What did the study look at?
In bone-cutting and realignment operations around the knee (osteotomies), correcting the leg's mechanical axis accurately is considered essential for a good result. Valgus alignment (knock knees) can cause pain and increases the risk of meniscal and cartilage damage in the outer compartment of the knee, leading to early osteoarthritis.
The authors note that computer-assisted navigation is effective for measuring overall limb alignment but has not been shown to control shin-bone alignment or its backward slope, which is why patient-specific instrumentation has been called for. The aim of the article is to describe, step by step, a medial closing wedge high tibial osteotomy performed with a 3D patient-specific cutting guide to correct residual valgus deformity after a failed distal femoral osteotomy.
How was it done?
This is a surgical technique article with a video.
- Planning: full-length leg x-rays from hip to ankle are used to decide whether the deformity comes from the shin bone or thigh bone. Computed tomography (CT) scans and the surgeon's chosen correction angle are sent to the manufacturer, whose engineers virtually plan the cutting planes, wedge size, plate and screw positions and the length of every pin and screw. The surgeon approves the plan and a guide matching the patient's bone is produced.
- Surgery: an incision of about 10 cm is made over the front-inner surface of the shin bone. The guide is placed on the bone, its position is confirmed with fluoroscopy (live x-ray) and it is fixed with pins. Two cuts are made to a preset depth, preserving a bony hinge at least 1 cm thick on the outer side.
- Correction and fixation: the wedge is removed and closed; alignment is checked with a long metal rod and fluoroscopy. A plate is then fixed with screws of pre-calculated length.
After surgery, no weight is borne for the first 2 weeks in a hinged brace locked straight, and non-weight-bearing with crutches continues until 6 weeks. High-impact activities such as jogging may begin by 12 months.
What did it find?
The article does not report its own patient outcomes. In the discussion, the authors cite earlier work: in a study of 20 patients treated with patient-specific cutting guides, the difference between planned and achieved correction was under 2 degrees in 19 patients; another study of 14 people reported a mean difference of 0 degrees in the coronal plane.
Advantages listed by the authors include a guide unique to the patient's bone, preoperative determination of cut location and depth, wedge and screw sizes, shorter operating time and less fluoroscopy exposure.
The authors' conclusion
The authors state that 3D patient-specific cutting guides allow cuts and hinge positions to be visualised and planned better, especially in complex deformities. While clinical studies are needed, they suggest these guides may improve precision in achieving the desired correction and reduce variables associated with complications of osteotomies around the knee.
Limitations
- Waiting for the guide to be manufactured lengthens the time to surgery.
- A relatively larger incision may be needed for the guide to sit correctly on the bone.
- Because the guide is made from the CT scan, bony spurs (osteophytes) cannot be removed during surgery; removing them may cause the guide to sit incorrectly.
Reference
Fortier LM, Gürsoy S, Knapik DM, Chahla J. (2022). Three-Dimensional Patient Specific Instrumentation and Cutting Guide for Medial Closing Wedge High Tibial Osteotomy to Correct Valgus Malalignment. Arthroscopy Techniques, 11(1), e13-e23. Licence: CC BY-NC-ND 4.0.
DOI: 10.1016/j.eats.2021.08.030
Free full text: PubMed Central (PMC8807722)
This article summarises a published scientific paper for general information; it does not replace an examination or a personal medical assessment. Please consult your doctor about your symptoms.
