Aims

Although there are various pelvic osteotomies for acetabular dysplasia of the hip, shelf operations offer effective and minimally invasive osteotomy. Our study aimed to assess outcomes following modified Spitzy shelf acetabuloplasty.

Developmental dysplasia of the hip (DDH) represents a heterogeneous group of deformities that are commonly associated with secondary osteoarthritis. Affected hips may require total hip arthroplasty (THA) for endstage disease and these cases can present unique challenges for the reconstructive surgeon. While the severity of deformity varies greatly, optimizing THA can be challenging even in the “mildly” dysplastic hip. These disorders are commonly characterised by acetabular deficiency with inadequate coverage of the anterolateral femoral head and proximal femoral abnormalities including excessive femoral antetorsion, coxa valga and femoral stenosis. In more severe cases, major femoral head subluxation or dislocation can add additional complexity to the procedure. In addition to the primary deformities of DDH, secondary deformities from previous acetabular or proximal femoral osteotomies may also impact the primary THA. Primary THA in the DDH hip can be optimised by detailed understanding of the bony anatomy, careful pre-operative planning, and an appropriate spectrum of techniques and implants for the given case. This presentation will review the abnormal hip morphologies encountered in the dysplastic hip and will focus on the more challenging aspects of THA. These include acetabular reconstruction of the severely deficient socket and in the setting of total dislocation, femoral implant procedures combined with corrective osteotomy or shortening, and issues related to arthroplasty in the setting of previous pelvic osteotomy. Despite the complexity of reconstruction for various dysplastic variants the clinical outcomes and survivorship of these procedures are good to excellent for most patients. Nevertheless, more complex procedures are associated with an increased complication rate and this should be considered in the surgical decision-making process

Introduction: Hip arthroplasty for dysplasia of the hip provides a challenge to all hip surgeons. The choice of prosthesis used depends on the severity of the deformity, and the challenge of acetabular reconstruction. We report a review of 105 of our cases operated since 1992 with a minimum two-year follow-up. Methods: The data in this study has been collected and entered prospectively since 1992 on an arthroplasty database. A total of 105 cases were identified and reviewed. The indication for surgery was painful hip osteoarthritis secondary to dysplasia. All patients were reconstructed with some attempt at restoration of the hip centre, and without femoral osteotomy. Results: There were 96 patients (10 bilateral), 66 females and 29 males whose mean age at surgery was 53 years (23 to 97 years). The mean follow-up period was 59 months (27 to 107 months). The hip was exposed via a posterior approach in 98% of cases. The majority (94%) of cases had no previous surgery. Depending on the degree of dysplasia either an ABG or S-ROM prosthesis was used. There were 78 Crowe I & II, and 18 Crowe III & IV hips. The more dysplastic hips required the versatility of the SROM stems to avoid excessive lengthening or femoral osteotomy. These cases also had significantly more inferior reconstruction of the hip centre, and medialisation of the hip centre. Complications occurred in 8/106 (8%) of cases, the mean time to occurrence being 25 months. The majority were dislocations 7 (7%). There were no sciatic nerve palsies. Revision was required for 5 cups and 1 stem. Clinical evaluation showed all patients were living at home and 85% had no activity restrictions. Mean Harris Hip Score was 92/100. None or mild thigh pain only was reported in 90% of cases. In 98% of cases patients were satisfied with their outcome. Radiographic evaluation showed stem ingrowth occurred in all cases. Minor osteolysis was apparent in 6% of cases. Spot welds were identified in 76% of cases. One case demonstrated pedestal formation. Conclusion: Reconstructing hip joint mechanics is a challenge in the dysplastic hip. The use of different prostheses for the varying severity in dysplasia has been an effective approach to optimise hip mechanics. Our results using this approach with cementless implants has given excellent short term clinical and radiographic results

Direct anterior approach (DAA) is one of the best way to the hip joint for prevention of post-operative dislocation. We have applied this method as minimum invasive surgery (MIS) to more than two hundred developmental dysplastic hip of Japanese patients in total hip arthroplasty (THA) and there is no post-operative dislocation within three years of last observation carried forward (LOCF). The reason of this benefit is derived from the accuracy of cup positioning and keeping good muscle balance. But the learning curve is very important and some technical pitfalls are there in this approach. We have chosen thirty four patients that the duration of operating time more than one and half hours and loss of blood more than five hundred gram in hour series. The most important factors of the difficulties are the combinations of shortening of femoral neck, especially Perthes like deformity of developmental deformities of the hip joint (DDH) and widening of pelvic bone for the reason of insufficiency working spaces and the difficulties of broaching insertion (8/34). The second factor is the contracture of hip and knee joints combinations for the difficulties of lift up the proximal femur as broaching stem (3/34). The obesity, Body Mass Index (BMI) above thirty is not the reason of difficulties of women in our series. DAA can be extended to Smith-Petersen approach and very useful technique for primary THA in Japanese dysplastic hip patients

BACKGROUND. There is no report of additional type of bulk bone grafting (Ad-BG) method with impaction morselized bone graft for reconstruction of shallow dysplastic hip in total hip arthroplasty. The purpose of this study was to define the shallow acetabulum and to evaluate the clinical and radiographic results of primary total hip arthroplasty (THA) with Ad-BG method. MATERIALS and METHODS. With modification of Crowe's classification, shallow dysplasia was defined and classified (Fig. 1). Between October 1999 and August 2008, 120 hips of 302 THAs for dysplastic hip were defined as shallow and Ad-BG was done in 96 hips (80% of shallow hips). For 24 hips with shallow dysplasia, THA were performed by using conventional type of interpositional bulk bone graft (Ip-BG) (8 hips) or without bone graft by using rigid lateral osteophyte. All patients were followed clinically using the Japanese Orthopaedic Association (JOA) score and also Merle d'Aubigne and Postel (M&P) scores in a prospective fashion, and radiographs were analyzed retrospectively. The criteria used for determining loosening were migration or total radiolucent zone between the prosthesis (or bone cement) and host bone. The mean follow-up periods were 8.0 ± 2.3 (5.0–13.5) years. Operative technique. Resected femoral head was sliced with thickness of 1–2 cm, and then a suitable size of the bulk bone block was placed on the lateral cortex of the ilium and fixed by polylactate absorbable screws. Autogenous impaction morselized bone grafting with or without hydroxyapatite granules was performed in conjunction with a cemented socket (Fig. 2). The same surgeon assisted by his colleagues operated all of the cases. RESULTS. No acetabular components were revised except for a case with shallow and Crowe type IV acetabulum. The mean JOA and M&P score for the hips improved from preoperative 39 and 6 points to postoperative 93 and 17 points respectively. Radiographically, the Ad-BGs in most of the cases were remodeled and recognized reorientation within 2 years postoperatively. CONCLUSIONS. The authors report good results of acetabular reconstruction with the use of Ad-BG technique in conjunction with impaction morselized bone graft for shallow dysplastic hip in primary THA. Osteointegration and good clinical outcome were achieved in most of cases. However longer term outcome should be the subject of further investigation

Background. BHA is popular surgery for femoral neck fractures expecially elderly patients. However, clinical results are variable that factors affecting results are questionable. Therefore we investigated radiologic fators, dysplastic hip whether influences results of BHA. Methods. Between 2004 and 2009, 200 patients undergoing bipolar hemiarthroplasty for femoral neck fracture were divided two groups; a lateral center edge (LCE) angle of < 16 degree or > 16 degree on anteroposterior radiographs. All surgical procedures were performed by a single surgeon. Dermogrpahic data, the harris hip score, WOMAC index, Koval activity level, and complication were recorded. The minimum follow up interval was 4 years (mean, 7.8 years). Result. Late postoperative complications such as periprosthetic joint infection, acetabular erosion, and subluxation of bioplar head were commonly observed in a group <16 degree of center edge angle. Clinical score was significantly lower in dysplastic group. Revision rate was higher in dysplastic group compared with group LCE angle of above the 16 degree. Conclusion. These results suggest that the dysplastic nature might be affected result of bipolar hemiarthroplasty in femroal neck fracture especially elderly patients

Introduction. Acetabular bone deficiency, especially proximal and lateral deficiency, is a difficult technical problem during primary total hip arthroplasty (THA) in developmental hip dysplasia (DDH). We report a configuration-based acetabular classification, a modification of the Crowe's classification, of DDH, including a definition of shallow acetabuli. We also report a new reconstruction method using a medial reduced cemented socket andadditional bulk bone in conjunction with impaction morselized bone grafting (Ad-BBG method). We aimed to evaluate usefulness of the classification and the method's clinical/radiographic outcomes. Methods. One hundred thirty one hips of 330 THAs for DDH (40%) were defined shallow. The Ad-BBG methodwas performed on 102 hips (78% shallow hips). For the 24 remaining hips, THA was performed using the conventional interposition bulk bone grafting (Ip-BBG) (8 hips)or without bone grafting by using rigid lateral osteophyte (16 hips). Japanese Orthopaedic Association (JOA) scores and the Merle d'Aubigne and Postel (M&P) scores were used in follow-up; radiographs were analyzed retrospectively. The criteria used for determining loosening were migration or a total radiolucent zone between the prosthesis/bone cement and host bone. The follow-up period was 9.2 ± 2.6 (range, 5.0–14.0) years. Operative Technique. Theresected femoral head was sectioned at 1–2-cm thickness, and a suitable size of the bulk bone graft was placed on the lateral iliac cortex and fixed by polylactate absorbable screws. Autogenous impaction morselized bone grafting, with or without hydroxyapatite granules, was performed along with the implantation of medial reduced cemented prosthetic hip socket. The same surgical team performed all surgical procedures. Results. Acetabular component was revised in only one case with a shallow and Crowe Type IV acetabulum. The mean JOA and M&P scores improved from preoperative 39.3 and 6.8 points to postoperative 93.9 and 17.2 points, respectively. Within 2 years postoperatively, most Ad-BBGs cases showed successful bone remodeling and bone graft reorientation on radiographs. Conclusions. We had good results of acetabular reconstruction in primary THA using the medial reduced cemented socket and bone grafting methods including the Ad-BBG technique in conjunction with impaction morselized bone grafting for shallow dysplastic hip. Osteointegration and good clinical outcomes were achieved in most cases. However, long-term outcomes should be subject of further investigation. Summary. Reconstruction methods for shallow dysplastic hip using medial reduced cemented socket and additional bulk bone grafting in conjunction with impaction morselized bone grafting are presented

Background and Aims: Concentric pressure of the femoral head on acetabulum is the necessary prerequisite for normal hip development. In the case of diminished hip joint area an elevation of hip joint pressure ensues. If this pressure elevation lasts for a long period of time early degenerative changes are proposed to occur. The aim of our study is to substantiate the connection between hip joint pressure and occurrence of hip osteoarthritis in dysplastic hips. Methods: From 1955 to 1965 112 patients were treated non-operatively for hip dysplasia in developmental dysplasia of the hip in Dept. of Orthopaedic Surgery, Ljubljana. Using mathematical model of the hip, peak joint stress was measured in 27 patients, which met the enrolment criteria consisting of: a.) initial rentgenograph taken at least 20 years ago, b.) closed triradiate cartilage and no rentgenographic signs of osteoarthritis at the time of initial radiograph, c.) no neurological deþcit of lower limbs and no operative procedure during follow up period. All hips were re-examined clinically in year 2000. Results: Mean age at the latest follow up was 47 years (35 years to 61 years). Mean time interval between the rentgenograph from which the hip joint stress was measured and clinical examination was 27 years (20 years to 33 years). Signiþcant correlation was found between peak hip joint stress and Harris hip score (p 0.0013). Discussion and conclusions: Our results indicate that occurrence osteoarthritis of the hip could be related to the degree of hip dysplasia at the end of skeletal growth. The correlation between peak hip joint stress and Harris hip score was one order of magnitude larger than the corresponding correlation between CE angle and Harris hip score, which indicates that hip joint stress represents a valuable parameter describing the status of the hip joint

Aims. The effect of pelvic tilt (PT) and sagittal balance in hips with pincer-type femoroacetabular impingement (FAI) with acetabular retroversion (AR) is controversial. It is unclear if patients with AR have a rotational abnormality of the iliac wing. Therefore, we asked: are parameters for sagittal balance, and is rotation of the iliac wing, different in patients with AR compared to a control group?; and is there a correlation between iliac rotation and acetabular version?. Methods. A retrospective, review board-approved, controlled study was performed including 120 hips in 86 consecutive patients with symptomatic FAI or hip dysplasia. Pelvic CT scans were reviewed to calculate parameters for sagittal balance (pelvic incidence (PI), PT, and sacral slope), anterior pelvic plane angle, pelvic inclination, and external rotation of the iliac wing and were compared to a control group (48 hips). The 120 hips were allocated to the following groups: AR (41 hips), hip dysplasia (47 hips) and cam FAI with normal acetabular morphology (32 hips). Subgroups of total AR (15 hips) and high acetabular anteversion (20 hips) were analyzed. Statistical analysis was performed using analysis of variance with Bonferroni correction. Results. PI and PT were significantly decreased comparing AR (PI 42° (SD 10°), PT 4° (SD 5°)) with dysplastic hips (PI 55° (SD 12°), PT 10° (SD 6°)) and with the control group (PI 51° (SD 9°) and PT 13° (SD 7°)) (p < 0.001). External rotation of the iliac wing was significantly increased comparing AR (29° (SD 4°)) with dysplastic hips (20°(SD 5°)) and with the control group (25° (SD 5°)) (p < 0.001). Correlation between external rotation of the iliac wing and acetabular version was significant and strong (r = 0.81; p < 0.001). Correlation between PT and acetabular version was significant and moderate (r = 0.58; p < 0.001). Conclusion. These findings could contribute to a better understanding of hip pain in a sitting position and extra-articular subspine FAI of patients with AR. These patients have increased iliac external rotation, a rotational abnormality of the iliac wing. This has implications for surgical therapy with hip arthroscopy and acetabular rim trimming or anteverting periacetabular osteotomy (PAO). Cite this article: Bone Jt Open 2021;2(10):813–824

Aims. The aim of this study was to determine the association between knee alignment and the vertical orientation of the femoral neck in relation to the floor. This could be clinically important because changes of femoral neck orientation might alter chondral joint contact zones and joint reaction forces, potentially inducing problems like pain in pre-existing chondral degeneration. Further, the femoral neck orientation influences the ischiofemoral space and a small ischiofemoral distance can lead to impingement. We hypothesized that a valgus knee alignment is associated with a more vertical orientation of the femoral neck in standing position, compared to a varus knee. We further hypothesized that realignment surgery around the knee alters the vertical orientation of the femoral neck. Methods. Long-leg standing radiographs of patients undergoing realignment surgery around the knee were used. The hip-knee-ankle angle (HKA) and the vertical orientation of the femoral neck in relation to the floor were measured, prior to surgery and after osteotomy-site-union. Linear regression was performed to determine the influence of knee alignment on the vertical orientation of the femoral neck. Results. The cohort included 147 patients who underwent knee realignment-surgery. The mean age was 51.5 years (SD 11). Overall, 106 patients underwent a valgisation-osteotomy, while 41 underwent varisation osteotomy. There was a significant association between the orientation of the knee and the coronal neck-orientation. In the varus group, the median orientation of the femoral neck was 46.5° (interquartile range (IQR) 49.7° to 50.0°), while in the valgus group, the orientation was 52.0° (IQR 46.5° to 56.7°; p < 0.001). Linear regression analysis revealed that HKA demonstrated a direct influence on the coronal neck-orientation (β = 0.5 (95% confidence interval (CI) 0.2 to 0.7); p = 0.002). Linear regression also showed that realignment surgery was associated with a significant influence on the change in the coronal femoral neck orientation (β = 5.6 (95% CI 1.5 to 9.8); p = 0.008). Conclusion. Varus or valgus knee alignment is associated with either a more horizontal or a more vertical femoral neck orientation in standing position, respectively. Subsequently, osteotomies around the knee alter the vertical orientation of the femoral neck. These aspects are of importance when planning osteotomies around the knee in order to appreciate the effects on the adjacent hip joint. The concept may be of even more relevance in dysplastic hips. Cite this article: Bone Jt Open 2021;2(12):1057–1061

A study by Harris reported a 40% incidence of femoral and acetabular dysplasia in routine idiopathic osteoarthritic patients. Due to pediatric screening in the United States, today most cases are minimally dysplastic requiring little modification from standard total hip surgical techniques. As the degree of dysplasia increases numerous anatomic distortions are present. These include high hip centers, relative acetabular retroversion, soft bone in the true acetabular area, increased femoral neck anteversion and relative posteriorly positioned greater trochanters, metaphyseal/diaphyseal size mismatch, and small femoral canals. Total hip replacements for these patients have known higher risks for earlier loosening, dislocation, and neurovascular injuries.

Use of medialised small uncemented acetabular components placed in the anatomic acetabulum, modular uncemented femoral components, and diaphyseal rotational and shortening osteotomies has become a preferred method of treatment. In 2007, we reported our experience with this technique in 23 cases utilizing a subtrochanteric femoral osteotomy with a 5–14 year follow-up. There were 4 Crowe I, 3 Crowe II, 5 Crowe III, and 11 Crowe IV cases. All osteotomies healed. There were no femoral components revised. In most cases, small (mean 46 mm) hemispherical components were used without bulk allografts in all but 5 early cases. One acetabular component was revised for a recalled component. 3 acetabular liners were revised for wear (2 were very small cups with 4.7 mm poly thickness). Four patients sustained dislocations, with 2 closed and 2 open reductions. There were no neurovascular injuries.

The Crowe classification is commonly used to preoperatively classify the degree of dysplasia. However, there are large variations in these anatomic distortions within each class, so it is difficult to preoperatively plan the acetabular component size needed and if one will need to do shortening and/or rotational osteotomy. So the surgeon needs to be prepared for these cases with smaller acetabular components and be prepared to perform a femoral osteotomy.

From June 1983 up to the end of 2000, we performed Chiari’s osteotomy at 61 dysplastic hips in 54 women from 18 – 53 years (M.A. 35 years). In 47 cases, the osteotomy was performed at left and in 14 at right hip. In all cases the angle CE was measured preoperatively and after the operation. The angle was measured from −20° up to +18° (Mean 13°), preoperatively. The increase of the CE angle means better covering of femoral head, improvement of hip function for the many years and creation of good anatomic conditions in acetabulum for hip replacement in the future

Background

Hip Hemiarthroplasty is one of the commonest orthopaedic operation done in UK with recent NHFD data from 2017 report showing that 43% of the 77000 patients who presented to hospital had hemiarthroplasty. Literature suggests dislocation rate of 0.8% – 6.1% for Hip Hemiarthroplasty. Dislocation of hemiarthroplasty may lead to significant morbidity and mortality.

The endoprosthetic treatment of secondary osteoarthritis resulting from congenital hip dysplasia is difficult due to the small diameter of the acetabulum and the hypoplastic anterolateral bone stock. On the femoral side the increased femoral anteversion, insufficient femoral offset and proximal femoral deformities (mostly valgus deformities) as well as the small diameter and straight form of the intramedullary canal pose challenges. Careful preoperative planning is mandatory. The Crowe classification is usually used to describe these pathologies. In severe cases (Crowe 3 and especially Crowe 4) a shortening and derotating femoral osteotomy should be taken into account. Small acetabular components, acetabular augments, and modular femoral components must be available at all times.

For acetabular fixation press-fit cups are preferred today, but excellent results were also described for threaded cups. The advantage of press-fit cups is the extensively documented and superior track record, but threaded cups allow for an easier reconstruction of the original hip center as well as slight medialization. As a result of medialization a reduction in polyethylene wear together with a low rate of loosening lead to very good long-term results in a younger patient population.

Cementless straight stems are documented to be preferable for the small femoral diameter and the straight anatomic shape of the proximal femur. Nevertheless, the higher complication rate, especially the increased rate of nerve palsies, should be preoperatively discussed with the patient. The ideal bearing surface is currently unclear, ceramic-on-ceramic seems to be promising, although the longest data available support the use of metal-on-polyethylene.

Important issues related to total hip replacement for dysplasia are: placement of the cup and bone stock; the role of femoral osteotomy, and the choice of acetabular and femoral components.

The cup can be placed at the correct or near correct anatomical level with or without a bone graft, in a high position (high hip center) or at the right level in a protruded position. All three techniques can provide adequate coverage of the cup. In the high hip position bone graft is not usually necessary to obtain cup coverage. There is however a higher rate of component loosening, a higher dislocation rate, and lengthening is limited to the femoral side. Placing the cup in a protruded position to obtain coverage does not restore bone stock for future surgery, but it does place the hip at the correct level. Placing the cup in the correct anatomical position (i.e. at the right level and not protruded) may require a structural autograft which adds to the complexity of the case. However, bone stock is restored for future surgery. In a radiographic study of 31 shelf grafts with an average follow-up of 14 years, 22 grafts had mild resorption, and 9 moderate resorption. Ten patients required cup revision, 2 at 9 years, 2 at 10 to 15 years, and 6 at over 15 years. Only 2 hips required another structural graft.

Femoral osteotomy may be used as part of the exposure for diaphyseal shortening or for derotation of excessive anteversion. The osteotomy is carried out in the sub-trochanteric region and may be oblique, step-cut or transverse. Fixation of the osteotomy is achieved via the stem, a plate, or a cortical strut.

Cementless components are usually used because of the relatively young age of this patient population. Small components may be necessary. On the femoral side, the stem should be straight or modular so excessive anteversion can be neutralised.

A study by Harris reported a 40% incidence of femoral and acetabular dysplasia in routine idiopathic osteoarthritic patients. Fortunately most are minimally dysplastic requiring little modification from standard total hip surgical techniques. However, as the degree of dysplasia increases numerous anatomic distortions are present. These include high hip centres, relative acetabular retroversion, soft bone in the true acetabular area, increased femoral neck anteversion and relative posteriorly positioned greater trochanters, metaphyseal/diaphyseal size mismatch, and small femoral canals. Total hip replacements for these patients have known higher risks for earlier loosening, dislocation, and neurovascular injuries.

Use of medialised small uncemented acetabular components placed in the anatomic acetabulum, modular uncemented femoral components, and diaphyseal rotational and shortening osteotomies has become the standard method of treatment. In 2007, we reported our experience with this technique in 23 cases utilising a subtrochanteric femoral osteotomy with a 5–14 year follow-up. There were 4 Crowe I, 3 Crowe II, 5 Crowe III, and 11 Crowe IV cases. All osteotomies healed. There were no femoral components revised. One acetabular component was revised for a recalled component. 3 acetabular liners were revised for wear (2 were very small cups with 4.7 mm poly thickness). 4 patients sustained dislocations, with 2 closed and 2 open reductions. There were no neurovascular injuries.

The Crowe classification is commonly used to pre-operatively classify the degree of dysplasia. However, there are large variations in these anatomic distortions within each class, so it is difficult to pre-operatively plan the acetabular component size needed and if one will need to do shortening and/or rotational osteotomy. So the surgeon needs to bring their entire bag of tricks and tools for these surgeries.

For the surgical approach a trochanteric osteotomy should be utilised if lengthening is to be carried out. The leg can be lengthened up to 4 cm but the nerve should be monitored by exploration, a wake up test, or electrical monitoring.

Bone grafting for reconstruction of the dysplastic acetabulum in total hip arthroplasty has certain distinct advantages. It provides bone support for the acetabular prosthesis at the correct or near correct level. It restores anatomy and corrects leg lengths. It restores bone stock for future surgery. The alternatives, the high hip center, or medialisation are acceptable if adequate bone stock is available and leg lengths are not a problem (i.e. bilateral disease). The potential problem of these two techniques is that they do not restore bone stock for future surgery.

Cemented or uncemented components can be used. Small straight stems must be available in order to fit the dysplastic femur. Most implant designs carry CDH components. The dysplastic femur is not only small in diameter, but also excessively anteverted. If an anatomic stem is used it will be too anteverted. A straight narrow stem allows the surgeon to position the stem correctly.

Between May of 1982 and May of 1994, 67 hips in 58 patients underwent total hip replacement for congenital dislocation with the use of bulk autograft to augment the acetabulum. The average follow-up was 10 years. The revision rate for the cups was 16% (11 hips), and for the stem 6% (four hips). The clinical and radiographic failure rate for the 67 hips was 25% (12 revised, one waiting revision, and four definitely loose). The Kaplan-Meier survivorship for the cups at 14 years was 78%, and the stem 85%. There were three graft nonunions all of which required revision. Resorption of over one-third occurred in 10% of grafts (seven grafts), with four requiring further revision, but only one requiring another structural graft.

Introduction: Various techniques have been described for cup position in deficient acetabuli. Medialization allows an optimal cup position in the true acetabulum affording cover of the implant in the superolateral area by the bony roof and avoiding the need for a structural graft to cover the protruding lateral edge of the cup.

Materials and Methods: During the last 5 years 51 cases of cup medialization have been done during Resurfacing Replacement or THR with hard-hard bearing surfaces (mean follow up 35.2 month). 15 cases were done with the medial acetabuloplasty technique and 36 cases were done by simple over-reaming the medial wall and morselized bone grafting. The mean followed up was 16 months.

Surgical technique: Medial Acetabuloplasty: After a cartilage removal, we drill perforations in a horizontal line to weaken the central area of the medial wall. Using an impactor the medial wall is fractured and shifted medially for a few millimeters and the cavitation so produced is filled with morselized bone graft. This technique preserves a shell of bone medially which together with the graft brings about medial bony wall preservation. In extreme acetabular deficiency, this technique is also useful by minimizing the extent of morselized bone grafting needed in the superolateral area for lateral roof bone formation.

Results: The medial wall defect was consistently reformed during the first year. In neither the over-reaming with morselized bone graft nor in the group using the medial acetabuloplasty was the stability of the cup compromised.

Conclusion: The lateral structural graft techniques are more cumbersome, take more time and the results are less certain.

In the short term there was no difference in hip scores or in the radiological assessment between medialization with or without acetabuloplasty. We suggest this technique seems to have the potential for very good long term results.

Positioning and secure fixation of the acetabular component without bone cement in dysplastic and deficient acetabulum is technically challenging because of the distorted anatomy of the acetabulum such as shallow and very thin medial and anterior wall, deficient super-olateral dome. Several treatment options have been reported to solve these problems when total hip arthroplasty is needed.

The author developed a new technique of circumferential acetabular medial wall displacement osteotomy to get secure fixation of the cementless hemispherical acetabular component at the site of the original acetabulum. This technique preserves the thin medial wall, deepens, and enlarges the acetabulum without additional structural bone graft. The procedure can also provide appropriate positioning and sufficient coverage of the acetabular cup.

From October 1989 to October 1995, we analyzed 84 hips in 80 patients who had a cementless total hip replacement with circumferential acetabular medial wall osteotomy at the Kyung Hee University Hospital. There were 28 male and 52 female patients with an average age of 49 years (range 25–71). Initial diagnoses were congenital dislocation, severe dysplasia, infection sequelae, and secondary osteoarthritis. The follow-up period ranged from 5 years to 11 years, the average being 7.2 years. All acetabular components used in this procedure were cementless porous coated hemispherical Harris-Galante (HG) I or II cup. The acetabular cup had secure fixation at the site of the original acetabulum without bone cement in all cases. Cup coverage ratio has become 97.7% in average. There was no radiolucent line around the cup or loosening. None of the acetabular cups with circumferential acetabular medial wall osteotomy had signs of medial migration. Bone union at the site of osteotomy was achieved in all cases. Bony ingrowth into the porous surface and remodeling around osteotomized acetabular medial wall was excellent. Technical pitfalls and advantages in biomechanical viewpoint of the procedure will be discussed.

Introduction: In total hip arthroplasty, the angle of acetabular component is a critical factor for the postoperative dislocation and the longevity of prostheses. The angle is principally determined in relation to anterior pelvic plane. It is reported that the pelvis tends to tilt posteriorly along with aging. Furthermore, the pelvic tilt might change after THA. The changes might be infiuenced by the hip condition and lumbar lordosis. We measured the pelvic tilt and the lumbar lordosis, and evaluated the effects of contralateral hip and lumbar lordosis on pelvic tilt after THA.

Materials and Methods: Fifty-one unilateral patients and 30 bilateral patients were enrolled in this study. The diagnosis was dysplastic osteoarthritis in all patients. In unilateral patients, the hip was affected in one side and the other hip was normal or acetabular dysplasia without symptoms. In bilateral patients, THAs in both hips were done within two months.

Pelvic inclination angle (PIA) and lumbar lordotic angle (LLA) were measured on the standing lateral X-rays before operation and 1-month, 6-month and 1-year post-operation. The effects of patient age, BMI, ROM of the hip, preoperative PIA and LLA on the changes of PIA were statistically investigated using multiple linear regression analysis. We divided the patients into three groups with regard to pre-operative PIA (anterior group: PIA < 0, intermediate group: 0 < PIA < 10, posterior group: PIA > 10) and with regard to pre-operative LLA (insufficient group: LLA < 20, moderate group: 20 < LLA < 40, severe group: LLA > 40).

Results: Overall, significant factor was only preoperative PIA. In bilateral cases, preoperative PIA and patient age affected the changes of PIA after THA. In patients with severe lordosis, preoperative PIA and LLA were significant factors. PIA increased in anterior tilt group and PIA did not change in intermediate group, while PIA gradually decreased in posterior group. In insufficient lordosis group, PIA remarkably increased after THA compared with that in severe group.

Discussion: Pelvic tilt after THA has been reported without considering the conditions of contralateral hip and lumbar spine. By categorizing patients with regard to the conditions of hips and lumbar spine, we can prospect the tendency of the direction of PIA changes. These results indicated that pre-operative PIA was related the changes of PIA in bilateral group. PIA slightly increased in all bilateral patients, PIA tended to close each other in unilateral patients. Further investigation is necessary to prospect the estimated PIA value after THA.