Effect of Cross-sectional Area of the Hamstring Tendon Autograft on Failure Rate or Clinical Outcomes After Double-Bundle ACL Reconstruction: Tendon Autograft.

Background: In previous studies examining the relationship between graft size and failure rate after anterior cruciate ligament reconstruction (ACLR), graft size was determined as diameter of the bone tunnel, and graft failure was defined as revision surgery. Consequently, the correlation between graft size and postoperative recurrent instability could not be assessed. Purpose: (1) To intraoperatively measure the cross-sectional area (CSA) of the hamstring tendon (HT) autograft and compare the CSA of the autograft with the bone tunnel and (2) to assess the effect of the graft CSA on postoperative graft failure among patients who underwent double-bundle ACLR. Study Design: Case-control study; Level of evidence, 3. Methods: The study included 129 patients who underwent double-bundle ACLR using an HT autograft (mean ± SD age, 16.7 ± 1.7 years; all with a Tegner activity level ≥6). All patients had a minimum follow-up of 2 years. During surgery, the graft CSA was measured using an area micrometer, combining the anteromedial (AM) and posterolateral (PL) grafts. The total area of the bone tunnel was defined as the combined CSAs of the AM and PL tunnels as calculated by the diameter of the drill. The relationship between the CSAs of the combined HT graft and the bone tunnel was statistically compared, as was the relationship between graft CSAs and graft failure, defined as reinjury, recurrent instability manifested as quantitative laxity measurement, or revision ACLR. Results: The CSAs of the midsubstance of the combined AM and PL graft significantly correlated with those of the bone tunnels (femoral side, R 2 = 0.334, P < .0001; tibial side, R 2 = 0.421, P < .0001). As for the relationship between the graft CSA and ACLR failure, there was no significant difference in the graft CSAs between the groups with and without graft failure in any of the failure criteria (P = .188). Conclusion: The graft CSA was not a predictor of early failure after double-bundle ACLR using an HT autograft in this patient population.

Analysis of bone union after medial closing wedge distal femoral osteotomy using a new radiographic scoring system.

INTRODUCTION: To compare bone union after medial closing wedge distal femoral osteotomy (MCWDFO) with that after lateral closing wedge distal femoral osteotomy (LCWDFO) using a novel scoring system. MATERIALS AND METHODS: The data of 30 patients who received biplanar MCWDFO for valgus knees (MCWDFO group) were retrospectively examined and compared to that of 22 patients (25 knees) who underwent biplanar LCWDFO via a double-level osteotomy (DLO) for varus knees (LCWDFO group). The progression of bone union of the transverse osteotomy plane in the femur was assessed using a newly developed scoring system using radiographs taken immediately after surgery and 3 and 6 months postoperatively. The scoring system is based on a scale of zero to six points with higher scores indicating better bone union. The incidence of hinge fractures was assessed using CT images, and the rates of reoperation were evaluated using medical record data. RESULTS: The mean bone union score was significantly lower in the MCWDFO group than in the LCWDFO group 3 months (2.1 ± 1.9 vs. 3.7 ± 1.7, P < 0.01) and 6 months (3.8 ± 2.1 vs 4.9 ± 1.5, P < 0.05) postoperatively. The incidence ratio of hinge fractures was significantly higher in the MCWDFO group than in the LCWDFO group (70.0% vs. 32.0%, P < 0.01). Two patients in the MCWDFO group underwent reoperation for delayed bone union or non-union. CONCLUSION: Bone union progression was slower and hinge fractures were more frequently observed after MCWDFO than after LCWDFO via DLO. MCWDFO is technically challenging, and patients must be monitored closely during and after surgery.

Deterioration of patellofemoral cartilage status after medial open-wedge high tibial osteotomy.

PURPOSE: To identify parameters associated with deterioration of patellofemoral (PF) cartilage after open-wedge high tibial osteotomy (OWHTO) and determine predictive values. It was hypothesized that cartilage injuries in PF joints would progress after OWHTO in patients who need a large alignment correction. METHODS: Fifty-two knees in 47 patients who underwent bi-planer OWHTO for the treatment of medial compartment osteoarthritis from 2012 to 2017 and received a second-look arthroscopy at the time of plate removal (mean 14 months post-OWHTO) were assessed. Clinical outcomes were evaluated by the Knee Society Scores. Cartilage status in PF joints were evaluated arthroscopically using the International Cartilage Repair Society (ICRS) grading system. Patients were divided into two groups and patients who had progressed PF cartilage injury (progressed group) were compared with those who did not have progressed PF cartilage injuries (non-progressed group) using various parameters. The relationships between medial opening gap or change in the medial proximal tibial angle (ΔmPTA) and progression of PF cartilage injuries were examined by receiver operating characteristic (ROC) curve analysis. RESULTS: The mean Knee Society Scores were significantly improved after surgery (P < 0.01). The grades for the patella and trochlea progressed in 12 (23.0%) and 16 knees (30.8%), respectively. The mean preoperative hip-knee-ankle (HKA) angle, mechanical axis, and mPTA in the progressed group were significantly smaller than those in the non-progressed group (P < 0.01). The mean medial opening gap and ΔmPTA in the progressed group were significantly larger than those in the non-progressed group (P < 0.01). ROC curve analysis showed that the cut-off values of the medial opening gap and ΔmPTA for progression of PF cartilage injuries were 13 mm and 9°, respectively. Progression of PF cartilage injuries was more frequently observed in knees with a medial opening gap ≥ 13 mm (P = 0.019, odds ratio = 4.60) or a ΔmPTA ≥ 9° (P = 0.003, odds ratio 6.93) than knees with those of < 13 mm or 9°, respectively. CONCLUSIONS: Cartilage injuries in PF joints tended to progress after OWHTO in patients with medial opening gap ≥ 13 mm or ΔmPTA ≥ 9°. If medial opening gap is ≥ 13 mm or ΔmPTA is ≥ 9° in planning for OWHTO, other type of surgery may need to be considered to avoid early progression of PF cartilage injuries. LEVEL OF EVIDENCE: Level IV, therapeutic case series.

Analysis of Graft Length Change Patterns in Medial Patellofemoral Ligament Reconstruction via a Fluoroscopic Guidance Method.

BACKGROUND: A fluoroscopic guidance method for medial patellofemoral ligament (MPFL) reconstruction has been widely used to determine the anatomic femoral attachment site. PURPOSE: To examine the graft length change patterns in MPFL reconstruction with a fluoroscopic guidance method. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: Forty-four knees of 42 patients who underwent MPFL reconstruction for the treatment of recurrent patellar dislocation were examined prospectively. During surgery, suture anchors were inserted into the proximal one-third and center of the patella. A guide pin for the femoral tunnel was inserted into the position reported by Schöttle et al based on the true lateral view of the knee under fluoroscopic control. Changes in graft length patterns of the proximal and center anchors were examined through 0° to 120° of knee flexion. Favorable changes in length patterns were defined as meeting 2 of 3 criteria: (1) not long during flexion (≤3 mm between 30° and 120° of flexion) and either (2) nearly isometric during flexion between 0° and 90° or (3) slightly long during maximum extension (≤3 mm). Other patterns were considered unfavorable. If the change in length pattern was unfavorable, then the pin for the femoral tunnel was moved to different positions until it was favorable. Knees were separated into the favorable group and the unfavorable group. Differences between the groups regarding radiographic parameters were assessed. Student t test or chi-square test was used for statistical analysis. RESULTS: Of the 44 knees, 31 (70.5%) showed favorable patterns. However, 13 knees (29.5%) showed unfavorable patterns; therefore, the position of the pin was changed. The mean ± SD distance from the original position to the final position was 5.3 ± 1.1 mm distal for 7 patients and 5.2 ± 0.4 mm posterodistal for 6 patients. Technical errors, including a nontrue lateral view and the tip of the wire not being in the determined area, were found for 4 of 13 knees in the unfavorable group. There was no statistical difference in radiographic parameters between the groups. CONCLUSION: The graft length change pattern could be nonphysiologic at the position determined through the fluoroscopic guidance method; thus, caution may be necessary. The change in length pattern should be checked before graft fixation. If the length change pattern is unfavorable, then it is advisable to move it approximately 5 to 7 mm distally or posterodistally from the first position.

Tibiofemoral rotational alignment affects flexion angles in navigated posterior-stabilized total knee arthroplasty.

PURPOSE: To investigate the tibiofemoral rotational profiles during navigated posterior-stabilized (PS) total knee arthroplasty (TKA) and investigate the effect on post-operative maximum flexion angles. METHODS: Twenty-five subjects, treated with navigated PS TKA, were enrolled, and the effect of posterior cruciate ligament (PCL) resection and component implantation on tibiofemoral rotational kinematics was statistically evaluated. Then, the effect of rotational alignment changes on the post-operative maximum angles was retrospectively examined in 96 subjects using the multiple regression analysis. RESULTS: Tibial internal rotation was significantly increased in full extension (p < 0.01 and <0.001, respectively) and at 60° and 90° flexion (p < 0.05) after PCL resection, which further increased after implantation, compared with that before resection. The amount of tibial internal rotation from 90° flexion to maximum flexion was significantly decreased after PCL resection and implantation, compared with that before resection (p < 0.05). The internal changes in the rotational alignment were independent factors for the minimal improvement in the post-operative maximum flexion angles (R 2 = 0.078, p = 0.0067). CONCLUSION: PCL resection changed the tibial rotational alignment and decreased the amount of tibial internal rotation. The implantation of PS components further increased the internal rotational alignment and could not compensate for the tibiofemoral rotation. Finally, the internal changes in rotational alignment affected the improvement of the maximum flexion angles, suggesting that rotational alignment is an important factor for improving post-operative maximum flexion angles. LEVEL OF EVIDENCE: II.

Prothrombin time-international normalized ratio is a useful marker for edoxaban efficacy in preventing venous thromboembolism after total knee arthroplasty.

BACKGROUND: Deep vein thrombosis (DVT) is one of the main complications following total knee arthroplasty (TKA). In this study, oral administration of 15 mg edoxaban (a factor Xa inhibitor) once daily for 14 days efficiently prevented the incidence of DVT. Our hypothesis was that prothrombin time-international normalized ratio (PT-INR) on the third postoperative day could predict the incidence of DVT following TKA. METHODS: In this study, 286 subjects were enrolled and divided into two groups according to the presence or absence of DVT. Several variables [age, body mass index, postoperative D-dimer level, PT-INR, and functional recovery findings (standing)] were analysed to determine the predictors of DVT, and for DVT diagnosis, ultrasonography was performed for seven days after surgery. RESULTS: The PT-INR levels were significantly higher in the group that did not develop DVT (p = 0.01). Further analysis with logistic regression analysis and receiver operating characteristic curve was performed. The PT-INR on the third postoperative day was an independent factor of the incidence of DVT (odds ratio 0.210; p = 0.035). The cut-off PT-INR was calculated to be 1.425. CONCLUSION: PT-INR level is a useful marker in determining whether 15 mg edoxaban administration can prevent DVT after TKA. It is suggested that increment of edoxaban to control PT-INR over the cut-off point might prevent the incidence of DVT.

Stress distribution is deviated around the aperture of the femoral tunnel in the anatomic anterior cruciate ligament reconstruction.

PURPOSE: Final tunnel location in the anterior cruciate ligament (ACL) reconstruction is unpredictable due to tunnel widening and/or transposition. The mechanical stress around the tunnel aperture seems to be a major factor but is not fully investigated. The purpose of this study was to measure the stress from the ACL graft around the tunnel aperture when the ACL graft tension reaches its peak. METHODS: Six cadaveric knees were used. Single-bundle ACL reconstruction was performed using a hamstrings graft. Both femoral and tibial tunnels were created at the centre of the original ACL footprint. A 7-mm-internal-diameter aluminium cylinder with pressure sensors was placed in the femoral tunnel. Hamstrings graft with a microtension sensor was inserted. After fixation, passive extension-flexion was performed while monitoring the tunnel aperture pressure and the graft tension simultaneously. The pressure on the femoral tunnel aperture when the ACL graft tension reach its peak was compared between four directions. RESULTS: The ACL graft tension peaked (67 ± 49 N) at full extension (-5.8 ± 4.1°). Pressure at the femoral tunnel aperture was different between different directions (p < 0.01). Distal part had significantly larger pressure (1.7 ± 1.3 MPa) than the other directions (p < 0.01). Second largest pressure was carried in the anterior part (0.6 ± 0.5 MPa), followed by proximal and posterior parts (0.4 ± 0.3, 0.2 ± 0.2 MPa respectively). CONCLUSION: The stress distribution at the femoral tunnel aperture is not equal in different directions, while the distal part dominantly bears the stress from the ACL graft. Surgeons should pay close attention to the distal edge of the femoral tunnel which should be inside the anatomic ACL footprint eventually.

Posterior condylar offset influences the intraoperative soft tissue balance during posterior-stabilized total knee arthroplasty.

PURPOSE: This study aimed to clarify the influence of the posterior condylar offset (PCO) on intraoperative soft tissue balance including the joint component gap and varus ligament balance measured by an offset-type tensor during posterior-stabilized (PS) total knee arthroplasty (TKA). METHODS: In this study, 35 patients with osteoarthritis of the knee underwent PS TKA. Intraoperative soft tissue balance including the joint component gap and varus/valgus ligament balance were assessed at 0°, 10°, 45°, 90°, and 135° of flexion with an offset-type tensor that could be used with the femoral component placement and patellofemoral joint reduction. The correlations between the postoperative PCO and the intraoperative soft tissue balance parameters were assessed using simple regression analysis. RESULTS: The joint component gap at 0° extension was inversely correlated with the PCO (R = -0.41, p < 0.05). The joint component gap of 10°-0° was positively correlated with the PCO (R = 0.35, p < 0.05). No other soft tissue balance parameters were correlated with the PCO. CONCLUSIONS: A larger PCO was confirmed to reduce joint component gap in extension but not always in flexion in PS TKA.

Patient-based outcomes after medial patellofemoral ligament reconstruction.

PURPOSE: The purpose of this study was to evaluate subjective outcomes after medial patellofemoral ligament (MPFL) reconstructions. METHODS: Fifty-four knees of 46 patients who received MPFL reconstruction for recurrent patellar dislocations were examined with a minimum follow-up of two years. To assess patient-based outcomes, the Knee Injury and Osteoarthritis Outcome Score (KOOS) and the Kujala score were assessed. RESULTS: The mean Kujala score was significantly improved from 64.6 ± 22.1 pre-operatively to 84.7 ± 11.8 post-operatively (P < 0.001). The mean KOOS was also significantly improved post-operatively in all five subscales. Further, the mean scores of 41 out of the 42 questions for the KOOS were significantly improved after surgery, except those of the question about "grinding and clicking". When the KOOS was assessed individually, the scores on one or more subscales out of the five were worsened post-operatively in eight patients, and seven of the eight patients had decreased post-operative pain subscale scores. Furthermore, those eight patients (worse group) were compared with patients without any worsened scores on any of the subscales (better group). The mean pre-operative pain and sports/recreation function subscale scores were significantly higher in the worse group whereas the mean post-operative pain and symptoms subscale scores were significantly lower in the worse group than in the better group. CONCLUSIONS: Overall, satisfactory patient-based outcomes were obtained after MPFL reconstruction in most of the patients. However, patients who only have mild pain pre-operatively tend to have worse subjective outcomes, and a caution may be needed when performing MPFL reconstruction on these patients.

Local Administration of Simvastatin Stimulates Healing of an Avascular Meniscus in a Rabbit Model of a Meniscal Defect.

BACKGROUND: Repair of an avascular meniscus is challenging because of its low capacity for healing. Several reports have shown that simvastatin stimulates the anabolic activity of intervertebral fibrochondrocytes, suggesting that simvastatin may be used for the treatment of meniscal defects. PURPOSE: To test whether the local administration of simvastatin stimulates healing of an avascular meniscus in rabbits. STUDY DESIGN: Controlled laboratory study. METHODS: In 30 Japanese White rabbits, a cylindrical defect (1.5-mm diameter) was introduced into the avascular zone of the anterior part of the medial meniscus in bilateral knees. Either a gelatin hydrogel (control group) or simvastatin-conjugated gelatin hydrogel (simvastatin group) was implanted into the defect. Histological assessments were performed using qualitative scoring systems, and immunohistochemical analysis was performed at 12 weeks after surgery. The occupation ratio (OR) and safranin O staining occupation ratio (SOR) were evaluated quantitatively at each time point. Stiffness of the regenerated tissue was analyzed biomechanically at 12 weeks after surgery. Rabbit meniscal cells were cultured in the presence or absence of 0.5 µM simvastatin, and then real-time polymerase chain reaction was performed to evaluate gene expression. RESULTS: The qualitative score was significantly higher in the simvastatin group after 8 and 12 weeks (P = .031 and .035, respectively). The mean OR and SOR were also significantly higher in the simvastatin group (OR at 8 weeks: 0.396 ± 0.019 [control] vs 0.564 ± 0.123 [simvastatin], P = .008; OR at 12 weeks: 0.451 ± 0.864 [control] vs 0.864 ± 0.035 [simvastatin], P = .001; SOR at 8 weeks: 0.071 ± 0.211 [control] vs 0.487 ± 0.430 [simvastatin], P = .009; SOR at 12 weeks: 0.093 ± 0.088 [control] vs 0.821 ± 0.051 [simvastatin], P = .006). Immunohistochemical analysis showed that at 12 weeks, the reparative tissue was more strongly positive for type I collagen (COL1), type II collagen (COL2), bone morphogenetic protein 2 (BMP-2), and BMP-7 in the simvastatin group than in the control group. Biomechanical analysis showed significantly higher stiffness in the simvastatin group (2.417 ± 1.593 N/ms [control] vs 5.172 ± 1.078 N/ms [simvastatin]; P = .005). In rabbit meniscal cells, BMP-2 and BMP-7 were upregulated after 4 and 8 hours and after 7 and 14 days, whereas COL1A1 and COL2A1 were significantly upregulated by simvastatin after 7 and 14 days. CONCLUSION: The local administration of simvastatin promotes the regeneration of an avascular meniscus in the rabbit model of a meniscal defect. The mechanism may involve the upregulation of BMPs and the subsequent upregulation of COL1 and COL2. CLINICAL RELEVANCE: This study suggests that simvastatin stimulated intrinsic healing of an avascular meniscus. The local administration of simvastatin is safe and inexpensive and seems to be a promising treatment of meniscal injuries.

Histological analysis of the tibial anterior cruciate ligament insertion.

PURPOSE: This study was performed to investigate the morphology of the tibial anterior cruciate ligament (ACL) by histological assessment. METHODS: The native (undissected) tibial ACL insertion of six fresh-frozen cadaveric knees was cut into four sagittal sections parallel to the long axis of the medial tibial spine. For histological evaluation, the slices were stained with haematoxylin and eosin, Safranin O and Russell-Movat pentachrome. All slices were digitalized and analysed at a magnification of 20×. RESULTS: The anterior tibial ACL insertion was bordered by a bony anterior ridge. The most medial ACL fibres inserted from the medial tibial spine and were adjacent to the articular cartilage of the medial tibial plateau. Parts of the bony insertions of the anterior and posterior horns of the lateral meniscus were in close contact with the lateral part of the tibial ACL insertion. A small fat pad was located just posterior to the functional ACL fibres. The anterior-posterior length of the medial ACL insertion was an average of 10.8 ± 1.1 mm compared with the lateral, which was only 6.2 ± 1.1 mm (p < 0.001). There were no central or posterolateral inserting ACL fibres. CONCLUSIONS: The shape of the bony tibial ACL insertion was 'duck-foot-like'. In contrast to previous findings, the functional mid-substance fibres arose from the most posterior part of the 'duck-foot' in a flat and 'c-shaped' way. The most anterior part of the tibial ACL insertion was bordered by a bony anterior ridge and the most medial by the medial tibial spine. No posterolateral fibres nor ACL bundles have been found histologically. This histological investigation may improve our understanding of the tibial ACL insertion and may provide important information for anatomical ACL reconstruction.

Fibular axes are not a reliable landmark for tibial mechanical axes of osteoarthritic knees that underwent total knee arthroplasty.

PURPOSE: The sagittal fibular axis serves as an intra-operative landmark during conventional total knee arthroplasty (TKA); however, only a few relevant anatomical studies have been published regarding its use as an extramedullary guide. Furthermore, the correlation between the coronal fibular and tibial mechanical axes in osteoarthritic knees has been only reported once. Here, the hypothesis of this study is that the fibula can be a reliable intra-operative landmark, in the sagittal and coronal planes, among patients with osteoarthritis who have undergone TKA. METHODS: Osteoarthritic knees (n = 62) after TKA were evaluated using three-dimensional image-matching software. The angles between the tibial mechanical axis and the fibular shaft axis were measured in the sagittal and coronal planes. Moreover, correlations between the angles and patient-specific factors were evaluated. RESULTS: The mean angle between the tibial mechanical and fibular shaft axes was 2.6° ± 2.3° for posterior inclination in the sagittal plane and 0.9° ± 2.0° for varus inclination in the coronal plane. The percentage of subjects with the fibular shaft axis within 2° of the tibial mechanical axis was 17.7 and 69.3 % in the sagittal and coronal planes, respectively. No patient-specific factors were correlated with the angle between the tibial mechanical and fibular shaft axes. CONCLUSIONS: The angle between the tibial mechanical and fibular shaft axes differed among patients, independent of patient-specific factors, and did not appear to be a reliable intra-operative landmark. Surgeons should use values from individual pre-operative evaluations of the axis as reference for conventional TKA. LEVEL OF EVIDENCE: Case series with no comparison group, Level IV.

Joint gap assessment with a tensor is useful for the selection of insert thickness in unicompartmental knee arthroplasty.

BACKGROUND: The success of unicompartmental knee arthroplasty relies on a lot of factors such as correct osteotomy and proper soft-tissue tensioning. A selection of insert thickness depends solely on the surgeon's subjective feeling. Recently, a tensor that is designed to assess soft tissue balance during unicompartmental knee arthroplasty has been developed. The purpose of this study was to compare the component gap throughout the range of motion among different distraction forces and examine the correlation between the component gap and the insert thickness. METHODS: 30 cases of 29 patients were included. All the patients received a conventional medial Zimmer Unicompartmental High Flex Knee System. Using a tensor under 10, 20, 30, and 40 lb distraction forces, after femoral component placement, the component gaps were assessed throughout the range of motion. The correlations between the component gap and the insert thickness selected were examined. FINDINGS: The component gap showed the same kinematic pattern among the different distraction forces and the value increased in proportion to the increase of the distraction force in unicompartmental knee arthroplasty. The insert thickness in unicompartmental knee arthroplasty was found to have a strong positive correlation with the component gap from 10 to 45° of knee flexion with a distraction force of more than 20 lb INTERPRETATION: With the use of the tensor, surgeons can quantify the component gap and objectify their insert thickness decision compared with the use of tension gauge.

Three-dimensional analysis of bone tunnel changes after anatomic double-bundle anterior cruciate ligament reconstruction using multidetector-row computed tomography.

BACKGROUND: The femoral and tibial bone tunnel enlargement after anatomic double-bundle anterior cruciate ligament reconstruction (ACL-R) has not been fully documented. PURPOSE: To evaluate the region-specific bone tunnel volume changes and those transpositions using 3-dimensional multidetector-row computed tomography (MDCT) after anatomic double-bundle ACL-R. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: Eleven patients who underwent unilateral double-bundle ACL-R with hamstring tendon autografts were included in this study. MDCT scanning of their knees was performed at 3 weeks and 1 year after surgery. The bone tunnel regions were extracted from the MDCT images, and the longitudinal axis of each bone tunnel was divided into 3 equal sections. The centroids of the outside and the articular thirds were then extracted from the bone tunnel position. Changes in the bone tunnel volume and the transposition of the articular third were calculated and compared. RESULTS: At 1 year postoperatively, as compared with the 3-week postoperative value (set at 100%), the femoral bone tunnel volume of the anteromedial bundle (AMB) and posterolateral bundle (PLB) changed to 77.4% ± 15.3% and 102.3% ± 19.2% in the outside third and 122.3% ± 31.8% and 112.5% ± 34.4% in the articular third, respectively. The tibial bone tunnel volume of the AMB and the PLB changed to 108.6% ± 28.7% and 105.4% ± 22.6% in the tibial articular third and 54.9% ± 25.8% and 52.5% ± 26.9% in the outside third, respectively. The femoral outside third of the AMB and the tibial outside third of both the AMB and PLB were significantly reduced in bone tunnel volume. The centroid of the femoral articular third of the AMB moved 13°, 1.1 ± 0.6 mm posterodistally, and that of the PLB moved 35°, 0.8 ± 0.4 mm anterodistally. Furthermore, the centroid of the tibial articular third of the AMB moved 14°, 2.0 ± 1.6 mm posterolaterally, and that of the PLB moved 72°, 1.0 ± 1.3 mm posterolaterally. CONCLUSION: Compared with 3 weeks postoperatively, the articular side outlets of the femoral and tibial bone tunnels at 1 year postoperatively had enlarged slightly but statistically maintained their volume, and they had moved a little in the direction that the grafts were pulled.

Simulation of the optimal femoral insertion site in medial patellofemoral ligament reconstruction.

PURPOSE: To develop and validate a new simulation system to predict the optimal femoral insertion site of the medial patellofemoral ligament (MPFL) using preprogrammed conditions of graft length change. METHODS: A computed tomography scan was performed for constructing bone surface models of the patella and the femur. Lateral radiographs of the knee and axial radiographs of the patellofemoral joint at knee flexion were used for constructing a three-dimensional patellofemoral joint model by 3D-2D image matching at each knee flexion angle. To determine the optimal femoral insertion site, the following three conditions were devised: (1) MPFL behaves isometric from 0° to 60°, (2) MPFL is most taut at full extension, and (3) MPFL is slack at more than 60° of knee flexion. Every condition was applied to the femoral bone surface model, and the area that fulfilled all three conditions was defined as the optimal femoral insertion site of MPFL. Twenty knees of ten healthy volunteers were assessed to verify the simulation. Comparison between simulated optimal femoral insertion and anatomical insertion was done. RESULTS: The mean simulated optimal femoral insertion was close to the anatomical insertion site. There were no significant differences in the proximal-distal position and anterior-posterior position between the simulated insertion and the anatomical insertion sites. CONCLUSION: The system can be useful for predicting the optimal femoral insertion site as a part of a preoperative plan for MPFL reconstruction, and it may help surgeons to determine the optimal femoral insertion site during MPFL reconstruction.

Clinical outcomes of medial patellofemoral ligament reconstruction in patients with an increased tibial tuberosity-trochlear groove distance.

PURPOSE: Medial patellofemoral ligament (MPFL) reconstruction is performed to treat recurrent patellar dislocation (RPD). However, the effectiveness of MPFL reconstruction in patients with a severely lateralised tibial tuberosity remains unknown. In this study, the clinical outcomes of MPFL reconstruction in patients with an increased tibial tuberosity-trochlear groove (TT-TG) distance were examined. METHODS: A total of thirty-four patients who underwent MPFL reconstruction for RPD were retrospectively examined. Nineteen patients with a TT-TG distance of >20 mm (increased TT-TG distance group) were compared with 15 patients with a TT-TG distance of <20 mm (control group). Clinical outcomes of MPFL reconstruction were evaluated by occurrence of re-dislocation, Crosby and Insall grading system, apprehension sign, and Kujala and Lysholm scores. RESULTS: None of the patients reported re-dislocation. Apprehension sign remained in three patients in the increased TT-TG distance group and in one patient in the control group. According to the Crosby and Insall grading system, 9 patients (47%) were excellent, 9 (47%) were good, and 1 (5%) was fair to poor in the increased TT-TG distance group, while 6 (40%) were excellent and 9 (60%) were good in the control group. Kujala and Lysholm scores were significantly improved post-operatively in both groups. No significant correlations were observed between TT-TG distance and post-operative Kujala or Lysholm score. CONCLUSION: Overall clinical outcomes of MPFL reconstruction were favourable even in patients with an increased TT-TG distance. TT-TG distance of >20 mm may not be an absolute indication for medialisation of the tibial tuberosity when performing MPFL reconstruction. LEVEL OF EVIDENCE: Case-control study, Level III.

The influence of the tibial slope on intra-operative soft tissue balance in cruciate-retaining and posterior-stabilized total knee arthroplasty.

PURPOSE: This study aims to make clear the influence of the tibial slope on intra-operative soft tissue balance measurements using a tensor in cruciate-retaining and posterior-stabilized total knee arthroplasty (TKA). METHODS: Forty patients with osteoarthritis of the knee received TKAs (20 cruciate-retaining TKAs and 20 posterior-stabilized TKA). Soft tissue balance was measured using an offset type tensor at 0, 10, 45, 90, 135 degrees of knee flexion. The tibial slopes were measured by post-operative lateral radiograph. The correlation between the tibial slope and values of soft tissue balance were assessed. RESULTS: Joint component gap at 90° (R = 0.537, p < 0.01) and 135° (R = 0.463, p < 0.05) of flexion and joint component gap change value of 90-0° (R = 0.433, p < 0.05) showed positive correlations with tibial slope in posterior-stabilized TKA. There was no relationship between the tibial slope and the value of soft tissue balances in cruciate-retaining TKA. CONCLUSIONS: In the present study, we confirmed that increasing the tibial slope resulted in a larger flexion gap compared to extension gap in posterior-stabilized TKA. Surgeons should be aware that increasing the tibial slope is one factor responsible for widening the flexion-extension gap difference in posterior-stabilized TKA.

Tibial internal rotation is affected by lateral laxity in cruciate-retaining total knee arthroplasty: an intraoperative kinematic study using a navigation system and offset-type tensor.

PURPOSE: The purpose of this study was to test the hypothesis that intraoperative soft-tissue balance assessed by an offset-type tensor influences post-operative knee kinematics after cruciate-retaining (CR) total knee arthroplasty (TKA). METHODS: The influence of intraoperative soft-tissue balance on knee kinematics in CR-TKA was retrospectively analysed in 30 patients. Intraoperative soft-tissue balance parameters such as varus angle (varus ligament balance), joint component gap (centre gap), and medial and lateral compartment gaps were measured in the navigation system while applying 40-lb joint distraction force at 0°, 10°, 30°, 60°, 90°, and 120° of knee flexion using an offset-type tensor with the patella reduced. Tibial internal rotation and tibial anterior translation were measured as the differences between the values at 60° and 120° of flexion using the navigation system. Correlations between the soft-tissue parameters and post-operative knee kinematics were analysed. RESULTS: The varus ligament balance was positively correlated with tibial internal rotation at 60° and 90° of flexion (R = 0.54, P < 0.05; R = 0.60, P < 0.01, respectively). Furthermore, the joint component gap was positively correlated with tibial internal rotation at 90° of flexion (R = 0.44, P < 0.05), and the lateral compartment gap was positively correlated with tibial internal rotation at 60°, 90°, and 120° of knee flexion. CONCLUSIONS: The intraoperative varus ligament balance and joint component gap values were factors that predicted post-operative knee kinematics after CR-TKA. Lateral laxity at mid-to-deep knee flexion plays a significant role in tibial internal rotation. LEVEL OF EVIDENCE: III.

Kinematic factors affecting postoperative knee flexion after cruciate-retaining total knee arthroplasty.

PURPOSE: The purpose of this study was to investigate kinematic factors affecting postoperative knee flexion after cruciate-retaining (CR) total knee arthroplasty (TKA) by analysing pre- and postoperative knee kinematics. METHODS: We retrospectively analysed 58 patients with osteoarthritis who received the same implant series. Pre- and postoperative kinematics were measured intraoperatively using a navigation system. As a clinical outcome, we measured the knee flexion angle before and one year after surgery. Correlations among pre- and postoperative kinematics and postoperative flexion were analysed using simple linear regression analyses. RESULTS: Preoperative knee kinematics, including tibial internal rotation and anterior translation (R = 0.87, P < 0.001; R = 0.53, P < 0.001, respectively), were significantly correlated with postoperative kinematics. Preoperative varus-valgus movements improved significantly postoperatively; however, tibial internal rotation remained unchanged. Furthermore, postoperative knee flexion angle was significantly correlated with postoperative tibial internal rotation (R = 0.45, P < 0.001). CONCLUSIONS: Preoperative knee kinematics were unchanged even after CR-TKA. Postoperative tibial internal rotation is one of the most important factors affecting postoperative knee flexion.

Different pattern in gap balancing between the cruciate-retaining and posterior-stabilized total knee arthroplasty.

PURPOSE: In order to permit soft tissue balance under more physiological conditions during total knee arthroplasties (TKAs), an offset-type tensor was developed to obtain soft tissue balancing throughout the range of motion with reduced patello-femoral (PF) and aligned tibiofemoral joints. The main purpose of the present study was to assess intra-operative soft tissue balance using a navigation system with the offset-type tensor in both cruciate-retaining (CR) and posterior-stabilized (PS) TKAs. METHODS: One hundred and twenty TKAs--80 CR and 40 PS--were performed in patients with varus-type osteoarthritis using a computed tomography-free navigation system. The offset-type TKA tensor with a reduced and repaired PF joint and femoral component in place was used with the tibia first gap technique to balance soft tissues (joint component gap and ligament balance) at 0°, 10°, 30°, 60°, 90°, and 120° of flexion. The achievement in equalized rectangular gap at extension and flexion--joint component gap within ±3 mm between extension and flexion and ligament balance within ±3° at extension and flexion--was assessed retrospectively. RESULTS: Both types of implants showed similar patterns of soft tissue balance throughout the range of motion, whereas PS TKA had larger values especially at 60° or 90° of flexion than did CR TKA. In the achievement of equalized rectangular gaps at extension and flexion, CR TKA was superior to PS TKA. CONCLUSION: Using the tibia first gap technique with the tensor allows appropriate soft tissue balancing, especially in CR TKA. LEVEL OF EVIDENCE: Therapeutic studies, Level II.