Clinical Benefits of Cartilage Repair in High Tibial Osteotomy Can Only Be Expected in Patients with Successfully Regenerated Cartilage

Abstract

Background: The clinical benefits of combining cartilage procedures with high tibial osteotomy (HTO) remain undetermined. This study aimed to evaluate the additional clinical benefits by comparing a combined procedure group with an isolated HTO group, with stratification based on the success of cartilage regeneration.

Methods: Patients who underwent medial open-wedge HTO from 2010 to 2022 with a minimum 2-year follow-up were retrospectively reviewed. Patients were divided into 2 groups: HTO + combined cartilage procedures (C group) and isolated HTO (I group). C group was further divided into 2 subgroups based on the medial femoral condyle (MFC) cartilage status assessed on second-look arthroscopy: well-regenerated cartilage (C1 group) and poorly regenerated cartilage (C2 group). Propensity score-matched I groups were formed for each C1 and C2 group (C1-matched and C2-matched group I), based on baseline factors affecting clinical outcomes. Comparative analysis was performed for each matched pair based on patient-reported outcomes (PROs).

Results: A total of 313 patients were retrospectively reviewed in this study, with 199 patients included in the analysis: 83 patients in the C group (49 in the C1 group and 34 in the C2 group) and 116 patients in the I group. Baseline characteristics showed no significant difference between the matched groups after propensity score matching. The mean follow-up period for all groups was approximately 3 years with no significant differences. The C1 group showed significantly better PROs and improved PROs at the final follow-up compared to the C1-matched I group (visual analog scale score, p < 0.001; Lysholm, p = 0.004; Knee injury and Osteoarthritis Outcome Score subscales, p ≤ 0.018). However, the C2 group did not show any differences in PROs compared to the C2-matched I group at the final follow-up.

Conclusions: Only patients with well-regenerated cartilage after combined cartilage repair procedures showed additional clinical outcome improvements with HTO. When considering combined cartilage repair procedures with HTO, selecting appropriate candidates for achieving successful cartilage regeneration is necessary to yield additional clinical benefits.

Keywords: Articular cartilage; Cartilage injuries; Cartilage sugery; Osteoarthritis; Osteotomy.

Fig. 1. Combined cartilage repair procedures. (A) Arthroscopic microfracture awl and 1.5-mm diameter drill bit used for the microdrilling procedure. (B) Arthroscopic microfracture on the medial femoral condyle (MFC) cartilage defect. (C) Arthroscopic microdrilling on the MFC cartilage defect. (D, E) Umbilical cord blood-derived mesenchymal stem cell-hyaluronic acid composite (UCB-MSC-HA) implantation procedures. (D) Baseline MFC cartilage defect. (E) Multiple drill holes were made after cartilage defect preparation. (F) UCB-MSC-HA implantation.

Fig. 2. Assessment of the repaired medial femoral condyle cartilage using International Cartilage Repair Society Cartilage Repair Assessment (ICRS CRA). Second-look arthroscopic images of patients who underwent umbilical cord blood-derived mesenchymal stem cell-hyaluronic acid composite implantation (A-C) and of a patient who underwent arthroscopic microdrilling (D). These images were classified according to the ICRS CRA grading system as follows: grade 1 (A), grade 2 (B), grade 3 (C), and grade 4 (D).

Fig. 3. Patient flow diagram. The C1 group is the group of patients with good cartilage regeneration, assessed as International Cartilage Repair Association Cartilage Repair Assessment (ICRS CRA) grade I–II. The C2 group is the group of patients with poor artilage regeneration, assess as ICRS CRA grade III–IV. C1-matched group I and C2-matched group I were formed by the 1:1 propensity matching using the factors indicated by the asterisk (^*) in the flow diagram. ACL: anterior cruciate ligament, PCL: posterior cruciate ligament, MCL: medial collateral ligament, HTO: high tibial osteotomy, K-L: Kellgren-Lawrence, MFC: medial femoral condyle.

Fig. 4. Receiver operating characteristics (ROC) curve analysis to determine the cutoff value for cartilage defect size in predicting the failure of cartilage regeneration combined with high tibial osteotomy. The analysis identified a cutoff value of 5.7 cm², with area under curve of 0.647 (95% CI, 0.526–0.768).

Fig. 5. Comparison of patient-reported outcomes (PROs) and minimal clinically important difference (MCID) achievement rate between the C group and I group. C group showed significantly higher PROs in several preoperative, improved, and final postoperative PROs. The MCID achievement rate did not differ significantly between the groups. VAS: visual analog scale, KOOS: Knee injury and Osteoarthritis Outcome Score, ADL: activities of daily living, QOL: quality of life. ^*p < 0.05.

Fig. 6. Comparison of patient-reported outcomes (PROs) and minimal clinically important difference (MCID) achievement rate between the C1 group versus C1-matched I group (A) and C2 group versus C2-matched I group (B). C1 group showed significantly higher PROs in preoperative, improved, and final postoperative PROs compared to C1-matched I group, including MCID achievement rates (A). However, C2 group showed no significant differences in all measures compared to the C2-matched I group. VAS: visual analog scale, KOOS: Knee injury and Osteoarthritis Outcome Score, ADL: activities of daily living, QOL: quality of life. ^*p < 0.05.