Case 1 - Malposition with overstuffing of the femoral component.

This 62 year old lady presents with typicallateral facet patellofemoral arthritis. A patellofemoral arthroplasty was performed. In the post-operative period she had severe pain and inability to flex the knee. In spite of vigorous rehabilitation, physiotherapy, manipulationunder anaesthesia and continuous passive motion she had continual stiffness and pain.'

Post-operative radiographs show that the prosthesis was positioned in 15° of extension leading to overstuffing of the trochlea.

Pre operative lateral X ray

Revision operation confirmed that the femoral cut was in some 15° of extension and the prosthesis had not been fully inset congruous with the articular surface of the medial and lateral femoral condyles.

    
Operative findings with elevated trochlear

The femoral component was repositioned with adjustment of the femoral cut and the prosthesis inset so that it was congruous with the medial and lateral femoral condyles.

After reinsertion of the trochlea

Post-operative recovery proceeded satisfactorily and she quickly regained over 90° of flexion with complete relief of pain.

Post operative lateral view

At four months she had achieved a range of movement to 120° and was able to walk normally.

At 5 years she had no pain, a full range of movement and maximum functional scores.

The error in the primary operation was,therefore, malposition of the femoral component in extension and it had not been fully inset congruous with the articular surfaces.

Case 2 - Post patellectomy problems

This 46 year old woman presented with pain,swelling and instability of the knee thirty years following a patellectomy. The symptoms of pain and weakness had been present since the original operation but had got worse in the last six to twelve months.

An MR scan showed that there was trochlea dysplasia and the residual extensor tendon was flattened and positioned over the lateral femoral trochlea.

An Avon femoral trochlea replacement was performed and the extensor mechanism was realigned with releasing of the lateral structures and plication of the medial structures so that the extensor tendon was centralised in the new patellar groove.

The patient made an excellent recovery and two years later had full function with no pain and excellent stability of the joint.

Ref: Ackroyd CE,  Smith EJ , Newman JH. Trochlear resurfacing for extensor mechanism instability following patellectomy. Knee 2004. 11: 109 -111.

Case 3 - Persistant dislocation of patella with trochlea dysplasia

This 45 year old woman presents with pain and stiffness in the left knee with a persistently dislocated left patella. There was marked restriction of the range of movement to only 40° of flexion.

The knee was approached through a lateral incision and the markedly deformed dysplastic trochlea was replaced with an Avon patella, which was inset with external rotation. The patella itself was resurfaced and an Elmslie distal realignment procedure was performed.

                  
      Deformed and dysplastic trochlear                  Avon trochlear inset with slight external rotation

Post-operatively the patella tracked satisfactorily and she made a good recovery with full extension and a good range of flexion.

         
Post operative x rays with good function

Case 4 - Failure to resurface the patella

This 62 year old woman presented with severe lateral facet patellofemoral arthritis. At operation the trochlea was replaced with a small size component, which fitted well and was well inset. The patella itself was extremely small with marked erosion of the lateral facet. At the time it was considered that it was not possible to resurface the patella, which was left unchanged.

		Post operative tangential x ray

The patient continued to complain of persistent pain, swelling, stiffness and giving way. It was decided then to carry out a resurfacing procedure. A peri-patellar sub periosteal lateral retinacular release procedure was performed to expose the lateral osteophyte and the patella was exposed to present the odd facet. A thin sliver of bone was removed mainly removing the medial facet keeping the lateral osteophyte intact in order to contain the bone defect of the lateral facet. A small button fitted well and after shortening of the lateral peg the component fitted well and was stable.It was cemented into good position with the lateral osteophytes forming a containment rim for the defect. After the cement had set any residual osteophytes were trimmed. The patella tracked satisfactorily at the end of the procedure and she made a good recovery from operation with complete resolution of the symptoms.

Post-operative X-rays after patella resurfacing showing anteroposterior, lateral and tangential views.