Satisfactory intermediate and long-term results of rotational acetabular osteotomy (RAO) for the treatment of early osteoarthritis secondary to developmental dysplasia of the hip have been reported. The purpose of this study is to examine the 30-year results of RAO. Between 1987 and 1994, we treated 49 patients (55 hips) with RAO for diagnosis of pre- OA or early-stage OA. Of those patients, 35 patients (43 hips) were available at a minimum of 28 years. The follow-up rate was 78.2% and the mean follow-up was 30.5 years. The mean age at the time of surgery was 34 years. Clinical evaluation was performed with the Merle d'Aubigne and Postel rating scale, and radiographic analyses included measurements of the center-edge angle, acetabular roof angle, and head lateralization index on preoperative, postoperative AP radiographs of the pelvis. Postoperative joint congruency was classified into four grades. The radiographic evidence of progression of OA was defined as the minimum joint space less than 2.5mm. The mean preoperative clinical score was 14.0, which improved to a mean of 15.3 at the time of the latest follow-up. The mean center-edge angle improved from 0.6° preoperatively to 34° postoperatively, the mean acetabular roof angle improved from 28.4°preoperatively to 1.0°postoperatively, the mean head lateralization index improved from 0.642 preoperatively to 0.59 postoperatively. Postoperative joint congruency was excellent in 11 hips, good in 29 hips, and fair in 3 hips. Nineteen patients (20 hips) had radiographic OA progression, and 10 patients (11 hips) were converted to THA. Kaplan-Meier survivorship analysis, with radiographic OA progression as the end point, predicted survival of 75.6% at 20 years and 48.8% at 30 years, and with THA conversion as the end point, 90.2% at 20 years and 71.2% at 30 years. The RAO is an effective surgical procedure for symptomatic dysplastic hips of pre- and early-stage OA and could change the natural history of the dysplastic hip

[Introduction]. Total hip arthroplasty (THA) markedly improves pain, gait, and activities of daily living for most patients with osteoarthritis. However, pelvic osteotomy has been recommended for young and active patients with hip dysplasia, because THA in that population is associated with high rates of revision THA. The rotational acetabular osteotomy (RAO) of Ninomiya and Tagawa, and the eccentric rotational acetabular osteotomy of Hasegawa for hip dysplasia reportedly are successful in young and active patients. However, even after the surgery of RAO, osteoarthritis developed in some cases and leaded to the conversion to THA. The differences of bone quality of acetabulum have been reported between at the surgery of THA after RAO and at the surgery of primary THA. We should not discuss the results of these two THA equally. The purpose of this study is to report the results of THA after RAO. [Patients and Methods]. We retrospectively reviewed 33 patients (37 hips) treated by total hip arthroplasty after rotational acetabular osteotomy between 1992 and 2012. Five cases were performed RAO with valgus osteotomy. At the time of THA surgery, the overall mean age of the patients was 57.5 years (range, 39–72 years). The average of follow-up period was 7.0 years (range, 8–258 months). One surgeon (TT) evaluated the hips clinically using the Japanese Orthopaedics Association (JOA) score. The radiographic measurements were performed by the other physician (JY) blinded to the clinical scores. Radiographical examination was performed using AP X-ray. We evaluated the presence of osteolysis and loosening of the implants. We evaluated the stability of stem implants using Engh classification and of cup implants using Hodgkinson classification. [Results]. The cases of this study were converted to THA in an average 17.2 years after the surgery of RAO. JOA score was 55.7 points before THA and 86.7 points at the final follow-up. Osteolysis were found in five cases. Thirty-three cases showed good implant stability, but four cases showed fibrous union between cup and acetabulum. Three cases were converted to the revision THA due to fibrous union. All revision cases were acetabular side. [Discussion]. There were no reports about results of THA after RAO. Osteotomy should be considered for young patients because of the high rates of revision THA needed owing to prolongation of the average lifespan. McAuley et al reported the results of THA in patients 50 years and younger patients. They described the survival rates for femoral and acetabular components, using any revision as the end point, were 89% at 10-year followup and 60% at 15-year followup. Osteosclerosis of the acetabular roof bone should be careful in the case of THA after RAO. The cancellous bone could hardly be founded, even if the enough reaming was performed. Osteosclerosis may cause the difficulty in ingrowth of new bone into the implant, and lead to fibrous union between the acetabular roof bone and the implant. These two revision cases showed fibrous union before their THA. Primary fixation is very important in the case of THA after RAO. Primary fixation is very important in the case of THA after the RAO

Aims: To evaluate technical and clinical results of a new 2-incision technique of rotational acetabular osteotomy. Methods: 27 patients, with a mean age of 40 years, were reviewed after a minimum of 1 year subsequently to rotational acetabular osteotomy, which was done through short low midline and iliac approaches. An analysis of complications, the length of rehabilitation period, time to union of the osteotomy, radiographic correction of acetabular roof, proceeding of hip arthrosis, as well as of clinical status at follow-up, using scores by Merle DñAubigne and Harris, was performed. Results: No major operative complications were observed. The median time to union of osteotomy and a painless status was 10 weeks. Femoral head covering by acetabular roof increased signiþcantly, whereas the range of motion of the operated hip was not compromised by the operation. A signiþcant increase in the mean scores, mainly caused by a decrease in pain, were observed in a subgroup of 20 patients with a minimum follow-up of 2 years. The most signiþcant factor predisposing poor outcome was grave preoperative arthrosis of the hip. Conclusions: This new technique of osteotomy is safe and less traumatic than previous methods, allowing early weight bearing and a fast recovery. The early clinical results are satisfactory

Background. The rotational acetabular osteotomy (RAO), that was developed in Japan, has been used successfully in patients with developmental dysplasia of the hip (DDH) (Figure 1). However there are some patients who are forced to have a total hip arthroplasty (THA) due to the progression of osteoarthritis. It is unknown if a RAO poses technical difficulties or increases the chances of complications if a THA must be performed afterwards becausethere is not much data on patients who underwent a THA after a previous RAO. Objectives. The purpose of this study was to investigate the mid-term results of a THA after a RAO. Methods. We compared 22 THAs (2 males and 16 females) that were performed after previous RAOs (group R) with a control group of 28 patients (30 hips) who only underwent THAs (2 males and 27 females, group C). The average age at surgery in Group R and C was 53.6 years and 55.8 years, the average follow-up period was 7.2 years (range, 6–10 years), 7.7 years (range, 6–11 years). The average interval from osteotomy to THA was 12.7 years. Trilogy acetabular components (Zimmer) were used for all patients. Results. No acetabular or femoral components exhibited loosening or revision in both groups. No osteolysis was seen in both groups and there was no significant difference in terms of the incidence of ectopic ossification. The Harris hip score (HHS) at the most recent follow-up was not compromised (Group R: mean, 93.2, Group C: 94.3), there were no significant differences in intraoperative blood loss and operative times between the two groups (Group R: mean, 136.0 ml; 89.5 mins, Group C: 131.3 ml; 96.3 mins) Group R did not have higher rates of infection, dislocation, intraoperative fracture or deep venous thrombosis compared with group C. Acetabular components in group R were placed more superiorly and laterally than group C (Figure 2, Table 1). On the other hand, the acetabulum after RAO often gets harder than the one that did not undergo a previous osteotomy. The Screw that is used to fix the acetabular component has been found to work well in securing the sclerotic acetabulum, thus screw fixation of a cementless cup is a feasible option for a THA after a RAO. Conclusions. Patients who underwent aTHA after a successful RAO had mid-term results similar to those of other dysplastic hips. The results of this study found RAOs do not lead to higher revisions rates, compromised HHSs, or shortened survivorships in eventual THAs in DDHs. However there was a tendency of superolateral placement of the acetabular component, therefore a longer follow-up is required to confirm if polyethylene wear increases. The results of this study indicated rotational acetabular osteotomies do not lead to higher revisions rates, compromised HHSs, or shortened survivorships in eventual total hip arthroplasties in developmental dysplasia of the hip

Introduction. Several reports demonstrated the overcoverage of the anterior acetabulum. Anterior CE angle over 46°may be a probable risk factor for pincer FAI syndrome after a rotational acetabular osteotomy. In addition, a highly anteverted femoral neck, reported as a risk factor for posterior impingement, has been found in DDH patients. These findings indicate proper acetabular reorientation is essential to avoid anterior or posterior impingement after periacetabular osteotomy (PAO). The aim of this study was to evaluate the relationship between acetabular three-dimensional (3D) alignment reorientation and clinical range of motion (ROM) after periacetabular osteotomy (PAO). Methods. A total of 53 patients who underwent curved PAO (CPO) for DDH from January 2014 to April 2017 were selected. Three (5.7%) of them were lost to follow-up. Therefore, the data from 58 hips, contributed by 50 patients (44 women and 6 men), were included in the analysis. Pre- and postoperative computed tomography (CT) scans from the pelvis to the knee joint were performed and transferred to a 3D template software (Zed Hip; Lexi, Tokyo, Japan). The pelvic plane axis was defined according to the functional pelvic plane. The pre- and postoperative lateral and anterior 3D center-edge (CE) angles were measured on the coronal and sagittal views through the center of the femoral head. The pre- and postoperative 3D center-edge (CE) angles and femoral anteversion were measured and compared with clinical outcomes, including postoperative ROM. Results. The radiographical outcomes of our study are demonstrated in Figure 1. The mean values of pre- and postoperative lateral CE angles were 12.6º±8.7 and 30.2º±9.7, respectively (p<0.001), and mean pre- and postoperative anterior CE angles were 42.4º±15.3 and 63.9º±12.1, respectively (p<0.001). Both CE angles were significantly improved. The correlation between pre- and postoperative acetabular coverage and postoperative ROM was evaluated. Postoperative abduction and internal rotation ROM were significantly associated with postoperative lateral CE angles (abduction; p < 0.001, internal rotation; p = 0.028); flexion and internal rotation ROM was significantly associated with postoperative anterior CE angles (flexion; p < 0.001, internal rotation; p = 0.028). Femoral anteversion was negatively correlated with postoperative abduction (p = 0.017) and external rotation (p = 0.047) ROM (Table 1). Postoperative abduction ROM was strongly positively correlated with femoral anteversion, whereas postoperative external rotation was strongly negatively correlated (Table 2). The total anteversion was strongly correlated with pre- or postoperative ROMs during flexion and internal rotation ROM (Table 2). Conclusion. Postoperativeanterior acetabular coverage may affect internal rotation ROM more than the lateral coverage. Therefore, the direction of acetabular reorientation should be carefully determined according to 3D alignment during PAO. For any figures or tables, please contact the authors directly

Adolescent and young adult patients with a history of DDH and residual hip dysplasia tend to have an early presentation of symptoms. In these patients, a severe acetabular dysplasia, aspheric femoral head and/or high greater trochanter are often observed. We evaluated the long-term results of rotational acetabular osteotomy (RAO) for symptomatic hip dysplasia in patients younger than 21 years. We performed 492 RAOs for hip dysplasia from 1987 to 2017. In these cases, patients younger than 21 years at the time of surgery were 40 patients (46 hips). We evaluated 34 patients (40 hips, follow-up rate; 85%) retrospectively. There were 32 females and two males; their mean age at the time of surgery was 17.8 years (12–21). The mean follow-up period was 16.8 years (1–30). In eight hips, isolated RAO was not adequate to correct instability and/or congruency. For these hips, four varus femoral osteotomies, two valgus femoral osteotomies and two greater trochanter displacement were combined with RAO. The mean clinical score (JOA) was improved from 80 to 90 significantly at the final follow-up. The mean CE angle was improved from −3.4 (−35–10) degrees to 27 (8–42) degrees, acetabular roof angle from 30 (15–60) degrees to 6.7 (−3–30) degrees, head lateralization index from 0.665 (0.5–1.0) to 0.614 (0.429–0.7) postoperatively. Radiographic OA progression was observed in four hips, but no hip was converted to THA. The RAO is an effective technique for surgical correction of a relatively severe dysplastic hip in adolescent and young adults

Objective. To investigate the biomechanical basis and report preliminary clinical efficacy of eccentric rotational acetabular osteotomy (ERAO) when treating developmental dysplasia of the hip (DDH). Methods. Biomechanical model of the hip joint was established on cadaveric hips. After performed ERAO on the biomechanical model, we explored the impact of this surgery on biomechanics of the hip joint. Meanwhile, we reported postoperative follow-up cases who underwent ERAO in our hospital between November 2007 to July 2012. A total of 14 patients (15 hips) were reported, including 4 males and 10 females, mean age was 30 years old. Harris hip score was defined as clinical evaluation standard and radiographic assessment was based on the measurement and further comparison of pre- and post-operative AHI (Acetabular-head index), CE angle (Center-edge angle) and Sharp angle. Results. The established biomechanical model was accord with the physiological state of normal hip joint. Postoperative stress was not statistically significant compared with the preoperative stress. Meanwhile, by the end of follow-up, 13 patients (14 hips) were followed for an average time of 26 months, thus, the follow-up rate was 92.9%. Harris hip score improved from preoperative (67.1 ± 8.7) points to (88.1 ± 7.3) points; postoperative AHI increased an average of 39.6%, CE angle increased an average of 33.2 ° and sharp angle reduced an average of 9.6 °. Conclusions. Both biomechanical study and preliminary clinical observation show that ERAO has the ability to correct the deformity of acetabulum. It enlarges the acetabular coverage of the femoral head and thus corrects the abnormal stress pattern. No bone graft is needed during the operation and postoperative rehabilitation is short, therefore, ERAO may have good curative effect when treating the DDH

Introduction. Pelvic osteotomy such as Chiari osteotomy and rotational acetabular osteotomy (RAO) have been used successfully in patients with developmental dysplasia of the hip (DDH). However, some patients are forced to undergo total hip arthroplasty (THA) because of the progression of osteoarthritis. THA after pelvic osteotomy is thought to be more difficult because of altered anatomy of the pelvis. We compared six THAs done in dysplastic hips after previous pelvic osteotomy between 2008 and 2015 with a well-matched control group of 20 primary procedures done during the same period. Materials and methods. Six THAs for DDH after previous Pelvic osteotomy (three Chiari osteotomies and three RAOs) were compared with 20 THAs for DDH without previous surgery. The patients were matched for age, sex, and BMI. Minimum follow-up for both groups of patients was one year (range, 12–79 months and 12–77 months, respectively). The average interval from pelvic osteotomy to total hip arthroplasty was 19.8 years (range 12–26 years). Clinical and Radiological evaluations were performed. Results. Both groups had similar short-term results except clinical score. There were no signiï¬ï¿½cant differences in range of motion, intraoperative blood loss and operative time between the two groups. There were no infections, dislocations, intraoperative fractures, damaged nerves, or deep vein thromboses in either group. Clinical score according to Japanese Orthopaedic Association rating system at the most recent follow-up were significantly lower in previous pelvic osteotomy group (P=0.003). Lower clinical score was assumed to be caused by one patient with previous Chiari osteotomy who had contralateral sciatic nerve palsy which was unrelated to the surgery. Although we were concerned about the failures on the acetabular side in patients with THA after pelvic osteotomy because of osteosclerotic acetabular bone, no acetabular component exhibited loosening or revision. This result supports the thought that the pelvic osteotomy fragment maintains its blood supply and allows porous acetabular components to ingrow. Conclusion. Pelvic osteotomies do not seem to compromise the short-term clinical or radiographic outcome

Objective. To investigate the biomechanical mechanism and report preliminary clinical efficacy of eccentric rotational acetabular osteotomy (ERAO) when conduct treatment for developmental dysplasia of the hip (DDH). Methods. Biomechanical model of the hip joint was established on six female cadaveric hips embalmed by formalin and stimulate ERAO was then performed on the model. Vertical force was loaded on the cadaveric spine from 0 N to 500 N and strain value on femoral head was measured preoperatively and postoperatively when loading force on spine reached the point of 100, 200, 300, 400 and 500 N. Stress value were then calculated base on the measurements. Besides, we reported postoperative follow up cases which were underwent ERAO to treat DDH in our hospital from July 2007 to October 2014. A total of 25 patients (26 hips) were reported, including 6 males and 19 females. Age varies from 11 to 57 years old, and the average age was 31 years old. Postoperative hip function was evaluated by Harris hip score and anteroposterior X⁃ray of pelvic was taken preoperatively and postoperatively to measure the Acetabular⁃head index (AHI), CE angle and Sharp angle. Results. Preoperative stress increased when loaded on spine became larger, but postoperative stress changed its increasing trend into decreasing when the load was greater than 300 N (turning point), which showed a parabolic trend. Compared with the preoperative stress under different load varying from 100 N to 500 N, postoperative stress was not statistically significant. Meanwhile, by the end of follow up period, 18 patients (19 hips) were followed form 7 to 85 months. The average follow up time was 40months and the follow up rate was 72%. Harris hip score improved from preoperative 64.3±7.2 points to 85.6±5.3 points; postoperative AHI increased an average of 36.5%, CE angle increased an average of 33.1° and sharp angle reduced an average of 12.3°. All differences between pre and post operative indexes were statistically significant. Conclusion. ERAO has the ability to correct the deformity of acetabulum. It enlarges the acetabular coverage of the femoral head and thus reduces the pressure of weight bearing area

Background. CT-based navigation system in total hip arthroplasty(THA) is widely used to achieve accurate implant placement. The purpose of this study was to evaluate the influence of initial error correction according to the differences in the shape of the acetabulum, and correction accuracy associated with operation approach after localization of registration points at anterior or posterior area of the acetabulum. Methods. We set the anterior pelvic plane(APP) as the reference plane, and defined the coordinates as follows: X-axis for external direction, Y-axis for anterior direction, and Z-axis for proximal direction. APP is defined by the anterior superior iliac spines and anterior border of the pubic symphysis. We made a bone model of bilateral acetabular dysplasia of the hip, after rotational acetabulum osteotomy(RAO) on one side, and performed registration using infrared-reflective markers. At first, we registered the initial error on navigation system, and calculated the accuracy of the error correction based on each shape of the acetabulum as we increased the surface matching points. Based on the actual operation approach, we also examined the accuracy of the error correction when concentrating the matching points in anterior or posterior areas of the acetabulum. Results. For the rotational acetabular osteotomy model, the range of possible initial error correction increased as the surface matching points increased on both X-axis and Y-axis: On the X-axis, the range increased from 6mm to 10mm as the surface matching point increased from 10 to 20; and on the Y-axis, the range increased from 2mm to 10mm as the point increased 10 to 50. The range did not increase on the Z-axis. For the acetabular dysplasia model, the range of possible initial error correction increased on the X-axis(the range increased from 2mm to 8mm as the point increased from 10 to 50); however, no increase was observed for the Y- and Z-axis. Furthermore, concentrating the surface matching points in the posterior area around the acetabulum was more effective for the correction of the initial rotational error. Discussion. Because of the different anatomical shapes of the acetabulum, the error directions that were difficult to correct tended to vary between dysplasia and post-RAO. The error correction of Z-axis was difficult on both shapes of the acetabulum. Thus, the careful initial setting on Z-axis is important to minimize the error. Surface matching point on the posterior part of the acetabulum is more effective in correcting the initial rotational error compared with the anterior part of the acetabulum. It was shown that the difference in the error correction was affected by the localization of the registration points around the acetabulum. We presumed that using surface matching points on posterior area of the acetabulum improves the accuracy of the CT-based navigation system on the anterior approach. When using the system, it is important to understand the tendency that the shape of the acetabulum and the localization of the surface matching points have influence on correction of the initial error

The periacetabular osteotomies are effective but technically demanding surgical procedures in the treatment of adult dysplastic hips. We developed a modified technique which combines the two most popular surgeries: the rotational acetabular osteotomy (RAO), and the Bernese osteotomy. Transtrochanteric approach was used in our new spherical osteotomy and provided a good surgical exposure for redirecting the acetabulum with minimal complications. This article describes the surgical procedures in detail and reports the preliminary results in the first 32 hips. As the experiences are encouraging in terms of technical ease and reproducibility, the authors feel that this new osteotomy with transtrochanteric exposure is an ideal choice of surgery in treating residual hip dysplasia in the adult. Key words: osteotomy, periacetabular, hip dysplasia, adult

Purpose. To evaluate the clinical and radiologic midterm results of rotational acetabular osteotomy (RAO) in incongruent hip joints. Material and Methods. A consecutive series of 15 hips in 14 patients who underwent RAO in incongruent hip joint were evaluated at an average follow-up of 52.3 months (range from 36 to 101 months). The average age at operation was 27 years (range from 12 to 38 years) old. The preoperative diagnoses were developmental dysplasia in 4 hips, sequelae of Legg-Calvé-Perthes disease in 8 hips, and multiple epiphyseal dysplasia in 3 hips. The RAO procedures were combined with a femoral valgus oseotomy in 10 hips, advance osteotomy of greater trochanter in 4 hips, derotational osteotomy in 2 hips. Clinically, Harris hip score, range of motion, leg length discrepancy(LLD) and hip joint pain were evaluated. Radiological changes of anterior and lateral center-edge(CE) angle, acetabular roof angle, acetabular head index(AHI), ratio of body weight moment arm to abductor moment arm, and a progression of osteoarthritis were analyzed. Results. The Harris hip score ha been improved from average from 67.5 points preoperatively to 97.6 points postoperatively. There have been no significant changes in the range of motion. The anterior CE angle increased from an average of 9.0°(-19.7□18.6°) to 32.5°(22.6□39.1°), the lateral CE angle from 7.6°(-12.1□14.1)° to 31.7°(26.5□37.8°) and the AHI from 61%(33□73%) to 86%(65□100%). The average ratio of body weight moment arm to abductor moment arm was changed 1.88 to 1.49. There was no case showing progression of osteoarthritis. None of the patients experienced revision surgery. Conclusion. The conventional salvage operation, such as Chiari osteotomy, has been recommended in incongruent hip. However, if we can expect to have a congruency after RAO with/without any femoral osteotomies, it would be a hopeful procedure for the incongruent joints by enhancing acetabular coverage, taking joint surface with normal articular cartilage, increasing abductor moment arm with additional improvement in LLD

BACKGROUND. Our modified procedure for rotational acetabular osteotomy (RAO) aimed to reduce operative invasion of soft tissue and to minimize incision length. SURGICAL TECHNIQUE. A shortened skin incision (10–15 cm versus 20–30 cm in traditional RAO) is curved over greater trochanter and exposed by transtrochanteric approach. Medial gluteus muscle is retracted to expose the ilium without detachment from iliac crest. Similarly the rectus femoris muscle tendon was retracted, not excised, from the anterior inferior iliac spine. The lateral part of the osteotomized ilium is cut in lunate and trapezoid shape to form the bone graft instead of the outer cortical bone of the ilium. PATIENTS. We performed RAO on 66 patients (75 hips) using this modified procedure between 2000 and 2009. Follow-up rate was 95% (71/75 hips). Of 71 hips, 28 had early-stage, and 43 had advanced-stage osteoarthritis. Mean patient age was 39.7 years at time of surgery. Mean length of follow-up was 5.3 years. Clinical assessment was performed using the Merle d'Aubigne & Postel scores. Radiographically, the lateral center-edge (CE) angle, the Sharp angle and acetabular head index (AHI) were evaluated pre- and post-operatively. RESULTS. Mean CE angle, Sharp angle and AHI improved pre- to post-operatively from −1.3 degrees to 36.5 degrees (p<0.00001), 50.3 degrees to 39.4 degrees (p<0.00001), 54.0 % to 95.7 % (p<0.00001), respectively. Clinical hip scores at latest follow-up were significantly improved. No progression of osteoarthritis was seen in hips with early-stage osteoarthritis. Ten hips with advanced-stage osteoarthritis preoperatively had radiographic evidence of progression of osteoarthritis, and six of those were converted to total hip arthroplasty. Complications included two transient lateral femoral cutaneous nerve palsies and ectopic bone formation in 15 hips, one of which required excision 1.5 years post-RAO. Kaplan-Meier survivorship analysis, with decreased clinical scores from pre-operatively and radiographic signs of progression of osteoarthritis as the end point, predicted a 10-year survival rate of 100% for early-stage osteoarthritis hips and 72.1 % for advanced-stage osteoarthritis. CONCLUSIONS. Less invasive surgical procedure for RAO preserved function of hip abductor muscle and did not adversely influence on clinical or radiographic outcome

Background. Rotational acetabular osteotomy (RAO) is an effective treatment option for symptomatic acetabular dysplasia. However, excessive lateral and anterior correction during the periacetabular osteotomy may lead to femoroacetabular impingement. We used preoperative planning software for total hip arthroplasty to perform femoroacetabular impingement simulations before and after rotational acetabular osteotomies. Methods. We evaluated 11 hips in 11 patients with available computed tomography taken before and after RAO. All cases were female and mean age at the time of surgery was 35.9 years. All cases were early stage osteoarthritis without obvious osteophytes or joint space narrowing. Radiographic analysis included the center-edge (CE) angle, Sharp's acetabular angle, the acetabular roof angle, the acetabular head index (AHI), cross-over sign, and posterior wall sign. Acetabular anteversion was measured at every 5 mm slice level in the femoral head using preoperative and postoperative computed tomography. Impingement simulations were performed using the preoperative planning software ZedHip (LEXI, Tokyo, Japan). In brief, we created a three-dimensional model. The range of motion which causes bone-to-bone impingement was evaluated in flexion (flex), abduction (abd), external rotation in flex 0°, and internal rotation in flex 90°. The lesions caused by impingement were evaluated. Results. In the radiographic measurements, the CE angle, Sharp's angle, acetabular roof angle, and AHI all indicated improved postoperative acetabular coverage. The cross-over sign was recognized pre- and postoperatively in each case. Acetabular retroversion appeared in one case before RAO and in three cases after RAO. Preoperatively, there was a tendency to reduce the acetabular anteverison angle in the hips from distal levels to proximal. In contrast, there was no postoperative difference in the acetabular anteversion angle at any level. In our simulation study, bone-to-bone impingement occurred in flex (preoperative/postoperative, 137°/114°), abd (73°/54°), external rotation in flex 0°(34°/43°), and internal rotation in flex 90°(70°/36°). Impingement occurred within internal rotation 45°in flexion 90°in two preoperative and eight postoperative cases. The impingement lesions were anterosuperior of the acetabulum in all cases. Discussion. It is easy to make and assess an impingement simulation using preoperative planning software, and our data suggest the simulation was helpful in a clinical setting, though there were some remaining problems such as approximation of the femoral head center and differences in femur movement between the simulation and reality. In the postoperative simulation there was a tendency to reduce the range of motion in flex, abd, and internal rotation in flex 90°. There was a correlation between acetabular anteversion angle and flex. Since impingement occurred within internal rotation 45°in flexion 90°in eight postoperative simulations, we consider there is a strong potential for an increase in femoroacetabular impingement after RAO

Background: A retroverted acetabulum has been hypothesized as a cause of osteoarthritis. This study was performed to evaluate whether radiographical cross-over sign influence the painful femoro-acetabular impingement or the radiographical progression of osteoarhritis after rotational acetabular osteotomy (RAO) for dysplastic hip. Methods: Between 1987 and 1999, 104 patients (115 hips) who had pre- or early stage osteoarthritis of the hip due to dysplasia underwent a RAO. There were 99 women and five men; their mean age at the time of surgery was 34.7 years. The mean follow-up period was 13 years. Clinical follow-up was performed with use of the system of Merle d’Aubigne and the impingement sign was evaluated. Radiographical analyses included measurements of the center-edge angle, acetabular roof angle, head lateralization index, joint congruency, cross-over sign, posterior wall sign, acetabular index of depth to width, pistol grip deformity and femoral head-femoral neck ratio. Results: The mean clinical score improved significantly from 14.6 preoperatively to 17.0 at follow-up. The impingement sign at the follow-up was observed in 14 hips (12.2%). The center-edge angle improved significantly from mean −0.6 degrees to a postoperative mean of 34 degrees. The acetabular roof angle improved from 30 degrees to 2.2 degrees, and head lateralization index from 0.64 to 0.60. The cross-over sign was observed in 8 hips (7.0%) preoperatively and in 49 hips (42.6%) postoperatively. The posterior wall sign was observed in 70 hips (60.9%) preoperatively and observed in 73 hips (63.5%) postoperatively. The mean preoperative acetabular index of depth to width was 35.5% and the mean preoperative femoral head to femoral neck ratio was 1.49. The pistol grip deformity was observed in only 4 hips (3.5%) preoperatively. The impingement sign after the RAO was positive significantly in the postoperative cross-over sign positive hips (p=0.0074). Radiographical progression of osteoarthritis was observed in 11 hips (cross over sign positive; 7 hips, cross over sign negative; 4 hips). The Kaplan-Meier survivorship analysis predicted a survival rate of 84.6 % at 15 years. The only factors significantly associated with radiographic signs of progression of osteoarthritis after RAO were fair (rather than excellent and good) postoperative joint congruency (p< 0.0001) and age at surgery (p=0.0042). Presence of postoperative cross-over sign had no effect on the outcome (p=0.2073). Conclusions: Although there was no significant radiographical progression of osteoarthritis despite a significant retroversion in most cases, the goal of RAO should be a correct alignment of the acetabulum including a correct version with a negative cross-over sign

Developmental dysplasia of the hip is a condition in which the acetabulum provides insufficient coverage of the femoral head in the hip joint. This configuration gives poor biomechanical load distribution, with increased stress at the superior aspect of the joint surfaces, and can often lead to degenerative arthritis. Morphologically, the poor coverage may be due to an acetabulum that is too shallow or oriented in valgus. The dysplastic deformity can be treated surgically with a group of similar procedures, often labeled periacetabular osteotomies or rotational acetabular osteotomies. Each involves separating the acetabulum from the pelvis and fixating the fragment back to the pelvis in an orientation with increased coverage of the femoral head. This redistributes the biomechanical loads relative to acetabulum. Bone remodeling at the level of trabeculae is an accepted concept under research; however, it is unclear whether the hip undergoes gross morphology changes in response to changes in biomechanical loading. An understanding of the degree to which this remodeling occurs (if at all) may have an impact on surgical planning. In this retrospective study, computed tomography (CT) scans of 13 patients (2 male, 11 female, 40 ± 9 years of age) undergoing unilateral periacetabular osteotomies were examined; scans were taken both pre-operatively and at least a year post-operatively with an in-plane resolution of 0.55 mm and a slice thickness of 1.25 mm. Scans were segmented to produce triangulated meshes for the proximal femurs and the pelvis. These scans were manually processed to isolate the articular portions of the femoral heads and acetabulums, respectively; the fovea, acetabular fossa, any osteophytes and any segmentation artifacts were excluded. Post-operative meshes were registered to their pre-operative counterparts for both the femoral head and the acetabulum, for both the operative and non-operative hips, using the iterative closest point (ICP) algorithm to 20 iterations. To account for differences in defining the edges of the articular surfaces in the manual isolation, metrics were only calculated using points that were within 0.3 mm of a normal from the opposing mesh. With the resulting matched data, nearest neighbour distances were calculated to form the remodeling metrics. Select spurious datapoints were removed manually. For the operative femoral heads, the registered post-operative points were 0.24±0.53 mm outside of the pre-operative points. The maximum deviation was on average 1.94 mm with worst-case of 2.99 mm; the minimum deviation was −0.62 mm with worst-case of −2.06 mm. Positive numbers indicate the post-operative points are ‘outside’ of the pre-operative points – that is, farther from the head centre. The non-operative femoral heads have similar deviation values, 0.21±0.46 mm outside, with maximum and minimum deviation averaging to 1.24 mm and −0.74 mm respectively, with worst cases of 2.99mm and −1.80mm. For the operative acetabulums, the post-operative deviations were −0.08±0.43mm. The maximum and minimum deviations averaged to 0.62mm and −0.82mm, with worst cases of 2.14mm and −1.51mm across the set. Again, the non-operative acetabulums were very similar; post-operative deviations were −0.02±0.43mm, maximum and minimum deviations averaged to 1.24mm and −0.65mm, with worst cases of 1.97mm and −2.00mm. These quantitative measurements were reflected in manual examination of the meshes; generally speaking, there were small deviations with no overarching patterns across the anatomy. All metrics were very similar across the same anatomy (that is, femoral head or acetabulum) regardless of whether the hip operative or non-operative. Femurs tended to ‘grow’ slightly post-operatively, but by less than a half voxel in size. Given that the CT voxels are large compared to the measured deviations, it is possible the results may be sensitive to the manual segmentations used as source data. Manual examination of the deviations indicated a few potential trends. Seven operative and eleven non-operative acetabulums had a small patch of positive deviation (1mm to 1.5mm) in the anterosuperior aspect. This can be seen in the plot as the yellow-red area near the top right of the leftmost rendering. Other high-deviation areas included the superior aspect of the acetabulum (both positive and negative) and the superior aspect of the femoral head (generally positive). The edges of the mesh were often a source of high deviation. This is likely an artifact of over-inclusion the manual isolation of the articular surfaces, as joint surfaces become non-articular as they move away from the joint interface. Overall, the superior and anterosuperior aspects of the acetabulum and the superior aspect of the femoral head showed some indication of systemic changes; further study may clarify whether these data represent consistent anatomical changes. However, as the magnitude of the deviations between pre- and post-operative scans are on or below the order of the CT voxel size, we conclude that (in the absence of other strongly compelling evidence) periacetabular osteotomies for adults should be planned without the expectation of gross remodeling of the articular surfaces

As our understanding of hip function and disease improves, it is evident that the acetabular fossa has received little attention, despite it comprising over half of the acetabulum’s surface area and showing the first signs of degeneration. The fossa’s function is expected to be more than augmenting static stability with the ligamentum teres and being a templating landmark in arthroplasty. Indeed, the fossa, which is almost mature at 16 weeks of intrauterine development, plays a key role in hip development, enabling its nutrition through vascularization and synovial fluid, as well as the influx of chondrogenic stem/progenitor cells that build articular cartilage. The pulvinar, a fibrofatty tissue in the fossa, has the same developmental origin as the synovium and articular cartilage and is a biologically active area. Its unique anatomy allows for homogeneous distribution of the axial loads into the joint. It is composed of intra-articular adipose tissue (IAAT), which has adipocytes, fibroblasts, leucocytes, and abundant mast cells, which participate in the inflammatory cascade after an insult to the joint. Hence, the fossa and pulvinar should be considered in decision-making and surgical outcomes in hip preservation surgery, not only for their size, shape, and extent, but also for their biological capacity as a source of cytokines, immune cells, and chondrogenic stem cells.

Cite this article: Bone Joint Res 2020;9(12):857–869.

Objectives

Sagittal alignment of the lumbosacral spine, and specifically pelvic incidence (PI), has been implicated in the development of spine pathology, but generally ignored with regards to diseases of the hip. We aimed to determine if increased PI is correlated with higher rates of hip osteoarthritis (HOA). The effect of PI on the development of knee osteoarthritis (KOA) was used as a negative control.