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LETTER TO THE EDITOR

Valid and Relevant Outcome Measures Are Critical for Objective Hypothesis-Testing

Department of Anesthesiology; University of California San Diego; San Diego, California (Ilfeld) Department of Orthopedics; University of Florida; Gainesville, Florida (Wright) Department of Outcomes Research; The Cleveland Clinic; Cleveland, Ohio (Sessler) Department of Physical Therapy; University of Florida; Gainesville, Florida (Chmielewski)

To the Editor:

Regarding Hofmann-Kiefer et al.'s article,1 we question the appropriateness of using the Constant-Murley Assessment score as the investigation’s primary endpoint. To test the study hypothesis, the Constant score was assessed the day before surgery and then 96 h postoperatively.1 However, the Constant score was originally designed "to assess function after injury"— not surgery2; and it has not been validated for patients in the immediate postoperative period.3 Among articles using the Constant score, none involved patients within 4 wk of surgery: five, including the initial report, included healthy volunteers and/or nonsurgical clinic patients3–7; another included postrotator cuff repair patients at least 1 mo postoperatively8; and the last studied preoperative patients.9 The authors of the current study indirectly acknowledge this lack of validation in the immediate postoperative period when they explain, "because most of our (postoperative) patients were not completely pain-free, even at rest, one item of the Constant score had to be adopted for our purposes [emphasis added]."1 Moreover, it is doubtful that the Constant score is even relevant to the hospitalized population studied by Hofmann-Kiefer and colleagues.

Among the 100 possible points comprising the Constant score, maximum active shoulder abduction (10%), flexion (10%), external rotation (10%), strength (25%), and limb positioning (10%) comprise 65% of the total.3 Although there are no universally accepted post-open acromioplasty and rotator cuff repair rehabilitation guidelines, most patients receive passive range-of-motion within safe and pain-free ranges to prevent a loss of shoulder mobility, and progression to active exercises occurs only after "1–3 wk, but much more gradually after an open procedure."10–12 This is to avoid injuring the supraspinatus and/or deltoid repairs. And, predictably, the authors found that "only 5.9% of the patients in the PCA group and 13.5% in the PCISB group were able to perform the strength test."1 The majority of active range-of-motion and strength tests are simply inapplicable and irrelevant for this patient population in the immediate postoperative period. Eight additional Constant score points are determined by "activity level" during "work" and "recreation/sport," which is, again, irrelevant in these hospitalized patients.3

Given that at least 73% of the Constant score is inapplicable or irrelevant to this hospitalized patient population, it is apparent why this measure has never been validated in the immediate postoperative period. We thus conclude that the Constant score was an inappropriate primary endpoint and that the study’s hypothesis was therefore inadequately tested. Drawing conclusions from the study results is a subjective exercise, and not an objective analysis. It would be unfortunate and counterproductive if the medical community assumed the Constant score is a valid, reproducible, and relevant assessment tool in the immediate postoperative period. We welcome a thoughtful discussion of this topic with our valued colleagues.

REFERENCES

1. Hofmann-Kiefer K, Eiser T, Chappell D, Leuschner S, Conzen P, Schwender D. Does patient-controlled continuous interscalene block improve early functional rehabilitation after open shoulder surgery? Anesth Analg 2008;106:991–6[Abstract/Free Full Text]
2. Constant CR. An evaluation of the Constant-Murley shoulder assessment. J Bone Joint Surg Br 1997;79:695–6
3. Constant CR, Murley AH. A clinical method of functional assessment of the shoulder. Clin Orthop Relat Res 1987; (214):160–4
4. Fialka C, Oberleitner G, Stampfl P, Brannath W, Hexel M, Vecsei V. Modification of the Constant-Murley shoulder score-introduction of the individual relative Constant score Individual shoulder assessment. Injury 2005;36:1159–65[Web of Science][Medline]
5. Johansson KM, Adolfsson LE. Intraobserver and interobserver reliability for the strength test in the Constant-Murley shoulder assessment. J Shoulder Elbow Surg 2005;14:273–8[Web of Science][Medline]
6. Grassi FA, Tajana MS. The normalization of data in the Constant-Murley score for the shoulder. A study conducted on 563 healthy subjects. Chir Organi Mov 2003;88:65–73[Medline]
7. Conboy VB, Morris RW, Kiss J, Carr AJ. An evaluation of the Constant-Murley shoulder assessment. J Bone Joint Surg Br 1996;78:229–32[Medline]
8. Livain T, Pichon H, Vermeulen J, Vaillant J, Saragaglia D, Poisson MF, Monnet S. [Intra- and interobserver reproducibility of the French version of the Constant-Murley shoulder assessment during rehabilitation after rotator cuff surgery]. Rev Chir Orthop Reparatrice Appar Mot 2007;93:142–9[Web of Science][Medline]
9. Boehm D, Wollmerstedt N, Doesch M, Handwerker M, Mehling E, Gohlke F. [Development of a questionnaire based on the Constant-Murley-Score for self-evaluation of shoulder function by patients]. Unfallchirurg 2004;107:397–402[Web of Science][Medline]
10. Ellenbecker TS, Elmore E, Bailie DS. Descriptive report of shoulder range of motion and rotational strength 6 and 12 weeks following rotator cuff repair using a mini-open deltoid splitting technique. J Orthop Sports Phys Ther 2006;36: 326–35[Web of Science][Medline]
11. Boissonnault WG, Badke MB, Wooden MJ, Ekedahl S, Fly K. Patient outcome following rehabilitation for rotator cuff repair surgery: the impact of selected medical comorbidities. J Orthop Sports Phys Ther 2007;37:312–9[Web of Science][Medline]
12. Kisner C, Colby LA. Application of therapeutic exercise techniques to regions of the body, therapeutic exercise: foundations and techniques. 4th ed. Philadelphia: FA Davis Company, 2002

This article has been cited by other articles:

				K. F. Hofmann-Kiefer, T. Eiser, D. Chappell, S. Leuschner, P. Conzen, and D. Schwender Valid and Relevant Outcome Measures Are Critical for Objective Hypothesis-Testing Anesth. Analg., August 1, 2008; 107(2): 722 - 723. [Full Text] [PDF]

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a colleague Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Ilfeld, B. M. Articles by Chmielewski, T. L. Search for Related Content PubMed PubMed Citation Articles by Ilfeld, B. M. Articles by Chmielewski, T. L.