Steve A. Petersen

Anatomical Acromioclavicular Ligament Reconstruction A Biomechanical Comparison of Reconstructive Techniques of the Acromioclavicular Joint

Background Current surgical treatments for acromioclavicular separations do not re-create the anatomy of the acromioclavicular joint. Hypothesis Anatomical acromioclavicular reconstruction re-creates the strength of the native acromioclavicular joint and is stronger than a modified Weaver-Dunn repair. Study Design Controlled laboratory study. Methods The native acromioclavicular joint in 6 fresh-frozen cadaveric upper extremities was stressed to failure under uniaxial tension in the coronal plane. A modified Weaver-Dunn procedure, anatomical acromioclavicular reconstruction using a palmaris longus graft, and anatomical acromioclavicular reconstruction using a flexor carpi radialis graft were then performed sequentially. Each repair was stressed to failure. Load-displacement curves and mechanism of failure were recorded for each. Results Loads at failure for the native acromioclavicular joint complex, modified Weaver-Dunn procedure, anatomical acromioclavicular reconstruction using a palmaris longus tendon graft, and anatomical acromioclavicular reconstruction using a flexor carpi radialis tendon graft were 815 N, 483 N, 326 N, and 774 N, respectively. The strength of the native acromioclavicular joint complex was significantly different from the modified Weaver-Dunn repair (P <. 001) and the anatomical acromioclavicular reconstruction using a palmaris longus tendon graft (P <. 001) but not from the anatomical acromioclavicular reconstruction using a flexor carpi radialis tendon graft (P =. 607). Conclusion The strength of the described anatomical acromioclavicular reconstruction is limited by the tendon graft used. Anatomical acromioclavicular reconstruction with a flexor carpi radialis tendon graft re-creates the tensile strength of the native acromioclavicular joint complex and is superior to a modified Weaver-Dunn repair.

REVISION OF FAILED TOTAL SHOULDER ARTHROPLASTY

The complexity of revision shoulder surgery remains a supreme challenge for the experienced shoulder surgeon. The difficulty of surgery is often accompanied by unpredictable patient cooperation during the postoperative rehabilitation program. Recognition of the problems associated with the failed shoulder arthroplasty is necessary for successful revision surgery. Numerous reconstructive techniques are necessary for restoration of soft tissue and bony deficiencies. Component revision is often necessary in treating component loosening or glenohumeral instability. Glenoid component removal may be necessary in the presence of severe rotator cuff insufficiency or marked glenoid bone deficiency. Humeral revision is most predictably treated with methylmethacrylate fixation. Humeral fractures associated with humeral arthroplasty are most successfully treated surgically, except in those instances where a long oblique or spiral fracture is not associated with prosthetic loosening. Deep infection is most predictably treated by extensive debridement, parenteral antibiotics, and delayed exchange of the components. The success of revision shoulder arthroplasty is often unpredictable, with 60% of revisions offering satisfactory pain relief and restoration of function. Critical to the success of revision arthroplasty is the status of the soft tissues, particularly the anterior deltoid and rotator cuff.

The coracoacromial arch: MR evaluation and correlation with rotator cuff pathology

The relative prevalence of various acromial shapes, appearance of the coracoacromial ligament and enthesophytes along the inferior aspect of the acromioclavicular joint in patients with and without rotator cuff tears were evaluated. Of 76 patients with clinical instability and impingement, 31 had a normal rotator cuff and 45 demonstrated a partial or full tear of the supraspinatus tendon at surgery. Results were compared with those from magnetic resonance (MR) scans of 57 asymptomatic volunteers. Of the 45 patients with a supraspinatus tear, 38% (17) had a flat acromial undersurface (type I), 40% (18) had a concave acromial undersurface (type II), 18% (8) had an anteriorly hooked acromion (type III), and 4% (2) had an inferiorly convex acromion (type IV). Among the 31 patients with a normal rotator cuff at surgery and the 57 asymptomatic volunteers, the respective prevalences of the type I acromion were 39% (12) and 44% (25), of type II 48% (15) and 35% (20), type III 3% (1) and 12% (7), and type IV 10% (3) and 9% (5). Shoulders with surgically proven rotator cuff tears showed a tendential association with a type III acromion (8/45) and statistically significant associations with a thickened coracoacromial ligament (17/45) and acromioclavicular enthesophytes (18/45). For the association between inferiorly directed acromioclavicular joint enthesophytes and rotator cuff tears, age appears to be a confounding factor. The type IV acromion, newly classified by this study, does not have a recognizable association with rotator cuff tears. Assessment of the osseous-ligamentous coracoacromial outlet by may prove helpful to the orthopedic surgeon in patients for whom surgical decompression is contemplated.

POSTERIOR SHOULDER INSTABILITY

Understanding the anatomic restraints to posterior shoulder instability and the resulting pathophysiology helps the treating physician make a correct diagnosis and formulate an appropriate treatment plan. A nonoperative program directed at reducing pain and increasing stability through comprehensive shoulder strengthening methods has generally been successful in treating recurrent posterior shoulder subluxation. Surgical options for treatment are reserved for those patients who fail to recognize improvement after six months of therapy and have no evidence of a psychological disturbance as the cause of their posterior instability.

Unicompartmental knee arthroplasty. Sequential radiographic and scintigraphic imaging with an average five-year follow-up.

Clinical, radiographic, and scintigraphic results of 33 consecutive unicompartmental knee arthroplasties were reviewed after a mean follow-up period of 68 months (range, 24 to 112 months). Clinical grades employing criteria established by the Hospital for Special Surgery showed 74% good to excellent and 11% fair to poor results. Four knees (15%) required revision to a total knee arthroplasty after an average postoperative interval of 7.4 years. Within the subset of surviving medial compartment arthroplasties (23 knees), superior clinical results were associated with a central or slightly medialized mechanical axis (p < 0.05). Periprosthetic radiolucency showed no correlation with clinical scores or failures resulting in revision surgery. There was no radiographic evidence of progressive arthrosis within the unreplaced compartments. Comparative analysis of preoperative and annual postoperative technetium bone scans showed no temporally related changes indicative of impending prosthetic failure or disease progression within the unoperated compartments. The surgically treated compartments maintained uniformly intense femorotibial activity, whereas the unoperated compartments, including the patellofemoral joint, remained scintigraphically quiescent. Disease progression in unreplaced compartments is unusual after contemporary unicompartmental knee arthroplasty. Most failures and poor results arise from mechanical inadequacies amendable to surgical technique and/or future design considerations.

A prospective comparison of computerized arthrotomography and magnetic resonance imaging of the glenohumeral joint

Twenty-five patients with shoulder instability or shoul der pain of undetermined etiology were prospectively evaluated with magnetic resonance imaging and com puterized arthrotomography. Actual lesions were de termined by arthroscopy or at the time of open surgical repair. The images obtained were interpreted independ ently by three radiologists blinded to both surgical results and the results of previous diagnostic tests. Sensitivity, specificity, and accuracy were determined for each imaging technique for a variety of pathologic entities, including anterior and posterior labral abnor malities, capsular redundancy, biceps-labral complex abnormalities, humeral head (Hill-Sachs) impression le sions, and glenohumeral loose bodies. Analysis of im aging techniques also included construction of receiver operator curves for labral abnormalities. Magnetic resonance imaging showed better diagnos tic results in the evaluation of glenoid labral and humeral head impression lesions (P < 0.05). Both imaging tech niques were equally successful in identifying biceps- labral lesions and intraarticular loose bodies within the glenohumeral joint. Neither imaging technique was con sistent in the evaluation of capsular redundancy. Re ceiver operator curve analysis confirmed that magnetic resonance imaging was the more accurate imaging study in evaluating anterior and posterior glenoid labral abnormalities.