Role of magnetic resonance imaging in the diagnosis of the painful unicompartmental knee arthroplasty

Pulsed electromagnetic fields improve pain management and clinical outcomes after medial unicompartmental knee arthroplasty: A prospective randomised controlled trial

BACKGROUND

To assess pain relief and clinical outcomes in patients undergoing unicompartmental knee arthroplasty (UKA) stimulated with pulsed electromagnetic fields (PEMFs) compared to a control group.

METHODS

A prospective randomised controlled trial (RCT) was performed in which 72 patients undergoing medial UKA were randomised into a control group or an experimental PEMFs group. The patients allocated to the experimental group were instructed to use PEMFs for 4 h per day for 60 days. They were evaluated before a surgery and then during the time points corresponding to 1 month, 2 months, 6 months, 12 months, and 36 months after the surgery. No placebo group was included in the RCT. Clinical assessment included the Visual Analogue Scale (VAS) for pain, Oxford Knee Score (OKS), the Short Form 36 (SF-36) health survey questionnaire, and joint swelling. During each follow-up visit, the consumption of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) was recorded.

RESULTS

The VAS decreased on follow-up visits in both the groups; a statistically significant difference between the groups was observed during the 6 (p = 0.0297), 12 (p = 0.0003), and 36 months (p = 0.0333) follow-ups in favour of the PEMFs group. One month after UKA, the percentages of patients using NSAIDs in the PEMFs and control group were 71% and 92%, respectively (p = 0.0320). At the 2 months point, 15% of the patients in the PEMFs group used NSAIDs compared to 39% in the control group (p = 0.0317). The objective knee girth evaluation showed a statistically significant difference at 6 (p = 0.0204), 12 (p = 0.0005), and 36 (p = 0.0005) months with improved values observed in the PEMFs group. The subjective assessment of the swelling demonstrated a statistically significant difference at 2 (p = 0.0073), 6 (p = 0.0006), 12 (p = 0.0001), and 36 (p = 0.0011) months with better values noted in the PEMFs group. Last, the OKS result was significant higher in the experimental group during all the follow-ups (1mth: p = 0.0295; 2mths: p = 0.0012; 6mths: p = 0.0001; 12mths: p < 0.0001; 36mths: p = 0.0061).

CONCLUSIONS

The use of PEMFs leads to significant pain relief, better clinical improvement, and lower NSAIDs consumption after medial UKA when compared to the control group.

LEVEL OF EVIDENCE

II.

A Comparison of Mobile- and Fixed-Bearing Unicompartmental Knee Arthroplasties in the Treatment of Medial Knee Osteoarthritis: A Systematic Review and Meta-analysis of 1,861 Patients

Many studies have compared mobile-bearing (MB) and fixed-bearing (FB) unicompartmental knee arthroplasties (UKAs) in patients with unicompartmental knee osteoarthritis (OA). The present systematic review and meta-analysis examined the differences in the clinical and radiological outcomes of MB UKA and FB UKA. PubMed, EMBASE, and Cochrane databases, as well as Google Scholar were searched for relevant studies. Randomized controlled trials (RCTs) and cohort studies that compared MB UKA and FB UKA were included. The weighted mean difference in the knee scores and range of motion (ROM) as well as the summary odds ratio of postoperative mechanical axis alignment, radiolucency, revision rate, and complications were calculated in the MB UKA and FB UKA groups. Finally, 2 RCTs and 11 cohort studies that involved 1,861 patients (1,996 knees) were included. The FB UKA group showed better postoperative Knee Society score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and ROM than the MB UKA group. However, the MB UKA group had more knees with a neutral limb alignment and a lower incidence of polyethylene wear than the FB UKA group. No significant differences were observed between the groups with respect to radiolucency, revision rate, and complications, such as arthritis progression, aseptic loosening, and postoperative pain. This meta-analysis has demonstrated that both prostheses provided excellent clinical outcomes and survivorship in patients with unicompartmental knee OA. The MB UKA group achieved the expected postoperative neutral limb alignment as compared with the FB UKA group, while the FB UKA group showed higher knee scores and superior ROM than the MB UKA group. Limited evidence is currently available; therefore, the results of our meta-analysis should be interpreted with caution.

Ten-Year Survivorship, Patient-Reported Outcomes, and Satisfaction of a Fixed-Bearing Unicompartmental Knee Arthroplasty

BACKGROUND

We sought to determine the 10-year survivorship and reasons for revision for a fixed-bearing unicompartmental knee arthroplasty (UKA) design. In addition, we report on patient-reported outcomes and satisfaction and compare results of medial vs lateral compartment UKA and cemented vs cementless UKA with the same design.

METHODS

We performed a retrospective cohort study on a single-surgeon case series using a single fixed-bearing UKA design in 158 consecutive patients who underwent 177 UKA procedures between July 2000 and December 2010. Cases missing follow-up within the last year, clinically or via telephone, were excluded (n = 17, 10%). A cumulative incidence competing risk model was used to evaluate the cumulative incidence of failure.

RESULTS

Cumulative incidence of revision at a mean follow-up of 10 years was 13%. The majority of revisions (43%, 10/23) were for aseptic tibial component loosening, followed by progression of osteoarthritis (5/23, 22%). All Patient Reported Outcomes Measurement Information System measures demonstrated mean T-scores within one standard deviation from the US population norm. The mean Knee Injury and Osteoarthritis Outcome Score for Joint Replacement was 96.9 (range, 40-100). The mean pain score was 3.8 (range, 0-8). Eighty-six percent of patients were satisfied with the UKA.

CONCLUSIONS

At 10-year follow-up, the most common causes for revision were aseptic tibial loosening and adjacent compartment knee arthroplasty, and similar results were found for medial vs lateral compartment and for cemented vs cementless UKA. Surgeons should consider these findings for future UKA designs, and this represents the first study reporting on survivorship and outcomes of this specific UKA design.

MRI as Diagnostic Modality for Analyzing the Problematic Knee Arthroplasty: A Systematic Review

Background

Various diagnostic modalities are available to assess the problematic knee arthroplasty. Visualization of soft‐tissue structures in relation to the arthroplasty and bone remains difficult. Recent developments in MRI sequences could make MRI a viable addition to the diagnostic arsenal.

Purpose

To review the diagnostic properties of MRI, to identify certain causes of complaints that may be directly related to implant failure of total (TKA) or unicompartmental knee arthroplasty (UKA); infection, loosening and wear, instability, malalignment, arthrofibrosis, or patellofemoral problems.

Study Type

Systematic review.

Population

Twenty‐three studies were included: 16 TKA, four UKA, and three cadaveric studies. Causes of knee arthroplasty complaints analyzed were; infection (three), loosening and wear (11), malalignment (five) and instability (four).

Field Strength and Sequences

No field strength or sequence restrictions.

Assessment

PubMed, SCOPUS, and EMBASE were searched. Risk of bias was assessed using the COnsensus‐based Standards for the selection of health Measurement Instruments (COSMIN) and the QUality Assessment of Diagnostic Accuracy Studies‐2 (QUADAS‐2).

Statistical Tests

The results of the original research articles are stated.

Results

Fifteen studies assessed the reproducibility of analyzing infection, loosening and wear, and malalignment. Fourteen of 15 studies were deemed as adequate to good quality. Results showed a moderate to excellent agreement (ICC/K 0.55–0.97). Fourteen studies addressed the accuracy. For infection and loosening and wear the sensitivity and specificity estimates varied between 0.85–0.97 and 0.70–1.00, respectively. The accuracy for malalignment was excellent (r ≥ 0.81). For these studies QUADAS‐2 analysis suggested few risks of bias. A meta‐analysis was not possible due to the heterogeneity of the data.

Data Conclusion

This study supports that MRI can be used with overall reproducible and accurate results for diagnosing infection, loosening and wear, and malalignment after knee arthroplasty. Nonetheless, studies regarding the diagnosis of instability, arthrofibrosis or patellofemoral complaints using MRI are limited and inconclusive.

Level of Evidence: 3

Technical Efficacy: Stage 2

J. Magn. Reson. Imaging 2020;51:446–458.

Management of the Failed Medial Unicompartmental Knee Arthroplasty

With recent design modifications, proper patient selection, and sound surgical technique, medial unicompartmental knee arthroplasty has demonstrated long-term success in the management of degenerative joint disease. Nevertheless, complications do occur, most often aseptic loosening, tibial fracture, polyethylene wear, bearing dislocation, disease progression, infection, and unexplained pain. Some failures can be managed with retention of the implant, whereas others require revision to total knee arthroplasty (TKA), possibly including augments and stems. Although outcomes of unicompartmental knee arthroplasty may not match those of a primary TKA, they tend to exceed results of revision of a previous TKA.

MRI Findings at the Bone-Component Interface in Symptomatic Unicompartmental Knee Arthroplasty and the Relationship to Radiographic Findings

BACKGROUND

The most common modes of failure of cemented unicompartmental knee arthroplasty (UKA) designs are aseptic loosening and unexplained pain at short- to mid-term follow-up, which is likely linked to early fixation failure. Determining these modes of failure remains challenging; conventional radiographs are limited for use in assessing radiolucent lines, with only fair sensitivity and specificity for aseptic loosening.

QUESTIONS/PURPOSES

We sought to characterize the bone-component interface of patients with symptomatic cemented medial unicompartmental knee arthroplasty (UKA) using magnetic resonance imaging (MRI) and to determine the relationship between MRI and conventional radiographic findings.

METHODS

This retrospective observational study included 55 consecutive patients with symptomatic cemented UKA. All underwent MRI with addition of multiacquisition variable-resonance image combination (MAVRIC) at an average of 17.8 ± 13.9 months after surgery. MRI studies were reviewed by two independent musculoskeletal radiologists. MRI findings at the bone-cement interface were quantified, including bone marrow edema, fibrous membrane, osteolysis, and loosening. Radiographs were reviewed for existence of radiolucent lines. Inter-rater agreement was determined using Cohen's κ statistic.

RESULTS

The vast majority of symptomatic UKA patients demonstrated bone marrow edema pattern (71% and 75%, respectively) and fibrous membrane (69% and 89%, respectively) at the femoral and tibial interface. Excellent and substantial inter-rater agreement was found for the femoral and tibial interface, respectively. Furthermore, MRI findings and radiolucent lines observed on conventional radiographs were poorly correlated.

CONCLUSION

MRI with the addition of MAVRIC sequences could be a complementary tool for assessing symptomatic UKA and for quantifying appearances at the bone-component interface. This technique showed good reproducibility of analysis of the bone-component interface after cemented UKA. Future studies are necessary to define the bone-component interface of symptomatic and asymptomatic UKA patients.

Regional Femoral and Tibial Radiolucency in Cemented Unicompartmental Knee Arthroplasty and the Relationship to Functional Outcomes

BACKGROUND

Femoral and tibial radiolucent lines (RLL) after unicompartmental knee arthroplasty (UKA) can be categorized in physiological and pathological radiolucencies. Although physiological tibial radiolucency is assessed extensively in literature, studies reporting femoral radiolucency are lacking. Therefore, a retrospective study was performed to assess physiological femoral RLL and its relationship to short-term functional outcomes.

METHODS

A total of 352 patients were included who underwent robotic-assisted medial UKA surgery and received a fixed-bearing metal-backed cemented medial UKA. Radiographic follow-up consisted of standard anteroposterior and lateral radiographs. Functional outcomes, using the Western Ontario and McMaster Universities Arthritis Index questionnaire, of patients with RLL were compared with a matched cohort, based on gender, age, and body mass index.

RESULTS

In this cohort, 101 patients (28.8%) had physiological regional radiolucency around the femoral (10.3%) and/or tibial (25.3%) components, of which 6.8% concerned both components. Tibial RLL were more frequently seen compared with femoral RLL (P < .001). Our data suggest that the time of onset of femoral radiolucency develops later (1.36 years) than tibial radiolucency (1.00 years, P = .02). No difference in short-term functional outcomes was found between the RLL group and the matched cohort group without radiolucency.

CONCLUSION

This study acknowledges that tibial and femoral physiological radiolucencies may develop after cemented medial UKA. Furthermore, this was the first study showing that physiological femoral RLL occur later than tibial RLL. Prospective studies with longer follow-up and larger numbers are necessary to compare radiolucency in different UKA designs and the relationship to outcomes.

Why do patellofemoral arthroplasties fail today? A systematic review

BACKGROUND

Historically poor results of patellofemoral arthroplasty (PFA) were reported in the setting of isolated patellofemoral osteoarthritis (OA). In order to lower PFA failure rates, it is important to identify failure modes using a standardized method. In this systematic review, PFA failure modes were assessed and compared in early vs. late failures and older vs. recent studies.

METHODS

Databases of PubMed, Embase and Cochrane and annual registries were searched for studies reporting PFA failures. Failure modes in studies with mean follow-up <5years were classified as early failures while >5years were classified late failures. Cohorts started before 2000 were classified as older studies and started after 2000 as recent studies.

RESULTS

Thirty-nine cohort studies (10 level II and 29 level III or IV studies) and three registries were included with overall low quality of studies (GRADE criteria). A total of 938 PFA failures were included and were caused by OA progression (38%), pain (16%), aseptic loosening (14%) and patellar maltracking (10%). Pain was responsible for most early failures (31%), while OA progression was most common in late failures (46%). In older studies, OA progression was more commonly reported as failure mode than in more recent studies (53% vs. 39%, p=0.005).

CONCLUSION

This level IV systematic review with low quality of studies identified OA progression and pain as major failure modes. Reviewing these studies, appropriate patient selection could prevent PFA failures in select cases. Future studies assessing the role of PFA in isolated patellofemoral OA are necessary.

Survivorship and clinical outcome of the minimally invasive Uniglide medial fixed bearing, all-polyethylene tibia, unicompartmental knee arthroplasty at a mean follow-up of 7.3years

BACKGROUND

Medial UKA performed in England and Wales represents seven to 11% of all knee arthroplasty procedures, and is most commonly performed using mobile-bearing designs. Fixed bearing eliminates the risk of bearing dislocation, however some studies have shown higher revision rates for all-polyethylene tibial components compared to those that utilize metal-backed implants. The aim of the study is to analyse survivorship and maximum eight-year clinical outcome of medial fixed bearing, Uniglide unicompartmental knee arthroplasty performed using an all-polyethylene tibial component with a minimal invasive approach.

METHODS

Between 2002 and 2009, 270 medial fixed UKAs were performed in our unit. Patients were reviewed pre-operatively, five and eight years post-operatively. Clinical and radiographic reviews were carried out. Patients' outcome scores (Oxford, WOMAC and American Knee Score) were documented in our database and analysed.

RESULTS

Survival and clinical outcome data of 236 knees with a mean of 7.3years follow-up are reported. Every patient with less than 4.93years of follow-up underwent a revision. The patients' average age at the time of surgery was 69.5years. The American Knee Society Pain and Function scores, the Oxford Knee Score and the WOMAC score all improved significantly. The five-year survival rate was 94.1% with implant revision surgery as an end point. The estimated 10years of survival rate is 91.3%. Fourteen patients were revised before the five-year follow-up.

CONCLUSION

Fixed bearing Uniglide UKA with an all-polyethylene tibial component is a valuable tool in the management of a medial compartment osteoarthritis, affording good short-term survivorship. Level of evidence IV.

Different optimal alignment but equivalent functional outcomes in medial and lateral unicompartmental knee arthroplasty

INTRODUCTION

Several differences in kinematics, functional outcomes and alignment exist between medial and lateral unicompartmental knee arthroplasty (UKA). Therefore, the purpose of this study was (1) to compare functional outcomes between both procedures with the hypothesis that both have equivalent outcomes and (2) to assess the role of preoperative and postoperative alignment on functional outcomes in both procedures.

METHODS

Patients who underwent UKA were included when overall function - using Western Ontario and McMaster Universities Arthritis (WOMAC) score - and joint awareness - using Forgotten Joint Score (FJS) - were available preoperatively and at minimum two-year follow-up. A total of 143 medial UKA and 36 lateral UKA patients reported outcomes at mean 2.4-years follow-up (range 2.0 to 5.0year).

RESULTS

Preoperatively and postoperatively, no differences were seen between medial and lateral UKA in overall function (89.8±11.7 vs. 90.2±12.4, respectively, p=0.855) and joint awareness (71.2±24.5 vs. 70.9±28.2, respectively, p=0.956). With neutral postoperative alignment (-1° to three degrees), less joint awareness was noted following medial UKA than lateral UKA (72.6±22.6 vs. 55.3±28.5, p=0.024). With undercorrection (three degrees to seven degrees), however, following lateral UKA less joint awareness (85.3±19.5 vs. 68.2±26.8, p=0.020) and better functional outcomes (96.0±5.4 vs. 88.5±11.6, p=0.001) were noted than medial UKA.

CONCLUSION

Equivalent functional outcomes were noted between medial and lateral UKA at short-term follow-up but different optimal alignment angles seem to exist for both procedures.

LEVEL OF EVIDENCE

Level III therapeutic study.

Muscle and Joint Factors Associated With Forefoot Deformity in the Diabetic Neuropathic Foot

BACKGROUND

Diabetic forefoot joint deformities are a known risk factor for skin breakdown and amputation, but the causes of deformity are not well understood. The purposes of this study were to determine the effects of intrinsic foot muscle deterioration and limited ankle joint mobility on the severity of metatarsophalangeal joint (MTPJ) deformity, and determine the relationships between these potential contributing factors and indicators of diabetic complications (peripheral neuropathy and advanced glycation end products).

METHODS

A total of 34 participants with diabetic neuropathy (average age, 59 years; range 41-73) were studied. MTPJ angle and intrinsic foot muscle deterioration were measured with computed tomography and magnetic resonance imaging, respectively. Maximum ankle dorsiflexion was measured using kinematics. Skin intrinsic fluorescence served as a proxy measure for advanced glycation end product accumulation.

RESULTS

Total forefoot lean muscle volume (r = -0.52, P < .01) and maximum ankle dorsiflexion (r = -0.42, P < .05) were correlated with severity of MTPJ deformity. Together they explained 35% of the variance of MTPJ angle. Neuropathy was correlated with forefoot muscle deterioration (ρ = 0.53, P < .01). Skin intrinsic fluorescence was correlated to severity of neuropathy (r = 0.50, P < .01) but not maximum ankle dorsiflexion, or forefoot deterioration when controlling for neuropathy.

CONCLUSION

These results suggest that the interplay of intrinsic foot muscle deterioration and limited ankle mobility may be the primary contributor to the development of MTPJ deformity. Identifying these muscle and ankle motion impairments as risk factors for MTPJ deformity supports the need for targeted interventions early in the disease process to slow, or possibly stop the progression of deformity over time and reduce the risk of amputation.

LEVEL OF EVIDENCE

Level IV, case series.

Why Do Medial Unicompartmental Knee Arthroplasties Fail Today?

BACKGROUND

Failure rates are higher in medial unicompartmental knee arthroplasty (UKA) than total knee arthroplasty. To improve these failure rates, it is important to understand why medial UKA fail. Because individual studies lack power to show failure modes, a systematic review was performed to assess medial UKA failure modes. Furthermore, we compared cohort studies with registry-based studies, early with midterm and late failures and fixed-bearing with mobile-bearing implants.

METHODS

Databases of PubMed, EMBASE, and Cochrane and annual registries were searched for medial UKA failures. Studies were included when they reported >25 failures or when they reported early (<5 years), midterm (5-10 years), or late failures (>10 years).

RESULTS

Thirty-seven cohort studies (4 level II studies and 33 level III studies) and 2 registry-based studies were included. A total of 3967 overall failures, 388 time-dependent failures, and 1305 implant design failures were identified. Aseptic loosening (36%) and osteoarthritis (OA) progression (20%) were the most common failure modes. Aseptic loosening (26%) was most common early failure mode, whereas OA progression was more commonly seen in midterm and late failures (38% and 40%, respectively). Polyethylene wear (12%) and instability (12%) were more common in fixed-bearing implants, whereas pain (14%) and bearing dislocation (11%) were more common in mobile-bearing implants.

CONCLUSION

This level III systematic review identified aseptic loosening and OA progression as the major failure modes. Aseptic loosening was the main failure mode in early years and mobile-bearing implants, whereas OA progression caused most failures in late years and fixed-bearing implants.