Total Knee Arthroplasty Design and Kinematics: Past, Present, and Future.

Total knee arthroplasty has undergone significant improvement in design and clinical application over the past 45 years. Unfortunately, 15-20% of patients are not satisfied with their result. While the explanation for this discrepancy is multifactorial, prosthetic design and the motion of the knee in space has come under greater scrutiny. The early designs attempted to copy the anatomic appearance of the knee joint without considering how the knee would move. Kinematics is now considered to be of paramount importance and may be the key to the future of knee arthroplasty.

Bicruciate Retaining Total Knee Arthroplasty: Short-Term Clinical Outcomes Using a Novel Prosthesis.

There is renewed interest in bicruciate retaining (BCR) total knee arthroplasty (TKA), which preserves anatomy and more closely replicates native kinematics, theoretically allowing for improved functional results when compared to posterior stabilized (PS) TKA or cruciate retaining (CR) TKA. The purpose of this study is to report early clinical and radiographic results for a novel BCR TKA design.

Synthetic Mesh Allograft Reconstruction for Extensor Mechanism Insufficiency After Knee Arthroplasty.

Extensor mechanism (EM) insufficiency after knee arthroplasty is a rare but devastating complication resulting in severe disability. To date, primary repair and allograft reconstructive options have produced suboptimal results. A synthetic mesh allograft reconstruction technique has recently been introduced with promising outcomes. A retrospective chart review was performed to identify all patients who experienced EM failure after total or unicompartmental knee arthroplasty and subsequently underwent synthetic mesh EM reconstruction using a previously described technique. Patient demographics, pre- and postoperative knee range of motion and residual extensor lag, pre- and postoperative pain and functional outcome scores, and complications were extracted during the chart review. Twelve patients met inclusion criteria: 3 with patellar tendon and 9 with quadriceps tendon defects. At mean follow-up of 27.0 months, all patients were ambulatory, with a mean residual extensor lag of 12.9° (range, 0°-30°). Mean visual analog scale pain score decreased significantly after EM reconstruction: 4.6±2.3 (range, 1-8) preoperatively vs 1.8±2.4 (range, 0-7) postoperatively (P=.01). The mean Knee Society knee score improved from 41.5±11.1 (range, 21-57) preoperatively to 79.5±13.8 (range, 54-90) postoperatively (P<.0001). The mean Knee Society function score improved from 14.6±12.3 (range, 0-40) preoperatively to 64.2±27.1 (range, 5-95) postoperatively (P<.0001). One clinical failure occurred as a result of prosthetic joint infection. Synthetic mesh EM reconstruction effectively restores knee function for a variety of EM deficiencies following knee arthroplasty. [Orthopedics. 2019; 42(4):e385-e390.].

Choices, Compromises, and Controversies in Total Knee Arthroplasty.

Although condylar total knee arthroplasty (TKA) has been performed for almost 40 years, many choices, compromises, and controversies remain. In the effort to provide optimal care and beneficial, enduring treatment for an expanding population of patients with debilitating arthritis of the knee and who are using ever-diminishing provider and financial resources, orthopaedic surgeons must carefully examine the available evidence to determine best practices. First, there is debate as to who should be a candidate for TKA. Beyond the established criteria of disease severity, should all patients who can benefit from TKA undergo the procedure, or should surgeons develop exclusion criteria based on complication risk? Current concepts for identifying and managing modifiable risk factors should be considered. Second, there is debate regarding the choice of TKA versus partial knee arthroplasty to manage unicompartmental arthritis. Third, surgeons continue to debate the ideal implant design for primary condylar TKA, whether to proceed with an anatomic approach of preserving one or both cruciate ligaments or a functional approach of resecting and substituting for the cruciate ligaments in various ways.

The Cruciate Ligaments in Total Knee Arthroplasty.

The early knee replacements were hinge designs that ignored the ligaments of the knee and resurfaced the joint, allowing freedom of motion in a single plane. Advances in implant fixation paved the way for modern designs, including the posterior-stabilized (PS) total knee arthroplasty (TKA) that sacrifices both cruciate ligaments while substituting for the posterior cruciate ligament (PCL), and the cruciate-retaining (CR) TKA designs that sacrifice the anterior cruciate ligament but retain the PCL. The early bicruciate retaining (BCR) TKA designs suffered from loosening and early failures. Townley and Cartier designed BCR knees that had better clinical results but the surgical techniques were challenging.Kinematic studies suggest that normal motion relies on preservation of both cruciate ligaments. Unicompartmental knee arthroplasty retains all knee ligaments and closely matches normal motion, while PS and CR TKA deviate further from normal. The 15% to 20% dissatisfaction rate with current TKA has renewed interest in the BCR design. Replication of normal knee kinematics and proprioception may address some of the dissatisfaction.

The Utility of Increased Constraint in Primary Total Knee Arthroplasty for Obese Patients.

Total knee arthroplasty (TKA) for obese patient entails more preoperative comorbidities and complications, and shorter longevity. This article is a retrospective review comparing longevity of the constrained implant with a standard prosthesis. Patient-specific data, Knee Society Scores, complications, and revisions were recorded and compared. No statistical differences were found. The constrained condylar knee for obese patients improves the intramedullary alignment of the prosthesis and supports the surrounding soft tissues. The clinical results are similar to a standard implant in the nonobese with similar longevity at midterm follow-up.

Can Both Cruciate Ligaments Be Preserved in Knee Arthroplasty? Eight- to Nine-Year Follow-Up of a Bicompartmental Knee Replacement.

Preservation of native knee anatomy may confer improved patient satisfaction, as suggested by patient satisfaction scores in unicondylar versus total knee replacement. Bicompartmental knee replacement (BKR) implants similarly promote native tissue preservation. We retrospectively reviewed 42 consecutive patients who underwent BKR from 2006 to 2007. Outcome measures were evaluated. At an average follow-up of 103 months (range 87-110), 34/42 (81%) of implants survived. Among the retained implants, the Knee Society Score (KSS) grade was excellent in 26/34 (76.5%), good in 5/34 (14.7%), fair in 3/34 (8.8%), and poor in 0/34 (0%) of cases. Midterm results of BKR demonstrated 81% survival and 76% with excellent KSS grading. Despite a 20% revision rate at the short-term follow-up, the retained implants functioned well at the midterm follow-up.

Minimally invasive knee arthroplasty: An overview.

Minimally invasive surgery (MIS) for arthroplasty of the knee began with surgery for unicondylar knee arthroplasty (UKA). Partial knee replacements were designed in the 1970s and were amenable to a more limited exposure. In the 1990s Repicci popularized the MIS for UKA. Surgeons began to apply his concepts to total knee arthroplasty. Four MIS surgical techniques were developed: quadriceps sparing, mini-mid vastus, mini-subvastus, and mini-medial parapatellar. The quadriceps sparing technique is the most limited one and is also the most difficult. However, it is the least invasive and allows rapid recovery. The mini-midvastus is the most common technique because it affords slightly better exposure and can be extended. The mini-subvastus technique entirely avoids incising the quadriceps extensor mechanism but is time consuming and difficult in the obese and in the muscular male patient. The mini-parapatellar technique is most familiar to surgeons and represents a good starting point for surgeons who are learning the techniques. The surgeries are easier with smaller instruments but can be performed with standard ones. The techniques are accurate and do lead to a more rapid recovery, with less pain, less blood loss, and greater motion if they are appropriately performed.

Bicompartmental knee arthroplasty: the clinical outcomes.

Replacement of the patellofemoral and medial tibiofemoral joints has been performed since the 1980s. Bicompartmental replacement was modified. Two different designs were developed: one custom implant and one with multiple predetermined sizes. The surgical technique and instruments are unique and training is helpful. There are no clinical reports for the custom design as of yet. The standard implant has several reports in the literature with only fair to good results and has subsequently been withdrawn from the market. Bicompartmental arthroplasty remains a questionable area of knee surgery. At present, the two separate implant technique is the best choice.

Bicompartmental arthroplasty of the knee.

Combined replacement of the patellofemoral and medial tibiofemoral joints has been performed in the past. The original approaches placed two separate implants during the same surgical procedure. Results were acceptable; however, with the increasing success of total knee arthroplasty, partial knee replacements lost favor. In the 1990s, a limited incision for unicondylar arthroplasty was introduced that encouraged interest in partial knee replacements. The newer implants combine the medial and patellofemoral articulations into a single femoral implant with a medial tibial tray and a polyethylene patella. The surgical technique and instruments are somewhat unique and training is helpful. Bicompartmental arthroplasty preserves all of the ligaments of the knee while replacing two compartments. The procedure is more complicated than unicompartmental knee arthroplasty, less invasive than total knee arthroplasty, and may have a place in replacement surgery.

Avoiding pitfalls in minimally invasive total knee arthroplasty.

Minimally invasive total knee arthroplasty started in the early 1990s with the introduction of unicondylar knee arthroplasty using a limited surgical incision. The techniques were initially received with remarkable enthusiasm; however, enthusiasm waned when results were compromised by the limited visibility of the approaches. Minimally invasive total knee arthroplasty can produce better early results than the traditional approach and can increase the final range of motion of the knee. The techniques are somewhat demanding, and the results can be improved with more careful patient selection, a thorough review of the preoperative radiographs, appropriate choice of the prosthesis, strict attention to the surgical technique, and an aggressive postoperative rehabilitation program.

Minimally invasive total knee arthroplasty: past, present, and future.

Choices for a limited approach to total knee arthroplasty (TKA) now include the mini-arthrotomy, the mini-midvastus, the subvastus, and the quadriceps-sparing technique. These newer approaches suggest use of modified instruments at least smaller in overall size; call for early ambulation and range of motion with modified pain management protocols; demonstrate improved early recovery of the knee; and lead to less visualization and can contribute to an increase in outliers. Use of navigation for TKA remains controversial. Prophylaxis against deep venous thrombosis is necessary and is used at the discretion of the operating surgeon. Complications are sometimes higher with these approaches, and patient preference and choice of surgical technique are extremely important. Minimally invasive surgery approaches are still evolving for TKA, and long-term results are not available. These techniques are certainly not for all patients or all surgeons, and the indications are still being developed.

The evolving role of navigation in minimally invasive total knee arthroplasty.

Surgical navigation systems are either image-guided (computed tomography or fluoroscopy) or imageless-guided. Each system type has its advantages and disadvantages and can be used with minimally invasive surgery (MIS) total knee arthroplasty (TKA). A newer imageless-guided system that incorporates electromagnetic field transmitters and detectors has distinct advantages over imageless-guided systems with bulky, problematic arrays. Navigated surgery holds significant promise for future applications, but navigation technologies should be used with caution for MIS TKA because of their associated anomalies (these technologies sometimes return incorrect information during surgical procedures).

Quadriceps-sparing total knee arthroplasty using the posterior stabilized TKA design.

Minimally invasive TKA is in the early stages of development. Healthy skepticism is appropriate until long-term data has been reported. Early results with the quadriceps-sparing technique are encouraging. It appears to be less painful and entail a shorter recovery time. We hope the results will remain stable as the follow-up time increases.

MIS unicondylar knee arthroplasty: surgical approach and early results.

Unicondylar arthroplasty of the knee has seen a resurgence of interest in the United States. The principles of unicondylar arthroplasty of the knee are different from those for total knee arthroplasty, allowing replacement of only the affected joint compartment with less bone loss. Minimally invasive surgery allows for less soft tissue dissection with the potential for less morbidity. The key question is: will the changes associated with the minimally invasive surgery procedure improve the clinical results of the standard unicondylar arthroplasty of the knee or will the changes make the procedure too difficult and lead to an increasing failure rate? This study reviews the surgical technique and presents the 2 to 4 year results of the minimally invasive unicondylar arthroplasty of the knee 47 knees in 41 patients. The average range of motion increased from 121 degrees -132 degrees . The Knee Society pain score improved from 45-80 and the function score improved from 47-78. Only one knee has been revised. With proper patient selection, minimally invasive unicondylar arthroplasty of the knee allows for results that are at least equal to those of the standard open procedure at 2 to 4 years after the surgery.

Different surgical options for monocompartmental osteoarthritis of the knee: high tibial osteotomy versus unicompartmental knee arthroplasty versus total knee arthroplasty: indications, techniques, results, and controversies.

The decision of what procedure to perform for the treatment of monocompartmental osteoarthritis of the knee when nonsurgical treatment methods fail remains controversial. Recent advances using osteotomy, unicompartmental knee replacement, and total knee replacement have been reported. For example, there are new concepts for performing high tibial osteotomies rather than the traditional Coventry method. Many techniques now involve osteotomies below the tibial tubercle. Unicompartmental knee replacement can be done using a standard approach, but less invasive approaches exist, along with minimally invasive approaches for total knee replacement, rather than the standard large incision, that promote decreased soft-tissue destruction.

Minimally invasive total knee arthroplasty: the importance of instrumentation.

MIS TKA is in the early stages of development. There are many opponents who believe that the technique is nothing more than a cosmetic modification of the standard TKA that leads to more complications and less patient satisfaction. It is important to respect these comments and to thoroughly address them. MIS surgery should not be based on the length of the incision or the cosmetic result. The term "minimally invasive" should refer to the extent of disruption of the anatomic structures about the involved joint. In the knee, the MIS approach should not violate the extensor mechanism and should not violate the suprapatellar pouch. MIS should be a capsular approach, and as such it should produce less discomfort and a faster recovery. Modifications of the MIS technique that extend the arthrotomy into the extensor mechanism, violate the suprapatellar pouch, and evert the patella while using a limited incision are not truly minimally invasive. The MIS procedure should allow the patient to recover faster while keeping the incidence of complications at the same or lower levels as the open procedure. There will certainly be a learning curve for this operation and a smaller incision with standard TKA techniques maybe the interim step for the surgeon attempting to master the new approach. MIS TKA must be performed with accurate instruments that are coordinated with the procedure. It is not possible to perform the operation with the traditional instruments that have been made for the open operations. The older instruments do not fit into the knee joint and do not allow visualization of the joint at the same time that the cuts and balancing are performed. The visual appearance is totally different and new. The surgeon must learn a completely new image of the knee joint while continuing to apply the basic principles that have been well established. The instruments are a critical part of this new technology and are central to its success. There is no room for guessing or "eye balling" the bone cuts or the alignment and balancing. Instruments and computer-assisted technology will help advance MIS surgery in the next few years. The results of MIS TKA must be thoroughly studied and compared with the existing literature. The author has tried to advance this development ina logical fashion. The initial step was to design instruments that would allow implantation of the presently accepted knee prostheses. This step has now been completed; however, the operation is not simple and is time consuming. The next step therefore is to change the prostheses to facilitate the surgery. The femoral and tibial components are presently too large for the working incision. They are now being modified so that they can be implanted in two or more pieces. This will permit less soft tissue dissection and work better with the smaller incision. The final step will incorporate computer navigational systems. All of the present instruments are designed with attachments for the appropriate arrays to interact with these systems. Ideally, the computer image will allow precise visualization of the knee, particularly the lateral side. All new surgical approaches and devices must be introduced with the expectation to improve the surgical results. There is no doubt that the final goal of this work should be technical improvement without early clinical failures or complications.