Nonoperative Treatment of Patellar Instability

"Knee-Ding" a Diagnosis: A Case of Nail Patella Syndrome

Nail Patella Syndrome (NPS) is a rare genetic disorder with pathognomonic signs including dystrophic fingernails, iliac horns, and limb abnormalities, which commonly include hypoplastic development of the patellae, causing patients to experience patellar instability. This resulting patellar instability increases susceptibility to recurrent subluxations or dislocations in NPS patients. Since these anatomical abnormalities are present at birth or in childhood, early recognition may prevent the need for surgical intervention if appropriate preventive measures are taken. This case report describes a 54-year-old woman with a history of NPS, diagnosed later in adulthood, with a prior patellectomy at age 18 secondary to an unspecified left knee injury that occurred at age 4. A combination of radiographic and clinical findings are presented, which support the diagnosis of NPS, including dystrophic nails, left knee x-ray consistent with prior patellectomy, and right knee x-ray showing inferolateral subluxation of a hypoplastic patella. Additional signs associated with NPS are also discussed, including mood disorders, Raynaud's, and a high hairline which may assist in early diagnosis. This case report emphasizes earlier identification of NPS by clinicians through recognition of signs and symptoms while also considering proactive measures to lessen recurrent subluxations or dislocations to preserve patellar integrity and reduce the need for surgical intervention.

Patellar malalignment: A common disorder associated with knee pain

Pain-associated knee joint disorders are common in daily life. Practically, knee pain should be divided into the origin from the isolated tibiofemoral (TF), isolated patellofemoral (PF) joint, or a combination thereof. The TF joint controls the actions of level walking, while the PF joint controls knee flexion-extension. Owing to its sufficient inherent stability, non-traumatic disorders of the isolated TF joint in young individuals are uncommon. In contrast, because of its insufficient inherent stability, non-traumatic disorders of the isolated PF joint are common in young individuals. Patellar malalignment (PM) associated with knee pain is common in all age groups, and the most common predisposing factor is imbalanced peripatellar soft-tissue tension. The outward forces acting on the patella are caused by pulling from the quadriceps femoris during knee flexion to extension (manifested by the quadriceps angle [Q-angle]), and sliding backward of the iliotibial band (ITB) during knee extension to flexion. Once the muscle power of the vastus medialis (especially the vastus medialis obliquus [VMO]) decreases, which lowers the counteracting effect against outward forces, the patella displaces or rotates laterally. The reduced contact surface between the patella and the femoral condyle significantly increases the compressive pressure and injures the articular cartilage. Subsequently, progressive PF degeneration occurs. Although other factors may also cause PM, they are relatively uncommon. In principle, nonsurgical treatment of PM should be considered first, while surgical treatment should follow established indications. Some nonsurgical techniques are currently widely used that feature high satisfaction rates. Surgical techniques are continuously being developed, and their success rates have gradually improved. This study aimed to review the current literature for relevant studies and report related publications of the author's institution to emphasize the universality and importance of PM management. Conceptually, simply focusing on problems of the TF joint cannot treat all knee disorders.

Is Caton–Deschamps Index Reliable and Reproducible in Preoperative Assessment of Patellar Height for Patellar Instability Surgery?

The patellar height measurement is fundamental for surgical planning in patellar instability. The Caton–Deschamps index (CDI) is a widely employed method, but a gold standard is still lacking. The aim of this study was to evaluate the reliability and reproducibility of the CDI in a patellar height assessment and to hypothesize its employment in the preoperative planning of patellar stabilization surgery. A total of 29 cases of recurrent patellar instability undergoing surgical treatment were analyzed. The preoperative and postoperative CDI were measured by six different raters (three seniors and three juniors). The interclass correlation coefficient (ICC) of the six raters was calculated to evaluate the interobserver agreement. The seniors’ and juniors’ measurements were compared to assess the CDI reproducibility. The Fleiss kappa was calculated among the six raters to estimate the agreement in favor of an anterior tibial apophysis (ATA) transposition surgery. This study shows excellent absolute agreement in terms of the ICC for the raters’ average and for single raters as units, both preoperatively (p < 0.001) and postoperatively (p < 0.001). The agreement of the surgical choice between the six observers corresponds to “substantial agreement”. This study demonstrates that the CDI is reliable and reproducible, and it could represent a valuable tool in the clinical assessment, treatment choice and pre-surgical planning of patellar instability surgery.

Current practice trends in the surgical management of patellofemoral instability: a survey of the Paediatric Research in Sports Medicine (PRiSM) Society

PURPOSE

Patellofemoral instability (PFI) in young athletes presents both diagnostic and management dilemmas for which consensus often does not exist. The purpose of this study was to identify trends in management of PFI in children and adolescents in the United States and nationwide.

METHODS

A 27-question multiple choice survey was distributed in 2018 to the members of the Pediatric Research in Sports Medicine (PRiSM) Society regarding treatment of PFI in paediatric and adolescent patients.

RESULTS

In all, 56 of the respondents who were orthopaedic surgeons that manage patellar instability in children and adolescents and had performed PFI surgery more than five times in the past year completed the entire survey. A total of 41% of respondents reported that surgery for fragment refixation or loose body removal was indicated when a loose body or osteochondral fragment was evident, regardless of fragment size. Overall, 74% reported that if surgery was performed for an osteochondral loose body, primary repair (36%) or reconstruction (38%) of medial patellofemoral ligament (MPFL) was also completed. A total of 89% of members reported MPFL reconstruction in the absence of alignment or rotational abnormalities, tibial tubercle lateralization or trochlear dysplasia in skeletally immature patients; 59% reported performing the MPFL reconstruction with hamstring allograft, while 30% prefer autograft (hamstring, quadriceps). For patients with significant trochlear dysplasia, 87% reported no surgical management of trochlea in first-time or in revision surgery.

CONCLUSION

There is a lack of consensus regarding optimal diagnostic and treatment algorithms in the management of PFI, however, consistent trends have emerged among paediatric sports medicine surgeons.

LEVEL OF EVIDENCE

Level V - survey of expert opinion and experience.

Prevalence of lateral patellofemoral maltracking and associated complications in patients with Osgood Schlatter disease

OBJECTIVE

To evaluate adults with history of Osgood Schlatter disease (OSD) for imaging features of lateral patellofemoral maltracking.

METHODS

In a span of four years, 10,181 unique non-contrast knee MRIs were performed on patients aged 20-50. Patients with acute trauma, prior surgery, and synovial pathologies were excluded. 171 exams had imaging findings of OSD, and an age-matched control group of 342 patients without OSD was randomly selected. Two radiologists retrospectively reviewed MRIs for features of lateral patellofemoral maltracking. Maltracking was defined as edema in superolateral Hoffa's fat or a tibial tuberosity-trochlear groove (TT-TG) distance ≥20 mm with either patellar tilt/translation. Binomial logistic regression identified predictors of maltracking in OSD. Optimal TT-TG distance to indicate maltracking was determined by receiver operating characteristic curve.

RESULTS

59% (101/171) of the knees with OSD showed findings of maltracking, with patella alta, trochlear dysplasia, and quadriceps tendinosis as significant predictors of maltracking (p < 0.001). Patellofemoral chondrosis was present in 63% (107/171), with maltracking contributing to higher grade chondrosis more so than increasing age (OR 8.4 versus 1.07). 13 mm was the optimal cut-off TT-TG distance to indicate maltracking (sensitivity 83%, specificity 80%). The prevalence of maltracking in the control group was 15% (p < 0.001 compared with the OSD group).

CONCLUSION

Adults with sequelae of OSD are at high risk of maltracking and are likely to develop patellofemoral chondrosis. A lower threshold for identifying maltracking patients, including a lower cut-off TT-TG distance can help identify those at risk. Radiologists should maintain a high index of suspicion for maltracking in adults with OSD to guide clinical intervention.

Effects of Photoperiod on Acetaminophen-Induced Hepatotoxicity in Mice

PURPOSE

Acetaminophen (APAP) is a clinically popular analgesic and antipyretic drug, but excessive APAP can cause fatal hepatotoxicity. Many factors affect the degree of APAP-induced liver injury. This study aimed to investigate how circadian rhythm affects the development of APAP-induced hepatotoxicity and to clarify the roles of photoperiod and dietary rhythm on APAP-induced hepatotoxicity in mice.

METHODS

APAP-induced hepatotoxicity models were established by intraperitoneal injection of APAP (400 mg/kg) to mice. The mice were then divided into three treatment groups: normal diet, reversed diet, and reversed photoperiod.

RESULTS

More severe liver injury was observed at zeitgeber time 12 (ZT12) than at zeitgeber time 0 (ZT0) in all treatment groups, suggesting that photoperiod played a critical role in APAP-induced liver injury. We observed a change in the expression of the circadian gene Per2, which may be responsible for regulation of liver injury by photoperiod. Our results showed negligible change in Per2 expression with diet reversion, whereas Cry1, Cry2, and Dbp expressions were more highly affected by diet reversion than was Per2 expression. Downstream effects including liver enzyme expression, GSH level, and inflammation factors were also examined to identify the mechanism of liver injury. The results indicated that the circadian gene Per2 participated in APAP biometabolism by regulating the expression of Cyp2e1, which may explain the more severe hepatotoxicity at ZT12 than at ZT0.

CONCLUSION

APAP-induced hepatotoxicity can be mediated by photoperiod through the circadian gene Per2, suggesting that medicines containing APAP should be administered not only with food but also according to the appropriate photoperiod.

Patellar maltracking: an update on the diagnosis and treatment strategies

Patellar maltracking occurs as a result of an imbalance in the dynamic relationship between the patella and trochlea. This is often secondary to an underlying structural abnormality. The clinical evaluation can provide useful clues for the presence of such entity; however, the diagnosis can often be challenging especially in the absence of a documented history of patellar dislocation. Imaging, particularly MRI, can detect subtle features that could lead to the diagnosis, probably even more importantly when there is no clear history of patellar dislocation or before its development. This can provide a road map for formulating a treatment strategy that would be primarily aimed at stabilizing the patellofemoral joint to halt or slow the progression of articular cartilage loss. The purpose of this article is to discuss the clinical and radiologic evaluation of patellar maltracking providing an update on the cross-sectional imaging assessment and also a synopsis of the management options.

Patellar Instability in the Skeletally Immature

PURPOSE OF REVIEW

This review will focus on the evaluation and management of patellar instability in the developing patient.

RECENT FINDINGS

A large number of surgical techniques have been described to prevent recurrent patellofemoral instability in the pediatric population, including both proximal and distal realignment procedures. The wide variety of treatment options highlights the lack of agreement as to the best surgical approach. However, when a comprehensive exam and workup are paired with a surgical plan to address each of the identified abnormalities, outcomes are predictably good. Patellar instability is a common knee disorder in the skeletally immature patient that presents a unique set of challenges. Rates of re-dislocation in pediatric and adolescent patients are higher than in their adult counterparts. Careful consideration of the physeal and apophyseal anatomy is essential in these patients. While the majority of primary patellar instability events can be treated conservatively, multiple events often require surgical intervention.