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Shoulder replacement begins with careful preoperative planning. The integrity of the rotator cuff tendons, contracture of the subscapularis tendon, and irregular glenoid wear should be assessed before surgery as each can affect the choice of surgical technique. The integrity of the rotator cuff mechanism is usually evident after a clinical examination. In the case of cuff arthropathy, it can be assessed from the superior subluxation of the humeral head as seen on plain radiographs. A preoperative MRI can be extremely useful in evaluating the patients with significant rotator cuff weakness on examination to determine those who are candidates for hemiarthroplasty and not TSA.
Similarly, the surgeon must be aware of any bony irregularities that require special consideration. Erosion of the posterior glenoid in osteoarthritis will change the version of the glenoid and interfere with postoperative motion if not addressed during the procedure. In extreme cases, posterior instability can develop after replacement because these changes were not bone grafted. Preoperative radiographs, in particular the axillary view, can help in the evaluation of the glenoid fossa morphology. Computed tomography scanning can also be used to assess the degree of glenoid erosions.
Several different shoulder prostheses are available. In the early days of shoulder replacement, constrained or fixed fulcrum designs were used. This design theoretically was an adaptation for patients with a deficient or absent rotator cuff mechanism. Due to the high forces on the relatively small glenoid-bone interface, however, these designs were associated with unacceptable early failure rates. As a result, these implants lost popularity.[3]
Neer and others developed an unconstrained humeral head replacement initially for reconstruction of displaced proximal humerus fractures.[4,5] These one-piece design implants consist of a prosthetic humeral head and stem that is cemented into the intramedullary canal of the proximal humerus.[4,5] Later, a cemented glenoid component was developed to resurface glenoid irregularities and to provide a better fulcrum in which to seat the humeral head. More recent modular designs allow the surgeon to independently size the stem, prosthetic head, and glenoid.[6] The choice of implant largely depends on the specific application and, most importantly, on the surgeon's familiarity with the technique.
Although the following technique is specific to the Global Total Shoulder Arthroplasty System[7] (DePuy Inc, Warsaw, Indiana), the indications, preoperative planning, exposure, soft-tissue and bony management, intraoperative assessment, and postoperative rehabilitation apply to most shoulder replacement procedures. The surgical technique will focus on elective reconstructive procedures. Surgical reconstruction of displaced 3- and 4-part proximal humerus fractures will not be discussed. Further information on this challenging procedure can be found in the article by Moeckel and colleagues.[6]
Currently, there is some debate over the indications for glenoid resurfacing in shoulder arthroplasty.[8] While the published literature supports glenoid resurfacing in most cases, there are several points to consider. Surgically implanting a glenoid component is often technically demanding, requiring more surgical trauma to provide adequate exposure, more operative time, and greater blood loss than hemiarthroplasty. In addition, a high rate of glenoid loosening has been noted in patients with rotator cuff deficiencies, including many rheumatoid patients, and in those with cuff tear arthropathy, due to the eccentric forces placed on the superior glenoid rim.
Hemiarthroplasty is not as surgically demanding, is associated with less blood loss, and satisfactory outcomes are seen in the majority of cases. There is also a concern that a high rate of glenoid loosening is noted over time. Some surgeons favor hemiarthroplasty first, especially in younger patients, and then revising to TSA when and if painful degenerative changes occur in the glenoid.
According to a review of the literature, there is a 3.2% revision rate for symptomatically loosened glenoid components compared with a 1.8% revision rate for symptomatically loosened humeral components in patients who have undergone TSA. Proponents of hemiarthroplasty argue that the higher rate of glenoid loosening compared with humeral loosening suggests that replacements performed without glenoid resurfacing will remain asymptomatic longer than those with TSA.[8] Five separate reviews noted greater pain relief and postoperative range of motion associated with TSA compared with that associated with hemiarthroplasty in similar populations of patients.[9-13] In a more recent review of 114 prosthetic shoulders in patients younger than 50 years, there was no difference with respect to long-term pain relief and active range of motion at an average of 12.3 years (minimum 5 years) after either hemiarthroplasty or TSA.[14]
Each surgeon should decide between performing TSA or hemiarthroplasty on a case-by-case basis depending on his or her experience and outcomes and an individual interpretation of the literature. This author has obtained satisfactory outcomes and range of motion with hemiarthroplasty alone in the majority of cases.
Hemiarthroplasty over TSA is indicated in cuff arthropathy, in patients with a deficient rotator cuff mechanism and in patients with insufficient glenoid bone stock to support a glenoid component. Relative indications for hemiarthroplasty include osteoarthritis, AVN, and posttraumatic cases in which there is little destruction of the glenoid bone stock, normal glenoid version, no subchondral cysts, and a minor degree of soft-tissue contracture. These represent the great majority of cases in this author's practice. If a patient fails to meet any of these criteria, the surgeon should seriously consider TSA.
Before the patient enters the operating room, preoperative radiographs should be measured using transparent overlays (supplied by most major manufacturers with the surgical implant instruments) to determine the optimal stem diameter and humeral head size of the implant. Inventory should be checked to ensure that the preoperatively measured implant size, as well as implants both one size above and below are available.
Either general anesthesia or an interscalene block can be used with this procedure. A combination of both techniques provides comfort during and after the procedure and is this author's choice. Prophylactic intravenous antibiotics with a broad-spectrum coverage should be administered at least 30 minutes before the procedure to ensure proper tissue levels at the time of incision.
Proper positioning of the patient allows the surgeon access to both the intramedullary canal of the humerus and the glenoid. Most surgeons prefer placing the patient in a modified "beach chair" position. Some surgeons recommend removing the upper portion of the operating table and replacing it with a neurosurgical type headrest to allow greater access to the shoulder and improve the surgeon's ability to extend the shoulder during the procedure (Figure 7). This author has found that by simply moving the patient to the extreme ipsilateral edge of the table and gently bending the head and neck away from the shoulder being operated on, use of the headrest is seldom necessary. A rolled towel is placed under the ipsilateral scapula to stabilize the shoulder and to project the shoulder forward. This step is critical if a glenoid is to be replaced.
The shoulder should be examined to ensure that the arm can be maximally extended with ease. If the surgeon is not able to comfortably extend the arm, insertion of humeral stem will not be possible and the patient should be repositioned. The head and torso should be held in position with secure straps and the ipsilateral arm should be left free. Placing an arm board under the elbow and forearm, but not under the shoulder, provides an "extra hand" to manage the extremity during the exposure and closure, without interfering with other portions of the surgical procedure.
Once the patient is anesthetized and secured in place, range of motion is assessed. Shoulder elevation, internal rotation, abduction, and adduction across the body should be assessed and compared with the preoperative examination. Large differences in awake and anesthetized measurements, as is usually the case in patients with rheumatoid arthritis and early stage AVN, indicate the relative amount of motion restricted by pain. Small differences in these 2 measurements indicate the degree of soft-tissue contracture and bony blocks to motion that will have to be addressed during the procedure. External rotation motion with the elbow held firmly on the patient's torso is measured. If rotation is less than 30° to 40° under anesthesia, as is the case in many patients with osteoarthritis, and no bony block to motion is identified, a surgical approach that allows lengthening of the subscapularis tendon will be necessary.
The shoulder is prepared and draped according to individual preferences. The deltopectoral interval is carefully drawn out with a marking pen from the clavicle to the deltoid insertion of the humerus. The interval is usually easily palpable by gently pressing one's fingers into the deltopectoral crease. In cases where the interval is not easily identified, it is helpful to locate the coracoid process, which lies in the proximal portion of the interval (Figure 7). The skin markings should be made before applying a transparent plastic drape, if one is to be used.
Figure 7. The patient on the operating room table in a modified beach chair position with the torso at the extreme edge of the table. The shoulder can be extended maximally as shown.
The incision is then made through the skin, taking care not to injure the cephalic vein. This vein is a major source of venous return from the limb and should be protected . The interval is then developed from the clavicle to the insertion of the pectoralis major on the humerus. This author recommends that the cephalic vein should be taken medially, instead of laterally as is shown in several of the manufacturer's illustrations included in this article. Lateral retraction of the vein places it in a position in which it can be injured during reaming and implantation of prosthetic stem. The proximal 1 cm of pectoralis tendon can be released to gain better exposure if necessary. Deep retractors are then inserted. Self-retaining retractors (the Hawkins-Bell Retractor System, DePuy, Warsaw, Indiana, and others) can also be used to retract the deltoid and pectoralis eliminating the need for another assistant (Figure 8).
Figure 8. The deltopectoral incision is extended from the clavicle to the deltoid tuberosity. The coracoid can be used as a reference to ensure proper positioning of the incision.
The lateral edge of the conjoined tendon is identified and dissected free of the underlying subscapularis tendon. The muscle belly of the coracobrachialis often protrudes laterally to the tendon and should be preserved. There is usually a thickened bursa overlying the subscapularis that should be sharply excised. To identify the musculocutaneous nerve, gently sweep a finger underneath the conjoined tendon approximately 3 cm inferior to the medial border of the coracoid process. Because of the proximity of this nerve, retractors should never be placed underneath the conjoined tendon. Gentle retraction on the lateral border is preferred. The lateral half of the conjoined tendon can be recessed off of the coracoid using a cautery device and reattached later if greater exposure is necessary. Similarly, gently sweeping a finger underneath the conjoined tendon and hooking a fingertip underneath the inferior border of the subscapularis tendon will locate the axillary nerve. It is critical that this nerve be identified so that it can be retracted out of the way during the later steps of the procedure (Figure 9).
Figure 9. Self-retaining retractors can retract the deltoid and pectoralis major reducing the need for a second assistant (Hawkins-Bell Retractor System, DePuy Inc., Warsaw, Indiana).
The superior, inferior, and lateral borders of the subscapularis tendon should be identified and marked. The biceps tendon marks the lateral most point of the subscapularis tendon. The thin layer of tissue over the rotator interval is easily palpable at the superior border of the subscapularis tendon. The inferior border is less defined. The subscapularis has both tendonous and direct muscle insertions into bone inferiorly. The anterior humeral circumflex vessels that overlie this area should be carefully dissected and cauterized individually.
The subscapularis tendon is vertically incised approximately 0.5 cm from the biceps tendon (Figure 10). Unless there is a need to lengthen the subscapularis the incision is carried through the joint capsule and directly to bone. One or two sutures should be placed in the tendon for traction. The superior border of the tendon is transversely incised to the lateral border of the coracoid. This transverse incision is then directed laterally to the insertion of the tendon on the humerus. Care must be taken not to cut the biceps tendon, which lies directly beneath this tissue. Failure to carry out this seemingly small release will make dislocation of the humeral head difficult (Evan Flatow, MD, oral communication, February 2000). A Darrach or other flat smooth retractor is carefully placed inferior to the subscapularis tendon to retract and protect the axillary nerve. A Cobb elevator can be used if other retractors are not available. The inferior border of the tendon is dissected medially to the glenoid. The circumflex vessels should be avoided, as they can still bleed despite previous ligation. External rotation of the shoulder with the arm in slight abduction will greatly improve exposure. Finally, the superficial and deep surfaces of the tendon should be dissected free of any tissue that is restricting its movement. Care is taken to avoid injury to the musculocutaneous nerve previously identified.
Figure 10. The subscapularis tendon is incised medial to the long head of the biceps tendon. Unless there is a need to lengthen the subscapularis tendon, this incision is made through joint capsule and directly to bone (see DePuy protocol text[7] for further details).
Occasionally, it will be necessary to lengthen the subscapularis tendon, particularly in patients with long-standing osteoarthritis or posttraumatic arthritis associated with malunion. Preoperative range external rotation should be 20° to 30° or more with the patient anesthetized. If significant restriction of motion is noted, the subscapularis tendon should be lengthened. Instead of incising the tendon and capsule as a single layer, the subscapularis tendon should be incised to the level of the capsule (Figure 11). A plane is created sharply between the tendon and the capsule, or through the tendon if the anatomic plane is scarred, similar to the approach used in an open Bankart repair or anterior capsular shifting procedure. The dissection is carried medially over the glenoid and the deep layer is sharply released from the labrum. Both the medial and lateral tissues are tagged with traction sutures and protected. The laterally based flap can then be used to lengthen the subscapularis at the end of the procedure.
Figure 11. If there is a need to lengthen the subscapularis tendon, a plane is created between the subscapularis and joint capsule similar to that of a Neer anterior-inferior capsular shift . The capsule remains attached to the humerus laterally and is resected off of the labrum medially (middle illustration). After the prosthesis is inserted, the capsule can be used to appropriately lengthen the subscapularis as shown (lower illustration). (See DePuy protocol text[7] for further details.)
The joint capsule can then be dissected off of the tendon and the labrum discarded. An assistant should continue to externally rotate the arm while the surgeon carefully releases the capsule of the humeral neck, until the 7-o'clock position is reached posteriorly (ie, posterior to the inferior glenoid rim). Holding the arm only slightly abducted and maintaining gentle retraction on the axillary nerve avoids injury to vital structures.
Large osteophytes occasionally block access to the inferior capsule. They should be carefully removed with a rongeur or similar instrument. Otherwise, this author prefers to leave the osteophytes in place until the trial prosthesis is in place. Externally rotating and extending the arm easily dislocates the humeral head (Figure 12). Difficulty with dislocating the head is usually due to inadequate capsular release or extremely large osteophyte formations. Check to ensure that the rotator interval has been released to the coracoid medially and laterally to the humeral insertion of the capsule. If exposure remains difficult, continue the capsular release further around the posterior humeral head. In most cases the capsule will remain intact from the 7 o'clock to 11 o'clock position posteriorly. In a tight shoulder, however, a circumferential release may be necessary for adequate exposure. Further exposure can be obtained by resecting the osteophytes and by releasing the capsule off of the glenoid.
Figure 12. Once adequate capsular releases are performed, the shoulder is easily dislocated with gentle external rotation and extension. In this photograph, a canal reamer is inserted through the humeral head as part of another procedure.
After adequate exposure is obtained, the portion of humeral head to be resurfaced is resected with a motorized saw. Only the portion of humeral head covered with articular cartilage is resected. Removing more bone will result in a prominent greater tuberosity and lead to impingement and poor rotator cuff mechanics. When using the Global system, the humeral head should be concentrically located in the glenoid fossa and the elbow held firmly at the patient's side. The upper arm should be in line with the torso. The shoulder is externally rotated to approximately 30° to set the proper degree of humeral head retroversion. The cutting guide is placed as illustrated in Figure 13. A Darrach retractor is used to protect the undersurface of the supraspinatus and the long head biceps tendon while the cut is made. The arm should remain externally rotated and the saw cut directed straight downward. Proper retroversion of the humeral head will be adversely affected if changes are made in either arm position or the direction of the saw blade. The guide is positioned to allow the humeral head cut to exit superiorly at the rotator cuff insertion.
Figure 13. A template is used to mark the appropriate amount of humeral head to be resected. The arm must be held at the patient's side and externally rotated approximately 30° (DePuy protocol[7]).
The resected bone is removed and saved for bone graft, if necessary. The diameter of the resected head should be measured with a caliper as an approximation for the size of the prosthetic head to be implanted. The actual implant size is based on the fit of the trial components in the shoulder, or in the case of the Global system, based on the radius of the glenoid component, if one is used. The proximal humerus is again dislocated and brought out of the wound with extension of the arm. The surgeon can maintain position and exposure by gently compressing the arm to the table with his body. Care must be taken to avoid contamination of the surgical field with this maneuver.
The medullary canal of the humerus is identified with a t-handle reamer. It is best to enter the canal as laterally as possible on the cut surface to optimize the eventual placement of the implant. Two Darrach retractors, one placed superiorly and one directly medially, are used to protect the biceps tendon and posterior rotator cuff structures, respectively (Figure 14). Once the canal is entered, extreme care is taken not to perforate the cortex of the bone. The first reamer should easily slide into the medullary canal. If this is not the case, the reamer should be removed and another starting point considered. The canal is progressively reamed with hand-held reamers until the reamers just bite the cortex. Additional bone removal is not necessary (Figure 15). Power reaming should be avoided. The reamers increase in size by 2-mm increments and correspond to the stem diameters of the implants. Excessive torque placed on the reamers can result in intra-operative fracture of the humeral shaft. Should this complication occur, the fracture is reduced with a cerclage wire, and the fracture bypassed with a long stemmed implant.
Figure 14. A t-handle reamer is used to identify the medullary canal. The starting point should be made as laterally as possible on the cut surface of the humerus. In this illustration, the cephalic vein has been retracted laterally and is at risk for injury during the reaming process (DePuy protocol[7]).
Figure 15. The canal is progressively reamed until the reamer contacts the cortical bone. Additional reaming is not necessary and carries the risk of fracturing the humerus (DePuy protocol[7]).
Once the canal diameter is determined, the appropriate body-sizing osteotome is assembled. For example, if canal reaming was stopped at 10 mm, a 10-mm intramedullary rod is attached to a 10-mm body sizing osteotome. The collar is attached as shown in Figure 16, and the rod is placed into the intramedullary canal. Using this collar can be confusing. Be sure that "left" or "right" shoulder markings are facing up as appropriate. Slide the collar up on the handle and place the rod into the medullary canal. The lateral cutting fin of the osteotome should be pointed at the bicipital groove anteriorly. Once all of the cutting fins are in contact with the bone, slide the collar down on the osteotome until it is seated on the cut surface of the humerus. The proper version of the implant is again checked by completely seating the collar on the cut surface. If the collar doesn't seat completely, check to see if the anterior cutting fin is aligned with the biceps, make any necessary corrections, and start again. If the body sizing osteotome is properly aligned and the collar is not seated, the head cut is incorrect and will need to be revised.
Figure 16. The body-sizing osteotome is inserted into the canal and rotated until the collar can be seated on the humerus. The fins in the osteotome cut grooves into the humerus that guide the prosthesis into proper version (DePuy protocol[7]).
The osteotome properly aligns the implant by cutting grooves into the proximal humerus to guide the prosthesis into proper version during implantation and to remove bone from the proximal humeral metaphysis to receive the body of the prosthesis. The osteotome is removed. A small osteotome or curette is used to remove the remaining bone from the proximal humerus (Figure 17). It is not necessary to remove any more bone than that outlined by the osteotome.
Figure 17. Once the osteotome is removed, additional bone is removed with an osteotome. There is not any need to remove additional bone from the proximal humerus (DePuy protocol[7]).
The humerus is further prepared by attaching the appropriate size broach (a broach with the same diameter as the reamer) to the impaction handle. The broach is inserted into the canal so that its fins enter the grooves made by the body-sizing osteotome (Figure 18). The broach is carefully impacted until the collar is seated on the bone. The handle is removed. Any large osteophytes are removed at this time (Figure 19). These osteophytes should be removed from the entire circumference (anterior, inferior, and posterior) of the humerus or they will constrain motion.
Figure 18. A broach is inserted into the humerus and impacted until the collar is seated flush to the humeral surface. The broach also serves as a trial prosthesis (DePuy protocol[7]).
Figure 19. With the trial prosthesis in place, any overhanging osteophytes are removed (DePuy protocol[7]).
If a hemiarthroplasty is to be performed, an appropriate diameter humeral head is attached and the shoulder reduced. Soft-tissue balance is obtained by selecting the proper size and thickness of the head implant, which allows full passive range of motion without dislocating and allows passive translation of the seated humeral head approximately 50% posteriorly with moderate force. The diameter of the head (40, 44, 48, 52, 56, and so forth) refers to the radius of curvature, in millimeters, of the implant. The size of the head should be determined by measuring the diameter of the resected humeral head. Small, medium, and large sizes are available and refer to the thickness of the implanted head. In most instances, the medium head that corresponds to the measured diameter of the bone is used. In cases of cuff arthropathy, there has been a trend to "over-stuff" the glenoid with an extra-large humeral head (Evan Flatow, MD, oral communication, February 2000). The theory is that the large head will articulate with the acromion and the glenoid, providing stability to the cuff-deficient shoulder. In this author's experience, over-stuffing the glenoid limits rotation and results in pain and the need for early revision.
The prosthesis can be cemented or inserted with a "press fit" according to the preferences of the surgeon. This author tends to press fit the prosthesis in younger, more active patients, based on the hypothesis that they may require a revision later in life. Otherwise, this author tends to cement the proximal portion of the prosthesis using the distal stem to align the prosthesis during insertion.
The shoulder is once again dislocated, and the trial components are removed. Often, the posterior labrum is redundant. Any intra-articular flaps of tissue should be sharply excised to prevent clicking with movement. The canal is prepared according to the surgeon's preferences. This author uses pulsed lavage and epinephrine soaked sponges similar to those used in total hip arthroplasty. If any portion of the proximal humerus needs reattachment, holes are drilled into the shaft and sutures passed at this time (see "Complications" section below). Rockwood has recommended re-attachment of the subscapularis through drill holes placed in the anterior humerus[7] (Figure 20). If this technique is used, these holes should be drilled and sutures passed at this time. Bone cement is mixed and allowed to set until it is a doughy consistency. The proximal portion of the prosthesis is coated with a generous amount of cement. The sponges are removed and the canal suctioned dry. Bone cement is manually packed into the cut surface of the humerus. The prosthesis is attached to the insertion handle and inserted into the canal aligning the fins with the grooves in the bone. The prosthesis is gently impacted into the bone until the collar is seated. Excess cement is removed before hardening. An assistant should gently slide the sutures for subscapularis reattachment 2 or 3 times to facilitate their use later.
Figure 20. One method to reattach the subscapularis tendon. If this method is to be used, the bone tunnels must be drilled and the sutures passed before inserting the humeral component. As the bone cement is curing, it is helpful to slide the sutures 1 or 2 times to prevent binding of the sutures (DePuy protocol[7]).
Once the cement has hardened, the previously selected humeral head is impacted into the stem (Figure 21) and the shoulder is reduced. Range of motion, posterior translation, and stability should be assessed once again. The subscapularis is then reattached to the tuberosity with multiple sutures or repaired via the Rockwood method.[7] Subscapularis lengthening is performed, if necessary, at this time. The goal should be 30° of external rotation passively with the arm held at the patient's side. If the conjoined tendon was recessed, it should also be repaired with 1 or 2 sutures at this time. The space should be irrigated free of all debris. A small drain can be brought out inferiorly through a separate stab incision if the wound is not completely dry. The deltopectoral interval is loosely approximated using absorbable sutures. If this step is omitted, an unsightly scar can develop with the skin becoming insinuated into the interval. This author prefers to close the skin with buried absorbable sutures and a subcuticular prolene pullout suture. Long-acting local anesthetics can be injected into the skin and deep into the wound for early postoperative analgesia. Steri-strips, a sterile dressing, and a sling are applied. The patient is recovered and transferred to the recovery room.
Figure 21. The humeral component and head replacement in place before relocation.
If a glenoid component is to be implanted, the broach/trial prosthesis is left in place to provide (relative) protection from fracturing the proximal humerus during retraction. A modified Crego retractor or Fukuda retractor is inserted posterior to the glenoid and used for retracting the proximal humerus posteriorly to expose the glenoid face. Exposure of the glenoid can be difficult, often secondary to inadequate capsular releases. It is often helpful to release the capsule off of the inferior and posterior insertions of the glenoid, even though the same capsule was previously released from the humerus (Evan Flatow, MD, oral communication, February 2000). A Darrach retractor is placed on the superior and posterior surface of the glenoid to protect the long head biceps tendon. A Richardson retractor or a glenoid neck retractor (pickle fork) is used to retract the medial structures (pectoralis, conjoined tendon, subscapularis (Figure 22). Finally, a Darrach or modified Crego retractor is placed on the anterior and inferior surface of the glenoid to protect the axillary nerve and further retract the medial structures. This author strongly recommends that the surgeon ensure these retractors are available in the operating room before starting the case. In addition, the surgeon must be familiar with either the retraction sequence outlined above or another equally successful method to be successful and avoid frustration. This point cannot be overemphasized.
Figure 22. The exposure of the glenoid by the illustrated method is critical to obtaining adequate exposure for glenoid resurfacing. See text for details. (DePuy protocol[7]).
Two types of glenoid implants are supplied with the Global system. The keeled glenoid is similar to that of other implant systems and will be discussed here. The pegged implant is designed to preserve bone stock for a (potential) future revision. In the author's opinion, glenoid preparation and insertion of the pegged implant are more difficult for inexperienced surgeons to implant correctly. Those interested in this component are referred to the manufacturer's information for further details.[7]
The anterior and inferior surface of the glenoid should be stripped of all soft tissue and labrum. The posterior labrum should also be removed. The capsular tissue should be sharply resected to prevent postoperative scarring and restriction of motion. Ideally, the only soft-tissue attachments to the glenoid remaining will be the biceps tendon and the capsule from 7 o'clock to 11 o'clock posteriorly. If further exposure is necessary, this tissue can also be released. The biceps tendon attachment should be preserved.
The size of the glenoid is determined by selecting the glenoid sizer that most closely fits the area of the glenoid fossa. If the size falls between two disks, the smaller one should be chosen to avoid any overhang of the implant. The disk diameter then determines the diameter of the humeral head implant. By selecting from small, medium, or large head thickness, proper soft-tissue balancing is obtained.
Two sets of glenoid preparation instruments are provided: one straight set and another angled set for use when the humeral head cannot be posteriorly translated. The author strongly recommends that the surgeon become familiar with the angled set, as difficulties with exposure are common.
The selected glenoid sizer disk is manually centered on the glenoid and the center of the glenoid is marked with an awl (Figure 23).
Figure 23. The appropriate glenoid sizing disk is selected and the center of the glenoid is marked with an awl (DePuy protocol[7]).
The disk is removed and the hole inspected to ensure that it is in the exact center of the glenoid face. Inserting a drilling guide and drill bit into the central hole and drilling it to exact length creates a central hole for the peg on the glenoid reamer (Figure 24). The author recommends inserting the drill and guide together, centering the guide on the glenoid awl hole and then drilling the hole, particularly in tight shoulders.
Figure 24. The glenoid drill guide and drill bit are used to make an exact size hole in the center of the glenoid to accommodate the peg on the glenoid reamer. (DePuy protocol[7]).
The glenoid face is reamed until the surface is smooth (Figure 25). The back of all 7 glenoid implants will conform exactly to curvature reamed. If the glenoid is worn eccentrically, the surgeon has several options to restore the proper version. Most commonly, the posterior wear is minimal (3-5 mm). In this case, a motorized burr is used to remove several millimeters of bone from the anterior glenoid and gently sculpt the surface until the anterior glenoid height is at the level of the posterior glenoid. The reamer can then be inserted into the central hole and the glenoid face reamed as previously outlined. If larger defects are seen on the preoperative imaging studies, bone grafting will be necessary. This is an extremely demanding procedure. In the author's opinion, these cases should be referred to a surgeon highly experienced in shoulder reconstruction. Information on the techniques of bone grafting is provided in the Suggested Reading section on Glenoid Bone Deficiencies.
Figure 25. The glenoid reamer is used to create an exact fit with the back surface of the glenoid components. With this system, the back of every size glenoid component will conform to the radius of the reamer (DePuy protocol[7]).
A glenoid burring template is used to mark the keel slot utilizing a motorized burr (Figure 26). Curettes and the burr are used to remove enough bone to accommodate the keel of the prosthesis. A conforming fin broach is used to ensure that enough bone is removed. Cancellous bone should be removed to the base of the coracoid and down the lateral edge of the scapula to help lock in the keel with cement. Extreme care should be taken to avoid perforation of the cortex. The trial glenoid is inserted, as is the trial head of the same diameter. Retractors are removed and the shoulder located. Proper soft-tissue tension is achieved with the same technique used for hemiarthroplasty. The trial components are removed, and the glenoid is irrigated free of debris. The glenoid is then dried with a sponge.
Figure 26. A burring template assists in creating the appropriate size slot to accommodate the keel of the prosthesis (DePuy protocol[7]).
Components are now opened, and the cement is mixed. Once the cement is doughy, it is hand packed into the glenoid, taking care not to leave any cement on the glenoid surface. The backing of the glenoid component is made to precisely fit with the reamed surface of the glenoid. Any cement left on the glenoid surface will interfere with this fit and may be a cause of early glenoid loosening. The keeled prosthesis is slowly inserted and held firmly in place with a finger (Figure 27). Excess cement should be removed before it hardens. With the glenoid firmly in place, the procedure continues with the same technique used for hemiarthroplasty.
Figure 27. Once the glenoid is packed with cement, the glenoid component is slowly inserted with finger pressure until it is firmly seated on the glenoid surface. Pressure must be maintained until the cement has hardened (DePuy protocol[7]).
An appropriate, well-planned postoperative rehabilitation program is critical to the success of shoulder replacement surgery. The overall goals of rehabilitation are to restore active and passive range of motion and muscle strength without damaging the newly reconstructed shoulder.[15]
Rehabilitation is divided into 3 phases, each with its own set of goals and pitfalls. Recovery from the surgery begins on the day of the procedure. It has been the author's practice to perform shoulder replacements as the first case of the day to maximize the benefits of hospital therapy. Currently, most insurance companies allow patients a 2-night hospital stay after the procedure. Performing the procedure in the morning of the first hospital day allows time for the patient to have therapy that afternoon, instead of waiting until the following day. By carefully discussing these goals with the anesthesiologist, the surgeon can minimize the "hang-over effect" of anesthesia and contribute to a positive outcome. Interscalene block supplemented by a light general is ideal.
The patient arrives in the hospital room in a protective sling that is worn at all times until the block has worn off. To avoid confusion and possible injury, one therapist should have the charge of performing all rehabilitative exercises for every shoulder replacement. The surgeon and therapist should have discussed initial therapy beforehand and agreed on a rehabilitation plan .
The therapist begins the first session with a discussion of the goals of the therapy program. Gentle, passive range-of-motion exercises out of the sling are initiated within the specifications set forth by the surgeon. Unless there are special circumstances, the desired goals of the passive motion exercises are to obtain full forward elevation and flexion and external rotation to 30° to 40° at the side. It is critical that the therapist be aware that externally rotating the shoulder more than the desired amount can rupture the subscapularis repair. Internal rotation and horizontal adduction stretching are also performed. The sling is then re-applied and worn every night for the first month. This ensures that the shoulder will not fall back into an extended position during sleep and stretch out the subscapularis repair (Brian Donahue, MD, oral communication, April 2000).
On the morning of the following day, the surgeon removes the sling and examines the passive elevation. This author prefers that the patients are left out of the sling during the day and encouraged to use the arm in activities of daily living. One useful exercise is to ask the patient to reach forward for a cup on the meal stand with both hands, retrieve a cup of water, and take a drink. This emphasizes that the shoulder is already useful and can be used for simple tasks.
The following morning, the therapist instructs the patient in an active-assisted range-of-motion program, including the use of an overhead pulley device to obtain flexion and elevation. External rotation exercises are aided by using a stick. Pendulum and circular Codman-type exercises are also started. Passive range-of-motion stretching is once again performed. Instruction in personal care is also given. The patient is encouraged to walk with a normal arm swing. Pulley exercises are performed once every 2 hours. Therapy sessions are continued twice a day until discharge.
At the time of discharge, the patient is given the sling to be worn every night, the pulley device for home use several times a day, and a referral to the visiting nurses association (VNA) or other home health care agency for home therapy. This 2- to 3-day per week in-home therapy continues to emphasize passive range of motion and develops self-reliance techniques for activities of daily living. Isometrics for the external rotators and deltoid can be started at 10-14 days. Skilled nursing services, home health aide services, and meals-on-wheels referrals can be made as necessary.
This author prefers to remove the bandages and sutures in the office 3-5 days after surgery. Radiographs are taken at that time to ensure proper location of the prosthesis and to provide a radiographic picture that will be monitored for evidence of loosening with time. The therapy program is also reviewed with the patient. Patients with severe preoperative pain, and especially those with rheumatoid disease, will become pain-free rather quickly, and in this author's experience, will be able to elevate the shoulder fully in the first postoperative week. This group of patients needs to be cautioned that overuse will quickly develop, leading to rapid loss of active range of motion at this stage. Frequent overhead lifting is to be minimized. Home therapy is continued until 4 weeks after surgery. The patient should understand that the assisted exercises are to be performed 4-5 times per day, every day.
Four weeks after the procedure, the night sling is discontinued. Although patients continue to have some discomfort, particularly at night, shoulder pain is usually less than preoperative levels. The patient is encouraged to use the arm for light activities. Gentle strengthening exercises for the scapular stabilizer muscles (upper trapezius, serratus anterior, and so forth), biceps, and triceps are added. Resistive internal rotation exercises should be avoided until 6 weeks after surgery to avoid injury to the subscapularis tendon repair. At this stage, a referral can be made to an outpatient therapy setting. Again, the patient must understand the importance of performing the assisted exercises 4-5 times per day.
Eight weeks after the procedure, the patient should be independent in a home exercise program. Elevating the shoulder above 120° or more is usually possible at this stage. In patients with significant rotator cuff deficiency or other anatomic abnormality, active elevation usually remains limited. The patient should be encouraged to continue therapeutic exercises at home or to continue with a therapist if necessary. As strength increases, household activities, and recreational activities, such as golf, can be allowed, usually after 4-5 months. Heavy lifting, especially over the chest level should be avoided. This author recommends that the exercises should be continued for at least 1 year to ensure maximal strength returns.
