Clinical Outcomes and Survivorship of Lateral Unicompartmental Knee Arthroplasty: Does Surgical Approach Matter?

Background

Lateral unicompartmental knee arthroplasty (UKA) has been shown to be an effective procedure to treat isolated lateral compartment osteoarthritis with excellent long-term survivorship. Whether a medial parapatellar approach or a lateral parapatellar approach is superior in lateral UKA is unknown. The purpose of this study was to determine if there is a difference in intermediate-term clinical outcomes in patients undergoing lateral UKA through a lateral vs medial parapatellar approach.

Unicompartmental Versus Total Knee Arthroplasty Database Analysis: Is There a Winner?

Background  

TKA and unicompartmental knee arthroplasty (UKA) are both utilized to treat unicompartmental knee arthrosis. While some surgeons assume UKA provides better function than TKA, this assumption is based on greater final outcome scores rather than on change in scores and many patients with UKA have higher preoperative scores.     

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

BackgroundLateral 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.MethodsPreferred 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).ResultsThe 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.ConclusionConsidering 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.     

Revision of Unicompartmental to Total Knee Arthroplasty: Does the Unicompartmental Implant (Metal-Backed vs All-Polyethylene) Impact the Total Knee Arthroplasty?

Background

The aim of this study is to investigate differences in implant requirement, outcomes, and re-revision when total knee arthroplasty (TKA) was performed following unicompartmental knee arthroplasties (UKAs) with metal-backed (MB) compared to all-polyethylene (AP) tibial components.

Clinical and Patient-Reported Outcomes of Medial Stabilized Versus Non–Medial Stabilized Prostheses in Total Knee Arthroplasty: A Systematic Review and Meta-Analysis

BackgroundThe aim of this systematic review and meta-analysis was to compare the clinical and patient-reported outcome measures (PROMs) of medial stabilized total knee arthroplasty (TKA) with non–medial stabilized TKAs.MethodsA systematic search of multiple databases was conducted in October 2019. A meta-analysis was conducted for the Knee Society Score (KSS), Knee Society Functional Score (KFS), range of motion (ROM), Oxford Knee Score (OKS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Forgotten Joint Score (FJS).ResultsA total of 857 articles yielded 21 studies eligible for inclusion with 13 studies used for quantitative analysis. The meta-analysis revealed that the medial stabilized group had a mean FJS that was 13.8 points higher than that of the non–medial stabilized TKA (mean difference [MD]: 13.83, P ≤ .0001, 95% confidence interval [CI]: 8.90-18.76, I² = 0%) which was less than the minimal clinically important difference of 14. The medial stabilized group also demonstrated a statistically significant difference in the postoperative ROM (MD = 2.52, P = .05, 95% CI: ?0.03 to 5.07, I² = 85%) and OKS when compared with the non–medial stabilized group (MD = 1.25, P = .02, 95% CI: 0.17-2.33, I² = 27%), but these were not clinically significant. There was no statistically or clinically significant difference in the KSS, KFS, and WOMAC scores.ConclusionMedial stabilized knee prostheses demonstrated no clinically significant differences for the ROM, OKS, WOMAC, KSS, and KFS. The FJS demonstrated the greatest MD and warrants further investigation. Future research is required using patient-reported outcome measures with a lower ceiling effect such as the FJS.     

Is the Medial Wall of the Intercondylar Notch Useful for Tibial Rotational Reference in Unicompartmental Knee Arthroplasty?

Background  

It is difficult to implant components in the correct rotational position in the narrow operating field in a unicompartmental knee arthroplasty. Although no rotational reference has been confirmed for unicompartmental knee arthroplasty, the AP axis of the tibia may serve as a reference for unicompartmental knee arthroplasty and TKA. However, it is difficult to identify the AP axis during unicompartmental knee arthroplasty, especially with the tibia first-cut technique.     

Is Mobile-Bearing Medial Unicompartmental Knee Arthroplasty Appropriate for Asian Patients With the Risk of Bearing Dislocation?

BackgroundMobile-bearing unicompartmental knee arthroplasty (UKA) is an attractive operation for medial unicompartmental knee arthritis, but unexpected bearing dislocation is a drawback. Bearing dislocation occurs more frequently in Asians, whose lifestyle involves deeper knee flexion than Westerners. This study investigated whether mobile-bearing medial UKA is appropriate for Asians by analyzing (1) the rate of bearing dislocation and (2) the results of patients with bearing dislocation.MethodsWe retrospectively reviewed 531 consecutive mobile-bearing medial UKA in the previous 15 years, including 22 patients with bearing dislocation who had at least 2 years of follow-up. The entire patient cohort was divided into 2 groups: the symmetrical bearing (187 knees) and the anatomic bearing (344 knees) groups. In the anatomic bearing group, patients who underwent surgery using the conventional phase III (283 knees) vs the Microplasty (61 knees) instrumentation systems were compared.ResultsThe overall incidence of bearing dislocation was 4.1% (22/531). Patients with the symmetrical bearing displayed a relatively high dislocation rate of 9.6% (18/187), which significantly decreased to 1.1% (4/344) after changing to the anatomic bearing (P < .001). In the anatomic bearing group, the dislocation rate with the conventional phase III system was 1.4% (4/283). There were no bearing dislocations in the Microplasty system group (0%, 0/61) after at least 2 years of follow-up.ConclusionAlthough mobile-bearing medial UKA was reported to have a high incidence of bearing dislocation in Asians, this frequency of dislocation is drastically decreased by bearing design and implantation system improvements. We consider mobile-bearing medial UKA appropriate for Asians.     

Anterior Cruciate Ligament Deficiency is Not Always a Contraindication for Medial Unicompartmental Knee Arthroplasty: A Retrospective Study in Nondesigner’s Japanese Hospital

BackgroundAn intact anterior cruciate ligament (ACL) is thought to be prerequisite for successful unicompartmental knee arthroplasty (UKA), but recent studies reported successful midterm results of UKA in ACL-deficient (ACLD) knees. We hypothesized that ACLD is not always a contraindication for medial UKA when preoperative radiographs showed typical anteromedial knee patterns.MethodsFrom April 2012 to March 2016, 401 Oxford mobile-bearing UKAs in 282 patients were retrospectively identified from our database. Patients whose ACL was severely damaged, but preoperative X-rays showed typical anteromedial osteoarthritis patterns, were categorized into the ACLD group. From intraoperative data, those whose ACL was intact were categorized into the ACL functional (ACLF) group. There were 32 and 369 knees in the ACLD and ACLF groups, respectively, and mean follow-up periods were 66.1 and 63.8 months for the ACLD and ACLF groups, respectively. We compared the postoperative clinical outcome and component survivorship, with an endpoint of component revision, between ACLD groups and ACLF groups.ResultsIn both groups, the Oxford knee score, Knee Society score, Tegner activity score, and knee range of motion in extension were improved after surgery. The UKA component survival rate at five years was 100% in the ACLD group and 98.9% in the ACLF group. There were no significant differences between the groups.ConclusionMid-term clinical outcomes of Oxford mobile-bearing UKA in ACLD knees were similar to those in ACLF knees. ACL deficiency is not always a contraindication for medial unicompartmental knee arthroplasty in patients with typical anteromedial osteoarthritis radiographs.     

Accuracy of Computed Tomography–Based Navigation-Assisted Total Knee Arthroplasty: Outlier Analysis

Background

Achieving neutral limb alignment during total knee arthroplasty (TKA) has been identified as a potential factor in long-term prosthesis survival. This study aimed to analyze the accuracy of component orientation and postoperative alignment of the leg after computed tomography (CT)–based navigation-assisted TKA, compare these parameters with those of a conventional technique, and analyze differences in the data of outliers.

Tibial Tubercle Osteotomy vs the Extensile Medial Parapatellar Approach in Revision Total Knee Arthroplasty: Is Tibial Tubercle Osteotomy a Harmful Approach?

BackgroundAs the frequency of total knee arthroplasty (TKA) is increasing, long-term follow-up of patients has become essential, and the frequency of revision total knee arthroplasty (R-TKA) due to the occurrence of various complications has also increased. There is controversy regarding which approach has minimal complications and an adequate visual field in R-TKA. Therefore, we compared the clinical and radiological results between the extensile medial parapatellar (EMP) approach and tibial tubercle osteotomy (TTO) for R-TKA.MethodsBetween March 1, 2000, and December 31, 2015, we compared 35 patients who underwent the EMP approach and 31 who underwent the TTO approach for R-TKA. In this study, the preoperative range of motion (ROM) was an important criterion for the choice of approach in R-TKA. The EMP approach was applied to patients with a ROM above 60°. The TTO approach was applied to patients with knee flexion limited to 0°-30°. We clinically assessed knee ROM, Knee Society scores, and Hospital for Special Surgery scores at the time of the last follow-up. We radiographically measured femorotibial alignment and patellar height. We also examined the complication rates. The average length of the TTO was 1.0 × 2.5 cm × 10 cm. We used 3 or more 3.5-mm half-threaded screws.ResultsThe mean postoperative ROM of the knee joint at the time of the last follow-up was 103° (flexion contracture 5° and further flexion 108°) in the group that underwent the EMP approach and 101° (flexion contracture 4° and further flexion 109°) in the group that underwent the TTO approach. The mean Knee Society scores were 86 (71-96) and 85 (72-94), and the mean Hospital for Special Surgery scores were 82 (70-93) and 83 (68-92) for the 2 groups, respectively, with no statistically significant difference. The mean femorotibial angles were 0.6° (±3.3°) and 0.1° (±2.9°), and the mean Insall-Salvati ratios were 1.0 (±0.34) and 0.8 (±0.14), respectively, with no statistically significant difference. The group that underwent TTO achieved bone union at an average of 11.8 weeks after surgery. In the group that underwent the EMP approach, 2 patients had extensor lag of more than 10°. In the group that underwent TTO, 2 subjects had skin necrosis at the operative site.ConclusionThe clinical and radiological outcomes were similar in the 2 groups after R-TKA. To increase the ROM and obtain adequate exposure, TTO is also considered a useful surgical approach. However, complications related to TTO should be minimized.Level of EvidenceTherapeutic level III, retrospective comparative study.     

Freeman-Swanson Arthroplasty of the Knee in Rheumatoid Arthritis: A 2–7 Year Experience

Sixty-six Freeman-Swanson arthroplasties were performed on 59 patients with rheumatoid arthritis from 1972 through 1979. The patients were followed prospectively and longitudinally. Thus, a detailed protocol was filled out preoperatively and once a year thereafter. This report is based on a total of 299 observations, with a follow-up period ranging from 2 to 7 years (mean 4.4 years).

Pain was the main indication for surgery and relief of pain the most gratifying and consistent finding over the years. Of 56 knees remaining in the study in 1979, 61 per cent were considered to be good, 27 per cent satisfactory, and 12 per cent were failures.

Early complications were observed in 20 per cent of the knees, late complications in 24 per cent. The majority of the complications resolved after treatment but six knees (9 per cent) deteriorated following a late complication. Thirteen reoperations were performed, of which five were prosthetic revisions.

In conclusion, the results were good over a 7-year period provided the deformity was corrected, stability restored and the prosthetic components positioned perpendicular to the mechanical axis of the leg. Tibial component loosening was the most important reason for failure.     

What Is the Critical Tibial Resection Depth During Unicompartmental Knee Arthroplasty? A Biomechanical Study of Fracture Risk

BackgroundFracture after medial unicompartmental knee arthroplasty (UKA) is a rare complication. Biomechanical studies evaluating association between depth of resection and maximum load to failure are lacking. The purpose of this study is to establish the relationship between depth of resection of the medial tibial plateau and mean maximum load to failure.MethodsMedial tibial resections were performed from 2 to 10 mm in 25 standardized fourth-generation Sawbones composite tibias (Sawbones, Vashon Island, Washington). A metal-backed tibial component with a 9-mm polyethylene bearing was used (Stryker PKR). Tibias were mounted on a biomechanical testing apparatus (MTESTQuattro) and axially loaded cyclically 10 times per cycle and incrementally increased until failure occurred.ResultsLoad to failure was recorded in 25 proximal tibia model samples after medial UKA using sequential resections from 2 to 10 mm. Analysis of variance testing identified significant differences in mean maximum load to failure between groups (P = .0003). Analysis of regression models revealed a statistically significant fit of a quadratic model (R² = 0.59, P = .0001). The inflection point of this quadratic curve was identified at 5.82 mm, indicating that the maximum load to failure across experimental models in this study began to decline beyond a resection depth of 5.82 mm.ConclusionIn this biomechanical model, medial tibial resections beyond 5.82 mm produced a significantly lower mean load to failure using a quadratic curve model. Resections from 2 to 6 mm showed no significant differences in mean load to failure. Identification of the tibial resection depth at which the mean load to failure significantly decreases is clinically relevant as this depth may increase the risk of periprosthetic fracture after a medial UKA.     

Navigating the Reaming of the Acetabular Cavity in Total Hip Arthroplasty: Does it Improve Implantation Accuracy?

Computer navigation in total hip arthroplasty is used to improve accuracy of component implantation. Reaming of the acetabular cavity during total hip arthroplasty (THA) can be navigated although this is not done routinely. We hypothesised that navigating the reaming of the acetabular cavity will improve implantation accuracy. A single surgeon series of 100 navigated THAs were analysed retrospectively. In 49 the reaming of the acetabular cavity was done using navigation and in 51 this was done freehand. The verified cup position and the error from the planned position were recorded. The mean error from planned to verified inclination was 2.20 degrees (SD 1.59°) in the navigated group versus 2.33 degrees (SD 1.96°) in the freehand group. The mean anteversion error was 1.92 degrees (SD 1.51°) for the navigated group and 1.45 degrees (SD 1.38°) for the freehand group. This was not statistically significant. This rejects our hypothesis. Navigating the reaming of the acetabular cavity did not improve the accuracy of the implantation against the set inclination and anteversion target during computer navigated THA.     

Electromagnetic Navigated Versus Conventional Total Knee Arthroplasty—A Five-Year Follow-Up of a Single-Blind Randomized Control Trial

BackgroundThe objective of this study is to provide the 5-year follow-up results of a randomized study comparing conventional versus electromagnetic computer navigated total knee arthroplasty.MethodsAnalysis of 127 patients (66 navigated and 61 conventional surgeries) was performed from a prospective, single-blinded, randomized controlled trial. Patient-reported outcome measures were collected at 5 years after surgery and compared with previously published 1-year clinical outcomes. Five-year surgical revision rates were collated and compared between intervention groups.ResultsOverall, there have been continued improvements in the clinical scores of patients in both groups when compared with clinical data at 1 year; however, at 5 years, there is no statistical difference in any of the patient-reported outcome measures between conventional and navigated surgery. Interestingly, improved implant survivorship was observed in the navigated (0% revision rate) compared with the conventional group (4.9% all-cause revision rate).ConclusionElectromagnetic computer navigated technology produces similar clinical outcomes compared with traditional surgery. Further work is required to monitor implant survivorship, and clinical outcomes with long-term follow-up, to determine the cost effectiveness of this technology.     

Do Fixed or Mobile Bearing Implants Have Better Survivorship in Medial Unicompartmental Knee Arthroplasty? A Study From the Australian Orthopaedic Association National Joint Replacement Registry

BackgroundDuring the last 5 years, there has been an increase in the use of unicompartmental knee arthroplasty (UKA) to treat knee osteoarthritis in Australia, and these account for almost 6% of annual knee replacement procedures. However, there is debate as to whether a fixed bearing or a mobile bearing design is best for decreasing revision for loosening and disease progression as well as improving survivorship. Small sample sizes and possible confounding in the studies on the topic may have masked differences between fixed and mobile bearing designs.Questions/purposesUsing data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), we selected the four contemporary designs of medial compartment UKA: mobile bearing, fixed modular, all-polyethylene, and fixed molded metal-backed used for the treatment of osteoarthritis to ask: (1) How do the different designs of unicompartmental knees compare with survivorship as measured by cumulative percentage revision (CPR)? (2) Is there a difference in the revision rate between designs as a function of patient sex or age? (3) Do the reasons for revision differ, and what types of revision procedures are performed when these UKA are revised?MethodsThe AOANJRR longitudinally maintains data on all primary and revision joint arthroplasties, with nearly 100% capture. The study population included all UKA procedures undertaken for osteoarthritis between September 1999 and December 2018. Of 56,628 unicompartmental knees recorded during the study period, 50,380 medial UKA procedures undertaken for osteoarthritis were included in the analysis after exclusion of procedures with unknown bearing types (31 of 56,628), lateral or patellofemoral compartment UKA procedures (5657 of 56,628), and those performed for a primary diagnosis other than osteoarthritis (560 of 56,628). There were 50,380 UKA procedures available for analysis. The study group consisted of 40% (20,208 of 50,380) mobile bearing UKA, 35% (17,822 of 50,380) fixed modular UKA, 23% (11,461 of 50,380) all-polyethylene UKA, and 2% (889 of 50,380) fixed molded metal-backed UKA. There were similar sex proportions and age distributions for each bearing group. The overall mean age of patients was 65 ± 9.4 years, and 55% (27,496 of 50,380) of patients were males. The outcome measure was the CPR, which was defined using Kaplan-Meier estimates of survivorship to describe the time to the first revision. Hazard ratios from Cox proportional hazards models, adjusted for sex and age, were performed to compare the revision rates among groups. The cohort was stratified into age groups of younger than 65 years and 65 years and older to compare revision rates as a function of age. Differences among bearing groups for the major causes and modes of revision were assessed using hazard ratios.ResultsAt 15 years, fixed modular UKA had a CPR of 16% (95% CI 15% to 17%). In comparison, the CPR was 23% (95% CI 22% to 24%) for mobile bearing UKA, 26% (95% CI 24% to 27%) for all-polyethylene UKA, and 20% (95% CI 16% to 24%) for fixed molded metal-backed UKA. The lower revision rate for fixed modular UKA was seen through the entire period compared with mobile bearing UKA (hazard ratio 1.5 [95% CI 1.4 to 1.6]; p < 0.001) and fixed molded metal-backed UKA (HR 1.3 [95% CI 1.1 to 1.6]; p = 0.003), but it varied with time compared with all-polyethylene UKA. The findings were consistent when stratified by sex or age. Although all-polyethylene UKA had the highest revision rate overall and for patients younger than 65 years, for patients aged 65 years and older, there was no difference between all-polyethylene and mobile bearing UKA. When compared with fixed modular UKA, a higher revision risk for loosening was shown in both mobile bearing UKA (HR 1.7 [95% CI 1.5 to 1.9]; p < 0.001) and all-polyethylene UKA (HR 2.4 [95% CI 2.1 to 2.7]; p < 0.001). The revision risk for disease progression was higher for all-polyethylene UKA at all time points (HR 1.4 [95% CI 1.3 to 1.6]; p < 0.001) and for mobile bearing UKA after 8 years when each were compared with fixed modular UKA (8 to 12 years: HR 1.4 [95% CI 1.2 to 1.7]; p < 0.001; 12 or more years: HR 1.9 [95% CI 1.5 to 2.3]; p < 0.001). The risk of revision to TKA was higher for mobile bearing UKA compared with fixed modular UKA (HR 1.4 [95% CI 1.3 to 1.5]; p < 0.001).ConclusionIf UKA is to be considered for the treatment of isolated medial compartment osteoarthritis, the fixed modular UKA bearing has the best survivorship of the current UKA designs.Level of EvidenceLevel III, therapeutic study.     

No Detectable Polyethylene Wear 15 Years After Implantation of a Mobile–Bearing Total Knee Arthroplasty With Electron Beam–Irradiated Polyethylene

BackgroundThe present study was designed to evaluate the risk of significant polyethylene (PE) wear 10 years or more after implantation of a total knee arthroplasty (TKA) using electron beam–irradiated highly cross-linked PE component.MethodsAll patients operated between 2001 and 2004 for implantation of this particular TKA in the two participating centers were eligible for this study. All patients were contacted after the 10-year follow-up for repeat clinical examination and radiological evaluation. The occurrence of a revision prior to the final evaluation and its reason were recorded. The thickness of the PE piece was measured on plain X-rays.ResultsFive hundred seventy-eight TKAs were implanted during the study time-frame. One hundred sixteen patients deceased prior to the 10-year follow-up (20%). An additional 121 patients were lost to follow-up prior to the 10-year follow-up (21%). Complete follow-up at 10 years or more (including death or revision) was obtained for 448 cases (78%). Ten prosthetic revisions were performed for mechanical reasons during the follow-up time (2%). One single revision was performed because PE wear after 13 years. No significant PE wear was detected at the final radiographic evaluation for nonrevised cases. The 10-year survival rate for mechanical revision only was 98.0% and decreased to 96.2% at 15 years.ConclusionThe use of electron beam–irradiated PE was associated with an extremely low incidence of wear. This technology may be considered as safe regarding PE behavior for TKA after more than 10 years. Further improvement of PE manufacturing may be not required.     

Knee Arthroplasty and Risk of Hip Fracture: A Population-Based,Case–Control Study

The majority of knee arthroplasties (KAs) are performed in patients with osteoarthritis (OA). Although bone mass may be increased in these patients, subjects with knee OA may have an increased risk of hip fracture, possibly due to an increased severity of falls. However, in patients with KAs, risk of hip fracture has not been studied extensively. We evaluated the association between KAs and hip fracture risk in a population-based case–control study using the Dutch PHARMO Record Linkage System (1991–2002, n = 33,104). Cases were patients with a first admission for hip fracture; controls were matched by age, gender, and geographic location. Neither group had a previous history of fracture. Time since first KA was calculated. Analyses were adjusted for disease and drug history. A 54% increased hip fracture risk was found in patients who underwent KA (adjusted [adj.] OR = 1.54, 95% CI 1.19–2.00). We found a strong effect modification by age in these patients: the youngest patients (aged 18–70 years) were at more increased risk for hip fracture (adj. OR = 2.76, 95% CI 1.16–6.59), while we could not detect a statistical increase in patients aged >80 years. Furthermore, the association tended to be greater during the first few years after surgery, although it did not reach statistical significance. We found that KAs are associated with a 54% increased risk of hip fracture, in particular among adult patients aged <71 years old. Fracture risk assessment could be considered in patients who are about to undergo a KA.