Patella Fracture Fixation with Suture and Wire: you Reap what you Sew

Abstract

Introduction

Operative fixation of displaced inferior pole patella fractures has now become the standard of care. This study aims to quantify clinical, radiographic and functional outcomes, as well as identify complications in a cohort of patients treated with non-absorbable braided suture fixation for inferior pole patellar fractures. These patients were then compared to a control group of patients treated for mid-pole fractures with K-wires or cannulated screws with tension band wiring.

Methods

In this IRB approved study, we identified a cohort of patients who were diagnosed and treated surgically for a displaced patella fracture. Demographic, injury, and surgical information were recorded. All patients were treated with a standard surgical technique utilizing non-absorbable braided suture woven through the patellar tendon and placed through drill holes to achieve reduction and fracture fixation. All patients were treated with a similar post-operative protocol and followed up at standard intervals. Data were collected concurrently at follow up visits.

For purpose of comparison, we identified a control cohort with middle third patella fractures treated with either k-wires or cannulated screws and tension band technique. Patients were followed by the treating surgeon at regular follow-up intervals. Outcomes included self-reported function and knee range of motion compared to the uninjured side.

Results

Forty-nine patients with 49 patella fractures identified retrospectively were treated over 9 years. This cohort consisted of 31 females (63.3%) and 18 males (36.7%) with an average age of 57.1 years (range 26 - 88 years). Patients had an average BMI of 26.48 (range 19 - 44.08).

Thirteen patients with inferior pole fractures underwent suture fixation and 36 patients with mid-pole fractures underwent tension band fixation (K-wire or cannulated screws with tension band). In the suture cohort, one fracture failed open repair (7.6%), which was revised again with sutures and progressed to union. Of the 36 fractures repaired with a tension band fixation, 11 underwent secondary surgery due to hardware pain or fixation failure (30.6%).

At one year, no difference was seen in knee range of motion between cohorts. All fractures healed radiographically. Those patients who required reoperation or removal of hardware had significantly diminished range of motion about their injured knee (p > 0.005).

Conclusions

Patients who sustain inferior pole patella fractures have limited options for fracture fixation. Suture repair is clinically acceptable, yielding similar results to patella fractures repaired with metal implants. Importantly, patients undergoing suture repair appear to have fewer hardware related postoperative complications than those receiving wire fixation for midpole fractures.

Introduction

Patella fractures comprise 1% of all fractures encountered in the emergency department, and only a third of these require surgical intervention¹². Among patellar fractures treated surgically, approximately 20% involve the inferior patellar pole³. Historically, a debate existed between resection of the inferior pole versus surgical reduction and fixation. Currently, clinical and biomechanical studies have provided definitive evidence that resection disrupts the extensor mechanism by decreasing the lever arm at the knee joint^4,5. Operative fixation of displaced patella fractures has now become the standard of care for these injuries⁶.

The Modified Anterior Tension Band technique with Kirschner wires (K-wires) is one of the most common methods used for fixation of simple mid-pole patella fractures. Although the K-wire and tension band technique remains popular, patients frequently complain of discomfort secondary to prominent hardware, leading to high rates of removal of hardware (ROH). Other techniques, such as the fixed angle plate and the basket plate, intended for use in distal pole fractures, have been developed^7-9. These alternatives have yet to supplant techniques involving tension banding, which are still considered the gold-standard for fracture care^10,11. Furthermore, some comminuted and inferior pole fractures are not amenable to standard fixation techniques. Recent studies have suggested that sutures such as 5- Ethibond and Fiberwire are similar in strength to, yet avoid the irritation associated with, 18-gauge stainless steel wires^12-13-14.

This study aims to quantify clinical, radiographic and functional outcomes, as well as identify complications in a cohort of patients treated with non-absorbable braided suture fixation for inferior pole patellar fractures. These patients were then compared to a control group of patients treated for mid-pole fractures with K-wires or cannulated screws with tension band wiring. We hypothesize there will be no observable difference in outcomes between the two groups.

Methods

In this IRB approved study, we performed a retrospective chart review which identified 49 patients who sustained 49 displaced patella fractures and were treated surgically over a 9 year period (2002-2011); no patients were excluded. Patient demographics, injury pattern and mechanism, and surgical information were extracted from the record. The treating surgeons followed each of their patients at standard intervals. Radiographs and functional data were recorded at these follow-up visits.

A standard surgical technique for suture repair was employed. Two non-absorbable braided sutures were placed in a Krackow type fashion yielding four proximal suture ends. Three longitudinal drill holes were made along the long axis of the patella. Suture ends were passed through the drill holes with a Beath Needle, and following reduction with a tenaculum clamp, tied down over top of the patella (Fig 1a, 1b and 1c). Correction of patella alta and fracture reduction was confirmed using intraoperative image intensification. Post-operatively, all patients were allowed to bear weight in extension while in a knee immobilizer for six weeks. Knee range of motion was limited for six weeks. Radiographs were obtained at standard intervals to assess fracture healing. Lysholm Knee Score¹⁵ and Tegner Activity Scale¹⁶ scores were obtained to objectively quantify knee function and SF-36¹⁷ was used to assess general well-being. Data were collected at follow up visits.

Figure 1a. Lateral view of patient presenting with an inferior pole patella fracture.

Figure 1b. Sutures are woven in Krackow fashion and passed through holes made lengthwise in the patella with a Beath needle.

Figure 1c. The sutures are tied down over the top of the patella after reduction.

For purpose of comparison, we utilized a control cohort of patients who sustained a mid-pole patella fracture treated with either K-wire or cannulated screws and wire tension band technique. This procedure was performed using a modified AO technique where 18-gauge wire is crossed in a figure-of-eight fashion over the anterior patellar surface and tensioned with knots superiorly. Patients were followed by their treating surgeon and outcomes, including self-reported function and knee range of motion compared to the uninjured side, were recorded. Statistical comparison was made with Fisher's exact test and students paired t-test with a significance threshold set at p = 0.05.

Results

We identified 49 patients who sustained 49 displaced patella fractures that were treated surgically by 2 surgeons over a 9 year period, from 2002 to 2011. This cohort consisted of 31 females (63.3%) and 18 males (36.7%) with an average age of 57.1 years (range 26 - 88 years). Patients had an average BMI of 26.48 (range 19.7 - 44.1). Patients in each surgical intervention cohort had statistically identical BMI and age. The most common cause of injury reported was a low energy fall; one patient was involved in an MVA. Patients were followed clinically at standard intervals and functional outcomes were assessed at one year (Table 1).

Table 1.

Demographics and outcomes from suture and wire tension band fixation at one year

	Suture Cohort (N= 13)	Tension Band Cohort (N=36)
Sex	30.8% Male	38.9% Male
BMI	25.8 (19.7 - 38.9)	26.7 (20.2 - 44.1)
Age	55.3 (36 - 75)	57.8 (26 - 88)
Reoperation	1	11
SF-36	84.1 (68.4 - 96.9)	75.8 (14.1 - 99.4)
Lysholm	82 (56 - 100)	78.4 (22 - 100)
Tegner	2.77 (1 - 4)	2.53 (1 - 4)
ROM Change (Degrees)	-9.6 (-50 - 0)	-8.3 (-30 - 0)

Thirteen patients with 13 fractures involving the inferior pole of the patella underwent suture fixation (Fig 1) and 36 patients whose fractures involved the mid-pole region underwent K-wire or cannulated screw and wire tension band fixation (Fig 2). Of the suture cohort, one patient had an initial failed fixation (7.6%). Revision surgery consisted of inferior pole patellectomy and patella tendon advancement. Of the 36 patients receiving tension band fixation, 11 had secondary surgery due to hardware pain or failure (30.6%). Hardware removal occurred at an average of 46 weeks. Though clinically relevant, the aforementioned reoperation results are not statistically significant (p=0.14). None of the patients with cannulated screw and tension band construct required re-operation (p =. 016); all secondary surgery occurred in patients treated with K-wires. No infections were reported in either cohort.

Figure 2. Cannulated screw and wire tension band construct.

At one year, all fractures had healed radiographically. There was no significant difference in knee range of motion or functional score (Lysholm and Tegner scores) between the two cohorts. Patients undergoing wire fixation for midpole fractures had a lower composite total SF-36 score (75.8) compared to inferior pole fractures repaired with sutures (84.1) (p=0.03). Those patients who experienced reoperation or post-operative complication had a significantly lessened arc of knee motion (mean 113 degrees) about their injured knee compared to those who did not (mean 126 degrees) (p = 0.005). Finally, when compared to the contralateral knee, the injured knee of patients requiring removal of hardware had significantly greater decrease in range of motion than those patients not requiring removal of hardware: -17.1° versus -6.0°, respectively (p=.005).

Discussion

Patients who sustain inferior pole patella fractures have limited options for fracture fixation. Suture repair is clinically acceptable and biomechanically verified^18,19, and in our study, yielded results similar to midpole patella fractures that underwent ORIF with metal implants. In our study, patients undergoing suture repair had fewer hardware related postoperative complications and achieved higher composite SF-36 scores at one year follow-up. The reoperation rate was four times higher for patients receiving standard tension band fixation as opposed to suture fixation. This result is consistent with other reports demonstrating an increased reoperation rate for patients receiving metal implants^20,21.

Partial patellectomy remains an option for treatment for comminuted inferior pole fractures; however, this treatment may potentially lead to patella baja, which is defined by an Insall-Salvati index less than 0.6^11,22. Not only may patients report discomfort, but they may also lose proper functioning of the patellofemoral joint²³ leading to patellofemoral arthritis²⁴. A study by Hung, et al. on partial patellectomies confirms this relationship, noting radiographic evidence of arthritis in 55% of patients in a retrospective cohort and evidence of patella baja in many patients²⁵.

Prior studies on patella fracture fixation have reported reoperation rates between 20% and 50% following use of Kirschner wires^20,21,25,26. A recent study with 6.5 years mean follow-up by LeBrun reported a rate of 56% in a cohort similar to that used as a control in our study²⁷. Interestingly, all hardware removals in our study occurred in the K-wire group, accounting for 93% of all reoperations in the cohort; the remaining reoperations were indicated due to treatment failure. No removal of hardware was required in the subset of patients treated with cannulated screws and tension band wiring. This discrepancy between removal of hardware rates for K-wire and cannulated screw is similar to a study by Tian, which showed no post-op complications for the cannulated screw group, but a 20% removal of hardware rate in the K-wire fixation group²¹. Furthermore, our study showed that patients requiring reoperation had significantly restricted range of motion in their affected knee, and remained significant after exclusion of patients receiving pole resection.

Though a previous study investigated the use of #5 Ethibond suture fixation over K-wire fixation²⁰, it did not employ quantitative methods to asses patient outcome. Our study made use of accepted patient outcome metrics to quantify any differences between the two groups, as well as basic chart review. Aforementioned studies with rigorous outcome metrics, like LeBrun, et al., and Tian, et al., did not include a cohort treated with sutures.

Studies on basket plates, including a recent case series by Huang, are specific to inferior pole fractures but are limited by their small cohorts⁹ or control with pole resection²⁴ - a method inferior to osteosynthesis due to reduced range of motion and increased incidence of patella baja^25,28. In a study using basket plates by Kastelec et al., 64% of patients receiving internal fixation underwent hardware removal. Though the authors report no significant difference in functionality between patients who underwent hardware removal and those who retained hardware, no standardized outcome measure was used to compare the two groups.

Our study is limited by a small patient population, which limit the statistical analysis. There was no algorithm for selection of fixation type; the decision was solely based upon fracture pattern, which may have created a selection bias. In general, simple two-part fractures with large fragments were fixed with cannulated screws, comminuted fractures were fixed with K-wire tension band, and small inferior pole fractures were repaired with suture. Finally, the retrospective nature of our analysis is not ideal for a rigorous comparison of the two surgical methods. Despite this, our inclusion of quantitative outcome measures supported and expanded upon qualitative conclusions of previous studies.

This study demonstrates that mid-pole patella and inferior pole patella fractures treated surgically compared similarly with regards to knee outcome scores, range of motion, and healing. Distal pole fractures treated with suture technique did not necessitate removal of hardware whereas some patients in the tension band cohort required another operation. Suture fixation was also associated with a lower overall reoperation rate. Our results indicate that distal pole fractures are successfully treated with heavy braided non-absorbable suture fixation and achieve outcomes equal to or better than wire fixation for mid-pole fractures.