High Hip Center Research Articles

High Hip Center Technique in Total Hip Arthroplasty for Crowe Type II-III Developmental Dysplasia: Results of Midterm Follow-up.

ObjectivesWe aimed to show the utility of high hip center technique used in patients with Crowe II–III developmental dysplasia of the hip at the midterm follow‐up and evaluated the clinical and radiographic results between different heights of hip center.MethodsFrom December 2003 to November 2013, we retrospectively evaluated 69 patients (85 hips) with Crowe II–III dysplasia who underwent a high hip center cementless total hip arthroplasty. The patients were divided into two groups according to the height of hip center, respectively group A (≥ 22 mm and < 28 mm) and group B (≥28 mm). The survivorship outcomes and radiographic and clinical results, including the vertical and horizontal distances of hip center, femoral offset, abductor lever arm, cup inclination, leg length discrepancy, Trendelenburg sign, and limp were evaluated.ResultsThe mean follow‐up time was 8.9 ± 1.8 years. The mean location of the hip center from the inter‐teardrop was 25.1 ± 1.6 mm vertically and 30.0 ± 3.8 mm horizontally in group A, and 33.1 ± 4.8 mm vertically and 31.4 ± 6.1 mm horizontally in group B. Eleven hips of group B showed a lateralization over 10 mm, and the same was shown in one hip in group A (P = 0.012). There were no statistically significant differences between two groups in postoperative femoral offset, abductor lever arm, leg length discrepancy and cup inclination. At the final follow up, the mean WOMAC and Harris hip score were significantly improved in both groups. Of the 85 hips, four hips in group A and three hips in group B showed a positive Trendelenburg sign. Additionally, four patients in group A and two patients in group B presented with a limp. No significant differences were shown regarding the Harris hip score, WOMAC score, Trendelenburg sign, and limp between two groups. One hip of group A was revised by reason of dislocation at 8.3 years after surgery. One hip of group B was diagnosed with osteolysis and underwent a revision at 8.1 years after surgery. The Kaplan–Meier implants survivorship rates at the final follow‐up for all‐causes revisions in group A and group B were similar (96.7% [95% confidence interval, 90.5%–100%] and 96.2% [95% confidence interval, 89.0%–100%], respectively).ConclusionsThe high hip center technique is a valuable alternative to achieve excellent midterm results for Crowe II–III developmental dysplasia of the hip. Further, between the groups with differing degrees of HHC, there were no significant differences in outcomes or survivorship in our study.

Total Hip Arthroplasty for Crowe Type IV Hip Dysplasia: Surgical Techniques and Postoperative Complications.

Total hip arthroplasty (THA) of Crowe type IV developmental dysplasia of the hip (DDH) is challenging. Although traditional (lateral, posterolateral, and posterior) THA approaches have been used with great anatomic success, they damage periarticular muscles, which are already quite weak in type IV DDH. The recently developed direct anterior approach (DAA) can provide an inter‐nerve and inter‐muscle approach for THA of type IV dysplasia hips. However, femur exposure with the DAA could be difficult during surgery and it is hard to apply femoral shortening osteotomy. THA techniques used for type IV DDH include anatomic hip center techniques (true acetabular reconstruction) and high hip center techniques, wherein an acetabulum is reconstructed above the original one. Although anatomic construction of the hip center is considered “the gold standard” treatment, it is impossible if the anatomical acetabular is too small and shallow. Procedures used to support type IV DDH reduction with anatomic hip center techniques include greater trochanter osteotomy, lesser trochanter osteotomy, and subtrochanteric osteotomy. However, these techniques have yet to be standardized, and it is unclear which is best for type IV DDH. One‐state and two‐state non‐osteotomy reduction techniques have also been introduced to treat type IV DDH. Potential complications of THA performed in patients with type IV DDH include leg length discrepancy (LLD), peri‐operative femur fracture, nonunion of the osteotomy site, and nerve injury. It is worth noting that nowadays an increasing number of Crowe type IV DDH patients are more sensitive to postoperative LLD.

Postoperative radiographic evaluation and simulation study for optimal cup placement in high-hip centre total hip arthroplasty.

Achieving favourable outcomes in high-hip centre reconstruction in hip dysplasia requires the optimal cup height and size, which can provide sufficient bone coverage for stable cup fixation that fits the anteroposterior acetabular rim without increasing the cup height more than necessary. We retrospectively reviewed 214 patients who underwent primary total hip arthroplasty (THA) and identified 30 hips with Crowe II (n = 15) or III (n = 15) developmental dysplasia of the hip (DDH). We measured the cup-centre-edge angle (cup-CE) and the vertical and horizontal distances from the teardrop. In a simulation study, we examined the cup-CE and optimal cup size by changing the cup height in 5-mm increments over a distance of 15-40 mm above the inter-teardrop line using a 3-dimensional template system. Postoperative radiographic evaluation revealed a mean cup-CE of 19.9° in Crowe II hips and 15.2° in Crowe III hips; the respective mean vertical distances were 26.6 mm and 27.6 mm (p = 0.511). There was no evidence of cup loosening or lateralisation at a minimum of 7 years (7-11 years) follow-up. Simulation showed that the hip centre needed to be elevated to 20 mm to acquire a cup-CE of more than 0°. More than 10° of cup-CE could be expected by elevating the hip centre to 25 mm in both Crowe II and III. Even in severe DDH, a high-hip centre positioned approximately 25 mm superior to the inter-teardrop line was sufficient to achieve optimal bone coverage, which could lead to more secure cup fixation.

Bilateral High Hip Center Provides Gait Parameters Similar to Anatomical Reconstruction: A Gait Analysis Study in Hip Replacement Patients With Bilateral Developmental Dysplasia

BackgroundTotal hip arthroplasty in severe dysplasia is challenging due to diminished periacetabular bone stock and the highly placed femoral head. Although anatomical reconstruction of the hip, with required interventions such as subtrochanteric osteotomy and graft usage, is the main aim of the procedure, good long-term clinical outcomes of the high hip center technique have also been reported. Information regarding the effect of hip center placement on gait characteristics is limited; therefore, the aim of this study is to analyze the differences in gait parameters between the high hip center technique and anatomical reconstruction of the hip. MethodsTwenty patients (40 hips) with bilateral Crowe type III-IV developmental dysplasia of the hip who underwent bilateral total hip arthroplasty and completed at least 2 years of follow-up were included. Group 1 comprised 10 patients (20 hips) who underwent anatomical hip center reconstruction, while group 2 comprised 10 patients (20 hips) who underwent high hip center reconstruction. The gait characteristics of patients were examined through markers placed in certain anatomical regions, the cameras placed around, and the force plates embedded in the walking platform. ResultsThere was no significant difference in the gait characteristics according to the location of the hip rotation center. The mean temporospatial, kinematic, and kinetic values were similar between the groups. The most prominent difference was in the peak dynamic hip extension, which was lower in group 2 (−9.71° ± 7.46°) compared to group 1 (−6.80° ± 11.44°), although it was not statistically significant (P = .09). ConclusionThe bilateral high hip center technique can provide similar gait characteristics as anatomical reconstruction and may be preferred in particularly difficult cases based on the surgeon’s decision.

High Hip Center Reduces the Dynamic Hip Range of Motion and Increases the Hip Load: A Gait Analysis Study in Hip Arthroplasty Patients With Unilateral Developmental Dysplasia

BackgroundLong-term favorable clinical outcomes of anatomical or high hip center techniques in total hip arthroplasty (THA) are reported in patients with developmental dysplasia of the hip (DDH). However, there is little information about the effect of the hip center location on gait characteristics. The purpose of this study was to compare these surgical techniques with gait analysis, analyze the effect of the hip rotation center location on gait parameters, and discuss the possible problems that may arise. MethodsA total of 40 patients who underwent THA due to unilateral coxarthrosis secondary to Crowe type III-IV DDH and completed 5 years of follow-up were included in the study. Group 1 included 20 patients who underwent anatomical hip center reconstruction, while group 2 included 20 patients who underwent high hip center reconstruction. Gait analysis was performed, and the groups were compared according to the gait characteristics. ResultsThe mean temporospatial values were similar between the groups. The extension of the operated side was significantly lower in group 2 (−9.11 ± 8.92) than in group 1 (−1.87 ± 11.51) (P = .04). The mean longitudinal hip joint force was found to be significantly higher in group 2 (8.92 N/kg ± 0.54) than in group 1 (8.16 N/kg ± 0.66) (P = .04). The high hip center technique has been shown to increase the load on the hip and restrict the dynamic range of motion. ConclusionThe high hip center technique can decrease the survival of the implant and increase the fall risk as it increases the load on the hip and reduces the dynamic range of motion. The hip center should be reconstructed anatomically when possible in DDH patients who undergo unilateral THA.

Le centre de rotation influence-t-il la récupération du moment des abducteurs après arthroplastie totale de hanche

BackgroundIn total hip arthroplasty (THA), placing the cup in an anatomic position is not always possible in case of deformities related to developmental dysplasia of the hip (DDH). Thus far, the influence of a hip center on the abductor moment after THA has not been clearly elucidated. Therefore, we performed a retrospective study to assess 1) how abductor muscle moment recovers postoperatively in THA and 2) whether acetabular cup position affects the recovery of abductor moment. HypothesisA high hip center affects the recovery of abductor moment of a dysplastic hip after THA. Patients and methodsWe evaluated 100 patients, who underwent unilateral primary THA, at 12 months postoperatively. The study included 86 women and 14 men, with a mean age of 65.5±9.9 years (range, 40 to 86 years). Patients with secondary osteoarthritis due to DDH were included (Crowe 1: 76; Crowe 2: 15, Crowe 3: 9, and Crowe 4: none). A cementless straight stem was implanted in all hips. Hip abductor moment was measured using a belt-stabilized handheld dynamometer. The ratio of moment of the affected side to that of the contralateral side was calculated as moment ratio. The horizontal and vertical centers of rotation (H-COR and V-COR) (with respect to the inter teardrop line) and vertical shift (V-shift) (difference in V-COR between the affected hip and the contralateral normal hip) were determined. ResultsAt 6 and 12 months postoperatively, the abductor moment ratios were 95.1 and 94.7%, respectively. Significant negative correlation was observed between the postoperative abductor moment ratio and V-COR at 6 months postoperatively (r=−0.2436, p=0.0238). Significant delay in the recovery of abductor moment ratio was observed in the groups with higher hip center (V-shift>15mm) (odds ratio=12.7; 95% CI, 2.11–232.1, p=0.0034) at 6 months postoperatively, which was fully recovered at 12 months postoperatively. DiscussionSuperior placement of a hip center, more than 15mm above the true hip center, delayed the recovery of abductor muscle moment after THA. Level of evidenceIII, retrospective comparative study.

Acetabular cup position on high hip and anatomical position in total hip arthroplasty for Crowe III developmental dysplasia of hip joint

To evaluate clinical outcomes of acetabular cup position on high hip and anatomical position in total hip arthroplasty for Crowe III developmental dysplasia of hip joint. Forty-six patients(58 hips) treated with high hip center THA from January 2010 to December 2015, including 6 males (8 hips) and 40 females(50 hips) aged from 40 to 70 years old with an average of(54.3±7.6) years old. While 20 patients(28 hips) treated with anatomical position in THA from January 2004 and December 2009 were analyzed as control, including 4 males (5 hips) and 16 females (23 hips), aged from 42 to 68 years old with an average of (53.0±7.1) years old. Operative time, blood loss, Harris score (HHS), gait analysis, Trendelanburg signal, imaging examinations and prosthesis survivorship were compared between two groups. Operative time and blood loss in high hip group(75.1±13.3) min and (108.4±47.1) ml respectively were lower than that of in anatomical position group(107.7±17.1) min and(201.0±58.6) ml respectively. There was no statistical difference in HSS score at 2 years after operation in high hip group(92.3±3.7) scores and anatomical position group(91.4±3.6) scores. No obvious meaning in lower limb differences in high hip group (3.8±2.1) mm and anatomical position group (3.5±1.6) mm. The vertical distance between center of rotation to teardrop in high hip group(31.6±7.8) mm was higher than that of anatomical group(19.3±7.4) mm;while there was no significant differences in horizontal distance between high hip group (30.1±7.7) mm and anatomical group(29.4±7.5) mm. There was no statistical significance in prosthesis survivorship. The gait was good without lameness and positive features of Trendelanburg signal caused by insufficient of abductor. For Crowe III DDH, a high hip center cementless cup without bone graft is a liable method with good function and high rate of prosthesis survivorship. And satisfying short-term clinical and radiographic results could be achieved by this method.

Does hip center location affect the recovery of abductor moment after total hip arthroplasty?

BackgroundIn total hip arthroplasty (THA), placing the cup in an anatomic position is not always possible in case of deformities related to developmental dysplasia of the hip (DDH). Thus far, the influence of a hip center on the abductor moment after THA has not been clearly elucidated. Therefore, we performed a retrospective study to assess (1) how abductor muscle moment recovers postoperatively in THA and (2) whether acetabular cup position affects the recovery of abductor moment. HypothesisA high hip center affects the recovery of abductor moment of a dysplastic hip after THA. Patients and MethodsWe evaluated 100 patients, who underwent unilateral primary THA, at 12 months postoperatively. The study included 86 women and 14 men, with a mean age of 65.5±9.9 years (range, 40 to 86 years). Patients with secondary osteoarthritis due to DDH were included (Crowe 1: 76; Crowe 2: 15, Crowe 3:9, and Crowe 4: none). A cementless straight stem was implanted in all hips. Hip abductor moment was measured using a belt-stabilized hand-held dynamometer. The ratio of moment of the affected side to that of the contralateral side was calculated as moment ratio. The horizontal and vertical centers of rotation (H-COR and V-COR) (with respect to the inter teardrop line) and vertical shift (V-shift) (difference in V-COR between the affected hip and the contralateral normal hip) were determined. ResultsAt 6 and 12 months postoperatively, the abductor moment ratios were 95.1 and 94.7%, respectively. Significant negative correlation was observed between the postoperative abductor moment ratio and V-COR at 6 months postoperatively (r=−0.2436, p=0.0238). Significant delay in the recovery of abductor moment ratio was observed in the groups with higher hip center (V-shift>15mm) (odds ratio=12.7; 95% CI: 2.11–232.1, p=0.0034) at 6 months postoperatively, which was fully recovered at 12 months postoperatively. DiscussionSuperior placement of a hip center, more than 15mm above the true hip center, delayed the recovery of abductor muscle moment after THA. Level of evidenceIII, retrospective comparative study.

Does high hip centre affect dislocation after total hip arthroplasty for developmental dysplasia of the hip?

To achieve sufficient socket coverage by the native bone, high placement of cementless acetabular cup is often required. We previously reported, using computer simulation, that higher hip centre improved the bone coverage but decreased the range of motion in total hip arthroplasty (THA) for patients with hip dysplasia. However, in a clinical setting, the correlation between the hip centre height and dislocation after primary THA is still unclear. We examined whether a high hip centre affects dislocation after THA. A total of 910 patients, with 1079 dysplastic hips, who underwent primary THA were retrospectively reviewed. The age at THA averaged 63.0years and mean follow-up was 74.3months. Vertical centre of rotation (V-COR) was defined as the distance from the head centre to the interteardrop line. Uni- and multivariate logistic regression models were applied to identify significant factors affecting dislocation. Ten hips in nine patients (0.9%) had dislocation after THA. In univariate analysis, age at surgery and V-COR were significant risk factors for dislocation. Multivariate analysis identified advanced age at operation (odds ratio [OR] 1.8/5years), Crowe classification (OR 15.6), V-COR (OR 3.1/5mm), and femoral head size (OR 11.6) as independent risk factors for dislocation. Receiver operating characteristic curve analysis revealed the cutoff value of the V-COR for dislocation as 23.9mm. A higher hip centre with the V-COR > 23.9mm affected dislocation after THA for DDH. Our results would be useful for reconstruction of the hip centre, particularly with cementless acetabular cups.

Developmental Dysplasia Treated With Cementless Total Hip Arthroplasty Utilizing High Hip Center Reconstruction: A Minimum 13-Year Follow-up Study

BackgroundThe primary aim of this study was to determine the clinical outcomes at 13-year follow-up of patients diagnosed with developmental dysplasia of the hip and subsequently treated with total hip arthroplasty (THA). The secondary aim was to investigate the effect of hip center location on clinical outcomes and polyethylene wear. MethodsWe reviewed data from a consecutive series of 104 patients (123 hips) from a single center. Patients were treated with THA with the high hip center (HHC) technique using cementless acetabular shells and highly cross-linked liners. Radiographs were collected preoperatively and through 13-year follow-up to assess degree of dysplasia (Crowe classification), component positioning, occurrence of bone resorption, and polyethylene wear. The Harris Hip Score (HHS) was administered at 4 and 13 years. ResultsNo patients were lost to follow-up, and one was revised for femoral loosening. Radiolucency was seen in 20% of patients and was not associated with HHC (P = .560). No patients developed osteolysis. The wear rate was low for all patients (mean: 3 ± 19 μm/y) and not associated with HHC (P = .852). The median 13-year HHS was 91.9 (interquartile range: 84.8-97.0). There was a statistically significant decline from the 4- to 13-year HHS (P < .001) for the Crowe II-IV group, although 82% of these patients remained above 80 points at 13 years. The nondysplastic and Crowe I group showed no longitudinal change in HHS (P = .243). ConclusionThis cup design and highly cross-linked polyethylene liner combination demonstrates excellent clinical outcomes, similar to THA for primary osteoarthritis, through 13-year follow-up in patients with various degrees of developmental dysplasia of the hip and HHC reconstructions.

Long-term retrospective study on the placement of the cementless acetabular cup and clinical outcomes in patients undergoing femoral head autografting for hip dysplasia and total hip arthroplasty.

Placement of acetabular cup in the dysplastic hip is a challenging procedure. Using bulk femoral headautograft to increase the bony coverage of the cup is one of the techniques, which have been described. Theimpact of cup position on cup and autograft survival is a controversial issue. We aimed to determine whether the position of cementless acetabular cup used in conjunction with femoral head autograft in dysplastic hips affected the autograft-host incorporation with its final radiographic appearance and the cup survivorship into the second decade. Thirty-eight dysplastic hips with varying Crowe types in 31 patients (30 women and one man) were included. The mean age was 47 years (range, 29-64 years) and the mean follow-up was 20.3 years (range, 14.8-25.9 years). The initial postoperative and final radiographs were evaluated. The survival rate of the cups was analysed using Kaplan-Meier statistics and the log-rank test. Multivariate analysis was used to evaluate the effect of variables (Crowe type, radiographic initial host bone coverage over the cup and position of the cup) on survivorship. The acetabular cups were positioned anatomical in 27/38 hips according to Ranawat measurement technique. Trabecular bridging at graft-host interface was seen in all cases at an average 22.1 months. Neither acetabular cup position nor initial host bone coverage over acetabular cup less than 50% had any significant effect on either cup survival or final radiographic appearance of the graft. The 20-year cup survival rate without aseptic revision was 66% (95 CI, 52%-84%). No revision was performed due to graft resorption. Twenty-year survival rate of the cementless cup combination with femoral head autograft showed no significant differences whether it was placed at high or anatomic hip centre. The final radiographic appearance of the autograft was not affected from either the cup location or the initial radiographic horizontal host bone coverage.

Minimum 10-Year Outcome of One-Stage Total Hip Arthroplasty Without Subtrochanteric Osteotomy Using a Cementless Custom Stem for Crowe III and IV Hip Dislocation

BackgroundOptions for total hip arthroplasty (THA) in high dislocated hips include subtrochanteric osteotomy (STO), high hip center positioning, and 2-stage surgery with progressive lowering using an external fixator before THA. We described the long-term results of 1-stage THA performed without STO, using a cementless customized stem associated if necessary with sequential tenotomies and/or greater trochanteric osteotomy. MethodsNinety-eight consecutive THA without STO were performed using this technique. Of those 98 hips, 26 hips with high dislocation (12 class III and 14 class IV according to the Crowe classification) were evaluated at an average follow-up of 16 (10-22) years. ResultsAt the time of last follow-up, the mean Harris Hip Score was 86 points (37-100). The mean leg-length discrepancy was 7 ± 5 mm (0-17). Two transient (7.7%) nerve palsies (1 sciatic and 1 femoral) were notified. A revision was required for 6 hips (23.1%). Kaplan-Meier survivorship analysis at 15 years regarding aseptic loosening of the femoral component was 87.5% (95% confidence interval, 76.5-99.1). During the same period, acetabular implant survivorship free from revision for aseptic loosening was 96.1% (95% confidence interval, 92.7-99.9). ConclusionThe combination of intramedullary fit and extramedullary adaptation for offset and anteversion provided by the custom stem can avoid additional procedures associated to THA in high developmental dysplasia of the hip. The clinical function and long-term survival reported in this series is encouraging for THA performed in case of high hip dislocation.

Cementless Total Hip Arthroplasty in Crowe III and IV Dysplasia: High Hip Center and Modular Necks

BackgroundTotal hip arthroplasty (THA) in severe developmental dysplasia of the hip (DDH) is a challenging procedure. The most used techniques involve anatomic cup positioning, augmentation femoral osteotomy. However, anatomic cup positioning is not always feasible in severe DDH and osteotomy nonunion may ensue. The purpose of the study was to assess the survivorship, the hip score results, the radiological parameters (fixation, loosening, component position) of a large cohort of patients with Crowe III and IV DDH, treated with high hip center and modular necks THAs. MethodsEighty-four THAs in Crowe III and IV DDH were evaluated, achieving a final follow-up of 15.1 years. All the patients were treated with the same cementless implant (modular necks and ceramic-on-ceramic coupling) and the same approach (high cup placement with slight medialization). The patients were clinically evaluated (Harris Hip score and Merle d'Aubigne and Postel score). A radiographic evaluation was performed, analyzing the orientation of the cup. ResultsEighty patients were available at the last follow-up. The clinical scores were good at the final follow-up. Two sciatic lesions occurred: one patient fully recovered. The overall survivorship was 90.5% at 15 years: only 2 cases of aseptic loosening were reported. The mean center of rotation height was 33 ± 8 mm and the medialization was 30 ± 5 mm. ConclusionA high cup placement with slight medialization is a valid technique in DDH patients. A good restoration of the offset, ceramic-on-ceramic coupling and a porous socket may provide durable results, overcoming the effects of increasing joint reaction forces related to high cup placement.

Computed Tomographic Evaluation of Bone Stock in Patients With Crowe Type III Developmental Dysplasia of the Hip: Implications for Guiding Acetabular Component Placement Using the High Hip Center Technique

BackgroundWe evaluated acetabular cup coverage (CC) and rim contact (RC) to evaluate the bone stock above the acetabulum for guiding acetabular component placement using the high hip center technique in patients with Crowe type III developmental dysplasia of the hip. MethodsUsing hip computed tomography and image processing software, pelvises were reconstructed digitally in 20 hips with Crowe type III developmental dysplasia of the hip. Mimicked cup was placed with anteversion angles of 0° (group I), 5° (group II), and 10° (group III) respectively. In each group, the cup was placed at the anatomical hip center at first, and then the cup was moved up to 40 mm vertically about the native rotation center with an increment of 2.5 mm at each step. CC and RC were calculated and documented with each movement. ResultsCC was 65.87%, 67.77%, and 68.98% for group I, group II, and group III at the native rotation center, and increased progressively to 86.45%, 85.85%, and 84.71% at 25 mm above. RC was 49.17%, 50.25%, and 51.92% for group I, group II, and group III at the native rotation center, and increased progressively to 86.87%, 86.39%, and 84.94% at 22.5 mm above. CC and RC were positively correlated, despite the different anteversion angles (r = 0.687 at 0°, 0.683 at 5°, and 0.645 at 10°; P < .001). ConclusionComputed tomography analysis and computer stimulation demonstrate that it is feasible to use high hip center technique in Crowe type III hips.

Is high hip center technique an acceptable choice for total hip arthroplasty of the developmental dysplasia of the hip?

Total hip arthroplasty (THA) is a successful method to treat osteoarthritis secondary to the developmental dysplasia of the hip (DDH). As anatomic deformity of acetabulum, anatomic hip center placing of the socket may lead insufficient host bone coverage, therefore, high hip center (HHC) technique is an alternative choice. Location of the hip rotation center can be referenced by inter teardrop line, the highest point of the obturator foramen, summit of the iliac crests, ischial tuberosities and other anatomic landmarks. The HHC technique is supposed to increase host bone coverage of socket without structural bone grafts, simplify surgical procedures, reduce anesthetic and surgical time, conserve adequate healthy bone stock for revision, however, it leads to insufficiency of the abductor muscles, is speculated to increase the hip load, lower the range of hip flexion and internal rotation (IR). Loosening rates and polyethylene wear vary in different studies. Concerning about these factors, HHC technique is acceptable while center of rotation located at a horizontal level with distance less than 35 mm from the inter teardrop line, moreover, medialization of these HHC reconstructions is suggested.

Anatomic placement of the acetabulum improves the survival rate in patients with Crowe type-II dysplasia undergoing total hip arthroplasty.

Total hip replacement in patients with developmental dysplasia of the hip (DDH) is a difficult, technical procedure for surgeons to perform because of the potential risks for these patients to have severe abnormalities in their bones and soft tissues (1,2).. The procedure is more demanding and is associated with a higher rate of complication compared to total hip arthroplasty (THA) for the treatment of primary degenerative osteoarthrosis of the hip (3). In general, the accepted practice is that placement of the acetabulum in the anatomic location is more advantageous biomechanically and may lead to higher prosthetic survival rates in these patients (4-6). Some of the most experienced hip surgeons agree that the optimum location for the center of rotation of a THA is the anatomic position. Therefore, recent literatures suggest placing the acetabular component in the anatomic hip-center for different types of DDH. Several techniques have been used to reconstruct the acetabulum during THA in DDH patients, including augmentation with bone grafting with cemented or noncemented acetabular component (7-9) or using high hip centre (10,11) when there is no better choice. Yet, there still remain some controversies as to whether a high hip center, particularly without bone graft, is the best option for patients with severe hip dysplasia.

Feasibility of biological acetabular component with high placement technique in hip revision arthroplasty

Objective To investigate the feasibility of biological acetabular component with high placement technique in hip revision arthroplasty. Methods From March 2006 to March 2015, 34 patients (35 hips) underwent hip revision arthroplasty with biological acetabular components with high placement technique. There were 15 males (15 hips) and 19 females (20 hips) with an average of 55 years (range, 26-74 years). There were 22 hips caused by aseptic loosening and 13 hips by infection. The acetabular bone defects included Paprosky IIA in 3 cases, IIB in 4, IIC in 2, IIIA in 17, and IIIB in 9. Modular tapered stems with distal fixation were performed in most femoral sides. The height of hip center was greater than 2.5 cm for all the patients, which were divided into two groups according to the degree of placement: 2.5-3.5 cm for the high placement group, greater than 3.5 cm for the high hip center group. Harris hip score, pain visual analogue score (VAS), leg length difference, gait characteristics were compared between two groups postoperatively and at the final follow-up respectively. The height of hip center and the horizontal distance between hip center and teardrop were measured in the hip X-ray. Radiolucent lines and migrations were also recorded. Results The average operation time and blood loss was 108 min (100-220 min) and 525 ml (300-1 200 ml) in two groups respectively. All the patients were followed up for average 49.2 months (range, 12-116 months). At the final follow-up, the average Harris hip score improved from 36.52±17.17 points preoperatively to 83.46±7.63 (t=18.99, P=0.001). The average VAS score decreased from 8.06±1.24 points preoperatively to 1.91±1.62 postoperatively (t=18.57, P=0.001). The height of hip center was 1.47±0.33 cm preoperatively and 3.85±1.13 cm postoperatively (t=12.15, P=0.001). The horizontal distance was 3.33±0.53 cm pre-operatively and 3.23±0.63 cm post-operatively (t=0.98, P=0.640). At the final follow-up, Trendelenburg sign improved from 25/10 (positive/negative, hips) preoperatively to 7/28 (χ2=18.65, P=0.001). There was 1 case of severe limp, moderate in 1, mild in 8 and other cases had no limp. The leg length discrepancy decreased from 1.84±1.92 cm preoperatively to 0.71±1.57 postoperatively (t=4.24, P=0.001). There were 6 cases of Paprosky IIIb with the use of ultra small cup and extremely high placement. The average Harris hip score improved from 26.65±13.46 points preoperatively to 79.83±10.55 (t=12.33, P=0.001). The average VAS score decreased from 8.50 ± 1.38 points preoperatively to 2.83 ± 2.64 postoperatively (t=4.61, P=0.006). One case had acetabular loosening at 4 years later postoperatively and re-revision surgery was performed. Other patients had no infection, dislocation, periprosthetic fracture or any other complications at the final follow-up. Conclusion Highly placement of biological acetabular component with a distal tapered modular stem can get enough contact with the host bone and achieve optimal clinical outcomes, regardless of the degree of high placement. Particularly, using ultra small cup in extremely high placement shows good effectiveness in simplified operation, and it can be used in many complicated or even impossible acetabular reconstruction. Key words: Arthroplasty, replacement, hip; Reoperation; Acetabulum; Osteolysis; Prosthesis-related infections

Favorable Results of Primary Total Hip Arthroplasty With Acetabular Impaction Bone Grafting for Large Segmental Bone Defects in Dysplastic Hips

BackgroundThe aim of the present study was to assess midterm results after acetabular impaction bone grafting (IBG) in primary total hip arthroplasty (THA) for developmental dysplasia of the hip (DDH) with large acetabular segmental defect. MethodsPrimary THA with IBG for DDH with large acetabular segmental defect was performed in 40 hips of 38 patients. The average age was 61.6 years (range: 33-82 years), and the average follow-up period was 7.5 years (range: 3-10.3 years). The Merle d'Aubigné and Postel hip score and complications were assessed. For radiological assessment, postoperative location of the hip rotation center, the socket inclination angle, and the socket center-edge angle were assessed. Kaplan-Meier survival analysis was performed with the end points of any type of reoperation and aseptic acetabular loosening. ResultsThe mean Merle d'Aubigné and Postel hip score improved from 10.4 points to 16.2 points at the final follow-up. Reoperation was performed in 1 case for acute infection without loosening. In 39 out of 40 hips (97.5%), the center of hip rotation was located beneath the “high hip center.” The average socket inclination angle was 39.3° (range: 30°-54°), and the average socket center-edge angle was −11.8° (range: −23° to 9°). Survival rate of acetabular component at 8 years with the end point of any reoperation and of aseptic loosening was 96.6% (95% confidence interval: 89.9%-100%) and 100%, respectively. ConclusionAcetabular IBG represents one of the useful options for restoring a normal hip center and acetabular bone stock in primary THA for DDH with large acetabular defect.

Does High Hip Center Decrease Range of Motion in Total Hip Arthroplasty? A Computer Simulation Study

BackgroundHigh placement of a cementless acetabular cup is often required to have sufficient bone coverage in hip dysplasia. We examined whether a high hip center decreases the postoperative range of motion (ROM) in total hip arthroplasty. MethodsUsing a computer software, ROM and bone coverage were examined in 32 patients with unilateral osteoarthritis of the hip with Crowe type II or III hip dysplasia. The cup was placed at the anatomic hip center and moved vertically in 5-mm increments. Vertical center of rotation (V-COR) was defined as the distance from the head center to the interteardrop line. The required ROM was defined as flexion ≥110°, internal rotation (IR) at 90° flexion ≥30°, extension ≥30°, and external rotation ≥30°. We determined the V-COR to satisfy the required ROM and cup center-edge angle (Cup-CE) ≥0°. ResultsOnly 40.6% of the patients satisfied Cup-CE ≥0° at the anatomic hip center. Bone coverage increased with the peak at 30, 35 mm of V-COR (90.6% satisfied Cup-CE ≥0°) and decreased at ≥40 mm. Higher V-COR resulted in lower range of flexion and IR, but increased the range of extension and external rotation. The cutoff value from the receiver-operating characteristic curve for both flexion and IR was a V-COR of 35 mm. ConclusionThe higher hip center gained more bone coverage but decreased the range of hip flexion and IR. Acceptable V-COR in hip dysplasia was around 35 mm, about 20 mm above the true hip center, in terms of ROM.

The jumbo acetabular component for acetabular revision: Curtain Calls and Caveats.

The 'jumbo' acetabular component is now commonly used in acetabular revision surgery where there is extensive bone loss. It offers high surface contact, permits weight bearing over a large area of the pelvis, the need for bone grafting is reduced and it is usually possible to restore centre of rotation of the hip. Disadvantages of its use include a technique in which bone structure may not be restored, a risk of excessive posterior bone loss during reaming, an obligation to employ screw fixation, limited bone ingrowth with late failure and high hip centre, leading to increased risk of dislocation. Contraindications include unaddressed pelvic dissociation, inability to implant the component with a rim fit, and an inability to achieve screw fixation. Use in acetabulae with < 50% bone stock has also been questioned. Published results have been encouraging in the first decade, with late failures predominantly because of polyethylene wear and aseptic loosening. Dislocation is the most common complication of jumbo acetabular revisions, with an incidence of approximately 10%, and often mandates revision. Based on published results, a hemispherical component with an enhanced porous coating, highly cross-linked polyethylene, and a large femoral head appears to represent the optimum tribology for jumbo acetabular revisions.