Influence of avascular necrosis of the femoral head on hip prosthesis integration: a radiological analysis.

BACKGROUND: Avascular osteonecrosis of the femoral head (AVN) often results in total hip arthroplasty (THA). The cause for increased THA revision rates among patients with AVN is not yet fully understood. PURPOSE: To perform a comparative radiological analysis of implant integration between patients with AVN and osteoarthritis (OA). MATERIAL AND METHODS: After a matched pair analysis of 58 patients, 30 received THA due to OA, 28 due to AVN. X-ray images were evaluated after one week ("baseline") and on average 37.58 months postoperatively ("endline"). The prosthesis was grouped into 10 regions of interest (ROI): seven femoral and three acetabular. Incidence, width, and extent of "radiolucent lines" were measured within each zone. RESULTS: Between baseline and endline, width and extent progressed more noticeably in all femoral and acetabular zones among patients with AVN. In femoral ROI 1, the width increased in 40% of AVN cases compared to 6.7% of OA cases. For acetabular ROI 3, the width increased in 26.7% of AVN cases compared to no perceived changes in the OA group. No signs of prosthetic loosening were found in the AVN group. CONCLUSION: The increase of width and extent of radiolucent lines over time in patients with AVN could be a sign of lack of osteointegration. However, prosthetic loosening in absence of clinical symptoms cannot be deduced from radiological findings after medium-term postoperative follow-up. Further long-term studies are required to monitor how radiolucent lines develop in respect to long-term implant loosening. Dependent on bone quality, individually adapted reaming and broaching of the implant site are recommended.

Surgical management and outcomes following atypical subtrochanteric femoral fractures - results from a matched-pair analysis of the registry for geriatric trauma of the German Trauma Society.

BACKGROUND AND OBJECTIVES: The outcomes of patients with atypical subtrochanteric fractures (ASFs) remain unclear. Data from a large international geriatric trauma registry were analysed to examine the outcome of patients with ASFs compared to patients with typical osteoporotic subtrochanteric fractures (TSFs). MATERIALS AND METHODS: Data from the Registry for Geriatric Trauma of the German Trauma Society (Deutsche Gesellschaft für Unfallchirurgie [DGU]) (ATR-DGU) were analysed. All patients treated surgically for ASFs or TSFs were included in this analysis. Across both fracture types, a paired matching approach was conducted, where statistical twins were formed based on background characteristics sex, age, American Society of Anesthesiologists (ASA) score and walking ability. In-house mortality and mortality rates at the 120-day follow-up, as well as mobility at 7 and 120 days, the reoperation rate, hospital discharge management, the hospital readmission rate at the 120-day follow-up, health-related quality of life, type of surgical treatment and anti-osteoporotic therapy at 7 and 120 days, were assessed as outcome measures using a multivariate logistic regression analysis. RESULTS: Amongst the 1,800 included patients, 1,781 had TSFs and 19 had ASFs. Logistic regression analysis revealed that patients with ASFs were more often treated with closed intramedullary nailing (RR = 3.59, p < 0.001) and had a higher probability of vitamin D supplementation as osteoporosis therapy at 120 days (RR = 0.88, p < 0.002). Patients with ASFs were also more likely to live at home after surgery (RR = 1.43, p < 0.001), and they also tended to continue living at home more often than patients with TSFs (RR = 1.33, p < 0.001). Accordingly, patients with TSFs had a higher relative risk of losing their self-sufficient living status, as indicated by increased rates of patients living at home preoperatively and being discharged to nursing homes (RR = 0.19, p < 0.001) or other hospitals (RR = 0.00, p < 0.001) postoperatively. CONCLUSIONS: Surgical treatment of ASFs was marked by more frequent use of closed intramedullary fracture reduction. Furthermore, patients with ASFs were more likely to be discharged home and died significantly less often in the given timeframe. The rate of perioperative complications, as indicated by nonsignificant reoperation rates, as well as patient walking abilities during the follow-up period, remained unaffected.

Avascular necrosis of the femoral head: three-dimensional measurement of drilling precision reveals high accuracy and no difference between fluoroscopically controlled core decompression and cancellous bone grafting.

INTRODUCTION: Avascular osteonecrosis of the femoral head (AVN) is a widespread disease affecting mostly young and active people, often exacerbating in progressive stages, ending in joint replacement. The most common joint preserving operative therapy for early stages is core decompression (CD), optional with cancellous bone grafting (CBG). For success it is vital that the necrotic area is hit and the sclerotic rim is broken by drilling into the defect zone to relieve intraosseous pressure. The aim of this study was to investigate if both techniques are precise enough to hit the center of the necrosis and if there is a difference in precision between drilling with small pins (CD) and the trephine (CBG). PATIENTS AND METHODS: 10 patients underwent CD, 12 patients CBG with conventional C-arm imaging. Postoperatively 3D MRI reconstructions of the necrotic area and the drilling channels were compared. The deviation of the drilling channel from the center of the necrotic area was measured. PROMs (HHS, HOOS, EQ-5D, SF-36) were evaluated to compare the clinical success of these procedures. RESULTS: Neither with CD nor with CBG the defect zone was missed. The drilling precision of both procedures did not differ significantly: distance to center 3.58 mm for CD (range 0.0-14.06, SD 4.2) versus 3.91 mm for CBG (range 0.0-15.27, SD 4.7). PROMs showed no significant difference. CONCLUSION: Concerning the most important difference between the two procedures-the surgical higher demanding technique of CBG-we suggest applying the less invasive technique of CD alone.

The effects of soft tissue lateral release on the stability of the ligament complex of the knee.

PURPOSE: Valgus deformity presents a particular challenge in total knee arthroplasty. This condition regularly leads to contractures of the lateral capsular ligament complex and to overstretching of the medial ligamentous complex. Reconstruction of the knee joint kinematics and anatomy often requires lateral release. However, data on how such release weakens the stability of the knee are missing in the literature. This study investigated the effects of sequential lateral release on the collateral stability of the ligament complex of the knee in vitro. METHODS: Ten knee prostheses were implanted in 10 healthy cadaveric knee joints using a navigation device. Soft tissue lateral release consisted of five release steps, and stiffness and stability were determined at 0, 30, 60 and 90° flexion after each step. RESULTS: Soft tissue lateral release increasingly weakened the ligament complex of the lateral compartment. Because of the large muscular parts, the release of the iliotibial band and the M. popliteus had little effect on the stability of the lateral and medial compartment, but release of the lateral ligament significantly decreased the stability in the lateral compartment over the entire range of motion. Stability in the medial compartment was hardly affected. Conversely, further release of the posterolateral capsule and the posterior cruciate ligament led to the loss of stability in the lateral compartment only in deep flexion, whereas stability decreased significantly in the medial compartment. CONCLUSION: Our study shows for the first time the association between sequential lateral release and stability of the ligamentous complex of the knee. To maintain the stability, knee surgeons should avoid releasing the entire lateral collateral ligament, which would significantly decrease stability in the lateral compartment.

Customized implants for acetabular Paprosky III defects may be positioned with high accuracy in revision hip arthroplasty.

PURPOSE: In revision hip arthroplasty, custom-made implants are one option in patients with acetabular Paprosky III defects. METHODS: In a retrospective analysis, we identified 11 patients undergoing cup revision using a custom-made implant. The accuracy of the intended position of the implant was assessed on post-operative 3D CT and compared to the pre-operative 3D planning in terms of inclination, anteversion, and centre of rotation. In addition, the accuracy of post-operative plain radiographs for measuring implant position was evaluated in relation to the 3D CT standard. RESULTS: We found a mean deviation between the planned and the final position of the custom-made acetabular implant on 3D CT of 3.6° ± 2.8° for inclination and of - 1.2° ± 7.0° for anteversion, respectively. Restoration of center of rotation succeeded with an accuracy of 0.3 mm ± 3.9 mm in the mediolateral (x) direction, - 1.1 mm ± 3.8 mm in the anteroposterior (y) direction, and 0.4 mm ± 3.2 mm in the craniocaudal (z) direction. The accuracy of the post-operative plain radiographs in measuring the position of the custom-made implant in relation to 3D CT was 1.1° ± 1.7° for implant inclination, - 2.6° ± 1.3° for anteversion and 1.3 mm ± 3.5 mm in the x-direction, and - 0.9 mm ± 3.8 mm in the z-direction for centre of rotation. CONCLUSION: Custom-made acetabular implants can be positioned with good accuracy in Paprosky III defects according to the pre-operative planning. Plain radiographs are adequate for assessing implant position in routine follow-up.

Weakening of the knee ligament complex due to sequential medial release in total knee arthroplasty.

PURPOSE: The purpose of this study was to investigate the effects of sequential medial release on the stiffness and collateral stability of the ligament complex of the knee. Irrespective of the implantation technique used, varus deformity frequently requires release of the capsular ligament complex. Yet, no data are available on how stiffness and stability of the knee ligament complex are weakened by such release. METHODS: After total knee arthroplasty, ten healthy Thiel-fixed knee joints were subjected to sequential medial release consisting of six release steps. After each step, stiffness and stability were determined at 0°, 30°, 60°, and 90°. RESULTS: Sequential medial release increasingly weakened the ligament complex. In extension, release of the anteromedial tibial sleeve 4 cm below the joint line already weakened the ligament complex by approximately 13%. Release 6 cm below the joint line reduced stiffness and stability by 15-20% over the entire range of motion. After detachment of the medial collateral ligament, stability was only about 60% of its initial value. CONCLUSION: Our study showed for the first time the association between medial release and stiffness and stability of the knee ligament complex. To maintain stability, vigorous detachment of the knee ligament complex should be avoided. Release of the anteromedial tibial sleeve already initiates loss of stability. The main stabiliser is the medial ligament, which should never be completely detached. LEVEL OF EVIDENCE: IV.

Predictors of Outcome After Primary Total Joint Replacement.

BACKGROUND: Total hip and knee replacements are frequently performed curative treatment options in end-stage arthritis. In this study, we analyzed clinical outcome, complications, and predictors of outcome in modern joint replacement. METHODS: In a retrospective analysis of over 2000 primary total hip and knee replacements from our institutional joint registry, responder rates for positive outcome as defined by the OMERACT-OARSI criteria, postoperative complication rates, and patient-reported outcome measures (EQ-5D, WOMAC) within the first year were compared between hip and knee replacements. Furthermore, preoperative risk factors associated with nonresponder rate were evaluated. RESULTS: Positive responder rate was higher for hip replacements with 92.8% (1145/1234) than for knee replacements with 86.1% (839/975, P < .001). Infection rates were lower (P = .04), whereas intraoperative fracture occurred more frequently (P = .001) in hip than in knee replacements. Patient-reported outcome measures 1 year after surgery were higher in hip than in knee replacements with EQ-5D (0.88 ± 0.17 to 0.81 ± 0.19, P < .001) and WOMAC (84.58 ± 16.73 to 74.31 ± 18.94, P < .001). Besides the type of joint replacement (hazard ratio [HR] 2.0, P < .001), high preoperative outcome measures (HR 7.4, P < .001) and male gender (HR 1.4, P = .05) were independent risk factors of nonresponders after joint replacement. CONCLUSION: Both total hip and knee replacements are safe procedures with low complication rates. Still, postoperative outcome is higher in hip than in knee arthroplasty. High preoperative clinical scores are a risk factor for poor clinical improvement following total joint replacement and can be used in counseling patients in the office.

The final implant position of a commonly used collarless straight tapered stem design (Corail®) does not correlate with femoral neck resection height in cement-free total hip arthroplasty: a retrospective computed tomography analysis.

BACKGROUND: In total hip arthroplasty, inadequate femoral component positioning can be associated with instability, impingement and component wear and subsequently with patient dissatisfaction. In this study, we investigated the influence of femoral neck resection height on the final three-dimensional position of a collarless straight tapered stem (Corail®). We asked two questions-(1) is neck resection height correlated with version, tilt, and varus/valgus alignment of the femoral component, and (2) dependent on the resection height of the femoral neck, which area of the stem comes into contact with the femoral cortical bone? MATERIALS AND METHODS: Three-dimensional computed tomography scans of 40 patients who underwent minimally invasive, cementless total hip arthroplasty were analyzed retrospectively. We analyzed the relationship between femoral neck resection height and three-dimensional alignment of the femoral implant, as well as the contact points of the implant with the femoral cortical bone. This investigation was approved by the local Ethics Commission (No.10-121-0263) and is a secondary analysis of a larger project (DRKS00000739, German Clinical Trials Register May-02-2011). RESULTS: Mean femoral neck resection height was 10.4 mm (± 4.8) (range 0-20.1 mm). Mean stem version was 8.7° (± 7.4) (range - 2° to 27.9°). Most patients had a varus alignment of the implant. The mean varus/valgus alignment was 1.5° (± 1.8). All 40 patients (100%) had anterior tilt of the implant with a mean tilt of 2.2° (± 1.6). Femoral neck resection height did not correlate with stem version, varus/valgus alignment, or tilt. Independent from femoral neck resection height, in most patients the implant had contact with the ventral and ventromedial cortical bone in the upper third (77.5%) and the middle third (52.5%). In the lower third, the majority of the implants had contact with the lateral and dorsolateral cortical bone (92.5%). CONCLUSION: Femoral neck resection height ranging between 0 and 20.1 mm does not correlate with the final position of a collarless straight tapered stem design (Corail®). LEVEL OF EVIDENCE: Level 3.

Posterior lesser trochanter line should not be used as reference for assessing femoral version in CT scans: a retrospective reliability and agreement study.

Background The estimation of femoral version in preoperative planning of total hip arthroplasty and to assess complications after total hip arthroplasty is crucial. Recent studies have recommended the posterior lesser trochanter line as an intraoperative reference for estimating femoral version. We hypothesized, that if there is a correlation, the posterior lesser trochanter line could be used to assess femoral version in computed tomography (CT) scans. Purpose To evaluate the correlation between the posterior lesser trochanter line and the posterior femoral condyle axis. Material and Methods CT scans of 126 patients after unilateral total hip arthroplasty were analyzed by means of a newly developed digital planning software for CT scans. Both hips were measured, the angle between the posterior lesser trochanter line and the posterior femoral condyle axis was determined, and the relationship between both lines was evaluated. Results We found significant differences between male and female patients ( P < 0.001) and between left and right femora ( P = 0.001). There was no significant difference between healthy hips and hips with osteoarthritis after total hip arthroplasty ( P = 0.901). Conclusion There is no reliable correlation between posterior lesser trochanter line and posterior femoral condyle axis. Therefore, posterior lesser trochanter line should not be used to assess femoral version in CT scans. As a consequence, the gold standard for measuring femoral version should still be a three-dimensional CT scan of the whole femur.

Lesser Trochanter Size on Plain Anteroposterior Radiographs Correlates With Native Femoral Anteversion.

BACKGROUND: Assessing femoral version in orthopedic surgery is important for preoperative planning of total hip arthroplasty, especially for recognizing excessive anteversion or retroversion. The present study addressed the following: (1) Is the position of the lesser trochanter correlated to the femoral neck axis? (2) If so, may femoral version be assessed by means of plain pelvic radiographs? METHODS: Three-dimensional computed tomography scans of 60 patients undergoing minimally invasive cement-free total hip arthroplasty were retrospectively analyzed, particularly with regard to the relation between the femoral neck axis and the lesser trochanter, the femoral version, and the size of the projected lesser trochanter in different rotational positions. Based on linear regression, a biomathematical formula was developed to assess femoral anteversion on plain radiographs depending on the visible part of the lesser trochanter. RESULTS: The mean difference between the location of the lesser trochanter axis and the femoral neck axis was 43.3° ± 6.2°. Eighty-seven percent of patients (52 of 60) had a deviation of <10° from the mean value of 43.3°. By virtual rotation of the femur in steps of 10°, the visible part of the lesser trochanter linearly increased with anteversion of the femur: femoral version = (lesser trochanter size - 5.57) × 4.17. There was a high correlation between the visible part of the lesser trochanter and femoral version (R2 = 0.75; P < .001). The lesser trochanter was no longer visible with femoral retroversion in each of the 60 data sets. CONCLUSION: The projected size of the lesser trochanter as available on plain pelvic AP radiographs correlates with native femoral anteversion.

Accuracy of measuring acetabular cup position after total hip arthroplasty: comparison between a radiographic planning software and three-dimensional computed tomography.

PURPOSE: Various methods are available for measuring acetabular cup position after total hip arthroplasty (THA) on standard anterior-posterior (AP) radiographs. We compared the accuracy of a commercial radiographic planning software program with that of three-dimensional computed tomography (3D-CT) scans. METHODS: We obtained plain AP radiographs and 3D-CTs from 65 patients after THA. In addition to calculating cup anteversion and inclination with 3D-CT, we determined the cup position using the radiographic planning software program mediCAD® 2.5 (Hectec, Niederviehbach, Germany). Furthermore, we compared the measurements using the inter-teardrop and bi-ischial lines as pelvic landmarks. RESULTS: The mean difference in anteversion between 3D-CT and mediCAD® software was 0.1° using the inter-teardrop line (standard deviation [SD], 8.8°; range, -21° to 23°; p = 0.97) and 0.4° using the bi-ischial line (SD, 8.8°; range, -23° to 21°; p = 0.72). Inclination showed a mean difference of 0.6° using the inter-teardrop line (SD, 4.4°; range, -9° to 21°; p = 0.24) and 0.5° using bi-ischial line (SD, 4.6°; range, -9° to 22°; p = 0.35). The means for absolute differences were 7.2° for anteversion and 3.1° for inclination. With regard to using the bi-ischial or inter-teardrop line, no significant difference was found between the two pelvic landmarks. The intra-class correlation coefficient (ICC) was analysed for anteversion and inclination using either the inter-teardrop line or the bi-ischial line as radiographic baseline. CONCLUSIONS: A radiographic planning software program (mediCAD®) is a helpful tool for measuring cup inclination on AP radiographs. With respect to anteversion, measurements are rather susceptible to mistakes with mean inaccuracies of over 7°. Thus, 3D-CT remains the "gold standard" if a lower tolerance limit (±3°) is required for more complex biomechanical evaluations. As a pelvic landmark, the interteardrop line is preferential to the bi-ischial line because of its lower impact on the position of the pelvis.

Soft tissue restricts impingement-free mobility in total hip arthroplasty.

PURPOSE: Impingement is a major source for decreased range of motion (ROM) and dislocation in total hip arthroplasty (THA). In the current study we analyzed the impact of soft tissue impingement on ROM compared to bony and/or prosthetic impingement. METHODS: In the course of a prospective clinical trial 54 patients underwent cementless total hip arthroplasty in the lateral decubitus position using imageless navigation. The navigation device enabled intra-operative ROM measurements indicating soft tissue impingement. Post-operatively, all patients received postoperative 3D-CT. Absolute ROM without bony and/or prosthetic impingement was calculated with the help of a collision-detection-algorithm. RESULTS: Due to soft tissue impingement we found a reduced ROM of over 20° (p < 0.001) compared to bony and/or prosthetic impingement regarding flexion, extension, abduction and adduction and of over 10° regarding external rotation (p < 0.001). In contrast, soft tissue impingement showed less impact on internal rotation in 90° of flexion (p = 0.76). Multivariate analysis showed an association between BMI and flexion, whereas all other ROM directions were independent of BMI. CONCLUSIONS: Soft tissue has a major impact on impingement-free ROM after THA. For the majority of movements, soft tissue restrictions are more important than bony and prosthetic impingement. Future models of patient individual joint replacement including pre-operative (CT) planning and intra-operative navigation should include algorithms additionally accounting for soft tissue impingement.

Native femoral anteversion should not be used as reference in cementless total hip arthroplasty with a straight, tapered stem: a retrospective clinical study.

BACKROUND: Improper femoral and acetabular component positioning can be associated with instability, impingement, component wear and finally patient dissatisfaction in total hip arthroplasty (THA). The concept of "femur first"/"combined anteversion", incorporates various aspects of performing a functional optimization of the prosthetic stem and cup position of the stem relative to the cup intraoperatively. In the present study we asked two questions: (1) Do native femoral anteversion and anteversion of the implant correlate? (2) Do anteversion of the final broach and implant anteversion correlate? METHODS: In a secondary analysis of a prospective controlled trial, a subgroup of 55 patients, who underwent computer-assisted, cementless THA with a straight, tapered stem through an anterolateral, minimally invasive (MIS) approach in a lateral decubitus position were examined retrospectivly. Intraoperative fluoroscopy was used to verify a "best-fit" position of the final broach. An image-free navigation system was used for measurement of the native femoral version, version of the final broach and the final implant. Femoral neck resection height was measured in postoperative CT-scans. This investigation was approved by the local Ethics Commission (No.10-121-0263) and is a secondary analysis of a larger project (DRKS00000739, German Clinical Trials Register May-02-2011). RESULTS: The mean difference between native femoral version and final implant was 1.9° (+/- 9.5), with a range from -20.7° to 21.5° and a Spearman's correlation coefficient of 0.39 (p < 0.003). In contrast, we observed a mean difference between final broach and implant version of -1.9° (+/- 3.5), with a range from -12.7° to 8.7° and a Spearman's correlation coefficient of 0.89 (p < 0.001). In 83.6 % (46/55) final stem version was outside the normal range as defined by Tönnis (15-20°). The mean femoral neck resection height was 7.3 mm (+/- 5.6). There was no correlation between resection height and version of the implant (Spearman's correlation coefficient 0.14). CONCLUSION: Native femoral version significantly differs from the final anteversion of a cementless, straight, tapered stem and therefore is not a reliable reference in cementless THA. Measuring anteversion of the final "fit and fill" broach is a feasible assistance in order to predict final stem anteversion intraoperatively. There is no correlation between femoral neck resection height and version of the implant.

Radiographic Assessment of Femoral Stem Torsion in Total Hip Arthroplasty-A Comparison of a Caput-Collum-Diaphyseal Angle-Based Technique With the Budin View.

BACKGROUND: Correct assessment of femoral stem torsion is crucial in total hip arthroplasty (THA). In this study, we aimed to compare a recently published novel method based on anteroposterior (AP) hip radiographs using the projected caput-collum-diaphyseal (CCD) angle (AP CCD) with the modified posteroanterior Budin view. METHOD: AP radiographs, modified Budin views, and 3-dimensional computed tomography (3D-CT) images were obtained in 30 patients after minimally invasive, cementless THA. Radiographic measurements performed by 4 observers twice in a 6-week interval were compared with 3D-CT measurements. Furthermore, correlations between the radiographic deviation to 3D-CT and patient specific characteristics were evaluated. RESULTS: We found a mean difference of 2.2 ± 6.8° between AP CCD and 3D-CT measurements of femoral stem torsion and -0.5 ± 4.2° between the modified Budin view and 3D-CT. We found a high correlation between mean radiographic and 3D-CT stem torsion (r = 0.78, P < .001 for AP CCD and r = 0.84, P < .001 for Budin view). The observers had excellent agreements within (intraclass correlation coefficient, ≥0.88 for AP CCD and intraclass correlation coefficient, ≥0.94 for Budin view) and between (mean concordance correlation coefficient, ≥0.79 for AP CCD and concordance correlation coefficient, ≥0.86 for Budin view) their radiographic measurements. CONCLUSION: Both radiographic methods enable a simple orientation and a practical conventional radiographic estimation of stem torsion on hip radiographs after THA. However, CT remains the golden standard for exact estimation of stem torsion.

No difference in patellar kinematics between fixed-bearing cruciate-retaining and cruciate-substituting total knee arthroplasty: a cadaveric investigation.

PURPOSE: The influence of cruciate-ligament-retaining (CR-TKA) and cruciate-ligament-substituting (CS-TKA) TKA on tibiofemoral kinematics was analysed in many investigations. However, the influence on patellar kinematics is unclear so far. The aim of this study was to compare patellar kinematics of the natural knee with those after CR- and CS-TKA. METHODS: Patellar kinematics of nine healthy whole-body cadaveric knees before and after CR- and CS-TKA was investigated using a commercial optical computer navigation system. Patellar kinematics of the healthy knee was compared with those after CR- and CS-TKA. RESULTS: No significant difference between the natural knee and the knee after TKA or between both types of TKA for patellar kinematics could be found. Interestingly, both types of TKA resulted in a more medial patellar shift and a contrary patellar tilt and rotation behaviour. CR- and CS-TKA resulted in smaller values for patellar epicondylar distance at all flexion angles. CONCLUSIONS: Our study found no influence of prosthesis type on patellar kinematics. Factors like component alignment and prosthesis design seem to be more important in terms of adequate restoration of patellar kinematics in TKA than whether choosing CR- or CS-TKA.

Current standard rules of combined anteversion prevent prosthetic impingement but ignore osseous contact in total hip arthroplasty.

PURPOSE: In this prospective study of 135 patients undergoing cementless total hip arthroplasty (THA) we asked whether six current definitions of combined anteversion prevent impingement and increase postoperative patient individual impingement-free range-of-motion (ROM). METHODS: Implant position was measured by an independent, external institute on 3D-CT performed six weeks post-operatively. Post-operative ROM was calculated using a CT-based algorithm detecting osseous and/or prosthetic impingement by virtual hip movement. Additionally, clinical ROM was evaluated pre-operatively and one-year post-operatively by a blinded observer. RESULTS: Combined component position of cup and stem according to the definitions of Ranawat, Widmer, Dorr, Hisatome and Yoshimine inhibited prosthetic impingement in over 90 %, while combined osseous and prosthetic impingement still occurred in over 40 % of the cases. The recommendations by Jolles, Widmer, Dorr, Yoshimine and Hisatome enabled higher flexion (p ≤ 0.001) and internal rotation (p ≤ 0.006). Clinically, anteversion rules of Widmer and Yoshimine provided one-year post-operatively statistically but not clinically relevant higher internal rotation (p ≤0.034). CONCLUSION: Standard rules of combined anteversion detect prosthetic but fail to prevent combined osseous and prosthetic impingement in THA. Future models will have to account for the patient-individual anatomic situation to ensure impingement-free ROM.

Comparative clinical study of the prophylaxis of heterotopic ossifications after total hip arthroplasty using etoricoxib or diclofenac.

PURPOSE: This study investigated whether etoricoxib (COX-II blocker) has a superior efficacy of preventing heterotopic ossification (HO) after total hip arthroplasty (THA) compared to diclofenac (non-selective NSAID). METHODS: One hundred patients were included (50 in each group) in this single centre, prospective, double-blinded, randomized, controlled trial. Etoricoxib (90 mg) was administered once and diclofenac (75 mg) twice per day for a perioperative period of nine days. The incidence of HO was evaluated on radiographs of the pelvis six months after surgery. RESULTS: Eighty nine of 100 (89 %) patients could be analysed. The overall HO incidence was 37.8 %. There was no significant difference between both study groups. Twelve patients (27.3 %) of the DIC group and 13 patients (28.9 %) of the ETO group showed Brooker grade I ossifications. Five patients (11.4 %) of the DIC and four patients of the ETO (8.9 %) group showed grade II HO formations. No class III or IV HO formations occured in both groups. Ad hoc analysis detected a negative correlation between HO incidence and limited abduction and internal rotation of the hip. CONCLUSIONS: Etoricoxib and diclofenac are equally effective for oral HO prophylaxis after primary cementless THA when given for nine peri-operative days to ensure a full recovery and high patient satisfaction.

Visual intraoperative estimation of range of motion is misleading in minimally invasive total hip arthroplasty.

INTRODUCTION: Generally range of motion (ROM) in total hip arthroplasty (THA) is intraoperatively assessed by eye. Can we assume that visual estimation of ROM is reliable? METHODS: 60 patients underwent cementless THA in a subgroup analysis of a clinical prospective trial using a minimally invasive anterolateral approach in lateral decubitus position. Four experienced surgeons intraoperatively estimated ROM visually by assessment of the femur relative to the alignment of the patient's pelvis. These estimations were compared with computer navigation measurements. RESULTS: We found a mean difference between navigation measurements and intraoperative estimations by eye of -5.6° (±10.9°; -17° to 30°) for flexion, respectively, -0.4° (±10.7°; -24° to 30°) for extension, 8.7° (±9.0°; -10° to 34°) for abduction, 5.9° (±18.3°; -58° to 68°) for external rotation and -5.8° (±12.1°; -38° to 22°) for internal rotation. Multivariate analysis showed no association between the visual accuracy of estimation of ROM and patient characteristics, such as BMI, sex, grade of osteoarthritis and treatment side except for a significant correlation of visual accuracy of estimation of extension and the level of professional experience. Otherwise, the level of professional experience had no impact on the accuracy of estimation of ROM by eye. CONCLUSIONS: Even the experienced surgeon's intraoperative estimation of ROM by eye is not reliable and differs up to 30° compared to objective measurements in minimally invasive THA. For accurate intraoperative assessment of ROM, the use of technical devices is recommended. TRIAL REGISTRATION: DRKS00000739.

Decreased femoral periprosthetic bone mineral density: a comparative study using DXA in patients after cementless total hip arthroplasty with osteonecrosis of the femoral head versus primary osteoarthritis.

INTRODUCTION: Trabecular properties in osteonecrosis of the femoral head (ONFH) are altered for bone volume and structure in the femoral head and proximal femoral canal. We analysed the periprosthetic bone mineral density (BMD) as a correlate to bony ingrowth in patients with ONFH who received a cementless THA. MATERIALS AND METHODS: We performed a matched-pair analysis of 100 patients with ONFH (n = 50) and primary osteoarthritis (n = 50) who received the same, unilateral cementless THA. We compared the periprosthetic BMD 5 years after surgery by means of dual energy X-ray absorptiometry (DXA) analysing the seven femoral regions of interest (ROIs) according to Gruen. RESULTS: Within the ONFH group, significantly lower BMD values were found in the ROI 1 and 7 (p < 0.05). No statistically significant difference was found for ROIs 2-6. CONCLUSIONS: An altered periprosthetic bone stock in the proximal femur in patients with prior ONFH might be a possible risk factor for premature loosening of the femoral stem in THA. Surgeons need to consider coating and fixation philosophy of cementless implants when choosing the right stem for patients with ONFH.

Visual intraoperative estimation of cup and stem position is not reliable in minimally invasive hip arthroplasty.

Background and purpose - In hip arthroplasty, acetabular inclination and anteversion-and also femoral stem torsion-are generally assessed by eye intraoperatively. We assessed whether visual estimation of cup and stem position is reliable. Patients and methods - In the course of a subgroup analysis of a prospective clinical trial, 65 patients underwent cementless hip arthroplasty using a minimally invasive anterolateral approach in lateral decubitus position. Altogether, 4 experienced surgeons assessed cup position intraoperatively according to the operative definition by Murray in the anterior pelvic plane and stem torsion in relation to the femoral condylar plane. Inclination, anteversion, and stem torsion were measured blind postoperatively on 3D-CT and compared to intraoperative results. Results - The mean difference between the 3D-CT results and intraoperative estimations by eye was -4.9° (-18 to 8.7) for inclination, 9.7° (-16 to 41) for anteversion, and -7.3° (-34 to 15) for stem torsion. We found an overestimation of > 5° for cup inclination in 32 hips, an overestimation of > 5° for stem torsion in 40 hips, and an underestimation < 5° for cup anteversion in 42 hips. The level of professional experience and patient characteristics had no clinically relevant effect on the accuracy of estimation by eye. Altogether, 46 stems were located outside the native norm of 10-20° as defined by Tönnis, measured on 3D-CT. Interpretation - Even an experienced surgeon's intraoperative estimation of cup and stem position by eye is not reliable compared to 3D-CT in minimally invasive THA. The use of mechanical insertion jigs, intraoperative fluoroscopy, or imageless navigation is recommended for correct implant insertion.