Total knee arthroplasty (TKA) is one of the success stories of modern surgery, providing high patient satisfaction outcomes despite the high volume. Primary TKA is most frequently used to treat advanced osteoarthritis in one or more of the three knee compartments: medial femoral-tibial, lateral femoral-tibial, or femoral-patellar.1 TKA may be considered when nonsurgical treatments fail and the patient's knee pain significantly impairs activities of daily living (ADLs). TKA also may be used in patients with rheumatoid arthritis or traumatic osteoarthritis caused by lower extremity trauma.2,3 However, careful patient selection is advised in these populations because of the increased risk for poor TKA outcomes.
Demand for TKA is expected to grow 673% between 2005 and 2030, putting a tremendous strain on the healthcare system.4 Medicare pays for about 60% of total joint arthroplasties in the United States.5 However, the current US healthcare payment system is unsustainable. Because of the expected increase in TKA cases, evaluating new technologies is key to improving clinical efficiency and patient outcomes, and to justify increased costs. This article reviews current literature for significant findings in TKA perioperative management, computer-aided navigation, patient-specific cutting blocks, and the medial pivot knee.
Managing a patient's response to the stress of surgery can increase the chances of a favorable postoperative outcome.6,7
Reducing blood loss
Aguilera and colleagues studied the use of IV tranexamic acid, an antifibrinolytic drug, in patients undergoing revision TKAs.8 They found that relative to controls, patients who received tranexamic acid had significantly reduced blood loss (P=0.015), although their need for transfusion was not significantly lower (P=0.057).8
MacGillivray and colleagues examined the effectiveness of a two-dose IV tranexamic acid regimen in two groups of patients who had bilateral TKA.9 Mean blood loss for those who received 15 mg/kg of tranexamic acid was 462 mL compared with 918 mL for patients who received placebo (P<0.01).9 Current practice is to administer 1 g of IV tranexamic acid administration before tourniquet inflation followed by 1 g delivered after tourniquet deflation. Because of the drug's short (2-hour) half-life, two-dose administration is recommended to help with postoperative hemostasis.10,11
Another study evaluated topical versus systemic tranexamic acid.12 A variety of methods were used in patients undergoing TKA, including injection into the intra-articular drain and local application before capsule closure.12 Researchers found that topical application of tranexamic acid significantly lowered blood loss and reduced patients' need for transfusions. Because of the high cost of transfusion and low cost of tranexamic acid, routine use of tranexamic acid may be a considerable cost-saver in patients undergoing joint arthroplasty.6
Many surgeons use a multimodal drug cocktail injection to the periarticular region to assist with analgesia in the initial postoperative period. The effectiveness of this regimen was recently examined in a study of 60 patients randomized among intra-articular injection, periarticular injection, and control groups.13 The intra-articular injection group received a saline mixture of 0.5% bupivacaine, 10 mg morphine hydrochloride, and 0.3 mg epinephrine. The periarticular injection group received a saline mixture of 0.75% ropivacaine, 10 mg morphine hydrochloride, 4 mg betamethasone, and 0.25 mg epinephrine. Based on visual analog scale pain scoring and additional parameters, the authors concluded that periarticular injection of the multimodal drug provided significant reduction in the requirement for TKA analgesia without any observed cardiac or central nervous system toxicity.
Periarticular TKA pain management was also recently evaluated in a randomized double-blinded clinical study of bupivacaine injection in 60 patients.14 The treatment group received 0.25% bupivacaine by periarticular injection before wound closure. The investigators assessed patients' postoperative pain using visual analog scoring and morphine administration. They found a significant reduction in postoperative morphine use in the treatment group (P=0.01) in the first 6 hours. They concluded that administering a periarticular injection of bupivacaine prior to TKA wound closure is an effective method of ensuring postoperative analgesia with few complications and ease of use.
Rehabilitation is key to successful recovery from TKA and to optimizing joint function; however, the rising demand for TKA is stressing outpatient and in-home rehabilitation services. A recent study of 41 patients who had TKA suggested telerehabilitation as a possible solution.15 The experimental group received in-home telerehabilitation services via online videoconferencing. Investigators compared that group with a conventional home care/outpatient rehabilitation control group. The authors recorded measures of range of motion, balance, strength, knee function, walking, and autonomy at three points over about 6 months. The study results showed that home telerehabilitation for TKA is a practical and effective alternative to conventional rehabilitation therapy.
One of the most critical aspects of TKA is ensuring component alignment, which is directly linked to survivability of the implants. Newly developed computer-aided navigation systems are a viable way to improve component alignment. A recent randomized prospective study compared 151 patients in two groups who were to undergo TKA either with computer-aided navigation or with conventional arthroplasty.16 Both groups received minimally invasive surgical approaches. Researchers compared clinical and radiographic outcomes across initial, 6-week, and midterm (6.1 year) time points. They observed no significant differences in the clinical and radiographic groups in initial, 6-week, and midterm outcomes. However, the authors note that use of computer-aided navigation required significant additional operating time, which may not be justified without substantial improvement in patient midterm outcomes.
A second recent study, which came to a similar conclusion, compared 520 patients who had TKA with computer-aided navigation for one knee to patients who had conventional surgery for the contralateral knee.17 Subjects underwent clinical and radiographic assessment at 3 months, 1 year, and annually thereafter to a mean follow-up of 10.8 years. The authors reported no differences in clinical function or component survivorship between the two methods.17
PATIENT-SPECIFIC CUTTING BLOCKS
Patient-specific cutting blocks are a compromise between conventional TKA approaches and computer-aided navigation (Figures 1 through 4). Conventional TKA uses intramedullary and extramedullary alignment jigs to set the spatial orientation of the femoral and tibial implants. Computer-aided navigation uses landmark registration to optimize component placement; this reduces the risk of the malalignment that is associated with conventional approaches.18,19 However, both approaches have shortcomings. Alignment jigs can have inherent errors and also require violation of the femoral intramedullary canal, which raises the patient's risk for fat embolism.20 Computer-aided navigation relies on the entry of landmark registration data to guide surgical steps. The associated increase in operating time, risk of incorrect data entry, and increased cost of computer-aided navigation instruments present significant shortcomings.18,19
The patient-specific cutting block approach bridges these two methods. Surgeons use MRI or CT knee data to create patient-specific models of the distal femur and proximal tibia. They can then fabricate disposable plastic cutting blocks according to the preoperative plan for resecting the distal and proximal bones. These resections correlate with setting an accurate foundation for subsequent implant manufacturer cutting blocks that complete femur and tibia resurfacing. Through the patient-specific process, no intramedullary rods are used and there is no need for tedious landmark data input. All landmark registration for accurate cutting block fitting are accounted for in preoperative planning using the CT or MRI data.
Yeo and colleagues investigated the intraoperative accuracy of patient-specific cutting blocks relative to the preoperative template.21 An independent research officer recorded and processed bone resection measurements. The surgical team was blinded to measurements throughout the study. The authors reported that 85% of all collected readings were within the 1.5 mm or less margin of error, indicating that using patient-specific cutting blocks yields results similar to conventional TKA.
Nunley and colleagues examined whether using patient-specific cutting blocks improved operating time and coronal alignment.5 They compared 57 patients who had TKA using patient-specific cutting blocks with 57 matched patients undergoing conventional TKA during the same time period. The results showed similar tourniquet times between the two groups, no difference in the femorotibial angle in the coronal plane, and a 12-minute reduction in OR time for the patient-specific cutting block group. The authors concluded that although a trend of improvement in OR time reduction was apparent, it may not be substantial enough to justify the increased cost of patient-specific technology.
A cost-benefit assessment of patient-specific cutting blocks, conventional TKA, and TKA using computer-aided navigation also found that OR time was reduced with cutting block use.22 The investigators compared fixed and time-dependent OR costs, processing, and ancillary procedure costs. They found that using cutting blocks saved 28 minutes of additional OR time per case over conventional TKA. Although this is a measurable benefit with probable economic effect, the authors reported that patient-specific TKA was not cost-saving in the study when compared with conventional TKA.
MEDIAL PIVOT KNEE
About 20% of patients are not satisfied with the outcome of their TKAs. Although negative outcomes can result from many factors, residual pain is the most significant.23 The medial pivot knee system was designed to address residual pain and the patient's desire for fully restored anatomic function after TKA. It is configured to confer anteroposterior stability, account for medial and lateral femoral condyle asymmetry in conjunction with medial and lateral meniscus anatomic and functional differences, and to restore natural kinematics by allowing lateral femoral condyle motion.24 These design characteristics attempt to approximate normal anatomic motion; conventional TKAs typically do not allow for lateral femoral condyle motion. The design is intended to increase patient satisfaction outcomes by eliminating anterior femoral translation, increasing maximum flexion outcomes, reducing polyethylene insert wear characteristics, and reducing chronic postoperative pain.
Although more research is needed, several studies have found positive patient satisfaction, reduced patellofemoral pain, improved deep knee flexion, and excellent range of motion with medial pivot knee systems compared with conventional TKA.25-27
In one prospective study Macheras and colleagues reported 6-year results of 123 medial pivot knee replacements.25 They evaluated results of clinical and radiographic testing according to Knee Society scoring. Patients also completed a questionnaire on pain, function, satisfaction, and patellofemoral symptoms (such as crepitus and pain). The authors reported overall results as excellent for 103 knees and good for 13 knees. The overall patellofemoral symptom rate was 6%. There were no reports of component loosening, and the 6-year implant survivorship rate was 97%. In another prospective study, Cho and colleagues reported 2-year follow-up results from 30 patients undergoing consecutive medial pivot TKAs.26 Patient clinical evaluation consisted of Knee Society scoring and radiographic assessment of patellofemoral translation. The authors reported that patients' mean Knee Society and functional scores improved significantly compared with preoperative scoring. Knee Society scoring was excellent in 15 knees and good in 9. Consistent posteriorly located tibiofemoral anteroposterior positions were found in all cases, indicating that no anterior femoral translation was detected. These outcomes improved knee flexion results. Mean maximum knee flexion showed good linear association between pre- and postoperative measurements (r=0.53, P=0.0027), although no significant flexion improvement was noted compared with preoperative data. The authors concluded that the clinical outcome was satisfactory. Consistent posterior femoral translations during progressive knee flexion were noted as an important factor in increasing knee flexion in longer medial pivot knee follow-ups. The authors propose that consistent posterior translations correlate with decreased posterior clearance and reduced femoro-tibial impingement.
A cross-sectional survey by Nishio and colleagues compared Knee Society scoring and clinical outcomes of 20 patients receiving medial pivot TKAs and 20 patients receiving conventional TKAs.27 The results of the comparative evaluation showed a significant improvement in patient satisfaction and knee flexion angle in the medial pivot group.
Improvements in clinical efficiency and patient outcomes are apparent with most of the recent advances in TKA described in the literature. Tranexamic acid, whether administered IV or topically, has been shown to be an effective hemostasis agent for patients undergoing orthopedic surgery. On a comparative basis, literature suggests that using tranexamic acid can reduce the need for transfusions, resulting in significant cost savings. Multimodal periarticular injections can optimize pain management and reduce a patient's need for postoperative analgesia. However, reviewed literature suggests that using only a local anesthetic in the injection could probably be as effective in reducing postoperative morphine use. This method would likely present a measurable cost savings compared with the multimodal injection regimen. Telerehabilitation may be a cost-saving substitute for conventional in-home and outpatient rehabilitation services, which pilot studies have shown to provide outcomes of comparable quality for patients after TKA.
Compared with conventional TKA, computer-aided navigation has not significantly improved patient outcomes or clinical efficiency. Patient-specific cutting blocks have shown consistent accuracy in bone resection with good reproducibility, and they can save OR time and reduce the risk for fat embolism compared with conventional TKA. Although no data were available on the clinical efficiency of the medial pivot knee system, the discussed clinical results suggest that patient outcomes are significantly improved relative to conventional TKAs.
More research is needed on some of the recent advances in TKA. Tranexamic acid use, reducing postoperative periarticular injections to local anesthetic only, and telerehabilitation may all improve clinical efficiency. Patient-specific cutting blocks and the medial pivot knee systems may also lead to improvements, although more research is necessary. Additional studies with larger populations and longer terms are needed to support the observed trend for favorable outcomes with the medial pivot knee system relative to conventional TKA.
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Keywords:Copyright © 2016 American Academy of Physician Assistants
total knee arthroplasty; patient-specific cutting blocks; intra-articular injection; medial pivot knee; tranexamic acid; cyclokapron