Hemiarthroplasties

Wear and Lubrication In-Vitro Study. Polyurethane surface layers with viscoelastic properties similar to natural articular cartilage has been proposed for use with hemiarthroplasty, a single component joint replacement in which the implant is intended to bear against a natural cartilage surface. Medley and... 

The Smith-Petersen implant is an early example of a hemiarthroplasty, in which only the femoral side of the hip joint is replaced. By contrast, in a total hip joint replacement, both the femoral and acetabular surfaces are replaced. The radiograph, shown in Figure 6.1, was obtained at the Chamley Museum at Wrightington Hospital (Wigan, England) and illustrates this early design. 

The number of shoulder arthroplasty procedures done yearly has grown from an estimated 5000 per year in the United States between 1990 and 1992 (Wirth and Rockwood, Jr. 1996) to around 15,000 per year between 2002 and 2003 (Jackson 2003). Of these, a substantial portion are hemiarthroplasties. The prevalence of hemiarthroplasties as a percentage of the total number of replacements ranges from 14% (Edwards et al. 2002) in a multicenter study of OA, to 65% in a study of fracture repair (Boileau et al. 2001), to 87% in the Swedish shoulder arthroplasty register started in 1999 (Rahme, Jacobsen, and Salomonsson 2(X)1). Dr. Charles Neer, II, the pioneer of tiie procedure, estimates that overall, aroimd 20% of shoulder replacements are hemiarthroplasties (2003). 

The modern era of shoulder replacement was ushered in by Dr. Charles Neer, II. In 1953, in response to the relatively poor results of humeral head resection for patients with proximal humeral fractures. Dr. Neer implanted a vital-hum humeral component of his own design in a hemiarthroplasty procedure (Figure 9.4). In 1955, he reported on his first series of 12 pahents treated in this way. 

Humeral component designed and used by Dr. Neer for his first shoulder hemiarthroplasties (image courtesy of Howmedica Osteonics, Allendale, NJ). 

Bio-Modular . A modular cobalt chromium humeral component with keeled and three-pegged UHMWPE glenoid components developed with Drs. Russell Warren and David Dines and introduced in 1986. The glenoid components are sterilized by gamma in argon. It is intended for primary, hemiarthroplasty, total, and fractme use with cemented fixation. 

BiPolar. A modular head with a cobalt chromium shell and an inner UHMWPE bearing surface and retaining ring capturing an inner cobalt chromium head. The concept was originally developed in the 1970s and was intended for use in a hemiarthroplasty salvage procedure. 

Integrated . A collection of monoblock and modular cobalt chromium humeral prostheses within a single system. Included are the Kirschner n-C monoblock, and the Atlas modular design. Glenoid components include all-poly UHMWPE keeled and pegged components as well as a metal-backed, screw-fixed design. Components of the system are intended for primary, hemiarthroplasty, total, and fracture use with cemented and press-fit fixation. 

GlobaF and GlobaF Advantage and GlobaF FX. Modular cobalt chromium humeral prostheses developed with Drs. Charles Rockwood and Fredrick Matsen, III, and first introduced in 1990. They include UHMWPE keeled and five-pegged glenoid components sterilized by gas plasma. They are intended for primary, hemiarthroplasty, total, and fracture use (FX specifically) with press-fit fixation. 

Edwards T.B., N.R. Kadakia, A. Boulahia, et al. 2003. A comparison of hemiarthroplasty and total shoulder arthroplasty in the treatment of primary glenohumeral osteoarthritis Results of a multicenter study. / Shoulder Elbow Surg 12 207-213. 

Sperling J.W., R.H. Cofield, and C.M. Rowland. 1998. Neer hemiarthroplasty and Neer total shoulder arthroplasty in patients fifty years old or less Long-term results. J Bone Joint Surg 80 464 473. 

Foy JR, Williams 3rd PF, Powell GL, Ishihara K, Nakabayashi N, LaBerge M. Effect of phospholipidic boundary lubrication in rigid and comphant hemiarthroplasty models. Proc InstMech Eng H 1999 213(1) 5-18. 

SMITH. T.J. and MEDLEY, J.B. Elastohydrodynamic lubrication models to aid in the development of compliant surfaced components for hemiarthroplasty, 6th Annual Meeting of the Canadian Biomaterials Society, 1985,. Kingston, Ontario, 44-45. 

Martinez de Aragon, J.S. et al. Early outcomes of pyrolytic carhon hemiarthroplasty for the treatment of trapezial-metacarpal arthritis. / Hand SurgAm, 2009. 34(2) 205-12. 

In either case, to replace the humeral articular surface, the humeral head is resected at its base and the medullary cavity of the proximal humeral bone is prepared to accept the stem of a metal humeral prosthesis. In a fracture repair procedure, the bone fragments are reapproximated and held in place around the stem and under the head of a metal humeral component by wires. Many humeral components include holes in the stem to faciUtate this reattachment. One type of humeral component used in hemiarthroplasty... 

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