Aims

The aim of this study was to investigate whether anterior pelvic plane-pelvic tilt (APP-PT) is associated with distinct hip pathomorphologies. We asked: is there a difference in APP-PT between young symptomatic patients being evaluated for joint preservation surgery and an asymptomatic control group? Does APP-PT vary among distinct acetabular and femoral pathomorphologies? And does APP-PT differ in symptomatic hips based on demographic factors?

Aims

Hyaline cartilage has a low capacity for regeneration. Untreated osteochondral lesions of the femoral head can lead to progressive and symptomatic osteoarthritis of the hip. The purpose of this study is to analyze the clinical and radiological long-term outcome of patients treated with osteochondral autograft transfer. To our knowledge, this study represents a series of osteochondral autograft transfer of the hip with the longest follow-up.

To investigate whether anterior pelvic plane-pelvic tilt (APP-PT) is associated with distinct hip pathomorphologies, we asked: (1) Is there a difference in APP-PT between symptomatic young patients eligible for joint preservation surgery and an asymptomatic control group? (2) Does APP-PT vary between distinct acetabular and femoral pathomorphologies? (3) Does APP-PT differ in symptomatic hips based on demographic factors?

IRB-approved, single-center, retrospective, case-control, comparative study in 388 symptomatic hips (357) patients (mean age 26 ± 2 years [range 23 to 29], 50% females) that presented to our tertiary center for joint preservation over a five year-period. Patients were allocated to 12 different morphologic subgroups. The overall study group was compared to a control group of 20 asymptomatic hips (20 patients). APP-PT was assessed in all patients based on AP pelvis X-rays using the validated HipRecon software. Values between overall and control group were compared using an independent samples t-test. Multiple regression analysis was performed to examine the influences of diagnoses and demographic factors on APP-PT. Minimal clinically important difference (MCID) of APP-PT was defined as >1 standard deviation.

No significant differences in APP-PT between the control group and overall group (1.1 ± 3.0° [−4.9 to 5.9] vs 1.8 ± 3.4° [−6.9 to 13.2], p = 0.323) were observed. Acetabular retroversion and overcoverage groups showed higher APP-PT compared to the control group (both p < 0.05) and were the only diagnoses with significant influence on APP-PT in the stepwise multiple regression analysis. However, all observed differences were below the MCID. Demographic factors age, gender, height, weight and BMI showed no influence on APP-PT.

APP-PT across different hip pathomorphologies showed no clinically significant variation. It does not appear to be a relevant contributing factor in the evaluation of young patients eligible for hip preservation surgery.

Aims

Femoroacetabular impingement (FAI) patients report exacerbation of hip pain in deep flexion. However, the exact impingement location in deep flexion is unknown. The aim was to investigate impingement-free maximal flexion, impingement location, and if cam deformity causes hip impingement in flexion in FAI patients.

Aims

Avascular femoral head necrosis in the context of gymnastics is a rare but serious complication, appearing similar to Perthes’ disease but occurring later during adolescence. Based on 3D CT animations, we propose repetitive impact between the main supplying vessels on the posterolateral femoral neck and the posterior acetabular wall in hyperextension and external rotation as a possible cause of direct vascular damage, and subsequent femoral head necrosis in three adolescent female gymnasts we are reporting on.

Aims

The frequency of severe femoral retroversion is unclear in patients with femoroacetabular impingement (FAI). This study aimed to investigate mean femoral version (FV), the frequency of absolute femoral retroversion, and the combination of decreased FV and acetabular retroversion (AR) in symptomatic patients with FAI subtypes.

Femoral head necrosis in the context of high impact gymnastics of young adolescents is rare but seems a more serious complication compared to a Perthes like necrosis.

Between 2017 and 2019, three young females aged from12 to 14 years were referred due incapacitating hip pain and severe collapsing femoral head necrosis. The indication of hip preserving surgery was based on the extent of the necrosis, presence of a vital lateral pillar and joint subluxation.

In one of our 3 cases total head involvement made THR necessary, which was performed elsewhere. In the remaining 2 cases, head reduction osteotomy plus periacetabular osteotomy led to a good and a fair result.

Repetitive impact between the main supplying vessels on the posterolateral femoral neck and the posterior acetabular wall in hyperextension/ external rotation could be the cause of severe femoral head necrosis in three adolescent female gymnasts we are reporting on. Supra-selective angiography or sonography may be helpful to improve indication. Targeted adaptation of training methods should be discussed. Due to the severe vascular insult, results have to be considered moderate.

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?

Aims

The prevalence of combined abnormalities of femoral torsion (FT) and tibial torsion (TT) is unknown in patients with femoroacetabular impingement (FAI) and hip dysplasia. This study aimed to determine the prevalence of combined abnormalities of FT and TT, and which subgroups are associated with combined abnormalities of FT and TT.

Aims

Abnormal femoral torsion (FT) is increasingly recognized as an additional cause for femoroacetabular impingement (FAI). It is unknown if in-toeing of the foot is a specific diagnostic sign for increased FT in patients with symptomatic FAI. The aims of this study were to determine: 1) the prevalence and diagnostic accuracy of in-toeing to detect increased FT; 2) if foot progression angle (FPA) and tibial torsion (TT) are different among patients with abnormal FT; and 3) if FPA correlates with FT.

Aims

The modified Dunn procedure has the potential to restore the anatomy in hips with severe slipped capital femoral epiphyses (SCFE). However, there is a risk of developing avascular necrosis of the femoral head (AVN). In this paper, we report on clinical outcome, radiological outcome, AVN rate and complications, and the cumulative survivorship at long-term follow-up in patients undergoing the modified Dunn procedure for severe SCFE.

Posterior extraarticular ischiofemoral hip impingement can be caused by high femoral torsion and is typically located between the ischium and the lesser trochanter. We asked if patients undergoing derotational femoral osteotomies for posterior FAI have (1) decreased hip pain and improved function and evaluated (2) subsequent surgeries and complications?

Thirty-three hips undergoing derotational femoral osteotomies between 2005 and 2016 were evaluated retrospectively. Of them 15 hips underwent derotational femoral osteotomies and 18 hips underwent derotational femoral osteotomies combined with varisation (neck-shaft angle >139°). Indication for derotational osteotomies was a positive posterior impingement test in extension and external rotation, high femoral torsion (48° ± 9) on CT scans and limited external rotation. Offset improvement was performed to avoid intraarticular impingement in hips with a cam-type FAI. All patients were female and mean followup was 3 ± 2 (1 – 11) years.

At latest followup the positive posterior and anterior impingement test decreased from preoperatively 100% to 5% (p< 0.001) and from preoperatively 85% to 30% (p< 0.001). The mean Merle d'Aubigné Postel score increased from 14 ± 1 (11 – 16) to 16 ± 1 (13 – 17) at latest followup (p< 0.001). At followup 32/33 hips had been preserved and one hip had been converted to a total hip arthroplasty (THA). In two hips (6%) revision osteosynthesis was performed for delayed healing of the femoral osteotomy.

Derotational femoral osteotomies for the treatment of posterior extraarticular ischiofemoral impingement caused by high femoral torsion result in decreased hip pain and improved function at midterm followup but had 6% delayed healing rate requiring revision surgery.

Purpose

To validate a small, easy to use and cost-effective augmented marker-based hybrid navigation system for peri-acetabular osteotomy [PAO] surgery.

Aims

The aims of this study were to determine the cumulative ten-year survivorship of hips treated for acetabular fractures using surgical hip dislocation and to identify factors predictive of an unfavourable outcome.

Introduction

Acetabular retroversion is an accepted cause of Pincer-type femoroacetabular impingement. There is increasing evidence that acetabular retroversion is rather a rotational abnormality of the pelvis than an overgrowth of the acetabular wall or even a dysplasia of the posterior wall. Initially, patients with a retroverted acetabulum were treated with an open rim trimming through a surgical hip dislocation (SHD) based on the early understanding of the pathomorphology. Theoretically, the reduction of the anterior wall can decrease the already small joint contact area in retroverted hips to a critical size. Based on the most recent literature, anteverting periacetabular osteotomy (PAO) seems to be the more appropriate surgical treatment. With this technique, the anterior impingement conflict can be treated efficiently without compromising the joint contact area. However, it is unknown whether this theoretical advantage in turn results in better mid term results of treatment.

Introduction

Torsional deformities are increasingly recognized as an additional factor in young patients with hip pain resulting from pincer- and cam-deformities. For example decreased femoral torsion can worsen an anterior Femoroacetabular impingement (FAI) conflict while an increased torsion can be beneficial with the same configuration.

It is unknown how often torsional deformities are present in young patients presenting with hip pain that are eligible for joint preserving surgery. We questioned (1) what is the prevalence of a pathological femoral torsion in hips with FAI or hip dysplasia? (2) which hip disorders are associated with an abnormal torsion?

Introduction

Hips following in-situ pinning for slipped capital femoral epiphysis (SCFE) have an altered morphology of the proximal femur with cam type deformity. This deformity can result in femoroacetabular impingement and early joint degeneration. The modified Dunn procedure allows to reorientate the slipped epiphysis to restore hip morphology and function.

Introduction

The limited field of view with less-invasive hip approaches for total hip arthroplasty can make a reliable cup positioning more challenging. The aim of this study was to evaluate the accuracy of cup placement between the traditional transgluteal approach and the anterior approach in a routine setting.

Introduction

Navigation in total hip arthroplasty (THA) has the goal to improve accuracy of cup orientation. Measurement of cup orientation on conventional pelvic radiographs is susceptible to error due to pelvic malpositioning during acquisition. A recently developed and validated software using a postoperative radiograph in combination with statistical shape modelling allows calculation of exact 3-dimensional cup orientation independent of pelvic malpositioning.

Objectives

Delayed gadolinium enhanced MRI of cartilage (dGEMRIC) is a novel MRI-based technique with intravenous contrast agent that allows an objective quantification of biochemical cartilage properties. It enables a ‘monitoring' of the loss of cartilage glycosaminoglycan content which ultimately leads to osteoarthritis. Data regarding the longitudinal change of cartilage property after joint preserving hip surgery is sparse. We asked (1) if and how the dGEMRIC-index changes in patients undergoing open/arthroscopic treatment of femoroacetabular impingement (FAI) one year postoperatively compared to a control group of patients with non-operative treatment; (2) and if a change correlates with the clinical short term outcome.

Introduction

Since its first description in 1988, periacetabular osteotomy has become the gold-standard worldwide in surgical treatment of developmental dysplasia of the hip. Several long-term studies have proven the efficacy of this procedure. In this study, we evaluated the mean 30-years results of this procedure of the first 63 patients (75 hips) operated at the institution where this procedure had been developed.

Introduction

Magnetic resonance imaging with intraarticular contrast (arthro-MRI) and radial cuts is the gold standard to quantify labral and chondral lesions in the setting of femoroacetabular impingement. To date, no study exists that has evaluated these findings as potential predictors of outcome for the long term follow-up after surgical treatment of FAI.

Introduction & Objective

Labral refixation has established as a standard in open or arthroscopic treatment for femoroacetabular impingement (FAI). The rationale for this refixation is to maintain the important suction seal in the hip. To date, only few short-term results are available which indicate a superior result in FAI hips with labral refixation compared to labral resection. Scientific evidence of a beneficial effect of labral refixation in the long-term follow-up is lacking.

Aim of this study was to evaluate if labral refixation can improve the cumulative 10-year survivorship in hips undergoing surgical hip dislocation for FAI compared to labral resection.

Introduction

Torsional deformities of the femur have been recognized as a cause of femoroacetabular impingement (FAI) and hip pain. High femoral antetorsion can result in decreased external rotation and a posterior FAI, which is typically located extraarticular between the ischium and trochanter minor. Femoral osteotomies allow to correct torsional deformities to eliminate FAI. So far the mid-term clinical and radiographic results in patients undergoing femoral osteotomies for correction of torsional deformities have not been investigated.

Young patients have been reported to have a higher risk of revision following total hip arthroplasty than older cohorts. This was attributed to the higher activity level which led to increased wear, osteolysis, and component fracture. We prospectively assessed the clinical results, wear and osteolysis, the incidence of squeaking, and the survivorship of ceramic on ceramic THA in patients younger than 50 years (mean age of 42 [18–50] years). The series included 425 THAs in 370 patients with 368 hips followed for a minimum of 2 years (mean 7.1 years, range 2–14 years). All patients received uncemented acetabular components with flush-mounted acetabular liners using an 18 degree taper. No osteolysis was observed in any uncemented construct. There was osteolysis around one loose cemented femoral component. The survivorship for reoperation for implant revision was 96.7%. There were only two acetabular liner fractures (0.47%) and one femoral head fracture (0.24%). Two of the three fractures involved a fall from a significant height. There were no hip dislocations. Five patients (1.17%) noted rare or occasional squeaking. None had reproducible squeaking. In summary, the current study shows that ceramic-on-ceramic THAs in the young patient population are extremely reliable with a very low revision rate and an absence of wear-induced osteolysis. In addition, it shows that both bearing fracture in this young patient population typically occurs with polytrauma and squeaking issues that have been raised relative to ceramic bearings occur very rarely with the flush-mounted ceramic liner design used in this study.

Traumatic hip dislocation is a rare injury in orthopaedic practice and typically occures in high energy trauma. The goal of this study was to analyze hip morphology in patients with low energy traumatic hip dislocations and to compare it with a control group.

We performed a retrospective comparative study. The study group included 45 patients with 45 traumatic posterior hip dislocation. Inclusion criteria were traumatic hip dislocation with simple acetabular rim or Pipkin I or II fracture. Traumatic dislocations combined with other acetabular or femoral fractures were excluded. The control group consisted of 90 patients (180 hips) that underwent radiographic examination for urogenital indication and had no history of hip pain. Hip morphology was assessed on antero-posterior and axial views.

The study group showed significantly increased incidence (p<0.001) of positive cross-over sign (82% vs. 27%) with a increased retroversion index (26 ± 17 [0–56] vs. 6 ± 12 [0–53]), positive ischial spine sign (70% vs. 34%), and positive posterior wall sign (79% vs. 21).

Hips that underwent an low energy posterior traumatic hip dislocation show significanly more radiographic signs for acetabular retroversion compared to a control group. Therefore, acetabular retroversion seems to be a contributing factor for posterior traumatic hip dislocation.

The Bernese Periacetabular Osteotomy (PAO) has become the established method for treating developmental dysplasia of the hip. In the 1990s, the surgical technique was modified to avoid postoperative cam impingement due to uncorrected head neck offset or pincer impingement due to acetabular retroversion after reorientation. The goal of the study was to compare the survivorship of two series of PAOs with and without the modifications of the surgical technique and to calculate predictive factors for a poor outcome.

A retrospective, comparative study of two consecutive series of PAOs with a minimum follow-up of 10 years was carried out. Series A included 75 PAOs performed between 1984 and 1987 and represent the first cases of PAO. Series B included 90 hips that underwent PAO between 1997 and 2000. In this series, emphasis was put on an optimal acetabular version next to the correction of the lateral coverage. Additionally, a concomitant arthrotomy was performed in every hip to check impingement-free range of motion after reorientation and in 50 hips (56%) an additional offset correction was performed. Survivorship analyses according to Kaplan and Meier were carried out and the endpoint was defined as conversion to a total hip arthroplasty, progression of osteoarthritis, or a Merle d'Aubign score 14. Predictive factors for poor outcome were calculated using the Cox-regression analysis.

The cumulative 10-year survivorship of Series A was significantly decreased (77%; 95%-confidence interval [CI] 72–82%) compared to Series B (86%; 95%-CI 82–89%, p=0.005). Hips with an aspherical head showed a significantly increased survivorship if a concomitant offset correction was performed intraoperatively (90% [95%-CI 86–94%] versus 77% [95%-CI 71–82%], p=0.003). Preoperative factors predicting poor outcome included a high age at surgery, a Merle d'Aubign score 14, a positive impingement test, a positive Trendelenburg sign, limp, an increased grade of osteoarthritis according to Tönnis, and (sub-) luxation of the femoral head (Severin > 3). In addition, predictive factors related to the three dimensional orientation of the acetabular fragment were identified. These included total, anterior, and posterior acetabular over-coverage or under-coverage, acetabular retroversion or excessive anteversion, a lateral center edge angle < 22 °, an acetabular index > 14 °, and no offset correction in aspherical femoral heads.

A good long term result after PAO mainly depends on optimal three-dimensional orientation of the acetabulum and impingement-free range of motion with correction of an aspherical head neck junction if necessary.

Femoroacetabular impingement (FAI) is a pathologic condition of the hip that leads to osteoarthrosis. The goal of the surgical hip dislocation is to correct the bony malformations to prevent the progression of osteoarthrosis. We investigated the topographical cartilage thickness variation in patients with FAI and early stage osteoarthrosis using an ultrasonic probe during surgical hip dislocation.

We performed a prospective case-series of 38 patients (41 hips) that underwent surgical hip dislocation. The mean age at operation was 30.6 (range, 18–48) years. Indication for surgery was symptomatic FAI with 4 hips (10%) with pincer-type, 7 hips (17%) with cam-type, and 20 hips (73%) with mixed-type of FAI. Cartilage thickness was measured intraoperatively using an A-mode 22 MHz ultrasonic probe at 8 locations on the acetabular cartilage.

The thickest acetabular cartilage was found in the weight bearing zone (range 2.8–3.5mm), whereas the thinnest cartilage was in the posterior acetabular horn (1.0–2.2 mm). In all hips, cartilage was thicker in the periphery area compared to the central area. In the anterior and posterior acetabular horn, the anterior area, and the superior area (central parts) a significantly decreased cartilage thickness in pincer-type compared to cam-type of FAI was found (p<0.05).

Cartilage thickness shows topographical differences in all types of FAI with pincer-type of FAI having generally thinner cartilage than cam-type FAI. This is the first study measuring in vivo cartilage thickness in the human hip.

Introduction

The use of less invasive techniques for total hip arthroplasty (THA) has remained controversial with some studies showing a higher incidence of complications. The technique of performing total hip arthroplasty through a superior capsulotomy was developed to maximally preserve the soft tissue envelope surrounding the hip. The current study assesses the recovery and complications of hips replaced using conventional and tissue preserving techniques.

Total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH) has been associated with increased rates of complications and revision. Hip instability and wear-induced osteolysis are among the more common and serious of these problems. The current investigation prospectively assessed the survivorship and clinical results of patients with DDH treated by alumina ceramic-ceramic THA.

We investigated 161 consecutive hips in 145 patients with DDH classified as Crowe type I (131 hips, 81%), II (26 hips, 16%), III (2 hips, 1%), and IV (2 hips, 1%). All patients had an uncemented titanium acetabular component with a flush mounted alumina ceramic-ceramic bearing. The mean age at operation was 48.0 ± 12.2 years (range, 18 – 79 years). The preoperative Merle d'Aubigné score was 11.4 ± 1.7 (6 – 15). 27 hips (17%) had at least one previous surgical procedure. 92 hips (57%) were replaced with the use of surgical navigation for acetabular component positioning. The mean cup diameter was 49.9 ± 3.4 mm (46 – 60 mm). 88 (55%) bearings were 28mm and 73 (45%) bearings were 32mm.

At a mean follow-up of 6.1 ± 2.5 years (2 – 11.3 years), the mean Merle d'Aubigné score was 17.4 ± 0.9 (14 – 18). There were no cases of osteolysis or dislocation. There was one reoperation of an early displaced cup. In addition, there was one calcar crack that was cerclaged, one intraoperative trochanteric fracture also repaired at surgery. No patient complained of squeaking. 94 patients with 100 hips (61%) completed a questionnaire specifically asking for squeaking. None of these patients reported squeaking. The 10-year Kaplan Meier survivorship of the implants (revision of any component for any reason) was 99.4% (95% confidence interval 98.2-100%).

Results of ceramic-ceramic THA in young patients with low to middle graded DDH after two to eleven years follow-up are promising with no radiographic signs of osteolysis or dislocation.

Patients who are less than 50 years old at the time of total hip arthroplasty (THA) have been known to have higher failure rates than patients who are older. Wearinduced osteolysis and associated component loosening is the most common mode of failure reported. The current investigation prospectively assessed the survivorship and clinical results of alumina ceramic-ceramic THA in patients younger than 50 years.

238 consecutive hips in 201 patients treated by alumina ceramic-ceramic THA were studied. The mean age at operation was 41.4 ± 7.5 years (range, 18 – 50 years).

The preoperative Merle d’Aubigné score was 11.1 ± 1.6 (6 – 15). The preoperative diagnosis included primary osteoarthritis or impingement (105 hips, 44%), developmental dysplasia of the hip (90 hips, 38%), osteonecrosis of the femoral head (17 hips, 7%), post-traumatic osteoarthrosis (16 hips, 7%), and rheumatoid arthritis (6 hip, 3%). 144 hips (61%) were replaced with the use of surgical navigation for acetabular component positioning. The mean cup diameter was 51.8 ± 3.7 (range, 46 – 60 mm). 73 (31%) bearings were 28 mm and 165 (69%) bearings were 32 mm.

At mean follow-up of 5.6 ± 2.3 years (2 – 11 years), the mean Merle d’Aubigné score was 17.4 ± 0.9 (14 – 18). There were no radiographic signs of osteolysis. There were two revisions (0.8%): one for acute cup displacement and one for a ceramic liner fracture. In addition, one hip was treated by I& D for acute infection and another with I& D but without evidence of infection. Other complications included one greater trochanter fracture and one calcar fracture, both repaired at surgery, and one transient peroneal nerve palsy. The 10-year Kaplan Meier survivorship of the implants (revision of any component for any reason) was 98.7% (95% confidence interval 96.3–100%). There were no hip dislocations.

Results of THA in patients less than 50 years using alumina ceramic-ceramic bearings at two to eleven years follow-up are promising with no case of osteolysis or dislocation.

Acetabular component malpositioning increases the risk of impingement, dislocation, and wear. The goal of computer-assisted techniques is to improve the accuracy of component positioning, in particular optimizing the orientation of the acetabular cup.

The goal of the current study was to measure accuracy of cup placement in a large clinical series of hips that underwent CT-based computer-assisted THA.

146 hips in 140 patients underwent CT-based computer-assisted THA between 2006 and 2008. In all cases cup orientation was planned according to the individual preoperative CT and the anterior pelvic plane with an inclination of 41° and anteversion of 30°. For the procedure, all patients were placed in the lateral position and the cup was implanted using angled instruments. Intra-operatively all cases were navigated using an optoelec-tronic camera and tracked instruments (Vector Vision prototype, BrainLab, Germany).

Post-operatively, cup orientation was measured using a previously validated technique of 2D/3D-matching using the preoperative CT and post-operative radiographs. This technique allows for accurate measurement of cup position from plain radiographs corrected for individual pelvic orientation.

The mean accuracy for inclination was −2.5° ± 4.0° (−12° – 10°) and for anteversion it was 0.7° ± 5.3° (−11° – 15°). In 2 hips (1.4%) a deviation of more then 10° in inclination and in 4 hips (2.7%) a deviation of more then 10° in anteversion were found.

The current study demonstrates that the acetabular component can routinely be implanted with the assistance of CT-based navigation with reasonable agreement between the navigation measurements of component orientation at the time of surgery. Nonetheless, outliers still occasionally occur. These might be due to unrecognized loosening of the pelvic reference base, inaccurate registration or the use of the ipsilateral surface-based registration algorithms which rely heavily on points near the center of rotation of the hip.

Femoroacetabular impingement (FAI) is a pathologic condition of the hip joint that leads to hip pain and osteoarthrosis (OA), especially in the young and active patient population. It is characterized by an early pathologic contact during hip motion between osseous malformation of the femoral neck and acetabular rim. The goal of the surgical dislocation of the hip is to prevent the development of OA by correcting these malformations. We investigated the clinical and radiographic outcome, the survivorship, and factors predicting poor outcome at 5-year followup.

We retrospectively evaluated 101 hips in 78 patients that underwent surgical hip dislocation at a mean age of 32 ± 8.4 (range, 15 – 52) years. The mean followup was 5.7 ± 1.0 (0.9 – 7.1) years. The series included pincer type impingement in 5 hips (5%), cam type in 9 hips (9%), and mixed type of FAI in 87 hips (87%). Pre-operatively, the patients presented with a mean Merle d’Aubigné score of 14.3 ± 3.3 (8 – 17) and a mean osteoarthrosis score according to Tönnis of 0.13 ± 0.34 (0 – 1). At followup, the clinical results were graded using the Merle d’Aubigné score and the radiographic results using the Tönnis score. Failure was defined as a conversion to a total hip arthroplasty (THA), a Merle d’Aubigné score of less than 15 or a progression of osteoarthrosis with a Tönnis score ≥2 at last followup. Demographic, clinical, radiographic, and surgical factors were tested for predictive factors for poor outcome using the Cox regression.

At followup the mean Merle d’Aubigné score was 17.2 ± 1.2 (12 – 18) and the mean Tönnis score was 0.19 ± 0.47 (0 – 2). Failures (13 hips, 13%) included 6 hips (6%) with a progression of osteoarthrosis, 5 hips (5%) hips that converted to a THA, and 2 (2%) hips presenting with a Merle d’Aubigné score of less than 15. This resulted in a cumulative survivor ship at 5 years of 97.0 ± 3.3 % (95%-confidence interval, 93.6 – 100%). Factors predicting poor outcome were a preoperative Tönnis score of 1, a cartilage tear in the Arthro-MRI, and increased age or BMI at operation.

Surgical hip dislocation has the potential to prevent the progression of osteoarthrosis and to decrease hip pain in patients with FAI. The optimal patient is young, with a decreased BMI and no sign of degeneration in the conventional radiograph or Arthro-MRI.

The ultimate goal of surgery for acetabular fractures is hip joint preservation for the rest of the patient’s life. However, besides Letournel’s series, long term survi-vorship in this predominantly young patient group has never been published in a very large series. The aim of this study was to determine the cumulative 20-year sur-vivorship of the hip after fixation of acetabular fractures and to identify factors predicting the need for total hip arthroplasty.

A Kaplan-Meier survivorship analysis of 1218 consecutive surgically treated acetabular fractures was carried out. 816 fractures were available for analysis with a mean follow up of 10.3 years (range 2–29 years). All the surgeries were performed by a single surgeon in accordance to an established treatment protocol based on Letournel’s principles. Inclusion criteria were a minimum follow-up of two years or failure at any time. Failure was defined as conversion to total hip arthroplasty of hip arthrodesis. A Cox-regression analysis identified significant risk factors predicting the need for total hip arthroplasty. Analyzed parameters comprised data on patient history, preoperative clinical examination, associated injuries, fracture pattern, radiographic and intra-operative features, and the accuracy of reduction.

The cumulative 20-years survivorship was 79% (95% CI, 76–81%). Statistically significant factors influencing the need for artificial hip replacement/arthrodesis were: age over 40 years (Hazard ratio [HR] 2.4), femoral head damage (HR 2.6), acetabular impaction (HR 1.5), postoperative incongruence of the acetabular roof (2.9), involvement of the posterior wall (HR 1.6), anterior dislocation (5.9), initial displacement > 20mm (HR 1.6), and a malreduction with residual displacement > 1mm (HR 3.0). There was a significantly different survivorship of the individual fracture types. The worst survivorship occurred in anterior wall fractures (34% at 20 years) and the best survivorship in both column fractures (87% at 20 years). The accuracy of reduction improved significantly over time.

In summary, the hip joint can be successfully preserved and prosthetic replacement avoided in 79% of displaced acetabular fractures at 20 years. Many of the factors influencing the long term prognosis are already determined at the time of injury. The factors that can be influenced by the surgeon are anatomic reduction, achievement of congruency of the acetabular roof and correction of marginal impaction. The presented unique results even exceed Letournel’s series in size and follow up. Therefore, they provide benchmark data for any type of comparative evaluation studies dealing with surgical treatment of acetabular fractures in future.

The iliocapsularis muscle is a little known muscle that originates in part from the inferior border of the anterior-inferior iliac spine, but the main origin arises from an elongated attachment of the anteromedial hip capsule and inserts just distal to the lesser trochanter. Nevertheless, this muscle is an important landmark for exposure of the anteromedial hip capsule and psoas tendon interval during performance of the Bernese periacetabular osteotomy. Speculations about the function of this muscle as a tightener of the hip capsule and femoral head stabilisator have grown when an apparent hypertrophy of this muscle was encountered in patients with dysplasia of the hip. The aim of this study was to compare the morphology of the iliocapsularis muscle between patients with decreased (developmental dysplasia of the hip) and increased acetabular coverage (pincer-type of femoroac-etabular impingement) using Arthro-MRIs.

Dysplasia of the hip (Group I) was defined as an LCE angle of less than 25° with a minimal acetabular index of 14° and pincer type of FAI (Group II) was defined as and LCE angle exceeding 39° on conventional radiographs. This resulted in 37 hips in Group I and 45 hips in Group II. The morphology of the iliocapsularis muscle was measured on axial slices of Arthro-MRIs. The parameters were muscle thickness, width and cross section at 4cm distal of the spina iliaca anterior inferior and also distal of the femoral head. Additionally, the volume of the muscle from its origins to the cross section distal of the femoral head was computed.

All parameters were significantly increased in Group I compared to Group II (p< 0.05). In Group I the mean thickness was 20 ± 4.5 (range, 12 – 29) mm, width 25 ± 5.2 (range, 17 – 37), and cross section 281 ± 10.7 (range, 139 – 591) mm2 compared to Group II with a mean thickness of 17 ± 4.4 (range, 10 – 27) mm, width 22 ± 5.0 (range, 11 – 31), and cross section 235 ± 10.3 (range, 90 – 535) mm2. The muscle volume in Group I was 6.8 ± 2.9 (range, 2.2 – 13.0) cm3 compared to Group II with 8.7 ± 3.7 (range, 3.4 – 18.1) cm3. The results differed more when corrected for gender with the largest differences found for women.

In hip dysplasia the anterior acetabular coverage is decreased. Because of the iliocapsularis muscle’s origination on the hip capsule, contrition of the muscle theoretically can tighten the anterior hip capsule, thus helping to stabilized the femoral head within the dysplastic acetabular. Although the true function of the iliocapsularis muscle remains unknown, constant use of this muscle in attempting to stabilize the femoral head in hip dysplasia theoretically would explain the apparent hypertrophy of this muscle.

Pelvic tilt is a characteristic feature of the individual patients’ posture. Large differences in pelvic tilt are well known among individuals, over time or related to activity. To our knowledge, it is unknown how patients with developmental dysplasia of the hip (DDH) behave in terms of pelvic tilt. One can assume that patients with a dysplastic acetabulum might compensate for their acetabular under coverage by functionally increasing pelvic tilt. Theoretically, this effect should be reversible when an acetabular redirection osteotomy is performed. We therefore hypothesized that pelvic tilt decreases after periacetabular osteotomy.

Sixty-three consecutive patients (67 hips) with documented PAO at our institution were analyzed. 39 patients (40 hips) were excluded because of indications than other DDH (e.g. acetabular retroversion), incomplete radiographic documentation or insufficient follow-up leaving us 24 patients (27 hips) for evaluation. Preoperative, intraoperative (under general anesthesia), and at least 1 year postoperative anteroposterior radiographs were analysed. All x-rays were done in a standardized manner. Two distances were measured: the vertical/horizontal distance between the mid point of the sacrococcygeal joint and the symphysis. The change of these distances allows exact determination of the pelvic tilt.

A significant decrease for pelvic tilt was found between the preoperative x-ray and the one after at least one year. Pelvic tilt did not change significantly between the pre- and the intraoperative x-ray, and between the intra- and follow-up x-ray.

Our findings support the hypothesis that patients with DDH try to compensate for their insufficient acetabular coverage by increasing the tilt of their pelvis. After PAO, i.e. after iatrogenically increasing acetabular coverage, the patients’ pelvis significantly turns back in to less lordosis.

Surgical dislocation of the hip in the treatment of acetabular fractures allows the femoral head to be safely displaced from the acetabulum. This permits full intra-articular acetabular and femoral inspection for the evaluation and potential treatment of cartilage lesions of the labrum and femoral head, reduction of the fracture under direct vision and avoidance of intra-articular penetration with hardware. We report 60 patients with selected types of acetabular fracture who were treated using this approach. Six were lost to follow-up and the remaining 54 were available for clinical and radiological review at a mean follow-up of 4.4 years (2 to 9).

Substantial damage to the intra-articular cartilage was found in the anteromedial portion of the femoral head and the posterosuperior aspect of the acetabulum. Labral lesions were predominantly seen in the posterior acetabular area. Anatomical reduction was achieved in 50 hips (93%) which was considerably higher than that seen in previous reports. There were no cases of avascular necrosis. Four patients subsequently required total hip replacement. Good or excellent results were achieved in 44 hips (81.5%). The cumulative eight-year survivorship was 89.0% (95% confidence interval 84.5 to 94.1). Significant predictors of poor outcome were involvement of the acetabular dome and lesions of the femoral cartilage greater than grade 2. The functional mid-term results were better than those of previous reports.

Surgical dislocation of the hip allows accurate reduction and a predictable mid-term outcome in the management of these difficult injuries without the risk of the development of avascular necrosis.

Since 1984, more than 1000 Bernese periacetabular osteotomies (PAO) have been performed for the treatment of developmental dysplasia of the hip (DDH) in adolescents and adults at the institution where this technique was developed. We present a concise 20-year follow-up of the first 75 PAOs whose initial and 10-year results had been published previously.

A retrospective study of the first 75 consecutive hips (63 patients) treated with PAO for DDH between April 1984 and December 1987 was performed. The mean patient age at surgery was 29.3 years ± 11.4 (13 – 56) and in 31% of all hips a previous surgical attempt to achieve sufficient coverage had been performed. Preoperatively, 58% of all hips presented with osteoarthritis and 49% with dysplasia Class 4 or higher according to Severin. Four patients (5 hips) were lost-to-follow-up and 1 patient (2 hips) died unrelated to surgery. The remaining 58 patients (68 hips) were followed for a mean of 20.4 years ± 1.1 (18.8 – 22.9) and 41 hips (60%) were preserved at last follow-up. Regarding the surviving hips with preoperatively no or slight osteoarthritis (52 hips), the survivor ship rate was 75%.

Twenty-seven hips were converted to a THA (26 hips) or hip arthrodesis (1 hip) which were defined as endpoints. The cumulative Kaplan-Meier survivorship at 20 years was 61%. The Cox regression analysis was performed to detect predictive factors for poor outcome and to calculate the corresponding hazard ratios. Six predictive factors for poor outcome were found: age over 30, a preoperative Merle d’Aubigné score less than 15, a positive preoperative anterior impingement test and limp, preoperative OA grade of more than 1, and a postoperative extrusion index of more than 20%.

Despite the fact that this series represented the learning curve of a technically demanding intervention of a very inhomogeneous patient group with various previous surgical attempts to achieve sufficient coverage and several concomitant intertrochanteric osteotomies, the 20-year results on the first 75 hips are promising.

Increased survivorship rates are expected for more recent series after identification of relative contraindications based on or analysis. PAO is an effective and successful surgical technique for correction of DDH.

The long-term result of a total hip arthroplasty (THA) strongly depends on the correct component positioning of the acetabular cup and stem. To measure cup orientation out of a postoperative anteroposterior (AP) pelvic radiograph is highly inaccurate due to the wide variation of individual pelvic tilt and rotation. The goal of this study was to develop and validate a 2D-3D matching software (HipMatch) that allows matching a postoperative AP pelvic radiograph with a preoperative CT to accurately measure cup orientation corrected for individual pelvic orientation.

The software is based on a spline-based multi-resolution 2D-3D image registration algorithm and a Markov random field theory based on similarity measurement. Based on a cone projection (imitating the path of the x-rays), the software is able to match the three-dimensional CT-based data set with the contours of the projected pelvis on the AP pelvic radiograph. This gives the possibility to correct the measured cup orientation (inclination and anteversion) by measuring it according to an anatomical defined coordinate system (anterior pelvic plane). The validation of the software consisted of accuracy, reproducibility and observer reliability measurements using cadaver and clinical data. For the cadaver validation 10 human pelves (20 hips) were used. From each pelvis 2 CT scans, one with and one without an inserted cup were acquired. The CT scan with the cup was used as the ground truth. With the cup inserted 4 AP pelvic radiographs with the pelvis in an unknown arbitrary position during acquisition were performed resulting in 80 measurements for accuracy. These measurements were performed by 2 observers at 2 different occasions resulting in a total of 320 measurements for reproducibility and observer reliability. The intraclass correlation coefficient (ICC) was used for quantification of reproducibility and observer reliability and the Bland-Altman analysis was used to detect systemic errors. The clinical validation included 33 patients with a pre- and a postoperative CT and 49 patients with only a postoperative CT in addition to the postoperative radiographs. In the cases with only a postoperative CT, for the 2D-3D matching the postoperative CT after manual excision of the cup from the CT slice sticks was used. In all cases the postoperative CT was used as the ground truth. For each patient all the available postoperative radiographs were used resulting in 236 measurements of accuracy.

In the cadaver validation the cup orientation ranged from 34° – 57° for the inclination and from 1° – 24° for the anteversion measured on the CT. The accuracy showed a mean difference for the inclination of 0.9° ± 1.6° (−3.2° – 4.0°) and of 1.2 ± 2.4° (−5.3° – 5.6°) for the anteversion. The ICC for the reproducibility ranged from 0.96 to 0.99 and for the interobserver reliability from 0.95 to 0.98. No relevant systematic error was detected. In the clinical validation the cup orientation measured on the postoperative CT ranged for the inclination from 22° – 57° and for the anteversion from 7° – 35°. In the clinical setup the accuracy showed a mean difference for inclination of 1.8° ± 1.6° (−4.0° – 5.3°) and of −1.1° ± 2.9° (−5.9° – 5.7°) for the anteversion.

The 2D-3D matching technique showed a good accuracy and a very good reproducibility and observer reliability. This technique allows to measure the exact cup orientation out of an AP pelvic radiograph with the help of a preoperative CT and to correct the parameters for the individual pelvic position. Therefore this software is a powerful tool to measure accuracy of CT-based computer-assisted cup placement in a large clinical series.

Traditional total hip arthroplasty (THA) using metal-on-polyethylene bearings has been established as a reliable procedure but wear and wear debris-associated osteolysis are among the most frequent reasons for revision. Ceramic-ceramic bearings represent an alternative for THA with improved wear characteristics and low biological reactivity of wear particles. We investigated the clinical outcome of alumina ceramic-ceramic THA in a series of more than 400 THAs.

A total 418 alumina ceramic-ceramic THAs performed in 360 patients treated between 1997 and 2007 were studied prospectively. All patients had an uncemented titanium acetabular component with a flush mounted alumina ceramic-ceramic bearing (Wright Medical Technology, Inc. and Ceramtec AG). The mean age at operation was 51.7 ± 12.3 years (range, 18 – 79 years). 47 cases (11%) had previous hip surgery. The indication for surgery included primary osteoarthritis or impingement (58%), developmental dysplasia of the hip (32%), osteonecrosis of the femoral head (5%), post-traumatic osteoarthrosis (2%), and other indications (3%). In 202 (48%) a minimally invasive approach, the superior capsulotomy, was used with the help of the surgical navigation for acetabular component placement.

There were no cases of osteolysis or wear. We found 7 (1.1%) implant revisions: 1 acute cup displacement, 1 acetabular liner fracture, 1 case with failure of osseointegration of the cup, and 4 trochanteric wafer nonunions. A dislocation of the hip was found in 2 (0.5%) cases. The 10-year Kaplan Meier survivorship of the implants (revision of any component for any reason) was 98.4% (95% confidence interval 97.1–100%).

The results of alumina ceramic-ceramic THA after one to ten years are promising, especially considering the young age and high incidence of previous surgery in this patient population. The data are especially encouraging since no hip has demonstrated osteolysis. In particular, we are not aware of any other bearing that has shown an absence of lysis and 10 years follow-up. Since many of these patients are quite young, we await further assessment at 15 and 20 years.

An ample number of radiographic hip parameters on anteroposterior (AP) pelvic radiographs vary significantly with individual pelvic tilt and rotation. We developed specific computer software Hip2Norm to perform 3D analysis of the individual hip joint morphology using 2D AP pelvic radiographs. Twenty-five parameters can be calculated for a neutral orientation. The aim of the study was to evaluate the validity of this method for tilt and rotation correction of the acetabular rim and associated radiographic parameters. The validation comprised three steps:

External and

A series of x-rays of 30 cadaver pelves were available for step 1 and 2. External validation comprised the comparison of radiographical parameters of the cadaver hips when determined with Hip2Norm in comparison with CT-based measurements or actual radiographs in a neutral pelvic orientation. Internal validation evaluated the consistency of the parameters when each single pelvis was calculated back from different random orientations to the same neutral pelvic position. The intra-/interob-server analysis investigated the reliability/reproducibility of all parameters with the help of 100 randomised, blinded radiographs of a consecutive patient series.

All but two parameters (acetabular index, ACE angle) showed a good to very correlation with the CT-measurements.

The software could be shown to be an accurate, reliable and reproducible method for correction of AP pelvic radiographs. This computer-assisted method allows standardised evaluation of all relevant radiographic parameters for detection of anatomic morphologic differences. It will be used to study the influence of pelvic malorientation on the radiographic appearance of each individual parameter and the clinical significance of standardising pelvic parameters.

Introduction: Recently, the correct interpretation of anteroposterior (AP) pelvic radiographs has regained increased attention, particularly in the field of joint preserving hip surgery. The diagnosis of acetabular retroversion associated with femoroacetabular impingement or hip dysplasia is made regardless the individual pelvic orientation due to the lack of a method of correction. Furthermore, it is known that a substantial number of the most common radiographical hip parameters can vary with the individual pelvic orientation. The goal of the study was to evaluate which parameter can be measured accurately on an AP radiograph.

Methods: Digital AP pelvic radiographs of 100 consecutive hips were used for evaluation. The blinded and randomized x-rays were examined by two independent observers with special software that has been validated previously. The software is able to correct the projected acetabular rim and the associated parameters for pelvic malpositioning. The following parameters were investigated: femoral head coverage in craniocaudal and anteroposterior direction (in total and for each single quadrant of the femoral head), the lateral center edge angle, the acetabular index, the ACM-angle, the extrusion index, the cross-over sign, the retroversion index, and the posterior wall sign. All parameters were first measured regardless to the individual tilt and rotation. These non-standardized values were then compared to the standardized values for a neutral pelvic orientation. This was defined with a pelvic inclination of 60 degrees which was detected with one single strong lateral pelvic radiograph.

Results: There were no differences in evaluation of the radiographs between the two observers concerning the significance of standardized and non-standardized values for the measured features. All but three parameters were significantly different when measured to the anatomically reference neutral orientation. The only parameters that did not change after standardization were the total femoral coverage, the acetabular index and the ACM.

Discussion: Except from the ACM and the acetabular index, basically all parameters change when standardized to a neutral orientation. Although from a statistical point of view, the total craniocaudal femoral coverage did not change, it is likely that this is due to an inverse effect of the anterior and posterior part of the acetabulum. We conclude that the most common hip parameters can not be reliably measured without standardization. It remains to be proven that the standardization of the parameters correlates with the clinical symptoms.

Introduction: It could be shown that an ample number of classical hip parameters for radiographic quantification of hip morphology on anteroposterior (AP) pelvic radiographs vary significantly with individual pelvic tilt and rotation. This could be proven not only for classical hip parameters (e.g. the lateral centre edge angle) but also for more recently described radiographic features such as acetabular retroversion. The resulting misdiagnosis and misinterpretation can potentially impair a correct therapy for the patient.

We developed fast and easy-to-use computer software to perform three-dimensional (3D) analysis of the individual hip joint morphology using two-dimensional (2D) AP pelvic radiographs. Landmarks extracted from the radiograph were combined with a cone beam x-ray projection model and a strong lateral pelvic radiograph to reconstruct 3D hip joints. Twenty-five parameters including quantification of femoral head coverage can be calculated for a neutral orientation. The aim of the study was to evaluate the validity of this method for tilt and rotation correction of the acetabular rim and associated radiographic parameters.

Methods: The validation comprised three steps:

External validation;

A series of x-rays of 30 cadaver pelves mounted on a flexible holding device were available for step 1 and 2. External validation comprised the comparison of radiographical parameters of the cadaver hips when determined with our software in comparison with CT-based measurements or actual radiographs in a neutral pelvic orientation as gold standard. Internal validation evaluated the consistency of the parameters when each single pelvis was calculated back from different random orientations to the same neutral pelvic position. The intra-/interobserver analysis investigated the reliability and reproducibility of all parameters with the help of 100 randomized, blinded AP pelvic radiographs of a consecutive patient series.

Results:

All but one parameter (acetabular index) showed a substantial to almost perfect correlation with the CT-measurements.

Conclusion: The software could be shown to be an accurate, reliable and reproducible method for correction of AP pelvic radiographs. This computer-assisted method allows standardized evaluation of all relevant radiographic parameters for detection of anatomic morphologic differences. It will be used to study the influence of pelvic malorientation on the radiographic appearance of each individual parameter. In addition, it allows evaluating the clinical significance of standardizing pelvic parameters.

Introduction: In the treatment of polytraumatised patients acetabular fractures are challenging because of the necessity of perfect open reduction of the articular surface over an anatomy respecting approach. Luxation of the femoral head with accompanying Pikin fracture, interponated fragments and labral lesions are relevant additional injuries compromising a good result after correct operative treatment. The choice of the approach is a limiting factor for the visualization of the hip joint and is of capital importance for adequate internal fixation. A modified Kocher-Langenbeck- approach with osteotomy of the grater trochanter allows an anatomic reduction under perfect visualization with protection of the soft tissue.

Patients and Methods: This prospective study was accomplished from 1995–2003 including 60 patients (16 female, 16–80years) with an actabulary fracture (posterior wall-, T-type-, and transverse fracture) treated over a modified Kocher-Langenbeck-appraoch with osteotomy of the grater tro-chanter. The included patients had a minimum follow-up of 2 years with clinical and radiological examination. The outcome was assessed with the Merle d’Aubigné-score and degenerative changes with the Tönnis classification.

Results: Within 57 patients an anatomic reduction was achieved. In 3 patients the reduction was not anatomical but satisfactory (1–3mm). Arthrotic changes in the minimujm follow-up of 2 years were observed in 14 patients (8 Ps grade I, 3 Ps grade II, 3 Ps grade III). In 3 patients posttraumatic arthritis had to be treated with THR (1, 3, 8 years postoperatively). A avascular necrosis was not objected.

Conclusion: The treatment of suitable acetabular fractures over a modified Kocher-Langenbeck-approach with a osteotomy of the greater trochanter and dislocation of the femoral head is a safe method for anatomic reduction and internal fixation