A 36-Year-Old Woman

and Iain McNamara¹

(1)

Trauma & Orthopaedics, Norfolk & Norwich University Hospital, Norwich, United Kingdom

A 36-year-old medical secretary with recurrent left patellar dislocation since the age of 15 years old was sent for a second opinion. The original injury occurred when playing hockey where she had twisted her knee on the planted foot. The patella had reduced spontaneously. The knee was then treated in a cylinder plaster of Paris cast. Subsequently, the knee returned to functionally normal. She was able to return to her sports at the same level.

When she was 25 years old, she had a second left patellar dislocation. Subsequently, she underwent an arthroscopy and then later a lateral release. She then had physiotherapy with significant improvement, but not back to her original level. She was able to return to kickboxing.

At the age of 32 years old, her left knee suddenly gave way with a feeling that the patella had moved medially. She was subsequently treated with a tibial tubercle transfer following which the knee was worse. At presentation, she was on crutches wearing a knee orthosis, barely able to get about, could not manage stairs, and had significant pain around the front of the knee interfering with all activities.

Her Kujala score was 11.

Past Medical History

Nil relevant

Family History

None

Current Medication

Co-codamol, tramadol, and paracetamol

Examination

She hobbled about on crutches wearing her hinged knee orthosis. Her BMI was 21 and Beighton score 0 out of 9.

She had a longitudinal scar over the front of her knee, well healed, from her previous operations.

Her overall lower limb alignment was normal with straight legs, normal hip version, and 5^° external tibial torsion. She had no effusion, the VMO was absent and marked patellar apprehension (+++). It was not possible to test her ML glide due to discomfort. She tracked with a slight-J and had a range of knee motion of 0^°/10^°/100^°. She had a palpable trochlear boss. Her tibiofemoral joint was normal.

Question 1

What is the overall problem and how do you expect to manage it?

Question 2

What do you expect the plain X-ray films to show?

Images

She brought hard copy plain images which showed a trochlear dysplasia type D with a boss height of 7 mm. Her Caton-Deschamps ratio was 1.3 (Insall-Salvati ratio 1.5). The patellofemoral joint space was well preserved.

CT Scan Report (Performed Elsewhere and Images Not Available)

“Bilateral trochlear dysplasia with flattening of the trochlear grooves and reduced lateral inclination angle measuring 9^° on the right and 7^° on the left. There has been previous surgery on the left side presumably tibial tubercle transfer with two screws through the proximal tibia. The TTTG distances are within normal limits measuring 9 mm on the right and 8 mm on the left. The knees were scanned at 30^° flexion at which angle the right patella is normally engaged in the trochlear groove. The left patella is slightly displaced medially by 4 mm and shows some incongruity of the patellar articular surface relative to the trochlear groove with an exostosis at the inferior aspect of the medial patellar facet almost on contact with the anterior aspect of the medial femoral condyle. The patellofemoral joint spacing is maintained with no significant loss of articular cartilage

Axial views in full extension were not performed due to pain from the recent injury.”

Question 3

What operation would you plan to undertake and why?

Operation Left Knee

Examination Under Anaesthesia

Patella tracked straight with full extension to 120^° flexion possible
ML glide+, unable to dislocate laterally, and no obvious medial subluxation
Lateral retinacular tightness

Procedure

The old wound was opened and a medial parapatellar approach was performed. On eversion the patella only had minor inferior pole chondral damage which required no treatment.
Scar tissue in the suprapatellar pouch was cleared.
A thick-flap technique deepening trochleoplasty was performed.
Following this the patella tracked in the groove without medial displacement but subluxated laterally at 90^° flexion. A lateral release was therefore performed which corrected this.

Follow-Up 6 Weeks

Slow progress was being made with range of knee motion 0^°–50^°. The wound was well healed. The patella tracked normally. She was awaiting hydrotherapy.

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