Finite element analysis of unicompartmental knee arthroplasty

Concerns over accelerated damage to the untreated compartment of the knee following unicompartmental knee arthroplasty (UKA), as well as the relatively poor success rates observed for lateral as opposed to the medial arthroplasty, remain issues for attention. Finite element analysis (FEA) was used to assess changes to the kinematics and potential for cartilage damage across the knee joint in response to the implantation of the Oxford Mobile Bearing UKA. FE models of lateral and medial compartment arthroplasty were developed, in addition to a healthy natural knee model, to gauge changes incurred through the arthroplasty. Varus–valgus misalignments were introduced to the femoral components to simulate surgical inaccuracy or over-correction. Boundary conditions from the Stanmore knee simulator during the stance phase of level gait were used. AP translations of the tibia in the medial UKA models were comparable to the behaviour of the natural knee models (±0.6 mm deviation from pre-operative motion). Following lateral UKA, 4.1 mm additional posterior translation of the tibia was recorded than predicted for the natural knee. IE rotations of the medial UKA models were less consistent with the pre-operative knee model than the lateral UKA models (7.7° vs. 3.6° deviation). Varus misalignment of the femoral prosthesis was more influential than valgus for medial UKA kinematics, whereas in lateral UKA, a valgus misalignment of the femoral prosthesis was most influential on the kinematics. Resection of the cartilage in the medial compartment reduced the overall risk of progressive OA in the knee, whereas removing the cartilage from the lateral compartment, and in particular introducing a valgus femoral misalignment, increased the overall risk of progressive OA in the knee. Based on these results, under the conditions tested herein, both medial and lateral UKA can be said to induce kinematics of the knee which could be considered broadly comparable to those of the natural knee, and that even a 10° varus–valgus misalignment of the femoral component may not induce highly irregular kinematics. However, elevated posterior translation of the tibia in lateral UKA and large excursions of the insert may explain the higher incidence of bearing dislocation observed in some clinical studies.     

Provoked anterior knee pain in medial osteoarthritis of the knee

The incidence and the causes of provoked anterior knee pain in medial osteoarthritis (OA) of the knee were investigated clinically and radiographically. A retrospective study was performed in 179 primary osteoarthritic knees of 129 patients. Provocative tests were conducted on the patellofemoral (PF) joint to induce retropatellar crepitation, grating pain, tenderness around the patella, and pain on deviating the patella. The femorotibial angle (FTA) was measured on standing anteroposterior radiographs as a parameter of limb alignment. The widths of the medial and lateral joint space of the PF joint were measured on skyline views of standing or 30, 60 or 90° knee flexion. The angle of flexion contracture was measured on lateral radiographs of knees with maximum extension. The lateral shift and tilt of the patella were measured on standing skyline views. Retropatellar crepitation was found in 70% of knees, while provoked anterior knee pain was observed in 35–45% of knees with medial OA of the knee. Standing FTA was significantly greater in knees with tenderness around the patella and pain on deviating the patella than in those without these symptoms (P<0.05). The angle of flexion contracture was significantly greater in knees with provoked symptoms in the PF joint than in those without symptoms (P<0.05). The degree of lateral shift was greater in knees with provoked symptoms (P<0.05). Flexion contracture and varus deformity of the knee with lateralization of the patella may be factors aggravating provoked PF symptoms in medial OA of the knee. The radiographic assessment in this series failed to show a significant relationship between the width of the PF joint space and the incidence of provoked PF symptoms.     

Radiographic findings in osteoarthritis of the knee joint are not correlated with cartilage histomorphology or immunohistochemistry

The purpose of this study was to investigate whether radiographic joint space narrowing (JSN) of the lateral knee compartment predicts the histomorphological or immunhistochemical grading in cases of osteoarthritis of the knee joint. The lateral joint space was measured on weight-bearing radiographs. Femoral osteochondral plugs of 29 patients undergoing total knee replacement were obtained from lateral condyles. All these patients had severe osteoarthritis of the medial compartment, with the lateral compartment showing different stages of osteoarthritis. The specimens were histomorphologically evaluated with the Mankin score, and the expression of the cartilage-degrading enzymes MMP1 and MMP3 was measured. There was no correlation between the joint space and histomorphological or immunohistochemical data, whereas the enzyme expression was correlated with histomorphological grading. We conclude that radiographic assessment alone is not sufficient to evaluate the cartilage damage of the lateral condyle.     

Comparison of medial and lateral posterior femoral condyle articular cartilage wear patterns

Background

While degenerative changes to the articular cartilage of the anterior and distal portions of the femoral condyles have been well studied in the literature, the changes that occur on the posterior femoral condyle are not as clear. The purpose of this study was to assess the difference in articular cartilage thickness between the medial and lateral posterior femoral condyles in knees undergoing unicompartmental knee arthroplasty.

Skyline patellofemoral radiographs can only exclude late stage degenerative changes

Accurate preoperative assessment of the patellofemoral joint is especially important in compartment specific knee arthritis. This study aims to show the actual intraoperative grade of patellofemoral cartilage damage that may be reliably detected or excluded by preoperative standard radiographic views.100 consecutive knees awaiting arthroplasty underwent preoperative lateral and skyline radiographs and were scored using the Ahlback score. Intraoperative cartilage damage was assessed using the Collins score. The sensitivity and specificity were calculated for each grade of cartilage damage. Preoperative anterior knee pain and function were assessed and correlated to the degree of cartilage damage.The lateral radiograph shows poor sensitivity for all grades of disease (0.05-0.23). The skyline shows good sensitivity for grade 4 (large full thickness) damage (0.90) but decreases substantially for grades 1-3 (0.19-0.46). Significantly more people with skyline radiograph joint space narrowing complained of anterior knee pain than those with a normal radiograph (p < 0.001). There was only a poor correlation between preoperative anterior pain and intraoperative patellofemoral cartilage damage (r = 0.24).The lateral radiograph cannot exclude even large areas of full thickness cartilage damage whereas a normal skyline radiograph can reliably exclude significant (grade 4) patellofemoral disease and should be used in addition to the lateral view.     

UKA 关节线安装误差对膝关节接触力学和运动学影响

目的 针对单髁膝关节置换(unicompartmental knee arthroplasty, UKA)内侧假体松动和外侧关节软骨退化问题,通过骨肌多体动力学方法研究不同生理活动中UKA关节线安装误差对膝关节接触力学和运动学的影响。方法 以内侧自然关节线为0 mm误差,分别考虑±2 mm、±4 mm、±6 mm共6种关节线安装误差情况,建立7个内侧UKA置换的骨肌多体动力学模型,对比研究步行和下蹲运动中膝关节接触力学和运动学的变化。结果 在步行步态周期70%时,相比于0 mm误差UKA假体关节线升高2 mm时内侧假体接触力增大127.3%,外侧软骨接触力减少12.0%;在UKA假体关节线降低4 mm时内侧假体接触力接近0 N,外侧软骨接触力增大10.1%;胫股关节总接触力在关节线升高和降低2 mm时分别增大19.7%和减小14.2%。在下蹲屈膝100°时,相比于0 mm误差膝关节内侧假体接触力和胫股骨关节总接触力在UKA假体关节线升高2 mm时分别增大31.6%和11.1%,在UKA假体关节线降低2 mm时分别减小24.5%和8.5%,而膝关节外侧软骨接触力变化不大。同时,在步行步态...     

Lateral and patellofemoral compartment osteoarthritis progression after medial unicompartmental knee arthroplasty: A five- to 10-year follow-up study

BackgroundThe purpose of the study was to evaluate lateral and patellofemoral osteoarthritis (OA) progression after medial unicompartmental knee arthroplasty (UKA) and identify factors affecting the progression that were not identified previously.MethodsWe evaluated 146 patients who underwent medial UKA between 2009 and 2014. Kellgren–Lawrence grading of lateral and patellofemoral OA was performed on preoperative and final follow-up knee radiographs. Radiographic and clinical characteristics, SF-36, and Oxford knee scores were compared between the OA progressed and non-progressed groups. Risk factors for lateral and patellofemoral OA progression were evaluated.ResultsThe lateral OA progressed and non-progressed groups significantly differed in side, preoperative flexion contracture, preoperative joint line convergence angle, postoperative tibiofemoral angle, insert size, revision status (P < 0.05), and the patellofemoral OA progressed and non-progressed groups significantly differed in age, pre- and postoperative flexion contracture, postoperative tibiofemoral angle and pre- and postoperative patellofemoral OA grade (P < 0.05). At the final follow-up, Visual Analogue Scale, Oxford Knee Scores, and SF-36 sub-scores were significantly better in the lateral OA non-progressed group (P < 0.001).Dominant leg (odds ratio (OR): 2.759), insert size (> 4, OR: 2.219), revision status (+, OR: 6.692), and postoperative tibiofemoral angle (> 5.5°, OR: 1.177) were independent risk factors for lateral OA progression, whereas age (> 60 years, OR: 3.222), preoperative patellofemoral OA grade (> 1, OR: 2.085), and postoperative flexion contracture (> 10°, OR: 1.919) were those for patellofemoral OA progression.ConclusionsMild radiographic progression of 1 KL grade is frequently seen five to 10 years after medial UKA. Postoperative outcomes are significantly affected by lateral compartment OA progression but not by patellofemoral OA progression.     

基于MRI的成人正常膝关节软骨形态学测量

目的：了解正常膝关节软骨分布及股骨髁承重区的软骨厚度特点,为膝关节病变早期诊断和动态观察提供依据。方法：选取100名成人志愿者,男、女各50名,年龄20—30岁,平均25．3岁,膝关节均行MRI扫描。应用MIMICS软件对图像进行处理,在矢状位窗面上测量膝关节各部位软骨最大厚度。选择膝关节正常运动时的承重区,测量承重区域软骨的最大厚度并与其他区域进行比较。基于MRI图像行膝关节软骨三维重建,观察膝关节软骨的三维形态特征。结果：膝关节各部位的最大软骨厚度如下。胫骨外侧平台3．19mm,胫骨内侧平台3．07mm,股骨外侧髁2．93mm,股骨内侧髁3．19mm,股骨滑车软骨3．57mm,髌软骨3．75mm。不同性别与左右侧之间的软骨厚度差异无统计学意义（P〉0．05）。胫股关节承重区软骨厚度大于其他区域,有统计学差异（P〈0．05）。结论：成人正常膝关节各区域软骨厚度不同,胫股关节承重区软骨厚度大于非承重区域。基于MRI可以准确地测量膝关节各部软骨的厚度及重建膝关节软骨的三维形态。     

Does resurfacing of asymptomatic full-thickness localized articular defects of the trochlea influence the outcome following unicompartmental knee arthroplasty of the medial compartment?: A retrospective cohort study with minimum seven-year follow-up

BackgroundPatellofemoral joint (PFJ) degeneration has been found not to affect outcome following medial unicompartmental knee arthroplasty (UKA). However, PFJ disease occasionally presents as isolated trochlear cartilage lesions, with little available evidence regarding treatment options or necessity. We evaluated the effectiveness of concomitant trochlear resurfacing in patients undergoing medial UKA with asymptomatic trochlear lesions.MethodsWe included 60 patients undergoing medial UKA with an associated full thickness lesion of the trochlea. A fixed bearing UKA implant (PKR™, Stryker, Warsaw, IND) was used in all cases. In 30 patients, trochlear lesions were resurfaced with a HemiCAP® PF Classic (HemiCAP® PFC) implant (Arthrosurface, Franklin, MA). Outcome measures included VAS-, KOOS-, WOMAC-, SF-36 scores and radiological assessment.ResultsAverage length of follow-up was 97.4 months (range: 88–106 months). Both groups showed significant improvement for all clinical scores post-operatively compared to pre-operatively (p < 0.001 for all). The UKA group showed a better VAS score at all follow-up moments (p < 0.01 for all), but no differences were found between both groups at all time points for other outcome measures. None of the HemiCAP® PFC implants needed to be revised within the timeframe of the study.ConclusionsIn this retrospective cohort study, we found a 100% survivorship of the HemiCAP® PFC implant at an average eight-year follow-up. However, no clinical benefits were found in performing trochlear resurfacing in conjunction with medial UKA for asymptomatic end-stage trochlear cartilage lesions. Therefore, these lesions can be safely ignored when performing a medial UKA.     

The association between radiographic severity and pre-operative function in patients undergoing primary knee replacement for osteoarthritis

ObjectiveTo determine the association between radiographic osteoarthritis (OA) and pre-operative function in patients undergoing primary knee replacement.MethodsSingle centre study examining pre-operative outcomes in a consecutive series of 525 patients who underwent primary knee replacement for OA between January 2006 and December 2007. Pre-operative data included: demographics, American Society of Anaesthesiologists (ASA) status and OA in the contralateral knee. The International Knee Society (IKS) rating and Short Form-12 (SF-12) were recorded for each patient. Pre-operative radiographs were read by a single observer for Kellgren and Lawrence (K&L) grading and Osteoarthritis Research Society International (OARSI) atlas features. Multiple linear regression was used to assess the strength of associations between radiographic OA severity and function, adjusting for clinically relevant variables.ResultsLateral tibiofemoral osteophyte grade was an independent predictor of pre-operative function as determined by the functional sub-scale of the IKS in patients undergoing primary knee replacement (coefficient = 2.58, p = 0.033). No associations were evident between pre-operative function and modified K&L, joint space narrowing, Ahlbäck attrition and coronal plane deformity. Other statistically significant predictors of poorer pre-operative function included: advancing age, female gender, knee pain and poorer SF-12 mental component summary scores which including osteophyte grade accounted for 24.6% of the variation in functional scores, (r = 0.496).ConclusionOsteophytes in the lateral compartment of the knee were associated with pre-operative function in patients with advanced knee OA. Further studies are required which examine individual radiographic features specifically in patients with advanced knee OA to determine their relationship to pre-operative pain and function.     

The radiographic predictors of symptom severity in advanced knee osteoarthritis with varus deformity

Information concerning the abilities of radiographic parameters to predict the symptoms of advanced osteoarthritis (OA) of the knee would be valuable, because plain knee radiographs are used as one of the primary tools for the selection of treatment modalities. We aimed to identify the radiographic predictors of symptom severity in patients with varus knee OA advanced enough to warrant total knee arthroplasty (TKA). In 341 knees with primary varus OA warranting TKA, pertinent radiographic features of the medial and lateral tibiofemoral joint (TFJ), and the patellofemoral joint (PFJ) were assessed separately and scored. In addition, TF alignment was assessed on standing full-limb radiographs. Symptoms and functions were evaluated using WOMAC pain and function scores. In the univariate analyses with generalized estimating equations (GEE), multiple radiographic features (subluxation of the TFJ, overall severity of the medial TFJ, and degree of TF varus alignment) were associated with poorer WOMAC function scores, whereas only the degree of TF varus alignment was associated with poorer WOMAC pain scores. None of radiographic parameters in the PFJ or lateral TFJ (except TFJ subluxation) was associated with WOMAC scores. Multivariate analyses revealed that the degree of TF varus alignment was the strongest predictor of poorer WOMAC pain and function scores. We propose that extent of TF varus malalignment should be considered as the primary indicator of objective disease severity when selecting treatment options for patients with advanced knee OA.     

Predictors of a forgotten joint after medial fixed-bearing unicompartmental knee arthroplasty

BackgroundA forgotten joint is considered the ultimate goal of joint replacement. We aim to explore the predictive factors of a forgotten joint after fixed-bearing unicompartmental knee arthroplasty (UKA).MethodsThis retrospective cohort study used prospectively collected data from 302 cases of medial-compartment UKA with a minimum of 2-year follow-up. The primary outcome was the achievement of a forgotten joint after UKA, according to the Forgotten Joint Score (FJS-12) at the last follow-up. Patients with FJS-12 > 84 were considered to have forgotten UKA. Univariate and multivariate logistic regression analyses were conducted with preoperative patient characteristics and surgery-related factors as potential predictors.ResultsOf patients, 94 (31.1%) achieved a forgotten joint post-surgery. Multivariate logistic regression analysis revealed that preoperative hip-knee-ankle angle (HKAA), anatomic lateral distal femoral angle (aLDFA), and postoperative HKAA and HKAA changes were independent predictors of a forgotten joint. The probability of achieving a forgotten joint increased by 29% (OR = 1.29, 95% CI: 1.12–1.51) with a 1° increase in aLDFA. Preoperative HKAA, postoperative HKAA, HKAA changes (ΔHKAA), and outcomes exhibited a non-linear relationship. The probability of achieving a forgotten joint was the highest with preoperative HKAA > 172.0°, postoperative HKAA of 176.0–178.5°, and ΔHKAA < 5.5°.ConclusionTo achieve the forgotten joint state, the ideal HKAA range after medial fixed-bearing UKA is 176.0–178.5° and ΔHKAA should be <5.5°. Patients with smaller preoperative aLDFA and HKAA have a lower probability of achieving a forgotten joint after UKA.     

Occupational activity is associated with knee cartilage morphology in females

Introduction

Knee osteoarthritis (OA) is a major cause of pain and disability in women, becoming a major health problem in mid to later life. A better understanding of factors contributing to deleterious structural knee changes may be important for preventing OA. In men, occupations associated with frequent knee bending have been shown to be associated with damage to knee cartilage. This has not been examined in women. The aim of this study was to examine the effect of occupational specific knee activities on tibial and patella cartilage morphology among healthy females.

Methods

96 females aged 26–62 years with no history of knee injury or symptoms were recruited as part of a study of community-based study of lifestyle factors on knee health. Occupational activity data examining the frequency of tasks such as heavy lifting, knee bending, stair climbing, walking and standing were obtained by questionnaire. Tibial and patella cartilage volumes and defects were measured from magnetic resonance imaging using validated methods.

Results

Heavy lifting/bending/squatting, knee bending, stair climbing and walking were all associated with an increased risk of patella, but not tibial, cartilage defects (odds ratio 1.8–2.9; p ≤ 0.05) after adjustment for potential confounders, including knee alignment and radiographic joint space narrowing. There was a trend towards knee bending being associated with a reduction in patella cartilage volume (p = 0.07).

Conclusion

Our results demonstrate that asymptomatic adult females with occupations requiring frequent knee bending have patella, but not tibial cartilage damage. These findings suggest that vocational tasks requiring knee bending are detrimental to the structure of cartilage in females and may be an area to consider in the prevention of knee OA.     

Medium term results of per-operative knee arthroscopy in confirming suitability for unicompartmental arthroplasty

IntroductionThe status of the lateral compartment of the knee is a determining factor in the long-term outcome of medial unicompartmental arthroplasty (UKA). Various methods of assessing the lateral compartment have been used including stress radiography, radioisotope bone scanning, magnetic resonance imaging and visualisation at the time of surgery. Arthroscopy is another means of directly assessing the integrity of the articular cartilage and the meniscus in the lateral compartment.PurposeThis study aims to show that per-operative arthroscopy is a safe and effective means of deciding whether to proceed with UKA or convert to total knee arthroplasty (TKA).MethodWe have used arthroscopy of the lateral compartment to assess suitability for UKA in 151 knees over 8 years.ResultsAt time of arthroscopy 34 knees underwent a change of surgical plan from UKA to TKA (22.5%). There has been one revision to TKA and 2 bearing exchanges for dislocation.ConclusionImmediate per-operative arthroscopy is a reliable method for assessing the suitability of a knee for UKA, in particular the lateral compartment.     

Fixed bearing lateral unicompartmental knee arthroplasty—Short to midterm survivorship and knee scores for 101 prostheses

BackgroundIsolated unicompartmental knee arthritis is less common laterally than medially. Lateral unicompartmental knee arthroplasty (UKA) constitutes only 1% of all knee arthroplasty performed. Use of medial UKA is supported by several published series showing good long-term survivorship and patient satisfaction, in large patient cohorts. Results of lateral UKA however have been mixed. We present the short and mid-term survivorship and 5-year clinical outcome of 101 lateral UKAs using a single prosthesis.MethodsOver a 9 year period, 100 patients who satisfied inclusion criteria underwent a lateral fixed-bearing unicompartmental arthroplasty. American Knee Society (AKSS), Oxford Knee (OKS) and modified Western Ontario McMaster Universities Arthritis Index (WOMAC) scores were completed preoperatively and at 1, 2 and 5 years postoperatively. Kaplan–Meier survival analysis was used to determine the 2-year and 5-year survivorship, using revision for any cause as end point.ResultsSurvivorship was 98.7% and 95.5% at 2 and 5 years respectively. 1 knee was revised for subsidence of the tibial component and 1 knee for progression of medial compartment osteoarthritis. Of a possible 35 knees in situ at 5 year follow-up, 33 knees were fully scored. Median AKSS, OKS and modified WOMAC scores were 182, 41, and 16 respectively.ConclusionsThe mid-term survivorship and outcome scores at 5-years suggest that lateral unicompartmental knee arthroplasty provides a valuable alternative to total joint replacement in selected patients with isolated lateral tibio-femoral arthritis at mid-term follow-up.Level II evidence.     

MRI-determined preoperative lateral meniscus degeneration is not associated with adverse mid-term clinical results after mobile-bearing unicompartmental knee arthroplasty

BackgroundOne of the conditions constituting surgical indication for medial mobile-bearing unicompartmental knee arthroplasty (UKA) is that there is full-thickness cartilage in the lateral compartment under valgus stress radiography. However, it is unclear whether medial unicompartmental knee arthroplasty should be performed if there is degeneration of the lateral meniscus on preoperative magnetic resonance imaging (MRI).MethodsThe records of 77 patients (77 knees) who underwent Oxford mobile-bearing UKA were retrospectively reviewed. Based on the status of the lateral meniscus in each knee using preoperative MRI with Stoller's classification system, the patients were divided into two groups; a normal group and a lateral meniscus degenerated group (grades 1–3). The preoperative personal data and the outcome data three years postoperatively were compared.ResultsThe normal group contained 31 knees while the lateral meniscus degenerated group comprised 46 knees. There was no difference in clinical outcome or knee function between the groups at three years after UKA. There was no difference in re-operation and revision rate between the groups with no revisions in either group.ConclusionsIt may not be necessary to exclude UKA indications for cases with degenerative findings in the lateral meniscus on preoperative MRI.     

Proximal tibiofibular division in lateral closing wedge high tibial osteotomy does not increase varus instability of the knee

PurposeWhen performing lateral closing wedge high tibial osteotomy (LCWHTO), fibular untethering can be performed with either fibular shaft osteotomy (FSO) or proximal tibiofibular division (TFD). The aim of this study was to compare the degree of varus instability between the two methods after LCWHTO and to analyze the determinants of varus instability.MethodsThis study retrospectively analyzed 108 consecutive patients with medial compartment osteoarthritis who underwent LCWHTO and had > 2 years of follow-up. Patients who underwent unilateral LCWHTO without a previous history of ligament injury were included. Forty-five patients who received LCWHTO with TFD and 51 patients who received LCWHTO with FSO were finally analyzed. The mean follow-up duration was 5.3 years in LCWHTO with TFD and 4.1 years in LCWHTO with FSO. The shortest distance between the lateral tibial plateaus and the corresponding most distal subchondral bone surface of the lateral femoral condyle was measured on varus stress radiographs and compared with that on the unaffected contralateral knee. Multivariable logistic regression analyses were conducted to identify predictors of varus instability.ResultsLateral joint space width showed no significant between-group difference. Multivariable logistic regression analysis revealed that the pre-operative hip-knee-ankle angle was positively correlated with the lateral joint space width. The type of fibular untethering procedure was not associated with postoperative varus instability.ConclusionThe degree of pre-operative varus malalignment is associated with postoperative varus instability after LCWHTO. Proximal tibiofibular division is not a variable for postoperative varus instability after LCWHTO.Level of evidenceLevel III, Retrospective comparative study.     

Differences in impact on adjacent compartments in medial unicompartmental knee arthroplasty versus high tibial osteotomy with identical valgus alignment

BackgroundIt is unclear why medial unicompartmental knee arthroplasty (UKA) with postoperative valgus alignment causes adjacent compartment osteoarthritis more often than high tibial osteotomy (HTO) for moderate medial osteoarthritis of the knee with varus deformity. This study used a computer simulation to evaluate differences in knee conditions between UKA and HTO with identical valgus alignment.MethodsDynamic musculoskeletal computer analyses of gait were performed. The hip–knee–ankle angle in fixed-bearing UKA was changed from neutral to 7° valgus by changing the tibial insert thickness. The hip–knee–ankle angle in open-wedge HTO was also changed from neutral to 7° valgus by opening the osteotomy gap.ResultsThe lateral tibiofemoral contact forces in HTO were larger than those in UKA until moderate valgus alignments. However, the impact of valgus alignment on increasing lateral forces was more pronounced in UKA, which ultimately demonstrated a larger lateral force than HTO. Valgus alignment in UKA caused progressive ligamentous tightness, including that of the anterior cruciate ligament, resulting in compression of the lateral tibiofemoral compartment. Simultaneously, patellofemoral shear forces were slightly increased and excessive external femoral rotation against the tibia occurred due to the flat medial tibial insert surface and decreased lateral compartment congruency. By contrast, only lateral femoral slide against the tibia occurred in excessively valgus-aligned HTO.ConclusionsIn contrast to extra-articular correction in HTO, which results from opening the osteotomy gap, intra-articular valgus correction in UKA with thicker tibial inserts caused progressive ligamentous tightness and kinematic abnormalities, resulting in early osteoarthritis progression into adjacent compartments.     

膝关节单髁置换术胫骨假体不同后倾角对假体磨损和功能的影响

目的 建立单髁置换术胫骨假体后倾3°和7°膝关节不同屈膝角度三维有限元模型,研究两种后倾角膝关节生物力学特性和假体磨损及其对功能的影响.方法 结合人体膝关节CT与MRI图像和第3代Oxford假体,建立胫骨假体后倾3°和7°下屈膝单髁置换术有限元模型,在股骨内外侧髁中心点上施加1 kN载荷模拟人体站立相负重,分析不同屈...     

Readmissions and mortality after outpatient vs inpatient unicompartmental knee arthroplasty in Denmark – A propensity score matched study of 5,384 procedures

BackgroundLimited nationwide data on the development of outpatient unicompartmental knee arthroplasty (UKA) practice and patient safety exist. The primary objective of this study on patients receiving a medial or lateral UKA was to investigate 7-, 30- and 90-day readmission risk and 90-day mortality in outpatient vs inpatient surgeries. Secondary to investigate the nationwide development of outpatient UKA surgery in 2014–2018.MethodsIncluded patients received a medial or lateral UKA in the period January 1, 2014 to December 31, 2018 in any Danish hospital. Data were collected from the Danish National Patient Register. The cohort consisted of 1,059 outpatient and 4,325 inpatient surgeries, hereof 5,182 medial and 202 lateral UKA. After propensity score matching (1:1) 1,057 patients were included in each group.ResultsWe found a 7-day readmission risk of 1.5 % vs 1.4 % (p = 0.8), 30-day readmission risk of 2.6 % vs 3.2 % (p = 0.3), and 90-day readmission risk of 4.2 % vs 4.8 % (p = 0.4) after outpatient vs inpatient UKA. Similar results were found after matching. We found no significant differences in 90-day mortality for the unmatched or matched cohorts. The amount of outpatient UKA surgeries in Denmark increased from 86 in 2014 to 214 in 2018.ConclusionOutpatient medial or lateral UKA seem to be as safe as inpatient UKA on a nationwide basis.