Search

Osteonecrosis of the femoral head or avascular necrosis of the femoral head (HKN) is a complex disease that, without treatment, leads to infraction of the femoral head in most cases. In these cases, only replacement of the hip joint will help, although there is no clear recommendation of an arthroplasty type. In the last two decades, the treatment of primary and secondary coxarthrosis with short-shaft prostheses with different anchoring philosophies has increased. Since short-shaft fitting is a possible option especially in younger patients, the question arises about possible fittings of advanced HKN with these stem types, especially with metaphyseal anchorage. The aim of this study was to review the existing literature on the results of short stem prosthesis in HKN and to present the advantages and disadvantages of short stem prosthesis in osteonecrosis of the femoral head.This review analyzes the existing studies on short stem arthroplasty for HKN.Only a few studies exist that have analyzed clinical and radiologic outcomes of short stem replacement in HKN.The existing short- and medium-term results show mostly good outcomes. However, it is difficult to draw a general conclusion due to differences in stem design and fixation. Short stems with primary diaphyseal fixation do not show an increased risk of failed osseointegration or loosening. Constructions with primary metaphyseal fixation should undergo MRI to rule out the possibility of necrosis extending beyond the femoral neck.EINLEITUNG: Die Hüftkopfnekrose oder avaskuläre Nekrose des Hüftkopfes (HKN) ist eine komplexe Erkrankung, die ohne Behandlung in den meisten Fällen zu einer Infraktion des Femurkopfes führt. In diesen Fällen hilft nur noch ein Ersatz des Hüftgelenkes, wobei es keine eindeutige Empfehlung eines Endoprothesentyps gibt. In den letzten beiden Jahrzehnten hat die Versorgung der primären und sekundären Koxarthrose mit Kurzschaftprothesen mit unterschiedlichen Verankerungsphilosophien zugenommen. Da gerade bei jüngeren Patienten eine Kurzschaftversorgung eine mögliche Option ist, stellt sich die Frage nach möglichen Versorgungen der fortgeschritten HKN mit diesen Schafttypen, insbesondere mit einer metaphysären Verankerung. Ziel dieser Studie war es, die vorhandene Literatur zu den Ergebnissen der Kurzschaftprothese bei HKN zu überprüfen und die Vor- und Nachteile der Kurzschaftprothese bei Osteonekrose des Hüftkopfes darzustellen.Diese Übersichtsarbeit analysiert die vorhandenen Studien zur Kurzschaftversorgung bei HKN.Es existieren nur wenige Studien, die klinische und radiologische Ergebnisse bei einer Kurzschaftversorgung bei HKN analysiert haben.Die kurz- bis mittelfristigen Ergebnisse zeigen überwiegend gute Ergebnisse. Aufgrund von Unterschieden im Design der Kurzschäfte und ihrer Fixierung ist es jedoch schwierig, eine allgemeine Schlussfolgerung zu ziehen. Kurzschäfte mit primärer diaphysärer Fixierung weisen kein erhöhtes Risiko einer fehlgeschlagenen Osseointegration oder Lockerung auf. Bei Konstruktionen mit einer primären metaphysären Verankerung sollte eine MRT durchgeführt werden, um auszuschließen, dass die Nekrose über den Schenkelhals hinausragt.

Kinematic alignment is a philosophy for individual knee prosthesis implantation in a three-dimensional view. The key of the concept is to understand the femoral flexion-extension axis as the centre of a cylinder within the posterior condyles. This axis defines the knee in three dimensions over the entire range of motion. The tibia follows the femur, is balanced on the knee in extension and flexion, and shows individual laxities in flexion and deep flexion.As a consequence, limbs will be reconstructed along their constitutional leg axis, which in most patients is different to a straight hip-knee-ankle centre axis. The method aims at perfectly reconstructing the natural joint lines, which in many patients leads to the natural oblique joint lines. This results in considerable advantages, as the natural stability of the knee is restored, and native patella kinematics are maintained. From a static view, polyethylene and the implant-bone interface may be vulnerable to mechanical overloading due to altered adductor moments. However, a growing body of evidence shows that naturally oriented knee joints show a more balanced loading pattern. Moreover, dynamic gait patterns actually show the mechanism of even reduced knee adductor moments, explaining the clinical results of up to 10 years follow up.HINTERGRUND: Das kinematische Alignment ist eine Philosophie zur individuellen Knieprothesenimplantation in einer dreidimensionalen Betrachtung. Der Kern des Konzeptes ist das Verständnis der femoralen Flexions-Extensions-Achse als Zentrum eines Zylinders in den posterioren Kondylen. Diese Achse definiert das Knie dreidimensional über den gesamten Bewegungsablauf. Die Tibia folgt dem Femur, ist in Extension und Flexion auf das Knie balanciert, zeigt in Flexion und tiefer Flexion dann individuelle Laxitäten, häufig mit einer asymmetrisch lateral laxeren Einstellung als medial.Als Konsequenz zeigt sich eine konstitutionelle Beinachse, die von der klassischen mechanischen Achse abweicht. Als wesentliche weitere Konsequenz wird die natürliche Gelenklinie exakt rekonstruiert. Dieses ergibt erhebliche Vorteile, da die natürliche Stabilität des Knies wiederherstellt wird und gleichzeitig eine natürliche patellare Gleitkinematik erlaubt wird. Aktuell ist nicht gänzlich geklärt, inwieweit sich Konsequenzen aus extremer Achseinstellung und Interaktion mit Gelenklinienabweichungen ergeben. Das Polyethylen als tribologisches Material und das Implantat-Knochen-Interface sind gegenüber Überlastungen vulnerabel und bedeuten möglicherweise verkürzte Standzeiten. Der menschliche Organismus verfügt jedoch offensichtlich über dynamische Mechanismen zur Reduktion des Adduktorenmomentes mit Anpassung des Gangbildes. Klinische Erfahrungen über 10 Jahre und multiple randomisierte Studien zeigen neben dem deutlichen funktionellen Vorteil der Methode keine Hinweise auf frühzeitiges Versagen und lassen die vorsichtige Verbreitung der Methode als sinnvoll erscheinen.

Treatment of pathologies of the central and peripheral compartment of the hip using arthroscopic assisted mini-open arthrotomy via the Smith-Petersen approach.Cam- and pincer-type femoroacetabular impingement (FAI), labral tear, loose bodies.Osteoarthritis of the hip with Tönnis classification grade ≥ 2.After mini-open approach to the hip joint via direct anterior muscular gap, the anterior capsule is split with protection of the labrum. Decompression allows the joint to be inspected using an arthroscope. Depending on the intra-articular findings, additional procedures can be performed (e.g., curettage of the cartilage, microfracturing, matrix-induced autologous chondrocyte implantation [MACI]). Cases with pincer-type FAI or labral tear can also be addressed. After partial release, the cam-type FAI can be resected using a surgical burr.Partial weightbearing for 2-6 weeks with 10-20 kg or half body weight using crutches depending on the intraoperative treatment.Radiological analysis of the pre- and postoperative X‑rays (n = 69) prove that this surgical technique is suitable to address pathologies especially FAI syndromes. The α‑angle according to Nötzli could be reduced from a mean preoperative value of 72.8° to 49.4° postoperative. In combined cam-type and Pincer-type FAI syndrome (n = 16), the lateral center-edge angle could be reduced from a mean preoperative value of 50.2° to 37.6° postoperatively. The clinical follow-up (n = 29) revealed good midterm outcomes after arthroscopic assisted mini-open arthrotomy (modified Harris Hip Score [mHHS] 84.8 points after 4.9 years [range 4.2-5.7; ±0.43]).OPERATIONSZIEL: Therapie von Pathologien des zentralen und peripheren Kompartiments des Hüftgelenks über eine arthroskopisch assistierte Mini-open-Arthrotomie via Smith-Petersen-Intervall.Femoroazetabuläres Impingement (FAI) Typ CAM und Typ Pincer, Labrumläsionen, lokale Knorpelläsionen, freie Gelenkkörper.Koxarthrose mit einem Arthrosegrad nach Tönnis ≥ 2.Nach einem minimal-invasiven direkt vorderen Zugang (Mini-open-Arthrotomie) zum Hüftgelenk erfolgt die Eröffnung der anterioren Gelenkkapsel unter Schonung des Labrums. Durch Distraktion kann mit dem Arthroskop das Gelenk inspiziert werden. Je nach intraartikulärem Befund können weitere Maßnahmen (z. B. Knorpelkürettage, Mikrofrakturierung, MACI) erfolgen. Bei FAI-Syndrom Typ Pincer oder einer Labrumläsion können diese Pathologien problemlos adressiert werden. Nach partiellem Nachlassen der Distraktion kann das Abtragen des FAI-Syndrom Typ CAM mit der Kugelkopffräse durchgeführt werden.Teilbelastung für 2 bis 6 Wochen mit 10–20 kg oder mit halbem Körpergewicht an Unterarmgehhilfen in Abhängigkeit vom intraoperativen Vorgehen.Die radiologische Analyse der prä- und postoperativen Röntgenbilder (n = 69), die aufgrund eines FAI-Syndroms operiert wurden, belegt, dass diese operative Technik gut geeignet ist, um pathologische Veränderungen zu adressieren. Der α‑Winkel nach Nötzli konnte von durchschnittlich 72,8° präoperativ auf 49,4° postoperativ reduziert werden. Bei einem kombinierten FAI-Syndrom (n = 16) wurde der LCE-Winkel von präoperativ durchschnittlich 50,2° auf postoperativ 37,6° reduziert. Die klinische Nachuntersuchung (n = 29) zeigte gute mittelfristige Ergebnisse nach Behandlung des FAIs mittels arthroskopisch assistierter Mini-open-Arthrotomie (mHHS 84,8 Punkte nach 4,9 Jahren [4,2–5,7; ±0,43]).

Femoroacetabular impingement of the hip is considered a prearthrotic deformity, which should be treated at an early state to prevent complications.This video demonstrates the arthroscopic-assisted mini-open technique for the treatment of femoroacetabular impingement of the hip. In the case presented a combined Pincer and Cam-deformity is treated with rim trimming, translabral labral refixation with two suture anchors and reconstruction of the head-neck junction.The arthroscopic-assisted mini-open technique is a safe and reproducible procedure for treatment of femoroacetabular impingement. It provides an alternative to hip arthroscopy and an additional treatment option in the portfolio of hip surgeons.

There are still a high number of dissatisfied knee arthroplasty patients. This situation has not changed much for decades, despite many innovations focusing on implant longevity and higher procedural precision. In this context, there is a growing discussion on possible systematic errors made in knee arthroplasty, especially regarding the alignment philosophy of the implants.It was reported that a more anatomical alignment might result in improved patient outcome. However, current technologies have severe limitations to achieving optimized and individual alignment. In this context, the aim of this manuscript was to assess whether image-based robot-guided knee arthroplasty might represent an opportunity for achieving individualized alignment.The literature on this subject was evaluated and analyzed. Furthermore, research projects and expert recommendations were discussed.The precision of preoperative planning is higher with robotic techniques than with other computer-assisted or manual technologies. In addition, the individual soft tissue situation of the patient is taken into account and the prosthesis position is optimized. This ensures optimum soft tissue balancing and stability of the prosthesis.Modern robot-assisted systems are the mechanical bridge between imaging and patient. This technique provides objective control over the results produced with alternative alignments. This applies to both the prosthesis position itself and the resulting soft tissue balancing.

The story of ShapeMatch® custom-fit cutting guides for primary total knee arthroplasty (TKA) is special compared to other available techniques. First, it was the first such patient-specific instrument (PSI) on the market. Second, the underlying philosophy of kinematic alignment is unique compared to other competitors. Finally, it is the only PSI technique that has been withdrawn from the market.The objective of this paper is to summarize the history of the ShapeMatch® technology and to review the current literature regarding clinical evidence for kinematically aligned TKA.In the recent literature, faster rehabilitation, better knee function and higher patient satisfaction are described for kinematically aligned TKA compared to conventional alignment. However, there is also evidence for inaccuracies by using the PSI technology as a possible cause of treatment failures. Due to those problems, this technology was recalled from the market. As an alternative method to achieve kinematic alignment in TKA, manual as well as computer-assisted techniques are currently under development and are discussed here.

We report an unusual case of a 38-year-old physically active patient, who suffered a Ewing sarcoma during adolescence and was therefore treated with a tumor endoprostheses ex domo (replacement of distal femur and proximal tibia). Since then he had undergone a couple of surgical interventions for revision and is currently suffering from persistent pain in the leg concerned. An aseptic loosening of the tibial component was evident after radiologic examinations. Because he had suffered for so long our patient refused further surgery to retain the affected limb and he preferred amputation.We would have taken the risk of a femoral residual limb that is much too short compared with a classical above-knee amputation. In this regard we saw difficulties in exoprosthetic treatment with functional limitations that could easily have influenced the outcome negatively.Consequently, we decoupled the tibial component from the femoral one within the knee joint and thus performed a knee disarticulation leaving the femoral component.Postoperatively, we found a mostly harmonious gait pattern with a pure mechanical interim prosthesis regarding time-distance parameters, which may be even further improved with the final prosthesis. Sagittal joint angles are comparable to conventionally knee exarticulated ones.To date, no comparable case of such an alloarthroplasty, which could regain mobility with an exoprosthetic treatment has been highlighted in the literature. In the result, a knee disarticulation within the area of a knee arthroplasty leaving the femoral component is not inferior to"ordinary" knee disarticulation.

Against the background that 20 % of patients are dissatisfied after total knee arthroplasty, there is ongoing controversy about optimal alignment. In this context, orientating the prosthetic components to the natural kinematic axes of the knee appears to be an interesting new concept.The objective of this paper is to provide a critical review of the current literature and our own research data regarding the concept of kinematically aligned total knee arthroplasty with the current evidence base and potential limitations.In the recent literature faster rehabilitation, better knee function, and higher patient satisfaction are described compared to conventional alignment, even if the postoperative alignment deviates more than 3° from the mechanical axis. However, the technique may not be suitable for every patient and pathology, and further research is necessary to set the correct indication.

Interdisciplinary collaboration between orthopedic and plastic surgeons is indicated in reconstructive surgery of the extremities for both traumatic orthopedic fractures with extensive soft tissue damage and musculoskeletal tumor resection. We want to emphasize the need for close cooperation starting in the preoperative planning for reconstruction after tumor resection in order to discuss and establish a unified approach. This is particularly important to establish a joint approach with special consideration of possibly necessary adjuvant therapies. One collaborative approach is for the orthopedic surgeon to resect the tumor and the plastic surgeon to carry out the defect reconstruction for exclusive soft tissue coverage including flap surgery as well as for functional reconstruction depending on the location and extent of tumor resection. Thus, careful preoperative and postoperative communication on the precise location, extent of tumor resection and the therapy timing between the orthopedic surgeon and the plastic surgeon will allow the most effective subsequent repair of the resection site.

Femoroacetabular impingement (FAI) and its therapy has gained importance in the last decade and several studies could show that if untreated it may lead to osteoarthritis of the hip joint. In this article an overview of the pathology of FAI, the diagnosis and treatment options are presented. A closer look is taken at the treatment of elite athletes regarding the different techniques. The first own clinical and radiological results of 91 patients treated by the arthroscopically-assisted anterior mini-open approach are presented with very good results and significant postoperative improvement regarding the hip injury and osteoarthritis outcome score (HOOS), the Western Ontario and McMasters University (WOMAC) osteoarthritis index and the University of California Los Angeles (UCLA) activity score, as well as alpha angle correction. This technique which is poorly represented in the literature can be used as a treatment option for FAI. The rehabilitation program is comparable to hip arthroscopy.

Common reasons for juvenile neurogenic pes planovalgus are hypoxic brain damage, birth defects of the spinal canal, trauma and cerebral cancer. When symptoms persist despite conservative treatment of symptomatic pes planovalgus, surgery is indicated. Objectives of the operation are improved gait and mobilization as well as an improved basis for wearing shoes. Joint preserving and ankylosing procedures as well as combinations of both are available. The aim of this study was a retrospective comparison of the Grice/Green extra-articular arthroreisis versus the Evans calcaneal lengthening operation.Between October 2001 and October 2009 a total of 75 arthroereisis operations were performed according to Grice/Green and in the period from April 2006 to February 2010 a total of 83 calcaneal lengthening operations according to Evans. The focus of the study was on patients with an underlying neurogenic disease which resulted in 72 cases in the Grice/Green group and 70 cases in the Evans group. The average age was 14.6 ± 5.0 years in the Evans group and 10.1 ± 3.4 years in the Grice/Green group. Of the patients in the Grice/Green group 17 had infantile cerebral palsy (ICP) and 25 had other neuromuscular diseases and in the Evans group 14 patients had ICP and 28 patients had other neuromuscular diseases. The medical records, preoperative and postoperative radiographs were analyzed. In addition information was obtained on the quality of life (EQ-5D), mobility and the supply of mobility aids using a specially designed questionnaire. The radiological evaluation was based on preoperative and postoperative lateral and dorso-plantar radiographs. The follow-up time for the questionnaire was on average 54 months (range 12-109 months) for the Grice/Green group and 22 months (range 9-53 months) for the Evans group. The postoperative treatment was similar in both groups.The talometatarsal (TMT) index could be improved by surgery according to Grice/Green from - 50.2° to - 28.1° and in the Evans group a correction from - 49.6° to - 31.8° was possible. Considering the cases with severe preoperative deformities (TMT index -50°) there was a significantly greater correction of the lateral talocalcaneal (TC) angle by the method of Grice/Green. In 67 % of patients in the Grice/Green group and 57 % in the Evans group a significant improvement in terms of pain was possible. A significant improvement in gait and possible walking distance was found in 33 % of the Grice/Green group and 43 % of the Evans group and an average improvement was possible in 40 % and 43 %, respectively. The operation was considered to be very successful by 67 % of patients in the Grice/Green group and in 57 % of patients in the Evans group but the difference was not significant. In the Grice/Green group no revisions were necessary and revision was performed in two cases after surgery in the Evans group due to wound infections.Both of the processes investigated in this study are suitable for treatment of pes planovalgus. In cases of neurogenic pes planovalgus and also in extreme cases (TMT index -50°) the procedure according to Grice/Green has radiological advantages for reconstruction of the lateral TC angle.

Maintaining the corrected position of the first metatasophalangeal axis. Reducing postoperative stiffness by forgoing a medial capsular shift.Hallux valgus deformities or recurrent hallux valgus deformities.Existing osteoarthritis, joint stiffness, large bone defects, osteonecrosis. General medical contraindications to surgical interventions and anesthesiological procedures.Operation under regional anesthesia (foot block) or general anesthesia. Tourniquet. Longitudinal skin incision medial over the pseudexostosis of the first metatarsal bone. Preparing the tendon of the Musculus abductor hallucis. Detaching the tendon from the capsule. Incision of the joint capsule with protection of the extensor hallucis longus tendon and the dorsal neurovascular bundle in an L-wise manner. Osteotomy of the first metatarsal bone. Lax sutures of the capsule in correct position and reattachment of the Musculus abductor hallucis tendon shifted toward distal and dorsal, regarding the rotation of the hallux.Postoperative elevation of the operated foot. Analgesia with nonsteroidal antiinflammatory drugs. Postoperative weight-bearing according to the osteotomy. Passive mobilization of the metatarsophalangeal joint. Dressing for 4 weeks postoperatively in the corrected position. Radiologic control after 6 weeks. Hallux valgus orthosis at night and a toe spreader for a further 6 weeks.A total of 30 isolated hallux valgus deformities with a mean preoperative intermetatarsal (IMA) angle of 12.9° (range 11-15°) were operated with a chevron osteotomy. The mean follow-up was 14.4 (range 8-17) months. The mean dorsiflexion at the last follow-up was 44° (range 20-60°). Only 2 patients had a dorsiflexion40°. The mean reduction of the IM angle was 5.6° (range 3-7°). One patient required wound revision. There was no infection or avascular necrosis of the metatarsal head observed in the patients. At follow-up, 20 (67%) patients were completely satisfied, 9 (30%) satisfied, and 1 (3%) was not satisfied.

Microfractures of the femoral head during implantation of the femoral components are suspected to be a cause of fractures at the implant/neck junction which represent a common failure mode in hip resurfacing arthroplasty. Callus formation observed in femoral head retrievals suggests the occurrence of microfractures inside the femoral head, which might be inadvertently caused by the surgeon during implantation. The aim of this biomechanical study was to analyse whether or not the implantation of a cementless femoral component hip resurfacing system causes microfractures in the femoral head.After the preparation of 20 paired human cadaveric femoral heads, the cementless femoral component ESKA Typ BS (ESKA Implants GmbHCo., Lübeck) was implanted on 9 specimens with an impaction device that generates 4.5 kN impaction force. On 9 specimens the femoral component was implanted by hand. One head was used as a fracture model, 1 specimen served as control without manipulation. The femoral component used for impaction was equipped with hinges to enable its removal without further interfering with the bone stock. Specimens were scanned with a microCT device before and after impaction and the microCT datasets before and after impaction were compared to identify possible microfractures.Twenty strikes per hand or with the impaction device provided sufficient implant seating. Neither the macroscopic examination nor the 2-dimensional microCT analysis revealed any fractures of the femoral heads after impaction.At least macroscopically and in the 2-dimensional microCT analysis, implantation of the cementless hip resurfacing femoral component ESKA Typ BS with 4.5 kN or by hand does not seem to cause fractures of the femoral head.

In the last decade biodegradable synthetic implant materials have been established for various clinical applications. Ceramic materials such as calcium phosphate, bioglass and polymers are now routinely used as degradable implants in the clinical practice. Additionally these materials are now also used as coating materials or as microspheres for controlled drug release and belong to a series of examples for applications as scaffolds for tissue engineering. Because immense local concentrations of degradation products are produced during biodegradation, this review deals with the question whether allergic immune reactions, which have been reported for classical metallic and organic implant materials, also play a role in the clinical routine for synthetic biodegradable materials. Furthermore, possible explanatory theories will be developed to clarify the lack of clinical reports on allergy or sensitization to biodegradable synthetic materials.

Intraoperative periprosthetic femoral fractures (PFF) during the implantation of primary non-cemented total hip arthroplasties (THA) are an increasing problem. Thus, the goal of this study was to analyse the postoperative performance of primary non-cemented THA in patients with intraoperative PFFs, with respect to the patient's subjective health-related satisfaction.42 PFFs in 1216 primary THAs using the non-cemented BiCONTACT stem were monitored. Patients were compared to a control group of 42 non-cemented THA patients without intraoperative fracture complications, using the matched-pair analysis. Preoperative and after 2.2 years (0.8-3.2 years), patients were followed-up clinically and radiographically. Clinical parameters were Harris hip score, SF-36 health score, function and pain score and postoperative complications. Radiographic parameters were bone union, stem and trochanter migration. Fractures were graded using the Vancouver classification.Results showed a significant increase in both Harris hip score and motion score and a significant decrease in pain score in both groups (p0.001). The SF-36 health score increased significantly in nearly every dimension in both groups. Except for 2 patients with trochanter migrations of 25 and 20 mm, all fractures showed bony union. In 3 patients the stems subsided by 4.7 +/- 2.9 mm. The stems showed no further migration at final follow-up. 2 patients without intraoperative fractures underwent stem revision. Overall increases and postoperative complication rates were not significantly different between the groups.Mid-term THA performance and patient satisfaction are not influenced by intraoperative Vancouver A and B1 fractures during implantation of the non-cemented BiCONTACT stem compared to a collective without intraoperative fractures during implantation.

We have investigated the value of flexion osteotomy for femoral head necrosis with regard to the survival rate.We examined 40 patients who were treated by flexion osteotomy for femoral head necrosis at the Hannover Medical School in the years 1969 to 1995. The mean follow-up period was 14.1 years.The mean survival time of the flexion osteotomies was 9.6 years. In 23 of the 40 patients, it failed within 10 years after surgery, which implies a 10-year survival rate of 42.5 %. For these 23 patients, the implantation of a total hip arthroplasty (THA) became necessary after an average time of 6.6 years.Due to the poorly predictable success of the flexion osteotomy and the comparatively poor patient satisfaction, the indication for flexion osteotomy in such cases should be reconsidered.

In this study we present the first results of the investigation of polymer-coated titanium implants implanted in the proximal tibia and distal femora of New Zealand white rabbits. The results of DEXA scans, micro-CT, and histological analysis showed an increase of osseointegration. We suggest that controlled release kinetics after coupling of these polymers with BMP-2 can additionally increase osseointegration.

This study addresses work sharing during navigation-assisted total knee arthroplasty. Specifically, the concept is introduced of a "navigator" assistant who operates the navigation system during surgery while the surgeon concentrates on the primary steps of surgery.In a prospective study of 40 total knee arthroplasties, one group of patients was treated using the navigator concept, a second group was treated using a conventional navigation setup, and a third group was treated with conventional internal and external alignment jigs. Surgery time and outcome parameters were compared.Results show a significant difference in surgery time between the three groups. The conventional and navigator concept groups showed similar surgery times; however, the navigation group without navigation concept exhibited longer surgery time.The navigator concept represents a highly effective principle to minimize surgery time needed during navigated total knee arthroplasty.

The characterization and cloning of growth factors for bone healing provide an enormous potential for minimally invasive treatment procedures for bone defects or fractures. However, the clinical application of injection vehicles for these growth factors must be made user-friendlier. In this study, two different injection vehicles were tested for their practicability and efficacy to enhance callus maturation during distraction osteogenesis. Calcium phosphate carriers showed a rather low user-friendliness and were less efficient in the animal model of distraction osteogenesis in sheep. Collagen carriers provided both a higher practicability for injection procedures and a higher efficacy.

The present article describes a newly developed device for the quantitative assessment of torsional in vivo stiffness of regenerating bone under callus distraction. Both the design and function of this device, and its use during bony consolidation are discussed. The device exhibited an accuracy of +/- 18% for stiffness under 0.1 Nm/degree, and +/- 5% stiffness above 0.1 Nm/degree. The average accuracy was +/- 14%. The data scatter for the stiffness measurement ranged between +/- 1.43% and +/- 7.68% (average: +/- 3.99%). The precision of a test machine was between +/- 0.01% and +/- 11.3% (average: +/- 3.65%). The method has the following advantages over existing methods for investigating healing: 1. no need to dismantle the external fixation for measurement; 2. preservation of the bone axis with minimal risk of misalignment during the bone healing process; 3. minimal technical requirements, with easy, noninvasive measurement; 4. no exposure to X-radiation.

Recent operative techniques with percutaneous screw fixation of the tibial plateau require a high level of patient compliance. Geriatric, non-cooperative patients and fractures with severe soft tissue injury have had to be excluded so far from this therapeutic regimen. Since September 1993, composite hybrid fixation, as a combination of ring fixation of the epimetaphyseal tibia with monolateral AO fixation of the tibial shaft, has been performed in 12 patients. The data were collected prospectively. Fractures were classified according to the AO and Moore classification; soft tissue damage was classified according to Tscherne and Gustilio. Fixation was performed with the cannulated AO system, 2.0 mm titanium K wires and 5.0 mm AO Schanz screws. In five patients, additional arthroscopic control of the reposition was performed. Average removal of the external fixator was 16 weeks postoperatively. Pin-tract infections occurred in all patients, mainly in the metaphyseal region. In one patient, a knee infection resulted from a subchondral intra-articular pin, which was treated by repetitive arthroscopic synovectomy. In two patients, a secondary loss of reposition (5-7 degrees varus) occurred. Despite a high rate of soft tissue damage (8/12), no osteitis or non-union occurred. As an alternative to extensive methods of ORIF, supportive composite hybrid fixation offers a new perspective of early functional treatment, weight bearing and a rare loss of reposition. It is favored in geriatric, non-cooperative patients and in fractures with severe soft tissue damage.