Tapered titanium femoral implant allows immediate weight-bearing

Issue: June 2006

ByBarry J. Waldman, MD

Barry J. Waldman, MD [photo]
Barry J. Waldman

Titanium, wedge-shaped, femoral implants have been used worldwide for over 25 years with excellent clinical results.^1,2 One advantage of these implants is the ability to allow immediate weight-bearing following surgery.

Wedge-shaped implants are designed to obtain immediate three-point fixation in the proximal femur, providing excellent initial fixation and resistance to rotational and axial instability. Any subsidence that may occur increases the tight fixation of the implant, preventing further subsidence.

The titanium substrate encourages early and copious bone ingrowth. Multiple studies with similarly designed implants demonstrate low subsidence rates with immediate weight-bearing after 10- to 15-year follow-up.^1,2

The position of the implant in varus or valgus does not affect the long-term survival of the implant nor do proximal femur fractures at the time of surgery that are properly treated, according to previous studies.¹Immediate weight-bearing is well-established and aids in patient comfort, independence and rehabilitation.

Degenerative hips

Between 1998 and 2002, I treated 453 consecutive degenerative hips with titanium, wedge-shaped, grit-blasted stems (Taperloc, Biomet Orthopedics, Inc, Warsaw, Ind.) followed by immediate weight-bearing.

The mean age of the patients at the time of the index arthroplasty was 64 years (range, 36 years to 95 years). The mean body weight was 83.7 kg ± 11.4 kg (range, 41 kg to 201 kg), and the mean body mass index was 31.7 ± 3.7 (range, 16.5 to 54.3). The most common diagnosis was osteoarthritis (93%), followed by osteonecrosis (4%) and inflammatory arthritis (3%).

I used a variety of acetabular bearing surfaces: traditional polyethylene in 43% and metal-on-metal in 57%. All hips were performed in an uncemented fashion. Approaches consisted of a mini-incision posterior approach in 52%, mini-anteriolateral approach in 37% and a traditional anteriolateral approach in 11%.

At least two years of follow-up were obtained for 391 patients (mean, 2.9 years). All patients were followed with preoperative, immediate postoperative, six-week and one-year follow-up radiographs. Radiographs were examined for evidence of loosening, subsidence and osteolysis. Outcomes were followed prospectively with the SF-36 score and the Harris Hip Score at the same time intervals.

Positive outcomes

There were no hip revisions due to loosening at the most recent follow-up. The mean Harris Hip Score was 95 (range, 61 to 100). Major complications were rare.

There were three dislocations in three patients (0.8%). One stem required revision due to subsidence and subsequent dislocation. The stem was well ingrown at the time of surgery and treated by lengthening the modular neck.

There were three acute infections. Two were treated with early irrigation and debridement and one with delayed exchange arthroplasty, all successfully.

There were 15 patients with intraoperative femoral fracture, all treated with circlage wiring.

All patients were allowed to weight-bear as tolerated, and none experienced further complications or subsidence. Periprosthetic osteolysis was not observed in any hip. Three hips showed subsidence greater than 2 mm. One required revision as previously described.

All patients were able to ambulate with assistive devices on postoperative day 1. The mean time to resuming stair climbing with assistance was 2.8 days (range, 1 day to 7 days). The mean time to discontinuance of assistive devices was 38 days (range, 7 days to 62 days). The mean time to resuming driving a car was 36 days (range, 15 days to 70 days).

Early weight-bearing

Weight-bearing increases bone density and muscle strength without further complications, provided that bony stability is available. The benefits of early weight-bearing are shown for a number of orthopedic procedures, including total hip replacement. Immediate postoperative weight-bearing results in improved abduction strength and bone density in the early postoperative period.^3,4 Patients also experience an earlier return to stair climbing, an earlier discontinuation of assistive devices and an earlier ability to rise from a chair without assistance.^3,4

Minimally invasive techniques rely on aggressive physical therapy and early weight-bearing to achieve rapid recovery. Any uncemented stem that allows early weight-bearing without significant subsidence must obtain excellent initial fixation, regardless of the bone type, configuration and density. The stem must also give surgeons the confidence to allow early weight-bearing without concerns of loosening.

Because tapered titanium stems obtain excellent initial fixation through three-point fixation, they are especially suited to early weight-bearing. They are not dependent on slavish accuracy in broaching the femoral canal. Any subsidence that occurs results in increased fixation, and the three-point fixation into the medullary canal is increased. Significant subsidence is usually seen only in those stems that are grossly undersized.

Subsidence greater than 2 mm was observed in only three patients in the current study, and only one was symptomatic, resulting in dislocation due to the shortened effective femoral neck. This stem was well ingrown at the time of revision and was treated with a longer head/neck combination.

In two separate studies of subsidence in tapered stems followed by early weight-bearing, more subsidence was seen in the early weight-bearing group with a difference of 0.4 mm between the delayed and early weight-bearing groups.^5,6 No patients experienced ill consequences due to the slightly increased subsidence rate. At the last follow-up, the investigators did not observe a lasting effect in Harris Hip Score in any of the studies, including the current study, depending on weight-bearing status. Overall, patient function and return to normal activities are enhanced by early weight-bearing after surgery with no apparent adverse effects.

Early weight-bearing after total hip arthroplasty is a safe and effective strategy that leads to early return of strength, function and unassisted ambulation. Adverse consequences related to bony ingrowth or osteolysis were not observed in this study. The ability to allow immediate weight-bearing after surgery is a well-documented feature of wedge-shaped titanium implants.

References

Sherrington C, Lord SR, Herbert RD A randomised trial of weight-bearing versus non-weight-bearing exercise for improving physical ability in inpatients after hip fracture. Aust J Physiother. 2003;49(1):15-22.
Boden H, Adolphson P. No adverse effects of early weight bearing after uncemented total hip arthroplasty: a randomized study of 20 patients. Acta Orthop Scand. 2004;75(1):21-29.
Rao RR, Sharkey PF, Hozack WJ, et al. Immediate weightbearing after uncemented total hip arthroplasty. Clin Orthop Relat Res. 1998;349:156-162.
Bottner F, Zawadsky M, Su EP, et al. Implant migration after early weightbearing in cementless hip replacement. Clin Orthop Relat Res. 2005;436:132-137.
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(7 Suppl 1):116-121.
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(3):288-295.

Barry J. Waldman, MD is director, Center for Joint Preservation and Replacement at Rubin Institute for Advanced Orthopaedics, Baltimore and clinical instructor in the department of orthopaedic surgery at The Johns Hopkins School of Medicine in Baltimore.

Thigh pain

Thomas P. Schmalzried, MD: Some patients who are active before a prosthesis osseointegrates may experience thigh pain. Is thigh pain a persistent issue with proximally porous-coated tapered stem designs?

Roger H. Emerson, Jr, MD: Thigh pain is rare. Few patients may experience early thigh pain as part of healing. Surgeons and patients must determine how much load a patient’s leg will tolerate. Press-fit stems are slightly more activity-sensitive than cemented stems.

Some patients with hip replacements function well but endure a period of high activity and develop thigh pain, which can be persistent. Surgeons could consider this thigh pain a stress injury. I recommend that patients with delayed onset of thigh pain return to using support. My protocol includes possibly using a cane or eliminating one particular type of activity until the thigh pain subsides.

In my experience, less than 1% of my patients experience thigh pain. Only one of my patients developed significant thigh pain, which subsided after two years.

William C. Head, MD: Stem design, stem material and bone quality is important. Generally, with tapered stems, I am confident that any thigh pain decreases with time and protection. My experience with non-tapered, stiffer stems demonstrates that thigh pain does not respond to time or protection.

Adolph V. Lombardi, Jr, MD, FACS: Significant thigh pain is not an issue with proximally porous-coated titanium tapered stems. Few of my patients experience thigh pain, and surgeons can sometimes predict when a patient may have pain. In one patient, I implanted a 17-mm stem and predicted he would experience thigh pain for 6 to 9 months. After 6 to 9 months, the thigh pain subsided, and the patient returned for the same procedure with the same stem size in the contralateral side.

John M. Cuckler, MD: Ten to 15 years ago, at the majority of arthroplasty meetings, at least two to three speakers spoke on thigh pain. The presentations generally covered cobalt chrome implants, which have cylindrical distal sections with or without extensive porous coating. Contrastingly, tapered stems do not commonly produce thigh pain.