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Treating Humeral Bone Loss in Shoulder Arthroplasty: Modular Humeral Components or Allografts

February 15, 2018 | Surgery
Ian Power, MD ; Thomas W. Throckmorton, MD
Author and Disclosure Information

Authors’ Disclosure Statement: Dr. Throckmorton reports that he receives royalties and consultant fees from Zimmer Biomet, consulting fees from Pacira, and publishing royalties from Saunders/Mosby-Elsevier. Dr. Power reports no conflict of interest in relation to this article.

Dr. Power is a Sports, Shoulder, and Elbow Fellow, and Dr. Throckmorton is Professor, Residency Program Director, University of Tennessee-Campbell Clinic Department of Orthopaedic Surgery and Biomedical Engineering, Memphis, Tennessee.

Address correspondence to: Thomas W. Throckmorton MD, 1211 Union Avenue, Suite 510, Memphis, TN 38104 (tel, 901-759-3270; fax, 901-759-3278; email, tthrockmorton@campbellclinic.com).

Ian Power, MD Thomas W. Throckmorton, MD . Treating Humeral Bone Loss in Shoulder Arthroplasty: Modular Humeral Components or Allografts. Am J Orthop. February 15, 2018

TAKE-HOME POINTS

  • Proximal humeral bone loss presents a significant challenge for the shoulder arthroplasty surgeon.
  • Unsupported long-stemmed humeral components in this setting are prone to early loosening.
  • APCs can rebuild proximal humeral bone stock, but have concerns with graft resorption and long-term failure.
  • Modular endoprosthetic reconstruction of proximal humeral bone loss potentially allows those deficiencies to be addressed in a more durable fashion.
  • Longer-term and larger studies are needed to determine the optimal reconstruction technique for proximal humeral bone loss.

In a prospective study of RTSA using structural allografts for failed hemiarthroplasty in 25 patients with an average bone loss of 5 cm, 19 patients (76%) reported good or excellent results, 5 reported satisfactory results, and 1 patient reported an unsatisfactory result.1 Patients had significantly improved forward flexion, abduction, and external rotation and improved outcome scores (ASES and SST). Graft incorporation was good, with 88% and 79% incorporation in the metaphysis and diaphysis, respectively. This technique used a fresh-frozen proximal humeral allograft to fashion a custom proximal block with a lateral step-cut, which was fixed around the stem with cables. A long stem and cement were used. If there was no cement mantle remaining or if the medial portion of the graft was longer than 120 mm, the cement mantle was completely excised. The allograft stump of the subscapularis was used to repair the subscapularis tendon either end-to-end or pants-over-vest. The authors noted that the subscapularis repair provided increased stability; the only dislocation not caused by trauma did not have an identifiable tendon to repair. In this manner, APC reconstruction provided structural and rotational support to the humeral stem as well as bone stock for future revision.1,20

One significant concern with APC reconstruction is the potential for graft resorption, which can lead to humeral stem loosening, loss of contour of the tuberosity, or weakening to the point of fracture.24,25 This may be worsened by stress shielding of the allograft by distal stem cement fixation.26 Other concerns include the cost of the allograft, increased risk of de novo infection, donor-to-host infection, increased operative time and complexity, and failure of allograft incorporation.

The use of a proximal femoral allograft has been described when there is a lack of a proximal humeral allograft.1,27 Kelly and colleagues27 described good results in 2 patients in whom proximal femoral allograft was used along with bone morphogenetic protein, cemented long-stemmed revision implants, and locking plate augmentation.

ENDOPROSTHETIC RECONSTRUCTION

Various forms of prosthetic augmentation have been described to compensate for proximal humeral bone loss, with the majority of reports involving the use of endoprosthetic replacement for tumor procedures.28-31 Use of endoprostheses has also been described for revision procedures in patients with rheumatoid arthritis with massive bone loss, demonstrating modest improvements compared to severe preoperative functional limitations.32

Tumor patients, as well as revision arthroplasty patients, may present difficulties with prosthetic fixation due to massive bone loss. Chao and colleagues29 reported about the long-term outcomes after the use of implants with a porous ongrowth surface and extracortical bridging bone graft in multiple anatomic locations, including the proximal humerus, the proximal and distal femur, and the femoral diaphysis. In 3 patients with proximal humeral reconstruction, the measured ongrowth was only 30%. Given the small number of patients with a proximal humerus, no statistical significance was observed in the prosthesis location and the amount of bony ongrowth, but it was far less than that in the lower extremity.

Continue to: Endoprosthetic reconstruction...

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