Patient-specific cutting guides increase accuracy of medial opening wedge high tibial osteotomy procedure: A retrospective case-control study

Abstract

Purpose: To compare the accuracy of patient-specific guides (PSCG) to the standard technique in medial open-wedge high tibial osteotomy (OWHTO). Secondary objectives were to evaluate factors that could influence accuracy and to compare the complication rate and operating time for both procedures.

Methods: A retrospective analysis of prospective collected data was performed. Between March 2011 and May 2018, 49 patients with isolated medial knee osteoarthritis who were operated for OWHTO using PSCG and 38 patients using the standard technique were included. Preoperative and postoperative deformities were evaluated on long leg radiographs by measuring the mechanical medial proximal tibial angle, mechanical lateral distal femoral angle, hip knee ankle angle (HKA), and joint line convergence angle. Pre- and postoperative posterior tibial slope was also evaluated. Accuracy was evaluated by analysing the difference between the preoperative planned and the actual postoperative HKA. Operating time and complication rate were also recorded in both groups.

Results: The mean preoperative HKA was 173.4° (±3.1°) in the PSCG group and 173.3° (±2.4°) in the standard group (p = 0.8416). Mean planned HKA were 182.8° (±1.1°) and 184.0° (±0°) respectively for the PSCG and the standard group. Mean postoperative HKA were 181.9° (±1.9°) and 182.6° (±3.1°) respectively for the PSCG and the standard group. An accuracy of ±2° in the HKA was achieved in 44 (90%) in the PSCG group and 24 (65%) in the standard group (p = 0.006). The probability of achieving a HKA accuracy was four times higher for patients in the PSCG group (odds ratio [OR] = 4.06, [1.1; 15.3], p = 0.038). Also, higher preoperative Ahlback grade was associated with precision, all other parameters being equal (OR = 4.2, [0.13; 0.97], p = 0.04).

Conclusion: In this study, the PSCG technique was significantly more accurate for achieving the planned HKA in OWHTO. Complication rates and operating times were comparable between groups.

Level of evidence: Level IV, case-control study.

Keywords: 3D; medial open‐wedge high tibial osteotomy; patient‐specific cutting guide; tibial osteotomy accuracy.

Figure 1

(a) Full‐length lower limb preoperative radiograph. Hip knee ankle angle was defined as the angle formed by the intersection of a line from the centre of the femoral head to the knee centre landmark and a second line from the centre of the ankle talus to the knee centre landmark. Lateral distal femoral angle was defined as the lateral angle between mechanical axis of the femur and the tangent line of the distal femoral condyles. Medial proximal tibial angle was defined as the medial angle between the mechanical axis of the tibia and the tangent line of the tibial plateaus. (b) Joint line convergence angle was defined as the lateral angle between the tangent line of the femoral condyles and the tangent line of the tibial plateaus. (c) Posterior tibial slope angle is formed between a line perpendicular to the longitudinal axis of the tibia and a line passing through the anterior and posterior high points of the tibial plateau.

Figure 2

3D nylon® printed instrument.

Figure 3

Inte‐rater intraclass correlation coefficient (ICC) for hip knee ankle angle (HKA) measured preoperatively. Cicchetti (1994) provides the following, often cited, guidelines for interpreting ICC measurements: Less than 0.40: poor/Between 0.40 and 0.59: fair/Between 0.60 and 0.74: good/between 0.75 and 1.00: excellent.

Figure 4

Interrater intraclass correlation coefficient (ICC) for hip knee ankle angle (HKA) measured postoperatively.