Consensus Statement on Epidemiological Studies of Medical Conditions in Tennis, April 2009

Abstract

Background: 

The reported incidence, severity and nature of injuries sustained in tennis vary considerably between studies. While some of these variations can be explained by differences in sample populations and conditions, the main reasons are related to differences in definitions and methodologies employed in the studies.

Objective: 

This statement aims to review existing consensus statements for injury surveillance in other sports in order to establish definitions, methods and reporting procedures that are applicable to the specific requirements of tennis.

Design: 

The International Tennis Federation facilitated a meeting of 11 experts from 7 countries representing a range of tennis stakeholders. Using a mixed methods consensus approach, key issues related to definitions, methodology and implementation were discussed and voted on by the group during a structured one-day meeting. Following this meeting, 2 members of the group collaborated to produce a draft statement, based on the group discussions and voting outcomes. Three revisions were prepared and circulated for comment before the final consensus statement was produced.

Results: 

A definition of medical conditions (injuries and illnesses) that should be recorded in tennis epidemiological studies and criteria for recording the severity and nature of these conditions are proposed. Suggestions are made for recording players' baseline information together with recommendations on how medical conditions sustained during match play and training should be reported.

Conclusions: 

The definitions and methodology proposed for recording injuries and illnesses sustained during tennis activities will lead to more consistent and comparable data being collected. The surveillance procedures presented here may also be applicable to other racket sports.

INTRODUCTION

In a review of research papers published in the period 1966 to 2005, Pluim et al¹ identified that reported incidences of tennis injuries ranged over 2 orders of magnitude (0.04 to 3 injuries/1000 player-hours). Although some of this variation can be accounted for by the different sample populations used in the studies, the authors stated that the main reason for the differences was more likely to be due to the variation in injury definitions and protocols employed in the studies. Consensus statements for cricket², football³ and rugby union⁴ have previously outlined the benefits associated with developing and implementing consistent definitions, data collection procedures and methods of reporting results in injury surveillance studies. Although these consensus statements were specifically developed for team sports, the International Olympic Committee (IOC) and the International Association of Athletics Federations (IAAF) demonstrated that the principles were also relevant to individual sports.^5,6 This extension of the methodology by the IOC and IAAF broadened the application of the team sports consensus statements; however, the current team-based procedures are still not wholly applicable to the specific requirements of surveillance studies for individual sports such as tennis.

Managing the risks of injury and illness associated with professional and community-level tennis presents additional problems compared to those encountered with team sports such as football and rugby. Firstly, there is a perception that tennis players are susceptible to more chronic injuries and illnesses than are normally reported in contact team sports.^7-9 Secondly, professional tennis players do not usually have their own dedicated medical support to manage their conditions in the way that footballers do within a team environment. Tennis players generally rely on the medical support provided by the organisers of individual tennis tournaments and individual governing bodies around the world. Consequently, several medical/health care practitioners could be called on to manage a player's long-term condition and the full recovery of a player's medical condition is therefore unlikely to be reported by the same person who recorded the onset of the condition. Thirdly, responsibility for decisions related to return to training and competition (and hence condition severity) often rests with individual players and their support network rather than medical/health care practitioners at tournaments. Perhaps the greatest challenge, however, is that responsibility for the sport of tennis worldwide is shared among 3 international governing bodies: ATP Tour, Inc (ATP), which is responsible for the men's professional tennis tour; WTA Tour, Inc (WTA), which is responsible for the women's professional tennis tour; and the International Tennis Federation (ITF), which is responsible for amateur junior tennis tournaments, entry-level men's and women's professional tennis tournaments, the Olympic Games, Davis Cup and Fed Cup, and collaborates with the Grand Slam competitions in Australia, England, France and United States. The ITF is also responsible for governing other aspects of the men's and women's tennis game, including the Rules of Tennis. It is important that all governing bodies develop a similar understanding and approach for the management of medical issues in tennis. The first stage in achieving this is the adoption of a common approach for recording and reporting medical conditions. This statement aims to review the existing published consensus statements for injury surveillance in other sports in order to establish definitions, methods and reporting procedures that are applicable to the specific requirements of surveillance of medical conditions at all levels of tennis.

Consensus Procedure

Following discussions between several national and international tennis governing bodies, the International Tennis Federation facilitated a Tennis Consensus Group with a remit to develop a consensus statement for the surveillance of tennis injuries and illnesses. Based on experience gained from the development of football and rugby consensus statements, a mixed methods consensus methodology, encapsulating elements of the Nominal, Delphi, National Institutes for Health (NIH) and Glaser's State of the Art approaches,^10-12 was adopted as the most appropriate method to address the issues involved. In summary, the consensus process included the following stages:

• Key stakeholders within tennis (doctors, physiotherapists, athletic trainers, administrators, coaches and players) identified the need for a consensus statement on injury surveillance in tennis (Glaser).
• A group of international experts with experience of managing tennis injuries was identified. These experts then nominated other experts with relevant knowledge and experience to join the consensus group (Delphi, Glaser, Nominal).
• A non-medical moderator was appointed to facilitate the consensus meeting (Glaser, Nominal).
• A formal, structured procedure for conducting the consensus meeting was circulated and agreed to prior to the meeting (Nominal).
• An agenda and the consensus statement for football were circulated to all members of the group to provide the basis for discussions; participants were formally requested to identify any additional topics to be added to the agenda of the consensus meeting (Delphi).
• During the consensus meeting, each topic was discussed openly, including suggesting modifications to definitions and procedures (Nominal).
• The moderator ensured that all delegates were provided the opportunity to present their views on each topic but the discussions were constrained within the agreed timescales of the agenda. On conclusion of the discussion about each topic, the moderator called for a vote on each proposal (NIH).
• Following the consensus meeting, a draft statement was prepared by the 2 lead authors based on the discussions and voting outcomes recorded during the meeting. This document was circulated to all group members with a request for comments to be returned within a 3-week period. All comments received were reviewed by the 2 lead authors and, where appropriate, incorporated into a subsequent revision of the statement. Where a suggested change was not incorporated, a written explanation was prepared and circulated to all members of the group. This process was repeated for 3 iterations (Delphi).
• After the final iteration, all members of the group were asked to confirm their agreement with this final statement.

The consensus meeting took place over one day in April 2009 at the ITF offices in Roehampton, London. Nine members of the Tennis Consensus Group were present at the meeting in person and 2 members took part via a telephone conference link.

DISCUSSION

The recommendations presented in this statement draw extensively on the proposals made for football³ and rugby union⁴ but they reflect the specific issues facing tennis at both the elite and community levels of play. The discussion is presented in a similar format and sequence to that used in the football and rugby union statements in order to facilitate comparisons between the statements.

Definitions

Medical Condition (Injury/Illness)

A medical condition is defined as:

▪Any physical or psychological complaint or manifestation sustained by a player that results from a tennis match or tennis training, irrespective of the need for medical attention or time loss from tennis activities.

The term ‘medical condition’ was adopted in this statement rather than ‘injury’, which was used in previous consensus statements, in order to reflect the desire to collect information on both injuries and illnesses. The term ‘manifestation’ was added to the term ‘complaint’, as players are not always aware that they have an ailment, precipitating a complaint, even though the player may have external signs and symptoms that would alert a medical/health care practitioner to a condition such as heat-related illness. Finally the term ‘psychological’ was added to encompass the full range of conditions sustained by tennis players, eg, burn-out.¹³ Medical conditions that result from tennis match play and training should be recorded in surveillance studies but conditions that are not directly related to tennis should not be included. For example, sun-related skin problems, exercise-induced asthma, and hypothenar hammer syndrome resulting from tennis should be recorded but road traffic incidents and falls at home should not.

Most surveillance studies will record conditions that require medical attention or result in time loss from tennis match play and training. In this context, medical attention refers to an assessment of a player's medical condition by a qualified medical/health care practitioner, such as a doctor, physiotherapist, osteopath, chiropractor, or athletic trainer. An on-court request by a player for medical attention for adjustment of a knee taping, for example, should not be recorded as a ‘medical condition’ unless it is identified as a treatable medical condition with evidence of aggravation of the player's existing knee condition.

Recurrent Medical Condition

A recurrent medical condition is defined as:

▪A medical condition of the same type and at the same site linked to an index medical condition and which occurs after a player's return to full participation from the index medical condition.

Recurrent injuries are relatively easy to identify, although, as proposed in the football consensus statement, injuries such as contusions and lacerations should not be recorded as recurrent injuries, as they are unlikely to be related to a previous injury³. Repeat episodes of illnesses such as skin infections, exercise-induced asthma, arrhythmias and upper respiratory tract infections should be recorded as recurrences.

Severity of Medical Conditions

Severity of a medical condition is defined as:

▪The number of days that have elapsed from the date of onset of the medical condition to the date of the player's return to full participation in tennis training and availability for match play.

The day on which a medical condition first occurs does not count towards the severity of the condition; the assessment of severity (days lost) commences on the following day if the player is unable to take part in full training or match play. This issue is particularly important in tennis, as it is not unusual for a player to retire from a doubles match due to a medical condition but to play in a singles match later on the same day or on the following day. Although incidents of this type should be considered as medical conditions, they should not be counted as time-loss medical conditions. Because players have a variable schedule of play and the time between tournaments varies considerably, the phrase ‘availability for match play’ is an important part of the definition and is intended to indicate whether a player had recovered sufficiently to be able to play in a match irrespective of whether one was actually scheduled to take place.

The severity of a medical condition is defined solely on this pragmatic basis rather than by clinical judgement. If this approach were not adopted, determining the severity of some medical conditions experienced in tennis would present difficulties, as many acute and gradual-onset medical conditions develop into chronic conditions, with players returning to play/training while still experiencing adverse effects. For example, a player may suddenly develop acute shoulder pain, as a result of tendinopathy of the rotator cuff, and miss 2 weeks of training before returning to competition while still experiencing pain; some 6 weeks later the pain level increases to such an extent that the player misses a further 4 weeks of training. The first episode should be recorded as an acute onset shoulder tendinopathy with a severity of 14 days, while the second episode should be recorded as a recurrence with a severity of 28 days.

A ‘career-ending’ medical condition is one that leads to a player's retirement from tennis at the standard played at the time of sustaining the condition. If the player subsequently returns to play tennis at a lower standard, the original condition should still be considered as career-ending for the purposes of the surveillance study. As there is no end-point to a career-ending medical condition, these incidents should be reported separately and not included in calculations of mean and median severity.

Classification of Medical Conditions

Whenever possible, a qualified medical/health care practitioner should provide a written diagnosis of each condition or use sport-specific codes, such as the Orchard¹⁴ or University of Calgary¹⁵ coding systems. In addition to recording whether a condition is an index or a recurrent condition, medical conditions should also be classified according to their mode of onset, body location and side and type.

Acute and Gradual-Onset Condition

Conditions can be classified according to the way in which they present. An acute-onset condition refers to a condition resulting from a specific, identifiable event or when there is a sudden onset of (relatively severe) pain or disability. A gradual-onset condition refers to a condition that manifests itself over a period of time, or when there is a gradual increase in the intensity of pain or disability, without a single, identifiable event being responsible for the condition. Examples of acute-onset conditions include muscle tears and fractures, while gradual-onset conditions include tendinopathy and overtraining syndrome.

Location of Medical Condition

The location of medical conditions (injuries and illnesses) should be categorised within one of the 4 general body regions: head/neck, upper limbs, trunk, and lower limbs. In larger injury surveillance studies conditions should be further divided into the sub-locations shown in Table 1.

TABLE 1: Main Groupings and Sub-categories for Classifying the Location of Medical Conditions

Type of Condition

Medical conditions should be categorised according to the structure(s) or system(s) affected. Injuries should be categorised within one of the general structures: bone, joint (non-bone)/ligament, muscle/tendon, skin and central/peripheral nervous system; in larger injury surveillance studies, injuries should be further divided into the sub-structures shown in Table 2. Illnesses should be recorded within one of the medical systems shown in Table 3.

TABLE 2: Main Groupings and Sub-categories for Classifying the Types of Injuries

TABLE 3: Illness Classification by System

Exposure

Match exposure is defined as:

▪Play (including on-court warm-up) between competing players.

A tennis match is usually preceded by a formal 5-minute on-court warm-up period of tennis under the control of the match referee¹⁶. Any medical conditions sustained during this on-court warm-up period should be recorded as a match medical condition. Any medical condition sustained during off-court warm-up or cool down should be recorded as a training condition.

Training exposure is defined as:

▪Individual physical activities that are aimed at maintaining or improving a player's tennis skills or physical condition

The off-court warm-up/cool down period before/after a match should be recorded as training exposure. Only activities specifically aimed at improving a player's tennis skills or physical condition should be included as training exposure; this includes skills, strength and conditioning and cross-training (eg, cycling, swimming). Exercise and social sports activities that are not scheduled as part of a player's formal training programme should not be included as training exposure.

Recording Information

Studies should be approved by a recognised institutional ethics committee. As with previous recommendations^3,4, studies should normally follow a prospective, cohort design, as this approach reduces errors associated with information recall. Standardised data collection forms, which can be presented in an electronic or paper format, should be used consistently throughout a study and the use of guidance documents for studies greatly improves the accuracy and reliability with which the report forms are completed. It is essential that all medical condition data are recorded and transmitted in a secure format to preserve the confidentiality of players' personal information.

Player Baseline Information Form

Baseline information required in most surveillance studies should include the player's study reference number, age, gender, height, body mass, dominant arm, and use of single or double-handed backhand and forehand strokes. It would normally be appropriate to also record standard of play and in the case of studies among professional tennis players to record the player's world ranking.

Medical Condition Report Form

The report form should provide the player's study reference number, date of condition, whether the condition was sustained during match play or training, type of match (singles, doubles, mixed), the type of court surface played on (clay, hard, grass, indoor), information describing the circumstances leading to the condition and the date of the player's return to full participation. The nature of the condition (acute or gradual-onset; body location, type and side; index or recurrence) should also be recorded on the form. A section should be provided to enable a specific diagnosis or classification code to be recorded; free-text sections may be required for some studies if additional study-specific information is required. Report forms should be completed as soon as possible after conditions are sustained but information should be updated as additional information becomes available through the use of, for example, imaging or surgery.

For studies of medical conditions at the non-professional level of play, a medical/health care practitioner involved with the study should complete each condition report form. At the professional level, this approach can be adopted for surveillance studies implemented at individual tournaments where the tournament physician, for example, could provide the necessary data. This approach, however, is not feasible for extended epidemiological studies that involve several tournaments on the professional tours. These tournaments take place in many countries and there are different cohorts of players participating in them. Although the ATP and WTA provide travelling physiotherapists/athletic trainers to work with the players on these tours, it would remain extremely difficult to track the progress and record the details of conditions for every player at every tournament. For this type of study, appropriate data could only be collected if centralised systems were available to access medical data for all tournaments within the men's and women's professional tours. This situation is currently being examined by the major governing bodies in tennis¹⁸ and this consensus statement should provide the core methodology required for establishing such a system.

Match and Training Exposure Form

This form should record the date, type and duration (hours and minutes) of each exposure together with the playing/training court surface used (clay, hard, grass, indoor). In many competitions, an umpire will record the duration of a match. In the absence of this information, the number of games played should be recorded and this number multiplied by the average duration of a game played on an equivalent playing surface (Table 4)^19,20 to provide a reliable estimate of the match exposure. At the time of writing this statement, published data on game duration were only available for men's and women's singles play on clay, hard and grass courts. Match play exposure should be recorded separately for men and women and for singles, doubles and mixed doubles playing formats.

TABLE 4: Average Game Duration on Different Court Surfaces for Men's and Women's Singles Match Play^19,20

Training exposure (hours and minutes), recorded separately for men and women and for singles, doubles and mixed doubles playing formats, should preferably be collected for each training session but as a minimum it should be collected on a weekly basis. Training data can be collected on a grouped basis, whereby the total training exposure in hours is given by the sum of values for (P_T × D_T/60) for every training session throughout the study: P_T represents the number of players involved in the training session, and D_T represents the duration of the training session in minutes. Collecting individual exposure times is very time consuming but necessary for studies where the intention is to investigate the relationship between medical conditions and players' risk factors.

Reporting Information

The cohort should be clearly defined before the start of the study with the number of participants, their age (mean and range), gender and level of play reported. Acute injuries should be reported separately for match and training exposures as an incidence (number of injuries/1000 player hours). Incidence should not be reported with respect to athletic exposures, as the duration of one exposure in tennis varies greatly (eg, number of points played in a game and number of games played in a set), depending on a number of factors such as the nature of the competition (eg, singles, doubles, mixed); the format (eg, best of 3 or 5 sets); the relative ranking of the opposing players; and the playing surface.¹⁷ Illnesses and gradual-onset injuries should be reported as a seasonal (or annual) prevalence (ie, number of players reported with the medical condition in the season or year × 100/number of players included in the study) because it is not possible to reliably identify the match and training exposures leading to these conditions. Results should be reported separately for men's singles, women's singles, men's doubles, women's doubles and mixed doubles. If the times when medical conditions are sustained in a match are recorded, the time of occurrence of conditions should be presented in defined 1-hour periods of play (0-1 hour, 1-2 hours, etc) together with the number of games played.

The overall severity of conditions recorded in a study should be reported as both the mean and the median number of days-lost; however, severity can also be grouped according to the period of time lost - namely, slight (0 days), minimal (1-3 days), mild (4-7 days), moderate (8-28 days), severe (>28 days - 6 months) and long-term (>6 months).

This paper provides a proposal for the definition of medical conditions that should be recorded in tennis epidemiological studies, including criteria for recording the severity and nature of these conditions. Suggestions are made for recording players' baseline information, and match and training exposures. Finally, recommendations are presented on how medical conditions should be reported. The definitions and methodology proposed within this consensus statement should lead to more consistent and comparable medical data being collected in tennis. The recommendations could also be applicable to other racket sports and individual sports such as golf.