Evaluating rotational kinematics of the knee in ACL-ruptured and healthy patients using 3.0 Tesla magnetic resonance imaging

Purpose

Rotational knee laxity is an important measure in restoring knee stability following anterior cruciate ligament (ACL) injury, but is difficult to quantify with current clinical tools. The hypothesis of the study is that there is greater tibial rotation (TR) in women than men, and also in ACL-deficient than healthy knees.

Methods

Sixteen healthy (8 men, 26.8?±?6.4?years; 8 women, 26.9?±?3.8?years) and ten ACL-deficient (5 men, 33.6?±?10.5?years; 5 women, 36.3?±?10.7?years) subjects received bilateral knee MRI in 15° of flexion using a custom device to apply a constant axial compressive load (44?N). A rotational torque (3.35?Nm) was sequentially applied to obtain images at internal and external rotation positions. T ₂-weighted images were acquired in internal and external rotation. Images were segmented and TR was calculated. To assess reproducibility, six knees were scanned twice on separate days. Group comparisons were made with unpaired t tests, while intrasubject comparisons were made using paired t tests.

Results

Healthy women demonstrated greater TR than men (13.6°?±?4.7° vs. 8.3°?±?3.6°; P?=?0.001). Male ACL-deficient knees showed greater TR than the contralateral knee (15.7°?±?6.9° vs. 7.7°?±?5.6°; P?=?0.003), and compared to male controls (P?=?0.002). ACL-deficient women showed greater TR compared to their contralateral leg (15.1°?±?2.3° vs. 10.0°?±?4.3°; P?=?0.01). The intraclass correlation coefficient of the TR measurement was 0.913, and the SEM?=?1.1°.

Conclusions

Kinematic MRI is a reproducible method to quantify total knee rotation. Women have more rotational laxity than men, particularly in the external rotation position. ACL rupture leads to increased rotational laxity of the knee.

Level of evidence

Retrospective case–control series, Level III.     

Functional knee brace use effect on peak vertical ground reaction forces during drop jump landing

Purpose

The aim of the study was to investigate the landing strategies used by non-injured athletes while wearing functional knee braces (FKB, BR condition) during a drop jump task compared with non-injured, non-braced (NBR condition) subjects and also to ascertain whether accommodation to a FKB was possible by non-injured BR subjects.

Methods

Twenty-three healthy male provincial and national basketball and field hockey athletes (age, 19.4?±?3.0?years) were tested. Each subject was provided with a custom-fitted FKB. Five NBR testing sessions were performed over 3?days followed by five BR testing sessions also over 3?days, for a total of 17.5?h of testing per condition. Each subject performed eight trials of the drop jump task during each testing session per condition. Single-leg peak vertical ground reaction forces (PVGRF) and the time to PVGRF were recorded for each NBR and BR trail.

Results

The BR group mean PVGRF at landing was significantly lower (1,628?±?405?N, 2.1?±?0.5 BW versus 1,715?±?403?N, 2.2?±?0.5 BW, F _1,22?=?6.83, P?=?0.01) compared with NBR subjects, respectively. The group mean time to PVGRF was not statistically longer during the BR condition (F _1,22?=?0.967, P?=?0.3). Further, an accommodation trend was noted as percent performance difference decreased with continued FKB use.

Conclusions

The significantly lower group mean PVGRF while using a FKB could keep traumatic forces from reaching the ACL until the active neuromuscular restraints are activated to provide protection to the knee joint ligaments. Also, accommodation to FKB is possible after approximately 14.0?h of brace use. The results of this paper will assist clinicians in providing information to their patients regarding a FKB ability to offer protection to an ACL-deficient knee or to address concerns about early muscle fatigue, energy expenditure, heart rate, and decrease in performance level.

Level of evidence

Prospective study, Level I.     

Length-change patterns of the collateral ligaments after total knee arthroplasty

Purpose

Total knee arthroplasty (TKA) is a procedure with function dependent upon correct tensioning of the soft-tissue constraints. The purpose of this study was to examine the length-change behaviour of the collateral ligaments during knee flexion–extension before and after TKA. The influence of differing degrees of internal-external rotation of the femoral component on slackening/tightening of the collateral ligaments during knee flexion was to be studied.

Methods

The length-change patterns of the collateral ligaments were measured in eight intact knees in vitro: sutures were passed along the ligaments and attached to displacement transducers. Measurements were repeated after TKA with the femoral component in neutral rotation, then with 5° internal and 5° external rotation.

Results

Both the MCL and LCL slackened during knee flexion from 0° to 110° flexion, at all stages of the experiment. In the native knee, the MCL slackened 2?mm, whilst the LCL slackened 7?mm. The MCL slackened a further 3?mm and the LCL a further 4?mm during flexion post-TKA. A 5° external rotation of the femoral component slackened the MCL 2?mm more and tightened the LCL by 2?mm. The opposite effects resulted from 5° internal rotation.

Conclusions

The collateral ligaments slackened more than normal following TKA, and these length changes were increased by femoral component rotation. External rotation of the femoral component to address patellar tracking may slacken the MCL and thus lead to valgus instability in the flexed knee.     

Less femorotibial rotation and AP translation in deep-dished total knee arthroplasty. An intraoperative kinematic study using navigation

Purpose

Hyper-congruent inserts have been proposed as another means of posterior stabilization in total knee arthroplasty. Their kinematics, partially unexplored, is reported to be possibly erratic. The objectives of the present study were to detect whether prostheses with such a constrained design would provide antero-posterior (AP) stability without interfering with high flexion.

Methods

The kinematics of 10 knees replaced with hyper-congruent inserts was tested intra-operatively with a specially designed navigation system (Praxim, La Tronche, Isère, France), to measure AP displacements of femoro-tibial contact points at knee flexion.

Results

Femoro-tibial contact points in full extension were in a posterior position compared to their initial position before implantation (8?±?6?mm medially, 15?±?10?mm laterally, P?P?P?Conclusions Hyper-congruent prostheses partially stabilized femoral condyles at knee flexion. Posterior displacements were reduced with no consequence on range of flexion. Posterior stabilization was imperfect, and paradoxical displacements were detected by navigation, which could therefore help optimize knee balance.

Level of evidence

Diagnostic study, Level II.     

An alternative method to create extramedullary references in total knee arthroplasty

Purpose

Historically, extramedullary techniques have focused on finding the femoral head center and referred mainly to the anterosuperior iliac spine (the FHC method) in total knee arthroplasty (TKA). The purpose of this study was to evaluate a new extramedullary alignment system that uses neutral overall limb mechanical alignment as an extramedullary reference (the MA method).

Methods

A retrospective review of 1018 TKAs (508 FHC group, 510 MA group) was performed to compare the radiographic results obtained using these two methods. There were 75 male patients and 577 female patients with varus osteoarthritis of the knee. Limb and prosthesis alignments in the coronal plane were investigated at 2?months after surgery.

Results

The accuracies of postoperative alignments of implanted prostheses were better in the MA group than in the FHC group, as assessed by (1) overall limb alignment (MA group, varus 1.4°?±?2.7°; FHC group, varus 2.2°?±?2.9°), and (2) femoral component coronal alignment (MA group, 89.4°?±?2.3°; FHC group, 88.0°?±?2.7°). Overall limb alignment was within 0°?±?5° of the mechanical axis in 96.1% of the MA group and in 86.6% of the FHC group. Mean femoral component medial angle was within 0°?±?5° in 98.4% of the MA group and in 92.5% of the FHC group.

Conclusion

The accuracies of the postoperative radiographic alignments of implanted prostheses were found to be improved when the mechanical axis of the overall lower limb was used as an extramedullary reference. This new reference system would help to achieve correct limb and prostheses alignments during TKA.

Level of evidence

III.     

No difference between tibia-first and femur-first techniques in TKA using computer-assisted surgery

Purpose

The measured resection technique and the gap-balancing technique are two philosophies used in total knee surgery. It is still unknown whether one or the other technique provides superior results when computer-assisted surgery is performed. We hypothesized that the gap-balancing technique improves joint stability because the technique relies primarily on the soft tissue.

Methods

A prospective controlled study was performed in 116 patients using the tibia-first or femur-first technique. The Columbus^TM total knee system and the Orthopilot^? (Aesculap^? AG, Tuttlingen, Germany) navigation system were used in all cases. Sixty-three patients were allocated to the femur-first technique (group F) and 53 patients to the tibial first technique (group T). The mean follow-up time was 11.4?±?1.1?months. The KSS, KOOS and SF-36 were taken prior to surgery and at the time of follow-up for clinical assessment. Long-leg weight-bearing radiographs were performed to assess ligament alignment. Radiographs in varus and valgus stress were performed using the Telos^?-Instrument (Telos^? GmbH, Greisheim, Germany) under a force of 15 N at the time of follow-up for the assessment of medial–lateral stability. The nonparametric t test (Mann–Whitney U-test) was used in order to compare the ligament stability and the scores between group F and group T.

Results

The lateral joint space opening for groups F and T was 3.4°?±?1.4° and 3.9°?±?1.7°, respectively (n.s.), and the medial joint space opening for groups F and T was 4°?±?1.4° and 4.1°?±?1.7°, respectively (n.s.). The femorotibial mechanical axis for groups F and T revealed 1.4°?±?1.2° and 0.7°?±?2.0° of varus, respectively (p?=?0.138). The clinical assessment showed significant improvement according to KSS, KOOS and SF-36 in all subscales. Neither of the sores showed significant differences between the two groups.

Conclusion

The surgeon should use his/her preferred surgical technique providing the implantation is performed with computer assistance. It remains unclear whether the same findings will occur after conventional surgery.

Level of evidence

II.     

Lateral release and medial plication for recurrent patella dislocation

Purpose

This study aims to report the long-term results of lateral release and medial plication in patients with recurrent patellar dislocation.

Methods

In this study, 31 patients who underwent surgery for recurrent patellar dislocation were retrospectively reviewed between 1994 and 2004. Among the 31 patients were 12 male and 19 female patients. The average age was 23.9?±?4.8?years, and the mean follow-up period was 11.6?±?2.4?years.

Results

Three patients had postoperative dislocations. The mean Kujala score significantly improved from 57.5?±?13.2 points preoperatively to 89.2?±?8.7 points at the final follow-up (P?<?0.0001). The median Tegner activity score significantly improved from 3 (range, 1?C5) at preoperative examination to 7 (range, 3?C9) at the final follow-up (P?<?0.0001). Ten patients were rated as excellent, 18 as good, 2 as fair, and 1 as poor. The congruence angle improved from 16.5°?±?3.0° to ?2.8°?±?2.7°, and the lateral patellofemoral angle improved from ?4.2°?±?1.9° to 8.2°?±?2.5°. There was no case of osteoarthritis at the final follow-up.

Conclusions

Percutaneous lateral release and medial plication showed satisfactory results with limited morbidity in the long-term follow-up. This traditional method remains a simple and effective surgical procedure for recurrent patellar dislocation.

Level of evidence

Therapeutic, Level IV.     

Clinical evaluation of a commercial surface-imaging system for patient positioning in radiotherapy

Background

Laser scanning-based patient surface positioning and surveillance may complement image-guided radiotherapy (IGRT) as a nonradiation-based approach. We investigated the performance of an optical system compared to standard kilovoltage cone-beam computed tomography (CBCT) and its potential to reduce the number of daily CBCTs.

Patients and methods

We analyzed the patient positioning of 153 treatment fractions in 21 patients applied to three different treatment regions. Patients were first scanned with CBCT, shifted to the optimal isocenter position, and an optical scan was performed to verify the matching in relation to CBCT.

Results

For the head-and-neck region, the lateral/longitudinal/vertical/rotational/roll and pitch shift was 0.9?±?1.8?mm/?2.7±?3.8?mm/?0.8±?3.6?mm/0.0±?1.1°/?0.5±?2.1°/0.2±?1.6°. For the thorax, the lateral/longitudinal/vertical/roll and pitch shift was ?1.2±?3.6?mm/0.8±?5.1?mm/0.8±?4.3?mm/0.6±?1.4°/0.1±?0.9°/0.3±?1.0°. For the pelvis, the respective values were ?2.5±?4.1?mm/4.6±?7.3?mm/?5.1±?7.4?mm/0.3±?1.1°/-0.5±?1.0°/0.3±?2.1°. In total, the recorded disagreement was ?1.0±?3.6?mm/1.0±?6.3?mm/?1.8±?5.9?mm/0.3±?1.2°/?0.3±?1.5°/0.2±?1.7°.

Conclusion

This analysis showed good agreement between the optical scanner approach and CBCT. The optical system holds potential to ensure precise patient positioning and reduced CBCT frequency in tumor locations with fixed relation to surface structures.     

Alteration in skin sensation following knee arthroplasty and its impact on kneeling ability: a comparison of three common surgical incisions

Purpose

Disturbance in skin sensation is a recognised, often unpleasant consequence of knee replacement for many patients and may affect function especially kneeling. The aim of this study was to compare post-operative changes in skin sensation following total (TKA) and unicompartmental knee (UKA) arthroplasties using three different incision types and its effect on kneeling ability.

Methods

Skin sensation was recorded using a purpose-designed grid over the front of the knee in 72 patients (78 knees) following knee arthroplasty. Surface area of sensory change, length of incision, and kneeling ability were recorded and compared between three different types of incision; long antero-medial and midline for TKA, and short medial for UKA.

Results

The average length of the long antero-medial incision was 19?±?5?cm with an average area of sensory alteration of 88?±?56?cm². The average length of the midline incision was 18?±?3?cm with an average area of sensory alteration of 57?±?52?cm². The short medial incision used for UKA averaged 11?±?3?cm in length with an average area of sensory alteration of 54?±?45?cm². Long antero-medial produced a significantly greater area of sensory alteration than standard short medial (P?=?0.017), but not the midline incision. There was a significant positive correlation of incision length with reduced sensation. Patients unable to kneel demonstrated a significantly larger area of hypersensitivity than patients who could kneel (P?=?0.002).

Conclusions

Increased length of incision results in a greater surface area of sensory change in the front of the knee. This finding was greatest in the long antero-medial incisions used in TKA. The inability to kneel following knee arthroplasty is associated with increased area of hypersensitivity of the anterior knee.

Level of evidence

Prospective comparative study, Level II.     

Muscle activity around the knee and gait performance in unicompartmental knee arthroplasty patients: a comparative study on fixed- and mobile-bearing designs

Purpose

Unicompartmental knee arthroplasty (UKA) offers clinical and functional advantages over total knee arthroplasty. The aim of this study was to compare the functional recovery of patients with mobile UKA versus fixed-bearing designs by state-of-the-art gait analysis and, in particular, by assessing muscular activity.

Methods

Ten patients with the Oxford (mobile bearing) and ten patients with Optetrak (fixed bearing) UKA were evaluated at a minimum follow-up of 1?year post-operatively by gait analysis, which includes the main time–distance parameters, kinematics and kinetics of the replaced knee, and muscular activity of the main relevant muscles. Twenty healthy young subjects were used as controls.

Results

The mean International Knee Society score was 92.7?±?11.2 for all 20 UKA knees; for the Oxford UKA, it was 94.1?±?9.5; and for the Optetrak UKA, it was 91.5?±?12.9, although follow-up was significantly lower for the latter. Time–distance parameters showed a slower gait in both groups compared with that of controls, and the Oxford group had values closer to the controls. Knee joint flexion was similar to that of controls at initial contact and loading response with no differences between groups. In all patients, the joint moments were smaller to that of controls. Residual abnormalities such as the prolonged rectus femoris activity were present in both designs, and the only difference distinguishing the Optetrak group from the others was the combined co-contraction of the hamstrings.

Conclusions

A good restoration of gait was achieved by most unicompartmental knee patients independently of the UKA design, although some abnormalities persisted in muscle activity around the knee.

Level of evidence

Retrospective comparative study, Level III.     

High-resolution ultrasound evaluation of extrinsic wrist ligaments in patients affected by rheumatoid arthritis

Objectives

To evaluate the ultrasound features of the extrinsic wrist ligaments in rheumatoid arthritis (RA) patients in comparison with healthy volunteers.

Methods

Twenty-one consecutive patients affected by RA (12 men, 9 women; mean age 57?±?14.6 years) were compared with 21 controls (12, 9; 54?±?12.1, respectively). Wrists were evaluated using ultrasound on both palmar and dorsal sides along each ligament, using carpal bones as references. The following ligaments were studied: radioscaphocapitate, radiolunotriquetral, palmar ulnolunate, palmar ulnotriquetral, dorsal radiotriquetral, dorsal ulnotriquetral, and radial collateral ligament. Ligament number and thickness were noted. Echotexture was rated as fibrillar, fragmented, or heterogeneous; the surface was rated as smooth or blurred.

Results

The number of palmar ulnolunate and palmar ulnotriquetral ligaments detected by ultrasound in patients was significantly lower than in controls (P?=?0.031 and P?=?0.037, respectively). All ligaments had significantly more fragmented or heterogeneous echotexture and blurred surface and were significantly thinner in patients than in controls (P?Conclusions Extrinsic wrist ligaments were less detectable and thinner in patients affected by RA compared with healthy volunteers matched for age and sex. Ligament thinning did not directly correlate with RA duration and clinical parameters.

Key Points

? Ultrasound is increasingly used to evaluate normal anatomy of extrinsic wrist ligaments. ? Extrinsic wrist ligaments are thinner in rheumatoid arthritis patients than in controls. ? Extrinsic wrist ligaments are less easy to detect in rheumatoid arthritis patients. ? Ligament thinning and detectability are not related to clinical parameters.     

MR findings associated with positive distraction of the hip joint achieved by axial traction

Purpose

To determine which MR-arthrography findings are associated with positive hip joint distraction.

Materials and methods

One hundred patients with MR arthrography of the hip using axial traction were included. Traction was applied during the MR examination with an 8 kg (females) or 10 kg (males) water bag, attached to the ankle over a deflection pulley. Fifty patients showing joint space distraction were compared to an age- and gender-matched control group of 50 patients that did not show a joint distraction under axial traction. Two radiologists assessed the neck-shaft angle, lateral and anterior center-edge (CE) angles, CE angles in the transverse plane, extrusion index of the femoral head, acetabular depth, alpha angle, acetabular version, ligamentum teres, joint capsule and ligaments, iliopsoas tendon and the labrum.

Results

Mean joint space distraction in the study group was 0.9?±?0.6 mm. Patients with positive joint space distraction had significantly higher neck-shaft angles (control group 131.6?±?5.4°/study group 134.1?±?6.1°, p?<?0.05), smaller lateral CE angles (38.1?±?5.9°/34.6?±?7.2°, p?<?0.05), smaller overall transverse CE angles (161.4?±?9.9°/153.6?±?9.6°, p?<?0.001), smaller acetabular depth (4.1?±?2.4 mm/5.8?±?2.5 mm, p?<?0.01), higher alpha angles (53.5?±?7.8°/59.2?±?10.1°, p?<?0.01) and a thicker ligamentum teres (4.7?±?1.4 mm/5.4?±?1.8 mm, p?<?0.05). The other parameters revealed no significant differences. ICC values for interobserver agreement were 0.71–0.95 and kappa values 0.43–0.92.

Conclusion

Increased neck-shaft angles, small CE angles, small acetabular depth, higher alpha angles and a thick ligamentum teres are associated with positive joint distraction.

     

The in vivo effects of unloading and compression on T1-Gd (dGEMRIC) relaxation times in healthy articular knee cartilage at 3.0 Tesla

Purpose

The purpose was to investigate the in vivo effects of unloading and compression on T1-Gd relaxation times in healthy articular knee cartilage.

Materials and methods

Ten volunteers were enrolled, and dGEMRIC images of their right knee joints were obtained using 3.0-T MR at three timepoints: directly following exercise (“baseline”), approximately 15 min after unloading (“unloading”) and during application of a compressive force (50% of the body weight) generated by a loading device via a footplate (“compression”).

Results

Our analysis of variance of pooled data from all cartilage zones demonstrated a significant mean T1-Gd decrease of 56.6 ms between baseline and compression (p?<?0.001), and a significant mean decrease of 42.1 ms between unloading and compression (p?<?0.001). No significant difference was found between baseline and unloading. Higher mean T1-Gd values were observed in the cartilage contact zone (central femoral and tibial zones; 698.3?±?162.2 ms) than in the non-contact zone (anterior and posterior femoral and tibial zones, and dorsal femoral zone; 662.9?±?149.3 ms; p?<?0.01).

Conclusion

T1-Gd times appear to be sensitive to mechanical cartilage stress, and thus, further studies are warranted that investigate the relationship between the biochemical load response and the biomechanical properties of articular cartilage.     

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 anterior–posterior 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.     

Variation in joint stressing magnitudes during knee arthroscopy

Purpose

When performing knee arthroscopy, joint stressing is essential to increase the operative joint space. Adequate training of joint stressing is important, since high stressing forces can damage knee ligaments, and low stressing might not give sufficient operative space. As forces are difficult to transfer since they cannot be seen, simulators might be suited to train joint stressing as they can visualise the amount of applied stress. This requires the joint stressing thresholds to be validated. The purpose of this study was to measure the variation in the maximum joint stressing forces applied by various surgeons in vivo in a human population and based on that derive thresholds for safe stressing.

Methods

From studies on ligament failure properties, we inferred a theoretical maximum stressing force of 78 N. Twenty-one patients were included, and knee arthroscopies were performed by five experienced surgeons. Forces solely performed in the varus and in valgus direction were measured. A load sensor was mounted on a belt, which was rotated along the hip to measure both varus and valgus stressing. The measurements started as soon as the interior of the knee joint was visualised using joint stressing.

Results

The average maximum stressing force was 60 N (SD = 28 N). The mean first frame force was 47 N (SD = 34 N). No significant differences were found between varus and valgus stressing.

Conclusion

Since variation in stressing forces is high, offering training cases on simulators where the complete range of stressing forces can be experienced is recommended. Abiding to safety levels is essential to increase patient safety.     

Conventional or navigated total knee arthroplasty affects sagittal component alignment

Purpose

Navigation systems have recently been developed to achieve highly reliable prosthetic alignment in total knee arthroplasty (TKA). However, component alignment in the sagittal plane is less reliable than that in the coronal plane even when navigation systems are used. Previous reports examining men showed differences in targeted sagittal prosthetic alignments of TKA achieved using the conventional technique and various navigation systems. However, there have been few studies examining the use of this technique in women, who are the primary candidates for TKA.

Methods

Radiographs of the entire lower extremity were obtained from 20 elder women while standing and sagittal prosthetic alignments in TKA were planned using the conventional technique as well as three navigation approaches to establish reference frames, and the observations were compared.

Results

Sagittal alignments simulated using the radiographs for the conventional technique and navigation systems differed within a mean of 3.2°?±?1.7° (mean?±?SD) to 6.3°?±?2.0°. The use of different reference points on the distal femoral condyles (insertion point of the intramedullary rod, center of the anteroposterior direction of the femoral condyles, and most distal point of the femoral condyles) for each navigation system resulted in differences in the sagittal plane up to 3.0°?±?1.5°. The use of navigation systems resulted in a more hyperextended position between the femoral and tibial components compared to that for the conventional technique.

Conclusions

Targeted sagittal prosthetic alignments of TKA achieved using the conventional technique and various navigation systems differed in elderly women. The use of different reference points on the distal femoral condyle for navigation systems resulted in different alignment in the sagittal plane. This study showed that alignment tendencies are similar in men and women.

Level of evidence

Prognostic studies, IV.     

3-T MRI assessment of osteophyte formation in patients with unilateral anterior cruciate ligament injury and reconstruction

Objective

To define the number and distribution of osteophytes (OPs) in bilateral knee MRI (magnetic resonance imaging) of patients with unilateral anterior cruciate ligament (ACL) rupture.

Materials and methods

Bilateral knee MRIs of 20 patients with unilateral ACL rupture and reconstruction were retrospectively analyzed for OPs. OPs were graded following the KOSS (knee OA scoring system) classification and their compartmental distribution was assessed following the WORMS (Whole-Organ Magnetic Resonance Imaging Score) classification.

Results

All examined knees revealed OPs. Knees with ACL rupture showed significant (p?<?0.001) higher total numbers of OPs (mean 11.6; SD?±?4.4) than knees with intact ACL (mean 5.1; SD?±?2.3). Knees with ACL rupture showed increased OP formation in all knee compartments with predominance of marginal OPs in the lateral femorotibial compartment especially on the tibia.

Conclusions

Our results show that after knee injury with ACL rupture and reconstruction, all knee compartments were involved in post-traumatic increase of OP formation. The most affected compartment was the lateral femorotibial compartment on the tibial side.     

The shiny corner of the knee: a sign of meniscal osteochondral unit dysfunction

Objective

The purpose of this retrospective study is to describe the MRI findings of the “shiny corner” of the knee (bone marrow lesions at the meniscal-covered portions of the tibial plateau) and to determine its association with compromise of the medial meniscal-osteochondral unit.

Materials and methods

A retrospective review of 200 knee MRI exams was performed and images were evaluated in consensus by two musculoskeletal radiologists. Presence and location of a shiny-corner lesion was recorded, which was defined as a focal, peripheral hyperintense lesion on fluid-sensitive images at the superior portion of the medial tibial plateau. Meniscal and root ligament abnormalities were recorded, including tearing, degeneration, and extrusion.

Results

Sixty exams demonstrated a shiny-corner lesion. Shiny corners involved the medial rim of the medial tibial plateau in 50 cases, only involved the posterior rim in seven cases, and only involved the anterior rim in two cases. Patients with shiny corners were older than patients without shiny corners (mean, 53 years vs. 44 years, p?=?0.01). The shiny-corner sign was associated with tears of the medial meniscus, root ligament, and meniscal extrusion (p?Conclusions Shiny-corner lesions of the knee are associated with tears of the menisci and root ligaments. This observation supports the concept that the menisci protect the underlying covered portions of the tibial plateau.