Hari K. Parvataneni

Adductor canal block may just be an (unreliable) indirect femoral nerve block.

To the Editor: I t is with interest that we read the case report by Chen et al. To be successful when doing continuous peripheral nerve blocks, we must have meticulous indications for the blocks, must block the correct nerve(s), and must use the correct techniques and equipment. These requirements may well be satisfied when using an adductor canal block (ACB) for total knee arthroplasty (TKA), but according to our knowledge of the innervation of the knee joint, it is difficult to understand how we can possibly satisfy the second basic requirement of blocking the correct nerve(s). The case reported by Chen and colleagues, with help from others, helps to further clarify this issue. The subsartorial space (adductor canal) contains the subsartorial plexus (formed by the medial cutaneous nerve of the thigh, the saphenous nerve, and branches of the obturator nerves) and the nerve to the vastus medialis muscle. The saphenous nerve innervates the skin overlying the knee and therefore, according to Hilton’s law of anatomy, may also innervate the knee joint via the subpatellar plexus. These nerves, however, are irrelevant because the surgeon usually cuts them during surgery. Lateral numbness, which is common after surgery, confirms the minimal role a saphenous nerve block would have in postoperative pain control. The subsartorial plexus nerves, being only cutaneous and not innervating the deeper tissues, which are the typical pain generators, thus contribute almost nothing to the total innervation of the knee. The principal innervation of the knee is via 3 of the 4 (deep) muscular branches of the femoral nerve. The branch to the rectus femoris has a branch to the hip joint but not to the knee joint and therefore, interestingly, does not violate Hilton’s law because this law refers to groups of muscles, not individual muscles. The largest nerve that innervates the knee goes to the vastus lateralis. The branch to the vastus medialis descends through the upper part of the adductor canal and can usually be traced downward on the surface of the muscle to the knee joint, whereas the branches to the vastus intermedius (2 or 3 of them) descend through the muscle to the knee joint. Genicular branches of the tibial and common fibular nerves accompany the medial, middle, and lateral genicular arteries, with the posterior branch of the obturator nerve (not the cutaneous branch that joins the subsartorial plexus), to form a plexus that innervates the posterior capsule. In TKA, trauma to the capsule is the most important pain generator. It therefore logically follows that all the nerves that innervate the capsule must be blocked for effective analgesia. The number of patients receiving ACB who have effective analgesia and the number who have quadriceps muscle paresis seem disproportionate and unexplained at present, and this requires further research. Proximal spread to involve the entire femoral nerve, however, is undisputable. The only unknown factor at this stage is how reliable this spread is. That it attracts case reports at this stage may suggest that it is not very reliable at all. The knee joint (similar to all the other major joints of the leg) receives innervation from almost the entire lumbosacral plexus. Therefore, a controlled, predictable, continuous femoral nerve block (CFNB) that stays clear of the tourniquet and surgical field combined with some form of sciatic nerve block or posterior capsule analgesic infiltration by the surgeon to block the posterior geniculate branches seems to be a much better strategy than as-yet inconsistent, unpredictable femoral nerve blockade by indirect spread from the ACB. Finally, it is well established that the preexisting disease and the surgery itself, and not the CFNB, are the most important temporary causes of quadriceps dysfunction after TKA. This dysfunction is only fully resolved approximately 4 to 6 weeks after surgery, whereas effective analgesia as supplied by CFNB and sciatic nerve block plays an important role in early ambulation, physical therapy, and rehabilitation.

Everybody Knows That the Dice Are Loaded: How Can We Block the Nerves That Innervate the Knee Joint Without Blocking the Nerves That Innervate That Joint?

In arguably the best and most beautifully illustrated account of the innervation of the knee joint to date, a truly international group of very accomplished authors from Denmark, Austria, and Canada—Drs Bendtsen, Moriggl, Chan, and Børglum—asks in this issue whether there is a nerve block or combination of nerve blocks available, discovered or not yet discovered, for the management of postoperative pain associated with total knee arthroplasty (TKA) that does not interfere with the motor function of the leg. The most daring part of their discourse, if one translates the question that they ask, is of course the question itself: How can we block the nerves that innervate the kneewithout blocking the nerves that innervate the knee? This, as they elegantly demonstrate, is the real challenge, because, with the exception of the saphenous nerve (the infrapatellar branch of which is often transected during the anteromedial approach to TKA), all the nerves that innervate the knee joint and surrounding tissue (the pain generators following TKA) are mixed motor and sensory nerves—and everybody knows we should not block the motor nerves. Until we have a drug that can selectively block the sensory and pain fibers of a nerve, this may well be a bridge too far. It was not long ago (a few decades) that patients who received total joint replacement were kept in the hospital for weeks and were not mobilized immediately but rehabilitated progressively as the physiologic responses from surgery abated. Since that time, there has been a progressive shift toward anesthetic and surgical optimization to allow for immediate rehabilitation starting even the day of surgery. The focus of all anesthetic work in this regard had been on safer options for anesthesia and pain control. Selective nerve blocks, especially continuous femoral nerve block (CFNB), have become the criterion standard for this. Now, the main focus, including of this article, seems to be on providing optimal analgesia for TKA via nerve blocks while preserving muscle function (especially the quadriceps muscles). And, of course, everybody knows that we have to preserve the quadriceps function with our nerve blocks to optimize the surgical outcome. But does everybody really know this? Is this a scientific fact? Or is it perhaps dogma, folklore, culture, or belief that is not based on solid scientific evidence? Can what we do to block all the nerves that innervate the knee joint for a day or two really have a detrimental effect on the outcome of TKA in the short, medium, and long run? We must confront the question: “What has the most significant and prolonged effect on muscle (especially quadriceps function) during the recovery phase of TKA: pain control modality, the disease itself, or the surgery?” While we would not be daring enough to venture into politics, this question reminds one a bit of the arguments around global warming. Everybody knows that the earth is warming and that we humans are causing it. Similarly, everybody knows that with continuous nerve blocks (CNBs) we may paralyze one or more of the quadriceps muscles, which worsens the surgical outcome of TKA. But does everybody know that? Over many millions or billions (who knows) of years, the earth has been warming and cooling in cycles lasting millions of years, and now we as humans think we can, in our short time here, influence this. Similarly, can we negatively influence the outcome of TKAwith our short-termworsening of the quadriceps muscle function? Humans compulsively, impulsively, intuitively, and repeatedly feel the need to explain and control (or feel in control of ) events that we may not fully understand. Quadriceps (and other muscle) function is clearly weakened by surgery and arthrogenic muscle inhibition (AMI), in addition to any preoperative weakness. This persists for weeks and months after surgery and is a variable independent of anesthetic or surgical type (patient factors are a major contributor). Why is there pressure on us to address this long-term multifactorial issue simply with nerve block techniques that are a factor for 24 to 48 hours, at the most (if at all)? The only direct controlling factor related to this subject is pain-related AMI. Optimal pain control that is safe and includes modalities to reduce inflammation via the inflammatory cascade should be the strategy—not muscle-sparing approaches for muscles that have already been weakened by surgery and

Long-acting local anesthetic agents and additives: snake oil, voodoo, or the real deal?

The onset, spread, density, and duration of a nerve block are functions of what local anesthetic drug is injected, where it is injected, and for how long the nerve is exposed to it. Over the past 27 or more years, as far back as 1988 [1], researchers and companies, initially with topical tetracaine [1], and later as injectable liposomal bupivacaine [2], have been searching for the “magic bullet” to be injected somewhere near a nerve, or infiltrated into tissue, that will eliminate a patients acute or perioperative pain for as long as the pain lasts without unwanted side effects. The work of the Williams and colleagues, reported in this edition of Pain Medicine , is a further report on such efforts [3–5]. Although we have no or very little evidence of this, which points to a bigger problem eluded upon below, we instinctively know that most pain, especially surgical pain, outlasts our single-injection blocks, and we also know that we have to offer patients nerve blocks that last at least as long as the pain does without causing discomfort and unwanted side effects.nnOver the years, the challenge of developing a blocking drug that lasts long enough to outlast pain but that does not have similarly long-lasting unwanted side effects has been addressed by combining different drugs and developing new presentations of drugs. Few adjuvant agents, other than perhaps dexamethasone, have stood the test of time [6]. Another attempt was to add epinephrine to the existing arsenal of drugs [7] to cause vasoconstriction and decreased blood flow, thus slowing down the washout of the drugs and increasing the time that the nerve is exposed to the local anesthetic agent. We now know, that epinephrine does not increase the duration of action of bupivacaine or ropivacaine …

Impact of Total Knee Arthroplasty with General Anesthesia on Brain Networks: Cognitive Efficiency and Ventricular Volume Predict Functional Connectivity Decline in Older Adults

Using resting state functional magnetic resonance imaging (RS-fMRI), we explored: 1) pre- to post-operative changes in functional connectivity in default mode, salience, and central executive networks after total knee arthroplasty (TKA) with general anesthesia, and 2) the contribution of cognitive/brain reserve metrics these resting state functional declines. Individuals age 60 and older electing unilateral total knee arthroplasty (TKA; nu200a=u200a48) and non-surgery peers with osteoarthritis (nu200a=u200a45) completed baseline cognitive testing and baseline and post-surgery (post-baseline, 48-h post-surgery) brain MRI. We acquired cognitive and brain estimates for premorbid (vocabulary, reading, education, intracranial volume) and current (working memory, processing speed, declarative memory, ventricular volume) reserve. Functional network analyses corrected for pain severity and pain medication. The surgery group declined in every functional network of interest (pu200a<u200a0.001). Relative to non-surgery peers, 23% of surgery participants declined in at least one network and 15% of the total TKA sample declined across all networks. Larger preoperative ventricular volume and lower scores on preoperative metrics of processing speed and working memory predicted default mode network connectivity decline. Premorbid cognitive and premorbid brain reserve did not predict decline. Within 48 hours after surgery, at least one fourth of the older adult sample showed significant functional network decline. Metrics of current brain status (ventricular volume), working memory, and processing speed predicted the severity of default mode network connectivity decline. These findings demonstrate the relevance of preoperative cognition and brain integrity on acute postoperative functional network change.

Concise Review of the Effects of Orthopedic Surgery or Trauma on Muscle Function

Musculoskeletal injury and surgery both impact the short-term and long-term health and function of muscle. Muscle injury is a complicated process that can ultimately result in loss of muscle, formation of scar, and diminished function over the course of weeks to months. The extent of initial trauma (from injury) as well as on-going trauma (eg, from an unstable extremity) determines the amount of muscle damage. This has direct and distinct implications for pain, rehabilitation, and long-term functional outcomes in orthopedic trauma patients. Both the extent and the location of surgical injury of muscle can affect surgical outcomes. As a result, techniques have evolved which aim to minimize muscle injury in trauma procedures, arthroplasty and other elective orthopedic procedures. Exposure related muscle damage in total hip arthroplasty has significant implications for functional outcomes. Much of this is short lived and reversible but permanent weakness and limp can result from muscle injury. In total knee arthroplasty, more prolonged muscle weakness is an unavoidable part of the postoperative recovery and appears unrelated to surgical approach or pain management strategy. In spine surgery, muscle injury is related to persistent postoperative pain and intermuscular or muscle sparing techniques more reliably result in improved functional outcomes. Normal muscle physiology is disrupted by immobilization and neural inhibition from trauma or surgery. It is important to consider the complex and varying nature of muscle injury and recovery in orthopedic patients. Rehabilitation and pain management strategies factoring in these considerations over the entire spectrum of injury and recovery are more effective than strategies that simply focus on the short term.

Early Experience with Bilateral Continuous Femoral Nerve Block and Single-Injection Spinal Anesthesia for Bilateral Total Knee Arthroplasty: A Case Series

ObjectivenTotal knee arthroplasty (TKA) is a commonly performed surgery in the United States, with demand for unilateral and simultaneous bilateral TKAs (BTKAs) expected to increase significantly over the coming decades. This study reports the authors early experience in a consecutive series of simultaneous BTKAs performed under regional anesthesia and mild sedation.nnnMethodsnIn this retrospective case series, the authors examined all simultaneous BTKAs performed over two years by a single surgeon. Only patients receiving bilateral continuous femoral nerve blockade (CFNB) and single-injection sciatic nerve blockade in combination with single-injection subarachnoid block were included in the study. Of the 32 patients who underwent BTKAs during this period, 25 met the inclusion criteria. The patients anesthesia records, physician notes, nursing notes, pharmacy records, and physical therapy records were then reviewed systematically to create a database of information.nnnResultsnOnly one of 25 patients required conversion to general anesthesia during surgery. There were no major perioperative complications. The average Defense and Veterans Pain Rating Scale score immediately postoperation was 0.6/10, and the average daily score remained below 3.5/10 throughout the hospital stay. The use of bilateral CFNB did not prevent patients from ambulating during physiotherapy.nnnConclusionsnThis early retrospective case series suggests that it is feasible to effectively manage the postoperative pain associated with BTKA with staged bilateral CFNB and single-injection sciatic nerve blockage in combination with single-injection subarachnoid block as the sole anesthetic technique without negatively influencing early ambulation.

Arthroplasty care redesign related to the Comprehensive Care for Joint Replacement model: results at a tertiary academic medical center

Background Total joint arthroplasty (TJA) remains the highest expenditure in the Centers for Medicare and Medicaid Services (CMS) budget. One model to control cost is the Comprehensive Care for Joint Replacement (CJR) model. There has been no published literature to date examining the efficacy of CJR on value-based outcomes. The purpose of this study was to determine the efficacy and sustainability of a multidisciplinary care redesign for total joint arthroplasty under the CJR paradigm at an academic tertiary care center. Methods We implemented a system-wide care redesign, affecting all patients who underwent a total hip or total knee arthroplasty at our academic medical center. The main study outcomes were cost (to CMS), discharge destination, complications and readmissions, and length of stay (LOS); these were measured using the 2017 initial CJR reconciliation report, as well as our institutional database. Results The study included 1536 patients (41% Medicare). Per-episode cost to CMS declined by 19.5% to 11% below the CMS-designated national target. Home discharge increased from 62% to 87%. CMS readmissions declined from 15% to 6%; major complications decreased from 2.3% to 1.9%; and LOS declined from 3.6 to 2.1 days. Conclusions A mandatory episode-based bundled-payment program can induce favorable changes to value-based metrics, improving quality and outcomes for health-care consumers. Quality and value were improved in this study, evidenced by lower 90-day episode cost, more home discharges, lower readmissions and complications, and shorter LOS. This approach has implications not just for CMS, but for private payers, corporate health programs, and fixed-budget health-care models.

“Everybody-Knows-isms” and Unloading the Dice: A Reply to Drs YaDeau and Liguori

To the Editor: In a recent editorial, 1 we tried to highlight the fact that what everybody knows is not always based on scientific facts, but often on dogma, tradition, custom, and even fantasy. Drs YaDeau and Liguori submitted a letter to the editor raising concerns about implications of cheating, fraud, and scientific misconduct. The editor-in-chief did a great job of explaining what we meant by “the dice are loaded,” but we feel we should elaborate on this considering the magnitude of the misinterpretation and sentiments raised in their letter. It is unfortunate that referencing a superb anatomic description to question

Tranexamic Acid Effectively Reduces Blood Loss and Transfusion Rates during Simultaneous Bilateral Total Knee Arthroplasty

Abstract Tranexamic acid (TXA) can reduce blood loss and decrease transfusion rates after total knee arthroplasty (TKA). The purpose of our study was to evaluate the efficacy of TXA in a homogenous, consecutive cohort of patients undergoing simultaneous bilateral primary TKA. This was a retrospective study of 50 consecutive patients who underwent bilateral simultaneous primary TKA between 2011 and 2015. Of these, 20 patients received TXA and 30 patients did not receive TXA and served as the control group. Primary outcome measurements were intraoperative estimated blood loss, hemoglobin (Hb) and Hematocrit (Hct) levels on postoperative day (POD) 1 and POD2, and blood transfusion rates. Secondary outcomes included length of stay (LOS), knee flexion/extension range of motion (ROM), and postoperative complications. There was no difference between groups for preoperative Hb and Hct (all p > 0.05). The TXA group demonstrate higher Hb levels at POD1 (11.7 in TXA vs. 10.4 controls; p < 0.001) and POD2 (10.5 in TXA vs. 9.6 controls; p < 0.001), as well as higher Hct levels at POD1 (35.6 in TXA vs. 32.1 controls; p < 0.001) and POD2 (31.9 in TXA vs. 29.3 controls; p < 0.001). There was less percentage variation in Hb levels in the TXA group from preoperative to POD1 (17.7% in TXA vs. 25.7% controls; p < 0.0001) and POD2 (26.1% TXA vs. 31.8% controls; p = 0.019). Similarly, less percentage variation in Hct levels in the TXA group from presurgery to POD1 (17.0% TXA vs. 25.7% controls; p < 0.0001) and POD2 (25.0% TXA vs. 31.3% controls; p = 0.005). A total of 23.3% of patients in the control group required transfusions compared with no patients in the TXA (p = 0.044). There were no differences in LOS, knee ROM, or number of complications. No thromboembolic events occurred. TXA in bilateral simultaneous TKA effectively reduces blood loss, maintains postoperative Hb and Hct levels, and significantly decreases blood transfusion rates. The level of evidence is level III (therapeutic study).

Proximal tibial resorption in a modern total knee prosthesis

Background In an effort to minimize backside polyethylene wear and osteolysis associated with titanium tibial baseplates, many manufacturers have transitioned to cobalt chromium alloys. Recent literature has implicated thicker cobalt chromium designs as a potential source of increased stress shielding and resorption. We report the incidence of proximal tibial bone resorption in a large consecutive series of patients undergoing total knee arthroplasty, with a modern total knee design. Methods Four hundred thirty-two consecutive primary total knee arthroplasties, performed by 2 fellowship-trained arthroplasty surgeons were identified over a 24-month period. In addition to review of the medical records, analysis of preoperative and postoperative radiographs was performed. Utilizing a novel classification system, the severity of resorption was quantified and correlated with patient and implant characteristics. Results After exclusions, 339 knees were evaluated in 292 patients. Mean follow-up was 13.2 months (range 6-41). Resorption was present in 119 knees (35.1%). Average time to diagnosis of bone loss was 6.9 months (range 2-32) postoperatively. There was a statistically significant difference between resorption and nonresorption groups with regards to gender and preoperative alignment. Most cases were classified as Grade 1. During the study period, 2 patients required revision for aseptic tibial loosening. Conclusions Our findings suggest that proximal tibial resorption is common with this particular implant, particularly in men and patients with preoperative varus deformity. Although this typically occurs relatively early in postoperative period and in most cases appears to remodel and stabilize, its ultimate clinical significance and effect on implant survivorship remains unclear.