Unicompartmental Knee Arthroplasty for Osteoarthritis Eliminates Lateral Thrust: Associations between Lateral Thrust Detected by Inertial Measurement Units and Clinical Outcomes.

The purpose of this study was to investigate the relationship between clinical outcomes and lateral thrust before and after unicompartmental knee arthroplasty (UKA) using inertial measurement sensor units. Eleven knees were evaluated with gait analysis. The varus angular velocity was used to evaluate lateral thrust. The femorotibial angle (FTA) and hip-knee-ankle angle (HKA) were used to evaluate lower-limb alignment, and the Oxford Knee Score (OKS) and Japanese Orthopaedic Association Score (JOA) were used to evaluate clinical outcomes. The mean pre-UKA peak varus velocity was 37.1 ± 9.8°/s, and that for post-UKA was 28.8 ± 9.1°/s (p = 0.00003), such that instabilities clearly improved. Assuming the definition of lateral thrust is when the varus angular velocity is more than 28.1°/s, 81.8% of patients had lateral thrust preoperatively, but this decreased to 55.6% postoperatively, such that the symptoms and objective findings improved. Both OKS and JOA improved after surgery. In addition, HKA was -7.9° preoperatively and -5.8° postoperatively (p = 0.024), and FTA was 181.4° preoperatively and 178.4° postoperatively (p = 0.012). There was a positive correlation between postoperative JOA and FTA, indicating that changes in postoperative alignment affected clinical outcomes. This study quantitatively evaluated the disappearance of lateral thrust by UKA, and it found that the stability can be achieved by UKA for unstable knees with lateral thrust.

Pediatric femoral shaft fracture requiring revision surgery for nonunion associated with vitamin D and K deficiencies: a case report.

BACKGROUND: Nonunion of femoral shaft fractures in children is rare, and there is no clear treatment protocol. In this case report, a pediatric femoral shaft fracture that developed in nonunion due to vitamin deficiency after osteosynthesis, which was successfully treated with vitamin augmentation and replacement with a rigid antegrade intramedullary nail, is described. CASE PRESENTATION: The patient is an 11-year-old Japanese girl. She injured her right femoral shaft fracture when she hit a wall after kickboarding down a hill and underwent osteosynthesis with a titanium elastic nail. Six months postoperatively, she developed nonunion, was found to be deficient in vitamins D and K, and was started on vitamin supplementation. She underwent replacement with a rigid antegrade intramedullary nail at 7 months postoperatively, and bone union was achieved 3 months after reoperation. CONCLUSION: When delayed union of a fracture is observed postoperatively, even in children without underlying disease, the cause of the problem must be investigated and treated promptly.

Evaluation of Medial Meniscal Extrusion Using Radiography.

Recently, there has been increasing interest in medial meniscal extrusion (MME), but few reports have evaluated MME via X-ray. In this study, the amount of MME and meniscal height at the medial border of the tibia were measured via X-ray with gradation processing. The extrusion length divided by the meniscal height yields the meniscal extrusion ratio, which was used as an index. In addition, the medial meniscal length of the part protruding from the medial border of the tibia on MRI was measured as an absolute value. Then, the correlation between the meniscal extrusion ratio and the amount of MME on MRI was examined, and there was a strong correlation between the meniscal extrusion ratio via X-ray and the amount of MME on MRI (correlation coefficient 0.860, p < 0.0001). The cut-off value of the meniscal extrusion ratio via X-ray for positive meniscal extrusion on MRI was 0.50, with an AUC of 0.9825, sensitivity of 0.9063, and specificity of 0.8663. From the present study, it was possible to measure the extrusion length and meniscal height via gradation processing, with X-ray and without MRI, and to calculate the meniscal extrusion ratio, which strongly correlates with the amount of MME on MRI.

Postoperative clinical outcomes for kinematically, restricted kinematically, or mechanically aligned total knee arthroplasty: a systematic review and network meta-analysis of randomized controlled trials.

BACKGROUND: Mechanically aligned total knee arthroplasty (MATKA) is a well-established procedure. Kinematically aligned TKA (KATKA) has been proposed to restore and preserve pre-arthritic knee anatomy. However, normal knee anatomy varies widely, and there have been concerns regarding restoring unusual anatomy. Accordingly, restricted KATKA (rKATKA) was introduced to reproduce constitutional knee anatomy within a safe range. This network meta-analysis (NMA) aimed to evaluate the clinical and radiological outcomes of the surgeries. METHODS: We performed a database search on August 20, 2022, which included randomized controlled trials (RCTs) comparing any two of the three surgical TKA techniques for knee osteoarthritis. We conducted a random-effects NMA within the frequentist framework and evaluated confidence in each outcome using the Confidence in Network Meta-Analysis tool. RESULTS: Ten RCTs with 1,008 knees and a median follow-up period of 1.5 years were included. The three methods might result in little to no difference in range of motion (ROM) between methods. In patient-reported outcome measures (PROMs), the KATKA might result in a slight improvement compared with the MATKA (standardized mean difference, 0.47; 95% confidence interval [CI], 0.16-0.78; very low confidence). There was little to no difference in revision risk between MATKA and KATKA. KATKA and rKATKA showed a slight valgus femoral component (mean difference [MD], -1.35; 95% CI, -1.95-[-0.75]; very low confidence; and MD, -1.72; 95% CI, -2.63-[-0.81]; very low confidence, respectively) and a slight varus tibial component (MD, 2.23; 95% CI, 1.22-3.24; very low confidence; and MD, 1.25; 95% CI, 0.01-2.49; very low confidence, respectively) compared with MATKA. Tibial component inclination and hip-knee-ankle angle might result in little to no difference between the three procedures. CONCLUSIONS: KATKA and rKATKA showed similar ROM and PROMs and a slight variation in the coronal component alignment compared with MATKA. KATKA and rKATKA are acceptable methods in short- to mid-term follow-up periods. However, long-term clinical results in patients with severe varus deformity are still lacking. Surgeons should choose surgical procedures carefully. Further trials are warranted to evaluate the efficacy, safety, and subsequent revision risk.

A Novel Classification of Coronal Plane Knee Joint Instability Using Nine-Axis Inertial Measurement Units in Patients with Medial Knee Osteoarthritis.

The purpose of this study was to propose a novel classification of varus thrust based on gait analysis with inertial motion sensor units (IMUs) in patients with medial knee osteoarthritis (MKOA). We investigated thigh and shank acceleration using a nine-axis IMU in 69 knees with MKOA and 24 (control) knees. We classified varus thrust into four phenotypes according to the relative medial-lateral acceleration vector patterns of the thigh and shank segments: pattern A (thigh medial, shank medial), pattern B (medial, lateral), pattern C (lateral, medial), and pattern D (lateral, lateral). Quantitative varus thrust was calculated using an extended Kalman filter-based algorithm. We compared the differences between our proposed IMU classification and the Kellgren-Lawrence (KL) grades for quantitative varus thrust and visible varus thrust. Most of the varus thrust was not visually perceptible in early-stage OA. In advanced MKOA, increased proportions of patterns C and D with lateral thigh acceleration were observed. Quantitative varus thrust was significantly increased stepwise from patterns A to D. This novel IMU classification has better clinical utility due to its ability to detect subtle kinematic changes that cannot be captured with conventional motion analysis even in the early stage of MKOA.

Risk Factors for Glenohumeral Internal Rotation Deficit in Adolescent Athletes: A Comparison of Overhead Sports and Non-overhead Sports.

Background A glenohumeral internal rotation deficit (GIRD) occurs in baseball players due to the repetitive pitching motion. However, few reports have addressed associations between GIRD and sports other than baseball. In this study, we investigated whether GIRD occurs in adolescent athletes playing overhead sports other than baseball, and also, the risk factors that cause GIRD in these sports were examined. Methods A total of 214 junior high school athletes who had undergone medical checks were evaluated. Seventy-five athletes playing sports requiring overhead motions were classified into the overhead sports group (39 tennis, 18 handball, 12 badminton, and 6 softball players). Eighty athletes participating in sports requiring the use of the upper limbs but not requiring frequent overhead motions were classified into the non-overhead sports group (31 kendo, 20 fencing, 19 basketball, and 10 table tennis players); 59 athletes who mainly did not use an upper limb were classified into the contact sports group (22 judo, 15 wrestling, 13 soccer, and 9 rugby football players). The range of shoulder motion (internal rotation, external rotation, and total arc), background factors, general laxity, and flexibility of the lower body were compared among the three groups. Results Thirty-four (16%) of 214 players were classified as having GIRD (internal rotation deficit >15°). Significantly more athletes had GIRD in the overhead sports group than in the other groups (p=0.007). The internal rotation deficit was significantly worse in the overhead sports group than in the other groups (p=0.006, p=0.02, respectively). Background factors, general laxity, and lower body flexibility did not differ significantly among the groups. Conclusion The sole risk factor for GIRD was participating in any sport that required overhead movements. Thus, not only baseball players, but also other athletes who participate in sports requiring overhead movements should receive correct information to prevent GIRD.

Diagnostic accuracy of ultrasonography for occult femoral neck fracture.

Background: A delay in the diagnosis and treatment of an occult femoral neck fracture (OFNF) can negatively affect the subsequent quality of life. We investigated the diagnostic accuracy of ultrasonography for OFNF in patients confirmed with this condition by magnetic resonance imaging (MRI), and compared these results with other clinical findings. Methods: Ninety-four outpatients aged above 70 years with acute hip pain but without radiographic abnormal findings who were suspected of having an occult femoral neck fracture (11 men and 83 women with a mean age of 81.8 ± 6.0 years) were enrolled. Both ultrasonography and MRI were performed in all cases within 24 h. The ultrasonographic distance between the anterior aspect of the femoral neck and the anterior joint capsule (ultrasound joint swelling) was measured. Results: By MRI findings, 27 patients were assigned to an occult femoral neck fracture (OFNF) group (1 man, 26 women) and 67 patients to a non-OFNF group (10 men, 57 women). The mean ultrasound joint swelling in both groups was 7.53 ± 1.52 mm and 3.45 ± 0.89 mm, respectively (p = 0.006, 95% CI, 3.58-4.59). A cut-off value of 5.3 mm showed a sensitivity of 0.96 (0.89-0.96) and a specificity of 0.98 (0.92-1.00). Conclusions: Ultrasonography shows very high diagnostic accuracy for occult femoral neck fracture. This modality can thus contribute to initial bed-side examinations for this condition in patients over 70 years with acute hip pain.

Fibrin monomer complex on postoperative day 1 is correlated with the volume of deep vein thrombosis after knee surgery.

PURPOSE: Patients undergoing knee surgery are at high risk for deep vein thrombosis (DVT), which is infrequent but potentially life-threatening. It has not been identified how to efficiently detect high-risk DVT while minimizing bleeding complications from anticoagulation. We hypothesized that the degree of activation of thrombotic markers may correlate with the size of the thrombus. Therefore, we investigated the correlation between thrombotic markers and DVT thrombus volume in patients after knee surgery. METHODS: This retrospective study involved 29 patients who underwent around knee osteotomy or total / unicompartmental knee arthroplasty from 2018 to 2020. Fibrin monomer complex (FMC) at 1, and 7 days after surgery, and D-dimer at 4, and 7 days after surgery were investigated. In addition, the volume of DVT was estimated with ultrasonography at the 7 days after surgery. Body mass index, surgical time, and total volume of blood loss were also evaluated. Factors related to thrombus volume were examined statistically. RESULTS: Nine patients (31.0%) exhibited asymptomatic distal DVT, whereas 1 patient (3.4%) experienced asymptomatic proximal DVT. No patients had pulmonary embolism. Statistical analysis showed that only FMC concentration on postoperative day 1 was significantly correlated with thrombus volume (p <  0.001, 95% confidence interval 0.41 to 0.839, r = 0.679). CONCLUSIONS: The FMC concentration was a useful early indicator of deep vein thrombosis after knee surgery. Monitoring the FMC concentration could enable selective identification of patients with a high thrombus volume, which is associated with a high risk for pulmonary embolism.

Causes and Clinical Outcomes of Patellar Post Impingement.

BACKGROUND: Patellar post impingement (PPI), which occurs when the post impinges on the patella, may reportedly cause poor total knee arthroplasty (TKA) outcomes. The causes of PPI and its effect on clinical outcomes and symptoms were investigated. MATERIAL AND METHODS: The study subjects were 100 patients who underwent TKA (65 posterior stabilized TKA, 35 bi-cruciate stabilized [BCS] TKA). Whether PPI occurred during surgery was investigated; the patients were then classified into a PPI+ group and a PPI- group, and whether the implant or patellar shape was related to the occurrence of PPI was examined. The measurement parameters included patellar shape, joint range of motion (ROM), and clinical outcome using the new Knee Society Score. RESULTS: There were 38 knees in the PPI+ group and 62 knees in the PPI- group. There was no difference in patellar shape between the 2 groups, but PPI was more frequent in patients with short patellar tendon and those with low patellar height. In terms of implant type, the PPI+ group included 12 patients (18.5%) who underwent posterior stabilized TKA and 26 (74.3%) who underwent BCS TKA. There was no difference between the 2 groups in either joint ROM or new Knee Society Score. These results suggest that the position of the patella and implant shape that causes the post to be positioned anteriorly may contribute to PPI. CONCLUSION: PPI occurred more frequently in knees with low patellar height and in patients who had undergone BCS TKA. PPI had no effect on joint ROM or clinical outcome.

Long-term effect of immobilization in external rotation after first-time shoulder dislocation: an average 18-year follow-up.

BACKGROUND: Immobilization in external rotation (ER) after a first-time shoulder dislocation was introduced to reduce the risk of recurrence compared with immobilization in internal rotation (IR), but its efficacy remains controversial. The purpose of this study was to determine the long-term effect of immobilization in ER after a first-time shoulder dislocation. METHODS: Between October 2000 and March 2004, 198 patients with a first-time anterior dislocation of the shoulder (average age 37) were randomly assigned to immobilization in ER (ER group = 104 shoulders) or IR (IR group = 94 shoulders) for 3 weeks. At an average 2-year follow-up, 159 patients (80.3%) were available for evaluation. In the current study, these 159 patients were further followed up and interviewed by telephone. The following items were evaluated: recurrent instability, apprehensive feeling, surgical intervention, limitation in the range of motion, return to sports, and the Single Assessment Numeric Evaluation (SANE) score. RESULTS: The average follow-up period was 18.2 years (range, 16-20 years). Fifty-six patients were available for follow-up with the follow-up rate of 35%. The number of recurrent patients was 6 of 27 (22%) in the ER group and 6 of 29 (21%) in the IR group (P = .889). The number of surgically stabilized patients was 3 of 27 (11%) in the ER group and 10 of 29 (34%) in the IR group (P = .038). In total, the recurrence rate was 33% (9 of 27) in the ER group and 55% (16 of 29) in the IR group (P = .100). Adding the surgical cases and those with the SANE score ≤70% as failure cases, the failure rate in the ER group (26%) was significantly lower than that in the IR group (52%) (P = .048). Among those who survived without surgical intervention, there were no significant differences in apprehensive feeling, return to sports, limited range of motion, and the SANE score between the groups. CONCLUSIONS: Immobilization in ER reduced the risk of surgical intervention compared with IR in the long term.

Evaluation of anteroposterior accelerometric change after bi-cruciate stabilized total knee arthroplasty and posterior stabilized total knee arthroplasty.

BACKGROUND: In conventional total knee arthroplasty (TKA), the anterior cruciate ligament (ACL) is resected. ACL dysfunction causes knee instability and is regarded as one factor in poor TKA outcomes. In bi-cruciate stabilized (BCS) TKA, the implant reproduces ACL function and provides anterior stability. The objective of this study was to evaluate preoperative and postoperative X-rays and accelerometer gait measurements in patients who underwent BCS TKA and posterior-stabilized (PS) TKA to assess the postoperative acceleration changes of knees after these procedures and to compare them in terms of joint range of motion (ROM) and the New Knee Society Score (New KSS). METHODS: The subjects were 60 patients, 30 of whom underwent BCS TKA and 30 PS TKA. Joint ROM, New KSS, lateral X-rays of the standing extended knee, and accelerometer data were evaluated 12 months postoperatively. RESULTS: There was no significant difference in joint ROM between the groups. Both had good New KSS results, but the functional activity score was significantly higher after BCS TKA than after PS TKA. X-rays showed a lower posterior offset ratio after BCS TKA than after PS TKA, with anteroposterior positioning closer to that of the normal knee. Accelerometer data showed that postoperative anteroposterior acceleration on the femoral side in the stance phase and swing phase was lower after BCS TKA than after PS TKA. CONCLUSION: Compared with PS TKA, BCS TKA resulted in a higher functional activity score, closer positioning to that of the normal knee on lateral X-ray, and lower anteroposterior acceleration on the femoral side.

Diagnostic Accuracy of the Mobile Assessment of Varus Thrust Using Nine-axis Inertial Measurement Units.

OBJECTIVES: The purpose of this study was to clarify the diagnostic accuracy of the mobile assessment of varus thrust using inertial measurement units (IMUs). METHODS: A total of 80 knees in 49 patients were enrolled in this study. On visual analysis of gait to determine the presence or absence of varus thrust, 23 knees were assigned to the Present group, 17 to the Ambiguous group, and 40 to the Absent group. The peak knee varus angular velocities (PVVs), measured by quantitative gait analysis using nine-axis IMUs, were compared between these three groups. A receiver operating characteristic curve for the relationship between the visual assessment of varus thrust (Present and Ambiguous) and the measured PVV was created, and the cut-off PVV for visualized varus thrust was determined as the highest point for both sensitivity and specificity. RESULTS: The mean PVVs were significantly different between the three groups (Present, 47.7 ± 8.2 degree/s, Ambiguous, 34.1 ± 10.5 degree/s, and Absent, 28.1 ± 8.3 degree/s, respectively, ANOVA P=0.000). The PVV cut-off value for visualized varus thrust was 28.1 degree/s, yielding a sensitivity of 0.957 and a specificity of 0.579. CONCLUSIONS: A PVV <28.1 degree/s is useful for ruling out varus thrust during gait. This quantitative varus thrust assessment method using IMUs has clinical utility as a screening test.

A new double level osteotomy procedure to restore a joint line and joint angles in severe varus osteoarthritis. - Double level osteotomy associated with tibial condylar valgus osteotomy (DLOTO).

High tibial valgus osteotomy (HTO) is a well-established surgical procedure to correct a varus malalignment and treat medial compartment osteoarthritis. Recently, double level osteotomy (DLO) was recommended for extensive varus knees as a single level osteotomy (SLO) approach may create an excessive joint line obliquity and eventually result in a new bony deformity. However, a severe varus knee in cases of advanced osteoarthritis involves not only a bony deformity (extra-articular deformity) but also a medial joint space narrowing with a widened lateral joint space (intra-articular deformity). A DLO alone cannot reduce this intra-articular deformity. However, tibial condylar valgus osteotomy (TCVO) can complement DLO as to reduce this intra-articular deformity. This technical note describes a novel modified DLO procedure associated with TCVO which can restore a normal alignment and a joint line and achieve joint preservation even in cases of extensive varus osteoarthritis.

Effectiveness of Ilizarov external fixation in elderly patients with pilon fractures.

BACKGROUND: Pilon fractures are associated with soft tissue complications such as skin necrosis, and deep infections have been reported very often. This study retrospectively compared the treatment effects of Ilizarov external fixation and of internal fixation methods in elderly patients with pilon fractures. METHODS: A total of 37 patients >60 years old with pilon fractures (AO classification type 43) were investigated. Patients were treated either with internal fixation (n = 15) or Ilizarov external fixation (n = 22). The patients' mean age was 74.2 (range, 60-78) years in the internal fixation group and 76.1 (range, 60-82) years in the Ilizarov external fixation group. Many patients in the internal fixation group received toe-touch to 1/3 partial weight-bearing at 2-4 weeks postoperatively and full weight-bearing by 6-8 weeks postoperatively. Many patients in the Ilizarov external fixation group received partial weight-bearing (as tolerated) 1 day postoperatively, 1/2 partial weight-bearing at 2 weeks postoperatively, and full weight-bearing at 4 weeks postoperatively. RESULTS: The mean duration of hospitalization was 79.1 ± 30.1 days for the internal fixation group and 29.1 ± 18.8 days for the Ilizarov external fixation group (p < 0.05). Bone mineral density (T-score) was 2.6 ± 0.7 for the internal fixation group and 3.6 ± 1.2 for the Ilizarov external fixation group (p < 0.05). The incidence of skin disorders that required additional surgical treatment was 33.3% (5/15 patients) in the internal fixation group and 0% (0/22 patients) in the Ilizarov external fixation group (p < 0.05). CONCLUSIONS: In elderly patients with periarticular fractures of the ankle, those who underwent Ilizarov external fixation had a shorter duration of hospitalization and fewer complications than those who underwent internal fixation.

Successful treatment of valgus knee osteoarthritis involving external tibial torsion with a double level osteotomy: A case report.

INTRODUCTION: Abnormal torsion of the lower leg affects the alignment of the knee joint and foot, and causes impairment of both knee joint function and gait. We here present a successful adult case treated with a double level osteotomy at the distal femur and tibia. PRESENTATION OF CASE: A 59-year-old woman complained of right knee pain for three years and had a deformity of her right lower limb since childhood. An advanced right tibial external torsion deformity with valgus alignment was revealed. We performed a double level osteotomy to correct both the valgus knee osteoarthritis and the external tibial torsional deformity. At the 2 year follow-up, the patient could run without pain and sit normally. DISCUSSION: The indications for surgery for abnormal rotation in the lower extremity are also not clear. In addition, most prior surgical reports on torsional deformity of the lower leg have been on childhood cases. Surgical treatment of valgus knee osteoarthritis involving external tibial torsion in adult has been rarely reported. CONCLUSIONS: In our current report, we present an adult case of valgus knee osteoarthritis involving external tibial torsion that was successfully treated using a double level osteotomy. A longer follow-up is still needed however despite these positive outcomes. LEVEL OF EVIDENCE: Ⅴ.

Effectiveness of circular hexapod external fixation with soft tissue reconstruction in treating severe knee dislocation due to burn scarring: a case report.

BACKGROUND: Severe varus deformity and soft tissue injury caused by a burn around a complex knee dislocation is a rare injury. Soft tissue reconstruction and deformity correction with circular hexapod external fixation of the knee and hinged total knee arthroplasty (TKA) are challenging and can lead to major complications if not performed appropriately. We present a case in which a combination of soft tissue reconstruction, circular hexapod external fixation, and TKA was used treat severe knee dislocation due to burn scarring. CASE PRESENTATION: We report the case of a 58-year-old woman who presented for knee surgery with soft tissue reconstruction, deformity correction with circular hexapod external fixation, and hinged TKA for a severe complex deformity and soft tissue injury caused by a burn injury at 6 months of age. The left leg was shorter by 35 mm in terms of functional leg length discrepancy. She walked with a limp, with a marked varus deformity of the left knee during the stance phase of walking. After a 3-stage repair, the patient was able to walk without assistance, confirming improvement of mobility. CONCLUSION: The treatment method was an effective use of a combination of soft tissue reconstruction, circular hexapod external fixation, and rehearsal surgery using a 3D printed bone model of the modular rotating hinge component of TKA, which was successfully used to treat a severe knee dislocation due to burn scarring. This staged surgery maintained the leg length and ultimately achieved a satisfactory alignment.

Successful treatment of a habitual patellar dislocation after a total knee arthroplasty with a closing-wedge distal femoral varus osteotomy and medial patello-femoral ligament reconstruction.

A 68-year-old female suffering from habitual patellar dislocations following a mal-positioned total knee arthroplasty (TKA) was successfully treated with a biplanar closed wedge distal femoral osteotomy (CWDFO) and medial patello-femoral ligament (MPFL) reconstruction. To the best of our knowledge, no such case has been previously described. Our experience with this case suggests that treatment for a patella dislocation following valgus mal-positioning of TKA should be considered positively. LEVEL OF EVIDENCE: V.

Effectiveness of circular external fixator in periprosthetic fractures around the knee.

BACKGROUND: The incidence of periprosthetic fractures after total joint arthroplasty (TJA) is rising due to an increasing number of TJAs performed annually and the growing elderly population. In many elderly patients with periprosthetic fractures, the bone strength is lowered due to the deterioration of bone quality and a decrease in bone quantity; rigid fixation of the fracture is difficult. It is a challenging operation for orthopedic surgeons. The usefulness of circular external fixation for periprosthetic fractures has been reported in several case studies. The aim of this study was to investigate the rate of union and complications associated with circular external fixation in periprosthetic fractures around the knee. METHODS: We included 19 patients with periprosthetic femur and tibial fractures who underwent osteosynthesis using a circular external fixator and had at least 2 years of follow-up. All patients had comorbidities and high risks associated with anesthesia. Tourniquets were not used in any of the patients. There were no cases in which the skin incision was placed, and the closed reduction technique was used in all cases. RESULTS: A 100% union rate was achieved with no serious complications. All fractures healed after a mean time of 14.3 ± 5.2 weeks (range, 8-38 weeks). The walking ability was the same level as before the injury in 13 cases. DISCUSSION: There are many comorbidities associated with periprosthetic fractures in elderly patients. Double-plate or revision surgery were largely invasive and had high risks associated with anesthesia. Circular external fixation is a feasible and effective treatment option because it provides stable fixation, prompt postoperative mobilization, and has no major complications, especially in elderly patients who are treated for periprosthetic fractures. CONCLUSION: Circular external fixation is a safe and reliable method for periprosthetic fractures around the knee in elderly patients. LEVEL OF EVIDENCE: Level IV, retrospective case series.

Radiographic deformities of the lower extremity in patients with spontaneous osteonecrosis of the knee.

BACKGROUND: Spontaneous osteonecrosis of the knee (SONK) is one of the acute knee pain disorders arising in elderly patients. The presence of knee varus alignment and the size of necrotic area have been reported as the negative prognostic factors in prior studies. However, no previous study has yet clarified the radiological analysis of the lower extremity in SONK compared with that in osteoarthritis. The purpose of this study was therefore to identify the radiographic findings of the lower extremity in SONK. METHODS: Sixty-three knees of Kellgren-Lawrence classification grade 1 or 2 without any trauma treated between April 2012 and March 2014 were enrolled in this study. These knees were divided into two groups according to their magnetic resonance imaging (MRI) findings: SONK group (31 knees) and OA group (32 knees). Using a long leg standing X-ray, femorotibial angle (FTA), mechanical axis deviation (MAD), mechanical lateral distal femoral angle (mLDFA), medial proximal tibial angle (MPTA) and joint line convergent angle (JLCA) were compared between groups. Correlation between each parameter and the width ratio (WR) of the necrotic lesion were analyzed. RESULTS: FTA, MAD, MPTA and JLCA showed significant differences between the SONK and OA groups. In the SONK group, FTA was positively correlated with WR, and, MAD and MPTA was negatively correlated with WR. CONCLUSIONS: Compared with OA, SONK is associated with a significantly larger varus deformity at the proximal tibia, and larger joint play in the coronal plane.

Snapping Pes Syndrome Caused by the Gracilis Tendon: Successful Selective Surgery with Specific Diagnosis by Ultrasonography.

We report the case of painful snapping pes syndrome caused by the gracilis tendon. A 26-year-old man presented with acute right knee pain and restricted extension. Although snapping could not be reproduced due to severe pain, the snapping of the gracilis tendon could be specifically diagnosed using ultrasonography and lidocaine injection. Because of the failure of conservative treatment, surgery was performed. The distal attachment of the gracilis tendon was released, and the symptom disappeared quickly. There was no recurrence at the 10-month follow-up.