Historical Perspective

Unicompartmental knee arthroplasty was originally popularized in the 1970s, promising minimal bone sacrifice and the potential ease of future revision to a total knee arthroplasty, if required. Unfortunately, an incomplete understanding of appropriate indications and surgical techniques, combined with flawed early prosthetic designs, resulted in a high rate of failure. Subsequently, unicompartmental knee arthroplasty was all but abandoned in the United States by the late 1980s. Fortunately, renewed interest in the concept was initiated by Repicci and colleagues,^1,2 who in the 1990s described a minimally invasive technique for unicompartmental knee arthroplasty. Subsequently, unicompartmental knee arthroplasty has increased in usage secondary to a combination of interest in less invasive knee arthroplasty^1–3 and reports from multiple centers of survivorship that rivals that of total knee arthroplasty in appropriately selected patients.⁴

In the past decade, efforts have been made to improve the short-term outcomes of both total knee arthroplasty and unicompartmental knee arthroplasty with respect to pain control and early functional recovery with the implementation of minimally invasive surgical techniques.^5–10 The evolution of many orthopedic procedures has had this progression. Anterior cruciate ligament reconstruction has evolved from an inpatient to an outpatient procedure. In addition, spinal diskectomy has also had similar changes over the past decade. As in these procedures, minimizing soft tissue trauma is one part of a greater protocol that has led to decreased inpatient needs and, at our institution, the now commonplace outpatient unicompartmental knee arthroplasty. A comprehensive perioperative approach is essential to allow same-day discharge of unicompartmental knee arthroplasty patients. This paradigm shift involves not only the patient and surgeon, but also the patient’s family, the hospital, anesthesia team, therapists, and nursing staff. A successful protocol and pathway includes pain management, decreasing medication side effects, and accelerated therapy that is delivered in a timely fashion.

Indications/Contraindications

Outpatient unicompartmental knee arthroplasty continues to evolve, and the indications and contraindications are continuing to evolve as well. Furthermore, patient expectations are expanding from pure pain relief to include high functional demands. The great success and rapid recovery of unicompartmental knee arthroplasty surgery has allowed both surgeons and patients to undertake the procedure in an expanded age group, and now include younger patients. While it is easy to imagine our younger patients motivated to return to work and life as soon as possible, it is evident that older patients desire the same early functional recovery to travel, golf, and time spent with family and friends. Subsequently, fewer patients are willing to spend multiple days in the hospital, and fewer still want to spend time in a rehabilitation center or recovering slowly at home. Outpatient unicompartmental knee arthroplasty surgery represents a new style of patient care, and some patients, surgeons, and institutions simply are not yet ready for this dramatic change. However, we have found that with a few exceptions, if a patient is independent and functional at home prior to surgery, a carefully planned outpatient unicompartmental knee arthroplasty can allow resumption of the patient’s preoperative status the same evening of the day of surgery.

Preoperative Planning

Preoperative planning occurs in many stages and is the most important part of the process. It begins long before the day of surgery and includes much more than the historic medical clearance and implant choice that we have become accustomed to. The main components are planning, perioperative education, teamwork, and follow-through. The entire plan is customized for each individual patient and is created in the office at the time the patient decides to have surgery. After choosing the surgery date, the patient’s medical history is carefully scrutinized to identify relevant problems such as cardiac, pulmonary, thromboembolic, anticoagulation, and any other issues that may require more thorough preoperative investigation or an altered postoperative management. All patients attend a comprehensive educational class prior to surgery. During the same visit to our medical center for the teaching class, the patient’s medical clearance appointments and laboratory tests are scheduled, as well as an appointment to donate a unit of autologous blood. Each patient is given a complete packet of information in the office when they sign up for surgery. The contents follow a clear and logical format—these are summarized in Box 28–1.

Comprehensive patient education is required for partial knee arthroplasty to be successfully performed on an outpatient basis. The first step in this process begins in the office by helping patients set appropriate goals and realistic expectations. To achieve these goals and expectations, we have established a mandatory preoperative group class that patients and their spouses (or caregivers) attend 2–3 weeks prior to their surgery. This class gives patients the chance to review the educational packet prior to the class and generate further questions. Our clinical support staff teaches each class, and the curriculum outlines the perioperative experience from start to finish; from the initial office visit to routine annual follow-up. At the mandatory class, the risks and benefits of total knee arthroplasty are again reviewed. The preoperative requirements are reviewed, including preoperative testing, medical clearance, and medication prior to surgery. Furthermore, the surgical day is outlined in detail from arrival to check-in, anesthesia, positioning, postanesthesia care unit, physical therapy, and finally discharge. Lastly, strong emphasis is placed on postoperative strategies that will allow same-day discharge by meeting functional, nutritional, and symptomatic goals efficiently during the immediate postoperative period.

The most significant hurdle to outpatient partial knee arthroplasty is effective pain management. Much of the difficulty stems from patient fears and beliefs. A significant portion of the preoperative class therefore focuses on pain control strategies. The patients receive their postoperative pain medications from the hospital pharmacy at the time of the class to avoid any unnecessary delays the day of surgery. We employ a long-acting narcotic for baseline pain control, a short-acting breakthrough narcotic, and a nonsteroidal anti-inflammatory. In addition, we proactively reduce side effects such as nausea and constipation. The postoperative medication strategy is outlined in Tables 28–1 and 28–2. Table 28–1 is the routine table we use for our patients, while Table 28–2 is for the elderly patient or the patient who cannot or will not take oxycodone (OxyContin). Furthermore, it is difficult to predict the most appropriate dose of oral narcotic pain medication, even when considering the patient’s weight and age. Therefore, all patients are asked to take one dose of the strongest pain medication they will take the week before surgery and to report any side effects. The postoperative dose can then be modified appropriately. The stool softener and antinausea medication are initiated prior to surgery and continued as shown in Tables 28-1 and 28-2. Finally, the patients are given two additional sheets that give an overview (Table 28–3) and a detailed view (Box 28–2) of their medications so that they understand what to take, when, and why.

Table 28–3 Overview of Postoperative Medication Protocol

Physical therapy and rehabilitation are also a large focus of the teaching class. The goals of therapy, both preoperative and postoperative, are discussed. Patients are given a cane, and the techniques for bed transfer, gait training, and assisted walking are reviewed. Rarely is crutch training or walker training anticipated or taught. A handout is provided with diagrams that detail the exercises and therapy regimen for preoperative training and postoperative rehabilitation. Finally, the importance of motion is stressed, and patients are made aware they must achieve at least 100° of flexion by 1 week after surgery. The final part of the teaching class reviews the postoperative period. Patients are given a copy of the discharge sheet, medication protocol, and postoperative directions. The normal postoperative course is reviewed so that patients may feel comfortable recognizing symptoms and situations that are unusual and need to be reported. An understanding of the perioperative protocols and the roles of both patient and provider facilitate early recovery after surgery.

Successful outpatient partial knee surgery not only requires careful planning and preparation, but also requires cooperation between the patient and surgical team. This team includes the surgeon, office staff, anesthesia team, and the hospital team of nurses and therapists. For patients to be discharged the day of surgery, the patient must meet specific goals. To meet these requirements in a timely fashion requires an early surgical start time for patients who are planning to go home the same day. A strategy is utilized for prophylactic prevention of and treatment of pain, hypovolemia, and nausea. This approach is necessary in minimizing any symptoms or problems that would otherwise delay recovery. Preoperative medication protocols are employed to establish baseline blood levels of both narcotic and anti-inflammatory medication. Most patients take 10 mg of OxyContin and 400 mg of celecoxib (Celebrex) with a sip of water the morning of surgery. Most patients are placed on the standard postoperative protocol (see Table 28–1). Patients who are unable to take narcotics, had an adverse reaction to the trial dose of medication, or are extremely elderly are placed on an alternative pathway (see Table 28–2) and therefore just take 400 mg of Celebrex with a sip of water the morning of surgery.

Cooperation between the surgical team and the anesthesia team is a very important aspect of successful outpatient partial knee surgery. The anesthetic goal is appropriate intraoperative pain relief that minimizes postoperative symptoms.^11,12 While there are many anesthetic choices that allow outpatient partial knee replacement, our patients receive a straight bupivacaine epidural in the holding area prior to entering the operating room. A small dose of midazolam (Versed) is administered in conjunction with epidural placement. Intraoperative sedation is accomplished with propofol, which is titrated as needed for the individual patient. Narcotic use is avoided, or at least minimized as much as possible, to avoid unwanted side effects, which typically include increased nausea and sedation. Another important strategy that includes the anesthesia team is the prevention of nausea and hypovolemia. A big part of the technique begins by restricting narcotic use intraoperatively. To prevent nausea, the anesthesiologist administers 20 mg famotidine (Pepcid) IV, 4 mg ondansetron (Zofran) IV, and 10 mg metoclopramide (Reglan) IV during the surgery. This combination helps to prevent nausea postoperatively. The anesthesiologist is encouraged to aggressively manage fluid balance. To aid in this cause, if the patient has donated autologous blood, it is transfused intraoperatively to prevent anemia and hypovolemia. If the patient has not donated autologous blood, patients are typically given a fluid bolus of hetastarch in sodium chloride (Hespan) at the conclusion of the surgery. Alternatively, as another method to prevent fluid loss, a re-transfusion device can be utilized.

The surgical technique itself plays a pivotal role in our outpatient partial knee protocol. Multiple minimally invasive techniques have been described for partial and total knee arthroplasty.^{1-3,5,6,8,10,13} These surgical techniques all share the common goal of limiting soft tissue injury in order to limit pain and allow early function after surgery. These strategies include making in situ bone cuts, not dislocating the knee or the patella, and preserving the quadriceps mechanism.

Postoperative Management

The patient’s knee is infused with 0.25% bupivacaine (Marcaine) at the conclusion of the surgery to cover pain control prior to the oral agent initiation but after the epidural being discontinued. After completion of the surgery, the patient is transferred to the recovery room. There, after verification of neurologic status of the operative extremity, an epidural drip is started with bupivacaine 0.1% and fentanyl 5 mcg/ml. The drip is run with a continuous infusion of 6 ml/hr in addition to a patient-controlled bolus of 1 ml/15 min with a 40-ml total infusion per hour maximum. The patient can be discharged from the recovery room or can be transferred to the inpatient ward and discharged from there. At the preoperative teaching class, patients are taught to expect a well-planned and rapid progression aimed at discharge in approximately 6 hours. Timing is critical, and we employ strict order sets to facilitate drain removal, dressing change, transition to oral pain medication, diet advancement, and physical therapy.

The patient’s diet is advanced almost immediately, and patients typically receive lunch in the early afternoon. The epidural catheter and urinary catheter are removed 6 hours after surgery. A 10-mg dose of OxyContin is administered 2 hours prior to epidural removal as a bridge for pain management. Patients who experience significant postoperative pain may receive 30 mg ketorolac intramuscularly. This pain management protocol minimizes narcotic use and side effects while effectively controlling pain. Patients are required to pass physical therapy prior to discharge. Therapy sessions typically begin in the early afternoon, depending on when the patient reaches the floor. It is imperative that patients are not experiencing hypotension or nausea when therapy is initiated. If they are experiencing either of these symptoms, we temporarily hold therapy until we correct the problem (Table 28–4). Therapy starts by sitting the patient on the side of the bed and progressing if he or she is symptom free. Ambulatory aids are used as needed as determined by the therapist. Physical therapy goals include walking 150 feet and managing a single flight of stairs. Achieving these goals takes approximately 30 minutes.

Table 28–4 Summary of Remedies for Potential Problems

Discharge is dependent not only on physical therapy, but also upon pain and nausea control. The discharge instructions are reviewed and patients are instructed not to operate a motor vehicle if they are using any narcotic medication. The patients must have a family member or friend to drive them home and stay with them during the immediate postoperative period. The patient’s postdischarge care plan is clearly delineated at the teaching class and outlined on written materials that the patients take home. Patients are encouraged to work on range of motion on their own and are weight bearing as tolerated. They already have their postoperative long-acting and short-acting pain medications. The 1-week follow-up appointment is prearranged and they are seen again at 3 and 6 weeks. A wide variety of anticoagulation protocols exist, and any of them may be utilized in conjunction with rapid rehabilitation techniques. We choose to use 325 mg of aspirin twice a day for 3 weeks after surgery. We also use graded compression stockings for the first 3 weeks. Several other aspects of the overall protocol also decrease the rate of thrombosis.¹⁴ The minimally invasive techniques themselves do not require patellar eversion, hyperflexion, or tibial dislocation. Autologous blood donation and epidural anesthesia contribute as well.

Patients begin therapy in their homes with a visiting therapist three times per week. The therapy prescription at home is identical to our outpatient protocol. The protocol focuses on motion, extension when at rest, and flexion to a minimum of 100° by 1 week. The patient and therapist determine when the patient progresses to a cane and then no walking aid. Patients are encouraged to bike, golf, and engage in aqua therapy as soon as they feel ready. A wound check is performed at 1 week after the surgery. Most patients are ready to transition to outpatient therapy by this visit. This often depends on their ability to drive, which is prohibited if they are still using narcotic pain medication. Patients arrange their outpatient therapy at a convenient location and typically attend sessions 3 days per week for 6 weeks. The actual length of time in therapy depends on progress and success in achieving functional goals.

This entire protocol is outlined in Box 28–3.

Results

We have previously reported results with outpatient partial and total knee arthroplasty.^5,6,13 The successes of our initially conservative selection criteria have led us to expand the indication to all patients. In fact, in our most recent report,¹³ we found that 94% of the partial and total knee arthroplasties performed before noon were done on an outpatient basis. In this study of all comers, we assessed the feasibility and perioperative complications following outpatient total knee and unicompartmental knee replacement where no patient was excluded. To accomplish these goals, a minimally invasive surgical technique, improved perioperative anesthesia, and an expedited rehabilitation protocol were developed. One hundred twenty-one consecutive patients who had primary partial or total knee replacement completed by noon were prospectively studied.¹³ While no patient was excluded by the investigator, 10 patients refused participation. The remaining 25 unicompartmental knee arthroplasty and 86 total knee arthroplasty patients (111 total) followed the comprehensive perioperative clinical pathway described above (see Box 28–3), which included preoperative teaching, regional anesthesia, preemptive oral analgesia, and preemptive antiemetics. In addition, a rapid rehabilitation pathway with full weight bearing and range of motion was implemented within a few hours after surgery. Only if standard discharge criteria were met did the patient have the option of discharge to home the day of surgery.

Twenty-four of the 25 unicompartmental knee replacement patients (96%) and 80 of the 86 total knee replacement patients were discharged directly to home on the day of surgery.¹³ The remaining seven patients were hospitalized overnight and discharged the next day. The only unicompartmental knee arthroplasty patient who required overnight stays experienced nausea that could not be adequately controlled on the day of surgery. Four patients who had undergone total knee replacement remained hospitalized due to difficulty with pain control; all had their surgeries completed between 11:00 am and noon. One total knee patient had chest pain that required a workup for myocardial infarction, which was negative, and another total knee patient chose not to leave the hospital due to apprehension and fear of discharge. All of these seven patients successfully and easily met discharge criteria by the morning of postoperative day 1 and were discharged to home at that time. There were no statistically significant differences with regard to average age (p = .46), body weight (p = .47), or body mass index (p = .17) between the 104 patients who were successfully treated as outpatients and the seven patients who required an overnight stay. There were no readmissions or emergency room visits within the 3 months following surgery for any of the unicompartmental patients. There were no deaths, cardiac events, or pulmonary complications during this study. This study has shown that the comprehensive perioperative clinical pathway that we have developed and described above not only is effective for allowing early discharge and rehabilitation for unicompartmental knee surgery patients, but also is safe.¹³

In 2009, we started a study of patients undergoing partial knee replacements using the anesthesia, pain management, and early discharge protocol. In this prospective study, 56 consecutive patients who had primary partial knee replacements completed by noon were invited to participate in this study evaluating the above-described protocol. While we excluded no patients, 6 patients declined participation. Among the remaining 50 partial knee replacement patients, 34 had medial unicompartmental replacements, 10 had lateral unicompartmental replacements, and 6 had patellofemoral replacements. The average age was 71 (range 57–81), the average weight was 180 lbs (range 120–320 lbs), 21 were females and 29 were males. This group of 50 partial knee replacement patients followed the comprehensive perioperative clinical pathway described above, which included preoperative teaching, regional anesthesia, preemptive oral analgesia, and preemptive antiemetics. In addition, a rapid rehabilitation pathway with full weight bearing and range of motion was implemented within a few hours after surgery. Only if standard discharge criteria were met did the patient have the option of discharge to home the day of surgery. We found that, in this group of 50 consecutive patients who agreed to be in this study, all 50 were discharged home the day of surgery. There were no readmissions following surgery for any of these 50 patients. There were no deaths, cardiac events, or pulmonary complications during this study. This study has again demonstrated that the comprehensive perioperative clinical pathway that we have developed and described above is effective for allowing early discharge and is safe.

Possible Concerns, Future Of The Technique

Through the use of minimally invasive surgical techniques for partial and total knee arthroplasty, rapid rehabilitation, and comprehensive pain management, we have successfully instituted a protocol for outpatient partial and total knee arthroplasty at our institution. The techniques and protocols are evolving. A great deal of planning must be done prior to embarking upon such a pathway to ensure patient safety and success. The high rate of discharge to home the day of surgery was in part due to our team’s responsiveness to early signs of nausea and hypotension, which were swiftly acted upon. Continuing work in this arena may make it possible to perform outpatient minimally invasive partial knee arthroplasty in specialized surgical centers in the future. Future developments in technique that require even less soft tissue disruption may broaden the scope of outpatient partial and total knee arthroplasty. Improved fluid management, pain control, and side effect reduction will also allow more patients and surgeons to explore this pathway. The same financial pressures and patient demands that have led to successful outpatient anterior cruciate ligament reconstruction and diskectomy apply to partial and total knee replacement patients, and a response by the orthopaedic community has the potential to meet patient, surgeon, and health-care system goals.