Clinical outcome of treatment of patella fractures

                 Clinical outcome of treatment of patella fractures  

                                                Dr KS Dhillon

Introduction

The patella is a sesamoid bone located in the quadricep tendon in the front of the knee.Three quarters of its surface is articular and articulates with the femoral condyles and the distal quarter is non-articular. Fractures of patella comprise about 1% of skeletal injuries. Ninety three percent of patella fractures are close fractures and 78% of the fractures of the patella are due to motor vehicle accidents. Fractures of the patella are also seen in patient undergoing knee replacement, patella tendon anterior cruciate ligament reconstruction and medial patellofemoral ligament reconstruction (1).

Classification

The AO/ASIF classification of patella fractures divides the fractures into 3 groups:

• Extra-articular: 34 A1 and A2

              A1 avulsion fracture of the inferior pole
              A2 isolated body fracture not involving the articular surface

• Partial articular: 34 B1 and B2

              B1 vertical lateral fracture
              B2 vertical medial fracture

• Complete articular fracture: 34 C1, C2 and C3

               C1 transverse fracture
               C2 Transverse with a second fragment
               C3 complex (comminuted) fracture

Treatment

Fractures of the patella can be broadly divided into two i.e stable and unstable fracture.  Stable fractures can be treated conservatively with a brace while unstable fractures are treated surgically.
Stable minimally displaced fractures can be treated conservatively with a knee brace. Fractures with less than 2mm-3mm articular step-off and less than 3mm-5mm separation are considered as minimally displaced fracture (2). Stability is tested with flexion of the knee to 60 degrees under image intensifier. However, all chondral or osteochondral fractures, even those that are minimally displaced are treated surgically. Arthroscopic removal of small fragments and internal fixation of larger fragments is the usual mode of treatment (1).

Unstable displaced fractures are treated surgically. The most commonly used technique is open reduction and internal fixation with tension band wiring. In some situations screw fixation and cerclage wiring can be used to stabilize the fractures (1).

Partial patellectomy may be required in patients with grossly comminuted lower pole fractures where the fracture cannot be stabilized (3). All attempts are made to preserve at least two thirds of the patella to optimise function of the extensor mechanism. Complete patellectomy after fractures of the patella may occasionally be necessary when the patella cannot be salvaged due to infection or gross comminution (1).

Clinical outcome

There is scarcity of literature on the clinical outcome of patella fractures (1). Levank et al (4) did a retrospective review of  64 out 75 patients  treated for fractures of the patella at an average of 6.2 years follow up. Of the 64 patients 34 had a patellectomy and 30 had internal fixation of the fracture. The results were good in 60%, fair in 20% and poor in 20% of the patients with patellectomy. In the group (30 patients) with internal fixation 31% had good, 33% fair and 36% had poor results. The best results were seen in patients who had transverse fractures which were treated with tension band wiring. Cerclage wiring did not give good results. Patellectomy had twice as many good results as compared to open reduction and internal fixation. The authors concluded that if an accurate reduction and stable fixation cannot be achieved then a patellectomy appears to be good option. However patients with a patellectomy would require prolonged rehabilitation and can only reach maximum function in about 2 years.

Lazaro et al (5) prospectively studied the functional outcome in 30 patients with unilateral fractures of the patella at 3, 6 and 12 months after internal fixation of the fractures. In this level IV study fracture union was obtained in all patients. Two patients (7%) had complications in the form of wound dehiscence and refracture. Thirty-seven percent had removal of symptomatic implants. Eighty percent had anterior knee pain during activities of daily living. Clinical improvement occurred over six months but there was residual deficit in quadriceps strength and power at 12 months.
LeBrun et al (6) in a therapeutic level IV study of 40 out of 110 patients (36%) with fracture of the patella who had internal fixation were followed up for a minimum of 1 year and an average of 6.5 years. They reported significant symptomatic complaints and functional deficits at an average of 6.5 years follow up. Hardware removal was required in half the patients. Twenty percent had 5 degree extension lag, 15% had 5 degree extension loss and 38% had more than 5 degree loss of flexion.
Although short and intermediate term follow up studies paint a negative picture of the clinical outcome of fractures of the patella, long term studies appear to paint a better picture. Sorensen (7) reviewed 64 patients with fracture of the patella at 10 to 30 years follow up period. Twenty two were treated surgically and the rest conservatively. Sixty-four percent of the patients (41 patients) were asymptomatic during the follow up period and 23 patients (36%) ‘ had lately suffered from mild, periodical, and non-disabling, osteoarthritic complaints which did not require treatment’. Nine patient (14%) had similar complaints in the uninjured knee. Objective changes on examination were of no practical significance. There was no difference in outcome in patients treated surgically and those treated conservatively. Patellofemoral osteoarthritis was significantly  more common in knees with patella fracture ( 45 knees  as compared to 20 knees). There was no significant difference in the incidence tibiofemoral OA in the knees with and without patellar fracture. None of the patients had patellofemoral symptoms which were severe enough to warrant a patellectomy.

Edwards et al (8) reported a 30 years follow up of 40 patients with fracture of the patella. Four of the patients had a patellectomy. Thirty five percent of the patients (14 patients) had subjective complaints. In patients with more than 2mm diastasis and more than 1 mm of incongruity, about two thirds had complaints and associated reduced quadriceps strength. The quadricep strength was reduced in all patient with patellectomy. The outcome was good in majority of the patients at 30 year follow up. Tibiofemoral OA was seen in 10% of the injured knees and in 5% of the uninjured knees.
Bostrom (9) studied 416 patients with 422 fractures of the patella. Two hundred and eighty two patient with 287 fractures were treated non-operatively and 134 patients with 135 fractures were treated surgically. The follow up ranged between 5 to 12 years with an average of 8.9 years. Seventy percent of the patients were satisfied with the outcome, with 49% having no pain, 20% having slight pain, 18% having moderate pain and 3% having severe pain. The function was not affected in 63% of the patients, slight impairment in 16%, moderate impairment in 6% and considerable impairment in 15% of the patients. Fibrous union was seen in 6% and pseudarthrosis in 3% of the patients. There were no poor results in patients with pseudarthrosis and fibrous union.

Patellofemoral OA was seen in 22% of the injured knee and 8%  of the uninjured knees. Tibiofemoral OA was seen in 18% of the injured knees and in 9% of the uninjured knees. The total incidence of OA of the knee on the injured side was 29% and on the uninjured side was 11%. The presence of OA was related to age and sex of the patient. It was more common in females and in patients who were older than 60 years. Progressive OA was seen in the patellofemoral joint in 10% of the patients and no progressive OA was seen in the tibiofemoral joint. There appeared to be no correlation between articular step off and OA.

In patients treated conservatively the results were excellent in 56%, good in 43% and poor in 1% of the patients. In patients who had operative treatment 25% had excellent,  54% good and 21% poor results.

Mehdi et al (10) reported the outcome of treatment of fractures of the patella with tension band wiring in 203 patients. The average follow up was 6 years (1 -10 years). The incidence of sepsis was 5%, implant loosening 10%, malunion 4.5%, nonunion 4% and  patellofemoral OA 8.5%. The result were excellent or good in 83% and fair to poor in 17% of the patients.

Saltzman et al (11) in 1990 published the results of treatment of displaced fractures of the patella by partial patellectomy. They reviewed 40 patients, who had partial patellectomy, at an average of 8.4 years follow up. They found that the mean active range of knee motion was 94%, thigh girth 100% and quadriceps strength was 85% as compared to the contralateral side. The overall results were excellent in 20, good in 11, fair in 6 and poor in 3 patients. The results were good or excellent in 77.5% of the patients and this implies that partial patellectomy is  an effective treatment option in some patients with displaced fractures of the patella.

Patellectomy for the treatment of patellar fractures has always been controversial. The earliest support for patellectomy came from Brooke who presented 30 cases, in 1937, all with excellent results and there were many publication till 1971 which supported such mode of treatment (4).  However in 1945 Fairbank took a firm stand against patellectomy and described the outcome of patellectomy as disastrous and this made internal fixation of patella fracture more popular (4). Despite the stand against patellectomy there have been encouraging reports of patellectomy in patients where it is not possible to salvage the patella by internal fixation. In Levack’s study of 64 patella fractures, the results in patients who had patellectomy was good in 60%, fair in 20% and poor in 20% of the patients. In this study internal fixation gave poorer results unless it was possible to obtain accurate and stable fixation (4).

Jakobsen et al (12) in 1985 reported the outcome of 28 patellectomy in 27 patients at an average follow up of 20 years (11 to 31 years). The indication for patellectomy was Chondromalacia in 12 knees and patella fracture in 16 knees. They found that the outcome was similar for both groups. The results were excellent in 43%, fair 36% and poor in 21% of the knees. The average quadriceps atrophy was 2 cm and average quadriceps power was ⅔ of the opposite limb. They also found that patellectomy does cause OA of the knee.

Wilkinson (13) reviewed 31 patients who had a patellectomy for the treatment of patella fractures at 4.5 years to 13 years follow up. In this study only 22% had excellent results, 39% had good and 39% had poor results. There was no evidence that a patellectomy in humans leads to OA of the knee  as has been found in laboratory rabbits. Maximal recovery can take upto 3 years.

Peeples and Margo (14) reported satisfactory results in 85% of the patients who had a patellectomy for a fracture of the patella at a mean follow up of 4.6 years. Some quadriceps weakness was present in these patients but quadriceps strengthening exercises overcame the weakness.

Günal et al (15)  in a prospective study comparing simple patellectomy and a patellectomy with vastus medialis obliquus (VMO) advancement found, at a minimum of 3 years follow up, that the outcome was significantly better in patients with VMO advancement. The VMO advancement overcame the problem of quadriceps weakness.

Patellectomy is not a bad procedure as it has been made out to be by some authors. Where it is has to be done it should be combined with a VMO advancement. Ficat and Hungerford (16) has rightly said that “ good patellectomy is better than a bad patella”.

Conclusion

Fractures of the patella constitute about 1% of skeletal injuries. Stable patella fractures are treated conservatively while unstable fractures and all osteochondral fracture are treated by surgery. There is scarcity of literature on the clinical outcome of treatment of patella fractures. Most of the short and intermediate term outcome studies paint a rather negative picture about the clinical outcome, however some long term studies report good results. Relative good results have also been reported in patients who had partial or total patellectomy for the treatment of patella fractures. The outcome is good in majority of the patients with fractures of the patella at 30 years follow up.

The incidence of patellofemoral OA varies between 8% to 22% in patients with fractures of the patella and in about 10% of the patients the OA is progressive. The incidence of tibiofemoral OA is about 18% in the injured knee and about 9% in the uninjured knee. The tibiofemoral OA is usually nonprogressive.
     

References

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