Modular Prosthesis Research Articles

Limb Salvage After Infected Knee Arthroplasty With Bone Loss and Extensor Mechanism Deficiency Using a Modular Segmental Replacement System

Multiple total knee arthroplasty revisions pose significant surgical challenges, such as bone loss and soft tissue compromise. For patients with bone loss and extensor mechanism insufficiency after total knee arthroplasty, arthrodesis is a treatment option for the avoidance of amputation. However, arthrodesis is both difficult to achieve in situations with massive bone loss and potentially undesirable due to the dramatic shortening that follows. Although intramedullary nailing for knee arthrodesis has been widely reported, this technique has traditionally relied on the achievement of bony union. We report a case of a patient with massive segmental bone loss in which a modular intercalary prosthesis was used for arthrodesis to preserve limb length without bony union.

Modular tumor prostheses of the humerus

The humerus is a common location of musculoskeletal tumors. Modular prostheses of the humerus, besides APC and biological reconstructions, allow restoration of resulting bone defects. The functional outcome is determined by the extent of bone and soft tissue loss. Anatomical shoulder prostheses have a limited abductor function, while shoulder function could be improved by an inverse prosthetic design and implants for ligament repair. Elbow prostheses provide satisfactory function. Our own results in 101 patients showed a 23% revision rate. The median overall survival was 171 months with an overall 5-year survival of 53%. With respect to good oncological outcomes modular reconstruction of the humerus is a feasible treatment option for cancer patients.

Radial head arthroplasty with an uncemented modular metallic radial head prosthesis: short- and mid-term results.

In comminuted radial head fractures, arthroplasty is an alternative treatment to open reduction and internal fixation or radial head excision. The purpose of this study was to evaluate the short- and mid-term results after the implantation of the EVOLVE™ uncemented modular metallic radial head prosthesis. Twenty-five patients with an unreconstructible comminuted radial head fracture were treated with the EVOLVE™ prosthesis. Two groups were formed in order to evaluate short-term (mean 1.6years, range 1-2.3years) and mid-term (mean 5.1years, range 3-7.2years) results. The short-term group consisted of 10 patients and the mid-term group of 15 patients. Objective physical outcome (ROM, grip strength) and outcome scores (Broberg/Morrey score, DASH) as well as radiological findings (periprosthetic lucency, prosthetic sizing, heterotopic ossification, posttraumatic osteoarthritis) were evaluated. Significant impairments in ROM and grip strength were observed in the affected arm. Differences in impairment of the affected arm between the two groups were not significant. There were no significant differences in the outcome scores between the two groups, with good results obtained overall. Understuffing was observed in 3 patients. Three patients had severe and 5 had no periprosthetic lucency. The groups barely differed in periprosthetic lucency. Radial head arthroplasty with the EVOLVE™ prosthesis gave good results in terms of objective physical outcome and outcome scores at short- and mid-term follow-up. Periprosthetic lucency does not affect the outcome negatively. We assume that periprosthetic lucency does not necessarily imply prosthesis loosening in which revision is required. Radiological findings and the severity of the initial injury do not necessarily correlate with results.

Septic versus aseptic hip revision: how different?

BackgroundThe few available studies directly comparing aseptic and septic joint revision surgery report conflicting results. We investigated whether two-stage revision of septic hip prosthesis with a preformed antibiotic-loaded spacer and an uncemented prosthesis provides hip function and quality of life similar to those provided by aseptic revision surgery in the medium term, as well as the associated direct hospital costs.Materials and methodsWe prospectively evaluated the hip function (Harris hip score) and quality of life (WOMAC and SF-12 scores) of 80 patients who underwent one-stage revision for aseptic loosening (Group A, 40 patients) or two-stage revision for septic total hip prostheses (Group S, 40 patients). Patients were matched for gender, age, and bone loss. A preformed antibiotic-loaded cement spacer was used for two-stage revision, and uncemented modular prostheses were implanted at revision in both groups. The minimum follow-up was 2 years (average 4 years; range 2–6 years).ResultsWe found no difference in infection recurrence or aseptic loosening rate in the two groups. Average Harris hip score increased similarly in both groups: from 19.1 to 74.0 in Group A versus 15.0–71.2 in Group S. Patient-reported quality-of-life questionnaires (SF-12 and WOMAC) at last follow-up were similar postoperatively, but the complication rate for Group S was twice that of Group A (20.8 versus 10%). Mean overall hospital-related costs of two-stage procedures were 2.2 times greater than those for aseptic revisions.ConclusionsTwo-stage revision for infected hip prostheses, using a preformed antibiotic-loaded cement spacer and uncemented revision prosthesis, offers a success rate comparable to noninfected revisions in the medium term but is associated with a higher complication rate and costs.

Management of septic complications following modular endoprosthetic reconstruction of the proximal femur

In a retrospective single-centre study 170 consecutive patients were included who received a Kotz modular prosthesis after resection of bone tumours of the proximal femur to evaluate the management of prosthetic infection. Infection occurred in 12 of 166 patients available for follow-up (six males; six females; mean age, 47years; range, ten to 75years) after a mean of 39months (range, one to 166months; infection rate, 7.2%). Mean follow-up was 54months (range, four to 200months). One patient died of septic shock. Two patients were treated by wound revision only. Treatment of infection in the remaining patients was one-stage revision in eight and hip disarticulation in one. Infection control by one-stage revision was achieved in five of eight patients; re-infection occurred in three patients and was successfully treated by further revision in all of them. The overall success rate for controlling infection was 83.3%.

Primary cemented total hip arthroplasty: 10 years follow-up.

Background:Primary cemented total hip arthroplasty is a procedure for non-traumatic and traumatic affections of the hip. Long term follow-up is required to assess the longevity of the implant and establish the procedure. Indo-Asian literature on long term result of total hip arthroplasty is sparse. We present a 10-year follow-up of our patients of primary cemented total hip arthroplasty.Materials and Methods:We operated 31 hips in 30 patients with primary cemented total hip arthroplasty. We followed the cases for a minimum period of 10 years with a mean follow-up period of 12.7 years. The mean age of the patients was 60.7 years (range 37–82 yrs) male to female ratio was 2:1. The clinical diagnoses included - avascular necrosis of femoral head (n=15), sero positive rheumatoid arthritis (n=5), seronegative spondylo-arthropathy (n=4), neglected femoral neck fractures (n=3), healed tubercular arthritis (n=2) and post traumatic osteoarthritis of hip (n=2). The prostheses used were cemented Charnley’s total hip (n=12) and cemented modular prosthesis (n=19). The results were assessed according to Harris hip score and radiographs taken at yearly intervals.Results:The mean follow-up is 12.7 yrs (range 11-16 yrs) Results in all operated patients showed marked improvement in Harris hip score from preoperative mean 29.2 to 79.9 at 10 years or more followup. However, the non-inflammatory group showed more sustained long term improvement as compared to the inflammatory group, as revealed by the Harris hip score. Mean blood loss was 450ml (±3.7 ml), mean transfusion rate was 1.2 units (±.3). The complications were hypotension (n=7), shortening >1.5 cm (n=9), superficial infection (n=2) and malposition of prosthesis (n=1).Conclusion:The needs of Indian Asian patients, vary from what is discussed in literature. The pain tolerance is greater than western population and financial constraints are high. Thus revision surgery among Indian-Asian patients is less compared to western yard sticks.

How Long Do Endoprosthetic Reconstructions for Proximal Femoral Tumors Last?

BackgroundAs the life expectancy of patients with musculoskeletal tumors improves, long-term studies of endoprosthetic reconstructions are necessary to establish realistic expectations for the implants and compare them to other reconstruction approaches.Questions/purposes(1) What is the long-term survival of cemented bipolar proximal femoral replacements? (2) How does prosthesis survival compare to patient survival among patients with Stage I, II, and III disease? (3) Do modular implants outperform custom-built prostheses? (4) Do some proximal femoral replacements require conversion to THA?Patients and MethodsWe retrospectively reviewed all 86 proximal femoral replacements used for tumor reconstruction from 1982 to 2008. Primary diagnoses were 43 high-grade tumors (IIA/IIB), 20 low-grade tumors (IA/IB or benign), and 23 with metastatic disease. We reviewed prosthesis survival, patient survival, complication rates, functional outcomes, and rates of conversion to THA.ResultsFive of 86 patients (5.8%) required revision of the femoral component. Five-, 10-and 20-year implant survivorships were 93%, 84%, and 56%, respectively. All patients with low-grade disease survived; the 5-year survival rate for patients with metastatic disease was 16%; the 5-, 10-, and 20-year survival for IIA/IIB patients was 54%, 50%, and 44%, respectively. Five of 86 patients (5.8%) underwent conversion to THA for groin pain.ConclusionsCemented bipolar proximal femoral replacements after tumor resection proved a durable reconstruction technique. The implants outlived patients with metastatic disease and high-grade localized disease while patients with low-grade disease outlived their implants. The survival of modular prostheses was comparable to that of older, one-piece custom designs.Level of Evidence Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Mechanical Failure of the Repiphysis Expandable Prosthesis

The current treatment of osteosarcoma includes neoadjuvant chemotherapy followed by wide resection of the tumor and postoperative chemotherapy. While amputation of the extremity was once the mainstay of treatment, medical and surgical developments over the last several decades have led to the success of limb-salvage surgery1,2. In the very young patient, this has led to the challenge of achieving limb-length equality. Recently, the introduction of an endoprosthesis, expandable by noninvasive means, has allowed for reconstruction of the affected limb while addressing limb-length discrepancy in skeletally immature patients3. The latest generation of the expandable prosthesis is the Repiphysis expandable limb salvage system (Wright Medical Technology, Arlington, Tennessee), originally manufactured as the Phenix prosthesis. As the prosthesis has been followed for greater than ten years, failures are being described. Aseptic loosening and prosthetic breakage have been reported, but we know of no detailed report of the mechanism of failure of this prosthesis4. We report the case of a patient who had failure of an expandable prosthesis attributable to internal prosthetic component failure that was salvaged with conversion to an adult modular prosthesis. The patient’s family was informed that data concerning the case would be submitted for publication, and they consented. A fourteen-year-old boy who had had resection of an osteosarcoma in the proximal end of the right tibia at the age of nine years and had reconstruction with use of a proximal tibial replacement, the Repiphysis expandable prosthesis, presented for a routine follow-up evaluation. The patient had undergone two prior limb-lengthenings without complication and had continued growth from the distal femoral physis documented by scanograms. At the time of the latest follow-up, the limb-length discrepancy was <1 cm. The patient complained of slowly progressive pain and a “spongy sensation” with walking. He denied any …

Functional outcomes and complications of reconstruction of the proximal humerus after intra-articular tumor resection

To evaluate functional outcomes and complications of reconstruction of the proximal humerus after intra-articular tumor resection. Twenty-five patients who underwent Malawer I type resection and reconstruction of the proximal humerus for treatment of malignant or invasive benign tumors from August 1999 to August 2005 were evaluated. A variety of reconstructive procedures, including modular tumor prosthesis, osteoarticular allograft, and allograft-prosthetic composite (APC), were performed after resection of tumor. Oncological and radiographic parameters were evaluated. The modified Musculoskeletal Tumor Society (MSTS) evaluation system was used to assess limb functional outcome. The study group consisted of 10 male and 15 female patients, among which there were 20 malignant and 5 benign tumors. Restoration of shoulder function was achieved with a prosthesis in 6 patients, osteoarticular allograft in 12, and allograft-prosthesis composite in 7. At a mean of 48 months follow-up, 2 patients had died of disease. Two patients had local recurrence and 2 had metastatic disease. On the basis of the modified MSTS functional evaluation, the mean scores were 22.50 in the modular prosthesis group, 24.58 in the osteoarticular allograft group, and 27.00 in APC group, respectively. Joint instability and subluxation were serious complications affecting shoulder function in 10 patients. Reconstruction of the proximal humerus is an option that provides good relief of pain and preserves manual dexterity. Functional outcomes are better for APC and allograft than for modular prosthesis, due to retention of the rotation cuff. Complications in the APC group were less than in the allograft one.

Complications of limb salvage surgery in childhood tumors and recommended solutions

Bone and soft tissue malignancies are associated with serious diagnostic and therapeutic problems in every level of pubertal growth in children. Current treatment modality preferred in bone and soft tissue tumors is wide resection of tumor followed by the reconstruction of consequent defect by various methods. Chemotherapy and radiotherapy are applied for systemic effects to the patient pre- and post-operatively and for local effects that facilitate the surgical procedure. Mostly, it is very difficult to control problems following wide resection and reconstruction. In this study, our aim is to discuss the problems encountered in different resection and reconstruction approaches in childhood bone and soft tissue tumors, and the recommended solutions addressed to these problems. From 1990 to 2003, a total of 68 patients (38 female, 30 male) with a mean age of 13.1 (1.5–18) were included in the study. 85.3% of patients were diagnosed as osteosarcoma and the rest was Ewing’s sarcoma. Seventy-five percent of patients had stage IIB disease. The lesions of 34 patients were detected to be in distal femur, 26 in proximal tibia and fibula, 4 in foot and ankle joint, and the remaining 4 in pelvis. As reconstructive surgery, 40 patients had modular prosthesis, vascularized fibular graft was performed in 13 patients, and 10 patients underwent arthrodesis with vascularized fibular graft. 20.6% of patients had shortened limb, infection was detected in 4 patients, laxity in 5, and restricted motion in 4 as complication of prosthesis. With sacrificed physis, 13 patients had a mean value of 4.6 cm limb shortness. Limb salvage surgery has been considered as the gold standard treatment in orthopedic oncological surgery. More understanding of the biology of sarcoma, introduction of new effective chemotherapeutic agents, development of new techniques concerning the surgical resection, advances in diagnostic methods, and improvements in reconstructive surgery all make a major contribution to limb salvage surgery. Since some problems are still encountered, we offer a therapeutic algorithm for complications in the management of childhood tumors that we have encountered so far.

Tecnica chirurgica di revisione in due tempi: protesi di anca

118 patients with infected total hip arthroplasty were treated with two-stage revision, using a preformed antibiotic-loaded cement spacer and a cementless modular hip revision prosthesis. At a minimum follow-up of 2 years (maximum 9 years), 106 patients did not show any clinical or laboratory sign of infection recurrence, 4 (3.6%) had infection recurrence while 8 are lost to follow-up. Survival after 9 years is 91.2% and 87.7% considering as end points infection recurrence or all reasons for revision, respectively. Preformed antibiotic spacers and non-cemented hip revision prostheses appear an effective solution for infected total hip prosthesis.

The surgical treatment of metastatic periacetabular tumors

To retrospectively review the experience with different surgical procedures for periacetabular metastasis. The data of 43 patients with periacetabular metastasis between July 2000 and July 2007 was reviewed. There were 21 patients with primary malignant tumors at the beginning, and 10 patients diagnosed metastasis by preoperative biopsy. The other 12 patients presented skeletal involved as initial manifestations of metastasis prior to the pathological diagnosis of the primary tumor. Twelve patients had solitary metastasis, and the others had multiple bone metastasis. The surgical procedure included curettage (35 cases) and en-blot excision (8 cases). The techniques of reconstruction of acetabular defect included total hip replacement (THR) with cemented components or titanium acetabular reconstruction cup (12 cases), THR with partial pelvis replacement with Candal Hook (16 cases), THR with Steinmann pins and cement augmented or titanium cup reconstruction (7 cases), and modular hemipelvic prosthesis reconstruction (8 cases). All the patients received successful operations. The average score for preoperative pain of 7.2 was assessed. Forty-one patients (95.4%) were evaluated for relief of pain and resumption of walking, and the pain score improved to 3.5 after surgery. The average functional score was 24.5 postoperatively. Six of 32 patients had local recurrence. Fourteen patients died of diseases. The average blood loss during the operation was 1600 ml in 43 patients and the bleeding exceeded 3000 ml was in 3 patients with renal carcinomas. Major complications included two superficial wound infections, one multiple organ failure and two dislocations. Although surgery will not typically cure patients of their metastatic disease, surgery that is well planned and well executed can help many people by relieving their suffering and improving their quality of life.

Cementless Total Hip Replacement in an Alpaca

To report management of a chronic slipped capital femoral epiphysis (SCFE) in an alpaca using cementless total hip replacement (THR). Case report. An 18-month-old, 47 kg alpaca male. Cementless THR was performed in an alpaca with a chronic, right SCFE, and secondary osteoarthritis. Force plate gait analysis was performed before and 8 weeks after surgery. Outcome was determined through clinical evaluation, radiography, and force plate gait analysis. Cementless THR resulted in marked improvement in the alpaca's comfort level, degree of lameness, and range of motion. On preoperative force plate gait analysis there was decreased contact time (P=.01) and vertical impulse (P<.01) of the affected limb, whereas at 8 weeks postoperatively significant differences in gait analysis between pelvic limbs were not apparent. THR using a BioMedtrix canine cementless modular prosthesis restored hip function in an alpaca with coxofemoral osteoarthritis from chronic SCFE. THR may be an appropriate treatment for selected traumatic and degenerative conditions of the coxofemoral joint in alpacas.

Types and evaluation of reconstruction approach for malignant pelvic tumors around acetabulum

Objective To evaluate the functional outcome of malignant periacetabular tumors treated by en bloc resection and reconstructed with different limb-salvage procedures. Methods Seventy-two pa-tients with tumors around acetabular were treated surgically in People's Hospital of Peking University be-tween July 2000 and July 2007, including 42 males and 30 females with an average age of 41 years (range,16-78). 39 patients were diagnosed with chondrosarcoma, and 10 with osteosarcoma, 9 with giant cell tumorand 5 with Ewing sarcoma, etc. Type Ⅱ, Ⅰ + Ⅱ, Ⅱ + Ⅲ, Ⅰ - Ⅲ, Ⅰ -Ⅳ, Ⅱ + Ⅲ +Ⅴ pelvic resection were 4,16, 29, 7, 10 and 6, respectively. Of 72 patients, 50 were reconstructed with modular hemipelvic prosthesis,7 with saddle prosthesis, 8 with cauterized tumor bone implantation and 7 with proximal femur and pelvicbone fusion. Results Sixty-one patients were successfully followed up, and the average time was 3.5 years.Eleven patients (18%) had local relapse, 8 deep infection and 6 dislocation. The average ISOLS evaluationscore was 22 for 45 patients with modular pelvic prosthetic reconstruction, including excellent in 7, good in24, fair in 9 and poor in 5, respectively. Type Ⅱ and Ⅱ +Ⅲ pelvic resection with reconstruction was ratedexcellent or good, in contrasted to type Ⅳ was poor. The average ISOLS evaluation score for 5 saddle pros-thetic reconstruction, 5 recycled tumor bone reimplantation and 6 proximal femur and pelvic bone fusion was11, 17 and 14, respectively. Conclusion Among the 4 different reconstruction methods, the patients withmodular pelvic prosthetic reconstruction had best function results, and the saddle prosthetic reconstructionhad the worst. In terms of different types of pelvic resection with modular pelvic prosthetic reconstruction,type Ⅱ had the best functional result, followed by type Ⅱ + Ⅲ, Ⅰ + Ⅱ, Ⅰ - Ⅲ, Ⅱ + Ⅲ + Ⅴ, and type Ⅰ - Ⅳhad the worst. Key words: Acetabulum; Bone neoplasms; Surgical procedures, operative; Prosthesis implantation

Limitations of Structural Allograft in Revision Total Knee Arthroplasty

Management of large bone defects in total knee arthroplasty (TKA) usually has involved modular prostheses with metal augments, structural allografts, and megaprostheses. We retrospectively reviewed the outcome of treatment of major bone defects for 74 patients (79 knees) who had revision TKAs with structural allografts; nine patients were lost to followup before 5 years, leaving 65 patients (70 knees, or 88%) followed for a minimum of 5 years or until revision or death. Medical records, radiographs, patient surveys, and correspondence were used for all data. Sixteen patients (22.8%) had failed reconstructions and underwent additional revision surgery; eight of the 16 were secondary to allograft failure, three were secondary to failure of a component not supported by allograft, and five were secondary to infection. In patients not requiring revision surgery, the Knee Society score improved from 49 preoperatively to 87 postoperatively. We observed revision-free survival of 80.7% (95% confidence interval, 71.7-90.8) at 5 years and 75.9% (95% confidence interval, 65.6-87.8) at 10 years. Our data support the selective use of structural allograft for large cavitary defects encountered during TKA. However, the rates of complications and reoperations suggest efforts to improve results or develop more durable alternative methods are warranted for these challenging reconstructions. Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Modular endoprosthetic replacement for tumours of the proximal femur

Endoprosthetic replacement of the proximal femur may be required to treat primary bone tumours or destructive metastases either with impending or established pathological fracture. Modular prostheses are available off the shelf and can be adapted to most reconstructive situations for this purpose. We have assessed the clinical and functional outcome of using the METS (Stanmore Implants Worldwide) modular tumour prosthesis to reconstruct the proximal femur in 100 consecutive patients between 2001 and 2006. We compared the results with the published series for patients managed with modular and custom-made endoprosthetic replacements for the same conditions. There were 52 males and 48 females with a mean age of 56.3 years (16 to 84) and a mean follow-up of 24.6 months (0 to 60). In 65 patients the procedure was undertaken for metastases, in 25 for a primary bone tumour, and in ten for other malignant conditions. A total of 46 patients presented with a pathological fracture, and 19 presented with failed fixation of a previous pathological fracture. The overall patient survival was 63.6% at one year and 23.1% at five years, and was significantly better for patients with a primary bone tumour than for those with metastatic tumour (82.3% vs 53.3%, respectively at one year (p = 0.003)). There were six early dislocations of which five could be treated by closed reduction. No patient needed revision surgery for dislocation. Revision surgery was required by six (6%) patients, five for pain caused by acetabular wear and one for tumour progression. Amputation was needed in four patients for local recurrence or infection. The estimated five-year implant survival with revision as the endpoint was 90.7%. The mean Toronto Extremity Salvage score was 61% (51% to 95%). The implant survival and complications resulting from the use of the modular system were comparable to the published series of both custom-made and other modular proximal femoral implants. We conclude that at intermediate follow-up the modular tumour prosthesis for proximal femur replacement provides versatility, a low incidence of implant-related complications and acceptable function for patients with metastatic tumours, pathological fractures and failed fixation of the proximal femur. It also functions as well as a custom-made endoprosthetic replacement.

Disassembly of a Distal Femur Modular Prosthesis After Tumor Resection

We report and analyze the causes of a disassembly of a newly marketed distal femur modular prosthesis in a 20-year-old man with stage IIB osteosarcoma. The disassembly occurred after discharge from the hospital, after a minor trauma. Because of the unique displacement of the femoral component, sudden operative management was performed. Disassembly should be considered as a potential complication when choosing a modular prosthesis despite improvements in the design of some recent devices. In cases with a substantial amount of functional muscle excised at the time of tumor resection, adequate postoperative rehabilitation is recommended.

Modular endoprosthetic replacement for metastatic tumours of the proximal femur

Background and aimsEndoprosthetic replacements of the proximal femur are commonly required to treat destructive metastases with either impending or actual pathological fractures at this site. Modular prostheses provide an off the shelf availability and can be adapted to most reconstructive situations for proximal femoral replacements. The aim of this study was to assess the clinical and functional outcomes following modular tumour prosthesis reconstruction of the proximal femur in 100 consecutive patients with metastatic tumours and to compare them with the published results of patients with modular and custom made endoprosthetic replacements.Methods100 consecutive patients who underwent modular tumour prosthetic reconstruction of the proximal femur for metastases using the METS system from 2001 to 2007 were studied. The patient, tumour and treatment factors in relation to overall survival, local control, implant survival and complications were analysed. Functional scores were obtained from surviving patients.Results and conclusionThere were 45 male and 55 female patients. The mean age was 60.2 years. The indications were metastases. Seventy five patients presented with pathological fracture or with failed fixation and 25 patients were at a high risk of developing a fracture. The mean follow up was 15.9 months [range 0–77]. Three patients died within 2 weeks following surgery. 69 patients have died and 31 are alive. Of the 69 patients who were dead 68 did not need revision surgery indicating that the implant provided single definitive treatment which outlived the patient. There were three dislocations (2/5 with THR and 1/95 with unipolar femoral heads). 6 patients had deep infections. The estimated five year implant survival (Kaplan-Meier analysis) was 83.1% with revision as end point. The mean TESS score was 64% (54%–82%).We conclude that METS modular tumour prosthesis for proximal femur provides versatility; low implant related complications and acceptable function lasting the lifetime of the patients with metastatic tumours of the proximal femur.

Navigated modular short-stem total hip arthroplasty by a less invasive technique

Since November 2004 we have been using a modular short-stem hip prosthesis with a less invasive anterolateral approach in 154 cases. The modified Watson-Jones [1] approach allows the insertion of the hip prosthesis without detaching muscles. The modularity of the prosthesis offers the choice of different degrees of anteversion and CCD angles to restore hip biomechanics. This is simulated by the navigation system. We evaluated primary stability, ease of minimally invasive implantation and restoration of biomechanics. We found good functional results and a low complication rate, without any dislocation. The navigation helps to insert the cup more precisely and to restore the center of rotation, leg length and offset. It suggests the best choice of modular neck to use and helps to predict and influence the safe range of motion. The emphasis is placed on the description of the surgical steps.

Limb salvage surgery for children and adolescents with malignant bone tumors in a developing country

To describe the 5-year experience of a multidisciplinary limb salvage program for children and adolescents with malignant bone tumors in Lebanon. Between January 2002 to February 2007, 30 children and adolescents (2 with Ewing sarcoma and 28 with osteosarcoma) underwent Limb Salvage Surgeries (LSS) at the American University of Beirut Medical Center after partnering with the multidisciplinary team at St. Judes Children's Research Hospital (SJCRH). Procedures performed included 12 Repiphysis, noninvasively expandable, prostheses inserted in skeletally immature children, 15 modular prostheses, 2 allografts and 1 rotationplasty. All patients received pre- and postoperative chemotherapy. With a mean follow-up of 31 months, 20 patients are now off therapy, 4 died, and 6 are receiving chemotherapy (3 due to pulmonary recurrence). Complications of surgery included infections in three cases, failure of the expansion mechanism in two, femoral stem fracture in one, prostheses femoral stem loosening in one and wound dehiscence in one. Lengthening of Repiphysis prostheses was achieved by subjecting the limb to an electromagnetic field that would allow controlled release of the Repiphysis expansion mechanism. Ten patients underwent a total of 42 lengthening procedures with an average of 9 mm lengthened per procedure (range 2-15 mm). All patients have good function of the affected limb. Our LSS results are comparable to those reported in the literature. Collaboration with SJCRH and fund raising were critical to the program's success. This endeavor could serve as a model for establishing LSS programs in developing countries.