1 Principles top
There exist circumstances in which the patellar fragments cannot be reduced adequately and when function of the extensor apparatus remains compromised. Salvage procedures can produce surprisingly acceptable results. The secret is attention to operative detail by a skilled surgeon.
There are various techniques for patellar salvage:
- Partial patellectomy
- Total patellectomy
- Patellar reconstruction for central articular impaction injuries
- Repair of sleeve fractures of the patella (a detailed description of this technique is available in the dedicated section)
Partial patellectomy is preferred to total patellectomy, whenever possible, as it maintains the extensor lever arm.
If patellar salvage fails, patellofemoral osteoarthritis may well occur. Late salvage after patellar fractures may ultimately require a specialist knee arthroplasty, such as some form of semi-constrained knee prosthesis.
2 Patient preparation and approach topenlarge
This procedure is normally performed with the patient in a supine position with the knee flexed 30°.
For this procedure a mid-axial longitudinal approach is used.
3 Debridement topenlarge
The knee joint and fracture lines must be irrigated and cleared of blood clots and small debris to allow exact reconstruction.
If the comminuted area is significant, the bone fragments should be removed to prevent osteophyte formation.
Large patellar fragments can usually be reconstructed to try to save as much patella as possible.
If the articular surface is badly injured, it should still be salvaged as the patient may get many years from this reconstruction before another procedure need be done.
4 Partial patellectomy topenlarge
A comminuted upper or lower pole is best managed by taking out all small bone fragments.
It is most often the distal pole of the patella that is fractured.
Suture the most proximal part of the remaining patellar tendon to the remaining patella, using transosseous sutures, or suture anchors. To avoid tilting the patellar fragment and increasing patellofemoral contact forces, the patellar tendon should be attached near the posterior aspect of the remaining patellar fragment.
Then repair the lateral and medial parapatellar retinacula.
The biomechanics of the remaining patellofemoral joint will be abnormal but will give a better clinical outcome than a total patellectomy.
The addition of a patellotibial cerclage wire should be used to protect the sutures.
5 Total patellectomy topenlarge
Total patellectomy is reserved for severe multifragmentary fractures of the patella, which may be combined with significant osteochondral damage to the patellofemoral joint. In situations where repair is not possible, the entire patella is excised.
Remove the entire patella by sharp dissection, as close to the bone as possible.
Suture the proximal extensor mechanism, with a nonabsorbable suture, to the distal extensor mechanism.
The lateral and medial patellar retinacula – if torn – should also be repaired.
After total patellectomy early functional results are surprisingly good, but deteriorate with time.
Pearl: When “shelling out” the bony portions of the patella from the extensor mechanism, use a series of new, sharp scalpel blades (they blunt quickly) and cut into the “axilla” of the fiber attachments to the bone. This keeps the dissections as close to the bone as possible, ensuring maximal preservation of the extensor tendinous tissue. This is especially important over the front of the patella.
6 Patellar reconstruction for central articular impaction injuries topenlarge
Severe central comminution of the patella is a rare, but very difficult injury to treat.
As a salvage procedure, the injured segment may be removed by transverse osteotomy.
The osteotomy may be secured with two 3.5 mm partially threaded, cortical, cannulated screws inserted as lag screws.
Ensure that there is maximally possible alignment of the articular surfaces of the residual 2 portions of the patella: this may result in an anterior step at the osteotomy, which is of no consequence.
This patellar construct may well require augmentation of the fixation with a cerclage or tension band wire.
7 X-ray control top
The final result is checked in the AP and lateral planes using an image intensifier or X-ray.