Printer Friendly

Role of subscapularis repair on muscle force requirements with reverse shoulder arthroplasty.

Reverse total shoulder arthroplasty (rTSA) has found great success over the last decade, evolving from a salvage procedure used in difficult situations to a more mainstream procedure. This procedure has been widely accepted to treat conditions, such as massive rotator cuff tears, cuff tear arthropathy, and proximal humerus fractures. (1-9) Distinct from anatomic total shoulder arthroplasty (aTSA), rTSA is inherently more constrained as a result of its conforming articular geometry and inverted anatomic concavities. Specifically, the rTSA prosthesis has a convex glenoid and concave humerus that function as a fixed fulcrum articulation to prevent superior humeral migration. While this inverted arrangement is common to all rTSA prosthesis designs, significant inter-manufacturer variability exists, particularly as it relates to the position of the joint center of rotation (CoR) and the position of the humerus. (10-14) Given the variety of different rTSA prosthesis design configurations available in the worldwide marketplace, the anatomic shoulder can be altered by rTSA as follows: 1. 15 mm to 30 mm medial shift in the CoR, 2. a 25 mm to 40 mm distal shift in the position of the humerus, and 3. a 10 mm to 25 mm medial shift in the position of the humerus. (12) Such joint configuration changes modify the normal anatomic relationships between the origins and insertions of the shoulder muscles, altering their resting lengths, operational envelopes, and moment arms. (10-24) These geometric changes have been demonstrated to improve deltoid efficiency (10-22); however, their effect on the rotator cuff is not as clearly known. (12,23-25)

Of particular interest is the effect of different rTSA prosthesis designs on the performance of the subscapularis muscle. Controversy exists surrounding concomitant repair of the subscapularis with rTSA. It has been reported that repair of the subscapularis is necessary to ensure joint stability, (26) and indeed orthopaedic surgeons are very accustomed to repairing the subscapularis in aTSA. However, this muscle has relatively little potential for increased excursion, and the integrity of these repairs after rTSA is questionable given the typical involvement in the pathology. Prosthesis designs that are associated with a more medial humeral position have been shown to have greater risk for instability if the subscapularis is not repaired, (10,11,25,26) whereas prosthesis designs that position the humerus more laterally have been shown to not have any increased risk of instability when the subscapularis is not repaired and are associated with more anatomic muscle tensioning. (10-12,25,27)

The native subscapularis muscle is known to operate in a biphasic manner. The superior portion inserts on the lesser tuberosity proximal to the CoR causing abduction, whereas the inferior portion inserts distal to the CoR causing adduction. (25,28-30) These two portions of the subscapularis also have separate innervation. (31-33) By shifting the position of the humerus in an inferior-medial position with rTSA, the proximal subscapularis is generally shifted below the CoR, converting it into an adductor for most of the range of motion (ROM). Its action as an adductor would, therefore, counteract the work of the deltoid, increasing its force required to elevate the arm and also increasing the overall joint reaction force, which may be deleterious to the long-term life of the device. (10,11,25)

It is hypothesized that concomitant subscapularis repair will increase the deltoid force required for abduction, the posterior rotator cuff required for external rotation, and the overall joint reaction force with rTSA. To that end, the purpose of this cadaveric shoulder controller study is to quantify the different muscle forces required to abduct the arm in the scapular plane from 20[degrees] to 70[degrees] when the elbow is flexed at 90[degrees] and compare in three different scenarios: 1. supraspinatus tear in the native anatomic shoulder, 2. two different RTSA prostheses designs, and 3. subscapularis repair with rTSA.

Methodology

A second-generation cadaveric shoulder controller that utilizes simulated neuromuscular control was used for this study. This shoulder controller is similar to that described by Hansen and coworkers with upgrades and a greater refresh rate for the control loop. (34) Stepper motors (Industrial Devices Corporation, Salem, New Hampshire) actuate cables that are attached to the rotator cuff tendons and deltoid tuberosity. Force transducers measure the tension developed in each cable as active closed-loop position, and orientation control algorithms control each motor. This active controller allows the cadaveric model to simulate in vivo glenohumeral kinematics and muscle loads during various motions. As presently configured, the controller utilizes active optical markers (Northern Digital, Inc., Waterloo, Ontario, Canada) to track motion, and a six-axis load cell measures the resultant joint reaction force at the glenohumeral joint. Specifically, the cable and eyelet configurations simulate the three heads of the deltoid (middle, posterior, anterior), the supraspinatus, the subscapularis, the pectoralis major, the infraspinatus, and teres minor.

To simulate more-physiologic joint compression and induce more-anatomic deltoid wrapping around the greater tuberosity, (10-12,35-37) a deltoid surrogate model was created. Deltoid wrapping has also been demonstrated to vary with different rTSA prosthesis designs and implantation techniques. 10-12 This muscle model was made from VytaFlex[R] 50 Liquid Urethane Rubber (Smooth-On, Inc.) and physically connected to three cables through three polyethylene tubes embedded within, to route the muscle lines for the anterior, middle, and posterior deltoid to the respective eyelets as shown during the ROM (Fig. 1).

Five male cadaveric full upper extremity specimens (age: 65.6 [+ or -] 6.3 years) were selected with similar height and BMI (height: 71.6 [+ or -] 2.0 inches; BMI: 30.2 [+ or -] 9.8) to ensure similar anthropometrics and tested in scapular plane abduction without any artificial external constraints from 20[degrees] to 70[degrees] with the full mass of the upper extremity. The tests were performed with the elbow flexed at 90[degrees] to simulate the passive internal rotation gravitational torque associated with many activities of daily living (ADL). Five conditions were tested in 5[degrees] increments over the ROM: 1. native shoulder, 2. native shoulder with a supraspinatus tear, 3. 42 mm Equinoxe[R] rTSA with subscapularis repair (as simulated by a constant 15 N subscapularis force which was previously deemed to be the minimum force necessary to maintain a stable joint using this controller (38,39)), 4. 42 mm Equinoxe[R] rTSA without subscapularis repair, and 5. a 42 mm Delta III Grammont rTSA without subscapularis repair. Five trials were performed for each condition and each trial was averaged. A Student's two-tailed unpaired t-test was conducted on the mean muscle forces over the ROM for each condition where p < 0.05 deemed significance.

Results

Both the 42 mm Grammont and 42 mm Equinoxe[R] rTSA prostheses significantly decreased the mean force required by the infraspinatus, teres minor, total posterior cuff, and pectoralis major muscles and also significantly decreased the mean joint reaction force during scapular abduction with the elbow flexed to 90[degrees] relative to the native joint with a rotator cuff tear (supraspinatus), (Table 1). Specifically, the mean force required by the posterior rotator cuff was observed to decrease by 18.7% to 23.8%, and the meanjoint reaction force decreased by 24.2% to 20.4% for the 42 mm Grammont and 42 mm Equinoxe[R] prostheses, respectively. No difference in the mean muscle force requirements were noted between the two rTSA prosthesis designs without subscapularis repair, and no difference was noted between the native shoulder with and without a supraspinatus tear.

Repair of the subscapularis with rTSA significantly increased the force required by the posterior deltoid, total deltoid, infraspinatus, teres minor, total posterior cuff, and pectoralis major muscles and also significantly increased the meanjoint reaction force during scapular abduction with the elbow flexed to 90[degrees] relative to when the subscapularis was not repaired (Table 1). Specifically when the subscapularis was repaired using the 42 mm Equinoxe[R], the mean force required by the posterior deltoid and posterior rotator cuff increased by 31.7% to 34.4%, respectively, during the ROM. Additionally, this increased deltoid force (Fig. 2), posterior cuff force (Fig. 3), and joint reaction force (Fig. 4) were most pronounced between 20[degrees] and 60[degrees] of scapular abduction, though these increases persisted throughout the ROM.

Discussion

The results of this cadaveric shoulder controller study demonstrate that repair of the subscapularis with rTSA significantly increased the force required by the posterior deltoid and posterior rotator cuff to elevate the arm when the elbow is flexed and also significantly increased the joint reaction force relative to when the subscapularis is not repaired. These results also demonstrate that both the 42 mm Grammont and 42 mm Equinoxe[R] rTSA prostheses significantly decreased the mean force required by the posterior rotator cuff and also significantly decreased the mean joint reaction force over the ROM relative to the native joint with a rotator cuff tear (supraspinatus). No differences in the mean muscle force requirements were noted between the two rTSA prosthesis designs without subscapularis repair, and no difference was noted between the native shoulder with and without a supraspinatus tear.

These results provide support for the hypothesis that rTSA with concomitant subscapularis repair creates a biomechanically unfavorable condition during arm elevation. By shifting the subscapularis insertion in the inferior-medial direction below the CoR, the subscapularis converts from being primarily an abductor to being primarily an adductor throughout the ROM, counteracting the abduction torque generated by the deltoid. This explains the observations in this study that more force was required by the deltoid when the subscapularis was repaired as opposed to when the subscapularis was not repaired.

We chose to perform the study with the cadaver elbow fixed in 90[degrees] of flexion to better simulate functional arm positions, such as those that are required by activities of daily living (ADL). This may be a more realistic scenario because elbow flexion is required for most ADL, such as washing hair, brushing teeth, drinking from a cup, etc. As the shoulder is abducted while the elbow is flexed, shoulder internal rotation torque is produced by gravity acting on the forearm and hand. Clinically, this internal rotation torque is manifest as hornblower's sign and is associated with posterior rotator cuff deficiency. (40) Such patients typically exhibit shoulder abduction but have difficulty with ADL that require bringing the hand near the head because their shoulder falls into internal rotation. Experimental setups that test the shoulder while the elbow is extended do not have the same magnitude of internal rotation torque. Because the posterior rotator cuff and posterior deltoid produce an external rotation torque at the shoulder, these muscles oppose the internal rotation torque caused by gravity.

Clinical improvement after rTSA is greater if there is some remaining functional posterior rotator cuff or if additional external rotation torque is provided by other means, such as a latissimus dorsi muscle transfer to the posterior proximal humerus. (41-44) If the subscapularis is intact and also producing internal rotation torque, the total magnitude of internal rotation torque may be greater than can be overcome by the posterior cuff and the hornblower's sign and accompanying shoulder dysfunction may be worsened. This explains the observations in this study that more force was required by the posterior cuff when the subscapularis was repaired as opposed to when the subscapularis was not repaired. Furthermore, this study showed increased joint reaction force for the subscapularis repair condition. This increased force is a result of increased co-contraction of the subscapularis, the posterior cuff, and the posterior deltoid. Elevated joint reaction forces may increase polyethylene component wear and increase risk of aseptic glenoid loosening, acromial stress fractures, and deltoid fatigue. These results related to increased deltoid, posterior cuff, and joint reaction force with subscapularis repair provides support for avoiding subscapularis repair with rTSA.

Not repairing the subscapularis with rTSA contradicts the recommendation of Edwards and colleagues where it was reported that the instability rate increases when the subscapularis is not repaired with rTSA. (26) As previously explained by Routman and associates and others, repair of the subscapularis may be dependent on prosthesis design, where rTSA designs that medialize the humerus less may be more inherently stable due to improved deltoid wrapping and more anatomic muscle tensioning. (10-12,25) Indeed, Edwards and colleagues justification for subscapularis repair is to decrease dislocations rather than to improve external rotation strength. (26)

The two rTSA designs used in this study are fundamentally different. (10-14,45-47) The Grammont design shifts the glenoid (and CoR) medially and shifts the humerus medially. The Equinoxe[R] design also has a medial glenoid shift, but the design of the humeral component causes a lateral shift of the humerus compared to the native shoulder and the Grammont design. Because of the greater moment arm imparted to the deltoid with the Equinoxe[R] design, it was expected that less deltoid force would be required with this design. This effect has been observed in computer studies (13,14) but could not be demonstrated in this cadaveric shoulder controller study. However, both rTSA designs did show decreased deltoid force compared to the native shoulder with rotator cuff tear. This is consistent with expectations for rTSA. It should be noted that 42 mm sizes of each device were utilized in this study to simulate the use of rTSA in these relatively large (height: 71.6 [+ or -] 2.0 inches; BMI: 30.2 [+ or -] 9.8) shoulder specimens; we recognize that shoulder surgeons often utilize smaller size reverse components but may use larger sizes in such larger shoulders to improve stability by increasing jump distance or reducing the risk of scapular impingement. (45-48) As the moment arms are similar between the 36 mm, 38 mm, and 42 mm sizes of each prosthesis tested and as each also positions the CoR and humerus similarly, we do not think that the use of larger size rTSA prostheses in this study in anyway limits our results to other sizes of these prosthesis designs.

As with other cadaver shoulder loading models, the main limitation of the study is that the set of muscle forces determined by the shoulder controller for each shoulder position is not unique. Other muscle force combinations may yield the same positions. Future work should utilize the shoulder controller to evaluate the role of subscapularis repair on multiple different rTSA prosthesis designs and determine if these observed biomechanical improvements are generalizable to all prosthesis designs.

Conclusions

Whether concomitant subscapularis repair should be performed during rTSA is controversial. (25-27) This cadaveric shoulder controller study provides biomechanical data that recommends avoiding the repair to reduce the forces required by the shoulder muscles during scapular abduction with the elbow flexed. Specifically, repairing the subscapularis significantly increased the force required by the posterior rotator cuff and posterior deltoid and also increased the overall joint reaction force relative to when the subscapularis was not repaired with rTSA. As the posterior rotator cuff is often compromised in patients undergoing rTSA, patients may not be able to sustain these elevated forces in the infraspinatus and teres minor required to counteract the adduction and internal rotation moments generated by the subscapularis during activities of daily living. Similarly, the elevated posterior deltoid force and joint reaction loads could be deleterious to the long-term life of the prosthesis and can also increase the risk of loosening and fractures. For all these reasons, rTSA functional outcomes may be compromised if the subscapularis is repaired.

Conflict of Interest Statement

Matthew L. Hansen, M.D., is a consultant for Exactech, Inc., Gainesville, Florida. Aniruddh Nayak, M.S., Madu Santhia, Ph.D., Kellen Worhacz, B.S., and Marc C. Jacofsky, Ph.D., are employees of the MORE Foundation, Phoenix, Arizona. Richard Stowell, M.D., is an employee of the CORE Institute, Phoenix, Arizona. Christopher P. Roche, M.S., M.B.A., is an employee of Exactech, Inc., Gainesville, Florida.

References

(1.) Sirveaux F, Favard L, Oudet D, et al. Grammont inverted total shoulder arthroplasty in the treatment of glenohumeral osteoarthritis with massive rupture of the cuff. J Bone Joint Surg Br. 2004 Apr; 86(3):388-95.

(2.) Frankle M, Siegal S, Pupello D, et al. The reverse shoulder prosthesis for glenohumeral arthritis associated with severe rotator cuff deficiency. A minimum two-year follow-up study of sixty patients. J Bone Joint Surg Am. 2005 Aug; 87(8):1697-705.

(3.) Werner C, Steinmann PA, Gilbart M, Gerber C. Treatment of painful pseudoparaesis due to irreparable rotator cuff dysfunction with the Delta III reverse ball and socket total shoulder prosthesis. J Bone Joint Surg Am. 2005 Jul; 87(7):1476-86.

(4.) Boileau P, Watkinson D, Hatzidakis AM, Hovorka I. The Grammont reverse shoulder prosthesis: results in cuff tear arthritis, fracture sequelae, and revision arthroplasty. J Shoulder Elbow Surg. 2006 Sep-Oct; 15(5):527-40.

(5.) Wall B, Nove-Josserand L, O'Connor DP, et al. Reverse total shoulder arthroplasty: a review of results according to etiology. J Bone Joint Surg Am. 2007 Jul; 89(7):1476-85.

(6.) Stechel A, Fuhrmann U, Irlenbusch L, et al. Reversed shoulder arthroplasty in cuff tear arthritis, fracture sequelae, and revision arthroplasty. Acta Orthop. 2010 Jun; 281(3):367-72.

(7.) Smith CD, Guyver P, Bunker TD. Indications for reverse shoulder replacement, a systematic review. J Bone Joint Surg Br. 2012 May; 9(5):577-83.

(8.) Mizuno N, Denard PJ, Raiss P, Walch G. Reverse total shoulder arthroplasty for primary glenohumeral osteoarthritis in patients with a biconcave glenoid. J Bone Joint Surg Am. 2013 Jul 17; 95(14):1297-304.

(9.) Jiang JJ, Toor AS, Shi LL, Koh JL. Analysis of perioperative complications in patients after total shoulder arthroplasty and reverse total shoulder arthroplasty. J Shoulder Elbow Surg. 2014 Dec; 23(12):1852-9.

(10.) Roche C, Crosby L. Kinematics and biomechanics of reverse total shoulder arthroplasty. In: Nicholson GP (ed): Orthopaedic Knowledge Update: Shoulder and Elbow. Rosemont, IL: American Academy of Orthpaedic Surgeons 2013, pp. 45-54.

(11.) Roche C, Hansen M, Flurin PH, et al. Biomechanical Summary of Reverse Shoulder Arthroplasty. Animation. AAOS Orthopaedic Video Theater. OVT-34. 2015. Available at: http://orthoportal.aaos.org/emedia/abstract. aspx?resource=EMEDIA_OSVL_15_34.

(12.) Roche CP, Diep P, Hamilton M, et al. Impact of inferior glenoid tilt, humeral retroversion, bone grafting, and design parameters on muscle length and deltoid wrapping in reverse shoulder arthroplasty. Bull Hosp Jt Dis (2013). 2013; 71(4):284-93.

(13.) Hamilton MA, Roche CP, Diep P, et al. Effect of prosthesis design on muscle length and moment arms in reverse total shoulder arthroplasty. Bull Hosp Jt Dis (2013). 2013; 71 Suppl 2:S31-5.

(14.) Hamilton MA, Diep P, Roche C, et al. Effect of reverse shoulder design philosophy on muscle moment arms. J Orthop Res. 2015 Apr; 33(4):605-13.

(15.) Terrier A, Reist A, Merlini F, Farron A. Simulated joint and muscle forces in reversed and anatomic shoulder prostheses. J Bone Joint Surg Br. 2008 Jun; 90(6):751-6.

(16.) Kontaxis A, Johnson GR. The biomechanics of reverse anatomy shoulder replacement--a modelling study. Clin Biomech (Bristol, Avon). 2009 Mar; 24(3):254-60.

(17.) Ackland DC, Roshan-Zamir S, Richardson M, Pandy MG. Moment arms of the shoulder musculature after reverse total shoulder arthroplasty. J Bone Joint Surg Am. 2010 May; 92(5):1221-30.

(18.) Ackland DC, Richardson M, Pandy MG. Axial rotation moment arms of the shoulder musculature after reverse total shoulder arthroplasty. J Bone Joint Surg Am. 2012 Oct 17; 94(20):1886-95.

(19.) Henninger HB, Barg A, Anderson AE, et al. Effect of lateral offset center of rotation in reverse total shoulder arthroplasty: a biomechanical study. J Shoulder Elbow Surg. 2012 Sep; 21(9):1128-35.

(20.) Langohr GD, Giles JW, Athwal GS, Johnson JA. The effect of glenosphere diameter in reverse shoulder arthroplasty on muscle force, joint load, and range of motion. J Shoulder Elbow Surg. 2015 Jun; 24(6):972-9.

(21.) Ladermann A, Williams MD, Melis B, et al. Objective evaluation of lengthening in reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2009 Jul-Aug; 18(4):588-95.

(22.) Ladermann A, Walch G, Lubbeke A, et al. Influence of arm lengthening in reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2012 Mar; 21(3):336-41.

(23.) Roche CP, Hamilton MA, Diep P, et al. Design rationale for a posterior/superior offset reverse shoulder prosthesis. Bull Hosp Jt Dis (2013). 2013; 71 Suppl 2:S18-24.

(24.) Herrmann S, Konig C, Heller M, et al. Reverse shoulder arthroplasty leads to significant biomechanical changes in the remaining rotator cuff. J Orthop Surg Res. 2011 Aug 16; 6:42.

(25.) Routman HD. The role of subscapularis repair in reverse total shoulder arthroplasty. Bull Hosp Jt Dis (2013). 2013; 71 Suppl 2:108-12.

(26.) Edwards TB, Williams MD, Labriola JE, et al. Subscapularis insufficiency and the risk of shoulder dislocation after reverse shoulder arthroplasty. J Shoulder Elbow Surg. 2009 NovDec; 18(6):892-6.

(27.) Clark JC, Ritchie J, Song FS, et al. Complication rates, dislocation, pain, and postoperative range of motion after reverse shoulder arthroplasty in patients with and without repair of the subscapularis. J Shoulder Elbow Surg. 2012 Jan; 21(1):36-41.

(28.) Clark JM, Harryman DT 2nd. Tendons, ligaments, and capsule of the rotator cuff. Gross and microscopic anatomy. J Bone Joint Surg Am. 1992 Jun; 74(5):713-25.

(29.) Klapper RC, Jobe FW, Matsuura P. The subscapularis muscle and its glenohumeral ligament-like bands. A histomorphologic study. Am J Sports Med. 1992 May-Jun; 20(3):307-10.

(30.) Morag Y, Jamadar DA, Miller B, et al. The subscapularis: anatomy, injury, and imaging. Skeletal Radiol. 2011 Mar; 40(3):255-69.

(31.) Kato K. Innervation of the scapular muscles and its morphological significance in man. Anat Anz. 1989; 168(2):155-68.

(32.) Kadaba MP, Cole A, Wootten ME, et al. Intramuscular wire electromyography of the subscapularis. J Orthop Res. 1992 May; 10(3):394-7.

(33.) O'Connell NE, Cowan J, Christopher T. An investigation into EMG activity in the upper and lower portions of the subscapularis muscle during normal shoulder motion. Physiother Res Int. 2006 Sep; 11(3):148-51.

(34.) Hansen ML, Otis JC, Johnson JS, et al. Biomechanics of massive rotator cuff tears: implications for treatment. J Bone Joint Surg Am. 2008 Feb; 90(2):316-25.

(35.) Lee SB, An KN. Dynamic glenohumeral stability provided by three heads of the deltoid muscle. Clin Orthop Relat Res. 2002 Jul; (400):40-7.

(36.) Lemieux PO, Hagemeister N, Tetreault P, Nuno N. Influence of the medial offset of the proximal humerus on the glenohumeral destabilising forces during arm elevation: a numerical sensitivity study. Comput Methods Biomech Biomed Engin. 2013; 16(1):103-11.

(37.) De Wilde LF, Audenaert EA, Berghs BM. Shoulder prostheses treating cuff tear arthropathy: a comparative biomechanical study. J Orthop Res. 2004 Nov; 22(6):1222-30.

(38.) Onstott, B. et al. Consequences of Concomitant Subscapularis Repair with Reverse Total Shoulder Arthroplasty. Presented at the 58th Annual Orthopaedic Research Society Annual Meeting, San Francisco, CA, February 4-7, 2012.

(39.) Onstott B, et al. Deltoid force and excursion demands of the reverse total shoulder prosthesis compared to massive rotator cuff. Presented at the 58th Annual Orthopaedic Research Society Annual Meeting, San Francisco, CA, February 4-7, 2012.

(40.) Walch G, Boulahia A, Calderone S, Robinson AH. The "dropping" and "hornblower's" signs in evaluation of rotator-cuff tears. J Bone Joint Surg Br. 1998 Jul; 80(4):624-8.

(41.) Boileau P, Chuinard C, Roussanne Y, et al. Reverse shoulder arthroplasty combined with a modified latissimus dorsi and teres major tendon transfer for shoulder pseudoparalysis associated with dropping arm. Clin Orthop Relat Res. 2008 Mar; 466(3):584-93.

(42.) Boileau P, Rumian AP, Zumstein MA. Reversed shoulder arthroplasty with modified L'Episcopo for combined loss of active elevation and external rotation. J Shoulder Elbow Surg. 2010 Mar; 19(2 Suppl):20-30.

(43.) Gerber C, Maquieira G, Espinosa N. Latissimus dorsi transfer for the treatment of irreparable rotator cuff tears. J Bone Joint Surg Am. 2006 Jan; 88(1):113-20.

(44.) Grey SG. Combined latissimus dorsi and teres major tendon transfers for external rotation deficiency in reverse shoulder arthroplasty. Bull Hosp Jt Dis (2013). 2013; 71 Suppl 2:82-7.

(45.) Roche C, Flurin PH, Wright T, Zuckerman JD. Geometric analysis of the Grammont reverse shoulder prosthesis: an evaluation of the relationship between prosthetic design parameters and clinical failure modes. Presented at the 2006 ISTA Meeting, New York, New York, October 6-9, 2006.

(46.) Roche C, Flurin PH, Wright T, et al. An evaluation of the relationships between reverse shoulder design parameters and range of motion, impingement, and stability. J Shoulder Elbow Surg. 2009 Sep-Oct; 18(5):734-41.

(47.) Roche CP, Marczuk Y, Wright TW, et al. Scapular notching and osteophyte formation after reverse shoulder replacement: Radiological analysis of implant position in male and female patients. Bone Joint J. 2013 Apr; 95-B(4):530-5.

(48.) Roche CP, Marczuk Y, Wright TW, et al. Scapular notching in reverse shoulder arthroplasty: validation of a computer impingement model. Bull Hosp Jt Dis (2013). 2013; 71(4):278-83.

Matthew L. Hansen, M.D., Aniruddh Nayak, M.S., Madusudanan Sathia Narayanan, Ph.D., Kellen Worhacz, B.S., Richard Stowell, M.D., Marc C. Jacofsky, Ph.D., and Christopher P. Roche, M.S., M.B.A.

Matthew L. Hansen, M.D., Mezona Orthopaedic Clinic, Gilbert, Arizona. Aniruddh Nayak, M.S., Madusudanan Sathia Narayanan, Ph.D., Kellen Worhacz, B.S., The MORE Foundation, Phoenix, Arizona. Richard Stowell, M.D., The CORE Institute, Phoenix, Arizona. Marc C. Jacofsky, Ph.D., MORE Foundation and the CORE Institute, Phoenix, Arizona. Christopher P. Roche, M.S., M.B.A., Exactech, Gainesville, Florida.

Correspondence: Christopher P. Roche, M.S., M.B.A., Exactech, Inc., 2320 NW 66th Court, Gainesville, Florida 32653; chris. roche@exac.com.

Caption: Figure 1 Representative image of the surrogate deltoid model used with the cadaveric shoulder controller.

Caption: Figure 2 Comparison of deltoid force requirements during scapular abduction with the elbow flexed to 90[degrees].

Caption: Figure 3 Comparison of posterior rotator cuff force requirements during scapular abduction with the elbow flexed to 90[degrees].

Caption: Figure 4 Comparison of joint reaction force requirements during scapular abduction with the elbow flexed to 90[degrees].

Table 1 Comparison of Mean Muscle Forces during Scapular Abduction
with the Elbow Flexed at 90[degrees]

Avg Muscle Force              Mid Deltoid          Post Deltoid

Native                     65.0 [+ or -] 15.6   53.4 [+ or -] 53.4
Native with SS Tear        67.8 [+ or -] 13.3   64.2 [+ or -] 30.6
% Change                         -4.3%                -20.3%
P-value                          0.6600               0.4254

Native with SS Tear        67.8 [+ or -] 13.3   64.2 [+ or -] 30.6
Equinoxe[R] w/o Subscap    73.1 [+ or -] 3.1    56.7 [+ or -] 21.7
% Change                         -7.8%                11.7%
P-value                          0.2155               0.5126

Native with SS Tear        67.8 [+ or -] 13.3   64.2 [+ or -] 30.6
Grammont w/o Subscap       76.6 [+ or -] 6.3    49.1 [+ or -] 11.6
% Change                         -13.0%               23.5%
P-value                          0.0609               0.3189

Equinoxe[R] with Subscap   74.2 [+ or -] 13.8   83.0 [+ or -] 24.0
Equinoxe[R] w/o Subscap    73.1 [+ or -] 3.1    56.7 [+ or -] 21.7
% Change                          1.5%                31.7%
P-value                          0.7957               0.0139

Grammont w/o Subscap       76.6 [+ or -] 6.3    49.1 [+ or -] 11.6
Equinoxe w/o Subscap       73.1 [+ or -] 3.1    56.7 [+ or -] 21.7
% Change                          4.6%                -15.4%
P-value                          0.1103               0.3189

Avg Muscle Force              Ant Deltoid         Total Deltoid

Native                     38.9 [+ or -] 8.7   157.3 [+ or -] 55.3
Native with SS Tear        40.8 [+ or -] 7.7   172.8 [+ or -] 51.1
% Change                         -4.9%                -9.8%
P-value                         0.5939               0.5032

Native with SS Tear        40.8 [+ or -] 7.7   172.8 [+ or -] 51.1
Equinoxe[R] w/o Subscap    43.8 [+ or -] 1.9   173.5 [+ or -] 3.1
% Change                         -7.4%                -0.4%
P-value                         0.2209               0.9637

Native with SS Tear        40.8 [+ or -] 7.7   172.8 [+ or -] 51.1
Grammont w/o Subscap       45.5 [+ or -] 3.7   171.2 [+ or -] 17.8
% Change                        -11.7%                0.9%
P-value                         0.0784               0.9267

Equinoxe[R] with Subscap   44.4 [+ or -] 8.2   201.6 [+ or -] 14.5
Equinoxe[R] w/o Subscap    43.8 [+ or -] 1.9   173.5 [+ or -] 3.1
% Change                         1.5%                 13.9%
P-value                         0.7951               0.0008

Grammont w/o Subscap       45.5 [+ or -] 3.7   171.2 [+ or -] 17.8
Equinoxe w/o Subscap       43.8 [+ or -] 1.9   173.5 [+ or -] 3.1
% Change                         3.9%                 -1.3%
P-value                         0.1751               0.7720

Avg Muscle Force             Infraspinatus         Teres Minor

Native                     77.1 [+ or -] 4.7    38.4 [+ or -] 2.3
Native with SS Tear        75.6 [+ or -] 6.5    37.6 [+ or -] 3.2
% Change                          1.9%                 2.1%
P-value                          0.5489               0.5002

Native with SS Tear        75.6 [+ or -] 6.5    37.6 [+ or -] 3.2
Equinoxe[R] w/o Subscap    57.4 [+ or -] 21.9   28.9 [+ or -] 10.8
% Change                         24.1%                23.2%
P-value                          0.0155               0.0181

Native with SS Tear        75.6 [+ or -] 6.5    37.6 [+ or -] 3.2
Grammont w/o Subscap       61.4 [+ or -] 19.7   30.6 [+ or -] 9.5
% Change                         18.7%                18.7%
P-value                          0.0344               0.0313

Equinoxe[R] with Subscap   87.6 [+ or -] 16.9   43.9 [+ or -] 8.2
Equinoxe[R] w/o Subscap    57.4 [+ or -] 21.9   28.9 [+ or -] 10.8
% Change                         34.5%                34.2%
P-value                          0.0017               0.0015

Grammont w/o Subscap       61.4 [+ or -] 19.7   30.6 [+ or -] 9.5
Equinoxe w/o Subscap       57.4 [+ or -] 21.9   28.9 [+ or -] 10.8
% Change                          6.6%                 5.5%
P-value                          0.6515               0.7009

                             Total Posterior
Avg Muscle Force                   RC                Pec Major

Native                     115.5 [+ or -] 6.9    27.3 [+ or -] 5.2
Native with SS Tear        113.2 [+ or -] 9.7    32.2 [+ or -] 6.6
% Change                          2.0%                -17.9%
P-value                          0.5310               0.0672

Native with SS Tear        113.2 [+ or -] 9.7    32.2 [+ or -] 6.6
Equinoxe[R] w/o Subscap    86.2 [+ or -] 32.7    16.5 [+ or -] 5.5
% Change                          23.8%                48.7%
P-value                          0.0163              < 0.0001

Native with SS Tear        113.2 [+ or -] 9.7    32.2 [+ or -] 6.6
Grammont w/o Subscap       92.0 [+ or -] 29.2    19.6 [+ or -] 2.0
% Change                          18.7%                39.1%
P-value                          0.0333              < 0.0001

Equinoxe[R] with Subscap   131.5 [+ or -] 25.1   25.9 [+ or -] 8.9
Equinoxe[R] w/o Subscap    86.2 [+ or -] 32.7    16.5 [+ or -] 5.5
% Change                          34.4%                36.2%
P-value                          0.0016               0.0075

Grammont w/o Subscap       92.0 [+ or -] 29.2    19.6 [+ or -] 2.0
Equinoxe w/o Subscap       86.2 [+ or -] 32.7    16.5 [+ or -] 5.5
% Change                          6.3%                 15.7%
P-value                          0.6675               0.0928

                             Joint Reaction
Avg Muscle Force                  Force

Native                     296.1 [+ or -] 56.3
Native with SS Tear        293.4 [+ or -] 56.0
% Change                          0.9%
P-value                          0.9132

Native with SS Tear        293.4 [+ or -] 56.0
Equinoxe[R] w/o Subscap    233.4 [+ or -] 53.2
% Change                          20.4%
P-value                          0.0180

Native with SS Tear        293.4 [+ or -] 56.0

Grammont w/o Subscap       222.5 [+ or -] 44.0
% Change                          24.2%
P-value                          0.0035

Equinoxe[R] with Subscap   324.7 [+ or -] 43.4
Equinoxe[R] w/o Subscap    233.4 [+ or -] 53.2
% Change                          28.1%
P-value                          0.0003

Grammont w/o Subscap       222.5 [+ or -] 44.0
Equinoxe w/o Subscap       233.4 [+ or -] 53.2
% Change                          -4.9%
P-value                          0.6033


----------

Please note: Illustration(s) are not available due to copyright restrictions.
COPYRIGHT 2015 J. Michael Ryan Publishing Co.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2015 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Hansen, Matthew L.; Nayak, Aniruddh; Narayanan, Madusudanan Sathia; Worhacz, Kellen; Stowell, Richar
Publication:Bulletin of the NYU Hospital for Joint Diseases
Article Type:Report
Date:Oct 1, 2015
Words:5244
Previous Article:Subscapularis preserving technique in anatomic total shoulder arthroplasty: the superior and inferior approach.
Next Article:Assessment of the anatomic neck as an accurate landmark for humeral head resurfacing implant height placement.
Topics:

Terms of use | Privacy policy | Copyright © 2021 Farlex, Inc. | Feedback | For webmasters |