The Length of Incision in Unicondylar Knee Arthroplasty Is More Affected by the Patient's Height Than Their Weight

Objective Obesity leads to osteoarthritis due to increased loading forces on joint cartilage and inflammatory agents released from adipose tissue. In patients with a high body mass index (BMI), during hip and total knee arthroplasty, surgical technical challenges such as longer incisions and wider exposure are encountered, resulting in increased postoperative complications (wound healing problems and infection, venous thromboembolism (VTE)- pulmonary embolism (PE), dislocation, early implant failure) and ultimately decreased patient satisfaction and implant survival. This study investigates whether BMI, height, weight, and patient age are associated with longer incisions in patients undergoing unicondylar knee prosthesis (UKP) placement. Method Between January 2017 and December 2018, 30 patients (29 females and 1 male) who underwent UKP surgery due to medial gonarthrosis were included in the study. The UKP used in the procedures was the Oxford Knee Phase III by Biomet Ltd., UK. The study comprised 43 knees, 13 being bilateral cases, 8 on the right, and 9 on the left. Data regarding the patient's height, weight, BMI, age, and the operated side were collected and compiled. The relationships between these variables and the surgical incision length were statistically analyzed. Results The average age of the patients was 66.3 years, with an average weight and height of 77.6 kg (ranging from 62 to 98 kg) and 167 cm (ranging from 150 to 184 cm), respectively. The lengths of the surgical incisions ranged from 70 mm to 160 mm, with an average length of 124.5 mm. When comparing the incision lengths between the right and left sides, it was observed that the incisions on the left side were longer. The average incision length on the right side was 122.09 mm, while on the left, it was 126.86 mm. Moreover, in the 13 patients who underwent bilateral surgery, this difference in incision length was even more pronounced. The average incision length on the right side was 117.15 mm, whereas on the left, it was 124.23 mm. Bivariate correlation analyses were performed to examine the relationship between the length of the incision and BMI and age. However, no significant relationship was found between the incision length and BMI or age. On the other hand, there was a correlation between the patient's weight values and the incision length (p < 0.05, correlation 0.335). Furthermore, a higher correlation was observed between the patient's height and the incision length (p < 0.01, correlation 0.595). Conclusion The latest advances in surgical techniques and instrumentation have enabled surgeons to perform the procedure using a reliable mini-incision approach. Mid-term evaluation of UKP with mini-incision shows faster recovery and lower morbidity. The findings show that in UKP, the length of the surgical incision is more strongly related to the patient's height than their weight.