Patellar dislocation following distal femoral replacement after extraarticular knee resection for bone sarcoma:A case report

BACKGROUND For the treatment of bone sarcoma in the distal femur,wide-margin resection and knee reconstruction with tumor endoprosthesis are standard therapies.Extraarticular knee resection is required in cases of tumor invasion of the knee joint;however,the incidence of complications,such as aseptic loosening,prosthesis infection,and implant failure,is higher than that following intra-articular knee resection.To the best of our knowledge,there are three reports of patellar dislocations after replacement of a tumor endoprosthesis.CASE SUMMARY A 36-year-old man with no significant past medical history was admitted to our institution with continuous pain in his left knee for 4 mo.An open biopsy was performed,and the patient was diagnosed with a left distal femoral malignant bone tumor.Extra-articular knee resection and knee reconstruction with a tumor endoprosthesis were performed.Although the alignment of the tumor prosthesis was acceptable,knee instability was noticed postoperatively.The axial radiographic view of the patellar and computed tomography showed lateral patellar dislocation at 4 wk postoperatively.The patient had to undergo a lateral release and proximal realignment.He could perform his daily activities at 9 mo postoperatively.Radiography revealed no patellar re-dislocation.CONCLUSION Proximal realignment may be considered during primary surgery if there is an imbalance in the forces controlling the patellar tracking.

Horizontal Inferior Patellar Dislocation in an Elderly Patient: A Case Report and Review of Literature

Intra-articular patellar dislocation due to acute trauma is considered a rare presentation and is less commonly encountered in practice than extra-articular patellar dislocation. This case study presents a rare type 2 inferior dislocation of the patella in an elderly patient which was successfully reduced and managed non-operatively.

Combination of medial patellofemoral ligament reconstruction with vastus medialis advancement for chronic patellar dislocation

Background The medial patellofemoral ligament （MPFL） reconstruction is popular in clinical practice for chronic patellar dislocation; however, the combination with vastus medialis advancement is rare. The aim of this study was to evaluate the clinical outcome of the combination of MPFL reconstruction with vastus medialis advancement.Methods We retrospectively analyzed 69 patients with chronic patellar dislocation between July 2004 and October 2008： twenty eight cases with isolated MPFL reconstruction （group Ⅰ）, forty one cases with the combination of MPFL reconstruction with vastus medialis advancement （group C）. All patients had CT scans available for review with knee flexion at 30 degree, on which the congruence angle, patellar tilt angle and patellar lateral shift were measured. Physical apprehension tests were examined and the redislocation was recorded. In addition, knee function was evaluated using the Kujala score and subjective questionnaires.Results Patients were followed up for a mean of 42 months （12-65 months） without a recurrent dislocation reported.Postoperatively, all indexes on CT scan were within the normal range without a statistical difference between the two groups. Results from the apprehension test showed eight patients in group Ⅰ and three in group Chad patellar lateral shift exceeding 1.5 cm with a hard end point （P 〈0.05）. The Kujala score improved significantly from 51.3±4.5 to 79.9±6.2 in group Ⅰ and from 53.7±5.2 to 83.9±6.5 in group C （P 〉0.05）. However, the subjective questionnaire revealed a significant difference （P 〈0.05）, including 12 excellent, seven good and nine fair in group Ⅰ and 30 excellent, six good and five fair in group C.Conclusion The combination of MPFL reconstruction with vastus medialis advancement is better than isolated reconstruction to improve the subjective effects and decrease the patellar instability rate for chronic patellar dislocation.

Significance of Diffusion Tensor Imaging of Vastus Medialis Oblique in Recurrent Patellar Dislocation

Background： Numerous studies have investigated the influence of osseous factors on patellofemoral joint instability, but research on the influence of dynamic muscle factors in vivo is still in the exploratory stage. This study aimed to use magnetic resonance imaging （MRI） and diffusion tensor imaging （DTI） to evaluate vastus medialis oblique （VMO） fiber bundles in patients with recurrent patellar dislocation to explore the changes in muscle morphology and function. Methods： This prospective study involved 30 patients （7 males and 23 females; average age, 21.4 ± 3.8 years） clinically diagnosed with recurrent patellar dislocation in Peking University Third Hospital and 30 healthy volunteers matched for age, sex, and body mass index in our medical school between January 2014 and October 2014. None of the patients had a recent history of traumatic patellar dislocation or transient patellar dislocation. All patients underwent conventional MRI and DTI of the knee. The cross-sectional area of the VMO on MRI and the fractional anisotropy （FA）, apparent diffusion coefficient （ADC）, and primary （λ1）, secondary （λ2）, and three-level characteristic （λ3） values on DTI were measured. The independent-samples t-test was used to compare these parameters between the two groups. Results： Compared with the control group, the patient group showed significantly higher FA values （0.39 ± 0.05 vs. 0.33 ± 0.03） and significantly lower ADC （1.51 ± 0.13 vs. 1.58± 0.07）, λ2 （4.96 ±0.13 vs. 5.04 ± 0.07）, and λ3 values （4.44 ± 0.14 vs. 4.58 ± 0.07; t = 5.99, t = -2.58, t = 3.02, and t = -4.88, respectively： all P 〈 0.05）. Cross-sectional VMO area and λ1 values did not differ between the two groups （t = 1.82 and t = 0.22, respectively; both P 〉 0.05）. Conclusions： The functional status of the VMO is closely associated with recurrent patellar dislocation. MRI, especially DTI （FA, ADC, λ2, and ,λ3）, can detect early changes in VMO function and might lhcilitate the noninvasive monitoring of the functional status of the VMO in patients with recurrent patellar dislocation.

Fixation versus Excision of Osteochondral Fractures after Patellar Dislocations in Adolescent Patients： A Retrospective Cohort Study

Background： Patellar dislocation is one of the most common knee injuries in the adolescent population. It is often combined with osteochondral fracture. The purpose of this study was to cornpare the outcomes between fixation and excision of osteochondral fractures not involving the bearing surface in adolescent patients with patellar dislocations. Methods： Patients who underwent surgery for osteochondral fracture following patellar dislocation in our institution from 2007 to 2014 were retrospectively evaluated. Visual analog scale （VAS） of pain and the International Knee Documentation Committee （IKI）C） form were used to assess knee pain and function at follow-up. Patient satisfaction was evaluated. Differences in the values of variables among groups were assessed using t-test if equal variance or Mann-Whitney U-test if not equal variance. The Pearson＇s Chi-square test was applied for dichotomous variables if expected frequency was 〉5 or Fisher＇s exact test was applied if not. A value of P 〈 0.05 was considered statistically significant. Results： Forty-three patients were included, with the average age of 14.1 ± 2.3 （range, 9.0-17.0） years. Nineteen underwent fixation of osteochondral fractures and 24 did not. The average follow-up time was 28 ± 10 months. There was no significant difference in age, gender, follow-up time, causes of injury, times of dislocation, and location of osteochondral fracture between fixation and excision groups. The fixation group had a significantly longer surgery time （82± 14 rain） and larger size of osteochondral fracture （2.30 ±0.70 cm2） than the excision group （43 ± 10 min, 1.88 ± 0.62 cm2, respectively, t = 10,77, P 〈 0.01 and t = 0.84, P 〈 0.05）. At the last follow-up, the average I KDC score in the fixation group （82.52 ± 8.71 ） was significantly lower than that in the excision group （89.51 ± 7.19, t 2.65, P 〈 0.01 ）. There was no significant difference in VAS of pain and patients＇ satisfaction. There were 7 （16%） patients with recurrent dislocation. Conclusion： Excision of osteochondral fractures has equivalent or better outcomes compared to fixation in adolescent patients with patellar dislocations when these fractures do not involve the bearing surface.

Repair of a large patellar cartilage defect using human umbilical cord blood-derived mesenchymal stem cells:A case report

BACKGROUND Patellar dislocation may cause cartilage defects of various sizes.Large defects commonly require surgical treatment;however,conventional treatments are problematic.CASE SUMMARY A 15-year-old male with a large patellar cartilage defect due to patellar dislocation was treated via human umbilical cord blood-derived mesenchymal stem cell(hUCB-MSC)implantation.To our knowledge,this is the first report of this treatment for this purpose.The patient recovered well as indicated by good visual analog scale,International Knee Documentation Committee and McMaster Universities Osteoarthritis Index scores.Magnetic resonance imaging showed cartilage regeneration 18 mo postoperatively.CONCLUSION Umbilical cord blood-derived hUCB-MSCs may be a useful treatment option for the repair of large patellar cartilage defects.

Dislocation of a constrained total knee arthroplasty with patellar tendon rupture after trivial trauma

Constrained total knee prostheses are used in knees with severe deformities and insufficiency of collaterals to provide stable and mobile knees. Dislocation after constrained knee prosthesis is an extremely rare and dreaded complication. When dislocation is associated with patellar tendon rupture, the management includes restoration of the extensor apparatus along with a stable knee. Repair of the patellar tendon is challenging due to poor soft tissue coverage in the area and a bulky repair can put tension on the wound closure. Ideal method of restoration of the extensor apparatus is a matter of debate. There are various modalities used ranging from primary end-to-end repair, augmentation by medial gastrocnemius flap, semitendinosus and synthetic implants and allograft tendoachilles. We report a rare case of a posterior dislocation of a constrained total knee arthroplasty in association with patellar tendon rupture due to a minor fall after a few weeks of surgery. The first episode was managed by reposition of the dislocation and V-Y plasty of the quadriceps and primary repair. The second episode of dislocation with re-rupture needed augmentation by semitendinosus along with the insertion of the thicker insert. The management of this complex problem along with the review of literature is discussed in this case reoort.

Reconstruction of the medial patellofemoral ligament with a suture-tie technique of patellar side fixation

Background Medial patellofemoral ligament （MPFL） reconstruction is the preferred operative treatment for recurrent patellar dislocation. The purpose of this study was to report a novel suture-tie technique of patellar side fixation in medial patellofemoral ligament reconstruction for recurrent patellar dislocation, and to evaluate the intermediate-term results. Methods We retrospectively reviewed the results of 22 MPFL reconstructions in 21 patients （6 male and 15 female） with a suture-tie technique performed by a single surgeon between March 2004 and July 2009. All patients had been diagnosed with recurrent patellar dislocation. Outcomes were assessed preoperatively and postoperatively by physical and radiographic examination as well as with Kujala and Lysholm scores. Results At the mean follow-up month 37.5 （range： 24-56 months）, there was no graft failure. Primary healing was achieved in all cases. At the final follow-up, the mean Kujala score improved from 53.9 （range： 46-62 points） to 84.1 （range： 78-90 points） postoperatively （P 〈0.05）, and the mean Lysholm score improved from 47.2 points （range： 37-57 points） to 82.8 points （range： 76-89 points） postoperatively （P 〈0.05）. To date, no patients have reported redislocation or subluxation; however, there is one patient with a positive apprehension test. Conclusion A suture-tie technique in medial patellofemoral ligament reconstruction can restore patella stability without significant complication.