Long-term results and comparison of the three different high tibial osteotomy and fixation techniques in medial compartment arthrosis

Background The purpose of this study is to report and analyze the long-term outcomes of the patients who underwent high tibial osteotomy (HTO) with three different techniques for the treatment of medial compartment arthrosis. Methods A total of 187 patients (195 knees) who underwent HTO between 1990 and 2010 were retrospectively evaluated. Eighty-eight knees, opening-wedge osteotomy with Puddu plate (group A); 51 knees, transverse osteotomy below the tubercle with external fixator (group B); and 29 knees, closing-wedge osteotomy with staple fixation (group C) were included in the study. The patients (mean age 44.9 ± 10.6 years, mean follow-up of 12.4 ± 3.2 years) were called for final controls and survival rates of the knees, and functional evaluations of the patients were performed using Knee Society Score (KSS) and Hospital for Special Surgery (HSS) knee score assessments. Results In the comparison of the three groups, there were no differences regarding the mean age, preoperative arthrosis levels, or preoperative deformity analyses (n.s.). The main finding of these comparisons showed that the closing-wedge osteotomy has the greatest lateralization effect on mechanical axis deviation (MAD) (p = 0.024), the greatest valgization effect on medial proximal tibial angles (MPTA) (p = 0.026), and the lowest posterior tibial slope (PTS) angles (p = 0.032) in comparison to the other groups. There were no functional differences between the three groups in the long-term assessment of patients with KSS and HSS knee scores. According to the Kaplan–Meier survival analysis, the probability of the survival of the native knee joint after HTO was 93.4% in 5 years and 71.2% in 10 years in our study group. During the follow-up of the 168 knees, revision surgery with total knee replacement was needed in 27 knees (16%). The mean time from HTO to total knee replacement was 8.9 years in these patients. Conclusions HTO has acceptable long-term clinical and functional results that should not be underestimated by orthopedic surgeons under pressure to perform arthroplasty operations.


Background
The management of medial compartment arthrosis remains challenging in orthopedic practice, particularly in young active patients [1][2][3]. High tibial osteotomy (HTO) is the main biologic treatment option for most of these cases, especially in those with an intact lateral compartment [4][5][6]. Some degree of varus malalignment should be expected in patients with the indication of HTO. The aim of an HTO is to redirect the mechanical axis from the degenerated area of the joint to the relatively well-preserved compartment [4][5][6].
There are many surgical options for medial compartment arthrosis, such as arthroscopic debridement, HTO, resurfacing procedures, unicompartmental arthroplasty, and total knee arthroplasty [7][8][9][10]. Although biologic treatment methods should be chosen primarily in young and active patients, HTO procedures have been ignored by most surgeons due to the technological improvements and the early term success of the resurfacing and unicompartmental knee arthroplasty procedures [11,12]. HTO is a good option in middle-aged or older patients who are not good candidates for arthroplasty procedures due to the social differentiation and habits of the patients or the reluctance of the patients to undergo arthroplasty [13,14].
The purpose of this study is to report and analyze the long-term outcomes of the patients who underwent HTO as a treatment for medial compartment osteoarthritis and to evaluate the survival rates of the joints using a comparison of three different techniques.

Methods
A total of 187 patients (195 knees) who underwent HTO in the same department due to medial compartment arthrosis between 1990 and 2010 were retrospectively evaluated and included in our study. The following patients were excluded from this study: 25 patients (27 knees) who we could not contact, 13 patients who could not complete a final assessment, 2 patients who had a lower extremity injury after surgery, 2 patients who had undergone hip arthroplasty, and 8 patients who did not want to participate in the study.
Preoperative and operative patient data were obtained from operative charts and patient files. The patients were called for final assessments, and the mean followup durations were set. Functional evaluations included measurements of range of motion (ROM), Knee Society Score (KSS) and the Hospital for Special Surgery (HSS) knee score. The indication for HTO operation had been accepted as grade 2 or grade 3 medial compartment arthrosis that had been evaluated by using standing AP and lateral x-rays according to the Kellgren-Lawrence classification [15]. Osteotomy types were based on surgeon preferences. Preoperative and postoperative mechanical axis deviation (MAD), posterior tibial slope (PTS), and medial proximal tibial angles (MPTA) were measured via long leg weight-bearing orthoroentgenograms. Subgroup evaluations were performed according to the osteotomy techniques to compare functional results and survival rates of the knees.
All patients signed an informed consent form to participate in the study. The local ethical committee approved this study.

Surgical techniques and postoperative rehabilitation
Detailed information on surgical interventions was provided to all patients. All patients signed an informed consent form that detailed the operative technique to be performed. Patients were also educated about the rehabilitation program.

Opening-wedge osteotomy
Under tourniquet, an approximately 8-10 cm incision was made parallel to the anterior border of the medial collateral ligament adjacent to the anteromedial aspect of the proximal tibia. The medial collateral ligament is stripped from the tibia posteriorly to expose the whole proximal medial surface of tibia. Then, under the guidance of the fluoroscopy, a guide wire was advanced medially from 1-2 cm distal to the level of the joint up to the lateral cortex, and an osteotomy apparatus was mounted on the guide wire. Afterwards, a second Kirschner wire was introduced at an appropriate angle up to the lateral cortex. After that, medial, anterior, and posterior cortices were cut immediately under the guide wire up to 1 cm to the lateral cortex. The osteotomy was opened till the lower limb mechanical axis passed across the Fujisawa point [16]. The osteotomy was fixed with a Puddu plate (Arthrex, Naples, Florida), and the osteotomy site was grafted with an autogenic or allogenic bone graft. After the closure of the layers and the placement of a drain, the patient's knee was placed into a hinged immobilizer. The patients were allowed to walk via two crutches without full weight bearing for 6 weeks. Full weight bearing was allowed 6 weeks postoperatively, and strengthening exercises were initiated.

External fixator
The fibular osteotomy was performed prior to the application of the frame in the middle thirds of fibula. A previously prepared frame that was composed of three carbon rings of a circular external fixator (Tasarım Medical, Turkey) was applied to the extremity. With the guidance of fluoroscopy, the rings were secured to the tibia using 1.8-mm stainless steel wires and 6-mm stainless steel half pins. Using an anteromedial skin incision approximately 4 cm long and starting inferomedial to the tibial tubercle, the tibial osteotomy was performed 1-2 cm distal to the tibial tubercle using the multiple drilling osteotomy technique. An acute intraoperative correction was performed with a medial opening wedge and translation of the distal tibia. The operation ended after checking the MAD with fluoroscopy that passed from the Fujisawa point. Minor corrections in the mechanical axis alignment were performed at the early postoperative follow-up visits after the evaluation of postoperative orthoroentgenograms. Patients were allowed to weight bear as tolerated.

Closing-wedge osteotomy
An approximately 8-10-cm curved oblique incision was utilized extending from the tip of the fibula to the tibial tuberosity anteriorly before descending approximately 3 cm along the lateral border of the tibial tuberosity. After the opening of the anterior compartment, the proximal tibia was exposed by a periosteal elevator. A blunt retractor was then placed around the posterior border of the tibia. With caution to the patellar tendon and posterior tibial structures, the desired amount of wedge was resected by a saw blade and osteotome according to the preoperative measurements. After excision of the wedge, the medial cortex was broken gently with a valgus stress, and the osteotomy was fixed with two or three offset staples. The patients were allowed to walk with a long hinged knee brace via two crutches without full weight bearing for 6 weeks. Full weight bearing was allowed 6 weeks postoperatively, and strengthening exercises were initiated.

Statistical analysis
The Statistical Package for Social Sciences, version 19.0, software (SPSS, Chicago, IL) was used for statistical analysis. The preoperative values were analyzed using analysis of variance and a post hoc Tukey highly significant difference test. The time between HTO and total knee replacement was referred to as "survival of native joint." Survival rates were calculated using the Kaplan-Meier method. To standardize the values for comparing preoperative and postoperative scores of different patient groups, ANCOVA (analysis of covariance) was used to compare the delta difference between the subgroups. The level of statistical significance was accepted as p < 0.05.

Results
In the preoperative arthrosis evaluation of the patients, 39 knees had grade 2 arthrosis and 129 knees had grade 3 arthrosis. The patient demographics are summarized in Table 1.
The mean MPTA of the patients was 83.3 ± 3.1°, the mean MAD of the patients was 28.2 ± 7.5 mm varus alignment, and the mean tibial slope of the patients was 7.2 ± 4.2°. Postoperatively, the mean MPTA, MAD, and tibial slope values of the patients were 89.6 ± 5.5°, 3.5 ± 4.9 mm valgus alignment, and 8.1 ± 5.2°, respectively (p = 0.001). In the functional evaluation of the patients, KSS and HSS knee scores were used. The mean preoperative KSS score of the patients was 56.3 ± 13.4, and the mean preoperative HSS score of the patients was 51.3 ± 9.7. At the last assessment of the patients, the mean KSS and HSS scores of the patients were 70.3 ± 14.9 and 64.7 ± 13.5, respectively.
We detected complications in 13 patients (8%), transient peroneal nerve palsy in 1 patient who had been treated with closing-wedge osteotomy, and implant failure in 3 patients who had been treated with openingwedge osteotomy. Delayed union in 2 patients and nonunion in 1 patient were revised with autogenous bone grafting and an external fixator. Grade 3 pin tract infections in 3 patients were treated with pin extraction, a deep infection in 1 patient was treated with During the follow-up of the 168 knees, revision surgery with total knee replacement was needed in 27 knees (16%). The mean time from tibial osteotomy to total knee replacement was 8.9 years in these patients. We uncovered a superficial wound infection in 1 patient and a periprosthetic infection in 1 patient in these revision cases. According to the Kaplan-Meier survival analysis, the probability of the survival of the native knee joint after HTO was 93.4% in 5 years and 71.2% in 10 years in our study group (Fig. 1).
At the last assessment of the patients, an arthrosis evaluation was performed; 55 knees (32.7%) had grade 4 medial compartment arthrosis, 81 knees (48.1%) had grade 3 arthrosis, and 5 knees (3%) had grade 2 arthrosis. Although we had offered total knee arthroplasty to these 49 patients (55 knees) who had grade 4 arthrosis at the last assessment, only 12 of them wanted an arthroplasty operation.
Subgroup analyses were performed according to osteotomy and fixation technique to compare the functional results of patients in the three different groups. Of the 188 knees, 88 knees underwent opening-wedge osteotomy (group A), 51 knees underwent HTO with external fixator (group B), and 29 knees underwent closing-wedge osteotomy (group C). In the comparison of these three groups, there were no differences regarding the mean age, preoperative arthrosis levels, and preoperative deformity analysis (MPTA, MAD, PTS) (n.s.). However, the mean follow-up time in group C was higher than that in the other groups and was statistically significant (p = 0.043). In the evaluation of patients' complications, there were no differences between the three groups. In the comparisons of the mean postoperative correction in MPTA, MAD, and PTA in the three groups, the mean MPTA and MAD were statistically higher in group C in comparison to the other groups (p = 0.024, p = 0.026, respectively). In addition, the mean postoperative PTS of patients was 8.9 ± 5.1 in group A, 7.8 ± 3.2 in group B, and 6.2 ± 7.3 in group C. These differences were statistically significant (p = 0.032).
At the last follow-up of the patients, there were no differences between the three groups in the functional assessment according to KSS and HSS knee scores. However, statistically, there were a high number of conversions to total knee arthroplasty in the external fixation group (p = 0.035) ( Table 2).

Discussion
Although many treatment options have been described for medial compartment arthrosis, HTO is still the most effective method, especially for young to middle-aged patients who are not eligible for arthroplasty procedures [6,7]. In this retrospective study, we aimed to analyze the long-term outcomes of medial compartment arthrosis patients who were treated with HTO and compared three different osteotomy and fixation techniques.
HTO was popularized by Coventry and Insall in the 1970s, and since that time, many different osteotomy techniques and fixation methods have been described [17][18][19][20][21][22][23]. The basic principle of the HTO in medial compartment arthrosis is to redirect the mechanical axis from the degenerated area to the relatively well-reserved lateral compartment [24]. This treatment is a very wellknown technique to prolong the lifespan of the native joint in the short-to mid-term follow-up [22,25]. In the long-term assessment of these patients, the efficacy of the HTO, especially for preserving the native joint, is variable, and survival rates of the native joint range from 61 to 98% in the literature over a 10-year follow-up period [26][27][28][29]. In a prospective study, 20 patients were treated with opening-wedge osteotomy and plate fixation, and the authors reported 70% native joint survival with a mean follow-up of 8 years [26]. Polizois et al. reported the results of their closing-wedge osteotomy treatment in 95 patients. The authors reported 61% good-excellent results, with a mean follow-up of 8 years [5,11,27]. Gstöttner et al. reported the long-term results of 111 patients (mean age 54, 134 knees) whom they had treated with closing-wedge osteotomy. With a mean follow-up of 12 years (1-25 years), the authors reported 80% native joint survival at 10 years and 66% Fig. 1 Chart shows the survival analysis of the 168 knees after HTO native joint survival at 15 years [28]. Akuziki et al. reported his series of 132 patients (mean age 63 years) that were treated with closing-wedge osteotomy and plate fixation. With a mean follow-up of 16 years, the authors reported 98% native joint survival at 10 years and 90% native joint survival at 15 years [29]. In our study group, according to the Kaplan-Meier survival analysis, the probability of the survival of the native knee joint after HTO was 93.4% at 5 years, 71.2% at 10 years, and 60.1% at 15 years.
Although conversion from HTO to total knee arthroplasty is technically demanding, especially in cases of previous closing-wedge osteotomies, in the literature, there were no significant differences between these cases and primary total knee arthroplasty cases [30,31]. In our series of 168 knees, we detected 27 knees in which total knee arthroplasty was needed during the follow-up period. In these 27 knees (16%), the mean time from HTO to total knee replacement was 8.9 ± 3.8 years.
The HTO operation has complications such as neurovascular injury, nonunion, infection, loss of correction, and implant failure. In a recent study, the authors reported a 10.9% complication rate in their patients who were treated with opening-wedge osteotomy [32]. In another study in the literature, the authors compared the complication rates of closing-wedge and opening-wedge osteotomies. The authors reported significantly higher complication rates for nonunion, loss of correction, and material failure in the opening-wedge osteotomy group [33]. We detected complications in 13 patients (8%) in our study. In the subgroup analysis, we found an 8.4% complication rate in group A, an 8.1% complication rate in group B, and a 7.1% complication rate in group C (n.s.). There were no statistically significant differences between the three groups.
In the treatment of medial compartment arthrosis, different types of osteotomies have been described for the valgization of the proximal tibia [17,23,24,26]. Although many studies have investigated the clinical outcomes of these osteotomies, only a few of them compared these osteotomy types regarding biomechanical stability, clinical outcomes, complication rates, etc. [34][35][36]. The authors compared the external fixation and Coventry wedge technique in 30 patients with a mean follow-up of 28.1 months. The external fixation technique was associated with an outcome comparable to the classic lateral closing-wedge osteotomy [34]. Opening-wedge and closing-wedge osteotomy have been widely used, and some studies have compared these two techniques [37][38][39][40]. Hoell et al. reported similar treatment results with these two techniques in a group of 57 patients, with a mean follow-up of 22.5 months [37]. In addition, Brouwer et al. compared these two techniques in his prospective randomized study and reported similar treatment outcomes with a higher implant removal rate in the opening-wedge group [38]. Although the primary result of both osteotomy techniques is the realignment of the mechanical axis to the unaffected lateral medial opening wedge) who were followed for 12 months and described obesity (body mass index >27.5 kg/m 2 ) as an independent risk factor [41]. Some authors investigated this issue in a meta-analysis and reported no significant difference between opening-wedge and closing-wedge techniques according to the analysis of 324 opening-wedge and 324 closing-wedge HTO patients in 20 studies regarding clinical outcomes and complication rates. Although the authors reported similar clinical outcomes in this meta-analysis, they reported a significantly greater posterior tibial slope and a greater angle of correction in the opening-wedge group [39]. Duivenvoorden et al. compared the 6-year outcomes of 92 patients who were treated with opening-wedge and closing-wedge osteotomies. The authors reported higher complication rates in the opening-wedge osteotomy group and a higher rate of conversion to total knee arthroplasty in the closing-wedge osteotomy group with a total conversion rate of 14.1% [40]. Closing-wedge, opening-wedge, and transverse osteotomy below tuberosity with external fixation are three commonly used techniques; in the present study, retrospective subgroup analyses were performed to compare the functional results of patients in these three groups. The main finding of this comparisons showed that the closing-wedge osteotomy has the greatest lateralization effect on MAD, the greatest valgization effect on MPTA, and the lowest PTS angles in comparison to the other groups. There were no functional differences between the three groups in the long-term assessment of patients according to the KSS and HSS knee scores. In the comparison of the three groups regarding revision with total knee arthroplasty, the external fixation group had higher arthroplasty rates after more than 10 years of follow-up (p = 0.041). Although the mean preoperative arthrosis level of the subgroups was similar, the body mass index of the external fixation group was higher (p = 0.0029). This might be a weakness of our study because arthritic changes are much more common in obese patients [42].
To the best of our knowledge, this is the first study to compare the results of the three techniques in HTO. All patients had a minimum of 5 years of follow-up and a mean follow-up of 12.4 years. Its retrospective nature was the main limitation of our study. Another weakness of the present study was the small sample size and the lack of a satisfaction survey such as SF-12 or SF-36.

Conclusions
All of the three HTO techniques were effective in the treatment of medial compartment arthrosis, with correction of the MAD and favorable short-to mid-term results. Long-term results of the HTO were hypervariable: 60 to 90% at more than 10 years of follow-up in studies originating from different cultures [28,29].
HTO is still the main biological reconstruction method in medial compartment arthrosis with acceptable long-term clinical and functional results that should not be underestimated by orthopedic surgeons who are under pressure to perform arthroplasty operations.