Trivector Retaining Arthrotomy for TKR - a True Mechanical Approach

Introduction

Success of TKR depends upon soft tissue balance and component alignment. The alteration of quadriceps mechanism while approaching knee for TKR can affect outcome of the surgery.

Aim

To analyse the results of Trivector retaining arthrotomy for TKR

Methods

A prospective study of 448 cases between 2008–2011. All the cases were performed by the author.

Inclusion criteria: Primary TKR with any degree of deformity.

Exclusion criteria: Revision TKR

Patients operated previously with a parapatellar arthrotomy.

Surgical Technique – Approach includes dividing distal 30% of VMO along with medial retinaculum 1 cm. medial to patella distally up to the Tibial tuberosity, raised as a single flap. Patella is everted with knee in extension. Knee flexed to expose the knee articulation and rest of the arthroplasty carried out. The closure of the arthrotomy is by 1 no. vicryl interrupted stitches. (video clipping)

Results

None of the cases were lost to FU. 258 cases Varus + FFD, 153 Varus alone, 21 Valgus, 11 hyperextension deformity and 5 neutral alignment cases were included. Results showed 87% pt.s at 1^st postop day and 96% by 4^th day regained ability to perform unassisted SLR. 4% had 5 to 10 degree quadriceps lag at discharge which recovered to neutral by 4 wks. The surgical field was adequate in all cases and did not have to be extended the arthrotomy incision. KSS score improved from av. Pre op of 54 (38–71) to an average post op of 93 (84–96). All patients by 7 to 10 days were walking unaided or with a single cane in case of Bilateral TKRs.

Discussion

Medial parapatellar arthrotomy divides the quadriceps tendon. The alteration in various vector limbs of Quadriceps can change the balance and laterally maltrack the patella. Incidence of Lateral release is higher in this group.

Subvastus approach is non extensile and hence poor visibility during surgery. Incidence of malalignment is higher in this group.

Trivector retaining arthrotomy approach is extensile and retains 70% strength of vastus medialis. At the closure the quads mechanism is perfectly aligned and hence the incidence of lateral maltracking and lateral release minimised. It is easily reproducible and can be used in stiff knees, severe varus, valgus, obese and post HTO TKRs with consistent results.

The 4% cases who had quadriceps lag were probably transient neuropraxia to the muscular branch of the medial superior genicular nerve. They all recovered at 4 wks. Follow up.

Conclusion

The extensile nature of the approach and minimal disruption of the quadriceps mechanism encourages us to use this approach for all our cases. It is a true mechanically sound approach for all knees for TKRs.