Abstract
Background:
Recently, a lesser tuberosity osteotomy has been promoted as an alternative to tenotomy for release of the subscapularis during shoulder arthroplasty. To our knowledge, no direct comparison of the clinical results of the two techniques has been presented.
Methods:
Thirty-five shoulders in thirty-four consecutive patients with osteoarthritis who had a primary total shoulder arthroplasty, performed with use of a standard subscapularis tenotomy (Group 1) or lesser tuberosity osteotomy (Group 2) to release the subscapularis, were evaluated retrospectively at an average of thirty-three months. Group 1 consisted of fifteen shoulders in fourteen patients (seven in males and eight in females, with an average age of sixty-seven years). Group 2 consisted of twenty shoulders in twenty patients (fourteen males and six females, with an average age of sixty-nine years). Assessment included a physical examination, clinical outcome questionnaires, conventional radiography, ultrasound examination of the subscapularis, and measurement of internal rotation strength.
Results:
The postoperative total Penn Shoulder Scores improved significantly from the preoperative levels in both groups (mean and standard deviation, 29 ± 15 points to 81 ± 20 points [p < 0.00001] in Group 1 and 29 ± 16 points to 92 ± 11 points [p < 0.00001] in Group 2). However, the postoperative mean total Penn Shoulder Score was higher in Group 2 (92 ± 11 points) than in Group 1 (81 ± 20 points) (p = 0.04). At one year, an abnormal subscapularis on ultrasound was associated with a lower mean Penn Shoulder Score in Group 1 (73 ± 19 points compared with 92 ± 3 points; p = 0.01). However, at a minimum two-year follow-up, this difference was not significant (mean, 74 ± 24 points and 86 ± 15 points, respectively; p = 0.25). There were more abnormal subscapularis tendons in Group 1 (six attenuated tendons and one full-thickness tear) than in Group 2 (two attenuated tendons). Internal rotation strength did not differ between the groups when controlled for sex (mean, 117 ± 8 N and 127 ± 21 N for males in Group 1 and Group 2, respectively [p = 0.22] and 77 ± 27 N and 101 ± 26 N, respectively, for females [p = 0.1]).
Conclusions:
Both techniques resulted in improved clinical outcome scores. The lesser tuberosity osteotomy resulted in higher clinical outcome scores, a lower rate of subscapularis tendon tears, and universal healing of the osteotomy. This technique offers a means by which the rate of postoperative subscapularis tears may be reduced in patients undergoing total shoulder arthroplasty.
Level of Evidence:
Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.
Mobilization of the subscapularis tendon is a requisite element of total shoulder arthroplasty when the deltopectoral approach is used. Traditionally, the subscapularis is mobilized by means of a tenotomy medial to its insertion at the lesser tuberosity or with direct detachment from the lesser tuberosity, with subsequent direct repair1-4. However, the prevalence of postoperative subscapularis dysfunction has remained substantial5-7. Recently, subscapularis mobilization through a lesser tuberosity osteotomy has been presented as a means of providing a stronger repair through the potential of bone-to-bone healing6-9. To our knowledge, no data directly comparing the clinical and radiographic results of the two techniques, performed by the same surgeon using the same prosthesis in a uniform patient population, have been presented. The purpose of this study was to determine, in comparison with a traditional subscapularis tenotomy, whether the technique of mobilizing the subscapularis through a lesser tuberosity osteotomy results in better clinical outcomes and less subscapularis dysfunction in a contemporaneous group of patients undergoing primary total shoulder arthroplasty for the treatment of osteoarthritis.
Inclusion Criteria
Patients with osteoarthritis who underwent primary total shoulder arthroplasty with either a subscapularis tenotomy or lesser tuberosity osteotomy, performed by the senior author (J.P.I.), during the study period were eligible. Preoperative radiographs and charts were reviewed to confirm the diagnosis of primary glenohumeral osteoarthritis. Glenohumeral joint-space narrowing, subchondral sclerosis, and the presence of osteophytes constituted the radiographic inclusion criteria. Operative reports were reviewed to confirm that a standard procedure for mobilizing and repairing the subscapularis was used for both techniques (see Surgical Technique). All patients had an intact subscapularis at the time of surgery. Postoperatively, radiographs were reviewed to confirm anatomic placement and size of the prosthetic components. The same prosthetic system (Global Advantage; DePuy, Warsaw, Indiana), which was used in a cementless, metaphyseal press-fit configuration for the humeral side, was used in all patients. All patients adhered to the same standard postoperative rehabilitation program.
Exclusion Criteria
Patients with inflammatory arthritis, traumatic arthritis, or osteonecrosis were excluded. Patients with a concomitant rotator cuff tear or patients with a hemiarthroplasty were excluded. Patients with prior shoulder surgery or an immediate postoperative infection were excluded. Deviation from the standard postoperative rehabilitation protocol was also considered a basis for exclusion.
We began using a lesser tuberosity osteotomy technique to mobilize the subscapularis in all patients undergoing primary total shoulder arthroplasty in August 2005. Prior to this, a standard tenotomy was used to mobilize the subscapularis in all patients. Therefore, collecting data on the consecutive patients before and after the change in technique allowed for a comparison of the outcomes for a contemporaneous set of patients from a single surgeon in a retrospective manner. A power analysis indicated that twelve patients in each group would be needed to show a substantial difference in the clinical outcome score (see below). The surgeon had performed greater than 1000 shoulder arthroplasties prior to any of the surgeries in the present study. All surgical procedures were performed by the senior author with a resident or fellow as a first assistant. During the performance of this study, the prosthetic design was unchanged as was the surgical technique other than that related to the subscapularis.
We reviewed the cases of forty-eight patients (fifty shoulders) with end-stage osteoarthritis who underwent primary total shoulder arthroplasty, performed by a single surgeon, between April 2004 and July 2006. Three patients were lost to follow-up. Eight patients were not available to return for follow-up because of the excessive distance needed to travel. Three patients were excluded because of a preexisting Erb palsy (one patient), an intraoperative partial laceration of the axillary nerve during capsular excision after a subscapularis tenotomy with postoperative deltoid weakness (one patient), and severe glenoid bone loss requiring bone-grafting (one patient). The remaining thirty-four patients, who were followed for an average of thirty-three months, could be divided into two groups. Group 1 (the subscapularis tenotomy group) consisted of fifteen shoulders in fourteen patients (seven were male), with a mean age of sixty-seven years (range, fifty to eighty years) and a mean duration of follow-up of thirty-nine months (range, twenty-four to fifty-one months). Group 2 (the lesser tuberosity osteotomy group) consisted of twenty shoulders in twenty patients (fourteen were male), with a mean age of sixty-nine years (range, fifty to eighty-three years) and a mean duration of follow-up of thirty months (range, twenty-four to thirty-five months). We initially intended to have matched groups, and we had not planned on stratifying the results according to sex. As the final group totals revealed more shoulders in female patients in Group 1 than in Group 2, we were compelled to stratify the strength results by sex so as to avoid falsely interpreting possible differences because of unmatched groups. Comorbidities within the groups included non-insulin-dependent diabetes mellitus (one of fourteen patients in Group 1 and three of twenty patients in Group 2) and tobacco use (two patients in Group 1 and one patient in Group 2). All data were collected and analyzed with approval from our institutional review board.
Clinical Evaluation
All patients underwent an evaluation in the office preoperatively and at a minimum follow-up of one year. Active and passive shoulder ranges of motion and status of the belly-press test (negative or positive) were recorded by an orthopaedic surgeon blinded to the operative technique used. The belly-press test is a simple test of subscapularis function that is easily reproduced6,10-12. The patient is instructed to keep the hand pressed on the abdomen with the wrist in neutral and the elbow anterior to the midline of the torso (possible only with active internal rotation of the humerus). The inability to maintain the elbow anterior to the torso or wrist and palm against the abdomen constitutes a positive result indicating subscapularis dysfunction. All patients had a second longer-term evaluation by completion of a shoulder self-assessment questionnaire to include the Penn Shoulder Score in our office or by mail at least twenty-four months after surgery.
Outcome Evaluation
Subjective clinical outcomes were measured with a shoulder-specific questionnaire stratifying pain, satisfaction, and function (the Penn Shoulder Score), which has been previously validated13-16. The best possible total score is 100 points, with 30 points for pain, 10 points for satisfaction, and 60 points for function. The minimum detectable clinically important difference of this shoulder score is 11 points15.
Radiographic Evaluation
Preoperative and minimum one-year postoperative radiographs were made for all patients. These included anteroposterior, true anteroposterior, and axillary lateral radiographs. Healing of the osteotomy was defined as continuity between the lesser tuberosity and the adjacent cortices of the proximal part of the humerus on the axillary radiograph. Tuberosity position was also assessed on the plain radiographs. More advanced imaging to assess osteotomy healing was not utilized because both magnetic resonance and computed tomography images often have pronounced metal-induced artifact at the critical position of the osteotomy, making interpretation problematic. Postoperative radiographs were also assessed for evidence of prosthetic loosening.
Ultrasound Evaluation
All ultrasound studies were performed by one operator and were interpreted by one reader with the same equipment as that used in a previous study, which defined the accuracy in diagnosing rotator cuff tears with use of the same criteria as those utilized in the present study17. Ultrasound examination of the subscapularis was performed on all patients at the minimum one-year follow-up evaluation by a single technician who was trained in the technique of rotator cuff ultrasound evaluation. Ultrasonography of the subscapularis was performed with an Agilent Image Point HC ultrasound unit (Agilent Technologies, Palo Alto, California) and an L-1038 linear transducer (4.5 cm). The depth of the ultrasound was adjusted to accommodate for differences in soft-tissue mass among the patients and ranged from 3 to 5 cm with use of a 7.5-MHz transducer. The subscapularis tendon was viewed longitudinally, with dynamic images of the tendon recorded during active internal and external rotation the shoulder. All ultrasound examinations were recorded on videotape, which an orthopaedic surgeon, who was experienced in the interpretation of rotator cuff ultrasound studies but blinded to the surgical technique and to the clinical outcome, used to make an anatomic diagnosis.
The integrity of the subscapularis was recorded as being intact, having an attenuated tendon, or having a full-thickness tear. An intact subscapularis demonstrated continuity from the tendinous insertion at the lesser tuberosity to the muscular belly inferior and medial to the coracoid process. An attenuated tendon demonstrated a distinct hypoechoic or mixed hyperechoic and hypoechoic defect with a focal decrease of =50% in the normal thickness of the tendon but less than complete absence of the tendon and some retraction of the muscle belly18. Full-thickness tears demonstrated a gap in the tendon substance, with retraction from the bone along with medial retraction of the muscle belly17.
Strength Measurement
A handheld dynamometer (CSD200; Chatillon Systems, Largo, Florida) was used to measure isometric internal rotation strength of the shoulder of each patient at the minimum one-year follow-up evaluation by either a physician-assistant or orthopaedic surgeon experienced in the use of the dynamometer yet blinded to the surgical technique performed and the digital readout of results. Use of a handheld dynamometer has been shown to provide reliable and reproducible measurements of internal rotation strength of the shoulder19-29. The patient was seated and the shoulder was positioned at 0° of abduction and 0° of external rotation with the elbow flexed to 90° and forearm in neutral rotation19,21,23. The elbow was stabilized to the patient's side. The dynamometer was placed on the volar surface of the forearm just proximal to the wrist. The subjects were asked to maintain this arm position while the tester applied an increasing external rotation force to the arm through the dynamometer until the isometric contraction was overcome20,29. One practice contraction was followed by three recorded test contractions. The contralateral shoulder was not used as a control for internal rotation strength because eleven of the thirty-four patients had a shoulder disorder bilaterally and/or prior surgery of the contralateral shoulder.
Surgical Technique
In each case, the patient was placed in the modified beach-chair position. A standard deltopectoral approach was utilized to expose the proximal part of the humerus from the pectoralis major insertion to the rotator interval. The biceps tendon was tenodesed in all patients. The rotator interval was incised from the bicipital groove to the glenoid. The muscular inferior border of the subscapularis was defined, and the axillary nerve was protected. A Cobb elevator was passed from the inferior border of the subscapularis superiorly between the muscle belly and the joint capsule. This maneuver facilitated separation of the subscapularis from the capsule and the subsequent anterior-inferior capsulectomy.
Tenotomy
The subscapularis tendon is sharply elevated off its lesser tuberosity insertion and separated from the underlying capsule. Releases of any subcoracoid adhesions, the coracohumeral ligament from the base of the coracoid, and the remaining attachments to the capsule medially at the glenoid margin yield a complete so-called 360° mobilization of the subscapularis tendon6,30,31. An anterior and inferior glenohumeral capsulectomy is then performed in each shoulder. A series of 2-mm drill-holes are placed lateral to the lesser tuberosity, parallel to the cut surface of the proximal part of the humerus, for subsequent subscapularis repair. Temporary suture loops are then passed to be used as shuttles for subsequent tendon fixation (Fig. 1, A). The final total shoulder prosthetic components are implanted next. A series of modified Mason-Allen sutures utilizing a number-2, high-tension, nonabsorbable suture (FiberWire; Arthrex, Naples, Florida) are passed through the tendon32 (Fig. 1, B). Each limb of the tendon sutures is then shuttled through the drill-holes and is tied over a bone bridge (Fig. 1, C). The lesser tuberosity is debrided of fibrocartilage to promote tendon healing. The rotator interval is closed with the same suture material. A minimum of 45° of passive external rotation without tension on the repair was achieved in all shoulders.
Osteotomy
After complete exposure of the subscapularis and identification of the interval between the muscular portion of the subscapularis and the underlying joint capsule, an oscillating saw is used to perform the lesser tuberosity osteotomy just medial to the bicipital groove and parallel to the subscapularis tendon. The osteotomy continues to the junction of the articular cartilage medially and to the anatomic neck inferiorly. The osteotomized fragment is 5 to 10 mm thick and 3 to 4 cm long. Any remaining capsular attachments to the lesser tuberosity are released, and a complete 360° mobilization of the subscapularis musculotendinous unit is performed, as described above, and the anterior and inferior capsule is excised from its humeral to glenoid insertions. Before the final humeral prosthetic components are implanted, four 2-mm drill-holes are created in two parallel rows lateral to the lesser tuberosity footprint (Fig. 2, A). The medial row is made in the dense cortical bone of the bicipital groove and consists of superior and inferior drill-holes placed 3 cm apart. A similar second row is placed 2 cm more lateral. A number-2, high-tension, nonabsorbable suture (FiberWire) is passed (outside-in) through the superior hole of the medial row and then back through the inferior medial hole (inside-out), leaving a loop of suture in the humeral canal. A second suture is passed in the same configuration through the lateral holes, again leaving a loop of suture in the canal. The stem of the final humeral prosthesis is then placed inside the two loops. Before final impaction of the implant, the sutures are pulled tight around the prosthetic stem (Fig. 2, B). This configuration eliminates the chance of the sutures "cutting out" of the proximal humeral bone, which may be osteopenic in some patients, and it provides a very robust foundation for secure fixation of the lesser tuberosity. To repair the tuberosity, the superior limb of the medial suture is passed from an inferior-to-superior direction through the subscapularis tendon just medial to its insertion on the tuberosity and is tied to the inferior limb. The lateral suture is passed in the same manner just medial to the first suture (Fig. 2, C). This arrangement creates a tension band such that external rotation of the humerus results in further compression of the tuberosity to the osteotomy bed. The medial side of the lesser tuberosity is placed under the anterior edge of the humeral prosthesis, and the lateral sutures are tied. The first suture is tied with the humerus in 0° of rotation and the second, with 30° of external rotation. In no shoulder did placement of the osteotomy cut affect final fixation of the tuberosity. There were no osteotomy-related complications. The rotator interval was closed with the same suture material. As with the tenotomy, a minimum of 45° of passive external rotation without tension on the repair was achieved.
The postoperative course for all patients was identical. The shoulder was immobilized in a sling for twenty-four hours followed by passive range-of-motion exercises beginning on postoperative day 1. These included pendulum exercises, full passive elevation in the forward plane with the patient supine, and passive external rotation. During the first six weeks, passive external rotation was limited to 10° less than the amount noted at the time of wound closure, and in all patients it was at least 30°. Progressive strengthening exercises and unrestricted range of motion in a supervised therapy regimen were initiated at six weeks after surgery. At twelve weeks after surgery, the patient continued a home-based program along with supervised exercises based on need and anticipated activity level.
Statistical Analysis
A power analysis determined that a minimum of twelve shoulders in each group would provide 95% power (a = 0.05 and ß = 0.05) to detect an 11-point difference in Penn Shoulder Scores15. The Student t test was used to evaluate differences in variables (outcome scores, strength, range of motion, and ultrasound results). Nonparametric tests were used when the data were not normally distributed. The Spearman rank correlation coefficient was used to evaluate relationships between ultrasound results and the belly-press test.
Source of Funding
There was no external funding for this study.
The data are summarized in Table I. Preoperative total Penn Shoulder Scores were not different between the groups (29 ± 15 points for Group 1 and 29 ± 16 points for Group 2; p = 0.98), and they improved significantly postoperatively (81 ± 20 points for Group 1 [p < 0.00001] and 92 ± 11 points for Group 2 [p < 0.00001]). However, postoperative Penn Shoulder Scores were significantly higher in Group 2 (81 ± 20 points for Group 1 and 92 ± 11 points for Group 2; p = 0.04). For patients within Group 1, seven shoulders had an abnormal subscapularis ultrasound study (six had attenuated tendons and one had a full-thickness tear) and eight had normal studies. At the one-year follow-up evaluation, the patients in Group 1 with an abnormal subscapularis on ultrasonography had a significantly lower Penn Shoulder Score compared with the patients with a normal ultrasound study (73 ± 19 and 92 ± 3 points, respectively; p = 0.01). However, at the time of final follow-up, the difference was no longer significant (74 ± 24 and 86 ± 15 points, respectively; p = 0.25). With only two abnormal ultrasound studies, insufficient data were available for a similar comparison within Group 2.
Seven of fifteen shoulders in Group 1 demonstrated an abnormal subscapularis tendon on ultrasonography (six had an attenuated tendon, and one had a full-thickness tear). However, only two of twenty patients in Group 2 had abnormal ultrasound examinations (two had attenuated tendons). This difference was significant (p = 0.01). Abnormal ultrasound results demonstrated a moderate correlation with a positive belly-press test in both Group 1 and Group 2 (r = 0.52 and r = 0.69, respectively).
All of the lesser tuberosity osteotomies in Group-2 shoulders demonstrated anatomic union on postoperative radiographs. There was no evidence of glenoid or humeral prosthetic loosening or instability in either group.
Passive external rotation increased significantly from its preoperative measurement for both groups (15° ± 11° to 57° ± 15° in Group 1 and 17° ± 9° to 50° ± 11° in Group 2; p = 0.00001 for both). Postoperative passive external rotation was not significantly different between groups (57° ± 15° in Group 1 and 50° ± 11° in Group 2; p = 0.19). Sufficient numbers of patients may not have been present to detect a difference in range-of-motion measurements, given that the power analysis was performed relative to the Penn Shoulder Score. Preoperatively, all patients demonstrated an intact subscapularis tendon at the time of surgery. Subscapularis function preoperatively was difficult to assess because many patients had loss of passive external rotation, making this test unreliable. Postoperatively, all patients had sufficient passive range of internal rotation to at least the coronal plane of the body, and the belly-press test was positive in three of fifteen shoulders in Group 1 and one of twenty shoulders in Group 2 (p = 0.19). The belly-press test was negative in all patients with a normal ultrasound examination.
Overall, Group 1 demonstrated less mean internal rotation strength (95 ± 29 N) compared with Group 2 (119 ± 25 N) (p = 0.01). However, further analysis by sex was necessary because of the greater proportion of females in Group 1, leading to artificially lower strength measurements in that group on average. When controlled for sex, internal rotation strength was not different between groups (117 ± 8 N and 127 ± 21 N for males in Group 1 and Group 2, respectively [p = 0.22] and 77 ± 27 N and 101 ± 26 N, respectively, for females [p = 0.1]). After controlling for sex, sufficient numbers of patients may not have been present to detect a difference in strength measurements.
There were no other complications, infections, or revisions in either group.
The technique of mobilizing the subscapularis musculotendinous unit by means of a lesser tuberosity osteotomy has been introduced to reduce the prevalence of subscapularis dysfunction following shoulder arthroplasty6-9. To our knowledge, this study presents the first direct comparison of the combined clinical and radiographic outcomes of the osteotomy and the traditional tenotomy techniques for subscapularis mobilization during total shoulder arthroplasty. Although both techniques clearly resulted in improved clinical outcomes at a minimum two-year follow-up interval, the osteotomy technique resulted in a higher total Penn Shoulder Score, a lower prevalence of subscapularis abnormalities on ultrasonography, and anatomic healing of the osteotomy in all patients.
Gerber et al. reported excellent results in thirty-six patients who were managed with the lesser tuberosity osteotomy technique, but their results were not compared with a tenotomy cohort6. Although no subscapularis tears were demonstrated on postoperative computed tomography, 40% of the shoulders demonstrated a postoperative increase in fatty infiltration by one stage and 15%, by at least two stages. In the present series, an abnormal subscapularis was demonstrated on ultrasonography in two patients in Group 2. It may be that the same fatty infiltration phenomenon experienced by Gerber et al. may have been associated with the abnormal ultrasound appearance of the subscapularis (a thinner muscle belly with tendon continuity) in these patients. Alternatively, it may be that fatty infiltration of the muscle belly, despite an intact tendon, may have negatively influenced the strength measurements, accounting, in part, for the similar internal rotation strengths in Groups 1 and 2. We did not assess for fatty infiltration of the muscle belly in our patients.
The lower Penn Shoulder Scores at the time of the two-year follow-up in Group-1 subjects with an abnormal subscapularis on ultrasonography did not reach significance. Most of the abnormal findings on ultrasonography in this group were attenuated subscapularis tendons that did not adversely affect the long-term outcomes of these patients. It may be that the greater time interval allowed for some compensation and adaptation from other muscles to help to offset any differences measured by the Penn Shoulder Score, which assesses overall function and satisfaction subjectively. Ultrasound data were not collected at the minimum two-year follow-up evaluation, and their potential relationship to clinical outcomes at long-term follow-up is not conclusive from our results. We acknowledge that additional long-term studies are needed to more completely assess the implications of rotator cuff integrity with respect to functional outcomes. It is unclear specifically how clinically relevant an attenuated subscapularis tendon is to postoperative function after shoulder arthroplasty. A "tear in continuity," in which attenuation of the tendon insertion with some interval scar replacement is present with some retraction of the muscle belly, represents a degree of deficiency of the subscapularis. This phenomenon can be detected by ultrasound examination in the postoperative setting. This may have adversely affected the overall outcomes scores (pain and satisfaction) as seen in our results. It is possible that the lower Penn Shoulder Scores in the tenotomy group may be a reflection of a longer interval of follow-up (an average of nine months), allowing for the subscapularis tears to affect these scores to a greater degree.
When controlled for sex, internal rotation strength did not differ significantly between Groups 1 and 2 despite a fivefold increase in the proportion of patients in Group 1 with a subscapularis tear on ultrasonography. Because the group demographics were initially designed to be matched, we had not planned on stratifying the results according to sex. As the final group totals had more shoulders in female patients in Group 1, we stratified the strength results by sex so as to avoid falsely interpreting possible differences due to unmatched groups. Although not significant in the stratified groups, we did note a trend toward increased strength in Group 2. However, definitive conclusions cannot be made, given the limited number of subjects in each group.
Given that seven of the nine subscapularis abnormalities identified on ultrasonography were attenuated tendons, it is likely that the other muscles of humeral internal rotation (pectoralis major, latissimus dorsi, and teres major) provided sufficient power to compensate for any subscapularis dysfunction. Although the status of the rotator cuff in their subjects was unknown, Andrews et al.19 presented normative data for "shoulder medial rotation" strength. For subjects in the sixty to sixty-nine-year age group, the shoulder medial rotation strength of the dominant arm was a mean (and standard deviation) of 163 ± 29 N for males and 92 ± 19 N for females. The manner in which internal rotation strength may be affected following shoulder arthroplasty is not clear, but these normative data provide a general comparison.
Miller et al. noted a positive belly-press test in 67% of their patients after total shoulder arthroplasty7. The finding that only four of nine patients in our series demonstrated a positive belly-press test despite abnormal ultrasonography findings might be explained by the fact that the belly-press test is less sensitive to partial tears of the subscapularis than is the lift-off test10,12,33. However, the lift-off test can be painful to perform for patients lacking the requisite amount of passive internal rotation. The belly-press test has therefore been suggested as being more useful11,12.
Subsequent to the completion of this work, we modified the osteotomy suture fixation technique. In the period following the completion of the surgery for this study, we noticed intraoperatively that the medial aspect of the tuberosity can lift off the osteotomy surface when the shoulder is internally rotated. This phenomenon occurred only when the anterior edge of the prosthetic humeral head was flush with the surface of the humeral osteotomy. This did not occur during any of the surgical procedures included in our study. In all of the patients in the study and in almost 90% of all subsequent patients to date, the anterior edge of the prosthetic humeral head component is 2 to 3 mm anterior to the osteotomy surface. When this occurs, the osteotomy fragments are locked under the humeral head when sutured as described in this report, there is no medial lift-off with internal rotation, and all of the osteotomy fragments are very stable intraoperatively. To prevent lift-off problems, we now use an additional number-2 nonabsorbable suture, which is passed as a simple loop around the head-shaft junction of the prosthesis. Each limb of the suture is passed through the bone-tendon junction of the lesser tuberosity, creating a medial row for fixation. This simple addition prevents osteotomy instability regardless of the amount of overhang of the prosthetic humeral head.
The retrospective nature of this study represents a potential limitation. However, we took advantage of the fact that we changed our preferred operative technique from tenotomy to osteotomy and were able to follow and assess those patients in a twenty-four-month period on either side of that transition point. This provided a consecutive series of patients for each group and helped to minimize selection bias.
Any new technique is associated with a learning curve, no matter how small. In this study, surgeon familiarity with the execution of the lesser tuberosity osteotomy and its durable repair may have impacted outcomes.
Subscapularis tenotomy is overwhelmingly the most common method used to mobilize the subscapularis musculotendinous unit during shoulder arthroplasty. This procedure has been associated with excellent patient outcomes. However, a substantial prevalence of postoperative subscapularis dysfunction has been the impetus for many to suggest that the technique of lesser tuberosity osteotomy may offer a means to improve postoperative function of the subscapularis unit. Although differences in internal rotation strength were not apparent with the available data, compared with the tenotomy method, the lesser tuberosity osteotomy technique resulted in significantly better postoperative Penn Shoulder Scores and a lower rate of subscapularis tendon tears on ultrasonography at a minimum two-year follow-up period in patients managed with total shoulder arthroplasty.
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