Pigmented villonodular synovitis of the knee: A retrospective analysis of 214 cases at a UK tertiary referral centre.

AIMS: Pigmented villonodular synovitis (PVNS) is a rare, locally aggressive and potentially recurrent synovial disease. We present the largest single-centre experience of knee PVNS. Our aim was to evaluate our tertiary hospital's experience in the management of knee PVNS. PATIENTS AND METHODS: Retrospective data collection of consecutive cases of knee PVNS from 2002 to 2015. RESULTS: In total, 214 cases of knee PVNS were identified which represented 53.4% of all PVNS (12.1% were recurrent at presentation). 100 were localised PVNS (LPVNS), 114 diffuse PVNS (DPVNS) and two malignant PVNS. Knee PVNS was more likely to occur in females with a mean age of 39. Following surgery, 47.6% had recurrence with DPVNS as opposed to 8.6% with LPVNS. In LPVNS, there was no significant difference in recurrence between open and arthroscopic synovectomy (8.7% vs 9.1%, P>0.05). However, in DPVNS, there was a significantly higher risk of recurrence with arthroscopic compared to open synovectomy (83.3% vs 44.8%, RR=1.86 95% CI 1.32-2.62, P=0.0004). CONCLUSION: PVNS can be difficult to treat. We found no difference in local recurrence rates between open and arthroscopic treatment of LPVNS but significantly increased rates of recurrence for DPVNS following arthroscopic treatment. We would therefore recommend open synovectomy for DPVNS.

Metal-on-polyethylene versus metal-on-metal bearing surfaces in total hip arthroplasty: a prospective randomised study investigating metal ion levels and chromosomal aberrations in peripheral lymphocytes.

The long term biological effects of wear products following total hip arthroplasty (THA) are unclear. However, the indications for THA are expanding, with increasingly younger patients undergoing the procedure. This prospective, randomised study compared two groups of patients undergoing THA after being randomised to receive one of two different bearing surfaces: metal-on-polyethylene (MoP) n = 22 and metal-on-metal (MoM) n = 23. We investigated the relationship between three variables: bearing surface (MoP vs MoM), whole blood levels of chromium (Cr) and cobalt (Co) and chromosomal aberrations in peripheral lymphocyte pre-operatively and at one, two and five years post-surgery. Our results demonstrated significantly higher mean cobalt and chromium (Co and Cr) blood levels in the MoM group at all follow-up points following surgery (p < 0.01), but there were no significant differences in the chromosomal aberration indices between MoM and MoP at two or five years (two years: p = 0.56, p = 0.08, p = 0.91, p = 0.51 and five years: p = 0.086, p = 0.73, p = 0.06, p = 0.34) for translocations, breaks, loss and gain of chromosomes respectively. Regression analysis showed a strong linear relationship between Cr levels and the total chromosomal aberration indices in the MoM group (R(2) = 0.90016), but this was not as strong for Co (R(2) = 0.68991). In the MoP group, the analysis revealed a poor relationship between Cr levels and the total chromosomal aberration indices (R(2) = 0.23908) but a slightly stronger relationship for Co (R(2) = 0.64292). Across both groups, Spearman's correlation detected no overall association between Co and Cr levels and each of the studied chromosomal aberrations. There remains no clear indication which THA bearing couple is the most biocompatible, especially in young active patients. While THA continues to be very successful at alleviating pain and restoring function, the long-term biological implications of the procedure still require further scrutiny.

Uncemented, custom-made, hydroxyapatite-coated collared distal femoral endoprostheses: up to 18 years' follow-up.

We reviewed the outcome of 69 uncemented, custom-made, distal femoral endoprosthetic replacements performed in 69 patients between 1994 and 2006. There were 31 women and 38 men with a mean age at implantation of 16.5 years (5 to 37). All procedures were performed for primary malignant bone tumours of the distal femur. At a mean follow-up of 124.2 months (4 to 212), 53 patients were alive, with one patient lost to follow-up. All nine implants (13.0%) were revised due to aseptic loosening at a mean of 52 months (8 to 91); three implants (4.3%) were revised due to fracture of the shaft of the prosthesis and three patients (4.3%) had a peri-prosthetic fracture. Bone remodelling associated with periosteal cortical thinning adjacent to the uncemented intramedullary stem was seen in 24 patients but this did not predispose to failure. All aseptically loose implants in this series were diagnosed to be loose within the first five years. The results from this study suggest that custom-made uncemented distal femur replacements have a higher rate of aseptic loosening compared to published results for this design when used with cemented fixation. Loosening of uncemented replacements occurs early indicating that initial fixation of the implant is crucial.

Occurrence and Characterization of Bean common mosaic virus Strain NL1 in Iowa.

A legume survey in Story County was conducted to characterize legume viruses present in Iowa and potentially problematic to soybeans. Symptomatic (chlorosis, leaf curl, or vein banding) and non-symptomic leaves were selected from Apios americana, Cyamopsis tetragonolobus, Desmodium spp., Glycine max, Lablab purpureus, Lotus japonicus, Phaseolus coccineus, Phaseolus vulgaris, Vicia faba, Vigna ungulculata, and Chenopodium quinoa (an indicator species), and sent to Agdia Inc. for their Crop Screen: "Bean (Soybean)" tests. Cowpea mosaic virus (in L. purpureus), Southern bean mosaic virus (in A. americana), Soybean dwarf virus (in L. purpureus), and Tobacco streak virus (in Desmodium spp.) were identified. In addition, P. vulgaris was found positive in the serological Potyvirus group test, and was further characterized using reverse transcription (RT)-PCR using total RNA (Qiagen RNeasy extraction kit) from symptomatic leaves. A ~1-kb fragment of virus genome was amplified using degenerate primers, forward: 5' TGYGTNGAYGAYYTYAAYAA 3' (3) and reverse: 5' TCRTARAARTCRAAIGCRTAICKIG 3' (2). The closest GenBank BLAST hits for the sequence were BCMV strain NL1 (GenBank Accession No. AY112735) and BCMV MS1 (EU761198), both at 97% identity. RNA sequencing using an Illumina HiSeq 2500 (100 base paired ends) allowed construction of a nearly complete viral sequence from positions 38 to 10,037 nt (KM023744). This showed 99% similarity to BCMV-NL1 (AY112735) and 98% similarity to BCMV MS1 (EU761198). The BCMV isolate was recovered on the P. vulgaris cv. Taos Red and tested against a panel of Phaseolus, Glycine, and other hosts. Symptomatic hosts (vein-banding, mosaic, stunting, and leaf curl) were P. vulgaris cvs. Starlight, Tohono O'odham vaya Amarillo, Black Valentine Stringless, Sutter Pink, Hidatsa red, Stringless Green Refugee, Burpees Stringless Improved Bush, Princess d'Artois, Princess Double de Holland, and Dubelle Witte. Asymptomatic hosts included P. vulgaris cvs. Sierra, Great Northern Tara, Tara, and Vigna radiata. Non-host plants were P. vulgaris cvs. Michelite 62, Great Northern UI 31, Great Northern UI 123, Pure Gold Wax, Top Crop, Redlands Greanleaf B, Red Mexican UI 34, Imuna, Monroe, Pinto UI 114, Widusa, Othello, Sacramento, Red Kidney, Provider, Black Turtle Soup, Victor, and Witte boon, G. max cv. Williams, Cucumis sativus cv. Straight 8, Solanum lycopericum cv. Reine des Hatives, Vicia faba, Pisum sativum var. macrocarpon, V. unguiculata, and A. americana. The host range of the BCMV isolate on common bean differential species concurred with pathogenicity group I (1) and agreed with assignment as strain NL1. To our knowledge, this is the first complete characterization of a pathotype I strain NL1 of BCMV in the United States, combining biological typing and whole genome sequencing. References: (1) R. E. Klein et al. Plant Dis. 76:1263, 1992. (2) H. Yamamoto et al. J. Gen. Plant Pathol. 74:97, 2008. (3) L. Zheng et al. PLoS One 3:e1586, 2008.

Large tumoral calcinosis in the gluteal region: a case report.

BACKGROUND. Tumoral calcinosis is a poorly understood phenomenon. It can be described as a syndrome of calcium deposits principally affecting the juxta-articular areas. It is a rare entity that has been poorly understood. Our aim is to highlight a special and unusual case of an 11-year-old with a large, relatively painless lump in her buttock. CLINICAL CASE. An 11-year-old girl of African descent presented to our Bone Tumour Unit after being referred by her local hospital. The girl presented with a large lump on the posterolateral aspect of the right buttock, measuring 15cm in diameter. Due to the delay in referral/diagnosis, tethering of the skin had progressed to necrosis, with a sinus discharging milky-white fluid. A MRI scan further characterised the lump as a densely calcified area within the gluteus maximus, extending to the subcutaneous tissue. The characteristic features of the calcified mass on the images led to the diagnosis of tumoral calcinosis. Laboratory test did not demonstrate any metabolic disturbances. Pathology reports further confirmed the diagnosis and the lump was successfully resected. There were no recurrences on follow-up. CONCLUSION. Several cases of tumoral calcinosis have been described in the literature; however, it remains a rare entity. Being aware of the possibility and having knowledge of tumoral calcinosis is paramount in preventing confusion and delay in diagnosis for patients and clinicians.

The outcome of extra-abdominal fibromatosis treated at a tertiary referral centre.

PURPOSE: To review the outcomes of patients with extra-abdominal fibromatosis treated at a tertiary referral centre. METHODS: A retrospective review of a series of 72 patients with fibromatosis treated at the Royal National Orthopaedic Hospital (RNOH) between 1980 and 2009, with a median follow up of 4 years (1-17 years). RESULTS: Forty patients were primary referrals, and 32 more had operations at the referring hospital. Five were treated non-operatively; 48 patients were treated by operation alone and 19 patients underwent surgery supplemented by adjuvant therapy. Recurrence was seen in 24 of the operation alone group and 10 in the operation and adjuvant therapy group. The rate of recurrence was lower with complete excision. However, complete excision was impossible in some cases because of extension into the chest or spinal canal, or involvement with the axial vessels and lumbosacral or brachial plexus. CONCLUSION: We suggest that operative excision should seek to preserve function and that supplementary adjuvant therapy may reduce the risk of recurrence, although excision margin appears to be the most important factor. The aggressive, infiltrative behaviour of deep fibromatoses and the associated genetic mutations identified, clearly distinguish them from the superficial fibromatoses and makes their treatment more difficult and dangerous, especially where vital structures are involved.

Custom rotating-hinge primary total knee arthroplasty in patients with skeletal dysplasia.

Patients with skeletal dysplasia are prone to developing advanced osteoarthritis of the knee requiring total knee replacement (TKR) at a younger age than the general population. TKR in this unique group of patients is a technically demanding procedure owing to the deformity, flexion contracture, generalised hypotonia and ligamentous laxity. We retrospectively reviewed the outcome of 11 TKRs performed in eight patients with skeletal dysplasia at our institution using the Stanmore Modular Individualised Lower Extremity System (SMILES) custom-made rotating-hinge TKR. There were three men and five women with mean age of 57 years (41 to 79). Patients were followed clinically and radiologically for a mean of seven years (3 to 11.5). The mean Knee Society clinical and function scores improved from 24 (14 to 36) and 20 (5 to 40) pre-operatively, respectively, to 68 (28 to 80) and 50 (22 to 74), respectively, at final follow-up. Four complications were recorded, including a patellar fracture following a fall, a tibial peri-prosthetic fracture, persistent anterior knee pain, and aseptic loosening of a femoral component requiring revision. Our results demonstrate that custom primary rotating-hinge TKR in patients with skeletal dysplasia is effective at relieving pain, with a satisfactory range of movement and improved function. It compensates for bony deformity and ligament deficiency and reduces the likelihood of corrective osteotomy. Patellofemoral joint complications are frequent and functional outcome is worse than with primary TKR in the general population.

The medium-term results of the Stanmore non-invasive extendible endoprosthesis in the treatment of paediatric bone tumours.

In skeletally immature patients, resection of bone tumours and reconstruction of the lower limb often results in leg-length discrepancy. The Stanmore non-invasive extendible endoprosthesis, which uses electromagnetic induction, allows post-operative lengthening without anaesthesia. Between 2002 and 2009, 55 children with a mean age of 11.4 years (5 to 16) underwent reconstruction with this prosthesis; ten patients (18.2%) died of disseminated disease and one child underwent amputation due to infection. We reviewed 44 patients after a mean follow-up of 41.2 months (22 to 104). The mean Musculoskeletal Tumor Society score was 24.7 (8 to 30) and the Toronto Extremity Salvage score was 92.3% (55.2% to 99.0%). There was no local recurrence of tumour. Complications developed in 16 patients (29.1%) and ten (18.2%) underwent revision. The mean length gained per patient was 38.6 mm (3.5 to 161.5), requiring a mean of 11.3 extensions (1 to 40), and ten component exchanges were performed in nine patients (16.4%) after attaining the maximum lengthening capacity of the implant. There were 11 patients (20%) who were skeletally mature at follow-up, ten of whom had equal leg lengths and nine had a full range of movement of the hip and knee. This is the largest reported series using non-invasive extendible endoprostheses after excision of primary bone tumours in skeletally immature patients. The technique produces a good functional outcome, with prevention of limb-length discrepancy at skeletal maturity.

Custom-made rotating hinge total knee replacement in a patient with congenital tibial deficiency avoids the need for amputation.

We report a unique case of a patient with type 2 congenital tibial deficiency and disabling knee osteoarthritis in whom a custom-made rotating hinge knee replacement was successfully performed, allowing continued mobilisation with a below-knee prosthesis, thereby avoiding the need for an above-knee amputation. Level of evidence Therapeutic study, Level IV.

Intercalary diaphyseal endoprosthetic reconstruction for malignant tibial bone tumours.

The best method of reconstruction after resection of malignant tumours of the tibial diaphysis is unknown. In the absence of any long-term studies analysing the results of intercalary endoprosthetic replacement, we present a retrospective review of 18 patients who underwent limb salvage using a tibial diaphyseal endoprosthetic replacement following excision of a malignant bone tumour. There were ten men and eight women with a mean age of 42.5 years (16 to 76). Mean follow-up was 58.5 months (20 to 141) for all patients and 69.3 months (20 to 141) for the 12 patients still alive. Cumulative patient survival was 59% (95% confidence interval (CI) 32 to 84) at five years. Implant survival was 63% (95% CI 35 to 90) at ten years. Four patients required revision to a proximal tibial replacement at a mean follow-up of 29 months (10 to 54). Complications included metastases in five patients, aseptic loosening in four, peri-prosthetic fracture in two, infection in one and local recurrence in one. The mean Musculoskeletal Tumor Society score and the mean Toronto Extremity Salvage Score were 23 (17 to 28) and 74% (53 to 91), respectively. Although rates of complication and revision were high, custom-made tibial diaphyseal replacement following resection of malignant bone tumours enables early return to function and provides an attractive alternative to other surgical options, without apparent compromise of patient survival.

Proximal humeral replacement using a fixed-fulcrum endoprosthesis.

Between 1997 and 2007, 68 consecutive patients underwent replacement of the proximal humerus for tumour using a fixed-fulcrum massive endoprosthesis. Their mean age was 46 years (7 to 87). Ten patients were lost to follow-up and 16 patients died. The 42 surviving patients were assessed using the Musculoskeletal Tumor Society (MSTS) Score and the Toronto Extremity Salvage Score (TESS) at a mean follow-up of five years and 11 months (one year to ten years and nine months). The mean MSTS score was 72.3% (53.3% to 100%) and the mean TESS was 77.2% (58.6% to 100%). Four of 42 patients received a new constrained humeral liner to reduce the risk of dislocation. This subgroup had a mean MSTS score of 77.7% and a mean TESS of 80.0%. The dislocation rate for the original prosthesis was 25.9; none of the patients with the new liner had a dislocation at a mean of 14.5 months (12 to 18). Endoprosthetic replacement for tumours of the proximal humerus using this prosthesis is a reliable operation yielding good results without the documented problems of unconstrained prostheses. The performance of this prosthesis is expected to improve further with a new constrained humeral liner, which reduces the risk of dislocation.

Use of metal proximal radial endoprostheses for treatment of non-traumatic disorders: a case series.

We have reviewed five adult patients treated with endoprosthetic reconstruction of the proximal radius following resection of non-traumatic lesions. The patients had a mean age of 33.4 years (20 to 60) at the time of surgery and the mean follow-up was 7.6 years (0.8 to 16). Following surgery, all elbows were clinically stable and there was 100% survivorship of the prosthesis. Evaluation of function was assessed clinically and by the Mayo Elbow Performance Score, achieving a mean of 86% (70 to 100). Results at medium-term follow-up are encouraging with regards to elbow stability, implant survivorship and functional outcome.

Custom-made endoprostheses for the femoral amputation stump: an alternative to hip disarticulation in tumour surgery.

Disarticulation of the hip in patients with high-grade tumours in the upper thigh results in significant morbidity. In patients with no disease of the proximal soft tissue a femoral stump may be preserved, leaving a fulcrum for movement and weight-bearing. We reviewed nine patients in whom the oncological decision would normally be to disarticulate, but who were treated by implantation of an endoprosthesis in order to create a functioning femoral stump. The surgery was undertaken for chondrosarcoma in four patients, pleomorphic sarcoma in three, osteosarcoma in one and fibrous dysplasia in one. At follow-up at a mean of 80 months (34 to 132), seven patients were alive and free from disease, one had died from lung metastases and another from a myocardial infarction. The mean functional outcome assessment was 50 (musculoskeletal tumor society), 50 and 60 (physical and mental Short-form 36 scores). Implantation of an endoprosthesis into the stump in carefully selected patients allows fitting of an above-knee prosthesis and improves wellbeing and the functional outcome.

Femoral diaphyseal endoprosthetic reconstruction after segmental resection of primary bone tumours.

Segmental resection of malignant bone disease in the femoral diaphysis with subsequent limb reconstruction is a major undertaking. This is a retrospective review of 23 patients who had undergone limb salvage by endoprosthetic replacement of the femoral diaphysis for a primary bone tumour between 1989 and 2005. There were 16 males and seven females, with a mean age of 41.3 years (10 to 68). The mean overall follow-up was for 97 months (3 to 240), and 120 months (42 to 240) for the living patients. The cumulative patient survival was 77% (95% confidence interval 63% to 95%) at ten years. Survival of the implant, with failure of the endoprosthesis as an endpoint, was 85% at five years and 68% (95% confidence interval 42% to 92%) at ten years. The revision rate was 22% and the overall rate of re-operation was 26%. Complications included deep infection (4%), breakage of the prosthesis (8%), periprosthetic fracture (4%), aseptic loosening (4%), local recurrence (4%) and metastases (17%). The 16 patients who retained their diaphyseal endoprosthesis had a mean Musculoskeletal Tumour Society score of 87% (67% to 93%). They were all able to comfortably perform most activities of daily living. Femoral diaphyseal endoprosthetic replacement is a viable option for reconstruction following segmental resection of malignant bone disease. It allows immediate weight-bearing, is associated with a good long-term functional outcome, has an acceptable complication and revision rate and, most importantly, does not appear to compromise patient survival.

Elastofibroma dorsi: management, outcome and review of the literature.

Elastofibroma dorsi is an uncommon, benign, slow-growing soft-tissue tumour of uncertain aetiology. It classically presents as an ill-defined mass at the inferior pole of the scapula with symptoms which include swelling, discomfort, snapping, stiffness and occasionally pain. We report the symptoms, function and outcome after treatment of 21 elastofibromas in 15 patients. All were diagnosed by MRI and early in the series four also underwent CT-guided biopsy to confirm the diagnosis. In all, 18 tumours were excised and three were observed. After excision, the mean visual analogue score for pain decreased from 4.6 (0 to 10) pre-operatively to 2.4 (0 to 8) post-operatively (p = 0.04). The mean shoulder function, at a mean follow-up of 4.2 years (3 months to 16 years), was 78.1% (30 to 100) using the Stanmore percentage of normal shoulder assessment scoring system. The mean range of forward flexion improved from 135 degrees (70 degrees to 180 degrees ) to 166 degrees (100 degrees to 180 degrees ) after excision (p = 0.005). In four patients a post-operative haematoma formed; one required evacuation. Three patients developed a post-operative seroma requiring needle aspiration and one developed a superficial infection which was treated with antibiotics. Our findings support previous reports suggesting that a pre-operative tissue diagnosis is not necessary in most cases since the lesion can be confidently diagnosed by MRI, when interpreted in the light of appropriate clinical findings. Surgical excision in symptomatic patients, is helpful. It has been suggested that elastofibroma is caused by a local tissue reaction and is not a true neoplastic process. A strong association has been noted between elastofibroma and repetitive use of the shoulder, which is supported by our findings.

Custom-made hinged spacers in revision knee surgery for patients with infection, bone loss and instability.

Polymethyl methacrylate spacers are commonly used during staged revision knee arthroplasty for infection. In cases with extensive bone loss and ligament instability, such spacers may not preserve limb length, joint stability and motion. We report a retrospective case series of 19 consecutive patients using a custom-made cobalt chrome hinged spacer with antibiotic-loaded cement. The "SMILES spacer" was used at first-stage revision knee arthroplasty for chronic infection associated with a significant bone loss due to failed revision total knee replacement in 11 patients (58%), tumour endoprosthesis in four patients (21%), primary knee replacement in two patients (11%) and infected metalwork following fracture or osteotomy in a further two patients (11%). Mean follow-up was 38 months (range 24-70). In 12 (63%) patients, infection was eradicated, three patients (16%) had persistent infection and four (21%) developed further infection after initially successful second-stage surgery. Above knee amputation for persistent infection was performed in two patients. In this particularly difficult to treat population, the SMILES spacer two-stage technique has demonstrated encouraging results and presents an attractive alternative to arthrodesis or amputation.

Total femoral endoprosthetic replacement following excision of bone tumours.

We undertook a retrospective review of 33 patients who underwent total femoral endoprosthetic replacement as limb salvage following excision of a malignant bone tumour. In 22 patients this was performed as a primary procedure following total femoral resection for malignant disease. Revision to a total femoral replacement was required in 11 patients following failed segmental endoprosthetic or allograft reconstruction. There were 33 patients with primary malignant tumours, and three had metastatic lesions. The mean age of the patients was 31 years (5 to 68). The mean follow-up was 4.2 years (9 months to 16.4 years). At five years the survival of the implants was 100%, with removal as the endpoint and 56% where the endpoint was another surgical intervention. At five years the patient survival was 32%. Complications included dislocation of the hip in six patients (18%), local recurrence in three (9%), peri-prosthetic fracture in two and infection in one. One patient subsequently developed pulmonary metastases. There were no cases of aseptic loosening or amputation. Four patients required a change of bushings. The mean Musculoskeletal Tumour Society functional outcome score was 67%, the mean Harris Hip Score was 70, and the mean Oxford Knee Score was 34. Total femoral endoprosthetic replacement can provide good functional outcome without compromising patient survival, and in selected cases provides an effective alternative to amputation.

Myolipoma affecting the erector spinae: a case report in a child.

Myolipoma is a rare, benign, lipomatous tumour which most commonly occurs in the retroperitoneum, pelvis, and abdomen. A 4-year-old boy presented with a painless enlarging mass in the left paraspinal region. Magnetic Resonance Imaging (MRI) revealed a soft tissue lesion with high fat content and areas of calcification. Excision and histopathological analysis revealed a tumour composed of lobules of mature adipose tissue and broad septa of well-differentiated smooth muscle tissue. The smooth muscle nature of the nonfatty component was demonstrated by a diffuse and strong immunoreactivity for smooth muscle actin and desmin. The mass was reported as a myolipoma. The patient made an unremarkable recovery from surgery and remains healthy with no signs of recurrence at seven years. This paper represents the youngest patient diagnosed with this rare soft tissue tumour which is normally confined to the adult population. A newly reported site of the tumour is also highlighted.

Non-invasive extendible endoprostheses for limb reconstruction in skeletally-mature patients.

We describe the application of a non-invasive extendible endoprosthetic replacement in skeletally-mature patients undergoing revision for failed joint replacement with resultant limb-length inequality after malignant or non-malignant disease. This prosthesis was developed for tumour surgery in skeletally-immature patients but has now been adapted for use in revision procedures to reconstruct the joint or facilitate an arthrodesis, replace bony defects and allow limb length to be restored gradually in the post-operative period. We record the short-term results in nine patients who have had this procedure after multiple previous reconstructive operations. In six, the initial reconstruction had been performed with either allograft or endoprosthetic replacement for neoplastic disease and in three for non-neoplastic disease. The essential components of the prosthesis are a magnetic disc, a gearbox and a drive screw which allows painless lengthening of the prosthesis using the principle of electromagnetic induction. The mean age of the patients was 37 years (18 to 68) with a mean follow-up of 34 months (12 to 62). They had previously undergone a mean of six (2 to 14) open procedures on the affected limb before revision with the non-invasive extendible endoprosthesis. The mean length gained was 56 mm (19 to 107) requiring a mean of nine (3 to 20) lengthening episodes performed in the outpatient department. There was one case of recurrent infection after revision of a previously infected implant and one fracture of the prosthesis after a fall. No amputations were performed. Planned exchange of the prosthesis was required in three patients after attainment of the maximum lengthening capacity of the implant. There was no failure of the lengthening mechanism. The Mean Musculoskeletal Tumour Society rating score was 22 of 30 available points (18 to 28). The use of a non-invasive extendible endoprosthesis in this manner provided patients with good functional results and restoration of leg-length equality, without the need for multiple open lengthening procedures.

The early results of joint-sparing proximal tibial replacement for primary bone tumours, using extracortical plate fixation.

This paper describes the preliminary results of a proximal tibial endoprosthesis which spares the knee joint and enables retention of the natural articulation by replacing part of the tibial metaphysis and diaphysis. In eight patients who had a primary malignant bone tumour of the proximal tibia, the distal stem, which had a hydroxyapatite-coated collar to improve fixation, was cemented into the medullary canal. The proximal end had hydroxyapatite-coated extracortical plates which were secured to the remaining proximal tibial metaphysis using cortical screws. The mean age of the patients at operation was 28.9 years (8 to 43) and the mean follow-up was for 35 months (4 to 48). The mean Musculoskeletal Tumour Society score was 79% (57% to 90%), the mean Oxford Knee score was 40 points of 48 (36 to 46) and the mean knee flexion was 112 degrees (100 degrees to 120 degrees). In one patient, revision to a below-knee amputation through the prosthesis was required because of recurrence of the tumour. Another patient sustained a periprosthetic fracture which healed with a painful malunion. This was revised to a further endoprosthesis which replaced the knee. In the remaining six patients the prosthesis allowed preservation of the knee joint with good function and no early evidence of loosening. Further follow-up is required to assess the longevity of these prostheses.