This chapter reviews the indications, surgical technique, complications, and outcomes of tibial tubercle osteotomy (TTO) for revision TKA. Particular attention is paid to technique, which creates a long osteotomy for wide exposure and is followed by rigid fixation that allows for early motion and reproducible healing. TTO is a reliable method to achieve the best possible revision outcome.
Exposure presents a difficult challenge in revision TKA. Adequate visualization is often achieved by resection of fibrotic scar, release of the lateral retinaculum, or quadriceps snip as needed to obtain access to component interfaces for removal and subsequent reconstruction. However, deformity, long-standing joint contracture, and scarring may obviate a more extensile approach in revision surgery. Without careful handling of the soft tissues, rupture of the extensor mechanism and consequent problems become a risk.
Extensile exposures may be used either proximally through the quadriceps mechanism or distally at the patellar tendon insertion to the tibial tubercle. These maneuvers allow access to the knee by displacing the extensor mechanism away from the surgical field. Each of these approaches has specific advantages and potential complications.
This chapter focuses on tibial tubercle osteotomy (TTO) for extended exposure in revision TKA. Specifically, we discuss indications and contraindications, surgical technique, and outcomes of TTO, and we include specific advice to increase success and avoid potential complications.
Indications and Contraindications
TTO is an extended exposure that is indicated only if the standard techniques used in all revision TKAs are unsuccessful in achieving adequate visualization for component removal and subsequent reconstruction. The following sequence should be undertaken routinely in all revision TKAs before resorting to a TTO or other extensile exposure:
Extended skin incision and full medial parapatellar arthrotomy
Resection of fibrotic scar from the suprapatellar region, the medial and lateral gutters, and the deep surface of the patellar tendon
Quadriceps snip (if needed)
If these maneuvers are unable to provide adequate exposure, a TTO may be indicated. Mendes and colleagues recommended TTO if, after standard exposure techniques have been tried, the patella cannot be displaced from the operative field at 90 degrees of flexion without undue risk of avulsion of the patellar tendon from the tibial tubercle.
Quadriceps turndown may also provide adequate exposure if an extended approach is needed. The benefits and risks of quadriceps turndown and TTO have been reported by Barrack and colleagues. Relative indications for TTO, as opposed to turndown, include the need to avoid extensor lag, the need to access the tibial canal for removal of a well-fixed stem or cement mantle, and patella baja. TTO allows the surgeon to proximally translate the patella tendon insertion if patella baja is present.
The only absolute contraindication to TTO is massive tibial osteolysis that, in the opinion of the surgeon, does not leave adequate bone stock for fixation of the osteotomy. Also, loss of anterior cortical continuity with TTO may convert a contained defect to an uncontained one, possibly necessitating a structural rather than a particulate bone graft, as noted by Reis and Richman. Use of a TTO as part of a two-stage resection and reimplantation for infection and use of repeat TTO have been reported by previous authors and are not contraindications. Also, previous osteotomy has not been shown to be a negative prognostic indicator for outcome and therefore is not a contraindication.
TTO surgical technique is largely based on the work of Whiteside. The skin incision is extended distally from the joint line 8 to 10 cm to allow for a long osteotomy. A long osteotomy is preferred because of earlier reports of failure with shorter osteotomies. A micro-sagittal saw is used from the medial to the lateral side of the tibial tubercle to create an osteotomy with a minimum thickness of 1 cm but without penetration of the far cortex. The osteotomy is completed laterally with an osteotome to maintain the periosteal and muscular attachments to the lateral side of the osteotomy fragment. The distal extent of the osteotomy is tapered to prevent creation of a stress riser. Proximally, a transverse step cut is made just proximal to the patellar tendon insertion to provide a restraint to proximal migration of the osteotomy fragment.
This technique creates an osteotomy fragment 8 to 10 cm long with a thickness of at least 1 cm. The osteotomy fragment and extensor mechanism are then retracted laterally to displace them from the operative field and fully expose the TKA components, as depicted in Figure 9.1 . If removal of a well-fixed stem is part of the reconstructive preparation, the thickness of the osteotomy can be deeper to access the tibial canal. Furthermore, if a long stem is present, the osteotomy fragment can be extended farther distally as needed.
On completion of the reconstructive procedure, fixation of the osteotomy fragment is performed. The osteotomy is manually reduced into its bed, with particular attention to flush reduction of the fragment against the proximal step cut to prevent proximal migration. If proximal translation of the osteotomy is planned to treat patella baja, bone is removed from the proximal extent of the osteotomy fragment at this time, followed by routine fixation. With the osteotomy reduced, a small drill bit is used to drill from the medial to the lateral cortex deep to the osteotomy bed. Three holes are drilled in this fashion, after which wires are passed. If these wires pass through the prepared hole for a stem, an instrument is inserted down the tibial canal, and the wires are pushed to the posterior cortex. This allows the prosthetic stem extension to pass anterior to the fixation wires. Because the wires add extra thickness around the stem, the stem should be downsized by 1 mm to account for the thickness of the wires.
After the prosthetic components have been placed, the wires are fixed around the osteotomy fragment and sequentially tightened (see Fig. 9.1 ). It is of particular importance to ensure equal tension on each wire, because if there is unequal tension, a single point of fixation may bear most of the stress, increasing the likelihood of failure. The wire knots are bent away from the overlying skin, because their prominence could lead to skin irritation or wound breakdown. Soft tissue closure then proceeds in the normal fashion, with particular attention to soft tissue approximation over the fixation wires. Preoperative and postoperative radiographs are shown in Figure 9.2 .