[Application of a new type of angle-adjustable osteotomy guide in closing wedge distal femoral osteotomy]

Objective: To explore the feasibility of fast and accurate osteotomy using a new angle adjustable osteotomy guide (AAOG) in closing wedge distal femoral osteotomy(CWDFO). Methods: The clinical data of 14 patients (17 knees) with valgus knee treated with CWDFO at Department of Integrated Chinese and Western Medicine Orthopedics, Honghui Hospital, Xi'an Jiaotong University from January 2018 to July 2019 were analyzed retrospectively. There were 3 males and 11 females, aging (41.4±16.4) years (range: 18 to 56 years). The body mass index was (23.5±3.5) kg/m(2) (range: 18.1 to 28.9 kg/m(2)). The guide pins were placed with the assistance of the self-designed AAOG. Before the surgery, Solidworks software was used to calculate the correction angle and the osteotomy radius accurately. The osteotomy guide was adjusted according to these two parameters. During the surgery, the adjusted osteotomy guide was placed to the surface of bone closely and the guide pins were drilled into the bone through the guide holes. The position of the guide pins was confirmed under fluoroscopy. The osteotomy was finished under guide of pins and fixed with Tomofix plate (Synthes). The times and duration of placement of the guide pins, the times of X-ray examination, the planned and actual thickness of the osteotomy wedge, the top and bottom area of the osteotomy wedge, the posterior distal femoral angle(PDFA), the correction of the weight line, and the American Knee Society Score(AKSS) and Tegner scores were collected and compared by paired t test or Kruskal-Wallis non-parametric test. Healing time after osteotomy and complications were recorded. Results: The guide pins were successfully placed once in 10 knees, adjusted once in 5 knees and twice in 2 knees. The time spent in placing all the 6 pins was 82.4 seconds (range: 51 to 125 seconds), and the times of X-ray examination was 1.5 times (range: 1 to 5 times). The top and bottom areas of the osteotomy wedge were (5.52±0.52)cm(2) and (5.36±0.49)cm(2). PDFA was (85.2±2.6)° preoperatively and (85.5±1.4)° postoperatively (t=-0.401, P>0.05). The thickness of the osteotomy was (11.3±1.9)mm according to the preoperative plan, and the actual thickness was (8.1±1.7)mm. All the patients were followed up for 6 months after surgery and AKSS and Tegner scores improved significantly (all P<0.05). The correction of the weight lines was within the ideal range. Fractures of the hinge point occurred in 3 knees. All of the osseous healing without complications. Conclusion: The new osteotomy guide helps to place the guide pins rapidly and precisely according to the preoperative planning, which should be widely used in clinical applications with promising outcomes.