Biomechanical evaluation of current patella fracture fixation techniques

Non-metallic implant for patellar fracture fixation: A systematic review

INTRODUCTION

Despite good clinical outcome proposals, there has been relatively little published regarding the use of non-metallic implant for patellar fracture fixation. The purpose of the study was to perform a systematic literature review to summarize and evaluate the clinical studies that described techniques for treating patella fractures using non-metallic implants.

METHODS

A comprehensive literature search was systematically performed to evaluate all studies included in the literature until November 2015. The following search terms were used: patellar fracture, patella suture, patella absorbable, patella screw, patella cerclage. Two investigators independently reviewed all abstracts and the selection of these abstracts was then performed based on inclusion and/or exclusion criteria.

RESULTS

A total of 9 studies involving 123 patients were included. Patients had a mean age of 33.7 years and were followed up for a mean of 18.9 months. The most common method for fracture fixations included the use of suture material. Good clinical outcomes were reported among all studies. Thirteen patients (10.5%) presented complications, while 4 patients (3.2%) required additional surgery for implant removal.

CONCLUSION

There is a paucity of literature focused on the use of non-metallic implant for patellar fracture fixation. However, this systematic review showed that non-metallic implants are able to deliver good clinical outcomes reducing the rate of surgical complications and re-operation. These results may assist surgeons in choosing to use alternative material such as sutures to incorporate into their routine practice or to consider it, in order to reduce the rate of re-operation.

Internal Fixation of Transverse Patella Fractures Using Cannulated Cancellous Screws with Anterior Tension Band Wiring

Aims: To evaluate the effectiveness and safety of anterior tension band wiring technique using two cannulated cancellous screws in patients with transverse (AO34-C1) or transverse with mildly comminuted (AO34-C2) patellar fractures.

Materials and Methods: This is a prospective study of 25 patients with transverse fracture or transverse fracture with mildly comminuted patella fractures. All the patients were treated with open reduction and internal fixation using two parallel cannulated screws and 18G stainless steel wire as per the tension band principle.

Results: There were eighteen males (72%) and seven females (28%). The age group ranged from 24 to 58 years, with mean age of 38 years. The most common mode of injury was fall (72%) followed by road traffic accident (20%) and violent quadriceps contraction (8%). Transverse fracture was present in 60% and transverse fracture with mild comminution in 40% of patients. Mean time to achieve union was 10.7 weeks (range 8-12 weeks). Mean ROM at three months was 113.8 degree (90-130) and at final follow up this improved to 125.4 degrees (range 100-140). There was one case of knee stiffness and no case of implant failure was observed. Patients were evaluated using Bostman scoring, the mean score at three months being 26.04 which improved to 27.36 at the end of final follow up at one year.

Conclusion: Cannulated cancellous screws with anterior tension band wiring is a safe, reliable and reproducible method in management of transverse patellar fractures, with less chances of implant failure and soft tissue irritation.

Current concepts review: Fractures of the patella

Fractures of the patella account for about 1% of all skeletal injuries and can lead to profound impairment due to its crucial function in the extensor mechanism of the knee. Diagnosis is based on the injury mechanism, physical examination and radiological findings. While the clinical diagnosis is often distinct, there are numerous treatment options available. The type of treatment as well as the optimum timing of surgical intervention depends on the underlying fracture type, the associated soft tissue damage, patient factors (i.e. age, bone quality, activity level and compliance) and the stability of the extensor mechanism. Regardless of the treatment method an early rehabilitation is recommended in order to avoid contractures of the knee joint capsule and cartilage degeneration.

For non-displaced and dislocated non-comminuted transverse patellar fractures (2-part) modified anterior tension band wiring is the treatment of choice and can be combined – due to its biomechanical superiority – with cannulated screw fixation. In severe comminuted fractures, open reduction and fixation with small fragment screws or new angular stable plates for anatomic restoration of the retropatellar surface and extension mechanism results in best outcome. Additional circular cerclage wiring using either typical metal cerclage wires or resorbable PDS/non-resorbable FiberWires increases fixation stability and decreases risk for re-dislocation. Distal avulsion fractures should be fixed with small fragment screws and should be protected by a transtibial McLaughlin cerclage. Partial or complete patellectomy should be regarded only as a very rare salvage operation due to its severe functional impairment.

Comparison of Tension-Band Wiring With the Cable Pin System in Patella Fractures: A Randomized Prospective Study

OBJECTIVES

To compare the outcome of tension-band wiring (TBW) with the cable pin system (CPS) for transverse fractures of the patella.

DESIGN

Randomized prospective study.

SETTING

Academic Level I trauma center.

PATIENTS/PARTICIPANTS

From February 2008 to December 2011, 73 consecutive patients with transverse fractures of the patella were prospectively enrolled in this study.

INTERVENTION

The patients were randomly divided into 2 groups: one group was treated using the CPS, and the other group was treated using the modified TBW.

MAIN OUTCOME MEASUREMENTS

The clinical outcome assessment included analyses of the radiographic images, the modified Hospital for Special Surgery scoring system, and complications.

RESULTS

The follow-up time ranged from 12 to 29 months. All fractures healed, with a union rate of 100%. The fracture healing time was significantly shorter in the CPS group (8.51 ± 2.59 weeks, n = 34) compared with the TBW group (11.79 ± 3.04 weeks, n = 39). Postoperative complications in the CPS and TBW groups were observed in 1 and 9 patients, respectively, a difference that was statistically significant. The mean Hospital for Special Surgery score for the CPS group (90.53 ± 5.19 points) was significantly higher than that for the TBW group (81.36 ± 12.71 points).

CONCLUSIONS

The CPS is a viable option for transverse fractures of the patella and is associated with a shorter healing time, fewer complications, and better function than TBW.

LEVEL OF EVIDENCE

Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

Multiplanar Fixation for Patella Fractures Using a Low-Profile Mesh Plate

Patella fractures are challenging orthopaedic injuries. Many commonly used fixation techniques can be ineffective and lead to poor clinical outcomes even with satisfactory reductions and fracture healing. In this investigation, we present the technique of cage plate fixation of patella fractures and the clinical outcomes of 9 initial patients surgically treated at our institution. This technique allows direct visualization of the articular reduction, provides multiplanar fixation, effectively stabilizes inferior pole comminution, and reduces the risk of patella vascular disruption. Using this technique, we have achieved excellent functional and radiographic outcomes.

Comparison of the outcomes of cannulated screws vs. modified tension band wiring fixation techniques in the management of mildly displaced patellar fractures

BACKGROUND

K wire fixation with tension band wiring has conventionally been used for the open reduction and internal fixation of the patella. However, it suffers from distinct disadvantages such as implant irritation, need for open reduction, incidence of palpable implants, and need for subsequent implant removal. A smaller incision with percutaneous fixation may be an alternative to this established conventional technique. Thus, the purpose of this trial was to compare the treatment outcomes of patients with mildly displaced patellar fractures treated with closed reduction and percutaneous cannulated screw fixation (CRCF) as compared to open reduction and tension band wiring fixation (ORTF). Specifically, we aimed to determine whether cannulated screw fixation was associated with improved clinical outcomes at 12 months as measured using the Lysholm score, pain scores, degree of flexion, range of motion, time to radiographic union, radiographic outcomes, and complication rates.

METHODS

Sixty-three patients with transverse patellar fractures displaced less than 8 mm were included in this prospective, randomized, controlled trial, with 52 patients in the final data analysis. Thirty-two patients were operatively treated by CRCF with either two or three cannulated screws. Thirty-one patients were operatively treated by conventional ORTF using the modified tension band technique. At postoperative intervals of 3, 6, and 12 months, knee function was evaluated using the Lysholm score, pain was assessed using the visual analog scale (VAS) score, and active knee extensions and flexion were measured in degrees by goniometry.

RESULTS

The CRCF group had average Lysholm scores of 84.4 ± 5.8, 86.7 ± 6.4, and 93.2 ± 5.3 after 3, 6, and 12 months, respectively, which were significantly greater than those of the ORTF group (79.0 ± 5.3, p = 0.001; 81.5 ± 4.6, p = 0.002; and 89.8 ± 6.2, p = 0.039, respectively). Lower pain and squatting scores were the main reasons for the poorer Lysholm scores in the ORTF group. The VAS scores showed that the CRCF group had lower pain scores and better flexion and total range of motion (ROM) compared with the ORTF group after 3 and 6 months, although both groups had similar outcomes after 12 months. The mean fracture healing time of 2.65 months was similar in the CRCF groups (2.77 months; p = 0.440). Complication rates were 3/26 (11.5 %) in the CRCF group and 14/26 (53.4 %) in the ORTF group. Two patients in the CRCF group and eight patients in the ORTF group experienced skin irritation. In addition, two (7.7 %) patients in the CRCF group and 11 (42.3 %) patients in the ORTF group required implant removal because of symptoms due to the presence of the implants.

CONCLUSION

Surgical treatment of mild displaced (less than 8 mm) transverse patellar fractures by the CRCF technique provides satisfactory clinical results and excellent knee function, with little pain and a low incidence of complications at early follow-up (up to 6 months). These results suggest that the CRCF technique may be a superior alternative to conventional ORTF. Registration Trial (Chinese Clinical Trial Register): Current Controlled Trials ChiCTR-PRCH-14005017, registration dates 2014-06-14.

Biomechanical Assessment of Locked Plating for the Fixation of Patella Fractures

OBJECTIVE

To analyze the mechanical stability of locked plating in comparison with tension-band wiring for the fixation of fractures of the patella.

METHODS

Biomechanical tests were performed on artificial foam patella specimens comparing an angular stable plate and monocortical screws with tension-band wiring. Tests were performed under combined tension and bending until failure simulating physiological loading of the tibia during walking.

RESULTS

Tension-band wiring failed at 66% of the failure load of plating (1052 N, P = 0.002) and had 5 times larger fracture gap displacements (P = 0.002).

CONCLUSIONS

Based on the biomechanical advantages, locked plating of the patella may constitute a reasonable alternative in the treatment of patella fractures.

FiberWire tension band for patellar fractures

BACKGROUND

Symptomatic hardware represents the most frequent complication reported following surgical treatment of patellar fracture. For this reason, some authors suggested using nonabsorbable sutures to fix the fracture with various techniques. The aim of this study was to evaluate clinical and radiological results of patients treated following a modified Pyriford technique using a FiberWire suture (Arthrex, Naples, FL, USA).

MATERIALS AND METHODS

We retrospectively evaluated a case series of seventeen patients with displaced patellar fractures treated by open reduction and internal fixation with a modified tension band using FiberWire sutures. Clinical and radiological outcome were evaluated. Union time, complications, and reoperation rate were observed and recorded.

RESULTS

All fractures healed (time to union 9.2 ± 2 weeks), and no fixation failure was observed. Slight losses of reduction (<4 mm) were noted in two patients at 4 weeks postoperatively. The average Lysholm and Bostman scores at the final follow-up were 91 ± 5.7 (range 83-100) and 28.3 ± 1.6 (range 26-30), respectively.

CONCLUSION

Modified tension band using FiberWire sutures showed satisfactory clinical results, with a low incidence of complications and reoperations. FiberWire tension bands could be used in place of metal-wire tension bands to treat patellar fracture, reducing the rate of symptomatic hardware.

LEVEL OF EVIDENCE

4.

Treatment of patella fracture by claw-like shape memory alloy

INTRODUCTION

Titanium-nickel shape memory alloy (Ti-Ni SMA) is characterized by shape-memory effect, super-elasticity, excellent fatigue behavior, corrosion resistance, acceptable biocompatibility and high damping capacity.

MATERIALS AND METHODS

Claw-like Ti-Ni SMA fixator (SMA-claw) has been used to treat transverse fracture of patella. 29 patients (19 males, 10 females) aged from 21 to 71 years old (averaged 43.0 years old) have been received open reduction and internal fixation with SMA-claw from January 2011 to December 2011. After operation, patients have been received gradual knee function exercises, followed by radiographic analysis and Lysholm Knee Score at 1, 2, 3, 6, 9 and 12 months postoperation.

RESULTS

The mean follow-up time was 11.48 months (25 patients finished, 1 lost after 6 months and 3 lost after 9 months). Radiographic bone union occurred at 2 months (7 patients) or 3 months (22 patients). Satisfied range of motion for the knee joint has been observed with 1.90/141.72° (hyperextension/flexion) at 3 months, 4.83/143.97° at 6 months, 4.82/144.82° at 9 months and 5.2/145° at 12 months postsurgery.

CONCLUSION

The Ti-Ni SMA-claw fixator produced good osteosynthesis effect by continuous recovery stress with relatively simple and minimally invasive handling process, which can be introduced as an alternative to traditional tension band technique for treatment of patellar transverse fracture.

Current Treatment Strategies for Patella Fractures

Patella fractures can be caused by excessive tension through the extensor mechanism or a direct impact. Non-displaced fractures with an intact extensor mechanism can be treated nonoperatively. Surgical treatment is recommended for fractures that either disrupt the extensor mechanism or have greater than 2 to 3 mm of step-off and greater than 1 to 4 mm of displacement. Tension band fixation is the most commonly employed surgical technique; however, this can be technically demanding, especially in multifragmentary fractures. Symptomatic hardware is the most common complication following operative treatment. Functional impairment remains common after treatment of patella fractures. The purpose of this article is to review current treatment strategies to help optimize the management of patients with such patella fractures.

Titanium mesh as a low-profile alternative for tension-band augmentation in patella fracture fixation: A biomechanical study

OBJECTIVES

We performed a simple biomechanical study to compare the fixation strength of titanium mesh with traditional tension-band augmentation, which is a standard treatment for transverse patella fractures. We hypothesised that titanium mesh augmentation is not inferior in fixation strength to the standard treatment.

METHODS

Twenty-four synthetic patellae were tested. Twelve were fixed with stainless steel wire and parallel cannulated screws. Twelve were fixed with parallel cannulated screws, augmented with anterior titanium mesh and four screws. A custom test fixture was developed to simulate a knee flexed to 90°. A uniaxial force was applied to the simulated extensor mechanism at this angle. A non-inferiority study design was used to evaluate ultimate force required for failure of each construct as a measure of fixation strength. Stiffness of the bone/implant construct, fracture gap immediately prior to failure, and modes of failure are also reported.

RESULTS

The mean difference in force at failure was -23.0 N (95% CI: -123.6 to 77.6N) between mesh and wire constructs, well within the pre-defined non-inferiority margin of -260 N. Mean stiffness of the mesh and wire constructs were 19.42 N/mm (95% CI: 18.57-20.27 N/mm) and 19.49 N/mm (95% CI: 18.64-20.35 N/mm), respectively. Mean gap distance for the mesh constructs immediately prior to failure was 2.11 mm (95% CI: 1.35-2.88 mm) and 3.87 mm (95% CI: 2.60-5.13 mm) for wire constructs.

CONCLUSIONS

Titanium mesh augmentation is not inferior to tension-band wire augmentation when comparing ultimate force required for failure in this simplified biomechanical model. Results also indicate that stiffness of the two constructs is similar but that the mesh maintains a smaller fracture gap prior to failure. The results of this study indicate that the use of titanium mesh plating augmentation as a low-profile alternative to tension-band wiring for fixation of transverse patella fractures warrants further investigation.

Vertical open patella fracture, treatment, rehabilitation and the moment to fixation

Patella fracture is relatively uncommon and the vertical trace fracture represents almost 12-17%. The open patella fracture expresses 6-30%. The association of these two uncommon conditions was the aim of this case report even as the treatment and the moment of fixation (definitive surgical treatment). A 27-year-old man after a motorcycle accident showed an open patella fracture classified as a Gustilo and Anderson type IIIA lesion. The patient was immediately treated with precocious surgery fixation with a modified tension band which consists of two parallel K-wires positioned orthogonal to the fracture line and a cerclage wire shaped anteriorly at patella as an eight. The premature fixation benefited the infection prevention and provided earlier joint motion, which increased the nutrition of articular cartilage. Six months postoperatively, the patient had a satisfactory joint motion with full extension and 116° of joint flexion and returned to his daily life activities without restriction. Twelve months postoperatively, the patient had full extension and 120° of knee flexion without pain, joint effusion and instability. Muscle strength force was considered normal at grade V. In conclusion, early chirurgic treatment and precocious articular mobilization improve prognosis, suggesting that the employment of these practices should be adopted whenever possible in most of the open fractures.

Plating of patella fractures: techniques and outcomes

Operative treatment of displaced patella fractures with tension band fixation remains the gold standard, but is associated with a significant rate of complications and symptomatic implants. Despite the evolution of tension band fixation to include cannulated screws, surprisingly little other development has been made to improve overall patient outcomes. In this article, we present the techniques and outcomes of patella plating for displaced patella fractures and patella nonunions.

Comparison of cannulated screws with FiberWire or stainless steel wire for patella fracture fixation: A pilot study

PURPOSE

This pilot study tested whether FiberWire provides similar protection to steel wire against repair displacement in patella fractures.

METHODS

Thirteen cadaver knees were cyclically loaded with 10 cycles (0-90° flexion) and fracture displacement was recorded. Fixation methods were also tested in load to failure (>3 mm displacement).

RESULTS

There was no difference between wire types in fracture displacement (1.4 mm ± 0.33 mm vs 1.2 mm ± 0.34 mm, respectively; p = 0.418) or in the load to failure (714.7 N ± 110.9 N vs 744.5 N ± 92.8 N, respectively; p = 0.360).

CONCLUSION

FiberWire provides similar protection to steel wire against repair displacement after fixation of patellar fractures.

Separate vertical wiring for the fixation of comminuted fractures of the inferior pole of the patella

PURPOSE

Among patients over 50 years of age, separate vertical wiring alone may be insufficient for fixation of fractures of the inferior pole of the patella. Therefore, mechanical and clinical studies were performed in patients over the age of 50 to test the strength of augmentation of separate vertical wiring with cerclage wire (i.e., combined technique).

MATERIALS AND METHODS

Multiple osteotomies were performed to create four-part fractures in the inferior poles of eight pairs of cadaveric patellae. One patella from each pair was fixed with the separate wiring technique, while the other patella was fixed with a combined technique. The ultimate load to failure and stiffness of the fixation were subsequently measured. In a clinical study of 21 patients (average age of 64 years), comminuted fractures of the inferior pole of the patellae were treated using the combined technique. Operative parameters were recorded from which post-operative outcomes were evaluated.

RESULTS

For cadaveric patellae, whose mean age was 69 years, the mean ultimate loads to failure for the separate vertical wiring technique and the combined technique were 216.4±72.4 N and 324.9±50.6 N, respectively (p=0.012). The mean stiffness for the separate vertical wiring technique and the combined technique was 241.1±68.5 N/mm and 340.8±45.3 N/mm, respectively (p=0.012). In the clinical study, the mean clinical score at final follow-up was 28.1 points.

CONCLUSION

Augmentation of separate vertical wiring with cerclage wire provides enough strength for protected early exercise of the knee joint and uneventful healing.

Horizontal versus vertical orientation of the loop for tension band wiring of transverse patella fractures

Conventional operative treatments of patella fractures are frequently associated with implant failure or displacement. Recent biomechanical studies showed that the orientation of the wire loop and the site of the wire twist can affect the fixation strength. The purpose of this study was to compare the clinical outcome of the tension band technique with loops in different orientations and different knot positions. For this retrospective study, 72 patella fractures (71 patients) were fixed with figure-of-eight configurations in combination with 2 K-wires. Patients were divided into 3 groups according to the orientation of tension band construct. A total of 40 patella fractures were placed with figure-of-eight configurations in a vertical orientation either with 1 wire twist (group 1; 16 patella fractures) or with 2 wire twists at the adjacent corners (group 2; 24 patella fractures). Thirty-two patella fractures were placed with figure-of-eight configurations in a horizontal orientation with 2 wire twists at the adjacent corners (group 3). Range of motion, complication rates, and knee scoring scales (Hospital for Special Surgery and Lysholm) were assessed during serial follow-up. Satisfactory reductions were achieved in all groups, but functional results in the early stage were different. Group 3 had better Hospital for Special Surgery and Lysholm scores at 3 months postoperatively; however, at 6 months and 1 year postoperatively, all groups had similar scores. At the 1-year follow-up, all groups achieved acceptable flexion and range of motion. The overall complication rate was lower in the horizontal group (12.5%). Placing the figure-of-eight tension band construct in a horizontal orientation can provide functional benefits in the early stage after patella fractures.

Adjustable patella grapple versus cannulated screw and cable technique for treatment of transverse patellar fractures

BACKGROUND

Although the cannulated screw and cable (CSC) tension band technique is an effective method for fixation of transverse patellar fractures, it has shortcomings, such as extensive soft tissue damage, osseous substance damage, and complex manipulation. We conducted a retrospective comparison of the adjustable patella grapple (APG) technique and the CSC tension band technique.

PATIENTS AND METHODS

We retrospectively reviewed 78 patients with transverse patellar fractures (45 in the APG group and 33 in the CSC group). Follow-up was 18 months. Comparison criteria were operation time, fracture reduction, fracture healing time, the knee injury and osteoarthritis outcome score for knee function, and complications.

RESULTS

The APG group showed shorter operation time and equal fracture reduction, fracture healing time, and knee function compared with the CSC group. Eleven patients in the APG group experienced skin irritation generated by implants. There was no complication in the CSC group.

CONCLUSIONS

The APG technique should be considered as an alternative method for treatment of transverse patellar fractures.

Percutaneous cannulated screws with tension band wiring technique in patella fractures

Introduction

Most patellar fractures are transverse involving the central third. Open reduction and stabilization of transverse patellar fractures is indicated if there is more than 2-3 mm of fragment separation and/or articular incongruity.

Surgical Technique

This study describes a percutaneous 2 cannulated screws and modified tension band wiring technique to treat transverse patellar fractures.

Materials and Methods

We performed 30 cases of displaced transverse patellar fractures with this technique. The clinical outcomes of these patients were evaluated with simple radiographs, range of motion and Lyshom score.

Results

This technique has shown to provide satisfactory clinical results and excellent knee functions.

Conclusions

This technique provide stable fixation, allows early motion exercise by minimizing injury to extensor mechanism and reduce cosmetic problem in scar.

Fixation of multifragmentary patella fractures using a bilateral fixed-angle plate

This biomechanical study is the first to compare 3 fixation methods-bilateral fixed-angle plate, modified anterior tension wiring, and cannulated lag screws with anterior tension wiring-in multifragmentary distal patella fractures. A T-shaped 3-part fracture simulating a multifragmentary articular distal patella fracture (AO/OTA 34-C2.2) was created in 18 human cadaver knee specimens. Three groups were created using homogenous ages and bone mineral densities based on the fixation method received. Repetitive testing over 100 cycles was performed by moving the knee against gravity from 90° flexion to full extension. Failure was defined as fracture displacement greater than 2 mm. In all patellae using fixed-angle plates, an anatomical fracture reduction could be maintained throughout cyclic testing, whereas anterior tension wiring and lag screws with tension wiring showed significant fracture displacement after 100 cycles, with mean fracture gaps of 2.0±1.3 and 1.9±1.6 mm, respectively. The differences in fracture gaps between the fixed-angle plate group and the other 2 groups were statistically significant. In both groups using tension wiring, half of the constructs (3 of 6 in each group) failed due to a fracture displacement greater than 2 mm. The bilateral fixed-angle plate was the only fixation method that sustainably stabilized a multifragmentary articular distal patella fracture during cyclic loading when compared with modified anterior tension wiring and cannulated lag screws with anterior tension wiring.

Symptomatic heterotopic ossification: seven years after patella fracture

We describe a case of heterotopic ossification (HO) of the lateral patella becoming symptomatic after 7 years following horizontal patella fracture. The patient presented peripatellar pain in full knee flexion and kneeling position. We resected the ossification, and the patient was immediately relieved from pain and was mobilised under full weight bearing with no limitation of knee flexion. The patient was able to return to his previous level of daily activities with no further episodes of pain. To our knowledge, this is the first case of heterotopic peripatellar ossification becoming symptomatic 7 years after a patellar fracture to be reported in the literature.

Comparison of the cable pin system with conventional open surgery for transverse patella fractures

BACKGROUND

The cable pin system is an effective device for fixation of transverse patella fractures. However, whether this device provides superior results using a minimally invasive technique instead of conventional open surgery using the K wire tension band method is unclear.

QUESTIONS/PURPOSES

We asked whether a minimally invasive technique would be associated with (1) increased operative time; (2) reduced postoperative pain; (3) faster recovery of ROM; (4) higher knee scores; and (5) reduced complications.

METHODS

Forty patients with displaced transverse fractures of the patella participated in this prospective, randomized, controlled trial. Twenty of these patients underwent a minimally invasive technique and the others had conventional open surgery using K wires. Some data for six of the 20 patients who underwent the minimally invasive technique were published in an earlier prospective, observational trial. At postoperative intervals of 1, 3, 6, 12, and 24 months, pain was measured by VAS scores, active flexion and extension of the knee were measured in degrees by goniometry, and knee function was evaluated using the Böstman clinical grading scale.

RESULTS

Operative time was longer in the minimally invasive surgery group (54.3 ± 9.8 minutes versus 48.5 ± 6.1 minutes). Pain scores were better (lower) in the minimally invasive surgery group at 1 and 3 months but not at 6 months. Early flexion, ultimate flexion, and knee scores from 3 to 24 months, likewise, were better in the minimally invasive surgery group. Complications mostly related to symptomatic hardware were less common in the minimally invasive surgery group.

CONCLUSIONS

The minimally invasive technique is superior to conventional open surgery using K wires in terms of less early postoperative pain, better mobility angles of the injured knee, higher functional score of the injured knee, and decreased incidence of complications.

LEVEL OF EVIDENCE

Level I, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

An alternative patellar fracture fixation: a biomechanical study

OBJECTIVES

The purpose of this study is to compare open reduction and internal fixation of the patella with a locking plate and tension-band construct (PF) versus cannulated screws and tension-band fixation (SF). The hypothesis is that both constructs will have similar failure loads with simulated extension loading.

METHODS

Transverse patellar fractures were created in 10 cadaveric pairs of legs and were fixed with either PF or SF. Dual-energy X-ray Absorptiometry (DXA) scans of all calcanei measured bone mineral density (BMD). Using an MTS 810 servohydraulic testing machine, each leg cycled to full extension 10 times before loading to failure. A differential variable reluctance transducer measured the distraction of the patella. Data were analyzed using paired t test analysis and bivariate analysis for Pearson correlation coefficients.

RESULTS

There was no difference in the BMD between the PF and the SF groups (P = 0.367). No measurable differences occurred during the 10 cycles, and load at clinical failure was not significantly different between the 2 fixation groups (P = 0.38). Stiffness during the final loading cycle was significantly higher for the SF group (P = 0.008). Ultimate strength of fixation was significantly higher in PF group (P = 0.048). BMD was not correlated to the ultimate strength of SF (P = 0.112), but was correlated for PF (P = 0.025).

CONCLUSIONS

Based on our results, PF provides comparable strength to SF, and it seems to be a safe and effective alternative to the current gold standard.

Complications following tension-band fixation of patellar fractures with cannulated screws compared with Kirschner wires

BACKGROUND

Displaced patellar fractures are commonly stabilized with a modified anterior tension-band construct. The goal of the current study was to compare the incidence of complications after tension-band fixation of the patella with Kirschner wires as compared with cannulated screws.

METHODS

We performed a retrospective cohort study of consecutive, surgically treated patellar fractures. Patients were divided into two cohorts: fractures fixed with use of Kirschner wires and fractures fixed with use of cannulated screws. The primary outcome measure was early loss of fixation that necessitated revision surgery. Secondary outcomes included early postoperative infection and the need for implant removal.

RESULTS

Four hundred and forty-eight patellar fractures were studied. Kirschner wires were used for fixation in 315 (70%), and cannulated screws were used for fixation in 133 (30%). The incidence of fixation failure was 3.5% in the Kirschner-wire group and 7.5% in the screw group (p = 0.065). A postoperative infection occurred in 4.4% of patients in the Kirschner-wire group and 1.5% of patients in the screw group (p = 0.17). One hundred sixteen (37%) patients in the Kirschner-wire group and 30 (23%) in the screw group underwent elective implant removal (p = 0.003). After adjusting for confounding variables, a trend toward increased incidence of fixation failure with screws as compared with Kirschner wires was present (p = 0.083). Patients treated with Kirschner wires were twice as likely to undergo implant removal compared with those treated with screws (p = 0.002).

CONCLUSIONS

Serious complications are uncommon following treatment of patellar fractures with a modified tension-band technique, with use of either Kirschner wires or cannulated screws. In both groups the rate of fixation failure was low, as was the rate of postoperative infection. Symptomatic implants, the most common complication observed, were twice as frequent in patients treated with Kirschner wires.

Cyclic long-term loading of a bilateral fixed-angle plate in comparison with tension band wiring with K-wires or cannulated screws in transverse patella fractures

PURPOSE

A bilateral fixed-angle plate was biomechanically compared to the two currently preferred methods of osteosynthesis for transverse patella fractures. It was hypothesized that the new angle-stable implant would provide a secure and sustainable fracture fixation, superior to the established standard techniques.

METHODS

Twenty-one identical patellae made of polyurethane foam (Sawbones(®)), osteotomized to create a transverse two-part fracture, were fixed with modified anterior tension wiring, cannulated lag screws with anterior tension wiring or bilateral polyaxial 2.7-mm fixed-angle plates. The testing protocol consisted of 10,000 repetitive cycles using a non-destructive physiological load between 100 and 300 N at a simulated knee flexion of 60°.

RESULTS

All 21 Sawbone(®)-patellae sustained repetitive loading up to 10,000 cycles without failing. The anterior tension wire group displayed significant displacement of the fracture gap (0.7 ± 0.2 mm) during cyclic loading, while both lag screws with tension wiring and bilateral fixed-angle plates showed no fracture gap widening at all (p < 0.01).

CONCLUSION

The bilateral fixed-angle plate and cannulated lag screws with anterior tension wiring preserved a constantly reduced fracture gap over 10,000 tensile cycles in contrast to modified anterior tension wiring, which exhibited significant widening of the gap after initial loading. Results of in vitro testing indicate that bilateral fixed-angle plates provide sustainable fixation stability offering a promising new option in the treatment for transverse patella fractures.

Biomechanical studies on transverse olecranon and patellar fractures: a systematic review with the development of a new scoring method

INTRODUCTION

Several methods of transverse patellar and olecranon fixation have been described. This article compares biomechanical studies of various fixation methods using a newly developed scoring method.

SOURCE OF DATA

The databases PubMed, Web of Science, Science Direct, Google Scholar and Google were searched for relevant studies.

AREAS OF AGREEMENT

Fixation hardware failure remains a problem. Various materials and fixation techniques have been tested to provide an improved fixation of transverse olecranon and patellar fractures.

AREAS OF CONTROVERSY

The difference in biomechanical testing setup between the studies makes it hard to compare different fixation techniques.

GROWING POINTS

The newly developed grading method was proved to be unbiased and reliable; however, extra specifications need to be added at some criteria when adopting the scoring method.

AREAS TIMELY FOR DEVELOPING RESEARCH

Non-metallic constructs may provide an improvement to the currently used metallic tension band wiring technique; however, clinical research is required.

Treatment of transverse patellar fractures: a comparison between metallic and non-metallic implants

INTRODUCTION

Several methods of transverse patellar fixation have been described. This study compares the clinical outcome and the occurrence of complications of various fixation methods.

SOURCES OF DATA

The databases PubMed, Web of Science, Science Direct, Google Scholar and Google were searched.

AREAS OF AGREEMENT

A direct comparison between fixation techniques using mixed or non-metallic implants and metallic K-wire and tension band fixation shows no significant difference in clinical outcome between both groups. Additionally, studies reporting novel operation techniques show good clinical results.

AREAS OF CONTROVERSY

Studies describing the treatment of patients using non-metallic or mixed implants are fewer compared with those using metallic fixation.

GROWING POINTS

A large variety of clinical scoring systems were used for assessing the results of treatment, which makes direct comparison difficult.

AREAS TIMELY FOR DEVELOPING RESEARCH

More data of fracture treatment using non-metallic or mixed implants is needed to achieve a more balanced comparison.

Comparison of cannulated screw with tension band wiring versus compressive cannulated locking bolt and nut device (CompresSURE) in patella fractures-a cadaveric biomechanical study

OBJECTIVE

The purpose of this study was to determine if proximity of cannulated lag screws to the articular surface of the patella combined with the tension band technique affects resistance to fracture gap opening, and if an alternative locking nut and bolt device without a tension band behaves in a biomechanically similar fashion.

METHODS

Thirty-three cadaveric knees were allocated to 3 transverse patella fracture fixation groups: cannulated lag screw placement close to the articular (TBA) or non-articular (TBNA) surface with tension, and placement of a compressive locking nut and bolt device without tension band (CompresSURE) close to the articular surface. Knees were cycled through flexion-extension motion for 1000 cycles during which the fracture gap opening was quantified after the first flexion-extension cycle and after the 1,000 th cycle using an optoelectronic motion analysis system.

RESULTS

After the first range of motion cycle, there was no significant difference in fracture gap opening between the 3 groups on the articular surface (P > 0.600). Total fracture gap displacement after the 1,000 th cycle was not significantly different between groups (P > 0.408). In general and irrespective of fixation technique, fractures opened in a wedge-like fashion with larger measured gap on the ventral surface relative to the articulating surface.

CONCLUSIONS

When combined with the tension band, the proximity of cannulated lag screws to the articular surface did not affect resistance to fracture gap opening. Additionally, the stand-alone CompreSURE cannulated locking nut and bolt device without tension band was able to resist fracture gap opening in transverse fractures as effectively as the cannulated screw with tension band technique.

Biomechanical cadaver testing of a fixed-angle plate in comparison to tension wiring and screw fixation in transverse patella fractures

INTRODUCTION

Operative treatment of patella fractures is frequently associated with implant failure and secondary dislocation which can be attributed to the employed hardware. Therefore, a 2.7 mm fixed-angle plate designed for the treatment of patella fractures was tested biomechanically against the currently preferred methods of fixation. It was hypothesized that under simulated cyclic loading fixed-angle plating would be superior to modified anterior tension wiring or cannulated lag screws with anterior tension wiring.

MATERIALS AND METHODS

Eighteen human cadaver knees, matched by bone mineral density and age, were divided into three groups of six. After setting a transverse patella fracture each group received one of the osteosyntheses mentioned above. Repetitive testing over 100 cycles was performed at non-destructive loads by simulating knee motion from 90° flexion to full extension.

RESULTS

Anterior tension wiring as well as lag screws with tension wiring showed significant fracture displacement after the initial cycle already. Both constructs, lag screws plus wiring (3.7 ± 2.7 mm) as well as tension wiring alone (7.1 ± 2.2 mm) displayed fracture displacement of >2 mm which is clinically regarded as failure. Those patellae stabilized with fixed-angle plates showed no significant fracture gap widening after completion of 100 cycles (0.7 ± 0.5 mm). The differences between the fixed-angle plate group and the other two groups were statistically significant (p<0.05).

CONCLUSION

In contrast to modified anterior tension wiring and cannulated lag screws with anterior tension wiring the bilateral fixed-angle plate was the only fixation device to stabilize transverse patella fractures securely and sustainably.

Factors predicting failure of patella fixation

BACKGROUND

Surgical fixation of patella fractures is frequently indicated due to disruption of the quadriceps mechanism. Operative technique varies; however, failure rates can be high. The purpose of this study was to compare the effectiveness of various techniques for the fixation of patella fractures and the etiology of fixation failure.

METHODS

We retrospectively reviewed 173 patella fractures treated operatively at two Level I trauma centers. Patients with less than 90 days of follow-up, inadequate radiographic studies, and partial or total excision were excluded. Failure was defined as hardware breakage, nonunion, or displacement of fragments from their initial reduced position. Twelve factors were examined independently for predictive value using both univariate and multivariate analyses. A comparison between groups based on reoperation and hardware removal was also performed.

RESULTS

One hundred nine patients met the inclusion criteria, and 13 were found to have failed (12%). Both older patient age (p < 0.02) and use of K-wires, with or without tension-band wires (p < 0.04), were found to be significant predictors of failure. Increasing follow-up time was the only significant predictor of reoperation (p < 0.001) and hardware removal (p < 0.001).

CONCLUSIONS

As anticipated, increasing age was found to correlate with higher failure rates. Use of K-wires with or without tension-band wires correlated with higher failure rates, compared with the use of screws, both K-wires and screws, or other fixation. Increasing follow-up time predicted both reoperation and hardware removal, with patients having symptomatic hardware and other complications naturally returning to clinic for evaluation and treatment.

[Classification and treatment of patella fractures]

Patella fractures are rare and account for approximately 1% of all fractures. They are classified regarding their localization (proximal, distal) and appearance. The aim of any treatment is reconstruction of the extensor mechanism and joint surface. If dislocation and cartilage steps are less than 2 mm, conservative treatment may be indicated. Operative treatment is only necessary if a dislocation is more than 2 mm or when the extensor mechanism is unstable. Depending on the shape of the fracture, tension band wiring, interfragmentary screw fixation and combinations are the main techniques. Because patellectomy has functionally the worst result it should be avoided. Sleeve fractures (children) need exact reconstruction of the joint surface. In elderly patients conservative treatment or surgical patella-enclosing wiring techniques for stabilization are the best options due to low bone quality.

Patellar nonunions: Comparison of various surgical methods of treatment

BACKGROUND

Nonunion of patella is an uncommon entity prevalent more commonly in developing countries. Many of them have a functional knee joint and only those with a wide gap and failed extensor mechanism need surgery. We report an analysis of nonunion of fracture patella treated by 3 surgical method.

MATERIALS AND METHODS

35 patients of nonunion/delayed union of patella with significant gap and failure of quadriceps mechanism, underwent three different methods surgically: 1) V-Y plasty and tension band wiring (n=10); 2) patellar traction followed by tension band wiring without V-Y plasty (n=15); and 3) patellar traction followed by partial or total patellectomy (n=10). We compared the results of the treatment in terms of Knee Society Score (KSS), Melbourne patella score, time of union, pain, range of movement, quadriceps power, and ability to do daily activities and complications encountered.

RESULTS

The 15 cases of patellar traction followed by tension band wiring showed the best results in terms of time to return to normal activities and complications encountered. Cases with patellectomy showed the next best results but they had a longer period of rehabilitation with ultimately lesser patient satisfaction. V-Y plasty gave the worst results both in complication rate and function return.

CONCLUSION

Preoperative patellar traction followed by tension band wiring is a good procedure giving better results than either patellectomy or V-Y plasty.

Cannulated screw and cable are superior to modified tension band in the treatment of transverse patella fractures

BACKGROUND

Although the modified tension band technique (eg, tension band supplemented by longitudinal Kirschner wires) has long been the mainstay for fixation of transverse fractures of the patella, it has shortcomings, such as bad reduction, loosening of implants, and skin irritation.

QUESTIONS/PURPOSES

We conducted a retrospective comparison of the modified tension band technique and the titanium cable-cannulated screw tension band technique.

PATIENTS AND METHODS

We retrospectively reviewed 101 patients aged 22 to 85 years (mean, 56.6 years) with AO/OTA 34-C1 fractures (n = 68) and 34-C2 fractures (n = 33). Fifty-two patients were in the modified tension band group and 49 were in the titanium cable-cannulated screw tension band group. Followup was at least 1 year (range, 1-3 years). Comparison criteria were fracture reduction, fracture healing time, and the Iowa score for knee function.

RESULTS

The titanium cable-cannulated screw tension band group showed improved fracture reduction, reduced healing time, and better Iowa score, compared with the modified tension band group. In the modified tension band group, eight patients experienced wire migration, three of these requiring a second operation. There were no complications in the titanium cable-cannulated screw tension band group.

CONCLUSIONS

The titanium cable-cannulated screw tension band technique showed superior results and should be considered as an alternative method for treatment of transverse patellar fractures.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Double fixation of displaced patella fractures using bioabsorbable cannulated lag screws and braided polyester suture tension bands

PURPOSE

To evaluate the effectiveness and safety of a new double fixation technique for displaced patellar fractures using bioabsorbable cannulated lag screws and braided polyester suture tension bands.

METHODS

Fifteen patients (mean age of 46.2 years) with displaced transverse or comminuted patella fractures were enrolled in this prospective study. All of the patients were treated via the open reduction internal fixation (ORIF) procedure using bioabsorbable cannulated lag screws and braided polyester suture tension bands. The patients were followed post-surgery to evaluate (1) the time required for radiographic bone union, (2) the knee joint range of motion at the time of radiographic bone union, (3) the degree of pain assessed using the visual analogue scale (VAS), (4) the function of the knee using the Lysholm score and (5) the presence of any additional complications from the surgery.

RESULTS

All of the patients were followed post-treatment for more than 1 year (range, 12-19 months; mean post-treatment follow up time, 14 months). The bone union of the fractures as seen radiographically occurred approximately 3 months from surgery in all cases without implant failure or redisplacement of the fractured site. The mean knee joint range of motion was from 0 to 134.6°, and the mean VAS score was 0.7 at the time of bone union. The mean Lysholm scores at the time of bone union and 12 months post-surgery were 86.7 and 95.7, respectively. No postoperative complications, such as infection, dislocation or breakage of the implants, were observed. Moreover, all of the patients returned to their previous activity level.

CONCLUSION

This new double fixation technique using bioabsorbable cannulated lag screws and braided polyester suture tension bands resulted in satisfactory outcomes for patella fractures without any obvious complications.

Arthroscopically assisted percutaneous osteosynthesis of displaced transverse patellar fractures with figure-eight wiring through paired cannulated screws

INTRODUCTION

For treatment of displaced transverse patellar fractures, open reduction and internal fixation is the standard reconstructive method. The role of percutaneous osteosynthesis is still unclear and worth of further investigation. Our hypothesis is that satisfactory reduction and rigid fixation is possible for the treatment of displaced transverse patellar fractures with some percutaneous techniques. Here, we present and evaluate a minimally invasive technique for these patellar fractures.

PATIENTS AND METHODS

This is a retrospective study. Twenty-one patients with 21 transverse patellar fractures were treated with our percutaneous technique in acute phase. The minimally invasive surgery was achieved by closed reduction and fixation with modified Carpenter's technique, using figure-eight wiring through two parallel cannulated screws under the assistance of arthroscopy and fluoroscopy. The patients were followed up to an average of 38.8 months (range 26-48). Main outcome measurements included radiographic assessment, range of motion, Lysholm scores, complications, and reoperations.

RESULTS

Radiographically, all fractures healed at a mean of 11.0 weeks (range 9-13). Mean total range of motion of knee joint was 140.1° (range 127-152). Functional assessment of Lysholm scores was 93.9 points (range 86-100). Malreduction, loss of reduction, and infection were not observed in 21 patients. Complications were three cases (14%) of hardware irritation, and needed a second operation for removal.

CONCLUSIONS

Under the control of arthroscopy and fluoroscopy, we successfully treated 21 displaced transverse patellar fractures by percutaneously osteosynthesis. This is a safe and reproducible method for transverse patellar fractures. However, it is not indicated for severely comminuted fractures.

Open reduction and internal fixation of displaced patella inferior pole fractures with anterior tension band wiring through cannulated screws

OBJECTIVE

To present the treatment outcome for patients with displaced inferior pole patella fractures treated with anterior tension band wiring through cannulated screws.

DESIGN

Case series.

SETTING

Academic Level I trauma center.

PATIENTS/PARTICIPANTS

During a 2-year period between January 2007 and December 2008, 10 consecutive patients (mean age, 59.8 years) with distal pole fractures of the patella (Orthopaedic Trauma Association 45.A.1) were prospectively enrolled in this study.

INTERVENTION

All 10 patients underwent vertical skin exposure, fracture open reduction, and internal fixation by anterior tension band wiring through 4.0-mm cannulated screws.

MAIN OUTCOME MEASUREMENTS

The range of motion, loss of fracture reduction, implant migration, material failure, soft tissue irritation, and Bostman score and Short Musculoskeletal Functional Assessment dysfunction score were primary outcome measures.

RESULTS

There were three single-fragment fractures and seven comminuted fractures. With 1-year follow-up, all fractures healed clinically in an average of 8 weeks and radiographically on average by 12 weeks. The average range of knee motion arc was 122.5° (range, 95°-140°). Five patients have an average flexion lag of 17° (range, 10°-30°). No patient had loss of fracture reduction, implant migration, material failure, or soft tissue irritation. The average Bostman score was 28.7 out of 30 (range, 27-30), and average Short Musculoskeletal Functional Assessment dysfunction score was 24.1 out of 100 (range, 15-39). All 10 patients stated they were highly satisfied.

CONCLUSION

Anterior tension band wiring through cannulated screws for displaced inferior pole patella fractures is a safe, simple, and reliable alternative treatment with minimal soft tissue irritation. Good functional results and recovery can be expected.

Patellar fractures in adults

Patellar fracture is a common injury caused by excessive tension through the extensor mechanism or a direct blow. The intact patella increases the leverage and efficiency of the extensor mechanism and articulates with the femoral trochlea. Patellar fractures can lead to stiffness, extension weakness, and patellofemoral arthritis. Nonsurgical management is indicated for nondisplaced fractures with an intact extensor mechanism. Surgical fixation is recommended for fractures that either disrupt the extensor mechanism or demonstrate >2 to 3 mm step-off and >1 to 4 mm of displacement. Anatomic reduction and fixation with a tension-band technique is associated with the best outcomes; however, symptomatic hardware is a frequent complication. Open fractures are associated with more complications than closed fractures. These complications can be mitigated with timely débridement, irrigation, and internal fixation.

Fixed-angle plates in patella fractures - a pilot cadaver study

Objective

Modified anterior tension wiring with K-wires and cannulated lag screws with anterior tension wiring are currently the fixation of choice for patellar fractures. Failure of fixation, migration of the wires, postoperative pain and resulting revision surgery, however, are not uncommon. After preliminary biomechanical testing of a new fixed-angle plate system especially designed for fixation of patella fractures the aim of this study was to evaluate the surgical and anatomical feasibility of implanting such a plate-device at the human patella.

Methods

In six fresh unfixed female cadavers without history of previous fractures around the knee (average age 88.8 years) a bilateral fixed-angle plate fixation of the patella was carried out after previous placement of a transverse central osteotomy. Operative time, intra-operative problems, degree of retropatellar arthritis (following Outerbridge), quality of reduction and existence of any intraarticular screw placement have been raised. In addition, lateral and anteroposterior radiographs of all specimens were made.

Results

Due to the high average age of 88.8 years no patella showed an unimpaired retropatellar articular surface and all were severely osteoporotic, which made a secure fixation of the reduction forceps during surgery difficult. The operation time averaged 49 minutes (range: 36-65). Although in postoperative X-rays the fracture gap between the fragments was still visible, the analysis of the retropatellar surface showed no residual articular step or dehiscence > 0.5 mm. Also in a total of 24 inserted screws not one intraarticular malposition was found. No intraoperative complications were noticed.

Conclusions

Osteosynthesis of a medial third patella fracture with a bilateral fixed-angle plate-device is surgically and anatomically feasible without difficulties. Further studies have to depict whether the bilateral fixed-angle plate-osteosynthesis of the patella displays advantages over the established operative procedures.

Transverse fractures of the olecranon: a biomechanical comparison of three fixation techniques

INTRODUCTION

The gold standard for treating transverse olecranon fractures is tension band fixation. A problem with this technique is migration of the K-wires leading to premature hardware removal. The aim of this study is to compare stability provided by two new techniques designed to eliminate the problem with backing out of K-wires, with that of the recommended tension band technique, performed with a biomechanical in vitro investigation. Our hypothesis was that the two new techniques would provide at least equal stability as the traditional tension band fixation.

METHODS

Transverse olecranon osteotomies were created in human cadaveric elbows to simulate a type 21-B1.1 fracture. Three groups of 8 specimens were instrumented with: (1) recommended AO tension band technique; (2) modified K-wires with eyelets and tension band; (3) staples across the fracture with tension band. Each elbow was tested in a 90° flexed position. The triceps tendon was sinusoidally loaded by applying two load steps at 500 and 700 N for 4000 cycles each. Relative movements between the fragments were determined.

RESULTS

At the end of the first and second load step the displacement of the osteotomy at the posterior ulnar side was significantly less for the staples across the fracture with tension band as compared to both other groups. There were no significant differences between groups 1 and 2.

CONCLUSION

Since clinical results depend partly on stable fixation, it is concluded that using staples in the clinical situation might provide better results than the currently recommended tension band technique.

[Fractures of the patella]

Fractures of the patella account for approximately 0.5% to 1.5% of all skeletal injuries. The diagnosis is made by means of the mechanism of injury, physical and radiological findings. The kind of treatment of patella fractures depends on the type of fracture, the size of the fragments, the integrity of the extensor mechanism and the congruity of the articular surface. Independent of the kind of treatment an early rehabilitation is recommended. Modified tension band wiring is the most commonly used surgical treatment for patella fractures and can be used for almost every type of fracture. Due the superior stability in biomechanical studies two parallel cannulated lag screws combined with a tension band wiring are the treatment of choice for horizontally displaced two-part fractures. In comminuted fractures a partial or total patellectomy may be necessary. However, since the loss of quadriceps muscle power and the poor outcome total patellectomy should be considered as a salvage procedure.

Fixed-angle plate osteosynthesis of the patella - an alternative to tension wiring?

BACKGROUND

The goal of this study is carry out a biomechanical evaluation of the stability of a bilateral, polyaxial, fixed-angle 2.7 mm plate system specifically designed for use on the patella. The results of this approach are then compared to the two currently most commonly used surgical techniques for patella fractures: modified anterior tension wiring with K-wires and cannulated lag screws with anterior tension wiring.

METHODS

A transient biomechanical analysis determining material failure points of all osteosyntheses were conducted on 21 identical left polyurethane foam patellae, which were osteotomized horizontally. Evaluated were load (N), displacement (mm) and run-time (s) as well as elastic modulus (MPa), tensile strength (MPa) and strain at failure (%).

FINDINGS

With a maximum load capacity of 2396 (SD 492) N, the fixed-angle plate proved to be significantly stronger than the cannulated lag screws with anterior tension wiring (1015 (SD 246) N) and the modified anterior tension wiring (625 (SD 84.9) N). The fixed-angle plate displayed significantly greater stiffness and lower fracture gap dehiscence than the other osteosyntheses. Additionally, osteosynthesis deformation was found to be lower for the fixed-angle plate.

INTERPRETATION

A bilateral fixed-angle plate was the most rigid and stable osteosynthesis for horizontal patella fractures with the least amount of fracture gap dehiscence. Further biomechanical trials performed under cycling loading with fresh cadaver specimen should be done to figure out if a fixed-angle plate may be an alternative in the surgical treatment of patella fractures.

A study of the long-term effects of anatomical open reduction of patella on patellofemoral articular cartilage in follow up arthroscopy

Anatomical open reduction is the choice treatment method in patellar fractures and the sole approach to study the cartilage surface healing is arthroscopy. This study is to evaluate the cartilage healing, long after the complete union of the fractures and the long-term effects of simple transverse patellar fractures with perfect results on patellofemoral cartilage surface. Free of charge standard diagnostic arthroscopy was done on 22 patients whose simple transverse pattelar fractures had happened at least 3 years ago with the mean age of 36.4 years. Fractures had happened at least 3 years ago and all cases had excellent union results. The data collected from cartilage surface studies were recorded. No other statistical tests were used except for X2 test to study the relation between clinical and radiological findings and arthroscopies. The elapsed time from the fracture occurrence to the arthroscopy was 39.2 months, at least 36 months. Five patients (22.6%) showed complete cartilage healing in cartilage surface arthroscopy and 10 patients (45.2%) proved to have Grade I chondral lesions. Four patients had Grade II chondral lesions and 3 patients had Grade III chondral lesions along with fibrillation. In 2 patients mirror cartilage lesions were observed in the opposite trochlea. In 3 patients with normal radiological signs, step-off was observed on cartilage surface. There was no relation between clinical signs and radiological characteristics of the patients with the healing on cartilage surface (p = 0.84). Having a diagnostic arthroscopy in an appropriate time after fusion, especially during extracting the metal instrument, is effective on evaluating patient's prognosis. Extracting metal instruments along with the simultaneous chondroplasty has low cost and complications, though leading to a decrease in the prevalence of secondary osteoarthritis and probably the eruptive swelling due to the debris released from probable fibrillations.