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Porous, plasma-sprayed, titanium-tapered cementless stems achieve versatility

Issue: June 2006

ByAdolph V. Lombardi Jr., MD, FACS

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Nearly 25 years ago, Sir John Charnley expounded on the importance of the development of a roughened surface to create an intimate bond with bone without the use of polymethylmethacrylate.¹ If an ideal bond were established between a porous textured surface and living bone, the pumping action that draws particles into the implant-bone interface would be blocked. Throughout the past 25 years, cementless fixation evolved to be the gold standard for fixation of acetabular and femoral components in total hip arthroplasty.

It is now recognized that circumferential porous coatings are required to prevent the migration of particulate debris along the interface.

Porous, plasma-sprayed, tapered cementless stems with circumferential coating are shown in numerous articles to be resistant to osteolysis. Multiple studies demonstrate minimal osteolysis with the use of plasma-spray technology in tapered designs.^2-11 Porous, plasma-sprayed, titanium-tapered stems demonstrate excellent long-term survivorship.

Young patients

Porous, plasma-sprayed, titanium-tapered cementless stems are successful in young patients. There is an ever-increasing demand to treat younger patients who have severe, disabling hip arthrosis, and these patients will place significant demands upon the prosthetic device.

At my institution between 1987 and 2000, surgeons performed 249 total hip replacements (THRs) in 201 patients age 40 years or younger (submitted for publication). All THRs were performed with the Mallory-Head Porous (MHP) (Biomet Orthopedics, Inc., Warsaw, Ind.) femoral component, which is a porous, plasma-sprayed, titanium-tapered component.

Since its original design in 1983, plasma spray was added to the lateral aspect of the MHP to facilitate a circumferential proximal plasma-spray coating. This component continues to be used today both nationally and internationally.

The follow-up in this group of patients averaged 91 months with 125 hips having a minimum five-year follow-up and 51 THRs having a minimum 10-year follow-up.

Harris Hip Scores significantly improved. Four stems failed for an overall 98.2% survivorship. One failure was due to pain and malposition, one stem failed secondary to sepsis, and two stems failed secondary to aseptic loosening. One of these THRs represented a conversion total hip arthroplasty in which a gamma nail device was removed and the MHP stem was placed. In young patients, the MHP femoral component has provided outstanding long-term fixation and function with significant pain relief into the second decade. At up to 18 years follow-up, the overall stem survivorship is 98.2% with an average 7.6 years follow-up.

Other studies performed with the MHP and Taperloc (Biomet Orthopedics, Inc., Warsaw, Ind.) illustrate excellent results in young patients.^9,11

Elderly patients

Porous, plasma-sprayed, titanium-tapered stems are appropriate for cementless fixation in elderly patients. The Dorr classification stratifies the femur into three types.¹³ Type A, the typical funnel-shaped or champagne-flute femur, is amenable to cementless fixation. Type B has slight osteopenia and atrophy of the posterior calcar femorale. Cementless fixation, however, is still thought to be appropriate for type B. Type C, the stovepipe femur with significant thinning of the femoral cortex, is suggested to be inappropriate for cementless fixation.

My colleagues and I identified a consecutive series of patients, age 75 years or older, undergoing primary cementless THR for end-stage arthrosis between 1996 and 2000.¹⁴ The cohort consisted of 49 total hips in 47 patients; one simultaneous bilateral and one staged. The average age of this patient population was 79.1 years. No patient was lost to follow-up, and seven deaths occurred from unrelated causes during the follow-up period.

My standard postoperative protocol indicated immediate full weight-bearing. Patients were instructed to use ambulatory aids until they were pain-free, or walking with minimal or no limp. The mean follow-up was 60 months, with a range of 28 to 82.5 months.

Harris Hip Scores significantly improved, and 87.5% of the patients had minimal or no pain. Two patients had moderate thigh pain. No differences were noted between Dorr bone quality groups, Charnley class groups or stem sizes. With aseptic loosening as the end point, there was 100% survivorship. One stem was revised to a cemented component at another institution for unexplained leg pain that was not located in the thigh. The well-fixed component required an extended trochanteric osteotomy for removal. The patient did not have relief of pain with revision to the cemented device. At an average five-year follow-up the overall implant survival was 98%.

Other studies show cementless tapered components function satisfactorily even in older patients with less-than-optimal bone quality.^15,16 Proximally porous, plasma-sprayed, titanium-tapered femoral components seem to defy the dogma that cementless devices are inappropriate in type C bone of elderly patients.

Varus malalignment

Varus malalignment of a porous, plasma-sprayed, titanium-tapered stem does not necessarily affect outcome. To evaluate the effect of varus malalignment on cementless fixation of proximally porous, plasma-sprayed, titanium-tapered devices, 1080 primary MHP femoral components implanted at my institution (in press) between 1986 and 1997 were evaluated. Varus malalignment of 5° or greater was identified in 26 total hip arthroplasties in 25 patients (2.4%). The mean follow-up for this cohort of patients was 10 years with a minimum of five years follow-up.

Significant improvement in the postoperative Harris Hip Score was observed. One stem was revised at an outside institution for unexplained pain at 2.5 years postoperatively. In the operative report the stem was described as being well fixed. The overall survival is 96% at 10 years with no failures secondary to aseptic loosening. In this study, varus malalignment did not affect the ability of the porous, plasma-sprayed, titanium-tapered femoral component to achieve biological fixation.

Calcar fracture

Porous, plasma-sprayed, titanium-tapered stems remain stable after intraoperative fracture, with the potential for immediate full weight-bearing.

My colleagues and I evaluated a cohort of 1320 primary cementless THRs performed with the MHP at my institution between 1985 and 2000.¹⁷ A cohort of 50 THRs in 47 patients with intraoperative proximal femoral fracture was reviewed. All fractures were identified intraoperatively and were treated with cerclage wire or cable, and full immediate weight-bearing. The mean follow-up was 7.5 years with a range of 2 to 16 years.

Significant improvement in Harris Hip Scores was observed, and survivorship was 100% at 16 years. No stems were radiographically loose, and no revisions were pending. One stem subsided into a stable and ingrown position radiographically and had an excellent clinical result.

Intraoperative fractures with tapered stems are inevitable, and treatment should consist of cerclage wire or cable. Immediate full weight-bearing is acceptable, and results are excellent.

Long-term survivorship

Porous, plasma-sprayed, titanium-tapered cementless stems demonstrate excellent long-term survivorship, which is well-documented in the literature. One hundred twenty THRs performed at my institution with the MHP femoral component with a minimum 10-year follow-up and range of 10 to 15 years were reviewed.^18,19 The overall survivorship at an average 12.2 years was 97.5%. Other authors reported that survivorship of the MHP and Taperloc femoral components at 10 years or more is between 97.3% and 100%.^12,15,19-24

Test of time

Porous, plasma-sprayed, titanium-tapered femoral components have withstood the test of time. They are applicable in all patient populations presenting for THR, successful in young patients and obtain stable fixation in elderly patients with poor bone quality. Varus malalignment may not affect the stability and durability of the construct. When facing intraoperative fracture, stabilization of the fracture with cerclage wire or cable, and allowing immediate full weight-bearing produced excellent results. Porous, plasma-sprayed, titanium-tapered femoral components are extremely versatile, and obtain fixation proximally and offload distally. To date, I have seen no evidence that deterioration of fixation will occur once a tapered proximally porous-coated component becomes ingrown. As noted by Mallory in debating the merits of cementless vs. cemented fixation with Callaghan, cementless fixation may hold the promise of an ageless interface.²⁵

References

1. Charnley J. Low Friction Arthroplasty of the Hip. Theory and Practice. New York, NY: Springer Verlag; 1979.
2. Rothman RH. Hip arthroplasty: assessment and choices. Fit and fill: fact or fiction? Orthopedics. 1994;17:803.
3. Hearn SL, Bicalho PS, Eng K, et al. Comparison of cemented and cementless total hip arthroplasty in patients with bilateral hip arthroplasties. J Arthroplasty. 1995;10:603-608.
4. Mulliken BD, Bourne RB, Rorabeck CH, Nayak N. A tapered titanium femoral stem inserted without cement in a total hip arthroplasty. Radiographic evaluation and stability. J Bone Joint Surg Am. 1996;78:1214-1225.
5. Rorabeck CH, Bourne RB, Mulliken BD, et al. The Nicolas Andry award: The comparative results of cemented and cementless total hip arthroplasty. Clin Orthop Relat Res. 1996;325:330-344.
6. Mallory TH, Head WC, Lombardi AV Jr, et al. Clinical and radiographic outcome of a cementless, titanium, plasma spray-coated total hip arthroplasty femoral component. Justification for continuance of use. J Arthroplasty. 1996;11:653-660.
7. Hozack WJ, Rothman RH, Eng K, Mesa J. Primary cementless hip arthroplasty with a titanium plasma sprayed prosthesis. Clin Orthop Relat Res. 1996;333:217-225.
8. Mallory TH, Head WC, Lombardi AV Jr. Tapered design for the cementless total hip arthroplasty femoral component. Clin Orthop Relat Res. 1997;344:172-178.
9. Dowdy PA, Rorabeck CH, Bourne RB. Uncemented total hip arthroplasty in patients 50 years of age or younger. J Arthroplasty. 1997;12:853-862.
10. Mauerhan DR, Mesa J, Gregory AM, Mokris JG. Integral porous femoral stem. 5-to 8-year follow-up study. J Arthroplasty. 1997;12:250-255.
11. 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.
12. McLaughlin JR, Lee KR. Total hip arthroplasty in young patients. 8- to 13-year results using an uncemented stem. Clin Orthop Relat Res. 2000;373:153-163.
13. Dorr LD, Faugere MC, Mackel AM, et al. Structural and cellular assessment of bone quality of proximal femur. Bone. 1993;14:231-242.
14. Berend KR, Lombardi AV, Mallory TH, et al. Cementless double-tapered total hip arthroplasty in patients 75 years of age and older. J Arthroplasty. 2004;19:288-295.
15. Reitman RD, Emerson R, Higgins L, Head W. Thirteen year results of total hip arthroplasty using a tapered titanium femoral component inserted without cement in patients with type C bone. J Arthroplasty. 2003;18:116-121.
16. Keisu KS, Orozco F, Sharkey PF, et al. Primary cementless total hip arthroplasty in octogenarians. Two to eleven-year follow-up. J Bone Joint Surg Am. 2001;83-A:359-363.
17. Berend KR, Lombardi AV Jr, Mallory TH, et al. Cerclage wires or cables for the management of intraoperative fracture associated with a cementless, tapered femoral prosthesis: results at 2 to 16 years. J Arthroplasty. 2004;19:17-21.
18. Mallory TH, Lombardi AV Jr, Leith JR, et al. Why a taper? J Bone Joint Surg Am. 2002;84-A:81-89.
19. Mallory TH, Lombardi AV Jr, Leith JR, et al. Minimal 10-year results of a tapered cementless femoral component in total hip arthroplasty. J Arthroplasty. 2001;16:49-54.
20. Head WC, Mallory TH, Emerson RH Jr. Orthopedics. 1999;22:813-815.
21. Bourne RB, Rorabeck CH, Patterson JJ, Guerin J. The proximal porous coating alternative for primary total hip arthroplasty.Clin Orthop Relat Res. 2001;393:112-120.
22. Park MS, Choi BW, Kim SJ, Park JH. Plasma spray-coated Ti femoral component for cementless total hip arthroplasty. J Arthroplasty. 2003;18:626-630.
23. Purtill JJ, Rothman RH, Hozack WJ, Sharkey PF. Total hip arthroplasty using two different cementless tapered stems. Clin Orthop Relat Res. 2001;393:121-127.
24. Parvizi J, Keisu KS, Hozack WJ, et al. Primary total hip arthroplasty with an uncemented femoral component: a long-term study of the Taperloc stem. J Arthroplasty. 2004;19:151-156.
25. Callaghan JJ, Mallory TH. Optimal fixation for femoral components: cemented or cementless. J Arthroplasty. 1995;10:401-404.

Adolph V. Lombardi, Jr, MD, FACS, practices at Joint Implant Surgeons, Inc., is president of Medical Staff Services at New Albany Surgical Hospital, clinical assistant professor in the department of orthopedics and clinical assistant professor in the department of biomedical engineering at Ohio State University in Columbus, Ohio.