We assessed the reproducibility and accuracy of four ratios used to measure patellar height, namely the Blackburne-Peel, Caton-Deschamps, Insall-Salvati and modified Insall-Salvati, before and after total knee arthroplasty. The patellar height was measured, by means of the four ratios, on the pre- and post-operative lateral radiographs of 44 patients (45 knees) who had undergone total knee arthroplasty. Two independent observers measured the films sequentially, in identical conditions, totalling 720 measurements per observer. Statistical analysis, comparing both observers and ratios, was carried out using the intraclass correlation coefficient.

Before operation there was greater interobserver variation using either the Insall-Salvati or modified Insall-Salvati ratios than when using the Caton-Deschamps or Blackburne-Peel methods. This was because of difficulty in identifying the insertion of the patellar tendon. Before operation, there was a minimal difference in reliability between these methods. After operation the interobserver difference was greatly reduced using both the Caton-Deschamps and Blackburne-Peel methods, which use the prosthetic joint line, compared with the Insall-Salvati and modified Insall-Salvati, which reference from the insertion of the patellar tendon.

The theoretical advantage of using the Insall-Salvati and modified Insall-Salvati ratios in measuring true patellar height after total knee arthroplasty needs to be balanced against their significant interobserver variability and inferior reliability when compared with other ratios.

We prospectively studied the clinical, arthroscopic and histological results of collagen-covered autologous chondrocyte implantation (ACI-C) in patients with symptomatic osteochondritis dissecans of the knee. The study included 37 patients who were evaluated at a mean follow-up of 4.08 years.

Clinical results showed a mean improvement in the modified Cincinnati score from 46.1 to 68.4. Excellent and good clinical results were seen in 82.1% of those with juvenile-onset osteochondritis dissecans but in only 44.4% of those with adult-onset disease.

Arthroscopy at one year revealed International Cartilage Repair Society grades of 1 or 2 in 21 of 24 patients (87.5%). Of 23 biopsies, 11 (47.8%) showed either a hyaline-like or a mixture of hyaline-like and fibrocartilage, 12 (52.2%) showed fibrocartilage.

The age at the time of ACI-C determined the clinical outcome for juvenile-onset disease (p = 0.05), whereas the size of the defect was the major determinant of outcome in adult-onset disease (p = 0.01).

We investigated the prognostic indicators for collagen-covered autologous chondrocyte implantation (ACI-C) performed for symptomatic osteochondral defects of the knee.

We analysed prospectively 199 patients for up to four years after surgery using the modified Cincinnati score. Arthroscopic assessment and biopsy of the neocartilage was also performed whenever possible. The favourable factors for ACI-C include younger patients with higher pre-operative modified Cincinnati scores, a less than two-year history of symptoms, a single defect, a defect on the trochlea or lateral femoral condyle and patients with fewer than two previous procedures on the index knee. Revision ACI-C in patients with previous ACI and mosaicplasties which had failed produced significantly inferior clinical results. Gender (p = 0.20) and the size of the defect (p = 0.97) did not significantly influence the outcome.

We developed an in vivo model of the attachment of a patellar tendon to a metal implant to simulate the reconstruction of an extensor mechanism after replacement of the proximal tibia. In 24 ewes, the patellar tendon was attached to a hydroxyapatite (HA)-coated titanium prosthesis. In 12, the interface was augmented with autograft containing cancellous bone and marrow. In the remaining ewes, the interface was not grafted.

Kinematic gait analysis showed nearly normal function of the joint by 12 weeks. Force-plate assessment showed a significant increase in functional weight-bearing in the grafted animals (p = 0.043). The tendon-implant interface showed that without graft, encapsulation of fibrous tissue occurred. With autograft, a developing tendon-bone-HA-implant interface was observed at six weeks and by 12 weeks a layered tendon-fibrocartilage-bone interface was seen which was similar to a direct-type enthesis.

With stable mechanical fixation, an appropriate bioactive surface and biological augmentation the development of a functional tendon-implant interface can be achieved.

Autologous chondrocyte implantation (ACI) is used widely as a treatment for symptomatic chondral and osteochondral defects of the knee. Variations of the original periosteum-cover technique include the use of porcine-derived type I/type III collagen as a cover (ACI-C) and matrix-induced autologous chondrocyte implantation (MACI) using a collagen bilayer seeded with chondrocytes. We have performed a prospective, randomised comparison of ACI-C and MACI for the treatment of symptomatic chondral defects of the knee in 91 patients, of whom 44 received ACI-C and 47 MACI grafts.

Both treatments resulted in improvement of the clinical score after one year. The mean modified Cincinnati knee score increased by 17.6 in the ACI-C group and 19.6 in the MACI group (p = 0.32). Arthroscopic assessments performed after one year showed a good to excellent International Cartilage Repair Society score in 79.2% of ACI-C and 66.6% of MACI grafts. Hyaline-like cartilage or hyaline-like cartilage with fibrocartilage was found in the biopsies of 43.9% of the ACI-C and 36.4% of the MACI grafts after one year. The rate of hypertrophy of the graft was 9% (4 of 44) in the ACI-C group and 6% (3 of 47) in the MACI group. The frequency of re-operation was 9% in each group.

We conclude that the clinical, arthroscopic and histological outcomes are comparable for both ACI-C and MACI. While MACI is technically attractive, further long-term studies are required before the technique is widely adopted.

Metal-on-metal hip bearings are being implanted into younger patients. The consequence of elevated levels of potentially carcinogenic metal ions is therefore a cause for concern. We have determined the levels of cobalt (Co), chromium (Cr), titanium (Ti) and vanadium (Va) in the urine and whole blood of patients who had had metal-on-metal and metal-on-polyethylene articulations in situ for more than 30 years. We compared these with each other and with the levels for a control group of subjects.

We found significantly elevated levels of whole blood Ti, Va and urinary Cr in all arthroplasty groups. The whole blood and urine levels of Co were grossly elevated, by a factor of 50 and 300 times respectively in patients with loose metal-on-metal articulations when compared with the control group. Stable metal-on-metal articulations showed much lower levels. Elevated levels of whole blood or urinary Co may be useful in identifying metal-on-metal articulations which are loose.

This preliminary report demonstrates the effective use of Apapore in the management of benign cystic bone lesions.

The use and development of bone graft substitutes over the past ten years has increased dramatically to improve their osseo-integration to a level similar to autografting techniques without the drawbacks of comorbidity from the graft site.

Apapore is a synthetic bone graft substitute which consists of a scaffold of synthetic phase-pure hydroxy apatite with micro- and macroporosity and inter-connectivity to favour bone repair.

Nineteen patients (12M:7F) with a mean age of 18.6years (8–33 years) having had procedures for the management of benign cystic lesions of bone with grafting using Apapore were followed up retrospectively for a mean period of 8 months (1–16months). In each case the diagnosis of a benign cystic lesion was made histologically prior to surgery. The subsequent definitive procedure was performed by a consultant on the Bone Tumour Unit at the Royal National Orthopaedic Hospital (Stanmore) in each case involving curettage and impaction of Apapore into the cavity in a standard fashion as a general anaesthetic procedure in the operating theatre.

There have been no complications to date. All patients have made uneventful recoveries. Short-term radiological follow-up demonstrates excellent incorporation of the bone graft substitute and osseo-integration.

Autologous chondrocyte implantation (ACI) is a technique used for the treatment of symptomatic osteochondral defects of the knee. A variation of the original periosteum membrane technique is the matrix-induced autologous chondrocyte implantation (MACI) technique. The MACI membrane consists of a porcine type-I/III collagen bilayer seeded with chondrocytes. Osteochondral defects deeper than 8 to 10 mm usually require bone grafting either before or at the time of transplantation of cartilage. We have used a variation of Peterson’s ACI-periosteum sandwich technique using two MACI membranes with bone graft which avoids periosteal harvesting. The procedure is suture-free and requires less operating time and surgical exposure. We performed this MACI-sandwich technique on eight patients, five of whom were assessed at six months and one year post-operatively using the modified Cincinnati knee, the Stanmore functional rating and the visual analogue pain scores.

All patients improved within six months with further improvement at one year. The clinical outcome was good or excellent in four after six months and one year. No significant graft-associated complications were observed. Our early results of the MACI-sandwich technique are encouraging although larger medium-term studies are required before there is widespread adoption of the technique.

A case report of an 11 year old boy who underwent tibial osteotomy to prevent angulation of his right tibia.

As a 7 year old, LH sufered a minor injury to his right tibia. A lump appeared at the same site. Soon the lump grew to be similar to “a second knee cap”. However, it only caused him pain when he traumatised it. He and his parents were disturbed by the lump, and the fact that it was creating an anterior-posterior bowing of his tibia. They sought medical advice. His original hospital carried out X rays that demonstrated the deformity and a cloud like lump at the tibial tuberosity.

A bone scan confirmed a solitary osseous lesion. In July 2002 he was referred to the RNOH, where the decision was taken to resect the tibial tuberosity and undertake a corrective osteotomy. Post surgery in August 2002, LH was mobilised in a full cast for 9 weeks and graduated slowly from non to full weight bearing. Histology revealed a probable endchondroma, or unusual growth plate reaction.

A year after the procedure LH is a symptom free, happy and active boy. Radiographs confirm normal angulation of his Tibia.

In conclusion an osteotomy can be a very successful treatment for a childhood lesion that leads to progressive deformity.

We performed a retrospective analysis of massive endoprostheses inserted at our unit in the management of Giant Cell Tumours of the distal femur with a minimum follow up of 5 years.

Methods. Twenty-five massive articulating endoprostheses were inserted between 1986 and 1998 at our unit. The case notes and radiographs of all patients were reviewed. A functional and radiological analysis was performed using the MTOS and ISOLS scoring systems. Kaplan-Meier Cumulative Survival Graphs were created for amputation and revision for septic and aseptic loosening. Two patients had died (8%) from unrelated causes. No cases were lost to Follow Up.

Results. Massive replacements were performed for stage 3 (aggressive), pathological fracture (30%) or recurrent disease. The mean follow up was twelve years (range 5–18 years). The average age at time of insertion was 37 years; no patients were skeletally immature. Fifteen implants were fixed hinge devices and ten were rotating hinge devices with HA collars (since 1993). No cases were revised for sepsis. There had been no cases of recurrent disease or amputation. There have been six (26%) revisions for aseptic loosening. Only one of these occurred in the rotating hinge and HA collar group. In the fixed hinge group (38% aseptic loosening rate) revision occurred after an average of six years. There have also been five re-bushings all of which have occurred in the fixed hinge group. The average MTOS score was 74 (range 47–97).

Conclusion. Young patients with fixed hinged devices developed a high incidence of aseptic loosening. They also had a significant rate of re-bushing. Results of the rotating hinge prosthesis with HA collar were much more promising. Functional scores were good after a period of twelve years despite the young age group.

Growing prostheses have been utilised in the United Kingdom since the late 1970s. Various mechanisms have been tried, but to date all have required some form of surgical intervention. This has led to multiple hospital admissions and a large amount of resources, both in theatre time and rehabilitation. Over the last ten years the Department of Bio-Medical Engineering at University College, London, together with the Royal National Orthopaedic Hospital, Stanmore, have developed a prosthesis which does not require surgical intervention to elongate. The total cost of the development has been something in the order of £350,000.00. The design features are the power worm screw mechanism where one turn equals 1 mm of elongation, but attached to this mechanism is an epicyclic gearbox, which has been reduced in size so that it can fit in to the body of the prosthesis. The speed reduction achieved by the gear box is 13061 to 1. The mechanism is capable of withstanding an axial load of 1,350 newtons. When an external magnetic field is applied an external coil speed of 3,000 revs per minute leads to a lengthening of 0.23 mm per minute. To date the prosthesis has been inserted in three patients ages 11, 12 and 13. All were suffering from osteosarcoma of the distal femur and had previously received neo-adjuvant chemotherapy. Early elongation had been achieved in all patients without any major discomfort and without the need for either analgesia or inpatient admission. There had been no loss of range of movement in the early post-lengthening period.

This new prosthesis represents a significant advance in the management of skeletal sarcomas in children.

We report the case of a 12-year-old boy with polyostotic fibrous dysplasia of the upper femur in whom a massive customised polyethylene prosthesis functioned successfully for more than fifty years.

We have performed a prospective, single-surgeon study analysing the histological results of autologous chondrocyte implantation.

Fourteen patients underwent autologous chondrocyte implantation of the knee and were evaluated at one year by clinical assessment and arthroscopy. Standard staining was used to examine the sections. In addition, in situ hybridisation was used to establish type-IIa and type-IIb collagen mRNA expression and immunolocalisation techniques demonstrated the positions of type-II and type-X collagen.

Eight patients regenerated hyaline cartilage and also contained type-X collagen in the deepest layers and type-II collagen in the deep layers. Three demonstrated fibrocartilage and had type-II collagen in the deep layers. In situ hybridisation revealed that all 14 samples had the potential to express both type-IIa and type-IIb collagen.

We have shown that one year after the initial implantation chondrocytes are capable of producing type-II collagen and that they continue to proliferate and mature.

We discuss the management and outcome of 52 patients who presented with malignant tumours of the fibula over a 15-year period between1983 and 1998.

The tumour type was Osteosarcoma (23 patients), Ewing’s sarcoma (16), Chondrosarcoma (11 – of which 10 low grade) and Malignant Fibrous Histiocytoma (2). We concentrate on the two most common frankly malignant groups: Osteosarcoma and Ewing’s.

The male:female ratio of patients with Osteosarcoma was 11:12 and with Ewing’s Sarcoma was 11:5. Mean age for Osteosarcoma was 21. 5 years and for Ewing’s Sarcoma was 14. 2. The most common site of tumour was in the proximal fibula in both Osteosarcoma (19 / 23) and Ewing’s Sarcoma (10 / 16). The stage of disease at presentation was IIa or IIb in the majority of patients, with seven patients presenting with metastases.

The current investigative procedures are Radiographs, Magnetic Resonance Imaging, Radioisotope Bone Scans, Computerised Tomography of the chest and needle biopsy whereas in the past CT of the lesion and open biopsy were common. Chemotherapy was administered as per protocol at the time of diagnosis and radiotherapy was given in selected cases.

Surgery was performed on all but 3 patients, who were unfit and died. This consisted of local en bloc resection in 86. 3% and above knee amputation in 6. 8%. Whereas all the diaphyseal and distal lesions were completely excised, 9 out of 26 proximal lesions had a marginal excision, 4 of which had open biopsies. The common peroneal nerve was sacrificed in 50% of cases and this had no link to survival.

The overall 5-year survival was 33% for Osteosarcoma and 40% for Ewing’s Sarcoma, with proximal lesions doing much worse than diaphyseal and distal lesions. Patients who had marginal excisions all died within 2. 5 years.

We present the management and outcome of patients who presented following internal fixation of primary malignant tumours of the femur.

This is a retrospective study of eleven patients. All underwent internal fixation of pathological or impending fractures of the femur in the assumption of metastatic disease, or prior to diagnosis of primary malignancy. Data was collected from database records and case notes.

The mean age was 47 years (range 13 – 73). Six patients were male and five female. Tumour type was osteosarcoma (3), MFH (3), chondrosarcoma (2), Ewing’s sarcoma (1), fibrosarcoma (1) and liposarcoma (1). The site of the lesion was proximal in six cases and distal in five. Nine patients presented initially with pathological fractures and two with lytic lesions. The mode of fixation was DHS (3), AO screws (1), antegrade IM nailing (2), retrograde IM nailing (3), Blade plate (1) and DCS fixation (1). No patients underwent biopsy prior to fixation. Surgical treatment at the Bone Tumour Unit was excision and segmental endoprosthetic replacement (5), total femoral replacement (2), hip disarticulation (2), above knee amputation (1) with one patient dying prior to surgery. Eight patients also received chemotherapy and three radiotherapy. Four patients had local recurrences, three presented with metastatic disease and five more went on to develop metastases. Two patients died within one year of initial surgery, three more within two years and none have so far survived five years. Three patients are still alive.

We believe that internal fixation of primary malignant tumours has a detrimental effect on limb salvage and survival, emphasising the absolute necessity of pre-operative investigation of solitary bone lesions.

The aim of surgery in the treatment of tumours of the distal radius is to achieve satisfactory clearance whilst best preserving function of the hand and wrist. Since 1992 a technique of distal radial tumour excision with reconstruction by autologous free fibula strut grafting has been employed in the treatment of thirteen patients at our unit. The procedure employs fixation of the non-vascularised fibula shaft to the proximal radius by step-cuts and a dynamic compression plate. The fibula head substitutes for the distal limit of the radius and articulates with the carpus.

We have treated 10 cases of primary or recurrent giant cell tumour and cases of osteosarcoma, chondrosarcoma and Ewings’ sarcoma by this technique. The patients were reviewed at a mean of 50 months post surgery, with assessment of their functional outcome and measurement of the range of wrist movement and grip strength.

The patient with Ewings tumour had died of meta-static disease 62 months post grafting. Three patients treated for giant cell tumour had required further surgery, two of these had forearm amputation for malignant transformation. In comparison to the unoperated wrist, range of movement was well preserved. The power of grip strength was 57% of the contralateral wrist and hand.

These results compare well with published rates of recurrence of benign giant cell tumour treated by other methods. This technique would seem to offer an acceptable functional result without compromise of the tumour prognosis.

Background: The purpose of this prospective study is to analyse the histological results of the treatment of deep chondral defects with autologous chondrocyte transplantation in patients with articular cartilage defects of the knee joint.

Methods: Patients with articular cartilage defects of the knee joint were recruited prospectively and underwent autologous chondrocyte transplantation. Chondrocytes from a non-weight bearing area of the knee were harvested, isolated and cultured in vitro. Subsequent reimplantation involved injection of the chondrocytes into the defect which was then sealed with a porcine IIIII collagen membrane. Postoperatively, patients were evaluated at one year by clinical assessment, arthroscopy and histological examination. The presence of hyaline cartilage in the transplanted region was determined by staining with Erlich’s H & E, Safranin 0 and polarised light microscopy and by imimmohistochemical analysis with S100. Confirmation of the presence of hyaline cartilage was further assessed by examination of Type 11 collagen messenger RNA expression using PCR.

Results: Thirty four patients were recruited between July 1998 and November 2001, with a median age of 31 years (range 15–51 years). Of the 34 patients treated, 17 had right-sided lesions, 15 had left-sided lesions and two patients had bilateral lesions. Solitary lesions were treated in 36 knees with two defects being treated in one knee (37 defects in total). The defects were located on the medial femoral condyle in 22 cases, the lateral femoral condyle in eight, the trochlea in two and the patella in five cases. The defect size ranged from 1–7 cm2 (mean area 2.88cm2). The follow-up of the patients ranged from 1–39 months (mean 19 months). Twenty five patients had at least one-year follow-up. Of these patients, using the BritIberg Rating, six patients had excellent results, with 11 good, six fair and two poor. The mean Lysholin and GilIquist scores improved from 44.7 pre-op to 76.2 one-year post-op and the mean Verbal Numerical Pain Scores improved from 7.1 to 1.1. Arthroscopy revealed that the transplants were level with the surrounding surface in most cases. Biopsy at one year confirmed the presence of hyaline cartilage in 13 out of 19 cases (70%).

Conclusion: Although long-term follow-up is currently unavailable, autologous chondrocyte transplantation can provide, with careful patient selection and meticulous surgical technique, an effective treatment for cartilage defects of the knee. The histological results are extremely encouraging and chondrocyte transplantation may be the only procedure to allow regeneration of hyaline cartilage.

Introduction: Articular cartilage defects within the knee joint have poor capacity for repair. The purpose of this study is to analyse the short-term clinical and histological results of the treatment of deep chondral defects with autologous chondrocyte transplantation.

Methods: This is a prospective study involving twenty-two consecutive patients receiving autologous chondrocyte transplantation. Chondrocytes from a non weight bearing area of the knee are harvested, then isolated and cultured in vitro. Re-implantation involves injection of the chondrocytes into the defect which is then sealed with a porcine I/III collagen membrane. Evaluation consists of clinical assessment, arthroscopy and histological examination. Histological evaluation consists of examination of a biopsy of the transplanted area one-year post-op. Staining techniques include the use of Erlich’s H & E, Safranin O and S100. Using polarised light, the absence of the fibrillar nature of fibrocartilage confirms the presence of hyaline cartilage. Further confirmation can be gained by the examination of messenger RNA content, confirming the presence of type II collagen.

Results: The patients were treated between July 1998 and December 2000. The age range of the patients was 15–51 years (mean age 31 years). Of the 22 patients treated, 13 had right-sided lesions, 11 had left-sided lesions with two patients receiving bilateral procedures. Solitary lesions were treated in 23 knees with two defects being treated in one knee (25 defects in total). The defects were located on the medial femoral condyle in 17 cases, the lateral femoral condyle in five, the trochlea in two and the patella in one case. The defect size ranged from 1–5.4cm2 (mean area 2.65cm2). The follow-up of the patients ranges from 3-30 months (mean 16 months). Thirteen patients have at least one-year follow-up. Of these patients, using the Brittberg Rating, two patients have excellent results, with six good, four fair and one poor. The mean Lysholm and Gillquist scores improved from 50 pre-op to 72 one-year post-op and the mean Verbal Numerical Pain Scores improved from 7.2 to 2.6. Arthroscopy revealed that the transplants were level with the surrounding surface in most cases. Biopsy at one year confirmed the presence of hyaline cartilage in 10 out of 13 cases.

Conclusion: Although the results are short-term, autologous chondrocyte transplantation can provide, with careful patient selection and meticulous surgical technique, an effective treatment for cartilage defects of the knee. The histological results are extremely encouraging and chondrocyte transplantation may be the only procedure to allow regeneration of hyaline cartilage.

Introduction: We discuss the use of the SMILES (Stanmore Modular Individualised Lower Extremity System) in revision knee arthroplasty and review the outcome of 32 cases.

Methods: The SMILES prosthesis incorporates a rotating hinge knee joint. It can overcome the major problems of bone loss and ligamentous laxity. 32 prostheses were used in 30 patients as salvage revision procedures between Sept. 1991 and Sept. 1998. Patients receiving surgery for tumours were excluded. The minimum follow-up was two years with a mean follow-up of 4 years and six months. The age of the patients ranged from 36–85 years (mean 68years and 6months). 18 of the patients were male. The original pathology was OA in 23 patients and RA in 7 patients. The number of previous arthroplasties ranged from 1–4. The main indications for a SMILES prosthesis were aseptic loosening, periprosthetic fracture and infection, in the presence of bone loss and ligamentous laxity.

Results: The patients were assessed using the Knee Society Rating Score. The mean knee score improved from 26 pre-op to 68 post-op while the mean fiction score improved from 27 to 75. Overall Knee Society scores improved from a mean of 26 to 72. The average range of motion was 60 degrees pre-op and 90 degrees post-op. Complications included: failure to eradicate infection in two patients, with one patient needing amputation; infection of the prosthesis leading to revision in one, and failure of the tibial component needing revision.

Conclusion: The Smiles has produced satisfactory results in the short to medium term, offering an alternative to amputation in some cases. The cost compares favourably with other designs and the use is increasing in frequency.

Introduction: Articular cartilage defects in the knee joint have poor capacity for repair. The purpose of this study is to analyse the short-term results of the treatment of deep chondral defects with autologous chondrocyte transplantation with the use of a collagen membrane.

Methods: This is a prospective study involving twentytwo consecutive patients receiving autologous chondrocyte transplantation. Chondrocytes from a non weight bearing area of the knee are harvested, then isolated and cultured in vitro. Re-implantation involves injection of the chondrocytes into the defect which is then sealed with a porcine I/III (Chondro-gide) membrane. Evaluation consists of clinical assessment, arthroscopy and histological examination.

Results: The patients were treated between July 1998 and December 2000. The age range of the patients was 15–51 years (mean age 31 years). Of the 22 patients treated, 13 had right-sided lesions, 11 had left-sided lesions with two patients receiving bilateral procedures. Solitary lesions were treated in 23 knees with two defects being treated in one knee (25 defects in total). The defects were located on the medial femoral condyle in 17 cases, the lateral femoral condyle in five, the trochlea in two and the patella in one case. The defect size ranged from 1–5.4cm² (mean area 2.65cm²). The follow-up of the patients ranges from 1–28 months (mean 14 months). Thirteen patients have at least one-year follow-up. Of these patients, using the Brittberg Rating, two patients have excellent results at one year, with six good, four fair and one poor. The mean Lysholm and GilIquist scores improved from 50 pre-op to 72 one-year post-op and the mean Verbal Numerical Pain Scores improved from 7.2 to 2.6. Arthroscopy revealed that the transplants were level with the surrounding surface in most cases. Biopsy at one year confirmed the presence of hyaline cartilage in 10 out of 13 cases.

Conclusion: Although the results are short-term, autologous chondrocyte transplantation using the Chondro-gide membrane can provide, with careful patient selection, an effective treatment for cartilage defects of the knee. Chondrocyte transplantation may be the only procedure to allow regeneration of hyaline articular cartilage.

Osteofibrous dysplasia is a rare condition usually affecting the tibiae and fibulae of males in the first two decades of life. Involvement at the ulna has also been reported in some cases. We describe an extensive, rapidly progressive lesion of the ulna in a three-year-old girl. The progression of the disease accelerated after a local marginal removal, and required extensive resection of the ulna with reconstruction using a fibular autograft.

The particular features of this case are the change in the aggressive nature of the condition, which has not been previously reported. We believe that this is only the second recorded case of histologically proven involvement of the ulna.

We reviewed the outcome of 422 primary cemented Kinemax total knee arthroplasties implanted into 369 patients over a period of five years, from January 1989. The operations were carried out at two NHS district general hospitals and one teaching hospital by 31 surgeons. During the period of review, 49 patients died and ten knees were lost to follow-up (68 knees). The mean Knee Society score improved from 28 before to 89 after surgery, and the mean function score increased from 23 to 79. The range of flexion improved from 92° to 105°.

These improvements were maintained throughout the period of study. At the latest review radiolucent lines of 1 mm were seen around 15% of tibial components, 1.4% of patellar components and 9.5% of femoral components. In no case were these changes progressive. Using revision as the endpoint, cumulative survival was 99% after five years and 96.95% after nine years. All revisions were undertaken for deep infection or secondary trauma.

Our study has shown that the Kinemax total knee replacement, when carried out with retention of the posterior cruciate ligament by surgeons of varying experience, produces very satisfactory results in the medium term.

The use of extendible distal femoral replacements is a relatively new treatment alternative for malignant bone tumours in growing individuals. Although their appearance was widely appreciated, questions about functional practicality and longevity remain unclear. With longer follow-up, advantages of immediate functional restoration and beneficial psychological aspects seem to be overshadowed by an increase in complications such as aseptic loosening, infection or prosthetic failure.

We have reviewed 18 children with such tumours who were treated between 1983 and 1990 by custom-made Stanmore extendible distal femoral replacements. Four died from metastatic disease within 2.5 years of operation and two required amputation for local recurrence or chronic infection.

The remaining 12 patients were followed for a mean of 8.7 years (6 to 13.2). A mean total lengthening of 5.2 cm was achieved, requiring, on average, 4.3 operations. Using the Musculoskeletal Tumor Society rating score the functional result at review was, on average, 77% of the expected normal function, with seven patients achieving ≥ 80%. Revision of the prosthesis was required in ten patients, in six for aseptic loosening, at a mean of 6.2 years after the initial procedure.