Cup Arthroplasty for Shoulder Resurfacing: Technical Tips and “Pearls”

Surgical Technique 

The technique of cup arthroplasty as developed by Copeland1, 2 is intended to restore relative anatomicity to the articular surface of the humeral head by applying a “cap” over the reamed surface of the humeral head at an anatomic position restoring the normal degree of retroversion (average 30°) and valgus (average 140°), allowing the tuberosities to be maintained with their rotator cuff attachments and preserving the normal force-couple generated by rotator cuff musculature.1, 2 This allows the humeral head to be directed at the glenoid and provide normal anatomic apposition. However, in cases of cuff tear arthropathy in which there has been superior migration of the humeral head but in which there is still “capture” of the humeral head within the coracoacromial arch, the humeral head forms a new “acetabularized” articulation within the confines of the arch. If allowed to remain in this position with a smooth surface, surface replacement in a “hyper valgus” position can allow articulation within this area of altered mechanics to provide improved function while significantly reducing pain (Fig. 5). In this situation the direction of reaming and application of the large-size humeral head may be as high as 170#x00B0; valgus as the implant covers the entire proximal humerus including tuberosities and provides a domed resurfacing of the entire upper humerus.

In either application the steps of the surgical technique are similar; the angle of approach is what differs.

A deltopectoral approach is utilized in all cases. The interval between the deltoid and the pectoralis major is developed and opened. Some of the upper insertion fibers of the pectoralis major are released and the subscapularis tendon is visualized. In cases of cuff tear arthropathy, the upper subscapularis may have been eroded; the supraspinatus and infraspinatus tendons are usually retracted medial to the humeral head. The humeral head rides high in the subacromial space contained within the subacromial arch. In this situation it is usually possible to inferiorly retract the humeral head and dislocate it into the field without removing any additional subscapularis. If this is not possible then the subscapularis is released adequately to allow anterior dislocation and visualization of the entire humeral head (Fig. 6). In other forms of arthropathy in which the rotator cuff is intact the subscapularis is incised leaving a stump for later repair. The dissection stops at the rotator interval avoiding any injury to insertion of the supraspinatus and again the head is dislocated anteriorally. In all cases great care is taken to avoid any injury to the coracoacromial ligament to prevent any later superior migration and loss of containment (especially in cuff tear arthropathy). Once the humeral head has been delivered into the wound and well-visualized peripheral osteophytes are removed, in the case of anatomic articular resurfacing, the center guide wire is placed at the normal angle of inclination of the humeral head perpendicular to the apex of the natural articular surface. In the case of cuff tear arthropathy, after removing all osteophytes and shaving down prominences of the greater and lesser tuberosity, the guide wire is placed in a “hyper valgus” position, which will allow ultimate seating of the cup arthroplasty over the entire superior humeral surface creating a domed effect (Fig. 6). The location and quality of the biceps tendon is then assessed. In the situation of anatomic resurfacing, if the biceps tendon remains viable and healthy and does not show any signs of significant damage, it is retracted and left in place.

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Figure 6. Surgical technique: In the case of cuff tear arthropathy a deltopectoral incision has been utilized to gain access to the humeral head. A superior central guide wire has been placed in a “hyper valgus” position. (Color version of figure is available online.)

In conditions of cuff tear arthropathy in which the biceps remains attached to the superior labrum, it has usually fallen out of its normal position in the bicipital groove into a more inferior position, which now acts as an elevator of the humeral head by lying inferior to the normal center of rotation. In this case the biceps is released from its insertion and an external tenodesis is performed at the time of closure. A head sizer is now placed over the guide wire to select the appropriate-sized reamer (Fig. 7). The surface reamer is then placed over the guide wire. (Caution should be taken to start the reamer before actual application to the bone to avoid grabbing and fracturing the surface of the bone) (Fig. 8). In cases of anatomic resurfacing, only the articular surface is reamed down to bleeding subchondral bone, while, in cases of cuff tear arthropathy, the entire humeral head is reamed to be able to accommodate the cup arthroplasty applied to create a resurfacing of the entire upper humerus. Once reamed to a smooth subchondral bone surface, the central peg drill is applied over the guide wire and is used to develop the pilot hole for the central peg of the implant (Fig. 9). Once this has been completed, the guide wire is removed and trial implants are then chosen corresponding to the size of the humeral head itself and the size of the reamer as determined by the initial sizing instrumentation. Once the appropriate size of the implant has been determined, the definitive implant is chosen. If there is an area of bone defect (such as in avascular necrosis) some of the harvested bone from the reamer can be used to fill the defect (Fig. 10) and the hydroxyappetite-coated definitive implant is applied and impacted into place ensuring secure fixation (Fig. 11).

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Figure 7. Surgical Technique: A head sizer is slid over the guide wire to determine the appropriate-sized surface reamer. (Color version of figure is available online.)

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Figure 8. (A-C) The surface reamer is slid over the guide wire and the entire humeral head is reamed, creating a smooth dome over the articular surface and the tuberosities. (Color version of figure is available online.)

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Figure 9. Once the surface has been prepared, the central peg drill is placed over the guide wire and the central pilot hole for the implant is drilled. (Color version of figure is available online.)

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Figure 10. The resurfacing implant is coated with cancellous shavings from the humeral head and prepared for impaction. (Color version of figure is available online.)

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Figure 11. (A and B) The definitive humeral head resurfacing implant is applied next and impacted into position, creating a seamless coverage of the entire humeral head. (Color version of figure is available online.)

In cases in which additional glenoid resurfacing may be required, fascial resurfacing may be accomplished by retracting the humeral head very carefully with a Fakuda retractor. In rare cases implantation of a glenoid component may be possible (Fig. 3). In most cases of cuff tear arthropathy, capsular tissue may be dissected off the subscapularis and in-folded to provide fascial resurfacing of the glenoid and acromial surfaces in cuff tear arthropathy. Occasionally bank fascia (Achilles tendon) maybe used for the same purpose. This technique is accomplished by placing small drill holes through the periphery of the glenoid and undersurface of the acromion and passing nonabsorbable polyester sutures through these drill holes and advancing grasping sutures through the fascial tissue, pulling it into place circumferentially4 (Fig. 12). Exposure for suturing fascia requires less retraction than that needed for actual glenoid implant preparation and insertion.

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Figure 12. Before inserting the guide wire, once the deltopectoral incision has been made and the humeral head has been debrided of its osteophites, it is retracted posteriorly with a Fakuda rectractor exposing the glenoid and subacromial arch. Thickened capsular tissues from the anterior and posterior glenohumeral joint are dissected off the overlying rotator cuff and in-folded across the glenoid, creating a fascial resurfacing. Anchoring sutures are seen here pulling the in-folded capsule down over the eroded glenoid surface. (Color version of figure is available online.)

Closure is performed by repairing the portion of the released subscapularis and, when present, the rotator interval with nonabsorbable polyester suture. The patient’s arm is placed in a sling and, on postoperative day 1, a waterproof (Tegaderm, 3M Healthcare, St. Paul, MN) dressing is applied, allowing the patient to shower and begin pendulum exercises. Patients perform passive exercises for 6 weeks, avoiding active use of the arm during that time. They may remove their sling to work at a desk, eat their meals, groom themselves and perform tabletop or desktop activities, but active contraction of the shoulder muscles is avoided during the first 6 weeks. After 6 weeks active and active assisted exercises are begun both on land and in a water environment. At 3 months resistive and endurance type exercises are begun again both on land and in water. We have found the buoyancy effect of water makes muscle reeducation and graduation into active functional use of the shoulder much easier for the patient to learn and accomplish.

Discussion 

The goals of treatment depend on the severity of the underlying disease. In situations of otherwise healthy shoulder anatomy in which anatomic resurfacing is performed, our goal is to have near normal shoulder function. In cases of cuff tear arthropathy the patients fall into a more “limited goals” category in which pain control and reasonable function at least below the horizontal are our primary goals, recognizing the possibility for improved motion above 90° when deltoid function is strong.7, 8 It has been our experience that cup arthroplasty resurfacing in cuff tear arthropathy has provided a “seamless” and smooth fulcrum for reduction of pain and improved mobility and is a viable, conservative alternative to more invasive management of these patients. Certainly hemiarthroplasty and even attempt at total shoulder arthroplasty has demonstrated reasonable relief of symptoms in cuff tear arthropathy.9 More recent reports of reverse shoulder arthroplasty have demonstrated surprisingly good early results but with significant complications depending on the type of prosthesis used, including loosening, breakage, dislocation, infection, fracture, and, most troubling, the appearance of progressive “notching” or erosion of the inferior glenoid neck due to a combination of mechanical impingement and particulate synovitic reaction.10 Therefore, although promising, the technique of reverse prosthetic reconstruction is generating new problems and complications for which, at this point, we have few answers.

It has, therefore, been our practice to reserve use of the reverse prosthesis for conditions of failed primary surgery in which containment within the coracoacromial arch has been lost and in which there has been “escape” of the humeral head above the coracoracromial arch, utilizing the more conservative cup arthroplasty in primary conditions with maintenance of “head capture.”7, 8, 10