Experts' Perceived Patient Burden and Outcomes of Knee-ankle-foot-orthoses (Kafos) Vs. Microprocessor-stance-and-swing-phase-controlled-knee-ankle-foot Orthoses (Mp-sscos)

BACKGROUND

Patients with neuromuscular knee-instability assisted with orthotic devices experience problems including pain, falls, mobility issues and limited engagement in daily activities.

OBJECTIVES

The aim of this study was to analyse current real-life burden, needs and orthotic device outcomes in patients in need for advanced orthotic knee-ankle-foot-orthoses (KAFOs).

METHODOLOGY

An observer-based semi-structured telephone interview with orthotic care experts in Germany was applied. Interviews were transcribed and content-analysed. Quantitative questions were analysed descriptively.

FINDINGS

Clinical experts from eight centres which delivered an average of 49.9 KAFOs per year and 13.3 microprocessor-stance-and-swing-phase-controlled-knee-ankle-foot orthoses (MP-SSCOs) since product availability participated. Reported underlying conditions comprised incomplete paraplegia (18%), peripheral nerve lesions (20%), poliomyelitis (41%), post-traumatic lesions (8%) and other disorders (13%). The leading observed patient burdens were "restriction of mobility" (n=6), followed by "emotional strain" (n=5) and "impaired gait pattern" (n=4). Corresponding results for potential patient benefits were seen in "improved quality-of-life" (n=8) as well as "improved gait pattern" (n=8) followed by "high reliability of the orthosis" (n=7). In total, experts reported falls occurring in 71.5% of patients at a combined annual frequency of 7.0 fall events per year when using KAFOs or stance control orthoses (SCOs). In contrast, falls were observed in only 7.2 % of MPSSCO users.

CONCLUSION

Advanced orthotic technology might contribute to better quality of life of patients, improved gait pattern and perceived reliability of orthosis. In terms of safety a substantial decrease in frequency of falls was observed when comparing KAFO and MP-SSCO users.

[Surgical procedures for the correction and stabilization of pes planovalgus]

The medial column of the foot is a relevant factor of the pathogenesis of pes planovalgus. Crucial anatomic structures are the tibiocalcaneonavicular ligament complex, the naviculocuneiform joints, including the ossa cuneiformia, and the first tarsometatarsal joint. A combination of bony and soft tissue reconstructive techniques must, therefore, be taken into account when treating pes planovalgus. The present article presents stabilizing and correcting surgical procedures for the medial column of the foot, including basic anatomy and biomechanics.

Subjective outcome following neurostimulator implantation as drop foot therapy due to lesions in the central nervous system-midterm results

BACKGROUND

Drop foot can be caused by many conditions. Stroke is one of the major causes of drop foot and 5% of stroke survivors suffer from hemiplegia, which in some cases, can manifest as drop foot. The abnormal gait resulting from the lack of innervation of the extensor muscles may result in a secondary malposition of the foot and lead to a steppage gait. Among the several therapy options for the treatment of drop foot, functional electrostimulation (FES) with a transcutaneous peroneal nerve stimulator (tPNS) or an implantable peroneal nerve stimulator (iPNS) represents the two recent approaches.

OBJECTIVE

Although therapy with an iPNS has been proven to be effective, a subjective patient assessment has not yet been executed. The aim of this study was to assess the patient's satisfaction with the therapy by using two established surveys.

METHODS

The Rivermead Mobility Index (RMI) and the Reintegration to Normal Life Index (RNLI) were used for this retrospective study. The RMI includes 15 questions which are to be answered as either "yes" or "no" and given a value of 1 or 0, respectively, with a maximum of 15 points possible. The RNLI includes 11 questions which are to be answered with the use of a visual analog scale (VAS, 0 to 10 cm). In this case, a maximum adjusted score of 100 points is possible.

RESULTS

The total study cohort involved 56 patients treated with an iPNS. Thirty-five complete data sets for the RMI and 29 for the RNLI could be achieved. A significant difference in the total score of both surveys was observed between the deactivated and the activated iPNS (RMI: p = 0.02; RNL: p = 0.01).

CONCLUSION

A significant improvement in patient satisfaction was detected with the use of an activated iPNS after a mean time span of 4 years. Due to the marked mobility, an increase in the social satisfaction and integration could be achieved. Both aspects represent essential components for the recovery and quality of life of the patients.

Comparative measurements of bone mineral density and bone contrast values in canine femora using dual-energy X-ray absorptiometry and conventional digital radiography

BACKGROUND

Aseptic loosening due to bone remodelling processes after total hip replacement is one common cause for revision surgery. In human medicine, dual-energy X-ray absorptiometry (DEXA) is the gold standard for quantitative evaluation of bone mineral density, whereas in veterinary medicine conventional radiography is used for follow-up studies. Recently, a method has been described using digital X-ray images for quantitative assessment of grey scale values of bone contrast. Therefore, the aim of the present study was to evaluate the correlation of bone mineral density (BMD) measured by DEXA with grey scale values (GV) measured in digital X-ray images (RX50, RX66) ex vivo.

RESULTS

The measured GV in the chosen X-ray settings showed on average a good correlation (r = 0.61) to the measured BMD with DEXA. Correlation between the two X-ray settings was very good (r = 0.81). For comparisons among regions of interests (ROIs) a difference of 8.2% was found to be statistically significant, whereas in the case of RX50 and RX66 differences of 5.3% and 4.1% were found to be statistically significant.

CONCLUSIONS

Results indicate that measuring absolute changes in bone mineral density might be possible using digital radiography. Not all significant differences between ROIs detectable with DEXA can be displayed in the X-ray images because of the lower sensitivity of the radiographs. However, direct comparison of grey scale values of the periprosthetic femur in one individual patient during the follow-up period, in order to predict bone remodelling processes, should be possible, but with a lesser sensitivity than with DEXA. It is important that the same X-ray settings are chosen for each patient for follow-up studies.

[Distal osteotomy for the treatment of hallux valgus (Chevron osteotomy)]

Distal osteotomies, like the Chevron osteotomy, is indicated for mild to moderate hallux valgus deformities. Splayfoot, painful pseudoexostosis, and transfer metatasalgia are observed in the clinical examination. Radiographic examination should be done with weight bearing in two planes. Preoperatively the intermetatarsal (IM), hallux valgus, and distal metatarsal articular (DMAA) angles should be measured. The operative technique is based on soft tissue and bony correction. Modifications of the osteotomy allow a shortening, lengthening, or neutral correction of the first metatarsal. With a modified Chevron osteotomy, an increased DMAA can be also corrected.

[Soft tissue techniques in hallux valgus surgery]

The hallux valgus represents combined bony and soft tissue pathology. In addition to known bony surgical procedures, addressing the soft tissue with regard to the anatomical structures, the surgical technique and the extent of correction are discussed.The goal of the operation is the restoration of the physiological balance between the active and passive stabilizing factors of the MTP-I-joint. The joint capsule, the ligaments and the tendons of the first ray act directly as stabilizing structures, whereas the hind foot and the position of the upper ankle have an indirect influence on the MTP-I-joint.The present work gives an overview of the pathoanatomy of the MTP-I-joint in the hallux valgus pathology. The individual anatomical structures are presented with regard to their physiological and pathological influence and the possible therapeutic options.

[Hallux amputation]

OBJECTIVE

Debridement of infected tissue with the main aim being the re-establishment of mobilization with preservation of standing and walking ability. Prevention of secondary pressure points or amputations due to inadequate resection or deficient soft tissue cover.

INDICATIONS

In the case of increasing necrosis of the big toe, surgical abrasion and/or amputation is considered unavoidable. Other indications where surgery could be considered include diabetes and its associated angiopathies together with peripheral arterial angiopathy.

CONTRAINDICATIONS

In the case of insufficient blood supply an expansion of the resection margins should be taken into account. If there are possible alternatives to amputation. Surgery for patients with renal failure requiring dialysis associated with increased complication rate.

SURGICAL TECHNIQUE

A dorsal cuneiform resection is performed to facilitate implantation of a plantar skin transplant and wound healing. Important is the resection of bone in a slide oblique technique. Amputation scars should be outside pressure zones. Partial amputations in the area of the first ray as exarticulation or via the individual amputated segments possible (as opposed to toes 2-5).

POSTOPERATIVE MANAGEMENT

Direct postoperative weight-bearing with rigid insole and dispensing aid for 6-8 weeks. Following complete wound healing, foot support with orthopedic arch and transverse strain relief should be advocated, together with a joint roll in ready-made individual shoes.

RESULTS

Both trauma and nontrauma cases were included in our present cohort. A total of 7 cases were surgically revised in 2014 due to superficial skin necrosis that was likely the result of skin tension from the wound stitches.

Inflammatory response to burn trauma: nicotine attenuates proinflammatory cytokine levels

OBJECTIVE

The immune response to an inflammatory stimulus is balanced and orchestrated by stimulatory and inhibitory factors. After a thermal trauma, this balance is disturbed and an excessive immune reaction with increased production and release of proinflammatory cytokines results. The nicotine-stimulated anti-inflammatory reflex offsets this. The goal of this study was to verify that transdermal administration of nicotine downregulates proinflammatory cytokine release after burn trauma.

METHODS

A 30% total body surface area full-thickness rat burn model was used in Sprague Dawley rats (n = 35, male). The experimental animals were divided into a control group, a burn trauma group, a burn trauma group with additional nicotine treatment, and a sham + nicotine group with 5 experimental animals per group. The last 2 groups received a transdermal nicotine administration of 1.75 mg. The concentrations of tumor necrosis factor alpha, interleukin 1 beta, and interleukin 6 were determined in homogenates of hearts, livers, and spleens 12 or 24 hours after burn trauma.

RESULTS

Experimental burn trauma resulted in a significant increase in cytokine levels in hearts, livers, and spleens. Nicotine treatment led to a decrease of the effect of the burn trauma with significantly lower concentrations of tumor necrosis factor alpha, interleukin 1 beta, and interleukin 6 compared to the trauma group.

CONCLUSIONS

This study confirms in a standardized burn model that stimulation of the nicotinic acetylcholine receptor is involved in the regulation of effectory molecules of the immune response. Looking at the results of our study, further experiments designed to explore and evaluate the potency and mechanisms of the immunomodulating effects of this receptor system are warranted.

[Preoperative perfusion analysis before total ankle arthroplasty]

PURPOSE

Soft tissue management is of paramount importance in ankle surgery. As such, full thickness necrosis of the soft tissue envelope represents a severe complication following total ankle joint arthroplasty (TAA) potentially leading to implant exposure, infection and thus, substantially compromised patient outcomes. One of the main factors leading to soft tissue complications is an undetermined arterial perfusion of the lower leg or ankle joint. We report on clinical cases suffering soft tissue complications following TAA with the respective plastic surgical therapy regimen and present a simple algorithm for preoperative perfusion evaluation.

METHODS

The medical records of 30 consecutive primary TAA patients were retrospectively reviewed after observing a higher than expected rate of severe soft tissue defects which have been referred to our plastic surgery department.

RESULTS

3 patients (10%, all females, age 63 ± 5 years; BMI 27 ± 3 kg/m2) presented with a soft tissue defect leading to angiography revealing one case of severe arterial obstruction. Wound closure could be reached in one case by conservative therapy consisting of regular dressing changes. In the further patients definite soft tissue reconstruction could only be performed by surgical intervention. One could be covered by split-thickness skin grafting and one by a microsurgical transplantation of a free latissimus dorsi flap. On the basis of these complications we established an easy algorithm for the preoperative evaluation of the arterial perfusion in the ankle region. First, (I) the pulses of the dorsal foot artery and posterior tibial artery should be examined. In the case of not palpable pulses (II) the ankle-brachial index should be performed. Values of <0.9 or >1.2 recommend (III) to perform angiography. In the case of stenosis or complete obstruction (IV) the arterial blood flow should be reconstituted by interventional radiological stenting or vascular surgical procedures.

CONCLUSION

The identification of the arterial perfusion status of patients undergoing TAA using a straightforward clinical algorithm might overcome TAA-related soft tissue complications and improve patient-related outcome measures.

[A special soft tissue procedure for treatment of hallux valgus]

OBJECTIVE

Maintaining the corrected position of the first metatasophalangeal axis. Reducing postoperative stiffness by forgoing a medial capsular shift.

INDICATIONS

Hallux valgus deformities or recurrent hallux valgus deformities.

CONTRAINDICATIONS

Existing osteoarthritis, joint stiffness, large bone defects, osteonecrosis. General medical contraindications to surgical interventions and anesthesiological procedures.

SURGICAL TECHNIQUE

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 MANAGEMENT

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.

RESULTS

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 dorsiflexion <40°. 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.

[Tendinopathy of the tibialis anterior tendon : surgical management]

A tendinopathy of the tibialis anterior tendon is a rare clinical problem. MRI is the diagnostic tool of choice. The first-line therapy should be conservative. We report about five patients who underwent operative therapy after failed conservative treatment. The operation included débridement and augmentation of the tendon. The follow-up was at least 6 months. The mean preoperative Kitaoka score was 63 (50-68) points. After 3 months follow-up the mean Kitaoka score was up to 84 (80-90) points and at the 6-month follow-up up to 96 (94-100) points. The results showed a significant reduction of pain. Operative therapy should be considered in cases of failed conservative therapy.

The uncemented primary Bicontact stem in revision total hip arthroplasty in young patients

AIM

The purpose of this study was to evaluate the uncemented primary Bicontact stem (B.Braun-Aesculap, Tuttlingen, Germany) as a possible adequate alternative to other revision systems in revision total hip arthroplasty.

METHODS

Twenty patients aged up to 58 years (34-58 years, mean age 5.7 +/- 5.8 years) with minor bone defects underwent a revision total hip arthroplasty with the uncemented primary Bicontact stem. The patients were assessed clinically and radiologically at follow-up (follow-up: 8.0 +/- 3. years).

RESULTS

The postoperative Harris Hip Score, Motion and Pain Score improved significantly. There was only one further revision in these patients because of infection and only one case with mild stress shielding.

CONCLUSION

The uncemented primary Bicontact stem seems to be a good alternative to other revision systems in total hip revision arthroplasty in young patients.

Strain adaptive bone remodelling: influence of the implantation technique

Total hip arthroplasties (THA) can be performed with cemented and uncemented femoral components. Aseptic loosening of the joint replacement still illustrates a problem for both implantation techniques. This loosening can be caused, among other factors, by resorption of the bone surrounding the implant due to stress shielding. In order to analyse the absolute influence of the implantation technique on the bone degeneration in the periprosthetic femur, the strain adaptive bone remodelling after THA was investigated in a three-dimensional finite element (FE) simulation of a femur provided with a cemented and uncemented BICONTACT (Aesculap, Tuttlingen, Germany) femoral component. For this, a bone density evolution theory was implemented in the FE code MSC.MARC. In these static FE simulations, the muscle and hip resultant forces represent the maximum loading situation in the normal walking cycle. To describe the mechanical properties of the bone, an isotropic material law dependent upon density was used. The situation directly after implantation without any bone ingrowth was simulated. The cemented femoral component was bonded to the bone by a homogenous cement mantle. The numerical results show that proximally, the bone resorption areas surrounding the BICONTACT stem are heavily dependent upon anchoring technique. Furthermore, no significant bone remodelling is calculated in the distal periprosthetic femur in both models.

Schenkelhalsendoprothesen

The survival rates of cementless femoral neck prostheses are lower than for cementless standard stems. Nevertheless, femoral neck prostheses have the advantage of preserving the femoral neck as well as not opening the diaphyseal marrow cavity. Should the need to change the endoprosthesis arise, a standard stem anchored in the diaphysis can be implanted after resection of the femoral neck. Since there is a relationship between surgical error and the learning curve for a new implant, the surgeon should be experienced in the field of total hip arthroplasty. In addition, the implantation of femoral neck prostheses is technically demanding. Therefore, careful patient selection is necessary and patients have to be informed of the advantages as well as the disadvantages of the different implant models.

Experimental measurement of tibiofemoral contact area in a meniscectomized ovine model using a resistive pressure measuring sensor

Animal models are necessary for the development and analysis of surgical techniques in meniscal surgery because they are the only means of preclinically determining the influence of biological factors such as healing processes and joint remodeling. Furthermore, little is known about the biomechanical effect of meniscectomy in sheep. The aim of the study was thus to investigate the efficacy of using a resistive pressure measuring sensor to quantify the effect of chronic meniscectomy in an ovine model. Twelve sheep were divided into two groups (n = 6): a sham operated control group (A), and a medially meniscectomized group (B). After six months, lower limb specimens were loaded with a joint-compressive force of 500 N during which the pressure measuring sensor was positioned underneath the meniscus to determine contact area, mean and peak contact pressure. A significant reduction in contact area of about 55% was observed in the meniscectomized knees compared to the controls. Peak contact pressure of the meniscectomized knees significantly increased an average of 260.4% compared to the control knees. Based on the results of this study, we conclude that the resistive pressure measuring sensors provide a means to experimentally measure tibiofemoral contact mechanics even in this relatively small (compared to human) animal model.

Evaluation of the learning curves associated with uncemented primary total hip arthroplasty depending on the experience of the surgeon

The aim of the paper is to prove and to portray the learning curve in total hip arthroplasty. This prospective study included 168 patients who were operated on by three surgeons, all demonstrating different degrees of experience in performing total hip arthroplasty. Perioperative complications and postoperative radiographs were analysed. Patients were re-examined clinically and radiologically five years postoperatively. In addition, a second study with 41 patients was performed, evaluating especially the learning curve of the highly skilled surgeon in using a femoral neck prosthesis. Radiological complications presented by the first 84 operated patients (2 nd study: 25 hips) were significantly higher than those in the following 84 patients (2 nd study: 26 hips). The learning curve of all surgeons was completed after 20 operations regardless of their experience. Clinical results at follow-up were not influenced by the learning curve. Intensive preoperative planning and exchange of experiences will reduce the length of the learning curve within and outside every clinic.

Das Navigatorkonzept

BACKGROUND

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.

METHODS

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

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.

CONCLUSIONS

The navigator concept represents a highly effective principle to minimize surgery time needed during navigated total knee arthroplasty.

Welchen Einfluss hat Übergewicht auf die Ergebnisse von Hüft- und Knieendoprothesen

As the prevalence of obesity worldwide continues to rise, defining the relationship between obesity and arthroplasty outcomes becomes increasingly important. The effect of obesity on the outcome of total hip or knee arthroplasty has been reported to be variable. Some authors believe that a high body weight will lead to less than optimal arthroplasty outcomes, because increased body weight leads to increased stress across the components and an increased load on the surrounding bone. Although this should, in turn, lead to a higher incidence of aseptic loosening or prosthetic failure in obese patients, studies have suggested that the effect of increased body weight and arthroplasty outcome are not so straightforward. The lower activity level typically observed in obese patients may partially counter the negative effects of increased weight on the bone-prosthesis interface. Although results do not show significant differences in all studies, it appears that obesity has negative impact on the results of total hip and knee arthroplasty. Therefore, long-term studies using large sample sizes should be conducted. If significant differences are demonstrated, an altered course of treatment, such as having a patient lose weight before considering a total hip or knee arthroplasty, might be advocated.

Effect of high tibial flexion osteotomy on cartilage pressure and joint kinematics: a biomechanical study in human cadaveric knees. Winner of the AGA-DonJoy Award 2004

INTRODUCTION

Valgus high tibial osteotomy is an established treatment for unicompartmental varus osteoarthritis. However, only little is known about the effect of osteotomy in the sagittal plane on biomechanical parameters such as cartilage pressure and joint kinematics. This study investigated the effects of high tibial flexion osteotomy in a human cadaver model.

MATERIALS AND METHODS

Seven fresh human cadaveric knees underwent an opening wedge osteotomy of the proximal tibia in the sagittal plane. The osteotomy was opened anteriorly, and the tibial slope of the specimen was increased gradually. An isokinetic flexion-extension motion was simulated in a kinematic knee simulator. The contact pressure and topographic pressure distribution in the medial joint space was recorded using an electronic pressure-sensitive film. Simultaneously the motion of the tibial plateau was analyzed three-dimensionally by an ultrasonic tracking system. The traction force to the quadriceps tendon which was applied by the simulator for extension of the joint was continuously measured. The experiments were carried out with intact ligaments and then after successively cutting the posterior and anterior cruciate ligaments.

RESULTS

The results demonstrate that tibial flexion osteotomy leads to a significant alteration in pressure distribution on the tibial plateau. The tibiofemoral contact area and contact pressure was shifted anteriorly, which led to decompression of the posterior half of the plateau. Moreover, the increase in the slope resulted in a significant anterior and superior translation of the tibial plateau with respect to the femoral condyles. Posterior subluxation of the tibial head after cutting the posterior cruciate ligament was completely neutralized by the osteotomy. The increase in slope resulted in a significant higher quadriceps strength which was necessary for full knee extension.

CONCLUSIONS

We conclude from these results that changes in tibial slope have a strong effect on cartilage pressure and kinematics of the knee. Therapeutically a flexion osteotomy may be used for decompression of the degenerated cartilage in the posterior part of the plateau, for example, after arthroscopic partial posterior meniscectomy. If a valgus osteotomy is combined with a flexion component of the proximal tibia, complex knee pathologies consisting of posteromedial cartilage damage and posterior and posterolateral instability can be addressed in one procedure, which facilitates a quicker rehabilitation of these patients.

Quadriceps function after TKA--an in vitro study in a knee kinematic simulator

OBJECTIVE

The purpose of this in vitro study was to investigate the amount of quadriceps force required to extend the knee during an isokinetic extension cycle before and after total knee arthroplasty.

DESIGN

The magnitude of the extension torque used in simulating a constant moment extension exercise was derived from tests made using a dynamometer on patients who had received a total knee arthroplasty. Quadriceps force needed to extend the knee was measured.

METHODS

Human knee specimens (n=8, mean age=65 SD 7 years, all male) were tested in a kinematic knee simulating machine untreated and after implantation of two different knee prosthesis. During simulation, a hydraulic cylinder applied sufficient force to the quadriceps tendon to produce an extension moment of 31 Nm about the knee.

RESULTS

The quadriceps forces needed to extend the knee during the physiologic simulation reached levels as high as 1238.9 N (SD 46.6). After implantation the Interax-prosthesis, quadriceps force increased up to 13.9% (P=0.003), in conjunction with resurfacing of the patella 11.9% (P=0.01). With the LCS-prosthesis implanted, quadriceps force showed a somewhat smaller increase of up to 6.6% (P=0.007).

RELEVANCE

The following study helps to clarify postoperative problems related to the extensor mechanisms of the knee after implantation of total knee arthroplasty.

[Dynamic in vitro measurement of retropatellar pressure after knee arthroplasty]

The purpose of this study was to examine the contact pressure between the patellofemoral interface of the physiologic, native, and prosthetic patella and the femoral component in total knee arthroplasty. An electronic sensor was used to measure contact pressure in five cadaver knees. The average peak contact pressure measured on the prosthetic patella was 9.8 MPa and was significantly higher than the physiologic and native patella. Average peak contact pressures increased with flexion. Although contact pressure reflects only a part of the dynamics of the patellofemoral articulation, these data support the selective retention of the native patella in total knee arthroplasty. Nevertheless, besides the indication for prosthetic replacement of the patella, design and operative techniques should also be part of the discussion.

[Dynamic in vitro measurement of pressure and movement with the LCS prosthetic system]

This study measured the femoral inlay pressure and the movement of mobile bearing inlays after implantation of the LCS knee prosthetic system (DePuy,Warsaw, USA). The prostheses were implanted in seven fresh frozen knee specimens. This system offered three different types of inlays [classic (CL), A/P glide (APG), and rotating platform (ROT)] with the same type of femoral component. A pressure-sensitive film (Tekscan,Boston, USA) was attached on the surface of the inlay.T he movement of the inlay was measured by an ultrasonic positioning system (Zebris, Isny,Germany). The specimens were fixed in a hydraulic knee apparatus simulating an isokinetic extension movement from 120 degrees flexion to full extension. The hydraulic cylinder that simulated the musculus quadriceps femoris extended up to 1200 N. The pressure measurement showed a peak pressure of 4.4+/-1.5 MPa (CL),3.6+/-1.0 MPa (APG),and 9.8+/-1.3 MPa (ROT). The mobile bearing inlays moved 1.4+/-2.7 mm (CL) and 2.9+/-5.8 mm (APG) from posterior to anterior during extension of the knee. During the extension the inlays rotated 0.8+/-2.6 degrees (CL), 0.9+/-5.2 degrees (APG), and 3.2+/-6.9 degrees (ROT) internally.

Relative motion of a mobile bearing inlay after total knee arthroplasty--dynamic in vitro study

OBJECTIVE

The purpose of this study was to measure the in vitro range of motion of a mobile bearing inlay knee prosthesis under dynamic isokinetic loading conditions. Additionally, the effect on the range of motion of rotational malalignment of the tibia baseplate was determined.

DESIGN

Specimens with implanted knee prostheses were mounted onto a custom built knee simulator. 3-D inlay movement was measured by an ultrasonic tracking system.

BACKGROUND

More recent knee prostheses include mobile bearing inlays type designs. These systems are intended to allow higher conformity of the tibiofemoral joint and thereby decrease contact stress without decreasing the knee's range of motion.

METHODS

Dynamic testing in the knee simulator mimicked both the speed and resulting moment of a knee isokinetic extension test. The tibia baseplate was first implanted with no rotational malalignment, followed by sequential internal and external rotation of upto 15 degrees.

RESULTS

Correctly aligned, the inlay center moved 3.5 mm (SD, 1.5 mm) posterior during extension. With the tibia baseplate externally rotated more than 10 degrees the movement pattern changed.

CONCLUSION

At up to 10 degrees of rotational malalignment the primary motion pattern of the mobile bearing is maintained. However, beyond 10 degrees unintended motion may occur.

RELEVANCE

These test results correlate to radiographic measurements of in vivo movements of mobile bearing inlays showing "paradoxical" movement of the mobile inlay compared to physiologic meniscal movement.

High tibial osteotomy versus unicompartmental joint replacement in unicompartmental knee joint osteoarthritis: 7-10-year follow-up prospective randomised study

The clinical outcome of patients treated either by high tibial osteotomy or unicompartmental arthroplasty for medial unicompartmental osteoarthritis of the knee was compared in a prospective randomised study. In total, 32 patients received a high tibial osteotomy (HTO) and 28 patients a unicompartmental arthroplasty (UKA). More intra- and postoperative complications were observed after HTO. Patients were assessed at an average of 2.5 (1.6-5), 4.5 (3.6-7), and 7.5 years (6.6-10) after the operation. Using the Knee Society Score, 71% (15) of patients after osteotomy and 65% (13) after replacement had a knee score of excellent or good 7-10 years postoperatively. The Kaplan-Meier survival analysis 7-10 years postoperatively showed a survivorship of 77% for UKA and 60% for HTO. Although the unicompartmental prosthesis used in this series has not shown promising results, we conclude that with the advanced design of unicompartmental prosthesis today, UKA offers better long-term success.

[Valgus tibial head reconstruction, monocondylar sled prosthesis or bicondylar gliding surface replacement in therapy of medial gonarthrosis--a cost analysis]

AIM

Three to a certain extent competing methods for the treatment of unicompartmental osteoarthritis of the knee are compared regarding the costs they cause. These methods comprise the high tibial valgus osteotomy (HTO), the unicompartmental knee arthroplasty (UKA), and the total knee arthroplasty (TKA).

METHODS

We compared the in-patient costs and out-patient costs of 20 patients (drawn by lot) in each group who received one of the above-named operative methods at our hospital between 1988 and 1993. The results were extrapolated according to the expected survival rate of the applied method.

RESULTS

The average total costs of patients who received a HTO were 9.487,-; for the unicompartmental arthroplasty the average cost were 11.687,-; the implantation of a TKA resulted in average costs of 16.940,-. All operative procedures exceeded a particular global amount, the socalled "Fallpauschale".

CONCLUSION

Regarding the total costs that arise for the operative treatment of the degenerative arthritis of the knee, the HTO (with or without hardware removal) proves to be the cheapest of the applied methods. Projecting the results on the survival rate of each treatment method, no statistically significant differences could be recognized between the three operative procedures.

[Knee endoprosthesis: clinical aspects]

Despite improvements in component design, instruments, and operative technique, there remains a significant complication and failure rate in total knee arthroplasty (TKA). Revision TKA accounts for every tenth operation in TKA. From June 1991 to June 1994, 209 TKAs (182 patients) were performed. Of these, 73% were uncemented, 11.2% cemented, and 15.8% hybrid. The patella was resurfaced in 96% with a cemented polyethylene or an uncemented metal-backed patella component. Follow-up showed significant improvement in knee and function scores 1 and 5-7 years postoperatively. Of the patients, 77% showed no general and 80% no local postoperative complications. Overall, 42 revisions (41 patients) were performed during the 7-year follow-up. Revision surgery was necessary because of aseptic loosening (8.1%), polyethylene wear (4.8%), complications of the extensor mechanism (2.4%), traumatic periprosthetic fractures or knee luxation (1.4%), and septic loosening (3.3%). Further improvements of polyethylene will reduce polyethylene wear. Uncemented fixation of this prosthesis can only be recommended with hydroxyapatite coating.

[Knee endoprosthesis: biomechanical requirements and consequences]

The experiments described herein permitted the dynamic in vitro measurement of the mechanical efficiency of the quadriceps muscle, both before and after total knee arthroplasty (TKA). The measurement of tibiofemoral pressure on fixed and mobile polyethylene inlays, as well as the movement of mobile inlays, is described. The Interax TKA system was implanted in 8 fresh frozen knee cadavers which were then mounted onto a knee-simulating machine. An isokinetic extension motion was simulated by extending the knee specimens under a constant extension torque of 31 Nm. The quadriceps muscle force required for this motion was not found to increase after implantation of the prostheses. Pressure on the mobile inlay was 60% lower than that measured on the fixed inlay. A 4-mm posterior migration of the mobile inlay on the tibial base plate was observed, with no motion of the inlay femoral component contact surface, which migrated posteriorly in the fixed bearing prosthesis. Thus, instead of moving posteriorly, the mobile inlay femoral component contact area remained at the center of the inlay during the entire extension motion.

[Resection of the tendon of the peroneal brevis muscle in "clicking" peroneal tendons--a report of 3 cases]

INTRODUCTION

The following article deals with the problem of peroneal clicking. This means a clicking of the two peroneal tendons against each other. It has to be differentiated from peroneal tendon dislocation or subluxation.

METHOD

In three patients, a peroneal click was found without symptoms of dislocation of the tendons over the fibula. In these cases the indication for resection of the peroneal brevis tendon was seen.

RESULTS

Postoperatively no pain, swelling, and peroneal click were present. The partial loss of function of the peroneal brevis tendon seems to be negligible.

CONCLUSION

In case of pain and swelling over the peroneal tendons, peroneal clicking should be included in a differential diagnosis. Resection of the peroneal brevis tendon is an effective treatment in these cases.