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Rotator cuff repair tension as a determinant of functional outcome
Rotator cuff repair tension as a determinant of functional outcome Philip A. Davidson, MD, and Dennis W. Rivenburgh, PA-C, ATC, St Petersburg, Fla
This study evaluated the effect of rotator cuff repair tension on surgical outcome. A total of 67 consecutive rotator cuff repairs for full-thickness tendon tears were prospectively evaluated. Rotator cuff repair tension was quantified by means of an intraoperative calibrated tensiometer after cyclic loading. The point of maximum repair tension was measured. Patients were evaluated for pain and improvement before and after surgery through use of Constant scores, American Shoulder and Elbow Surgeons’ functional criteria, isokinetic strength-testing, and visual analog scale scores. Increased repair tension correlated with lesser gains in postoperative Constant score, a decrease in perceived improvement, decreased isokinetic strength measurements, and increased pain. Tension on repaired rotator cuff tendons should be minimized. High-tension repairs—those greater than 8 lb—are associated with poor subjective and objective outcomes and are not recommended. (J Shoulder Elbow Surg 2000;9:502-6.)
M
inimization of rotator cuff repair tension is a longestablished goal of surgical repair of rotator cuff tendon tears. Rotator cuff tear size, acuity, retraction, tissue quality, repair integrity, activity level, number of involved tendons, and patient age all variably affect surgical results.5,7,8,9,12,14,15 This report quantitatively analyzes the correlation between rotator cuff repair tension and postoperative outcome. Tension in the myotendinous unit is a function of both passive and active forces. Retraction occurs in the detached or torn myotendinous complex. The torn tendon is usually stretched or lengthened to reattach to the humeral tuberosity. Interstitial structural changes occur in the dystrophic or torn rotator cuff, affecting the tissue elasticity and, subsequently, the resting tenFrom the University of South Florida and Tampa Bay Orthopaedic Specialists. Reprint requests: Philip A. Davidson, MD, and Dennis W. Rivenburgh, PA-C, ATC, Tampa Bay Orthopaedic Specialists, 4000 Park Street North, St. Petersburg, FL 33709. Copyright © 2000 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2000/$12.00 + 0 32/1/109385 doi:10.1067/mse.2000.109385
502
sion.1,17 Reattachment of the tendon under tension adversely changes the muscular length-tension relationship and diminishes active force generation.11 High-tension repair can lead to tendon rerupture and subsequent failure. We studied the clinical effect of rotator cuff repair tension by prospectively evaluating 67 consecutive rotator cuff repairs, using quantitative measurements to assess repair tension. The purpose of the study was to evaluate isokinetic strength, pain, perceived improvement, and Constant scores,4 as correlated to tension of the repair.
MATERIALS AND METHODS Prospective evaluation of 63 consecutive patients with 67 full-thickness rotator cuff tears was performed. Four patients had bilateral repairs. Minimum follow-up was 24 months. The mean age was 62.5 years (range, 41 to 83 years). The dominant extremity was involved in 40 cases. Thirty-nine of the patients were male and 24 were female. One surgeon (P.A.D.) performed all of the procedures, using a similar technique in each case. Mean rotator cuff tear size was 6.6 cm2 (range, 0.6 to 25.0 cm2). Small and medium rotator cuff tears were repaired through use of the mini-rotator cuff repair method with arthroscopic subacromial decompression. Large and massive rotator cuff tears were treated with open subacromial decompression and a deltoid detaching approach. Sequential releases were performed to minimize tension; the releases included lysis of adhesions, coracohumeral ligament release from the coracoid, and glenohumeral capsular release, in that order. When necessary, slight medialization (up to 1.0 cm) of the tuberosity reattachment site was performed. In certain cases of large or massive tears, a partial, “non-watertight” repair was performed. The tendon or tendons were reattached to the tuberosity onto a cancellous bed, not a bone trough. A combination repair in which suture anchors and transosseous sutures were used was performed. Principally, nonabsorbable #2 Ethibond sutures (Ethicon, Inc, Johnson & Johnson, New Brunswick, NJ) were used in a modified Mason-Allen configuration. Side-to-side sutures were used when this was permitted by the tear configuration. Preoperative data collection included isokinetic strengthtesting, American Shoulder and Elbow Surgeons’ functional criteria,16 visual analog scale (VAS) pain scores,6 and Constant scores.4 Postoperatively, similar data were obtained, as were VAS perceived improvement scores. Isokinetic testing was performed without anesthetic preoperatively and at 6, 12, and 24 months. Postoperative visits
Davidson and Rivenburgh
J Shoulder Elbow Surg Volume 9, Number 6
503
Figure 1 Constant score vs rotator cuff repair tension.
with data collection were scheduled for 6, 12, 24, 52, and 104 weeks after surgery. Isokinetic strength measurements were performed through use of the Lido Active Isokinetic Rehabilitation System (Loredan, Davis, Calif). Patients were tested in flexion, extension, internal rotation, and external rotation in the supine position. Testing was performed at 60 and 360 degrees per second on both the involved and the uninvolved shoulders. Tests were performed preoperatively and at 6, 12, and 24 months postoperatively. Intraoperative data were collected to include tear size, concurrent pathosis, and maximal rotator cuff repair tension. Procedures performed, in addition to the index rotator cuff repair, were as follows: 13 distal clavicle resections, 42 arthroscopic subacromial decompressions, and 30 open subacromial decompressions. Vicryl tag sutures were used to facilitate tissue mobilization of the rotator cuff tendon. The tag suture at the point of maximal tension was manually determined. This suture, along with adjacent tag sutures, was then cyclically tensioned by manual traction for 50 cycles. The amount of tension applied was that required to approximate the tendon edge to the intended reattachment site. A Chatilon Precision tensiometer (John Chatilon & Sons, Kew Gardens, NY) was then attached to the chosen tag suture. The tendon was pulled to the site of the planned attachment; after 30 seconds, allowing for stress relaxation, the tension was measured. This 30-second duration was randomly chosen but consistently applied in an attempt to account for stress relaxation. A 6lb tensiometer was used for most measurements. In those repairs in which tension exceeded 6 lb, a 12-lb tensiome-
ter from the same manufacturer was used. These tensiometers were calibrated in a laboratory certified by the National Institute of Standards and Technology. Student t tests and correlation coefficient analysis were used as statistical parameters for the comparison of variables. The relationship between variables was summarized with 95% confidence intervals. Linear regression analysis was used to determine statistical correlation between tension and VAS pain score, improvement, and Constant scores.
RESULTS Rotator cuff repair tension varied between 0 and 10 lb; the mean tension was 2.5 lb. Preoperative Constant scores ranged between 27 and 76; the mean score was 56.5. Postoperatively, Constant scores ranged between 39 and 99; the mean score was 68.2. Analysis of a change in Constant score versus tension over time revealed a direct relationship between lower Constant score and increased tension (P < .001; Figure 1). Patient perception of postoperative improvement was evaluated as a function of rotator cuff repair tension over time. The patient’s perceived improvement related in a directly inverse manner to repair tension. With increased rotator cuff repair tension, patients reported lower VAS improvement scores (P < .005; Figure 2). Isokinetic strength-testing was highly correlated with rotator cuff repair tension. Lower strength measurements were associated with increased tension (P <
504
Davidson and Rivenburgh
J Shoulder Elbow Surg November/December 2000
Figure 2 Perceived improvement (VAS 0-10 scale) vs rotator cuff repair tension.
.001; Figure 3). We observed that VAS pain scores correlated with rotator cuff repair tension to a lesser degree than did other measured parameters, at the level of P < .01 (Figure 4). The size of rotator cuff tear correlated with repair tension at the P < .005 level. Larger tears were associated with higher tension. The group of 10 patients with repair tension greater than 8 lb had significantly worse results than members of the other groups. Although statistical trends show a steady decline of functionality at increased tension, this group was noted for their inferior objective results at all measured parameters.
DISCUSSION Several authors have described increased tension in ruptured and dystrophic rotator cuff myotendinous units. Hersche and Gerber10 reported on the increase of passive tension within the supraspinatus after longstanding tendon rupture. They found that the passive tension increased up to 100% in chronically ruptured tendons, elongated from 10 to 20 mm, in comparison with controls with no retraction. The authors concluded that this increase in passive tension was associated with a decreased capacity for active tension generation; their clinical findings, which included both manual and isokinetic muscle testing, support their conclusions. Jerosch and Castro13 used Hall-Effect strain gauges to assess tension in ruptured and intact supraspinatus tendons. They found almost no tension in the intact tendons. Adduction and external rotation produced a very slight increase in measured tension in
these intact specimens. Increased tension was measured in small and large tendon repairs. In addition, they documented a decrease in tension with coracohumeral ligament and capsular release. Rotator cuff tendon repairs are usually under some degree of increased tension. Tension on the suture repair can be decreased by performing surgical releases. The ability to create active force, be it concentric, eccentric or static, is dependent on minimizing passive tension. Furthermore, increased tension may stretch the contractile unit to a dysfunctional extent or lead to attritional degeneration or rerupture. Burkhart et al2 have suggested that lower rotator cuff repair tension may provide less mechanoreceptor stimulation and, therefore, potentially less pain. The purport of these observations—that increased tension is deleterious—is in accord with our findings that functional outcome is inversely proportional to rotator cuff repair tension. Failure of rotator cuff tendon repair can occur as a result of tension overload. Burkhart et al3 experimentally evaluated the effect of cyclically loading rotator cuff repairs. They designed their experiment to replicate in vivo, physiologic cyclic loading of the repaired rotator cuff. These authors postulated that physiologically simulated loading of the repair construct more aptly assesses integrity than does single load-to-failure testing. They found that the central repair suture, under the greatest load, always failed first and by the greatest magnitude. Their conclusions were that tension within the repair should be minimized and that care should be taken to maximize repair strength through technical
Davidson and Rivenburgh
J Shoulder Elbow Surg Volume 9, Number 6
505
Figure 3 Isokinetic strength measurement vs rotator cuff repair tension.
Figure 4 Pain (VAS 0-10 scale) vs rotator cuff repair tension.
means. The present study supports their finding—namely, that rotator cuff repair tension should be minimized. Constant score was used as a means of reporting compilation data of shoulder function.4 This scoring
system is based on a 100-point scale; 15 points are allocated for pain, 20 for activities of daily living, 40 for range of motion, and 25 for power. Among the variables analyzed, we found the highest correlation
506
Davidson and Rivenburgh
between postoperative Constant score and increased repair tension. Specifically, an increased repair tension correlated with a lower postoperative Constant score. The results of this series are in keeping with results of rotator cuff repair reported in other studies, whereby functionality (in terms of Constant score), subjective improvement, pain relief, and strength all improved over time in the first 2 postoperative years.5,7,9,12,15 Increased pain relief is associated with lower tension repairs. This may be explained in terms of pain relief resultant from an intact repair or less neural stimulation from a lower tension construct. Pain relief would potentially be expected in all patients, regardless of repair tension, from debridement, bursectomy, and decompression. Patients with higher-tension repairs obtained less pain relief than those with low-tension tendon repairs. The study design and clinical implementation of this project did not allow for postsurgical imaging of the repaired rotator cuffs. Additional information might be have been gleaned from that data, but financial and practical considerations precluded postoperative magnetic resonance imaging or ultrasound scanning. Isokinetic muscle testing was performed without anesthesia. Pain inhibition of muscular function confounds the data obtained in this manner. Anesthetized shoulders may have demonstrated greater isokinetic strength. An additional study limitation concerned the mechanism for intraoperative data collection. A mechanical digitized tensiometer, such as that used by Hirsch and Gerber10 in conjunction with their data collection equipment, might have yielded potentially more accurate tension data. Rotator cuff repair tension correlates directly with surgical outcome. Increased repair tension was associated with inferior outcomes by all measured parameters, including Constant scores, perceived improvement, strength, and pain. Constant scores, as a sensitive measure of overall functional outcome, are negatively correlated with increased tension. The value of minimizing rotator cuff repair tension is emphasized by the findings of this report. Repairs with tension greater than 8 lb are not recommended.
J Shoulder Elbow Surg November/December 2000
REFERENCES 1. Berquin A, Schmit P, Moens P, LeBacq J. Compliance of normal, dystrophic and transplanted mouse muscles. J Biomech 1994;27:1331-7. 2. Burkhart SS, Athanasiou KA, Wirth MA. Margin convergence: a method of reducing strain in massive rotator cuff tears. Arthroscopy 1996;12:335-8. 3. Burkhart SS, Johnson TC, Wirth MA, Athanasiou KA. Cyclic loading of transosseous rotator cuff repairs: tension overload as a possible cause of failure. Arthroscopy 1997;13:172-6. 4. Constant CR, Murley AHG. A clinical method of functional assessment of the shoulder. Clin Orthop1987;214:160-4. 5. Ellman H, Hanker G, Bayer M. Repair of the rotator cuff: endresult study of factors influencing reconstruction. J Bone Joint Surg 1986;68A:1136-44. 6. Fahndrich E, Linden M. Reliability and validity of the visual analogue scale (VAS). Pharmacopsychiatria 1982;15:90-4. 7. Gazielly DF, Gleyze P, Montagnon C. Functional and anatomical results after rotator cuff repair. Clin Orthop 1994;304:43-53. 8. Gore DR, Murray MP, Sepic SB, Gardner GM. Shoulder-muscle strength and range of motion following surgical repair of fullthickness rotator cuff tears. J Bone Joint Surg 1986;68:266-72. 9. Harryman DT 2nd, Mack LA, Wang KY, Jackins SE, Richardson ML, Matsen FA 3rd. Repairs of the rotator cuff: correlation of functional results with integrity of the cuff. J Bone Joint Surg 1991;73:982-9. 10. Hersche O, Gerber C. Passive tension in the supraspinatus musculotendinous unit after long-standing rupture of its tension: a preliminary report. J Shoulder Elbow Surg 1998;7:393-6. 11. Huxley HE, Kress M. Crossbridge behavior during muscle contraction. J Muscle Res Cell Motil 1985;6:153-61. 12. Iannotti JP, Bernot MP, Kuhlman JR, Kelley MJ, Williams GR. Postoperative assessment of shoulder function: a prospective study of full-thickness rotator cuff tears. J Shoulder Elbow Surg 1996;5:449-57. 13. Jerosch J, Castro WH. Stress on the rotator cuff sutures in relation to joint position. Z Orthop Ihre Grenzgeb 1993;131:317-22. 14. Kirschenbaum D, Coyle MP Jr, Leddy JP, Katsaros P, Tan F Jr, Cody RP. Shoulder strength with rotator cuff tears: pre and postoperative analysis. Clin Orthop 1993;288:174-8. 15. Kronberg M, Wahlstrom P, Brostrom L-A. Shoulder function after surgical repair of rotator cuff tears. J Shoulder Elbow Surg 1997;6:125-30. 16. Richards RR, An K-N, Bigliani LU, Friedman RJ, Gartsman GM, Gristina AG, et al. A standardized method for the assessment of shoulder function. J Shoulder Elbow Surg 1994;3:347-52. 17. Stauber WT, Miller GR, Grimmett JG, Knack KK. Adaptation of rat soleus muscles to 4 wk of intermittent strain. J Appl Physiol 1994;77:58-62.
This study evaluated the effect of rotator cuff repair tension on surgical outcome. A total of 67 consecutive rotator cuff repairs for full-thickness tendon tears were prospectively evaluated. Rotator cuff repair tension was quantified by means of an intraoperative calibrated tensiometer after cyclic loading. The point of maximum repair tension was measured. Patients were evaluated for pain and improvement before and after surgery through use of Constant scores, American Shoulder and Elbow Surgeons’ functional criteria, isokinetic strength-testing, and visual analog scale scores. Increased repair tension correlated with lesser gains in postoperative Constant score, a decrease in perceived improvement, decreased isokinetic strength measurements, and increased pain. Tension on repaired rotator cuff tendons should be minimized. High-tension repairs—those greater than 8 lb—are associated with poor subjective and objective outcomes and are not recommended. (J Shoulder Elbow Surg 2000;9:502-6.)
M
inimization of rotator cuff repair tension is a longestablished goal of surgical repair of rotator cuff tendon tears. Rotator cuff tear size, acuity, retraction, tissue quality, repair integrity, activity level, number of involved tendons, and patient age all variably affect surgical results.5,7,8,9,12,14,15 This report quantitatively analyzes the correlation between rotator cuff repair tension and postoperative outcome. Tension in the myotendinous unit is a function of both passive and active forces. Retraction occurs in the detached or torn myotendinous complex. The torn tendon is usually stretched or lengthened to reattach to the humeral tuberosity. Interstitial structural changes occur in the dystrophic or torn rotator cuff, affecting the tissue elasticity and, subsequently, the resting tenFrom the University of South Florida and Tampa Bay Orthopaedic Specialists. Reprint requests: Philip A. Davidson, MD, and Dennis W. Rivenburgh, PA-C, ATC, Tampa Bay Orthopaedic Specialists, 4000 Park Street North, St. Petersburg, FL 33709. Copyright © 2000 by Journal of Shoulder and Elbow Surgery Board of Trustees. 1058-2746/2000/$12.00 + 0 32/1/109385 doi:10.1067/mse.2000.109385
502
sion.1,17 Reattachment of the tendon under tension adversely changes the muscular length-tension relationship and diminishes active force generation.11 High-tension repair can lead to tendon rerupture and subsequent failure. We studied the clinical effect of rotator cuff repair tension by prospectively evaluating 67 consecutive rotator cuff repairs, using quantitative measurements to assess repair tension. The purpose of the study was to evaluate isokinetic strength, pain, perceived improvement, and Constant scores,4 as correlated to tension of the repair.
MATERIALS AND METHODS Prospective evaluation of 63 consecutive patients with 67 full-thickness rotator cuff tears was performed. Four patients had bilateral repairs. Minimum follow-up was 24 months. The mean age was 62.5 years (range, 41 to 83 years). The dominant extremity was involved in 40 cases. Thirty-nine of the patients were male and 24 were female. One surgeon (P.A.D.) performed all of the procedures, using a similar technique in each case. Mean rotator cuff tear size was 6.6 cm2 (range, 0.6 to 25.0 cm2). Small and medium rotator cuff tears were repaired through use of the mini-rotator cuff repair method with arthroscopic subacromial decompression. Large and massive rotator cuff tears were treated with open subacromial decompression and a deltoid detaching approach. Sequential releases were performed to minimize tension; the releases included lysis of adhesions, coracohumeral ligament release from the coracoid, and glenohumeral capsular release, in that order. When necessary, slight medialization (up to 1.0 cm) of the tuberosity reattachment site was performed. In certain cases of large or massive tears, a partial, “non-watertight” repair was performed. The tendon or tendons were reattached to the tuberosity onto a cancellous bed, not a bone trough. A combination repair in which suture anchors and transosseous sutures were used was performed. Principally, nonabsorbable #2 Ethibond sutures (Ethicon, Inc, Johnson & Johnson, New Brunswick, NJ) were used in a modified Mason-Allen configuration. Side-to-side sutures were used when this was permitted by the tear configuration. Preoperative data collection included isokinetic strengthtesting, American Shoulder and Elbow Surgeons’ functional criteria,16 visual analog scale (VAS) pain scores,6 and Constant scores.4 Postoperatively, similar data were obtained, as were VAS perceived improvement scores. Isokinetic testing was performed without anesthetic preoperatively and at 6, 12, and 24 months. Postoperative visits
Davidson and Rivenburgh
J Shoulder Elbow Surg Volume 9, Number 6
503
Figure 1 Constant score vs rotator cuff repair tension.
with data collection were scheduled for 6, 12, 24, 52, and 104 weeks after surgery. Isokinetic strength measurements were performed through use of the Lido Active Isokinetic Rehabilitation System (Loredan, Davis, Calif). Patients were tested in flexion, extension, internal rotation, and external rotation in the supine position. Testing was performed at 60 and 360 degrees per second on both the involved and the uninvolved shoulders. Tests were performed preoperatively and at 6, 12, and 24 months postoperatively. Intraoperative data were collected to include tear size, concurrent pathosis, and maximal rotator cuff repair tension. Procedures performed, in addition to the index rotator cuff repair, were as follows: 13 distal clavicle resections, 42 arthroscopic subacromial decompressions, and 30 open subacromial decompressions. Vicryl tag sutures were used to facilitate tissue mobilization of the rotator cuff tendon. The tag suture at the point of maximal tension was manually determined. This suture, along with adjacent tag sutures, was then cyclically tensioned by manual traction for 50 cycles. The amount of tension applied was that required to approximate the tendon edge to the intended reattachment site. A Chatilon Precision tensiometer (John Chatilon & Sons, Kew Gardens, NY) was then attached to the chosen tag suture. The tendon was pulled to the site of the planned attachment; after 30 seconds, allowing for stress relaxation, the tension was measured. This 30-second duration was randomly chosen but consistently applied in an attempt to account for stress relaxation. A 6lb tensiometer was used for most measurements. In those repairs in which tension exceeded 6 lb, a 12-lb tensiome-
ter from the same manufacturer was used. These tensiometers were calibrated in a laboratory certified by the National Institute of Standards and Technology. Student t tests and correlation coefficient analysis were used as statistical parameters for the comparison of variables. The relationship between variables was summarized with 95% confidence intervals. Linear regression analysis was used to determine statistical correlation between tension and VAS pain score, improvement, and Constant scores.
RESULTS Rotator cuff repair tension varied between 0 and 10 lb; the mean tension was 2.5 lb. Preoperative Constant scores ranged between 27 and 76; the mean score was 56.5. Postoperatively, Constant scores ranged between 39 and 99; the mean score was 68.2. Analysis of a change in Constant score versus tension over time revealed a direct relationship between lower Constant score and increased tension (P < .001; Figure 1). Patient perception of postoperative improvement was evaluated as a function of rotator cuff repair tension over time. The patient’s perceived improvement related in a directly inverse manner to repair tension. With increased rotator cuff repair tension, patients reported lower VAS improvement scores (P < .005; Figure 2). Isokinetic strength-testing was highly correlated with rotator cuff repair tension. Lower strength measurements were associated with increased tension (P <
504
Davidson and Rivenburgh
J Shoulder Elbow Surg November/December 2000
Figure 2 Perceived improvement (VAS 0-10 scale) vs rotator cuff repair tension.
.001; Figure 3). We observed that VAS pain scores correlated with rotator cuff repair tension to a lesser degree than did other measured parameters, at the level of P < .01 (Figure 4). The size of rotator cuff tear correlated with repair tension at the P < .005 level. Larger tears were associated with higher tension. The group of 10 patients with repair tension greater than 8 lb had significantly worse results than members of the other groups. Although statistical trends show a steady decline of functionality at increased tension, this group was noted for their inferior objective results at all measured parameters.
DISCUSSION Several authors have described increased tension in ruptured and dystrophic rotator cuff myotendinous units. Hersche and Gerber10 reported on the increase of passive tension within the supraspinatus after longstanding tendon rupture. They found that the passive tension increased up to 100% in chronically ruptured tendons, elongated from 10 to 20 mm, in comparison with controls with no retraction. The authors concluded that this increase in passive tension was associated with a decreased capacity for active tension generation; their clinical findings, which included both manual and isokinetic muscle testing, support their conclusions. Jerosch and Castro13 used Hall-Effect strain gauges to assess tension in ruptured and intact supraspinatus tendons. They found almost no tension in the intact tendons. Adduction and external rotation produced a very slight increase in measured tension in
these intact specimens. Increased tension was measured in small and large tendon repairs. In addition, they documented a decrease in tension with coracohumeral ligament and capsular release. Rotator cuff tendon repairs are usually under some degree of increased tension. Tension on the suture repair can be decreased by performing surgical releases. The ability to create active force, be it concentric, eccentric or static, is dependent on minimizing passive tension. Furthermore, increased tension may stretch the contractile unit to a dysfunctional extent or lead to attritional degeneration or rerupture. Burkhart et al2 have suggested that lower rotator cuff repair tension may provide less mechanoreceptor stimulation and, therefore, potentially less pain. The purport of these observations—that increased tension is deleterious—is in accord with our findings that functional outcome is inversely proportional to rotator cuff repair tension. Failure of rotator cuff tendon repair can occur as a result of tension overload. Burkhart et al3 experimentally evaluated the effect of cyclically loading rotator cuff repairs. They designed their experiment to replicate in vivo, physiologic cyclic loading of the repaired rotator cuff. These authors postulated that physiologically simulated loading of the repair construct more aptly assesses integrity than does single load-to-failure testing. They found that the central repair suture, under the greatest load, always failed first and by the greatest magnitude. Their conclusions were that tension within the repair should be minimized and that care should be taken to maximize repair strength through technical
Davidson and Rivenburgh
J Shoulder Elbow Surg Volume 9, Number 6
505
Figure 3 Isokinetic strength measurement vs rotator cuff repair tension.
Figure 4 Pain (VAS 0-10 scale) vs rotator cuff repair tension.
means. The present study supports their finding—namely, that rotator cuff repair tension should be minimized. Constant score was used as a means of reporting compilation data of shoulder function.4 This scoring
system is based on a 100-point scale; 15 points are allocated for pain, 20 for activities of daily living, 40 for range of motion, and 25 for power. Among the variables analyzed, we found the highest correlation
506
Davidson and Rivenburgh
between postoperative Constant score and increased repair tension. Specifically, an increased repair tension correlated with a lower postoperative Constant score. The results of this series are in keeping with results of rotator cuff repair reported in other studies, whereby functionality (in terms of Constant score), subjective improvement, pain relief, and strength all improved over time in the first 2 postoperative years.5,7,9,12,15 Increased pain relief is associated with lower tension repairs. This may be explained in terms of pain relief resultant from an intact repair or less neural stimulation from a lower tension construct. Pain relief would potentially be expected in all patients, regardless of repair tension, from debridement, bursectomy, and decompression. Patients with higher-tension repairs obtained less pain relief than those with low-tension tendon repairs. The study design and clinical implementation of this project did not allow for postsurgical imaging of the repaired rotator cuffs. Additional information might be have been gleaned from that data, but financial and practical considerations precluded postoperative magnetic resonance imaging or ultrasound scanning. Isokinetic muscle testing was performed without anesthesia. Pain inhibition of muscular function confounds the data obtained in this manner. Anesthetized shoulders may have demonstrated greater isokinetic strength. An additional study limitation concerned the mechanism for intraoperative data collection. A mechanical digitized tensiometer, such as that used by Hirsch and Gerber10 in conjunction with their data collection equipment, might have yielded potentially more accurate tension data. Rotator cuff repair tension correlates directly with surgical outcome. Increased repair tension was associated with inferior outcomes by all measured parameters, including Constant scores, perceived improvement, strength, and pain. Constant scores, as a sensitive measure of overall functional outcome, are negatively correlated with increased tension. The value of minimizing rotator cuff repair tension is emphasized by the findings of this report. Repairs with tension greater than 8 lb are not recommended.
J Shoulder Elbow Surg November/December 2000
REFERENCES 1. Berquin A, Schmit P, Moens P, LeBacq J. Compliance of normal, dystrophic and transplanted mouse muscles. J Biomech 1994;27:1331-7. 2. Burkhart SS, Athanasiou KA, Wirth MA. Margin convergence: a method of reducing strain in massive rotator cuff tears. Arthroscopy 1996;12:335-8. 3. Burkhart SS, Johnson TC, Wirth MA, Athanasiou KA. Cyclic loading of transosseous rotator cuff repairs: tension overload as a possible cause of failure. Arthroscopy 1997;13:172-6. 4. Constant CR, Murley AHG. A clinical method of functional assessment of the shoulder. Clin Orthop1987;214:160-4. 5. Ellman H, Hanker G, Bayer M. Repair of the rotator cuff: endresult study of factors influencing reconstruction. J Bone Joint Surg 1986;68A:1136-44. 6. Fahndrich E, Linden M. Reliability and validity of the visual analogue scale (VAS). Pharmacopsychiatria 1982;15:90-4. 7. Gazielly DF, Gleyze P, Montagnon C. Functional and anatomical results after rotator cuff repair. Clin Orthop 1994;304:43-53. 8. Gore DR, Murray MP, Sepic SB, Gardner GM. Shoulder-muscle strength and range of motion following surgical repair of fullthickness rotator cuff tears. J Bone Joint Surg 1986;68:266-72. 9. Harryman DT 2nd, Mack LA, Wang KY, Jackins SE, Richardson ML, Matsen FA 3rd. Repairs of the rotator cuff: correlation of functional results with integrity of the cuff. J Bone Joint Surg 1991;73:982-9. 10. Hersche O, Gerber C. Passive tension in the supraspinatus musculotendinous unit after long-standing rupture of its tension: a preliminary report. J Shoulder Elbow Surg 1998;7:393-6. 11. Huxley HE, Kress M. Crossbridge behavior during muscle contraction. J Muscle Res Cell Motil 1985;6:153-61. 12. Iannotti JP, Bernot MP, Kuhlman JR, Kelley MJ, Williams GR. Postoperative assessment of shoulder function: a prospective study of full-thickness rotator cuff tears. J Shoulder Elbow Surg 1996;5:449-57. 13. Jerosch J, Castro WH. Stress on the rotator cuff sutures in relation to joint position. Z Orthop Ihre Grenzgeb 1993;131:317-22. 14. Kirschenbaum D, Coyle MP Jr, Leddy JP, Katsaros P, Tan F Jr, Cody RP. Shoulder strength with rotator cuff tears: pre and postoperative analysis. Clin Orthop 1993;288:174-8. 15. Kronberg M, Wahlstrom P, Brostrom L-A. Shoulder function after surgical repair of rotator cuff tears. J Shoulder Elbow Surg 1997;6:125-30. 16. Richards RR, An K-N, Bigliani LU, Friedman RJ, Gartsman GM, Gristina AG, et al. A standardized method for the assessment of shoulder function. J Shoulder Elbow Surg 1994;3:347-52. 17. Stauber WT, Miller GR, Grimmett JG, Knack KK. Adaptation of rat soleus muscles to 4 wk of intermittent strain. J Appl Physiol 1994;77:58-62.