Biomechanical evaluation of self-cinching stitch techniques in rotator cuff repair: The single-loop and double-loop knot stitches.

In rotator cuff repair, strong and reliable suturing is necessary to decrease failure rates. The biomechanics of two self-cinching stitches - the single-loop knot stitch (SLKS) and the double-loop knot stitch (DLKS) - and the modified Mason-Allen stitch (mMAS) were compared. Twenty-seven porcine infraspinatus tendons were randomized among the three stitches. Each was cyclically loaded (10-80-200 N for 50 cycles each) while the gap formation was measured. Next, ultimate load to failure was tested. The gap widths after cyclic loading were 8.72 ± 0.93 mm for the DLKS, 8.65 ± 1.33 mm for the mMAS, and 9.14 ± 0.89 mm for the SLKS, without significant differences. The DLKS showed the highest ultimate load (350.52 ± 38.54 N) compared with the mMAS (320.88 ± 53.29 N; p = 0.304) and the SLKS (290.54 ± 60.51 N; p < 0.05). The DLKS showed similar reliability and better strength compared with the mMAS, while the SLKS showed a slight but not significant decrease in performance. In our experience, the DLKS and SLKS have clinical advantages, as they are easy to perform and the self-cinching loop knot allows the surgeon to grasp degenerative tendon tissue. Initial intraoperative tightening of the suture complex (preloading) before locking is important in order to decrease postoperative elongation.

Comparison of the double loop knot stitch and Kessler stitch for Achilles tendon repair: A biomechanical cadaver study.

Tendon elongation after Achilles tendon (AT) repair is associated with the clinical outcome. Reliable suture techniques are essential to reduce gap formations and to allow early mobilization. Cyclic loading conditions represent the repetitive loading in rehabilitation. The aim of this study was to compare the Kessler stitch and double loop knot stitch (DLKS) in a cyclic loading program focussing on gap formation. Sixteen human cadaveric ATs were transected and sutured using either the Kessler stitch or DLKS (eight matched pairs). The suture-tendon configurations were subjected to cyclic loading and additional ultimate load to failure testing using the Zwick 1446 universal testing machine. Each AT survived cyclic loading, with a mean gap formation less than 5 mm after 1000 cycles. The mechanical properties of the Kessler stitch and DLKS were not significantly different after cyclic loading with a mean displacement of 4.57 mm (± 1.16) for the Kessler stitch and 4.85 mm (± 1.14) for the DLKS (P = .76). There were no significant differences in the ultimate load testing (P = .85). Both bioprotective techniques prevent excessive gaping in cyclic testing when tendon loading is moderate. Our data and those from literature of gap formation in cyclic and ultimate loading allow the conclusion, that early aggressive AT loading after repair (e.g. full weightbearing) overstrain simple as well as complex suture configurations. Initial intraoperative tightening of the knots (preloading) before locking is important to decrease postoperative elongation.

Sagittal magnetic resonance imaging-scan orientation significantly influences accuracy of femoral posterior condylar offset measurement.

BACKGROUND: In total knee arthroplasty the femoral posterior condylar offset (PCO) may serve as a potential branch for correct femoral component positioning. The technique of adjusting the sagittal magnetic resonance imaging (MRI)-scan on which it is measured has not been investigated in previous literature, but may be subject to variances due to knee joint positioning or axial localizer scan angulation. The purpose of this study was to investigate the effect of simulated femur rotation on the accuracy of PCO measurement. MATERIALS AND METHODS: Ten asymptomatic knee joints underwent MRI investigations. A sagittal plane perpendicular to the transepicondylar axis was defined as the true-sagittal plane (tsP). Sagittal images were reformatted in the tsP and angulated by 5° and - 5° in medial and lateral direction. In total each knee received three scans in 0°, 5° and - 5° axial localizer scan angulation. Medial and lateral PCO measurement was performed in each MRI-scan angulation. RESULTS: Simulated external rotation decreased medial PCO size by 1.7 mm (95% CI 0.5994-3.127) (p = 0.012), and simulated internal rotation increased medial PCO size by 2.1 mm (95% CI 1.142-2.994) (p = 0.001). Lateral PCO size increased by 1.9 mm (95% CI 0.5660-3.412) and decreased by 2.1 mm (95% CI 1.142-2.994) with simulated external and internal rotation, respectively (p = 0.011; p = 0.0007). CONCLUSION: This study shows the high sensitivity of medial and lateral PCO measurements to small changes of MRI axial localizer scan angulations simulating minor degrees of internal or external femur rotation. Thus, absolute PCO values should be interpreted with caution if the sagittal image acquisition is not standardized.

Accuracy of femoral tunnel placement in medial patellofemoral ligament reconstruction: the effect of a nearly true-lateral fluoroscopic view.

BACKGROUND: Reconstruction of the medial patellofemoral ligament (MPFL) is an established operative procedure for patients with recurrent episodes of lateral patellar instability. However, recent articles have reported remarkable complication rates, with nonanatomic femoral tunnel positioning in up to 64% of patients. PURPOSE: To evaluate the sensitivity of femoral tunnel placement using lateral fluoroscopic guidance to minor degrees of deviation from the true-lateral view using established radiographic landmarks. STUDY DESIGN: Controlled laboratory study. METHODS: Six human cadaveric femora were used for this study. A 6-mm radiopaque eyelet was used to mark the native femoral insertion of the MPFL according to previously described radiographic landmarks. Radiographic landmarks were also applied with the femur positioned in 2.5° and 5° of internal and external rotation, respectively, and with the femur in 2.5° and 5° of hip abduction and adduction, respectively. The distance between the center of the 6-mm eyelet to the center of the native femoral MPFL insertion, as established in the true-lateral view, was measured and determined as the degree of shift in each position. RESULTS: Hip adduction, abduction, and internal and external rotations of 2.5° resulted in a shift from the native femoral MPFL insertion point to a more distal (adduction), proximal (abduction), anterior (internal rotation), and posterior location (external rotation) of 2.7 ± 0.7, 2.0 ± 0.7, 2.7 ± 1.1, and 3.0 ± 1.3 mm, respectively (all P < .05). Malpositioning increased to a distance of 5.0 ± 0.7 mm distally, 3.6 ± 1.0 mm proximally, 5.2 ± 0.8 mm anteriorly, and 6.2 ± 0.6 mm posteriorly to the native insertion point when the attachment was marked with 5° of divergence from the true-lateral view (all P < .05). CONCLUSION: The results of this study indicate the high sensitivity of femoral tunnel placement using lateral fluoroscopic guidance to minor degrees of deviation from the true-lateral view. CLINICAL RELEVANCE: The study highlights the importance of an exact lateral view when fluoroscopic guidance is used for femoral tunnel positioning in the daily practice of MPFL reconstruction, and a possible explanation for the high incidence of nonanatomic tunnel placement is suggested.

Novel single-loop and double-loop knot stitch in comparison with the modified Mason-Allen stitch for rotator cuff repair.

PURPOSE: In rotator cuff repair, strong and long-lasting suturing techniques that do not require additional implants are needed. This study examines the ultimate load to failure and the Young's modulus at the suture-tendon interface for a novel single-loop knot stitch and double-loop knot stitch. These values are compared to those of the modified Mason-Allen stitch. METHODS: Twenty-four infraspinatus muscles with tendons were dissected from porcine shoulders (twelve Goettingen minipigs). The preparations were randomly allocated to three groups of eight samples. Load-to-failure testing of the single-loop knot stitch, the double-loop knot stitch and the mMAS were performed using a Zwick 1446 universal testing machine (Zwick-Roell AG, Ulm, Germany). RESULTS: The highest ultimate load to failure for the three techniques occurred with the double-loop knot stitch with a median value of 382.2 N (range 291.8-454.2 N). These values were significantly higher than those of the single-loop knot stitch, which had a median value of 259.5 N (range 139.6-366.3 N) and the modified Mason-Allen stitch, which had a median value of 309.3 N (range 84.55-382.9 N). The values of the single-loop knot stitch and the modified Mason-Allen stitch did not differ significantly. Regarding the Young's modulus, no significant differences were found between the double-loop knot stitch with a median value of 496.02 N/mm² (range 400.4-572.6 N/mm²) and the modified Mason-Allen stitch with 498.5 N/mm² (range 375.5-749.2 N/mm²) with respect to the stiffness of the suture-tendon complex. The median value for the Young's modulus of the single-loop knot stitch of 392.1 N/mm² (range 285.7-510.6 N/mm²) was significantly lower than those of the double-loop knot stitch and modified Mason-Allen stitch. CONCLUSION: This in vitro animal study demonstrated that both the single-loop knot stitch and the double-loop knot stitch have excellent ultimate load-to-failure properties when used for rotator cuff repair. The introduced single-loop knot stitch and double-loop knot stitch offer an alternative to other common used stitch techniques in rotator cuff repair.

Characteristics of femorotibial joint geometry in the trochlear dysplastic femur.

The medial and lateral tibia plateau geometry has been linked with the severity of trochlear dysplasia. The aim of the present study was to evaluate the tibial slope and the femoral posterior condylar offset in a cohort of consecutive subjects with a trochlear dysplastic femur to investigate whether the condylar offset correlates with, and thus potentially compensates for, tibial slope asymmetry. Magnetic resonance imaging was used to assess the severity of trochlear dysplasia as well as the tibial slope and posterior offset of the femoral condyles separately for the medial and lateral compartment of the knee joint in 98 subjects with a trochlear dysplastic femur and 88 control subjects. A significant positive correlation was found for the medial tibial slope and the medial posterior condylar offset in the study group (r(2) = 0.1566; P < 0.001). This relationship was significant for all subtypes of trochlear dysplasia and was most pronounced in the severe trochlear dysplastic femur (Dejour type D) (r(2) = 0.3734; P = 0.04). No correlation was found for the lateral condylar offset and the lateral tibial slope in the study group or for the condylar offset and the tibial slope on both sides in the control group. The positive correlation between the medial femoral condylar offset and the medial tibial slope, that is, a greater degree of the medial tibial slope indicated a larger offset of the medial femoral condyle, appears to represent a general anthropomorphic characteristic of distal femur geometry in patients with a trochlear dysplastic femur.

Which patellae are likely to redislocate?

PURPOSE: The purpose of this study was to identify the risk factors for recurrent lateral patellar dislocations and to incorporate those factors into a patellar instability severity score. METHODS: Sixty-one patients [male/female 35/26; median age 19 years (range 9-51 years)] formed the study group for this investigation. Within the study group, 40 patients experienced a patellar redislocation within 24 months after the primary dislocation, whereas 21 patients, who were assessed after a median follow-up of 37 months (range 24-60 months), had not experienced a subsequent episode of lateral patellar instability. In all patients, age at the time of the primary dislocation, gender, the affected body side, body mass index, bilateral instability, physical activity according to Baecke's questionnaire, the grade of trochlear dysplasia, patellar height, tibial tuberosity-trochlear groove (TT-TG) distance, and patellar tilt were assessed. The odds ratio (OR) of each factor with regard to the patellar redislocation was calculated using contingency tables. Based on these data, a "patellar instability severity score" was calculated. RESULTS: The patellar instability severity score has six factors: age, bilateral instability, the severity of trochlear dysplasia, patella alta, TT-TG distance, and patellar tilt; the total possible score is seven. Reapplying this score to the study population revealed a median score of 4 points (range 2-7) for those patients with an early episode of patellar redislocation and a median score of 3 points (range 1-6) for those without a redislocation (p=0.0004). The OR for recurrent dislocations was 4.88 (95% CI 1.57-15.17) for the patients who scored 4 or more points when compared with the patients who scored 3 or fewer points (p=0.0064). CONCLUSION: Based on the individual patient data, the patellar instability severity score allows an initial risk assessment for experiencing a recurrent patellar dislocation and might help differentiate between responders and non-responders to conservative treatment after primary lateral patellar instability. LEVEL OF EVIDENCE: Case-control study, Level III.

Radiologically hyperdense zones of the patella seem to be partial osteonecroses subsequent to fracture treatment.

The blood supply to the proximal patella is provided primarily via intraosseous vessels from the inferior patella. Two vascular systems within the patella are distinguished: Tiny arteries penetrate the middle third of the anterior patellar surface via vascular foramina and continue in a proximal direction. Additional vessels enter the patella at its distal pole, between the patellar ligament and the articular surface, and also run proximally. As a result of the double vascular supply to the distal portion and the vulnerable blood supply to the proximal part, localized osteonecroses subsequent to fracture may occur within the patella and nearly exclusively affect the upper portion of the patella. Such focal regions of osteonecrosis may appear radiographically as localized regions of hyperdensity within the patella. The aim of this study was to investigate the extent to which radiologically hyperdense areas, possibly representing localized osteonecrosis, may occur subsequent to surgical treatment of a patella fracture and the influence that they have on the outcome of the fracture. Retrospective analysis of 100 patients who had been treated operatively for a patella fracture from January 1998 to December 2008 was conducted. The subjective pain rating, clinical scores, and patient satisfaction scores were recorded. Existing X-rays were assessed with regard to possible increased radiological dense areas. After an average of 60.61 ( ± 33.88) months, it was possible to perform a clinical follow-up on 60 patients aged 45.48 ( ± 18.51) years. Radiographic follow-up of all patients revealed that nine patients (9%) exhibited a hyperdense area in the proximal patella portion. X-rays showed radiopaque areas between 1 and 2 months after surgery. In seven cases, the radiological finding disappeared after six months. In two patients with persisting radiologically dense areas, bone necrosis was verified by means of magnetic resonance imaging (MRI) examination and a histological assessment, respectively. The clinical outcome of these patients with a hyperdense area on the patella, in this small series, was not shown to be worse than those who demonstrated normal healing. Radiologically hyperdense areas subsequent to patella fracture may represent partial osteonecrosis caused by localized vascular compromise. This was confirmed by MRI and histological examinations in two patients with persistent hyperdense lesions. The clinical outcome of patients with hyperdense zones seems to be poorer than that of patients without such findings, but no statistical difference was shown in this small series. It is possible that earlier surgical treatment and thus a shorter ischemic period as well as tissue-conserving operative techniques could prevent the occurrence of partial necroses. This hypothesis would require further study.

Influence of tibial slope asymmetry on femoral rotation in patients with lateral patellar instability.

PURPOSE: The geometry of the tibial plateau and its influence on the biomechanics of the tibiofemoral joint has gained increased significance. However, no quantitative data are available regarding the inclination of the medial and lateral tibial slope in patients with patellar instability. It was therefore the purpose of this study to evaluate tibial slope characteristics in patients with patellar dislocations and to assess the biomechanical effect of medial-to-lateral tibial slope asymmetry on lateral patellar instability. METHODS: Medial and lateral tibial slope was measured on knee magnetic resonance images in 107 patients and in 83 controls. The medial-to-lateral tibial slope asymmetry was assessed as the intra-individual difference between the medial and lateral tibial plateau inclination considering severity of trochlear dysplasia. The effect of tibial slope asymmetry on femoral rotation was calculated by means of radian measure. RESULTS: Severity of trochlear dysplasia was significantly associated with an asymmetric inclination of the tibial plateau. Whereas the medial tibial slope showed identical values between controls and study patients (n.s.), lateral tibial plateau inclination becomes flatter with increasing severity of trochlear dysplasia (p < 0.01). Consequently, the intra-individual tibial slope asymmetry increased steadily (p < 0.01) and increased internal femoral rotation in 20° and 90° of knee flexion angles in patients with severe trochlear dysplasia (p < 0.01). In addition, the extreme values of internal femoral rotation were more pronounced in patients with patellar instability, whereas the extreme values of external femoral rotation were more pronounced in control subjects (p = 0.024). CONCLUSION: Data of this study indicate an association between tibial plateau configuration and internal femoral rotation in patients with lateral patellar instability and underlying trochlear dysplasia. Thereby, medial-to-lateral tibial slope asymmetry increased internal femoral rotation during knee flexion and therefore might aggravate the effect of femoral antetorsion in patients with patellar instability. LEVEL OF EVIDENCE: III.

Navigated cementless total knee arthroplasty - medium-term clinical and radiological results.

PURPOSE: The objective of this prospective study was to evaluate the medium-term clinical and radiological results after navigated cementless implantation, without patella resurfacing, of a total knee endoprosthesis with tibial and femoral press-fit components, with a focus on survival rate and clinical outcome. The innovation is the non-cemented fixation together with the use of a navigation system. SCOPE AND METHODS: Sixty patients with gonarthrosis were included consecutively in this study. In all cases, the cementless Columbus total knee endoprosthesis with a coating out of pure titanium was implanted, using a navigation system. The Knee Society Score showed a statistically significant increase from 75 (± 21.26) before surgery to 180 (± 16.15) after a mean follow-up of 5.6 (± 0.25) years. The last radiological examination revealed no osteolysis. No radiolucent lines were seen at any time in the area of the femoral prosthetic components. In the tibial area, radiolucent lines were seen in 24.4 % of the cases, mostly in the distal uncoated part of the stem. During follow-up, no prosthesis had to be replaced because of aseptic loosening while in 2 cases revision surgery was necessary due to septic loosening and in 1 case due to unexplainable pain. RESULTS AND CONCLUSIONS: Navigated cementless implantation of the Columbus total knee endoprosthesis yielded good clinical and radiological results in the medium term. The excellent radiological osteointegration of the prosthetic components, coated with a microporous pure titanium layer and implanted with a press-fit technique, should be emphasized.

Bioabsorbable interference screw versus bioabsorbable cross pins: influence of femoral graft fixation on the clinical outcome after ACL reconstruction.

PURPOSE: The aim of this study was to evaluate the clinical outcome and differences in anterior­posterior laxity of ACL reconstruction using a bioabsorbable interference screw for femoral graft fixation when compared to femoral bioabsorbable cross pin fixation. METHODS: Clinical outcome was evaluated among 59 patients 1 year after arthroscopic ACL reconstruction with hamstrings graft in a prospective, non-randomised study. In 31 cases, femoral fixation of the graft was performed using a bioabsorbable interference screw. In 28 cases, two bioabsorbable cross pins were used for femoral fixation. Patients were evaluated using Tegner, Lysholm and Marshall scores, the visual analogue scale for pain and KT-1000 arthrometer measurement. RESULTS: No significant difference (P ≥ 0.05) was observed at follow-up for the knee scores. The average Tegner score was 5.83 points (±2.00) for the interference screw fixation and 5.83 points (±1.24) for the cross pin fixation; the average Lysholm score was 93.58 (±5.79) to 92.72 (±6.34) points; and the average Marshall score 46.72 (±2.4) to 47.30 (±2.35) points. No significant difference was found for the visual analogue scale for pain. KT-1000 arthrometer measurement revealed a significant (P < 0.05) difference in the mean side-to-side anterior translation at all applied forces. At 67 N, the mean difference was 1.53 mm (±1.24) in the interference screw group and 0.47 mm (±1.18) in the cross pin group (P < 0.05). At 89 N, the mean differences were 1.85 mm (±1.29) versus 0.59 mm (±1.59), respectively, (P < 0.05), and maximum manual displacements were 2.02 mm (±1.26) versus 1.22 mm (1.18; P < 0.05). CONCLUSIONS: In ACL reconstruction with hamstrings graft, similar clinical results are obtained for the use of bioabsorbable cross pins when compared to bioabsorbable interference screws for femoral fixation. Cross pin fixation was superior with regard to the anteroposterior laxity as measured with KT-1000.

MRI but not arthroscopy accurately diagnoses femoral MPFL injury in first-time patellar dislocations.

PURPOSE: The purpose of this study was to investigate whether the femoral part of the medial patellofemoral ligament (MPFL) and its injury can be accurately assessed by standard knee arthroscopy in first-time patellar dislocations or whether preoperative MRI is required to determine injury location in patients where primary MPFL repair is attempted. METHODS: Twelve patients with acute first-time dislocations and MRI-based injury of the femoral MPFL and ten patients with recurrent patellar dislocations underwent knee arthroscopy with the use of a 30-degree optic and standard antero-medial and antero-lateral portals. The femoral origin was marked with a cannula under lateral fluoroscopy. Arthroscopic findings of the location of the native femoral MPFL and its injury were compared to the results of MRI and mini-open exploration. RESULTS: In acute cases, the average time from primary patellar dislocation to MRI evaluation was 3 days (1-9 days), and the average time from MRI to surgery was 8 days (3-20 days). The native femoral origin of the MPFL was not visible in any of the chronic cases during arthroscopy. In addition, in all acute cases, arthroscopy failed to directly visualize injury of the femoral MPFL (0 of 12), but mini-open exploration confirmed injury in 11 of 12 patients. This means that arthroscopy was less accurate than MRI for the diagnosis of femoral MPFL injury (P < 0.05). CONCLUSION: The results of this study indicate the limitations of knee arthroscopy in identifying the femoral disruption of the MPFL, a crucial injury that occurs in patellar dislocations. Thus, if a primary MPFL repair is planned, determination of the site of repair should be based on the preoperative MRI. LEVEL OF EVIDENCE: Diagnostic study of non-consecutive patients, Level III.

Total knee replacement with natural rollback.

A novel class of total knee replacement (AEQUOS G1) is introduced which features a unique design of the articular surfaces. Based on the anatomy of the human knee and differing from all other prostheses, the lateral tibial "plateau" is convexly curved and the lateral femoral condyle is posteriorly shifted in relation to the medial femoral condyle. Under compressive forces the configuration of the articular surfaces of human knees constrains the relative motion of femur and tibia in flexion/extension. This constrained motion is equivalent to that of a four-bar linkage, the virtual 4 pivots of which are given by the centres of curvature of the articulating surfaces. The dimensions of the four-bar linkage were optimized to the effect that constrained motion of the total knee replacement (TKR) follows the flexional motion of the human knee in close approximation, particularly during gait. In pilot studies lateral X-ray pictures have demonstrated that AEQUOS G1 can feature the natural rollback in vivo. Rollback relieves the load of the patello-femoral joint and minimizes retropatellar pressure. This mechanism should reduce the prevalence of anterior knee pain. The articulating surfaces roll predominantly in the stance phase. Consequently sliding friction is replaced by the lesser rolling friction under load. Producing rollback should minimize material wear due to friction and maximize the lifetime of the prosthesis. To definitely confirm these theses one has to wait for the long term results.

Construction-conditioned rollback in total knee replacement: fluoroscopic results.

Firstly, the way of implementing approximatively the initial rollback of the natural tibiofemoral joint (TFJ) in a total knee replacement (AEQUOS G1 TKR) is discussed. By configuration of the curvatures of the medial and lateral articulating surfaces a cam gear mechanism with positive drive can be installed, which works under force closure of the femoral and tibial surfaces. Briefly the geometric design features in flexion/extension are described and construction-conditioned kinematical and functional properties that arise are discussed. Due to a positive drive of the cam gear under the force closure during the stance phase of gait the articulating surfaces predominantly roll. As a result of rolling, a sliding friction is avoided, thus the resistance to motion is reduced during the stance phase. Secondly, in vivo fluoroscopic measurements of the patella tendon angle during flexion/extension are presented. The patella tendon angle/ knee flexion angle characteristic and the kinematic profile in trend were similar to those observed in the native knee during gait (0°-60°).

Patellar dislocations in children, adolescents and adults: a comparative MRI study of medial patellofemoral ligament injury patterns and trochlear groove anatomy.

PURPOSE: The first aim was to compare medial patellofemoral ligament injury patterns in children and adolescents after first-time lateral patellar dislocations with the injury patterns in adults. The second aim was to evaluate the trochlear groove anatomy at different developmental stages of the growing knee joint. MATERIALS AND METHODS: Knee magnetic resonance (MR) images were collected from 22 patients after first-time patellar dislocations. The patients were aged 14.2 years (a range of 11-15 years). The injury pattern of the medial patellofemoral ligament was analysed, and trochlear dysplasia was evaluated with regard to sulcus angle, trochlear depth and trochlear asymmetry. The control data consisted of MR images from 21 adult patients who were treated for first-time lateral patellar dislocation. RESULTS: After patellar dislocation, injury to the medial patellofemoral ligament was found in 90.2% of the children and in 100% of the adult patients. Injury patterns of the medial patellofemoral ligament were similar between the study group and the control group with regard to injury at the patellar attachment site (Type I), to the midsubstance (Type II) and to injury at the femoral origin (Type III) (all p>0.05). Combined lesions (Type IV) were significantly less frequently observed in adults when compared to the study group (p=0.02). The magnitude of trochlear dysplasia was similar in children, adolescents and adults with regard to all three of the measured parameter-values (all p>0.05). In addition, the articular cartilage had a significant effect on the distal femur geometry in both paediatrics and adults. CONCLUSION: First, the data from our study indicated that the paediatric medial patellofemoral ligament injury patterns, as seen on MR images, were similar to those in adults. Second, the trochlear groove anatomy and the magnitude of trochlear dysplasia, respectively, did not differ between adults and paediatrics with patellar instability. Thus, physicians are confronted with similar anatomical risk factors and similar injuries to the medial soft-tissue restraints in children when compared to adults with patellar instability.

[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.

Anatomy of lateral patellar instability: trochlear dysplasia and tibial tubercle-trochlear groove distance is more pronounced in women who dislocate the patella.

BACKGROUND: A trend toward young women being at greatest risk for primary and recurrent dislocation of the patella is evident in the current literature. However, a causative factor is missing, and differences in the anatomical risk factors between men and women are less defined. PURPOSE: To identify differences between the sexes in the anatomy of lateral patellar instability. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: Knee magnetic resonance images were collected from 100 patients treated for lateral patellar instability. Images were obtained from 157 patients without patellar instability who served as controls. Using 2-way analyses of variance, the influence of patellar dislocation, gender, and their interaction were analyzed with regard to sulcus angle, trochlear depth, trochlear asymmetry, patellar height, and the tibial tubercle-trochlear groove (TT-TG) distance. Mechanisms of injury of first-time dislocations were divided into high-risk, low-risk, and no-risk pivoting activities and direct hits. RESULTS: For all response variables, a significant effect was observed for the incidence of patellar dislocation (all P < .01). In addition, sulcus angle, trochlear asymmetry, and trochlear depth depended significantly on gender (all P < .01) but patellar height did not (P = .13). A significant interaction between patellar dislocation and gender was observed for the TT-TG distance (P = .02). The mean difference in TT-TG distance between study and control groups was 4.1 mm for women (P < .01) and 1.6 mm for men (P = .05). Low-risk and no-risk pivoting injuries were most common in women, whereas first-time dislocations in men occurred mostly during high-risk pivoting activities (P < .01). CONCLUSION: The data from this study indicate that trochlear dysplasia and the TT-TG distance is more prominent in women who dislocate the patella. Both factors might contribute to an increased risk of lateral patellar instability in the female patient as illustrated by the fact that dislocations occurred most often during low-risk or no-risk pivoting activities in women.

A new posterolateral approach without fibula osteotomy for the treatment of tibial plateau fractures.

The selection of a surgical approach for the treatment of tibia plateau fractures is an important decision. Approximately 7% of all tibia plateau fractures affect the posterolateral corner. Displaced posterolateral tibia plateau fractures require anatomic articular reduction and buttress plate fixation on the posterior aspect. These aims are difficult to reach through a lateral or anterolateral approach. The standard posterolateral approach with fibula osteotomy and release of the posterolateral corner is a traumatic procedure, which includes the risk of fragment denudation. Isolated posterior approaches do not allow sufficient visual control of fracture reduction, especially if the fracture is complex. Therefore, the aim of this work was to present a surgical approach for posterolateral tibial plateau fractures that both protects the soft tissue and allows for good visual control of fracture reduction. The approach involves a lateral arthrotomy for visualizing the joint surface and a posterolateral approach for the fracture reduction and plate fixation, which are both achieved through one posterolateral skin incision. Using this approach, we achieved reduction of the articular surface and stable fixation in six of seven patients at the final follow-up visit. No complications and no loss of reduction were observed. Additionally, the new posterolateral approach permits direct visual exposure and facilitates the application of a buttress plate. Our approach does not require fibular osteotomy, and fragments of the posterolateral corner do not have to be detached from the soft tissue network.

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.