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    Femoral Head Size: Bigger Is Better

    At ICJR’s Pan Pacific Orthopaedic Congress, Dr. Adolph Lombardi discussed the benefits of using larger femoral heads in primary total hip arthroplasty. Following is the abstract of his presentation.

    Dislocation continues to be an unfortunate, frequent complication of primary total hip arthroplasty (THA). Reported incidence ranges from less than 1% to 5% with a recent Medicare claims data analysis of 58,521 patients reporting 3.9% dislocation in the first 26 weeks postoperative. [1]

    Numerous patient factors may contribute to increased dislocation risk:

    • Aging
    • Female gender
    • Lower muscular disorders
    • Cognitive dysfunction
    • Dysplasia
    • Previous femoral neck fracture
    • Rheumatoid arthritis

    The correlation between higher surgeon and hospital volume and lower dislocation rates has also been established. [2]

    Recent advances in implant design allow for use of larger prosthetic heads that more accurately reconstruct native femoral head size and improve head-neck ratio. The desire for larger heads is based on literature that shows a direct relationship between increasing femoral head size improving implant stability. [3-10] Because the neck of a femoral component is much smaller than the native human femoral neck, matching head size markedly improves head/neck ratio – a benefit in younger patients and those with high-demand lifestyle.

    Increased volumetric polyethylene wear has previously limited femoral head size to 32 mm or less. However, the development of highly cross-linked polyethylene and its superior wear characteristics allows use of larger – greater than 32 mm – femoral heads, with several reports documenting improved wear characteristics independent of head size. [11-20] Large femoral heads offer the benefit of increasing the ROM before component-to-component impingement, while increasing the displacement necessary before dislocation.

    It has been recognized that by increasing femoral head component size, a corresponding increase in head-neck ratio occurs, thereby allowing greater ROM. [21] A study conducted on an anatomic full size hip model found femoral heads greater than 32 mm virtually eliminate component-to-component impingement. [22]

    The benefit of increased head size was seen in a study of 22-mm and 40-mm femoral heads; the displacement required for dislocation increased by approximately 5 mm with 40-mm heads when the acetabular component is in 45 ̊ of abduction. [6]

    A number of studies have shown increasing femoral head size increases implant stability, thereby reducing postoperative dislocations. [3,5-8,23] We previously reported an incidence of 12 dislocations in 1,518 primary THAs (0.8%) done with femoral heads 32 mm or less through a standard direct lateral approach. [24] More recently, we reported on dislocation rates in primary THA with large-heads ≥36mm in diameter in several material combinations in 1748 patients (2020 hips). [25] With mean follow up of 2.8 years only 1 dislocation occurred, for a rate of 0.05%.

    Dr. Lombardi’s presentation can be found here.

    Author Information

    Adolph V. Lombardi Jr., MD, FACS, is from Joint Implant Surgeons, Inc., New Albany, Ohio.

    References

    1. Philips CB, Barrett JA, Losina E, Mohamed NN, Lingard EA, Guadagnoli E, Baron JA, Harris WH, Katz JN. Incidence rates of dislocation, pulmonary embolism, and deep infection during the first six months after elective total hip replacement. J Bone Joint Surg Am. 2003;85:20-26.
    2. Katz JN, Losina E, Barrett J, Phillips CB, Mohamed NN, Lew RA, Guadagnoli E, Harris WH, Poss R, Baron JA. Association between hospital and surgeon procedure volume and outcomes of total hip replacement in the United States Medicare population. J Bone Joint Surg Am. 2001;83:1622-1629.
    3. Bartz RL, Noble PC, Kadakia NR, Tullos HS. The effect of femoral component head size on posterior dislocation of the artificial hip joint. J Bone Joint Surg Am. 2000;82:1300-1307.
    4. Berry DJ, von Knoch M, Schleck CD, Harmsen WS. Effect of femoral head diameter and operative approach on risk of dislocation after primary total hip arthroplasty. J Bone Joint Surg Am. 2005;87:2456-2463.
    5. Conroy JL, Whitehouse SL, Graves SE, Pratt NL, Ryan P, Crawford RW. Risk factors for revision for early dislocation in total hip arthroplasty. J Arthroplasty. 2008;23:867-872.
    6. Crowninshield RD, Maloney WJ, Wentz DH, Humphrey SM, Blanchard CR. Biomechanics of large femoral heads: what they do and don’t do. Clin Orthop Relat Res. 2004;429:102-107.
    7. Cuckler JM, Moore KD, Lombardi AV, McPherson E, Emerson R. Large versus small femoral heads in metal-on-metal total hip arthroplasty. J Arthroplasty. 2004;19:41-44.
    8. Peters CL, McPherson E, Jackson JD, Ereckson JA. Reduction in early dislocation rate with large-diameter femoral heads in primary total hip arthroplasty. J Arthroplasty. 2007;22:140-144.
    9. Smith TM, Berend KR, Lombardi AV, Emerson RH, Mallory TH. Metal-on metal total hip arthroplasty with large heads may prevent early dislocation. Clin Orthop Relat Res. 2005;441:137-142.
    10. Stuchin SA. Anatomic diameter femoral heads in total hip arthroplasty: a preliminary report. J Bone Joint Surg Am. 2008;90(Suppl 3):52-56.
    11. Bragdon CR, Greene ME, Freiberg AA, Harris WH, Malchau H. Radiostereometric analysis comparison of wear of highly cross-linked polyethylene against 36- vs 28-mm femoral heads. J Arthroplasty. 2007;22:125-129.
    12. Bragdon CR, Jasty M, Muratoglu OK, Harris WH. Third-body wear testing of a highly cross-linked acetabular liner: the effect of large femoral head size in the presence of particulate poly(methylmethacrylate) debris. J Arthroplasty. 2005;20:379-385.
    13. Burroughs BR, Rubash HE, Harris WH. Femoral head sizes larger than 32 mm against highly cross-linked polyethylene. Clin Orthop Relat Res. 2002;405:150-157.
    14. Digas G, Kärrholm J, Thanner J, Malchau H, Herberts P. Highly cross-linked polyethylene in cemented THA: randomized study of 61 hips. Clin Orthop Relat Res. 2003;417:126-138.
    15. Digas G, Kärrholm J, Thanner J, Malchau H, Herberts P. Highly cross-linked polyethylene in total hip arthroplasty: randomized evaluation of penetration rate in cemented and uncemented sockets using radiostereometric analysis. Clin Orthop Relat Res. 2004;429:6-16.
    16. Geller JA, Malchau H, Bragdon C, Greene M, Harris WH, Freiberg AA. Large diameter femoral heads on highly cross-linked polyethylene: minimum 3-year results. Clin Orthop Relat Res. 2006;447:53-59.
    17. Hermida JC, Bergula A, Chen P, Colwell CW, D’Lima DD. Comparison of the wear rates of twenty-eight and thirty-two-millimeter femoral heads on cross-linked polyethylene acetabular cups in a wear simulator. J Bone Joint Surg Am. 2003;85:2325-2331.
    18. Manning DW, Chiang PP, Martell JM, Galante JO, Harris WH. In vivo comparative wear study of traditional and highly cross-linked polyethylene in total hip arthroplasty. J Arthroplasty. 2005;20:880-886.
    19. Muratoglu OK, Bragdon CR, O’Connor DO, Jasty M, Harris WH. A novel method of cross-linking ultra-high-molecular-weight polyethylene to improve wear, reduce oxidation, and retain mechanical properties. J Arthroplasty. 2001;16:149-160.
    20. Muratoglu OK, Bragdon CR, O’Connor D, Perinchief RS, Estok DM, Jasty M, Harris WH. Larger diameter femoral heads used in conjunction with a highly cross-linked ultra-high molecular weight polyethylene: a new concept. J Arthroplasty. 2001;16:24-30.
    21. D’Lima DD, Urquhart AG, Buehler KO, Walker RH, Colwell CW. The effect of the orientation of the acetabular and femoral components on the range of motion of the hip at different head-neck ratios. J Bone Joint Surg Am. 2000;82:315-321.
    22. Burroughs BR, Hassstrom B, Golladay GJ, Hoeffel D, Harris WH. Range of motion and stability in total hip arthroplasty with 28-, 32-, 38-, and 44-mm femoral head sizes. J Arthroplasty. 2005;20:11-19.
    23. Berry DJ, von Knoch M, Schleck CD, Harmsen WS. The cumulative long-term risk of dislocation after primary Charnley total hip arthroplasty. J Bone Joint Surg Am. 2004;86:9-14.
    24. Mallory TH, Lombardi AV, Fada RA, Herrington SM, Eberle RW. Dislocation after total hip arthroplasty using the anterolateral abductor split approach. Clin Orthop Relat Res. 1999;358:166-172.
    25. Lombardi AV Jr, Skeels MD, Berend KR, Adams JB, Franchi OJ. Do large heads enhance stability and restore native anatomy in primary total hip arthroplasty? Clin Orthop Relat Res. 2011 Jun;469(6):1547-53