Coronal Plane Alignment of the Knee (CPAK) distribution in a diverse Asian population: Influence of ethnicity, sex and bilaterality
Abstract Purpose In total knee arthroplasty (TKA), it remains unclear which patients benefit from correction versus restoration of native knee alignment. The Coronal Plane Alignment of the Knee (CPAK) classification system was introduced in 2021 to describe native alignment, helping to characterise...
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| Format: | Article |
| Language: | English |
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Wiley
2025-04-01
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| Series: | Journal of Experimental Orthopaedics |
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| Online Access: | https://doi.org/10.1002/jeo2.70192 |
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| author | Azmi Rahman Merrill Lee Lenice Tan Sabine Wong Michael Saturnino Glen Purnomo Ming Han Lincoln Liow Keng Jin Darren Tay Hee Nee Pang Seng Jin Yeo |
| author_facet | Azmi Rahman Merrill Lee Lenice Tan Sabine Wong Michael Saturnino Glen Purnomo Ming Han Lincoln Liow Keng Jin Darren Tay Hee Nee Pang Seng Jin Yeo |
| author_sort | Azmi Rahman |
| collection | DOAJ |
| description | Abstract Purpose In total knee arthroplasty (TKA), it remains unclear which patients benefit from correction versus restoration of native knee alignment. The Coronal Plane Alignment of the Knee (CPAK) classification system was introduced in 2021 to describe native alignment, helping to characterise the effect of different TKA alignment techniques. This study aims to describe CPAK in an ethnically diverse population and characterise the relationship between CPAK and ethnicity, as well as the bilaterality of osteoarthritis and other patient factors. Methods 503 primary TKAs were performed in a large tertiary institution in Singapore from 2014 to 2021. Pre‐operative anteroposterior knee radiographs were collected for 441 procedures—all had ethnicity, age, sex and body mass index data. The medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA) were measured with good inter‐observer correlation. Knees were then classified into nine CPAK categories based on arithmetic hip–knee–ankle (aHKA) angle and joint line obliquity (JLO). Results 77% of the cohort were apex‐distal (CPAK 1, 2 and 3), and 59% were varus (CPAK 1, 4 and 7); 44% were CPAK 1 (varus + apex‐distal). Chinese and Indian knees followed near‐identical patterns: CPAK 1 (46%) > CPAK 2 (20%) > CPAK 4 (15%). Malay knees had significantly fewer CPAK 1 (p = 0.0183), with CPAK 1 (29%) ≈ CPAK 2 (29%) ≈ CPAK 4 (21%). Thirty‐eight patients had bilateral TKA. Identical categories were recorded bilaterally in 45% of CPAK, 67% of JLO and 70% of aHKA. Bilateral TKA were more likely when knees were in valgus alignment than unilateral TKA (p = 0.00457). Conclusion Malay knees are less likely to be CPAK‐1; this novel finding may explain ethnic differences in TKA outcomes described in the literature. Less than half of the bilateral knees had the same CPAK category bilaterally. The implications of this bilateral CPAK incongruence are unclear and require further study. Level of Evidence Level II, prospective cohort study. |
| format | Article |
| id | doaj-art-3b464fc02e8c4e0eb1566f5761ff3081 |
| institution | Kabale University |
| issn | 2197-1153 |
| language | English |
| publishDate | 2025-04-01 |
| publisher | Wiley |
| record_format | Article |
| series | Journal of Experimental Orthopaedics |
| spelling | doaj-art-3b464fc02e8c4e0eb1566f5761ff30812025-08-20T03:46:58ZengWileyJournal of Experimental Orthopaedics2197-11532025-04-01122n/an/a10.1002/jeo2.70192Coronal Plane Alignment of the Knee (CPAK) distribution in a diverse Asian population: Influence of ethnicity, sex and bilateralityAzmi Rahman0Merrill Lee1Lenice Tan2Sabine Wong3Michael Saturnino4Glen Purnomo5Ming Han Lincoln Liow6Keng Jin Darren Tay7Hee Nee Pang8Seng Jin Yeo9University of Oxford Oxford UKSingapore General Hospital SingaporeNational University of Singapore SingaporeNational University of Singapore SingaporePhilippine Orthopaedic Centre Manila PhilippinesSt. Vincentius a Paulo Catholic Hospital Surabaya IndonesiaSingapore General Hospital SingaporeSingapore General Hospital SingaporeSingapore General Hospital SingaporeSingapore General Hospital SingaporeAbstract Purpose In total knee arthroplasty (TKA), it remains unclear which patients benefit from correction versus restoration of native knee alignment. The Coronal Plane Alignment of the Knee (CPAK) classification system was introduced in 2021 to describe native alignment, helping to characterise the effect of different TKA alignment techniques. This study aims to describe CPAK in an ethnically diverse population and characterise the relationship between CPAK and ethnicity, as well as the bilaterality of osteoarthritis and other patient factors. Methods 503 primary TKAs were performed in a large tertiary institution in Singapore from 2014 to 2021. Pre‐operative anteroposterior knee radiographs were collected for 441 procedures—all had ethnicity, age, sex and body mass index data. The medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA) were measured with good inter‐observer correlation. Knees were then classified into nine CPAK categories based on arithmetic hip–knee–ankle (aHKA) angle and joint line obliquity (JLO). Results 77% of the cohort were apex‐distal (CPAK 1, 2 and 3), and 59% were varus (CPAK 1, 4 and 7); 44% were CPAK 1 (varus + apex‐distal). Chinese and Indian knees followed near‐identical patterns: CPAK 1 (46%) > CPAK 2 (20%) > CPAK 4 (15%). Malay knees had significantly fewer CPAK 1 (p = 0.0183), with CPAK 1 (29%) ≈ CPAK 2 (29%) ≈ CPAK 4 (21%). Thirty‐eight patients had bilateral TKA. Identical categories were recorded bilaterally in 45% of CPAK, 67% of JLO and 70% of aHKA. Bilateral TKA were more likely when knees were in valgus alignment than unilateral TKA (p = 0.00457). Conclusion Malay knees are less likely to be CPAK‐1; this novel finding may explain ethnic differences in TKA outcomes described in the literature. Less than half of the bilateral knees had the same CPAK category bilaterally. The implications of this bilateral CPAK incongruence are unclear and require further study. Level of Evidence Level II, prospective cohort study.https://doi.org/10.1002/jeo2.70192AsianChineseCoronal Plane Alignment of KneeCPAKIndianMalay |
| spellingShingle | Azmi Rahman Merrill Lee Lenice Tan Sabine Wong Michael Saturnino Glen Purnomo Ming Han Lincoln Liow Keng Jin Darren Tay Hee Nee Pang Seng Jin Yeo Coronal Plane Alignment of the Knee (CPAK) distribution in a diverse Asian population: Influence of ethnicity, sex and bilaterality Journal of Experimental Orthopaedics Asian Chinese Coronal Plane Alignment of Knee CPAK Indian Malay |
| title | Coronal Plane Alignment of the Knee (CPAK) distribution in a diverse Asian population: Influence of ethnicity, sex and bilaterality |
| title_full | Coronal Plane Alignment of the Knee (CPAK) distribution in a diverse Asian population: Influence of ethnicity, sex and bilaterality |
| title_fullStr | Coronal Plane Alignment of the Knee (CPAK) distribution in a diverse Asian population: Influence of ethnicity, sex and bilaterality |
| title_full_unstemmed | Coronal Plane Alignment of the Knee (CPAK) distribution in a diverse Asian population: Influence of ethnicity, sex and bilaterality |
| title_short | Coronal Plane Alignment of the Knee (CPAK) distribution in a diverse Asian population: Influence of ethnicity, sex and bilaterality |
| title_sort | coronal plane alignment of the knee cpak distribution in a diverse asian population influence of ethnicity sex and bilaterality |
| topic | Asian Chinese Coronal Plane Alignment of Knee CPAK Indian Malay |
| url | https://doi.org/10.1002/jeo2.70192 |
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