The scientific basis for total knee arthroscopy (TKA) has had an interesting and exciting journey over the last five decades. A few pragmatic and visionary surgeons laid foundational principles, moderated the designs, and founded this specialty. I have no doubt that Dr. Krackow was among those select few. Dr. Krackow believed in an equitable distribution of opportunity and propagation of knowledge across borders for the benefit of humanity. The eclectic bunch of fellows from various backgrounds whom he encouraged and recruited stands testimony to that philosophy. His prescience in recording audio during patient counseling and providing one tape to the patient and retaining one for internal documentation is a genius technique to avoid long-term dissonance if there are adverse outcomes and to encourage family members to partake in decision making in absentia. He encouraged intellectual debate and insisted on hands-on training of fellows and residents with paternal firmness and rigorous academic pursuit. His patient-counseling strategy always began with no assumption of patient knowledge of disease pathology and progressed on to the usage of metal and plastic to accomplish pain relief described in simple language. He combined science, humor, and grace to convey information, and his sartorial taste communicated class and confidence in his surgical skills. This compendium is a tribute to a great human being, excellent teacher, and a master artisan.
Patients who have knee arthritis present mostly with a painful, stiff knee with or without deformity with significant limitations in the quality of life (QOL). The expectation after a knee arthroplasty is a long-lasting, pain-free functional range to full range of motion (ROM) with no deformity. The surgeon’s role is to educate the patient about the possibility of success and help define a successful outcome from the patient’s perspective. The desirable outcomes after knee arthroplasty are symptomatic relief, recovery of function and restoration of desirable alignment . One of the important aspects of the surgical discussions with patients involves reviewing the risk of surgical complications. Knee arthroplasty surgery does provoke anxiety in some patients and a candid discussion helps to clear doubts about the surgery. Evidence-based discussion on complications eases anxiety and helps with objective decision making.
Each surgeon’s philosophy of patient counseling evolves over time, with contributions from mentors, patient behavior, societal expectation, and cultural imperatives. The fundamental question is how much information is too much for the patient in decision-making. The surgical discussion has ethical, moral, and legal dimensions. The information provided should be factually accurate and balanced about the advantages, limitations, and success rates.
Outcomes
Patient satisfaction is an important factor in the outcomes assessment of TKA in end-stage arthritis. There are many tools that assess total knee outcomes, but recently the patient-reported outcome measures (PROMs), where there is direct patient reporting rather than an indirect assessment, have increased in importance. The orthopedic registries are an important source of decision-making. At present, there is a heterogeneity between the registry and PROMs used in a particular country. European quality five-dimension health survey–three level (EQ-5D-3L), European quality five-dimensional health survey–five level (EQ-5D-5L), 36-item Short Form Health Survey (SF-36), 12-item Short Form Health Survey (SF-12), and Patient-Reported Outcomes Measurement Information System (PROMIS) have all been used in general functional improvement assessment. The Oxford Knee Score (OKS), Knee Injury and Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster Universities Arthritis Index (WOMAC), University of California Los Angeles (UCLA) activity score, and Visual Analog Scale (VAS) for pain are used in the focused assessment of knee functional outcome. The 2011 Knee Society Score (KSS) included patient expectation and functional activity in addition to information that has to be assessed by the clinician, which was an improvement from its previous version. Although useful for patient counseling, synthesizing information from registry data represents a challenge as a different indexes are used by different registries. The New Zealand (NZOA) Joint Registry has 20-year patient satisfaction data measured by Oxford-12 Knee Score scale from 0 to 48, and the data are categorized as excellent outcomes (>41), good outcomes (34–41), fair outcomes (27–33), and poor outcome (<27). Table 13.1 summarizes the serial outcomes using the OKS.
| Time | 6 months | 5 years | 10 years | 15 years | 20 years |
|---|---|---|---|---|---|
| Number of patients | 29,816 | 11,768 | 6572 | 2364 | 128 |
| Excellent or good outcomes | 75% | 84% | 82% | 79% | 75% |
| Average score | 37.65 | 40.5 | 39.96 | 39.39 | 39.04 |
The American Joint Replacement Registry has shown that 88.5% of patients at 1-year postoperative follow-up had meaningful improvement in KOOS score. During 2017, the Swedish Knee Arthroplasty Registry demonstrated that 87% of patients at 1-year follow-up were very satisfied or satisfied with TKA as assessed by the VAS. In a study of satisfaction using OKS at 1 year postsurgery in 10,000 patients who underwent surgery in England and Wales the National Joint Registry noted that 81.8% (6625 of 8095) were satisfied, 11.2% (904 of 8095) were unsure, and 7.0% (566 of 8095) were not satisfied.
In a systematic review of 208 studies and 95,560 patients Kahlenberg et al. determined that the median reported percentage of satisfied patients was 88.9%. The same study also showed that the most commonly reported predictor of satisfaction was a higher absolute postoperative patient-reported functional score. Preoperative anxiety and/or depression was the most common preoperative predictor of dissatisfaction, and persistent pain was the most common postoperative predictor of dissatisfaction. Certain activities are easier than others in the postoperative period. In a study by Bourne et al. using WOMAC scoring for pain relief in 1703 patients 72% were satisfied with their ability to go up or down stairs compared with 85% with walking on a flat surface and 84% with sitting or lying. For restored function, patients were least satisfied with getting in or out of a bus or car (70%) and ascending stairs (73%) compared with rising from a bed (82%), lying in a bed (84%), and performing light domestic duties (83%). For overall satisfaction, which was used as the proxy for the satisfaction outcome, 81% (1375) of patients claimed that they were satisfied or very satisfied and 19% (328) were very dissatisfied, dissatisfied, or neutral. The same study also showed that the strongest contributing variables to patient dissatisfaction after primary TKA using odds ratios (ORs) were expectations not met (10.79), a low 1-year WOMAC (2.59), a low preoperative WOMAC pain score while sitting or lying (2.49), and a complication requiring hospital admission (1.99).
With the available data, it is safe to say that 75% to 89% of patients are satisfied after TKA. It has also been shown that expectations not being met is a critical factor in the lack of postoperative satisfaction, and presurgical discussion should include clear goal setting of achievable objectives.
Cost-Effectiveness
Many patients are worried about the cost-effectiveness and QOL improvement in financial terms concerning TKA. Many studies are looking into the cost-effectiveness of TKA and have concluded that TKA is a cost-effective surgery in improving QOL. A study by Losina et al. showed an incremental cost of $18,300 per quality-adjusted life year gained, and they concluded that TKA is a highly cost-effective procedure for the management of end-stage knee osteoarthritis (OA) among Medicare-aged persons compared with nonoperative management. In a systematic review of 23 studies Kamaruzaman et al. concluded that TKA and total hip arthroplasty are cost-effective and should be recommended for the management of patients with end-stage knee and hip OA. Surgeons can convey to their patients that TKA is a cost-effective surgical procedure to improve QOL.
Complications
In 2013 the Knee Society TKA Complications Workgroup published a list of 22 important complications that have a bearing on the outcome of TKA. They can be classified as relating to the surgical procedure, to certain processes, and to the property of the materials used ( Table 13.2 ). This classification helps not only with patient communication regarding the rationale for complications but also with the possible strategies to minimize them. Certain complications such as neurovascular injury, ligament injury, and extensor mechanism disruption are operator-dependent and can be reduced by strict attention to detail.
| Procedure (Intraoperative) | Process (Medium to Long Term) | Property (Mechanical Factors) |
|---|---|---|
| Bleeding | Instability and dislocations | Osteolysis |
| Wound complications | Malalignment | Loosening |
| Nerve (0.79%) and vessel injury (0.08%) | Stiffness | Wear |
| Periprosthetic fracture | |
| Deep venous thrombosis | ||
| Extensor mechanism disruption (0.17%–2.5%) | ||
| Reoperation, revision, readmission | ||
| Infection | ||
| Death |
Nerve and Vessel Injury
Nerve and vessel injury can be caused by direct injury, pressure effect, or secondary damage. Patients who have preexisting flexion or valgus deformity, prolonged tourniquet usage, or rheumatoid arthritis are at increased risk for nerve palsy, primarily of the peroneal nerve. Jacob et al. found that the majority (62%) of neurological deficits completely resolved during the median follow-up of 5.1 years, with an additional 36% of patients reporting partial recovery.
Vascular injuries are a rare but devastating complication of TKA. The popliteal vessels are vulnerable to excessive manipulation, direct injury during bony cuts and during posterior midline soft tissue dissection, and cement polymerization. In a large population database study by Lin et al. there were 15 direct vascular injuries in 111,497 patients, and the primary risk factor was surgeon volume; there was a higher risk of injury in procedures performed by surgeons with lower volume.
Extensor Mechanism Complications
The extensor mechanism complications can include quadriceps tendon and patellar tendon rupture, patellar or tibial tuberosity fracture, or subluxation of the patellofemoral joint. Extensor mechanism rupture can occur in 0.17% to 2.5% of cases as seen in a study by Schoderbek et al. Extensor mechanism disruption is a difficult problem with complicated surgical solutions. The risk factors that predispose to the extensor mechanism dysfunction are inflammatory joint disease, diabetes mellitus, hyperthyroidism, and repeated corticosteroid injections into the knee joint.
Bleeding
Bleeding is a well-known side effect of TKA. With transfusion rates varying from 2.5% to 35.3%, significant postoperative anemia can warrant a blood transfusion. Postoperative allogeneic blood transfusion (ALBT) has been shown to be associated with an increased incidence of early postoperative confusion (OR = 3.44), cardiac arrhythmia (OR = 5.90), urinary catheterization (OR = 1.60), incidence of deep infection (OR = 4.03), and mortality (OR = 2.35). Anemia in the postoperative period is not a benign condition and has the potential to be preventable and correctable. Strategies available are listed in Table 13.3 . Of all the surgical strategies, intraarticular and intravenous (IV) tranexamic acid (TXA) has been known to significantly reduce blood loss. In a systematic review it was found that TXA reduced total blood loss by a mean of 591 mL.
| Iron deficiency anemia |
|
| Intraoperative blood loss |
|
| Postoperative blood loss |
|
Wound Complications
The knee is a superficially located joint with minimal soft tissue covering. In a study by Galat et al. 59 out of 17,784 patients required surgical intervention within 30 days of TKA. More importantly, the need for immediate surgical intervention increased the subsequent need for surgeries by 8 to 10 times. Diabetes, obesity, presurgical albumin <3.5 g/dL, and anemia all increase the risk of superficial surgical site infection (SSI).
Ligament Injury
The medial collateral ligament (MCL) medially stabilizes the knee joint. Disruption of this ligament can affect the functional and long-term outcomes of TKA. Although studies have shown that it is uncommon, adverse outcomes can occur if not recognized and managed appropriately. In a study by Leopold et al. 2.6% of patients were reported to have a midsubstance damage or avulsion of the MCL from the femoral and tibial attachment. The management of an MCL injury consists of end-to-end repair with nonabsorbable material, varus/valgus constrained insert, reconstruction of the MCL using semitendinosus graft, or suture anchor repair of avulsions.
Instability
Instability after TKA is one of the most common causes for revision TKA. Effective gap balancing is imperative for successful TKA outcomes. The Australian Orthopedic Association National Joint Replacement Registy (AOANJRR) has shown that 0.4% of primary TKA warrant a revision surgery at 5 years because of instability. The sagittal balance of the flexion and extension spaces is not as important as the coronal varus/valgus gap balancing. Patients must recognize that certain factors are determined by the surgeon, such as symmetrical gaps after bony cuts and appropriate ligament releases. However, patients who have advanced deformity with bony defects, rheumatoid arthritis, uncemented TKA, and neuromuscular arthritis are at a higher risk for instability.
Suboptimal Alignment
The issue of alignment and the outcome of TKA is a topic of intense discussion. Some studies point to the direct relationship between suboptimal alignment and poor outcomes with a higher risk of revision, whereas other studies do not show any significant differences. A systematic review of studies published from 2000 to 2014 found that suboptimal alignment may be correlated with outcomes. Currently, there are no clear guidelines regarding the ideal alignment in the sagittal and coronal planes. The rotational alignment of the implants and its effect on outcomes is better defined. In a systematic review by Valkering et al. it was found that a positive correlation of 0.44 (95% confidence interval [CI], 0.27 to 0.59) for tibial rotation and of 0.68 (95% CI, 0.64 to 0.73) for femoral rotation would indicate that a higher degree of external rotation coincides with a higher total KSS. The same review also determined that TKA revision for an internal malrotation of the tibial component of 4.3 degrees and for an internal malrotation of the femoral component of 7.1 degrees resulted in marked improvement, but because of certain limitations, it is difficult to give a cutoff value for revision TKA. However, standard principles of external rotation of both femoral and tibial components are crucial to achieve satisfaction and avoid complications.
The coronal plane alignment of TKA is 90 degrees to mechanical axis alignment, with ±3 degrees as tolerance for a predictable outcome in TKA. Two articles published simultaneously in Clinical Orthopaedics and Related Research in 1985 discussed differing philosophies of coronal plane alignment. Insall et al. was an advocate for cemented fixation and mechanical alignment. Alternatively, Hungerford and Krackow advocated for uncemented fixation and anatomical alignment, where the knee is aligned in 2 to 3 degrees of varus similar to the natural knee alignment and primarily relied on uncemented fixation.
Major amounts of resources are expended on achieving target alignment with technology, which includes computer-assisted orthopedic surgery in TKA (CAOS), patient-specific instrumentation (PSI), and robotic-assisted TKA. In a 10-year follow-up study the robotic TKA reduced the outliers and improved accuracy; however, there was no difference in the functional outcome of either conventional jig-based or robotic TKA. Similarly, in a systematic review of robotic TKA, Kayani et al. concluded that there are no differences in medium- to long-term functional outcomes between conventional jig-based TKA and robotic TKA. In a meta-analysis of 23 studies, it was found that CAOS reduced femoral component outlier’s rate by 87% and for the tibial implant a reduction in outlier’s rate of approximately 80% but concluded that clinical significance of these findings though has to be proven in the future.37 In a metaanalysis by Kizaki et al. PSI in TKA did not improve PROMs, surgery time, or complication rates compared with standard TKA. Although the current consensus is that technology has allowed for innovative changes to performing a TKA, clinical or functional outcomes may not improve.
Stiffness
Stiffness is a painful limitation in functional ROM after a TKA. The exact definition of stiffness varies according to studies, but most commonly it can be defined as the presence of flexion contracture with available ROM of the knee being <70 degrees that leads to functional limitations. Stiffness has been reported as a complication 1.3% to 5.3% of the time. Risk factors associated with stiffness are preoperative ROM (the most important risk factor), diabetes, lung disease, smoking, and previous surgery on the knee joint. Surgeon-determined factors can contribute to stiffness in TKA and can include component size mismatch, mal-alignment, or improper ligament balancing. The treatment for stiffness consists of identifying the primary cause and intervening appropriately. In the early postoperative period and up to 3 months after surgery stiffness is managed by manipulation under anesthesia (MUA); long-standing stiffness is managed by arthroscopic arthrolysis or revision surgery if there is an identifiable cause of implant mal-alignment.
Periprosthetic Fracture
Periprosthetic fractures are fractures of the femur or tibia within 15 cm of the knee joint or 5 cm from the end of the prosthesis and any patellar fractures post- TKA. According to multiple studies, fractures are seen primarily in the femur, with an incidence of 0.1% to 2.5% compared with an incidence of 0.4% and 0.68% in the tibia and patella, respectively. The risk factors are mentioned in Box 13.1 . The treatment of periprosthetic fractures is predicated on bone integrity and stability of the implant fixation.
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