Chondrocyte Culture Parameters for Matrix-Assisted Autologous Chondrocyte Implantation Affect Catabolism and Inflammation in a Rabbit Model.

Cartilage defects represent an increasing pathology among active individuals that affects the ability to contribute to sports and daily life. Cell therapy, such as autologous chondrocyte implantation (ACI), is a widespread option to treat larger cartilage defects still lacking standardization of in vitro cell culture parameters. We hypothesize that mRNA expression of cytokines and proteases before and after ACI is influenced by in vitro parameters: cell-passage, cell-density and membrane-holding time. Knee joint articular chondrocytes, harvested from rabbits (n = 60), were cultured/processed under varying conditions: after three different cell-passages (P1, P3, and P5), cells were seeded on 3D collagen matrices (approximately 25 mm³) at three different densities (2 × 105/matrix, 1 × 106/matrix, and 3 × 106/matrix) combined with two different membrane-holding times (5 h and two weeks) prior autologous transplantation. Those combinations resulted in 18 different in vivo experimental groups. Two defects/knee/animal were created in the trochlear groove (defect dimension: ∅ 4 mm × 2 mm). Four identical cell-seeded matrices (CSM) were assembled and grouped in two pairs: One pair giving pre-operative in vitro data (CSM-i), the other pair was implanted in vivo and harvested 12 weeks post-implantation (CSM-e). CSMs were analyzed for TNF-α, IL-1ß, MMP-1, and MMP-3 via qPCR. CSM-i showed higher expression of IL-1ß, MMP-1, and MMP-3 compared to CSM-e. TNF-α expression was higher in CSM-e. Linearity between CSM-i and CSM-e values was found, except for TNF-α. IL-1ß expression was higher in CSM-i at higher passage and longer membrane-holding time. IL-1ß expression decreased with prolonged membrane-holding time in CSM-e. For TNF-α, the reverse was true. Lower cell-passages and lower membrane-holding time resulted in stronger TNF-α expression. Prolonged membrane-holding time resulted in increased MMP levels among CSM-i and CSM-e. Cellular density was of no significant effect. We demonstrated cytokine and MMP expression levels to be directly influenced by in vitro culture settings in ACI. Linearity of expression-patterns between CSM-i and CSM-e may predict ACI regeneration outcome in vivo. Cytokine/protease interaction within the regenerate tissue could be guided via adjusting in vitro culture parameters, of which membrane-holding time resulted the most relevant one.

A matched-pair comparison of inlay and onlay trochlear designs for patellofemoral arthroplasty: no differences in clinical outcome but less progression of osteoarthritis with inlay designs.

PURPOSE: To compare clinical and radiographic results after isolated patellofemoral arthroplasty (PFA) using either a second-generation inlay or onlay trochlear design. The hypothesis was that an inlay design will produce better clinical results and less progression of tibiofemoral osteoarthritis (OA) compared to an onlay design. METHODS: Fifteen consecutive patients undergoing isolated PFA with an onlay design trochlear component (Journey™ PFJ, Smith & Nephew) were matched with 15 patients after isolated PFA with an inlay design trochlear component (HemiCAP® Wave, Arthrosurface). Matching criteria were age, gender, body mass index, and follow-up period. An independent observer evaluated patients prospectively, whereas data were compared retrospectively. Clinical outcome was assessed using WOMAC, Lysholm score, and pain VAS. Kellgren-Lawrence grading was used to assess progression of tibiofemoral OA. RESULTS: Conversion to total knee arthroplasty was necessary in one patient within each group, leaving 14 patients per group for final evaluation. The mean follow-up was 26 months in the inlay group and 25 months in the onlay group (n.s.). Both groups displayed significant improvements of all clinical scores (p < 0.05). No significant differences were found between the two groups with regard to the clinical outcome and reoperation rate. No significant progression of tibiofemoral OA was observed in the inlay group, whereas 53 % of the onlay group showed progression of medial and/or lateral tibiofemoral OA (p = 0.009). CONCLUSION: Isolated PFA using either a second-generation inlay or onlay trochlear component significantly improves functional outcome scores and pain. The theoretical advantages of an inlay design did not result in better clinical outcome scores; however, progression of tibiofemoral OA was significantly less common in patients with an inlay trochlear component. This implant design may therefore improve long-term results and survival rates after isolated PFA. LEVEL OF EVIDENCE: III.

Prospective evaluation of anatomic patellofemoral inlay resurfacing: clinical, radiographic, and sports-related results after 24 months.

PURPOSE: To prospectively evaluate the clinical, radiographic, and sports-related outcomes at 24 months after isolated and combined patellofemoral inlay resurfacing (PFIR). METHODS: Between 2009 and 2010, 29 consecutive patients with patellofemoral osteoarthritis (OA) were treated with the HemiCAP(®) Wave Patellofemoral Resurfacing System (Arthrosurface, Franklin, MA, USA). Based on preoperative findings, patients were divided into two groups: group I, isolated PFIR (n = 20); and group II, combined PFIR with concomitant procedures to address patellofemoral instability, patellofemoral malalignment, and tibiofemoral malalignment (n = 9). Patients were evaluated preoperatively and at 24 months postoperatively. Clinical outcomes included WOMAC, subjective IKDC, Pain VAS, Tegner activity score, and a self-designed sports questionnaire. Kellgren-Lawrence grading was used to assess progression of tibiofemoral OA. The Caton-Deschamps Index was used to assess differences in patellar height. RESULTS: Twenty-seven patients (93 %) were available for 24-month follow-up. Eighty-one per cent of the patients were either satisfied or very satisfied with the overall outcome. Significant improvements in the WOMAC, subjective IKDC, and Pain VAS were seen in the overall patient cohort and in both subgroups. The median Tegner score and sports frequency showed a significant increase in the overall patient cohort and in group II. The number of sports disciplines increased significantly in both subgroups. No significant progression of tibiofemoral OA or changes in patellar height were observed. CONCLUSION: Patellofemoral inlay resurfacing is an effective and safe procedure in patients with symptomatic patellofemoral OA. Significant improvements in functional scores and sports activity were found after both isolated and combined procedures. LEVEL OF EVIDENCE: Prospective case series, Level III.

Combined trochleoplasty and MPFL reconstruction for treatment of chronic patellofemoral instability: a prospective minimum 2-year follow-up study.

PURPOSE: Excessive trochlear dysplasia may be responsible for recurrent patellofemoral instability (PFI) due to a missing bony guidance for the patella in early flexion. Thus, an isolated medial patellofemoral ligament reconstruction (MPFLR) can be insufficient, since it mainly addresses instability close to extension and additionally can increase patellofemoral pressure leading to pain in flat or convex trochlear dysplasia. Therefore, in combination with a trochleoplasty, an anatomical trochlear groove is created, resulting in patellofemoral stability also in flexion, while patellofemoral pressure is normalized. In this prospective study, we evaluated the outcome of open trochleoplasty in combination with MPFLR with a minimum follow-up of 2 years for treatment of excessive PFI. METHODS: In between 2007 and 2009, 18 knees of 17 consecutive patients (mean age of 22.2 ± 4.9 years) with trochlear dysplasia type B, C or D according to Dejour et al. and positive apprehension from 0 to 60° of flexion were included. Tegner, Kujala and IKDC scores, apprehension and pain, trochlear dysplasia, sulcus angle, tibial tuberosity trochlear groove, patellar tilt and shift, Caton-Deschamps index as well as patellofemoral arthrosis according to the classification of Iwano et al. were assessed pre- and postoperatively. RESULTS: At a mean of 30.5 ± 5.9 months, all but one patient were subjectively satisfied with the outcome of the procedure, all showing absence of positive apprehension or redislocation. Significant (p < 0.001) reduction in pain (5.6 to 2.5 ± 2.8 points, VAS) and increase in Tegner (2, range 0-4 points to 6, range 3-8 points), Kujala (51.1 to 87.9 ± 20.0 points) and IKDC (49.5 to 80.2 ± 21.0%) scores could be achieved. Radiologically significant (p < 0.02) improvement of patellofemoral positional parameters leading to more normal anatomy was recorded, while short-term arthrosis was absent. CONCLUSIONS: Combined treatment for trochleoplasty with MPFLR serves as a successful therapy for chronic PFI. This combinatory treatment concept is a reliable option not only as salvage therapy but also as primary procedure regarding treatment for excessive PFI. LEVEL OF EVIDENCE: Prospective case series, Level IV.

Prospective clinical and radiological two-year results after patellofemoral arthroplasty using an implant with an asymmetric trochlea design.

PURPOSE: The purpose was to prospectively evaluate the two-year results after implantation of the Journey PFJ(®) (Smith & Nephew, Andover, MA). The authors hypothesized that patellofemoral arthroplasty would result in improved outcomes after 24 months in patients treated with an isolated procedure as well as in patients demonstrating concomitant patellofemoral instability (PFI), which were treated with a combined surgical procedure. METHODS: Patients were included between 02/2006 and 08/2008. According to the history and clinical findings, patients were grouped into group I with no history or clinical signs of PFI, and patients with concomitant PFI were assorted to group II. Patients were then treated with an isolated (group I) or a combined (group II) surgical procedure to additionally treat the PFI. Visual analogue scale (VAS), Lysholm score and WOMAC score were recorded preoperatively, 6, 12 and 24 months postoperatively. Patellar height was evaluated according to the index of Caton-Deschamps (CDI), and osteoarthritic changes were evaluated according to Kellgren and Lawrence. RESULTS: A total of 25 patients were enrolled, of them three discontinued interventions and were excluded from final analysis. An isolated implantation of the Journey PFJ(®) was performed in 14 patients (group I) and a combined procedure in 8 (group II). Daily pain and clinical scores significantly improved at 6, 12 and 24 months compared to preoperative values (P < 0.05). Significant decrease (P = 0.02) of mean CDI could be noticed. Significant increase in tibiofemoral OA within the medial but not in the lateral tibiofemoral joint was assessed (P = 0.011; n.s.). CONCLUSIONS: Patellofemoral arthroplasty using the Journey(®) PFJ for treatment of significant patellofemoral OA demonstrated improved clinical scores at the 2-year follow-up in both groups. Comparing the primary OA (I) and OA + instability (II) groups, patients with patellofemoral OA treated with a combined procedure for concomitant stabilization of patellofemoral instability may benefit more from such a combined procedure, than patients treated with an isolated procedure for treatment of isolated patellofemoral OA. LEVEL OF EVIDENCE: Prospective case series, Level III.

The arthroscopic deepening trochleoplasty.

Since a dysplastic trochlea has been identified as the main pathomorphology in recurrent patellofemoral instability, trochleoplasty became a surgical solution in some of these cases. However, in comparison to other surgical procedures stabilizing the patellofemoral joint, trochleoplasty is a major operation with an arthrotomy, and associated typical risks of open surgery such as arthrofibrosis. Therefore, we developed a technique to perform an arthroscopic deepening trochleoplasty via suprapatellar portals using shaver burrs. Comparable to the open procedure, a cartilage flake is released and a new bony trochlea is created according to the normal anatomy. Then, the cartilage flake is re-fixated using Vicryl tapes and anchors. This method seems to be an obvious advantage in patellofemoral surgery, since an arthrotomy can be avoided, and postoperative pain as well as soft tissue healing time can be reduced.

Anatomical double-bundle MPFL reconstruction with an aperture fixation.

Since biomechanical studies have shown that the medial patellofemoral ligament (MPFL) is the main restraint against lateral patella displacement, reconstruction of the MPFL has become an accepted method of restoring patellofemoral stability and numerous techniques were described. Due to biomechanical examinations and clinical results, an anatomical double-bundle reconstruction of the "sail-like" MPFL is a reasonable method for achieving stability during complete extension and lower flexion degree. This method also serves to avoid rotation of the patella, providing immediate stability throughout the normal range of motion. However, until today, an aperture fixation technique at the patellar insertion with two bundles has not been described previously. This technique can provide an immediate stability to allow an early rehabilitation with full range of motion.

Comparison of native axial radiographs with axial MR imaging for determination of the trochlear morphology in patients with trochlear dysplasia.

INTRODUCTION: A dysplastic trochlea. may be missed on conventional roentgenography due to superimposition effects of the distal femoral groove. METHODS: Measurements of (1) the sulcus angle, (2) the lateral trochlear slope angle and (3) the lateral to medial trochlear ratio were compared between plain axial radiographs and axial magnetic resonance images (MRI) in 24 patients suffering from clinical patellofemoral instability. Trochlear dysplasia was classified into type A through D on MR images. RESULTS: Measurements for (1) were significantly different among all dysplasia types. It was 135.6 degrees +/- 19.8 degrees on X-ray while it was above 180 degrees on MRI within dysplasia type D patients. Measurements for (2) were different among all dysplasia types, reaching statistical significance in type B dysplasia patients. Differences between radiographs and MRI for (3) were not significant, while only on MRI the ratio increased with increasing degree of dysplasia. CONCLUSION: The investigation illustrates that plain axial radiographs do not represent the natural bony trochlear morphology and may mislead further clinical management.

Fibrosis and adventitious bursae in plantar fat pad of forefoot: MR imaging findings in asymptomatic volunteers and MR imaging-histologic comparison.

PURPOSE: To retrospectively evaluate plantar fat pad (PFP) signal intensity alterations in magnetic resonance (MR) imaging studies of asymptomatic volunteers and to compare PFP alterations with histopathologic findings in cadavers and patients. MATERIALS AND METHODS: After appropriate institutional review board approval and any required informed consent were obtained, MR imaging studies of 70 asymptomatic volunteers (35 women, 35 men; mean age, 45 years; range, 21-69 years) obtained for another investigation were retrospectively analyzed by two musculoskeletal radiologists in consensus. The location, signal intensity, margin, extent, and size of PFP alterations were determined. MR imaging-histopathologic comparison was performed in six cadaveric feet and six feet of symptomatic patients (one woman, five men; mean age, 43 years; range, 31-60 years). For volunteers, the relationship between PFP alterations and Morton neuroma, age, and sex was analyzed by using the Fisher exact test, Spearman rank correlation, and the Wilcoxon rank sum test, respectively. Bonferroni correction was applied, and P < .01 was considered to indicate a significant difference. RESULTS: Fifty-nine (84%) volunteers had PFP signal intensity alterations. Forty-nine (70%), six (9%), one (1%), four (6%), and 43 (61%) volunteers had alterations beneath the first, second, third, fourth, and fifth metatarsal heads, respectively. Ninety-four (91%) of 103 signal intensity alterations were in the form of hypointensity on T2-weighted images. Blurred margins were present in 90 (87%) alterations. Ninety percent of all PFP alterations in asymptomatic volunteers were 14 mm or smaller. The relationship between PFP alterations and Morton neuroma, age, and sex was not statistically significant. In cadaveric forefeet, PFP alterations corresponded histopathologically to a variable amount of fibrosis. In nine PFP alterations, development of fluid-containing spaces resembling bursae was present. Among the six patients with PFP alterations, histopathologic examination revealed fibrosis and adventitious bursae in two, fibrosis with inflammation in three, and a soft-tissue chondroma in one. CONCLUSION: PFP signal intensity alterations are commonly seen in asymptomatic volunteers under the first and fifth metatarsal heads. At histologic examination, PFP signal intensity alterations correspond most commonly to fibrosis and adventitious bursae.

Radiographic landmarks for femoral tunnel placement in medial patellofemoral ligament reconstruction.

BACKGROUND: Reconstruction of the medial patellofemoral ligament has recently become popular for restoring patellofemoral stability. Femoral insertion site anatomy of the medial patellofemoral ligament has been described. This anatomical insertion has been inferred to be the isometric point in medial patellofemoral ligament reconstruction, but data about radiographic landmarks for a postoperative or intraoperative control are missing. PURPOSE: To determine the radiographic landmarks for control of postoperative and intraoperative femoral medial patellofemoral ligament insertion. STUDY DESIGN: Descriptive laboratory study. METHODS: Eight fresh-frozen human knees were dissected, and the medial patellofemoral ligament was exposed. After identification of the femoral medial patellofemoral ligament insertion site, the insertion center was marked with a lead ball of 2-mm diameter. Straight lateral radiographs were taken, and posterior-anterior as well as proximal-distal position were evaluated. RESULTS: Six of 8 insertion points were anterior to a line representing an extension of the posterior cortex, 1 point was touching this line, and 1 point was posterior to it. All points were situated distal to the posterior origin of the medial femoral condyle and proximal to the most posterior point of the Blumensaat line. CONCLUSION: A reproducible anatomical and radiographic point, 1 mm anterior to the posterior cortex extension line, 2.5 mm distal to the posterior origin of the medial femoral condyle, and proximal to the level of the posterior point of the Blumensaat line on a lateral radiograph with both posterior condyles projected in the same plane, shows the mean femoral medial patellofemoral ligament center. CLINICAL RELEVANCE: This radiographic point may be useful both intraoperatively and postoperatively.

Management of posterior cruciate ligament reconstruction after previous isolated anterior cruciate ligament reconstruction.

PURPOSE: The aim of our study was to analyze 20 patients who underwent secondary posterior cruciate ligament (PCL) reconstruction after previous isolated anterior cruciate ligament (ACL) reconstruction had been performed. Our analysis sought to assess ACL graft preservation or failure in these patients. A secondary aim of our study was to identify a testing protocol to be used before any surgery that would help diagnose PCL deficiency and avoid unneeded ACL reconstruction. METHODS: A total of 180 PCL reconstructions were prospectively documented, and 20 patients (11%) were identified who underwent previous isolated ACL reconstruction. Cases were analyzed to determine the quantity of ACL graft failures that had occurred and the need for ACL graft removal due to a fixed posterior subluxation. Patient charts were thoroughly reviewed, so investigators could identify the number of patients with incorrect diagnosis (PCL involvement was overlooked or an intact ACL was replaced) and the number with incorrect management (isolated ACL reconstruction was performed even though PCL involvement was recognized). RESULTS: A fixed posterior subluxation was present in 4 cases; this necessitated subsequent ACL graft resection in 2 patients to release subluxation prior to PCL reconstruction. In all, 7 ACL grafts failed because of overlooked posterolateral instability. In only 11 of 20 cases, the initial ACL graft could be preserved. ACL reconstruction was performed because of incorrect diagnosis in 16 patients and incorrect management in 4. CONCLUSIONS: A considerably high number of overlooked or underestimated PCL injuries led to isolated ACL reconstruction, which indicates that diagnostic difficulties still occur among orthopaedic surgeons who are not highly specialized. Beside persistent posterior laxity, a failed ACL graft was the main reason for a second operation, which required bicruciate ligament reconstruction. To avoid incorrect management and incorrect diagnosis, leading to isolated ACL reconstruction in PCL deficiency, we recommend that stress radiography be performed to detect eventual posterior instability. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Arthroscopic medial retinacular repair after patellar dislocation with and without underlying trochlear dysplasia: a preliminary report.

PURPOSE: This study was undertaken to evaluate the influence of underlying trochlear dysplasia (TD) on clinical outcomes of arthroscopic medial retinacular repair. METHODS: Between January 2000 and October 2004, a total of 91 patients underwent arthroscopic medial retinacular repair. Inclusion criteria for this study included an arthroscopic medial retinacular repair, a follow-up time of 12 months, and trochlear grading based on axial computed tomography (CT) scans (n = 48). TD, if present, was graded as types A through D, and patients were separated into group I (no or low-grade type A TD) and group II (types B through D TD). Redislocation was recorded, and Tegner, Lysholm, and International Knee Documentation Committee (IKDC) scores were determined. RESULTS: No or grade A TD was detected in 26 knees (group I), and TD of grade B or C was found in 22 knees (group II). Type D TD was not observed. At a follow-up time of 12 months, 4 redislocations had been noted, all belonging to group II. Neither the Tegner nor the Lysholm score reached preinjury levels, but in a comparison with preoperative status, we could find a significant increase in all scores in both groups. Group I reached a significantly better postoperative outcome than was attained by group II. CONCLUSIONS: Arthroscopic repair of the medial retinaculum is an effective technique by which patellofemoral instability can be addressed when normal or nearly normal trochlear geometry is present. In patients with underlying TD, patellofemoral stability cannot be completely restored, and clinical results are less successful. Precise preoperative radiologic determination of trochlear geometry may help the clinician to predict short-term outcomes in patients with patellofemoral instability. LEVEL OF EVIDENCE: Level III, retrospective comparative therapeutic study.

The patella morphology in trochlear dysplasia--a comparative MRI study.

BACKGROUND: Trochlear dysplasia is suspected to have a genetic basis and causes recurrent patellar instability due to insufficient anatomical geometry. Numerous studies about trochlear morphology and the optimal surgical treatment have been carried out, but no attention has been paid to the corresponding patellar morphology. PURPOSE: The aim of this study was the evaluation of the patellar morphology in normal and trochlear dysplastic knees. STUDY DESIGN: Biometric analysis. METHODS: Twenty two patellae with underlying trochlear dysplasia (study group--SG) were compared with 22 matched knees with normal trochlear shape (control group--CG) on transverse and sagittal MRI slices. We compared transverse diameter, cartilaginous thickness, Wiberg-index and -angle, length and radius of lateral and medial facet, patellar shape and angle, retropatellar length, and type of trochlear dysplasia. For statistical analysis we used the Wilcoxon signed ranks test. RESULTS: The transverse and sagittal diameter, mean length of medial patellar facet, and mean cartilaginous and subchondral Wiberg-index showed statistical differences between the two groups. CONCLUSIONS: Although the insufficient trochlear depth and decreased lateral trochlear slope are responsible for patellofemoral instability, the patella shows morphological changes in trochlear dysplastic knees. Its overall size and the medial facet are smaller. Although the femoral sulcus angle is larger, the Wiberg-angle and -index are equal to the control group. This may indicate that the patellar morphology may not be a result of missing medial patellofemoral pressure in trochlear dysplastic knees, but a decreased medial patellofemoral traction. This seems to be caused by hypotrophic medial patellofemoral restraints in combination with an increased lateral patellar tilt, both resulting in a decreased tension onto the medial patella facet. Whether there is a genetic component to the patellar morphology remains open.

Biomechanical evaluation of a novel dynamic posterior cruciate ligament brace.

BACKGROUND: Use of a rigid brace or cast immobilization is recommended in conservative treatment or postoperative rehabilitation after a posterior cruciate ligament injury. To prevent the loss of knee joint function and muscle activity often associated with this, a flexible knee brace has been developed that allows an adjustable anteriorly directed force to be applied to the calf in order to prevent posterior tibial translation. The purpose of this biomechanical study was to evaluate the impact of this novel dynamic brace on posterior tibial translation after posterior cruciate ligament injury and reconstruction. METHODS: A Telos stress device was used to provoke posterior tibial translation in seven human lower limb specimens, and stress radiographs were taken at 90° of knee flexion. Posterior tibial translation was measured in the native knees with an intact posterior cruciate ligament; after arthroscopic posterior cruciate ligament dissection with and without a brace; and after posterior cruciate ligament reconstruction with and without a brace. The force applied with the brace was measured using a pressure sensor. FINDINGS: Posterior tibial translation was significantly reduced (P=0.032) after application of the brace with an anteriorly directed force of 50N to the knees with the dissected posterior cruciate ligament. The brace also significantly reduced posterior tibial translation after posterior cruciate ligament reconstruction in comparison with reconstructed knees without a brace (P=0.005). INTERPRETATION: Posterior tibial translation was reduced to physiological values using this dynamic brace system that allows an anteriorly directed force to be applied to the calf.

Isolated and combined medial patellofemoral ligament reconstruction in revision surgery for patellofemoral instability: a prospective study.

BACKGROUND: Persistent pain and redislocations after surgical treatment of patellofemoral instability are described in up to 40% of patients. However, prospective outcome data about revision surgery are missing. PURPOSE: To evaluate the clinical outcome after revision medial patellofemoral ligament (MPFL) reconstruction using isolated and combined procedures, with a follow-up of 24 months. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Study participants were 42 patients (median age, 22 years; range, 13-46 years) who underwent revision surgery between January 2007 and December 2009 because of persistent patellofemoral instability after a mean of 1.8 previous failed surgical interventions (lateral release, medial imbrication/vastus medialis obliquus distalization, medialization of the tuberosity). An isolated MPFL reconstruction was performed in 15 cases, while a combination procedure was performed in 27 cases. The clinical results were evaluated preoperatively and 24 months postoperatively using the International Knee Documentation Committee (IKDC), Kujala, and Tegner scores as well as a subjective questionnaire. Patellar shift, tilt, and height, as well as level of degeneration, were defined preoperatively and at the latest follow-up on plain radiographs and magnetic resonance imaging. RESULTS: At 24-month follow-up, 87% of the patients were satisfied or very satisfied with the treatment. No apprehension or redislocation was reported at follow-up, and there was a significant decrease in pain during daily activities. There were significant improvements (P < .001) in IKDC (from 50 to 80), Kujala (from 51 to 85), and Tegner scores (from 2.4 to 4.9). Patellar shift, tilt, and height decreased significantly (P < .05) to anatomic values, and there was no aggravation to the level of pre-existing degeneration. No significant difference was noticed between the isolated and combined procedures. CONCLUSION: As patellofemoral instability is a multifactorial problem, revision surgery should be indicated only after a comprehensive examination. The results of this study show that MPFL reconstruction, alone or in combination, seems to be an effective treatment for recurrent patellar dislocations after a failed previous surgery, leading to significant increases in stability and functionality as well as a reduction in pain.

The dependence of autologous chondrocyte transplantation on varying cellular passage, yield and culture duration.

Matrix-assisted chondrocyte transplantation (m-ACI) still lacks any standardization in its execution in terms of cell passage (P), cell yield (C) and in vitro membrane-holding time (T). It was the goal of this study to analyze the effect of shifting cell culture parameters (P, C, T) on the in vitro as well as in vivo effort of a regulated animal m-ACI. Autologous rabbit knee articular chondrocytes were seeded within bilayer collagen I/III 3-D matrices in variation of P, C and T. Each time, 2 PCT-identical by 2 PCT-identical cell-matrix-constructs (CMC)/animal were created. Simultaneously 2 (PCT-distinct) were re-implanted (CMC-e) autologous into artificial trochlear pristine chondral defects in vivo to remain for 12 weeks while the remaining 2 were harvested (CMC-i) for immediate in vitro analysis at the time of transplantation of their identical twins. mRNA of both, CMC-e regenerates and CMC-i membranes, was analyzed for Collagen-1,-2,-10, COMP, Aggrecan, Sox9 expression by use of a mixed linear model, multiple regression analysis. Generally, CMC-i values were higher than CMC-e values for differentiation targets; the opposite was true for dedifferentiation targets. Regarding individual gene expression, in vivo regenerate cell-matrix properties were significantly dependent on initial cell-matrix in vitro values as a sign of linearity. The parameter membrane-holding time (T) had strongest effects on the resulting mRNA expression with slightly less impact of the parameter passage (P), whereas cell yield (C) had clearly less effects. Noting differences between in vitro and in vivo data, in general, optimal expression patterns concerning chondrogenic differentiation were achieved by few passages, medium cellular yield, short membrane-holding time. Clinical m-ACI may benefit from optimal orchestration of the cell culture parameters passage, yield and time.

[Double-bundle technique--anatomic reconstruction of the posterior cruciate ligament]. / Die Zwei-Bündel-Technik--eine anatomische Rekonstruktion des hinteren Kreuzbandes.

OBJECTIVE: To improve the posterior translational stability of the knee joint by anatomic reconstruction of the posterior cruciate ligament in double-bundle technique. The functional bundles are reconstructed by native grafts from semitendinosus and gracilis muscles. The grafts are fixed with bioabsorbable screws in aperture technique. INDICATIONS: Symptomatic tears of the posterior cruciate ligament (classification by Harner) or chronic posterior or posterolateral instabilities; combined instabilities may need extended operative procedure. CONTRAINDICATIONS: Open growth plate. Fixed posterior drawer position. Nonjustifiable operative risks. Decline of the operation by the patient. Noncompliance. SURGICAL TECHNIQUE: Graft harvest of the semitendinosus and gracilis tendons via a 3-cm skin incision parallel to pes anserinus. Preparation, multilooping and arming of the tendons with sutures, arthroscopy, resection of the stump of the posterior cruciate ligament and clearing of its origin and insertion (using an additional posteromedial portal). Tunnel placement by means of aiming devices in the following order: femoral anterolateral, femoral posteromedial, and tibial (by accurate protection of the popliteal structures). Passing in the bundles, fixation in biomechanical functional positions in the following order: posteromedial bundle femoral (90° flexion), tibial (extension 0°), and anterolateral bundle femoral (90° flexion) with bioabsorbable interference screws. POSTOPERATIVE MANAGEMENT: 6 weeks PTS orthesis for 24 h/7 days with partial weight bearing (20 kg). Increased weight bearing from 7th postoperative week with PCL support orthesis during daytime and PTS orthesis during nighttime for further 6 weeks. Return to sports after 6 months at the earliest, no contact sports and competition for at least 9 months. RESULTS: First studies show positive results after reconstruction of the posterior cruciate ligament in double-bundle technique. A comparison with the single-bundle technique with a sufficient number of cases has not been published yet.

Regulation of the patellofemoral contact area: an essential mechanism in patellofemoral joint mechanics?

Although the relationship between contact area and pressure under physiological loading has been described in the feline patellofemoral joint, this interaction has only been examined under simplified loading conditions and/or considerably lower forces than those occurring during demanding activities in humans. We hypothesized that patellofemoral contact area increases non-linearly under an increasing joint reaction force to regulate patellofemoral pressure. Eight human cadaveric knees were ramp loaded with muscle forces representative of the stance phase of stair climbing at 30° knee flexion. Continuous pressure data were acquired with a pressure sensitive film that was positioned within the patellofemoral joint. While pressure was linearly dependent upon the resulting joint reaction force, contact area asymptotically approached a maximum value and reached 95% of this maximum at patellofemoral forces of 349-723N (95% CI). Our findings indicate that the regulatory influence of increasing contact area to protect against high patellofemoral pressure is exhausted at relatively low loads.

Stair climbing results in more challenging patellofemoral contact mechanics and kinematics than walking at early knee flexion under physiological-like quadriceps loading.

The mechanical environment during stair climbing has been associated with patellofemoral pain, but the contribution of loading to this condition is not clearly understood. It was hypothesized that the loading conditions during stair climbing induce higher patellofemoral pressures, a more lateral force distribution on the trochlea and a more lateral shift and tilt of the patella compared to walking at early knee flexion. Optical markers for kinematic measurements were attached to eight cadaveric knees, which were loaded with muscle forces at instances of walking and stair climbing cycles at 12 degrees and 30 degrees knee flexion. Contact mechanics were determined using a pressure sensitive film. At 12 degrees knee flexion, stair climbing loads resulted in higher peak pressure (p=0.012) than walking, more lateral force distribution (p=0.012) and more lateral tilt (p=0.012), whilst mean pressure (p=0.069) and contact area (p=0.123) were not significantly different. At 30 degrees knee flexion, although stair climbing compared to walking loads resulted in significantly higher patellofemoral mean (p=0.012) and peak pressures (p=0.012), contact area (p=0.025), as well as tilt (p=0.017), the medial-lateral force distribution (p=0.674) was not significantly different. No significant differences were observed in patellar shift between walking and stair climbing at either 12 degrees (p=0.093) or 30 degrees (p=0.575) knee flexion. Stair climbing thus leads to more challenging patellofemoral contact mechanics and kinematics than level walking at early knee flexion. The increase in patellofemoral pressure, lateral force distribution and lateral tilt during stair climbing provides a possible biomechanical explanation for the patellofemoral pain frequently experienced during this activity.