Abstract
Background: Continuous femoral or lumbar plexus blocks have been demonstrated to provide effective postoperative analgesia of the lower extremity following total joint arthroplasty. The purpose of this study was to compare these two techniques when used with intravenous patient-controlled analgesia and the use of patient-controlled analgesia alone for postoperative pain management following unilateral primary hip arthroplasty.
Methods: Two hundred and twenty-five patients undergoing unilateral total hip arthroplasty for a diagnosis of osteoarthritis were randomly allocated into one of three postoperative treatment groups: continuous lumbar plexus block with patient-controlled analgesia, continuous femoral block with patient-controlled analgesia, and patient-controlled analgesia alone. Scores on a visual analog pain scale administered during physiotherapy twenty-four hours postoperatively were used as the primary outcome measured. Secondary outcomes included scores on a visual analog pain scale at rest, hydromorphone consumption, opioid-related side effects, complications, sensory and motor blockade, and patient satisfaction.
Results: Continuous lumbar plexus block significantly reduced pain scores during physiotherapy on postoperative day 1 (p < 0.0001) and day 2 (p < 0.0001) compared with either continuous femoral block or patient-controlled analgesia alone. There were no significant differences for pain at rest between the two regional analgesic techniques. Both regional anesthesia techniques significantly reduced total hydromorphone consumption (p < 0.05) and delirium (disorientation to time and/or place) compared with patient-controlled analgesia alone (p < 0.023). In addition, the use of continuous lumbar plexus block was associated with fewer patients with opioid-related side effects (p < 0.05), greater distances walked (p < 0.05), and enhanced patient satisfaction (p < 0.05) compared with the use of a continuous femoral nerve block with patient-controlled analgesia or with patient-controlled analgesia alone.
Conclusions: Continuous lumbar plexus and femoral blocks significantly reduce the need for opioids and decrease related side effects. Continuous lumbar plexus block is a more effective analgesic modality than is a continuous femoral block or patient-controlled intravenous administration of hydromorphone alone during physical therapy following primary unilateral total hip arthroplasty.
Level of Evidence: Therapeutic Level I. See Instructions to Authors for a complete description of levels of evidence.
Postoperative pain management for total joint arthroplasty recently has been the object of considerable attention1,2. The magnitude of pain following primary total hip arthroplasty is generally considered to be mild to moderate at rest, but mobilization of the joint is usually associated with an increased level of pain and an increased need for opioids. Since it is well established that the frequency and magnitude of opioid-related complications are dose-dependent3, a perioperative regimen that reduces the opioid requirement of patients who have undergone primary hip arthroplasty would be advantageous. Failure to provide adequate analgesia hinders the effective participation in early physiotherapy that is critical to accelerating the immediate functional recovery of patients undergoing lower-extremity joint replacement4-6.
Postoperative epidural analgesia with use of opioids has been shown to be an effective alternative to patient-controlled analgesia7, but the increased risks of epidural hematoma in patients receiving anticoagulation and central neuraxial blockade have precluded its use beyond the immediate postoperative period8. This has stimulated orthopaedic surgeons and anesthesiologists to seek other analgesic alternatives.
Single-injection femoral blocks or lumbar plexus blocks have been shown to provide limited postoperative analgesia. Biboulet et al. reported no analgesic benefit with either single-injection femoral or lumbar plexus block at rest and during mobilization after a primary hip arthroplasty, and approximately 50% of those patients had no evidence of a sensory block after twenty-four hours9. In contrast, the use of a continuous femoral or lumbar plexus block has been demonstrated to provide effective and lasting postoperative analgesia after total hip arthroplasty7,10,11. In the absence of a comparison between these techniques, it is difficult to assess which one should be recommended. On the basis of the observation that the hip achieves a substantial portion of its innervation from the lumbar plexus, we hypothesized that a comprehensive lumbar plexus block through a psoas approach would be superior to a less comprehensive block (through a femoral approach) in achieving postoperative analgesia.
This prospective, randomized clinical study was designed to compare the effectiveness of continuous lumbar plexus and femoral blocks with that of patient-controlled analgesia alone for the management of pain in patients undergoing primary total hip arthroplasty. We also compared the effects of each analgesic technique on opioid consumption and related side effects, including delirium, nausea, pruritus, the extent of sensory and motor block, complications related to the analgesic technique, the ability to walk, and patient satisfaction.
Following institutional review board approval, and after written informed consent had been provided, 225 patients who were between eighteen and eighty years of age and had an American Society of Anesthesiologists classification of 1, 2, or 3; a primary diagnosis of osteoarthritis; and were scheduled for unilateral primary total hip arthroplasty through the posterolateral approach12 were enrolled. This study was registered with (NCT00790179). The study design was a prospective, randomized clinical trial conducted from May 2003 through November 2005. Exclusion criteria included allergy to local anesthetics, peripheral neuropathy, proven opioid dependency, laboratory evidence of a coagulopathy (with an international normalized ratio of >1.4), a platelet count of <100,000, and dementia as assessed by evidence of memory loss indicated by a lack of orientation to person, place, and time. On the morning of surgery, the patients were randomly allocated by the primary investigator, according to a computer-generated randomization schedule that was arranged in permuted blocks of three, to one of three postoperative analgesia treatment groups: the patient-controlled analgesia group (control), which received intravenous hydromorphone alone administered with a patient-controlled analgesia pump (LifeCare 4100 PCA Plus II infuser; Abbott Laboratories, Chicago, Illinois); the lumbar plexus block group, which received a continuous lumbar plexus block and intravenous patient-controlled analgesia with hydromorphone; and the femoral block group, which received a continuous femoral block and intravenous patient-controlled analgesia with hydromorphone.
Patient-controlled analgesia with hydromorphone was initiated in the recovery room and was provided to all patients for forty-eight hours. It was calibrated to deliver a dose of 0.3 mg of hydromorphone every ten minutes with a maximum of 1.2 mg per hour. A supplemental bolus of 1.0 mg of intravenous hydromorphone was available (every six hours) for breakthrough pain when pain scores exceeded a visual analog scale score of 5 (with 0 indicating no pain and 10, the worst imaginable pain). To provide a multimodal analgesic approach, all patients also received an intramuscular injection of 30 mg of ketorolac in the recovery room13. The administration of ketorolac was repeated six hours later.
Prior to surgery, each patient received oral premedication consisting of 20 mg of famotidine and 10 mg of metoclopramide. Anesthesia (0.75% hyperbaric bupivacaine for a total dose of 1.4 mg) was provided through a spinal route and was supplemented with intravenous doses of =0.05 mg/kg of midazolam and 100 µg of fentanyl at the discretion of the individual anesthesiologist. Intraoperative monitoring consisted of a continuous two-lead electrocardiogram, noninvasive blood-pressure monitoring, and oxygen saturation.
The continuous nerve blocks were administered in the recovery room by one of six anesthesiologists, all of whom were experienced in regional anesthesia. The blocks were administered on resolution of the spinal anesthetic below the L1 dermatome. The continuous femoral block14 and the continuous lumbar plexus block10 were performed with use of an 18G insulated Tuohy needle (B. Braun Medical, Bethlehem, Pennsylvania) connected to a nerve stimulator (Stimuplex Dig; B. Braun Medical). Irrespective of the type of block, the optimal needle placement was verified by a brisk quadriceps contraction (proximal movement of the patella) with a current output of 0.5 mA, frequency of 2 Hz, and pulse width of 100 µs. After the stimulating introducing needle was properly positioned, a loading dose of 0.6 mL/kg of 0.5% ropivacaine (maximum dose, <300 mg) was injected in the continuous femoral block group. This was followed by the placement of a perineural catheter advanced a maximum distance of 10 cm.
The patients receiving continuous lumbar plexus block received a bolus of 0.6 mL/kg of 0.5% ropivacaine after the perineural catheter was advanced 3 cm past the introducing needle. The position of the lumbar plexus catheter was confirmed with an injection of 10 mL of iohexol contrast medium (Omnipaque 180; Amersham Health, Oslo, Norway) followed by an anteroposterior radiograph. Prior to discharge of the patient from the postanesthetic care unit, the perineural catheters were connected to an infusion pump (Abbott Plum A+; Abbott Laboratories) set up to infuse 0.2% ropivacaine at a rate of 0.15 mL/kg/hr for forty-eight hours. Successful continuous blockade was evaluated in both groups and was defined as a loss of sensation to cold touch and pinprick in the cutaneous distributions of the femoral nerve twenty-four hours after the initial local anesthetic injection bolus.
Following surgery, each patient was enrolled in the same clinical pathway consisting of a standard postoperative physiotherapy regimen with passive and active hip flexion (flexion to 70°) and extension exercises for one hour on the mornings of the first and second postoperative days. On these days, all patients were asked to get out of bed and to perform assisted walking with use of a walker and supervised by a physical therapist (once per day). On each postoperative day, the maximum degree of hip flexion achieved and the distances walked were recorded by the physical therapist using the following scale: 0 to 10 ft (0 to 3 m), 11 to 20 ft (3.35 to 6 m), 21 to 40 ft (6.4 to 12.2 m), and >40 ft (>12.2 m).
Pain scores were measured with use of a visual analog scale at rest at two hours and one hour before beginning physical therapy, at twenty-four and forty-eight hours postoperatively, and during each physiotherapy session. Time zero was defined as the time of complete resolution of the spinal anesthetic. Hydromorphone consumption, opioid-related side effects (nausea, vomiting, pruritus, delirium, and respiratory depression), and patient satisfaction (with use of a 10-point categorical scale, with 0 indicating no satisfaction with analgesic modality and 10, complete satisfaction with analgesic modality) were recorded at two, twelve, twenty-four, and forty-eight hours. In the group receiving the continuous lumbar plexus block, the international normalized ratio was recorded on removal of the perineural catheter.
Sensory and motor function were evaluated after block placement at two, twenty-four, and forty-eight hours postoperatively. The intensity of the sensory block was assessed at the level of the anterior aspect of the thigh (the femoral nerve), the lateral aspect of the thigh (the lateral femoral cutaneous nerve), and over the lateral aspect of the foot (the sciatic nerve) with use of cold and light touch with alcohol and a cotton swab. Because the cutaneous contribution of the obturator nerve is variable15, successful blockade of the obturator nerve was evaluated by assessment of adductor muscle strength (thigh adduction against resistance of the examiner's hand)16. Femoral motor block was evaluated by assessment of quadriceps muscle strength. The degree of motor block of the obturator and femoral nerves was assessed with use of a 4-point Bromage scale17 (with 0 corresponding to full active flexion-extension ability; 1, impaired active hip flexion; 2, impaired active hip and knee flexion; and 3, total motor blockade) at twenty-four and forty-eight hours.
Finally, symptoms of block-related nerve injury (dysesthesia or persistent sensory deficit assessed twenty-four hours after discontinuation of the ropivacaine infusions) were assessed by the study investigators just prior to hospital discharge and by the primary orthopaedic surgeon on the first postoperative office visit. Nurses recorded opioid consumption and opioid-related side effects, and physical therapists recorded pain scores before and during physical therapy, the rehabilitation milestones, and the Bromage scores17.
Statistical Methods
The primary end point was the visual analog scale score during physiotherapy at twenty-four hours postoperatively. A power analysis was performed with use of a one-way analysis of variance comparing the expected visual analog scale scores for the three groups on the basis of data reported by Singelyn and Governeur7. It yielded a sample size of sixty-seven patients per group to detect an effect size of 0.5, with a power of 80% and a level of significance of 0.05.
All data are presented as the mean and the standard deviation or the mean and the 95% confidence interval. Data were analyzed with use of an intention-to-treat approach and a repeated-measures analysis of variance (repeated-measures analysis of variance with group-by-time interaction) to compare differences in visual analog scale scores, opioid consumption, satisfaction scores, and range of motion among the groups. As none of the group-by-time interactions were significant, only the results for main effects are presented. Alpha was set at a level of 0.05. When significant, pairwise comparisons were performed with use of a Bonferroni correction whereby any pairwise comparison was considered significant only if p < 0.017 (0.05/3). The differences in the frequency of opioid-induced delirium, complications, motor and sensory blocks, and ability to walk >40 ft (12.2 m) were analyzed with use of the chi-square or Fisher exact test where appropriate. Bromage scores were compared with use of the Mantel-Haenszel chi-square test.
Source of Funding
There was no external funding for this study.
The flow of the 225 patients who participated in the study is presented in Figure 118.
The demographic data, duration of surgery, and duration of hospitalization were similar in all three groups and are presented in a table in the Appendix.
Radiographic Analysis
All lumbar plexus catheters injected with 10 mL of iohexol contrast medium (Omnipaque) were examined with use of anteroposterior radiographs. The injection of sixty-three (84%) of seventy-five lumbar plexus catheters produced a spindle-like opacification, suggesting that the catheter tip was within the psoas muscle, and twelve (16%) produced a blotchy-type opacification, suggesting that the catheter tip placement was between the quadratus lumborum and psoas muscles10,19 (see Appendix).
Postoperative Pain
Figure 2 depicts the pain scores on the visual analog scale at rest at two, twenty-four, and forty-eight hours and during physical therapy at twenty-four and forty-eight hours postoperatively. The mean pain scores on the visual analog scale during physical therapy (at twenty-four and forty-eight hours) were significantly lower in the continuous lumbar plexus block group (3.5 [95% confidence interval, 3.0-4.0] and 2.6 [95% confidence interval, 2.0-3.2], respectively) compared with the continuous femoral block group (5.8 [95% confidence interval, 5.2-6.4] and 4.7 [95% confidence interval, 4.1-5.3]) (p < 0.05) or the group that had patient-controlled analgesia alone (6.4 [95% confidence interval, 5.9-6.9] and 4.8 [95% confidence interval, 4.3-5.3]) (p < 0.05), illustrating that a continuous lumbar plexus block provided more effective pain control during mobilization than either patient-controlled analgesia alone or a continuous femoral block for the entire forty-eight-hour study period. Pain at rest was moderate (<4 in all groups) and was not affected by the modality of postoperative pain treatment.
Hydromorphone Consumption
Table I presents the cumulative consumption of hydromorphone for each group over the forty-eight-hour study period. The use of either peripheral nerve block technique was associated with a significant reduction in cumulative hydromorphone consumption compared with patient-controlled analgesia alone (p < 0.05). A significantly higher number of patients requiring no opioid during the forty-eight-hour study period was observed in the continuous lumbar plexus block group (nine of seventy-five patients) compared with the continuous femoral block group (four of seventy-five patients) (p < 0.05).
Complications Related to the Postoperative Analgesia Technique
Continuous Nerve Block Techniques
The performance of a lumbar plexus block was associated with an epidural spread in five (7%) of seventy-five patients. Postoperatively, two lumbar plexus catheters (3%) clotted compared with none of the femoral catheters. In addition, two (3%) of the seventy-five femoral catheters were found to be ineffective postoperatively. Therefore, the total failure rate for both the lumbar plexus and femoral catheters was 3%. There was no evidence of any untoward neurologic sequelae or local anesthetic toxicity in either of the catheter groups.
At the time of removal of the lumbar plexus catheters, the mean international normalized ratio (and standard deviation) was 1.8 ± 0.2 and no perineural hematoma was recorded.
Patient-Controlled Analgesia with Hydromorphone
The use of patient-controlled analgesia with hydromorphone alone led to significantly more frequent serious delirium and/or confusion (defined as a complete loss of orientation to time and space) (10.7%) than when patient-controlled analgesia was combined with either a continuous lumbar plexus (0%) or femoral nerve block (1.3%) (p < 0.05).
As indicated in Table II, the opioid-related side effects paralleled hydromorphone consumption. Nausea, ondansetron (Zofran) consumption, and pruritus were more frequent in the group that had patient-controlled analgesia alone than in the continuous lumbar plexus block and continuous femoral block groups. In addition, except for pruritus, opioid-related side effects were significantly more frequent with the use of a femoral catheter than with a lumbar plexus catheter.
Patient Satisfaction
The continuous lumbar plexus block group, continuous femoral block group, and patient-controlled analgesia group had overall patient satisfaction scores of 8.9 (95% confidence interval, 8.4 to 9.4), 7.2 (95% confidence interval, 6.7 to 7.7), and 6.1 (95% confidence interval, 5.3 to 6.9), respectively. As indicated in Table II, the use of a continuous lumbar plexus block was associated with a significantly higher score for patient satisfaction compared with the use of patient-controlled analgesia alone or a continuous femoral nerve block (p < 0.05).
Sensory and Motor Block Intensity
Sensory blockade of the femoral and lateral femoral cutaneous nerves occurred with a high frequency in the continuous lumbar plexus block and continuous femoral nerve block groups throughout the forty-eight-hour study period. Three patients in the continuous lumbar plexus block group also demonstrated sciatic sensory blockade at two hours. Significant (p < 0.05) intergroup differences regarding blockade of the obturator nerve were recorded at two hours (Fig. 3). A motor block of the obturator nerve was demonstrated in 74% of the patients with a lumbar plexus block compared with 20% of the patients with a femoral nerve block. In addition, blockade in the femoral nerve distribution was more evanescent in the continuous lumbar plexus block group compared with the continuous femoral block group over the forty-eight-hour period (Fig. 3). Table III presents the degree of motor block measured with Bromage scores17 at twenty-four and forty-eight hours, demonstrating a significantly more pronounced motor block with the femoral compared with the lumbar plexus approach at both time points.
Physical Therapy
Although all patients walked on the first postoperative day and completed the physiotherapy protocol sustaining the maximum duration and achieving the prescribed 70° of hip flexion at twenty-four and forty-eight hours, the number of patients who were able to walk >40 ft (12.2 m) at forty-eight hours was significantly greater in the continuous lumbar plexus block group compared with both the femoral block group and the patient-controlled analgesia group (14.7%, 1.3%, and 1.3%, respectively; p < 0.003).
This study demonstrates that a continuous lumbar plexus block with patient-controlled analgesia provided better analgesia during physiotherapy than either patient-controlled analgesia alone or a continuous femoral block with patient-controlled analgesia. The use of a continuous lumbar plexus block also favorably affected secondary outcomes such as decreased opioid use, nausea, rescue antiemetic use, patient satisfaction, and the ability to walk longer distances. The beneficial effects associated with the use of a continuous lumbar plexus block extended over the entire forty-eight-hour study period. Our findings confirm the earlier results of Capdevila et al., who demonstrated that the use of a continuous lumbar plexus block provides effective analgesia at rest and during physiotherapy after primary hip arthroplasty10. However, those authors did not compare the benefit of this technique with either patient-controlled analgesia or continuous femoral nerve block.
In the present study, the prolonged reduction in opioid consumption was associated with a significant decrease in opioid-related side effects and serious complications. Nine octogenarians experienced opioid-induced delirium and/or confusion necessitating premature discontinuation of the intravenous infusion; eight patients were in the patient-controlled analgesia group and one was in the continuous femoral block group. These patients were placed in a monitored setting for twenty-four hours and ultimately were discharged without any adverse long-term sequelae. These results confirm the problematic potential of the systemic administration of postoperative opioids in a fragile elderly population20-22. Our findings also illustrate the increasing concern related to the use of patient-controlled opioid administration voiced by a recent Anesthesia Patient Safety Foundation workshop3.
Anatomical differences between the femoral and lumbar plexus approaches likely account for some of the difference between the effectiveness of a continuous lumbar plexus block and a continuous femoral nerve block. The hip joint is mostly supplied by the branches of the lumbar plexus (femoral, obturator, and lateral femoral cutaneous nerves) and the sciatic nerve. Clinical and radiographic studies have demonstrated the inability of a femoral nerve block to provide simultaneous blockade of the three branches of the lumbar plexus, especially the obturator nerve23,24. In contrast, the lumbar plexus block provides a more consistent blockade of these three principal branches25,26. A continuous infusion of local anesthetic into the lumbar plexus is likely to produce a more complete block of the femoral, obturator, and lateral femoral cutaneous nerves since the nerves course closely through the psoas muscle27. In this study, significantly more patients with a lumbar plexus block demonstrated adductor weakness compared with those with a femoral block (Fig. 3). These results confirm the result previously reported by Kaloul et al. who demonstrated an extension of the blockade into the obturator territory in a substantially higher percentage of patients with a continuous lumbar plexus compared with those with a continuous femoral infusion following a total knee arthroplasty27. In these conditions, it is not surprising that less pain was recorded in the patients treated with a lumbar plexus catheter. Radiographic analysis of the distribution of contrast medium in the continuous lumbar plexus block group revealed a substantially higher rate of catheter tip placement within the psoas muscle rather than into the area between the psoas and quadratus lumborum muscles10. However, comparable visual analog scale pain scores and hydromorphone consumption rates between these two types of contrast medium distribution (data not presented) indicate that catheter tip placement within the psoas muscle is not required for optimal analgesic efficacy.
Continuous perineural injection techniques have resulted in accelerated physiotherapy and reduced length of stay after major joint surgery28. Although all patients in our study achieved the prescribed degree of hip flexion during physiotherapy and walked on the first postoperative day, patients in the continuous lumbar plexus block group walked significantly greater distances than those in either the continuous femoral block or patient-controlled analgesia groups. Improved analgesia, less motor block, and a lower prevalence of opioid-related side effects likely account for these findings.
Two limitations concerning our study design merit discussion. It is well established that length of stay is dependent on both effective postoperative analgesia and a clinical pathway including early and consistent intensive physical therapy sessions28. Our protocol included only one daily physical therapy session. Therefore, an additional study is required to determine if the use of a more aggressive physical therapy program combined with a continuous lumbar plexus block may lead to a reduction in length of stay. Another limitation of the study is the difference in the timing of local anesthetic bolus administration. Bolus placement through the stimulating needle in the continuous femoral block group as opposed to through the multiorifice catheter into the psoas muscle in the continuous lumbar plexus block group may have led to the more pronounced motor block registered in the continuous femoral block group. As indicated in Table III, patients in the continuous femoral block group experienced a significantly greater degree of motor block compared with those in the continuous lumbar plexus block group. The increased intensity of the motor block in the continuous femoral block group may have affected the ability of patients to participate in active physical therapy, limiting their ability to reach the same milestone demonstrated in the continuous lumbar plexus block group.
There are important differences between academic and community practice, which often present obstacles to the effective management of pain. In a recent survey of orthopaedic surgeons, operating room delay was the principal reason for not favoring regional anesthesia29 and, not surprisingly, avoiding delaying surgery has been shown to be the greatest source of production pressure among anesthesiologists30. Community practice environments usually lack dedicated personnel and an accommodating infrastructure, which would facilitate the practice of regional anesthesia. Community practice generally operates at an accelerated pace and volume as evidenced by the striking difference between the median duration of surgery for private practice (1.5 hours) and academic centers (2.6 hours)31. This accelerated surgical pace can influence the choice and performance of regional anesthetic procedures. We found that postoperative placement of continuous peripheral nerve blocks in the postanesthesia care unit was successful in maintaining operating room efficiency and successfully integrating this analgesic technique into community practice.
In conclusion, the use of continuous lumbar plexus or femoral blocks reduces the postoperative need for opioids and decreases the associated side effects and opioid-related delirium. Furthermore, a continuous lumbar plexus block provides better analgesia during physical therapy and better functional recovery than either patient-controlled analgesia alone or a continuous femoral block in patients undergoing primary hip replacement.
Figures showing spindle spread and blotch-type spread following the injection of contrast medium into a lumbar plexus catheter and a table depicting patient demographics are available with the electronic versions of this article, on our web site at (go to the article citation and click on "Supplementary Material") and on our quarterly CD/DVD (call our subscription department, at 781-449-9780, to order the CD or DVD). 
Note: The authors thank the departments of Nursing and Physical Therapy for their assistance and data collection in this study and Cristina Sison, PhD, and Dr. Marty Lesser for their assistance with the statistical analysis.
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