Aims

Perthes’ disease (PD) often results in femoral head deformity and leg length discrepancy (LLD). Our objective was to analyze femoral morphology in PD patients at skeletal maturity to assess where the LLD originates, and evaluate the effect of contralateral epiphysiodesis for length equalization on proximal and subtrochanteric femoral lengths.

Introduction

Legg-Calvé-Perthes disease (LCPD) often results in femoral head deformity and leg length discrepancy (LLD). Objective of this study was to analyse femoral morphology in LCPD patients at skeletal maturity to assess where the LLD originates, and evaluate the effect of contralateral epiphysiodesis for length equalisation on proximal and subtrochanteric femoral lengths.

Introduction

Leg length discrepancy (LLD) in patients with unilateral developmental dysplasia of the hip (DDH) can be problematic for both patients and surgeons. Patients can acquire gait asymmetry, back pain, and arthritis. Surgical considerations include timing of correction and arthroplasty planning. This study audits standing long leg films performed at skeletal maturity in our patients. The aim of this study is to identify if surgical procedure or AVN type could predict the odds of needing an LLD Intervention (LLDI) and influence our surveillance.

Aims

Despite advances in the treatment of paediatric hip disease, adolescent and young adult patients can develop early onset end-stage osteoarthritis. The aims of this study were to address the indications and medium-term outcomes for total hip arthroplasty (THA) with ceramic bearings for teenage patients.

Purpose

To review the natural history of posteromedial bowing of the tibia and the outcome of limb reconstruction in this condition.

Purpose

To determine (i) the relationship between osteonecrosis and hip function, physical function and quality of life in adolescents and young adults treated for DDH; and (ii) how affected children change over 10 years.

Aims

Our aim was to assess the effectiveness of a protocol involving a standardised closed reduction for the treatment of children with developmental dysplasia of the hip (DDH) in maintaining reduction and to report the mid-term results.

Purpose of the study is to investigate the outcome of the patients with Perthes disease who have had a surgical dislocation of their hip for the treatment of resultant symptoms from the disease process.

Retrospective review of consecutive patients treated with surgical dislocation of the hip for Perthes disease. Review of clinical case notes and radiological imaging. Patient outcome was assessed at follow-up.

Between 2010 and 2015, 31 cases of surgical hip dislocation were performed for Perthes disease at our institution by 2 senior surgeons. Age range at time of surgery was 12–33. Male:female ratio was 13:18; right:left ratio was 15:17. Age at the time of Perthes diagnosis was between 3 and 13 years, with 3 diagnosed retrospectively. Mean follow-up was 18months. All patients had an EUA and arthrogram while 61.3%(19/31) had previous surgery for Perthes. 71%(22/31) required a labral repair, 6.5%(2/31) had a peri-acetabular osteotomy at the time of surgery and 3.2%(1/31) required a proximal femoral valgus osteotomy. 22.5%(7/31) required microfracture (femoral head or acetabulum): all of whom had evidence of contained area of degenerative changes on preoperative MRI. 64.5%(20/31) had the trochanteric screws removed.

Complications included 1 greater trochanter non-union, 1 pain secondary to suture anchor impinging on psoas tendon, 1 AVN leading to early THR 12 months post-op. Another 2 had further deterioration of degenerative changes and pain leading to THR 18 and 24 months post-op. All 3(9.7%) had microfracture at the time of the dislocation for established degenerative change and also required custom made prostheses.

Surgical hip dislocation is an option in treating Perthes patient with resultant symptoms such as impingement. Improved outcome is seen in patients who are younger with a congruent hip joint in contrast to those with established degenerative change evident on MRI / intraoperatively and have an arrow shaped femoral head.

Slipped upper femoral epiphysis (SUFE) is the most common hip disorder to affect adolescents. Controversy exists over the optimal treatment of severe slips, with a continuing debate between in situ fixation versus corrective surgery. We present our experience in a series of 57 patients presenting with severe unilateral SUFE (defined > 50°) managed with a subcapital cuneiform osteotomy.

Between 2001 and 2011, 57 patients (35 male, 22 female) with a mean age of 13.1 years (9.6 to 20.3, SD 2.3) were referred to our tertiary referral institution with a severe slip. The affected limb was rested in slings and springs before corrective surgery which was performed via an anterior Smith-Petersen approach. Radiographic analysis confirmed an improvement in mean head–shaft slip angle from 53.8^o (standard deviation (sd) 3.2) pre-operatively to 9.1^o (sd 3.1) post-operatively, with minimal associated femoral neck shortening. In total 50 (88%) patients were complication free at a mean follow-up of seven years (2.8 to 13.9 years, sd 3). Their mean Oxford hip score was 44 (37 to 48) and median visual analogue pain score was 0 out of 10 (interquartile range 0 to 4). A total of six patients (10.5%) developed avascular necrosis requiring further surgery and one (1.8%) patient developed chondrolysis but declined further intervention.

This is a technically demanding operation with variable outcomes reported in the literature. We have demonstrated good results in our tertiary centre.

Cite this article: Bone Joint J 2015;97-B:1718–25.

Proximal femoral varus osteotomy improves the biomechanics of the hip and can stimulate normal acetabular development in a dysplastic hip. Medial closing wedge osteotomy remains the most popular technique, but is associated with shortening of the ipsilateral femur.

We produced a trigonometric formula which may be used pre-operatively to predict the resultant leg length discrepancy (LLD). We retrospectively examined the influence of the choice of angle in a closing wedge femoral osteotomy on LLD in 120 patients (135 osteotomies, 53% male, mean age six years, (3 to 21), 96% caucasian) over a 15-year period (1998 to 2013). A total of 16 of these patients were excluded due to under or over varus correction. The patients were divided into three age groups: paediatric (< 10 years), adolescent (10 to 16 years) and adult (> 16 years). When using the same saw blades as in this series, the results indicated that for each 10° of angle of resection the resultant LLD equates approximately to multiples of 4 mm, 8 mm and 12 mm in the three age groups, respectively.

Statistical testing of the 59 patients who had a complete set of pre- and post-operative standing long leg radiographs, revealed a Pearson’s correlation coefficient for predicted versus radiologically observed shortening when using a wedge of either 10° or 20° of 0.93 (p <  0.001). The 95% limits of agreement from the Bland–Altman analysis for this subgroup were –3.5 mm to +3.3 mm. It has been accepted that a 10 mm discrepancy is clinically acceptable.

This study identified a geometric model that provided satisfactory accuracy when using specific saw blades of known thicknesses for this formula to be used in clinical practice.

Cite this article: Bone Joint J 2014;96-B:1124–9

Aim:

Audit of the outcome of subcapital osteotomy for a series of cases of severe unstable slipped capital femoral epiphysis.

Purpose of study

We hypothesised that Vitamin D deficiency could be related to SUFE in children without endocrinological abnormalities. We therefore sought to examine prevalence and severity of Vitamin D insufficiency in a cross-section of SUFE patients.

Total hip arthroplasty (THA) in teenagers is uncommon and previously associated with poor survival rates. However it is sometimes the only option remaining to relieve pain and improve function in patients with advanced hip disease. We report on the clinical and radiological outcomes of THA in teenage patients. Medical records and radiographs of all consecutive teenage patients undergoing THA at a tertiary referral centre between 2006–2011 were reviewed. Mean follow-up was 3.4 years (range 0.6–6.8) with 9 patients having at least 5 years follow-up. Post-operative Harris hip, Oxford hip (OHS) and University of California Los Angeles (UCLA) activity scores were recorded. 51 THAs were performed in 43 patients (21 male, 22 female) with a mean age of 17 years (range 12–19). The 5 most common indications were slipped upper femoral epiphysis osteonecrosis 15 (29.4%), developmental hip dysplasia osteonecrosis 5 (9.8%), multiple/spondylo-epiphyseal dysplasia 5 (9.8%), chemotherapy-induced osteonecrosis 4 (7.8%) and idiopathic osteonecrosis 4 (8.2%). 46 (90%) were uncemented THAs and 5 (10%) were reverse hybrid THAs with 7 computer assisted design/manufacture (CADCAM) femoral implants. Articular bearings were ceramic/ceramic in 40 (78.4%), metal/metal 6 (11.8%), metal/polyethylene 3 (5.9%) and ceramic/polyethylene 2 (3.9%). The survival rate was 96% with 2 acute head revisions for 1 sciatic nerve palsy and 1 instability. Other complications (8.2%) included 1 dislocation, 1 sciatic nerve palsy that resolved, 1 surgical site infection and 1 unexplained pain. At latest follow-up, the mean Harris hip score was 90 (68–99), OHS was 42 (32–48) and UCLA activity score was 6 (4–9). Radiological analysis showed 2 patients with lucent lines around the acetabular component, but no signs of osteolysis or wear. As one of the largest studies on teenagers undergoing THA, we report good clinical and radiological outcomes at short to intermediate term follow-up.

Introduction

Many patients who had previous proximal femoral osteotomies develop deformities that may not be amenable to total hip replacement (THR) with standard off-the-shelf femoral stems. Previous studies have shown high revision rates (18% at 5–10 years follow-up). Computer-assisted-design computer-assisted-manufacture (CAD-CAM) femoral stems are indicated but the results are not known. We assessed the clinical results of THR using CAD-CAM femoral stems specifically for this group of patients.

Purpose

To document the success rate of closed reduction and soft tissue release in the treatment of bilateral true dislocation in developmental dysplasia of the hip (DDH).

Purpose

To investigate the effect of soft tissue release (STR) and the length of postoperative immobilisation on the long term outcomes of closed reduction (CR) of the hip for developmental dysplasia of the hip.

Introduction: Avascular necrosis (AVN) is a serious complication affecting the femoral head following an unstable slipped capital femoral epiphysis (SCFE) particularly if the slip is severe. The incidence of AVN may be as high as 47%.

Purpose: To determine whether or not the avascular insult associated with a massive unstable SCFE is a temporary event and whether this may resolve in the second week post injury.

Methods: 6 patients (4 male:2 females), mean age 14.9 yrs (13.2–17.5yrs) with acute severe unstable SCFE were reviewed. The mean Southwick slip angle was 51.20 deg (40.1 – 66.60). 5 of 6 cases were severe. All cases underwent a subcapital cuneiform femoral neck osteotomy at a mean 14 days (7–24 days) after the acute event. Pre-operatively, the hip/limb was rested in ‘slings and springs’. No hip underwent a manipulative procedure. All hips underwent an MRI scan at a mean 8.6 days post injury (range 4–15 days) to determine the viability of the femoral head.

Results: In all 6 cases, the femoral head was reported to be viable. All femoral heads showed signs of bone oedema and other features indicative of a blood supply.

Following the cuneiform osteotomy, patients were mobilized partial weight bearing for 8 weeks. At a mean 12 month follow up, radiographs confirmed that all oste-otomies had united and no hip showed evidence of AVN.

Conclusion: If the acute severe unstable slip is associated with an avascular insult to the femoral head, this may be a temporary phenomenon and assuming the hip is not subjected to any immediate secondary trauma such as operative reduction, then there may be a spontaneous recovery in the blood supply as evidenced by the viable femoral head seen on MRI.

Significance: Our study suggests that there may be a time period during which the slipped femoral head may be vulnerable to a second insult and hence AVN. The timing of any surgical intervention designed at reducing the slip should take this into account and be performed carefully to ensure that the blood vessels on the posterior aspect of the femoral neck are not disrupted. When the presentation of an acute unstable and severe SCFE is delayed beyond 24 hours, we favour delaying subsequent operative correction for a further 2–3 weeks to maximize the chance of a viable femoral head.

Introduction: Abnormal hip morphology, seen with conditions such as slipped capital femoral epiphyses and femoral head necrosis, can lead to repetitive contact between the femoral neck and the acetabular rim. Impingement is a significant cause of hip pain in young adults and may be a mechanism for the development of early osteoarthritis. The senior surgeon has modified a technique to debride the pathology responsible for femoroacetabular impingement through a mini anterior approach, obviating the need to dislocate the hip. We describe this technique and present early clinical outcomes.

Method: Between Jan 2006 and June 2008, ‘notchplasty’ for the surgical treatment of femoroacetabular impingement was performed by the senior author (AHN) or directly under his supervision in 38 hips. There were 17 male patients and 21 female patients with an average age of 31 years. Patients have been followed according to a prospective protocol with Oxford and Iowa hip scores obtained pre-operatively, at 3 months and at 1 year.

Results: This study is still in progress. Twenty nine patients have had 3 month follow up and 13 of these have now been followed up to one year. Four patients are still less than 3 months post op. Data was unobtainable for 5 patients. 1 patient was excluded from the study.

The overall Oxford hip score improved significantly from a mean pre-operative value of 35 to a mean post operative value of 22.9 at 3 months (p< 0.001).

The mean score at 1 year increased slightly to 27.3 points but this remains lower than the pre operative average.

We report no cases of osteonecrosis. One patient has since been scheduled to undergo resurfacing arthroplasty.

Conclusions: The technique described is a new method for managing these patients whilst avoiding the pit-falls of current operative methods. The method avoids detaching the straight head of rectus, thereby tremendously improving postoperative mobilisation. However, the long term benefit of debridement of the head-neck junction for Cam-type femoroacetabular impingement remains to be seen.

Scoliosis and hip subluxation/dislocation are common and often coexistent problems encountered in patients with cerebral palsy (CP). The underlying mechanism may be related to muscle imbalance. Surgical correction may become necessary in severe symptomatic cases. The effect of surgical correction of one deformity on the other is not well understood.

We retrospectively reviewed a series of 17 patients with total body cerebral palsy with diagnoses of both scoliosis and hip subluxation who had undergone either surgical correction of their scoliosis (9 patients) or a hip reconstruction to correct hip deformity (8 patients). In all patients, the degree of progression of both deformities was measured, radiographically, using the Cobb angle for the spine and the percentage migration index for hip centre of rotation at intervals before and at least 18 months post surgery.

All patients who underwent scoliosis correction had a progressive increase in the percentage of hip migration at a rate greater than that prior to scoliosis surgery. Similarly, patients who underwent a hip reconstruction procedure demonstrated a more rapid increase in their spine Cobb angles post surgery.

There may be a relationship between hip subluxation/dislocation and scoliosis in CP patients. Surgery for either scoliosis or hip dysplasia may in the presence of both conditions lead to a significant and rapid worsening of the other. The possible negative implications on the overall functional outcome of the surgical procedure warrants careful consideration to both hip and the spine before and after surgical correction of either deformity. In selected cases there may be an indication for one procedure to follow soon after the other.

Introduction: Percutaneous epiphyseodesis is a simple method of achieving leg length equality in cases of minor leg length discrepancy, however few studies document its effectiveness. A retrospective study was undertaken to assess this.

Materials and methods: Patient notes and radiographs were reviewed. The growth remaining method was used to estimate timing. Percutaneous epiphyseodesis was performed with a drill and curette under radiological guidance.

Results: A total of 24 skeletally mature patients with a mean preoperative leg length discrepancy (LLD) of 2.8cm were identified. Skeletal age was significantly different from chronological age in 5 of 11 cases where it had been performed. In all patients, there was radiographic evidence of physeal closure soon after epiphyseodesis. At skeletal maturity, 14 patients have a LLD of 0–1cm and are considered to have a satisfactory outcome. 10 patients have a LLD> 2cms. In 6 of these, either presentation was too late or the amount of discrepancy too large for complete correction to be expected. In the other 4, skeletal age assessment may have been useful in 3, and in one additional case of overgrowth of the short limb prior to maturity. A successful outome was more likely when skeletal age assessment had been used (82% versus 57%). Of the 18 cases where there was sufficient time for a full correction to be achieved, the overall success rate was 72%. There were no significant clinical or radiological complications.

Conclusions:

Percutaneous drill epiphyseodesis is an effective method of achieving physeal ablation with no significant complications.

Introduction: The management of severe slipped upper femoral epiphysis (SUFE) is controversial. Many types of operation have been advocated. The cuneiform osteotomy offers the potential to restore normal anatomy and hence reduce the development of osteoarthritis, but it is not without its risks. This aim of this study was to quantify the long-term clinical & radiological results of Fish’s cuneiform osteotomy at skeletal maturity.

Method: Twenty-seven patients underwent a cuneiform osteotomy between 1990 – 2003. Two patients were lost to follow-up. Therefore 25 hips in 24 patients were reviewed at a mean follow-up of 8 years and 3 months. The mean slip angle was 77 ± 13 degrees and all were categorized as unstable. Sex distribution was equal and the average age at follow-up was 21.5 years (range 14 – 31 years). The Iowa hip-rating, Harris Hip Score and radiographic classification of degenerative joint disease according to Boyer et al.,¹ were determined at follow-up.

Results: The mean Iowa hip-rating at follow-up was 93.7 ± 7.7 with a mean range of motion score of 8.1 ± 1.8. The Harris Hip Score was 95.6 ± 5.9. Nineteen patients were classified as Grade 0 on Boyer’s radiographic assessment, four Grade 1 and two Grade 2. Correction to neutral ± 10 degrees was achieved in all patients. The rate of avascular necrosis was 12 % and chondrolysis 16 %.

Discussion: Cuneiform osteotomy for severe SUFE is a valid treatment option and complication rates were no higher than other operative interventions reported in the literature. Patients enjoyed an excellent range of motion and were extremely satisfied with the outcome. The restoration of anatomy equates to better function and possibly the delay in onset of osteoarthritis.

We reviewed prospectively, after skeletal maturity, a series of 24 patients (25 hips) with severe acute-on-chronic slipped capital femoral epiphysis which had been treated by subcapital cuneiform osteotomy. Patients were followed up for a mean of 8 years, 3 months (2 years, 5 months to 16 years, 4 months). Bedrest with ‘slings and springs’ had been used for a mean of 22 days (19 to 35) in 22 patients, and bedrest alone in two, before definitive surgery. The Iowa hip score, the Harris hip score and Boyer’s radiological classification for degenerative disease were used.

The mean Iowa hip score at follow-up was 93.7 (69 to 100) and the mean Harris hip score 95.6 (78 to 100). Degenerative joint changes were graded as 0 in 19 hips, grade 1 in four and grade 2 in two. The rate of avascular necrosis was 12% (3 of 25) and the rate of chondrolysis was 16% (4 of 25). We conclude that after a period of bed rest with slings and springs for three weeks to gain stability, subcapital cuneiform osteotomy for severe acute-on-chronic slipped capital femoral epiphysis is a satisfactory method of treatment with an acceptable rate of complication.

Avascular necrosis is a serious complication of slipped capital femoral epiphysis and is difficult to treat. The reported incidence varies from 3% to 47% of patients. The aims of treatment are to maintain the range of movement of the hip and to prevent collapse of the femoral head. At present there are no clear guidelines for the management of this condition and treatment can be difficult and unrewarding.

We have used examination under anaesthesia and dynamic arthrography to investigate avascular necrosis and to determine the appropriate method of treatment. We present 20 consecutive cases of avascular necrosis in patients presenting with slipped capital femoral epiphysis and describe the results of treatment with a mean follow-up of over eight years (71 to 121 months). In patients who were suitable for joint preservation (14), we report a ten-year survivorship of the hip joint of 75% and a mean Harris hip score of 82 (44 to 98).

Introduction: Avascular necrosis (AVN) is a devastating complication of slipped capital femoral epiphysis (SCFE) and is difficult to treat. The incidence of AVN in this condition varies considerably and is reported to appear in 3–47% of patients. The aims of the treatment of AVN are to maintain range of movement of the hip whilst preventing collapse of the femoral head. Clear treatment guidelines of this condition do not currently exist and the treatment of this condition can be difficult and unrewarding.

Method: Dynamic arthrograms were used to assess of cases of AVN in order to determine the method of treatment. We present 20 sequential cases of AVN in patients presenting to our unit with SCFE and report the long-term results of treatment with a mean follow-up in excess of 10 years.

Results: In 100 consecutive cases of SUFE there were 20 cases of AVN. There were 18 cases of salvage surgery and one patient refused surgery. Of the 18, there were 2 acetabuloplasty procedures, 12 proximal valgus osteotomies and 4 arthrodeses. At a later date there were 3 proximal femoral osteotomies and 5 total hip replacements.

Discussion: There is a good functional result in the majority of cases and a logical approach delays the need of total hip replacement in the majority of cases. The management depends on the radiography, the arthogram and the EUA. If there is early AVN with no collapse the treatment is a shelf procedure. If there is hinge abduction the treatment is a valgus femoral osteotomy. If there is instable movement and the hip is not congruent the treatment is hip arthrodesis.

Acetabular dysplasia may present as previously undiagnosed or as a sequel to treated DDH in a young adult, with a natural history of subsequent development of early osteoarthritis.

Patients with acetabular dysplasia and a normal neck shaft angle, no significant leg length inequality and who demonstrate congruency at arthrogram are considered suitable for realignment pelvic osteotomy.

We report the results of 15 young adults who underwent a modified Tonnis triple osteotomy with a mean 21-month follow up. The modification was the ischial osteotomy being performed through a groin incision.

The only common complication was the requirement of catheterisation post-operatively (60%). There were no infections. There was 1 delayed union but no non-unions. One patient developed a deep vein thrombosis. All patients reported an improvement in their symptoms and level of activity, with a mean post-operative Harris hip score of 92. All showed an improved centre-edge angle of 28° (mean increase of 18°) and acetabular angle 37° (mean decrease of 13°).

The early results of this procedure show this to be a safe and useful option to delay the natural history of early osteoarthritis in the young adult.

37 patients (38 hips) underwent sub-capital osteotomy for slipped upper femoral epiphysis (SUFE) between 1980 and 1999. All slips were severe, and 28 (74%) were unstable. Patients were followed-up at a mean 6. 9 years (range 2. 2–20 years) to identify the relationship between the timing of surgery and complications.

Stable slips underwent urgent elective operations. Unstable slips, admitted as emergencies, were operated upon following two different protocols. 17 cases underwent the Dunn procedure on the next available list at a mean 1. 7 days after admission. 21 cases underwent the Fish procedure after a mean 22. 2 days of bedrest on “slings and springs”.

Of 23 patients (24 hips) who suffered no complications and for whom on Iowa Flip Score was available, the means score was 96. 5 (range 91–100). There were 6 cases of Avascular Nervosis (AVN) (16%), all occurring after unstable slips, and 4 cases of chondrolysis (10%).

Amongst unstable slips, shorter periods of pre-operative bedrest were associated with a higher incidence of avascular necrosis (AVN) (p< 0. 025). Direct comparison of the two surgical procedures showed no statistically significance difference in the incidence of AVN.

Sub-capital osteotomy is valid treatment for severe SUFE. More than 20 days of pre-operative bedrest decreased the incidence of AVN in unstable SUFE

Valgus extension osteotomy (VGEO) is a salvage procedure for ‘hinge abduction’ in Perthes’ disease. The indications for its use are pain and fixed deformity. Our study shows the clinical results at maturity of VGEO carried out in 48 children (51 hips) and the factors which influence subsequent remodelling of the hip. After a mean follow-up of ten years, total hip replacement has been carried out in four patients and arthrodesis in one. The average Iowa Hip Score in the remainder was 86 (54 to 100). Favourable remodelling of the femoral head was seen in 12 hips. This was associated with three factors at surgery; younger age (p = 0.009), the phase of reossification (p = 0.05) and an open triradiate cartilage (p = 0.0007). Our study has shown that, in the short term, VGEO relieves pain and corrects deformity; as growth proceeds it may produce useful remodelling in this worst affected subgroup of children with Perthes’ disease.

After open reduction for developmental dysplasia of the hip (DDH), a pelvic or femoral osteotomy may be required to maintain a stable concentric reduction. We report the clinical and radiological outcome in 82 children (95 hips) with DDH treated by open reduction through an anterior approach in which a test of stability was used to assess the need for a concomitant osteotomy. The mean age at the time of surgery was 28 months (9 to 79) and at the latest follow-up, 17 years (12 to 25). All patients have been followed up until closure of the triradiate cartilage with a mean period of 15 years (8 to 23).

At the time of open reduction before closure of the joint capsule, the position of maximum stability was assessed. A hip which required flexion with abduction for stability was considered to need an innominate osteotomy. If only internal rotation and abduction were required, an upper femoral derotational and varus osteotomy was carried out. For a ‘double-diameter’ acetabulum with anterolateral deficiency, a Pemberton-type osteotomy was used. A hip which was stable in the neutral position required no concomitant osteotomy.

Overall, 86% of the patients have had a satisfactory radiological outcome (Severin groups I and II) with an incidence of 7% of secondary procedures for persistent dysplasia including one hip which redislocated. The results were better (p = 0.04) in children under the age of two years. Increased leg length on the affected side was associated with poor acetabular development and recurrence of joint dysplasia (p = 0.01). The incidence of postoperative avascular necrosis was 7%. In a further 18%, premature physeal arrest was noted during the adolescent growth spurt (Kalamchi-MacEwen types II and III). Both of these complications were also associated with recurrence of joint dysplasia (p = 0.01). Studies with a shorter follow-up are therefore likely to underestimate the proportion of poor radiological results.

We reviewed 32 children after the treatment of simple bone cysts by intralesional injections of methyl-prednisolone acetate. The age of the child and the activity and size of the cyst did not significantly affect the radiological outcome. The earliest time at which the radiological response could be reliably determined was three months. After a median period of review of five years, four (13%) cysts had healed, 20 (62%) cysts were partially visible but sclerotic, four (12.5%) were still visible but opaque and four (12.5%) were clearly visible. The healed and partially visible but sclerotic cysts were classified as having satisfactory radiological healing. This was observed in 13 of 32 cysts (41%) after the first injection, in eight of 21 (38%) after the second injection, but in relatively few of the remaining cysts after subsequent injections.

A satisfactory symptomatic outcome was achieved in all of the 18 children with humeral cysts and in the one child with a fibular cyst irrespective of the radiological outcome, but only in nine (67%) of the 13 children with femoral or tibial lesions, in whom the cysts were healed or sclerotic. The remaining four children had exertional bone pain and repeated fractures of their femoral or tibial cysts which were incompletely healed with sclerosis in one and opacities in three.

We conclude that the healing response to intralesional corticosteroids is unpredictable and usually incomplete even after multiple injections. The failure rate in weight-bearing bones is too high.

Failure of an acetabular cup is uncommon and has been attributed to wear or creep, trauma or bony irregularities in the acetabulum. We report ten cases in which fracture of the cup occurred at the site of drill holes used to anchor the marker wire. The role of such indentations as stress raisers has not been previously reported; we suggest that deep indentations or grooves should not be placed in the most highly stressed areas and that the cup thickness should allow for predicted wear rates.