Failure of fracture plate fixation

Endosteal strut augment reduces complications associated with proximal humeral locking plates

BACKGROUND

Locking-plate technology has renewed interest in plate fixation for treating proximal humerus fractures. Complications associated with these devices, including loss of reduction, screw cutout, and intra-articular penetration, are frequent. Establishing a second column of support may reduce complications and improve clinical outcome scores.

QUESTIONS/PURPOSES

We asked whether addition of an endosteal cortical allograft strut, used as an augment to locking-plate fixation for displaced proximal humerus fractures, would reduce complications and improve clinical outcome scores.

PATIENTS AND METHODS

We retrospectively reviewed the charts and radiographs of 38 patients treated by this method. All patients were evaluated with serial radiographs, as well as the Disabilities of the Arm, Shoulder, and Hand and Constant-Murley scores. There were seven two-part, 19 three-part, and 12 four-part fractures. The minimum followup was 49 weeks (average, 75 weeks; range, 49-155 weeks).

RESULTS

No patient had intra-articular screw penetration or cutout. No patient had complete osteonecrosis, but one had partial osteonecrosis. The reduction was lost in one patient. The mean Disabilities of the Arm, Shoulder, and Hand score was 15 (range, 0-66.4). The mean Constant-Murley score was 87 (range, 51-95).

CONCLUSIONS

Low rates of complication and high clinical outcome scores can be achieved when treating complex proximal humerus fractures with locking-plate fixation and an endosteal strut augment.

LEVEL OF EVIDENCE

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

A New System to Improve Screw Fixation to Bones

Plates and non-locked screws used in the treatment of osteoporotic bone fractures frequently become loose due to everyday mechanical demands. Currently, locking plates and screws are the gold standard treatment for these fractures. However, their use has several limitations and complications as they are technically demanding, and their cost is very expensive. To improve the fixation strength of traditional unlocked plate and screw constructs, we have developed a new fixation system based on a very old concept. The system consists of a screw locking element (SLE) manufactured from PEEK, which is attached to the end of the screw shaft once it has traversed both bone cortices. A specially designed tool is used to facilitate its attachment to the screw. This tool makes it possible for the screw to traverse an osteosynthesis plate or lockwasher as well as both bone cortices and to easily find the SLE, fixing it against the far cortex. We tested the pull-out strength of SLEs and compared the results with previously published data for human femoral cortex pull-out strength. Our laboratory tests demonstrate that the mean SLE pull-out strength was 3864 ± 47.61 N, while that observed for a human femoral diaphysis cortex was 4071.54 ± 1461.69 N. This difference was not significant (p > 0.05). This new system can easily be used with any type of osteosynthesis in osteoporotic or osteopenic bones, with the screws being placed on weakened areas of the bone (e.g., fissure lines, previous orifices, or thinned metaphyseal bone cortex), or to replace over-torqued screws. It is particularly suitable for veterinary trauma, where immediate weight-bearing protection after fracture treatment is nearly impossible.

Screw locking elements: a means to modify the flexibility of osteoporotic fracture fixation with DCPs without compromising system strength or stability

This paper analyses whether it is possible to use dynamic compression plates (DCPs) and screw locking elements (SLEs) to vary the flexibility of osteoporotic fracture fixation without compromising the strength and stability of the construct. Compression, torsion and four-point bending static strength tests were conducted. Cyclic load tests of up to 10,000 load cycles were also carried out to determine stiffness performance. Four fixation systems were mounted onto polyurethane bone models. Group 1 consists of the DCP and six cortical screws. Group 2, idem, but with the addition of two SLEs. Group 3, idem, but with the addition of six SLEs. Group 4 used the locking compression plate (LCP) and locking screws. The results indicated no significant difference (p>0.05) in the strength of groups 2-4. It was also observed that the torsional stiffness of group 3 (0.30 Nm/°) was higher than that of group 2 (0.23 Nm/°) and similar to that of group 4 (0.28 Nm/°). Compression stiffness of group 4 (124 N/mm) was higher than that of group 2 (102 N/mm), but lower than that of group 3 (150 N/mm). No notable differences were observed for structural bending stiffness. It is concluded that by using the DCP with SLEs it is possible to modify the stiffness of the fixation construct for the repair of osteoporotic fractures and, in this way, facilitate the conditions suitable on secondary bone healing.

Evidence for success with locking plates for fragility fractures

Fixation of fragility fractures with plates and screws often results in loss of fixation and need for revision surgery. Locking plates and screw were introduced to improve fixation of fragility fractures and have been in use for a decade. This review was conducted to compile evidence that locking plates and screws improve fixation of fragility fractures. A search of PubMed was performed to identify biomechanical studies as well as clinical series of fragility fractures treated with locking plates. Biomechanics papers had to use models of osteoporotic bone and had to directly compare locking plates with traditional plates. Clinical studies included case series in which locking plates were applied to elderly patients with fractures of the proximal humerus and periprosthetic distal femur fractures. Most studies are retrospective case series. Locking plates lead to greater stability and higher loads to failure than traditional plates. When applied to proximal humerus fractures, uncomplicated healing occurs in 85% of patients. Constant and Dash scores approach normal values. For distal femoral periprosthetic fractures, union rates of 75% are reported with a malunion rate of 10%. Early evidence suggests that locking plates improve results of treatment of proximal humerus fractures and distal femoral periprosthetic fractures in the elderly. Loss of fixation is associated with failure to achieve stability at the fracture site. Principles of fracture fixation in osteoporotic bone defined prior to the introduction of locking plates should still be applied.

Fibula-pro-tibia in plating tibial non-unions

PURPOSE

Plating non-unions of the tibial diaphysis often presents the technical problem of poor purchase of screws due to osteoporosis. To improve the stabilization, insertion of one or more screws through the plate across the tibio-fibular space to the fibula (fibula-pro-tibia plating) has been practiced. The aim of this study is to evaluate the effectiveness of the fibula-pro-tibia plating technique in managing difficult diaphyseal tibial non-unions.

METHODS

Between 2000 and 2008, 30 patients with diaphyseal non-union of tibia were managed with this technique. The time between injury and index operation ranged between six and 24 months (average, 11 months). Sixteen patients had three surgical procedures before the index operation, ten had two procedures and four patients had one.

RESULTS

The duration of follow-up ranged between ten and 38 months (average 26 months). The mean healing time was 3.5 months. Complications were minimal and included two cases of delayed union which required regrafting after four months and two cases, which had infected nonunion, had reactivation of the infection, which resolved completely after achieving union and removing the plates. There was no negative effect from this fixation technique on the ankle joint motion.

CONCLUSION

The fibula-pro-tibia plating technique is an effective variation in plating diaphyseal tibial non-unions.