Anatomical locked plate versus Ilizarov’s ring fixator for high tibial osteotomy in medial compartment osteoarthritic knee: A pilot study

INTRODUCTION

In those over 40 years, osteoarthritis (OA) of the knee has become widespread, with a global prevalence estimated at 22.9%.^[1] The most common type of tibiofemoral OA is medial compartment OA (MCOA), which can occur alone or in conjunction with patellofemoral joint OA in as many as 27% and 23% of patients, respectively.^[2]

An aberrant distribution of weight-bearing stresses within the joint accelerates degenerative changes in the medial femoro-tibial compartment, making varus deformity, also known as medial coronal plane malalignment of the knee joint, a risk factor for OA of the compartment. Patients with OA on their knees may complain of pain, swelling, and stiffness, leading to reduced productivity and activity. Characteristic radiologic alterations such as joint space narrowing and related bone abnormalities are traditionally included in diagnostic criteria.^[3,4]

The primary management for most patients should be non-surgical and may encompass physiotherapy, bracing, orthoses, and non-steroidal anti-inflammatory drugs. Modifications in daily work and activities may be essential, as obesity is recognized as a risk factor for knee OA, and weight reduction has demonstrated efficacy in decelerating the disease’s progression.^[5]

Due to the degenerative nature of the condition, numerous people ultimately have surgical intervention. A range of techniques has been delineated for managing OA knees, encompassing arthroscopic lavage and debridement to complete knee arthroplasty. The severity of the disease, the number of compartments involved, the patient’s age, and their expectations for activity all influence the choice of surgery.^[6]

Orthopedic practices continue to face challenges in managing MCOA, particularly in young, active patients. In these circumstances, high tibial osteotomy (HTO) is considered one of the best treatment options, particularly for patients whose lateral compartment remains intact. Since patients with the indication of HTO have some degree of varus malalignment, HTO aims to reroute the mechanical axis from the deteriorated joint to the comparatively well-preserved compartment.^[7]

HTO has regained popularity for treating OA in the young population, and the need for realignment surgery is a new joint preservation technique.^[8,9]

Following the study by Ivarsson I in 1990, HTO gained acceptance as a surgical technique for OA of the knee in the 1960s and is now a recognized practice.^[10,11] This operation is frequently used to treat OA of the knee’s medial compartment. There are several methods for performing an HTO, including dome, chevron, and closing wedge osteotomies. However, the most frequent osteotomies are opening (medial) and closing (lateral).

A medial open wedge high tibial osteotomy (MOWHTO) could be secured with a locking plate, a simple plate, or an Ilizarov fixator. In obese patients, osteotomies requiring a high angle of correction and unstable osteotomies after a lateral tibial cortical fracture, a locking anatomical plate creates a structurally stable build and demonstrates noteworthy benefits.^[9,12]

According to a recent literature review, there is disagreement about the most effective ways to treat MCOA brought on by varus knee.^[13]

Therefore, this prospective cohort study aimed to assess the clinical and radiological outcomes following treatment of MCOA with a varus knee by HTO using either progressive correction with an Ilizarov frame or acute correction and fixation with a TomoFix locking plate.

MATERIALS AND METHODS

A prospective cohort pilot study using a case series of 39 patients, including 40 knees (19 patients in each group and one patient with bilateral knee involvement), who complained of knee pain with MCOA and varus malalignment, was conducted between March 2022 and February 2025 in the hospitals of Al- Azhar university in Egypt. Patients were randomly assigned to two equal groups using the closed envelope method.

Twenty knees were managed by HTO and acute correction and fixation using a TomoFix locked plate (Group 1). The other 20 knees were managed with HTO and gradual correction and fixation using the Ilizarov method (Group 2). The average post-operative follow-up was 12 months.

The following were the inclusion criteria: Males under age 65 and females under age 60, grade 1–2 arthritis based on Kellgren–Lawrence stage, active in their daily lives, had a full range of motion (ROM), and a stable knee with intact ligaments.

Among the exclusion criteria are all patients with post-traumatic knee deformity, advanced arthritis grade 0, 3, 4 based on Kellgren–Lawrence stage, rheumatoid arthritis, ischemic compromise of the limb, severe synovitis with effusion, and local or systemic infection.

Pre-operative evaluation

Each patient underwent a thorough medical history and general checkup upon recruitment. Clinical examinations were performed to assess alignment, gait for varus or hyperextension thrust, ROM, ligamentous stability, and a neurovascular examination. The authors assessed patient symptoms, activity, knee function, and post-operative patient satisfaction using the International Knee Documentation Committee (IKDC) score^[14] and the Oxford Knee Score (OKS).^[15]

Radiological evaluation including a whole lower limb weight-bearing radiograph (scanogram) anteroposterior (AP) with centralization of patella and lateral radiographs in full extension [Figure 1]. Using the Kellgren–Lawrence staging,^[16] the extent of OA in the knee was evaluated based on these radiographs.

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Figure 1:

(a) Pre-operative scanogram of the lower limb (anteroposterior view) for planning. (b) Lateral view.

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Radiological measurements [Figure 2] include the following metrics: Joint line convergence angle, varus angle or mechanical femorotibial angle, tibial slope angle or posterior proximal tibial angle, mechanical axis deviation (MAD), mechanical medial proximal tibial angle (MPTA), and mechanical lateral distal femoral angle (MLDFA). OA-consistent structural knee pathological alterations are detected by magnetic resonance imaging.

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Figure 2:

A scanogram of the lower limb shows pre-operative measurements, including mechanical axis deviation, mechanical lateral distal femoral angle, mechanical medial proximal tibial angle, and joint line convergence angle.

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Pre-operative planning, angle calculation, and required osteotomy correction were performed according to the deformity principles outlined by Paley^[17] to determine the osteotomy gap’s height and corrective angle. The adopted technique, based on a study by Fujisawa^[18] and Miniaci,^[19] was used.

All patients underwent the standard laboratory, cardiac, chest, and anesthetic evaluations before surgery to determine their surgical suitability and obtain their consent.

Operative technique

The patients were all placed in a supine position. The procedure was carried out using fluoroscopic guidance and under spinal anesthesia. Antibiotics were administered intravenously as prophylaxis to all patients.

Group A: The periosteum was reached by a medial incision made over the proximal tibia and extending into the skin and subcutaneous tissue. The superficial medial collateral ligament was freed as necessary, and the muscle insertions onto the pes anserine and medial soft tissue sleeve were peeled and retracted posteriorly. After determining the tibia’s metaphyseal flare, a subchondral wire and hinge wire [Figure 3a] were inserted, and a guidewire [Figure 3b] was positioned obliquely from medial to lateral, 4 cm below the joint line, with the tip of the fibular head positioned 1 cm below the lateral articular surface. An osteotome was used to execute osteotomy while adhering to the guide wires. The patellar tendon attachment is protected anteriorly, and the neurovascular structures are protected posteriorly following subperiosteal elevation [Figure 3c]. Another osteotome [Figure 3d] and a laminar spreader [Figure 3e] were used to gradually open the osteotomy site, hinging by the intact lateral cortex, to accomplish the intended correction. Under fluoroscopy, the mechanical axis of the lower extremity was measured using a 5-mm alignment rod with a slight overcorrection. A locking TomoFix plate and 4.5–5.0 mm screws were used to secure the osteotomy site [Figure 3f].

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Figure 3:

(a) Subchondral wire and hinge wire. (b) The oblique wire extended from 4 cm below the medial tibial plateau to the tip of the fibular head. (c) Cutting the bone with an osteotome and protecting of neurovascular by the posterior Hohmann retractor. (d) Opening of the osteotomy site by 2 or 3 osteotomes. (e) Opening of the osteotomy site using a laminar spreader. (f) Fixation of the TomoFix plate after planned correction is achieved.

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Group B: The operation consisted of three elements: application of the Ilizarov apparatus, percutaneous osteotomy of the tibia, and osteotomy of the fibula. An oblique osteotomy was performed on the middle portion of the fibula [Figure 4a]. The first K-wire then went from the proximal tibia parallel to the knee joint at the fibular head level, and the second K-wire went 1 cm above the surface of the ankle joint. After applying the frame [Figure 4b], the tibia’s alignment and mechanical axis were examined under fluoroscopy in the lateral and AP planes. The frame was fastened to the K-wires both proximally and distally. Schanz screws and extra K-wires finished the fixation. At this point, fluoroscopic management of the hinges is required to bring them up to the level of the center of rotation angulation (CORA). Finally, a percutaneous transverse osteotomy is performed using a multiple-drilling technique above the level of the tibial tuberosity. Before the osteotomy, the distraction rod and both hinges are taken out.

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Figure 4:

(a) Minimal incision for mid-shaft oblique fibular osteotomy. (b) Intraoperative frame application with minimal invasive 2 cm incision for tibial osteotomy with one proximal construction ring and two distal construction rings to the osteotomy site connected to a distractor unit on the medial aspect for gradual distraction.

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The accuracy of the reduction was assessed using radiographs taken immediately after surgery. The outpatient clinic routinely took follow-up radiographs [Figure 5] to measure the corrected angles [Figure 6] and track osteotomy healing. All patients were routinely monitored every 3–4 weeks until the fracture had healed, then every 3 months for a year, and finally every 6 months thereafter.

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Figure 5:

(a) Scanogram of the lower limb showing (antero-posterior view) after correction by TomoFix plate on the left side and by Ilizarov frame on the right side. (b) Lateral view after correction.

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Figure 6:

Scanogram of the lower limb showing post-operative measurements, including axis deviation, mechanical lateral distal femoral angle, and mechanical medial proximal tibial angle.

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Post-operative follow-up for group A included immobilization in an above-knee slab for 2 weeks. Quadriceps strengthening exercises began with hinged knee braces that allowed for full extension and flexion up to 60° for 2–4 weeks. From 4–6 weeks, flexion up to 90° is permitted. After 4 weeks, partial weight bearing began. After 6 weeks, the brace was removed, full ROM was permitted, and full weight-bearing was permitted.

Post-operative follow-up for group B included patients who were permitted to move as much as they could without experiencing pain. Correction started on day 7 postoperatively at a rate of 1 mm/day for 1 week and then continued with adjustments of the medial hinges only. Radiological measurement checks were performed during each visit to ensure correction. The fixator was removed after the osteotomy site had healed, and a walking orthosis supporting the patellar tendon was advised for a month. Serial long film radiography every three months for a follow-up period of one year was done.

RESULTS

Thirty-nine patients with 40 knees presented with medial knee joint pain due to varus and MCOA, treated by MOWHTO, and were split into two equal groups. The first group, group A (n = 20), was treated with acute correction using internal fixation with a TomoFix locked plate. A gradual correction was applied to the second group (n = 20) using an Ilizarov ring fixator, designated as group B.

According to the demographic data, there are no statistically significant differences in the distribution of ages or sexes. The mean age for group A was 45.4 years (SD ± 7.23), while for group B, it was 47.8 years (SD ± 8.50). In addition, the sex distribution was similar across both groups, with males comprising 65% of group A and 55% of group B [Table 1].

In both groups, the most prevalent symptoms were medial knee joint pain in 100% of patients pre-operatively, indicating no statistically significant variation between the two groups. The mean follow-up was 14.56 ± 5.23 (6–24 months) in group A and 15.65 ± 6.84 (6–24 months) in group B.

Postoperatively, group A exhibits a lower rate of medial joint pain (5%) compared to group B (10%), with no statistically notable difference between the two groups [Table 2]. The highly significant test values (P < 0.001) suggest the effectiveness of both techniques in addressing joint pain.

Concerning radiological results, the mean post-operative tibial slope was 9.60° ± 2.16° with a mean correction of 4.90° in group A and 9.55° ± 2.11° with a mean correction of 4.75° in group B. Both groups achieved a statistically significant reduction in the tibial slope [Table 2]. The mean post-operative MPTA was 89.1° ± 2.10° with a mean correction of 9.9° in group A and was 89.2° ± 2.92° with a mean correction of 10.9° in group B. Both groups showed a marked increase in MPTA, which is statistically significant (P < 0.001) for both methods, indicating that each method effectively corrects MPTA [Table 2].

Regarding the clinical evaluation results, the IKDC score indicates a significant improvement within both groups, it showed moderate improvement in knee function of 30.4 in group A and 33.7 in group B, which is extremely significant as the pre-operative mean was 35.2 ± 6.46 in group A and 33.7 ± 6.4 in group B, while the post-operative mean was 65.6 ± 6.15 in group A and 67.6 ± 5.38 in group B [Table 3].

Furthermore, the OKS shows significant improvement in both groups, with an average improvement of 14.8 as it increased from 22.7 ± 3.91 pre-operative to 37.5 ± 3.33 postoperative in group A and an average improvement of 15.9 as it increased from 21.2 ± 2.30 pre-operative to 37.1 ± 2.68 post-operative in group B [Table 3].

No statistically significant difference in group A was noted regarding the overall limb alignment MAD. Thirty percent of patients achieved a natural varus alignment, while 70% exhibited a valgus alignment. In group B, 10% of patients had a natural varus alignment, and 90% had valgus [Table 4].

Regarding the complication rate, in group A, two patients developed a hinge fracture type 1 due to large wedge opening more than 14 mm which addressed intraoperative and not need more fixation other than TomoFix plate but extend 6 weeks without bearing any weight, one patient had varus under correction post-operative and had persistent medial joint pain, osteotomy site union was delayed in one case at 6-month post-operative and addressed by bone marrow injection. In group B, oral antibiotics and pin tract care were used to treat five individuals who acquired pin tract infections; one patient developed a deep infection in the muscular planes drained by surgical incision and antibiotics. No neurovascular complications were recorded in either group. Finally, the complications reported in both groups [Table 5] ranged between 1 and 3a according to the Clavien– Dindo classification.^[20]

DISCUSSION

Our findings are comparable to those of Khurana et al.^[21] who employed a similar methodology; however, with dynamic axial fixators (similar to Ilizarov fixators) in group B cases and locked plate fixation in group A. All patients demonstrated significantly improved knee alignment, with no major discrepancies in post-operative MPTA or tibial slope correction between the two methods. However, the external fixator group had an increased likelihood of complications, for example, pin-site infections, and persistent discomfort, while rigid stabilization provided by locked plates minimizes soft tissue irritation and enhances postoperative pain resolution, making it a preferable option for patients seeking a more comfortable and expedited recovery. Like we did with our patients, they also employed the OKS to assess their functional activity after surgery.

Chaudhary^[22] and Hernigou et al.^[23] reported that both fixation methods are suitable for restoring proper knee alignment, improving knee function, and quality of life postoperatively. Furthermore, Sen et al.^[24] reported that patients treated with the Ilizarov method were allowed early mobilization, with knee and ankle exercises initiated on the 1^st post-operative day and partial weight-bearing allowed as early as the 3^rd day. In contrast, Balta et al.^[25] found that locked plate fixation in medial open wedge HTO required a delayed weight-bearing period, typically allowing only partial loading for approximately 4 weeks before progressing to full weight-bearing. These findings highlight the advantages of the Ilizarov technique for patients requiring a faster rehabilitation process, thereby reducing the risk of complications associated with prolonged immobilization.

The complications associated with Ilizarov and locked plate fixation methods in HTO are well-documented in the literature. Ilizarov fixation commonly leads to pin loosening and pin tract infections, significantly increasing infection risk, requiring debridement and antibiotic management. In contrast, locked plates carry different risks, including implant failure, screw loosening, and soft tissue irritation, as well as lower stiffness in bending and torsion, which can potentially affect long-term stability.^[26,27]

Beyond medical complications, cosmetic and psychological concerns are significant factors influencing patient satisfaction with Ilizarov fixation, due to the bulky external frame and prolonged treatment duration. These findings underscore the importance of patient-specific surgical planning in mitigating complications and optimizing outcomes in HTO. In contrast, the Ilizarov fixator offers the advantage of early mobility and fine-tuned corrections; it necessitates more frequent follow-ups due to the need for adjustments and pin-site care, thereby increasing long-term costs despite a shorter initial hospital stay.

Finally, our study has some limitations. First, Ilizarov readjustments necessitate experience and skill. Therefore, it might be challenging to extrapolate these findings to a wide range of practices. Second, the study has a small sample size and short follow-up periods, which necessitate further investigation in a larger patient cohort and with longer-term follow-up.

CONCLUSION

Based on the reported outcomes and complication rates, both methods are considered valid options for safe and effective surgical management for knee MCOA. They improve knee function, alignment, and achieve high patient satisfaction. However, each method has distinct advantages and disadvantages.