[A minimally invasive dorsal approach to the medial femoral condyle as a donor site for osteochondral transfer procedures]. / Entnahme osteochondraler Zylinder aus der medialen dorsalen Femurkondyle über einen minimalinvasiven Zugang.

OBJECTIVE: Long-lasting reconstruction of joint surface by using an osteochondral transfer procedure (OCT). Reduction of donor site morbidity by using a minimally invasive approach to the dorsal medial femoral condyle. INDICATIONS: Grade 3 and 4 cartilage lesions (according to ICRS [International Cartilage Repair Society]), osteochondral lesions, and osteochondrosis dissecans. CONTRAINDICATIONS: Grade 2 or higher-graded cartilage lesions at the dorsal medial femoral condyle, infection, axis deviation of more than 5 degrees in the frontal plane, advanced osteoarthritis. SURGICAL TECHNIQUE: Cylinders at recipient site are removed first, thereby determining number and diameter of donor cylinders. Supine position, skin incision over the dorsal medial femoral condyle. After dissection of soft tissue and superficial fascia, semitendinosus tendon and medial gastrocnemius muscle are retracted to the lateral side, followed by arthrotomy, introduction of two Hohmann retractors medial and lateral of the condyle, and harvesting of the donor cylinders with a tubular chisel. Advantages of the described approach: reduction of soft-tissue trauma, easy surgical technique, additional donor site area besides femoral trochlea and intercondylar notch. POSTOPERATIVE MANAGEMENT: Partial weight bearing of 10-20 kg for 4-6 weeks. Limitation of knee flexion to 90 degrees for 6 weeks. RESULTS: Between 01/2006 and 04/2007, the dorsal medial femoral condyle was used as a donor site in 16 patients. All patients were evaluated preoperatively and after 1 year using the American Knee Society Score (KSS), the Western Ontario and McMaster Universities (WOMAC) Score, the Tegner Score, and the visual analog scale (VAS) pain. The mean follow- up was 13.9 (+/-4.3) months. The mean defect area was 4.6 (+/-2.2) cm(2). The mean KSS, Tegner Score, and WOMAC Score improved from 123.1 (+/-41.5), 2.8 (+/-0.9), and 73.3 (+/-50.2) points preoperatively to 171.3 (+/-16.9), 3.4 (+/-0.6), and 26.1 (+/-17.6) points after 13.9 months (p < 0.05). The VAS pain improved from 5.3 (+/-2.7) to 2.4 (+/-1.8) points (p < 0.05). One patient with an osteochondral defect of 8 cm(2) at the medial femoral condyle (Ahlbäck's disease) still complains of pain during deep squatting. The dorsal medial femoral condyle can be recommended as donor site for OCT. The minimally invasive approach has proven to be safe and simple with a low complication rate.

Magnetic resonance imaging characteristics of the medial patellofemoral ligament lesion in acute lateral patellar dislocations considering trochlear dysplasia, patella alta, and tibial tuberosity-trochlear groove distance.

PURPOSE: The objective of this study was to analyze the injury patterns of the medial patellofemoral ligament (MPFL) in acute lateral patellar dislocations (LPDs) considering the anatomically relevant factors of patellar instability. METHODS: Knee magnetic resonance images were collected from 73 patients within 7 weeks after LPD, and the injury patterns of the MPFL were evaluated for trochlear dysplasia, for patellar height, and for the tibial tuberosity-trochlear groove (TT-TG) distance. RESULTS: Injury to the MPFL was found in 98.6% of the patients (72 of 73) after the acute LPD, with a complete tear in 51.4% (37 of 72), most frequently localized at the femoral attachment site, and a partial tear in 48.6% (35 of 72). Injury to the femoral origin (Fem), to the midsubstance (Mid), and to the patellar insertion (Pat) of the MPFL was found in 50.0% (36 of 72), 13.9% (10 of 72), and 13.9% (10 of 72), respectively. More than 1 site of injury was found in 22.2% (16 of 72), most frequently as a combined injury at the femoral origin and at the patellar insertion sites (Pat+Fem) (13 of 16). The study population, as well as the Pat, Fem, and Pat+Fem subgroups, showed significantly different values of trochlear dysplasia and patellar height when compared with the control group, whereas the data of the Mid group were not significantly different. In addition, injury at the patellar insertion (Pat) was accompanied by a significantly increased TT-TG distance when compared not only with the control group but also with the Fem, Mid, and Pat+Fem groups. CONCLUSIONS: The data from our study indicate that patterns of MPFL injury depend on trochlear dysplasia, patellar height, and TT-TG distance. They show a new aspect in the complex interplay between active, passive, and static stabilizers of the patellofemoral joint. LEVEL OF EVIDENCE: Level IV, diagnostic case-control study.

Impact of monopolar radiofrequency energy on subchondral bone viability.

The purpose of this study was to analyze the impact of monopolar radiofrequency energy treatment on subchondral bone viability. The femoral grooves of six chinchilla bastard rabbits were exposed bilaterally to monopolar radiofrequency energy for 2, 4 and 8 s, creating a total of 36 defects. An intravital fluorescence bone-labeling technique characterized the process of subchondral bone mineralization within the 3 months following exposure to radiofrequency energy and was analyzed by widefield epifluorescence optical sectioning microscopy using an ApoTome. After 2 s of radiofrequency energy exposure, regular fluorescence staining of the subchondral bone was evident in all samples when compared to untreated areas. The depth of osteonecrosis after 4 and 8 s of radiofrequency energy treatment averaged 126 and 942 microm at 22 days (P < .05; P < .01). The 4 s treatment group showed no osteonecrosis after 44 days whereas the depth of osteonecrosis extended from 519 microm at 44 days (P < .01), to 281 microm at 66 days (P < .01) and to 133 microm at 88 days (P < .05) after 8 s of radiofrequency energy application. Though radiofrequency energy may induce transient osteonecrosis in the superficial zone of the subchondral bone, the results of this study suggest that post-arthroscopic osteonecrosis appears to be of only modest risk given the current clinical application in humans.