Long-term performance of oxidized zirconium on conventional and highly cross-linked polyethylene in total hip arthroplasty.

INTRODUCTION: Polyethylene wear and subsequent osteolysis remain obstacles to the long-term survivorship of total hip arthroplasty (THA). Highly cross-linked polyethylene (XLPE) with radical quenching represents a massive leap forward with dramatically improved wear rates compared to ultra-high molecular weight polyethylene (UHMWPE). In this study we evaluate the wear of UHMWPE and XLPE coupled with oxidized zirconium (OxZr) femoral heads. METHODS: A longitudinal, retrospective analysis was performed identifying consecutive patients who received a 28-mm OxZr-on-polyethylene primary THA from 2003 to 2004 by a single, high-volume arthroplasty surgeon. Patients were divided into two groups: those that received (1) UHMWPE liner and (2) a highly XLPE liner. Patients were included if clinical follow-up was complete to 2014 or later. Radiographic analysis was performed by two blinded observers. Measures included cup position, annual linear wear rate, and presence of osteolysis. Pairwise comparisons, correlations, and inter-rater reliability were calculated. RESULTS: Eighty patients were in the UHMWPE group with an average follow-up of 10 ± 1.23 years and 88 patients in the XLPE group with an average of 10 ± 1.03-year follow-up. Average age (68) was similar between groups (p = 0.288). Observer reliability was excellent for cup abduction (ICC = 0.940), anteversion (ICC = 0.942), and detection of osteolysis (ICC = 0.811). Annual linear wear rates were significantly higher (p = 1 × 10-19) with UHMWPE (0.21 ± 0.12 mm/year) compared to XLPE (0.05 ± 0.03 mm/year). Linear wear rate was significantly correlated to decreasing acetabular abduction (p = 0.035). Osteolysis was noted only in the UHMWPE group, with 17 patients (21.2%) exhibiting acetabular osteolysis and 37 (46.3%) patients exhibiting femoral osteolysis. CONCLUSIONS: OxZr coupled with XLPE showed minimal wear and no osteolysis at 10-year follow up. The yearly linear penetration rate is similar to that seen in other studies of XLPE THA. A careful longitudinal follow-up will be required to determine if advanced bearings such as OxZr or ceramic can show improved performance in the second decade of implantation.

Posterior Soft Tissue Repair After Primary THA is Durable at Mid-term Followup: A Prospective MRI Study.

BACKGROUND: The enhanced posterior soft tissue repair has reduced the frequency of dislocation after primary THA performed through the posterolateral approach. However, the long-term integrity of the repair is unknown and could influence surgeon choice regarding surgical technique and THA approach. QUESTIONS/PURPOSES: We asked: (1) What is the durability of the enhanced posterior soft tissue repair at a minimum of 49 months using MRI to evaluate soft tissue to bone integrity? (2) How does the appearance of the posterior soft tissues change during this time? (3) Are there patient characteristics associated with the long-term imaging appearance of the posterior repair? METHODS: All patients without a contraindication for MRI who were undergoing unilateral primary uncemented THA through a posterior approach between February and May 2005 were eligible for inclusion. Ninety percent consented to participate (36 of 40 patients), and 30 patients were followed prospectively with MRI postoperatively and again at 3 months; of those, 22 (73%; 12 men, 10 women) completed the study by having another MRI study at a minimum of 49 months (mean, 51 months; range, 49-59 months). Each patient underwent metal-artifact-reduction sequence MRI to evaluate the integrity of the posterior soft tissues, which had been repaired anatomically during primary THA at a minimum of 4 years earlier. The results were compared with those of prior MR images obtained immediately after surgery and at 3 months postoperatively. All patients were given a self-reported modified Harris hip score at the time of the most recent MRI study (maximum score = 81). RESULTS: At latest followup, 21 of 22 (96%) patients had a posterior capsule in contact with bone, and 21 of 22 (96%) had an intact quadratus femoris. Twenty-one patients (96%) had soft tissue or a scar from the piriformis and conjoined tendons in continuity with bone. In these cases, the interface between the piriformis and conjoined tendons and the greater trochanter observed immediately postoperatively and at 3 months postoperatively became filled with hypointense tissue, with signal characteristics similar to tendon. Time from surgery was most associated with changes in native tendon-to-bone distances (p < 0.001) and MRI signal intensity of the repair (p < 0.001). CONCLUSIONS: At followup of just more than 4 years, the posterior capsule and quadratus femoris most often were healed to bone. In the majority of patients, scar tissue between the piriformis and conjoined tendons and bone matured to achieve orientation and signal intensity resembling native tendon. We believe the enhanced posterior soft tissue repair facilitates this process. Our results provide a plausible explanation for improved postoperative stability observed in patients receiving an enhanced soft tissue repair compared with those in whom a repair is not performed. LEVEL OF EVIDENCE: Level IV, therapeutic study.

Ceramic liner fractures presenting as squeaking after primary total hip arthroplasty.

BACKGROUND: Squeaking after ceramic-on-ceramic total hip arthroplasty is a relatively uncommon phenomenon. It usually does not require treatment in the absence of pain, mechanical symptoms, and/or relentless squeaking. The purpose of this investigation was to report on four patients who presented with hip pain and squeaking due to fractured ceramic liners after ceramic-on-ceramic total hip arthroplasty. METHODS: Four patients with painful squeaking after ceramic-on-ceramic total hip arthroplasty were seen at our institution. One patient had a revision for suspected loosening and excessive anteversion of the cup noted on radiographs and magnetic resonance imaging (MRI). The remaining three patients had a revision for audible squeaking with progressive pain. RESULTS: Intraoperatively, the ceramic liners of all four patients were fractured. CONCLUSIONS: Squeaking after ceramic-on-ceramic total hip arthroplasty rarely is a functional issue. However, painful squeaking without notable trauma may indicate fracture of the ceramic liner. Painful squeaking is difficult to evaluate by conventional imaging. When painful squeaking occurs, exploration via surgical revision is recommended in selected patients, as ceramic liner fractures may go unnoticed on radiographs and/or MRI and thus their actual prevalence may be higher than estimated.

MRI shows biologic restoration of posterior soft tissue repairs after THA.

Although posterior capsule repair reduces the incidence of dislocation after THA, radiographic imaging studies suggest a high failure rate of the repair. Using MRI, we prospectively followed patients to evaluate the integrity of the posterior soft tissue repair after primary THA. Thirty-six patients (21 men, 15 women) underwent arthroplasty using a standard posterior approach. The posterior capsule and external rotators were repaired as separate layers using nonabsorbable sutures through two drill holes in the greater trochanter. Patients observed postoperative hip precautions for 6 weeks after surgery. All patients underwent initial MRI between postoperative Days 2 and 4. Thirty patients returned for followup MRI 3 months after surgery. At 3 months followup, the posterior capsule remained intact in 27 of 30 patients (90%) and the quadratus femoris repair remained intact in 29 of 30 patients (97%). Thirteen of 30 piriformis tendon repairs (43%) and 17 conjoined tendon repairs (57%) showed a gap between the hypointense tendon end and the greater trochanter greater than 25 mm. Our data show repaired posterior soft tissues provide a biologic scaffold allowing formation of a posterior pseudocapsule.

Failure mechanisms and closed reduction of a constrained tripolar acetabular liner.

Unlike traditional bipolar constrained liners, the Osteonics Omnifit constrained acetabular insert is a tripolar device, consisting of an inner bipolar bearing articulating within an outer, true liner. Every reported failure of the Omnifit tripolar implant has been by failure at the shell-bone interface (Type I failure), failure at the shell-liner interface (Type II failure), or failure of the locking mechanism resulting in dislocation of the bipolar-liner interface (Type III failure). In this report we present two cases of failure of the Omnifit tripolar at the bipolar-femoral head interface. To our knowledge, these are the first reported cases of failure at the bipolar-femoral head interface (Type IV failure). In addition, we described the first successful closed reduction of a Type IV failure.

Randomized trials to modify patients' preoperative expectations of hip and knee arthroplasties.

UNLABELLED: Patients have multiple expectations of THA and TKA. We asked whether preoperative educational classes addressing recovery during the first year could modify patients' expectations of their 12-month postoperative recovery. Participants were enrolled consecutively in two randomized, controlled trials, one for THA (177 patients) and one for TKA (143 patients). Control patients preoperatively received a standard THA or TKA class addressing recovery immediately after surgery. Intervention patients preoperatively received the standard class plus a joint-specific module addressing recovery during the first 12 months. Before and after the class, patients completed either a hip-specific or knee-specific validated expectations survey. The main outcome was the within-patient change in expectation scores (maximum increase, +100; maximum decrease, -100) before and after the class but preoperatively. Mean changes in hip scores were +3.3+/-8 for intervention patients (range, -22+/-32) and +4.9+/-8 for control patients (range, -13+/-29). Mean changes in knee scores were -3.4+/-10 for intervention patients (range, -26+/-33) and +2.4+/-10 for control patients (range, -30+/-30). Patients' preoperative expectations of their recovery from THA or TKA can be modified by preoperative educational classes. LEVEL OF EVIDENCE: Level I, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Constrained condylar knee without stem extensions for difficult primary total knee arthroplasty.

Two hundred forty-eight constrained condylar total knee arthroplasties consecutively implanted without the use of diaphyseal stem extensions were studied in 180 patients. Preoperative deformity was severe (82% Ahlbäck grade 4-5). One hundred ninety-two knees (148 patients) were reviewed at mean 47-month follow-up (range: 24-72 months). Knee Society score improved from 36 to 89 points, and function score improved from 42 to 76 points. Failure rate was 2.5% (2 infections, 1 aseptic loosening, 1 supracondylar femoral fracture, and 1 tibial post fracture). Five (2.5%) knees had patellofemoral complications. Nonprogressive radiolucent lines were present in 16% of cases. Use of a nonmodular constrained condylar knee for primary severely damaged knees demonstrated reliable short- to mid-term results with a low complication rate and questioned the routine use of intramedullary stem extensions in all such cases.

Varus rotational osteotomies for adults with hip dysplasia: a 20-year followup.

Untreated hip dysplasia predisposes young adults to early arthritis. Varus rotational osteotomies are considered one option to delay or eliminate total hip arthroplasty. We update a report from 1991 by retrospectively reviewing 40 of 48 patients (83.3%) who had 45 varus rotational osteotomies from 1971 to 1986 with a minimum followup of 15 years (mean, 22.6 years; range, 15-34 years). Results were assessed using Hospital for Special Surgery hip scores and radiographic parameters. The average age of the patients at followup was 57.2 years (range, 38-81 years). Fourteen patients (35%) (16 hips) had no additional procedures at 21.2 years followup (range, 15-27 years). The average Hospital for Special Surgery hip score was 33.7 with a Tönnis scale of 1.7 (mild-moderate osteoarthritis). Twenty-six patients (65%) (29 hips) had total hip arthroplasties an average of 9.75 years (range, 2-27 years) after varus rotational osteotomy. As in the initial study, the degree of preoperative osteoarthritis was a predictive value for success of the varus rotational osteotomy. Additionally, younger patients with minimal hip subluxation and osteoarthritis, and a better preoperative Hospital for Special Surgery hip score were predictors of success.

Analysis of cement mantles in collared versus collarless femoral components.

The purpose of this study was to compare the cement mantles of 100 consecutive collared cemented stems with those of 100 consecutive collarless cemented stems of similar design. All stems were implanted by the same surgeon. Two independent examiners retrospectively reviewed the results. Between the 2 femoral stem types, there was no statistical difference in proximal medial cement mantle size, stem orientation, canal-fill percentage, or cement mantle grade, and there was no radiographic difference in cement mantle quality or stem position.

Integrity of repaired posterior structures after THA.

Various studies have questioned the benefit of repairing the posterior structures after total hip arthroplasty because their integrity can appear disrupted at followup. However, these studies did not directly examine the posterior structures. We hypothesized that repaired posterior structures remain intact after total hip arthroplasty, and that their integrity could be evaluated by ultrasonography. We performed evaluations in the hips of 18 patients that had either the short external rotators and capsule repaired, or the capsule, short external rotators, and quadratus femoris repaired. Nine patients in each group were examined using ultrasonography at 6 weeks and 3 months postoperatively. The short external rotators and capsule were intact in 89% of patients in both groups at 6 weeks and 3 months postoperatively. At both time points, the quadratus femoris had continuity in 44% of hips with the standard posterior repair and 78% of hips with the enhanced posterior repair (p = 0.15). Ultrasonography can be used to effectively assess the integrity of the posterior repair after total hip arthroplasty. The posterior structures were intact in the majority of patients 3 months after total hip arthroplasty.

Prevalence of infection in bilateral total hip arthroplasty: a comparison of single-stage 565 bilateral procedures performed with 1 or 2 sets of instruments.

Single-stage bilateral total hip arthroplasty can be performed with a completely new sterile setup for the second side or with the same instruments for both sides. The latter could theoretically lead to a higher prevalence of infection in the second side. We retrospectively determined the prevalence of deep infection during the first postoperative year in 271 consecutive patients operated on with different sterile setups (group 1) and 289 patients operated on with the same setup (group 2). There was one deep infection affecting the first side of a patient in group 1. In group 2, there were no deep infections (P is approximately 1.0) and one developed a superficial infection on the second side requiring readmission and intravenous antibiotics. Given the very low prevalence of deep infection of the first and second side (0.2% and 0%, respectively), it would be necessary to analyze more than 2,300 patients in each group to achieve statistical significance. Based on this experience, the use of the same set of instruments for the second side in the operating conditions described in this study appears safe.

Primary constrained condylar knee arthroplasty without stem extensions for the valgus knee.

UNLABELLED: Avoiding stem extensions in total knee arthroplasties may decrease operative time, prosthetic cost, and canal invasion at surgery. A constrained condylar knee implant without stem extensions also likely will be easier to revise and will eliminate the risk of end of stem pain. Our hypothesis was that a constrained condylar knee implant for primary severely deformed knees would show excellent midterm results with a low rate of aseptic loosening, even without diaphyseal-engaging stems. We retrospectively reviewed 70 consecutive primary constrained condylar knee implants without stem extensions from 1998 to 2001 in 61 patients with knees in 15 degrees valgus or greater. Forty-nine patients (55 knees) were followed up for 44.5 months (range, 2-6 years). Outcome was assessed using the Knee Society scoring system. Knee Society score and functional scores improved from 34 points and 40 points to 93 and 74 points, respectively. No radiographic loosening or wear was found. There were no peroneal nerve palsies, and no patients had flexion or medial instability. One patient was affected by chronic patellar dislocation. Constrained condylar knee implants in patients with severe valgus deformity resulted in pain relief and improved function, without substantial complications at midterm followup, without diaphyseal-engaging stem extensions. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series). See the Guidelines for Authors for a complete description of levels of evidence.

Late fatigue fracture of a modern cemented [corrected] cobalt chrome stem for total hip arthroplasty: a report of 10 cases.

We report 10 fatigue fractures of a modern, cemented, cobalt chromium alloy stem (Osteonics Omnifit) for total hip arthroplasty occurring between 1995 and 2004. The primary total hip arthroplasties had been performed between 1989 and 1996. The average age at the time of surgery was 54 years (range, 34-70 years), and the average body mass index was 29 (range, 20-38). The time in situ of the prosthesis at the time of fracture averaged 8 years (range, 4-12 years). Intermediate follow-up radiographs before the fracture were available in 7 cases, all of which demonstrated loss of calcar support. Scanning electron microscopy of the fracture surfaces in 3 of the components showed porosity near the initiation site. Metallography of polished and etched cross sections near the fracture surface revealed large grain size. In the presence of a spontaneous onset of thigh pain at intermediate follow-up in patients with this stem, particularly if associated with loss of calcar support, a fatigue fracture should be considered.

The role of constrained liners in total hip arthroplasty.

Recurrent instability after total hip replacement is a complex problem with extensive literature detailing multiple etiologies and solutions. It has been shown that the success of surgical treatment depends on the identification of the cause. Unfortunately, in certain situations, there may not be an optimal solution for dealing with the cause, or the cause may remain unidentified. In these cases, the success rate of surgical treatment of the unstable total hip replacement is only 40% to 50%. Constrained acetabular liners were developed to address the problem of recurrent instability by holding the femoral head captive within the socket. Before the use of constrained liners, there were no reliable solutions to dislocation arising from inadequate soft tissues, a deficient abductor mechanism, or neuromuscular disorders. We have used a constrained liner for these situations, with poor patient compliance and instability without a clear cause as relative indications for its use. Our experience with attaining joint stability using one type of constrained liner has resulted in a 97.6% success rate (83 of 85 hips) at 4.8 years, surpassing the outcomes achieved by other means. The intermediate followup after implantation of a constrained liner has not shown significant rates of component wear or loosening.

The use of a constrained acetabular component for recurrent dislocation.

The poor results of surgical treatment of chronic instability after total hip arthroplasty (THA) led to the development of a constrained acetabular component. In this study, 87 constrained THAs implanted for recurrent instability were reviewed retrospectively. Eighty-five hips were available for follow-up evaluation, with an average follow-up period of 58 months. These 85 hips were evaluated at a minimum of 3 years. Two recurrent dislocations were seen, caused by dissociation of the liner from the shell. Four acetabular components and 1 femoral component were revised. Overall, a 2.4% dislocation rate and an 8.2% revision rate were seen. The recurrent dislocation rate of 2.4% represents a significant improvement over other methods reported. Repeat dislocation was only seen in dissociation of cemented liners into well-fixed shells. We do not recommend this mode of fixation.

Complications in primary total hip arthroplasty: avoidance and management of dislocations.

Dislocation in primary total hip arthroplasty is common and problematic and is attributable to several factors, including previous hip surgery, neuromuscular disorders, cerebral dysfunction, psychosis, alcoholism, and female gender. Factors under the control of the surgeon include component orientation and restoration of soft-tissue tension. Prosthetic factors lowering the risk of dislocation include increasing the size of the prosthetic femoral head, keeping femoral neck circumference to a minimum, and optimizing the geometry of the acetabular component. Postoperatively, patients should be expected to comply with standard hip precautions. Treatment is with immediate closed reduction. Multiple dislocations can be treated by advancing the trochanter in the presence of inadequate soft-tissue tension, revision arthroplasty in the presence of malpositioned components, or the use of a constrained cup when intraoperative instability persists. Because the risk of redislocation is much higher than that for first-time dislocation, prevention is critical. An enhanced repair technique can be used to reconstruct the posterior soft-tissue sleeve during the posterior surgical approach. This technique has been successful in lowering the dislocation rate from 4% to 0% in a series of 395 consecutive patients.

Single-stage bilateral total hip arthroplasty.

The number of single-stage bilateral total hip arthroplasties done each year is increasing. The risk of postoperative complications in medically stable patients is acceptable; complications are approximately 1.3 times more frequent than with unilateral total hip arthroplasty. Although there are no absolute indications for a single-stage bilateral total hip arthroplasty, the procedure is usually contraindicated in patients with such comorbidities as heart disease, pulmonary insufficiency, or diabetes, and it is absolutely contraindicated in patients with a documented patent ductus arteriosus or septal defect. The primary postoperative concern is that the cardiopulmonary insult associated with two surgical wounds and surgeries can lead to an increase in thromboembolic events. The cost for single-stage bilateral total arthroplasty is less than that for a two-stage bilateral total hip arthroplasty, with savings predominantly due to reduced length of acute hospital stay. However, the decision to undergo single-stage bilateral total hip arthroplasty is one that must be made in concert with the patient.