Abstract
Mini-invasive technique relies on mini skin incision: 5–8 cm long, no tourniquet, no Hoffa’s fat pad, and patellar tendon stress. The incision has to allow the inspection in flexion of the contralateral compartments and the inspection–treatment of the patella in extension (osteophyte removal). During the procedure it is mandatory to check the proper position of the prosthesis components. In case of varus or valgus degeneration, we can perform a parapatellar medial or lateral minimally invasive approach.
In my own experience, from 1984 to 1996, I performed 1067 unicondylar knee replacements (UKR) by the traditional approach. From 1997 to 2001, I operated using the mini-invasive technique on 1091 UKRs. The comparison between these two groups of patients has shown less postoperative pain, quicker recovery and shorter hospitalisation time in the mini-invasive group. There were no differences between groups for shortterm results. For long-term results, in March 2001 we evaluated 112 patients with a UKR (AllegrettoTM – Sulzer Medica) and a relative standard approach with 8–10 years follow-up.
These implants were performed between November 1990 and March 1993, in 105 cases in the medial compartment and in seven cases in the lateral. The preoperative indications were: 98 arthritis, four HTO sequelae, four condyle osteonecrosis, three post-traumatic sequelae, three UKR revision, in eight cases the ACL had degenerated. At follow-up, seven patients were dead, 0 were lost, three revised and two submitted to an arthroscopy (lateral meniscus degeneration). The cause of three revisions (2.5%) was one femoro-patellar degeneration and two aseptic loosening, no septic revision. We think that these survival rates cannot be modified by a minimally invasive technique.
Technically, the mini skin incision needs the observance of some basic rules. A preoperative plan is mandatory to address the thickness and slope of bone cuts as well as prosthesis size. Prosthesis instruments and hardware must be designed to be suitable for minimal bone exposure. With experience we can utilise free hand surgical technique; this technique reduces the operative time and invasiveness. Skin landmarks have to be easily recognised on the anatomical region to preserve the soft tissue around the approach. Skin incision is para-patellar medial or lateral. It starts proximally 1 cm below the superior margin of the patella. It ends distally within 1 cm below the joint line. To expose the femoral condyle it is not necessary to dislocate the patella, but it should be relatively subluxed. When the prosthesis is fitted, the mini-incision allows for a reliable check of stability, alignment, and prosthesis component relation.
The mini-invasive technique permits faster surgery and is particularly suitable for one-stage bilateral UKR procedures and patients with systemic heart and vascular disease. Concerns may arise: the learning curve. The mini para-patella skin incision, among the superior and inferior geniculata arteries, allows a safe and straight approach to the knee.
The abstracts were prepared by Mrs Dorothy L. Granchi, Course Coordinator. Correspondence should be addressed to her at PMB 295, 8000 Plaza Boulevard, Mentor, Ohio 44060, USA.
