All patients undergo a process of informed consent prior to surgery. Under general or spinal anaesthetic, the patient is placed in the prone position, and a mid-thigh tourniquet is applied and inflated to 300–350 mmHg. A lateral support and bolster are used to maintain the knee in approximately 90° flexion. A standard aseptic preparation and drape is used.
Through a medial parapatellar approach the extensor retinaculum is incised from the apex of the quadriceps tendon to the tibial tubercle. Where significant further release is required the tibial tubercle is exposed entirely.
The tibial tubercle osteotomy segment is created using an osteotome medially to provide a maximum thickness of approximately 1 cm. Care is taken to include all of the insertion of the patellar tendon (Figure 1). The osteotome is passed through the medial cortical bone, the cancellous bone and partially through the lateral cortical bone (Figure 2). The lateral periosteum is left intact to act as a hinge for the osteotomy segment. No proximal or distal steps are made. The osteotome is then used to lever the segment from the tibia (Figure 3), providing access to the medullary canal of the tibia (Figure 4).
Realignment is made under direct vision with the segment usually restored to its initial position. Where it is moved to compensate for patellar malignment the periosteal sheath is partially released and stretched to facilitate realignment prior to making drill holes.
Drill holes of 2 mm in diameter are made in the cortex of the osteotomy segment and native medial tibial surface. Drill holes should be positioned carefully to avoid fracture (Figure 5).
The drill holes are positioned so as to allow a 55 mm, 1/2 circle tapercut needle to pass through the cortical surfaces of the osteotomy segment and the tibia. Ideally the distance between the two drill holes should be approximately the same as the diameter of the needle. The paired drill holes in the tibia and osteotomy segment are located approximately equidistant from the cut line.
Drill holes are placed at a minimum distance of 1 cm apart vertically on the tibial surface. The number of sutures used therefore depends on the size of the osteotomy segment and its profile. A minimum of two sutures are required for adequate fixation however three sutures are ideal.
Number 5 Ethibond (Ethicon, Somerville, NJ) braided polyester sutures are used to secure the osteotomy. A single pass through each drill hole is used with the knot placed medially to reduce prominence and discomfort when kneeling (Figure 6).
Ethibond is preferred for its high tensile strength and ease of handling. Ethibond is less cumbersome than wires and less prominent than screws. The 55 mm, 1/2 circle, Tapercut needle allows improved bone penetration when passing sutures.
Post operative care
Patients are encouraged to weight bear with crutches 24 hours post operation, and are assessed by a physiotherapist to ensure safe mobilisation prior to discharge. Patients are also prescribed a course of outpatient physiotherapy focussing on range of motion and strengthening of the musculature around the knee. Follow-up regimen does not differ from other revision arthroplasty patients (Figure 7).
