Several studies have reported that the transverse acetabular ligament (TAL) can be used to orient the acetabular component during total hip arthroplasty and that it can be identified in nearly all patients.
We attempted to determine how often the TAL could be identified during primary THA and its accuracy as a guide for acetabular component positioning.
In a prospective series of 63 patients (64 hips) undergoing primary THA, two surgeons attempted to identify the TAL and, if it was found, to use it for acetabular component orientation. Patients in whom the TAL was identified served as the study group and the ligament was used for cup orientation in those patients; the remaining patients in whom the ligament could not be identified served as a control group and had free-hand cup positioning. Anteversion was determined by radiographic measurement from true lateral views.
The TAL was identified in only 30 hips (47%) and was more likely to be found in patients who did not have inferior acetabular osteophytes. Acetabular position was not improved using this ligament for reference.
The TAL could not be routinely identified at surgery and when used for cup orientation it was no more accurate for cup positioning than free-hand technique.
The transverse acetabulum ligament (TAL) has been used as an intraoperative anatomical landmark to position the acetabulum cup in total hip arthroplasty (THA). However, the validity of the use of TAL has not been clarified. The purpose of this study was to examine the orientation of the cup component aligned with the TAL in cadaveric study. The 31 hips in 25 whole-body embalmed cadavers were examined. The donors were 12 men and 13 women. Simulated THA procedure using image-free navigation system was performed and a trial cup with a diameter of approximately 2 mm less than the size of the acetabulum were inserted and snugly fitted on the TAL through the posterior wall of acetabulum. The orientation of the cup component was measured using an image-free THA navigation system. The measured radiographic anteversion and inclination angles averaged 18.2±7.2° (range: 2.0–33.2°) and 43.5±4.2° (range: 33.1–51.0°) respectively. Based on the Lewinnek's safe zone criteria, 26 hips (80.6%) were judged to be within the. Moreover, in the analysis of the gender difference of TAL angles, the average anteversion angle was shown to be significant larger in female than male population. The TAL can be effectively used an intraoperative landmark to align the acetabulum component helping reduce the risk of dislocation after surgery. In the intraoperative judgment, a gender difference in the alignment of the TAL should be taken into consideration.
transverse acetabulum ligament; THA; cup orientation; cadaveric study.
Although surgical navigation reduces the rate of malpositioned acetabular cups in total hip arthroplasty (THA), its use has not been widely adopted. As a result of our perceived need for simple and efficient methods of navigation, we developed a mechanical navigation device for acetabular cup orientation.
We assessed accuracy of cup orientation (mean error of cup inclination and anteversion) of a novel mechanical navigation device, percentage of outliers, length of operation, and compared the results with a series of CT-based computer-assisted THAs.
Cup orientation of 70 THAs performed using the mechanical navigation device was compared with a historical control group of 146 THAs performed using CT-based computer navigation. Postoperative cup orientation was measured using a validated two-dimensional/three-dimensional matching method. An outlier was defined outside a range of ± 10° from the planned inclination and/or anteversion.
Using the mechanical navigation device, we observed a decrease in the errors of inclination (1.3° ± 3.4° [range, −6.6° to 8.2°] versus 3.5° ± 4.2° [−12.7° to 6.9°]), errors of anteversion (1.0° ± 4.1° [−8.8° to 9.5°] versus 3.0° ± 5.8° [−11.8° to 19.6°]), percentages of outliers (0% versus 9.6%), and length of operation (112 ± 22 [78–184] minutes versus 132 ± 18 [90–197] minutes) compared with CT-based navigation.
Compared with CT-based surgical navigation, navigation of acetabular cup orientation using a mechanical device can be performed in less time, lower mean errors, and minimal equipment.
Increasingly, acetabular retroversion is recognized in patients undergoing hip arthroplasty. Although prosthetic component positioning is not determined solely by native acetabular anatomy, acetabular retroversion presents a dilemma for component positioning if the surgeon implants the device in the anatomic position.
We asked (1) whether there is a difference in ROM between surface replacement arthroplasty (SRA) and THA in the retroverted acetabulum, and (2) does increased femoral anteversion improve ROM in the retroverted acetabulum?
Using a motion analysis tracking system, we determined the ROM of eight cadaveric hips and then created virtual CT-reconstructed bone models of each specimen. ROM was determined with THA and SRA systems virtually implanted with (1) the acetabular component placed in 45° abduction and matching the acetabular anteversion (average 23° ± 4°); (2) virtually retroverting the bony acetabulum 10°; and (3) after anteverting the THA femoral stem 10°.
SRA resulted in ROM deficiencies in four of six maneuvers, averaging 25% to 29% in the normal and retroverted acetabular positions. THA restored ROM in all six positions in the normal acetabulum and in four of the six retroverted acetabula. The two deficient positions averaged 5% deficiency. THA with increased femoral stem anteversion restored ROM in five positions and showed only a 2% deficiency in the sixth position. Compared with the intact hip, ROM deficits were seen after SRA in the normal and retroverted acetabular positions and to a lesser extent for THA which can be improved with increased femoral stem anteversion.
Poor ROM may result after SRA if acetabular retroversion is present.
Total hip arthroplasty restores lost mobility to patients suffering from osteoarthritis and acute trauma. In recent years, navigated surgery has been used to control prosthetic component placement. Furthermore, there has been increasing research on what constitutes correct placement. This has resulted in the definition of a safe-zone for acetabular cup orientation. However, there is less definition with regard to femoral anteversion and how it should be measured. This study assesses the validity of the femoral anteversion measurement method used in imageless navigation, with particular attention to how the neutral rotation of the femur is defined. CT and gait analysis methodologies are used to validate the reference which defines this neutral rotation, i.e., the ankle epicondyle piriformis (AEP) plane. The findings of this study indicate that the posterior condylar axis is a reliable reference for defining the neutral rotation of the femur. In imageless navigation, when these landmarks are not accessible, the AEP plane provides a useful surrogate to the condylar axis, providing a reliable baseline for femoral anteversion measurement.
Total hip arthroplasty; biomechanics; computer-assisted navigation; computed tomography; femoral anteversion; gait analysis
Minimally invasive total hip arthroplasty (MITHA) remains considerably controversial. Limited visibility and prosthesis malposition increase the risk of post-surgical complications compared to those of the traditional method.
A meta-analysis was undertaken of all published databases up to May 2011. The studies were divided into four subgroups according to the surgical approach taken. The radiological outcomes and complications of minimally invasive surgery were compared to traditional total hip arthroplasty (TTHA) using risk ratio, mean difference, and standardized mean difference statistics.
In five studies involving the posterolateral approach, no significant differences were found between the MITHA groups and the TTHA groups in the acetabular cup abduction angle (p = 0.41), acetabular anteversion (p = 0.96), and femoral prosthesis position (p = 0.83). However, the femoral offset was significantly increased (WMD = 3.00; 95% CI, 0.40–5.60; p = 0.02). Additionally, there were no significant differences among the complications in both the groups (dislocations, nerve injury, infection, deep vein thrombosis, proximal femoral fracture) and revision rate (p>0.05). In three studies involving the posterior approach, there were no significant differences in radiological outcomes or all other complications between MITHA or TTHA groups (p>0.05). Three studies involved anterolateral approach, while 2 studies used the lateral approach. However, the information from imaging and complications was not adequate for statistical analysis.
Posterior MITHA seems to be a safe surgical procedure, without the increased risk of post-operative complication rates and component malposition rates. The posterolateral approach THA may lead to increased femoral offset. The current data are not enough to reach a positive conclusion that lateral and anterolateral approaches will result in increased risks of adverse effects and complications at the prosthesis site.
In a prospective manner to evaluate the range of acetabular component anteversion actually achieved by the use of a cup positioner in cementless revision and primary THA.
We operated 71 patients with cementless primary THA, and 26 patients with cementless acetabular revision surgery. We aimed to obtain cup anteversion of 10 to 30° with an impactor-positioner. In all cases we used elevated liners and a ceramic head with diameter 28. At 3 months postoperatively the component versions were measured using CT with the patient in supine position.
The acetabular component version in the primary hips ranged from 28° of retroversion to 42° of anteversion with a mean of 17.4 ± 14.0°, while the cup version in the revision hips ranged from 4° of retroversion to 32° of anteversion with a mean of 15.0 ± 9.6°(p=0.427). The anteversion of 40 (56%) of the primary acetabular components were within the target zone of 10 to 30°, while 19 (27%) were below the target zone and and 12 (17%) were above the target range. The anteversion of 19 (73%) of the revision acetabular components were within the target zone, while 6 (23%) were below the target zone and 1 (4%) were above the target range. The differences in distribution between the primary and revision operations were not significant (p=0.183).
The intraoperative estimation of acetabular anteversion by free hand technique in many cases was not within the intended range of 10 to 30° in either primary or revision THA and with no differences between the two series
Anteversion; acetabular component; arthroplasty; CT; revision.
At present, the indications for femoral derotational osteotomy remain controversial due to the inconsistent findings in femoral neck anteversion in developmental dysplasia of the hip (DDH). Moreover, combined anteversion is not assessed in unilateral DDH using three dimensional-CT. Therefore, the purposes of our study were to observe whether the femoral neck anteversion (FA), acetabular anteversion (AA) and combined anteversion (CA) on the dislocated hips were universally presented in unilateral DDH according to the classification system of Tönnis.
Sixty-two patients with unilateral dislocation of hip were involved in the study, including 54 females and eight males with a mean age of 21.63 months (range, 18–48 months). The FA, AA and CA were measured and compared between the dislocated hips and the unaffected hips.
Although no significant difference was observed in FA between the dislocated hips and the unaffected hips (P = 0.067, 0.132, respectively) in Tönnis II and III type, FA was obviously increased on the dislocated hips compared with the unaffected hips in Tönnis IV type. Increased AA on the dislocated hips was a universal finding in Tönnis II, III and IV types. Meanwhile, a wide safe range of CA from 24° to 62° was demonstrated on the unaffected hips.
Femoral derotational osteotomy seems not to be necessary in Tönnis II and III types in unilateral DDH. Femoral derotational osteotomy should be considered in DDH, especially in Tönnis IV type, if the CA is still above 62° and the hip joints present instability in operation after abnormal acetabular anteversion, acetabular index and acetabular coverage of the femoral head are recovered to normal range through pelvic osteotomy.
The size of the femoral head and acetabular anteversion are crucial for stability in total hip replacements. This study examined the effects of head diameter and acetabular anteversion on the posterior instability after total hip replacement in an in vivo setting. The acetabular shell was inserted at 0–20° of anteversion at five degree intervals. By using different head sizes (28 mm, 32 mm, 36 mm), the degrees of dislocation were recorded by computer navigation. The 36-mm group consistently showed better stability compared with the 32- and 28-mm groups, regardless of the degree of cup anteversion. Within each group of head size, the hip was significantly more stable when the cup anteversion increased from 0° to 10°. The difference became insignificant when it increased from 15° to 20°.
Hip resurfacing is femoral bone preserving, but there is controversy regarding the amount of bone removed at the acetabular side. We therefore compared the implanted acetabular cup sizes in primary THAs between two resurfacing devices and a conventional press-fit cup using a series of 2134 THAs (Allofit® cup 1643 hips, Durom® Hip Resurfacing 249 hips, and Birmingham Hip® Resurfacing 242 hips). The effects of patient demographics and cup position in the horizontal plane also were assessed. After controlling for gender, patients were matched for height, weight, body mass index, and age. The mean size for Allofit® cups was smaller than the sizes for Durom® and Birmingham Hip® Resurfacing cups in women (49.9 mm, 51.6 mm, 52.3 mm, respectively) and men (55.1 mm, 56.7 mm, 57.8 mm; respectively). Although patient height was associated with the implanted cup size, the cup position in the horizontal plane had no effect on the size used. Larger cups were used with hip resurfacing than for THA with a conventional press-fit cup. However, additional studies are needed to determine whether these small differences have any clinical implications in the long term. The association of cup size and patient height should be considered in future studies comparing component sizes among different implants.
Level of Evidence: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
Optimal positioning of acetabular components is crucial for maintaining stability of THA. Postoperative assessment of acetabular anteversion is a vital but difficult task. Various methods have been devised with good results for measuring anteversion on plain radiographs but these methods are either too complicated or require special objects like scientific calculators, special protectors, tables, etc. A new simplified method of measuring anteversion on plain radiographs was created based on basic geometry.
Anteversion of acetabular components was estimated on computer generated images of the acetabular cup by our method and compared with two previously established methods of Liaw and Pradhan. Measurement was done at 400 different positions of acetabular cup and compared with actual values. Another analysis was done after adding the femoral head to the acetabular component, thus obscuring some of the acetabular rim.
Mean and standard deviation of error for our method was 0.77° ± 0.75° as compared to 0.93° ± 0.86° and 0.72° ± 0.68° for the methods of Liaw and Pardhan, respectively, with no significant differences from actual values. Maximal errors for our method, Liaw’s and Pradhan’s method were 3°, 4°, and 2.91°, respectively. On analysis, after the adding femoral head, there was a significant error of measurement with Liaw’s method, while our method as well as Pardhan’s remained accurate. All methods showed high inter- and intraobserver reliability.
Our new simplified method of measuring acetabular anteversion on plain radiographs is acceptable in comparision to other established methods and requires only routinely used goniometer and calliper.
There is limited morphological data on the sex differences between the commonly used pelvic parameters. This study analysed the CT scans of 100 consecutive Caucasian patients, 61 males and 39 females, undergoing hip resurfacing arthroplasty surgery for hip osteoarthritis in one institution.
There were no sex differences in femoral torsion/anteversion, femoral neck angle and acetabular inclination. Males had a mean femoral torsion/anteversion of 8 degrees (range -5 to 26 degrees), a mean femoral neck angle of 129 degrees (range 119 to 138 degrees) and a mean acetabular inclination of 55 degrees (range 40 to 86 degrees). Females had a mean femoral torsion/anteversion of 9 degrees (range -2 to 31 degrees), a mean femoral neck angle of 128 degrees (range 121 to 138) and a mean acetabular inclination of 57 degrees (range 44 to 80 degrees). Females had a significantly greater acetabular version of 23 degrees (range 10 to 53) compared with 18 degrees in males (range 7 to 46 degrees (p = 0.02) and males had a significantly greater femoral offset of 55 mm (range 42 to 68 mm) compared with 48 mm (range 37 to 57 mm) in females (p = 0.00). There were no significant differences between measurements taken from each patient's right and left hips.
These findings may be useful for the future design and the implantation of hip arthroplasty components.
Several studies have demonstrated a correlation between the acetabular cup position and the risk of dislocation, wear and range of motion after total hip arthroplasty. The present study was designed to evaluate the accuracy of the surgeon’s estimated position of the cup after freehand placement in total hip replacement. Peroperative estimated abduction and anteversion of 200 acetabular components (placed by three orthopaedic surgeons and nine residents) were compared with measured outcomes (according to Pradhan) on postoperative radiographs. Cups were placed in 49.7° (SD 6.7) of abduction and 16.0° (SD 8.1) of anteversion. Estimation of placement was 46.3° (SD 4.3) of abduction and 14.6° (SD 5.9) of anteversion. Of more interest is the fact that for the orthopaedic surgeons the mean inaccuracy of estimation was 4.1° (SD 3.9) for abduction and 5.2° (SD 4.5) for anteversion and for their residents this was respectively, 6.3° (SD 4.6) and 5.7° (SD 5.0). Significant differences were found between orthopaedic surgeons and residents for inaccuracy of estimation for abduction, not for anteversion. Body mass index, sex, (un)cemented fixation and surgical approach (anterolateral or posterolateral) were not significant factors. Based upon the inaccuracy of estimation, the group’s chance on future cup placement within Lewinnek’s safe zone (5–25° anteversion and 30–50° abduction) is 82.7 and 85.2% for anteversion and abduction separately. When both parameters are combined, the chance of accurate placement is only 70.5%. The chance of placement of the acetabular component within 5° of an intended position, for both abduction and anteversion is 21.5% this percentage decreases to just 2.9% when the tolerated error is 1°. There is a tendency to underestimate both abduction and anteversion. Orthopaedic surgeons are superior to their residents in estimating abduction of the acetabular component. The results of this study indicate that freehand placement of the acetabular component is not a reliable method.
Freehand cup positioning; Accuracy; Total hip arthroplasty
Short-stem hip arthroplasty preserves femoral bone stock which includes the femoral neck. This implies that the stem has to follow the anatomy of the femoral neck. Therefore, it has been questioned whether biomechanical reconstruction of the hip can be safely achieved with SHA.
Biomechanical reconstruction of the hip was analysed for 50 modular short-stem hip arthroplasties (SHA) and compared to 50 conventional total hip arthroplasties (THA). Biomechanical parameters were analysed on pre- and postoperative pelvic overviews and compared to those of the contralateral side.
The position of the acetabular cup (vertical and horizontal hip centre of rotation) changed slightly and was comparable for both groups. Horizontal femoral offset increased more in SHA (6.2 mm) than in THA (2.0 mm). Compared to the contralateral side it was significantly greater after SHA (+3.6 mm) but almost balanced after THA (−0.2 mm). Limb length increased with both procedures (8.0 mm SHA, 9.1 mm THA), but showed a significantly greater discrepancy after SHA (3.3 mm) as compared to THA (1.3 mm). According to the different implant designs, the stem-shaft axis showed a wider varus-valgus range for SHA (6.2° varus to 8.8° valgus) than for THA (2.6° varus to 3.3° valgus).
Horizontal femoral offset increased more with modular SHA than with conventional THA, but was within a beneficial range. Restoration of limb length appears more difficult in SHA and has a tendency to prolong limb length, which is probably related to the higher femoral resection level. This should be taken into consideration when considering SHA for a patient as well as during implantation.
Appraisal of the orientation of implants in THA dislocations currently is based on imaging done with the patient in the supine position. However, dislocation occurs in standing or sitting positions. Whether measured anteversion differs in images projected in the position of dislocation is unclear.
We compared measured acetabular cup orientations on axial CT scans taken with the patient in a supine position with those from CT sections at angles to the sacral slope reflecting standing and sitting positions.
We retrospectively reviewed the radiographs of 328 asymptomatic patients who had THAs. Anatomic acetabular anteversion (AAA) was measured from the plain CT scan (supine position, axial CT sections). The AAA also was measured on reformatted CT scans in which the orientation was adjusted individually to the sacral slope on lateral radiographs with patients in the standing and sitting positions.
The mean/(SD) AAA changed from 24.2° (6.9°) in the supine position to 31.7° (5.6°) and 38.8° (5.4°) in simulated standing and sitting positions, respectively. The supine AAA correlated with the standing AAA (r = 0.857) but not with the sitting AAA (r = 0.484).
These data suggest measurement of the AAA on a plain CT scan used in current practice is biased. In patients with recurrent posterior dislocation from a sitting position, accounting for the functional variations in measurement of the position of the acetabular cup provides more relevant information regarding component positioning.
The anatomic femoral component and Harris-Galante porous II (HGPII) cup were developed to provide more reliable bone ingrowth. We performed 20 cementless total hip arthroplasties (THAs) with anatomic stem/HGPII cup with 22-mm head in 14 consecutive patients, and evaluated the clinical and radiological results for a mean follow-up of 12.8 years. The all-anatomically designed stem provided excellent clinical and radiographic results. Four acetabular components underwent revision: three for fracture of the locking mechanism and wear of the polyethylene liner and one for the locking mechanism failure with dislocation of the HGPII cup. The abduction angles of the four revised acetabular components were apparently higher. The survivorship 13 years after surgery was 78%. Our findings show good long-term results using the anatomic femoral component, while the HGPII cup combined with 22-mm head seems to have poor durability due to locking mechanism failure.
Precise evaluation of acetabular cup version is necessary for patients with recurrent hip dislocation after THA. We retrospectively studied 42 patients, who underwent THAs, with multiple cross-table lateral radiographs and CT scans to determine whether radiographic or CT measurement of acetabular component version is more accurate. One observer measured cup version on all radiographs. CT scans were interpreted by one observer. Twenty radiographs were measured twice each by two observers to determine intraobserver and interobserver reliability. We implanted cups in four model pelvises using navigation and compared measurements of anteversion made with radiographs and CT scans. Intraclass correlation coefficients (ICC) for anteversion measurements of two observers were 0.9990 and 0.9998, respectively, when comparing measurements of identical radiographs (intraobserver). Paired values for two observers measuring the same radiograph had an ICC of 0.9686 (interobserver) compared with 0.7412 for measurements from serial radiographs of the same component. The ICC comparing radiographic versus CT-based measurements was 0.6981. CT measurements had stronger correlations with navigated values than radiographic measurements. Accuracy of anteversion measurements on cross-table radiographs depends on radiographic technique and patient positioning whereas properly performed CT measurements are independent of patient position.
Level of Evidence: Level III, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.
The rotational position of the acetabulum to the pelvis (acetabular tilt) may influence acetabular version and coverage of the femoral head. To date, the pathologic significance of acetabular tilt in hip dysplasia is unknown.
We determined whether acetabular tilt in hip dysplasia is different from that in normal hips and whether this correlates with acetabular version and coverage.
We measured the acetabular tilt angle on the lateral view of three-dimensional pelvic CT images of 40 patients (72 hips) with hip dysplasia. Forty normal hips from 40 patients were used as controls. The acetabular sector angle was measured as an index for acetabular coverage of the femoral head.
The mean acetabular tilt angle was increased in dysplastic hips compared with controls. In dysplastic hips, a posteriorly rotated acetabulum (increased acetabular tilt) was associated with increased acetabular anteversion and with decreased anterior and anterosuperior acetabular coverage. No correlation was found in controls. In dysplastic hips with a posterior acetabular deficiency, the acetabulum was rotated anteriorly (decreased acetabular tilt) compared with hips with anterior and lateral deficiencies.
We observed a correlation between the rotational position of the acetabulum in the pelvis with acetabular version and coverage in hip dysplasia. Our observations confirmed anterior rotation of the acetabular fragment during periacetabular osteotomies is an anatomically reasonable maneuver for hips with anterolateral acetabular deficiencies, while the maneuver can exacerbate posterior coverage and should be avoided in hips with a posterior acetabular deficiency.
Level of Evidence
Level IV, diagnostic study. See the Guidelines for Authors for a complete description of levels of evidence.
Abnormal femoral neck anteversion (FNA) and/or acetabulum anteversion (AA) have long been implicated in the etiogenesis of hip osteoarthritis (OA), developmental dysplasia of the hip (DDH), and impingement, instability and wear in total hip arthroplasty (THA). Since studies on the Indian population are sparse on this topic, the purpose of this study was to report the normal values of FNA, AA and the combined anteversion (CA= FNA+ AA) in Indian adults.
Materials and Methods:
FNA, AA and CA were prospectively measured in 172 normal hips in 86 Indian adults using standardized computed tomographic (CT) methods and this data was compared with the established Western values.
The median values and interquartile ranges were 8° (6.5-10.0°) for FNA, 19° (16.0-22.0°) for AA and 27° (23.5-30.0°) for CA. AA and CA values were significantly (P<0.05) lower in males, and there was also a trend towards lower FNA in males. Although a negative correlation was observed between the FNA and AA, this was not strong and may not be clinically relevant.
When compared with the Western data, the FNA values were 3-12° lower and the CA values were 3-5° lower in Indian adults. The AA values were comparable, but were skewed towards the higher side. Further studies are needed to assess the clinical relevance of our basic science data in pathogenesis of OA, and to validate it in relation to hip surgeries like corrective osteotomies and THA.
Acetabular anteversion; combined anteversion; computed tomography; developmental dysplasia of the hip; femoral neck anteversion; hip anthropometry; hip impingement; Indian hips; proximal femoral morphology; total hip replacement
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°; however, 17% varied by 10° to 15° and 11% by more than 15°. The mean of native femoral anteversion and prosthetic femoral anteversion was 13.8° (range, −6.1°–32.7°) and 22.5° (range, 1°–39°), respectively. Based on our data, we believe the surgeon should not use the native acetabular anteversion as a target for positioning the acetabular component.
Objective: In order to achieve accurate implantation of the acetabular prosthesis in total hip arthroplasty (THA), we designed individual templates based on a three-dimensional (3D) model generated from computed tomography (CT) scans. Methods: Individual templates were designed for 12 patients who underwent THA. A physical template was designed to conform to the contours of the patient’s acetabulum and to confirm the rotation of the acetabular center. This guided the acetabular component orientation. Results: The preoperative and postoperative X-ray and CT scans were obtained to assess the location with respect to the accuracy of the acetabular component. For all patients, the abduction angle of the acetabular component was 46.7° to 54.3° and the anteversion angle was 11.3° to 18.5°. Conclusions: The assessment of postoperative CT scans demonstrated higher accuracy of the acetabular component bore when used with the individual template. Therefore, the individual template can be an alternative to the computer-assisted navigation systems, with a good cost-performance ratio.
Total hip arthroplasty; Templates; Acetabular prosthesis
We studied 105 patients who received a total hip arthroplasty between June 1985 and August 2001 using freehand positioning of the acetabular cup. Using pelvic CT scan and the hip-plan module of SurgiGATE-System (Medivision, Oberdorf, Switzerland), we measured the angles of inclination and anteversion of the cup. Mean inclination angle was 45.8°±10.1° (range: 23.0–71.5°) and mean anteversion angle was 27.3°±15.0° (range: −23.5° to 59.0°). We compared the results to the “safe” position as defined by Lewinnek et al. and found that only 27/105 cups were implanted within the limits of the safe position. We conclude that a safe position as defined by Lewinnek et al.  was only achieved in a minority of the cups that were implanted freehand.
Malalignment of the cup in total hip arthroplasty (THA) increases the risks of postoperative complications such as neck cup impingement, dislocation, and wear. We asked whether a tailor-made surgical guide based on CT images would reduce the incidence of outliers beyond 10° from preoperatively planned alignment of the cup compared with those without the surgical guide. We prospectively followed 38 patients (38 hips, Group 1) having primary THA with the conventional technique and 31 patients (31 hips, Group 2) using the surgical guide. We designed the guide for Group 2 based on CT images and fixed it to the acetabular edge with a Kirschner wire to indicate the planned cup direction. Postoperative CT images showed the guide reduced the number of outliers compared with the conventional method (Group 1, 23.7%; Group 2, 0%). The surgical guide provided more reliable cup insertion compared with conventional techniques.
Level of Evidence: Level II, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.
Rapidly destructive osteoarthritis (RDO) of the hip is a rare condition characterized by rapid joint degeneration and destruction similar to findings of infection, osteonecrosis, or Charcot disease but without a definitive diagnosis. The cause and natural history of RDO are unclear, but total hip arthroplasty has been utilized as a treatment modality due to the severity of the symptoms. We reviewed retrospectively the records of total hip arthroplasties performed between 1990 and 2003 and identified ten hips in eight patients who fit the profile of the diagnosis of RDO. The mean age at time of surgery was 70. Nine hips were treated with total hip arthroplasty with a hybrid configuration; one hip was treated with a non-cemented total hip arthroplasty. Average follow-up was 6 years with no radiographic evidence of acetabular loosening or osteolysis and no evidence of asymmetric cup wear. One femoral component had evidence of loosening but has not been revised. RDO is an idiopathic condition with no single diagnostic laboratory, pathological, or radiographic finding. A complete preoperative work-up for other causes of hip disease prior to arthroplasty for suspected RDO is necessary to rule out treatable disease. Our series of patients with RDO responded well to hybrid and non-cemented total hip arthroplasty with good clinical and radiographic results.
rapidly destructive osteoarthritis; total hip arthroplasty; level of evidence: IV—case series
A CT-based navigation system is helpful to evaluate the reamer shaft and the impactor position/orientation during unilateral total hip arthroplasty (THA). The main objective of this study is to determine the accuracy of the Navitrack system by measuring the implant's true anteversion and inclination, based on pre- and postoperative CT scans (n = 9 patients). The secondary objective is to evaluate the clinical validity of measurements based on postop anteroposterior (AP) radiographs for determining the cup orientation. Postop CT-scan reconstructions and postop planar radiographs showed no significant differences in orientation compared to peroperative angles, suggesting a clinical validity of the system. Postoperative AP radiographs normally used in clinic are acceptable to determine the cup orientation, and small angular errors may originate from the patient position on the table.