Abstract
Objective
Symptomatic venous thromboembolism (VTE) and prosthesis failure are the most serious complications after total knee arthroplasty (TKA). However, whether knee valgus deformity aggravates these complications has not been fully clarified. To study the difference between perioperative symptomatic VTE and prosthesis revision rate in patients with valgus knee osteoarthritis by comparing with patients undergoing TKA for varus deformity and analyze the reasons for revision. At the same time, the distribution and radiographic features of lower extremity deep venous thrombosis were recorded.
Methods
The data of patients who underwent TKA in two tertiary hospitals from January 2016 to December 2020 were retrospectively reviewed, and a total of 8917 patients were included. According to preoperative manifestations of knee malformations, all patients were divided into two groups: valgus group (n = 412) and varus group (n = 8505). Main indicators included the incidence of symptomatic VTE and prosthesis revision. Secondary outcomes included general information on operative time, Kellgren and Lawrence score, total hospital stay, and total costs. The patient data of the two groups were analyzed by Pearson chi‐square test, Student t test, or Mann–Whitney U test. The revision was evaluated using Kaplan–Meier survival analysis.
Results
The proportion of valgus knees in TKA patients was 4.62% (412/8917). The incidence of VTE was 6.23‰ (53/8505) and 16.99‰ (7/412) in the varus and valgus groups, and the results were statistically different (p = 0.009). There was no significant difference in echogenicity, number of occluded vessels, and thrombus length between the valgus group (p = 0.102; p = 0.645; p = 0.684). Patients with valgus deformity had 12.14‰ (5/412) prosthesis revision, the incidence of varus deformity was 4.82‰ (41/8505), and the revision risk of valgus group was 2.5 times higher than varus group, and the results were statistically different (p = 0.043). The operation time and hospital stay in the valgus group were longer than those in the varus group, and the results were statistically different (p = 0.018; p < 0.001).
Conclusions
Valgus deformity increases risk of symptomatic VTE and prosthesis revision after TKA. These results have guiding significance for the prevention of complications after TKA in patients with valgus deformity.
Keywords: Total Knee Arthroplasty, Valgus, Varus, Venous Thromboembolism, Revision
To study the difference of perioperative symptomatic venous thromboembolism (VTE) and prosthesis revision rate in patients with valgus knee osteoarthritis by comparing with patients undergoing total knee arthroplasty (TKA) for varus deformity and analyze the reasons for revision. At the same time, the distribution and radiographic features of lower extremity deep venous thrombosis were recorded.
Introduction
Total knee arthroplasty (TKA) is a reliable treatment for intermediate and advanced knee osteoarthritis, and previous studies have found that valgus deformity occurs in 10–15% of TKA patients. 1 , 2 , 3 , 4 Unfortunately, in Asian populations, there is no large sample of studies that count the ratio of valgus knees in TKA patients. Symptomatic VTE and revision of prostheses after TKA are serious complications, and the specific pathologic deformity of a valgus knee requires more skills to achieve perfect prosthesis position and restore soft tissue balance, anatomical features that increase the difficulty of TKA, and postoperative complications. 5 , 6 Clinical outcomes and prosthesis revision rates after TKA differ in their comparison with varus knees, and a retrospective study found that patients with valgus knees more than 2 years after TKA showed as good clinical results as varus knees, and no difference in revision rates was found. 7 However, Mazzotti et al. 8 found a significantly higher risk of revision after TKA for valgus deformity compared with varus deformity. In previous reports, there were limitations in the small sample size, and our study may make a more accurate comparison of the difference in prosthesis revision rates and reasons for revision after TKA for valgus and varus knees with a larger number of study subjects.
Symptomatic VTE is a serious complication after TKA and, in severe cases, can lead to patient death because of pulmonary embolism (PE). Previous research has found that the risk of VTE development is closely related to ethnic differences, and the incidence of VTE is significantly lower in Asians compared to Caucasians. 9 , 10 Chang et al. 11 found an incidence of VTE of 0.4% in 253 patients who underwent TKA. So far, no report has evaluated the difference in VTE after TKA between valgus and varus knees in patients receiving anticoagulant prophylaxis, and no study has reported the distribution of deep venous thrombosis in veins or the characteristics of thrombosis.
The aims of our study include two aspects: (1) to retrospectively analyze 8917 patients who underwent primary unilateral TKA from 2016 to 2020 to obtain the proportion of valgus knees in TKA patients and further compare the differences in epidemiological characteristics between valgus knees and varus knees; (2) to analyze and compare the differences in prosthesis revision rates after TKA between valgus and varus knees and to compare the reasons for revision. Also, the incidence of symptomatic VTE, the location of the thrombus, and the imaging characteristics were compared between groups for differences.
Materials and Methods
Patient Selection
This retrospective study included the clinical data of 8917 patients who underwent TKA in the Affiliated Hospital of Qingdao University (Shandong, China) and the Third Hospital of Hebei Medical University (Hebei, China) from 2016 to 2020.
Inclusion criteria: (1) clinical diagnosis in line with knee osteoarthritis; no other fractures or tumors; (2) initial unilateral total knee replacement; (3) imaging integrity; (4) formal conservative treatment is ineffective; (5) all patients gave informed consent to the treatment plan and signed informed consent forms.
Exclusion criteria: (1) long‐term use of anticoagulant drugs or coagulation abnormalities in patients; previous history of thrombosis or preoperative diagnosis of lower limb VTE; (2) recent history of fracture or at the same time other surgeries: (3) with severe systemic disease that can't tolerate surgery; (4) knee revision surgery or simultaneous bilateral TKA; (5) incomplete or lost clinical data.
This study was approved by the Ethics Committee of the Affiliated Hospital of Qingdao University (approval number 26408), and all patients signed an informed consent form.
Surgical Technique and Rehabilitation Interventions
A tourniquet was used throughout the operation. Patellar replacement was not routinely performed. The femoral prosthesis and tibial prosthesis were fixed with bone cement. A polyethylene spacer was installed. The thumbless test, knee joint stability, and good range of motion were examined. Negative pressure drainage tubes were placed in the knee after TKA and removed within 24 hours. All patients were treated with ERAS enhanced recovery after TKA. Two weeks after surgery, CPM was administered. Twelve hours after operation, 10 mg of rivaroxaban tablets (Bayer AG, BJ57529, Germany) were orally administered daily for anticoagulant therapy for 2 weeks, and passive flexion and extension function exercises were performed with continuous passive movement of the lower limbs. The skin temperature, color, and swelling of the lower limbs of the patients were observed daily. The patient was discharged after the knee flexion exceeded 90°, and self‐assisted functional exercise was performed after discharge.
Data Collection
We identified and recorded the Ranawat classification of all patients' knee joints 12 using their hospital records, preoperative anteroposterior X‐rays of the knee, and full‐length weight‐bearing X‐rays of both lower limbs to see if their knee was varus or valgus. Through outpatient follow‐up, the medical record system, and telephone follow‐up, we determined the revision of prostheses after TKA and counted the reasons for revision.
The occurrence of symptomatic VTE events within 14 days after TKA was recorded. The index diagnosis of symptomatic venous thromboembolism includes: (1) clinical manifestations: persistent pain, swelling, local deep tenderness, back flexion pain and limited mobility of the lower extremities, and other discomfort, lower limb VTE should be suspected; unexplained shortness of breath, dyspnea, chest pain, syncope, hypotensive shock, etc. after surgery should be suspected of PE; (2) laboratory tests showed elevated D‐dimer; (3) if the above conditions occur, color Doppler ultrasonography and diagnosis of the deep veins of both lower limbs are immediately performed. 13 If PE was suspected, the diagnosis was confirmed by transpulmonary CT angiography. Each location where thrombus occurred was documented, including whether bilateral lower extremities and multiple vessels were accumulated. At the same time, thrombus echogenicity (hyperechoic, isoechoic, and hypoechoic), number of embolized vessels, and total thrombus length were recorded.
Statistical Analysis
Data entry analysis was performed using SPSS 25.0 statistical software (IBM, Armonk, NY, USA) to detect the normal distribution of the valgus group data. Measurement data in accordance with normal distribution were expressed as mean ± standard deviation; measurement data such as age, operation time, and total cost were compared between the two groups using independent sample t‐test; enumeration data such as gender and prosthesis revision rate were compared by chi‐square test. Revisions were analyzed using Kaplan–Meier survival curves. Test level α = 0.05.
Results
During the study period, 11,514 patients with degenerative arthritis were assessed. According to the exclusion criteria, 2597 patients were excluded. A total of 228 patients were excluded if they underwent TKA in conjunction with other procedures. A total of 1163 patients were excluded from simultaneous bilateral TKA. A total of 1114 patients had incomplete clinical data or were lost to follow‐up. A total of 92 patients had a history of VTE or a history of bleeding risk. Finally, there were 8917 patients who were included in this study. Of these, 2498 were men and 6419 were women, with a mean age of 65.76 ± 7.2 years (range, 23–87 years) and a mean BMI of 27.36 ± 3.64 kg/m2 (range, 18.9–36.1 kg/m2). Finally, the valgus group (n = 412) and varus group (n = 8505) were included in the study, and the proportion of valgus knee in TKA patients was 4.62%. General clinical data of the valgus group and varus group is shown in Table 1. The operation time and mean hospital stay were higher in the valgus group than varus group, and the results were statistically different (p = 0.018; p < 0.001) (Table 2).
TABLE 1.
Comparison of general clinical data between the two groups.
| Variable | Valgus deformity (n = 412) | Varus deformity (n = 8505) | t/χ 2 | p |
|---|---|---|---|---|
| Sex | 0.025 | 0.874 | ||
| Male，n (%) | 114 | 2384 | ||
| Female，n (%) | 298 | 6121 | ||
| Age, years | 65.62 ± 8.98 | 65.76 ± 7.10 | 0.136 | 0.752 |
| Affected side | 1.591 | 0.207 | ||
| Left，n (%) | 159 | 3549 | ||
| Right，n (%) | 253 | 4956 | ||
| BMI，Kg/m2 | 27.20 ± 3.18 | 27.37 ± 3.66 | 1.074 | 0.283 |
| Number of complicated underlying diseases | 4.674 | 0.197 | ||
| None | 106 | 2165 | ||
| 1 | 198 | 3815 | ||
| 2 | 69 | 1567 | ||
| ≥3 | 39 | 958 |
Note: Data are shown as the number or the mean ± standard deviation.
Abbreviation: BMI, Body mass index.
TABLE 2.
Comparison of hospitalization data between the two groups.
| Variable | Valgus deformity (n = 412) | Varus deformity (n = 8505) | t/χ 2 | p |
|---|---|---|---|---|
| Total days in hospital，days | 9.53 ± 3.73 | 8.71 ± 3.50 | −4.395 | <0.001 |
| Operative time，mins | 90.20 ± 27.20 | 86.84 ± 28.24 | −2.363 | 0.018 |
| Anesthesia method | 1.689 | 0.430 | ||
| General anesthesia | 314 | 6237 | ||
| Epidural anesthesia | 96 | 2226 | ||
| Other | 2 | 42 | ||
| Total expense，RMB | 49871.55 ± 16023.64 | 49192.70 ± 17190.29 | −0.785 | 0.432 |
Distribution and Characteristics of VTE
The incidence of VTE events after TKA was 6.73‰ (60/8917), 6.23‰ (53/8505) in the varus group, and 16.99 ‰ (7/412) in the valgus group, and the results were statistically different (p = 0.009) (Table 3). Most deep venous thrombi occurred in the distal lower extremities, mainly in the intermuscular veins (Table 4).The two groups did not differ statistically in terms of thrombus echogenicity, number of occluded vessels, and thrombus length (p = 0.102, p = 0.645, p = 0.684) (Table 5).
TABLE 3.
Comparison of VTE and prosthesis revision after TKA between the two groups.
| Variable | Valgus deformity | Varus deformity | χ2 | p |
|---|---|---|---|---|
| VTE，n (%) | 7 (1.7%) | 53 (0.6%) | 6.806 | 0.009 |
| Prosthesis revision，n (%) | 5 (1.2%) | 41 (0.5%) | 4.097 | 0.043 |
Abbreviations: TKA, Total knee arthroplasty; VTE, Venous thromboembolism.
TABLE 4.
Comparison of distribution of deep venous thrombosis between the two groups.
| Variable | Valgus deformity (n) | Varus deformity (n) |
|---|---|---|
| Proximal | ||
| CFV | 1 | 0 |
| DFV | 1 | 0 |
| SFV | 3 | 1 |
| PV | 4 | 1 |
| Distal | ||
| PTV | 6 | 2 |
| PeV | 1 | 0 |
| ATV | 0 | 0 |
| Inv | 56 | 7 |
Abbreviations: ATV, Anterior tibial vein; CFV, Common femoral vein; DFV, Deep femoral vein; InV, Intermuscular vein，including gastrocnemius vein and soleal vein; PeV, Peroneal vein; PTV, Posterior tibial vein; PV, Popliteal vein; SFV, Superficial femoral vein.
TABLE 5.
Comparison of imaging characteristics of lower limb vascular ultrasound between the two groups.
| Variable | Valgus deformity n (%) | Varus deformity n (%) | t/χ2 | p |
|---|---|---|---|---|
| Echogenicity | 4.572 | 0.102 | ||
| Hyperechoic | 1 | 1 | ||
| Isoechoic | 2 | 1 | ||
| Hypoechoic | 50 | 5 | ||
| Number of embolized vessels, n (%) | 0.876 | 0.645 | ||
| One | 37 | 4 | ||
| Two | 13 | 2 | ||
| Three | 3 | 1 | ||
| Mean vein diameter (mm) | 44.5 ± 33.57 | 35.5 ± 27.58 | 0.411 | 0.684 |
Comparison of Prosthesis Revision Rate and Prosthesis Retention Rate
After TKA, the total prosthesis revision rate was 5.16‰ (46/8917).The revision rate of valgus group was 12.14‰ (5/412), varus group was 4.82‰ (41/8505), and the revision rate of valgus group was 2.5 times that of varus group, and the difference had statistical significance (p = 0.043) (Table 3). In 46 revision patients, infection was the main reason for revision (27/46). The main reasons for revision in the varus group were infection (26/41), revision in the valgus group in five cases, one periprosthetic joint infection, one aseptic loosening of the prosthesis, one unexplained postoperative pain, and two experiencing valgus deformity of the knee due to knee instability (Table 6).
TABLE 6.
Reason for revision for the deformity category and revision rate.
| Valgus deformity | Varus deformity | ||||||
|---|---|---|---|---|---|---|---|
| Reason for revision | Rate | ‰ | % Distribution of failure causes | Reason for revision | Rate | ‰ | % Distribution of failure causes |
| Periprosthetic joint infection | 26/8505 | 3.06 | 61.41 | Periprosthetic joint infection | 1/412 | 2.43 | 20 |
| Aseptic loosening | 8/8505 | 0.94 | 19.51 | Aseptic loosening | 1/412 | 2.43 | 20 |
| Dislocation | 1/8505 | 0.12 | 2.44 | Knee instability | 2/412 | 4.95 | 40 |
| Pain without loosening | 3/8505 | 0.35 | 7.32 | Pain without loosening | 1/412 | 2.43 | 20 |
| Liner wear | 1/8505 | 0.12 | 2.44 | Total | 5/412 | 12.13 | 100.0 |
| Periprosthetic Fracture | 1/8505 | 0.12 | 2.44 | ||||
| Stiffness | 1/8505 | 0.12 | 2.44 | ||||
| Total | 41/8505 | 4.82 | 100.0 | ||||
The survival rate of prosthesis was 99.51% in varus group, and the valgus group was 99.03%. It could be observed from the Kaplan–Meier prosthesis survival curve of the two groups that the prosthesis retention rate of the two groups gradually decreased with the increase of follow‐up time, until the follow‐up, The prosthesis retention rate was significantly higher in the varus group than in the valgus group (Figure 1).
FIGURE 1.
Survival curves of Kaplan–Meier prosthesis in two groups.
Representative Case
A 67‐year‐old woman with valgus deformity of the right knee underwent TKA. At 6 and 11 months after surgery, X‐ray of the right knee revealed that the valgus deformity gradually worsened (Figure 2), and knee instability with pain was found. On readmission, the right knee was treated with spacer replacement (the original 12 mm was replaced with 14 mm) and extrusion nail at the bone tunnel to fix the posterior bundle of the medial collateral ligament. The patient and an extrusion recovered well after revision.
FIGURE 2.
A 67‐year‐old woman with valgus deformity of the right knee underwent TKA. (A) One month before surgery, weight‐bearing radiographs of the whole lower limb were taken. (B) Anteroposterior position of right knee joint 3 days after TKA. (C) Lateral position of right knee joint 3 days after TKA. (D) Anteroposterior position of right knee joint 6 months after TKA. (E) Lateral position of right knee joint 6 months after TKA. (F) Anteroposterior position of right knee joint 11 months after TKA. (G) Lateral position of right knee joint 11 months after TKA. (H) Anteroposterior position of right knee joint 2 days after revision. (I) Lateral position of right knee joint 2 days after operation. (J) Anteroposterior position of right knee joint 1 month after revision. (K) Lateral position of right knee joint 1 month after operation.
Discussion
After we reviewed the medical records and preoperative imaging data of 8917 patients, we re‐counted the proportion of valgus knees in TKA patients, accounting for 4.62%, which is lower than previous studies. 1 , 2 , 3 , 4 Moreover, we compared preoperative knee valgus deformity with varus deformity in terms of symptomatic VTE and prosthesis revision rates. Most importantly, this study showed that the risk of prosthesis revision after TKA for preoperative valgus deformity was 2.5 times that of varus deformity, and the risk of VTE was 2.7 times greater than that of varus. Through this study, more attention should be paid when performing TKA in patients with valgus deformity and new strategies are sought to reduce the risk of prosthesis failure and VTE.
While differences in clinical outcomes and complications after TKA between preoperative valgus deformity and varus deformity have been compared in previous studies, 4 , 5 , 6 , 14 , 15 , 16 we think our study has improved previous research. The previous studies all had the limitation of small sample size, our study has the advantage, and the sample size in the study has increased greatly. The follow‐up of VTE after TKA has been rarely reported in previous studies, which only focused on overall postoperative complications. 17 , 18 , 19 Differently, in our study, the incidence of symptomatic VTE, the distribution of thrombus, and the radiographic features were described and recorded in detail for both the valgus and varus groups, and the differences in reasons for prosthesis revision were compared, which is more meaningful for clinical prevention and treatment.
Effect of Valgus Deformity of Knee Joint on VTE after TKA
Common clinical manifestations of lower extremity VTE are lower extremity swelling, local deep tenderness, and dorsalis pedis flexion pain, and typical clinical signs are positive Homans sign and Heuhof sign. 20 Tsunami et al. 21 found that asymptomatic thrombi dissolved spontaneously after TKA in Asian populations without pulmonary embolism and thrombophlebitis, and 25% of untreated lower leg thrombi resulted in pulmonary embolism, 22 while the time to pulmonary embolism in orthopaedic surgery was mainly within 14 days. 23 Therefore, this study mainly focused on the occurrence of symptomatic VTE after TKA, and those without special signs and clinical manifestations were not included in our research. In our research, through rigorous statistical analysis, the results showed statistically difference in the incidence of symptomatic VTE after TKA between varus and valgus knees, and to our knowledge, there is no relevant article reporting the incidence of symptomatic VTE. Maynard et al. 24 found that the incidence of VTE on the first day after TKA was 47%, and 87% of thrombi had formed on the first day. White et al. 25 reported that the duration of symptomatic embolic events after TKA averaged 7 days. Previous studies have analyzed the causes of VTE after TKA, which include age and underlying diseases, among others, 26 , 27 and in the prevention of VTE, anticoagulants are widely used after TKA in the elderly. 28 Itou et al. 14 found that the incidence of VTE was 31.6% in the presence of chemoprophylaxis after TKA. The incidence of VTE in our study was 6.73%, and this data is lower than previous reports. 15 , 16 This conclusion is consistent with the previously reported lower incidence of VTE in Asians than in Caucasians. 9 , 10 Differences in morbidity may be due to differences in the number of study subjects, duration of follow‐up, and anticoagulant drugs. In addition, the method of diagnosing VTE in this study was lower extremity vascular ultrasound, which had a lower diagnostic accuracy than lower extremity deep venography. 29 With chemoprophylaxis, our study found that most deep venous thrombi occurred in the intermuscular veins with predominantly hypoechoic echogenicity in both the varus and valgus knees. There is a significant correlation between soleus thrombus greater than 7 mm in diameter and pulmonary embolism. 23 There was no statistically significant difference between the two groups in terms of characteristics such as thrombus length, number of embolized vessels, and echogenicity, but a larger sample size is needed for more in‐depth studies.
Effect of Valgus Deformity of Knee Joint on Prosthesis Revision after TKA
TKA has a good clinical effect in the treatment of valgus knee deformities. 30 A review of the 8‐year follow‐up of primary TKA for severe valgus deformity using different types of implants confirms that TKA can treat severe valgus knee deformity. 1 Valgus deformity is often accompanied by lateral femoral condyle dysplasia and bone defects, and structural dissolution and absorption may lead to bone defects again, further causing knee prosthesis loosening. 31 In addition, lateral structure release via the medial parapatellar approach disrupts the blood supply of the patella and increases the incidence of postoperative patellar fractures. 17 It is not difficult to find from previous studies that valgus knees are significantly more difficult to operate than patients with varus knees because of their special pathological deformity, so the comparison of clinical efficacy and complications after varus and valgus TKA has been the focus of clinical research, and there is also extensive controversy. In a study of the postoperative subjective stability of valgus and varus knees, the results showed that subjective instability was associated with postoperative MCL deficits. 18 In addition, differences in the severity of preoperative knee osteoarthritis and grade of valgus deformity were not associated with clinical outcome after TKA. 19 In our study, patients with valgus deformity had a total of five revisions, two of which were due to laxity of the medial collateral ligament, recurrence of valgus deformity of the knee, and instability. In terms of complications, Chou et al. 5 followed 83 valgus knees and 1084 varus knees for 72 months and found that patients with valgus knees had a higher proportion of patellar subluxation than patients with varus knees. Fiddian et al. 6 found problems with knee instability, recurrence of valgus deformity, and patellar maltracking after TKA for valgus deformity. While recent studies have found 4 that valgus deformity has an increased risk of revision compared with varus deformity, infection is the main reason for revision. Our study found that prosthesis loosening was the main cause of revision in the valgus group, which was different from the cause in the varus group. In our study, we could clearly find that patients with valgus deformity had longer operative time and hospital stay compared to patients with varus deformity, and that longer operative time means increased blood loss and longer tourniquet time, so higher revision rates may be associated with longer operative times.
Potential Clinical Significance and Limitations
This study was a large‐scale multicenter study, and a sufficiently large number of patients (8917 patients) from two tertiary hospitals were reviewed. The results of this study may provide valuable guidance for the prevention and intervention of complications after TKA in patients with knee valgus deformity. However, our study still has many limitations. First of all, this is a retrospective study, and in the future, more prospective studies are needed. Second, as a study of two centers, the two hospitals differ in the selection of surgical techniques and implants. At the same time, the rehabilitation plans of all patients are difficult to achieve complete consistency. Finally, the follow‐up and evaluation of knee functional recovery after knee replacement were not conducted in this study.
Conclusions
Valgus deformity increases the risk of symptomatic VTE and prosthesis revision after TKA. Through this study, more attention should be paid when performing TKA in patients with valgus deformity, and new strategies are sought to reduce the risk of prosthesis failure and VTE.
Author Contributions
Authors KSX and TBY designed the study; LZ analyzed the data; KSX wrote the manuscript; YZZ and XZ supervised the study. All authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work. All authors read and approved the final manuscript.
Conflict of Interest Statement
We declare that we have no conflict of interest.
Ethics Statement
This study was approved by the Institutional Review Board of the affiliated hospital of Qingdao University. No children (under 16 years old) were included in this study. Informed consent was obtained from all participants. All patients signed the preoperative written informed consent. Patients' identification information had been removed. The study is in line with the Declaration of Helsinki.
Acknowledgements
This research was supported by the grant from the National Natural Science Foundation of China (No. 31872310 to TBY).
Kuishuai Xu and Liang Zhang contributed equally to this work.
Contributor Information
Xia Zhao, Email: zhaoxia3032@163.com.
Yingze Zhang, Email: yzling_liu@163.com.
Data Availability Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.