Decision-making in unicompartmental knee arthroplasty using radiological parameters in South Asian populations

Aswin Vijay; Виджай Асвин; Haemanath Pandian; Пандиан Хаманатх; Pradeep Elangovan; Элангован Прадип; Arunkumar K. Vijayakumari; Виджаякумари Арункумар К.; Ganesh Anantharaman; Анантхараман Ганеш; Sheik M. Tajudeen; Таджудин Шейх М.; Rajan Raghul; Рагхул Раджан

doi:10.17816/vto629134

Decision-making in unicompartmental knee arthroplasty using radiological parameters in South Asian populations

Authors: Vijay A.¹, Pandian H.¹, Elangovan P.¹, Vijayakumari A.K.¹, Anantharaman G.¹, Tajudeen S.M.¹, Raghul R.¹
Affiliations:
1. Chettinad Hospital and Research Institute
Issue: Vol 31, No 3 (2024)
Pages: 305-314
Section: Original study articles
Submitted: 15.03.2024
Accepted: 13.05.2024
Published: 17.07.2024
URL: https://journals.eco-vector.com/0869-8678/article/view/629134
DOI: https://doi.org/10.17816/vto629134
ID: 629134

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Abstract

Background: Many patients who visit orthopedic surgeons mainly complained of knee pain, which is often diagnosed as osteoarthritis affecting the medial compartment, whereas the lateral compartment and patello-femoral joint remain relatively unaffected.

AIM: This study aimed to establish criteria for patient selection and validate an evidence-based approach for selecting candidates for unicompartmental knee arthroplasty (UKA). Key considerations in patient selection for UKA include identifying the presence of bone-on-bone osteoarthritis in the medial compartment, ensuring a functionally normal anterior cruciate ligament, maintaining full-thickness cartilage in the lateral compartment, verifying a functionally normal medial collateral ligament, and confirming the absence of severe damage lateral to the patello-femoral joint.

MATERIALS AND METHODS: From a consecutive cohort of 390 patients with medial knee pain, preoperative radiographs of bilateral knee including anteroposterior/lateral/Rosenberg/20° valgus stress views were collected, and results were tabulated. Patients were categorized into appropriate groups. The suitability for UKA was determined based on the Oxford radiological decision aid, history, examination, and radiographic assessment including stress radiographs.

RESULTS: The Oxford radiological decision aid demonstrated 92% sensitivity and 88% specificity. According to the radiographic assessment, 49% of the knees were considered suitable for Oxford UKA (OUKA), whereas 51% were deemed unsuitable. Among the 51 knees identified as unsuitable for OUKA, 40% did not meet one radiographic criterion, 38% did not meet two criteria, 22% did not meet three criteria, and <1% did not meet four criteria.

CONCLUSION: The Oxford radiographic decision aid safely and reliably identifies the appropriate patients for meniscal-bearing UKA and achieves good results in this population. The widespread use of this radiological decision aid should improve the results of UKA.

Keywords

Oxford radiological decision aid, unicompartmental knee arthroplasty, osteoarthritis

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BACKGROUND

Most commonly found in older individuals, knee osteoarthritis (OA), which results from the wear and tear of knee joint, is a degenerative joint disease that leads to articular cartilage loss [1]. OA is a progressive disease that can lead to disability. The intensity of clinical symptoms may differ among individuals; however, they generally become more severe, frequent, and debilitating with time [1]. The progression rate also varies individually. Common clinical symptoms encompass gradual onset of knee pain aggravated by activity, knee stiffness, swelling, pain after prolonged sitting or resting, and worsening pain. Treatment for knee OA is initiated with conservative methods and advanced to surgical options if conservative treatment proves ineffective [2].

Many patients who visit orthopedic surgeons complained of knee pain, which is often diagnosed as OA affecting the medial compartment, whereas the lateral compartment and patello-femoral joint remain relatively unaffected [3]. Total knee arthroplasty (TKA) has been the conventional treatment of choice; however, this procedure involves removing healthy joint surfaces. Recently, a trend has developed toward less invasive surgery with unicompartmental knee replacement (UKR) gaining a high popularity [3].

Compared with TKA, patients who underwent UKA experience faster recovery, achieve superior functional outcomes, face lower morbidity and mortality rates, and report higher levels of satisfaction. Moreover, UKA was reported to be more cost-effective than TKA in both the short and long terms. UKA has been in existence since the 1950s; however, the initial designs were plagued with complications [4]. With the evolution of component designs and instrumentation, the survivorship of UKA has significantly improved. In the United States, the utilization rates of UKA from 2002 to 2008 had steadily increased, followed by a subsequent decline [3]. According to data from the 2018 Australian National Joint Replacement Registry, partial knee replacement constituted 8.6% of primary knee arthroplasties in 2017, showing a decline from its previous representation of 16.9% in 2003 [5]. The National Joint Registry of England and Wales also reported a similar UKA use rate of 8.9% in 2017, which has remained consistent over the past decade [6].

Since the establishment of the Indian Joint Registry in 2016, a similar trend of UKA use has been observed. UKA utilization has steadily increased, starting from 0.33% of TKAs in 2016, to 2.85% in 2019. However, the trend declined in 2020, with UKA accounting for 1.67% of TKAs.

However, not all arthroplasty surgeons perform UKA, and a small percentage of surgeons perform most of these procedures. In addition, attitudes toward UKA tend to be quite rigid among surgeons, with some being strong advocate, whereas others are vocal critics [7].

AIM: this study aimed to establish the criteria for patient selection and validate an evidence-based approach for selecting candidates for UKA. Key considerations in the patient selection for UKA include identifying bone-on-bone OA in the medial compartment, ensuring a functionally normal anterior cruciate ligament, maintaining full-thickness cartilage in the lateral compartment, verifying a functionally normal medial collateral ligament, and confirming the absence of severe damage laterally to the patello-femoral Joint.

MATERIALS AND METHODS

Research design

From a consecutive cohort of 390 patients with medial knee pain, preoperative radiographs of both knees including standing anteroposterior (AP), true lateral, posteroanterior (PA) view with 20° flexion, valgus stress view with 20° flexion, and skyline view were taken (Fig. 1), and results were tabulated. UKA suitability was determined using the Oxford Radiological Criteria (decision aid), history, examination, and radiographic assessment including stress radiographs.

Fig. 1. Patient positioning for X-rays.

The X-ray knee instability and degenerative scoring system (X-KIDS) is currently being used as a tool to determine the optimal treatment choice between UKA or TKA for an individual knee.

Regarding UKA, the X-KIDS scoring system lacks robust evidence to support its application.

Fig. 2. Oxford radiological decision aid.

Consequently, a novel atlas-based radiographic Oxford decision aid has been developed. This new tool is tailored for medial Oxford UKA (OUKA) within the context of anteromedial OA (AMOA).

The Oxford decision aid (Fig. 2) comprises five distinct sections, each dedicated to evaluating one of the five criteria: standing AP, true lateral, PA view with 20° flexion, valgus stress view with 20° flexion, and skyline view. Within these sections, radiographic views are presented alongside illustrative radiographs that showcase instances where the criteria are fulfilled. Conversely, exemplar radiographs were also included to illustrate situations where the criteria are not satisfied. The assessment of each criterion was conducted through a binary, yes-or-no question format, characterized by a polar response. Importantly, all five criteria must be met collectively to warrant the consideration of OUKA as a suitable intervention for AMOA.

Fig. 3. Decision aid’s predictive performance in identifying suitability for unicompartmental knee arthroplasty.

Fig. 4. Sensitivity analysis of skyline and stress X-rays.

To evaluate the effectiveness of this decision aid, its sensitivity, specificity, positive predictive value, negative predictive value, and accuracy in identifying cases suitable for OUKA were determined (Fig. 3, 4). This evaluation was conducted solely through radiographic assessment.

Conformity criteria

Inclusion criteria:

patient with knee pain, aged >30 years.

Exclusion criteria:

age <30 years;
fractures around the knee and tibia;
ligamentous injury of the knee;
tumors;
Charcot’s disease;
skeletally immature knees.

Research facilities

Chettinad Hospital and Research Institute, Chennai, India.

Research duration

Two years.

The main research outcome

In this section, the primary endpoints were described. They could be “true” (lethal outcome, serious adverse effects, etc.) or “substitute” finishing point (biochemical parameters and quality of life assessment scores). Usually, the main research outcome is characterized by safety, efficiency, and affordability.

Ethical review

Ethical committee approval was obtained from Chettinad Academy of Higher Education — Institutional Human Ethics Committee for Student Research (CARE IHEC-I) with ID no. IHEC-I/1219/22 approved on 06/09/2022.

Statistical analysis

Principles of samples size calculating: sample size cross-sectional study.

N=z^(2 )SD^2/e^2/,

n=1.64^2×0.6×(1-62)/0.05^2=390~400,

where z=1.64 (I.e) 90% CI, SD=0.6%.

RESULTS

Research sample (participants / respondents)

A total of 390 knees were subjected to assessment based on the Oxford decision aid criteria. The use of the radiographic decision aid led to the identification of 49% (191 knees) of the knees as suitable candidates for OUKA, whereas the remaining 51% (199 knees) were not deemed suitable. Remarkably high levels of agreement were observed, both within observers (intraobserver agreement with Cohen’s kappa of 0.90) and between different observers (interobserver agreement with Cohen’s kappa of 0.85).

Among the knees identified as unsuitable for OUKA (51%), 40% (79 knees) failed to meet a single radiographic criterion, 38% (75 knees) fell short of meeting two criteria, 22% (43 knees) did not meet the three criteria, and an insignificant portion <1% (1 knee) did not fulfill the four criteria (Fig. 5).

Fig. 5. Radiographic assessment of X-rays.

In knees that did not meet the radiographic criteria, observations were as follows: 67 knees (46%) showed partial-thickness cartilage loss in the medial compartment, 69 (45%) exhibited posterior bone loss on true lateral radiographs, signifying ACL insufficiency, 113 (67%) displayed evidence of lateral compartment disease, 21 (11%) demonstrated signs of MCL shortening, and 31 (16%) exposed evidence of bone loss with grooving affecting the lateral patello-femoral joint (Fig. 6).

Fig. 6. Specific findings in X-rays of patients that failed to meet the criteria.

Undesirable phenomena

No undesirable phenomenon was observed in this study.

DISCUSSION

The X-KIDS was conducted based on the evaluation of five radiographic views, namely, standing AP, lateral, PA, varus, and valgus stress views. The knees were assessed for narrowing, presence of osteophytes, and subluxation in the coronal and sagittal planes [7].

The evaluation for joint space narrowing included examining both the medial and lateral compartments. A compartment is deemed narrowed when bone-on-bone arthritis is detected in standing AP, standing PA 15° flexion, or varus and valgus stress views. Upon identifying the bone-on-bone arthritis compartment, 3 points were credited, provided that the opposite knee compartment maintains a joint space width of ≥5 mm on all views. However, if the joint space width in the other compartment is <5 mm, it was scored 6 points [1].

Osteophytes are assigned a score of 1 point for the presence of either a medial or lateral osteophyte. Subluxation is evaluated using both standing AP and lateral views. In the AP view, 1 point is allotted for subluxation; however, this point is deducted if the subluxation is corrected on varus or valgus stress views. Subluxation observed in the lateral view credited 2 points, with a maximum total of 3 points achievable if uncorrectable subluxation is evident on both AP and lateral views [6].

Overall, knees can accumulate a maximum of 10 points. A score of 3–4 indicates that UKA is the preferred treatment. A score of 5 suggests that UKA might be suitable pending clinical findings and surgical correlation, while a score exceeding 5 points indicates that TKA is the more appropriate choice [6].

However, in clinical practice, the standing radiographs of some patients exhibit bone-on-bone arthritis, particularly in the medial compartment. In such cases, the value of conducting standing AP view in 15° flexion and varus stress views in 20° flexion to further evaluate the medial compartment appears limited because it does not alter the knee scores.

The X-KIDS score raises additional concerns, one of which pertains to the incorporation of osteophytes as a predictive factor for outcomes. However, these osteophytes do not affect functional outcomes or likelihood of surgery failure. Moreover, X-KIDS falls short in its evaluation of the patello-femoral joint. Lastly, inherent problems occurred in the calculation of scores using the X-KIDS system. Given its reliance on a points-based framework, a risk of misinterpretation associated with X-KIDS utilization is possible [7].

Collectively, these findings imply that the Oxford decision aid holds valuable utility in identifying suitable candidates for OUKA among individuals who fulfill the criteria for joint arthroplasty.

Summary of the primary research results

The Oxford radiological decision aid has shown high sensitivity and specificity in predicting the suitability of medial OUKA. Its use is expected to be associated with improved implant durability and better functional outcomes.

Research limitations

The functional outcome of patients selected for UKA was not evaluated in the study.

CONCLUSION

The Oxford radiological decision aid demonstrates high sensitivity and specificity in forecasting the appropriateness of medial OUKA. Its application is anticipated to correlate with superior implant longevity and favorable functional results. Furthermore, the decision aid maintains a low false-positive rate. Given that surgeons meticulously assess the knee during the surgical procedure, any false positives can be promptly recognized, thus averting the occurrence of OUKA in any patients.

ADDITIONAL INFO

Autor contribution. All authors confirm that their authorship meets the international ICMJE criteria (all authors have made a significant contribution to the development of the concept, research and preparation of the article, read and approved the final version before publication). The greatest contribution is distributed as follows: A. Vijay, H. Pandian — research, data collection and write up; P. Elangovan, A.K. Vijayakumari, A. Ganesh, S.M. Tajudeen — research and write up.

Funding source. The authors state that there is no external funding when conducting the research and preparing the publication.

Competing interests. The authors declare that they have no competing interests.

Consent for publication. The patients gave their written consent for publication of their medical data (date: August 6, 2022).

Acknowledgements. We thank Dr. Nalli R. Uvaraj, Head of the Department, Department of Orthopaedics, Chettinad Hospital and Research Institute, Chennai.

ДОПОЛНИТЕЛЬНО

Вклад авторов. Все авторы подтверждают соответствие своего авторства международным критериям ICMJE (все авторы внесли существенный вклад в разработку концепции, проведение исследования и подготовку статьи, прочли и одобрили финальную версию перед публикацией). Наибольший вклад распределён следующим образом: А. Виджай, Х. Пандиан — проведение исследования, подготовка и написание статьи; П. Элангован, А.К. Виджаякумари, Г. Анантхараман, Ш.М. Таджудин — проведение исследования и написание статьи.

Источник финансирования. Авторы заявляют об отсутствии внешнего финансирования при проведении исследования и подготовке публикации.

Конфликт интересов. Авторы декларируют отсутствие явных и потенциальных конфликтов интересов, связанных с проведённым исследованием и публикацией настоящей статьи.

Информированное согласие. Авторы получили письменное согласие пациентов на публикацию их медицинских данных (06.08.2022).

Благодарности. Авторы выражают свою признательность доктору Налли Р. Уварадж, заведующему отделением ортопедии в больнице и исследовательском институте Четтинад, Ченнай, Индия.

About the authors