High Tibial Osteotomy (HTO) is an established surgical procedure in orthopedics that is primarily used to address knee joint issues caused by malalignment. This technique aims to redistribute weight from the affected medial compartment of the knee to healthier areas, potentially alleviating pain and delaying the progression of osteoarthritis (OA). Understanding the indications, patient selection, surgical methods, and postoperative care is crucial for ensuring the best outcomes.
Overview of High Tibial Osteotomy
HTO is a surgical intervention aimed at correcting knee malalignment, particularly in patients suffering from isolated medial compartment OA associated with varus malalignment. The procedure involves realigning the knee joint to shift the mechanical axis from a more medial to a slightly lateral position. This adjustment helps distribute the weight more evenly across the knee, reducing the stress on the affected compartment and improving function. The benefits are particularly significant in younger patients with less advanced OA, who can expect substantial improvements in knee function and quality of life post-surgery.
Indications for High Tibial Osteotomy
HTO is traditionally used to treat varus deformities of the knee, particularly in younger, active individuals with isolated medial compartment OA. However, the indications for this procedure have expanded to include cases involving meniscal transplantation following total medial meniscectomy, isolated chondral defects, and ligamentous instability with a varus thrust. Furthermore, recent studies suggest that HTO may even be beneficial in treating varus ankle malalignment, providing further versatility for addressing various knee and lower limb disorders.
The ideal candidate for HTO is typically a moderately active, young individual (40-60 years old) with a BMI under 30, who exhibits isolated pain in the medial joint line. Severe osteoarthritis, significant ligamentous instability, or severe deformities are contraindications for this procedure. Additionally, patients with inflammatory arthritis, advanced OA (Ahlback grade III or higher), or those with a limited range of motion (less than 120°) are generally not considered suitable candidates.
Preoperative Planning and Patient Selection
The preoperative planning process is critical for determining the appropriate surgical approach and achieving optimal results. Accurate assessment of knee alignment is essential and is typically performed using various radiographic views, including the anteroposterior (AP) and lateral knee views, axial view of the patellofemoral joint, and weight-bearing alignment views of the lower extremities. The tibial bone varus angle (TBVA) is a key measurement, with a TBVA greater than 5° considered a favorable prognostic factor for successful outcomes after osteotomy.
Mechanical, anatomical, and weight-bearing axes must be carefully analyzed to determine the appropriate correction angle. The goal of HTO is typically to achieve a slight valgus alignment—typically between 3° to 5°—to avoid recurrence of deformity while ensuring the health of the lateral knee compartment.
Surgical Techniques
There are three main techniques for performing HTO: medial opening wedge, lateral closing wedge, and dome osteotomy. Among these, the medial opening wedge osteotomy (MOWHTO) has gained significant popularity due to its advantages, such as the ability to correct alignment in both the coronal and sagittal planes, minimal risk of peroneal nerve injury, and no leg shortening. However, it does require the use of bone grafts to fill the osteotomy gap, and there is a risk of delayed union or nonunion.
On the other hand, lateral closing wedge osteotomy has been the traditional approach and is still favored by some surgeons. This method allows for a greater potential for correction and faster healing but comes with the risk of complications such as peroneal nerve injury and fibular osteotomy. The choice of technique largely depends on the surgeon’s experience and the specific needs of the patient.
Fixation Methods
The fixation method used in HTO plays a crucial role in the success of the procedure. Plate fixation is the most commonly used method, with options including spacer plates and locking compression plates (LCP). Spacer plates are small, low-profile implants that allow for a less invasive procedure but may be associated with complications such as delayed union or nonunion. In contrast, locking compression plates like the TomoFix plate offer more rigid fixation, allowing for earlier weight-bearing and faster recovery.
In some cases, bone grafts or substitute materials like hydroxyapatite or beta-tricalcium phosphate are used to promote healing and enhance stability. Studies have shown that the use of autograft (patients’ own bone tissue) yields better outcomes compared to allograft or synthetic materials, especially in patients at higher risk for nonunion, such as smokers and those with obesity.
Postoperative Rehabilitation and Recovery
The postoperative protocol largely depends on the fixation method. For patients treated with plate fixators, partial weight-bearing (15-20 kg) is typically allowed immediately after surgery, with full weight-bearing permitted after about two weeks. For those who undergo MOWHTO with spacer plates, a more conservative approach is necessary, with partial weight-bearing allowed for at least six weeks to ensure proper healing.
Rehabilitation is focused on restoring range of motion, strengthening the muscles around the knee, and gradually returning to functional activities. The full recovery process can take several months, but most patients experience a significant reduction in pain and improvement in knee function, which can delay the need for more invasive interventions such as knee arthroplasty.
Complications and Long-Term Outcomes
As with any surgery, HTO carries the risk of complications, including nonunion, infection, and nerve injury. However, the incidence of major complications has decreased with advancements in surgical techniques and improved patient selection. The success of HTO is heavily dependent on maintaining proper alignment during surgery, as malalignment can lead to poor outcomes, such as joint degeneration in the lateral compartment.
Long-term outcomes for HTO are generally favorable, particularly for patients under the age of 50 with appropriate alignment. Studies have shown that 10-year survival rates for HTO can range from 51% to 93%, with patients experiencing significant delay in the need for total knee replacement. However, the benefits tend to diminish after 15 years, especially in older patients or those with more advanced OA.
Conclusion
High Tibial Osteotomy remains a cornerstone procedure in orthopedic surgery for managing knee malalignment and medial compartment OA. With proper patient selection, preoperative planning, surgical technique, and postoperative care, HTO can provide excellent long-term outcomes, significantly improving patients’ quality of life and delaying the need for total knee arthroplasty. However, as with any surgical procedure, the key to success lies in the careful management of complications, rigorous rehabilitation, and close follow-up to ensure optimal recovery.
