Posterior cruciate-retaining total knee arthroplasty for valgus osteoarthritis.

UNLABELLED: The valgus, osteoarthritic knee is challenging technically and it is unknown whether and how technical and implant variables influence outcomes. We therefore determined the influence of surgical technique of soft tissue balancing and patient and implant factors from 100 unselected cruciate-retaining TKAs for valgus osteoarthritis in patients younger than 75 years of age. From 1987 to 1990, lateral soft tissue balancing was done with an outside-in progression in which the lateral collateral ligament and popliteus were typically released from the femur. From 1991 to 1994, an inside-out technique was use in which the lateral collateral ligament and/or popliteus were typically preserved. The minimum followup was 0.1 year (mean, 8.2 years; range, 0.1-18.2 years). Fourteen of 16 revisions were for wear and/or instability. Popliteus release, lateral collateral ligament release, or greater polyethylene shelf age increased the risk of revision. At 10 postoperative years, survival (end point, revision) was 89% (100 knees), 94% when the shelf age was less than 1 year (n = 73 knees), 97% when the popliteus or lateral collateral ligament was not released (n = 57 knees), and 100% when both conditions were met (n = 39 knees). Cruciate-retaining implants can be successfully used in knees with any degree of valgus osteoarthritis and survival is improved when the surgeon preserves at least one of the structures providing lateral stability in flexion and uses polyethylene with a short shelf life. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

The effect of alignment of the knee on the outcome of unicompartmental knee replacement.

Many authors have recommended undercorrection of the deformity when carrying out unicompartmental knee arthroplasty (UKA). The isolated effect of alignment of the knee on the outcome of UKA has, however, received little attention. We reviewed 185 UKAs at a minimum of five years after surgery. They had been carried out by a single surgeon using metal-backed tibial components in the management of arthritis of the medial compartment. We measured the tibiofemoral angle (TFA) before and at four months after operation and at the most recent assessment. The amount of correction of the TFA and any subsequent loss were recorded. While adjusting for the effects of age, weight and gender of the patients and the type and thickness of the implants, the mean correction was significantly less for those with a Marmor rating of failure (6.8 degrees) than for those rated excellent (9.2 degrees). The mean correction was also significantly less for patients with a Marmor rating of failure (6.8 degrees) than for those rated poor (11.1 degrees). The mean correction for the UKAs which were revised (6.6 degrees) was significantly less than for those not revised (9.1 degrees). Additionally, revised UKAs had a significantly higher percentage (63%) of thinner tibial implants (<8 mm) than the surviving UKAs (27%). These findings suggest that undercorrection of the TFA in UKA of the medial compartment should be avoided, particularly if a thin tibial polyethylene insert is used.

Revision of failed unicompartmental knee arthroplasty.

Little information has been published on the salvage of failed unicompartmental knee arthroplasty. The current authors examined the failure mechanisms, complexity of surgery, and complications in such revisions. Of 39 consecutive unicompartmental knee revisions, two patients died within 2 years of surgery, four had inadequate followup, and one was excluded because of infection before revision. Therefore, 30 patients (32 knees) were followed up a mean 53 months. The patients were a mean age of 59 years at the time of unicompartmental knee arthroplasty and were predominantly male (60%). Revisions were done 9 to 204 months after the unicompartmental knee arthroplasty. The predominant failure mechanism was polyethylene wear; however, nine failed because of loosening. The mean polyethylene thickness of the failed arthroplasties was 7.3 mm. Revision procedures were straightforward. Ten patients required local autograft but no allografts were used. Primary femoral components were used in all patients; 25 were cruciate-retaining. Fourteen patients had stemmed tibial components; eight had wedge augments. The mean range of motion after revision was 111 degrees. Six patients had complications not requiring intervention. Three patients had rerevision surgery for polyethylene wear at 76, 77, and 102 months, respectively, two of whom required polyethylene insert and patellar component revision. The third patient also required tibial component revision for osteolysis. Although this is a small series, the simplicity of the procedure and the complications encountered compare favorably with those of total knee revision.

In vivo deterioration of tibial baseplate locking mechanisms in contemporary modular total knee components.

BACKGROUND: The results of recent studies documenting the backside wear of polyethylene inserts retrieved from total knee implants call into question the stability of the locking mechanisms of modular tibial components. Wear of the metal tibial baseplate suggests that the capture mechanisms of some modular fixed-bearing tibial components do not adequately restrict in vivo motion of the insert. The purposes of this study were (1) to present a method for evaluating locking-mechanism stability and (2) to investigate the stability of modular tibial components after an interval in vivo. METHODS: We measured the anteroposterior and mediolateral motion between the polyethylene insert and the tibial tray in a variety of modular total knee tibial components. A uniaxial mechanical testing machine was used to evaluate the stability of ten unimplanted components (control group), fifteen implants obtained from patients who were undergoing revision total knee arthroplasty (revision group), and fifteen devices retrieved post mortem (autopsy group). We applied loads along the anteroposterior and mediolateral axes of the tibial component and recorded the maximum insert displacement that occurred. From this value, we calculated an insert-motion index, the magnitude of a two-dimensional vector that represented the total motion in the transverse plane. RESULTS: For the control group, the mean insert-motion index was 64 +/- 13 microm (range, 6 to 157 microm); for the revision group, it was 341 +/- 51 microm (range, 104 to 718 microm); and for the autopsy group, it was 380 +/- 45 microm (range, 122 to 657 microm). The insert-motion index for the control group was significantly lower than that for the revision group (p = 0.001) or autopsy group (p < 0.001). CONCLUSIONS: Motion between the polyethylene insert and the metal baseplate in contemporary modular tibial designs increases after a period of in vivo loading. CLINICAL RELEVANCE: Although there are several advantages to the use of modular tibial components, these advantages must be weighed against the disadvantage of backside wear debris secondary to motion of the modular insert. Debris from backside wear combined with wear from the articular side might account for the increasing prevalence of osteolysis since modular components have become widely used.

Does implant selection affect outcome of revision knee arthroplasty?

We reviewed 139 consecutive femoral or tibial revision knee arthroplasties to determine if the outcome of revision knee arthroplasty using revision implant systems was superior to revisions using primary implant systems. Group 1 (n = 42) consisted of revisions performed with implants designed for primary total knee arthroplasty. Group 2 (n = 42) consisted of revisions performed with modified primary components. Group 3 (n = 55) consisted of revisions performed with components specifically designed for revision arthroplasty. The implant status was known in 123 of 139 knees at a mean follow-up of 7 years (range, 5-12 years). The implant-related failure rate, defined as reoperation requiring component revision or removal, was 26% for group 1, 14% for group 2, and 6% for group 3 (P<.05). Revision implants exhibited superior performance and durability despite their use in more difficult reconstructions. The improved longevity of revision implants justifies the evolution of modular revision components.

Comparison of proprioception in arthritic and age-matched normal knees.

BACKGROUND: Proprioception--one's ability to sense joint position and joint motion--is affected by factors such as age, muscle fatigue, and osteoarthritis. Most proprioception studies have focused on young active subjects or on recipients of total knee replacements. Few have involved a population with arthritic knees prior to total knee replacement or persons similar in age to patients with advanced knee arthritis who are to have total knee arthroplasty. The purpose of the present study was to determine (1) if proprioception in arthritic knees differs from proprioception in nonarthritic, age-matched, normal knees; (2) if, when proprioception in one knee is reduced by the presence of advanced gonarthrosis, it also is reduced in the contralateral knee irrespective of the presence of arthritis; and (3) if a person's grade of arthritis is associated with his or her level of proprioception. METHODS: This study compared the proprioception levels of a group of 117 patients who were scheduled for total knee arthroplasty because of severe arthritis (mean age, 67.9 years) with those of a control group of forty patients who were recruited from a hospital-based cardiac rehabilitation program and did not have knee arthritis (mean age, 68.3 years). We used a customized Biodex System 2 Multi-Joint Testing and Rehabilitation System to compare proprioception (the threshold to detection of passive motion) between the two groups. RESULTS: Middle-aged and elderly persons with advanced knee arthritis were significantly less able to detect passive motion of the knee than were middle-aged and elderly persons without knee arthritis. Patients who had arthritis in only one knee had a reduced ability to detect passive motion of both knees. There was no significant association between the radiographic severity of arthritis and the threshold to detection of passive motion in patients with advanced knee arthritis. CONCLUSIONS: Knee proprioception in middle-aged and elderly persons with advanced knee arthritis is reduced in comparison with that in middle-aged and elderly persons without arthritis. Such loss of proprioception is independent of the severity of knee arthritis and may foretell the development of arthritis. When a patient has reduced proprioception with regard to one knee affected by arthritis, he or she also has reduced proprioception with regard to the contralateral knee, independent of the presence or severity of degenerative arthritis. When an investigator is evaluating changes in proprioception after knee arthroplasty, it is best to compare the knee with the patient's untreated knee rather than with age-matched controls.

Clinical results of modular polyethylene insert exchange with retention of total knee arthroplasty components.

BACKGROUND: Modular polyethylene inserts have enabled surgeons to perform an isolated tibial insert exchange while retaining well fixed components. The purpose of this study was to review the results of insert revision and to clarify the role of this option compared with that of revision total knee arthroplasty. METHODS: Fifty-six patients (sixty-three knees) were managed with revision of a tibial polyethylene insert and retention of well aligned and stable femoral and tibial components. The implants had been in situ for an average of fifty-nine months (range, two to 108 months) at the time of the insert exchange. The inserts that were removed at the time of exchange were evaluated with regard to wear of the articular surface according to the classification system of Hood et al. and with regard to undersurface wear according to the method described by Wasielewski et al. Forty-eight knees were followed for an average of 7.4 years (range, 3.0 to 12.2 years) after the insert exchange. Knees that did not require an additional operation were considered to have had a successful exchange. RESULTS: Seven of the forty-eight exchanges failed, at an average of fifty-four months, because of accelerated wear of the new insert. All seven knees required complete revision of all components. Of the twenty-two exchanges that were performed because of severe wear of the primary insert, six (27 percent) failed at an average of less than five years; thus, knees in which the exchange was performed because of advanced wear were more likely to fail again (p < 0.05). In addition, primary inserts that were removed from knees in which the exchange procedure subsequently failed had higher delamination scores than those that were removed from knees in which the exchange was successful (p < 0.05). Most of the primary inserts had substantial undersurface wear at the time of the exchange procedure. Metallosis (thirty knees) and osteolysis (nineteen knees) were unrelated to failure of the exchange. CONCLUSIONS: An isolated revision of the tibial polyethylene insert should not be performed when there is accelerated wear of the insert with severe delamination and grade-3 or 4 undersurface wear within ten years after the primary procedure. Because a variety of patient-related, implant-related, and technical factors influence polyethylene wear, the orthopaedist must consider multiple variables whenever contemplating a limited revision.

Results of total knee arthroplasty with medial epicondylar osteotomy to correct varus deformity.

The clinical results of using medial epicondylar osteotomies to correct varus deformities in total knee arthroplasties were investigated. Unlike the traditional method of subperiosteal stripping of tibial ligaments, this alternative does not damage ligaments. Between 1991 and 1996, the senior author performed medial epicondylar osteotomies in 80 patients (93 knees) with primary total knee arthroplasty; of these, 60 patients (70 knees) were available for 2- to 4-year followup. At followup, no patients reported knee instability. Mean varus and valgus stability measured 14.2 points (Knee Society scale, 0-15 points). The Knee Society clinical score was 93 points, compared with a preoperative score of 42 points. The mean range of motion at followup was 111 degrees, compared with a preoperative mean of 101 degrees. The postoperative tibiofemoral angle on full limb radiographs taken with the patient weightbearing averaged 7 degrees valgus, compared with an average 6 degrees varus preoperative angle. Ninety-five percent of the patients were satisfied and reported less pain and improved knee function. Bone union occurred in 54% of the knees and fibrous union occurred in 46%. Focal tenderness, restricted motion, or other symptoms were not associated with fibrous union. The results show that epicondylar osteotomy for varus knee deformity provides excellent patient satisfaction, knee stability, motion, and deformity correction.

Clinical manifestations of a sometimes silent disease.

Although the host tissue response to debris is rarely symptomatic, the clinical manifestations of implant wear are profound. Even the most experienced orthopedic surgeon can be challenged in managing this sometimes silent disease.

Medial epicondylar osteotomy: a technique used with primary and revision total knee arthroplasty to improve surgical exposure and correct varus deformity.

The epicondylar osteotomy is a valuable tool for use in both primary and revision knee arthroplasty. Without damaging the ligamentous structures, this technique provides the surgeon with a means of accessing the knee, correcting deformity, and restoring knee stability. I have not experienced any clinical problems associated with this procedure.

Bone loss with revision total knee arthroplasty: defect classification and alternatives for reconstruction.

Although the best method for managing large bone defects has not been established, the variables to consider are: (1) implant constraint (posterior-stabilized, varus-valgus-constrained, rotating hinge); (2) stem configuration (straight versus tapered, standard, or long-stemmed); (3) stem fixation (cement versus press-fit); and (4) method of bone-defect repair (cement, augments, bone graft). In principle, an implant with the least constraint required for satisfactory knee stability is selected to reduce stress on the implant-fixation interface with compromised bone. The severity of bone loss largely influences stem length. Canal-filling stems and cementless stem fixation are indicated when major structural allografts are used. Bone defects can be successfully and reliably repaired with metal augments, allograft bone, or cement, as long as long-stemmed components without excessive constraint are selected. Because structural allografts do not revascularize, the major advantage of the allograft, as compared to cement fill or augments, is the ability to unite to damaged host bone that has a poor cancellous structure.

Surgical technique of the midvastus arthrotomy.

For more than 25 years most surgeons have used a medial parapatellar surgical approach for total knee arthroplasty because this technique affords simplicity and excellent exposure to all compartments of the knee. This article describes how the midvastus muscle splitting approach achieves surgical exposure equivalent to that of the standard medial parapatellar approach, while preserving the integrity of the vastus medialis insertion into the medial border of the quadriceps tendon. This total knee arthroplasty approach divides the vastus medialis muscle in the direction of its fibers, as opposed to the traditional method of splitting the quadriceps tendon above the patella. The limited disruption of the extensor mechanism improves the rapid restoration of quadriceps muscle control. In addition, a more stable patellofemoral articulation is evidenced by a marked reduction in the need for lateral retinacular releases.

4- to 10-year results with the anatomic modular total knee.

The outcome of 186 consecutive total knee arthroplasties performed with the Anatomic Modular Knee is reported. One hundred forty-two knees had followup of 4 to 10 years (mean, 6.9 years). Two knees required revision of all components, one because of infection and the other for instability. Seven patients underwent exchange of the modular tibial polyethylene insert at an average of 84 months postoperatively. The mean age of these seven patients at primary arthroplasty was 54 years. No implant showed clinical or radiographic evidence of loosening and there were no complications related to patellofemoral articulation. The revision rate of the femoral, tibial, and patellar components was two of 142 or 1.4%. The revision rate including exchange of the polyethylene insert was nine of 142 or 6.3%. This minimally constrained posterior cruciate retaining modular design performed well at intermediate followup. The absence of patellofemoral complications and aseptic loosening was notable. Wear related phenomena were the most common indications for reoperation and these occurred in younger, active individuals with relatively thin polyethylene bearings. The relative value of modular tibial inserts and the outcome of isolated polyethylene exchanges warrant additional study.

Classification and preoperative radiographic evaluation: knee.

Preoperative radiographic planning for revision total knee arthroplasty begins with obtaining excellent quality AP and lateral radiographs that permit: 1. Evaluation of the extent of bone loss in the metaphyseal region of the femur and tibia. 2. Full visualization of the patient's intramedullary canal for determining appropriate stem size and length. The surgeon should then determine the appropriate bone defect classification, keeping in mind the provisions needed to address Type 2 and 3 defects. These provisions include any augments or allografts, stemmed components, and the degree of component constraint needed in the patient's revision surgery. Through preoperative templating, the surgeon can determine whether a particular implant system provides the options necessary to achieve an optimal surgical result. Whenever templating leaves unanswered questions regarding the extent of bone damage or the degree of knee instability, the surgeon must prepare for the worst case scenario to ensure that the appropriate components and graft material are made available.