Arthroscopic Shoulder Stabilization in High School Football Players

Background

Destabilizing shoulder injuries are common in high school American football players; however, the rate of recurrent glenohumeral instability and return to play after arthroscopic labral stabilization surgery remains unknown.

Purpose/Hypothesis

The purpose of this study was to determine the rate of recurrent instability on return to competitive high school football after arthroscopic shoulder labral stabilization and capsulorrhaphy procedures. It was hypothesized that the instability rate would be greater in players with more years of eligibility remaining (YER) to play at the high school level.

Study Design

Case series; Level of evidence, 4.

Methods

Consecutive male high school football players with at least 1 YER who sustained at least 1 anterior traumatic inseason shoulder instability episode and underwent arthroscopic stabilization between 2012 and 2017 were identified. Patients and/or families were contacted by phone to discuss (1) recurrent instability episodes and (2) return to competitive sport and/or recreational athletic activity. Statistical analysis was conducted using chi-square tests to compare recurrent shoulder instability with return to play and YER.

Results

A total of 45 football players aged 14 to 17 years were included, with a mean follow-up of 4.1 years. Most patients (60%) chose not to return to competitive football, due mainly to fear of recurrent injury. Overall, the recurrent instability rate was 15.6% (7/45). The instability rate in players who returned to football was 16.7%, with 66.7% requiring revision surgery. The instability rate in patients who did not return to football was 14.8%, with no revision procedures required. In players who returned to football, the instability rate in YER group 4 was significantly higher than that in YER groups 1 to 3 (42% vs 10.5%, respectively, P = .03), with each year of play conferring an additional 10% risk of reinjury. There was a significant difference in the type of recurrent instability in players who returned to any sport versus those who did not (P = .029).

Conclusion

High school football players who returned to competitive play after arthroscopic shoulder stabilization surgery experienced a higher rate of recurrent instability that was dependent on their YER. Over half of the players chose not to return to football, with fear of reinjury being the most common reason.

DNA damage to a single chromosome end delays anaphase onset

Chromosome ends contain nucleoprotein structures known as telomeres. Damage to chromosome ends during interphase elicits a DNA damage response (DDR) resulting in cell cycle arrest. However, little is known regarding the signaling from damaged chromosome ends (designated here as "TIPs") during mitosis. In the present study, we investigated the consequences of DNA damage induced at a single TIP in mitosis. We used laser microirradiation to damage mitotic TIPs or chromosome arms (non-TIPs) in PtK2 kidney epithelial cells. We found that damage to a single TIP, but not a non-TIP, delays anaphase onset. This TIP-specific checkpoint response is accompanied by differential recruitment of DDR proteins. Although phosphorylation of H2AX and the recruitment of several repair factors, such as Ku70-Ku80, occur in a comparable manner at both TIP and non-TIP damage sites, DDR factors such as ataxia telangiectasia mutated (ATM), MDC1, WRN, and FANCD2 are specifically recruited to TIPs but not to non-TIPs. In addition, Nbs1, BRCA1, and ubiquitin accumulate at damaged TIPs more rapidly than at damaged non-TIPs. ATR and 53BP1 are not detected at either TIPs or non-TIPs in mitosis. The observed delay in anaphase onset is dependent on the activity of DDR kinases ATM and Chk1, and the spindle assembly checkpoint kinase Mps1. Cells damaged at a single TIP or non-TIP eventually exit mitosis with unrepaired lesions. Damaged TIPs are segregated into micronuclei at a significantly higher frequency than damaged non-TIPs. Together, these findings reveal a mitosis-specific DDR uniquely associated with chromosome ends.

Targeting telomere-containing chromosome ends with a near-infrared femtosecond laser to study the activation of the DNA damage response and DNA damage repair pathways

Telomeres are at the ends of chromosomes. Previous evidence suggests that laser-induced deoxyribose nucleic acid (DNA) breaks at chromosome ends during anaphase results in delayed cytokinesis. A possible explanation for this delay is that the DNA damage response (DDR) mechanism has been activated. We describe a live imaging method to study the effects of DDR activation following focal point near-infrared femtosecond laser microirradiation either at a single chromosome end or at a chromosome arm in mitotic anaphase cells. Laser microirradiation is used in combination with dual fluorescent labeling to monitor the co-localization of double-strand break marker γH2AX along with the DDR factors in PtK2 (Potorous tridactylus) cells. Laser-induced DNA breaks in chromosome ends as well as in chromosome arms results in recruitment of the following: poly(ADP-ribose) polymerase 1, checkpoint sensors (p-Chk1, p-Chk2), DNA repair protein Ku70/Ku80, and proliferating cell nuclear antigen. However, phosphorylated p53 at serine 15 is detected only at chromosome ends and not at chromosome arms. Full activation of DDR on damaged chromosome ends may explain previously published results that showed the delay of cytokinesis.