Unicompartmental knee arthroplasty versus total knee arthroplasty: Which type of artificial joint do patients forget?

Can ChatGPT Answer Patient Questions Regarding Total Knee Arthroplasty?

The internet has introduced many resources frequently accessed by patients prior to orthopaedic visits. Recently, Chat Generative Pre-Trained Transformer, an artificial intelligence-based chat application, has become publicly and freely available. The interface uses deep learning technology to mimic human interaction and provide convincing answers to questions posed by users. With its rapidly expanding usership, it is reasonable to assume that patients will soon use this technology for preoperative education. Therefore, we sought to determine the accuracy of answers to frequently asked questions (FAQs) pertaining to total knee arthroplasty (TKA).Ten FAQs were posed to the chatbot during a single online interaction with no follow-up questions or repetition. All 10 FAQs were analyzed for accuracy using an evidence-based approach. Answers were then rated as "excellent response not requiring clarification," "satisfactory requiring minimal clarification," satisfactory requiring moderate clarification," or "unsatisfactory requiring substantial clarification."Of the 10 answers given by the chatbot, none received an "unsatisfactory" rating with the majority either requiring minimal (5) or moderate (4) clarification. While many answers required nuanced clarification, overall, answers tended to be unbiased and evidence-based, even when presented with controversial subjects.The chatbot does an excellent job of providing basic, evidence-based answers to patient FAQs prior to TKA. These data were presented in a manner that will be easily comprehendible by most patients and may serve as a useful clinical adjunct in the future.

Clinical Outcomes and Survivorship of Lateral Unicompartmental Knee Arthroplasty: A Large Single Surgeon Cohort

BACKGROUND

Lateral unicompartmental knee arthroplasty (UKA) is an effective treatment for isolated lateral compartment osteoarthritis. However, due to the rarity of the procedure, long-term outcomes and survivorship are poorly understood. We report the clinical and radiographic outcomes after lateral UKA.

METHODS

We retrospectively reviewed a consecutive series of patients who underwent lateral UKA by a single fellowship-trained arthroplasty surgeon from 2001 to 2021 with a minimum 2 year follow up. There were 161 knees in 153 patients (average age 69 years) that met inclusion criteria, with a mean follow up of 10.0 years (range 0.05 to 22.2). All patients underwent the procedure via a minimally invasive lateral parapatellar approach with a fixed-bearing implant. Patient demographics, complications, radiographic findings, patient-reported outcomes, and the need for revision surgery were evaluated. Survivorship was defined with the end point as revision of components.

RESULTS

There were 8 patients (5.0%) who underwent conversion to total knee arthroplasty for lateral UKA implant failure or progression of arthritis. There were 3 patients (1.9%) who underwent ipsilateral medial UKA due to medial compartment arthritis progression with preserved mechanical alignment and patellofemoral joint. There were 8 additional procedures that did not require implant changes, including 5 irrigation and debridements for acute periprosthetic joint infection (3.1%), 2 wound closures for dehiscence (1.3%), and one loose body removal (0.6%).

CONCLUSIONS

Lateral UKA showed a survivorship rate of 98.0% at 5 years, 96.0% at 10 years, and 94.5% at 15 years. When including patients who underwent additional surgery for the progression of arthritis, survivorship was 97.4% at 5 years, 95.4% at 10 years, and 91.3% at 15 years. Lateral UKA should be seen as a durable treatment option for isolated lateral compartment osteoarthritis.

[Evolving indications for partial knee replacement : New aspects]

BACKGROUND

Partial knee replacement has proven to be an effective therapy for advanced unicompartmental arthrosis of the knee. Despite continuous advancements in implants and surgical techniques over the past decades, the global preference for total knee arthroplasty still persists for historical reasons.

OBJECTIVES

This report aims to illuminate advantages and disadvantages of partial knee replacement considering long-term results, the evolution of indication criteria over recent decades and new aspects in patient selection with potential improvements through emerging technologies.

MATERIAL AND METHODS

The analysis involves the examination of long-term results from clinical studies and registry data, highlighting the risk factors for potential failures and their influence on the development of indication criteria.

RESULTS

Present-day long-term results demonstrate excellent prosthetic survival, aligning with outcomes from total knee arthroplasty. New perspectives for expanding indication criteria are discussed, including the possible application of partial knee replacement in cases of severe varus deformity > 15°, anterior cruciate ligament insufficiency, young active patients, anterior knee pain, and/or patellofemoral arthritis, as well as mild radiographic arthritis with degenerative medial meniscus root tear and meniscal extrusion.

DISCUSSION

Indication criteria have consistently expanded in recent years, taking into account modern insights, and the application of advanced technologies can enhance precision and minimize surgical errors. Furthermore, this report emphasizes that revision rates are not the sole criterion for success and underscores the necessity for a comprehensive examination of clinical results.

Combination of a High Residual Varus and Joint-Line Lowering Strongly Increases the Risk of Early Implant Failure in Medial Unicompartmental Knee Arthroplasty

BACKGROUND

Outliers in implant positioning, malalignment, and joint line height change are risk factors for unicompartmental knee arthroplasty (UKA) failure. However, their relationships and patterns in large datasets remain unexplored. This study assessed medial UKA survival in a large cohort and explored associated risk factors.

METHODS

This was a retrospective cohort study on medial UKA patients (2011 to 2019). Radiological outcomes included tibial implant positioning in the coronal plane, posterior tibial slope, residual knee deformity, and joint line restitution. Survival rate at last follow-up was recorded. Multinomial logistic regression analyzed risk factors, incorporating demographic and univariate analysis data.

RESULTS

Three hundred and sixty-six knees met inclusion criteria, with 10 lost to follow-up (2.7%). Mean follow-up was 61.3 months [24.1 to 135.1]. 5- and 10-year implant survival rates were 92% ± 1.6 and 88.4% ± 3.8, respectively. Multivariate analysis identified post-operative hip-knee-ankle angle (HKA) ≤ 175° (OR = 5.30 [1.64 to 17.13], P = .005) and joint line lowering ≥2 mm (OR = 8.86 [2.06 to 38.06]) as significant risk factors for tibial implant failure. Their combination carried a significantly high risk of failure (OR = 10.3 [3.1 to 34.3]). Post-operative HKA < 175° was common in knees with pre-operative HKA < 172°.

CONCLUSION

This study reports encouraging 5- and 10-year survival outcomes for medial UKA. Tibial loosening was the main reason for revision. Patients with joint line lowering ≥ 2 mm and post-operative HKA ≤ 175° were at high risk of tibial implant failure. Surgeons should carefully restore the joint line in cases of pre-operative HKA < 172°.

Efficacy of tranexamic acid supplemented with local infiltration analgesia in reducing blood loss in patients undergoing unicompartmental knee arthroplasty

This study aimed to investigate the efficacy of tranexamic acid supplemented with local infiltration analgesia in reducing blood loss in patients undergoing unicompartmental knee arthroplasty (UKA). This retrospective study was conducted on 176 individuals with a mean age of 64.27 (standard deviation [SD], 7.16) years undergoing unicompartmental cemented knee arthroplasty. The patients were divided into three groups according to patient blood management: I, patients without additional bleeding protocol (control group); II, patients intravenously administered tranexamic acid (TXA) (TXA group); and III, patients with exact TXA protocol combined with intraoperative local infiltration analgesia (LIA) (TXA + LIA group). Blood loss was measured as a substitute for blood loss by the maximal haemoglobin (Hb) drop compared with the preoperative Hb level. The mean Hb drops for the control, TXA, and TXA + LIA groups were 2.24 (16.0%), 2.14 (15.4%), and 1.81 (12.6%) g/dl, respectively. The mean hospitalisation days for patients in the control, TXA, and TXA + LIA groups were 5.91 (SD 1.24), 5.16 (SD 0.95), and 4.51 (SD 0.71) days, respectively. The combination of TXA with LIA reduces perioperative blood loss for patients after UKA.

Comparison of joint awareness after total knee arthroplasty, medial unicompartmental knee arthroplasty, and high tibial osteotomy: a retrospective study

INTRODUCTION

This study aimed to compare the Forgotten Joint Score-12(FJS) outcomes and the minimum clinically important difference (MCID) of the FJS after high tibial osteotomy (HTO), unicompartmental knee arthroplasty (UKA), and total knee arthroplasty (TKA) with short-term follow-up (at least 2 years). Another objective of the study is to investigate the factors influencing FJS. It is hypothesized that there are differences in FJS outcomes among the three procedures.

METHODS

Patients who underwent HTO, UKA, and TKA from January 2016 to December 2020 and were followed up for a minimum of 2 years were included in the study. The FJS were analyses from a cohort of people who submitted data to two years. The preoperative and postoperative clinical outcomes were compared and evaluated the patient-related factor. The FJS scores were predicted using multiple linear regression analysis. Additionally, Patient's Joint Perception (PJP) questions were used as anchors to determine the achievement of the forgotten joint, and FJS MCID were calculated using the receiver operating characteristic curve (ROC).

RESULTS

Three hundred eighty-nine patients were included in the final study, and there were 111 patients in HTO groups,128patients in UKA groups, and 150 patients in TKA groups. The mean follow-up was 47.0 months. There was a significant difference in the total FJS, between the HTO, UKA, and TKA groups (FJS:59.38 ± 7.25, 66.69 ± 7.44 and 56.90 ± 6.85, p < 0.001. We found the MCID of the FJS of HTO, UKA, and TKA were 63.54, 69.79, and 61.45, respectively. In multiple linear regression, younger age, and higher FS were significant predictors of better FJS.

CONCLUSION

Medial UKA demonstrated lower patient awareness in comparison to HTO and TKA, as assessed by the FJS. Younger age and higher FS were identified as significant predictors of improved FJS, providing valuable guidance for surgical decision-making.

Unicompartmental knee arthroplasty (UKA) for primary spontaneous osteonecrosis of the knee (SONK): a systematic review

Introduction

The role of unicompartmental knee arthroplasty (UKA) in spontaneous osteonecrosis of the knee (SONK) is still controversial.

Materials and methods

We performed a systematic review to evaluate all available current literature on UKA in the setting of SONK. A comprehensive electronic research was performed using the PubMed, Embase, Web of Science, and Cochrane databases with keywords related to SONK and knee arthroplasty. Studies were selected with predetermined inclusion criteria: 1) studies that specifically assessed SONK treated with UKA; 2) studies reporting implant survival rate and global clinical outcomes; 3) studies with a minimum follow up of 1 year. We excluded articles not written in English, articles that did not differentiate between primary and secondary osteonecrosis and articles published before 2000.

Results

The overall research process produced 19 studies. We extrapolated data of a total of 717 unicompartimental knee arthroplasty procedures (1,39% lateral UKA, 98,61% medial UKA). Extracted data include years of follow-up, patient demographics, laterality of lesion, radiological findings, unicompartimental knee arthroplasty implants, reason of revision, revision rate, maximum knee flexion, knee clinical outcomes score, and Kaplan-Meier survival curves. The data collected show that UKA had acceptable survival rates as well as revision rates and good clinical outcomes both in the short- and long-term.

Conclusion

UKA is an optimal treatment choice for primary SONK when correctly indicated in a carefully selected subset of patients, with no significant difference compared to osteoarthritis. Attention must be paid to distinguish the primary from secondary SONK, as the latter could lead to worse outcomes.

Proximal tibia osteotomy with absorbable spacer combined with fibular osteotomy versus high tibial osteotomy for medial compartmental knee osteoarthritis

PURPOSE

The study aimed to compare the perioperative complications, short-term clinical outcomes, patient-reported outcomes, and radiographic parameters of tibiofibular proximal osteotomy combined with absorbable spacer insertion (TPOASI) and open-wedge high tibial osteotomy (OWHTO) in a two year postoperative time period.

METHODS

A total of 160 patients with Kellgren-Lawrence classification grade 3 medial compartmental knee OA were randomized to receive either TPOASI (n = 82) or OWHTO (n = 78). The primary and secondary outcomes were measured preoperatively, postoperatively, and at each follow-up examination. The primary outcomes were the between-group change in the Western Ontario and McMaster Universities Global score (WOMAC). Secondary measures included visual analog scale (VAS), radiographic parameters, American Knee Society Score (KSS), operation time, blood loss, length of incision, hospital stay, and relevant complications. Postoperative radiographic parameters, including the femorotibial angle (FTA), varus angle (VA), and joint line convergence angle (JLCA), were measured to evaluate the correction of varus deformity.

RESULTS

No significant differences were found in the baseline data between the two groups. Both methods improved functional status and pain postoperatively. For primary outcomes of both groups, statistical difference was observed in WOMAC scores at the 6-month follow-up (P < 0.001). For secondary outcomes, no statistical difference was observed between the groups during the 2-year follow-up (P > 0.05). For TPOASI vs. OWHTO, the mean hospital stay (6.6 ± 1.3 days vs. 7.8 ± 2.1 days) was shorter (P < 0.001), and both blood loss (70.56 ± 35.58 vs. 174.00 ± 66.33 mL) and complication rate (3.7% vs. 12.8%) were significantly lower (P < 0.005 for both).

CONCLUSIONS

Both approaches showed satisfactory functional outcomes and alleviated pain. However, TPOASI is a simple, feasible method with few complications, and it could be widely used.

A comparison of clinical thresholds for revision following total and unicompartmental knee arthroplasty

Unicompartmental knee arthroplasty (UKA) has higher revision rates than total knee arthroplasty (TKA). As revision of UKA may be less technically demanding than revision TKA, UKA patients with poor functional outcomes may be more likely to be offered revision than TKA patients with similar outcomes. The aim of this study was to compare clinical thresholds for revisions between TKA and UKA using revision incidence and patient-reported outcomes, in a large, matched cohort at early, mid-, and late-term follow-up. Analyses were performed on propensity score-matched patient cohorts of TKAs and UKAs (2:1) registered in the New Zealand Joint Registry between 1 January 1999 and 31 December 2019 with an Oxford Knee Score (OKS) response at six months (n, TKA: 16,774; UKA: 8,387), five years (TKA: 6,718; UKA: 3,359), or ten years (TKA: 3,486; UKA: 1,743). Associations between OKS and revision within two years following the score were examined. Thresholds were compared using receiver operating characteristic analysis. Reasons for aseptic revision were compared using cumulative incidence with competing risk. Fewer TKA patients with 'poor' outcomes (≤ 25) subsequently underwent revision compared with UKA at six months (5.1% vs 19.6%; p < 0.001), five years (4.3% vs 12.5%; p < 0.001), and ten years (6.4% vs 15.0%; p = 0.024). Compared with TKA, the relative risk for UKA was 2.5-times higher for 'unknown' reasons, bearing dislocations, and disease progression. Compared with TKA, more UKA patients with poor outcomes underwent revision from early to long-term follow-up, and were more likely to undergo revision for 'unknown' reasons, which suggest a lower clinical threshold for UKA. For UKA, revision risk was higher for bearing dislocations and disease progression. There is supporting evidence that the higher revision UKA rates are associated with lower clinical thresholds for revision and additional modes of failure.

Clinical and Functional Results of Cementless Unicompartmental Knee Arthroplasty with a Minimum Follow Up of 5 Years-A Consecutive Cohort of 201 Patients

The number of unicompartmental knee replacements (UKR) is increasing. Alongside various advantages, the revision rate of cemented UKR is higher compared to total knee arthroplasty (TKR). In contrast, cementless fixation shows reduced revision rates, compared to the cemented UKR. However, most of the recent literature is based on designer-dependent studies. In this retrospective, single-center cohort study, we investigated patients who underwent cementless Oxford UKR (OUKR) between 2012 and 2016 in our hospital with a minimum follow-up of five years. Clinical outcome was evaluated using the OKS, AKSS-O, AKSS-F, FFbH-OA, UCLA, SF-36, EQ-5D-3L, FJS, ROM, pain, and satisfaction measures. Survival analysis was performed with reoperation and revision as endpoints. We included 201 patients (216 knees) for clinical evaluation. All outcome parameters increased significantly from pre- to postoperative stages. The five-year survival rate was 96.1% for revision surgery and 94.9% for reoperation. The main reasons for revision were the progression of osteoarthritis, inlay dislocation, and tibial overstuffing. Two iatrogenic tibial fractures appeared. Cementless OUKR shows excellent clinical outcome and high survival rates after five years. The tibial plateau fracture in cementless UKR represents a serious complication and requires modification of the surgical technique.

Does a Uni "Feel Better" than a Total Knee? Not Necessarily, When Using Modern Implant Designs

Background: When comparing functional outcomes of patients with unicompartmental knee arthroplasty (UKA) versus total knee arthroplasty (TKA), studies often report the UKA as the preferred procedure; however, recent improvements in the design of modern TKA implants have aimed at narrowing this gap. Purpose: We sought to compare the "feel" of modern TKA implants to that of UKA, using the Forgotten Joint Score (FJS), a validated patient-reported outcome measure. Methods: We performed a retrospective review of patients who underwent TKA and UKA at 2 institutions between 2014 and 2017. All UKA procedures were robotic arm-assisted with a single implant, "traditional TKAs" were performed using traditional posterior-stabilized implants, and "modern TKAs" were performed using posterior-stabilized implants with a modern design. Differences in FJS were assessed using 1-way analysis of variance and independent 2-sample t tests. Results: A total of 600 patients were included in our study, with 200 patients in each surgical subcategory. Mean age was 62.8 ± 10.2 years and mean body mass index was 29.9 ± 4.9. Modern TKA and UKA had similar FJS at 1 year. While modern TKA had a significantly higher FJS than traditional TKA, UKA did not have a significantly higher FJS than traditional TKA. Conclusion: Our retrospective analysis found no significant differences in the FJS of patients who underwent UKA and TKA with a modern design; however, both had superior scores than traditional TKA designs. This finding suggests that modern TKA designs may have the potential to achieve the natural feeling that is typically associated with joint-conserving surgeries such as UKA, although longer follow-up is necessary.

Comparative efficacy of the different cutting guides in unicompartmental knee arthroplasty: A systematic-review and network meta-analysis

BACKGROUND

Several cutting guides including conventional, navigation, patient specific instrumentation (PSI) and robotic are currently used in unicompartmental knee arthroplasty (UKA). A network meta-analysis was conducted to compare the most widely used cutting guides regarding the improvement of radiological, functional outcomes and the rate of complications.

METHODS

Randomised controlled trials (RCTs) comparing UKA cutting guides were searched in electronic databases, major orthopaedics journals, and oral communications in major orthopaedics meetings, until May 1st, 2022. The primary outcomes were the rate of outliers for the tibial and femoral components in the frontal plane, KSS score and the complication rate.

RESULTS

Eighteen RCTs involving 1562 patients with 1564 UKA were included Regarding the prosthetic components' positions, we found a significant increase of the outliers rate using PSI for the femoral component, compared to robotic surgery (risk ratio 0.00 [95% CI 0.00 to 0.55]) and navigated surgery (risk ratio 305.1 [95% CI 1.50 to 1,27e + 07]). We didn't emphasize any difference regarding the tibial component's position, the KSS value at 24 months postoperatively, and the complication rate. Regarding secondary outcomes, robotics provided a better precision in bone cuts in the sagittal plane for the tibial component and the lower limb alignment. No other differences were observed.

CONCLUSION

In the light of these results, the robot seems to be the most precise cutting instrument to perform UKA. However, this did not demonstrate any difference in functional or clinical outcome. The cost of this technology can be a major economic brake, especially in surgical centers that do not have an exclusive prosthetic activity. Further outcome and survivorship data is needed to recommend one cutting instrument over the other.

Partial versus total knee arthroplasty for isolated antero-medial osteoarthritis - An analysis of PROMs and satisfaction

AIM

This study aimed to compare the patient-reported functional outcomes and patient satisfaction after medial Unicompartmental Knee Arthroplasty (UKA) versus Total Knee Arthroplasty (TKA), performed for anteromedial osteoarthritis (AMOA) of the knee in patients from an Indian population, at a minimum 3-year follow-up.

METHODS

This is a prospective matched cohort study (1:2 ratio). One hundred and one UKA cases were matched to 206 TKA cases by propensity score matching for age, body mass index (BMI), gender distribution, and the Charlson Comorbidity Index (CCI). The primary outcome (Oxford knee score, OKS) was assessed at a 3-year follow-up, along with secondary outcomes (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC] Score, Forgotten Joint Score (FJS), Anterior Knee Pain (Kujala) score, patient satisfaction, and revision rate at the final follow-up).

RESULTS

The UKA group was superior to the TKA group in patient-reported functional outcomes based on the OKS (p = 0.004). Using the FJS score, UKA was more likely to be a forgotten joint compared to TKA (p < 0.001). However, differences in the OKS and FJS did not meet the reported minimal clinically important difference (MCID) thresholds. Quality of life (EuroQol-5D VAS scale) was found to be significantly higher in the UKA group (p < 0.001). Patients in the UKA group were more likely to be very satisfied (75.2%) versus the TKA group (62.1%, p = 0.023).

CONCLUSION

For AMOA, UKA was associated with improved patient satisfaction compared to TKA. Although patient-reported outcome measures were statistically in favour of UKA over TKA, the differences were not clinically significant. Multicenter and randomized studies comparing the two procedures are warranted.

EVIDENCE

Level-II Therapeutic.

Slight cartilage damage in weight-bearing area of lateral femoral condyle do not compromise short-term outcomes of medial unicompartmental knee arthroplasty

INTRODUCTION

Medial unicompartmental knee arthroplasty (mUKA) requires full-thickness cartilage in the lateral compartment, but slight damage of the cartilage surface can be ignored. However, as this statement lacks literature support, we investigated whether slight cartilage damages in the weight-bearing area of the lateral femoral condyle would affect the outcome of mUKAs.

MATERIALS AND METHODS

Outerbridge grading was performed on the cartilage in the weight-bearing area of the lateral femoral condyle intraoperatively. The patients, grouped as normal or as having lateral condyle cartilage of Outerbridge grade 1-2 (slight cartilage damage), underwent mUKA. Full-length lower extremity radiographs were taken and hip-knee-ankle angles (HKAAs) were measured both preoperatively and postoperatively. Using magnetic resonance imaging, the lateral meniscal extrusion distance was also measured. In addition, the Oxford Knee Score (OKS) was assessed preoperatively and at the last follow-up, in addition to the patient satisfaction assessment.

RESULTS

We enrolled 152 knees of 142 patients proposed for mUKAs. The mean age of participants was 69.5 years (51-89 years) and they were followed up for a mean of 25.4 months (15-44 months). There was no significant difference in preoperative (p = 0.746) and postoperative (p = 0.202) mean OKS between the normal, Outerbridge grade 1 and Outerbridge grade 2 groups. While the normal group had a higher change in OKS than the group with cartilage damage, this difference was not significant (p = 0.910). The UKA corrected the patients' mean HKAA from 171.1° (preoperatively) to 176.1° (postoperatively). From all patients, only four had slight lateral meniscus extrusion with MEDs of ≤ 0.25 mm. With the exception of one patient with a poor outcome in normal group, the rest were satisfied with the outcome of mUKA. No patients had prosthesis-related complications or revision surgery.

CONCLUSIONS

Cartilage damage of Outerbridge grade 1 and grade 2 in the weight-bearing area of the lateral femoral condyle will not compromise the short-term outcome of medial mobile-bearing UKA.

Reliability and validity of commonly used patient-reported outcome measures (PROMs) after medial unicompartmental knee arthroplasty

INTRODUCTION

Many patient-reported outcome measures (PROMs) have been utilized to assess outcomes after unicompartmental knee arthroplasty (UKA). However, most are not specifically designed for UKA and the measurement properties of these PROMs have never been elucidated in the setting of UKA. This study aimed to evaluate the reliability and validity of commonly used PROMs after UKA, which includes the Oxford knee score (OKS), Knee Society Score (KSS)-function score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Knee Injury and Osteoarthritis Outcome Score (KOOS).

HYPOTHESIS

The four commonly used PROMs after UKA are of good reliability and validity, but with different floor/ceiling effect.

MATERIAL AND METHODS

Prospectively collected postoperative follow-up PROMs scores of patients after medial UKA cases for osteoarthritis between May 2015 and June 2018 were retrospectively analyzed. All of the PROMs were finished on the same electronic questionnaires. Reliability (internal consistency, test-retest reliability, measurement error), construct validity and floor/ceiling effects were assessed.

RESULTS

The whole cohort was composed of 207 cases, with a median age of 62.0 years and a male ratio of 59/207 (28.50%). Internal consistency was high in the OKS, weak in the KSS-function score and with redundancy in the WOMAC and KOOS scores (Cronbach alpha=0.915, 0.610, 0.953, 0.961, respectively). Each of the four PROMs had a high test-retest reliability (all intraclass correlation coefficient (ICC) >0.97). Convergent validity of the four PROMs with the physical component score of the 12-Item Short Form Health Survey (SF-12 PCS) were proven (all r>0.5; p<0.001). While no ceiling effect occurred in the OKS, one was detected in the KSS-function score with 19.81% of patients achieving the best possible score, as well as in the WOMAC sub-score for pain (54.11%) and stiffness (50.72%), in addition to the KOOS sub-score for symptoms (27.54%) and pain (38.16%).

DISCUSSION

The four commonly used PROMs after UKA showed good test-retest reliability and construct validity. The OKS is more recommended for its better performance in internal consistency and ceiling effect than the KSS-function score, the WOMAC and KOOS scores.

LEVEL OF EVIDENCE

III; Diagnostic study.

Occupational Outcomes and Revision Rates for Medial Unicondylar Knee Arthroplasty in U.S. Military Servicemembers

This study evaluates return to work and revision rates for medial unicondylar knee arthroplasty (UKA) in a high-demand military cohort. Patient demographic and clinical variables were isolated from the medical records of active-duty military servicemembers with at least 2 years of postoperative follow-up and correlated with return to work, medial UKA survivorship, and perioperative complications. The medial UKA annual revision rate was calculated as the percentage of implants revised per observed component year. A total of 39 servicemembers underwent 46 primary medial UKAs (32 unilateral and 7 bilateral) with a mean follow-up of 3.9 (2.0-6.6) years. At a minimum of 2 years postoperatively, 33 (85%) servicemembers returned to military service or successfully completed their service obligation. Older servicemembers (odds ratio [OR] = 0.67; 95% confidence interval [CI]: 0.45, 0.99) had a significantly decreased OR for knee-related medical separation. Nine servicemembers (20%) had conversion to TKA at an average of 2.4 (range, 0.6-5.6) years with a medial UKA annual revision rate of 5%. When compared with Navy/Air Force, Army/Marine servicemembers had an increased TKA conversion rate (OR = 5.40; 95% CI: 1.13, 25.81). Older age decreased the likelihood of medical separation and Army/Marines service was the sole risk factor associated with conversion to TKA. The level of evidence is IV, therapeutic case series.

Robotic-arm assisted total knee arthroplasty has a learning curve of 16 cases and increased operative time of 12 min

BACKGROUND

Robotic-arm assisted systems are increasingly used for knee arthroplasty, however introduction of new systems can involve a learning curve. We aimed to define the learning curve in terms of operative time and component placement/sizing of a robotic system for total knee arthroplasty (TKA) in a team of experienced surgeons, and to investigate mid-term patient outcomes.

METHODS

A total of 101 consecutive patients underwent primary robotic-arm assisted TKA by three surgeons (mean 2 year follow-up). Operative times, component placement, implant sizing and reoperations were recorded. Cumulative Summation (CUSUM) was used to analyse learning curves. Patient outcomes were compared between learning and proficiency phases.

RESULTS

The learning curve was 16 cases, with a 12-min increase in operative time (P < 0.01). Once proficiency was achieved, the greatest time reductions were seen for navigation registration (P = 0.003) and bone preparation (P < 0.0001). A learning curve was found with polyethylene (PE) insert sizing (P = 0.01). No differences were found between learning and proficiency groups in terms of implant survival (100% and 97%, respectively, NS) or patient-reported outcome measures at 2 years (NS).

CONCLUSION

Introduction of a robotic-arm assisted system for TKA led to increased operative times for navigation registration and bone preparation, and a learning curve with PE insert sizing. No difference in patient outcomes between learning and proficiency groups at 2 years was found. These findings can inform surgeons' expectations when starting to use robotic-assisted systems.

Excellent outcomes with combined single stage Physica ZUK medial unicompartment knee replacement and anterior cruciate ligament reconstruction results in young, active patients with instability and osteoarthritis with a mean follow up of 5 years

BACKGROUND (INCLUDING THE AIM OF THE STUDY)

Young and more active patients with medial compartment osteoarthritis (OA) in conjunction with anterior cruciate ligament (ACL) deficiency are difficult to treat. The aim of this study was to explore the outcomes of combined fixed bearing Physica ZUK medial unicompartmental knee replacement (UKR) (Lima Corporate, Udine Italy) with ACL reconstruction for patients presenting with isolated medial compartment OA and symptomatic ACL deficiency.

METHODS

Patients who underwent simultaneous single stage ACL reconstruction and medial UKR between 2012 and 2020 by a single surgeon (GG) were included. Preoperative outcome measures including Lysholm, Tegner, Oxford Knee Score and VAS pain score were evaluated and were repeated postoperatively at the most recent follow up appointment.

RESULTS

Twenty four patients underwent simultaneous combined ACL and ZUK Medial UKR with a mean follow up of 5.1 years. Significant improvements in Lysholm (p < 0.001), Tegner (p < 0.001), Oxford Knee Score (p < 0.001) and VAS pain scores (p < 0.001) were seen with this combined approach with all patients returning to sport. Two patients had a minor peri-operative complication, which was treated conservatively. There were no revision procedures, and no evidence of implant loosening, however one patient had deceased due to an unrelated illness.

CONCLUSION

UKR combined with ACL reconstruction can be an effective treatment option for selected patients suffering from medial unicompartmental knee osteoarthritis and symptomatic ACL deficiency. This allowed active patients to return to sports, addressing both instability and OA pain in a specific patient population.

Comparison of joint awareness after medial unicompartmental knee arthroplasty and high tibial osteotomy: a retrospective multicenter study

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) and high tibial osteotomy (HTO) are established treatments for medial compartment osteoarthritis (OA) or osteonecrosis (ON) of the knee joint, and the predominance of either procedure is inconclusive. We compared the awareness of the knee after UKA and HTO using the Forgotten joint score-12 (FJS).

MATERIALS AND METHODS

This was a retrospective, multicenter study. Ninety-six knees of 90 patients who received UKA or HTO and were followed-up for at least 1 year were analyzed. Postoperative FJS was compared between the two groups and evaluated for the effect of patient-related factors and clinical outcomes. Multiple linear regression analysis was performed to predict FJS.

RESULTS

There was no significant difference in the FJS between the UKA and HTO groups (p = 0.24). FJS did not correlate with any of the patient-related factors. There was a correlation between the FJS and each item of the Knee Injury and Osteoarthritis Outcome Scores (KOOS) and Lysholm Knee Scoring Scale (LKS). In multiple linear regression analysis, lower BMI, the diagnosis of OA Kellgren-Lawrence (KL) grade ≥ 3, and ON were significant predictors of better FJS. In both groups, FJS was correlated with each item of the KOOS and LKS. Internal consistency in terms of Cronbach's alpha was excellent.

CONCLUSIONS

There was no significant difference in FJS between patients who underwent UKA and HTO. Lower BMI, the diagnosis of OA KL grade ≥ 3, and ON were significant predictors of better FJS.

Mobile Bearing versus Fixed Bearing for Unicompartmental Arthroplasty in Monocompartmental Osteoarthritis of the Knee: A Meta-Analysis

Introduction: Whether mobile-bearing (MB) unicompartmental knee arthroplasty (UKA) performs better than fixed-bearing (FB) implants in patients with monocompartmental osteoarthritis (OA) still remains unclear. Therefore, a meta-analysis comparing MB versus FB for UKA was conducted to investigate the possible advantages of MB versus FB in patient-reported outcome measures (PROMs), range of motion (ROM), and complications. We hypothesised that the MB design performs better than FB. Methods: This systematic review was conducted according to the 2020 PRISMA guidelines. In December 2021, PubMed, Web of Science, Google Scholar, and Embase were accessed, with no time constraints. All the clinical investigations comparing MB versus FB bearing for UKA were accessed. Only studies published in peer-reviewed journals were considered. Studies reporting data on revision settings were excluded, as were those combining unicompartmental and total knee arthroplasty. Results: Data from 25 studies (4696 patients) were collected; 58% (2724 of 4696 patients) were women. The mean length of follow-up was 45.8 ± 43.2. The mean age of the patients was 65.0 ± 5.6 years. No difference was found in range of motion (p = 0.05), Knee Scoring System (p = 0.9), function subscale (p = 0.2), and Oxford Knee Score (p = 0.4). No difference was found in the rate of revision (p = 0.2), aseptic loosening (p = 0.9), deep infections (p = 0.99), fractures (p = 0.6), and further extension of OA to the contralateral joint compartment (p = 0.2). Conclusion: The present meta-analysis failed to identify the possible superiority of the MB implants over the FB for UKA in patients with monocompartmental knee osteoarthritis. Long observational investigations are required to evaluate possible long-term complications and implant survivorship. These results should be interpreted within the limitations of the present study.

5-Year Survivorship and Outcomes of Robotic-Arm-Assisted Medial Unicompartmental Knee Arthroplasty

Purpose

While unicompartmental knee arthroplasty (UKA) has demonstrated benefits over total knee arthroplasty (TKA) in selected populations, component placement continues to be challenging with conventional surgical instruments, resulting in higher early failure rates. Robotic-arm-assisted UKA (RA-UKA) has shown to be successful in component positioning through preop planning and intraop adjustability. The purpose of this study is to assess the 5-year clinical outcomes of medial RA-UKA.

Methods

This study was a retrospective review of a single-center prospectively maintained cohort of 133 patients (146 knees) indicated for medial UKA from 2009 to 2013. Perioperative data and 2- and 5-year Knee injury Osteoarthritis Outcome Score (KOOS), Western Ontario and McMaster Universities Osteoarthritis Score (WOMAC), and Forgotten Joint Score (FJS) outcome measures were collected. Five-year follow-up was recorded in 119 patients (131 knees).

Results

Mean follow-up was 5.1 ± 0.2 years. Mean age and BMI were 68.0 ± 8.1 years and 29.3 ± 4.7 kg/m², respectively. At 2-year follow-up, mean KOOS, WOMAC, and FJS were 71.5 ± 15.3, 14.3 ± 7.9, and 79.1 ± 25.8, respectively. At 5-year follow-up, mean KOOS, WOMAC, and FJS were 71.6 ± 15.2, 14.2 ± 7.9, and 80.9 ± 25.1, respectively. Mean change in KOOS and WOMAC was 34.6 ± 21.4 and 11.0 ± 13.6, respectively (p < 0.001 and p < 0.001). For patient satisfaction at last follow-up, 89% of patients were very satisfied/satisfied and 5% were dissatisfied. For patient activity expectations at last follow-up, 85% met activity expectations, 52% were more active than before, 25% have the same level of activity, 23% were less active than before, and 89% were walking without support. All patients returned to driving after surgery at a mean 15.2 ± 9.4 days. Survivorship was 95% (95% CI 0.91-0.98) at 5 years. One knee (1%) had a patellofemoral revision, two knees (1.3%) were revised to different partial knee replacements, and five knees (3.4%) were converted to TKA.

Conclusion

Overall, medial RA-UKA demonstrated improved patient-recorded outcomes, high patient satisfaction, met expectations, and excellent functional recovery. Midterm survivorship was excellent. Longitudinal follow-up is needed to evaluate long-term outcomes of robotic-arm-assisted UKA procedures.

Midterm Survivorship of Robotic-Assisted Lateral Unicompartmental Knee Arthroplasty

BACKGROUND

Lateral unicompartmental knee arthroplasty (UKA) is a popular alternative to total knee arthroplasty (TKA) for patients with isolated lateral compartment osteoarthritis. Few studies have investigated outcomes following robotic-assisted lateral UKA. The purpose of this study is to evaluate mid-term survivorship and patient-reported outcomes of robotic-assisted lateral UKA.

METHODS

A retrospective case series was conducted on all robotic-assisted lateral UKAs performed by a single surgeon between 2013 and 2019. Patient demographics, surgical variables, and Kozinn and Scott criteria were collected. Implant survivorship was estimated using the Kaplan-Meier method with all-cause reoperation and conversion to TKA as endpoints. Participating patients were assessed for patient satisfaction and the Forgotten Joint Score-12. Correlations between patient demographics and patient outcome scores were investigated.

RESULTS

In total, 120 lateral UKAs were identified, 84 of which met inclusion criteria, with a mean follow-up of 4.0 years (range 2.0-7.0). Five-year survivorship was 92.9% (95% confidence interval [CI] 84.5-96.7) with all-cause reoperation as the endpoint, and 100% (95% CI 95.0-100) with conversion to TKA as the endpoint. One patient was converted to TKA after the 5-year mark, resulting in a 6-year survival for conversion to TKA of 88.9% (95% CI 44.9-98.5). Average Forgotten Joint Score-12 score was 82.7/100, and patient satisfaction 4.7/5. Mean coronal plane correction was 2.5° ± 1.9° toward the mechanical axis. Neither final postoperative alignment nor failure to meet classic Kozinn and Scott criteria for UKA resulted in differences in patient-reported outcomes.

CONCLUSION

The current study demonstrates high mid-term survivorship and excellent patient-reported outcomes with robotic-assisted lateral UKA. Robotic-assisted lateral UKA is a viable treatment option for isolated lateral compartment arthritis even in patients who do not meet classic indications.

Robotic arm-assisted versus manual unicompartmental knee arthroplasty : a systematic review and meta-analysis of the MAKO robotic system

AIMS

This systematic review aims to compare the precision of component positioning, patient-reported outcome measures (PROMs), complications, survivorship, cost-effectiveness, and learning curves of MAKO robotic arm-assisted unicompartmental knee arthroplasty (RAUKA) with manual medial unicompartmental knee arthroplasty (mUKA).

METHODS

Searches of PubMed, MEDLINE, and Google Scholar were performed in November 2021 according to the Preferred Reporting Items for Systematic Review and Meta--Analysis statement. Search terms included "robotic", "unicompartmental", "knee", and "arthroplasty". Published clinical research articles reporting the learning curves and cost-effectiveness of MAKO RAUKA, and those comparing the component precision, functional outcomes, survivorship, or complications with mUKA, were included for analysis.

RESULTS

A total of 179 articles were identified from initial screening, of which 14 articles satisfied the inclusion criteria and were included for analysis. The papers analyzed include one on learning curve, five on implant positioning, six on functional outcomes, five on complications, six on survivorship, and three on cost. The learning curve was six cases for operating time and zero for precision. There was consistent evidence of more precise implant positioning with MAKO RAUKA. Meta-analysis demonstrated lower overall complication rates associated with MAKO RAUKA (OR 2.18 (95% confidence interval (CI) 1.06 to 4.49); p = 0.040) but no difference in re-intervention, infection, Knee Society Score (KSS; mean difference 1.64 (95% CI -3.00 to 6.27); p = 0.490), or Western Ontario and McMaster Universities Arthritis Index (WOMAC) score (mean difference -0.58 (95% CI -3.55 to 2.38); p = 0.700). MAKO RAUKA was shown to be a cost-effective procedure, but this was directly related to volume.

CONCLUSION

MAKO RAUKA was associated with improved precision of component positioning but was not associated with improved PROMs using the KSS and WOMAC scores. Future longer-term studies should report functional outcomes, potentially using scores with minimal ceiling effects and survival to assess whether the improved precision of MAKO RAUKA results in better outcomes. Cite this article: Bone Joint J 2022;104-B(5):541-548.

Does Implant Design Influence Failure Rate of Lateral Unicompartmental Knee Arthroplasty? A Meta-Analysis

BACKGROUND

Lateral unicompartmental knee arthroplasty (UKA) is a viable solution for isolated lateral compartment arthritis. Several prosthetic designs are available such as fixed-bearing metal-backed (FB M-B), fixed-bearing all-polyethylene (FB A-P), and mobile-bearing metal-backed (MB M-B) implants. The purpose of this meta-analysis is to compare failure rates of different prosthetic designs.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses systematic review was conducted using 4 databases (MEDLINE, EMBASE, Cochrane, and PubMed) to identify all studies that investigate outcomes of lateral UKA. Twenty-one studies met the inclusion criteria, and failure rates were compared by implant type and follow-up time separately in order to assess potential confounding factors. Two separate analyses have been performed among different implant designs (FB M-B vs FB A-P vs MB M-B) and different follow-ups (<5 years, between 5 and 10 years, >10 years).

RESULTS

The failure rate of FB M-B lateral UKA was significantly lower compared to other lateral UKA designs present in the market (0.8% vs 8.6% and 7.1% for FB M-B, FB A-P, and MB M-B, respectively). No significative difference among groups has been detected when comparing all implants with regard to follow-up time.

CONCLUSION

Considering actual evidence, for a surgeon approaching lateral UKA, the FB M-B design is preferable, given the lower failure rates and subsequently a longer implant survivorship.

Biomechanical effects of fixed-bearing femoral prostheses with different coronal positions in medial unicompartmental knee arthroplasty

Background

To study the biomechanical effects of femoral prostheses at different coronal positions using finite element analysis and provide a clinical reference for unicompartmental knee arthroplasty (UKA).

Methods

A normal knee joint model was established and verified, establishing 13 working conditions for the femoral prosthesis: the standard position, varus and valgus angles of 3°, 6° and 9° and medial and lateral translations of 1 mm, 3 mm and 5 mm. The stress changes at different positions were analysed, including the polyethylene (PE) insert upper surface, the surface of lateral compartment cartilage and the surface of cancellous bone under tibial prosthesis.

Results

The stresses on the PE insert upper surface and the cancellous bone surface increased with increasing femoral prosthesis valgus/varus, and the stress increased gradually during medial to lateral translation. The stress change is more significant during valgus and lateral translation. However, the stress on the cartilage surface decreases in the process of varus to valgus and medial translation to lateral translation.

Conclusion

The fixed-bearing femoral prosthesis of the medial UKA should avoid translation or varus/valgus tilt on the coronal plane as much as possible. The obvious misalignment of the femoral prosthesis will significantly affect the stress on the internal structure of the knee joint, especially the PE insert and cartilage surface. A femoral prosthesis coronal tilt of more than 6° may significantly increase the stress on the PE surface, and varus of more than 6° may significantly increase the stress on the cartilage surface. For the femoral prosthesis position at the distal end of the femoral condyle, it is recommended to be placed in the centre.

Early results of fixed-bearing unicompartmental knee replacement designed for the lateral compartment

Background

Isolated lateral compartment knee arthritis is less prevalent than medial. While the reported results of medial unicompartmental knee replacement (UKR) have been good and comparable to total knee replacement, the results of lateral UKR have been mixed. We present the short-term results and survivorship of a fixed-bearing UKR designed specifically for the lateral compartment.

Methods

We report the result of 130 primary fixed-bearing lateral Oxford (FLO) UKRs (123 patients) performed between 2015 and 2019 with a minimum follow-up of 1 year. The indications for lateral UKR were: isolated lateral osteoarthritis (n = 122), post-trauma (n = 5) and osteonecrosis (n = 3). The mean age was 69.1 (± 11.6), mean BMI 28.4 (± 4.9), 66.9% female, 60% right-sided, and mean follow-up 3 (range 1–4.8 years, standard deviation ± 1) years. The primary outcome measure was the Oxford knee score (OKS). Survival analysis was performed with “revision for any reason”, “reoperation”, and “implant failure” as the endpoints.

Results

Six patients died from unrelated reasons. None of the implants failed. One required the addition of a medial UKR for medial arthritis. There were no other reoperations. At 4 years, the survival for implant failure was 100% and for both revision and all reoperations was 99.5% (95% CI 96.7–99.9%). At the last review, at a mean of 3 years, the mean Oxford knee score was 41.

Conclusion

The good survivorship and outcome scores suggest that UKR designed for the lateral compartment is an excellent alternative to total knee replacement in selected patients with isolated lateral tibiofemoral arthritis at short-term follow-up.

Improved joint awareness two years after total knee arthroplasty with a handheld image-free robotic system

Literature into the short-term follow-up of total knee arthroplasty (TKA) using a handheld image- free robotic system are scarce. The purpose of this study was to compare the clinical outcomes and patient-reported outcome measures (PROMs) between patients operated for TKA with an image- free robotic system (robot group) or conventionally TKA (conventional group) 2 years postoperatively. A total of 147 patients were evaluated after TKA, respectively 73 in the robot and 74 in conventional group. Outcome measures included adverse events (AEs), hospital readmission rate, patient satisfaction and the following PROMs: Pain Visual Analogue Score (VAS), Oxford Knee Score (OKS), Forgotten Joint Score Knee (FJS-12) and the EuroQOL-5D (EQ-5D). There were no statistically significant differences in the number of AEs; 8 (10.8%) in the conventional group versus 7 (9.7%) in the robot group. The FJS (p ≤ 0.05) and OKS (p ≤ 0.05) differed statistically in favour of the robot group. The EQ-5D and EQ-5D VAS did not statistically differed between the groups (p=0.231 and p=0.373 respectively). The VAS pain improved statically significant in both groups when comparing the pre- and postoperative values (5.8 points). Patients operated with a handheld image-free robotic system have the ability to forget their artificial knee joint in everyday life as measured with the FJS-12 at short-term follow-up.

The effect of gender, age, BMI and Kellgren-Lawrence grade on functional outcome after Physica ZUK medial unicompartmental knee replacement

PURPOSE

Several factors influence the outcome of unicompartmental knee replacements. This study investigates the correlation of specific preoperative patient variables with postoperative functional outcomes-measured with the American Knee Society Knee (KS-KS) and Function Scores (KS-FS), as well as the difference in knee flexion pre- and postoperatively.

METHODS

In a retrospective study of 242 patients who underwent a medial Physica ZUK unicompartmental knee replacement (UKR), the American KS-KS, KS-FS as well as knee flexion were analyzed preoperatively and at 2-year follow-up. The absolute scores and improvement in scores were calculated per subgroup for gender, age, body mass index (BMI) and Kellgren-Lawrence (KL) radiological grade and compared between the subgroups.

RESULTS

All groups had a significant improvement in range of flexion, KS-KS and KS-FS. Female patients had lower preoperative scores and significantly larger improvement in knee flexion and KS-FS. Age does not seem to be associated with the postoperative functional outcome. Patients with a BMI of 30 or higher had a lower postoperative KS-KS and KS-FS as well as knee flexion. Patients with KL grade IV changes had larger gain in KS-KS compared to patients with grade III.

CONCLUSION

Overall, KS-KS, KS-FS and knee flexion improve significantly 2 years following a Physica ZUK UKR in all groups. Although excellent results were found in patients with a BMI of 30 or higher, a decrease in BMI was associated with an increase in functional outcome. KL IV grade preoperatively was associated with a better KS-KS improvement compared to the KL III group 2 years postoperatively. This information can aid surgeons in patient selection and to counsel patients on outcomes.

EVIDENCE LEVEL

III.

Revision indications for medial unicompartmental knee arthroplasty: a systematic review

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) has advantages over total knee arthroplasty including fewer complications and faster recovery; however, UKAs also have higher revision rates. Understanding reasons for UKA failure may, therefore, allow for optimized clinical outcomes. We aimed to identify failure modes for medial UKAs, and to examine differences by implant bearing, cement use and time.

MATERIALS AND METHODS

A systematic review was conducted by searching MedLine, EMBASE, CINAHL and Cochrane databases from 2000 to 2020. Studies were selected if they included ≥ 250 participants, ≥ 10 failures and reported all failure modes of medial UKA performed for osteoarthritis (OA).

RESULTS

A total of 24 cohort and 2 registry-based studies (levels II and III) were selected. The most common failure modes were aseptic loosening (24%) and OA progression (30%). Earliest failures (< 6 months) were due to infection (40%), bearing dislocation (20%), and fracture (20%); mid-term failures (> 2 years to 5 years) were due to OA progression (33%), aseptic loosening (17%) and pain (21%); and late-term (> 10 years) failures were mostly due to OA progression (56%). Rates of failure from wear were higher with fixed-bearing prostheses (5% cf. 0.3%), whereas rates of bearing dislocations were higher with mobile-bearing prostheses (14% cf. 0%). With cemented components, there was a high rate of failure due to aseptic loosening (27%), which was reduced with uncemented components (4%).

CONCLUSIONS

UKA failure modes differ depending on implant design, cement use and time from surgery. There should be careful consideration of implant options and patient selection for UKA.

A 180° Spin of the Femoral Component in Unicompartmental Knee Arthroplasty: A Report of 2 Cases

CASE

We report 2 cases of undescribed lateral unicompartmental knee arthroplasty failure: a 180° rotation of the femoral component. The patients experienced a locking event several years after arthroplasty, and radiographs revealed a perfect 180° rotation of the implant. Each patient underwent revision surgery to a total knee arthroplasty. At the 13-year follow-up, the first patient had no pain and a range of motion of 140°. The second patient, at 3 months, could walk without crutches with a flexion at 145°.

CONCLUSION

Excessive laxity, coronal or sagittal, might be associated with this complication.

Two-stage revision for periprosthetic joint infection in unicompartmental knee arthroplasty: clinical and radiological results

INTRODUCTION

Unicompartmental knee arthroplasty (UKA) has an infection rate of 0.1-0.8%. Despite the wide amount of literature about septic total knee arthroplasty management, few data are available for UKA infection treatment. The aim is to present the clinical and radiological outcomes along with complication rates of a series of septic UKA treated with two-stage exchange.

METHODS

We retrospectively reviewed 16 patient treated with staged UKA revision for infection between June 2015 and September 2019 in a single bone infection unit. The main demographic and surgical data were recorded. Clinical scores (VAS, KSS, OKS, postoperative ROM), radiological parameters (osseointegration, loosening and radiolucencies) and complications were reported. The mean follow-up was 33.5 ± 6.9 months.

RESULTS

Mean age at surgery was 68.5 ± 9.1. All but two were medial UKA. The mean number of previous surgeries was 2.9 ± 1.9. The mean ROM, VAS, KSS and OKS of the entire population improved significantly (p < 0.01). Radiological analysis did not show any migration or implant loosening. Ten constrained condylar and six posterior stabilized prosthesis were finally implanted. One intraoperative pathogen isolation was recorded and managed with suppressive therapy and good final outcome. The implant survivorship free from infection was 100% at the final follow-up. The overall survival rate for any reason of revision was 100% CONCLUSION: According to our results, staged revision represents a reliable ad effective option in delayed and late UKA infections. This technique provides optimal clinical and radiological results with acceptable complication rates. To the best of our knowledge, this represent the widest case series on infected UKA managed with two-stage exchange.

The Medial Tibial Plateau Can Be Used as a Direct Anatomical Reference for the Posterior Tibial Slope in Medial Unicompartmental Knee Arthroplasty

There has been no consensus about how to determine the individual posterior tibial slope (PTS) intraoperatively. The purpose of this study was to investigate whether the tibial plateau could be used as a reference for reproducing individual PTS during medial unicompartmental knee arthroplasty (UKA). Preoperative computed tomography (CT) data from 48 lower limbs for medial UKA were imported into a three-dimensional planning software. Digitally reconstructed radiographs were created from the CT data as the lateral knee plain radiographs and the radiographic PTS angle was measured. Then, the PTS angles on the medial one-quarter and the center of the MTP (¼ and ½ MTP, respectively), and that on the medial tibial eminence (TE) were measured on the sagittal multiplanar reconstruction image. Finally, 20 lateral knee radiographs with an arthroscopic probe placed on the ¼ and the ½ MTP were obtained intraoperatively, and the angle between the axis of the probe and the tangent line of the plateau was measured. The mean radiographic PTS angle was 7.9 ± 3.0 degrees (range: 1.7-13.6 degrees). The mean PTS angles on the ¼ MTP, the ½ MTP, and the TE were 8.1 ± 3.0 degrees (1.2-13.4 degrees), 9.1 ± 3.0 degrees (1.4-14.7 degrees), and 9.9 ± 3.1 degrees (3.1-15.7 degrees), respectively. The PTS angles on the ¼ MTP and the ½ MTP were strongly correlated with the radiographic PTS angle (r =0.87 and 0.80, respectively, p < 0.001). A statistically significant difference was observed between the mean angle of the radiographic PTS and the PTS on the TE (p < 0.01). The mean angle between the axis of the probe and the tangent line of the tibial plateau was -0.4 ± 0.9 degrees (-2.3-1.3 degrees) on the ¼ MTP and -0.1 ± 0.7 degrees (-1.5-1.2 degrees) on the ½ MTP, respectively. An area from the medial one-quarter to the center of the MTP could be used as an anatomical reference for the individual PTS.

Knee Scores of Patients with Non-Lateral Compartmental Knee Osteoarthritis Undergoing Mobile, Fixed-Bearing Unicompartmental Knee and Total Knee Arthroplasties: A Randomized Controlled Trial

Objective

To evaluate knee scores and clinical efficacies of patients with non‐lateral unicompartmental knee osteoarthritis (OA) who randomly underwent mobile‐bearing (MB) unicompartmental knee arthroplasty (UKA), fixed‐bearing (FB) UKA, and total knee arthroplasty (TKA).

Methods

From September 2015 to February 2017, a prospective, randomized, parallel, single‐center trial of 180 patients (78 males and 102 females; 63.3 ± 6.9 years) with non‐lateral compartmental knee OA was performed in the first author‐affiliated hospital. The patients were randomly divided into three groups (each group included 60 patients) and received medial cemented Oxford phase 3 MB UKA, medial cemented Link FB UKA, or cemented DePuy Sigma PFC TKA, respectively. A similar perioperative management and fast‐track surgery program was carried out for all patients. The knee scores at 3‐year follow‐up after operation and clinical efficacies of these three groups of patients were recorded, investigated, and compared.

Results

Primarily, compared to the TKA group, the UKA groups (MB UKA and FB UKA) had shorter operative time (median 63.2 < 67.1 min), less bleeding (8.6 < 30.0 mL), earlier resumption of walking without crutches (3.0 < 8.0 days) and walking up and down the stairs (5.0 < 10.0 days) (P < 0.001), higher FJS scores (78.0 > 74.5) (P = 0.007), better results in all knee scores (except VAS and KSS function scores) (P < 0.05), and a larger maximum flexion angle of the knee at the 3‐year follow‐up (123.0° > 96.0°) (P = 0.001). Secondarily, compared to the TKA group, the MB UKA group showed better results in the Western Ontario and McMaster Universities index (WOMAC) stiffness (83.6 > 79.6), WOMAC total (86.3 > 83.2), Oxford knee score (OKS) (20.0 < 23.0), Forgotten Joint Score (FJS) (78.5 > 74.5), and a larger maximum flexion angle of the knee (123.0 > 96.0) (P < 0.05). Moreover, the FB UKA group showed higher Hospital for Special Surgery Knee Score (HSS) (91.0 > 88.5), WOMAC stiffness (84.3 > 79.6), WOMAC function (85.2 > 81.7), WOMAC total scores (87.6 > 83.2), and a larger maximum flexion angle of the knee (119.0° > 96.0°) than the TKA group (P < 0.05). Overall, there was no significant difference in all knee scores and maximum flexion angles of the knee for the MB UKA and FB UKA groups (P > 0.05). There was one case with original bearing dislocation in MB UKA group. One patient with displacement of the femoral component caused by a fall injury, and another patient, who lost his life in a car accident, were involved in the FB UKA group. There was an infection case and an intermuscular vein thrombosis case in TKA group.

Conclusion

UKA showed more advantages than TKA; however, there was no significant difference between the MB UKA and FB UKA groups for treatment of non‐lateral compartmental knee OA.

Joint awareness after unicompartmental and total knee arthroplasty: Which feels more natural?

Background/Purpose

The purpose of this study was to compare the joint awareness and knee function after unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) for the management of isolated medial compartment osteoarthritis.

Methods

Patients who underwent UKA or TKA at our institution for isolated medial compartment osteoarthritis from 2015 to 2020 with a minimum follow-up of 1 year were screened. 116 eligible patients were invited and 94 volunteer patients participated. All patients were evaluated with The Forgotten Joint Score-12 and Lysholm Knee Scale.

Results

Average follow-up period was 29.13±15.48 months for UKA and 31.66±2.91 months for TKA groups ( p=0.292). FJS-12 of the UKA group was significantly higher than that of the TKA group (79.74±15.06 and 63.25±19.86, respectively; p=0.024). The Lysholm Knee Scale score was also significantly higher in the UKA group compared with the TKA group (92.94±8.74 and 78.34±14.99, respectively; p = 0.002).

Conclusion

Our findings suggest that patients who underwent UKA were less aware of their artificial joints and had better knee function compared to patients who underwent TKA for medial osteoarthritis of the knee.

Joint awareness after unicompartmental knee arthroplasty and total knee arthroplasty: a systematic review and meta-analysis of cohort studies

PURPOSE

The purpose of this systematic review and meta-analysis is to evaluate the joint awareness after unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA). It was hypothesized that patients with UKA could better forget about their artificial joint in comparison to TKA.

METHODS

A search of major literature databases and bibliographic details revealed 105 studies evaluating forgotten joint score in UKA and TKA. Seven studies found eligible for this review were assessed for risk of bias and quality of evidence using the Newcastle-Ottawa Scale. The forgotten joint score (FJS-12) was assessed at 6 months, 1 year, and 2 years.

RESULTS

The mean FJS-12 at 2 years was 82.35 in the UKA group and 74.05 in the TKA group. Forest plot analysis of five studies (n = 930 patients) revealed a mean difference of 7.65 (95% CI: 3.72, 11.57, p = 0.0001; I² = 89% with p < 0.0001) in FJS-12 at 2 years. Further sensitivity analysis lowered I² heterogeneity to 31% after exclusion of the study by Blevin et al. (MD 5.88, 95%CI: 3.10, 8.66, p < 0.0001). A similar trend of differences in FJS-12 between the groups was observed at 6 months (MD 32.49, 95% CI: 17.55, 47.43, p < 0.0001) and at 1 year (MD 25.62, 95% CI: 4.26, 46.98, p = 0.02).

CONCLUSIONS

UKA patients can better forget about their artificial joint compared to TKA patients.

LEVEL OF EVIDENCE

III.

Robotic arm-assisted unicompartmental knee arthroplasty: high survivorship and good patient-related outcomes at a minimum five years of follow-up

PURPOSE

Robotic arm-assisted unicompartmental knee arthroplasty (RA-UKA) has been shown to improve component placement, reduce intraoperative variability, increase patient satisfaction and improve short-term survivorship results. The aim of this retrospective study was to determine the incidence of revision and the clinical performance at a minimum of 5-year follow-up for a cohort of patients who received a medial RA-UKA.

METHODS

Between April 2011 and July 2013, a total of 254 patients underwent medial RA-UKA at a single centre. Clinical performance was investigated using the Forgotten Joint Score-12 (FJS-12) and a 5-level Likert scale made of five items to assess joint perception and patient satisfaction. Kaplan-Meier implant survivorship was calculated and reasons for revision were collected. The effect of age, gender and body mass index (BMI) on the probability of reporting high FJS-12 and satisfaction were assessed.

RESULTS

After considering exclusion criteria and loss to follow-up, a total of 216 patients (224 medial RA-UKAs) were assessed at a mean 5.9 years of follow-up. Five RA-UKAs underwent implant revision, resulting in an overall Kaplan-Meier survivorship of 97.8%. Unexplained knee pain (0.9%) was the most common reason for RA-UKA revision. Good-to-excellent FJS-12 scores and high satisfaction levels were reported at mid-term follow-up. Male patients had higher probability of having FJS-12 > 90 (p < 0.05) and high satisfaction levels (p < 0.05).

CONCLUSIONS

RA-UKAs demonstrated high survivorship and good-to-excellent patient-reported outcome measures and satisfaction levels at minimum 5-year follow-up. Results for male patients had improved clinical performance when compared to female subjects.

LEVEL OF EVIDENCE

IV.

Total and unicondylar knee arthroplasty are equivalent treatment options in end-stage spontaneous osteonecrosis of the knee, and the size of the lesion has no influence on the results

PURPOSE

The purpose of the present study was to compare total (TKA) and unicondylar (UKA) knee arthroplasty for spontaneous osteonecrosis of the knee (SONK), and to investigate potential correlations to radiographic parameters.

METHODS

All consecutive patients with a magnetic resonance imaging (MRI) proven SONK treated with either TKA or UKA between 2002 and 2018 were analysed. The primary outcomes were postoperative complications and failure rates. Functional assessment included Knee Society Score (KSS), WOMAC Score, and range of motion. A novel three-dimensional measurement method was established to determine the size of the osteonecrotic lesion. All outcome parameters were correlated to the size of the necrotic lesion using Spearman's rank correlation.

RESULTS

The two treatment groups (34 TKAs, 37 UKAs) did not differ regarding age, body mass index, and ratio of the volume of the necrotic lesion to the volume of the femoral condyle (n.s.). At a mean follow-up of 6.6 years, patients with UKA had better functional outcomes compared to patients with a TKA (WOMAC Score 1.0 vs. 1.6, p = 0.04; KSS pain 86 vs. 83, n.s), with a similar complication rate. No correlation was found between necrotic lesion size and failure rate (n.s.).

CONCLUSION

UKA is a valuable treatment option for SONK leading to good functional results and a low failure rate. In case of a surgeon's concern regarding implant anchorage, TKA represents an equivalent solution. The MR-tomographic size of the osteonecrotic lesions seems to have no influence on the results.

LEVEL OF EVIDENCE

III.

Total versus partial knee replacement in patients with medial compartment knee osteoarthritis: the TOPKAT RCT

BACKGROUND

Late-stage medial compartment knee osteoarthritis can be treated using total knee replacement or partial (unicompartmental) knee replacement. There is high variation in treatment choice and insufficient evidence to guide selection.

OBJECTIVE

To assess the clinical effectiveness and cost-effectiveness of partial knee replacement compared with total knee replacement in patients with medial compartment knee osteoarthritis. The findings are intended to guide surgical decision-making for patients, surgeons and health-care providers.

DESIGN

This was a randomised, multicentre, pragmatic comparative effectiveness trial that included an expertise component. The target sample size was 500 patients. A web-based randomisation system was used to allocate treatments.

SETTING

Twenty-seven NHS hospitals (68 surgeons).

PARTICIPANTS

Patients with medial compartment knee osteoarthritis.

INTERVENTIONS

The trial compared the overall management strategy of partial knee replacement treatment with total knee replacement treatment. No specified brand or subtype of implant was investigated.

MAIN OUTCOME MEASURES

The Oxford Knee Score at 5 years was the primary end point. Secondary outcomes included activity scores, global health measures, transition items, patient satisfaction (Lund Score) and complications (including reoperation, revision and composite 'failure' - defined by minimal Oxford Knee Score improvement and/or reoperation). Cost-effectiveness was also assessed.

RESULTS

A total of 528 patients were randomised (partial knee replacement, n = 264; total knee replacement, n = 264). The follow-up primary outcome response rate at 5 years was 88% and both operations had good outcomes. There was no significant difference between groups in mean Oxford Knee Score at 5 years (difference 1.04, 95% confidence interval -0.42 to 2.50). An area under the curve analysis of the Oxford Knee Score at 5 years showed benefit in favour of partial knee replacement over total knee replacement, but the difference was within the minimal clinically important difference [mean 36.6 (standard deviation 8.3) (n = 233), mean 35.1 (standard deviation 9.1) (n = 231), respectively]. Secondary outcome measures showed consistent patterns of benefit in the direction of partial knee replacement compared with total knee replacement although most differences were small and non-significant. Patient-reported improvement (transition) and reflection (would you have the operation again?) showed statistically significant superiority for partial knee replacement only, but both of these variables could be influenced by the lack of blinding. The frequency of reoperation (including revision) by treatment received was similar for both groups: 22 out of 245 for partial knee replacement and 28 out of 269 for total knee replacement patients. Revision rates at 5 years were 10 out of 245 for partial knee replacement and 8 out of 269 for total knee replacement. There were 28 'failures' of partial knee replacement and 38 'failures' of total knee replacement (as defined by composite outcome). Beyond 1 year, partial knee replacement was cost-effective compared with total knee replacement, being associated with greater health benefits (measured using quality-adjusted life-years) and lower health-care costs, reflecting lower costs of the index surgery and subsequent health-care use.

LIMITATIONS

It was not possible to blind patients in this study and there was some non-compliance with the allocated treatment interventions. Surgeons providing partial knee replacement were relatively experienced with the procedure.

CONCLUSIONS

Both total knee replacement and partial knee replacement are effective, offer similar clinical outcomes and have similar reoperation and complication rates. Some patient-reported measures of treatment approval were significantly higher for partial knee replacement than for total knee replacement. Partial knee replacement was more cost-effective (more effective and cost saving) than total knee replacement at 5 years.

FUTURE WORK

Further (10-year) follow-up is in progress to assess the longer-term stability of these findings.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN03013488 and ClinicalTrials.gov NCT01352247.

FUNDING

This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 20. See the NIHR Journals Library website for further project information.

Unicompartmental Knee Replacement in Obese Patients: A Systematic Review and Meta-Analysis

Thanks to modern surgical techniques and implants, traditional exclusion criteria for unicompartmental knee arthroplasty (UKA) are no longer considered contraindications. The aim of this study is to clarify the impact of obesity on functional outcomes and revision rates of UKA. We performed a comprehensive systematic review using PubMed–Medline, Google Scholar and Cochrane Central. Then, we extracted data related to body mass index (BMI), age and follow-up, functional outcome scores and rate of revisions (all-cause, aseptic and septic). Patients were stratified according to BMI into two groups: non-obese (BMI < 30) and obese (BMI ≥ 30). We identified 22 eligible studies, of which 13 were included in the meta-analysis. Patients with a BMI > 30 had a significantly higher likelihood for revision (p = 0.02), while the risk of septic revision was similar (p = 0.79). The clinical outcome measures showed a significant difference in favor of patients with a BMI < 30 (p < 0.0001). The improvements in Oxford Knee Score and Knee Society Score were significant in both obese and non-obese patients, although the latter showed inferior results. The results of this systematic review and meta-analysis show that BMI is not a contraindication to UKA. However, obese patients have a higher risk for aseptic failure and lower improvement in clinical scores compared to non-obese patients.

Unicompartmental Knee Arthroplasty Is Associated With a Lower Rate of Periprosthetic Joint Infection Compared to Total Knee Arthroplasty

Background

Several studies have reported lower perioperative complications with unicompartmental knee arthroplasty (UKA) than with total knee arthroplasty (TKA). However, there is a paucity of data analyzing the incidence of periprosthetic joint infection (PJI) in similar patients undergoing UKA and TKA. As such, we sought to analyze the incidence of UKA and TKA PJI in a large matched population.

Material and Methods

The Mariner data set of the PearlDiver database was queried for all patients undergoing UKA or TKA during 2010-2017. Included patients were required to have at least 2 years of database inclusion after surgery. Patients were then matched at a 1:3 ratio (UKA:TKA) on age, gender, Elixhauser Comorbidity Index, tobacco use, and obesity. Rates of PJI requiring operative intervention within 90 days and 1 year were calculated.

Results

In total, 5636 patients having undergone UKA were matched to 16,890 patients having undergone TKA. Fifteen (0.27%) after UKA and 79 (0.47%) after TKA had a PJI surgically managed within 90 days (risk ratio = 0.57, 95% confidence interval = 0.33-0.99, P = .04). Thirty (0.53%) after UKA and 136 (0.81%) after TKA had a PJI surgically managed within 1 year (risk ratio = 0.66, 95% confidence interval = 0.45-0.98, P = .04).

Conclusions

In a large group of rigorously matched patients, UKA was associated with a significantly lower rate of surgically managed PJI than TKA at 90 days and 1 year; however, the rate of PJI in both groups remained low at <1% at 90 days and 1 year.

Minimally Invasive Inlay Prosthesis Unicompartmental Knee Arthroplasty for the Treatment of Unicompartmental Osteoarthritis: A Prospective Observational Cohort Study with Minimum 2-Year Outcomes and up to 14-Year Survival

There are limited medium-term outcome data available for the Repicci II device in unicompartmental knee arthroplasty (UKA). The purpose of this study was to report the medium-term (minimum 2 years) patient-reported outcomes and long-term (up to 14 years) procedure survival in a consecutive series of patients undergoing an inlay prosthesis UKA (Repicci II) at an independent orthopaedic clinic. Patients presenting with medially localized unicompartmental knee osteoarthritis and meeting the criteria appropriate for UKA were recruited to a clinical patient registry at the time of presentation. A cemented unicompartmental prosthesis (Repicci II) was implanted using minimally invasive techniques with rapid postoperative mobilization. Patients were asked to complete patient-reported outcomes preoperatively and annually postoperatively. A procedure list was cross-matched with the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), and an analysis of procedure survival was performed with comparison to the national data for UKA. Data from a cohort of 661 primary medial compartment UKA procedures performed in 551 patients over a 15-year period were extracted from the clinical patient registry. Significant improvements were maintained in general health, disease symptoms, pain, and function at an average follow-up of 9 years compared with preoperative data. Threshold analysis revealed that >65% of patients exceeded Patient Acceptable Symptom State at the latest follow-up, with >80% within or exceeding age-matched norms for general health. Cumulative revision rate was significantly lower than that reported for UKA in the AOANJRR at up to 13 years follow-up. This series represents a lower cumulative revision rate than previously reported, with >65% of patients reporting satisfactory functional outcomes at an average of 9 years from surgery. Surgical options for treating unicompartmental knee osteoarthritis could include UKA as a viable alternative; however, clear definitions of procedure success and its overall cost-benefit ratio in the context of ongoing management of knee osteoarthritis remain to be elucidated.

What is the effect of supervised rehabilitation regime vs. self-management instruction following unicompartmental knee arthroplasty? - a pilot study in two cohorts

PURPOSE

The optimal rehabilitation strategy after a unicompartmental knee arthroplasty (UKA) is unclear. This study aims to compare the effect of transitioning from a supervised to a self-management rehabilitation regime by pilot study of patient outcomes subsequent to UKA surgery.

METHODS

Fifty consecutive patients scheduled to undergo unilateral UKA surgery at our institution between 22nd February 2016 and 18thof January 2017 were prospectively identified via local medical database and included. Performed UKAs were grouped into two cohorts, Supervised Cohort and Self-management Cohort, temporally separated by introduction of new rehabilitation. Self-management Cohort(n = 25) received an extensive inpatient rehabilitation regime along with outpatient referral to rehabilitation center. The Self-management Cohort(n = 25) were only instructed in use of crutches and free ambulation at own accord. Follow-up (F/U) was 1 year from receiving UKA. A range of outcomes were recorded, and between-cohort differences compared: knee joint range of motion, pain and functional limitations, length of stay (LOS), readmission rate, pain during activity and rest, and knee circumference.

RESULTS

Complete data was obtained for n = 45 patients. The mean between-cohort difference in ROM (range of motion) from preoperatively to discharge was 15.4 degrees (CI:5.2,25.8, p = 0.004), favoring the supervised regime, with no difference detected in any outcome at 3- or 12 months F/U. Median LOS was 1 day in both cohorts.

CONCLUSION

Transition to a simple rehabilitation regime following UKA surgery was associated with decreased ROM at discharge, which was not present at 3-month F/U. We found no other between-cohort differences for any other outcomes at 3- and 12-month F/U including functional limitations, although the study was likely underpowered for these outcomes. We encourage large-scale replication of these findings using randomized designs.

LEVEL OF EVIDENCE

Therapeutic level II.

More Anterior in vivo Contact Position in Patients With Fixed-Bearing Unicompartmental Knee Arthroplasty During Daily Activities Than in vitro Wear Simulator

BACKGROUND

While in vitro wear simulation of unicompartmental knee arthroplasty (UKA) showed outstanding long-term wear performance, studies reported that polyethylene (PE) wear was responsible for 12% fixed-bearing (FB) UKA failure. This paper aimed to quantify the in vivo 6-degrees-of-freedom (6-DOF) knee kinematics and contact positions of FB UKA during daily activities and compare with the previous results of in vitro wear simulator.

METHODS

Fourteen patients following unilateral medial FB UKA received a CT scan and dual fluoroscopic imaging during level walking, single-leg deep lunge, and sit-to-stand motion for evaluating in vivo 6-DOF FB UKA kinematics. The closest point between surface models of the femoral condyle and PE insert was determined to locate the medial compartmental articular contact positions, which were normalized relative to the PE insert length. The in vivo contact area was compared with the in vitro wear region in previous simulator studies.

RESULTS

The in vivo contact positions during daily activities were more anterior than those in the previous in vitro wear simulator studies (p < 0.001). Significant differences in the femoral anteroposterior translation and tibial internal rotation during the stance phase were observed and compared with those in lunge and sit-to-stand motions (p < 0.05). The in vivo contact position located anteriorly and medially by 5.2 ± 2.7 and 1.8 ± 1.6 mm on average for the stance phase, 1.0 ± 2.4 and 0.9 ± 1.5 mm for the lunge, and 2.1 ± 3.3 and 1.4 ± 1.4 mm for sit-to-stand motion. The in vivo contact position was in the more anterior part during the stance phase (p < 0.05).

CONCLUSION

The current study revealed that the contact position of FB UKA was located anteriorly and medially on the PE insert during in vivo weight-bearing activities and different from previous findings of the in vitro wear simulator. We should take in vivo 6-DOF knee kinematics and contact patterns of FB UKA into account to reproduce realistic wear performance for in vitro wear simulator and to improve implant design.

Meaningful values in the Forgotten Joint Score after total knee arthroplasty

AIMS

The aim of this study was to identify the minimal clinically important difference (MCID), minimal important change (MIC), minimal detectable change (MDC), and patient-acceptable symptom state (PASS) threshold in the Forgotten Joint Score (FJS) according to patient satisfaction six months following total knee arthroplasty (TKA).

METHODS

During a one-year period 484 patients underwent a primary TKA and completed preoperative and six-month FJS and OKS. At six months patients were asked, "How satisfied are you with your operated knee?" Their response was recorded as: very satisfied, satisfied, neutral, dissatisfied, or very dissatisfied. The difference between patients recording neutral (n = 44) and satisfied (n = 153) was used to define the MCID. MIC for a cohort was defined as the change in the FJS for those patients declaring their outcome as satisfied, whereas receiver operating characteristic curve analysis was used to determine the MIC for an individual and the PASS threshold. Distribution-based methodology was used to calculate the MDC.

RESULTS

Using satisfaction as the anchor question, the MCID for the FJS was 16.6 (95% confidence interval (CIs) 8.9 to 24.3; p < 0.001) and when adjusting for confounding this decreased to 13.7 points (95% CI 4.8 to 22.5; p < 0.001). The MIC for the FJS for a cohort of patients was 17.7 points and for an individual patient was 10 points. The MDC90 for the FGS was 12 points; where 90% of patients scoring more than this will have experienced a real change that is beyond measurement error. The PASS was defined as 22 points or more in the postoperative FJS.

CONCLUSION

The estimates for MCID and MIC can be used to assess whether there is clinical difference between two groups and whether a cohort/patient has had a meaningful change in their FJS, respectively. The MDC90 of 12 points suggests a value lower than this may fall within measurement error. A postoperative FJS of 22 or more was predictive of achieving PASS. Cite this article: Bone Joint J 2021;103-B(5):846-854.

[Focal femoral resurfacing and unicompartmental knee replacement : Between osteotomy and total knee replacement]

Unicompartmental knee arthroplasty, especially for both femorotibial compartments of the knee, is an established partly joint-saving treatment option for osteoarthritis of the knee if the disease is limited to one compartment. Even smaller implants or resurfacing of the patellofemoral joint have been shown-in smaller patient collectives-to have the potential to yield good clinical results.

Lateral Unicompartmental Knee Arthroplasty

Lateral unicompartmental knee arthroplasty affords excellent functional results and implant survivorship for properly selected patients. More high-quality studies are necessary to determine whether expanded indications for medial unicompartmental knee arthroplasty also apply to lateral unicompartmental knee arthroplasty. Operative adjuncts such as robotics, custom implants, and navigation technology hold promise in minimizing the technical burden and unfamiliarity of lateral unicompartmental knee arthroplasty. Improvements in lateral-specific implants may translate to operational efficiency and improved outcomes, but few lateral-specific implants currently exist. Mobile-bearing devices have increased rates of failure due to bearing dislocation, and further studies are warranted to evaluate this complication with newer designs. Future registry and cohort studies should show medial unicompartmental knee arthroplasty and lateral unicompartmental knee arthroplasty separately to allow for better understanding of the nuances and technical differences between these uniquely different procedures.

Forgotten Joint Score: Comparison between total and unicondylar knee arthroplasty

BACKGROUND

The aim of this study is to assess the Forgotten Joint Score (FJS) for total knee arthroplasty (TKA) and unicondylar knee arthroplasty (UKA) with both short- and long-term follow-up.

METHODS

For a consecutive period of eight months, the FJS was sent to all patients who had undergone either a primary TKA or UKA either one, five or ten years previously at our institution. Patient demographics and operative details were recorded retrospectively. FJS were collected for three different TKA prosthesis and two different UKA prosthesis.

RESULTS

A total of 588 FJS questionnaires were completed consisting of 482 TKA and 106 UKA procedures. The mean FJS for patients with TKA and UKA were 50.2 and 65.4 respectively (p < 0.001). Mean FJS for the ZUK were statistically superior to the Oxford UKA, 73.1 versus 60.1 (p = 0.020). For TKA mean FJS were statistically better at five compared to one year follow up, 53.8 versus 44.8 (p = 0.007). For UKA the mean FJJs were greatest at 10 year follow up (69.0), but the difference between scores at one (60.4) and five (68.4) years was not statistically significant (p = 0.243).

CONCLUSION

This cross-sectional study has shown; superior FJSs for UKA compared to TKA and superior FJSs for a fixed bearing compared to a mobile bearing UKA and therefore supports the use of UKA opposed to TKA where the indications for UKA are satisfied. For TKA the FJS in the five-year post-operative group were significantly superior to those in the one-year post-operative group.

[Recommendations for unicondylar knee replacement in the course of time : A current inventory]

BACKGROUND

A higher patient satisfaction stands in contrast to higher revision rates of unicondylar knee joint endoprosthetics (UKE) compared to total knee joint endoprosthetics (TKE). Furthermore, old "dogmas" regarding indications and contraindications persist, which is still reflected in the significantly different case numbers.

AIM

The aim of this article is to provide an overview of the current literature regarding 1. indication and contraindication (BMI, age, sport, arthrosis of other compartments, ligament status) and 2. the "eternal rival" fixed or mobile bearing for UKE.

RESULTS

The choice of the right patient remains essential, even if all the old "dogmas" of contraindications have been relativized or even outdated. Arthroses of the contralateral (in medial UKE correspondingly lateral) compartment and advanced arthroses of the lateral patella facet remain the only persistent contraindications. In contrast, a high BMI, age, chondrocalcinosis, medial patella facet and a defective (but particularly functionally stable) ACL are not contraindications; however, severe obesity is responsible for a significantly higher complication rate and probably a higher rate of loosening. Rather, the experience and thus the number of UKEs of the individual surgeon is decisive for the outcome, to which the discussion about mobile or fixed inlays must also be completely subordinated.

CONCLUSION

The indications for UKE can, therefore, be extended with a clear conscience on the basis of literature, and the current 1:10 UKE:TKE ratio in Germany can be shifted significantly.