Gerald R. Williams

Variation of biomechanical, structural, and compositional properties along the tendon to bone insertion site.

The tendon to bone insertion site is a complex transitional region that links two very different materials. The insertion site must transfer a complex loading environment effectively to prevent injury and provide proper joint function. In order to accomplish this load transfer effectively, the properties of the insertion site were hypothesized to vary along its length. The quasilinear viscoelastic (QLV) Model was used to determine biomechanical properties, polarized light analysis was used to quantitate collagen orientation (structure), and in situ hybridization was used to determine the expression of extracellular matrix genes (composition). All assays were performed at two insertion site locations: the tendon end of the insertion and the bony end of the insertion. Biomechanically, the apparent properties of peak strain, the coefficients (A and B) that describe the elastic component of the QLV model, and one of the coefficients (tau(1)) of the viscous component of the model were significantly higher, while another of the coefficients (C) of the viscous component was significantly lower at the tendon insertion compared to the bony insertion. The collagen was significantly more oriented at the tendon insertion compared to the bony insertion. Finally, collagen types II, IX, and X, and aggrecan were localized only to the bony insertion, while decorin and biglycan were localized only to the tendon insertion. Thus, the tendon to bony insertion site varies dramatically along its length in terms of its viscoelastic properties, collagen structure, and extracellular matrix composition.

Tendon to bone healing: differences in biomechanical, structural, and compositional properties due to a range of activity levels.

Little knowledge exists about the healing process of the tendon to bone insertion, and hence little can be done to improve tissue healing. The goal of this study is to describe the healing of the supraspinatus tendon to its bony insertion under a variety of loading conditions. Tendons were surgically detached and repaired in rats. Rat shoulders were then immobilized, allowed cage activity, or exercised. Shoulders that were immobilized demonstrated superior structural (significantly higher collagen orientation), compositional (expression of extracellular matrix genes similar to the uninjured insertion), and quasilinear viscoelastic properties (A = 0.30 +/- 0.10 MPa vs. 0.16 +/- 0.08 MPa, B = 17.4 +/- 2.9 vs. 15.1 +/- 0.9, and tau 2 = 344 +/- 161 s vs. 233 +/- 40 s) compared to those that were exercised, contrary to expectations. With this knowledge of the healing response, treatment modalities for rotator cuff tears can be developed.

The localized expression of extracellular matrix components in healing tendon insertion sites: an in situ hybridization study

The localized expression of a number of extracellular matrix genes was evaluated over time in a novel rat rotator cuff injury model. The supraspinatus tendons of rats were severed at the bony insertion and repaired surgically. The healing response was evaluated at 1, 2, 4, and 8 weeks post‐injury using histologic and in situ hybridization techniques. Expression patterns of collagens (I, II, III, IX, X, XII), proteoglycans (decorin, aggrecan, versican, biglycan, fibromodulin), and other extracellular matrix proteins (elastin, osteocalcin, alkaline phosphatase) were evaluated at the healing tendon to bone insertion site. Histologic results indicate a poor healing response to the injury, with only partial recreation of the insertion site by 8 weeks. In situ hybridization results indicate a specific pattern of genes expressed in each zone of the insertion site (i.e., tendon, fibrocartilage, mineralized cartilage, bone). Overall, expression of collagen types I and XII, aggrecan, and biglycan was increased, while expression of collagen type X and decorin was decreased. Expression of collagen type I, collagen type XII, and biglycan decreased over time, but remained above normal at 8 weeks. Results indicate that the rat supraspinatus tendon is ineffective in recreating the original insertion site, even at 8 weeks post‐injury, in the absence of biological or biomechanical enhancements.

Evaluation of the Neer System of Classification of Proximal Humeral Fractures with Computerized Tomographic Scans and Plain Radiographs

The intraobserver reliability and interobserver reproducibility of the Neer classification system were assessed on the basis of the plain radiographs and computerized tomographic scans of twenty fractures of the proximal part of the humerus. To determine if the observers had difficulty agreeing only about the degree of displacement or angulation (but could determine which segments were fractured), a modified system (in which fracture lines were considered but displacement was not) also was assessed. Finally, the observers were asked to recommend a treatment for the fracture, and the reliability and reproducibility of that decision were measured. The radiographs and computerized tomographic scans were viewed on two occasions by four observers, including two residents in their fifth year of postgraduate study and two fellowship-trained shoulder surgeons. Kappa coefficients then were calculated. The mean kappa coefficient for intraobserver reliability was 0.64 when the fractures were assessed with radiographs alone, 0.72 when they were assessed with radiographs and computerized tomographic scans, 0.68 when they were classified according to the modified system in which displacement and angulation were not considered, and 0.84 for treatment recommendations; the mean kappa coefficients for interobserver reproducibility were 0.52, 0.50, 0.56, and 0.65, respectively. The interobserver reproducibility of the responses of the attending surgeons regarding diagnosis and treatment did not change when the fractures were classified with use of computerized tomographic scans in addition to radiographs or with use of the modified system in which displacement and angulation were not considered; the mean kappa coefficient was 0.64 for all such comparisons. Over-all, the addition of computerized tomographic scans was associated with a slight increase in intraobserver reliability but no increase in interobserver reproducibility. The classification of fractures of the shoulder remains difficult because even experts cannot uniformly agree about which fragments are fractured. Because of this underlying difficulty, optimum patient care might require the development of new imaging modalities and not necessarily new classification systems.

Postoperative assessment of shoulder function: a prospective study of full-thickness rotator cuff tears.

Forty patients underwent surgery by a single surgeon for chronic, symptomatic, full-thickness rotator cuff defects. The study evaluated preoperative and intraoperative factors that influence postoperative outcome. The study also correlated objective measures of shoulder function with postoperative symptoms, patient satisfaction, and disability. Follow-up history and physical examination and strength measurements were performed at 2 years after surgery by three independent observers. There were 88% good or excellent results. Postscores correlated most closely with preoperative tear size. Postoperative Constant scores also correlated significantly with the patients subjective rating of the end result. Preoperative cuff tear size also correlated with the presence of postoperative fatigue symptoms and objective measures of shoulder strength. Preoperative cuff tear size strongly correlated with other prognostic factors including the quality of the tendon tissue, the difficulty for tendon mobilization, and the presence of a rupture of the long head of the biceps. Together these factors adversely affect postoperative function, patient satisfaction, and overall shoulder score. Neither premorbid activity level nor the presence of a workers compensation claim adversely affected the postoperative Constant score. The premorbid activity level significantly influenced the postoperative disability rating and the ability to return to work. All patients who were gainfully employed before surgery returned to employment after surgery, although in some patients at a lesser activity level.

Intrarater and interrater reliability of three isometric dynamometers in assessing shoulder strength.

The purpose of this study was to evaluate the reliability of three separate isometric strength testing devices. Seventeen (10 female, 7 male) adult volunteers with no known shoulder dysfunction participated. Each subjects internal rotation, external rotation and abduction strength was measured with the Nicholas Manual Muscle Tester (MMT), Biodex Isokinetic Dynamometer, and Isobex 2.0. Two investigators administered the test to each subject with each device. Data were analyzed with intraclass correlation coefficients (ICCs). Ranges of the intrarater intraclass correlation coefficient (3,1) values for each muscle group with each device for both testers were as follows: Nicholas MMT = .84 to .97, Biodex = .97 to .99, and Isobex 2.0 = .95 to .98. Ranges of interrater intraclass correlation coefficient values for each device and muscle group were as follows: Nicholas MMT = .79 to .94, Biodex = .93 to .96, and Isobex 2.0 = .90 to .97. Time to complete testing was shortest for Nicholas MMT, followed by Isobex 2.0, then Biodex. Measurements taken on the same day by the same therapist appear to be highly reliable for all three devices. Measurements taken over a 3-day period by two therapists appear to be highly reliable for all devices and muscle groups with the exception of Nicholas MMT abduction (.79), which was moderately reliable.

Latissimus dorsi tendon transfer for irreparable posterosuperior rotator cuff tears. Factors affecting outcome.

BACKGROUNDnThe purpose of this study was to evaluate the clinical results of latissimus dorsi tendon transfer in patients with an irreparable posterosuperior rotator cuff tear to help determine which patient and anatomic factors affect clinical outcome.nnnMETHODSnFourteen patients with a latissimus dorsi tendon transfer were clinically evaluated with use of the PENN (University of Pennsylvania) shoulder score as well as with quantitative measurement of isometric muscle strength and the range of motion of both shoulders at a minimum of twenty-four months postoperatively. The anatomic results were evaluated with postoperative magnetic resonance imaging and electromyography.nnnRESULTSnNine patients were satisfied with the outcome, had significant clinical improvement, and reported that they would have the operation again under similar circumstances. The other five patients were dissatisfied with the result and had significantly worse PENN scores, active elevation, and objective measures of strength. Eight of the nine patients with a good clinical result were male, and four of the five with a poor result were female. Patients with a good clinical result had had significantly better preoperative function in active forward flexion and active external rotation compared with the patients with a poor result. The magnetic resonance imaging demonstrated healing of the tendon to the greater tuberosity in twelve patients and equivocal healing in two. There was no significant atrophy of any of the transferred muscles. Electromyography demonstrated clear activity in the transferred latissimus muscle during humeral adduction in all fourteen patients, some electrical activity with active forward elevation in only one patient, and some electrical activity with active external rotation in six of the nine patients with a good clinical result. None of the patients with a poor clinical result demonstrated electrical activity of the transferred muscle with active forward flexion or external rotation.nnnCONCLUSIONSnSynchronous in-phase contraction of the transferred latissimus dorsi is a variable finding following the surgical treatment of irreparable posterosuperior rotator cuff tears, but when it is present it is associated with a better clinical result. Preoperative shoulder function and general strength influence the clinical result. Female patients with poor shoulder function and generalized muscle weakness prior to surgery have a greater likelihood of having a poor clinical result.

Long durations of immobilization in the rat result in enhanced mechanical properties of the healing supraspinatus tendon insertion site.

Rotator cuff tears frequently occur and can lead to pain and decreased shoulder function. Repair of the torn tendon back to bone is often successful in relieving pain, but failure of the repair commonly occurs. Post-operative activity level is an important treatment component that has received minimal attention for the shoulder, but may have the potential to enhance tendon to bone healing. The objective of this study was to investigate the effect of short and long durations of various activity levels on the healing supraspinatus tendon to bone insertion site. Rotator cuff tears were surgically created in Sprague-Dawley rats by detaching the supraspinatus tendon from its insertion on the humerus and these tears were immediately repaired back to the insertion site. The post-operative activity level was controlled through shoulder immobilization (IM), cage activity (CA), or moderate exercise (EX) for durations of 4 or 16 weeks. The healing tissue was evaluated utilizing biomechanical testing and a quantitative polarized light microscopy method. We found that activity level had no effect on the elastic properties (stiffness, modulus) of the insertion site at four weeks post injury and repair, and a decreased activity level had a positive effect on these properties at 16 weeks (IM>CA=EX). Furthermore, a decreased activity level had the greatest positive effect on these properties over time (IM>CA=EX). The angular deviation of the collagen, a measure of disorganization, was decreased with a decrease in activity level at 4 weeks (IM<CA=EX), but was similar between groups at 16 weeks (IM=CA=EX). It appears from this study that decreasing the activity level by immobilizing the shoulder improves tendon to bone healing, which progresses by first increasing the organization of the collagen and then increasing the mechanical properties. Future studies in this area will investigate the effect of passive motion and remobilization on both tendon to bone healing and shoulder function.

Operative Treatment of Malunion of a Fracture of the Proximal Aspect of the Humerus

We retrospectively reviewed the medical records, operative reports, and preoperative and postoperative radiographs of thirty-nine patients who had been managed operatively for malunion of a fracture of the proximal aspect of the humerus. The malunions were categorized according to the presence of osseous abnormalities, including malposition of the greater or lesser tuberosity (type I; twenty-eight patients), incongruity of the articular surface (type II; twenty-six patients), and malalignment of the articular segment (type III; sixteen patients). Soft-tissue abnormalities, such as soft-tissue contracture, a tear of the rotator cuff, and impingement, were also recorded. At an average of forty-four months (range, twelve to fifty-three months) postoperatively, the patients were assessed for pain relief, the range of motion of the shoulder, and the ability to perform activities of daily living. The result was satisfactory for twenty-seven patients (69 per cent) and unsatisfactory for the remaining twelve (31 per cent) at the latest follow-up evaluation. Of the twenty-seven patients who had a satisfactory result, twenty-six (96 per cent) had had complete operative correction of all osseous and soft-tissue abnormalities. Of the twelve patients who had an unsatisfactory result, four had had complete operative correction of these abnormalities (p < 0.0001). Twenty-six patients (67 per cent) had incongruity of the glenohumeral joint at the time of presentation. Twenty-three of these patients had the incongruity corrected with prosthetic arthroplasty (twenty-two) or arthrodesis of the glenohumeral joint (one); the result was satisfactory for seventeen (74 per cent). In contrast, the result was unsatisfactory for all three patients in whom the incongruity had not been corrected at the time of the operation (p = 0.01). Eleven patients had malposition of the greater or lesser tuberosity but a congruent joint surface preoperatively. Ten patients in this group were managed with either osteotomy of the tuberosity or acromioplasty, and nine of them had a satisfactory result at the latest follow-up evaluation. The result was unsatisfactory for one patient who was managed with only correction of a soft-tissue contracture (that is, no treatment of the malposition) (p = 0.05). Both osseous and soft-tissue abnormalities were identified as the cause of pain and stiffness in patients who had malunion of a fracture of the proximal aspect of the humerus. We concluded that operative management of these patients is successful only if all osseous and soft-tissue abnormalities are corrected at the time of the operation.

Rotator cuff tears: Why do we repair them?

Rotator cuff tears are among the most common conditions affecting the shoulder. Despite their ubiquity, however, there is substantial debate concerning their management. Partial and complete rotator cuff tears are known to occur with increasing frequency with increasing age in asymptomatic people1-3. The clinical results of rotator cuff repair in symptomatic patients who have been followed for as long as ten years are good to excellent in a high percentage of cases, even though rerupture of the cuff is known to occur 20% to 65% of the time4-7. Moreover, the presence of a massive, irreparable rotator cuff tear is not incompatible with good overhead function8. These observations have traditionally made clinical decision-making in the treatment of symptomatic rotator cuff tears difficult. Historically, treatment recommendations have included rehabilitation, surgical repair, subacromial decompression without repair, tendon transfers, and tendon substitution techniques6,8-21.nnControversy regarding the management of patients with symptomatic, full-thickness rotator cuff tears is largely the result of the heterogeneity of the patient population and the dearth of well-controlled comparative data. Much progress toward a more unified understanding of the surgical indications and outcomes of rotator cuff repair has been made in recent years, although there is still considerable confusion. The purposes of this symposium are to review the history and current controversies of rotator cuff tears and their management, to outline the indications and outcomes of both nonoperative management and surgical repair of rotator cuff tears, and to summarize the surgical options and outcomes in patients with irreparable rotator cuff tears.nn### Rotator Cuff InjurynnInjuries of the rotator cuff have been known to occur since the earliest of medical writings. A description of a rotator cuff injury appeared in Edwin Smiths Surgical Papyrus, one of the oldest known …