Total hip arthroplasty (THA) is an efficacious and cost-effective treatment for degenerative hip disease. The survivorship rate of THA exceeds 90% and 76% at 10- and 25-year follow-up, respectively.1–5 Charnley and Cupic5 initially conceived THA as an operation for elderly patients with low functional demands. Currently, THA is increasingly viewed as a treatment option for younger patients. Indeed, patients younger than 65 years are currently the fastest growing subset of patients seeking THA. It has been projected that by 2030, 52% of patients seeking primary THA will be younger than 65 years.6 With the demand for primary THA on the rise among younger patients, there is increasing concern regarding the future revision THA burden. In a review of consecutive revision THAs performed between 2004 and 2014, Haynes et al7 noted 44% of their revision cohort was younger than 60 years and nearly 20% was younger than 50 years. Younger THA patients are believed to be at increased risk for revision because of their higher functional demands and potentially longer life span. Thus, younger patients are potentially at increased risk for polyethylene wear, osteolysis, early aseptic failure, and subsequent revision procedures.8
Several studies have noted an increased risk of early revision and decreased time to failure associated with younger patients following THA,9–14 but these studies have been limited by the inclusion of various indications for THA, including avascular necrosis and posttraumatic arthrosis. These diagnoses have a predilection toward presenting in younger patients and are themselves associated with an increased risk of complications following THA.15,16 Furthermore, the advent of highly cross-linked polyethylene liners has decreased the rate of polyethylene wear, which is associated with osteolysis, aseptic loosening, and subsequent revision. McAuley et al11 examined 561 THAs in patients 50 years and younger. They found a dramatic decrease in the 15-year component survival rate vs the 5-year component survival rate, hypothesizing that the polyethylene liner is the “weak link” that increases the risk of revision THA with time. Given the widespread implementation of highly cross-linked polyethylene liners, young patients may now be at a decreased risk for third body debris leading to early aseptic revision following THA. Because prior investigations assessing the impact of age on the rate of revision following THA have been confounded by the inclusion of various diagnoses and older-generation bearing surfaces, it remains unclear whether age impacts the time to revision and the rate of survival among patients undergoing THA for a primary diagnosis of osteoarthritis. The purpose of this study was to assess the revision rate, indications for revision, and time to revision among patients undergoing THA for a primary diagnosis of osteoarthritis stratified by age. The authors' hypothesis was that younger age would not impact the revision rate or the time to revision among patients undergoing primary THA for a diagnosis of osteoarthritis.
Materials and Methods
This retrospective review of prospectively collected data at a single institution received institutional review board approval. Using their institution's joint arthroplasty registry, the authors identified all patients with a diagnosis of primary osteoarthritis who underwent both a primary and a revision THA surgery at their institution between January 1996 and April 2016. All primary and revision surgeries were performed by 1 of 7 fellowship-trained arthroplasty surgeons who were credentialed as attending physicians at the hospital during the study period. Patients' clinical charts and operative records were reviewed by 1 of the authors (Z.M.) not involved in surgical care. Age, sex, date of index THA surgery, date(s) of revision THA, interval between the primary and the revision procedure, primary and revision THA component data, indications for revision, and extent of revision procedure performed were collected for the patients. Patients were excluded if their index primary THA had been performed at another institution or if they had a primary diagnosis other than osteoarthritis (ie, avascular necrosis, posttraumatic osteoarthritis, fracture).
The primary indication for THA revision for each patient was determined by reviewing the available electronic clinical records, operative reports, and radiographs. Revision indications were classified according to the following general diagnoses similar to the work of Haynes et al7: osteolysis (cup, stem, or both), aseptic loosening (cup, stem, or both), infection, metallosis (bearing or trunnion, with or without pseudotumor), periprosthetic fracture, instability, pain not otherwise specified, component malposition, mechanical failure of implants (fracture of components, dissociation of head–neck junction, breakage of liner locking ring), and other. Radiographic measurements of acetabular cup inclination, cup anterversion, and limb length discrepancy were obtained as described by Sadhu et al.17
Patients were stratified into 2 groups based on age at the time of their primary THA: 64 years or younger (group 1) or 65 years or older (group 2). Comparisons between the 2 age cohorts were performed using modified Wald confidence intervals, independent Student's t tests, and chi-square tests (P<.05 being significant) to assess for differences in the rate of revision, time to revision, and indications for revision surgery.
Between January 1996 and April 2016, a total of 4662 patients (5543 hips) with osteoarthritis underwent primary THA at the authors' institution. Of these patients, 104 hips in 100 patients went on to revision THA. Sixty-two of the revision patients were 64 years or younger at the time of their primary THA (group 1) and 42 were 65 years or older (group 2). The average age of all patients undergoing primary THA was 57.7 years. The mean age was 52.7±8.4 years (range, 29–64 years) in group 1 vs 73.4±6.3 years (range, 65–85 years) in group 2 (P<.001). The average body mass index of all patients undergoing primary THA was 29.4 kg/m2. The mean body mass index was not significantly different between the 2 groups (29.7±7.3 kg/m2 vs 28.4±4.6 kg/m2, P=.30). The average American Society of Anesthesiologists score for all patients undergoing THA was 2.2. The average American Society of Anesthesiologists score was not significantly different between group 1 and group 2 (2.2 vs 2.4, P=.08).
Among patients 64 years or younger, 62 of 3417 primary THAs underwent revision (revision rate, 1.8%). Among patients 65 years or older, 42 of 2216 primary THAs underwent revision (revision rate, 2.0%). The difference in revision rates between the groups was not statistically significant (P=.7). The average time from primary THA to revision was 3.0±3.2 years for group 1 and 1.1±2.1 years for group 2 (P=.001). Fifty percent (31 of 62) of revision THAs in group 1 were performed within 2 years of their index THA vs 78.6% (33 of 42) in group 2 (P=.003). By 5 years, 82.2% (51 of 62) of revision THAs in group 1 were performed vs 90.5% (38 of 42) in group 2 (P=.27).
Of the patients undergoing revision THA, 98% (61 of 62) of primary THAs in group 1 had been performed with both a cementless femoral stem and a cementless hemispherical acetabulum vs 90% (38 of 42) in group 2. One percent (1 of 62) of the primary THAs performed in group 1 were hybrid (cementless cup and cemented stem) vs 10% (4 of 42) in group 2. These differences were not statistically significant (P=.15) (Table 1).
Primary Total Hip Arthroplasty Component Data for Each Group
Seventy-six percent (47 of 62) of primary THAs in group 1 used a highly cross-linked polyethylene liner vs 93% (39 of 42) in group 2 (P=.04). Thirteen percent (8 of 62) of primary THAs in group 1 used a conventional polyethylene liner vs 7% (3 of 42) in group 2 (P=.5). The remaining 11% (7 of 62) of THAs performed in group 1 used a metal liner. Sixty-eight percent (42 of 62) of primary THAs in group 1 used a metal-on-polyethylene articulation vs 81% (34 of 42) in group 2 (P=.2). Twenty-one percent (13 of 62) in group 1 used a ceramic-onpolyethylene articulation vs 19% (8 of 42) in group 2 (P=.8). The remaining 11% (7 of 62) in group 1 used a metal-on-metal articulation.
Recurrent instability was the most common reason for revision in both groups (group 1, 35.5%; group 2, 40.5%), followed by infection (19.4%) and aseptic loosening (16.1%) in group 1 and periprosthetic fracture (28.6%) and infection (16.7%) in group 2 (Table 2).
Reasons for Total Hip Arthroplasty Revision in Each Group
An isolated head and liner exchange was the most common revision procedure in both groups (group 1, 41.9%; group 2, 52.4%), followed by cup, head, and liner revision (22.6%) and resection arthroplasty/explant (14.5%) in group 1 and stem and head revision (21.4%) and cup, head, and liner exchange (14.3%) in group 2.
Radiographs of the primary THA prosthesis were available for review in 51 of 62 patients in group 1 and 36 of 42 in group 2. The remaining radiographs had been archived and could not be retrieved for review. Radiographic measurements were obtained using HAS version 126.96.36.199 software (Martell Hip Analysis Suite, Chicago, Illinois) or using the anteroposterior pelvis and cross table lateral hip radiographs if the software was unable to adequately analyze the images. The reliability of the HAS software has been reported elsewhere.18 There were no significant differences in acetabular version, inclination, or limb length discrepancy. The average acetabular anteversion was 18.3° in group 1 and 21.3° in group 2 (P=.10). The average acetabular inclination was 45.5° in group 1 and 46.0° in group 2 (P=.75). The average limb length discrepancy was 2.7 mm in group 1 and 3.3 mm in group 2 (P=.57).
In the United States, the demand for THA continues to increase, especially among younger patients. Despite advances in bearing surface technology, surgical technique, and component design, concern remains regarding THA survival in the young population. As reimbursement for primary and revision THA increasingly moves toward a bundled care model that factors in patient-reported outcomes, hospital readmission, and implant cost, it is important to elucidate patient-related, implant-related, and technique-related causes of early and late revision in the young THA population.
This study was an attempt to address some of the issues posed by the changing THA population. The authors found that young age—defined as younger than 65 years—was not associated with an increased risk of revision or the extent of revision in patients with a primary diagnosis of osteoarthritis. In both age groups, most revisions occurred within 5 years of the index procedure. Furthermore, instability was the most common reason for revision in both groups, suggesting a technique-related rather than a patient-related issue. Observed rates of instability leading to revision THA in the very early period (<2 years) after index THA were similar in the 2 groups (25.8% and 33.3%) compared with rates previously reported by Haynes et al7 (29.8%), who analyzed reasons for revision in 870 consecutive cases. In their cohort, aseptic loosening was found to be the cause of revision in 38.3% and 40.6% of cases in the very early (<2 years) and the early (2 to 5 years) period, respectively, following index THA. In the very early period, the current authors found that aseptic loosening was the cause of revision in 8% of cases in group 1 and 7.2% in group 2. In the early period, aseptic loosening was the cause of revision in an additional 8.1% of cases in group 1 and no additional cases in group 2. Aseptic loosening after THA in the young adult population has been previously reported.19–21 In a review by Duffy et al,19 26.8% (22 of 82) of THAs with first-generation uncemented implants with a minimum of 10-year follow-up were revised due to aseptic loosening. It is unclear whether rates of aseptic loosening will decrease with more modern prostheses.
Similar to Ulrich et al,9 the current authors found that instability and infection accounted for greater than 50% of revisions within 5 years in both age groups. Unlike Ulrich et al,9 who noted an increase in the mean time to failure as patient age increased in a patient population with varied hip pathologies, the current authors did not find a significant relationship between age and time to revision in their cohort, which was strictly limited to patients with a diagnosis of osteoarthritis.
In this study, 6.4% (4 of 62) of patients 64 years or younger underwent a revision for metallosis. Two patients underwent revision within 2 to 5 years following their index procedures, and 2 underwent revision between 5 and 10 years following their index procedures. The current authors' observed rate of revision for metallosis in the entire cohort was 3.8%, consistent with the 5-year cumulative rate of 3.8% to 13.2% for revision for metallosis reported by the Australian Orthopaedic Association National Joint Replacement Registry.22 As evidence continues to mount against the use of metal-on-metal prostheses, in the future, younger patients may be spared from this implant-related cause of revision.23
This study had several limitations. First, it was a retrospective analysis of prospectively collected data. Second, it had inherent selection bias by only including patients who were treated at the authors' center for both their primary and their revision THA. It is possible that some patients who underwent primary THA during the study period who ultimately required revision went elsewhere for their revision procedure, thus limiting the accuracy of these revision rates and reasons. The authors intentionally limited their patient selection to control for surgeon experience and technique that may contribute to revision THA. Third, a multivariate analysis was not performed to determine whether the authors' results were truly attributable to age; however, the statistical analyses were robust, and American Society of Anesthesiologists scores and body mass index were the same for the groups. Finally, the authors' institution is a tertiary referral center. High-volume, fellowship-trained arthroplasty surgeons were included in this study. These characteristics limit the generalizability of the results of this study.
Among patients undergoing primary THA for a diagnosis of osteoarthritis, younger age (≤64 years) was not associated with an overall increased rate of revision or early failure vs older age (≥65 years). Although younger patients may be at greater risk for aseptic loosening and are more likely to undergo metal-on-metal THA, the authors did not find a significant difference in the overall revision rate compared with older patients. Additional studies are warranted to further determine patient-related, implant-related, and technique-related causes of early and late revision in the young adult THA population.
- Callaghan JJ, Albright JC, Goetz DD, Olejniczak JP, Johnston RC. Charnley total hip arthroplasty with cement: minimum twenty-five-year follow-up. J Bone Joint Surg Am. 2000; 82(4):487–497. doi:10.2106/00004623-200004000-00004 [CrossRef]
- Clohisy JC, Harris WH. The Harris-Galante porous-coated acetabular component with screw fixation: an average ten-year follow-up study. J Bone Joint Surg Am. 1999; 81(1):66–73. doi:10.2106/00004623-199901000-00010 [CrossRef]
- Berry DJ, Harmsen WS, Cabanela ME, Morrey BF. Twenty-five-year survivorship of two thousand consecutive primary Charnley total hip replacements: factors affecting survivorship of acetabular and femoral components. J Bone Joint Surg Am. 2002; 84(2):171–177. doi:10.2106/00004623-200202000-00002 [CrossRef]
- Clohisy JC, Harris WH. Matched-pair analysis of cemented and cementless acetabular reconstruction in primary total hip arthroplasty. J Arthroplasty. 2001; 16(6):697–705. doi:10.1054/arth.2001.24447 [CrossRef]
- Charnley J, Cupic Z. The nine and ten year results of the low-friction arthroplasty of the hip. Clin Orthop Relat Res. 1973; 95:9–25.
- Kurtz SM, Lau E, Ong K, Zhao K, Kelly M, Bozic KJ. Future young patient demand for primary and revision joint replacement: national projections from 2010 to 2030. Clin Orthop Relat Res. 2009; 467(10):2606–2612. doi:10.1007/s11999-009-0834-6 [CrossRef]
- Haynes JA, Stambough JB, Sassoon AA, Johnson SR, Clohisy JC, Nunley RM. Contemporary surgical indications and referral trends in revision total hip arthroplasty: a 10-year review. J Arthroplasty. 2016; 31(3):622–625. doi:10.1016/j.arth.2015.09.026 [CrossRef]
- Schmalzried TP, Shepherd EF, Dorey FJ, et al. The John Charnley Award. Wear is a function of use, not time. Clin Orthop Relat Res. 2000; 381:36–46. doi:10.1097/00003086-200012000-00005 [CrossRef]
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- Romness DW, Lewallen DG. Total hip arthroplasty after fracture of the acetabulum: long-term results. J Bone Joint Surg Br. 1990; 72(5):761–764.
- Sadhu A, Nam D, Coobs BR, Barrack TN, Nunley RM, Barrack RL. Acetabular component position and the risk of dislocation following primary and revision total hip arthroplasty: a matched cohort analysis. J Arthroplasty. 2017; 32(3):987–991. doi:10.1016/j.arth.2016.08.008 [CrossRef]
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Primary Total Hip Arthroplasty Component Data for Each Group
|Component||≤64 Years Old (Group 1)||≥65 Years Old (Group 2)||Percent of Total Cohort|
|Acetabular fixation, No.|
|Femoral fixation, No.|
|Bearing surface, No.|
| Metal on polyethylene||42||34||73|
| Ceramic on polyethylene||13||8||20|
| Metal on metal||7||0||7|
|Highly cross-linked polyethylene||76%||93%||83|
Reasons for Total Hip Arthroplasty Revision in Each Group
|Reason for Revision||≤64 Years Old (Group 1)||≥65 Years Old (Group 2)||Percent of Total Cohort||P|
|Pain not otherwise specified||4.8%||0||2.9||.2|