Search

Background: There is currently a lack of evidence to identify the optimal patellar implant design in total knee arthroplasty (TKA). The aim of this study was to assess clinical, intraoperative, radiographic, and scintigraphic differences between inlay (IN), onlay round (OR), and onlay oval (OO) patellar implants., Methods: A parallel-group, double-blinded, randomized trial compared IN, OR, and OO patellar implants using the same posterior-stabilized TKA prosthesis for each. Patient outcomes were prospectively followed for a minimum of 2 years, with survivorship outcomes followed for a mean of 5 years. The primary outcome was the between-group differences in the mean Kujala score change from preoperatively to 2 years postoperatively. The secondary outcomes included differences in other knee-specific and general health outcomes, intraoperative characteristics, radiographic parameters, patellar vascularity, and implant survivorship., Results: A total of 121 participants (40 in the IN group, 41 in OR group, 40 in the OO group) were allocated to 1 of 3 implant designs. At 2 years postoperatively, there were no significant differences in Kujala score changes between groups (p = 0.7; Kruskal-Wallis test). Compared with the IN group, the OR group showed greater improvements in Knee injury and Osteoarthritis Outcome Score (KOOS) Activities of Daily Living and in KOOS Quality of Life compared with the OO group. However, the OO design exhibited better bone coverage and lower lateral facetectomy rates compared with the IN and OR designs. The IN group had more lateral contact compared with the OO group (p = 0.02; Fisher exact test), but the overall value for lateral contact was not significant (p = 0.09; chi-square test). There were no differences in postoperative scintigraphic vascularity (p = 0.8; chi-square test). There was 1 revision for infection at 3 years postoperatively in the OO group, and no revision in the other groups., Conclusions: Patellar design did not influence patellofemoral outcomes or survivorship. However, OR implants showed improvements in some secondary patient-reported outcome measures, and OO implants exhibited superior bone coverage and improvements in several intraoperative, radiographic, and scintigraphic outcomes. These findings, combined with superior long-term implant survivorship from previous studies, add support for the use of onlay designs in TKA., Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/H318)., (Copyright © 2022 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: The optimal strategy to address osseous deficiencies of the patella during revision total knee arthroplasty (TKA) remains controversial. One possible solution is a cemented biconvex patellar component used such that the non-articular convexity both improves fixation and makes up for bone loss. The aim of this study was to determine the outcomes of the use of biconvex patellar components in a large series of revision TKAs., Methods: From 1996 to 2014, 262 revision TKAs were performed at a single institution using a biconvex patellar component. Implant survivorship, clinical and radiographic results, and complications were assessed. The mean patient age at the TKA revision was 69 years, and 53% of the patients were female. The mean follow-up was 7 years., Results: The 10-year survivorship free of revision of the biconvex patellar component due to aseptic loosening was 96%. The 10-year survivorship free of any revision of the biconvex patellar component was 87%. The 10-year survivorship free of any rerevision and free of any reoperation was 75% and 70%, respectively. The mean Knee Society Score (KSS) improved from 45.4 before the index revision to 67.7 after it. The mean residual composite thickness seen on the most recent radiographs was 18.1 mm. In addition to the complications leading to revision, the most common complications were periprosthetic patellar fracture (6%), of which 3 required revision; superficial wound infection (6%) requiring antibiotic therapy only or irrigation and debridement; and arthrofibrosis (3%)., Conclusions: In this cohort of 262 revision TKAs, biconvex patellar components used to treat marked patellar bone loss demonstrated excellent durability with a 10-year survivorship free of patellar rerevision due to aseptic loosening of 96%. The biconvex patellar components were reliable as evidenced by substantial improvements in clinical outcomes scores and a low risk of complications., Level of Evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence., Competing Interests: Disclosure: The authors indicated that no external funding was received for any aspect of this work. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work and “yes” to indicate that the author had other relationships or activities that could be perceived to influence, or have the potential to influence, what was written in this work (http://links.lww.com/JBJS/G412)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: The ability to estimate skeletal maturity using a knee radiograph would be useful in anterior cruciate ligament (ACL) injuries and limb-length discrepancy in immature patients. Currently, a quick, accurate, and reproducible method is lacking., Methods: Serial knee radiographs made 3 years before to 2 years following the chronologic age associated with 90% of final height (an enhanced skeletal maturity gold standard compared with peak height velocity) were analyzed in 78 children. The Pyle and Hoerr (PH) knee method was simplified by developing discrete stages for the distal part of the femur, the proximal part of the tibia, the proximal part of the fibula, and the patella. The Roche-Wainer-Thissen (RWT) knee method was simplified from the 36 original parameters to 14 parameters by removing parameters that were poorly defined, were not relevant to the peripubertal age range, were poorly correlated with 90% final height, or were poorly reliable on a 20-radiograph pilot analysis. We also compared the recently described central peak value (CPV) of the distal part of the femur. The Greulich and Pyle (GP) left-hand bone age was included for comparison., Results: In this study, 326 left knee radiographs from 41 girls (age range, 7 to 15 years) and 37 boys (age range, 9 to 17 years) were included. Stepwise linear regression showed higher correlation in predicting years from 90% final height using the modified RWT and demographic characteristics (R2 = 0.921) compared with demographic characteristics alone (R2 = 0.840), CPV and demographic characteristics (R2 = 0.866), GP and demographic characteristics (R2 = 0.899), and PH and demographic characteristics (R2 = 0.902). Seven parameters were excluded from the RWT and demographic characteristics model using stepwise linear regression and generalized estimating equations analysis, leaving 7 parameters (2 femoral, 4 tibial, and 1 fibular) in the final model. Compared with RWT and demographic characteristics (R2 = 0.921), there were minimal incremental increases by adding CPV (R2 = 0.921), GP (R2 = 0.925), or PH (R2 = 0.931)., Conclusions: This large analysis of knee skeletal maturity systems isolated 7 discrete radiographic knee parameters that theoretically outperform the GP bone age in estimating skeletal maturity., Clinical Relevance: We present a modified knee skeletal maturity system that can potentially preclude the need for additional imaging of the hand and wrist in reliably estimating skeletal maturity., Competing Interests: Disclosure: The authors indicated that no external funding was received for any aspect of this work. On the Disclosure of Potential Conflicts of Interest forms, which are provided with the online version of the article, one or more of the authors checked “yes” to indicate that the author had a relevant financial relationship in the biomedical arena outside the submitted work (http://links.lww.com/JBJS/G328)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: The medial patellofemoral ligament varies in attachment of its fibers to the patella and vastus intermedius tendon. Our aim was to identify and describe its anatomic midpoint. To account for the variability of the attachment site, we refer to it as the medial patellofemoral complex., Methods: Using AutoCAD software, we identified the midpoint of the medial patellofemoral complex attachment on photographs of 31 cadaveric knee dissections. The midpoint was referenced relative to the superior articular surface of the patella (P1) and was described in terms of the percentage of the patellar articular length distal to this point. A second point, at the junction of the medial border of the vastus intermedius tendon with the superior articular border of the patella, was identified (P2). The distances of the midpoint to P1 and P2 were calculated and were compared using paired t tests., Results: Twenty-five images had appropriate quality and landmarks for digital analysis. The midpoint of the medial patellofemoral complex was located a mean (and standard deviation) of 2.3% ± 15.8% of the patellar articular length distal to the superior pole and was at or proximal to P1 in 12 knees. In all knees, the midpoint was at or proximal to P2. After exclusion of 2 knees with vastus intermedius tendon attachments only, the medial patellofemoral complex midpoint was closer to P2 (5.3% ± 8.6% of the patellar articular length) than to P1 (9.3% ± 8.5% of the patellar articular length) (p = 0.06)., Conclusions: The midpoint of the medial patellofemoral complex was 2.3% of the articular length distal to the superior pole of the patella. Additionally, we describe an anatomic landmark at the junction of the medial border of the vastus intermedius tendon and the articular border of the patella that approximates the midpoint of this complex., Clinical Relevance: Our study shows that the anatomic midpoint of the attachment of the medial patellofemoral complex is proximal to the junction of the medial vastus intermedius tendon and the articular border of the patella, suggesting that graft placement may be more anatomic on the vastus intermedius tendon rather than on the patella., (Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: The main objective of this prospective randomized study was to compare the clinical and radiographic outcomes of the mini-midvastus (MMV) approach with the conventional approach for total knee arthroplasty at the 5-year follow-up., Methods: Ninety-seven patients (100 knees) with osteoarthritis were assigned to the MMV group or to a group receiving conventional total knee arthroplasty. Intraoperative and postoperative clinical data were collected. At 6 weeks and at 1, 2, and 5 years postoperatively, the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Oxford Knee Score (OKS), the Knee Society Score (KSS), and the Short Form (SF)-12 were completed. Radiographs of the knee were made preoperatively and at 1 day and 1 and 5 years postoperatively. Computed tomography (CT) scans were performed 2 years postoperatively., Results: In the MMV group, the mean skin incision was 2.5 cm shorter (p < 0.001) and the mean duration of the operation was 6 minutes longer than in the conventional total knee arthroplasty group (p < 0.05). Eight patients in the conventional group had a lateral parapatellar retinacular release compared with 1 in the MMV group; the difference was significant (p = 0.01). Three intraoperative complications, including 2 small lateral femoral condylar fractures and 1 partial patellar tendon laceration, occurred in the MMV group. Seven patients in the MMV group had postoperative blisters; all of them had a relatively large femoral component and 4 of them were large men. The radiographs and CT scans of the prostheses showed no significant differences between the MMV and conventional groups except for the posterior slope of the tibial component. In addition, no significance differences were detected between the groups with respect to the KOOS, OKS, KSS, and SF-12 scores determined at the 6-week and the 1, 2, and 5-year follow-up evaluations., Conclusions: In the rehabilitation period and at the short and mid-term follow-up, no relevant clinical and radiographic differences were found between the MMV and the conventional approach for total knee arthroplasty, making the advantage of MMV total knee arthroplasty cosmetic. We discourage the use of the MMV approach in large male patients because of the increased number of intraoperative complications and skin blisters postoperatively., Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence., (Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: Longitudinal changes in patellar stiffness following reconstruction of the medial patellofemoral ligament for recurrent patellar dislocation at full extension are unknown., Methods: Fifteen consecutive patients (three men and twelve women, with a mean age of twenty-two years) with seventeen knees were matched by sex and age to thirty-two reference subjects in this prospective study. The follow-up period was a minimum of twenty-four months. The medial patellofemoral ligament reconstruction used an autograft semitendinosus tendon and an interference screw system with or without lateral release under 10 N of laterally directed force. The medial patellar stiffness and lateral patellar stiffness were measured in 0° of knee extension using the Patella Stability Tester preoperatively; postoperatively at three, six, twelve, and eighteen months; and at the time of the latest follow-up. Before and after the surgical procedure, patients were evaluated for apprehension and Kujala and Lysholm scores; radiographic examinations were performed to evaluate changes, including osteoarthritic changes., Results: The medial stiffness of the affected side before the surgical procedure was significantly lower than the lateral stiffness (p = 0.004) and the stiffness for healthy reference knees (p = 0.004). Medial stiffness three months after the surgical procedure was significantly elevated compared with lateral values (p = 0.027), preoperative values (p < 0.001), and reference group values (p = 0.002); reached the reference level by six months; and was maintained for up to two years. Furthermore, medial stiffness and lateral stiffness were well balanced after six months and this balance was sustained for up to two years postoperatively. No recurrent dislocation occurred during the follow-up period; one patient experienced apprehension. Postoperative radiographic findings and clinical scores were significantly improved at the time of the latest follow-up (p < 0.05). One knee progressed to patellofemoral osteoarthritis., Conclusions: The value for medial stiffness was significantly improved three months after medial patellofemoral ligament reconstruction compared with the preoperative and lateral values and returned to the reference level by six months. Medial stiffness and lateral stiffness of the patella were well balanced by six months and retained that balance for up to two years, with good clinical results., Level of Evidence: Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence., (Copyright © 2016 by The Journal of Bone and Joint Surgery, Incorporated.)

Background: Patellar fractures are debilitating injuries that compromise the knee extensor mechanism and are frequently associated with poor outcomes. The purpose of this study was to quantify the functional outcomes of operative treatment of patellar fractures., Methods: Functional outcome data on thirty patients with an isolated unilateral patellar fracture were prospectively obtained at three, six, and twelve months postoperatively., Results: All fractures healed. There were two complications (7%) related to the surgery (wound dehiscence and refracture), and eleven patients (37%) underwent removal of symptomatic implants. The tibial plateau-patella angle demonstrated patella baja in seventeen (57%) of the patients. Anterior knee pain during activities of daily living was experienced by twenty-four (80%) of the patients. Clinical improvement occurred over the first six months. However, functional impairment persisted at twelve months, with objective testing demonstrating that the knee extensor mechanism on the injured side had deficits in strength (-41%), power (-47%), and endurance (-34%) as compared with the uninjured side., Conclusions: Despite advances in surgical protocols and acceptable radiographic outcomes, functional impairment remains common after treatment of patellar fractures. Rehabilitation strategies following surgical stabilization of these injuries will be a fruitful area for future clinical research.

Background: Patellar height variations can be responsible for many functional disorders in children. The Caton-Deschamps index to measure patellar height has been described for adults. Our goal was to determine Caton-Deschamps index values in a pediatric population., Methods: Lateral radiographs of the knee were analyzed in a cohort of 300 healthy patients. All radiographs were done to evaluate the patients after minor trauma and all were reported to be normal by a senior radiologist. The cohort was divided into ten groups on the basis of the age of the child. Radiographic measurements were done by a computer-assisted technique. Intraobserver and interobserver reliability studies were performed prior to the descriptive analysis of the data., Results: Mean patellar length (and standard deviation) was 33.39 ± 7.4 mm. Mean patellar tendon length was 34.57 ± 6.7 mm. The mean Caton-Deschamps index was 1.06 ± 0.21. Patellar and patellar tendon length significantly increased with age, whereas the Caton-Deschamps index significantly decreased. Intraobserver and interobserver reliability studies showed excellent reliabilities with an intraclass correlation coefficient that was between 0.930 and 0.944 (95% confidence interval)., Conclusions: The Caton-Deschamps index is a simple and reliable index for evaluating patellar height in children as well as adults. It is an alternative to the Insall-Salvati index measurement, in which reproducibility is poor due to difficulties in determining the distal point of the patellar tendon, and to the Koshino index, which is complex to use. In our study, there was a correlation between the Caton-Deschamps index and age, due to the progressive patellar ossification that begins at the proximal part of the patella. The Caton-Deschamps index is a pertinent and reliable ratio to evaluate patellar height in children and adolescents. To make an accurate diagnosis of patellar disorders in children, the normal, age-based Caton-Deschamps values need to be considered.

Background: Patellar height is evaluated with ratios that have been derived from measurements made on lateral radiographs of the knee. The importance of using a ratio is that magnification, physical size, and flexion angle are eliminated as factors that affect the values. The Insall-Salvati index was the first ratio to be described. It remains the most popular, possibly because normal values are easy to remember. As all of the currently accepted methods are cumbersome to use because they require two measurements as well as a calculation, a single angular measurement was devised (the plateau-patella angle) to offer a simpler alternative. The purpose of this study was to introduce the new method and to assess its validity by comparing it with three classic, commonly used ratios., Methods: In two groups of patients, after exclusions, 269 lateral radiographs of the knee were evaluated. All measurements required for the Insall-Salvati, the Blackburne-Peel, and the Caton-Deschamps indices plus the plateau-patella angle were recorded, along with basic demographics. For validation, the new method was compared with the established methods, and interobserver and intraobserver reliability were computed., Results: There was excellent correlation between the proposed angle and the three selected indices, especially with the Blackburne-Peel index. Interobserver and intraobserver reliability was high and compared favorably with that reported in the literature for the three classic ratios. The calculated ratios were in line with those described in the literature. The mean plateau-patella angle was 25°. Ninety percent of the measurements fell between 20° and 30°, and one standard deviation above and below was 21° to 29°., Conclusions: The plateau-patella angle, a new method of evaluating patellar height, can be measured rapidly with use of either a goniometer or digital software. Its range is easy to remember, it is reliably reproduced, and it correlates well with traditional methods. It is thus a valid and easy alternative method for the evaluation of patellar height.

Background: Radiographic assessment of the patella after total knee arthroplasty is typically performed with use of static, unloaded views that may not reproduce the in vivo patellofemoral kinematics. The purpose of the present study was to evaluate and validate the reliability and reproducibility of a weight-bearing radiographic assessment of the patellofemoral joint in patients who have undergone total knee arthroplasty., Methods: Radiographs were made for 100 knees in sixty-nine patients who had undergone total knee arthroplasty. Radiographic assessment of the patellofemoral joint was performed with use of both the standard Merchant axial view and a modification of that view. The Merchant axial view was modified by positioning the standing patient in the semi-squatted position with the knees in 45 degrees of flexion. The relationship between the x-ray source, the angle of incidence on the joint, and the cassette position was kept unchanged from the original view. The standing position and consequent muscle involvement were the only differences., Results: Compared with the standard Merchant axial view, the weight-bearing axial view showed a number of patellofemoral tracking changes. Specifically, lateral tilt and subluxation of the patella were significantly reduced; the rate of exposed, uncovered patellar bone contact with the femoral trochlea was significantly increased; and radiographic evidence of maltracking was more closely correlated with clinical symptoms., Conclusions: An axial weight-bearing radiographic view with the patient in the semi-squatting position was developed to reproduce patellofemoral joint loading. This view demonstrates that the position of the patella, as seen on the standard unloaded Merchant view, changes during squatting. Utilization of this axial weight-bearing view to evaluate total knee arthroplasty may provide additional information over standard radiographic views.

Background: The most common complications of total knee arthroplasty involve the patellofemoral joint. However, the long-term fate of the nonresurfaced patella after total knee arthroplasty has seldom been reported. The purpose of this study was to evaluate the long-term changes of the nonresurfaced patella after total knee arthroplasty., Methods: We retrospectively evaluated the nonresurfaced patella in 227 knees (181 patients) at an average of 8.5 years after total knee arthroplasty. Functional results were correlated with radiographic changes, and risk factors leading to abnormal changes of the patella were analyzed., Results: Preoperatively, 186 (82%) of the patellae tracked centrally, thirty-nine (17%) displaced or tilted laterally, and two (1%) subluxated laterally. At the time of the latest follow-up, 133 (59%) of the patellae still tracked centrally with preservation of the cartilage thickness, fifteen (7%) showed early lateral tilt, sixty-eight (30%) had progressive loss of lateral cartilage thickness with lateral tilt and/or displacement, seven (3%) had progressed to lateral subluxation, and four (2%) tilted medially. An abnormal patellofemoral joint did not affect the knee and functional scores (p = 0.90 and 0.89, respectively). However, symptoms such as difficulty rising from a chair or reluctance to use the involved lower limb while climbing stairs were noted. Preoperative patellar maltracking was identified as the only risk factor leading to postoperative patellar abnormalities (relative risk, 2.7; 95% confidence interval, 2.21 to 3.30; p = 0.003)., Conclusions: At the time of follow-up, at an average of 8.5 years, patellar tracking and the patellofemoral joint remained normal after approximately 60% of the total knee arthroplasties performed without resurfacing of the patella. Progressive degenerative changes of the nonresurfaced patella (mainly on the lateral facet) and patellar maltracking were the most common abnormal radiographic changes. Patients with preoperative patellar maltracking were at risk for the development of these changes and clinical symptoms. Resurfacing of the patella during total knee arthroplasty may benefit such patients.

Background: Problems with the patellofemoral articulation are the most common causes of failure after total knee arthroplasty. However, there are few reports describing outcomes following isolated revision of the patellar component., Methods: Forty knees with a Miller-Galante I prosthesis underwent isolated patellar revision (with or without lateral retinacular release). The Hospital for Special Surgery knee scores were collected prospectively, and radiographs made preoperatively and at the time of the final follow-up were analyzed with respect to alignment, component position, and patellar tracking. Particular attention was given to patients who had a reoperation or repeat revision and who had clinical or radiographic evidence of failure of the patellar revision., Results: At a mean follow-up of sixty-two months, fifteen (38%) of the forty knees that had had an isolated revision of the patellar component failed a second time. Eight of them required a total of twelve additional operations at a mean of forty-nine months after the patellar revision. Three of the failures were severe enough to require revision of two or more of the components. Of the twenty-five knees that had not failed, the average Hospital for Special Surgery knee score at the time of the final follow-up was 87 points. Of the seven knees that did not undergo reoperation but were deemed to be failures on the basis of the patients' symptoms, the average Hospital for Special Surgery knee score at the time of the final follow-up was 72 points., Conclusions: Isolated patellar revision, with or without concurrent lateral retinacular release, was associated with a high rate of reoperation and a relatively low rate of success. Elements of the implant design and component alignment contributed to the patellar component failure; both should be scrutinized carefully in patients who are seen with this problem, prior to proceeding with isolated revision of the patellar component of a total knee arthroplasty., Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See p. 2 for complete description of levels of evidence.

Background: The combined use of high-frequency ultrasound and mechanical indentation has been suggested for the evaluation of cartilage integrity. In this study, we investigated the usefulness of high-resolution B-mode ultrasound imaging and quantitative mechanical measurements for the diagnosis of cartilage degeneration and for monitoring tissue-healing after autologous chondrocyte transplantation., Methods: In the first study, osteochondral samples (n = 32) were obtained from the lateral facet of a bovine patella, and the samples were visually classified as intact (n = 13) or degenerated (n = 19) and were graded with use of the Mankin scoring system. Samples were imaged with use of a 20-MHz ultrasound instrument, and the dynamic modulus (Edyn) of cartilage was determined in unconfined compression with use of a high-resolution materials tester. In the second study, cartilage chondrocytes were harvested from the low-weight-bearing area of six-month-old porcine knee joints and cultured. A month later, a cartilage lesion was created on the facet of the femoral trochlea and was repaired with use of the autologous chondrocyte transplantation technique (n = 10). Three months later, to estimate cartilage Edyn, the repair tissue, the adjacent cartilage, and the sham-operated contralateral joint cartilage (control) were analyzed in situ with an arthroscopic indentation instrument. Subsequently, the same sites were imaged with ultrasound., Results: All visually degenerated bovine samples (mean Mankin score = 4) and five visually normal samples (Mankin score = 1) showed reduced Edyn (<2.1 MPa) as compared with histologically normal cartilage (Edyn = 13.8 +/- 3.2 MPa, Mankin score = 0). Cartilage stiffness, as shown by the indenter force, was lower (0.6 +/- 0.3 N, p < 0.05, Wilcoxon's signed-rank test) in the porcine tissue repaired with autologous chondrocyte transplantation than it was in the adjacent (1.6 +/- 0.1 N) or the control (1.9 +/- 0.4 N) tissue. The superficial and internal structure of the degenerated and repaired tissue, including the subchondral erosion at the repair site, was sensitively demonstrated by the ultrasound imaging., Conclusions: Measurement of cartilage Edyn is an objective method with which to follow changes in the mechanical integrity of cartilage. B-mode ultrasound imaging offers detailed information on the structural properties of cartilage and subchondral bone.

Background: Patellofemoral complications (osteoarthritis and impingement) have been rarely reported after unicompartmental arthroplasty, and their long-term consequences are not known. The purpose of the present study was to analyze these complications following unicondylar arthroplasty., Methods: We evaluated the results of ninety-nine unicompartmental arthroplasties that had been performed in eighty patients with osteoarthritis of the knee. The medial compartment was replaced in seventy-four knees and the lateral compartment, in twenty-five. All ninety-nine knees were evaluated with regard to patellar impingement and osteoarthritic changes on skyline radiographs after an average duration of follow-up of fourteen years (range, ten to twenty years). In addition, the seventy-seven knees (fifty-eight patients) that had not been revised were evaluated with use of the clinical scoring system of the Knee Society and specific questions regarding patellofemoral symptoms after an average duration of follow-up of fifteen years (range, ten to twenty years). The relationship between patellar complications (osteoarthritis and impingement) and the position of the femoral component was evaluated with use of lateral radiographs of the knee., Results: At the time of the most recent follow-up, twenty-nine knees had osteoarthritic changes in the portion of the patellofemoral joint opposite the compartment with the implant and twenty-eight knees had impingement of the femoral component on the patella. The knees that had impingement did not have osteoarthritic changes. Pain while ascending or descending stairs and pain on rising from a chair were noted more frequently in knees with patellar complications (impingement and osteoarthritis) (p = 0.02), and these symptoms affected the stair-climbing functional score. These symptoms were more severe in knees with patellar impingement than in knees with degenerative changes. One revision was performed because of patellar impingement. Patellar impingement was more frequent after lateral arthroplasty than after medial arthroplasty (p = 0.02) and was associated with placement of the femoral component too far anteriorly (p = 0.001)., Conclusion: After unicompartmental arthroplasty, the patellofemoral joint was affected by degenerative changes and patellar impingement. These complications appeared to have been mutually exclusive and affected the functional outcome of the arthroplasty. Patellar impingement affected the knee more severely with regard to both symptoms and the need for revision.

Thirteen patients who had fifteen painful bipartite patellae were managed with a new operative technique in which the vastus lateralis insertion to the painful patellar fragment is detached subperiosteally while the continuity of the tendon-periosteum complex to the main portion of the patella is preserved. A grossly mobile patellar fragment was removed from five patellae (three type-II and two type-III according to the classification of Saupe). A fragment that showed minimum mobility was left in situ in seven type-III and three type-II patellae. All of the patients had prompt relief of the pain and returned to full sports activity within two months after the operation. Six of the seven type-III fragments that had not been removed united by bone to the main portion of the patella within two years postoperatively, but all three type-II fragments failed to unite. Over-all, eleven patients (thirteen knees) had an excellent result at an average of five years postoperatively.

In a prospective, non-randomized study of 344 patients who had 392 primary total knee replacements with a Miller-Galante I prosthesis for the treatment of osteoarthrosis, the results of partial fixation with cement (insertion of the tibial and patellar components with cement and of the femoral component without cement) were compared with those of fixation without any cement. Of the 392 knees, 183 (163 patients) had fixation without cement (Group I) and 209 (181 patients), with and without cement (Group II). The average duration of follow-up was three years (range, two to five years). Nine patients died during the follow-up period, but no others were lost to follow-up. Analysis of the knee scores, range of motion of the knee, radiographs, and rates of complications revealed no differences between the outcomes in the two groups during the follow-up period. The rate of complications due to problems related to the extensor mechanism was high in both groups: a reoperation was performed in fifteen (8 per cent) of the knees that had had fixation without cement and in nineteen (9 per cent) of those that had had both types of fixation. Thirteen patients had additional operative treatment for recurrent patellar dislocations; twelve patients, for abnormal wear of the polyethylene of the patellar component: two patients, for avulsion of the patellar ligament from the tibia; and two patients, for unexplained pain in the knee. In addition, there were eight patellar fractures (two of which led to a reoperation) and three deep infections (all of which led to a reoperation).

The results of reconstruction of the anterior cruciate ligament with the central third of the patellar ligament as a free, autogenous, non-vascularized graft were retrospectively reviewed at our institution. Eighty reconstructions in seventy-nine patients were evaluated after a minimum of two years. In forty-eight (60 per cent) of the knees, the reconstruction was augmented with an extra-articular lateral sling of iliotibial band. The patients were evaluated with a physical examination, a KT-1000 arthrometer, radiographs, a subjective questionnaire, and a revision of the scale of The Hospital for Special Surgery for rating ligaments. Postoperatively, seventy-six (95 per cent) of the eighty knees no longer gave way, and the pivot-shift test was negative in sixty-seven (84 per cent) of the knees. The average score on the ligament-rating scale was 93 points. All of the patients who had clinical instability at the time of the most recent follow-up had associated ligamentous instability that had not been appreciated or addressed at the time of reconstruction. Arthrometric evaluation revealed that the laxity differed by three millimeters or less from that of the untreated knee in sixty (76 per cent) of the treated knees. In the patient who had bilateral reconstruction, the laxity was the same in both knees. Seventeen patients, who had more than three millimeters of translation, also had additional related ligamentous instability, most commonly posterolateral instability and insufficiency of the medial collateral ligament. We think that major associated ligamentous instability predisposes the reconstruction to failure and should be corrected in conjunction with the reconstruction.(ABSTRACT TRUNCATED AT 250 WORDS)

The results of partial patellectomy as a treatment for displaced patellar fractures were assessed retrospectively with use of clinical, radiographic, and isokinetic strength-testing criteria. Forty patients who had been followed for an average of 8.4 years were studied. In the extremity that had been operated on, the mean active range of motion was 94 per cent, the circumference of the thigh was 100 per cent, and the strength of the quadriceps was 85 per cent of these measurements in the contralateral extremity. The over-all result was rated as excellent in twenty patients, good in eleven, fair in six, and poor in three. There was a significant statistical correlation between the type of fracture and the outcome. The results of this study indicate that partial patellectomy can be an effective treatment for selected patellar fractures.

A review of the results of 192 kinematic total knee replacements five to nine years after the operation showed that the results were still satisfactory. At the time of the review, the ages of the patients ranged from twenty-two to eighty-seven years. About half of the patients had rheumatoid arthritis and the other half, osteoarthrosis. About 90 per cent of the results were rated good or excellent, and the average range of flexion was 109 degrees. Radiolucency was present around 40 per cent of the tibial components, 30 per cent of the femoral components, and 60 per cent of the patellar components, but the lines were thin and not progressive. The complications included loosening of the patellar components in five knees, one fracture of the tibial tray with loosening of the patellar component, one fracture of the patellar component, and one dislocation of the patellar component.

The reported incidence of patellar problems after total knee replacement has ranged from 5 to 30 per cent. Patellar dislocation is infrequent but can cause disabling symptoms. Between January 1974 and May 1982, eleven patients (twelve knees) with symptomatic lateral dislocation of the patella after total knee replacement were treated at The Hospital for Special Surgery by realignment of the extensor mechanism. All of the patients were women. Their average age was sixty-two years and average weight, eighty-seven kilograms. The diagnosis was osteoarthritis in seven knees and rheumatoid arthritis in five. Most of the patients had had preoperative valgus deformity (average, 18 degrees). The cause of dislocation was trauma in three knees, incorrect tracking of the patella after replacement in six, and malrotation of the tibial component in three. Four different prosthetic designs had been used. The design of the implant did not appear to be a factor causing dislocation in this group. The patellar dislocation was treated by proximal realignment of the quadriceps in ten knees, lateral retinacular release alone in one, and revision of the tibial and femoral components combined with proximal realignment in one. After an average follow-up of thirty-four months (range, twenty-four to fifty-seven months), the results according to The Hospital for Special Surgery knee-rating scale were excellent in ten knees and good in two, and there had been no redislocations.

The patellar and articular cartilages of the femoral and tibial condyles can be demonstrated well by double contrast arthrography, and abnormalities of the cartilage can be seen. A comparison of surgical findings with the preoperative arthrogram was made for 100 patients, and the diagnosis of chondromalacia of the patella and condyles had an accuracy of about 90 per cent.

The results in thirty-six knees that had a fracture of the patella after a total condylar arthroplasty were reviewed, and were analyzed according to the type of fracture and the alignment of the implant and the limb. Most of the fractures occurred two years or less after the initial operation. Fourteen knees were rated fair or poor and twenty-two, good or excellent. None of the thirty-six implants had been aligned in the neutral range. In sixteen knees, the alignment had a minor variation from the neutral range--that is, the knees were in minor malalignment. In general, these knees had the least severe fractures and the best over-all results. All had a good or excellent result except one, which was revised because of a loose patellar component. That knee was rated as fair at the latest follow-up. There was a major discrepancy in the alignment of twenty implants. These knees had more severe fractures and less satisfactory results than those in the other group. In two of these knees, the fracture was treated non-operatively; one had a good and the other, a poor result. Twelve of the remaining knees, which were treated surgically, were rated as fair or worse. Two knees that had revision of three components and restoration of alignment to the neutral range had an excellent result. The results of this study indicate that the alignment and fit of a component are important in determining the severity of a fracture of the patella after condylar total knee replacement and the long-term results after treatment of the fracture.

On roentgenograms made with the patient supine, the knees flexed 20 to 30 degrees, the x-ray tube between the ankles, and the cassette held proximal to the knees and perpendicular to the x-ray beam, it was found that a line between the femoral condyles and a line between the margins of the lateral facet of the patella formed the lateral patellofemoral angle, an angle that was of diagnostic value in patients with subluxation of the patella. In 100 clinically normal patients, these lines were parallel in three and formed an angle open laterally in ninety-seven. In thirty patients with subluxation of the patella, the lines were parallel in twenty-four and formed an angle open medially in six. In 100 patients with chondromalacia of the patella, however, the roentgenographic study was of no diagnostic value since the lines were parallel in ten and formed an angle open laterally in ninety.

We studied the complications involving the patella following total knee arthroplasty in eighty-six knees in which thirty-four unconstrained and fifty-two offset hinge prostheses had been implanted. The abnormalities that we studied included: patellar dislocation, five knees; subluxation, eighteen knees; localized wear, three knees; and generalized wear, four knees. In twenty-three patients these complications were associated with patellar malalignment, and occurred predominantly when the offset hinge model of prosthesis was used. The complications were attributed partly to mechanical factors inherent in the prosthetic design and partly to anatomical abnormalities. Failure of the surgeon to compensate adequately for both of those factors at the time of operation was a factor in most of the complications.

We encountered a complication that is unique to the use of a metal-backed patellar component in total knee replacement--namely, fracture and separation of the polyethylene bearing from its metal counterpart. The cases of seventeen patients who were treated at several institutions were studied. Patellar malalignment, especially in heavy patients who had a high level of activity, was a contributory cause of the complication, but we thought that deficiencies in the design of the prosthesis were also an important factor.

The Insall-Salvati method of assessing the position of the patella was applied to four groups of patients:normal patients, and those with dislocation of the patella, chondromalacia of the patella, and apophysitis of the tibial tubercle. The ratio of patellar length to tendon length was 1.0 in the normal patients, 0.8 in the patients with dislocations, 0.86 in those with chondromalacia, and 1.2 in those with apophysitis of the tibial tubercle. Patella alta may be an important cause of dislocating patella and of chondromalacia patellae. The significance of the patella infera found in the Osgood-Schlatter lesion may be one of either cause or effect.

Of five patients with a dorsal defect of the patella, four were followed for seven to thirteen years. The lesion causes a persistent change in the radiographic appearance of the bone and there may be some residual discomfort in the involved knee. It is best demonstrated on tomograms and on posterior oblique radiographs of the patella. The cause of the defect is unknown and its pathology has not been clearly defined.

In the total examination of the knee, degenerative changes and ossification in the quadriceps tendon easily recognized on the lateral roentgenogram may cause confusion in diagnosis when seen on the axial view. Vertical ridging of the osteophytes at the patellar insertion of the quadriceps tendon can resemble dentate structure ("tooth" sign). Two hundred and fifty examinations of the knee in different age groups were reviewed and several anatomical sections of the quadriceps-patella insertion were studied. The "tooth" sign represents the relief of severe osteophyte formation in the bundle of the quadriceps tendon at its insertion into the patella.

Special trauma oblique radiographs of the knee were designed for the purpose of demonstrating the patella radiographically in a manner that would free it from the shadow of the distal end of the femur. These radiographs are made by directing the x-ray tube at an angle of 45 degrees and making two exposures, with the film placed first on the lateral and then on the medial side of the injured knee. These two radiographs have been found to be useful for delineating the extent of fractures of the patella as well as abnormalities of the tibial plateau.

In sixty-five knees followed for an average of 4.5 years after treatment of subluxation or dislocation of the patella by the slot-block method of medial patellar-tendon transfer, the results were satisfactory in fifty-four (83%) and unsatisfactory in eleven (17%). Recurrent subluxation or dislocation occurred in three (5%) of the knees and was attributed to insufficient displacement. Chondromalacia of the patella became worse after transfer in three of the sixty-two knees in which the distal realignment was technically correct. Two knees (3%) required patellectomy because of patellofemoral symptoms and there were nineteen complications in seventeen knees, including loss of motion in six, wound infection in six, displacement of the bone block in three, recurrent dislocation in three, and rupture of the patellar ligament in one. The method is believed to give superior results but it is technically demanding.

Open reduction combined with external compressive skeletal fixation was used to treat twenty-seven patients who had a separated fracture of the patella. Fixation was obtained by the use of two compressive clamps applied to stainless-steel pins that were inserted just proximal and distal to the proximal and distal poles of the patella. Range-of-motion exercises for the knee were begun at two weeks and the pins were removed at three to four weeks. All of the fractures healed. Twenty-four patients regained a range of motion that was equal to that of the opposite knee. There was no evidence of chronic osteomyelitis. Osteoarthritis was noted in one patient who refused excision of a portion of the patella.

Sixty-six knees (sixty patients) that had had a proximal tibial osteotomy were evaluated to determine if any alteration of the patellar height had occurred as a result of the operation. Eighty-nine per cent of the patellae, as measured by the Insall-Salvati index, and 76.3 per cent, as measured by the Blackburne-Peel index, were observed to be lowered as they appeared on the postoperative lateral radiograph. This was probably due to shortening of the patellar ligament after prolonged immobilization in a cast, interstitial scarring of the patellar ligament, and new-bone formation in the area of insertion of the patellar ligament. There was no correlation between the postoperative height of the patella and the need for subsequent revision to a total knee replacement.

The knees of 210 institutionalized patients with Down syndrome were evaluated to determine the prevalence of patellofemoral instability and to assess the value of orthotic and surgical treatment. The cases of 151 non-institutionalized patients with Down syndrome were also reviewed. The patella was dislocatable or dislocated in thirty-five knees (8.3 per cent) in the institutionalized group and in twelve knees (4.0 per cent) in the non-institutionalized group. This interfered with walking in some patients, but only three of the patients were unable to walk because of patellofemoral instability. None of the institutionalized patients used any form of orthosis, and only three non-institutionalized patients used an orthosis. Eight knees in five patients had been operated on, and they had an average length of follow-up of 16.8 years. Four of these knees had a satisfactory result. Instability of the patellofemoral joint may occur in patients with Down syndrome but is rarely disabling. Almost all patients with patellofemoral instability adapted to the problem and were able to walk.