Overall functional status
Perhaps the most important conclusions of this study, is the absence of difference on the PRWE score between the boxers and the general population, and the lower (better) DASH score of the boxers’ group (Fig. 1). This shows that boxing reserves no serious long-term consequences regarding the functional status of the hands and arms of the average athlete, at least for the age groups compared. Consequently, it would be really interesting to examine this in older boxers (where perhaps the decreased musculature will give different results) or in professional boxers, as already a difference between competition and training is presented in research [11]. Apart from that, no difference was found in the prevalence of concussions, shoulder fractures, shoulder dislocations, biceps brachii strains, forearm fractures, wrist fractures, wrist sprains, fractures in metacarpals, wrist ganglion, carpal tunnel syndrome, wrist instability and ulnar sided wrist pain. However, physical therapy sessions (p = 0.012), thumb injuries (p < 0.001) and boxer’s knuckle (p = 0.036) occurred significantly more often in boxers, whereas the boxers faced fewer upper limb surgeries (p = 0.005). This comes in partial agreement to one of the largest studies conducted about hand and wrist injuries in boxing, as Loosemore et al. [10] found in 2016 that the 3 most common injuries were carpometacarpal (CMC) instability (21.6%), boxer’s knuckle (15.8%) and skier’s thumb (14.6%). Interestingly, wrist clunking (possibly correlated with carpometacarpal instability) was also correlated with higher DASH score in our study (p = 0.015). On the other hand, in our study we met a lower prevalence of upper limb surgeries. The explanation we could offer, speculatively, is that the increased musculature of the boxers compensates for the anatomical impairment of an injury and the loss of stability caused, thereafter decreasing the need for surgery. Lemme et al. [12] found the hand fractures to be one of the most common injuries among boxers, but this was a study conducted in emergency departments. Perhaps the severity (as found by the current study) of the hand fractures might bring those boxers to the emergency department often, but the real incidence is not so high, as neither our nor Loosemore et al. [11] could verify this finding. Finally, the high incidence of physical therapy sessions only among boxers, as highlighted by our study, could be an indicator of underreported injuries in the boxing population, as noted in our Limitations section.
Boxer’s knuckle and skier’s thumb (Fig. 2)
Boxer’s knuckle is more common among boxers according to our and numerous other studies [13, 14]. The severity of the injury can extend from mild capsular injury to frank dislocation of the extensor tendon. Diagnosis is usually clinical, but dynamic imaging is of high value, such as dynamic ultrasonography [15]. Conservative treatments such as splinting in extension, rest and medication can be applied successfully for mild injuries, but surgical treatment, with excellent return to play rates, should be preferred when there is a tendon dislocation as these do not respond well to conservative treatment, possibly due to fistula formation between the subcutaneous tissue and the capsule, and the development of chondromalacia/osteoarthritis if left untreated [16,17,18,19,20]. Skier’s thumb and thumb fractures although common among boxers, as verified by our and other studies, are not nearly as well documented as boxer’s knuckle, carpometacarpal bossing, or boxer’s fractures in the boxers’ population [21]. Undisplaced fractures or partial ulnar collateral ligament tears are treated with splinting in mild flexion for 4–6 weeks, whereas chronic tears, unstable displaced fractures, Stener’s lesions, acute unstable tears and volar plate injuries are indicated for surgical management including direct repair, reconstruction, arthrodesis, or arthroplasty [22, 23].
Glove size
The current study found strong association between size of gloves and finger fractures (p = 0.005) or ulnar sided wrist pain (p = 0.041), as the higher the size of gloves, the higher the incidence of these injuries (Fig. 3). In 2013, the AIBA (as of last year rebranded as International Boxing Association to signal a wide set of reforms) changed the regulations, removing the headgear, increasing the glove size and changing the scoring system [12]. This resulted to a change in the fighting style, as more long-range jabs were used instead of the hook and cross, which put the shoulder in the vulnerable position of external rotation and abduction and produce more force [24], while the bigger gloves supposedly provided better hand protection [25]. At the same time, a study conducted from 2012 to 2016 in US, found a lower rate of reported injuries from boxing after the change of rules in 2013 [12]. The traditional training technique would be to use bigger gloves during punching bag sessions. That is supported by lab research, as Lee & McGill e al. found that thicker gloves with less stiff padding present lower peak forces and lower loading rates, as expected [26]. So the advantages assumed of this practice are injury prevention through the heavier padding and higher hand speed during competition, where the gloves are lighter. However, bigger gloves could mean less stability and more rollover during punching, which could lead to more fractures and ligamentous injuries, as observed from our study. Or as Lee & McGill noted, padding deterioration on heavy gloves can have the opposite effect, as material failure can show higher peak forces and faster loading rates [26]. Another more plausible explanation could be that these injuries pre-existed and led the athletes to bigger glove size, as some pre-existing injuries could also be associated with worse functional status. Unfortunately, some of the above is speculation, and is provided after discussion with coaches and athletes. We report it to provide consideration for future research on the effect of glove size in boxing.
Other common injuries
Another well documented injury, the boxer’s fracture, is a fracture of the 4th or 5th metacarpal. However, the literature suggests that this injury is not met during boxing rather during bouts with bare knuckles [19], a finding confirmed by our study as we did not record a statistically significant higher incidence of boxer’s fracture among boxers. Finally, carpometacarpal (CMC) bossing is another common injury among boxers. It is well documented that there is little degree of movement in the 2nd and 3rd carpometacarpals (1° and 3° respectively) and more for the 4th and 5th carpometacarpals (8°–15° and 15°–40° respectively) [27,28,29]. This is one of the reasons why boxers hit the bag with their index and middle finger [30], when practicing correct punching technique. Despite the low degree of mobility in the 2nd and 3rd CMC, repetitive impact can cause a flexion downward force, with secondary dorsal flexion at the CMC joint. The first choice of treatment includes conservative management with immobilization, but recurrent injuries can result in bony hypertrophy, degenerative changes, and joint subluxation, requiring CMC arthrodesis [20, 25]. Other upper limb boxing injuries reported sparingly in the literature include avulsion fracture of the ECRB insertion in trapezium, scapula fractures, internal impingement of the coronoid and olecranon processes, teres major tendon tears and flexor carpal radialis avulsion [31,32,33,34,35].
Limitations
Unfortunately, there are multiple limitations to this study, which we should recognize. First of all, it is a retrospective study and the data collected were self-reported by the participants. No medical diagnosis was done for the conditions studied. As mentioned by Finlay et al. and Altaribba-Bartes et al. self reported data in boxing might not be always accurate [36, 37]. This could be attributed to the criticizing boxing is receiving for being dangerous (coaches want to highlight the numerous benefits of boxing so that more people join the sport) as well as due to the boxer’s mentality to fight through the injury especially before a bout [36, 37]. What is more, there is the side of boxing that is associated with underground activities and officially recording of any kind is not welcome by some clubs. The groups were only helped through photos and descriptions. Apart from that, no differences between injuries suffered during competition or training could be studied. Finally, there was not sufficient sample size to study the functional status of veteran (> 35 years-old) or female boxers, which would be really interesting.