Healio
Healio
Issue: June 2006
ByJeffrey R. McLaughlin, MD
June 01, 2006
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Porous-coated femoral components provide long-lasting fixation

Issue: June 2006
ByJeffrey R. McLaughlin, MD

Jeffrey R. McLaughlin, MD [photo]
Jeffrey R. McLaughlin

In the early 1980s, several porous-coated femoral components received FDA approval as investigational devices for primary total hip arthroplasty. Two of these implants, the Porous Coated Anatomic (PCA) (Howmedica, Rutherford, NJ) and the Harris Galante prosthesis (HGP) (Zimmer, Warsaw, Ind.), were developed at major academic centers. A third device, the Taperloc (Biomet Orthopedics, Inc., Warsaw, Ind.), was developed at a smaller clinic in northeast Wisconsin. The purpose of this paper is to present my experience using these three different femoral components as an orthopedic surgery resident, fellow and practitioner at three different joint replacement centers: Johns Hopkins Hospital, Massachusetts General Hospital (MGH) and the Kennedy Center for the Hip and Knee. As a result of this experience, I will review which prosthesis I am currently using, and why.

Mixed clinical results with PCA

The PCA hip was one of the most widely used total hip replacement implants in the United States in the 1980s. This cobalt chrome implant had a sintered bead porous coating and was designed to achieve anatomic fixation in the proximal femur. The orthopedic surgeons at Johns Hopkins had extensive clinical experience and were skilled technical surgeons.

The patients who underwent total hip arthroplasty were appropriate candidates for this procedure. These patients typically were from suburban Baltimore. There were few laborers or farmers, and few patients, if any, were obese.

The combination of experienced surgeons and ideal patient selection were a set up for success. The results using the PCA femoral component are mixed.

Tankersley and Hungerford reported their 5.5-year results using the PCA design. In their review of 42 patients, 14% underwent revision of the femoral component, and osteolysis was reported in 14%.1

Weidenhielm et al reported a 24% incidence of revision of the PCA femoral component at a follow up of seven years.2 Bojescul et al reported their 15.6-year results using the PCA femoral component. Seven percent underwent revision, and osteolysis occurred in 37.5%.3 These results were an improvement over the results in several series using first-generation cementing techniques on the femoral side, 4,5 but not as good as several reports using modern cement technique.6

Fibromesh stem provides poor results

The Harris Galante prosthesis was a different implant than the PCA. This titanium stem had a noncircumferential porous coating consisting of fibromesh pads. This femoral component was used at the MGH for a short period of time. Despite poor results using this implant, the investigators at MGH accurately and honestly reported their findings. It should be noted that during this same period of time, they also reported excellent results using a hybrid total hip replacement.

Goetz and Harris reported their six-year results using the HGP uncemented femoral component. Twelve percent of the femoral components underwent revision, and an additional 20% were loose. Femoral osteolysis occurred in 29%.7 At 10 years average follow-up, Clohisy and Harris reported a 25% incidence of aseptic loosening and a 19% rate of revision. Femoral osteolysis occurred in 60%.8 These results led the authors to abandon the use of this prosthesis.

Plasma-sprayed implant maintains low rate of revision

The Taperloc femoral component was designed at the Kennedy Center for the Hip and Knee. It received FDA approval as an investigational device in September 1983. Every primary total hip replacement at the Kennedy Center for the next 10 years was performed using the Taperloc.

The Taperloc femoral component is a wedge-shaped titanium stem, circumferentially porous-coated with plasma spray. The implant is designed to achieve fixation mediolaterally in the proximal femur.

The patient demographics at the Kennedy Center reflect the general population of northeast Wisconsin. This population includes laborers from the local iron and paper mills, and farmers. In addition, nearly 40% of our patients are obese or morbidly obese, reflecting Wisconsin’s designation as having the second heaviest population in the United States.

In 1997, my colleagues and I published our 10-year average results using the Taperloc femoral component in 145 consecutive total hip arthroplasties.9 In this series, 4% of the femoral components required revision for all reasons combined, and only 1% was revised for loosening. The femoral component revised for loosening was removed three days after the index procedure secondary to an unrecognized intraoperative fracture of the femoral calcar. Femoral osteolysis occurred in 6%.

In a separate review, my colleagues and I reported our results using the Taperloc femoral component in 100 consecutive hips in patients who were 50 years old or younger with a mean age of 37 years.10 In this series, no femoral component required revision for aseptic loosening, and 98% remained in place and rigidly fixed at 13 years. Osteolysis occurred in 7%. Forty-eight percent of the patients in this series were involved in moderate or strenuous manual labor.

Currently, we have reviewed 209 total hip arthroplasties performed in patients who have survived a minimum of 10 years following total primary hip replacement surgery (range, 10 to 18 years). At an average follow-up of 15 years, 95% of the femoral components remain in place and only two hips (1%) required revision for aseptic loosening. In those hips that did not require revision surgery, only 1.5% of the femoral components were loose by radiographic criteria, and osteolysis occurred in 8%.

Consistent results

In our practice, consisting of patients from the general Wisconsin population, my colleagues and I found that the Taperloc femoral component has provided excellent fixation for more than 18 years. These results are consistent among patients who are young, old, active and obese. As a result of these findings, we currently use the Taperloc femoral component in nearly all of our patients undergoing primary total hip arthroplasty.

References

  1. Barrack RL, Mulroy RD Jr, Harris WH. Improved cementing techniques and femoral component loosening in young patients with hip arthroplasty. A 12-year radiographic review. J Bone and Joint Surg [Br]. 1992;74:385-389.
  2. Bojescul JA, Xenos JS, Callaghan JJ, Savory CG. Results of porous-coated anatomic total hip arthroplasty without cement at 15 years. J Bone Joint Surg [Am]. 2003;85:1079-1083.
  3. Clohisy JC, Harris WH. The Harris-Galante uncemented femoral component in primary total hip replacement at 10 years. J Arthroplasty. 1999;14:915-917.
  4. Goetz DD, Smith EJ, Harris WH. The prevalence of femoral osteolysis associated with components inserted with and without cement in total hip replacements. J Bone Joint Surg [Am]. 1994;76:1121-1129.
  5. McLaughlin JR, Lee KR. Total hip arthroplasty with an uncemented femoral component. Excellent results at ten-year follow-up. J Bone Joint Surg [Br]. 1997;79:900-907.
  6. McLaughlin JR, Lee KR. Total hip arthroplasty in young patients. 8-13 year results using an uncemented stem. Clin Orthop Relat Res. 2000;373:153-163.
  7. Stauffer RN. Ten year follow-up study of total hip replacement. With particular reference to roentgenographic loosening of the components. J Bone Joint Surg [Am]. 1982;64:983-990.
  8. Sutherland CJ, Wilde AH, Borden LS, Marks KE. A ten-year follow-up of one hundred consecutive Muller curved-stem total hip replacement arthroplasties. J Bone Joint Surg [Am]. 1982;64:970-982.
  9. Tankersley WS, Mont MA, Hungerford DS. A second-generation cementless hip prosthesis: improved results over the first-generation prosthesis. Am J Orthop. 1997;26:839-844.
  10. Weidenhielm LR, Mikhail M, Nelissen RG, Bauer TW. Cementless collarless (Exeter-CPT) versus cementless collarless (PCA) femoral components. A 2-to 14- year follow-up evaluation. J Arthroplasty. 1995;10:592-597.

Jeffrey R. McLaughlin, MD, is director of The Kennedy Center for the Hip and Knee, Mercy Medical Center in Oshkosh, Wisc.

Design

Thomas P. Schmalzried, MD: The evolution of design for many implants on the market today includes a higher offset. What are the benefits of a lateral offset or an increased lateral offset?

Adolph V. Lombardi, Jr, MD, FACS: In my experience, high polyethylene wear is associated with not effectively reconstructing the offset.

Reconstructing offset stabilizes a hip without affecting leg length. Reconstructing offset is critical in preventing dislocation. With dislocation, tissues are stretched and compromised. A closed reduction will not resolve the issue.

My indications for a lateralized stem are based on a preoperative evaluation and a preoperative templating process to discover the appropriate restoration, whether with a standard-designed stem or with an offset-designed stem.

With a tapered stem, a surgeon can move the component further into the funnel of the femur and use a longer neck length that helps reconstruct offset. Surgeons will have flexibility. I will perform trials with a standard- or offset-designed stem. If I feel that I approximated the leg length, the hip is stable and I can maneuver through a full range of motion of not coming out, I will implant a standard stem. Otherwise, I will implant an offset-design stem.

Schmalzried: Compare and contrast the Taperloc stem (Biomet Orthopedics, Inc., Warsaw, Ind.) with the reduced distal Taperloc stem.

Jeffrey R. McLaughlin, MD: The Taperloc is porous-coated on the proximal 40%. In the reduced distal stem, the non-porous-coated portion of the stem is ground down an additional 3 mm to 4mm. The reduced distal stem is designed for patients with narrow femoral isthmi. Also, young patients or patients with dysplasia may benefit from the stem.

Schmalzried: Has the tapered stem solved the limb length issue?

William C. Head, MD: The limb length issue is not thoroughly resolved because a titanium tapered stem will seek its own level of stability and a surgeon may not be able to drive it in any further. Surgeons should put a trial prosthesis in place and check limb length and stability.

John M. Cuckler, MD: It is incumbent upon surgeons to achieve proper prosthetic positioning and, in particular, with hard-on-hard bearings of any material, ensure that impingement will not occur at the extremes of motion.

Large femoral heads enhance prosthesis stability if implants are properly positioned, limb length is properly restored and abductor tension is restored by using lateral offset stems. Prosthesis stability enhances due to the larger arc of motion without impingement of the prosthetic neck against the acetabular component and the larger hop height from the center of the femoral head to the equator of the acetabular component. The burden is still on surgeons, however, to properly align implants.

Schmalzried: Patients tend to be bothered by longer limbs and tolerate better and complain less about shorter limbs. With the current armamentarium of implants, do surgeons have an advantage in surgery when using a shorter implant?

Cuckler: The problem with lengthening or shortening of the extremity is that the musculature of a hip, like all skeletal muscle, operates over a fairly narrow band of efficiency beyond about 10 mm. The Hill-Starling curve for skeletal muscle reduces the effectiveness of the musculature. I do not recommend shortening or lengthening for stability. Lateral offset stems and careful attention to osteophytes is important in the selection of a large femoral head. Surgeons cannot shorten or lengthen the extremity beyond about 10 mm without risking instability or loss of function.

Lombardi: Surgeons should not sacrifice limb length because of a large head. If the abductor musculature remains loose, the hips still piston through the gate cycle. Surgeons may describe this as clicking. Surgeons must still achieve correct tension.

Head: Generally, with increased offset there is increased varus in the neck. Should surgeons be concerned about an overweight, active patient with increased offset?

Cuckler: The issue has been addressed in laboratory testing with regard to fatigue testing. Fatigue testing defines the level below which, in the absence of damage to the surface, mechanical failure of the material is not observed. Notching of the prosthetic femoral neck over time will alter the height of the plateau on the stress strain or fatigue curve.

I am not concerned about increased offset in overweight patients. Overweight patients have large skeletons, and from a developmental point of view, their muscles are similarly developed to optimize function of their large hips and minimize stresses across the joint. Surgeons must recreate the anatomy, and the modern tapered stem design is the tool surgeons can use.

Implant extraction

Schmalzried: Fixation of proximally porous-coated hip systems is well established and reviewed, and infection is rare. What have you learned about extraction of one of these implants when removal was necessary?

Roger H. Emerson, Jr, MD: Removing a proximally porous-coated stem is a significant concern. These implants are almost too well fixed and removing them is not easy. Surgeons must rethink the manner in which they treat infections. I recommend surgeons aggressively treat infection first because removing a well-fixed cementless implant will damage bone, and the possibility of achieving the same level of reconstruction is unlikely.

Medical management of infection is not always successful and removal of implants may be required. Implant removal results in prosthesis and function degradation.

Schmalzried: What technique do you use in removing a proximally porous-coated femoral component? Would you perform an extended trochanteric osteotomy?

Emerson: First, surgeons must access the implant interface with the bone in a manner that is safe for the femur. Surgeons can perform an anterior window or a lateral window procedure, but most will perform an extended osteotomy. I favor a shorter osteotomy, which allows me to access the proximal interface and disrupt the interface with small cutting tools. I recommend using a curved micro-saw blade. A giggly saw can be used medially. Frequently, surgeons will section the implant and use circular lines to remove the distal part. Although the procedure is possible, it is difficult to perform.

Cuckler: I am impressed with the tenacity of the grit-blasted surface distal to the plasma spray coating and the tenacity of the bone implant interface in proximally porous-coated hip systems. When removing a proximally plasma-sprayed and distally grit-blasted titanium-tapered stem, I bivalve the femur starting from the tip of the stem and extending proximally. This allows me, in combination with flexible, curved osteotomes, to gently loosen the implant-bone interface and repair the femur with simple monofilament cerclage wire and, if necessary, place an antibiotic spacer in the setting of infection. The process is tedious, and surgeons must be patient.

Lombardi: I bivalve the femur from the tip of the stem to the greater trochanter, unless the distal portion is smooth. By starting at the tip of the stem, surgeons can take and knock the stem from the medial side out laterally, disengaging the implant.

With other situations, surgeons may need to use a small micro-saw and work on the interface, or the Biomet Ultra-Drive system (Biomet Orthopedics, Inc., Warsaw, Ind.), which can be helpful to get into the interface.

Head: When the porous coating is proximal or the grit blast is proximal and the distal portion is smooth, I recommend resecting the proximal femur to accept a calcar prosthesis. Surgeons can use a pencil-type Midas Rex (Medtronic, Minneapolis) to gain access and work around the femur.

Emerson: With the short Mallory-Head femoral component (Biomet Orthopedics, Inc., Warsaw, Ind.), I do not bivalve the femur. I would bivalve the femur for a stem longer than 200 mm with bone ingrowth, however.