients in a prospective, observational trial and found that in 20 % of cases, patients complained of moderate-to-severe postoperative pain in PACU, despite a functioning femoral nerve block and multiple doses of postoperative opioids; all of these patients received rapid relief from a supplemental postoperative sciatic nerve block [26].

Some orthopedists have attempted to address the posterior pain of hamstring harvest more directly. Bushnell et al. conducted a comparative trial of injection of bupivacaine 0.25 % into the hamstring donor site, as compared to no injection, in which all patients received preoperative femoral nerve block [8]. Visual analog pain scores were 2–3.5 units higher in those without block during the immediate postoperative period. Likewise, Fauno et al. found that a directed hamstring injection of local anesthetic provided superior pain control in the PACU and immediate postoperative period [18].

While the obturator nerve is known to innervate the knee joint capsule and often innervates the skin over the medial aspect of the joint [15], its role in pain of ACLR is less certain. There are no comparative trials exploring the utility of the obturator nerve block in this setting. Anecdotally, a rare patient with refractory medial pain after ACLR may obtain relief when an obturator nerve block is provided as a “rescue” in the postoperative phase. Obturator block may be most effectively conducted in the proximal thigh [67] or with a posterior “lumbar plexus block” in the low lumbar region [36]; attempts to block this nerve as part of a multicomponent “three in one” block at the groin, with high volumes of local anesthetic solution, are considerably less successful.

The guidance technique by which PNB is carried out, for femoral and sciatic blocks, has gradually transitioned in North America from the use of peripheral nerve stimulation (PNS) to ultrasound (US) over the past 10 years. In prior decades, PNS offered both relative accuracy and a high degree of safety [5, 7]; however, US guidance offers many additional benefits. These include ability to image the anatomy at bedside and to plan the safest and most direct route of needle placement, reducing the likelihood of encountering a blood vessel [47]. While this is but a “surrogate” marker for intravascular injection, the use of US guidance has clearly been shown to reduce the likelihood of intravascular injection with local anesthetic systemic toxicity, which may be a life-threatening occurrence [6, 56, 63]. US guidance allows continuous imaging of the needle in its course toward the intended target, with less chance of insertion into the nerve. Finally, the use of US imaging allows ongoing evaluation of the disposition of the local anesthetic solution as it is injected, resulting in improved accuracy, higher degree of efficacy, shorter time required for block placement, more rapid onset of anesthesia, and increased duration of block [2]. While some practitioners prefer to use PNS in concert with US guidance, this has not been shown to enhance block success for femoral nerve block [62].

Surgeon-directed, specific local infiltration analgesia (LIA) during the surgery is becoming more popular during total knee arthroplasty. Some investigators have attempted to examine the effects of these techniques in ACLR as well. Dauri et al. performed a randomized trial in ALCR patients, of continuous FNB for postoperative analgesia, versus continuous infusion of ropivacaine into the patellar tendon donor site in concert with intra-articular infusion [12]. All patients received single-shot femoral and sciatic blocks. Pain scores at 12 and 24 h were lower in the group with the femoral nerve catheter infusion, as were oral analgesic requirements. In a comparative trial of LIA vs. femoral block for postoperative analgesia after ACLR, Kristensen reported no differences in pain or opioid consumption between the two groups [39].

Peripheral nerve block catheters allow for continuous infusion of local anesthetic solutions to provide ongoing analgesia after painful extremity surgeries. Most practitioners leave them in place for 48–72 h. Continuous techniques may be used for inpatients [30] as well as outpatients [66], in which case patients go home with a disposable pump and remove the catheter themselves. Catheters allow for prolonged pain relief, improved analgesia compared to opioids [58], reduced opioid use and side effects [29, 30], improved sleep and patient satisfaction [30], and earlier discharge from the hospital [6, 8], in studies in which this has been specifically investigated. Further, they allow a degree of titration, with adjustment of concentration or flow rates, that is not possible with single-shot blocks, as well as the ability to turn the infusion off immediately if any symptoms of toxicity should occur or if the extremity becomes insensate [50]. Multiple-day infusions of dilute concentrations of local anesthetic at standard infusion rates appear to be safe in those with normal volume of distribution and hepatic/renal function [35].