A case for partial patellectomy.

VA Mittal 
 E S I S Hospital, Marol, Andheri (E), Mumbai.

Correspondence Address:
V A Mittal
E S I S Hospital, Marol, Andheri (E), Mumbai.

Full Text

::   Introduction

The treatment of fractured patella varies. There are proponents for patellectomy and those for repair. Often, in a fracture of the patella, one fragment is half or more in size, not comminuted, not grossly arthritic. The other fragment or fragments are displaced more than half a centimetre. To perform a partial patellectomy with quadriceps repair seems to be reasonable. The following series explores this.

::   Methods

Eighteen cases of patellar fracture of the kind described in the introduction were treated in one orthopaedic unit, by the author, over a period of 6 years (19851991).

At admission, aspiration of the knee was done and a compression bandage with a knee back slab applied. Ail the cases were operated within one week of admission. All were treated by removal of the smaller fragment or fragments. The bigger fragment was examined for gross naked eye osteo-arthritic changes. (Only one case had gross fissures in the articular surface and exposure of bone beneath the articular surface at a couple of small areas. This case underwent a total patellectomy and is not included in this series). The quadriceps muscle was repaired using anchorage to the retained patella fragment y suturing through the bone with strong chromic catgut. The reattachment of the soft tissue was done as much away from the articular surface as possible. This prevents patellar tilt and consequent patellofemoral arthritis. [Figure:1]

Post operatively, a P O P cylinder cast, ankle to proximal thigh was used. Nonweight bearing, crutch walking was started the day after the operation. Quadriceps setting exercise were started after 2 days of the operation. The patients were discharged on the third or fourth postop day. At 3 weeks from the operation, the patients were readmitted. The P O P cast and sutures were removed. Knee mobilisation, quadriceps strengthening and weight bearing were started. When the patients were sufficiently adequate in knee function, usually knee bending 90 degrees or more and quadriceps power around grade four, they were once again discharged and continued on physiotherapy on an outdoor basis. Follow up was continually maintained till the patients had reached maximum recovery and thereafter at 3 monthly intervals for one year,

The results were graded as follows [Table:1]

::   Results

Of the 18 cases, 10 were females, 8 males. The age ranged from 30 years to 67 years, averaging 47 years. 11 fractures were of the left side, 7 of the right in 16 cases the proximal fragment was retained, in 2 cases distal.

Maximum recovery took between 6 weeks to one year averaging 5 months, after removal of the P 0 P cast and commencement of physiotherapy.

There were 6 excellent results, 9 good, 3 fair, nil bad. The cases with excellent and good results were of a relatively younger age (averaging 38 years) as compared to those with a fair result (averaging 55 years).

A feeling of subjective weakness persisted in 6 cases. Ossification of the quadriceps tendon was observed in 3 cases; 2 of these at 8 months, 1 at 11 months (average = 9 months) following surgery.

::   Discussion

Phylogenetic and ontogenetic development of the patella, indicate it probably has a function. Experimental work shows that the patella improves the efficiency of knee extension in the more important extended positions of the knee joint by holding the patellar tendon away from the axis and thereby increasing the extending moment of the quadriceps pull. Clinical investigation confirm these experimental findings[1]. Besides this, the patella provides a protective function for the knee and is of cosmetic value.

Opinions differ widely as to the proper treatment of a fractured patella.

The effect of patellectomy, total or partial, on the function of the knee, is a matter of controversy[2]. After total patellectomy, weakness of the quadriceps is due to shortening of the distance between the axis of movement of the knee and the quadriceps tendon[3]. Patellectomised knees may require 30% increase in quadriceps power for extension[4]. Patellectomy decreases quadriceps strength permanently by onethird and reduces joint stability in half the cases with complaints of giving way[5]. With partial patellectomy, the continued presence of the pay rope or pulley mechanism and repair of the quadriceps with reattachment to the retained bony patella giving a strong hold, help in good quadriceps function. However, the feel-ting of subjective weakness, though there is no demonstrable decrease in quadriceps strength is a known sequelae of patellectomy, partial or total[3]. This was observed in 6 cases in the present series of partial patellectomies.

In an experimental study in rabbits, early and severe arthritic changes were recorded in the femoral condyles after total pate-llectomy[6]. This was not corroborated in human as an inevitable sequel, especially with avoidance of patellar tilt and consequent patello femoral arthritis by suturing the quadriceps as far away from the articular surface as possible[7]. This procedure was followed in the present series. This is in contrast to Duthie and Hutchinson[8], who sutured the quadriceps as close as possible to the articular surface. In a recent report[9] it has been demonstrated that after partial patellectomy upto 40%, posterior reattachment of the patellar tendon created a movement about the patella, tilting the distal end anteriorly. Anterior attachment tended to minimise this effect. To Thomson also goes the credit for the first report on five fractures of the patella treated by excision of the smaller fragments and capsular repair. Cohn[10] recommended partial patellectomy whenever possible and showed reduced arthritis as compared to total patellectomy. Degenerative arthrosis of ageing complicates evaluation of traumatic arthritis and was not used as a criterion for evaluation of results in the present series.

Fixation of the fracture is an alternative. It is however beset with the usual problems of utilisation of implants. Percutaneous tension band wiring may be used in undisplaced or slightly displaced closed patella fracture where the gap is less than half a em and the patient mobilised immediately after the operation[11]. With open tension band wiring, pain because of skin stretch over the proximal ends of the Kirschner wires with the knee in flexion, bursa over the Kwires, proximal or distal migration of Kwire, have been reported[12]. Inability to start early movements because of inability to fix the fractured patella firmly, especially when comminuted or grossly displaced may compromise movement of the knee following this intraarticular fracture. Potential incongruities of the articular surface after fixation may persist with its consequences. Finally, a second operation for implant removal is required With these drawbacks, partial patellectomy, whenever possible is a good choice.

Duthie and Hutchinson[8] reported slight ossification of the quadriceps tendon in 2 out of 21 partial patellectomies. In their series of 24 total patellectomies, 8 had severe, 6 had slight ossification. This phenomenon was noted after 3 months of surgery, in one case out of 15 cases fixed with tension band wiring[12]. In the present series 3 cases had slight ossification, seen as calcific spots on Xrays at an average of 9 months following operation. This phenomenon probably needs to be studied with a longer duration of follow up. These 3 cases fell under good (one case) and fair (two cases) results. Ossification may be responsible for pain.

The choice of proximal versus distal patellectomy remains an unanswered question given a situation of midpatella, transverse, displaced fracture. There were only 2 cases of proximal fragment removal in the present series. Though both of these had a good result, no proper comparison can be made.

Lastly, with partial patellectomy, especially of either of the poles, patellar replacement can still be considered if needed in the future. Patients without patella may be at a higher risk for failure of total knee arthroplasty[13].

References