In vivo shoulder function after surgical repair of a torn rotator cuff: glenohumeral joint mechanics, shoulder strength, clinical outcomes, and their interaction

BACKGROUND

Surgical repair of a torn rotator cuff is based on the belief that repairing the tear is necessary to restore normal glenohumeral joint (GHJ) mechanics and achieve a satisfactory clinical outcome.

HYPOTHESIS

Dynamic joint function is not completely restored by rotator cuff repair, thus compromising shoulder function and potentially leading to long-term disability.

STUDY DESIGN

Controlled laboratory study and Case series; Level of evidence, 4.

METHODS

Twenty-one rotator cuff patients and 35 control participants enrolled in the study. Biplane radiographic images were acquired bilaterally from each patient during coronal-plane abduction. Rotator cuff patients were tested at 3, 12, and 24 months after repair of a supraspinatus tendon tear. Control participants were tested once. Glenohumeral joint kinematics and joint contact patterns were accurately determined from the biplane radiographic images. Isometric shoulder strength and patient-reported outcomes were measured at each time point. Ultrasound imaging assessed rotator cuff integrity at 24 months after surgery.

RESULTS

Twenty of 21 rotator cuff repairs appeared intact at 24 months after surgery. The humerus of the patients' repaired shoulder was positioned more superiorly on the glenoid than both the patients' contralateral shoulder and the dominant shoulder of control participants. Patient-reported outcomes improved significantly over time. Shoulder strength also increased over time, although strength deficits persisted at 24 months for most patients. Changes over time in GHJ mechanics were not detected for either the rotator cuff patients' repaired or contralateral shoulders. Clinical outcome was associated with shoulder strength but not GHJ mechanics.

CONCLUSION

Surgical repair of an isolated supraspinatus tear may be sufficient to keep the torn rotator cuff intact and achieve satisfactory patient-reported outcomes, but GHJ mechanics and shoulder strength are not fully restored with current repair techniques.

CLINICAL RELEVANCE

The study suggests that current surgical repair techniques may be effective for reducing pain but have not yet been optimized for restoring long-term shoulder function.

Tibiofemoral joint kinematics of the anterior cruciate ligament-reconstructed knee during a single-legged hop landing

BACKGROUND

Abnormal 3-dimensional tibiofemoral joint kinematics have been identified in anterior cruciate ligament-reconstructed knees during functional gait tasks, which is suggested to directly affect risk of knee osteoarthritis. However, the extent to which similar high-risk abnormalities are present during more demanding maneuvers, such as single-legged hopping, is largely unknown.

HYPOTHESIS

When performing a single-legged forward hop landing, the reconstructed knee will demonstrate altered sagittal, frontal, and transverse plane kinematics compared with the contralateral limb.

STUDY DESIGN

Controlled laboratory study.

METHODS

High-speed biplane radiography was used to quantify bilateral 3-dimensional tibiofemoral joint kinematics in 9 subjects with unilaterally reconstructed anterior cruciate ligaments (mean time after surgery, 4 months) during 3 single-legged, forward hop landing trials. Mean subject-based initial foot contact and maximum stance (0-250 ms) values were calculated for each kinematic variable. Two-tailed paired t tests were subsequently applied to examine for the main effect of limb (reconstructed vs contralateral).

RESULTS

The reconstructed knees exhibited significantly greater extension (P = .04), external tibial rotation (P = .006), and medial tibial translation (P = .02) than the contralateral knees at initial contact. Reconstructed knees underwent significantly greater maximum flexion (P = .05), maximum external tibial rotation (P = .01), and maximum anterior tibial translation (P = .02). No significant differences existed between limbs for initial contact (P = .65) or maximum adduction-abduction (P = .55).

CONCLUSION

Tibiofemoral joint kinematics of the anterior cruciate ligament-reconstructed knee are significantly different from those of the uninjured contralateral limb during a single-legged hop landing. This altered kinematic profile, in conjunction with the large impact loads associated with hopping, may further contribute to the risk of posttraumatic knee osteoarthritis.

CLINICAL RELEVANCE

Returning to sports involving dynamic single-legged landings at 4 months after anterior cruciate ligament reconstruction surgery may contribute to accelerated knee joint degeneration.

In Vivo Measurement of Glenohumeral Joint Contact Patterns

The objectives of this study were to describe a technique for measuring in-vivo glenohumeral joint contact patterns during dynamic activities and to demonstrate application of this technique. The experimental technique calculated joint contact patterns by combining CT-based 3D bone models with joint motion data that were accurately measured from biplane x-ray images. Joint contact patterns were calculated for the repaired and contralateral shoulders of 20 patients who had undergone rotator cuff repair. Significant differences in joint contact patterns were detected due to abduction angle and shoulder condition (i.e., repaired versus contralateral). Abduction angle had a significant effect on the superior/inferior contact center position, with the average joint contact center of the repaired shoulder 12.1% higher on the glenoid than the contralateral shoulder. This technique provides clinically relevant information by calculating in-vivo joint contact patterns during dynamic conditions and overcomes many limitations associated with conventional techniques for quantifying joint mechanics.

Measuring dynamic in-vivo glenohumeral joint kinematics: technique and preliminary results

Rotator cuff tears are a common injury that affect a significant percentage of the population over age 60. Although it is widely believed that the rotator cuff's primary function is to stabilize the humerus against the glenoid during shoulder motion, accurately measuring the three-dimensional (3D) motion of the shoulder's glenohumeral joint under in-vivo conditions has been a challenging endeavor. In particular, conventional motion measurement techniques have frequently been limited to static or two-dimensional (2D) analyses, and have suffered from limited or unknown in-vivo accuracy. We have recently developed and validated a new model-based tracking technique that is capable of accurately measuring the 3D position and orientation of the scapula and humerus from biplane X-ray images. Herein we demonstrate the in-vivo application of this technique for accurately measuring glenohumeral joint translations during shoulder motion in the repaired and contralateral shoulders of patients following rotator cuff repair. Five male subjects were tested at 3-4 months following arthroscopic rotator cuff repair. Superior-inferior humeral translation was measured during elevation, and anterior-posterior humeral translation was measured during external rotation in both the repaired and contralateral shoulders. The data failed to detect statistically significant differences between the repaired and contralateral shoulders in superior-inferior translation (p=0.74) or anterior-posterior translation (p=0.77). The measurement technique overcomes the limitations of conventional motion measurement techniques by providing accurate, 3D, in-vivo measures of glenohumeral joint motion during dynamic activities. On-going research is using this technique to assess the effects of conservative and surgical treatment of rotator cuff tears.

In vivo measurement of subacromial space width during shoulder elevation: technique and preliminary results in patients following unilateral rotator cuff repair

BACKGROUND

The shoulder's subacromial space is of significant clinical interest due to its association with rotator cuff disease. Previous studies have estimated the subacromial space width to be 2-17 mm, but no study has measured in vivo subacromial space width during shoulder motion. The purpose of this study was to measure the in vivo subacromial space width during shoulder elevation in patients following rotator cuff repair.

METHODS

Biplane X-ray images were collected during shoulder elevation of 11 patients who had undergone rotator cuff repair. Glenohumeral joint motion was measured from the biplane X-ray images for each subject's repaired and asymptomatic, contralateral shoulders. The joint motion data were combined with subject-specific CT models to measure the subacromial space width during shoulder motion.

FINDINGS

Subacromial space width decreased with shoulder elevation, ranging from 2.3 to 7.4 mm in the repaired shoulder and 1.2-7.1 mm in the contralateral shoulder. Subacromial space width in the repaired shoulder was only 0.5 mm less than the contralateral shoulder when averaged over 10-60 degrees of glenohumeral elevation.

INTERPRETATION

The results indicate that the humerus in the repaired shoulder is positioned more cranially on the glenoid than in the contralateral shoulder. It is unclear if these subtle differences in subacromial space width are due to the surgical procedure or post-operative stiffness, or if subacromial impingement contributed to the development of the rotator cuff tear. Future research will ascertain if these results represent a transient response to the surgery or a more fundamental difference in rotator cuff function between repaired and contralateral shoulders.

Fractures in patients who have myelomeningocele

Thirty-seven (20 per cent) of 186 children who had myelomeningocele whose records were reviewed had sustained a total of seventy-six fractures. The frequency with which the fractures occurred was related directly to the level of neurological involvement. Thirteen (41 per cent) of the patients who had involvement at the thoracic level, fifteen (36 per cent) who had involvement at the upper lumbar level, eight (10 per cent) who had involvement at the lower lumbar level, and one (3 per cent) who had involvement at the sacral level sustained fractures. Sixty-five (86 per cent) of the fractures occurred before the child was nine years old, fifty-eight (76 per cent) were judged to be secondary to the limb being in a cast, and seventy-four (97 per cent) involved the lower extremity. Eleven patients, all of whom had thoracic or upper lumbar involvement, sustained fractures of multiple extremities. All fractures of the lower extremity were distal to the level of neurological involvement; they occurred predominantly in the femur in patients who had thoracic involvement and in the tibia in patients who had lumbar involvement. All of the metaphyseal and diaphyseal fractures healed satisfactorily, whether they were treated by immobilization in a plaster cast or in a bulky Webril dressing, although there were fewer complications in the latter group. The seven fractures that involved the physeal plate were a major problem, as three (43 per cent) had delayed union and two (29 per cent) developed premature growth arrest.

Posterior tibial tendon rupture in pronation-external rotation ankle fractures

We have recently treated two patients with closed pronation-external rotation bimalleolar ankle fractures. During the surgical explorations, an avulsion type rupture of the posterior tibial tendon was observed. Open reduction and internal fixation of the fracture in conjunction with primary tendon repair has produced excellent clinical results. We wish to report these two cases of this uncommon injury. More important, we wish to point out the association of the tendon rupture in conjunction with a particular type of fracture pattern.

Maisonneuve fracture: case report of a missed diagnosis

We report the case of a Maisonneuve fracture of the fibula in which the diagnosis was initially missed. The patient presented with a chief complaint of medial ankle pain. Rentograms of the ankle were unremarkable, and the proximal fibula was not examined. He returned four days later with increased pain, at which time examination revealed tenderness along the proximal fibula and medial ankle. Roentgenograms showed widening of the medial joint space of the ankle and an oblique crush of the proximal fibula. The patient underwent open reduction and internal fixation of the syndesmosis and repair of the deltoid ligament, and recovered uneventfully. Physical examination of ankle injuries should include the proximal fibula.