Executing an extended retinacular flap containing the blood supply for the femoral head, reduction osteotomy (FHO) can be performed, increasing the potential of correction of complex hip morphologies. The aim of this study was to analyse the safety of the procedure and report the clinical and radiographic results in skeletally mature patients with a minimum follow up of two years.

Twelve symptomatic patients (12 hips) with a mean age of 17 years underwent FHO using surgical hip dislocation and an extended soft tissue flap. Radiographs and magnetic resonance imaging producing radial cuts (MRI) were obtained before surgery and radiographs after surgery to evaluate articular congruency, cartilage damage and morphologic parameters. Clinical functional evaluation was done using the Non-Arthritic Hip Score (NAHS), the Hip Outcome Score (HOS), and the modified Harris Hip Score (mHHS).

After surgery, at the latest follow-up no symptomatic avascular necrosis was observed and all osteotomies healed without complications. Femoral head size index improved from 120 ± 10% to 100 ± 10% (p<0,05). Femoral head sphericity index improved from 71 ± 10% before surgery to 91 ± 7% after surgery (p<0,05). Femoral head extrusion index improved from 37 ± 17% to 5 ± 6% (p< 0,05). Twenty five percent of patients had an intact Shenton line before surgery. After surgery this percentage was 75% (p<0,05). The NAHS score improved from a mean of 41 ± 18 to 69 ± 9 points after surgery (p< 0,05). The HOS score improve from 56 ± 24 to 83 ± 17 points after surgery (p< 0,05) and the mHHS score improved from 46 ± 15 before surgery to 76 ± 13 points after surgery (p< 0,05).

In this series, femoral head osteotomy could be considered as safe procedure with considerable potential to correct hip deformities and improve patients reported outcome measures (PROMS).

Level of evidence - Level IV, therapeutic study

Keywords - Femoral head osteotomy, Perthes disease, acetabular dysplasia, coxa plana

The Bernese periacetabular osteotomy (PAO) is not indicated for growing hips as it crosses the triradiate cartilage in its posterior branch, and experimental work has shown this can induce substantial deformations, similar to posttraumatic dysplasia, which is observed after pelvis crash injuries in childhood.

Upon examination, all injuries in the 19 cases of posttraumatic dysplasia described in literature plus 16 hips of our personal collection took place before the age of 6, which is striking as pelvic injuries in children increase with age.

Based on this observation, we started to extend the PAO indication to severe dysplasias in children with open growth plate, initially aged 9 years and older. Following the positive results, it was extended further, our youngest patient being 5 years old.

We retrospectively examined radiographic outcomes of 23 hips (20 patients), aged 10.6±1.8 years [range 5.0 – 13.2], operated by us in four centers. Pre- and 3-months postoperative, and the latest FUP radiograph at growth plate closure were measured. We evaluated the acetabular index (AI), lateral center-edge (LCE), ACM-value and compared them with reference values adjusted for age. The age at triradiate cartilage closure was compared with the non-operated side.

The follow-up time was 5.4±3.7 years [0.8 - 12.7]. In 5 hips, growth plate closure was delayed by a few months. All angles significantly normalized after PAO (LCE: 14±8° → 38±11°, AI: 20±8° → 7±4°, ACM: 53±5° → 48±4°), with >80% of them severe pathological pre-PAO, none afterwards. Acetabular molding was normal. Only few complications occurred; one had signs of coxarthosis, one sciatic nerve pain, one interfering osteosynthesis material that was removed, one had an additional valgus osteotomy, and all resolved.

Based on 20 cases with follow-up until complete triradiate cartilage closure, we believe to have sufficient information to extend the PAO indication to growing hips of 9 years and older.

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.

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

Femoroacetabular impingement (FAI) describes abnormal bony contact of the proximal femur against the acetabulum. The term was first coined in 1999; however what is often overlooked is that descriptions of the morphology have existed in the literature for centuries. The aim of this paper is to delineate its origins and provide further clarity on FAI to shape future research.

Severe femoral head deformities due to Perthes' disease are characterized by limitation of ROM, pain, and early degeneration, eventually becoming intolerable already in early adulthood. Morphological adaptation of the acetabulum is substantial and complex intra- and extraarticular impingement sometimes combined with instability are the underlying pathologies.

Improvement is difficult to achieve with classic femoral and acetabular osteotomies. Since 15 years we have executed a head size reduction. With an experience of more than 50 cases no AVN of the femoral head was recorded. In two hips fracture of the medial column of the neck has been successfully treated with subsequent screw fixation. The clinical mid-term results are characterized by substantial increase of hip motion and pain reduction.

Surgical goal is to obtain a smaller head, well contained in the acetabulum. It should become as spherical as possible and the gliding surface should be covered with best available cartilage. Together, it has to be accomplished under careful consideration of the blood supply to the femoral head. In the majority of cases acetabular reorientation is necessary to optimize joint stability.

Femoral head segment resections without guidance is difficult. Therefore, 3D-simulation for cut direction and segment size including the implementation of the resultant osteotomy configuration was developed using individually manufactured cutting jigs. First experience in five such cases have revealed good results. The forthcoming steps are the improvement of computer algorithm and automation. Goal is that with first cut decision the other cuts are automatically determined resulting in optimal head size and sphericity.

Topographic anatomy and general distribution of LFCA is well described in anatomy textbooks. Its contribution to the vascularization of specific anatomic structures in the hip region is poorly defined. The purpose of this study was to demonstrate the importance of LFCA in hip circulation, especially in the vascularization of hip abductors.

The LFCA was specifically studied in 30 hips from 26 fresh cadavers after injection of common iliac artery or aorta with colored silicone for a more extensive hip vascular study. 24 hours after intra-arterial setting of silicone, dissection was performed through the anterior iliofemoral approach to expose the artery and its branches from the origin to the terminal distribution.

In all specimens, the ascending branch of the LFCA was found as consistent supplier of gluteus minimus, gluteus medius, and tensor fasciae latae muscles by a variable number of branches. The proximal part of the abductor muscles was mainly supplied by the superior gluteal artery. We conclude, that ligating the ascending branch of the LFCA during anterior approach to the hip joint is likely to affect the vascularity and function of the abductor muscles especially in situations when perfusion of these muscles by the superior gluteal artery is compromised.

Aims

Several studies have reported the safety and efficacy of subcapital re-alignment for patients with slipped capital femoral epiphysis (SCFE) using surgical dislocation of the hip and an extended retinacular flap. Instability of the hip and dislocation as a consequence of this surgery has only recently gained attention. We discuss this problem with some illustrative cases.

The modified Smith–Petersen and Kocher–Langenbeck approaches were used to expose the lateral cutaneous nerve of the thigh and the femoral, obturator and sciatic nerves in order to study the risk of injury to these structures during the dissection, osteotomy, and acetabular reorientation stages of a Bernese peri-acetabular osteotomy.

Injury of the lateral cutaneous nerve of thigh was less likely to occur if an osteotomy of the anterior superior iliac spine had been carried out before exposing the hip.

The obturator nerve was likely to be injured during unprotected osteotomy of the pubis if the far cortex was penetrated by > 5 mm. This could be avoided by inclining the osteotome 45° medially and performing the osteotomy at least 2 cm medial to the iliopectineal eminence.

The sciatic nerve could be injured during the first and last stages of the osteotomy if the osteotome perforated the lateral cortex of ischium and the ilio-ischial junction by > 10 mm.

The femoral nerve could be stretched or entrapped during osteotomy of the pubis if there was significant rotational or linear displacement of the acetabulum. Anterior or medial displacement of < 2 cm and lateral tilt (retroversion) of < 30° were safe margins. The combination of retroversion and anterior displacement could increase tension on the nerve.

Strict observation of anatomical details, proper handling of the osteotomes and careful manipulation of the acetabular fragment reduce the neurological complications of Bernese peri-acetabular osteotomy.

Cite this article: Bone Joint J 2015;97-B:636–41.

The use of joint-preserving surgery of the hip has been largely abandoned since the introduction of total hip replacement. However, with the modification of such techniques as pelvic osteotomy, and the introduction of intracapsular procedures such as surgical hip dislocation and arthroscopy, previously unexpected options for the surgical treatment of sequelae of childhood conditions, including developmental dysplasia of the hip, slipped upper femoral epiphysis and Perthes’ disease, have become available. Moreover, femoroacetabular impingement has been identified as a significant aetiological factor in the development of osteoarthritis in many hips previously considered to suffer from primary osteoarthritis.

As mechanical causes of degenerative joint disease are now recognised earlier in the disease process, these techniques may be used to decelerate or even prevent progression to osteoarthritis. We review the recent development of these concepts and the associated surgical techniques.

Cite this article: Bone Joint J 2014;96-B:5–18.

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.

Introduction

Ectopic ossification (EO) at the acetabular rim has been suggested to be associated with pincer impingement and to lead to ossification of the labrum. However, this has never been substantiated with histological, radiographic and MRI findings in large cohorts of patients. We hypothesized that it is more a bone apposition of the acetabular rim and that it occurs more frequently in coxa profunda (CP) hips.

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.

Introduction: Periacetabular osteotomy is a complex procedure which is associated with significant complications during the learning period and difficult to maintain such expertise when it is undertaken infrequently. Results were reviewed to determine if this difficult PAO procedure can be safely learnt by a process of mentoring and review.

Methods: A structured mentoring program was adopted by the senior author. A double approach was used in the first 11 cases to enhance exposure and minimise the risk of complications. Fifteen osteotomies have subsequently been undertaken using a single approach. The median patient age was 28 years (13–41 years). The median follow-up was 5 years (2–14 years). The clinical and radiographic results were examined.

Results: Two cases in the double approach series progressed to total hip replacement and there were two other major reoperations. Two cases in the single approach series had an ischial non-union not requiring reoperation. The median Harris hip score at latest review was 82 (35–100) and 80 (26–100) for the double and single approach series respectively. All radiographic indices indicated correction of the acetabulum for both series.

Discussion and Conclusion: A structured program of mentoring and review has allowed a complex surgical procedure to be learnt and surgical expertise maintained at a distant centre while avoiding the complications previously associated with the learning curve and achieving the acetabular correction similar to the originator of the procedure.

Introduction: Patients who develop proximal femoral growth arrest present a typical deformity of short femoral neck, high riding greater trochanter, and caput valgum. This is seen usually seen in Perthes, AVN due to treatment of CDH, and sometimes in epiphyseal dysplasia.

Method: We present a series of 34 cases (34 hips) treated at the above institutes. The cases treated in Berne were prior to 2002. Twenty patients were females. There were 24 patients with Perthes, nine with old healed and treated DDH, and one with epipyhseal dysplasia. All had Trendelenburg or delayed Trendelenburg sign. They had an average shortening of 3.5 cms, and their age range was 14 yrs to 64 yrs. Pre-op assessement was done with plain radiographs, CT scan, and or MRI scan.

Results: Their Merle D’Aubigne score improved from 13 (10 to 15) to 17 (15 to 18) at the latest follow up. Twenty four (70%) had good to excellent result. Five have since undergone a total hip replacement, and five have some pain but can do reasonable amount of activity. The follow-up is 6 years (2 to 13 years). There was one trochanteric non-union, but no cases of AVN.

Discussion: We describe the technique of biomechanically improving the moment arm and muscle length with this procedure. This helps the soft tissues to strengthen, improve force vectors in the correct direct in the hip, perhaps improve the longevity of the joint and also prepare the hip soft tissues for future THR.

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.

Background: Acetabular retroversion has been proposed to contribute to the development of osteoarthritis of the hip. For the diagnosis of this condition, conventional AP pelvic radiographs may represent a reliable, easily available diagnostic modality as they can be obtained with a reproducible technique allowing the anterior and posterior acetabular rims to be visible for assessment. This study was designed to

establish a method to directly quantify anatomic acetabular version on AP pelvic radiographs and to

Methods: Using 43 desiccated pelves (86 acetabuli) the anatomic acetabular versions were measured at three different transverse planes (cranially, centrally and caudally). From these pelves, standardized AP pelvic radiographs were obtained. To directly measure central acetabular version (AV), a modified radiographic method is introduced for the use of AP pelvic radiographs. Moreover, the validity of the radiographic “cross-over-sign” to detect cranial acetabular retroversion was determined.

Results: The mean central and caudal anatomic AV were approximately 20°, the mean cranial AV was 8°. Cranial retroversion (AV < 0°) was present in 19 of 86 hips (22%). A linear correlation was found between the central and cranial AV. Below 10° of central AV, all acetabuli were cranially retroverted. Between 10° and 20°, 30% of the acetabuli were cranially retroverted and above 20°, only one of 45 acetabuli was cranially retroverted. The radiographic measurement of the central AV (20.3° ± 6.5) correlated strongly with the anatomic AV (20.1° ± 6.4). The sensitivity of the ‘cross-over-sign’ to detect an cranial acetabular anteversion of less than 4° was 96%, its specificity 95%, and the positive predictive and negative predictive values 90% and 98%, respectively.

Conclusions: The cranial AV is on average 12° lower than the central AV, with the latter directly measurable from AP pelvic radiographs. A central AV of less than 10° was associated with cranial retroversion. The presence of a positive ‘cross-over-sign’ is a highly reliable indicator of cranial AV of < 4°.

Background: Femoroacetabular Impingement is now considered a prearthritic hip mechanism. It frequently occurs in patients with subtle anatomic abnormalities of the acetabulum, “acetabular retroversion”, which is often difficult to detect on standart xrays. Early diagnosis is of utmost importance as surgical intervention in early stages can most likely halt progression of disease. The objective of this study was to assess wether an easily visible anatomic landmark on an anteroposterior (AP) pelvic xray can be used to screen patients with acetabular retroversion.

Methods: The AP pelvic xrays of 1010 patients who were seen at the autors’ institution for a painful hip were reviewed over a 16 year period. Those xrays that did not meet standardized criteria were excluded leaving 149 AP radiographs (298 hips) for analysis. The ‘crossover sign’ (COS), indicative of acetabular retroversion, was recorded for each hip. An easily visible landmark, the prominence of ischial spine (PRIS) into the true pelvis was also recorded and measured. Interobserver and intraobserver variability was assessed.

Results: The presence of the PRIS as diagnostic of acetabular retroversion showed a sensitivity of 91% (95%CI 0.85 to 0.95), a specifity of 98% (95% CI 0.94 to 1.00), a positive predictive value of 98% (95%CI 0.94 to 1.00), a negativ predictive value of 92% (95% CI 0.87 to 0.96). There was good and very good intraobserver and interobserver reliability for measurements of the COS and PRIS, respectively.

Conclusion: There was excellent sensitivity and positive predictive value of the PRIS as a radiographic marker of acetabular retroversion. The rims of the anterior and posterior walls are sometimes not clearly visible, and even if they are, their translation into a reliable interpretation of acetabular retroversion is difficult. The PRIS sign appears as a good visible prominence on the AP radiographs which can’t be easily confused.

To investigate the proportion of dysplastic hips which are retroverted. We studied the radiographs of over seven hundred patients with dysplastic hips who had had a periacetabular osteotomy in the period 1984–1998. We excluded patients with neuromuscular dysplasia, Perthes’ disease of the hip, post-traumatic dysplasia and proximal focal femoral deficiency. We selected 232 radiographs of patients with congenital acetabular dysplasia. A number of parameters were measured including lateral centre-edge angle, anterior centre-edge angle, acetabular index of weight-bearing surface, femoral head extrusion index and acetabular index of depth to width. Also recorded were acetabular version and congruency between femoral head and acetabulum.

The lateral centre-edge angle of Wiberg had a mean value of 6.4° (SD 8.9°), the mean anterior centre-edge angle was 1.3° (SD 13.5°) and the acetabular index of weight-bearing surface of the acetabulum had a mean value of 24.5° (SD 9.7°). The majority (192, 82.8%) of acetabula were anteverted as might be expected. However, a significant minority (40, 17.2%) were retroverted. The mean anterior centre-edge angle in retroverted hips was 6.7° (SD 9.4°) compared with 0.4° (SD 13.3°) in anteverted hips.

The authors have shown that, in a typical group of patients with congenital acetabular dysplasia significant enough to warrant periacetabular osteotomy, the majority of hips as expected have anteverted acetabula. However, a significant minority are retroverted. This finding has an important bearing on the performance of the osteotomy. We have also found that most if not all the information required prior to and following periac-etabular osteotomy can be obtained from an orthograde view of the pelvis.

Background: Numerous radiographic indices have been described to help define the degree of acetabular deficiency in adult patients with developmental dysplasia. The lateral centre-edge angle (LCE) of Wiberg and the anterior centre-edge (ACE) angle of Lequesne are two of the commonly measured indices that are reported in the evaluation of procedures that are used to correct acetabular deformity. Unfortunately much of the reported literature that tries to define abnormal indices has been extrapolated from the evaluation of “normal” pelvi or those with osteoarthritis. The purpose of this study was to evaluate the application and limitations of the LCE and ACE angles in a group of patients with developmental dysplasia treated with periacetabular osteotomy.

Methods: 50 cases were randomly selected from a larger cohort of over 500 patients with acetabular dysplasia treated at our institution with periacetabular osteotomy. The preoperative and post osteotomy false profile and anteroposterior plain radiographs were reviewed. Cases were first grouped into one of three categories based on a general estimation of the location of acetabular deficiency as determined from the AP radiograph.

A number of radiographic indices were measured and compared including the VCE angle, LCE angle, and acetabular angles of Tönnis and Sharp. Variation in both the VCE and LCE angle was evaluated by measuring the index using two different reference points. This included (1) the traditional mark of the furthest point along the sclerotic density of the weight bearing zone and (2) an alternate point representing the furthest extent of lateral or anterior bony coverage. Additional sources of measurement error were determined. The relationships between the centre-edge angles and other radiographic indices were determined. An evaluation of the indices and correction on post osteotomy radiographs was also performed.

Results: Fifty cases in 45 patients were reviewed. There were 31 female and 19 males. The mean age was 30 years (range, 17–45). A general review of all preoperative AP radiographs revealed that all hips displayed some degree of lateral deficiency.

Nineteen of these cases displayed a “classic” lateral and anterior deficiency. However, 19 cases displayed a more uniform deficiency and 12 cases were in fact retroverted.

Evaluation of the radiographic indices revealed:

A mean VCE angle of 2.3 degrees (SD±12.7) and LCE angle of 3.4 degrees (SD±9.3). These were corrected to 25.8 degrees (SD±11.6) and 28.6 degrees (SD±8.7) following osteotomy.

Potential sources of error in measurement that were identified include:

Deformity of the acetabulum and occasional abnormalities of the femoral head limit the ability to identify the center of the rotation necessary to measure the centre-edge angles. Subluxation of the femoral head also creates a degree of error. These difficulties were observed in over 20% of cases.

Conclusion: Centre-edge indices can be useful parameters in defining acetabular morphology. However, these parameters should not be used in isolation and the absolute values do little to define the overall location and degree of deficiency in hips with acetabular dysplasia. A number of significant sources of measurement error limit their accuracy especially in patients with hip dysplasia. Currently, it is our feeling that no single radiographic parameter fully defines the specific morphology in each individual case nor reflects the success of correction when treating patients with periacetabular osteotomy.

Femoroacetabular impingement recently was recognized as cause for osteoarthritis of the hip. There are two mechanism of impingement: (1) cam impingement caused by a non-spherical head, and (2) pincer impingement due to acetabular overcover. We hypothesized that both mechanism result in different articular damage patterns. Of 302 analyzed hips only 26 had an isolated cam and 16 an isolated pincer impingement. Cam impingement caused anterosuperior acetabular cartilage damage with a separation between labrum and cartilage. During flexion the cartilage is sheared off the bone by the non-spherical part of the femoral head. In pincer impingement the cartilage damage was located circumferentially, invovolving only a narrow strip along the acetabular rim. During motion the labrum is crushed between the acetabular rim and the femoral neck causing degeneration and ossification of the labrum.

Cam and pincer impingement are two basic mechanism that lead to osteoarthrosis of the hip. The articular damage pattern differs substantially. Isolated cam or pincer impingement is rare, in most hips a combination is present. Labral damage indicates ongoing impingement and rarely occurs alone.

Complete debridement for synovial chondromatosis of the hip joint is difficult to achieve by standard surgical approaches. The goal of this study was to report preliminary experiences and results for treatment of this disease by a recently developed technique for surgical dislocation of the hip. The technique offers a safe and entire access to the hip joint in order to perform a synovectomy and complete joint debridement. This technique was applied in 8 patients with mean age of 38 years (24–65yrs.). This was done as the initial treatment in 6 patients and for recurrent disease after previous surgery in 2 patients. The mean follow-up was 4.3 years (2–10yrs.). None of the patients had recurrence of synovial chondromatosis. Six of 8 patients showed a good or excellent clinical result without progressive radiographic signs of osteoarthritis (OA). None of the patients developed avascular necrosis. 2 patients underwent total hip joint replacement after 5 and 10 years. One of these two patients had three previous surgeries for recurrence. The other one had the surgical dislocation as initial treatment. Both presented with distinct radiographic signs of OA prior to the index surgery. The technique of surgical dislocation allowed a safe and reliable joint debridement for synovial chondromatosis of the hip. The results indicate that this approach is successful when performed at an early stage without distinct signs of OA.

Radiodense structures resembling ossicles at the acetabular rim have received multiple names including “Os acetabuli, Os supertilii, Os marginale superius acetabuli, and Os coxae quartum”.

Various theories regarding their origin have been postulated. These structures commonly are observed in dysplastic hips and hips suffering from femoro-acetabular impingement and represent fractures of the acetabular rim. In our series we observed acetabular rim fragments in 4.9% of the dysplastic hips and in 6.4% of the hips with femoro-acetabular impingement.

Two different pathomechanics are responsible for the occurrence of these rim fragments. In dysplasia the short acetabular roof reduces the amount of available loading surface which leads to an overload on the lateral margin of the acetabulum, propagating the development of a fatigue fracture. However, as in all hips additional cysts were visible, it must be postulated, that cysts have to be present additionally and act as stress risers through which the rim bone eventually will fail. In hips with femoro-acetabular impingement the mode of failure is different. The relative anterior overcover in retroverted hips is subjected to stress during flexion of the hip, which is further increased by the frequent presence of an non-spheric extension of the femoral head as seen in cam impingement. The nonspheric femoral head-neck junction is jammed into the rim area. By repetitive traumatization the anterior rim eventually will fracture.

The clinical importance of acetabular rim fractures in the dysplastic hip is readily understood even by an unexperienced observer. However, it has to be considered as a sign that the hip has decompensated and it usually goes with significant articular cartilage damage. Because the radiographic appearance of the hip with femoro-acetabular impingement seems normal at first sight, the mechanism leading to anterior rim fracture may be overlooked. However, recognition and adequate treatment is important to prevent further degeneration of the hip.

Lesions of the acetabular rim have been implicated as a cause of hip pain in various pathologic conditions and are considered to predispose the hip to development of accelerated degenerative disease. In developmental dysplasia of the hip (DDH) and anterior femoroacetabular impingement (FAI), intrinsically normal intraarticular soft tissue structures are exposed to joint loading forces that physically exceed their tolerance level posing these pathomorphologies as precursors of osteoarthritis. In DDH, the deficient acetabular coverage of the femoral head has been related to osteoarthrosis, while the orientation of the femoral head is considered to play a less important role. The resulting instability and anterolateral migration tendency of the femoral head leads to chronic shear stresses at the acetabular margin. In FAI, repetitive peak contact pressures occur when the femoral head-neck junction abuts against the acetabular rim during joint flexion. Predisposing morphologies are femoral abnormalities such as an insufficient femoral head-neck offset seen in head tilt or pistol grip deformities, slipped capital femoral epiphysis, or malunited femoral neck fractures with the orientation and shape of the acetabulum contributing to this pathology. In classical DDH and FAI, diagnosis is primarily based on clinical signs and symptoms and conventional radiography. However, in cases of clinical and radiographic borderline disease establishment of the correct diagnosis is sometimes difficult. This presentation reports how the MRarthrographic appearance of acetabular rim pathologies can be used to differentiate both conditions. In DDH and FAI, labral pathologies localize identically with a predilection to the anterosuperior quadrant of the acetabulum. Labral tears are found in 64% in both groups. The volume of the labrum is increased in 86% DDH hips but in none of the FAI hips. Ganglion formation in the periacetabular area is seen in 71% DDH and 21% FAI hips. These findings provide evidence that the anterosuperior acetabular rim represents the initial fatiguing site of the hip under both DDH and FAI. The capability of MR-arthrography to depict differences in labral pathologies suggests this method as a helpful diagnostic tool to define the most appropriate treatment strategy specifically in borderline cases.

Alignment, coverage and congruency are traditional keywords for the morphological interpretation of the hip joint. Most of the collected information come from ill-defined radiographs and are mainly used to characterize the capacity of a hip for load transmission. Accordingly threshold values for undercoverage are more precise than the definition of overcoverage.

The understanding of what is a normal hip anatomy is changing rapidly; other parameters have to be included as well. The impingement concept introducing motion as an important initiator of osteoarthritis is based on relatively minor morphological abnormalities of the hip which were of little interest until now. With high quality MRI we recently learned that a hip joint may have substantial cartilage damages although it looks radiographically normal.

This Symposium is a first attempt to update on our standards Puloski et al. point to weak radiographic parameters. Dora discusses hitherto barely noticed indicators like the acetabular version which has a high potential for morbidity. Beck et al explain the acetabular rim fragment, a structure which can be seen in dysplastic as well as in impinging hips. Finally Leunig et al. use the MRI-morphology of the labrum to distinguish between dysplasia and hip impingement in borderline hips.

The effects of NF-I on the hip have been underreported in literature. The bony changes in the hip can be mild to severe and are often present, but not diagnosed. Dislocation of the hip has been described but protrusio acetabulum is underdiagnosed and has only been reported from one institute. This is the first case where an open biopsy has been taken from the hip joint by surgical dislocation with preservation of the blood supply to the femoral head. Gross and microscopic pathology in the neurofibromatosis of the hip has been described for the first time in our report.

A 16-year-old girl presented with history of pain, limp and stiffness in the right hip for several years. Radiographs, CT scan showed severe protrusio acetabulum. Histological analysis from the tissue taken from the hip was a neurofibroma. There was very minimal hyaline cartilage in the acetabulum at operation. Therefore the floor of the acetabulum was grafted with the autologous cancellous bone chips obtained from her greater trochanter. The aim of this was to lateralize the hip center to a normal position. At six months follow up she was doing well. Her range of movements had increased by 20%.

Recently, femoroacetabular impingement has been recognised as a cause of early osteoarthritis. There are two mechanisms of impingement: 1) cam impingement caused by a non-spherical head and 2) pincer impingement caused by excessive acetabular cover. We hypothesised that both mechanisms result in different patterns of articular damage. Of 302 analysed hips only 26 had an isolated cam and 16 an isolated pincer impingement. Cam impingement caused damage to the anterosuperior acetabular cartilage with separation between the labrum and cartilage. During flexion, the cartilage was sheared off the bone by the non-spherical femoral head while the labrum remained untouched. In pincer impingement, the cartilage damage was located circumferentially and included only a narrow strip. During movement the labrum is crushed between the acetabular rim and the femoral neck causing degeneration and ossification.

Both cam and pincer impingement lead to osteoarthritis of the hip. Labral damage indicates ongoing impingement and rarely occurs alone.

It is generally agreed that in acetabular dysplasia the acetabulum lies excessively anteverted. Although this is true for the majority of hips, we have found that in some patients with dysplastic hips, the acetabulum lies unexpectedly in retroversion.

Aim: To investigate the proportion of dysplastic hips which are retroverted.

Method: We studied the radiographs of over seven hundred patients with dysplastic hips and who had had a periacetabular osteotomy in the period 1984–1998. We excluded patients with neuromuscular dysplasia, Perthes disease of the hip, post-traumatic dysplasia and proximal focal femoral deficiency. We selected 232 radiographs of patients with congenital acetabular dysplasia. A number of parameters were measured including, lateral centre edge angle, anterior centre-edge angle, acetabular index of weight bearing surface, femoral head extrusion index and acetabular index of depth to width. Also recorded was acetabular version and congruency between femoral head and acetabulum.

Results: The lateral centre-edge angle of Wiberg had a mean value of 6.4° (SD 8.9°), the mean anterior centre-edge angle was 1.3° (SD 13.5°) and the acetabular index of weight bearing surface of the acetabulum had a mean value of 24.5° (SD 9.7°). The majority (192, 82.8%) of acetabula were anteverted as might be expected. However, a significant minority (40,17.2%) were retroverted. The mean anterior centre-edge angle in retroverted hips was 6.7° (SD 9.4°) compared with 0.4° (SD 13.3°) in anteverted hips.

Conclusion: The authors have shown that in a typical group of patients with congenital acetabular dysplasia, significant enough to warrant periacetabular osteotomy, the majority of hips as expected have anteverted acetabula. However, a significant minority are retroverted. This finding has an important bearing in the performance of the osteotomy.

Acetabular dysplasia is the most common cause of secondary osteoarthritis of the hip joint resulting in many young adults requiring total hip replacement (THR). Although THR has a predictably good functional result, the longevity of prosthetic replacement in this young cohort of patients has been notably inconsistent. Therefore, there has been an increasing interest in better methods for treating acetabular dysplasia in young adults with the emphasis shifting from the femoral to the acetabular side during the last 10 years.

For reorientation of the acetabular fragment to improve coverage, various pelvic and periacetabular osteotomies have been proposed. Most necessitate more than one incision and change of patient position. The Bernese periacetabular osteotomy (PAO) combines complete and incomplete osteotomies, as well as a controlled fracture requiring only one approach. This is beneficial for the vascular supply of the acetabular fragment and allows an additional anterior capsulotomy without restrictions.

The osteotomies of the PAO are close to the joint and therefore allow a pronounced acetabular reorientation similar to juxta-articular triple osteotomies. Moreover, anteversion and medialization/lateralization of the center of rotation can be corrected with only minimal changes of the pelvic geometry. This enables a normal delivery in young females. The partially remaining posterior column protects the sciatic nerve from iatrogenic damage. The polygonal shape of the osteotomy and avoidance of soft tissue stripping (abductors) are advantageous for the stabilization of the reoriented fragment, thus facilitating early mobilization and rehabilitation.

Seventy-five dysplastic hips with a minimal follow-up of 10 years after PAO were evaluated. There were good to excellent result in 73% of these patients. The mean lateral center edge angle increased from 6° to 34° and the mean anterior center edge angle improved from 4° to 28°. The post-osteotomy index angle was successfully reduced from an average of 26° to 6°. Lateralisation of the femoral head was reduced from an average 16° to 10° compared to 11° on the contralateral side. Femoral head cranialisation also normalized from 9° to 4° compared to 5° on the opposite hip. Poor results were correlated with older patients, pre-existing arthritis, labral pathology, and mal-correction. Treatment of labral lesions was performed only as a supplementary measure if the labrum was unstable and included either refixation or resection.

The PAO is a technically demanding procedure, and is unforgiving of seemingly minor imprecision. With the fact that 85% of our major complications occurred within the first fifty osteotomies, it is obvious that a learning curve exists for this procedure. It is imperative that surgeons undertaking this procedure do so with a full understanding of each stage and have the necessary patience, attention to detail and adequate cadaveric experience with the technique.

The study reviews 24 patients with 27 total hip arthroplasties in which an acetabular reinforcement ring with hook was used for primary total hip arthroplasty (THA) due to underlying hip dysplasia.

There were 19 female and 5 male patients with a mean age of 50.6 years (31 to 70) at the time of surgery. A bulk autograft for acetabular reconstruction was used in four cases with Crowe Type III and IV dysplasia. In eight cases cancellous bone alone was used to fill the gap between the reinforcement ring and the acetabulum. All patients had a polyethylene cup cemented into the ring and 22 cases had a straight Müller CDH stem cemented into the shaft.

Mean follow-up was 10.7 years (range: 8.1 to 12.7). No clinical or radiographic signs of loosening of the reinforcement ring were found in 24 (88.9 %) of the 27 THAs. Two revisions (7.4%) were performed for aseptic loosening and one acetabular component had radiographic signs of loosening. The Merle D`Aubigné score had increased from 7 to 15 points.

The acetabular reinforcement ring continues to have favourable results in this specific patient group and may also prevent graft resorption and cup migration.

The study reviews 24 patients with 27 total hip arthroplasties in which an acetabular reinforcement ring with hook was used for primary total hip arthroplasty (THA) due to underlying hip dysplasia.

There were 19 female and 5 male patients with a mean age of 50.6 years (31 to 70) at the time of surgery. A bulk autograft for acetabular reconstruction was used in four cases with Crowe Type III and IV dysplasia. In eight cases cancellous bone alone was used to fill the gap between the reinforcement ring and the acetabulum. All patients had a polyethylene cup cemented into the ring and 22 cases had a straight Müller CDH stem cemented into the shaft.

Mean follow-up was 10.7 years (range: 8.1 to 12.7). No clinical or radiographic signs of loosening of the reinforcement ring were found in 24 (88.9 %) of the 27 THAs. Two revisions (7.4%) were performed for aseptic loosening and one acetabular component had radiographic signs of loosening. The Merle D`Aubigné score had increased from 7 to 15 points.

The acetabular reinforcement ring continues to have favourable results in this specific patient group and may also prevent graft resorption and cup migration.

In this prospective, randomised study, we have compared the wear rate of cemented, acetabular polyethylene cups articulating with either a 22 mm or a 32 mm cobalt-chromium head. We evaluated 89 patients who had a total of 484 radiographs. The mean follow-up period was 71.4 months (SD 29.1). All the radiographs were digitised and electronically measured.

The linear wear rate was significantly higher during the first two years and decreased after this period to a constant value. We suggest that this is partly due to a ‘run-in’ process caused by irregularities between surfaces of the cup and head and an initial plastic deformation of the polyethylene. The mean volumetric wear was 120.3 mm³/year for the 32 mm head, which was significantly higher than the 41.5 mm³/year for the 22 mm heads. The mean linear wear rate was not significantly different. We were, however, unable to find radiological signs of osteolysis in the patients who had higher wear rates.

We used laser Doppler flowmetry (LDF) with a high energy (20 mW) laser to measure perfusion of the femoral head intraoperatively in 32 hips. The surgical procedure was joint debridement requiring dislocation or subluxation of the hip. The laser probe was placed within the anterosuperior quadrant of the femoral head. Blood flow was monitored in specific positions of the hip before and after dislocation or subluxation.

With the femoral head reduced, external rotation, both in extension and flexion, caused a reduction of blood flow. During subluxation or dislocation, it was impaired when the posterosuperior femoral neck was allowed to rest on the posterior acetabular rim. A pulsatile signal returned when the hip was reduced, or was taken out of extreme positions when dislocated. After the final reduction, the signal amplitudes were first slightly lower (12%) compared with the initial value but tended to be restored to the initial levels within 30 minutes.

Most of the changes in the signal can be explained by compromise of the extraosseous branches of the medial femoral circumflex artery and are reversible. Our study shows that LDF provides proof for the clinical observation that perfusion of the femoral head is maintained after dislocation if specific surgical precautions are followed.

Osteonecrosis of the femoral head can be caused by a variety of disorders and affects the relatively young patient. Most studies have concentrated on the femoral changes; the sites of early lesions of the labrum and acetabular cartilage have not been recorded. We studied 17 hips with osteonecrosis and a wide congruent joint space on radiographs and by direct inspection of the femoral head, labrum and acetabular cartilage during surgery. All of the femoral heads had some anterosuperior flattening which reduced the head-neck ratio in this area. A consistent pattern of damage to the labrum and the acetabular cartilage was seen in all hips. Intraoperatively, impingement and the cam-effect with its spatial correlation with lesions of the labrum and acetabular cartilage were observed. These findings could be helpful when undertaking conservative surgery for osteonecrosis, since the recognition of early radiologically undetectable acetabular lesions may require modification of the surgical technique.

Surgical dislocation of the hip is rarely undertaken. The potential danger to the vascularity of the femoral head has been emphasised, but there is little information as to how this danger can be avoided. We describe a technique for operative dislocation of the hip, based on detailed anatomical studies of the blood supply. It combines aspects of approaches which have been reported previously and consists of an anterior dislocation through a posterior approach with a ‘trochanteric flip’ osteotomy. The external rotator muscles are not divided and the medial femoral circumflex artery is protected by the intact obturator externus. We report our experience using this approach in 213 hips over a period of seven years and include 19 patients who underwent simultaneous intertrochanteric osteotomy. The perfusion of the femoral head was verified intraoperatively and, to date, none has subsequently developed avascular necrosis. There is little morbidity associated with the technique and it allows the treatment of a variety of conditions, which may not respond well to other methods including arthroscopy. Surgical dislocation gives new insight into the pathogenesis of some hip disorders and the possibility of preserving the hip with techniques such as transplantation of cartilage.

We have observed damage to the labrum as a result of repetitive acetabular impingement in non-dysplastic hips, in which the femoral neck appears to abut against the acetabular labrum and a non-spherical femoral head to press against the labrum and adjacent cartilage. In both mechanisms anatomical variations of the proximal femur may be a factor. We have measured the orientation of the femoral neck and the offset of the head at various circumferential positions, using MRI data from volunteers with no osteoarthritic changes on standard radiographs. Compared with the control subjects, paired for gender and age, patients showed a significant reduction in mean femoral anteversion and mean head-neck offset on the anterior aspect of the neck. This was consistent with the site of symptomatic impingement in flexion and internal rotation, and with lesions of the adjacent rim. Furthermore, when stratified for gender and age, and compared with the control group, the mean femoral head-neck offset was significantly reduced in the lateral-to-anterior aspect of the neck for young men, and in the anterolateral-to-anterior aspect of the neck for older women. For patients suspected of having impingement of the rim, anatomical variations in the proximal femur should be considered as a possible cause.

The primary source for the blood supply of the head of the femur is the deep branch of the medial femoral circumflex artery (MFCA). In posterior approaches to the hip and pelvis the short external rotators are often divided. This can damage the deep branch and interfere with perfusion of the head.

We describe the anatomy of the MFCA and its branches based on dissections of 24 cadaver hips after injection of neoprene-latex into the femoral or internal iliac arteries.

The course of the deep branch of the MFCA was constant in its extracapsular segment. In all cases there was a trochanteric branch at the proximal border of quadratus femoris spreading on to the lateral aspect of the greater trochanter. This branch marks the level of the tendon of obturator externus, which is crossed posteriorly by the deep branch of the MFCA. As the deep branch travels superiorly, it crosses anterior to the conjoint tendon of gemellus inferior, obturator internus and gemellus superior. It then perforates the joint capsule at the level of gemellus superior. In its intracapsular segment it runs along the posterosuperior aspect of the neck of the femur dividing into two to four subsynovial retinacular vessels. We demonstrated that obturator externus protected the deep branch of the MFCA from being disrupted or stretched during dislocation of the hip in any direction after serial release of all other soft-tissue attachments of the proximal femur, including a complete circumferential capsulotomy.

Precise knowledge of the extracapsular anatomy of the MFCA and its surrounding structures will help to avoid iatrogenic avascular necrosis of the head of the femur in reconstructive surgery of the hip and fixation of acetabular fractures through the posterior approach.

In order to investigate the functional anatomy of gluteus minimus we dissected 16 hips in fresh cadavers. The muscle originates from the external aspect of the ilium, between the anterior and inferior gluteal lines, and also at the sciatic notch from the inside of the pelvis where it protects the superior gluteal nerve and artery. It inserts anterosuperiorly into the capsule of the hip and continues to its main insertion on the greater trochanter.

Based on these anatomical findings, a model was developed using plastic bones. A study of its mechanics showed that gluteus minimus acts as a flexor, an abductor and an internal or external rotator, depending on the position of the femur and which part of the muscle is active. It follows that one of its functions is to stabilise the head of the femur in the acetabulum by tightening the capsule and applying pressure on the head. Careful preservation or reattachment of the tendon of gluteus minimus during surgery on the hip is strongly recommended.

We carried out the Bernese periacetabular osteotomy for the treatment of 13 dysplastic hips in 11 skeletally mature patients with an underlying neurological diagnosis. Seven hips had flaccid paralysis and six were spastic. The mean age at the time of surgery was 23 years and the mean length of follow-up was 6.4 years. Preoperatively, 11 hips had pain and two had progressive subluxation.

Before operation the mean Tönnis angle was 33°, the mean centre-edge angle was −10°, and the mean extrusion index was 53%. Postoperatively, they were 8°, 25° and 15%, respectively. Pain was eliminated in 7 patients and reduced in four in those who had preoperative pain. One patient developed pain secondary to anterior impingement from excessive retroversion of the acetabulum. Four required a varus proximal femoral osteotomy at the time of the pelvic procedure and one a late varus proximal femoral osteotomy for progressive subluxation.

Before operation no patient had arthritis. At the most recent follow-up one had early arthritis of the hip (Tönnis grade I) and one had advanced arthritis (Tönnis grade III).

Our results suggest that the Bernese periacetabular osteotomy can be used successfully to treat neurogenic acetabular dysplasia in skeletally mature patients.

Free patellar tendon grafts used for the intra-articular replacement of ruptured anterior cruciate ligaments (ACL) lack perfusion at the time of implantation. The central core of the graft undergoes a process of ischaemic necrosis which may result in failure. Early reperfusion of the graft may diminish the extent of this process.

We assessed the role of peritendinous connective tissue in the revascularisation of the patellar tendon graft from the day of implantation up to 24 days in a murine model using intravital microscopy. The peritendinous connective-tissue envelope of the graft was either completely removed, partially removed or not stripped before implantation into dorsal skinfold chambers of recipient mice.

Initial revascularisation of the grafts with preserved peritendinous connective tissues began after two days. The process was delayed by five to six times in completely stripped patellar tendons (p < 0.05). Only grafts with preserved connective tissues showed high viability whereas those which were completely stripped appeared to be subvital.

The presence of peritendinous connective tissues accelerates the revascularisation of free patellar tendon grafts.

We compared 74 total hip arthroplasties (THAs) carried out after previous proximal femoral osteotomy with a diagnosis-matched control group of 74 primary procedures performed during the same period. We report the perioperative results and the clinical and radiological outcome at five to ten years.

We anticipated a higher rate of complications in the group with previous osteotomy, but found no significant difference in the rate of perioperative complications (11% each) or in the septic (8% v 3%) and aseptic (4% each) revision rates. There was a trend towards improved survival in the group without previous osteotomy (90% v 82%), but this difference was not statistically significant. The only significant differences were a higher rate of trochanteric osteotomy (88% v 14%) and a longer operating time in the osteotomy group.

Our study indicates that THA after previous osteotomy is technically more demanding but not necessarily associated with a higher rate of complications. Furthermore, proximal femoral osteotomy does not jeopardise the clinical and radiological outcome of future THA enough to exclude the use of osteotomy as a therapeutic alternative in younger patients.

Since January 1993 we have carried out MR arthrography on 23 patients with clinical symptoms and signs of abnormality of the acetabular labrum. Most of the patients were young adults. Such symptoms are known precursors of osteoarthritis, and therefore early and accurate evaluation is required.

We assessed the value of MR arthrography of the hip as a minimally-invasive diagnostic technique, in a prospective study and compared the findings with those at subsequent operations. All the patients complained of groin pain; 22 had a positive acetabular impingement test and 15 had radiological evidence of hip dysplasia.

In 21 of the patients, MR arthrography suggested either degeneration or a tear of the labrum or both. These findings were confirmed at operation in 18 patients, but there was no abnormality of the labrum in the other three. In two of the patients, MR arthrography erroneously suggested an intact labrum. Both MR arthrography and intraoperative inspection located lesions of the superior labrum most often, and these appeared slightly larger on arthrography than at operation.

We consider that MR arthrography is a promising diagnostic technique for the evaluation of abnormalities of the acetabular labrum.

We have treated 42 consecutive complex ununited fractures of the femoral shaft by wave-plate osteosynthesis at five different medical centres. There were 13 with previous infection, 12 with segmental cortical defects, and 3 were pathological fractures. In 39 cases there had been previous internal fixation and 21 patients had had more than one earlier operation.

Union was achieved in 41 patients at an average of six months, although three had required a second bone graft. Two patients had recurrence of infection and in one this resulted in the persistence of nonunion. There were no failures of the implant. All 41 patients with union are now fully weight-bearing, but four have a leg-length discrepancy, one has axial malalignment, and nine have residual stiffness of the knee. These results are surprisingly good, despite the complexity of the initial problem, and appear to confirm the biological and mechanical advantages of the wave plate over the conventional plate for such cases.

The Chiari osteotomy and various shelf procedures are used to augment the weight-bearing area in dysplastic acetabula. The new articular surface derives by metaplasia from the acetabular rim and joint capsule, and is therefore of poorer quality than congruous hyaline cartilage. We reviewed 32 patients after augmentation procedures, using conventional radiographs and three-dimensional reconstruction from CT scans. We showed that Chiari osteotomy and shelf procedures generally achieve less than complete cover, especially over the posterolateral quadrant of the femoral head. Our results suggest that alternative methods which reorientate the whole of the acetabulum are the treatment of choice. Augmentation procedures remain as a salvage option when reorientation is inappropriate or the original hyaline cartilage surface is absent, as in subluxed joints with a secondary acetabulum. Computerised assessment is recommended before operation to assess existing cover and the possible extent of provision of new cover.

The acetabular rim syndrome is a pathological entity which we illustrate by reference to 29 cases. The syndrome is a precursor of osteoarthritis of the hip secondary to acetabular dysplasia. The symptoms are pain and impaired function. All our cases were treated by operation which consisted in most instances of re-orientation of the acetabulum by peri-acetabular osteotomy and arthrotomy of the hip. In all cases, the limbus was found to be detached from the bony rim of the acetabulum. In several instances there was a separated bone fragment, or 'os acetabuli' as well. In acetabular dysplasia, the acetabular rim is subject to abnormal stress which may cause the limbus to rupture, and a fragment of bone to separate from the adjacent bone margin. Dysplastic acetabuli may be classified into two radiological types. In type I there is an incongruent shallow acetabulum. In type II the acetabulum is congruent but the coverage of the femoral head is deficient.

There is a specific type of displaced four-part fracture of the proximal humerus which consists of valgus impaction of the head fragment; this deserves special consideration because the rate of avascular necrosis is lower than that of other displaced four-part fractures. Using either closed reduction or limited open reduction and minimal internal fixation, 74% satisfactory results can be achieved in this injury.

In the Trillat procedure for recurrent anterior instability of the shoulder the coracoid process is osteotomised and tilted downward to act as a bone block, and a screw is used to fix it and the Bankart lesion to the anterior scapular neck. We reviewed 52 cases after a mean follow-up of 69 months. Results in 73% of shoulders were excellent, 10% were good, 7% fair and 10% poor. Dislocation recurred in 4%, but a positive apprehension sign was present in 10 other shoulders. Some degenerative changes were seen in 62% of shoulders, a complication known to be associated with bone-block procedures. The most important reason for loss of lateral rotation was iatrogenic impingement of the coracoid. This frequent and potentially serious complication can also cause posterior subluxation of the humeral head and osteoarthritis.

Symptomatic impingement of the rotator cuff between the humeral head and the coracoid process has been studied and three varieties recognised: idiopathic, iatrogenic and traumatic. In all three the clinical findings consisted of pain in front of the shoulder, referred to the upper arm and forearm, and especially felt during forward flexion and medial rotation; the pain could be reproduced by medial rotation with the arm in 90 degrees of abduction, or by adduction with the shoulder flexed to 90 degrees. Patients were relieved of their symptoms by restoring adequate subcoracoid clearance.