Fourteen Year Follow-Up of Randomized Clinical Trials of Active Robotic-Assisted Total Hip Arthroplasty.

BACKGROUND: Active robotic total hip arthroplasty (THA) has been used clinically for over 20 years, but long-term results have never been studied. The aims of this study are to determine whether active robotic THA improves clinical outcomes and results in fewer revisions over a long-term follow-up. METHODS: Patients from 2 US Food and Drug Administration clinical trials (1994-1998 and 2001-2006) who had undergone THA using either an active robotic system or a traditional manual technique were examined to determine if any differences existed in radiographic analysis and patient pain and function using the University of California, Los Angeles; visual analog scale; Health Status Questionnaire (HSQ) pain; HSQ role physical; HSQ physical functioning; Harris pain scores; and the total Western Ontario and McMaster Universities Osteoarthritis Index scores at a mean follow-up of 14 years. RESULTS: The ROBODOC group had statistically significant higher HSQ pain and Harris pain scores and lower Western Ontario and McMaster Universities Osteoarthritis Index scores. There was no statistically significant difference in probability of a revision for wear between the groups (χ2 = 1.80; P = .179), and no revisions for loosening in either group. CONCLUSION: Prior studies have demonstrated improved implant fit and alignment with the use of this active robot system. This long-term study now shows no failures for stem loosening at a mean follow-up of 14 years and small but potentially important improvements in clinical outcomes in the robot group.

A perspective on robotic assistance for knee arthroplasty.

Knee arthroplasty is used to treat patients with degenerative joint disease of the knee to reduce pain and restore the function of the joint. Although patient outcomes are generally quite good, there are still a number of patients that are dissatisfied with their procedures. Aside from implant design which has largely become standard, surgical technique is one of the main factors that determine clinical results. Therefore, a lot of effort has gone into improving surgical technique including the use of computer-aided surgery. The latest generation of orthopedic surgical tools involves the use of robotics to enhance the surgeons' abilities to install implants more precisely and consistently. This review presents an evolution of robot-assisted surgical systems for knee replacement with an emphasis on the clinical results available in the literature. Ever since various robotic-assistance systems were developed and used clinically worldwide, studies have demonstrated that these systems are as safe as and more accurate than conventional methods of manual implantation. Robotic surgical assistance will likely result in improved surgical technique and improved clinical results.

Robotic-assisted TKA reduces postoperative alignment outliers and improves gap balance compared to conventional TKA.

BACKGROUND: Several studies have shown mechanical alignment influences the outcome of TKA. Robotic systems have been developed to improve the precision and accuracy of achieving component position and mechanical alignment. QUESTIONS/PURPOSES: We determined whether robotic-assisted implantation for TKA (1) improved clinical outcome; (2) improved mechanical axis alignment and implant inclination in the coronal and sagittal planes; (3) improved the balance (flexion and extension gaps); and (4) reduced complications, postoperative drainage, and operative time when compared to conventionally implanted TKA over an intermediate-term (minimum 3-year) followup period. METHODS: We prospectively randomized 100 patients who underwent unilateral TKA into one of two groups: 50 using a robotic-assisted procedure and 50 using conventional manual techniques. Outcome variables considered were postoperative ROM, WOMAC scores, Hospital for Special Surgery (HSS) knee scores, mechanical axis alignment, flexion/extension gap balance, complications, postoperative drainage, and operative time. Minimum followup was 41 months (mean, 65 months; range, 41-81 months). RESULTS: There were no differences in postoperative ROM, WOMAC scores, and HSS knee scores. The robotic-assisted group resulted in no mechanical axis outliers (> ± 3° from neutral) compared to 24% in the conventional group. There were fewer robotic-assisted knees where the flexion gap exceeded the extension gap by 2 mm. The robotic-assisted procedures took an average of 25 minutes longer than the conventional procedures but had less postoperative blood drainage. There were no differences in complications between groups. CONCLUSIONS: Robotic-assisted TKA appears to reduce the number of mechanical axis alignment outliers and improve the ability to achieve flexion-extension gap balance, without any differences in clinical scores or complications when compared to conventional manual techniques.

Surgical technique: a cup-in-cup technique to restore offset in severe protrusio acetabular defects.

BACKGROUND: Severe medial and/or superior defects encountered in revision THA are currently managed with jumbo (≥ 66 mm) acetabular components and modular augments, with reconstruction cages, or with the cup-cage technique. Preoperative planning can indicate when these techniques may not restore vertical and horizontal offset. Failure to restore offset can lead to impingement, leg length inequality, abductor weakness, and dislocation. SURGICAL TECHNIQUE: We developed a "cup-in-cup" technique in which a porous tantalum acetabular shell was impacted into supportive medial host bone. A second tantalum shell was then cemented in, and this shell's diameter could be selected based on preoperative planning to achieve restoration of horizontal and vertical offset. PATIENTS AND METHODS: We implanted porous tantalum hemispheric shells in seven patients undergoing eight revision THAs. The average age was 73 years at the time of the procedure. Preoperative defects per the classification of Paprosky et al. were three IIC, four IIIA, and one IIIB. All patients were followed clinically and radiographically for a minimum of 12 months (average, 28 months; range, 12-50 months). RESULTS: Abductor strength was either improved by one grade (four hips) or unchanged (four hips). Horizontal offset was increased an average of 10.5 mm (range, 8-16 mm), and vertical offset improved by an average of 18.4 mm (range, 10-29 mm). There was no evidence of loosening or migration at the time of final followup. CONCLUSIONS: At short-term followup, the early experience cautiously supports the use of this construct. Long-term followup and a larger patient experience will be required to determine the durability of this novel technique. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

In vivo assessment of total hip femoral head separation from the acetabular cup during 4 common daily activities.

In vivo video fluoroscopies of well-functioning total hip arthroplasties (THA) have shown that femoral head separation from the medial articular bearing surface occurs during gait. Other activities may cause the same phenomenon. We examined this while patients performed the following 4 activities of daily living: pivoting to each side in stance, shoe tying, sitting down, and standing up. Ten healthy patients (5 men, 5 women, average age 66 years) all 1 year or more after cementless THA performed for degenerative arthritis, with Harris Hip Scores ≥90, were studied. Each patient performed the activities of daily living while data was captured using video fluoroscopy. Based on previously reported criteria, femoral head separation (the femoral head sliding lateral to the acetabular liner) was determined to be reliably predicted if the distance between the femoral head and acetabular cup was ≥0.5. Results showed that the greatest femoral head separation occurred during the pivoting activity (mean, 1.53 mm; range, 0.00-3.34 mm; SD, 1.05 mm). The separation values identified during pivoting occurred at the extremes of internal or external rotation for all patients. The other 3 activities showed lower separation distances. Separation during the pivoting activity exceeded the reported separations occurring during walking. This finding was seen in a small group of patients, and the data should be interpreted with caution. We conclude from this study that the evaluation of gait alone may not be sufficient to accurately assess femoral head separation occurring during activities of daily living for healthy, active patients.

A painful metal-on-metal total hip arthroplasty: a diagnostic dilemma.

Infection, loosening, osteolysis, or other causes can lead to the development of pain about a previously well-functioning total hip arthroplasty. An inflammatory reaction unique to metal on metal arthroplasty can lead to a painful total hip. A synovial biopsy is needed to make this specific diagnosis, and included in the differential diagnosis is infection. The workup of infection includes obtaining a C-reactive protein and erythrocyte sedimentation rate. Elevations of both the C-reactive protein and erythrocyte sedimentation rate are felt to indicate possible infection. This case report describes both of these findings and the treatment rendered in a painful subluxing metal-on-metal total hip arthroplasty presenting with ongoing pain and a large effusion.

Femoral anteversion in THA and its lack of correlation with native acetabular anteversion.

Several studies support the concept that, for optimum range of motion in THA, the combined femoral and acetabular anteversion should be some constant or fall within some "safe zone." When using a cementless femoral component, the surgeon has little control of the anteversion of the component since it is dictated by native femoral anteversion. Given this constraint, we asked whether the surgeon should use the native anteversion of the acetabulum as a target for implant position in THA. Forty-six patients scheduled for primary THA underwent CT scanning and preoperative planning using a computer workstation. The native acetabular anteversion and the native femoral anteversion were measured. Prosthetic femoral anteversion was measured on the workstation by three-dimensional templating of a straight-stemmed tapered implant. The mean of the sum of the native acetabular anteversion and native femoral anteversion was 28.9 degrees; however, 17% varied by 10 degrees to 15 degrees and 11% by more than 15 degrees. The mean of native femoral anteversion and prosthetic femoral anteversion was 13.8 degrees (range, -6.1 degrees-32.7 degrees) and 22.5 degrees (range, 1 degrees-39 degrees), respectively. Based on our data, we believe the surgeon should not use the native acetabular anteversion as a target for positioning the acetabular component.

Accuracy of computer navigation for acetabular component placement in THA.

The accuracy and precision of any computer-aided surgical device is critical to its utility. We asked the following question: how accurate and precise are the values measured by an imageless computer navigation system as compared with those measured using postoperative CT scans? Twenty-five patients (26 hips) underwent primary THA using an imageless computer navigation system for placement of the acetabular component. Inclination and anteversion were measured in the operative coordinate system as defined by Murray. Accuracy, precision, and bias were computed, and Bland-Altman analysis was used to assess levels of agreement. The accuracy (mean +/- standard deviation of the absolute difference between computer-assisted navigation and CT) was 1.8 degrees +/- 1.2 degrees for inclination and 2.0 degrees +/- 2.0 degrees for anteversion. Precision was 3.4 degrees for inclination and 5.5 degrees for anteversion. Bias was 0.52 degrees for inclination and 0.35 degrees for anteversion. Limits of agreement were 4.26 degrees for inclination and 5.58 degrees for anteversion. An imageless computer navigation system can precisely determine acetabular cup position.

Robots in orthopaedic surgery: past, present, and future.

Robots are increasingly being developed for use in surgery to aid physicians in providing more precision, especially during procedures requiring fine movements that may be beyond the scope of the human hand. In addition, robots enable the surgeon to provide improved accuracy and reproducibility with the goal of better outcomes. To date, most robotic surgical systems are in the design and experimental stage. For robotic systems to gain widespread acceptance in surgery, they must first prove their value in clinical application and ease of use as well as provide a favorable cost-to-benefit ratio. I provide an overview of the history of robotics in orthopaedic surgery and a review of their current applications with some predictions of the future for this technology.

Time to revision of primary THA is shorter for specialists than nonspecialists.

We asked if there was a shorter time to revision, and different indications for revision, for primary total hip arthroplasties performed in the community by general orthopaedic surgeons (nonspecialists) as compared with primary total hip arthroplasties performed by specialists. We retrospectively reviewed 560 revision total hip arthroplasties performed in 486 patients from 1998 to 2006 at our tertiary referral center. One hundred ninety revisions from the community (nonspecialists cohort) and 109 revisions for which the primary arthroplasty was performed by the specialists (specialist cohort) at our center met the criteria for inclusion. These cohorts were analyzed by the time to revision and the indications for revision. Our findings were that the specialists had a shorter mean time to revision (8.3 years versus 10.1 years). This result may reflect a greater concern by specialists over the potential complications of osteolysis as reflected by the finding that the indication for surgery was more often aseptic loosening for the nonspecialists (57.9% versus 12.8%) and osteolysis for the specialists (61.5% versus 15.8%). As a result of possible selection bias in cases referred by the non-specialists, the indications for revision may not represent the modes of failure for arthroplasties performed by nonspecialists.

Early aseptic loosening of a modern acetabular component secondary to a change in manufacturing.

Cementless acetabular reconstruction with a hemispheric acetabular shell in primary total hip arthroplasty has shown reproducible results. Ingrowth of bone into a porous coating of beads, a titanium fiber mesh, or a hydroxylapatite-containing bioactive coating has been histologically documented. Early failures of ingrowth of an acetabular component have been reported using a threaded acetabular design. A series showing high early (<1 year) failure of ingrowth into a modern acetabular component has never before been reported. We report a series showing a 33% early loosening rate of the Sulzer Interop TM acetabular component (Sulzermedica, acquired by Zimmer, Warsaw, IN).