Eliminating patellofemoral complications in total knee arthroplasty: clinical and radiographic results of 121 consecutive cases using the Duracon system

Surgical treatment of patellar tendon rupture after total knee arthroplasty with a double-row repair method using the hamstring tendons: A novel technique with functional results

BACKGROUND

Patellar tendon rupture (PTR) is extremely rare but serious complication after primary or revision total knee arthroplasty. Due to the serious failure rates of end-to-end repair techniques, various augmentation techniques have been described. In this study, the results of patients with PTR after reconstruction using our own technique with semitendinosus (ST) and gracilis tendons taken from the affected side were evaluated retrospectively.

METHODS

A total of 14 patients, whose diagnosis was made based on physical examination and clinical findings, and supported radiologically (ultrasonography), were included in the study. In these patients, reconstruction was performed using double-row repair technique with the ST and gracilis tendons. Active-passive knee joint range of motion, active knee extension loss, and the Caton-Deschamps index at preoperative and final follow-up visits were compared. Tegner-Lysholm knee score and Kujala score were used to evaluate functional results.

RESULTS

In 14 patients (8 women and 6 men) with a mean age of 68.1 years, the median time between injury and surgery was 6.6 weeks. In all patients, the rupture was in the distal part of the patellar tendon. While the median preoperative Caton-Deschamps index was 1.8, the postoperative median value was found to be 1.25 after an average follow-up of 3.8 years (P = .014). The median preoperative knee extension loss decreased from 25° to 5° postoperatively. Tegner-Lysholm knee score and Kujala score of the patients at their last follow-up were significantly increased (P < .01).

CONCLUSION

For PTR developing after total knee arthroplasty, the double-row reconstruction technique with ST and gracilis tendons is effective.

Patellar Component Design Does Not Impact Clinical Outcomes in Primary Total Knee Arthroplasty

BACKGROUND

Round or oval implants are used in patellar resurfacing during total knee arthroplasty (TKA). However, whether component geometry affects clinical outcomes is unclear. This study aimed to determine if one implant shape conferred superior outcomes to the other.

METHODS

A retrospective review of primary TKA cases performed from 2016 to 2020 was conducted at an urban, tertiary academic center. Four hundred consecutive, primary TKAs were included in these analyses. Cases were included if a surgeon used the round design then oval design for fifty consecutive cases. Baseline demographic data and radiographic measurements were assessed. Surgical data, reasons for revision, and patient-reported outcome measures were analyzed. Independent samples t-test and chi-square tests were used to compare means and proportions. There were no demographic differences between the cohorts.

RESULTS

Postoperative patellar tilt was statistically different between the cohorts. Sixteen patients required revision surgery; however, revision rates did not differ between the cohorts. Of the 9 rounds, 1 button was revised for infection. Of the 7 ovals, 1 button was revised for infection and 1 for loosening. Veterans RAND 12 Physical Component Score at 3 months postoperatively was higher for the round cohort, but no differences were observed at 1 year.

CONCLUSION

While radiographic patellar tilt was significantly different between the cohorts, there was no clinical correlation in outcomes at 3 months or 1 year postoperatively. Longer-term follow-up studies are needed to evaluate the implications of patellar component design on outcomes and function. Nevertheless, the current study affirms that both designs are clinically equivalent which should be used to guide clinical decision-making.

LEVEL III EVIDENCE

Retrospective Cohort.

Enhanced Biomechanical Performance of a Modern Polyester Surgical Mesh for Extensor Mechanism Reconstruction in Total Knee Arthroplasty

BACKGROUND

Extensor mechanism (EM) disruption following total knee arthroplasty is a devastating postoperative complication. Reconstruction with a synthetic mesh is one treatment option, although the optimal mesh material remains unknown. This study sought to compare the mechanical properties of 2 mesh material types that can be used for EM reconstruction.

METHODS

Mechanical properties of a polypropylene mesh (Marlex mesh) and Ligament Advanced Reinforcement System (LARS) mesh were compared using force-displacement data from a material testing machine simulating knee movement during normal human gait. Tension to failure/ultimate tensile load, stiffness coefficients, axial strain, and cyclic hysteresis testing were measured and calculated.

RESULTS

Compared to polypropylene mesh, LARS mesh demonstrated a significantly higher mean ultimate tensile load (2223 N vs 1245 N, P = .002) and stiffness coefficient (255 N/mm vs 14 N/mm, P = .035) in tension to failure testing, and significantly more energy dissipation (hysteresis) in hysteresis testing (771 kJ vs 23 kJ; P ≤ .040). LARS mesh also demonstrated significantly less maximum displacement compared to the polypropylene mesh (9.2 mm vs 90.4 mm; P ≤ .001).

CONCLUSION

Compared to polypropylene mesh, LARS mesh showed superior performance related to force-displacement testing. The enhanced mechanical performance of LARS mesh may correlate clinically to fewer failures, increased longevity, and higher resistance to plastic deformation (extensor lag). Future research should evaluate survivorship and clinical outcomes of these meshes when used for EM reconstruction.

Modified V-Y Turndown Flap Augmentation for Quadriceps Tendon Rupture Following Total Knee Arthroplasty: A Retrospective Study

BACKGROUND

Quadriceps tendon rupture following total knee arthroplasty (TKA) is an infrequent but potentially devastating adverse event. Although uncommon, the long-term sequelae of this injury can result in permanent inability to walk. Despite the severity of this injury, there is no single accepted treatment, with various surgical methods producing mixed results. Therefore, the purpose of this study was to assess the efficacy of a modified V-Y turndown flap as a viable alternative method of treatment for this injury.

METHODS

Twenty-four quadriceps tendon ruptures in 23 patients (10 men and 13 women) who underwent TKA (8 primary and 15 revision), including 1 tendon rerupture, were treated with use of a modified V-Y turndown. The average patient age at the time of the V-Y flap repair was 61 years (range, 41 to 86 years). Knee Society scores, range of motion, strength, medical comorbidities, nature of the procedure (i.e., primary versus revision), and the ability to walk were all recorded before and after the quadriceps reconstruction, along with general satisfaction and adverse events following the procedure.

RESULTS

Twelve patients (52%) had predisposing comorbidities, including obesity, diabetes, chronic dialysis, and steroid dependence. Prior to repair with the V-Y flap, none of the patients were able to walk independently, requiring either a wheelchair or walker. No patient had quadriceps strength greater than 3 (of 5), although all had full passive extension. Following the repair procedure, patients had significant (p < 0.0001) improvements in mean Knee Society knee score (88.7; range, 45 to 95) and mean strength (4.8; range, 3 to 5), and all were able to walk without assistive devices. Twenty knees exhibited active range of motion of 0° to 120°, whereas 4 had residual extensor lag of ≥5° (range, 5° to 35°). Major adverse events were limited to a single hematoma and an unacceptable extensor lag (35°) after repair.

CONCLUSIONS

The modified V-Y quadriceps tendon turndown flap was a reliable alternative treatment for achieving restoration of the extensor mechanism after complete quadriceps tendon rupture following TKA.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Suboptimal patellofemoral alignment is associated with poor clinical outcome scores after primary total knee arthroplasty

BACKGROUND

Proper patellofemoral alignment is an important goal in total knee arthroplasty (TKA). Acceptable patellar alignment is defined as patellar tilt less than or equal to 5° and patellar displacement less than or equal to 5 mm. Previous studies reported an incidence of post-operative patellar malalignment in TKA from 7 to 35%. However, correlation between patellar malalignment and clinical outcome after TKA remains unclear. The purpose of the present study was to evaluate the effect of patellar tilt and displacement on the clinical outcome of TKA.

METHODS

A retrospective review of 138 primary TKAs with a minimum of 2 year follow-up is reported. Pre-operative and post-operative mechanical axis, patellar tilting angle and patellar displacement were measured. Clinical outcomes were evaluated by the knee functional scores including the Knee Society Score (KSS), Knee injury and Osteoarthritis Outcome Score (KOOS), and Western Ontario McMaster University Osteoarthritis Index (WOMAC) at final follow-up.

RESULTS

Forty-two (30%) primary TKAs had suboptimal patellofemoral alignment with a patellar tilt angle greater than 5° or lateral patellar displacement of more than 5 mm. There was no statistical difference in pre-operative mechanical axis, pre-operative patellar tilt angle, or pre-operative lateral patellar displacement between the primary TKAs with proper patellofemoral alignment and those with suboptimal alignment. Patients with post-operative patellar tilt or displacement had clinically significant reductions in KSS, KOOS, and WOMAC when compared with patients without post-operative patellar tilt or displacement. The odds of having a fair or poor post-operative result, an odds ratio of 3.4 (95% CI 1.6-7.2) for KSS, 6.4 (95% CI 2.9-14.2) for KOOS, and 5.9 (95% CI 2.6-13.5) for WOMAC, were associated with suboptimal patellofemoral alignment.

CONCLUSION

Establishing proper patellofemoral alignment remains an essential goal of primary TKA. There is a strong association between suboptimal post-operative patellofemoral alignment and poor clinical outcome scores after primary TKA.

Bilateral Spontaneous Midsubstance Patellar Tendon Rupture after Bilateral Total Knee Arthroplasty

Introduction:

Patellar tendon rupture can occur due to multiple causes ranging from inflammatory pathologies to episodes of trauma. Extensor mechanism rupture is a rare complication of total knee arthroplasty (TKA). In most of these cases, the failure occurs as avulsion of patellar tendon from tibial tuberosity. We report a rare case with bilateral mid-substance patellar tendon rupture one month after bilateral total knee arthroplasty.

Case Presentation:

A 69-year-old male was operated for bilateral grade 4 osteoarthritis. On day 30 post-operative, he sustained bilateral patellar tendon rupture while getting up from toilet. He had a history of multiple steroid injections in the knee, which could have affected the tendon. The other etiologies could be inherent weakness of tendon due to diabetes and old age and micro-trauma/stretch associated with sudden correction of previous deformity by TKA. The management in our case was done by primary repair along with augmentation by autologous semitendinosus graft and suture anchor.

Conclusion:

The operating surgeon must be aware of the possibility of patellar tendon rupture following total knee arthroplasty. This will help the surgeon in early recognition and preparedness to handle such complications, should they arise. Surgeons may consider advising caution to both patient and rehabilitation team in cases with old age, chronic diabetes mellitus, and with a history of steroid injections.

Long-Term Survivorship and Clinical Outcomes Following Total Knee Arthroplasty

Total knee arthroplasty (TKA) is one of the most successful commonly performed orthopedic procedures; as such, the purpose was to assess the long-term outcomes and survivorship of primary TKAs with a dual-radius prosthesis. We evaluated 125-patients (145-knees), with a mean age of 63 years (37-90 years) for a mean 11-year follow-up (10-13 years). Outcomes were assessed with KSS, UCLA, SF-36, satisfaction scores, and aseptic survivorship analysis. At 10-year follow-up, the UCLA (6-points), KSS objective (84-points) and functional (73-points), SF-36 physical (41-points) and mental (51-points), and patient satisfaction (14-points) scores were reported to be good to excellent. The 10-year Kaplan-Meier survivorship rate was 99%; one TKA demonstrated radiographic loosening. At a minimum 10-year follow-up, this device demonstrated satisfactory outcomes and outstanding aseptic-survivorship rates.

Chronic extensor mechanism insufficiency in total knee arthroplasty (TKA)

Chronic insufficiency of the knee extensor mechanism is a very challenging pathology to treat. An insufficient extensor mechanism negatively affects implant survival and patient outcomes. The causes of insufficiency can be several, and the surgeon has to be prepared to manage them intraoperatively and postoperatively. Various reconstructive techniques have been proposed, but traditional results in patients with a total knee arthroplasty are usually inferior to those patients with native knee joints. It is of primary importance to understand the anatomy, and tailor the correct treatment to the patient.

Biomechanics of hyperflexion and kneeling before and after total knee arthroplasty

The capacity to perform certain activities is frequently compromised after total knee arthroplasty (TKA) due to a functional decline resulting from decreased range of motion and a diminished ability to kneel. In this manuscript, the current biomechanical understanding of hyperflexion and kneeling before and after TKA will be discussed. Patellofemoral and tibiofemoral joint contact area, contact pressure, and kinematics were evaluated in cadaveric studies using a Tekscan pressure measuring system and Microscribe. Testing was performed on intact knees and following cruciate retaining and posterior stabilized TKA at knee flexion angles of 90°, 105°, 120°, and 135°. Three loading conditions were used to simulate squatting, double stance kneeling, and single stance kneeling. Following TKA with double stance kneeling, patellofemoral contact areas did not increase significantly at high knee flexion angle (135°). Kneeling resulted in tibial posterior translation and external rotation at all flexion angles. Moving from double to single stance kneeling tended to increase pressures in the cruciate retaining group, but decreased pressures in the posterior stabilized group. The cruciate retaining group had significantly larger contact areas than the posterior stabilized group, although no significant differences in pressures were observed comparing the two TKA designs (p < 0.05). If greater than 120° of postoperative knee range of motion can be achieved following TKA, then kneeling may be performed with less risk in the patellofemoral joint than was previously believed to be the case. However, kneeling may increase the likelihood of damage to cartilage and menisci in intact knees and after TKA increases in tibiofemoral contact area and pressures may lead to polyethyelene wear if performed on a chronic, repetitive basis.

The management of extensor mechanism complications in total knee arthroplasty. AAOS exhibit selection

Complications involving the knee extensor mechanism and patellofemoral joint occur in 1% to 12% of patients following total knee arthroplasty and have major negative effects on patient outcomes and satisfaction. The surgeon must be aware of intraoperative, postoperative, and patient-related factors that can increase the rate of these problems. This review focuses on six of the most commonly encountered problems: patellar tendon disruption, quadriceps tendon rupture, patellar crepitus and soft-tissue impingement, periprosthetic patellar fracture, patellofemoral instability, and osteonecrosis of the patella. The goals of this report are to (1) review the relevant anatomy of the knee extensor mechanism, (2) present risk factors that may lead to extensor mechanism complications, (3) provide a diagnostic and treatment algorithm for each of the aforementioned problems, and (4) review the specific surgical techniques of Achilles tendon allograft reconstruction and synthetic mesh augmentation. Extensor mechanism disorders following total knee arthroplasty remain difficult to manage effectively. Although various surgical techniques have been used, the results in patients with a prior total knee arthroplasty are inferior to the results in the young adult without such a prior procedure. Surgical attempts at restoration of the knee extensor mechanism are usually warranted; however, the outcomes of treatment of these complications are often poor, and management of patient expectations is important.

Long-term survival and radiological results of the Duracon™ total knee arthroplasty

Purpose

The aim of this study was to analyse the long-term (>ten years) survival rate and radiological results of the Duracon TKA.

Methods

Between 1992 and 1999 159 Duracon TKA were implanted at our institution. A Kaplan-Meier survival analysis for the endpoints exchange, addition or removal of any component for any reason, revision due to aseptic loosening and mechanical failure was performed. Radiological long-term (>ten years) follow-up (FU) analysis was performed according to the Knee Society Radiographic Evaluation and Scoring System.

Results

Mean age at surgery was 74.3 years, 28 % were male, and 89 % had primary osteoarthritis as diagnosis. Mean FU for survival analysis was 10.9 years (SD 4.2). A total of 58 % of the patients died during follow-up. Three patients (2.1 %) were lost to follow-up and five TKA (3.1 %) were revised. After ten years the mean survival was 97.7 %, 99.4 % and 98.3 % for the aforementioned endpoints, respectively. Mean radiological FU was 11.8 years (SD 2.3). We found no significant change in alignment of the components or axis over time. Progressive radiolucencies were found in nine TKA (17 %), mainly around the tibial component (95 %).

Conclusion

The Duracon TKA showed excellent long-term survival comparable to data from national registers and to other successful designs. Radiological changes found on plain radiographs were scarce after almost 12 years of radiological follow-up indicating good implant stability.

Outcomes of 447 SCORE® highly congruent mobile-bearing total knee arthroplasties after 5-10 years follow-up

INTRODUCTION

The goal of mobile-bearing total knee arthroplasties (TKA) with an anatomical trochlea is to reduce polyethylene wear, the risk of loosening, and patellofemoral complications. Rotating mobile-bearing SCORE(®) TKA was designed according to these principles with standard instrumentation for component placement and a specific computer navigation system, Amplivision(®).

HYPOTHESIS

We hypothesized that the results of SCORE(®) TKA would be satisfactory and better using computer navigation with or without patellar resurfacing and that there would be no specific patellofemoral complications associated with this trochlear design.

MATERIALS AND METHODS

Four hundred and forty-seven SCORE(®) TKA were performed. Outcome assessment was based on the IKS score, and component survival calculated by Kaplan-Meier analysis.

RESULTS

Mean follow-up was 6.6 years (maximum 10.6 years). Six percent of patients were lost to follow-up. Ninety-eight percent of the patients were satisfied or very satisfied. The IKS knee score was 89 points and the function score was 86. The mechanical axis was 180° (174-186), and it was significantly improved if the initial deformity was severe and TKA was computer navigated. There were nine revisions (one for fracture, two for pain, two for stiffness, four for infection).

DISCUSSION

This study confirmed our hypothesis: the results of SCORE(®) TKA were very satisfying after at least 5 years of follow-up because there was no mechanical loosening, no bearing dislocation and no patellofemoral complications with or without patellar resurfacing. Results were identical whether patellar resurfacing was performed or not. Although clinical results were not better for computer- navigated TKA, radiological results were. At 98 months of follow-up, component survival in relation to the risk of aseptic loosening or patellofemoral complications was 100%.

LEVEL OF EVIDENCE

Level IV continuous retrospective study.

Excellent fixation achieved with cementless posteriorly stabilized total knee arthroplasty

Cementless posteriorly stabilized (PS) total knee arthroplasty has not been widely accepted primarily because of prior unpredictable results and concern about micromotion at the tibial fixation interface caused by the cam/post interaction. A prospective consecutive series of 114 cementless, tricompartmental periapatite-coated single-radius PS implants in 110 patients with a mean age 62 years was performed to determine if initial stability and biologic fixation could be achieved. At a mean follow-up of 36 months, all implants demonstrated radiographic evidence of stable biologic fixation with no evidence of loosening, osteolysis, stress shielding, or progressive radiolucent lines. Based on these early results, cementless, periapatite-coated single-radius PS total knee arthroplasty offers marked promise.

Early migration of tibial components is associated with late revision: a systematic review and meta-analysis of 21,000 knee arthroplasties

PURPOSE

We performed two parallel systematic reviews and meta-analyses to determine the association between early migration of tibial components and late aseptic revision.

METHODS

One review comprised early migration data from radiostereometric analysis (RSA) studies, while the other focused on revision rates for aseptic loosening from long-term survival studies. Thresholds for acceptable and unacceptable migration were determined according to that of several national joint registries: < 5% revision at 10 years.

RESULTS

Following an elaborate literature search, 50 studies (involving 847 total knee prostheses (TKPs)) were included in the RSA review and 56 studies (20,599 TKPs) were included in the survival review. The results showed that for every mm increase in migration there was an 8% increase in revision rate, which remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. Consequently, migration up to 0.5 mm was considered acceptable during the first postoperative year, while migration of 1.6 mm or more was unacceptable. TKPs with migration of between 0.5 and 1.6 mm were considered to be at risk of having revision rates higher than 5% at 10 years.

INTERPRETATION

There was a clinically relevant association between early migration of TKPs and late revision for loosening. The proposed migration thresholds can be implemented in a phased, evidence-based introduction of new types of knee prostheses, since they allow early detection of high-risk TKPs while exposing only a small number of patients.

Reconstruction of patellar tendon disruption after total knee arthroplasty: results of a new technique utilizing synthetic mesh

BACKGROUND

Patellar tendon disruption associated with total knee arthroplasty is an uncommon but potentially disastrous complication. Repair with isolated suture fixation is insufficient, and autograft and allograft tendon reconstruction techniques have variable results. The purpose of this study was to determine the results of a novel surgical technique in which readily available synthetic mesh is used for patellar tendon reconstruction.

METHODS

We retrospectively reviewed thirteen consecutive patients who underwent extensor mechanism reconstruction for subacute or chronic patellar tendon disruption following total knee arthroplasty at an average age of sixty years (range, thirty-seven to seventy-seven years). Five patients had already been treated unsuccessfully with an allograft extensor mechanism reconstruction and eight had a prior revision knee arthroplasty. The surgical technique included use of a knitted monofilament polypropylene graft to reconstruct the patellar tendon and to facilitate fixation of adjacent host tissue into the graft. Follow-up was available for all patients at a mean of forty-two months (range, eleven to 118 months).

RESULTS

Three patients had evidence of failure of the graft reconstruction, all within six months. One patient with previous sepsis had recurrent infection and was treated with a knee arthrodesis. The remaining nine patients all demonstrated an extensor lag of no greater than 10° and have had no loss of extension at the time of final follow-up. Knee flexion was maintained in all patients (a mean of 103° preoperatively versus a mean of 107° postoperatively). The mean Knee Society scores for pain and function improved significantly (p < 0.01). Synthetic mesh was significantly less expensive than allograft for this reconstruction.

CONCLUSIONS

The use of synthetic mesh to reconstruct a disrupted patellar tendon is a straightforward surgical procedure that was successful and durable in the majority of patients in our series. Compared with the use of an allograft, this technique eliminates the possibility of disease transmission and may be more cost-effective. No complications unique to the synthetic mesh were observed.

Mid-Term Results for Three Contemporary Total Knee Replacement Designs — A Comparative Study of 104 Patients with Primary Osteoarthritis

Aims:

The purpose of this study was to compare retrospectively the mid-term clinical and radiological results of three contemporary knee designs in cohorts operated on in the same hospital during the same time period.

Materials and Methods:

We evaluated mid-term clinical and radiographic outcome of three contemporary total knee designs (the AGC V2, the Duracon and the Nexgen) in 104 consecutive patients (129 knees) operate on for primary knee osteoarthritis at our hospital. The mean indexed age at the time of the operation was 69.2 years (range, 49.3 to 81.1 years). The mean follow-up time was 6.0 years (range, 0.2 to 7.9). All patients were followed for at least three years or until the first revision. In the survival analyses, the end point was defined as, revision for any reason.

Results:

The Kaplan-Meier survival analysis showed a 98% (95% CI 94–100) survival rate for the NexGen, a 98% (95% CI 93–100) for the AGC and a 90% (95% CI 81–99) for the Duracon design at six years. Both the mean KSS for pain, KSS for function and the mean clinical knee score improved significantly in all three groups. There was no difference between the three designs in mid-term survivorship.

Conclusions:

Most of the revisions could be directly linked to perioperative surgical errors. In conclusion, the most recently introduced knee replacements of the present study (Duracon and Nexgen) did not show any clinically significant benefit over the older design (AGC) in the mid-term.

Radiographic features predictive of patellar maltracking during total knee arthroplasty

Despite improvements in component design and surgical technique, some patients still require lateral retinacular release during TKA to improve patella tracking. We studied 148 fixed-bearing TKAs to identify parameters in pre-operative knee radiographs that would predict intraoperative patellar maltracking. Digital radiographs and software were used to measure coronal alignment, distal femoral valgus angle, proximal tibia varus angle, patellar tilt, patellar shift, Insall-Salvati ratio, and patellar component placement and alignment. Patellar tracking was assessed after all components had been cemented, using both no-touch and modified "towel clip" techniques. The only radiographic parameter independently associated with maltracking was patellar shift. The median pre-operative patellar lateral shift in patients who had maltracking was 4.1 mm compared to 0.0 mm in those who did not. Patients who had a patellar shift of more than 3.0 mm had a high likelihood of maltracking, with estimated positive and negative predictive values of 78 and 95%, respectively. Pre-operative patellar shift may thus be clinically relevant for identifying osteoarthritic patients who have a higher likelihood for patellar maltracking during TKA. Variations in the intrinsic risk for maltracking within patient study populations may account for the widely differing reported rates of patellar maltracking, and our data suggest that information on pre-operative patellar shift may be helpful in stratifying these sample populations.

The management of patients with painful total knee replacement

The management of patients with a painful total knee replacement requires careful assessment and a stepwise approach in order to diagnose the underlying pathology accurately. The management should include a multidisciplinary approach to the patient's pain as well as addressing the underlying aetiology. Pain should be treated with appropriate analgesia, according to the analgesic ladder of the World Health Organisation. Special measures should be taken to identify and to treat any neuropathic pain. There are a number of intrinsic and extrinsic causes of a painful knee replacement which should be identified and treated early. Patients with unexplained pain and without any recognised pathology should be treated conservatively since they may improve over a period of time and rarely do so after a revision operation.

Midterm outcome of the Duracon total knee arthroplasty

PURPOSE

To present midterm results of Duracon total knee arthroplasty (TKA) performed between 1991 and 2001.

METHODS

One man and 43 women (65 knees) aged 46 to 84 (mean, 63) years who underwent primary TKAs using the Duracon prosthesis performed by a single surgeon were followed up for a mean of 8.5 (range, 5-11) years. All TKAs were cruciate-retaining and cemented, with only 9 of the patellae resurfaced. The diagnosis was osteoarthritis in 42 patients (61 knees), and rheumatoid arthritis in 2 patients (4 knees). Patients were assessed using the Knee Society Clinical Rating System, the Oxford Knee Score, and the Knee Society Total Knee Arthroplasty Roentgenographic Evaluation and Scoring System.

RESULTS

The mean Knee Society knee score was 86 (range, 43-100) and the function score was 68 (0- 100). 94% of patients reported no or only mild pain. The mean Oxford Knee Score was 19. There was no patellofemoral complication, deep vein thrombosis or pulmonary embolism. Complications included a superficial infection and an uncontrolled deep infection. One patient had the insert exchanged for wear at the 11-year follow-up, and another had the polyethylene insert and tibial tray revised after a motorcycle accident.

CONCLUSION

The Duracon TKA had good midterm clinical results with absence of patellofemoral complications.

[Fixed-bearing versus mobile-bearing total knee arthroplasty: a prospective randomized clinical and radiological study]

PURPOSE OF THE STUDY

Mobile-bearing total knee arthroplasty has become increasingly popular over the last few years since this option presents several theoretical advantages compared with the fixed-bearing models. The clinical advantage remains to be demonstrated. We therefore conducted a prospective randomized trial to ascertain the potential benefits.

MATERIAL AND METHODS

This study included patients treated by three senior orthopedic surgeons. Each group included 52 prostheses in 52 patients in the fixed-bearing group and 50 patients in the mobile-bearing group. The per- and postoperative protocols were the same for both groups. Implants were cemented in all cases and patellae were resurfaced. The SF-12, the Knee Society Score (KSS), the Hospital of Special Surgery score (HSS) and pain and joint motion were noted before and after surgery.

RESULTS

Among the 104 prostheses implanted, 100 were reviewed at mean follow-up of 36 months (range 24-41). One patient in the fixed-bearing group died six months after surgery from an unrelated cause. Three patients were lost to follow-up: one in the fixed-bearing group and two in the mobile-bearing group. There was no difference between groups for the SF-12, KSS, HSS, pain and joint motion measured postoperatively. Postoperative femorotibial alignment was one degree varus on average in the fixed-bearing group and zero degree in the mobile-bearing group. At last follow-up, there were no radiological signs of prosthesis loosening. One patient in the fixed-bearing group developed a deep venous thrombosis, complicated by pulmonary embolism. Two of the mobile-bearing prostheses were revised, one for patellar fracture caused by a bicycle accident and one for prosthesis infection in a patient with endocarditis 1.5 years after implantation.

DISCUSSION

The clinical results were similar for the two groups in terms of function, pain, general status and complications. The outcome at 36 months was considered excellent or good in 90% of the fixed-bearing group and 88% in the mobile-bearing group. This study did not reveal any difference between the two groups regarding maximal flexion and anterior knee pain, two parameters which would theoretically show short-term improvement with the mobile bearing. Mid- and long-term follow will be required to confirm these findings and to determine the survival of these two types of implants.

An unusual case of pigmented villonodular synovitis after total knee arthroplasty

We describe a case of focal pigmented villonodular synovitis in the knee presenting 12 months after total knee arthroplasty. The abnormal synovial proliferation was noted at arthroscopy, and histological analysis of the resected tissue confirmed the diagnosis.

Gender-specific design in total knee arthroplasty

Total knee arthroplasty (TKA) has now been performed for more than 3 decades, with millions of implantations, and a tremendous volume of scientific data regarding its use. There is little, if anything, in the academic literature to suggest an inferior result when a TKA is performed in a female patient. Recently, implant manufacturers have introduced TKA designs with modified dimensions to accommodate the anatomical differences that occur between sexes. This article will attempt to clarify the known sex issues surrounding TKA, and outline the attempts by manufacturers to improve outcomes based on sex-specific or sex-friendly designs.

Patellofemoral evaluation after total knee arthroplasty. Validation of a new weight-bearing axial radiographic view

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.

Clinical and biomechanical assessment of patella resurfacing in total knee arthroplasty

BACKGROUND

Currently there is a limited understanding of the factors influencing range of motion by comparing patellar resurfacing vs non-resurfacing in total knee arthroplasty during activities of daily living. A recent meta-analysis of patellar replacement confirms better outcome with patella resurfacing; however, the result can be influenced by many other factors, such as: component design, surgeon experience, and technical aspects of the surgery. This study compares the biomechanics of the knee in patients after total knee arthroplasty with and without patellar resurfacing during stair climbing.

METHODS

Forty-seven patients with total knee arthroplasty were assessed at the mean follow-up of 24 months. In all of them a posterior stabilised fixed bearing prosthesis (Optetrak PS, Exactech) was implanted. Twenty-six patients were treated without patellar resurfacing and 21 with patellar resurfacing. Clinical evaluations were performed using the International Knee Society and the Hospital for Special Surgery scores. Ten patients with patellar resurfacing and 10 patients without patellar resurfacing were also studied with motion analysis during stair climbing; 10 healthy subjects were studied for statistical comparison.

FINDINGS

Clinical passive knee flexion, International Knee Society Function and Hospital for Special Surgery scores were significantly higher in the patellar resurfacing group. During stair climbing, active knee joint range of motion during the stance phase was greater in patients with patellar resurfacing. The maximum adduction moment was significantly higher in the group without patellar resurfacing.

INTERPRETATION

Patients with patellar resurfacing demonstrated better clinical scores, and kinematic and kinetic data while ascending stairs.

Patellofemoral instability after total knee arthroplasty

Despite advances in surgical technique and implant design, complications involving the extensor mechanism and patellofemoral joint after total knee arthroplasty (TKA) continue to be the most common cause of pain and the most commonly cited reason for revision TKA surgery. A thorough understanding of the etiologies of patellofemoral instability, careful preoperative planning, and meticulous surgical techniques will optimize clinical outcome. Evaluation of patellofemoral stability should begin in the operating room. Postoperatively, thorough history, physical examination, and dedicated radiographic studies should be obtained. Computed tomography scan is the most accurate and reliable way to assess component positioning. Treatment of patellofemoral instability is directed by its etiology. Revision of one or both components is indicated if malpositioning is present. If the components are determined to be in satisfactory positions, soft tissue procedures can be pursued. Future advancements in prosthetic design and the routine use of computer-assisted navigation systems will minimize patellofemoral instability.

LEVEL OF EVIDENCE

Therapeutic study, Level V (expert opinion). See the Guidelines for Authors for a complete description of levels of evidence.

Anatomic dimensions of the patella measured during total knee arthroplasty

The anatomic measurements of 92 patellae with normal underlying bony structure were studied during total knee arthroplasty before and after resection of the articular surface. The articular surface of the patella was found to have an oval shape with a width-to-height ratio (46 x 36 mm) of 1.30. The dome was 4.8 mm high and displaced medially 3.6 mm. The medial facet was slightly thicker than the lateral facet (18 vs 17 mm). The lateral facet is 25% wider than the medial facet. Coverage provided by oval patellar prostheses was significantly better than with round prostheses. The patellae in women were significantly smaller than in men. Size differences and deformity need to be taken into account when the patella is prepared for resurfacing. It is recommended that the bony resection should be no greater than one third of the maximum patellar thickness to avoid alteration of normal bony structure. Key words: patella, total knee arthroplasty, anatomy.

The outcome of total knee arthroplasty in obese patients

BACKGROUND

Evidence linking increased body weight to osteoarthritis of the knee and the high prevalence of obesity underscore the importance of defining the outcome of total knee arthroplasty in obese patients. The purpose of this study was to compare the clinical and radiographic results of total knee arthroplasties performed in obese patients with those of total knee arthroplasties performed in nonobese patients.

METHODS

Clinical and radiographic data on seventy-eight total knee arthroplasties in sixty-eight obese patients were compared with data on a matched group of nonobese patients. The analysis was also performed after stratification of the obese group for the degree of obesity. All patients had the same prosthesis. The clinical data that were analyzed included the Knee Society objective and functional scores, patellofemoral symptoms, activity level, and complications.

RESULTS

The percentage of knees with a Knee Society score of > or =80 points at an average of eighty months was 88% in the obese group, which was significantly lower than the 99% rate in the nonobese group at the same time. The morbidly obese subgroup had a significantly higher revision rate than did the nonobese group (p = 0.02).

CONCLUSIONS

The results of the present study suggest that any degree of obesity, defined as a body mass index of > or =30, has a negative effect on the outcome of total knee replacement.

Extensor mechanism failure associated with total knee arthroplasty: prevention and management

Extensor mechanism complications are the most commonly reported reasons for revision surgery after total knee arthroplasty and are a frequent source of postoperative morbidity. Patellofemoral instability is the most commonly reported extensor mechanism complication and has multiple etiologies, including prosthetic malalignment and soft-tissue imbabalce. Patellar fracture or rupture of either the quadriceps or patellar tendon can cause catastrophic disruption of the extensor mechanism. Although some stable fractures can be successfully managed nonsurgically, displaced fractures or tendon rupture often lead to poor results. Other complications include patellar clunk and soft-tissue adhesions, prosthetic wear or loosening, and osteonecrosis. Increased understanding of implant alignment, rotation, and soft-tissue balance, as well as improved design of the trochlear groove of femoral implants and patellar components, has resulted in a decline in extensor mechanism complications. Appropriate prosthetic selection and meticulous surgical technique remain the keys to avoiding unsatisfactory results and revision surgery.

Orthopaedic crossfire--All patellae should be resurfaced during primary total knee arthroplasty: in the affirmative

Patients with inflammatory arthritis, crystalline deposition disease, or severe patellofemoral arthritis have superior functional results with patellar resurfacing as compared with patellar retention. The only remaining issue is whether there is any advantage to resurfacing or retention in patients with osteoarthritic knees in the absence of severe patellofemoral arthritis. Although the answer is still unclear from available prospective randomized clinical trials, the evidence leans toward routine resurfacing of the patella during primary total knee arthroplasty in osteoarthritic knees too. Evidence exists that the results of patellar retention in osteoarthritic knees deteriorate with longer follow-up study. Long-term follow-up evaluations of available prospective clinical trials will be needed to assess this controversy more definitively.

Total knee arthroplasty for patellofemoral arthritis

BACKGROUND

Multiple treatment methods have been advocated for patellofemoral arthritis. The purpose of the present study was to report on our experience with the use of total joint replacement for the treatment of primarily severe patellofemoral arthritis of the knee in patients more than fifty-five years of age.

METHODS

Between January 1980 and December 1994, thirty knee replacements were performed in twenty-seven patients for the treatment of arthritis that primarily involved the patellofemoral joint. The Ahlbück radiographic evaluation scale was used to grade the severity of arthritis; the mean score was 4.83 points (range, 4 to 5 points) for the patellofemoral compartment and 0.6 point (range, 0 to 1 point) for both the medial and lateral compartments. The patients included eighteen women and nine men who had a mean age of seventy-three years (range, fifty-nine to eighty-eight years). None of the patients had had any prior procedures on the knee, but all had been treated for a minimum of six months with nonoperative measures. The mean preoperative Knee Society score was 50 points (range, 20 to 64 points).

RESULTS

At a mean duration of follow-up of eighty-one months (range, forty-eight to 133 months), there were twenty-eight excellent, one good, and one poor result. The mean Knee Society objective score was 93 points (range, 67 to 100 points). The poor result was in a patient who sustained a rupture of the patellar tendon postoperatively as the result of a fall, which necessitated a tendon reconstruction.

CONCLUSION

Total knee arthroplasty was found to be a viable treatment option in patients more than fifty-five years of age with primarily severe patellofemoral disease.

Total knee arthroplasty in patients </=50 years old

Thirty patients (30 knees) who underwent total knee arthroplasty at age </=50 were reviewed. These patients were operated on between July 1, 1991, and May 1, 1995, with final follow-up evaluation at a mean of 86 months (range, 60-107 months). At final evaluation, 18 knees (60%) had excellent Knee Society objective scores, 11 knees (37%) had good scores, and 1 knee (3%) had a poor score. There were no statistically significant differences in Knee Society objective scores among the cemented group (mean, 88 points), hybrid group (mean, 88 points), and noncemented group (mean, 90 points). One patient (3%) had a revision because of unexplained pain. In the other knees, there was no radiographic evidence of progressive loosening, lucencies, or change in position or alignment of the prosthesis. Total knee arthroplasty of this design, at least for the time period studied (7-year mean follow-up), has a high rate of success in patients who are </=50 years old.

Scoring systems in total knee arthroplasty

For assessment of total knee arthroplasty outcome, various scoring systems have been introduced. The current study assessed the interobserver correlation of four commonly used total knee arthroplasty outcome scores. One hundred eighteen total knee arthroplasties were investigated by two independent observers, using the Hungerford score, the Hospital for Special Surgery score, the Knee Society score, and the Bristol score. Each score consisted of three subscores: pain, knee, and function. For the highest interobserver correlation was computed for the Bristol score (interobserver correlation coefficient, 0.88). For knee range of motion, flexion contracture, and extension lag there was high interobserver correlation (interobserver correlation coefficient > 0.8 each). For walking distance and walking aids, there also was a high interobserver correlation (interobserver correlation coefficient > 0.7 each). For clinical assessment of total knee arthroplasty, pain should be measured on a four-step system, the knee should be assessed by measurement of range of motion, extension lag, and flexion contracture, and function should be measured on a separate score assessing walking distance and walking aids.

The patellofemoral joint in total knee arthroplasty: is the design of the trochlea the critical factor?

The outcome at 10 years is reported of a prospective study of 2 cohorts of total knee arthroplasties treated with (center A) or without (center B) patellar replacement. The same tibiofemoral components were used in all knees. The cohorts were demographically similar. A total of 124 patellae were treated by replacement, and 143 were treated without replacement. The clinical outcome and the patellofemoral revision rates were the same in the 2 cohorts: 1 patient required analgesia for anterior knee pain after replacement, and 1 without replacement required patellar replacement for pain. In the replaced group, patellofemoral survival on a best-case scenario was 100% at 10 years; on a worst-case scenario, 96%. One of the unreplaced patellae had been resurfaced for pain by 10 years. In view of the satisfactory and similar outcomes with and without replacement, we suggest that an appropriate design for the prosthetic trochlea, rather than the replacement or otherwise of the patella, is the main determinant of patellofemoral outcome in total knee arthroplasty. Patella replacement may be optional. Desirable trochlea design features are described.