Proximal Humeral Endoprosthetic Replacement for Tumour

Indication. A malignant tumour of the proximal humerus where limb salvage is appropriate and a wide margin is achievable: a high-grade primary sarcoma (osteosarcoma, Ewing sarcoma, chondrosarcoma) is the classic indication; selected solitary metastases or myeloma deposits with a favourable prognosis, and painful destructive metastases with impending fracture, are also reconstructed this way. The proximal humeral metaphysis is the most common away-from-the-knee site and the third most common site overall for primary bone sarcoma. Before the knife — staging sets the plan. A wide resection is only chosen after the tumour is fully defined: - MRI of the whole humerus — local extent, epiphyseal and joint involvement, extraosseous extension, the relationship to the axillary nerve in the quadrilateral space and to the deltoid, and skip lesions in the marrow.

• Systemic staging — CT chest and a bone scan or whole-body MRI/PET for metastases (and local staging of a sarcoma).
• Biopsy — image-guided, taken along the future resection route so the tract is excised en bloc; plan the definitive incision before the biopsy is done. The one decision that matters — can the abductor mechanism be saved? Read off the MRI whether the tumour respects the axillary nerve and deltoid. If it does, an abductor-sparing resection is possible and function is preserved. If the nerve or deltoid is involved, both are sacrificed with the specimen and active abduction is lost. This single decision sets the resection type, the reconstruction, and the result you counsel the patient to expect.

Consent specifically for instability or dislocation (the commonest problem), infection, nerve deficit (axillary, radial or musculocutaneous), limited active elevation, local recurrence, possible revision or amputation, allograft-specific risks if an APC is used, and lifelong surveillance. Setup. Beach-chair (or supine with a scapular bump), the arm free and draped to allow circumduction so the osteotomy and soft tissues can be reached. A tourniquet is usually avoided because proximal control of the axillary vessels is needed; the arm is exsanguinated only if a tourniquet is used. General anaesthesia with a regional block for postoperative pain, a cell saver on the field, antibiotics at induction, and an image intensifier available to confirm the osteotomy level and cementing.

The goal: remove the tumour with a wide margin and the biopsy tract in continuity, then reconstruct the proximal humerus with a cemented modular endoprosthesis and a mesh soft-tissue sleeve that gives the shoulder its stability. The exposure is laid out in full below (and in depth on the deltopectoral approach page) — the first steps are the approach, then the resection, then the reconstruction.

Rehabilitation | Phase | Timing | Immobilisation | Therapy | |-------|--------|----------------|---------| | 1 | 0 to 2 weeks | Shoulder immobiliser or sling | Active hand, wrist and elbow from day 1; gentle pendulums | | 2 | 2 to 6 weeks | Sling, removed for exercise | Assisted shoulder motion where the cuff and deltoid were reconstructed; protect abduction if the deltoid was sacrificed | | 3 | 6 to 12 weeks | Sling for comfort only | Progressive active motion and light activities of daily living | | 4 | 3 to 6 months | None | Graded strengthening (limited where the abductor mechanism was sacrificed) | Functional outcome tracks abductor preservation. With the deltoid and axillary nerve preserved, most patients regain useful assisted and some active elevation; when they are sacrificed, the result is a stable, painless shoulder with MSTS scores in the region of 50 to 70 per cent of normal, a fully functional hand and elbow, and little active abduction. Aseptic loosening and implant survivorship are favourable at ten years in modern modular series, with instability and infection the dominant reasons for revision. Complications

Epidemiology. The proximal humeral metaphysis is the most common site of primary bone sarcoma away from the knee and the third most common overall, after the distal femur and proximal tibia. Osteosarcoma and Ewing sarcoma dominate in adolescents and young adults; chondrosarcoma, metastatic carcinoma (breast, renal, thyroid, lung, prostate) and myeloma are the lesions of older adults. The same modular reconstruction is used for selected metastatic deposits with a reasonable prognosis and for impending pathological fracture. Pathoanatomy. Tumours arise in the proximal metaphysis and extend into the epiphysis (once the physis closes), the greater and lesser tuberosities, the rotator cuff and deltoid attachments, and along the medullary canal. Three relationships decide the operation: involvement of the glenohumeral joint (intra-articular versus extra-articular resection); involvement of the deltoid and the axillary nerve in the quadrilateral space (abductor-sparing versus abductor-sacrificing); and distal marrow extension (the osteotomy level). The anterior and posterior circumflex humeral arteries are ligated; the axillary artery and vein and the brachial plexus lie proximal and must be controlled before any resection.

The type is dictated by tumour extent on MRI, not by the surgeon's preference, and the overriding principle is that expected function is governed by abductor preservation — the axis that runs down the right-hand column of this table. Key evidence. Enneking's Musculoskeletal Tumor Society (MSTS) system standardised how function is reported after limb-salvage reconstruction and is the metric used in every series below. The consistent message from the proximal humeral literature is that a modular endoprosthesis is a durable reconstruction whose function is set by the axillary nerve and deltoid, and whose dominant mode of failure is instability — a soft-tissue problem that mesh reconstruction and pectoralis advancement are designed to prevent. Allograft-prosthetic composites improve the biological attachment available to the cuff and deltoid but bring allograft-specific risks.