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Intraoperative mobilisation of knee and its effect on the final functional outcome in patella fractures: a clinical study

Being the largest sesamoid bone in the body, patella is an important component of the extensor mechanism of knee. The extensor mechanism plays an important role to stabilise the knee when extended as in case of erect posture. Patella increases the lever arm of the extensor apparatus and thus enhances quadriceps power. These fracture constitute about 1% of all fractures in the body. Patellar fracture generally leads to stiffness and loss of knee movements. Even after bone healing, functional outcome deteriorates due to Stiffness of joints, continued swelling, muscle wasting and bone atrophy. This study was conducted to see for the effect of intraoperative mobilisation of knee on range of motion in postoperative period and functional outcome of tension band wiring in patella fractures.


INTRODUCTION
Being the largest sesamoid bone in the body, patella is an important component of the extensor mechanism of knee. 1 The extensor mechanism plays an important role to stabilise the knee when extended as in case of erect posture. Patella increases the lever arm of the extensor apparatus and thus enhances quadriceps power. 2 These fracture constitute about 1% of all fractures in the body. 3 Patellar fracture generally leads to stiffness and loss of knee movements. 4 Even after bone healing, functional outcome deteriorates due to Stiffness of joints, continued swelling, muscle wasting and bone atrophy. 5 This study was conducted to see for the effect of intraoperative mobilisation of knee on range of motion in postoperative period and functional outcome of tension band wiring in patella fractures.

METHODS
This prospective study was conducted in our tertiary care centre. We had 30 patients with transverse patella fracture from January 2016 to February 2018. 26 out of 30 were males.

Exclusion criteria
Exclusion criteria were open fractures; associated other fractures in the same limb.
When the patients presented to us, x rays were done, both anteroposterior and lateral views. Average duration of injury to surgery was 7 days. Tension band wiring was performed in all the patients.

Technique
Patient placed in supine position. Midline longitudinal incision ( Figure 1) given over patellar area. Skin and subcutaneous tissue were reflected. Joint was thoroughly irrigated and blood clots removed. Reduction achieved with Clamps. Articular surface of patella was checked for any loss of reduction. Two Kirschner wires of 2 mm inserted from superior to inferior poles, in parallel, about one finger breadth deep to anterior surface of patella.
With an 18 gauge stainless steel wire, passed transversely through the quadriceps tendon, figure of eight configuration of tension band wiring done. At the superolateral side, the wire was tightened.  The under surface of patella was checked for any loss of reduction. Upper ends of k wires were bent and buried into superior margin of patella posterior to wire loop. When the fixation was seemingly stable, then knee bending was done as much as the knee allowed, at least up to 90 degrees ( Figure 2). The tears in the retinaculum were repaired thorough wash given. Sutures applied. After sterile dressing, the limb was immobilized in a rigid knee brace. Preoperative and postoperative X rays compared (Figure 3 and 4). Patients were evaluated at 1 month, 4 month, 6 month and 1 year. Physiotherapy and touch down weight bearing started on 2 postoperative day. On final follow up, functional outcome seen with hospital score for special surgery knee (Table 1). 6 Range of motion was also recorded.

RESULTS
This prospective study was conducted in our tertiary care centre from January 2016 to February 2018 with mean age being 40 years (ranged from 25-65 years). Of the 30 patients, 26 (86.66%) patients were male and 4 (13.33%) patients were female. 20 (66.66%) patients had injury on right side. All had fracture due to road traffic accident. Mean duration of operation was 1 hour (30 minutes to 2 hours). At the end of 1 year follow up only 2 patients had range of motion <90, 4 patients had range of motion 90-120 degrees and 24 patients had range of motion >120 degrees (Table 2) and as per the hospital score for special surgery, functional outcome was, excellent in 24, good in 4, fair in 1 and poor in 1 (Table 3).

DISCUSSION
Our patients were mostly in the age group 20-40 years (range 20-65) with an average of 30 years. Both Smith and Bostrom mentioned the mean age as 48 years in their respective series. 7,8 Surgical treatment aims anatomic reduction; restoration of articular congruity, preservation of patella and extensor mechanism to get repaired. Surgical indications are displacement >2 mm, articular step off, or active extension loss. 9 In a study by Mehdi et al shows excellent and good results in 203 patellar fractures treated by TBW. 10 Decreased range of motion (ROM) is the commonest complication after patellar fractures. Improper rehabilitation is reported to be one of the main reasons. Also, the soft tissue damage leads to subcutaneous and intraarticular adhesions that may lead to decreased range of motion in knee. Nikiforidis et al, in his study found that mostly, only the terminal degrees of flexion range of motion are affected which patients usually tolerate well. 11 In such cases, intense physiotherapy is the well-known standard method. If physiotherapy fails to improve range of motion then partial or total hardware removal with arthroscopic arthrolysis of intra-articular adhesions can be done. 12 Lotke in his study found that those who had more prolonged immobilisation had experienced more diminished range of motion. 13 Hung et al studied the effectiveness of early range of motion exercise after stable fixation and found a similar satisfactory results. 14 So we can say that after stable fixation of patellar fractures early knee movement gives better functional outcomes. We can try to generalise similar results of knee movements intraoperatively, that may break some intraarticular adhesions and give good results. Muller et al noted that stable fixation by tension band wiring allows early knee mobilization and optimum return of knee flexion. 15 In contrast, Phieffer et al concluded in their study that despite appropriate surgical management, some loss of knee flexion is usually evident. 16 In the final follow up, our functional outcome was assessed according to the modified hospital for special surgery knee score as excellent in 24 (80%), good in 4 (13.33%), fair in 1 (3.3%) and poor in 1 (3.3%). Schimitschh et al mention that operatively fixed patellar fractures give good results but lack outcome measures with proven validity. 17 However, in their study, Gardner et al differ and say that long term outcomes from different clinical series have been modest. 18 We can say that intraoperative mobilisation of knee joint brings similar effect as early range of motion exercises of knee, though more studies are needed to support this.

CONCLUSION
Intraoperative mobilisation of knee after a stable fixation with tension band wiring of patella can prove to a very effective method for increasing postoperative range of motion and improving functional outcome as patient is under the effect of anesthesia and manipulation can be easily done which couldn't be that easy afterwards. That also leads to ease in postoperative physiotherapy.