Knee

Is the robot helpful in early rehab following unicondylar knee arthroplasty?

Unicondylar knee arthroplasty (UKA) for medial compartment osteoarthritis has recently been widely publicized, both in the medical literature and the national press. The advantages have been well documented, including the ability to preserve the patients’ own kinematics leading to better functional outcomes. However, this is balanced against the increased risk of implant failure and reduced survivorship compared with total knee arthroplasty. Some of these failures are due to poor surgical technique, which is often associated with lower-volume surgeons. While robotic-assisted surgery should never be seen as a replacement for surgical experience and training, it can help reduce intraoperative surgical errors. As such, robotic-assisted surgery is being used in specialist low-volume arthroplasty procedures such as unicompartmental knee arthroplasty. In addition to the potential benefits from a component alignment perspective, the authors of this paper from London (UK) proposed that robotic technology may also help preserve the periarticular soft-tissue envelope, and therefore aid a more rapid period of early postoperative rehabilitation.¹ This series reports the outcomes of patients undergoing either conventional jig-based UKA or robotic-arm assisted UKA. A total of 146 patients (146 knees) were included, with 73 consecutive patients undergoing the conventional UKA followed by 73 consecutive patients undergoing the robotic-assisted technique. All patients received a standardized postoperative care programme including patient-controlled analgesia (PCA) with additional oral paracetamol and ibuprufen was prescribed as required. The PCA was then stopped 24 hours after surgery and converted to oral medication. Patients undergoing the robotic-assisted surgery had significantly less pain than the conventional group with opiate usage also significantly lower in this group. Form a functional perspective, the robotic group were able to achieve a straight leg raise significantly quicker than the conventional group, and achieved greater knee flexion at discharge, requiring fewer physiotherapy sessions. Mean time to discharge was also statistically quicker in the robotic group. The results from this study were somewhat surprising. A reduction in surgical errors in implant positioning could be reasonably expected with this technology, but not intuitively less pain and easier rehabilitation. It has been postulated that a more conservative bone resection is associated with reduced bone oedema and, therefore, reduced pain and faster rehabilitation. In addition, with robotic assistance there could be better preservation of the supporting soft tissues as the burr used to remove the bone automatically shuts off should the surgeon stray away from the articular surface. With conventional surgery, inadvertent injury to the periarticular soft tissues could occur from the oscillating saw, which may go unnoticed. The authors suggest that with fewer iatrogenic injuries from an oscillating saw to the periarticular soft tissues, robotic-assisted surgery results in less pain and, therefore, faster rehabilitation. This is one of the first papers to suggest a clinical advantage with robotic-arm technology. The benefit observed in this study may only be in the early postoperative phase but this would still be a significant advantage. Most patients find the first few weeks after a UKA very painful, so anything that reduces patient perception of pain and enables quicker rehabilitation needs to be seriously considered. We look forward to a formal randomized study here.

Usually, selectively, or rarely resurfacing the patella during primary total knee arthroplasty: determining the best strategy

The debate about resurfacing the patella continues, with most practices performing resurfacing on a geographic or unit basis. The problem with a preference approach like this is that it has not been made readily apparent which preference is best. The authors of this study from Auckland (New Zealand) utilized an interesting methodology to try to establish which approach is best.² The authors categorized surgeons into three groups based on their preferences for patella resurfacing and on New Zealand Joint Registry (NZJR) data: ‘usually resurface’, ‘rarely resurface’, or ‘selectively resurface’. The study focuses on the results of the 203 surgeons performing 57 766 primary total knee arthroplasties (TKAs) between 1999 to 2015 with outcomes recorded on the NZJR. The authors arbitrarily defined < 10% as ‘rarely resurfacing’ and > 90% as ‘usually resurfacing’, with the remainder in the selective cohort. The outcomes were assessed using both likelihood of revision and Oxford Knee Scores (OKS) at six months and five years. Overall, the majority (57%) were categorized as ‘selective resurface’, and 37% ‘rarely resurface’. This left 14 surgeons (7%) in the ‘usually resurface’ group. With such a small subgroup of surgeons in this group, very little can be inferred from the findings of this study for that group, as there are so many other factors (such as implant choice, surgical skill, etc.) that have an impact on both knee survival and clinical outcome measures. Despite the limitations of sample size, the authors report that those in the ‘usually resurface’ group achieved the highest mean OKS at both timepoints, followed by the ‘selective resurface’ group. This was not associated with any apparent differences in revision rate per 100 observed component years (‘rarely’ (0.46), ‘selectively’ (0.52), or ‘usually’ (0.46)). There was a difference, however, in the success of posterior-stabilized implants with ‘selective’ resurfacers having a significantly lower revision rate. This is, of course, again subject to the limitations of the small group sizes. As this study demonstrates, the geographic preference in New Zealand leans heavily on selectively resurfacing, yet the usual resurfacing patients had higher OKS. The revision rate was similar between groups, leading to the conclusion that orthopaedic surgeons will not be faulted if they do or do not resurface the patella.

Injection prior to total knee arthroplasty and infection

Intra-articular corticosteroid injection or hyaluronic acid injection is routinely performed as conservative therapy for knee osteoarthritis. On many care pathways, patients are encouraged to exhaust a package of conservative care including lifestyle and risk factor modification, physiotherapy, and injection (usually of steroid). There is both professional opinion and case-controlled series evidence that there is an increased risk of implant associated infection in those undergoing total knee arthroplasty (TKA) after local injection into the knee. What is not known is an accurate assessment of the risk and exposure time. This paper from New York, New York (USA) aims to establish what the relative risks of infection are with either steroid or hyaluronic acid injections prior to TKA.³ This study builds on work that demonstrates that recent injections (within three months) into the knee are associated with a higher infection rate when a subsequent arthroplasty is performed. This is an insurer-based database study from the USA and sets out to establish what the effects of recent injection of either corticosteroid or hyaluronic acid are on subsequent TKA infection rates through activity and billing code data. The authors utilized episode data on a total of 58 337 patients, all of whom underwent a TKA.

Of these, 3249 patients (5.6%) received hyaluronic acid and 16 656 patients (28.6%) received corticosteroid less than or equal to one year before TKA. The authors estimated the incidence of infection as 2.7% in the whole group. However, a multivariable regression model demonstrated independent prosthetic joint infection for both corticosteroid (odds ratio (OR), 1.21; p = 0.014) and hyaluronic acid (OR, 1.55; p = 0.029) given less than or equal to three months before TKA. However, they also established that there was no increased risk for those who underwent injections over 12 weeks prior to undergoing their TKA.

This is a large data set that essentially establishes that patients should not be offered a TKA within three months of an injection into the joint. While the injection itself does not bar undergoing a joint arthroplasty, there are clear indications here that whatever the type of injection, a three-month cooling off period prior to undertaking a TKA is required.

Does the institution matter in prosthetic joint infection?

Amputation after total knee arthroplasty: not a great option

When situations are unsalvageable, the only option can be an above-knee amputation. Modern advances in military injuries have demonstrated how well patients can get on after amputations. The results of these young men, usually at the peak of fitness with superb medical care and great amounts of resolve and commitment to their rehabilitation, is often applied to other populations. There is rising awareness that an 80-year-old with several years of immobility and diabetes cannot expect to do anything like as well with an amputation as the young combat veteran. The route of final resolution for the untreatable revision knee (usually for infection) is, of course, amputation. This in itself is a last-resort operation with the only other option a knee fusion. However, little is known about the outcomes in this group, and the suspicion has been for a number of years that they may not do as well as those veterans with the same operation. A multicentre group from across the United States conducted an important study detailing the outcomes of precisely these patients.⁵ In their retrospective multicentre review, the authors of this paper drew together 111 patients, all of whom had an above knee amputation following a failed total knee arthroplasty. Patients were from a representative age range (42 to 88 years old) and had, on average, 3.7 operations to the knee prior to the amputation. The authors report demographic and comorbidity information along with postoperative mortality and functional data. Just shy of 90% of patients underwent amputation for chronic infection, and the overall five-year survival rate for the patients was 52%, which was reflective of the frailty of the group as a whole. For the survivors, this study frankly reports what really happens to arthroplasty patients who undergo an above-knee amputation. Only 53% were satisfied. Only 55% use a prosthesis, 55% were primarily reliant on a wheelchair for mobility, and 80% reported phantom limb pain. This stark and realistic picture of patients following an above-knee amputation in older life is definitely food for thought for the arthroplasty surgeons among us.

Synovial fluid alpha-defensin as a diagnostic adjunct

Implant survival and function ten years after kinematically aligned total knee arthroplasty

Total knee arthroplasty (TKA) innovations undergo years of scrutiny before becoming part of general clinical practice, including kinematic knee alignment (KA), which is a relatively new approach to total knee arthroplasty alignment. In KA, the surgeon orients the replacement knee as close to the native alignment as possible, the rationale being that this maintains the best soft tissue balance and that this in itself will result in superior outcomes. Randomized trials evaluating kinematic KA have shown better pain relief, function, flexion, and a normal feeling knee compared with those treated with a mechanically aligned (MA) knee. The long-term effects of using KA are still unknown, and are of concern since the prosthetic components are set in orientations outside the suggested values for MA knees. Advocates of MA believe that alignment outside of those set values poses a higher risk of implant failure than those in range, due to uneven loading of the components and the potential for macroscopic failure. This study focuses on the long-term results of the KA TKA by noting implant survival, yearly revision rate, and patient-reported outcomes including the Oxford Knee Score (OKS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores. The authors of this study from Davis, California (USA) focus on the results of a cohort of 207 TKAs performed in 2007; the mean age for the cohort was 77 years (sd 10, 49 to 97) and 38% were male.⁷ The yearly revision rate was 0.3%, with an implant survival of 97.4% for all-cause revision at ten years. There were five patients who were revised for aseptic failure and two for postoperative infection. Tibial component loosening occurred in one revision patient; the component subsided posteriorly associated with a reverse tibial slope of 8°. Patellar complications were found in four knees: one underwent a full revision and two were treated with arthroscopic lateral releases for lateral patellofemoral instability, while the last patient had a revision of the patella for a loose patellar implant. At ten years, functional scores were available for 144 knees: OKS had an average score of 43 (0 to 48, with 48 being the best), and the average score for WOMAC was found to be 7 (0 best, 96 worst). There was no significant difference between the in-range and outlier aligned knees. Patients who are kinematically aligned at the time of TKA do well at a long-term follow-up of ten years, suggesting it to be an appropriate surgical technique for surgeons to use.

A predictive model for satisfaction after primary total knee arthroplasty

Bundled payments have become more popular as the payment method for a total knee arthroplasty (TKA). As the US population grows older, the number of TKAs performed annually is expected to rise, with the revision and readmission rates increasing proportionally with it. The current rate of dissatisfaction after TKA remains surprisingly high, with reported percentages ranging from 17% to 41%. The need for additional postoperative care for unsatisfied patients will ultimately put a strain on the healthcare system’s economy because of the financial burden incurred from bundled payments. Identifying factors that are indicative of TKA dissatisfaction may be helpful in potentially improving postoperative outcomes to offset the financial burden of revisions and re-hospitalizations. This study analyzed the answers given by patients on an 11-item TKA questionnaire to identify potential indicators of complications and dissatisfaction following surgery. The knee survey took into account both modifiable risk factors (body mass index (BMI), diabetes, opioid use, comorbidities, smoking status) as well as the patient’s own medical history (drug allergies, osteophyte score, patellar thickness to soft-tissue shadow skin thickness, flexion contracture, previous knee surgery, and surgical indication). Patients were also given functional outcome evaluations (patient-reported health state (PRHS), Knee Society Score (KSS), and KSS functional outcome (KSS-F) both preoperatively and at a minimum of one-year postoperatively. Responses were available from 484 patients undergoing TKA and were included in the analysis; 69.0% of the patient population was female and the mean age was 66.3 years old. The mean BMI was 34.2 kg/m2. All components of the 11-item questionnaire were significantly and positively correlated with the total knee survey score (p < 0.0001). Risk tiers were found to be significantly associated with postoperative satisfaction. Four tiers in the questionnaire score were identified according to the risk of postoperative dissatisfaction: low (survey score of 96.5 to 110), mild (score of 75 to 96.4), medium (score of 60 to 74.9), and high (score of 59.9 and below), with the high-risk cohort most likely to be unsatisfied. Regardless of postoperative satisfaction, all patients improved their functional outcomes according to the KSS, KSS-F, and PRHS scores and knee flexion increased from 109.5° ± 15.1° to 113.3° ± 11.1°. Overall, this study team in Chicago, Illinois (USA) found that the 11-item TKA questionnaire is a significant predictor of functional outcomes following TKA when age, BMI, and sex were controlled.⁸ Patients that scored higher on the knee survey score had a greater chance of achieving postoperative satisfaction compared with others. The survey had a 97.5% sensitivity and 95.7% negative predictive value in patients at risk for postoperative dissatisfaction – perhaps this survey can be useful to surgeons when optimizing patients postoperatively to decrease their readmission/revision rate.

Text-messaging follow-up is effective in patients undergoing TJA