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Problems of total knee replacement from a sports orthopedics point of view
Abstract
Patienten möchten sich nach einer Knieprothese häufig wieder sportlich betätigen. Die bisherigen Empfehlungen basieren jedoch auf dem Gefühl des Orthopäden und nicht auf wissenschaftlich fundierten Daten. Jede sportliche Aktivität bewirkt im Gelenk einen zusätzlichen Abrieb, was die Lebensdauer einer Prothese negativ beeinflussen kann. Um diesen Abrieb möglichst gering zu halten, sollten sportlichen Aktivitäten eine geringe Spannung auf dem Polyethylen Inlay hervorrufen.
Die folgende Arbeit versucht anhand der Literatur sowie biomechanischer Überlegungen sportliche Aktivitäten mit möglichst geringen Belastungen des Inlays zu finden. Beim Gehen auf der Ebene können Kniegelenkskräfte von 3- bis 4-mal Körpergewicht bei 20 ° Knieflexion auftreten. Beim abwärts Gehen steigen die Gelenkkräfte aufs 8 fache des Körpergewichts bei 40 ° Knieflexion.
Beim Fahrrad Fahren besteht eine Kniegelkenksbelastung von 1,2-mal Körpergewicht bei 80 ° und beim langsamen Joggen 8- bis 9-mal Körpergewicht bei 50 ° Knieflexion. Wegen der Geometrie der Femurkomponente spielt beim Kniegelenk, im Gegensatz zur Hüftprothese, auch der Flexionswinkel für die Kontaktfläche und die Inlay Spannung eine große Rolle. So kann eine Knieprothese extensionsnahe stärker belastet werden als in starker Flexion.
Aktivitäten wie Joggen produzieren sehr hohe Inlayspannungen und sollten nach einer Knieprothese gemieden werden. Auch abwärts Gehen produziert wegen der grossen Gelenkkraft und des Flexionswinkels hohe Inlay Spannungen. Beim Wandern sollten sich die Patienten auf das aufwärts Gehen beschränken und abwärts die Bahn benutzen. Falls die Patienten dennoch abwärts gehen müssen, sollten unbedingt Stöcke zur Entlastung gebraucht werden. Dies bringt eine Reduktion der Kniegelenksbelastung bis zu 20 %. Weiter empfiehlt sich ein Verzicht auf Abkürzungen sowie langsames Gehen. Fahrradfahren oder Power-Walking scheinen geeignete Sportaktivitäten nach einer Knieprothese zu sein.
... The knee joint is loaded with eight times body weight when going downhill. There are recommendations that patients following TKA should use skipoles and walk slowly when descending to reduce the load on the knee joint [22,23]. However, the impact of hiking or mountaineering on the implants of TKA patients is not yet clear. ...
Purpose and hypothesis:
Improvements in pain, function and sports activity are the main goals of patients following total knee arthroplasty (TKA). Participation in sports has become an increasingly important contributor to patients' quality of life (QoL). Hiking is one of the most popular summer activities among elderly people in alpine regions. Consequently, this randomized controlled trial investigates the impact of a 3-month guided hiking programme on patients' functional abilities and QoL following TKA. It was hypothesized that patients who participate in this programme would demonstrate improvements in functional and QoL parameters compared with a control group.
Methods:
Forty-eight TKA patients were included and randomized into either the intervention group (IG; n = 25) or the control group (CG; n = 23). The IG participated in a 3-month hiking programme (2-3 times a week), whereas the CG performed activities of daily living. The stair climb test (SCT), QoL questionnaires and isokinetic force measurements were completed at three time points (i.e. pre-test, post-test, retention-test). ANOVAs for repeated measurements were conducted for the SCT results. The Friedman test and the Mann-Whitney U test were performed for the QoL parameters.
Results:
After the 3-month hiking programme, the IG achieved faster overall walking times on the SCT. The time decreased from 4.3 ± 0.6 s (pre-test) to 3.6 ± 0.4 s (post-test) for the stair ascent (p = 0.060) and from 3.6 ± 0.6 s (pre-test) to 3.2 ± 0.5 s (post-test) for the stair descent (p = 0.036). The IG showed significant improvement on some of the subscales of the Knee Injury and Osteoarthritis Outcome Score from pre-test to retention-test (p < 0.01). In the CG, no significant changes were observed (n.s.).
Conclusions:
The results indicate moderate improvement in the functional abilities and QoL of TKA patients who participated in a 3-month guided hiking programme compared with the patients in the CG. Hiking did not have any acute detrimental effects on the TKA patients during this study period.
Level of evidence:
II.
Abstract
BACKGROUND
Total talar dislocation (TTD) is very uncommon for many orthopedic surgeons and emergency/trauma specialists. Scarce cases of TTD have been reported, mainly in the form of open fracture-dislocation injury.
CASE SUMMARY
We report a very rare injury of closed TTD with a follow-up period of 36 mo. Initial closed reduction was not successful because of a fractured highly unstable medial malleolus displaced into the ankle mortise, blocking the relocation of the talus. The patient was able to walk pain-free after the 3rd month of surgery. At the 36-mo follow-up, there were 10 degrees of flexion loss and 10 degrees of extension loss in the tibiotalar joint. Furthermore, 5 degrees of subtalar joint inversion-eversion loss was present.
CONCLUSION
Open reduction should be performed for closed TTDs unless closed reduction is successful.
Key words: Total talar dislocation; Pan-talar dislocation; Talus; Case report
Die Gonarthrose ist eine degenerative Erkrankung des Kniegelenks, die durch einen fortschreitenden, irreversiblen Verlust an hyalinem Gelenkknorpel mit Umbau des subchondralen Knochens gekennzeichnet ist. Symptome sind je nach Stadium Morgensteifigkeit, belastungsabhängige Schmerzen bis hin zum Ruheschmerz mit Bewegungseinschränkung und Ergussbildung. Um operative Eingriffe hinauszuzögern oder zu vermeiden, können die Symptome durch eine Reihe konservativer Maßnahmen behandelt werden, wie Gewichtsabnahme, regelmäßiges Bewegungstraining, verschiedene Formen der physikalischen und physiotherapeutischen Behandlung, manuelle Therapie sowie Verwendung orthopädischer Hilfsmittel. Zusätzlich können begleitend nichtsteroidale Antirheumatika sowie intraartikuläre Glukokortikoide angewendet werden. Chondroprotektive Substanzen wie Glukosamin und Chondroitinsulfat sowie intraartikulär applizierte Hyaluronsäure bewirken eine zeitlich begrenzte Linderung der Symptomatik. Ihre therapeutische Wirksamkeit wird aber weiterhin diskutiert.
Routine patella resurfacing in total knee arthroplasty (TKA) has been the standard management in TKA and is considered the gold standard in most centers worldwide. However, studies have reported comparable long-term results in TKA without resurfacing the patella. When resurfaced, the patella component consists of either full polyethylene (PE) with a button or a more anatomical shape, or is metal backed with or without mobile PE bearings. Despite hypothetical advantages, mobile bearing metal-backed components have yet to prove acceptable outcomes, since considerable problems have been reported, such as increased PE wear, metallosis, fracture, or dissociation (spinout) requiring revision surgery.
The increasing life expectancy and the rising number of total joint replacements together with an increasing desire for activity of the elderly leads to the question of the load capacity of implants. Former studies demonstrated, that patients with total hip replacements increased their sports activities after the operation, whereas patients with total knee replacements reduced their activities. There are only limited data about the load capacity of total joint replacements. Different studies reveal inconsistent results concerning the loosening rates by sports activities, but the authors agree on the increase in abrasion. Biomechanical considerations suggest, that some loads are especially suitable for patients with endoprosthesis (bicycling, swimming) whereas others are not (jogging, downhill skiing). We believe that patients with endoprothesis have to be advised individually. The experience of the patient with a special sport discipline is important since optimal movements and reasonable intensity help to reduce the load of the joints. Risks and advantages as well as the quality of life of the individual patient should be taken into account for the doctor's advice.
This article presents a literature review of the current recommendations regarding sports after total joint replacement and also suggests scientifically based guidelines. Patients should be encouraged to remain physically active for general health and also for the quality of their bone. There is evidence that increased bone quality will improve prosthesis fixation and decrease the incidence of early loosening. To recommend a certain activity after total knee or hip replacement, factors such as wear, joint load, intensity and the type of prosthesis must be taken into account for each patient and sport. It has been shown that the reduction of wear is one of the main factors in improving long-term results after total joint replacement. Wear is dependent on the load, the number of steps and the material properties of total joint replacements. The most important question is, whether a specific activity is performed for exercise to obtain and maintain physical fitness or whether an activity is recreational only. To maintain physical fitness an endurance activity will be performed several times per week with high intensity. Since load will influence the amount of wear exponentially, only activities with low joint loads such as swimming, cycling or possibly power walking should be recommended. If an activity is carried out on a low intensity and therefore recreational base, activities with higher joint loads such as skiing or hiking can also be performed. It is unwise to start technically demanding activities after total joint replacement, as the joint loads and the risk for injuries are generally higher for these activities in unskilled individuals. Finally, it is important to distinguish between suitable activities following total knee and total hip replacement. To recommend suitable physical activities after total knee replacement, it is important to consider both the load and the knee flexion angle of the peak load, while for total hip replacement, which involves a ball and socket joint, the flexion angle does not play an important role. During activities such as hiking or jogging, high joint loads occur between 40 and 60° of knee flexion where many knee designs are not conforming and high polyethylene inlay stress will occur. Regular jogging or hiking produces high inlay stress with the danger of delamination and polyethylene destruction for most current total knee prostheses. Based on these design differences between hip and knee replacements it is prudent to be more conservative after total knee arthroplasty than after total hip arthroplasty for activities that exhibit high joint loads in knee flexion.
In a retrospective study with a population over 65 years, sports activity was conducted 6 years after cruciate retaining (CR) total condylar knee arthroplasty (TKA) with rotating platform (RP). 81 patients with a mean age of 71.8 ± 5.4 years were examined at the follow-up 6.4 ± 0.9 years postoperative. The mean of patients practiced active sport for 5.3 hours every week, and were active in sports 3.5 times per week. In mean 25% of the patients performed high impact sports, 47% medium impact sports and 52% low impact sports at follow-up. In KOOS sports patients reached a value of 60 ± 28, in WOMAC a total value of 12.1 ± 15.1. It can be concluded that in this population 50% of patients were active in medium and low impact sport 6 years after surgery. However, a quarter of patients was also active in high impact sports.
Die Gonarthrose ist eine degenerative Erkrankung des Kniegelenks, die durch einen fortschreitenden, irreversiblen Verlust an hyalinem Gelenkknorpel mit Umbau des subchondralen Knochens gekennzeichnet ist. Symptome sind je nach Stadium Morgensteifigkeit, belastungsabhängige Schmerzen bis hin zum Ruheschmerz mit Bewegungseinschränkung und Ergussbildung. Um operative Eingriffe hinauszuzögern oder zu vermeiden, können die Symptome durch eine Reihe konservativer Maßnahmen behandelt werden, wie Gewichtsabnahme, regelmäßiges Bewegungstraining, verschiedene Formen der physikalischen und physiotherapeutischen Behandlung, manuelle Therapie sowie Verwendung orthopädischer Hilfsmittel. Zusätzlich können begleitend nichtsteroidale Antirheumatika sowie intraartikuläre Glukokortikoide angewendet werden. Chondroprotektive Substanzen wie Glukosamin und Chondroitinsulfat sowie intraartikulär applizierte Hyaluronsäure bewirken eine zeitlich begrenzte Linderung der Symptomatik. Ihre therapeutische Wirksamkeit wird aber weiterhin diskutiert.
Aseptic loosening and other wear-related complications are one of the most frequent late reasons for revision of total knee arthroplasty (TKA). Periprosthetic osteolysis (PPOL) predates aseptic loosening in many cases indicating the clinical significance of this pathogenic mechanism. A variety of implant-, surgery-, and host-related factors have been delineated to explain the development of PPOL. These factors influence the development of PPOL due to changes in mechanical stresses within the vicinity of the prosthetic device, excessive wear of the polyethylene liner, and joint fluid pressure and flow acting on the peri-implant bone. The process of aseptic loosening is initially governed by factors such as implant/ limb alignment, device fixation quality, and muscle coordination/ strength. Later large numbers of wear particles detached from TKAs trigger and perpetuate particle disease, as highlighted by progressive growth of inflammatory/ granulomatous tissue around the joint cavity. An increased accumulation of osteoclasts at the bone-implant interface, an impairment of osteoblast function, mechanical stresses, and an increased production of joint fluid contribute to bone resorption and subsequent loosening of the implant. In addition, hypersensitivity and adverse reactions to metal debris may contribute to aseptic TKA failure but should be determined more precisely. Patient activity level appears to be the most important factor when the long-term development of PPOL is considered. Surgical technique, implant design, and material factors are the most important preventative factors because they influence both the generation of wear debris and excessive mechanical stresses. New generations of bearing surfaces and designs for TKA should carefully address these important issues in extensive preclinical studies. Currently, there is little evidence that PPOL can be prevented with pharmacological interventions.
An appropriate measuring instrument for assessing if sports activity changes after a surgical treatment is not available yet. We hypothesised that the Heidelberg Sport Activity Score is a valid and adequate instrument for measuring sport activity in patients before and after operative treatment.
This retrospective study presents a new score (Heidelberg Sports Activity Score - HAS) for measuring the sport activity in 11 selected sports. Validity, sensitivity and test-retest-reliability have been assessed.
The score includes importance of the sports for patients, impairment of the corresponding joint, and frequency and duration of the sporting activities undertaken. The HAS was validated using 3 criteria: external validation, internal comparison of groups and correlation with the Tegner Score.
A total of 655 patients were recruited for this study. The inclusion criterion was a planned or already received reconstruction (such as a high tibial osteotomy or implantation of a hip or knee prosthesis). The sport activity of these patients was evaluated before and after treatment.
The mean HAS was 32.1 points preoperatively and 37.0 postoperatively (p=0.017).
A high correlation was found between the HAS and the Tegner Score (TS) (r=0.729; p=0.010). The Test-Retest- Reliability was performed within a time interval of 2 weeks and a significant correlation of r=0.752 was found (p<0.01). Sensitivity was analysed using a sample of patients before and after high tibial osteotomy.
The HAS is a new, easy to use, effective and valid measuring instrument for the assessment of sports activity in patients before and after operative treatment.
Die Anforderungen an Gelenkendoprothesen nehmen stetig zu: Waren es früher Schmerzfreiheit und Mobilität, so sind es heutzutage
Langlebigkeit trotz starker Belastungen bis hin zur Möglichkeit der Sportausübung. Ein präoperativ sportlich aktiver Patient
möchte auch nach Endoprothesenversorgung seine bevorzugten Aktivitäten wie Wandern, Schwimmen und Radfahren, aber auch anspruchsvollere
Sportarten wie Schifahren, Tennis und Joggen ausüben. Dieser Artikel soll erläutern, welche Sportarten auf welchem Leistungsniveau
von Endoprothesenträgern ausgeübt werden. Gibt es Unterschiede im Vergleich prä- zu postoperativ? Mit welchen Risiken bzw.
negativen Einflüssen auf die Endoprothese ist bei intensiver Sportausübung zu rechnen? Welche Funktion hat der behandelnde
Arzt? Zusammenfassend werden Empfehlungen für Sportausübung nach Hüft- und Knietotalendoprothesen abgegeben.
The expectations of total joint replacement are constantly increasing: Freedom of pain and mobility used to be the primary
goal, while nowadays it is longevity despite heavy loading and intense sporting activity. A preoperative sportive patient
expects to be able to perform his favorite sporting activities like hiking, swimming and cycling, but also the more demanding
skiing, tennis and jogging, for example, after surgery. The aim of this article is to illustrate what level of sporting activities
can be performed by patients with total joint replacement. Are there differences between the pre- and postoperative levels?
What are the risks for, and negative influences on, the prosthesis during intense sporting activity? What is the role of the
physician? Finally, recommendations for sporting activities after total hip and knee replacement are given.
Recreational sport activity after total knee replacement (TKR) is of growing interest to patients. Therefore, the purpose
of this study was to evaluate dynamic loads acting on artificial and normal knees during cycling. A force measurement System
has been developed and was installed to evaluate the external loads on the pedals of a stationary bicycle. To analyze the
data, different evaluation algorithms were programmed to calculate pedal force levels of the subjects during cycling.
Sportliche Aktivität fördert die Bewegungssicherheit und Koordination der Patienten und ist drei Monate nach der Operation
möglich. Die Grundlage der gängigen Empfehlungen der Sportaktivitäten mit Endoprothesen ist nach wissenschaftlichen Kriterien
nicht evidenzbasiert und entspricht in der Regel den persönlichen Einschätzungen der behandelnden Ärzte. Hüftprothetisch versorgte
Patienten zeigen ein höheres Aktivitätsniveau als Träger von Knietotalendoprothesen.
Sporty activity promotes movement security and coordination of the patients and is possible three months after operation.
The basis of the usual recommendations of the sport activities with endoprostheses is not evidence-based according to scientific
criteria and usually corresponds to the personal estimates of treating physicians. Patients with total hip replacement show
a higher level of activity than carriers of knee total endoprostheses.
SchlüsselwörterEndoprothese-Sport-Lockerung-Patientenverantwortlichkeit
KeywordsEndoprosthesis-Sports-Loosening-Patient responsibility
This article presents a literature review of the current recommendations regarding sports after total joint replacement and also suggests scientifically based guidelines. Patients should be encouraged to remain physically active for general health and also for the quality of their bone. There is evidence that increased bone quality will improve prosthesis fixation and decrease the incidence of early loosening. To recommend a certain activity after total knee or hip replacement, factors such as wear, joint load, intensity and the type of prosthesis must be taken into account for each patient and sport. It has been shown that the reduction of wear is one of the main factors in improving long-term results after total joint replacement. Wear is dependent on the load, the number of steps and the material properties of total joint replacements. The most important question is, whether a specific activity is performed for exercise to obtain and maintain physical fitness or whether an activity is recreational only. To maintain physical fitness an endurance activity will be performed several times per week with high intensity. Since load will influence the amount of wear exponentially, only activities with low joint loads such as swimming, cycling or possibly power walking should be recommended. If an activity is carried out on a low intensity and therefore recreational base, activities with higher joint loads such as skiing or hiking can also be performed. It is unwise to start technically demanding activities after total joint replacement, as the joint loads and the risk for injuries are generally higher for these activities in unskilled individuals. Finally, it is important to distinguish between suitable activities following total knee and total hip replacement. To recommend suitable physical activities after total knee replacement, it is important to consider both the load and the knee flexion angle of the peak load, while for total hip replacement, which involves a ball and socket joint, the flexion angle does not play an important role. During activities such as hiking or jogging, high joint loads occur between 40 and 60 degrees of knee flexion where many knee designs are not conforming and high polyethylene inlay stress will occur. Regular jogging or hiking produces high inlay stress with the danger of delamination and polyethylene destruction for most current total knee prostheses. Based on these design differences between hip and knee replacements it is prudent to be more conservative after total knee arthroplasty than after total hip arthroplasty for activities that exhibit high joint loads in knee flexion.
A study of the walking activities of 243 individuals was carried out. The individuals came from four different occupations and had an age range of 17-83 years. The survey carried out in this investigation showed surprisingly little correlation between variables such as age, height, and weight of individuals and their speed of walking, length of stride, or distance walked. Correlation matrices were obtained for the whole sample and then for each sex, showing similar trends. The most significant correlation was between the height of an individual and the length of the stride, and there was a lesser correlation between age and the number of steps walked by an individual per day. Further statistical analyses showed that males in manual occupations walked most and those in sedentary occupations walked least. On the other hand, in the female groups housewives seemed to walk least and those in technical occupations walked most. The average number of steps walked per day by a male individual for the whole sample was 9537; that for females was 9839. The corresponding distances walked per day were 6.7 and 6.5 km. The differences were not statistically significant. Predictions of wear of prosthetic components made of ultrahigh molecular weight polyethylene were made on the basis of the above data and other variables affecting wear, such as the weight of the subject and the area available for contact during walking. Charts have been constructed of the penetration of the metallic component into the plastic one for both hip knee prostheses, thus enabling predictions of the wear of the plastic components of these two most widely used prostheses. Owing to the wide ranging values of the variables used in making the predictions of wear, these latter should be regarded only as 'safe' first estimates.
To determine the effect of minimal exercise on functional fitness following total hip replacement in elderly women, 20 women (13 exercisers, 7 controls) who had undergone unilateral or bilateral hip replacement surgery for primary osteoarthritis were studied. An exercise treadmill test with respiratory gas and blood lactate analyses, and a field test of walking speed on a measured course, were administered before and after a twice weekly exercise programme of three months' duration. Markers of cardiorespiratory fitness, including peak achieved oxygen uptake (VO2) and ventilatory and lactate thresholds were measured. Maximum self-selected walking speed was also measured over a flat course. Peak VO2 increased in the exercise group when compared to baseline (P < 0.05) but did not differ from the control group. The exercise group significantly improved their walking speed by 10.1% compared with non-exercising controls (1.41 vs 1.20 m/sec, P < 0.05), and increased VO2 at lactate threshold. The improvements occurred despite the twice weekly exercise sessions being below the recommended frequency of exercise for improving cardiorespiratory fitness. Minimal exercise in elderly women after hip surgery can substantially improve submaximal exercise capacity, as well as walking speed.
Estimates of knee joint loadings were calculated for 12 normal subjects from kinematic and kinetic measures obtained during both level and downhill walking. The maximum tibiofemoral compressive force reached an average load of 3.9 times body-weight (BW) for level walking and 8 times BW for downhill walking, in each instance during the early stance phase. Muscle forces contributed 80% of the maximum bone-on-bone force during downhill walking and 70% during level walking whereas the ground reaction forces contributed only 20% and 30% respectively. Most total knee designs provide a tibiofemoral contact area of 100 to 300 mm2. The yield point of these polyethylene inlays will therefore be exceeded with each step during downhill walking. Future evaluation of total knee designs should be based on a tibiofemoral joint load of 3.5 times BW at 20 degrees knee flexion, 8 times BW at 40 degrees and 6 times BW at 60 degrees.
Functional return after total joint replacement is the goal of the patient and orthopedic surgeon. Return to sports is possible and encouraged following replacement surgery. However, appropriate guidelines need to be followed to prevent complications. Overuse or a too rapid return to strenuous activity has been shown to result in an increased tendency for loosening of the prosthetic components. Recommendations for a safe return to sport activity are outlined.
Auf Grund von Untersuchungen der sportlichen und beruflichen Aktivität unserer Patienten mit und ohne Lockerung von Hüftgelenksendoprothesen konnte der positive Einfluß von körperlicher Aktivität auf die Dauerhaftigkeit der Prothesenverankerung bewiesen werden. Es gab keine Sportunfälle als Ursache von Frakturen bei den untersuchten Endoprothesenträgern.
For maintaining and developing motor mobility in old age motor activity is essential. We can take from the phylogenesis and ontogenesis of the human being how important physical activity is for personality development and for maintaining physical fitness in old age. Many phenomena, which have so far been thought to be due to natural consequences of the ageing process, can now be traced back to lack of physical activity. These findings are illustrated by examples referring to the most important subsystems of our organism (such as the central nervous system, the cardiovascular system, etc.). To keep these subsystems and with them our organism as a whole functioning as well as possible, we must improve their specific adaptability through sports and exercise. Sports and exercise for the elderly as well as gymnastics for senior citizens should therefore adequately improve co-ordinative skills, the ability of the muscles to relax, joint flexibility, muscle strength, endurance, vegetative adaptability, stress tolerance, controlling body-weight, and resistance to infections.
The major load-bearing joints of the body are the hip, knee and ankle. Arthritic disability manifests itself principally at the hip and knee. Information will be presented on the forces transmitted at the hip and knee joints in respect of magnitude, direction and variation with time. The activities to be reviewed will include walking, ramp and stair ascent and descent, and the data will include the magnitudes of the relative movements between adjacent segments and the corresponding rates.
Examination of a great number of tissue samples taken from the newly formed capsules surrounding artificial joints reveals small particles of prosthetic material. Abraded from the joint by wear and tear, these particles of plastic, metal, and acrylic cement initiate a foreign-body reaction and result in the formation of granulation tissue, including macrophages and foreign-body giant cells. Typical features of tissue reactions exist for each of the materials from which prostheses are made. The consequent formation of scar tissue produces a thickening of the capsule, which, in turn, may cause a reduction in the mobility of the joint.
In small amounts, the foreign-body particles are eliminated via the perivascular lymph spaces. Where this transport system is insufficient to handle the volume, however, the foreign-body response may extend to the whole environment surrounding the joint. In such cases, there may be loosening of the cemented prosthetic parts because of deterioration of contiguous bone anchors by the tissue membrane lining the bone cement.
Wear rates of orthopaedic polyethylene in 37 degrees C water are not very contact stress dependent below 1000 psi (6.9 MPa) but above that level they accelerate substantially. The pressure dependence overall follows an exponential function. Creep in the contact pressure range of 3--17 MPa and above is a much larger factor than wear in indentation effects. For accurate measurement of wear rates by depth measurements it is necessary to permit creep to proceed under static load until it ceases before beginning the wear test.
Total hip arthroplasty (THA) is commonly performed in an older population, for whom gold is often the only form of exercise. Members of the Hip Society do not feel that golfers have increased rates of complications after THA when compared to nongolfers and permit their patients to play gold with a THA. Most golfers will see their handicaps increase after total joint arthroplasty, although this does not appear to be a function of drive length. Most golfers with a successful primary total joint arthroplasty will not have pain while playing golf but will likely experience a mild ache in the hip region after playing. Hybrid and uncemented primary THAs appear to have lower rates of radiographic loosening in active golfers when compared to cemented THAs. However, symptoms of pain while playing or after playing do not differ among these groups, despite this radiographic difference.
The number of people participating in athletics does not equal the number of people with arthritis. There are no data to support the concern that athletic participation will make the onset of arthritic joints more likely. What is clear is that injuries that occur with athletics can increase the incidence of arthritis. If a patient does develop arthritis secondary to athletics, the treatment is not different than that offered for a spontaneously occurring arthritic joint. If an operation is necessary, the best operation depends a good deal on the goals of the patient. Continued athletic participation may be reasonable as long as the athletic activity is not vigorous and does not involve running and jumping or contact. The recommended athletic activities for patients with arthritis and for those having operations for arthritis are swimming, hiking, bicycling, walking, and golfing. The operations recommended for arthritic patients under the age of 30 should be biologic operations such as fusion or osteotomy. In patients aged 30 to 45, the operation should be correlated to lifestyle and desired level of activity. A biologic operation is better for highly active patients. When patients reach the age of 45 or are older, total joint replacement usually is preferable because of the improved clinical functional results and the decreased stress on surrounding joints with arthroplasty. If patients are older than 60 years, total joint replacement is the operation of choice and usually will include a cemented prosthesis. Some surgeons at this time do prefer cementless total-joint replacement for all patients regardless of age. Patients who have arthritis can have a satisfying athletic and exercise routine if they simply apply common sense to the manner in which they conduct their activities.
Six healthy subjects pedaled on a weight-braked bicycle ergometer at different workloads, pedaling rates, saddle heights, and pedal foot positions. The subjects were filmed with a cine-film camera and pedal reaction forces were recorded from a force transducer mounted on the left pedal. Net knee moments were calculated using a dynamic model, and the tibiofemoral shear and compressive force magnitudes were calculated using a biomechanical model of the knee. During cycling at 120 W, 60 rpm, midsaddle height, and anterior pedal foot position, the mean peak tibiofemoral compressive force was 812 N [1.2 times body weight (BW)]. The maximum anteriorly directed tibiofemoral shear force was found to be low (37 N). The compressive and shear forces were significantly increased by an increased ergometer workload. The pedaling rate had no influence on the tibiofemoral force magnitudes. The stress on the ACL was low and could be further decreased by use of the anterior foot position instead of the posterior.
We examined the physical activity and other life-style characteristics of 16,936 Harvard alumni, aged 35 to 74, for relations to rates of mortality from all causes and for influences on length of life. A total of 1413 alumni died during 12 to 16 years of follow-up (1962 to 1978). Exercise reported as walking, stair climbing, and sports play related inversely to total mortality, primarily to death due to cardiovascular or respiratory causes. Death rates declined steadily as energy expended on such activity increased from less than 500 to 3500 kcal per week, beyond which rates increased slightly. Rates were one quarter to one third lower among alumni expending 2000 or more kcal during exercise per week than among less active men. With or without consideration of hypertension, cigarette smoking, extremes or gains in body weight, or early parental death, alumni mortality rates were significantly lower among the physically active. Relative risks of death for individuals were highest among cigarette smokers and men with hypertension, and attributable risks in the community were highest among smokers and sedentary men. By the age of 80, the amount of additional life attributable to adequate exercise, as compared with sedentariness, was one to more than two years.
A saggital plane biomechanical analysis of I I slow jogging trials yielded joint moments of force. power curves and positive and negative work at each of the joinrs of the lower limb. The following can be summarized: 1. The total moment of force pattern of the lower limb was primarily extensor during stance and flexor during swing. The hip had an extensor peak at 20"". the knee at 40Y, and the ankle at 60"" of stance. 2. The variability of the moment patterns across all trials was considerably less than that seen during natural walking. 3. Two power bursts wereseen at the ankle, absorption early in stance followed by adominant generation peak during late push-off. The average peak of power generation was 800 W with individual maximums exceeding 1500 W. 4. Power patterns for all trials showed the knee to have fivedistinct phases: an initial shock absorbing peak during weight acceptance. a small generation burst during early push-off, a major absorption pattern during late push-08continuing until maximum knee flexion, a third absorption peak decelerating the leg and foot prior to impact,and a final small positive burst as the knee flexors rotate the leg posteriorly to further reduce the forward velocity of the foot prior to heel contact. 5. Power patterns at the hip were neither large nor consistent indicating the dual role of hip flexors and extensors relative to the trunk and lower limb stability. 6. Positive work done by the ankle plantarflexors averaged three times that done by the knee extensors, and in some joggers the ankle muscles generated eight times that of the knee muscles. 7. Over the entire stride the knee muscles absorbed 3.6 times as much energy as they generated: the ankle muscles generated 2.9 times as much as they absorbed.
Up to now, sporting activity after total hip arthroplasty has been limited or terminated completely because of the risk of failure. In the case of younger patients, it is desirable to know whether this attitude is justified. Consequently, an analysis has been made of 110 patients (all male, average age at the time of the operation 55 years, 42 bilateral). Sport was practised in 78 and 56% of the cases prior to an after the operation respectively. The patients with intense sporting activity were examined and the findings compared with those who did not participate in a sporting activity after the operation. The incidence of replacement due to loosening is surprisingly higher among the group of patients with no sporting activity (14.3% to 1.6%). In the light of these findings, there is no need to prohibit sport in these cases. To allow for a gradual resumption of sport, guidelines have been elaborated on the basis of present-day knowledge of quantitative and qualitative hip strain. The short load peaks appearing as the heel touches the ground on walking or running will be attenuated by means of a viscoelastic heel pad.
Seven knees were studied to determine the contact area and pressure distribution of the tibiofemoral joint, under various loads and at 0 degrees flexion, using the casting method and special sensor sheets. At a load of 1000N (Newton) the contact area of the knee was 11.5 x 10(2) mm2 with menisci and 5.2 x 10(2) mm2 without menisci, and the menisci occupied 70% of the total contact area. Peak pressure at 1000N was 3MPa (Mega Pascal) with the menisci and 6MPa without them. The high pressure areas were located on the lateral meniscus as well as on the uncovered part of the articular cartilage of the lateral compartment, and on the uncovered cartilage in the medial compartment. After removal of the menisci the contact area decreased to below one half that of the intact knee and the contact pressure considerably increased. These facts imply that the menisci have load bearing and load spreading functions. The contact areas were also measured in two osteoarthrotic knees and they were significantly larger than those in normal knees. In these arthrotic knees the menisci seemed to play a less significant role in transmission of weight than in the normal knees.
The results of total knee arthroplasty (TKA) in patients who actively exercise have not been previously studied. Golf is a frequent form of exercise for the older population in whom TKAs are usually performed. Members of The Knee Society permit their patients with TKA to play golf, if they desire to do so. They recommend waiting approximately 18 weeks after surgery before beginning to play. Most members of The Knee Society stated that they have no preferences as to the model of knee arthroplasties in golfers, although 35.2% did state that they would use a posterior-cruciate sparing model. After TKA, active golfers in the authors' study (83) invariably experienced a significant rise in their handicap (mean +4.6 strokes) and also a decrease in the length of their drives. Most (86.7%) use a cart while playing, but still a small percentage (15.7%) will have a mild ache in the knee while playing and a larger percentage (34.9%) will have a mild ache in the knee after playing. In addition, golfers with left TKAs have more difficulty with pain during and after play (P < .01) than do golfers with right TKAs. Radiolucencies were also common in our study, occurring in 53.7% of all knees studied and 79.1% of cemented TKAs.
No biomechanical evaluation of total knee designs exists for loads occurring during sports activities. It was the purpose of the present study to evaluate the contact stress distribution and contact area of different knee joint designs for loads that occur during four common recreational endurance activities.
Three different total knee designs were evaluated for loads occurring during cycling (1.2 body weight (BW) at 80 degrees of knee flexion), power walking (4 BW at 20 degrees), hiking (8 BW at 40 degrees), and jogging (9 BW at 50 degrees) using Fuji pressure-sensitive film. The designs consisted of a flat tibial inlay, a curved inlay, and an inlay with mobile bearings. Five measurements were conducted for each load. The pressure sensitive films were scanned and analyzed using an image analysis program.
During cycling, the area with stress levels above the yield point of polyethylene (overloaded area) was below 15 mm2 for each design. During power walking, the mobile bearing design showed no overloaded area, whereas it was below 50 mm2 for the flat and curved design. During downhill walking and jogging, more than 140 mm2 were overloaded for each design.
It was concluded that patients after total knee replacement should alternate activities such as power walking and cycling. For mountain hiking, patients are advised to avoid descents or at least use ski poles. Jogging or sports involving running should be discouraged after total knee replacement.
The effects of different conformity ratios and loads on the ultrahigh molecular weight polyethylene stress levels acting on knee implants were examined using a nonlinear, finite element analysis. The contact condition between a rigid cylinder with a radius of 30 mm and a polyethylene plate was modeled. Nonlinear behavior of polyethylene was assumed. The polyethylene plate was constructed with varying radii, with a minimal thickness of 6 mm and with a width of 40 mm. The ratio of the cylinder radius to the radius of the polyethylene plate was defined as the conformity ratio; a conformity ratio of 0 represented a flat tibial inlay, whereas the highest ratio modeled of 0.99 was nearly conforming. The conformity ratios modeled were 0, 0.2, 0.4, 0.6, 0.7, 0.8, 0.9, 0.95, and 0.99. The loads applied were 1000 N, 2000 N, 3000 N, 4000 N, 5000 N, and 6000 N. The effects of different conformity ratios and loads on the contact area (mm2), the compressive surface stress (MPa), the shear stress (MPa), and the von Mises stress (MPa) were investigated. It was found that all of these parameters were affected by changes to the conformity ratio and to a lesser extent by load changes. That is, increasing the load from 3000 N to 6000 N resulted in a surface and shear stress increase lower than the increase in stress caused by the small change of the conformity ratio from 0.99 to 0.95. The effect of an increasing conformity ratio on the reduction in stress was more pronounced for conformity ratios above 0.8. In addition, the effect of a load increase for a flat tibial inlay was two times greater than for one with near full conformity.
Kinematic and kinetic data were collected from 12 healthy subjects whilst they performed both downhill and level walking at a controlled cadence. A ramp of 6 m length and a gradient of -19% was used for downhill walking and this incorporated the same force platform that was used for level walking. Planar net joint moments and mechanical power at the ankle, knee, and hip joints were calculated for the sagittal view using force platform and video records based on standard inverse dynamics procedures. On the basis of differences in ankle, knee, and hip joint kinematics the ankle joint was seen to compensate for the gradient at push off and during the swing, the knee joint from early stance through until early swing phase, and the hip joint from early swing through until the early stance phase. The major differences in joint moments and muscle mechanical power were seen in the knee and ankle joint. Whereas peak moments and muscle power were much higher for downhill walking in the knee joint, these measures were significantly smaller at the ankle joint. Hip joint moments and muscle power estimates were only slightly larger for downhill walking. These data explain well the problems that patients with patellofemoral pathology and anterior cruciate ligament (ACL) deficiency encounter with downhill walking, and the muscle soreness experienced by mountain trekkers. RELEVANCE: Biomechanical estimates of musculoskeletal loadings in gait are invariably derived from laboratory studies of walking over a level surface. In this study comparisons were made between downhill and level walking in order to appreciate more fully the increased loadings on the lower extremity under more stressful but not atypical conditions. The data so derived provide the necessary basis for the prediction of loadings on specific muscle/joint structures and can serve as a foundation for exercise prescription with patients recovering from injury or orthopaedic surgery.