Wirkprinzipien der winkelstabilen Platten-Schrauben-Verbindung bei Fixateur-interne-Osteosynthesen

Complications during removal of conventional versus locked compression plates: is there a difference?

BACKGROUND

Osteosynthesis plate removal is one of the most commonly performed procedures in orthopaedic surgery. Due to technological advances and the quality of increasing osteosynthesis material, more and more locked plates have been implanted over the last 20 years. The aim of this study was to determine whether the complication rate during plate removal differs between conventional and locked plates.

MATERIAL AND METHODS

In this retrospective cohort study, 620 patients were included and divided into two groups based on the type of plate (locked and conventional). Technical complications during implant removal included screw breakage, destroyed screw head, implant breakage, remaining implant material, refracture, bony or soft tissue overgrowth. The following plate-associated complications were identified: osteosynthesis plate not detachable, plate bent or broken, necessity of special tools or plate loosened. Three types of screw-related complications were observed: screw not detachable, screw broken or screw dislocated.

RESULTS

Overall, complications related to the plate or screws were documented in 110 of the 620 cases. These complications occurred in 48 of the 382 cases involving conventional osteosynthesis (7.7% of all removals, 12.6% of all conventional removals) and in 62 of the 238 cases involving locked plate osteosynthesis (10.0% of all removals, 26.1% of all locked plate removals). The statistical analysis showed a significantly higher implant-related complication rate with locked plates compared to the conventional plates (p < 0.01).

CONCLUSIONS

Hardware removal can be a complication-afflicted operation, especially cases involving locked-plate removal should only be performed if a strong indication is evident. Possible benefits of the procedure should be considered carefully, taking the cost-benefit ratio into account.

An electronically instrumented internal fixator for the assessment of bone healing

Objectives

The monitoring of fracture healing is a complex process. Typically, successive radiographs are performed and an emerging calcification of the fracture area is evaluated. The aim of this study was to investigate whether different bone healing patterns can be distinguished using a telemetric instrumented femoral internal plate fixator.

Materials and Methods

An electronic telemetric system was developed to assess bone healing mechanically. The system consists of a telemetry module which is applied to an internal locking plate fixator, an external reader device, a sensor for measuring externally applied load and a laptop computer with processing software. By correlation between externally applied load and load measured in the implant, the elasticity of the osteosynthesis is calculated. The elasticity decreases with ongoing consolidation of a fracture or nonunion and is an appropriate parameter for the course of bone healing. At our centre, clinical application has been performed in 56 patients suffering nonunion or fracture of the femur.

Results

A total of 39 cases of clinical application were reviewed for this study. In total, four different types of healing curves were observed: fast healing; slow healing; plateau followed by healing; and non-healing.

Conclusion

The electronically instrumented internal fixator proved to be valuable for the assessment of bone healing in difficult healing situations. Cost-effective manufacturing is possible because the used electronic components are derived from large-scale production. The incorporation of microelectronics into orthopaedic implants will be an important innovation in future clinical care.

Cite this article: B. Kienast, B. Kowald, K. Seide, M. Aljudaibi, M. Faschingbauer, C. Juergens, J. Gille. An electronically instrumented internal fixator for the assessment of bone healing. Bone Joint Res 2016;5:191–197. DOI: 10.1302/2046-3758.55.2000611.

Management of Humeral Shaft Fractures With Intramedullary Interlocking Nail Versus Locking Compression Plate

Surgical fixation of humeral shaft fractures generally involves plating or nailing. It is unclear whether one method is more effective than the other. The aim of this study was to compare the results of the intramedullary nail and locking compression plate for the treatment of humeral shaft fractures. A total of 60 patients with humeral shaft fractures were randomized to undergo surgery with an intramedullary interlocking nail (n=30) or locking compression plate (n=30). The outcome was assessed in terms of intraoperative blood loss, operative time, hospital stay, union time, union rate, functional outcome, and incidence of complications. Functional outcome was assessed using the Constant score and the American Shoulder and Elbow Surgeons (ASES) score. Intraoperative blood loss, operative time, and hospital stay in group A (intramedullary interlocking nail) were significantly lower than those in group B (locking compression plate). No statistically significant difference was found regarding the union rate, mean Constant score, and mean ASES score between the groups. The average union time was found to be significantly lower for the intramedullary interlocking nail compared with the locking compression plate. The incidence of complications such as radial nerve palsy was found to be higher with the locking compression plate compared with the intramedullary interlocking nail. The intramedullary interlocking nail can be considered a better surgical option for the management of humeral shaft fractures because it offers decreased intraoperative blood loss; shorter operative times, hospital stays, and union times; and a lower incidence of serious complications such as radial nerve palsy.

Mechanisms of failure of locked-plate fixation of the proximal humerus: acoustic emissions as a novel assessment modality

OBJECTIVES

Locking plates are the predominant implants used for proximal humerus fractures. Despite a preponderance of good clinical outcomes, failures continue to occur. The purpose of this study was to investigate the failure mechanism of locked proximal humeral plate fixation and its relationship with bone density and screw length.

METHODS

Human cadaveric humeri were subjected to cyclic bending loads after an unstable 2-part fracture (Orthopedic Trauma Association classification 11 A-3) was created and stabilized with a locking proximal humeral plate. Acoustic emission (AE) sensors were mounted on the specimens to detect fracture displacement and generation of microcracks. The data were analyzed to evaluate construct failure.

RESULTS

Eight of 10 locking plate constructs in cadaver specimens failed in varus collapse. The primary influences on failure were cancellous bone density and cancellous bone screw length. AE monitoring demonstrated patterns of microcrack progression, predominantly along the inferior screws. The progression trends according to AE were similar to their respective actuator displacement versus time curves.

CONCLUSIONS

Cancellous bone density and total cancellous screw depth penetration seem to be critical variables. Although the patients' bone density cannot be controlled, surgeons may decrease the risk of failure by maximizing the length of the screws within the cancellous bone. Analysis of microcrack formation revealed that failures begin at the midportion and tips of the inferior screws and at the bone-plate interface of the inferior screws.

Telemetric assessment of bone healing with an instrumented internal fixator

In an interdisciplinary project involving electronic engineers and clinicians, a telemetric system was developed to measure the bending load in a titanium internal femoral fixator. As this was a new device, the main question posed was: what clinically relevant information could be drawn from its application? As a first clinical investigation, 27 patients (24 men, three women) with a mean age of 38.4 years (19 to 66) with femoral nonunions were treated using the system. The mean duration of the nonunion was 15.4 months (5 to 69). The elasticity of the plate-callus system was measured telemetrically until union. Conventional radiographs and a CT scan at 12 weeks were performed routinely, and healing was staged according to the CT scans. All nonunions healed at a mean of 21.5 weeks (13 to 37). Well before any radiological signs of healing could be detected, a substantial decrease in elasticity was recorded. The relative elasticity decreased to 50% at a mean of 7.8 weeks (3.5 to 13) and to 10% at a mean of 19.3 weeks (4.5 to 37). At 12 weeks the mean relative elasticity was 28.1% (0% to 56%). The relative elasticity was significantly different between the different healing stages as determined by the CT scans.

Incorporating load measuring electronics into implants is a promising option for the assessment of bone healing. Future application might lead to a reduction in the need for exposure to ionising radiation to monitor fracture healing.

The biomechanics of locked plating for repairing proximal humerus fractures with or without medial cortical support

BACKGROUND

Comminuted proximal humerus fracture fixation is controversial. Locked plate complications have been addressed by anatomic reduction or medial cortical support. The relative mechanical contributions of varus malalignment and lack of medial cortical support are presently assessed.

METHODS

Forty synthetic humeri divided into three subgroups were osteotomized and fixed at 0 degrees, 10 degrees, and 20 degrees of varus malreduction with a locking proximal humerus plate (AxSOS, Global model; Stryker, Mahwah, NJ) to simulate mechanical medial support with cortical contact retained. Axial, torsional, and shear stiffness were measured. Half of the specimens in each of the three subgroups underwent a second osteotomy to create a segmental defect simulating loss of medial support with cortex removed. Axial, torsional, and shear stiffness tests were repeated, followed by shear load to failure in 20 degrees of abduction.

RESULTS

For isolated malreduction with cortical contact, the construct at 0 degrees showed statistically equivalent or higher axial, torsional, and shear stiffness than other subgroups examined. Subsequent removal of cortical support in half the specimens showed a drastic effect on axial, torsional, and shear stiffness at all varus angulations. Constructs with cortical contact at 0 degrees and 10 degrees yielded mean shear failure forces of 12965.4 N and 9341.1 N, respectively, being statistically higher (p < 0.05) compared with most other subgroups tested. Specimens failed primarily by plate bending as the humeral head was pushed down medially and distally.

CONCLUSIONS

Anatomic reduction with the medial cortical contact was the stiffest construct after a simulated two-part fracture. This study affirms the concept of medial cortical support by fixing proximal humeral fractures in varus, if absolutely necessary. This may be preferable to fixing the fracture in anatomic alignment when there is a medial fracture gap.

Different stabilisation techniques for typical acetabular fractures in the elderly--a biomechanical assessment

OBJECTIVES

The tremendous increase of acetabular fractures in the elderly provides new challenges for their surgical treatment. The aim of this study was to evaluate the biomechanical properties of conventional and newly developed implants for the stabilisation of an anterior column combined with posterior hemitransverse fracture (ACPHTF), which represents the typical acetabular fracture in the elderly.

METHODS

Using a single-leg stance model we analysed four different implant systems for the stabilisation of ACPHTFs in synthetic and cadaveric pelvises. Applying an increasing axial load, fracture dislocation was analysed with a new multidirectional ultrasonic measuring system. Results of the different implant systems were compared by Scheffé post hoc test and one-way ANOVA.

RESULTS

In synthetic pelvises, the standard reconstruction plate fixed by 3 periarticular long screws and a new titanium fixator with multidirectional interlocking screws were associated with significantly less dislocation of the fractured quadrilateral plate of the acetabulum when compared to a standard reconstruction plate fixed by only one periarticular long screw and a locking reconstruction plate. No significant differences between the different osteosynthesis techniques could be observed in cadaver pelvises, probably due to a heterogeneous bone quality.

CONCLUSIONS

We conclude that the plate fixation by positioning of periarticular long screws as well as the multidirectional positioning of interlocking screws account for the most sufficient fracture stabilisation of ACPHTFs under experimental conditions.

Polyaxial Locked Implants in the Treatment of Type Vancouver B1 Periprosthetic Fractures of the Femur: Retrospective Clinical Examination in 58 Cases with Review of the Literature

We concluded a retrospective study of the outcomes of a consecutive series of Vancouver B1 and C femoral injuries using two specific locked implants. The study center is a dedicated trauma hospital with a large catchment area. Over a five-year period we treated 58 patients with a periprosthetic fracture of the femur with an angular stable plate, defined as the index procedure. The mean age at the index procedure was 72.4 years; 40 patients were female (69%). In 32 cases (55.2%) we saw a hip endoprosthesis, in 21 cases (36.2%) a knee endoprosthesis, and in five cases both (8.6%). Outcome measures were intra- and postoperative complications, bony union, degree of mobility and social status with comparison to the preoperative status, Barthel index, and timed ''up and go'' test. Union occurred in 56 cases (96.5%) after the index procedure. Three patients were bedridden before the injury; the remainder regained full weight-bearing status. The mean duration until full weight-bearing status in these patients was 8.6 weeks (4-13). Early implant failure with proximal dislocation of the screws occurred in two cases (3.5% revision rate). At follow up, 78% had maintained the same social status as before the injury. Fifty-two patients (89%) had regained their previous level of mobility. The mean Barthel index was 85 points (70-100) out of a possible 100, and improved from a mean of 35 points at the start of rehabilitation. It decreased on average by ten points compared to the preoperative status. The mean ''up and go'' time was measured as 21.4 s. In conclusion, polyaxial plates can achieve excellent surgical results. On the other hand, patients with this type of injury exhibit a clear deterioration in their social status, especially regarding lower limb motor function and self-independence.

Fixation of distal femoral fractures with the Less Invasive Stabilization System: a minimally invasive treatment with locked fixed-angle screws

BACKGROUND

The Less Invasive Stabilization System (LISS) is an internal fixator, which combines closed reduction of the diaphysis or metaphysis of distal femur fractures with locked unicortical screw fixation.

METHODS

In a retrospective consecutive study, 50 patients with Association for the Study of the Problems of Internal Fixation/Orthopaedic Trauma Association (AO/OTA) type 33-A1 to 33-C3 fractures were treated with the LISS between January 1999 and December 2003. Final results were assessed using the functional score of Neer after a median follow-up of 29 months (15-48 months).

RESULTS

Fifteen male and 16 female patients were followed up. The mean age was 49 years (17-90 years). Deep wound infection was seen in one patient (3%) and malpositioning with cutting-out of the proximal screws was in two patients (6%). All other fractures healed uneventfully without bone graft requirements after a mean of 12 weeks (7-20 weeks). A revised osteosynthesis was performed for correction of a valgus deformity of 20 degrees after 4 months. There was no difference in leg length exceeding 2 cm. One patient had a valgus deformity of 10 degrees combined with a rotational deformity of 10 degrees. Range of motion of the knee joint was >120 degrees in 15 patients (48%); 12 (39%) had a range of motion between 90 degrees and 120 degrees and 4 (13%) between 70 degrees and 90 degrees. The function according to the Neer score was excellent in 15 (48%), good in 10 patients (32%), and fair in 6 patients (20%). The mean Neer score was 80 (60-100).

CONCLUSIONS

The LISS promotes early mobilization and rapid rates of bony and clinical healing without bone grafting with low rates of infection.

Is the Wave Plate Still a Salvage Procedure for Femoral Non-union? Results of 75 Cases Treated with a Locked Wave Plate

OBJECTIVE

To analyse the results of the treatment of aseptic femoral non-unions using a singular locked implant.

DESIGN

Consecutive case series.

SETTING

A level-1 trauma center with a high number of specialist referrals.

PATIENTS

The study is based on a consecutive series of patients with prospective data evaluation. From 1993 to 2003, 75 patients were treated with a wave plate. All patients had persistent non-union of the femoral shaft without clinical or laboratory signs of infection and previous unsuccessful attempts to treat the non-union.

INTERVENTION

The method of treatment was standardized and included a lateral approach, cancellous bone hip grafting, osteosynthesis with a wave-shaped plate (PPF) and polyaxial locking screws as well as the application of a gentamicin-PMMA chain.

MAIN OUTCOME MEASUREMENTS

Time to achieve union, rate of implant failure and number of remaining nonunions after treatment. A total of 75 patients had full follow-up and were included in the study.

RESULTS

The union of the fracture was found in 64 patients after the initial procedure. In eight cases a second procedure was performed to achieve union in the form of a second bone graft because of a delay in callus formation. The mean time to union was 7.3 months with a range from 3 to 19 months. The implant failed in three cases accounting for 4% of the total.

CONCLUSION

The locked wave plate offers a further reliable treatment for complex aseptic femoral non-unions.

Minimally invasive plating for complex humeral shaft fractures

INTRODUCTION

The treatment for humeral shaft fracture is still controversial, especially for complex fractures. The purpose of this study was to evaluate the clinical and radiographic outcomes of treating complex humeral shaft fractures by using locking compression plate with minimally invasive technique.

MATERIALS AND METHODS

A total of 21 patients with 21 acute complex humeral shaft fractures (AO type C) were included in this study. All were treated with locking compression plate in a minimally invasive way. The average age of the patients was 42.9 years and there were 14 males and 7 females. Plain radiographs of humerus were used to assess bony union. Functional recovery of the shoulder joint was assessed using the Constant and HSS scoring systems.

RESULTS

The patients were followed for a mean of 28.7 months (range 19-37). With one operation, nineteen fractures (90.4%) achieved a solid union in an average of 14.3 weeks. At final follow-up, 20 patients (95.2%) had satisfactory alignment, except for one associated with olecranon fracture, all patients had a good to excellent elbow function with a mean HSS score of 91.7 points. Eighteen patients (85.7%) achieved satisfactory shoulder function with a mean Constant score of 83.1 points. One superficial infection (4.8%) and two non-unions (9.6%) were found postoperatively.

CONCLUSIONS

It was concluded that use of a minimally invasive plate osteosynthesis with locking compression plate is a safe alternative way to classic surgical methods in the treatment of complex humeral shaft fractures, which had a high union rate with less risk of complications.

Locked vs. unlocked plate osteosynthesis of the proximal humerus - a biomechanical study

BACKGROUND

Locked plates (internal fixators) have been found to be an optimal method for the fixation in proximal humeral fractures. In a biomechanical cadaver study the difference between locked and non-locked osteosyntheses was investigated.

METHODS

Paired humeri were harvested, bone density measured. Locked internal fixators were mounted on one specimen; identical plate-screw-systems without locking mechanism applied to the contralateral specimen for comparison. After that, a transverse subcapital osteotomy was performed. With 7 pairs of humeri static tests with increasing axial loads and with 5 pairs dynamic tests with 10 N preload and 80 N maximal axial load for up to 1 million cycles were performed.

RESULTS

In the static experiments the elastic stiffness of the construct was 74% higher in the locked group (median 80 N/mm, quartile range 77-86 N/mm) compared with the non-locked group (46 N/mm, 35.5-56.5 N/mm). The difference was statistically significant (Wilcoxon test for paired samples, P<0.05). Similarly, the linear range until failure was definitely extended in the locked group by 64% (92 N, 89-98 N vs. 56 N, 36.5-73.5 N, P<0.05). Under dynamic loading the non-locked group showed fixation failures between 97,000 and 500,000 cycles. In the locked group no failure was observed until the end of the experiment at 1 million cycles (P<0.0.5). The final deformation was found to be 1 mm (median, quartil range 1.0-1.2 mm) in the non-locked group and 0.3 mm (0.2-0.3 mm) in the locked group (P<0.05). The differences were found equally in lower as well as in higher bone density specimen.

INTERPRETATION

Because of the optimal load transfer between implant and cancellous bone, a locked screw plate interface will reduce fixation failure in proximal humeral fractures.

Die Behandlung hypertropher distaler Tibiapseudarthrosen mit perkutan eingebrachten winkelstabilen Implantaten

Hypertrophic nonunions of the distal, dia-/metaphyseal tibial shaft are still considered to be a problematic challenge. The use of a locking plate system (LCP) as an alternative treatment option was evaluated in these nonunions. This retrospective, nonrandomized study included four male patients (mean age 52.5 years) with hypertrophic nonunions of the distal dia-/metaphyseal tibial shaft treated with a locking compression plate (LCP) by percutaneous technique. The following parameters were evaluated: fracture type (AO), primary fracture care, operation technique of the nonunion, healing of the nonunion, ability to work, complications, and clinical result (function of the upper ankle joint). Primarily, there were 3 cases of open fractures. Three fractures were located in the dia-/metaphyseal region and primarily treated with an unreamed tibial nail (UTN), while 1 open metaphyseal fracture was treated with an external fixator. The mean interval between injury and operation of the nonunion was 9.1 (4.4-12) months. All nonunions healed within 3 (2-4) months. The mean clinical and radiological follow-up was 11.5 (9-14) months. All patients were able to work within an average of 2.3 months. The function of the upper ankle joint was unrestricted in 3 cases, and in 1 case there was a mild functional deficit. The use of an interlocking plate for the management of hypertrophic nonunions of the distal tibial shaft represents a reliable, new treatment option.

Delayed and non-union of the humeral diaphysis--compression plate or internal plate fixator?

In a retrospective study, two groups of patients with delayed or non-union of the humeral diaphysis were compared. In group A, a 4.5-mm low-contact dynamic compression plate (LCDCP) was used for internal fixation and in group B, an internal plate fixator with locked screws was used. In all patients autologous bone grafting was performed. Group A consisted of 14 patients (mean age 38.9 years) and group B consisted of 19 patients (mean age 54.3 years). The mean duration of the delayed or non-union was 9.3 months (range 3-26 months) in group A and 24.8 months (range 3-216 months) in group B. In group A an average of 1.1 (range 0-2) previous operations had been performed, and in group B an average of 1.6 (range 0-4). One primary nerve palsy was diagnosed in group A and six in group B. Although the patients of group B were older, had longer-lasting non-unions, more previous operations and more severe initial injuries, only in group A was there a hardware failure due to osteoporosis which required re-osteosynthesis. All other patients showed bony consolidation without further operations. The LCDCP and the internal plate fixator both showed high consolidation rates, but we feel that the internal plate fixator may be the more reliable implant, especially in patients with poor bone stock.