Proximal Humeral Osteoarticular Allograft
D. Luis Muscolo
Miguel A. Ayerza
Luis A. Aponte-Tinao
The proximal humerus is one of the primary sites of tumors in the upper extremity and is the fourth most common site for osteosarcoma, chondrosarcoma, and Ewing sarcoma. Several techniques have been described for replacement of the proximal humerus that include prostheses, osteoarticular allografts, or a combination. Osteoarticular allografts are utilized for reconstruction of one side of the joint after tumor resection and do not sacrifice the uninvolved side of the joint. They have the possibility of attaching soft tissues. Although osteoarticular allografts are an optimal material to reconstruct skeletal defects, biomechanically and biologically related complications including bone graft fractures and resorption, cartilage degeneration, joint instability, and delayed bone union or nonunion still occur. These biomechanically related complications can be grouped into two main categories, (a) related to geometric matching between the allograft and the host defect and (b) the stability achieved during surgery of the allograft-host bone and soft tissue junction sites.
INDICATIONS
The procedure is appropriate for the treatment of a massive osteoarticular defect after tumor resection or massive traumatic bone loss.
The major neurovascular bundle must be free of tumor (Figs. 29.1 and 29.2).
CONTRAINDICATIONS
Patients in whom preoperative imaging studies demonstrate evidence of intra-articular (glenohumeral) compromise of the tumor.
Inadequate host soft tissue to reconstruct the joint.
Patients with glenohumeral osteoarthritis.
PREOPERATIVE PREPARATION ALLOGRAFT SELECTION
Fresh-frozen allografts are obtained and stored according to a technique that has been previously described (1). Poor anatomical matching of both size and shape between the host defect and the graft can significantly alter joint kinematics and load distribution, leading to bone resorption or joint degeneration. To improve accuracy in size matching between the donor and the host, we developed measurable parameters based on CT scans of the proximal humerus. The allograft is selected on the basis of a comparison of these measures of potential allografts available at the bone bank with those of the host.
TECHNIQUE
All operations are performed in a clean-air enclosure with vertical airflow.
After administration of adequate regional and/or general anesthesia, the patient is placed in the semiupright “beach-chair position,” with the hips and knees flexed and all osseous prominences well padded.
The head is secured in a neutral position, and the entire upper extremity is prepared and draped to the level of the midclavicle. An extended deltopectoral approach is done that can be extended distally if more surgical exposure is needed (Fig. 29.3).
The cephalic vein is mobilized with the deltoid muscle and retracted laterally. The biopsy tract is left in continuity with the specimen.
Usually due to compromise from the tumor, a biceps tenotomy is performed. The conjoined tendon is not released from the coracoid. The subscapularis tendon is released off of the lesser tuberosity, just medial to the long head of the biceps, in order to allow atraumatic dislocation of the humeral head with gentle external rotation and extension of the arm.
If there is an extraosseous tumor component, a cuff of normal muscle must be excised. It is preferable to dissect out the axillary nerve and protect it with a vessel loop to confirm its location and thereby diminish the risk of a nerve injury. The capsule is then released completely around the humeral neck. Then the infraspinatus, supraspinatus, and teres minor tendons are released off of the greater tuberosity, and the tendons are tagged. The deltoid is then dissected free from the humeral shaft after the rotator cuff tendons are released, as well as the teres major, latissimus dorsi, and the pectoralis major tendons if necessary.
The humeral osteotomy is marked at the appropriate location as determined on the basis of the preoperative imaging studies (Fig. 29.4). All remaining soft tissues at the level of the transection are cleared.
The osteotomy is performed perpendicular to the long axis of the humerus. Following the osteotomy, the proximal humerus is then passed off the operative field revealing the remaining osseous defect within the patient (Fig. 29.5).
Simultaneous with or subsequent to the tumor resection, the allograft specimen is prepared on the back table. The graft is taken out of the plastic packaging and placed directly in a warm normal saline solution. After being thawed, the donor bone is cut to the proper length and soft tissue structures are prepared for implantation. It is crucial during the joint reconstruction to have adequate soft tissue structures from the donor in order to repair them to corresponding host tissues (Fig. 29.6).
The proximal humerus allograft is inspected to confirm that the size is appropriate and no degenerative changes are present on the humeral articular surface (Fig. 29.7). Then, the insertion of an allograft segment tailored to fit the bone defect is performed. Before the allograft bone is secured to the remaining host humerus, the shoulder joint reconstruction is performed. However, the plate can be secured to the allograft to help manage the graft during soft tissue reconstruction.
First, we repair the posterior capsule suturing autologous capsular tissues to the capsular tissues provided by the allograft with a number-1 nonabsorbable suture (Fig. 29.8Related posts:
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
