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Total condylar knee prosthesis is gradually proving fully reliable. It is an "all or nothing" type of surgery, with either good or bad results depending on the occurrence of complications, notably tibial decementation. With the experience acquired it may be said that the much dreaded wearing off of polyethylene components is not responsible for failures of total knee prosthesis.
Ten knees with early tissue breakdown after knee arthroplasty resulting in exposed prostheses were treated with different plastic surgical techniques. Six knees were successfully covered: four using a gastrocnemius musculocutaneous flap, one using a fasciocutaneous flap, and one using split-skin grafts. Four knees failed: two using local skin flaps and two using split-skin grafts. A gastrocnemius musculocutaneous flap seems to provide a reliable coverage of the exposed knee joint.
In knee arthroplasty, component malpositioning seems to be a fundamental cause for failure. The degree of malpositioning is important. To investigate this degree, 86 of 137 knee arthroplasties performed with the Townley semiconstrained bicondylar prosthesis were examined after a mean follow-up period of 6.5 years (range, 5.0-8.5 years). Five arthroplasties were excluded because of aseptic loosening, but none of these showed malalignment in postoperative roentgenograms. Clinical results and the patients' reports on deterioration of prosthetic function were correlated with positioning of the prosthetic components. Total alignment between 6 degrees of varus and 7 degrees of valgus was associated with good clinical results. Total alignment of more than 7 degrees of valgus, anterior tilting of the tibial component, or positioning of the femoral component in more than 12 degrees of valgus correlated with relatively poor clinical results.
The Noiles hinged knee prosthesis has been reported to diminish sheer and tensile loading on the cement-bone interface. Theoretically, this should eliminate the complication of loosening, commonly reported in hinged total knee prostheses. We reviewed the cases of all of the patients who have been treated with the Noiles knee prosthesis at our institution. Eighteen knees in fourteen patients were available, seventeen of which were followed for more than five years. Although all of the prostheses did well initially, ten knees in eight patients (56 per cent) had failed by an average of thirty-two months postoperatively. These eight patients included four of the five who weighed more than ninety kilograms and all of those who had had a prior arthroplasty. The failures were clearly defined along the lines of sex distribution. Measurements on the radiographs showed a significant difference between sexes in the metaphyseal diameter and thus in the percentage of the femoral canal that was filled by the prosthesis and cement. We concluded that prosthetic design must incorporate cortical cement support to reduce stress at the cement-bone interface, especially in a medullary canal with a larger diameter.
Since 1970, 170 knees have been operated upon using the Kodama-Yamamoto knee prosthesis. Of these 127 had the revised Mark-II prosthesis and of this group 91 cases have been followed for more than a year. Interim results suggest that the total knee score has improved. on the average, from 38 points preoperatively to 74 points after one year. A single early complication involved loosening of the prosthesis in a case of knee infection. Except for this case, no loosening and no radiolucent lines have been observed. Methacrylate bone cement is known to be harmful to bone and soft tissues, and our basic and clinical studies reveal that results improve when the total knee replacement is done without using cement.
The posterior stabilized knee prosthesis is a versatile and durable prosthesis with an excellent clinical record. It was designed to increase range of motion, improve stair climbing, and prevent posterior tibial subluxation.
The total condylar knee prosthesis evolved from previous experience with other prostheses at the Hospital for Special Surgery. This evolution includes patellar resurfacing. Subsequent modifications have led to the total condylar knee prosthesis II (a cruciate substituting prosthesis), and the total condylar knee prosthesis III (a TCP II with increased constraint). The surgical technique requires ligamentous balance with correction of preoperative deformity by a soft-tissue release. Subsequently a standard operation is performed. Four hundred and sixty-one knees were reviewed with a minimum of one year follow-up and a maximum of 5 years. Seventy-five per cent were osteoarthritic knees. Using the Hospital for Special Surgery Knee Rating Scale, the results were excellent in 312 knees (68%), good in 109 knees (23.5%), fair in 18 knees (4%) and poor in 22 knees (4.5%). Osteoarthritic knees (excellent or good 93.5%) did slightly better than rheumatoid knees (excellent or good 87%). Complications include 6 infections, 6 subluxations and 10 cases of component loosening. There were 15 reoperations (3%). The results approach total hip arthroplasty in quality and so far have not deteriorated with time.
The evaluation of a painful knee prosthesis remains a difficult problem for both orthopaedic surgeons and radiologists. We have compared digital subtraction arthrography with nuclear arthrography in 7 patients with a painful knee prosthesis. Three patients showed a loose tibial component, demonstrated by both digital subtraction and nuclear arthrography. All 3 underwent revision of their prosthesis. One patient had an equivocal digital subtraction arthrogram and negative nuclear arthrogram, while both studies were negative in the 3 remaining patients. Nuclear arthrography is a simple procedure and can provide useful additional information when combined with digital subtraction arthrography.
A 3-component sliding meniscus knee prosthesis was tested mechanically to evaluate the direct loads and the anteroposterior and mediolateral bending moments on the prosthetic components during the loading phase on a pendulum prosthesis testing machine. The bending moments changed with variation of the component positions. Tilting the tibial plateau produced the greatest change in lateral bending moment on the femoral component but alteration in plateau rotation or femoral tilting produced little change in the low values of the 2 bending moments. It is necessary to ensure that the tibial component is positioned horizontally on the tibial plateau, but it is not necessary to be concerned about the angle of the femoral component to the vertical or the misalignment rotationally of the tibial component. The load ideally passes through the condylar component to the tibia much more centrally than if it were a constrained prosthesis system during the loading range, reducing the likelihood of displacement of the 2 fixed components.
Prosthetic fitting in patients with below-knee amputations and concurrent knee flexion contractures poses inherent difficulties to the prosthetic rehabilitation team. The standard bent-knee prosthesis is bulky and awkward. It treats the patient functionally as a knee disarticulation and yields no potential for improving the patient's degree of contracture. This paper describes a case report with an alternative to the bent-knee prosthesis that not only offered improved function relative to the standard bent-knee prosthesis, but also acted therapeutically by reducing the patient's knee-flexion contracture.
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The three-dimensional kinematics of the Tricon-M knee prosthesis during active knee flexion and extension were recorded in 11 patients with arthrosis or rheumatoid arthritis using roentgen stereophotogrammetric analysis. Twenty-three normal knees constituted the control group. The prosthetic knees displayed the same degrees of freedom regarding rotational and translational movements as the normal knees, although the kinematics were different. A combination of internal rotation, abduction, and lateral translation of the tibia was recorded during flexion, and the reversed movements were recorded during extension. During the first 25 degrees of flexion, these movements were small, reflecting the high congruency between the articular surfaces, while beyond 25 degrees they increased. The normal knees displayed a combination of internal rotation, adduction, and medial translation of the tibia during flexion and the reversed movements during extension. The prosthetic knees also exhibited an increased posterior displacement during increasing flexion when compared with the normal knees. There was a correlation between the positioning of the femoral component in the sagittal plane and the recorded anterior/posterior translations. In conclusion, the kinematics of the Tricon-M knee prosthesis significantly differ from the normal knee, probably because of the design of the prosthesis and the absence of the cruciate ligaments.
Twenty-seven total knee arthroplasties (TKAs) were performed in 24 patients using the total condylar III knee prosthesis (TCP III) and were evaluated clinically and radiographically with a mean follow-up period of 4 years. Eighteen were revision TKAs, and nine were primary knee arthroplasties. Evaluations were made using the Hospital for Special Surgery (HSS) knee scale as well as the Knee Society radiographic evaluation method. Clinical results for all knees were 11% (3 of 27) excellent, 70% (19 of 27) good, 15% (4 of 27) fair, and 4% (1 of 27) poor. The one poor rating resulted from an intraoperative vascular injury. The results showed no statistical difference between revision and primary TKA. After operation, pain relief, range of motion, walking, function, and activity level improved in both the primary and revision patients. Radiolucencies 2 mm or greater in width were found in 6 of the 27 tibial components, in none of the 27 femoral components, and in 1 of the 19 patellar components. Only two tibial implants showed progressive radiolucencies. No correlation was found between the radiographic position of the implants and the clinical results. The authors conclude that the TCP III is a satisfactory choice for TKA in selected knees in which there is significant instability and in which intramedullary fixation is required.
Control of an active above-knee prosthesis has been simulated for a selected gait activity using a hierarchical closed-loop method. An extension of finite-state control, referred to as artificial reflex control, was adopted at the strategic level of control. At the actuator level of control an optimal tracking method, based on dynamic programming, is applied. This deals mainly with the actuator level of control, but considers the interaction of the leg dynamics and the switching effects of artificial reflex control. Optimal tracking at the actuator level of the above-knee prosthesis reduces the on-off effects of finite-state methods, such as artificial reflex control. The proposed method can also be used for the design of prosthetic elements. Specific attention is paid to the limited torque and power in the prosthetic joint actuator, which are imposed by the principle of self-containment in the artificial leg. The hierarchical structure, integrating artificial reflex control and optimal tracking, can be used in real time, as estimated from the number of computer operations required for the suggested method.
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Function of the knee and patellofemoral symptoms were correlated with the position of the implant in 101 consecutive patients with 116 posterior stabilized condylar knee prostheses. All of the patients were followed for a minimum of two and a half years with sequential physical examinations, radiographs, and functional evaluation of the knee. In sixteen knees (14 per cent), clicking or catching of the patella in terminal extension or painless crepitation throughout the arc of flexion developed without lowering the functional knee-evaluation score. Pain or mechanical problems, or both, that lowered the functional knee-evaluation score occurred in another fourteen knees (12 per cent), within the first postoperative year. Of these fourteen, eight required revision solely for patellofemoral complaints. Critical analysis of the tibial-patellofemoral mechanical axis identified three surgical variables that were found to markedly affect the functional result of the prosthesis: the distance from the center line of the tibial prosthesis to the center line of the tibial plateau, a change in the position of the joint line of the prosthesis relative to the hip and ankle, and the patellar height, measured as the perpendicular distance from the inferior pole of the patellar implant to the joint line of the prosthesis. Functional knee scores, range of motion, patellofemoral pain or mechanical symptoms, the need for revision, and the necessity of manipulation could all be statistically significantly correlated with the three independent variables. In addition, a range of neutral alignment was developed.(ABSTRACT TRUNCATED AT 250 WORDS)
The madreporic ("caviar") prosthesis is a hinged knee prosthesis that can be inserted without the use of cement. The surfaces of the intramedullary stems are constructed with contiguous spheres one mm in diameter. These spaces are filled by bone trabeculae and haversian bone, providing permanent biologic fixation. Experimental madreporic knee arthroplasties in dogs show that bone probes these surfaces and produces solid attachments. Histologically, the trabeculae remain separated from the metal by a fine layer of fibrous tissue. The method of insertion of the prosthesis is simple. Preparing the epiphyses before any bone resection avoids the possibility of rotational positioning errors. The form of the intramedullary stems offers good positioning in the frontal plane. The analysis of an initial series of 15 cases shows results that are far from outstanding. The 2 deaths, the 2 cases of sepsis, and the recuperation of only mediocre motion can be explained, at least in part, by the advanced age of the patients and the poor bone quality of the rheumatoid patients. Nevertheless, this type of prosthesis has 2 important advantages. It avoids the complications from the use of acrylic cement and allows for a revision operation for cases of failed surface replacement designs. Obviously further experimentation with noncemented designs will continue and definitive studies will be reported later.