Spacer-type tibial osteotomy versus open wedge high tibial osteotomy and unicompartmental knee arthroplasty for Kellgren-Lawrence grade 3–4 medial unicompartmental knee osteoarthritis in patients younger than 65 years

Abstract

Background

Spacer-type tibial osteotomy have been proven a novel and effective osteotomy to treat osteoarthritis, while lack of comparison with other surgical methods in younger patients. This study aims to evaluate the short-term clinical outcomes of spacer-type tibial osteotomy versus open wedge high tibial osteotomy (OWHTO) and unicompartmental knee arthroplasty (UKA) for Kellgren-Lawrence (K-L) grade 3–4 osteoarthritis (OA) in patients younger than 65 years.

Methods

This retrospective study analyzed a total of 224 patients with K-L grade 3–4 knee OA treated from March 2018 to November 2020. Three groups were created according to the operation type. The clinical outcomes recorded preoperatively and at 6, 12 and 24 months postoperatively were the range of motion (ROM), visual analogue scale (VAS), American Knee Society Score (KSS), Western Ontario and McMaster Universities Global (WOMAC) score, operation time, length of incision, relevant complications and failures. Radiographic parameters were measured to evaluate the correction of varus deformity.

Results

The cohort comprised 224 patients; 70 underwent spacer-type tibial osteotomy, 73 underwent OWHTO, and 81 underwent UKA. The spacer group had the shortest incision (P = 0.000), least amount of bleeding (P = 0.000), and shortest operation time (P = 0.000). UKA achieved the most significant pain relief based on VAS (P = 0.014), KSS pain score (0.030), and WOMAC score (P = 0.000) at 6 months postoperatively, but there were no differences between three groups at 12 and 24 months postoperatively. The spacer and OWHTO groups achieved significantly greater ROM changes compared with the UKA group (all P = 0.000). The complication rate did not significantly differ between the three groups. No surgical failures were identified in HTO but two spacer dislocations in spacer group and three polyethylene dislocations in UKA.

Conclusion

For younger patients with K-L grade 3–4 OA, OWHTO seems to be the most appropriate method through clinical comparisons. Although spacer-type tibial osteotomy offers shorter operation time and comparable clinical outcomes, it also has extended recovery phase, additional fibular incision and the risk of spacer dislocation, which did not appear to be superior to OWHTO and UKA under the indications outlined in this study.

Trial registration

Retrospectively registered, QYFY WZLL 27,021.

Background

High tibial osteotomy (HTO) is an effective method to treat medial unicompartmental knee osteoarthritis (OA) [1, 2]. This is because the main cause of OA pain is often varus deformity of the lower limbs, and HTO transfers the lower limb alignment during weight-bearing to release the unbalanced load distribution in the medial compartment [3].

Extensive research has established that both open wedge HTO (OWHTO) and unicompartmental knee arthroplasty (UKA) are suitable surgical options for knee OA [4,5,6,7]. However, while studies have reported no significant differences in the long-term outcomes of OWHTO versus UKA, UKA appears to result in better pain relief and satisfaction, especially in patients with obvious intra-articular lesions [8,9,10,11,12]. Furthermore, although UKA changes the autologous intra-articular structure, OWHTO results in a better postoperative range of motion (ROM) of the knee and a quicker recovery for young patients [1, 2, 9, 13, 14]. Even in patients requiring revision after surgical failure, OWHTO revised to total knee arthroplasty appears to achieve better outcomes than UKA [5, 15, 16]. Considering the service life of the knee joint for younger patients, OWHTO may be a more suitable choice to avoid the requirement for total knee arthroplasty replacement.

Although OWHTO technology has improved, the healing of the bone defect and persistent postoperative pain associated with the fixation implantation are the main shortcomings decreasing the surgical effectiveness. With the development of materials science, Yu [17] and Chen [18] reported a novel wedge-shaped spacer implantation that fills the bone defect area. The wedge-shaped spacer has a thin lateral side and anterior aspect, and a thick medial side and posterior aspect shape to ensure the attainment of the correct medial tibial extension and posterior tibial slope [19]. Many short-term follow-up clinical studies have shown that HTO using the wedge-shaped spacer is a simpler surgical process and achieves better outcomes than traditional OWHTO in the treatment of OA varus deformity [17, 18, 20]. The active ingredient of the novel spacer is mineralized collagen, which has good biocompatibility and mechanical properties [18]. Based on these advantages, it seems likely that spacer-type tibial osteotomy would be a better choice than traditional OWHTO, but there is a lack of systematic research that includes clinical scores, radiographic examinations, and surgical outcomes of spacer-type tibial osteotomy on Kellgren-Lawrence (K-L) grade 3–4 knee OA compared with OWHTO and UKA, especially in younger patients.

We hypothesized that spacer-type tibial osteotomy would achieve comparable and even better clinical outcomes than traditional OWHTO and UKA in younger patients with K-L grade 3–4 knee OA. The present study aimed to compare the clinical functional scores, radiographic parameters, and surgical technical indicators of spacer-type tibial osteotomy versus traditional OWHTO and UKA.

Methods

Study design and patient selection

This single-center retrospective study analyzed 224 consecutive non-randomized patients with medial compartment OA who underwent either spacer-type tibial osteotomy (spacer group), traditional OWHTO (HTO group) and UKA (UKA group) performed by one surgeon in our department between March 2018 and November 2020. All patients provided written informed consent. The study was approved by our university ethics committee, and all authors have read and understood the related ethical standards document.

The inclusion criteria were symptomatic medial compartment OA with a K-L grade of 3–4, age between 50 and 65 years, varus deformity of less than 12°, normal ROM ≥ 120°, and body mass index (BMI) < 35 kg/m². The exclusion criteria were (1) other knee diseases such as rheumatoid arthritis, osteoporosis, Charcot arthritis, Kaschin Beck disease, and acute knee infection, (2) limited knee flexion and extension ROM, (3) history of knee trauma, including fracture, meniscus injury, and ligament damage, or previous knee surgery, (4) symptomatic patellofemoral OA, (5) other diseases that rendered the patient intolerant to surgery or functional exercise postoperatively, and (6) other circumstances leading to loss of follow-up.

Surgical technique and postoperative rehabilitation

A total of 270 patients were operated on during this period and met our inclusion criteria; however, 46 patients declined to participate in this research or were lost to follow-up.

In the spacer-type tibial osteotomy group (spacer group), the surgical technique was performed in full accordance with the method reported by Yu et al. [17]. In this study, an array of spacers (Weigao Medical Company, WeiHai, China) with varying thicknesses could achieve varus correction within a range of 5° to 12°. An appropriate thickness of spacer was utilized in accordance with the extent of the varus deformity. All patients received the same postoperative treatment, including rehabilitation exercises and pain management. All patients were encouraged to perform quadriceps exercises and free knee flexion and extension motion. Half-weight-bearing walking wearing knee joint braces was allowed at 2 weeks postoperatively, while full weight-bearing was permitted at 1 month postoperatively.

In the HTO group, Tomofix locking plates (Synthes GmbH, Solothurn, Switzerland) were used as recommended by the manufacturer. All patients were encouraged to perform quadriceps exercises, free knee flexion and extension motion, and full weight-bearing postoperatively.

In the UKA group, the standard Oxford UKA technique was used as described by the manufacturer (Zimmer Biomet Ltd., Bridgend, UK). All patients were allowed to perform direct full weight-bearing postoperatively. To prevent knee joint stiffness, all patients underwent knee joint flexion training using continuous passive motion on the first day after surgery. Quadriceps exercises and straight leg lifting training were also performed during the entire rehabilitation period. The postoperative rehabilitation process of polyethylene dislocation cases were entirely in line with that of the initial surgery. However, the postoperative outcomes were documented based on the follow-up schedule of the initial surgery, rather than the time of anesthesia reduction.

Outcome evaluation

All patients were assessed at baseline and at 6, 12, and 24 months postoperatively by one assessor. The visual analogue scale (VAS) for pain (ranging from 0 to 10 points, with 0 = no pain and 10 = worst pain), Western Ontario and McMaster Universities Global (WOMAC) score (including pain, stiffness, and function sections), American Knee Society Score (KSS) (including pain and function sections), and ROM of the knee for all three groups were recorded preoperatively, postoperatively, and at each follow-up timepoint by the same assessor; these outcomes were also reviewed by another orthopedist.

Radiographic examinations, including standard anteroposterior and lateral radiographs of the knee and weight-bearing full-leg anteroposterior radiographs, were performed for all patients at baseline and at each follow-up timepoint. The radiographic measurements were evaluated independently by one radiologist with 10 years of experience, and were reviewed and verified by another radiologist with 5 years of experience in orthopedic radiology using the picture archiving system. The radiographic parameters, namely the K-L grade, medial-proximal tibial angle (MPTA), hip-knee-ankle angle (HKA), posterior tibial slope angle (PTS), Caton-Deschamps index (CDI), and Insall-Salvati index (ISI), were compared between the spacer group and HTO group. We did not compare the outcomes of the UKA group because the surgical methods were totally different.

The other recorded surgical outcomes were the operation time, amount of bleeding, incision length, hospital stay, relevant complications and failures. The amount of bleeding was measured by one anesthesiologist based on the weight of the soaked gauze swabs and aspirated fluids. The skin incision was intraoperatively measured using a scale. The complications (infection, hematoma, and venous thrombosis) and failures were recorded by the same assessor during hospitalization and during the follow-up period.

Statistical analysis

Statistical analyses were performed using SPSS software (version 19.0, SPSS Inc., Chicago, IL, USA). Results were reported as the mean and standard deviation or the number and percentage. The intraclass correlation coefficient (ICC) or predominate κ value and 95% confidence interval (CI) were used to determine the intra- and inter-observer reliabilities of the K-L grade, functional knee scores, and radiographic measurements. Measurement data were checked for normality. Normally distributed data were analyzed using the Tukey’s post hoc test or Kruskal–Wallis test. Count data were analyzed using the Pearson chi-squared test. Data that did not meet the normality assumption were analyzed with the Mann-Whitney U test and exact probability method. Pre- and postoperative clinical scores were compared using the ANOVA (analysis of variance) of randomized complete-block design. The follow-up data were compared between the three groups using ANOVA, and multiple comparisons were made using the least significant difference (LSD) test. The complications were compared between the three groups using the Kruskal–Wallis H test, and multiple comparisons were made using the Nemenyi test. The radiographic measurements were compared between the spacer group and HTO group using the independent t-test. Differences were defined as statistically significant at P < 0.05.

Results

Patient demographic characteristics

A total of 224 patients with K-L grade 3–4 knee OA were included (Table 1). There were 82 men and 142 women with a mean age of 60.74 ± 4.58 years (range, 50–65 years) and mean BMI of 27.74 ± 6.76 kg/m². The spacer-type tibial osteotomy was performed in 70 patients (31.25%), whereas traditional OWHTO and UKA was performed in 73 (32.59%) and 81 (36.16%) (Table 1). While in HTO group, 8 patients (10.96%) had their plate removed within two years. The intra- and inter-observer reliabilities were excellent (Supplemental Table 1). Regarding the surgical characteristics, spacer group had a significantly shorter incision, smaller bleeding volume, and shorter operation time than traditional OWHTO and UKA (Table 1; Fig. 1, all P < 0.001).

Table 1 Demographic data

Fig. 1

Comparison of incision, bleeding volume and operation time among the spacer-type, HTO and UKA group

Functional outcomes

All patients were followed up at 6, 12, and 24 months postoperatively. The overall postoperative scoring systems assessing pain and function indicated significant improvements in all three groups at final follow-up compared with preoperatively (Fig. 2, all P < 0.001).

Fig. 2

Within-group comparison of function and pain relief at per-operation and 6,12,24 months postoperative in the spacer, HTO and UKA groups

The WOMAC score at 6 months postoperatively significantly differed among the three groups and showed that the UKA group achieved the most significant improvement in knee joint function (Supplemental Tables 2 and Fig. 3, P = 0.000). However, the WOMAC scores did not significantly differ between the three groups at 12 (P = 0.283) and 24 months (P = 0.061; Supplemental Tables 2 and Fig. 3) postoperatively. The KSS functional scores also did not differ between the three groups at 6, 12, and 24 months postoperatively (all comparative data, P > 0.05; Supplemental Tables 2 and Fig. 3).

Table 2 Comparison of preoperative and postoperative radiographic measurements between spacer and HTO group

Fig. 3

Among-group comparison of function and pain relief of the spacer, HTO and UKA groups

The VAS pain score significantly differed between the UKA group and the other two groups at 6 months postoperatively (P = 0.014), but not at 12 months (P = 0.061) and 24 months (P = 0.958) postoperatively (Supplemental Tables 2 and Fig. 3). Similarly, the KSS pain scores showed significantly greater pain relief in the UKA group than in the other two groups at 6 months postoperatively (P = 0.030), but did not differ between the three groups at 12 months (P = 0.276) and 24 months (P = 0.097) postoperatively (Supplemental Tables 2 and Fig. 3).

The three groups all achieved significant pre- to postoperative ROM changes (all comparative data, P = 0.000; Supplemental Tables 2 and Fig. 4). However, the spacer group and the HTO group achieved significantly better improvements in ROM than the UKA group at 6, 12, and 24 months postoperatively compared with preoperatively (all comparative data, P = 0.000; Supplemental Tables 2 and Fig. 4).

Fig. 4

Comparison of ROM of knee among the spacer, HTO and UKA groups

Radiographic measurement

The radiographic outcomes were compared between the spacer group and HTO group (all comparative data shown in Table 2). The change in limb alignment was evaluated by the hip-knee-ankle angle (HKA) and medial-proximal tibial angle (MPTA); these parameters did not significantly differ between the spacer group and HTO group preoperatively and at 6, 12, and 24 months postoperatively (all comparative data, P > 0.05). The flexion and extension of the knee was evaluated based on the PTS, which did not significantly differ between the spacer group and HTO group pre- or postoperatively (all comparative data, P > 0.05). The CDI and ISI were used to evaluate the changes in the patellar position, especially the postoperative patellar displacement. There were no differences between the two groups in the CDI and ISI pre- and postoperatively (all comparative data, P > 0.05). All radiographic parameters were significantly changed postoperatively compared with preoperatively in both the spacer group and HTO group (all comparative data, P < 0.05, Table 2).

Surgical complication

The complication rate was 4.29% (3/70) in the spacer group, 8.22% (6/73) in the HTO group, and 4.94% (4/81) in the UKA group (Table 3). No patients in the spacer group developed an infection, while one case of infection occurred in each of HTO and UKA groups (Table 3). Hematoma developed in two patients in the spacer group, three patients in the HTO group, and one patient in the UKA group (Table 3). Venous thrombosis developed in one patient in the spacer group, two patients in the HTO group, and two patients in the UKA group (Table 3).

Table 3 Comparison of the surgical complications of the three methods

Surgical failure

The occurrence of the following conditions was delineated as surgical failure in our study.

Spacer dislocation: The spacer dislocation refers to a situation where the spacer fails to support the tibial cortex and instead sinks into the cancellous bone of the tibial plateau, resulting in less than anticipated HKA correction. In the spacer group, two cases of spacer dislocation (failure rate 2.86%, 2/70) were identified (Fig. 5).

Fig. 5

Efficient and failed X-ray visualization of patients receiving spacer treatment. a - b shows the preoperative anteroposterior and weight-bearing full-leg anteroposterior radiographs of the knee, c - d shows the spacer treated knee at postoperative 12 and 24 months, respectively. e - h shows one female patients with spacer dislocation, e, f shows the projections of the treated knee at postoperative one month, spacer have sunk into the cancellous bone of the tibial plateau, failing to provide support to the posterior tibial cortex in red cycle; g, h shows the projections of spacer dislocation at postoperative 12 months. i - l shows another male patients with spacer dislocation, i, j shows the projections of the treated knee at postoperative one month, the blue cycle reveals an inadequate osteotomy of the posterior cortical bone of tibia, resulting in the spacer’s submersion into the tibial plateau’s anterior cancellous bone; k, l shows the projections of spacer dislocation at postoperative 12 months

Loose /broken hardware: Loose or broken hardware may result in the failure of the TomoFix plate to maintain tibial stability. While in HTO group, no such instance was identified.

Polyethylene dislocation and prosthesis loosening: In UKA group, three cases of polyethylene dislocation (failure rate 3.70%, 3/81) were identified, yet no cases of prosthesis loosening were detected.

Discussion

The present study found that spacer-type tibial osteotomy, traditional OWHTO, and UKA had similar short-term efficacy in treating K-L grade 3–4 knee OA in patients younger than 65 years. All three approaches effectively alleviated the clinical symptoms of knee OA and improved the knee function. There were differences between the three groups during the perioperative and postoperative recovery periods, especially in terms of postoperative knee joint function and pain. However, considering all the outcomes within the two-year short-term follow-up, OWHTO appears to be the more suitable method based on clinical comparisons. The spacer-type tibial osteotomy and UKA both exhibit notable drawbacks in certain aspects of postoperative evaluation.

Although OWHTO and UKA share the same indications in previous studies of medial unicompartmental knee OA, age and K-L grade are still the main factors affecting the surgical options [5, 6]. OWHTO is more suitable for patients younger than 55 years, while UKA appears to be more suitable for patients older than 65 years [5]. This age-related difference is mainly related to the significantly quicker return to sports activities and previous professional activities offered by OWHTO compared with UKA [1, 2, 9, 14, 21, 22]. A French database analysis of 108,007 patients reported that OWHTO has a better medium-term survival than UKA in patients younger than 70 years, and that the choice of the optimal surgery also depends on the OA stage [13]. Previous researches reported that the spacer-type tibial osteotomy share similar indications with traditional OWHTO, through simplifying surgical procedures to make more minimally invasive [17,18,19]. The present study found that the age and K-L grading distribution did not significantly differ between the three groups, meaning that the spacer-type tibial osteotomy could be considered for this age range (50–65 years) and the order of severity (K-L grade 3–4) without contraindication.

Regarding postoperative pain relief and functional improvement, UKA achieved more significant improvements than the two types of HTO (spacer-type tibial osteotomy and the traditional OWHTO) in the present study, especially within the first 6 months postoperatively; however, there are still no significant differences in these variables during long-term follow-up. Systematic reviews have showed that UKA achieves better postoperative pain relief and lower revision rates than OWHTO [8, 11, 12, 23], which is related to the earlier postoperative implementation of weight-bearing activities to maintain the muscle strength of the lower limb [2, 10]. However, in the present study, OWHTO achieved better postoperative knee ROM than UKA, which is even more important for young patients to resume physical activity. Previous studies have reported the same viewpoint [2, 9, 12, 14]. UKA is more suitable for elderly patients with poor exercise ability and low exercise demands [1, 5]. Young and active patients prefer OWHTO over UKA because they have greater participation in work and high-impact sports, and OWHTO completely preserves the proprioceptive and motor abilities of the knee [2, 14, 24]. Another reason why some studies have reported that OWHTO is better than UKA for young patients is the risk of earlier UKA revision [4]. A previous study showed that in the general population, OWHTO has a higher mid- to long-term survival rate (< 10 years) than UKA, while the opposite is true for the long-term survival rate (> 10 years) [25]. The survival rate is higher for OWHTO until 12 years postoperatively, but is higher for UKA thereafter [25]. Another study reported that OWHTO is effective for periods longer than 15 years [26]. However, more studies have reported that UKA has better clinical outcomes and a superior survival rate compared with OWHTO [7, 9, 10, 23, 27, 28], while the two methods result in similar radiographic outcomes.

In the present study that compared three surgical techniques, spacer-type tibial osteotomy and OWHTO could be considered the superior choice for young patients. While as an improved OWHTO method, spacer-type tibial osteotomy requires the shortest time and comprises the simplest operation of the three assessed techniques, while also having the smallest wound size, causing less damage to soft tissues, and causing less intraoperative blood loss [17,18,19,20]. As young patients have a good ability to adequately heal the bone defect, spacer-type tibial osteotomy may achieve a consistent clinical effect with minimal trauma in this population. However, spacer-type tibial osteotomy uses an unfixed implant system, which cannot guarantee the stability of the postoperative tibial osteotomy and is more prone to complications such as hinge fracture and osteotomy failure [17,18,19]. Furthermore, the use of the gasket in spacer-type tibial osteotomy requires the patient to only partially weight-bear on the lower limb for at least 1 month postoperatively, which affects the patient’s satisfaction and early clinical outcomes [17,18,19]. Thus, the surgical risks and prolonged rehabilitation associated with the spacer have somewhat impacted its clinical evaluation, whereas OWHTO presents no such issues.

All three surgical methods resulted in a low incidence of postoperative complications in the present study. Similarly, Karasavvidis et al. [27] reported no differences between OWHTO and UKA in early complications, namely venous thromboembolism, urinary tract infection, transfusion, surgical site infection, and re-operation. In contrast, several reviews have reported that UKA has lower rates of postoperative complications (infection, hematoma, and venous thrombosis) than OWHTO, because of the generally quicker postoperative recovery after UKA [4, 11, 12, 23, 29]. However, a South Korean registry study reported higher rates of deep venous thrombosis and surgical site infection after UKA than after OWHTO [30]. The common complications of the two types of OWHTO in the present study were transfusion, hematoma, and superficial surgical site infection. With the extension of follow-up, these early postoperative complications all disappear but leading to a longer rehabilitation period. The present study found no significant differences in the incidences and numbers of complications between the three approaches. Therefore, when considering surgical characteristics and complication rate, the spacer-type tibial osteotomy appears to be a more convenient method that should be prioritized for young patients with OA who have appropriate indications.

No case of surgical failure was identified within the HTO group. However, three cases of polyethylene dislocation were identified in UKA group. The dislocation of a polyethylene insert in a UKA could result in catastrophic consequences, potentially leading to anesthesia reduction or necessitating revision surgery. One case of manipulative reduction and two cases of surgical reduction in our study. However, no revision surgeries were performed since the knee prostheses were not loose. Two spacer dislocation were identified in the spacer group. While spacer dislocation typically occurs within the first month post-surgery, often due to premature weight-bearing or improper rehabilitation exercises. Consequently, it is imperative to adhere to restricted activity protocols during this period to prevent early spacer dislocation. Thus, in terms of surgical failure, OWHTO is significantly more reliable with a minimal chance of hardware loosening or broken.

Spacer-type tibial osteotomy, despite its drawbacks in postoperative rehabilitation and surgical risks, continues to necessitate improvements. However, its advantages are also notable. We still believe that this procedure holds considerable promise for individuals who meet the indications. Here we present several essential insights regarding spacer-type surgery. In the present study, the spacer-type tibial osteotomy resulted in a smaller medial tibial skin incision and shorter operation time than traditional OWHTO and UKA. Due to the blocking effect of the lateral fibula on the tibial distraction osteotomy, many surgeons choose to also perform a fibular osteotomy at 6–8 cm inferior to the fibular head to reduce the pressure load on the lateral knee compartment [17,18,19]. However, whether or not to perform the fibular osteotomy seems vary with each individual and not entirely necessary in our subsequent clinical findings, which could avoid additional damage and preserve the weight-bearing function of the fibula. Successful spacer-type tibial osteotomy needs strict surgical indications. Wang et al. [19] reported that age and a high K-L grade are the main prognostic factors associated with the outcomes of the spacer-type tibial osteotomy. Hence for the advanced age and severe knee degeneration patients, the spacer-type tibial osteotomy are not recommended. Due to the lack of internal fixation, the spacer-type tibial osteotomy cannot guarantee the longitudinal stability of the cut tibia and is not recommended for use in persons with a high BMI [17]. For spacer-type tibial osteotomy in appropriate patients, we do not suggest the use of an electric saw blade for osteotomy, as thermal injury may delay the healing of the tibial defect. Furthermore, to avoid intra-articular fracture of the tibial plateau, the medial osteotomy line must be separated from the tibial plateau by a sufficient distance [31]. Lastly, the margin of the spacer must be aligned with the posterior cortical bone of the tibia so that the spacer does not become stuck in the cancellous bone of the proximal tibia [32].

The present study has some limitations. Firstly, this was a single-center study that lacked long-term follow-up, and follow-up data at 5 and 10 years postoperatively are more clinically significant. As this was not a randomized study, selection bias was likely present. Secondly, eight patients in HTO group had their plates removed within two years, which could impact postoperative results in this study, such as pain and patient-reported outcome measures (PROMs). Finally, the K-L classification under Rosenberg views offers a more dependable approach for assessing the suitability of HTO. However, this method was not utilized in our study.

Conclusion

For the treatment of young patients (50–65 years) with K-L grade 3–4 knee OA, OWHTO achieved superior clinical outcomes compared to spacer-type tibial osteotomy and UKA. UKA does not offer sufficient advantages in the assessment of postoperative knee ROM, surgical characteristics, or surgical failures. Contrary to our hypothesis, the spacer-type tibial osteotomy did not demonstrate superiority over OWHTO and UKA under the indications outlined in our study, including the drawbacks of prolonged postoperative immobilization, the requirement for an assistant fibular osteotomy, and the risk of spacer dislocation. Nevertheless, the spacer-type tibial osteotomy remains a viable alternative treatment for patients who fit the surgical criteria. This method presents several advantages, including a smaller medial tibial incision, shorter operation times, a lower complication rate, and comparable radiographic and functional outcomes to those of OWHTO and UKA.