Patellofemoral Compartment Research Articles

Avoidance of Patello-Femoral Overstuffing

Reconstruction of the patello-femoral compartment and by that avoidance of an overstuffing is one of the important steps for a successful TKA. A revision rate of around 15 % due to problems of the patello-femoral compartment demonstrates that this is not achieved in all cases. There can be many reasons for an overstuffing and also the symptoms can be very variable, showing sometimes a limited flexion, patello-femoral maltracking or anterior knee pain. Due to its relevance the following paper demonstrates the different reasons for a patello-femoral overstuffing. Further possible solutions for avoidance of overstuffing are described. The reasons for patello-femoral overstuffing are multiple. The majority is caused on the femoral side, however additional patellar and tibial reasons exist. During positioning of the femora resection blocks, the distal resection plane (extension/flexion) as well as the AP block for sizing is crucial. For that a pre-op analysis and implant planning in the lateral view of the X-ray should be performed in order to optimise implant size and position. For the patella the correct resection height and plane are important to avoid an overstuffing. A lateral patella component position can be another reason for an overstuffing. In conclusion, it can be stated that an anatomic reconstruction of the patello-femoral compartment is an important part of TKA surgery. The avoidance of a patello-femoral overstuffing can be achieved by exact pre-op planning of the femoral component size and position, and by precise surgery with sufficient bone resection.

The distribution of superficial zone protein (SZP)/lubricin/PRG4 and boundary mode frictional properties of the bovine diarthrodial joint

The diarthrodial, knee joint is a remarkably efficient bearing system; articulating cartilage surfaces provide nearly frictionless performance with minimal wear. The low friction properties of the cartilage surfaces are due in part to the boundary lubricant, superficial zone protein (SZP); also known as lubricin or proteoglycan 4 (PRG4). In previous work, SZP localization and cartilage friction were examined across the femoral condyles. Studies in the literature have also individually investigated the other tissues that comprise the human knee and four-legged animal stifle joint, such as the meniscus or patella. However, comparisons between individual studies are limited due to the variable testing conditions employed. Friction is a system property that is dependent on the opposing articulating surface, entraining speed, and loading. A cross-comparison of the frictional properties and SZP localization across the knee/stifle joint tissues utilizing a common testing configuration is therefore needed. The objective of this investigation was to determine the friction coefficient and SZP localization of the tissues comprising the three compartments of the bovine stifle joint: patella, patellofemoral groove, femoral condyles, meniscus, tibial plateau, and anterior cruciate ligament. The boundary mode coefficient of friction was greater in tissues of the patellofemoral compartment than the lateral and medial tibiofemoral compartments. SZP immunolocalization followed this trend with reduced depth of staining and intensity in the patella and patellofemoral groove compared to the femoral condyles and tibial plateau. These results illustrate the important role of SZP in reducing friction in the tissues and compartments of the knee/stifle joint.

Meniscus and cartilage injuries concomitant with isolated rupture of posterior cruciate ligament and its risk factors

To investigate the risk factors associated with meniscus and cartilage lesions concomitant with isolated rupture of posterior cruciate ligament (PCL). A total of 147 patients with rupture of PCL from January, 2005 to June, 2013 were retrospectively analyzed for associations of distribution, incidence of meniscal tears or cartilage injuries with gender, age, sides, duration, body mass index, cause or degree of instability. Incidence for meniscal injuries was 14.3%, which was statistically different among groups in gender, age, sides, duration and degree of instability (P<0.05). Chondral lesions were mainly appeared in medial tibiofemoral compartment and patellofemoral compartment, and the incidence was statistically different among groups in gender, age, duration, and degree of instability (P<0.05). No independent risk factor was found to be associated with meniscal and chondral injuries. Severe cartilage lesions and less meniscal tears can be induced by the rupture of PCL. Medical treatment at the early stage is necessary to restore stability and reduce chondral injuries.

Prospective randomised trial comparing unlinked, modular bicompartmental knee arthroplasty and total knee arthroplasty: A five years follow-up

BackgroundA significant proportion of patients with knee osteoarthritis have articular degeneration that is limited to the medial and patellofemoral compartments. The objective of this study was to compare clinical outcomes of unlinked bicompartmental knee arthroplasty (BCA) and total knee arthroplasty (TKA) at 5years in this subset of patients. Methods48 patients were randomised into two groups: unlinked, modular bicompartmental arthroplasty and total knee arthroplasty. Data on demographics and clinical outcomes were collected (Bartlett Knee Score, Oxford Knee Score, Knee Society Score). Data on intra-operative blood loss in both groups were also recorded. ResultsOut of the 48 patients, 26 underwent BCA and 22 had TKA. Both groups shared similar demographic profiles. At five years post surgery, there was significant improvement across all functional scores in both groups. However, there was no significant difference in outcome scores in the BCA group compared to the TKA group. The drop in serum haemoglobin levels postoperatively was 1.55 and 2.30g/dl for the BCA and TKA groups respectively (p<.001). The total amount of blood loss was 397 and 647ml respectively (p=.001). ConclusionsUnlinked, modular BCA results in similar clinical and functional scores as TKA for medial and patellofemoral arthritis in the mid-term. Intra-operative blood loss was significantly lower in the BCA group compared to the TKA group. BCA is a viable option for a select group of young and active patients with the advantage of reduced intra-operative blood loss and equivalent functional outcomes as TKA.

Frontal Plane Analysis During Lunging After Knee Replacement Surgeries

It is reported that 70% of the Knee OA patients have cartilage degeneration isolated to the medial and patellofemoral (PF) compartments. Majority of these patients receive total knee replacements (TKR). The iDuo knee is a customized, individually made bi-compartmental knee replacement (BKR) treating OA at medial/lateral and PF compartments. The BKR keeps the contra-lateral compartment intact, retains the anterior and posterior cruciate ligaments, and regains normal knee geometry with good knee alignment. Thus, the BKR knee could have similar knee mechanics to that of a normal healthy knee. To date, there is no information regarding the mechanics during daily activities (e.g. lunging) with a BKR. There are no in vivo biomechanical comparisons between a BKR and a limb with an off-the-shelf TKR. PURPOSE: To examine differences in frontal plane knee moment between three participant groups during a lunging exercise: (1) BKR, (2) TKR, and (3) healthy controls. METHODS: To date, 21 participants have been tested, which included 5 TKR patients (66±12 yr.; 105±42 kg; 1.75±0.12 m) (Persona, Zimmer Inc.) (post-op: 11±4 mo.), 4 BKR patients (63±7 yr.; 93±18 kg; 1.66±0.06 m) (iDuo, ConforMIS Inc.) (post-op: 21±3 mo.), and 12 healthy controls (57±6 yr.; 82±12 kg; 1.75±0.11 m). 3D motion data (100Hz) and ground reaction forces (2000Hz) were collected during forward lunges. Peak internal knee abduction moments (ABDM) were calculated during both the down and up phases of a lunge. Student t tests were performed. α = 0.05. RESULTS: he means ± SDs of the ABDM of the BKR, TKR, and control participants were: 0.10±0.03, 0.15±0.06, 0.11±0.10 Nm/kg during down phase, respectively; and 0.11±0.05, 0.23±0.13, 0.08±0.09 Nm/kg during up phase, respectively. No differences were found between the BKR and control participants for either the down (p=0.43) or up phases (p=0.31). The TKR patients showed greater ABDM than the controls during the up phase (p=0.01). There was a trend that the BKR was associated with smaller ABDM than the TKR (p=0.06). CONCLUSION: Normal frontal plane mechanics appear to be achievable outcomes with customized BKR surgeries. BKR patients demonstrated similar frontal plane mechanics to the healthy controls during lunging. Off-the-shelf TKR patients showed significantly different mechanics from healthy controls.

Modes of failure and revision of failed lateral unicompartmental knee arthroplasties

BackgroundEven with the resurgence of interest in unicompartmental knee arthroplasty (UKA) in recent years, lateral UKA is still performed 10 times less frequently than medial UKA. Hence, because of the infrequency of this procedure, a paucity of outcome studies exist on lateral unicompartmental knee arthroplasty. This retrospective study was performed to analyze the main causes of failure, as well as the time to failure following lateral UKA. MethodsA total of 16 consecutive failed lateral UKAs were revised at our institution and were retrospectively reviewed. Causes of failure and time to failure were analyzed based on the medical records and radiographs at the time of revision. ResultsThe mean time from index arthroplasty to revision surgery was 9.4years. In three cases, lateral UKA was converted to primary TKA and in the remaining thirteen cases, revision knee joint systems were used. Seven out of the 16 patients (43.8%) were revised within five years after the index surgery. Overall, the most common reason for failure was progression of arthritis of the medial and/or patellofemoral compartments (56.3%) followed by aseptic loosening (18.8%). ConclusionsIn conclusion, similar to published reports on medial UKA, the main reason for early and late failure after lateral UKA was progression of arthritis in other compartments. Level of evidenceIV

Early knee osteoarthritis is evident one year following anterior cruciate ligament reconstruction: a magnetic resonance imaging evaluation.

To determine the prevalence and factors associated with knee osteoarthritis (OA) defined by magnetic resonance imaging (MRI) and specific OA features on MRI 1 year after anterior cruciate ligament reconstruction (ACLR). Isotropic 3.0T MRI scans were obtained for 111 participants (71 men; mean ± SD age 30 ± 8 years) 1 year after ACLR as well as for 20 age-, sex-, and activity level-matched uninjured controls. The MRI OA Knee Score was used to score specific OA features. MRI-defined tibiofemoral and patellofemoral OA was evaluated based on published criteria. Logistic regression identified factors associated with MRI-defined OA and specific OA features after ACLR. Following ACLR, medial and lateral tibiofemoral OA on MRI was observed in 7 participants (6%) and 12 participants (11%), respectively, while 19 participants (17%) had patellofemoral OA on MRI. The femoral trochlea was the region most affected by bone marrow lesions (19% of participants), cartilage lesions (31% of participants), and osteophytes (37% of participants). Meniscectomy at the time of ACLR (odds ratio 6.8 [95% confidence interval 2.0-23.3]) and body mass index (BMI) >25 kg/m(2) (odds ratio 3.0 [95% confidence interval 1.3-6.9]) predicted MRI-defined tibiofemoral OA and osteophytes, respectively. Men had higher odds of patellofemoral osteophytes (odds ratio 6.3 [95% confidence interval 2.4-16.2]). No uninjured controls had tibiofemoral or patellofemoral OA on MRI, and specific OA features were uncommon. OA 1 year following ACLR was more common than previously recognized, while being absent in uninjured control knees. The patellofemoral compartment seems to be at particular risk for early OA after ACLR, especially in men. The association with meniscectomy and BMI demonstrates the construct validity of MRI criteria.

Retrospective Clinical and Radiological Outcomes after Robotic Assisted Bicompartmental Knee Arthroplasty.

Purpose. Bicompartmental knee arthroplasty (BiKA) is a favorable alternative to total knee arthroplasty for degenerative disease limited to two knee compartments. Recently developed robotic-assisted systems improved the clinical efficacy of unicompartmental knee arthroplasty by providing enhanced component positioning with dynamic ligament balancing. The purpose of this study was to evaluate the short-term outcomes of patients, undergoing bicompartmental knee arthroplasty at a single institution by a single surgeon using a robotic-assisted system. It was hypothesized that robotic assisted BiKA is a prevailing choice for degenerative disease limited to two knee compartments with good functional results. Methods. A search of the institution's joint registry was conducted to identify patients that underwent robotic-assisted BiKA of the patellofemoral compartment and the medial or lateral compartment. Results. A total number of 29 patients (30 BiKA) with a mean age of 63.6 years were identified who received a patellofemoral resurfacing in combination with medial or lateral compartment resurfacing. Twenty-four out of 29 patients had good to excellent outcome. Conclusion. Robotic assisted bicompartmental arthroplasty using broad indications and only excluding patients with severe deformity and those that have less than 4 mm of joint space in the surviving compartment demonstrated 83% good to excellent results.

Fracture of the Tibial Baseplate in Bicompartmental Knee Arthroplasty

Introduction. Bicompartmental knee arthroplasty (BKA) addresses combined medial and patellofemoral compartment osteoarthritis, which is relatively common, and has been proposed as a bridge between unicompartmental and total knee arthroplasty (TKA). Case Presentation. We present the case report of a young active man treated with BKA after unsuccessful conservative therapy. Four years later, loosening with fracture of the tibial baseplate was identified and the patient was revised to TKA. Discussion. Although our case is only the second fractured tibial baseplate to be reported, we believe that the modular titanium design, with two fixation pegs, is too thin to withstand daily cyclic loading powers. Light daily routine use, rather than high-impact sports, is therefore advised. Failures may also be related to the implant being an early generation and known to be technically complex, with too few implant sizes. We currently use TKA for the treatment of medial and patellofemoral compartment osteoarthritis.

Quantitative T2* assessment of knee joint cartilage after running a marathon

ObjectiveTo study the effect of repetitive joint loading on the T2* assessment of knee joint cartilage. Materials and methodsT2* mapping was performed in 10 non-professional marathon runners (mean age: 28.7±3.97 years) with no morphologically evident cartilage damage within 48h prior to and following the marathon and after a period of approximately four weeks. Bulk and zonal T2* values at the medial and lateral tibiofemoral compartment and the patellofemoral compartment were assessed by means of region of interest analysis. Pre- and post-marathon values were compared. ResultsThere was a small increase in the T2* after running the marathon (30.47±5.16ms versus 29.84±4.97ms, P<0.05) while the T2* values before the marathon and those after the period of convalescence were similar (29.84±4.97ms versus 29.81±5.17ms, P=0.855). Regional analyses revealed lower T2* values in the medial tibial plateau (P<0.001). ConclusionsIt appears that repetitive joint loading has a transient influence on the T2* values. However, this effect is small and probably not clinically relevant. The low T2* values in the medial tibial plateau may be related to functional demand or early cartilage degeneration.

Kinematics of monoblock bicompartmental knee arthroplasty during weight-bearing activities.

There is an increased interest in treating arthritis of the medial and patellofemoral compartments without using a total knee arthroplasty. The purpose of this study was to measure kinematics in knees with a monoblock bicompartmental arthroplasty to see whether maintaining the cruciate ligaments and lateral compartment resulted in consistent kinematics more similar to healthy knees than those observed in replaced knees. The kinematics of ten knees with monoblock bicompartmental arthroplasty were observed using fluoroscopy during three weight-bearing activities. Model-image registration techniques were used to quantify the three-dimensional motions of the knee joints. During kneeling, lunging, and stair-step activities, the medial condyle remained relatively close to the centre of the tibial plateau, while the lateral condyle typically moved posteriorly with flexion. Knees generally exhibited motion patterns consistent with retained cruciate ligament function, but individual patterns varied significantly. Bicompartmental knee arthroplasty has the potential to retain more natural knee function. Improved tools for aligning the implants and increased implant sizing options may be required to achieve highly consistent results and realize the clinical benefit of a knee arthroplasty with intact cruciate ligaments. III.

CORR Insights®: Do various factors affect the frequency of manipulation under anesthesia after primary total knee arthroplasty?

T he gold standard for the surgical treatment of patients with advanced arthritis remains TKA. Its reliability in relieving pain and improving function in the shortand long-term is well proven. Despite our best efforts, however, joint replacement surgery is not without its complications. In particular, the development of arthrofibrosis can be substantially disabling to the 1% to 12% [2, 6, 9] of patients who develop it. The etiology is multifactorial, often unknown, and frequently resistant to treatment. There is a large quantity of literature on arthrofibrosis. Recent studies [11] have identified both patient-dependent and independent risk factors, which include limited ROM preoperatively, prior knee surgery, complex regional pain syndrome, lack of patient compliance with therapy, and diminished patient pain threshold. Other patientrelated factors associated with the development of arthrofibrosis include nonwhite race younger than 65 years of age, diabetes, hypercholesterolemia, and smoking [5]. Technical factors include ‘‘overstuffing’’ the knee (both tibiofemoral and patellofemoral compartments), component malalignment in all planes, instability, balance flexion-extension gap failure, joint line elevation, infection, and heterotopic ossification [10]. But even when these risk factors are absent, some patients can still develop the condition through an exaggerated fibroblastic response, tissue metaplasia, or revision interventions [4]. Numerous treatments options have been used, but their results are inconsistent. These options include manipulation under anesthesia with or without arthroscopic intervention, open arthrolysis, and revision surgery [3].

Patellofemoral arthroplasty: outcomes and factors associated with early progression of tibiofemoral arthritis.

The purpose of this study was to review the results of patellofemoral arthroplasty (PFA) performed by a single surgeon at a single institution in order to determine factors associated with clinical outcomes and progression of tibiofemoral degenerative joint disease. Sixty-one patients with isolated patellofemoral osteoarthritis were treated with a PFA by a single surgeon between 2003 and 2009. Fifty-nine patients were available for analysis with a mean follow-up of 4 years (range 2-6 years). Patients were evaluated by measuring range of motion and with the use of the Knee Society clinical rating system, the Tegner Activity Level Scale, and the UCLA Activity Score. In addition, preoperative radiographs were evaluated for patellofemoral and tibiofemoral compartment osteoarthritis and presence of trochlear dysplasia, and post-operative radiographs were reviewed for progression of tibiofemoral degenerative arthritis. Furthermore, multivariate statistical methods were applied to study factors that had potential to influence the final outcome. There was no statistically significant association between age, gender, history of prior knee surgery, patellar height, patellofemoral osteoarthritis severity, patellar and femoral component size, or performance of lateral release with patient pain and function (as measured by the Knee Society scores) or progression of tibiofemoral joint osteoarthritis at final follow-up. Increased preoperative body mass index (BMI) was associated with lower post-operative Knee Society function scores (p=0.03). Patients with preoperative trochlear dysplasia had significantly less radiographic evidence of tibiofemoral joint osteoarthritis progression compared with patients without trochlear dysplasia at final follow-up (p<0.0001). In this study, patients with preoperative radiographic evidence of trochlear dysplasia experienced less progression of tibiofemoral degenerative joint disease than patients without trochlear dysplasia at a mean follow-up of 4 years. IV.

Is Patellofemoral Osteoarthritis Common in Middle‐Aged People With Chronic Patellofemoral Pain?

To document the prevalence of radiographic osteoarthritis (OA) in the medial and lateral patellofemoral (PF) joint compartments relative to the prevalence of tibiofemoral (TF) joint OA in middle-aged and older adults with chronic PF knee pain. A convenience sample of 224 people who volunteered for a clinical trial underwent weight-bearing posteroanterior and skyline knee radiographs of their most symptomatic eligible knee. Radiographic severity in the TF joint and in the medial and lateral PF joint compartments was independently graded by 2 examiners using the Kellgren/Lawrence (K/L) grading system. K/L grades ≥2 were considered evidence of OA. OA was common in this cohort, and the most prevalent pattern was combined TF joint and PF joint OA (n = 98 [44%]), followed by isolated PF joint OA (n = 57 [25%]). Isolated TF joint OA was rare. Overall, more people demonstrated radiographic OA in the PF joint (n = 155 [69%]) than in the TF joint (n = 100 [45%]). The majority of people with PF joint OA had OA in both the medial and lateral PF joint compartments (n = 98 [63%]). Even in people ages <50 years, radiographic OA was common (isolated PF joint OA, 26% [n = 21]; combined TF joint and PF joint OA, 29% [n = 23]). The severity of PF joint OA was similar across men and women. PF joint OA was highly prevalent, more so than TF joint OA, and even in individuals ages <50 years. Further research is needed to elucidate the cause and effect relationship between chronic PF pain and PF joint OA.

Parameniscal Cyst with Associated Extensive Proximal Tibial Bone Erosion: A Case Report and Literature Review.

Meniscal cysts are common, with a reported prevalence of 1% to 22% for patients undergoing meniscectomy1-4. Parameniscal cysts can extend beyond the articular surface and can enlarge sizably, prompting confusion with soft-tissue tumors. Parameniscal cysts that cause bone erosion, however, are considered rare2,4-6. Physical examination, diagnostic imaging, and aspiration of the cyst can all aid in the diagnosis. We present the case of a patient with advanced medial and patellofemoral compartment osteoarthritis with a large parameniscal cyst that extended distal to the joint line with resultant erosion of the medial aspect of the proximal tibial metaphysis. The associated bone loss was believed to compromise the structural integrity of the medial tibial plateau. The patient underwent combined cyst excision and total knee arthroplasty with a stemmed tibial component. To our knowledge, this degree of bone loss associated with a parameniscal cyst and the treatment necessitated by such loss have not been previously discussed in the literature. The patient was informed that information concerning the case would be submitted for publication, and he consented. An eighty-five-year-old man presented to the orthopaedic clinic with mild pain on the medial side of the right knee during walking. The patient also noted a small mass over the medial aspect of the knee. Physical examination revealed the mass to be soft, nontender, and mobile. Range-of-motion testing showed a 10° flexion contracture with flexion to 115°. The knee was stable to varus and valgus stress. Radiographs of the knee revealed advanced osteoarthritis of the medial and patellofemoral compartments and a normal appearance of the medial tibial metaphysis. Magnetic resonance imaging (MRI) showed a chronic tear in the anterior cruciate ligament (ACL) and a benign-appearing cystic structure, consistent with a parameniscal cyst, which extended from the joint line …

THU0202 Changes in Serum C-Reactive Protein and Erythrocyte Sedimentation Rate do not Associate with Radiographic Progression in Patients with Knee Osteoarthritis: A 2 Years Follow-Up Study in the AMS-OA Cohort

ObjectivesTo examine the associations of elevated serum c-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) with radiographic progression in patients with established knee osteoarthritis (OA), over two-years.MethodsData from 186 patients...

Assessment of the lateral patellar facet in varus arthritis of the knee

BackgroundLateral patellar arthritis has been associated with poor outcomes in unicompartmental knee arthroplasty. The current study correlates intraoperative findings with MRI imaging, skyline radiographs and the presence of anterior knee pain. MethodsIn 92 consecutive knees with varus arthritis, the patellofemoral compartment was assessed during surgery, on skyline radiographs and on MRI. Anterior knee pain was recorded on a visual-analog-scale. Intraoperative assessment was based on the Outerbridge grading scale. Skyline radiographs were evaluated according to the Ahlbäck grading scale; MRIs were assessed according to a modified Outerbridge grading scale. ResultsThere was an excellent correlation (rs=0.833; p<0.001) in the cartilage assessment of the lateral patellar facet between MRI and surgery. A good correlation (rs=0.664; p<0.001) was seen between Ahlbäck Grades and macroscopic Outerbridge Grades of the lateral patella. Ahlbäck Grades and MRI modified Outerbridge Grades showed a good correlation (rs=0.643; p<0.001) for the lateral patella. Twelve percent of knees (seven out of 60) with Ahlbäck Grade 0 or 1 and mild to moderate anterior knee pain had a macroscopic Outerbridge Grade of 3 on the lateral patella. None of these 60 knees had a full-thickness cartilage defect on MRI. ConclusionNormal skyline radiographs in patients with mild to moderate anterior knee pain can rule out full-thickness cartilage defects of the lateral patellar facet as observed during surgery and on MRI. The MRI allows for the most accurate assessment of the patellofemoral joint and is warranted in all patients with radiographic abnormalities or severe anterior knee pain. Level of evidenceDiagnostic study, Level II.

Modern unicondylar knee arthroplasty. Tips and tricks

Unicondylar knee arthroplasty (UKA) is an established therapeutic option for advanced medial or lateral gonarthrosis. The cornerstones of a successful UKA, careful patient selection, preoperative planning and precise operation technique, are discussed in this overview article. In contrast to total knee arthroplasty, UKA allows preservation of the contralateral and patellofemoral compartments as well as the cruciate ligaments and is often associated with rapid postoperative recovery, improved knee kinematics and knee function. However, UKA is technically very demanding. High revision rates have been reported in particular with widespread application, according to national joint replacement registries. Successful UKA relies on meticulous patient selection, preoperative planning and surgical technique. It is justified to broaden classic UKA indications. In medial and lateral UKA three types of mechanical varus-valgus deformity can be encountered: type1 (isolated intraarticular deformity), type2 (pronounced deformity due to extraarticular varus deformity in medial UKA or valgus deformity in lateral UKA), type3 (reduced deformity due to extraarticular valgus deformity in medial UKA or varus deformity in lateral UKA). We believe these deformities should be addressed accordingly with surgical technique.

A Prospective Randomized Study of Bicompartmental vs. Total Knee Arthroplasty with Functional Testing and Short Term Outcome

The purpose of this study was to compare 50 bicompartmental knee arthroplasty (BKA) and total knee arthroplasty (TKA) cases, particularly in restoring knee function. Patients were between 30 and 65years old, with a BMI under 35, and had osteoarthritis in the medial and patellofemoral compartments. Knee Society scores, Oxford questionnaires, radiographs, and functional tests were performed preoperatively, and at 1, 4, 12, and 24months postoperatively. Functional testing included gait analysis, stair climbing, lunging, and sit-to-stand analysis. Both groups achieved equivalent Knee Society scores (2year mean 93.6 vs. 92.6, P=0.43) and Oxford scores (2-year mean 43 vs. 41, P=0.35). Functional testing showed significant improvement. Two years postoperatively the BKA and TKA groups achieved equivalent results in clinical scores and functional testing.

Significantly worse isokinetic hamstring–quadriceps ratio in patellofemoral compared to condylar defects 4 years after autologous chondrocyte implantation

Detailed biomechanical analysis including isokinetic muscle strength measurements after autologous chondrocyte implantation (ACI) are still rare, but might be of crucial importance for long-term outcomes. The present prospective study was performed to evaluate whether defect location had any influence on clinical and biomechanical outcomes 4years after ACI. Forty-four patients with full-thickness cartilage defects ICRS grade III B and C underwent ACI and were assigned to two groups, the femoral condyle group or the patellofemoral joint group. Clinical scores were gathered preoperatively and 6, 12 and 48months after implantation using the International Knee Documentation Committee (IKDC) score and the International Cartilage Repair Society (ICRS) form. Isokinetic strength measurements were performed 48months postoperatively comparing healthy and operated knee joint of each patient. Clinical scores (ICRS, IKDC) showed continuous significant (p<0.05) improvement over the study period for both groups. Isokinetic muscle strength measurements showed significantly reduced maximum strength capacities for the operated knee joint compared to the healthy knee in both groups (p<0.05). Hamstring-quadriceps ratios of the operated extremity revealed a significant change in physiological muscle balancing (ratios >1.0) based on significantly impaired extensor muscle strength in the patellofemoral joint group. All patients showed significant strength deficits on the operated extremity 4years after ACI. Furthermore, the patellofemoral compartment in particular showed significantly worse hamstring-quadriceps ratios compared to condylar defects. Consequently, more efforts should be made to restore muscular strength especially of the quadriceps and the rehabilitation protocol should be adjusted accordingly. II.