The Primary Cemented Femoral Stem

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CHAPTER SYNOPSIS:

The history of cemented femoral stems dates back to the pioneer of the hip replacement, Sir John Charnley. Understanding the scientific and historical rationale behind cemented femoral stems can help the surgeon properly fit patients into this type of implant and better understand the gold standard of implants. This chapter compares modern designs.

IMPORTANT POINTS:

1

The polymerization of polymethylmethacrylate occurs with shrinkage of the cement mantle.
2

Cement is not an adhesive; fixation is achieved by interdigitation.
3

The cemented femoral stem acts as a composite structure, transmitting body weight through three layers (metal, cement, and bone) and through the two interfaces between them (metal-cement and cement-bone). This load transfer is determined by the cement-metal and cement-bone interface, stem geometry and structural properties, and the patient weight and activity level.
4

Removal of the intramedullary contents by frequent irrigation and aspiration reduces the load of procoagulants.

CLINICAL/SURGICAL PEARLS:

1

The surgeon should not rely only on the preoperative plan for stem sizing. The tactile feedback during broaching is important when selecting the stem size and minimizes the risk of fracture.
2

Failure to scrutinize the lateral radiographic view and inadequate position of the proximal femoral opening can result in a deficient cement mantle.
3

The intramedullary canal should be clean and dry with repeated pulsatile lavage and aspiration to remove loose bone debris, blood clots, and marrow before cement injection.
4

The authors prefer to occlude the proximal femur with the surgeon’s thumb rather than with a rubber seal during pressurization of the cement column.
5

The stem is then inserted at a slow pace, without changes in rotation or alignment, while the surgeon continues to occlude the proximal femoral opening with his or her thumb.
6

Once fully seated, gentle pressure should be applied without changes in alignment or rotation until the cement is fully polymerized.

CLINICAL/SURGICAL PITFALLS:

1

Heating the cement and stem to a certain point speeds cement polymerization, reducing femoral work time, venous stasis and cement porosity at the implant interface.
2

Incomplete irrigation of the femoral canal can result in poor interdigitation and a weak cement mantle.
3

An improper starting point for canal preparation can cause malpositioning of the stem in the transverse plane.

INTRODUCTION

In the 1960s Charnley introduced to clinical practice his low-friction arthroplasty with a highly polished cemented femoral stem. The satisfactory long-term results of this and other cemented femoral stems support the use of cement for fixation of total hip arthroplasty stems ( Tables 10-1 and 10-2 ).

TABLE 10-1

Long-Term Results of the Original, Highly Polished Charnley Stem

Author	Year of Publication	No. of Hips	Mean Age at Surgery (yr)	Radiographic Aseptic Loosening	Revisions for Femoral Aseptic Loosening	Follow-Up (yr)
McCoy et al	1988	40	60	7%	5%	15.3
Wroblewski et al	1999	320	43.3	13.7%	2.5%	22
Wroblewski et al	2002	1368	41	NA	4.9%	15
Berry et al	2002	2000	63.5	NA	6%	≥25
Older *	2002	5089	63	NA	8.4%	15–20
Callaghan et al	2004	317	65	7.6%	3.2%	15

NA, Not available.

Modified from Comba F, González Della Valle A, Salvati EA: The role of surface finish on the survivorship of cemented femoral stems for total hip arthroplasty, Minerva Ortop Traumatol 56:65–79, 2005.

* Multicenter study.

TABLE 10-2

Mid-Term Results of Other Polished Stems

Author	Year of Publication	Femoral Stem	No. of Hips	Mean Age at Surgery (yr)	Revisions for Femoral Aseptic Loosening	Follow-up (yr)
Fowler et al	1998	Exeter Original	375	66.8	1.86%	13.4
Wroblewski et al	2001	C-Stem	500	53.7	0%	3.5
Williams et al	2002	Exeter Universal	325	67.5	0%	10–12
Yates et al	2002	CPT	76	65	0%	5
González Della Valle et al	2006	VerSys CT	73	69	0%	6.1

Modified from Comba F, González Della Valle A, Salvati EA: The role of surface finish on the survivorship of cemented femoral stems for total hip arthroplasty, Minerva Ortop Traumatol 56:65–79, 2005

The constituents of acrylic cement have remained virtually unchanged since the 1960s. However, in the last 3 decades advances in the understanding of cement fixation, mixing techniques, application, pressurization, stem materials, and design have improved the clinical results.

The technical changes in cementing technique that have proved to be beneficial include femoral preparation to diminish interface bleeding, careful lavage, reduced cement porosity by vacuum mixing, a cement restrictor, preheating of the stem and polymer, retrograde canal filling and pressurization with a cement gun, stem centralization, and stem geometries that increase the intramedullary pressure and cement intrusion into the cancellous structure of the bone.

Other changes proved to be detrimental and were abandoned, such as the use of Boneloc cement (Biomet Inc., Warsaw, Ind.), which polymerized at a low temperature, and roughening and precoating of the stem surface.

In recent years the use of cementless femoral fixation for primary total hip arthroplasty has been increasing. The shift in the type of fixation followed the consistent, durable fixation obtained with first-generation and modern uncemented acetabular cups, ease of implantation, and misinformation about the so called “cement disease.” The phenomenon was compounded by the poor results of cemented femoral fixation of rough and precoated stems ( Tables 10-3 and 10-4 ).

TABLE 10-3

Failures with Different Roughened or Precoated Stems

Author	Year of Publication	Femoral Stem	No. of Hips	Mean Age at Surgery (yr)	Revisions for Femoral Aseptic Loosening	Follow-up (yr)
Callaghan et al	1996	Iowa Precoat	131	68	6.1%	8–9
Sporer et al	1998	Iowa Precoat	45	<50	18%	5–10
Dowd et al	1998	Harris Precoat	154	70	13.6%	6.3
Kawate et al	1999	Harris Precoat	55	67	5.5%	8
Cannestra et al	2000	Iowa grit blasted	82	69	1.2%	5.5
Sylvain et al	2001	Centralign Precoat	84	61.4	11%	2.9
Ong et al	2002	Harris Design-2	192	59	4.16%	13.5
Ong et al	2002	Harris Precoat	429	55	10%	8.4
Sanchez-Sotelo et al	2002	Harris Design-2	249	66	7%	10–20
Grose et al	2006	Spectron EF	20	62	25%	5.2

Modified from Comba F, González Della Valle A, Salvati EA: The role of surface finish on the survivorship of cemented femoral stems for total hip arthroplasty, Minerva Ortop Traumatol 56:65–79, 2005.

TABLE 10-4

Comparative Studies Analyzing Clinical Results of Total Hip Arthroplasty Performed with Cemented Femoral Stems with Different Surface Finishes

			No. of Revisions for Aseptic Loosening/No. of Total Hip Replacements Available at Last Follow-up
Study	Stem	Follow-up (yr)	Polished	Smooth/Satin	Matte/Rough	Precoat	P Value	Stem Geometry
Middleton et al (1998)	Exeter	6 to 12	0/36		6/17		—	Identical
Howie et al (1998)	Exeter	≥9	0/20		4/20		—	Identical
Collis and Mohler (1998)	T-28 vs. TR 28	10.76	4/209 *		5/227 *		—	Similar
Sporer et al (1999)	Iowa	9.75	2/36		7/45		<.05	Identical
Meding et al (2000)	T-28 vs. TR-28	11.6	42/378 ^†	22/171 ^†			.05	Similar
Collis et al (2002)	Iowa	5.65	0/99		4/83		.05	Similar
Hinrichs et al (2003)	Marburg	8.25		12/220 ^‡	26/343 ^‡		—	Identical
Vail et al (2003)	Luster vs. Endurance	4.8	0/113		0/113		.05	Identical
Vaughn et al (2003)	VerSys satin vs. precoated	<2		0/112		4/88	<.05	Identical
Rasquinha et al (2004)	Ranawat Burnstein Interlok	6.6		1/112	0/111		.05	Identical
González Della Valle, et al (2005)	VerSys satin vs. rough	5.5		0/138	6/64		<.05	Identical

Modified from Comba F, González Della Valle A, Salvati EA: The role of surface finish on the survivorship of cemented femoral stems for total hip arthroplasty, Minerva Ortop Traumatol 56:65–79, 2005.

* None of the loose polished T-28 stems had femoral osteolysis; three of the five loose rough TR-28 stems demonstrated significant femoral osteolysis. The polished T-28 group has 5 more years of follow-up than did the rough TR-28 group.

† Radiographic loosening in 42 (11.1%) of 378 polished T-28 stems vs. 27 (15.8%) of 171 rough TR-28 stems ( P = .03).

‡ Significantly more femoral osteolysis in the rough stem group

Unlike cementless femoral fixation, modern cemented femoral fixation has numerous advantages; it is versatile, durable, and can be used regardless of the diagnosis, proximal femoral geometry, anteversion, or bone quality. It can be used in combination with antibiotics in patients with a history or predisposition for hip infection. Intraoperative femoral fractures and postoperative thigh pain are extremely rare. Survivorship has not been surpassed by uncemented femoral fixation, and it continues to be the authors’ preferred form of fixation. However, heavy, young male patients may have a higher failure rate.

POLYMERIZATION AND PRINCIPLES OF CEMENT FIXATION

During polymerization, cement viscosity increases until final curing. Polymerization also is accompanied by shrinkage (volume contraction of approximately 5%), increase in temperature, and liberation of unpolymerized monomer. Some authors have speculated about the potential for bone necrosis, toxicity, and loosening induced by these factors. However, the long-term successful clinical and radiographic results of cemented femoral fixation discredit these theoretical concerns. Moreover, the interface temperature during polymerization in vivo is below that of collagen denaturation as a result of the heat dispersion mechanisms that include operating room temperature, irrigation, metal dissipation of heat and, most importantly, local blood circulation.

Cement is not an adhesive; fixation is achieved by interdigitation. The cemented femoral stem acts as a composite structure, transmitting body weight through three layers (metal, cement, and bone) and through the two interfaces between them (metal-cement and cement-bone). This load transfer is determined by the cement-metal surface interaction and cement-bone interface, stem geometry, the structural properties of the implant, and patient weight and activity level.

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