Humeral stem removal and glenoid exposure

Technique for Humeral Stem Removal

Tenotomy of the subscapularis with subsequent release of the superior, middle, and inferior glenohumeral ligaments (see Chapters 9 and 37 ) is performed if the subscapularis is intact. If the subscapularis is absent, any subscapularis bursa is excised to expose the anterior aspect of the humeral component ( Fig. 38.2 ). A humeral head retractor is placed for retraction of the proximal humerus posteriorly ( Fig. 38.3 ). If this provides sufficient visualization of the anterior glenoid and inferior capsule, inferior capsular release is performed, as described in the following section on glenoid exposure. However, because of its size, the humeral implant frequently sufficiently hinders glenoid visualization to prevent inferior capsular release. In these cases, it is necessary to remove the humeral stem before proceeding with glenoid exposure.

The proximal humerus must be dislocated before attempts at removal of the humeral stem. The dislocation must be done with great care to avoid humeral injury. Frequently, capsular stiffness prevents dislocation by simple external rotation and extension of the arm. If this maneuver is not initially successful, a humeral-based inferior capsular release is performed ( Fig. 38.4 ). Progressive release of the inferior medial capsule from the humerus with the needle tip electrocautery allows dislocation of the proximal humerus. Care must be taken to keep the electrocautery in contact with the humerus to avoid injury to the axillary nerve. Dislocation maneuvers must be done slowly and with great care in revision cases to prevent humeral fracture because the humerus is often osteopenic and compromised ( Fig. 38.5 ).

After the humerus has been dislocated, the humeral head portion of the arthroplasty is circumferentially exposed by removing any fibrous tissue at its margins with the needle tip electrocautery ( Fig. 38.6 ). Nearly all implants currently encountered during revision surgery have a modular head fixed onto a stem via a Morse taper mechanism. However, it is important for a surgeon unfamiliar with the type of implant being removed to obtain any information available about the implant from the manufacturer. The surgeon must discover whether the implant is modular or monoblock and whether any accessory mechanisms have been used to fix the humeral head to the stem portion of the component. If the humeral component is modular with only Morse taper fixation of the humeral head portion to the stem portion of the component, the humeral head is usually easily removed by disimpacting the humeral head from the stem with a Cobb elevator at the inferior aspect of the humeral head component ( Fig. 38.7 ). Often, fibrous tissue covers the proximal aspect of the stem portion of the component ( Fig. 38.8 ). This fibrous tissue is completely removed with the needle tip electrocautery to delineate the peripheral proximal portion of the stem circumferentially ( Fig. 38.9 ). The condition of the superior and posterior rotator cuff tendons can be evaluated at this point ( Fig. 38.10 ).

After all soft tissue has been released peripherally from the proximal aspect of the stem portion of the implant, the extraction device specific for the implant, if available, is attached ( Fig. 38.11 ). Attempts are made with the extraction device (generally with an attached slap hammer). If attempts to extract the implant are initially unsuccessful, the extraction device is removed and small, thin osteotomes are used to delicately separate the proximal humerus from the proximal aspect of the humeral implant ( Fig. 38.12 ). The extraction device is reattached, and additional attempts are made to remove the humeral component. If these attempts are unsuccessful, a humeral osteotomy is performed for removal of the humeral implant (see later).

If no extraction device for the type of implant being removed exists, small, thin osteotomes are used to delicately separate the proximal humerus from the proximal aspect of the humeral implant after all soft tissue has been released peripherally from the proximal portion of the stem portion of the implant. A large Cobb elevator is used to disimpact the humeral implant from the proximal humerus by striking it at its medial portion ( Fig. 38.13 ). The Cobb elevator is directed as parallel as possible to the humeral implant stem. If attempts at implant extraction are unsuccessful with this technique, humeral osteotomy should be performed.

Humeral Osteotomy

After the necessity for humeral osteotomy is established, the surgical approach is extended distally, as detailed in Chapter 37 . The humerus is exposed from its proximal aspect to the area distal to the pectoralis major insertion ( Fig. 38.14 ). The planned osteotomy site is demarcated with the needle tip electrocautery and extended along the anterior humerus by starting just medial to the bicipital groove and continuing distally between the pectoralis major insertion and the deltoid insertion ( Fig. 38.15 ). The distal extent of the osteotomy is determined by the length of the humeral stem to be removed.

Before performing the osteotomy, cerclage cables are placed for subsequent osteotomy fixation. Depending on the length of the osteotomy, we place two or three cables composed of a nylon monofilament core wrapped in braided ultrahigh-molecular-weight polyethylene (Kinamed Inc., Camarillo, California). The cables are placed subperiosteally with the cable-passing instrumentation provided ( Fig. 38.16 ). In cases in which the osteotomy extends beyond the junction of the proximal third and middle third of the humeral shaft, the radial nerve must be identified and protected before passing cables posterior to the humerus (see Chapter 37 ). After the cables are passed, the free ends of each cable are clamped together with Kocher clamps ( Fig. 38.17 ).

A unicortical humeral osteotomy is performed by penetration of the anterior cortex with a sagittal saw along the humerus at the demarcated osteotomy site down to the humeral implant ( Fig. 38.18 ). A -inch straight osteotome is impacted into the osteotomy site proximally ( Fig. 38.19 ). The osteotome is turned to open the osteotomy by plastically deforming the proximal humerus ( Fig. 38.20 ). The humeral stem can then be removed with the extraction instrumentation provided or by disimpaction with a Cobb elevator, as described earlier ( Fig. 38.21 ).

After the humeral stem and any necessary cement (see later) are removed, the osteotomy must be fixated. This is performed by first preparing the proximal humerus for insertion of the revision humeral component with the instrumentation provided. The trial humeral stem is inserted, and the cables are tightened with the tensioning device provided ( Fig. 38.22 ). The cables are tightened in a distal-to-proximal direction. In cases in which the native humeral cortex is excessively thin, fresh frozen allograft cortical struts are placed around the native humerus beneath the cables before tightening to provide additional support to the proximal humerus ( Fig. 38.23 ).