Posterior Cruciate Ligament-retaining Total Knee Research Articles

Soft tissue impingement at the femorotibial joint after a posterior cruciate ligament-retaining total knee arthroplasty

Abstract Introduction: Impingement of soft tissue at the femorotibial (FT) joint after a total knee arthroplasty (TKA) can lead to poor postoperative performance and pain. In this report, we have described a case of FT joint impingement by scar tissue formation extending over the anterior surface of the intercondylar fossa after a posterior cruciate ligament (PCL)-retaining TKA. Patient concerns: A 78-year-old woman developed crepitations and discomfort during left knee extension and stair climbing at about 10 months after TKA. Diagnosis: Plain radiographs of her knee revealed that the patella baja present from before her TKA had progressed. Impression marks in the distal pole of the patella caused by the impingement of the scar tissue between the femoral component of PCL-retaining TKA and the PCL insertion during knee extension were also observed. The impingement was confirmed by direct arthroscopy. Interventions: We treated her by performing a resection of the scar tissue, excision of the distal pole of the patella, and replacement of the patella. Outcomes: Recovery period was unremarkable, with no recurrence of symptoms over the subsequent 5-year follow-up period. Conclusion: Our case demonstrates that a chronic mechanical irritation can induce proliferation of the residual synovial tissue at the insertion of the PCL. This, in turn, could result in the growth of a scar-like tissue, which could extend over the anterior surface of the intercondylar fossa and grow into the distal pole of the patella, causing an impingement at the FT joint. The presence of a patella baja before TKA could be a risk factor for FT impingement after PCL-retaining TKA, warranting a careful follow-up of these patients.

Comparative study of outcome between posterior-stabilized versus posterior cruciate ligament-retaining total knee arthroplasty

To compare the functional outcome of Posterior stabilized and Posterior Cruciate retaining total knee arthroplasties done at a tertiary care centre like Government Medical College Thiruvananthapuram. We also study and compare the Incidence of complications including surgical site infection, hematoma formation and neurovascular injury in the different techniques. Posterior-stabilized and posterior cruciate retaining total knee arthroplasty prostheses have had high success rates, but it is unclear whether one design has superior outcomes. The purpose of the present study was to directly compare the outcomes of these two designs. Forty- five patients who received a posterior-stabilized prosthesis were compared to 46 consecutive patients who received a cruciate-retaining implant. At a mean follow- up time of 60 months (range, 49 to 69 months), the mean Knee Society knee scores improved from 38 points (range, 20 to 73 points) to 88 points (range, 39 to 100 points) for the cruciate-retaining group and from 38 points (range, 20 to 70 points) to 90 points (range, 60 to 100 points) for the posterior-stabilized group. The mean Knee Society functional scores improved from 32 points (range, 10 to 60 points) to74 points (range, 15 to 100 points) for the cruciate-retaining group and from 32 points (range, 10 to 70 points) to 72 points (range, 32 to 100 points) for the posterior-stabilized group. The ranges of motion were 125° (range, 100 to 140°) and 118° (range, 87 to 135°) in the cruciate-retaining and posterior-stabilized groups, respectively, at final follow-up. Radiographic analysis revealed no radiolucencies that were progressive or were greater than 1 millimeter in length. There were no re-operations in either group. This study did not conclusively demonstrate the superiority of one knee design over the other, suggesting that the choice of implant should be based on surgeon preference and existing pathology of the posterior cruciate ligament.

Intact, pie-crusting and repairing the posterior cruciate ligament in posterior cruciate ligament-retaining total knee arthroplasty: A 5-year follow-up.

BACKGROUNDThe posterior cruciate ligament (PCL) is important for cruciate-retaining (CR) total knee arthroplasty (TKA). Whether the entire PCL should be retained during CR-TKA is controversial.AIMTo evaluate the clinical outcomes of PCL preservation in CR-TKA and the methods used to deal with the PCL during surgery.METHODSA retrospective review of patients with osteoarthritis undergoing primary CR-TKA (176 patients, 205 knees) in our institution between March 2012 and March 2014 was performed. A PCL protector was used to preserve the intact PCL bone block. The status of the PCL was recorded during surgery. Intact PCL preserved, pie-crusting and repairing were used to balance the tension of the PCL. Range of motion (ROM) and the Knee Society Clinical Rating system (KSS) were evaluated preoperatively and at the endpoint of follow-up.RESULTSThe mean ROM of the knee was 103.2 ± 17.2°, KSS clinical score was 47.6 ± 9.5 and KSS functional score was 46.3 ± 11.9 before surgery. The mean ROM of the knee was 117.5 ± 9.7°, KSS clinical score was 89.2 ± 3.6 and KSS functional score was 84.6 ± 9.8 at 5 years follow-up. ROM, KSS clinical scores and KSS functional scores were significantly improved after surgery (P < 0.01). Thirty-two (23.7%) TKAs involved PCL pie-crusting and 18 (13.3%) involved PCL repair. Eighty-five (63.0%) TKAs applied standard operating procedures and preserved intact PCL. At 5 years follow-up, in the intact PCL group, the mean ROM of the knee was 118.0 ± 8.3°, KSS clinical score was 89.1 ± 3.7 and KSS functional score was 84.9 ± 9.6. In the PCL pie-crusting group, mean ROM of the knee was 114.0 ± 13.5°, KSS clinical score was 88.8 ± 3.4 and KSS functional score was 83.8 ± 10.5. In the PCL repair group, mean ROM of the knee was 120.3 ± 7.0°, KSS clinical score was 89.0 ± 3.6 and KSS functional score was 89.4 ± 4.5. There were no significant differences in ROM, KSS clinical scores and KSS functional scores among the three groups (P > 0.05).CONCLUSIONThe clinical outcomes of preserving the PCL in CR-TKA are encouraging. Pie-crusting and PCL repair do not affect the function. The PCL protector effectively protected the PCL bone block.

Knee Extensor Strength and Gait Characteristics After Minimally Invasive Unicondylar Knee Arthroplasty vs Minimally Invasive Total Knee Arthroplasty: A Nonrandomized Controlled Trial

BackgroundIn light of the existing lack of evidence, it was the aim of this study to compare gait characteristics and knee extensor strength after medial unicondylar knee arthroplasty (MUKA) with those after total knee arthroplasty (TKA), given the same standardized minimally invasive surgery (MIS) approach in both groups. MethodsPatients scheduled for MIS-MUKA or MIS-TKA as part of clinical routine were invited to participate. A posterior cruciate ligament-retaining total knee design was used for all MIS-TKA. A 3-dimensional gait analysis was performed preoperatively with a VICON system and at 8 weeks postoperative to determine temporospatial parameters, ground reaction forces, joint angles, and joint moments. At the same 2 times, isokinetic tests were performed to obtain peak values of knee extensor torque. A multivariate analysis of variance was conducted and included the main effects time (before and after surgery) and surgical group and the group-by-time interaction effect. ResultsFifteen MIS-MUKA patients and 17 MIS-TKA patients were eligible for the final analysis. The groups showed no differences regarding age, body mass index, sex, side treated, or stage of osteoarthritis. We determined neither intergroup differences nor time × group interactions for peak knee extensor torque or any gait parameters (temporospatial, ground reaction forces, joint angles, and joint moments). ConclusionIt is concluded that MUKA is not superior to TKA with regard to knee extensor strength or 3-dimensional gait characteristics at 8 weeks after operation. As gait characteristics and knee extensor strength are only 2 of the various potential outcome parameters (knee scores, activity scores…) and quadriceps strength might take a longer time to recover, our findings should be interpreted with caution.

Intra-operative gaps affect outcome and postoperative kinematics in vivo following cruciate-retaining total knee arthroplasty

The following investigation evaluates the effect of intra-operative gaps after posterior cruciate ligament-retaining total knee arthroplasty using two-dimensional/three-dimensional registration and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Patients were divided into two groups according to their 90°-0° component gap changes using a device designed by our laboratory. The wide gap group was defined as more than 3 mm (4.3 ± 0.7 mm), and the narrow gap group was defined as less than 3 mm (1.3 ± 1.3 mm). Under non-WB (weight bearing) conditions, the wide flexion gap group (N = 10) showed a significant anterior displacement of the medial femoral condyle as compared with the narrow flexion gap group (N = 20). Despite no significant differences observed under WB conditions, both femoral condyle positions during flexion were significantly more posterior than during extension. WOMAC of the tight gap group showed worse scores for two functional items demanding knee flexion (bending to floor and getting on/off toilet). The large flexion gap could influence the late rollback under non-WB conditions and better WOMAC functional scores in the flexion items. Three to four millimetre laxity at 90°-0° component gaps may be adequate and might be necessary to carry out daily life activities.

Significant Effect of the Posterior Tibial Slope on the Weight-Bearing, Midflexion In Vivo Kinematics After Cruciate-Retaining Total Knee Arthroplasty

The purpose of the present study was to compare weight bearing (WB) and non-WB conditions, and to evaluate the effect of the posterior tibial slope (PTS) on the in vivo kinematics of 21 knees after posterior cruciate ligament-retaining total knee arthroplasty during midflexion using 2-dimensional/3-dimensional registration. During WB, medial pivot and bicondylar rollback were observed. During non-WB, both the medial and lateral condyles moved significantly more anteriorly as compared to the WB state. These patients were divided into 2 groups according to their PTS. The large PTS group showed a significant posterior displacement of the medial femoral condyle as compared with the small PTS group, but no significant difference was observed at the lateral femoral condyle during both WB and non-WB. The PTS influenced knee kinematics through gravity (124/125).

Late Abnormal Skin Changes Overlying Total Knee Arthroplasty: A Case Report.

More than 600,000 total knee arthroplasties are performed in the United States every year1. Superficial wound complications occur infrequently, and the overall appearance of the incision is important to judge appropriate healing. Ecchymosis about the knee is common postoperatively and typically resolves within the first few weeks. Persistent skin changes around the incision and knee are rare, and they prompt additional investigation regarding the etiology. We report on a seventy-four-year-old woman who had undergone an uncomplicated right total knee arthroplasty and, almost three and one-half years later, developed an atraumatic ecchymotic-appearing lesion involving the superior aspect of the incision. She was diagnosed with biopsy-proven pigmented purpuric dermatosis (PPD). To our knowledge, this is the first such case reported in the orthopaedic literature. The patient was informed that data concerning the case would be submitted for publication, and she provided consent. A seventy-four-year-old woman with a past medical history of hypertension, hypothyroidism, and a prior left total knee arthroplasty presented for a right total knee arthroplasty. She underwent femoral and sciatic nerve blocks followed by general anesthesia. A posterior cruciate ligament-retaining total knee prosthesis (Vanguard; Biomet, Warsaw, Indiana) was implanted uneventfully. The patella was resurfaced, and a lateral release was performed. She did well in the postoperative period with regard to …

Evaluation of the relationship between anteroposterior translation of a posterior cruciate ligament-retaining total knee replacement and functional outcome

The success of total knee replacement (TKR) depends on optimal soft-tissue balancing, among many other factors. The objective of this study is to correlate post-operative anteroposterior (AP) translation of a posterior cruciate ligament-retaining TKR with clinical outcome at two years. In total 100 patients were divided into three groups based on their AP translation as measured by the KT-1000 arthrometer. Group 1 patients had AP translation < 5 mm, Group 2 had AP translation from 5 mm to 10 mm, and Group 3 had AP translation >10 mm. Outcome assessment included range of movement of the knee, the presence of flexion contractures, hyperextension, knee mechanical axes and functional outcome using the Knee Society score, Oxford knee score and the Short-Form 36 questionnaire. At two years, patients in Group 2 reported significantly better Oxford knee scores than the other groups (p = 0.045). A positive correlation between range of movement and AP translation was noted, with patients in group 3 having the greatest range of movement (mean flexion: 117.9° (106° to 130°)) (p < 0.001). However, significantly more patients in Group 3 developed hyperextension > 10° (p = 0.01). In this study, the best outcome for cruciate-ligament retaining TKR was achieved in patients with an AP translation of 5 mm to 10 mm.

Posterior Cruciate Ligament-Retaining Total Knee Arthroplasty in Patients with Rheumatoid Arthritis

7We previously reported the minimum eight-year follow-up results of cruciate-retaining total knee arthroplasty in a consecutive series of seventy-two knees in patients with rheumatoid arthritis. In the present study, we evaluated the longer-term outcomes after twenty to twenty-five years of follow-up. Since the publication of our original study, ten knees have been revised: three because of periprosthetic fracture, three because of infection, two because of patellofemoral failure, and two because of posterior instability. The rate of implant survival at twenty years after surgery was 69% (95% confidence interval [CI], 56% to 79%) with revision for any reason as the end point, 81% (95% CI, 69% to 89%) with femoral or tibial component revision for any reason as the end point, and 93% (95% CI, 83% to 97%) with posterior instability as the end point. These long-term results demonstrate that posterior cruciate ligament insufficiency with instability was rarely the cause of failure following cruciate-retaining total knee arthroplasty in patients with rheumatoid arthritis.

Sagittal Laxity After Posterior Cruciate Ligament-Retaining Mobile-Bearing Total Knee Arthroplasty

Posterior cruciate ligament stretching after posterior cruciate ligament-retaining (CR) total knee arthroplasty (TKA) can lead to an increase in sagittal laxity, knee dysfunction, or accelerated damage to the tibial bearing surface. We conducted a prospective study on 74 consecutive mobile-bearing CR TKA to determine if knee laxity changed with time or if knees with large initial laxity experienced greater increases in laxity. Patients were studied with radiographic posterior and anterior drawer examinations at 3 and 23 months. Model-based shape-matching techniques were used to measure TKA kinematics. We found a 1-mm increase in posterior drawer. Knees with large postoperative drawers did not exhibit increased laxity at last follow-up. The use of a mobile-bearing CR TKA did not significantly modify the midterm knee sagittal laxity.

Three-Dimensional Tibiofemoral Articular Contact Kinematics of a Cruciate-Retaining Total Knee Arthroplasty

Accurate knowledge of the location of tibiofemoral articular contact following total knee arthroplasty is important in order to understand polyethylene wear and the mechanisms of component failure. The present study was performed to determine the three-dimensional tibiofemoral articular contact patterns of a posterior cruciate ligament-retaining total knee replacement during in vivo weight-bearing flexion. Nine osteoarthritic patients who were managed with a single design of a posterior cruciate ligament-retaining total knee implant were investigated with the use of an innovative dual orthogonal fluoroscopic imaging system. The position of the components during in vivo weight-bearing flexion was measured from full extension to maximum flexion in 15 degrees intervals. Tibiofemoral articular contact was determined by the overlap of the tibiofemoral articular surfaces. The centroid of the surface intersection was used to report the point of contact location. The average tibiofemoral contact points on both the medial and lateral tibial component surfaces were reported as a function of flexion. The average maximum weight-bearing flexion angle was 113.3 degrees +/- 13.1 degrees (range, 96 degrees to 138 degrees ). In the anteroposterior direction, the contact location was relatively constant in the medial compartment and moved posteriorly by 5.6 mm in the lateral compartment as the knee flexed from full extension to 90 degrees of flexion. The range of the contact location in the mediolateral direction was 3.7 mm in the medial compartment and 4.8 mm in the lateral compartment. For both compartments, posterior translation of the contact point was significant from 90 degrees to maximum flexion, but the contact point at maximum flexion was not observed to reach the posterior edge of the polyethylene tibial insert articular surface. While the minimum anteroposterior translation of the contact point on the medial side might be interpreted as a medial pivot rotation during knee flexion, the contact point did move in the mediolateral direction with flexion. Beyond 90 degrees , both medial and lateral contact points were shown to move posteriorly but stopped before reaching the posterior edge of the polyethylene tibial insert articular surface. It seemed that the current component design did not allow the femoral condyle to roll off the polyethylene edge at high degrees of flexion because of the geometry at the posterior lip.

THREE-DIMENSIONAL TIBIOFEMORAL ARTICULAR CONTACT KINEMATICS OF A CRUCIATE-RETAINING TOTAL KNEE ARTHROPLASTY

Background: Accurate knowledge of the location of tibiofemoral articular contact following total knee arthroplasty is important in order to understand polyethylene wear and the mechanisms of component failure. The present study was performed to determine the three-dimensional tibiofemoral articular contact patterns of a posterior cruciate ligament-retaining total knee replacement during in vivo weight-bearing flexion. Methods: Nine osteoarthritic patients who were managed with a single design of a posterior cruciate ligament-retaining total knee implant were investigated with the use of an innovative dual orthogonal fluoroscopic imaging system. The position of the components during in vivo weight-bearing flexion was measured from full extension to maximum flexion in 15° intervals. Tibiofemoral articular contact was determined by the overlap of the tibiofemoral articular surfaces. The centroid of the surface intersection was used to report the point of contact location. The average tibiofemoral contact points on both the medial and lateral tibial component surfaces were reported as a function of flexion. Results: The average maximum weight-bearing flexion angle was 113.3° ± 13.1° (range, 96° to 138°). In the anteroposterior direction, the contact location was relatively constant in the medial compartment and moved posteriorly by 5.6 mm in the lateral compartment as the knee flexed from full extension to 90° of flexion. The range of the contact location in the mediolateral direction was 3.7 mm in the medial compartment and 4.8 mm in the lateral compartment. For both compartments, posterior translation of the contact point was significant from 90° to maximum flexion, but the contact point at maximum flexion was not observed to reach the posterior edge of the polyethylene tibial insert articular surface. Conclusions: While the minimum anteroposterior translation of the contact point on the medial side might be interpreted as a medial pivot rotation during knee flexion, the contact point did move in the mediolateral direction with flexion. Beyond 90°, both medial and lateral contact points were shown to move posteriorly but stopped before reaching the posterior edge of the polyethylene tibial insert articular surface. It seemed that the current component design did not allow the femoral condyle to roll off the polyethylene edge at high degrees of flexion because of the geometry at the posterior lip. Clinical Relevance: These three-dimensional tibiofemoral contact data may provide new insight for determining polyethylene tibial insert wear patterns in vivo and for designing the articulating surfaces by accounting for contact location in both the anteroposterior and mediolateral directions.

Comparison of Posterior Cruciate Ligament Retentionversus Substitution in PFCSigma Rotating-Platform Total Knee Arthroplasty

Purpose : The purpose of this study was to assess the results of posterior cruciate ligamentretaining and posterior cruciate ligament-sacrificing total knee arthroplasty using PFC Sigma rotating-platform (RP). Materials and Methods : The subjects for this study were 43 patients who had undergone total knee arthroplasties by means of PFC Sigma RPs from February 2002 to July 2002 and, thereafter, had been observed for a period of at least 36 months. Twenty-two of the patients were categorized to group I, which retained the posterior cruciate ligament and 21 to group II, which substituted for the ligament. All the patients were evaluated for pre- and post-operative ranges of motion, the Hospital for Special Surgery (HSS) knee rating system, and radiographic analysis. Results : The average flexion contracture was 6.5˚ (±1.0˚) in group I and 6.7˚ (±0.8˚) in group II pre-operatively, and 1.1˚ (±0.3˚) in group I and 0.9˚ (±0.2˚) in group II at the last follow-up. The average active range of knee motion improved from 87.6˚ (±6.5˚) in group I and 86.6˚ (±6.1˚) in group II pre-operatively, to 123.0˚ (±7.8˚) and 125.1˚ (±7.3˚), respectively, at the last follow-up. The average HSS score improved from 41.1˚ (±7.1˚) in group I and 40.3˚ (±5.3˚) in group II preoperatively, to 87.3˚ (±6.0˚) and 88.9˚ (±4.9˚), respectively, at the last follow-up. There was also improvement in the average tibio-femoral angle from 8.0˚ in varus to 5.7˚ in valgus in group I and from 10.9 in varus to 5.4˚ in valgus in group II. Radiolucent lines were observed in 4 cases from group I and in 1 case from the group II. No significant progressive periprosthetic osteolysis was observed in the follow-up radiographs of both groups. Conclusion : There were no clinical and radiographic differences between the posterior cruciate ligament-retention and ligament-substitution groups, which indicates the necessity for long-term observation.

Long-term Followup of Posterior–Cruciate-retaining TKR in Patients with Rheumatoid Arthritis

A consecutive series of 220 primary posterior-cruciate ligament-retaining total knee replacements were done in 148 patients with rheumatoid arthritis. From this group, 212 total knee replacements (141 patients) were followed up for an average of 10 years. Average knee scores at 5, 10, 15, and 20 years after operation improved to 86, 83, 88, and 89, respectively, and average function scores improved to 70, 72, 64, and 88, respectively. Five knees (2.4%) were revised for deep infection. Posterior instability, recurvaum, or mediolateral instability, combined or otherwise, occurred in 15% (32 knees; in 31 patients). Three tibial components (1.4%) were revised: one for suspected aseptic loosening and two for instability. Excluding infections and failed metal-backed patellas, Kaplan-Meier survival rates were 99.5%, 97.9%, and 96.5%, respectively. Favorable long-term results may be achieved with posterior-cruciate ligament-retaining total knee replacements in patients with rheumatoid arthritis. Concern remains, however, about rotational instability in certain cases associated with preoperative genu-valgum and ipsilateral planovalgus deformity.

Polyethylene damage and knee kinematics after total knee arthroplasty.

This study characterizes the relationship between in vivo knee kinematics and polyethylene damage by combining fluoroscopic analysis of tibiofemoral contact during dynamic activities and implant retrieval analysis in the same patients. Six patients (eight knees) underwent posterior cruciate ligament-retaining total knee arthroplasty. All patients participated in fluoroscopic analysis during a stair-rise and descent activity and treadmill gait an average of 18 months after arthroplasty, and articular contact was measured. Subsequently, all polyethylene tibial inserts were retrieved after an average of 26 months in vivo function: three at autopsy and five at revision. There was a statistically significant correlation between the damage location on the retrieved inserts and the articular contact location measured fluoroscopically during the activities. The femoral contact and polyethylene damage occurred predominantly on the posterior half of the tibial articular surface, and the damage pattern was largest in the compartment with the greatest range of in vivo femoral contact for each patient. This study showed that in vivo fluoroscopic analysis can predict the damage location on the polyethylene articular surface.

Posterior cruciate ligament-retaining total knee arthroplasty in patients with rheumatoid arthritis.

Although initial reports on posterior cruciate ligament-retaining total knee arthroplasty in patients with rheumatoid arthritis have been encouraging, a high rate of late instability necessitating revision has been reported recently. The purpose of the present prospective study was to analyze the results of posterior cruciate ligament-retaining total knee arthroplasty in patients with rheumatoid arthritis. Seventy-two posterior cruciate ligament-retaining total knee arthroplasties in fifty-one patients with rheumatoid arthritis were studied prospectively. All procedures were performed with the Miller-Galante I prosthesis. Eighteen patients (twenty-four knees) died before the eight-year follow-up and one patient (two knees) was lost to follow-up, leaving forty-six knees (thirty-two patients) for review. These forty-six knees were evaluated clinically (with particular attention to posterior instability) and radiographically at annual intervals for a mean of 10.5 years (range, eight to fourteen years). Forty-four (95%) of forty-six knees had a good or excellent result at a mean of 10.5 years. However, nine (13%) of the original seventy-two knees had revision of the implant, with six of the revisions performed because of failure of a metal-backed patellar component. The rate of survival at ten years was 93% 4% with femoral or tibial revision for any reason as the end point and 81% 5% with any reoperation as the end point. There was no aseptic loosening in any knee. Posterior instability was identified clinically and/or radiographically in two (2.8%) of the original seventy-two knees; both unstable knees were in the same patient. Posterior cruciate ligament-retaining total knee arthroplasty yielded satisfactory clinical and radiographic results in patients with rheumatoid arthritis at intermediate-term follow-up (mean, 10.5 years). Therefore, we believe that it remains an excellent treatment option for these patients.

Influence of intramedullary versus extramedullary alignment guides on final total knee arthroplasty component position: A radiographic analysis

A prospective study of 116 consecutive Kinemax cemented posterior cruciate ligament-retaining total knee arthroplasties was carried out. Similar surgical technique was used with a single variable: 61 were implanted using intramedullary guides on the tibia and 55 were implanted using extramedullary guides on the tibia. A radiographic study was performed after at least 1 year of follow-up to evaluate postoperative component position and compare the difference in the accuracy of positioning of the femoral and tibial components. Radiographic analysis showed that satisfactory position was achieved using both types of instrumentation. No statistically significant difference was observed in either the coronal or sagittal plane of the femoral component and the sagittal plane positioning of the tibial component. However, the coronal plane positioning of the tibial component revealed a statistically significant difference ( P <.01), with intramedullary guides being superior to extramedullary guides. Also observed, was that using either technique, patients with less accurate postoperative positioning tended to be obese, with wide intramedullary canals. Patients with significant extraarticular deformities, marked bowing, and those with prior surgery or fractures may not be suitable for intramedullary guides, and they may require the use of extramedullary guides and intraoperative radiographic control. The ideal indication for the use of intramedullary instrumentation is in the patient who is not obese, with no extraarticular deformity, and with a well-defined, but not excessively wide, tibial medullary canal. Since tibial component malalignment in general, and coronal plane malalignment in particular, may adversely affect the long-term survival of total knee arthroplasties, the use of intramedullary alignment instrumentation is recommended when possible.

Posterior polyethylene wear in posterior cruciate ligament-retaining total knee arthroplasty: A case study

Controversy over whether to retain the posterior cruciate ligament (PCL) during primary total knee arthroplasty continues. Both the retaining and substituting designs have their respective advantages and disadvantages. In order to capitalize on the advantages of the PCL retaining design, precise techniques in ligament balancing are required. An incorrectly tensioned PCL—too tight or too loose—may exaggerate the disadvantages of the retaining design and lead to early catastrophic failure. Three cases of early catastrophic posterior wear are presented. Although no definite documentation of excessive PCL tension is available, the authors feel that this may have had a significant role in the etiology of this wear pattern. Possible causes of incorrect PCL tension as well as intraoperative techniques to balance the PCL properly are discussed.