Mid Vastus; Mini Mid Vastus Approaches

Key Concepts

Patient is positioned supine without the use of a leg holder or hip rest to give the surgeon maximum intraoperative flexibility to change the position of the knee.
The skin incision is medial to the midline from 4 cm proximal to the superior pole of the patella ending just medial to the tibial tubercle.
The intersection of a transverse line marking the superior pole of the patella and a line along the medial patella marks the location where the arthrotomy should intersect the vastus medialis obliquus (VMO) muscle. The arthrotomy is then angled proximally at 50° in line with the fibers of the VMO.
The arthrotomy closure is started at the clearly defined corner defined by the intersection of the medial arthrotomy and VMO at the level of the superior pole of the patella.
The sutures closing the VMO muscle itself are specifically not overtightened; instead the VMO muscle belly is simply reapproximated.

Sterile Instruments and Implants

Two 90° bent Hohmann retractors
One posterior cruciate ligament (PCL) retractor
Two Kocher clamps
One knee retractor
One ¾-inch curved osteotome
One mallet
One lamina spreader
One large rongeur

Preoperative Planning

The limb is examined for prior incisions, contractures, patellar immobility, and deformity.
Neurovascular status of the limb is always documented.
Four radiographic views of the knee (anteroposterior standing, lateral, posteroanterior flexion standing, and patella view) and a standing, full-length, hip-to-ankle radiograph are obtained and examined.
Preoperative templating is performed to maximize intraoperative efficiency and determine the proper orientation and level of the bone cuts.

Bone, Implant, and Soft Tissue Techniques

Introduction

The mid-vastus approach to the knee is a safe and reproducible way to access the knee joint. With this approach there is minimal violation of the extensor mechanism by angling the proximal portion of the arthrotomy along the midsubstance fibers of the VMO when reaching the superior pole of the patella. This minimally invasive approach allows for a smaller skin incision and reliable closure of the arthrotomy.
Those patients with a very stiff knee, patella baja from any cause, or retained hardware from prior surgery may be better served with a standard medial patellar approach.

Technique

Positioning and draping
- The patient is positioned supine on the operating room table (Figure 46.1). No leg holder or hip rests are used to stabilize the knee. This allows the surgeon to have maximum flexibility in changing the position of the knee intraoperatively.
- A tourniquet is placed on the proximal thigh and the knee prepped and draped in a sterile fashion.
- Transverse lines are drawn anteriorly on the knee before applying iodine-impregnated drapes to all exposed skin (Figure 46.2).
Superficial exposure
- With the knee flexed, a skin incision is made medial to the midline from 4 cm proximal to the superior pole of the patella and extended just medial the tibial tubercle (Figure 46.2).
- The knee is then placed in extension on the table. A clean scalpel or cautery may be used to develop a medially based skin flap to visualize the VMO, while preserving the overlying fascia. The tissue plane just superficial to the VMO fascia is used to verify correct dissection depth.
- A lateral skin flap is made to the lateral border of the patella to allow for improved intraoperative patellar mobility.

Arthrotomy

The superior pole of the patella is marked by a transverse line with a marker (Figure 46.3). A longitudinal line from just medial to the tibial tubercle along the medial aspect of the patellar tendon and patella is marked. The location where these 2 lines intersect marks where the arthrotomy should be angled proximally at 50° in line with the fibers of the VMO (Figure 46.4A and B).