Tibial Tuberosity Transfer

Patella tracking is governed by a complex interaction between soft issue and bony structures. The bony structures that control patella stability are trochlea dysplasia, patella height and tibial tuberosity trochlea groove distance(TT-TG). Patella lateral tracking is common in patients with patella femoral pain and also with patella instability. Hence tibial tuberosity transfer is a well established technique in the management of both patella instability and patellofemoral pain.

Medialisation of the patella was done indiscriminately for non-anatomical reasons of patella instability. Hence the procedure historically has high complication rate. With better understanding of the various factors contributing to patella maltracking, a combination approach is now used to correct TT-TG distance and provide medial passive stabilisers like the MPFL at the same time.

The decision on tibial tuberosity transfer is made for PF pain/instability after

  • Clinical examination
  • Imaging measurement of TT-TG distance and patella height
  • Arthroscopic assessment of the pattern of articular cartilage damage

It is difficult is place a single numerical value of TT-TG distance as indication for surgery but a distance of less than 1.5 makes it less likely necessary. measurements can be made with both CT and MRI.

Technical Tips

  • Mark the proximal extent of the osteotomy
  • The author prefers a low energy osteotomy without use of a saw
  • Keep the distal hinge narrow but retain distal soft tissue attachment
  • For Distalisation osteotomy mark the pre-planned amount of distal tuberosity to be resected as shown
  • Take care about the length and obliquity of the osteotomy
  • Fixation is best achieved with 2 x 4.5 large fragment screws with screw heads countersunk so they do not cause irritation

Rehabilitation

  • Weight bearing mobilisation in an extension splint
  • Intermittent range of motion outside splint started early
  • Keep splint for all walking until 6 weeks

Clinical Assessment

  • Hyperlaxity score(see picture)
  • Beighton P, Horan F. Orthopaedic aspects of the Ehlers Danlos syndrome. J Bone Joint Surg Br. 1969;51-B:444-453.
  • Coronal and rotational alignment
  • Flat feet
  • Quadriceps and core strength
  • Functional valgus on single leg squat
  • Lateral patella eversion
  • Patella displacement
  • Tibial tuberosity offset

Radiological Assessment

Radiological assessment to look at soft tissue and bony constituents and also to assess Patellofemoral cartilage damage

Imaging in patellofemoral instability: an abnormality-based approach.

  • Saggin PR, Saggin JI, Dejour D.
  • Sports Med Arthrosc. 2012 Sep;20(3):145-51