Influence of kinematic alignment on femorotibial kinematics in medial stabilized TKA design compared to mechanical alignment.

INTRODUCTION: Worldwide more and more primary knee replacements are being performed. Kinematic alignment (KA) as one of many methods of surgical alignment has been shown to have a significant impact on kinematics and function. The aim of the present study was to compare KA and mechanical alignment (MA) with regard to femorotibial kinematics. MATERIALS AND METHODS: Eight fresh frozen human specimens were tested on a knee rig during active knee flexion from 30 to 130°. Within the same specimen a medial stabilized (MS) implant design was used first with KA and then with MA. RESULTS: The femorotibial kinematics showed more internal rotation of the tibia in KA compared to MA. At the same time, there was a larger medial rotation point in KA. Both alignment methods showed femoral rollback over the knee bend. CONCLUSION: Relating to an increased internal rotation and a more precise medial pivot point, it can be concluded that KA combined with a MS implant design may partially support the reproduction of physiological knee joint mechanics.

A systematic review and meta-analysis on the value of the external rotation stress test under fluoroscopy to detect syndesmotic injuries.

Purpose: The aim was to conduct a systematic literature review and meta-anaylsis to analyze the diagnostic accuracy of the external rotation stress test (ERST) for syndesmotic injuries. Methods: The systematic review was conducted according to the PRISMA-P guidelines (Prospero ID: CRD42021282457). Four common databases were searched from inception to September 29, 2021. Eligible were any studies facilitating the ERST under fluoroscopy in a defined state of syndesmotic instability. Syndesmotic ligament-specific rupture must have been proven by MRI, arthroscopy, or controlled dissection (cadaver study). Two reviewers independently conducted each step of the systematic literature review. The risk of bias was assessed by the Quality Appraisal for Cadaveric Studies Score scale. The data analysis was performed qualitatively and quantitatively. Results: Eight studies were eligible for a qualitative analysis, and six studies were eligible for a quantitative analysis. All studies included were cadaver studies. The qualitative analysis comprised 94 specimens and revealed considerable heterogeneity. Six studies allowed for a quantitative analysis of the tibiofibular clear space (TFCS) and five studies for the medial clear space (MCS) during the ERST. The quantitative analysis of the TFCS revealed no significant differences between intact and any stage of syndesmotic injury. The MCS was able to differentiate between intact and 2-ligament- (Z = 2.04, P = 0.02), 3-ligament- (Z = 3.2, P = 0.001), and 3-ligament + deltoid ruptures (Z = 3.35, P < 0.001). Conclusion: The ERST is the only noninvasive test to assess syndesmotic instability and can be conducted bilaterally. The uninjured contralateral side can serve as a baseline reference. Based on the conducted quantitative analysis, the MCS seems to be able to differentiate between stable (intact/1-ligament) and unstable (2-ligament/3-ligament) lesions.

Conversion hip arthroplasty via the direct anterior approach: pearls, pitfalls and personal experience.

OBJECTIVE: Conversion total hip arthroplasty (CTHA) through a direct anterior approach (DAA) in supine position. INDICATIONS: Failed osteosynthesis of proximal femoral fractures or failed conservative hip surgery, with hardware in situ. CONTRAINDICATIONS: Decayed general conditions, infection (peri-implant or systemic infection), need for greater trochanter reconstruction, severe proximal femur deformity. SURGICAL TECHNIQUE: Supine position. Mark DAA and expected limited incisions for hardware removal (HR) with the help of a C-arm. Use guidewire and extraction devices for HR. Perform a DAA with particular attention to a wide release of the femur. POSTOPERATIVE MANAGEMENT: Full progressive weight-bearing starting on day 1, depending on bone quality. Discharge with crutches following patient walking capability. Precautions for 6 weeks. RESULTS: In all, 27 conversion THAs through a DAA. Mean age at the time of surgery 59.8 (range 18-81) years. Mean body mass index was 23.5 (range 17-31.6). Reasons of previous surgery failures were avascular necrosis of the femoral head, posttraumatic arthritis and nonunion with or without hardware migration. Mean surgical time was 125.8 min (range 58-190 min, standard deviation [SD] 38.2 min). Mean follow-up time was 6.9 years (range 2-15, SD 5.03 years). Mean pre-Harris Hip Score (mHHs) was 24.4 (range 19-36, SD 5.4), while the mean post-mHHS was 90.3 (range 89-91, SD 0.95). Two patients required postoperative osteosynthesis for periprosthetic fractures due to falls. Overall complication rate was 10%.

Immune and stem cell compartments of acetabular and femoral bone marrow in hip osteoarthritis patients.

OBJECTIVE: Hip osteoarthritis (OA) affects all components of the osteochondral unit, leading to bone marrow (BM) lesions, and unknown consequences on BM cell functionality. We analyzed the cellular composition in OA-affected acetabula compared to proximal femur shafts obtained of hip OA patients to reveal yet not explored immune and stem cell compartments. DESIGN: Combining flow cytometry, cellular assays and transcription analyses, we performed extensive ex vivo phenotyping of acetabular BM cells from 18 hip OA patients, comparing them with their counterparts from patient-matched femoral shaft BM samples. Findings were related to differences in skeletal sites and age. RESULTS: Acetabular BM had a greater frequency of T-lymphocytes, non-hematopoietic cells and colony-forming units fibroblastic potential than femoral BM. The incidence of acetabular CD45+CD3+ T-lymphocytes increased (95% CI: 0.1770 to 0.0.8416), while clonogenic hematopoietic progenitors declined (95% CI: -0.9023 to -0.2399) with age of patients. On the other side, in femoral BM, we observed higher B-lymphocyte, myeloid and erythroid cell frequencies. Acetabular mesenchymal stromal cells (MSCs) showed a senescent profile associated with the expression of survival and inflammation-related genes. Efficient osteogenic and chondrogenic differentiation was detected in acetabular MSCs, while adipogenesis was more pronounced in their femoral counterparts. CONCLUSION: Our results suggest that distinctions in BM cellular compartments and MSCs may be due to the influence of the OA-stressed microenvironment, but also acetabular vs femoral shaft-specific peculiarities cannot be excluded. These results bring new knowledge on acetabular BM cell populations and may be addressed as novel pathogenic mechanisms and therapeutic targets in OA.

[Scaffold-based Bone Tissue Engineering]. / Gerüstträgerbasiertes Knochen-Tissue-Engineering.

Tissue engineering provides the possibility of regenerating damaged or lost osseous structures without the need for permanent implants. Within this context, biodegradable and bioresorbable scaffolds can provide structural and biomechanical stability until the body's own tissue can take over their function. Additive biomanufacturing makes it possible to design the scaffold's architectural characteristics to specifically guide tissue formation and regeneration. Its nano-, micro-, and macro-architectural properties can be tailored to ensure vascularization, oxygenation, nutrient supply, waste exchange, and eventually ossification not only in its periphery but also in its center, which is not in direct contact with osteogenic elements of the surrounding healthy tissue. In this article we provide an overview about our conceptual design and process of the clinical translation of scaffold-based bone tissue engineering applications.

Bicompartmental individualized knee replacement : Use of patient-specific implants and instruments (iDuo™).

OBJECTIVE: Bicompartmental knee replacement in patients with combined osteoarthritis (OA) of the medial or lateral and patellofemoral compartment. Patient-specific instruments and implants (ConforMIS iDuo™) with a planning protocol for optimal implant fit. INDICATIONS: Bicompartmental OA of the knee (Kellgren & Lawrence stage IV) affecting both the medial or lateral and patellofemoral compartment after unsuccessful conservative or joint-preserving surgery. CONTRAINDICATIONS: Tricompartmental OA, knee ligament instabilities, knee deformities >15° (varus, valgus, extension deficit). Relative contraindication: body mass index >40; prior unicompartmental knee replacement or osteotomies. SURGICAL TECHNIQUE: Midline or parapatellar medial skin incision, medial arthrotomy; identify mechanical contact zone of the intact femoral condyle (linea terminalis); remove remaining cartilage and all osteophytes that may interfere with the correct placement of the individually designed instruments. Balance knee in extension with patient-specific balancing chips. Resection of proximal tibia with an individual cutting block; confirm axial alignment using an extramedullary alignment guide, balance flexion gap using spacer blocks in 90° flexion. Final femur preparation with resection of the anterior trochlea. After balancing and identification of insert heights, final tibial preparation is performed. Implant is cemented in 45° of knee flexion. Remove excess cement and final irrigation, followed by closure. POSTOPERATIVE MANAGEMENT: Sterile wound dressing; compressive bandage. No limitation of active/passive range of motion (ROM). Partial weight bearing the first 2 weeks, then transition to full weight bearing. Follow-up directly after surgery, at 12 and 52 weeks, then every 1-2 years. RESULTS: In all, 44 patients with bicompartmental OA of the medial and patellofemoral compartment were treated. Mean age 59 years. Minimum follow-up 12 months. Implant converted to TKA due to tibial loosening (1 patient); patella resurfacing (3 patients). No further revisions or complications. Radiographic analyses demonstrated ideal fit of the implant with less than 2 mm subsidence or overhang. KSS pain scores improved from preoperatively 5.7 to 1.7 postoperatively with level walking, and from 7.3 preoperatively to 2.8 postoperatively with climbing stairs or inclines. The WOMAC score improved from preoperatively 43 to 79 postoperatively.

[Individualized unicondylar knee replacement : Use of patient-specific implants and instruments]. / Individualisierte unikondyläre Kniegelenkendoprothetik : Einsatz patientenspezifischer Implantate und Instrumente.

OBJECTIVE: Unicompartmental knee replacement in patients with osteoarthritis (OA) of the medial compartment. Individualized instruments and implants with a planning protocol for optimal fit. The individualized instruments and implants (ConforMIS Inc.; Burlington, MA, USA) are manufactured based on a computed tomography scan of the affected lower extremity and are provided together with a planning protocol (iView®) of the surgery. INDICATIONS: Unicompartmental OA of the knee (Kellgren & Lawrence stage IV) or Morbus Ahlbäck after unsuccessful conservative or joint preserving surgery. CONTRAINDICATIONS: Bi- or tricompartmental OA, knee ligament instabilities, knee deformities >15° (varus, valgus, extension deficit). Relative contraindication: body mass index >40. SURGICAL TECHNIQUE: Limited medial arthrotomy, identification of mechanical contact zone of the femoral condyle (linea terminalis); removal of remaining cartilage and all osteophytes that may interfere with the correct placement of the individually designed instruments. Balancing of knee in extension using patient-specific balancing chips of incremental heights. Resection of tibia with a fitted individualized tibial cutting block; confirmation of axial alignment with an extramedullary alignment tower; balancing flexion gap using spacer blocks in 90° flexion. Final femur preparation with the individual cutting instruments. Final tibial preparation with an individual drill jig for the placement of cavities fitting the cement pegs of the prosthesis. Lavage, cementing of implants in 45° of knee flexion, removal of excess cement, and wound closure. POSTOPERATIVE MANAGEMENT: Sterile wound dressing, compressive bandage. Unlimited active/passive range of motion. Functional rehabilitation with partial weight bearing first 2 weeks, then transition to full weight bearing. Clinical/radiographic follow-up directly after surgery, at 12 and 52 weeks, then every 1-2 years. RESULTS: In all, 31 patients with medial OA (27 medial knee osteoarthritis, 4 osteonecrosis) were treated. Mean age 60 years. Minimum follow-up 17 months. One aseptic loosening needed exchange; one acute late-onset infection with consecutive implant removal. No further revisions/reoperations or complications. X-rays showed an ideal fit of the implant with less than 2 mm subsidence or overhang in all cases. Clinically the VAS changed from 6.51 preoperatively to 1.11 postoperatively. The mean KSS (Knee Society Score) improved from 111.23 preoperatively to 180.61 postoperatively; the functional part of KSS improved from mean 60.39 to 94.51.

Acetabular defect classification in times of 3D imaging and patient-specific treatment protocols.

Parallel to the rising number of revision hip procedures, an increasing number of complex periprosthetic osseous defects can be expected. Stable long-term fixation of the revision implant remains the ultimate goal of the surgical protocol. Within this context, an elaborate preoperative planning process including anticipation of the periacetabular defect form and size and analysis of the remaining supporting osseous elements are essential. However, detection and evaluation of periacetabular bone defects using an unsystematic analysis of plain anteroposterior radiographs of the pelvis is in many cases difficult. Therefore, periacetabular bone defect classification schemes such as the Paprosky system have been introduced that use standardized radiographic criteria to better anticipate the intraoperative reality. Recent studies were able to demonstrate that larger defects are often underestimated when using the Paprosky classification and that the intra- and interobserver reliability of the system is low. This makes it hard to compare results in terms of defects being studied. Novel software tools that are based on the analysis of CT data may provide an opportunity to overcome the limitations of native radiographic defect analysis. In the following article we discuss potential benefits of these novel instruments against the background of the obvious limitations of the currently used native radiographic defect analysis.

Periosteum tissue engineering in an orthotopic in vivo platform.

The periosteum plays a critical role in bone homeostasis and regeneration. It contains a vascular component that provides vital blood supply to the cortical bone and an osteogenic niche that acts as a source of bone-forming cells. Periosteal grafts have shown promise in the regeneration of critical size defects, however their limited availability restricts their widespread clinical application. Only a small number of tissue-engineered periosteum constructs (TEPCs) have been reported in the literature. A current challenge in the development of appropriate TEPCs is a lack of pre-clinical models in which they can reliably be evaluated. In this study, we present a novel periosteum tissue engineering concept utilizing a multiphasic scaffold design in combination with different human cell types for periosteal regeneration in an orthotopic in vivo platform. Human endothelial and bone marrow mesenchymal stem cells (BM-MSCs) were used to mirror both the vascular and osteogenic niche respectively. Immunohistochemistry showed that the BM-MSCs maintained their undifferentiated phenotype. The human endothelial cells developed into mature vessels and connected to host vasculature. The addition of an in vitro engineered endothelial network increased vascularization in comparison to cell-free constructs. Altogether, the results showed that the human TEPC (hTEPC) successfully recapitulated the osteogenic and vascular niche of native periosteum, and that the presented orthotopic xenograft model provides a suitable in vivo environment for evaluating scaffold-based tissue engineering concepts exploiting human cells.

[Treatment of acetabular bone defects in revision hip arthroplasty using the Revisio-System]. / Defektadaptierte Versorgung azetabulärer Knochendefekte mit dem Revisio-System.

BACKGROUND: Many different systems for the management of primary and secondary acetabular defects are available, each with its inherent advantages and disadvantages. The Revisio-System is a press-fit oval mono-block implant that makes a defect-oriented reconstruction and restoration of the center of rotation possible. MATERIAL AND METHODS: In this study, we retrospectively reviewed the outcome of 92 consecutive patients treated with this oval press-fit cup due to periacetabular bone loss. The average follow-up was 58.2 months. Defects were classified according to D'Antonio. There were 39 type II, 38 Type III, and 15 type IV defects. After an average of 4.9 years, the implant survival rate was 94.6% with cup revision as the end point and 89.1% with revision for any reason as the end point. The Harris Hip Score increased from 41.1 preoperatively to 62.3 postoperatively. The mean level of pain measured with the Visual Analogue Scale (VSA) was reduced from 6.9 preoperatively to 3.8 postoperatively. RESULTS: The Revisio-System represents a promising toolbox for defect-orientated reconstruction of acetabular bone loss in revision hip arthroplasty. Our results demonstrate that the implantation of the Revisio-System can result in a good mid-term clinical outcome.

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.

Impaction bone grafting for the reconstruction of large bone defects in revision knee arthroplasty.

OBJECTIVE: Regeneration of autologous bone stock and formation of a stable implant bed by impaction of morselized bone allograft. INDICATIONS: Bone loss after septic and aseptic loosening or tumour resection. CONTRAINDICATIONS: Persistent infection, one-stage septic revision, poor therapeutic compliance, extensive uncontained metaphyseal defects with cortical thinning of the diaphysis. SURGICAL TECHNIQUE: Whilst the surgeon removes the loose prosthesis, the assistant prepares the graft. The medullary canal is sealed with a cement restrictor. Graft particles of different sizes are densely impacted around a trial stem. The highest level of stability is achieved by using large particles interspersed with small filler particles. Low-viscosity cement facilitates cement penetration and ensures strong interdigitation with the impacted graft mass after implantation of the prosthesis. Uncontained metaphyseal defects are treated with prosthetic augments. POSTOPERATIVE MANAGEMENT: Gait training, physiotherapy with isometric quadriceps exercises, partial weight-bearing for 6 weeks, resistance training begins 8 weeks postoperatively. RESULTS: Between 2010 and 2012, 28 patients with large bone defects [Anderson Orthopaedic Research Institute (AORI) grade: 21 × F3, 3 × F2, 13 × T3, 8 × T2] underwent total knee revision with impaction bone grafting. The mean follow-up was 27.7 months (range 21-47 months). On average, patients had undergone 2.5 previous revisions. Implant survival was 82.0 % (95 % CI = 62.5 %-92.1 %) for any reason of revision as the endpoint and 93.1 % (95 % CI = 74.5-98.4 %) for aseptic revision as the endpoint. The mean postoperative Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score was 35.4 (range 3.3-101.6, SD ± 26.2). The mean KSS was 70.6 (range 20-100, SD ± 26.8).

[The distally based adipofascial sural artery flap for the reconstruction of distal lower extremity defects]. / Der distal gestielte adipofasziale Suralislappen zur Rekonstruktion von Defekten der distalen unteren Extremität.

OBJECTIVE: Problematic tissue defects in the distal one-third of the lower leg represent a special challenge for the operative therapy. The distally based adipofascial sural artery flap is a safe and effective modification of the classical fasciocutaneous sural artery flap technique and makes the reconstruction in this problematic area more feasible. The surgical aim is soft tissue reconstruction with local tissue avoiding free tissue transfer. INDICATIONS: Complex or chronic wounds (maximum width of 8 cm) of the distal lower leg with exposed bone, joints, tendons, and/or neurovascular structures, especially in cases of missing skin perforators. CONTRAINDICATIONS: Arterial vascular disease (stage III-IV), especially peroneal artery occlusion. Postthrombotic syndrome with occlusion of the small saphenous vein. Chronic lymphedema. SURGICAL TECHNIQUE: Preparation of the vascular pedicle of the distally based flap (including small saphenous vein, sural artery and nerve), the adjacent crural fascia and the subcutaneous fat without a skin island. The pivot point is about 6 cm cranial to the malleolus lateralis. The flap can be raised proximally up to the heads of the gastrocnemius muscle. After harvesting the flap there will be a change in blood flow direction in the small saphenous vein. The donor site can be closed primarily. The flap is covered with meshed split skin graft at the end of surgery. POSTOPERATIVE MANAGEMENT: Strict elevation of the extremity for 5 days, then flap conditioning. RESULTS: Between 1997 and 2012, this technique was used in 104 consecutive patients with soft tissue defects in the distal one-third of the lower leg. Flap survival was achieved 91 patients. In 2 patients amputation of the lower leg was necessary at the mid tibia level. In 3 cases flap necrosis occurred, requiring free tissue transfer.

[Open biopsy of bone and soft tissue tumors : guidelines for precise surgical procedures]. / Offene biopsie von knochen- und weichteiltumoren : richtlinien für ein korrektes chirurgisches vorgehen.

OBJECTIVE: The objective of an open biopsy is to obtain a sufficient amount of representative tumor tissue in terms of adequate quality and quantity, without adverse effects on later therapy. INDICATIONS: Suspected malignancy after non-invasive diagnostic procedures. Histopathologic evaluation of tumor entity and grading. Planning of the definitive tumor resection and initiation of neoadjuvant therapeutic regimen. Obtaining unfixed, fresh-frozen tumor samples for molecular/genetic analyses or tumor tissue bank. CONTRAINDICATIONS: Hemorrhagic diathesis. Tumor is only accessible with a surgical approach leading to a significant damage of the surrounding tissue. High probability of tumor cell contamination with incisional biopsy. Poor physical status. Poor therapeutic compliance. SURGICAL TECHNIQUE: The biopsy tract should be carefully planned according to oncological principles. The operation begins with a small incision in longitudinal direction to the extremity. The shortest path between skin and lesion that avoids contamination of other compartments is selected. The biopsy tract should be located within the surgical approach which is later used for definitive tumor resection. During the definitive procedure it should be possible to resect the biopsy approach with adequate surgical margins because it is considered to be contaminated with tumor cells. In principle, a wide resection of the biopsy tract should be possible. During the operation meticulous hemostasis has to be performed because any hematoma around a tumor may contaminate the entire extremity. In cases of an intraosseous tumor a cortical window should be made to obtain intramedullary tumor tissue. Drains should be located in continuity with the skin incision or in direct extension of the wound. Wound closure with intracutaneous suture technique. Excisional biopsy in terms of marginal resection should be performed only in the presence of small, epifascial lesions that are assumed to be benign after completion of basic diagnostic procedures. In cases of larger or subfascial tumors an incisional biopsy should be conducted. POSTOPERATIVE MANAGEMENT: Compressive dressing to prevent postoperative hematoma. In cases of tumors affecting load-bearing bones, weight-bearing should be prohibited after biopsy, if there is any fracture risk. Upon receipt of the histopathological results the definitive tumor resection is planned.

[Tumors of the foot: diagnostics and therapy]. / Fußtumoren: Diagnostik und Therapie.

Despite the compact anatomy with thin soft tissue coverage, diagnosis of both benign and malignant tumors of the foot is often delayed. Diagnostic errors are more common than in other body regions, as neoplasias are rarely considered. Barring a few exceptions the foot is not a typical predilection site for malignant musculoskeletal tumors, although, basically any tumor entity of the musculoskeletal system can affect the foot. Delays in specific diagnostic and therapeutic procedures of these lesions can entail serious consequences for patients as tumor size is a major prognostic factor for recurrence-free survival. In cases of an indistinct persistent swelling or bone lesion a tumorous process should always be considered to ensure early diagnosis and therapy of foot tumors.

[Partial pelvic resection (internal hemipelvectomy) and endoprosthetic replacement in periacetabular tumors]. / Beckenteilresektion (innere Hemipelvektomie) und endoprothetischer Ersatz bei hüftgelenksnahen Tumoren.

OBJECTIVE: Treatment of tumors of the pelvic girdle by resection of part or all of the innominate bone with preservation of the extremity. Implantation and stable fixation using a custom-made megaprosthesis to restore painless joint function and loading capacity. The surgical goal is to obtain a wide surgical margin and local tumor control. INDICATIONS: Primary bone and soft tissue sarcomas, benign or semi-malignant aggressive lesions, metastatic disease (radiation resistance and/or good prognosis). CONTRAINDICATIONS: Limited life expectancy and poor physical status, extensive metastatic disease, persistent deep infection or recalcitrant osteomyelitis, poor therapeutic compliance, local recurrence following a previous limb-sparing resection, extensive infiltration of the neurovascular structures and the intra- and extrapelvic soft tissues. SURGICAL TECHNIQUE: Levels of osteotomy are defined preoperatively by a CT-controlled manufactured three-dimensional 1:1 model of the pelvis. Using these data, the custom-made prosthesis and osteotomy templates are then constructed by the manufacturer. The anterior (internal, retroperitoneal) and posterior (extrapelvic, retrogluteal) aspects of the pelvis are exposed using the utilitarian incision surgical approach. The external iliac and femoral vessels are mobilized as they cross the superior pubic ramus. The adductor muscles, the rectus femoris and sartorius muscle are released from their insertions on the pelvis and the obturator vessels and nerve are transected. If the tumor extends to the hip joint, the femur is transected at a level distal to the intertrochanteric line to ensure hip joint integrity and to prevent tumor contamination. A large myocutaneous flap with the gluteus maximus muscle is retracted posteriorly. The pelvitrochanteric and small gluteal muscles are divided near their insertion in the upper border of the femur. To release the hamstrings and the attachment of the sacrotuberous ligament, the ischial tuberosity is exposed. After osteotomy using the prefabricated templates, the pelvis is released and the specimen is removed en bloc. The custom made prosthesis can either be fixed to the remaining iliac bone or to the massa lateralis of the sacrum. The released muscles are refixated on the remaining bone or the implant. POSTOPERATIVE MANAGEMENT: Time of mobilization and degree of weight-bearing depends on the extent of muscle resection. Usually partial loading of the operated limb with 10 kg for a period of 6-12 weeks, then increased loading with 10 kg per week. Thrombosis prophylaxis until full weight bearing. Physiotherapy and gait training. At follow-up, patients are monitored for local recurrence and metastases using history, physical examination, and radiographic studies. RESULTS: Between 1994 and 2008, 38 consecutive patients with periacetabular tumors were treated by resection and reconstruction with a custom-made pelvic megaprosthesis. The overall survival of the patients was 58% at 5 years and 30% at 10 years. One or more operative revisions were performed in 52.6% of the patients. The rate of local recurrence was 15.8%. Deep infection (21%) was the most common reason for revision. In two of these cases (5.3%), a secondary external hemipelvectomy had to be performed. There were four cases of aseptic loosening (10.5%) in which the prosthesis had to be revised. Six patients had recurrent hip dislocation (15.8%). In four of them a modification of the inserted inlay and an implantation of a trevira tube had to be performed respectively. Peroneal palsy occurred in 6 patients (15.8%) with recovery in only two. There were 4 operative interventions because of postoperative bleeding (10.5%). The mean MSTS score for 12 of the 18 living patients was 43.7%. In particular, gait was classified as poor and almost all patients were reliant on walking aids. However, most patients showed good emotional acceptance.

[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.

[Nerve lesions after minimally invasive total hip arthroplasty]. / Nervenläsionen nach minimal-invasiver Hüftendoprothetik.

Although there is no clear evidence, minimally invasive hip arthroplasty seems to be associated with slightly higher complication rates compared to standard procedures. Major nerve palsy is one of the least common but most distressing complications. The key for minimizing the incidence of nerve lesions is to analyze preoperative risk factors, accurate knowledge of the anatomy and minimally invasive techniques. Once clinical signs of nerve injury are evident, the first diagnostic steps are localization of the lesion and quantification of the damage pattern. Therefore, clinical assessment of the neurological deficits should be performed as soon as possible. Apart from rare cases of isolated transient conduction blockade or complete transection, the damage pattern is mostly combined. Thus, there can be evidence for dysfunction of nerve conduction (neuropraxia) and structural nerve damage (axonotmesis or neurotmesis) simultaneously. Because the earliest signs of denervation are detectable via electromyography after 1 week, it is not possible to make any reliable prognosis within the first days after nerve injury using electrophysiological methods. This review article should serve as a guideline for prevention, diagnostics and therapy of neural lesions in minimally invasive hip arthroplasty.