Aims. Developmental dysplasia of the hip (DDH) is a complex musculoskeletal disease that occurs mostly in children. This study aimed to investigate the molecular changes in the hip joint capsule of patients with DDH. Methods. High-throughput sequencing was used to identify genes that were differentially expressed in hip joint capsules between healthy controls and DDH patients. Biological assays including cell cycle, viability, apoptosis, immunofluorescence, reverse transcription polymerase chain reaction (RT-PCR), and western blotting were performed to determine the roles of the differentially expressed genes in DDH pathology. Results. More than 1,000 genes were differentially expressed in hip joint capsules between healthy controls and DDH. Both gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed that extracellular matrix (ECM) modifications, muscle system processes, and cell proliferation were markedly influenced by the differentially expressed genes. Expression of Collagen Type I Alpha 1 Chain (COL1A1), COL3A1, matrix metalloproteinase-1 (MMP1), MMP3, MMP9, and MMP13 was downregulated in DDH, with the loss of collagen fibres in the joint capsule. Expression of transforming growth factor beta 1 (TGF-β1) was downregulated, while that of TGF-β2, Mothers against decapentaplegic homolog 3 (SMAD3), and WNT11 were upregulated in DDH, and alpha smooth muscle actin (αSMA), a key myofibroblast marker, showed marginal increase. In vitro studies showed that fibroblast proliferation was suppressed in DDH, which was associated with cell cycle arrest in G0/G1 and G2/M phases. Cell cycle regulators including Cyclin B1 (CCNB1), Cyclin E2 (CCNE2), Cyclin A2 (CCNA2), Cyclin-dependent kinase 1 (CDK1), E2F1, cell division cycle 6 (CDC6), and CDC7 were downregulated in DDH. Conclusion. DDH is associated with the loss of collagen fibres and fibroblasts, which may cause loose joint capsule formation. However, the degree of differentiation of fibroblasts to myofibroblasts needs further study. Cite this article: Bone Joint Res 2021;10(9):558–570

Aims. To describe the epidemiology of acetabular fractures including patient characteristics, injury mechanisms, fracture patterns, treatment, and mortality. Methods. We retrieved information from the Swedish Fracture Register (SFR) on all patients with acetabular fractures, of the native hip joint in the adult skeleton, sustained between 2014 and 2020. Study variables included patient age, sex, injury date, injury mechanism, fracture classification, treatment, and mortality. Results. In total, 2,132 patients with acetabular fractures from the SFR were included in the study. The majority of the patients were male (62%) and aged over 70 years old (62%). For patients aged > 70 years, the 30-day mortality was 8% and one-year mortality 24%. For patients aged ≤ 70 years, the 30-day mortality was 0.2% and one-year mortality 2%. Low-energy injuries (63%) and anterior wall fractures (20%) were most common. Treatment was most often non-surgical (75%). Conclusion. The majority of patients who sustain an acetabular fracture are elderly (> 70 years), of male sex, and the fracture most commonly occurs after a simple, low-energy fall. Non-surgical treatment is chosen in the majority of acetabular fracture patients. The one-year mortality for elderly patients with acetabular fracture is similar to the mortality after hip fracture, and a similar multidisciplinary approach to care for these patients should be considered. Cite this article: Bone Jt Open 2023;4(9):652–658

Aims. The aim of this study was to investigate the association between fracture displacement and survivorship of the native hip joint without conversion to a total hip arthroplasty (THA), and to determine predictors for conversion to THA in patients treated nonoperatively for acetabular fractures. Methods. A multicentre cross-sectional study was performed in 170 patients who were treated nonoperatively for an acetabular fracture in three level 1 trauma centres. Using the post-injury diagnostic CT scan, the maximum gap and step-off values in the weightbearing dome were digitally measured by two trauma surgeons. Native hip survival was reported using Kaplan-Meier curves. Predictors for conversion to THA were determined using Cox regression analysis. Results. Of 170 patients, 22 (13%) subsequently received a THA. Native hip survival in patients with a step-off ≤ 2 mm, > 2 to 4 mm, or > 4 mm differed at five-year follow-up (respectively: 94% vs 70% vs 74%). Native hip survival in patients with a gap ≤ 2 mm, > 2 to 4 mm, or > 4 mm differed at five-year follow-up (respectively: 100% vs 84% vs 78%). Step-off displacement > 2 mm (> 2 to 4 mm hazard ratio (HR) 4.9, > 4 mm HR 5.6) and age > 60 years (HR 2.9) were independent predictors for conversion to THA at follow-up. Conclusion. Patients with minimally displaced acetabular fractures who opt for nonoperative fracture treatment may be informed that fracture displacement (e.g. gap and step-off) up to 2 mm, as measured on CT images, results in limited risk on conversion to THA. Step-off ≥ 2 mm and age > 60 years are predictors for conversion to THA and can be helpful in the shared decision-making process. Cite this article: Bone Joint J 2023;105-B(9):1020–1029

Aims. Dislocation of the hip remains a major complication after periacetabular tumour resection and endoprosthetic reconstruction. The position of the acetabular component is an important modifiable factor for surgeons in determining the risk of postoperative dislocation. We investigated the significance of horizontal, vertical, and sagittal displacement of the hip centre of rotation (COR) on postoperative dislocation using a CT-based 3D model, as well as other potential risk factors for dislocation. Methods. A total of 122 patients who underwent reconstruction following resection of periacetabular tumour between January 2011 and January 2020 were studied. The risk factors for dislocation were investigated with univariate and multivariate logistic regression analysis on patient-specific, resection-specific, and reconstruction-specific variables. Results. The dislocation rate was 13.9% (n = 17). The hip COR was found to be significantly shifted anteriorly and inferiorly in most patients in the dislocation group compared with the non-dislocation group. Three independent risk factors were found to be related to dislocation: resection of gluteus medius (odds ratio (OR) 3.68 (95% confidence interval (CI) 1.24 to 19.70); p = 0.039), vertical shift of COR > 18 mm (OR 24.8 (95% CI 6.23 to 128.00); p = 0.001), and sagittal shift of COR > 20 mm (OR 6.22 (95% CI 1.33 to 32.2); p = 0.026). Conclusion. Among the 17 patients who dislocated, 70.3% (n = 12) were anterior dislocations. Three independent risk factors were identified, suggesting the importance of proper restoration of the COR and the role of the gluteus medius in maintaining hip joint stability. Cite this article: Bone Joint J 2022;104-B(10):1180–1188

Aims. The aim of this study was to describe services available to patients with periprosthetic femoral fracture (PPFF) in England and Wales, with focus on variation between centres and areas for care improvement. Methods. This work used data freely available from the National Hip Fracture Database (NHFD) facilities survey in 2021, which asked 21 questions about the care of patients with PPFFs, and nine relating to clinical decision-making around a hypothetical case. Results. Of 174 centres contributing data to the NHFD, 161 provided full responses and 139 submitted data on PPFF. Lack of resources was cited as the main reason for not submitting data. Surgeon (44.6%) and theatre (29.7%) availability were reported as the primary reasons for surgical delay beyond 36 hours. Less than half had a formal process for a specialist surgeon to operate on PPFF at least every other day. The median number of specialist surgeons at each centre was four (interquartile range (IQR) 3 to 6) for PPFF around both hips and knees. Around one-third of centres reported having one dedicated theatre list per week. The routine discussion of patients with PPFF at local and regional multidisciplinary team meetings was lower than that for all-cause revision arthroplasties. Six centres reported transferring all patients with PPFF around a hip joint to another centre for surgery, and this was an occasional practice for a further 34. The management of the hypothetical clinical scenario was varied, with 75 centres proposing ORIF, 35 suggested revision surgery and 48 proposed a combination of both revision and fixation. Conclusion. There is considerable variation in both the organization of PPFF services England and Wales, and in the approach taken to an individual case. The rising incidence of PPFF and complexity of these patients highlight the need for pathway development. The adoption of networks may reduce variability and improve outcomes for patients with PPFF. Cite this article: Bone Jt Open 2023;4(5):378–384

Objectives. To validate the precision of digitally reconstructed radiograph (DRR) radiostereometric analysis (RSA) and the model-based method (MBM) RSA with respect to benchmark marker-based (MM) RSA for evaluation of kinematics in the native hip joint. Methods. Seven human cadaveric hemipelves were CT scanned and bone models were segmented. Tantalum beads were placed in the pelvis and proximal femoral bone. RSA recordings of the hips were performed during flexion, adduction and internal rotation. Stereoradiographic recordings were all analyzed with DRR, MBM and MM. Migration results for the MBM and DRR with respect to MM were compared. Precision was assessed as systematic bias (mean difference) and random variation (Pitman’s test for equal variance). Results. A total of 288 dynamic RSA images were analyzed. Systematic bias for DRR and MBM with respect to MM in translations (p < 0.018 mm) and rotations (p < 0.009°) were approximately 0. Pitman’s test showed lower random variation in all degrees of freedom for DRR compared with MBM (p < 0.001). Conclusion. Systematic error was approximately 0 for both DRR or MBM. However, precision of DRR was statistically significantly better than MBM. Since DRR does not require marker insertion it can be used for investigation of preoperative hip kinematics in comparison with the postoperative results after joint preserving hip surgery. . Cite this article: L. Hansen, S. De Raedt, P. B. Jørgensen, B. Mygind-Klavsen, B. Kaptein, M. Stilling. Marker free model-based radiostereometric analysis for evaluation of hip joint kinematics: A validation study. Bone Joint Res 2018;7:379–387. DOI: 10.1302/2046-3758.76.BJR-2017-0268.R1

Objectives. The high revision rates of the DePuy Articular Surface Replacement (ASR) and the DePuy ASR XL (the total hip arthroplasty (THA) version) have led to questions over the viability of metal-on-metal (MoM) hip joints. Some designs of MoM hip joint do, however, have reasonable mid-term performance when implanted in appropriate patients. Investigations into the reasons for implant failure are important to offer help with the choice of implants and direction for future implant designs. One way to assess the performance of explanted hip prostheses is to measure the wear (in terms of material loss) on the joint surfaces. Methods. In this study, a coordinate measuring machine (CMM) was used to measure the wear on five failed cementless Biomet Magnum/ReCap/ Taperloc large head MoM THAs, along with one Biomet ReCap resurfacing joint. Surface roughness measurements were also taken. The reason for revision of these implants was pain and/or adverse reaction to metal debris (ARMD) and/or elevated blood metal ion levels. Results. The mean wear rate of the articulating surfaces of the heads and acetabular components of all six joints tested was found to be 6.1 mm. 3. /year (4.1 to 7.6). The mean wear rate of the femoral head tapers of the five THAs was 0.054 mm. 3. /year (0.021 to 0.128) with a mean maximum wear depth of 5.7 µm (4.3 to 8.5). Conclusion. Although the taper wear was relatively low, the wear from the articulating surfaces was sufficient to provide concern and was potentially large enough to have been the cause of failure of these joints. The authors believe that patients implanted with the ReCap system, whether the resurfacing prosthesis or the THA, should be closely monitored. Cite this article: S. C. Scholes, B. J. Hunt, V. M. Richardson, D. J. Langton, E. Smith, T. J. Joyce. Explant analysis of the Biomet Magnum/ReCap metal-on-metal hip joint. Bone Joint Res 2017;6:113–122. DOI: 10.1302/2046-3758.62.BJR-2016-0130.R2

Aims. In the native hip, the hip capsular ligaments tighten at the limits of range of hip motion and may provide a passive stabilizing force to protect the hip against edge loading. In this study we quantified the stabilizing force vectors generated by capsular ligaments at extreme range of motion (ROM), and examined their ability to prevent edge loading. Methods. Torque-rotation curves were obtained from nine cadaveric hips to define the rotational restraint contributions of the capsular ligaments in 36 positions. A ligament model was developed to determine the line-of-action and effective moment arms of the medial/lateral iliofemoral, ischiofemoral, and pubofemoral ligaments in all positions. The functioning ligament forces and stiffness were determined at 5 Nm rotational restraint. In each position, the contribution of engaged capsular ligaments to the joint reaction force was used to evaluate the net force vector generated by the capsule. Results. The medial and lateral arms of the iliofemoral ligament generated the highest inbound force vector in positions combining extension and adduction providing anterior stability. The ischiofemoral ligament generated the highest inbound force in flexion with adduction and internal rotation (FADIR), reducing the risk of posterior dislocation. In this position the hip joint reaction force moved 0.8° inbound per Nm of internal capsular restraint, preventing edge loading. Conclusion. The capsular ligaments contribute to keep the joint force vector inbound from the edge of the acetabulum at extreme ROM. Preservation and appropriate tensioning of these structures following any type of hip surgery may be crucial to minimizing complications related to joint instability. Cite this article: Bone Joint Res 2021;10(9):594–601

Aims

Research on hip biomechanics has analyzed femoroacetabular contact pressures and forces in distinct hip conditions, with different procedures, and used diverse loading and testing conditions. The aim of this scoping review was to identify and summarize the available evidence in the literature for hip contact pressures and force in cadaver and in vivo studies, and how joint loading, labral status, and femoral and acetabular morphology can affect these biomechanical parameters.

To confirm whether developmental dysplasia of the hip has a risk of hip impingement, we analysed maximum ranges of movement to the point of bony impingement, and impingement location using three-dimensional (3D) surface models of the pelvis and femur in combination with 3D morphology of the hip joint using computer-assisted methods. Results of computed tomography were examined for 52 hip joints with DDH and 73 normal healthy hip joints. DDH shows larger maximum extension (p = 0.001) and internal rotation at 90° flexion (p < 0.001). Similar maximum flexion (p = 0.835) and external rotation (p = 0.713) were observed between groups, while high rates of extra-articular impingement were noticed in these directions in DDH (p < 0.001). Smaller cranial acetabular anteversion (p = 0.048), centre-edge angles (p < 0.001), a circumferentially shallower acetabulum, larger femoral neck anteversion (p < 0.001), and larger alpha angle were identified in DDH. Risk of anterior impingement in retroverted DDH hips is similar to that in retroverted normal hips in excessive adduction but minimal in less adduction. These findings might be borne in mind when considering the possibility of extra-articular posterior impingement in DDH being a source of pain, particularly for patients with a highly anteverted femoral neck. Cite this article: Bone Joint J 2014;96-B:580–9

1. One hundred patients with dislocation of the hip joint have been reviewed, many having been re-examined at intervals ranging from two to five years after injury. 2. There were forty-six simple dislocations, forty-three dislocations with fracture of the acetabular rim, seven dislocations with fracture of the acetabular floor, and five dislocations with fracture of the femoral head. 3. Complete recovery, as judged by clinical and radiographic examination, was observed in 76 per cent. of simple dislocations, 63 per cent. of dislocations with fracture of the acetabular rim, and 40 per cent. of dislocations with fracture of the femoral head; in no case of dislocation with fracture of the acetabular floor was recovery complete. 4. Only in one case did myositis ossificans develop, and that was the only case treated by "massage and movements" throughout the first ten weeks after injury. 5. Avascular necrosis of the femoral head was recognised in a smaller proportion of patients than had been expected, but since the follow-up review extended only to four years after injury the results, in this respect, are unreliable. The incidence of this complication after injury to the hip joint cannot be assessed unless the follow-up period is at least five to ten years. 6. Early traumatic arthritis developed in 26 per cent. of patients—in 15 per cent. of simple dislocations, 25 per cent. of dislocations with fracture of the acetabular margin, 60 per cent. of dislocations with fracture of the femoral head, and 100 per cent. of dislocations with fracture of the acetabular floor. 7. When central or posterior dislocations are accompanied by fracture of the acetabular floor, early arthrodesis is the treatment of choice. 8. Displacement of marginal acetabular fragments is usually corrected by manipulative reduction or by traction. 9. Sciatic paralysis in dislocation of the hip joint is nearly always due to damage of the nerve by a displaced acetabular fragment. In such cases, if the fragment is not replaced accurately by manipulation or traction, operative reduction is urgently indicated

Aims. Our aim in this study was to describe the long-term survival of the native hip joint after open reduction and internal fixation of a displaced fracture of the acetabulum. We also present long-term clinical outcomes and risk factors associated with a poor outcome. Patients and Methods. A total of 285 patients underwent surgery for a displaced acetabular fracture between 1993 and 2005. For the survival analysis 253 were included, there were 197 men and 56 women with a mean age of 42 years (12 to 78). The mean follow-up of 11 years (1 to 20) was identified from our pelvic fracture registry. There were 99 elementary and 154 associated fracture types. For the long-term clinical follow-up, 192 patients with complete data were included. Their mean age was 40 years (13 to 78) with a mean follow-up of 12 years (5 to 20). Injury to the femoral head and acetabular impaction were assessed with CT scans and patients with an ipsilateral fracture of the femoral head were excluded. Results. A total of 36 patients underwent total hip arthroplasty (THA). The overall ten-year survival of the hip joint was 86% (95% confidence interval (CI) 81% to 90%) and the 20-year survival was 82% (95% CI 76% to 87%). Injury to the femoral head and acetabular impaction were the strongest predictors of failure, with the long-term survival rate falling towards 50% in these patients. The survival fell to 0% at three years when both these risk factors were present in patients aged > 60 years. Conclusion. The long-term survival of the native hip joint after acetabular fractures was good, but the presence of injury to the femoral head and acetabular impaction proved to be strong predictors of failure, especially in patients aged > 60 years. These patients may be better treated with a combination of open reduction and internal fixation and primary arthroplasty. Cite this article: Bone Joint J 2017;99-B:834–40

1. This is a simple clinical study of the end-results of arthrodesis of the hip joint in patients followed up and re-examined five to twenty-five years after operation. 2. The study was stimulated by our astonishment at recent reports which suggested that arthrodesis of the hip caused serious operative mortality, a high rate of wound infection, and failure of sound fusion in one of every two cases; and that even when sound fusion was gained there was always pain in the back and usually stiffness of the knee. To say that we were astonished puts it mildly. 3. This review includes 120 patients aged from ten to seventy years, treated for osteoarthritis of the hip joint by intra-articular arthrodesis with the internal fixation of a nail, usually with an iliac graft, and with immobilisation in plaster for not less than four months. 4. Of these 120 patients there was sound fusion of the joint, proved radiographically, in 94 per cent; a mortality of nil; and recovery of free movement of the knee joint to the right angle or far beyond in 91·5 per cent. Almost half of the patients regained normal movement, the heel touching the buttock. Only in eight patients was there less than right-angled flexion. 5. There was no pain in the back—none whatever—in 64 per cent of the patients. In 36 per cent there was some pain or discomfort. One alone said that the low back pain was worse than before the operation. Many others said that pain in the back had been relieved by the operation. 6. It is emphasised that these results were gained only from sound fixation of the joint in the mid-position with neutral rotation, no more abduction than is needed to correct true shortening, and no more flexion of the joint than that with which the patient lies on the table. The limb was immobilised in plaster for at least four months after operation. The stiff knee was mobilised by the patient's own exercise without passive stretching, force or manipulation. 7. Two other groups of patients are considered. There are fourteen treated by fixation of the joint with nail alone, an operation that was never intended to arthrodese the joint and which has long since been abandoned. The other small group is that of patients with old unreduced traumatic dislocation of the hip, a procedure in which the risks of operation are so great and the number of successful results so small as to dissuade us from attempting operative reduction. 8. After successful arthrodesis of the hip joint patients can return to every household activity and every recreation including ski-ing, mountaineering, rock climbing, or whatever else they want

Aims

To analyze whether the addition of risk-based criteria to clinical examination-based selective ultrasound screening would increase the rates of early detected cases of developmental dysplasia of the hip (DDH) and decrease the rate of late detected cases.

Aims

The present study seeks to investigate the correlation of pubofemoral distances (PFD) to α angles, and hip displaceability status, defined as femoral head coverage (FHC) or FHC during manual provocation of the newborn hip < 50%.

In this study we used subject-specific finite element analysis to investigate the mechanical effects of rotational acetabular osteotomy (RAO) on the hip joint and analysed the correlation between various radiological measurements and mechanical stress in the hip joint. We evaluated 13 hips in 12 patients (two men and ten women, mean age at surgery 32.0 years; 19 to 46) with developmental dysplasia of the hip (DDH) who were treated by RAO. Subject-specific finite element models were constructed from CT data. The centre–edge (CE) angle, acetabular head index (AHI), acetabular angle and acetabular roof angle (ARA) were measured on anteroposterior pelvic radiographs taken before and after RAO. The relationship between equivalent stress in the hip joint and radiological measurements was analysed. The equivalent stress in the acetabulum decreased from 4.1 MPa (2.7 to 6.5) pre-operatively to 2.8 MPa (1.8 to 3.6) post-operatively (p < 0.01). There was a moderate correlation between equivalent stress in the acetabulum and the radiological measurements: CE angle (R = –0.645, p < 0.01); AHI (R = –0.603, p < 0.01); acetabular angle (R = 0.484, p = 0.02); and ARA (R = 0.572, p < 0.01). The equivalent stress in the acetabulum of patients with DDH decreased after RAO. Correction of the CE angle, AHI and ARA was considered to be important in reducing the mechanical stress in the hip joint. Cite this article: Bone Joint J 2015;97-B:492–7

The pressure distribution between the cartilaginous surfaces in the human hip joint was measured using pressure-sensitive film. Five cadaveric hip joints (aged between 58 and 87 years) were measured at three positions and loads, representing three instants in the stance phase of the walking cycle. The pressure distribution was not uniform, indicating that the cartilage did not, to any great extent, distribute the applied load. The maximum pressures recorded were about 10 MN/m2. The anterosuperior surface of the cartilage was identified as an area of high pressure

Aims

The aim of this study was to understand the experience of mature patients who undergo a periacetabular osteotomy (PAO), a major hip-preserving surgical procedure that treats symptomatic hip dysplasia by realigning the acetabulum. Our aim was to improve our understanding of how the operation affected the lives of patients and their families, with a long-term goal of improving their experience.

1. In this series of 150 cases of arthritis of the hip joint treated by vitallium mould arthroplasty (182 arthroplasties), 80 per cent. of late results are satisfactory to both patient and surgeon. 2. Striking features are the relative painlessness, smooth hip joint movement, progressive improvement in function, and reformation of the joint lines as seen radiographically in the post-operative period. 3. Function after arthroplasty for traumatic and degenerative arthritis approaches the normal hip joint much more closely than in cases of infective and rheumatoid arthritis. 4. There is a complete absence of low back symptoms or postural difficulties, and there is no difficulty in preventing stiffness of the knee joint. 5. Different technical procedures are indicated according to the degree of absorption of the femoral head or neck, and the stability of the mould in the acetabulum. 6. The operative mortality rate in this series was nil, and during the six-year follow-up period only one case died as the result of a complication of the arthroplasty. 7. In addition to meticulous operative technique and the use of special instruments, the importance of careful and prolonged after-treatment must be stressed. 8. It must also be emphasised that secondary operative revisions are often necessary, particularly in cases of infective and rheumatoid arthritis

1. Three cases of osteochondromatosis of the hip joint are described. 2. Attention is drawn to the diagnostic importance of erosions at the junction of head and neck of the femur, and the conical shape of the femoral neck. 3. Arthrography is of particular value in diagnosis when the loose bodies are radio-translucent

1. The operation of pseudarthrosis of the hip joint is described and the results are assessed in ninety-three patients. 2. The result was good in eighty-three cases and poor in seven cases. Three patients died as a result of the operation. 3. Pseudarthrosis is the most satisfactory and the most reliable operation: 1) in ankvlosing spondylitis, and 2) in patients over sixty years of age with disabling osteoarthritis. 4. The more formidable operation of cup arthoplasty may prove to be superior in younger patients with osteoarthritis

Aims

This study aimed to evaluate sagittal spinopelvic alignment (SSPA) in the early stage of rapidly destructive coxopathy (RDC) compared with hip osteoarthritis (HOA), and to identify risk factors of SSPA for destruction of the femoral head within 12 months after the disease onset.

1. Fifty cases of arthrodesis of the hip joint in tuberculous arthritis are analysed; in forty cases the late end-result has been ascertained two or more years after operation. 2. The indications for arthrodesis are discussed. The operation should not be performed when disease is active; it should not be undertaken before the age of twelve to thirteen years; it is not advisable in elderly patients; it may be contra-indicated when there are multiple foci of infection. Subject to these limitations every patient with unsound ankylosis after adequate conservative treatment should be treated by arthrodesis; painful fibrous ankylosis and late onset of deformity are definite indications. 3. Three types of operation have been used: intra-articular arthrodesis; extra-articular ilio-femoral arthrodesis; combined intra- and extra-articular arthrodesis. Extra-articular ilio-femoral arthrodesis is preferred, deformity being first corrected by traction or osteotomy. 4. Post-operation complications were few; the mortality rate was low (2 per cent.). 5. There was bone ankylosis with solid incorporation of the graft in 87·5 per cent., failure of union of the graft (to the trochanter) in 10 per cent., and destruction of the graft in 2·5 per cent. 6. Late end-results show full working capacity in 87·5 per cent. of patients, part working capacity in 2·5 per cent. and inability to work in 7·5 per cent. The writer wishes to express his thanks to Professor Harry Platt and Professor T. P.. McMurray for criticism and advice in the preparation of this paper, and to Dr F. C. S. Bradbury, Central Consultant Tuberculosis Officer of the Lancashire County Council, for permission to publish these cases

Photoelastic techniques were used to study the stresses in models which represented the central frontal plane of a normal hip joint. The pelvis and the femur were inclined and the direction of the resultant thrust on the joint was estimated. Inward tilting of the pelvis causes a force which tends to push the head of the femur out of joint. The load distribution on the joint is not significantly changed if the line of action of the load is moved relative to the joint. The directions of the lines of principal stress in both bones are shown

1. A specially designed loading apparatus and dyeing technique have been used to demonstrate the weight-bearing areas in fifty-one normal adult hip joints. 2. Under loads and positions typical of the stance phase of walking the entire articular surface of the acetabulum is involved in weight-bearing. This contact area is reproduced on the femoral head, and its position determined by the attitude of the femur to the acetabulum. 3. With loads typical of the swing phase, the dome of the acetabulum and corresponding areas on the femoral head are not involved in weight-bearing. 4. The results are compared with the conclusions of previous investigators and their possible significance with regard to joint degeneration is discussed

This is the first time that the principle of the mould—the principle of guiding the repair of nature for the purpose of recreating a destroyed or damaged structure, has been applied to surgery. The evolution of the method to its present encouraging stage is the result of the co-operative, professional family spirit of the Massachusetts General Hospital. We all share in it. We share it with the general surgeon because of his contributions to surgical technique. We share it with the "medical man" because of his pre-operative and post-operative care of the patient; because of his guidance as to when, and when not, to operate; and because of the many friendly arguments which are productive of so much good. We share it with the anaesthetist because of his clinical judgment of the patient, his selection of anaesthetic agent, and his continuous, conscientious administration of the anaesthetic throughout the operation. I am going to change from "we" to "I." I owe so much to my assistants, from the first to the last: Bill Rogers, Eddie Cave, George Van Gorder, Paul Norton, Milton Thompson, Otto Aufranc, and Carroll Larson. I want to thank them all for helping to carry the load, for remembering the things that I forgot, and for making helpful suggestions which often led to improvement in surgical technique or to the construction of a useful instrument. I want to pay tribute to the staff of the Orthopaedic Service of the Massachusetts General Hospital and to thank its members for kindly scepticism, constructive criticism, and neverfailing loyal support. The subject of this lecture, "Evolution of Mould Arthroplasty of the Hip Joint," is appropriate for a Moynihan lecture. It is not the work of one man alone. It is the work of one man, supported by a co-operative, helpful, and friendly hospital staff. This is what Lord Moynihan strove so hard to bring about at a time when surgeons viewed one another as rivals. To quote Dr William Mayo: "It is to Lord Moynihan's everlasting credit that, largely as a result of his unceasing efforts, surgeons came to consider themselves as fellow-workers in a cause."

1. The early signs of Paget's disease of the acetabulum and femur are described. 2. The pattern of arthritis is presented in 199 hips in which Paget's disease of bone occurred in either the femur, the acetabulum or both bones. Distinct patterns of disease occur with different bone involvement. 3. Selective narrowing of the medial segment of the joint is common and is particularly associated with pelvic disease. Why the narrowing occurs here preferentially is unexplained. 4. Protrusio acetabuli occurred in only 25 per cent of hips and usually when both the femur and the acetabulum were involved. This may be due to the presence simultaneously of weakened bone and coxa vara, the latter leading to an alteration in the direction of the resultant force across the hip joint. 5. Degenerative arthritis was present with Paget's disease in 14 per cent of hips but it may be a chance relationship in half of these hips

1. Congenital dislocation of the hip can be diagnosed clinically immediately after birth and the diagnosis confirmed radiologically by a special technique. 2. If the affected joint is reduced during the first two or three days after birth and held reduced for a period not exceeding three months, the joint will remain stable. 3. This treatment probably leads to normal development of the hip joint. 4. The cause of congenital dislocation of the hip may be laxity of the soft tissues of the joint and not a primary dysplasia of the acetabulum

1. The operation of "dynamic" osteotomy is designed to secure a stable and freely mobile pseudarthrosis in cases of quiescent tuberculosis of the hip joint. 2. The principles and technique of the operation are described and illustrated. 3. The results of 224 operations are presented

1. A lateral intermuscular approach to the hip joint is described for replacement of the head of the femur by a prosthesis. 2. Advantages claimed for it are that it is attended by little or no shock, because the operation is rapid and relatively bloodless; that adequate exposure can be gained without dividing muscle or tendon; and that muscle function is unimpaired and so walking can be allowed early. The exposure is easily extended if unexpected difficulty is encountered. 3. Prosthetic replacement of the femoral head through this incision is advocated as a primary measure for elderly or unfit patients with fractured femoral neck

Arthrodesis of the hip joint performed between the ages of twelve and fifteen years, is the most satisfactory treatment for cases of pathological dislocation after acute suppurative arthritis in infants

1. Dissection of forty-four developing human hip joints has shown that while the embryonic acetabulum is a deeply set cavity which almost totally encloses the head it gradually becomes more shallow as birth approaches. During the same period the femoral head becomes less globular and at the end of foetal life is almost hemispherical. The cover afforded to the femoral head by the acetabulum also becomes decreased. 2. After birth these trends reverse: the acetabulum becomes deeper again and the femoral head more globular. This process continues throughout childhood. 3. The findings provide a possible explanation for the increased liability to dislocation of the infantile hip

Aims

Femoroacetabular impingement (FAI) has been highlighted and well documented primarily in Western countries and there are few large studies focused on FAI-related morphological assessment in Asian patients. We chose to investigate this subject.

1. A thousand arthritic hips have been replaced by an uncemented metal-on-metal prosthesis, and 942 followed by annual review. The mortality of the operation has been 1·1 per cent, the rate of deep-seated infection 0·7 per cent and the incidence of dislocation 0·3 per cent.

2. Of 169 hips replaced by an earlier type of the prosthesis and followed for five to eight years, 45 per cent have remained excellent and 29 per cent good, but 14 per cent have required revision, mainly for loosening of the femoral component.

3. The current types of prosthesis, now used for five years, have given excellent results in 69 per cent and good results in 21 per cent of 535 patients followed for one to five years. Revision for loosening has been necessary in 2 per cent.

4. The improvement in results has been obtained by the introduction of a tapered screw thread on the pelvic component, and by a range of femoral components that ensures a good cortical fit.

A casting method for measuring the intra-articular space in the loaded hip is described. The results of tests on 22 hips from 22 cadavers show that the joint space is variable both in location and size and can disappear under light loads. It seems likely that the size and shape of the space influence how much access synovial fluid has for lubrication and nutrition.

1. Transient synovitis is an acute, and at times exudative, condition of the synovial membrane.

2. There is no particular association with injury or with upper respiratory infection.

3. The course is short and benign with complete resolution. The occasional hip with chronic or recurrent symptoms can be distinguished from Legg-Perthes' disease by the shorter history, normal radiographs and the complete resolution.

4. There is no evidence that transient synovitis leads to avascular changes in the femoral head.

The findings in a child with bilateral congenital dislocation of the hips who died shortly after birth are described. The only significant abnormality present was redundancy of the capsular ligaments and elongation of the ligament of the femoral head. The relationship between the orientation of the femoral neck and of the acetabulum was within normal limits. The significance of these findings in relation to etiology and management are discussed.

1. The results of treatment of twenty-five disintegrated tuberculous hips by excision, arthrodesis and anti-tuberculous drugs are reported.

2. The methods used are described.

3. Sound healing and bony fusion was obtained in all but three of the twenty-five hips treated.

General remarks–Comparison of the two reviews shows that patients with good results return more readily for a review than those with poor results. In middle-aged patients with some disability for walking an attendance of 80 per cent at least is necessary in order to obtain a representative follow-up five to ten years after operation.

An outstanding feature of all the operations reviewed is the degree of lasting relief of pain. It is rare to find that a patient with severe hip pain before operation has pain of the same severity after any of these operations at least up to ten years afterwards, and probably for much longer. Generally speaking, although in advancing years stiffness of the hip is undoubtedly a handicap, it is preferable to instability, particularly if this is progressive. A patient can adapt himself to and accept a disability that is permanent and unaltering, but instability increasing in later years can be distressing mentally and incapacitating physically.

Cup arthroplasty–There is an element of unpredictability in the results, especially the late results, of cup arthroplasty. Movement decreases and there is a tendency for pain and instability to increase after four or five years. There is little to indicate which case will be successful although the results vary according to the condition for which operation is performed. The operation gives good results, on the whole, for osteoarthritis, particularly when the operation is done on one hip only. Stability is much more important when both hips are involved, and, unless this is good in at least one hip, the results of bilateral operations are poor. "Excellent" results are not obtained in rheumatoid arthritis but few results are "poor." Operations for congenital dislocation of the hip give the most disappointing results. In operations for ankylosing spondylitis there is a high incidence of stiffening of the hip, but many patients are greatly improved in comparison to their state before operation.

Displacement osteotomy–The hazard in displacement osteotomy is ankylosis, particularly when internal fixation is not used. Relief of pain and stability are well maintained. The results in general, and for pain in particular, are less good when internal fixation is used. Adduction of the upper fragment of the femur appears to be of value in the production of a good result. In the series examined it was less often achieved when internal fixation was the method of immobilisation. The best results were obtained in cases of congenital dislocation of the hip and there were few "poor" results in cases of congenital subluxation.

Excision of the head and neck of the femur and Batchelor's operation–Rehabilitation may take a long time, but the late results are more predictable than in the other operations reviewed. A "fair" result is more likely than an "excellent" one, but late "poor" results are few. Relief of pain is better after excision of the head and neck than after any other operation reviewed.

1. The synovial membrane and capsule in osteoarthritis of the hip have been studied in twenty-five cases. Dissections have been made on fresh cadavers to establish the normal structure and function of these tissues at different ages.

2. Fragments of bone and cartilage were found beneath the synovial surface in twenty-three cases of the twenty-five cases of osteoarthritis.

3. The source of these fragments is the degenerate articular surfaces.

4. The fibrosis of the synovial membrane and capsule follows the synovial hyperplasia which accompanies the phagocytosis of these fragments.

5. A similar histological picture has been produced by injecting fragmented cartilage into the knee joints of rabbits. The injected fragments are found beneath the surface, and synovial hyperplasia is followed by subsynovial fibrosis.

6. The greatest amount of this joint debris is found in the lowest part of the joint cavity.

7. The joint capsule is particularly sensitive to traction.

8. All parts of the capsule are tight in extension, which is the weight-bearing position.

9. Fibrotic shortening of the capsule in the lowest part of the joint cavity explains many of the symptoms and signs of the disease: pain is caused by an attempt to stretch the capsule; muscle spasm occurs in the muscles supplied by the sensory nerves of this part of the capsule; extension, medial rotation and abduction, which tighten this area, are lost first; progressive shortening causes deformity in the opposite direction, namely flexion, lateral rotation and adduction; the loss of extension causes a more rapid wearing of articular cartilage on weight bearing; subperiosteal new bone is formed on the under-surface of the neck of the femur.

10. The symptomatology is discussed.

1. Experimental evidence is advanced to suggest that the effect of the McMurray displacement osteotomy in osteoarthritis of the hip is to diminish the load carried by the head of the femur, firstly by correction of deformity, and secondly by a "pelvic support" action.

2. A review of seventy-five cases has revealed certain important details in selection and operative management. The end-results indicate that the operation, when correctly performed, is successful in relieving pain and diminishing disability.