Failure of an uncemented press-fit acetabular cup in primary total hip arthroplasty

We reviewed fifteen primary total hip replacements performed using the uncemented, non-porous coated press-fit AcSys Shearer Cup. A modular titanium straight femoral stem with a 32mm head was used in all cases. The mean age of the group containing five males and 10 females was 66 years. Eight cups have been revised for aseptic loosening at a mean of seven years and the remaining four cups are radiologically loose. At revision surgery none of the cups showed any evidence of bony ingrowth. Our 10-year results with this cup indicate an unacceptably high failure rate of 80%. Absence of bony ingrowth and the lack of a secure locking mechanism between the polyethylene liner and the metal shell are the most important causes of failure. The use of a 32-mm diameter head and implantation of the cup in an open position contributed to this failure. Even though this cup is no longer manufactured, our experience suggests that all non-porous coated cups should be closely followed up. (Hip International 2002; 4: 371-7).

Expression of growth factors, cytokines and matrix metalloproteinases in frozen shoulder

Frozen shoulder is a chronic fibrosing condition of the capsule of the joint. The predominant cells involved are fibroblasts and myofibroblasts which lay down a dense matrix of type-I and type-III collagen within the capsule. This subsequently contracts leading to the typical features of pain and stiffness. Cytokines and growth factors regulate the growth and function of the fibroblasts of connective tissue and remodelling of the matrix is controlled by the matrix metalloproteinases (MMPs) and their inhibitors.

Our aim was to determine whether there was an abnormal expression or secretion of cytokines, growth factors and MMPs in tissue samples from 14 patients with frozen shoulder using the reverse transcription/polymerase chain reaction (RT/PCR) technique and to compare the findings with those in tissue from four normal control shoulders and from five patients with Dupuytren’s contracture.

Tissue from frozen shoulders demonstrated the presence of mRNA for a large number of cytokines and growth factors although the frequency was only slightly higher than in the control tissue. The frequency for a positive signal for the proinflammatory cytokines Il-1β and TNF-α and TNF-β, was not as great as in the Dupuytren’s tissue. The presence of mRNA for fibrogenic growth factors was, however, more similar to that obtained in the control and Dupuytren’s tissue. This correlated with the histological findings which in most specimens showed a dense fibrous tissue response with few cells other than mature fibroblasts and with very little evidence of any active inflammatory cell process. Positive expressions of the mRNA for the MMPs were also increased, together with their natural inhibitor TIMP. The notable exception compared with control and Dupuytren’s tissue was the absence of MMP-14, which is known to be a membrane-type MMP required for the activation of MMP-2 (gelatinase A).

Understanding the control mechanisms which play a part in the pathogenesis of frozen shoulder may lead to the development of new regimes of treatment for this common, protracted and painful chronic fibrosing condition.

Expression of growth factors, cytokines and matrix metalloproteinases in frozen shoulder

Frozen shoulder is a chronic fibrosing condition of the capsule of the joint. The predominant cells involved are fibroblasts and myofibroblasts which lay down a dense matrix of type-I and type-III collagen within the capsule. This subsequently contracts leading to the typical features of pain and stiffness. Cytokines and growth factors regulate the growth and function of the fibroblasts of connective tissue and remodelling of the matrix is controlled by the matrix metalloproteinases (MMPs) and their inhibitors. Our aim was to determine whether there was an abnormal expression or secretion of cytokines, growth factors and MMPs in tissue samples from 14 patients with frozen shoulder using the reverse transcription/polymerase chain reaction (RT/PCR) technique and to compare the findings with those in tissue from four normal control shoulders and from five patients with Dupuytren's contracture. Tissue from frozen shoulders demonstrated the presence of mRNA for a large number of cytokines and growth factors although the frequency was only slightly higher than in the control tissue. The frequency for a positive signal for the proinflammatory cytokines Il-beta and TNF-alpha and TNF-beta, was not as great as in the Dupuytren's tissue. The presence of mRNA for fibrogenic growth factors was, however, more similar to that obtained in the control and Dupuytren's tissue. This correlated with the histological findings which in most specimens showed a dense fibrous tissue response with few cells other than mature fibroblasts and with very little evidence of any active inflammatory cell process. Positive expressions of the mRNA for the MMPs were also increased, together with their natural inhibitor TIMP. The notable exception compared with control and Dupuytren's tissue was the absence of MMP-14, which is known to be a membrane-type MMP required for the activation of MMP-2 (gelatinase A). Understanding the control mechanisms which play a part in the pathogenesis of frozen shoulder may lead to the development of new regimes of treatment for this common, protracted and painful chronic fibrosing condition.

Prosthetic reconstruction of the femur for primary bone sarcoma

The survival of patients and implants, complications and functional outcome were reviewed in 25 consecutive femoral endoprosthetic reconstructions for treatment of primary bone sarcoma. The diagnosis was chondrosarcoma in 11, osteosarcoma in 10, MFH in 3 and Ewing's tumour in 1. Median follow up was 64 months (34 to 219) and median age at operation was 29 years (10 to 70). Twelve remained disease free at review. One had amputation for local recurrence and another was alive with metastases. 11 patients died at a median of 13 months (5 to 128); 8 from metastatic disease and 3 from other causes. Four implants were revised, at a median of 95 months (53 to 136); two for fractures of the stem and two for aseptic loosening. Three implants had radiological evidence of loosening at a median of 43 months (34 to 49). Fourteen patients had significant complications. The median functional score using the Musculoskeletal Tumour Society system was 68%. In our experience, prosthetic reconstruction of the femur does not compromise survival, although there is a significant complication rate.

Sclerosing epithelioid fibrosarcoma

A case of sclerosing epithelioid fibrosarcoma arising in the thigh of a 40-year-old man is reported. This recently described sarcoma has a distinctive histological appearance which may cause confusion with a variety of other sarcomas with an epithelioid pattern, and indeed with benign soft tissue tumours showing hyalinization. Despite its bland cytology, sclerosing epithelioid fibrosarcoma is capable of metastases, often several years after surgical removal. The patient described here developed lung metastases five years after excision and remains alive a further three years later. The differential diagnosis and possible histogenesis are discussed.

Fracture stiffness measurement in tibial shaft fractures: a non-invasive method

This paper presents a non-invasive method of assessing healing by measurement of fracture stiffness. The method works on the principle that if the load (F) applied at a certain known distance (Y) from the fracture is measured, then the moment (M = FY) at the fracture site can be calculated. By measuring the angle/deflection (straight theta) occurring at the fracture site using a suitable instrument (electrogoniometer), the necessary data to calculate fracture stiffness (FY/straight theta) would be available. The method was employed to assess the stiffness in a series of tibial shaft fractures treated conservatively, all of which healed uneventfully. This paper concentrates on a group of tibial shaft fractures in which the radiological criteria for fracture union were not satisfied even after a mean duration of 20 weeks treatment. The non-invasive method of measuring fracture stiffness supported the clinical impression of union in most cases at the first test, but was repeated on two more occasions to confirm the trend of progressive healing. The objective evaluation of fracture healing led to avoidance of surgical intervention in these patients, who went on to sound union.

Stromelysin, gelatinase A and TIMP-1 in prosthetic interface tissue: a role for macrophages in tissue remodelling

Aseptic loosening of prosthetic components is the most important long-term complication of total joint replacement. To investigate the underlying destructive mechanisms, periprosthetic tissues from both well-fixed and loosened sites from six patients, undergoing surgery for aseptic loosening of knee or hip prostheses, were analysed in detail by immunohistochemical methods for the presence of matrix metalloproteinases and tissue inhibitor of metalloproteinases-1 (TIMP-1). The tissues contained small numbers of cells positive for either collagenase, stromelysin, gelatinase A or TIMP-1; these were randomly distributed, neither specifically next to the bone interface nor to wear particles, and the number of positive cells did not correlate with macroscopic observations at operation. Gelatinase A was co-localized in cells with prolyl-4-hydroxylase, an enzyme involved in collagen synthesis. The predominant cell type in these tissues was shown to be the macrophage by the use of cell marker antibodies. Dual localization was not technically possible but the results strongly suggest that monocyte/macrophages were the primary source of gelatinase A and TIMP-1. Stromelysin was immunolocalized on connective tissue matrix in four patients, and gelatinase A in one patient, and were also observed in tissues in which there was no evidence of cellular synthesis of these enzymes. This suggests that secretion had taken place previously, resulting in enzyme bound to matrix for some time. Taken together, these data indicate that localized focal connective tissue remodelling occurs in periprosthetic tissues from both well fixed and loosened sites.

The effect of the hypermobility syndrome on knee joint proprioception

Proprioceptive sensory feedback is utilized by the central nervous system for conscious appreciation of the position and movement of the body and limbs. In patients with the hypermobility syndrome (HMS), it has been suggested that there is alteration of proprioceptive acuity. Proprioceptive performance of the knee joint was investigated in 10 female subjects who suffered from HMS using a threshold detection paradigm (accurate determination of the onset and direction of knee joint displacement at constant angular velocity). Compared to age- and sex-matched controls, HMS subjects showed significantly higher detection levels at starting knee flexion angles of 30 degrees P < 0.001) and 5 degrees (P < 0.001). Control subjects showed no significant difference in threshold acuity between the sexes (at 5 degrees P = 0.63, at 30 degrees P = 0.48). The increased acuity in proprioception observed towards full extension in the control population (P < 0.001) was absent in the HMS subjects (P = 0.596). Findings reported here suggest that HMS subjects have poorer proprioceptive feedback than controls. Reduced sensory feedback may lead to biomechanically unsound limb positions being adopted. Such a mechanism may allow acceleration of degenerative joint conditions, and may account for the increased prevalence of such conditions seen with HMS subjects.

Immunolocalisation studies on six matrix metalloproteinases and their inhibitors, TIMP-1 and TIMP-2, in synovia from patients with osteo- and rheumatoid arthritis

OBJECTIVE

To assess the likely importance of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) in the arthritic process.

METHODS

Synovial samples from seven joints with rheumatoid arthritis and three osteoarthritic joints were analysed by indirect immunofluorescence microscopy. Using specific human antisera, we documented the frequencies and distributions of collagenase, stromelysins 1 and 2, matrilysin, gelatinases A and B, TIMP-1, and TIMP-2.

RESULTS

Stromelysin 1 was found in all synovia, bound to extracellular matrix, within cells, or both, indicating stromelysin synthesis. Matrilysin was present in only one active inflammatory synovium, and focal synthesis of collagenase and gelatinase A was seen in four synovia. Stromelysin 2 and TIMP-2 were not observed, but TIMP-1 synthesis was seen in five synovia, and in two active synovia the distribution of TIMP-1 positive cells was more widespread than that of MMPs.

CONCLUSIONS

The presence of stromelysin 1 in all synovia clearly implicates this enzyme in joint damage. Collagenase, gelatinase A and matrilysin may also have a role in rheumatoid arthritis, but are not significant in osteoarthritis. However, marked regional variations were found in the synthesis of these MMPs, indicating not only that these diseases are episodic but that control of enzyme synthesis is focal. Only TIMP-1 may be considered an inhibitory factor.

Methicillin-resistant Staphylococcus epidermidis in infection of hip arthroplasties

We investigated the incidence of cephalosporin-resistant bacteria in infected hip arthroplasties. Of 740 patients having hip replacement or related procedures performed over three years, 30 had positive bacteriological cultures from tissue removed at the time of surgery. In 18 of the 30 cultures Staphylococcus epidermidis was grown and 12 of these were methicillin-resistant. A prospective study of skin swabs taken from 100 consecutive patients at the time of admission for THR showed methicillin-resistant Staphylococcus epidermidis in 25. This cephalosporin-resistant organism was shown to be the commonest proven cause of infection, and its presence as a skin commensal raises important questions about current antibiotic prophylaxis for joint replacement.

Methicillin-resistant Staphylococcus epidermidis in infection of hip arthroplasties

We investigated the incidence of cephalosporin-resistant bacteria in infected hip arthroplasties. Of 740 patients having hip replacement or related procedures performed over three years, 30 had positive bacteriological cultures from tissue removed at the time of surgery. In 18 of the 30 cultures Staphylococcus epidermidis was grown and 12 of these were methicillin-resistant. A prospective study of skin swabs taken from 100 consecutive patients at the time of admission for THR showed methicillin-resistant Staphylococcus epidermidis in 25. This cephalosporin-resistant organism was shown to be the commonest proven cause of infection, and its presence as a skin commensal raises important questions about current antibiotic prophylaxis for joint replacement.

Image analysis derived ploidy and proliferation indices in soft tissue sarcomas: comparison with clinical outcome

AIMS

To compare prognostic information obtained by image analysis cytometry of paraffin wax embedded soft tissue sarcomas with conventional assessment.

METHODS

A CAS 200 image analyser was used to determine DNA content of Feulgen stained cytology preparations and tissue sections and to quantify immunostaining by Ki67 and PC10 antibodies. A mitotic count in 50 high power fields was undertaken and histological grade assigned by the Trojani system. Clinical details including follow up and outcome were obtained by case note review. The Kruskal-Wallis one way analysis test, Spearman rho significance test, Kaplan-Meier method, and log-rank test were applied in statistical analysis.

RESULTS

Ploidy status, DNA index, 2.5c exceeding rate, 5c exceeding rate, mitotic count and Trojani grade all correlated significantly with clinical outcome. The relation between Ki67 index and outcome did not reach significance. The PC10 index and outcome were not related. Only 2.5c exceeding rate, 5c exceeding rate, and mitotic count correlated significantly with Trojani grade.

CONCLUSIONS

DNA content determination of soft tissue sarcomas by image analysis provides quantifiable information of benefit in prediction of outcome. Larger series are required to determine the independent value of ploidy. In this study quantification of anti-Ki67 and anti-PC10 immunostaining was not of prognostic benefit) by contrast with mitotic count and Trojani grade.

Diagnosis of infection and the role of permanent excision arthroplasty

The symptoms, signs, and investigation of the infected hip replacement are reviewed. Aspiration, combined with needle biopsy of the interface tissue, gives the best opportunity for establishing a bacteriologic diagnosis. The surgical technique for excision arthroplasty is described, and the complications of this procedure reviewed. The functional results of permanent excision arthroplasty are described in relation to the altered biomechanics of the hip pseudarthrosis.

Evaluation of pre-admission screening of elderly patients accepted for major joint replacement

Valuable orthopaedic operating time is frequently lost because patients are found to be medically unfit for surgery on admission. One hundred and forty seven consecutive patients aged 60 years or older, who had been accepted for major joint replacement and who lived within 15 miles of the Western Infirmary, Glasgow were screened at a preadmission clinic. The screening protocol had been agreed by orthopaedic and anaesthetic staff involved in major joint replacement surgery. Some 42 patients had medical illnesses which would have resulted in surgery being postponed and a further five had their surgery cancelled. Six patients passed fit for surgery at the pre-admission screening clinic were unfit for surgery on admission. Two patients in this group had their surgery cancelled. Using the guidelines suggested, pre-admission screening could be carried out by the patient's general practitioner (GP) or by a member of the medical staff when the patient attends the orthopaedic out-patient clinic. By following a simple protocol the amount of valuable operating time lost through unrecognised or poorly controlled medical illness could be greatly reduced. Pre-admission screening should result in more efficient use of scarce hospital resources and improved patient care.

Quantitative gamma-ray computed tomography of the radius in normal subjects and osteoporotic patients

A new design of gamma-ray computed tomography (CT) scanner was used to measure bone density in 516 normal adults and in 116 female patients with osteoporotic fractures. Trabecular bone density (TBD) was measured for a core of the ultradistal radius; cortical bone mass per unit length (MLS) and mass per unit volume (MVS) were computed for the radius shaft. TBD, MLS and MVS peaked at the age of about 40 in females and fell by 32%, 15% and 24%, respectively, by the age of 65. In males, TBD decreased from the third decade and MLS and MVS peaked in the fourth decade. The corresponding falls by 65 years were 20%, 6% and 7%. In patients with Colles' fracture TBD and MLS were reduced by 13% and 10%, respectively, relative to age matched normal female subjects. For patients with vertebral crush fracture the reductions relative to age matched normal females were 36%, 17% and 16% for TBD, MLS and MVS. In fracture patients the deficit in TBD was significantly greater than that for cortical bone but TBD was no better at discriminating normal and osteoporotic individuals because of its larger normal range. We conclude that gamma-ray CT may best be used for monitoring changes in bone rather than as a diagnostic screening tool.

An investigation of occlusive polyester surgical clothing

The bacterial dispersion rate of people wearing operating room clothing made from several types of polyester fabric was compared to conventional cotton clothing, total-body exhaust gowns and disposable clothing. Airborne bacteria were measured in a chamber, three ultra-clean air operating rooms and a conventionally ventilated operating room. The polyester clothing was demonstrated to be much superior to conventional cotton clothing and at least as good as the total-body exhaust gowns and disposable clothing.

Compression-fixation of long bone fractures: problems and pitfalls revisited

We have carried out a retrospective study, over a 2.5 year period, of the results of compression-fixation for diaphyseal long bone fractures (forearm 49, tibia 18, others 9). The method was used in forearm fractures mainly for fresh fractures, whilst in fractures of the tibia it was predominantly for delayed union. In forearm fractures, although 10 per cent showed failure of fixation, only 2 per cent developed infection, and 90 per cent recovered a full range of movement. Conversely, plating of fractures of the tibia with delayed union resulted in a 37 per cent deep infection rate. It is concluded that while compression-fixation gives excellent results when applied to displaced forearm fractures, alternative methods should be used in fractures of the tibia with delayed union. This unexpected finding illustrates the value of periodic audit of surgical results.

Prospective randomised study of an orthopaedic geriatric inpatient service

A randomised controlled trial of two management regimens was carried out in women patients over 65 years of age with hip fractures. Ninety seven patients were admitted to a designated orthopaedic geriatric unit and 125 to orthopaedic wards. No difference was observed in mortality, length of stay, or placement of patients between the two groups. More medical conditions were recognised and treated in patients in the orthopaedic geriatric unit group. It is concluded that designated orthopaedic geriatric units can provide medical care to these patients and should be administered without additional cost.

Distal metatarsal osteotomy for hallux valgus in the middle-aged patient

Thirty-eight distal metatarsal osteotomies for hallux valgus in middle-aged patients between the ages of 50 and 67 years were performed over a period of five years. None of the patients could be rated with an excellent result. Good results were noted in only 52.6%. Poor results were attributable to imperfect surgical technique, severity of preoperative deformity, osteoporosis, and preexisting osteoarthritic changes at the first metatarsophalangeal joint.

Sarcoma at the site of a single hip screw. A case report

We report a case of malignant fibrous histiocytoma of the hip which occurred 30 years after the insertion of a single chrome-cobalt alloy screw for a slipped femoral epiphysis. The possible aetiological association between malignant tumours and metallic implants is discussed.

Surgical stabilisation of the rheumatoid cervical spine. A review of indications and results

We have reviewed 32 patients with rheumatoid disease of the cervical spine who underwent a total of 40 operations aimed at correcting instability and improving any associated neurovascular deficit. Apart from four patients with intractable pain, the main indication for surgery was progressive neurological impairment. Of the 32 primary operations, 19 (60%) were successful; the remainder failed to achieve their objective and there were two deaths in the immediate postoperative period. Of eight secondary operations performed for recurrence of symptoms or failure to relieve cervical myelopathy, only four were successful. Of nine operations for bony decompression to relieve cord compression from irreducible subluxation, only four were successful. The overall results show a success rate of 57% and a failure rate of 35% with early operative mortality in 8%. Indications for operation are discussed and earlier diagnosis is considered to be the key to improved results.

Vascular complications of osteochondroma

Apart from trauma, symptoms arising from peripheral arteries are very unusual in adolescents and young adults. Three cases of osteochondroma associated with rare vascular complications are presented, together with a review of the literature. The development of pain in relation to osteochondroma does not necessarily imply trauma or the onset of malignancy and vascular complications should be considered, particularly if the bone lesion occurs around the knee. In this situation, arteriography is considered essential in planning surgical treatment and the importance of angiography in two planes is emphasised.

A bacteriologically occlusive clothing system for use in the operating room

A comparison was made in a laminar-flow operating room between total-body exhaust gowns and a clothing system made from Fabric 450. This disposable clothing was found to be much more comfortable and convenient than the total-body exhaust gowns. The average airborne bacterial counts obtained during total hip replacement operations from each of the clothing systems were identical when the downflow method of ventilation was used (0.7 per cubic metre) and no significant difference could be demonstrated when the crossflow system was used (2.2 per cubic metre with the total-body exhaust gowns and 3.1 per cubic metre with the disposable clothing). Tests in a dispersal chamber were carried out to find the effectiveness of each item of the disposable clothing in reducing bacterial dispersion. These tests demonstrated the relative ineffectiveness of wearing a surgical gown as compared with wearing the complete system. It was confirmed bacteriologically that the downflow system of ventilation was more efficient than the crossflow type; the importance of this observation with respect to clothing and sepsis is discussed in this paper.

Surgery of the rheumatoid hip

The incidence and pattern of involvement of the hip in rheumatoid arthritis are reviewed. The criteria for the selection of patients for surgery are described and the points in preparation emphasised. The surgical procedures available are discussed with the results and complications to be expected. The clinical results of total replacement arthroplasty are gratifying despite the increased incidence of infection and mechanical loosening compared with osteoarthritic hips.

Biomechanical assessment of patients treated by joint surgery

Surgical replacement of lower limb joints has been practised for twenty years although there is little quantitative information on loads transmitted either by implants or by other related joints. The results of tests are presented which evaluate the variation in external forces developed between the ground and foot during walking, together with the configuration of the lower limbs and the moments acting about the hips and knees. Two groups of patients were investigated; patients who were assessed prior to joint replacement and at intervals thereafter, and patients for whom the Girdlestone procedure was performed following a failed implant. The results area compared with those from similar tests on clinically normal subjects. There is a significant improvement post-operatively in the mechanical aspects of hip function for the replacement patients. The improvement continues after the first six months post-operatively and may result in abnormally high loading at other joints. At twelve months the performance of the patients with joint replacement differs significantly from the normal subjects and is generally better than the Girdlestone patients.

Problems and pitfalls of compression fixation of long bone fractures: a review of results and complications

The complications encountered in the compression fixation of 70 cortical long bone fractures are reviewed. The results represent the initial experience with the AO fixation equipment following its introduction to a centre with staff relatively untrained in the technique. Infection was the most serious complication, with a deep sepsis rate of 10.5 per cent, but fixation failure, delayed union and refracture also occurred. The various problems are discussed in detail and suggestions are made as to how they can be avoided.

Influence of oxygen tension on somatomedin activity in vitro

Somatomedins are the intermediaries through which growth hormone acts on the epiphyseal growth plate to effect linear skeletal growth. Rat epiphyseal chondrocytes were isolated and cultured in vitro in the presence of somatomedin. Two sources of somatomedin were used, foetal calf serum and rat liver perfusates. The chondrocytes proliferated and synthesized sulphated glycosaminoglycans when grown in the presence of somatomedin from either source, but were not metabolically active in chemically defined medium alone. Some differences in the growth patterns in response to serum or liver somatomedins are reported and discussed. Chondrocyte metabolic activity in the presence of somatomedin in vitro showed a graded response to alterations in the atmospheric oxygen, being greatest at low oxygen pressure, and almost completely inhibited at 95% oxygen. A gradient of local oxygen tension has been reported to exist across the epiphyseal plate in vivo. The effects of somatomedin combined with changing oxygen levels may help to explain the divergence of cell proliferation and matrix synthesis seen in the various regions of the growth plate.

The effects of hyperoxia upon bone in organ culture

Hyperoxia has been reported to stimulate both resorption and synthesis of bone in vitro. The effects of increased oxygen tension were re-investigated using calvaria from infant mice maintained in a stationary grid culture system for 48 48 hours with an unsupplemented chemically defined medium. Resting resorption due to osteoclastic activity was demonstrated in the explants in air by Von Kossa staining, histology, and 45 Ca release. Resorption was inhibited by exposure to 95 per cent oxygen or hyperbaric oxygenation at 2 atmospheres pressure. Hyperoxia also depressed new bone formatin by osteoblasts although the production of a new collagen, as measured by the incorporation of 3H-proline, was greater in calvaria cultured in hyperbaric oxygen than in paired explants in 95 per cent oxygen. Thus hyperoxia was toxic for both synthetic and resorptive activity of bone cells; these effects may stem from the loss of vital factors present in natural MEDIA supplements.

The pathology of the degenerate meniscus lesion

The incidence of horizontal cleavage lesions of the menisci was studied in 100 random necropsy examinations. Sixty per cent of subjects had at least one such tear, the incidence being 29 per cent out of the 400 menisci. Eighty-five per cent of the subjects showed changes of osteoarthritis in the patello-femoral or tibio-femoral joint compartments. The coincidence of horizontal cleavage lesion and osteoarthritis was frequent. Horizontal cleavage lesions were commoner in medial or larger menisci and in males. Eighteen per cent of the menisci were calcified and this was twice as common in those menisci with a degenerate tear. Because the horizontal cleavage lesion was so common in the older knee, it must usually remain unrecognised clinically with other factors causing symptoms of night pain and tenderness.

OCCIPITO-CERVICAL FUSION

1. Thirteen cases of occipito-cervical fusion performed in the past fifteen years at the London Hospital are described.

2. Seven of the patients had congenital anomalies in the region of the foramen magnum, six had spontaneous atlanto-axial dislocations, and in one case the operation was performed prophylactically to stabilise a severely disorganised cervical spine.

3. Nine of the patients had evidence of neurological involvement before operation due to pressure on the spinal cord or nerve roots.

4. Operative fusion was successful in all cases and there was no operative mortality.

5. The clinical results were good in eight cases and four patients were improved. The condition of one patient, in whom progressive disseminated sclerosis was also present, deteriorated.

6. The technique of operation is described, and it is recommended that it should always be performed as a combined orthopaedic and neurosurgical procedure.

PSEUDOGOUT SIMULATING ACUTE SUPPURATIVE ARTHRITIS

1. Two cases of pseudogout are described with an onset acute enough to be mistaken for septic arthritis.

2. The radiological and laboratory investigations for diagnosis are described.