Dieter Kohn

Enhanced repair of articular cartilage defects in vivo by transplanted chondrocytes overexpressing insulin-like growth factor I (IGF-I)

Traumatic articular cartilage lesions have a limited capacity to heal. We tested the hypothesis that overexpression of a human insulin-like growth factor I (IGF-I) cDNA by transplanted articular chondrocytes enhances the repair of full-thickness (osteochondral) cartilage defects in vivo. Lapine articular chondrocytes were transfected with expression plasmid vectors containing the cDNA for the Escherichia coli lacZ gene or the human IGF-I gene and were encapsulated in alginate. The expression patterns of the transgenes in these implants were monitored in vitro for 36 days. Transfected allogeneic chondrocytes in alginate were transplanted into osteochondral defects in the trochlear groove of rabbits. At three and 14 weeks, the quality of articular cartilage repair was evaluated qualitatively and quantitatively. In vitro, IGF-I secretion by implants constructed from IGF-I-transfected chondrocytes and alginate was 123.2±22.3 ng/107 cells/24 h at day 4 post transfection and remained elevated at day 36, the longest time point evaluated. In vivo, transplantation of IGF-I implants improved articular cartilage repair and accelerated the formation of the subchondral bone at both time points compared to lacZ implants. The data indicate that allogeneic chondrocytes, transfected by a nonviral method and cultured in alginate, are able to secrete biologically relevant amounts of IGF-I over a prolonged period of time in vitro. The data further demonstrate that implantation of these composites into deep articular cartilage defects is sufficient to augment cartilage defect repair in vivo. These results suggest that therapeutic growth factor gene delivery using encapsulated and transplanted genetically modified chondrocytes may be applicable to sites of focal articular cartilage damage.

Reliability and interobserver variability in radiological patellar height ratios

Abstract This study evaluated the reliability and interobserver variability of five patellar height ratios as measured by two examiners on standard radiographs: Insall-Salvati (IS), modified Insall-Salvati (MIS), Blackburne-Peel (BP), Caton-Deschamps (CD), and Labelle-Laurin (LL). Plain lateral radiographs with a knee flexion angle of 20° for IS, MIS, BP, and CD ratios and 90° for the LL method of 22 knees of 21 patients with varying pathological knee conditions were analyzed. Statistical results revealed a low interobserver variability with high correlation coefficients (0.86 for IS, 0.82 for MIS, 0.86 for BP, 0.92 for CD, and 0.81 for LL; P > 0.3) and low mean interobserver errors. However, regarding the reliability of the radiographic results of the different methods for patella alta, baja, or norma we found varying results in 68% of the patients. In two patients the patellar height was classified as alta, norma, or baja depending on the ratio used. Regarding the definitions of patellar height used by the authors of these methods, we found the lowest number of normal patellae with the IS ratio and no patella alta for the CD ratio. The LL method revealed the highest number of patella alta. The BP ratio showed intermediate results for both patella alta and baja, being the most moderate method. This study showed that there was a good interobserver reliability for the evaluation of patellar height according to the common radiological ratios. However, the high frequency of differing results between the different radiographic ratios showed that patellar height classification as “alta,”“norma,” or “baja” depends heavily on the chosen index. The differing results were due mainly to the normative patellar height data and to anatomical differences. Based on these findings we recommend a ratio using the articular surface of the patella in relation to the joint line. We recommend the BP method because it revealed the lowest interobserver variability and discriminated best among the groups alta, norma, and baja.

Sports Injuries in Team Handball A One-Year Prospective Study of Sixteen Men’s Senior Teams of a Superior Nonprofessional Level

One hundred eighty-six players of 16 teams in 2 male team handball senior divisions were observed prospectively for 1 season to study the injury incidence in relation to exposure in games and practices. Ninety-one injuries were recorded. Injury incidence was evaluated at 2.5 injuries per 1000 player-hours, with a significantly higher incidence in game injuries (14.3 injuries per 1000 game-hours) compared with practice injuries (0.6 injuries per 1000 practice-hours). Practice injury incidence was higher in the lower performance level group, and game injury incidence was higher in the high-level group. The upper extremity was involved in 37% of the injuries, and the lower extremity in 54%. The knee was the most commonly injured joint, followed by the finger, ankle, and shoulder. Knee injuries were the most severe injuries, and they were more frequent in high-level players. There was an increase in the severity of injury with respect to performance level. The injury mechanism revealed a high number of offensive injuries, one-third of them occurring during a counterattack. The injury pattern showed certain variations with respect to player position and performance level. Prophylactic equipment was used by a majority of players at the higher performance level.

Comparison of Initial Fixation Strength Between Biodegradable and Metallic Interference Screws and a Press-Fit Fixation Technique in a Porcine Model:

The objective of this study was to evaluate the initial fixation strength of a biodegradable interference screw compared with press-fit fixation and a titanium interference screw in anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft. Porcine lower limbs were used. The specimens underwent 500 loading cycles between 60 and 250 N. This corresponds to loads in the graft during aggressive rehabilitation. Thereafter, intact specimens were loaded to failure. Failure mode was defined by visual analysis. Under cyclic loads none of the interference screw fixations failed. In the press-fit group (angle between load axis and tunnel axis 80°), five specimens failed. The mean maximal load to failure was 945 N ( 87) for the titanium screw, 797 N ( 60) for the biodegradable screw, and 708 N ( 211) for the five press-fit specimens that did not fail during cyclic loading. With respect to primary fixation strength, biodegradable screws are a reasonable alternative to titanium interference screws. The press-fit fixation did not provide a secure fixation in all cases. Five press-fit specimens failed under cyclic loads comparable with those seen under conditions of accelerated rehabilitation.

Cyclic loading of rotator cuff reconstructions: single-row repair with modified suture configurations versus double-row repair.

Background Double-row repair is suggested to have superior biomechanical properties in rotator cuff reconstruction compared with single-row repair. However, double-row rotator cuff repair is frequently compared with simple suture repair and not with modified suture configurations. Hypothesis Single-row rotator cuff repairs with modified suture configurations have similar failure loads and gap formations as double-row reconstructions. Study Design Controlled laboratory study. Methods We created 1 × 2-cm defects in 48 porcine infraspinatus tendons. Reconstructions were then performed with 4 single-row repairs and 2 double-row repairs. The single-row repairs included transosseous simple sutures; double-loaded corkscrew anchors in either a double mattress or modified Mason-Allen suture repair; and the Magnum Knotless Fixation Implant with an inclined mattress. Double-row repairs were either with Bio-Corkscrew FT using modified Mason-Allen stitches or a combination of Bio-Corkscrew FT and PushLock anchors using the SutureBridge Technique. During cyclic load (10 N to 60-200 N), gap formation was measured, and finally, ultimate load to failure and type of failure were recorded. Results Double-row double-corkscrew anchor fixation had the highest ultimate tensile strength (398 ± 98 N) compared to simple sutures (105 ± 21 N; P < .0001), single-row corkscrews using a modified Mason-Allen stitch (256 ± 73 N; P = .003) or double mattress repair (290 ± 56 N; P = .043), the Magnum Implant (163 ± 13 N; P < .0001), and double-row repair with PushLock and Bio-Corkscrew FT anchors (163 ± 59 N; P < .0001). Single-row double mattress repair was superior to transosseous sutures (P < .0001), the Magnum Implant (P = .009), and double-row repair with PushLock and Bio-Corkscrew FT anchors (P = .009). Lowest gap formation was found for double-row double-corkscrew repair (3.1 ± 0.1 mm) compared to simple sutures (8.7 ± 0.2 mm; P < .0001), the Magnum Implant (6.2 ± 2.2 mm; P = .002), double-row repair with PushLock and Bio-Corkscrew FT anchors (5.9 ± 0.9 mm; P = .008), and corkscrews with modified Mason-Allen sutures (6.4 ± 1.3 mm; P = .001). Conclusion Double-row double-corkscrew anchor rotator cuff repair offered the highest failure load and smallest gap formation and provided the most secure fixation of all tested configurations. Double-loaded suture anchors using modified suture configurations achieved superior results in failure load and gap formation compared to simple suture repair and showed similar loads and gap formation with double-row repair using PushLock and Bio-Corkscrew FT anchors. Clinical Relevance Single-row repair with modified suture configurations may lead to results comparable to several double-row fixations. If double-row repair is used, modified stitches might further minimize gap formation and increase failure load.

Primary Stability of Press-Fit-Implanted Osteochondral Grafts Influence of Graft Size, Repeated Insertion, and Harvesting Technique

The aim of this study was to evaluate the fixation strength of press-fit-implanted osteochondral grafts with respect to graft size (length and diameter), the effect of repeated insertion after pullout, and harvesting technique. Experiments were performed using the Osteochondral Autograft Transfer System on porcine femoral condyles. Failure loads of 10-mm-long grafts (mean, 47 N) were significantly lower than failure loads of 15-mm-long grafts (mean, 93 N) and 20-mm-long grafts (mean, 110 N) (all grafts, 11 mm in diameter). Reinsertion of the 15-mm-long grafts after initial pullout resulted in a significant reduction of failure loads (mean, 93 N versus 44 N). Failure loads of 8-mm-diameter grafts (mean, 41 N) were significantly lower than those of 11-mm-diameter grafts (mean, 92 N) (all 15 mm long). Levering of the tubular chisel during graft harvest significantly decreased press-fit stability as compared with simple turning of the chisel (mean, 32 N versus 52 N) (8-mm diameter and 15-mm length). These results suggest that primary fixation strength of press-fit-inserted osteochondral grafts depends on the size of the grafts and that repeated pullout and reinsertion of grafts as well as a nonoptimal harvesting technique (levering) will reduce primary stability.

The risk of growth changes during transphyseal drilling in sheep with open physes.

PURPOSE A sheep model was used to evaluate the risk of growth disturbances of transphyseal drilling and anterior cruciate ligament (ACL) reconstruction. METHODS In group A, comprised of six 4-month-old Merino sheep, the ACL was resected and 5-mm tunnels were drilled and left empty. Unilateral ACL reconstruction using an autologous Achilles tendon graft, extracortical fixation, and tunnel diameters of 5 mm was performed in group B. A single-stranded graft with a diameter of 5 mm was used in group B-1 (N = 6) and a 3-mm double-stranded graft in group B-2 (N = 6). Six months after the procedure, the animals were euthanized. Growth changes were evaluated macroscopically, by magnetic resonance imaging, and by histology. RESULTS Central growth plate lesions on the tibia did not induce growth abnormalities. On the peripheral femur, posterolateral growth plate injuries with empty tunnels led to a shortening of the lateral femur of 8 mm (7 to 10 mm), a valgus deformity of 12.8 degrees (12 degrees to 14 degrees ), and a flexion deformity of 8.6 degrees (5 degrees to 15 degrees ). Histology revealed a strong bone bridge over the physis and an injury to the perichondral structures. Transphyseal ACL replacements did not cause growth disturbances on either the tibia or the femur, even if a drilling injury of the perichondral structures occurred. CONCLUSIONS Despite consistent physeal damage, ACL reconstructions did not lead to clinically relevant growth disturbances. CLINICAL RELEVANCE The results suggest that transphyseal ACL reconstruction procedures might yield similar results in children with substantial growth remaining.

Drill hole position in endoscopic anterior cruciate ligament reconstruction Results of an advanced arthroscopy course

Abstract In 24 cadaver knees the anterior cruciate ligament (ACL) was replaced by a bone-tendon-bone patellar tendon autograft in an endoscopic technique. This was carried out during an advanced arthroscopy course after intensive instruction and practice on a plastic model. When the knees were opened and evaluated according to the recent orthopaedic literature, only four good results with correct tunnels and a non-impinging graft were found. In 12 knees the femoral tunnel was too far anterior (10) or had broken through the posterior femoral cortex (2). In 6 knees the tibial tunnel was too far anterior (2) or too far posterior (4). The notchplasty was insufficient in 6 knees. We conclude that endoscopic ACL reconstruction cannot be mastered after attending a course alone. Expert help is necessary during the first clinical cases.

Local stimulation of articular cartilage repair by transplantation of encapsulated chondrocytes overexpressing human fibroblast growth factor 2 (FGF-2) in vivo†

Defects of articular cartilage are an unsolved problem in orthopaedics. In the present study, we tested the hypothesis that gene transfer of human fibroblast growth factor 2 (FGF‐2) via transplantation of encapsulated genetically modified articular chondrocytes stimulates chondrogenesis in cartilage defects in vivo.

Influence of cage geometry on sagittal alignment in instrumented posterior lumbar interbody fusion

Study Design. Retrospective radiographic evaluation of the sagittal alignment of the lumbar spine in patients undergoing short-segment instrumented posterior lumbar interbody fusion with cage systems of different shape. Objectives. To determine whether rectangular and wedge-shaped cages have a different influence on the sagittal alignment of the lumbar spine in patients undergoing short-segment instrumented posterior lumbar interbody fusion. Summary of Background Data. Previous studies of sagittal alignment after posterior lumbar interbody fusion have focused on the impact of intraoperative patient, hip, and knee positioning, as well as instrumentation characteristics on sagittal posture. The influence of the cage shape on indexes of total and segmental sagittal alignment of the lumbar spine is yet unknown. Methods. Forty-two patients having undergone instrumented short-segment posterior lumbar interbody fusion were reviewed retrospectively. Twenty-two patients (12 women and 10 men, 38–78 years of age) had posterior lumbar interbody fusion with rectangular cages. The fused segments were: 4 at L3–L4, 16 at L4–L5, 11 at L5–S1. Thirteen patients had single- and nine patients double-level fusion. Twenty patients (8 women and 12 men, 34–81 years of age) had posterior lumbar interbody fusion with wedge-shaped cages. The fused segments were: 4 at L3–L4, 15 at L4–L5, 11 at L5–S1. Ten patients had single- and 10 patients double-level fusion. Cages were packed with cancellous bone from the posterior iliac crest and/or bone fragments harvested by laminectomy. All patients had additional pedicle screw fixation. Pre- and postoperative standing lateral radiographs were assessed for segmental and lumbar lordosis as well lumbar and sacral tilt. Data were analyzed with repeated measures analysis of variance. Results. The mean follow-up period was 18 months with a minimum follow-up period of 14 months. Mean segmental lordosis of the fused segments showed significant changes between the two implant groups (P < 0.05). Segmental lordosis decreased in the rectangular cage group from 10° to 2° at L3–L4, from 10° to 5° at L4–L5, and from 9° before to 6° after fusion surgery at L5–S1. In the wedge-shaped cage group, segmental lordosis increased from 4° to 7° at L3–L4, from 2° to 8° at L4–L5, and from 9° to 17° at L5–S1. Analysis of changes in lumbar lordosis and lumbar and sacral tilt did not show significant differences though opposite trends: lumbar lordosis decreased from 55° to 48° in the rectangular cage group and increased from 45° to 53° in the wedge-shaped cage group. Lumbar tilt measured 98° before and 102° after surgery in the rectangular cage group and 97° before and 94° after surgery. Sacral tilt measured 44° before and 40° after surgery in the rectangular cage group and measured 42° before and 45° after surgery in the wedge-shaped cage group. Conclusions. The cage geometry has a significant impact on the alignment of the lumbar spine after instrumented posterior lumbar interbody fusion. With rectangular cages, lumbar lordosis and segmental lordosis of the segments fused decrease; sagittal balance is maintained by compensatory changes of the sacral tilt. Wedge-shaped cages significantly increase segmental lordosis, enhance lumbar lordosis, and therefore should be preferred for restoring sagittal alignment in instrumented posterior lumbar interbody fusion procedures.