The Role of Locking Plates in the Treatment of Proximal Humerus Fractures

Tousief Hussain, M.D., BSC, FRCSC
Saskatoon, SK

Proximal humerus fractures represent one of the most common fractures in the elderly. They account for 10% of all fractures in patients over the age of 65 years and are the third most common fracture in the elderly1,2. Seventy-five percent of these fractures occur in patients > 60 years of age3. The management of these fractures can be a significant challenge especially in the presence of osteoporosis and multiple fracture segments. Treatment options include conservative therapy, fixation, and arthroplasty. A good outcome can be regarded as pain free abduction and elevation of ≈ 90, external rotation of ≈ 25, and an internal rotation good enough to touch the L1 vertebra4.

In general, displaced two, three, and selected four part fractures are treated by internal fixation. In three and four part proximal humerus fractures, fixation and arthroplasty are superior to conservative treatment4. Fixation is the best option for preserving bone alignment, joint surface congruity, humeral head vascularity, and stability to allow early mobilization.

The option of locking plate technology has become a growing trend for the treatment of proximal humerus fractures. The ability of screws to lock to a plate gives angular stability to the construct. In experimental studies conducted on cadaveric specimens, Hessman and colleagues3 demonstrated that rigid locked plates versus nonlocked plates underwent less irreversible deformation during axial and torsional loading. The implants were also stronger when loaded to failure. Thus, locking plates will better maintain postoperative reduction during early functional rehabilitation.

Lill and colleagues5 also found that locking plates minimized the peak stress at the bone implant interface making them better suited for osteoporotic bone as they had less implant loosening and migration. In regards to humeral head vascularity, locking plates screws do not compress the plate against the bone. Lthi and colleagues 6,7 demonstrated the danger of a high compressive force on bone by showing that plate bone contact disturbed periosteal blood circulation. This issue can only be avoided when stabilization requires no frictional forces between the implant and fracture fragments. Locking plates avoid this problem by interlocking the screw head to the plate. In doing so, the plate now acts as a force carrier. In conventional plating, the plate and bone act as a force carrier, which is accomplished by friction between plate and bone6,8. In essence, locking plates work like external fixators and is why they are also known as internal fixators.

Fracture healing occurs by callus formation unless rigid stability is obtained at the fracture site, such as with the placement of a lag screw. Presently, two clinical case series have reported good results with their use. Bartsch and colleagues3,9 reported on locked plate fixation in 47 patients. They found that 43 patients had good pain relief, and observed secondary displacement with early physiotherapy in two cases. Mckter and colleagues3,10 reported good results in 27 of their 32 patients with one implant failure. However, caution should be exercised with the use of these plates as failures are currently being seen when not applied correctly or applied inappropriately. Further study of locking plates in the treatment of proximal humerus fractures is needed.

References

1. Baron J.A. et al. Basic Epidemiology of fractures of the upper and lower limb among Americans over 65 years of age. Epidemiology. 7:612 618, 1996.

2. Lind T., Kroner T.K., and Jensen J. The epidemiology of fractures of the proximal humerus. Arch Orthop Trauma Surg. 108:285 287, 1989.

3. Hessmann M.H. et al. Internal Fixation of Proximal Humeral Fractures: Current Concepts. Eur J Trauma. 29:253 261, 2003.

4. Misra A., Kapur R., and Maffulli N. Complex proximal humeral fractures in adults a systematic review of management. Injury. 32:363372, 2001.

5. Lill H. et al. Proximal humeral fractures: how stiff should an implant be? A comparative mechanical study with new implants in human specimens. Arch Orthop Trauma Surg. 123:7481, 2003.

6. Schtz M. and Sdkamp N.P. Revolution in plate osteosynthesis: new internal fixator systems. J Orthop Sci. 8:252258, 2003.

7. Luthi U. et al. [Area of contact between osteosynthesis plate and bone in internal fixation.] Akt Traumatol. 10:1316, 1980.

8. Seebeck J. et al. Comparison of stresses at the bone/screw interface of conventional andangularly stable fixation systems in osteoporotic bone. 12th Conference of the European Society of Biomechanics, Dublin, 2000

9. Bartsch S. et al. Die Osteosynthese der dislozierten Humeruskopffrakturen mit der winkelstabilen proximalen Oberarm-Platte. Akt Traumatol. 31:6471, 2001.

10. Mckter H. al. Die winkel- und rotationsstabile Osteosynthese proximaler Humerusfrakturen mit der Humerus-Fixateurplatte. Chirurg. 72:132735, 2001.

11. Wagner M., General principles for the clinical use of the LCP. Injury. 34:S-B31S-B42, 2003.

12. Gautier E. and Sommer C., Guidelines for the clinical application of the LCP. Injury. 34:S-B63S-B76, 2003.

13. Perren S.M., Backgrounds of the technology of internal fixators Injury. 34:S-B1S-B3, 2003.

Figure legends

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Figure 1: 52 year old blind right hand dominant male who fell fracturing right proximal humerus.

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Figure 2: AP radiograph after undergoing an open reduction internal fixation using an AO synthes proximal humeral locking plate.

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Figure 3: Lateral radiograph after undergoing an open reduction internal fixation using an AO synthes proximal humeral locking plate.

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