Functional outcomes after arthroscopic treatment of lateral epicondylitis

J Orthop Sci (2009) 14:167–174 DOI 10.1007/s00776-008-1304-9

Original article Functional outcomes after arthroscopic treatment of lateral epicondylitis TAKURO WADA1, TAMAMI MORIYA1, KOSUKE IBA1, YASUHIRO OZASA1, TOMOKO SONODA2, MITSUHIRO AOKI1, and TOSHIHIKO YAMASHITA1 1 2

Department of Orthopaedic Surgery, Sapporo Medical University, South 1, West 16, Sapporo 060-8543, Japan Department of Public Health, Sapporo Medical University, Sapporo, Japan

Abstract Background. The purpose of this study was to evaluate surgical outcomes of arthroscopic débridement for lateral epicondylitis using a validated, patient-assessed scoring system as well as conventional outcome measures. We also wanted to identify potential predictive factors that may be associated with the outcomes. Methods. A total of 20 elbows in 18 patients with chronic lateral epicondylitis who underwent arthroscopic surgery were included. There were nine men and nine women with a mean age of 54 years (range 42–71 years). Operative treatment consisted of débridement of the extensor carpi radialis brevis (ECRB) origin and resection of the radiocapitellar synovial plica interposed in the joint. Outcomes were assessed using a patient rating, visual analogue scale (VAS) pain score, the Japanese Orthopaedic Association (JOA) elbow score, and the Disability of the Arm, Shoulder, and Hand (DASH) questionnaire. The average length of follow-up was 28 months (range 24–40 months). Results. After surgery, according to the patients’ reports, 14 of 20 elbows were much better, and 6 elbows were better. A mean preoperative VAS pain score at rest of 3.9 points improved to 0.3 points (P < 0.0001), and that during activity improved from 7.8 points to 0.9 points (P < 0.0001). The mean preoperative JOA elbow score of 29 points was improved to 90 points (P < 0.0001). The mean postoperative DASH score was 10.6 (range 0–50). Absent of T2-weighted high signal focus of the ECRB origin on preoperative magnetic resonance imaging (MRI) (P = 0.02) and receiving public assistance (P = 0.01) were significantly associated with worse DASH scores. Conclusions. Arthroscopic release was a satisfactory procedure for chronic lateral epicondylitis. Preoperative MRI of the ECRB origin and socioeconomic factors were significantly associated with postoperative residual symptoms evaluated with the DASH score.

Offprint requests to: T. Wada Received: June 18, 2008 / Accepted: November 4, 2008

Introduction Lateral epicondylitis remains one of the most common pain syndromes in the upper extremities. It can be caused by a microscopic rupture with formation of reparative tissue in the extensor carpi radialis brevis (ECRB).1 Studies have estimated that 90% of patients have significant improvement at the end of 1 year of nonoperative treatment.2 Despite conservative management, approximately 10% of patients may require operative release. Traditionally, surgery for lateral epicondylitis has involved resection of the degenerative tendon tissue through an open incision.1,3 More recently, this surgery has been performed arthroscopically.4–11 A systematic review12 indicated that patients reported improvement of their condition over the preoperative status, regardless of the surgical technique used. However, approximately 10%–20% of patients are unable to continue with their previous level of activity owing to residual symptoms.13,14 To date, few studies15,16 have evaluated these symptoms and related disabilities with a contemporary and validated, patient-assessed scoring system. Moreover, factors that lead to good or poor outcomes after treatment have not been well characterized. The purpose of this study was to evaluate surgical outcomes of arthroscopic débridement for lateral epicondylitis using a validated, upper extremity-specific questionnaire that is self-reported by patients, the Disability of the Arm, Shoulder, and Hand (DASH) questionnaire as well as conventional measures. We also attempted to identify demographic factors, socioeconomic factors, and radiographic and arthroscopic findings that may be associated with the outcomes after arthroscopic surgery for lateral epicondylitis.

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Materials and methods Patients Between January 2003 and April 2006, a total of 20 consecutive patients with 22 affected elbows were treated for lateral epicondylitis with arthroscopic surgery. In all, 18 (89%) of 20 patients with affected elbows elected to participate in the study (Table 1). Approval was given by the institutional review board, and informed consent was obtained from each patient. Inclusion criteria were symptomatic lateral epicondylitis refractory to conservative care for a minimum of 6 months and clinical follow-up of at least 24 months. There were 9 men and 9 women with an average age of 54 years (range 42–71 years). No patients had a history of fracture or other elbow disorders. One patient was receiving workers’ compensation. The dominant side was involved in nine patients and bilateral sides in two patients. The predominant symptoms were pain with grasping and lifting. All patients underwent a trial of conservative treatment for at least 6 months (range 6–36 months). It included rest, activity modification, counterforce bracing, nonsteroidal antiinflammatory medication, and an average of two cortisone injections (one to five injections). On physical examination, patients consistently had point tenderness over the lateral epicondyle as well as pain with resisted wrist dorsiflexion with the elbow extended. One patient complained of painful snapping in the lateral aspect of the elbow upon 90°–100° of elbow flexion with forearm pronation. Elbow range of motion (ROM) was full in all elbows. On plain radiographs, two patients showed calcified lesions over the lateral epicondyle. Magnetic resonance imaging (MRI) revealed high signal intensity of the ECRB origin (Fig. 1) in 14 elbows. Operative procedure Operative treatment consisted of an arthroscopic inspection, débridement of the ECRB origin, and resection of the radiocapitellar synovial plica if it was interposed in the joint. The patient was positioned in the lateral decubitus position. The procedure was performed under tourniquet control. The joint was insufflated with 20– 30 ml of lactated Ringer’s solution. A proximal anteromedial portal was established first, and the anterior compartment of the joint was examined. The surgery was performed primarily with a 4.0-mm, 30° arthroscope positioned in the medial portal. The working instruments were passed through the proximal lateral portal. Surgical findings of the ECRB origin were evaluated according to Baker et al.4 and those of the radiocapitellar synovial plica were evaluated according to Mullett et al.6

Fig. 1. T2-weighted fat suppression magnetic resonance imaging shows a high signal focus (white arrow) in the extensor carpi radialis brevis (ECRB) tendon at the lateral epicondyle

The débridement of the ECRB origin was primarily performed with a 3.5-mm full radius shaver. The arthroscopic débridement involved resection of the degenerative area of the extensor tendon and the closely apposed joint capsule while not violating healthy tendon or muscle. Disease tissue was easily excised with the shaver, whereas healthy tendon tissue was more resistant to resection. The ECRB tendon was released from the lateral edge of the epicondyle extending medially to the capitellum (Fig. 2). To avoid injury to the lateral ulnar collateral ligament, the tendon débridement stayed on the anterior aspect of the lateral epicondyle. The lateral epicondyle was then abraded with the shaver to stimulate a healing response. The synovial plica interposed in the radiocapitellar joint was also débrided (Fig. 3). After completion, the portals were closed in the standard fashion with a single suture. The elbow was then placed in a soft dressing and arm sling for 2–3 days. Rehabilitation consisted of early ROM exercises and eventual return to full activity as tolerated. Patients were allowed to resume unrestricted activity at 6–8 weeks, pending a satisfactory physical examination. In all, 20 elbows in the 18 patients were clinically evaluated in the outpatient clinic and were specifically reviewed for the purpose of this study by the authors, who were not involved in any of the operations. The average length of follow-up was 28 months (range 24–50 months). Patients were asked if their elbows were “much better,” “better,” “the same,” or “worse” and were also asked to assess their elbow pain on a scale

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Table 1. Data on 20 elbows of 18 patients MRI Patient no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Age (years) 71 49 42 44 45 43 55 50 62 63 60 60 54 56 50 46 59 44 64 55

Sex

Occupation

Public assistancea

M M M M M

Retiree Carpenter Cook Office worker Carpenter

YES NO NO NO NO

M M F F F

Office worker Teacher Housewife Housewife Clerk

NO NO YES YES YES

F F F F F F M M

Clerk Housewife Housewife Cleaner Clerk Nurse Office worker Carpenter

NO NO NO NO NO NO NO NO

Affected sideb

Duration of symptoms (months)

Follow-up period (months)

High signal focus of the ECRB originc

D N N N N D D D D N N D D N D D D N N D

4 8 14 11 14 36 6 19 16 12 6 48 6 24 120 6 13 12 12 8

28 24 39 40 24 52 36 44 24 24 26 31 25 29 32 24 25 40 24 24

No Yes Yes No Yes No Yes No Yes No No Yes Yes Yes Yes Yes Yes Yes Yes Yes

Bilateral elbows were involved in patients 5 and 6 a Yes, receiving public assistance; No, receiving no public assistance b D, dominant side; N, nondominant side c T2-weighted high signal focus of the ECRB origin at the lateral epicondyle

Patient no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Visual analogue scale pain score

Arthroscopic findings

With activity

At rest

JOA elbow score

ECRB

Plica

Patient rating

Pre

Post

Pre

Post

Pre

Post

I I II II I III I II I III I III III I I I II II III I

3 3 2 3 2 2 1 1 2 2 1 1 3 2 3 2 1 3 1 2

Much better Much better Much better Better Better Much better Much better Much better Much better Better Better Better Much better Much better Much better Much better Much better Better Much better Much better

7 7 10 7 9 8 8 9 6 8 8 8 8 7 8 10 5 8 7 9

0 1 0 0 4 0 1 1 0 3 3 2 0 0 0 0 0 2 0 0

7 0 3 0 5 6 0 1 0 8 8 8 8 3 1 8 0 5 3 6

0 0 0 0 2 0 0 0 0 3 0 0 0 0 0 0 0 1 0 0

38 39 40 45 22 18 18 23 26 27 29 28 29 26 59 27 27 20 22 21

100 98 75 95 75 100 80 75 93 58 90 84 100 100 100 100 90 85 100 100

DASH, Disability of the Arm, Shoulder, and Hand questionnaire; Pre, preoperative; Post, postoperative ECRB (extensor carpi radialis brevis), arthroscopic classification of the ECRB origin according to Baker et al.4 Plica, arthroscopic classification of the radiocapitellar synovial plica according to Mullett et al.6

DASH score 8 3 9 8 13 1 7 42 50 31 1 3 0 1 2 6 0 0

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A

B Fig. 2. Anterolateral elbow with a 30° arthroscope inserted through the proximal medial portal. A Extensor tendons before débridement, with tearing of the lateral elbow capsule

(arrow) at the ECRB origin. C, capitellum; R, radial head B Same area of the elbow after arthroscopic débridement

Table 2. JOA elbow score for lateral epicondylitis I.

Pain (30 points)

II. Function (20 points) ADL (12 points) Lift a heavy object Wring a wet towel Pour a glass of water MMT (8 points) Elbow flexion Elbow extension III. Lateral epicondylitis (50 points) Tenderness over the lateral epicondyle Pain with resisted wrist extension

None 30

25

Mild 20

Easy 4 4 4 5 5 3

Difficult 2 2 2 4 4 3

Impossible 0 0 0 3 2 3 2 2 1

− 20 − 30

± 10 ± 20

+ 5 + 10

15

Moderate 10 5

1 1 0

Severe 0

0 0 0

++ 0 ++ 0

These data are from ref. 17 JOA, Japanese Orthopaedic Association; ADL, activities of daily living; MMT, manual muscle test

from 0 (no pain) to 10 (severe pain). The patients completed the physical examination, and their elbows were rated according to the Japanese Orthopaedic Association (JOA) elbow score for lateral epicondylitis, which consists of assessing the pain (30 points), function (20 points), and two important physical findings of lateral epicondylitis (50 points) (Table 2).17 The Japanese Society of Surgery of the Hand version of the Disability of the Arm, Shoulder, and Hand (DASH) questionnaire18 was used to assess the functional outcomes as a validated, patient-based subjective questionnaire. The DASH score quantifies pain and disability related to the

upper extremity and ranges between 0 and 100 points. The lower DASH scores represent less pain and disability. A study on a nonclinical population19 indicated that the DASH score in healthy employed adults is 13 ± 15. Thus, in this study, a DASH score below 14 points was considered a good result. Statistical analysis Statistical analyses were performed by a statistician using SPSS version 12 software. The Wilcoxon signed ranks test was used to compare the preoperative and

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B

A

C Fig. 3. Anterolateral elbow with a 30° arthroscope inserted through the proximal medial portal. A, B Synovial plica (arrows) before débridement, with partial covering of the radial head in elbow flexion (A) and with impingement into

the radiocapitellar joint in elbow extension and pronation (B). C, capitellum; R, radial head. C Same area of the elbow after resection of the plica

postoperative visual analogue scale (VAS) for pain and the JOA elbow score. The Mann-Whitney U-test was performed to assess the effect of variables on patient outcome evaluated with the DASH questionnaire. This study used predictors that have been suggested in other studies to be associated with outcomes after surgical and nonsurgical treatment of lateral epicondylitis. Potential predictors included baseline variables representing patient characteristics, MRI findings, and arthroscopic findings. The baseline variables included age,20 sex,20 occupation (desk job or manual labor),21 and whether the dominant side was affected.22 We also considered a socioeconomic factor (whether receiving public assistance).23 A preoperative variable on MRI findings included T2-weighted high signal focus of the ECRB origin.24 Variables on arthroscopic findings included whether a tear of the

ECRB origin was present (Baker’s type I/type II and III) 4 and whether a synovial plica was interposed in the radiocapitellar joint (Mullet’s type 1 and 2/type 3).6 As the DASH score evaluates pain and disability related to the bilateral upper extremity, variables on the elbow with the latest surgery were taken for the analyses in two patients with bilateral involvement. Statistical significance was defined as P < 0.05.

Results Surgical findings of the ECRB origin according to Baker et al.4 were 10 type I lesions, 5 type II lesions, and 5 type III lesions. A type I lesion appears arthroscopically as a smooth capsule without irregularity. A type II lesion appears as a linear, or longitudinal, tear in the capsule.

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A type III lesion appears as complete rupture and retraction of the capsule and the frayed ECRB tendon, which is visible behind it. Surgical findings of the radiocapitellar synovial plica, according to Mullett et al.,6 were six type I variant, eight type 2 variant, six type 3 variant, and no type 4 variant. A type 1 arrangement appears arthroscopically as normal if the radial head is uncovered during flexion and extension and in full pronation and supination. A type 2 variant is present if the radial head is partially covered by a loose fold that is not interposed in the radiocapitellar joint in flexion and extension. A type 3 variant is present when the radial head is obscured by the radiocapitellar capsular complex, which became interposed in the radiocapitellar joint during flexion and extension. A type 4 arrangement is present when there is a fully developed thickened band completely obscuring the radial head and requiring extensive débridement to expose the bone. There were no complications, including nerve injury or instability. Before surgery, 15 of 18 patients were employed and they returned to their previous job after a mean of 3.4 ± 1.8 weeks (range 2–7 weeks). According to the patients’ reports, after surgery 14 of 20 elbows were much better, and 6 elbows were better. A highly statistically significant improvement was identified comparing preoperative with postoperative VAS for pain. The scores for pain at rest improved from 4.0 ± 3.9 (range 0–8) to 0.3 ± 0.8 (range 0–3) (P = 0.0003). The scores for pain during activity improved from 7.9 ± 1.2 (range 5–10) to 0.9 ± 1.3 (range 0–4) (P < 0.0001). The mean JOA elbow score was 89.9 ± 12.1 (range 58– 100) at the latest follow-up evaluation compared to 29.2 ± 10.3 (range 18–59) preoperatively (P < 0.0001). Evaluation of functional outcomes with the DASH score was obtained in all 18 patients. The mean DASH score was 10.6 ± 15.0 (range 0–50). In 15 of 18 patients, the DASH score was <14 (range 0–13), which was considered a good result. In the remaining three patients, DASH scores were >14 (range 42–50). A Mann-Whitney U–test was performed to assess the effect of variables on the DASH score (Table 3). Absence of T2-weighted high signal focus of the ECRB origin on MRI (P = 0.02) and receiving public assistance (P = 0.03) were significantly associated with a higher DASH score, representing a poorer outcome. No significant association was identified between the variables and improvement after surgery in regard to pain at rest, pain during activity, or the JOA elbow score (data not shown).

Discussion We showed an operative result of 20 elbows in 18 patients with chronic lateral epicondylitis treated with

T. Wada et al.: Arthroscopic surgery for tennis elbow

arthroscopic débridement of the ECRB origin and radiocapitellar synovial plica. All of the patients reported that their elbows were “much better” or “better” as a result of the arthroscopic débridement. The VAS pain and JOA elbow scores were significantly improved after surgery. The results were comparable to those reported previously.6–10,25 Functional outcomes evaluated with the DASH score showed a below normal value in 4 of the 18 patients. Lack of T2-weighted high signal focus of the ECRB origin on preoperative MRI and lower income were significantly associated with a worse DASH score. To our knowledge, this study is the first to evaluate operative results after an arthroscopic procedure by the DASH score as well as conventional functional measures. We could find only two studies evaluating surgical results of lateral epicondylitis with the DASH score. Thornton et al.16 reported on 20 patients treated with an open excision and suture anchor repair of the ECRB. All of the patients considered the condition of their elbows to be better than they were preoperatively. Three of the patients had DASH scores that were below normal, suggesting residual pain and disability. The patient who had the worst DASH score was receiving workers’ compensation. Dunkow et al.15 compared the open Nirschl procedure with percutaneous release in 47 elbows and showed substantially improved DASH scores in both groups. However, the median postoperative DASH score was 53 for the open group and 49 for the percutaneous group, indicating residual symptoms. This study showed two patient-related factors that influenced outcomes. Lack of high signal focus of the ECRB origin on preoperative MRI and receiving public assistance were significantly associated with a poor DASH score. A meta-analysis26 indicated that the increased T2-weighted signal intensity of the common extensor tendon is the most common finding and is present in 90% of patients with lateral epicondylitis. The authors thought that the pathological role of the MRI findings in lateral epicondylitis was questionable as it was also shown in 14% of healthy controls and 50% of the contralateral elbows. On the other hand, Aoki et al.24 and Thornton et al.16 reported that an increased T2-weighted signal of the ECRB tendon corresponds to the granulation tissue and that resection of this tissue results in excellent pain relief and functional recovery. We hypothesized that the T2-weighted high signal focus may be a localized tendinopathy of the ECRB close to the joint capsule. Complete resection of the lesion could be performed easily by arthroscopic débridement. Alternatively, a lesion without a high signal MRI focus might be diffuse and/or located close to the fascia. Part of the lesion may remain after arthroscopic débridement. Indeed, in vivo assessment of arthroscopic

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Table 3. Factors predicting postoperative DASH score DASH score Variable Background Sex Male Female Agea <55 Years ≥55 Years Dominant/nondominant Dominant Nondominant Duration of symptomsa <12 Months ≥12 Months Socioeconomic background Income Receiving public assistance No assistance Occupation Desk job Manual labor MRI findings High signal focus of the ECRB origin Yes No Arthroscopic findings ECRB originb No tear Tear Synovial plicac No interposition Interposition

No. of patients

Median

9 9

6.7 2.6

9 9

5.8 2.6

9 9

0.9 8.3

13 5

2.1 6.3

4 14

36.5 2.2

12 6

4.7 4.5

13 5

1.7 14.0

9 9

3.3 5.8

12 6

4.7 4.5

P 0.76 0.76 0.14 0.15

0.03 0.74

0.02

0.66 0.74

DASH, Disability of the Arm, Shoulder, and Hand (DASH) questionnaire; MRI, magnetic resonance imaging; ECRB, extensor carpi radialis brevis a A total of 18 patients were divided into two groups by their median values b No tear indicated by Baker’s type I classification; tear indicated by type II and III classification4 c No interposition in the radiocapitellar joint indicated by Mullett’s type a and 2 arrangement; interposition indicated by Mullett’s type 36

débridement indicated that residual microscopic tendinopathy correlates with poorer surgical outcomes.11 Lower income with regard to receiving public assistance, which can be used as a proxy for socioeconomic status, was found to be a potential predictor of poorer outcome after arthroscopic surgery for lateral epicondylitis. A recent epidemiological study showed that a lower income is associated with fair and poor selfrelated health in Japanese adults.27 It is possible that the baseline level of the DASH score may be worse in patients with lower income than in patients with higher income. The poor general health status associated with lower income might be attributed to a worse postoperative DASH score in patients with chronic lateral epicondylitis. Our operative procedure consisted of débridement of the ECRB origin and resection of the radiocapitellar

synovial plica if it was interposed in the joint. The radiocapitellar synovial fold identified by arthroscopy is a capsular tissue located on the proximal edge of the annular ligament. It is distinct from the annular ligament but has a close correlation with the common extensor tendon enthesis at the lateral epicondyle. It is possible that the primary pathology of lateral epicondylitis, such as inflammation and angiofibrosis in the extensor origin, might affect the hypertrophy of the synovial fold.28 The postoperative DASH score shown in the current investigation compares favorably with that shown in the study by Dunkow et al.15 This might be due to the difference in operative procedures. Our arthroscopic procedure consisted of débridement of the ECRB origin and resection of radiocapitellar plica. In contrast, both the open and percutaneous procedures of Dunknow

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et al.15 consisted of resecting the damaged portion of the ECRB origin. We recognize that this study has several limitations inherent in any retrospective study. First, there was no preoperative documentation of the DASH score, and therefore no DASH score improvement could be statistically assessed. Patients in the early clinical experience could not be evaluated with the DASH preoperatively because the Japanese version was not yet available. Second, owing to the small number of patients, multivariate analysis could not be done. We could not determine if the prognostic factors are independent or associated. Last, this was a retrospective study, and there were no comparative groups. Despite these limitations, this report is the first in the English literature to identify potential predictive factors of functional outcome after arthroscopic surgery for chronic lateral epicondylitis measured by a validated patient-based subjective questionnaire. This information may help surgeons select proper patients for arthroscopic débridement of lateral epicondylitis. Moreover, this retrospective study provides data with which to design future prospective comparisons of this technique with other established and novel techniques. Acknowledgment. We thank Drs. Eijun Yamamoto, Osamu Yamamoto, Takayuki Chiba, and Hideki Tsuji for referring patients.

References 1. Nirschl RP, Pettrone FA. Tennis elbow: the surgical treatment of lateral epicondylitis. J Bone Joint Surg Am 1979;61:832–9. 2. Boyer MI, Hastings H 2nd. Lateral tennis elbow: “Is there any science out there?” J Shoulder Elbow Surg 1999;8:481–91. 3. Bosworth DM. Surgical treatment of tennis elbow; a follow-up study. J Bone Joint Surg Am 1965;47:1533–6. 4. Baker CL Jr, Murphy KP, Gottlob CA, Curd DT. Arthroscopic classification and treatment of lateral epicondylitis: two-year clinical results. J Shoulder Elbow Surg 2000;9:475–82. 5. Kuklo TR, Taylor KF, Murphy KP, Islinger RB, Heekin RD, Baker CL Jr. Arthroscopic release for lateral epicondylitis: a cadaveric model. Arthroscopy 1999;15:259–64. 6. Mullett H, Sprague M, Brown G, Hausman M. Arthroscopic treatment of lateral epicondylitis: clinical and cadaveric studies. Clin Orthop 2005;439:123–8. 7. Owens BD, Murphy KP, Kuklo TR. Arthroscopic release for lateral epicondylitis. Arthroscopy 2001;17:582–7. 8. Jerosch J, Schunck J. Arthroscopic treatment of lateral epicondylitis: indication, technique and early results. Knee Surg Sports Traumatol Arthrosc 2006;14:379–82. 9. Peart RE, Strickler SS, Schweitzer KM Jr. Lateral epicondylitis: a comparative study of open and arthroscopic lateral release. Am J Orthop 2004;33:565–7.

T. Wada et al.: Arthroscopic surgery for tennis elbow 10. Szabo SJ, Savoie FH 3rd, Field LD, Ramsey JR, Hosemann CD. Tendinosis of the extensor carpi radialis brevis: an evaluation of three methods of operative treatment. J Shoulder Elbow Surg 2006;15:721–7. 11. Cummins CA. Lateral epicondylitis: in vivo assessment of arthroscopic débridement and correlation with patient outcomes. Am J Sports Med 2006;34:1486–91. 12. Lo MY, Safran MR. Surgical treatment of lateral epicondylitis: a systematic review. Clin Orthop 2007;463:98–106. 13. Nirschl RP. Lateral extensor release for tennis elbow. J Bone Joint Surg Am 1994;76:951. 14. Verhaar J, Walenkamp G, Kester A, van Mameren H, van der Linden T. Lateral extensor release for tennis elbow: a prospective long-term follow-up study. J Bone Joint Surg Am 1993;75:1034– 43. 15. Dunkow PD, Jatti M, Muddu BN. A comparison of open and percutaneous techniques in the surgical treatment of tennis elbow. J Bone Joint Surg Br 2004;86:701–4. 16. Thornton SJ, Rogers JR, Prickett WD, Dunn WR, Allen AA, Hannafin JA. Treatment of recalcitrant lateral epicondylitis with suture anchor repair. Am J Sports Med 2005;33:1558–64. 17. Ito Y, Oka Y, Ochiai N, Shibata M, Tanaka J, Ryu J. Japanese Orthopaedic Association elbow score. J Jpn Soc Surg Elbow 2004;11:3–12 (in Japanese). 18. Imaeda T, Toh S, Nakao Y, Nishida J, Hirata H, Ijichi M, et al. Validation of the Japanese Society for Surgery of the Hand version of the Disability of the Arm, Shoulder, and Hand questionnaire. J Orthop Sci 2005;10:353–9. 19. Jester A, Harth A, Germann G. Measuring levels of upperextremity disability in employed adults using the DASH Questionnaire. J Hand Surg [Am] 2005;30:1074–82. 20. Bot SD, van der Waal JM, Terwee CB, van der Windt DA, Bouter LM, Dekker J. Course and prognosis of elbow complaints: a cohort study in general practice. Ann Rheum Dis 2005;64: 1331–6. 21. Lewis M, Hay EM, Paterson SM, Croft P. Effects of manual work on recovery from lateral epicondylitis. Scand J Work Environ Health 2002;28:109–16. 22. Haahr JP, Andersen JH. Prognostic factors in lateral epicondylitis: a randomized trial with one-year follow-up in 266 new cases treated with minimal occupational intervention or the usual approach in general practice. Rheumatology 2003;42: 1216–25. 23. Smidt N, Lewis M, Van Der Windt DA, Hay EM, Bouter LM, Croft P. Lateral epicondylitis in general practice: course and prognostic indicators of outcome. J Rheumatol 2006;33:2053–9. 24. Aoki M, Wada T, Isogai S, Kanaya K, Aiki H, Yamashita T. Magnetic resonance imaging findings of refractory tennis elbows and their relationship to surgical treatment. J Shoulder Elbow Surg 2005;14:172–7. 25. Baker CL Jr, Baker CL 3rd. Long-term follow-up of arthroscopic treatment of lateral epicondylitis. Am J Sports Med 2008;36: 254–60. 26. Pasternack I, Tuovinen EM, Lohman M, Vehmas T, Malmivaara A. MR findings in humeral epicondylitis: a systematic review. Acta Radiol 2001;42:434–40. 27. Fukuda Y, Nakao H, Imai H. Different income information as an indicator for health inequality among Japanese adults. J Epidemiol 2007;17:93–9. 28. Tsuji H, Wada T, Oda T, Iba K, Aoki M, Murakami G, et al. Arthroscopic, macroscopic, and microscopic anatomy of the synovial fold of the elbow joint in correlation with the common extensor origin. Arthroscopy 2008;24:34–8.