LARS® band and tube for extensor mechanism reconstructions in proximal tibial modular endoprostheses after bone tumors.

UNLABELLED: Wide tumor resections around the proximal tibia (pT) are related to compromised function and high complication rates. This retrospective study aims to present the technique employed as well as functional and surgical outcomes of patients undergoing a Ligament Advanced Reinforcement System (LARS®) reconstruction of the knee extensor apparatus after tumor resection and modular endoprosthetic reconstruction of the proximal tibia. Twenty-five patients who received an artificial ligament after pT resection (11 men and 14 women; mean age, 29years; range 11 to 75years, with a minimum follow-up of 24months) were analyzed regarding the ISOLS failure mode classification. Twenty patients received LARS® during primary surgery, five patients during a revision of a pT modular endoprosthesis. LARS® was available as a band or a tube. The mean extension lag was nine degrees (range, 0 to 30°), the mean flexion was 103° (range, 60 to 130°). The mean extension lag and active flexion in primary implanted LARS were 7.8° and 101° versus secondarily implanted 45° and 115° (p<0.0001; p=0.15). Eleven out of 14 primary implanted LARS® band/tubes (71%) did well with extension lag (0 to 10°). LARS® usage as a band or as a tube showed similar results. The estimated five-year survival of LARS® was 92%. The median survival of LARS® implanted primarily was better than in the case of secondary implantation (p=0.006). Extensor mechanism reconstruction by LARS® band or tube shows excellent function and satisfactory implant survival after primary reconstruction of the extensor mechanism after proximal tibia resection. We experienced no LARS® rupture for only mechanical reasons. LEVEL OF EVIDENCE: Level IV retrospective study.

Sodium magnetic resonance imaging of ankle joint in cadaver specimens, volunteers, and patients after different cartilage repair techniques at 7 T: initial results.

OBJECTIVES: The goal of cartilage repair techniques such as microfracture (MFX) or matrix-associated autologous chondrocyte transplantation (MACT) is to produce repair tissue (RT) with sufficient glycosaminoglycan (GAG) content. Sodium magnetic resonance imaging (MRI) offers a direct and noninvasive evaluation of the GAG content in native cartilage and RT. In the femoral cartilage, this method was able to distinguish between RTs produced by MFX and MACT having different GAG contents. However, it needs to be clarified whether sodium MRI can be useful for evaluating RT in thin ankle cartilage. Thus, the aims of this 7-T study were (1) to validate our sodium MRI protocol in cadaver ankle samples, (2) to evaluate the sodium corrected signal intensities (cSI) in cartilage of volunteers, (3) and to compare sodium values in RT between patients after MFX and MACT treatment. MATERIALS AND METHODS: Five human cadaver ankle samples as well as ankles of 9 asymptomatic volunteers, 6 MFX patients and 6 MACT patients were measured in this 7-T study. Sodium values from the ankle samples were compared with histochemically evaluated GAG content. In the volunteers, sodium cSI values were calculated in the cartilages of ankle and subtalar joint. In the patients, sodium cSI in RT and reference cartilage were measured, morphological appearance of RT was evaluated using the magnetic resonance observation of cartilage repair tissue (MOCART) scoring system, and clinical outcome before and after surgery was assessed using the American Orthopaedic Foot and Ankle Society score and Modified Cincinnati Knee Scale. All regions of interest were defined on morphological images and subsequently transferred to the corresponding sodium images. Analysis of variance, t tests, and Pearson correlation coefficients were evaluated. RESULTS: In the patients, significantly lower sodium cSI values were found in RT than in reference cartilage for the MFX (P = 0.007) and MACT patients (P = 0.008). Sodium cSI and MOCART scores in RT did not differ between the MFX and MACT patients (P = 0.185). No significant difference in sodium cSI was found between reference cartilage of the volunteers and the patients (P = 0.355). The patients showed significantly higher American Orthopaedic Foot and Ankle Society and Modified Cincinnati scores after treatment than they did before treatment. In the volunteers, sodium cSI was significantly higher in the tibial cartilage than in the talar cartilage of ankle joint (P = 0.002) and in the talar cartilage than in the calcaneal cartilage of subtalar joint (P < 0.001). Data from the cadaver ankle samples showed a strong linear relationship between the sodium values and the histochemically determined GAG content (r = 0.800; P < 0.001; R = 0.639). CONCLUSIONS: This study demonstrates the feasibility of in vivo quantification of sodium cSI, which can be used for GAG content evaluation in thin cartilages of ankle and subtalar joints at 7 T. A strong correlation observed between the histochemically evaluated GAG content and the sodium values proved the sufficient sensitivity of sodium MRI to changes in the GAG content of cartilages in the ankle. Both MFX and MACT produced RT with lower sodium cSI and, thus, of lower quality compared with reference cartilage in the patients or in the volunteers. Our results suggest that MFX and MACT produce RT with similar GAG content and similar morphological appearance in patients with similar surgery outcome. Sodium MRI at 7 T allows a quantitative evaluation of RT quality in the ankle and may thus be useful in the noninvasive assessment of new cartilage repair procedures.

Treatment of Full-Thickness Chondral Defects With Hyalograft C in the Knee: Long-term Results.

BACKGROUND: Matrix-associated autologous chondrocyte transplantation (MACT) has become an established articular cartilage repair technique. It provides good short-term and midterm results; however, long-term results are lacking. PURPOSE: To prospectively assess the clinical outcome after MACT in the knee to report long-term results. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Fifty-three subjects (females/males, 22/31; mean age, 32 ± 12 years) were treated between 2000 and 2006 with a hyaluronan-based MACT product and were followed prospectively. The mean body mass index (BMI) was 24.5 ± 3.8 kg/m(2) and the mean defect size was 4.4 ± 1.9 cm(2). Fifty patients had single defects and 3 had multiple defects (41 medial femoral condyle, 6 lateral femoral condyle, 2 patella, 1 tibia). Two patients had 2 defects (medial femoral condyle [MFC]/lateral femoral condyle and tibial/MFC), and in 1 case, multiple defects on the MFC were treated. The patients were stratified into 23 "simple," 22 "complex," and 8 "salvage" cases. Instability or malalignment was treated before or at the time of graft implantation. For 6 patients with small defects (<2 cm(2)), microfracturing was used as first-line treatment before MACT. Clinical assessment was performed once a year with the subjective and objective International Knee Documentation Committee (IKDC) scores, Lysholm score, and a modified Cincinnati Knee Rating System. RESULTS: The mean follow-up time was 9.07 ± 2.9 years (range, 5-12 years). Treatment failure occurred in 12 of 53 cases (22.6%) an average of 2.99 ± 1.40 years after surgery. There was 1 failure (4.3%) among the simple cases, 4 failures (18.2%) in complex cases, and 7 failures (87.5%) in salvage cases. Statistically significant increases were observed in all scores at all time points compared with presurgery levels (P < .05). The subjective IKDC score improved from median 40.4 preoperatively to 74.7 at 10-year follow-up (n = 13 patients; P < .05). CONCLUSION: MACT is an excellent surgical therapy for full-thickness cartilage defects of the knee, with good long-term results for simple defects. However, it should not be used in salvage cases.

Repair tissue quality after arthroscopic autologous collagen-induced chondrogenesis (ACIC) assessed via T2* mapping.

OBJECTIVE: A novel single-stage approach using arthroscopic microdrilling and atelocollagen/fibrin-gel application is employed for cartilage repair of the knee. The purpose of our study was to investigate the morphological and biochemical MRI outcome after this technique. MATERIALS AND METHODS: A retrospective case series of ten patients (mean age 45 years) with symptomatic chondral defects in the knee who were treated arthroscopically with microdrilling and atelocollagen application was analyzed. All defects were ICRS grade III or IV and the sizes were 2-8 cm(2) intra-operatively. All patients underwent morphological MRI and T2-star mapping at 1.5 T at 1-year follow-up. The magnetic resonance observation of cartilage repair tissue (MOCART) score was assessed. T2* relaxation time values of repair tissue and a healthy native cartilage area was assessed by means of region of interest analysis on the T2* maps. RESULTS: The mean MOCART score at 1-year follow-up was 71.7 ± 21.0 ranging from 25 to 95. The mean T2* relaxation times were 30.6 ± 11.3 ms and 28.8 ± 6.8 ms for the repair tissue and surrounding native cartilage, respectively. The T2* ratio between the repair tissue and native cartilage was 105% ± 30%, indicating repair tissue properties similar to native cartilage. CONCLUSIONS: An arthroscopic single-stage procedure using microdrilling in combination with atelocollagen gel and fibrin-glue can provide satisfactory MRI results at 1-year follow-up, with good cartilage defect filling. The T2* values in the repair tissue achieved similar values compared to normal hyaline cartilage.

Cartilage repair of the knee with Hyalograft C:® magnetic resonance imaging assessment of the glycosaminoglycan content at midterm.

PURPOSE: The aim of this study was to assess the stability of the glycosaminoglycan (GAG) content in the long term after matrix-associated autologous chondrocyte transplantation (MACT) with Hyalograft C in the knee over a follow-up period of one year. METHODS: In this cross-sectional evaluation, 11 patients after MACT of the knee consented to delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) measurements. The mean post-operative interval before the first MR examination was 40.6 ± 22.0 months, and the second MR examination was carried out after another 12 months. The Lysholm score was assessed for clinical evaluation. Quantitative T1 measurements after intravenous negatively charged MR contrast agent administration were performed. Global post-contrast T1 of the reference cartilage and the repair tissue and a relative post-contrast T1 value were calculated. RESULTS: The Lysholm score improved significantly from 59.8 ± 12.9 at baseline to 86.1 ± 15.7 at the second visit (p < 0.01). The mean global T1 of the repair tissue (1st visit 581.3 ± 126.4 ms; 2nd visit 684.1 ± 169.9 ms; p = 0.104) and the mean relative T1 value showed stable results over one year (1st visit 0.81 ± 0.28; 2nd visit 0.76 ± 0.32; p = 0.4). CONCLUSIONS: The study demonstrated stable glycosaminoglycan content of the repair tissue after MACT at midterm.

Sodium MR imaging of Achilles tendinopathy at 7 T: preliminary results.

PURPOSE: To investigate the feasibility of sodium magnetic resonance (MR) imaging in the diagnosis of Achilles tendinopathy. MATERIALS AND METHODS: Institutional review board approval and written informed consent were obtained. Twenty healthy volunteers and eight patients with Achilles tendinopathy were examined by using a 7-T whole-body MR imager with a 15-channel sodium knee coil. The sodium signal-to-noise ratio (SNR) from each region, as well as from the whole Achilles tendon, was compared between patients and healthy control subjects. The changes in SNR were assessed with a two-tailed unpaired t test in three regions of the Achilles tendon: the insertion area, the middle portion, and the muscle-tendon junction. P values less than .05 were considered to indicate a statistically significant difference. To validate a relationship between the sodium SNR and the glycosaminoglycan content in tendon, five cadaver ankles were examined with MR imaging and immunohistologically. The Pearson correlation coefficient between sodium SNR and glycosaminoglycan content was calculated. RESULTS: Significant differences (P < .05) in the mean sodium SNR of healthy control subjects (mean SNR, 4.9 ± 2.1 [standard deviation]) and patients with chronic Achilles tendinopathy (mean SNR, 9.3 ± 2.3) were observed. Similar results were found at the insertion (mean SNR in control subjects, 6.7 ± 2.3; mean SNR in patients, 12.3 ± 4.5; P < .05) and the midportion (mean SNR in control subjects, 5.1 ± 1.9; mean SNR in patients, 9.4 ± 3.0; P < .05) of the Achilles tendon. At the muscle-tendon junction, the sodium SNR difference between control subjects and patients was small but still bellow the significance level (P = .0137). The increase in sodium SNR was observed in all regions independently of the location of morphologic findings. The Pearson correlation coefficient between sodium SNR and glycosaminoglycan content was 0.71. CONCLUSION: Sodium MR imaging may allow detection of the proteoglycan content increase in Achilles tendinopathy and thus identify the biochemical changes in the early stages of tendinopathy.

Delayed gadolinium-enhanced MRI of cartilage in the ankle at 3 T: feasibility and preliminary results after matrix-associated autologous chondrocyte implantation.

PURPOSE: To demonstrate the feasibility of delayed gadolinium-enhanced magnetic resonance imaging (MRI) of cartilage (dGEMRIC) in the ankle at 3 T and to obtain preliminary data on matrix associated autologous chondrocyte (MACI) repair tissue. MATERIALS AND METHODS: A 3D dual flip angle sequence was used with an eight-channel multipurpose coil at 3 T to obtain T1 maps both pre- and postintravenous contrast agent (Magnevist, 0.2 mM/kg). Postcontrast T1 over time was evaluated in three volunteers; a modified dGEMRIC protocol was then used to assess 10 cases after MACI in the ankle. RESULTS: Forty-five minutes were found sufficient for maximum T1 decrease. MACI cases had a precontrast mean T1 of 1050 +/- 148.4 msec in reference cartilage (RC) and 1080 +/- 165.6 msec in repair tissue (RT). Postcontrast T1 decreased to 590 +/- 134.0 msec in RC and 554 +/- 133.0 msec in RT. There was no significant difference between the delta relaxation rates in RT (9.44 x 10(-4) s(-1)) and RC (8.04 x 10(-4) s(-1), P = 0.487). The mean relative delta relaxation rate was 1.34 +/- 0.83. CONCLUSION: It is feasible to assess the thin cartilage layers of the ankle with dGEMRIC at 3 T; MACI can yield RT with properties similar to articular cartilage.

MRI monitoring of cartilage repair in the knee: a review.

Various treatment options for deep cartilage defects are presently available. The efficacy of bone marrow stimulation with microfracture, of mosaicplasty and of various autologous chondrocyte implantation (ACI) techniques has been subject to numerous studies recently. Magnetic resonance imaging (MRI) has gained a major role in the assessment of cartilage repair. The introduction of high-field MRI to clinical routine makes high resolution and three-dimensional imaging readily available. New quantitative MRI techniques that directly visualize the molecular structure of cartilage may further advance our understanding of cartilage repair. The clinical evaluation of cartilage repair tissue is a complex issue, and MR imaging will become increasingly important both in research and in clinical routine. This article reviews the clinical aspects of microfracture, mosaicplasty, and ACI and reports the recent technical advances that have improved MRI of cartilage. Morphological evaluation methods are recommended for each of the respective techniques. Finally, an overview of T2 mapping and delayed gadolinium-enhanced MR imaging of cartilage in cartilage repair is provided.

Cartilage T2 assessment at 3-T MR imaging: in vivo differentiation of normal hyaline cartilage from reparative tissue after two cartilage repair procedures--initial experience.

PURPOSE: To prospectively compare cartilage T2 values after microfracture therapy (MFX) and matrix-associated autologous chondrocyte transplantation (MACT) repair procedures. MATERIALS AND METHODS: The study had institutional review board approval by the ethics committee of the Medical University of Vienna; informed consent was obtained. Twenty patients who underwent MFX or MACT (10 in each group) were enrolled. For comparability, patients of each group were matched by mean age (MFX, 40.0 years +/- 15.4 [standard deviation]; MACT, 41.0 years +/- 8.9) and postoperative interval (MFX, 28.6 months +/- 5.2; MACT, 27.4 months +/- 13.1). Magnetic resonance (MR) imaging was performed with a 3-T MR imager, and T2 maps were calculated from a multiecho spin-echo measurement. Global, as well as zonal, quantitative T2 values were calculated within the cartilage repair area and within cartilage sites determined to be morphologically normal articular cartilage. Additionally, with consideration of the zonal organization, global regions of interest were subdivided into deep and superficial areas. Differences between cartilage sites and groups were calculated by using a three-way analysis of variance. RESULTS: Quantitative T2 assessment of normal native hyaline cartilage showed similar results for all patients and a significant trend of increasing T2 values from deep to superficial zones (P < .05). In cartilage repair areas after MFX, global mean T2 was significantly reduced (P < .05), whereas after MACT, mean T2 was not reduced (P > or = .05). For zonal variation, repair tissue after MFX showed no significant trend between different depths (P > or = .05), in contrast to repair tissue after MACT, in which a significant increase from deep to superficial zones (P < .05) could be observed. CONCLUSION: Quantitative T2 mapping seems to reflect differences in repair tissues formed after two surgical cartilage repair procedures. (c) RSNA, 2008.