Clin Orthop Relat Res DOI 10.1007/s11999-013-3393-9
Clinical Orthopaedics and Related Research® A Publication of The Association of Bone and Joint Surgeons®
SYMPOSIUM: PERIOPERATIVE PAIN MANAGEMENT IN ORTHOPAEDIC SURGERY
Is L2 Paravertebral Block Comparable to Lumbar Plexus Block for Postoperative Analgesia After Total Hip Arthroplasty? Richa Wardhan MD, Anne-Sophie M. Auroux PharmD, Bruce Ben-David MD, Jacques E. Chelly MD, PhD, MBA
Ó The Association of Bone and Joint Surgeons1 2014
Abstract Background Continuous lumbar plexus block (LPB) is a well-accepted technique for regional analgesia after THA. However, many patients experience considerable quadriceps motor weakness with this technique, thus impairing their ability to achieve their physical therapy goals. Questions/purposes We asked whether L2 paravertebral block (PVB) provides better postoperative analgesia
Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained. This work was performed at University of Pittsburgh Medical Center, Pittsburgh, PA, USA. R. Wardhan, A.-S. M. Auroux, B. Ben-David, J. E. Chelly (&) Department of Anesthesiology, University of Pittsburgh Medical Center, 532 S Aiken Avenue, Suite 407, Pittsburgh, PA 15232, USA e-mail: [email protected] R. Wardhan Department of Anesthesiology, Yale School of Medicine, New Haven, CT, USA A.-S. M. Auroux Institut des Sciences Pharmaceutiques et Biologiques-Faculte´ de Pharmacie de Lyon Universite´, Lyon, France
(defined as decreased postoperative opioid consumption and lower pain scores), better preservation of motor function, and decreased length of hospital stay (LOS) compared to LPB in patients undergoing THA. Methods Sixty patients undergoing minimally invasive THA under standardized spinal anesthesia were enrolled in this randomized controlled study. After exclusions, 53 patients were randomized into the L2 PVB (n = 27) and LPB (n = 26) groups. Patient-controlled analgesia was available for 24 hours. Motor and pain assessments were performed in the recovery room and at the end of 24 hours. LOS was also noted. Results Postoperative opioid consumption during the first 24 hours was less in the LPB group (mean ± SD: 24 ± 15 mg morphine) than in the L2 PVB group (32 ± 15 mg morphine; p = 0.005); however, postoperative pain scores were not different between groups. Postoperative motor and rehabilitation outcomes and LOS were also similar. Conclusions Our study demonstrates that use of a LPB results in slightly less morphine consumption but comparable pain scores when compared with continuous L2 PVB. No difference was noted in terms of motor preservation or LOS. Although the difference in morphine consumption was only slightly in favor of the LPB group, the advantage of L2 PVBs noted by previous authors as preservation of motor function, was not seen. At our institute where LPBs have been performed for years, there seems to be no real advantage in switching to L2 PVBs. However, L2 PVB could be a reasonable alternative for operators who are wary of LPBs due to their high potential for complications and/or requiring advanced skills for its placement. But, since L2 PVBs are relatively new, not much is known about their complication profile. We recommend a thorough understanding of both techniques before attempting to place them.
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Level of Evidence Level I, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
Introduction Lumbar plexus block (LPB) is a well-accepted technique for pain management after THA. It provides effective analgesia for THA, reducing intra- and postoperative opioid requirements [20]. While LPB provides mostly favorable postoperative analgesia over intravenous opioids, these blocks may lead to excessive motor blockade [9]. Motor blockade is deleterious after hip surgery as it inhibits progress with postoperative physical therapy and ambulation and may predispose patients to in-hospital falls [11]. Paravertebral somatic nerve blockade produces ipsilateral segmental analgesia through injection of local anesthetic onto the spinal nerve roots alongside the vertebral column. It is advocated predominantly for unilateral procedures such as thoracotomy, breast surgery, chest wall trauma, hernia repair, or renal surgery, although it can be used for bilateral surgeries as well [17]. Bilateral paravertebral block (PVB) has been used successfully in the thoracic, abdominal, and pelvic regions, sometimes obviating the need for general anesthesia [18]. Recently, the use of an L2 PVB has been described as an effective postoperative analgesic technique in the case of hip arthroscopy. Lee et al. [12] chose L2 PVB over the more commonly used LPB in an attempt to limit quadriceps motor weakness and thereby permit early discharge in patients undergoing hip arthroscopy. The L1 through L2 PVBs held out the potential for neural block with a relatively specific and limited sensory block and the possibility of greater preservation of quadriceps strength [12]. We therefore performed a randomized controlled trial to determine whether L2 PVB would provide better postoperative analgesia (defined as decreased postoperative opioid consumption and decreased pain scores), better preservation of motor function, and decreased length of hospital stay (LOS) compared to LPB in patients undergoing THA.
Patient and Methods Patient Selection and Study Design After approval by our institutional review board (PRO09010511), 60 patients scheduled to undergo elective primary minimally invasive THA at our institution from May 2009 to October 2011 were enrolled in the study. These patients were 18 to 75 years old and had a BMI of less than 40 and an American Society of Anesthesiologists
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Table 1. Patient characteristics Variable
L2 PVB group (n = 27)
LPB group (n = 26)
p value
Age (years)*
59 ± 9
62 ± 8
0.56
Weight (kg)*
85 ± 18
84 ± 19
0.87
Sex (male/female) (number of patients)
13/13
15/12
0.85
* Values are expressed as mean ± SD; PVB = paravertebral block; LPB = lumbar plexus block.
grade of I to III. The 60 patients signed an informed consent form and were randomly assigned to either the L2 PVB group or the LPB group on the day of surgery. Assignment was determined by a computer-generated list and kept in a sealed envelope. A research assistant (AMA) administered a health survey to the patients discussing the scoring system used for pain assessment. Laterality (site of surgery) and vital signs, including heart rate, blood pressure, respiratory rate, and temperature, were checked. The research assistant was blinded to the type of nerve block procedure performed, along with postoperative assessments of muscle strength, opioid consumption, and other parameters for all patients. The exclusion criteria included a serum creatinine level of greater than 1.4 g/dL, respiratory support via ventilator postoperatively, other chronic painful conditions besides hip arthritis, preoperative opioid use, any female patient who was pregnant or lactating, dementia as assessed by evidence of memory loss indicated by a lack of orientation to person, place, and time, and any contraindication to the placement of PVB or LPB, including local infection, hypercoagulable state, and allergy to any medications used during the surgery. Seven patients were excluded from the study for the following reasons: inability to identify the lumbar plexus via routine nerve stimulation technique requiring use of loss of resistance technique for LPB placement (one patient), discharged from the hospital before the completion of the study (three patients), protocol change related to the nerve block infusion (rate of 7 mL/hour instead of 10 mL/hour; two patients), and blood aspiration through the catheter during the block placement (one patient). These exclusions left 53 patients who were randomized into the L2 PVB (n = 27) and LPB (n = 26) groups. Demographic characteristics were similar between groups (Table 1).
Regional Anesthetic Techniques Blocks were performed outside of the operating room in a designated area where suitable monitoring was used. An intravenous infusion was established and standard monitors
Continuous L2 Paravertebral Block
and oxygen were applied. Patients were provided with adequate sedation using intravenous fentanyl citrate and midazolam (maximum 100 lg and 2 mg, respectively). For the placement of L2 PVB, the patient was placed in a sitting position, the point of needle entry was marked on the skin corresponding to the catheter placement. The second lumbar spine was counted from the L4 spinous process at the level of the iliac crest. The needle entry site was marked 2.5 cm lateral to the superior aspect of the L2 spinous process. The area was prepared and draped in a sterile fashion, and 1% lidocaine infiltrated subcutaneously at the point of anticipated needle entry. For the catheter placement, a sterile 18-gauge 9-cm Tuohy needle (Prefix1 continuous anesthesia set; B Braun Medical Inc, Bethlehem, PA, USA) was introduced perpendicularly to the skin until the transverse process was encountered. The needle was then readjusted in a caudad direction and reinserted inferior to the corresponding transverse process to a depth approximately 1 cm deep to the transverse process. After final needle placement and negative aspiration of blood or cerebrospinal fluid, 5 mL 0.5% ropivacaine was injected and a nerve block catheter (20-gauge closed tip) was inserted to a depth of 5 cm beyond the tip of the needle. The depth to the skin was noted. An additional 10 mL 0.5% ropivacaine was then injected in 5-mL increments through the catheter to complete a total initial dose of 15 mL 0.5% ropivacaine. The catheter was secured with Steri-stripsTM (3M, St Paul, MN, USA) and transparent occlusive dressings. Vital signs were recorded every 5 minutes until the patient was taken to the operating room. Adequate block was then tested after 20 minutes with comparison of temperature in bilateral L1 and L2 dermatomes. For placement of a continuous unilateral lumbar plexus catheter, similar preblock preparation was followed. With the patient in a lateral position, the point of needle entry was marked on the skin corresponding to the catheter placement. The fourth lumbar spine was marked at the level of the iliac crest. The needle entry site was 5 cm lateral to the superior aspect of the L4 spinous process. The area was prepared and draped in a sterile fashion, and 1% lidocaine was infiltrated subcutaneously at the point of anticipated needle entry. A sterile 18-gauge 10-cm insulated Tuohy needle connected to a nerve stimulator (Contiplex1 Tuohy continuous nerve block set; B Braun Medical Inc) was introduced perpendicularly to the skin. Using a peripheral nerve stimulator (Stimuplex1; B Braun Medical Inc) set at 1.5 mA, 2 Hz, and 0.1 milliseconds, the stimulation of the quadriceps muscle response was sought at 0.4 mA and at no less than 0.2 mA. After final needle placement and previous negative aspiration, 5 mL 0.5% ropivacaine was injected followed by insertion of the nerve block catheter (20-gauge closed tip) to a depth of 5 cm beyond the tip of the needle. An additional 10 mL 0.5%
ropivacaine was then injected in 5-mL increments to complete a total initial dose of 15 mL 0.5% ropivacaine. The catheter was secured and vital signs recorded. Adequate block was tested 20 minutes afterwards, with comparison of temperature in the L1 and L2 dermatomes bilaterally.
Perioperative Management The anesthetic regimen for both groups was identical, using spinal anesthesia with hyperbaric bupivacaine and sedation with propofol and midazolam, according to the discretion of the anesthesiologist in charge of the case in the operating room. All patients had spinal anesthesia conducted in standard fashion in addition to the block to which they were randomized as part of this study.
Surgical Technique All patients underwent minimally invasive hip surgery performed by one surgeon. The surgeon and his team were blinded to the kind of block used. The surgery involved two incisions through the anterior approach. Multimodal pain management therapy is often utilized at our institute, but for this trial none of such agents were used. No intrathecal/ oral narcotics or NSAIDS were administered besides the intravenous patient-controlled analgesia (PCA).
Postoperative Assessment In the postanesthesia care unit, an infusion of 0.0625% bupivacaine (which is a standard solution for most nerve block infusions at our institution) was started at 10 mL/ hour. The patients in both groups were given access to PCA morphine (1-mg bolus, 8-minute lock-out, no basal infusion, 6-mg 1-hour limit). PCA morphine was continued for 24 hours. Additional pain relief was available via nurseadministered 5-mL boluses of 0.0625% bupivacaine via catheter pump in the recovery room. Once on the floors, additional pain relief was available via nurse-administered 5-mL boluses of 0.0625% bupivacaine via catheter pump given no more than hourly. In addition, a nurse-administered intravenous bolus of morphine 3 mg every 30 minutes as needed for up to two doses could be given to the patient via the PCA. All patients were assessed daily. The infusion rates via the lumbar plexus catheter were adjusted at the discretion of the pain service up to a rate of 12 mL/hour (standard
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infusion rate used at our institution). The PCA dose was adjusted as deemed necessary by the acute pain team to provide adequate analgesia. All LPBs were stopped and removed on Postoperative Day 2 as standard of care at our institution. No other adjuvant medications were administered to the patients in the first 48 hours. The nurses involved with these patients received training by their preceptor to take care of the nerve block infusions including the administration of boluses. Postoperative opiate consumption was recorded as morphine intravenous milligram equivalent for the first 24 hours. Pain scores at rest and during physical therapy were recorded at 24 hours.
Motor Rehabilitation and LOS A battery of tests was performed to assess motor strength in all patients, including the straight-leg raise test, long arc quadriceps (LAQ) test, and timed up and go (TUG) test. The straight-leg raise test was performed as follows. In supine position with the extremity being tested lying flat on the bed, the contralateral knee was flexed with the foot flat on the surface. The patient was instructed to lift the extremity to the level of the contralateral knee. Inability to lift the entire lower extremity off the surface to the level of the contralateral knee was considered indicative of hip flexor weakness. If the patient was able to lift the lower extremity off the surface, but the knee flexed or the patient was unable to maintain full knee extension, this was indicative of quadriceps weakness. For the LAQ test, the patient sat at the edge of the bed or chair and was asked to extend the lower leg fully on the side being tested. If the patient was able, it was indicative of intact quadriceps function. If the patient was unable to fully extend the knee, it was considered quadriceps weakness. For these first two tests, a score of 0, 1, or 2 was given for absent, intermediate, or strong function, respectively. The TUG test is a measurement of mobility. It includes a number of tasks such as standing from a seating position, walking, turning, stopping, and sitting down, which are all important tasks needed for a person to be independently mobile. For the test, the patient was asked to stand up from a standard chair and walk a distance of 10 feet (3 m), turn around and walk back to the chair, and sit down again. The individual used his/her usual footwear and could use any assistive walking device normally used, such as a cane. The patient was seated with his/her back to the chair, arms resting on the arm rest, and any walking aid used in his/her hand. Timing began when the individual started to rise from the chair and ended when he/she was once again seated in the chair. Finally, any signs of local anesthetic toxicity or
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complications related to the lumbar puncture (hematoma, infection) were reported in both groups. LOS was noted in days for all patients who underwent the study.
Statistical Analysis We performed statistical analysis using SPSS1 19.0 software (SPSS Inc, Chicago, IL, USA). The normal distribution was evaluated using a Shapiro-Wilk test. Categorical outcomes were compared using the chi-square test with Pearson correction or Fisher exact test as appropriate. Moreover, continuous end points were evaluated using either a Student’s t-test or a Mann-Whitney U test according to the data distribution. Other data were summarized using appropriate descriptive: mean ± SD for normally distributed or symmetric data, median with interquartile range for skewed variable, and number with percentage for categorical data. A p value of less than 0.05 was considered statistically significant. Two-sided tests were used for all experimental outcomes. The sample size was calculated, assuming that the mean of morphine consumption in 24 hours was 15.24 mg with an SD of 6.73 mg obtained from data collected from patients with LPB in hip arthroplasty. With a power of 85%, a decrease of 30% in morphine consumption for L2 PVB required a sample size of 27 patients per group with alpha set at 0.05. To account for patients who could potentially fail screening or drop out of the study, our sample size was 30 per group.
Results Morphine consumption during the first 24 hours was greater in the L2 PVB group than in the LPB group (32 ± 15 mg [95% CI, 26–38 mg] versus 24 ± 15 mg [95% CI, 18–30 mg]) (p = 0.05) (Fig. 1). Numeric rating scale pain scores at all time points (Table 2) and volume of local anesthetic (243 versus 246) were not different between groups (p [ 0.05). There were no differences in motor function either before surgery (Table 3) or after surgery (Table 4) and no differences in postoperative rehabilitation scores between groups. Motor function as assessed by hip flexor function (preoperative: p = 0.15; postoperative: p = 0.26) (Fig. 2), quadriceps function (preoperative: p = 0.64; postoperative: p = 0.92) (Fig. 2), and median TUG test times (L2 PVB group: 83.0 seconds [interquartile range, 55.0–98.0 seconds]; LPB group: 61.0 seconds [49.0–107.0 seconds]) were similar between groups (Table 4). No signs of local
Continuous L2 Paravertebral Block Table 3. Baseline motor strength Variable
L2 PVB group LPB group p value (n = 27) (n = 26)
Quadriceps strength (points) 1.8 ± 0.5
1.7 ± 0.7
0.64
Hip flexor strength (points)
1.6 ± 0.8
1.3 ± 0.8
0.15
Anterior thigh
1.8 ± 0.5
1.2 ± 0.9
0.006
Lateral thigh
1.7 ± 0.6
1.3 ± 1
0.063
Sensation (points)
Values are expressed as mean ± SD; PVB = paravertebral block; LPB = lumbar plexus block.
Table 4. Postoperative motor strength Variable Fig. 1 A graph shows the total morphine consumption during 24 hours reported by the LPB and L2 PVB groups. Data are expressed as means with 95% CIs (error bars). Morphine consumption during 24 hours was higher in the L2 PVB group (31.7 ± 15.1 mg) than in the LPB group (23.6 ± 14.8 mg) (p = 0.05).
L2 PVB group (n = 27)
LPB group (n = 26)
p value
Mean 24-hour 20 quadriceps weakness (points)
16
0.33
Mean 24-hour hip 4 flexor weakness (points)
4
1.00
23 (88.5%)
0.71
Ability to perform TUG test Table 2. Pre- and postoperative pain scores Assessment time
VAS score for pain (points)
p value
L2 PVB (n = 27) LPB group (n = 26) Preoperative at rest 3.0 (0–6.0)
3.0 (0–4.3)
0.72
24-hour postoperative At rest
2.0 (0–3.0)
2.5 (1.0–4.0)
0.26
On movement
6.0 (3.0–8.0)
5.0 (4.0–8.0)
0.64
Values are expressed as median, with interquartile range in parentheses; PVB = paravertebral block; LPB = lumbar plexus block.
anesthetic toxicity or complications related to the procedure were reported for either group. LOS was similar between groups: 1.8 ± 1.5 days for the L2 PVB group versus 1.5 ± 0.6 days for the LPB group (p = 0.96).
Discussion Minimally invasive hip arthroplasty provides all of the benefits of modern THA, along with shorter recovery and faster rehabilitation [4, 8, 15]. Often overlooked in the discussion of minimally invasive THA is the role that an integrated program of anesthesia and accelerated rehabilitation instituted with minimally invasive methods may play an important role in facilitating shorter hospital stays [5]. We determined whether a L2 PVB provided better postoperative analgesia and motor preservation than LPB and evaluated its impact on LOS. We found that the two techniques were comparable with regard to pain scores,
Test completed (number of patients)
23 (85.1%)
Time (seconds)*
83.0 (55.0–98.0) 61.0 (49.0–107.0) 0.55
* Values are expressed as median, with interquartile range in parentheses; TUG = timed up and go; PVB = paravertebral block; LPB = lumbar plexus block.
motor preservation, and LOS, with only slightly less morphine consumption seen in the LPB group. Our study had some limitations. The motor strength assessment could have been limited by the pain experienced by the patient during the examination. However, this is unlikely to have affected the outcome, as pain scores were fairly similar between the two groups. Also, the statistical analysis revealed a miniscule difference in opioid consumption between the two groups and similar pain scores, but the study did reveal that L2 PVB offered no benefit in preserving motor strength compare to the LPB. The nerve stimulator-guided technique for continuous LPB is commonly utilized for management of postoperative pain management after THA largely because it provides effective analgesia after what otherwise would be a painful procedure. Marino et al. [14] conducted a randomized controlled trial to compare continuous LPB with femoral nerve block and concluded that continuous LPB is a more effective analgesic modality than a continuous femoral block or patient-controlled intravenous administration of hydromorphone alone during physical therapy after primary unilateral THA. Siddiqui et al. [19] came to a similar conclusion that continuous perioperative LPB provides superior analgesia
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Fig. 2A–B Graphs show the assessment of motor function before nerve block placement (preoperative) and 24 hours after receiving LPB or L2 PVB (postoperative): (A) hip flexor assessment and (B) quadriceps assessment. Data are expressed as means with 95%
CIs (error bars). Preoperative and postoperative scores were similar between groups for hip flexor assessment (p = 0.15 and 0.26, respectively) and quadriceps assessment (p = 0.64 and 0.92, respectively).
and reduces opioid requirements and opioid-related adverse effects compared with systemic opioids alone after hip arthroplasty. LPB provides mostly favorable postoperative analgesia but can produce incomplete analgesia. Incomplete analgesia may perhaps be due to the various components of the lumbar plexus being physically separated by muscle tissue such that the infused local anesthetic solution cannot reach them all [1, 2, 10]. The case reports of Lee et al. [12] demonstrated that L1–L2 PVBs provided adequate pain relief in patients undergoing hip arthroscopy; however, the study of Bogoch et al. [6] demonstrated that opioid consumption was significantly less during the first 4 hours after performing paravertebral blocks compared to a sham
procedure in patients undergoing THA, but no significant difference was seen in opioid consumption thereafter. We found no differences in pain scores at rest or during physical therapy for the first 24 hours between the PVB and LPB groups, and morphine consumption was only slightly less in the LPB group than in the L2 PVB group (Fig. 1). Motor blockade, which is an unwelcome side effect of a LPB, is deleterious after hip surgery as it inhibits progress with postoperative physical therapy and ambulation and may predispose patients to falls [16]. LPB-induced muscle weakness has several possible explanations. First, LPB may be associated with variable distribution of the local anesthetic [7, 9, 13]. Second, having sought a motor end
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point (quadriceps twitch) for needle placement, perhaps the technique is biased toward localization and blockade of these motor fibers. We found no difference in the incidence of motor weakness affecting the hip flexors or the quadriceps muscle groups between groups (Fig. 2). Lee et al. [12] published two case reports where L1–L2 PVBs were performed in an attempt to limit quadriceps motor weakness and thereby permit early discharge. They argued that L1– L2 PVBs held the potential for neural block with a relatively specific and limited sensory block and the possibility of greater preservation of quadriceps strength and highquality analgesia [12]. The motor preservation aspect of the L2 PVBs was not noted in our study, even though the pain relief was comparable. It probably can be explained by the relatively smaller volume of local anesthetic used on the patients in their case report as compared to our study. We observed no differences between the two study groups in terms of LOS. A retrospective review of THA performed at our institution showed that hospital discharge in less than 24 hours was achieved in 295 of the 665 patients (44.4%) who underwent minimally invasive THA with multimodal analgesic regimen including LPB [15]. Many patients in our study were able to be discharged on Postoperative Day 1 and almost all patients performed physical therapy on the day of surgery. Such ambitious goals are possible only when a nerve block catheter is placed in combination with a local anesthetic concentration that provides not only adequate pain relief but preservation of motor strength. Other studies have also shown that multimodal anesthetic and pain regimes with rapid rehabilitation protocols can result in discharge within 24 hours after THA [3, 4, 15]. Our study showed that there was no difference between L2 PVB and LPB in terms of pain scores, motor preservation, and LOS and only a barely significant difference in morphine consumption favoring LPB. Considering that L2 PVB is relatively a newer technique and does not have enough data to support its safety and efficacy, it cannot be recommended by the authors as a safe and effective alternative to a LPB.
References 1. Anloague PA, Huijbregts P. Anatomical variations of the lumbar plexus: a descriptive anatomy study with proposed clinical implications. J Man Manip Ther. 2009;17:e107–e114. 2. Banagan K, Gelb D, Poelstra K, Ludwig S. Anatomic mapping of lumbar nerve roots during a direct lateral transpsoas approach to the spine: a cadaveric study. Spine (Phila Pa 1976). 2011;36:E687–E691. 3. Berger RA. A comprehensive approach to outpatient total hip arthroplasty. Am J Orthop (Belle Mead NJ). 2007;36:4–5.
4. Berger RA, Sanders SA, Thill ES, Sporer SM, Della Valle C. Newer anesthesia and rehabilitation protocols enable outpatient hip replacement in selected patients. Clin Orthop Relat Res. 2009;467:1424–1430. 5. Berry DJ, Berger RA, Callaghan JJ, Dorr LD, Duwelius PJ, Hartzband MA, Lieberman JR, Mears DC. Minimally invasive total hip arthroplasty: development, early results, and a critical analysis. Presented at the Annual Meeting of the American Orthopaedic Association, Charleston, South Carolina, USA, June 14, 2003. J Bone Joint Surg Am. 2003;85:2235–2246. 6. Bogoch ER, Henke M, Mackenzie T, Olschewski E, Mahomed NN. Lumbar paravertebral nerve block in the management of pain after total hip and knee arthroplasty: a randomized controlled clinical trial. J Arthroplasty. 2002;17:398–401. 7. Capdevila X, Macaire P, Dadure C, Choquet O, Biboulet P, Ryckwaert Y, D’Athis F. Continuous psoas compartment block for postoperative analgesia after total hip arthroplasty: new landmarks, technical guidelines, and clinical evaluation. Anesth Analg. 2002;94:1606–1613, table of contents. 8. Chimento GF, Pavone V, Sharrock N, Kahn B, Cahill J, Sculco TP. Minimally invasive total hip arthroplasty: a prospective randomized study. J Arthroplasty. 2005;20:139–144. 9. Chudinov A, Berkenstadt H, Salai M, Cahana A, Perel A. Continuous psoas compartment block for anesthesia and perioperative analgesia in patients with hip fractures. Reg Anesth Pain Med. 1999;24:563–568. 10. Farny J, Girard M, Drolet P. Posterior approach to the lumbar plexus combined with a sciatic nerve block using lidocaine. Can J Anaesth. 1994;41:486–491. 11. Ilfeld BM, Duke KB, Donohue MC. The association between lower extremity continuous peripheral nerve blocks and patient falls after knee and hip arthroplasty. Anesth Analg. 2010;111: 1552–1554. 12. Lee EM, Murphy KP, Ben-David B. Postoperative analgesia for hip arthroscopy: combined L1 and L2 paravertebral blocks. J Clin Anesth. 2008;20:462–465. 13. Mannion S, O’Callaghan S, Walsh M, Murphy DB, Shorten GD. In with the new, out with the old? Comparison of two approaches for psoas compartment block. Anesth Analg. 2005;101:259–264, table of contents. 14. Marino J, Russo J, Kenny M, Herenstein R, Livote E, Chelly JE. Continuous lumbar plexus block for postoperative pain control after total hip arthroplasty: a randomized controlled trial. J Bone Joint Surg Am. 2009;91:29–37. 15. Mears DC, Mears SC, Chelly JE, Dai F, Vulakovich KL. THA with a minimally invasive technique, multi-modal anesthesia, and home rehabilitation: factors associated with early discharge? Clin Orthop Relat Res. 2009;467:1412–1417. 16. Nye ZB, Horn JL, Crittenden W, Abrahams MS, Aziz MF. Ambulatory continuous posterior lumbar plexus blocks following hip arthroscopy: a review of 213 cases. J Clin Anesth. 2013;25:268–274. 17. Richardson J, Lo¨nnqvist PA. Thoracic paravertebral block. Br J Anaesth. 1998;81:230–238. 18. Richardson J, Lo¨nnqvist PA, Naja Z. Bilateral thoracic paravertebral block: potential and practice. Br J Anaesth. 2011;106:164–171. 19. Siddiqui ZI, Cepeda MS, Denman W, Schumann R, Carr DB. Continuous lumbar plexus block provides improved analgesia with fewer side effects compared with systemic opioids after hip arthroplasty: a randomized controlled trial. Reg Anesth Pain Med. 2007;32:393–398. 20. Stevens RD, Van Gessel E, Flory N, Fournier R, Gamulin Z. Lumbar plexus block reduces pain and blood loss associated with total hip arthroplasty. Anesthesiology. 2000;93:115–121.
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Clinical Orthopaedics and Related Research® A Publication of The Association of Bone and Joint Surgeons®
SYMPOSIUM: PERIOPERATIVE PAIN MANAGEMENT IN ORTHOPAEDIC SURGERY
Is L2 Paravertebral Block Comparable to Lumbar Plexus Block for Postoperative Analgesia After Total Hip Arthroplasty? Richa Wardhan MD, Anne-Sophie M. Auroux PharmD, Bruce Ben-David MD, Jacques E. Chelly MD, PhD, MBA
Ó The Association of Bone and Joint Surgeons1 2014
Abstract Background Continuous lumbar plexus block (LPB) is a well-accepted technique for regional analgesia after THA. However, many patients experience considerable quadriceps motor weakness with this technique, thus impairing their ability to achieve their physical therapy goals. Questions/purposes We asked whether L2 paravertebral block (PVB) provides better postoperative analgesia
Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. Each author certifies that his or her institution approved the human protocol for this investigation and that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained. This work was performed at University of Pittsburgh Medical Center, Pittsburgh, PA, USA. R. Wardhan, A.-S. M. Auroux, B. Ben-David, J. E. Chelly (&) Department of Anesthesiology, University of Pittsburgh Medical Center, 532 S Aiken Avenue, Suite 407, Pittsburgh, PA 15232, USA e-mail: [email protected] R. Wardhan Department of Anesthesiology, Yale School of Medicine, New Haven, CT, USA A.-S. M. Auroux Institut des Sciences Pharmaceutiques et Biologiques-Faculte´ de Pharmacie de Lyon Universite´, Lyon, France
(defined as decreased postoperative opioid consumption and lower pain scores), better preservation of motor function, and decreased length of hospital stay (LOS) compared to LPB in patients undergoing THA. Methods Sixty patients undergoing minimally invasive THA under standardized spinal anesthesia were enrolled in this randomized controlled study. After exclusions, 53 patients were randomized into the L2 PVB (n = 27) and LPB (n = 26) groups. Patient-controlled analgesia was available for 24 hours. Motor and pain assessments were performed in the recovery room and at the end of 24 hours. LOS was also noted. Results Postoperative opioid consumption during the first 24 hours was less in the LPB group (mean ± SD: 24 ± 15 mg morphine) than in the L2 PVB group (32 ± 15 mg morphine; p = 0.005); however, postoperative pain scores were not different between groups. Postoperative motor and rehabilitation outcomes and LOS were also similar. Conclusions Our study demonstrates that use of a LPB results in slightly less morphine consumption but comparable pain scores when compared with continuous L2 PVB. No difference was noted in terms of motor preservation or LOS. Although the difference in morphine consumption was only slightly in favor of the LPB group, the advantage of L2 PVBs noted by previous authors as preservation of motor function, was not seen. At our institute where LPBs have been performed for years, there seems to be no real advantage in switching to L2 PVBs. However, L2 PVB could be a reasonable alternative for operators who are wary of LPBs due to their high potential for complications and/or requiring advanced skills for its placement. But, since L2 PVBs are relatively new, not much is known about their complication profile. We recommend a thorough understanding of both techniques before attempting to place them.
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Level of Evidence Level I, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
Introduction Lumbar plexus block (LPB) is a well-accepted technique for pain management after THA. It provides effective analgesia for THA, reducing intra- and postoperative opioid requirements [20]. While LPB provides mostly favorable postoperative analgesia over intravenous opioids, these blocks may lead to excessive motor blockade [9]. Motor blockade is deleterious after hip surgery as it inhibits progress with postoperative physical therapy and ambulation and may predispose patients to in-hospital falls [11]. Paravertebral somatic nerve blockade produces ipsilateral segmental analgesia through injection of local anesthetic onto the spinal nerve roots alongside the vertebral column. It is advocated predominantly for unilateral procedures such as thoracotomy, breast surgery, chest wall trauma, hernia repair, or renal surgery, although it can be used for bilateral surgeries as well [17]. Bilateral paravertebral block (PVB) has been used successfully in the thoracic, abdominal, and pelvic regions, sometimes obviating the need for general anesthesia [18]. Recently, the use of an L2 PVB has been described as an effective postoperative analgesic technique in the case of hip arthroscopy. Lee et al. [12] chose L2 PVB over the more commonly used LPB in an attempt to limit quadriceps motor weakness and thereby permit early discharge in patients undergoing hip arthroscopy. The L1 through L2 PVBs held out the potential for neural block with a relatively specific and limited sensory block and the possibility of greater preservation of quadriceps strength [12]. We therefore performed a randomized controlled trial to determine whether L2 PVB would provide better postoperative analgesia (defined as decreased postoperative opioid consumption and decreased pain scores), better preservation of motor function, and decreased length of hospital stay (LOS) compared to LPB in patients undergoing THA.
Patient and Methods Patient Selection and Study Design After approval by our institutional review board (PRO09010511), 60 patients scheduled to undergo elective primary minimally invasive THA at our institution from May 2009 to October 2011 were enrolled in the study. These patients were 18 to 75 years old and had a BMI of less than 40 and an American Society of Anesthesiologists
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Table 1. Patient characteristics Variable
L2 PVB group (n = 27)
LPB group (n = 26)
p value
Age (years)*
59 ± 9
62 ± 8
0.56
Weight (kg)*
85 ± 18
84 ± 19
0.87
Sex (male/female) (number of patients)
13/13
15/12
0.85
* Values are expressed as mean ± SD; PVB = paravertebral block; LPB = lumbar plexus block.
grade of I to III. The 60 patients signed an informed consent form and were randomly assigned to either the L2 PVB group or the LPB group on the day of surgery. Assignment was determined by a computer-generated list and kept in a sealed envelope. A research assistant (AMA) administered a health survey to the patients discussing the scoring system used for pain assessment. Laterality (site of surgery) and vital signs, including heart rate, blood pressure, respiratory rate, and temperature, were checked. The research assistant was blinded to the type of nerve block procedure performed, along with postoperative assessments of muscle strength, opioid consumption, and other parameters for all patients. The exclusion criteria included a serum creatinine level of greater than 1.4 g/dL, respiratory support via ventilator postoperatively, other chronic painful conditions besides hip arthritis, preoperative opioid use, any female patient who was pregnant or lactating, dementia as assessed by evidence of memory loss indicated by a lack of orientation to person, place, and time, and any contraindication to the placement of PVB or LPB, including local infection, hypercoagulable state, and allergy to any medications used during the surgery. Seven patients were excluded from the study for the following reasons: inability to identify the lumbar plexus via routine nerve stimulation technique requiring use of loss of resistance technique for LPB placement (one patient), discharged from the hospital before the completion of the study (three patients), protocol change related to the nerve block infusion (rate of 7 mL/hour instead of 10 mL/hour; two patients), and blood aspiration through the catheter during the block placement (one patient). These exclusions left 53 patients who were randomized into the L2 PVB (n = 27) and LPB (n = 26) groups. Demographic characteristics were similar between groups (Table 1).
Regional Anesthetic Techniques Blocks were performed outside of the operating room in a designated area where suitable monitoring was used. An intravenous infusion was established and standard monitors
Continuous L2 Paravertebral Block
and oxygen were applied. Patients were provided with adequate sedation using intravenous fentanyl citrate and midazolam (maximum 100 lg and 2 mg, respectively). For the placement of L2 PVB, the patient was placed in a sitting position, the point of needle entry was marked on the skin corresponding to the catheter placement. The second lumbar spine was counted from the L4 spinous process at the level of the iliac crest. The needle entry site was marked 2.5 cm lateral to the superior aspect of the L2 spinous process. The area was prepared and draped in a sterile fashion, and 1% lidocaine infiltrated subcutaneously at the point of anticipated needle entry. For the catheter placement, a sterile 18-gauge 9-cm Tuohy needle (Prefix1 continuous anesthesia set; B Braun Medical Inc, Bethlehem, PA, USA) was introduced perpendicularly to the skin until the transverse process was encountered. The needle was then readjusted in a caudad direction and reinserted inferior to the corresponding transverse process to a depth approximately 1 cm deep to the transverse process. After final needle placement and negative aspiration of blood or cerebrospinal fluid, 5 mL 0.5% ropivacaine was injected and a nerve block catheter (20-gauge closed tip) was inserted to a depth of 5 cm beyond the tip of the needle. The depth to the skin was noted. An additional 10 mL 0.5% ropivacaine was then injected in 5-mL increments through the catheter to complete a total initial dose of 15 mL 0.5% ropivacaine. The catheter was secured with Steri-stripsTM (3M, St Paul, MN, USA) and transparent occlusive dressings. Vital signs were recorded every 5 minutes until the patient was taken to the operating room. Adequate block was then tested after 20 minutes with comparison of temperature in bilateral L1 and L2 dermatomes. For placement of a continuous unilateral lumbar plexus catheter, similar preblock preparation was followed. With the patient in a lateral position, the point of needle entry was marked on the skin corresponding to the catheter placement. The fourth lumbar spine was marked at the level of the iliac crest. The needle entry site was 5 cm lateral to the superior aspect of the L4 spinous process. The area was prepared and draped in a sterile fashion, and 1% lidocaine was infiltrated subcutaneously at the point of anticipated needle entry. A sterile 18-gauge 10-cm insulated Tuohy needle connected to a nerve stimulator (Contiplex1 Tuohy continuous nerve block set; B Braun Medical Inc) was introduced perpendicularly to the skin. Using a peripheral nerve stimulator (Stimuplex1; B Braun Medical Inc) set at 1.5 mA, 2 Hz, and 0.1 milliseconds, the stimulation of the quadriceps muscle response was sought at 0.4 mA and at no less than 0.2 mA. After final needle placement and previous negative aspiration, 5 mL 0.5% ropivacaine was injected followed by insertion of the nerve block catheter (20-gauge closed tip) to a depth of 5 cm beyond the tip of the needle. An additional 10 mL 0.5%
ropivacaine was then injected in 5-mL increments to complete a total initial dose of 15 mL 0.5% ropivacaine. The catheter was secured and vital signs recorded. Adequate block was tested 20 minutes afterwards, with comparison of temperature in the L1 and L2 dermatomes bilaterally.
Perioperative Management The anesthetic regimen for both groups was identical, using spinal anesthesia with hyperbaric bupivacaine and sedation with propofol and midazolam, according to the discretion of the anesthesiologist in charge of the case in the operating room. All patients had spinal anesthesia conducted in standard fashion in addition to the block to which they were randomized as part of this study.
Surgical Technique All patients underwent minimally invasive hip surgery performed by one surgeon. The surgeon and his team were blinded to the kind of block used. The surgery involved two incisions through the anterior approach. Multimodal pain management therapy is often utilized at our institute, but for this trial none of such agents were used. No intrathecal/ oral narcotics or NSAIDS were administered besides the intravenous patient-controlled analgesia (PCA).
Postoperative Assessment In the postanesthesia care unit, an infusion of 0.0625% bupivacaine (which is a standard solution for most nerve block infusions at our institution) was started at 10 mL/ hour. The patients in both groups were given access to PCA morphine (1-mg bolus, 8-minute lock-out, no basal infusion, 6-mg 1-hour limit). PCA morphine was continued for 24 hours. Additional pain relief was available via nurseadministered 5-mL boluses of 0.0625% bupivacaine via catheter pump in the recovery room. Once on the floors, additional pain relief was available via nurse-administered 5-mL boluses of 0.0625% bupivacaine via catheter pump given no more than hourly. In addition, a nurse-administered intravenous bolus of morphine 3 mg every 30 minutes as needed for up to two doses could be given to the patient via the PCA. All patients were assessed daily. The infusion rates via the lumbar plexus catheter were adjusted at the discretion of the pain service up to a rate of 12 mL/hour (standard
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infusion rate used at our institution). The PCA dose was adjusted as deemed necessary by the acute pain team to provide adequate analgesia. All LPBs were stopped and removed on Postoperative Day 2 as standard of care at our institution. No other adjuvant medications were administered to the patients in the first 48 hours. The nurses involved with these patients received training by their preceptor to take care of the nerve block infusions including the administration of boluses. Postoperative opiate consumption was recorded as morphine intravenous milligram equivalent for the first 24 hours. Pain scores at rest and during physical therapy were recorded at 24 hours.
Motor Rehabilitation and LOS A battery of tests was performed to assess motor strength in all patients, including the straight-leg raise test, long arc quadriceps (LAQ) test, and timed up and go (TUG) test. The straight-leg raise test was performed as follows. In supine position with the extremity being tested lying flat on the bed, the contralateral knee was flexed with the foot flat on the surface. The patient was instructed to lift the extremity to the level of the contralateral knee. Inability to lift the entire lower extremity off the surface to the level of the contralateral knee was considered indicative of hip flexor weakness. If the patient was able to lift the lower extremity off the surface, but the knee flexed or the patient was unable to maintain full knee extension, this was indicative of quadriceps weakness. For the LAQ test, the patient sat at the edge of the bed or chair and was asked to extend the lower leg fully on the side being tested. If the patient was able, it was indicative of intact quadriceps function. If the patient was unable to fully extend the knee, it was considered quadriceps weakness. For these first two tests, a score of 0, 1, or 2 was given for absent, intermediate, or strong function, respectively. The TUG test is a measurement of mobility. It includes a number of tasks such as standing from a seating position, walking, turning, stopping, and sitting down, which are all important tasks needed for a person to be independently mobile. For the test, the patient was asked to stand up from a standard chair and walk a distance of 10 feet (3 m), turn around and walk back to the chair, and sit down again. The individual used his/her usual footwear and could use any assistive walking device normally used, such as a cane. The patient was seated with his/her back to the chair, arms resting on the arm rest, and any walking aid used in his/her hand. Timing began when the individual started to rise from the chair and ended when he/she was once again seated in the chair. Finally, any signs of local anesthetic toxicity or
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complications related to the lumbar puncture (hematoma, infection) were reported in both groups. LOS was noted in days for all patients who underwent the study.
Statistical Analysis We performed statistical analysis using SPSS1 19.0 software (SPSS Inc, Chicago, IL, USA). The normal distribution was evaluated using a Shapiro-Wilk test. Categorical outcomes were compared using the chi-square test with Pearson correction or Fisher exact test as appropriate. Moreover, continuous end points were evaluated using either a Student’s t-test or a Mann-Whitney U test according to the data distribution. Other data were summarized using appropriate descriptive: mean ± SD for normally distributed or symmetric data, median with interquartile range for skewed variable, and number with percentage for categorical data. A p value of less than 0.05 was considered statistically significant. Two-sided tests were used for all experimental outcomes. The sample size was calculated, assuming that the mean of morphine consumption in 24 hours was 15.24 mg with an SD of 6.73 mg obtained from data collected from patients with LPB in hip arthroplasty. With a power of 85%, a decrease of 30% in morphine consumption for L2 PVB required a sample size of 27 patients per group with alpha set at 0.05. To account for patients who could potentially fail screening or drop out of the study, our sample size was 30 per group.
Results Morphine consumption during the first 24 hours was greater in the L2 PVB group than in the LPB group (32 ± 15 mg [95% CI, 26–38 mg] versus 24 ± 15 mg [95% CI, 18–30 mg]) (p = 0.05) (Fig. 1). Numeric rating scale pain scores at all time points (Table 2) and volume of local anesthetic (243 versus 246) were not different between groups (p [ 0.05). There were no differences in motor function either before surgery (Table 3) or after surgery (Table 4) and no differences in postoperative rehabilitation scores between groups. Motor function as assessed by hip flexor function (preoperative: p = 0.15; postoperative: p = 0.26) (Fig. 2), quadriceps function (preoperative: p = 0.64; postoperative: p = 0.92) (Fig. 2), and median TUG test times (L2 PVB group: 83.0 seconds [interquartile range, 55.0–98.0 seconds]; LPB group: 61.0 seconds [49.0–107.0 seconds]) were similar between groups (Table 4). No signs of local
Continuous L2 Paravertebral Block Table 3. Baseline motor strength Variable
L2 PVB group LPB group p value (n = 27) (n = 26)
Quadriceps strength (points) 1.8 ± 0.5
1.7 ± 0.7
0.64
Hip flexor strength (points)
1.6 ± 0.8
1.3 ± 0.8
0.15
Anterior thigh
1.8 ± 0.5
1.2 ± 0.9
0.006
Lateral thigh
1.7 ± 0.6
1.3 ± 1
0.063
Sensation (points)
Values are expressed as mean ± SD; PVB = paravertebral block; LPB = lumbar plexus block.
Table 4. Postoperative motor strength Variable Fig. 1 A graph shows the total morphine consumption during 24 hours reported by the LPB and L2 PVB groups. Data are expressed as means with 95% CIs (error bars). Morphine consumption during 24 hours was higher in the L2 PVB group (31.7 ± 15.1 mg) than in the LPB group (23.6 ± 14.8 mg) (p = 0.05).
L2 PVB group (n = 27)
LPB group (n = 26)
p value
Mean 24-hour 20 quadriceps weakness (points)
16
0.33
Mean 24-hour hip 4 flexor weakness (points)
4
1.00
23 (88.5%)
0.71
Ability to perform TUG test Table 2. Pre- and postoperative pain scores Assessment time
VAS score for pain (points)
p value
L2 PVB (n = 27) LPB group (n = 26) Preoperative at rest 3.0 (0–6.0)
3.0 (0–4.3)
0.72
24-hour postoperative At rest
2.0 (0–3.0)
2.5 (1.0–4.0)
0.26
On movement
6.0 (3.0–8.0)
5.0 (4.0–8.0)
0.64
Values are expressed as median, with interquartile range in parentheses; PVB = paravertebral block; LPB = lumbar plexus block.
anesthetic toxicity or complications related to the procedure were reported for either group. LOS was similar between groups: 1.8 ± 1.5 days for the L2 PVB group versus 1.5 ± 0.6 days for the LPB group (p = 0.96).
Discussion Minimally invasive hip arthroplasty provides all of the benefits of modern THA, along with shorter recovery and faster rehabilitation [4, 8, 15]. Often overlooked in the discussion of minimally invasive THA is the role that an integrated program of anesthesia and accelerated rehabilitation instituted with minimally invasive methods may play an important role in facilitating shorter hospital stays [5]. We determined whether a L2 PVB provided better postoperative analgesia and motor preservation than LPB and evaluated its impact on LOS. We found that the two techniques were comparable with regard to pain scores,
Test completed (number of patients)
23 (85.1%)
Time (seconds)*
83.0 (55.0–98.0) 61.0 (49.0–107.0) 0.55
* Values are expressed as median, with interquartile range in parentheses; TUG = timed up and go; PVB = paravertebral block; LPB = lumbar plexus block.
motor preservation, and LOS, with only slightly less morphine consumption seen in the LPB group. Our study had some limitations. The motor strength assessment could have been limited by the pain experienced by the patient during the examination. However, this is unlikely to have affected the outcome, as pain scores were fairly similar between the two groups. Also, the statistical analysis revealed a miniscule difference in opioid consumption between the two groups and similar pain scores, but the study did reveal that L2 PVB offered no benefit in preserving motor strength compare to the LPB. The nerve stimulator-guided technique for continuous LPB is commonly utilized for management of postoperative pain management after THA largely because it provides effective analgesia after what otherwise would be a painful procedure. Marino et al. [14] conducted a randomized controlled trial to compare continuous LPB with femoral nerve block and concluded that continuous LPB is a more effective analgesic modality than a continuous femoral block or patient-controlled intravenous administration of hydromorphone alone during physical therapy after primary unilateral THA. Siddiqui et al. [19] came to a similar conclusion that continuous perioperative LPB provides superior analgesia
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Fig. 2A–B Graphs show the assessment of motor function before nerve block placement (preoperative) and 24 hours after receiving LPB or L2 PVB (postoperative): (A) hip flexor assessment and (B) quadriceps assessment. Data are expressed as means with 95%
CIs (error bars). Preoperative and postoperative scores were similar between groups for hip flexor assessment (p = 0.15 and 0.26, respectively) and quadriceps assessment (p = 0.64 and 0.92, respectively).
and reduces opioid requirements and opioid-related adverse effects compared with systemic opioids alone after hip arthroplasty. LPB provides mostly favorable postoperative analgesia but can produce incomplete analgesia. Incomplete analgesia may perhaps be due to the various components of the lumbar plexus being physically separated by muscle tissue such that the infused local anesthetic solution cannot reach them all [1, 2, 10]. The case reports of Lee et al. [12] demonstrated that L1–L2 PVBs provided adequate pain relief in patients undergoing hip arthroscopy; however, the study of Bogoch et al. [6] demonstrated that opioid consumption was significantly less during the first 4 hours after performing paravertebral blocks compared to a sham
procedure in patients undergoing THA, but no significant difference was seen in opioid consumption thereafter. We found no differences in pain scores at rest or during physical therapy for the first 24 hours between the PVB and LPB groups, and morphine consumption was only slightly less in the LPB group than in the L2 PVB group (Fig. 1). Motor blockade, which is an unwelcome side effect of a LPB, is deleterious after hip surgery as it inhibits progress with postoperative physical therapy and ambulation and may predispose patients to falls [16]. LPB-induced muscle weakness has several possible explanations. First, LPB may be associated with variable distribution of the local anesthetic [7, 9, 13]. Second, having sought a motor end
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point (quadriceps twitch) for needle placement, perhaps the technique is biased toward localization and blockade of these motor fibers. We found no difference in the incidence of motor weakness affecting the hip flexors or the quadriceps muscle groups between groups (Fig. 2). Lee et al. [12] published two case reports where L1–L2 PVBs were performed in an attempt to limit quadriceps motor weakness and thereby permit early discharge. They argued that L1– L2 PVBs held the potential for neural block with a relatively specific and limited sensory block and the possibility of greater preservation of quadriceps strength and highquality analgesia [12]. The motor preservation aspect of the L2 PVBs was not noted in our study, even though the pain relief was comparable. It probably can be explained by the relatively smaller volume of local anesthetic used on the patients in their case report as compared to our study. We observed no differences between the two study groups in terms of LOS. A retrospective review of THA performed at our institution showed that hospital discharge in less than 24 hours was achieved in 295 of the 665 patients (44.4%) who underwent minimally invasive THA with multimodal analgesic regimen including LPB [15]. Many patients in our study were able to be discharged on Postoperative Day 1 and almost all patients performed physical therapy on the day of surgery. Such ambitious goals are possible only when a nerve block catheter is placed in combination with a local anesthetic concentration that provides not only adequate pain relief but preservation of motor strength. Other studies have also shown that multimodal anesthetic and pain regimes with rapid rehabilitation protocols can result in discharge within 24 hours after THA [3, 4, 15]. Our study showed that there was no difference between L2 PVB and LPB in terms of pain scores, motor preservation, and LOS and only a barely significant difference in morphine consumption favoring LPB. Considering that L2 PVB is relatively a newer technique and does not have enough data to support its safety and efficacy, it cannot be recommended by the authors as a safe and effective alternative to a LPB.
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