CORR Insights®: Can Multimodal Pain Management in TKA Eliminate Patient-controlled Analgesia and Femoral Nerve Blocks?

Where are We Now?

The role and effectiveness of specific components of multimodal pain management protocols in TKA is the subject of intense debate [2, 4, 7, 8]. Yu and colleagues, focusing on the question of whether femoral nerve blocks (FNB) or patient-controlled analgesia (PCA) have a continued role in multimodal pain management for primary TKA, compared three historical patient cohorts in one institution. The authors reported that the most-recent cohort, those receiving liposomal bupivacaine without either a FNB or a postoperative PCA, received less in the way of narcotics, mobilized more quickly, achieved comparable pain scores overall, and were more likely to be discharged home than to a postacute care setting. These findings support the idea that PCA and FNBs may represent inferior alternatives to an opioid-minimization multimodal pain protocol that includes locally injected analgesics [1, 3, 6]. As such, the authors demonstrate within a high-volume arthroplasty center that both modalities have a diminished role for pain control in this population. In this regard, the authors are to be commended in identifying two key factors that appear to drain value from accelerated recovery protocols after knee arthroplasty.

Where Do We Need to Go?

Advancing quality and efficiency around accelerated recovery protocols has become a critical objective for high-impact elective procedures such as joint arthroplasty [5, 8]. However, designing valid comparisons of promising pain management approaches is particularly challenging because of the multitude of potentially confounding variables inherent in the study populations and the care pathways employed. Nevertheless, drawing valid conclusions from studies that compare the effectiveness of different pain management protocols after TKA requires that confounding variables within comparison groups be controlled. One key premise of the current investigation is that the care pathway for all patients was consistent, differing only when using FNB, liposomal bupivacaine, or PCA. Regardless of the consistency of hospital-based care pathways, there are still several patient and treatment variables that must be controlled to reach valid study conclusions.

Similar to this study, future investigations should incorporate explicitly standardized recovery pathways. In addition, the validity of research findings around pain management for knee arthroplasty will be accelerated by: (1) Establishing a specific set of patient exclusions for standardizing the patient populations under study, (2) ensuring that the entire treatment milieu (beyond hospital based care pathways) is comparable between groups, and (3) selecting endpoints that are unencumbered by multiple variables. While this will require considerably greater resources in terms of identifying suitable patient populations and standardizing large segments of the episode of care, it will improve the internal validity such studies. Treatment standardization should cover factors related to presurgical education, surgery, pain assessments, narcotic minimization protocols, and professional activities related to mobilization and discharge to home. One study endpoint that should be critically evaluated in future studies is hospital length of stay. While traditionally serving as a proxy for early mobilization and competence in activities of daily living, length of stay is influenced by several variables independent of the pain management protocol under study. Among these are insurance status, social support, comorbidities, and discharge destination. Moreover, length of stay is becoming a less relevant endpoint as we evolve to short stay and outpatient arthroplasty.

How Do We Get There?

Three keys to controlling for confounding variables within the study environment where pain management protocols are under investigation include: (1) Standardizing the patient population under investigation, (2) standardizing interventions that potentially impact the experience of pain, and (3) choosing highly specific endpoints that reflect the relative experience of pain. Future study populations should exclude patients with a history of substance abuse, addiction, chronic narcotic use, painful conditions aside from knee arthritis, and comorbidities that may impact any of the study endpoints. In addition, patients lacking social support or with insurance issues that represent a barrier to early discharge or to reaching other defined endpoints must be excluded. Controlling for variation in all interventions across the episode of care is admittedly unrealistic. However, standardization is necessary where treatment variation potentially affects the measurement of pain or any results of the study.

Once a surgical approach is agreed upon, a preoperative education program that minimizes uncertainty and is consistent with the care pathway must be employed. This includes establishing appropriate expectations as related to social support, specific discharge plan, length of stay, pre-emptive medications, perioperative mobilization, exercise schedule, and the specific pain management strategy, including an emphasis on narcotic minimization. Many hospitals, taking their cue from organizations referencing pain as a “fifth vital sign” focus inordinate attention on pain symptoms with frequently scheduled pain assessments and offers of narcotic medications. This is an arguably counterproductive practice as it results in potentially excessive narcotic administration. Moreover, narcotics administration should be driven by patient request rather than scheduled encouragement if narcotic consumption is to remain a valid study endpoint for clinical investigations. Accomplishing this requires changes at several points in the care pathway and includes monitoring providers for compliance with the expectations. There is a growing awareness of the effects that surgical variables have on the experience of pain, and these must be either controlled or documented. For example, tourniquet times between surgeons must be relatively consistent and reflect standards of efficient surgery. In addition, soft-tissue releases are factors contributing the surgical trauma and, thereby, the total experience of pain. Intraoperative local analgesic injection techniques must be consistent between surgeons to avoid questions relating to the effectiveness of a given regimen. In one recent Level I study [4], the consistency of the injection technique lends credibility to the finding that liposomal bupivacaine resulted in superior pain relief after TKA.

Finally, measurable endpoints must evolve with the rapid change in the pace of recovery after knee arthroplasty and with the progress in our understanding of the pain experience. For example, as perioperative care for joint arthroplasty extends beyond the walls of the traditional hospital, length of stay will have less relevance in future studies. On the other hand, documenting whether expected length of stay was achieved as a binary data point may continue to offer value as a proxy for successful mobilization after surgery. Likewise, total narcotic consumption as an endpoint is usually dependent on the total exposure time to the environment in which it is measured (ie, total hospital time or length of stay); therefore, future studies should consider narcotic consumption within a limited number of hours postoperatively, independent of the length of stay. Developing more-effective opioid minimizing, multimodal pain management strategies should include new endpoints that more-accurately measure pain and mobility improvements for this population. Adapting validated PROs tools such as the KOOS Jr. for the acute recovery environment may provide valid data that compliments VAS or numeric pain scores currently in use.

In any case, the findings of future studies will be more generalizable to a wide variety of perioperative environments and patient populations if the focus shifts from length of stay or narcotic consumption to measurable endpoints that represent comfort, mobility, and a satisfactory patient experience.