Rockwood Adults CH34

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CHAPTER 34 • Glenohumeral Instability

POSTERIOR GLENOHUMERAL INSTABILITY Indications/Contraindications

Graft osteolysis can occur after coracoid transfers and bone block procedures for anterior instability. A large systematic review of 45 studies on Latarjet procedures reported graft oste- olysis to be approximately 3.2%. 76 In a CT analysis study of 26 patients, Di Giacomo et al. 61 found a higher mean of 59.5% osteolysis of the coracoid graft. However, this extensive osteoly- sis was not found to be of any great clinical significance in terms of recurrence of instability. The osteolysis was most commonly seen in the superficial part of the proximal coracoid, while the deep portion of the distal region of the graft was the least involved in osteolysis and exhibited the best rates of bone heal- ing. 79 If the osteolysis results in implant problems such as the screws becoming prominent, this can be managed with removal of the screws. In the rare case where coracoid graft osteolysis results in recurrence of instability, this can be managed with revision to an autograft or allograft bone block reconstruc- tion. 71,141,203,235 Incidence of neurologic injury after anterior instability repair varies depending on the surgical technique. Arthroscopic approaches have an exceedingly low rate of neurologic injury (0.2%) versus open procedures such as Latarjet (1.8%) with the musculocutaneous and axillary nerve at the greatest risk. 76,177 Fortunately, most of the neurologic injuries reported were tran- sient in nature with the majority of patients recovering with- out further sequelae. 58,76 One suggested treatment protocol if a neurologic injury is recognized in follow-up includes a CT scan of the shoulder to evaluate for correct screw placement and graft positioning in bone augmentation procedures. 79 If there is no radiologic abnormality noted, the patient is followed at 6 weeks and 3 months. If no improvement is noted at the 3 months’ follow-up, an EMG is obtained to evaluate the extent of the injury. At 6 months’ follow-up, if no recovery is noted, the patient is referred to a specialist in brachial plexus injuries. Consultation of a brachial plexus injury specialist should also occur earlier in the postoperative care to help manage these challenging cases. Postsurgical osteoarthritis after arthroscopic or open Bankart repairs has not been studied extensively. A recent systematic review noted that radiographic evident osteoarthritis was seen in 45.9% (range 24.4 to 67.4) and 45.1% (29.8 to 58.4) of patients after arthroscopic or open Bankart repairs, respec- tively. Arthrosis after bone augmentation procedures, such as Latarjet, has been estimated to be 42.0% (29.3 to 54.8). The development of osteoarthritis after instability surgery, however, is likely at least partly due to the recurrent instability events itself. Hovelius et al. 91 reported an 11% rate of mild osteoar- thritis and 9% rate of moderate osteoarthritis 10 years after primary shoulder dislocation. At 25-years follow-up, Hovelius et al. 93 reported that the prevalence of severe arthritis in their cohort of patients was similar between those who had been treated without surgery and those who were surgically stabilized. In the case of Latarjet and bone block augmenta- tion procedures, aberrant graft positioning, especially with intra-articular hardware, has been implicated as a cause of postsurgical arthrosis. 4,95,114,157 Accurate intraoperative graft placement to ensure that the graft is congruent with the joint articular surface and to avoid lateralization of the graft mini- mizes this potential complication.

Persistent pain and instability refractory to conservative man- agement consisting of activity modification and a rotator cuff strengthening protocol are the primary indications for the treatment of posterior shoulder instability. Locked posterior shoulder fracture dislocations require surgical treatment. Con- traindications include an inability to be compliant with post- operative restrictions, an uncontrolled seizure disorder, an inability to participate in postoperative rehabilitation, or medi- cal comorbidities preventing safe surgical treatment. Arthroscopic Posterior Labral (Bankart) Repair Preoperative Planning ✔ ✔ Arthroscopic Posterior Labral (Bankart) Repair: PREOPERATIVE PLANNING CHECKLIST

❑❑ Regular OR table with rails that allows placement of the arm traction apparatus ❑❑ Beach chair table with arm holder ❑❑ Lateral decubitus or beach chair ❑❑ Bean bag or peg board to stabilize the patient ❑❑ 30-degree arthroscope ❑❑ 6–8-mm diameter threaded cannulas ❑❑ Labral elevator or CoVator ❑❑ Disposable and nondisposable curved and straight labral suture passers ❑❑ Suture anchors (knotless or knotted) with percutaneous insertion instruments ❑❑ Drill and drill guide (2.9-mm drill bit) ❑❑ Arthroscopic suture and tissue graspers

OR table

Position/ positioning aids

Equipment

Plain radiographs including an axillary radiograph should be obtained. Advanced imaging including a CT scan with 3D reconstruction is useful for evaluating bone loss, dysplasia, and fractures. Bone loss from attritional, chronic instability may require consideration for a bone augmentation procedure. While there are no established parameters for determining when a soft tissue versus a bony reconstructive procedure should be used, one can draw upon similar guidelines established for anterior glenoid bone loss. Greater than 20% to 25% bone loss from the posterior glenoid is an indication for a glenoid reconstructive procedure with bone, either autograft iliac crest or distal tibial osteoarticular allograft. Ten to 20% bone loss may also require consideration for bone grafting of the glenoid depending on other factors such as soft tissue labral and capsular deficiency, decentering of the humeral head, and prior failed instability sur- gery. MRA evaluation is necessary for preoperative planning as it is more sensitive and specific for identification of subtle labral and capsular pathology than MRI. Positioning The surgery can be performed in either the lateral decubitus or beach chair position, depending on the surgeon’s training and comfort. In the lateral decubitus position, the patient is intubated