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The Journal of Bone and Joint Surgery (American). 2007;89:1874-1885. doi:10.2106/JBJS.G.00509 © 2007 The Journal of Bone and Joint Surgery, Inc. What's New in Total Hip Arthroplasty
1 Department of Orthopedic Surgery, University of Texas Southwestern Medical
Center, 1801 Inwood Road, Dallas, TX 75390-8883. E-mail address for M.H. Huo:
michael.huo{at}utsouthwestern.edu
Specialty Update has been developed in collaboration with the Council
of Musculoskeletal Specialty Societies (COMSS) of the American Academy of
Orthopaedic Surgeons.
Total hip arthroplasty continued to receive much attention during the past year. The demand for total hip arthroplasty continues to increase. Following the outlines from previous updates, this year's review is organized in the following sections: (1) epidemiology and public health, (2) clinical outcome of primary total hip arthroplasty, (3) clinical outcome of revision total hip arthroplasty, (4) current status of minimal incision total hip arthroplasty, (5) hip resurfacing, (6) complications, (7) bearing surfaces, and (8) other clinical and scientific studies.
Resource utilization in total hip arthroplasty has continued to escalate because of the increase in the number of patients undergoing arthroplasty. Vessely et al., using the age-adjusted database of residents of a single United States county, reported a 55% increase in the number of total hip arthroplasties between the years 1969 through 1975 and 2000 through 2003. Women had higher utilization rates than men did. The largest increase was for patients who were less than fifty years old. The burden and resource utilization associated with revision total hip arthroplasties are even greater. Ong et al. quantified the projected economic burden of revision total hip arthroplasty and total knee arthroplasty. Medicare (1997 to 2004) and United States census data were incorporated into a Poisson regression model to determine the projected economic burden through 2015 for both hospitals and surgeons. On the basis of their analysis, the annual hospital and surgeon charges for primary total hip arthroplasty in the United States are likely to increase to $17.7 billion and $1.9 billion, respectively. Revision total hip arthroplasty poses a greater economic burden than revision total knee arthroplasty does. Using the Nationwide Inpatient Sample (NIS), which includes a survey of approximately 1000 hospitals and the computation of the future population size, Kurtz et al. predicted that periprosthetic infection has the potential to be the most dominant reason for the failure of total joint arthroplasty in the United States over the next two to three decades. Suboptimal outcomes and complications associated with these procedures will result in an even greater burden on society. Zhan et al.1 screened more than eight million hospital discharge records in 2003 and identified approximately 200,000 total hip arthroplasties, 100,000 partial hip arthroplasties, and 36,000 revision total hip arthroplasties. Sixty percent of the patients were more than sixty-five years of age, and 75% had at least one medical comorbidity. The in-hospital mortality rates for the three procedures were 0.33%, 3.04%, and 0.84%, respectively. With respect to complications, the rates of infection were 0.05%, 0.06%, and 0.25%, respectively, and the rates of venous thromboembolism were 0.68%, 1.36%, and 1.08%, respectively. The rates of readmission within ninety days for any reason were 8.94%, 21.14%, and 15.72%, respectively, and the rates of readmission within ninety days for problems related to the hip were 2.15%, 1.61%, and 3.99%, respectively. Advanced age and an increased number of medical comorbidities were the most predictive of mortality and complications. Finally, the mean hospital charges were $34,951, $35,985, and $46,849, respectively, in 2003 dollars. A study from the Swedish hip arthroplasty registry also identified comorbidities as an important parameter influencing the outcome. That study on 4055 total hip arthroplasties from thirty-seven different centers demonstrated that patient anxiety/depression was a very important predictor of outcome. Some researchers have investigated the effects of delay in performing surgery on the outcome of total hip arthroplasty. Garbuz et al.2 conducted a prospective study of 201 patients who were on a surgical waiting list for total hip arthroplasty to specifically determine whether waiting for surgery would result in a less successful outcome. They found that waiting time was strongly associated with a reduced probability of a better-than-expected outcome after total hip arthroplasty. There was an 8% reduction in outcome with every additional month of waiting. They also found the strongest association of a worse outcome in patients with more pain, lower function, and more hip stiffness preoperatively. Roder et al.3 performed a retrospective cohort study evaluating the association between preoperative functional status and post-operative outcome. Those investigators reviewed 13,766 total hip arthroplasties that had been prospectively entered into a multi-nation registry (International Documentation and Evaluation System [IDES]) from 1967 to 2002. They found a strong association between both preoperative walking time and hip flexion arc and the postoperative outcome. Most importantly, the preoperative pain level did not have an impact on the postoperative pain relief. It is hoped that data from studies such as these will enable the clinician to select patients at least partially on the basis of predictors of good outcome. Given an expected reduction in resources, prioritization for total hip arthroplasty may ultimately reduce utilization.
Stem The evolution favoring cementless fixation of the femoral component continues as the long-term results of uncemented components become available. Engh et al. reported the twenty-year follow-up results of the initial series of 223 total hip arthroplasties performed with use of the extensively coated AML stem (DePuy, Warsaw, Indiana). The mean age at the time of surgery was fifty-five years. The mean duration follow-up for the 130 living patients (136 stems) was 19.2 years. Only three stems were revised because of loosening. Fibrous-stable fixation of the stem was observed in another three hips. The rate of stem survival free of any revision was estimated to be 97.2% at twenty years. Reports of the long-term outcome associated with the tapered wedge-shaped femoral stem are also becoming available. McLaughlin and Lee reported the twenty-year results of 145 total hip arthroplasties that had been performed with a tapered stem. No stem was revised because of loosening. Among the stems that remained in situ, 96% demonstrated osseous fixation, 3% demonstrated stable fibrous fixation, and 1% demonstrated radiographic loosening. The rate of revision because of infection was 4%. The rate of survival was estimated to be 91% at twenty-two years. The use of stem designs with a higher offset has increased because of their ability to better restore the anatomy, increase abductor efficiency, reduce joint-reaction forces, and minimize impingement. Some have questioned if the increased offset would result in a higher prevalence of trochanteric bursitis, thigh pain, and stem loosening. Berend et al. compared two groups of forty-nine consecutive total hip arthroplasties that had been performed by the same surgeons with use of identical stem geometry, surface texture, and surgical techniques. One group had increased stem offset. The mean duration of follow-up was thirty-eight months for the high-offset group and forty-six months for the normal-offset group. The investigators found lower rates of bursitis (6% compared with 12%; p < 0.05) and thigh pain (0% compared with 6%; p < 0.05) in the high-offset group. Moreover, limb-length discrepancy was observed in only one patient in the high-offset group, compared with six patients in the normal-offset group. The authors believed that more accurate restoration of femoral offset and soft-tissue tension resulted in the better results.
Cup
Stem Revision Continuing efforts have been made to use newer techniques and implant designs in the hope of improving the success of revision total hip arthroplasty. It appears that the newer generation of modular fluted stems, with a reinforced taper junction, may be a better choice for reconstruction of the femur in patients with bone loss. Even the advocates of monoblock, extensively coated stems have reported a better outcome in association with the use of modular stems. Paprosky, in a study of thirty-two patients, reported the outcome of revision total hip arthroplasty with use of a modular tapered stem after a mean duration of follow-up of 5.3 years. The mean stem diameter was 21 mm (range, 17 to 26 mm). All revisions were performed through an extended trochanteric osteotomy. Femoral bone deficiencies were classified as Paprosky type IIIA in two hips, type IIIB in twenty-three hips, and type IV in seven hips. One stem was revised because of infection, and one was revised because of loosening. One additional stem had subsidence but was not revised. The author concluded that the modular tapered stems performed better than did the extensively coated stems, particularly when there was marked femoral bone deficiency. Garbuz et al.5, in a matched-pair analysis in which a monoblock extensively coated femoral stem was compared with a modular fluted stem, also noted a better outcome in terms of pain, function, and overall rating in the group of patients who received the modular, tapered stem. One major problem of the latter study was that some important parameters such as operating time, blood loss, surgical approach, use of the extended trochanteric osteotomy, bone-grafting, concomitant cup revision, and preoperative functional status were not matched. The modular stem does, however, pose a potential problem. Surgeons and engineers have long been concerned with the potential for corrosion and fretting at taper junctions in modular implant designs, leading to reduction in fatigue strength and the potential for catastrophic failure of the implant. Furthermore, the generation and migration of fretting and corrosion products could add to the particulate burden and lead to accelerated bearing surface wear from third-body abrasion. Jacobs et al. performed a detailed analysis of thirty retrieved modular stems of three different designs. Fretting and corrosion damage were observed at the stem-sleeve or stem-body junction in twenty of thirty stems. Qualitative grading revealed that the damage was minimum in ten, mild in eleven, moderate in six, and severe in three. Fortunately, severe changes resulting in a potential risk for structural failure of the stem were observed in only one hip.
Cup Revision Jumbo cups and pelvic reinforcement cages have also been used for reconstruction of the acetabulum in hips with marked bone loss. While both methods have been associated with failures, a combination technique known as the "cage over cup" technique is believed to be a viable option for challenging acetabular revision cases. The proposed advantages of this combination are that (1) the porous cup will allow for long-term durability of fixation by osseous ingrowth to the host, and (2) the cage will protect the cup, which may have failed in the short term because of poor host-bone quantity and quality. Noiseux et al. reported the results of this combination technique in a study of thirty-one complex revisions. The acetabulum was reconstructed with use of a hemispherical shell, over which a cage was placed, and the polyethylene liner was cemented into the cage, thus unitizing the entire composite. The mean duration of follow-up was 2.3 years. No revision was done for the treatment of loosening. Radiolucent lines were observed in 42% of the hips, especially over the ischial flange of the cage. Partial bone-graft resorption occurred in 26% of the hips. Revision was necessary in two hips for the treatment of recurrent dislocation. Eighty-two percent of the hips were rated good to excellent. Longer-term follow-up is necessary to determine if this new technique will be more durable than either a jumbo cup or a cage alone. Controversies exist with regard to the best way to address pelvic osteolysis around stable cups. Engh et al. injected a semi-liquid calcium sulfate bone graft substitute to fill pelvic defects. The investigators performed two pilot studies: one involving cadaveric specimens, and the other involving clinical revisions. All patients had a preoperative computed tomographic scan to quantify the defect volume. The mean volume of the experimental defects was 6.7 cm3. The mean volume of osteolysis in the patients was 34.5 cm3. The surgeons were successful in filling 89.3% of the small lesions in the cadaveric model. However, they were successful in filling only 44.7% of the defect volume in the patients. No data were given with regard to the degree of healing of these lesions. Surgeons have utilized one of several treatment options for pelvic osteolysis around a well-fixed cup: (1) liner exchange only, (2) liner exchange with bone-grafting of the lesions, (3) cementation of a liner in cases of an incompetent locking mechanism with or without bone-grafting, and (4) revision of the shell. Talmo et al. reviewed the results of 128 cup reoperations that had been performed for the treatment of osteolysis over a period of twelve years. All cups were of the same design, which was known to have a suboptimal locking mechanism but a high success rate for durable bone fixation. Fifty-two percent of the procedures involved liner exchange into the preexisting shell, 27% involved shell revision, and 21% involved cementation of a new liner into the preexisting shell. The mean duration of follow-up was 5.1 years. In the liner-exchange-only group, 24% of the hips required reoperation, one-half because of liner dislodgment and one-half because of progressive polyethylene wear and pelvic osteolysis. In the liner-cementation group, 29% required reoperation, two-thirds because of dislocation and one-third because of shell loosening. In the shell-revision group, 15% required reoperation, one-half because of dislocation and one-half because of infection. The authors recommended shell revision as the optimal treatment of polyethylene wear and osteolysis for this particular cup design.
Outcome of Revision Total Hip Arthroplasty
Recent clinical data have provided conflicting evidence with regard to the efficacy and safety of minimal incision total hip arthroplasty. Some of the most recent studies have focused not specifically on minimal incision total hip arthroplasty but rather on the impact of a different surgical exposure on the soft tissues around the hip and on the clinical outcome with regard to gait and muscle strength. Picado et al.8 specifically evaluated the effect of the lateral approacvh (partial detachment of the abductors) on Trendelenburg gait. The investigators studied forty consecutive patients with sequential examinations and electromyographic studies that were performed preoperatively and at four, eight, twelve, and twenty-four weeks. One-half of the patients had a Trendelenburg gait before surgery, and 25% still did at one year after surgery. Electromyographic findings consistent with muscle and nerve injury were found in 42.5% of the patients at four weeks. Three of the patients still had some electromyographic changes at six months. There was no correlation between the electromyographic findings and a clinical Trendelenburg gait. While the authors did not provide data with regard to the functional outcome, it is clear that a persistent Trendelenburg gait is common after total hip arthroplasty involving the direct lateral approach. One of the clinical impacts of minimal incision total hip arthroplasty has been the development of newer instrumentation to facilitate surgery. Baad-Hansen et al.9 performed a cadaver study in which conventional acetabular reamers were compared with chamfered reamers designed for minimal incision total hip arthroplasty. The purpose was to compare the accuracy of bone preparation with use of these reamers of different geometries. The investigators used a three-dimensional digital scanning technique to determine the best-fit sphere created by the various reamers. On the average, there was 0.1 mm and 0.3 mm of deviation from a perfect fit for the minimal incision total hip arthroplasty and conventional reamers, respectively. Another important finding was that the difference between the labeled reamer size and the actual reamer dimension could vary as much as 3 mm. Further refinement of instrumentation is necessary in order to ensure more accurate bone preparation, and surgeons should try to identify any differences between the reamers and actual cup dimension prior to surgery. One potential complication of minimal incision total hip arthroplasty is malpositioning of the components because of limited visualization. Rittmeister and Callitsis10 reviewed 500 consecutive total hip arthroplasties that had been performed by multiple surgeons at one center. Four hundred of these procedures had been performed with use of conventional surgical approaches, whereas 100 had been performed with use of a minimal-incision technique without navigation. For all 500 procedures, 19.8% of the cups fell outside of the desirable abduction angle range (35° to 55°) and 11.2% fell outside of the desirable anteversion range (5° to 25°). There was no difference between conventional and minimal incision approaches. Most important, some surgeons consistently placed the cups in positions outside of the range. Those studies suggest that much more instrumentation work remains to be done to help surgeons more consistently achieve desirable acetabular preparation and cup placement. Some surgeons have reported accelerated recovery following two-incision minimal incision total hip arthroplasty. Pagnano et al. conducted gait analysis and muscle-strength testing in patients following minimal incision total hip arthroplasty with use of either the two-incision approach or a miniposterior approach. Ten patients were randomized to each group. Both groups had similar demographic characteristics, preoperative hip scores, and functional status. Both groups had marked improvement in gait velocity, stride length, and step width at eight weeks. There was no difference in any of the gait or muscle-testing parameters between the groups. In the study by Meneghini and Pierson, sixteen patients (seventeen hips) were randomized to one of three surgical approaches: two-incision, mini-posterior, and mini-anterolateral. The mean age of the patients was fifty-three years, and the mean body mass index was 26 kg/m2. All patients received comprehensive preoperative instruction with an expectation to be discharged on the day after surgery. All patients received identical anesthesia, pain management, and physiotherapy. The patients were blinded with regard to the surgical approach, as were the hospital nursing and therapy staff. Fourteen of the seventeen hips met physical therapy criteria for discharge by the next morning. With these small numbers, surgical approach did not appear to have an effect on early discharge. Pagnano et al., in a prospective, randomized study of seventy-two patients, compared the two-incision technique with a mini-posterior minimal incision approach. All procedures were performed by the same surgeon. Outcome measures were focused on early functional recovery. The mean duration of discontinuation of narcotic medication was shorter for the patients in the two-incision group. Discontinuation of walking aids and return to daily activities were faster for the patients in the mini-posterior incision group. The authors found no evidence that the two-incision minimal incision total hip arthroplasty had any dramatic effect on early return of function. In another study, Sirianni et al. evaluated forty-eight patients with instrumented gait analysis following three different surgical approaches: conventional posterior, mini-posterior, and mini-lateral. For all patients, gait velocity increased 10% at six weeks from the preoperative value. At six weeks, there was no difference among the groups with regard to velocity, cadence, stride length, or single-limb-support time. The authors concluded that (1) the patients recovered to near-normal gait parameters by six weeks and (2) the surgical approach did not influence recovery.
Navigation
Hip resurfacing has received much attention in the past year since the approval of the first implant system by the United States Food and Drug Administration. It is the fastest growing joint arthroplasty procedure worldwide. Surgeon advocates, patient information sites, and the device companies all have proposed that hip resurfacing is associated with superior function and faster recovery as compared with conventional total hip arthroplasty. Fowble, dela Rosa, and Schmalzried questioned if the observed clinical outcome of hip resurfacing was a function of patient selection and expectation rather than the procedure itself. The investigators evaluated two groups of patients: (1) fifty patients managed with hip resurfacing procedures, and (2) thirty-five patients managed with total hip arthroplasty procedures performed with use of a large-diameter head. These patients were prospectively followed for two to four years. There were demographic differences between the groups, with the patients in the hip resurfacing group being more frequently male (62%), being younger (by nine years), being less obese (lower body mass index), and having a lower anesthesia risk than those in the total hip arthroplasty group. Patients in the hip resurfacing group also had a lower Harris hip score, more pain, a higher activity score, and better range of motion before surgery. The operating time was 18% longer in the hip resurfacing group, but that group had less blood loss and fewer transfusions. There was no difference between the groups with regard to the Harris hip score after surgery. Patients in the hip resurfacing group had higher Short Form-12 physical, function, and activity scores. However, they also had a higher prevalence of mild pain. There was no difference between the groups with regard to the postoperative range of motion. There was one dislocation in each group. The preoperative differences between the groups, rather than the procedure itself, may have contributed to some of the observed differences after surgery. A study involving three-dimensional simulation demonstrated that the flexion-extension arc following resurfacing was significantly less than that in the native hip and that following conventional total hip arthroplasty. The large neck-to-head ratio and the presence of a large prosthetic posterior acetabular wall with resurfacing were postulated to account for these findings. Femoral neck fracture is the most important complication following hip resurfacing. Most surgeons identify notching of the femoral neck as the most important factor leading to fracture. The other controversy is whether the femoral component should be placed in neutral or in a valgus position. Masri et al. tested ten paired fresh-frozen cadaver specimens. On one side the femoral component was placed in neutral, and on the other side it was placed in 10° of valgus. A standardized notch (3 mm wide and 2 mm deep) was created in the superolateral aspect of the femoral neck. The investigators also determined the bone mineral density of each specimen. All specimens were loaded to fracture. There were two fracture patterns: (1) simple fracture (noted in fourteen specimens [70%], with eight in neutral and six in valgus) and (2) crush fracture (noted in six specimens [30%], with two in neutral and four in valgus). The crush pattern reflected failure in compression in specimens with low bone mineral density. For those that failed in a simple fracture pattern, valgus placement increased the load to fracture by 30% over neutral placement, but component placement did not have an impact on fracture load in specimens with a low bone mineral density. These results suggest that placement of the femoral component in 10° of valgus in patients with normal-to-high bone mineral density can provide substantial protection against femoral neck fracture following notching when compared with neutral placement. Davis et al. conducted a similar cadaver experiment without notching of the neck. Placement of the femoral component in 10° of varus was associated with a 12% reduction in ultimate fracture strength, whereas placement of the femoral component in 20° of valgus was associated with a 32% increase in fracture strength. The results of these studies should help to define optimal patient selection criteria and surgical technique in order to minimize fracture following hip resurfacing. Another potential factor related to fractures and femoral fixation failure is compromised femoral head vascularity. In the study by Beaule et al.11, ten patients undergoing surgery were evaluated with use of laser Doppler flowmeter recordings during femoral head reaming. There was a mean 70% decrease in blood flow from baseline during reaming. The authors recommended keeping the reamer as close to the inferomedial neck as possible in order to minimize damage to the retinacular vessels. Hip resurfacing may be especially difficult in patients with femoral head deformity. Boyd et al. reported the results of hip resurfacing in a study of eighteen hips with deformity resulting from Legg-Calvé-Perthes disease. After a mean duration of follow-up of 4.2 years, 95% had a good to excellent Harris hip score. No fractures or loosening were reported. The authors recommended careful removal of marginal osteophytes around the neck to minimize impingement. Obesity poses another controversy in patient selection. Amstutz and Le Duff presented the results of 148 hip resurfacing procedures that were performed in 138 patients with a body mass index of >30 kg/m2. The mean age was 49.4 years, and the mean body mass index was 33.4 kg/m2. There were no cases of acetabular or femoral component loosening. Two hips were revised, one because of a femoral neck fracture and the other for cup placement. In a smaller subset of patients with a body mass index of >35 kg/m2, there were no cases of fracture or implant loosening. With respect to patient age, Amstutz et al. followed 295 hip resurfacing arthroplasties in patients who were younger than fifty years old. The mean age was 41.2 years. The mean duration of follow-up was 6.4 years. No cup revision was done. Ten hips required femoral revision because of loosening. Another hip was revised because of a femoral neck fracture. Radiolucent lines were observed in another eight hips. The five-year survival rate was 97.8% in patients with good bone stock and proper surgical preparation. Hashmi and Holland reported on a prospective study of 107 consecutive Birmingham hip resurfacing procedures after a mean duration of follow-up of 6.5 years. The mean age was 52.2 years for the seventy-four male patients and 47.8 years for the twenty-six female patients. Two revisions were done because of femoral neck fracture. All surviving hips were rated as excellent. That study, which represented one of the first series of Birmingham hip resurfacing procedures performed by surgeons other than the designers, demonstrated the efficacy of hip resurfacing in properly selected patients.
Dislocation Instability remains among the most frequent causes of reoperation following total hip arthroplasty, and it is especially frequent following revision total hip arthroplasty. Ries and Kung reviewed the effect of head size in a study of 218 revision total hip arthroplasties. There were four groups. Group 1 included hips with an intact abductor mechanism and a 28-mm head, Group 2 included hips with an absent abductor mechanism and a 28-mm head, Group 3 included hips with an intact abductor mechanism and a 36-mm head, and Group 4 included hips with an absent abductor mechanism and a 36-mm head. The dislocation rates were 11.7%, 38%, 0%, and 38%, respectively, for the four groups. There was significant difference between Groups 1 and 2 and between Groups 3 and 4. Thus, the integrity of the abductor mechanism had a greater impact on the dislocation rate than did the head diameter. Constrained liners have been used to address instability in patients with an incompetent abductor mechanism. Guyen et al. reviewed forty-three failed constrained liners of a single design (tripolar type). These failures represented 11% of the 390 total hip arthroplasties performed with use of this liner design. The mean time to failure was twenty-eight months (range, one to seventy-eight months). Most of the failures occurred in hips that had had multiple previous revision procedures, and the most common mechanism of failure was infection (28%). Among the different mechanical failure mechanisms, the most common were fixation failure between shell and bone (26%), dislocation of the bipolar component (21%), and failure of the locking mechanism between the liner and the shell (14%). The authors suggested judicious use of tripolar constrained liners in salvage situations.
Infection Currently, there is no consensus regarding the principles of empiric antibiotic treatment of suspected infection. Fulkerson et al.12 conducted a retrospective review of positive cultures of specimens that had been obtained from the sites of 110 total hip arthroplasties and eighty-four total knee arthroplasties over thirteen years at a tertiary joint arthroplasty center. Seventy percent of the infections were classified as chronic; 17%, as acute postoperative; and 13%, as acute hematogenous. Gram-positive organisms were isolated in 84% of the cases. Staphylococcus aureus was the most common organism isolated from the site of total hip arthroplasty (45%), and Staphylococcus epidermidis was the most common organism isolated from the site of total knee arthroplasty (40%). Ninety-six percent of all organisms were sensitive to vancomycin; 88%, to gentamycin; and only 61%, to cefazolin. Cultures were positive for multiple organisms in 9.3% of the cases. Resistant organisms were most commonly found in specimens from patients who had had a failure of previous treatment and those from patients who had an acute postoperative infection. The investigators recommended the use of empirical antibiotic therapy. Specifically, they recommended (1) that chronic infection should be treated with vancomycin, (2) that acute hematogenous infection should be treated with gentamycin and cefazolin, and (3) that infections involving multiple organisms should be treated with vancomycin and a third or fourth-generation cephalosporin. Last, they recommended that, if cultures were negative after four days, empiric therapy should be discontinued.
Venous Thromboembolism Lachiewicz and Soileau14 prospectively evaluated 936 patients managed with 1032 primary and revision total hip arthroplasties, 95% of which were performed with use of regional anesthesia. Prophylaxis against deep-vein thrombosis included the use of a thigh-high sequential compression device while the patient was in the use of aspirin (325 mg, administered twice daily for six weeks). Screening duplex ultra-sonography was performed an average of four days after surgery. Deep-vein thrombosis was documented in forty-one patients (thirty-five of whom were asymptomatic), symptomatic pulmonary embolism occurred in seven patients, and fatal pulmonary embolism occurred in only one patient. In that cohort, the overall thirty-day mortality rate from all causes was 0.3%. Keeney et al.13 evaluated the efficacy and safety of using a multimodal prophylaxis protocol that included seven days of adjusted-dose warfarin, mechanical prophylaxis, and accelerated mobilization. Screening was done by means of bilateral ultrasonography on Day 3 or 4. Seven hundred and five patients undergoing primary or revision total hip arthroplasty were included. An asymptomatic deep-vein thrombosis was documented in twenty-five patients (3.5%), and two-thirds of these clots were proximal. An additional five patients (0.7%) were managed for symptomatic deep-vein thrombosis. Symptomatic pulmonary embolism occurred in one patient. There were no deaths, readmissions, or late symptomatic deep-vein thromboses or pulmonary emboli. The authors found that a prior deep-vein thrombosis or pulmonary embolism, increased age, and male gender were significant risk factors for the development of deep-vein thrombosis or pulmonary embolism within ninety days after total hip arthroplasty. One current controversy is the duration of prophylaxis. Dhupar et al.15 evaluated 2364 patients who were managed with primary total hip arthroplasty and total knee arthroplasty from 1994 to 2001 with use of duplex ultrasonography as screening protocol. All patients received thromboembolic prophylaxis with use of adjusted-dose warfarin. Forty percent underwent screening at the time of hospital discharge, and the others underwent screening at two weeks after surgery. The rate of proximal deep-vein thrombosis in the thigh was not different between the groups (2.5% and 2.2%, respectively). As a result of that study, the authors no longer perform routine screening for asymptomatic patients. Some orthopaedic surgeons have questioned whether the ACCP guidelines are safe, especially with regard to perioperative morbidity. Burnett et al.16 conducted a prospective, nonrandomized study of 129 consecutive total hip arthroplasties that were performed over six months at a single institution. All patients received low-molecular-weight heparin (30 mg, administered every twelve hours for ten days). The results were compared with those from the previous study involving short-term adjusted-dose warfarin from the same institution. The prevalence of major complications was 9% in the low-molecular-weight heparin group and 2.1% in the warfarin group (p < 0.001). The prevalence of symptomatic deep-vein thrombosis was significantly higher in the low-molecular-weight heparin group (7% compared with 1.6%; p < 0.001). As many patients travel long distances to undergo surgery, extended travel shortly after total hip arthroplasty is of concern, particularly because of the risk of venous throm-boembolism. Ball et al. followed 502 patients who had a mean age of fifty-one years. All patients received either low-molecular-weight heparin or adjusted-dose warfarin as prophylaxis. The patients traveled an average of 1319 miles (2123 km) (range, 200 to 8000 miles [322 to 12,875 km]) at a mean of 6.5 days after surgery, 74% by airplane and 26% by automobile. No deaths or pulmonary emboli were recorded. Symptomatic deep-vein thrombosis was identified in three patients. Of interest, none of the 104 patients who had to travel continuously for a minimum of six hours had development of deep-vein thrombosis. The authors concluded that there was minimal risk of deep-vein thrombosis during travel within the first six weeks after total hip arthroplasty for patients receiving prophylaxis.
Periprosthetic Fractures Intraoperative acetabular fracture is a rare complication of total hip arthroplasty. Haidukewych et al.18 reported twenty-one such fractures in a joint registry of 7121 total hip arthroplasties that had been performed over eleven years at a tertiary joint replacement center. No fractures occurred in association with cups that had been inserted with cement. The fracture rate associated with cementless cups was 0.4%. All fractures united without cup loosening. The investigators found a greater risk of acetabular fracture in association with elliptical monoblock shells than in association with either elliptical modular or hemispherical modular designs. That report raises concern with regard to preparation and cup insertion with use of minimal incision total hip arthroplasty techniques as well as with regard to the potential for fractures during resurfacing arthroplasty as many resurfacing cups have an elliptical monoblock geometry.
Metal-on-Metal Metal-on-metal articulations were initially introduced more than four decades ago. The resurgence of this alternative bearing surface over the past decade was driven primarily by the hope to reduce wear and osteolysis. It has remained popular with the current enthusiasm for hip resurfacing and large-head articulation total hip arthroplasties. In this update last year, we cited several recent reports on the histological features of hypersensitivity in tissues retrieved from the sites of total hip replacements with a metal-on-metal bearing. Korovessis et al.19 reported on the histological characteristics of tissues retrieved from the sites of eleven total hip replacements with a metal-on-metal bearing. These hips were part of a cohort of 194 total hip replacements with a contemporary tapered stem, a threaded cup, and a 28-mm metal-on-metal articulation coupled with a polyethylene inlay design. The metallurgy was a low-carbine, wrought cobalt-chromiummolybdenum alloy with a thickness of 3 mm. The investigators consistently found histiocytes and giant cells with fine intracellular metallic debris. Moreover, a predominantly perivascular lymphoplasmacytic infiltrate was observed. The investigators found no correlation between the histological grade and the presence of osteolysis on the radiographs. In another report, Milosev et al.20 followed 640 total hip arthroplasties that had been performed with use of a similar metal-on-metal bearing design. The mean duration of follow-up was seven years. Thirty-four hips were revised. Linear or expansile femoral osteolysis was observed in 64% of the hips that were revised because of aseptic loosening. Histological analysis of retrieved tissue demonstrated perivascular lymphocyte and plasma cell infiltrates. Wear analysis of retrieved components demonstrated that the mean total linear wear was 31 µm, with a mean annual wear rate of 6.3 µm/year. An abrasive wear pattern was consistently observed with electron microscopy on the bearing surfaces of both the femoral head and the cup. Those two reports further documented hypersensitivity as a possible mechanism of failure following total hip arthroplasties performed with this metal-on-metal bearing, particularly when there is loosening. Serum and urine metal ion levels in patients managed with metal-on-metal total hip arthroplasty have been reported by investigators from several centers. MacDonald et al. reported additional data in a prospective, randomized, blinded clinical trial of twenty-three patients with a metal-on-metal bearing and eighteen patients with a metal-on-polyethylene bearing. The bearings had identical designs. After a mean duration of follow-up of 7.2 years, the metal-on-metal group continued to have elevated ion levels and the erythrocyte cobalt levels were eleven times elevated compared with those in the metal-on-polyethylene group. Most importantly, there was no decrease over time in the erythrocyte cobalt levels after six months following surgery. Moreover, compared with the values in the metal-on-polyethylene group, the urine cobalt levels in the metal-on-metal group were thirty-nine times elevated (p < 0.001) and the chromium levels were twenty-eight times elevated (p < 0.001). These data may be specific to this particular bearing coupling. Nonetheless, it is of concern that the levels continued to be elevated.
Ceramic-on-Ceramic
Polyethylene Larger-diameter femoral heads have the advantages of more clearance, greater range of motion, less impingement, and greater offset. However, polyethylene wear is of concern. Bragdon et al. evaluated penetration into highly cross-linked polyethylene liners in a study of thirty patients who were randomized to treatment with either a 28-mm head or a 36-mm head; the implant design was identical in both groups. The mean duration of follow-up was three years. There was no significant difference between the groups following an initial bedding-in of 0.075 mm. Dorr et al. followed eighty-nine total hip arthroplasties involving a single cup design. Each hip had received the largest-possible diameter femoral head (28, 32, 38, or 44 mm) to provide 5 mm of polyethylene thickness. There was no difference in clinical or radiographic outcome among the groups. Although wear reduction is consistently documented with highly cross-linked polyethylene, the ability of this bearing surface to minimize osteolysis continues to be studied. Leung et al. evaluated seventy-six hips with computed tomography to detect and monitor pelvic osteolysis. The cups were randomized to either conventional polyethylene sterilized in an inert environment or to highly cross-linked polyethylene. The mean duration of follow-up was 6.1 years. Osteolysis was detected in 30% of the hips in the conventional group and 16.7% of those in the highly cross-linked group, and the mean volume of the osteolysis lesion was significantly less in the highly cross-linked group (1.2 cm3 compared with 7.0 cm3; p = 0.001). Kitamura et al.21 examined a minimum of six serial radiographs for 145 hips that had undergone total hip arthroplasty with use of a cementless cup. The minimum duration of follow-up was ten years. The liners were made of either conventional polyethylene or high-crystalline polyethylene. The femoral heads were 28 mm and were made of either cobalt-chromium alloy or alumina ceramic. Pelvic osteolysis was present in 17.2% of the hips. The investigators determined the two-dimensional lesion size and the progression of the lesions over time. The mean rate of lesion expansion was 42.7 ± 49.0 mm2/year. The mean time to the first observation of a lesion was 5.7 years. However, the mean x-intercept for the regression line was 1.3 ± 3.0 years, indicating that the onset of osteolysis was much earlier than was detectable on radiographs. There was a tendency for dome lesions to expand faster than peripheral lesions, and more expansion occurred in men. No difference in osteolysis expansion was noted between the two types of polyethylene or the two head types. That study provided valuable data that will be helpful for formulating practice guidelines related to the frequency of radiographic follow-up for patients managed with total hip arthroplasty, although the osteolysis rate may vary between different polyethylene liners and cup designs.
Bearing surface wear is affected by many factors. Some surgeons have found
greater polyethylene wear in cups with high inclination. Gallagher et al.
analyzed wear in a study of forty-two cups of a single design and polyethylene
type at a minimum of five years. The mean linear wear rate was 0.12 mm/year,
and the mean volumetric wear rate was 56 mm3/yr. There was a
difference in linear wear between cups with an inclination of
Standardized Care Plans It is necessary to achieve high efficiency in order to reduce utilization and costs associated with total hip arthroplasty. Care plan standardization has been used for more than fifteen years in total joint arthroplasty. Mahomed et al. reported the results after the institution of a standardized care plan within a group of twenty-three partner organizations in the Total Joint Network in Toronto, Ontario, Canada. Comprehensive outcome measurements were used. Patients were prospectively evaluated. The care plan involved preoperative streaming of patients to inpatient or home-based rehabilitation. More than 50% of the patients were discharged to home. More than half of the patients who went to inpatient rehabilitation units were discharged within seven days. The mean pain and physical scores were slightly higher in patients who went home (80.5% and 76.6%) than in those who went to inpatient rehabilitation (77.5% and 72.5%), but only 5% of the patients reported dissatisfaction with the care plan. These data demonstrated that there was no deterioration in outcome with more patients being discharged to home. Accelerated rehabilitation and discharge from the hospital has received much attention, especially with the evolution of minimal incision total hip arthroplasty. Gullotta et al. evaluated the feasibility of a two-day hospital stay protocol at a tertiary joint arthroplasty center in a study of 147 relatively healthy patients who were less than seventy years of age and were able to walk independently before surgery. All of the patients received preoperative instructions and education. Fifty-seven percent of the patients were discharged within two days. Forty-six of the remaining sixty-three patients went home on Day 3. There were six readmissions: three for dislocation, two for revision because of implant mechanical problems, and one for blood transfusion. Nausea and vomiting on Day 1 and insufficient pain relief on Days 1 and 2 were the most significant predictors of the success or failure of this fast-track discharge protocol; however, controversy remains with regard to the safety of early discharge.
Pain Management
Return to Athletic Activities After Total Hip Arthroplasty
Future Meetings
The editorial staff of The Journal reviewed a large number of recently published research studies related to the musculoskeletal system that received a Level of Evidence grade of I. Over 100 medical journals were reviewed to identify these articles, which all have high-quality study design. In addition to articles cited already in this Update, five level-I articles were identified that were relevant to total hip arthroplasty. A list of these titles is appended to this review after the standard bibliography. We have provided a brief commentary about each of the articles to help guide your further reading, in an evidencebased fashion, in this subspecialty area.
von Schewelov T, Sanzen L, Onsten I, Carlsson A, Besjakov J. Total hip replacement with a zirconium oxide ceramic femoral head: a randomised roentgen stereophotogrammetric study. J Bone Joint Surg Br. 2005;87:1631-5. Four different articulation couplings in 114 total hip arthroplasties were investigated. All arthroplasties were performed with use of an identical implant design with cement fixation. Wear and migration were measured with roentgen stereophotogrammetric analysis techniques at standard intervals of as long as five years after surgery. Patients were randomized to treatment with (1) a stainless steel head against standard polyethylene, (2) a stainless steel head against extended-chain polyethylene, (3) a zirconium head against standard polyethylene, or (4) a zirconium head against extended-chain polyethylene. The wear rates for the four groups were 0.11, 0.34, 0.17, and 0.40 mm/year, respectively (p < 0.008). There was no difference between the two types of heads against extended-chain polyethylene (p = 0.26). There was no advantage associated with the use of a zirconium head. These data may be unique to the 22-mm head diameter articulating against cemented cups. Conflicting wear characteristics of zirconium against polyethylene have been reported by other groups. Johansson T, Engquist M, Pettersson LG, Lisander B. Blood loss after total hip replacement: a prospective randomized study between wound compression and drainage. J Arthroplasty. 2005;20:967-71. A multicenter prospective, randomized study was undertaken to evaluate the efficacy of wound compression after total hip arthroplasty. Fifty-one patients were randomized to treatment with a wound compression girdle, and fifty-four patients served as controls. All procedures were performed with the patient under normotensive spinal anesthesia. All implants were cemented. There was no difference between the groups in terms of total blood loss (p = 0.13). However, the compression girdle group had fewer transfusions (p = 0.05) and less bloody drainage from the incision (p = 0.04). There was no difference between the groups i |
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Introduction
Epidemiology
45° and
those with an inclination of <45° (0.16 mm/year compared with 0.09
mm/year; p < 0.001). Factors such as head size and locking mechanism may
affect the wear rate associated with other cup designs and polyethylene
types.