Posterior Mini-Incision With Primary Total Hip Arthroplasty: A Nine to Ten Year Follow Up Study.

The question has been raised as to whether small incision surgery will compromise long term results of total hip arthroplasty. We report nine to ten years' outcome with posterior mini-incision. Radiographs were measured for component position, polyethylene wear, fixation, and osteolysis. Sixty-two of the original 86 patients (76 of 100 hips) were alive and available for study with 17 patients deceased (with known results) and seven (8%) lost to follow-up. The result was rated as excellent in 70 of 75 remaining hips (93%). Eighty-nine of 93 hips (96%) with known results had the original implants. Radiographically, wear was a mean 0.015 ± 0.009 mm/year, and no hip had impending failure. There were four revisions, 2 for dislocation, 1 for fracture, and 1 for loose cup.

Precision of robotic guided instrumentation for acetabular component positioning.

Robotic computerized instrumentation that guides bone preparation and cup implantation in total hip arthroplasty was studied. In 38 patients (43 hips) intraoperative cup inclination and anteversion were validated by postoperative CT scans. Planned inclination was 39.9°±0.8° and with robotic instrumentation was 38. 0°±1.6° with no outliers of 5°; on the postoperative CT scan there were 5 outliers (12%). Planned anteversion was 21.2°±2.4° and intraoperatively was 20.7°±2.4° with no outlier of 5°; on the CT there were 7 outliers (16%). The center of rotation (COR) was superior by a mean 0.9±4.2 mm and medial by 2.7±2.9 mm. This robotic instrumentation achieved precision of inclination in 88%, anteversion in 84% and COR in 81.5%.

Tourniquet use during cementation only during total knee arthroplasty: a randomized trial.

BACKGROUND: Total knee arthroplasty with the use of a tourniquet during the entire operation has not been shown to improve the performance of the operation and may increase the risk of complications. QUESTIONS/PURPOSES: We asked whether the limited use of a tourniquet for cementation only would affect (1) surgical time; (2) postoperative pain and motion of the knee; (3) blood loss; or (4) complications such as risk of nerve injuries, quadriceps dysfunction, and drainage compared with use of a tourniquet throughout the procedure. METHODS: Seventy-one patients (79 knees) were randomized to either use of a tourniquet from the incision through cementation of the implants and deflated for closure (operative tourniquet group) or tourniquet use only during cementation (cementation tourniquet group). The initial study population was a minimum of 30 knees in each group as suggested for randomized studies by American Society for Testing and Materials standards; termination of the study was determined by power analysis performed after 40 knees in each group showed any statistical solution to our questions would require a minimum of 260 more cases. Patients were excluded who were considered in previous randomized studies as high risk for complications, which might be attributed to the tourniquet. RESULTS: There were no differences in terms of surgical time, pain scores, pain medicine requirements, range of motion, hemoglobin change, or total blood loss. One major complication (compartmental syndrome) occurred in a patient with tourniquet inflation until closure. No other complications were attributed to the use of a tourniquet. CONCLUSIONS: With the numbers available, our results suggest that there are no important clinical differences between patients who had a tourniquet inflated throughout the procedure compared with those who had it inflated only during cementation. Tourniquet inflation for cementation only provides the benefit of bloodless bone for fixation and may eliminate the risks associated with prolonged tourniquet use.

Preformed articulating knee spacers in 2-stage total knee revision arthroplasty: minimum 2-year follow-up.

Two-stage revision arthroplasty using articulating spacers for the treatment of infected total knee arthroplasty (TKA) is a successful management technique. Our purpose was to report our results using preformed, commercially available articulating spacers made of gentamicin-impregnated cement. Thirty-three patients with infected primary or revision TKAs were treated with these spacers using a 2-stage revision technique. In most cases, the spacers were modified intraoperatively by adding a stem of reinforced antibiotic-impregnated acrylic cement. Successful eradication was achieved in 30 of 33 cases at a minimum 2-year follow-up interval. Two patients required a second spacer before successful revision TKA. No spacer fractures or dislocations occurred in this series. No adverse soft tissue effects were noted from the use of this type of articulating spacer.

Hip offset in total hip arthroplasty: quantitative measurement with navigation.

BACKGROUND: Offset in THA correlates to abductor muscle function, wear, and impingement. Femoral offset after THA is not independent of the cup center of rotation (COR) so hip offset, a combination of femoral offset and change in hip COR, becomes the important measurement. QUESTIONS/PURPOSES: We therefore asked whether hip offset in arthritic hips would correlate with cup COR; whether offset could always be balanced within 6 mm of contralateral normal hips; and whether hip length could also be kept within 6 mm. METHODS: We compared hip offset of arthritic and contralateral normal hips on radiographs in 82 patients (82 hips) who had THA. We used computer navigation in all patients with the aim of reconstructing the hip offset and to compare hip offset change to the quantitative change of the hip COR. RESULTS: The preoperative radiographic change to equalize the offset ranged from -12 to +21 mm (mean, 1.5); postoperatively the change was 1.4 ± 6.4 mm and was within ± 6 mm in 78 of 82 hips. As COR displaced superiorly from 3 to 6+ mm the offset had to be substantially increased. Only with COR 0-3 mm superior and 0-5 mm medial was offset always within 5 mm. CONCLUSIONS: Hip offset reconstruction was directly related to the position of the hip COR, and navigation allowed quantitative control of offset and hip length.

Primary hip arthroplasty with 28-mm Metasul articulation.

This follow-up study reports on 69 patients at mean 13 years with total hip arthroplasty using 28-mm Metasul (Zimmer, Winterthur, Switzerland) metal-on-metal articulation. These results are not transferable to large-diameter head metal-on-metal articulations. Four new revisions, 3 for disassociation of the liner and 1 for mechanical loosening of the acetabulum, occurred since the previous report of mean 7.3 years. The prevalent cause of late revision is disassociation, which suggests a high frictional torque or impingement in these articulation surfaces. No revision was done for osteolysis. Overall, of the original 127 hips, 116 (91%) were known to have maintained their original components.

Quantification of pelvic tilt in total hip arthroplasty.

UNLABELLED: In THA, anterior or posterior tilt of the pelvis changes the position of the acetabular component on the coronal plane of the body as compared with its anatomic position in the pelvic bone. To understand the occurrence and clinical importance for patients with pelvic tilt on an operating room table in the lateral decubitus position, we studied 436 patients (477 hips) undergoing primary THA using an imageless computer navigation system that measured tilt. We determined the distribution and magnitude of pelvic tilt, especially tilt of 10 degrees or greater. The distribution of tilt had a range of 25 degrees posterior to 20 degrees anterior. Twenty-nine of 477 (6.1%) hips had zero tilt; 251 (52.6%) had tilt of 1 degrees to 5 degrees; 120 (25.2%) had tilt of 6 degrees to 9 degrees; and 77 (16.1%) had tilt of 10 degrees or greater. The conversion factor for acetabular anteversion has been determined by a mathematical formula by Lembeck et al. and was confirmed by us in practice. Measurement of pelvic tilt during the performance of THA will improve the accuracy of cup position, especially allowing anteversion to be measured on the coronal plane. LEVEL OF EVIDENCE: Level II, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.

Failure of the Durom Metasul acetabular component.

UNLABELLED: Large-diameter metal-on-metal articulations reportedly provide better stability and range of motion than smaller diameter bearings. We therefore asked whether a large-diameter (44- to 50-mm) metal-on-metal articulation (Durom) would eliminate dislocation and provide similar functional scores and clinical and radiographic failure rates as those with 28-mm articulation. We prospectively followed 181 patients (207 hips) who had a large-diameter articulation implanted between May 2006 and November 2007. We compared these patients with a historical control of 54 patients who had a small-diameter (28-mm Metasul) articulation. All patients had a Harris hip score and a self-assessment of outcome and radiographic followup. The minimum followup was 1 year (mean, 1.6 years; range, 1-2 years). During the followup period, we performed revisions on 29 patients (30 hips [15%]) with 21 of 29 (72%) having radiographic criteria of loosening. Thirteen retrieved cups and acetabular tissue were examined histologically. Twenty-eight of 151 unrevised patients had radiographic impending failure; 12 without revision had clinical failure. Eight patients (nine hips) had both clinical failure and impending radiographic failure. Cup inclination was 41.3 degrees +/- 5.4 degrees and anteversion was 20.2 degrees +/- 7 degrees. The revision rate and quality of clinical results were unacceptable as compared with our historical controls. We do not recommend use of the Durom implant. LEVEL OF EVIDENCE: Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Wear and range of motion of different femoral head sizes.

Femoral head sizes greater than 32 mm are more prevalent with current total hip arthroplasty. We hypothesized that linear wear rates of Durasul highly cross-linked polyethylene would not differ with different head sizes. We also compared the range of motion of the hip. Ninety-four consecutive arthroplasties in 84 patients were studied for a mean 3.6 +/- 0.7 years. There was no statistical difference in linear wear rates and annual or total penetration rates when 28-mm and 32-mm heads were compared to 38-mm and 44-mm heads. Volumetric wear was 12.4 mm(3)/y higher with bigger heads. Range of motion did not differ. Larger femoral head sizes show no evidence of an accelerated wear pattern when used with Durasul.

A validation model for measurement of acetabular component position.

There is no agreement on a standard approach to evaluating acetabular cup orientation, ideal target orientation, or a standardized measurement method for cup orientation in total hip arthroplasty. The purpose of this study was to investigate a simple method for validating measurements of acetabular orientation obtained using computer navigation and computed tomography scans. This study validated the imageless navigation system to be accurate with a precision of 1 degrees and a bias of 0.02 degrees for inclination and a precision of 1.3 degrees and a bias of 0 degrees for anteversion measurements. From this study, we propose that acetabular cup alignment is accurately assessed using computer navigation. We suggest acetabular orientation be reported in the radiographic plane (coronal plane), which incorporates pelvic tilt and therefore is more functional definition of cup position.

Combined anteversion technique for total hip arthroplasty.

UNLABELLED: Combined cup and stem anteversion in THA based on femoral anteversion has been suggested as a method to compensate for abnormal femoral anteversion. We investigated the combined anteversion technique using computer navigation. In 47 THAs, the surgeon first estimated the femoral broach anteversion and validated the position by computer navigation. The broach was then measured with navigation. The navigation screen was blocked while the surgeon estimated the anteversion of the broach. This provided two estimates of stem anteversion. The navigated stem anteversion was validated by postoperative CT scans. All cups were implanted using navigation alone. We determined precision (the reproducibility) and bias (how close the average test number is to the true value) of the stem position. Comparing the surgeon estimate to navigation anteversion, the precision of the surgeon was 16.8 degrees and bias was 0.2 degrees ; comparing the navigation of the stem to postoperative CT anteversion, the precision was 4.8 degrees and bias was 0.2 degrees , meaning navigation is accurate. Combined anteversion by postoperative CT scan was 37.6 degrees +/- 7 degrees (standard deviation) (range, 19 degrees -50 degrees ). The combined anteversion with computer navigation was within the safe zone of 25 degrees to 50 degrees for 45 of 47 (96%) hips. Femoral stem anteversion had a wide variability. LEVEL OF EVIDENCE: Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Imaging and navigation measurement of acetabular component position in THA.

There are six different definitions of acetabular position based on observed inclination and anteversion made in either the (1) anterior pelvic plane or (2) coronal planes and based on whether each of the observations made in one of these two planes is (1) anatomic, (2) operative, or (3) radiographic. Anteroposterior pelvic tilt is the angle between the anterior pelvic plane and the coronal plane of the body. The coronal plane is a functional plane and the anterior pelvic plane is an anatomic pelvic plane. A cup may be in the "safe zone" by one definition but may be out of the "safe zone" by another definition. We reviewed published studies, analyzed the difference in varying definitions, evaluated the influence of the anterior pelvic tilt, and provided methods to convert from one definition to another. We recommend all inclination and anteversion measurements be converted to the radiographic inclination and anteversion based on the coronal plane, which is equivalent to the inclination and anteversion on the anteroposterior pelvic radiograph.

Early pain relief and function after posterior minimally invasive and conventional total hip arthroplasty. A prospective, randomized, blinded study.

BACKGROUND: Few prospective randomized studies have demonstrated benefits of minimally invasive total hip arthroplasty when compared with conventional total hip arthroplasty. We hypothesized that patients treated with a posterior mini-incision would have better results than those treated with a posterior long incision with regard to the achievement of established goals for pain relief and functional recovery permitting hospital discharge by the second postoperative day. METHODS: Sixty of 231 eligible patients were randomized (with thirty in each group) to have a total hip arthroplasty performed through either a posterior mini-incision (10 +/- 2 cm) or a traditional long incision (20 +/- 2 cm). After completion of the total hip arthroplasty, the mini-incision group underwent extension of the skin incision to 20 cm. Patients were evaluated on the basis of self-determined pain scores, requirements for pain medicine, need for assistive gait devices, and time until discharge. Gait analysis provided objective functional assessment. RESULTS: The average hospital stay was 63.2 +/- 13.3 hours in the mini-incision group and 73.6 +/- 23.5 hours in the long-incision group (p = 0.04). More patients with a mini-incision were discharged by the second postoperative day (p = 0.003) and more were using just a single assistive device at the time of discharge (p = 0.005). As scored on a verbal analog scale of 0 to 10 points, patients with a mini-incision had less pain on each postoperative day and the pain score remained significantly lower at the time of discharge (mean, 2.2 +/- 1.0 points compared with 3.1 +/- 0.9 points in the long-incision group; p = 0.002). After hospital discharge, there were no clinical differences in pain or function between the two groups of patients. CONCLUSIONS: Compared with conventional total hip arthroplasty performed through a posterior incision, posterior minimally invasive total hip arthroplasty resulted in better early pain control, earlier discharge to home, and less use of assistive devices. Subsequent evaluations at six weeks and three months showed equivalency between the clinical results in the two groups. LEVEL OF EVIDENCE: Therapeutic Level I.

Clinical performance of a Durasul highly cross-linked polyethylene acetabular liner for total hip arthroplasty at five years.

BACKGROUND: Highly cross-linked polyethylene is currently the most common articulation surface used for total hip arthroplasty. The hypothesis of the present study was that the Durasul highly cross-linked polyethylene acetabular liner would have less wear at five years than would a conventional polyethylene liner used in association with the same total hip replacement system. METHODS: Forty-three consecutive patients (fifty hips) underwent total hip replacement with an uncemented titanium porous-coated metal cup and a Durasul liner that was mated with a 28-mm cobalt-chromium femoral head. Thirty-one patients (thirty-seven hips) were followed for at least five years. Thirty-five other patients (thirty-seven hips) underwent total hip arthroplasty with the same system but with a conventional polyethylene liner, and these patients also were followed for five years. Clinical assessment was performed with use of the Harris hip score and a patient self-assessment examination. Radiographic analysis included measurements of acetabular component position, fixation, and osteolysis. Femoral head penetration of the Durasul liners was compared with that of the conventional liners. RESULTS: The clinical results as determined on the basis of Harris hip scores and patient self-assessment examinations did not differ between the Durasul group and the control group. The mean bedding-in penetration was 0.054 +/- 0.07 mm for the Durasul group and 0.059 +/- 0.154 mm for the control group. The subsequent penetration, with elimination of the bedding-in wear, resulted in a linear wear rate of 0.029 +/- 0.02 mm per year for the Durasul group, compared with 0.065 +/- 0.03 mm per year for the control group (p < 0.005). The annual penetration at one and five years was 0.074 mm and 0.011 mm, respectively, for the Durasul group, compared with 0.151 mm and 0.04 mm, respectively, for the control group. CONCLUSIONS: While the qualitative wear pattern of the highly cross-linked polyethylene liner was the same as that of the conventional polyethylene liner, the annual linear wear rate was 45% of that seen with the conventional polyethylene liner. Therefore, we believe that these early data support the continued use of this highly cross-linked polyethylene liner for total hip arthroplasty.

Development of imageless computer navigation for acetabular component position in total hip replacement.

The purpose of this study was to develop an imageless (without preoperative computerized tomography (CT) scans or intraoperative fluoroscopy) computer navigation system for total hip replacement. One-hundred and ninety-five hips were operated with imageless computer navigation. Eighty-five hips were operated prior to obtaining precise results, with precision refined in the subsequent 110 hips. Computer accuracy for cup-adjusted anteversion was achieved in 100% of the final 40 hips, and for adjusted inclination in 96.6%. The factors necessary for accurate measurements are mechanical stability of the tools with the light-emitting diodes, adjusted computer anteversion and inclination for the tilt of the pelvis (tilt in the AP plane), and check-and-balance techniques for confirmation of measurements of tilt, anteversion and inclination.

Cementless hemispheric porous-coated sockets implanted with press-fit technique without screws: average ten-year follow-up.

BACKGROUND: Press-fit implantation of a porous-coated hemispheric acetabular component without screws is an option for primary total hip replacement. The purpose of the present study was to evaluate the results of this technique after an average duration of follow-up of ten years to determine if there was any loss of fixation or increase in osteolysis over time. METHODS: From June 1988 to November 1990, 132 primary total hip replacements were performed with a porous-coated socket that was implanted with use of a press-fit technique. Twenty-two hips were excluded because the patient had died or had been lost to follow-up, leaving 110 hips (103 patients) available for inclusion in the study after an average duration of follow-up of 10.2 +/- 1.0 years. The average age of the patients at the time of operation was 60.7 years (range, 23.7 to 86.2 years). Radiographs were evaluated with regard to initial gaps, radiolucent lines, migration, polyethylene wear, and osteolysis. Kaplan-Meier survivorship analysis was performed to calculate the rate of survival of the acetabular component. RESULTS: One hip (0.9%) had revision of the socket because of aseptic loosening, and four hips (4%) had revision of a stable socket. With the numbers available, the presence of gaps on the initial postoperative radiographs was not associated with the occurrence of radiolucent lines (p = 0.039). Pelvic osteolysis was seen in four hips, with an average time to radiographic appearance of six years. Increased wear was directly related to an abduction angle of >40 degrees. The twelve-year survival rate was 99.1% with revision because of failure of fixation of the metal shell as the end point, 95.3% with revision for any reason as the end point, and 79.6% with exchange of the liner as the end point. CONCLUSIONS: The fixation of this press-fit socket did not deteriorate over time and was associated with a low rate of osteolysis. The most common reasons for reoperation were wear and dissociation of the polyethylene insert.

Comparison of proximal porous-coated and grit-blasted surfaces of hydroxyapatite-coated stems.

BACKGROUND: It remains controversial whether a proximal porous coating is superior to a grit-blasted surface with regard to providing femoral stem fixation in total hip arthroplasty. We examined the hypothesis that a proximal porous coating would provide better fixation than would a fully grit-blasted surface of otherwise identical proximally hydroxyapatite-coated stems. METHODS: In a prospective study, seventeen patients (thirty-four hips) underwent bilateral sequential total hip replacement with the Anatomic Porous Replacement at the same operation. A proximally porous-coated femoral stem was implanted on one side, and a stem of the same design but with a proximal grit-blasted surface was implanted in the contralateral hip. A proximal hydroxyapatite coating was applied to the metallic substrate of both stems. The patients were followed for a mean 2.5 years and then were assessed radiographically and clinically with the Harris hip score. RESULTS: With the numbers available, no significant clinical or radiographic differences were found between the two cohorts. Thirty of the thirty-four hips had an excellent result, two were rated good, and two were rated fair. All hips had stable osseous fixation of the stem radiographically. The two types of stems were associated with the same pattern of adaptive bone-remodeling. CONCLUSIONS: In the first two years following total hip arthroplasty, hydroxyapatite-coated proximally porous-coated femoral stems do not provide fixation that is superior to that provided by hydroxyapatite-coated grit-blasted stems. LEVEL OF EVIDENCE: Therapeutic study, Level II-1 (prospective cohort study). See Instructions to Authors for a complete description of levels of evidence.

Predictability of Acetabular Component Angular Change with Postural Shift from Standing to Sitting Position.

BACKGROUND: The angles of the acetabular component of a total hip replacement change with body postural changes, and this change can affect stability and wear. We sought to correlate the intraoperative angles of inclination and anteversion of the cup with the changes in these angles when patients moved from standing to sitting and determine if these changes were predictable. METHODS: Eighty-five patients (eighty-five hips) had sagittal (lateral) spinopelvic radiographs made while they were standing and while they were sitting before and after undergoing total hip replacement. The spinosacral tilt and the pelvic tilt were measured on these radiographs. The angles of acetabular inclination and anteversion achieved at surgery changed during sitting. Each patient was classified according to the stiffness of the spine/pelvis as measured by the change in posterior sacral or pelvic tilt between the standing and sitting positions. The magnitude of change of the sagittal cup position (termed ante-inclination) was correlated to the stiffness classification of the pelvis. An experimental phantom model reproduced possible combinations of intraoperative inclination and anteversion and correlated them to sagittal ante-inclination according to pelvic tilt. RESULTS: The pelves with normal stiffness tilted posteriorly 20° to 35° with the postural change from standing to sitting. Ante-inclination of the acetabular cup averaged 29.6° ± 8.4° (95% confidence interval [CI] = 13.1° to 46°) with standing and 54.6° ± 10.2° (95% CI = 44.4° to 64.8°) with sitting. The stiff pelves had a mean of 4° less tilt than those with normal stiffness and 13° less than the hypermobile pelves with the postoperative sitting position. The phantom model showed ante-inclination could be predicted by measuring the preoperative degrees of change in sacral/pelvic tilt from standing to sitting. CONCLUSIONS: Ante-inclination during sitting results in a more vertical acetabular cup, which can result in hip instability, especially drop-out dislocation, and edge-loading wear. Patients with supine coronal cup inclination of ≥50° and anteversion of ≥25° and those with a hypermobile pelvis are at risk. It is the pelvic spatial position during postural change that creates the postoperative consequences of the surgical cup placement.

A comparison of surgeon estimation and computed tomographic measurement of femoral component anteversion in cementless total hip arthroplasty.

BACKGROUND: The intraoperative estimation of the anteversion of the femoral component of a total hip arthroplasty is generally made by the surgeon's visual assessment of the stem position relative to the condylar plane of the femur. Although the generally accepted range of intended anteversion is between 10 degrees and 20 degrees, we suspected that achieving this range of anteversion consistently during cementless implantation of the femoral component was more difficult than previously thought. METHODS: We prospectively evaluated the accuracy of femoral component anteversion in 109 consecutive total hip arthroplasties (ninety-nine patients), in which we implanted the femoral component without cement. In all hips, we measured femoral stem anteversion postoperatively with three-dimensional computed tomography reconstruction of the femur, using both the distal femoral epicondyles and the posterior femoral condyles to determine the femoral diaphyseal plane. The bias and precision of the measurements were calculated. RESULTS: The surgeon's estimate of femoral stem anteversion was a mean (and standard deviation) of 9.6 degrees +/- 7.2 degrees (range, -8 degrees to 28 degrees). The anteversion of the stem measured by computed tomography was a mean of 10.2 degrees +/- 7.5 degrees (range, -8.6 degrees to 27.1 degrees) (p = 0.324). The correlation coefficient between the surgeon's estimate and the computed tomographic measurement was 0.688; the intraclass coefficient was 0.801. Anteversion measured by computed tomography found that forty-nine stems (45%) were between 10 degrees and 20 degrees of anteversion; forty-three stems (39%) were between 0 degree and 9 degrees of femoral anteversion; eight stems (7%) were in anteversion of >20 degrees; and nine stems (8%) were in retroversion. CONCLUSIONS: The surgeon's estimation of the anteversion of the cementless femoral stem has poor precision and is often not within the intended range of 10 degrees to 20 degrees of anteversion. The implications of this finding increase the importance of achieving a safe range of motion by evaluating the combined anteversion of the stem and the cup.

The influence of acetabular component position on wear in total hip arthroplasty.

Our experience has implicated cup inclination as an important factor in wear, whereas others have suggested that the hip center of rotation (COR) must be closely reestablished to reduce wear. We conducted a retrospective study to determine the relative importance of these 2 factors. One hundred thirty-nine total hip arthroplasties were studied after a mean follow-up of 9.2 years (range, 6-3 years). Forty-nine of 139 operated hips had a contralateral normal hip, which allowed the most accurate measurement of the influence of change in the COR. Wear was related to the inclination of the cup but not to a change in the COR. Secondarily, wear was less with a ceramic-polyethylene polyarticular surface than with metal-polyethylene. The importance of this data is related to cup implantation techniques. The hip COR can be moved superiorly and/or medially to permit cup inclination below 45 degrees with correct cup coverage.