Due to the modern lifestyle, the overweight and obese populations are gradually increasing. Some studies [12, 13] have shown that from 1976 to 2016, there was an increasing trend in obesity globally, with an increase of 5.6% in adult women and 7.8% in men, and 230 million children and adolescents were overweight. In addition, the increase in the prevalence of overweight and obesity was larger than the decrease in the prevalence of underweight. Five percent of individuals with disability due to a high BMI also had musculoskeletal diseases. A number of studies have proven that obesity is a high-risk factor leading to the onset and progression of KOA [14, 15]. Adipose tissue can release a variety of inflammatory factors that affect cartilage matrix synthesis and metabolism, thereby damaging cartilage, causing subchondral bone proliferation, and increasing the risk of knee osteoarthritis [16, 17].
Due to the anatomical structure of the knee joint, the medial compartment is more likely to wear than is the lateral compartment. The medial compartment bears 2/3 of the weight of the whole knee joint, which leads to the narrowing of the medial space and wear, resulting in varus knee deformities. Moreover, obesity can lead to an increase in the angle of the lower limb line of force and aggravate the progression of KOA . HTO is an effective treatment for varus knee osteoarthritis and can effectively correct varus deformities of the knee.
This operation transfers the joint load from the medial compartment affected by osteoarthritis to the relatively healthier lateral compartment, which consequently decompresses the medial compartment of the knee joint. Owing to the realignment of the mechanical alignment of the lower limb, the load on the knee joint is ultimately redistributed to relieve pain and restore knee function. Moreover, HTO combined with arthroscopy can further eliminate articular lesions, can restore the internal environment, and is considered efficacious [19, 20]. Gedam and Supe  conducted a 3-year follow-up of 32 patients who underwent HTO combined with arthroscopy and found that 96.9% of the patients had significant improvements in knee joint function and fewer complications.
DTT-HTO is an improved and easier surgical procedure to perform and has some obvious advantages. First, this technique requires only one singular plane transverse osteotomy at the bottom third of the distal tibial tubercle, and the neurovascular and soft tissue near this area requires fewer osteotomies than that above the tibial tubercle. Second, this technique modifies the intersecting angle between femoral condyles and the fibula axis to 93°. A large number of clinical cases have verified Antonescu's claim that the optimal surgical results can last at least 10 to 15 years when overcorrection by 3° to 6° is performed . Third, five holes are drilled along the transverse plane to lessen the stress on the cortical bone and thus prevent bone fractures during the surgical procedure.
Meidinger et al.  believe that a higher BMI is associated with a higher risk of postoperative internal fixation looseness. In this operation, the osteotomy area was fixed with a new patented π-plate (Fig. 6). The special two-leg design was used to disperse stress to lessen the load on the main leg and to prevent rotation of the tibia after surgery. Both legs were arranged in a three-point plane with the head to resist the tendency of external rotation. The multiscrew locked design offers superior strength and stability to prevent the screws from breaking or loosening. For obese patients, the high internal fixation force can reduce the extent of correction angle loss, and good stability promotes the early healing of the osteotomy end.
Postoperative rehabilitation for obese patients with varus knee osteoarthritis has received increasing attention from many scholars. Due to insufficient lower limb support and internal fixation loosening, postoperative rehabilitation exercises are commonly delayed. DTT-HTO with the π-plate can prevent the internal fixation instruments from breaking or loosening easily because three-dimensional multi-screw locked fixation is performed, which offers superior strength and stability. At the same time, it allows obese patients to exercise the next day, which is conducive to early postoperative recovery.
This study has several limitations. First, there may have been patient selection bias because this study was not a prospective study, and the data were retrospectively extracted from medical records. Second, this study had a small sample size and a short follow-up time, so only the efficacy in the short and medium term can be confirmed to be good. Additional clinical studies with larger sample sizes and long-term follow-up periods need to be conducted. Third, the maximal BMI in this study was only 38.5 kg/m2, and additional studies are required to reach a strong conclusion on the efficacy of DTT-HTO using the π plate in patients with a higher BMI.