Bulk osteochondral allograft for massive Hill-Sachs defect combined with Latarjet procedure for bipolar bone loss in anterior instability

Abstract

A proportion of patients with anterior glenohumeral instability present with bipolar bone loss comprising large Hill-Sachs lesions and substantial glenoid defect. These are surgically difficult cases to treat. We describe a novel surgical procedure of bulk size-matched osteochondral allograft reconstruction for massive Hill-Sachs lesions combined with the Latarjet procedure for these challenging cases.

Keywords: Hill–Sachs lesion; Latarjet; anterior instability; bipolar bone loss; humeral head osteochondral bulk allograft.

Figure 1.

(a) Measurements of glenoid bone loss. For estimation of the intact glenoid, the ‘best-fit circle’ method was applied, fitting a circle to the posterior and inferior parts of the glenoid. This circle is considered to approximate the original shape of the glenoid. The diameter of the circle ‘D’ represents the width of the intact glenoid and radius r = D/2. The radial extent of the perimeter of the circle towards the defect is the amount of bone that is lost and is expressed as ‘d’. The size of the defect is expressed as: linear glenoid bone loss = d/D. The intact glenoid surface area, SA_G, can be calculated, SA_G = πr². The surface area of the glenoid defect, a circular segment, can be obtained by using the length of the linear glenoid defect, d. The formula for this is: $S{A}_d=r^{2}co{s}^{-1}((r-d)/r))\text{–}(r-d)\surd (2rd-d^2).$ (b) Measurements of Hill–Sachs defect. Hill–Sachs width was estimated by measuring the distance from rotator cuff insertion to the medial border of Hill–Sachs lesion where it meets the articular cartilage. The articular surface area of the humeral head is assumed to be a hemisphere, hence the surface area covered by articular cartilage on the humeral head is: SA_H = ½ x (4πr²) = 2πr². The articular surface of the Hill–Sachs lesion is regarded as a ‘lune’, the curved surface area of a wedge. By estimating the angle of the wedge, the angle subtended by the radii of head projected onto the defect surface, ϴ, the surface area of the lune can then be calculated. The formula for this is: SA_HS = ϴ/360 x (4πr²).

Figure 2.

(a) Exposure of the Hill–Sachs lesion. Following an anterior capsulotomy, the humeral head is delivered, and the Hill–Sachs lesion exposed through extension and external rotation of the arm, while translating the humeral head anteriorly. Excessive extension and traction are avoided to prevent axillary nerve and brachial plexus injury. (b) Preparation of the Hill–Sachs osteochondral allograft. The edges of the Hill–Sachs defect are prepared and dimensions measured. The surface area of the defect is then traced onto sterile paper and drawn onto the size-matched osteochondral allograft. A 2 mm K-wire is used to handle the allograft when the wedge allograft is harvested at a back table with a surgical saw. (c) Implantation of the osteochondral allograft. The allograft is then presented onto the defect and further adjustments are made to fit into the prepared Hill–Sachs defect. The allograft is secured with three 4.5 mm headless compression screws. (d) Latarjet procedure, capsular repair and closure. The Latarjet procedure is then completed through transfer of the coracoid onto the anterior glenoid edge, followed by the repair of the ‘T’ capsulotomy. The subscapularis tenotomy is then repaired, followed by repair of the pectoralis minor onto the coracoid ‘stump’. (e) Intra-operative radiographs depicting the congruence of the allograft with the humeral head curvature, secured with three 4.5 mm headless compression screws. Note also the coracoid transfer of the Latarjet procedure, held with two screws, and a suture anchor at base of the excised coracoid for reattachment of pectoralis minor.

Figure 3.

Osteolysis of osteochondral graft. Patient 6. (a) Immediate post-operative radiograph. (b) Radiographs at 51 months: osteolysis of the allograft is observed. The patient suffered an epileptic fit 3 weeks after surgery. Also note that the headless compression screws were smaller than the preferred 4.5 mm screws. Patient 9. (c) Intra-operative radiograph. (d) Radiographs at 18 months: minor osteolysis around one of the screws but the allograft has incorporated. Although the screw heads appeared higher than the subchondral bone, the screws were level against the chondral cartilage of the allograft.