Prediction of loss of correction after hemiepiphysiodesis for the alignment of lower limb angular deformities.

ABSTRACT: Guided growth by temporary hemiepiphysiodesis (HEPD) is established for the alignment of lower limb angular deformities. This retrospective cohort study was designed to assess the effect of HEPD in idiopathic coronal plane deformities around the knee and on the frontal knee joint line orientation, and to test the frontal knee joint line as predictive means for recurrence.Fourty-four patients (78 deformities: valgus n = 64, varus n = 14) were enrolled in the retrospective observational study. Mechanical axis deviation, mechanical lateral distal femoral angle, and mechanical medial proximal tibial angle were assessed prior to surgery and during follow-up. The facultative frontal knee joint line angle (FKJLA) was used as predictive tool. Cases of remaining growth potential (n = 45/78) after implant removal were followed to assess rebound deformity.Pre-operative angles of the mechanical axis were corrected average 9.0 months after HEPD. Pre-operative assessment of the frontal knee joint line revealed a mean of 3.9° in valgus, and -1.0° in varus deformities. At time of complete deformity correction, mean FKJLA was -0.2° in valgus, and -0.8° in varus deformities. Mean shift of FKJLA was significantly higher after singleHEPD compared to combiHEPD (P < .001). Patients having an unphysiological FKJLA (>/<0°-3°) after correction of mechanical axis had a significantly higher risk of rebound deformity (P = .01). Regression analysis showed a 60.5% higher risk of rebound deformity per each degree deviating from the FKJLA physiological range. Age, gender, or body mass index had no impact.Temporary HEPD offers great potential for the correction of the mechanical axis and the frontal knee joint line. An unphysiological change of the frontal knee joint line is associated with a high risk of recurrent angular deformities. CombiHEPD instead of singleHEPD seems to be safer to prevent detrimental frontal knee joint line shift.Level of Evidence: Retrospective comparative therapeutic study, Level III.

Pathological fracture of the femoral neck following septic coxitis and chronic osteomyelitis: a potential complication of Lemierre's syndrome.

We portray the case of a 16-year-old girl who was initially admitted to the paediatric emergency department with non-specific symptoms of a severe cold and was first treated symptomatically on an ambulatory basis. Within 6 days she developed the full clinical picture of Lemierre's syndrome with the extraordinary manifestation of involvement of her right hip. Despite an interdisciplinary coordinated treatment as well as surgical therapy, a full-blown sepsis evolved within a short time period and resulted in almost 2 months of intensive care. While the primary focus could be successfully controlled, a progressive avascular necrosis of the right proximal femur developed on the basis of a chronic osteomyelitis. This finally led to a pathological fracture of the femoral neck. After excluding the possibility of an enduring bacterial infection, the fracture was treated with a total hip replacement.

Quality-Adjusted Life Years Gained by Hip and Knee Replacement Surgery and Its Aftercare.

OBJECTIVES: To determine the lifetime quality-adjusted life years (QALYs) gained by total joint arthroplasty (TJA), and assess the QALYs attributed to specific postoperative rehabilitation interventions. DESIGN: Secondary analysis of 2 multicenter, randomized controlled trials (RCTs) with 3-, 6-, 12-, and 24-month follow-up. SETTING: Two university hospitals, 2 municipal hospitals, and 1 rural hospital. PARTICIPANTS: Patients (N=827) who underwent total hip arthroplasty (THA) or total knee arthroplasty (TKA). INTERVENTIONS: RCT A: 465 patients were randomly assigned to receive aquatic therapy (pool exercises aimed at training of proprioception, coordination, and strengthening) 6 versus 14 days after THA or TKA. RCT B: 362 patients were randomly assigned to either perform or not perform ergometer cycling beginning 2 weeks after THA or TKA. MAIN OUTCOME MEASURE: QALYs, based on the Short Form-6 Dimensions utility, measured at baseline and 3, 6, 12, and 24 months' follow-up. RESULTS: After hip arthroplasty, the lifetime QALYs increased by 2.35 years in the nonergometer group, and by 2.30 years in the early aquatic therapy group. However, after knee arthroplasty, the lifetime QALYs increased by 1.81 years in the nonergometer group, and by 1.60 years in the early aquatic therapy group. By ergometer cycling, .55 additional QALYs could be gained after hip and .10 additional QALYs after knee arthroplasty, while the additional QALYs attributed to the timing of aquatic therapy were .12 years after hip and .01 years after knee arthroplasty. CONCLUSIONS: This analysis provides a sound estimate for the determination of the lifetime QALYs gained by THA and TKA. In addition, this analysis demonstrates that specific postoperative rehabilitation can result in an additional mean QALY gain of .55 years, which represents one fourth of the effect of surgery. Even if this is interpreted as a small effect at an individual level, it is important when extrapolated to all patients undergoing TJA. At a national level, these improvements appear to have a similar magnitude of QALY gain when compared with published data regarding medications to lower blood pressure in all persons with arterial hypertension.

Successful treatment of extensively drug-resistant Pseudomonas aeruginosa osteomyelitis using a colistin- and tobramycin-impregnated PMMA spacer.

Discovered in 1949, the antibiotic colistin was initially used for therapeutic purposes. Parenteral use of colistin was gradually abandoned because of its side-effect profile, especially its nephrotoxicity and neurotoxicity. Despite the risk of these potentially serious adverse effects, increasing resistance of Gram-negative bacteria has led to a renaissance of intravenous use of colistin in the last few years. Local administration of colistin is an alternative method to minimise the risk of systemic toxicity. We present a case of extensively drug-resistant Pseudomonas aeruginosa osteomyelitis treated successfully with high-dose colistin- and tobramycin-impregnated bone cement as a drug delivery vehicle. For the first time, local colistin concentrations in drainage and synovial fluid were quantified in order to determine the optimal dose and to minimise serious side effects. Insertion of a bone cement spacer loaded with a high dose of tobramycin and colistin resulted in local colistin levels at the infection site that exceeded the minimum inhibitory concentration (MIC) of colistin against the isolated P. aeruginosa five-fold on Day 4. Thus, the treatment may be expected to exert a prolonged effect. Whereas systemic administration of colistin alone was not sufficient to treat the infection, combined local and parenteral therapy led to eradication of P. aeruginosa in this patient. Plasma colistin levels remained in the therapeutic range, which confirms the systemic safety of the method.

Multicenter randomized controlled trial comparing early versus late aquatic therapy after total hip or knee arthroplasty.

OBJECTIVE: To evaluate if the timing of aquatic therapy influences clinical outcomes after total knee arthroplasty (TKA) or total hip arthroplasty (THA). DESIGN: Multicenter randomized controlled trial with 3-, 6-, 12-, and 24-month follow-up. SETTING: Two university hospitals, 1 municipal hospital, and 1 rural hospital. PARTICIPANTS: Patients (N=465) undergoing primary THA (n=280) or TKA (n=185): 156 men, 309 women. INTERVENTION: Patients were randomly assigned to receive aquatic therapy (pool exercises aimed at training of proprioception, coordination, and strengthening) after 6 versus 14 days after THA or TKA. MAIN OUTCOME MEASURES: Primary outcome was self-reported physical function as measured by the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at 3-, 6-, 12-, and 24-months postoperatively. Results were compared with published thresholds for minimal clinically important improvements. Secondary outcomes included the Medical Outcomes Study 36-Item Short-Form Health Survey, Lequesne-Hip/Knee-Score, WOMAC-pain and stiffness scores, and patient satisfaction. RESULTS: Baseline characteristics of the 2 groups were similar. Analyzing the total study population did not result in statistically significant differences at all follow-ups. However, when performing subanalysis for THA and TKA, opposite effects of early aquatic therapy were seen between TKA and THA. After TKA all WOMAC subscales were superior in the early aquatic therapy group, with effect sizes of WOMAC physical function ranging from .22 to .39. After THA, however, all outcomes were superior in the late aquatic therapy group, with WOMAC effect sizes ranging from .01 to .19. However, the differences between treatment groups of these subanalyses were not statistically significant. CONCLUSIONS: Early start of aquatic therapy had contrary effects after TKA when compared with THA and it influenced clinical outcomes after TKA. Although the treatment differences did not achieve statistically significance, the effect size for early aquatic therapy after TKA had the same magnitude as the effect size of nonsteroidal anti-inflammatory drugs in the treatment of osteoarthritis of the knee. However, the results of this study do not support the use of early aquatic therapy after THA. The timing of physiotherapeutic interventions has to be clearly defined when conducting studies to evaluate the effect of physiotherapeutic interventions after TKA and THA.

Thirty-year follow-up after Wagner resurfacing hip arthroplasty: Case report.

Wagner hip arthroplasty has been used as a resurfacing and thereby bone-preserving method for the treatment of disabling osteoarthritis particularly in younger individuals. The underlying rationale was to replace exclusively diseased tissue, to restore anatomy and function and to optimize range of motion and stress transfer to the proximal femur. Wagner's approach was designed to reduce the risk of infection and to make later revisions easier. The technique was however associated with a high revision rate due to early aseptic wear induced component loosening and neck fractures. Nevertheless, we report a case of a 30 years follow-up of a Wagner resurfacing hip arthroplasty.

Ergometer cycling after hip or knee replacement surgery: a randomized controlled trial.

BACKGROUND: The optimal treatment strategy following primary total hip or knee replacement remains unknown. The purpose of this study was to evaluate the effect of ergometer cycling after hip or knee replacement surgery on health-related quality of life and patient satisfaction. METHODS: Three hundred and sixty-two patients were randomly assigned to either perform or not perform ergometer cycling beginning two weeks after total hip or knee replacement. The primary outcome was self-reported physical function as measured with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at three, six, twelve, and twenty-four months postoperatively. Results were compared with published thresholds for minimal clinically important improvements. RESULTS: The baseline characteristics of the two groups were similar. After the hip arthroplasties, all of the outcome parameters were superior in the ergometer cycling group at all follow-up intervals, and the primary outcome, physical function as measured with the WOMAC, was significantly better at three months (21.6 compared with 16.4 points, effect size = 0.33, p = 0.046) and twenty-four months (14.7 compared with 9.0 points, effect size = 0.37, p = 0.019). After the hip arthroplasties, a higher percentage of the ergometer cycling group was "very satisfied" at all follow-up intervals (for example, 92% compared with 80% at three months; p = 0.027). The significant differences in the primary outcome exceeded the absolute minimal clinically important improvement threshold by a factor of 2.0. No significant differences between the study groups were seen after the knee arthroplasties. CONCLUSIONS: Ergometer cycling after total hip arthroplasty is an effective means of achieving significant and clinically important improvement in patients' early and late health-related quality of life and satisfaction. However, this study does not support the use of ergometer cycling after knee arthroplasty.

Cell-Laden and Cell-Free Matrix-Induced Chondrogenesis versus Microfracture for the Treatment of Articular Cartilage Defects: A Histological and Biomechanical Study in Sheep.

OBJECTIVE: The aim of this study was to evaluate the regenerative potential of cell-laden and cell-free collagen matrices in comparison to microfracture treatment applied to full-thickness chondral defects in an ovine model. METHODS: Animals (n = 30) were randomized into 5 treatment groups, and 7-mm full-cartilage-thickness defects were set at the trochlea and medial condyle of both knee joints and treated as follows: 2 scaffolds in comparison (collagen I/III, Chondro-Gide(®); collagen II, Chondrocell(®)) for covering microfractured defects (autologous matrix-induced chondrogenesis), both scaffolds colonized in vitro with autologous chondrocytes (matrix-associated chondrocyte transplantation), or scaffold-free microfracture technique. One year after surgery, cartilage lesions were biomechanically (indentation test), histologically (O'Driscoll score), and immunohistochemically (collagen type I and II staining) evaluated. RESULTS: All treatment groups of the animal model induced more repair tissue and showed better histological scores and biomechanical properties compared to controls. The average thickness of the repair tissue was significantly greater when a scaffold was used, especially the collagen I/III membrane. However, none of the index procedures surpassed the others from a biomechanical point of view or based on the histological scoring. Collagen type II expression was better in condylar defects compared to the trochlea, especially in those treated with collagen I/III membranes. CONCLUSION: Covering of defects with suitable matrices promotes repair tissue formation and is suggested to be a promising treatment option for cartilage defects. However, it failed to improve the biomechanical and histological properties of regenerated articular cartilage compared to microfracture alone in an ovine model under the given circumstances.

A simple measuring device for laboratory indentation tests on cartilage.

Mechanical testing of articular cartilage and repair tissue enables judgment of their capacity in withstanding mechanical loading. In the past, different methods have been developed requiring a complex technical setup and extensive data analysis. Therefore, the aim of the present project was to build up a simple measuring apparatus for laboratory indentation tests. The device consists of an incremental optical displacement transducer with a sleeve bearing guided plunger and a spherical tip made of polished steel (radius: 0.75 or 1.5 mm), a sensitive load cell and a stiff frame. The indentation force results from the plunger's gravity plus the force of the spring inside the displacement transducer and levels at 0.170 N or 0.765 N. The displacement transducer is fixed to the frame via the load cell that enables one to detect the initial contact of the tip with the tissue. The load cell has a standard uncertainty of 2 mN and the displacement transducer of 1 microm. From indentation-creep tests, a "0.25-s elastic modulus" is calculated. Measurements on thin rubber sheets were carried out to determine the quality of the measuring device. Compression tests on cylinders made of these rubber sheets yielded control data, and a good agreement with the "0.25-s elastic modulus" was found. Indentation tests on cartilage at different sites of sheep femoral condyles yielded a very good repeatability of the measurement results (+/-7.5%).

Radial extracorporeal shock wave therapy is safe and effective in the treatment of chronic recalcitrant plantar fasciitis: results of a confirmatory randomized placebo-controlled multicenter study.

BACKGROUND: Radial extracorporeal shock wave therapy is an effective treatment for chronic plantar fasciitis that can be administered to outpatients without anesthesia but has not yet been evaluated in controlled trials. HYPOTHESIS: There is no difference in effectiveness between radial extracorporeal shock wave therapy and placebo in the treatment of chronic plantar fasciitis. STUDY DESIGN: Randomized, controlled trial; Level of evidence, 1. METHODS: Three interventions of radial extracorporeal shock wave therapy (0.16 mJ/mm(2); 2000 impulses) compared with placebo were studied in 245 patients with chronic plantar fasciitis. Primary endpoints were changes in visual analog scale composite score from baseline to 12 weeks' follow-up, overall success rates, and success rates of the single visual analog scale scores (heel pain at first steps in the morning, during daily activities, during standardized pressure force). Secondary endpoints were single changes in visual analog scale scores, success rates, Roles and Maudsley score, SF-36, and patients' and investigators' global judgment of effectiveness 12 weeks and 12 months after extracorporeal shock wave therapy. RESULTS: Radial extracorporeal shock wave therapy proved significantly superior to placebo with a reduction of the visual analog scale composite score of 72.1% compared with 44.7% (P = .0220), and an overall success rate of 61.0% compared with 42.2% in the placebo group (P = .0020) at 12 weeks. Superiority was even more pronounced at 12 months, and all secondary outcome measures supported radial extracorporeal shock wave therapy to be significantly superior to placebo (P < .025, 1-sided). No relevant side effects were observed. CONCLUSION: Radial extracorporeal shock wave therapy significantly improves pain, function, and quality of life compared with placebo in patients with recalcitrant plantar fasciitis.

[The influence of bone quality and the fixation procedure on the primary stability of cementless implanted tibial plateaus]. / Der Einfluss der Knochenmineraldichte und des Verankerungsverfahrens auf die Primärstabilitat von zementfrei implantierten Tibiakomponenten.

BACKGROUND: An overview of prospective studies on cementless and cemented primary knee joint endoprosthetics carried out between 1988 and 2004 reveals that the aseptic tibial loosening rate of cemented prostheses implanted with fixed meniscal bearings amounts to 2-6% within a period of 4-14 years, while cementless implanted prostheses show loosening rates of up to 28% within a period of 4-10 years. If these results arise from a lack of proper initial osseointegration as a result of insufficient primary stability, and how this is influenced by the tibial bone quality and the tibial fixation procedure has not yet been investigated. MATERIALS AND METHODS: Tibial plateaus were press-fit implanted, both screwed and unscrewed, into each of six pairs of tibial heads from corpses. Stability testing was conducted applying eccentric axial load, shear and torsion. RESULTS: The average amounts of relative movement at the medial and lateral plateau are clearly different in the screwed version and the unscrewed version when loaded axially, but the difference was significant (p = 0.016) only at the medial plateau. Relative movements under shear and torsion showed no significant differences. The bone density of the tibial metaphyses had no significant effect on the primary stability of the cementless implanted tibial plateau. CONCLUSION: When using cementless knee endoprostheses, the fixation of the tibial plateau with screws--in addition to a flawless press-fit and form-fit customization of the tibial head--appears indispensable for guaranteeing proper osseointegration under physiological axial loads.

Magnetic resonance imaging and correlative gross anatomy of the ligamentum semicirculare humeri (rotator cable).

The purpose of this study has been to demonstrate macroscopic and MRI anatomy of the so-called rotator cable, otherwise known as the ligamentum semicirculare humeri (LSCH) of the superior shoulder joint capsule. Twelve shoulder joints from eight cadavers were dissected; seven of which, from four of the cadavers, were studied using MR arthrography (1.5-Tesla device Somatom Symphony, Siemens, Erlangen, Germany) prior to dissection. The MRI protocol included T1WI, PDWI, and DESS 3D WI standard sequences. The results of MRI were compared with gross anatomic dissection findings. The macroscopically recognizable capsular bundle of LSCH fibers was identified by anatomic dissection in all specimens. On MRI, the entire ligament or parts of it could be identified in six of seven cases. It was best visualized on axial images. In the evaluation of magnetic resonance images of superior shoulder joint structures, additional knowledge on the anatomy of the LSCH can be used by the radiologist to facilitate detailed interpretation of the shoulder MRI.

The intraindividual agreement of the bone density of the human proximal tibia.

The interindividual variability in the biomechanical properties of cadaver bones has remained an unsolved problem in biomechanical investigation procedures. For this reason, it is postulated to use matched bone pairs from the same individual for comparative biomechanical tests. The rationale behind this procedure is based on the assumption that biomechanically similar behaviour is to be expected in an intraindividual rather than an interindividual comparison. Systematic studies confirming this thesis were performed on the human femur. However, investigations regarding the intraindividual properties of the proximal tibial metaphysis with respect to the underlying bone densities, have not yet been performed. In order to verify the hypothesis that matched proximal tibial metaphyses from the same donor imply corresponding bone density values, densitometric measurements (pQCT) were performed in 14 matched cadaver tibias (average age 61 years, 9 men, 5 women) which were fresh-frozen at -40 degrees C after removal. After statistical analysis of the bone density values, five tibial pairs were identified as differing on the basis of missing correlations and the existence of systematic differences within the pairwise data. In other words, only about 2/3 of the data in the random sample available was classified as comparable. As the bone density measured by pQCT technique significantly correlates with the biomechanical properties of the bone, it can be concluded from the test result available that matched human tibiae show no concurring bone density values in 1/3 of cases. Thus the pairing of corpse tibiae does not necessarily imply suitability for comparative biomechanical experiments.

[Designing a surgical device for harvesting autologous fascia lata grafts as a minimal invasive procedure]. / Entwicklung eines Operationsgerätes zur minimal-invasiven Fascia lata-Entnahme.

AIMS: Fascia lata is used in different shapes and sizes as a graft material in surgical procedures. The conventional method of harvesting a fascia lata graft is through a long skin incision on the lateral aspect of the thigh. Minimal invasive procedures have been established to reduce the disadvantages of an extensive surgical approach for obtaining the autotransplant. However, they do not facilitate to suture the remaining fascia after harvesting the transplant and therefore bear the risk of a symptomatic herniation of the muscle belly. The aim of this study was to design a surgical device to harvest a fascia lata graft and close the resulting fascia defect as a minimal invasive procedure. MATERIALS AND METHODS: The prototype was tested in 11 human cadaver specimens. It was introduced subcutanously via two small skin incisions. The device contained a special fixation- and working mechanism which enabled the fascial closure using a continuous suture. After the harvest procedure, both the transplant and the sutured fascia lata were examined. RESULTS: The experiments demonstrated the suitability of this method for minimal invasive harvesting of fascia lata. The removed transplants complied in all experiments with the expected dimensions. The continuous suture of the femoral fascia ran with accurate gaps between the sutures and constant tension without dehiscence. Neither the transplant nor the tissue in the region of harvest have shown unduly macroscopic damage due to the use of the device. CONCLUSION: The designed prototype can be used for harvesting a fascia lata graft and repairing the resulting defect minimal invasively. Clinical implementation seems possible. However, improvements could be made mainly concerning the handling of the device.

Matrix-associated autologous chondrocyte transplantation/implantation (MACT/MACI)--5-year follow-up.

Matrix-associated autologous chondrocyte transplantation/implantation (MACT/MACI) is a new operation procedure using a cell seeded collagen matrix for the treatment of localized full-thickness cartilage defects. A prospective clinical investigation was carried out in order to clarify whether this proves suitable and confirms objective and subjective clinical improvement over a period of up to 5 years after operation. Thirty-eight patients with localised cartilage defects were treated with MACT. Within the context of clinical follow-up, these patients were evaluated for up to 5 years after the intervention. Four different scores (Meyers score, Tegner-Lysholm activity score, Lysholm-Gillquist score, ICRS score) as well as the results of six arthroscopies and biopsies obtained from four patients formed the basis of this study. For 15 patients, 5 or more years had elapsed since the operation at the time this study was completed. It was possible to obtain results 5 years postoperatively from 11 (73.3%) of these 15 patients. Overall, we included 25 patients into the evaluation with a 2-year or longer postoperative period. Five years after transplantation 8 out of 11 patients rated the function of their knee as much better or better than before. Three of the four scores showed significant improvement compared to the preoperative value. One score, the Tegner-Lysholm score showed improvement, which, however, did not prove to be significant. The significantly improved results on three scores after 5 years suggest that MACT represents a suitable but cost-intensive alternative in the treatment of local cartilage defects in the knee.

Zebra sign: cerebellar bleeding pattern characteristic of cerebrospinal fluid loss. Case report.

Supratentorial subdural hematoma is a well-known complication following spinal interventions. Less often, spinal or supratentorial interventions cause remote cerebellar hemorrhage (RCH). The exact pathomechanism accounting for RCH remains unclear, but an interventional or postinterventional loss of cerebrospinal fluid (CSF) seems to be involved in almost all cases. Hemorrhage is often characterized by a typical, streaky bleeding pattern due to blood spreading in the cerebellar sulci. Three different cases featuring this bleeding pattern following spinal, supratentorial, and thoracic surgery are presented. Possible pathomechanisms leading to RCH are discussed. Based on data from the underlying cases and the reviewed literature, the authors concluded that this zebra-pattern hemorrhage seems to be typical in a postoperative loss of CSF, which should always be considered on presentation of this bleeding pattern.

Patellar tendon reconstruction using a free latissimus dorsi flap following resection of a prepatellar myxofibrosarcoma: case report.

The authors' experience indicates that good functional results are achievable in cases with wide resection of the knee extensor mechanism. They report a low-grade myxoid fibrosarcoma patient in whom a one-stage functional reconstruction was carried out by transfer of a free latissimus dorsi flap without secondary surgical procedures.

Periosteum stimulates subchondral bone densification in autologous chondrocyte transplantation in a sheep model.

In this sheep study, we have tested the hypothesis that an osteogenic response is triggered in the subchondral bone by periosteum implanted in full thickness cartilage defects and can be prevented by replacing the periosteum by a cell-free collagen type I/III membrane. Two 7-mm diameter osteochondral defects were made in the trochlea groove and in the medial femoral condyle of one of the knees in each of 15 adult sheep. The animals were divided into three groups (n=5): a control group with untreated cartilage defects, a group treated with autologous chondrocyte transplantation (ACT) and periosteum, and a group treated with ACT in combination with a collagen I/III membrane cover. Histological examination was performed 1 year later. The optical density of the subchondral bone in the histological sections was measured with digital imaging software. There was a dramatic, statistically significant (P<0.0001; power=1) increase in bone density of 45%-70% under defects that were treated with the periosteal cover, compared with the collagen membrane and control groups, which displayed the same bone density. There was no difference in the cartilaginous reparative tissue in the defects in the three groups. Periosteum thus stimulates the remodelling process in subchondral bone. Stiffening of the subchondral bone can lead to degeneration of the overlying reparative cartilaginous tissue because of an increase in the mechanical stress in the tissue. These findings warrant evaluation of subchondral bone changes in patients treated by ACT and the correlation of these changes with clinical outcome.

Apoptotic chondrocyte death in cell-matrix biocomposites used in autologous chondrocyte transplantation.

Tissue engineering may be a promising approach for the treatment of focal articular cartilage defects. Programmed cell death (apoptosis) plays an important role in multiple degenerative processes of cartilage (e.g. osteoarthritis). It is known that matrix provides a trophic signal for the cells and an altered matrix may influence the availability of factors that regulate apoptosis. In this study we investigate the viability of chondrocytes seeded on a Chondrogide scaffold (Geistlich Biomaterials, CH), which we use in matrix-induced autologous chondrocyte transplantation (MACT). By now, we have studied material from 29 patients treated for localized articular cartilage defects in the knee. Our results indicate that light microscopy (Mayer's hematoxylin-eosin, Masson-Goldner, Trypan-blue and TUNEL method) and electron microscopy can be used to investigate for apoptotic cells grown on a Chondrogide resorbable scaffold. Neither the handling of the cell-matrix biocomposite nor the procedures for fixation could destroy the scaffold or the cell sheet adhering firmly to the matrix. Apoptotic cells were revealed in all samples and with all techniques used. Mayer's hematoxylin-eosin and Masson-Goldner staining show cells with a condensed, pycnotic nucleus and shrunken cytoplasm. In electron microscopy we observed cells with chromatin condensation and volume shrinkage consistent with apoptosis. The results of the Trypan-blue staining show a mean viability of 92.1 +/- 9.8% (range 57-100%). The TUNEL method revealed 44.6 +/- 20.4% positive cells. Our results indicate that apoptosis plays an important role in chondrocytes grown on a scaffold. An optimal scaffold will determine the growth, morphology and phenotype of the chondrocytes by its physical and chemical characteristics.