Abstract
Objective
Patients who undergo a biplanar ascending medial open‐wedge high tibial osteotomy with an excessive correction angle might experience patella infera and even knee pain after surgery. The purpose of this study was to identify the cut‐off points for the degree of knee varus correction of open‐wedge high tibial osteotomy, which is related to the symptomatic patellar position change.
Methods
This retrospective study included 124 patients (mean age 61.69 ± 6.28 years; 78 women, 46 men) with varying degrees of varus knee osteoarthritis. All patients had undergone standard biplanar medial open‐wedge high tibial osteotomy. They were divided into nine groups according to the change in hip–knee–ankle angle. Plain radiographs and three‐dimensional CT images were obtained preoperatively and 18 months postoperatively. Patellar height was assessed using the Caton–Deschamps index, the Insall–Salvati index, and the Blackburne–Peel index. The patellofemoral index and patellar tilt were used to evaluate the degree of horizontal displacement of the patella. The varus correction, medial–proximal tibial angles, joint line convergence angles, and hip–knee–ankle angles were also measured. The subjective score was evaluated using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC).
Results
There were significant changes in patella indexes in each group after surgery, among which there was no significant difference in patellar height changes for Groups A to F (p > 0.05), which were significantly lower than those in Group G, H, and I (p < 0.001). The patellar tilt and patellofemoral index also followed the same trend. The improvement in WOMAC scores for Groups G, H, and I was also significantly less for Groups A to F (p < 0.001).
Conclusion
The patellar height, patellar tilt, and patellofemoral index all changed significantly in parallel with increasing degrees of osteotomy correction. The cut‐off points for correction angle are 12.5° to 13.4°. When the correction angle is larger than this range, the patellar position can be significantly affected. Postoperative patellofemoral joint pain may be related to the changes in patella position.
Keywords: Hip–Knee–Ankle Angle, Medial Open‐Wedge High Tibial Osteotomy, Patellar Height, Patellar Tilt, Patellofemoral Index
When the high tibial osteotomy correction angle is greater than 12°, the patella height significantly decreases and the WOMAC score increases after surgery.
Introduction
Osteoarthritis (OA) of the knee is the main cause of disability in middle‐aged and older adults and typically eventually necessitates total knee arthroplasty (TKA). 1 , 2 , 3 Medial open‐wedge high tibial osteotomy (HTO) is a well‐established procedure for managing medial compartment OA caused by genu varus deformity. It improves knee‐related symptoms by reducing pain and correcting the axial alignment of the lower extremity. 4 , 5 , 6
However, medial open‐wedge HTO (OWHTO) can result in a decrease in patellar height (PH) and an increase in tibial slope, significantly affecting the postoperative prognosis. 7 , 8 , 9 , 10 In a retrospective study of 39 patients by Bito et al., the mean modified Blackburne–Peel ratio decreased from 0.9 to 0.7 (p < 0.01) after surgery, and the mean tibial slope increased from 8.4 to 11.9 (p < 0.01). 8 To avoid this potential problem, some researchers have performed modified HTO. Examples including descending medial OWHTO, distal tuberosity osteotomy, and spacer implantation HTO. These procedures can maintain the PH and prevent patellofemoral pain. 11 Ihle et al. recently described a modified PH measurement index, according to which PH did not change with the degree of osteotomy opening. 12 Carissimia et al. reported similar results from a retrospective study of posteromedial OWHTO. 13 Most orthopaedic surgeons believe that HTO has a potential effect on the patellofemoral joint; however, this notion remains somewhat controversial. 11 The extent of that effect has not yet been established. In our follow‐up of patients who had previously undergone operations, our team noticed that not all patients who had undergone HTO had definite changes in PH: we found that significant changes occurred only after wide‐angle osteotomy. This suggests that the OWHTO correction angle can be controlled within a certain range to avoid the potential effects on the patellofemoral joint. Therefore, it is particularly important to determine the safe range of the OWHTO correction angle to avoid the height drop of the patella after surgery. It can provide a reference for orthopaedic doctors when choosing the surgical method.
To determine the cut‐off points for osteotomy angles that are associated with changes in patellar position after ascending medial OWHTO, we analyzed multiple imaging measurements in relation to patellar position and degree of osteotomy angle in this retrospective study. We propose two hypotheses. First, the patellar position will change after OWHTO. Second, there is a critical osteotomy angle beyond which the patellar position is significantly affected and postoperative anterior knee pain can result.
Materials and Methods
Ethics Statements
The ethics committee of our center approved the study (QYFYWZLL27523). We have read and understood the relevant ethical standards guidelines.
Participant and Study Design
In this single‐center retrospective study, we analyzed data on 124 knees treated with OWHTO for medial compartment OA in our department from November 2019 to February 2021. The inclusion criteria were: (i) patients with symptomatic medial compartment osteoarthritis, articular lesions of the medial knee joint, and varus limb alignment of varying degrees of severity; (ii) the size of the osteotomy gap was not limited; (iii) patients underwent OWHTO; and (4) patients were followed up for at least 18 months after surgery. The exclusion criteria were: (i) previous knee‐opening surgery; (ii) limited range of flexion and extension; (iii) other knee conditions such as rheumatoid arthritis, osteoporosis, Charcot arthritis, Kashin Beck disease, and acute knee infection; (iv) conversion to TKA or revision surgery during follow‐up; and (v) other circumstances leading to loss of follow‐up. A total of 142 patients who met our inclusion criteria underwent HTO during the study period; however, 18 of them declined to participate in this research or were lost to follow‐up. TomoFix locking plates (Synthes GmbH, Solothurn, Switzerland) were used in all study patients.
Radiological Assessment
Radiographic examination included long‐leg full‐weight‐bearing anteroposterior radiographs, anteroposterior views in full extension, lateral views in 30° of flexion of the knee joint, and axial views of the patella in 30°, 60°, and 90° of flexion of the knee joint. All radiological evaluations were performed preoperatively and at 1, 3, 6, 12, and 18 months postoperatively. Three‐dimensional CT was performed preoperatively and at 18 months. Preoperative and postoperative radiographic measurements were made twice by two independent observers for assessment of intra‐observer reproducibility. The most commonly measured indices for assessing the degree of lower limbs varus and the degree of varus osteotomy correction were the medial proximal tibial angle, the joint line convergence angle, and the hip–knee–ankle angle (HKAA). 14 The PH was measured on a lateral view in 30° of knee flexion, whereas the patellofemoral index (PFI) and patellar tilt angle (PTA) were measured on axial views of the patella in 30° degrees of knee flexion (Figure 1). 15 , 16 , 17 In this study, the Caton–Deschamps index (CDI), the Insall–Salvati index (ISI), and the Blackburne–Peel index (BPI) were used to assess the PH in all patients. Patella baja was defined as a <0.6 decrease in the PH in the CDI, <0.8 in the ISI, and <0.54 in the BPI. Patella alta was defined as >1.2 in the CDI, >1.2 in the ISI, and >1.06 in the BPI. 16 , 17 , 18 The normal value for the PFI is <1.6. A PFI greater than 1.6 indicates excessive patellar tilt or patellar subluxation. 15 The PTA represents the degree of external tilt of the patella; the greater the value, the more serious the patellar external tilt. 19 , 20 , 21
FIGURE 1.
Definition and measurement of HKAA, CDI, ISI, BPI, PFI, and PTA. Angle α expresses hip–knee–ankle angle (HKAA) (A). The Caton–Deschamps index (CDI) is equal to b/a (B). The Insall–Salvati index (ISI) is equal to b/a (C). The Blackburne–Peel index (BPI) is equal to b/a (D). The patellofemoral index (PFI) is equal to a/b (E). The angle β expresses the patellar tilt angle (PTA).
Surgical Procedure and Grouping
All patients were operated on by the same experienced surgeon, and standard ascending medial OWHTOs were performed on them. A wire rod from the center of the femoral head to the midpoint of the talus was used intraoperatively as a simulated weight‐bearing line; the surgery was performed as wire rod passed through the lateral intercondylar ridge of tibial plateau, as monitored by intraoperative C‐arm fluoroscopy. In response to different degrees of change in osteotomy corrective angles (ΔHKAA = postoperative HKAA−preoperative HKAA), successive groups of measurements were obtained and compared with the target radiographic measurements. 14 The 124 patients were divided into nine groups: A 6.5°–7.4° (group A); B 7.5°–8.4° (group B); C 8.5°–9.4° (group C); D 9.5°–10.4° (group D); E 10.5°–11.4° (group E); F 11.5°–12.4° (group F); G 12.5°–13.4° (group G); H 13.5°–14.4° (group H); and I 14.5°–15.4° (group I).
Statistical Analysis
All results are expressed as the mean and standard deviation. Preoperative and postoperative PH, PFI, PTA, and Western Ontario and McMaster Universities osteoarthritis index (WOMAC) score means were compared in each group using paired Student t‐tests. Postoperative outcome scores were compared between groups using analysis of variance (ANOVA), and multiple comparisons were made using least significant difference tests. The χ2‐test was used to compare the enumeration data between groups. Intraclass correlation coefficients with 95% confidence intervals (CIs) were used to evaluate the reproducibility of radiographic measurements and WOMAC scores; intraclass correlation coefficients >0.75 were considered to denote excellent agreement. All statistical evaluations were performed using PASW Statistics software (25.0, SPSS, Chicago, IL, USA). A p‐value < 0.05 was considered to denote statistical significance.
Results
Demographics and Characteristics of Patients
A total of 124 patients were eligible for our study protocol, with an average age of 61.69 ± 6.28 years old, and the average body mass index was 27.56 ± 3.47 kg/m2. Of the 124 patients, 78 were women and 46 were men. Sixty‐four of them had surgery on their left leg and 60 on their right. Data for each group is shown in Table 1.
TABLE 1.
Basic information
| Group A (n = 12) | Group B (n = 14) | Group C (n = 18) | Group D (n = 19) | Group E (n = 21) | Group F (n = 15) | Group G (n = 10) | Group H (n = 8) | Group I (n = 7) | F/Z | p‐value | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Sex (male, %) | 4 (33.3%) | 5 (35.7%) | 7 (38.9%) | 7 (36.8%) | 8 (38.1%) | 6 (40.0%) | 4 (40.0%) | 3 (37.5%) | 2 (28.6%) | 0.427 | 1 |
| Age (years) | 64.92 ± 7.43 | 64.43 ± 5.14 | 60.83 ± 5.86 | 60.68 ± 5.29 | 60.9 ± 5.61 | 60.8 ± 6.47 | 60 ± 7.77 | 62.88 ± 7.14 | 61 ± 6.28 | 1.051 | 0.402 |
| Operative side (left, %) | 6 (50%) | 7 (50%) | 10 (55.6%) | 9 (47.4%) | 11 (52.4%) | 9 (60%) | 5 (50%) | 4 (50%) | 3 (42.9%) | 0.937 | 0.999 |
| BMI (kg/m2) | 26.63 ± 3.68 | 27.2 ± 3.66 | 27.25 ± 307 | 27.6 ± 2.48 | 28.11 ± 3.99 | 27.89 ± 4.37 | 27.41 ± 3.68 | 27.13 ± 3.29 | 28.74 ± 3.47 | 0.332 | 0.954 |
Abbreviation: BMI, body mass index.
Data Repeatability
The repeatability of all preoperative and postoperative radiology measurement data and WOMAC scores was excellent (ICCs = 0.872–0.931) (95% CI).
Radiographic Data
The PH and PFI in each group decreased after operation (p < 0.05), and PTA decreased significantly after operation (p < 0.001) (Table 2). ANOVA was performed for ΔPH (ΔPH = postoperative PH − preoperative PH), ΔPFI (ΔPFI = postoperative PFI − preoperative PFI), and ΔPTA (ΔPTA = postoperative PTA − preoperative PTA) of each group, and there were significant differences among the groups (p < 0.001) (Table 3). Then multiple comparisons were made using the least significant difference test, and there was no significant difference among the first six groups (Groups A to F) (p > 0.05), but there was a significant difference between the first six groups and the last three groups (Groups G, H, and I) (p < 0.001) (Tables 4 and 5) (Figures 2 and 3).
TABLE 2.
Comparison of PH, PTA, PFI, and WOMAC in each group before and after operations
| Group A (n = 12) | Group B (n = 14) | Group C (n = 18) | Group D (n = 19) | Group E (n = 21) | Group F (n = 15) | Group G (n = 10) | Group H (n = 8) | Group I (n = 7) | ||
|---|---|---|---|---|---|---|---|---|---|---|
| CDI | Pre‐CDI | 0.92 ± 0.10 | 1.00 ± 0.13 | 1.02 ± 0.11 | 0.99 ± 0.16 | 1.04 ± 0.11 | 1.02 ± 0.10 | 1.07 ± 0.09 | 1.00 ± 0.10 | 1.03 ± 0.09 |
| Post‐CDI | 0.90 ± 0.09 | 0.97 ± 0.11 | 0.98 ± 0.11 | 0.95 ± 0.15 | 1.00 ± 0.10 | 0.97 ± 0.10 | 0.90 ± 0.08 | 0.81 ± 0.12 | 0.82 ± 0.08 | |
| p‐value | 0.041 | 0.007 | 0.001 | <0.001 | <0.001 | 0.001 | <0.001 | <0.001 | <0.001 | |
| ISI | Pre‐ISI | 1.02 ± 0.11 | 1.04 ± 0.11 | 1.06 ± 0.08 | 1.03 ± 0.12 | 1.09 ± 0.10 | 1.05 ± 0.09 | 1.09 ± 0.08 | 1.03 ± 0.10 | 1.07 ± 0.09 |
| Post‐ISI | 0.98 ± 0.09 | 1.00 ± 0.11 | 1.01 ± 0.09 | 0.98 ± 0.11 | 1.04 ± 0.09 | 1.00 ± 0.10 | 0.91 ± 0.07 | 0.84 ± 0.12 | 0.86 ± 0.03 | |
| p‐value | 0.008 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |
| BPI | Pre‐BPI | 0.79 ± 0.11 | 0.84 ± 0.11 | 0.85 ± 0.09 | 0.82 ± 0.12 | 0.88 ± 0.10 | 0.85 ± 0.09 | 0.90 ± 0.08 | 0.83 ± 0.09 | 0.86 ± 0.09 |
| Post‐BPI | 0.76 ± 0.10 | 0.81 ± 0.10 | 0.82 ± 0.09 | 0.78 ± 0.12 | 0.83 ± 0.09 | 0.80 ± 0.09 | 0.73 ± 0.07 | 0.64 ± 0.11 | 0.64 ± 0.09 | |
| p‐value | 0.003 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |
| PTA | Pre‐PTA | 11.33 ± 1.87 | 11.84 ± 1.81 | 11.41 ± 1.61 | 12.07 ± 1.20 | 11.76 ± 1.66 | 12.19 ± 1.54 | 12.41 ± 0.48 | 11.84 ± 1.46 | 12.49 ± 1.41 |
| Post‐PTA | 10.93 ± 1.88 | 11.45 ± 1.78 | 10.97 ± 1.48 | 11.64 ± 1.24 | 11.30 ± 1.72 | 11.66 ± 1.52 | 9.35 ± 0.51 | 7.94 ± 1.46 | 8.16 ± 1.44 | |
| p‐value | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | |
| PFI | Pre‐PFI | 0.99 ± 0.06 | 1.02 ± 0.11 | 0.99 ± 0.09 | 1.06 ± 0.16 | 1.00 ± 0.18 | 1.04 ± 0.12 | 1.06 ± 0.13 | 1.09 ± 0.13 | 1.04 ± 0.10 |
| Post‐PFI | 0.97 ± 0.59 | 0.99 ± 0.11 | 0.95 ± 0.09 | 1.03 ± 0.16 | 0.97 ± 0.20 | 0.98 ± 0.11 | 0.77 ± 0.19 | 0.79 ± 0.17 | 0.66 ± 0.10 | |
| p‐value | 0.029 | 0.046 | 0.001 | 0.014 | <0.001 | 0.046 | <0.001 | <0.001 | <0.001 | |
| WOMAC | Pre‐WOMAC | 79.25 ± 8.18 | 80.36 ± 3.54 | 78.83 ± 9.47 | 77.63 ± 7.52 | 79.24 ± 4.84 | 75.00 ± 8.58 | 77.40 ± 6.80 | 81.75 ± 3.11 | 76.71 ± 7.30 |
| Post‐WOMAC | 25.75 ± 7.70 | 22.07 ± 9.37 | 23.11 ± 10.43 | 22.07 ± 12.37 | 22.3 ± 9.54 | 22.87 ± 6.28 | 43.60 ± 5.19 | 44.75 ± 6.84 | 45.00 ± 6.66 | |
| p‐value | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 | <0.001 |
Abbreviations: BPI, Blackburne–Peel index; CDI, Caton–Deschamps index; ISI, Insall–Salvati index; PH, patellar height; PFI, patellofemoral index; PTA, patellar tilt angle; WOMAC, Western Ontario and McMaster Universities osteoarthritis index.
TABLE 3.
Comparison of changes of PH, PTA, PFI, and WOMAC among groups
| Group A (n = 12) | Group B (n = 14) | Group C (n = 18) | Group D (n = 19) | Group E (n = 21) | Group F (n = 15) | Group G (n = 10) | Group H (n = 8) | Group I (n = 7) | F | p‐value | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| ΔCDI | −0.02 ± 0.03 | −0.02 ± 0.03 | −0.04 ± 0.04 | −0.04 ± 0.03 | −0.04 ± 0.03 | −0.05 ± 0.02 | −0.17 ± 0.04 | −0.19 ± 0.06 | −0.21 ± 0. 05 | 44.80 | <0.001 |
| ΔISI | −0.04 ± 0.04 | −0.03 ± 0.01 | −0.04 ± 0.04 | −0.05 ± 0.03 | −0.04 ± 0.03 | −0.06 ± 0.03 | −0.18 ± 0.03 | −0.18 ± 0.04 | −0.21 ± 0. 03 | 54.76 | <0.001 |
| ΔBPI | −0.03 ± 0.03 | −0.03 ± 0.02 | −0.03 ± 0.03 | −0.04 ± 0.02 | −0.04 ± 0.03 | −0.06 ± 0.02 | −0.16 ± 0.04 | −0.18 ± 0.06 | −0.19 ± 0. 05 | 58.19 | <0.001 |
| ΔPTA (°) | −0.39 ± 0.13 | −0.39 ± 0.10 | −0.44 ± 0.24 | −0.46 ± 0.18 | −0.43 ± 0.26 | −0.53 ± 0.14 | −3.06 ± 0.18 | −3.90 ± 0.16 | −4.33 ± 0. 26 | 719.96 | <0.001 |
| ΔPFI | −0.02 ± 0.03 | −0.03 ± 0.05 | −0.04 ± 0.04 | −0.03 ± 0.05 | −0.03 ± 0.03 | −0.06 ± 0.03 | −0.29 ± 0.10 | −0.30 ± 0.06 | −0.38 ± 0. 05 | 91.02 | <0.001 |
| ΔWOMAC | −53.50 ± 8.96 | −58.29 ± 8.82 | −55.72 ± 9.89 | −54.26 ± 8.44 | −56.90 ± 8.89 | −52.13 ± 9.13 | −33.80 ± 7.89 | −37.00 ± 7.67 | −31.71 ± 4.82 | 15.38 | <0.001 |
Abbreviations: BPI, Blackburne–Peel index; CDI, Caton–Deschamps index; PH, patellar height; ISI, Insall–Salvati index; PFI, patellofemoral index; PTA, patellar tilt angle; WOMAC, Western Ontario and McMaster Universities osteoarthritis index.
TABLE 4.
p‐value of LSD‐t for changes of CDI, ISI, and BPI among groups
| Group A | Group B | Group C | Group D | Group E | Group F | Group G | Group H | |
|---|---|---|---|---|---|---|---|---|
| Group I | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | 0.033/0.081/0.001 | 0.181/0.151/<0.047 |
| Group H | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | 0.441/0.801/0.145 | |
| Group G | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | ||
| Group F | 0.037/0.133/0.058 | 0.075/0.049/0.029 | 0.196/0.189/0.092 | 0.298/0.365/0.174 | 0.328/0.179/0.276 | |||
| Group E | 0.184/0.721/0.306 | 0.333/0.416/0.193 | 0.703/0.987/0.488 | 0.927/0.653/0.748 | ||||
| Group D | 0.220/0.462/0.465 | 0.386/0.231/0.323 | 0.776/0.654/0.714 | |||||
| Group C | 0.335/0.739/0.690 | 0.551/0.439/0.523 | ||||||
| Group B | 0.707/0.699/0.841 |
Note: Each value a/b/c represents the CDI/ISI/BPI value from front to back.
Abbreviations: BPI, Blackburne–Peel index; CDI, Caton–Deschamps index; ISI, Insall–Salvati index; LSD‐t, least significant difference test.
TABLE 5.
p‐value of LSD‐t for changes of PTA, PFI, and WOMAC among groups
| Group A | Group B | Group C | Group D | Group E | Group F | Group G | Group H | |
|---|---|---|---|---|---|---|---|---|
| Group I | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/0.627 | <0.001/<0.001/0.243 |
| Group H | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/0.109/ 0.440 | |
| Group G | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | <0.001/<0.001/<0.001 | ||
| Group F | 0.075/0.035/0.686 | 0.066/0.059/0.059 | 0.199/0.157/0.240 | 0.137/0.069/0.480 | 0.292/0.069/0.107 | |||
| Group E | 0.353/0.574/0.282 | 0.339/0.800/0.646 | 0.770/0.704/0.673 | 0.617/0.968/0.339 | ||||
| Group D | 0.629/0.605/0.812 | 0.626/0.833/0.192 | 0.844/0.682/0.611 | |||||
| Group C | 0.515/0.383/0.494 | 0.507/0.557/0.410 | ||||||
| Group B | 0.988/0.767/0.165 |
Note: Each value a/b/c represents the PTA/PFI/WOMAC value from front to back.
Abbreviations: LSD‐t, least significant difference test; PFI, patellofemoral index; PTA, patellar tilt angle; WOMAC, Western Ontario and McMaster Universities osteoarthritis index.
FIGURE 2.
Postoperative PH changes in different groups. Changes in Caton–Deschamps index (CDI) in different groups after operation (A). Changes of Insall–Salvati index (ISI) in different groups after operation (B). Changes in CDI in different groups after operation (C). The decrease in patellar height (PH) after operation in the last three groups was significantly greater than that in the first six groups.
FIGURE 3.
Postoperative patellofemoral index (PFI), patellar tilt angle, and Western Ontario and McMaster Universities osteoarthritis index score changes in different groups. Changes in PFI in different groups after operation (A). Changes in PTA in different groups after operation (B). Changes in Western Ontario and McMaster Universities osteoarthritis index (WOMAC) score in different groups after operation (C). When ΔHKAA was greater than 12°, the decrease in PFI and PTA increased obviously, but the decrease in WOMAC decreased significantly.
Western Ontario and McMaster Universities Osteoarthritis Index Score
The scores of each group of patients after the operation were significantly improved compared with those before the operation (p < 0.001) (Table 2). There was a significant difference in ΔWOMAC scores of patients among the nine groups (p < 0.001) (Table 3). There was no significant difference between the first six groups, but they were significantly reduced compared with the last three groups (Table 5 and Figure 3).
Complications
Among the 124 patients who completed the follow‐up, one patient experienced redness, swelling, and pain in the surgical incision from the 7th day after surgery, and was diagnosed as an incision infection. After 1 week of intravenous antibiotic treatment, the incision had healed well. No other complications occurred. Fourteen patients complained of obvious pain in the anterior knee area at 3 months after the operation, and the pain was relieved or disappeared spontaneously after functional exercise. Two patients opted for reoperation to remove the plates at 18 months after surgery (Figure 4).
FIGURE 4.
Pain and a decrease in patellar position occurred in a 64‐year‐old woman after undergoing a large corrective angle open‐wedge high tibial osteotomy. Long‐leg full‐weight‐bearing anteroposterior radiographs before surgery showed that this patient had severe medial compartment knee osteoarthritis (A). Long‐leg full‐weight‐bearing anteroposterior radiographs at 1 month after surgery showed that there was no fracture around the osteotomy site, the knee varus was fully corrected. (B). Long‐leg full‐weight‐bearing anteroposterior radiographs at 3 months after surgery showed that the corrected angle was not failured (C). Lateral radiographs of the knee were taken before surgery and 1, 3, and 18 months after surgery, and postoperative imaging showed obvious patellar position decline (D–F).
Discussion
In this study, we found that the patellar position will change after OWHTO, and when the osteotomy correction angle is greater than 12.4°, the patellar position will change significantly, which can lead to postoperative pain.
Because the coronal osteotomy line of biplanar ascending medial OWHTO is located above the tibial tubercle, opening the osteotomy region inevitably results in downward displacement of the patella. Not all patella infera and patellofemoral malalignment causes patellofemoral symptoms in the short term after ascending medial HTO; however, the contact forces in the patellofemoral joint after development of patella infera increase the risk of onset or progression of patellofemoral OA. Descending medial HTO can be considered with the aim of avoiding patella infera, but it is also feasible to choose a safe range of osteotomy angle without changing the original biplanar ascending surgical procedure.
Influence of Different High Tibial Osteotomy Methods on Patellar Position
Besides achieving a suitable spread width when performing proximal tuberosity osteotomy, other procedures as well as the conventional one for keeping the PH stable have been proposed. Gaasbeek et al. reported that distal tuberosity osteotomy prevents postoperative patella infera. 22 , 23 In distal tuberosity osteotomy, the osteotomy site is located under the tibial tuberosity. The resultant avoidance of scarring and consequent shortening of the patellar tendon thus maintains the correct PH, and patella infera does not occur. 24 , 25 Compared with proximal tuberosity osteotomy, the second osteotomy line, which is perpendicular to the OWHTO line, is associated with more difficult technical conditions, risks, and limitations. Additionally, the pitfalls are more complex and the surgeon should carefully design the plan bdfore the oparation. 26 In 2019, Akiyama et al. proposed a modified open‐wedge distal tuberosity tibial osteotomy procedure for minimizing the reduction of PH. 27 Through setting an arc osteotomy around the hinge, this technique both increases the bone‐to‐bone contact of the distal osteotomy surface and provides cortical support at the first osteotomy site, which can provide extra support for weight‐bearing stress. The methods above incorporate a distal tuberosity osteotomy to avoid patellofemoral complications related to postoperative patella infera; however, because these procedures are relatively complex, they are not widely performed.
Various surgical strategies incorporating a conventional proximal tuberosity osteotomy procedure with modifications of the procedure itself, cutting‐guides, and other special osteotomies continue to be proposed. In 2017, Schröter et al. reported a new PH index for evaluating the influence of OWHTO on the tibial slope and PH; they found no change in PH following OWHTO using the new index. 28 In addition, Micicoi et al. performed a single‐center retrospective study that included 129 patients and reported unchanged tibial slope and PH after use of patient‐specific cutting guides. Zhang et al. modified the uniplanar MOWHTO technique by using a novel wedge‐shaped spacer implant. 29 Use of this implant decreases the posterior tibial slope, maintaining the correct patellar position. Because the osteotomy line is above the tibial tuberosity, postoperative patella infera seems inevitable after OWHTO. Over longer periods, the resultant increase in patellofemoral cartilage pressure can lead to cartilage deterioration. However, in some retrospective studies, no changes in the condition of the patellofemoral cartilage and clinical scores were found after OWHTO. 30 , 31 Sang et al. reported that the patellofemoral joint, including the condition of the cartilage and clinical scores, did not change after OWHTO. 32 Within a certain range of degree of correction, the ligamentum patellae can adapt to the changes in patella baja by lengthening.
Cause Analysis of Patella Position Change
For patients with osteotomy correction angle greater than or equal to 13°, we believed that the significant patellar position decline might be related to the time of landing and the amount of activity after surgery. Because of the large osteotomy angle, these patients might have obvious pain or discomfort after surgery, which prolongs their time to bear load after surgery and limits their amount of activity. Inadequate early postoperative rehabilitation exercise might lead to patellar ligament fibrosis and scar formation and ultimately lead to a significant decline in patellar position and pain.
Limitations and Clinical Significance
The current study had some limitations. First, the retrospective design and relatively small number of patients are major problems. Large prospective studies utilizing a variety of radiological evaluation methods are required. Moreover, the relative short follow‐up time has limited ability to assess longer‐term changes in patellar position or symptoms. Symptomatic patellofemoral OA needs to be monitored long‐term through consistent follow‐up. Despite these limitations, to the best of our knowledge, this is the first study to determine a safe range of degree of osteotomy correction, providing a reference for orthopaedic doctors when choosing the surgical method, avoiding postoperative patella infera and patellofemoral pain.
Conclusion
With increasing osteotomy angles, the PH and patellofemoral index change significantly. However, within the range of 12.4° of osteotomy, we found no significant differences in any of the assessed patellar indexes. The cut‐off points for the correction angle are 12.5° to 13.4°. When the correction angle is larger than this range, the patellar position can be significantly affected. Postoperative patellofemoral joint pain might be related to the changes in patella position. The results of this study might provide a useful reference for intraoperative management and indications for osteotomy.
Author Contributions
YZ and TBY proposed the research idea. RJC, CHY, and HNP collected and analyzed the data. RJC wrote the first draft of the manuscript. JLC and YZ performed the all operations. YZ and TBY made constructive amendments to the manuscript. All authors agree to the final manuscript.
Conflict of Interest Statement
There is no conflict of interest between the authors.
Ethics Statement
The Ethics Committee of the Affiliated Hospital of Qingdao University approved the study (QYFYWZLL27523).
Acknowledgments
We thank Dr. Trish Reynolds from Liwen Bianji (Edanz) (http://www.liwenbianji.cn/), for editing the English text of a draft of this manuscript. This study was supported by the National Natural Science Foundation of China (No. 31802022).
Contributor Information
Renjie Chen, Email: crj9710@163.com.
Yi Zhang, Email: zhangsports2021@sina.com.
Data Availability Statement
The datasets for 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 for the current study are available from the corresponding author on reasonable request.