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Total Hip Arthroplasty and Hemiarthroplasty in Mobile, Independent Patients with a Displaced Intracapsular Fracture of the Femoral Neck

A Randomized, Controlled Trial

Baker, R.P., MRCS1; Squires, B., FRCS(Tr&Orth)2; Gargan, M.F., FRCS(Orth)3; Bannister, G.C., MD, FRCS Ed(Orth)1

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doi: 10.2106/JBJS.E.01373
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Abstract

The optimal treatment of mobile, independent patients who have sustained a displaced intracapsular fracture of the femoral neck remains controversial. Randomized, controlled trials that have compared internal fixation with either total hip arthroplasty or hemiarthroplasty have demonstrated inferior results for internal fixation, with reoperation rates ranging from 18% to 47%1-4. The major long-term problem associated with hemiarthroplasty is painful acetabular erosion. The reported rates of acetabular erosion have ranged from 0%5 to 26%6 for bipolar designs and from 2.2%5 to 36%7 for unipolar designs. In one series7, 38% of the hips with a unipolar prosthesis required revision because of acetabular erosion. In contrast, the major early complication of total hip arthroplasty is dislocation, the rate of which is increased in association with the use of a posterior approach and a smaller prosthetic head size8. The reported rates of dislocation after total hip arthroplasty performed for the treatment of a displaced intracapsular fracture of the femoral neck have ranged from 2% to 20%9-14.

In a previous publication7, we suggested that hemiarthroplasty was inferior to total hip arthroplasty in mobile, independent patients with a displaced intracapsular fracture of the femoral neck. The weakness of that study, and the difficulty of trying to determine which of these procedures is preferable for the management of patients who have sustained this type of injury, is that it included confounding variables such as different prosthetic designs, operative approaches, and patient-selection criteria that precluded a meaningful analysis of the two types of arthroplasty. In planning the present study, we determined the required power needed to perform a randomized, prospective, controlled trial and sought to answer the question of whether total hip arthroplasty was indeed superior to hemiarthroplasty for the management of mobile, independent patients who had sustained a displaced intracapsular fracture of the femoral neck.

Materials and Methods

The present study was approved by all of the participating hospitals' local research ethics committees (institutional review boards).

Patients who were admitted to one of three participating hospitals with a diagnosis of a displaced fracture of the femoral neck were initially assessed with use of the Abbreviated Mini Mental Test score15, Oxford hip score16, and Short Form-36 physical and mental health summary scales17. The Oxford hip score is a validated twelve-item patient questionnaire on which lower scores indicate superior function and lower pain in the affected hip (best score, 12; worst score, 60) (see Appendix). In addition, we recorded the self-reported prefracture walking distance of each patient in miles. The patients were then prospectively randomized into one of two treatment arms. Randomization was performed with use of sealed envelopes that were opened before surgery.

The inclusion criteria were an age of more than sixty years, a normal Abbreviated Mini Mental Test score15, the ability to walk ≥0.5 mi (≥0.8 km), the ability to live independently (without reliance on a caregiver), a nonpathological fracture, and a hip with no or minimal osteoarthritic changes.

The exclusion criteria included age of less than sixty years (it is our practice to perform internal fixation in this group), medical or physical comorbidities that limited the walking distance to <0.5 mi (0.8 km), a preexisting hip abnormality requiring total hip arthroplasty, or a pathological fracture secondary to malignant disease.

With use of a power of 80% and a p value of 0.05, it was determined that thirty-nine patients in each treatment arm were required to demonstrate a difference, based on previous results7. Eighty-one patients were prospectively randomized into two groups: forty-one patients were managed with hemiarthroplasty, and forty were managed with total hip arthroplasty. The mean age of the patients was seventy-five years. There were no significant differences between the two groups with regard to demographic characteristics or mental and functional scores (Table I). The operations were equally distributed among the three participating hospitals.

TABLE I - Preoperative Demographic Data, Mental Scores, and Functional Scores
Hemiarthroplasty (N = 41) Total Hip Arthroplasty (N = 40)
Age*(yr) 75.83 (66 to 86) 74.2 (63 to 86)
Female:male ratio (no. of patients) 32:9 32:8
Walking distance*(mi, km) 2.17 (0.5 to 6), 3.5 (0.8 to 9.7) 2.17 (0.5 to 5), 3.5 (0.8 to 8.0)
Abbreviated Mini Mental score*(points) 9.98 (9 to 10) 9.83 (7 to 10)
Oxford hip score*(points) 12.12 (12 to 14) 12.90 (12 to 24)
Short Form-36 score*(points)
    Physical 44.35 (19.7 to 66.8) 48.01 (25.2 to 56.6)
    Mental 54.76 (35.9 to 66.9) 55.52 (33.8 to 64.2)
Median ASA grade* 2 (1 to 3) 2 (1 to 3)
*The data are given as the mean, with the range in parentheses. †ASA = American Society of Anesthesiologists.

The delay from the time of the fracture to the time of surgery was 1.95 days in the hemiarthroplasty group and 1.75 days in the total hip arthroplasty group. The operations were performed by surgeons with similar levels of training. Thirty-one hemiarthroplasties were performed by residents, seven were performed by consultants, two were performed by senior house officers, and one was not documented. Thirty-one total hip arthroplasties were performed by residents, and nine were performed by consultants. There was no significant difference between the groups with regard to the American Society of Anesthesiologists grades18 of the patients (Table I).

All patients received the same cemented femoral component, the CPT collarless polished tapered stem (Zimmer, Warsaw, Indiana). All operations were performed through a transgluteal lateral approach. The femoral canal was restricted distally with use of a Hardinge cement restrictor (DePuy International, Leeds, United Kingdom). Palacos cement (Schering-Plough, Hertfordshire, United Kingdom) impregnated with gentamicin was inserted with a venting tube in place with use of a cement gun (Biomet Europe, Dordrecht, Netherlands) and digital pressure.

The hemiarthroplasty group received an Endo Femoral Head (Zimmer). The prosthetic head size was available in 2-mm increments that allowed accurate reproduction of the patient's femoral head, which was measured intraoperatively with a hemispherical template. The total hip arthroplasty group received a 28-mm femoral head articulating with an all-polyethylene Zimmer cemented acetabular cup without a long posterior wall (Zimmer).

The mean operative time was seventy-eight minutes (range, forty-five to 120 minutes) for the hemiarthroplasty group and ninety-three minutes (range, sixty to 135 minutes) for the total hip arthroplasty group (p < 0.001).

The mean femoral head size in the hemiarthroplasty group was 48 mm (range, 43 to 59 mm). The mean outer diameter of the acetabular component in the total hip arthroplasty group was 47 mm (range, 44 to 55 mm).

Postoperatively, patients were mobilized with full weight-bearing on the second postoperative day and graduated from a walker to a cane prior to discharge.

Patients were evaluated at three months, one year, and three years after surgery. At the time of the final follow-up, patients were assessed with use of the Oxford hip score16 and the Short Form-3617. The walking distance at the time of the final follow-up was reported by the patients themselves. Anteroposterior and lateral radiographs of the involved hip were made.

Initial postoperative radiographs were reviewed to determine the cementing grade according to the criteria of Barrack et al.19. In addition, femoral component alignment was assessed in the anteroposterior and lateral planes.

Final radiographs were analyzed with regard to acetabular erosion, polyethylene wear, femoral stem subsidence, and component migration. Acetabular erosion was graded on the basis of its radiographic appearance as grade 0 (no erosion), grade 1 (narrowing of articular cartilage, no bone erosion), grade 2 (acetabular bone erosion and early migration), and grade 3 (protrusio acetabuli) (Fig. 1).

Statistical Analysis

Statistical analysis was performed by a medical statistician with use of the Statistical Package for the Social Sciences package (SPSS, Chicago, Illinois). The Mann-Whitney test was used to compare groups with regard to the delay to surgery, stem size, Oxford hip score, and physical and mental Short Form-36 component scores at three years. The Wilcoxon rank test was used to compare Oxford hip scores, Short Form-36 scores, and walking distances in each individual after three years. The time-to-discharge and walking-distance comparisons required log transformation, and then the Student t test was performed. Chi-square analysis was used to assess Barrack cement grading and anteroposterior and lateral femoral stem alignment; the Fisher exact test was used to assess the mortality, revision, and complication rates; the Student t test was used to assess operative time and stem subsidence; and Kendall's Tau-b coefficient was used to assess the correlation between subsidence and Barrack grading. The level of significance was set at p < 0.05.

Results

There were two immediate postoperative deaths in the hemiarthroplasty group, both as a result of pulmonary embolism. Five additional patients in the hemiarthroplasty group died and one refused to be evaluated for a three-year review, leaving thirty-three of the original forty-one patients available for final follow-up at a mean of thirty-nine months (range, thirty to sixty-six months) postoperatively. All five of the patients who died after the immediate postoperative period but before the final follow-up died of causes unrelated to the hemiarthroplasty. Two had remained mobile and independent. One patient died before any formal follow-up arrangement. The other two patients had decreased walking capability; one relied on a wheelchair, and the other used a cane.

Three patients in the total hip arthroplasty group died of causes unrelated to the procedure before the final follow-up and one patient refused to have a follow-up evaluation, leaving thirty-six of the original forty patients available for final follow-up at a mean of forty-one months (range, thirty to sixty-eight months) postoperatively. There was no difference between the two groups with regard to the rate of mortality (p = 0.194). The patient who refused follow-up was confined to a wheelchair following a cerebrovascular accident. Two patients died of cancer; of these, one was able to walk 3 mi (4.8 km) before his terminal illness and one was confined to a wheelchair secondary to metastatic disease. One patient died fourteen months after the hip replacement from complications of bronchopneumonia; at the time of the last follow-up, she was mobile with no walking aids.

Clinical Outcome

At the time of the final follow-up, the hemiarthroplasty group had significantly greater hip disability, represented by higher Oxford hip scores (p = 0.033) and shorter self-reported walking distances (p = 0.039), than the total hip arthroplasty group did. The hemiarthroplasty group also had slightly, but not significantly, lower Short Form-36 physical scores than the total hip arthroplasty group did (p = 0.356) (Table II).

TABLE II - Mean Outcome Scores at Time of Final Follow-Up*
Outcome Measure Hemiarthroplasty (N = 33) Total Hip Arthroplasty (N = 36) P Value
Oxford hip score (points) 22.3 (12 to 48) 18.8 (12 to 47) 0.033
Walking distance (mi, km) 1.17 (0 to 4), 1.9 (0 to 6.4) 2.23 (0 to 25), 3.6 (0 to 40.2) 0.039
Short Form-36 score (points)
    Physical 38.10 (16 to 58.8) 40.53 (16.2 to 56.5) 0.356
    Mental 55.32 (39 to 66.6) 52.00 (24.2 to 68.4) 0.349
*The values are given as the mean, with the range in parentheses. †Mann-Whitney test. ‡Student t test on log-transformed data.

Of interest, compared with the preoperative scores, both groups had significantly higher (worse) Oxford hip scores (p < 0.001) and lower scores on the Short Form-36 physical component (p = 0.021 for the hemiarthroplasty group and p = 0.001 for the total hip arthroplasty group), indicating decreased function. Compared with the preoperative status, patient-reported walking distance decreased significantly after hemiarthroplasty (p < 0.001) but increased after total hip arthroplasty (p = 0.023).

Fig. 1
Fig. 1:
Illustration depicting the acetabular erosion grading system and the number of hips in each category following hemiarthroplasty at the time of the final follow-up.

Radiographic Results

Acetabular Component

In the total hip arthroplasty group, radiographs were available for thirty-two hips after a mean duration of follow-up of forty months (range, twelve to sixty-six months). These radiographs demonstrated no evidence of wear of the cemented polyethylene cup in any hip.

In the hemiarthroplasty group, radiographs were available for thirty-two hips after a mean duration of follow-up of thirty-six months (range, thirteen to sixty months). Acetabular erosion was seen in twenty-one (66%) of the thirty-two hips. The prevalence and severity of acetabular erosion are shown in Figure 1.

Femoral Component

Cementing technique, as assessed on the immediate postoperative radiographs, was significantly superior in the total hip arthroplasty group (p = 0.028) (see Appendix). Alignment of the stems was similar in both groups on the anteroposterior (p = 0.066) and lateral radiographs (p = 0.084) (see Appendix).

After three years, the mean amount of subsidence of the femoral stem at the stem-cement interface was 1.94 mm (range, 0 to 11 mm) in the hemiarthroplasty group and 1.74 mm (range, 0 to 18 mm) in the total hip arthroplasty group (p = 0.767). The Barrack19 cementing grade was not associated with stem subsidence (correlation coefficient, 0.147). Subsidence occurred only at the stem-cement interface.

Complications

Perioperative complications that occurred within thirty days after surgery are presented in Table III. With the numbers available, there were no significant differences between the two groups.

TABLE III - Postoperative Complications Within Thirty Days After Surgery
Complication Hemiarthroplasty Total Hip Arthroplasty P Value*
Dislocation 0 3 0.116
Wound infection 1 3 (1 required débridement) 0.298
Thromboembolic events 3 pulmonary emboli (2 fatal) 4 deep-vein thromboses (2 distal to knee) 0.486
Pneumonia 2 3 0.488
Atrial fibrillation 1 0 0.506
Hematemesis 1 0 0.506
Pressure sore 0 1 0.494
Hyponatremia 0 1 0.494
Other infection 1 vaginal candidiasis 1 urinary tract infection 0.747
*Fisher exact test.

No dislocations occurred in the hemiarthroplasty group, but three patients (7.5%) in the total hip arthroplasty group had early dislocation in the immediate postoperative period. Two of these three patients sustained a dislocation after a fall on Days 8 and 14, and the third patient sustained a dislocation after turning awkwardly in bed on Day 2. Two of the three patients had no additional instability after closed reduction. The remaining patient had development of dementia, sustained multiple dislocations that were treated with closed reduction, and was not a candidate for revision arthroplasty.

Revisions

In the hemiarthroplasty group, two hips were revised to total hip arthroplasty because of severe pain associated with acetabular erosion. After the revision procedure, these two patients had improved Oxford hip scores and markedly improved walking distances that were comparable with those in the total hip arthroplasty group. Two additional patients had grade-2 and 3 acetabular erosion. At the time of the most recent follow-up, one was awaiting revision to total hip arthroplasty and the other had declined additional intervention. Another patient had severe pain in association with grade-1 acetabular erosion, was undergoing additional investigation, and was likely to need revision. One patient in the hemiarthroplasty group required revision surgery because of a periprosthetic fracture thirty-three months postoperatively. In the total hip arthroplasty group, one patient required revision because of pain secondary to massive femoral stem subsidence (18 mm). No other patient in the total hip arthroplasty group required revision. The overall rate of revision or planned revision was 14.6% (six of forty-one) in the hemiarthroplasty group, compared with 2.5% (one of forty) in the total hip arthroplasty group. This difference between the groups approached significance (p = 0.058).

Discussion

Displaced intracapsular fracture of the femoral neck can be treated with internal fixation, unipolar or bipolar hemiarthroplasty, or total hip replacement. In a meta-analysis, Bhandari et al.20 concluded that arthroplasty was associated with lower revision rates but a higher prevalence of infection, greater blood loss, and longer operative time when compared with internal fixation. In that report, no distinction was made between the use of hemiarthroplasty and total hip replacement.

Other comparative studies have demonstrated that total hip arthroplasty and hemiarthroplasty are superior to internal fixation for achieving pain relief and restoring function9,11,21,22.

A number of studies have compared total hip arthroplasty with hemiarthroplasty for the treatment of this problem.

In the study by Dorr et al.13, eighty-nine patients with a displaced femoral neck fracture were prospectively randomized to receive total hip arthroplasty with cement, hemiarthroplasty with cement, or hemiarthroplasty without cement. After a minimum duration of follow-up of two years, there was no difference between the results associated with total hip arthroplasty with cement and hemiarthroplasty with cement but the results associated with hemiarthroplasty without cement were poor. Function improved with time after total hip replacement but not after hemiarthroplasty.

In a retrospective study of 166 displaced femoral neck fractures, Gebhard et al.23 found that total hip arthroplasty demonstrated superior longevity when compared with hemiarthroplasty with and without cement. After a mean duration of follow-up of fifty-six months, the revision rate was 2.2% after total hip replacement, 7.9% after hemiarthroplasty with cement, and 13% after hemiarthroplasty without cement. Pain was the main reason for revision in two-thirds of the patients managed with hemiarthroplasty.

In the study by Lee et al.24, 126 consecutive patients with a displaced intracapsular fracture of the femoral neck were managed with total hip arthroplasty. With revision as the end point, the survival rate was 95% after five years, 94% after ten years, and 84% after twenty years. Six patients required revision because of aseptic loosening.

Increased rates of femoral stem loosening have been reported after total hip arthroplasty for the treatment of intracapsular femoral neck fractures in active patients with no preexisting hip pathology25. In the present series, in which a cemented collarless polished tapered stem was used, there was only one revision because of massive subsidence (18 mm) at the stem-cement interface, albeit after a mean duration of follow-up of only three years.

In a randomized, prospective study of octogenarians who had sustained a displaced fracture of the femoral neck, Calder et al.5 reported that the rate of acetabular erosion at two years postoperatively was 2.2% for hips that had been treated with a unipolar prosthesis and 0% for hips that had been treated with a bipolar prosthesis. However, Soreide et al.6 reported an acetabular protrusion rate of 26% for patients older than seventy-five years of age who had been managed with a bipolar Christiansen prosthesis.

In the study by D'Arcy and Devas26, 361 femoral neck fractures were treated with a Thompson hemiarthroplasty with cement. Acetabular erosion developed after 11% of the procedures. Importantly, acetabular erosion occurred more frequently in younger patients. In addition, the surgeons used a hemiarthroplasty head design that allowed sizing increments of only 3.2 mm. In our previous study7, we used acetabular components with head sizes that were available in 2-mm increments and reported a 36% rate of revision because of acetabular erosion. In the present study, we again used hemiarthroplasty head sizes that were available in 2-mm increments and found that 66% of the patients had acetabular erosion. We suggest that the ability to precisely fit an acetabular component, while desirable, is less important than the activity level of the patient. We believe that our relatively younger and more active patients had a higher rate of acetabular erosion because of increased physical demands. This observation has been commented on by other authors23,26.

Dislocation is the major concern after primary total hip arthroplasty for the treatment of intracapsular femoral neck fractures. Berry et al.8 demonstrated a 1.8-fold increased hazard estimate of dislocation risk when the preoperative diagnosis of hip fracture was compared with osteoarthritis.

Tidermark et al.9 reported the lowest dislocation rates (2%) for total hip arthroplasty, using the transgluteal approach in patients who had sustained a displaced intracapsular fracture of the femoral neck. Our standard postoperative protocol for the prevention of dislocation includes the use of an abduction wedge, patient education, and physiotherapy supervision in activities of daily living.

The strengths of the present study are that it was a prospectively randomized, controlled trial that eliminated treatment variables such as the type of femoral component, the method of implantation, and the surgical approach. In addition, the populations were comparable, allowing for a meaningful analysis of the two types of arthroplasty.

Our findings suggest that total hip arthroplasty is superior to hemiarthroplasty for the treatment of mentally competent, independent, and active patients. In the present study, total hip arthroplasty was associated with better functional outcomes, fewer complications, and fewer revisions after a mean duration of follow-up of three years. Both groups experienced functional deterioration postoperatively as compared with the preoperative levels; however, patients in the total hip arthroplasty group had less deterioration and maintained their walking distances.

The present study did not address the role of total hip arthroplasty in older, less active, and less mentally competent patients. The critical issue in that group is whether hemiarthroplasty would be a sufficient procedure because of their reduced activity and life expectancy. Painful acetabular erosion was the principal cause of revision in our active patients. It may be that in less active, older patients, bipolar hemiarthroplasty confers the stability needed to reduce the risk of dislocation yet avoids acetabular erosion. Additional studies should be considered in that group of patients.

Appendix

The Oxford hip score questionnaire and tables showing postoperative Barrack cementing grade and femoral stem positions are available with the electronic versions of this article, on our web site at jbjs.org (go to the article citation and click on Supplementary Material) and on our quarterly CD-ROM (call our subscription department, at 781-449-9780, to order the CD-ROM). ▪

The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.

Investigation performed at Southmead Hospital, Frenchay Hospital, and Bristol Royal Infirmary, Bristol, United Kingdom

Note: The authors thank Sister Sandy Shaw for her invaluable help in ensuring that the prostheses were available to all hospitals involved in the study. They also thank Michael Spratt and Elise Whitely, medical statisticians, North Bristol NHS Trust, for their help with the statistical analysis.

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