- Email: [email protected]
In Reply to a Letter “Not All Continuous Femoral Nerve Blocks Are Equivalent”
Letters to the Editor
days for those with femoral catheters (“Sig. = 0.000 [sic]”). Unfortunately, we believe that the results of the study are not applicable to most providers’ current practice because the reported method of block administration is inconsistent with typical continuous peripheral nerve block protocols utilized over the last 10–15 years. We draw this conclusion from the confluence of two critical elements of the Shah–Jain study protocol: (1) the local anesthetic administration regimen combined with (2) the fact that “the mobilization tests were performed 24 h post block…” [1] Regarding the first, Drs. Shah and Jain administered, “a loading dose of 30 cc inj. Ropivacaine 0.75% [emphasis added].” However, even a 30 mL bolus of 0.1% ropivacaine results in a profound motor block; [2] and, a smaller bolus (20 mL) of 0.75% ropivacaine results in a median sensory and motor block of 18 and 15 h, respectively [3]. The authors subsequently administered yet additional ropivacaine, with “repeated boluses of inj. Ropivacaine 0.25%, 30 cc” 4, 8, 12, 16, 20, and 24 h following the initial bolus (continuing every 4 h through postoperative day 2). With the large initial bolus of a long-acting local anesthetic combined with even more ropivacaine doses, it is highly probable that the overwhelming majority of subjects of both treatment groups experienced dense sensory and motor blocks at the single time point of mobility evaluation “24 h post block [sic].” The purpose of using a femoral nerve perineural catheter instead of a single-injection femoral nerve block after knee arthroplasty is two-fold: (1) the post-surgical pain usually far outlasts the duration of the longest-acting single-injection peripheral nerve block and therefore analgesia duration may be prolonged with additional subsequent local anesthetic administration; [4,5] and, (2) a single-injection nerve block with a bolus of local anesthetic results in profound sensory and motor block [2]. A dense sensory and motor block is obviously undesirable following knee arthroplasty because it inhibits quadriceps function and thus mobilization [2,6,7]. As Drs. Shah and Jain noted in their introduction, “…the ideal analgesia modality should facilitate early rehabilitation, prevent knee stiffness, improve patient satisfaction, reduce the length of hospital stay and promote good functional outcomes… In addition, several studies reported that peripheral nerve blocks involving the femoral nerve may be associated with the risk of falling.” [1] Although the precise etiology of the increased falling risk remains unknown, possible/ p r o b ab l e c o n t r i b u t i n g f a c t o rs i n c l u d e p e r i n e u r a l l o c a l anesthetic-induced proprioception, sensory, and muscle strength decreases [8]. It is for this reason that for the past 10–15 years, a continuous infusion of dilute local anesthetic (typically ropivacaine 0.2% at 5–8 mL/h) is the overwhelming choice for “continuous” femoral nerve blocks since these provide analgesia while minimizing the sensory and motor block [9]. We do not wish to imply that the protocol used by Drs. Shah and Jain is inappropriate; but, rather, that the combination of a prolonged, dense peripheral nerve block and the measurement of mobilization outcomes at only a single time-point 24 h after the initial large bolus of long-acting local anesthetic evaluates more of a prolonged single-injection surgical-quality block than the “continuous” femoral nerve blocks used in the overwhelming majority of knee arthroplasty subjects today [9]. This is an important distinction, because a single-injection adductor canal block has already been demonstrated in at least three high-quality studies to be far superior than a single-injection femoral nerve block in reducing quadriceps weakness and enabling active mobilization [2,6,7]. In contrast, for those healthcare providers who currently offer knee arthroplasty patients a multiple-day continuous femoral nerve block – and who are rightfully concerned with mobilization inhibition [2] and the risk of falling [10] – the remaining question is whether they should switch to continuous adductor canal catheters. Unfortunately, for the overwhelming majority of practitioners currently using continuous femoral nerve blocks, the study by Drs. Shah and Jain does not provide data that are particularly relevant to answer this critical question.
897
Brian M. Ilfeld, MD, MS Department of Anesthesiology and the OUTCOMES RESEARCH Consortium University of California San Diego, San Diego, California Reprint requests: Brian M. Ilfeld, MD, MS, Department of Anesthesiology 200 West Arbor Drive, MC 8770, San Diego, California 92103-8770 Alparslan Turan, MD Departments of Anesthesiology and OUTCOMES RESEARCH, Cleveland Clinic, Cleveland, Ohio Scott T. Ball, MD Department of Orthopaedic Surgery, University of California San Diego San Diego, California
http://dx.doi.org/10.1016/j.arth.2014.11.031
References 1. Shah NA, Jain NP. Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: a randomized controlled trial. J Arthroplasty 2014;29:2224. 2. Jaeger P, Nielsen ZJ, Henningsen MH, et al. Adductor canal block versus femoral nerve block and quadriceps strength: a randomized, double-blind, placebo-controlled, crossover study in healthy volunteers. Anesthesiology 2013;118:409. 3. Cuvillon P, Nouvellon E, Ripart J, et al. A comparison of the pharmacodynamics and pharmacokinetics of bupivacaine, ropivacaine (with epinephrine) and their equal volume mixtures with lidocaine used for femoral and sciatic nerve blocks: a doubleblind randomized study. Anesth Analg 2009;108:641. 4. Ilfeld BM, Le LT, Meyer RS, et al. Ambulatory continuous femoral nerve blocks decrease time to discharge readiness after tricompartment total knee arthroplasty: a randomized, triple-masked, placebo-controlled study. Anesthesiology 2008;108:703. 5. Ilfeld BM, Mariano ER, Girard PJ, et al. A multicenter, randomized, triple-masked, placebo-controlled trial of the effect of ambulatory continuous femoral nerve blocks on discharge-readiness following total knee arthroplasty in patients on general orthopaedic wards. Pain 2010;150:477. 6. Kwofie MK, Shastri UD, Gadsden JC, et al. The effects of ultrasound-guided adductor canal block versus femoral nerve block on quadriceps strength and fall risk: a blinded, randomized trial of volunteers. Reg Anesth Pain Med 2013;38:321. 7. Kim DH, Lin Y, Goytizolo EA, et al. Adductor canal block versus femoral nerve block for total knee arthroplasty: a prospective, randomized, controlled trial. Anesthesiology 2014;120:540. 8. Ilfeld BM, Yaksh TL. The end of postoperative pain—a fast-approaching possibility? And, if so, will we be ready? Reg Anesth Pain Med 2009;34:85. 9. Ilfeld BM. Continuous peripheral nerve blocks: a review of the published evidence. Anesth Analg 2011;113:904. 10. 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.
In Reply to a Letter “Not All Continuous Femoral Nerve Blocks Are Equivalent”
To the Editor: We would like to appreciate and thank the authors of the letter for their interest in our study and their questions regarding our recent publication exploring and comparing the effects of continuous adductor canal block and continuous femoral nerve block post total knee arthroplasty [1]. We share the authors concern over the protocols used in the study. However, we tried to depict a clear comparison between the two block No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2014.12.008.
898
Letters to the Editor
techniques without any confounding factors. With regard to the local anesthetic administration regimen, a volume of 30 ml of local anesthetic was injected for both the block techniques. A previous MRI based study on adductor canal block considered 30 ml of volume as deemed appropriate for adductor canal block [2]. Moreover, a loading dose of 0.75% ropivacaine was considered appropriate based on several previous studies on adductor canal block technique following total knee arthroplasty using similar concentration and volume of ropivacaine [2–4]. Furthermore, we used an equal volume and concentration of local anesthetic for both continuous femoral blockade and continuous adductor canal blockade, to maintain the uniformity and comparability between the two groups and prevent confounding effects of varying volume and concentration of local anesthetic on postoperative pain and ambulation ability. The authors of the letter raise two important points. 1. Was the dosage of the blockade appropriate or was it excessive? 2. Whether the assessment on the second day appropriate or too early? The authors of the letter suggest that had we used a continuous femoral nerve block with ropivacaine — 0.20 % at 5–8 ml per hour, we may have had a lesser weakness of quadriceps post-operatively and probably similar results to our adductor canal block patients. The reason we did not use a continuous infusion is due to our observation that our patients were reluctant to get out of bed when the infusion was going on with a syringe pump. Additionally 5 ml per hour of 0.2 % ropivacaine would imply 20 ml of 0.2 % ropivacaine at 4 hourly intervals — the exact dose that we have utilized for our femoral nerve blocks. If you consider 8 ml per hour as a continuous hourly infusion, we have in fact injected a lesser amount. Hence we believe that we have not given any excessive blockade as compared to other studies. The ambulation assessment was carried out on the first day post-surgery to assess which group of patients were able to ambulate better as early as the first day post-surgery. We were interested in the early functional recovery. The adductor group was able to ambulate better as there was minimal to no discernible quadriceps weakness. We believe that our study does unequivocally show the superiority of the adductor canal blockade over the femoral nerve block as regard early functional recovery and ambulatory ability post TKA. We are thankful to the authors of letter for their interest in our study. The advantages and the excellent results achieved by use of continuous adductor canal block technique are clearly reported in our study. Based on our conclusion, health care providers concerned with mobilization inhibition and the risk of falling from multiple day continuous femoral block techniques, may switch over to use continuous adductor canal block technique. We believe that it is a game-changer. Nilen A. Shah, MS, MCH ⁎ Nimesh P. Jain, MS Bombay Hospital and Research Centre, Marine Lines, Mumbai Maharashtra, India ⁎Reprint requests: Nilen. A. Shah, MS, MCH (orth), Flat no. 2, Building no. 2, India House, Kemps corner, Mumbai, 400 026, Maharashtra, India
3. Jaeger P, Grevstad U, Henningsen MH, et al. Effect of adductor-canal-blockade on established, severe post-operative pain after total knee arthroplasty: a randomised study. Acta Anaesthesiol Scand 2012;56(8):1013. 4. Jenstrup MT, Jaeger P, Lund J, et al. Effects of adductor-canal-blockade on pain and ambulation after total knee arthroplasty: a randomized study. Acta Anaesthesiol Scand 2012;56(3):357.
Adverse Clinical Outcomes in a Primary Modular Neck/Stem System
To the Editor: I would like to comment about the article titled “Adverse Clinical Outcomes in a Primary Modular Neck/Stem System” (The Journal of Arthroplasty, vol 29, no. 9, supplement, 2014). The authors of this article dedicate a small part on radiographic study of the cases analyzed, detailing “Radiographs at minimum two year follow-up were available in 109 patients at the time of writing this text. Two year minimum radiographs were available in 68/85 patients with symptoms. Loosening of the femoral component was identified in 1 patient and symptomatic medial calcar osteolysis was seen in another one. These 2 patients were in the revised group. All other radiographs showed well fixed components with no adverse bone reaction. “ At the end of the article the authors proposed an algorithm of treatment where it was completely omitted in a decision tree to assess the patients. I think the radiographic assesment remains today a fundamental tool in the follow-up of patients with hip arthroplasty, available in different health care systems. Furthermore, the follow-up of these group of patients was at a minimum of 2 years, so in some cases, it is premature to assess and highlight any kind of progression of pathological signs visible on the radiographs, in one hand, important in the follow-up visits, and in the other hand, founding areas of osteolysis, a crucial factor along with other tools for the decision of revision surgery. I believe that the most serious problem to evaluate these patients is to determine the timing for revision of the components to provide in long term follow-up the maximum satisfaction of the patient and to reduce risk of re-revision. Even the use of the dosage of the Cr and Co should be carefully evaluated because the values available to date in the literature refer to metal on metal systems. The estimated level range limit (10–20 mg/l Co and Cr) for a systemic toxic effect should be included in the algorithm as a factor of alarm for closer monitoring [1]. More data and more systematic descriptions of the histopathology are needed to define the problem and develop strategies for proper treatment of these patients. Sincerely, Alessandro Calistri, MD ANCA Clinic Rome, Rome, Italy Reprint requests: Alessandro Calistri, MD, ANCA Clinic Rome Rome, Italy Catherine Van der Straeten, MD Koen A. De Smet, MD ANCA Medical Centre, Ghent, Belgium
http://dx.doi.org/10.1016/j.arth.2014.12.008
References 1. Shah NA, Jain NP. Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: a randomized controlled trial. J Arthroplasty 2014;29(11):2224. 2. Lund J, Jenstrup MT, Jaeger P, et al. Continuous adductor-canal-blockade for adjuvant post-operative analgesia after major knee surgery: preliminary results. Acta Anaesthesiol Scand 2011;55(1):14.
http://dx.doi.org/10.1016/j.arth.2014.11.038 Reference 1. Van Der Straeten C, Grammatopoulos G, Gill HS, et al. The 2012 Otto Aufranc Award: the interpretation of metal ion levels in unilateral and bilateral hip resurfacing. Clin Orthop Relat Res 2013;471(2):377.
days for those with femoral catheters (“Sig. = 0.000 [sic]”). Unfortunately, we believe that the results of the study are not applicable to most providers’ current practice because the reported method of block administration is inconsistent with typical continuous peripheral nerve block protocols utilized over the last 10–15 years. We draw this conclusion from the confluence of two critical elements of the Shah–Jain study protocol: (1) the local anesthetic administration regimen combined with (2) the fact that “the mobilization tests were performed 24 h post block…” [1] Regarding the first, Drs. Shah and Jain administered, “a loading dose of 30 cc inj. Ropivacaine 0.75% [emphasis added].” However, even a 30 mL bolus of 0.1% ropivacaine results in a profound motor block; [2] and, a smaller bolus (20 mL) of 0.75% ropivacaine results in a median sensory and motor block of 18 and 15 h, respectively [3]. The authors subsequently administered yet additional ropivacaine, with “repeated boluses of inj. Ropivacaine 0.25%, 30 cc” 4, 8, 12, 16, 20, and 24 h following the initial bolus (continuing every 4 h through postoperative day 2). With the large initial bolus of a long-acting local anesthetic combined with even more ropivacaine doses, it is highly probable that the overwhelming majority of subjects of both treatment groups experienced dense sensory and motor blocks at the single time point of mobility evaluation “24 h post block [sic].” The purpose of using a femoral nerve perineural catheter instead of a single-injection femoral nerve block after knee arthroplasty is two-fold: (1) the post-surgical pain usually far outlasts the duration of the longest-acting single-injection peripheral nerve block and therefore analgesia duration may be prolonged with additional subsequent local anesthetic administration; [4,5] and, (2) a single-injection nerve block with a bolus of local anesthetic results in profound sensory and motor block [2]. A dense sensory and motor block is obviously undesirable following knee arthroplasty because it inhibits quadriceps function and thus mobilization [2,6,7]. As Drs. Shah and Jain noted in their introduction, “…the ideal analgesia modality should facilitate early rehabilitation, prevent knee stiffness, improve patient satisfaction, reduce the length of hospital stay and promote good functional outcomes… In addition, several studies reported that peripheral nerve blocks involving the femoral nerve may be associated with the risk of falling.” [1] Although the precise etiology of the increased falling risk remains unknown, possible/ p r o b ab l e c o n t r i b u t i n g f a c t o rs i n c l u d e p e r i n e u r a l l o c a l anesthetic-induced proprioception, sensory, and muscle strength decreases [8]. It is for this reason that for the past 10–15 years, a continuous infusion of dilute local anesthetic (typically ropivacaine 0.2% at 5–8 mL/h) is the overwhelming choice for “continuous” femoral nerve blocks since these provide analgesia while minimizing the sensory and motor block [9]. We do not wish to imply that the protocol used by Drs. Shah and Jain is inappropriate; but, rather, that the combination of a prolonged, dense peripheral nerve block and the measurement of mobilization outcomes at only a single time-point 24 h after the initial large bolus of long-acting local anesthetic evaluates more of a prolonged single-injection surgical-quality block than the “continuous” femoral nerve blocks used in the overwhelming majority of knee arthroplasty subjects today [9]. This is an important distinction, because a single-injection adductor canal block has already been demonstrated in at least three high-quality studies to be far superior than a single-injection femoral nerve block in reducing quadriceps weakness and enabling active mobilization [2,6,7]. In contrast, for those healthcare providers who currently offer knee arthroplasty patients a multiple-day continuous femoral nerve block – and who are rightfully concerned with mobilization inhibition [2] and the risk of falling [10] – the remaining question is whether they should switch to continuous adductor canal catheters. Unfortunately, for the overwhelming majority of practitioners currently using continuous femoral nerve blocks, the study by Drs. Shah and Jain does not provide data that are particularly relevant to answer this critical question.
897
Brian M. Ilfeld, MD, MS Department of Anesthesiology and the OUTCOMES RESEARCH Consortium University of California San Diego, San Diego, California Reprint requests: Brian M. Ilfeld, MD, MS, Department of Anesthesiology 200 West Arbor Drive, MC 8770, San Diego, California 92103-8770 Alparslan Turan, MD Departments of Anesthesiology and OUTCOMES RESEARCH, Cleveland Clinic, Cleveland, Ohio Scott T. Ball, MD Department of Orthopaedic Surgery, University of California San Diego San Diego, California
http://dx.doi.org/10.1016/j.arth.2014.11.031
References 1. Shah NA, Jain NP. Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: a randomized controlled trial. J Arthroplasty 2014;29:2224. 2. Jaeger P, Nielsen ZJ, Henningsen MH, et al. Adductor canal block versus femoral nerve block and quadriceps strength: a randomized, double-blind, placebo-controlled, crossover study in healthy volunteers. Anesthesiology 2013;118:409. 3. Cuvillon P, Nouvellon E, Ripart J, et al. A comparison of the pharmacodynamics and pharmacokinetics of bupivacaine, ropivacaine (with epinephrine) and their equal volume mixtures with lidocaine used for femoral and sciatic nerve blocks: a doubleblind randomized study. Anesth Analg 2009;108:641. 4. Ilfeld BM, Le LT, Meyer RS, et al. Ambulatory continuous femoral nerve blocks decrease time to discharge readiness after tricompartment total knee arthroplasty: a randomized, triple-masked, placebo-controlled study. Anesthesiology 2008;108:703. 5. Ilfeld BM, Mariano ER, Girard PJ, et al. A multicenter, randomized, triple-masked, placebo-controlled trial of the effect of ambulatory continuous femoral nerve blocks on discharge-readiness following total knee arthroplasty in patients on general orthopaedic wards. Pain 2010;150:477. 6. Kwofie MK, Shastri UD, Gadsden JC, et al. The effects of ultrasound-guided adductor canal block versus femoral nerve block on quadriceps strength and fall risk: a blinded, randomized trial of volunteers. Reg Anesth Pain Med 2013;38:321. 7. Kim DH, Lin Y, Goytizolo EA, et al. Adductor canal block versus femoral nerve block for total knee arthroplasty: a prospective, randomized, controlled trial. Anesthesiology 2014;120:540. 8. Ilfeld BM, Yaksh TL. The end of postoperative pain—a fast-approaching possibility? And, if so, will we be ready? Reg Anesth Pain Med 2009;34:85. 9. Ilfeld BM. Continuous peripheral nerve blocks: a review of the published evidence. Anesth Analg 2011;113:904. 10. 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.
In Reply to a Letter “Not All Continuous Femoral Nerve Blocks Are Equivalent”
To the Editor: We would like to appreciate and thank the authors of the letter for their interest in our study and their questions regarding our recent publication exploring and comparing the effects of continuous adductor canal block and continuous femoral nerve block post total knee arthroplasty [1]. We share the authors concern over the protocols used in the study. However, we tried to depict a clear comparison between the two block No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2014.12.008.
898
Letters to the Editor
techniques without any confounding factors. With regard to the local anesthetic administration regimen, a volume of 30 ml of local anesthetic was injected for both the block techniques. A previous MRI based study on adductor canal block considered 30 ml of volume as deemed appropriate for adductor canal block [2]. Moreover, a loading dose of 0.75% ropivacaine was considered appropriate based on several previous studies on adductor canal block technique following total knee arthroplasty using similar concentration and volume of ropivacaine [2–4]. Furthermore, we used an equal volume and concentration of local anesthetic for both continuous femoral blockade and continuous adductor canal blockade, to maintain the uniformity and comparability between the two groups and prevent confounding effects of varying volume and concentration of local anesthetic on postoperative pain and ambulation ability. The authors of the letter raise two important points. 1. Was the dosage of the blockade appropriate or was it excessive? 2. Whether the assessment on the second day appropriate or too early? The authors of the letter suggest that had we used a continuous femoral nerve block with ropivacaine — 0.20 % at 5–8 ml per hour, we may have had a lesser weakness of quadriceps post-operatively and probably similar results to our adductor canal block patients. The reason we did not use a continuous infusion is due to our observation that our patients were reluctant to get out of bed when the infusion was going on with a syringe pump. Additionally 5 ml per hour of 0.2 % ropivacaine would imply 20 ml of 0.2 % ropivacaine at 4 hourly intervals — the exact dose that we have utilized for our femoral nerve blocks. If you consider 8 ml per hour as a continuous hourly infusion, we have in fact injected a lesser amount. Hence we believe that we have not given any excessive blockade as compared to other studies. The ambulation assessment was carried out on the first day post-surgery to assess which group of patients were able to ambulate better as early as the first day post-surgery. We were interested in the early functional recovery. The adductor group was able to ambulate better as there was minimal to no discernible quadriceps weakness. We believe that our study does unequivocally show the superiority of the adductor canal blockade over the femoral nerve block as regard early functional recovery and ambulatory ability post TKA. We are thankful to the authors of letter for their interest in our study. The advantages and the excellent results achieved by use of continuous adductor canal block technique are clearly reported in our study. Based on our conclusion, health care providers concerned with mobilization inhibition and the risk of falling from multiple day continuous femoral block techniques, may switch over to use continuous adductor canal block technique. We believe that it is a game-changer. Nilen A. Shah, MS, MCH ⁎ Nimesh P. Jain, MS Bombay Hospital and Research Centre, Marine Lines, Mumbai Maharashtra, India ⁎Reprint requests: Nilen. A. Shah, MS, MCH (orth), Flat no. 2, Building no. 2, India House, Kemps corner, Mumbai, 400 026, Maharashtra, India
3. Jaeger P, Grevstad U, Henningsen MH, et al. Effect of adductor-canal-blockade on established, severe post-operative pain after total knee arthroplasty: a randomised study. Acta Anaesthesiol Scand 2012;56(8):1013. 4. Jenstrup MT, Jaeger P, Lund J, et al. Effects of adductor-canal-blockade on pain and ambulation after total knee arthroplasty: a randomized study. Acta Anaesthesiol Scand 2012;56(3):357.
Adverse Clinical Outcomes in a Primary Modular Neck/Stem System
To the Editor: I would like to comment about the article titled “Adverse Clinical Outcomes in a Primary Modular Neck/Stem System” (The Journal of Arthroplasty, vol 29, no. 9, supplement, 2014). The authors of this article dedicate a small part on radiographic study of the cases analyzed, detailing “Radiographs at minimum two year follow-up were available in 109 patients at the time of writing this text. Two year minimum radiographs were available in 68/85 patients with symptoms. Loosening of the femoral component was identified in 1 patient and symptomatic medial calcar osteolysis was seen in another one. These 2 patients were in the revised group. All other radiographs showed well fixed components with no adverse bone reaction. “ At the end of the article the authors proposed an algorithm of treatment where it was completely omitted in a decision tree to assess the patients. I think the radiographic assesment remains today a fundamental tool in the follow-up of patients with hip arthroplasty, available in different health care systems. Furthermore, the follow-up of these group of patients was at a minimum of 2 years, so in some cases, it is premature to assess and highlight any kind of progression of pathological signs visible on the radiographs, in one hand, important in the follow-up visits, and in the other hand, founding areas of osteolysis, a crucial factor along with other tools for the decision of revision surgery. I believe that the most serious problem to evaluate these patients is to determine the timing for revision of the components to provide in long term follow-up the maximum satisfaction of the patient and to reduce risk of re-revision. Even the use of the dosage of the Cr and Co should be carefully evaluated because the values available to date in the literature refer to metal on metal systems. The estimated level range limit (10–20 mg/l Co and Cr) for a systemic toxic effect should be included in the algorithm as a factor of alarm for closer monitoring [1]. More data and more systematic descriptions of the histopathology are needed to define the problem and develop strategies for proper treatment of these patients. Sincerely, Alessandro Calistri, MD ANCA Clinic Rome, Rome, Italy Reprint requests: Alessandro Calistri, MD, ANCA Clinic Rome Rome, Italy Catherine Van der Straeten, MD Koen A. De Smet, MD ANCA Medical Centre, Ghent, Belgium
http://dx.doi.org/10.1016/j.arth.2014.12.008
References 1. Shah NA, Jain NP. Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: a randomized controlled trial. J Arthroplasty 2014;29(11):2224. 2. Lund J, Jenstrup MT, Jaeger P, et al. Continuous adductor-canal-blockade for adjuvant post-operative analgesia after major knee surgery: preliminary results. Acta Anaesthesiol Scand 2011;55(1):14.
http://dx.doi.org/10.1016/j.arth.2014.11.038 Reference 1. Van Der Straeten C, Grammatopoulos G, Gill HS, et al. The 2012 Otto Aufranc Award: the interpretation of metal ion levels in unilateral and bilateral hip resurfacing. Clin Orthop Relat Res 2013;471(2):377.