Rehabilitation after total shoulder arthroplasty.

Physical therapy constitutes an essential determinant of clinical outcome after total shoulder arthroplasty. We reviewed our results in 81 shoulders at a minimum of 2 years' follow-up, with specific focus on the maintenance of motion and the development of soft tissue healing problems. Our findings show that our graduated rehabilitation program allows most patients to obtain motion comparable to that possible intraoperatively with few complications. Of patients, 70% maintained their elevation, and 90% maintained external rotation. Patients with a diagnosis of rheumatoid arthritis, traumatic arthritis, and osteonecrosis were identified as being at risk for failure to regain motion and for tendon healing complications.

Tendon-Defect and muscle-unloaded models for relating a rotator cuff tear to glenohumeral stability.

Rotator cuff tear and glenohumeral instability are closely related. Any tear may disturb muscle force generation due to pain inhibition. In addition, a full-thickness tear may foster instability by removing a structural element constraining the joint. It was hypothesized that the loss of both dynamic force and static constraint with a rotator cuff tear will affect glenohumeral stability. In a tendon-defect model, dynamic and static elements of the joint were sacrificed. In a muscle-unloaded model, only the dynamic element was removed. The location and size of the defect were also investigated. The effect on instability of a small tendon defect was less than that of muscle unloading, implying that a patient with a small tear would have less instability than a patient with weak or nonfunctioning supraspinatus and infraspinatus muscles. On the other hand, with a larger tear the defect had a greater effect than muscle-unloading because sectioning of the glenohumeral and coracohumeral ligaments was included in the model. Clinically, such a defect in the front is critical for anterior stability because it might insult the important anterior capsule ligamentous complex. Orthopaedic surgeons should pay attention, therefore, to the effect of possible associated lesions of static constraints based on the size and location of the tear in addition to the dynamic stabilizer.

Neurologic complications of shoulder surgery.

Nerve injuries do occur during shoulder surgery. Studies of regional anatomy have defined the nerves at risk. The suprascapular nerve may lie no more than 1 cm from the glenoid rim. The axillary nerve may run no more than 3 mm from the inferior shoulder capsule and passes near the lower extent of the deltoid split used as an approach to the shoulder. The musculocutaneous nerve passes as near as 3.1 cm below the coracoid. Interscalene nerve block is not commonly implicated in nerve injuries. Three-dimensional knowledge of nerve anatomy is essential during arthroscopy for safe portal placement and trochar direction. Nerve injuries are reported to occur in 1% to 2% of patients undergoing rotator cuff surgery, 1% to 8% of patients undergoing surgery for anterior instability, and 1% to 4% of patients undergoing prosthetic arthroplasty. Surgical techniques for the shoulder are improving and nerves seldom are injured by direct laceration or incorporation in suture repair. Commonly, the nerve injuries occur secondary to traction or contusion. These are avoided best by careful attention to patient positioning, retractor placement, and arm manipulation during surgery. Because of the contemporary nature of these nerve injuries, observation is almost always the treatment of choice, with delayed electrodiagnostic testing should nerve recovery not occur within a 3 to 6-week period.

Effects of tenorraphy on the gliding function and tensile properties of partially lacerated canine digital flexor tendons.

Management of a partially lacerated digital flexor tendon within zone II remains controversial. To address this issue, we undertook an evaluation of the impact of tenorrhaphy on the gliding function and tensile properties of canine flexor tendons with lacerations involving either 30% or 70% of their cross-sectional area. Assessment of tendon excursion and joint rotation after 6 weeks of postoperative controlled passive mobilization failed to reveal any statistically significant benefit from tenorrhaphy on the gliding function. In fact, we demonstrated a significant negative effect of repair on tendons with 30% lacerations. Moreover, no significant differences between the structural properties or integrity of the repaired and nonrepaired tendons could be demonstrated. Thus, in light of the inherent tensile properties in these partially lacerated tendons, our data suggest that digital function of partially lacerated tendons of up to 70% of the cross-sectional area may be preserved without primary repair. However, additional work is needed to more definitively address this issue in a clinical context.

Tensile properties of canine intrasynovial and extrasynovial flexor tendon autografts.

This study compared the biomechanical properties of intrasynovial and extrasynovial flexor tendon autografts in an adult canine model. Flexor digitorum profundus (FDP) tissue from the fifth toe of the hindpaw was harvested and transplanted as an intrasynovial graft to the second toe of the left forepaw of each animal. Peroneus longus tendon from the lateral compartment of the hind leg served as the source for the extrasynovial graft that was transplanted to the fifth toe of each dog's left forepaw. The second and fifth FDP tendons of the right forepaw constituted the respective contralateral controls. Postoperatively, each animal underwent a regimen of daily controlled passive mobilization. Three and 6 weeks after grafting, 6 animals were euthanized and their grafts evaluated for gliding function and tensile properties. Results reveal significantly greater angular rotation of the proximal interphalangeal joint in the digits that received intrasynovial grafts relative to those that received transplanted extrasynovial tendon at both 3 and 6 weeks postoperatively. The linear stiffness of the tendons receiving extrasynovial graft significantly exceeded that of the intrasynovial group. These findings correlated with histologic data that postoperative adhesions existed in the specimens with an extrasynovial graft. In addition, the extrasynovial tendon graft complex exhibited significantly higher ultimate loads than intrasynovial tendon graft complex at 6 weeks.

Tensile properties of the interosseous membrane of the human forearm.

The interosseous membrane is a structure deep in the forearm that joins the radius and the ulna. It is made up of membranous and ligamentous regions. Two main ligamentous structures have been described: a prominent central fiber group, the "central band," and a smaller proximal fibrous band, the "oblique cord." Many authors believe that the central band plays a biomechanical role in the normal and fractured forearm and that it may function much like a ligament. The objective of this study was to determine the tensile properties of the central band. Eighteen fresh frozen forearms from cadavers (45-70 years of age, both sexes) were used. A fiber bundle of the central band was subjected to a uniaxial tensile test to failure in a materials testing machine, and its tensile properties were calculated. Stiffness, ultimate load, and energy absorbed to failure were expressed as a function of specimen width. The central band structure had a stiffness of 13.1 +/- 3.0 N/mm per mm width and an ultimate load of 56.6 +/- 15.1 N per mm width (mean +/- SD). The tissue of the central band displayed a modulus of 608.1 +/- 160.2 MPa, ultimate tensile strength of 45.1 +/- 10.3 MPa, and strain at failure of 9.0 +/- 2.0%. This study demonstrated that the central band is comprised of strong tissue. The material properties of the central band compare with those of patellar tendon: modulus is 120% and ultimate tensile strength is 84% that of patellar tendon. As a structure, the interosseous membrane is stiff and capable of bearing high loads. Although load distribution across the central band is unknown, a 1.7 cm wide, evenly loaded homogenous portion of the central band would possess a stiffness comparable with that of the anterior cruciate ligament. The results of this study provide a basis for future analyses of radioulnar stability and load transfer.

Tensile properties of the superior glenohumeral and coracohumeral ligaments.

Recent evidence has shown that the superior glenohumeral ligament (SGHL) and coracohumeral ligament (CHL) are important static stabilizers. To clarify the function of these two ligaments, we studied their tensile properties with bone-ligament-bone complexes from fresh-frozen shoulders, 10 SGHLs and 10 CHLs. Each ligament's cross-sectional area was measured, and uniaxial tensile testing of each complex was performed. The stiffness, ultimate load, percent elongation, and energy absorbed to failure of each bone-ligament-bone complex were derived from its load-elongation curve. The cross-sectional area of the coracohumeral ligament was significantly greater than that of the superior glenohumeral ligament of their midportions (CHL, 53.7 +/- 3.2 mm2 vs. SGHL, 11.3 +/- 1.6 mm2, p < 0.05). Results also reveal significant differences between the tensile properties for the two ligaments, with the coracohumeral ligament possessing greater stiffness (CHL, 36.7 +/- 5.9 N/mm vs. SGHL, 17.4 +/- 1.5 N/mm, p < 0.05) and ultimate load (CHL, 359.8 +/- 40.3 N vs. SGHL, 101.9 +/- 11.5 N, p < 0.05) than the superior glenohumeral ligament. Our findings confirm that the coracohumeral ligament is an important capsuloligamentous structure of the glenohumeral joint.

A biomechanical analysis of rotator cuff deficiency in a cadaveric model.

We conducted this cadaveric study to define a biomechanical rationale for rotator cuff function in several deficiency states. A dynamic shoulder testing apparatus was used to examine change in middle deltoid muscle force and humeral translation associated with simulated rotator cuff tendon paralyses and various sizes of rotator cuff tears. Supraspinatus paralysis resulted in a significant increase (101%) in the middle deltoid force required to initiate abduction. This increase diminished to only 12% for full glenohumeral abduction. The glenohumeral joint maintained ball-and-socket kinematics during glenohumeral abduction in the scapular plane with an intact rotator cuff. No significant alterations in humeral translation occurred with a simulated supraspinatus paralysis, nor with 1-, 3-, and 5-cm rotator cuff tears, provided the infraspinatus tendon was functional. Global tears resulted in an inability to elevate beyond 25 degrees of glenohumeral abduction despite a threefold increase in middle deltoid force. These results validated the importance of the supraspinatus tendon during the initiation of abduction. Glenohumeral joint motion was not affected when the "transverse force couple" (subscapularis, infraspinatus, and teres minor tendons) remained intact. Significant changes in glenohumeral joint motion occurred only if paralysis or anatomic deficiency violated this force couple. Finally, this model confirmed that rotator cuff disease treatment must address function in addition to anatomy.

Clinical management of partially lacerated digital flexor tendons: a survey [corrected] of hand surgeons.

A survey was taken of one thousand members of the American Society for Surgery of the Hand to determine the methods by which clinicians currently treat partial lacerations of flexor tendons. Results from 591 respondents show that most surgeons use a modified Kessler technique and begin protected mobilization within the first 48 hours.