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

Anterior variable angle locking neutralisation plate superiority over traditional tension band wiring for treating transverse patella fractures

Purpose

This paper investigates the biomechanical benefits of using hybrid constructs that combine cannulated screws with tension band wiring (TBW) cerclage compared to cannulated screws with anterior Variable Angle locking neutralisation plates (VA LNP). These enhancements can bear heavier loads and maintain the repaired patella's integrity, in contrast to traditional methods.

Method

Eighteen fresh-frozen human cadaver patellae were carefully fractured transversely at their midpoints using a saw. They were then divided into two groups of nine for subsequent utilisation. Fixation methods included Cannulated Screw Fixation added with either TBW or VA LNP Fixation Technique. Cyclic loading simulations (500 cycles) were conducted to mimic knee motion, tracking fracture displacement with Optotrak. After that, the constructs were secured over a servo-hydraulic testing machine to determine the load-to-failure on axial mode.

Results

The average fracture displacement for the anterior neutralisation plate group was 0.09 ± 0.12 mm, compared to 0.77 ± 0.54 mm for the tension band wiring with cannulated screw group after 500 cyclic loading. This result is statistically significant (p = 0.004). The anterior neutralisation plate group exhibited a mean load-to-failure of 1359± 21.53 N, whereas the tension band wiring group showed 780.1 ± 22.62 N, resulting in a significant difference between the groups (p = 0.007).

Conclusion

This research highlights the superior biomechanical advantage of VA LNP over TBW for treating simple transverse patella fractures with two cannulated screws. It also highlights how the TBW is still a valuable option considering the load-to-failure limit.

Level of Evidence

Not Applicable.

Comparative study of locking neutralization plate construct versus tension band wiring with a cannulated screw for patella fractures: experimental and finite element analysis

Transverse patella fractures, accounting for approximately 1% of Orthopedic injuries, pose intricate challenges due to their vital role in knee mechanics. This study aimed to compare the biomechanical performance of a construct, integrating cannulated screws and an anterior locking neutralization plate, with the conventional tension band wiring technique for treating these fractures. Experimental testing and Finite Element Analysis were employed to evaluate the constructs and gain profound insights into their mechanical behavior. Sixteen cadaveric knees were prepared, and transverse patella fractures were induced at the midpoints using a saw. The plate construct and tension band wire fixation were randomly assigned to the specimens. A cyclic test evaluated the implants' durability and stability, simulating knee movement during extension and flexion. Tensile testing assessed the implants' maximum failure force after cyclic testing, while Finite Element Analysis provided detailed insights into stress distribution and deformation patterns. Statistical analysis was exclusively performed for the experimental data. Results showed the plate enhanced stability with significantly lower deformation (0.09 ± 0.12 mm) compared to wire fixation (0.77 ± 0.54 mm) after 500 cycles (p = 0.004). In tensile testing, the construct also demonstrated higher failure resistance (1359 ± 21.53 N) than wire fixation (780.1 ± 22.62N) (p = 0.007). Finite Element Analysis highlighted distinct stress patterns, validating the construct's superiority. This research presents a promising treatment approach for transverse patella fractures with potential clinical impact and future research prospects. This study presents a promising advancement in addressing the intricate challenges of transverse patella fractures, with implications for refining clinical practice. The construct's improved stability and resistance to failure offer potential benefits in postoperative management and patient outcomes.

A Comparison of the Efficacy of Cannulated Screws against Modified Tension Band Wire in the Management of Slightly Displaced Fractures of the Patella: A Novel Technique

AIM

The study aimed to compare the outcomes of Open Reduction and Cannulated Screw Fixation (ORCF) and Open Reduction and Tension Band Wire Fixation (ORTF) for treating minimally displaced patellar fractures, with the intention to discern the more efficacious surgical method in terms of various clinical and radiographic parameters.

METHODS

The research was a retrospective controlled trial encompassing 63 patients, culminating in a final data set of 52 patients with transverse patellar fractures with less than 8 mm of displacement. Patients were assessed postoperatively at three, six, and twelve months using measures such as the Lysholm score, Visual Analog Scale (VAS) for pain, and goniometry for active knee extensions and flexion. Statistical analyses were performed using SPSS version 22.0.

RESULTS

Results indicated superior clinical outcomes for the ORCF group at twelve months post-treatment, with notable higher Lysholm scores and lower VAS scores for pain at three-, six-, and twelve-month intervals. The ORCF group also demonstrated improved flexion and range of motion, with an average fracture healing time of 2.65 months and significantly lower complication rates, compared to the ORTF group.

CONCLUSIONS

The ORCF method, leveraging headless compression screws and cerclage wire fixation, emerges as a promising approach for managing minimally displaced transverse patellar fractures, potentially offering improved clinical results and patient satisfaction in comparison to the traditional ORTF method. Further expansive and diverse studies are warranted to substantiate these findings.

Transosseous suture versus suture anchor fixation for inferior pole fractures of the patella in osteoporotic bone: a biomechanical study

BACKGROUND

The surgical treatment of inferior patellar pole fractures can be a challenge, especially in geriatric patients, who are particularly frequently affected by osteoporosis. The objective of this biomechanical study was to compare the performance of suture anchor and transosseous suture fixation in fractures of the inferior patellar pole in context of bone mineral density.

METHODS

Twelve fresh-frozen human cadaveric knees received a transverse osteotomy, simulating an AO/OTA 34C1.3 inferior pole fracture of the patella. These fractures were fixated with either suture anchors (SA; Corkscrew® FT 4.5 mm) or transosseous suture (TS; #2 FiberWire®). Cyclic loading tests were performed by pulling the quadriceps tendon against gravity from 90° flexion to almost full extension (5°) for 1000 cycles. Motion and fracture gap displacement were tracked until failure occurred. Subsequently, loading to failure tests followed. Differences between groups were compared using unpaired t-tests, and correlations were calculated with Pearson's correlation coefficient.

RESULTS

The suture anchor group showed significantly fewer cycles to failure than the transosseous suture group (SA: 539.0 ± 465.6 cycles, TS: 1000 ± 0 cycles, P = 0.04). Bone mineral density correlated positively with cycles to failure in the suture anchor group (Pearson's r = 0.60, P = 0.02). No differences in fracture gap displacement could be proven after 100 cycles (SA: 4.1 ± 2.6 mm, TS: 6.5 ± 2.6 mm, P = 0.19); 500 cycles (SA: 6.4 ± 6.1 mm, TS: 9.6 ± 3.8 mm, P = 0.39); and 1000 cycles (SA: 4.0 ± 0.4 mm, TS: 11.0 ± 4.5 mm, P = 0.08). Furthermore, the mean destructive load to failure in the suture anchor group was also significantly lower than in the transosseous suture group (SA: 422.4 ± 212.2 N, TS: 825.7 ± 189.3 N, P = 0.04).

CONCLUSIONS

Suture anchors may be a viable alternative to transosseous suture in younger patients for clinical advantages, but in osteoporotic bone, the more stable osteosynthesis with transosseous suture continues to prove superior. Therefore, trauma surgeons might consider the use of transosseous suture in elderly patients, especially in those presenting with low bone mineral density values.

Triangular configuration with headless compression screws in the fixation of transverse patellar fracture

A triangular configuration with three parallel cannulated screws is an established treatment for fixing transverse patellar fractures; however, the stability achieved with this approach is slightly lower than that attained with cannulated screws combined with anterior wiring. In the present study, triangular configurations were modified by partially or totally replacing the cannulated screws with headless compression screws (HCSs). Through finite element simulation involving a model of distal femoral, patellar, and proximal tibial fractures, the mechanical stability levels of the modified triangular configurations were compared with that of two cannulated screws combined with anterior wiring. Four triangular screw configurations were developed: three HCSs in a forward and backward triangular configuration, two deep cannulated screws along with one superficial HCS, and two superficial cannulated screws with one deep HCS. Also considered were two parallel cannulated screws (inserted superficially or deeply) combined with anterior wiring. The six approaches were all examined in full knee extension and 45° flexion under physiological loading. The highest stability was obtained with the three HCSs in a backward triangular configuration, as indicated by the least fragment displacement and the smallest fracture gap size. In extension and flexion, this size was smaller than that observed under the use of two deeply placed parallel cannulated screws with anterior wiring by 50.3% (1.53 vs. 0.76 mm) and 43.2% (1.48 vs. 0.84 mm), respectively. Thus, the use of three HCSs in a backward triangular configuration is recommended for the fixation of transverse patellar fractures, especially without the use of anterior wiring.

Clinical outcomes of isolated acute instability of the syndesmosis treated with arthroscopy and percutaneous suture-button fixation

INTRODUCTION

To present the short- to midterm clinical outcomes of a series of patients with isolated acute syndesmosis instability treated with arthroscopy and percutaneous suture-button fixation.

MATERIALS AND METHODS

A review of 17 patients treated through the arthroscopic approach. The mean age of the patients was 27.8 years and the mean follow-up was 31.5 months. Clinical and functional evaluations were based on the VAS, AOFAS ankle-hindfoot score and time of return to preinjury level of activities. Imaging analysis was performed with stress radiographs, MRI and CT scan with stress.

RESULTS

The average VAS was 0.5 and the mean AOFAS score was 95.5. Out of the 17 patients, 15 were able to return to their preinjury level of activities. The mean time of return to activities was 5.06 months.

CONCLUSION

Arthroscopic approach and percutaneous suture-button fixation provided satisfactory clinical and functional results for selected patients with ASI at short- to midterm follow-up.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

Patella fracture fixation with a non-locked anterior plating technique: A biomechanical study

OBJECTIVES

The purpose of this study was to compare the biomechanical attributes of patella fracture fixation with either anterior plating utilizing two parallel, longitudinal 2.0 mm plates technique versus a cannulated screw tension band technique.

METHODS

Five matched pairs (ten specimens) of fresh frozen cadavers were utilized. A transverse patella fracture (OTA 34C1.1) was fixed using either two 4.0 mm cannulated screw anterior tension band (CATB) or with two 2.0 mm stainless steel non-locking plates along the anterior cortex secured with 2.4 mm cortical screws traversing the fracture site. Specimens underwent 1000 cycles of simulated active knee range of motion before load to failure destructive testing.

RESULTS

During cyclic loading there were no failures in the plate fixation group, and 2 out of 5 specimens catastrophically failed in the CATB group (p = 0.22). Average fracture displacement at the end of fatigue testing was 0.96 mm in the plate fixation group and 2.72 mm in the CATB group (p = 0.18). The specimens that withstood cyclic testing underwent a destructive load. Mean load to failure for the plate fixation specimens was 1286 N, which was not significantly different from the CATB group mean of 1175 N (p = 0.48). The mechanism of failure in the plate fixation cohort was uniformly via a secondary vertical patella fracture around the plates in all five specimens. In the CATB group, the mechanism of failure was via wire elongation and backing out of the screws.

CONCLUSIONS

Patella fixation with anterior plating technique statistically performed equivalent to cannulated screw anterior tension band in ultimate load to failure strength and fatigue endurance under cyclical loading. No failures were observed cyclic simulated active range of motion in the anterior plate group. There was a trend towards improved fatigue endurance in the plate fixation group, however this did not reach statistical significance. We believe plate fixation technique represents a low-profile implant option for treatment of transverse patella fractures, which may allow for early active range of motion, and these data support biomechanical equivalency to standard of care.

Role of an additional third screw in the fixation of transverse patellar fracture with two parallel cannulated screw and anterior wire

BACKGROUND

Two parallel cannulated screws along with an anterior wire to construct a tension band is a popular approach in transverse patellar fractures. However, the optimal screw proximity, either deep or superficial screw placements, remains controversial. Hence, a new concept of the addition of a third screw to form a triangular configuration along with the original two parallel screws was proposed in this study. Therefore, the biomechanical effect of the additional third screw on the stability of the fractured patella was investigated with finite element (FE) simulation.

METHODS

An FE knee model including the distal femur, proximal tibia, and fractured patella (type AT/OTA 34-C) was developed in this study. Four different screw configurations, including two parallel cannulated screws with superficial (5-mm proximity) and deep (10-mm proximity) placements and two parallel superficial screws plus a third deep screw, and two parallel deep screws plus a third superficial screw, with or without the anterior wire, were considered for the simulation.

RESULTS

Results indicated that the addition of a third screw increased stability by reducing the dorsal gap opening when two parallel screws were deeply placed, particularly on the fractured patella without an anterior wire. However, the third screw was of little value when two parallel screws were superficially placed. In the existence of two deep parallel screws and the anterior wire, the third screw reduced the gap opening by 23.5% (from 1.15 mm to 0.88 mm) and 53.6% (from 1.21 mm to 0.61 mm) in knee flexion 45° and full extension, respectively. Furthermore, in the absence of the anterior wire, the third screw reduced the gap opening by 73.5% (from 2 mm to 0.53 mm) and 72.2% (from 1.33 mm to 0.37 mm) in knee flexion 45° and full extension, respectively.

CONCLUSION

Based on the results, a third cannulated screw superficially placed (5-mm proximity) is recommended to increase stability and maintain contact of the fractured patella, fixed with two parallel cannulated screws deeply placed (10-mm proximity), particularly when an anterior wire was not used. Furthermore, the third screw deeply placed is not recommended in a fractured patella with two parallel superficial screws.

Role of screw proximity in the fixation of transverse patellar fractures with screws and a wire

PURPOSE

Clinical and biomechanical studies have reported that using supportive screws and a wire instead of the common Kirschner wires for modified tension band wiring improves the stability of fractured patellae. However, the effect of screw proximity on the fixation of a fractured patella remains unclear. Therefore a numerical study was conducted to examine the effects of screw proximity on biomechanical responses in a simulated patellar fracture fixed using two parallel cannulated screws and anterior tension band wiring.

METHODS

A patellar model with a transverse fracture and loads simulating patellar tendon forces applied on the patella were used in the present simulation. The surgical fixation consisted of two 4.0-mm parallel partially threaded cannulated screws with a figure-of-eight tension band made using a 1.25-mm stainless steel wire. Biomechanical responses at two screw proximities, 5 and 10 mm from the leading edge of the patella, were investigated.

RESULTS

Superficial screw placement (5 mm) yielded higher stability, lower wire loads, and lower bone contact pressures than the deep placement (10 mm). The deep placement of screws exerted a higher load on the wire but a lower force on the screw than superficial placement did.

CONCLUSION

This is the first numerical study to examine the effects of screw location on the fixation of a fractured patella using cannulated screws and tension band wiring. Considering the favorable biomechanical responses, superficial placement (5 mm below the leading edge of the patella) is recommended for screw insertion when treating a transverse fractured patella.

Roles of the screw types, proximity and anterior band wiring in the surgical fixation of transverse patellar fractures: a finite element investigation

BACKGROUND

Cannulated screws with an anterior wire are currently used for managing transverse patellar fracture. However, the addition of anterior wiring with various types of screws via open surgery to increase the mechanical stability is yet to be determined. Hence, this study aimed to compare the mechanical behaviors of a fractured patella fixed with various screws types and at various screw locations with and without the anterior wire. The present study hypothesized that using the anterior wire reduces the fracture gap formation.

METHODS

A finite element (FE) model containing a fractured patella fixed with various types of cannulated screws and anterior wiring was created in this study. Three types of screws, namely partial thread, full thread, and headless compression screws, and two screw depths, namely 5 and 10 mm away from the anterior surface of the patella, were included. The effect of the anterior wire was clarified by comparing the results of surgical fixation with and without the wire. Two magnitudes and two loading directions were used to simulate and examine the mechanical responses of the fractured patella with various fixation conditions during knee flexion/extension.

RESULTS

Compared with partial thread and headless compression screws, the full thread screw increased the stability of the fractured patella by reducing fragment displacement, fracture gap formation, and contact pressure while increasing the contact area at the fracture site. Under 400-N in the direction 45°, the full thread screw with 5-mm placement reduced the gap formation by 86.7% (from 2.71 to 0.36 mm) and 55.6% (from 0. 81 to 0. 36 mm) compared with the partial thread screw with 10-mm placement, respectively without and with the anterior wire.

CONCLUSION

The anterior wire along with the full thread screw is preferentially recommended for maintaining the surgical fixation of the fractured patella. Without the use of anterior wiring, the full thread screw with 5-mm placement may be considered as a less invasive alternative; however, simple screw fixation at a deeper placement (10 mm) is least recommended for the fixation of transverse patellar fracture.

A Biomechanical Study of an Alternative Internal Fixation Method for Transverse Patella Fractures

Pain and reoperation after fixation using tension band wiring and K-wires is not uncommon. A novel hook plate was designed to improve the treatment of patella fractures. The aim of this study was to compare the stability of the hook plate with that of tension band wiring and K-wires in a simulated patellar transverse fracture model (AO/OTA classification 34-C1.1). The authors tested 16 embalmed cadaver knee joints fixed with the hook plate and tension band wiring and K-wires under cyclic loading. Specimens underwent 100 cycles extending the knee joint from 90° of flexion to full extension at a velocity of 50 mm/min. The fracture gap was measured after the initial and last cycles. Data were assessed statistically using the t test, with significance set as P<.05. The fatigue test showed that the fracture gap after 100 cycles was 2.97±1.39 mm using tension band wiring and K-wires and 1.53±0.93 mm for the hook plate (P=.029). Six of 8 specimens in the tension band wiring and K-wires group met the failure criterion of fracture gap greater than 2 mm vs 1 in the hook plate group (P=.041). From a biomechanical point of view, the hook plate is a valid alternative to tension band wiring and K-wires for fixing patella transverse fractures. Compared with tension band wiring and K-wires, the hook plate may have superior ability in sustaining a reduced transverse patella fracture. [Orthopedics. 2018; 41(5):e643-e648.].

Surgical Management of Patellar Fractures

The patella plays a crucial role in the extensor mechanism to increase the mechanical advantage of the quadriceps. Fractures can be classified based on displacement, comminution, and fracture pattern, which often guide treatment. Modern treatment options include internal fixation using tension bands with Kirschner wires or cannulated screws, lag screw fixation, partial patellectomy, and rarely total patellectomy. Nondisplaced, closed patellar fractures or fractures with less than 2-mm articular steps can be successfully treated conservatively. Open fractures, articular step of 2 mm or greater, and loss of knee extension are indications for surgical intervention.

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.

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.

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.

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.