Functional Improvement and Expectations Are Diminished in Total Knee Arthroplasty Patients Revised for Flexion Instability Compared to Aseptic Loosening and Infection

The Definition and Diagnostic Criteria for Flexion Instability after Total Knee Arthroplasty is Highly Variable in the Published Literature

INTRODUCTION

Flexion instability (FI) is increasingly being recognized as a common reason for failure after total knee arthroplasty (TKA). However, the diagnosis remains loosely defined and is often described by a constellation of symptoms and findings with the exclusion of other clinical entities. The purpose of this study was to examine the definition and diagnostic criteria of FI used in the current peer-reviewed literature.

METHODS

Clinically oriented primary research articles reporting on patients who have FI after TKA and published in English from 2010 to 2023 were systematically identified. Included publications were independently evaluated by multiple reviewers to determine how FI was defined. Of papers that defined FI, the diagnostic criteria were evaluated for several metrics including clinical symptoms, physical exam findings, aspiration results, lab evaluations, and radiographic parameters.

RESULTS

Of 19 eligible articles, only 58% clearly defined FI, with significant variation among studies. Of these publications, 89% directly described clinical symptoms and physical examination findings that aided in diagnosis. Also, 74% of authors described using radiographic analysis, 53% used aspiration, and 47% used lab values to aid in excluding other causes of failure such as periprosthetic joint infection. Only 16% of authors distinguished FI from mid-flexion instability.

CONCLUSION

Less than two-thirds of clinical studies focusing on patients who have FI after TKA provided a clear, concrete definition of FI. The use of aspiration, lab values, and radiographic factors was highly variable. Importantly, many authors defined the diagnosis loosely without objective criteria, which may hinder comparison between clinical studies. A standardized definition of FI could improve research and clinical care on this topic.

Fellowship-Trained Surgeons Experience a Learning Curve Performing Revision Total Joint Arthroplasty

BACKGROUND

Revision total hip arthroplasty (rTHA) and revision total knee arthroplasty (rTKA) require considerable surgical proficiency, but are frequently delegated to the least experienced surgeons. This study examined the influence of surgeon experience on revision outcomes.

METHODS

Prospective data on confirmed aseptic rTHAs (n = 122) and rTKAs (n = 195) performed by 4 fellowship-trained surgeons in the same practice were retrospectively analyzed. Surgeons were grouped based on years in practice (inexperienced [IE] first 2 years, early experience [EE] 4 to 6 years, and senior experience [SE] 15 to 17 years). Procedure duration, estimated blood loss (EBL), and reoperation rates were compared, controlling for potential covariates.

RESULTS

Procedure durations varied based on surgeon experience for 3 of 4 rTHA diagnoses (P ≤ 0.001). Relative to the SE surgeon, procedure duration was 80.0 (95% confidence interval 61.7 to 98.4, P < 0.001) minutes longer for IE surgeons and 30.9 (95% confidence interval 17.5 to 44.3, P < 0.001) minutes longer for the EE surgeon. Procedure durations also varied based on surgeon experience for 3 of 4 rTKA diagnoses (P < 0.001), with the longest durations for IE surgeons. Procedure durations varied based on the interaction of surgeon experience, patient age, and body mass index. The EBL did not differ in rTHA based on surgeon experience (P = 0.978), but did differ for rTKA (P = 0.004). There were 25% of rTHAs performed by IE surgeons compared to 15.5% for the EE surgeon and 3.6% for the SE surgeon that underwent reoperation within a year of the index procedure (P = 0.064), with significantly more reoperations for the same indication among IE and EE surgeons (P = 0.046).

CONCLUSIONS

Complex procedures completed by less experienced surgeons may result in longer procedures, higher EBL, and more early reoperations. Study findings implicate a learning curve for revision arthroplasty that continues for several years, warranting consideration of existing patient allocation and referral patterns.

The Estimated Lifetime Risk of Revision After Primary Knee Arthroplasty Is Influenced by Implant Design and Patient Age: Data From the National Joint Registries

BACKGROUND

The aim of this study was to determine the lifetime risk of revision surgery after primary knee arthroplasty (KA) according to implant choice and patient age.

METHODS

The risk of revision according to the implant type (unicondylar, unconstrained, semiconstrained, and fully constrained) was obtained from the National Joint Registry of England and Wales. Mortality risk according to age was estimated from the Scottish Arthroplasty Project (1998 to 2019). The cumulative incidence of revision and death was calculated up to 20 years. The lifetime risk was calculated as a percentage using a multiple decrement life-table methodology.

RESULTS

The lifetime risk of revision varied according to the implant, with unconstrained having the lowest risk and fully constrained and unicondylar having the highest risks, which increased with younger age. For an "average" patient aged between 65 and 69 years, the revision risks for an unconstrained (3.6%, 95% confidence interval [CI] 3.4 to 3.9), semiconstrained (7.2%, 95% CI 3.9 to 13.6), unicondylar (13.7%, 95% CI 12.4 to 15.2), and fully constrained (15.4%, 95% CI 9.2 to 25.7) total KA gradually increased. Relative to an unconstrained KA, the risk of revision for a semiconstrained implant was similar in patients aged < 65 years (relative risk < 2), whereas when this was employed in those ≥ 65 years, the relative risk was more than double (relative risk ≥ 2). Relative to an unconstrained KA, the risk of revision for a fully constrained or a unicondylar KA was more than double in patients aged < 55 years (relative risk > 2) and more than triple (relative risk ≥ 3) in patients ≥ 55 years CONCLUSION: The estimated lifetime risk of revision following KA was dependent on patient age and implant type, with fully constrained and unicondylar KA being associated with a higher lifetime revision risk. There are limitations in the data, and the indication for surgery and the reasons for revision were not assessed.

LEVEL OF EVIDENCE

III.

An Evaluation of Anatomic Referencing for Femoral Component Sizing Using Computed Tomography-Based Computer Modeling

One of the critical steps in total knee arthroplasty is femoral component positioning and sizing. Historically, there was wider variability between femoral component sizes, necessitating the concepts of anterior referencing (AR) and posterior referencing (PR). With the introduction of smaller increments between sizes, the concept of anatomic referencing has been introduced to replace AR and PR. The intent of this study was to validate the concept of anatomic referencing and show that with 2 mm increments in femoral sizes, the femoral component can be placed flush to the anterior cortex while maintaining posterior condylar offset (PCO). Digital surface models were created using 515 femurs from an established computed tomography database. Virtual bone resections, component sizing and placement were performed assuming neutral mechanical axis and a cartilage thickness of 2 mm. The appropriately sized femoral component, which had 2 mm incremental sizes, was placed flush with the anterior cortex with restoration of the PCO. The anterior-posterior distance from the posterior surface of the component to the medial and lateral surfaces of the posterior condylar cartilage were measured. The medial condyle was the limiting condyle in the majority of cases (73%). The average medial gap after appropriate femoral component matching was 0.6 mm (0.39-1.41 mm) across all sizes. The overall average condylar gap was 1.02 mm. The most common femoral component was a size 7 (57.2 mm) and the average femoral AP width was 55.9 mm. Anatomic referencing with an implant system that has 2-mm increments in femoral component sizing provides an alternative to AR and PR without compromise. Anatomic referencing allows for perfect alignment of the anterior flange of the femoral component to the anterior cortex of the femur while restoring the native PCO to within 1 mm. This avoids having to choose between AR or PR when in between femoral sizes.

Evaluation of anterior translation in total knee arthroplasty utilizing stress radiographs

BACKGROUND

Flexion instability is a common cause for revision after total knee arthroplasty (TKA); however, little objective criteria exist to determine excessive laxity in flexion. This study sought to determine the reliability of stress radiographs for flexion laxity using manual stress as well as a commercially available flexion stress device, with the hypothesis that a commercially available force device would provide increased translation compared to manual stress, and radiographic measurements would be reproducible.

METHODS

Ten patients who previously underwent TKA with non-hinged components were prospectively and consecutively enrolled at a single center to undergo stress radiographs. Three lateral radiographs with the knee at 90° of flexion were obtained for each patient: rest, commercial stress device at 150N, and manual stress. Calibrated radiographs were evaluated by two raters, and inter-rater and intra-rater reliability were determined using intraclass correlation coefficients (ICC).

RESULTS

Ten patients (seven female) with mean age 72 (range 55-82) years and average duration from surgery 36 (range 12-96) months were evaluated. The commercial stress device provided significantly less anterior translation than manual stress (- 0.3 mm vs. 3.9 mm; p < 0.01). Two patients reported pain with use of the stress device. Inter-observer reliability of measurements was good for commercial stress (ICC = 0.86) and excellent for manual stress (ICC = 0.94). Eighty-five percent of measurements were within 1 mm between observers. Intra-observer reliability of measurements was good to excellent for both the stress device and manual stress.

CONCLUSIONS

Lateral stress radiographs may assist in the objective evaluation of flexion instability. A commercially available product provided less translation than manual stress; however, measurements were reliable and reproducible between observers. Further research is required to correlate translation with stress radiographs to patient outcomes following revision arthroplasty.

A mapping review on preoperative prognostic factors and outcome measures of revision total knee arthroplasty

To map literature on prognostic factors related to outcomes of revision total knee arthroplasty (rTKA), to identify extensively studied factors and to guide future research into what domains need further exploration. We performed a systematic literature search in MEDLINE, Embase, and Web of Science. The search string included multiple synonyms of the following keywords: "revision TKA", "outcome" and "prognostic factor". We searched for studies assessing the association between at least one prognostic factor and at least one outcome measure after rTKA surgery. Data on sample size, study design, prognostic factors, outcomes, and the direction of the association was extracted and included in an evidence map. After screening of 5,660 articles, we included 166 studies reporting prognostic factors for outcomes after rTKA, with a median sample size of 319 patients (30 to 303,867). Overall, 50% of the studies reported prospectively collected data, and 61% of the studies were performed in a single centre. In some studies, multiple associations were reported; 180 different prognostic factors were reported in these studies. The three most frequently studied prognostic factors were reason for revision (213 times), sex (125 times), and BMI (117 times). Studies focusing on functional scores and patient-reported outcome measures as prognostic factor for the outcome after surgery were limited (n = 42). The studies reported 154 different outcomes. The most commonly reported outcomes after rTKA were: re-revision (155 times), readmission (88 times), and reinfection (85 times). Only five studies included costs as outcome. Outcomes and prognostic factors that are routinely registered as part of clinical practice (e.g. BMI, sex, complications) or in (inter)national registries are studied frequently. Studies on prognostic factors, such as functional and sociodemographic status, and outcomes as healthcare costs, cognitive and mental function, and psychosocial impact are scarce, while they have been shown to be important for patients with osteoarthritis.

Physical activity after revision knee arthroplasty including return to sport and work: a systematic review and meta-analysis including GRADE

BACKGROUND

The number of primary knee arthroplasties (KAs) performed annually is rising, especially among active, working age patients. Consequently, revision KA is also increasingly performed. Our aim was to systematically review the extent to which patients were physically active following revision KA, and the rate and timing of return to sport and work.

METHODS

A search was conducted in the databases Medline and Embase until February 24th, 2023. Studies describing patients with revision total knee arthroplasty (rTKA) or revision unicondylar knee arthroplasty (rUKA), with outcomes regarding physical activity or return to sport (RTS) or work (RTW) were included. Quality of studies was assessed using the Newcastle-Ottawa scale, meta-analyses were performed using RevMan 5.4 and Grading of Recommendations, Assessment, Development, and Evaluations (GRADE).

RESULTS

Of the 4,314 articles screened, 22 studies were included describing 2,462 rTKA patients (no rUKA), 42% were male with a mean age of 67 years (range 24 - 95). No studies reported objective physical activity measurements. Twenty-two studies reported patient reported outcome measures (PROMs). The PROMs that were pooled on a scale from zero to ten were the UCLA Activity Score, the Tegner Activity Level Scale, the Lower-Extremity Activity Scale, Devane Activity Score, and physical activity related subscales of the Knee injury and Osteoarthritis Outcome Score. The retrospective studies of moderate quality showed a statistically significant postoperative improvement of 1.7 points (MD = 1.71, 95% CI 1.48 - 1.94 (p < 0.0001); 14 studies, n = 1,211). For the prospective moderate-quality studies, a statistically significant postoperative increase of 0.9 points was found (MD = 0.89, 95% CI 0.48 - 1.30 (p < 0.0001); 6 studies, n = 1,027). Regarding RTS, 12% of patients participated in so-called 'non-recommended' activities (i.e., hockey, soccer, football, gymnastics, jogging, singles tennis, and basketball) after rTKA (1 study, n = 206). The pooled RTW was 86% (2 studies, range 18-95%, n = 234).

CONCLUSIONS

The majority of patients self-reported an improved postoperative activity level after rTKA. Patients could maintain an active lifestyle in daily life, including sports and work. For reliable physical activity, RTS and RTW estimations, more studies are required. In terms of GRADE, the quality of evidence for the five prospective studies was rated as low.

LEVEL OF EVIDENCE

Level 3.

Mid-Flexion Instability After Total Knee Arthroplasty: Diagnosis, Implant Design, and Outcomes

Mid-flexion instability (MFI) in total knee arthroplasty refers to a distinct clinical entity where the knee is stable at full extension and 90° of flexion, but unstable somewhere between these 2 points. The presentation of MFI is often vague, and studies defining objective clinical or intraoperative measurements are limited. In this review, we aim to properly define the condition, describe diagnostic criteria and risk factors contributing to MFI, review current implant design, and present outcomes of revision surgery performed for MFI. [Orthopedics. 2023;46(1):e13-e19.].

Revision total knee arthroplasty for flexion instability : a concise follow-up of a previous report

AIMS

We have previously reported the mid-term outcomes of revision total knee arthroplasty (TKA) for flexion instability. At a mean of four years, there were no re-revisions for instability. The aim of this study was to report the implant survivorship and clinical and radiological outcomes of the same cohort of of patients at a mean follow-up of ten years.

METHODS

The original publication included 60 revision TKAs in 60 patients which were undertaken between 2000 and 2010. The mean age of the patients at the time of revision TKA was 65 years, and 33 (55%) were female. Since that time, 21 patients died, leaving 39 patients (65%) available for analysis. The cumulative incidence of any re-revision with death as a competing risk was calculated. Knee Society Scores (KSSs) were also recorded, and updated radiographs were reviewed.

RESULTS

The cumulative incidence of any re-revision was 13% at a mean of ten years. At the most recent-follow-up, eight TKAs had been re-revised: three for recurrent flexion instability (two fully revised to varus-valgus constrained implants (VVCs), and one posterior-stabilized (PS) implant converted to VVC, one for global instability (PS to VVC), two for aseptic loosening of the femoral component, and two for periprosthetic joint infection). The ten-year cumulative incidence of any re-revision for instability was 7%. The median KSS improved significantly from 45 (interquartile range (IQR) 40 to 50) preoperatively to 70 (IQR 45 to 80) at a mean follow-up of ten years (p = 0.031). Radiologically, two patients, who had not undergone revision, had evidence of loosening (one tibial and one patellar). The remaining components were well fixed.

CONCLUSION

We found fair functional outcomes and implant survivorship at a mean of ten years after revision TKA for flexion instability with a PS implant. Recurrent instability and aseptic loosening were the most common indications for re-revision. Components with increased constraint, such as a VVC or hinged, should be used in these patients in order to reduce the risk of recurrent instability.Cite this article: Bone Joint J 2022;104-B(10):1126-1131.

Inter-Rater Reliability of Clinical Testing for Laxity After Knee Arthroplasty

BACKGROUND

The clinical examination for laxity has been considered a mainstay in evaluation of the painful knee arthroplasty, especially for the diagnosis of instability. More than 10 mm of anterior-posterior (AP) translation in flexion has been described as important in the diagnosis of flexion instability. The inter-observer reliability of varus/valgus and AP laxity testing has not been tested.

METHODS

Ten subjects with prior to total knee arthroplasty (TKA) were examined by 4 fellowship-trained orthopedic knee arthroplasty surgeons. Each surgeon evaluated each subject in random order and was blinded to the results of the other surgeons. Each surgeon performed an anterior drawer test at 30 and 90 degrees of flexion and graded the instability as 0-5 mm, 5-10 mm or >10 mm. Varus-valgus testing was also graded. Motion capture was used during the examination to determine the joint position and estimate joint reaction force during the examination.

RESULTS

Inter-rater reliability (IRR) was poor at 30 and 90 degrees for both the subjective rater score and the measured AP laxity in flexion (k = 018-0.22). Varus-valgus testing similarly had poor reliability. Force applied by the rater also had poor IRR.

CONCLUSION

Clinical testing of knee laxity after TKA has poor reliability between surgeons using motion analysis. It is unclear if this is from differences in examiner technique or from differences in pain or quadriceps function of the subjects. Instability after TKA should not be diagnosed strictly by clinical testing and should involve a complete clinical assessment of the patient.

Treatment of Flexion Instability After Primary Total Knee Arthroplasty: Operative and Nonoperative Management of 218 Cases

BACKGROUND

For patients with flexion instability, there is a paucity of literature on the effectiveness of nonoperative management, and series on revision TKAs are limited. The purpose of this study is to evaluate effectiveness and prognostic factors of nonoperative management of flexion instability, and report survivorship, clinical outcomes, and radiographic results after revision TKA for flexion instability.

METHODS

We identified 218 patients with flexion instability after primary TKA through our total joint registry between 1990 and 2019. Mean age was 66 years, 59% were women, and 58% had a cruciate-retaining (CR) implant. Initially, 152 patients (70%) were treated nonoperatively. First-time revision TKA was ultimately performed in 173 patients. Kaplan-Meier survivorship was calculated. Knee Society Scores and radiographs were reviewed. Mean follow-up was 6 years.

RESULTS

Of the 152 patients treated nonoperatively, 66% reported no improvement. Patients with a CR design (hazard ratio [HR] 3.3, P < .001), inflammatory arthritis (HR 1.6, P = .03), smokers (HR 2.1, P = .04), and patient-reported instability (HR 3.8, P < .001) or effusions (HR 3.5, P < .001) were more likely to undergo revision. Of the 173 revised, the 10-year survivorship free of any re-revision was 87% with recurrent flexion instability (7), global instability (3), and infection (3) being most common. Knee Society Scores improved from 50 to 65 (P = .14). At final follow-up, all implants were well-fixed.

CONCLUSION

In this large series of flexion instability after primary TKA, nonoperative management led to improvement in one third. Patients with a CR design or with patient-reported instability and/or effusions were most likely to undergo revision. Revision TKA demonstrated modest 10-year functional improvements and good survivorship.

LEVEL OF EVIDENCE

IV (retrospective), Therapeutic.

Does Blood Flow Restriction Therapy Improve Leg Strength in Patients With a Painful Total Knee Arthroplasty?

BACKGROUND

Blood flow restriction (BFR) therapy has been proposed to help patients build strength with fewer repetitions than standard physical therapy (PT). We sought to determine if BFR would improve quadriceps and hamstring strength in patients with instability and perceived weakness >1 year after primary total knee arthroplasty (TKA).

METHODS

We retrospectively reviewed 48 patients with painful TKAs and flexion instability as well as quadriceps and hamstring weakness who performed a 6-week PT program and received isokinetic strength measurements (ISMs). Thirty-six patients completed a standard PT program (non-BFR) and 12 patients completed a BFR regimen. ISMs were taken before and after PT to quantify quadriceps and hamstring power, torque, and work compared to the contralateral leg. Statistical analysis was conducted on pre-PT and post-PT ISMs and decisions for revision surgery.

RESULTS

There were no differences in ISMs after PT between the BFR and non-BFR groups. The non-BFR group showed statistically significant strength improvements in flexion but not extension (+28.7%-32.8%, P = .0145-.255). Although no significant difference was found in the BFR group, they saw improvements in all extension strength metrics (19.4%-23.4%, P = .3315-.3901) and flexion (25.7%-29.9%, P = .1994-.2392). No difference was observed between the groups in the rates of subsequent revision TKA (8.3% vs 16.7%, P = .3362).

CONCLUSION

BFR did not improve quadriceps and hamstring strength compared to PT alone in patients with instability and weakness after TKA. Over 80% of total patients chose to avoid revision TKA after completion of focused PT with or without BFR.

The Effect of Joint Line Elevation on Patient-Reported Outcomes After Contemporary Revision Total Knee Arthroplasty

BACKGROUND

Joint line elevation in revision total knee arthroplasty (rTKA) is considered a risk factor for inferior outcomes, engendering a dogmatic protocol of joint line restoration. However, this precedent is based on historical data using rudimentary revision systems and unvalidated outcome measures. This study's purpose was to evaluate the effect of joint line height elevation on validated patient-reported outcome measures (PROMs) using modern revision implants.

METHODS

A total of 327 rTKAs performed at a single institution were reviewed. Surgical technique prioritized flexion-extension gap balancing and accepted joint line elevation if necessary to achieve a balanced flexion space. Radiographic measurements included changes in joint line height (from preoperative and calculated "intended" anatomic/native) and change in posterior condylar offset. Prospectively collected PROMs were evaluated using multivariate regression.

RESULTS

The mean joint line elevation from preoperative and "intended" to postoperative joint line was 4.9 ± 5.7 mm and 7.2 ± 6.6 mm, respectively. The mean increase in posterior condylar offset was 1.0 ± 4.6 mm. Patients within ±5 mm of preoperative joint line height were 3.88× more likely to achieve the substantial clinical benefit for Knee Injury and Osteoarthritis Outcome Score for Joint Replacement (P = .004). An increase from intended joint line height >5 mm was not associated with differences in any other PROMs (P ≥ .165).

CONCLUSIONS

In contemporary rTKA, recreating the joint line within 5 mm of preoperative improves knee-specific health outcomes. These data support approximating native joint line height as a viable technique to optimize flexion gap balance and subsequent patient outcomes in rTKA.

LEVEL OF EVIDENCE

Level III retrospective cohort study.

Primary Total Knee Arthroplasty Revised for Instability: A Detailed Registry Analysis

BACKGROUND

Instability after total knee arthroplasty is a common but poorly understood complication.

METHODS

Data from a large national registry was used to study patient and prosthesis characteristics of 2605 total knee arthroplasty revisions for instability. The cumulative percent revision was calculated using Kaplan-Meier estimates, and Cox proportional models used to compare revision rates. The rate of further revision was analyzed with regard to prostheses used in the first revision.

RESULTS

Instability increased from 6% of all first revision procedures in 2003 to 13% in 2019. The revision risk was lower for minimally stabilized prostheses, males, and patients aged ≥65 years. Polyethylene insert exchange was used for 55% of revision procedures, using a thicker insert in 93% and a change in insert conformity in 24% of cruciate-retaining knees. The increase in either thickness or conformity had no effect on the rate of further revision. After a revision for instability, 24% had a second revision by 14 years. Recurrent instability accounted for 32% of further revisions. A lower second revision rate was seen after revision of both femoral and tibial components, and where constrained components were used.

CONCLUSION

Revision for instability is increasing. Revising both femoral and tibial components led to a lower rate of second revision compared to a change in insert alone. Recurrent instability was common.

Patient-reported outcome measures following revision knee replacement: a review of PROM instrument utilisation and measurement properties using the COSMIN checklist

OBJECTIVES

To identify: (1) patient-reported outcome measures (PROMs) used to evaluate symptoms, health status or quality of life following discretionary revision (or re-revision) knee joint replacement, and (2) validated joint-specific PROMs, their measurement properties and quality of evidence.

DESIGN

(1) Scoping review; (2) systematic review following the COnsensus-based Standards for selection of health status Measurement INstruments (COSMIN) checklist.

DATA SOURCES

MEDLINE, Embase, AMED and PsycINFO were searched from inception to 1 July 2020 using the Oxford PROM filter unlimited by publication date or language.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies reporting on the development, validation or outcome of a joint-specific PROM for revision knee joint replacement were included.

RESULTS

51 studies reported PROM outcomes using eight joint-specific PROMs. 27 out of 51 studies (52.9%) were published within the last 5 years. PROM development was rated 'inadequate' for each of the eight PROMs studied. Validation studies were available for only three joint-specific PROMs: Knee Injury and Osteoarthritis Outcome Score (KOOS), Lower Extremity Activity Scale (LEAS) and Western Ontario and McMaster Universities Arthritis Index (WOMAC). 25 out of 27 (92.6%) measurement properties were rated insufficient, indeterminate or not assessed. The quality of supporting evidence was mostly low or very low. Each of the validated PROMs was rated 'B' (potential for recommendation but require further evaluation).

CONCLUSION

Joint-specific PROMs are increasingly used to report outcomes following revision knee joint replacement, but these instruments have insufficient evidence for their validity. Future research should be directed toward understanding the measurement properties of these instruments in order to inform clinical trials and observational studies evaluating the outcomes from joint-specific PROMs.

Utility and Prognostic Ability of a Diagnostic Injection Before Revision Total Knee Arthroplasty

BACKGROUND

Diagnostic injections are commonly utilized in the workup of painful total knee arthroplasties (TKA), particularly when the diagnosis remains unclear. However, current literature provides limited evidence regarding the utility and prognostic capability of anesthetic injections in this scenario. This study sought to establish the role of diagnostic injections in predicting successful revision TKA.

METHODS

A retrospective review was conducted on 144 consecutive aseptic revision TKAs receiving diagnostic anesthetic injections. Instability (57.6%) and aseptic loosening (33.3%) comprised most revision etiologies. Patient-reported percentage pain relief after the injection was statistically correlated with KOOS JR, Knee Society Score, UCLA Activity Level, and satisfaction scores.

RESULTS

About 74.3% (107/144) of revision TKAs reported >50% pain relief after injection. There were no differences in pain relief based on revision indication (P = .841). Improvement from preoperative activity level was greater in the >50% pain relief group (P = .024). Four-month patient satisfaction did not differ between patients who reported >50% and ≤50% pain relief (67% vs. 66%, P = .130). About 64% of patients who reported >50% pain relief were satisfied at minimum 1-year follow-up, compared with only 47% of those who reported ≤50% pain relief after diagnostic injection (P < .001).

CONCLUSION

Study results show that patients reporting >50% pain relief after diagnostic injection have improvements in activity level and maintain greater satisfaction at minimum 1-year than those reporting ≤50% pain relief. Expectations for improvement after revision TKA should be tempered if diagnostic anesthetic injection yields minimal subjective pain relief.

Variation and trends in reasons for knee replacement revision: a multi-registry study of revision burden

Background and purpose - Studies describing time-related change in reasons for knee replacement revision have been limited to single regions or institutions, commonly analyze only 1st revisions, and may not reflect true caseloads or findings from other areas. We used revision procedure data from 3 arthroplasty registries to determine trends and differences in knee replacement revision diagnoses.Patients and methods - We obtained aggregated data for 78,151 revision knee replacement procedures recorded by the Swedish Knee Arthroplasty Register (SKAR), the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), and the Kaiser Permanente Joint Replacement Registry (KPJRR) for the period 2003-2017. Equivalent diagnosis groups were created. We calculated the annual proportions of the most common reasons for revision.Results - Infection, loosening, and instability were among the 5 most common reasons for revision but magnitude and ranking varied between registries. Over time there were increases in proportions of revisions for infection and decreases in revisions for wear. There were inconsistent proportions and trends for the other reasons for revision. The incidence of revision for infection showed a uniform increase.Interpretation - Despite some differences in terminology, comparison of registry-recorded revision diagnoses is possible, but defining a single reason for revision is not always clear-cut. There were common increases in revision for infection and decreases in revision for wear, but variable changes in other categories. This may reflect regional practice differences and therefore generalizability of studies regarding reasons for revision is unwise.

Posterior Cruciate Ligament Resection Does Not Consistently Increase the Flexion Space in Contemporary Total Knee Arthroplasty

INTRODUCTION

It is accepted dogma in total knee arthroplasty (TKA) that resecting the posterior cruciate ligament (PCL) increases the flexion-space by approximately 4mm. Unfortunately, this doctrine is based on historical studies of limited size with variable technique. The aim of this study was to determine the effect of PCL-resection on in vivo tibiofemoral joint space dimensions in a cohort of modern TKAs.

METHODS

Tibiofemoral joint space measurements were made during 129 standardized TKAs by two arthroplasty surgeons. A medial parapatellar approach, computer navigation and provisional bone cuts were performed in all cases with particular attention to preserving PCL integrity. The tibiofemoral gap was measured with a calibrated tension device at extension, 45-degrees, and 90-degrees before and after complete PCL-resection.

RESULTS

51% of patients were female (66/129) with mean age and BMI of 69.5 years and 34.2 kg/m², respectively. After PCL-resection, mean change in center joint space dimension increased 0.33mm at extension, 0.95mm at 45-degrees, and 1.71mm at 90-degrees (P < .001). The 90-degree flexion-space opened ≥4mm in only 10% of patients. Dividing the flexion-space change by femoral implant dimension to account for patient size, the flexion-space at 90-degrees significantly increased more in females compared to males (P = .020).

CONCLUSION

The tibiofemoral joint space increased progressively from extension to mid-flexion through deep-flexion after PCL-resection, yet was substantially less than reported in historical studies. However, large variation in flexion-space opening was observed with some patients failing to increase the flexion-space whatsoever with PCL-resection. This runs counter to conventional TKA understanding and should be considered in modern surgical education.

LEVEL OF EVIDENCE

Therapeutic Level III.

Improvements in Isokinetic Quadriceps and Hamstring Strength Testing After Focused Therapy in Patients With Flexion Instability

BACKGROUND

There is a paucity of literature to guide non-operative treatment for patients with problems after total knee arthroplasty (TKA). We sought to quantify how quadriceps and hamstring strength could improve with focused physical therapy (PT) and whether improving leg strength may prevent revision surgery for patients with flexion instability (FI) after TKA.

METHODS

This retrospective study included patients diagnosed with FI by one of the 4 fellowship-trained arthroplasty surgeons at a single academic institution. Patients with FI were referred for strength measurements and a focused PT program. In total, 166 patients completed isokinetic testing to quantify their relative quadriceps and hamstring power, torque, and work measures compared to their contralateral leg. Fifty-five (33.5%) patients subsequently completed post-PT isokinetic testing. Statistical analysis was conducted to evaluate strength deficits in the knee with FI.

RESULTS

Patients with FI were found to be 20.5%-38.4% weaker in all strength domains compared to the contralateral leg (P < .001). Patients who completed PT and pre-isokinetic and post-isokinetic testing demonstrated statistically significant gains in all extension metrics by a net range of 24.7%-34.2% (P = .011-.029) and their flexion strength metrics improved by 32.5%-40.2% (P = .002-.005). About 81.9% of patients in this subgroup did not undergo revision TKA. Those subjects who went on to revision did not statistically improve in any strength domain (P = .063-.121).

CONCLUSION

Patients with FI after TKA have significantly weaker quadriceps and hamstrings in the operative compared to contralateral leg. Patients who did not undergo revision knee arthroplasty and completed a formal PT program improved quadriceps and hamstring strength by 30%.

LEVEL OF EVIDENCE

IV (Case series).

Variation in ligamentous laxity in well-functioning total knee arthroplasty is not associated with clinical outcomes or functional ability

BACKGROUND

Around 20% of revision knee arthroplasty procedures are carried out for a diagnosis of instability. Clinical evaluation of instability is primarily through physical stress testing of knee ligamentous laxity and joint space opening. It is assumed that increased knee ligament laxity is associated with instability of the knee and, by association, reduced physical function. The range of knee ligament laxity in asymptomatic patients with total knee arthroplasty has however not been reported, nor has the association with measures of physical outcomes.

METHODS

Patients who reported being happy with the outcomes of TKA and denied any feelings of knee instability were evaluated at routine follow-up clinicas. Knee ligamentous stability was evaluated seperately by 2 blinded assessors in both coronal and saggital planes. Assessors classified the ligamentous stability as 'tight', 'neutrol' or 'loose'. Clinical outcome was evaluated by Oxford Knee Score, patient satisfaction metric, timed performance test, range of motion and lower limb power. Analysis of variance was employed to evaluate variables between groups with post hoc pairwise comparisons.

RESULTS

In total, 42 patients were evaluated. Mean time since index surgery was 46 (SD 8) months. In the coronal plane, 11 (26.2%) were categorised as 'tight', 22 (52.4%) as 'neutral' and 9 (21.4%) as 'loose'. In the sagittal plane, 15 (35.7%) were categorised as 'tight', 17 (40.5%) as 'neutral' and 10 (23.8%) as 'loose'. There were no between-group differences in outcomes: Oxford Knee Score, range of motion, lower limb power, timed functional assessment score or in satisfaction response in either plane (p = 0.05).

CONCLUSIONS

We found a range of ligamentous laxity in asymptomatic patients satisfied with the outcome of their knee arthroplasty, and no association between knee laxity and physical ability.

Characterizing the Use of Expectations in Orthopedic Surgery Research: A Scoping Review

OBJECTIVE

Orthopedic literature on expectations is limited by lack of uniformity in how expectations are defined, conceptualized, and measured. Within this scoping review, we present a conceptual framework for understanding the construct of expectations and its derivatives (ie, expectation, expectancy, expectancies, etc) in studies of elective surgical orthopedic procedures. We also utilize this framework to map the current orthopedic surgery literature on expectations, highlighting its strengths, weaknesses, and gaps in its knowledge base.

METHODS

We included articles that mentioned both expectations and one or more of 10 selected surgeries in their title or abstract. We focused on representative elective orthopedic surgeries that covered the body's major regions. We operationalized each study's individual expectation items into one of the expectation concept types within the presented conceptual model. We also extracted the name and type of expectations measurement tool used, whose expectations were measured, and descriptive information (eg, surgery type, publication date, country of origin, and study type).

RESULTS

Ninety studies were included, with 70% published after 2008. A total of 64% investigated total knee and total hip arthroplasty, whereas 90% of studies investigated the expectations of patients, 5.6% investigated the expectations of physicians, and 4.4% investigated both. Of all studies, 72% utilized either study-specific instruments with close-ended, Likert-type response formats or modifications of existing expectations questionnaires. Most studies focused on desirable, nontimeline-related, treatment outcome expectations. Many studies aggregated multiple expectation results into a single score.

CONCLUSION

Adopting the standardized framework for expectations presented in this study will foster clearer communication and permit researchers to aggregate results across studies.

Flexion Instability After Total Knee Arthroplasty

Flexion instability after total knee arthroplasty (TKA) is caused by an increased flexion gap compared with extension gap. Patients present with recurrent effusions, subjective instability (especially going downstairs), quadriceps weakness, and diffuse periretinacular pain. Manual testing for laxity in flexion is commonly done to confirm a diagnosis, although testing positions and laxity grades are inconsistent. Nonsurgical treatment includes quadriceps strengthening and bracing treatment. The mainstays to surgical management of femoral instability involve increasing the posterior condylar offset, decreasing the tibial slope, raising the joint line in combination with a thicker polyethylene insert, and ensuring appropriate rotation of implants. Patient outcomes after revision TKA for flexion instability show the least amount of improvement when compared with revisions for other TKA failure etiologies. Future work is needed to unify reproducible diagnostic criteria. Advancements in biomechanical analysis with motion detection, isokinetic quadriceps strength testing, and computational modeling are needed to advance the collective understanding of this underappreciated failure mechanism.

Are the Outcomes of Revision Knee Arthroplasty for Flexion Instability the Same as for Other Major Failure Mechanisms?

BACKGROUND

Aseptic loosening, infection, and flexion instability have emerged as the leading etiologies for revision after total knee arthroplasty (TKA). Although studies have reported improved outcomes after revision TKA, the relative functional and clinical outcomes of patients revised for flexion instability and other failure etiologies have not been extensively reported. The aim of the study was to compare the functional and patient-reported outcomes of revision TKA for the common failure etiologies.

METHODS

We retrospectively reviewed records of 228 consecutive cases of revision TKA from 2008 to 2014. Revisions performed for aseptic loosening (n = 53), septic revisions (n = 48), and isolated flexion instability (n = 45) with a minimum of 18 months follow-up were included for analysis. Revision for all other etiologies (n = 82) were excluded. The Modified Knee Society Score (KSS), KSS Function, and Western Ontario and McMaster Universities Osteoarthritis Index were recorded for all cases. A 7-point Likert scale was used to record patient's perception of outcomes after revision surgery and analyzed based on etiology.

RESULTS

Although all groups showed improvement in outcome after revision TKA, the changes in Modified KSS and KSS-Function varied according to the etiology of failure of the primary procedure with the smallest improvement being reported by the flexion instability group.

CONCLUSION

Patients undergoing revision for isolated flexion instability have less improvement in functional outcome as compared with other etiologies. We hypothesize this is due to a higher baseline preoperative knee function in the flexion instability group.