Although autologous chondrocyte implantation (ACI) is a well-established therapy for the treatment of isolated cartilage defects of the knee joint, little is known about typical complications and their treatment after ACI. Unsatisfactory outcome after ACI is associated with technique-related typical complications. Case series; Level of evidence, 4. A total of 309 consecutive patients with 349 ACI procedures of the knee joint were analyzed. Three different ACI techniques were used: periosteum-covered ACI in 52 cases (14.9%), Chondrogide (Geistlich Biomaterials, Wolhusen, Switzerland) membrane-covered ACI in 215 cases (61.6%), and a 3-dimensional matrix-associated ACI (BioSeed-C, Biotissue Technologies, Freiburg, Germany) in 82 cases (23.5%). In 52 patients, revision surgery was performed for persistent clinical problems. These patients were analyzed for defect size and location, technique of ACI, and intraoperative findings during revision surgery. The mean time of follow-up for patients after ACI was 4.5 years (standard deviation, ±1.5). Four typical major complications were identified: hypertrophy of the transplant, disturbed fusion of the regenerative cartilage and the healthy surrounding cartilage, insufficient regenerative cartilage, and delamination. These diagnoses covered a total of 88.5% of the patients who underwent revision surgery. The overall complication rate was highest in the group of patients treated with periosteum-covered ACI (P = .008). The incidence of symptomatic hypertrophy was 5.2% for all techniques and defect locations; the highest incidence was in patients treated with periosteum-covered ACI (15.4%) (P = .001). The incidence of disturbed fusion was highest in the Chondrogide-covered ACI (3.7%) and the matrix-associated ACI group (4.8%). Concerning the incidence of complications by defect location, there was a tendency for increased complications in patellar defects (P = .095). Within the patellar defects group, no correlation was found for the occurrence of delamination, insufficient regeneration, and disturbed fusion. As a statistical trend, an increased rate of hypertrophy was found for patellar defects (P = .091). A major proportion of complications after ACI can be summarized by 4 major diagnoses (symptomatic hypertrophy, disturbed fusion, delamination, and graft failure). Among those, the overall complication rate and incidence of hypertrophy of the transplant were higher for periosteum-covered ACI. Furthermore, an increased rate of symptomatic hypertrophy was found for patellar defects. Therapeutic concepts need to be developed to treat these typical complications of ACI.

Pelvic and acetabular fractures are rare injuries and account for approximately 3% to 8% of all fractures. Often the result of high energy blunt trauma, most of the patients sustaining pelvic injuries are at high risk of associated injuries strongly influencing outcome and survival rates. Because of anatomic differences it has been suggested that pediatric pelvic fractures are different injuries as compared with that of adults. However, this has been controversially discussed. Aim of this multicenter register study was to identify similarities and differences between pediatric and adult pelvic trauma and evaluate the influence of changes in medical treatment by comparison of two treatment periods. In this multicenter register study, data of 4,291 patients treated from 1991 to 1993 (n = 1,723) or 1998 to 2000 (n = 2,568) for pelvic fractures in one of the 23 participating hospitals were evaluated for age, gender, Injury Severity Score (ISS), Hannover Polytrauma Score (PTS), fracture type (using Tile's classification), peripelvic soft tissue injury, need for emergency measures, mortality, cause of death, and need for operative stabilization. We compared the patients' characteristics of the two treatment periods and pediatric with adult pelvic injuries. Statistical analysis was performed using SAS software. There was no difference in terms of ISS, PTS, and presence of peripelvic soft tissue injuries between the two observation periods. Mortality rate dropped significantly from 7.9% to 5% (p < 0.0001) in the latter treatment period. Death was directly attributed to the pelvic injury in 11% from 1991 to 1993. This rate dropped significantly to 7% in the period from 1998 to 2000 (p = 0.020). A type fractures decreased from 61.1% (1991-1993) to 57.1% (1998-2000) of patients (p = 0.028) and except for these simple fractures there was a significant overall trend toward surgical treatment. Multivariate analysis revealed ISS, PTS, concomitant soft tissue injuries, and need for emergency measures as independent risk factors for death whereas surgical stabilization and treatment in the latter treatment period were associated with an increased survival rate. We found no difference between the adult and the pediatric group in terms of ISS and concomitant peripelvic soft tissue injuries. Children were less likely to receive surgical treatment (19.4% vs. 34.5%, p < 0.0001) but requirement for emergency measures was higher in the pediatric group (17.9% vs. 11.1%, p = 0.033). Moreover, we found no significant differences in mortality between both groups (6.1% vs. 8.2%, p = 0.28). Multivariate analysis showed age