Aims. We retrospectively report our experience of managing 30 patients with a primary malignant tumour of the distal tibia; 25 were treated by limb salvage surgery and five by amputation. We compared the clinical outcomes of following the use of different methods of reconstruction. Patients and Methods. There were 19 male and 11 female patients. The mean age of the patients was 19 years (6 to 59) and the mean follow-up was 5.1 years (1.25 to 12.58). Massive allograft was used in 11 patients, and autograft was used in 14 patients. The time to union, the survival time of the reconstruction, complication rate, and functional outcomes following the different surgical techniques were compared. The overall patient survival was also recorded. Results. Out of 14 patients treated with an autograft, 12 (86%) achieved union at both the proximal and distal junctions. The time to union at both junctions of the autograft was significantly shorter than in those treated with an allograft (11.1 vs 17.2 months, p = 0.02; 9.5 vs 16.2 months, p = 0.04). The complication rate of allograft reconstruction was 55%. The five patients treated with an amputation did not have a complication. Out of the 25 patients who were treated with limb salvage, three (12%) developed local recurrence and underwent amputation. The mean functional Musculoskeletal Tumor Society (MSTS) score after autograft reconstruction was higher than after allograft reconstruction (81% vs 67%; p = 0.06), and similar to that after amputation (81% vs 82%; p = 0.82). The two- and five-year overall rates of survival were 83% and 70%, respectively. Conclusions. This consecutive case series supports the safety of limb salvage and the effectiveness of biological reconstruction after the resection of a primary tumour of the distal tibia. Autograft might be a preferable option. In some circumstances, below-knee amputation remains a valid option

To assess the sustainability of our institutional bone bank, we calculated the final product cost of fresh-frozen femoral head allografts and compared these costs with the use of commercial alternatives. Between 2007 and 2010 all quantifiable costs associated with allograft donor screening, harvesting, storage, and administration of femoral head allografts retrieved from patients undergoing elective hip replacement were analysed. . From 290 femoral head allografts harvested and stored as full (complete) head specimens or as two halves, 101 had to be withdrawn. In total, 104 full and 75 half heads were implanted in 152 recipients. The calculated final product costs were €1367 per full head. Compared with the use of commercially available processed allografts, a saving of at least €43 119 was realised over four-years (€10 780 per year) resulting in a cost-effective intervention at our institution. Assuming a price of between €1672 and €2149 per commercially purchased allograft, breakeven analysis revealed that implanting between 34 and 63 allografts per year equated to the total cost of bone banking. . Cite this article: Bone Joint J 2014;96-B:1307–11

Aims. We present a retrospective review of patients treated with extracorporeally irradiated allografts for primary and secondary bone tumours with the mid- and long-term survivorship and the functional and radiographic outcomes. Patients and Methods. A total of 113 of 116 (97.4%) patients who were treated with extracorporeally irradiated allografts between 1996 and 2014 were followed up. Forms of treatment included reconstructions, prostheses and composite reconstructions, both with and without vascularised grafts. Survivorship was determined by the Kaplan-Meier method. Clinical outcomes were assessed using the Musculoskeletal Tumor Society (MSTS) scoring system, the Toronto Extremity Salvage Score (TESS) and Quality of Life-C30 (QLQ-30) measures. Radiographic outcomes were assessed using the International Society of Limb Salvage (ISOLS) radiographic scoring system. Results. There were 61 (54%) men with a mean age of 22 years (6 to 70) and 52 (46%) women with a mean age of 26 years (3 to 85). There were 23 deaths. The five-year patient survivorship was 82.3% and the ten-year patient survivorship was 79.6%. The mean follow-up of the 90 surviving patients was 80.3 months (2 to 207). At the last follow-up, 105 allografts (92.9%) were still in place or had been at the time of death; eight (7%) had failed due to infection, local recurrence or fracture. Outcome scores were comparable with or superior to those in previous studies. The mean outcome scores were: MSTS 79% (. sd. 8); TESS 83% (. sd. 19); QLQ 82% (. sd. 16); ISOLS 80.5% (. sd. 19). . Pearson correlation analysis showed a strong relationship between the MSTS and ISOLS scores (r = 0.71, p < 0.001). Conclusion. This study shows that extracorporeal irradiation is a versatile reconstructive technique for dealing with large defects after the resection of bone tumours with good functional and radiographic outcomes. Functional outcomes as measured by MSTS, TESS and QLQ-30 were strongly correlated to radiographic outcomes. Cite this article: Bone Joint J 2017;99-B:1681–8

Aims. To compare radiographic failure and re-operation rates of anatomical coracoclavicular (CC) ligament reconstructional techniques with non-anatomical techniques after chronic high grade acromioclavicular (AC) joint injuries. . Patients and Methods. We reviewed chronic AC joint reconstructions within a region-wide healthcare system to identify surgical technique, complications, radiographic failure and re-operations. Procedures fell into four categories: (1) modified Weaver-Dunn, (2) allograft fixed through coracoid and clavicular tunnels, (3) allograft loop coracoclavicular fixation, and (4) combined allograft loop and synthetic cortical button fixation. Among 167 patients (mean age 38.1 years, (standard deviation (. sd. ) 14.7) treated at least a four week interval after injury, 154 had post-operative radiographs available for analysis. . Results. Radiographic failure occurred in 33/154 cases (21.4%), with the lowest rate in Technique 4 (2/42 4.8%, p = 0.001). Half the failures occurred by six weeks, and the Kaplan-Meier survivorship at 24 months was 94.4% (95% confidence interval (CI) 79.6 to 98.6) for Technique 4 and 69.9% (95% CI 59.4 to 78.3) for the other techniques when combined. In multivariable survival analysis, Technique 4 had better survival than other techniques (Hazard Ratio 0.162, 95% CI 0.039 to 0.068, p = 0.013). Among 155 patients with a minimum of six months post-operative insurance coverage, re-operation occurred in 9.7% (15 patients). However, in multivariable logistic regression, Technique 4 did not reach a statistically significant lower risk for re-operation (odds ratio 0.254, 95% CI 0.05 to 1.3, p = 0.11). Conclusion. In this retrospective series, anatomical CC ligament reconstruction using combined synthetic cortical button and allograft loop fixation had the lowest rate of radiographic failure. . Take home message: Anatomical coracoclavicular ligament reconstruction using combined synthetic cortical button and allograft loop fixation had the lowest rate of radiographic failure. Cite this article: Bone Joint J 2016;98-B:512–18

Aims. For paediatric and adolescent patients with growth potential, preservation of the physiological joint by transepiphyseal resection (TER) of the femur confers definite advantages over arthroplasty procedures. We hypothesized that the extent of the tumour and changes in its extent after neoadjuvant chemotherapy are essential factors in the selection of this procedure, and can be assessed with MRI. The oncological and functional outcomes of the procedure were reviewed to confirm its safety and efficacy. Methods. We retrospectively reviewed 16 patients (seven male and nine female, mean age 12.2 years (7 to 16)) with osteosarcoma of the knee who had been treated by TER. We evaluated the MRI scans before and after neoadjuvant chemotherapy for all patients to assess the extent of the disease and the response to treatment. Results. The mean follow-up period was 64.3 months (25 to 148) after surgery and no patients were lost to follow-up. On MRI evaluation, 13 tumours were near but not in contact with the physes and three tumours were partially in contact with the physes before neoadjuvant chemotherapy. Bone oedema in the epiphysis was observed in eight patients. After neoadjuvant chemotherapy, bone oedema in the epiphysis disappeared in all patients. In total, 11 tumours were not in contact and five tumours were in partial contact with the physes. The postoperative pathological margin was negative in all patients. At the last follow-up, 12 patients were continuously disease-free and three had no evidence of disease. One patient died due to the disease. Functionally, the patients with retained allograft or recycled autograft had a mean knee range of flexion of 126° (90° to 150°). The mean Musculoskeletal Tumor Society functional score was 27.6 (23 to 30). Conclusion. TER is an effective limb-salvage technique for treating malignant metaphyseal bone tumours in paediatric and young osteosarcoma patients with open physes when a good response to chemotherapy and no progression of the tumour to the epiphysis have been confirmed by MRI. Cite this article: Bone Joint J 2020;102-B(6):772–778

We report the use of an allograft prosthetic composite for reconstruction of the skeletal defect in complex revision total hip replacement for severe proximal femoral bone loss. Between 1986 and 1999, 72 patients (20 men, 52 women) with a mean age of 59.9 years (38 to 78) underwent reconstruction using this technique. At a mean follow-up of 12 years (8 to 20) 57 patients were alive, 14 had died and one was lost to follow-up. Further revision was performed in 19 hips at a mean of 44.5 months (11 to 153) post-operatively. Causes of failure were aseptic loosening in four, allograft resorption in three, allograft nonunion in two, allograft fracture in four, fracture of the stem in one, and deep infection in five. The survivorship of the allograft-prosthesis composite at ten years was 69.0% (95% confidence interval 67.7 to 70.3) with 26 patients remaining at risk. Survivorship was statistically significantly affected by the severity of the pre-operative bone loss (Paprosky type IV; p = 0.019), the number of previous hip revisions exceeding two (p = 0.047), and the length of the allograft used (p = 0.005)

Deficiencies of acetabular bone stock at revision hip replacement were reconstructed with two different types of allograft using impaction bone grafting and a Burch-Schneider reinforcement ring. We compared a standard frozen non-irradiated bone bank allograft (group A) with a freeze-dried irradiated bone allograft, vitalised with autologous marrow (group B). We studied 78 patients (79 hips), of whom 87% (69 hips) had type III acetabular defects according to the American Academy of Orthopaedic Surgeons classification at a mean of 31.4 months (14 to 51) after surgery. At the latest follow-up, the mean Harris hip score was 69.9 points (13.5 to 97.1) in group A and 71.0 points (11.5 to 96.5) in group B. Each hip showed evidence of trabeculation and incorporation of the allograft with no acetabular loosening. These results suggest that the use of an acetabular reinforcement ring and a living composite of sterile allograft and autologous marrow appears to be a method of reconstructing acetabular deficiencies which gives comparable results to current forms of treatment

Aims. This single-centre observational study aimed to describe the results of extensive bone impaction grafting of the whole acetabular cavity in combination with an uncemented component in acetabular revisions performed in a standardized manner since 1993. Methods. Between 1993 and 2013, 370 patients with a median age of 72 years (interquartile range (IQR) 63 to 79 years) underwent acetabular revision surgery. Of these, 229 were more than ten years following surgery and 137 were more than 15 years. All revisions were performed with extensive use of morcellized allograft firmly impacted into the entire acetabular cavity, followed by insertion of an uncemented component with supplementary screw fixation. All types of reoperation were captured using review of radiographs and medical charts, combined with data from the local surgical register and the Swedish Hip Arthroplasty Register. Results. Among patients with possible follow-up of ten and 15 years, 152 and 72 patients remained alive without revision of the acetabular component. The number of deaths was 61 and 50, respectively. Of those who died, six patients in each group had a reoperation performed before death. The number of patients with a reoperation was 22 for those with ten-year follow-up and 21 for those with 15 years of follow-up. The Kaplan-Meier implant survival rate for aseptic loosening among all 370 patients in the cohort was 96.3% (95% confidence interval (CI) 94.1 to 98.5) after ten years and 92.8% (95% CI 89.2 to 96.6) after 15 years. Conclusion. Extensive bone impaction grafting combined with uncemented revision components appears to be a reliable method with favourable long-term survival. This technique offers the advantage of bone stock restoration and disputes the long-standing perception that uncemented components require > 50% of host bone contact for successful implant survival. Cite this article: Bone Joint J 2020;102-B(2):198–204

Aims. Reconstruction of the acetabulum after resection of a periacetabular malignancy is technically challenging and many different techniques have been used with varying success. Our aim was to prepare a systematic review of the literature dealing with these techniques in order to clarify the management, the rate of complications and the outcomes. Patients and Methods. A search of PubMed and MEDLINE was conducted for English language articles published between January 1990 and February 2017 with combinations of key search terms to identify studies dealing with periacetabular resection with reconstruction in patients with a malignancy. Studies in English that reported radiographic or clinical outcomes were included. Data collected from each study included: the number and type of reconstructions, the pathological diagnosis of the lesions, the mean age and follow-up, gender distribution, implant survivorship, complications, functional outcome, and mortality. The results from individual studies were combined for the general analysis, and then grouped according to the type of reconstruction. . Results. A total of 57 studies met the inclusion criteria and included 1700 patients. Most lesions were metastatic (41%), followed by chondrosarcoma (29%), osteosarcoma (10%), Ewing’s sarcoma (7%), and multiple myeloma (2%). The techniques of reconstruction were divided into seven types for analysis: those involving a Harrington reconstruction, a saddle prosthesis, an allograft and allograft prosthesis composite, a pasteurised autograft, a porous tantalum implant, a custom-made prosthesis and a modular hemipelvic reconstruction. The rate of complications was 50%, with infection (14%) and instability (8%) being the most common. Mortality data were available for 1427 patients (84%); 50% had died of disease progression, 23% were alive with disease, and 27% had no evidence of disease at a mean follow-up of 3.4 years (0 to 34). . Conclusion. Both the rate of complications and mortality are high following resection of oncological periacetabular lesions and reconstruction. Many types of reconstruction have been used with unique challenges and complications for each technique. Newer prostheses, including custom-made prostheses and porous tantalum implants and augments, have shown promising early functional and radiographic outcomes. . Cite this article: Bone Joint J 2018;100-B(1 Supple A):22–30

Aims. Although internal hemipelvectomy is associated with a high incidence of morbidity, especially wound complications, few studies have examined rates of wound complications in these patients or have identified factors associated with the consequences. The present study aimed to: 1) determine the rate of wound and other complications requiring surgery after internal hemipelvectomy; and 2) identify factors that affect the rate of wound complications and can be used to stratify patients by risk of wound complications. Methods. The medical records of 123 patients undergoing internal hemipelvectomy were retrospectively reviewed, with a focus on both overall complications and wound complications. Logistic regression analyses were performed to examine the association between host, tumour, and surgical factors and rates of postoperative wound complications. Results. The overall rate of postoperative complications requiring surgery was 49.6%. Wound complications were observed in 34.1% of patients, hardware-related complications in 13.2%, graft-related complications in 9.1%, and local recurrence in 5.7%. On multivariate analysis, extrapelvic tumour extension (odds ratio (OR) 23.28; 95% confidence interval (CI), 1.97 to 274.67; p = 0.012), both intra- and extrapelvic tumour extension (OR 46.48; 95% CI, 3.50 to 617.77; p = 0.004), blood transfusion ≥ 20 units (OR 50.28; 95% CI, 1.63 to 1550.32; p = 0.025), vascular sacrifice of the internal iliac artery (OR 64.56; 95% CI, 6.33 to 658.43; p < 0.001), and use of a structural allograft (OR, 6.57; 95% CI, 1.70 to 25.34; p = 0.001) were significantly associated with postoperative wound complications. Conclusion. Internal hemipelvectomy is associated with high rates of morbidity, especially wound complications. Several host, tumour, and surgical variables are associated with wound complications. The ability to stratify patients by risk of wound complications can help refine surgical and wound-healing planning and may lead to better outcomes in patients undergoing internal hemipelvectomy. Cite this article: Bone Joint J 2020;102-B(3):280–284

Aims. To assess complications and failure mechanisms of osteoarticular allograft reconstructions for primary bone tumours. Patients and Methods. We retrospectively evaluated 38 patients (28 men, 74%) who were treated at our institution with osteoarticular allograft reconstruction between 1989 and 2010. Median age was 19 years (interquartile range 14 to 32). Median follow-up was 19.5 years (95% confidence interval (CI) 13.0 to 26.1) when 26 patients (68%) were alive. In addition, we systematically searched the literature for clinical studies on osteoarticular allografts, finding 31 studies suitable for analysis. Results of papers that reported on one site exclusively were pooled for comparison. Results. A total of 20 patients (53%) experienced graft failure, including 15 due to mechanical complications (39%) and three (9%) due to infection. In the systematic review, 514 reconstructions were analysed (distal femur, n = 184, 36%; proximal tibia, n = 136, 26%; distal radius, n = 99, 19%; proximal humerus, n = 95, 18%). Overall rates of failure, fracture and infection were 27%, 20%, and 10% respectively. With the distal femur as the reference, fractures were more common in the humerus (odds ratio (OR) 4.1, 95% CI 2.2 to 7.7) and tibia (OR 2.2, 95% CI 1.3 to 4.4); infections occurred more often in the tibia (OR 2.2, 95% CI 1.3 to 4.4) and less often in the radius (OR 0.1, 95% CI 0.0 to 0.8). Conclusion. Osteoarticular allograft reconstructions are associated with high rates of mechanical complications. Although comparative studies with alternative techniques are scarce, the risk of mechanical failure in our opinion does not justify routine employment of osteoarticular allografts for reconstruction of large joints after tumour resection. Cite this article: Bone Joint J 2017;99-B:522–30

Impaction allograft is an established method of securing initial stability of an implant in arthroplasty. Subsequent bone integration can be prolonged, and the volume of allograft may not be maintained. Intermittent administration of parathyroid hormone has an anabolic effect on bone and may therefore improve integration of an implant. Using a canine implant model we tested the hypothesis that administration of parathyroid hormone may improve osseointegration of implants surrounded by bone graft. In 20 dogs a cylindrical porous-coated titanium alloy implant was inserted into normal cancellous bone in the proximal humerus and surrounded by a circumferential gap of 2.5 mm. Morsellised allograft was impacted around the implant. Half of the animals were given daily injections of human parathyroid hormone (1–34) 5 μg/kg for four weeks and half received control injections. The two groups were compared by mechanical testing and histomorphometry. We observed a significant increase in new bone formation within the bone graft in the parathyroid hormone group. There were no significant differences in the volume of allograft, bone-implant contact or in the mechanical parameters. These findings suggest that parathyroid hormone improves new bone formation in impacted morsellised allograft around an implant and retains the graft volume without significant resorption. Fixation of the implant was neither improved nor compromised at the final follow-up of four weeks

An uncemented hemispherical acetabular component is the mainstay of acetabular revision and gives excellent long-term results. Occasionally, the degree of acetabular bone loss means that a hemispherical component will be unstable when sited in the correct anatomical location or there is minimal bleeding host bone left for biological fixation. On these occasions an alternative method of reconstruction has to be used. A major column structural allograft has been shown to restore the deficient bone stock to some degree, but it needs to be off-loaded with a reconstruction cage to prevent collapse of the graft. The use of porous metal augments is a promising method of overcoming some of the problems associated with structural allograft. If the defect is large, the augment needs to be protected by a cage to allow ingrowth to occur. Cup-cage reconstruction is an effective method of treating chronic pelvic discontinuity and large contained or uncontained bone defects. . This paper presents the indications, surgical techniques and outcomes of various methods which use acetabular reconstruction cages for revision total hip arthroplasty. Cite this article: Bone Joint J 2016;98-B(1 Suppl A):73–7

An experimental sheep model was used for impaction allografting of 12 hemiarthroplasty femoral components placed into two equal-sized groups. In group 1, a 50:50 mixture of ApaPore hydroxyapatite bone-graft substitute and allograft was used. In group 2, ApaPore and allograft were mixed in a 90:10 ratio. Both groups were killed at six months. Ground reaction force results demonstrated no significant differences (p > 0.05) between the two groups at 8, 16 and 24 weeks post-operatively, and all animals remained active. The mean bone turnover rates were significantly greater in group 1, at 0.00206 mm/day, compared to group 2 at 0.0013 mm/day (p < 0.05). The results for the area of new bone formation demonstrated no significant differences (p > 0.05) between the two groups. No significant differences were found between the two groups in thickness of the cement mantle (p > 0.05) and percentage ApaPore-bone contact (p > 0.05). The results of this animal study demonstrated that a mixture of ApaPore allograft in a 90:10 ratio was comparable to using a 50:50 mixture

We reviewed 29 patients who had undergone intercalary resection for malignant tumours. Of these, 14 had received segmental allograft reconstruction and 15 extracorporeally-irradiated autograft. At a mean follow-up of 71 months (24 to 132), 20 were free from disease, five had died and four were alive with pulmonary metastases. Two patients, one with an allograft and one with an irradiated autograft, had a local recurrence. Reconstruction with extracorporeally-irradiated autograft has a significantly lower rate of nonunion (7% vs 43%, p = 0.031) but an insignificantly higher rate of fracture (20% vs 14%, p = 0.535) than that with segmental allograft. Using the Enneking functional evaluation system, the mean postoperative score for the patients without local recurrence was 87% (80% to 96%) and was similar in both groups. Extracorporeally-irradiated autograft could be an acceptable alternative for reconstruction after intercalary resection, especially in countries where it is difficult to obtain allografts

The treatment of substantial proximal femoral bone loss in young patients with developmental dysplasia of the hip (DDH) is challenging. We retrospectively analysed the outcome of 28 patients (30 hips) with DDH who underwent revision total hip replacement (THR) in the presence of a deficient proximal femur, which was reconstructed with an allograft prosthetic composite. The mean follow-up was 15 years (8.5 to 25.5). The mean number of previous THRs was three (1 to 8). The mean age at primary THR and at the index reconstruction was 41 years (18 to 61) and 58.1 years (32 to 72), respectively. The indication for revision included mechanical loosening in 24 hips, infection in three and peri-prosthetic fracture in three. Six patients required removal and replacement of the allograft prosthetic composite, five for mechanical loosening and one for infection. The survivorship at ten, 15 and 20 years was 93% (95% confidence interval (CI) 91 to 100), 75.5% (95% CI 60 to 95) and 75.5% (95% CI 60 to 95), respectively, with 25, eight, and four patients at risk, respectively. Additionally, two junctional nonunions between the allograft and host femur required bone grafting and plating. An allograft prosthetic composite affords a good long-term outcome in the management of proximal femoral bone loss in revision THR in patients with DDH, while preserving distal host bone

We studied, ten patients (11 elbows) who had undergone 14 allograft-prosthesis composite reconstructions following failure of a previous total elbow replacement with massive structural bone loss. There were nine women and one man with a mean age of 64 years (40 to 84), who were reviewed at a mean of 75 months (24 to 213). One patient developed a deep infection after 26 months and had the allograft-prosthesis composite removed, and two patients had mild pain. The median flexion-extension arc was 100° (95% confidence interval (CI) 76° to 124°). With the exception of the patient who had the infected failure, all the patients could use their elbows comfortably without splints or braces for activities of daily living. The mean Mayo Elbow Performance Index improved from 9.5 (95% CI 4.4 to 14.7) pre-operatively to 74 (95% CI 62.4 to 84.9) at final review. Radiologically, the rate of partial resorption was similar in the humeral and ulnar allografts (three of six and four of eight, respectively; p > 0.999). The patterns of resorption, however, were different. Union at the host-bone-allograft junction was also different between the humeral and ulnar allografts (one of six and seven of eight showing union, respectively; p = 0.03). At medium-term follow-up, allograft-prosthesis composite reconstruction appears to be a useful salvage technique for failed elbow replacements with massive bone loss. The effects of allograft resorption and host-bone-allograft junctional union on the longevity of allograft-prosthesis composite reconstruction, however, remain unknown, and it is our view that these patients should remain under long-term regular review

Aims

Proximal humeral fractures are the third most common fracture among the elderly. Complications associated with fixation include screw perforation, varus collapse, and avascular necrosis of the humeral head. To address these challenges, various augmentation techniques to increase medial column support have been developed. There are currently no recent studies that definitively establish the superiority of augmented fixation over non-augmented implants in the surgical treatment of proximal humeral fractures. The aim of this systematic review and meta-analysis was to compare the outcomes of patients who underwent locking-plate fixation with cement augmentation or bone-graft augmentation versus those who underwent locking-plate fixation without augmentation for proximal humeral fractures.

Aims

The scapula is a rare site for a primary bone tumour. Only a small number of series have studied patient outcomes after treatment. Previous studies have shown a high rate of recurrence, with functional outcomes determined by the preservation of the glenohumeral joint and deltoid. The purpose of the current study was to report the outcome of patients who had undergone tumour resection that included the scapula.

We reviewed 25 patients who had undergone resection of a primary bone sarcoma which extended to within 5 cm of the knee with reconstruction by a combination of a free vascularised fibular graft and a massive allograft bone shell. The distal femur was affected in four patients and the proximal tibia in 21. Their mean age at the time of operation was 19.7 years (5 to 52) and the mean follow-up period 140 months (28 to 213). Three vascularised transfers failed. The mean time to union of the fibula was 5.6 months (3 to 10) and of the allograft 19.6 months (10 to 34). Full weight-bearing was allowed at a mean of 21.4 months (14 to 36). The mean functional score at final follow-up was 27.4 (18 to 30) using a modfied 30-point Musculoskeletal Tumour Society rating system. The overall limb-salvage rate was 88%. The results of our study suggest that the combined use of a vascularised fibular graft and allograft is of value as a limb-salvage procedure for intercalary reconstruction after resection of bone tumours around the knee, especially in skeletally immature patients