Patellofemoral Cartilage Degeneration After Closed- and Open-Wedge High Tibial Osteotomy With Large Alignment Correction

Abstract

Background:

Previous studies have reported patellofemoral cartilage degeneration and analyzed the factors affecting degeneration after open-wedge high tibial osteotomy (OWHTO). However, no studies have evaluated patellofemoral cartilage degeneration or examined the factors affecting degeneration after closed-wedge high tibial osteotomy (CWHTO).

Purpose:

To investigate and compare patellofemoral cartilage degeneration after CWHTO and OWHTO via arthroscopic evaluation and to analyze the factors affecting the degeneration.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A total of 54 CWHTOs and 50 OWHTOs were performed with first-look arthroscopy between 2013 and 2017 at one institution. Hardware removal and second-look arthroscopy were performed, on average, 30.2 months after CWHTO and 26.8 months after OWHTO (P = .178). Patient characteristics did not differ significantly between the groups. Radiographically, the mechanical axis, posterior tibial slope, and modified Blackburne-Peel ratio were evaluated. Arthroscopically, the percentage of patient with patellofemoral cartilage degeneration was evaluated according to the International Cartilage Repair Society grading system. Logistic regression analysis was used to identify the factors affecting patellofemoral cartilage degeneration in terms of demographics and the change of mechanical axis (correction angle), tibial posterior slope angle, and modified Blackburne-Peel ratio. The Anterior Knee Pain Scale was used for clinical comparison between the patellofemoral degenerative and nondegenerative groups.

Results:

No significant differences were observed in pre- and postoperative radiographic results between the CWHTO and OWHTO groups, except that the postoperative modified Blackburne-Peel ratio was significantly smaller among the OWHTOs. The percentage of patients with patellofemoral cartilage degeneration were 29.6% in the CWHTO group and 44% in the OWHTO group (P = .156) at second-look arthroscopy. The correction angle was the only significant factor affecting cartilage degeneration in the CWHTO group (odds ratio, 2.324; P = .013; cutoff value, 9.6°) and the OWHTO group (odds ratio, 1.440; P = .041; cutoff value, 10.1°). The postoperative Anterior Knee Pain Scale score was significantly lower in the patellofemoral degenerative group as compared with the nondegenerative group among the OWHTO group (81.6 vs 76.4; P = .039); among the CWHTO group, there was a lower tendency in the degenerative group, but this was without significance (81.1 vs 79.6; P = .367).

Conclusion:

Patellofemoral cartilage degeneration progressed after CWHTO and OWHTO with large alignment correction. High tibial osteotomy should be selected with careful consideration of the osteoarthritic status of the patellofemoral joint and required correction angle, regardless of applying a closed- or open-wedge technique.

Keywords

knee patellofemoral osteotomy open-wedge closed-wedge degeneration

High tibial osteotomy (HTO) has been accepted as an appropriate treatment option for medial compartmental arthritis with varus deformity in young active patients.¹² Satisfactory long-term results after HTO have been well-documented.^1,11 Various approaches for HTO have been introduced; among them, closed- and open-wedge HTO (CWHTO and OWHTO) are 2 of the most frequently applied techniques.²⁵ OWHTO has recently become more popular as a result of innovations in lower-profile plates and fixation techniques alongside the ease of adjustment of the correction angle during the operation.³ However, CWHTO is still used widely and recommended rather than OWHTO in several clinical situations, such as insufficient anterior cruciate ligament, patella baja, steep tibial posterior slope angle, poor bone quality, or heavy smoking history.^16,19,20

A possible negative effect on the patellofemoral joint has been an established concern when OWHTO is performed. Biomechanical studies have suggested that OWHTO can alter patellofemoral congruency and elevate patellofemoral joint pressure by lowering the patella.^9,22 Arthroscopic studies have directly revealed patellofemoral cartilage degeneration after OWHTO.^6,10,26 Factors affecting such patellofemoral cartilage degeneration after OWHTO have been analyzed.^14,23,26

In contrast, few studies have addressed patellofemoral cartilage status after CWHTO. Although several biomechanical and radiographic analyses evaluated patellofemoral contact pressure or tracking,^5,8,22 no studies have evaluated patellofemoral cartilage degeneration after CWHTO or compared the degeneration between patients undergoing CWHTO and OWHTO with arthroscopic evaluation. Furthermore, no studies have investigated the factors affecting patellofemoral cartilage degeneration after CWHTO.

The purpose of our study was to evaluate and compare patellofemoral cartilage degeneration after CWHTO and OWHTO with arthroscopic evaluation. It was hypothesized that patellofemoral cartilage degeneration occurs less frequently in patients undergoing CWHTO. The other purpose of this study was to analyze factors affecting patellofemoral cartilage degeneration, where it was hypothesized that coronal or sagittal alignment alterations of the patellofemoral joint affect the cartilage degeneration.

Methods

Patients

Using our hospital database, we retrospectively searched for patients who underwent index CWHTO or OWHTO with first-look arthroscopy and hardware removal with second-look arthroscopy. The inclusion criteria were (1) patients who underwent appropriate arthroscopic observation of the patellofemoral joint during first- and second-look arthroscopy, (2) patients whose appropriate arthroscopic images of the patellofemoral joint captured during first- and second-look arthroscopy were saved in our database, and (3) patients with available appropriate pre- and postoperative radiographs. The exclusion criteria were (1) a history of trauma, infection, or previous surgery on the affected knee; (2) instability of the affected knee owing to any ligament problem; or (3) a concurrent cartilage procedure on the patellofemoral joint during HTO.

According to the criteria, 54 CWHTOs and 50 OWHTOs performed between 2013 and 2017 were included. The surgical indications for CWHTO and OWHTO were same: (1) symptomatic medial compartment osteoarthritis (Kellgren-Lawrence grades 2 and 3); (2) varus deformity from 5° to 15°; (3) flexion contracture <15° and flexion angle >90°; (3) absence of symptomatic lateral compartmental and patellofemoral arthritis, active infection, inflammatory arthritis, and lateral tibial subluxation >1 cm; and (4) International Cartilage Repair Society (ICRS) grade ≤3 for patellofemoral cartilage on preoperative magnetic resonance imaging.

There was no significant difference in patient characteristics, range of motion, varus deformity, tibial posterior slope angle (PSA), or patellar height between the groups preoperatively (Table 1). Informed consent was obtained from all patients before the review, and this study was approved by the institutional review board of our hospital.

Table 1

Patient Characteristics^a

	Closed-Wedge HTO	Open-Wedge HTO	P Value
Operation period	Oct 2013–Dec 2017	Jul 2013–Dec 2017
Knees	54	50
Age, y	57.7 ± 6.1	56.1 ± 9.5	.305
Female:male	46:8	44:6	.778
Right:left	26:28	32:18	.118
Body mass index, kg/m²	25.9 ± 2.7	26.8 ± 3.8	.146
Period from index HTO to hardware removal, mo	30.2 (21-37)	26.8 (20-39)	.178

Data are presented as No. or mean ± SD (range). HTO, high tibial osteotomy.

Surgical Technique and Rehabilitation

Two senior surgeons (S.J.S., K.H.Y.) performed each procedure according to their preferences; specifically, one surgeon (S.J.S.) performed all CWHTOs and the other (K.H.Y.) did all OWHTOs. Both surgeons used the same indications and surgical principles for HTO and had similar surgical experiences, having performed >50 procedures of each type before the study period.¹³ Anteroposterior long-leg weightbearing radiography was used for preoperative planning with the Miniaci method.¹⁷ The postoperative mechanical axis and percentage of the mechanical axis were targeted to be valgus 3° and 62% in both groups.⁴ Concomitant first-look arthroscopy was performed before osteotomy to evaluate the cartilage, menisci, and ligaments of the knee joint. Additional arthroscopic procedures were performed when necessary, including cartilage debridement in the medial tibiofemoral compartment, partial meniscectomy for the medial meniscus, plica excision, and loose body removal (Table 2). The frequency of the additional procedures was not significantly different between CWHTO and OWHTO. No additional procedures were performed in the patellofemoral joint.

Table 2

Additional Arthroscopic Procedures During HTO^a

	Closed-Wedge HTO	Open-Wedge HTO	P Value
Cartilage debridement in the medial tibiofemoral compartment	50 (92.6)	47 (94)	≥.999
Partial meniscectomy for the medial meniscus	37 (68.5)	33 (66)	.836
Plica excision	5 (9.3)	2 (4)	.439
Loose body removal	1 (1.9)	2 (4)	.607

Data are presented as No. (%). HTO, high tibial osteotomy.

In the CWHTO group, the surgical incision was made transversely on the anterolateral side of the proximal tibia. Thereafter, the tibialis anterior muscle was dissected. A partial resection of the fibular head was conducted to avoid a fibular tethering effect on the wedge closing. One pin was inserted in the proximal plane of the tibial osteotomy 1.5 cm below the joint line, and another was placed in the distal plane under fluoroscopic guidance to determine the alignment correction, with wedge size based on the preoperative radiographic planning. Finally, the wedge was removed, and the osteotomy site was carefully closed. A miniplate staple (U&I Co) was used as a fixative hardware.

In the OWHTO group, a vertical incision was made on the anteromedial side of the proximal tibia. The pes anserinus and superficial fibers of the medial collateral ligament were released to expose the bone. Two guide pins were inserted obliquely, aimed toward a point just proximal to the tibiofibular joint. The initial osteotomy was performed according to these guide pins with an oscillating saw and chisels. A biplanar cut of a separate ascending osteotomy was made posterior to the tibial tuberosity. The osteotomy site was opened with an opener until the aimed alignment was reached, and it was maintained with a spreader. A medial locking anatomic plate (Cellumed) was used for fixation.

Osteotomy level was proximal to the tibial tuberosity in CWHTO and OWHTO procedures. Care was taken to minimize changes to the PSA.²¹ Alignment was confirmed intraoperatively with a cable or a long metal rod in both procedures.

A similar rehabilitation protocol was used for all patients: isometric exercises were recommended on the day of operation; straight leg raising exercises were started 3 days postoperatively, partial weightbearing was begun 3 to 7 days postoperatively, and full weightbearing without crutches was started at 6 to 12 weeks after surgery based on the patient’s condition.

Once the bone union at the osteotomy site was confirmed by radiography, hardware removal and second-look arthroscopy were recommended at 2 years after HTO. The interval from HTO to hardware removal was not different between the groups (P = .178) (Table 1).

Arthroscopic Evaluation

The cartilage status of the patellofemoral joint, including the patella and femoral trochlea, was evaluated via first- and second-look arthroscopy. The ICRS grading system was used to quantify the evaluation results. A primary evaluation was conducted by the senior surgeons during the operation, and the determined grade was recorded in our database. Additionally, an author with >5 years of arthroscopic surgical experience (C.H.P.) retrospectively evaluated the cartilage status of the patellofemoral joint using arthroscopic images saved in the database. Interobserver agreement between the surgeons and retrospective reviewer for determining ICRS grading was checked via the Cohen kappa coefficient. All kappa coefficients for OWHTOs and CWHTOs were >0.8. Thus, the ICRS grades determined by the senior surgeons were used for the study.

Second-look arthroscopic grading results were compared with those of first-look arthroscopic grading. Patellofemoral cartilage degeneration was determined when ≥1 ICRS grade progression on the patella or femoral trochlea was observed.

Clinical Evaluation

The Western Ontario and McMaster Universities Arthritis Index (WOMAC), range of motion, and Anterior Knee Pain Scale (Kujala score) were evaluated.

Radiographic Evaluation

Radiographic parameters were elucidated from radiographs taken before HTO and at the time of hardware removal. Long-leg and lateral radiographs were obtained in full knee extension under weightbearing conditions.

The mechanical axis was measured on long-leg radiographs and was defined as the angle between the femoral and tibial mechanical axes.¹⁸ The correction angle was defined as the difference between pre- and postoperative mechanical axes.¹⁸

Lateral knee radiographs were used to assess the PSA and modified Blackburne-Peel (mBP) ratio. The PSA was measured with the angle formed by a line perpendicular to the reference line and the medial tibial plateau.¹⁸ The tibial intramedullary reference line of the PSA was defined as the line connecting the center of the medullary canal 10 and 20 cm distal to the tibial plateau. The change in the PSA was defined as the postoperative minus preoperative PSA, with a larger value indicating an increase in the PSA. The mBP ratio was defined as the perpendicular distance from the lower margin of the patellar articular surface to the tibial plateau line divided by the length of the patellar articular surface (normal range, 0.5-0.9).⁶ The change in mBP ratio was defined as the post- minus preoperative mBP ratio, with a negative value indicating a decrease in patellar height.

The quality of radiographic evaluations was improved by the radiographic protocol of standardizing the position of the knee and creating an identical distance between the x-ray beam and cassette.¹⁸ The images were transferred digitally to a picture archiving and communication system (Infinitt) and then manipulated for radiographic measurement. Assessments were performed on a 61-cm (24-in) monitor (SyncMaster 249HM; Samsung) in portrait mode with picture archiving and communication system software. The minimum difference that the software could detect was 0.1°.

Two orthopaedic fellows who did not participate in the surgery measured all of the radiographic parameters to reduce observation bias. The interobserver reliability of the measurements was assessed with an intraclass correlation coefficient. The intraclass correlation coefficients for all measurements were >0.8, and the mean values were used for the study.

Statistical Analysis

The pre- and postoperative clinical and radiographic results were compared with a paired t test. The clinical and radiographic results between the CWHTO and OWHTO groups were compared with an independent t test. The arthroscopic cartilage status presented by ICRS grade was compared between first- and second-look arthroscopy with the Wilcoxon signed rank test. The percentage of patients with patellofemoral cartilage degeneration was compared between the groups with the chi-square or Fisher exact test. A logistic regression analysis was used to evaluate the effect of age, sex, body mass index, correction angle, change in PSA, and change in mBP ratio.^{9,14,22,23,26} A point biserial correlation analysis was used to confirm the correlation between the identified factors in logistic regression and the patellofemoral cartilage degeneration. A receiver operating characteristic curve was used to obtain the cutoff value for the identified factor associated with the degeneration. To verify the cutoff value, the proportion of patellofemoral cartilage degeneration was compared between the groups above and below the cutoff value (high- and low-risk groups, respectively). The Anterior Knee Pain Scale was compared between groups with and without patellofemoral cartilage degeneration via an independent t test; the scales of the groups were normally distributed (Kolmogorov-Smirnov test; P > .05). Statistical analyses were performed with SPSS (v 18.0; IBM Corp), and a P value <.05 was considered statistically significant.

Post hoc power analysis with significance levels set to an alpha of .05 was performed to determine whether the sample had sufficient power to detect significant differences. A power level >80% was considered sufficient, and all of the variables that were significantly different met this criterion. Thus, we determined that our study was adequately powered.

Results

Clinical Results

WOMAC, range of motion, and Anterior Knee Pain Scale results improved postoperatively in the CWHTO and OWHTO groups (P < .001). There were no significant differences in pre- and postoperative clinical results between the groups (Table 3).

Table 3

Clinical and Radiographic Results^a

	Closed-Wedge HTO	Open-Wedge HTO	P Value
WOMAC
Preoperative	59.0 ± 6.0	60.1 ± 5.4	.117
Postoperative	19.4 ± 3.2	20.3 ± 4.1	.227
Range of motion, deg
Preoperative	125.1 ± 36.9	123.2 ± 45.4	.819
Postoperative	132.4 ± 4.5	132.2 ± 8.3	.896
Anterior Knee Pain Scale
Preoperative	67.6 ± 6.5	65.6 ± 10.6	.229
Postoperative	80.0 ± 7.5	78.7 ± 9.6	.441
Mechanical axis, deg
Preoperative, varus	8.2 ± 2.2	7.9 ± 5.0	.612
Postoperative, valgus	3.2 ± 2.3	3.6 ± 4.4	.556
Correction angle	11.4 ± 1.8	11.4 ± 3.3	.964
Posterior tibial slope angle
Preoperative	11.1 ± 3.2	11.6 ± 2.1	.341
Postoperative	10.6 ± 4.0	12.1 ± 4.8	.083
Change	−0.5 ± 3.9	0.5 ± 5.0	.255
Modified Blackburne-Peel ratio
Preoperative	0.79 ± 0.21	0.79 ± 0.14	.993
Postoperative	0.73 ± 0.17	0.61 ± 0.11	<.001
Change	−0.06 ± 0.17	−0.18 ± 0.15	<.001

Data are presented as mean ± SD. HTO, high tibial osteotomy; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index.

Radiographic Results

There were no significant differences in terms of pre- and postoperative mechanical axis and PSA between the groups (Table 3). Changes in mechanical axis (correction angle) and PSA were also similar. The postoperative mBP ratio was significantly smaller in the OWHTO group, despite there being similar preoperative values between the groups. The lowering of the patellar height after OWHTO was significantly greater than that after CWHTO.

Arthroscopic Results

As compared with first-look arthroscopic ICRS grading, second-look ICRS grading of the patellofemoral cartilage was changed in the CWHTO group (for patella and femur, P = .013 and .001, respectively) and the OWHTO group (for patella and femur, P = .001 and P < .001) (Table 4).

Table 4

Change in ICRS Grade in Patellofemoral Cartilage After HTO^a

	ICRS Grade (0:1:2:3:4)
	Closed-Wedge HTO	Open-Wedge HTO
Patella
Preoperative	10:26:12:6:0	6:16:18:10:0
Postoperative	10:20:12:11:1	4:10:17:16:3
Cases that progressed	8 (14.8)	12 (24)
Femur
Preoperative	4:22:10:18:0	6:14:18:12:0
Postoperative	4:12:10:26:2	4:6:12:23:5
Cases that progressed	12 (22.2)	20 (40)

Values are presented as No. (%). HTO, high tibial osteotomy; ICRS, International Cartilage Repair Society.

The percentage of patients with patellofemoral cartilage degeneration were 29.6% (16/54) in the CWHTO group and 44% (n = 22/50) in the OWHTO group (P = .156). Separately, the proportions of cartilage degeneration in the patella were 14.8% (8/54) in the CWHTO group and 24% (12/50) in the OWHTO group (P = .320). Finally, those in the femoral trochlea were 22.2% (12/54) ad 40% (20/50) in the CWHTO groups and OWHTO groups, respectively (P = .058) (Table 4).

Factors Affecting Patellofemoral Cartilage Deterioration

Correction angle was the only significant factor affecting patellofemoral cartilage degeneration in the CWHTO group (odds ratio, 2.324; P = .013; Nagelkerke R² = 0.544; P value for regression model, <.001) and OWHTO group (odds ratio, 1.440; P = .041; Nagelkerke R² = 0.564; P value for regression model, <.001) (Table 5). Point biserial analysis also confirmed the correlation between correction angle and degeneration in the CWHTO (r = 0.465; P < .001) and OWHTO groups (r = 0.442; P = .001).

Table 5

Analysis of Factors Affecting Patellofemoral Cartilage Degeneration^a

	Closed-Wedge HTO		Open-Wedge HTO
	Odds Ratio	P Value	Odds Ratio	P Value
Age	1.091	.251	0.847	.150
Sex	0.000	.999	0.763	.798
BMI	1.201	.256	1.152	.373
Correction angle	2.324	.013	1.440	.041
Change of PSA	1.275	.078	0.804	.154
Change of mBP ratio	3.551	.597	4.282	.116

The 95% CI of the odds ratio for the correction angle in closed-wedge HTO was 1.197 to 4.510; in open-wedge HTO, 1.016 to 2.042. BMI, body mass index; HTO, high tibial osteotomy; mBP, modified Blackburne-Peel; PSA, tibial posterior slope angle.

In the receiver operating characteristic curve, the cutoff value for correction angle associated with the patellofemoral cartilage degeneration was 9.6° in the CWHTO group (are a under the curve [AUC] = 0.808) and 10.1° in the OWHTO group (AUC = 0.801) (Figure 1). The percentage of patients with patellofemoral cartilage degeneration was significantly higher in the high-risk group (with a correction angle ≥10°) as compared with the low-risk group in both the CWHTO and OWHTO groups (Table 6).

Table 6

Percentage of Patients With Patellofemoral Cartilage Deterioration in the High- and Low-Risk Groups^a

HTO	Low-Risk Group^b	High-Risk Group^c	P Value
Closed wedge (n = 54)	6/34 (17.6)	10/20 (50)	.016
Open wedge (n = 50)	4/22 (18.2)	18/28 (64.3)	.002

Data are presented as the total number of cases with patellofemoral cartilage deterioration / number of cases in the high- or low-risk group. HTO, high tibial osteotomy.

Correction angle <10°.

Correction angle ≥10°.

Anterior Knee Pain Scale Between Groups With Patellofemoral Degeneration and Nondegeneration

Anterior Knee Pain Scale scores did not differ preoperatively between the degenerative and nondegenerative cases: total (mean [SD]: 65.7 [9.3] vs 67.8 [7.7]; P = .308), OWHTO group (67.1 [7.1] vs 68.9 [4.9]; P = .366), and CWHTO group (67.1 [7.1] vs 68.9 [4.9]; P = .399).

The score was significantly lower postoperatively in the degenerative group among total cases (mean [SD]: 81.4 [4.6] vs 78.2 [9.9]; P = .028) and OWHTOs (81.6 [4.9] vs 76.4 [11.6]; P = .039). The postoperative scale of the degenerative group was also lower in the CWHTO group, but there was no significance (81.1 [4.1] vs 79.6 [8.5]; P = .367).

Discussion

The most important finding of the present study was that there was comparable patellofemoral cartilage degeneration on arthroscopic evaluation after CWHTO and OWHTO, although the degeneration tended to occur more frequently after the latter. A correction angle >10° was associated with patellofemoral cartilage degeneration after both CWHTO and OWHTO.

Many previous studies reported a degenerative change in patellofemoral cartilage after OWHTO.^{6,10,14,23,26} Of these, when we consider the research from second-look arthroscopy performed at a time similar to ours (approximately 2 years after HTO), cartilage degeneration was observed in 23.7% of patellae and 39.3% of trochleae in the study by Yoon et al,²⁶ 25% of patellae and 42% of trochleae in the study by Kim et al,¹⁰ and 30% of either patellae or trochleae in the study by Lee et al.¹⁴ Our study showed cartilage degeneration in 44% of either patellae or trochleae (ie, 24% of patellae and 40% of trochleae) at approximately 2 years after OWHTO, seemingly consistent with previous studies.

Favorable results in the patellofemoral joint after CWHTO were suggested in several biomechanical and radiographic analyses. Stoffel et al²² reported that CWHTO did not significantly influence patellofemoral contact pressure at any flexion angle, while OWHTO increased contact pressure relative to that observed in the intact knee. A biomechanical study demonstrated that changes in patellar tracking parameters were more pronounced after OWHTO than CWHTO.⁵ In a radiographic analysis, Ishimatsu et al⁸ found that hybrid CWHTO led to more favorable outcomes in patellofemoral congruity when compared with OWHTO, despite there being more severe preoperative patellofemoral osteoarthritis in the hybrid CWHTO group. These studies implicated the lowering of patellar height owing to the distalization of the tibial tuberosity as an important cause of poor patellofemoral results, especially after OWHTO, and recommended CWHTO as a better treatment option in patients with patellofemoral problems.^5,8,22

On the basis of these studies, we expected significantly better results concerning patellofemoral cartilage degeneration after CWHTO than OWHTO. However, the results were different from our expectation, despite the more significant reduction in patellar height seen after OWHTO.

Previous studies with OWHTO demonstrated that postoperative alignment and change in alignment are factors affecting patellofemoral cartilage degeneration. Lee et al¹⁴ suggested that postoperative mechanical axis, which might be related to overcorrection, is correlated with patellofemoral cartilage degeneration. Yoon et al²⁶ found that a postoperative mechanical axis >62% (62.1% for femoral trochleae and 62.2% for patellae) was the only risk factor for degeneration. Tanaka et al²³ reported that patellofemoral cartilage injury tended to progress after OWHTO in patients with a medial gap opening >13 mm or a change in medial proximal tibial angle >9°. These studies postulated that the reported factors increase the Q-angle, aggravating patellofemoral cartilage degeneration.

In the present study, a correction angle >10° was the only risk factor for patellofemoral cartilage degeneration in the CWHTO and OWHTO groups. Therefore, patellofemoral cartilage degeneration should be a concern after not only OWHTO but also CWHTO, especially when a large correction is expected.

Interestingly, change in patellar height was not a factor found to affect patellofemoral cartilage degeneration in our study. This outcome is not consistent with the results of other biomechanical research in which a decrease in patellar height was related to an increase in patellofemoral contact pressure.^5,9,22 However, previous arthroscopic studies involving OWHTO showed that patellar height was not a risk factor for cartilage degeneration, which was in line with our results.^14,26 It is thought that patellar height might not need to be excessively changed to induce patellofemoral cartilage degeneration.⁶ Lee et al¹⁵ reported that the absolute decrease in patellar height after OWHTO was relatively lower when compared with the decrease after total knee arthroplasty.

Although several radiographic studies reported that patellofemoral alignment did not affect clinical outcomes,^6,15 recent arthroscopic studies have demonstrated that patellofemoral cartilage status is associated with clinical results. Kim et al¹⁰ reported that postoperative anterior knee pain was related to the ICRS grade of the patellofemoral joint in second-look arthroscopy. Yoon et al²⁶ found that functional clinical scores were significantly worse in patients with alignment-overcorrected OWHTO, which also resulted in a significantly higher incidence of patellofemoral degeneration. Likewise, our study found a significantly lower Anterior Knee Pain Scale score for the group with patellofemoral cartilage degeneration among total cases and OWHTOs. The score in the CWHTO group also tended to be lower in the degenerative group, with no significant difference.

To date, the CWHTO technique is preferred when HTO is performed in patients with patellofemoral problems. However, surgeons should recognize that patellofemoral cartilage can deteriorate after both CWHTO and OWHTO when a large correction angle is required. The possibility of patellofemoral degeneration needs to be mentioned to patients preoperatively when a correction angle >10° is expected. The surgical indication also should be decided by referring to the cartilage status of the patellofemoral joint in patients undergoing CWHTO and OWHTO.

There were several limitations in the present study. First, the sample size was relatively small. Although there was no statistical significance, the percentage of patients with patellofemoral cartilage degeneration tended to be higher in the OWHTO group. If the sample size was larger, the interpretation of our results may have changed. Second, the study presented short-term results based on the time of hardware removal. Longer-term follow-up review will be required to clarify the fate of the patellofemoral joint after HTO. Third, the design of the study was retrospective. In addition, there was no randomization in group assignment, which could have caused selection bias. Although there were no significant differences in patient characteristics or preoperative status between the OWHTO and CWHTO groups, a prospective randomized study with a more elaborate design would provide more robust data. Fourth, there was no control group with similar characteristics that did not undergo HTO, which would have shown the natural progression of the patellofemoral joint over the same follow-up period. Using magnetic resonance imaging, Wijayaratne et al²⁴ showed that patellar cartilage loss occurred naturally over 2 years even among healthy middle-aged women. However, it would be inappropriate to perform 2-stage arthroscopy in healthy humans to check the natural progression of the patellofemoral joint. Furthermore, the degree of alignment correction attributed to HTO was clearly related to patellofemoral degeneration in our study. Fifth, the ICRS grading system was used to evaluate patellofemoral cartilage, which is based solely on cartilage lesion depth and does not account for lesion size. A grading system with criteria for lesion size was not used because the surface area could not be evaluated on retrospective review of medical records and saved arthroscopic images. However, the size of cartilage lesions tends to increase as the ICRS grade of the lesion progresses in the patellofemoral joint.^2,7 Accordingly, it is reasonable to evaluate the overall degeneration of patellofemoral cartilage based on ICRS grade. In addition, the use of the ICRS grading system can be advantageous when comparing our results with previous literature employing the ICRS system for evaluating patellofemoral cartilage after HTO.^6,10,26 Sixth, the 2 techniques were performed by different surgeons, which introduces the possibility of performance bias, although both surgeons used the same indications and surgical principles and had similar surgical experience with HTO. Last, most patients in the present study were female with an Asian lifestyle; this needs to be considered when extrapolating our findings to other populations.

In conclusion, patellofemoral cartilage degeneration progressed after CWHTO and OWHTO with large alignment correction. HTO should be selected with careful consideration of the osteoarthritic status of the patellofemoral joint and required correction angle, regardless of applying a CWHTO or OWHTO technique.

Footnotes

Acknowledgements

The authors thank Se Gu Kang and Jong Hwan Lee for their help in measuring the radiographic parameters.

Submitted January 22, 2020; accepted May 16, 2020.

The authors declared that they have no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

References

Aglietti

Buzzi

Vena

Baldini

Mondaini

. High tibial valgus osteotomy for medial gonarthrosis: a 10- to 21-year study. J Knee Surg. 2003;16(1):21-26.

Aroen

Loken

Heir

, et al. Articular cartilage lesions in 993 consecutive knee arthroscopies. Am J Sports Med. 2004;32(1):211-215.

Cho

Song

Rhyu

Jang

Park

. Clinical and radiologic results after open-wedge high tibial osteotomy in haemophilic knee arthropathy with varus deformity. Haemophilia. 2018;24(5):792-799.

Fujisawa

Masuhara

Shiomi

. The effect of high tibial osteotomy on osteoarthritis of the knee: an arthroscopic study of 54 knee joints. Orthop Clin North Am. 1979;10(3):585-608.

Gaasbeek

Welsing

Barink

Verdonschot

van Kampen

. The influence of open and closed high tibial osteotomy on dynamic patellar tracking: a biomechanical study. Knee Surg Sports Traumatol Arthrosc. 2007;15(8):978-984.

Goshima

Sawaguchi

Shigemoto

Iwai

Nakanishi

Ueoka

. Patellofemoral osteoarthritis progression and alignment changes after open-wedge high tibial osteotomy do not affect clinical outcomes at mid-term follow-up. Arthroscopy. 2017;33(10):1832-1839.

Gudas

Siupsinskas

Gudaite

, et al. The patello-femoral joint degeneration and the shape of the patella in the population needing an arthroscopic procedure. Medicina (Kaunas). 2018;54(2):21.

Ishimatsu

Takeuchi

Ishikawa

, et al. Hybrid closed wedge high tibial osteotomy improves patellofemoral joint congruity compared with open wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc. 2019;27(4):1299-1309.

Javidan

Adamson

Miller

, et al. The effect of medial opening wedge proximal tibial osteotomy on patellofemoral contact. Am J Sports Med. 2013;41(1):80-86.

10.

Kim

Song

Lee

Bae

. Medial open-wedge high tibial osteotomy may adversely affect the patellofemoral joint. Arthroscopy. 2017;33(4):811-816.

11.

Koshino

Yoshida

Ara

Saito

. Fifteen to twenty-eight years’ follow-up results of high tibial valgus osteotomy for osteoarthritic knee. Knee. 2004;11(6):439-444.

12.

Kyung

. High tibial osteotomy for medial knee osteoarthritis. Knee Surg Relat Res. 2016;28(4):253-254.

13.

Lee

Kim

Ham

Yun

Kim

. The learning curve for biplane medial open wedge high tibial osteotomy in 100 consecutive cases assessed using the cumulative summation method. Knee Surg Relat Res. 2018;30(4):303-310.

14.

Lee

Jung

Kim

Lee

Wang

. Predictive factors for patellofemoral degenerative progression after opening-wedge high tibial osteotomy. Arthroscopy. 2019;35(6):1703-1710.

15.

Lee

Kwon

Lee

. Changes in patellofemoral alignment do not cause clinical impact after open-wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc. 2016;24(1):129-133.

16.

Marcheggiani Muccioli

Fratini

Cammisa

, et al. Lateral closing wedge high tibial osteotomy for medial compartment arthrosis or overload. Clin Sports Med. 2019;38(3):375-386.

17.

Miniaci

Ballmer

Jakob

. Proximal tibial osteotomy: a new fixation device. Clin Orthop Relat Res. 1989;246:250-259.

18.

Park

Bae

Kim

Lee

Song

. Serial changes in the joint space width and joint line convergence angle after closed-wedge high tibial osteotomy. Am J Sports Med. 2017;45(14):3254-3261.

19.

Portner

. High tibial valgus osteotomy: closing, opening or combined? Patellar height as a determining factor. Clin Orthop Relat Res. 2014;472(11):3432-3440.

20.

Ranawat

Nwachukwu

Pearle

Zuiderbaan

Weeks

Khamaisy

. Comparison of lateral closing-wedge versus medial opening-wedge high tibial osteotomy on knee joint alignment and kinematics in the ACL-deficient knee. Am J Sports Med. 2016;44(12):3103-3110.

21.

Song

Bae

. Computer-assisted navigation in high tibial osteotomy. Clin Orthop Surg. 2016;8(4):349-357.

22.

Stoffel

Willers

Korshid

Kuster

. Patellofemoral contact pressure following high tibial osteotomy: a cadaveric study. Knee Surg Sports Traumatol Arthrosc. 2007;15(9):1094-1100.

23.

Tanaka

Matsushita

Miyaji

, et al. Deterioration of patellofemoral cartilage status after medial open-wedge high tibial osteotomy. Knee Surg Sports Traumatol Arthrosc. 2019;27(4):1347-1354.

24.

Wijayaratne

Teichtahl

Wluka

, et al. The determinants of change in patella cartilage volume—a cohort study of healthy middle-aged women. Rheumatology (Oxford). 2008;47(9):1426-1429.

25.

Lin

Jin

Cai

Gao

. Comparison of clinical and radiological outcomes between opening-wedge and closing-wedge high tibial osteotomy: a comprehensive meta-analysis. PLoS One. 2017;12(2):e0171700.

26.

Yoon

Choi

Kim

Jung

. Effect of medial open-wedge high tibial osteotomy on the patellofemoral joint according to postoperative realignment. Am J Sports Med. 2019;47(8):1863-1873.