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Increased prevalence of lateral trochlear groove wear among valgus alignment subtypes by coronal knee alignment classification: A retrospective single-center study
⁎Corresponding author: Danielle DeMoes. ddemoes@inov8hc.com
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Received: ,
Accepted: ,
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Abstract
The Coronal Plane Alignment of The Knee (CPAK) classification aims to restore the constitutional knee alignment, although it neglects the patellofemoral joint. Therefore, this study aims to examine the correlation between trochlear groove wear (TGW) patterns and CPAK classifications.
Our institutional database was queried to include unilateral primary total knee arthroplasties (TKA) between 2021 and 2025. TGW was categorized into central, medial, lateral, and no TGW based on the most prominent wear observed intraoperatively. Using OMNIBotics® surgical navigation system (Corin Ltd.), nine CPAK phenotypes were determined by intraoperative registration of the arithmetic hip–knee–ankle angles (aHKA), joint line obliquity (JLO), lateral distal femoral angle (LDFA), and medial proximal tibial angle (MPTA).
Among 559 cases, central TGW (53.7 %), followed by lateral (21.8 %) and medial (15.2 %), were the most frequent TGW. Lateral TGW had a higher mean of MPTA (88.5 ± 2.3), while medial TGW had a significantly higher mean of LDFA (87.3 ± 2.2) than the other groups. Central TGW was the most prevalent wear in all aHKA groups, with the lateral TGW being more frequent (33 %) in the valgus knees than the medial TGW (8.4 %). Forty-two percent of cases with lateral TGW had CPAK type Ⅲ, followed by CPAK type Ⅱ (30 %) and CPAK type Ⅵ (13.0 %). The most frequently observed CPAK phenotypes with the central TGW were type Ⅱ (40 %), type Ⅲ (25 %), and typeⅠ (17 %). The same trend was detected for medial TGW and those without wear.
The interplay between joint health and structural alignment can impact surgical planning, as we observed a significant association between the TGW and CPAK parameters. Surgeons may adjust femoral component rotation in CPAK Ⅲ with lateral TGW to address patellar maltracking, though further research is needed.
Abstract
Highlights
•Valgus Knee Association: Central TGW was most common; Lateral TGW was prevalent in valgus knees (33% vs. 8.4% for medial wear) showing distinct wear.•Alignment-Specific Findings: Lateral TGW cases had a higher MPTA, and medial TGW cases had a higher LDFA, showing knee alignment affects PFJ wear.•ClinicalImplications for Surgical Planning: 42% of lateral TGW cases were CPAK III, showing a potential need to adjust femoral rotation in TKA for patellar maltracking.
Keywords
Total knee arthroplasty
Kinematic alignment
Patellofemoral joint
Trochlear groove wear
1 Introduction
Despite significant advances in total knee arthroplasties (TKA), approximately 10 % of patients still report dissatisfaction with their outcomes due to issues such as anterior knee pain, aseptic loosening, and instability.1,2 Current efforts focus on restoring constitutional alignment to improve outcomes, lower revision rates, and enhance patient satisfaction.3
TKA traditionally adhered to mechanical alignment (MA), positioning the implant for a neutral mechanical axis.4,5 Yet only a small (0.10 %) number of individuals exhibit a neutral mechanical axis naturally.3 In contrast, kinematic alignment (KA) aims to improve knee function and alleviate pain by restoring constitutional alignment and focusing on ligament balancing.6,7 The Coronal Plane Alignment of the Knee (CPAK) alignment classification, used with KA, categorizes knee alignment into nine phenotypes based on arithmetic hip-knee-ankle angle ([aHKA] varus, valgus, or neutral) and joint line obliquity ([JLO] apex proximal, apex distal, neutral), offering a more intuitive framework than traditional alignment techniques.8,9 However, CPAK focuses solely on the tibiofemoral joint (TFJ) and neglects the patellofemoral joint (PFJ).9
Abnormal patellar alignment and maltracking within the trochlear groove increases contact pressure, asymmetry, and stress, contributing to patellofemoral OA (PFOA).10 Current alignment techniques, particularly kinematic alignment (KA), aims to account for variations in individual anatomy, thereby more effectively restoring the trochlear groove.11 However, challenges remain due to the inherent variability of the trochlear groove, and addressing these challenges through optimal surgical alignment techniques can enhance surgical planning.11,12
Despite the widespread use of the CPAK classification, the literature lacks information on its association with PFOA. This study aims to investigate potential correlations between PFOA, assessed by the location of trochlear groove wear (TGW), and CPAK classifications. We hypothesize that lateral trochlear groove wear is associated with valgus knees.
2 Methods
2.1 Patient selection
This retrospective, single-center study recruited patients from the Surgical Joint Registry, an institutional database that includes all patients with hip or knee conditions. The database collects demographic features, preoperative data, intraoperative measures, clinical outcomes, and patient-reported complications. This retrospective study involving human participants was in accordance with the ethical standards of the institutional review board and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The institutional review board reviewed and approved this prospectively collected registry (IRB: 20203266). Informed consent was obtained from all individual participants included in the study.
The database has been queried from March 2021 until January 2025 to include all adult patients (age >18 years old) who underwent primary unilateral TKA. Revision or conversion TKAs and unicompartmental knee arthroplasties have been excluded. Fig. 1 shows the patient selection flowchart.
The severity and location of the trochlear groove wear were visually assessed and recorded by the surgeon. Based on the most prominent TGW observed during the surgery, the patients were categorized into four groups: no wear, medial, lateral, and central TGW. Preoperative CPAK classification has been reported in our database since March 2021. The preoperative CPAK was determined by factoring in femoral and tibial compartmental wear, which was recorded intraoperatively using the OMNIBotics surgical navigation system (Corin Ltd.), similar to the method described by Edelstein et al.13 As an imageless navigation system, the OMNIBotic uses registered tibial and femoral condylar landmarks to determine the medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA). These landmarks were acquired using digitizing points by the OMNIBotic probe. LDFA was then measured relative to the mechanical axis of the femur and the center of the distal femur. MPTA was calculated as the angle between the mechanical axis of the tibia and the center of the tibia. JLO and aHKA were automatically generated by subtracting and adding the LDFA to the MPTA, respectively. CPAK phenotypes were determined based on the study by MacDessi et al.9
2.2 Surgical approach
All patients underwent cemented TKAs with patellar resurfacing via a medial parapatellar approach based on KA using the Corin robotic-assisted technology. The patella was laterally subluxated, and with the knee in 90° flexion, the accessible osteophytes were excised. The TGW, MPTA, LDFA and the CPAK phenotype were determined as mentioned above. All the tibial and femoral resections were performed using Corin robotic-assisted technology. The proximal tibial cut was performed and rechecked with navigation, followed by resections of the distal femur. The femoral rotation measured relative to the trans-epicondylar line was placed in a neutral position for all cases. Trial prostheses confirmed alignment, stability, range of motion, and patellar tracking.
2.3 Data analysis
Descriptive statistics were reported as number (%) for the categorical variables and mean ± standard deviation (SD) for the continuous variables. The independent sample t-test with Bonferroni adjustment was used to compare demographic features and CPAK parameters by the TGW groups. The Chi-square test assessed the possible association between the categorical variables. Analyses were performed with the R environment for statistical computing (version 4.1.0). A p-value ≤0.05 was set as the level of significance.
3 Results
Given the established inclusion and exclusion criteria, 559 cases with a mean age of 69.46 ± 7.54 years (range 47–91) were included. The majority of the patients were female (335 patients, 59.9 %), with Charnley classification type Ⅰ(74.4 %) and ASA grade Ⅲ (77.6 %). The TGW groups were similar in terms of demographic features, as shown in Table 1. Central TGW was the most frequently observed wear (53.7 %), followed by the lateral (21.8 %) and medial (15.2 %). No trochlear wear was detected in 52 knees (9.3 %). The most frequent observed CPAK phenotypes in our population were type Ⅱ (221 knees, 39.5 %), followed by type Ⅲ (158 knees, 28.3 %), type Ⅰ(74 knees, 13.2 %), type Ⅴ (45 knees, 8.1 %), and type Ⅵ (44 knees, 7.9 %), type Ⅳ (12 knees, 2.1), type Ⅷ (3 knees, 0.5 %), and type Ⅸ (2 knees, 0.4 %).
| Trochlear Groove Wear | ||||||
| Variables | Total | None (n = 52) | Central (n = 300) | Lateral (n = 122) | Medial (n = 85) | P-value |
| Age (47–91)a | 69.46 ± 7.54 | 68.33 ± 7.96 | 69.74 ± 7.46 | 69.44 ± 7.80 | 69.16 ± 7.22 | 0.632 |
| BMI (kg.m−2)a | 29.57 ± 5.25 | 28.08 ± 4.98 | 30.09 ± 5.40 | 29.37 ± 5.34 | 28.96 ± 4.49 | 0.036 |
| Height (cm)a | 169.40 ± 10.68 | 169.40 ± 11.07 | 169.23 ± 10.61 | 169.58 ± 11.04 | 169.73 ± 10.334 | 0.980 |
| Weight (kg)a | 85.30 ± 18.81 | 80.87 ± 17.45 | 86.65 ± 19.22 | 84.81 ± 18.92 | 83.97 ± 17.71 | 0.177 |
| Gender | 0.769 | |||||
| Female | 335 (59.9) | 31 (59.6) | 175 (58.3) | 78 (63.9) | 51 (60.0) | |
| Male | 224 (40.1) | 21 (40.4) | 125 (41.7) | 44 (36.1) | 34 (40.0) | |
| Side, n (%) | 0.190 | |||||
| Right | 297 (53.1) | 32 (61.5) | 162 (54.0) | 66 (54.1) | 37 (43.5) | |
| Left | 262 (46.9) | 20 (38.5) | 138 (46.0) | 56 (45.9) | 48 (56.5) | |
| Charnley Classification | 0.900 | |||||
| I | 416 (74.4) | 38 (73.1) | 224 (74.7) | 93 (76.2) | 61 (71.8) | |
| II | 143 (25.6) | 14 (26.9) | 76 (25.3) | 29 (23.8) | 24 (28.2) | |
| ASA classification | 0.379 | |||||
| I | 1 (0.2) | – | – | 1 (0.8) | 0 | |
| II | 124 (22.2) | 14 (26.9) | 60 (20.0) | 32 (26.2) | 18 (21.2) | |
| III | 434 (77.6) | 38 (73.1) | 240 (80.0) | 89 (73.0) | 67 (78.8) | |
A standard independent sample t-test with Bonferroni adjustment was performed to compare the MPTA, LDFA, aHKA, and JLO across the TGW (Fig. 2). Lateral TGW (88.5 ± 2.3) had a higher MPTA angle than central TGW (87.2 ± 2.7, p < 0.0001) and medial TGW (86.9 ± 2.5, p < 0.0001). The Medial TGW had significantly higher LDFAs (87.3 ± 2.2) than other TGW groups (Fig. 2b). Of note, the lateral TGW had a higher mean of aHKA angle (2.6 ± 3) compared to the central (0.8 ± 4, p < 0.0001) and medial TGW (−0.3 ± 3.3, p < 0.0001), as shown in Fig. 2c. However, there was no significant difference in terms of JLO angle by the TGW groups (Fig. 2d).
A chi-square test has shown that the aHKA alignment was significantly associated with the trochlear groove wear location [χ2 (6, 559) = 37.32, p < 0.001]. Central TGW was the most prevalent wear in all aHKA groups, particularly with varus alignment (67.8 %), followed by neutral (53.5 %), and valgus (47.8 %) alignments. In the valgus alignment, the lateral TGW was more frequent (33 %) than the medial TGW (8.4 %), whereas in the neutral and varus alignment the medial TGW was more frequent than the lateral TGW (Fig. 3a). However, JLO was not associated with the trochlear groove wear [χ2 (6, 559) = 7.14, p = 0.308].
Fig. 4 illustrates the distribution of TGW by the CPAK phenotypes, with a significant association observed between them [χ2 (21, 559) = 50.46, p < 0.001]. 42 % of cases with lateral TGW had CPAK type Ⅲ, followed by CPAK type Ⅱ (30 %) and CPAK type Ⅵ (13.0 %). The most frequently observed CPAK phenotypes with the central TGW were type Ⅱ (40 %), type Ⅲ (25 %), and type Ⅰ (17 %). The same trend was detected for medial TGW and those without wear.
4 Discussion
This study had shown that specific CPAK phenotypes were associated with distinct trochlear groove wear patterns. Our most frequently observed CPAK types were Ⅱ, followed by type Ⅲ and type Ⅰwhich is similar to CPAK distributions from other studies, although some heterogeneities have been reported. MacDessi et al. showed that types Ⅱ, Ⅰ, and Ⅴ were the most frequent subtypes in the arthritic population.9Huber et al. concluded that CPAK types Ⅰ, Ⅱ, and Ⅲ are the most frequent phenotypes.14 Moreover, a recent systematic review, including seven reports from India, Taiwan, Japan, Australia, and the USA, discussed the significant geographical variations in CPAK phenotypes.15 Second, this heterogeneity may be related to the use of intra-operative navigation techniques in our study versus long-leg radiographs (LLR) in previous studies.9,14,15 In the current study, CPAK was measured intra-operatively with Corin robotic-assisted technology.13 It has been documented that imageless navigated TKA can determine CPAK phenotypes more accurately than LLRs because it looks at the joints' dynamics, alignment, and stability in contrast to a static snapshot, which could potentially miss aspects of joint movement and alignment.13,16
We found that aHKA alignment was significantly associated with the TGW location. Significantly, valgus aHKA, more specifically, CPAK type Ⅲ was associated with lateral TGW. To the best of our knowledge, this is the first study to examine CPAK classification and trochlear groove wear; however, prior research has linked PFJ and TFJ parameters. Orsi et al. reported that varus phenotypes had a wider trochlear angle range than the valgus and neutral phenotypes.11 Recent findings by Jeremic et al. highlighted that medial deviation of a 6° prosthetic trochlear groove in kinematically aligned TKA occurs across multiple CPAK types, with CPAK III (valgus) exhibiting the highest incidence (89 %).17 While we observed a relationship between CPAK parameters and trochlear wear, analyzing trochlear-related angles was beyond the scope of this study.
Several factors could be attributed to the observed association between the valgus knees and lateral TGW. It has been shown that valgus alignment correlates with lateral TGW, potentially due to increased lateralizing forces causing secondary OA.18 Moreover, using magnetic resonance imaging, Wang et al. found that valgus knees had higher contact on the lateral facet of the PFJ.19 By analyzing 144 patients with osteoarthritis, Flury et al. demonstrated that increased femoral ante-torsion, which was found to be more severe in the valgus knees, was associated with higher lateral PFJ wear.20
4.1 Clinical application
The patella within the trochlear groove may look like it tracks adequately; however, this is not always clinically relevant intraoperatively. Adjusting the femoral rotation intraoperatively may fail to address the postoperative patellar tracking. Notably, we have observed that patients with CPAK type Ⅲ, often associated with lateral TGW, may be more susceptible to patellar maltracking. The senior surgeon advises that externally rotating the femoral component in these patients may be a consideration to potentially address patellar maltracking.
It should be mentioned that not all the knees with CPAK type Ⅰ and Ⅲ had medial and lateral trochlear groove wear. Therefore, in such phenotypes, further subclassification based on the location of the trochlear groove wear could help us understand the potential differences between these categories. However, further studies are warranted to increase our understanding regarding the CPAK and PFJ interactions.
4.2 Limitations
Several limitations should be acknowledged. Being a registry-based and retrospective study, our findings may be susceptible to bias, as the data relies on pre-existing records that may not capture all relevant variables or outcomes consistently. Our findings might not universally apply to all CPAK, indicating a nuanced relationship between predictive analytics, kinematic alignment, and biomechanical optimization. A further limitation to improving outcomes lies in the fact that trochlear groove implant inventory and design have largely remained static. Newer, more anatomically tailored implants specifically designed for the KA technique could potentially enhance patient outcomes, considering the significant anatomical variability within the trochlear groove.21 An inherent limitation of our study lies in the novelty of the topic investigated, as there are limited existing studies that have explored the importance of PFJ and trochlear wear within CPAK classifications. While this novelty underscores the originality and pioneering nature of our research, it also presents a challenge in terms of contextualizing our findings with existing research. Moreover, the generalizability of our findings to broader populations or diverse clinical scenarios may be constrained as this was a single-center study.
4.3 Conclusions
Our findings showed that lateral trochlear groove wear is associated with valgus aHKA and CPAK type Ⅲ. Clinically, in CPAK Ⅲ cases with lateral TGW, surgeons may consider externally rotating the femoral component to address patellar maltracking. However, further investigation is needed to fully understand these complex relationships.
CRediT authorship contribution statement
Danielle DeMoes: contributed to the study, Conceptualization, and design, Material preparation, data collection and, Formal analysis, The first draft of the manuscript was written, All authors read and approved the final manuscript. Roham Borazjani: Material preparation, data collection and, Formal analysis, contributed heavily to commenting on previous versions of the manuscript, All authors read and approved the final manuscript. Alexander D. Orsi: Material preparation, data collection and, Formal analysis, All authors read and approved the final manuscript. Christopher Plaskos: Writing – review and editing. Stefan Kreuzer: contributed to the study, Conceptualization, and design, All authors read and approved the final manuscript.
Consent to participate/publish
This retrospective, single-center study recruited patients from the Surgical Joint Registry, an institutional database that includes all patients with hip or knee conditions. The database collects demographic features, preoperative data, intraoperative measures, clinical outcomes, and patient-reported complications.
This retrospective study involving human participants was in accordance with the ethical standards of the institutional review board and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The institutional review board reviewed and approved this prospectively collected registry (IRB: 20203266). Informed consent was obtained from all individual participants included in the study.
Institutional ethical committee approval
This retrospective, single-center study recruited patients from the Surgical Joint Registry, an institutional database that includes all patients with hip or knee conditions. The database collects demographic features, preoperative data, intraoperative measures, clinical outcomes, and patient-reported complications.
This retrospective study involving human participants was in accordance with the ethical standards of the institutional review board and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The institutional review board reviewed and approved this prospectively collected registry (IRB: 20203266). Informed consent was obtained from all individual participants included in the study.
Ethical statement
This study was performed in line with the principles of the Declaration of Helsinki.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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