Ununited diaphyseal fractures of the humerus: techniques for fixation of osteoporotic bone

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.

Use of a "hybrid" locking plate for complex metaphyseal fractures and nonunions about the humerus

PURPOSE

To review one surgeon's experience with a novel type of "hybrid" locking plate (which has both 3.5mm and 4.5mm locking holes) for difficult fractures of the meta-diaphyseal humeral shaft.

METHODS

Over a 2-year period, 24 patients who presented with a metaphyseal humeral fracture or nonunion (proximal or distal) were treated surgically by a single surgeon. A "hybrid" locking plate containing 3.5mm locking holes on one end and 4.5mm locking holes on the other end (Metaphyseal plate, Synthes, Paoli, Pa) was used in all patients. The selection of this implant was based on fracture location and bone quality. Fractures were operated on through an anterolateral or direct posterior approach. All fractures were secured with a minimum of three 4.5mm screws on one side of the fracture and three 3.5mm screws on the other side. All patients were treated with a similar post-operative protocol for early range of shoulder and elbow motion.

RESULTS

Three patients were lost to follow-up. The cohort consisted of 15 women and 6 men with a mean age of 49 years (range 18-78). There were 14 acute fractures and 7 nonunions. Twelve fractures involved the distal metaphyseal segment and 9 involved the proximal metaphyseal segment. Twenty-two patients completed a minimum 6-month clinical and radiographic follow-up and form the basis for this report. All 21 patients healed their fractures or nonunions at a mean of 4.5 months. There were no infections or hardware failures. In every case the "hybrid" nature of the plate design was felt to be advantageous.

CONCLUSION

This "second generation" metaphyseal locking plate, which affords the surgeon the ability to place a greater number of smaller calibre screws within a short bone segment, while using traditional large fragment screw fixation in the longer segment, is clearly an improvement in plate design. Meta-diaphyseal upper extremity long bones may serve as the most ideal location for this implant.