‘Umbrella construct’ – an innovative technique for reconstruction of the proximal humerus after curettage in locally aggressive benign bone tumours

Abstract

Aim

Reconstructing locally aggressive benign bone tumours of the proximal humerus after intralesional curettage is a challenge. We present a novel reconstruction technique ‘Umbrella construct’ where a femoral head and a strut allograft are combined to reconstruct the cavity. Complications, graft incorporation time, functional (Musculoskeletal Tumor Society score [MSTS]) and oncological outcomes were evaluated.

Methods

Between January 2006 and June 2017, 11 cases (10 giant cell tumours, 1 chondroblastoma) underwent curettage followed by reconstruction with Umbrella construct. There were six females and five males with a mean age of 23 years (range 14–36 years). The maximum longitudinal extent of disease was 9 cm (range 5–9 cm).

Results

The median follow-up was 54 months (range 34–122 months). The mean allograft incorporation time was 7 months (5–8 months). One patient had a graft fracture which was managed conservatively. Two cases developed local recurrence and the construct was revised to a prosthesis in both. The mean MSTS score for the nine cases with retained graft was 27 (23–29).

Conclusions

Umbrella construct is an effective reconstruction modality which helps to maintain joint congruity and limb length. It has acceptable oncological outcomes with good function.

Introduction

The proximal humerus is the common site for occurrence of benign aggressive bone tumours like giant cell tumour of bone (GCT), chondroblastoma and aneurysmal bone cyst.^1–3 These tumours grow rapidly, often leading to destruction of the peri-articular bone with eventual loss of joint function. Surgery, which involves intralesional curettage or resection, is the mainstay of treatment. Large lesions with an extraosseous soft tissue component or damage to the articular surface are treated with resection (requiring sacrifice of attachment of rotator cuff muscles, deltoid or axillary nerve) resulting in weakness of abduction and overhead activities. Wherever possible a less morbid and function preserving intralesional extended curettage is preferred over resection.⁴ Bone grafts (allo/auto graft) or bone cement is used to reconstruct post curettage cavities. Biological bone reconstructions are the preferred modality in young individuals as they help preserve native bone stock and shoulder joint congruity.

We present a series of large benign aggressive lesions of the proximal humerus with minimal subchondral bone which were treated with extended curettage and reconstructed with a novel technique – ‘Umbrella construct’ (UC) where a femoral head and a strut allograft are combined to reconstruct the cavity (Figure 1(e) and (f)) in an attempt to retain joint congruity and maintain shoulder function. Complications, graft incorporation time, functional (Musculoskeletal Tumor Society Score [MSTS]) and oncological outcomes were evaluated.

Figure 1.

(a) Pre-operative radiograph showing giant cell tumour of left proximal humerus, (b) femoral head and radius strut allograft, (c) graft preparation, (d) defect, (e) Umbrella construct and (f) immediate post-operative radiograph showing Umbrella construct in situ.

Materials and methods

Between January 2006 and June 2017, 56 cases of benign aggressive lesions of the proximal humerus were operated at our institute. These were identified from a prospectively maintained surgical database. Of these 56, one underwent a forequarter amputation, 14 cases underwent resection and 41 cases were treated with extended intralesional curettage. While 11 of these 41 cases were reconstructed with UC, the other 30 were reconstructed in assorted ways (cement only in 10, auto graft in three, allograft [morsellized only/and/or strut] in 15 and two cases had no fillers). Clinical and imaging details, intraoperative findings, complications, oncological and functional outcomes were retrieved from the hospital electronic medical records.

The cases reconstructed with UC were carefully selected by the senior authors based on certain criteria. Campanacci grade 1 tumours and lesions with adequate subchondral bone which were amenable to curettage were reconstructed with other modalities (as above). Large volume Campanacci grade 2 or 3 tumours with involvement of more than 75% of bone in subchondral region that did not necessitate resection were reconstructed with UC. Cases with soft tissue extension in multiple planes or involvement of the articular surface which were not amenable to curettage were treated with resection.

Of the 11 cases, six were females. Mean age was 23 years (range 14–36 years). There were 10 cases of GCT (Campanacci grade 3 – nine cases, grade 2 – one case) and one case of chondroblastoma. The maximum longitudinal extent of disease was 9 cm (range 5–9 cm). Six patients underwent pre-operative angioembolization to reduce intraoperative blood loss anticipated in view of a large extraosseous component and two patients received pre-operative denosumab (to facilitate curettage). All curetted cavities were reconstructed with a combination of femoral head allografts and strut grafts.

Surgical technique

A detailed pre-operative evaluation was done with the help of radiographs in two planes and magnetic resonance imaging. Surgical planning included determining the surgical approach, identifying areas of cortical breach, extent of soft tissue component and identifying the site for an appropriate curettage window. Pre-operative radiographic assessment of the size of the humeral head and extent of curettage helped in selecting the appropriate allograft required (femoral head to reconstruct the subchondral region and a strut graft to support the head). Allografts were procured from the institutional bone bank.

The operative procedure was performed in a beach chair position under general anaesthesia. A linear anterior skin incision was taken extending from coracoid process superiorly till the desired extent distally as per pre-operative planning. The biopsy scar was islanded; skin and subcutaneous tissue were raised as a single flap. The anterior deltoid muscle was identified and split to expose the underlying bone. Care was taken to preserve uninvolved muscle without disease contamination. The surrounding soft tissues were protected by placing hydrogen peroxide-soaked gauze pieces to prevent local contamination. A window of adequate dimensions was made over the exposed bone using an oscillating saw. The disease cavity was thoroughly curetted using multiple sharp curettes. The margins were extended to normal appearing bone with the help of a high-speed burr (60,000 r/min). A lavage was given using hydrogen peroxide alternating with pulsatile jet lavage using normal saline. Dental mirrors and an endoscopic light were used to confirm complete disease clearance. No other chemical adjuvants were used.

The cavity was reconstructed with a combination of femoral head and a strut allograft (fibula/ulna/radius) to create UC (Figure 1[b] and [c]). Appropriately selected allografts were thawed in a solution of warm (39 ± 2℃) 0.9% normal saline⁵ and vancomycin for 10–15 min. The cartilage of the femoral head was denuded, and the grafts were shaped as per the cavity. Following this, the grafts were lavaged with high-speed jet lavage.

The femoral head was made to fit snugly against the cartilage or minimal subchondral bone of the proximal humerus and a strut autograft or allograft (fibula/radius/ulna) was used to support the femoral head (Figure 1[e]). Trial reduction and size matching was done, and grafts were shaped as per requirement. The final placement and construct was prepared in either of the two methods as follows:

1. In vitro –The whole construct was prepared outside and then placed into the curetted cavity. This technique is comparatively easier but only possible when a large window is available to insert the femoral head directly without angulation. The free end of the strut graft was inserted first into the medullary cavity of the humerus after preparation while the proximal end of the graft (femoral head) was positioned to support the subchondral area of the proximal humerus. Grafts were stabilized by either K wires or screws.

2. In vivo – In this technique, graft preparation was done as stated earlier. Both the grafts were placed in the curetted cavity one after the other. The grafts were impacted and if required stabilized using K wires or screws.

The grafts snugly fit in the cavity in order to retain normal length and prevent collapse of the proximal humeral component. There was no need to additionally fill the residual cavity after positioning of the UC (Figure 1[e]). The graft stability and shoulder range of motion were checked intraoperatively. Wound closure was done in layers over a negative suction drain after achieving haemostasis. A sterile dressing was applied over the wound and sutures were removed after three weeks. The limb was supported with an arm sling/pouch for six weeks.

All patients were permitted immediate gravity eliminated elbow range of motion and wrist/hand exercises following which passive shoulder range of motion and pendulum exercises were started after one week.

Patients were followed up four monthly for the first two years, six monthly for the next three years and yearly for the next five years. Each follow-up visit consisted of clinical examination and biplanar radiographs. Functional outcome was evaluated using the MSTS scoring system⁶ and updated for every patient at their most recent follow-up.

Results

All cases were reconstructed using femoral head allografts in combination with strut grafts (strut allografts in 10 and fibular autograft in one patient) (Table 1). Additional fixation using K wires (seven patients), cortical screws (one patient) and combination of both (two patients) was done as required. Mean blood loss for cases with pre-operative angioembolization was 930 ml compared to 2000 ml in those operated without embolization. The mean surgical duration was 150 min (range 120–210 min).

Table 1.

Details of patients who underwent UC reconstruction.

S. No.	Age	Sex	Side	Diagnosis	Pre-op adjuvant	Grafts used	Implant used	Blood loss (ml)	Duration (Min)	Union (months)	MSTS	F/U (months)
1	30	F	L	GCT	No	Allo FH + autograft fibula	Screw	2000	210	6	27	122
2	31	M	R	GCT	AE	Allo FH + fibula	K wires	1200	170	6	28	113
3	36	F	L	GCT	No	Allo FH + radius	K wires	1400	180	7	29	107
4	14	F	R	GCT	AE	Allo FH + fibula	K wires	2000	120	8	30	101
5	22	M	R	GCT	AE	Allo FH + fibula	K wires + screw	600	195	8	–	14 (LR)
6	20	F	L	GCT	AE + ZOL	Allo FH + fibula	K wires	600	180	7	28	63
7	31	M	L	GCT	ZOL	Allo FH + fibula	K wires	2500	135	8	28	54
8	27	M	R	GCT	AE + Deno	Allo FH + fibula	K wires	750	160	7	23	54
9	21	F	L	GCT	AE	Allo FH + ulna	K wires + screw	700	160	LR before union	–	4 (LR)
10	18	M	R	CB	No	Allo FH + metacarpal	None	500	135	8	27	39
11	15	F	R	GCT	Deno	Allo FH + fibula	K wires	3000	150	6	30	34

AE: angioembolization; Allo FH: femoral head allograft; CB: chondroblastoma; Deno: denosumab; F: female; GCT: giant cell tumour; L: left; LR: local recurrence; M: male; MSTS: ; R: right; UC: Umbrella construct; ZOL: Zolendronic acid; MSTS: Musculoskeletal Tumor Society Score.

The mean allograft incorporation time (three cortex union evaluated on biplanar radiographs) was 7 months (5–8 months). One patient had strut graft fracture (fibula) which occurred after an accidental fall. It was managed conservatively and progressed to union. No other complications were encountered. Two cases developed local recurrence (n = 2/11, LR = 18%) (Case 5 and 9) at 4 and 14 months, respectively. Both underwent excision of the proximal humerus and reconstruction with tumour prosthesis. The remaining nine patients had a median follow-up of 54 months (range 34–122 months). The local recurrence free survival was 80% at five years.

The mean MSTS score for the nine cases with retained graft was 27/30 (range 23–29). All patients recovered well and returned to their pre-disease work.

Discussion

The shoulder being one of the most mobile joints in the body provides a large range of motion in various planes including circumduction. Curettage alone, curettage with reconstruction (bone graft or cement) and resection followed by reconstruction are practised for management of benign aggressive lesions of the proximal humerus. The decision to retain or excise the proximal humerus is complex and seeks to balance oncological clearance and function preservation. Though resection usually provides the best oncological clearance, it is associated with poorer function, making function preserving intralesional curettage and reconstruction a preferred choice for benign bone lesions.^3,7 Post curettage, either bone grafts or bone cement is utilized to reconstruct the cavity. Non-biologic cement reconstruction may help in further sterilizing the margins due to its exothermic reaction and permit early mobilization.⁸ Though less pertinent in the upper limb, there have been reservations about the use of cement in close proximity to articular surfaces because of the fear of articular degeneration. Bone graft, a more biological method of reconstructing contained defects, undergoes permanent incorporation along the lines of stress. Autografts are associated with issues of limited quantity and donor site morbidity.⁴ Allografts can be used as an alternative source to provide biologic reconstruction. While allograft complications like delayed union/incorporation, infections and graft fractures are not infrequent when these are utilized to reconstruct intercalary defects,⁹ studies with allograft reconstruction have shown encouraging results after curettage of cavities.^10,11 Morsellized allografts have been associated with graft resorption and collapse in the subchondral region leading to articular incongruence.¹⁰ Hence, in cases where a large area of subchondral bone is suboptimal we prefer to use frozen femoral head allograft in the subchondral area and strut allografts to reconstruct these cavities and provide better structural support. The femoral head used in UC helps in maintaining the contour of the humeral head and prevents articular surface collapse. The strut graft provides stability to the femoral head allograft and helps in maintaining the length of the curetted cavity. All the cases except one (fibular autograft) in the present study were reconstructed with allograft procured from our bone bank. There was only one graft fracture which occurred after an accidental fall on the operated shoulder. This was treated conservatively and progressed to union. All allografts incorporated well with the host bone. As these allografts were placed within a contained curetted cavity (a vascular bed with good potential for union), the incorporation time (mean 7 months; range 5–8 months) was shorter than conventional intercalary strut allografts.¹²

Irrespective of the length of the defect, none of the cases required any implant apart from K wires and screws, hence limiting operative time and reducing costs. A stable biological construct reduces the chances of construct failure and graft fractures. Strength of the well-fitted strut allograft was adequate to provide stable reconstruction at a non-weight bearing location.^9,13 UC reconstruction helped in maintaining the humerus length and shoulder joint congruity. Allografts also prevented donor site morbidity.⁴

The mean MSTS score (90%) in our study was better than that achieved after proximal humerus resection.¹⁴ Functional scores range from 61 to 77% for prosthesis, 57 to 91% for allograft-prosthesis composites and 50 to 78% for osteoarticular graft reconstructions. Retaining the host bone and maintaining an intact rotator cuff and shoulder joint capsule contributed to a stable shoulder in the cases in our series (Figures 2 and 3). This resulted in a significantly better outcome compared to resection which leads to an unstable shoulder joint.³

Figure 2.

(a) Radiograph showing giant cell tumour of left proximal humerus, (b) radiograph taken five months post bisphosphonates, (c) immediate post-operative radiograph, (d) five-year follow-up radiograph showing graft union and remodelling and (e) functional outcome.

Figure 3.

(a) Pre-operative radiograph showing giant cell tumour of left proximal humerus, (b) immediate post-operative radiograph, (c) eight-year follow-up radiograph showing graft union and remodelling and (d) functional outcome.

Our local recurrence rate of 18% (2 of 11) is comparable to other published studies.^15,16 Both occurred in Campanacci grade 3 tumours. One case had an open biopsy done elsewhere and the other occurred in a multifocal GCT, which is known to have high rates of local recurrence.¹⁷ Campanacci grade 3 lesions inherently have a higher recurrence rate^15,16 compared to lower grade lesions. Our attempts to retain the native joint in spite of the fact that most of the cases had an extraosseous component with minimal subchondral bone intact appear to be justified in view of these results.

Our study has limited numbers and medium term follow-up, but the present results are very encouraging and support a less morbid modality of reconstruction in treating large aggressive benign bone lesions of the proximal humerus. The reconstruction method outlined is reproducible, easy to perform and has a shallow learning curve. Preservation of host bone and rotator cuff results in better function in comparison to other reconstruction modalities. UC also helps to maintain the shoulder contour which is cosmetically better for patients.

Ethical Review and Patient Consent

Ethical review was not applicable as it was a retrospective audit. Consent was obtained from all the patients.