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Z-PLASTY FOR A DISLOCATING KNEECAP

Method
Soft-tissue balancing in instability of the kneecap
Duration
30 to 45 minutes
Recovery time
about 6 weeks

The Z-plasty is a surgical procedure for balancing the soft tissue where the kneecap is unstable. The aim is to reduce the pull of the lateral retinacula and so bring the kneecap into a more stable, more medial track. The ligaments on the outer side – in particular the lateral retinaculum – are deliberately lengthened or repositioned without weakening the anatomical structures.

How does the Z-plasty work?

The shortened lateral retinaculum is exposed through a small incision on the outer side of the kneecap. It is then divided in a Z shape so that it can be stretched and sutured again in a lengthened position. This reduces the sideways pull on the kneecap.

The Z-plasty is particularly suited to patients with excessive lateral tension and no bony deformity. The correction is made precisely and gently on the tissue, so that instability in the opposite direction usually does not arise. The operation is generally carried out in a minimally invasive way.

Rehabilitation after a Z-plasty

The Z-plasty is followed by targeted physiotherapy to restore movement and to stabilise the track of the kneecap muscularly.

Phase I (0-2 weeks): protection and mobilisation
  • Partial weight-bearing with crutches
  • Movement splint (for instance 0-30°) for mobilisation
  • Cooling and lymphatic drainage to reduce swelling
  • Isometric activation of the quadriceps
Phase II (2-6 weeks): building up load
  • Building up to full weight-bearing once the gait is stable
  • Active mobilisation exercises to about 90° of flexion
  • Exercise-bike training without resistance
  • Co-ordination and balance training
Phase III (from week 6): stabilisation and function
  • Strengthening the thigh muscles
  • Joint stability training
  • Increasing movement beyond 120°
  • Sport-specific training