In the early 1990s orthopaedic surgeons moved from the open to the arthroscopic anterior cruciate ligament reconstruction (ACLR). This dramatically changed the postoperative approach needed for pain control, allowing these procedures to be done on an outpatient basis. Studies done since that time have looked at how best to treat pain for this procedure and facilitate postoperative rehabilitation. Femoral nerve blocks contributed significantly to multimodal analgesia in the immediate postoperative period, but concerns about neurological complications and prolonged quadriceps palsy encouraged continued investigations for alternatives. With the rapid progress and application of ultrasound, the ability to provide a purely sensory block of the saphenous nerve with reliability became possible. This chapter explores the historical development of the saphenous nerve block as a postoperative analgesic adjuvant for orthopaedic surgery and the way this experience is now being applied to provide pain relief following ACLR.

The anatomy of the saphenous nerve and its importance for knee innervation have long been generally understood. A branch of the posterior division of the femoral nerve, the saphenous nerve enters the adductor canal and exits through the intermuscular septum at the medial side of the knee joint, providing sensory innervation to the medial and anterior aspects of the leg. However, the way this general understanding of the saphenous nerve specifically contributed to knee innervation continued to improve. In 1982 integrating anatomical and neurophysiological studies, Kennedy et al. identified the infrapatellar nerve splitting from the saphenous nerve between the sartorius and gracilis muscles to supply innervation to the medial capsule, patellar tendon, and anterior aspect of the knee. Additionally, they noted the branch to the vastus medialis supplies a portion of the anteromedial capsule.

Expanding upon this histologic work, Horner and Dellon illustrated the innervation of the medial aspect of the knee, describing the course of the terminal branch of the medial femoral cutaneous nerve and finding that it often runs through Hunter’s (adductor) canal and “pairs” with the infrapatellar branch of the saphenous nerve. Deep to these structures and branching off at a more proximal level is the terminal branch of the nerve to the vastus medialis, which innervates the medial retinacular and articular surfaces. They reported that in a small percentage of specimens, a branch of the obturator nerve contributed to the subsartorial plexus in the adductor canal.

In turn, this broader and more detailed understanding of saphenous nerve anatomy and innervation has led to a variety of efforts to block the saphenous nerve for pain relief. In 1989 investigators described using local anatomical landmarks to inject a local anesthetic-steroid mixture into the adductor canal of patients meeting clinical criteria for saphenous nerve entrapment. Eighty percent experienced pain relief. Additionally, to improve saphenous nerve blockade below the knee, van der Wal et al. investigated a blind transsartorial approach to the saphenous nerve with and without nerve stimulation. With stimulation, the success rate was 95% in a volunteer population. Nerve stimulation was then intentionally utilized to elicit muscle contraction of the medial thigh during saphenous nerve blockade performed at the midthigh level. This approach was confirmed by others who noted that they found no associated quadriceps weakness with the block.

Though either blind or nerve-stimulator-assisted blind techniques continued to be reported, by 2005 the use of ultrasound to identify and anesthetize peripheral nerves was well established. Three different approaches to saphenous nerve blockade have been investigated: first, a perifemoral approach at the midthigh (otherwise referred to as an adductor canal block or subsartorial saphenous nerve block); second, a more distal approach 5–10 cm proximal to the medial femoral condyle, termed the “modified vastus medialis” or “transsartorial” approach; and third, by isolation and blockade of the infrapatellar nerve at its branch point from the saphenous nerve. A recent meta-analysis of saphenous nerve block effectiveness using these various ultrasound approaches for knee surgery is encouraging.

Three recent studies (2008–2014) have looked at the use of the saphenous nerve block for meniscal surgery. Utilizing an ultrasound transsartorial approach, investigators blocked the saphenous nerve for supplemental analgesia of the knee following medial menisectomy. Their success rate improved to 100%, versus the 80% success of the previously described blind technique. Additionally, both opioid consumption and pain with walking were lower in the treatment group for the first 24 hours. The authors considered this a “pioneering” study, demonstrating that the saphenous nerve block could be effective in arthroscopy. A second study employed the adductor canal block for medial menisectomy. In addition to the block, patients received a multimodal regimen, which included local anesthetic infiltration of the portals, acetaminophen, nonsteroidal anti-inflammatories, and opioids on an as-needed basis. Pain scores upon arrival to the postanesthesia care unit, the study’s primary outcome, were significantly lower in the treatment group (mean Numerical Rating Scale score: 3.25 versus 1.71). A third study, again using an adductor canal block in addition to multimodal analgesia for minor arthroscopic surgery, found no difference between treatment and placebo except a small reduction in initial opioid use. The authors of the second two studies acknowledged that the levels of pain following these procedures may be adequately addressed through multimodal analgesia alone, although specific patients with lower pain thresholds might benefit from this additional intervention. Overall, these studies demonstrated that ultrasound-guided saphenous nerve block could be a successful and effective adjuvant, particularly for more painful procedures.

To date, there are conflicting results on saphenous nerve block for ACLR. In 2011 Lundblad et al. utilized an infrapatellar block compared with placebo control in 64 patients undergoing ACLR with semitendinosus autografts. They hypothesized that local infiltration of the knee provides pain relief during the first 12 hours postoperatively. When a block, having previously been demonstrated to last 27 hours, is added, pain control should be extended and sleep improved for the first 24 hours. The block was placed preoperatively, and a multimodal regimen included intra-articular local anesthetic injection, local infiltration of portals, cryotherapy, acetaminophen, and opioids as needed. Their results concurred with their hypothesis. Observations postoperatively were divided into the early period (1–12 hours) and late period (13–24 hours). The percentage of pain assessments—visual analogue scale/numerical rating scale (VAS/NRS) pain scores >3 (moderate to severe pain) at rest—was significantly lower in the treatment group ( P = .019), particularly in the late period ( P = .0117), as was pain with activity (late period: P = .0039). The block lasted a median of 23 hours and was found to increase the number of sleep hours ( P = .0269) following ACLR.

In 2013 Espelund et al. published contrasting results. A randomized control trial with 50 patients undergoing ACLR also using semitendinosus autografts was conducted. After the surgical procedure was completed, patients received an adductor canal block and a postoperative multimodal analgesic regimen. Unlike the Lundblad study, where the primary outcome was improved pain scores in the latter half of the first 24 postoperative hours, this study was powered to detect a difference for a time point 2 hours following surgery. No difference was found. Additionally, they found no difference in their secondary outcomes, the weighted average of pain scores at rest, during standing or after walking for the first 24 hours. The authors acknowledged that pain scores overall were significantly lower than anticipated (VAS: median 20 mm in both groups), suggesting that multimodal analgesia alone is a satisfactory postoperative analgesic regimen. As with minor arthroscopic procedures, they posited that a nerve block may prove beneficial in a select subset of patients with lower pain thresholds.

In 2014 Chisholm et al. published a randomized control study comparing saphenous nerve block to femoral nerve block in patients undergoing bone–tendon–bone, rather than semitendinosus, autograft ACLR. The primary outcome was the number of hours patients reported NRS pain scores of less than 5 (with scores of 5 or above reflecting moderate to severe pain) for the immediate 48 hours postoperatively. This period demonstrated similar scores for both groups. Patient satisfaction scores were higher for the femoral nerve block on postoperative day one, equalizing with the study group on postoperative day two. However, this was not seen to be clinically significant, as the side effect profile (nausea, vomiting, use of antiemetics, drowsiness, itching, dry mouth, and headaches) was similar in each group. The authors concluded that saphenous nerve blockade provided similar analgesia to the femoral nerve block for patellar tendon ACLR.

Studies in total knee arthroplasty patients that compare femoral nerve blocks with the saphenous nerve block have also found comparable levels of postoperative analgesia, with the added benefit of increased ambulation in those who received the saphenous nerve block. These studies all demonstrate that the saphenous nerve block can be an effective alternative to the femoral nerve block for pain relief.

Still, the question persists: Is postoperative pain severe enough to warrant adjuvant blockade in addition to multimodal analgesic regimen for ACLR? This question was continuously debated with respect to femoral nerve blockade throughout the previous decade. One study in particular demonstrated significant pain relief from a single injection femoral nerve block for patients undergoing ACLR. Despite this, some concluded that a femoral nerve block provided little benefit. In response, others argued that this first 24-hour benefit should not be minimized.

Acknowledging the importance of the first 24 hours postoperatively, and with findings in both total knee arthroplasty and ACLR patients showing that the saphenous nerve block is not inferior to the femoral nerve block for pain control, evidence suggests that it can be a useful adjuvant to a multimodal pain regimen following ACLR. This is particularly true following reconstruction with bone–tendon–bone autograft, where the nerve block includes the site of the graft.

Ongoing issues revolve around where specifically to perform the block and whether or not there is a risk of quadriceps weakness related to each location. As previously mentioned, studies describe performing the ultrasound-guided block at three general locations: at the midthigh for the adductor canal block; at a point 7–10 cm proximal to the medial condyle for the transsartorial or trans-vastus saphenous nerve block; and again more distally for a selective infrapatellar block. The two approaches distal to the adductor canal can be recommended to prevent quadriceps weakness since theoretically they avoid local anesthetic backflow, which might block the femoral nerve or lead to associated weakness from isolated vastus medialis nerve blockade. However, most interventionalists now perform a perifemoral nerve block at the adductor canal. It is technically easier, since the superficial femoral artery is readily identifiable on ultrasound and provides an easy landmark because the saphenous nerve runs just adjacent to it. This is the recommended approach for the less experienced interventionalist. Kent et al. demonstrated a 100% success rate with this approach, compared with an 80% success rate for the trans-vastus approach.

Since this block is now more commonly performed in the proximal thigh, concerns about associated quadriceps weakness arise. Jaeger et al. compared maximum voluntary isometric contraction (MVIC) in volunteers receiving an adductor canal block, a femoral nerve block, or placebo. Results showed that the mean quadriceps MVIC was 51% for femoral nerve blocks, 92% of baseline for adductor canal blocks, and 6% above baseline for placebo. A second study found quadriceps strength preserved with adductor canal block in comparison to the femoral nerve block. Jaeger et al. evaluated postoperative quadriceps strength in total knee arthroplasty patients randomized to either adductor canal block or femoral nerve block. The adductor canal group had improved quadriceps function following surgery that promoted early ambulation. A more recent study also showed improved quadriceps function following adductor nerve blockade after total knee replacement. Admittedly, this is a very different cohort than those who present for ACLR. Future studies comparing baseline to postoperative quadriceps strength following saphenous nerve blockade are warranted.

The debate continues over what specifically is blocked at the adductor canal. This debate also highlights the confusion in the literature regarding the block name: subsartorial saphenous nerve block and adductor canal block are both used, and controversy continues over what specifically is blocked and where. Some believe that other nerves in addition to the saphenous nerve are blocked at the midthigh: the infrapatellar branch, the medial cutaneous femoral nerve, the nerve to the vastus medialis, and branches of the obturator nerve. Together the anesthetization of these nerves may enhance the analgesic effect at the knee and hence the name for this collective block: adductor canal block. Others argue that, though these nerves may be present, no studies to date have definitively demonstrated that anything other than the saphenous nerve is blocked, hence subsartorial —even though the location remains the adductor canal.

To date, very little is known about complication rates following the saphenous nerve block. In 2013 a very limited study looked at the prevalence of saphenous nerve injury following adductor canal block in total knee arthroplasty. No patient had persistent sensory changes related to in the medial aspect of the lower leg. In the region of the infrapatellar nerve, 82% did have sensory changes, which the authors report was consistent with well-known complications associated with the surgical procedure. Collective data over time is needed to provide a more reliable incidence of complications.

In summary, the saphenous nerve block is a useful adjuvant to a multimodal analgesic regimen for ACLR. This is especially true for patients undergoing bone–tendon–bone autograft, although a subset of patients with lower pain thresholds receiving semitendinosus autografts may also benefit from this intervention. No saphenous nerve blockade studies were done in patients undergoing ACLR with allografts. It seems appropriate to categorize this as another type of minor arthroscopic procedure, where saphenous nerve blockade might be a helpful adjuvant decided on a case-by-case basis. Studies done in total knee arthroplasty patients showed preserved strength and improved ambulation following blockade, but further study in the ACLR population is needed to address postoperative quadriceps strength following saphenous nerve blockade. Evidence to date suggests that it is indeed a motor-sparing block. In this regard, the evaluation of postoperative quadriceps strength over time, information defining the appropriate volume of local anesthetic injectate, and comparison of the different approaches to saphenous nerve blockade would all be important avenues for future investigation.

In the early 1990s orthopaedic surgeons moved from the open to the arthroscopic anterior cruciate ligament reconstruction (ACLR). This dramatically changed the postoperative approach needed for pain control, allowing these procedures to be done on an outpatient basis. Studies done since that time have looked at how best to treat pain for this procedure and facilitate postoperative rehabilitation. Femoral nerve blocks contributed significantly to multimodal analgesia in the immediate postoperative period, but concerns about neurological complications and prolonged quadriceps palsy encouraged continued investigations for alternatives. With the rapid progress and application of ultrasound, the ability to provide a purely sensory block of the saphenous nerve with reliability became possible. This chapter explores the historical development of the saphenous nerve block as a postoperative analgesic adjuvant for orthopaedic surgery and the way this experience is now being applied to provide pain relief following ACLR.

The anatomy of the saphenous nerve and its importance for knee innervation have long been generally understood. A branch of the posterior division of the femoral nerve, the saphenous nerve enters the adductor canal and exits through the intermuscular septum at the medial side of the knee joint, providing sensory innervation to the medial and anterior aspects of the leg. However, the way this general understanding of the saphenous nerve specifically contributed to knee innervation continued to improve. In 1982 integrating anatomical and neurophysiological studies, Kennedy et al. identified the infrapatellar nerve splitting from the saphenous nerve between the sartorius and gracilis muscles to supply innervation to the medial capsule, patellar tendon, and anterior aspect of the knee. Additionally, they noted the branch to the vastus medialis supplies a portion of the anteromedial capsule.

Expanding upon this histologic work, Horner and Dellon illustrated the innervation of the medial aspect of the knee, describing the course of the terminal branch of the medial femoral cutaneous nerve and finding that it often runs through Hunter’s (adductor) canal and “pairs” with the infrapatellar branch of the saphenous nerve. Deep to these structures and branching off at a more proximal level is the terminal branch of the nerve to the vastus medialis, which innervates the medial retinacular and articular surfaces. They reported that in a small percentage of specimens, a branch of the obturator nerve contributed to the subsartorial plexus in the adductor canal.

In turn, this broader and more detailed understanding of saphenous nerve anatomy and innervation has led to a variety of efforts to block the saphenous nerve for pain relief. In 1989 investigators described using local anatomical landmarks to inject a local anesthetic-steroid mixture into the adductor canal of patients meeting clinical criteria for saphenous nerve entrapment. Eighty percent experienced pain relief. Additionally, to improve saphenous nerve blockade below the knee, van der Wal et al. investigated a blind transsartorial approach to the saphenous nerve with and without nerve stimulation. With stimulation, the success rate was 95% in a volunteer population. Nerve stimulation was then intentionally utilized to elicit muscle contraction of the medial thigh during saphenous nerve blockade performed at the midthigh level. This approach was confirmed by others who noted that they found no associated quadriceps weakness with the block.

Though either blind or nerve-stimulator-assisted blind techniques continued to be reported, by 2005 the use of ultrasound to identify and anesthetize peripheral nerves was well established. Three different approaches to saphenous nerve blockade have been investigated: first, a perifemoral approach at the midthigh (otherwise referred to as an adductor canal block or subsartorial saphenous nerve block); second, a more distal approach 5–10 cm proximal to the medial femoral condyle, termed the “modified vastus medialis” or “transsartorial” approach; and third, by isolation and blockade of the infrapatellar nerve at its branch point from the saphenous nerve. A recent meta-analysis of saphenous nerve block effectiveness using these various ultrasound approaches for knee surgery is encouraging.

Three recent studies (2008–2014) have looked at the use of the saphenous nerve block for meniscal surgery. Utilizing an ultrasound transsartorial approach, investigators blocked the saphenous nerve for supplemental analgesia of the knee following medial menisectomy. Their success rate improved to 100%, versus the 80% success of the previously described blind technique. Additionally, both opioid consumption and pain with walking were lower in the treatment group for the first 24 hours. The authors considered this a “pioneering” study, demonstrating that the saphenous nerve block could be effective in arthroscopy. A second study employed the adductor canal block for medial menisectomy. In addition to the block, patients received a multimodal regimen, which included local anesthetic infiltration of the portals, acetaminophen, nonsteroidal anti-inflammatories, and opioids on an as-needed basis. Pain scores upon arrival to the postanesthesia care unit, the study’s primary outcome, were significantly lower in the treatment group (mean Numerical Rating Scale score: 3.25 versus 1.71). A third study, again using an adductor canal block in addition to multimodal analgesia for minor arthroscopic surgery, found no difference between treatment and placebo except a small reduction in initial opioid use. The authors of the second two studies acknowledged that the levels of pain following these procedures may be adequately addressed through multimodal analgesia alone, although specific patients with lower pain thresholds might benefit from this additional intervention. Overall, these studies demonstrated that ultrasound-guided saphenous nerve block could be a successful and effective adjuvant, particularly for more painful procedures.

To date, there are conflicting results on saphenous nerve block for ACLR. In 2011 Lundblad et al. utilized an infrapatellar block compared with placebo control in 64 patients undergoing ACLR with semitendinosus autografts. They hypothesized that local infiltration of the knee provides pain relief during the first 12 hours postoperatively. When a block, having previously been demonstrated to last 27 hours, is added, pain control should be extended and sleep improved for the first 24 hours. The block was placed preoperatively, and a multimodal regimen included intra-articular local anesthetic injection, local infiltration of portals, cryotherapy, acetaminophen, and opioids as needed. Their results concurred with their hypothesis. Observations postoperatively were divided into the early period (1–12 hours) and late period (13–24 hours). The percentage of pain assessments—visual analogue scale/numerical rating scale (VAS/NRS) pain scores >3 (moderate to severe pain) at rest—was significantly lower in the treatment group ( P = .019), particularly in the late period ( P = .0117), as was pain with activity (late period: P = .0039). The block lasted a median of 23 hours and was found to increase the number of sleep hours ( P = .0269) following ACLR.

In 2013 Espelund et al. published contrasting results. A randomized control trial with 50 patients undergoing ACLR also using semitendinosus autografts was conducted. After the surgical procedure was completed, patients received an adductor canal block and a postoperative multimodal analgesic regimen. Unlike the Lundblad study, where the primary outcome was improved pain scores in the latter half of the first 24 postoperative hours, this study was powered to detect a difference for a time point 2 hours following surgery. No difference was found. Additionally, they found no difference in their secondary outcomes, the weighted average of pain scores at rest, during standing or after walking for the first 24 hours. The authors acknowledged that pain scores overall were significantly lower than anticipated (VAS: median 20 mm in both groups), suggesting that multimodal analgesia alone is a satisfactory postoperative analgesic regimen. As with minor arthroscopic procedures, they posited that a nerve block may prove beneficial in a select subset of patients with lower pain thresholds.

In 2014 Chisholm et al. published a randomized control study comparing saphenous nerve block to femoral nerve block in patients undergoing bone–tendon–bone, rather than semitendinosus, autograft ACLR. The primary outcome was the number of hours patients reported NRS pain scores of less than 5 (with scores of 5 or above reflecting moderate to severe pain) for the immediate 48 hours postoperatively. This period demonstrated similar scores for both groups. Patient satisfaction scores were higher for the femoral nerve block on postoperative day one, equalizing with the study group on postoperative day two. However, this was not seen to be clinically significant, as the side effect profile (nausea, vomiting, use of antiemetics, drowsiness, itching, dry mouth, and headaches) was similar in each group. The authors concluded that saphenous nerve blockade provided similar analgesia to the femoral nerve block for patellar tendon ACLR.

Studies in total knee arthroplasty patients that compare femoral nerve blocks with the saphenous nerve block have also found comparable levels of postoperative analgesia, with the added benefit of increased ambulation in those who received the saphenous nerve block. These studies all demonstrate that the saphenous nerve block can be an effective alternative to the femoral nerve block for pain relief.

Still, the question persists: Is postoperative pain severe enough to warrant adjuvant blockade in addition to multimodal analgesic regimen for ACLR? This question was continuously debated with respect to femoral nerve blockade throughout the previous decade. One study in particular demonstrated significant pain relief from a single injection femoral nerve block for patients undergoing ACLR. Despite this, some concluded that a femoral nerve block provided little benefit. In response, others argued that this first 24-hour benefit should not be minimized.

Acknowledging the importance of the first 24 hours postoperatively, and with findings in both total knee arthroplasty and ACLR patients showing that the saphenous nerve block is not inferior to the femoral nerve block for pain control, evidence suggests that it can be a useful adjuvant to a multimodal pain regimen following ACLR. This is particularly true following reconstruction with bone–tendon–bone autograft, where the nerve block includes the site of the graft.

Ongoing issues revolve around where specifically to perform the block and whether or not there is a risk of quadriceps weakness related to each location. As previously mentioned, studies describe performing the ultrasound-guided block at three general locations: at the midthigh for the adductor canal block; at a point 7–10 cm proximal to the medial condyle for the transsartorial or trans-vastus saphenous nerve block; and again more distally for a selective infrapatellar block. The two approaches distal to the adductor canal can be recommended to prevent quadriceps weakness since theoretically they avoid local anesthetic backflow, which might block the femoral nerve or lead to associated weakness from isolated vastus medialis nerve blockade. However, most interventionalists now perform a perifemoral nerve block at the adductor canal. It is technically easier, since the superficial femoral artery is readily identifiable on ultrasound and provides an easy landmark because the saphenous nerve runs just adjacent to it. This is the recommended approach for the less experienced interventionalist. Kent et al. demonstrated a 100% success rate with this approach, compared with an 80% success rate for the trans-vastus approach.

Since this block is now more commonly performed in the proximal thigh, concerns about associated quadriceps weakness arise. Jaeger et al. compared maximum voluntary isometric contraction (MVIC) in volunteers receiving an adductor canal block, a femoral nerve block, or placebo. Results showed that the mean quadriceps MVIC was 51% for femoral nerve blocks, 92% of baseline for adductor canal blocks, and 6% above baseline for placebo. A second study found quadriceps strength preserved with adductor canal block in comparison to the femoral nerve block. Jaeger et al. evaluated postoperative quadriceps strength in total knee arthroplasty patients randomized to either adductor canal block or femoral nerve block. The adductor canal group had improved quadriceps function following surgery that promoted early ambulation. A more recent study also showed improved quadriceps function following adductor nerve blockade after total knee replacement. Admittedly, this is a very different cohort than those who present for ACLR. Future studies comparing baseline to postoperative quadriceps strength following saphenous nerve blockade are warranted.

The debate continues over what specifically is blocked at the adductor canal. This debate also highlights the confusion in the literature regarding the block name: subsartorial saphenous nerve block and adductor canal block are both used, and controversy continues over what specifically is blocked and where. Some believe that other nerves in addition to the saphenous nerve are blocked at the midthigh: the infrapatellar branch, the medial cutaneous femoral nerve, the nerve to the vastus medialis, and branches of the obturator nerve. Together the anesthetization of these nerves may enhance the analgesic effect at the knee and hence the name for this collective block: adductor canal block. Others argue that, though these nerves may be present, no studies to date have definitively demonstrated that anything other than the saphenous nerve is blocked, hence subsartorial —even though the location remains the adductor canal.

To date, very little is known about complication rates following the saphenous nerve block. In 2013 a very limited study looked at the prevalence of saphenous nerve injury following adductor canal block in total knee arthroplasty. No patient had persistent sensory changes related to in the medial aspect of the lower leg. In the region of the infrapatellar nerve, 82% did have sensory changes, which the authors report was consistent with well-known complications associated with the surgical procedure. Collective data over time is needed to provide a more reliable incidence of complications.

In summary, the saphenous nerve block is a useful adjuvant to a multimodal analgesic regimen for ACLR. This is especially true for patients undergoing bone–tendon–bone autograft, although a subset of patients with lower pain thresholds receiving semitendinosus autografts may also benefit from this intervention. No saphenous nerve blockade studies were done in patients undergoing ACLR with allografts. It seems appropriate to categorize this as another type of minor arthroscopic procedure, where saphenous nerve blockade might be a helpful adjuvant decided on a case-by-case basis. Studies done in total knee arthroplasty patients showed preserved strength and improved ambulation following blockade, but further study in the ACLR population is needed to address postoperative quadriceps strength following saphenous nerve blockade. Evidence to date suggests that it is indeed a motor-sparing block. In this regard, the evaluation of postoperative quadriceps strength over time, information defining the appropriate volume of local anesthetic injectate, and comparison of the different approaches to saphenous nerve blockade would all be important avenues for future investigation.