Effect of Shoulder Stabilization on Career Length in National Football League Athletes

Abstract

Background: Shoulder instability and surgical stabilization are common in college football athletes. The effect of shoulder stabilization during college on the length of an athlete’s career in the National Football League (NFL) has not been well examined.

Hypothesis: Athletes with a history of shoulder stabilization before the NFL combine have a shorter career than do matched controls.

Study Design: Cohort study; Level of evidence, 3.

Methods: A database containing the injury history and career NFL statistics of athletes from 1987 to 2000 was used to match athletes with a history of shoulder stabilization and no other surgery or significant injury to controls without a history of any previous surgery or significant injury. Athletes were matched by position, year drafted, round drafted, and additional minor injury history.

Results: Forty-two athletes with a history of shoulder stabilization were identified and matched with controls. A history of shoulder stabilization significantly reduced the length of career in terms of years (5.2 ± 3.9 vs 6.9 ± 3.6 years; P = .01) and games played (56 ± 53 vs 77 ± 50, P = .03) as compared with controls. By position, linemen and linebackers (20 athletes) with a history of shoulder stabilization had a significantly shorter career in years (4.7 ± 3.8 vs 6.7 ± 3.4 years; P = .049) and games played (51 ± 58 vs 81 ± 48; P = .046) than did controls. Among the other positions (22 athletes), the difference was not statistically significant in this small cohort.

Conclusion: A history of shoulder stabilization shortens the expected career of a professional football player, particularly for linemen and linebackers. Further research is warranted to better understand how these injuries and surgeries affect an athlete’s career and what can be done to improve the long-term outcome after treatment.

Keywords

shoulder instability stabilization American football

Shoulder instability is a common condition in athletes that generally occurs after 1 or more episodes of glenohumeral joint dislocation. The glenohumeral joint is the most common major joint to dislocate in the human body.³⁵ Whereas both anterior and posterior instability can occur after dislocation, anterior instability accounts for more than 90% of all traumatic instability cases.¹³ Shoulder instability leads to significant morbidity in the form of recurrent dislocation, pain, and shoulder weakness. Although nonoperative management of a glenohumeral dislocation may be attempted, many athletes experience recurrent dislocation or subluxation episodes with continued participation in their chosen athletic activities. In these individuals, surgical stabilization is often performed in an attempt to lower the rate of recurrent instability episodes and allow for return to recreational and athletic activities.

Shoulder instability and surgical treatment of this disorder are common in football players. When college football athletes are likely to be drafted by teams in the National Football League (NFL), they are invited to the NFL combine for evaluation, which includes history, physical examination, and review of medical records and imaging studies. Almost 10% of athletes at the combine have a history of shoulder instability.³ Shoulder stabilization is the fourth most common procedure among all athletes seen at the combine, and 4.7% have a history of surgical treatment of instability by shoulder stabilization.³ Among college football athletes with a history of shoulder injury, instability is the second most common diagnosis (24%) and accounts for 58% of all procedures performed on the shoulder.¹⁸ Previous studies have shown a negative effect of the diagnosis of shoulder instability on an NFL athlete’s career.^4,6 A history of shoulder instability in athletes at the NFL combine significantly decreases the likelihood of playing in the NFL for offensive and defensive lineman.⁶ The current study used a case-control model to examine what effect shoulder instability and subsequent stabilization before entry into the league have on the length of an NFL athlete’s career. We hypothesized that athletes with a history of shoulder stabilization before the NFL combine would have shorter careers than matched controls.

Methods

A database containing the injury and surgery history for all 5047 athletes reviewed at the annual NFL combine by the medical staff of 1 NFL team from 1987 to 2000 was created and linked to a data set of NFL career statistics from the Elias Sports Bureau (New York, New York). This data set contained the round drafted, the number of seasons played, and the number of games played (regular season and/or playoffs) for the 2845 athletes who went on to play at least 1 game in the NFL. All athletes with a history of shoulder stabilization before the combine who played at least 1 game in the NFL were identified. Individuals with a history of any other surgery or more than 2 nonmeniscal, non–anterior cruciate ligament diagnoses were excluded from the analysis. Athletes with 1 or 2 additional diagnoses were then screened to exclude those who had a major injury that might confound the analysis (essentially, anything more than a muscle sprain, minor fracture, or burner).

A control was identified for each injured athlete in the cohort, matched by position. Controls could not have any history of surgery, and they had the same number of (or 1 fewer) minor nonshoulder instability diagnoses as the injured athlete; athletes with a history of any other significant injury (eg, knee ligament or meniscal injuries) were excluded. When possible, the other diagnoses were matched exactly (eg, both had a history of hamstring strain). Matching criteria were then based on entering the league within ±2 years and being drafted within ±2 rounds. When multiple matches were possible, those closest in year and round were chosen. The athletes were not matched on age, but the ages of the injured athletes were compared with the ages of the controls to ensure that there was no potential bias due to this variable. Years in the league and games played in the league were used as markers for length of career. Games started were used as a marker of length of career and performance.

Summary statistics for these measures of length of career and performance in the NFL were calculated separately for the athletes with a history of shoulder stabilization as well as their respective controls. Independent-samples t tests were calculated to compare the cases to the controls for each outcome measure. One-way analysis of variance and post hoc least squares difference tests were used to compare the mean length of career between athletes with histories of shoulder stabilization and athletes without prior surgeries. Finally, survival analysis using Cox regression was performed to assess the effect of shoulder stabilization on length of career in the NFL.

Results

Forty-two athletes with an isolated history of shoulder stabilization were identified. Data regarding the type of instability and surgery (open vs arthroscopic) was available for 80% of the athletes. Most athletes with data available had a history of anterior instability (91%) and were treated with an open procedure (91%). Twenty athletes played line or linebacker positions. Controls for each athlete were selected using the approach outlined above. The data set was reviewed to ensure that each control was only used once. Overall, 18 athletes were matched to controls with the same year and round drafted, whereas 21 had controls within ±1 year and/or round. Only 3 athletes required a match within ±2 years and/or rounds.

Tables 1 to 3 summarize the results. A history of shoulder stabilization significantly reduced the length of career in terms of years (5.2 ± 3.9 vs 6.9 ± 3.6 years, P = .01) and games played (56 ± 53 vs 77 ± 50, P = .03). There was a trend toward fewer games started in those with a history of shoulder stabilization (29 ± 49 vs 45 ± 44, P = .06). Linemen and linebackers (20 athletes) with a history of shoulder stabilization had a significantly shorter career in years (4.7 ± 3.8 vs 6.7 ± 3.4 years, P = .05) and games played (51 ± 58 vs 81 ± 48, P = .05) compared with controls. Among other position players (22 athletes), the difference was not statistically significant in this small cohort.

Table 1

Career Length of Athletes With Shoulder Stabilization Surgery Versus Controls (n = 42)

	Mean	Median	SD	P
Years
Stabilization	5.2	4	3.9	.01
Control	6.9	6.5	3.6
Games played
Stabilization	56	36	53	.03
Control	77	36	50
Games started
Stabilization	29	7	49	.06
Control	45	48	44

Table 2

Career Length of Linemen and Linebackers With Shoulder Stabilization Surgery Versus Controls (n = 20)

	Mean	Median	SD	P
Years
Stabilization	4.7	4	3.8	.05
Control	6.7	6.5	3.4
Games played
Stabilization	51	30.5	58	.05
Control	81	88	48
Games started
Stabilization	37	16	53	.07
Control	61	66	47

Table 3

Career Length of Nonlinemen and Nonlinebackers With Shoulder Stabilization Surgery Versus Controls (n = 22)

	Mean	Median	SD	P
Years
Stabilization	5.6	5	3.9	.10
Control	7.0	6.5	3.9
Games played
Stabilization	59	52	50	.30
Control	74	62	53
Games started
Stabilization	22	4	45	.06
Control	31	14	37

Survival analysis (Figure 1) demonstrated a shorter career in athletes with a history of shoulder stabilization (P = .04). There was no significant difference in length of career based on survival analysis in the position-specific cohorts.

Discussion

A history of shoulder stabilization for recurrent anterior instability is relatively common among elite football players at the collegiate and professional levels. The current study attempted to quantify the effect of shoulder stabilization on the length and quality of career in the NFL in athletes who had undergone shoulder stabilization before league entry. Compared with well-matched controls, athletes with a history of previous shoulder stabilization had a shorter career in terms of years and games played. This effect was noticeable in linemen and linebackers, who played more than 30% fewer games and years than controls did. In our relatively small cohort, no statistical difference in career length was seen in other position players with a history of shoulder stabilization.

Shoulder instability is a condition known to lead to significant morbidity in athletes who participate in contact sports. In a study of professional rugby players, Headey et al¹⁴ found that shoulder dislocation and instability led to an average of 81 days absent from competition, with a 62% recurrence rate. In a prospective multicenter study of more than 200 nonoperatively treated patients with a primary shoulder dislocation under the age of 40 years, 57% were found to have at least 1 more dislocation episode after the index injury. Almost 30% of these patients eventually required shoulder stabilization for recurrent instability.¹⁶ The recurrence rate in young high school and collegiate athletes is likely even higher. Hovelius et al¹⁵ found that 70% of athletes younger than 20 years of age had at least 1 recurrent dislocation, compared with 21% in individuals between the ages of 30 and 40 years. Marans et al²⁴ reported a 100% recurrence rate in 21 pediatric patients treated with immobilization after a traumatic anterior dislocation, and Mazzocca et al²⁵ stated that the recurrence rate in patients younger than 20 approaches 95%. The high incidence of recurrent injury in young athletes leads to significant morbidity and is especially relevant to the current study, because all the individuals had shoulder stabilization procedures performed at a relatively young age before entering the NFL.

Numerous studies have reported successful outcomes after shoulder stabilization in athletes, including American football players, based on an open or arthroscopic technique.^{2,11,20,25,26,31} Historically, open shoulder stabilization was preferred in football players, although arthroscopic stabilization may be approaching equivalent long-term efficacy owing to advances in surgical technique.¹ Additionally, arthroscopic shoulder stabilization potentially has the added benefit of faster recoveries, higher subjective outcomes scores, less subscapularis trauma, and less loss of external rotation, compared with open procedures.^9,12,17,22 Although a recent Cochrane Database systematic review found insufficient evidence from randomized trials favoring arthroscopic or open techniques,²⁹ many surgeons prefer performing open stabilizations in collision athletes. One meta-analysis found that open treatment of anterior shoulder instability led to significantly lower rates of recurrent instability and dislocation and higher rates of return to sports, as compared with arthroscopic stabilization,²² although a recent systematic review did not find any difference in recurrence rates between the 2 surgical techniques.⁷ In the current study, the majority of the football players underwent open stabilization procedures.

The previously mentioned studies show that operative intervention for recurrent shoulder instability enables many athletes to return to a high level of play with fewer episodes of recurrent instability, compared with nonoperative management. Despite this success, the current study shows that a history of shoulder stabilization has significant negative long-term consequences on the careers of collision and contact athletes. Unfortunately, the limitations of our database prevent us from definitively stating the causes of the shortened careers in these athletes. Several explanations seem likely. Some of this morbidity is almost certainly related to recurrent instability episodes. Reported rates of recurrent instability after shoulder stabilization range from 7% to 23%.^{20,23,28,31,36} This rate may be even higher in collision sports such as football. Cho et al⁸ reported a postoperative instability rate of 28.6% in collision athletes, compared with 6.7% in noncollision athletes. Hubbell et al¹⁷ reported a postoperative instability rate of 67% in collision athletes, compared with 0% in noncollision athletes. Roberts et al³⁰ reported that 30% of Australian Rules football athletes who underwent open stabilization and 70% who underwent arthroscopic stabilization had recurrent subluxations or dislocations upon return to their sport. Recurrent instability in an NFL athlete could shorten a career by the direct effect of time missed after instability episodes and by the possibility of being cut or losing a starting position after a significant injury.

A history of shoulder stabilization may also decrease career length by increasing the risk of, or hastening the progression of, posttraumatic arthritis in the glenohumeral joint, either through recurrent instability or because of altered loading of the joint resulting from the stabilization itself. The risk of posttraumatic arthritis could be increased by abnormal forces across the joint in an unstable or surgically altered shoulder or by direct cartilage damage from injury. Rates of glenoid bone loss have been reported to be as high as 56% in patients with traumatic instability, and the incidence Hill-Sachs lesions in the humeral head has been reported to be greater than 90%.²³ An arthritic joint, even if surgically stabilized, could certainly lead to significant pain and morbidity in NFL athletes, which could significantly affect career length and quality.

Subscapularis weakness is another possible cause of the shortened career in NFL athletes with a history of shoulder stabilization. Most athletes in this study underwent open shoulder stabilization, which has been shown to be associated with subscapularis muscle insufficiency.^32,33 Such a deficiency could pose a problem for NFL athletes, potentially affecting their ability to endure the necessary strength training as well as shoulder contact in practice and games. Unfortunately, no data were available on the incidence of subscapularis weakness in the current cohort.

In the current study, the effect of shoulder stabilization on career length (compared with that of controls) was larger in future NFL lineman and linebackers than in other positions. Several potential reasons explain why shoulder instability with subsequent stabilization may be more detrimental in this select group of athletes. For these athletes, the constant physical contact at the line, with frequent blocking and tackling, and the intense strength training regimen put heavy loads on the shoulder joint. Linemen have a higher mean weight than do athletes that play any other position.^19,34 Laurson and Eisenmann²¹ found that 45% of high school football linemen are overweight, at an age when shoulder instability first presents. By the time that linemen reach the professional level, many are considered obese. For example, in 2005, more than 500 NFL athletes weighed greater than 300 pounds.³⁴ Because the arm is a long lever that magnifies force across the glenohumeral joint, it is possible that larger athletes may place increased stress across the glenohumeral joint as compared with smaller athletes.

Linemen and linebackers may more frequently than other players place their shoulders in positions that increase stress across a surgical repair. The shoulder positions most likely to negatively affect a surgically stabilized shoulder are abduction and external rotation. Von Eisenhart-Rothe et al³⁷ found that patients with a history of traumatic shoulder dislocation had significantly increased anterior-inferior translation of the glenohumeral joint (3.6 vs 0.7 mm) in 90° of abduction and external rotation compared with normal controls. Pavlik et al²⁷ found that the primary reason for inability of professional athletes to return to sports after shoulder stabilization was pain when the arm was in positions of extreme abduction and external rotation. Defensive linemen and linebackers frequently place the shoulders in extreme abduction and external rotation when pass-rushing, with activities such as the “swim move.” Offensive linemen may also place the shoulders in positions of instability—especially external rotation—in the course of run and pass blocking. Offensive linemen also impart significant additional force across the shoulder joint during practices and games because most of their functional activities involve collision with large defensive linemen.

Football players have been shown to be 15 times more likely than nonfootball players to have a posterior labral injury on magnetic resonance arthrogram of the shoulder.¹⁰ Because of the position of the arm during blocking, posterior instability is likely to be more of an issue for linemen compared with athletes in other positions. The majority of the athletes in this cohort with a verified diagnosis suffered from anterior instability. The only 2 cases of known posterior instability in this cohort were in offensive linemen. Further study of the incidence and impact of posterior instability in linemen is warranted.

In the present investigation, no significant difference was seen in career length of nonlinemen and nonlinebackers as compared with controls. Although this lack of significance may be related to a relatively small sample size, it is possible that shoulder stabilization procedures in these individuals enable a full return to elite football without long-term morbidity. A lack of morbidity in these individuals would likely be related to less demand placed on the postsurgical shoulder in carrying out the duties of their respective positions. Future studies with larger numbers of individuals are needed to determine if a difference truly exists in the function of nonlineman or nonlinebacker athletes after shoulder stabilization procedures.

The limitations of the current study include the fact that it is a retrospective review rather than a prospective or randomized study. Although every effort was made to match the athletes with a history of shoulder stabilization to controls, it is possible that confounding variables still exist between the 2 groups. Although any significant injury with a subsequent need for surgery would have similar results in terms of career shortening or decrease in games played, a previous study using the same database did not find any effect of anterior cruciate ligament reconstruction on career length,⁵ which suggests that the findings with shoulder stabilization are specific to the injury and surgery. Another limitation is that we lack specific data, including integrity of the articular cartilage at the time of surgery, size of associated bony lesions, and the number of previous dislocations before stabilization. A final limitation was that the study involved athletes who entered the NFL between 1987 and 2000 and that most of the procedures were open stabilizations. It is possible that advances in surgical techniques in recent years would mean that an athlete who has a shoulder stabilization today would have a better prognosis than would an athlete who had the procedure performed in the past.

Despite its limitations, this is a well-matched case-control study that shows a significant correlation between a history of shoulder stabilization and decreased career length in the NFL. Although shoulder stabilization typically improves an athlete’s function when compared with nonoperative management, the morbidity of shoulder instability should not be underestimated. The negative effect of this condition appears to be magnified in lineman and linebackers, likely secondary to the significant forces on the shoulder joints in the extremes of motion used by these athletes during training and games. Further studies are needed to optimize outcomes after shoulder stabilization in elite football players to minimize morbidity associated with shoulder instability and to improve the quality and duration of these athletes’ careers.

Footnotes

The authors declared that they had no conflicts of interest in their authorship and publication of this contribution.

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