1 Discuss the use of regional anesthesia in the setting of ACL repair

ACL rupture is one of the most frequent knee injuries, affecting 100,000 to 200,000 people in the United States each year [1]. After arthroscopically assisted knee procedures, patients often report severe postoperative pain aggravated by both passive and active movement and potentially resulting in poor functional outcome. Following ACL repair, regional anesthesia (RA) can provide excellent postoperative pain relief and allow early rehabilitation [2]. Better pain control leads to improved patient satisfaction and earlier mobilization, with associated decreased hospital stay and costs [3]. Regional anesthesia techniques have a record of safety and reliability for patients undergoing ACL repair [4] and do not compromise operating room efficiency [5].

For arthroscopic and open-knee procedures, the femoral nerve block (FNB) is frequently used for postoperative analgesia, in combination with intraoperative anesthesia [6]. When compared with intra-articular or intravenous opioids, FNB has been demonstrated to improve postoperative pain control, provide early mobilization, and increase patient satisfaction [7]. Other authors, though, have questioned its efficacy in improving patient outcome when compared with intra-articular opioids alone for arthroscopic ACL reconstruction [8].

Other RA techniques employed for postoperative pain relief after ACL repair include fascia iliaca blocks (FIB) [9], lumbar plexus blocks [10], the combination of femoral and obturator nerve blocks [11], and saphenous block [12]. Combined peripheral techniques of lumbar and sacral plexus blocks together have also been described as an alternative to spinal or general to provide intraoperative anesthesia [13].

The FIB, a block of the femoral nerve and lateral femoral cutaneous nerve of the thigh, is relatively simple, safe, and provides effective analgesia postoperatively. A recent study found an opioid-sparing effect for at least 24 hours after ACL reconstruction in 47 patients randomized either to saline or to 0.2% bupivacaine injections for FIB [9].

Lumbar plexus blocks are more effective than 3-in-1 block (a block of the femoral, lateral femoral cutaneous, and obturator nerves) for ACL patients. A study by Cappelleri et al. showed that patients receiving a lumbar plexus block achieved higher rate of successful sensory and motor block of all three of those nerves [10]. In fact, 78% of the lumbar plexus group showed a complete loss of pinprick sensation in the distribution of the lateral femoral cutaneous nerve vs. only 17% in the 3-in-1 group. Obturator nerve motor block was also better achieved with the lumbar plexus approach.

The involvement of the obturator nerve during ACL reconstruction has been extensively demonstrated. The addition of the obturator nerve block to femoral and sciatic nerve blocks improves intraoperative anesthesia specifically when ACL repair is performed with gracilis autograph [11]. However, it is questionable whether continuing obturator analgesia into the postoperative period is necessary in this patient population [11].

The adductor canal block (ACB) was recently compared with FNB in 80 patients undergoing ACL reconstruction with patellar tendon autograft, and ACB was shown to provide similar and adequate postoperative analgesia [12]. The advantage of performing an ACB instead of a more proximal FNB is evidenced by its quadriceps motor-sparing effect. When compared with FNB in total knee arthroplasty, ACB showed less quadriceps weakness while demonstrating comparable effective pain control and opioid consumption in the first postoperative hours [14].

2. Elaborate on the outcomes achieved by employing regional vs. only general anesthesia

Since the 1990s, many authors have investigated the effects of general, regional, and combined general–regional anesthesia on ambulatory orthopedic procedures, with the aim to achieve the optimal combination of patient perioperative comfort and rapid hospital discharge.

Patients receiving regional analgesia combined with general anesthesia (GA) show improved recovery profiles and lower unexpected admission rates [15]. Although increased costs could be required for local anesthetics and materials when combined general–regional anesthesia is performed, many authors demonstrated that regional anesthesia (RA) allows fewer nursing interventions for common postoperative symptoms and reduces the duration of stay in the PACU [16–17]. Many authors agree that regional techniques for outpatient orthopedics may play a significant role in simultaneously containing costs and improving patient care [15–16, 18–19].

Reports of direct comparisons of GA vs. RA in this setting are lacking. However, the improvement in postoperative pain associated with an FNB compared to GA alone has significant advantages, especially in the early postoperative hours. In the pediatric population after arthroscopic knee surgery, femoral nerve block is associated with shortened hospital stays, reduced opioid requirements, decreased postoperative pain scores, as well as lower postoperative admission rates [20].

Femoral nerve block also improves postoperative pain when combined with spinal anesthesia [21–22]. However, some other authors have questioned the long-term benefits of FNB in association with subarachnoid anesthesia in this patient population [23].

3. Describe how the use of autograph vs. allograft can affect the postoperative recovery

Suture repair of the ACL is avoided, given it has a technique failure rate of 40 to 100%. This is because the synovial fluid and cellular metabolism are altered with injury and lead to poor functional healing [24–26]. Due to the high failure rate associated with primary repair, injury is corrected with reconstruction of the ligament. In ligament reconstructions, the ACL tissue is removed and replaced with a tendon graft harvested either from the medial hamstrings (semitendinosus or gracilis muscles) or the middle third of the patellar tendon, or by using allograft tissue.

Although ACL reconstruction is an excellent operation for restoring knee stability, the procedure is associated with several morbidities, including a risk for early post-injury osteoarthritis [27]. Others argue that ACL reconstruction may not alter the natural course of the injured knee [28]. The type of graft chosen for reconstruction also has a role. A recent large prospective study found patients receiving patellar tendon autografts to have lower incidence of the need for revision compared with patients receiving hamstring autografts [29].

Regardless of the technique, arthroscopic ACL reconstruction is a painful procedure requiring adequate postoperative pain management. Different regional techniques are required according to the surgical technique performed. When patellar tendon is used for autograph, continuous FNB provides better analgesia than continuous patellar tendon wound or intra-articular infusions [30]. However, when donor grafts other than patella tendon are used, femoral nerve block may not cover the donor site. In these cases, local infiltration analgesia can cover the donor site and is associated with few complications [31]. Some also suggest blocking the obturator nerve when using a hamstring autograft, particularly if it is performed with the gracilis tendon. The semitendinosus tendon is innervated by the tibial nerve, while the gracilis tendon is innervated by the obturator nerve. Thus the combination of only femoral and sciatic nerve blocks may be insufficient for intraoperative anesthesia. Allografts are well covered by FNB.

4. Review the utility of sciatic nerve blocks for postoperative analgesia

In a recent study, subjects scheduled for an ACL reconstruction, requesting GA and preoperative placement of a peripheral nerve block, were randomized to receive a femoral nerve block alone or combined with a sciatic nerve block. Significantly higher analgesic requirements, pain scores, and lower satisfaction scores were noted in the femoral group when compared to the femoral–sciatic group [32]. The sciatic nerve block provided superior postoperative analgesia in patients receiving an ACL reconstruction and should be included in the anesthetic care plan to facilitate postoperative analgesia. These results were confirmed in a pediatric population of 36 children undergoing ACL reconstruction where femoral and sciatic blocks provided better analgesia with fewer side effects than intra-articular infusions [33]. However, caution must be taken when performing sciatic nerve block when a hamstring autograft is to be used, as nerve injury has been reported during the tendon harvest at this donor site [34].