Einsatz eines modularen Knierevisionssystems MML im Rahmen des Knieprothesenwechsels und der Tumorendoprothetik

Increasing age and a higher level of mobility lead to an increasing incidence in revision arthroplasty after total knee replacement and tumor surgery. So far, the reconstruction of large defects in bony and soft tissue environments can be accomplished by the modern modular components of revision implants. The consecutive reconstruction of the extensor mechanism in extended revision has its own drawbacks and is often associated with significant functional limitations for the patient. Specially designed implants and methods are required to generate good functional results. The modular knee revision system MML provides specific modifications of the tibial component for reconstruction of the extensor mechanism. Combined with artificial strips, an excellent functional outcome could be achieved. In this study, 70 patients were operated with the MML endoprosthesis in knee revision or tumor surgery. An excellent functional outcome could be determined. At 7 years after surgery, an average of 32+/-13 points was achieved on the Oxford Knee Score. The outcome measurement using the functional scoring system of the American Knee Society (AKS score) showed similarly good results with 71+/-25 points out of 100. A minor deficit of only 2 degrees in active extension could be observed after reconstruction of the extensor mechanism. In conclusion, we have demonstrated that the MML modular revision system is appropriate for reconstruction of segmental bone defects.     

Extensor mechanism failure associated with total knee arthroplasty: prevention and management

Extensor mechanism complications are the most commonly reported reasons for revision surgery after total knee arthroplasty and are a frequent source of postoperative morbidity. Patellofemoral instability is the most commonly reported extensor mechanism complication and has multiple etiologies, including prosthetic malalignment and soft-tissue imbabalce. Patellar fracture or rupture of either the quadriceps or patellar tendon can cause catastrophic disruption of the extensor mechanism. Although some stable fractures can be successfully managed nonsurgically, displaced fractures or tendon rupture often lead to poor results. Other complications include patellar clunk and soft-tissue adhesions, prosthetic wear or loosening, and osteonecrosis. Increased understanding of implant alignment, rotation, and soft-tissue balance, as well as improved design of the trochlear groove of femoral implants and patellar components, has resulted in a decline in extensor mechanism complications. Appropriate prosthetic selection and meticulous surgical technique remain the keys to avoiding unsatisfactory results and revision surgery.     

Minimalinvasiver unikompartimenteller Kniegelenkersatz

Unicompartmental knee replacement is an attractive treatment option for patients with isolated medial or lateral compartment osteoarthritis of the knee. Correct indication and accurate surgical technique are essential to achieve a good clinical result. In experienced hands excellent long-term results can be achieved. The routinely used minimally invasive surgical technique is technically demanding and requires adequate training and routine. Due to the minimally invasive approach the extensor mechanism is preserved and very good functional results and accelerated rehabilitation can be achieved. Compared to total knee replacement several advantages such as improved range of motion, less bleeding, lower infection rates and easier revision have been reported. Moreover by preserving the cruciate ligament complex and therefore the proprioception the knee feels normal. However, midterm and long-term revision rates are higher.     

Management of extensor mechanism deficit as a consequence of patellar tendon loss in total knee arthroplasty: a new surgical technique

Extensor mechanism disruption is an uncommon but devastating complication of total knee arthroplasty. A new technique of extensor mechanism reconstruction for patellar tendon loss, after total knee arthroplasty, with the help of extensor mechanism composite allograft is described. Four patients with chronic extensor mechanism-deficient total knee arthroplasty were undertaken for revision surgery along with reconstruction of extensor mechanism with an innovative technique using an extensor mechanism composite allograft consisting of a patella-patellar tendon-tibial tubercle. On final follow-up, none of the patients had extensor lag but for 10 degrees of extensor lag in 1 patient only. Providing an environment for bone-to-bone healing both proximally as well as distally and supervised postoperative rehabilitation led to encouraging results in the management of a failed extensor mechanism after total knee arthroplasty.     

Is There a Place for Rotating-Hinge Arthroplasty in Knee Revision Surgery for Aseptic Loosening?

We reviewed the results of 78 revision total knee arthroplasties using a rotating-hinge device, performed from 1993 through 2002. The average follow-up was 7.83 years. Only patients requiring revision arthroplasty due to aseptic loosening were included. Reasons for revision were malalignment with or without polyethylene wear (47), instability (24), extensor mechanism failure (3), and periprosthetic fracture (4). The mean preoperative scores according to the American Knee Society rating scale was 37.5 points for knee score and 32.8 points for function score. Postoperatively, the knee score improved to 85.7 points and the function score improved to 61.4 points. Nineteen patients had complications related to the design prostheses (mostly minor complications). Fifty-seven patients (73%) had excellent results, with a range of motion of 104 degrees in flexion and complete extension. For extreme circumstances, such as gross instability of the medial collateral ligament, massive bone loss, comminuted fracture, and chronic dysfunction of the extensor mechanism, there is a place for hinged revision implant surgery with good clinical results and quality of life.     

Management of the patella in revision total knee arthroplasty

Problems with the patellofemoral joint comprise the most common complication in primary and revision total knee arthroplasty (TKA). The difficulties can range from instability and anterior knee pain at one end of spectrum of severity, to fracture and extensor mechanism disruption at the other end. These complications are generally higher in revision TKA due to compromised bone stock and blood supply. Despite the particular challenges posed by the bone-deficient patella, reasonable results can be achieved.     

High rate of failure of allograft reconstruction of the extensor mechanism after total knee arthroplasty

BACKGROUND: Disruption of the extensor mechanism is an uncommon but devastating complication of total knee arthroplasty. Several techniques for reconstruction of the extensor mechanism after total knee arthroplasty have been reported, but we do not know of any study in which the results of one group's method were corroborated by a second group using the same technique. In the present series, we evaluated the results of reconstruction of the extensor mechanism with use of allograft according to the method described by Emerson et al. METHODS: Seven reconstructions of the extensor mechanism with use of a bone-tendon-bone allograft were performed with the technique of Emerson et al. in six patients. The patients were evaluated before and after the operation. The knee score according to the system of The Hospital for Special Surgery, evidence of an extensor lag, use of walking aids, and the ambulatory status of each patient were recorded. The patients were also asked about, and the medical records were reviewed for, episodes of falling related to weakness of the quadriceps after the reconstruction. The mean duration of follow-up was thirty-nine months (range, six to 115 months). As these reconstructions often fail early, the minimum duration of follow-up was six months. RESULTS: All seven reconstructions were rated as clinical failures on the basis of a persistent or recurrent extensor lag of more than 30 degrees. All but one patient needed an assistive device full time for walking, and four patients (five knees) had at least one documented episode of falling that was due to giving-way of the affected knee. Four of the reconstructions were revised; one revision was performed with use of another extensor mechanism allograft and three were performed with use of a medial gastrocnemius rotation flap. The other three clinical failures had not been revised at the time of writing. At the time of the most recent follow-up (or at the time of revision of the extensor reconstruction), the mean extensor lag was 59 degrees and the mean knee score was 52 points (a poor result). CONCLUSIONS: Undertensioning of the allograft reconstruction at the time of the operation and attenuation of the allograft both may have played a role in the inability of the patients to regain active extension of the knee postoperatively. Alternative techniques for reconstruction of the extensor mechanism or modifications of this technique should be considered in the treatment of this difficult problem.     

Rekonstruktion der Strecksehneninsertion im Rahmen des Knieprothesenwechsels und der Tumorendoprothetik

Reconstruction of the extensor mechanism in extended revision after total knee replacement and tumor surgery remains a clinically relevant problem. Due to large tibial bone defects with resection of the extensor insertion area, the specific problem of patella ligament refixation frequently arises. Several biological approaches and augmentation techniques have been published. Most of these are associated with a high rate of revision surgery because of failed replacement of the extensor mechanism and unsatisfactory functional outcome. Surgical reconstruction of these tendon defects is complicated by the difficulty of completely neutralizing tensional force across the repair. To overcome this problem, methods have been developed to reinforce the reconstruction with overlapping flaps; in addition, artificial materials are being increasingly used for tension neutralization. These artificial strips need special fixation mechanisms on the tibial component and specific technical modifications of the prosthesis.The present study gives an overview of reconstruction modalities of the extensor mechanism and provides an improved technology for better reconstruction by using artificial strips combined with specific modifications of the tibial component.     

New concepts in revision total knee arthroplasty

Revision knee arthroplasty should be regarded as a discipline separate from primary surgery. A disciplined approach to diagnosis is mandatory in which the following categories for failure are useful: (a) sepsis, (b) extensor mechanism rupture, (c) stiffness, (d) instability, (e) periprosthetic fracture, (f) aseptic loosening and osteolysis, (g) patellar complications and malrotation, (h) component breakage, and (i) no diagnosis. In the event of no coherent explanation for pain and disability, the possibilities of chronic regional pain syndrome, hip or spine pathology, and inability of current technology to meet patient expectations should be considered and revision surgery should be avoided. Revision arthroplasty cannot be performed as if it were a primary procedure and indeed will be eight (or more) different surgeries depending on the cause of failure. Though perhaps counterintuitive, there is a logical rationale and empirical evidence to support complete revision in virtually every case. In general, revision implant systems are required. The early dependence on the "joint line" is inadequate, failing as it does to recognize that the level of the articulation is a three-dimensional concept and not simply a "line." The key to revision surgery technique is that the flexion gap is determined by femoral component size and the extension gap by proximal distal component position. Accordingly, a general technical pathway of three steps can be recommended: 1) tibial platform; 2) stabilization of the knee in flexion with (a) femoral component rotation and (b) size selected with evaluation of (c) patellar height as an indication of "joint line" in flexion only; and 3) stabilization of the knee in extension, an automatic step. Stem extensions improve fixation and, if they engage the diaphysis, may be used as a guide for positioning. Porous metals designed as augments for bone defects may prove more important as "modular fixation interfaces." It is postulated that with the exception of septic and extensor mechanism complications, first revision knee arthroplasty may exceed the durability of primary knee arthroplasty.     

Reconstruction of a ruptured patellar tendon with achilles tendon allograft following total knee arthroplasty

BACKGROUND: Rupture of the patellar tendon after total knee arthroplasty is a rare and debilitating complication. Proper surgical management of this condition remains controversial. The purpose of this study was to review the results of reconstruction of a ruptured patellar tendon with an Achilles tendon allograft following total knee arthroplasty. METHODS: We reviewed our experience with the use of a fresh-frozen Achilles tendon allograft with an attached calcaneal bone graft to restore extensor function in nine patients with patellar tendon rupture following total knee arthroplasty (five primary and four revision). All patients were examined clinically and radiographically at an average of twenty-eight months. RESULTS: The average knee and functional scores improved from 26 and 14 points, respectively, before the surgery to 81 and 53 points after the surgery. The average extensor lag decreased from 44 degrees preoperatively to 3 degrees postoperatively, and the average range of motion of the knee increased from 88 degrees to 107 degrees. Two grafts failed in the early postoperative period. Both were repaired successfully. Radiographs showed an average proximal patellar migration of 17.8 mm, which did not appear to affect extensor function. CONCLUSIONS: This short-term follow-up study showed that once an Achilles allograft has healed, it can serve as a reliable reconstruction of a ruptured patellar tendon following total knee arthroplasty. This technique may be particularly suited for patients in whom the extensor mechanism was compromised by multiple prior operations. Continued follow-up is necessary to determine the long-term durability of these results.     

Revision total knee arthroplasty for aseptic failure

Twenty-four patients with 28 failed total knee arthroplasties replaced with porous-coated anatomic (PCA) primary or revision components were studied over a two- to four-year period. Overall, there were 68% good and excellent results and three failures. When evaluated according to mode of failure, 83% of the patients who had a definable mechanical problem achieved good or excellent results. Patients who had revision operations for incapacitating pain or in whom no clearly definable problem could be ascertained before operation were not significantly improved. Complications that led to poor results were deep sepsis, wound necrosis, and extensor mechanism abnormalities.     

The "banana peel" exposure method in revision total knee arthroplasty

We present an exposure technique, the "banana peel," that has been used exclusively for revision total knee arthroplasty (TKA) for more than 20 years. We retrospectively reviewed use of this technique in 102 consecutive patients (mean age, 62 years; range, 41-92 years) who underwent tibial-femoral stemmed revision TKA. There were 5 deaths, leaving 97 patients (98 knees) for the study. The technique involves peeling the patella tendon as a sleeve off the tibia, leaving the extensor mechanism intact with a lateral hinge of soft tissue. A quadriceps "snip" is also done proximally. Patients with a minimum follow-up of 24 months were included. Telephone interviews and chart reviews were conducted, and Knee Society scores were obtained. Mean follow-up was 39 months (range, 24-56 months). No patient reported disruption of the extensor mechanism or decreased ability to extend the operative knee. Mean Knee Society score was 176 (range, 95-200). Mean postoperative motion was 106 degrees. No patient reported pain over the tibial tubercle. The banana-peel technique for exposing the knee during revision TKA is a safe method that can be used along with a proximal quadriceps snip and does not violate the extensor mechanism, maintaining continuity of the knee extensors.     

Custom-made Articulating Spacer in Two-stage Revision Total Knee Arthroplasty. An Early Follow-up of 14 Cases of at Least 1 Year After Surgery

Total knee replacement (TKR) infection represents only a small percentage of all the potential complications in joint replacement, but one that can lead to disastrous consequences. Two-stage revision, which has been proven to be the most effective technique in eradicating infection, includes prosthesis removal, positioning of an antibiotic-loaded spacer, and systemic antimicrobial therapy for at least 6 weeks. It has been suggested that there is better performance in terms of range of motion, pain, extensor mechanism shortening, and spacer-related bone loss if articulating spacers are used instead of fixed spacers. In this paper, we describe our results in two-stage revision of infected total knee arthroplasty with a minimum follow-up of 12 months on 14 patients treated by antibiotic-loaded custom-made articulating spacer as described by Villanueva et al. (Acta Orthop 77(2):329–332, 2006). The mean flexion achieved after the second stage of the revision was 120°, ranging from 97° to 130°. The mean Hospital for Special Surgery score was 84. At 1 year after surgery, none of the knees showed any evidence of recurrence of the infection. Articulating spacers are a suitable alternative to fixed spacers with good range of motion after reimplantation and effectiveness against total knee replacement deep infections.     

Patella inversion method for exposure in revision total knee arthroplasty.

Satisfactory performance of revision total knee arthroplasty (TKA) requires adequate exposure. This article shows the patella inversion method of exposure in a large consecutive series of revision TKAs.Between 1987 and 1999, 420 revision TKAs were performed. Exposure was facilitated by the patella inversion method. No attempt was made to evert the patella. This technique of exposure was used in 95% (397 of 420) of patients. There were no episodes of patellar tendon avulsion in this series. Multiple exposure options are available in revision TKA. Extensile techniques violate the extensor mechanism. For most patients, these methods were unnecessary. The patella inversion method afforded adequate exposure in most patients without violating the extensor mechanism.     

Fracture of the Proximal Tibia After Revision Total Knee Arthroplasty With an Extensor Mechanism Allograft

Extensor mechanism reconstruction with an extensor mechanism allograft (EMA) remains one of the most reliable methods for treating the extensor mechanism deficient total knee arthroplasty. We report 3 patients who were treated with an EMA who sustained a proximal tibial shaft fracture. In all 3 cases, a short tibial component was present that ended close to the level of the distal extent of the bone block. When performing an EMA, it is important to recognize that the tibial bone block creates a stress riser and revision to a long-stemmed tibial component should be strongly considered to bypass this point to minimize the risk of fracture.     

Revision unikondylärer Knieprothesen

Despite the good midterm survivorship reported for unicondylar knee arthroplasty, an increase in revision surgery has to be expected due to increased replacement rates. The reasons for failure as well as distribution are different for unicondylar knee arthroplasty compared to total knee arthroplasty. The main reasons for revision are aseptic loosening and the progression of osteoarthritis. In most cases, unicondylar knee arthroplasty will be revised to total knee arthroplasty. To obtain good revision results, the cause of implant failure has to be analysed carefully. In the case of contained bone defects, the reconstruction can be supported with bone grafting. For those cases with uncontained defects, implants with augmentation and, in some cases, stem extensions are needed. The modularity of the revision implant should cover different intraoperative requirements.     

The unstable patella after total knee arthroplasty: etiology, prevention, and management

In total knee arthroplasty, most complications related to the extensor mechanism are caused by patellar maltracking or instability. Patellar maltracking may result from component malpositioning and limb malalignment, prosthetic design, improper patellar preparation, or soft-tissue imbalance. Patellofemoral instability likely results most frequently from internal malrotation of the femoral or tibial components. Although a patellofemoral radiograph may display the lateral subluxation of the patella, only computed tomography can quantify rotational malalignment of the femoral or tibial component. Nonsurgical treatment is generally unsuccessful; major malposition of components is best managed by implant revision. In the absence of component malposition, proximal realignments (lateral patellar retinacular release with lateral advancement of the vastus medialis obliquus muscle) or tibial tubercle transfers have been used. Surgical procedures on the patellar tendon itself may risk rupture of the extensor mechanism.     

Extensor Mechanism Disruption After Contralateral Middle Third Patellar Tendon Harvest for Anterior Cruciate Ligament Revision Reconstruction

The contralateral central third patellar tendon autograft is a reliable graft choice for revision, and recently, for primary reconstruction of the anterior cruciate ligament (ACL). We report 2 complications including a lateral third tibial tuberosity fracture and a distal patellar tendon avulsion with contralateral patellar tendon autograft with disruption of the extensor mechanism of the donor knee. A patient sustained a lateral tibial tuberosity fracture of the donor knee and underwent open reduction and internal fixation. At 1-year follow-up, she had no extensor lag and full range of motion. Another patient sustained a distal patellar tendon avulsion of the donor knee and underwent primary repair. Three years postoperatively, she had a full range of motion and no extensor lag. Although contralateral middle third patellar tendon autograft for primary and revision ACL reconstruction is established in the literature, extensor mechanism complications can occur. Technical considerations are important to avoid weakening the remaining patellar tendon insertion. Postoperative nerve blocks or local anesthetics may alter pain feedback for regulation of weight bearing and contribute to overload of the donor knee.     

Stiffness following total knee arthroplasty: evaluation and treatment

Total knee arthroplasty (TKA) for advanced arthritis of the knee is one of the most successful orthopaedic reconstructive procedures performed with excellent patient satisfaction and functional outcomes. Stiffness following total knee arthroplasty is relatively common and has a multifactorial etiology with associated pain and decreased range of motion. Preoperative flexion is found to be an important variable of post-operative range of motion and hence, the patients should be well informed of the outcomes, activity restrictions and questioned as to their expectations before surgery to achieve an optimum result. Detailed analysis of the etiology of stiffness with specific reference to patient factors, technical errors and others factors during the course of operative treatment and rehabilitation need to be assessed after ruling out infection. Treatment methods for stiffness following TKA include non-operative management, extensive physiotherapy, manipulation under anesthesia, arthroscopic arthrolysis, open arthrolysis with or without component exchange and revision arthroplasty. Treatment should be directed towards the specific cause, and poor results are likely for revision TKA surgery without identifying the specific etiology.     

Porous tantalum patellar components in revision total knee arthroplasty minimum 5-year follow-up

Revision total knee arthroplasty can be complicated by severe patellar bone loss, precluding the use of standard cemented patellar components. This study evaluated the midterm outcomes of porous tantalum (PT) patellar components. Twenty-three PT components were used in 6 men and 17 women (average age, 62 years). All patellae had less than 10-mm residual thickness. The PT shell was secured to host bone, and a 3-peg polyethylene component was cemented onto the shell. In 2 patients, the PT component was sutured directly to extensor mechanism. Average follow-up was 7.7 years (range, 5-10 years). At follow-up, the Knee Society scores for pain and function averaged 82.7 and 33.3, respectively, whereas the mean Oxford knee score was 32.6. Four patients underwent revision surgery. Survivorship was 19 (83%) of 23 patients. Porous tantalum patellar components can provide fixation where severe bone loss precludes the use of traditional implants. Failures were associated with avascular residual bone and fixation of components to the extensor mechanism.