[Stress fractures of the lower limbs]. / Stressfrakturen der unteren Extremität.

Stress reactions and fractures represent an important differential diagnostic entity, especially in patients active in sports. The lower extremities have predilection sites for stress fractures, which require special treatment in the context of the underlying risk factors. Clinically, patients usually complain of stress-dependent pain in the affected region and sport activities are mostly limited or even impossible. The detection of acute stress fractures is usually missed by conventional X­ray within the first 4-6 weeks. The gold standard diagnostic tool is magnetic resonance imaging (MRI). Depending on the location, a distinction must be made between low-risk and high-risk stress fractures. Low-risk fractures show a high healing rate after conservative treatment including load and stress reduction as well as avoiding risk factors. High-risk fractures can take a complicated course under conservative treatment measures and in some cases, surgical intervention is required.

[Avulsion injuries of the gluteus medius and gluteus minimus muscles]. / Avulsionsverletzungen des M. glutaeus medius und M. glutaeus minimus.

Avulsion injuries of the gluteus medius and gluteus minimus muscles represent a diagnostic and therapeutic challenge. Such injuries are rarely to be expected in high-energy trauma. Degenerative damage or iatrogenic injuries in the context of hip surgery are more frequently identified as the cause. Clinically, in addition to lateral hip pain, limping is an important finding and depends on the extent of the tendon damage. In addition to the medical history and clinical examination, imaging by means of sonography and, above all, magnetic resonance imaging (MRI, possibly with artifact-reduced sequences in the presence of an endoprosthesis) are diagnostically groundbreaking. Therapeutically, a stepwise approach is indicated according to the extent of rupture and quality of the gluteal tendon and muscle tissues. Specific conservative training regimens, mini-open/endoscopic anatomic reconstruction techniques in cases of gluteal muscle integrity and muscle transfer techniques as salvage option with chronic mass ruptures are available. The common goal is the restoration of everyday occupational and private activities to regain the quality of life.

[Gluteal insufficiency]. / Gluteale Insuffizienz.

Gluteal insufficiency or hip abductor mechanism deficiency mainly following (revision) total hip replacement is associated with highly painful complaints and severe suffering of patients. It represents a great diagnostic and therapeutic challenge. Differentiated conservative treatment pathways, open surgical and endoscopic anatomic repair techniques with intact gluteal musculature and muscle transfer are available as salvage procedures for chronic not anatomically reconstructable mass ruptures. A stepwise diagnostic and therapeutic approach is required for restoration of the quality of life and painless or almost painless mobility of affected patients in occupation and daily life.

[Surgical refixation of gluteal tendon tears by mini-open double-row technique]. / Knotenlose Doppelreihenrefixation bei Glutealsehnenruptur.

OBJECTIVE: Stable refixation of gluteal tendons at the anatomic footprint by large-area contact by the means of knotless double-row anchor fixation (HipBridge technique). INDICATIONS: Symptomatic tear of gluteus medius and/or gluteus minimus tendon with persisting pain after nonsurgical treatment, or primarily reconstructable mass rupture with gluteal insufficiency, revision surgeries. CONTRAINDICATIONS: Primary nonreconstructable mass ruptures, atrophic or fatty degeneration of gluteal muscles grade Goutallier 4, local infections. SURGICAL TECHNIQUE: Lateral position, longitudinal skin incision over greater trochanter, longitudinal incision of iliotibial band, resection of trochanteric subgluteus maximus bursa, longitudinal splitting of gluteal tendons over tear, debridement and mobilisation of tendons for sufficient distalisation to tendon footprint at anterior and lateral trochanteric facet, debridement of sclerotic greater trochanter, punching and tapping of proximal row, placement of two proximal anchors loaded with nonresorbable suture tape, fan-shaped four times gluteal tendon perforation at myotendinous transition zone, double-V-shape crossing of suture tapes, punching and tapping of distal row, fixation of crossed tapes with two distal knotless suture anchors under mild pretensioning of gluteal tendons, side-to-side tendon suture, vastogluteal and iliotibial band closure, wound closure. POSTOPERATIVE MANAGEMENT: Stage-dependent physiotherapy with partial weight-bearing with 20 kg for 6 weeks, no active abduction, no adduction and no external rotation in flexion for 6 weeks after surgery. From week 7 after surgery, free range of motion, active-assisted abduction and increase in weight-bearing by 15 kg/week. No peak load for 4 months. Thromboembolic prophylaxis until full weight-bearing is reached. RESULTS: Success rates of 80-90% can be expected in cases with no or only minor muscle atrophy.

The natural alpha angle of the femoral head-neck junction: a cross-sectional CT study in 1312 femurs.

Aims: Asphericity of the femoral head-neck junction is common in cam-type femoroacetabular impingement (FAI) and usually quantified using the alpha angle on radiographs or MRI. The aim of this study was to determine the natural alpha angle in a large cohort of patients by continuous circumferential analysis with CT. Methods: CT scans of 1312 femurs of 656 patients were analyzed in this cross-sectional study. There were 362 men and 294 women. Their mean age was 61.2 years (18 to 93). All scans had been performed for reasons other than hip disease. Digital circumferential analysis allowed continuous determination of the alpha angle around the entire head-neck junction. All statistical tests were conducted two-sided; a p-value < 0.05 was considered statistically significant. Results: The mean maximum alpha angle for the cohort was 59.0° (sd 9.4). The maximum was located anterosuperiorly at 01:36 on the clock face, with two additional maxima of asphericity at the posterior and inferior head-neck junction. The mean alpha angle was significantly larger in men (59.4°, sd 8.0) compared with women (53.5°, sd 7.4°; p = 0.0005), and in Caucasians (60.7°, sd 9.0°) compared with Africans (56.3°, sd 8.0; p = 0.007) and Asians (50.8°, sd 7.2; p = 0.0005). The alpha angle showed a weak positive correlation with age (p < 0.05). If measured at commonly used planes of the radially reconstructed CT or MRI, the alpha angle was largely underestimated; measurement at the 01:30 and 02:00 positions showed a mean underestimation of 4° and 6°, respectively. Conclusion: This study provides important data on the normal alpha angle dependent on age, gender, and ethnic origin. The normal alpha angle in men is > 55°, and this should be borne in mind when making a diagnosis of cam-type morphology. Cite this article: Bone Joint J 2018;100-B:570-8.

[Surgical therapy of ischiofemoral impingement by lateralizing intertrochanteric osteotomy]. / Chirurgische Therapie des ischiofemoralen Impingements mittels lateralisierender intertrochantärer Korrekturosteotomie.

OBJECTIVE: Lateralizing, derotating intertrochanteric varus osteotomy to increase the ischiofemoral space to counter painful impingement of the lesser trochanter and the os ischium with resulting entrapment of quadratus femoris muscle. INDICATIONS: Symptomatic ischiofemoral impingement (IFI) caused by Coxa valga et antetorta, Coxa valga or Coxa antetorta, or a short femoral neck. CONTRAINDICATIONS: Anatomic configuration suggestive of IFI in asymptomatic patients. Symptomatic IFI caused by another underlying pathology. Valgus deformity of the knee. SURGICAL TECHNIQUE: Measurement of femoral antetorsion. Planning of the osteotomy, lateralization, varus angle for correction, rotation and offset correction, leg length change, and osteosynthesis plate. General or spinal anesthesia in supine or lateral position. Skin incision (15 cm) beginning lateral of the greater trochanter tip, distally along the axis of the femur. Preparation onto the femur by L­shaped dissection of the vastus lateralis from the bone. A Kirschner(K-)wire is then positioned along the anterior femoral neck to designate the femoral neck antetorsion. A triangle set on the lateral femoral cortexis is used to determine the osteotomy angle. In the thus determined angle, a second K­wire is shot centrally along the femoral neck axis just inferior to its cranial cortex. About 5 mm distal to the second wire, the entry for the blade is prepared using a drill. Using the blade setting instrument, the blade is introduced into the femoral neck, then slightly pulled back. The rotation is then marked on the anterior femoral cortex proximal and distal to the planned osteotomy and the osteotomy is performed. A blade plate without displacement is impacted. The osteotomy is then reduced, the distal fragment pulled laterally onto the plate, and the screws inserted after compression of the osteotomy with a tension device. POSTOPERATIVE MANAGEMENT: Touch-toe bearing for 6 weeks, then radiological assessment of osteotomy healing before an increase in weight bearing (15 kg/week). Hip flexion limited to 90° for 6 weeks. Elective implant removal after 12-18 months. RESULTS: Studies of this lateralizing varus osteotomy have not been published. The 25-year results of the conventional derotating intertrochanteric varus osteotomy technique show good functional results and low complication rates, with non-union being the most common. Arthroscopic resection of the lesser trochanter has been reported as a surgical alternative in the treatment of IFI in case reports and small series. Advantages of the osteotomy are the restoration of biomechanics and preservation of iliopsoas tendon insertion.

International consensus on the definition and classification of fibrosis of the knee joint.

AIMS: The aim of this consensus was to develop a definition of post-operative fibrosis of the knee. PATIENTS AND METHODS: An international panel of experts took part in a formal consensus process composed of a discussion phase and three Delphi rounds. RESULTS: Post-operative fibrosis of the knee was defined as a limited range of movement (ROM) in flexion and/or extension, that is not attributable to an osseous or prosthetic block to movement from malaligned, malpositioned or incorrectly sized components, metal hardware, ligament reconstruction, infection (septic arthritis), pain, chronic regional pain syndrome (CRPS) or other specific causes, but due to soft-tissue fibrosis that was not present pre-operatively. Limitation of movement was graded as mild, moderate or severe according to the range of flexion (90° to 100°, 70° to 89°, < 70°) or extension deficit (5° to 10°, 11° to 20°, > 20°). Recommended investigations to support the diagnosis and a strategy for its management were also agreed. CONCLUSION: The development of standardised, accepted criteria for the diagnosis, classification and grading of the severity of post-operative fibrosis of the knee will facilitate the identification of patients for inclusion in clinical trials, the development of clinical guidelines, and eventually help to inform the management of this difficult condition. Cite this article: Bone Joint J 2016;98-B:1479-88.

[Gluteal insufficiency: Pathogenesis, Diagnosis and Therapy]. / Gluteale Insuffizienz: Pathogenese, Diagnostik und Therapie.

INTRODUCTION: Gluteal insufficiency is a common and challenging complaint. New concepts in pathobiomechanics and improved clinical understanding of chronic gluteal dysfunction have unmasked gluteus medius (GMed) tears as an underlying cause of enhanced trochanteric pain syndrome (GTPS). These tears are often missed or misdiagnosed as bursitis, but lead to prolonged chronic peritrochanteric pain. Clinic: The clinical signs are often dull pain on the lateral hip aspect, reduced hip abduction strength with positive Trendelenburg testing and a tendency for the leg to external rotation, as the internal rotation strength is reduced. IMAGING: Radiography and ultrasound may be used to confirm the diagnosis, whereas MRI is the modality of choice for imaging. Compensatory hypertrophy of the tensor fascia latae muscle (TFL) and fatty involution (especially of the GMed) are also seen. THERAPY: Conservative treatment regimens for partial thickness tears involve hip joint centering and strengthening of abductor muscles, sparing TFL. Failed conservative treatment and full thickness tears are treated surgically. Partial tears can be addressed endoscopically with suture anchors for tendon footprint reconstruction. Larger tears involving the anterior and/or lateral facets of the tendon or failed conservative treatment are repaired with minimally invasive open reduction techniques. Double row suture anchor techniques provide anatomical tendon footprint reconstruction. Postoperative rehabilitation is prolonged, due to high acting forces in the peritrochanteric region, and needs to be carried out under professional surveillance. CONCLUSION: Reconstruction of gluteal tendon tears is often the only solution in the treatment of chronic hip pain due to gluteal insufficiency. Available data suggest that reduction in pain and restoration of abduction power can be achieved in mid-term follow-up.

[Hip arthroscopy]. / Hüftarthroskopie.

Hip arthroscopy represents an important component in the treatment of diseases of the hip joint and is nowadays an indispensible tool in modern hip-preserving surgery. This article provides a review of the basic technical principles, typical indications and complications of hip arthroscopy. Furthermore, current developments as well as possibilities and limitations of the arthroscopic technique are reviewed.

[Synovial biomarkers for differential diagnosis of painful arthroplasty]. / Synoviale Biomarker für die Differenzialdiagnostik der schmerzhaften Endoprothese.

BACKGROUND: The diagnosis and treatment of periprosthetic joint infection (PJI) remain true clinical challenges. PJI diminishes therapeutic success, causes dissatisfaction for the patient and medical staff, and often requires extensive surgical revision(s). At the present time, an extensive multimodal algorithmic approach is used to avoid time- and cost-consuming diagnostic aberrations. However, especially in the case of the frequent and clinically most relevant "low-grade" PJI, the current diagnostic "gold standard" has reached its limits. EVALUATION: Synovial biomarkers are thought to close this diagnostic gap, hopefully enabling the safe differentiation among aseptic, (chronic) septic, implant allergy-related and the arthrofibrotic genesis of symptomatic arthroplasty. Therefore, joint aspiration for obtaining synovial fluid is preferred over surgical synovial tissue biopsy because of the faster results, greater practicability, greater patient safety, and lower costs. In addition to the parameters synovial IL-6, CRP, and leukocyte esterase, novel biomarkers such as antimicrobial peptides and other proinflammatory cytokines are currently highlighted because of their very high to excellent diagnostic accuracy. CONCLUSION: Independent multicenter validation studies are required to show whether a set of different innovative synovial fluid biomarkers rather than a few single parameters is favorable for a safe "one-stop shop" differential diagnosis of PJI.

Function of the extensor mechanism of the knee after using the 'patellar-loop technique' to reconstruct the patellar tendon when replacing the proximal tibia for tumour.

The aim of this study was to analyse the gait pattern, muscle force and functional outcome of patients who had undergone replacement of the proximal tibia for tumour and alloplastic reconstruction of the extensor mechanism using the patellar-loop technique. Between February 1998 and December 2009, we carried out wide local excision of a primary sarcoma of the proximal tibia, proximal tibial replacement and reconstruction of the extensor mechanism using the patellar-loop technique in 18 patients. Of these, nine were available for evaluation after a mean of 11.6 years (0.5 to 21.6). The strength of the knee extensors was measured using an Isobex machine and gait analysis was undertaken in our gait assessment laboratory. Functional outcome was assessed using the American Knee Society (AKS) and Musculoskeletal Tumor Society (MSTS) scores. The gait pattern of the patients differed in ground contact time, flexion heel strike, maximal flexion loading response and total sagittal plane excursion. The mean maximum active flexion was 91° (30° to 110°). The overall mean extensor lag was 1° (0° to 5°). The mean extensor muscle strength was 25.8% (8.3% to 90.3%) of that in the non-operated leg (p < 0.001). The mean functional scores were 68.7% (43.4% to 83.3%) (MSTS) and 71.1 (30 to 90) (AKS functional score). In summary, the results show that reconstruction of the extensor mechanism using this technique gives good biomechanical and functional results. The patients' gait pattern is close to normal, except for a somewhat stiff knee gait pattern. The strength of the extensor mechanism is reduced, but sufficient for walking.

[Periprosthetic infections of the hip joint : Clinical approach]. / Periprothetischer Infekt des Hüftgelenks : Klinisches Vorgehen.

BACKGROUND: Increasing rates of periprosthetic joint infections (PJI) will present orthopedic surgeons and the health care system with challenges in the next few years. New concepts in diagnostic and surgical pathways allow specialized centers to offer differentiated therapy of PJI. AIM: This article presents an overview of recent treatment concepts for PJI of the hip emphasizing diagnosis and the clinical approach. METHOD: A selective literature search was performed focusing on evidence-based concepts including diagnostics, surgical treatment, and biofilm active antibiotics. RESULTS: PJI of the hip are classified as mature biofilm or immature biofilm infections. The most important step in the diagnostic procedure is to identify the pathogen and its antimicrobial susceptibility. Preoperative joint aspiration and leukocyte count, differentiation, and microbiological culture should be standard. Arthroscopic biopsy may be necessary to identify the pathogen. Depending on the biofilm maturity and the antimicrobial susceptibility, implant retention or two-stage revisions should be performed. Combination of surgical therapy and biofilm-active antibiotics are of utmost importance for successful treatment. DISCUSSION: PJI represents a significant challenge for the orthopedic surgeon. Evidence-based and standardized clinical pathways are necessary for accurate and rapid diagnosis as well as patient-specific treatment concepts.

[Sportsmen's groin. Definition, differential diagnostics and therapy]. / Sportlerleiste. Begriffsbestimmung, Differenzialdiagnostik und Therapie.

Groin pain in athletes is a common problem and can have extensive consequences for professional athletes. The anatomical and functional complexity of the groin as well as radiating pain from remote anatomical regions can make the differential diagnostic a challenge and requires special attention. As there are a wide variety of possible causes for groin pain, a multidisciplinary approach is required. The treating orthopedic surgeon needs to pay special attention to prearthritic hip deformities to avoid irreversible damage of the hip joint. By a meticulous patient history and identification of the pain character, followed by clinical, sonographic and radiographic investigations, a differential diagnosis can usually be achieved. Besides typical orthopedic causes pathological findings particularly in the area of the groin need to be considered, clarified and adequately treated; therefore, a clear terminology of the different diseases is necessary. Sportsmen's groin is not a hernia but should be perceived as a separate entity due to its typical pain character and detection of a measurable protrusion of the posterior wall of the inguinal canal by ultrasound.

[Greater trochanteric pain syndrome]. / Peritrochantäre Schmerzsyndrome.

Greater trochanteric pain is one of the common complaints in orthopedics. Frequent diagnoses include myofascial pain, trochanteric bursitis, tendinosis and rupture of the gluteus medius and minimus tendon, and external snapping hip. Furthermore, nerve entrapment like the piriformis syndrome must be considered in the differential diagnosis. This article summarizes essential diagnostic and therapeutic steps in greater trochanteric pain syndrome. Careful clinical evaluation, complemented with specific imaging studies and diagnostic infiltrations allows determination of the underlying pathology in most cases. Thereafter, specific nonsurgical treatment is indicated, with success rates of more than 90 %. Resistant cases and tendon ruptures may require surgical intervention, which can provide significant pain relief and functional improvement in most cases.

[Conservative treatment of chronic tendinopathies]. / Konservative Therapie der chronischen Enthesiopathien.

The majority of insertional and noninsertional tendinopathy cases are associated with repetitive or overuse injuries. Certain tendons are particularly vulnerable to degenerative pathology; these include the Achilles and patella tendon, the rotator cuff, and forearm extensors/flexors. Disorders of these tendons are often chronic and can be difficult to manage successfully in the long term. Eccentric exercise has the strongest evidence of therapeutic efficacy. Extracorporeal shock wave treatment, sclerosing agents as well as nitric oxide patches show promising early results but require long-term studies. Corticosteroid and nonsteroidal antiinflammatory medications have not been shown to be effective except for temporary pain relief for rotator cuff tendinopathy. Platelet-rich plasma injections show encouraging short-term results.

[Characteristics of 200 patients with suspected implant allergy compared to 100 symptom-free arthroplasty patients]. / Charakteristika von 200 Patienten mit Verdacht auf Implantatallergie im Vergleich zu 100 beschwerdefreien Endoprothesenträgern.

BACKGROUND: Data on implant allergies are incomplete; therefore, we compared the data on allergy history, patch test (PT) and lymphocyte transformation test (LTT) results in a patient series from the Munich implant allergy outpatient department with symptom-free arthroplasty patients. PATIENTS AND METHODS: In this study 200 arthroplasty patients with complaints involving the prosthesis (130 female, 187 knee and 13 hip prostheses) and in parallel 100 symptom-free patients (75 female, 47 knee and 53 hip prostheses) were investigated. A questionnaire-aided history including implant type, cementing, intolerance of dental materials, atopy, cutaneous metal intolerance (CMI) and PT, including a standard series with Ni, Co, Cr, seven bone cement components, including gentamicin and benzoyl peroxide and LTT for Ni, Co and Cr. RESULTS: In the knee arthroplasty patients with complaints 9.1% showed dental material intolerance, 23.5% atopy, 25.7% CMI, 18.2% metal allergies, 7.4% gentamicin allergy and 27.8% positive metal LTT (mostly to Ni). In symptom-free patients 0% showed dental material intolerance, 19.1% atopy, 12.8% CMI, 12.8% metal allergy, 0% gentamicin allergy and 17% positive metal LTT. CONCLUSIONS: Characteristics of the patients with complaints were increased intolerance of dental materials, higher rates of atopy, CMI, metal and gentamicin allergy and LTT reactivity.

[Conservative therapy of osteoarthritis]. / Konservative Therapie der Gonarthrose.

Osteoarthritis of the knee is a degenerative joint disease with progressive degradation of articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking and joint effusion depending on the stage of the disease. In an effort to delay major surgery, patients with knee osteoarthritis are offered a variety of nonsurgical modalities, such as weight loss, exercise, physiotherapy, bracing, orthoses, nonsteroidal anti-inflammatory drugs (NSAIDs) and intra-articular viscosupplementation or corticosteroid injection. In general, the goals of these therapeutic options are to decrease pain and improve function. Some of these modalities may also have a disease-modifying effect by altering the mechanical environment of the knee. Chondroprotective substances, such as lucosamine, chondroitin sulphate and hyaluronic acid are safe and provide short-term symptomatic relief while the therapeutic effects remain uncertain.

[Joint preserving surgery of the adult hip: pelvic osteotomies]. / Gelenkerhaltende Hüftchirurgie im Erwachsenenalter: Beckenosteotomien.

Deformity and malposition of the acetabulum can occur during the development of the hip. Developmental hip dysplasia and acetabular retroversion are possible causes of osteoarthritis in the young adult. Surgical management with reorientation of the acetabulum allows causal therapy of the deformity and preservation of the native hip joint. Established techniques are the Bernese periacetabular osteotomy (PAO) and the Tönnis and Kalchschmidt triple osteotomy of the pelvis. Both techniques permit three-dimensional correction of the position of the acetabulum. Advantages and disadvantages of each technique must be considered and are summarized in the present paper. If performed early (osteoarthritis grade Tönnis 0 and 1) with correct indication and proper technique, good results can be expected.

[Joint-preserving surgery of the adult hip. Intertrochanteric femoral osteotomy]. / Gelenkerhaltende Hüftchirurgie im Erwachsenenalter. Intertrochantäre Femurosteotomie.

Due to advances in total joint replacement, intertrochanteric osteotomy (ITO) is performed more infrequently in spite of good clinical results. Nevertheless, there are several good indications for this joint-preserving procedure in adults. Detailed biomechanical knowledge and precise clinical examination are prerequisites for correct indications and planning of ITO. The main target of this surgical procedure is improvement of joint congruency and normalization of load transfer to protect damaged cartilage. Very good results can be obtained in hip dysplasia, non-union of the femoral neck and proximal femoral deformities if the therapeutic principles are followed. Higher failure rates have to be expected in femoral head necrosis and osteoarthritis, depending on the degree of pre-existing cartilage damage.

[Proximal tibial replacement and alloplastic reconstruction of the extensor mechanism after bone tumor resection]. / Proximaler Tibiaersatz und alloplastische Rekonstruktion des Streckapparats nach Resektion kniegelenksnaher Tumoren.

OBJECTIVE: The goal of the operation is limb-sparing resection of tumors arising from the proximal tibia with adequate surgical margins and local tumor control. Implantation of a constrained tumor prosthesis with an alloplastic reconstruction of the extensor mechanism to restore painless joint function and loading capacity of the extremity. INDICATIONS: Primary bone and soft tissue sarcomas. Benign or semimalignant aggressive lesions. Metastatic disease (radiation resistance and/or good prognosis). CONTRAINDICATIONS: Poor physical status. Extensive metastatic disease with life expectancy <6 months. Tumor penetration through the skin. Local infection or recalcitrant osteomyelitis. Poor therapeutic compliance. Large popliteal extraosseous tumor masses with infiltration of neurovascular structures. SURGICAL TECHNIQUE: A single incision is made from the anteromedial aspect of the distal femur to the distal one third of the medial lower leg. Preparation of large medial and lateral fasciocutaneous flaps. The popliteal vessels are explored through a medial approach by releasing the pes anserinus and semimembranosus tendon, mobilizing the medial gastrocnemius muscle and detaching the soleus muscle from the tibial margo medialis. The anterior tibial artery and vein are ligated. If the knee joint is free of tumor, circumferential dissection of the knee capsule is performed and the patellar ligament is dissected. An osteotomy of the tibia shaft is performed with safety margins according to preoperative planning. In order to obtain adequate surgical margins, in some cases an en bloc resection of the tibiofibular joint becomes necessary. Therefore, the peroneal nerve is exposed. Parts of the M. tibialis anterior, a portion of the M. soleus and the entire M. popliteus are left on the resected tibial bone. After implantation of the prosthesis and coupling of the femoral and tibial component, the extensor mechanism is reconstructed using an alloplastic cord. It is passed transversely through the distal end of the quadriceps tendon looping the proximal margin of the patella. Both ends are passed distally through a subsynovial tunnel and are fixed under adequate pretension in a metal block of the tibial component. The detached hamstrings and remaining ligaments can be fixed on preformed eyes of the prosthesis. A medial gastrocnemius muscle flap is used to provide soft tissue coverage of the tibial component. POSTOPERATIVE MANAGEMENT: Immobilization and elevation of the extremity for 5 days, then flap conditioning. Mobilization in a hinged knee brace locked in extension for 6 weeks without weight bearing. During this time active flexion with a stepwise progress, isometric quadriceps training. Then beginning of straight leg raising exercises, stepwise unlocking of the brace with 30° every 2 weeks. Weight-bearing is increased by 10 kg/week. Thrombosis prophylaxis until full weight-bearing. At follow-up, patients are monitored for local recurrence and metastases using history, physical examination and radiographic studies. RESULTS: Between 1988 and 2009, endoprosthetic replacement and alloplastic reconstruction of the extensor mechanism after resection of tibial bone tumors was performed in 17 consecutive patients (9 females and 8 males) with a mean age of 31.1 years (range 11-65 years). There were no local recurrences. Until now, 5 patients have died of tumor disease. One or more operative revisions were necessary in 53.9% of the patients. According to Kaplan-Meier survival analysis, the implant survival at 5 years was 53.6% and 35.7% at 10 years, respectively. In 2 cases, a distal transfemoral amputation had to be performed due to deep infection. There were 3 cases of tibial stem revision due to implant failure and aseptic loosening, respectively. In 3 patients, the hinge of the prosthesis had to be revised. Impaired wound healing occurred in 2 cases. Peroneal nerve palsy was observed in 3 patients with recovery in only one. The mean Oxford knee score for 9 of the 12 living patients was 30.7 ± 7.5 (24-36). No patient had a clinically relevant extension lag. The mean range of motion at the last follow-up was 90.2° ± 26.7 (range 35-130°). All patients were well satisfied with their postoperative outcomes.